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Design Manual - Town of Chapel Hill

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1. NES COPS SR IN TN LL UM an S MESES we RISERS AER gt aun SAS PAG SSE AS SA M Ce LIN IN EN INL SX I Rainfall P inches PN TAIN LALY LINE T RNITIN LS EN INIM LETT IS LE LN IN AIN NX NM LINE TL NLIS IN AAA AY FIGURE 2 A 1 SOLUTION OF RUNOFF EQUATION AAT PST SL UNAS sayout 0 330414 338414 210 55 Second Ed June 1986 APPENDIX 2 P 5 of 7 se ino pue 9g e d ejejodueyu Jequiny ng youny pesodolg SN 717 vA i VVSY LI YT Y VV vi LA a V 0 A ULLA Y vL Y 422220244 AZ VV V tALAAAALL SV 2242 CAAA Ae COC COE ec ec eee ue jo suypeipunu euinjoA youny 3ueuidojoAeq e1d 0 peunbey 10 0 d XOA SOS TV T JequimwN youny APPENDIX 2 P 6 of 7 00 7 7 uo LEA VA TADA EN LAZY 1477 LLAMVV Y Y Y Y VY Y 127 LAZY VY Y yvy 222727
2. APPENDIX 2 P 1 of 2 OUTLET FT2OTECTION ENERGY DISIPATER FILTER FABRIC SECTION AA STILUNG BASIN Sd MN x 4 FILTER FABRIC 4 MIN fc Figure 2 F 1 1 tLe tS THE TOTAL LENGTH OF THE RIP RAP APRON THE MUNINUN LENGTH SHALL BE 4 TIMES THE DIAMETER OF THE AFE THE MIMMUM VADTH HIS 5 TIMES THE DIAMETER OF THE AFE LARGER APRONS MAY BE REQUIRED BASED ON THE VELOCITY AND SCOUR CALCULATION 2 h 5 TIMESTHE MAXIMUM STONE DIAMETER BUT NOT LESS THAN 2 IN 5 iN A WELL DEFINED CHANNEL THE APRON SHALL EXTEND TO THE TOP OF THE BANK OR 6 WN ABOVE THE MAXIMUM TAIL VVATER ELEVATION FOR THE DESIGN STORM VHHICH EVER 5 LESS 4 FILTER FABRIC SHOULD BE INSTALLED BETWEEN RIP RAP AND SOIL FOUNDATION STILLING BASINS ARE THE PREFERRED OUT TREATMENT THE MIMMUM FOOL LENGTH IS TIMES THE AFE DIAMETER THE MINIMUM TOTAL LENGTH OF THE RIP RAP APRON SHALL BE 4 TIMES THE DIAMETER OF THE EXIT VELOCITY IN FEET PER SECOND APPENDIX 2 F P 2 of2 FIGURE 2 F 2 STONE WEIGHT IN POUNDS 5 20 60 200 600 1000 2000 4000 1 10 40 100 400 800 1500 3000 5000 FOR STONE WEIGHING 165 LBS PER CU FT EQUIVALENT SPHERICAL DIAMETER OF STONE IN FEET RIPRAP SIZE FOR USE DOWNSTREAM OF ENERGY DISSIPATORS Source U S D O T APPENDIX 2 G P 1 of 6 Town of Chapel Hill Stormwater Impact Statement and Stormwater Management Plan Guidelines Revised March 14 2003 R
3. 2 Any tree roots exposed by construction will be severed cleanly with an appropriate pruning tool 3 The soil within the critical root zones of existing trees will not be driven on or otherwise disturbed during the installation of landscaping On development applications for non residential and multi family construction the following additional note should also be included on the plans 4 Landscape Protection Supervisor who is registered with the Town of Chapel will be present on site at all times when the following activities are taking place clearing grubbing excavation grading trenching moving of soil installation and removal of tree protection fencing and the delivery transporting and placement of construction materials and equipment Tree Protection Fencing To properly protect and ensure the health of existing trees to remain protective fencing should be installed to protect no less than 75 of a tree s critical root zone When erecting fencing near trees that are not individually identified on the Landscape Protection Plan the fencing location should be shifted where possible or a tree removed if its critical root zone is not adequately protected land disturbing activity storage of equipment building material soil and other debris should be kept within the area of development activity and outside of the protective fencing The Town s standard for tree protection fencing is o
4. Grey owl red cedar Across N C Shrub evergreen Magnolia virginiana Sweetbay magnolia Coastal plain piedmont Tall green evergreen Myrica cerfera Wax myrtle Across N C Large shrub Pinus palustris Longleaf pine Coastal plain piedmont Tall tree evergreen Pinus taeda Lobolly pine Piedmont coastal plain Medium tree evergreen Quercus padogda Cherrybark oak Piedmont coastal plain Large tree Sambucus canadensis American elderberry Across N C Medium shrub Scuttellaria integrifolia Scull cap Across N C Ground cover Note Plant sources include the NCDENR DWQ Stormwater Manual and the NCDWQ Wetlands Restoration Program Document Guidelines for Riparian Buffer Restoration Jan 2001 APPENDIX 2 D P 15 of 21 S GENERAL DESIGN CRITERIA FOR DETENTION RETENTION AND RE USE FACILITIES 1 Detention facilities shall be designed to meet one or all of the general performance criteria They shall be designed to fully drain the design storm runoff within a period of 2 to 5 days It is recommended that the facility fully drain within 72 hours They may serve as an infiltration device with engineered soils and a drainage system or may be conventional utilizing existing soils The following general design criteria apply Must include an engineered outlet riser structure and an emergency ov
5. floridanum Florida Anise Several varieties available Itea virginica Virginia Willow Leucothoe fontanesiana Drooping leucothoe Lonicera sempervirens Coral Honeysuckle Myrica cerifera nana Dwarf Waxmyrtle c Groundcovers and Grasses Scientific Name s Common Name s Remarks Andropogon gerardii Big Bluestem Coreopsis spp Tickseed Echinacea purpurea Purple Coneflower Monarda didyma Bee Balm Panicum virgatum Switchgrass Rudbeckia spp Black eye Susan 33 LANDSCAPE INSTALLATION AND MAINTENANCE SPECIFICATIONS 3 3 4 _ Materials Requirements a Plant Materials The American Standard for Nursery Stock published by the American Society of Nurserymen should be used for determining caliper heights widths and ball sizes for all plants Plant material should be free of any diseases funguses or insect infestations Town standard minimum planting sizes are listed below Larger sizes may be required however for specific sereening landscape applications including parking lot screening Ground Cover 2 pots Shrubs 18 in height Small Trees 5 in height Large Trees 2 caliper Street Trees 12 in height limbed up to a minimum of 7 in areas of pedestrian traffic b Topsoil Mix topsoil mixes used for finish grading and planter applications should be the site s original topsoil or should be tested by N C Department of Agriculture t
6. 444 2222222 Vv 22277 VVV ZA AAA 444200767 WV AVV PY vvv PALA 74 4444 AZ V VOR A VY VV 44424 47 LAL s n udep pue g e2g ejejodieju 1 ening jjoumJ pesodosg to JequinN youny Bunspx3 e you ue stppeipunu jueuidojaAoq o14 urejurey NOILVN04 SOS V 7 FUNDA APPENDIX 2 A P 7 of 7 RDU N C RAINFALL FREQUENCY DATA TABLE 2 A 2 DEPTH DURATION FREQUENCY TABLE Return Period Duration 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year inches inches inches inches inches inches 5 minutes 0 48 0 55 0 60 0 68 0 75 0 81 10 minutes 0 79 0 92 1 02 1 17 1 28 1 40 15 minutes 1 01 1 18 1 31 1 51 1 66 1 81 30 minutes 1 35 1 64 1 85 2 16 2 40 2 64 60 minutes 1 70 2 12 2 41 2 84 3 17 3 50 2 hours 1 91 2 40 2 74 3 23 3 61 4 00 3 hours 2 12 2 68 3 07 3 62 4 06 4 49 6 hours 2 65 3 38 3 90 4 62 5 19 5 75 12 hours 3 13 4 02 4 64 5 52 6 20 6 88 24 hours 3 60 4 65 5 38 6 41 7 21 8 00 TABLE 2 3 INTENSITY DURATION FREQUENCY DATA Return Period Duration 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year in hr in hr in hr in hr in
