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(2015) Surface Water Engineering Standards

1. TABLE 3 2 24 Hour Design Storm Hyetograph Values Cont Time from Beginning Percent Cumulative Percent of Storm Rainfall Rainfall 440 1 80 31 24 450 1 80 33 04 460 3 40 36 44 470 5 40 41 84 480 2 70 44 54 490 1 80 46 34 500 1 34 47 68 510 1 34 49 02 520 1 34 50 36 530 0 88 51 24 540 0 88 52 12 550 0 88 53 00 560 0 88 53 88 570 0 88 54 76 580 0 88 55 64 590 0 88 56 52 600 0 88 57 40 610 0 88 58 28 620 0 88 59 16 630 0 88 60 04 640 0 88 60 92 650 0 72 61 64 660 0 72 62 36 670 0 72 63 08 680 0 72 63 80 690 0 72 64 52 700 0 72 65 24 710 0 72 65 96 720 0 72 66 68 730 0 72 67 40 740 0 72 68 12 750 0 72 68 84 760 0 72 69 56 770 0 57 70 13 780 0 57 70 70 790 0 57 71 27 800 0 57 71 84 810 0 57 72 41 820 0 57 72 98 830 0 57 73 55 840 0 57 74 12 850 0 57 74 69 860 0 57 75 26 870 0 57 75 83 D3 5 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 TABLE 3 2 24 Hour Design Storm Hyetograph Values Cont Time from Beginning Percent Cumulative Percent of Storm Rainfall Rainfall 880 0 57 76 40 890 0 50 76 90 900 0 50 77 40 910 0 50 77 90 920 0 50 78 40 930 0 50 78 90 940 0 50 79 40 950 0 50 79 90 960 0 50 80 40 970 0 50 80 90 980 0 50 81 40 990 0 50 81 90 1000 0 50 8
2. D 60 AMENDED SOUS ua o te dece d etui dec indue NDP 1 BIORBIEBNTIONACBLL s sa sasay ueste etm ae pedi o NDP 2 BIORETENTION NDP 3 BIORETENTION PLANTER NDP 4 BIORETENTION PLANTER INFILTRATION 2 NDP 4A BIORETENTION PLANTER FLOW THROUGH WITH OVERFLOW CONNECTED TO STORM SYSTEM ae ec eee NDP 5 BIORETENTION OVERFLOW WITH CONVEYANCE NDP 6 BIORETENTION OVERFLOW WITH PIPE CULVERT n NDP 7 OVERFLOW CONFIGURATIONS FOR BIORETENTION NDP 8 OBSERVATION PORT FOR 0 NDP 9 DRAIN CURB CUT OPENING FOR BIORETENTION eren NDP 10 PERVIOUS ASPHALT OR CONCRETE PAVEMENT SECTION NDP 11 PERVIOUS PAVER SX STEMS aaro irt ta edidere a ees NDP 12 PERVIOUS PAVEMENT SIDEWALK IN PLANTING NDP 13 PERVIOUS PAVEMENT SIDEWALK iiec cct eee road abo teat cie eoe pea deben NDP 14 CHECK DAM AND INTERCEPTOR FOR PERVIOUS PAVEMENT ON SLOPES NDP 15 OBSERVATION PORT FOR PERVIOUS PAVEMENT nm NDP 16 OBSERVATION PORT COVERS FOR PERVIOUS PAVEMENT
3. JANUARY 2015 3NVN AMONDIOJd ON anna FLOW N Nc LEVELI G PAD 1 8 X 3 4 X 2 1 4 6 MIN 23 3 4 FOR SLOT DETAIL SEE nel STD DTL NO D 7 EVATION 5 DRAFT N X NOTES 1 JANUARY 2015 USE WITH TWO LOCKING BOLTS 5 8 11 NC STAINLESS TYPE 304 STEEL SOCKET HEAD ALLEN HEAD BOLTS 2 LONG NOTE SLOT DETAIL MATERIAL IS DUCTILE IRON ASTM 556 GRADE 80 55 06 OUTFALL TO STREAM DUMP NO POLLUTANTS RAISED LETTERS SHALL BE LOCATED ON GRATE S SHOWN OR ON BORDER AREA HALL CONFORM TO SEC 7 05 OF THE STANDARD PECIFICATIONS ELDING IS NOT PERMITTED EDGES SHALL HAVE 0 125 RADIUS 0 125 CHAMBER OR COMPLETE DEBURRING USE BI DIRECTIONAL VANED GRATE IN SAG VERTICAL CURVES City of STORM AND SURFACE Bellevue WATER UTILITY NO SCALE VIEW FOUNDARY NAME 1 2 7 1 4 FOR LETTERS RECESSED FLUSH LEARANCE SINN L pE T AR 1 r 8 pe T TYP 4 ES z 1 5 8 IS AREA 1 1 8 4 TYP BAR THIS SIDE TO CURB
4. MIN 4 DIA PVC SDR 35 PIPE BIORETENTION S lt lt lt TO APPROVED SSS LOCATION PER 4 gt CITY OF PER STANDARD BELLEVUE DETAIL NDP 2 ENGINEERING EXISTING STANDARDS SUBGRADE OA ADI CELL OVE IVES ATRIUM GRATE SEE QUALIFIED PRODUCTS LIST NDP CHAPTER HEREIN BIORETENTION CELL PER STANDARD 6 FREEBOARD DETAIL 2 n ig Ae RS Bas lt S TO APPROVED LOCATION PER MIN 4 DIA PVC SDR CITY OF 55 PIPE 12 MIN BELLEVUE SLOPE ENGINEERING STANDARDS NWI W n SII A Cit of STORM AND SURFACE Bellevue WATER UTILITY ION OVERFLOW CULVERT JANUARY 2015 NO NDP 7 OVERFLOW CLEANOUT ATRIUM GRATE CLEANOUT MAX PONDING DEPTH VARIES OVERFLOW PIPE SEE NOTES PERFORATED DISTRIBUTION PIPE TO RUN LENGTH OF FACILITY SEE DETAIL A SSD OR PERFORATED PIPE PER STD DTL 3 DETAIL 1 MIN SLOPE COUPLING SOLID PVC SDR 35 PIPE TO APPROVED DISCHARGE A PLAN VIEW PIPE W UNDERDRAIN amp DISCHARGE POINT SASS SS XS SSO S Ex RS EX Si X Q 1 INFILIRATION OVERFLOW DIRECTED TO DRAIN ROCK 0 25 INCH HR OR GREATER NATIVE
5. a D8 7 D8 08 2 Abandoning Structures D8 8 D8 08 3 Demolition or Removal of Structures D8 8 D8 09 TESTING OF GRAVITY STORM DRAINS 1 4 eerte D8 9 ipsom ME i edi M E D8 9 DS5 09 2 Air darin D8 10 D8 9 3 Deflection Test for Flexible Pipe D8 11 D8 IO TELEVISION INSPECTION laani insana D8 11 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 08 11 TESTING OF CONCRETE STRUCTURES D8 11 T D8 11 5 11 22 aka aaa D8 12 3 ACCS PLANO vee cacti SD aswaa bti ot e nen au D8 12 D8 12 TRENCHLESS D8 13 D5 15 TRENCH EXCAVATION 02 u ana a eei apis Dake ae VT D8 13 TABLES Table 5 09 sma ua ace ore ma aR Su u E Lo D8 9 iU rU ME D8 10 Pale NM D8 12 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D8 METHODS OF CONSTRUCTION D8 01 GENERAL All construction on City rights of way shall be done in accordance with the City s standards and the procedures and m
6. STORM SURFACE WATER UTILITY INSTALLATION NO STANDA 0 9 7 77 X 5 8 11NC HOLES 7 1 8 X 3 4 X 2 1 4 THRU FRAME LEVELING PAD PLAN 18 17 3 4 SEE NOTE 3 MIN DRAFT THIS SIDE M E 2 1 DIAM HOLES E n FOR 3 4 BOLT WASHER amp NUT SEE NOTE 4 C C NOTES MATERIAL SHALL CONFORM TO SECTION 9 05 15 2 OF THE STANDARD SPECIFICATIONS I PATTERN ON SURFACE OF HOOD SHALL 3 16 NON SKID DIAMOND BOLT WASHER AND NUT SHALL BE GALVANIZED OR CORROSION RESISTANT SEE DETAIL 0 11 FOR INSTALLATION HL TH L City of STORM AND SURFACE Bellevue WATER UTILITY THROUGH CURB INLET FRAME JANUARY 2015 NO SCALE PLANTING OR SIDEWALK CLASS A CONC CURB CONCRETE amp GUTTER w WISI OL 12100 ROADWAY SURFACE GUTTER PAVEMENT DEPTH me
7. TEST PLUG ABOVE MODIFICATION FOR CREST GAGE OPTIONAL ee a MATERIALS BERM SIDE e 4 6 FEET OF 1 INCH DIAMETER OF FACILITY 80 PVC CORK DUST _ SOLID WALL INSTRUCTIONS EA SLE 1 CUT THE CREST GAGE TO LENGTH Be 1 FIELD SIZE THE CREST GAGE TO FIT INSIDE THE OBSERVATION PORT CASING THE CREST GAGE RE CONDITION SHOULD SIT IN THE BOTTOM OF THE CASING AND BE FLUSH WITH THE TOP OF THE CASING EAS SLOPE j ADD CORK DUST 90 SCHEDULE REMOVE THE CREST GAGE FROM THE OBSERVATION PORT CASING ADD ABOUT ONE HALF EM 80 PVC TEASPOON OF CORK DUST INTO THE OBSERVATION PORT CASING IF YOU MAKE YOUR OWN SOLVENT WELDED OR CORK DUST GRIND IT THE TEXTURE OF COARSELY GROUND COFFEE PLACE THE CREST SCREWABLE PLUG GAGE IN THE OBSERVATION PORT REPLACE THE OBSERVATION PORT TOP PLUG OR CAP PA ELEVATION BOTTOM COUPLING READING THE MAXIMUM WATER LEVEL A CREST GAGE RECORDS THE MAXIMUM WATER LEVEL BETWEEN READINGS AS THE WATER OF FACILITY VARIES TABLE RISES SO WILL THE CORK DUST AS THE WATER LEVEL DROPS A RING OF CORK DUST REMAINS ON THE CREST GAGE REMOVE THE CREST GAGE FROM THE OBSERVATION PORT MEASURE FROM THE TOP OF THE CREST GAGE TO THE CORK DUST RING CONVERT THE MEASUREMENT TO DEPTH OF WATER TABLE BELOW GROUND SURFACE BY SUBTRACTING THE DETAIL A NOTES LENGTH OF THE RISER ABOVE THE GROUND THIS MEASUREMENT IS THE DEPTH OF THE A TIT RISUS S STORM AND SURFACE M
8. D8 2 DS 04 3o Storm Drain Me et pec D8 2 DS204 4 Pipe Beddi coin otio SS usa D8 2 Ds O45 Layme Storm Sewer Pipe ices MO kan pee D8 3 D8 04 6 Ba kfillins Trete Besse oo dotata ION pea anni iae tat D8 3 In EGER D8 4 D8 04 8 Private Drainage Systems uses ote e era nd CE de QUE D8 4 08 05 MANHOLES CATCH BASINS amp INLETS eene D8 4 D8051 D8 4 ID8 05 2 gt Bacektilline SG Q tede emendi D8 4 D8 05 3 Adjusting Manholes and Catch Basins to Grade D8 5 D8 06 FLOW CONTROL DETENTION FACILITIES D8 5 D 06 1 Control 5 ee D8 5 D 3806 2 AA Nie D8 5 D8 06 3 Underground Detention Systems essere nennen nennen D8 6 D8 06 4 Storm Water Detention Facility Leakage Testing D8 8 D8 07 FLOW CONTROL INFILTRATION SYSTEMS D8 7 D8 08 ABANDONING FACILITIES sd D8 7 D8 08 1 Abandoning Pipe In Place
9. D7 1 D7 01 1 Manufacturer s Certificates of Compliance D7 1 07 05 CONVEYANCE SYSTEMS La sasana f as eec dene buta D7 1 D7021 a Sy aa suan ss D7 1 D7 022 Open Channels nece us ADO dst QS D7 1 D7 02 3 Storm Drain Pipe and Culvert Materials D7 1 D72024 Pipe BeddIng ot teda sitters Pasa t tes voce We bees ta D7 3 137 02 5 Bae KB Tos Gi b dehet o e aet D7 4 D7 02 6 Private Conveyance Systems One edu ic te ass D7 4 D7027 asas qta anita Tasa D7 4 97 028 GCouplilgs uu u ARA eO rtt Risa ti D7 5 D7 02 9 Sicel CASINGS D7 5 D7 02 10 Casing Spacer aasawa apaqaspa D7 5 07 03 MANHOLES CATCHBASINS AND INLETS D7 6 D7 03 1 Precast Concrete Products usc Pg tUe Mns ee M D7 6 D72033 Structure Backfill naa y eas a netus E dvd alte cus D7 7 D7 04 FLOW CONTROL DETENTION FACILITIES D7 7 07 041 General D7 7 DJ 042 Control SIC ese oce
10. gt lt N E 50 2 o 2 g 2 4 gt gt 9 gt Q S 2 5 wo E Diameter 8961 OL L 99 0 joo Bp 1e3euieig euojs IeSui uds 3uejeAinb3 LO L i l p I rS 9 uo 7 7 c et 3 1 1 ES z y F j A 7 7 1 is is i f 18 001 Ww 4 4 Ww 980 A ouols 021 g u 990 5p sql 92 AA esn Su lnquni yH sql S 9 AA es od 8 A euois adojs ejduiex3 cj Jed sql p Z9 ey Jed sq M cp 9 AA MM MM 62 A 001 puooes Jad 04 12 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 2 Riprap Filter Example Gradation Curve 20 RIP RAP lt 10 c N o o Coarse Aggregate size number 57 ASTM
11. gt 2 CATCH ECTION A A NOTES 1 SET TO GRADE AND CONSTRUCT ROAD AND GUTTER TO BE FLUSH WITH FRAME 2 HOOD SHALL MATCH TOP OF CURB ELEVATION City of STORM AND SURFACE Bellevue WATER UTILITY IHROUGH CURB INLET FRAME INSTALLATION JANUARY 2015 NO SCALE LEVELING PAD 8 3 4 X 2 1 4 X 1 8 MEE DUIFALL TO STREAMZBUMP NO POLLUTANIS J FON 08 08 08 08 DD NL NN Nea N 1 2 LET RECESSE BE FLUSH L T 1 5 8 TYP TYP 17 1 4 ECTION NOTES 1 FRAME MATERIAL IS CAST IRON ASTM A48 CLASS 30 3 Cit of STORM AND SURFACE Bellevue WATER UTILITY FRAME amp GRATE FOR EXISTING ROLLED CURB JANUARY 2015 NO SCALE 226 e Y TRANSITION lt 3 FLUSH 2 LETTERS RECESSED Z TO B OUTFALL STREAM DUMP POLLUTANTS STREET PAVEMENT SN ON PN ON EON PUN HON NA YY YY YY YY BACK EDGE OF FRAME EVEN WITH BACK FACE OF CURB LE TRANSITIO P C C GUTTER ROLLED CURB FRONT
12. ES ALL PIPE STAKES HARDWARE AND MATERIALS SHALL BE HOT DIPPED GALVANI FABRICATION Cit of STORM AND SURFACE Bellevue WATER UTILITY r ANCHOR ASSE JANUARY 2015 NO SCALE PROFILE V wes o GRAVEL BORROW aan 122 95 COMPACTION Wee Cow 4 MODIFIED PROCTOR faa as 212 CULVERT PIPE 12 DIA MIN AND MATCH LARGEST PIPE UPSTREAM OR DOWNSTREAM 2 1 SIDE SLOPE MAX HEADWALL OR FLARED END SECTION PRIVATE PROPERTY V ECT ORY SSN S on RRA REINA S 52555 STAPLE SOD OVER DISTURBED AREAS IN DITCHLINE TYP NOTES Nes INIMUM BACKFILL COVER OVER PIPE IS 2FT F LESS THAN 2FT COVER PIPE SHALL BE CLASS 52 DUCTILE IRON City of STORM AND SURFACE DRIVEWAY CULVERT SHALL BE DESIGNED TO WATER UTILITY UPSTREAM AND DOWNSTREAM STORM SYSTEM MINIMUM 12 Bellevue PIPE MATERIAL SHALL BE PER THE UTILITIES ENGINEERING STANDARDS EWAY CULVE JANUARY 2015 NO SCALE L 4d OR 8 WHICHEVER IS GREATER 6 QUARRY ROCK PIPE DIA D SEE PLAN TAPERED END TYP ALL INLETS AND OUTLETS d TOP OF BANK 6 QUARRY ROC ES 1 DISCHARGE VELOCITY IS 2 6 FT SEC 100 YR STORM EVENT THEREFORE A RIP RAP PAD S REQUIRED RIP RAP SHALL BE IN ACCORDANCE W SECTION 9 15 1
13. 7 8 4 SEE TYP SLOT DETAIL LEVELING PADS 8 3 4 X px SINVLNTIOd ON aes OL KD N 3 4 X 8 1 11 4 BA 3 8 5 AREA 7 8 END VIEW 17 5 4 23 1 2 17 1 2 SLOT DETAIL SEE NOTE 1 m E ELLIPTICAL 1 z BETWEEN e TWO RADII OPTIONAL DESIGN FOR NOTES GRATE OPENINGS ENDS SLOT FORMED AND RECESSED FOR 5 8 11 NC X 2 SOCKET HEAD ALLEN HEAD BOLT GRATE SHALL BE DUCTILE IRON SHALL CONFORM TO SEC 9 05 15 OF THE STANDARD SPECIFICATIONS City of STORM AND SURFACE USE VANED GRATE IN CURB LINE WATER UTILITY USE FRAME SHOWN IN STANDARD DETAIL PARKING LOT ARE GRATE JANUARY 2015 NO SCALE R 3 4 SEE NOTE 2 JN FOUNDAR Y NAME NOTES 1 USE LOCK USE STAI HEAD COVE SHALL STAN COVE v 5 O m e x Q O 1 2 LETTERS RECESSED BE FLUSH LEVELING PAD 8 1 8 X 3 4 X 1 3 4 PLAN COVER WITH FRAME DRILLED AND TAPPED FOR ING BOLTS WITH TWO LOCKING BOLTS 5 8 11 NC LESS STEEL TY
14. TYPICAL DATA PROPERTY ASTM METHOD UNITS VALUE Specific Gravity D 792 gm cc 934 Tensile Strength Break D 638 PSI 3500 Elongation Break D 638 380 Izod Impact D 256 Ft Lbs in of notch No break Hardness D 2240 Shore D 67 Coefficient of Friction D 1894 0 11 0 13 Heat Distortion Temp 66 PSI D 648 C 88 Coefficient of Thermal D 696 1 5 5 x 10 5 ABRASION CHARACTERISTICS Taber Abrasion D 1044 Mg loss N Sand Slurry 7 Sand slurry condition 7 hours in one part sand one part water slurry at 1725 RPM Carbon steel 100 Hifax 15 The lower the value the more resistant to abrasion Casing spacers shall be center positioning type Height of risers and runners combined shall be sufficient to keep the carrier pipe bell couplings or fittings at least 0 75 from the casing pipe wall at all times and provide at least 1 clearance between runners and top of casing wall to prevent jamming during installation D7 03 MANHOLES CATCHBASINS AND INLETS D7 03 1 Precast concrete products for manholes inlets and catch basins shall comply with Section 7 05 2 of the Standard Specifications D7 03 2 A Castings Metal castings for manhole rings round covers frames grates and rectangular covers shall conform to the Standard Details and Section 9 05 15 of the Standard Specifications as modified herein Precast Concrete Products Metal Covers All catch basin grated covers in roadways shall
15. aia vers D4 70 Control S FUCUITeS eia anaes D4 70 POTS eT D4 71 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D4 06 6 Underground Detention Systems D4 73 D4 06 7 Tatiltration U unas eacus qe D4 75 D4 06 8 DisperSIion SyStemSs usa nere eee Tn D4 84 D4 06 9 Non Gravity Systems Pumps eed icio raten D4 84 D4 06 10 Non Gravity Systems Pumps for Properties where 100 Lot Coverage is Allowed by City s Land Use Code usi eec eite rhe d oe D4 85 D4 07 SETBACK REQUIREMENTS D4 86 D4 07 1 Setback Requirements for Surface Water BMBs D4 86 D4 08 EASEMENT REQUIREMENTS D4 89 D4 08 1 Sid cM TU D4 89 D4 08 2 Easement Documentation Requirements D4 89 D4 08 3 Easement Width Require ments ee D4 90 D4 08 4 Easement Documentation Requirements D4 90 D4 09 PIPE COVERINGS AND 22 24 22 22224 D4 90 TABLES Table 4T Rock Protection At Outfalls u a u uide a dut D4 3 Table 4 2 Channel Protection ene ee au SS S
16. P V C SLEEVE MIN 12 LONG FOR SLEEVE DIAMETER SEE TABLE STANDARD DETAIL 11 OBS PORT PIPE RING AND COVER P V C SLEEVE DIAMETER DIAMETER DIAMETER 3 12 12 NOTES BOLT LOCKING CAST IRON RING AND COVER SHALL BE USED IN RIGHT OF WAY AND EASEMENTS AND MUST RATED HS 20 IF USED IN TRAFFIC AREAS SEE TABLE FOR SIZES MID STATES PLASTIC BOX OR EQUAL MAY BE USED IF OBSERVATION PORT IS OUTSIDE OF RIGHT OF WAY OR EASEMENT SEE TABLE FOR SIZES THE COVER FOR THE PLASTIC BOX SHALL BE DUCTILE IRON AND READ STORM OR BE BLANK NO LABEL CAST IRON COVER SHALL READ STORM DO NOT BURY OR EQUIVALENT LOCKING BOLTS SHALL BE 5 8 11 N C 304 STAINLESS STEEL SOCKET ALLEN HEAD 4 City of STORM AND SURFACE 2 LONG WATER UTILITY 14 BOLT LOCKING CAST IRON COVER SHALL Bellevue BE EQUAL TO INLAND FOUNDRY NUMBER 209 OR 210 FOR TRAFFIC AREAS SEE STANDARD TITLE DETAIL D 52 FRVATION PORT COVE SPECIAL DECORATIVE CASTING MAY BE USED IF PREAPPROVED BY CITY OF BELLEVUE ERVIOUS PAVEME JANUARY 2015 NO SCALE NO mas LEAF ROCK SCREEN DOWNSPOUT CONNECTION LATCH OR LOC STAINLESS STEEL SCREEN E K SEE DOE MANUAL FOR DISPERSAL METHODS AS MODIFIED HEREIN PROVIDE OVERFLOW PIPING TO ADDITIONAL TANKS OR D
17. Ku 5 MIN VARIES P ETBACK REQU PROFILE NO SCALE 6 CLEAN OUT WITH CAP MIN EMERGENCY TRENCH SHALL NOT BE LOCATED WITHIN 100 OF STORAGE DEPTH E WELL OR 30 FROM ANY PART OF SEPTIC eT YSTEM GEOTEXTILE TOP amp BOTTOM CENTER PERF PIPE HORIZONTALLY RENCH 5 DES LAP 12 MIN E E REMOVE SEDIMENT AND FLOATABLES FROM TYPE 1 CATCH BASIN AT LEAST ANNUALLY 4 OR 6 DIA PERF PVC PIPE W TEE WASHED ROCK Qf STORM AND SURFACE 3 4 1 2 WATER UTILITY l 2 PLUG F DOWNSPOUT SECTION RATION TRENCH JANUARY 2015 NO SCALE NDP 23 GRATE NDS 1280 OR 1290 1 1 8 RIM 12 x12 CATCH BASIN RISER NDS 1216 1 1 8 RIM 12 x12 RISER WITH 2 OPENINGS NDS 1217 4 PVC TEE FROM 4 PVC OUTFLOW PIPE DOWNSPOUTS 1 1 8 RIM 1 2 HARDWARE CLOTH SCREENING BOTTOM ONLY 12 x12 SUMPBOX NDS 1225 a L I gt o NOTES 1 THIS DETAIL USES NDS PRODUCTS TO CREATE A LIGHT WEIGHT YARD CATCH BASIN FOR USE IN NON ROADWAY AREAS OTHER PRODUCTS MAY BE ACCEPTABLE AS APPROVED BY BELLEVUE UTILITIES SUMP DEPTH MUST BE A MINIMUM OF 2x DIAMETER OF INLET PIPE SDR35 OR EQUAL FOR TEE AND PIPE GRATE SHAL
18. L gt current previous cross section cross section BWCHAN VARIABLE DEFINITIONS YC IN Critical Depth ft at current section based on incoming flow rate YC OUT Critical Depth ft at current section based on outgoing flow rate YN IN Normal Depth ft at current section based on incoming flow rate channel grade YN OUT Normal Depth ft at current section based on outgoing flow rate channel grade Y1 Final Water Depth ft at current cross section N Y1 Composite n factor of current section for final depth Y1 A Y1 Cross sectional Area of current section for final depth Y1 WP Y1 Wetted Perimeter ft of current section for final depth Y1 V Y1 Average Velocity fps of current section for final depth Y 1 5 El Total Energy Head ft at current section ri Ch 2 Total Energy Head ft at pervious downstream section SFI Friction Slope of current section SF2 Friction Slope of previous or downstream section Distance expressed as a fraction of the current reach length from the previous or DXY downstream section to where the flow profile would intersect the final water depth Y1 assuming Y1 were to remain constant EC Energy Coefficient Q TW The flow rate used to determine Tailwater Height from an inputted HW TW Data File D4 24 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 TW HT Tailwater Height Q Y1 Flow rate cfs in channel at current section for depth Y1 VU Y1 Upstream Veloc
19. lt gt 5 b b q 54 94 lt lt lt lt lt lt SS 22 XD lt 9 Q2 22 502 lt Q2 RSLS GRAV ROW PER WSDOT 5 9 05 14 1 OR SUITABLE EXCAVATED o 6 MIN MATERIAL COMPACT TO 95 OF MAXIMUM DENSITY UNPAVED AREAS ES PAVED AREAS MAXIMUM WIDTH OF TRENCH OF 30 FOR PIPE UP TO O D PLUS 16 FOR EXCAVATIONS OVER 4 D PIPE AND INCLUDING 12 NOMINAL DIAMETER PE LARGER THAN 12 NOMINAL DIAMETER DEEP SHALL COMPLY WITH E SAF DESCRIBED IN CHAPTER 296 155 OF THE SEE BACKFILLING TRENCHES PTER D8 OF F ENGI FOR ADDITIONAL CONSTRUCTIO IREMENTS ETY STANDARD RING STANDA STORM AND SURFACE WATER UTILITY JANUARY 2015 NO SCALE SOLID COVER MARKED DRAIN WITH BOLT LOCKING RING AND COVER
20. NDP 17 RAIN RECYCLING SYSTEM RAIN BARREL 2 4 1 NDP 18 RAIN RECYCLING SYSTEM CISTERN 4i ete be enel NDP 19 POP UP DRAINAGE BEMTTTER dope NDP 20 REVERSE SLOPE SIDEWALK 45e hod eR Ma e deae Cele NDP 21 ROOF DOWNSPOUT DISPERSAL TRENCH 2 4 2 NDP 22 ROOF DOWNSPOUT INFILTRATION TRENCH eee NDP 23 RESIDENTIAL Y ARD CATCH NDP 24 RESIDENTIAL ROOF DOWNSPOUT PERFORATED PIPE CONNECTION NDP 25 A D1 3 JANUARY 2015 FRAME AND GRATE SEE APPLICABLE STANDARD DETAILS 6 RISER SECTION 4 n lt gt PRECAST BASE SECTION MEASUREMENT AT THE TOP OF THE BASE NO SCALE NOTES 1 CONCRETE IN ASTM 478 OR amp C890 UNLESS OTHERWISE SHOWN O THE STANDARD SPECIFICATIONS LET BE CONSTRUCTED IN ACCORDANCE WITH PLANS AS AN ACCEPTABLE ALTERNATIVE TO REBAR WELDED WIRE FABRIC PER FOOT MAY BE USED COMPLY TO PLACED IN KNOCKOUTS VERTICAL GAM ASTM A497 WIRE FABRIC SHALL NOT AREA OF 0 12 SQUARE INCHES WELDED WIRE FABRIC SHALL BE EDGE OF RISER OR BRICK SHALL NOT BE MORE THAN 2 FROM VERTICAL EDGE OF CONCRETE INLET RECAST OCKOUTS F 2 MIN AM PLUS ROUND KNOCKOUTS MAY BE O DIAM OF 16
21. Manning s n value Outlet Elevation of pipe segment Inlet Elevation of pipe segment Barrel Area this is the full cross sectional area of the pipe Barrel Velocity this is the full velocity in the pipe as determined by V Q A or Col 8 Col 1 Col 7 2 2 Barrel Velocity Head V 2g or Col 8 2g where g 32 2 ft sec acceleration due to gravity Tailwater TW Elevation this is the water surface elevation at the outlet of the pipe segment If the pipe s outlet is not submerged by the TW and the TW depth is less than D d 2 set TW equal to D d 2 to keep the analysis simple and still obtain reasonable results D pipe barrel height and d critical depth both in feet See Figure 4 14 for determination of de Friction Loss SfxL Sfx Col 2 where Sf is the friction slope or head loss per linear foot of pipe as determined by Manning s equation expressed in the form Sf nV 222 R Hydraulic Grade Line HGL Elevation just inside the entrance of the pipe barrel this is determined by adding the friction loss to the TW elevation Col 12 Col 11 Col 10 If this elevation falls below the pipe s inlet crown it no longer represents the true when computed in this manner The true HGL will fall somewhere between the pipe s crown and either normal flow depth or critical flow depth whichever is greater To keep the analysis simple and still obtain reasonable results i e erring on the
22. 11 PERVIOUS PAVEMENT SIDEWALK ADJACENT TO BIORETENTION OR DITCH GRADE SYS S P pO 2 d gt HA SRE UES 2 77 SI gt 7 4 MIN DEPTH SUBGRADE MATERIALS PER CHAPTER D6 04 PERVIOUS CONCRETE TON SOIL MIX 5 MIN DEPTH SEE EQUIRED STD DTL NDP 11 GEOTEXTILE FABRIC OPTIONAL SEE NOTE 1 E FOR UNDERGROU EPARATION REQUIRED ONLY PE E SHOULD NOT BE ACTED PROTECT SURFACE IL FINAL LANDSCAPING COMPLETE Cit of STORM AND SURFACE Bellevue WATER UTILITY ERVIOUS JANUARY 2015 NO SCALE INTERCEPTOR INFILIRATION TRENCH LONGITUDINAL SLOPE MAXIMUM 10 SE RVIOUS PAVEMENT R STANDARD D GEOTEXTIL 11 OR 12 OPTIONAL ERVIOUS INFILTRATION TRENCH 16 x16 PTIONAL CHECK DAM MAXIMUM 10 SEE WATER STORAGE WITHIN ELI Ce FRVIOUS PAVEMENT NOI ER STANDARD D ERVIOUS
23. 3 I 1 TYP END SECTION 1102 METAL PLASTIC EVATION ERMO PLASTIC NOTE 1 SIDE SLOPE SHALL BE WARPED TO MATCH THE BEVELED PIPE END WHEN CULVERT IS ON SKEW BEVELED END SHALL BE ROTATED TO CONFORM TO SLOPE IF SLOPE DIFFERS FROM 5 1 PIPE SHALL BE BEVELED IO MATCH SLOPE City of STORM AND SURFACE Bellevue WATER UTILITY JANUARY 2015 NO SCALE VARIES PER PLAN COMPACTED S FILL ORIGINAL GROUNDLINE Da OY 0 p DITCH IS LOCATED ORIGINAL es AT TOE OF FILL GROUNDLINE OVER EXCAVATE TO GRAVEL FILTER LAYER OR ACCOMMODATE ROCK GEOTEXTILE MAY BE REQUIRED DUE TO SOIL TYPE ROCK LINED SHOULDER DITCH IN FILL SECTION VARIES PER PLA SEHN GRAVEL FILTER LAYER OR OVER EXCAVATE TO lt GEOTEXTILE MAY BE REQUIRED ACCOMMODATE ROCK DUE TO SOIL ROCK LINED SHOULDER DITCH SECTION NOTES j SE ED n City of STORM AND SURFACE WATER UTILITY ROCK SIZE AND DEPTH DEPENDENT ON Bellevue FLOW VELOCITY MINIMUM ROCK SIZE 27 4 QUARRY SPALLS ROCK LINED DITCH JANUARY 2015 NO SCALE yal r 1 0 FREEBOARD MIN NY binky 47 V GRASS SEED OR SOD ABOVE THE WATER SURFACE ELEV
24. NDP Description Applicability Requirements Bioretention Rain Garden Bioretention Cells All projects Comply with Section Bioretention Swale or Downspout D6 03 2 A Planter Box Pervious Pervious concrete or asphalt Modular All projects Comply with Section Pavement block underlying aggregate stores water D6 03 2 B LUC 20 20 460 G may Roof runoff may be directed to pervious apply impervious pavement surface limits Rain Recycling Rain barrels or cisterns for flow control All projects Comply with Section irrigation or indoor reuse of harvested D6 03 2 C water Vegetated Roof Roof with light weight soil mix and All projects Comply with Section plants D6 03 2 D Reverse Slope Sidewalk or walkway sloped towards All projects Comply with Section Sidewalk wide vegetated area D6 03 2 E Minimal Building deck or walkway supported projects Comply with Section Excavation pin pile or post systems minimal grading D6 03 2 F Foundation of native soil Systems Tier 3 Infiltrate or Disperse Runoff Prior to Discharging After evaluating and implementing all possible techniques and BMPs from Tiers 1 and 2 the following techniques must be implemented in the order presented below and used to D6 5 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 infiltrate or disperse as much of the remaining runoff as possible as site conditions allow without causing flooding or erosion Table 6 3 Required Tier 3 BMPs
25. NOTES 1 PROPRIETARY CATCH BASI ANDHOLDS AND STEPS ACCEPTABLE PROVIDED THAT THEY CONFORM TO SEC R ASTM C478 AASHTO 199 AND MEET ALL WISHA REQUIREMENTS CATCH BASIN STEP HANDHOLD LEGS SHALL BE PARALLEL OR APPROXIMATELY RADIAL AT THE OPTION OF THE MANUFACTURER XCEPT THAT ALL STEPS IN ANY CATCH BASIN SHALL BE SIMILAR ENETRATION OF OUTER WALL BY A LEG IS PROHIBITED DETAIL PROTUBERANCES TO PREVENT SIDEWAYS SLIP E P HANDHOLDS AND STEPS SHALL HAVE DROP RUNGS AS SHOWN s LAB OPENING MAY BE 24 X 20 OR 24 DIAM 96 SLAB PLASTIC STEPS SHALL BE POLYPROPYLENE AND CONFORM TO ASTM D 4101 WITH 1 2 ASTM 615 GRADE 60 STEEL REINFORCING BAR LANE P 13938 PS2 PF OR EQUAL STEPS OF LADDERS OR STEPS SHALL EXTEND TO WITHIN 16 OF BOTTOM OF CATCH BASIN R 3 4 ele HANGING LADDERS SHALL BE PERMANENTLY FASTENED AT TOP BY 3 ANGING ON STEP OR BY BOLTING OR EMBEDDING IN CONCRETE 6 EACH SHALL BE EMBEDDED AT BOTTOM BASE ADDITIONAL SAFETY FEATURES MAY BE REQUIRED IN VERY DEEP 8 GALV OR UNUSUAL STRUCTURES DEFORMED SQUARE OPENING ALLOWED ONLY FOR CATCH BASINS DESIGNED TO REBAR COLLECT WATER 7 GALV SMOOTH Ck Cit y STORM AND SURFACE m 3 4 3 Bellevue WATER UTILITY PREFABRICATED LAD
26. accordance with the NDP materials specifications in Section D6 04 2 D6 18 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Be placed between the reservoir course and bioretention soil mixture or subgrade Wrap around and over reservoir course and secure Pass water at a rate greater than the infiltration rate of the existing subgrade Underdrain Optional For sites with lower infiltration rates underdrain systems can be installed in the base of the facility to drain excess stormwater when the infiltration capacity of the surrounding soil is insufficient to meet minimum ponding drawdown time requirements When specified by the project engineer the design requirements shall include Slotted thick walled plastic pipe or other underdrain materials as specified in Section D6 04 3 shall be used underdrain shall be placed in the retention zone at least 6 inches above the bottom and with at least 1 foot of retention zone material above the top of the pipe 1 minimum retention zone depth of 24 inches for a 6 inch diameter pipe and 26 inches for an 8 inch diameter pipe Retention zone aggregate shall meet specifications in Section D6 04 1 and placed to a minimum uncompacted depth of 12 inches without an underdrain or 24 inches with an underdrain Liner or Soil Barrier for Hydraulic Restriction Optional Adjacent roads foundations slopes utilities or other infrastructure may require that in
27. Ayo ORISHeS z z z z Y pewoyog punoy 2 3092 4 Vz ti 2 3022 a 1 Pu z 1 4 6a 0z z 4 lt 4 l6uelo u pasausoo punoy amp 4 4 0 9 EES q 4 7 q 0 9 95 D ag 41 i n c do B P s Gl U guis q 07 i n pos Z I 9 G q d q 4 4 BENE M d V snipe 2 1ejeuiued D4 21 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 6 Open Channel Flow Profile Computation D4 22 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 7 Direct Step Backwater Method Example J gt gt gt 2 8 1 so eo see 3 o sos fo car so 22 ese veo ames sone 54978 osos 7140 a ses 2525 oor snas osos 2 sons 94772 90066 7995 4 0 0496 3 0496 0 4772 0 00076 0 000547 0 00645 73 95 432 85 0 1029 2 6029 0 4467 0 00201 0 001387 0 00561 79 58 512 43 80 089 086 375 0 2511 2 2511 0 3518 0 00663 0 004320 0 00268 131 27 643 70 The step computations are carried out as shown in the above table The values in each column of the table are explained as follows 0268 3 5268 0 48
28. Use Full Dispersion or Full Infiltration Meets flow control Do site conditions allow Full requirements Dispersion or Full Infiltration Tier 1 M Runoff Generation Roof Downspout Infiltration Sheet or Concentrated Flow site amp design criteria met Dispersion site amp design criteria met Roof Downspout Dispersion Choose one or more Implement site amp design criteria met Roof Downspout Infiltration Dispersion or install Bioretention Pervious Pavement Pervious Pavement Rain Recycling Choose one or more Vegetated roof Splash Block May not be used alone to Pop up Emitter meet MR5 or MR7 per Bioretention D6 03 Pervious Pavement Rain Recycling Natural Drainage Practices are encouraged Vegetated Roof to manage any additional runoff Bioretention Pervious pavement Rain recycling Vegetated roof Reverse slope sidewalk Minimal excavation foundation May not be used alone to meet MR5 or MR7 per D6 03 N O 4 gt a w a l N i Will site have piped connection to City aa Perforated Stub out Connection site Dispersion Trench site amp amp design criteria met criteria Install Dispersion Install Perforated Trench Stub out Connection Return to D4 for additional connection discharge and or flow control requirements Tier 3 Infiltrate Disperse Runoff Prior to Discharge Figure 6 1 On site Stormwater M
29. esi dU Or Nm duet e papaq PAGE 13 A D2 1 WATER SYMBOLS SYMBOL DESCRIPTION BLOCK LAYER EXIST PROP H FE ADAPTER FL x M J WAFM SAME WA FITT 3333 SYM BENDS 90 DEGREE FL W90F SAME WA FITT 3333 SYM 45 DEGREE BEND FL W45F SAME WA FITT 3333 SYM v 22 5 DEGREE BEND FL W22F SAME WA FITT 3333 SYM tH tH 11 25 DEGREE BEND FL W11F SAME WA FITT 3333 SYM Lt Lt 90 DEGREE BEND M J W90M SAME WA FITT 3333 SYM t t 45 DEGREE BEND M J W45M SAME WA FITT 3333 SYM y 22 5 DEGREE BEND M J W22M SAME WA FITT 3333 SYM T t T 11 25 DEGREE BEND M J W11M SAME WA FITT 3333 SYM rH PH VERTICAL BEND FL WVTF SAME WA FITT 3333 SYM HL FEL VERTICAL BEND M J WVTM SAME WA FITT 3333 SYM REDUCERS pi REDUCER FL WRF WRFP WA FITT 3333 SYM TE REDUCER M J WRM WRMP WA FITI 3333 SYM a gt REDUCER M J x FL WRMF WRMFP WA FITT 3333 SYM gt gt REDUCER M J x P E WRMB WRMBP WA FITT 3333 SYM REDUCER M J FL x M J WRBM WRBMP WA FITT 3333 SYM TEES TAPPING amp VALVE FL x MJ WA VALV 3333 SYM TEE FL WIF SAME 5533 5 Lr str TEE Mal WIM SAME WA FIIT 3333 SYM Ta Tr TEE MJ x FL WTMF SAME MA FITT 3333 SYM VALVES IM BUTTERFLY VALVE FL WBFV WBF VP WA VALV 333 33 S YM KC BUTTERFLY VALVE FL M J WBVFM WBVFMP WA
30. B Implementation The following describes how the Flow Control Credits are used to evaluate the amount of impervious area mitigated to meet the applicable Minimum Requirements for on site BMPs that do not fully achieve flow control requirements 1 il Retained Trees Retaining trees alone will not achieve flow control requirements however some flow control benefits are achieved with this BMP Credits for retained trees are provided in Table 6 14 for deciduous and evergreen trees This credit can be applied to reduce the effective impervious surface area used in downstream conveyance and flow control calculations Since partial credit only is applied additional flow control measures will be required To use the Flow Control Credit the retained trees must meet the following specific requirements Retained trees shall have a minimum six 6 inches diameter at a height of four 4 feet above the existing ground on the uphill side of a tree The tree trunk center must be within 20 feet of new and or replaced ground level impervious surface Tree credits do not apply to trees in native vegetation areas used for flow dispersion or other Flow Control Credit The total tree credit for retained trees shall not exceed 25 percent of impervious surface requiring mitigation New Trees Newly planted trees alone will not achieve flow control requirements however some flow control benefits are achieved with this BMP Credits for n
31. B Developed basin areas threshold discharge areas and flows should be shown on a map and cross referenced to computer printouts or calculation sheets Developed basin flows should be listed and tabulated C Any documents used to determine the developed site hydrology should be included Whenever possible maintain the same basin name as used for the pre developed site hydrology If the boundaries of a basin have been modified by the project that should be clearly shown on a map and the name modified to indicate the change D If treatment facilities are proposed provide a listing of the water quality menus used per Section D5 03 If flow control facilities are proposed provide a confirmation of the flow control standard being achieved e g the DOE flow duration standard E A drawing of the flow control and treatment facilities and appurtenances Show basic measurements necessary to calculate the storage volumes available from zero to the maximum head all orifice restrictor sizes and head relationships control structure restrictor placement and placement on the site F Include computer printouts calculations equations references storage volume tables graphs as necessary to show results and methodology used to determine the storage facility volumes Runoff model documentation files should be included See D3 02 for a list of approved models D2 11 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 G H Present an analys
32. LET TAPPING FLANGED COUPLING ADAPIOR PIPE BEDDING UNDISTURBED EARTH AIN STORM DRAIN ELEVATION VIEW UNDISTURBED FLANGED PIPE COUPLING BEDDING ADAPTOR SECTION ES D THE INSIDE DIAM OF THE INLET SHALL BE 8 OR LESS OF FOR LARGER VALUES F D USE A MANHOLE OR CATCH BASIN O CASE SHALL THE OUT AM OF INLET PIPE EXCEED O E INSIDE OF THE MAIN STOR E LET PIPE SHALL BE ON RADIU E 5 ORM DRAIN OPENING INTO THE EXISTING STORM SHALL BE E OUTSIDE DIAM OF THE PE PLUS 1 IN PLAN VIEW E SHALL HAVE 12 DIAM STAINLESS STEEL T FULL CIRCLE SEAL BE STAINLESS STEEL 3 City Of STORM AND SURFACE ALL TEES TO BE WATER TESTED BEFORE TAP WATER UTILITY Bellevue TAPPING TEE MAY BE SIZE ON SIZE AP SHALL AT LEAST 2 SMALLER DIAMETER HAN THE EXISTING STOR AIN EES SHALL HAVE BOLTS AND NUTS SHALL TAPPING TEES FOR DRAIN PIPE JANUARY 2015 NO SCALE TONGUE FND ON INLET END GROOVE END ON OUTLET END ENDS TO FIT ADJACENT PIPE SECTIONS ie q72 1 END SECTION
33. Note These n values are normal values for use in analysis of channels For conservative design of channel capacity the maximum values listed in other references should be considered For channel bank stability the minimum values should be considered D4 15 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 2 Direct Step Backwater Method The Direct Step backwater method may be used to compute backwater profiles on prismatic channel reaches ie reaches having uniform cross section and slope where a backwater condition or restriction to normal flow is known to exist The method be applied to a series of prismatic channel reaches in secession beginning at the downstream end of the channel and computing the profile upstream Calculating the coordinates of the water surface profile using this method is an iterative process achieved by choosing a range of flow depths beginning at the downstream end and proceeding incrementally up to the point of interest or to the point of normal flow depth This is best accomplished by the use of a table see Figure 4 7 To illustrate analysis of a single reach consider the following diagram Equating the total head at cross sections 1 and 2 the following equation may be written 2 2 S Ax y pane hs S Ax 4 1 28 28 where distance between cross sections ft 2 depth of flow ft at cross sections 1 2 Vi V2 velocity fps at cr
34. VARIES FOR 4 6 OR 8 P DIAMETER OUTLET 5 DA 4 CONCRETE BE POURED IN PLACE NOTES FOR USE IN NON TRAFFIC AREAS ONLY 2 AREA INLET EITHER CONCRETE AS of SHOWN OR PVC STRUCTURE WITH 2 SURF AC ER UTILITY DUCTILE IRON GRATE AS MANUFACTURED BY NYLOPLAST JANUARY 2015 NO SCALE RING amp COVER ADJUSTMENT SECTION LEVELING BRICKS 2 ROWS MAX OR GRADE RINGS 28 MAX STEPS 2 PRECAST CONE ECCENTRIC HEIGHT 25 MAX PRECAST RISER SECTIONS SLOPE 1 2 LADDER OR STEPS FT TYP 21 CONSTRUCT IN FIELD CHANNEL SHELA SHELF TO THE CROWN OF THE PIPE PRECAST BASE amp INTEGRAL RISER 1 0 Queens RR KRIMI GRAVEL BACKFILL FOR FOUNDATIONS 6 ogo ERI MIN COMPACTED DEPTH O 00 0 2 gt lt lt lt Ox Oo dO HOLES SHALL BE CONSTRUCTED IN ACCORDANCE WITH AASHTO M199 UNLESS OTHERWISE SHOWN ON PLANS NOTED IN THE STANDARD SPECIFICATIONS DHOLDS IN ADJUSTMENT SECTION SHALL HAVE 3 MIN CLEARANCE STEPS IN MANHOLE SHALL HAVE 6 CLEARANCE SEE STD DTL 0 15 MANHOLE DETAILS MANHOLDS SHALL BE PLACED IN ALTERNATING DE RINGS OR LEVELING BRICK COURSE WITH A MIN OF ONE FAND HOLD BETWEEN THE LAST STEP AND TOP OF THE MANHOLE PRECAST CONCRETE SHALL BE CLASS 4000 ON REINFORCED CONCRETE
35. D7 02 6 Private Conveyance Systems Private conveyance systems shall comply with all criteria and standards for drainage systems set forth herein unless specifically exempted D7 02 7 Outfalls Rock riprap for scour protection and energy dissipation shall conform to Section 9 13 of the Standard Specifications Gabions for energy dissipators shall conform to Section 6 09 3 6 Gabion Cribbing and Section 9 27 3 Gabion Cribbing of the Standard Specifications Precast concrete products for energy dissipators shall comply with Section 7 05 2 of the Standard Specifications 7 4 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Acceptable pipe materials for all outfall sections of storm pipe shall include those listed in D7 02 3 of these Standards except that PVC pipe is not permitted due to light sensitivity and degradation D7 02 8 Couplings Approved couplings for use on storm drainage mains with differing materials or diameters or non approved materials shall be ductile iron mechanical couplings equal to D7 02 9 Steel Casings Steel casing shall be black steel pipe conforming to ASTM A 53 Before installation coat casing exterior with shop applied anticorrosive coating conforming to AWWA C210 Minimum coating thickness shall be 16 mils dry film thickness DFT however thickness shall not exceed manufacturer s recommended thickness Coating type shall be a polyamide epoxy coal tar equal to Tnemec Hi Build T
36. Mean High Water MHW Water MHW 93 206 206 o o Mean Lower Low Water 2 98 6 56 12 52 6 47 MLLW KCAS datum Sea Level Datum 1929 a k a NGVD 1929 D4 32 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D4 04 6 Bridges A Hydraulic Criteria Bridges Bridges shall conform to Hydraulic Code Section WAC 220 110 070 and Land Use Code Section 20 25 H 110A B Freeboard Requirements Bridges The water surface elevation for the 100 year storm shall be a least one 1 foot below the lowest bridge girder to allow for the passage of floating debris D4 04 7 Culverts A Hydraulic Criteria Culverts When an abrasive bed load is anticipated or when velocities exceed 10 feet per second protective measures shall be implemented to minimize pipe damage When a culvert is approved by the City in lieu of a bridge per Section 20 25 of the Land Use Code such culverts shall Span the bank full width of the channel lined with bed material that is similar to the adjacent channel bed have a slope similar to the existing channel have sufficient capacity and one 1 foot freeboard to pass the 100 year design storm and meet the Washington State Hydraulic Code Rules B Manning n values For culverts use the factors set forth in Table 4 9 of these Standards Design Flow Rate Conveyance systems shall be sized to accommodate the peak runoff from a 100 year storm D
37. bo 1 017 4 cREEK DITCH CENTERLINE EXIST WHITE DITCH SF DTCH EXST LIN 0 05 NO 0 PEN mw a CREEK DITCH CENTERLINE PROP GREEN DITCH SF DTCH PROP LIN NO 2 5 PEN CURB PAVEMENT SIDEWALK EX WHITE CONTINUOUS SF 222A EXST LIN NO 0 PEN CURB PAVEMENT SIDEWALK PROP CYAN CONTINUOUS SF 222A PROP LIN NO 1 PEN pence EXISTING YELLOW SF FENC EXST LIN 10 075 000 yy y PROPOSED FNC SF FENC PROP LIN w NO 1 PEN L 007 8 GUARDRAIL EXISTING YELLOW EGRI SF GURD EXST LIN 0 075 NO 000 PEN m GUARDRAIL PROPOSED CYAN PGRI SF GURD PROP LIN I NO 1 PEN EIU V LAKE POND WHITE LAKE SF LAKE EXST LIN 0 4 MARSH PERIMETER WHITE MARSH SF SWMP EXST LIN T NO 0 PEN 0 5 RAILROAD WHITE RIRI SF RLRD EXST LIN Loa 0 125 NO 0 PEN 2227212722277777777772 RETAINING WALL EXISTING WHITE ERWI SF WALL EXST LIN 0 078 NO PEN arar RETAINING WALL PROPOSED CYAN PRWI SF WALL PROP LIN NO 1 PEN RIVERBANK SHORELINE CYAN CONTINUOUS SF 222B EXST LIN NO 1 PEN 222A USE CURB PVMT 2228 USE RIVR SHOR American Washington Public Works State E Cit y of Association Chapter 3 we Bellevue A D2 10 PAGE 10 LINETYPES LINETYPE DESCRIPTION COLOR LT NAME LAYER SURVEY 12 414 0 05 CENTERLINE EXISTING YELLOW EXCNTL SV CNTL
38. 25 COMPACTED BEDDING GRAVEL PER SECTION 9 03 12 3 GRAVEL BACKFILL FOR PIPE ZONE BEDDING OF THE WSDOT STANDARD SPECIFICATION OR OTHER MATERIAL IF SPECIFIED UNDATION GRAVEL IF REQUIRED SEE NOTE 2 CONCRETE ENCASEMENT SEE 1 2000 P S I CONCRETE SEE NOTE 3 m FOUNDATION GRAVEL IF REQUIRED SEE NOTE 2 DETENTION PIPES WITH UNDERDRAINS GID OR FLEXIBLE PIPE BEDDING PER ABOVE EOTEXTILE WRAP AROUND GRAVEL BACKFILL ROVIDE 12 MIN OVERLAP AT SEAMS WASHED ROCK FROM BOTTOM OF UNDERDRAIN PIPE TO CROWN OF ETENTION PIPE UNDERDRAIN PIPE TYP 6 MIN PERF PER STANDARDS SEE NOTE 5 FOUNDATION GRAVEL IF REQUIRED SEE NOTE 2 PERMEABLE GEOTEXTILE WRAP FOR PIPES 15 INCHES AND UNDER TRENCH WIDTH I D 30 INCHES FOR PIPES 18 5 AND OVER TRENCH WIDTH 1 5 x D 18 INCHES PER SECTION 2 09 4 MEASUREMENT OF THE WSDOT STANDARD SPECIFICATIONS EXCAVATE UNSTABLE MATERIAL DOWN TO FIRM SOIL AND REPLACE WITH FOUNDATION GRAVEL PER SECTION 9 03 9 3 BALLAST OF THE WSDOT STANDARD SPECIFICATIONS THE CONTRACTOR SHALL BE RESPONSIBLE PIPE FOR ANCHORING PIPE TO PREVENT FLOTATION 3 City Of STORM AND SURFACE DURING CONCRETE EMENT COMPACTED CRUS URFACING PER SECTION WATER UTILITY 9 03 9 3 CRUS URFACING OF THE B el evu e WSDOT STANDARD FICATIONS CAN BE USED AS BEDD RAVEL PRO
39. 3333 SYM WA VALV 3333 SYM 3333 5 WA VALV 3333 SYM WA VALV 3333 SYM WA VALV 3333 SYM WA FITT 3333 SYM WA FITT 3333 SYM 5333 5 3335 5 WA FITT 3333 SYM 3333 5 WA FHYD 3333 SYM WA FHYD 3333 SYM WA FITT 3333 SYM WA FITT 3333 SYM 3333 5 3333 lt 5 3333 USE EXST PROP SYMBOLS LAYER SS STCR 3333 SYM SS STCR 3333 SYM SD STCR 3333 SYM SD GLIN 3333 SYM SD STCR 3333 S 3333 USE of Cit Bellevue SURVEY SYMBOLS SYMBOL DESCRIPTION ABBR BLOCK LAYER FOUND EXIST PROP A ANGLE POINT AP SAP SAPP SV CTRL 3333 SYM BENCH MARK BM SBM SBMP SV CTRL 3333 SYM BLOCK CORNER BC SBC SBCP SV CTRL 3333 SYM IRON IP SIP SIPP SV CTRL 3333 SYM 6 MONUMENT IN CASE MIC SMIC SMICP SV CTRL 3333 S YM MONUMENT SURFACE MON SMON SMONP SV CTRL 3333 SYM OWNERSHIP TIE SOT SV LOTN 3333 SYM SECTION DATA of ota C SECTION CENTER 55 SV SECT 3333 SYM SECTION CORNER ssc sscP SV SECT 3333 SYM m QUARTER CORNER SQC SQCP SV QSCT 3333 SYM SIXTEENTH CORNER SSXC SSXCP SV 16ST 3333 SYM CLOSING CORNER SCC SCCP SV 222A 3333 SYM MEANDER CORNER
40. All storm main extensions within the public right of way or in easements must be staked by a surveyor licensed in Washington State for line and grade and cut sheets provided to the Engineer prior to starting construction The Contractor shall use a vacuum street sweeper to remove dust and debris from pavement areas as directed by the Engineer Flushing of streets shall not be permitted without prior City approval Storm drainage mainlines stubs and fittings shall be constructed using the same pipe material and manufacturer Connections between stubs and the mainline will be made with a tee fitting Tee fitting shall be from same manufacturer as pipe Cut in connections are only allowed when connecting a new stub to an existing mainline Manholes catch basins and vaults are considered to be permit required confined spaces Entry into these spaces shall be in accordance with Chapter 296 809 WAC Placement of surface appurtenances MH lids valve lids etc in tire tracks of traffic lanes shall be avoided whenever possible Call 1 800 424 5555 or 8 1 1 72 hours before construction for utility locates The Contractor shall perform a video inspection and provide a DVD of the storm pipe interior for the City s review The video shall provide a minimum of 14 lines per millimeter resolution and cover the entire length of the applicable pipe The camera shall be moved through the pipe at a uniform rate lt 30 ft min stopping wh
41. City of Bellevue Utilities Department standard detail drawings Standard Plans Latest edition of the Standard Plans for Road and Bridge Construction Washington State Department of Transportation and the American Public Works Association including all amendments Standard Specifications Latest edition of the Standard Specifications for Road Bridge and Municipal Construction English edition Washington State Department of Transportation and the American Public Works Association including all amendments Words and Phrases Whenever the words as directed as required as permitted or words of like effect are used it shall be understood that the direction requirement or permission of the City is intended The words sufficient necessary proper and the like shall mean sufficient necessary or proper in the judgment of the City The words approved acceptable satisfactory or words of like import shall mean approved by or acceptable to the City Work The work necessary to manufacture and deliver machinery equipment and material and or the furnishing of all labor tools material equipment construction equipment working drawings where required and other necessities for the construction or erection D1 4 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 of the structures shown and called for in the plans specifications and permit Developer Extension Agreement and the act of construc
42. MINIMUM DIAMETER BERM SLOPE MAY BE 2 1 WHEN TOP SUBMERGED 1 BELOW WATER QUALITY DESIGN W S E PENETRATE CARRIER PIPE THROUGH WALL 1 STORM AND SURFAC SE APPROVED WATERTIG STRUCTURE w DAPTOR of WATER UTILITY LIP 5 HORIZONTAL LEG OF LOW CONTROL TEE INSIDE CARRIER PIPE O FLOW CONTROL JOINT OUTSIDE OF STRUCTURE ER QUALITY JANUARY 2015 NO SCALE NO D 30A ELEVATION VIEW CROWN OF INLET PIPES OVERFLOW Pn LOCKING RING amp COVER FINISHED GRADE ET LE TE eo 2000 I AIR VENT DESIGN 2 MIN AT CROWN WSE 2 MIN DIA ACCESS GATE PER imesh SAND STANDARDS VIEW MIN DIA COLLAR SEE NOTE 2 OR KOR N SEAL 0 005 FT FT BOOT TYPICAL 24 MIN DIA 24 MIN D mn CONNECTOR CONNECTOR CATCH PIPE PIPE TYPE 2 CATCH BASIN 54 S SAY SQ 2 Mee SENG SPILL CONTROL SEPARATOR VERTICLE BASIN W STUB END amp VENT RISER SECTION SHALL BE ALIGNED PLUMB 54 DIA LOW RESTRICTOR VERTICLE RISER SECTION SHALL 2 2 SHALL MIN E ALIGNED PLUMB VERTICALLY HORIZONTAL ECTION SHALL MATCH OUTLET PIPE SLOPE PLAN VIEW ACCESS RISERS CORRUGATED 4 SEE SIANDARD METAL MANHOLE PER STANDARDS DETAIL D 46 FOR OP WITH LADDERS MIN 2 PER PARALLEL PIPE UNDERDRAINS PIP CONTROL 24 MIN DIAMETER STRUCTURE CONNECTOR PIPE OUTLET
43. NOTE ATTACH SCREEN TO SEE NOTE 11 CMP CROSS W 6 1 METAL SCREWS 2 PER STRAP OR USE STAINLESS FRAME amp LADDER OR STEEL PIPE CLAMP STEPS OFFSET SEE NOTE 8 SIZED TO FIT OUTER DIAMETER OVERFLOW ELEV PER PLANS SEE NOTE 10 AND 1 1 4 9 1 12 GA P GALV STRIPS TACK WELD TO WIRE MESH PIPE SUPPORTS 2 MN SCREW TYPE SHEAR m 3 x 090 ALUMINUM W SEE STD DTL D 28 AND Z 0 5 50 5 416 CON 5 8 STAINLESS BOLTS d 7 SOLID 12 GA TACK WELD WIRE MESH ae oan ST TO BOTTOM PLATE CONNECTOR bPE 247 MIN DIA OUTLET PIPE FLOW CONTROL SCREEN INVERT ELEVATION PER 597 RESTRICTOR ORIFICE AS SPECIFIED PLATE BOLTED TO FLANGE OR DRILLED CAP INVERT ELEV PER PLAN REMOVABLE WATER TIGHT COUPLING 2 0 MN 2 0 FLOW CONTROL SCREEN PLATE WITH ORIFICE AS SPECIFIED BOLTED TO FLANGE OR DRILLED CAP 54 MIN CATCH BASIN TYPE 2 ELBOW DETAIL DIAM AS REQUIRED BY PLANS NOTES PIPE SIZES INVERT ELEVATIONS ORIFICE SIZES OVERFLOW ELEVATIONS AND SLOPES PER ENGINEER APPROVED STAMPED PLANS FLOW OUTLET CAPACITY NOT LESS THAN COMBINED INLETS RESTRICTOR EXCEPT AS SHOWN OR NOTED UNITS SHALL BE CONSTRUCTE
44. PE INVERT E GROUTED IF WALL IS LEFT P K PROVIDED KNOCKOUTS B KNOCKOUT OR CUTOUT HOLE SIZE IS EQUAL TO P D E MAX DEPTH FROM KNOCKOUTS SHALL ALL PIPE SHALL BE AVE A WALL TH NTACT CONCRETE INLET WALL THICKNESS ALL 4 SIDES WITH IS 4 0 E TAPER ON THE SIDES OF THE PRECAST BASE D RISER SECTION SHALL NOT EXCEED 1 2 FT CONCRETE INLET FRAME AND GRATES SHALL BE IN WITH STANDARD SPECIFICATIONS FINISHED TO POSITION MATING SURFACE ASSURE FIT WITH ANY APPLY NON SHRINK GROUT TO INSIDE AND OUTSID JOINTS RINGS RISERS AND FRAMES City of Bellevue WATER UTIL BASES SHALL BE FURNISHED WITH CUTOUTS OR ICKNESS NSTALLED IN FACTORY UNUSED KNOCKOUTS NEED NOT PE OUTER MAX THE FINISHED GRADE TO THE SECTION ACCORDANCE S SHALL BE COVER E OF ALL STORM AND SURFACE NOTES 1 CATCH BASINS SHALL BE CONSTRUCTED IN ACCORDANCE WITH ASTM C478 AASHTO 199 amp C890 UNLESS OTHERWISE SHOWN ON PLANS OR NOTED IN THE STANDARD SPECIFICATIONS AS FAB R FOOT MAY BE USED WELDED WIRE FABRIC SHALL PE COMPLY TO ASTM A497 AASHTO M 221 WIRE FABRIC SHALL NOT BE PLACED IN KNOCKOUTS AN ACCEPTABLE ALTERNATIVE TO REBAR WELDED WIRE RIC HAVING A MIN AREA OF 0 12 SQUARE INCHES FRAME AND GRATE SEE APPLICABLE STANDARD DETAILS PPLY NON SHRINK GROUT T
45. Q wD wD WH Q W sd W W arn as sp go 099 Aj sso sso 5501 sso SSO A93 IA EV ej I dd yua 0 Ju u6 s Quo JOH Uo ML IA Iueg jeueg anu NNO edid ount pueg no xg ug Ju ueg oz e eD 20 90 sD v cp L o o 9 02 9 s o 0 p uogeneyo 1 joojog NOILVINIDIVID HalVMMOVa8 01 6 cfs FLOW JUNCTION Q3 4 cfs D4 57 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 20 Bend Head Losses In Structures Bend at Manhole no Special Shaping Loss Coefficient K Bend at Manhole Curved or Deflector Curved Sewer r D 2 0 20 40 60 80 90 100 Deflection Angle Degrees 04 58 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 21 Junction Head Loss In Structures Qs 100 1 Typical junction chamber 130 Q2 195 Q3 65 _ O TA LA Q 0 50 50 EEEREN Head Loss 0 940 50 Q4 X D 9 G Qs 30 Q4 Qs 10 Q4 N o in s pipe V ne D4 59 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Pipe System Analysis and Sizing with the Rational Method Figure 4 22 has been provided to allow for the tabular computation of C A values used in sizing a new pipe system Following computation of t
46. Q1 n2 Q2 D4 53 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 17 Circular Channel Ratios PROPORTIONAL AREA DISCHARGE VELOCITY HY DRAULIC RADII RT ATA MEN NN S LIN ALD JN b 1 0 9 0 8 0 7 0 6 0 4 0 2 0 1 0 RATIO OF FLOW DEPTH TO DIAMETER d D _ _ 0 2 VADA F D4 54 JANUARY 2015 SURFACE WATER ENGINEERING STANDARDS w o um S 5 S Q S z 87 9 5 ea 2 m 5 oh E 0 0 a 60 Q2 Q2 GJ 0 0 sd urbs y y ezs p 6 goo go 5501 5501 9 3 AS F 5801 5801 9 3 5501 9 3 easy 000 edig uu MH peah 79H uon ML 9A J luj jenno edid ounf pueg Jddy Uy 9u4 jaueg oz 61 8b 6D Gb p D CD 00 69 9 2 9 0 O SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 18 Backwater Calculation Sheet Notes Column 1 Column 2 Column 3 Column 4 Column 5 Column 6 Column 7 Column 8 Column 9 Column 10 Column 11 Column 12 Design flow to be conveyed by pipe segment Length of pipe segment Pipe Size indicate pipe diameter or span x rise
47. SANITARY SEWER WHITE s SS GLIN EXST LIN NO 0 PEN STEAM MAGENTA STE ST PLIN EXST LIN NO 0 PEN p STORM DRAINAGE WHITE D SD 2222 EXST LIN NO 0 PEN 0 25 tes Ee TELEPHONE AERIAL RED AT TL ALIN EXST LIN NO 0 PEN TELEPHONE BURIED RED T TL BLIN EXST LIN NO 0 PEN 0 05 s Se UTILITY SERVICE LINE GENERAL YELLOW SERV TI SERV EXST LIN NO 000 PEN wa WAR MAGENTA W WA 2222 EXST LIN NO 0 PEN UTILITIES PROPOSED MAIN LINE LIST TYPE SIZE ETC CONTINUOUS 11 2222 PROP LIN NO 0 PEN P LINE 04 WIDE SERMCE LIST TYPE SIZE ETC CONTINUOUS 11 SERV PROP LIN NO 0 PEN COLOR DEPENDS ON TYPE OF UTILITY E G POWER WATER ETC TEXT IN UTILITY LINETYPES SPACED AT 3 INTERVALS 11 INDICATE UTILITY TYPE 2222 USE ALIN BLIN GLIN PLIN ALIN AERIAL te aia BLIN BURIED CONDUIT GRAVITY LINE PUN PRESSURE LINE American Washington Public Works State City of Association Chapter Bellevue A D2 12 TEXT STYLES EXAMPLE DESCRIPTION STYLE EX CONIFER EXISTING FEATURES 80 SCALE DRAWING SCALE SCALE PROJECT PROJECT TITLE 200 PROPOSED GENERAL INSTRUCTION 120 SEWER PROPOSED SANITARY 120 SEWER INSTRUCTIONS WATER PROPOSED WATER 120 INSTRUCTIONS S TR STREET NAMES 240 NOTES FONT SIMPLEX ITALIC SIMPLEX SIMPLEX SIMPLEX SIMPLEX SIMPLEX HEIGHT 0 08 INCH 0 1
48. SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Site diagram of the constructed As Built storm drainage system identifying the components with profiles as needed Agreement to maintain facilities in accordance with City of Bellevue Storm and Surface Water Code 24 06 065 and the Storm and Surface Water Maintenance Standards now or as hereafter amended The final O amp M Manual for MR 1 5 must be submitted and approved by the Utilities Department prior to the Storm Connection Permit acceptance where applicable or prior to occupancy The O amp M Manual for MR 1 5 must conform to King County s recording format requirements and be recorded against the property as a covenant running with the land A copy of the manual shall be retained onsite or within reasonable access to the site and shall be transferred with the property to the new owner D2 09 2 Storm Drainage O amp M Manual Agreement for Utilities Extension Agreements MR 1 9 The Storm Drainage O amp M Manual Agreement for Utilities Extension Agreements MR 1 9 at a minimum shall include name of the party or parties responsible for maintenance and operation of the system such as a Home Owners association management company or the legal property owner Property legal description address and project if applicable Agreement to maintain facilities in accordance with City of Bellevue Storm and Surface Water Code 24 06 065 and the Sto
49. The next step is to identify areas where shallow seasonal groundwater will limit the infiltration capacity of the site or not allow sufficient water quality treatment prior to discharge to the groundwater table Section D4 06 7 C provides instructions for evaluating the depth to groundwater Projects that do not trigger runoff treatment MR6 or flow control MR7 are not required to monitor groundwater levels and may rely on observations made using the simple infiltration test Section D4 06 7 D and or preliminary data available from the Pacific Northwest Center for Geologic Mapping Studies at the GeoMapNW web site see Section D1 03 C Step 1c Characterize Site Soils and Determine Infiltration Rates In areas where there is sufficient depth to the groundwater table determine the soil type texture and infiltration rate of site soils in various locations where infiltration facilities such as bioretention cells pervious pavement or infiltration trenches may be constructed If modeling will be used determine soil type categories as Natural Resource Conservation Services NRCS formerly Soil Conservation Service Hydrologic Soil Group A B outwash C D till or saturated wetland While both till and outwash soils are capable of meeting flow control requirements till soils typically have lower infiltration rates and larger facility sizes may be required However the minimum design infiltration rate for which Infiltration NDPs bioreten
50. gt 0 1 cubic feet per second increase in T the 100 year flood frequency Note 1 Estimated using the Western Washington Hydrology Model or other approved model See Chapter D3 Hydrology For MR5 On site Stormwater Management see Chapter D6 For MR6 Runoff Treatment see Chapter D5 For MR7 Flow Control see Chapter D4 For Hydrologic Analysis information see Chapter D3 D2 06 STORMWATER SITE PLANNING AND SUBMITTALS Based upon the analysis of existing site conditions locate the buildings roads parking lots utilities and landscaping features for the proposed development Consider the following points when laying out the site 1 Fit development to the terrain to minimize land disturbance Confine construction activities to the least area necessary and away from critical areas 2 Preserve areas with natural vegetation especially forested areas as much as possible 3 On sites with a mix of soil types locate impervious areas over less permeable soil e g till and try to restrict development over more porous soils e g outwash 4 Cluster buildings together 5 Minimize impervious areas and 6 Maintain and utilize the natural drainage patterns D2 7 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 The development layout designed here will be used for determining threshold discharge areas for calculating whether thresholds for Minimum Requirements are exceeded and for the drawings and ma
51. 6 month 24 hour storm Alternatively the 91st percentile 24 hour runoff volume indicated by an approved continuous runoff model may be used Wetpool facilities are sized based upon the volume of runoff predicted through use of the Natural Resource Conservation Service curve number equations in Chapter 2 of Volume III of the DOE Manual for the 6 month 24 hour storm D5 03 3 Water Quality Design Flow Rate 1 Preceding Detention Facilities or when Detention Facilities are not required Treat the flow rate at or below which 91 of the runoff volume as estimated by an approved continuous runoff model Design criteria for treatment facilities are assigned to achieve the applicable performance goal at the water quality design flow rate e g 80 TSS removal 2 Downstream of Detention Facilities The water quality design flow rate must equal the full 2 year release rate from the detention facility Alternative methods may be used if they identify volumes and flow rates that are at least equivalent That portion of any development project in which the PGIS or PGPS thresholds are not exceeded See D2 05 in a threshold discharge area shall apply On site Stormwater Management BMPs in accordance with MRS D5 2 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D5 03 4 Treatment Facility Selection Stormwater treatment facilities shall be selected in accordance with the process identified in Volume 1 Chapter 4 of the DOE Manual Follow th
52. AND COVER SHALL BE RATED HS 20 AND COVER MATERIAL IS DUCTILE IRON City of STORM AND SURFACE A536 GRADE 80 55 06 OR CAST ASTM 48 CLASS 30 Bellevue WATER UTILITY FOUNDRY MH30A OR EQUAL T COVER SHALL HAVE T OF 150 LBS UCTILE OR CAST RING SHALL EIGHT OF 210 LBS HAVE MINIMUM 24 MANHOLE RING AN JANUARY 2015 NO SCALE NON SKID INTEGRAL PATTERN TO BE CAST ON TOP OF COVER 8 WEBS 1 2 THICK 1 DIAMETER LIFT HOLE 8 1 2 FROM CENTER OF COVER SEE NOTES 6 SEE NOTE 7 26 3 8 _251 4 24 MACHINED SEAT 23 3 4 MACHINED SEAT 33 3 4 25 FCTION ALL HAVE THE WORD DRAIN CAST IN 3 RAISED LETTERS D COVER MATERIAL DUCTILE IRON ASTM AS36 GRADE 80 55 06 OR CAST IRON ASTM A48 CLASS 30 R CAST COVER SHALL HAVE MINIMUM WEIGHT OF 150 LBS R CAST RING SHALL HAVE MINIMUM WEIGHT OF 210 LBS LL HAVE THREE 5 8 11 N C OLES AT 120 DEGREES ALL HAV REE COUNTERSUNK 3 City of
53. F HEIGHT MAP ar 2 SAND COLLAR OR EXISTI 1 MIN FRE KOR N SFAL BOOT GROUN COMPACT PROFIL Y I 95 MAX WSE DRY DENSITY DETENTION POND GASKETED D CAP OUTLET 6 MAX DEPTH TRASH RACK SEE N STANDARD DETAIL CLE RISER D 53 TION SHALL LIGNED P KEY EXCAVATED CALLY INTO NATIVE D ZONTAL RIS LAN VIEW GROUND TION SHALL ATCH OUTLET PIPE SLOPE PRIMARY OVERFLOW THROUGH FLOW RESTRICTOR SECONDARY OVERFLOW SPILLWAY OR PIPE SYSTEM INVERT IS 1 ABOVE POND BOTTOM RAP PAD RIP RAP PAD CONIROL STRUCTURE WITH FLOW RESTRICTOR ES 1 LANDSCAPE EQUIRED TO BEAUTIFY USE APPROVED WATERTIGHT STRUCTURE ADAPTOR OR SCREE SLIP SMOOTH BORE HORIZONTAL LEG OF FLOW 6 MINIMU OF EMBANKMENT CONTROL TEE INSIDE CARRIER PIPE 15 MINIMU E ACCESS TO CONTROL S NO FLOW CONTROL JOINT OUTSIDE OF STRUCTURE SCREW TYP E REQUIRED FOR NTAINED BY THE 1 STORM AND SURFAC City of WATER UTILITY TY O LET PIPE MUST BE B OR GREATER THAN DISCHARGE ERGENCY OVERFLOW CONDITION evue F E ERFLOW IS USED IN LIEU OF PILLWAY 8 INCH MINIMUM DIAMETER 5 ENETRATE CARRIER PIPE
54. IN ACCORDANCE WITH THE REQUIREMENTS FOR CATCH BASIN TYPE 2 54 MIN DIAM OUTLET CONNECTOR PIPE SUPPORTS AND RESTRICTOR SHALL BE OF SAME MATERIAL PIPE AND BE ANCHORED AT 3 MAX SPACING BY 5 8 DIAMETER STAINLESS STEEL EXPANSION BOLTS OR EMBEDDED 2 IN WALL E RESTRICTOR SHALL BE FABRICTED FROM 0 060 ALUMINUM E SAND COLLAR OR PVC CPE OR HDPE PIPE PER THESE ENGINEERING STANDARDS KOR N SEAL BOOT OUTLET SHALL BE CONNECTED TO STORM DRAINAGE PIPE WITH SUITABLE COUPLER OR GROUTED INTO THE BELL OF CONCRETE PIPE THE VERTICAL RISER STEM OF THE RESTICTOR SHALL BE THE SAME DIAM AS THE HORIZONTAL OUTLET PIPE WITH AN 8 MIN DIAM VERTICLE RISER SECTION SHALL BE ALIGNED PLU VERTICALLY HORIZONTAL SECTION SHALL MATCH OUTLET PIP SLOPE FRAME AND LADDER OR STEPS OFFSET SO THAT PENETRATE CARRIER PIPE THROUGH VAULT WALL SCREW TYPE SHEAR GATE 5 VISIBLE FROM TOP B CLIMB DOWN SPACE IS CLEAR OF RISER AND USE APPROVED WATERTIGHT STRUCTURE ADAPTOR SCREW TYPE SHEAR GATE C FRAME IS CLEAR OF CURB SLIP SMOOTH BORE HORIZONTAL LEG OF FLOW CONTROL TEE INSIDE CARRIER PIPE IF METAL OUTLET PIPE CONNECTS TO CEMENT CONCRETE PIPE OUTLET PIPE TO HAVE SMOOTH EQUAL TO NO FLOW CONTROL JOINT OUTSIDE OF STRUCTURE CONCRETE PIPE 1 0 LESS 1 4 MULTI ORIFICE ELBOWS MAY BE LOCATED AS SHOWN OR ALL ON ONE SIDE OF RISER TO ASSURE LADDER CLEARANCE STORM AND SURFACE IF PIVOTIN
55. OR 210 SPECIAL DECORATIVE CASTING MAY BE USED IF PREAPPROVED BY CITY EANOUT GRA JANUARY 2015 NO SCALE 5 4 DIAM BAR FRAME REMOVABLE RACK 1 2 SCH 40 ALUM PIPE 3 4 4 CLEAR SPACING INSERT ALUMINUM TRASH RACK INTO BEVELED PIPE END GROUND SURFACE a v 6 CLEAR FROM DEBRIS BARRIER TO FINISHED GRADE 4 CLEAR SPACING MP m lx SURFACE 9 2 6 CLEAR FROM DEBRIS BARRIER TO FINISHED GRADE TO FIT INNER DIAMETER ROLLED SMOOTH OF PIPE Lic CLEAR SPACING X GA ALUM PLATE 1 4 x2 ANCHOR STRAPS FASTEN WITH 1 2 GALVANIZED OR NON CORROSIVE ALUMINUM TRASH RACK BOLTS amp NUTS TYP 4 PLACES NOTES 1 ALL STEEL PARIS MUST BE GALVANIZED AND ASPHALT COATED TREATMENT 1 o City of STORM AND SURFACE OR BETTER WATER UTILITY CONTRACTOR TO VERIFY DIMENSIONS Bellevue TO BE USED IN DETENTION PONDS AND AND PIPES GREATER THAN 18 DIAMETER TRASH RACK DEBRIS BARRI JANUARY 2015 NO SCALE BACKFILL PER STANDARD DETAIL D 25 SOIL MIX OR CONCRETE BLOCKS PLACED AS DIRECTED BY ENGINEER PIPE CLAMP SECTION BED PIPE PER STANDARD DETAIL D 46 m 2 ENT MIX OR CONCRETE BLOCKS ON PIPE SLOPES OF 20 OR IENT BLOCKS PLACED OVER AND TAMPED INTO PLACE BEFORE 3 Cit
56. OVERFLOW ELEVATION TEST PLUG EXPANDING MATERIALS e 2 10 FEET OF 3 DIAMETER PVC PIPE SCH40 IF IN FACILITY SCH80 IF OFFSET 3 ELEVATION OVERFLOW 4 FEET 3 DIAMETER WELL SCREEN CANAL LAKE SCREEN 0 01 SLOTS PVC SCH40 ELEVATION 5 DIAMETER COUPLING TEST PLUG EXPANDING AND OR LOOSE FITTING TOP CAP EMERGENCY OVERFLOW ZONE 5 DIAMETER PVC END CAP i i BENTONITE USE MEDIUM SIZED CHIPS OR CONCRETE i I ELEVATION TOP SAND PACK 2959 MESH PONDING ZONE i i INSTRUCTIONS 1 AUGER THE PORT HOLE COMPOST MULCH BORE THE PORT HOLE IN BOTTOM OF FACILITY OR RUN PIPE FROM TOP OF FACILITY ALONG BOTTOM TO OBSERVATION PORT VERTICAL PIPE IN BERM SEE DETAIL A USING FOUR INCH 14 CONCRETE OR BENTONITE COLLAR DIAMETER HAND AUGER OR POST HOLE DIGGER THE PORT HOLE SHOULD EXTEND 6 BELOW DETENTION FILTER THE BOTTOM OF THE FACILITY CONSTRUCT THE OBSERVATION PORT CASING LAYER TEE In MEASURE THE DISTANCE FROM THE EXISTING GRADE TO THE BOTTOM OF THE PORT HOLE AND 2 RECORD THIS DISTANCE PERMANENTLY IN THE STORMWATER OPERATIONS amp MAINTENANCE TOR DE coun MANUAL AND ON THE AS BUILT DRAWING CUT THE WELL SCREEN AND RISER TO FIT WHEN P US ae ASSEMBLED THE PVC COUPLING WHICH JOINS THE WELL SCREEN AND THE RISER SHOULD BE MIR TUS COUPLING 14 INCHES BELOW THE GROUND SURFACE THE SOLID PVC
57. PIPE FLOW ACCESS RISER CORRUGATED METAL MANHOLE PER STANDARDS SPILL CONTROL H LADDER SEE NOTES 5 AND 6 SEPARATOR NOTES NEOPRENE GASKETS REQUIRED AT ALL CMP AND CPE PIPE JOINTS 36 MINIMUM PIPE DIAMETER PROVIDE TYPE 2 CATCH BASIN AT EACH END OF PIPE MAXIMUM SPACING SHALL BE 50 FEET ALL METAL PARTS AND SURFACES SHALL BE CORROSION RESISTANT STEEL HARDWARE SHALL BE GALVANIZED PIPE SHALL BE GALVANIZED ASPHALT COATED TREATMENT 1 OR ALUMINIZED COMPLETE CORROSIO PROTECTION MUST BE ASSURED CAPACITY OF OUTLET PIPE MUST BE EQUAL TO OR GREATER THAN ALL INLET PIPES COMBINED ACCESS RISERS REQUIRED CENTERED OVER EVERY 50 OF DETENTION PIPE WHEN TYPE 2 CATCH BASINS ARE PROVIDED ON EACH END OR AT EITHER END OF A 50 LONG PARALLEL PIPE AS SHOWN ABOVE ADDITIONAL ACCESSES ARE REQUIRED FOR EVERY 50 ADDITIONAL FEET OF DETENTION PIPE SEE STANDARD DETAIL D 51 FOR ACCESS MANHOLE N AREAS WITH VEHICULAR TRAFFIC PROVIDE TRAFFIC BEARING ACCESS 5 20 OVER CORRUGATED METAL MANHOLE PER STANDARD DETAIL 51 BEDDING SHALL BE ACCORDANCE WITH DETAIL D 46 FLEXIBLE PIPE BENDING PENETRATE CARRIER PIPE THROUGH VAULT WALL USE APPROVED WATERTIGHT STRUCTURE ADAPTOR SLIP 5 HORIZONTAL LEG OF FLOW CONTROL TEE INSIDE CARRIER PIPE O FLOW CONTROL JOINT OUTSIDE OF j STORM AND SURFACE STRUCTURE ZA City of WATER UTILITY PRIOR TO STARTUP DETENTION PIPE SHALL Bellevue PASS 1 PER DAY LEAK TEST WHE
58. a vertical drop in the water surface profile at any point within culvert influence is for all flows between the high and low flow design discharges D4 47 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 4 8 Fish Passage Design Criteria Adult Trout Adult Pink Chum Adult Chinook Coho Salmon Sockeye Steelhead 1 Max Velocity fps Culvert Length 10 60 ft 60 100 ft 100 200 ft 2 Min Flow Depth ft I C Methods of Analysis High Flow Design Discharge The high flow design discharge shall be estimated by one of the following The 10 exceedance flow for October through April inclusive for the nearest hydrologically similar gauged stream proportioned by tributary area The 5 exceedance flow determined through duration analysis with an approved continuous model The 10 exceedance flow for October through April inclusive determined with an approved continuous model using the full historical record for SeaTac rainfall region Bellevue Adjustment factor 1 065 Low Flow Design Discharge The low flow design discharge shall be estimated by one of the following The 95 exceedance flow for October through April inclusive for the nearest hydrologically similar gaged stream proportioned by tributary area The 95 exceedance flow for October through April inclusive determined by an approved continuous model using the full historical record for SeaTac rainfall region adjusted for Bellevue If using KCRT
59. as needed When a project includes the construction of a drainage system private drainage systems shall connect to the proposed storm drain manholes catch basins stub outs or tees The use of sidewalk drains shall not be permitted In areas without an existing drainage system the private drainage system shall discharge in accordance with Section D4 02 Outfalls and Discharge Locations Properties that can drain directly to Lake Washington or Lake Sammamish shall ensure that sufficient capacity to pass the 100 year storm peak flow rate for all drainage in the pipe is provided and that the pipe invert matches the ordinary high water elevation to prevent erosion B Roof Footing and Yard Drains If MR5 On site Stormwater Management applies roof footing and yard drainage shall be managed using on site practices if site conditions allow per Chapter D6 D4 63 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Roof and footing drain pipes shall be separate lines which may only be Joined at an elevation at least one 1 foot below the lowest footing drain invert elevation The minimum cover over the storm drain stub at the property line shall be two 2 feet Clean outs 4 inch minimum diameter with factory manufactured fittings shall be provided at all Junctions and bends greater than 45 degrees The maximum spacing between clean outs shall not exceed 100 feet Roof footing and yard drains shall not be connected to the sanit
60. cast in place structures require submitted and stamped drawings by the Design Engineer to the City All manholes catchbasins inlets and lids shall be designed for H 20 loading D4 66 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D4 05 2 Spacing Requirements Table 4 10 Pipe Sizes And Lengths Between Structures Upstream Structure Pipe Diameter Minimum Pipe Slope Maximum Structure To Downstream Structure Inches Spacing ft Inlet MH to Inlet MH 12 2 0 150 300 i iii Inlet MH to CB 8 2 096 100 Inlet MH to CB 12 1 0 150 CB to CB 8 1 0 150 300 ii iii CB to CB MH 12 or greater 0 5 150 300 iii MH to MH 12 or greater 0 5 400 iv i Compensatory catchment must be provided in downstream on site catch basin s H Driveways parking lots and private systems only Maximum spacing between grates shall be 150 feet on surface grades less than 1 and 200 feet on surface grades from 1 to 3 and 300 feet on surface grades over 3 or required by grate flow capacities iv Access points only no stormwater inputs v type 2 catch basin is required to be installed for every 800 linear feet of storm drain pipeline Table 4 11 Allowable Structures And Pipe Sizes Maximum Pipe Diameter Structure Type i SOLID WALL PIPE PROFILE WALL PIPE HDPP PVC DI CMP v CPE RCP CPE Concrete Inlet ii iii 12 12 Type CB ii 15 12 Type IL CB iv 24
61. or Flow Control Credits for roof downspout dispersion from Chapter 3 Volume Ill of the DOE Manual may be applied This credit can be applied to reduce the effective impervious surface area used in drainage calculations Since partial credit is applied additional flow control measures will be required To use the Flow Control Credit roof downspout dispersion concentrated flow dispersion or sheet flow dispersion must meet the general requirements outlined in Section D6 03 1 Rain Recycling Rain Barrels Rain barrels alone will not achieve flow control requirements however some flow control benefits are achieved with this BMP Credits for rain barrels are provided in Table 6 14 This credit can be applied to reduce the effective impervious surface area used in downstream conveyance and flow control calculations Since partial credit only is applied additional flow control measures will be required To use the Flow Control Credit the rain barrels must meet the general requirements for rain barrels outlined in Section 6 03 2 A minimum of four 4 rain barrels must be installed to receive Flow Control Credit Vegetated Roof Vegetated roofs alone will not achieve flow control requirements however some flow control benefits are achieved with this BMP Credits for vegetated roofs are provided in Table 6 14 organized by growth medium depth This credit can be applied to reduce the effective impervious surface area used in downstream conveyan
62. otherwise regional parameters may be used Consult Utilities Department Engineering Division for available data and guidance Determining Flood Elevations Profiles and Floodway Reconnaissance The applicant s design engineer is responsible for the collection of all existing data with regard to flooding in the study area This shall include a literature search of all published reports in the D4 29 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 study area and adjacent communities and an information search to obtain all unpublished information on flooding in the immediate and adjacent areas from federal state and local units of government This search shall include specific information on past flooding in the area drainage structures such as bridges and culverts that affect flooding in the area available topographic maps available flood insurance rate maps photographs of past flood events and general flooding problems within the study area A field reconnaissance shall be made by the applicant s design engineer to determine hydraulic conditions of the study area including type and number of structures locations of cross sections and other parameters including the roughness values necessary for the hydraulic analysis Base Data Cross sections used in the hydraulic analysis shall be representative of current channel and floodplain conditions obtained by surveying When cross sections data is obtained from other studies the dat
63. overflow and hose bib per Standard Detail NDP 18 The following plastic rain barrels or Equal are approved Poly material Chicago model 18122 Suncast model RB5010PK Emsco model 2771 1 Mayne model 5847WH D6 62 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Fiskars model 5997 D6 04 8 The plants listed in Table 6 16 are suitable for use on vegetated roofs This list is provided as a convenience and is not considered complete These and other plants may be used as recommended by a vegetated roof design professional based on site conditions Vegetated Roofs Table 6 16 Plants for Vegetated Roofs Scientific Name Common Name Plant Type Achillea tomentosa Woolly yarrow Herb Arctostaphylos uva ursi Kinnikinnick Groundcover woody Armeria maritime Sea pink sea thrift Herb Carex inops pensylvanica Long stoloned sedge Sedge Eriophyllum lanatum Oregon sunshine Herb Festuca brachyphylla Pt Joe fescue Grass Festuca rubra Red creeping fescue Grass Festuca idahoensis Idaho fescue Grass Gaultheria shallon Salal Shrub Phlox subulata Creeping phlox Herb Polystichum munitum Sword fern Fern Saxifraga caespitosa Tufted saxifrage Herb Sedum album White stonecrop Succulent Sedum oregonum Oregon stonecrop Succulent Sedum reflexum Spruce leaved stonecrop Succulent Sedum spectabile Frosty Morn Variegated blush stonecrop Succulent Sedum sp
64. paved areas or 90 unpaved areas of the maximum dry density per Section 2 03 3 14 D Compaction and Moisture Control Tests of the Standard Specifications When requested by the City test reports shall be provided by the Contractor to certify that the compaction meets the required levels D8 04 8 Private Drainage Systems The footing drainage system and the roof downspout system shall not be interconnected unless such connection is at least 1 foot below the footing drainage system and down slope of the building foundation Corrugated polyethylene tubing CPT for overbank drains shall be a continuous piece of tubing from the top of the slope to the discharge point at the bottom of the slope No joints between the connection to the roof footing and yard drains and the discharge point will be allowed CPT is not allowed in the right of way D8 05 MANHOLES CATCH BASINS amp INLETS D8 05 1 General The construction of manholes catch basins and inlets shall conform to Section 7 05 3 Construction Requirements of the Standard Specification as modified herein Manholes catch basins and inlets shall be precast concrete unless approved otherwise by the City All structure ladders when used shall be firmly attached using stainless steel hardware and extend to the bottom of the structure When connecting to a concrete structure openings must be core drilled unless an existing knockout is available Connections shall be made
65. pervious pavement rain recycling and vegetated roofs New impervious surface A new non vegetated surface area that either prevents or retards the entry of water into the soil mantle as under natural conditions prior to development A new non vegetated surface area which causes water to run off the surface in greater quantities or at an increased rate of flow from the flow present under natural conditions prior to development Common impervious surfaces include but are not limited to new roof tops walkways patios driveways parking lots or storage areas concrete or asphalt paving gravel roads packed earthen materials and oiled macadam or other surfaces which similarly impede the natural infiltration of stormwater Open uncovered retention detention facilities shall not be considered as impervious surfaces for purposes of determining whether the thresholds for application of minimum requirements are exceeded Open uncovered retention detention facilities shall be considered impervious surfaces for purposes of runoff modeling Or Equal Any manufactured article material method or work which in the opinion of the City is equally desirable or suitable for the purposes intended in these standards as compared with similar articles specifically mentioned herein Plans All approved drawings or reproductions of approved drawings made or to be made pertaining to the work provided for in the permit or Developer E
66. s latest version of the Highway Runoff Manual design procedures for RT 04 Biofiltration Swales RT 05 Wet Biofiltration Swale and RT 06 Continuous Flow Biofiltration Swale except where modified herein The DOE Manual calls bioretention swale biofiltration swale Some or all of the components may be used for a given application depending on the site characteristics and restrictions pollutant loading and design objectives Flow Inlet D6 17 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Maximum side slope shall be 25 percent 4 1 where sheet flow enters the facility Absolute maximum side slope shall be 40 percent 2 5 1 for planted slopes If steeper side slopes are necessary modular block walls concrete walls or geotextile retaining wall systems may be used Inflows from pipes must be protected from erosion using flow energy dissipation e g rock pad pop up drainage emitter or flow dispersion weir Cell Ponding Area The ponding depth shall be a minimum of 2 inches for Single Family Residential lots and a minimum of 6 inches and maximum of 12 inches for non Single Family Residential projects The minimum bottom width shall be 1 foot Maximum drawdown time for the ponded area shall be 48 hours when flow control is required Bioretention Soil Imported bioretention soil shall meet the requirements of Section D6 04 1 and shall have a minimum depth uncompacted of 12 inches for flow control
67. satisfied The surface pool drawdown time may be estimated as the ponding depth divided by the long term design infiltration rate For cells with longitudinal slopes greater than two 2 percent the model must account for the effects that slope has on reducing the amount of wetted area that is available for infiltration This may be done by adjusting the Bottom Length and Effective Total Depth inputs to the model as shown in Table 6 6 based on the number of cells maximum ponding depth in each cell and longitudinal bottom slope of each cell See Figure 6 2 for a schematic illustration and Table 6 6 for additional details The overflow shall be sized for 100 year 24 hour conveyance TOTAL LENGTH Figure 6 2 Schematic for calculating Bottom Length and Effective Total Depth for bioretention or pervious pavement on slopes where check dams berms are used Refer to D6 22 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 6 6 for Bioretention Cells and Bioretention Swales and Table 6 8 for Pervious Pavement formulas Table 6 6 Continuous Modeling Assumptions for Bioretention Cells and Bioretention Swales Precipitation Series SeaTac 50 year hourly time series with appropriate scaling factor based on project location Inflows to Facility Surface flow and interflow from drainage area routed to facility Precipitation and Evaporation Applied Yes to Facility Bottom Length For longitudinal slopes