7. greater width may be required with the presence of on street parking narrow lanes for motorized vehicles unsuitable curb and gutter conditions or high volumes of truck traffic Pavement Design The surface shall be smooth with a uniform riding surface For maintenance reasons the bicycle lane should be constructed to the same standards as the adjacent traffic lane 4 15 WORK ZONE TRAFFIC CONTROL The developer is responsible for notifying the Engineering Department Emergency Medical Services Police and Fire Departments and residents of the area prior to implementation of work zone traffic control Street closings are not allowed unless approved by the Town Manager Lane closings are allowed only from 9 00 am to 4 00 pm on weekdays with the approval from the Town Engineering Department Work in the public right of way other than between 9 00 am and 4 00 pm weekdays is subject to approval by the Town Manager work zone traffic control devices and procedures shall conform to the requirements of the latest edition of the Manual on Uniform Traffic Control Devices MUTCD and the current edition of the North Carolina Department of Transportation NCDOT Supplement to the MUTCD for Streets and Highways the NCDOT Roadway Drawings and the current edition of the NCDOT Standard Specifications for Roads and Structures 4 16 DISABILITY ACCESS public pedestrian facilities shall to the extent practicable b
8. Between 1 and 6 inches per hour for imported soil sandy loam or loamy sand Constant or falling head permeability test USDA textural classification 15 required for approval by Town Engineer prior to installation Maximum depth of water 9 inches standard Some applications have deeper water allowances which make plant growth difficult Relative size of rain garden Varies but typically 5 to 9 percent of contributing watershed depending upon the amount of impervious surfaces Topographic feature locationing Flat areas that are downstream of impervious surfaces and adjacent to an existing storm sewer network or in an appropriate soil zone Existing water table Seasonally high water table should be below the bottom of the rain garden typically 4 to 6 feet below the surface of the rain garden Places to avoid placing rain gardens Areas that flood regularly at least yearly for at least two weeks hydric soils area and areas immediately adjacent to building and road foundations Mulches 3 to 4 inches Mulch should be double shredded hardwood not pine bark nuggets Pine straw may be used in some cases Native grass may be used in lieu of mulch Rock for gravel layer reservoir Washed 57 stone Separate gravel from fill soil and sub grade soil with a permeable geotextile fabric Drainage pipes perforated Design to c
9. MIN FILTER FABRIC TYHCAL DRY WELL WITH PRE TREATMENT SUMP Figure 2 D 3 APPENDIX 2 D P 10 of 21 P GENERAL DESIGN CRITERIA FOR BIO RETENTION AREAS RAIN GARDEN Sizing a Bio Retention Area The area size of the rain garden should generally vary between 5 percent and 7 percent of its drainage area depending upon the percentage of impervious surface Size the rain garden large enough to pond runoff from the first inch of rainfall in the drainage area To compute this multiply 0 79 inches by the impervious surface area draining to the bio retention area This will yield a ponding volume for standard bio retention areas If the bio retention area is also designed to meet the Town volume control criteria the larger of the two calculated volumes controls Note that the Town volume control criteria allows for total storage volume to include the sum of the volumes of ponding and voids in soil pipe and gravel reservoirs The rain garden shall be designed to pond water 9 inches deep before exiting the basin as surface flow The surface area required of a rain garden can be found using the following equation Rain Garden surface area Rain garden volume ponding Average depth of water 9 inches typical In the example given this equation would be Surface area 130 cubic feet 9 inches x 1 foot 12 inches 170 square feet The shape may be designed to best fit the site Minimum width is 15
10. Table of Contents Design Manual Chapel Hill North Carolina SECTION 1 INTRODUCTION 1 1 1 2 COMPLIANCE SECTION 2 STORMWATER MANAGEMENT 2 1 2 2 2 3 2 4 2 2 2 6 INTRODUCTION PERFORMANCE CRITERIA Total Suspended Solids Volume Rate Land Disturbance HYDROLOGIC DESIGN Hydrologic Methodology SCS Method Rational Method INTEGRATED MANAGEMENT PRACTICES BEST MANAGEMENT PRACTICES Structural IMP s BMP s Non structural IMP s BMP s STORMWATER IMPACT STATEMENT AND STORMWATER MANAGEMENT PLAN CRITERIA Application Submittal Checklist DRAINAGE FACILITY DESIGN Design Storms and Check Storms Design Standards Storm Drainage Pipe Inlet Location and Spacing Open Channels Ditches Curb and Gutter Subsurface Drainage APPENDIX 2 A SCS Runoff Curve Method APPENDIX 2 B Rational Method APPENDIX 2 C Rational Runoff Coefficients APPENDIX 2 D General Design Criteria for Structural Level Spreaders General Design Criteria for Buffers and Filter Strips General Design Criteria for Infiltration Devices General Design Criteria for Bio retention Areas Rain Gardens General Design Criteria for Detention Retention Re use Facilities General Design Criteria for Porous Pavement General Design Criteria for Manufactured Products APPENDIX 2 E Design Manual Hydrology Technical Note APPENDIX 2 F Outlet Protection APPENDIX 2 G Stormwater Impact Statement and Stormwater Management Plan Guidelines SECTION 3 LANDSCAPING
11. STORMWATER MANAGEMENT SECTION 2 STORMWATER MANAGEMENT AND DRAINAGE A HYXDROLEOGIC DBESIGN 21 INTRODUCTION Development and re development within the Chapel Hill Planning Jurisdiction is required to manage stormwater in accordance with Article 5 4 of the Chapel Hill Land Use Management Ordinance This section of the Design Manual provides information on the design and application of acceptable means and measures to comply with the requirements of the Ordinance The Ordinance requires that development and re development activities properly manage and control stormwater runoff rate volume pollutants and erosion sedimentation as necessary to protect and safeguard the environment property health safety and welfare of citizens within the Town s jurisdiction Low Impact Design LID using integrated best management practices is encouraged to meet the stormwater management performance criteria in the Land Use Management Ordinance Acceptable stormwater management practices include those found in this Design Manual and in the most recent addition of the North Carolina Division of Water Quality Stormwater Best Management Practices Manual The Town reserves the right to modify amend or otherwise change these accepted practices as may be necessary to achieve stated stormwater management goals Considerations in selecting and using stormwater management means and measures for a specific development will include b