68. 03 9 3 Crushed Surfacing of the Standard Specifications shall be used as trench backfill for pipe For longitudinal trenches trenches parallel to the centerline of the roadway in paved areas backfill material 4 feet and deeper below finished grade shall conform to Section 9 03 14 1 Gravel Borrow of the Standard Specifications The Contractor may request to use excavated material as trench backfill and must demonstrate to the Engineer that the suitable excavated material conforms to Section 9 03 14 1 Gravel Borrow of the Standard Specifications and proper compaction levels can be achieved Admixtures and or additives may not be used to modify the moisture content in order to meet compaction specifications The top 4 feet of longitudinal trenches shall be backfilled with crushed rock conforming to Section 9 03 9 3 Crushed Surfacing of the Standard Specifications In unpaved areas trench backfill material shall conform to Section 9 03 14 1 Gravel Borrow of the Standard Specifications The Contractor may request to use excavated material as trench backfill when it has been determined by the Engineer to be suitable and conforms to Section 9 03 14 1 Gravel Borrow of the Standard Specifications and proper compaction levels can be achieved In paved areas within the public right of way backfilling storm drain trenches shall be as specified in Standard Detail D 25 Controlled Density Fill CDF may be used lieu of Crushed Surfacing Top Course
69. 06 04 MATERIALS PIPING SHALL BE CAST IRON PVC SDR 35 MINIMUM OR PVC SCHEDULE 40 3 PIPE REQUIRED FOR UP TO 1 500 SQ FT OF CONTRIBUTING AREA OTHERWISE 4 MIN PIPING MUST HAVE 1 GRADE AND FOLLOW THE UNIFORM PLUMBING CODE IF WITHIN 3 OF A STRUCTURE DRAIN ROCK A SIZE PER NDP MATERIALS CHAPTER 06 04 DEPTH OF SIMPLIFIED 12 DEPTH OF ENGINEERED 0 48 DRAIN ROCK NOT REQUIRED FOR INFILTRATION PLANTERS WITHOUT UNDERDRAINS SEPARATION BETWEEN DRAIN ROCK AND GROWING MEDIUM USE GRAVEL LENS 4 INCH WASHED CRUSHED ROCK 2 TO 3 INCHES DEEP JANUARY 2015 NO SCALE 7 GROWING MEDIUM BIORETENTION SOIL MIX PER NDP MATERIALS CHAPTER 06 04 8 VEGETATION A PLANT WITH ZONE 1 OR 2 TREES SHRUBS AND OR GROUND COVER SEE APPENDIX 3 IN THE LID TECHNICAL GUIDANCE MANUAL FOR PUGET SOUND 2005 OR CURRENT OR RAIN GARDEN HANDBOOK FOR HOMEOWNERS FOR A PLANT LIST B PLANTING SHALL CONSIST OF NATIVE SPECIES ABLE TO TOLERATE VARIABLE SOIL MOISTURE CONDITIONS PONDING WATER FLUCTUATIONS AND VARIABLE SOIL MOISTURE CONTENT 9 PLANTER WALLS MATERIAL SHALL BE STONE BRICK CONCRETE WOOD OR OTHER DURABLE NO CHEMICALLY TREATED WOOD INSTALL WASHED PEA GRAVEL OR 17 4 STREAMBED COBBLES PER STANDARD SPECIFICATIONS 9 03 11 2 TO TRANSITION FROM INLET OR SPLASH PAD TO GROWING MEDIUM SEE LAND USE CODE AND 04 07 IN THESE STANDARDS FOR SETBACKS INSTALL OBSERVATION PORT PER STAN
70. 12 SQUARE INCHES PER FOOT MAY BE USED WELDED WIRE FABRIC SHALL COMPLY TO ASTM A497 AASHTO 221 WIRE FABRIC SHALL NOT BE PLACED IN KNOCKOUTS FRAME AND GRATE APPLY NON SHRINK GROUT TO INSIDE AND OUTSID F ALL SEE APPLICABLE JOINTS RINGS RISERS AND FRAMES STANDARD DETAILS PRECAST BASES SHALL BE FURNISHED WITH CUTOUTS OR OCKOUTS KNOCKOUTS SHALL HAVE A WALL THICKNESS F 2 MIN ALL PIPE SHALL BE INSTALLED IN FACTORY ROVIDED KNOCKOUTS UNUSED KNOCKOUTS NEED NOT E GROUTED IF WALL IS LEFT INTACT OCKOUT OR CUTOUT HOLE SIZE IS EQUAL TO PIPE OUTER AM PLUS CATCH BASIN WALL THICKNESS OCKOUTS MAY BE ON ALL 4 SIDES WITH MAX DIAM OF 28 OCKOUTS MAY BE EITHER ROUND OR D SHAPE THE TAPER ON THE SIDES OF THE PRECAST BASE SECTION AND RISER SECTION SHALL NOT EXCEED 1 2 FT ATCH BASIN FRAME AND GRATE SHALL BE IN ACCORDANCE WITH STANDARD SPECIFICATIONS MATING SURFACES SHALL BE FINISHED TO ASSURE FIT WITH ANY COVER POSITION MAX DEPTH FROM FINISHED GRADE TO PIPE INVERT SHALL BE 5 0 VERTICAL EDGE OF REDUCING SECTION SHALL MORE THAN 2 FROM VERTICAL EDGE OF CATCH BASIN WALL City Of STORM AND SURFACE WATER UTILITY Bellevue PRECAST BASE SECTION MEASUREMENT THE tae OF THE BASE CATCH BASIN TY JANUARY 2015 F
71. 14 C 33 1 0 1 0 10 20 30 40 50 60 70 80 90 100 96 Finer by Weight D4 13 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Methods of Analysis Design Flows Design flows for sizing and assessing the capacity of open channels shall be determined using the hydrologic analysis methods described in Chapter D3 Hydrologic Models Flow control credits may not be used to reduce the required size of conveyance facilities Conveyance Capacity There are three acceptable methods of analysis for sizing and analyzing the capacity of open channels Manning s equation for preliminary sizing Direct Step backwater method and Standard Step backwater method 1 Manning s Equation for Preliminary Sizing Manning s equation is used for preliminary sizing of open channel reaches of uniform cross section and slope 1 prismatic channels and uniform roughness This method assumes the flow depth or normal depth and flow velocity remain constant throughout the channel reach for a given flow The charts in Figure 4 3 and Figure 4 4 may be used to obtain graphic solutions of Manning s equation for common ditch sections For conditions outside the range of these charts or for more precise results Manning s equation can be solved directly from its classic forms shown in Equations 4 10 and 4 11 jf J Table 4 3 provides reference for selecting the appropriate n values for open channels number of engineering reference books such
72. 18 2 48 inch diam 30 24 Type 2 54 inch diam 36 30 Type 2 60 inch diam 48 36 Type 2 72 inch diam 54 42 Type 2 84 inch diam 60 54 Type 2 96 inch diam 72 72 i Catch basins manholes and inlets including steps ladders and handholds shall conform to COB Standard Details H Maximum four 4 vertical feet allowed between grate cover and pipe invert elevation iii Limited to one inletting pipe 6 inches or less in diameter iv Maximum five 5 vertical feet allowed between grate cover and pipe invert elevation v CMP allowed for detention pipe only The number and size of pipes that may be connected to any one structure is limited in order to maintain the integrity of the structure For angled connections or those with several pipes on the same plane a larger structure than set forth in the Table 4 11 above may be required For structural integrity minimum undisturbed wall edge of pipe opening to edge of pipe opening shall be 8 inches For 72 inch and 96 inch diameter structures the minimum undisturbed wall D4 67 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 between openings is 12 inches Detailed plans of structures with multiple pipes or angled connections may be required to ensure proper structure selection D4 05 3 Maintenance Access Where no direct maintenance vehicle access from a maintenance access road can be provided or when greater than 15 feet from a roadw
73. 2 PLATE UPPER BAND 1 2 MH OUTER DIAMETER 48 54 SE I 5 4 BAR DRILL HOLES FOR LOCK i SEE NOTE 5 INNER DIAM N 5 4 CLEAR 2 9 16 HOLES SEE NOTE 4 EQUALLY SPACED 8 TOTAL GALVANIZED FLAT BAR 1 2 x3 4 LOWER BAND NOTES 1 27 TOTAL LENGTH VARIES CONCRETE WITH 2 1 2 DIA BOLTS EACH LEG WELD BAND ENTRY GATE DETAII EVATION 1 ALL STEEL IN PLATES BARS AND BANDS SHALL CONFORM TO THE REQUIREMENTS OF ASTM A36 STEEL DEBRIS CAGE SHALL BE GALVANIZED IN ACCORDANCE WITH AS A123 AASHTO M111 ALUMINUM IS AN O PTIONAL CAGE MATERIAL AND MUST BE BOLTED TO THE CONCRETE STRUCTURE LOWER BAND DIME STRUCTURE PROVIDE 4 CLEARANCE BETWEEN THE TOP OF THE Bellevue LOWER BAND AND CONCRETE STRUCTU JANUARY 2015 SIONS TO MATCH City of STORM AND SURFACE WATER UTILITY RE EBRIS CAGE NO SCALE FRAME AND GRATE 2 12 RISERS MIN SAND COLLAR OR KOR N SEAL BOOT TYPICAL INLET PIPE 2 MIN MAX DESIGN WSE TYPE 1 P CB BASE UNIT SEE APPLICABLE STANDARD DETAILS CONFORMS TO i WASH STATE APWA WSDOT 50 ORCS STANDARD SPECIFICATIONS AND STANDARD PLAN NOTES 1 MAX OUTLET PIP
74. 2 847 PRECAST CONE ECCENTRIC UNLESS OTHERWISE SPECIFIED x PRECAST RISER SECTIONS LADDER 5 5 HEIGHT 25 MAX TOP SLAB ME CONSTRUCT IN FIELD CHANNEL AND SHELF TO THE SPRINGLINE OF THE PIPE PRECAST BASE amp INTEGRAL RISER 2 0 m GRAVEL BACKFILL FOR FOUNDATIONS 6 MIN COMPACTED DEPTH j l zh ER i NOD NOTES 1 ANHOLES SHALL BE CONSTRUCTED IN ACCORDANCE WITH AASHTO M199 UNLESS OTHERWISE SHOWN ON PLANS OR NOTED IN THE STANDARD SPECIFICATIONS ANDHOLDS IN ADJUSTMENT SECTION SHALL HAVE 3 MIN CLEARANCE STEPS IN MANHOLE SHALL HAVE 6 IN CLEARANCE SEE STD DTL D 15 MANHOLE DETAILS MANHOLDS SHALL BE PLACED IN ALTERNATING GRADE RINGS OR LEVELING BRICK COURSE WITH A MIN OF ONE HANDHOLD BETWEEN THE LAST STEP AND THE TOP OF THE MANHOLE ON REINFORCED CONCRETE 1 ANNEL AND SHELF SHALL BE CLASS 3000 ALL PRECAST CONCRETE SHALL E CLASS 4000 RECAST BASES SHALL BE FURNISHED WITH CUTOUTS OR KNOCKOUTS KNOCKOUTS SHALL HAVE WALL THICKNESS OF 2 MIN UNUSED KNOCKOUTS NEED NOT BE GROUTED IF WALL IS LEFT INTACT PIPES ALL BE INSTALLED LY IN FACTORY KNOCKOUTS UNLESS OTHERWISE APPROVED BY THE ENGINEER OCKOUT OR CUTOUT ZE SHALL EQUAL PIPE OUTER DIAM PLUS MANHOLE WALL THICKNESS MAX OLE SIZE BE 60 FOR ANHOLE 84 FOR 96 MANHOLE IN DISTANCE BETWEEN HO
75. 200 square feet 20 x 100 sf x 10 evergreen trees retained This further reduces the total impervious area requiring mitigation to 12 650 square feet Only the unmitigated impervious area 12 650 square feet is then included in the continuous hydrologic model to size the downstream flow control facilities Section D3 02 for the project To use these Flow Control Credits the facility must meet all specified design requirements in accordance with Sections D6 03 1 and D6 03 2 and the respective Standard Details A Applicability For BMPs that do not fully meet the flow control requirement Flow Control Credits can be applied to reduce the size of flow control facilities The Flow Control Credit values are based on the degree to which these facilities achieve the flow control standard per Chapter D3 These credits represent impervious area reductions applied to the amount of impervious surface area requiring flow control or mitigation Flow Control Credits are presented in Table 6 14 Section D6 03 4 C Generalized assumptions were used to develop the Flow Control Credits that may underestimate actual flow control benefits for some sites Developers have the option to use the Flow Control Credits provided in this section or to follow the demonstrative approach Section D6 03 2 and submit an alternative facility Flow Control Credit with supporting engineering calculations for review D6 50 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015
76. 30 inches for infiltration planters Maximum drawdown time for the ponded area shall be 48 hours when flow control is required Bioretention Soil Mix D6 25 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Imported bioretention soil mix must meet the materials specifications in the NDP materials section D6 04 1 and shall have a minimum depth of 18 inches If native soil meets the aggregate specification in the NDP materials Section D6 04 1 it may be amended with compost per the specification therein rather than importing materials Underdrain For flow through planters or infiltration planters in locations with lower infiltration rates underdrain systems can be installed in the base of the facility to drain excess stormwater when the infiltration capacity of the surrounding soil is insufficient to meet minimum ponding drawdown time requirements When specified by the designer design requirements shall include material shall be a thick walled plastic pipe or another material type listed in D6 04 3 or a type approved by the City Pipe shall have a minimum diameter of three 3 inches and a maximum diameter of eight 8 inches underdrain shall be placed in the retention zone at least 6 inches above the bottom of the retention zone and with at least 1 foot of retention zone material above the pipe 1 minimum uncompacted retention zone depth of 2 inches for a 3 inch diameter pipe and 26 inches
77. ACCESS CYAN ROWL1 SV LROW EXST LIN NO 1 PEN ZZZ Z Z ZZ Z Z Z Z Z Z Z Z Z Z ZZ RGIT OF WAY LIMITED ACCESS GREEN ROWL1 SV LROW PROP LIN n in NO 2 5 PEN B n ime c SECTION LINE GREEN SECT SV SECT EXST LIN NO 2 5 PEN ard k P27 1 QUARTER SECTION LINE CYAN QTRSECT SV QSCT EXST LIN NO 1 PEN T a ot seem SECTION LINE CYAN 16THSECT SV 16ST EXST LIN NO 1 PEN F 0 8 0 1 asas Ar STATE COUNTY CORPORATE LIMIT GREEN STATE SV 222B EXST LIN F o2 NO 2 5 PEN SS z i GREEN STATE SV 222B PROP LIN STATE COUNTY CORPORATE LIMIT PEN NO 2 5 03 WIDE 222A USE RANG TWNS 2228 USE STAT CNTY CITY INSERT ELEVATION AT 6 INTERVALS TEXT 0 1 HIGH American Washington A Ci t f Public Works State a ity o Association Chapter ia B ellevue A D2 11 LINETYPES DESCRIPTION COLOR LT NAME LAYER UTILITIES EXISTING F o 25 A Rex 2 221 CABLE TELEVISION AERIAL RED ATV TV ALIN EXST LIN NO 0 PEN ly CABLE TELEVISION BURIED RED TV BLIN EXST LIN 0 Fa FORCE MAIN MAGENTA FM SS PLIN EXST LIN NO 0 PEN eee MAGENTA G GS PLIN EXST LIN NO 0 PEN 0 MAGENTA 0 OL PLIN EXST LIN NO 0 PEN 0 25 a 2159 power AERIM RED AP PO ALIN EXST LIN NO 0 PEN P POWER BURIED RED P PO BLIN EXST LIN NO O PEN 5
78. ADJUST MANHOLE CATCH BASIN TO GRADE BY INSERTING NEW BARREL ECTION BETWEEN THE CONE SLAB AND EXISTING BARREL RADE RINGS CONCRETE RISERS AND CONCRETE BRICK SHALL BE SET IN 3 4 NON SHRINK GROUT PLASTER OOTH INSIDE AND OUT TEPS OR HAND HOLDS SHALL BE ADDED AS NEEDED RECAST GRADE RINGS AND RISERS MUST BE CAST WITH GROOVE TO ALLOW FIELD INSTALLATION OF SAFETY STEP EPLACE EXISTING FRAME AND COVER GRATE IF NON STANDARD OR WORN ROUT INSIDE AND OUTSIDE OF MANHOLE ATCH BASIN NECK TO ACHIEVE WATER TIGHT B ONSTRUCTION FINISH SMOOTH THE INSIDE Cit of STORM AND SURFACE F THE NECK USE NON SHRINK GROUT WATER UTILITY LY OCKING RING AND COVERS ARE REQUIRED Bellevue ALL UNPAVED AREAS AND EASEMENTS LOCKING RING AND COVER SHALL CONFORM TO STANDARD DETAIL D 22 MANHOLE CA ADJUSTMEN uU JANUARY 2015 SCALE ss k q1 L 28 MAX AS REQUIRED CONTINUOUS E SLABS TOP VIEW CONCENTRIC ELEVATION ECCENTRIC SECTION LEGEND BOLT LOCKING MANHOLE RING AND COVER PER DETAIL D 22 CONCRETE GRADE RINGS AS NEEDED TO MATCH FINISHED GRADE DETAIL D 23 CONCRETE TOP SLAB FOR TYPE 2 CATCH BASIN BEARS ON CONCRETE COLLAR CMP RISER 10 GAUGE HELICAL OR ANNULAR CORRUGATED METAL PIPE DIAMETER TO MATCH DETENTION PIPE CORRUGATED METAL STUBS AND DETENTION PIPE TO BE SAME GAUGE STUB LENGTHS TO
79. B Freeboard Requirements Design conveyance systems shall have non pressurized non surcharged flow during the 100 year design storm except that the last pipe run upstream of a detention facility or open outfall into a stream or lake may be inundated during the 100 year event to a maximum distance of 200 linear feet and if all the other conditions of the Engineering Standards are met This also applies for outfalls into streams where the outfall elevation is set at the bank full water surface elevation 2 year storm according to D4 02 B Design Flows Design flows for sizing or assessing the capacity of pipe systems shall be determined using the hydrologic analysis methods described in Chapter 3 Hydrologic Analysis D Conveyance Capacity Two methods of hydraulic analysis are used sequentially for the design and analysis of pipe systems First either the Rational Method or the Uniform Flow Analysis method is used for calculating the design flow rates that are used for the preliminary sizing of new pipe systems Second the Backwater Analysis method is used to analyze both proposed and existing pipe systems to verify adequate capacity Note Use of the Uniform Flow Analysis method or the Rational Method to determine preliminary pipe sizes is only suggested as a first step in the design process it is not required Results of the Backwater Analysis method determine final pipe sizes in all cases D4 49 SURFACE WATER ENGINEERING
80. BMP Description Applicability Requirements Perforated Stub Runoff to existing All projects with Required for any connection to a out Connection storm pipe directed via storm conveyance storm conveyance system where underground perforated system connection design criteria are met pipe in a rock trench Comply with Section D6 03 1 H Dispersion Gravel filled trench Use only where Required as an outfall when Trench with adequate vegetated other BMPs do not connection to a storm conveyance flow path May include fully mitigate system is not available and design pump if site conditions runoff criteria are met require Comply with Section D6 03 1 F Refer to Sections D6 03 1 and D6 03 2 for design sizing construction and maintenance methods for on site BMPs and NDPs Sizing Factors for determining the minimum sizes necessary to meet on site stormwater management requirements based on the amount of impervious area draining to each facility are provided in Section D6 03 3C B Runoff Treatment Minimum Requirement 6 Full dispersion and Infiltration NDPs including bioretention and pervious pavement are preferred methods for meeting water quality treatment requirements Full dispersion may be applied to entire sites or portions of sites with at least 35 of native vegetation preserved in a dedicated NGPE or to road projects meeting the requirements for full dispersion credit in Section 7 2 of the LID Manual Sit
81. D 39 NOTESED asnasan aqa sta t as D 40 NOT S eet es D 41 SPILL CONTROL SC SEPARATOR TYPE 1 222 2 2 D 42 SPILL CONTROL SC SEPARATOR TYPE 2 nnne D 43 SPILL CONTROL SC SEPARATOR TYPE 3 D 43A DRAINAGE FACILITY MAINTENANCE ACCESS D 44 GATE BOLLARD PLACEMENT ee a aasan u peu ED UH M e YR D 45 PIPE BEDDING D nanpi qaqpas aaa usa D 46 RUNOFF TREATMENT VAULT WET VAULT D 47 COMBINED VAULT DETENTION AND RUNOFF TREATMENT D 48 SUMP WITH napas aqasha unas D 49 D 50 omitted TRAFFIC BEARING ACCESS FOR CORRUGATED METAL MANHOLE D 51 ace aqu atleti uus D 52 TRASH RACK DBBRIS D 53 SOIL CEMENT PIPE ANCHORS EU T snasnacedensa D 54 D 55 omitted CASINGINSTALPEATION Qs Z a h A vs ev te rp ns TY D 56 PIPE STAKE ANCHOR ASSEMBLY ont eit e D 57 A D1 2 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 DRIVEWAY CULVERT 2 ud dte DR Ue RR DUI I utr RI HE D 58 ROCK PROTECTION OU TEILE Qusa snn D D 59 BIRD CAGE TRASH RACK STRUCTURE
82. Development Services Department determines that a proposed project contains or is adjacent to a flood hazard area for a river stream lake wetland closed depression or other water feature Furthermore when development is proposed within the floodplain the floodplain floodway study is used to show compliance with the critical areas code BCC 20 25H 175 flood hazard area regulations There are four conditions affecting the requirements for floodplain floodway studies Each condition is considered a threshold for determining the type of studies required and the documentation needed to meet the study requirements Each study threshold and related study requirements are shown in the table below and described further in this section D4 25 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 4 4 Floodplain Floodway Study Thresholds And Requirements Threshold Study Requirements The project site is on land that is outside of No floodplain study e Show delineation of floodplain on an already delineated floodplain and above required the site improvement plan and the floodplain s base flood elevation based indicate base flood elevation on best available floodplain data determined in accordance with BCC See Section D4 04 5 B for more 20 25H 175 and associated public rule details The project site is on land that is at least Approximate Floodplain e Submit an engineering plan with 10 vertical feet above the ordinary high Stud
83. Freeboard Requirements Culverts For Type S and F streams the water surface elevation for the 100 year storm shall be at least one 1 foot below the crown of the culvert to allow for the passage of floating debris E Minimum Diameter Slope and Velocity The minimum diameter of any driveway culvert shall be 12 inches Where minimum cover requirements can be met a minimum 18 inch diameter culvert shall be used to minimize debris blockages Headwalls cut off walls and or anti seep collars shall be provided on culverts where the hydraulic piping of bedding and backfill materials is possible F Energy Dissipation When discharging to an existing ditch swale or stream energy dissipation is required to avoid erosion Design energy dissipation measures pursuant to Section D4 02 D4 33 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 G Maintenance Access Provide maintenance access to the upstream and downstream ends of the culvert for inspection and debris removal H Design Criteria Headwater For culverts 18 inch diameter or less the maximum allowable headwater elevation measured from the inlet invert shall not exceed 2 times the pipe diameter or arch culvert rise at design flow 1 the 100 24 hr peak flow rate For culverts larger than 18 inch diameter the maximum allowable design flow headwater elevation measured from the inlet invert shall not exceed 1 5 times the pipe diameter or arch culvert
84. JANUARY 2015 See Table 3 2 in 2005 DOE Manual Volume V Chapter 3 Section 3 4 for types of facility combinations that are appropriate for the two facility treatment train D5 03 6 Oil Control Treatment to achieve Oil Control applies to projects that have high use sites High use sites are those that typically generate high concentrations of oil due to high traffic turnover or the frequent transfer of oil High use sites include 1 An area of a commercial or industrial site subject to an expected average daily traffic ADT count equal to or greater than 100 vehicles per 1 000 square feet of gross building area 2 An area of a commercial or industrial site subject to petroleum storage and transfer in excess of 1 500 gallons per year not including routinely delivered heating oil 3 An area of a commercial or industrial site subject to parking storage or maintenance of 25 or more vehicles that are over 10 tons gross weight trucks buses trains heavy equipment etc 4 A road intersection with a measured ADT count of 25 000 vehicles or more on the main roadway and 15 000 vehicles or more on any intersecting roadway excluding projects proposing primarily pedestrian or bicycle use improvements All Oil Control facilities shall be designed in accordance with criteria set forth in Volume V of the DOE Manual as modified herein Locate a spill control separator upstream from the detention system or immediately before leaving
85. King County Surface Water Design Manual D4 7 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Open channels may be classified as either natural or constructed Natural channels are generally referred to as rivers streams creeks or swales while constructed channels are most often called ditches or simply channels The Critical Areas Shorelines and Clearing and Grading Codes should be reviewed for requirements related to streams Natural Channels Natural channels are defined as those that have occurred naturally due to the flow of surface waters or those that although originally constructed by human activity have taken on the appearance of a natural channel including a stable route and biological community They may vary hydraulically along each channel reach and should be left in their natural condition wherever feasible or required in order to maintain natural hydrologic functions and wildlife habitat benefits from established vegetation Constructed Channels Constructed channels are those constructed or maintained by human activity and include bank stabilization of natural channels Constructed channels shall be either vegetation lined rock lined or lined with appropriately bioengineered vegetation Vegetation lined channels are the most desirable of the constructed channels when properly designed and constructed The vegetation stabilizes the slopes of the channel controls erosion of the channel surface and removes pol
86. MSBCF 1730 12 X E XX gt gt CAP WITHOUT GASKET lt COMPACT GRAVEL BASE RIGHT OF WAY OR EASEMENT UNPAVED PAVEMENT FINISHED amp seve 5000 P S I i 54 CLASS COLLAR CAST IN PLACE CONCRE TE P V C SLEEVE MIN 12 LONG FOR SLEEVE DIAMETER SEE TABLE To FILL WITH SAND OR C O PIPE RING AND COVER P V C SLEEVE CRUSHED SURFACING DIAMETER DIAMETER DIAMETER 2 COURSE MATERIAL 47 12 12 6 14 15 is RISER 8 14 15 P COMPACTED BACKFILL 6 OR 8 STORM PIPE IF CLEANOUT IS AT THE HEAD OF THE SYSTEM INSTALL GASKETED CAP NOTES BOLT LOCKING CAST IRON RING AND COVER SHALL BE USED IN RIGHT OF WAY AND EASEMENTS AND MUST BE RATED HS 20 IF USED IN PAVED AREAS SEF TABLE FOR SIZES MID STATES PLASTIC BOX OR EQUAL MAY BE USED IF IS OUTSIDE OF RIGHT OF WAY OR EASEMENT SEE TABLE FOR SIZES THE COVER FOR THE PLASTIC BOX SHALL BE DUCTILE IRON AND READ DRAIN OR BE BLANK NO LABEL CAST IRON COVER SHALL READ DRAIN LOCKING BOLTS SHALL BE 5 8 11 N C 304 Cit of STORM AND SURFACE STAINLESS STEEL SOCKET ALLEN HEAD Y y WATER UTILITY 2 LONG 14 BOLT LOCKING CAST IRON COVER SHALL Bellevue BE EQUAL TO INLAND FOUNDRY NUMBER 209
87. Natural Resources Washington State Department of Ecology Washington State Department of Health Federal Highway Administration Public Health Seattle and King County Natural Resource Conservation Service formerly Soil Conservation Service Revised Code of Washington United States Environmental Protection Agency Washington Administrative Code Washington Department of Fish amp Wildlife Washington State Department of Transportation 01 04 GOVERNMENTAL AGENCY REQUIREMENTS All construction on City County or State roads or right of way shall be done in accordance with that agency s standards and requirements and in accordance with all franchise and or permit requirements The Contractor is responsible to determine these requirements prior to construction Where conflict exists between these Standards and permit requirements the most stringent permit requirements shall take precedence SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 END OF CHAPTER D1 SURFACE WATER ENGINEERING STANDARDS D2 01 D2 02 D2 02 1 D2 02 2 D2 02 3 D2 03 D2 04 D2 05 D2 05 1 D2 05 2 D2 05 3 D2 06 D2 06 1 D2 06 2 D2 06 3 D2 07 D2 07 1 D2 07 2 D2 08 D2 08 1 D2 08 2 D2 09 D2 09 1 D2 09 2 JANUARY 2015 CHAPTER D2 THRESHOLDS AND PLAN SUBMITTAL TABLE OF CONTENTS GBENEREI numas ua tese ana D2 1 ADJUSTMENTS AND DEVIATIONS a D2 1 General ea a eH CSE SE
88. OF THE STANDARD SPECIFICATIONS RIP RAP SHALL BE 3 City of STORM AND SURFACE REASONABLY WELL GRADED W THE FOLLOWING GRADATION Bellevue WATER UTILITY AX STONE SIZE PERCENT PASSING 8 100 6 40 60 A 0 10 OUTFALL JANUARY 2015 NO SCALE NO D 59 ELEVATION DEBRIS CAGE SEE STANDARD DETAIL D 39 4 8 QUARRY SPALLS 48 DIA TYPE MANHOLE BASE MIN SIZE e IC e ity of STORM AND SURFACE 1 WATER UTILITY Bellevue BIRD CAGE TRASH RACK STRUCTUR JANUARY 2015 NO SCALE AMENDMENT FOR LANDSCAPED AREAS 4 2 INCHES OF WOOD NUR i mu Ae 2 AUS ee ie m INCORPORATED INTO 5 OF SOIL OR AMEND FOR 8 SETTLED SOIL AT 10 8 MINIMUM AFTER SETTLING ORGANIC CONTENT AFTER AMENDING Scar IE a N BEDS AND REMOVE IIIS DAMETER BEFORE NATIVE SOIL _ RR lt lt lt MULCHING MYL YY NA NN d SOIL AMENDMENT FOR GRASS OR TURF AREAS 1 75 OF COMPOST INCORPORATED INTO SEE D6 04 5 MATERIALS 6 25 SOIL GOAL OF 5 ORGANIC MATTER IN 8 8 MINIMUM AFTER SETTLING OF SETTLED SOIL r AFTER AMENDING WATER OR ROLL WALK BEHIND DRUMROLLER FOR COMPACTION KIKKX KKK S r APPROXIMATELY 85 OF 606606659666 s 5 JUSS lt MAXIMUM DRY DENS
89. PERVIOUS CONCRETE MUST BE INSTALLED BY A CERTIFIED PERVIOUS CONCRETE INSTALLER PERVIOUS ASPHALT MUST BE INSTALLED BY AN EXPERIENCED PERVIOUS ASPHALT NSTALLER SEE NDP CHAPTER D6 04 HEREIN FOR ALL MATERIALS City of STORM AND SURFACE WATER UTILITY w Bellevue OR ECTION NO NDP 11 JANUARY 2015 NO SCALE PERVIOUS CONCRETE BLOCK OR PAVER SYSTEMS PAVERS WITH 1 MAX OPEN SURFACE SPACERS FINISH GRADE SEE NOTE 2 ASTM NO 8 STONE FILL WEARING COURSE LEVELING COURSE OPTIONAL RESERVOIR COURSE 54 N x lt 2 56 S W ASE RUNOFF TREATMENT LAYER IF REQUIRED NON WOVEN GEOTEXTILE BOTTOM AND SIDES OPTIONAL EXTEND GEOTEXTILE ABOVE PAVERS AFTER INSTALLATION IS COMPLETE CUT GEOTEXTILE AT FINISHED GRADE TYP SUBGRADE SAK POOR BRL SK gt LN 2500 5 S lt lt 0 2 2 X xP SS lt 2 lt S BR 2 55 X SX lt e e 0 e gt 5 555 tef SS Z 2 52 gt x 5 15 lt lt A lt N lt lt gt KKK gt lt 2 l
90. Pervious Concentrated or Pervious Infiltration Pervious Pavement Sheet Flow Pavement Pavement Rain Concentrated or Dispersion Pervious Recycling Perforated Sheet Flow Pavement Stub out Connection Dispersion Traffic Roof Downspout Pervious Pervious Pavement Pervious Infiltration Pervious Pavement Pavement Pavement Rain Recycling 0 15 Slope Natural Splash Block Pop up Concentrated or Concentrated or Amended Vegetation Emitter Sheet Flow Sheet Flow Sheet Flow Soils 0 25 Dispersion Rain Dispersion Dispersion Reverse Concentrated inch hour Recycling Minimal Slope Sidewalk or Sheet Flow Infiltration Excavation Foundation Dispersion Landscape Lawn Splash Block Pop up Amended Soils Amended Soils Amended Emitter Bioretention Concentrated or Concentrated or Soils Rain Recycling Dispersion Sheet Flow Sheet Flow Concentrated Trench Perforated Stub Dispersion Dispersion or Sheet Flow out Connection Bioretention Bioretention Dispersion Reverse Slope Sidewalk Minimal Excavation Foundation Bioretention Pedestrian Bike Rain Recycling Perforated Stub out Connection Concentrated or Sheet Flow Dispersion Concentrated or Sheet Flow Dispersion Not applicable Traffic not high use site Rain Recycling Not applicable Not applicable Not applicable D6 11 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 6 5 On site Stormwater BMP Sele
91. SOIL INFILTRATION RATE BIORETENTION SOIL MIX RETENTION ZONE DEPTH VARIES EXISTING 2 27 SUBGRADE OVERFLOW CLEANOUT PERFORATED PIPE PER STD DTL NDP 3 DETAIL A COUPLING SOLID PVC ASTM D3034 SDR 35 PIPE TO APPROVED DISCHARGE ATRIUM GRATE CLEANOUT MAX PONDING DEPTH VARIES SAKA CRAY 5 LSS ALALA OVERFLOW PIPE SEE NOTES PERFORATED DISTRIBUTION PIPE TO RUN LENGTH OF FACILITY SEE DETAIL A BIORE TENTION SOIL MIX RETENTION ZONE DEPTH VARIES EXISTING SUBGRADE A CROSS SECTION VIEW PIPE W UNDERDRAIN amp DISCHARGE POINT NOTES 1 PIPE OVERFLOW NOT REQUIRED IF FACILITY INFILTRATES THE 100 YEAR STORM MEETS FLOW CONTROL STANDARD OVERLAND OVERFLOW PATH REQUIRED ADEQUATELY STABILIZE WITH STREAMBED COBBLE STANDARD SPECIFICATIONS 9 03 11 2 AND DIRECT TO AN APPROPRIATE DOWNSTREAM DRAINAGE AREA OVERFLOW PIPE PVC 3 MINIMUM USE SCHEDULE 80 FOR 3 DIAMETER PIPE FOR ALL OTHERS USE 50 35 JANUARY 2015 NO SCALE OUTLET TO APPROVED DISCHARGE POINT PER CITY OF BELLEVUE ENGINEERING STANDARDS LESS THAN 0 25 INCH HR NATIVE SOIL INFILTRATION RATE of Cit Bellevue WATER PARTIAL INFILTRATION OR FLOW THRO UGH STORM AND SURFACE UTILITY IGURATI ENTION ONS NO NDP 8 HOW TO CONTRUCT AND INSTALL AN OBSERVATION PORT TO MEASURE WATER DEPTI RR
92. STANDARDS JANUARY 2015 Uniform Flow Analysis Method This method is used for preliminary sizing of new pipe systems to convey the design flow 1 the 100 year peak flow rate Assumptions Flow is uniform in each pipe 1 depth and velocity remain constant throughout the pipe for a given flow Friction head loss in the pipe barrel alone controls capacity Other head losses e g entrance exit junction etc and any backwater effects or inlet control conditions are not specifically addressed Each pipe within the system is sized and sloped such that its barrel capacity at normal full flow computed by Manning s equation is equal to or greater than the design flow The nomograph in Figure 4 16 may be used for an approximate solution of Manning s equation For more precise results or for partial pipe full conditions solve Manning s equation directly 1 49 m s 4 10 n or use the continuity equation Q AV such that Qe E aR Ss 4 11 n Where discharge cfs velocity fps area sf Manning s roughness coefficient see Table 4 9 hydraulic radius area wetted perimeter ft slope of the energy grade line ft ft ADA gt lt I For pipes flowing partially full the actual velocity may be estimated from the hydraulic properties shown in Figure 4 17 by calculating Vun and using the Qaesignl Ofun to find V and d depth of flow Table 4 9 provides the recommend
93. STORM AND SURFACE H WATER UTILITY ye OCKING BOLTS SHALL BE 5 8 1 N G 27 Bellevue 04 STAINLESS STEEL SOCKET ALLEN HEAD LYMPIC FOUNDRY MH30AD T OR EQUAL NG AND COVER SHALL BE RATE BOLI LOCKING MANHOLE RING AND COVER gt U miU O C JANUARY 2015 RECAST GRADE E ER GRATE ERS OR RICKS AS LIMIT OF EXCAVATION TYP SM ROPOSED PAVEMENT E RFACE EXISTING PAVEM PHALT CONC PAVEM CL HMA CLASS A FIRST SI AXIMUM 18 PLACE amp COMPACT BELOW COVER CRUSHED SURFACING TOP COURSE EXIST MANHOLE nm CATCH BASIN PAVED AREAS RAME amp COVER GRATE LIMITS OF EXCAVATION 3000 D NSTALL PR RINGS RISE BRICKS AS FINAL GRAD FIRST STE AXIMUM 18 BELOW COVER P 5 G R B EXISTING MANHOL OR CATCH BASIN UNPAVED AREAS NOTES HERE DEPTH OF NECK EXCEEDS 24 INCHES
94. Show each type of impervious surface lawn and landscape areas non disturbance areas Note the square footage of each within each threshold discharge area B Show the proposed on site stormwater management facilities Show setbacks as required by Land Use Code and Chapter D4 GeoMapNW soils database where available primarily BelRed area If not available Natural Resources Conservation Service NRCS Soil Survey Map for the location with the site boundaries marked Drainage map showing flow path from site to receiving water up to 1 4 mile and threshold discharge areas Indicate the receiving water lake or major stream Include upstream information for any areas draining onto the site Include pipe sizes and structures Sizing calculations or simple sizing tables from Chapter D6 with applicable values circled for proposed on site stormwater management facilities Permanent Stormwater Control Plan including Show on site stormwater management facilities on site plan as required on Development Services Submittal Requirements sheets for single family residential or commercial sites Include sufficient profiles and details needed for review for the Contractor to construct the facilities and for the constructed facilities to be verified by the City inspector If a separate plan sheet is needed for clarity use of the submittal standards in D2 06 2 is recommended D2 9 SURFACE WATER ENGINEERING STANDARDS JANUA
95. Single Event Hydrograph Method SBUH NRSC or 55 is presented in Volume III Chapter 2 of the DOE Manual The design storm for all hydrograph analyses is a 24 hour duration standard SCS Type I A rainfall distribution resolved to 10 minute time intervals Table 3 2 herein See Figures 3 1 through 3 3 herein for the Bellevue 24 hour precipitation isopluvials D3 3 JANUARY 2015 SURFACE WATER ENGINEERING STANDARDS Table 3 2 24 Hour Design Storm Hyetograph Values Time from Beginning Percent Cumulative Percent of Storm Rainfall Rainfall 0 0 00 0 00 10 0 40 0 40 20 0 40 0 80 30 0 40 1 20 40 0 40 1 60 50 0 40 2 00 60 0 40 2 40 70 0 40 2 80 80 0 40 3 20 90 0 40 3 60 100 0 40 4 00 110 0 50 4 50 120 0 50 5 00 130 0 50 5 50 140 0 50 6 00 150 0 50 6 50 160 0 50 7 00 170 0 60 7 60 180 0 60 8 20 190 0 60 8 80 200 0 60 9 40 210 0 60 10 00 220 0 60 10 60 230 0 70 11 30 240 0 70 12 00 250 0 70 12 70 260 0 70 13 40 270 0 70 14 10 280 0 70 14 80 290 0 82 15 62 300 0 82 16 44 310 0 82 17 26 320 0 82 18 08 330 0 82 18 90 340 0 82 19 72 350 0 95 20 67 360 0 95 21 62 370 0 95 22 57 380 0 95 23 52 390 0 95 24 47 400 0 95 25 42 410 1 34 26 76 420 1 34 28 10 430 1 34 29 44 D3 4 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015
96. Standards Plotting shall be on mylar with a non smudging ink or ink like media Pencil drawings including corrections or alterations shall not be accepted Drafting standards symbols shall conform to Washington State APWA Chapter CAD Standards See Appendix D 3 Lettering shall be done with Leroy style font SIMPLEX font if using AutoCAD Text identifying existing features shall be 0 08 in height Leroy 80 template Text identifying street names shall be 0 24 in height Leroy 240 template Text for instructions and call outs for proposed facilities shall be 0 12 in height Leroy 120 template D2 14 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 21 22 23 24 On plans with more than one sheet stationing shall proceed from left to right or from bottom to top Upon completion of construction as builts shall be provided in digital format for as builting and permanent record The digital format shall be in AutoCAD Version 2004 through 2011 no older or newer The DWG file s on a CD ROM The AutoCAD files shall include all plans profiles notes and details of the surface water improvements Making Copies of Plans Blueline or blackline prints and photocopies are acceptable Brownline prints and microfilm copies of plans will not be accepted Type of Paper for Plan Copies Blueprint quality or standard drafting paper Tissue paper graph paper poster board cardboard and similar materials will not b
97. Such measures shall comply with the Land Use Code and these engineering standards Cables and or chains stretched across access roads are not acceptable D4 04 10 Private Drainage Systems When a new plat is developed and contains a portion of public right of way the flow control facility located in the public right of way tract or easement is owned and maintained by the City of Bellevue The flow control or other storm water facility will only be public if the area drained from the public right of way is new right of way created as part of the plat D4 04 11 Private Single Family Drainage Systems A General Private drainage systems shall comply with all criteria for stormwater systems set forth herein unless specifically exempted When 5 On site Stormwater Management applies first evaluate and implement all feasible on site stormwater management practices as described in Chapter D6 For any remaining D4 62 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 impervious areas not fully managed by on site practices connect stormwater outfalls as described herein In areas having an existing piped conveyance system the stormwater outfalls for parking lot driveway and roadway drainage shall be made by the following in order of preference 1 Connecting the conveyance pipeline to an existing manhole or catch basin or 2 Constructing a new manhole or catch basin on the existing storm drainage pipeline and connecting the
98. TSB TSBP TF SIGN 3333 SYM ae EN CANTILEVERED TSCL TSCLP TF SIGN 3333 SYM A SINGLE POST TSS TSSP TF SIGN 3333 SYM de DOUBLE POST TSD TSDP TF SIGN 3333 SYM oo Cm TRAFFIC SIGNAL POLE TPOL TPOLP TF SIGL 3333 SYM one ane TRAFFIC SIGNAL POLE TSPL TSPLP TF SIGL 3333 SYM W LUMINAIRE TRAFFIC SIGNAL TSPOL TSPOLP TF SIGL 3333 SYM 2s gt SUPPORT POLE xh VEHICLE SIGNAL HEAD TVH TVHP TF SIGL 3333 SYM VEHICLE SIGNAL HEAD TVHA TVHAP TF S GL 33335 SYM W ARROW INDICATOR N i WIRE NOTE TWN TF SIGL 3333 SYM 3333 USE EXST PROP American Washington Public Works State lt City of Association Chapter 2 Bellevue A D2 7 CHANNELIZATION SYMBOLS SYMBOL DESCRIPTION BLOCK LAYER EXIST PROP o cfo BIKE PATH CB CBP TF CHAN 3333 SYM amp HANDICAP SYMBOL CHS CHSP TF CHAN 3333 SYM H O V LANE SYMBOL CHOV CHOVP TF CHAN 3333 SYM M NI ONLY CO COP TF CHAN 3333 SYM i Y RAILROAD CROSSING CRR CRRP TF CHAN 3333 SYM DE M SCHOOL CSC CSCP TF CHAN 3333 SYM M WP STOP cs csP TF CHAN 3333 SYM LANE CONTROL ARROWS A STRAIGHT ARROW CSA CSAP TF CHAN 3333 SYM 4 4 LT RT STR ARROW CLRS CLRSP TF CHAN 3333 SYM QU lt gt LEFT RIGHT ARROW CLR CLRP TF CHAN 3333 SYM P gt 2 LEFT TURN C2W C2WP TF CHAN 3333 SYM Y 3333 USE EXST PROP American Washington do L Public Works State E ity of Association Chapter B el evu
99. The washed rock shall be protected from contamination by soil fines Clean outs on footing drains and underdrains shall be provided every 100 feet and at bends or drain pipe junctions Connection to the stormwater conveyance system shall be at a point where the hydraulic grade line in the conveyance pipe does not affect the free draining ability of the footing drains or underdrains Minimum Size The minimum diameter of a detention pipe shall be 36 inches The minimum height of any detention vault shall be 84 inches D Structural Design Use the criteria set forth in Volume III Section 3 2 2 and 3 2 3 of the DOE Manual and by the City Building Code Note that where the top of a vault is in a traveled way additional loading requirements to accommodate fire trucks will apply Please consult the Building Division of the Development Services Department for available information on Structural Slab Design Loadings Hydrostatic Pressure amp Buoyancy Use the criteria set forth in Volume III Section 3 2 2 and 3 2 3 of the DOE Manual as modified herein If permanently lowering the groundwater in the vicinity is not feasible pipes and vaults shall be designed to accommodate hydrostatic loading and buoyancy effects E Maintenance Access Use the criteria set forth in Volume III Section 3 2 2 and 3 2 3 of the DOE Manual as modified herein Since underground detention facilities are subject to confined space entry regulations such faciliti
100. VALV 3333 SYM BUTTERFLY VALVE M J WBVM WBVMP WA VALV 3333 SYM M GATE VALVE FL WGV WGVP WA VALV 3333 SYM SAME INDICATES 3333 USE EXST PRO USE SAME BLOCK FOR PROPOSED American Washington Public Works State lt City of Association Chapter Bell 2 2 WATER SYMBOLS SYMBOL EXIST PROP 3 N K lel 1 1 H gt gt m m A A c c SANITARY STORM SEWER SYMBOL EXIST PROP American Public Works Association DESCRIPTION ABBR GATE VALVE FL x M J GATE VALVE M J AIR RELIEF VALVE AIR BLOW OFF VALVE BO CHECK VALVE ck PLUG VALVE PV COUPLING CPL GUARD POST GP REDUCER RED THRUST BLOCK WATER METER HYDRANTS 2 3 PORT FH JOINTS FLANGE BLIND FL BL FL MECHANICAL MJ PUSH ON HUB THREAD DESCRIPTION ABBR SAN SEWER CLEAN OUT SAN SEWER MANHOLE STORM DRAIN CATCH BASIN STORM DRAIN CULVERT STORM DRAIN MANHOLE co SSMH SDMH Washington State Chapter A D2 3 BLOCK WGVFM WGVFMP WGVM WGVMP WARV WARVP WBOV WBOVP WCKV WCKVP WPV WPVP WCAP WCOUP WCOUPP WGP WGPP WRED WREDP WTB WTBP WMET WMETP WFH2 WFH2P WFH3 WFH3P WFL WMJ WHUB WiH BLOCK 55 0 55 SSMH SSMHP SDCB SDCBP SDC SDCP SDMH SDMHP PAGE 2 LAYER WA VALV
101. Volume Section 3 2 2 and 3 2 3 of the DOE Manual as modified herein All stormwater shall be routed through a catch basin with spill control prior to discharging to detention vaults or pipes to facilitate the easy removal of transported sediments and debris B Design Criteria For Detention Vault Tank Setbacks see D4 07 Detention vaults tanks shall not be located underneath any structure e g buildings sheds decks carports retaining walls etc except that under building detention is allowed in the Central Business District in areas of zero lot line or upon approval by the City Detention vaults tanks shall not be located where such facilities interfere with other underground utilities If vaults are constructed above ground they shall be provided with visual screening and landscaping When the design of vaults does not take into account buoyancy or hydrostatic pressure footing drains shall be provided Footing drains shall be backfilled to within two 2 feet of the top of the vault with Gravel Backfill for Drains conforming to Section 9 03 12 4 of the Standard Specifications The gravel backfill shall be protected from contamination by soil fines D4 73 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 When the design of tanks or pipes does not take into account buoyancy underdrains shall be provided Underdrains within the pipe trench shall be backfilled from the bottom of the pipe to the crown with washed rock
102. WITH ENGINEERED DESIGN ONLY REDUNDANT OVERFLOW SYSTEMS ARE RECOMMENDED City of STORM AND SURFACE Bellevue WATER UTILITY ECYCEING SYSTEM c CIS JANUARY 2015 NO SCALE NO NDP 19 DOWNSPOUT COVERED YARD DOWNSPOUT DRAIN WITH SUMP ADAPTER SET FLUSH WITH FINISHED GRADE SLOPE AND SURFACING PER PLAN 10 MIN VEGETATED FLOWPATH OR OTHER STORM FACILITY SEE NOTE 1 POP UP DRAINAGE EMITTER SEE NOTES 29252225957 RRR 22 gt M AAA NAT 55 200000777 N lt lt lt NOTES 1 DESIGN EMITTER TO DISCHARGE ONTO VEGETATED AREA WITH AMENDED SOILS OR OTHER SUITABLE LANDSCAPED AREA INFILTRATION OR DRAINAGE SYSTEM PER THE DOE MANUAL AS MODIFIED HEREIN Cit DO NOT CONNECT FOOTING DRAIN Bell SEE CHAPTER 06 04 HEREIN FOR ALL MATERIALS JANUARY 2015 NO SCALE of STORM AND SURFACE WATER UTILITY NO NDP 20 TOP ROADWAY REVERSE SLOPE SIDEWALK E MINIMUM X lt JANUARY 2015 CONCR SIDEWALK TYPICAL SECTION SE RANSPORTATION STA DETAIL TE 11 EGETATED AREA ITH NATIVE OR ENDED SOILS URB AND GUTTER SEE RANSPORTATION STANDARD ETAI
103. and Outlet NOTE See FHWA no 5 for other possible conditions D4 40 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 10 Headwater Depth For Smooth Interior Pipe Culverts With Inlet Control 10 000 1 2 3 8 000 EXAMPLE 1 D 42 inch 3 0 feet 6 000 eas SQUARE EDGE WITH 5 000 HEADWALL 4 000 Hw HW D feet 3 000 1 2 5 8 8 2 2 1 7 4 2 000 a 22 2 D in feet 1 000 800 600 p a 500 i 400 2 o 52 T 300 au z o 4 z i E20 g gt GROOVE END e _ E PROJECTING e lt 2 100 a gt 80 8 T e 9 50 ENTRANCE a SCALE TYPE W u 30 1 Square edge with x z headwall 20 2 Groove end with 5 headwall 3 Groove end projecting 8 6 To use scale 2 or 3 project 5 horizontally to scale 1 then use straight inclined line through 4 D and Q scales or reverse as 3 illustrated 1 0 D4 41 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 11 Headwater Depth For Corrugated Pipe Culverts With Inlet Control 10 000 1 8 000 EXAMPLE 1 6 000 D 36 inches 3 0 feet 2 5 000 Q 66 cfs 3 4 000 5 6 Hw HW ENTRANCE TYPE z 3 000 D feet 5 1 8 5 4 HEADWALL PLAN u 2 000 2 2 1 6 3 lt 2 2 6 6 a 3 D In feet zm 5 1 000 P 800 E 600 500 400 MITERED CONFORM 300 SLOPE o SECTION i
104. barrel or cistern and a dispersion system pipes hoses or trenches as in Standard Details NDP 18 NDP 19 and NDP 20 Rainwater harvest for reuse can be accomplished with either rain barrels or cisterns Cisterns are larger than rain barrels and can hold a greater volume of rainwater or several rain barrels can be linked together to achieve the desired storage volume for rainwater D6 34 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 1 il lil reuse on site Cisterns with detention can be used for on site stormwater management MRS or flow control MR7 in addition to rainwater harvest and reuse Applicability Storage for irrigating landscaped areas near buildings carports sheds or other structures Optimum reduction in runoff achieved when the overflow is directed to a rain garden bioretention swale or other on site stormwater management BMP Indoor use of recycled water is allowed per the Uniform Plumbing Code as described in the Seattle King County Department of Public Health s Rainwater Harvesting and Connection to Plumbing Fixtures January 30 2007 or current and requires a plumbing permit Canbeusedin residential or non residential applications Limitations The watered landscaped area should ideally be at least one half the area of the roof being collected Storage tanks must drain within 72 hours after a storm event unless sealed against entry by mosquitoes openings must be s
105. be installed on top of and secured to the pipe The Contractor shall furnish and install a No 12 AWG solid copper wire between drainage structures and extend the wire at least one 1 foot into the structure Ends of each storm drain stub at the property line shall be capped and located with a 2 X 4 board embedded to the stub cap with a copper locator wire attached and marked permanently STORM The stub depth shall be indicated on the marker D8 04 3 Storm Drain Trench Trenches shall be excavated to the width depth and grade as set forth in Standard Details herein Material excavated that is unsuitable for backfill shall not be used for filling on or around surface water facilities In paved areas within the public right of way provide a neat vertical cut in existing pavement by saw cutting D8 04 4 Pipe Bedding Pipe bedding shall conform to Section 7 08 3 1 C Bedding the Pipes of the Standard Specifications as modified herein in order to provide uniform support along the entire pipe barrel without load concentration at joint collars or bells D8 2 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Bedding disturbed by pipe movement by removal of shoring or by movement of trench shield or box shall be reconsolidated prior to placing backfill Pipe bedding shall be placed in loose layers and compacted to 90 maximum dry density Lifts not more than 6 inches in thickness shall be placed and compacted along the sides of the
106. be measured at X inches above the grade specified on the plans to allow for settling after the first storm X shall be calculated by depth of BSM multiplied by 0 15 and rounded up to the nearest whole number In areas to be planted with turf place BSM in loose lifts not exceeding 12 inches Compact BSM for turf to a relative compaction of 85 percent of modified maximum dry density ASTM D 1557 where slopes allow as determined by the Engineer Where turf BSM is placed in the 2 foot road shoulder compact to a relative compaction of 90 percent of modified maximum dry density ASTM D 1557 Final BSM depth shall be measured and verified only after final BSM compaction Type 1 Amend Existing On site Soils If existing soils on site are loam sandy loam or loamy sand texture as defined by the USDA texture triangle Figure 3 27 in Volume DOE Manual and free of debris the BSM can be composed of native soils excavated from the site mixed with compost to meet the above specifications On site soil mixing shall not be allowed if soil is saturated or has been subjected to water within 48 hours Projects required to meet MR1 9 After mixing send representative samples to a lab to verify that the BSM meets the specifications listed above Present the manufacturer s certificate of compliance to the Engineer Projects required to meet 1 5 only Use the following table to mix appropriate quantities of on site soils with approved comp
107. be performed at each backfilled structure or for every 50 CY of backfill placed If the structure e g manhole catch basin or inlet is part of a pipeline trench then trench compaction testing frequency governs For mechanical compaction methods hoe pack vibratory roller static roller etc the maximum backfill lift shall not exceed 2 feet between the application of compaction equipment For manual compaction methods all walk behind equipment jump jack etc the maximum backfill lift shall not exceed 1 foot between the application of compaction methods Jetting is not an allowable method to compact the structure backfill Surface restoration shall be as specified in the Right of Way Use Permit and as shown on the approved plans D8 05 3 Adjusting Manholes and Catch Basins to Grade Where shown on the approved plans or as directed by the City existing manholes catch basins and inlets shall be adjusted to conform to finished grade in accordance with Section 7 05 3 1 Adjusting Manholes and Catch Basins to Grade of the Standard Specifications as modified herein Where riser bricks blocks are used to bring the frame to grade the maximum height of the brick shall be two rows If more than two rows of bricks are required a precast riser section shall be used along with no more than two rows of bricks to complete the adjustment Bricks grade rings and risers shall be wetted just prior to being used and laid with sho
108. by Chapter 24 06 065 G of the Storm and Surface Water Utility Code analysis of the following flows for historic forested existing and post development shall be provided to determine flow control and treatment needs For water quality design of wet pool treatment facilities a single event hydrology model or the continuous hydrologic model may be used For the single event hydrologic modeling TR55 SBUH method the water quality design rates and treatment volumes shall be based on D3 14 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 the 6 month 24 hour storm which is assumed to be 72 percent of the 2 year storm 24 hours storms as per Chapter 4 of Volume 5 of the DOE Manual post developed conditions For the continuous hydrologic modeling Ecology approved model for post developed conditions the water quality design flow rate shall be based on the rate that would be capable of treating 91 percent of the annual runoff volume All other water quality designs must be based on the analysis from a continuous hydrologic model If treatment is being provided downstream from an engineered flow control facility that is sized in accordance with the default duration based Ecology standard the water quality design flow rate shall be the 2 year release from the flow control facility The water quality treatment volume shall be based on the 91 percentile 24 hour runoff volume shall be determined using the post developed conditions
109. can be used by the Developer without an engineer Sizing Factors are also presented for runoff treatment and flow control to provide general guidance for conceptual design only The Sizing Factors are presented in Table 6 13 Section D6 03 3 C A Applicability Sizing Factors may not be used to assign partial credit for on site facilities towards flow control or runoff treatment requirements Generalized assumptions were used to develop the Sizing Factors that may result in conservative sizing for some sites Developers have the option to use the Sizing Factors provided in this section or to follow an engineered sizing approach Section D6 03 2 and submit an alternative facility size with supporting engineering calculations for review The required BMP may be sized for on site stormwater management only when flow control and treatment are not required using the Sizing Factors provided in Table 6 13 For most BMPs Sizing Factors are used to calculate the BMP bottom surface area as follows BMP Area Contributing Impervious Area x Sizing Factor 100 Cistern and infiltration trenches represent exceptions for which the sizing factors are used to calculate the required infiltration trench length in feet or cistern volume in gallons respectively Example D6 45 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 To size a rain garden without an underdrain to meet Minimum Requirement 5 with six 6 inches of ponding storage
110. contact the underlying native soil If the native soils road subgrade will have to meet a minimum subgrade compaction requirement compact the native soil to that requirement prior to testing Note that the permeable pavement design guidance recommends compaction not exceed 90 92 Finally lay back the slopes sufficiently to avoid caving and erosion during the test Alternatively consider shoring the sides of the test pit e The horizontal surface area of the bottom of the test pit should be 12 to 32 square feet It may be circular or rectangular but accurately document the size and geometry of the test pit e Install a vertical measuring rod adequate to measure the ponded water depth and that is marked in half inch increments in the center of the pit bottom e Use a rigid pipe with a splash plate on the bottom to convey water to the pit and reduce side wall erosion or excessive disturbance of the pond bottom Excessive erosion and bottom disturbance will result in clogging of the infiltration receptor and yield lower than actual infiltration rates Use a 3 inch diameter pipe for pits on the smaller end of the recommended surface area and a 4 inch pipe for pits on the larger end of the recommended surface area Pre soak period Add water to the pit so that there is standing water for at least 6 hours Maintain the pre soak water level at least 12 inches above the bottom of the pit e At the end of the pre soak period add water to t
111. damage For this reason SPU needs to review plans and apply standard pipe protection procedures for any project in close proximity to or that will cross these pipelines In order to review any such project SPU will need 3 copies of scalable plans that show the proposed improvements as they are located in relation to SPU facilities or electronic plans in pdf format e Names addresses and telephone numbers for the appropriate contact persons of the entity ies responsible for the work including a contact person whom can be reached 24 hours a day e SPU s Record Plans be obtained from the City of Seattle Vault which is located at 47th floor of the City of Seattle Municipal Tower 700 5th Ave Seattle 98124 Phone 206 684 5132 http www seattle gov util Engineering Records_Vault Hours_ amp _Location COS_001833 asp SPU s General Design Requirements e When crossing SPU s pipelines the installed facility should be at a right angle to SPU s pipeline or parallel with the centerline of a controlling road e When crossing SPU s pipelines the vertical separation between the installed facility and SPU s pipelines should be 18 inches for a sewer line and 12 inches for all other facilities over the pipelines The separation should be a minimum of 24 inches for all facilities installed under the pipelines e Whencrossing SPU s pipelines with a water or sewer main of ductile iron pipe d i p one 19 to 20 foot section must be cente
112. depth This results in a series of level plateaus on which to erect the form boards The following equation can be used to reduce the roof area that can be modeled as pasture Al dC X 0 5 dP X Al A2 Where D6 44 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 A roof area draining to up gradient side of structure dC average depth of cut into the soil profile dP average permeable depth of soil over the dispersion area the A horizon plus an additional few inches of the B horizon where roots permeate into ample pore space of soil A2 roof area that can be modeled as pasture the native soil If roof runoff is dispersed down gradient of the structure in accordance with the design criteria and guidelines in Roof Downspout Dispersion Section D6 03 1 F and there is at least 50 feet of vegetated flow path through native material or lawn landscape area that meets the guidelines in Amended Soil Section D6 03 1 D model the tributary roof areas as landscaped area Runoff dispersed up gradient of a garage slab monolithic poured patio or driveway may not be included as applicable infiltration areas for these systems D6 03 3 Sizing Factors for On site Stormwater BMPs Sizing Factors may be used to simplify the design and review of on site BMPs sized to meet on site stormwater management MR5 when runoff treatment and or flow control are not required When used for this purpose these Sizing Factors
113. depth at a site with a native soil design infiltration rate of 0 25 inches per hour use the Sizing Factor of 8 6 percent from Table 6 13 If this rain garden were being sized to manage 10 000 square feet of impervious surface area the required bottom footprint area would be 860 square feet The top footprint area would depend on the total depth and side slopes of the rain garden In order to use these Sizing Factors the BMP must meet all of the specific design requirements e g side slopes freeboard soil characteristics gravel depth in accordance with Section D6 03 1 or D6 03 2 and the respective Standard Detail Developers may linearly interpolate between the design depths evaluated However design infiltration rates for the native soils must be rounded down to the nearest rate in Table 6 13 B Implementation The following describes how the Sizing Factors are to be used to size on site stormwater management BMPs 1 il Roof Downspout Infiltration Trench Sizing Factors for roof infiltration trenches receiving runoff from an impervious surface are provided in Table 6 13 Factors are organized by MR and native soil type Infiltration trenches are sized by linear feet required for a given contributing area rather than by bottom footprint area in square feet required To use these Sizing Factors the roof infiltration trench must meet the general requirements outlined in the DOE Manual Volume Section 3 3 11 Rain Gar
114. determined in accordance with BCC20 25H 175 and associated public rule then no floodplain study is required In this situation if the already determined floodplain covers any portion of the site the boundary of that floodplain and its base flood elevation must be shown on the project s site improvement plan C Approximate Floodplain Study If the proposed project site is on land that is at least 10 feet above the ordinary high water mark or 2 feet above the downstream overflow elevation of a water feature for which the floodplain has not been delineated in accordance with BCC20 25H 175 then an Approximate Floodplain Study may be used to determine an approximate floodplain and base flood elevation D4 26 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 The intent of the Approximate Floodplain Study is to reduce required analysis in those situations where the project site is adjacent to a flood hazard area but by virtue of significant topographical relief is clearly in no danger of flooding The minimum 10 vertical feet of separation from ordinary high water reduces the level of required analysis for those projects adjacent to streams confined to deep channels or ravines or near lakes or wetlands The minimum 2 feet clearance above the downstream overflow elevation is intended to avoid flood hazard areas created by a downstream impoundment of water behind a road fill or in a lake wetland or closed depression Use of the Approximate Flo
115. facilities appurtenant to public easements or tracts shall be given to the City D4 08 3 Easement Width Requirements For pipes and vaults the required utility easement width shall be 1 the minimum value set forth below or 2 determined by extending a line from the bottom edge of the structure or the bottom of the excavation at the outside diameter for pipes at a 1 IV slope until it intercepts the finished grade whichever is greater For pipes up to 18 inches in diameter the minimum easement width shall be 15 feet For pipes vaults greater than 18 inches and less than five 5 feet in width the minimum easement width shall be 20 feet For pipes vaults five 5 feet and greater in width the minimum utility easement width shall be outside dimension plus 15 feet rounded to the nearest whole foot but not less than 20 feet in width For open channels to be maintained by the City the utility easement width shall include the entire width of the channel top of bank to top of bank or width at freeboard elevation plus maintenance access when deemed necessary by the City For privately maintained open channels the private utility easement width shall be at minimum the width of the channel at freeboard elevation For maintenance access roads the minimum access easement width shall be 15 feet Storm drainage facilities shall be located in the center of the easement 20 minimum easement shall be provided between buildings on multi
116. failure remedies Access structures shall be accessible by City owned maintenance equipment such as 5 CY dump trucks and vactor type trucks Visual impact and potential problems such as mosquito breeding landscaping odors etc shall be addressed All lengths and dimensions shall be horizontal distances no slope distances on plans If working in existing streets indicate type of pavement restoration required by authority having jurisdiction or refer to Right of way use permit Dimension existing and new storm drain locations from right of way line and or property line or label stations and offsets Check with Utility Reviewer to determine how surrounding development will affect design e g serve to extreme of property if adjacent property has potential for future development On plans show existing manholes catch basins or give reference distances to existing manholes catch basins near project including manhole catch basin number and invert rim elevations Check with local jurisdiction for necessary permitting requirements Existing storm drain lines to be abandoned shall be filled completely with sand concrete or controlled density fill or removed Manholes connected to lines being abandoned shall be re channeled with 3 000 psi cement concrete D4 1 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 O Storm pipes side and main lines shall not be used for the grounding of electrical systems or for the maintenanc
117. family and commercial sites When passing between any two buildings residential or commercial etc which are 25 apart or less the easement width shall extend the full width between the buildings and the depth of the sewer line shall not exceed 10 D4 08 4 Easement Documentation Requirements See Section D4 08 2 D4 09 PIPE COVERINGS AND ENCASEMENT Al Pipeline Encasement and Crossing 1 D4 90 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Stormwater pipelines shall be encased in a steel or class 52 ductile iron casing when crossing under improvements e g retaining walls where the ability to remove and replace pipe without disturbance to the improvement is needed Casing is required when Crossing under rockeries over four 4 feet high measured from the bottom of the base rock to top of wall Crossing under retaining wall footings over five 5 feet wide Crossing under segmental block crib and reinforced earth type retaining walls and Crossing through retaining walls and pipe is buried Casings shall extend beyond the facing footing and backfill reinforcement zone a minimum of five 5 feet or a distance equal to the depth of the pipe whichever is greater The carrier pipe shall be supported by casing spacers when the casing length exceeds 10 feet Where casing spacers are not used the carrier pipe shall be more than 10 feet in length no pipe joints inside casing If the cover is less than 3 feet b
118. for an 8 inch diameter pipe Retention zone aggregates shall meet requirements per D6 04 1 and shall have a minimum uncompacted depth of one 1 foot without an underdrain or 21 inches with an underdrain Plant Materials Refer to NDP materials Section D6 04 1 for recommended bioretention plants Mulch Layer Refer to NDP materials Section D6 04 1 for mulch requirements Observation Port An observation port Standard Detail NDP 9 must be installed in each bioretention planter for projects required to meet runoff treatment and or flow control and may be combined with the overflow cleanout Overflow Overflow protection can be provided by vertical stand pipes that are connected to under drain systems NDP 8 by horizontal drainage pipes NDP 7 or armored channels NDP 6 installed at the designed maximum ponding elevations Overflow conveyance structures are necessary for all bioretention structures to safely convey flows that exceed the capacity of the facility and to protect downstream natural resources and property to an approved discharge point s D6 26 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Approved discharge points in order of preference include Surface waters Public storm drain pipes Conveyance to approved discharge points in order of preference include Direct pipe connections Ditch and culvert system Gutter or street flow line Surface dispersal Overflows may be to the app
119. four measurements shall be made over a period of one hour The acceptance water test shall be made after backfilling has been completed and compacted and ATB has been placed in areas to be paved D8 09 2 Air Testing The Contractor may use a low pressure air test at his option The following procedures shall be used on conducting the low pressure air test The Contractor shall furnish all facilities and personnel for conducting the test under the observation of the Engineer The equipment and personnel shall be subject to the approval of the Engineer The Contractor may desire to make an air test prior to backfilling for his own purposes However the acceptance air test shall be made after backfilling has been completed and compacted and ATB has been placed in areas to be paved All wyes tees or end of side storm drain stubs shall be plugged with flexible joint caps or acceptable alternate securely fastened to withstand the internal test pressures Such plugs or caps shall be readily removable and their removal shall provide a socket suitable for making a flexible jointed lateral connection or extension No double plugs shall be allowed Immediately following the pipe cleaning the pipe installation shall be tested with low pressure air Air shall be slowly supplied to the plugged pipe installation until the internal air pressure reaches 4 0 pounds per square inch greater than the average back pressure of any groundwater that may submerge
120. higher of the two peak flow rates shall then be used to size the conveyance facility The Tc is computed by summation of the travel times s T of overland flow across separate flow path segments defined by the six categories of land cover from the chart published in 1975 by the Soil Conservation Service shown in Table 3 5 The equation for time of concentration is Tc Ti T Where consecutive flow path segments of different land cover category or having significant difference in flow path slope D3 13 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table3 5 kg Values For Using The Rational Method LAND COVER CATEGORY kg Forest with heavy ground litter and meadow 2 5 Fallow or minimum tillage cultivation 4 7 Short grass pasture and lawns 7 0 Nearly bare ground 10 1 Grassed waterway 15 0 Paved area sheet flow and shallow gutter flow 20 0 Travel time for each segment is computed using the following equation Tt L 60V minutes Note the T through an open water body such as a pond shall be assumed to be zero with this method where L the distance of flow across a given segment feet avg velocity across the land cover feet second Average velocity V is computed using the following equation V ka VSO where kg time of concentration velocity factor feet second see Table 3 5 SO slope of flow path feet feet D3 03 SUMMARY OF DESIGN FLOW When required
121. length is to be based on horizontal distance between center of manholes iii Indicate direction of flow with arrows on end of pipe entering manhole b Profile View 1 List pipe length size material and slope to 4 decimal places ft per ft e g 150 8 PVC S 0 0125 Pipe material can be listed in a plan note in lieu of listing on profile Slope is based on invert elevation OUT of upstream manhole invert elevation INTO downstream manhole and horizontal distance between center of manholes Site Areas Total area Existing and Proposed Pervious and Impervious areas areas within Native Growth Protection Easements NGPE etc on the drainage plan sheet s Hydrologic and Hydraulic Data Design volumes and allowable release discharge rates for flow control and runoff treatment facilities shall be tabulated on the plans Provide space for as built volume and release rates Scale Be consistent and indicate your scale on each sheet using a bar symbol for Plan reproduction integrity Drawings are to be in a scale of 1 10 1 20 or 1 30 for combined utility plans Drawings at 1 40 or 1 50 scale shall show utility plans on separate sheets Architectural scales for utility drawings will not be D2 13 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 10 11 12 13 14 15 16 17 18 19 20 accepted If the scale results in more than three pages of plan sheet
122. on site conditions F Minimal Excavation Foundation Systems Minimal excavation foundation systems are defined as foundations that minimize disturbance to the natural soil profile within the footprint of the structure This preserves most of the hydrologic properties of the native soil Minimal excavation foundation systems are generally a combination of driven piles and a connection component at or above grade The piles allow the foundation system to reach or engage deep load bearing soils without having to dig out and disrupt upper soil layers which infiltrate store and filter stormwater flows Pin foundations are an example of a minimal excavation foundation system i Applicability and perimeter wall configurations for residential or commercial structures up to three stories high Elevated paths and foot bridges in environmentally sensitive areas Can be installed on Hydrologic Soil Group A B outwash and till soils provided that the material is penetrable and will support the intended type of piles Wall configurations are typically used on sites with slopes up to 10 percent and pier configurations are typically used on sites with slopes up to 30 percent v Limitations Prior to design the site soils must be reviewed and described by a licensed geotechnical engineer unless exempt by the City s Plan Review Department The structure shall be designed by a Washington State licensed architect or e
123. or a minimum depth of 18 inches for basic and enhanced water quality treatment or when 5 only applies If native soil meets the BSM aggregate specification in the Section D6 04 1 it may be amended with compost per the specification rather than importing bioretention soil mix materials Filter Criteria or Geotextile Fabric Optional The designer must check for the difference in size of the bioretention soil mixture BSM and the reservoir course to prevent migration on the fine materials from the BSM into the reservoir course The first check is to see if these two materials meet filter criteria as established in the design of seepage control measures in dams and embankments per filter criteria as given in the Design of Small Dams Bureau of Reclamation 1987 See D1 References The following criteria must exist to retain the protected material BSM allow the free movement of water over the protected material and provide sufficient discharge capacity otherwise the designer must provide a properly designed filter or a non woven geotextile approved by the Utility D15 is less than or equal to 5 x D85 and D15 is greater than or equal to 5 x D15 where DI5 is the 15 percentile of the grain size distribution for the reservoir course DI5 is the 15 percentile of the grain size distribution for the BSM D85 is the 85 percentile of the grain size distribution for the BSM When specified by the designer the geotextile fabric shall be
124. performing flood hazard studies for preparing flood insurance maps Other acceptable hydraulic models would include national numeric models meeting the minimum requirements of the Nation Flood Insurance Program for hydraulic models for determining the water surface elevation for riverine analysis as listed on the FEMA website The D4 17 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 professional engineer is responsible for the appropriate application and accuracy of the results and is responsible for the proper selection of the model D4 18 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 3 Ditches Common Sections PROPERTIES OF DITCHES HYDRAULICS af M A ER Slopes ap o ESSE e ue 938 832 35 L s e s B c e re e sis dq 3 2 re so ex sm a so rej se oi isi e so 121 irs Tin a c so n E 4e 1eo 3 1 5 be x tf aa 0585 E re 3 eral pala rf s 09 a 3 2 e i m s 0997 096 b 2 so 1206 x sj iso 2 1265 p i re we es 066 74 0 s 2 2824 059 Dj 73 so 424 1485 1302 20 D
125. pipe to a height of at least 6 inches above the top of the pipe Material shall be carefully worked under the pipe haunches and then compacted Jetting is not an allowable method to compact the bedding materials D8 04 5 Laying Storm Sewer Pipe Laying pipe shall be in accordance with Section 7 08 3 2 B Pipe Laying of the Standard Specifications and include the following Survey line and grade shall be furnished by the Developer in a manner consistent with accepted practices Existing flows shall be diverted away from the pipe segment being worked on by methods approved by the City Pipe shall be lowered into the trench by means of ropes tripod crane or other suitable means Pipe shall not be dropped or handled roughly Pipe shall be inspected for defects prior to use and any defective pipe shall be removed from the job site Tees and other fittings shall be installed as shown on the Standard Details and the approved plans or as otherwise directed by the City These items shall not be backfilled until the City has recorded their exact location D8 04 6 Backfilling Trenches Backfilling shall be accomplished in accordance with Section 2 09 Structure Excavation of the Standard Specifications as modified herein In paved areas trench backfill material shall be compacted to 95 maximum dry density per Section 2 03 3 14 D Compaction and Moisture Control Tests of the Standard Specifications In unpaved areas trench backfill materia
126. prevent erosion Use Compost in the bottom of the Bioretention facilities and use wood chip or other Mulch composed of shredded or chipped hardwood or softwood on bioretention slopes Apply Compost or Mulch on top of the Bioretention Soil Mix layer to a maximum depth of three 3 inches thick for compost or four 4 inches thick for wood chips thicker applications can inhibit proper oxygen and carbon dioxide cycling between the soil and atmosphere after plants have been installed Compost shall meet the following D6 56 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Fine Compost specification Standard Specifications 9 14 4 8 produced according to WAC 173 350 100 Solid Waste Handling Standards Definitions and 173 350 220 Compost Facilities or meeting pathogen and contaminant standards in the above WAC or having the US Composting Council s Seal of Testing Assurance STA Compost suppliers must be a participant in the STA testing program The following compost mixes are approved Cedar Grove compost Maple Valley GroCo Steerco many suppliers Mulch shall be free of weed seeds soil roots and other material that is not trunk or branch wood and bark Mulch shall not include grass clippings decomposing grass clippings are a source of nitrogen and are not recommended for mulch in bioretention areas mineral aggregate or pure bark bark is essentially sterile and inhibits plant establishment As an alt
127. procedures good housekeeping etc The goal of source control BMPs is to keep contaminants associated with a development s activities from entering the storm and surface water system rather than having to remove contaminants later When required by Section 24 06 065 of the Storm and Surface Water Utility Code source control BMPs shall be implemented Source Control BMPs shall be designed and implemented in accordance with Volume IV of the DOE Manual as modified herein Garbage dumpsters shall be designed not to leak Surface water from uncovered garbage dumpster areas shall discharge to the sanitary sewer if meeting the requirements of 53 01 4 of these Standards Any such dumpster area shall be bermed and drainage shall be routed through an oil water separator connected to the sanitary sewer D5 03 RUNOFF TREATMENT BMPS D5 03 1 General All water quality treatment facilities shall be designed in accordance with criteria set forth in Volume V of the DOE Manual as modified herein On site Stormwater Management BMPs are addressed in Chapter D6 of these standards Thresholds for determining the implementation of Treatment Facilities MR 6 versus On Site Stormwater BMPs MR 5 are defined in BCC 24 06 and Section D2 05 of these Standards D5 1 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 In a residential subdivision where the stormwater facilities will be owned and operated by the City runoff from the right of way and private p