12. 2 iv BE CONSTRUC USING TW CCORDANCE WITH iO COURSE PAVING IN THE DESIGN MANUAL gt Chapel Hill Jurisdictional Limits Area Requiring Standard Type Construction Area Requiring Special Type Il Construction APPENDIX 4 A P 1 of 5 STREET CLASSIFICATIONS AND STANDARDS STREET CLASSIFICATIONS Streets in Chapel Hill are classified by their functional relationship to through traffic service and land access service The three street classifications are l Arterial Arterial streets function primarily to serve through traffic movement Limited land access service may be accommodated but traffic controls and street design are intended to provide efficient through traffic movement 2 Collector Collector streets penetrate neighborhoods public service areas and districts They are intended to provide both through traffic and land access services in relatively equal proportions often linking the local street system to the arterial street system 3 Local Local streets primarily serve land access functions They are intended to accommodate land parcel ingress and egress Through traffic movement is difficult and discouraged by traffic controls and street design The relationship between functional street classifications is a continuous one without specific clear cut boundaries Streets are classified by the Town Traffic Engineer based on technical judgment and observed function of
13. 6 2 0 15 43 lt 0 06 Tatum 34 60 43 60 TaD TaE Enon 0 5 0 6 2 0 Urban land 0 9 2 0 6 0 EnB EnC 5 30 0 06 0 2 Ur 9 37 0 06 0 2 30 68 0 2 0 6 Vance VaB 37 60 Georgeville 0 7 0 6 2 0 Wedowee 0 12 2 0 6 0 GeB CeC GhC 7 59 0 6 2 0 WmD WmE 12 15 0 6 2 0 59 65 0 6 2 0 15 28 0 2 0 6 28 60 Goldston 0 10 2 0 6 0 White Store 0 5 0 06 2 0 GID 10 18 2 0 6 0 WsB 5 34 lt 0 06 18 24 2 0 6 0 34 50 Helena 0 14 2 0 6 0 WtC2 0 5 0 06 0 6 HeB 14 17 0 2 0 6 5 34 lt 0 06 17 36 0 06 0 2 34 50 36 60 Helena 0 14 2 0 6 0 WwC 0 5 0 06 0 6 HhA 14 17 0 2 0 6 White Store part 5 34 0 06 Helena part 17 36 0 06 0 2 34 50 36 70 Sedgefield part 0 13 2 0 6 0 Urban Land part 0 8 2 0 6 0 13 33 0 06 0 2 Wilkes 8 18 0 2 0 6 33 37 0 6 2 0 WxD WxF 18 60 0 6 2 0 37 65 Herndon 0 9 0 6 2 0 HrB HrC 9 58 0 6 2 0 58 62 0 6 6 0 This mapping unit is made up of two or more dominant kinds of soil See mapping unit description for the composition and behavior of the whole mapping unit Reference Orange County Soil Survey USDA APPENDIX 2 D P 9 of 21 SY AN DOWN SPOUT MU uus E FERFORATED Si did in m E TS MIN FOUNDATION DRAIN TE 5 E SAND AS 1 A BS Oe eS oe OP p es O oo s eux IMS 0
14. 7 0 84 1 24 1 68 212 12 60 310 362 415 4 69 525 5 82 641 6 76 8 0 1 25 174 2 25 2 78 13 33 3 89 446 5 04 5 60 621 6 81 740 7 76 9 0 1 71 2 29 2 88 349 1410 472 5 33 595 6 57 718 779 8 40 8 76 10 0 2 23 2 89 3 56 423 _ 4 90 5 56 6 22 6 88 7 52 8 16 8 78 9 40 9 76 11 0 2 78 3 52 14 26 5 00 5 72 643 713 7 81 8 48 913 977 10 39 10 76 12 0 3 38 419 5 00 579 6 56 7 32 8 05 8 76 9 45 10 11 10 76 11 39 11 76 13 0 4 00 4 89 5 76 6 61 17 42 821 8 08 9 71 10 42 11 10 11 76 12 39 12 76 14 0 4 65 5 62 6 55 7 44 18 30 912 9 91 10 67 11 39 12 08 12 75 13 39 13 76 15 0 5 33 6 36 7 35 829 919 10 04 10 85 11 63 12 37 13 07 13 74 14 39 14 76 Interpolate the values shown to obtain runoff depths for CN s or rainfall amounts not shown 210 VI TR 55 Second Ed June 1986 APPENDIX 2 A P 4 of 7 N RCAC SS PPC DSS NET NL COSCON CCP RISEN PCTEISCEISCEINCETNC PERCENT SCENE REE DSL
15. EAL b California Bearing Ratio CBR of underlayment soils Positive drainage considerations using underdrains and edge drains within the washed open graded aggregate reservoir d Geosynthetic fabric separation between stone reservoir and sub grade soil 3 Three 3 types of porous pavement Portand Cement Porous Pavement and Porous Asphalt Pavement bituminous and Permeable Pavestones a Portland Cement Porous Pavement may be used in parking lots private driveways sidewalks patios and other acceptable structures It may be used for light traffic paving loads only The design criteria and material specifications are not included in this design manual due to the complexity Methods of handling and placing porous concrete are different from other types of concrete Traditional PCC testing procedures based on strength air content and slump control are not acceptable to this type of pavement material Only concrete providers and contractors familiar and experienced in this product are acceptable for this application Reference the Carolina Ready Mix Concrete Association for technical specifications and other information b Porous Asphalt Pavement bituminous may be used in parking stalls and other acceptable structures The design and technical notes are not included this design manual Refer to the Federal Highway Administration NCDOT or other sources for accepted engineering standards designs handling
16. Figure 2 4 APPENDIX 2 P 1 of 7 SCS Runoff Curve Number CN method The SCS Runoff Curve Number CN method is described in detail in NEH 4 SCS 1985 The SCS runoff equation is Q P LY p L S Eq 2 1 Where Q runoff in P rainfall 1n S potential maximum retention after runoff begins in and 1 initial abstraction in Initial abstraction I is all losses before runoff begins It includes water retained in surface depressions water intercepted by vegetation evaporation and infiltration 1 is highly variable but generally is correlated with soil and cover parameters Through studies of many small agricultural watersheds I was found to be approximated by the following empirical equation I 0 28 Eq 2 2 By removing I as an independent parameter this approximation allows use of a combination of S and P to produce a unique runoff amount Substituting equation 2 2 into equation 2 1 gives P 0 25 0 85 2 3 S is related to the soil and cover conditions of the watershed through the CN has range of 0 to 100 and S is related to CN by S 1000 CN 10 Eq 2 4 Figure 2 1 and table 2 1 solve equations 2 3 and 2 4 for a range of CN s and rainfall Factors considered in determining runoff curve numbers The major factors that determine CN are the hydrologic soil group HSG cover type treatment hydrologic condition and antecedent runoff condition ARC Anot
17. TWO YEAR TWENTY FIVE YEAR RESULTS ONE YEAR STORM TWO YEAR STORM TWENTY FIVE YEAR STORM Q POST INCREASES BY 12 000 sq ft 0 27 acres 0 20 4 000 sq ft 3396 0 41 5 minutes 5 76 in hr 8 19 in hr 0 25 cfs 0 31 cfs 0 45 cfs 0 51 cfs 0 64 cfs 0 90 cfs 0 26 cfs 0 32 cfs 0 46 cfs Q POST INCREASES BY Q POST INCREASES BY Assume Grass Buffer 13 ft in length per cfs x 64 cfs 8 3 ft Therefore use 15 feet in length level spreader With 1 washed stone french drain NOTE For infiltration level spreaders use the following standards 1 Berm shall be constructed with sandy loam soil Use 2 wide x 6 deep washed stone french drain for every 15 feet in length of level spreader 3 Calculate length according to the two year storm post construction discharge See length criteria according to buffer type 4 Minimum length shall be 15 feet APPENDIX 2 D P 4 of 21 CONCENTRATED FLOW SPREAD FLOW RECEIVING STREAM FLAN VEW MATERIALVARIES Y GRASS GRAVEL ETC a GEO FABRIC TYHCAL 6 SECTION AA TYHCAL LEVEL SPREADER Figure 2 D 2 APPENDIX 2 D P 5 of 21 2 GENERAL DESIGN CRITERIA FOR BUFFERS AND FILTER STRIPS Filter strips are sections of vegetation designed to reduce pollutants in stormwater runoff before the runoff enters a stream or other receiving water Filter strips are carefully designed and constructed strips of relatively flat level land with grasses o
18. The peak discharge rate for the post developed conditions shall be no greater than the peak 2 a ee E T hare ia 52 calculation_centact the Fown Stormwater Management Engineer 22 c du qd ee shat baulie4oriseater bestmanasemen to praedee Bd Pas appeased by the treat 2022 22 Hu edet E doe oralternatives for BMP s to the Town Stormwater Management Engineer for review For the SCS Curve Number method peak discharge and volume calculations shall be based on a Type II precipitation distribution and total runoff depth using SCS equations curves and the appropriate depth duration frequency and intensity duration frequency tables provided in Appendix 2 A b Rational Method For catchments up to and including 25 acres the Rational Method may be used to calculate peak discharges for 1 2 yr amp 25 yr storm events unless site specific circumstances dictate that hydraulic routing and hydrograph generation are necessary The following procedure should be followed for Rational Method analyses 1 Determine the watershed size in acres A to the point of discharge 2 Calculate the time of concentration Tc using the equations found in Appendix 2 B 3 Determine the rainfall intensity I using th
19. Wells French Drains Sump and or trenches filled with high void ratio material such as uniformly graded gravel and sometimes including a perforated pipe under drain system CONCRETE PENNE poor LEVEL SPREADER CRASS CHANNEL ais vale m wilt wv NA NT Wer We whee M W We wh We INFILTRATION _ TRENCH fees BERM NOE WETS OBSERVATION WELL OVERFLOW WITH SCREW TYPE LID JOM Ca ANEL CLASS STONE SAND FILTER RUNOFF EXFIL TRATES THROUGH UNDISTURBED SUBSOILS OR GRAVITY DRAINS SUBSOLS MUST HAVE FERMEABIUTY RATE OF 0 5 IN HR OR GRAVITY DRAIN IS REQURED Figure 2 2 B Swales Shallow low velocity surface water conveyance typically grassed that allows slow moving water to infiltrate into the surrounding soil as it is conveyed pe APT 05 a eee Ell 3 07 ENGINEERED MODERATELY al PERMEABLE SOIL MIXTURE 57 WASHED STONE SOIL HFE FERFORATED FFE A FLAN VEW WATER QUALITY VOLUME FOND LIMIT 2 6 ENGINEERED SOIL MIXTURE FFRFOFRATFD DRAIN AFF SECTION AA NOTE CHECK DAM DESIGN VARIES FER ENGINEER TYHCAL INFILTRATION SWALE igure 2 2 1 A Typical Infiltration Swale Bio retention Areas Rain Gardens A relatively shallow landscaped depression designed to receive and detain stormwater runoff flows thus allowing for infiltration and removal of sus
20. adjacent properties To avoid conflicts with utility services applicants should review proposed plantings with affected utility providers prior to including such plantings on proposed planting plans standards applicable to screening parking lots shall be are required of utility service areas and the screening height should be equal to or greater than the structure to be screened Screening should be located to provide adequate access and workspace for the utility structure and the installation of plants with thorns or pointed leaves should be avoided adjacent to the service area Tree Placement Requirements When designing projects in the downtown area developers should refer to the Town s Downtown Streetscape Master Plan for information about planter design and planting standards along downtown streets For additional information developers should contact the Town s Public Works Department In all areas it is important to be certain that the placement of plantings does not interfere with site visibility at intersections For additional information about sight distance triangles developers should refer to the Town s Standard Details In general the following tree placement standards apply 1 Large Trees trees reaching a mature height of thirty five 35 feet or more should be planted a minimum of 3 1 2 feet from back of curb edge of street pavement and driveways allow for any proposed future wideni
21. and access around the dumpster s in these sample layouts Recycling rollcart sites zust be are typically grouped in multiples of 7 9 rollcarts arranged in any configuration allowing access to the front of each cart and providing one site per increment of 50 100 dwelling units depending on occupancy 8 4 2 Service Area Access In order to provide recyclables collection all service areas must be accessible to recyclables collection vehicles These vehicles are comparable in size to refuse dumpster collection vehicles and the access standards described in the multi family commercial institutional refuse collection section of this manual for 2 due aisle also pe here di weather pee In addition to providing accessible service areas the developer of any new multi family development should contact the Texas Orange County Solid Waste Department to complete a Solid Waste Management Plan addressing construction waste management the use of materials with recycled content during construction and space planning for storage and collection of refuse and recyclables eb eii may us service dor 252 Saut d This material must be Private contractors are avaiable for 22 pes RA non corrugated cardboard Hike that used to construet single layer cereal box type cartons may be ind 5 d le MultHfamHyReeycelng Nete Solid Wast