128. psi at 25 degrees C HDPP and fittings shall be Joined by the butt fusion process per ASTM D 2657 and the manufacturer s specific recommendations Mechanical bolted flange connections may be used to facilitate pipeline installation HDPP fittings shall be manufactured in accordance with ASTM D 2683 or ASTM D 3261 E Corrugated Polyethylene Tubing CPT Single wall corrugated polyethylene tubing CPT is approved for privately owned and maintained overbank drains only in accordance with Section D4 04 8 B herein CPT shall conform to ASTM F 405 Minimum CPT diameter is four 4 inches and maximum allowed diameter is six 6 inches Fittings for CPT shall be blow molded rotational molded or factory welded Thermoplastic pipe fittings shall meet the requirements set forth in AASHTO M 294 F Corrugated Polypropylene Pipe Double Wall Double wall corrugated polypropylene pipe is approved for use in culvert and storm drainage applications in 12 to 30 inch diameters Polypropylene pipe shall meet ASTM F2736 requirements All joints shall be made with a bell bell or bell and spigot coupling and shall conform to ASTM D3212 using elastomeric gaskets conforming to ASTM F477 All gaskets shall be factory installed on the pipe in accordance with the producer s recommendations D7 02 4 Pipe Bedding For Reinforced Concrete Pipe RCP Corrugated Metal Pipe CMP which includes steel and aluminum and Ductile Iron Pipe DIP b
129. rate shall be equal to the native soil design infiltration rate For imported bioretention soil porosity is 40 percent For compost amended native soil porosity is assumed to be 30 percent Minimum of 18 inches for flow control or water quality treatment In place aggregate porosity Measured infiltration rate with correction factor applied if applicable No only infiltration across the bottom area is modeled All water which enters the facility must be routed through the underdrain in situations with no native infiltration Water stored in the bioretention soil below the underdrain may be allowed to infiltrate in situations where native infiltration is acceptable Overflow elevation set at maximum ponding elevation excluding freeboard May be modeled as weir flow over riser edge or notch Note that total facility depth including freeboard must be sufficient to allow water surface elevation to rise above the overflow elevation to provide sufficient head for discharge When flow control is required either the default method or the demonstrative method can be used to calculate the amount of Flow Control Credit to be attributed to the bioretention planter in order to reduce the size of the downstream flow control facility as described in Section D3 03 The default method typically results in less credit The demonstrative method is described above in this section and involves using the model developed for sizing the bioreten
130. released onto the ground or into streams rivers lakes and other water bodies as a result of historical practices RCRA regulates the disposal of solid and hazardous waste at active and future facilities to protect human health and the environment by ensuring that wastes are managed in an environmentally sound manner EPA maintains a mapping tool that plots the locations of Superfund and RCRA regulated sites http Aaspub epa gov apex cimc f p 255 63 0 To obtain information about whether specific sites have groundwater contamination problems go to the websites for the individual programs A EPA Superfund Program site list http www epa gov superfund sites index htm B EPA RCRA Program site list http www epa gov epawaste hazard correctiveaction facility index htm D4 88 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Ecology manages contaminated sites e g sediment industrial sites hazardous waste sites and leaking underground storage tanks under its Toxics Cleanup Program Facility site locations can be found at Ecology s website http www ecy wa gov fs To obtain information about whether specific sites have groundwater contamination problems go to the toxics Cleanup Program website http www ecy wa gov cleanup html D4 08 EASEMENT REQUIREMENTS D4 08 1 General Section 24 06 085 of the Storm and Surface Water Utility Code defines when easements are required for stormwater facilities and other general
131. runoff volumes peak flow rates and the duration of erosive flows These BMPs are preferred for meeting flow control requirements See Section D3 05 of these Standards for flow control exemptions Full dispersion or full infiltration may be used to satisfy all flow control requirements on residential sites or road projects where design criteria are met Infiltration BMPs may be applied to fully or partially meet flow control requirements Partial infiltration BMPs including infiltration trenches and bioretention with underdrains can also be used to partially or fully satisfy flow control depending on native soil design infiltration rates and facility geometry Rain recycling cisterns with orifice controlled outlets can also be effective at detaining peak flows while rain recycling facilities that incorporate extensive reuse indoor and or outdoor of harvested rainwater can effectively reduce stormwater runoff volumes and peak durations Note indoor use of rainwater must conform to plumbing regulations Finally vegetated roofs can absorb and evapotranspirate some of the rain that falls onto the surface thereby reducing peak flow rates and providing some flow volume reduction Refer to Sections D6 03 1 and D6 03 2 for design sizing construction and maintenance methods for on site BMPs including NDPs Sizing Factors to meet flow control requirements are provided in Section D6 03 3 While these factors may be used as a guideline in preliminary s
132. seeks to preserve are habitat stormwater conveyance and attenuation open space and resource preservation recreation and aesthetics Impacts to natural systems streams lakes wetlands etc shall be minimized in order to ensure hydraulic capacity and water quality D9 02 STREAMS When modifications of a stream channel are included as part of a project such modifications shall not result in reasonably avoidable decreased hydraulic capacity and damage to existing drainage courses drainage facilities streams and surface waters by erosion siltation or sedimentation and water quality degradation and increases in downstream water velocity and deterioration of ground water resources and deterioration of aquatic wildlife habitat all as determined by the City It is the Developer s responsibility to ensure that all stream work be consistent with the floodplain management policies and regulations and as set forth in the Land Use Code 20 25H the Storm and Surface Water Utility Code 24 06 and the Clearing and Grading Code 23 76 All stream work shall be consistent with the requirements of any public agencies other than the City such as the Washington State Department of Fish amp Wildlife the Washington State Department of Ecology and or the Army Corps of Engineers It shall be the responsibility of the Developer to comply with any other agency s requirements Where fish bearing streams are rehabilitated as
133. shall include water stops to prevent leakage Concrete mix designs and placement shall produce compact dense and impervious concrete with smooth faces Admixtures should be considered to minimize porosity All rock pockets voids seams joints cracks and other defects shall be cleaned and repaired to prevent leakage Acceptable repairs include epoxy injection chemical grout injection epoxy grouting and or proprietary concrete repair methods as may be approved by the City Sacking with Portland cement grout will not be allowed All penetrations shall be grouted to prevent leaks Shear gates and valves shall not leak Vaults with footing or underdrain systems If in the opinion of the City workmanship or materials appear to contribute to excessive leakage the vault shall be tested for leakage Vaults shall be filled to the 2 year water surface elevation Pipe plugs shall be inserted into all inlet and outlet piping The maximum allowable leakage shall not exceed one percent 1 of volume below the 2 yr water surface elevation over a 24 hour test period D8 07 FLOW CONTROL INFILTRATION SYSTEMS Construction of infiltration systems shall conform to Chapter 3 3 of the DOE Manual except as modified herein Excavation of infiltration systems shall be done with a backhoe or excavator working at arms length to avoid the compaction and disturbance of the completed infiltration surface The facility site shall be cordoned off so that
134. site conditions between 5 5 and 18 from the DOE Manual Volume III Table 3 9 If the site conditions are unknown or uncertain use a higher correction factor Correction factors are not needed for bioretention facilities infiltration trenches or infiltration drywells Divide the measured infiltration rate by the correction factor The resulting number is the long term infiltration rate design infiltration rate in inches per hour If the measured infiltration rate is greater than 10 inches per hour drains in less than one hour use a maximum design infiltration rate of 10 inches per hour If the measured infiltration rate is less than 0 25 inches per hour takes more than 40 hours to drain a 10 inch deep column of water the site is not suitable for a rain garden or D4 77 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 E bioretention cell If the long term infiltration rate is less than 0 25 inches per hour the site is not suitable for pervious pavement For bioretention facilities the design infiltration rate used to size the facility will be whichever is lower the measured infiltration rate of the native soil beneath the facility site or infiltration rate of the bioretention soil mix layer For infiltration trenches and drywells use the measured infiltration rate To design other infiltration facilities use the long term infiltration rate of the underlying native soil Example The simplified infiltration te
135. sub basin area acres 3 C Values The allowable runoff coefficients to be used in this method are shown in Table 3 3 by type of land cover These values were selected following a review of the values previously acceptable for use in the Rational Method in Bellevue and as described in several engineering handbooks The values for single family residential areas were computed as composite values as illustrated below based on the estimated percentage of coverage by roads roof yards and unimproved areas for each density For drainage basins containing several land cover types the following formula may be used to compute a composite runoff coefficient Cc Cc Cix Ay Cox A2 Cox A Ai where total area acres Ai 2n areas of land cover types C i2n runoff coefficients for each area land cover type D3 11 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table3 3 Runoff Coefficients Values For The Rational Method GENERAL LAND COVERS LAND COVER LAND COVER C Dense forest 0 10 Playgrounds non paved 0 30 Light forest 0 15 Gravel areas 0 80 Pasture 0 20 Pavement and roofs 0 90 Lawns 0 25 Open water pond lakes 1 00 wetlands SINGLE FAMILY RESIDENTIAL AREAS Density is in dwelling units per gross acreage DU GA LAND COVER C LAND COVER C DENSITY DENSITY 0 20 DU GA 1 per 5 ac 0 17 3 00 DU GA 0 42 0 40 DU GA 0 20 3 50 DU GA 0 45 0 80 DU GA 0 27 4 00 DU GA 0 48
136. table is deep soil or rock strata up to 100 feet below a infiltration facility can influence the rate of infiltration Note that only the layers near and above the water table or low permeability zone e g a clay dense glacial till or rock layer need to be considered as the layers below the ground water table or low permeability zone do not significantly influence the rate of infiltration Also note that this equation for estimating Ksat assumes minimal compaction consistent with the use of tracked i e low to moderate ground pressure excavation equipment If the soil layer being characterized has been exposed to heavy compaction e g due to heavy equipment with narrow tracks narrow tires or large lugged high pressure tires the hydraulic conductivity for the layer could be approximately an order of magnitude less than what would be estimated based on grain size characteristics alone Pitt 2003 In such cases compaction effects must be taken into account when estimating hydraulic conductivity For clean uniformly graded sands and gravels the reduction in K 4 due to compaction will be much less than an order of magnitude For well graded sands and gravels with moderate to high silt content the reduction in Ksa will be close to an order of magnitude For soils that contain clay the reduction in Ksa could be greater than an order of magnitude If greater certainty is desired the in situ saturated conductivity of a specific layer can b
137. teret e iei ua D7 7 D7 04 5 Ponds 4 asse REID TA CU Ea UIS iays D7 8 D7 044 Underground Detention Systems incite ee D7 10 07 05 FLOW CONTROL INFILTRATION SYSTEMS D7 11 TABLES Table 7 1 Mix 3 Wet Area Seed MIX aaa D7 10 Table 7 2 Recommended Emergent Wetland Plant Species D7 9 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D7 MATERIALS D7 01 GENERAL D7 01 1 Manufacturer s Certificates of Compliance Contractor shall provide Manufacturer s Certificate of Compliance in accordance with Section 1 06 3 of the Standard Specifications when requested by the City for all pipe fittings precast concrete products castings and manufactured fill materials to be used in the project D7 02 CONVEYANCE SYSTEMS D7 02 1 General D7 02 2 Open Channels Rock riprap for channel armoring shall conform to Section 9 13 of the Standard Specifications Seed mixes for bio swales and roadside ditches are as follows Mix I Dry conditions 30 Colonial Bentgrass 30 Kentucky Bluegrass 20 Tall Fescue 15 Perennial Rye grass 5 White or Red Clover Application Rate 120 Ibs acre 2 High groundwater conditions 30 Creeping Red Fescue 30 Redtop Bentgrass 30 Meadow or Pacific Foxtail 5 Timothy 5 Birdsfoot Trefoil Application Rate 60 Ibs acr
138. the coupler to fit the PVC pipe used Solvent glued Joints are acceptable C End Plug Match the end cap and or pipe plug to fit the PVC pipe used Solvent glued joints are acceptable D Bentonite The manufacturer shall certify that the granular dry bentonite is suitable for sealing monitoring wells for potable water E Well Screen See manufactured slotted pipe Option 1 for Underdrain for Bioretention or Pervious Pavement or Option 3 Perforated PVC Schedule 40 for requirements D6 04 5 Amended Soil Amend soils using materials and techniques to meet BMP T5 13 Post Construction Soil Quality and Depth per the latest version of Guidelines and Resources for implementing Soil Quality and Depth BMP T5 13 at www soilsforsalmon org Permitted Composting Facilities in Washington that Sell Bulk Compost and Soil and Compost Analytical Labs Serving the Northwest from Section Seven are approved D6 04 6 Roof Downspout Dispersion A Pop up Drainage Emitter The following pop up emitters are approved NDS model L422G or Equal B Splash Blocks Place splash block minimum 11 inches wide by 14 inches long or pad of crushed rock 2 feet wide by 3 feet long by 6 inches deep under roof downspouts to direct water to an appropriate vegetated flow path D6 04 7 Rain Recycling A Rain barrels for use for rain recycling in single family applications 50 to 60 gallon storage capacity typical with screened lid
139. the site if there is no detention system per section D4 06 1 Design Requirements for API and CP Separators High Flow Bypass A high flow bypass is required if the separator is not capable of treating the 100 year storm peak runoff rate Bypassing storm flows greater than the treatment capacity of the separator prevents flushing during peak events substantially increases the effectiveness of the oil water separator and reduces size requirements Drainage Area Uncontaminated water roof runoff pervious area runoff etc should not drain to the oil water separator D5 03 7 Phosphorus Treatment All Phosphorus Treatment facilities shall be designed in accordance with criteria set forth in the DOE Manual Volume V Section 3 3 as modified herein Phosphorus treatment is required for land uses with potentially phosphorus rich runoff including but are not limited to nurseries gardening supplies animal care and boarding facilities golf courses turf sports fields livestock stables paddocks and pastures Runoff from all project areas tributary to Larsen Lake Phantom Lake and Lake Sammamish shall require Phosphorus Treatment except areas that typically do not generate pollutants Surfaces that typically do not generate pollutants include roof areas except uncoated metal D5 5 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 roofs that do not receive organic debris and sidewalks Such runoff need not be treated and may bypass th
140. to those the Geotechnical Report amp Stability Analysis Requirements required per Chapter D2 An adequate number of test holes shall be located over the proposed site to substantiate representative conditions for the final layout of the development As a minimum condition one test hole shall be located in each infiltration area for each 5 000 square feet of tributary area runoff to be infiltrated Test hole locations shall be clearly identified in the geotechnical report and labeled on the drainage plan Soil logs must be submitted to describe soil type and depth and a site map shall be submitted showing the location of each test hole Test pits or borings shall extend at least three 3 feet below the bottom of roof downspout systems and five 5 feet below the bottom of all other infiltration facilities Soil logs shall include the depth to the seasonally high ground water table and impervious strata The wet season water table elevation measurements shall be made with a piezometer during the period when the water table elevation is expected to be at its maximum November 15 through April 15 The geotechnical report shall address the potential impact of the infiltration system on downslope areas both on site and off site such as slope stability foundation capacity and other geotechnical information needed to design and assess constructability of the facility and the proximity from building foundations Determine whether there wo
141. twenty five percent 25 of the total structures shall be tested This process shall continue until a series of structures 25 of the total successfully tests with no more than 10 initial failure or until all stuctures have been tested Additional vacuum testing for specific structures in areas susceptible to infiltration shall be required and does not count toward the required 25 The Contractor shall furnish all equipment and labor required including necessary piping hoses pneumatic plugs test vacuum equipment vacuum pump and vacuum plate head vacuum gauge and second timer The vacuum gauge shall have a maximum range of 0 30 inches of mercury Hg and the vacuum gauge intervals shall be 1 2 inch increments The vacuum test shall be performed by the Contractor in the presence of City of Bellevue personnel The Contractor shall furnish test reports of each test to the Engineer D8 11 1 Testing If a coating or lining has been applied to the interior of the manhole the vacuum test must not be performed until the coating or lining has been cured according to the manufacturer s recommendations In addition if it is an existing manhole being tested it must be structurally sound prior to vacuum testing Drop connections shall be installed prior to testing D8 11 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 The vacuum test shall include testing of the seal between the cast iron frame and the concrete cone slab or grade rin
142. whichever is greater 10 feet from property line may be waived if on ROW with city approval or with agreement from adjacent owner 100 feet from contaminated soil or groundwater within 500 feet requires approval by a licensed hydrogeologist Comply with Critical Areas rules and associated buffer requirements No setback requirements If facility meets definition of Structure in LUC 20 50 046 apply setbacks per LUC 20 20 010 Generally a cistern would be considered a structure a rain barrel would not 50 feet from septic tank or drainfield unless discharge location is downhill of drainfield King County Public Health compliance also required Flow path requirements in the design guidelines apply Downhill property line from end of trench 20 feet Even or upslope property line from edge of trench 5 feet or as agreed by adjacent property owner Top of 20 or greater slope 50 feet may be revised with evaluation by geotechnical engineer or qualified geologist or in accordance with applicable Critical Areas Ordinance requirements whichever is greater Septic drainfield 100 feet 30 feet if discharge location is downhill of drainfield King County Public Health compliance also required Drinking water well or spring 100 feet King County Public Health compliance also required Pop up emitter 10 feet Property line 5 feet Structure from finish grade as measured from side of building 5 feet Do not locate underneath any st
143. with watertight rubber boots sand collars manhole adapters or other approved watertight connectors except for 1 concrete 2 ductile iron 3 corrugated metal pipe For 1 2 and 3 above connections shall be made with non shrink Portland Cement Grout to make a watertight connection Manholes catch basins or inlets in easements shall be constructed to provide a stable level grade for a minimum radius of 2 5 feet around the center of the access opening D8 05 2 Backfilling Structures Backfilling shall be accomplished in accordance with Section 2 09 Structure Excavation of the Standard Specifications as modified herein In paved areas backfill material shall be compacted to 95 maximum dry density per D8 4 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Section 2 03 3 14 D Compaction and Moisture Control Tests of the Standard Specifications In unpaved areas backfill material shall be compacted to 90 maximum dry density per Section 2 03 3 14 D Compaction and Moisture Control Tests of the Standard Specifications The Contractor shall arrange for compaction testing to be performed by a certified technician The Contractor shall provide the Engineer with one copy of the compaction test report within 24 hours of the completion of the test Compaction tests shall be made at a maximum of 4 foot depth increments with a minimum of one test for any backfilling less than 4 feet in depth At least one 1 compaction test shall
144. within the City the standards will not apply for all situations Compliance with these standards does not relieve the Developer of the responsibility to apply conservative and sound professional judgment These are minimum standards and are intended to assist but not substitute for competent work by design professionals The Utility may at its sole discretion due to special conditions and or environmental constraints require more stringent requirements than would normally be required under these standards 01 02 DEFINITIONS The following terms as used in this document shall be defined and interpreted below Other terms used in the Standards are defined and interpreted in the Storm and Surface Water Utility Code BCC 24 06 040 and the Clearing and Grading Code BCC 23 76 030 BMP Best Management Practice Contractor The person partnership firm or corporation contracting to do the work under these Documents The term shall also include the Contractor s agents employees and subcontractors Details or Additional Drawings All details or drawings prepared to further explain or amplify the Plans or for the revision of the same all as herein provided Developer Any individual company partnership Joint venture corporation association society or group that has made or intends to make application to the City for permission to construct a surface water system connection or extension to the surfa
145. x 2 200 o lI z z r 9 a 8 100 z 7 e x 80 lt gt 2 5 z PROJECTING o a E SECTION lt 40 4 ui u 30 HW haki ENTRANCE 4 u D SCALE TYPE lt 20 1 Headwall 2 Mitered to conform lt 5 to slope 9 10 3 Projecting 4 8 z 6 H 5 To use scale 2 or 3 project 4 horizontally to scale 1 then use straight inclined line through 3 D and Q scales or reverse as illustrated 2 a 1 0 5 D4 42 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 12 Head For Culverts Pipe W N 0 012 Flowing Full With Outlet Control S u Slope So 1000 z SUBMERGED OUTLET CULVERT FLOWING FULL 5 P d HW H ho LSg 800 120 For outlet crown not submerged compute HW by 6 methods described in the design procedure 500 96 1 0 400 84 300 72 66 200 60 2 54 z 2 48 Lr T Q H100 z lt Lu 219 lt 4 2 X 27 t 5 lt e 36 9 60 33 6 50 30 40 lt 8 ol 27 10 30 24 20 21 18 20 10 15 8 6 12 5 4 4 43 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 13 Head For Culverts Pipe W N 0 024 Flowing Full With Outlet Control 2000 2000 4 2 1000 2 z 5 2 800 EB Slope So gt 6 SUBMERGED OUTLET CULVERT FLOWING FULL 600 120 HW H ho LSo tlet t sub d te HW b 8 500 108 methods described in the design procedure gt 400 96 1 0 3
146. 00 84 200 12 66 2 60 o 54 z 2100 3 Es ge g z 42 u 4 OL eo lt 50 OF 36 5 40 6 SL 9 35 iac 30 wy 30 f 422 a 21 10 18 8 20 6 15 5 x 12 3 2 D4 44 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 14 Critical Depth Of Flow For Circular Culverts y 3 000 0 99 108 2 000 102 99 1 000 90 0 90 500 78 400 72 300 959 66 200 0 70 60 F 400 0 60 54 2 x r 50 i XE 4o SE 0 50 g aE 30 5 8 42 m 20 m 0 40 5 36 10 33 30 I 0 30 27 3 24 2 21 1 Note For all cross sectional shapes dc can be calculated by 0 20 18 trial and error knowing that the quantity Q2T gA 1 0 at critical depth 15 EXAMPLE D 66 inches Q 100cfs d D Ratio 0 50 12 d 0 50 66 inches 33 inches Y 12 inches ft d 2 75 feet D4 45 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 15 Computer Subroutines Bwpipe And Bwculv Variable Definitions ae ee p FLOW DATA VOH VCH HWO TW ea ul gt DXN X FLOW DATA DC Critical Depth ft COEFFICIENTS INLET DATA KE Entrance Coefficient under Outlet Control DN Normal Depth ft Bend Loss Coefficient TW Tailwater Depth ft KJ Junction Loss Coefficient DO Outlet Depth ft K Inlet Control Equation parameter See Table 4 6 DE Entrance Depth ft M Inlet Control Equ
147. 1 00 DU GA 0 30 4 50 DU GA 0 51 1 50 DU GA 0 33 5 00 DU GA 0 54 2 00 DU GA 0 36 5 50 DU GA 0 57 2 50 DU GA 0 39 6 00 DU GA 0 60 For land covers not listed above an area weighted C x At sum should be computed based on the following equation C x Ay Ci x A1 Cox Cy X An where Aa A An the total drainage basin area For use only in determining peak design flow for analyzing and sizing pipes culverts or channels Table 3 4 Coefficients For The Rational Method Ir Equation DESIGN STORM RETURN FREQUENCY YEARS ba 2 year 1 58 0 58 10 year 2 44 0 64 100 year 2 61 0 63 D3 12 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 4 TR Peak Rainfall Intensity The peak rainfall intensity Ig for the specified return frequency design storm is determined using a unit peak rainfall intensity factor ig for a given return frequency design storm using the following equation Ig P ig where P is the total precipitation at the project site for the 24 hour duration design storm event for the given return frequency from the Isopluvial Maps in Figures 3 1 through 3 3 bo the unit peak rainfall intensity factor Tc time of concentration minutes calculated using the method described below only Tc minimum value is 6 3 minutes and ba are coefficients from Table 3 4 used to adjust the equations f
148. 1 Segmental parable D 1c Curbed crowned street D 2 D 3 D 4 D 5 Trapezoidal Isosceles triangular D 6 through D 11 D4 19 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 4 Drainage Ditches Common Sections NOTE Chart based on Manning formula Q 1 49m A R2 3 S17 2 with n 0 030 except D 1C which is based on n 0 015 For other values of n multiply discharge by 0 030 n 1 ge a velocity of 1 ft per sec Example Given Slopez3 3 per 1000 discharge 6 3 c f s n 0 025 1 Fequired Size ditch velocity Solution use chart multiply discharge 6 3 by 03 025 7 56 c f s Point satisfying given conditions D 6A g lies between lines for D 24 and D 2B Select larger of the two ditches in 5 1 this case D 2B Velocity approx 2 1 ft per sec DISCHARGE IH CUBIC FEET PER SECOHD D 5C gt 0 001 0 01 0 1 SLOPE IH FEET PER FOOT D4 20 JANUARY 2015 SURFACE WATER ENGINEERING STANDARDS N S un lt S E 45 pm g N e oh amp q 2 1 z x r 9 SG n co 0 UIS ct 04 urs zP T ES d 9 em E g 44 1 2 10j26J Quis GO UuoissaJdxe joexe esn x u uAA L Ap X X gt 0 JO
149. 11 OR 12 MIN ENTIONAL ENT RESERVOIR COURSE 6 DAM EMBEDM EXTII NTO SUBGRA ES OPTIONAL CHECK DAM NON PERMEABI MATERIAL CDF OR EQUAL 16 16 BEDD RESERVOIR COU L 1 WIDE CONTROLLED D DAM OR INTERCEPTOR REQUIR SAM EXTEND JN GITUDINAL SLOPES gt 2 ecc HECK DAMS BASED ON SLOP bs E cay ne VE DESIGN AVERAGE PONDI EFORE OVERTOPPING DAM ATE STORAGE VOLUME BETW AND SLOPE FOR MODELING UDINAL SLOPE MAXIMUM VAR Se Bellevue WATER UTILITY EARING COURSE MATERIAL P idi N RD DETAI 11 AND U S D INTERCEPTOR ON SLOPES NO NDP 15 JANUARY 2015 NO SCALE TEST PLUG EXPANDING RVIOUS PAVEM R STANDARD AND INSIALL CLEAN R EMOVABLE COVER AND RTATION S
150. 2 40 1010 0 40 82 80 1020 0 40 83 20 1030 0 40 83 60 1040 0 40 84 00 1050 0 40 84 40 1060 0 40 84 80 1070 0 40 85 20 1080 0 40 85 60 1090 0 40 86 00 1100 0 40 86 40 1110 0 40 86 80 1120 0 40 87 20 1130 0 40 87 60 1140 0 40 88 00 1150 0 40 88 40 1160 0 40 88 80 1170 0 40 89 20 1180 0 40 89 60 1190 0 40 90 00 1200 0 40 90 40 1210 0 40 90 80 1220 0 40 91 20 1230 0 40 91 60 1240 0 40 92 00 1250 0 40 92 40 1260 0 40 92 80 1270 0 40 93 20 1280 0 40 93 60 1290 0 40 94 00 1300 0 40 94 40 D3 6 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 TABLE 3 2 24 Hour Design Storm Hyetograph Values Cont Time from Beginning Percent Cumulative Percent of Storm Rainfall Rainfall 1310 0 40 94 80 1320 0 40 95 20 1330 0 40 95 60 1340 0 40 96 00 1350 0 40 96 40 1360 0 40 96 80 1370 0 40 97 20 1380 0 40 97 60 1390 0 40 98 00 1400 0 40 98 40 1410 0 40 98 80 1420 0 40 99 20 1430 0 40 99 60 1440 0 40 100 00 Table 1 1 24 hour Design Storm Hyetograph Values from Stormwater Management Manual for the Puget Sound Department of Ecology 1992 D3 7 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 3 1 2 Year 24 Hour Precipitation FIGURE 3 1 2 Year 24 Hour Precipitation Eq 4 LA gt Legend Isopluvial of 2 Year 24 Hour Total Precipitation in Inches ZZ City Limits D3 8 SURFACE WATER ENGIN
151. 2 INCH 0 20 INCH 0 12 INCH 0 12 INCH 0 12 INCH 0 24 INCH PAGE 12 COLOR LAYER YELLOW SF INFO EXST TXT YELLOW SV NORA EXST TXT GREEN RE TITL EXST TXT CYAN RE INST PROP TXT CYAN SS INST PROP TXT CYAN WA INST PROP TXT GREEN RE STRT EXST TXT READ APWADOC2 DOC FOR MORE INFORMATION ON SYMBOL LINETYPE INSERTION AND USE OF APWA MENUS BP we de go ABOVE BLOCK NAME IS FL 6 COMPOSITE LINETYPES ARE DRAWN USING LISP ROUTINES IN APWA MENUS IS TO INSERT BLOCKS ALONG CONTINUOUS LINES AS FOLLOWS LINETYPE BLOCK SPACING INCHES EXISTING FENCE FP 1 0 PROPOSED FENCE FP 1 0 EXISTING GUARDRAIL GR 1 0 PROPOSED GUARDRAIL GRP 1 0 EXISTING RAILROAD RR 0 5 EXISTING RETAINING WALL EW 0 25 PROPOSED RETAINING WALL PW 0 25 DEPRESSION CONTOUR DEP 0 1 LIMITED ACCESS R O W LA 0 1 7 UNEWEIGHTS ARE BASED ON DISPOSABLE LIQUID INK PLOTTER POINT SIZES COLOR PEN SIZE NUMBER YELLOW 0 25 3x0 MAGENTA 0 35 o RED WHITE CYAN 0 5 1 GREEN 0 7 2 1 2 American Washington Public Works State Association Chapter A D2 13 INSERT MON OR MON IN CASE SYMBOLS INTO CENTER OF MONUMENTED SECTION CORNERS USE WATER VALVE AND FITTING SYMBOLS FOR SEWER FORCEMAIN VALVES AND FITTINGS LINETYPES ARE LOADED FROM THE APWALIN2 LIN LINETYPE FILE DITCH LINETYPE FLOW DIRECTION ARROW MUST BE INSERTED AT ENDS OF DASHED LINES AS SHOWN ALTERNATE METHOD es City of Se Relleviie Font size on 11 by 17 drawings all
152. 3 D4 or D5 of these Standards to proceed with standard requirements This process may be repeated for developed pervious areas lawns landscaping if additional runoff mitigation is required D6 10 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 6 5 On site Stormwater BMP Selection Matrix Step 1 Characterize Site Infiltration Step 2 Site Layout and Use Step 3 Runoff Sources and BMP Selection Capabilities Driveway Finished Street Parking Slope Design Use of Proposed Lot not High Infiltration BMP Location Vehicle Traffic Pedestrian Bike Landscape or Rate Roof Area Hardscape Lawn 0 15 Slope Natural Splash Block Pop up Concentrated or Concentrated or Amended Vegetation Emitter Sheet Flow Sheet Flow Sheet Flow Soils 20 25 Dispersion Rain Dispersion Dispersion Reverse Concentrated inch hour Recycling Minimal Slope Sidewalk or Sheet Flow Infiltration Excavation Foundation Dispersion Landscape Lawn Roof Downspout Amended Soils Amended Soils Amended Infiltration Roof Concentrated or Concentrated or Soils Downspout Dispersion Sheet Flow Sheet Flow Bioretention Rain Recycling Dispersion Dispersion Pervious Bioretention Sheet Flow Bioretention Bioretention Pavement 3 Dispersion Perforated Pervious Pervious Pavement Stub out Connection Pavement Reverse Slope Minimal Excavation Sidewalk Minimal Foundation Excavation Foundation Pedestrian Bike Roof Downspout
153. 3 W x 0 090 T shall be used Pipe supports shall be fastened to the structure wall with 5 8 inch stainless steel expansion bolts or lag and shield Orifice plates shall be fabricated from aluminum plate 0 125 high density polyethylene HDPE sheeting 0 25 or PVC sheeting 0 25 Orifice plates shall be bolted to the flange on the flow restrictor with stainless steel hardware Orifices may be fabricated by drilling the specified diameter hole in an end cap D7 7 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Protective screening for orifices less than one 1 inch in diameter shall be hot dipped galvanized 0 5 x 0 5 hardware cloth or polymer geo grid with the approximate same size openings D7 04 3 Ponds Embankment material for detention ponds shall conform to the guidelines set forth in Chapter 4 4 of the DOE Manual and Dam Safety Guidelines Part IV Design and Construction Chapter 3 Geotechnical Issues Seed mixes for normally dry detention ponds are as follows Mix 1 Dry conditions 30 Colonial Bentgrass 30 Kentucky Bluegrass 20 Tall Fescue 15 Perennial Rye grass 5 White or Red Clover Application Rate 120 Ibs acre Mix 2 High groundwater conditions 30 Creeping Red Fescue 30 Redtop Bentgrass 30 Meadow or Pacific Foxtail 5 Timothy 5 Birdsfoot Trefoil Application Rate 60 Ibs acre Mix 3 is the seed mix for normally wet detention ponds and is shown in T
154. 4 d AS NECESSARY ADJUSTMENT RINGS NS NAN CES zg 4 5 40 PVC STAND SCREEN SEE DETAIL ABOVE NOTE USED ONLY WHEN City of STORM AND SURFACE ALLOWED BY THE CITY WATER UTILITY Bellevue SUMP WIIH FIS JANUARY 2015 NO SCALE PRECAST CONCRETE SLAB FOR 84 CATCH BASIN 100 DIAMETER PLACE CEMENT MORTAR SEAL BETWEEN TOP SLAB AND CORRUGATED MANHOLE HANDHOLD CORRUGATED METAL MANHOLE PER STANDARD DETAIL D 24 ECCENTRIC SECTION NOTES 1 TOP SLAB SHALL BE RATED FOR HS 20 LOADING OUTSIDE OF ALL JOINTS RINGS RISERS AND 48 DIA CORRUGATED MANHOLE OFFSET ACCESS OPENING AS SHOWN LOCATE OVER ACCESS LADDER 24 BOLT LOCKING RING AND COVER PER STANDARDS ADJUSTMENT RINGS AS NECESSARY CRUSHED SURFACING TOP COURSE PER WSDOT STD SPEC 9 03 9 3 COMPACT TO 95 MAX DENSITY PER ASTM D1557 2 APPLY NON SHRINK GROUT TO INSIDE AND 3 City Qf STORM AND SURFACE FRAMES LADDER SHALL BE WELDED TO INSIDE OF MANHOLE FIELD APPLY ASPHALT COATING TO WELDS Bellevue TRAFFIC B CO JANUARY 2015 NO SCALE R WATER UTILITY EARING ACCESS FO METAL MANHOL BUILDING OR OUTSIDE OF R O W WALL C O PIPE MID STATES DIAMETER PLASTIC BOX 4 5 1118 18 6 MSBCF 1324 12 J 8
155. 4 Gravel Backfill for Drains of the Standard Specifications For precast vaults sealing between riser sections shall be accomplished by placing Portland cement mortar compressible neoprene foam gaskets asphaltic mastic material or asphalt impregnated gasket materials between sections as recommended by the manufacturer to produce a water tight seal Tanks or Pipe Only the pipe materials listed are approved for use in stormwater detention facilities Materials shall meet the following sections of the Standard Specifications and as modified herein Reinforced Concrete Pipe RCP CI 3 min 9 05 7 2 Corrugated Aluminum Culvert Pipe 9 05 5 Corrugated Steel Culvert Pipe Treatment 1 9 05 4 Corrugated Steel Pipe Arch Treatment 1 9 05 4 Corrugated Polyethylene Pipe 9 05 20 All corrugated metal pipe and pipe arch shall be furnished with annular ends neoprene gaskets and lap type couplings Underdrains shall be a minimum of 6 inch diameter PolyVinyl chloride PVC pipe SDR 35 with laser cut slotted perforations Underdrains within the pipe trench shall be backfilled with material which conforms to Section 9 03 12 4 Gravel Backfill for Drains of the Standard Specifications D7 10 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 For Reinforced Concrete Pipe RCP and other rigid pipe bedding material shall be in accordance with Section 9 03 12 3 Gravel Backfill for Pipe Bedding of the Standard Specifications For Corru
156. 61 R 4351 C R 4353 R 4351 B R 4351 D Olympic Foundry MH25 PERVIOUS PAVEMENT MATERIALS Wearing Course Invisible Structures GrassPave2 Presto Geosystems Uni Eco Stone Uni Ecoloc Eco Priori Hastings Check Block Grasscrete Turfstone Geoblock 5150 Tufftrack Grassroad Pavers Grassy Pavers Invisible Structures Gravelpave2 Turf amp Gravel Pavers Aqua Pave Old Countrystone Aqua Pave Standard Aqua Pave Venetian Cobble A D4 1 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Geotextile products Geotextile Nonwoven polypropylene Ling Industrial Fabrics Inc model 275EX TNS Advantaged Technologies models R060 R080 Carthage Mills models FX60HS FX70HS FX80HS DuPont DeNemours model SF65 Ten Carte Mirafi models 600 FW700 1120N Skaps Industries LLC model GT60 Propex Inc model GeoTex801 Underdrain Materials for Bioretention or Pervious Pavement Pipe Manufacturers Johnson CertainTeed Corporation Lodi CA Couplers Fernco Davision MI OBSERVATION PORTS FOR PERVIOUS PAVEMENTS OR BIORETENTION Expandable pipe plugs Cherne Gripper plugs models MC 99930 MC 99929 MC 99931 MC 99935 ROOF DOWNSPOUT DISPERSION MATERIALS Pop up drainage emitter NDS model L422G RAIN RECYCLING MATERIALS Rain barrels Chicago model 18122 Suncast model RB5010PK Emsco model 2771 1 Mayne model 5847WH Fiskars model 5997 STORM DRAIN PIPE AND CULVERT MATERIALS All manufacturers that meet the performance require
157. 8 96 DIAM 12 lt NO 00 lt H A 2 gt lt 96 NOTES d ANHOLES SHALL BE CONSTRUCTED IN ACCORDANCE WITH AASHTO M199 UNLESS OTHERWISE SHOWN ON PLANS OR NOTED IN THE STANDARD SPECIFICATIONS ANDHOLDS IN ADJUSTMENT SECTION SHALL HAVE 3 MIN CLEARANCE STEPS IN MANHOLE SHALL HAVE 6 IN CLEARANCE SEE STD DTL D 15 MANHOLE DETAILS MANHOLDS SHALL BE PLACED IN ALTERNATING GRADE RINGS OR LEVELING BRICK COURSE WITH A MIN OF ONE HAND HOLD BETWEEN THE LAST STEP AND THE TOP OF THE MANHOLE ON REINFORCED CONCRETE 1 ANNEL AND SHELF SHALL BE CLASS 3000 ALL PRECAST CONCRETE SHALL E CLASS 4000 RECAST BASES SHALL BE FURNISHED WITH CUTOUTS OR KNOCKOUTS KNOCKOUTS SHALL HAVE WALL THICKNESS OF 2 MIN UNUSED KNOCKOUTS NEED NOT GROUTED IF WALL IS LEFT INTACT PIPES ALL BE INSTALLED LY IN FACTORY KNOCKOUTS UNLESS OTHERWISE APPROVED BY THE ENGINEER OCKOUT OR CUTOUT ZE SHALL EQUAL PIPE OUTER DIAM PLUS MANHOLE WALL THICKNESS OLE SIZE BE 60 FOR ANHOLE 84 FOR 96 MANHOLE IN DISTANCE BETWEEN HOLES SHALL BE 12 ANHOLE RINGS AND COVERS SHALL BE IN ACCORDANCE WITH SEC 7 05 OF THE STANDARD SPECIFICATIONS ATING SURFACES SHALL BE FINISHED TO ASSURE FIT WITH ANY COVER POSITION R FOR GHTS OF 12 OR LESS MIN SOIL BEARING VALUE SHALL EQUAL 3 300 POUNDS PER SQUARE FO
158. 89 0 00033 0 000246 0 00675 72 38 358 90 Col 1 Depth of flow ft assigned from 6 to 2 feet Col 2 Water area f corresponding to depth y in Col 1 Col 3 Hydraulic radius ft corresponding to y in Col 1 Col 4 Four thirds power of the hydraulic radius Col 5 Mean velocity fps obtained by dividing 30 cfs by the water area in Col 2 Col 6 Velocity head ft Col 7 Specific energy ft obtained by adding the velocity head in Col 6 to depth of flow in Col 1 Col 8 Change of specific energy ft equal to the difference between the E value in Col 7 and that of the previous step Col 9 Friction slope S computed from V as given in Col 5 and in Col 4 Col 10 Average friction slope between the steps equal to the arithmetic mean of the friction slope just computed in Col 9 and that of the previous step Col 11 Difference between the bottom slope So and the average friction slope S Col 12 Length of the reach ft between the consecutive steps computed by Ax AEKS Sp or by dividing the value in Col 8 by the value in Col 11 Col 13 Distance from the beginning point to the section under consideration This is equal to the cumulative sum of the values in Col 12 computed for previous steps D4 23 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 8 BWCHAN Computer Subroutine Variable Definitions 2 SF1 SF2 X 2 E1 v E G L 1 EC 20 V
159. A PERF PVC PIPE W NOT TO BE USED IN CRITICAL AREA BUFFERS OR STEEP SLOPES gt 25 DREPI Cit of STORM AND SURFACE Bel evue WATER UTILITY P 2 MIN 4 ESIDENTIAL ROOF DOWNSPOUT SECTION ERFORATED PIPE CONNECTION JANUARY 2015 NO SCALE NO NDP 25 APPENDIX D 2 DRAFTING STANDARDS Also available AutoCAD format at http www bellevuewa gov utilities_maps_forms htm WATERSYMBOLS Pe PAGE 1 SANITARY STORM SEWER SYMBOLIS 2 SURVEY SYMBOLS SURFACE FEATURES LANDSCAPE SYMBODLS PAGE 4 SIGNALDZATION SYMBOLS 5 CHANNELIZATION SYMBOLS 7 GAS POWER TELEPHONE SYMBOLS eine eens elas PAGE 8 SURFACE FEATURES LINE TYPES I ane ae Saa due enu PAGE 9 SURVEY LINE TYPES 10 UTILITIES LINE TYPES ace PAGE 11 TEXT STYLES E PAGE 12 NOTES 12 TEXT AND SYMBOL SIZE
160. ANDARD DETAIL 11 OR 12 MIN SSD SEE AIL A STANDARD AIL NDP 3 FALL TO APPROVED LOCATION PER CITY OF BELLEVUE ENGINEERING STANDARDS CURB amp GUTTER PER TRANSPORTATION STANDARD DETAIL TE 10 PERVIOUS PAVEMENT PER SECTION A A STANDARD DETAIL 11 CONCRETE SID CURB amp GUTT STREET 4 CRUSHED SURFACING TOP COURSE PER TRANSPORTATION STANDARD DETAIL 11 SECTION STRE TREE AND GRATE PER PARKS STANDARD DETAIL 34 PERVIOUS PERVIOUS PAVEM SEE NOTE 1 4 MIN SSD SEE DETAIL A STANDARD DETAIL NDP 3 DAM NON POROUS MATERIAL IF REQUIRED PER 16 X16 BEDDING STANDARD DETAIL 15 NOTE 1 6 MIN DEPTH IN THE TREE PIT APPLIES TO PERVIOUS CEMENT CONCRETE SIDEWALK j City of STORM AND SURFACE WATER UTILITIES ONLY IF OTHER PERVIOUS PAVER 2 w Bellevue MATERIAL USED NO MIN DISTANCE IS SOFA REQUIRED ING RVIOUS PAVEMENT SI IN PLANTING STRI NO SCALE JANUARY 2015 PERVIOUS PAVEMENT SIDEWALK ADJACENT CURB VARIES E STD DTL NDP 11 PLANTER STRIP OPTIONAL SUBGRADE MATE GEOTEXTILE FABRIC CHAPTER D6 04 OPTIONAL SEE F ERVIOUS CONCRETE 5 MIN DEPTH SEE STD DTL
161. ANGE DEPTH TO TOP OF BASE SECTION OR BASE EXTENSION POLYTAPE BETWEEN TOP AND BASE SECTIONS VALVE BOX BASE SECTION WITH EXTENSION PIECE IF REQUIRED TO BRING OPERATING NUT EXTENSION TO WITHIN 2 TO 3 OF GROUND SURFACE PAVED AREAS UNPAVED AREAS NOTES 1 ALL PARTS SHALL BE CAST OR DUCTILE IRON AND COATED WITH ASPHALTIC VARNISH OLYMPIC FOUNDRY INC VB045 LID TOP AND BASE RICH VANRICH CASTING CORP TOP SECTION AND LID 4045 City of AND SURFAC WITH RICH STANDARD BASE Bellevue WATER UTILITY 4 12 ADJUSTING SLEEVE 044A BOX AND NSTALLATION JANUARY 2015 NO SCALE NO D 29A 2 SQUARE OPERATING E 4 1 4 DIA a 1 8 MIN THICKNESS 1 8 MIN THICKNESS x 1 4 INSIDE MEASUREMENT 2 1 4 DEPTH VALVE OPERATING NUT EXTENSION EXTENSIONS ARE REQUIRED WHEN THE VALVE NUT IS MORE THAN THREE 3 FEET BELOW FINISHED GRADE EXTENSIONS ARE TO BE A MINIMUM OF ONE 1 FOOT LONG ONLY ONE EXTENSION TO BE USED PER VALVE NOTES 1 ALL EXTENSIONS ARE TO BE MADE OF STEEL SIZED AS NOTED AND HOT DIPPED GALVANIZED Cit of STORM AND SURFACE WATER UTILITY Bellevue RATING ON JANUARY 2015 NO SCALE NO D 29B 18 DIA MIN SOD OR SEED VATION VI OUTLET RIM 24 DIAMETER POND INTERIOR UP 100 YEAR BOLT LOCKING COVER SEE NOTE 2 EMBANKMENT
162. AS input and output files printouts of these files and a detailed written description of the modeling approach and findings Previous Floodplain Studies If differences exist between a study previously approved by the Utility and the applicant s design engineer s calculated hydraulic floodways or flood profiles the design engineer shall provide justification and obtain Utility approval for these differences Zero Rise Calculation For a zero rise analysis the flow profile for the existing and proposed site conditions shall be computed and reported to the nearest 0 01 foot A zero rise analysis requires only comparisons of the computed water surface elevations and energy grade lines for the existing and proposed conditions Such comparisons are independent of natural dynamics and are not limited by the accuracy of the model s absolute water surface predictions Adequacy of Hydraulic Model At a minimum the Utility considers the following factors when determining the adequacy of the hydraulic model and flow profiles for use in floodway analysis Cross section spacing Differences in energy grade Note Significant differences in the energy grade from cross section to cross section are an indication that cross sections should be more closely spaced or that other inaccuracies exist in the hydraulic model Methods for analyzing the hydraulics of structures such as bridges and culverts Lack of flow continuity Use of a gra
163. ATER QUALITY TABLE OF CONTENTS D5 01 GENERA Dyosa uit S D MEUS D5 1 D5 02 SOURCE CONTROL aak 05 1 05 03 RUNOFF TREATMENT BMBS D5 1 95 031 Generale d D5 1 195 0352 Treatment Facility Sizing 05 2 D5 03 3 Water Quality Design Flow 0 D5 2 D5 03 4 Treatment Facility 1 D5 3 D5 03 5 Treatment Facility Maintenance D5 3 D5 03 6 Oil Control M D5 5 D5 203 7 Phosphorus Treated needed D5 5 D5 05 3 Buhanced Preatmelt a eco naci Mist hata qha een Q D5 6 D5 05 9 B sic Treatment a s na a eae e aue D5 6 TABLE No tables in this chapter FIGURE Figure 5 1 Treatment Facility Selection Flow D5 4 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D5 WATER QUALITY BEST MANAGEMENT PRACTICES D5 01 GENERAL When required by Section 24 06 065 of the Storm and Surface Water Utility Code and Section D2 05 of these Standards surface water Best Management Practices BMPs shall be
164. ATION 13 SOD TYPICAL SECTION OTES D W SIZED TO ACCOMMODATE DESIGN FLOW ROUND ALL CORNERS FOR EASE OF MOWING MAXIMUM DESIGN VELOCITY SHALL BE 4 F P S LOCATE ALL SEDIMENT TRAPS FOR EASE OF MAINTENANCE City of STORM AND SURFACE Bellevue WATER UTILITY GRASS LINED DITCH JANUARY 2015 NO SCALE SIDEWALK TOOL A CONIRACIION JOINI OVER CROWN GUTTER 6 CURB FLOWLINE DUCTILE IRON PIPE CLASS 52 4 THICKENED CURB AND SIDEWALK SECTION UNDER PIPE NOTES 1 SINGLE FAMILY RESIDENTIAL CONSTRUCTION ONLY 2 REQUIRES RIGHT OF WAY APPROVAL 5 PIPE AND CONTRACTION JOINT RUN PERPENDICULAR TO SIDEWALK City of STORM AND SURFACE B el evue WATER UTILITY EWALK DRAIN JANUARY 2015 NO SCALE JANUARY 2015 SPLITTER BLOCK 48 DIA TYPE MANHOLE BASE MIN SIZE NO SCALE DEBRIS CAGE H TYP Cit of STORM AND SURFACE Bellevue 4 8 QUARRY SPALLS RECYCLED CONCRETE OR LIGHT LOOSE RIPRAP AS REQUIRED WATER UTILITY DISSI 4 CLEARANCE SPACING FLAT BAR LEGS 4 TOTAL L PER BAND 3 4 DIAM SMOOTH ROUND BARS EQUALLY SPACED BARS SHALL BE WELDED TO UPPER amp LOWER BANDS 3 4 DIAM SMOOTH ROUND BARS EQUALLY SPAGED 4 MAX NOTE BARS OMITTED ON DRAWING UPPER BAND 3 4 DIAM BAR 1
165. AXIMUM WATER LEVEL SINCE THE LAST READING EXTEND OBSERVATION PORT WATER UTILITY RINSE DOWN CORK DUST ACROSS BOTTOM OF FACILITY AFTER YOU RECORD THE MEASUREMENT REMOVE THE CORK DUST FROM THE CREST GAGE RINSE THE INSIDE WALLS OF THE OBSERVATION PORT CASING WITH A SQUIRT BOTTLE PLACE THE CREST GAGE IN THE OBSERVATION PORT REPLACE THE OBSERVATION PORT TOP CAP OBSERVATION PORT INSTALL WITHIN THE 3 PVC OBSERVATION PORT FOR BIORETENTION NO SCALE NO NDP 9 JANUARY 2015 CURB DOWEL OPTIONAL MODIFIED CONC EAMBED COBBLES PER CURB amp GUTTI TANDARD SPECIFICATIONS 03 11 2 2 4 SEE NOT ROPOSED BIORE ER STANDARD D DP 2 5 OR 4A ROAD PAVEM SECTION 14 16 CURB GUTTER LIN TOP OF CURB GUTTER LINE 0 SLOPE BACK OF CURB f mn SLOPE EET SLOPE SECTION MODIFIED CONC LOW TO BIORE TE ER STANDARD D CURB amp GUTT DP 2 3 OR 4A ROA SWALE RAIN GARDEN PAVEM 2 5 5 Wy SWALE RAIN GARDEN BOTTOM PAK gt gt gt y F NI x A Rl VAN x lt
166. BE 12 MIN CONCRETE COLLAR CL 3000 STEEL BOTTOM 8 GAUGE BOTTOM PLATE WELDED TO RISER NOTES ALL METAL PARTS AND SURFACES MUST BE MADE OF CORROSION RESISTANT MATERIAL PIPES SHALL BE ASPHALT COATED TREATMENT 1 GALVANIZED STEEL OR ALUMINIZED STEEL NOT FOR USE IN ROADWAYS DRIVEWAYS AND OTHER VEHICULAR TRAFFIC AREAS FOR USE IN DETENTION PIPES ONLY APPLY NON SHRINK GROUT TO INSIDE AND OUTSIDE OF ALL JOINTS RISERS RINGS AND FRAMES 1 STORM AND SURFACE 2 WATER UTILITY ETAL MANHOLE JANUARY 2015 NO SCALE EQUIRED PAVEM ESIORATION SE SAWCUT TYP F WAY USE 12 MIN SURFACE 5 AS EXIST SPECIFIED ON PLANS OR SURFACE AS DIRECTED BY ENGINEER 9 lt Z ESS 4 4 CRUSHED SURFACING T Hin Oe ER WSDOT STD SPEC 9 05 COMPACT 95 ENSITY lt 99 52505 9 lt gt sS 59050 SES SESS lt gt gt gt gt lt gt lt gt o0 x 2224 Z 2 5 lt gt 9 Xx Q2 Q2 SS GRAVEL BORROW PE WSDOT STD SPEC 9 05 OR SUITABLE EXCAVATE MATERIAL COMPACT 90 OF MAX DENS Q2 X
167. Be Exceeded D4 04 3 Clearances Other Utilities A All clearances listed below are from edge to edge of each pipe B Check for crossing or parallel utilities Maintain minimum vertical horizontal clearances Avoid crossing at highly acute angles the smallest angle measure between utilities should be between 45 and 90 degrees For crossings of sanitary sewer pipes the DOE criteria will apply C Horizontal clearances from storm main amp NDPs Cable TV 5 5 Power 5 Sewer 5 Telephone Fiber Optics 5 Water 5 D Vertical clearances from storm main amp NDPs Cable TV 1 Gas 1 Power 1 Sewer 1 Telephone Fiber Optics 1 Water 1 E Where storm pipes cross over or below a water main one full length of pipe shall be used with the pipes centered for maximum joint separation F Send a letter and preliminary plan to existing utilities to inform them of new construction Request as built information and incorporate into plans At a minimum the following utilities should be contacted cable television natural gas power sanitary sewer telephone water and telecommunications companies G Seattle Public Utilities Transmission Pipelines See standards for utilities installed in proximity of Seattle Public Utilities Transmission Pipelines in Appendix D 5 Storm and Surface Water Reference Standards D4 04 4 Open Channel Design Criteria A General The methods and criteria below have been adapted from the 2009
168. CITY OF BELLEVUE UTILITIES DEPARTMENT Ow O m m 2 gt E rd TS HING SN N STORM AND SURFACE WATER ENGINEERING STANDARDS January 2015 http www bellevuewa gov utilities_codes_standards_intro htm SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 TABLE OF CONTENTS CHAPTER D1 GENERAL REQUIREMENTS D1 01 GENERAL CHAPTER D2 THRESHOLDS AND PLAN SUBMITTAL D2 01 GENERAL CHAPTER D3 HYDROLOGIC ANALYSIS D3 01 GENERAL D3 05 FLOW CONTROL EXEMPTIONS D3 06 SOIL TYPES DI 1 DI 1 D1 4 D1 5 D2 1 D2 1 D2 2 D2 2 D2 2 D2 7 D2 12 D2 19 D2 22 D3 1 D3 1 D3 14 D3 15 D3 16 D3 16 SURFACE WATER ENGINEERING STANDARDS D4 01 D4 02 D4 03 D4 04 D4 05 D4 06 D4 07 D4 08 D4 09 D5 01 D5 02 D5 03 D6 01 D6 02 D6 03 D6 04 CHAPTER D4 HYDRAULIC ANALYSIS amp DESIGN GENERAL EASEMENT REQUIREMENTS PIPE COVERINGS AND ENCASEMENT CHAPTER D5 WATER QUALITY BMPs GENERAL CHAPTER D6 ON SITESTORMWATER MANAGEMENT GENERAL JANUARY 2015 D4 1 D4 2 D4 5 D4 6 D4 67 D4 70 D4 94 D4 97 D4 99 D5 1 D5 1 D5 1 D6 1 D6 8 D6 12 D6 54 2015 SURFACE WATER ENGINEERING STANDARDS JANUARY CHAPTER D7 MATERIALS D7 01 GENERAL CHAPTER D8 METHODS OF CONSTRUCTION D8 01 GENERAL D8 03 CONNECTIONS MODIFICATIONS TO PUBLIC DRAINAGE SYSTEM D8 04 CONVEYANCE SYSTEMS D7 1 D7 1 D7 6 D7 9 D7 13 D8 1 D8 1 D8 1 D8 2 D8 4
169. CK SEE NOTE 5 197 MAX SLOPE 4 OR 6 DIA PE Re PIPE W TEE PIPE O D 7 2 8 GRADE BOARD 0 SLOPE L SEE NOT 10 927002009 WASHED ROCK 3 4 1 1 2 WRAP TRENCH SIDES W PERMEABLE GEOTEXTILE LEAVE EXPOSED BOLTS of STORM AND SURFACE WATER UTILITY 1 MIN T MIN 2 x4 SUP POS NOT SECTION CAP OR PLUG ROOF DOWNSPOUT JANUARY 2015 NO SCALE DISP ERSION TR ENCH NDP 22 ROOF ERFLOW ROUTE TO ERGENCY 5 4 OR 6 PERF SEE c O SS INFILTRATION SAFE s TRENCH O STREET DRAINAGE SYSTEM WHERE POSSIBLE L PLAN VIEW 3 DOWNSPOUT O SCALE OVER HERRING BONE RATE OR EQUAL TOP OF DRAIN PIPE 6 DIA CLEAN OUT A amp OBSERVATION WELL AX OVERFLOW ELEV MAX WSE 1 MIN E 0 5 DRAIN 4 OR 6 PERF 5 i KE CA PVC PIPE 2 CMN FS AX WS HARDWAR CLOTH SCREE BOTTOM ONLY
170. COBBLE PER WSDOT 9 03 11 2 2 4 MIN TO TRANSITION FROM INLET OR SPLASH PAD TO BIORETENTION SOIL MIX TO DISSIPATE ENERGY AND OR DISPERSE FLOW INSTALL OBSERVATION PORT PER STANDARD DETAIL NDP 9 IF FLOW CONTROL MR7 AND OR RUNOFF TREATMENT MR6 IS REQUIRED RETENTION ZONE OPTIONAL REQUIRED WITH UNDERDRAIN AND IF NATIVE SOIL INFILTRATION RATE 15 LESS THAN 0 25 HOUR SEE CHAPTER AND STANDARD DETAIL NDP 3 DETAIL A C COMPACT SUBSOILS MUST BE SCARIFIED TO 6 BELOW THE BIORETENTION SOIL SEE CHAPTER D6 04 HEREIN FOR ALL MATERIALS AND SPECIFICATIONS GEOTECHNICAL ANALYSIS AND STORM DRAINAGE REPORT REQUIRED PER SUBMITTAL REQUIREMENTS CHAPTER D2 HEREIN JANUARY 2015 A D n LAYER ye lt City of Bellevue STORM AND SURFACE WATER UTILITY SCALE BIORE TENTION SWALE W UNDERDRAIN ae 1 0 VARIES 1 0 CONCRETE CURB OPTIONAL z RY BIORETENTION SOIL COMPACTED TO 90 DENSITY 6 MIN SSD SEE DETAIL A TO OUTFALL PER CITY OF ENGINEERING STAND MIN BOTTOM SWALE MIN WIDTH 17 MIN 6 FREEBOARD DEPTH ar 6 12 MAX PONDING DEPTH Y MMA W HES T 2 1 Z p EXIST VAR 2 Z Z 3 DEPTH OF 2 7 OR COMPOST LINER OR SOIL BARRIFR 3 OF COMPOST
171. Cover Ground cover or shrubs Shrubs are appropriate only when growth medium is at least 6 inches Length of Rooftop ft The length of the surface flow path to the roof drain Slope of Rooftop ft ft Flat slope should be set to a minimum slope of 0 001 V 1 H 1 000H 1V Discharge from Facility Surface flow interflow and exfiltrated flow groundwater routed to point of compliance D6 41 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 E Reverse Slope Sidewalk Reverse slope sidewalks are standard concrete or asphalt pavement sidewalks which are sloped to drain away from the road and onto adjacent vegetated areas see Standard Details NDP 21 and TE 11 i Applicability Public transportation projects with frontage on parks open space or vegetated areas Public or private walks with adjacent vegetated areas ii Limitations Critical Area restrictions may apply Public transportation projects must have sufficient right of way easement or adjacent city owned property to accommodate the full required width of the vegetated area Private projects may require agreement from the adjacent property owner to allow unconcentrated sheetflow runoff from the surface of the reverse slope sidewalk only to flow onto the vegetated area if applicable ili Design Requirements The maximum width of the reverse slope sidewalk shall be 6 feet The cross slope of the reverse slope sidewalk shall be 2 percent The maximum longit
172. D TREATMENT 1 OR ALUMINIZED COMPLETE CORROSION PROTECTION MUST BE ASSURED APPLY NON SHRINK GROUT TO INSIDE AND OUTSIDE OF JOINTS RINGS RISERS AND FRAMES PENETRATE CARRIER PIPE THROUGH VAULT WALL USE APPROVED WATERTIGHT STRUCTURE ADAPTOR SLIP 5 HORIZONTAL LEG OF FLOW CONTROL TEE INSIDE CARRIER PIPE NO FLOW CONTROL JOINT OUTSIDE OF STRUCTURE 1 STORM AND SURFACE ET City of WATER UTILITY DIA D Bellevue TYPE 2 48 TYPE 2 54 PILL CONT JANUARY 2015 NO SCALE SECTION VIEW OFFSET FRAME SO FRAME AND GRATE OR IS VISIBLE EDGE OF OPENING RING AND COVER AND DIRECTLY OVER THE STEPS 36 DIAMETER ALUMINUM CMP CENTERED AROUND OUTLET OPENING SEE DETAIL MAX DESIGN WSE 9 16 HOLES FOR 1 2 ANCHORS INLET PIPE OUTLET 3 16 x3 ALUMINUM FLAT BAR FULLY WELDED WELDED TO HALF ROUND HALF ROUND DETAIL PLAN VIEW NOTES ALL METAL PARTS AND SURFACES MUST BE CORROSION RESISTANT STEEL HARDWARE SHALL BE GALVANIZED PIPES SHALL BE GALVANIZED ASPHALT COATED TREATMENT 1 OR ALUMINIZED COMPLETE CORROSION PROTECTION MUST BE ASSURED APPLY NON SHRINK GROUT TO INSIDE AND OUTSIDE OF JOINTS RINGS RISERS AND FRAMES TYPE 3 SC SEPARATOR BE USED AS AN ALTERNATE TO STANDARD DETAIL D 43 SC SEPARATOR TYPE 2 WHEN A TYPE 2 WILL NOT WORK DUE TO EXISTING C
173. D8 5 D8 7 D8 7 D8 9 D8 11 D8 11 D8 13 D8 13 CHAPTER D9 NATURAL SYSTEMS D9 01 GENEBRALD c ucu sun Oo N SNI u NS D9 02 STREAMS D9 1 D9 1 D9 2 SURFACE WATER ENGINEERING STANDARDS APPENDICES APPENDIX D 1 STANDARD DETAILS 2 APPENDIX D 2 DRAFTING STANDARDS oo APPENDIX D 3 SAMPLE TITLEBLOCK on nnt APPENDIX D 4 SURFACE WATER APPROVED MATERIALS LIST APPENDIX D 5 SURFACE WATER REFERENCE STANDARDS JANUARY 2015 A DI 1 A D2 1 A D3 1 A D4 1 5 1 CHAPTER D1 GENERAL REQUIREMENTS TABLE OF CONTENTS DIEI GENERAD nasa a ote De a cla D1 1 PIU NEN iori cO Op D1 1 DI O2 DEFINITIONS HR ia DI 1 D03 REFERENCES Dx tie ma IN iR ieu n D1 5 DI 04 GOVERNMENTAL AGENCY 6 D1 6 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D1 GENERAL REQUIREMENTS DI 01 GENERAL D1 01 1 Purpose These Engineering Standards set forth the minimum standards for the planning design and construction of storm and surface water systems The Storm and Surface Water Utility Code Chapter 24 06 of the Bellevue City Code adopted by Ordinance 5905 on October 5 2009 is the basis for these engineering standards Although these standards are intended to apply to physical development
174. DARD DETAIL NDP 9 IF FLOW CONTROL MR7 AND OR RUNOFF TREATMENT MR6 IS REQUIRED City of STORM AND SURFACE Bellevue WATER UTILITY NTION PLANTE FILTRATION BUILDING FOUNDATION r y DOWNSPOUT CLEAN OUT SCREW CAP a STRUCTURAL WALLS WYE GRAVEL SPLASH BLOCK 18 MIN WIDTH CLEAN OUT PER NDP MATERIALS 06 04 OVERFLOW ELEVATION 12 MIN SEE NOTE 4 5 10 SOIL MIX SEE NOTE 6 SEE NOTE 5 WASHED DRAIN ROCK OR OTHER APPROVED MATERIAL SEE NOTE 4 30 MIL PVC LINER OR EQUIVALENT ABOVE PLANTER BASE AND EN i APE F N N N WYE UNDERDRAIN TO RUN LENGTH OF PLANTER SEE NOTE 3 AND STD DTL 8 SUBGRADE WATERPROOF PVC BOOT AND CLAMP N ALONG SIDES OUTFLOW TO STORM SYSTEM OR APPROVED STORAGE FACILITY OR DISPERSAL AREA NS P Vivi L LLL AN gt A AN lt lt FOOTING DRAIN PER CLEAR AND GRADE STANDARDS SECTION CG5 16 DRAINS NOTES 1 DIMENSIONS A WIDTH OF FLOW THROUGH PLANTER 18 MINIMUM B DEPTH OF PLANTER FROM TOP OF GROWING MEDIUM TO OVERFLOW ELEVATION SIMPLIFIED 4 ENGINEERED 47 12 MAXIMUM C SLOPE OF PLANTER 0 5 OR LESS OVERFLOW A OVERFLOW REQUIRED B INLET ELEVATION MUST ALLOW FOR 2 MIN OF FREEBOARD 4 MIN FOR SIMPLIFIED C PROTECT FROM DEB
175. E NOV MAY AGGREGATE VARIES WITH UNDERDRAIN PIPE SELECTED SEE NOTE 5 NOTES 1 PROVIDE PROTECTION FROM ALL VEHICLE TRAFFIC EQUIPMENT STAGING AND FOOT TRAFFIC IN PROPOSED INFILTRATION AREAS PRIOR TO DURING AND AFTER CONSTRUCTION DIMENSIONS A PONDING ZONE FROM TOP OF GROWING MEDIUM TO OVERFLOW ELEVATION 2 6 MINIMUM AND 12 MAXIMUM DEPENDING ON INFILTRATION RATE AND DEVELOPMENT TYPE B FLAT BOTTOM WIDTH 1 MINIMUM C PLANTED SIDE SLOPES OF BASIN 2 5 1 MAXIMUM ADJACENT TO SIDEWALK 4 1 MAXIMUM FOR SHEET FLOW INLET OVERFLOW A OVERFLOW REQUIRED PIPE OR OVERLAND SEE STANDARD DETAILS 6 7 amp 8 B INLET ELEVATION MUST ALLOW FOR 6 OF FREEBOARD MINIMUM C PROTECT OVERFLOW INLET FROM DEBRIS AND SEDIMENT WITH STRAINER OR GRATE PIPE ONLY D DISCHARGE PER CITY OF BELLEVUE ENGINEERING STANDARDS BIORETENTION SOIL MIX A 18 MINIMUM DEPTH FOR MR 5 ONLY OR RUNOFF TREATMENT B 12 MINIMUM DEPTH FOR FLOW CONTROL VEGETATION A FLOOR OF PLANTING ISLAND SHOULD BE PLANTED WITH ZONE 1 TREES SHRUBS AND GROUND COVER SEE APPENDIX 3 IN THE LID TECHNICAL GUIDANCE MANUAL FOR PUGET SOUND JANUARY 2005 OR AS AMENDED OR RAIN GARDEN HANDBOOK FOR HOMEOWNERS FOR A PLANT LIST SIDE SLOPES SHOULD BE PLANTED WITH ZONE 2 OR 3 PLANTS USE AT LEAST 3 SPECIES OF EACH PLANT COVER TYPE NOT INCLUDING TREES INSTALL APPROXIMATELY 6 THICK LAYER WASHED DRAIN ROCK OR STREAMED
176. E DIAMETER IS 8 INCHES VERTICAL RISER SECTION SHALL BE ALIGNED PLUMB VERTICALLY HORIZONTAL RISER SECTION SHALL MATCH OUTLET PIPE SLOPE ALL METAL PARTS AND SURFACES MUST BE CORROSION RESISTANT STEEL HARDWARE SHALL BE GALVANIZED PIPES SHALL BE GALVANIZED ASPHALT COATED TREATMENT 1 OR ALUMINIZED COMPLETE CORROSION PROTECTION MUST BE ASSURED APPLY NON SHRINK GROUT TO INSIDE AND OUTSIDE OF ALL JOINTS RINGS RISERS AND FRAMES PENETRATE CARRIER PIPE THROUGH WALL USE APPROVED WATERTIGHT STRUCTURE 5 ADAPTOR a City of STORM AND SURFACE WATER UTILITY SLIP SMOOTH BORE HORIZONTAL LEG OF Bellevue FLOW CONTROL TEE INSIDE CARRIER PIPE NO FLOW CONTROL JOINT OUTSIDE OF STRUCTURE SPILL CONTROL SC SEPARATOR TYPE JANUARY 2015 NO SCALE 0 42 OFFSET FRAME SO THAT TEE IS VISIBLE AT EDGE OF OPENING FRAME AND GRATE OR AND DIRECTLY OVER THE 5 5 RING AND COVER SEE STANDARD DETAIL D 43A FOR ALTERNATIVE METHOD STRAP TO WALL J 2 5 5 MIN DESIGN REQUIRED WSE U SAND COLLAR OR KOR N SEAL BOOT TYPICAL INLET PIPE D 18 MAX 24 48 54 NOTES 1 MAX OUTLET PIPE DIAMETER IS 18 INCHES VERTICAL RISER SECTION SHALL BE ALIGNED PLUMB VERTICALLY HORIZONTAL SECTION SHALL MATCH OUTLET PIPE SLOPE ALL METAL PARTS AND SURFACES MUST BE CORROSION RESISTANT STEEL HARDWARE SHALL BE GALVANIZED PIPES SHALL BE GALVANIZED ASPHALT COATE
177. E RING amp D 22 MANHOLE CATCH BASIN ADJUSTMENT DETAIL enr D 23 CORRUGATED METAL MANHOL EE rc tetto S weenie ag D 24 TYPICAL TRENCH DEA 22 555 a aq eM es D 25 ELOW CONTROL STRUCTUNRE Seer entem D 26 PIVOTING SHEAR GATE DETA s iicet hd enn D 27 SCREW TYPESHEBEAR GATE endet rtu D 28 A DI 1 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 SHEAR GATE VALVE VAULT sasana aqanananaphnanaqaaqanaqanaya qaa D 29 VALVE BOX AND EXTENSION INSTALLATION D 29A VALVE OPERATING EXTENSION eas D 29B DRY DETENTION SOND otn ne MN D 30 WATER QUALITY POND noroi IW ya an usasqa D 30A DETENTION PIPE D 31 DETENTION VAULT akui s uwa ua qawa aus ck D 32 LAPPING TEES FOR DRAIN PIPE D 33 BEVELED END PIPE SECTION i D 34 ROCK LINED DITCHES u a as did ghey nanas D 35 GRASSIHINEIDJIM TIGE o dioe oH OD ott ore dine D 36 SIDEWALK DRAN L aguas D 37 ENERGY DISSIPATOR 4 lan gero dedere d qo usa D 38 DEBRIS CAGE epi e hisi EE
178. E e D2 1 Adjustment and Deviation Crifterla D2 1 Adjustment and Deviation Process one CQ URN eA D2 2 EXCEPTIONS cipine idis pa PRODI fln ua ede D2 2 ERRORS AND OMISSIONS uuu aaa od ens D2 2 THRESHOLDS ainai LO dca PE SUD ACD LORS de UA D2 2 Threshold Discharge NEC a saa dvd D2 2 Applicability ote D2 3 Projects Subject to Regulation eae ees D2 3 STORMWATER SITE PLANNING AND SUBMITTALS D2 7 Submittal Requirements for Minimum Requirements 1 through 5 only D2 8 Submittal Requirements for Minimum Requirements 1 through 9 When MR6 MR7 MR8 and or MR apply in addition to MR1 through MR5 D2 10 PLAN FORMAT AND NOTES asesino o gr eU MA RI D2 12 Submittal Staridards iei Reed eem ce D2 12 Storm Drainage General Plan D2 15 AS BUILT DOCUMENTATION ecsiseeo no Fecha eroe den D2 19 General Standards er eaa eaa E etre di D2 19 Required Information D2 20 OPERATION AND MAINTENANCE MANUAL D2 21 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 TABLES Table 2 1 Treatment Requirements by Threshold Discharge A
179. EDGE OF FRAME FLUSH WITH STREET GUTTER SURFACE P C C SIDEWALK TRANSITION DEPTH VARIES CATCH BASIN ECTION NOTES 1 SET FRAME TO GRADE AND CONSTRUCT 3 City Of STORM AND SURFACE ROAD AND CURB TO BE FLUSH AT FRONT a WATER UTILITY BACK FRAME Bellevue EXISTING ROLL E amp GRATE JANUARY 2015 NO SCALE amp BASE SIDEWALK REDUCED WID IH CB RISER ROLLED CURB SECTION OR BRICK ELEVATION ELEVATION SEE ROLLED CURB DETAIL 1 8 2 DUMMY JOINTS BACK OF CURB ADDITIONAL 2 CEMENT CONCRETE TO EDGE OF CB IN TRANSITION AREAS TYP BOTH SIDES FRAME AND VANED GRATE NOIES City of STORM AND SURFACE 1 WHEN A THRU CURB INLET IS REQUIRED WATER UTILITY USE A ROLLED CURB FRAME AND GRATE Bellevue EXISTING STALLATION JANUARY 2015 NO SCALE MODIFIED TYPE 1L CATCH BASIN REDUCING SECTION NOTES i STORM AND SURFACE 1 ITEMS SHOWN SHALL BE PRE CAST WATER UTILITY 2 APPLY NON SHRINK GROUT TO INSIDE AND OUTSIDE OF ALL JOINTS RISERS RINGS AND FRAMES ERSION RISER CATCH BASIN TYPE JANUARY 2015 NO SCALE OUTLET AREA INLET AVERAGE NYLOPLAST PIPE DIAMETER CONCRETE AREA INLET DIAMETER ib PIPE Ibs Ibs CAST IRON GRATE
180. EERING STANDARDS JANUARY 2015 Figure 3 2 10 Year 24 Hour Precipitation FIGURE 3 2 10 Year 24 Hour Precipitation 5 amp RTI FANE N UNIT Isopluvial of 10 Year 24 Hour Total Precipitation in Inches City Limits D3 9 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 3 3 100 24 Hour Precipitation FIGURE 3 3 100 Year 24 Hour Precipitation pe TA Isopluvial of 100 Year 24 Hour 77777 Total Precipitation in Inches ZZ Limits D3 10 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D3 02 03 Rational Method 1 General The Rational Method may be used with some specific limitations Only for use in predicting a conservative peak flow rate to determine there required capacity for conveyance facilities Drainage sub basin area A shall not exceed 25 acres for a single calculation time of concentration Tc must be computed using the method described below and shall not exceed 100 minutes It shall be made equal to 6 3 minutes when computed to be less than 6 3 minutes 2 Equation The following is the traditional Rational Method equation peak flow cfs for a storm of peak rainfall intensity Ig of a given return frequency R C estimated runoff coefficient ratio of rainfall that becomes runoff IR peak rainfall intensity inches hour for a given return frequency R A drainage
181. ESS OPENING ALL PIPES SHALL BE PERPENDICULAR TO FACE OF VAULT APPLY NON SHRINK GROUT TO INSIDE AND OUTSIDE OF ALL JOINTS RINGS RISER AND FRAMES PENETRATE CARRIER PIPE THROUGH VAUL WALL USE APPROVED WATERTIGHT STRUCTURE ADAPT SLIP 5 HORIZONTAL LEG OF FLOW CONTROL TEE INSIDE CARRIER PIPE MINA JOINT OUTSIDE City of STORM AND SURFACE PRIOR TO STARTUP COMBINED VAULT DETENTION B UTILITY RUNOFF TREATMENT SHALL PASS 1 PER DAY LEAK TEST WHERE MAXIMUM OF 1 WATER LOSS IS ALLOWED WITHIN A 24 HOUR PERIOD WITH VAULT FILLED TO 2 YEAR STORM ELEVATION TEST PER THE 2009 UNIFORM COMBINED VAUL PLUMBING CODE 712 2 ENTION AND RUNOFF JANUARY 2015 NO SCALE PLAN 4 9 x1 x12 GA GALV STRIPS TACK WELD TO WIRE MESH 0 5 x0 5 x16 GA GALV WIRE MESH 472 STAND PIPE N TACK WELD WIRE MES SOLID 12 GA m BOTTOM PLATE O BOTTOM PLATE SC NOTE ATTACH SCREEN TO CMP CROSS W 6 1 GALVANIZED METAL SCREWS 2 PER STRAP OR USE STAINLESS STEEL PIPE CLAMP n 2 PUMP STEEL METER BOX SM QUICK CONNECT HOSE 30 OLYMPIC FOUNDRY ADAPTER WITH CAP HOMELITE OR EQUAL MS CATCH BASIN LID SASS ZT ES
182. EXST LIN 000 CENTERLINE PROPOSED GREEN PROCNTL SV CNTL PROP LIN s NO 2 5 PEN n H04 CONTOUR DEPRESSION YELLOW DEC1 SV CONT DEPR LIN 0 05 NO 000 F953 01 contour EXISTNG YELLOW SV CONT EXST LIN NO 000 PEN EMPTORE E CONTOUR INDEX CYAN CON SV CONT INDX LIN NO 1 PEN 33 CONTOUR PROPOSED CYAN CONTINUOUS SV CONT PROP LIN NO 1 PEN ee DONATION LAND CLAIM EXIST CYAN DLC SV DLCM EXST LIN H 0 04 NO Sp S DONATION LAND CLAIM PROP GREEN DLC SV DLCM PROP LIN NO 2 5 PEN EASEMENT PERMANENT CONTINUOUS SV ESMT PERM LIN NO 1 PEN NL EM ANM e EN EASEMENT TEMPORARY CYAN TEMPESMT SV ESMT TEMP LIN NO EL Us RENE CHE 905 MEANDER LINE YELLOW MEANDER SV MEAN EXST LIN NO 000 PEN See PROPERTY LINE EXISTING YELLOW PROPERT SV PROP EXST LIN H 0 075 NO 000 A PROPERTY LINE PROPOSED CYAN PROPERT SV PROP PROP NO 1 PEN RANGE TOWNSHIP LINE GREEN CONTINUOUS SV 222A EXST LIN NO 2 5 PEN _ ESS ____ 2 08 gesRVATON PARK FOREST EX CYAN PARK SV PARK EXST LIN NO 1 PEN RESERVATON PARK FOREST PRO GREEN PARK SV PARK PROP LIN NO 2 LO cuneo RIBHISORCWAY EXISTING CYAN EXROW SV ROFW EXST LIN 410 05 NO 1 PEN RIGHT OF WAY PROPOSED GREEN CONTINUOUS SV ROFW PROP LIN For NO 2 5 PEN 2 777777242 RIGHT OF WAY LIMITED
183. For engineered flow control facilities not within an Ecology approved 40 20 basin detention design flows are generated with an Ecology approved continuous hydrologic model Stormwater discharges from flow control facilities shall match developed discharge durations to historic forested durations for the range of pre developed discharge rates from 50 of the 2 year peak flow up to the full 50 year peak For sites within an Ecology approved 40 20 basin stormwater discharges from flow control facilities shall match developed discharge durations to existing conditions durations for the range of pre developed discharge rates from 50 of the 2 year peak flow up to the full 50 year peak A comparison of the pre project and post project flow rates should also be conducted to verify that flow control facilities are required If the 100 year peak flow rate is increased by less than 0 1 cfs flow control factilities are not required For conveyance sizing design flows can be generated with a single event hydrology model continuous hydrologic model or the rational method For the single event hydrology model or the rational method the design flows is based on the 100 year 24 hour storm If using an Ecology approved continuous model the design flow for conveyance is based on the flow associated with a 100 year return period Continuous modeling for conveyance must use a 15 minute time step and preferably a rainfall time series that has been disaggregated to
184. G MEDIUM STORM AND SURFACE WATER UTILITY of Cit Bele PLAN ROUGH NO 27 4 MIN 4 12 MAX SEE NOTE 3B OUTFLOW TO STORM SYSTEMOR APPROVED STORAGE FACILITY OR DISPERSAL AREA TYP WATERPROOF PVC a MIN WIDTH j _ SEE NOTE 2 ATRIUM GRATE FOR OVERFLOW CLEAN OUT TYP SEE NOTE 3 OVERFLOW ELEVATION 90 9 9 o 10 4 i OQ SZ COCO ERDRAIN TO RUN LENGTH OF PLANTER IF NEEDED PER ENGINEER SEE NOTE 4 AND STD DTL NDP 8 FOR PLAN GRAVEL SPLASH BLOCK AT INLET SEE NOTE 10 INLET VIA PIPE OR OVERLAND GROWING MEDIUM SEE NOTE 7 SEE NOTE 6 WASHED DRAIN ROCK OR OTHER APPROVED MATERIAL SEE NOTE 5 PERCH ON SUBGRADE OR BURY AS NEEDED SEE NOTE 9 EXISTING SUBGRADE BOOT AND CLAMP VIEW NOTES 1 PROVIDE PROTECTION FROM ALL VEHICLE TRAFFIC EQUIPMENT STAGING AND FOOT TRAFFIC IN PROPOSED INFILTRATION AREAS PRIOR TO DURING AND AFTER CONSTRUCTION DIMENSIONS A WIDTH PLANTER 30 MINIMUM B PONDING DEPTH FROM TOP OF GROWING MEDIUM TO OVERFLOW ELEVATION SIMPLIFIED 4 ENGINEERED 12 MAXIMUM C SLOPE OF PLANTER 0 5 OR LESS OVERFLOW OVERFLOW REQUIRED PIPE OR WEIR INLET ELEVATION MUST ALLOW FOR 2 MIN OF FREEBOARD 4 MIN FOR SIMPLIFIED PROTECT PIPE FROM DEBRIS AND SEDIMENT WITH STRAINER OR GRATE SEE
185. G TYPE SHEAR GATE IS USED PRVATE SYSTEMS g ONLY SHEAR GATE HANDLE SHALL BE ATTACHED TO WATER UTILITY ADDER STEP LOCATED WITHIN 24 ACCESS SECTION IF NOTCHED WEIR IS USED IN LIEU OF ELBOW BAFFLE SHALL NOT OBSTRUCT ACCESS TO THE STRUCTURE APPLY NON SHRINK GROUT TO INSIDE AND OUTSIDE OF ALL JOINTS RINGS RISERS FRAMES AND PIPE FLOW CONTROL PENETRATIONS STRUCTURE JANUARY 2014 NO SCALE HANDLE WITH cm LOCK PIN ADJUSTABLE LOCK f L HOOK WITH LOCK SCREW 1 ROD OR TUBING VARIABLE LENGTH 4 HANDLE SHALL ATTACHED PER MANUFACTURER S RECOMMENDATIONS ES MAXIMUM OPENING OF GATE SHEAR GATE SHALL BE ALUMINUM ALLOY PER ASTM 26 276 32 OR CAST IRON ASTM A48 CLASS 30B AS REQUIRED GATE SHALL BE 8 DIAMETER FOR PIPE 12 INCHES OR LESS IN DIAMETER 12 DIAMETER FOR PIPES GREATER THAN 12 INCHES GATE SHALL BE JOINED TO TEE SECTION BY BOLTING THROUGH FLANGE LIFT ROD AS SPECIFIED BY MFR WITH HANDLE EXTENDING TO WITHI ONE FOOT OF COVER AND ADJUSTABLE HOOK LOCK FASTENED TO FRA OR UPPER HANDHOLD GATE SHALL NOT OPEN BEYOND THE CLEAR OPENING BY LIMITED HINGE MOVEMENT STOP TAB OR SOME OTHER DEVICE EOPRENE RUBBER GASKET REQUIRED BETWEEN RISER MOUNTI FLA AND GATE FLANGE STOP TAB OR SOME OTHER DEVICE ATING SURFACES OF LID AND BODY TO BE MACHINED FOR PROPER FIT SIX EVENLY SPACED HOLES FLANGE MOUNT
186. GINEERING STANDARDS JANUARY 2015 Table 6 8 Continuous Modeling Assumptions for Pervious Pavement Variable Assumption Precipitation Series SeaTac 50 year hourly time series with appropriate scaling factor based on project location Computational Time Step Hourly Inflows to Facility Model pavement area as impervious basin routed to a gravel filled trench with infiltration to underlying soil Precipitation Applied to No Precipitation is applied to the contributing basin before being Facility routing to the trench Evaporation Applied to Yes While evaporation is applied to the impervious basin before Facility routing to the trench additional evaporation occurs when water is stored in the storage reservoir Gravel Trench Bottom Length For longitudinal slopes up to 2 percent use actual bottom length based on design plans For longitudinal slopes greater than 2 percent use the total effective bottom length LErotai calculated as LEroa LE LE LE PM So PM So Where n Number of Cells LE Effective Bottom Length of Cell n ft PM Maximum Ponding Depth of Cell n ft So Bottom Slope of Cell n ft ft The effective bottom length input to the model may be no greater than the actual length based on design Figure 6 2 provides a schematic illustration of how to estimate this model input based on designs Gravel Trench Bottom Width Actual bottom width bas
187. GRAVEL BACKFILL FOR DRAINS SEE NOTE 1 MINIMUM 1 DEPTH TO HIGH GROUNDWATER TABLE NOV M W O UNDERDRAIN VARIES BELLEVUE DS I o 0 MIN MIN AR 1 0 1 0 EDGE BAND OR GUTTER OPTIONAL BIORETEN TION SOIL COMPACTED MIN BOTTOM SWALE MIN WIDTH 1 MIN 6 MINIMUM FREEBOARD DEPTH lie 6 12 MAX 3 DEPTH OF MU OR COMPOST EXIST R IRE PONDING DEPTH Y AW ARCA IPP PARANA ANE U Y amp ay ING GROUND ES MULCH IF DIRECTED BY ENGINEER SEE NOTE 2 BIORETENTION SOIL MIX SEE NOTE 1 AY LCH NG GROUND ES SOIL MIX SEE NOTE TO 90 DENSITY 3 OF COMPOST MINIMUM 1 DEPTH TO HIGH NOTES GROUNDWATER TABLE NOV MAY SEE CHAPTER D6 04 HEREIN FOR ALL MATERIALS LINER MAY BE ADDED IN FIELD AS DIRECTED BY ENGINEER BOTTOM SLOPE LESS THAN 8 INSTALL CHECK DAMS OR WEIRS FOR SLOPES GREATER THAN 2 GEOTECHNICAL ANALYSIS AND STORM DRAINAGE REPORT REQUIRED PER SUBMITTAL REQUIREMENTS CHAPTER D2 HEREIN DETAIL A SSD SLOTTED STORM DRAIN SOLID WALL PVC SDR 35 MINIMUM 6 MIN DIA NOTES C OF SLOT LOCATIONS 5 SLOT LOCATIONS ARE TO BE 0 047 0 069 WIDE IN 2 ROWS ON 45 DEGREE CE AND COVER 1 2 THE CIRCUMFERENCE THE PIPE BY 1 0 LONG AND SPACED APART SEE NDP MATERIALS CHAPTER D6 04 OTHER UNDERDRAI
188. IN CHANNEL AND SHELF SHALL CLASS 3000 ECAST BASES SHALL BE FURNISHED WITH CUTOUTS OR KNOCKOUTS KNOCKOUTS SHALL HAVE WALL CKNESS OF 2 MIN UNUSED KNOCKOUTS NEED NOT BE GROUTED IF WALL IS LEFT INTACT 5 ALL BE INSTALLED ONLY IN FACTORY KNOCKOUTS UNLESS OTHERWISE APPROVED BY THE ENGINEER UT OR CUTOUT HOLE SIZE SHALL EQUAL PIPE OUTER DIAM PLUS MANHOLE WALL THICKNESS MAX ZE BE 36 FOR 48 MANHOLE 42 FOR 54 MANHOLE 48 FOR 60 M H MIN DISTANCE BETWEEN ALL BE 8 E RINGS AND COVERS SHALL BE IN ACCORDANCE WITH SEC 7 05 OF THE STANDARD SPECIFICATIONS SURFACES SHALL BE FINISHED ASSURE NON ROCKING FIT WITH ANY COVER POSITION G TS 12 OR LESS MIN SOIL BEARING VALUE SHALL EQUAL 3 300 POUNDS PER SQUARE FOOT GHTS OVER 12 MIN SOIL BEARING VALUE SHALL EQUAL 3 800 POUNDS PER SQUARE FOOT R DETAILS SHOWING LADDER STEPS DHOLDS AND TOP SLABS SEE STD STORM AND SURFACE d py City of WATER UTILITY SEE THE STANDARD SPECIFICATIONS SEC 7 05 3 FOR JOINT REQUIREMENTS Bellevue APPLY NON SHRINK GROUT TO INSIDE AND OUTSIDE OF ALL JOINTS RISERS RINGS AND FRAMES MANHOLE TYPE 1 48 54 amp 60 JANUARY 2015 NO SCALE RING AND COVER Bt ADJUSTMENT SECTION LEVELING E BRICKS 2 ROWS MAX OR 22 GRADE RINGS 28 MAX
189. ING TY FOR CASING ERS SP 54 24 INIMUM RU WIDTH 2 INCHES ER HE ALL B O PROVIDE INIMU 75 BETWE RIER PIPE BELL AND CASING PIPE WALL AT ALL TIMES INIMU EARA WEEN RUNNERS AND TOP OF CASING WALL TO PREVENT AM G INS IO CASI ETERS UTSIDE DIAMETER FOR 16 AND LARGER O BA H SHA 12 FOR CARRIER PIPES THAT ARF 36 DIAM R GR EEL CASING PROV OP ED ANTI CORROSIVE CASING EXTERIOR CO 1 STORM AND SURFACE TO AWWA C210 MIN 2 City of ICK 6 MILS DFT Bellevue WATER UTILITY XCEE UFACTUR ICKNESS PRODUCT EQUAL AR SERIES 46H 413 CASING INSTALLATION JANUARY 2015 hme COLLAR OF 2 PIPE FLATTEN OR POINT G STD STAKE EACH SIDE OF 1 4 X 3 8 1 2 CARRIAGE OR UAE MACHINE BOLTS dece
190. ING BOLTS SHALL BE 3 8 DIAM STAINLESS STEEL FOR BOLTING TO FLANGE ALTERNATE SHEAR GATES TO THE DESIGN SHOWN ARE ACCEPTABLE CONNECTION PROVIDED THEY MEET THE MATERIAL SPECIFICATIONS ABOVE FOR PRIVATE USE ONLY City of STORM AND SURFACE Bellevue WATER UTILITY PIVOTING SHEAR GAI JANUARY 2015 NO SCALE 12 BRONZE SEAT EXTEND STEM TO GROUND SURFACE THROUGH OPERATING NUT EXTENSION SEE STD DTL D 29A AND 0 29 FRAME CAST IRON COVER CAST IRON ARCH CAST IRON RAILS 304 STN STL AS REQD CAST IRON THRU 14 YOKE CAST IRON THRUST NUT BRONZE THREADED STEM BRONZE COLLAR CAST IRON STEM EXT STEEL EXT STEM MATL AS 2 SQUARE OPERATING NUT CENTERLINE DIMENSIONS IN INCHES NOTES 1 FOR OUTLET PIPE DIAMETERS OF 12 INCHES OR LESS USE 8 INCH SHEAR GATE GREATER THAN 12 INCHES USE 12 INCH SHEAR GATE AWWA C509 RESILIENT SEATED GATE VALVE MAY BE SUBSTITUTED FOR GATE PER ENGINEER S APPROVAL JANUARY 2015 NO SCALE Bellevue FASTEN BRACE WALL RESTRICTOR A BC D E F G H K L M N P R s STORM AND SURFACE WATER UTILITY City of BOLT LOCKING FRAME AND COVER COREDRILL 3 CAST IRON VALVE BOX WITH LID SEE STD DTL D 29A FOR INSTALLATION O