22. and no owner or resident of such building shall fail to prevent the shutting off or disabling of such a system Provided however that a sprinkler system may be shut off in order to perform maintenance work on the system during the time that qualified maintenance personnel are on the premises performing necessary maintenance work Such maintenance work shall only be conducted after notice to and approval by the Town Fire Department 7 6 2 Multi Family An automatic fire sprinkler system meeting the requirements of NFPA Standard 13 or 13R is required to be installed in new multi family construction renovations and additions as follows a all new multi family residential structures of three or more attached housing units if 1 the building has more than 6 000 square feet of floor area or 2 20 or more of the total floor area is more than 200 feet of travel distance from the nearest access point for a fire truck or 3 the building exceeds two stories or 24 feet in height from the average grade of the lot to the windows on the topmost occupied floor In addition all connections shall be located on the street side of each building and activation of the sprinkler system shall activate both a local building alarm and a supervisory alarm at a twenty four 24 hour certified and licensed alarm monitoring service Upon the occupancy of any new renovated or expanded structure subject to this Section no person shall shut off or di
23. are intended to complement and supplement the general Design Guidelines included in the Comprehensive Plan Specific design criteria set forth herein provide a ready reference of those practices and techniques acceptable to the Town We also encourage design professionals to consider site characteristics closely in their design and to seek new and better practices and techniques for complying with Town development policies and regulation If in response to the characteristics of a particular site innovative practices and or technological changes a designer can make a valid case for application of standards that modify or substitute for the design standards contained herein he or she is encouraged to do so Where alternative standards can be shown to conform with applicable policies and regulations the Town may accept such alternative standards in lieu of the standards contained herein Similarly where a particular site is characterized by a large number or extent of impediments to developing land in compliance with applicable policies and standards or where technological changes provide for practices and techniques that better ensure compliance the Town itself may modify or substitute additional standards for the design standards contained herein These standards include deadlines for improvements Manager may allow extensions of deadlines provided these extensions 1 will not conflict with the intent of these standards and other land
24. conservation treatment Pasture or range land poor condition good condition Meadow good condition Wood or forest land thin stand poor cover no mulch good cover Open Spaces lawns parks golf courses cemeteries good condition grass cover on 75 or more fair condition grass cover on 50 to 75 Commercial and business areas 85 impervious Industrial districts 72 impervious 81 88 91 93 Residential Average lot size Average Impervious 1 8 acre or less 65 acre 38 1 3 acre 30 acre 25 l acre 20 Paved parking lots roofs driveways etc Streets and roads paved with curbs and storm sewers gravel dirt Source USDA Soil Conservation Service Technical Release 55 SCS TR 55 Urban Hydrology for Small Watersheds Jan 1971 SCS Method Note Other tables or methods may be used subject to approval by the Town Engineering Department to determine SCS Curve Numbers and or Rational Coefficients The average impervious surface percentages in Table 2 2 are for typical conditions The Chapel Hill Engineering Department may require use of adjusted curve numbers for developments which can be expected to differ significantly from the typical values shown for impervious surface area percentages For example developments with limits imposed by the Water Supply Watershed Protection or other regulations may be required to use adjusted curve numbers S Rel
25. development regulations and 2 include a practical justification for an extension 12 COMPLIANCE Compliance with these standards shall be required at the time property 15 developed whenever a major increase in the intensity of use is created as determined by the Town Manager or whenever a use group change occurs frem Use Group A te B er C er frem Use Group B to C as outlined in the Town of Chapel Hill Development Ordinance Land Use Management Ordinance A rice ud TOR a any development of a single or two family dwelling on a zoning lot or any uses accessory thereto b any_development or detailed plan _pursuantte a_Special_Use Permit site plan_or Certificate ofAppropriateness approvedpriortotheadoptiomofthesestandards atly affeet buffering dayvelonmern Op gt inage relati ildings to each other landscaping erdighting The Town Manager may exempt modifications to existing developments from individual provisions of these standards where in the opinion of the Town Manager compliance with those provisions would create a practical hardship upon the property owner and where the modification does not increase the a nonconformity The Design Manual and Standard Details will be updated as necessary and the revised pages will be available from the Town of Chapel Hill Engineering Department and on the Town web site at http www townofchapelhill org SECTION 2
26. discourage excessive vehicular speeds Traffic calming techniques are encouraged whenever practical where warranted by conditions ineluding Such traffic calming measures may include but are not limited to curved and or narrow streets offsets at intersections traffic islands chokers raised crosswalks ped humps traffic circles chicanes etc ot which in Design e far traffic calming means and measures included as a supplement to the Town s adopted Policy for Neighborhood Traffic Management Additional information can also be found in the Standard Details 4 2 4 Vertical Alignment Streets should be designed to provide gradual grade changes and to avoid a roller coaster effect Where possible streets should be designed to avoid deep cuts and fills 4 2 5 Horizontal Alignment Streets should be designed to provide long curves and to avoid sharp curves at the end s of straight sections or flat curves Compound curves and S curves are to be avoided 4 2 6 Barriers Physical barriers such as guardrails should be provided along roadway edges and in medians where warranted due to potential roadway safety hazards such as structures embankments ditches or bodies of water Guardrail shall be constructed within the right of way wherever the Town Manager determines that guardrails are necessary for public safety Reflectorized barriers shall be installed at the end of pave
27. hour See following Table for permeability rates 6 Type of infiltration devise include dry well infiltration level spreaders bio retention infiltration detention basin porous pavement amended soils and green roofs if All infiltration devices must include an observation well standpipe cleanout as a means to monitor the reservoir depths and drawdown capabilities as a part of the operations and maintenance of the facility Runoff Pretreatment Infiltration devices shall be preceded by a pretreatment facility Grease oil floatable organic materials and settleable solids should be removed from the runoff before it enters the device Vegetated filters grass strip at least 20 wide sediment traps or forebays are just a few of the available pretreatment strategies Devices with surface inlets should be engineered to capture sediment from the runoff before it enters the stone reservoir Any pretreatment facility design should be included in the design of the device complete with maintenance and inspection requirements APPENDIX 2 D 7 of 21 Sizing Procedure A Darcy s Law approach is recommended for sizing infiltration devices This will assume that the drain time of the facility is controlled by one dimensional flow through the bottom surface Q fISA where Q rate of exfiltratin into soil cfs f infiltration rate of the soil in ft hr Assume 0 5 hr washed stone I hydraulic gr
28. hr in hr 5 minutes 5 76 6 58 7 22 8 19 8 96 9 72 10 minutes 4 76 5 54 6 13 7 01 7 71 8 40 15 minutes 4 04 4 74 5 25 6 03 6 64 7 24 30 minutes 2 70 3 28 3 71 4 32 4 80 5 28 60 minutes 1 70 2 12 2 41 2 84 3 17 3 50 2 hours 0 95 1 20 1 37 1 62 1 81 2 00 3 hours 0 71 0 89 1 02 1 21 1 35 1 50 6 hours 0 44 0 56 0 65 0 77 0 86 0 96 12 hours 0 26 0 33 0 39 0 46 0 52 0 57 24 hours 0 15 0 19 0 22 0 27 0 30 0 33 2 P 1 of 7 TIME OF CONCENTRATION Kirpich Tc Equation For use of the Rational Method Kirpich s equation 1940 was developed for small agricultural watersheds It was derived by examining the required time for the stream to rise from low to maximum stage during a storm The time of concentration was then assumed equal to that time Tc 0 00013 L 0 77 0 385 or Te L H oP 128 where where Tc Time of concentration in hours Time of concentration in minutes L Length of the overland flow in feet L Longest flow path in feet S Average overland slope ft ft H Elevation of difference along L in feet This equation above left was developed for overland flow on bare earth For overland flow on grassy earth Tc should be multiplied by 2 0 On concrete and asphalt surface it should be multiplied by 0 4 2 2 of 7 SCS METHOD TIME OF CONCENTRATION Travel time T is the time it takes water to travel from one location to
29. lawns crops Or other vegetative areas b amount of year round cover c amount of grass or close seeded legumes rotations d percent of residue cover and e degree of surface roughness APPENDIX 2 3 7 Table 2 A 1 Runoff depth for selected CN s and rainfall amounts Runoff depth for curve number of 40 45 50 55 60 65 70 75 80 85 90 95 98 Rainfall Inches 1 0 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 03 0 08 017 0 32 0 56 0 79 1 2 00 00 00 00 00 00 03 07 15 27 46 74 99 1 4 00 00 00 00 00 02 06 13 24 39 61 92 1 18 1 6 00 00 00 00 01 05 41 20 34 52 76 1 11 1 38 1 8 00 00 00 00 03 09 17 29 44 65 93 129 1 58 2 0 00 00 00 02 06 14 24 38 56 80 1 09 1 48 1 77 2 5 00 00 02 08 17 03 46 65 89 1 18 1 53 1 96 2 27 3 0 00 02 09 19 33 51 71 95 1 25 1 59 1 98 2 45 277 3 5 02 08 20 35 53 75 1 01 1 30 1 64 2 02 2 45 294 3 27 4 0 06 18 33 53 76 1 03 1 33 167 2 04 246 12 92 343 3 77 4 5 14 30 50 74 1 02 1 33 1 67 2 05 2 46 2 91 340 3 92 4 26 5 0 24 44 69 98 130 165 2 04 245 2 89 3 37 3 88 442 4 76 6 0 50 80 1 14 152 1 92 2 35 2 81 1328 378 430 485 541 5 76
30. oroceupant of the residence should contact the Town s Solid Waste Departmentto obtaim an approved recyelngcontainer Recyeling eontainers are servieed Tn newh propesed_residential developments all streets_are required to_be bunt to Fown standards te forsterage and eollection of refuse and recyclables 8 3 1 Residential Recycling Note Thedist of materials that can be collected from the reeycling containers has changed over time in respense te changes in the market for these materials Contact the Tewn ef Chapel Hill Orange County Solid Waste Department for a current list of approved materials and for information on collection schedules and to obtain an approved recycling container 8 4 MULTI FAMILY RECYCLING Multi family development includes all sites zoned for multi family use with apartment buildings townhomes or condominiums with six 6 or more units This includes complexes or groups of buildings which are located on a single zoning lot or have shared driveways or common parking areas The Fewn Orange County Solid Waste Department provides recyclables collection at all sites that meet the Tewn County s standards for service area design and access 8 4 1 Service Area Design For developments of six 6 or more units a combination refuse dumpster and recyclables rollcart area is recommended see diagrams 9 and 10 Note the pad dimensions needed to provide rollcart storage
31. purposes a minimum of three foot wide graded shoulder must be provided on both sides of the pavement The minimum vertical clearance should be eight feet However a greater clearance may be needed for tunnels Grades Grades greater than 5 are undesirable If due to the terrain or other considerations the installation of a 5 or flatter grade is shown to be impractical then a steeper grade may be used for short distances if approved by the Town Manager Design Speed The typical design speed for a bicycle path is 20 mph When the grade exceeds 4 a design speed of 30 mph is advisable Horizontal Alignment The typical cross slope is 296 for tangent sections The minimum design radius of curvature shall be derived from the following list 30 mph 250 feet radius 35 mph 390 feet radius Pavement Design A hard all weather pavement shall be used A geotechnical report shall be provided by a licensed engineer with a recommendation for a pavement design suitable for bicycles and maintenance vehicles 4 14 BICYCLE LANE A bicycle lane is a portion of a street that has been designated by signs and pavement markings for the exclusive use of bicyclists Bicycle lanes are typically one way facilities that carry bicycle traffic in the same direction as adjacent motor vehicle traffic Width and Clearance The minimum width for a designated bicycle lane is four feet However