191. IS AND SEDIMENT WITH STRAINER OR GRATE SEE D6 04 MATERIALS PIPING SHALL BE CAST IRON PVC SDR 35 MINIMUM OR PVC SCHEDULE 40 3 PIPE REQUIRED FOR UP TO 1 500 SQ FT OF CONTRIBUTING AREA OTHERWISE 4 MIN PIPING MUST HAVE 1 GRADE AND FOLLOW THE UNIFORM PLUMBING CODE IF WITHIN 3 OF A STRUCTURE DRAIN ROCK A SIZE PER NDP MATERIALS CHAPTER 06 04 B DEPTH OF SIMPLIFIED 12 C DEPTH OF ENGINEERED 12 48 SEPARATION BETWEEN DRAIN ROCK AND GROWING MEDIUM USE GRAVEL LENS 34 A INCH WASHED CRUSHED ROCK 2 TO 3 INCHES DEEP GROWING MEDIUM BIORETENTION SOIL MIX PER NDP MATERIALS CHAPTER 06 04 NO SCALE 7 VEGETATION 8 9 10 A PLANT WITH ZONE 1 OR 2 TREES SHRUBS AND OR GROUND COVER SEE APPENDIX 3 IN THE LID TECHNICAL GUIDANCE MANUAL FOR PUGET SOUND 2005 OR CURRENT OR RAIN GARDEN HANDBOOK FOR HOMEOWNERS FOR A PLANT LIST PLANTING SHALL CONSIST OF NATIVE SPECIES ABLE TO TOLERATE VARIABLE SOIL MOISTURE CONDITIONS PONDING WATER FLUCTUATIONS AND VARIABLE SOIL MOISTURE CONTENT B PLANTER WALLS A MATERIAL SHALL BE STONE BRICK CONCRETE WOOD OR OTHER DURABLE NO CHEMICALLY TREATED WOOD B CONCRETE BRICK OR STONE WALLS SHALL BE INCLUDED ON FOUNDATION PLANS WATERPROOF LINER SHALL BE 30 MIL PVC OR EQUIVALENT INSTALL WASHED PEA GRAVEL OR 1 4 STREAMBED COBBLES PER STANDARD SPECIFICATIONS 9 03 11 2 TO TRANSITION FROM INLET OR SPLASH PAD TO GROWIN
192. ISCHARGE APPROPRIATELY AWAY FROM BUILDING BARREL 60 80 C GALLON 2 CAPACITY TYPICAL ee FAUCET SEE NOTE 1 x RRA YOUU Ui VLR 3 MIN STRUCTURAL BASE SAND CONCRETE OR GRAVEL NOTES 1 HOSE BIB FOR ATTACHING GARDEN HOSE FOR HAND WATERING 2 SEE NDP CHAPTER D6 04 HEREIN FOR ALL MATERIALS Uo City of STORM AND SURFACE Bellevue WATER UTILITY ECYCLING SYSI M RAIN BARREI JANUARY 2015 NO SCALE NO NDP 18 CYESS Ole ON LEAF ROCK RAINWATER STORAGE SCREEN SYSTEM INSTALLED ABOVE GROUND SEE NOTE 4 DOWNSPOUT CONNECTION PROVIDE OVERFLOW PIPING TO ADDITIONAL TANKS OR DISCHARGE TAI SEE LATCH APPROPRIATELY AWAY SCREEN OR LOCK FROM BUILDING SEE NOTE 5 COVER SEE STANDARD DETAIL NDP 20 AND NOTE 1 lt lt eaa FOR DISPERSAL METHODS WATER LEVEL FLOW CONTROL ORIFICE MIN DIAMETER 0 25 REMOVEABLE FOR RAIN CISTERN MAINTENANCE PER DESIGN FAUCET OR VALVE FOUNDATION PER ENGINEER SEE DOE MANUAL CHAPTER 3 VOLUME AND CHAPTER 5 VOLUME V FOR DISPERSION OPTIONS OR CONNECT TO IRRIGATION SYSTEM WITH PROPER BACKFLOW PROTECTION SEE NDP CHAPTER D6 04 HEREIN FOR MATERIALS AND QUALIFIED PRODUCTS ELECTRICAL PERMIT REQUIRED IF WATER PUMP IS TO BE INSTALLED STORAGE SYSTEM INSTALLATION UNDERGROUND
193. ISCHARGE TO FOREBAY MINIMUM ONE ACCESS MANHOLE PER CELL WITH AT LEAST ONE ACCESS PER 50 OF VAULT LENGTH OR WIDTH 5 VAULTS SHALL HAVE APPROVED BUBBER GASKET SYSTEM VAULT SHALL BE DESIGNED AND STAMPED BY A REGISTERED STRUCTURAL ENGINEER VAULT SHALL BE DESIGNED FOR HS 20 TRAFFIC LOADING MIN ALL METAL PARTS SHALL BE CORROSION RESISTANT RAVITY DRAIN SHOULD BE SIZED TO EMPTY VAULT IN 4 HOURS UMP STANDPIPE REQUIRED IF VAULT IS NOT EQUIPPED WITH GRAVITY DRAIN TO ENABLE VAULT TO BE DRAINED FOR MAINTENANCE OPERATIONS E STANDPIPE IS REQUIRED FOR EVERY 35 000 CF OF DEAD STORAGE SEE SUMP WITH RISER PIPE DETAIL ROVIDE LADDER RUNGS IMMEDIATELY ADJACENT TO INLET PIPES PPER BAFFLE PLATE MAY BE USED IN LIEU OF TEE SECTION ON INLET PIPES LOW SPLITTER BYPASS REQUIRED UPSTREAM OF WET VAULT TO DIVERT FLOWS THAT EXCEED THE PEAK FLOW FOR THE WATER QUALITY DESIGN TORM AROUND THE WET VAULT BYPASS STRUCTURE MUST BE EQUIPPED WITH SHUT OFF MECHANISM TO ENABLE THE VAULT TO BE TAKEN OFF LINE FOR MAINTENANCE EES SHALL BE ORIENTED VERTICALLY WITHIN THE VAULT REGARDLESS OF THE SLOPE OF THE INCOMING PIPE DAPTER FOR THREADED END CAP SHALL BE SECURED TO TEE WITH SCREWS F PROPOSED COVER IS GREATER THAN 1 THEN IT MUST BE 2 5 MINIMUM AND ACCESS MUST BE 48 ECCENTRIC CONE SET OVER 24 DIAMETER ACCESS OPENING NVERT ELEVATION OF INLET PIPE SHALL BE PER DESIGN ENGINEER S CALCULATIONS L PIPES SHALL BE PERPENDICULAR TO FACE OF VAULT PLY N
194. ITY RAKE N YY TO LEVEL AND REMOVE SURFACE ROCKS gt 1 DIAMETER NOTES AMEND SOILS PER ECOLOGY MANUAL VOL V 5 3 1 BMP 15 13 2005 OR CURRENT OR WWW SOILSFORSALMON ORG OT AMEND SOILS IN AREAS WITH Cit of STORM AND SURFACE ISTURBED SOIL AND NATIVE VEGETATION Y y WATER UTILITY ONAL ALTERNATIVE STOCKPILE NATIVE Bellevue TOPSOIL ONSITE AMEND IF NEEDED AND LACE BEFORE PLANTING OPTIONAL ALTERNATIVE IMPORT TOPSOIL MIX OF SUFFICIENT ORGANIC CONTENT A DEPTH TO MEET REQUIRE D SOILS JANUARY 2015 NO NDP 1 WITHOUT UNDERDRAIN STABILIZE INLET SEE NOTE 8 TOP WIDTH VARIES WITH UNDERDRAIN MIN FOR PARKING LOTS RAISED TIRE STOPS OR 3 1 SIDE SLOPES TYP FREEBOARD SEE NOTE 3 PONDING ZONE INLET ELEVATION BOTTOM WIDTH 3 DEPTH COMPOST MULCH CURBS W CUTS SEE STD DTL 10 12 x12 CLEAR FLOW SEE NOTE 2 6 MIN 212 DETENTION FILTER gt LAYER 12 36 ANA SEE NOTE 4 lt gt GROUNDWATER lt iA TABLE NOV MAY V MINIMUM 1 TO HIGH 03 GEOTEXTILE IF DIRECTED Q BY ENGINEER lt 5 50115 GEOTEXTILE OR LINER IF DIRECTED BY ENGINEER AW AREA AT CUTOUTS NYAS 22 MIX 12 MIN SEE NOTE 5 6 8 UNDERDRAIN SEE NOTE 10 BIORETENTION SOIL N 1 MIN RETENTION ZONE GROUNDWATER TABL
195. L 10 NOTE LONGITUDINAL SLOPE SHALL BE 10 MAXIMUM of STORM AND SURFACE WATER UTILITY E WALK NO SCALE NO _NDP 21 1 20 OR GREATER SLOPE 96 98 25 MIN VEGETATED FLOWPATH 100 GRADE BOARD 1 4 OR 6 PERFORATED i D OI 5 20 IF DOWNHILL DISPERSAL TRENCH FT OR SMALL CATCH BASIN OR YARD DRAIN FOR ROOF AREA lt 700 SQ FT C B MAY BE NSTALLED IN TRENCH go PLAN VIEW NO SCALE COVER HERRING BONE GRATE OR EQUAL MAX OVERFLOW ELEV 6 E GRADE BOARD ROOF DOWNSPOUT 6 DIA CLEAN OUT BEND IF NEEDED amp OBSERVATION PORT 4 OR 6 PERFORATED PVC PIPE SHALL NOT BE LOCATED 100 OF A WELL OR 30 ANY PART OF A SEPTIC HARDWARE H SCREENING BOTTOM ONLY 0 MIN CH SHALL BE CONSTRUCTED S TO PREVENT POINT ARGE AND OR EROSION GRAVITY ACCESS TO STREAM CONVEYANCE TY AND FLOW PATH REMENT CAN NOT BE MET BE PUMPED TO APPROVED ARGE E BOARD AND SUPPOR NTREATED CEDAR O ED PLASTIC SPACE UPPORT POSTS EVERY 10 MIN O KEEP GRADE BOARD LEVEL LEAVE ROCK PERMANENTLY EXPOSED DO NOT FILL 2 10 PROFILE SCALE EXPOSED ROCK 00 0 6 CLEAN OUT W CAP EXPOSED RO
196. L BE ATRIUM STYLE A SUMP BOX WITH ONE OPENING MAY BE SUBSTITUTED INSTEAD OF TWO OPENINGS A MINIMUM FREEBOARD OF 3 SHALL BE PROVIDED BETWEEN THE TOP OF THE TEE AND THE GRATE 1 STORM AND SURFACE 22 WATER UTILITY ENTIAL YARD CATCH BASIN JANUARY 2015 NO SCALE NO 24 PLAN VIEW ROOF MEI NO SCALE TYPE 1 CATCH BASIN IN ROADWAY OR TO APPROVED NDP 24 IN YARDS DRAINAGE CONNECTION PERFORATED SOLID WALL PIPE SEE NOTE 2 4 PVC PIPE 10 MIN YS INFILTRATION TRENCH TOP OF DRAIN PIPE D CWNSBOUT JOINT 1 ABOVE GROUND ELEVATION DRAIN PIPE COVER HERRING BONE GRATE OR EQUAL I BEND IF 4 PERFORATED ED ae PVC PIPE MIN LEVEL TYPE 1 CATCH BASIN 6 MINA e B MI IN ROADWAY OR RESIDENTIAL YARD MIN e DRAIN PER STANDARD DEATIL NDP 24 IN 1 2 r 1 YARDS WASHED ROCK 3 4 1 1 2 HARDWARE CLOTH SCREENING LEVEL BOTTOM ONLY Lo VARIES 10 MIN 5 MIN VARIES PER SETBACK REQU PROFILE VIEW NO SCALE NOTES TRENCH SHALL NOT BE LOCATED WITHIN 100 OF A WELL OR 30 FROM ANY PART OF A SEPTIC SYSTEM COMPACTED BACKFILL FILTER FABRIC lt CENTER PERF PIPE HORIZONTALLY IN TRENCH 4 DI
197. LES SHALL BE 12 ANHOLE RINGS AND COVERS SHALL BE IN ACCORDANCE WITH SEC 7 05 OF THE STANDARD SPECIFICATIONS ATING SURFACES SHALL BE FINISHED TO ASSURE NON ROCKING FIT WITH ANY COVER POSITION FOR HEIGHTS OF 12 OR LESS MIN SOIL BEARING VALUE SHALL EQUAL 3 300 POUNDS PER SQUARE FOOT FOR HEIGHTS OVER 12 MIN SOIL BEARING VALUE SHALL EQUAL 3 800 POUNDS PER SQUARE FOOT FOR DETAILS SHOWING GRADE RING LADDER STEPS HANDHOLDS AND TOP SLABS SEE STD DTL 0 5 3 City Of STORM AND SURFACE WATER UTILITY SEE THE STANDARD SPECIFICATIONS SEC 7 05 3 FOR JOINT REQUIREMENTS Bellevue APPLY NON SHRINK GROUT TO INSIDE AND OUTSIDE OF ALL JOINTS RISERS RINGS AND FRAMES MANHOLE TYP 72 amp 96 JANUARY 2015 NO SCALE RING amp COVER zil TL gt 21 7 ADJUSTMENT SECTION LEVELING d TOP NE W BRICKS 2 ROWS OR 3 GRADE RINGS LA x gt 2 48 54 60 Sle S STEPS OR LADDER 72 OR 96 ss SHELF SLOPE be CONSTRUCT CHANNEL amp SHELF IN FIELD HEIGHT 25 AX PRECAST BASE INTEGRAL RISER 1 0 FOR 48 54 amp 60 DIAM 2 0 FOR 72 amp 96 DIAM GRAVEL BACKFILL FOR FOUNDATIONS 6 MIN COMPACTED DEPTH FOR PRECAST BASE ONLY g 72 DIAM
198. Land Use Code and these engineering standards Cables and chains stretched across access roads are not acceptable D4 06 5 Ponds A General Use the criteria and methods set forth in Volume Ill Section 3 2 1 of the DOE Manual as modified herein Stormwater detention ponds may be used as interim sedimentation facilities if cleaned restored to approved plan conditions following completion of all on site construction Stormwater shall be routed through a catch basin with spill control prior to discharging to the pond in order to facilitate the easy removal of transported sediments and debris B Design Criteria Provide debris barriers or trash racks on the detention pond outlet to protect the outlet from blockage or plugging C Embankments All embankments for detention and treatment facilities shall comply with Dam Safety Guidelines as published by the Dam Safety Division of the Department of Ecology current edition The maximum embankment height is measured from the downslope toe to the crest of the embankment All embankments for detention facilities six 6 feet and higher shall be designed inspected and certified by a civil geotechnical engineer The civil geotechnical engineer shall submit a letter certifying that all embankment design requirements have been met during embankment construction The maximum height of rockeries subject to inundation due to fluctuating pond levels is four 4 feet The exposed face of the r
199. M STORM AND SURFACE WATER UTILITY City of Bellevue REI ROUGH PLAN ETEN R FLOW WTH CO ANCE HIGHER GROUND BERM DISCHARGE LOCATION A CONVEYANCE LOCATION LOW POINT FOR FURROW PER CITY OF OVERFLOW BELLEVUE ENGINEERING STANDARDS V 5555 asses x 0060000170 95959006020 CELL STANDARD DETAIL 2 as INVERT OF CONVEYANCE FURROW HIGHER vem SNE FURROW ESHON HON OVERFLOW WITH CONVEYANCE FURROW LOCATION A CONVEYANCE FURROW INVERT ELEVATION AT ENTRANCE 6 BELOW 6 MIN TOP OF LOWEST BANK SEE NOTE 1 DISCHARGE LOCATION PER CITY OF BELLEVUE CONVEYANCE EXISTING ENGINEERING FURROW SUBGRADE STANDARDS NOTE 1 LINE CONVEYANCE FURROW WITH STREAMBED COBBLE PER STANDARD 3 Cit Of STORM AND SURFACE SPECIFICATIONS 9 03 11 2 MIN 6 WATER UTILITY DEPTH FOR DESIGN FLOW UP TO 4 Bellevue F P S OR MIN 12 BIORETENTION SOIL MIX FOR DESIGN FLOW LESS THAN 4 F P S AND PLANT WITH BIORETENTION NTION OVERFLOW GROUND COVERS OR TURF OR PER u ENGINEER S DESIGN VEYANCE FURROW JANUARY 2015 NO SCALE NO NDP 6
200. M AND TO FINISHED GRADE TH CONCRETE LOCK HASP FACES E SIREET EAVY DUTY HASP ROVIDE ADEQUATE LEARANCE BETWEEN EMENT amp HASP TO LLOW HASP TO LAY LAT WHEN OPEN TT TI R R S D W 4 XED BOLLARD INSTALLATION ET FIXED BOLLARDS IN A 16 AMETER HOLE 30 DEEP AND ACKFILL WITH 6 GRAVEL ON 1 4 FILLET WELD OTTOM AND TO FINISHED GRADE BOTH SIDES TH CONCRETE n INCISE 1 4 TO FIT REMOVABLE BOLLARD TO BASE BRACKET STALL POST BRACKET UPPORT BURIED FLUSH CONCRETE 4 6 FIXED BOLLARD 17 9 REMOVABLE BOLLARD m O O T SLIDE THROUGH POST BRACKET 3 8 GALVANIZED A36 STEEL PLATE 3 7 16 HOLES FOR 7 16 x 3 LAG SCREWS EA SIDE City of STORM AND SURFACE Bellevue WATER UTILITY HEAVY DUTY HASP E BOLLARD PLAC JANUARY 2015 NO SCALE RIGID PIPE BEDDING SEE NOTE 1 COMPACTED BACKFILL COMPACTED DENSITY PERCENTAGE PER STANDARD DETAIL D 25 m m SPRING LINE COMPACTED BEDDING GRAVEL PER SECTION 9 03 12 3 GRAVEL BACKFILL FOR PIPE ZONE BEDDING OF THE WSDOT STANDARD SPECIFICATION OR OTHER MATERIAL IF SPECIFIED DATION GRAVEL IF REQUIRED SEE NOTE 2 ELEXIBLE PIPE BEDDING SEE NOTE 1 COMPACTED BACKFILL COMPACTED DENSITY PERCENTAGE PER STANDARD DETAIL D
201. MC SMC SMCP SV 222A 3333 SYM MC MC o WITNESS CORNER wo SWC SWCP SV SECT 3333 SYM wc WC Q e SOIL BORING SB SSB SSBP SV SO0IL 3333 SYM x SPOT ELEVATION SE SSE SSEP SV CTRL 3333 SYM C 3 TAX LOT PARCEL NUMBER STLN SV 222B 3333 SYM 222 USE RANG SECT TWNS 222B USE PRCL LOTN 3333 USE EXST PROP OR FOUN THEO BLOCK SNA BLOCK SDAT LAYER SV NORA 3333 SYM LAYER SV DATM 3333 SYM American Washington Public Works State City of Association Chapter Bellevue A D2 4 PAGE 4 SURFACE FEATURES LANDSCAPING SYMBOL DESCRIPTION BLOCK EXIST PROP BUS STOP SFBS SFBSP agi Y EMBANKMENT SFB SFBP a 5 5 885 SBE RIP RAP SFRR SFRRP on ROCKERY SFR SFRP Co Cs SHRUB SFS SFSP SIGN SFSN SFSNP X st TREE Conifer SFC SFCP TREE Deciduous SFD SFDP x x YARD LIGHT SFL SFLP American Washington Public Works State Association Chapter A D2 5 LAYER SF BUSS 3333 SYM SF EMBT 3333 SYM SF MAIL 3333 SYM SF RIPR 3333 SYM SF ROCK 3333 SYM SF VEGE 3333 SYM SF SIGN 3333 SYM SF VEGE 3333 SYM SF VEGE 3333 SYM SF LITE 3333 SYM 3333 USE EXST PROP amp City of Bellevue SIGNALIZATION SYMBOLS SYMBOL EXIST PROP a p G Mt lt qk B A g Z a e Q Q m o Tar Ep DESCRIPTION AERIAL DISCONNECT AERIAL TERMINAL CO
202. MPARTMENT DETECTORS DIPOLE DETECTOR QUADRAPOLE DETECTOR PEDESTRIAN DETECTOR BLOCK TAD TADP TATC TATCP TDD TDDP TQD TQDP TPD TPDP EMERGENCY VEHICLE INDICATOR LIGHTS INDICATOR LIGHTS OPTICOM SENSOR OPTICOM SENSOR W INDICATOR LIGHTS FLASHING WARNING SYSTEM JUNCTION BOX TYPE 1 11 PEDESTRIAN PUSHBUTTON POST W PUSHBUTTON PEDESTRIAN SIGNAL HEAD POLE NOTE R R CROSSING GATE R R CROSSING SIGNAL American Washington Public Works State Association Chapter A D2 6 TIL TILP Tos TOSP TOSL TOSLP TFWS TFWSP TJB1 TJB1P TJ82 TJB2P TJB3 TJB3P TPB TPBP TPSH TPSHP TPN TRG TRGP TRC TRCP LAYER TF SIGL 3333 SYM TF SIGL 3333 SYM TF SIGL 3333 SYM TF SIGL 3333 SYM TF SIGL 3333 SYM TF SIGL 3333 SYM TF SIGL 3333 SYM TF SIGL 3333 SYM TF SIGL 3 5353 SYM TF SIGL 3333 SYM TF SIGL 3333 SYM TF SIGL 3335 SYM TF SIGL 3333 SYM TF SIGL 3333 SYM TF SIGL 3333 SYM TF SIGL 33533 SYM TF SIGL 3333 SYM 3333 USE EXST PRO City of 42 Se Bellevue SIGNALIZATION SYMBOLS PAGE 6 SYMBOL DESCRIPTION BLOCK LAYER EXIST PROP lt m SIGNAL CONTROLLER TSC TSCP TF SIGL 3333 SYM DEI SIGNAL LOAD CENTER TSLC TSLCP TF SIGL 3333 SYM 9 STREET LIGHT TSLA TSLAP TF SIGL 3333 SYM ASSEMBLY TRAFFIC SIGNS 2d Ww M BRIDGE
203. N OPTIONS UNDERDRAIN SLOTS ORIENTED ON BOTTOM OF PIPE STORM AND SURFACE WATER UTILITY City of Bellevue ENTION SWALE JANUARY 2015 NO SCALE BUILDING FOUNDATION MIN WDTH 18 SEE NOTE 1 ATRIUM GRATE FOR OVERFLOW CLEAN OUT TYP SEE NOTE 2 OVERFLOW ELEVATION DOWNSPOUT OPTIONAL STRUCTURAL WALLS GRAVEL SPLASH BLOCK SEE NOTE 10 GROWING MEDIUM SEE NOTE 6 SEE NOTE 5 JA 27 4 MIN SEE NOTE 1B AN Y y W 20 47 12 MAX WASHED DRAIN ROCK OR OTHER APPROVED MATERIAL SEE NOTE 4 WATERPROOF BUILDING AND LINE AS NEEDED C Em LAE OUTFLOW TO STORM SYSTEM OR APPROVED STORAGE FACILITY OR DISPERSAL AREA TYP WATERPROOF PVC BOOT AND CLAMP LENGTH PLANTER SEE 5 SEE NOTE 9 EXISTING SUBGRADE X UNDERDRAIN TO RUN b LILY Wins STD DTL NDP 8 FOR AS S PLAN VIEW AND NOTE 3 N BASE SEE NOTES 1 AND 8 FOOTING DRAIN PER CLEAR AND GRADE STANDARDS SECTION CG5 16 DRAINS JANUARY 2015 NOTES DIMENSIONS A WIDTH OF PLANTER 18 MINIMUM B PONDING DEPTH FROM TOP OF GROWING MEDIUM TO OVERFLOW ELEVATION SIMPLIFIED 4 ENGINEERED 12 MAXIMUM C SLOPE OF PLANTER 0 5 OR LESS OVERFLOW OVERFLOW REQUIRED PER STANDARD DETAIL 8 INLET ELEVATION MUST ALLOW FOR 2 MIN OF FREEBOARD 4 MIN FOR SIMPLIFIED PROTECT FROM DEBR
204. NG STANDARDS JANUARY 2015 ii Pervious pavement in the right of way requires approval The structural capacity of pavement sections when subject to vehicular loads depends on several factors and must be designed by a licensed professional engineer Susceptible to clogging if receiving runoff from off site areas especially where soils are exposed and if not periodically maintained via vacuum sweeper and other recommended maintenance practices Section D6 03 5 May not be used in High Vehicle Traffic Areas as defined in Section 3 3 7 Volume of the DOE Manual Must meet setback requirements per D4 07 Design Requirements Inlet Flow diversion and erosion control measures shall protect the pervious pavement area from sedimentation until all upstream catchment areas are thoroughly stabilized Pervious Wearing Course Materials shall meet those listed in the NDP materials section D6 04 2 Positive surface drainage shall be provided to eliminate risk of ponding on pavement surface minimum surface slope shall be 0 5 percent Maximum surface slope shall not exceed five 5 percent for pervious asphalt six 6 percent for pervious concrete and ten 10 percent for pervious paver systems For grass pavers the grid shall be filled with sandy loam topsoil mix per Standard Detail NDP 12 For pervious driveways slope surface to direct drainage away from structures or direct water away using a trench drain Leveling Cour
205. NON ROCKING FIT WITH ANY COVER POSITION LL BE FINISHED TO ASSURE NON ROCKING FIT WITH ANY LL PRECAST CONCRETE SHALL BE CLASS 4000 R DETAILS SHOWING LADDER STEPS HANDHOLDS AND TOP SLABS SEE STD DIL D 5 T FOR USE IN TRAFFIC BEARING AREAS OLE DIAMETER SHALL EQUAL PIPE DIA R REINFORCED CONCRETE PIPE ONLY PPLY NON SHRINK GROUT TO INSIDE City of STORM AND SURFACE D OUTSIDE OF ALL JOINTS RISERS WATER UTILITY GS AND FRAMES Bellevue JANUARY 2015 SCALE 1 DIAMETER LIFT HOLE 8 1 2 FROM CENTER 8 WEBS 1 2 THICK OF COVER NON SKID INIEGRAL PATIERN TO BE CAST ON TOP OF COVER PLAN 26 3 8 25 1 4 24 i SEAT 1 1 4 e 23 3 42 MACHINED SEAT 33 3 4 Be 25 ECTION NOTES 1 COVER SHALL HAVE THE WORD DRAIN CAST 3 RAISED LETTERS LY FOR USE IN PUBLIC RIGHT OF WAY PAVED AREAS AND SIDEWALKS
206. O NGS RISERS AND FRAMES SIDE AND OUTSIDE OF ALL JOINTS RECAST BASES SHALL BE FURNISHED WITH CUTOUTS OR OCKOUTS KNOCKOUTS SHALL HAVE A WALL THICKNESS N ALL PIPE SHALL BE INSTALLED IN FACTORY ROVIDED KNOCKOUTS UNUSE OCKOUTS NEED NOT E GROUTED IF WALL 5 LEFT INTACT OCKOUT OR CUTOUT HOLE SIZE IS EQUAL TO PIPE OUTER AM PLUS CATCH BASIN WALL THICKNESS OUND KNOCKOUTS MAY BE ON ALL 4 SIDES WITH MAX AM OF 20 OCKOUTS MAY BE EITHER ROUND OR D SHAPE HE MAX DEPTH FROM THE FINISHED GRADE TO THE PE INVERT IS 4 0 THE TAPER ON THE SIDES OF THE PRECAST BASE SECTION AND RISER SECTION SHALL NOT EXCEED 1 2 FT CATCH BASIN FRAME AND GRATE SHALL BE IN ACCORDANCE WITH STANDARD SPECIFICATIONS MATING SURFACES SHALL BE FINISHED ASSURE NON ROCKING FIT WITH ANY COVER POSITION VERTICAL EDGE OF RISER OR BRICK SHALL NOT BE MORE THAN 2 FROM VERTICAL EDGE OF CATCH BASIN WALL City Of STORM AND SURFACE WATER UTILITY Bellevue PRECAST BASE SECTION MEASUREMENT AT THE TOP OF THE BASE BASIN TY JANUARY 2015 NO SCALE NOTES 1 CATCH BASINS SHALL BE CONSTRUCTED IN ACCORDANCE WITH ASTM C478 AASHTO M 199 amp C890 UNLESS OTHERWISE SHOWN NO PLANS OR NOTED IN THE STANDARD SPECIFICATIONS AS AN ACCEPTABLE ALTERNATIVE TO REBAR WELDED WIRE FABRIC HAVING A MIN AREA OF 0
207. OE Manual Volume V Section 5 3 1 Alternatively partial flow credits per Section D6 03 4 may be applied D6 15 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Maintenance Provide necessary maintenance if erosion or flooding on site or on downstream properties results Contributing impervious areas shall be kept free of oils soap and other substances considered Prohibited Discharges per BCC 24 06 125 B H Perforated Stub out Connection Description Applicability Desien and Sizing If a connection to a storm pipe is being made and the site meets the design criteria install a Perforated Stub out Connection per the DOE Manual Volume Section 3 1 3 and Standard Detail NDP 25 The stub out connection should be installed between the roof downspouts and the storm drain lot stub if roof downspout infiltration and dispersion are not feasible per above It should also be installed for any residential or small lot drain or storm facility that has a piped connection to the storm drain lot stub Maintenance Maintain per M2 07 Energy Dissipaters Requirements for Dispersion Trench Bellevue Maintenance Standards Perforated stub out connections shall be provided with access for ongoing maintenance at least three 3 feet in width D6 03 2 Natural Drainage Practices NDPs This section provides a brief description and discussion of the applicability limitations design requirements and sizing for the following NDPs Bior
208. ON SHRINK GROUT TO INSIDE AND OUTSIDE OF ALL NTS RINGS RISERS AND FRAMES NETRATE CARRIER PIPE THROUGH VAULT WALL E APPROVED WATERTIGHT STRUCTURE ADAPTOR SLIP SMOOTH BORE HORIZONTAL LEG OF FLOW CONTROL 3 STORM AND SURFACE TEE INSIDE CARRIER PIPE WATER UTILITY NO FLOW CONTROL JOINT OU P S TSIDE STRUCTURE RIOR TO STARTUP RUNOFF TREATMENT VAULT WET VAULT HALL PASS 1 PER DAY LEAK TEST WHERE A MAXIMUM OF 1 WATER LOSS IS ALLOWED WITHIN A 24 HOUR PERIOD WITH TITLE VAULT FILLED TO 2 YEAR STORM ELEVATION TEST PER THE 2009 UNIFORM PLUMBING CODE 712 2 RUNOFF TR ENT VAULT VAULT JANUARY 2015 NO SCALE CROWN OF INLET PIPES 24 ACCESS MANHOLE W OFFSET FRAME SO THAT AND GATES ATCH MAX WSE LOCKING RING AND COVER ARE VISIBLE AT EDGE OF OPENING AND STANDARD SEE NOTE 2 DIRECTLY OVER THE STEPS COVER PER FLOW RESTRICTOR PER STANDARDS 10 EVA FAR GATE VIE PER STANDARDS CAL RISER SECTION SHALL LIGNED PLUMB VERTICALLY 100 YEAR RIZONTAL SECTION SHALL STORM W S MATCH OUTLET PIPE SLOPE Q MAINTENANCE DRAIN W SHEAR GATE PER STANDARDS BM n b GRAVITY DRAIN IF GRADE 2 8 8 OPENINCS ALLOWS SEE NOTES 6 amp 7 FLUSH WITH VAULT BOTTOM SAND COLLA
209. ONSTRAINTS FASTEN HALF ROUND TO CATCH BASIN A WALL QUICK BOLTS Cit of STORM AND SURFAC WATER UTILITY Bellevue PILL CONT EPARATOR JANUARY 2015 NO SCALE NO D 43A ACCESS EASEMENT TRACT LINE STANDARD CONCRETE j 112 DRIVING SURFACE GATE OR BOLLARDS 15 OR B S B L WHICHEVER IS GRFATEST DRIVEWAY ENTRANCE ACCESS EASEMENT TRACT LINE 12 DRIVING SURFACE _ R 25 MIN TYPE TURNAROUND NI EON ACCESS EASEMENT TRACT LINE 12 DRIVING SURFACE HAMMERHEAD pm EASEMENT TYPE B TRACT LINE TURNAROUND Cit of STORM AND SURFACE Bellevue WATER UTILITY DRAINAGE MAIN TENANC JANUARY 2015 NO SCALE EDGE OF ROAD N 15 MIN FENCE ACCESS 15 MIN FASEMENT TRACT GATE TYPE amp HEIGHT TO LINE FIXED MATCH ADJACENT FENCES BOLLARD REMOVABLE BOLLARD GATE POST NOT ATTACHED TO FENCE B 6 MAX 6 MAX 12 MIN CLR 12 MIN CLR DRIVING SURFACE DRIVING SURFACE GATE PLACEMENT BOLLARD PLACEMENT POST BRACKET SUPPORT FINISHED 3 8 GALVANIZED A36 PAVING LLARD MANUFACTURED FROM x8 DOUGLAS FIR 42 OR BETI ESSURE TREATED W LP 22 OVABLE BOLLARD INSTALLATION OVABLE BOLLARD BASES ARE T IN A 12 DIAMETER HOLE 30 EP AND BACKFILLED W 6 GRAVEL BOTTO
210. OT GHTS OVER 12 MIN SOIL BEARING VALUE SHALL EQUAL 3 800 POUNDS PER SQUARE FOOT F E R DETAILS SHOWING LADDER STEPS DHOLDS AND TOP SLABS SEE STD m STORM AND SURFACE x City of WATER UTILITY SEE THE STANDARD SPECIFICATIONS SEC 7 05 3 FOR JOINT REQUIREMENTS Bellevue APPLY NON SHRINK GROUT TO INSIDE AND OUTSIDE OF ALL JOINTS RINGS RISERS AND FRAMES MANHOLE TYPE 3 48 54 60 72 amp 96 JANUARY 2015 NO SCALE RING AND COVER ADJUSTMENT SECTION LEVELING BRICKS 2 ROWS MAX OR GRADE RINGS 28 MAX PRECAST CONE ECCENTRIC UNLESS OTHERWISE SPECIFIED 5 PRECAST RISER LL SECTIONS MIN 48 DIAM RISER SECTION GRAFTED TO he WELD REINFORCING PIPE BY VARIES STELL OF JOINTS FABRICATOR MIN DIAM 48 fy NON SHRINK GROUT m EON REINFORCED CONCRETE PIPE 48 MIN DIAM EVA ION OLES SHALL BE CONSTRUCTED IN ACCORDANCE WITH AASHTO M199 UNLESS OTHERWISE SHOWN ON PLANS OTED IN THE STANDARD SPECIFICATIONS HOLDS IN ADJUSTMENT SECTION SHALL HAVE 3 MIN CLEARANCE STEPS IN MANHOLE SHALL HAVE 6 CLEARANCE SEE STD DTL D 5 OLE RINGS AND COVERS SHALL BE IN ACCORDANCE WITH SEC 7 05 OF THE STANDARD SPECIFICATIONS G SURFACES SHALL BE FINISHED TO ASSURE
211. OUT OR CUTOUT HOLE SIZE SHALL EQUAL PIPE OUTER DIAM PLUS CATCH BASIN WALL THICKNESS MAX HOLE SIZE SHALL BE 36 FOR 48 CATCH BASIN 42 FOR 54 C B 48 FOR 60 C B 60 FOR 72 C B 84 FOR 96 C B IN DISTANCE BETWEEN HOLES SHALL BE 8 FOR 48 54 AND 60 C B 12 FOR 72 AND 96 C B CATCH BASIN FRAMES AND GRATES OR COVERS SHALL BE IN ACCORDANCE WITH SEC 7 05 OF THE STANDARD SPECIFICATIONS MATING SURFACES SHALL BE FINISHED TO ASSURE FIT WITH ANY COVER POSITION FOR HEIGHTS OF 12 OR LESS MINIMUM SOIL BEARING VALUE SHALL EAUAL 3 300 POUNDS PER SQUARE FOOT FOR HEIGHTS OVER 12 IN SOIL BEARING VALUE SHALL EQU j City of STORM AND SURFACE POUNDS PER SQUARE FOOT s WATER UTY FOR DETAILS SHOWING LADDER STEPS x Bellevue HANDRAILS AND TOP SLABS SEE STD DTL O D 5 SEE THE STANDARD SPECIFICATIONS SEC CATCH BASIN TYPE 2 7 05 5 FO JOINT REQUIREMENTS 48 54 60 72 amp 96 JANUARY 2015 NO SCALE 24 5 1 CLEARANCE GRADE RING t ROUND 48 54 amp 60 SLAB TYPICAL ORIENTATION FOR ACCESS AND STEPS lI u HANDHOL CATCH BASIN STEP ALL STEPS amp RUNGS 8 GALV DEFORMED REBAR OR POLYPROPYLENE 12 MIN ls gt 2 uU JJ gt ELEVATION DROP RUNG CATCH BASIN STE
212. PE 304 STEEL SOCKET ALLEN HEAD BOLTS 2 LONG R MATERIAL IS DUCTILE IRON CONFORM TO SEC 7 05 OF THE DARD SPECIFICATIONS R SHALL HAVE THE WORD DRAIN IN 2 RAISED LETTERS JANUARY 2 015 NO SCALE LEVELING BAD ECTION City of STORM AND SURFACE S Bellevue WATER UTILITY SOLID COV CEMENT CONCRETE CURB PAVEMENT DEPTH VARIES GUTTER ERTICAL CUR LEVEL 16 3 4 x 2 EXTRUDED CURB PAVEMENT DEPTH VARIES NOTES DE TWO LOCKING TYPE 304 STEEL LTS 2 LONG DRILL A BOLTS 5 8 11 NC SI SOCKET HEAD ALLEN D FOR AND AINLESS HEAD BO ATERIAL IS CAST IRON PER ASTM A48 30 CLASS STRUCT ROAD FRAME CON WITH SET FRAME TO GRADE AND AND GUTTER TO BE FLUSH MATCH CENTERLINE OF CAI LINE FOR TYPE 1 AND ICH BASIN TO CURB TIT E JANUARY 2015 NO SCALE WAY X 1 8 h 1 4 SEE NOTE 1 2 PRECAST CONCRETE RISERS CATCH BASIN WALL 18 X 24 1 32 0 TYP 22 OPENING 17 3 4 X 23 3 4 1 32 0 TYP 25
213. PERATING EXTENSION SEE STD DTL D 29B 4 1 2 VALVE BOX PROVIDE SUPPORT BRACING SCREW TYPE SHEAR GATE SEE STD DTL D 28 FLOW RESTRICTOR SEE STD DTL 0 26 NOTES 1 CORE DRILL HOLE IN CATCH BASIN LID GROUT WATER VALVE BOX IN PLACE 2 ALL METAL PARTS amp SURFACES MUST BE CORROSION RESISTANT STEEL HARDWARE SHALL BE GALVANIZED PIPES SHALL BE GALVANIZED ASPHALT COATED TREATMENT 1 OR ALUMINIZED COMPLETE CORROSION PROTECTION MUST BE ASSURED APPLY NON SHRINK GROUT TO INSIDE AND OUTSIDE OF ALL JOINTS RINGS RISERS PIPE PENETRATIONS AND FRAMES ALL PIPES SHALL BE PERPENDICULAR TO FACE OF VAULT PENETRATE CARRIER PIPE THROUGH VAULT WALL USE APPROVED WATERTIGHT STRUCTURE ADAPTOR SLIP SMOOTH BORE HORIZONTAL LEG OF FLOW CONTROL TEE INSIDE CARRIER PIPE NO FLOW CONTROL JOINT OUTSIDE OF STRUCTURE BEL dem 4 e Ep FI ISHINGS JANUARY 2015 NO SCALE SAND COLLAR OR KOR N SEAL BOOT LIMIT PIPE SLOPE TO 2 MAXIMUM STORM AND SURFAC WATER UTILITY City of Bellevue VALVE BOX LID WITH RECESSED LIFTING HANDLE SECTION PLAN VIEW VALVE BOX TOP SECTION WITH HIGH FLANGE 8 DEEP COLLAR TACK SIDES WITH 55 1 AND SEAL 8 DEEP CONCRETE COLLAR EDGES WITH PG58 22 NEw ExSTNG PAVEMENT 6 MIN Ex T E SURFACE H 4 MIN BEYOND FLANGE 4 MIN BEYOND FL
214. R OR KOR N SEAL BOOT TYPICAL PLAN VIEW LADDER ees a RUNGS H RUNGS DRAINS FLOOR l BOTH SIDES Ed SUMP AREA SAND COLLAR OR TO PIPE 4 LEAST ONE ACCESS IE s MIN 4 x4 KOR N SEAL BOOT i R 54 DIA TYPICAL MANHOLE LOCATED BETWEEN HEADWALL AND UPPER BAFFLE 2 8x8 OPENI 4 BAFFLE WALL NOTES FLUSH WITH VAULT BOTTOM LOWER BAFFLE WALL TO DIV LT INTO TWO APPROXIMATELY EQUAL SIZE CELLS UPPER BAFFLE SET 25 OF VAULT SURFACE AREA 1 UM FROM HEADWALL MINIMUM ONE ACCESS MANH R CELL WITH AT LEAST ONE ACCESS PER 50 VAULT LENGTH OR WIDTH PROVIDE WATER STOP AT ALL CAST IN PLACE CONSTRUCTION JOINTS PRE CAST VAULTS SHALL HAVE APPROVED RUBBER GASKET SYSTEM VAULT SHALL BE DESIGNED D STAMPED BY A REGISTERED STRUCTURAL ENGINEER VAULT SHALL BE DEISGNED FOR HS 20 TRAFFIC LOADINGS MINIMUM ALL METAL PARTS SHALL BE CORROSION RESISTANT GRAVITY DRAIN SHOULD BE SIZED TO EMPTY VAULT IN 4 HOURS MP STANDPIPE REQUIRED IF VAULT IS NOT EQUIPPED WITH GRAVITY DRAIN TO ENABLE VAULT TO BE DRAINED FOR MAINTENANCE OPERATIONS ONE STANDPIPE IS REQUIRED FOR EVERY 35 000 CF OF DEAD STORAGE SEE SUMP WITH RISER PIPE DETAIL PROVIDE LADDER RUNGS IMMEDIATELY ADJACENT TO ALL INLET OUTLET PIPES AL LETS MUST DISCHARGE UPSTREAM OF UPPER BAFFLE IF PROPOSED COVER 15 GREATER THAN 1 THEN IT MUST BE 2 5 MINIMUM AND ACCESS MUST BE 48 ECCENTRIC CONE SET OVER 24 DIAMETER ACC
215. RAME amp GRATE OR RING amp COVER 4 MIN 18 MAX ADJUSTMENT SECTION LEVELING TOP TN BRICKS 2 ROWS MAX RISERS OR GRADE RINGS 11207247 OR 24 DIAM STEPS2 OR LADDER ORIENT 4 WITH INLET SO STEPS WILL 48 54 60 B CLEAR PIPES 72 0R 96 12 HEIGHT MAX PRECAST BASE amp INTEGRAL RISER 1 0 FOR 48 54 amp 60 DIAM 2 0 FOR 72 amp 96 DIAM GRAVEL BACKFILL FOR FOUNDATIONS 6 MIN COMPACTED DEPTH CATCH BASINS SHALL BE CONSTRUCTED IN ACCORDANCE WITH ASTM C478 AASHTO M199 AND ASTM C890 UNLESS OTHERWISE SHOWN ON PLANS OR NOTED IN THE WSDOT STANDARD SPECIFICATIONS HANDHOLDS IN ADJUSTMENT SECTION SHALL HAVE 3 MIN CLEARANCE STEPS IN CATCH BASIN SHALL HAVE 6 MIN CLEARANCE SEE STD DTL NO D 5 CATCH BASIN DETAILS HANDHOLDS SHALL BE PLACED IN ALTERNATING GRADE RINGS OR LEVELING BRICK COURSE WITH A MIN OF ONE HANDHOLD BETWEEN THE LAST STEP AND TOP OF THE FINISHED GRADE APPLY NON SHRINK GROUT TO INSIDE AND OUTSIDE OF ALL JOINTS RINGS RISERS AND FRAMES ALL PRECAST NCRETE SHALL BE CLASS 4000 BASES SHALL BE FUR ED WITH CUTOUTS OR KNOCKOUTS KNOCKOUTS SHALL HAVE WALL THICKNESS MIN UNUSED KNOCKOUT EED NOT BE GROUTED IF WALL IS LEFT INTACT 5 SHALL BE INSTALLED FACTORY KNOCKOUTS UNLESS OTHERWISE APPROVED BY THE ENGINEER KNOCK
216. RE A MAXIMUM OF 1 WATER LOSS IS ALLOWED WITHIN 24 HOUR PERIOD WITH VAULT FILLED TO 2 STORM ELEVATION TEST PER THE 2009 UNIFORM PLUMBING CODE 712 2 JANUARY 2015 NO SCALE CROWN OF INLET PIPES 24 ACCESS MANHOLE WITH TO MATCH Ss ELEVATION VIEW LOCKING G AND COVER STANDAR ETAIL D 22 S FLOW RESTRICTOR PER STANDARDS AXIMUM DE WATER SUR ELEVATION CAPACITY OF OUTLET PIPE MUST BE EQUAL TO OR GREATER THAN ALL SYSTEMS INBOUND LIMIT PIPE SLOPE TO 2 MAXIMUM A FLOW I 27 MIN 8 x8 OPENINGS BOTTOM OF OPENINGS E FLUSH WITH BOTTOM OF VAULT 2 5 MIN PLAN VIEW FLOW Q AS OUTLET PIPE ES 4 I SAND COLLAR SAND COLLAR al OR KOR N SEAL OR KOR N SEAL MIN 4x4 BOOT TYPICAL BOOT TYPICAL EI FFLE WALL TO DIVIDE VA TO TWO APPROXIMAT EQUAL SIZE CELLS MINIMUM ONE ACCESS MAN E PER CELL WITH AT LEAST ONE ACCESS PER 50 VAULT LENGTH OR WIDTH PRE CAST VAULTS SHALL HAVE APPROVED BBER GASKET SYSTEM VAULT SHALL BE DESIGNED D
217. RIS AND SEDIMENT WITH STRAINER OR GRATE PIPING SHALL BE CAST IRON PVC SDR 35 MINIMUM OR PVC SCHEDULE 40 3 PIPE REQUIRED FOR UP TO 1 500 SQ FT OF CONTRIBUTING AREA OTHERWISE 4 MIN PIPING MUST HAVE 1 GRADE AND FOLLOW THE UNIFORM PLUMBING CODE IF WITHIN 3 OF A STRUCTURE DRAIN ROCK A SIZE PER NDP MATERIALS CHAPTER 06 04 B DEPTH OF SIMPLIFIED 12 C DEPTH OF ENGINEERED 12 48 SEPARATION BETWEEEN DRAIN ROCK AND GROWING MEDIUM USE GRAVEL LENS INCH WASHED CRUSHED ROCK 2 TO 3 INCHES DEEP GROWING MEDIUM BIORETENTION SOIL MIX PER NDP MATERIALS CHAPTER 06 04 JANUARY 2015 NO SCALE VEGETATION A PLANT WITH ZONE 1 OR 2 TREES SHRUBS AND GROUND COVER SEE APPENDIX 3 IN THE LID TECHNICAL GUIDANCE MANUAL FOR PUGET SOUND JANUARY 2005 OR CURRENT OR RAIN GARDEN HANDBOOK FOR HOMEOWNERS FOR A PLANT LIST PLANTING SHALL CONSIST OF NATIVE SPECIES ABLE TO TOLERATE VARIABLE SOIL MOISTURE CONDITIONS PONDING WATER FLUCTUATIONS AND VARIABLE SOIL MOISTURE CONTENT PLANTER WALLS A MATERIAL SHALL BE STONE BRICK CONCRETE WOOD OR OTHER DURABLE NO CHEMICALLY TREATED WOOD CONCRETE BRICK OR STONE WALLS SHALL BE INCLUDED ON FOUNDATION PLANS WATERPROOF LINER SHALL BE 30 MIL PVC OR EQUIVALENT FOR FLOW THROUGH FACILITIES INSTALL WASHED PEA GRAVEL OR 1 4 STREAM BED COBBLE PER STANDARD SPECIFICATIONS 9 03 11 2 TO TRANSITION FROM INLET OR SPLASH PAD TO GROWING MEDIU
218. RISER SHOULD EXTEND ABOVE THE Y i asss OVERFLOW ELEVATION DRILL ONE QUARTER INCH HOLES IN THE BOTTOM AND SIDES OF THE WELL SCREEN WELL POINT TO ALLOW WATER TO FREELY FLOW ASSEMBLE THE COMPONENTS i f SAND PACK THE CASING WITH SAND RETENTION PLACE SAND IN THE 2 6 INCHES OF THE BORE HOLE CENTER THE CASING IN ZONE I PVC END CAP SEE DETAIL A IF INSTALLED THE PORT HOLE POUR SAND AROUND THE OUTSIDE OF THE CASING TAMP THE SAND AS OPTIONAL YOU POUR ADD SAND TO A DEPTH OF FOUR INCHES ABOVE THE COUPLING 1 oe FOR OFFSET PURPOSES SEAL WITH BENTONITE OR CONCRETE TO PREVENT SURFACE WATER FROM FLOWING DOWN THE OUTSIDE OF THE CASING FILL THE ELEVATION REMAINER OF THE HOLE WITH A LAYER OF BENTONITE OR CONCRETE ON TOP OF THE SAND ATO SO PEET BOTTOM OF FACILITY IF CONCRETE IS USED IT SHOULD RISE ONE HALF INCH ABOVE THE GROUND AND SHOULD HIGH ui Na SCARIFY BOTTOM OF TRENCH SLOPE AWAY FROM THE CASING LABEL AND MARK THE CASING USE A PERMANENT MARKER TO WRITE AN IDENTIFICATION NUMBER ON THE SIDE OF THE CASING MARK A REFERENCE POINT ON THE TOP EDGE OF RISER FROM WHICH ALL MEASUREMENTS WILL BE TAKEN READ WATER TABLE DEPTH A MEASURE DISTANCE FROM TOP EDGE OF RISER TO SOIL SURFACE B MEASURE DISTANCE FROM TOP EDGE OF RISER TO WATER SURFACE INSIDE OF PIPE OFFSET OBSERVATION PORT C SUBTRACT A FROM B FOR DEPTH TO WATER TABLE
219. RY 2015 Ifa Utility Developer Extension Agreement is required for water sewer or storm drainage facilities Plans for the drainage facilities may be combined with water and sewer if they remain readable As Built drawings must be submitted following inspection prior to occupancy and approved by the City Operation and Maintenance Manual O amp M Manual for Stormwater Management Facilities per Section D2 09 D2 06 3 Submittal Requirements for Minimum Requirements 1 through 9 When MR6 MR7 MR8 and or MR apply in addition to MR1 through MRS Geotechnical Report and Stability Analysis Requirements as described in Development Services plan description sheet Storm Drainage Report no pages may be larger than 11 x 17 including 1 Project Overview General description of project pre developed and developed site conditions site area square footage of each type of impervious surface lawn and landscape areas and non disturbance areas existing stormwater runoff conditions including runoff from off site natural and manmade drainage systems Summary of proposed on site stormwater management facilities Use Chapter D6 in these Standards to choose the facilities and explain why they were chosen Vicinity map showing the property location all roads bordering the site significant geographic features and critical areas and their buffers and flow path s from site to receiving water up to 1 mile Include upstream infor
220. S Table 6 1 Required Tier 1 On site Stormwater Management BMBSs D6 4 Table 6 2A Required Tier 2 On site Stormwater Management 5 D6 5 Table 6 2B Natural Drainage Practices NDPs Allowed as Alternatives to or in Addition to Required Tier 2 BMPS sxc aaa e D6 5 Table 6 3 Req ired Pier 3 BMPS etat pedis D6 6 Table 6 4 On site Stormwater Management BMPs for Runoff Treatment D6 7 Table 6 5 On site Stormwater BMP Selection MatrIX a D6 11 Table 6 6 Continuous Modeling Assumptions for Bioretention Cells and Bioretention Swales utto netu Cot Mtt tuto m D6 23 Table 6 7 Continuous Modeling Assumptions for Bioretention Planters D6 28 Table 6 8 Continuous Modeling Assumptions for Pervious Pavement D6 33 Table 6 9 Spreadsheet Based Modeling Assumptions for Rain Barrels or Cisterns with Water ROUSE c mS D6 37 Table 6 10 Continuous Modeling Assumptions for Cisterns with Detention D6 38 Table 6 11 Continuous Modeling Assumptions for Vegetated Roofs D6 41 Table 6 12 Continuous Modeling Assumptions for Reverse Slope Sidewalks D6 43 Table 6 13 Sizing Factors for On site BMPS noie onere ae nace D6 49 Table 6 14 Plow Co
221. S input data For the Sea Tac rainfall region O1 f 0 46A 0 56A yy 0 A6A 0 72 0 964 1 10 1000 4 9 D4 48 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 where Q low flow design discharge cfs f regional rainfall scale factor For Bellevue 1 065 area of till forest acres A area of till pasture acres A area of till grass acres A area of outwash forest acres Aop area of outwash pasture acres Aog area of outwash grass acres Note Minimum depths may also be met by providing an installed no flow depth per Title 220 WAC where the static water surface level meets minimum flow depth criteria D4 04 9 Storm Drains A General Storm drains shall be provided for curb street sections in accordance with the structure spacing requirements set forth in Section D4 05 2 herein Where trench lines may convey groundwater seepage barriers shall be installed Catch basins or manholes are required when joining pipes of different materials does not apply to taps and joining pipes of different slopes Vertical bends are not permitted If a vertical bend in a storm system is proposed by the Designer is found to conform to Section S3 04 N of the sewer section of these Engineering Standards and is approved by the City then the system must be designed for video camera inspection and be videotaped and pass inspection at the cost of the Developer before construction acceptance
222. SIZING CONSTRUCTION AND MAINTENANCE D6 12 D6 03 1 Required On Site Stormwater Management Practices D6 12 D6 03 2 Natural Drainage Practices D6 16 D6 03 3 Sizing Factors for On site Stormwater BMPs see D6 45 D6 03 4 Flow Control Credits for On site Stormwater Management 5 D6 49 D6 03 5 Maintenance Jose ne o esatto ier dt ra desee Sa ales D6 53 D6o 04 s eaten eiie en m aa ua Su Su aa as D6 53 6 041 Bior tentl N s ns ua Meet tat tates hue D6 53 D6 04 2 Pervious Pavement a aane needa D6 59 D6 04 3 Underdrain for Bioretention or Pervious Pavement D6 61 D6 04 4 Observation Ports for Bioretention or Pervious Pavement D6 61 D6 04 5 Amended Soll once ree teste e aee dee e Ps Une Me D6 62 D6 04 6 Roof Downspout Dispersion enhn enne enhn D6 62 7 Rain Recycling 06 62 D6 04 6 Vesetated ROOTS alami ted een oni 06 63 D6 04 9 Construction Requirements 06 63 D6 04 10 Miscellaneous Products n D6 63 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 TABLE
223. STAMPED A REGISTERED STRUCTURAL ENGINEER VAULT SHALL BE D A P ESIGNED FOR 5 20 TRAFFIC LOADINGS MINIMUM L METAL PARTS SHALL BE CORROSION RESISTANT ROVIDE LADDER RUNGS EDIATELY ADJACENT TO ALL INLET OUTLET PIPES ALL INLETS TO FIRST CE IF PROPOSED COVER IS C CONE SET OVE EATER THAN 1 THEN IT MUST BE 37 MINIMUM AND ACCESS MUST BE A 48 A 24 DIAMETER ACCESS OPENING LY NON SHRINK GROUT TO INSIDE AND OUTSIDE OF ALL JOINTS RINGS RISERS AND FRAMES PIPES SHALL BE PREPENDICULAR TO FACE OF VAULT EIRATE CARRIER PIPE THROUGH VAULT WALL E APPROVED WATERTIGHT STRUCTURE ADAP P SMOOTH BORE HORIZONTAL LEG OF LOW CONTROL TEE INISIDE CARRIER PIPE O FLOW CONTROL OUTSIDE OF 3 City of STORM AND SURFACE STRUCTURE PRIOR TO STARTUP ENTION VAULT SHALL Bellevue WATER UTILITY PASS 1 PER DAY TEST WHERE A AXIMUM OF 1 WA LOSS IS ALLOWED WITHIN A 24 HOUR TO 2 YEAR STORM ATION TEST r HE 2009 UNIFORM BING CODE 712 2 NTION VAULT JANUARY 2015 NO SCALE INLET FILL WITH CONTROLLED DENSITY FILL EDDING OF
224. Standard Step backwater method or the King County Backwater computer program as described in D4 04 4 C For lakes wetlands and closed depressions without an approved floodplain or flood hazard study the base flood elevation and the extent of the floodplain shall be determined using the point of compliance technique as defined in the 2009 King County Surface Water Design Manual Section 3 3 6 E Major Floodplain Floodway Study If the proposed project site is on land that is partially or fully within an already delineated floodplain of a river or stream or determined by a Minor Floodplain Study to be partially or fully within the floodplain of a river or stream then a Major Floodplain Floodway Study is required to determine the floodplain flood way and base flood elevation in accordance with the methods and procedures presented in this section This information will be used by to evaluate the project s compliance with the regulations specified in BCC 20 25H 175 for development or improvements within the floodplain Major Floodplain Floodway Studies must conform to FEMA regulations described in Part 65 of 44 Code of Federal Regulations CFR In addition the following information must be provided and procedures performed Information Required The applicant shall submit the following information for review of a floodplain floodway analysis in addition to that required for the drainage plan of a proposed project This analysis shall ex
225. Submittal Requirements for Minimum Requirements 1 through 5 only A Geotechnical Report as described in the Development Services plan description sheet Geotechnical Report and Stability Analysis Requirements is required when infiltration facilities including bioretention or pervious pavement are proposed and there is a stream wetland steep slope or landslide hazard area on or within 100 feet of the site Storm Drainage Report no pages may be larger than 11 x 17 including 1 Project Overview General description of project pre developed and developed site conditions site area square footage of each type of impervious surface lawn and landscape areas non disturbance areas and existing stormwater runoff conditions including runoff from off site natural and manmade drainage systems Summary of proposed on site stormwater management facilities Use Chapter D6 in these Standards to choose the facilities and explain why they were chosen D2 8 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 2 Site Maps A Existing Conditions a Existing site and drainage conditions Identify areas of high seasonal groundwater per geotechnical report requirements b Show infiltration test locations Note test method used calculated long term infiltration rates and correction factors Use the simplified infiltration test per Section D4 06 7 or a method from Volume 3 3 6 of the DOE Manual 3 Proposed Development A
226. TANDARD D ERF PVC P 3 DIAM UNCOMPACTE SUBGRADE ES D WATER TABLE DEPTH ED SURFACING TOP ER TRANSPORTATION DETAIL 11 ERVOIR COURSE E NDP MATERIALS D6 04 HEREIN EASURE DISTANCE FROM WATER SURFACE INSIDE OF PIPE EASURE DISTANCE FROM OP EDGE OF RISER S OP EDGE OF RISER ADD 1 AND 2 FOR DEPTH OIE IF B HAS CHANGED JANUARY 2015 WATER TABLE FROM PREVIOUS OBS O FINISH GRADE OF PERVIOUS ERVATIONS IF SHIFTING Cit of STORM AND SURFACE Bellevue WATER UTILITY ERVATION ERVIOUS PAV O ASEMEN BUILDING OR SIRUCTURE WALL TEST PLUG FINISHED ROPE 36 MIN m NS OBS PORT PIPE MID STATES DIAMETER PLASTIC BOX EX MSBCF 1118 18XL CIS ESERVOIR COURSE SEE STANDARD DETAIL NDP 11 RIGHT OF WAY OR EAS UNPAVED FINISHED GRADE Z PAVEMENT 3000 P S I TP COLLAR CAST IN PLACE
227. THROUGH VAULT WALL JANUARY 2015 NO SCALE SOD OR SEED EVATION 18 DIA MIN POND INTERIOR GER OUTLET RIM UP TO 100 YEAR SEE NOTE 2 EMBANKMENT ME PER STD DETAIL D 22 mapu EXISTING WATER QUALITY MIN FREEBOARD SAND COLLAR OR a DESIGN W S E KOR N SEAL BOOT PROFILE COMPACT OVERFLOW 1 5 MIN TO 95 er 1 DRY DENSITY SOD OR SEED DIKE 1 GASKETED END CAP FEP BARRIER 6 MAX DEPTH SEE NOTE 3 OUTLET PIPE TRASH RACK SEE I STANDARD DETAIL ZS VERTICLE RISER SECTION D 53 SHALL BE ALIGNED PLUMB VERTICALLY KEY EXCAVATED sw HORIZONTAL RISER INTO NATIVE SECTION SHALL MATCH GROUND OUTLET PIPE SLOPE PLAN PRIMARY OVERFLOW r SECONDARY OVERFLOW THROUGH FLOW RESTRICTOR Con OR PIPE SYSTEM INVERT IS 1 ABOVE POND BOTTOM RAP PAD BERM OR BAFFLE AT DESIGN W S OR SUBMERGED 1 BELOW WATER QUALITY DESIGN W S EXTEND BERM CONTROL STRUCTURE WITH ACROSS ENTIRE WIDTH OF WETPOOL FLOW RESTRICTOR NOTES LANDSCAPE PLAN IS REQUIRED TO BEAUTIFY OR SCREEN POND 6 MINIMUM TOP WIDTH OF EMBANKMENT 15 MINIMUM FOR VEHICLE ACCESS TO CONTROL STRUCTURE SCREW TYPE SHEAR GATE REQUIRED FOR ALL SYSTEMS TO BE MAINTAINED BY THE CITY CAPACITY OF OUTLET PIPE MUST BE EQUAL TO OR GREATER THAN DISCHARGE DURING EMERGENCY OVERFLOW CONDITION IF PIPE OVERFLOW IS USED IN LIEU OF SPILLWAY 8
228. TM RRR 52 oss x TYPICAL GUTTER ELEVATION NOTE City of STORM AND SURFACE WATER UTILITY MODIFY INLET TO BIORETENTION 2 PLANTER AS NEEDED Bellevue PREVENT EROSION RAIN CURB CUT OPENING FOR BIOR NTIO NO 10 JANUARY 2015 NO SCALE PERVIOUS ASPHALT OR CO WEARING COURSE SEF NOT LEVELING COURSE OPTIONAL E NOTE 4 ESERVOIR COURSE E NOTE 5 WOVEN GEOTEXTILE OPTIONAL BOTTO RUNOFF TREATMENT LAYER IF REQUIRED SUBGRAD PERVIOUS PAVEMENT WITHIN CITY RIGHT OF WAY REQUIRES APPROVAL BY THE CITY WHEN PLACED BENEATH A TRAVELED WAY HESE GUIDELINES PROVIDE A MINIMUM DEPTH FOR THE HYDROLOGIC PERFORMANCE OF THE PERVOUS PAVE HE STRUCTURAL CAPACITY OF PAVEMENT SECTIONS WHEN SUBJECT TO VEHICULAR LOADS DEPENDS SEVERAL FACTORS AND MUST BE DESIGNED BY A LICENS PROFESSIONAL ENGINEER LONGITUDINAL SLOPE O TO 5 MAX FOR PERVIOUS ASPH 6 AX FOR PERVIOUS CONCRETE USE CHECK DAM OR OTHER METHODS TO MAXIMIZE P THE SUBSURFACE FOR LONGITUDINAL SLOPES EXCEEDING 2 SEE STANDAR NDP 15 EVELING COURSE MATERIALS 1 5 TO U S NO 8 U GRADED CRUSHED ANGULAR THOROUGHLY WASHED STONE ESERVOIR COURSE MINIMUM DEPTH OF 6 WITHOUT UNDERDRAIN 22 MINIMUM WITH UNDERDRAIN
229. VIDE CLEANOUT UNDERDRAIN P EVERY 100 FEET A BENDS OR JUNCTIONS JANUARY 2015 OFFSET FRAME SO THAT TEE AND GATE ARE VISIBLE AT EDGE 24 ACCESS MANHOLE W BOLT OF OPENING AND DIRECTLY LOCKING RING AND COVER PER OVER THE STEPS STANDARDS SEE NOTE 2 COVER PER TEE SECTION WITH THREADED NOTE 13 8 END SEE NOTE 12 EVATION UPPER BAFFLE PLATE OPTIONAL SEE NOTE 9 WATER QUALITY _ FT DESIGN W S NOTES LOWER VERTICLE RISER SECTION SHALL i BAFFLE WALL BE ALIGNED PLUMB VERTICALLY SEE NOTE 1 HORIZONTAL SECTION SHALL MATCH OUTLET PIPE SLOPE SHEAR GATE PER STANDARDS MAX 20 GRAVITY DRAIN IF GRADE 228e OPENINGS TL ALLOWS SEE NOTES 6 amp 7 VERTICLE RISER SECTION SHALL FLUSH WITH BOTTOM i SAND COLLAR OR BE ALIGNED PLUMB VERTICALLY OF VAULT i KOR N SEAL BOOT HORIZONTAL SECTION SHALL TYPICAL MATCH OUTLET PIPE SLOPE PLAN LADDER RUNGS FLOOR TO UPPER BAFFL ENERGY DISSI FOREN EA SUMP AREA MIN SAND COLLAR OR L 4x4 OR 54 DIA KOR N SEAL BOOT TYPICAL LADDER RUNGS BOTH SIDES 2 8 x8 OPENINGS FLUSH 4 LOWER BAFFLE WALL WITH OF VAULT NOTES LOWER BAFFLE WALL TO DIVIDE VAULT INTO TWO CELLS WITH FIRST CELL FOREBAY TO OCCUPY 25 OF VAULT SURFACE AREA ALL INLET PIPES MUST D
230. a such as a roof Sizing Factors are also provided for runoff treatment and flow control but those are intended for conceptual design only The Developer is required to perform independent calculations for sizing and designing pervious pavement to meet runoff treatment and flow control requirements per Chapter D3 of these Standards When an approved continuous model is used to size pervious pavement with the demonstrative approach the assumptions listed in Table 6 8 shall be applied Pervious pavement should be modeled as an impervious area with runoff routed to a gravel filled infiltration trench of the same surface area The tributary areas including off site tributary areas if any pavement area and average water surface depth in the aggregate should be iteratively sized until runoff treatment and or flow control requirements are met For pervious pavement facilities with longitudinal slopes greater than two 2 percent the model must account for the effects that slope has on reducing the amount of wetted area that is available for infiltration This may be done by adjusting the Gravel Trench Bottom Length and Effective Total Depth inputs to the model as shown in Table 6 8 based on the number of interceptor infiltration trenches or check dams maximum ponding depth in each cell and longitudinal bottom slope of each cell See Figure 6 2 for a schematic illustration and Table 6 8 for more detailed guidance D6 32 SURFACE WATER EN
231. a 15 minute or smaller increment Rainfall based on the historic Seatac record is appropriate for use in Belleuve with a correction factor of 1 065 For modeling on site stormwater management design flows are generated with an Ecology approved continuous hydrology model When including on site stormwater management BMPs on a project credit maybe taken for flows controlled on site The credit maybe implemented in modeling efforts through either a default or demonstrative method The default method uses the default credits provided in Chapter 7 of the LID Manual as modified herein by Section D6 03 1 D6 03 3 and D6 03 4 The implementation of demonstrative credits is outlined in Chapter D6 On Site Stormwater Management Section D6 03 2 Natural Drainage Practices in these Standards D3 04 MINIMUM IMPERVIOUS AREAS For single family residential plat developments use Table 2 2 in Volume III of the DOE Manual for minimum values A higher percent impervious area shall be required if the proposed project land use impervious lot coverage allows a greater impervious area coverage Stormwater system designs shall take into account maximum future build out of the proposed development as D3 15 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 allowed by land use code For commercial and multi family residential developments use actual project values Site areas set aside in NGPAs NGPEs shall be excluded from the gross acreage value used
232. a shall be confirmed to represent current channel and floodplain conditions or new channel cross section data shall be obtained by field survey Topographic information obtained from aerial photographs may be used in combination with surveyed cross sections in the hydraulic analysis The elevation datum of all information used in the hydraulic analysis shall be specified All information shall be referenced directly to NAVD 1988 and include local correlation to NGVD 1929 unless otherwise approved by The Utility See Table 4 5 for correlations of other datum to NAVD 1988 Methodology Flood profiles and floodway studies shall be calculated using the U S Army Corps of Engineers HEC RAS computer model or subsequent revisions Floodway Determination Bellevue recognizes two distinct floodway definitions The FEMA floodway describes the limit to which encroachment into the natural conveyance channel can cause one foot or less rise in water surface elevation The zero rise floodway is based upon the limit to which encroachment can occur without any measurable increase in water surface elevation or energy grade line Floodway determinations studies are subject to the following requirements FEMA floodways are determined through the procedures outlined in the FEMA publication Guidelines and Specifications for Flood Hazard Mapping Partners using the 1 foot maximum allowable rise criteria Transitions shall take into account obstructions to
233. able 7 1 The application rate for Mix 3 60 Ibs acre Table 7 1 Mix 3 Wet Area Seed Mix Seed Type Weight Purity Germination Tall or meadow fescue 60 70 98 90 Festuca arundinacea or Festuca elatior Seaside Creeping bentgrass 10 15 98 85 Agrostis palustris Meadow foxtail 10 15 90 80 Alepocurus pratensis Alsike clover 1 6 98 90 Trifolium hybridum Redtop bentgrass 1 6 92 85 Agrostis alba Seed mix taken from Table 4 5 from BMP C120 Temporary and Permanent Seeding of the DOE Stormwater Management Manual for Western Washington 2005 Edition For ponds requiring emergent wetland plant species Table 7 2 lists recommended plant varieties D7 8 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 7 22 Recommended Emergent Wetland Plant Species Species Common Name Notes Maximum Depth INUNDATION TO 1 FOOT Agrostis exarata Spike bent grass Prairie to coast To 2 feet Carex stipata Sawbeak sedge Wet ground Eleocharis palustris Spike rush Margins of ponds wet meadows To 2 feet Glyceria occidentalis Western mannagrass Marshes pond margins To 2 feet Juncus effusus Soft rush Wet meadows pastures wetland To 2 feet magins Juncus tenuis Slender rush Wet soils wetland margins Oenanthe sarmentosa Water parsley Shallow water along stream and pond margins needs saturated soils
234. acceptable discharge point Drainage easements for this conveyance system must be secured from downstream property owners and recorded prior to engineering plan approval D4 02 3 Temporary Discharges to the Sanitary Sewer Surface water runoff into the sanitary sewer system is generally prohibited by the Utility Code Unavoidable temporary discharges into the sanitary sewer system must meet with the approval of King County Wastewater Treatment Division Industrial Waste Program The Engineering Division of the Utilities Department and The Operations amp Maintenance Division Water Quality Section of the Utilities Department D4 4 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 For approved temporary discharges Operations amp Maintenance Division Water Quality Section of the Utilities Department will review for approval the Location of connection to the sanitary sewer Method for the connection and pre connection requirements i e settling tanks sump pump etc Time of discharge Duration rate and volume of the discharge Other applicable discharge conditions Temporary discharges to sewer lakelines are prohibited The Developer is responsible for first obtaining permission and a sewer permit for constructed connections from the City prior to requesting a discharge permit from King County Wastewater Treatment Division Industrial Waste Program D4 03 OFF SITE CAPACITY ANALYSIS Pursuant to Secti
235. affic shall meet Building Code requirements Mulch mat or other measures to control erosion of growth media shall be maintained until 90 percent vegetation foliage coverage is attained increase flow control consider designing the growth media with water holding capacity on the high end of the specified range and a saturated hydraulic conductivity on the low end of the specified range Vegetation Vegetation foliage of the selected plants shall attain 90 percent coverage of the vegetated roof surface area within 2 years or additional plantings shall be provided until this coverage requirement is met Plant spacing and plant size shall be designed to achieve specified coverage by a certified landscape architect Vegetation shall be suited to harsh e g hot cold wet and windy rooftop conditions see plant list in NDP Materials Section D6 04 8 Plants shall not require fertilizer pesticides or herbicides after the 2 year establishment period has ended The Developer shall develop and implement a Landscape Management Plan to be submitted as part of the Operations and Maintenance Manual per Chapter D2 Irrigation Plan Minimum design requirements are as follows D6 40 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 lv Provisions shall be made for irrigation during the first two growing seasons following installation Sufficient irrigation shall be provided to achieve and maintain 90 percen
236. age Testing A Dry Ponds Leakage rates shall not exceed the maximum allowable infiltration rate of 2 inches per hour For infiltration rates in excess of the maximum a liner system shall be installed B Wet Ponds If in the opinion of the City workmanship materials or infiltration rates appear to contribute to excessive leakage the pond shall be tested for leakage Wet ponds shall be filled to the 2 year water surface elevation Pipe plugs shall be inserted into all inlet and outlet piping The maximum allowable leakage shall not exceed one percent 1 of volume below the 2 yr water surface elevation over a 24 hour test period C Pipe Tank Systems Pipe tanks systems shall be free from visible leaks All penetrations shall be sealed to prevent leaks Shear gates and valves shall not leak Pipe tank systems with footing or underdrain systems If in the opinion of the City workmanship or materials appear to contribute to excessive leakage the detention system shall be tested for leakage Systems shall be filled to the 2 year water surface elevation Pipe plugs shall be inserted into all inlet and outlet piping The maximum allowable D8 6 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 1 shall not exceed one percent 1 of volume below the 2 yr water surface elevation over a 24 hour test period D Precast and Cast In Place Vaults Precast and cast in place vaults shall be free from visible leaks Cold joints
237. ai auqa Sumas D 1 CATCH BAS UN TYPE Ta a han as een dee aul ee enses D 2 CATCH BASIN EY PES D 3 DUE FR Qu E II VEA D 4 LADDER STEP AND TOP SLAB DETAILS D 5 VANEDGRATE iioi uu ei ik D 6 PARKING LOT AREA eodeni E ERU tt Vot Ud D 7 SOLID COVER E D 8 STANDARD FRAMEINSTALLATION D 9 THROUGEECURB INLET FRAME u u nasaq anh aaa irs D 10 THROUGH CURB INLET FRAME INSTALLATION 2 D 11 FRAME amp GRATE FOR EXISTING ROLLED CURB a D 12 EXISTING ROLLED CURB FRAME amp GRATE INSTALLATION D 13 GRATE FOR EXISTING ROLLED CURB INSTALLATION D 14 CONVERSION RISER FOR CATCH BASIN TYPE I L m D 15 AREA INCE eec S D 16 MANHOLE TYPE Tacito eee i tae PEG IGI Ue tad mu Ud n vec D 17 MANHOLE TYPBE Distt sd aus DS r ee D 18 MANHOLE TYPE 25 a ususi a qapas D 19 annman eris RU D 20 24 MANHOLE RING AND COVER D 21 24 BOLT LOCKING MANHOL
238. al equipment The type of equipment needing access is dependent on the size of channel Large channels will need access for dump trucks and loaders For small ditches foot or pick up truck access may suffice D4 9 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 4 2 Channel Protection Velocity at Design REQUIRED PROTECTION Flow fps Greater Less than Type of Protection Thickness Minimum Height or equal to Above Design Water Surface Grass lining Or Bioengineered lining Rock lining Or Bioengineered lining Engineered Scour Protection Rock Lining shall be reasonably well graded as follows Maximum stone size 12 inches Median stone size 8 inches Minimum stone size 2 inches 9 Riprap shall be reasonably well graded as follows Maximum stone size 24 inches Median stone size 16 inches Minimum stone size 4 inches Note Riprap sizing is governed by side slopes on channel assumed to be approximately 3 1 Riprap Design When riprap is set stones are placed on the channel sides and bottom to protect the underlying material from being eroded Proper riprap design requires the determination of the median size of stone the thickness of the riprap layer the gradation of stone sizes and the selection of angular stones that will interlock when placed Research by the U S Army Corps of Engineers has provided criteria for selecting the median stone weight W50 Figure 4 1 If the riprap is to be used in a hig
239. all be final Any approved Adjustments or Deviations shall be included with the final approved drainage plan D2 03 EXCEPTIONS A request for an Exception to the Minimum Requirements may be submitted with a permit or approval listed in LUC 20 35 015 C or if none of the listed permits or approvals apply to the project or if a decision is necessary to finalize the site layout the applicant may submit a request for an Exception with submittal of a Predevelopment Services application The Director may approve a request for an exception provided the applicant can demonstrate compliance with the criteria contained BCC 24 06 065 D2 04 ERRORS AND OMISSIONS Any errors or omissions in the approved plans or information used as a basis for such approvals may constitute grounds for withdrawal of any approvals and or stoppage of any or all of the permitted work as determined by the City It shall be the responsibility of the Developer to show cause why such work should continue and make such changes in plans that may be required by the City before the plans are approved D2 05 THRESHOLDS D2 05 1 Threshold Discharge Area An onsite area draining to a single natural discharge location or multiple natural discharge locations that combine within one quarter mile downstream as determined by the shortest flow path is a threshold discharge area The examples in Figure 2 1 below illustrate this definition This definition is intended to cl
240. all summer Scirpus atrocinctus Woolgrass Tolerates shallow water tall formerly S cyperinus clumps Scirpus microcarpus Small fruited bulrush Wet ground to 18 inches depth 18 inches Sagittaria latifolia Arrowhead INUNDATION 1 TO 2 FEET Agrostis exarata Spike bent grass Prairie to coast Alisma plantago aquatica Water plantain Eleocharis palustris Spike rush Margins of ponds wet meadows Glyceria occidentalis Western mannagrass Marshes pond margins Juncus effusus Soft rush Wet meadows pastures wetland magins Scirpus microcarpus Small fruited bulrush Wet ground to 18 inches depth 18 inches Sparganium emmersum Bur reed Shallow standing water saturated soils INUNDATION 1 TO 3 FEET Carex obnupta Slough sedge Wet ground or standing water 1 5 to 3 feet Beckmania syzigachne Western sloughgrass Wet prairie to pond margins Scirpus acutus Hardstem bulrush Single tall stems not clumping To 3 feet Scirpus validus 2 Softstem bulrush INUNDATION GREATER THAN 3 FEET Nuphar polysepalum Spatterdock Deep water 3 to 7 5 feet Nymphaea odorata White waterlily Shallow to deep ponds To 6 feet Notes 9 Non native species Beckmania syzigachne is native to Oregon Native species are preferred Scirpus tubers must be planted shallower for establishment and protected from foraging waterfowl until established Emerging aerial stems should project above water surface to allow oxygen transport to the roots Primary sources Municipality of Me
241. anagement Facility Selection for MR5 and MR7 D6 3 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Tier 1 Minimize Runoff Generation The first priority in managing stormwater runoff on site 15 to minimize the amount of stormwater runoff that is generated Each project is required to evaluate these Tier 1 BMPs in the order presented in Table 6 1 and must implement all Tier 1 techniques that are applicable to the site without causing erosion or flooding on site or downstream Table 6 1 Required Tier 1 On site Stormwater Management BMPs BMP Description Applicability Requirements Smart Site Site layout and design All projects Comply with LUC 20 20 460 Impervious Design techniques that minimize surface limits disturbance of the Comply with Section D6 03 1 B hydrologic cycle Preserve Set aside native growth All projects Comply with LUC 20 20 900 Tree Native areas in Native Growth Preservation exceed where feasible Vegetation Protection Easement If possible record NGPE against property NGPE preserve per LUC 20 25H 030 B 2 significant trees Restore previously disturbed areas with native vegetation Comply with Section D6 03 1 Full Full Dispersion Disperse Limited No runoff treatment or flow control Dispersion runoff from 90 100 percent applicability required if site fully dispersed or fully or Full of impervious surfaces in see infiltrated Infiltration some cases retain 35 65 Requirements Comply
242. ance system or to on site stormwater facilities D2 15 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 5 6 7 8 9 10 11 12 13 14 15 16 Provide maintain temporary sedimentation collection facilities to ensure that sediment or other hazardous materials do not enter the storm drainage system in accordance with the sites approved CSWPPP For all construction during the rainy season downhill basins and inlets must be protected with catch basin inserts Simply placing filter fabric under the grate is not acceptable Prior to final inspection and acceptance of storm drainage work pipes and storm drain structures shall be cleaned and flushed Any obstructions to flow within the storm drain system such as rubble mortar and wedged debris shall be removed at the nearest structure Wash water of any sort shall not be discharged to the storm drain system or surface waters Ends of each storm drain stub at the property line shall be capped and located with an 8 long 2 x 4 board embedded to the stub cap and extending at least 3 feet above grade and marked permanently STORM A copper 12 ga locate wire firmly attached The stub depth shall be indicated on the marker All grates in roadways shall be ductile iron bolt locking vaned grates per the Standard Details Structures in traffic lanes outside of the curbline which do not collect runoff shall be fitted with round bolt locking s
243. and are not considered to be redevelopment per Section 24 06 065 F of the Storm and Surface Water Utility Code Removal of pavement to subgrade and subsequent replacement not including spot base repairs is considered to be complete reconstruction which qualifies as redevelopment and disturbance Such reconstruction is not considered to be routine maintenance Flow control facilities for the right of way shall be owned and operated by the City and shall be separate from private on site systems In a plat where the stormwater facilities will be owned and operated by the City runoff from the right of way and private properties in the plat may be combined and controlled in a single facility Private detention systems may accommodate public drainage e g from a public right of way if a hold harmless agreement is completed by the developer and recorded against the property and the proposal meets all the other design requirements of the Utility D4 06 2 Design Flow Rates A General Design flow rates are established in Section 24 06 065 E of the Storm and Surface Water Utility Code Upstream off site runoff must bypass the proposed flow control facilities unless the existing peak runoff rate from the upstream off site area for the 100 year peak flow rate is less than 50 percent of the allowable release rate for the 100 year peak flow rate of the proposed project If the runoff is above the 50 limit and bypassing detention is not practical t
244. and conveyed across the downstream properties to an approved discharge location The Developer shall secure drainage easements from the downstream owners and record such easements at the King County Office of Records and Elections prior to drainage plan approval if necessary Where no conveyance system exists at the abutting downstream property line and the natural existing discharge is unconcentrated any runoff concentrated by the proposed project must be discharged as follows If the 100 year peak discharge is less than or equal to 0 2 cfs under existing conditions and will remain less than or equal to 0 2 cfs under developed conditions then the concentrated runoff may be discharged onto a rock pad or to any other system that serves to disperse flows If the 100 year peak discharge is less than or equal to 0 5 cfs under existing conditions and will remain less than or equal to 0 5cfs under developed conditions then the concentrated runoff may be discharged through a dispersal trench or other dispersal system provided the applicant can demonstrate that there wil be no significant adverse impact to downhill properties or drainage system If the 100 year peak discharge is greater than 0 5 cfs for either existing or developed conditions or if a significant adverse impact to downhill properties or drainage systems is likely then a conveyance system must be provided to convey the concentrated runoff across the downstream properties to an
245. andards Conceptual site plans for all sites to be served by the proposed stormwater facilities shall be submitted to the City for review Construction of the facilities must occur in conjunction with the first project or phase to be served by the flow control facilities Flow control is waived for site areas which are or will be set aside in Native Growth Protection Areas and Easements NGPAs NGPEs provided such NGPAs NGPEs in separate tracts or in easements which are permanently fenced or permanently signed when included as part of the lot or the developed parcel Flow control system design shall assume that all other pervious areas will be landscaped as part of or following development The requirement for flow control is met for sites that implement full infiltration or full dispersion per Section D6 03 1 Flow control requirements may be partially offset by implementing on site stormwater management practices where site conditions allow See Chapter D6 to evaluate feasibility on site practices before designing flow control facilities The 100 year water surface elevation shall be at least 1 foot below the lowest habitable finished floor elevation in the area that is tributary to the stormwater detention facility D4 68 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 The 100 year water surface shall not surcharge roof footing and yard drains or underdrains Street and parking overlays are considered to be routine maintenance
246. anholes catch basins stub outs or tees The use of sidewalk drains shall not be permitted In areas without an existing drainage system the private drainage system shall discharge in accordance with Section D4 02 Outfalls and Discharge Locations herein Properties that can drain directly to Lake Washington or Lake Sammamish shall ensure that the 100 year storm capacity for all drainage in the pipe is provided and that the pipe invert matches the ordinary high water elevation to prevent erosion B Flow Control and Treatment Facilities Flow Control and Treatment Facilities shall comply with all criteria for stormwater systems set forth herein unless specifically exempted D4 65 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 C Other On site Drainage Facilities All drainage facilities which convey offsite stormwater must be built to City standards Drainage facilities for commercial and multi family properties shall comply with all criteria for stormwater systems set forth herein however they are exempt from sections D4 04 D4 05 D7 02 D7 03 D8 04 D8 05 and Appendix D 1 Standard Details except for any portions within these sections that relate to Flow Control and or Treatment Facilities and except for any facilities which convey offsite stormwater Other on site private drainage facilities shall be designed by a professional engineer licensed by the State of Washington to meet City Storm amp Surface Water Utility Code
247. ant hotspots When specified by the proJect engineer design requirements shall include Geomembrane shall be ultraviolet UV light resistant and minimum thickness of 30 mils A thickness of 40 mils shall be used in areas of maintenance access or where heavy machinery must be operated over the membrane Geomembranes shall bedded according to the manufacturer s recommendations Liners shall be installed so that they can be covered with 12 inches of top dressing forming the bottom and sides of the water quality facility except for liner sand filters Top dressing shall consist of 6 inches of crushed rock covered with 6 inches of native soil The rock layer is to mark the location of the liner for future maintenance operations As an alternative to crushed rock 12 inches of native soil may be used if orange plastic safety fencing or another highly visible continuous marker is embedded 6 inches above the membrane If possible liners should be of a contrasting color so that maintenance workers are aware of any areas where a liner may have become exposed when maintaining the facility Geomembrane liners shall not be used on slopes steeper than 5H 1V to prevent the top dressing material from slipping Textured liners may be used on slopes up to 3H 1V upon recommendation by a geotechnical engineer that the top dressing will be stable for all site conditions including maintenance Plant Materials Minimum re
248. arify how the thresholds are applied to project sites with multiple discharge points D2 2 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 The City s Land Use Code Includes thresholds for pervious pavement for Land Use Code purposes Those thresholds may be different for Storm amp Surface Water Utility Code purposes Use guidance herein for all Storm amp Surface Water Utility Code purposes Example of a Project Site Example of a Project Site Example of a Project Site with a Single Natural with Multiple Natural with Multiple Natural Discharge and a Single Discharges and a Single Discharges and Multiple Threshold Discharge Area Threshold Discharge Area Threshold Discharge Areas Natural Natural pees ischarge__ 1 Discharge Area 2 THRESHOLD THRESHOLD DISCHARGE DISCHARGE Natural Natural i i Natural Discharge i Discharge H Discharge Location Locations i i Locations V gt Mile Downstream UU UU U U UU Uu L L u E gt shortest flow path v N Figure 2 1 Threshold Discharge D2 05 2 Applicability Thresholds help define the applicability of the Minimum Requirements to development and redevelopment projects based on project type and size A narrative description of the threshold applicability process is included in Section 24 06 065 of the Storm and Surface Water Utility Code Figures 2 2 and 2 3 present the same applicability determination process in flow cha
249. ary sewer system Roof footing and yard drains shall not be located within the public right of way except where connecting to the municipal drainage system Roof footing and yard drain systems serving more than one parcel shall be within private utility easements Roof footing and yard drainage may be conveyed over steep banks in single wall corrugated polyethylene tubing provided the overbank drain is privately owned and maintained the minimum tubing slope is 1596 or greater the CPT is continuous and without joints from the top of the slope to the toe the CPT is a minimum of 4 inches and a maximum of 6 inches in diameter a yard drain or clean out is placed at the top of the slope the overbank drain is buried with a maximum cover of 1 foot a the outfall discharge is non erosive CPT may not be used in the right of way or for any other purpose except as a privately owned and maintained overbank drain C Maintenance Roof footing and yard drainage systems drainage systems on single family properties drainage facilities within private easements and drainage facilities otherwise denoted as private shall be designed to provide access for maintenance and operation by the owners of such facilities D4 04 12 Private Commercial and Multi Family Drainage Systems A General Private commercial and multi family drainage systems are to be privately inspected and certified Private commercial and multi fa
250. as Open Channel Hydraulics by Chow may also be used as guides to select n values Figure 4 5 contains the geometric elements of common channel sections useful in determining area A wetted perimeter WP and hydraulic radius R A WP If flow restrictions occur that raise the water level above normal depth within a given channel reach a backwater condition or subcritical flow is said to exist This condition can result from flow restrictions created by a downstream culvert bridge dam pond lake etc and even a downstream channel reach having a higher flow depth If backwater conditions are found to exist for the design flow a backwater profile must be computed to verify that the channel s capacity is still adequate as designed The Direct Step or Standard Step backwater methods presented in this section may be used for this purpose D4 14 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 4 3 Values Roughness Coefficient N For Open Channels Type of Channel and Description A Consiructed Channels a Earth straight and uniform 1 Clean recently completed 2 Gravel uniform section clean 3 With short grass few weeds b Earth winding and sluggish 1 No vegetation 2 Grass some weeds 3 Dense weeds or aquatic plants in deep channels 4 Earth bottom and rubble sides 5 Stony bottom and weedy banks 6 Cobble bottom and clean sides Rock lined 1 Smooth and uniform 2 Jagged and irregular Cha
251. as regulations BCC 20 25H Fish passage can generally be ensured by providing structures that do not confine the streambed that is a structure wide enough so that the stream can maintain its natural channel within the culvert Bridges bottomless arch culverts arch culverts and rectangular box culverts utility vaults can often be used to accommodate stream channels Where it is unfeasible to construct these types of structures round pipe culverts may be used if high flow velocities are minimized and low flow depths are maximized The Hydraulic Code Rules Title 220 WAC detail requirements for WDFW Hydraulic Project Approval See the WDFW manual Design of Road Culverts for Fish Passage for detailed design methodologies A Materials Galvanized metals leach zinc into the environment especially in standing water situations High zinc concentrations sometimes in the range that can be toxic to aquatic life have been observed in the region Therefore use of galvanized materials in stormwater facilities and conveyance systems is discouraged Where other metals such as aluminum or stainless steel or plastics are available they should be used See Materials D7 02 B Design Criteria Table 4 8 from Title 220 WAC lists allowable velocities flow depths and hydraulic drops for culverts in fish bearing streams Velocities are for the high flow design discharge water depths are for the low flow design discharge The hydraulic drop
252. ass water at a rate greater than the infiltration rate of the existing subgrade Runoff Treatment Layer Optional When permeable pavement is designed to provide water quality treatment the native underlying soils must meet the Soil Physical and Chemical Suitability for Treatment requirements in Section 3 3 7 of Volume III of the DOE Manual When the native soils cannot meet those requirements a treatment liner shall be installed that is functionally equivalent to Section 4 4 2 of Volume V of the DOE Manual Observation Port D6 31 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 1 An observation port in accordance with Standard Details NDP 16 NDP 17 shall be installed in the furthest downslope area for every 10 000 square feet of pervious pavement area for projects required to meet MR6 and or 7 Maintenance Provide minimum 8 eight feet minimum width access for ongoing maintenance Sizing If the pervious pavement area will not receive runoff from another impervious or pervious area it should be built according to the design criteria above to meet the minimum requirements for on site stormwater management MR5 Sizing Factors for pervious pavement are provided in Section D6 03 3 These Sizing Factors may be used to size pervious pavement to meet MR5 when runoff treatment and or flow control are not also required and when pervious pavement area will receive stormwater runoff from a different pervious or impervious are
253. atic channels In this method stations are established along the channel where cross section data is known or has been determined through field survey The computation is carried out in steps from station to station rather than throughout a given channel reach as is done in the Direct Step method As a result the analysis involves significantly more trial and error calculation in order to determine the flow depth at each station Computer Applications Because of the iterative calculations involved use of a computer to perform the analysis is recommended The King County Backwater KCBW computer program included in the software package available with this manual includes a subroutine BWCHAN based on the Standard Step backwater method which may be used for all channel capacity analysis It can also be combined with the BWPIPE BWCULYV subroutines to analyze an entire drainage conveyance system A schematic description of the nomenclature used in the BWCHAN subroutine is provided in Figure 4 8 See the KCBW program documentation for further information There are a number of commercial software programs for use on personal computers that use variations of the Standard Step backwater method for determining water surface profiles The most common and widely accepted program is called HEC RAS published and supported by the United States Army Corps of Engineers Hydraulic Engineering Center It is one of the models accepted by FEMA for use in