32. should be removed only in the areas indicated on the Landscape Protection Plan in such a manner that avoids damage to the limbs trunks and roots of the remaining vegetation If tree protection fencing is damaged during the clearing operation it should be repaired prior to the continuation of work If trees fall inside areas shown as being protected on the Landscape Protection Plan they should be removed without the use of heavy equipment p mE a PROPOSED GARAGE PROPERTY EXISTING H A REPLACEMENT 2 7 EZZ EXISTING EXISTING EXISTING EXISTING EXISTING EXISTING SIDEWALK a t H STREET TREES UE E SINGLE FAMILY HOME TREE LOCATION Figure 3 6 3 Construction Access within the Critical Root Zone of Rare and Specimen Trees In limited situations where no permanent changes are proposed within areas of the critical root zones of rare and specimen trees but where these areas may be needed to access construction a specialized root protection method may be required This method involves the installation of logging mats over a bed of mulch and areas where this is proposed should be clearly designated on Landscape Protection Plans Several different types of logging mats area available and can be utilized depending upon the type of equipment that will be utilizing the proposed access way Developers can contact the
33. site the site plan should be designed so that backing movements do not exceed 100 in length In these cases the turn around area should be dimensioned using a turning radii template of the appropriate scale In all cases the proposed site plan should be designed so that refuse collection vehicles do not need to back onto or off of any public street or over any public sidewalk Where dumpsters are proposed to be placed at angle to the centerline of the driveway or drive aisle this angle should not exceed 30 degrees On sloped sites the vehicle approach to the dumpster should be at the same slope as the dumpster pad and should not exceed 59 see figure 8 7 REFUSE TRUCK RADI Figure 8 6 In newly proposed multi family commercial and institutional development all driveways and drive aisles are required to be built to Town standards Drive aisles proposed to be used for refuse collection vehicle access shall be constructed with a minimum section of 10 inches stone base and 3 inches of asphalt surface course Developers should refer to the Town of Chapel Hill Engineering Department s Standard Details for driveway cut specifications vertical curve requirements and pavement sections ALIGNMENT SLOFE OF DUMPSTER SHALL NOT EXCEED 5 2 OF HORIZONTAL ALIGNMENT OF LIFTING FORKS p FIGURE 8 7 8 2 5 Overhead Clearance Electrical service drop connectors and other overhead utility wires are required by the National E
34. structural measures may include but are not limited to utilizing natural buffers limiting impervious surfaces and limiting disturbed areas Low impact design options are encouraged APPENDIX 2 G P 6 of 6 VI ADJUSTMENTS OR WAIVERS Information requirements may be adjusted or waived by the Town Manager for a particular development application upon written request of the applicant provided that at least one of the following circumstances can be demonstrated a Alternative measures for on site and or off site management of stormwater have been proposed and these measures are approved by the Town Manager and comply with local ordinance s b It 15 otherwise demonstrated that the proposed development will not produce significant change to the existing pre application hydrology If you have any questions regarding these Guidelines contact the Town Stormwater Management Engineer at 919 968 2833 REFERENCES CDM 1989 Watershed Management Study Lake Michie and Little River Reservoir Studies Field Richard M L O Shea and K K Chin 1993 Integrated Stormwater Management Lewis Publishers Boca Raton FL Haith D A et al 1992 Generalized Watershed Loading Functions User s Manual NY Hartigan J P et al 1983 Calibration of NPS Model Loading Factors Journal of Environmental Engineering Division 109 no 6 pp 1259 1272 Schueler Thomas R 1987 Controlling Urban Runoff A Practice Manual for Planning
35. that alternative roadway construction design s be submitted for approval by the Chapel Hill Engineering Department 4 18 GRASSING GROUNDCOVER WITHIN RIGHTS OF WAY pertiens ef the readway disturbed areas within the right of way including medians remaining unpaved shall be grassed groundcover established in accordance with Town specifications Grass Groundcover shall be installed in all rights of way at a time determined by the Town Manager providing however that it shall be installed and established prior to the release of the improvement bond Soil tests shall be submitted to the North Carolina Department of Agriculture by the contractor for all seeding lime and fertilizer requirements unless this requirement is waived by the Town Manager The contractor shall lime and fertilize according to the test results Tall Fescue Kentucky 31 is acceptable with 99 minimum purity and 85 minimum germination Application rate shall be 225 pounds of fescue grass seed per acre unless site conditions dictate a different rate All swerk herein referred te groundcover shall be maintained in accordance with Town Specifications and shall be kept at a height no greater than six 6 inches except on embankments until the roadway has been accepted by the Town Manager and the improvement bond has been released Typical Street Construction Zones Legend
36. the potential to be invasive in the Chapel Hill area This list includes plants that vary in their likelihood to become invasive Some plants such as chinaberry and norway maple have not yet become established as invasive species in the Chapel Hill area but are known to be invasive elsewhere in the Southeast number of other plants including the bamboos and periwinkles spread vegetatively but are unlikely to self sow and therefore can be specified for applications such as in planters where their spread can be carefully controlled Several other plants including english ivy and chinese silvergrass are shown on the list but include dwarf sterile or non vigorous varieties that likely pose only a minimal risk of becoming invasive Considering these issues the listed plants should not be specified for use on landscaping plans prepared for development applications requiring planting plan approval by the Town staff unless the variety specified or the method of installation is carefully researched The use of the listed plants is also discouraged in non regulated landscaping projects within the Town a Trees Scientific Name s Common Name s Remarks Acer platanoides Norway Maple Broussonetia papyrifera Paper Mulberry Melia azadarach Chinaberry Populus alba White poplar Quercus acutissima Sawtooth Oak Ulmus pumila Siberian Elm b Shrubs and Vines Scientific Name s