254. ation or saturation This area can be used to transition or blend with the existing landscape D6 04 2 Pervious Pavement This work shall consist of construction of the pervious pavement section as described in this section Three types are allowable pervious asphalt pervious concrete or pervious pavers which include grass and gravel paving systems A Wearing Course Pervious Asphalt or Pavers for specifications and construction methods use Low Impact Development Technical Guidance Manual for Puget Sound Puget Sound Partnership 2005 or current version Permeable Interlocking Concrete Pavements latest edition by the Interlocking Pavement Institute or per the designer or manufacturer The following pervious pavement products are approved Porous Permeable pervious pavers Invisible Structures GrassPave2 Presto Geosystems Uni Eco Stone Uni Ecoloc Eco Priori Hastings Check Block Grasscrete Turfstone Geoblock 5150 Tufftrack Grassroad Pavers Grassy Pavers Invisible Structures Gravelpave2 Turf amp Gravel Pavers Aqua Pave Old Countrystone Aqua Pave Standards Aqua Pave Venetian Cobble D6 59 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Pervious Concrete Use ACI 522 1 Specification for Pervious Concrete Pavement published by the American Concrete Institute Farmington Hills Michigan For projects larger than 5 000 square feet a test panel must be submitted to the inspector prior to installation B Res
255. ation parameter See Table 4 6 HWO Headwater ft assuming Outlet Control C Inlet Control Equation parameter See Table 4 6 HWI Headwater ft assuming Inlet Control Y Inlet Control Equation parameter See Table 4 6 DXN Distance expressed as a fraction of the pipe length Ratio Ratio of tributary flow to main upstream flow from the outlet to where the flow profile intersects with of Q3 O1 normal depth DXN will equal one under full flow 3 conditions and will equal zero when a hydraulic jump occurs at the outlet or when normal depth equals zero Q Junction Q ae normal depth will equal zero when the pipe grade is flat or reversed VBH Barrel Velocity Head ft based on the average velocity determined by V Q Afull VUH Upstream Velocity Head ft based on an inputted velocity EHU Upstream Energy Head ft available after bend losses and junction losses have been subtracted from VUH VCH Critical Depth Velocity Head ft VNH Normal Depth Velocity Head ft VEH Entrance Depth Velocity Head ft VOH Outlet Depth Velocity Head ft D4 46 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D4 04 8 Culverts Providing for Fish Passage Migration General In fish bearing waters water crossing structures must usually provide for fish passage as required for Washington State Department of Fish and Wildlife WDFW Hydraulic Project Approval or as a condition of permitting under Bellevue s Critical Are
256. atment requirements Amended soil areas shall be modeled as landscape unless used to meet full dispersion requirements Source Guidelines and Resources for Implementing Soil Quality and Depth BMP T5 13 in WDOE Stormwater Management Manual for Western Washington 2009 Edition Provides treatment if underlain by soils that meet Soil Physical and Chemical Suitability for Treatment requirements in Chapter 3 of Volume III of the DOE Manual including minimum depth 18 inches minimum cation exchange capacity minimum organic content and maximum infiltration rate These BMPs are not capable of meeting water quality treatment requirements Further some of these NDPs typically receive only roof runoff which does not require treatment Refer to Sections D6 03 1 and D6 03 2 for design sizing construction and maintenance methods for BMPs and NDPs See also Chapter D5 for more information on water quality treatment BMPs Sizing Factors for meeting runoff treatment are provided in Section D6 03 3 C While these factors may be used as a guideline in preliminary sizing and or as a simplified check for the reviewer the NDPs must be designed by a professional engineer to satisfy runoff treatment requirements MR6 D6 7 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 C Flow Control Minimum Requirement 7 Dispersion and infiltration BMPs including the Infiltration NDPs bioretention and pervious pavement are highly effective in controlling
257. ault or the bottom of the excavation at the outside diameter for tanks outside the 1 1 plane e Property line to the bottom edge of the vault or the bottom of the excavation at the outside diameter for tanks outside the 1 1 plane when an easement is not provided on the adjacent property Restrictions Specific to Contaminated Soil or Groundwater Infiltration has the potential to mobilize contaminants present in soil and groundwater Therefore stormwater infiltration systems may not be constructed on sites where soil and or groundwater contamination problems have been identified In addition infiltration is not permitted within 100 feet of a contaminated site or abandoned landfill Infiltration within 500 feet of contaminated sites or abandoned landfills requires analysis and approval by a licensed hydrogeologist to determine whether stormwater can be safely infiltrated Setbacks and exclusion areas shall be measured from the site of the proposed infiltration facility to the nearest extent of contamination or if not known the edge of the parcel where contamination has been found Contaminated sites are regulated by the U S Environmental Protection Agency EPA and the Washington State Department of Ecology Ecology EPA regulates contaminated sites under its Superfund and Resource Conservation and Recovery Act RCRA programs The Superfund program regulates uncontrolled or abandoned hazardous waste sites where contaminants have been
258. avement Rain Recycling Cistern Notes Design Variables Coarse sands and cobbles inf gt 10 in hr Medium sand inf gt 7 5 10 in hr Fine sand loamy sand inf gt 2 4 7 5 in hr Sandy loam inf gt 1 2 4 in hr Loam inf 0 25 1 in hr PD 5 inf 0 25 in hr PD 5 inf 1 in hr PD 1 inf 0 25 in hr PD 1 inf 1 in hr PD 5 inf 0 25 in hr PD 5 inf 1 in hr PD 1 inf 0 25 in hr PD 1 inf 1 in hr PD 5 inf 25 in hr PDz 5 inf 1 in hr BC 5 WC 33 ft inf 0 25 in hr BC 5 WC 33 ft inf 1 in hr Depth above orifice 3 0 low flow orifice diameter 0 25 Depth above orifice 4 0 low flow orifice diameter 0 25 N A not applicable PD ponding depth BC base course depth WC wearing course depth inf design infiltration rate measured infiltration rate with appropriate correction factors applied gal gallons On site Sizing Factor 5 20 LF 1 000 sf 30 LF 1 000 sf 75 LF 1 000 sf 125 LF 1 000 sf 190 LF 1 000 sf 10 4 2 34 gal sf 5 96 1 78 gal sf Runoff Treatment Sizing Factor MR6 Flow Control Sizing Factor MR7 20 LF 1 000 sf 30 LF 1 000 sf 75 LF 1 000 sf 125 LF 1 000 sf 190 LF 1 000 sf Engineered Design 13 84 Engineered Design 13 76 25 9 5 86 gal sf 14 9 4 46 gal sf a Roof infiltration trench Sizing Factors are provided as linear feet LF per 1 000 square foot sf of roof area b Rain recycling cistern Sizing Fa
259. ay all structures shall be channelized and shall not have catchment Provide an oversized catch basin to compensate for lost catchment at the first available access point for maintenance vehicles The maximum manhole spacing on conveyance pipelines which do not have any stormwater inlets shall be 400 feet Manholes catch basins or inlets in easements shall be constructed to provide a stable level grade for a minimum radius of 3 0 feet around the center of the access opening D4 06 FLOW CONTROL D4 06 1 General Flow control is required when a project triggers MR7 by definition of the project threshold discharge area Use the criteria set forth in Section 24 06 65 of the Storm and Surface Water Utility Code and design guidelines Volume III Section 3 2 of the DOE Manual as modified herein to plan design and construct stormwater detention systems Flow control systems shall be designed to maximize reliability minimize maintenance needs and maximize the distance between the inlet and outlet in order to improve runoff quality and minimize hazards to persons or property both on site and off site nuisance problems and risk of failure In areas of high groundwater the groundwater collection system flows shall bypass the detention system Flow control facilities that serve multiple sites or phases of development are subject to all of the engineering and design requirements contained in the Storm and Surface Water Utility Code and these St
260. be bolt locking vaned ductile iron grates with cast iron frames per these engineering standards or approved equal All grated covers shall have in raised letters Outfall to Stream Dump No Pollutants Manhole round covers and rectangular covers shall have the word DRAIN in block letters at least two 2 inches high recessed so as to be flush with the surface When bolt locking covers and grates are required the locking bolts shall be 5 8 11 NC stainless steel type 304 socket allen head bolts 2 inches long Dipping painting welding plugging or any repair of defects shall not be permitted in accordance with AASHTO M 306 B Hatches D7 6 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Metal hatches and access covers shall be constructed with a non slip treatment having a coefficient of friction between 0 6 and 1 0 wet as determined by ASTM C1028 89 Hatches and access covers located on slopes of 4 or greater shall have a coefficient of friction between 0 8 and 1 0 wet as determined by ASTM 1028 89 Prior to installation the Contractor shall supply the Engineer with a shop drawing of the appurtenance specifying a coefficient of friction meeting or exceeding the above requirement Hatches shall include recessed padlock hasps sized to accept the City of Bellevue Storm Division padlocks D7 03 3 Structure Backfill In paved areas backfill material 4 feet and deeper below finished grade shall conform to Sectio
261. caping shall comply with the requirements of Type III landscaping set forth in Section 20 20 520 of the Land Use Code and as specified herein Ponds with walls higher than six 6 feet shall be landscaped to Type II requirements set forth in Land Use Code Section 20 20 520 and as specified herein Deciduous trees shall not be utilized in and around detention ponds However deciduous shrubs and shrub trees e g Vine Maple may be used in the understory to provide needed diversity for a pleasing appearance All ponds shall be landscaped to provide for slope stability erosion control and low maintenance Landscape materials shall be fully compatible with use as a stormwater detention facility including runoff treatment Floatable or erodible material i e wood chips beauty bark straw mulch etc shall not be allowed in the pond interiors Vegetation on pond embankments shall be limited to shallow rooted varieties Vegetation shall be placed into topsoil above or adjacent to the engineered embankment Where detention pond landscaping shall be maintained by the Utilities Department landscaping shall be non irrigated low maintenance and drought tolerant and shall consist of native plant species Lawn or turf grass is not allowed Use the criteria set forth in Volume III Section 3 2 1 of the DOE Manual to assist in appropriate vegetation selection D4 06 6 Underground Detention Systems A General Use the criteria and methods set forth in
262. ccess roads are not acceptable F Safety Use the criteria set forth in Volume III Section 3 2 1 of the DOE Manual Fencing shall be required when vertical walls are used when more than 25 of the perimeter side slopes are steeper than 3 H IV and when the permanent dead pool depth exceeds three 3 feet For publicly owned and maintained ponds fencing shall be cyclone fencing with black vinyl coating at minimum 6 feet tall Fencing shall conform to the Standard Plans for Chain Link Fence Type 3 For privately owned and maintained ponds fencing shall be minimum 42 inches tall with no spaces between boards greater than 4 inch clear space G Overflow amp Spillways Use the criteria set forth in Volume III Section 3 2 1 of the DOE Manual as modified herein All detention storage facilities shall include a provision for non erosive control of overflows Overflows shall be directed to a safe discharge path to protect adjacent and downstream properties from damage Provide calculations and data to support the design Surface detention ponds shall be provided with a minimum of two controlled emergency overflows the primary overflow in the control structure and the secondary overflow in the engineered embankment The crest of the secondary overflow shall be at least 0 5 feet above the crest of the primary overflow D4 72 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 H Vegetation amp Landscaping Detention pond lands
263. ce and flow control calculations Since partial credit only is applied additional flow control measures will be required To use the Flow Control Credit the vegetated roof must meet the design requirements for vegetated roofs outlined in Section 6 03 2 plus the following specific requirements Roof slope shall have a pitch of up to 2 2 5 12 2 2 5 inch fall per foot 5H 1V or 20 percent C Flow Control Credits Table 6 14 summarizes the default Flow Control Credits for several on site stormwater management BMPs The Flow Control Credits represent the percentage or square footage of impervious area mitigated by the BMP This mitigated impervious area can be subtracted from the amount of impervious area input to the continuous hydrologic model used to size downstream flow control facilities as described in Section D3 03 Additional default Flow Control Credits for BMPs not included herein can be found in Chapter 7 of the LID Manual D6 52 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 6 14 Flow Control Credits BMP Design Variables Flow Control Credit D6 03 5 Long term maintenance is required for all runoff control and treatment facilities See Section Retained Trees Evergreen 20 canopy area minimum 100 sf Deciduous 10 canopy area minimum 50 sf New Trees Evergreen 50 sf tree Deciduous 20 sf tree Roof Downspout Concentrated Dispersion to compost amended lawn or 90 o
264. ce water system DOE Manual Stormwater Management Manual for Western Washington Washington State Department of Ecology February 2005 When referenced drainage systems shall SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 conform to the criteria set forth in the DOE Manual Such criteria unless modified herein shall be the minimum standard which surface water systems must meet Engineer The City of Bellevue Utilities Assistant Director for Engineering or his or her duly authorized assistants which includes Engineering managers amp staff Consulting Engineers and or Inspectors Equipment The machinery accessories appurtenances and manufactured articles to be furnished and or installed under the Project Flooding The term flooding as used in the Storm Code Chapter 24 06 065 G 5 shall mean any natural or human caused event that endangers the safety of the public through water entering a structure inhabited by the public Flow Control Credit Credit toward reducing the size of downstream flow control facility ies through the use of on site stormwater management Infiltration BMP or NDP A natural drainage practice that infiltrates stormwater without an underdrain resulting in all runoff being infiltrated or lost to evapotranspiration These facilities are distinguished from partial infiltration facilities which do include an underdrain and stora
265. cial and multi family project sites and parking lots of industrial and commercial project sites that do not involve pollution generating sources e g industrial activities customer parking storage of erodible or leachable material wastes or chemicals other than parking of employees private vehicles For developments with a mix of land use types the Basic Treatment requirement shall apply when the runoff from the areas subject to the Basic Treatment requirement comprises 50 or more of the total runoff within a threshold discharge area D5 7 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 END OF CHAPTER D5 D5 8 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D6 ON SITE STORMWATER MANAGEMENT TABLE OF CONTENTS 56 01 GENBRADS3 etd Mut d D6 1 D6 01 1 Using On Site Stormwater Management to meet Storm and Surface Water Utility Code Reguireme HIS ocio moves lus aspi estamos mre cos apes acon D6 1 D6 02 SITE SUITABILITY AND BMP SELECTION eene D6 8 Introduction siese Tu shot eid esie ts coetu s Dist et itat o Dat Doct D6 8 D6 02 2 Step 1 Characterize Site Infiltration Capabilities D6 8 D6 02 3 Step 2 Site Layout and D6 10 D6 02 4 Step 3 Runoff Sources and BMP Selection D6 10 D6 03 DESIGN
266. city head of zero should be assumed Bend Head Loss Kb x V 2g or Kb x Col 17 where Kb Bend Loss Coefficient from Figure 4 20 This is the loss of head energy required to change direction of flow in an access structure Junction Head Loss This is the loss in head energy that results from the turbulence created when two or more streams are merged into one within the access structure Figure 4 21 may be used to determine this loss or it may be computed using the following equations derived from Figure 4 21 Junction Head Loss Kj x V2g or Kj x Col 17 where Kj is the Junction Loss Coefficient determined by Kj 03 01 1 18 0 63 Q3 Q1 Headwater HW Elevation this is determined by combining the energy heads in Columns 17 18 and 19 with the highest control elevation in either Column 15 or 16 as follows Col 20 Col 15 or 16 Col 17 Col 18 Col 19 D4 56 JANUARY 2015 SURFACE WATER ENGINEERING STANDARDS Figure 4 19 Backwater Calculation Example 7850 00 o o 08S0L v9 S0l 8 0 oro D 001 0660 8 0 BEE 7 7 O0 OL OS LOL 00 OSL 06 9 3u z 0660 00 20 8 0 S6 Z0 0 8 0 600 72 0 Leo 9060 si o BEE 27 OS LOL 09001 COO 8 OLI 9 2 90 0 100 2000 8 0 9 01 Z OL oso SZO 2970 290 00200 090 696 271 06004 0000 2100 081 og OI
267. conservative side set the HGL elevation equal to the crown elevation Column 13 Column 14 Column 15 Column 16 Column 17 Column 18 Column 19 Column 20 Entrance Head Loss Kex V7 2g or Kex Col 9 where Ke Entrance Loss Coefficient from Table 4 7 This is the head lost due to flow contractions at the pipe entrance Exit Head Loss 1 0x V 2g or 1 0 x Col 9 This is the velocity head lost or transferred downstream Outlet Control Elevation Col 12 Col 13 Col 14 This is the maximum headwater elevation assuming the pipe s barrel and inlet outlet characteristics are controlling capacity It does not include structure losses or approach velocity considerations Inlet Control Elevation see SectionD4 04 7 J for computation of inlet control on culverts this is the maximum headwater elevation assuming the pipe s inlet is controlling capacity It does not include structure losses or approach velocity considerations Approach Velocity Head this is the amount of head energy being supplied by the discharge from an upstream pipe or channel section which serves to reduce the headwater elevation If the discharge is from a pipe the approach velocity head is equal to the barrel velocity head computed for the upstream pipe If the upstream pipe outlet is significantly higher in elevation as in a drop manhole or lower in elevation such that its discharge energy would be dissipated an approach velo
268. construction traffic does not traverse the area An inspection by the civil geotechnical engineer of record of the exposed soil shall be made after the infiltration system is excavated to confirm that suitable soils are present Infiltration systems for flow control shall not be utilized until construction is complete and disturbed areas have been stabilized as determined by the City to prevent sedimentation of the infiltration system Temporary flow control facilities may be needed to utilize this option D8 08 ABANDONING FACILITIES D8 08 1 Abandoning Pipe In Place Any property owner who plans to demolish or remove any structure connected to the public storm drainage system shall notify the utility and complete a utility abandonment form prior to the commencement of such work Storm drainage pipe demolition shall be performed prior to removal of building foundation The storm drainage pipe for each building shall be excavated and removed from the house connection to the property line or the main as specified by the Utility The Contractor shall cap the end of D8 7 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 the the storm drainage pipe to remain in place Storm drainage pipe demolition shall be performed in the presence of the City of Bellevue Sewer Maintenance Engineering Technician inspector The inspector will inspect the stub to determine whether the storm drainage pipe can be re used If the inspector determines that the
269. control and treatment facilities that are owned operated and maintained by private parties as well as City Parks Department and Civic Services Facilities For projects triggering Minimum Requirements 1 through 5 the Storm Drainage O amp M Manual Agreement for Utilities Storm Connections MR 1 5 shall be provided For projects triggering Minimum Requirements 1 through 9 the Storm Drainage O amp M Manual Agreement for Utility Extension Agreements MR 1 9 shall be provided Public drainage facilities located in the public right of way and in dedicated easements which are accepted by the City of Bellevue Storm and Surface Water Utility are operated and maintained as per the current edition of the City of Bellevue Storm and Surface Water Maintenance Standards now or as hereafter amended Individual O amp M Manuals are not provided for these public drainage facilities City Parks Department and Civic Services are required to provide an O amp M Manual agreement D2 09 1 Storm Drainage O amp M Manual Agreement for Utilities Storm Connections MR 1 5 The Storm Drainage O amp M Manual Agreement for Utilities Storm Connections MR 1 5 at a minimum shall include The name of the property owner s responsible for maintenance and operation of the system property address The Storm Connection Permit UB Permit number and issue date project is permitted under The on site stormwater management facility types permitted D2 21
270. conveyance pipeline to this new structure In areas having an existing piped conveyance system the stormwater outfalls for roof footing and yard drains may be made by the two methods mentioned above or by the following in order of preference 1 Connecting the private drainage pipe to an existing storm drain manhole catch basin or stub out if provided within 100 feet and downslope of the property line or 2 Tapping the abutting conveyance pipeline and installing a saddle tee and providing a clean out outside of the public right of way or 3 Tapping the abutting profile wall conveyance pipeline and installing an insert tee and clean out outside of the right of way or tapping the abutting concrete conveyance pipeline with a hole cut by a core drill and installing a saddle Note Blind tapping of corrugated metal pipe CMP is never allowed 4 Installing a tee fitting in the abutting conveyance pipeline and providing a clean out outside of the public right of way or 5 Connecting the private drainage pipe to an existing sidewalk drain or 6 Providing a new sidewalk drain if the closest existing drainage system or stub out is greater than 100 feet and downslope of the property line 7 Outfalling to an open channel or stream provided that the drainage path continues downstream to an established known and well functioning conveyance system adequate erosion protection is provided and permits from other agencies are obtained
271. ction Matrix Step 1 Step 2 Site Step 3 Runoff Sources and BMP Selection Characterize Layout and Use Site Infiltration Capabilities Driveway Finished Street Parking Slope Design Use of Proposed Lot not High Infiltration BMP Location Vehicle Traffic Pedestrian Bike Landscape or Rate Roof Area Hardscape Lawn gt 15 33 Slope Natural Splash Block Pop up Concentrated or Concentrated or Concentrated Vegetation Emitter Sheet Flow Sheet Flow Sheet Flow or Sheet Flow 20 25 Dispersion Rain Dispersion Dispersion Dispersion inch hour Recycling Minimal infiltration Excavation Foundation Landscape Lawn Splash Block Pop up Amended Soils Concentrated or Amended Emitter Rain Recycling Concentratedor Sheet Flow Soils Dispersion Trench Sheet Flow Dispersion Perforated Stub out Dispersion Connection Minimal Excavation Foundation Pedestrian Bike Rain Recycling Perforated Concentrated or Concentrated or Concentrated Stub out Connection Sheet Flow Sheet Flow or Sheet Flow Dispersion Dispersion Dispersion Traffic not high Rain Recycling Not applicable Not applicable Not applicable use site gt 33 Slope or All Vegetated Roofs Rain Recycling and Minimal Excavation Foundation Systems are High recommended Infiltration and dispersion BMPs are prohibited Groundwater Roof 0 20 with Excess Load Capacity Vegetated Roof Not applicable Not applicable Not app
272. ctors are also provided as gallons gal of storage per square foot of roof area D6 03 4 For on site BMPs that are not capable of meeting flow control alone Flow Control Credits can be used to calculate partial credit towards meeting flow control requirements to reduce the size Flow Control Credits for On site Stormwater Management BMPs D6 49 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 of downstream flow control facilities Flow Control Credits are presented in Table 6 14 Section D6 03 4 O Flow Control Credit may be achieved by implementing the following on site BMPs Retaining trees Planting new trees Installing rain barrels Downspout or sheet flow dispersion Installing a vegetated roof The impervious area mitigated is calculated as the product of the Flow Control Credit and the quantity of the BMP Example Flow control facilities must be sized to meet on site stormwater management MR5 flow control MR7 requirements for a site with 15 000 sf of impervious area The design plans include a 5 000 sf vegetated roof with a 4 inch deep growing medium The amount of impervious area mitigated is 43 percent of 5 000 sf or 2 150 square feet This reduces the total impervious surface area requiring mitigation from 15 000 square feet to 12 850 square feet Additionally ten 10 evergreen trees with canopy areas of approximately 100 square feet each are retained so the additional impervious area mitigated is
273. curb inlet Plastic sheeting must be available on site In case of rain any stockpiled material must be covered and secured Clearing and grubbing limits may be established by the Engineer for certain areas and the Contractor shall confine his operations within those limits Debris resulting from the clearing and grubbing shall be disposed of by the Contractor Trenches shall be excavated to the line and grade designated by the Engineer and in accordance with the Standard Details Trenches shall comply with OSHA and WISHA requirements regarding worker safety The trench width at the top of the pipe shall be 30 inches for pipe up to and including 12 inch inside diameter and the outside diameter of the pipe barrel plus 16 inches for pipe larger than 12 inch inside diameter Where higher strength pipe or special bedding is required because of excess trench width it shall be furnished The trench shall be kept free from water until joining has been completed Surface water shall be diverted so as not to enter the trench The Contractor shall maintain sufficient pumping equipment on the job to insure that these provisions are carried out The Contractor shall perform all excavation of every description and of whatever substance encountered as part of his trench excavation cost Unsuitable material below the depth of the bedding shall be removed and replaced with satisfactory materials as determined by the Engineer Trenching operations shall not proceed
274. d hydrogeologist Structure setbacks apply per LUC 20 20 010 if Flow through Planter meets definition of Structure in LUC 20 50 046 and or Building Code If the Planter is part of the building there is no building setback Pervious pavement with run on If accepting run on from another impervious area from pervious or impervious e Building setbacks from finish grade as measured from side of area building o basementor crawl space 10 feet Bioretention Flow through Planter D4 86 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Storm Drainage Feature Pervious Pavement without run on Amended Soil Rain Recycling Rain Barrel e Cistern Dispersion BMPs Concentrated Flow Dispersion e Sheet Flow Dispersion e Splash Blocks e See below for Dispersion Trench Dispersion Trench Perforated Stub Out Connection Piped Conveyance Systems Setback Requirement o slab on grade 5 feet o uphill from building 20 feet o driveways no setback required from garage if floor is slab on grade 50 feet from septic tank or drainfield King County Public Health compliance also required 100 feet from drinking water well or spring King County Public Health compliance also required 50 feet from top of a slope gt 15 may be revised with evaluation by geotechnical engineer or qualified geologist and city approval or in accordance with applicable Critical Areas Ordinance requirements
275. d root cutting if necessary Use solid PVC Schedule 40 for privately owned and maintained facilities only Use an appropriate coupling if connecting to a city owned pipe Use solid PVC per D7 02 3 for systems that will be owned and or maintained by the City of Bellevue Cut slots perpendicular to the long axis of the solid PVC pipe slots are 0 04 0 069 inches wide by 1 inch long and spaced 0 25 inches apart spaced longitudinally Arrange slots in four rows spaced on 45 degree centers and cover the circumference of the pipe Use filter materials with smallest aggregate larger than slot size Option 3 Perforated PVC Schedule 40 or slotted HDPE pipe for privately owned and maintained systems only Cleaning operations may be difficult or impossible The following underdrains or Equal are approved Manufacturers Johnson CertainTeed Corporation Lodi CA Coupler Match the coupler to fit the underdrain used Glue or bolt the coupler to the pipes if connecting from a privately owned or maintained system to a pipe or facility owned by the City of Bellevue The following couplers and Equal are approved Fernco Davison MI D6 04 4 Observation Ports for Bioretention or Pervious Pavement A Expandable Test Plugs D6 61 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 The following expandable test plugs for pipes are approved Cherne Gripper plugs models MC 99930 MC 99929 MC 99931 MC 99935 B Coupler Match
276. d to protect the pipeline due to the width and or depth of trenching in the vicinity of SPU pipelines If SPU s pipeline is exposed SPU wants to inspect the pipe prior to back filling Special fill and or compaction may be required depending on the method and depth of excavation Overhead wire installations typically require a minimum of 25 feet of vertical clearance from the ground Vibrations could damage some of SPU s pipelines therefore pile driving blasting and other vibration producing work may be restricted Heavy loads could damage some of SPU s pipelines Therefore pipe protection may be necessary if heavy equipment crosses the pipe Typical protection would include temporary bridging using timbers and steel plate SPU Operations requirements Notify SPU at least 48 hours notice prior to construction Locating SPU s pipeline by potholing must be supervised Call SPU s Lake Youngs Operations at 206 684 3933 Any work in close proximity to SPU s pipeline including locating by potholing must be supervised by SPU Call SPU s Lake Youngs Headquarters at 206 684 3933 at least 48 hours in advance Questions Teri Hallauer Sr Real Property Agent Seattle Public Utilities Real Estate Services 206 684 5971 Seattle Municipal Tower Fax 206 615 1215 700 Fifth Avenue Suite 4900 teri hallauer seattle gov P O Box 34018 Seattle WA 98124 4018 Audrey Hansen Manager Real Estate Services 206 684 5877 A D5 2
277. dens Sizing Factors for rain gardens with and without underdrains receiving runoff from an impervious surface are provided in Table 6 13 Factors are organized by MR facility ponding depth and native soil design infiltration rate A 6 or 12 inch facility ponding depth may be selected The design rate for the native soils must be rounded down to the nearest design infiltration rate in Table 6 13 To use these Sizing Factors the rain garden must meet the design requirements for rain gardens outlined in Section D6 03 2 plus the following specific requirements Bottom area shall be sized using the applicable sizing factor Bottom area shall be no more than two 2 percent slope When an underdrain is used the diameter shall be eight 8 inches and the gravel backfill depth shall be a minimum of 26 inches porosity 0 35 Side slopes within ponded area shall be no steeper than 2 5H 1V Bioretention soil mix shall have an infiltration rate of at least 2 5 inches per hour porosity 0 4 Bioretention soil mix depth shall be a minimum of 18 inches for on site stormwater management and runoff treatment D6 46 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Minimum ponding depth shall be set at the designated height 6 inches or 12 inches For intermediate ponding depths between 6 and 12 inches a Sizing Factor may be linearly interpolated lii Bioretention Planters lv Sizing Factors for bioretention planters r
278. ding are based on designs See discussion of the Bioretention Soil Depth input below Figure 6 2 provides a schematic illustration of how to estimate this model input based on designs Bioretention Soil Infiltration Rate For imported bioretention soil see specification Section D6 04 1 For compost amended native soil rate shall be equal to the native soil design infiltration rate Bioretention Soil Porosity For imported bioretention soil porosity is 40 percent For compost amended native soil porosity is assumed to be 30 percent Bioretention Soil Depth Minimum of 12 inches for flow control or 18 inches for basic and enhanced water quality treatment Native Soil Design Infiltration Rate Measured infiltration rate with correction factor applied if applicable Infiltration Across Wetted Surface Area Yes if side slopes are 3H 1V or flatter For steeper side slopes only infiltration across the bottom area is modeled Underdrain optional Water stored in the bioretention soil below the underdrain may be allowed to infiltrate Outlet Structure Overflow elevation set at maximum ponding elevation excluding freeboard May be modeled as weir flow over riser edge or notch Note that total facility depth including freeboard must be sufficient to allow water surface elevation to rise above the overflow elevation to provide sufficient head for discharge When flow control is required either the default method or the demonstrative m
279. dually varied flow model Note In certain circumstances such as weir flow over a levee or dike flow through the spillway of a dam or special applications of bridge flow rapidly varied flow techniques shall be used in combination with a gradually varied flow model Manning s values Calibration of the hydraulic model with past flood events D4 31 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Special applications some cases HEC RAS alone may not be sufficient for preparing the floodplain floodway analysis This may occur where sediment transport two dimensional flow or other unique hydraulic circumstances affect the accuracy of the HEC RAS hydraulic model In these cases the applicant shall obtain Utility approval of other methods proposed for estimating the water surface profiles Table 4 5 Datum Correlations Seattle Area Tide Tables NGVD amp NAVD USGS amp Navigation Correlation 1988 U S City of USC amp Charts 1954 From To KCAS Engineers Seattle GS 1947 amp Later sep ss om o om ae ars pes os Tew NGVD USGS amp 6 05 USC amp GS 1947 adjusted to the 1929 datum Seattle Area Tide Tables 2 98 6 56 4 12 52 6 47 amp Navigation Charts 1954 amp Later based on epoch 1924 1942 Design Tidal Tailwater 12 08 8 50 15 52 2 54 8 59 15 06 Elevation Mean High Water 11 78 1 20 11 32 MHHW Mean High Water MHW
280. dway driveway or parking lot runoff is conveyed or 3 When commercial and multi family stormwater pipes connect to the municipal conveyance system or 4 When connecting to CMP conveyance systems Roof footing yard drain pipes 8 inches or less in diameter from single family residences may be connected to the existing stormwater conveyance system by core drilling the appropriate hole and installing a saddle tee on concrete PVC and DI stormwater pipes only For profile wall PVC or CPE pipe an insert tee or saddle tee may be used For new stormwater conveyance systems roof footing yard drain pipes shall be connected with tee fittings When a connection is made without the benefit of a structure a clean out shall be provided upstream of each tee on the inletting private drainage system pipe When connecting pipes at structures match crowns when possible If finished floor elevation is lower than adjacent street top of curb and a connection to public street drainage system is made at minimum the property owner shall install a check valve D8 04 CONVEYANCE SYSTEMS D8 04 1 General Methods of construction for storm drain pipelines and culverts shall conform to Section 7 04 3 Construction Requirements of the Standard Specifications and Chapter 2 of the Ecology Manual as modified herein D8 04 2 Locators Installation of all non linear plastic pipe lot stubs and underdrains shall include a locator wire The locator wire shall
281. e D6 8 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Step 1 entails three sub steps including Step la Identify Site Slopes and Critical Areas Step lb Identify Depth to Groundwater and Step 1 Characterize Site Soils and Determine Infiltration Rates Each of these sub steps is described below A Step la Identify Site Slopes and Critical Areas Using the boundary and topographic survey for the site identify areas that have slopes between 0 to 15 slopes gt 15 to 33 slopes and greater than 33 slopes based on the existing contours Where grading is planned for proposed pavement or landscaped areas of the site use the proposed contours shown on the grading plan instead of the existing contours for this sub step Steep slope areas that are classified as Critical Areas Steep Slopes or Landslide Hazard areas must also be identified on the map along with required buffers Refer to LUC 20 25H for more information on Critical Areas Proposed Buildings For buildings identify the proposed slope and structural capacity of the roofs and whether vegetated roofs are being considered for the site Vegetated roofs are permitted on roofs with up to 20 percent slopes A licensed structural Engineer must design the vegetated roof and demonstrate that the building has sufficient structural capacity to support the expected loads Refer Section D6 03 2 D for design guidance on vegetated roofs B Step 1b Identify Depth to Groundwater
282. e A D2 8 CHANNELIZATION SYMBOLS dnd SYMBOL DESCRIPTION BLOCK LAYER EXIST PROP 5 4 LEFT TURN ARROW CLT CLTP 3333 5 2 RIGHT TURN ARROW CRT CRTP TF CHAN 3333 SYM qj 4 LEFT SRAIGHT ARROW CLS CLSP TF CHAN 3333 SYM I gt b RIGHT STRAIGHT ARROW CRS CRSP 3333 5 RAISED MARKERS e LANE MARKERS TYPE CLM1 CLM1P TF CHAN 3333 SYM n LANE MARKERS TYPE 1 CLM2 CLM2P TF CHAN 3333 SYM 3333 USE EXST PROP GAS POWER TELEPHONE SYMBOLS SYMBOL DESCRIPTION ABBR BLOCK LAYER EXIST PROP B nu GAS METER GM GMET GMETP GS METR 3333 SYM n t GAS VALVE GV GV GVP GS VALV 3333 SYM A A PAD MOUNTED P TRAN PTRAN PTRANP PO STCR 3333 SYM TRANSFORMER P P POWER VAULT Pow v PV PVP PO STCR 3333 SYM TRANSMISSION TRANS TWR PTWR PO STCR EXST SYM TOWER o e UTILITY POLE PP TP UP UPP 11 STCR 3333 SYM UTILITY POLE UPA UPAP 11 STCR 3333 SYM ae ANCHOR TELEPHONE TEL R TELR TELRP TL STCR 3333 SYM RISER TELEPHONE TEL V TL STCR 3333 SYM VAULT 11 USE PO TL 3333 USE EXST PROP American Washington A Public Works State 2 Association Chapter w E A D2 9 LINETYPES LINETYPE DESCRIPTION COLOR LT NAME LAYER SURFACE FEATURES ate 4 0 BUILDING LINE EXISTING GREEN EXBUILD SF BLDG EXST LIN NO 2 5 PEN BUILDING LINE PROPOSED GREEN CONTINUOUS SF BLDG PROP LIN NO 2 5 PEN
283. e D7 02 3 Storm Drain Pipe and Culvert Materials Only the pipe materials listed are approved for use in storm drain systems and culverts Materials shall meet the noted sections of the Standard Specifications and as modified herein Reinforced Concrete Pipe RCP Cl 3 min 9 05 7 2 Solid Wall PVC Pipe SDR 35 min 9 05 12 1 D7 1 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Profile Wall PVC Pipe 9 05 12 2 Ductile Iron Pipe Class 52 9 05 13 Corrugated Polyethylene Storm Sewer Pipe 9 05 20 High Density Polyethylene Pipe HDPP D7 02 3 D Corrugated Polyethylene Tubing single wall D7 02 3 E Corrugated Polypropylene Pipe double wall D7 02 3 F A Solid Wall Polyvinyl Chloride PVC Pipe PVC pipe must be at least SDR 35 and meet the requirements of ASTM D 3034 for diameters up to 15 inches and ASTM F 679 for sizes 18 to 27 inch diameter B Profile Wall PVC Pipe Profile wall PVC pipe shall conform to AASHTO M 304 Joints shall be an integral bell gasketed joint conforming to ASTM D 3212 Elastomeric gasket material shall conform to ASTM F 477 The minimum pipe diameter shall be 8 inches The maximum pipe diameter shall be 15 inches or the diameter for which a supplier has a joint conforming to ASTM D 3212 whichever is less Fittings for profile wall PVC pipe shall meet the requirements of AASHTO M 304 and shall be injection molded factory welded or factory solvent cemented C Corrugated Poly
284. e accepted D2 07 2 Storm Drainage General Plan Notes The following is a listing of General Notes that should be incorporated in the drainage plan set All the notes on the list may not pertain to every project The Developer may omit non relevant notes as determined by the Utility However do not renumber the remaining General Notes If additional notes are needed for specific aspects they should be added after the General Notes Storm Drainage General Notes 1 2 3 4 work shall conform to the 2013 edition of the City of Bellevue Utilities Department Engineering Standards and the Developer Extension Agreement Storm pipe shall be PVC conforming to ASTM D 3034 SDR 35 4 15 or ASTM F 679 18 27 Bedding and backfill shall be as shown in the Standard Details The locations of all existing utilities shown hereon have been established by field survey or obtained from available records and should therefore be considered approximate only and not necessarily complete It is the sole responsibility of the excavator to independently verify the accuracy of all utility locations shown and to further discover and avoid any other utilities not shown here on which may be affected by the implementation of this plan Immediately notify the Engineer if a conflict exists The footing drainage system and the roof downspout system shall not be interconnected and shall separately convey collected flows to the convey
285. e integrity or continuity of any grounding attachment or connection P Placement of surface appurtenances manhole lids catch basin lids etc In tire track of traffic lanes shall be avoided whenever possible Q Soil nails shall not be installed at or above pipes and shall include a minimum 5 foot clearance if installed below pipes R Clearly label public and private system on plans Private systems shall be marked Private and shall be privately owned and maintained D4 02 OUTFALLS AND DISCHARGE LOCATIONS A General Properly designed outfalls are critical to ensuring no adverse impacts occur as the result of concentrated discharges from pipe systems and culverts both on site and downstream Outfall systems include rock splash pads flow dispersal trenches or other energy dissipaters and tightline systems A tightline system is typically a continuous length of pipe used to convey flows down a steep or sensitive slope with appropriate energy dissipation at the discharge end In general it is recommended that conveyance systems be designed to reduce velocity above outfalls to the extent feasible Design Criteria At a minimum all outfalls shall be provided with a rock splash pad appropriately sized for the discharge see Bellevue Standard Detail NDP 4 and NDP 10 in Chapter D6 05 except as specified below and in Table 4 1 1 When discharging to an existing ditch swale or stream energy dissipation is required to minimiz
286. e obtained through the use of a pilot infiltration test PIT Note that these field tests generally provide a Ksat combined with a hydraulic gradient In some of these tests the hydraulic gradient may be close to 1 0 therefore in effect the test infiltration rate result D4 83 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 is the same as the hydraulic conductivity In other cases the hydraulic gradient may be close to the gradient that is likely to occur in the full scale infiltration facility The hydraulic gradient will need to be evaluated on a case by case basis when interpreting the results of field tests It is important to recognize that the gradient in the test may not be the same as the gradient likely to occur in the full scale infiltration facility in the long term i e when ground water mounding is fully developed Once the K for each layer has been identified determine the effective average Ksat below the pond Ksa estimates from different layers can be combined using the harmonic mean d dj Kequiv 2 Where d is the total depth of the soil column d is the thickness of layer i in the soil column and K is the saturated hydraulic conductivity of layer i in the soil column The depth of the soil column d typically would include all layers between the pond bottom and the water table However for sites with very deep water tables 2100 feet where ground water mounding to the base of th
287. e City of Bellevue Utilities Department Surface restoration of existing asphalt pavement shall be as required by the right of way use permit The Contractor shall maintain a minimum of five feet 5 horizontal separation between all water and storm drainage lines Any conflict shall be reported to the Utility and the Developer s Engineer prior to construction It shall be the Contractor s responsibility to ensure that no conflicts exist between storm drainage lines and proposed or existing utilities prior to construction Before commencement of trenching the Contractor shall provide filter fabric for all downhill storm drain inlets and catch basins which will receive runoff from the project site The contractor shall periodically inspect the condition of all filter fabric and replace as necessary Minimum cover over storm drainage pipe shall be 2 feet unless otherwise shown Avoid crossing water or sewer mains at highly acute angles The smallest angle measure between utilities should be 45 degrees At points where existing thrust blocking is found minimum clearance between concrete blocking and other buried utilities or structures shall be 5 feet When work is to occur in easements the Contractor shall notify the easement grantor and Bellevue Utilities in writing a minimum of 48 hours in advance of beginning work not including weekends or holidays Failure to notify grantor and Bellevue Utilities will result in a Stop Work O
288. e a minimum of four 4 inches deep and have the following characteristics Minimum total pore volume shall be 45 percent by volume for multi course systems and 30 percent by volume for single course systems per ASTM E2399 D6 39 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Water capacity shall be no less than 25 percent for single course systems 35 percent for extensive shallow multi course systems and 45 percent for intensive deep multi course systems per ASTM 2399 Saturated hydraulic conductivity permeability shall be between 14 and 1 200 inches per hour for single course systems and 2 8 and 28 inches per hour for multi course systems per ASTM E2396 05 Minimum air content at maximum water capacity shall be 5 percent by volume per ASTM 2396 05 Maximum total organic matter shall be four 4 percent by mass for single course systems six 6 percent by mass for extensive shallow multi course systems and eight 8 percent by mass for intensive deep multi course systems per loss on ignition test QGrowth media depth and characteristics must support growth for the plant species selected and shall be approved by a certified landscape architect Vegetated roofs must not be subject to any use that will significantly compact the growth medium Vegetated roof areas that are accessible to the public shall be protected e g signs railing and fencing and areas designed for foot tr
289. e are provided in Table 6 13 Factors are organized by MR and native soil design infiltration rate The design rate for the native soils must be rounded down to the nearest design infiltration rate in Table 6 13 To use these Sizing Factors the pervious pavement must meet the design requirements for pervious pavement outlined in Section 6 03 2 plus the following specific requirements C he pervious pavement area shall be sized using the applicable sizing factor The longitudinal bottom slope shall be 2 percent or less maximum subsurface water ponding depth in the reservoir course before overflow shall be at least 6 inches See Standard Detail NDP 15 for design measures to provide subsurface ponding The storage reservoir shall be composed of aggregate with a minimum void volume of 20 percent D6 47 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 No underdrain or impermeable liner shall be used v Rain Recycling Cistern Sizing Factors for cisterns receiving runoff from an impervious surface are provided in Table 6 13 Factors are organized by MR Cistern sizing factors are presented in two ways 1 percentage values that represent the top cross sectional area of the storage tank as a percentage of the contributing roof area and 2 the equivalent volume represented in terms of gallons per square feet of contributing roof area To use these Sizing Factors the cisterns must meet the design requirements for outlined
290. e completed pipeline Minimum length of circular portion shall be equal to the diameter of the pipe Pull shall be manual without mechanical assistance and the mandrel shall negotiate deflected section freely Testing shall be conducted on a manhole to manhole basis and shall be done after the line has been completely flushed out with water Contractor shall locate and repair any sections failing to pass the test and retest the section D8 10 TELEVISION INSPECTION The Developer shall provide the Utility with a videotape inspection of all storm drains prior to final project acceptance require that the Developer provide videotape inspection of any or all storm drains before expiration of the warranty The Contractor shall correct all deficiencies found during television inspection Maximum allowable ponding depth detected by video inspection shall be 0 5 inches D8 11 TESTING OF CONCRETE STRUCTURES Following backfilling concrete structures shall be vacuum tested per ASTM C1244 except as specified otherwise herein to ensure that the structure is watertight At least twenty five percent 25 of the total storm drainage manholes catch basins and other structures shall be vacuum tested Structures to be tested shall be selected by the Engineer at the time of testing No advance notice will be provided to the Contractor as to which structures will be tested If more than ten percent 10 of the structures tested fail the initial test an additional
291. e erosion 2 The flow dispersal trench shown in Bellevue Standard Detail D 40 shall be used as an outfall only after other on site BMPs have been determined infeasible due to site conditions per D6 See D6 03 1 for Roof Downspout Dispersion For outfalls with a velocity at a design flow greater than 10 fps an engineered energy dissipater shall be required per Standard detail D 38 or D 60 3 Tightline systems shall be used when on site storm water management is not required or where it is required does not fully mitigate stormwater flows per Chapter D6 4 Storm drain pipelines shall not be installed above ground Outfalls shall discharge at the bank full water surface elevation 2 yr storm in open channels or streams 6 Conveyance systems downstream of flow control facilities or treatment facilities shall be designed to prevent backwater conditions in those facilities 7 The use of pumped systems or backflow preventers shall not be used to prevent flooding due to backwater conditions D4 2 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 4 1 Rock Protection At Outfalls Discharge Velocity REQUIRED PROTECTION at Design Flow fps Minimum Dimensions Greater Less than than or equal to 1 foot Diameter Crown 6 feet 1 foot 4 x diameter whichever is greater Riprap 2 feet Diameter 12 feet Crown 6 feet or 1 foot or 4 x diameter 3 x diameter whichever is whichever is greater greater E
292. e hole fills with water the groundwater level is too close to the ground surface and the site is not appropriate for infiltration BMPs Examine soil on the sides of the hole and test for soil texture Make sure soil is moist If the soil is dry add water a few drops at a time and break down any chunks to work the water into the soil Take a handful and attempt to squeeze it into a ball If small orange specks of dirt known as mottles are present in the soil note the distance from the ground surface where they are first encountered this can be considered the depth of the seasonal high groundwater If mottles are present check groundwater depth design requirements before proceeding with the infiltration test Infiltration Test Secure a board or ruler in the hole with markings every inch increasing in number from the bottom to the top of the hole the hole with 10 inches of water Time how long it takes the water to drain completely out of the hole Do the test three times consecutively with each test immediately following each other and use the results of the third test in your infiltration rate calculation Site Suitability or Infiltration Rate Divide the number of inches of standing water initially added to the hole by the number of hours it takes for the water to drain out completely The resulting number is the measured short term infiltration rate in inches per hour Select a correction factor based on
293. e phosphorous treatment facility 1f feasible The approved options for providing Phosphorus Treatment are listed in Figure 5 1 and presented in more detail in Volume V of the DOE Manual Additional means of meeting the phosphorus treatment requirement may be approved by the City if the proposal fulfills the design criteria in the Department of Ecology s General Use Level Designation GULD approval process D5 03 8 Enhanced Treatment All Enhanced Treatment facilities shall be designed in accordance with criteria set forth in Volume V of the DOE Manual as modified herein Enhanced treatment for reduction in dissolved metals is required for the following types of projects throughout Bellevue Industrial project sites Commercial project sites Multi family project sites and High AADT roads as follows 1 Fully controlled and partially controlled limited access highways with Annual Average Daily Traffic AADT counts of 15 000 or more and 2 All other roads with an AADT of 7 500 or greater However such sites listed above that discharge directly to Lake Washington Basic Treatment Receiving Waters per Appendix I C of the DOE Manual except Lake Sammamish which requires Phosphorus Treatment via an entirely closed piped conveyance system or via sheet flow from waterfront property are not subject to Enhanced Treatment Requirements Areas of the above listed project sites that are identified as being subject to Basic Treatment requ
294. e pond is not likely to occur it is recommended that the total depth of the soil column in Equation 2 be limited to approximately 20 times the depth of pond but not more than 50 feet This is to ensure that the most important and relevant layers are included in the hydraulic conductivity calculations Deep layers that are not likely to affect the infiltration rate near the pond bottom should not be included in Equation 2 Equation 2 may over estimate the effective Ksa value at sites with low conductivity layers immediately beneath the infiltration pond For sites where the lowest conductivity layer is within five feet of the base of the pond it is suggested that this lowest Ksa value be used as the equivalent hydraulic conductivity rather than the value from Equation 2 Using the layer with the lowest Ksa is advised for designing bioretention facilities or permeable pavements The harmonic mean given by Equation 2 is the appropriate effective hydraulic conductivity for flow that is perpendicular to stratigraphic layers and will produce conservative results when flow has a significant horizontal component such as could occur due to ground water mounding D4 06 8 Dispersion Systems BMPs for dispersion systems such as those for meeting flow control requirements including Roof Downspout Dispersion and Full Dispersion are discussed in Chapter D6 03 D4 06 9 Non Gravity Systems Pumps Pump systems includes the pumps force mains electrical and pow
295. e step by step process for selecting the type of treatment facilities for individual projects as presented in Volume V Chapter 2 of the DOE Manual as modified by Sections D5 03 6 D5 03 7 D5 03 8 and D5 03 9 herein Figure 5 1 provides a graphical representation of the selection process An addition to the selection process shown in the DOE Manual is Step 2a Determine if Full Dispersion is practicable See Section D6 03 1 for applications and limitations of Full Dispersion to complete Step 2a of Figure 5 1 Bioretention or pervious pavement used for runoff treatment shall meet the requirements listed in Section D6 01 1B and D6 03 2 D5 03 5 Treatment Facility Maintenance Stormwater treatment facilities shall be maintained in accordance with the current and any future editions of the City of Bellevue Maintenance Standards and with the maintenance schedule in Volume V of the DOE Manual Maintenance requirements shall be included in the O amp M Manual described in D2 09 D5 3 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Step 1 Determine Receiving Waters and ES 2 Pollutants of Concern Step 2 Determine if an Oil Perform Off Ste Control Facility is Required Analysis No Apply Full Dispersion Step 2a Determine if Full applies to roofs Yes Dispersion is practicable per driveways small roads Ecology BMP 5 30 Full Apply Pretreatment e Pretreatment Basin Yes Step 3 Determine if or Infiltration for Pol
296. earing and Grading plans shall include measures to protect the native soil or subgrade from unnecessary compaction and clogging from sediment during construction iv Sizing D6 21 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Sizing Factors for Bioretention Cells are provided in Section D6 03 3 These Sizing Factors may be used to size rain gardens to meet on site stormwater management MRS when runoff treatment MR6 and or flow control MR7 are not required Bioretention Cell Sizing Factors are also provided for runoff treatment and flow control but those are intended for conceptual design only The Developer is required to perform independent calculations to size Bioretention Cells and bioretention swales to meet runoff treatment and flow control requirements per Chapter D3 of these Standards Sizing Factors for bioretention swales are not provided When using an approved continuous model to size Bioretention Cells or bioretention swales with the demonstrative approach the assumptions listed in Table 6 6 shall be applied Bioretention should be modeled as a layer of soil with specified infiltration rate and porosity with ponding detention via a restricted underdrain if applicable infiltration to underlying soil and overflow The tributary areas cell bottom area and ponding depth should be iteratively sized until runoff treatment and or flow control requirements are met and the maximum surface pool drawdown time of 48 hours is
297. easement requirements Drainage facilities that are constructed to serve predominantly public property or public right of way shall be publicly owned per Section 24 06 085 of the Storm and Surface Water Utility Code and shall be dedicated to the City Where possible public conveyance systems shall be constructed within the public right of way When site conditions make this infeasible public drainage easements or dedicated tracts shall be provided Private drainage facilities shall be constructed outside of the public right of way on private property Private easements may be needed When vehicle access for maintenance is required a dedicated tract or access easement shall be provided The access easement conditions shall prohibit the property owner from installing any structures improvements retaining walls etc which would hinder access to the drainage facility or necessitate restoration of access easement area Any required easement shall be obtained by the Developer at his sole expense D4 08 2 Easement Documentation Requirements All easements shall be shown on the project plans and identified as private or public together with the width dimension and utility use e g 20 Public Drainage Utility Easement All documents for public easements shall conform to these Utilities Engineering Standards will be provided on the City s easement template and shall comply with King County Recorder s Office formatting requir
298. eceiving runoff from an impervious surface are provided in Table 6 13 Factors are organized by MR facility ponding depth and native soil design infiltration rate A 6 or 12 inch facility ponding depth may be selected For infiltration planters the design rate for the native soils must be rounded down to the nearest design infiltration rate in Table 6 13 Planters with underdrains can only be used to meet requirements for basic or enhanced treatment MR6 Infiltration planters can be used to meet MRS 6 and 7 To use these Sizing Factors the bioretention planter must meet the design requirements outlined in Section 6 03 2 plus the following specific requirements bioretention planter area shall be sized using the applicable sizing factor Bottom area shall be flat 0 percent slope underdrain diameter shall be 8 inches Vertical side slopes Bioretention soil mix shall have an infiltration rate of at least 2 5 inches per hour porosity 0 4 Bioretention soil mix depth shall be a minimum of 18 inches for runoff treatment Gravel depth shall be a minimum of 26 inches porosity 0 35 Freeboard shall be 4 inches or greater Minimum ponding depth shall be set at the designated height 6 inches or 12 inches For intermediate ponding depths between 6 and 12 inches a Sizing Factor may be linearly interpolated Pervious Pavement Sizing Factors for pervious pavement receiving runoff from an impervious surfac
299. ed Length of pipe does not exceed 100 feet Pipe slope is greater than or equal to 2 and Only one stormwater inlet contributes surface runoff to the roadway lateral For individual single family residences conveyance pipes for roof footing and yard drains shall be a minimum of 4 inches in diameter Connections to the storm drain system shall be a minimum of 6 inches once outside the lot being connected For joint use lines between single family homes that portion of the line which is jointly used shall be 6 inches in diameter minimum Minimum slopes for single family storm drain lines footing and conveyance 2 on 4 inch and 6 inch diameter and 0 5 on 8 inch diameter if used The minimum velocity in all storm drain conveyance systems for the conveyance design storm 100 year 24 hour is 3 feet per second For driveways parking lots and situations not listed above the minimum diameter for conveyance pipes shall be 8 inches Any storm line with a 20 slope or greater shall provide pipe anchors and hill holders according to the applicable storm drainage standard details F Maintenance Access All stormwater facilities shall be accessible for maintenance and operation When vehicle access is necessary access roads shall be provided in dedicated tracts or dedicated access easements The minimum clear driving lane width is 12 feet Gates and or bollards are required when necessary to restrict access to stormwater facilities
300. ed Manning s n values for preliminary design using the Uniform Flow Analysis method for pipe systems Note The values for this method are 15 higher in order to account for entrance exit junction and bend head losses D4 50 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 4 9 Manning s Values for Pipes Type of Pipe Material Analysis Method Uniform Flow Backwater Flow Preliminary Capacity design Verification Concrete pipe and LCPE pipe Annular Corrugated Metal Pipe or Pipe Arch 1 2 7 5 x corrugation riveted a plain or fully coated b paved invert 40 of circumference paved 1 flow at full depth 2 flow at 80 full depth 3 flow at 60 full depth c treatment 5 2 3 x 1 corrugation 3 6 x 2 corrugation field bolted Helical 2 7 x 1 corrugation and CPE pipe Spiral rib metal pipe and PVC pipe Ductile iron pipe cement lined SWPE pipe butt fused only Backwater Analysis Method This method is used to analyze the capacity of both new and existing pipe systems to convey the 100 year peak flow Pipe system structures must be demonstrated to contain the headwater surface hydraulic grade line for the specified peak flow rate Structures may not overtop for the 100 year peak flow This method is used to compute a simple backwater profile hydraulic grade line through a proposed or existing pipe system for the purposes of verifying adequate capacity It incorpora
301. ed on design plans Effective Total Depth Effective Total Depth ETD is the Maximum Ponding Depth plus one foot of freeboard above the top of the riser For longitudinal slopes less than 2 percent evaluate the Maximum Ponding Depth based on design plans For longitudinal slopes greater than 2 percent use the Average Maximum Ponding calculated as follows 1 n x PA PA PA 1 20 PM PM Where n Number of Cells D6 33 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Variable Assumption PA Average Ponding Depth of Celln ft PM Maximum Ponding Depth of Cell n ft Figure 6 2 provides a schematic illustration of how to estimate this model input based on designs Reservoir Course Depth Average maximum subsurface water ponding depth in the storage reservoir averaged across the facility before berm overtopping or overflow occurs Reservoir Course Porosity Assume maximum 20 percent unless test is provided showing higher porosity for aggregate compacted and in place Native Soil Design Infiltration Measured infiltration rate with correction factor applied if applicable Rate Infiltration Across Wetted No Only infiltration across the bottom area is modeled Surface Area Underdrain optional If underdrain is placed at bottom extent of the reservoir course all water which enters the facility must be rou
302. edding material shall be in accordance with Section 9 03 12 3 Gravel Backfill for Pipe Zone Bedding of the Standard Specifications For convenience crushed rock bedding conforming to crushed surfacing top course material of Section 9 03 9 3 Crushed Surfacing of the Standard Specifications may also be used as bedding material for pipe In unpaved areas the Contractor may request to use excavated material used as pipe bedding where it has been determined by the Engineer as suitable meeting the requirements of Section 9 03 12 3 Gravel Backfill for Pipe Zone Bedding of the Standard Specifications and proper compaction levels can be achieved For PolyVinyl Chloride PVC pipe Corrugated PolyEthylene CPE pipe and other thermoplastic pipe bedding material shall be imported material conforming to crushed D7 3 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 surfacing top course material of Section 9 03 9 3 Crushed Surfacing of the Standard Specifications For ductile iron storm drain pipe the Contractor may request to use excavated material as pipe bedding where it has been determined by the Engineer as suitable material meeting the requirements of Section 9 03 12 3 Gravel Backfill for Pipe Zone Bedding of the Standard Specifications and proper compaction levels can be achieved D7 02 5 Trench Backfill For transverse trenches perpendicular to the roadway centerline in paved areas crushed rock backfill conforming to Section 9
303. efficient from Table 4 7 acceleration due to gravity 32 2 ft sec critical depth ft see Figure 4 14 lt I x Aan Note above procedure should not used to develop stage discharge curves for level pool routing purposes because its results are not precise for flow conditions where the hydraulic grade line falls significantly below the culvert crown 1 less than full flow conditions D4 37 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 4 7 Entrance Loss Coefficients Type of Structure and Design Entrance K Pipe Concrete PVC Spiral Rib DI and LCPE Projecting from fill socket bell end Projecting from fill square cut end Headwall or headwall and wingwalls Socket end of pipe groove end Square edge Rounded radius 1 12 Mitered to conform to fill slope End section conforming to fill slope Beveled edges 33 7 or 45 bevels Side or slope tapered inlet Pipe or Pipe Arch Corrugated Metal and Other Non Concrete or D Projecting from fill no headwall Headwall or headwall and wingwalls square edge Mitered to conform to fill slope paved or unpaved slope End section conforming to fill slope Beveled edges 33 7 or 45 bevels Side or slope tapered inlet Box Reinforced Concrete Headwall parallel to embankment no wingwalls Square edged on 3 edges Rounded on 3 edges to radius of 7 12 barrel dimension or beveled edges on 3
304. ements Include the King County tax parcel number s site address owner names and site legal description All pages must be numbered Sheets shall be 8 1 2 by 11 or 8 1 2 by 14 Margins and font size must conform to King County recording format requirements Easements shall be dedicated to and approved by the City prior to acceptance of a public utility system The Grantee shall be the CITY OF BELLEVUE a Washington municipal corporation its heirs successors and assigns The City may require indemnification agreements to hold the City harmless where maintenance access across private property is deemed necessary The description contained within the easement document shall be prepared and stamped by a land surveyor licensed in the State of Washington The description shall be identified as an Exhibit together with the title of the utility use e g Permanent Public Drainage Utility D4 89 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Easement The description shall be clearly written and referenced to the underlying property The description shall be accompanied by an additional graphic Exhibit which depicts a scaled drawing of the easement location relative to the subject parcel Off site easements shall be delivered to the Utility prior to issuing a Notification to Proceed with construction Submittal of on site easements may be delayed until completion of construction improvements Bills of Sale for all utility
305. en necessary to ensure proper documentation of the pipe condition The video shall be taken after installation and cleaning to insure that no defects exist The project will not be accepted until all defects have been repaired Clearly label public and private systems on the plans Private systems shall be marked private and shall be maintained by the property owner s All concrete structures vaults catch basins manholes oil water separators etc shall be vacuum tested Manholes catch basins and inlets in easements shall be constructed to provide a stable level grade for a minimum radius of 2 5 feet around the center of the access opening to accommodate confined space entry equipment Tops of manholes catch basins within public right of way shall not be adjusted to final grade until after paving Contractor shall adjust all manhole catch basin rims to flush with final finished grades unless otherwise shown D2 17 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 29 30 31 32 33 34 35 36 37 38 Contractor shall install at all connections to existing downstream manholes catch basins screens or plugs to prevent foreign materials from entering existing storm drainage system Screens or plugs shall remain in place throughout the duration of the construction and shall be removed along with collected debris at the time of final inspection and in the presence of a representative of th
306. engineering plan D Minor Floodplain Study If the proposed project site does not meet the conditions for no floodplain study required per Section D4 04 5 B or for use of the Approximate Floodplain Study per Section D4 04 5 C and the project site is either on land that is outside of an already delineated Zone A floodplain 1 without base flood elevations determined or is adjacent to a water feature for which a floodplain has not been determined in accordance with 20 25H 175 then a Minor Floodplain Study may be used to determine the floodplain However if the Minor Floodplain Study determines that all or a portion of the project site is at or below the base flood elevation of a river or stream and thus within the floodplain then the applicant must either redesign the project site to be out of the floodplain or complete a Major Floodplain Floodway Study per Section D4 04 5 E Use of the Minor Floodplain Study requires submittal of an engineering plan and supporting calculations That portion of the site that is at or below the determined base flood elevation must be delineated and designated as a floodplain on the engineering plan Methods of Analysis For streams without a floodplain or flood hazard study or for drainage ditches or culvert headwaters the base flood elevation and extent of the floodplain shall be determined using the D4 27 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Direct Step backwater method
307. ent requirements for example runoff can be dispersed through areas with amended soils In addition site design practices and vegetation retention be used to reduce the amount of PGIS and PGPS requiring treatment Rain recycling and vegetated D6 6 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 roofs cannot be used to satisfy runoff treatment No on site stormwater BMPs can be used for oil water separation Table 6 4 summarizes the type of water quality treatment for which each on site stormwater management BMP may be used and provides references to the appropriate design and sizing criteria Table 6 4 On site Stormwater Management BMPs for Runoff Treatment BMP Oil Water Phosphorous Enhanced Design Separation Treatment Treatment Treatment Sizing Criteria Amended Soil No No No No DOE Manual Chapter 5 of Vol V Soils for Salmon Full Dispersion No Yes Yes Yes LID Manual Chapter 7 Full Infiltration No Yes Yes Yes DOE Manual Volume 3 3 9 A Bioretention No No Yes Yes D6 03 2 A Pervious No No Yes Yes D6 03 2 B Pavement Rain Recycling No No No No D6 03 2C Vegetated Roofs No No No No D6 032D Reverse Slope No No No No D6 03 2 E Sidewalks Minimal No No No D6 03 2 F Excavation Foundation Systems Areas meeting the criteria for full dispersion or full infiltration credit shall be excluded from runoff tre
308. entified Drainage Problems D4 6 CONVEYANCE SY SLDENMS din todo nan a cece teste nes D4 6 Generali ciens D4 6 Conveyance System SetDacks i iiie e eR etra S ORI pt RA E RUE de CURE D4 7 Clearances Other Utilities eio pr D4 7 Open Channel Design Criterla a a D4 7 Floodplain Floodway 44000 D4 25 hog mM EE E D4 33 IT M DL DE ME D4 33 Culverts Providing for Fish Passage Migration D4 47 Storm Drains DT D4 49 Private Drainage Pe RU Ae REED o NUS a arent ds D4 62 Private Single Family Drainage Systems esee D4 62 Private Commercial and Multi Family Drainage Systems D4 64 MANHOLES CATCHBASINS AND INLETS D4 66 i R k Aca tma yaa d EL asya a D4 66 Spacing i DA i duke dus D4 67 Maintenance ACCESS iu ein as a ERR LEY REA eee Na D4 68 PLOW setis aesti D4 68 Getieralz c ou c ic Mt dc e D4 68 Desigm etel coo deep oed pee as D4 69 M lti P rpose USE san neta p bU tameii alus
309. ependent calculations used to size and design cisterns to meet flow control requirements For the demonstrative approach continuous modeling shall be used to size the cisterns The assumptions listed in Table 6 10 shall be used The cisterns are modeled as a flat bottomed detention vault or tank with an outlet structure that includes a low flow orifice Tributary areas detention bottom area overflow depth and orifice configuration should be iteratively sized until flow control is met or the desired reduction in downstream conveyance and flow control facilities is achieved D6 37 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D il Table 6 10 Continuous Modeling Assumptions for Cisterns with Detention Variable Assumption Precipitation Series SeaTac 50 year hourly time series with appropriate scaling factor based on project location Computational Time Step Hourly Inflows to Facility Surface flow and interflow from drainage area should be connected to facility Precipitation and Evaporation Applied to No Facility Infiltration No Total Depth The total depth is the cistern height including freeboard above the cistern bottom Outlet Structure Low flow orifice riser height and diameter Overflow The top of the overflow orifice should be set a minimum of 6 inches below the top of the cistern Low Flow Orifice Invert of low flow orifice should be set at a mini
310. er supply equipment structures and appurtenances are not an approved method of conveying storing or treating storm water A deviation must be approved in order to pump storm water If the deviation for a pump system is approved the system shall meet the following minimum requirements A The pump system shall not be used to circumvent any code engineering standard or permit condition The construction and operation of the pump system shall not violate any other City requirements D4 84 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 B The Developer shall demonstrate that the pump system is the only feasible alternative available to provide drainage C Pump systems shall be owned operated maintained repaired and replaced as needed by property owner s served by such system D Pumped flows shall not exceed the allowable discharge rates set forth herein E Each pump shall be capable of discharging the design flow rate for the 100 year 24 hour design storm F If a stormwater detention system 15 not required the pump system shall have a storage facility pond tank or vault sized to hold 25 percent of the total volume of runoff for the developed tributary drainage area for the 2 year storm G The pump system has dual alternating pumps with emergency on site automatic back up power supply and an external alarm system for system failure and high water level indicator H A safe emergency overflow route shall be prov
311. erial where D15 lt 5485 The variable d85 refers to the sieve opening through which 85 of the material being protected will pass and D15 has the same interpretation for the filter material A filter material with a D50 of 0 5 mm will protect any finer material including clay Where very large riprap is used it is sometimes necessary to use two filter layers between the material being protected and the riprap Example What embedded riprap design should be used to protect a streambank at a level culvert outfall where the outfall velocities in the vicinity of the downstream toe are expected to be about 8 fps From Figure 4 1 W50 6 5 lbs but since the downstream area below the outfall will be subjected to severe turbulence increase W50 by 400 so that W50 26 lbs D50 8 0 inches The gradation of the riprap is shown in Figure 4 2 and the minimum thickness would be 1 foot from Table 4 1 however 16 inches to 24 inches of riprap thickness would provide some additional insurance that the riprap will function properly in this highly turbulent area Figure 4 2 shows that the gradation curve for ASTM C33 size number 57 coarse aggregate used in concrete mixes would meet the filter criteria Applying the filter criteria to the coarse aggregate demonstrates that any underlying material whose gradation was coarser than that of a concrete sand would be protected D4 11 JANUARY 2015 SURFACE WATER ENGINEERING STANDARDS o
312. ernative to mulch a dense groundcover may be used Mulch is required in conjunction with the groundcover until groundcover is established C Retention Zone Aggregate for Bioretention Use retention zone material s pore spaces as additional storage reservoir for rain gardens with underdrains and bedding for underdrain pipe For retention zones with slotted underdrain pipe use either Gravel Backfill for Drains per Standard Specifications 9 03 12 4 or Type 26 Mineral Aggregate as follows Type 26 Mineral Aggregate Sieve Size Percent Passing 3 4 inch 100 inch 30 60 U S No 8 0 20 U S No 50 0 2 US No 200 0 1 5 Geotextile not required For an underdrain with perforated PVC underdrain pipe use the following aggregate for the retention zone 34 inch to 1 1 2 inch double washed drain rock ASTM No 57 aggregate or equivalent D Overflows for Bioretention When specified by the Developer an overflow device shall be provided that safely conveys overflow without causing flooding or erosion downstream Use the following for overflows also see Standard Detail NDP 8 and D7 02 3 Storm Drain Pipe and Culvert Materials Overflow drain pipe PVC SDR 35 or schedule 80 PVC pipe minimum diameter 3 D6 57 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Overflow grates screens Atrium grate Overflow strainer or grate grating and frame shall be aluminum stainless steel or plastic medium duty T
313. ertical distances between utility pipes are less than 6 inches and such installation is approved by the City a pad shall be placed between the pipes The pad shall be O D x O D x 2 5 inches thick minimum or as required to protect the pipes Above O D is equal to the outside diameter of the larger pipe The pad shall be a polyethylene foam plank Dow Plastics Ethafoam 220 or approved equal Additional measures may be necessary to ensure system integrity and may be required as evaluated by the City on a case by case basis D8 03 CONNECTIONS MODIFICATIONS TO PUBLIC DRAINAGE SYSTEM When connecting existing metal storm pipe to new catch basins the Contractor shall treat the newly exposed end of the pipe per Section 9 05 4 4 Asphalt Coatings and Paved Inverts of the Standard Specifications Where new pipe is connected to existing the Contractor shall verify the type of existing pipe and join in kind with new If the existing pipe is of a nonapproved material or of dissimilar materials the Contractor shall connect the new to the existing with an appropriate coupling device If a water tight coupling cannot be installed then connection will be made with a structure See Section D7 02 8 herein for coupling material requirements The following connections to a pipe system shall be made only at structures 1 When the inletting pipe is greater than 8 inches in diameter or D8 1 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 2 When roa
314. ervoir Course The reservoir course is designed to structurally support the pervious pavement wearing course as well as provide water storage Depth will be dependent on meeting the minimum depth requirement for the base course reservoir course plus the optional choker course of 6 and the need to store stormwater to meet flow control requirements Depth and area based on modeling results for MR5 when flow control and or runoff treatment do not apply per simplified sizing tables See Table 6 13 Use 2 5 inch to 0 5 inch uniformly graded crushed angular thoroughly washed stone AASHTO No 3 6 36 depth Of Use thoroughly washed clean Permeable Ballast meeting the requirements of Standard Specifications 2010 9 03 9 2 or alternatively use non washed Permeable Ballast that has minimum void ratio of 35 C Water Quality Treatment Layer The BSM specifications in D6 04 1 meet the soil requirements for Runoff Treatment see Section D6 01 1 for more Information D Leveling Course Also called Choker Course or Filter Course The Leveling Course is an optional layer that lies between the pervious pavement wearing course and the reservoir course and is considered part of the base course It is generally one inch to two inches in depth and is intended to provide a uniformly graded surface over which to place the wearing course reduce rutting from delivery vehicles during pavement installation and more evenly distribute loads t
315. es shall be designed to facilitate safe inspection and maintenance Access structures at each end of the facility shall be required Spacing between access openings shall not exceed 50 Covers grates and hatches shall be bolt locking If the vault or pipe contains cells one access minimum per cell is required Access openings shall be 24 in diameter per Standard Detail D 22 and centered over a ladder and or steps For control structures accesses must be located so that an 8 rigid vactor tube can reach the sump directly from the top and so that a person entering the structure can step off the ladder or steps onto the floor The opening shall allow visual inspection of the restrictor pipe while maintaining vertical vactor access to the sump area In order to achieve both requirements it may be necessary to increase the control structure size provide two 24 access openings or a hatched cover that conforms to the loading requirements given the proposed location Orifice elbows shall be located on the side of the stand pipe nearest the ladder for clear visual inspection from above D4 74 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Gates and or removable bollards may be required to restrict access to drainage facilities Such measures shall comply with the Land Use Code and these engineering standards Cables and or chains stretched across access roads are not acceptable D4 06 7 Infiltration Systems A General Infiltrati
316. es that correctly implement full dispersion in accordance with all applicable design requirements do not need additional runoff treatment Bioretention can be used to meet basic and enhanced water quality treatment requirements The bioretention facility must be sized to infiltrate at least 91 percent of the average annual runoff from the contributing pollution generating surface area into the bioretention soil mix layer The bioretention soil mix layer must meet the Soil Physical and Chemical Suitability for Treatment requirements in Chapter 3 of Volume Ill of the DOE Manual Underdrains may be used if needed to meet facility drawdown requirements See Section D6 03 2 A for bioretention design criteria Pervious pavement can also be used to meet basic and enhanced water quality treatment requirements if it is sized to infiltrate at least 91 percent of the average annual runoff from the contributing PGIS area into underlying soils that meet the Soil Physical and Chemical Suitability for Treatment requirements in Chapter 3 of Volume HI of the DOE Manual Underdrains may be used if needed to meet facility drawdown requirements provided that a treatment layer is installed over the underdrains in accordance with Section 4 4 2 of Volume V of the DOE Manual See Section D6 03 2 B for pervious pavement design criteria Some of the required on site stormwater BMPs including amended soil and dispersion can be used to partially satisfy runoff treatm
317. est well shall be a maximum of two 2 feet below the finished grade elevation and shall be plugged and exposed until completion of the test The time of exfiltration tests shall be a minimum of one 1 hour The leakage during the test shall not exceed the following allowances Allowable Leakage Exfiltration or Infiltration Allowable Leakage in gal 100 linear feet hr Head above Crown on Lower End of Test Section Table 8 09 1 6 0 6 0 7 0 7 0 8 0 8 0 9 8 0 8 0 9 1 0 1 0 12 10 1 0 LI 12 13 14 L5 12 12 13 1 4 1 6 17 L8 15 1 5 17 18 2 0 2 1 2 3 18 18 2 0 22 23 25 23 24 24 2 6 29 3 1 34 3 6 Repair by chemical grouting will not be allowed For static head above the basic eight feet at the crown of the storm drain at the lower end of the test section the allowable leakage shown above shall be increased at a ratio of 5 percent per foot increase D8 9 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Where the groundwater exceeds a height of six feet above the crown of the storm drain at the upper end of the test section the section shall be tested by infiltration The infiltration test shall be conducted by placing a plug in the mlet storm drain at the upper manhole and inserting an approved measuring device in the inlet storm drain at the lower manhole Prior to making measurements care shall be taken to assure that the flow over or through the measuring device is constant A minimum of
318. etention Bioretention Cells bioretention planters and bioretention swales Pervious Pavement Rain Recycling cisterns and rain barrels Vegetated Roof Other BMPs that DOE approves in writing as functionally equivalent to the NDPs listed here or that attain DOE s General Use Level Designation GULD rating are also allowed provided that they are installed per DOE s requirements Maintain NDPs in accordance with the Bellevue Maintenance Standards and or per manufacturer s recommendation for BMPs approved by DOE A Bioretention 1 Bioretention Cell and Bioretention Swale Bioretention Cells are shallow landscaped depressions containing an amended soil mix and native plants that receive stormwater runoff see Standard Details NDP 2 6 7 8 9 10 Bioretention Cells can be designed to mimic natural conditions where the soils and plants work together to store treat infiltrate and slow runoff Bioretention Cells are a landscape amenity that can be applied in various settings D6 16 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Bioretention swales are similar to Bioretention Cells except that they are typically linear e g narrower and longer than a Bioretention Cell see Standard Detail NDP 3 and the bottom may be sloped Bioretention swales can be designed with or without underdrains i Applicability Residential commercial and mixed use sites such as lawns that receive roof runoff
319. ethod can be used to calculate the amount of credit to be attributed to the Bioretention Cell or bioretention swale in sizing the downstream flow control facility as described in Section D3 03 The default method typically results in less Flow Control Credit The demonstrative method is described above in this section and involves using the model developed for sizing purposes to also evaluate the amount of residual flow control needed See Chapter D3 for guidance on hydrologic modeling for sizing flow control and runoff treatment facilities 2 Bioretention Planter A bioretention planter is similar to a Bioretention Cell or bioretention swale except that it is typically designed with vertical impervious walls and an impervious bottom to prevent infiltration or damage to nearby structures Stormwater enters the surface D6 24 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 via a roof downspout pipe and percolates through the bioretention soil mix layer The treated stormwater is discharged via an underdrain pipe to a storm drainage system approved storage facility or dispersal area Design options are provided in this standard for bioretention planters with and without underdrains and with and without infiltration The bioretention planter with infiltration is called an infiltration planter see Standard Detail NDP 4A the bioretention planter without infiltration is referred to as a flow through planter see Standard Deta
320. ethods set forth in the Standard Specifications as modified herein Prior to the final inspection the Contractor shall clean the storm drain system and any off site drainage systems affected by construction activities by a method approved by the City Wastewater from such cleaning operations shall not be discharged to the storm drainage system or surface waters Prior to the installation of impervious surfacing detention facilities shall be operational Prior to occupancy of any single phase of a phased development storm drainage facilities shall be completed and operational to provide conveyance flow control and water quality treatment for the phase for which occupancy is requested Contractor shall provide Manufacturer s Certificate of Compliance in accordance with Section I 06 3 of the Standard Specifications when requested by the City for all pipe fittings precast concrete products castings and manufactured fill materials to be used in the project Testing of the drainage system by the Contractor when required by the City shall conform to the testing requirements for the particular component of the system as set forth in the Standard Specifications and issued permits Documentation for the newly installed drainage facilities required by these Standards the Developer Extension Agreement or issued permits shall be submitted and approved prior to construction acceptance D8 02 CLEARANCE BETWEEN UTILITY LINES If the minimum v
321. ethylene Storm Sewer Pipe CPE Corrugated polyethylene storm sewer pipe shall meet the requirements of AASHTO M 294 Type S The minimum pipe diameter shall be 8 inches The maximum pipe diameter shall be 36 inches or the diameter for which a supplier has a joint conforming to ASTM D 3212 whichever is less Joints for corrugated polyethylene culvert pipe shall be classified as watertight Watertight joints shall be made with a sleeve or with a bell spigot and shall conform to ASTM D 3212 10 8 psi using elastomeric gaskets conforming to ASTM F 477 Gasketed joints shall be lubricated as recommended by the producer during installation Soiltight joints shall not be permitted Fittings for corrugated polyethylene storm sewer pipe shall be blow molded rotational molded or factory welded Thermoplastic pipe fittings shall meet the requirements set forth in AASHTO M 294 Pipes must meet the air leakage test see Section D8 09 herein for testing requirements D High Density Polyethylene Pipe HDPP HDPP shall be used outside of the traveled roadway Primary use of this material includes steep slope installations and overbank drains D7 2 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 HDPP shall be manufactured in accordance with ASTM F 714 or ASTM D 3035 Resin shall be Type II C5P34 as set forth ASTM D1248 The minimum Standard Dimension Ratio SDR is 32 5 with a design working pressure rating of at least 50
322. etween the bottom of footing or base rock a casing is required regardless of wall height A2 Pipeline Encasement and Crossing 2 PVC pipe shall be encased in a steel or ductile iron casing when crossing under improvements where the ability to remove and replace pipe without disturbance to the improvement is needed Casings are required when Crossing under rockeries over 4 high Crossing under retaining wall footings over 4 wide Crossing under reinforced earth retaining walls both wall and reinforcing material Casings shall extend a minimum of 5 past each edge of the improvement or a distance equal to the depth of pipe whichever is greater The carrier pipe shall be supported by casing spacers where casing length exceeds 10 Minimum clearance between bottom of rockery and top of pipe or casing shall be 2 feet The trench shall be backfilled with crushed rock B Pipe Cover for Culverts and Underground Detention Systems For high density polyethylene pipe AASHTO M 294 Type S the maximum fill depth is 15 feet measured to the top of the pipe For Polyvinyl chloride pipe profile and solid wall the maximum fill depth is 20 feet For reinforced concrete pipe the maximum fill depth is 15 feet for class III pipe and 25 feet for class V pipe For pipes greater than 25 feet pipe type shall be determined on a case by case basis with back up calculations provided by the Designer Minimum cover is 2 feet from the top of p
323. ew trees are provided in Table 6 14 for deciduous and evergreen trees This credit can be applied to reduce the effective impervious surface area used in downstream conveyance and flow control calculations Since only partial credit is applied additional flow control measures will be required To use the Flow Control Credit the new trees must meet the following specific requirements The tree trunk center must be within 20 feet of new and or replaced ground level impervious surface Tree credits do not apply to trees in native vegetation areas used for flow dispersion or other Flow Control Credit The total tree credit for newly planted trees shall not exceed 25 percent of impervious surface requiring mitigation Minimum five 5 foot setback from structures Minimum five 5 foot setback from underground utility lines Minimum two 2 foot setback from edge of any paved surface D6 51 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 New deciduous trees shall be at least 1 5 inches in diameter measured six 6 inches above the ground New evergreen trees shall be at least four 4 feet tall Roof Downspout Concentrated or Sheet Flow Dispersion 1 Dispersion will not achieve flow control requirements unless it meets the requirements of Full Dispersion as outlined in Section D6 03 1 some flow control benefits are achieved with more limited dispersion BMPs Credits for dispersion are provided in Table 6 14
324. filtration planter Roof Downspout Infiltration infiltration trench or drywell Infiltration Pond Biofiltration filter or other treatment system Setback Requirement Measure setback elevations and distances from edge of bottom area of facility From any structure or building from finish grade as measured from side of building o With basement or crawl space 10 feet o Foundation slab on grade 5 feet o Uphill from building and 5 000 square feet or more of contributing impervious area 100 feet o Uphill from building and less than 5 000 square feet of impervious contributing area 20 feet Septic drainfield King County Public Health compliance required 30 feet if downhill 100 feet if uphill Drinking water well or spring 100 feet King County Public Health compliance also required Steep Slope Landslide Hazard Area or other Critical Area per Land Use Code e of any slope greater than or equal to 15 50 feet may be revised with evaluation by geotechnical engineer or qualified geologist and approval or in accordance with applicable Critical Areas Ordinance requirements whichever is greater e Property line 10 feet may be reduced for right of way with City approval or with agreement from adjacent owner e Within the right of way where dense underground infrastructure exists only accept runoff from sidewalk areas e Contaminated soil or groundwater 100 feet infiltration within 500 feet requires approval by a license
325. filtration pathways are restricted to prevent excessive hydrologic loading Where clay or geomembrane liners are used for this purpose underdrain systems are required Two types of restricting layers can be incorporated into bioretention designs clay liners or geomembrane liners Clay bentonite liners are low permeability soil barriers When specified by the project engineer design requirements shall include Liner thickness shall be 12 inches minimum Clay shall be compacted to 95 minimum dry density modified proctor method ASTM D 1557 different depth and density sufficient to retard the infiltration rate to 2 4 x 10 5 inches per minute 1 x 10 6 cm s may also be used instead of the above criteria The slope of clay liners must be restricted to IV for all areas requiring soil cover otherwise the soil layer must be stabilized by another method so that soil slippage into the facility does not occur Any alternative soil stabilization method must take maintenance access into consideration Where clay liners form the sides of ponds the interior side slope should not be steeper than 3 1 irrespective of fencing This restriction is to ensure that anyone falling into the pond may safely climb out Geomembrane liners completely block flow and are used for groundwater protection when bioretention facilities are used for filtering storm flows from D6 19 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 pollut
326. flow such as road approach grades bridges piers or other restrictions General guidelines for transitions may be found in FEMA Guidelines and Specifications for Flood Hazard Mapping Partners and the HEC RAS User s Manual Hydraulic Reference Manual and Applications Guidelines Zero rise floodways are assumed to include the entire 100 year floodplain unless The Utility approves a detailed study that defines a zero rise floodway Zero rse means no measurable increase in water surface elevation or energy grade line For changes between the unencroached condition and encroachment to the zero rise floodway HEC RAS must report 0 00 as both the change in water surface elevation and the change in energy grade HEC RAS must further report D4 30 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 the exact same elevations for both the computed water surface and energy grade line Floodway studies must reflect the transitions mentioned in Requirement 2 above FEMA floodway boundaries are to follow stream lines and should reasonably balance the rights of property owners on either side of the floodway Use of the automatic equal conveyance encroachment options in the HEC RAS program will be considered equitable Where HEC RAS automatic options are otherwise not appropriate the floodway must be placed to minimize the top width of the floodway Submittal of floodway studies for the Utility review must include an electronic copy of the HEC R
327. g and vegetated roofs These NDPs are encouraged as an integral part of site designs New BMPs that DOE has approved for General Use GULD under DOE s emerging technology program per Chapter 12 Volume V of the DOE Manual are allowed Using NDPs in addition to or in place of the required on site BMPs where NDP substitution is allowed can significantly enhance the overall hydrologic performance of the developed site and further reduce downstream flooding erosion water quality impacts and long term maintenance requirements NDPs can also enhance site sustainability and aesthetics and may add points under LEED and Built Green certification programs This chapter provides detailed guidance on how to use the criteria set forth in Section 24 06 065 G of the Storm and Surface Water Utility Code and design guidelines in the LID Technical Guidance Manual and Chapter 3 of Volume III and Chapter 5 of Volume V of the DOE Manual as modified herein to plan design and construct on site stormwater management BMPs and NDPs The remainder of this section describes how to apply on site stormwater management BMPs to meet Minimum Requirement 5 On Site Stormwater Management MR6 Runoff Treatment and MR7 Flow Control D6 01 1 Using On Site Stormwater Management to meet Storm and Surface Water Utility Code Requirements Under the Storm and Surface Water Utility Code BCC 24 06 065 new development redevelopment and construction activities that meet t
328. g activities of 2 Yes 7 000 square feet or more See the Minimum Requirement 2 Construction Stormwater Pollution Prevention BCC 23 76 Clearing and Grading Code Figure 2 2 Flow Chart for Determining Requirements for New Development D2 4 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Do the new replaced or new plus replaced impervious surfaces total 2 000 square feet or more OR Does the land disturbing activity total 7 000 square feet or more Minimum Requirements 1 through 5 apply See the Minimum Requirement 2 to the new and replaced impervious surfaces Construction Stormwater Pollution Prevention and the land disturbed BCC 23 76 Clearing and Grading Code Next Question Does the project add 5 000 square feet or more of new impervious surfaces OR Convert 3 4 acres or more of native vegetation to lawn or landscaped areas OR Convert 2 5 acres or more of vegetation to pasture Next Question Minimum Requirements 1 through 9 apply to the new impervious surfaces and the converted pervious surfaces Is this a road related project No Does the project add 5 000 square feet or more of new impervious Is the total of the new plus replaced impervious surfaces 5 000 square feet or Do new impervious surfaces add 50 or more AND does the value of the proposed more to the existing impervious surfaces improvements including interior within the project limits improve
329. gated Metal Pipe CMP which includes steel and aluminum and other flexible pipe bedding material shall conform to Section 9 03 16 Bedding Material for Flexible Pipe per the Standard Specifications Trench backfill material shall conform to Section 9 03 14 Gravel Borrow of the Standard Specifications Excavated material may be used as pipe bedding and or trench backfill when it has been demonstrated by the Contractor to be suitable D7 05 FLOW CONTROL INFILTRATION SYSTEMS Perforated pipe for roof downspout systems and infiltration trenches shall conform to Section D7 02 3 herein Single wall CPE pipe is not allowed Gravel backfill for infiltration systems shall meet the requirements for coarse aggregate for Portland cement concrete Grading No 4 or 5 as listed in Section 9 03 1 3 C of the Standard Specifications D7 11 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 END OF CHAPTER D7 D7 12 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D8 METHODS OF CONSTRUCTION TABLE OF CONTENTS D8 01 oisessdie drin eO ed ip E vetere nt p UE E UA RS D8 1 D8 02 CLEARANCE BETWEEN UTILITY LINES eese D8 1 08 03 CONNECTIONS MODIFICATIONS TO PUBLIC DRAINAGE SYSTEM D8 1 D53 04 CONVEYANCE SYSTEMS bdo dut i uae ipe es D8 2 BS OA WGN aac cnet dota aus preis Rin m UTE D8 2 D 04 2 tei ied
330. ge BMPs which do not infiltrate at all LID Manual Low Impact Development Technical Guidance Manual for Puget Sound published by Puget Sound Partnership and Washington State University Pierce County Extension January 2005 or current Material or Materials These words shall be construed to embrace machinery manufactured articles materials of construction fabricated or otherwise and any other classes of material to be furnished in connection with the Project Minimum Requirements MRs Minimum Requirements refer to the regulations contained in BCC 24 06 065 and applicable engineering standards which describe requirements for storm water management for development and redevelopment as required by the NPDES Permit Briefly MRI Preparation of Storm Water Site Plans MR2 Construction Storm Water Pollution Prevention Plan MR3 Source Control of Pollution Preservation of Natural Drainage Systems and Outfalls D1 2 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 5 On site Storm Water Management MR6 Runoff Treatment MR7 Flow Control MRS Wetlands Protection MR9 Operations and Maintenance MS4 Municipal Separate Storm Sewer System as defined in the NPDES Permit Natural Drainage Practice NDP Small scale distributed BMP that controls the volume peak flow rate and amount of pollutants in stormwater runoff from a developed project site NDPs include bioretention
331. gs After cleaning the interior surface of the manhole the Contractor shall place and inflate pneumatic plugs in all the connecting pipes with the exception of storm laterals to isolate the manhole Complete storm services entering the manhole shall be a part of the manhole vacuum test The vacuum plate head shall be placed on top of the manhole lid frame The vacuum pump shall be connected to the outlet port with the valve open When a vacuum of ten 10 inches of mercury has been attained the outlet valve shall be closed and the test period is started The minimum test period is determined from the following table Table 8 11 1 Depth of Manhole Time Seconds Feet 48 Inch Dia 60 Inch Dia 72 Inch Dia 4 10 13 16 8 20 26 33 12 30 39 49 16 40 52 67 20 50 65 81 24 59 78 97 26 64 85 105 28 69 91 113 30 74 98 121 Add for each additional 2 feet of depth 5 6 66 8 Measurements taken from ASTM 1244 All pneumatic plugs shall be removed from the manhole after the test D8 11 2 Failure Any manhole that fails the initial vacuum test must be repaired with an approved non shrink grout on the interior and exterior of the manhole Any repair between the pipes and manhole gasket waterstop area requires the removal of the pipe by means of coring and the installation of a new pipe with waterstop grouting the annular opening Upon completion of the repairs the manhole shall be re
332. gular Maintenance Complaint or Problem Regular Maintenance D2 24 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 END OF CHAPTER D2 D2 25 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D3 HYDROLOGIC ANALYSIS TABLE OF CONTENTS D3 01 GENERAL ee cas D3 1 D3 02 HYDROLOGIC MODELS 52 sa e Dh aaa Wa D3 1 D3 02 01 Ecology Approved Continuous Simulation Hydrology Model D3 2 D3 02 02 Single Event Hydrograph Method a D3 3 D3 02 03 Rational IN CUA ap ENT MU aq a asp yes Out apaqsi D3 11 D3 03 SUMMARY OF DESIGN D3 14 D3 04 MINIMUM IMPERVIOUS D3 15 D3 05 FLOW CONTROL EXEMPTIONS D3 16 D3 0 et oai D3 17 LIST OF TABLES Table 3 1 Acceptable Uses of Runoff Computation Methods D3 2 Table 3 2 24 Hour Design Storm Hyetograph Values D3 4 Table 3 3 Runoff Coefficients C Values For The Rational Method D3 12 Table 3 4 Coefficients For The Rational Method Tr Equation D3 12 Tab
333. he detention facility shall be sized for the entire flow that is directed to it If the upstream offsite property is developed later the owner of that property is responsible to modify the facility and or control structure to ensure that flow control requirements are maintained B Sites with Existing Stormwater Detention Systems When flow control is required on a site with an existing flow control system the Developer may choose one of the following options 1 Retain the existing system modify the control structure and add volume as needed to meet the current codes for flow control or 2 Replace the existing flow control with a system designed to meet the current codes for flow control or 3 Retain the existing system to control runoff from existing impervious surfaces and design a second flow control system per the current codes to control runoff from new portions of the development When choosing options 1 or 2 the Developer must demonstrate that the combined discharge will meet the performance of the previous standards for the non project area and the flow control requirements of the current standards for the project area This requires a flow duration curve D4 69 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 based on continuous modeling to be developed at a point immediately downstream from the project that includes the predicted outflow from the existing pond under current conditions and the historic forested r
334. he following overflow products are approved Atrium Grate 37 4 6 round NDS models 70 75 80 Atrium grate ADS model 0663SDX Neenah grate R 4346 R 2560 E2 R 2561 R 4351 C R 4353 R 4351 B R 4351 D Olympic Foundry MH25 E Plants for Bioretention Rain Gardens Bioretention Swales Downspout Planter Boxes Native plants from the Pacific Northwest region shall be used whenever possible Hardy cultivars that are not invasive and do not require chemical inputs may also be used Plants may be chosen from lists provided in the Rain Garden Handbook for Western Washington Homeowners Washington State University 2007 the Low Impact Development Technical Guidance Manual for Puget Sound Puget Sound Partnership and Washington State University 2005 or current both available on the web see D1 References For areas within the public right of way trees that are tolerant of the site conditions and approved for streetscapes may be used Select and place bioretention plants to match the site s sun moisture and soil conditions Plants should be planted at high enough density to cover or shade the entire surface of the rain garden within two years of planting As a general guideline plant a minimum of three types of shrubs and three types of herbaceous plants in each facility to protect against facility failure due to disease or insect infestation of a single species All plant materials should have normal well developed branche
335. he pit at a rate that will maintain 6 12 inch water level above the bottom of the pit over a full hour The depth should not exceed the proposed maximum depth of water expected in the completed facility e Every 15 minutes record the cumulative volume and instantaneous flow rate in gallons per minute necessary to maintain the water level at the same point between 6 inches and 1 foot on the measuring rod The specific depth should be the same as the maximum designed ponding depth usually 6 12 inches e After one hour turn off the water and record the rate of infiltration the drop rate of the standing water in inches per hour from the measuring rod data until the pit is empty e A self logging pressure sensor may also be used to determine water depth and drain down At the conclusion of testing over excavate the pit to see if the test water is mounded on shallow restrictive layers or if it has continued to flow deep into the subsurface The depth of excavation varies depending on soil type and depth to hydraulic restricting layer and is determined by the engineer or certified soils professional The soils professional should judge whether a mounding analysis is necessary Data Analysis See the explanation under the guidance for large scale pilot infiltration tests D4 82 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 K Soil Grain Size Analysis Method For each defined layer below the infiltration pond to a de
336. he thresholds defined in Section D2 05 are required to provide on site stormwater management MRS runoff treatment and or flow control MR7 This section describes how on site stormwater management BMPs may be used to meet those minimum requirements A On Site Stormwater Management Minimum Requirement 5 Required for projects with new replaced or new plus replaced impervious surface areas equal to or greater than 2 000 square feet Following is a tiered list of Best Management Practices BMPs that must be evaluated for each project that triggers on site stormwater management Figure 6 1 The BMPs must be evaluated and implemented in the order presented within each of three tiers Tier 1 Minimize Runoff Generation Table 6 1 D6 1 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Tier 2 Retain Runoff On Site Tables 6 2 and 6 2B and 3 Infiltrate or Disperse Runoff Prior to Discharge Table 6 3 After required on site stormwater management implemented to the extent feasible additional BMPs from Table 6 2B may be implemented as site conditions allow On site stormwater management BMPs including NDPs may be used to reduce runoff treatment and or flow control requirements when designed and sized per Section D6 03 D6 2 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Site Design Requirements e Smart Site Design e Preserve Native Vegetation e Amend Soils
337. he time of concentration to the first structure where flow enters the proposed pipe system the travel times through the pipe lengths are added to become the Tc for the design flow at the next downstream pipe run The flows computed at structures manholes and catch basins may be used to estimate the water surface profile along the pipe system See Section D3 02 3 for additional information on rational method computational methods D4 60 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 of Typ n cfs U j j T min Sum C A TWP C CONVEYANCE SYSTEM ANALYSIS AND SIZING TABLE USING THE RATIONAL METHOD 1 4 Sec 1 4 Number ac prod Lp ss PEN ru mee INEST EXE M ERE E NE NND 22 2 3 p Location From Project Location Figure 4 22 Rational Method for Conveyance System Analysis and Sizing D4 61 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 E Minimum Diameter Slope and Velocity Minimum slope for conveyance pipes shall be 0 5 unless specified otherwise herein Minimum diameter for a conveyance pipes in a roadway shall be 12 inches except for roadway laterals and pipes connecting private drainage systems or wall drains to the drainage system For roadway laterals the minimum diameter is 8 inches provid
338. here run on is allowed e g pervious pavement dispersal areas and not allowed e g roadways D6 02 4 Step 3 Runoff Sources and BMP Selection In this step the designer will select appropriate on site BMPs using Table 6 5 Because development impacts are greatest where impervious surfaces will be created it is most efficient to first identify the appropriate BMPs to control runoff from each impervious surface on a case by case basis The nature of the runoff source is important in determining the appropriate BMP to use For example vegetated roofs are obviously appropriate only for mitigating roof runoff Runoff from streets or other traffic areas should ideally drain to facilities that can treat runoff To use the BMP selection matrix first divide the proposed site into the various runoff sources roofs streets including parking areas and driveways pedestrian hardscapes such as sidewalks and lawns landscaping Then look at the proposed impervious areas roofs streets and sidewalks and determine if BMPs at the source are possible e g pervious pavement or where runoff may be conveyed Finally for each potential area where runoff can be conveyed identify the character and use of the receiving location The BMPs to be considered are summarized in the appropriate cells of the selection matrix If on site stormwater BMPs are not feasible due to site limitations and design requirements return to the appropriate section of Chapters D
339. hly turbulent zone such as at a culvert outfall downstream of a stilling basin at sharp changes in channel geometry etc the median stone W50 should be increased from 200 to 60096 depending on the severity of the locally high turbulence The thickness of the riprap layer should generally be twice the median stone diameter D50 or at least that of the maximum stone The riprap should have a reasonably well graded assortment of stone sizes within the following gradation 1 25 Dmax D50 1 50 D15 D50 0 50 From paper prepared by Schaefer Dam Safety Section Washington State Department of Ecology D4 10 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Dmin D50 0 25 Detailed design methodology may be found in the Corps publication EM 1110 02 1601 Engineering and Design Hydraulic Design of Flood Control Channels For a more detailed analysis and design procedure for riprap requiring water surface profiles and estimates of tractive force refer to the paper by Maynord et al in Journal of Hydraulic Engineering A S C E July 1989 Riprap Filter Design Riprap should be underlain by a sand and gravel filter or filter fabric to keep the fine materials in the underlying channel bed from being washed through the voids in the riprap Likewise the filter material must be selected so that it is not washed through the voids in the riprap Adequate filters can usually be provided by a reasonably well graded sand and gravel mat
340. hut aan eS madres D4 10 Table 4 3 Values Roughness Coefficient N For Open Channels D4 15 Table 4 4 Floodplain Floodway Study Thresholds And Requirements D4 26 Table 4 5 Datum eee eu D4 32 Table 4 6 Constants For Inlet Control Equations D4 36 Table 4 7 Entrance Loss Coefficients iN UR a at aed et D4 38 Table 4 8 Fish Passage Design Criteria D4 48 Table 4 9 Manning s N Values for Pipes eae a BAG D4 51 Table 4 10 Pipe Sizes And Lengths Between 5 D4 67 Table 4 11 Allowable Structures And Pipe Sizes eese D4 67 Table 4 12 Setback Requirements For Storm Drainage Features D4 86 FIGURES Figure 4 1 Mean Channel Velocity Vs Medium Stone Weight W50 And Equivalent Stone lbi NI ETUR D4 12 SURFACE WATER ENGINEERING STANDARDS JANUARY 2055 Figure 4 2 Riprap Filter Example Gradation Curve aa D4 13 Figure 4 3 Ditches Common Section D4 19 Figure 4 4 Drainage Ditches Common Sections D4 20 Figure 4 5 Geometric Elements Of Common Sections serere D4 21 Figure 4 6 Open Channel Flo
341. ided if possible L The pump system shall discharge to an elevation higher than the downstream design water surface elevation to prevent backwater backflow conditions J Maintenance and Operation Schedule shall be prepared and submitted for review prior to permit issuance K A note on the approved plan shall stipulate that the private property owner s shall be responsible for any and all claims for injuries and damage due to the operation or failure of the pump system D4 06 10 Non Gravity Systems Pumps for Properties where 100 Lot Coverage is Allowed by the City s Land Use Code The pump system shall not be used to circumvent any code engineering standard or permit condition The construction and operation of the pump system shall not violate any other City requirements Pump systems shall be owned operated maintained repaired and replaced as needed by property owner s served by such system Storm detention facilities with flow restrictors shall be installed upstream and discharge by gravity to the pump system The pump system shall have a minimum of two pumps with emergency on site back up power supply and an external alarm system for system failure and high water level indicator The pump chamber shall be sized no greater than a 5 minute on off cycle time for one pump however the pump chamber shall not be larger than 1000 gallons The total pump capacity shall not exceed the design flow rate for the 1 year 24 hour s
342. identify the hydrologic soil group Hydrologic groups for some King County soils have been revised 11 88 Table 2 1 in Volume of the DOE Manual does not reflect those revisions Use the revised values presented below Table 3 6 Hydrologic Soil Groups for Soils in the Puget Sound Basin Soil Type Hydrologic Soil Group Arents Alderwood Beausite Buckley Earlmont Indianola Klaus Norma Woodinville TODAS oO D3 17 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 END OF CHAPTER D3 D3 18 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D4 01 D4 02 D4 02 1 D4 02 2 D4 02 3 D4 03 D4 03 1 D4 03 2 D4 04 D4 04 1 D4 04 2 D4 04 3 D4 04 4 D4 04 5 D4 04 6 D4 04 7 D4 04 8 D4 04 9 D4 04 10 D4 04 11 D4 04 12 D4 05 D4 05 1 D4 05 2 D4 05 3 D4 06 D4 06 1 D4 06 2 D4 06 3 D4 06 4 D4 06 5 CHAPTER D4 HYDRAULIC ANALYSIS amp DESIGN TABLE OF CONTENTS GENERAL RDUM RE n D D4 1 OUTFALLS AND DISCHARGE LOCATIONS D4 2 Discharge Location s eeu ede eae D4 4 Uhiconcentrated HOW eas Tas aa ns eui as D4 4 Temporary Discharges to the Sanitary Sewer D4 4 OFF SITE CAPACITY ANALYSIS a D4 5 Levels u na n ias e Eta bue ode qaqa D4 5 Solutions to Id
343. ight of way To be approved on a case by case basis The Contractor shall completely fill the pipeline to be abandoned with sand concrete or controlled density fill or remove it D8 08 2 Abandoning Structures Abandonment of structures shall be completed only after piped systems have been properly abandoned Structures within the public right of way a public easement or which is part of the publicly owned and maintained system must be Removed completely according to Section 2 02 of the current Standard Specifications or Abandoned according to Section 7 05 3 of the current Standard Specifications provided no conflicts with new utilities or improvements arise D8 08 3 Demolition or Removal of Structures Any property owner who plans to demolish or remove any structure connected to the public drainage system shall A Notify the Utility and complete a utility abandonment form prior to commencement of such work and B Verify the location of the existing on site drainage facilities and C Cap as necessary connections that are no longer needed D8 8 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D8 09 TESTING OF GRAVITY STORM DRAINS Methods of testing gravity storm drains shall be at the option of the Contractor unless otherwise specified herein D8 09 1 Water Test Tests for water tightness shall be made by the Contractor in the presence of the Engineer A test shall be made every section of the storm drai
344. ils NDP 4 and 5 Multiple smaller planters are encouraged to manage relatively small drainage areas rather than one large planter managing larger drainage areas il Applicability Flow through planters may receive roof runoff from residential commercial and mixed use sites Infiltration planters may receive roof runoff from residential commercial and mixed use sites as well as roadway parking lot or other paved surfaces provided that topography allows runoff to reach facility Bioretention planters can be used where space is limited Limitations For infiltration planters seasonal high groundwater must be more than 1 foot below the bottom of the facility Where the depth to groundwater is less than 3 feet below the bottom of the facility the contributing impervious drainage area must be no greater than 5000 square feet Infiltration planters shall meet infiltration BMP setback requirements per D4 07 Planters with underdrains will not satisfy MR5 or MR7 but can be designed to satisfy MR6 See Sizing Factors Section D6 03 3 Design Requirements Inlet Inflows from pipes should be directed to the top of the facility and protected from erosion using energy dissipation e g rock pad pop up emitter or flow dispersion weir Dimensions Ponding depth shall be a minimum of 4 inches and a maximum of 12 inches Minimum bottom width shall be 18 inches for flow through planters Minimum bottom width shall be
345. iltration rate See DOE Manual Volume III Table 3 9 for a selection of an appropriate infiltration correction factor Example The area of the bottom of the test pit is 8 5 ft by 11 5 ft Water flow rate was measured and recorded at intervals ranging from 15 to 30 minutes throughout the test Between 400 minutes and 1 000 minutes the flow rate stabilized between 10 and 12 5 gallons per minute or 600 to 750 gallons per hour or an average of 9 8 12 3 2 11 1 inches per hour J Small Scale Pilot Infiltration Test A smaller scale PIT can be substituted for the large scale PIT in any of the following instances e The drainage area to the infiltration site is less than 1 acre e The testing is for the LID BMP s of bioretention or permeable pavement that either serve small drainage areas and or are widely dispersed throughout a project site e The site has a high infiltration rate making a full scale PIT difficult and the site geotechnical investigation suggests uniform subsurface characteristics Infiltration Test e Excavate the test pit to the estimated surface elevation of the proposed infiltration facility In the case of bioretention excavate to the estimated elevation at which the imported soil mix will lie on top of the underlying native soil For permeable pavements excavate to the D4 81 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 elevation at which the imported subgrade materials or the pavement itself will
346. implemented to protect water quality in accordance with Volumes IV and V of the DOE Manual as modified herein These standards define approved water quality BMPs for new development and redevelopment in Bellevue Runoff treatment facilities including those that serve multiple sites are subject to all of the engineering and design requirements contained in the Storm and Surface Water Utility Code and these Standards Conceptual site plans for all sites to be served by the proposed stormwater facilities shall be submitted to the City for review Construction of facilities that serve multiple sites or a phased development must occur in conjunction with the first project or phase to be served by the runoff treatment facilities Pavement overlay or replacement shall comply with Redevelopment thresholds contained in BCC 24 06 065 Street and parking overlays are considered to be routine maintenance and are not considered to be redevelopment per Section 24 06 065 B and F of the Storm and Surface Water Utility Code Removal of pavement to subgrade and subsequent replacement not including spot base repairs is considered to be redevelopment and disturbance per Section 24 06 065 F of the Storm and Surface Water Utility Code Such reconstruction is not considered to be routine maintenance D5 02 SOURCE CONTROL BMPs Source Control BMPs are preventive best management practices and include site design use of alternative products operation and maintenance
347. in calculating dwelling units per gross acre D3 05 FLOW CONTROL EXEMPTIONS As specified in Chapter 24 06 065 G 7 of the Storm and Surface Water Utility Code flow control is not required for new development or redevelopment projects that discharge directly to Lake Washington Lake Sammamish or Mercer Slough via a conveyance system meeting the requirements set forth in these Standards The direct discharge to these water bodies is subject to the following restrictions 1 Direct discharge to the exempt receiving water does not result in the diversion of drainage from any perennial stream classified as Types 1 2 3 or 4 in the State of Washington Interim Water Typing System or Types S F or Np in the Permanent Water Typing System or from any category 1 IL or HI wetland and 2 Flow splitting devices or drainage BMP s are applied to route natural runoff volumes from the project site to any downstream Type 5 stream or category IV wetland A Design of flow splitting devices or drainage BMP s will be based on continuous hydrologic modeling analysis The design will assure that flows delivered to Type 5 stream reaches will approximate but in no case exceed durations ranging from 50 of the 2 year to the 50 year peak flow B Flow splitting devices or drainage BMP s that deliver flow to category IV wetlands will also be designed using continuous hydrologic modeling to preserve pre project wetland hydrologic conditio
348. in Section 6 03 2 plus the following specific requirements The low flow orifice diameter shall be 0 25 inches Screening to prevent leaves and debris from clogging the orifice shall be less than 0 1 inch mesh The inlet pipe shall have a self cleaning filter and if possible the top of the cistern shall also be screened The low flow orifice must be able to drain continuously from October 1 through June 30 Invert of overflow shall be set at the designated height 3 or 4 feet above invert of low flow orifice For intermediate ponding depths between 3 and 4 feet a Sizing Factor may be linearly interpolated The cistern shall have vertical walls to the designated overflow height C Sizing Factors Table 6 13 summarizes the Sizing Factors for on site stormwater management MR5 and provides sizing estimates for conceptual design for runoff treatment MR6 and flow control MR7 The Sizing Factors represent the required BMP size generally the bottom footprint area as a function of MR and design configuration e g ponding depth PD and native soil design infiltration rate inf D6 48 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 6 13 Sizing Factors for On site BMPs Roof Downspout Infiltration Trench Rain Garden or Bioretention Cells no Underdrain Rain Garden or Bioretention Cells with Underdrain Bioretention Planter with Underdrain Bioretention Planter Infiltration Pervious P
349. in Table 6 7 shall be applied The bioretention planter should be modeled as a layer of soil with specified infiltration rate and porosity with ponding detention via a restricted underdrain if applicable infiltration to underlying soil if applicable and overflow The tributary areas planter bottom area and ponding depth shall be iteratively sized until runoff treatment and flow control requirements are met and the maximum surface pool drawdown time of 48 hours is satisfied The surface pool drawdown time may be estimated as the ponding depth divided by the long term design infiltration rate The overflow shall be sized for 100 year 24 hour conveyance D6 27 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 6 7 Continuous Modeling Assumptions for Bioretention Planters SeaTac 50 year hourly time series with appropriate scaling factor based on project location Surface flow and interflow from drainage area routed to facility Precipitation Series Computational Time Step Inflows to Facility Precipitation and Evaporation Applied to Facility Bioretention Soil Infiltration Rate Bioretention Soil Porosity Bioretention Soil Depth Aggregate Porosity Native Soil Design Infiltration Rate optional Infiltration Across Wetted Surface Area Underdrain water quality treatment only Outlet Structure Yes For imported bioretention soil see specification Section D6 04 1 For compost amended native soil
350. ion facilities shall be maintained per DOE Manual Volume IV Chapter 2 BMPs for Maintenance of Stormwater Drainage and Treatment Systems Infiltration facilities shall be maintained per the Bellevue Maintenance Standards B Smart Site Design Description and Applicability When considering site layout use the principles of BMP 75 21 Better Site Design as described in the DOE Manual Volume V Section 5 3 2 to the maximum extent practicable in order to mitigate the development impact on stormwater quantity and quality Practices include Define Development Envelope and Protected Areas Minimize Directly Connected Impervious Areas Maximize Permeability Build Narrower Streets Maximize Choices for Mobility Use Drainage as a Design Element D6 13 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Comply with LUC 20 20 460 Impervious Surface Limits C Preserve Native Vegetation Apply BMP T5 20 Preserving Native Vegetation as described in the DOE Manual Volume V Section 5 3 2 and comply with LUC 20 20 900 Significant Tree Retention Partial flow credit for retaining or planting trees can be achieved in accordance with the requirements in Section D6 03 4 D Amended Soil Description and Applicability For all disturbed pervious surfaces amend soils to meet the specifications of BMP T5 13 Post Construction Soil Quality and Depth per the current Guidelines and Resources for Implementing Soil Quality a
351. ipe to the finished grade or as recommended in writing by the manufacturer whichever is greater D4 91 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 For installations where minimum cover requirements cannot be met use Ductile Iron DI Class 52 pipe C Pipe Cover for Storm Drains For corrugated polyethylene CPE pipe AASHTO M 294 Type S the maximum fill depth is 15 feet measured to the top of the pipe For Polyvinyl chloride pipe profile and solid wall the maximum fill depth is 25 feet For reinforced concrete pipe the maximum fill depth is 15 feet for class III pipe and 25 feet for class V pipe For depths of cover greater than 25 feet pipe type shall be determined on a case by case basis with back up calculations provided by the Designer Minimum cover is 2 feet from the top of pipe to the finished grade or as recommended in writing by the manufacturer whichever is greater Depth of cover over PVC pipe shall be 3 feet minimum and 20 feet maximum Pipe depths outside this range will require use of ductile iron DI Class 52 pipe or pressure class PVC conforming to C900 or AWWA C905 For corrugated polyethylene tubing CPT the maximum soil cover is one 1 foot All buried ductile iron pipe shall be encased 8 mil polyethylene per AWWA C105 D4 92 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 END OF CHAPTER D4 D4 93 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D5 W
352. ire irrigation and routine maintenance May require additional insurance Maximum roof slope of 20 percent Design Requirements Waterproof Membrane A waterproof membrane is required for all vegetated roof designs Root Barrier A root barrier shall be included in the vegetated roof design When waterproofing membrane is also to provide a root barrier function provide supporting manufacturer documentation with submittal Root barrier shall not contain leachable water quality contaminants e g herbicides copper and zinc Drainage Layer Intensive and extensive vegetated roofs shall include a drainage layer The aggregate for the drainage layer shall meet the following minimum requirements Minimum total pore volume of 25 percent by volume ASTM E2399 Minimum saturated hydraulic conductivity of 425 inches per hour per ASTM E2396 05 Maximum total organic matter of one 1 percent by mass per loss on ignition test Separation Fabric On all intensive and extensive vegetated roofs separation fabric shall be installed to separate the growth media from the drainage layer roof edges penetrations structures and all surrounding areas Separation fabric shall be a non woven geotextile Fabric shall have an average opening size sufficient to retain media Fabric shall have permissivity sufficient to pass the anticipated peak rainfall intensity Growth Medium Soil The growth medium shall b
353. irements are not subject to Enhanced Treatment requirements For developments with a mix of land use types the Enhanced Treatment requirement shall apply when the runoff from the areas subject to the Enhanced Treatment requirement comprises 50 or more of the total runoff within a threshold discharge area D5 03 9 Basic Treatment All Basic Treatment facilities shall be designed in accordance with criteria set forth in Volume V of the DOE Manual Basic Treatment generally applies to Project sites that discharge to the ground UNLESS 1 The soil suitability criteria for infiltration treatment are met see Chapter 3 of Volume III of the DOE Manual for soil suitability criteria or 2 The project uses infiltration strictly for flow control not treatment and the discharge is within 4 mile of a phosphorus sensitive lake use a Phosphorus Treatment facility or within 4 mile of a fish bearing stream or lake use an Enhanced Treatment facility Phosphorous sensitive lakes include Larsen Lake Phantom Lake and Lake Sammamish D5 6 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Residential proJects not otherwise needing phosphorus control as designated by Section D5 03 7 the US or the Department of Ecology and Project sites discharging directly to Lake Washington lakes listed in Appendix 1 of the DOE Manual except Lake Sammamish which requires Phosphorus Treatment and Landscaped areas of industrial commer
354. is of existing downstream conveyance system capacity if additional flow is being routed to that system Present an analysis and design of the proposed stormwater conveyance system for the project using an approved model All pipes culverts catch basins channels swales and other stormwater conveyance appurtenances must be clearly labeled and correspond directly to the engineering plans 7 Permanent Stormwater Control Plan A Show on site stormwater management facilities on the site plan as required on Development Services Submittal Requirements sheets for single family residential or commercial sites Include sufficient profiles and details needed for review for the Contractor to construct the facilities and for the City inspector to verify them If a Utility Developer Extension Agreement is required for water or sewer as well as storm drainage facilities plans for the drainage facilities may be combined with water and sewer if they remain readable As Built drawings must be submitted following inspection prior to occupancy and approved by the City Operation and Maintenance Manual O amp M Manual for Stormwater Management Facilities per Section D2 09 D2 07 PLAN FORMAT AND NOTES D2 07 1 1 2 Submittal Standards Submittal Standards vary by size and type of project Refer to handouts provided by City of Bellevue Development Services for Submittal Requirements Utility plans submitted for review shall meet
355. ity fps at current section for depth Y1 Adjust option V1 HD Channel Velocity Head ft at current section VU HD Upstream Velocity Head ft at current section D4 04 5 Floodplain Floodway Analysis The methods and criteria below have been adapted from the 2009 King County Surface Water Design Manual A General Floodplain floodway studies establish base flood elevations and delineate floodplains and or floodways when Bellevue s Development Services Department determines that a proposed project contains or is adjacent to a flood hazard area for a river stream lake wetland closed depression or other water feature Furthermore when development is proposed within the floodplain the floodplain floodway study is used to show compliance with the critical areas code BCC 20 25H 175 flood hazard area regulations There are four conditions affecting the requirements for floodplain floodway studies Each condition is considered a threshold for determining the type of studies required and the documentation needed to meet the study requirements Each study threshold and related study requirements are shown in the table below and described further in this section D4 04 5 Floodplain Floodway Analysis The methods and criteria below have been adapted from the 2009 King County Surface Water Design Manual A General Floodplain floodway studies establish base flood elevations and delineate floodplains and or floodways when Bellevue s
356. izing and or as a simplified check for the reviewer the NDPs must be designed by a professional engineer to satisfy flow control requirements MR7 Flow Control Credits that can be applied to reduce the size of downstream flow control facilities are provided in Section D6 03 4 D6 02 SITE SUITABILITY AND BMP SELECTION D6 02 1 Introduction This section contains guidelines to aid designers and reviewers in characterizing development sites in selecting the most appropriate BMPs for the site and in meeting on site stormwater management requirements These guidelines contain three steps for on site BMP site assessment and selection 1 Characterize Site Infiltration Capabilities 2 Site Layout and Use and 3 Runoff Sources and BMP Selection D6 02 2 Step 1 Characterize Site Infiltration Capabilities During Step 1 the Developer must map the development site according to its potential infiltration capabilities categorizing site areas based on the topographic and soil conditions that constrain the use and appropriateness of on site stormwater BMPs In general infiltration BMPs are more effective in flatter areas than steeper areas While outwash soils typically have higher infiltration rates than till soils soils with design infiltration rates as low as 0 25 inches per hour can be well suited for small scale infiltration or partial infiltration BMPs that receive runoff from small contributing drainage areas relative to the BMP footprint siz
357. l shall be compacted to 90 maximum dry density per Section 2 03 3 14 D Compaction and Moisture Control Tests of the Standard Specifications The Contractor shall arrange for compaction testing to be performed by a certified technician The Contractor shall provide the Engineer with one copy of the compaction test report within 24 hours of the completion of the test Compaction tests shall be made at a maximum of 4 foot depth increments with a minimum of one test for any backfilling less than 4 feet in depth The maximum space between tests shall not exceed 100 linear feet For mechanical compaction methods hoe pack vibratory roller static roller etc the maximum backfill lift shall not exceed 2 feet between the application of compaction equipment For manual compaction methods all walk behind equipment jump jack etc the maximum backfill lift shall not exceed 1 foot between the application of compaction methods D8 3 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Jetting is not an allowable method to compact the trench backfill Surface restoration shall be as specified in the Right of Way Use Permit and as shown on the approved plans See Appendix D 1 for trench backfill Standard Details D8 04 7 Compaction All backfill shall be mechanically compacted in accordance with Section 2 09 3 DE Backfilling Compaction of the Standard Specifications as modified herein Each layer shall be compacted to 95
358. le 3 5 kg Values For Using The Rational D3 14 Table 3 6 Hydrologic Soil Groups for Soils in the Puget Sound Basin D3 17 LIST OF FIGURES Figure 3 1 2 Year 24 Hour Precipitation pe da io eode D3 8 Figure 3 2 10 Year 24 Hour Precipitation EE oL obit ets D3 9 Figure 3 3 100 Year 24 Hour Precipitation aa D3 10 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D3 HYDROLOGIC ANALYSIS D3 01 GENERAL Hydrologic analysis is used to size conveyance determine flow control levels and size water quality treatment facilities This chapter describes the models and methods of analyses required or allowed by the City D3 02 HYDROLOGIC MODELS Various hydrologic models and methods assist in the planning and design of stormwater conveyance flow control and water quality treatment Table 3 1 below lists the models and methods approved for use D3 1 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D3 02 01 Ecology Approved Continuous Simulation Hydrology Model Table 3 1 Acceptable Uses of Runoff Computation Methods Ecology Approved TYPE OF Single Hydrograph COMPUTATION Allowed For Rational Method Method Continuous Simulation Model Tributary Areas lt REQUIRED for un OKAY if majority of 10 detai
359. let shall be protected from erosion by rock lining specified in Table 4 1 except the height shall be one foot above maximum tailwater elevation or one foot above the crown whichever is higher See KCSWD fig 4 2 2 A Pipe Culvert Discharge Protection L Methods of Analysis Conveyance Capacity The theoretical analysis of culvert capacity can be extremely complex because of the wide range of possible flow conditions that can occur due to various combinations of inlet and outlet submergence and flow regime within the culvert barrel exact analysis usually involves D4 34 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 detailed backwater calculations energy and momentum balance and application of the results of hydraulic model studies However simple procedures have been developed where the various flow conditions are classified and analyzed on the basis of a control section control section is a location where there is a unique relationship between the flow rate and the upstream water surface elevation Many different flow conditions exist over time but at any given time the flow is either governed by the culvert s inlet geometry inlet control or by a combination of inlet geometry barrel characteristics and tailwater elevation outlet control Figure 4 9 illustrates typical conditions of inlet and outlet control The procedures presented in this section provide for the analysis of both inlet and outlet control conditions
360. licable Roof 2096 and or No Excess Load Capacity Vegetated Roof prohibited Not applicable Not applicable Not applicable Natural vegetation areas may not be disturbed for BMP installation but may be used as vegetated flow paths See Section D6 03 for additional slope restrictions gt Grass paving in accordance with Standard Detail NDP 12 D6 03 DESIGN SIZING CONSTRUCTION AND MAINTENANCE D6 03 1 Required On Site Stormwater Management Practices Projects meeting the thresholds in D2 05 shall employ the required On site Stormwater Management Practices in this section or other practices approved in writing by DOE as functionally equivalent to infiltrate disperse and retain stormwater runoff on site to the maximum extent practicable without causing flooding or erosion impacts A Full Dispersion and Full Infiltration Description Applicability and Limitations Full dispersion should be considered for large residential developments parks commercial and road projects meeting the criteria in the LID Manual Section 7 2 These criteria D6 12 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 generally include substantial native vegetation long vegetated flow paths particular soil types low volume roads for road projects deep groundwater and slope restrictions Dispersion may be considered for runoff from roofs pavement and other impervious surfaces approved methods for roads inc
361. lude sheet flow or collecting and re dispersing stormwater Sites that can achieve full infiltration per the DOE Manual Volume III Section 3 3 9 or full dispersion per the DOE Manual Volume V Chapter 5 BMP T5 30 and Section 7 2 of the LID Manual are not required to provide additional runoff treatment MR6 or flow control MR7 facilities Design and Sizing Design and size full dispersion per the DOE Manual Volume V Section 5 3 3 BMP T5 30 Full Dispersion and the LID Manual Section 7 2 Full Dispersion credit will be given to sites with a maximum of 10 effective connected impervious area that is dispersed through 35 to 65 of the site maintained in natural vegetation and protected with a Native Growth Protection Easement see LUC 20 25H 030 B 2 Impervious surfaces that are not fully dispersed should be partially dispersed to the maximum extent practicable See Section D6 03 4 for hydrologic modeling procedures to be used for determining Flow Control Credits for partial dispersion Partial Flow Control Credit shall be given for sites that can implement partial dispersion per Section 7 2 3 in the LID Manual or per Section D6 03 4 Design and size full infiltration per the DOE Manual Volume HI Chapter 3 as modified herein per Section D4 06 7 Infiltration Systems Full infiltration credit towards flow control applies when 100 of the runoff is infiltrated per the DOE Manual Volume III Section 3 3 9 Maintenance Dispers
362. lutant Any Basic Removal is Practicable Treatment BMP Step 4 Determine if Phosphorous Control Apply Infiltration Is Required e Infiltration Basin e Infiltration Trench e Bioinfiltration Swale Step 5 Determine if Enhanced Treatment Is Required Yes Apply Oil Control Facility e API Separator Dispersion and Section D6 03 e CP Separator e Linear Sand Filter Apply Phosphorus Control Facility e Large Sand Filter Amended Sand Filter Large Wetpond Media Filter Two Facility Treatment Train Yes Step 6 Apply an Enhanced Apply a Basic Treatment Facility Treatment Facility Biofiltration Swales Filter Strips Basic Wetpond Wetvault Treatment Wetlands Combined Detention Wetpool Sand Filters Bioretention Rain Garden Pervious Pavement Ecology Embankment StormFilter ZPG Canister Type Filtration System Large Sand Filter Amended Sand Filter Treatment Wetland Compost amended Filter Strip Two Facility Treatment Train Bioretention Rain Garden Pervious Pavement Ecology Embankment Figure 5 1 Treatment Facility Selection Flow Chart Notes See DOE Manual Volume V Chapter 3 Section 3 5 for more information Facilities that have DOE General Use Level Designation GULD rating or that are deemed by DOE to be functionally equivalent to approved facilities are also allowed Medium must be of type approved by DOE D5 4 SURFACE WATER ENGINEERING STANDARDS
363. lutants The channel storage low velocities water quality benefits and greenbelt multiple use benefits create significant advantages over other constructed channels The presence of vegetation in channels creates turbulence that results in loss of energy and increased flow retardation therefore the design engineer must consider sediment deposition and scour as well as flow capacity when designing the channel Bioretention swales may also be designed to achieve flow control and or treatment per Section D6 03 Rock lined channels are necessary where a vegetative lining will not provide adequate protection from erosive velocities They may be constructed with riprap or slope mattress linings The rock lining increases the turbulence resulting in a loss of energy and increased flow retardation Rock lining also permits a higher design velocity and therefore a steeper design slope than in grass lined channels Rock linings are also used for erosion control at culvert and storm drain outlets sharp channel bends channel confluences and locally steepened channel sections Bioengineered vegetation lining is a desirable alternative to the conventional methods of rock armoring Soil bioengineering is a highly specialized science that uses living plants and plant parts to stabilize eroded or damaged land Properly bioengineered systems are capable of providing a measure of immediate soil protection and mechanical reinforcement As the plants grow they prod
364. maller than 1 16 inch Design Requirements Catchment Area Collection System A roof catchment area collection system includes the gutters downspouts piping and any other conveyance needed to route water to the rain barrel s or cistern The roof catchment area must be clearly delineated on the Plans Leaf Rock Screen A filter screen or other debris barrier is required to prevent insects leaves and other larger debris from entering the system A self cleaning inlet filter is recommended Cistern Rain Barrel All cisterns or rain barrels must be installed in accordance with manufacturer s installation instructions and the building code Screen all opening locations adequately to prevent mosquitoes and other life forms from entering the system Latch or lock covers to prevent wildlife and unauthorized human access into storage tanks Opaque containers must be used for aboveground cisterns and rain barrels to minimize algae growth Underground cisterns must be designed by an engineer D6 35 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 lv If an electric water pump is installed an electrical permit is required and a reduced pressure principle backflow assembly is required on the customer side of the water meter overflow conveyance capacity must be less than the capacity of the inflow pipe or downspout Connections to potable water systems or appliances require a reduced pre
365. mation for any areas draining onto the site Include pipe sizes and structures 2 Site Maps showing A Existing Conditions a Existing site and drainage conditions Identify areas of high seasonal groundwater b Infiltration test locations test method used calculated long term infiltration rates and correction factors B Proposed Development a Show each type of impervious surface lawn and landscape areas and non disturbance areas Note the square footage of each D2 10 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 3 4 5 Show proposed on site stormwater management facilities Show setbacks as required by Land Use Code and Chapter D4 GeoMapNW soil map or if not available NRCS Soil Survey Map for the location with the site boundaries marked Drainage map showing flow path from site to receiving water up to 1 4 mile and threshold discharge areas Indicate the receiving water lake or major stream Include upstream information for any areas draining onto the site Include pipe sizes and structures Sizing calculations for proposed on site stormwater management facilities These calculations shall bear the signature and stamp of the responsible Civil Engineer Include A Provide narrative mathematical and graphic presentations of model input parameters selected for the developed site condition including acreage soil types and land covers road layout and all drainage facilities
366. me series that is dissagregated to a comparable time step King County maintains a 15 minute rainfall data base that was created by disaggregating the historical hourly record MGSFlood has developed a long term 5 minute dissagregated rainfall time series 4 Default LID credits available in Appenidx of Volume 3 of the DOE Manual 5 Requires use of proprietary modeling software that includes approved LID modeling approaches or applicaion of HSPF incorporating modeling techniquesappropriate for characterizing LID The Western Washington Hydrologic Model WWHM has been developed to aid in the design of stormwater mitigation as required by Ecology There are other HSPF derivatives that Ecology has approved including the King County Runoff Time Series model KCRTS and the MGSFlood model All incorporate HSPF algorithims or HSPF generated time series and should D3 2 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 produce comparable results provided they are using the same HSPF parameters and are using similar rainfall records The City of Bellevue accepts Ecology approved models Some HSPF based models incorporate rainfall time series that have been dissaggregated to a smaller time step that is more appropriate to use in sizing conveyance Included are the KCRTS model and version 4 of the MGSFlood model The City will not accept 15 minute rainfall that has not been disaggregated D3 02 02 Single Event Hydrograph Method The
367. ments exceed 50 of the assessed value or replacement value of the existing No additional requirements Minimum Requirements 1 through 9 apply No additional to the new and replaced impervious requirements Figure 2 3 Flow Chart for Determining Requirements for Redevelopment Yes Yes The Developer may meet the Minimum Requirements for an equivalent flow and pollution characteristics area within the same site This method is known as Area Substitution For public road projects the water quality treatment for equivalent area does not have to be within the project limits but must drain to the same receiving water For flow control of public roads projects the equivalent area must be in same stream basin and capacity analysis must be done to demonstrate 100 year capacity is available If D2 5 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 used for a project the Developer must consult with the City to determine an appropriate equivalent area Appendix C of Volume Ill of the DOE Manual directs users to model impervious area directed to various low impact development facilities as landscaped area 50 landscaped area or pasture Those same modeling credits may be used when summing project areas to determine whether the thresholds are exceeded Project Thresholds for the construction of stormwater treatment facilities 6 Runoff Treatment are presented in Table 2 1 and include Projects in which the to
368. ments specified under the material section of the Standards including the following Profile Wall PVC Pipe PW Pipe Pacific Western Extruded Plastics Eugene OR Ultra Rib Ipex Inc Langley British Columbia Canada Corrugated Polyethylene Pipe Advanced Drainage Systems Inc Washougal WA Hancore Inc Olympia WA Corrugated Polyethylene Tubing Advanced Drainage Systems Inc Washougal WA Hancore Inc Olympia WA PRECAST MANHOLE AND CATCH BASIN SECTIONS Pacific International Pipe and Engineering Inc Associated Sand and Gravel Company POLYPROPYLENE MANHOLE STEPS Lane International Corporation P 13938 M A Industries Inc PS 2 PF A D4 2 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 MANHOLE FRAMES AND COVERS Inland Foundry Co Olympic Foundry East Jordan Iron Works CATCH BASIN FRAMES AND COVERS Inland Foundry Co Olympic Foundry East Jordan Iron Works MISCELLANEOUS MATERIALS Residential catch basins ADS models 0909SD2 0909SD4 1212SD2 1212SD4 Hanson Type 45 Nyloplast Drawing No 7001 110 374 NDS 1216 1217 1225 VAULT HATCH DOOR L W Products Company Inc Models HHD and HHS H 30 rated Hatches shall include recessed padlock hasp sized to accept City of Bellevue Surface Water Division padlocks Metal lids hatches and access covers shall be constructed with a gray non slip treatment by one of the approved products below Manufacturer COF Product LW Products 95 The
369. mily drainage systems are not required to adhere to City Standards and Specifications except where stated herein For new single family subdivision developments if a new public road is dedicated with the plat the detention system that serves both the new public roadway and the subdivision would be owned and operated by the City A hold harmless agreement needs to be provided to the City by the Developer if access to the detention facility is across a private roadway If the new subdivision includes only frontage improvements and no new public roadway is created the drainage facilities serving both the frontage improvements and the subdivision shall be private D4 64 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Private single family drainage systems are required to adhere to City Standards and Specifications and will require Inspection from a City Inspector If MR5 On site Stormwater Management applies private commercial and multi family drainage systems shall be managed using on site practices if site conditions allow per Chapter D6 In areas having an existing piped conveyance system the stormwater outfalls for parking lot driveway and roadway drainage shall be made by the following in order of preference 1 Connecting the conveyance pipeline to an existing manhole or catch basin or 2 Constructing a new manhole or catch basin on the existing storm drainage pipeline and connecting the conveyance pipeline to this new
370. more than 100 feet in advance of pipe laying except with written approval of the Engineer Providing sheeting shoring cribbing cofferdams and all aspects involved therein shall be the sole responsibility of the Contractor Such trench excavation protection shall comply with the requirements of Section 2 09 Structure Excavation and Section 7 08 3 1 B Shoring of the Standard Specifications Chapter 49 17 RCW of the Washington Safety and Health Act and Part N Excavation Trenching and Shoring of Chapter 296 155 WAC When trenching operations take place in the public right of way the pavement and all other improvements shall be restored as required by the Right Of Way Use Permit D8 13 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 END OF CHAPTER D8 D8 14 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D9 NATURAL SYSTEMS TABLE OF CONTENTS D9 01 GENERAL u aga v qoin Nd usto au au asul nakuy usus D9 1 D9 02 STREAMS D9 1 D9 03 WETLANDS Lu is iat e Me teda ubt ut D9 2 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D9 NATURAL SYSTEMS D9 01 GENERAL Over 60 miles of open streams wind through Bellevue and over 800 acres of wetlands have been protected preserving the City s natural setting in the midst of an urban environment The beneficial uses of small urban streams and wetlands which the City
371. mum of 3 inches above the bottom of the cistern Vegetated Roof Vegetative roofs are gently sloped roofs covered with soil and planted with vegetation in place of conventional roofing material These roofs may be either intensive designs with soils 6 inches or deeper multiple uses and more garden plant varieties or extensive designs with shallow lightweight soils less than 6 inches in depth and more drought tolerant groundcover plants Green roofs can be either single course consisting of a single media designed to be freely draining and support plant growth or multi course which includes both a growth media layer and a separate underlying drainage layer Commercially available modular systems consisting of prefabricated trays filled with growing media are considered multi course systems Applicability Effective stormwater management strategy in high density urban areas and or zero lot line situations Energy conservation conscious developments Retrofitting existing roofs with excess structural capacity Limitations The Developer shall demonstrate that all design components have been addressed by experienced and qualified professionals including loading structural waterproofing fire resistance and horticultural considerations Requires careful construction practices by an experienced vegetated roof contractor D6 38 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 requ
372. n including the side storm after completion of backfill Where the groundwater table is so high as to preclude a proper exfiltration test an infiltration test may be used The exfiltration test shall be made by plugging the inlets of the lower manhole and filling the test section with water to a height of six 6 feet above the crown of the storm drain at the upper end of the storm drain being tested In no case shall the static level be less than six 6 feet above the water table at the upper end of the storm drain being tested Where the static pressure on the lower manhole would exceed 20 feet the Contractor may test the storm drain between manholes in two or more sections The Contractor may provide for sectional testing by installing tees in the main line The tees shall be of a type that permit plugging of both the upper and lower run of the tee The required static water head may be obtained by installing vertical lengths of pipe in the tee or from the upper end of the storm drain pipe being tested at shallow catch basins The Contractor shall provide a groundwater observation well at each manhole for determining the level of the groundwater during the test The observation well shall consist of one inch plastic pipe installed vertically adjacent to the manhole The lower end of the test well shall be placed in a one 1 cubic yard pocket of washed gravel and shall be at the same elevation as the invert of the manhole The upper end of the t
373. n 9 03 14 1 Gravel Borrow of the Standard Specifications Contractor may request to use excavated material as trench backfill when it has been determined by the Engineer to be suitable and conforms to Section 9 03 14 1 Gravel Borrow of the Standard Specifications and proper compaction levels can be achieved The top 4 feet around structures shall be backfilled with crushed rock conforming to Section 9 03 9 3 Crushed Surfacing Top Course of the Standard Specifications In unpaved areas structure backfill material shall conform to Section 9 03 14 1 Gravel Borrow of the Standard Specifications The Contractor may request to use excavated material as structure backfill when it has been determined by the Engineer to be suitable and conforms to Section 9 03 14 1 Gravel Borrow of the Standard Specifications and proper compaction levels can be achieved D7 04 FLOW CONTROL DETENTION FACILITIES D7 04 1 General All covers and grates on access structures to the detention system shall be bolt locking D7 04 2 Control Structures Precast concrete products for control structures shall comply with Section 7 05 2 of the Standard Specifications Flow restrictors in detention control structures shall be fabricated from 0 060 aluminum pipe PVC pipe Profile Wall Schedule 40 or SDR 35 CPE or HDPP SDR 32 5 Pipe support materials shall match restrictor if metal For plastic materials aluminum 3 W x 0 060 or stainless steel
374. n and routine maintenance Infiltration systems with pre treatment facilities which are not abutting a roadway shall be provided with access to accommodate maintenance vehicles and construction equipment The minimum clear driving width shall be 12 feet For roof downspout infiltration systems access allowances for maintenance and construction equipment shall be made to facilitate routine maintenance activities and reconstruction if necessary in the future H Determining subgrade infiltration rates Determining infiltration rates of the site soils is necessary to determine feasibility of designs that intend to infiltrate stormwater on site It is also necessary to estimate flow reduction benefits of such designs when using the Western Washington Hydrologic Model WWHM or MGS Flood The following provides recommended tests for the soils underlying bioretention areas The test should be run at the anticipated elevation of the top of the native soil beneath the bioretention facility Method 1 e Small bioretention cells bioretention facilities receiving water from 1 or 2 individual lots or lt 1 4 acre of pavement or other impervious surface Small Scale Pilot Infiltration Test PIT See Section D4 06 7J for small scale PIT method description See the DOE Manual Volume III Table 3 9 to select an appropriate infiltration correction factor e Large bioretention cells bioretention facilities receiving water from several lots or 1 4 ac
375. nd Depth BMP 5 13 at www SoilsforSalmon org See Standard Detail NDP 1 Maintenance Maintain amended soils per the Bellevue Maintenance Standards E Roof Downspout Infiltration Description Applicability and Limitations Roof downspout infiltration systems can consist of either an infiltration trench or infiltration drywell They will be considered before other BMPs per Section D6 02 and used wherever site conditions allow including required setbacks per D4 07 and without causing flooding or erosion If site conditions allow infiltration direct roof runoff to one or more of the following infiltration trench infiltration drywell Bioretention Cell bioretention swale or planter or pervious pavement A vegetated roof or rain barrels or rain harvesting cistern may be used in addition as long as the overflow is directed to one of the BMPs above Design and Sizing Design and size infiltration trenches or drywells and apply Flow Control Credits per Volume III Sections 3 1 1 and 3 3 of the DOE Manual and Standard Detail NDP 23 If an alternative NDP is selected see the appropriate section for design criteria Sections of the roof that drain to different downspouts may be treated with different Infiltration BMPs Maintenance Maintain infiltration systems per the DOE Manual Volume III Section 3 3 11 F Roof Downspout Dispersion Description Applicability and Limitations If the site and design criteria for Roof Downspo
376. ned areas tributary area is measured to OKAY for detained okay if Te detained and 15 PEAK FLOW routing is performed 3 individual conveyance areas if storage minute time steps CONVEYANCE elements routing is performed are used SIZING DESIGN E ETE FLOWS OKAY if using 192 Tributary Areas gt OKAY if no storage OKAY if no storage minute time steps 10 routing is performed routing is performed storage routing is allowed CONTROL Projects requiring NEW EXISTING amp Water Quality OKAY must use 1 WQ FACILITY 6 and Flow Control hour time steps SIZING AND MR 7 ANALYSIS OKAY for tributary DOWNSTREAM OKAY M TONES gt ree itno okay Fusing 15 ANALYSIS All Projects routing is needed 100 storage routing is iens yr rainfall needed 100 year 24 c I d hr PEAK FLOWS FOR APPLYING All Proiects OKAY must use 1 EXEMPTIONS amp J hour time steps THRESHOLDS Apply Default LID ON SITE Credits or derive LID STORMWATER All Projects Credits with MANAGEMENT demonstrative modeling Notes 1 Undetained areas are those upstream of flow control facilities or other storage features 2 The majority of the tributary area is considered detained if the runoff from more than 50 of the tributary area is detained by a flow control or other storage facility 3 The 15 minute time step references a computational time step best used with a rainfall ti
377. neme Tar Series 46H 413 Casing wall thickness shall be 0 250 inch for casings 24 inches or less in diameter and 0 375 inch for casings over 24 inches in diameter Carrier pipe for sewage shall be PVC SDR 35 D7 02 10 Casing Spacer Casing spacers shall be installed in casings over 10 feet long Where casing spacers are not used the carrier pipe shall be more than 10 feet in length no pipe joints inside casing Casing spacer shell shall be manufactured in two pieces from heavy gauge T 304 stainless steel or 14 gauge hot rolled pickled steel joined with ribbed flanges The shell shall be lined with a PVC liner 0 090 inch thick with 85 90 durometer Carbon steel casing spacer shell and risers shall be coated with a heat fused PolyVinyl chloride coating or hot dip galvanized PolyVinyl Chloride Coating Specifications Durometer Shore A2 10 Sec ASTM D 80 1706 61T Max operating temperature constant 150 65 C Electrical properties ASTM D 149 61 short time 010 1380 V Mil Resistance Salt spray ASTM B 117 Excellent Acids Good Alkalies Good All nuts and bolts shall be 18 8 stainless steel Runners shall be supported by risers made from heavy gauge T 304 stainless steel or 12 gauge hot rolled pickled steel Runners shall be ultra high molecular weight polymer with high resistance to abrasion and sliding wear D7 5 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015
378. nergy As required As required As required Crown Dissipater 1 foot Standard Detail D 38 or D 60 Engineered energy dissipater required These sizes assume that erosion is dominated by outfall energy In many cases sizing will be governed by conditions in the receiving waters Rock lining shall be quarry spalls with gradation as follows Passing 8 inch square sieve 100 Passing 3 inch square sieve 40 to 60 maximum Passing 4 inch square sieve 0 to 10 maximum 9 Riprap shall be reasonably well graded with gradation as follows Maximum stone size 24 inches nominal diameter Median stone size 16 inches Minimum stone size 4 inches Note Riprap sizing governed by side slopes on outlet channel is assumed to be approximately 3 1 D4 3 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D4 02 1 Discharge Location Impacts Stormwater runoff from the project shall produce no significant adverse impact to downslope properties and shall discharge to the existing downstream drainage system if on site stormwater management does not fully mitigate flow D4 02 2 Unconcentrated Flow Where no downstream drainage system exists adjacent to the property and the runoff from the project site was previously unconcentrated flow on site stormwater management shall be implemented to the extent feasible Any remaining runoff shall be connected to the downstream drainage system which shall be extended to the property line
379. ng water to the pit until one hour after the flow rate into the pit has stabilized constant flow rate a goal of 5 variation or less variation in the total flow while maintaining the same pond water level The total of the pre soak time plus one hour after the flow rate has stabilized should be no less than 6 hours e After the flow rate has stabilized for at least one hour turn off the water and record the rate of infiltration the drop rate of the standing water in Inches per hour from the measuring rod data until the pit is empty Consider running this falling head phase of the test several times to estimate the dependency of infiltration rate with head e Atthe conclusion of testing over excavate the pit to see if the test water is mounded on shallow restrictive layers or if it has continued to flow deep into the subsurface The depth of excavation varies depending on soil type and depth to hydraulic restricting layer and is determined by the engineer or certified soils professional Mounding is an indication that a mounding analysis is necessary Data Analysis Calculate and record the saturated hydraulic conductivity rate in inches per hour in 30 minutes or one hour increments until one hour after the flow has stabilized Note Use statistical trend analysis to obtain the hourly flow rate when the flow stabilizes This would be the lowest hourly flow rate Apply appropriate correction factors to determine the site specific design inf
380. ngineer specifying lateral load connections to the foundation system Certain manufacturers may have pre engineered systems that do not require additional engineering for smaller projects such as decks walkways and exterior stairways Design calculations a lateral load analysis and foundation specifications shall be submitted by the Developer with the building permit application D6 43 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 During construction heavy equipment cannot be used within or immediately surrounding the building Terracing of the foundation may be accomplished by tracked blading equipment not exceeding 650 psf Construction must be in compliance with the selected product listing vi Design Requirements Sizing On relatively flat sites i e less than 5 percent slope grading shall be limited to knocking down the highs and lows to provide a better working surface The top organic duff layer shall not be removed from the site Re distribute the organic duff evenly over the site after grading activities are complete On sloped sites i e between 5 percent and 30 percent slope the soils may be graded smooth knocking down superficial highs and lows at their existing slope to provide a better working surface to receive pier systems pre cast walls or slope cut forms for pouring continuous walls To minimize the soil disturbed on sloped sites with terraces the width of each terrace must be limited
381. nnels not maintained weeds and brush uncut Dense weeds high as flow depth Clean bottom brush on sides Same as 2 highest stage of flow 4 Dense brush high stage B Natural Streams B 1 Minor streams top width at flood stage lt 100 ft a Streams on plain 1 Clean straight full stage no rifts or deep pools Same as 1 but more stones and weeds Clean winding some pools and shoals Same as 8 but some weeds Same as 4 but more stones Manning s w x n Normal Type of Channel Manning s and Description Normal 6 Sluggish reaches weedy deep pools 7 Very weedy reaches deep pools or floodways with heavy stand of timber and underbrush Mountain streams no vegetation in channel banks usually steep trees and brush along banks submerged at high stages 1 Bottom gravel cobbles and few boulders 2 Bottom cobbles with large boulders Floodplains Pasture no brush 1 Short grass 2 High grass Cultivated areas 1 Nocrop 2 Mature row crops 3 Mature field crops Brush 1 Scattered brush heavy weeds 2 Light brush and trees 3 Medium to dense brush 4 Heavy dense brush Trees Dense willows straight Cleared land with tree stumps no sprouts Same as 2 but with heavy growth of sprouts Heavy stand of timber a few down trees little undergrowth flood stage below branches Same as 4 but with flood stage reaching branches
382. ns unless specifically waived or exempted by regulatory agencies with permitting jurisdiction and C The project site must be drained by a conveyance system that is comprised entirely of manmade conveyance elements e g pipes ditches outfall protection etc and extends to the ordinary high water line of the exempt receiving water and D conveyance system between the project site and the exempt receiving water shall have sufficient hydraulic capacity to convey 100 yr 24 hour storm peak discharge from future build out conditions under current zoning of the site and the existing condition from non project areas from which runoff is or will be collected and E Any erodible elements of the manmade conveyance system must be adequately stabilized to prevent erosion under the conditions noted above 3 The invert elevation of any pipe outfall to Mercer Slough shall match the winter pool elevation of Lake Washington which is 16 77 NAVD88 Lake Washington and Mercer Slough have equivalent water surface elevations Flow control requirements for all other discharge situations are specified in Chapter 24 06 065 G 7 D3 16 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D3 06 SOIL TYPES Use site specific geotechnical information for the project site when available If not available use the Soil Survey King County Area prepared by the National Resource Conservation Service formerly Soil Conservation service to
383. ntrol Credits ede eo ede ete a D6 53 Table 6 15 Bioretention Soil Mix Quantities using on site native soils D6 56 Table 6 16 Plants for Vegetated Roofs Eee etae eaten D6 63 FIGURES Figure 6 1 On site Stormwater Management Facility Selection for MR5 and MRT D6 3 Figure 6 2 Schematic for calculating Bottom Length and Effective Total Depth for bioretention or pervious pavement on slopes where check dams berms are used Refer to Table 6 6 for Bioretention Cells and Bioretention Swales and Table 6 8 for Pervious Pavement formulas D6 22 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D6 ON SITE STORMWATER MANAGEMENT D6 01 GENERAL On site stormwater management BMPs infiltrate disperse and retain stormwater on site in order to reduce the volume peak flow rates and amount of pollutants in stormwater runoff leaving a developed project site The following on site stormwater management BMPs are required where site conditions allow without causing erosion or flooding Roof Downspout Control BMPs functionally equivalent to those described in Chapter 3 of Volume III of the DOE Manual and Dispersion and Soil Quality BMPs functionally equivalent to those in Chapter 5 of Volume V of the DOE Manual Natural Drainage Practices NDPs are included here as a sub set of on site stormwater management BMPs and include bioretention pervious pavement rain recyclin
384. numbered columns in Figure 4 18 described in Figure 4 19 An example calculation is performed in Figure 4 19 Note This method should not be used to compute stage discharge curves for level pool routing purposes Instead a more sophisticated backwater analysis using the computer software provided with this manual is recommended as described below Computer Applications The King County Backwater KCBW computer program includes a subroutine BWPIPE which may be used to quickly compute a family of backwater profiles for a given range of flows through a proposed or existing pipe system A schematic description of the nomenclature used in this program is provided in Figure 4 15 Program documentation providing instructions on the use of this and the other KCBW subroutines is available from King County Department of Natural Resources and Parks D4 52 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 4 16 Nomograph For Sizing Circular Drains Flowing Full Minimum Allowable 0001 Velocity Flowing 3 0 0002 Full SLOPE FOR n 0 024 8 0 a SLOPE FOR n 0 012 9 0 020 10 0 DISCHARGE IN C F S VELOCITY IN FEET PER SECOND DIAMETER OF PIPE IN INCHES 100 SAMPLE USE 8 24 dia CMP 2 slope yields 20 0 17cfs 5 4 fps velocity 0 024 Values Manning s equation Q 1 49 ARs S12 n 30 0 This be converted to other OnO values by applying formula 40 0
385. ny detail drawings that provide information associated with ponds and bioswales such as cross sections pond or bioswale lining material specifications e g grass plantings etc plan or profile views spillway elevation etc Location type size and elevation at tops inverts and bottoms of any drainage system facilities adjacent to each pond such as control structures catch basins etc Dimensions from Right of Way centerline or property line Notes and details about unusual situations and features Plant details including the type of plant D2 20 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 For private storm drainage systems collection runoff control and water quality treatment the Developer s Engineer shall submit a compliance letter on a form furnished by the Utilities Department for constructed the storm drain facilities Single Family Private Systems including 5 facilities on site stormwater management on individual lots Use the approved storm design as shown on the building permit site plan as the basis for the as built Make revisions as necessary to reflect field changes changes need not be drafted e g they can be edits marked on the site plan but they must be readable D2 09 OPERATION AND MAINTENANCE MANUAL A storm drainage operation and maintenance manual O amp M Manual agreement shall be provided for all constructed source controls on site stormwater management flow
386. o the underlying material Use 1 5 inch to U S No 8 uniformly graded crushed angular thoroughly washed stone E Geotextile Geotextile is optional If specified by the engineer use nonwoven geotextile for separation Standard Specifications 9 33 2 1 Table 3 separation nonwoven The following geotextile products are approved Geotextile Nonwoven polypropylene Ling Industrial Fabrics Inc model 275 TNS Advantaged Technologies models R060 R080 Carthage Mills models FX60HS FX70HS FX80HS DuPont DeNemours model SF65 Ten Carte Mirafi models 600X FW700 1120N Skaps Industries LLC model GT60 Propex Inc model GeoTex801 D6 60 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D6 04 3 Underdrain for Bioretention or Pervious Pavement A Underdrain Pipe Minimum 0 5 slope Do not wrap in filter fabric Attach 6 inch rigid non perforated pipe perpendicular at bottom of facility for clean out Option 1 Manufactured Slotted pipe Allows for pressurized water cleaning and root cutting if necessary Slotted subsurface drain PVC ASTM D1785 Schedule 40 for privately owned and maintained facilities only Use an appropriate coupling if connecting to a city owned pipe Slotted subsurface drain PVC per D7 02 3 for systems that will be owned and or maintained by the City of Bellevue 4 8 or as specified by the designer Option 2 Onsite Fabricated Slotted Pipe Allows for pressurized water cleaning an
387. ockery shall be above the permanent pool elevation Rockery drains shall drain through the detention system D4 71 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Ponds may be designed with retaining walls only as approved by the City on a case by case basis and provided that the design conforms to DOE Manual Volume Section 3 2 1 Public safety shall be a primary design consideration D Dimensions For ponds where the maximum design water depth is less than three 3 feet deep the minimum bottom width 15 six 6 feet For ponds where the maximum design water depth is three 3 feet deep and greater the minimum bottom width shall be three 3 times the maximum design water depth The pond bottom shall be sloped at 0 5 towards the outlet for drainage to help facilitate maintenance See D4 07 for detention pond setback requirements E Maintenance Access Use the criteria set forth in Volume III Section 3 2 1 of the DOE Manual as modified herein A vehicle access ramp shall be provided to the bottom of the detention pond when the bottom width is 15 feet or greater and or when the height of the interior pond embankment and or wall is greater than four 4 feet The grade of the access ramp shall be no steeper than 20 Gates and or removable bollards may be required to restrict access to drainage facilities Such measures shall comply with the Land Use Code and these engineering standards Cables and chains stretched across a
388. odplain Study requires submittal of an engineering plan showing the proposed project site is at least 10 feet above the ordinary high water elevation of the water feature in question or at least 2 feet above the downstream overflow elevation of the water feature whichever is less subject to the following conditions 1 The design engineer preparing the engineering plan shall determine an approximate base flood elevation and include a narrative describing his her level of confidence in the approximate base flood elevation The base flood elevation shall include calculations of Normal Depth for Uniform Flow as documented in Chow V T 1959 The narrative must include but is not limited to an assessment of potential backwater effects such as might result from nearby river flooding for example observations and or anecdotal information on water surface elevations during previous flood events and an assessment of potential for significantly higher future flows at basin build out Note Many of these issues will have been addressed in a Level 1 downstream analysis if required Acceptance of the approximate base flood elevation shall be at the sole discretion of The Utility If the approximate base flood elevation is not acceptable a Minor Floodplain Study or Major Floodplain Floodway Study may be required 2 That portion of the site that is at or below the calculated base flood elevation must be delineated and designated as a floodplain on the
389. of 2 percent or less use actual bottom length based on design plans For longitudinal slope greater than 2 percent use the total effective bottom length calculated as LEtota LE LE LE PM So PM So PM Son Where n number of cells LE Effective bottom Length of cell n ft PM Maximum ponding depth of cell n ft Son Bottom Slope of Cell n ft ft The effective bottom length input to the model may be no greater than the actual length based on design Figure 6 2 provides a schematic illustration of how to estimate this model input based on designs Bottom Width Actual bottom width based on design plans minimum 1 foot Effective Total Depth Effective Total Depth ETD is the distance in feet between the bottom of the bioretention soil layer and the top of over road flooding ETD Bioretention Soil Depth Maximum Ponding Depth Freeboard Maximum Depth of Over Road Flooding For longitudinal slopes of 2 percent or less use the Maximum Ponding Depth based on design plans For longitudinal slopes greater than 2 percent use the Average Maximum Ponding Depth rota calculated as follows 1 x PA PA PA 2n x PM PM PM D6 23 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Where n Number of cells PA Average ponding depth of celln ft PM Maximum ponding depth of cell n ft Freeboard and Maximum Depth of Over Road Floo
390. olid covers Off street structures which do not collect runoff shall be fitted with bolt locking solid covers Vegetation landscaping in the detention pond bioretention facility vegetated roof and or drainage swale s are an integral part of the runoff treatment system for the project Such drainage facilities will not be accepted until plantings are established All new manholes shall have a minimum inside diameter of 48 and shall conform to the Standard Details All new catch basins shall conform to the Standard Details Side storm stations are referenced from nearest downstream manhole catch basin All testing and connections to existing mains shall be done in the presence of a representative of the City of Bellevue Utilities Department All trenches shall be compacted and Hot Mix Asphalt in place in paved areas prior to testing storm lines for acceptance All public storm drains shall be air tested and have a video inspection performed prior to acceptance see 23 below Storm main constructed with flexible pipe shall be deflection tested with a mandrel prior to acceptance Storm stubs shall be tested for acceptance at the same time the main storm is tested All manholes catch basins in unpaved areas shall include a concrete seal around adjustment rings per Standard Details D2 16 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 17 18 19 20 21 22 23 24 25 26 27 28
391. on 24 06 070 D of the Storm and Surface Water Utility Code an offsite capacity analysis is required whenever the location of discharge will be changed by a proposed development or redevelopment If the rate of discharge will be changed an analysis may be required Different levels of analysis of the drainage system are required depending on both the location of the project in the basin and the information determined in the Level 1 analysis described below When required a Level 1 analysis must be submitted with the Developer Extension Agreement D4 03 1 Levels of Analysis Level 1 Analysis Physically inspect the existing on and off site drainage system and investigate any known problems The analysis must extend from the proposed project discharge location to the point downstream where the site runoff would join the existing drainage course On a map minimum USGS 1 24000 Quadrangle Topographic Map delineate the upstream tributary drainage areas to the site and to the downstream system Describe in narrative form observations regarding the makeup and general condition of the drainage system Include such information as pipe sizes channel characteristics and drainage structures Specifically the analysis must identify on the map and describe in the narrative any evidence of existing or anticipated problems Following review of the Level 1 analysis the City will determine whether the Level 2 analysis is required based on the e
392. on Systems for Flow Control Infiltration systems for projects triggering MR7 shall be designed in accordance with criteria set forth in Volume III Chapter 3 3 with exceptions and additions noted below A detention system may be required in conjunction with the infiltration system to meter flows at an infiltratable rate Infiltration areas shall not be 1 driven on or across by any vehicles or equipment 2 used for material storage or stockpiles or 3 used for vehicle or equipment parking Infiltration areas shall be secured with temporary fencing prior to clearing the site Approval of an infiltration system shall obligate the owner to repair replace or reconstruct the infiltration system if it fails to operate as designed The maintenance and operation schedule for an infiltration system shall include such a provision Roof Downspout Infiltration Systems Roof downspout infiltration systems shall be designed according to criteria set forth in Volume HI Chapter 3 1 1 of the DOE Manual with exception and additions noted in Chapter 6 of these Standards On Site Stormwater Management Areas proposed for infiltration shall be secured with temporary fencing prior to clearing the site Existing developed lots shall locate downspout infiltration systems in areas which have not previously been 1 driven on or across by vehicles or equipment 2 used for material storage or stockpiles or 3 used for vehicle or equipment parking Appr
393. on rate I I 2 5 inches per hour 10 0 25 inches per hour This infiltration rate 0 25 inches per hour is considered the Design Infiltration Rate and is used to size the pervious pavement patio Overflows Each flow control infiltration facility shall provide emergency surface storage at least 10 of the 100 year 24 hour design storm volume with a minimum depth of 0 5 on the site prior to discharging runoff to a safe overflow route The overflow route shall have the capacity for the 100 year 24 hour flow in the event of system failure The surface storage is intended to make the owner aware of a problem with the infiltration system Overflows shall be routed to the municipal storm drainage system if surface dispersion cannot be provided or in accordance with Section D4 02 if routing to the municipal storm drainage system is not feasible The overflow route must be contained on the owner s property and shall be shown on the plan F Runoff Treatment D4 78 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Inflow to flow control and runoff treatment infiltration facilities shall be pre treated for debris and sediment removal Where runoff is anticipated to also contain contaminants and pollutants it shall be treated using the appropriate BMPs set forth in the Chapter D5 Water Quality BMPs prior to being infiltrated G Maintenance Access Infiltration system components shall be accessible for periodic inspectio
394. on the site e Location and elevations of roadways water supply lines and sanitary sewer facilities both existing and proposed D4 28 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Study Report A Major Floodplain Floodway Study also requires submittal of two copies of a study report stamped by a licensed civil engineer which must include calculations or any computer analysis input and output information as well as the following additional information Valley cross sections showing the channel of the river or stream the floodplain adjoining each side of the channel the computed FEMA floodway the cross sectional area to be occupied by any proposed development and all historic high water information e Profiles showing the bottom of the channel the top of both left and right banks and existing and proposed base flood water surfaces e Plans and specifications for flood proofing any structures and fills construction areas materials storage areas water supply and sanitary facilities within the floodplain e Complete printout of input and output including any error messages for HEC RAS Liberal use of comments will assist in understanding model logic and prevent review delays e One ready to run digital copy of the HEC RAS input file used in the study Data shall be submitted on a disk in Windows format The applicant shall prepare a written summary describing the model development calibration hydraulic analysis and fl
395. oodway delineation The summary shall also include an explanation of modeling assumptions and any key uncertainties Determining Flood Flows One of two techniques are used to determine the flows used in the analysis depending on available information as determined by the Utilities Department Engineering Division The first technique is for basins in adopted basin plan areas The second technique is used on catchments without gauge data In both cases the design engineer shall be responsible for assuring that the hydrologic methods used are technically reasonable and conservative conform to the Guidelines and Specifications for Flood Hazard Mapping Partners and are acceptable by FEMA Refer to Table 3 1 in Chapter D3 Hydrologic Models for allowable models Flood Flows from Adopted Basin Plan Information For those areas with a basin plan prepared since 1986 flood flows shall be determined using information from the adopted basin plan Consult with Utilities Department Engineering Division for more information The hydrologic model used in the basin plan shall be updated to include the latest changes in zoning or any additional information regarding the basin that has been acquired since the adoption of the basin plan Flood Flows from a Calibrated Continuous Model Flood flows may be determined by utilizing a continuous flow simulation model such as HSPF Where flood elevations or stream gage data are available the model shall be calibrated
396. or Western Washington Homeowners Washington State University Pierce County Extension June 2007 http county wsu edu mason nrs water Documents Raingarden_handbook pdf Soil Survey King County Area Washington Natural Resources Conservation Service formerly Soil Conservation Service U S Department of Agriculture Stormwater Management Manual for Western Washington Washington State Department of Ecology February 2005 http www ecy wa gov programs wq stormwater manual html Surface Water Design Manual King County Washington January 9 2009 WDWFE Integrated Streambank Protection Guidelines published by Washington Department of Fish and Wildlife Wherever references are made to the standards specifications or other published data of the various national regional or local organizations such organizations may be referred SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 to by their acronym or abbreviation only As guide to the user the following acronyms or abbreviations which may appear shall have the meanings indicated herein AASHTO ACI ANSI APWA ASTM AWWA DNRP DOE DOH FHWA Health NRCS RCW USEPA WAC WDWF WSDOT American Association of the State Highway and Transportation Officials American Concrete Institute American National Standards Institute Inc American Public Works Association American Society for Testing and Materials American Water Works Association King County Department of
397. or the design storm return frequency This Ig equation was developed by King County SWM Division staff from equations originally developed by Ron Mayo P E It is based on the original Renton Seattle Intensity Duration Frequency LD F curves Rather than requiring a family of curves for various locations in King County this equation adjusts proportionally the Renton Seattle LD F curve data by using the 24 hour duration total precipitation isopluvial maps This adjustment is based on the assumption that the localized geo climatic conditions that control the total volume of precipitation at a specific location also control the peak intensities proportionally Note Tc must not be less than 6 3 minutes or greater than 100 minutes On the historic LD F curves the lower limit was set at 5 minutes 6 3 minutes was selected based on the mathematical limits of the equation coefficients 5 Time of Concentration Rational Method Only The time of concentration is defined as the time it takes runoff to travel overland from the onset of precipitation from the most hydraulically distant location in the drainage basin to the point of discharge Note that when the Cc of a drainage basin exceeds 0 60 it may be important to compute the Tc and peak rate of flow from the impervious area separately The computed peak rate of flow for the impervious surface alone may exceed that for the entire drainage basin using the total drainage basin Tc The
398. ors long term design infiltration rate in accordance with Sections D6 02 2 C and D4 06 7 D Clearing and Grading plans shall include instructions to protect the native soil or subgrade from unnecessary compaction and clogging from sediment during construction Underdrain Optional An underdrain system shall be installed in the base of the facility if necessary to accommodate water that exceeds the infiltration capacity of the underlying native soil When included minimum design requirements shall include Underdrain shall consist of slotted thick walled plastic pipe or other approved underdrain pipe per the NDP materials Section D6 04 3 Pipe shall have a minimum diameter of 4 inches and a maximum diameter of 8 inches Underdrain shall be placed in the Reservoir Course at least 6 inches above the bottom and with at least 1 foot of Reservoir Course material above the top of the pipe i e minimum Reservoir Course depth of 22 inches for a 4 inch diameter pipe and 26 inches for an 8 inch diameter pipe Geotextile Optional A non woven geotextile can be installed if necessary to prevent the migration of fines from the native soil into the reservoir course When specified by the designer geotextile fabric shall Bein accordance with the NDP materials specifications in Section D6 04 2 Be placed between the reservoir course and runoff treatment layer or subgrade Wrap around and over reservoir course and secure P
399. oss sections 1 and 2 A2 energy coefficient at cross sections 1 and 2 So bottom slope ft ft S friction slope n V Q 21R g acceleration due to gravity 32 2 ft sec If the specific energy E at any one cross section is defined as follows E y 4 2 2g D4 16 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 assuming o where ais the energy coefficient that corrects for the non uniform distribution of velocity over the channel cross section Equations 4 1 and 4 2 can be combined and rearranged to solve for Ax as follows Ax E E S 5 AEK S Sj 4 3 Typical values of the energy coefficient a as follows Channels regular section 1 15 Natural streams 1 3 Shallow vegetated flood fringes includes channel 1 75 For a given flow channel slope Manning s n and energy coefficient a together with a beginning water surface elevation y2 the values of Ax may be calculated for arbitrarily chosen values of yi The coordinates defining the water surface profile are obtained from the cumulative sum of Ax and corresponding values of y The normal flow depth y should first be calculated from Manning s equation to establish the upper limit of the backwater effect 3 Standard Step Backwater Method The Standard Step Backwater Method is a variation of the Direct Step Backwater Method and may be used to compute backwater profiles on both prismatic and non prism
400. ost see compost specification under D6 55 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Type 3 below Use the USDA soil textural triangle to determine site soil texture If the on site soils are not one of the types below use Type 2 or Type 3 BSM below Table 6 15 Bioretention Soil Mix Quantities using on site native soils On site Soil Type USDA Coarse Sand On site Soil Compost Texture Triangle by volume by volume by volume Loam 40 20 40 Sandy Loam 30 30 40 Loamy Sand 0 60 65 35 40 Type 2 Import BSM Test soil at time of delivery or mixing or have vendor provide certification that the soil meets the above BSM specifications Type 3 Import Sand Compost and Mix Import materials and mix on site or mix at supplier location to meet the requirements listed in Type 1 above as follows 60 65 gravelly sand by volume 35 40 compost by volume Gravelly Sand must meet the following gradation Sieve size Percent Passing 3 8 inch 100 US No 4 95 100 US No 10 75 90 US No 40 25 40 US No 100 4 10 US No 200 2 5 Approved gravelly sand Green Earth Screen Sand Green Earth Technologies Bellingham Miles Sand amp Gravel Utility Sand Miles Sand amp Gravel Roy Compost must meet the specifications per D6 04 1 B below B Compost and Mulch for Bioretention Compost and Mulch are applied on top of the BSM to hold in moisture prevent weeds and
401. ous concrete and ten 10 percent for pervious paver systems Interceptor infiltration trenches or check dams must be installed for slopes greater than two 2 percent See Standard Detail NDP 15 Limitations Requires special construction practices to reduce compaction and siltation of the underlying soils If the pervious pavement system will be installed in an area subject to vehicle traffic the underlying soils must be analyzed by a qualified engineer for load bearing capacity For some applications such as a sidewalk or patio the pervious pavement system may be designed by a property owner Pervious pavement materials shall be designed by a qualified engineer to provide the required structural support for the intended uses Certain manufacturers may have pre engineered systems that do not require additional engineering Pervious concrete shall only be installed by a Certified Pervious Concrete Installer See National Ready Mix Concrete Association certification program http www nrmca org certifications pervious Additional treatment liners functionally equivalent to those in Chapter 4 of Volume V of the DOE Manual may be necessary when used for treatment in highly permeable soils with short term infiltration rates of greater than 2 4 inches per hour to reduce the potential for groundwater contamination These treatment liners layers would also be needed to satisfy MR6 when underdrains are used D6 29 SURFACE WATER ENGINEERI
402. oval of a downspout infiltration system shall obligate the owner to repair replace or reconstruct the infiltration system if it fails to operate as intended All the general requirements of D4 06 7 A shall apply except that infiltration trenches may be located under new pavement B Design Criteria Infiltration Systems for Flow Control Infiltration systems for projects triggering MR7 shall be designed in accordance with criteria set forth in Volume III Chapter 3 3 of the DOE Manual as modified herein The Developer shall demonstrate through Infiltration testing Soil logs and D4 75 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 written opinion of a licensed civil geotechnical engineer that sufficient permeable soils exist on the site for an infiltration system meeting the requirements herein and site specific conditions to function properly Infiltration facilities shall not be located within required setback distances specified D4 07 Infiltration systems for flow control shall be designed to infiltrate such that any overflow bypass meets the flow duration standard Roof Downspout Infiltration Systems Design criteria for Roof downspout infiltration systems are contained in Chapter D6 Setbacks for Roof Downspout Infiltration Systems are listed in Section D4 07 Geotechnical Report Requirements for MR6 and MR7 Flow Control and Treatment These geotechnical report requirements are addition
403. p slab shall be no less than 0 5 feet The minimum clearance between the flow restrictor standpipe orifices shear gate etc and the steps ladder rungs shall be two 2 feet C Orifices Minimum orifice is one 1 inch in diameter without screening When screening is provided to prevent blockage the orifice size may be reduced to a minimum of 0 5 inch A notch weir may be incorporated into the tee type flow restrictor when a floatables baffle is provided See Figures 3 19 3 22 and 3 23 of the DOE Manual D Maintenance Access Covers grates and hatches shall be bolt locked D4 70 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 All stormwater detention system control structures shall be accessible for maintenance and operation In single family residential subdivisions control structures which are not abutting a roadway shall be provided with dedicated tracts at least 15 feet wide to accommodate maintenance vehicles The minimum clear driving width shall be 12 feet In multi family and commercial developments control structures which are not abutting a roadway shall be provided with access to accommodate maintenance vehicles The minimum clear driving width shall be 12 feet Maximum access road grades 15 paved 10 gravel Minimum turn around radius 25 feet or hammerhead Gates and or removable bollards are required to restrict access as necessary to drainage facilities Such measures shall comply with the
404. part of the project such rehabilitation shall be designed and constructed so as to provide diversified habitats for a variety of stream organisms considering the following Sufficient water depth to support fish and other aquatic life during low flows Diversity of water velocities through the use of pools and riffles meandering channel to facilitate features mentioned above and Sufficient stream bed gradient to provide proper flow velocities D9 1 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D9 03 WETLANDS Discharges to wetlands shall maintain the hydrologic conditions hydrophytic vegetation and substrate characteristics necessary to support existing and designated uses The hydrologic analysis shall use the existing land cover condition to determine the existing hydrologic conditions unless directed otherwise by a regulatory agency with jurisdiction Stormwater runoff from such discharges shall be limited to 1 50 percent of the existing 2 year design storm peak runoff rate for the area tributary to the wetland 2 a rate as determined by a qualified wetlands biologist to maintain the hydrologic conditions hydrophytic vegetation and substrate characteristics as required above or 3 a rate specified by a resource agency having jurisdiction over the wetlands that maintains the hydrologic conditions hydrophytic vegetation and substrate characteristics required above Runoff in excess of the specified rate shall be b
405. planter islands in parking lots and along the sides of roads Well suited to retrofit applications Can complement existing landscaping For sites with lower infiltration rates underdrain systems can be installed to accommodate water that exceeds the infiltration capacity of the surrounding soil ii Limitations Seasonal high groundwater must be more than foot below the bottom of the Bioretention Cell Where the depth to groundwater is less than 3 feet below the bottom of the facility the contributing impervious drainage area must be no greater than 5000 square feet Refer to Chapter D4 for methods to evaluate groundwater level Critical Area restrictions may apply Bioretention Cells bioretention swales shall meet setback requirements per Chapter D4 07 Bioretention Cells must have relatively flat bottom slopes Bioretention swales must have bottom slopes less than eight 8 percent Check dams or weirs must be installed for slopes greater than two 2 percent In some situations for bioretention swales the engineer may specify liners or soil barriers to avoid excessive hydrologic loading to adjacent structures such as basements crawl spaces utilities or steep slopes Design Requirements The following are design requirements and considerations for each component of a Bioretention Cell or bioretention swale Bioretention swales can be designed using the DOE Manual Volume V Chapter 9 or 2 WSDOT
406. ps required for the Drainage Report and Stormwater Site Plan D2 06 1 Submittal Requirements when site is vested in 2009 Storm Drainage Code Projects are vested as described in the Clearing and Grading Code 23 76 045 Generally a complete application for building permit or subdivision sets vesting Or a Clearing and Grading permit sets vesting if neither building nor subdivision processes are applicable Permit expiration results in loss of vesting Projects that are not required to submit a Utility Developer Extension Agreement Show the storm drainage connection on the site plan required with the permit application A Storm connection permit may also be required as determined by the Utilities reviewer If using On site Stormwater Management techniques rather than a conventional tightline connection use D2 06 2 below Projects that are required to submit a Utility Developer Extension Agreement Show the storm drainage connection on the site plan required with the permit application A Utility Developer Extension Agreement must be submitted with or prior to the Clearing and Grading and Building permits On site Stormwater Management techniques may be used to reduce the size of flow control and runoff treatment facilities Select and design on site facilities in accordance with Chapter D6 and size facilities to satisfy the vested code requirements using an approved model per Section D3 02 or the applicable standard D2 06 2
407. pth below the pond bottom of 2 5 times the maximum depth of water in the pond but not less than 10 feet estimate the initial saturated hydraulic conductivity Ksat in cm sec using the following relationship see Massmann 2003 and Massmann et al 2003 For large infiltration facilities serving drainage areas of 10 acres or more soil grain size analyses should be performed on layers up to 50 feet deep or no more than 10 feet below the water table logio K 1 57 1 90 0 015D60 0 013Doo 2 08frines 1 Where Dio Deo and Do are the grain sizes in mm for which 10 percent 60 percent 90 percent of the sample is more fine and ffines is the fraction of the soil by weight that passes the number 200 sieve Ksa is in cm s For bioretention facilities analyze each defined layer below the top of the final bioretention area subgrade to a depth of at least 3 times the maximum ponding depth but not less than 3 feet 1 meter For permeable pavement analyze for each defined layer below the top of the final subgrade to a depth of at least 3 times the maximum ponding depth within the base course but not less than 3 feet 1 meter If the licensed professional conducting the investigation determines that deeper layers will influence the rate of infiltration for the facility soil layers at greater depths must be considered when assessing the site s hydraulic conductivity characteristics Massmann 2003 indicates that where the water
408. quirements associated with the vegetation design include the following Plans shall specify that vegetation coverage of selected plants will achieve 90 percent coverage within 2 years or additional plantings will be provided until this coverage requirement is met For sites with 5 000 square feet or more new and replaced impervious surface plant spacing and plant size shall be designed to achieve specified coverage by certified landscape architect Plants shall be sited according to sun soil wind and moisture requirements At a minimum provisions must be made for supplemental irrigation during the first two growing seasons following installation Refer to the NDP materials Section D6 04 1 Mulch Layer Refer to the NDP materials Section D6 04 1 Observation Port D6 20 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 An observation port in accordance with Standard Detail NDP 9 shall be installed in each Bioretention Cell or bioretention swale cell near the outlet for projects required to meet runoff treatment MR6 and or flow control MR7 The observation port access must be located outside of the ponded area The use of an offset for access adjacent to the facility may be necessary Overflow Overflow protection can be provided by vertical stand pipes that are connected to under drain systems NDP 8 by horizontal drainage pipes NDP 7 or armored channels NDP 6 installed at the designed maximum ponding elevations O
409. r Boxes Functions as a Detention Filter layer and growth medium for plants BSM shall be as follows Placed to a minimum depth of 18 inches with the following characteristics Initial infiltration rate lt 12 inches per hour Cation exchange capacity CEC gt 5 meq 100 grams of dry soil D6 53 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Minimum 8 percent to maximum 10 percent organic matter content by dry weight and 2 5 percent fines passing the No 200 sieve Contain less than 5 clay by volume and A uniform soil mixture free of stones stumps roots or debris larger than 2 inches When required by the Engineer testing shall be done by a Contractor provided testing laboratory The laboratory must be accredited by STA AASHTO ASTM or other industry recognized standards organization and have current and maintained certification The testing laboratory shall be capable of performing all tests to the standards specified and shall provide test results with an accompanying Manufacturer s Certificate of Compliance to the Engineer Testing laboratories include but are not limited to those listed in Section 7 in Building Soil Guidelines and Resources for Implementing Soil Quality and Depth BMP T5 13 in WDOE Stormwater Management Manual for Western Washington This document may be downloaded at www soilsforsalmon org or www buildingsoilorg It is the responsibility of the contractor to verify
410. r Sheet Flow Dispersion landscape in accordance with D6 03 1 Rain Recycling Rain Barrels 4 50 60 gallon tanks 1 4 rain barrels Vegetated Roof 4 inch growing medium 43 8 inch growing medium 50 Notes sf square feet a Trees must be within 20 feet of ground level impervious surface The total tree credit shall not exceed 25 percent of impervious surface requiring mitigation b Minimum of 4 rain barrels shall be installed to receive Flow Control Credit Maintenance D2 09 for operation and maintenance manual O amp M Manual requirements maintenance shall be performed per DOE Manual Volume IV Chapter 2 page 2 40 BMPs for Maintenance of Stormwater Drainage and Treatment Systems In addition A For each required On site Stormwater BMP refer to Section D6 03 1 for general maintenance guidelines BMPs except splash blocks sheet flow dispersion and concentrated flow dispersion require a maintenance log be kept on site per D2 09 For Natural Drainage Practices D6 03 2 use the performance standards and inspection and maintenance schedules and techniques provided by the designer or manufacturer Comply with the maintenance guidelines in Bellevue Maintenance Standards and copy applicable maintenance procedures into the O amp M Manual for each facility D6 04 NDP MATERIALS D6 04 1 Bioretention A Bioretention Soil Mix BSM For use in Rain Gardens Bioretention Swales and Downspout Plante
411. rder being posted until the matter is resolved to the satisfaction of Bellevue Utilities A written release from the easement grantor shall be furnished to the Utilities Inspector prior to permit sign off The Contractor shall restore the Right of Way and existing public storm drainage easement s after construction to a condition equal or better than condition prior to entry The Contractor shall furnish a signed release from all affected property owners after restoration has been completed D2 18 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 39 Where a new utility line crosses below an existing main the AC pipe shall be replaced with DI pipe to 3 feet past each side of the trench as shown on Standard Detail W 8 Alternatively where directed by the Utility the trench shall be backfilled with controlled density fill CDF aka flowable fill from bottom of trench to bottom of AC main D2 08 AS BUILT DOCUMENTATION D2 08 1 General Standards For all storm drainage projects the Developer or City Department responsible for the project shall provide surveyed as built plans at completion of the project This includes private commercial or multi family systems that the Developer s Engineer provides a written compliance letter for As built plans shall be based on field survey information All survey work shall be performed under the supervision of a Professional Land Surveyor registered in the State of Washington The surveyed as b
412. re or more of pavement or other impervious surface Multiple small or one large scale PIT See Section D4 6 7I If using the small scale test measurements should be taken at several locations within the area of interest After completing the infiltration test excavate the test site at least 3 feet if variable soil conditions or seasonal high water tables are suspected Observe whether water is infiltrating vertically or only spreading horizontally because of ground water or a restrictive soil layer See DOE Manual Volume III Table 3 9 for a selection of an appropriate infiltration correction factor Bioretention swales approximately 1 small scale PIT per 200 feet of swale and within each length of road with significant differences in subsurface characteristics However if the site subsurface characterization including soil borings across the development site indicate consistent soil characteristics and depths to seasonal high ground water conditions the number of test locations may be reduced to a frequency recommended by a geotechnical professional See DOE Manual Volume III Table 3 9 for a selection of an appropriate infiltration correction factor D4 79 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Method 2 Soil Grain Size Analysis Method This method is restricted to sites underlain with soils not consolidated by glacial advance e g recessional outwash soils e Small bioretention cells Use the grain size analysis me
413. rea D2 6 Table 2 2 Flow Control amp On site Stormwater Management Requirements by Threshold AT COATS D2 7 FIGURES Figure 2 1 Threshold Discharge e ester o D2 3 Figure 2 2 Flow Chart for Determining Requirements for New Development D2 4 Figure 2 3 Flow Chart for Determining Requirements for Redevelopment D2 5 Figure 2 4 Sample Stormwater Facility Maintenance Activity Log D2 24 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D2 THRESHOLDS AND PLAN SUBMITTAL D2 01 GENERAL Following these standards to design the stormwater system will help ensure a timely review of the proposed project and keep review costs to a minimum A drainage system which includes unreasonable and intensive maintenance or operational requirements as determined by the City shall be rejected in favor of a drainage system which does not place undue burdens on the owner operators of such system D2 02 ADJUSTMENTS AND DEVIATIONS D2 02 1 General The applicant may propose an Adjustment to the Minimum Requirements described in BCC 24 06 065 D or a Deviation from the Storm and Surface Water Engineering Standards Proposed Adjustments or Deviations must be project specific An Adjustment or Deviation may take longer to review resulting in increa
414. reambank Protection Guidelines is another useful reference B Design Criteria General Open channels shall be designed to provide required conveyance capacity and bank stability while allowing for aesthetics habitat preservation and enhancement Open channels shall be consistent with the WDFW Integrated Streambank Protection Guidelines Channel cross section geometry shall be trapezoidal triangular parabolic or segmental as shown in Figure 4 3 through 4 5 Side slopes shall be no steeper than 3 1 for vegetation lined channels and 2 1 for rock lined channels Vegetation lined channels shall have bottom slope gradients of 6 or less and a maximum velocity at max design flow of 5 fps see Table 4 1 Rock lined channels or bank stabilization of natural channels shall be used when design flow velocities exceed 5 feet per second Rock stabilization shall be in accordance with Table 4 1 or stabilized with bioengineering methods as described above in Constructed Channels See D4 07 for open channel setback information Conveyance systems shall be sized to accommodate the peak runoff from a 100 year 24 hour storm Minimum freeboard requirements for open channels shall be one half 0 5 foot below the top of bank for the design flow rate The design shall consider the channel roughness both immediately after construction and when vegetation is well established Provide maintenance access for inspection and debris removal by convention
415. red on SPU s pipeline so that the section joints are not over or under any portion of SPU s pipeline The joints must be pressurized and tested for leaks e Whencrossing SPU s pipelines if the installed facility is not made of ductile iron pipe the facility must be installed in a steel casing with walls at least 1 4 inch thick e When crossing SPU s pipelines if the facility is installed within SPU fee owned right of way the steel casing must be installed the entire width of the right of way If the facility is installed within a street right of way the steel casing must extend at least 10 feet on each side of the pipeline e SPU s pipelines are set in a bed of pea gravel Construction must be performed in a manner that will not allow the pea gravel to escape from under the pipeline e Construction methods must be employed to support the pipeline during excavation 5 1 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Trenchless construction methods must be approved on a site by site basis due to the high probability of substantial collateral damage if one of SPU s pipelines is damaged Cathodic pipe protection methods may be required For parallel installations SPU would like 10 feet of separation on each side of its pipelines Shallow curb inlets can be closer than 10 feet if ductile iron is used and the drain line diverts the water to a catch basin at a remote location Special protections or bridging methods may be require
416. rise at design flow The maximum headwater elevation at design flow shall be below any road or parking lot subgrade Inlets and Outlets 1 All inlets and outlets in or near roadway embankments must be flush with and conforming to the slope of the embankment 2 For culverts 18 inch diameter and larger the embankment around the culvert inlet shall be protected from erosion by rock lining or riprap as specified in Table 4 1 except the length shall extend at least 5 feet upstream of the culvert and the height shall be at or above the design headwater elevation 3 Inlet structures such as concrete headwalls may provide a more economical design by allowing the use of smaller entrance coefficients and hence smaller diameter culverts When properly designed they will also protect the embankment from erosion and eliminate the need for rock lining 4 In order to maintain the stability of roadway embankments concrete headwalls wingwalls or tapered inlets and outlets may be required if right of way or easement constraints prohibit the culvert from extending to the toe of the embankment slopes All inlet structures or headwalls installed in or near roadway embankments must be flush with and conforming to the slope of the embankment 5 Debris barriers trash racks are generally not required on the inlets of all culverts except as specified by the Utility 6 For culverts 18 inch diameter and larger the receiving channel of the out
417. rm and Surface Water Maintenance Standards now or as hereafter amended log of maintenance activities that indicates what actions have been taken when and by whom Log shall be kept available for inspection by City of Bellevue at any time See Figure 2 4 below for recommended activity log format Prominently note the manual and log sheets location on site Maintenance instructions for any components not covered by the maintenance standards referenced above An engineer s statement describing the storm drainage facilities and overall system and how it is intended to function Site diagram of the constructed As Built storm drainage system identifying the components with profiles as needed D2 22 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 As Built details of components particularly flow control and treatment facilities as needed for maintenance A draft must be submitted to the Utilities Department during the plan review process The final O amp M Manual for MR 1 9 must be approved by the Utilities prior to Utility Extension acceptance where applicable or prior to occupancy The O amp M Manual for MR 1 9 must conform to King County s recording format requirements and be recorded against the property as a covenant running with the land A copy of the manual shall be retained onsite or within reasonable access to the site and shall be transferred with the property to the new owner The manual and log
418. rmion Arc Metal Spray SHpNOT Metal Safety Flooring 99 SHpNOT Grip Plate IKG Industries gt 80 MEBAC 1 Metal Bonded Anti Slip Coatings Grating Pacific LLC 92 ALGRIP Safety Floor Plates COF coefficient of friction as determined by ASTM C1028 89 See Section D6 04 NDP Materials and Chapter D 7 Materials for approved manufacturers of other materials for storm and surface water construction Where specific manufacturers are listed no other manufacturer may be used without prior approval by the Utility A D4 3 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 APPENDIX D 5 STORM AND SURFACE WATER REFERENCE STANDARDS 1 STANDARDS FOR UTILITIES INSTALLED IN PROXIMITY SEATTLE PUBLIC UTILITIES TRANSMISSION 22 22 A D5 1 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Standards for Utilities Installed in Proximity of Seattle Public Utilities Transmission Pipelines Seattle Public Utilities SPU operates several major water transmission pipelines within King County These pipelines supply nearly all the domestic water to the communities in western King County In some cases these pipelines are located within SPU s fee owned right of way within easements on private property or within the city streets county road or state highways Vibrations heavy loads and other construction activities can damage these pipelines Ifa pipeline is damaged there could be substantial collateral
419. roat 2 0 534 0 333 0 0196 0 89 Tapered Inlet Rough tapered inlet throat 0 519 0 64 0 0289 0 90 Source FHWA HDS 5 D4 36 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Outlet Control Analysis Nomographs such as those provided in Figure 4 12 and Figure 4 13 may be used to determine the outlet control headwater depth at design flow for various types of culverts and inlets Outlet control nomographs other than those provided can be found in FHWA HDS No 5 or the WSDOT Hydraulic Manual The outlet control headwater depth may also be determined using the simple Backwater Analysis method presented in Section D4 04 9 D for analyzing pipe system capacity This procedure is summarized as follows for culverts HW H TW LS 4 8 whereH He Hex H friction loss ft Vn LyQ 22R Note If Hf TW LS lt D adjust Hf such that Hf TW LS D This will keep the analysis simple and still yield reasonable results erring on the conservative side H entrance head loss ft KV 2g Ha exit head loss ft V 2g TW tailwater depth above invert of culvert outlet ft Note If TW lt D d 2 set TW D d 2 This will keep the analysis simple and still yield reasonable results length of culvert ft slope of culvert barrel ft ft interior height of culvert barrel ft barrel velocity fps Manning s roughness coefficient from Table 4 9 hydraulic radius ft entrance loss co
420. roperties in the subdivision may be combined and treated in a single facility If clean runoff is routed to the water quality facility those flows must be included in the sizing calculations for the facility Drainage from most landscaped areas 15 required to be treated Areas in native vegetation should not be mixed with untreated runoff from the development if feasible Once runoff from non pollutant generating areas is combined with runoff from contaminant generating areas it cannot be discharged without treatment Proprietary BMPs shall be accepted only if DOE has approved them for General Use GULD under DOE s emerging technologies program per Chapter 12 Volume V of DOE Manual and provided they meet required treatment level Runoff treatment BMPs are categorized by the type of contaminants most effectively removed These categories are Olil Water Separation Designed to remove and contain oil Phosphorus Treatment Designed to remove suspended and dissolved nutrients Enhanced Treatment Designed to remove more heavy metals than Basic Treatment Application is targeted to areas that discharge to fish bearing water bodies Basic Treatment Designed to remove particulates and contaminants typically associated with particulates such as heavy metals D5 03 2 Treatment Facility Sizing The Water Quality Design Storm Volume is the volume of runoff predicted from a 24 hour storm with a 6 month return frequency a k a
421. roposed infiltration facility Lay back the slopes sufficiently to avoid caving and erosion during the test Alternatively consider shoring the sides of the test pit The horizontal surface area of the bottom of the test pit should be approximately 100 square feet Accurately document the size and geometry of the test pit e Install a vertical measuring rod minimum 5 ft long marked in half inch increments in the center of the pit bottom e Usearigid 6 inch diameter pipe with a splash plate on the bottom to convey water to the pit and reduce side wall erosion or excessive disturbance of the pond bottom Excessive erosion and bottom disturbance will result in clogging of the infiltration receptor and yield lower than actual infiltration rates e Add water to the pit at a rate that will maintain a water level between 6 and 12 inches above the bottom of the pit A rotameter can be used to measure the flow rate into the pit Note The depth should not exceed the proposed maximum depth of water expected in the completed facility For infiltration facilities serving large drainage areas designs with multiple feet of standing water can have infiltration tests with greater than 1 foot of standing water D4 80 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Every 15 30 min record the cumulative volume and instantaneous flow rate in gallons per minute necessary to maintain the water level at the same point on the measuring rod Keep addi
422. roved discharge point s or through interflow to the surface or to surface discharge or in combination Overflows may be piped or daylighted through a storage reservoir or dispersion BMP or through overtopping of the facility Plans shall indicate all flow paths Designers are recommended to consider flooding and nuisance ponding risks associated with larger peak flows During large storm events capacity will be limited at the approved discharge point s and backwater calculations may be required If a facility is designed for full infiltration a constructed overflow is not required Plans should indicate surface flow paths in case of failure of the facility iv Sizing Sizing Factors for bioretention planters are provided in Section D6 03 3 These Sizing Factors may be used size bioretention planters to meet on site stormwater management 5 when runoff treatment MR6 and or flow control MR7 are not required Sizing Factors are also provided for runoff treatment and flow control but those are intended for conceptual design only Developer is required to perform independent calculations to size and design bioretention planters to meet runoff treatment and flow control requirements per Chapter D3 of these Standards Note that only infiltration planters are capable of meeting flow control requirements When using an approved continuous model to size bioretention planters with the demonstrative approach the assumptions listed
423. rt graphics For redevelopment if the runoff from the new impervious surfaces and converted pervious surfaces is not separated from runoff from other surfaces on the project site the stormwater treatment facilities must be sized for the entire flow that is directed to them D2 05 3 Projects subject to Regulation All project sites in Bellevue are subject to the Minimum Requirements per Chapter 24 06 065 unless exempt per 24 06 065 B and are subject to the Minimum Requirements for development and redevelopment as outlined in Figure 2 2 and Figure 2 3 D2 3 SURFACE WATER ENGINEERING STANDARDS Start Here Does the site have 35 or more of existing impervious coverage Does the project add 5 000 square feet or more of new impervious surfaces Yes All Minimum Requirements apply to new impervious surfaces and converted pervious surfaces No Yes Yes Does the project convert 3 4 acres or more of native vegetation to lawn or landscaped areas or convert 2 5 acres or more of native vegetation to pasture Minimum Requirements 1 through 5 apply to the new and replaced impervious surfaces and the land disturbed JANUARY 2015 See Figure 2 3 Flow Chart for Determining Minimum Requirements for Redevelopment No Does the project have 2 000 square feet or more of new replaced or new plus replaced impervious surfaces Yes No Does the project have land disturbin
424. ructure e g buildings sheds decks rockeries or retaining walls which run parallel to the pipeline carports etc except in the Central Business District zero lot line areas or upon approval by the City 10 feet or outside the 1 1 plane from the bottom edge of the pipe or structure to the finished grade at a building or structure whichever is greater 10 feet or outside the 1 1 plane from the bottom edge of the D4 87 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Storm Drainage Feature Setback Requirement pipe or structure to the property line at finished grade when easement is not provided on the adjacent property whichever is greater One half of the minimum easement width from a structure Open Channels e 10 feet from any structure foundation measured horizontally from the edge of the swale at the freeboard elevation Detention Ponds e Outside the 1 1 plane from the pond bottom to the finished grade at an adjacent building e Outside the 1 1 plane from the bottom edge of the pipe or structure to the property line at finished grade when an easement is not provided on the adjacent property e Topofacut embankment and the toe of a fill embankment to property lines at least 5 feet Detention Vault or Tank e Do not locate underneath any structure e g buildings sheds Wetvault or tank decks carports retaining walls etc e Finished grade at an adjacent structure foundation to the bottom edge of the v
425. s cover sheet showing the entire project site at a smaller scale shall be provided North Arrow Include on all plan view drawings North arrow shall face up and or to the right hand side of plan sheet Datum Show both horizontal NAD 83 NSRS 2011 and vertical NAVD 88 control points Specify the benchmark to be used for vertical control during construction For sites with FEMA mapped floodplains label the 100 year floodplain elevation with the NGVD29 and NAVD88 values The survey of the site for both design and as builting shall be accurately referenced to the Washington State Plane Coordinate System NAD 83 NSRS 2011 by field ties to at least two City of Bellevue survey control network monuments All elevations shall be referenced to the North American Vertical Datum of 1988 NAVD 88 Information on the City of Bellevue survey control network is available by contacting the Transportation Department Property Services Division at 425 452 6019 Vicinity Map Include on the plan for each utility The vicinity map covers the project site and surrounding streets and property within a minimum of 600 of the site Copies of a city map can be made from the Street Atlas in the Self Help area of the Permit Center Line types shall clearly distinguish existing utilities from new new facilities should be a heavier line type Drafting Media Plans sheets shall be on 24 x 36 or 22 x 34 mylar matte on both sides Drafting
426. s and root systems and be free from physical defects plant diseases and insect pests Small plant material is recommended for best survival and lowest expense Optimum planting time is typically fall beginning mid October Spring and summer planting likely will require more watering during the summer months and winter planting is acceptable but may result in mortalities from freezing temperatures Tf aluminum stainless steel or plastic are not available asphalt coated galvanized materials shall be used if available Avoid galvanized metals because they leach zinc into the environment especially in standing water situations and at high concentrations zinc can be toxic to aquatic life D6 58 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Bioretention Swales may be planted with a mixture of shrubs grasses and ground covers if the Developer can demonstrate that conveyance capacity will be maintained when the plants are mature Plant vegetation according to the following moisture tolerance zones Zone Generally the bottom of the facility area of periodic or frequent standing or flowing water Zone 1 plants will also tolerate the seasonally dry periods of summer in the Pacific Northwest without extra watering and may also be applicable in Zone 2 or 3 Zone 2 Periodically moist or saturated during larger storms Plants listed under Zone 2 will also be applicable in Zone 3 Zone 3 Dry soils infrequently subject to inund
427. s and using industry standards and practices D Maintenance Drainage systems on commercial and multi family properties drainage facilities within private easements and drainage facilities otherwise denoted as private shall be designed to provide access for maintenance and operation by the owners of such facilities D4 05 MANHOLES CATCHBASINS AND INLETS D4 05 1 General Stormwater inlets in a roadway shall be located in the curb line and shall be fitted with bolt locking vaned grates A through curb inlet frame shall be used where conditions limit the effectiveness of a flat grate inlet Examples of such conditions are where a high likelihood of clogging from leaf fall or other debris exists in sag vertical curves intersection curb returns and when the structure is a surface drainage end point such as in a cul de sac Bi directional vaned grates shall be used in sag vertical curves All manhole covers shall be set flush with ground surface except where otherwise designated by the Utility Manholes in unpaved areas and easements shall have bolt locking covers All manholes in paved areas and sidewalks shall have standard non bolt locking covers Vertical ladders or steps shall be installed immediately under the cover or grate opening to a walkable surface on all structures exceeding four feet deep to the pipe invert All manholes catchbasins inlets and or other concrete structures shall be precast If precast is not an option
428. se A leveling course shall be included when required by the designer or in accordance with the manufacturer s recommendations for proprietary products Reservoir Course Reservoir course aggregate depth shall be a minimum of 6 inches placed for pervious pavement or 4 inches for pervious paver systems beneath the pervious wearing course and leveling course when used for water storage or a minimum of 22 inches compacted if an underdrain is used Materials shall meet the specifications of Section D6 04 2 except for proprietary products shall follow the manufacturer s recommendations Thoroughly washed aggregate is recommended to limit the amount of fines in the delivered stone The reservoir course shall have a minimum total void volume of 20 percent after being compacted in place When the slope exceeds 2 percent design shall include an interceptor infiltration trench or check dams to create subsurface ponding per Standard Detail NDP 15 D6 30 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 The maximum ponding elevation shall be 6 inches below the top of the wearing course to prevent degradation from repeated freeze thaw Slope bottom of reservoir course away from structures Native Soil Suberade The correction factor used to calculate the design infiltration rate shall consider compaction of the native soil or subgrade during construction Determine the native soil infiltration rate and correction fact
429. sed processing costs The Applicant acknowledges these risks when submitting a request for an Adjustment or Deviation D2 02 2 Adjustment and Deviation Criteria The City s decisions to grant deny or modify proposed Adjustments or Deviations shall be based on evidence that the request meets the following criteria 1 Adjustment Criteria A The Adjustment provides substantially equivalent environmental protection and B The Adjustment is based on sound engineering practices and C The Adjustment meets the objectives of safety function environmental protection and facility maintenance 2 Deviation Criteria A The Deviation will achieve the intended result through a comparable or superior design and a The Deviation provides substantially equivalent environmental protection and b The Deviation is based on sound engineering practices and D2 1 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 c The Deviation meets the objJectives of safety function environmental protection and facility maintenance D2 02 3 Adjustment and Deviation Process Requests for Adjustments or Deviations shall be 1 Provided to the Utilities Reviewer in writing prior to implementation and 2 Demonstrate how the proposed Adjustment or Deviation meets criteria listed or referenced above e g written finding of fact and 3 May be reviewed by the Utilities Technical Team before a decision is made and 4 The decision by the City sh
430. sheets must be available for inspection by the City of Bellevue upon request The O amp M Manual for MR 1 9 shall be adjusted or revised at the end of the one 1 year watranty period if needed as a result of inspection findings and recommendations by the City The revised O amp M Manual shall be recorded against the property List regularly scheduled maintenance on a separate checklist based on the facility s O amp M Manual for MR 1 9 and keep the checklist with this maintenance activity log A sample Maintenance Activity Log is shown in Figure 2 4 D2 23 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Figure 2 4 Sample Stormwater Facility Maintenance Activity Log for NPDES Permit To be completed and provided to the City of Bellevue annually Send copy by fax to 425 452 7116 or by mail to Bellevue Utilities Water Quality Box 90012 Bellevue WA 98009 Property Name Owner Site Address Property Manager Contact Phone Storm Drainage Facility Type s Location s on Property indicate on site map if possible Reason for Date Inspection Action circle Condition Observed Action Taken Initials one Complaint or Problem Regular Maintenance Complaint or Problem Regular Maintenance Complaint or Problem Regular Maintenance Complaint or Problem Regular Maintenance Complaint or Problem Regular Maintenance Complaint or Problem Re
431. sides Wingwalls at 30 to 75 to barrel Square edged at crown Crown edge rounded to radius of 1 12 barrel dimension or beveled top edge Wingwall at 10 to 25 to barrel Square edged at crown Wingwalls parallel extension of sides Square edged at crown Side or slope tapered inlet Note End section conforming to fill slope are the sections commonly available from manufacturers From limited hydraulic tests they are equivalent in operation to a headwall in both inlet and outlet control Some end sections incorporating a closed taper in their design have a superior hydraulic performance D4 38 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Computer Applications The King County Backwater KCBW computer program available from King County contains two subroutines BWPIPE BWCULV that may be used to analyze culvert capacity and develop stage discharge curves for level pool routing purposes A schematic description of the nomenclature used in these subroutines is provided in Figure 4 15 The KCBW program documentation available from King County Department of Natural Resources and Parks includes more detailed descriptions of program features D4 39 JANUARY 2015 SURFACE WATER ENGINEERING STANDARDS Figure 4 9 Inlet Outlet Control Conditions ill HW SEN SS W p A 7 grade line VL 222 R hydraulic Outlet Control Submerged Inlet
432. site properties to install measures which will correct the existing or mitigate the anticipated problem In some cases existing public drainage system problems may already be scheduled for correction by the City In these cases the Developer should contact the Utilities Department to determine current capital improvement project schedules Any proposed drainage easements must be executed by the affected property owners and be recorded prior to approval for construction D4 04 CONVEYANCE SYSTEMS D4 04 1 General Use the criteria set forth in Section 24 06 070 B 4 of the Storm and Surface Water Utility Code and the information provided herein to plan design and construct stormwater conveyance systems Off site stormwater flows passing through the site shall be conveyed by a hydraulically adequate conveyance system as set forth herein Off site flows can only be routed to flow control or treatment facilities if allowed by D4 06 2 and if those facilities are properly sized for the additional flows Conveyance systems shall not be located where such facilities interfere with other underground utilities nor where allowable design loads would be exceeded See D4 07 for conveyance system setbacks D4 6 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D4 04 2 Conveyance System Setbacks Conveyance Systems Shall Not Be Located A Where Such Facilities Interfere With Other Underground Utilities B Where Allowable Design Loads Would
433. ssure backflow assembly and must comply with the Uniform Plumbing Code Low Flow Orifice for Cisterns with Detention The minimum diameter shall be 0 25 inches for orifices located above ground This is the only exception to the minimum orifice size in Section D4 06 4 C and these systems shall have screens to prevent debris from clogging the orifice The minimum diameter shall be 0 5 inches for orifices located below ground The low flow orifice invert must be at least 3 inches above the bottom of the cistern to prevent entraining sediment Overflow Overflows shall be designed to convey excess flow to an additional tank on site stormwater management BMP or discharge appropriately away from any structures on site sewage systems wells or steep slopes and shall not cause erosion or flooding on site or on downstream properties Sizing To receive Flow Control Credit for rain recycling with rain barrels or cisterns runoff reduction must be demonstrated by a water balance model indicating the amount of rooftop runoff the amount of harvested water that will be used and the amount of overflows from the rain recycling system A spreadsheet based modeling tool may be used for this purpose The minimum time step to be used in the water balance model shall be one 1 day so that the timing magnitude and duration of overflows are considered in sizing residual detention to meet flow control requirements for the site when needed or
434. st is being performed by a home owner installing a pervious pavement patio on their property The home owner is performing this test during the wet season for most accurate results They dig a hole that is 2 feet deep and 2 feet in diameter They first observe the soils and determine that the soils are sand mixed with silt and likely moderately draining Next they note that no groundwater was encountered After this they fill the hole with 10 inches of water and observe that it takes 4 hours to drain all the water completely from the hole They then calculate the measured short term infiltration rate as Short Term Infiltration Rate 10 inches 4 hours 2 5 inches per hour They then use the site conditions and Table 3 9 in the DOE Manual to determine the infiltration rate correction factor in order to determine the long term infiltration rate They did two infiltration tests in a small area so variability correction factor will be 3 They plan on maintaining the pervious pavement regularly but they may sell the property within 5 years a maintenance correction factor of 5 is selected Since the water flowing into the pervious pavement is from a screened pipe that drains the roof the influent correction factor is set at 2 The partial correction factors are added together to get the Total Correction Factor CP CF 3 5 2 10 Then the correction factor is applied to the short term infiltration rate by dividing to get the long term infiltrati
435. storm drainage pipe cannot be re used the property owner shall either abandon the storm drainage pipe or upgrade the portion of storm drainage pipe on private property through a storm drainage permit or through a storm system extension agreement The City will be responsible for repair or replacement of the portion of the storm drainage pipe located within public rights of way and public easements When a property is redeveloped the property owner shall abandon storm drainage pipes that are no longer needed In addition the property owner shall abandon all unused provisional storm drainage pipes within the scope of the redevelopment project The allowable methods of storm drainage pipe abandonment are as follows the storm drainage pipe at the main Install a cured in place liner in the mainline to cover the lateral storm drainage pipe inlet and fill storm drainage pipe to be abandoned with controlled density fill Install a cured in place spot repair liner in the mainline to cover the lateral storm drainage pipe inlet and fill storm drainage pipe pipe to be abandoned with controlled density fill The spot repair liner shall extend minimum of one foot upstream and downstream of the edge of the storm drainage pipe opening Other trenchless technology proposed by the property owner subject to City review and approval For single family sites the City may allow the property owner to cap the storm drainage pipe at the edge of r
436. structure In areas having an existing piped conveyance system the stormwater outfalls for roof footing and yard drains may be made by the two methods above or by the following in order of preference 1 Connecting the private drainage pipe to an existing storm drain manhole catch basin or stub out if provided within 100 feet and downslope of the property line or 2 Coring the abutting conveyance pipeline and installing a saddle tee and providing a clean out outside of the public right of way or 3 Coring the abutting profile wall conveyance pipeline PVC or corrugated polyethylene only CMP may not be blind tapped and installing an insert tee and clean out outside of the public right of way or 4 Installing a tee fitting in the abutting conveyance pipeline and providing a clean out outside of the public right of way or 5 Connecting the private drainage pipe to an existing sidewalk drain or 6 Providing a new sidewalk drain if the closest existing drainage system or stub out is greater than 100 feet and downslope of the property line or 7 Outfalling to an open channel or stream provided that the drainage path continues downstream to an established known and well functioning conveyance system adequate erosion protection is provided and permits from other agencies are obtained as needed When a project includes the construction of a drainage system private drainage systems shall connect to the proposed storm drain m
437. t NT 7 x ke X ZG gt gt GRASS PAVING MODULAR PLASTIC GRID OF GRID 1 FLUSH SYSTEM I E GRASS PAVE WITH TOP OF ASPHALT ASPHALT OR CONCRETE OR EQUAL SEE NOTES OR EXISTING SURFACE FILL GRID WITH SANDY LOAM TO 2 SLOPE TOPSOIL MIX SEE PARKS DETAIL NEW 1 TURF LAWN PLANTING 4 MIN DEPTH GRAVEL BACKFILL FOR DRAINS PER STANDARD SPECIFICATIONS 9 03 12 4 NOTES 1 PERVIOUS PAVEMENT WITHIN CITY RIGHT OF WAY REQUIRES APPROVAL BY THE CITY WHEN PLACED BENEATH TRAVELED WAY THESE GUIDELINES PROVIDE A MINIMUM DEPTH FOR THE HYDROLOGIC PERFORMANCE OF THE PERVIOUS PAVEMENT THE STRUCTURAL CAPACITY OF PAVEMENT SECTIONS WHEN SUBJECT TO VEHICULAR LOADS DEPENDS ON SEVERAL FACTORS AND MUST BE DESIGNED BY A LICENSED PROFESSIONAL ENGINEER LONGITUDINAL SLOPE 0 TO 10 MAX USE CHECK DAM OR OTHER METHODS TO MAXIMIZE PONDING IN THE SUBSURFACE IF SLOPE EXCEEDS 2 PER STANDARD DETAIL NDP 15 INSTALL PER LID TECHNICAL GUIDANCE MANUAL FOR PUGET SOUND 2005 OR CURRENT OR MANUFACTURER SEE NDP CHAPTER D6 04 HEREIN FOR ALL MATERIALS SOME INTERLOCKING CONCRETE PAVER SYSTEMS RECOMMEND A BASE COURSE BETWEEN THE LEVELING AND RESERVOIR COURSES Cit of STORM AND SURFACE Bellevue WATER UTILITY ERVIOUS JANUARY 2015 NO SCALE SIDEWALK PER TRANSPORTATION STANDARD DETAIL TE 11 TREE AND GRATE PER PARKS STANDARD DETAIL 54 PERVIOUS PAVEMENT PER ST
438. t documentation for Storm Drainage projects D2 19 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D2 08 2 Required Information Mains Length center of manhole catch basin to center of manhole catch basin diameter material slope direction of flow note private if applicable for privately maintained facilities Show private systems going to apartments condominiums commercial sites and joint use side storm drains Label private system components as PRIVATE SYSTEM Other than joint use systems do not show single family private systems other than stub from public main Ditches Length direction of flow material and slope of all constructed open channels note private if applicable Stubs Lengths depth station stationing of stubs referenced from downstream structure distance from property line List slope if different than standard 2 and size if different than standard 6 Existing Structures Where new pipes connect to existing structures the Utilities ID number of the existing structure shall be noted on the drawing ID numbers can be obtained from the Storm Drainage Maps Ponds Bioswales and Bioretention Facilities Locations topographic features and dimensions of all flow control and runoff treatment ponds bioswales and bioretention facilities Include bottom and top elevations and in plan view included labeled contour lines at one foot lintervals As built revisions to a
439. t plant coverage after 2 years following installation Irrigation design shall be included in the Landscape Management Plan Drain System Vegetated roofs shall include a drain system capable of safely collecting and conveying water to an approved discharge point Structural Roof Support Structural considerations for vegetated roofs shall include roof slope design loads including loads due to ponding slipping and shear considerations wind load snow load seismic load and fire resistance All vegetated roof structural designs must be prepared or stamped by a structural engineer Sizing Flow Control Credits for vegetated roofs are provided in Section D6 03 4 These Flow Control Credits may be used for small sites with 10 000 square feet of contributing impervious or less When using continuous modeling to size vegetated roofs with a demonstrative approach the assumptions listed in Table 6 11 shall be applied Vegetated roofs should be modeled as layers of aggregate with surface flows interflow and exfiltrating flow routed to an outlet Table 6 11 Continuous Modeling Assumptions for Vegetated Roofs Precipitation Series SeaTac 50 year hourly time series with appropriate scaling factor based on project location Precipitation and Evaporation Applied Yes to Facility Depth of Material inches Growth medium soil depth minimum of 4 inches Depth of underlying aggregate drainage layer if any is neglected Vegetative
440. tact s D6 54 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 4 E mail address es 5 Qualifications of laboratory and personnel including expiration date of current certification Bioretention Construction Requirements BSM shall be protected from all sources of additional moisture at the Supplier s site covered during transport at the Project Site and until incorporated into the Work Soil placement and compaction shall not occur when the ground is frozen or excessively wet gt 3 above optimum moisture content or when weather conditions are unsuitable as determined by the Engineer Bioretention Soil Placement The Contractor shall not place bioretention soil until the Project Site draining to the bioretention area has been stabilized and authorization is given by the Engineer Mixing placing BSM shall not be allowed if the area receiving BSM is wet or saturated or has been subjected to more than 2 inch of precipitation within 48 hours prior to mixing or placement The Engineer will have final authority to determine whether wet or saturated conditions exist In rain gardens and in areas to be landscaped with vegetation other than turf place BSM loosely Final BSM depth shall be measured and verified only after the soil has been water compacted which requires filling the cell with water without creating any scour or erosion to at least 1 inches of ponding If water compaction is not an option final BSM depth shall
441. tal of effective pollution generating impervious surface PGIS is 5 000 square feet or more in a threshold discharge area of the project or Projects in which the total of pollution generating pervious surfaces PGPS is three quarters 3 4 of an acre or more in a threshold discharge area and from which there is a surface discharge in a natural or man made conveyance system from the site Table 2 1 Treatment Requirements by Threshold Discharge Area lt 3 4 acres of gt 3 4 acres lt 5 000 sf gt 5 000 sf PGPS PGPS PGIS PGIS Treatment Facility v v On site Stormwater BMPs v v PGPS pollution generating pervious surfaces PGIS pollution generating impervious surfaces sf square ft Project Thresholds for the construction of flow control facilities MR7 and or on site stormwater management MR5 BMPs to achieve the standard flow control requirement for western Washington are shown in Table 2 2 D2 6 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 2 2 Flow Control amp On site Stormwater Management Requirements by Threshold Discharge Area Flow Control On site Stormwater Facilities Management BMPs lt 3 4 acres conversion to lawn landscape 5 Or 2 5 acres to pasture gt 34 acres conversion to lawn landscape Z or gt 2 5 acres to pasture lt 10 000 square feet of effective 3 impervious area gt 10 000 square feet of effective Z impervious area
442. te iae D4 59 Figure 4 22 Rational Method for Conveyance System Analysis and Sizing D4 61 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D4 HYDRAULIC ANALYSIS amp DESIGN D4 01 A a GENERAL Use the criteria set forth in Section 24 06 065 of the Storm and Surface Water Utility Code and the information provided herein to plan design and construct stormwater systems and facilities Design the on site stormwater system conveyance flow control runoff treatment and emergency overflow elements to accommodate runoff from the site and areas tributary to the site to prevent damage and injury Conveyance systems shall be sized to safely convey the 100 year peak runoff from areas tributary to the site to the discharge location An emergency overflow for flow control facilities shall be provided which prevents property damage or erosion caused by system failure Roof and footing drains yard drains underdrains ditches swales stormwater conveyance systems etc shall be installed to prevent damage or nuisance to adjacent properties and the public right of way due to the proposed development Consider drainage system reliability in terms of layout specification of materials and methods of installation and the influence of other activities in the area both during and after construction Minimize the frequency and difficulty of future maintenance by analyzing potential system failures and
443. ted through the underdrain e g no infiltration If there is no liner or impermeable layer and the underdrain is elevated within the storage reservoir water stored in the reservoir below the underdrain is allowed to infiltrate Outlet Structure Overflow elevation set at average maximum subsurface ponding depth May be modeled as weir flow over riser edge or notch Note that freeboard must be sufficient to allow water surface elevation to rise above the overflow elevation to provide sufficient head for discharge When downstream flow control is required either the default method or the demonstrative method can be used to calculate the amount of credit to be attributed to the pervious pavement in order to reduce the size of the downstream flow control facility as described in Section D3 03 The default method typically results in less credit The demonstrative method is described above in this section and involves using the model developed for sizing the pervious pavement to also evaluate the amount of residual flow control needed See Chapter D3 for guidance on hydrologic modeling for sizing flow control and runoff treatment facilities C Rain Recycling Rain recycling consists of capturing roof runoff and storing it for either later use or slow release to the surrounding landscaping see Standard Details NDP 18 and 19 The primary components of a rain recycling system are the collection system downspouts a storage tank rain
444. tend upstream and downstream a sufficient distance to adequately include all backwater conditions that may affect flooding at the site and all reaches that may be affected by alterations to the site Floodplain Floodway Map A Major Floodplain Floodway Study requires submittal of five copies of a separate floodplain floodway map stamped by a licensed civil engineer and a professional land surveyor registered in the State of Washington for the base survey The map must accurately locate any proposed development with respect to the floodplain and floodway the channel of the stream and existing development in the floodplain it must also supply all pertinent information such as the nature of any proposed project legal description of the property on which the project would be located fill quantity limits and elevation the building floor elevations flood proofing measures and any use of compensatory storage The map must show elevation contours at a minimum of 2 foot vertical intervals and shall comply with survey and map guidelines published in the FEMA publication Guidelines and Specifications for Flood Hazard Mapping Partners The map must show the following e Existing elevations and ground contours Locations elevations and dimensions of existing structures and fills e Size location elevation and spatial arrangement of all proposed structures fills and excavations including proposed compensatory storage areas with final grades
445. tes a re arranged form of Manning s equation expressed in terms of friction slope slope of the energy grade line in ft ft The friction slope is used to determine the head loss in each pipe segment due to barrel friction which can then be combined with other head losses to obtain water surface elevations at all structures along the pipe system The backwater analysis begins at the downstream end of the pipe system and is computed back through each pipe segment and structure upstream The friction entrance and exit head losses computed for each pipe segment are added to that segment s tailwater elevation the water surface elevation at the pipe s outlet to obtain its outlet control headwater elevation This elevation is then compared with the inlet control headwater elevation computed assuming the pipe s inlet alone is controlling capacity using the methods for inlet control presented in Section D4 04 7 J The condition that creates the highest headwater elevation determines the pipe s capacity The approach velocity head is then subtracted from the controlling headwater elevation and the junction and bend head losses are added to compute the total headwater elevation which is then used as the tailwater elevation for the upstream pipe segment D4 51 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 The Backwater Calculation Sheet in Figure 4 18 may be used to compile the head losses headwater elevations for each pipe segment
446. tested as described in the above test procedures Any manhole that fails the second vacuum test must be removed and replaced with a new manhole The new manhole shall not be backfilled until it has been tested and passed the above test procedures D8 11 3 Acceptance The manhole shall have passed the vacuum test if the manhole vacuum does not drop below 9 inches of mercury during the minimum specified test period D8 12 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D8 12 TRENCHLESS CONSTRUCTION The use of trenchless construction methods such as pipe bursting and horizontal directional drilling shall be considered by the City on a case by case basis under the following conditions A HDPE DR 26 or thicker walled pipe required B Romac 501 transition couplings 4 are required at both ends C The installed pipe must be electronically located and marked on the ground for measurement in order to draw the as built schematics D The pipe must be video taped following installation with water running The tape must be provided to the Inspector to approve the installation or require corrections E Pipe bursting is not allowed on private property or Right of Way without the appropriate permission such as an easement or Right of Way use permit D8 13 TRENCH EXCAVATION Before commencement of trenching provide mini gabions for all downhill storm drain catch basins per City of Bellevue Standards for temporary sediment trap at
447. text shall be 1 8 inch minimum size Font size on 24 by 36 drawings all text shall be 1 4 inch minimum size Symbol size on 11 by 17 drawings all symbols shall be 1 8 inch minimum size Symbol size on 24 by 36 drawings all symbols shall be 1 4 inch minimum size A D2 14 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 APPENDIX D 3 SAMPLE TITLE BLOCK Also available in AutoCAD format at http www bellevuewa gov utilities_maps_forms htm A D3 1 JANUARY 2015 SURFACE WATER ENGINEERING STANDARDS 034230 ago aes SSXHOCV X AWVN AWVN LOarodd ANVdWOO JI 51 5 ALVAVdAS NO AVW 4 NVId TIV9S A D3 2 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 APPENDIX D 4 STORM AND SURFACE WATER APPROVED MATERIALS LIST The following manufacturers have been approved for use for storm and surface water construction BIORETENTION SOIL MIX BSM MATERIALS Gravelly sands Green Earth Screen Sand Green Earth Technologies Bellingham Miles Sand and Gravel Utility Sand Miles Sand and Gravel Roy COMPOST AND MULCH FOR BIORETENTION Compost Mixes Cedar Grove compost Maple Valley GroCo Steerco many suppliers OVERFLOWS FOR BIORETENTION Overflow products Atrium grates 3 4 and 5 NDS models 70 75 and 80 Atrium grate ADS model 0663DX Neenah grate R 4346 R 2560 E2 R 25
448. the City s Boundary amp Topographic Survey and Site Plan B requirements Current copies of these requirements are available at the Bellevue Development Services Center and the City s website Combining Plans Water sanitary sewer and storm drainage designs complete plan and profile shall be on separate plan sheets although alignments of all Utilities shall be shown on each utility plan Plan sets for all 3 Utilities can be combined for small projects if information is readable Designs for water and sewer can be combined on the same plan sheets if plan scale is 17 10 V 20 or 1 30 Contact the Utility representative in the Permit Center for approval to combine plans D2 12 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 3 4 5 7 8 9 Plan submittals shall conform to Development Services Standards for Plans and Drawings and also include Title Block Border and title block shall conform to standard City of Bellevue format See Appendix D 2 Project Name Utility Extension UE permit number if applicable Section Township Range and Site Address shall be included in title block lower right hand corner Engineering Plans Plan profile and detail sheet s for the proposed drainage system a Plan View 1 List pipe length size and material alongside of pipe e g 150 L F 8 PVC Pipe material can be listed in a general note in lieu of listing along pipe ii Pipe
449. the laboratory s accreditations are up to date Submittal Requirements At least ten 10 working days prior to placement of the BSM the Contractor shall submit to the Engineer for approval 1 Grain size analysis results of Mineral Aggregate performed in accordance with ASTM D 422 Standard Test Method for Particle Size Analysis of Soils 2 Quality analysis results for compost performed in accordance with STA standards as specified in the Standard Specifications Section 9 14 4 8 3 Organic content test results for the mixed BSM Organic content test shall be performed in accordance with Testing Methods for the Examination of Compost and Composting TMECC 05 074 Loss On Ignition Organic Matter Method 4 Modified Proctor compaction testing for the mixed BSM performed in accordance with ASTM D 1557 Test Method for Laboratory Compaction Characteristics of Soil Using Modified Effort 5 Alist of the equipment and a description methods used to mix the Mineral Aggregate and compost to produce the BSM 6 Permeability or hydraulic conductivity testing of the BSM performed in accordance with ASTM D 2434 Standard Test Method for Permeability of Granular Soils For the landscape BSM assume a relative compaction of 85 percent of modified maximum dry density ASTM D 1557 and 7 The following information about the testing laboratory ies 1 Name of laboratory ies including contact person s 2 Address es 3 Phone con
450. the pipe At least two minutes shall be allowed for temperature stabilization before proceeding further The requirements of this specification shall be considered satisfied if the time required in seconds for the pressure to decrease from 3 5 to 2 5 pounds per square inch greater than the average back pressure of any groundwater is at least as follows Table 8 09 2 Seconds per Size of Pipe Lineal foot of Pipe 4 inch 0 11 6 inch 0 25 8 inch 0 46 10 inch 0 72 12 inch 1 04 15 inch 1 63 18 inch 2 35 21 inch 3 20 24 inch 4 18 The use of air pressure for testing storm drain lines creates hazards that must be recognized The Contractor shall be certain that all plugs are securely blocked to prevent blowouts An air supply regulator shall be installed on the air supply line to the storm drain that shall permit a maximum D8 10 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 of 10 psi in the line to be tested All pressure shall be relieved from the storm section being tested prior to removal of test plugs D8 9 3 Deflection Test for Flexible Pipe Storm drains constructed of flexible pipe shall be deflection tested not less than 30 days after the trench backfill and compaction has been completed and ATB has been placed in areas to be paved The test shall be conducted by pulling a solid pointed mandrel with a circular cross section with diameter equal to 95 of the inside pipe diameter through th
451. thod described in Section D4 06 7K based on the layer s identified in results of one soil test pit or boring e Large bioretention cells Use the grain size analysis method based on more than one soil test pit or boring The more test pits borings used and the more evidence of consistency in the soils the less of a correction factor may be used Bioretention swales Approximately 1 soil test pit boring per 200 feet of swale and within each length of road with significant differences in subsurface characteristics However if the site subsurface characterization including soil borings across the development site indicate consistent soil characteristics and depths to seasonal high ground water conditions the number of test locations may be reduced to the minimum frequency indicated above I Large Scale Pilot Infiltration Test PIT Large scale in situ infiltration measurements using the Pilot Infiltration Test PIT described below is the preferred method for estimating the measured initial saturated hydraulic conductivity Ksa of the soil profile beneath the proposed infiltration facility The PIT reduces some of the scale errors associated with relatively small scale double ring infiltrometer or stove pipe infiltration tests It is not a standard test but rather a practical field procedure recommended by Ecology s Technical Advisory Committee Infiltration Test Excavate the test pit to the estimated surface elevation of the p
452. ting or erecting said structures complete DI 03 REFERENCES 522 1 Specifications for Pervious Concrete Pavement Published by the American Concrete Institute Farmington Hills Michigan Dam Safety Guidelines Dam Safety Division Washington State Department of Ecology current edition Design of Small Dams Bureau of Reclamation United States Department of the Interior third edition 1987 Flood Insurance Study King County Washington and Incorporated Areas National Flood Insurance Program Federal Emergency Management Agency current edition Guidelines and Resources for Implementing Soil Quality and Depth BMP 5 13 in WDOE Stormwater Management Manual for Western Washington Multiple authors 2009 or current http soilsforsalmon org Guidelines for Bank Stabilizations Projects King County publication Hydraulic Code Rules Chapter 220 110 Washington Administrative Code Integrated Streambank Protection Guidelines Washington Department of Fish and Wildlife and Washington Department of Transportation April 2003 Land Use Code LUC Bellevue City Codes current edition Low Impact Development Technical Guidance Manual for Puget Sound Puget Sound Action Team and Washington State University Peirce County Extension January 2005 or current edition Online Geodatabase GeomapNW The Pacific Northwest Center for Geologic Mapping Studies http geomapnw ess washington edu Rain Garden Handbook f
453. tion pervious pavement may be used is 0 25 inches per hour which many till soils may exhibit For sites with relatively low infiltration rates it is important to keep the size of the contributing drainage area relatively small with respect to the available footprint for the infiltration BMP Section D6 03 3 provides Sizing Factors for infiltration BMPs for design infiltration rates ranging from 0 25 inches per hour to 1 0 inch per hour or greater All infiltration rates in Table 6 13 represent design infiltration rates measured infiltration rates with appropriate correction factors applied D6 9 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Refer to Sections D2 06 Site Planning and Submittals and D4 06 7 Infiltration Systems for methods to be used for identifying site soils and determining the infiltration rates for the native soils For projects not required to meet runoff treatment or flow control standards a simplified method for infiltration testing may be used per D4 06 7 D See Section D6 03 for on site BMP sizing D6 02 3 Step 2 Site Layout and Use Development projects that trigger on site stormwater management must use Smart Site Design practices Section D6 03 1 In addition to these Smart Site Design practices site layout and use also includes consideration of setback requirements Section D4 07 and locating BMPs to take advantage of existing topography and soils Consideration is also given in this step for w
454. tion planter to also evaluate the amount of residual flow control needed See Chapter D3 for guidance on hydrologic modeling for sizing flow control and runoff treatment facilities B Pervious Pavement Pervious pavements facilities are alternatives to conventional pavements asphalt or concrete that allow water to pass through the wearing course into a rock reservoir level where it can infiltrate naturally into the underlying soils see Standard Detail NDP 11 D6 28 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 17 There are many allowed varieties of pervious pavements that fall into three primary categories il Asphalt Concrete Pavers Applicability Pervious pavement can be used in areas such as parking lanes along residential streets low volume residential drives and access roads driveways sidewalks bike lanes and other paths or trails emergency and utility maintenance roads and parking lots that are not High Vehicle Traffic Areas see Section 3 3 7 Volume DOE Manual When pervious pavement is managing its own footprint only e g additional runoff not directed to it it can be used in areas with design infiltration rates as low as 0 25 inches per hour Grass or gravel pavers can be used in recreational or open spaces that are subject to occasional vehicle traffic e g maintenance vehicles or in fire lanes Slopes must be less than five 5 percent for pervious asphalt six 6 percent for pervi
455. to size overflow conveyance systems to properly route flows away from structures The assumptions to be used in the water balance model are summarized in Table 6 9 D6 36 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 6 9 Spreadsheet Based Modeling Assumptions for Rain Barrels or Cisterns with Water Reuse Variable Assumption Precipitation Series Obtain at least the last 10 years of historical rainfall data from SeaTac or other approved station A daily or finer time step must be used Computational Time Step Daily or finer Inflows to Facility Daily or finer rainfall volume assumed to equal daily or finer inflow to the facility This neglects abstraction or evaporation that may occur on the roof surface Storage Available storage volume in rain barrel or cistern tanks below the overflow invert elevation Water Reuse Daily or finer cumulative outflows corresponding with irrigation outdoor cleaning indoor plumbing or any other water use demands Overflow To be solved for in the model on a daily or finer time step Rain Barrel Flow Control Credits for rain barrels are provided in Section D6 03 4 Cisterns with Detention Sizing Factors for cisterns are provided in Section D6 03 4 for meeting on site stormwater management MRS and flow control MR7 requirements Sizing factors for flow control are intended for conceptual design only The Developer is required to show ind
456. to determine which governs Inlet Control Analysis Nomographs such as those provided in Figure 4 10 and Figure 4 11 may be used to determine the inlet control headwater depth at design flow for various types of culverts and inlet configurations These nomographs were originally developed by the Bureau of Public Roads now the Federal Highway Administration FHWA based on their studies of culvert hydraulics These and other nomographs can be found in the FHWA publication Hydraulic Design of Highway Culverts HDS No 5 Report No FHWA IP 85 15 September 1985 or the WSDOT Hydraulic Manual Also available in the FHWA publication are the design equations used to develop the inlet control nomographs These equations are presented below For unsubmerged inlet conditions defined by lt 3 5 Form 1 HW D HJD K Q AD 0 5S 4 4 Form 2 HW D K Q AD y 4 5 For submerged inlet conditions defined by gt 4 0 HWID Y 0 5S 4 6 where HW headwater depth above inlet invert ft D interior height of culvert barrel ft H specific head ft at critical depth dc Vc2 2g Q flow cfs A full cross sectional area of culvert barrel sf S culvert barrel slope ft ft K M c Y constants from Table 4 6 The specified head H is determined by the following equation D4 35 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 H d V Dg 4 7
457. to the width of the equipment blade A free draining compressible buffer material pea gravel corrugated vinyl or foam product shall be placed on the surface soils to prepare the site for placement of pre cast or site poured wall components This buffer material separates the base of the grade beam from the surface of the soil to prevent compaction from expansion or frost heave and in some cases is employed to allow the movement of the saturated flows under the beam or wall Where possible roof runoff must be infiltrated or dispersed upslope of the structure to take advantage of infiltration and subsurface storage areas that would otherwise be lost in construction and placement of conventional dug in foundation systems Passive gravity systems for dispersing roof runoff are preferred however active systems may be used if back up power sources are incorporated and a consistent manageable maintenance program is ensured See Section 6 5 of the LID Manual for additional design information Where roof runoff is dispersed on the up gradient side of a structure in accordance with the design criteria in Roof Downspout Dispersion Section D6 03 1 F model the tributary roof area as pasture on the native soil Where terracing or step forming is used on a slope the square footage of roof that can be modeled as pasture must be reduced to account for lost soils In step forming the building area is terraced in cuts of limited
458. torm All installation work for the pump electrical connections and piping will require applicable building electrical and plumbing permits The pump system force main shall connect into the top of a private storm drain pipe or connect to a private catch basin and gravity flow to the public stormwater system Direct pressure discharge to a gutter ditch or stream shall not be allowed D4 85 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 No public drainage shall be conveyed to the private pumped system A maintenance and Operation Schedule shall be prepared and submitted for review prior to UE acceptance and building occupancy A note on the approved plan shall stipulate that the private property owner s shall be responsible for any and all claims for injuries and damage due to the operation or non operation of the pump system D4 07 D4 07 1 SETBACK REQUIREMENTS Setback Requirements for Surface Water BMPs Standard clearances from other Utility pipes apply to all facilities per D4 04 3 Setbacks may be modified if the Developer adequately demonstrates that the potential for flooding or erosion impacts are minimal if approved by the Utilities Reviewer Table 4 12 Setback Requirements for Storm Drainage Features Storm Drainage Feature Flow Control Treatment and Onsite Facilities including Infiltration Systems unlined Wetponds Detention ponds Bioretention rain garden bioretention swale bioretention in
459. tropolitan Seattle Water Pollution Control Aspects of Aquatic Plants 1990 Hortus Northwest Wetland Plants for Western Oregon Issue 2 1991 Hitchcock and Cronquist Flora of the Pacific Northwest 1973 Table taken from Table 6 4 1A Emergent Wetland Plant Species Recommended for Wetponds from the 1998 Surface Water Design Manual D7 9 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 D7 04 4 A B Underground Detention Systems Vaults Materials for stormwater detention vaults shall be as approved by the City of Bellevue Building Official Any metal structural components shall be protected from corrosion and have a low maintenance coating The Developer shall submit proposed metal protective coatings with supporting documentation for review prior to drainage plan approval Coatings shall have 50 year design life Backfill material shall conform to Section 9 03 14 Gravel Borrow of the Standard Specifications Excavated material may be used as backfill when it has been demonstrated by the Contractor to meet gradation and compaction requirements When the structural design does not take into account hydrostatic pressure or buoyancy footing drains shall be provided around the perimeter of the vault Footing drains shall be a minimum of 6 inch diameter PolyVinyl chloride PVC pipe SDR 35 with laser cut slotted perforations Footing drains shall be backfilled with material which conforms to Section 903 12
460. uce a vegetative protective cover and a root reinforcing matrix in the soil mantle This root reinforcement serves several purposes The developed anchor roots provide both shear and tensile strength to the soil thereby providing protection from the frictional shear and tensile velocity components to the soil mantle during the time when flows are receding and pore pressure is high in the saturated bank The root mat provides a living filter in the soil mantle that allows for the natural release of water after the high flows have receded D4 8 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 The combined root system exhibits active friction transfer along the length of the living roots This consolidates soil particles in the bank and serves to protect the soil structure from collapsing and the stabilization measures from failing The vegetative cover of bioengineered systems provides immediate protection during high flows by laying flat against the bank and covering the soil like a blanket It also reduces pore pressure in saturated banks through transpiration by acting as a natural pump to pull the water out of the banks after flows have receded The King County publication Guidelines for Bank Stabilization Projects primarily focuses on projects on larger rivers and streams but the concepts it contains may be used in conjunction with other natural resource information for stabilization projects on smaller systems The WDFW Integrated St
461. udinal slope of the reverse slope sidewalk shall be 10 percent Runoff from the reverse slope sidewalk must sheetflow to an adjacent downslope vegetated surface that is at least 10 feet wide and not directly connected into the storm drainage system Vegetated area must be native soil or meet guidelines in BMP T5 13 of the DOE Manual Volume 5 Section 5 3 1 Vegetated area shall have a maximum slope of 8 percent perpendicular to the alignment of the reverse slope sidewalk see Standard Detail NDP 21 The shoulder on the downslope side of the reverse slope sidewalk shall be no greater than 1 foot wide Reverse slope sidewalks shall be designed in accordance with the above requirements and standard sidewalk design requirements see Standard Detail TE 11 iv Sizing When flow control is required the assumptions listed in Table 6 12 can be used to calculate the amount of credit to be attributed to the reverse slope sidewalk in sizing the downstream flow control facility See Chapter D3 for guidance on hydrologic modeling for sizing flow control and runoff treatment facilities D6 42 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 6 12 Continuous Modeling Assumptions for Reverse Slope Sidewalks Precipitation Series SeaTac 50 year hourly time series with appropriate scaling factor based on project location Land Use Input for Reverse Slope Landscaped area on underlying soil with flat or moderate Sidewalk slope based
462. uilt shall contain the following information submitted in both electronic AutoCAD format and on a mylar plan stamped and signed by the surveyor Horizontal locations shall be recorded to within one tenth 0 1 of a foot Rim and invert elevations at drainage structures shall be recorded to within one one hundredth 0 017 of a foot Use Washington Coordinate System NAD 83 NSRS 2011 North Zone as the basis of bearings for all surveys Prepare survey according to City of Bellevue NAVD 1988 vertical datum and state that it was the datum used All pipe lengths and dimensions are based on horizontal distances unless slope is greater than 1096 to measure horizontal distance inspector should note that length is slope distance References dimensions from right of way centerline for utility features in the public right of way or from property line for utility features located within easements As built information shall be recorded on plan and profile views of the contract drawings The profile view shall note any changes from the design finished grade over each pipe line As built plans shall be submitted to Bellevue Utilities using the approved mylar plan set as the basis for the redlined as built plans An as built plan set in digital format shall also be submitted The digital format shall be in AutoCAD Version 2004 through 2011 no older or newer The DWG file s shall be submitted on CD ROM The Developer will perform as buil
463. uld be any adverse effects caused by seepage zones on nearby building foundations basements roads parking lots or sloping sites An inspection of the soil by a civil geotechnical engineer shall be made after the system is excavated before the gravel backfill is placed to confirm that suitable soils are present The geotechnical report shall be amended to reflect this inspection and confirmation of suitable soils D Infiltration Test Requirement The design infiltration rate for flow control or treatment infiltration facilities shall be determined using one of the two methods outlined in Section D4 06 7H entitled Determining Subgrade infiltration rates in 1 PIT tests 2 Soil Grain Size Analysis Method D4 76 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 The design infiltration rate for on site stormwater management infiltration BMPs for projects where MRS applies but MR6 and MR7 do not may be determined with the Simplified Infiltration Test included below or by one of the two methods outlined in Section D4 06 7H entitled Determining Subgrade Infiltration Rates 1 PIT tests 2 Soil Grain Size Analysis Method Simplified Infiltration Test Soil Examination Locate potential site for on site stormwater management facility such as rain garden pervious pavement or infiltration system and dig a hole at least 1 foot below the subgrade of the proposed BMP in the location of the proposed BMP and 1 2 feet in diameter If th
464. unoff from the project site This combined duration curve would be used to design the new or modified flow control facility and demonstrate compliance for the performance of the existing pond and the new pond designed to current standards When choosing option 3 the Developer must demonstrate that both systems will operate as intended This option generally requires most of the existing detained development to be hydraulically separated from the proposed development D4 06 3 Multi Purpose Use Detention facilities designed for multiple use sport courts neighborhood parks play areas picnic areas etc are allowed Storage for runoff from more frequent storms shall be stored separately from the multiple use areas At a minimum the detained volume for the 2 year design storm shall be used to size the separate facilities Multi use amenities shall be anchored to prevent floatation Maintenance of multi use amenities will be by others and Developer shall make arrangement for such maintenance D4 06 4 Control Structures A General Use the criteria and methods set forth in Volume III Section 3 2 4 of the DOE Manual except as modified herein Allowable release rates shall be achieved using a tee type flow restrictor to meter flows All restrictor devices to be maintained by the City shall be equipped with a shear gate B Clearances The minimum clearance between the rim of the overflow standpipe and the bottom side of the structure s to
465. urium Two row stonecrop Succulent Sedum Vera Jameson Showy stonecrop Succulent Sisyrinchium idahoensis Blue eyed grass Grass Thymus serphyllum Thyme Herb woody Triteleia hyacintha Fool s onion Herb Allium cernuum Nodding wild onion Herb Polypodium hesperidum Western polypody Fern Lupinus polyphyllus Blue pod lupine Herb Fragaria chiloensis Sand strawberry Herb Native to the Pacific Northwest https www seattle gov dpd GreenBuilding Resources TechnicalBriefs DPDS_009485 asp des ign D6 04 9 For installation instructions and limits on use of materials for Natural Drainage Practices install per the design engineer s or manufacturer s direction or see the LID Manual available online per Section D1 03 Construction Requirements D6 04 10 A Catch basins for use in residential lots Miscellaneous Products The following plastic catch basins or Equal are approved 9 x 9 ADS models 0909SD2 0909SD4 D6 63 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 12 x 12 ADS models 1212SD2 1212SD4 NDS 1216 riser 1217 riser with two openings 1225 sump box 12 18 24 diameter Hanson Type 45 12 18 Diameter Nyloplast Drawing No 7001 110 374 D6 64 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 END OF SECTION D D6 65 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 CHAPTER D7 MATERIALS TABLE OF CONTENTS D7 01 GENERAL 5 setis nda p
466. ut Infiltration cannot be met as described above next evaluate the site for Roof Downspout Dispersion If the design criteria listed in the DOE Manual for splash blocks Volume III Section 3 1 2 Downspout Dispersion Systems or sheet flow dispersion Volume V 5 3 1 Dispersion and Soil Quality BMPs BMP T5 12 can be met install one of the following at each downspout splash block pop up emitter rain barrel s rain harvesting cistern or vegetated roof with a D6 14 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 splash block at the overflow or direct roof runoff to a bioretention facility or pervious pavement For surfaces that do not have concentrated flows use Sheet Flow Dispersion per Section D6 03 1 G Dispersion trenches should only be considered as an option to manage roof runoff if site and design conditions are not met for any of the BMPs listed prior in Tables 6 2 or 6 2B whether for a particular downspout or all roof runoff and a storm stub is not available or is too high Design and Sizing Design splash blocks per the DOE Manual Volume III Section 3 1 2 as modified by Section D6 04 6 Design pop up emitters per Standard Detail NDP 20 and Section D6 04 6 A maximum of 700 square feet of roof area may drain to each splash block or pop up emitter Vegetated flow paths requirements for splash blocks apply to pop up emitter discharge areas or runoff can be directed to a bioretention facility A catch basin or
467. ve joints Special care shall be taken to see that all joints are well filled with mortar D8 06 FLOW CONTROL DETENTION FACILITIES D8 06 1 Control Structures Follow construction practices set forth for manholes catch basins and inlets D8 06 2 Ponds A Embankments D8 5 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Hill placed around structures in the berm embankment shall be placed in four 4 inch maximum lifts and compacted to 95 percent of ASTM D 1557 B Vegetation amp Landscaping Vegetation and landscaping shall conform to Section 8 02 Roadside Planting of the Standard Specifications For City maintained facilities all plant material shall be guaranteed for a period of one 1 year after acceptance Defective materials shall be promptly replaced in like kind and size guarantee period be extended for those defective materials which replaced D8 06 3 Underground Detention Systems A Vaults Cast in Place and Precast concrete vaults shall conform to Section 6 02 Concrete Structures of the Standard Specifications as modified herein and as directed by the Building Official B or Pipes Tanks and pipes used for stormwater detention systems shall conform to the applicable sections of Division 7 Drainage Structures Storm Sewers Sanitary Sewers Water Mains and Conduits of the Standard Specifications as modified herein D8 06 4 Storm Water Detention Facility Leak
468. verflow conveyance structures are necessary for all bioretention structures to safely convey flows that exceed the capacity of the facility and to protect downstream natural resources and property to an approved discharge point s Approved discharge points in order of preference include Surface waters Public storm drain pipes Conveyance to approved discharge points in order of preference include Direct pipe connections Ditch and culvert system Gutter or street flow line Surface dispersal Overflows may be to the approved discharge point s or through interflow to the surface or to surface discharge or in combination Overflows may be piped or daylighted through a storage reservoir or dispersion BMP or through overtopping of the facility Plans shall indicate all flow paths Designers are recommended to consider flooding and nuisance ponding risks associated with larger peak flows During large storm events capacity will be limited at the approved discharge point s and backwater calculations may be required If a facility is designed for full infiltration a constructed overflow is not required Plans should indicate surface flow paths in case of failure of the facility Native Soil Subgrade Determine the native soil infiltration rate and correction factors to be applied long term design infiltration rate or design infiltration rate in accordance with Section D6 02 2 C and Section D4 06 7 D Cl
469. vidence of existing or anticipated problems D4 5 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Level 2 Analysis At each existing and or predicted drainage problem location identified in the Level 1 analysis develop hydrographs or Rational Method peak flow rates for the 100 year 24 hour design storm events for the total composite drainage area tributary to that location for existing runoff conditions excluding the proposed project site runoff Determine the capacity of the existing drainage system Non survey field data hand tapes hand level and rods etc and computations using Manning s equation for normal flow are acceptable for this analysis At each existing and or predicted drainage problem location compute the proposed project s developed runoff hydrograph Evaluate impacts of adding the controlled peak runoff from the proposed project site to the peak runoff from the total composite drainage area tributary to these locations Additional information may be required to determine that impacts have been adequately mitigated and to verify the capacity of the conveyance system D4 03 2 Solutions to Identified Drainage Problems For any anticipated off site problem resulting from the development or redevelopment the Developer must demonstrate that the proposed project has been designed to mitigate the anticipated problem As an alternative the Developer with approval by the City may arrange with the owners of the off
470. w Profile Computation eene D4 22 Figure 4 7 Direct Step Backwater Method Example D4 23 Figure 4 8 BWCHAN Computer Subroutine Variable Definitions D4 24 Figure 4 9 Inlet Outlet Control D4 40 Figure 4 10 Headwater Depth For Smooth Interior Pipe Culverts With Inlet D4 41 Figure 4 11 Headwater Depth For Corrugated Pipe Culverts With Inlet Control D4 42 Figure 4 12 Head For Culverts Pipe W N 0 012 Flowing Full With Outlet Control DA 43 Figure 4 13 Head For Culverts Pipe W N 0 024 Flowing Full With Outlet Control D4 44 Figure 4 14 Critical Depth Of Flow For Circular Culverts D4 45 Figure 4 15 Computer Subroutines Bwpipe And Bweulv Variable Definitions D4 46 Figure 4 16 Nomograph For Sizing Circular Drains Flowing Full D4 53 Figure 4 17 Circular Channel Ratios ioe Sih eie D4 54 Figure 4 18 Backwater Calculation Sheet dtes D4 55 Figure 4 19 Backwater Calculation Example uai D4 57 Figure 4 20 Bend Head Losses In Structures eia neo ed eni red peiores D4 58 Figure 4 21 Junction Head Loss In Structures ee de
471. where de critical depth ft see Figure 4 14 Ve flow velocity at critical depth fps g acceleration due to gravity 32 2 ft sec The appropriate equation form for various inlet types is specified in Table 4 6 For mitered inlets use 0 7S instead of 0 5S Note Between the unsubmerged and submerged conditions there is a transition zone 3 5 lt Q AD lt 4 0 for which there is only limited hydraulic study information The transition zone is defined empirically by drawing a curve between and tangent to the curves defined by the unsubmerged and submerged equations In most cases the transition zone is short and the curve is easily constructed Table 4 6 Constants For Inlet Control Equations Shape and Material Inlet Edge Description Equation Form M Circular Concrete Square edge with headwall gt 0 67 Groove end with headwall I 0 74 Groove end projecting 0 69 Circular Headwall 0 69 Mitered to slope 0 75 Projecting 0 54 Rectangular Box 30 to 75 wingwall flares 0 81 90 and 15 wingwall flares 0 80 0 wingwall flares 0 82 CM Boxes 90 headwall 0 69 Thick wall projecting I 0 64 Thin wall projecting 0 57 Arch CMP 90 headwall 0 57 Mitered slope 0 75 Projecting 0 53 Bottomless Arch 90 headwall 0 69 Mitered slope 5 0 75 Thin wall projecting 0 57 Circular with Smooth tapered inlet th
472. with Section D6 03 1 A native vegetation in a Native Growth Protection Easement Full Infiltration Infiltrate 100 of site runoff Amended Preserve native soils or All projects Required for all disturbed pervious areas Soils amend with compost Comply with Section D6 03 1 D Tier 2 Retain Runoff On site After all Tier 1 BMPs have been evaluated and implemented per the requirements in Table 6 1 the following Tier 2 BMPs must be evaluated for implementation in the order presented to retain runoff that is generated by the project All runoff from impervious surfaces should be managed with at least one of the following BMPs from Table 6 2A as site conditions allow without causing erosion or flooding on site or downstream NDPs may be substituted for the required roof downspout controls and dispersion BMPs or used in addition to those required BMPs wherever site conditions allow and design criteria can be met Table 6 2B Maximizing on site stormwater management through the use of roof downspout control and dispersion BMPs in combination with NDPs may eliminate or substantially reduce flow control requirements MR7 thereby reducing construction costs and long term maintenance requirements as well as help reduce local and regional flooding D6 4 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Table 6 2A Required Tier 2 On site Stormwater Management BMPs BMP Description Applicabilit
473. xtension Agreement Project The structure facility system or improvement to be constructed in whole or in part Reference Specifications Reference specifications shall mean the technical specifications of other agencies incorporated or referred to herein Replaced Impervious Surfaces SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 Means for structures the removal and replacement of impervious surfaces down to the foundation For other impervious surfaces the removal down to bare soil or base course and replacement Sizing Factor A number used to size an on site stormwater management facility to meet a particular Minimum Requirement expressed as a percentage of the contributing impervious area draining to the facility Slope Degree of deviation of a surface from a horizontal measured as a numerical ratio percent or degrees Expressed as a ratio the first number is the horizontal distance run and the second is the vertical distance rise as 2 1 2 1 slope is a 50 percent slope Expressed in degrees the slope is the angle from the horizontal plane with a 90 degree slope being vertical and 45 degrees being 1 1 or 100 percent Slopes of 20 percent of more shall be determined by those that have a rise of at least 5 feet and exceed 1 000 square feet in area Standards City of Bellevue Utilities Department Surface Water Engineering Standards Standard Details
474. y Requirements Roof Downspout Infiltration Trench or Drywell Residential and Required where design Infiltration small criteria and setbacks are Allowable alternatives include minimal commercial lots met excavation foundation or directing roof runoff to bioretention or pervious Comply with Section pavement can also combine with rain D6 03 1 E recycling or vegetated roof See Table 6 2B Roof Downspout Connect roof downspouts to splash Residential and Required where design Dispersion blocks or pop up drainage emitters small criteria and setbacks are Splash Blocks or commercial lots met if Downspout Pop up Drainage Allowable alternatives include minimal Infiltration is not Emitter excavation foundation or directing roof feasible runoff to bioretention or pervious pavement can also combine with rain Comply with Section recycling or vegetated roof See Table D6 03 1 F 6 2B Concentrated Flow dispersion for pavement patios and Residential and Required where design and Sheet Flow other impervious surfaces and roofs small criteria and setbacks are Dispersion without gutters commercial met lots roads Allowable alternatives include pervious Comply with Section pavement minimal excavation D6 03 1 G foundations and reverse slope sidewalks where conditions allow See Table 6 2B Table 6 2B Natural Drainage Practices NDPs Allowed as Alternatives to or in Addition to Required Tier 2 BMPs
475. y of STORM AND SURFACE G USE 10 CEMENT WITH 90 SOIL MIX ADD ENOUGH WATER TO Bellevue WATER UTILITY DRY MIX IHAT WILL HOLD 115 5 OLDED INTO A BALL LACE TWO PIPE CLAMPS 4 FROM BLOCK DS TO PROVIDE ANCHORAG L CEMENT MIX DErnaAwn Orrwoanm JANUARY 2015 MAXIMUM DIS SHALL 6 SEAL BOTH ENDS OF CASING WITH MANUFAC ED RUBBER SEALING D PLACE D SPACER MAXIMUM OF 1276 END OF CASING TYP E SPACER SHALL BE D OF EACH SEGMEN E LIMIT OF INSERTIO E JOINT IS COMPLE CONTACT WITH THE AT THE SPACER PU RELIEVES COMPRESSIO STEEL PIPE CASING MILL PIPE OR DUCTILE E 2 STAINLESS STEEL HOSE CLAMPS TO SECURE RUBBER FAL 1 ON CARRIER PIPE AND 1 ON CASING PIPE AWWA CARRIER PIPE PVC SDR 35 PVC C900 C905 DR 18 OR DI CLASS 52 CASING THICKNE ww o fe e ES CASING SPACERS SHALI ER POSITION
476. y per Section D4 approximate base flood elevation water 2 feet above the 04 5 C downstream overflow elevation of a water See further requirements in Section feature for which a floodplain has not been D4 04 5 C determined in accordance with BCC 20 25H 175 The project site does not meet the above Minor Floodplain Study e Backwater model thresholds and is either on land that is per Section D4 04 5 D e Submit an engineering plan with outside of an already delineated Zone A determined base flood elevation floodplain i e without base flood elevations determined or is adjacent to a See further requirements in Section water feature for which a floodplain has D4 04 5 D not been determined in accordance with 20 25 175 project site is land that is partially Major e Show mapped floodplain floodway or fully within an already delineated Floodplain Floodway on the site improvement plan and floodplain of a river or stream or is Study per Section D4 indicate base flood elevation determined by a Minor Floodplain Study 04 5 E to be partially or fully within the floodplain of a river or stream e See further requirements in Section D4 04 5 E B No Floodplain Study Required If the proposed project site is on land that is outside of an already delineated floodplain and is above the already determined base flood elevation for that floodplain based on best available floodplain data
477. yard drain at the base of the downspout upslope of the pop up emitter is recommended Design dispersion trenches per Standard Detail NDP 22 and size and apply flow credits per Volume III Section 3 1 2 of the DOE Manual Maintenance To maintain splash blocks and pop up emitters inspect for appropriate placement after a rain event and if flooding or erosion occurred regrade or place 2 4 washed rock or river rock at the discharge point if erosion is occurring Inspect splash blocks and pop up emitters annually for placement erosion and flooding and clear debris from downspouts and gutters Direct water downslope and away from structures Maintain dispersion trenches per Volume IV Section 2 2 of the DOE Manual Dispersion trenches shall be provided with access for ongoing maintenance at least three 3 feet in width G Concentrated and Sheet Flow Dispersion Description Applicability and Limitations For impervious surfaces that are not managed using the Roof Downspout techniques above evaluate the site for the use of Concentrated Flow Dispersion BMP T5 11 or Sheet Flow Dispersion BMP T5 12 Evaluate all unmanaged impervious surfaces meeting the criteria in the DOE Manual Volume V Section 5 3 1 including sport courts driveways roofs without gutters sloped areas cleared of vegetation non native landscaping or roadways Design and Sizing Design concentrated and sheet flow dispersion and apply flow credits per the D
478. ypassed around the wetland A wetland can be considered for hydrologic modification and or stormwater treatment in accordance with Guide Sheet 1B in Appendix I D on the Stormwater Management Manual for Western Washington 2005 Stormwater treatment and flow control facilities shall not be built within a natural vegetated buffer except for necessary conveyance systems as approved by the Permittee or as allowed in wetlands approved for hydrologic modification and or treatment in accordance with Guidesheet 1B in Appendix I D of the Stormwater Management Manual for Western Washington 2005 When stormwater treatment and flow control facilities can be built within a wetland the facilities must be designed in accordance with other sections in these Standards An adopted and implemented basin plan prepared in accordance with the provisions of BCC 24 06 140 may be used to develop requirements for wetlands that are tailored to a specific basin When a wetland is allowed to be filled per the Land Use Code runoff treatment and conveyance equivalent to that provided by the existing wetland to be filled is required in addition to any other runoff treatment required by these standards and applicable codes D9 2 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 END OF CHAPTER D9 D9 3 SURFACE WATER ENGINEERING STANDARDS JANUARY 2015 APPENDIX D 1 STANDARD DETAILS DETAIL NUMBER CONCRETE INLE Tarni a ansa sanu ma ut auqa a us

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