37. the street A list of existing Arterial and Collector Streets 18 available from the Town Engineering Department The list will be updated as new Collector and Arterial Streets are approved by the Town The construction of new private streets to serve new development is not allowed By definition herein a private street is a means of vehicular ingress or egress that is not publicly maintained and serves more than two single family lots Design Volume ADT TABLE 4 A 1 STREET STANDARDS APPENDIX 4 A 2 of 5 Design Speed 35 45 mph 25 35 mph 25 mph Overall Unlimited 2 miles typical lt mile typical Length Number of 4 typical 2 typical 2 typical Travel Lanes Right Left at intersections and major driveways 11 Width Min Turn Lanes Transit Provisions Sidewalks On street Parking Both sides of street typically 4 width min striping May be required on a site specific basis in accordance with Town policy Bus turnout and shelter where warranted for separation from through traffic and volume of loading passengers Both sides of street typically 5 width min Not permitted typically As warranted by turning traffic volume and or safety criteria 10 Width Min May be required on a site specific basis in accordance with Town policy Bus shelter where warranted for volume of loading passengers Both sides of street
38. travel lanes necessary for each street classification may vary depending on traffic volumes 2 Off street bicycle facilities may be provided in lieu of on street bike lanes if approved by the Town Manager Extra width minimun paving in the outer travel lanes may be considered to function as an unstriped bike lane Combination sidewalk bike paths may be considered 3 ener be based or tance i dense as oathned athe SidewalkChart below 3 Intersection spacing is measured along centerline of street between the centerlines of intersecting streets 4 Measured between closest edges of driveway connections and intersecting roadways Additional spacing may be required by Town Manager under special conditions 5 Refer to the Standard Details for further information regarding bus turnouts and shelters SIDEWALK CHART Hassia Musa SERE adu Sen Commercial and Industrial AH Streets Both sides Every effort should be madeto add sidewalks where 22 do notexistand te complete Residential Streets More than 4 pm Ro ees PEE CEeeal Streets 1 te 4 units per both sides One ee oo atteast4 feet acre Shoulder on_beth sides required Residential Streets Less than One S feet sheulder on beth Aecessing 8 units or Lc more Residential Cul de sacs Accessing 7 ed units orless Sidewalks may be omitted o
39. typically 5 width min One side typically Controlled adjacent to street and driveway intersections 7 500 40 000 1 000 7 500 1 000 As warranted by turning traffic volume and or safety criteria 9 10 width min May be required on a site specific basis in accordance with Town policy Bus shelter where warranted for volume of loading passengers One side of street Additional pedestrian facilities may be required on a site specific basis One side typically Controlled adjacent to street and driveway intersections Intersection 1000 minimum 400 minimum 200 minimum Spacing Driveway Spacing Access Control 750 min between driveways 250 minimum between driveway and street intersections Residential and non residential no access if alternative is possible to street of lower classification Maximum 2 driveways per lot 100 minimum between driveways and between driveway and street intersections Residential and non residential No access if alternative is possible to street of lower classification Maximum 2 driveways per lot 50 minimum between driveways and between driveway and street intersections Residential No access if alternative is possible to street of lower classification Non residential No access if alternative is possible to street of higher classification APPENDIX 4 P 3 of 5 Notes l The number of
40. 1 1 2 4 6 10 20 Average velocity ft sec 005 2 1 AVERAGE VELOCITIES FOR ESTIMATING TRAVEL TIME FOR SHALLOW CONCENTRATED FLOW 210 VI TR 55 Second Ed June 1986 P 3 of 7 3 2 Matercourse slope ft ft EHE BE coh E CET mrang man Pe HHHH LL LT VII LAA E 1 i 6 10 20 Average velocity ft sec Figure 3 1 Average velocities for estimating travel time for shallow concentrated flow 210 55 Second Ed June 1986 APPENDIX 2 B P 4 of 7 Sheet flow Sheet flow is flow over plane surfaces It usually occurs in the headwater of streams With sheet flow the friction value Manning s n is an effective roughness coefficient that includes the effect of raindrop impact drag over the plane surface obstacles such as litter crop ridges and rocks and erosion and transportation of sediment These n values are for very shallow flow depths of about 0 1 foot or so Table 2 B 1 gives Manning s n values for sheet flow for various surface conditions For sheet flow of less than 300 feet use Manning s kinematic solution Overton and Meadows 1976 to compute 0 007 nL P2 9 Eq 3 3 Table 2 B 1 Roughness coefficients Manning s n for sheet flow Surface descrip
41. 8248d ut 401 07 0 91 0 0 3 04 0 5 gt Velocity in Feet per Second APPENDIX 2 P 1 of 1 TABLE 2 C 1 Rational Runoff Coefficients DESCRIPTION C SOURCE Roof inclined 0 96 Malcom 2003 Street driveway sidewalk parking lot 0 96 Malcom 2003 Gravel 0 90 T O C H Commercial generalized 0 90 Malcom 2003 Apartments schools churches 0 84 Malcom 2003 Residences 10 dwellings acre 0 80 T O C H Residences 6 dwellings acre 0 60 T O C H Residences 4 dwellings acre 0 74 Malcom 2003 Residences 2 dwellings acre 0 70 Malcom 2003 Unimproved cleared area 0 50 Lawn dense soil steep gt 7 0 60 Malcom 2003 Lawn dense soil avg 2 796 0 50 T O C H Lawn dense soil flat 2 0 20 T O C H Lawn sandy gt 2 0 15 Chow 1964 Lawn sandy flat 296 0 10 Chow 1964 Wooded deep ground litter 0 40 Malcom 2003 Wooded sparse ground litter 0 40 T O C H Porous Asphalt 0 30 T O C H Park cemetery 0 50 T O C H Playground 0 60 Malcom 2003 Note Other tables or methods may be used subject to approval by the Town Engineering Department to determine SCS Curve Numbers and or Rational Coefficients APPENDIX 2 D P 1 of 21 1 GENERAL DESIGN CRITERIA FOR STRUCTURAL LEVEL SPREADERS Level spreaders are one means of providing diffuse flow through buffers or filter strips Concentrated flow causes erosion and scour and transports pollutan
42. AND TREE PROTECTION 3 1 3 2 3 3 3 4 DESIGN STANDARDS Buffer Requirements Parking Lot Requirements PLANT SELECTION STANDARDS Prohibited Invasive Exotic Species Restricted species Recommended Native Species LANDSCAPE INSTALLATION AND MAINTENANCE SPECIFICATIONS Materials Requirements Soil Preparation Planting Requirements General Pruning Requirements TREE PROTECTION STANDARDS Tree Protection Ordinance Requirements SECTION 4 ACCESS AND CIRCULATION 4 1 4 2 4 3 4 4 REQUIRED ACCESS GENERAL STANDARDS Relationship to Town Plans Relationship to Surrounding Access Ways Appropriate Speed Vertical Alignment Horizontal Alignment Barriers Intersections Sight Line Triangles at Intersections Dead End Streets STRUCTURAL STANDARDS Phased Completion of Streets TRAFFIC CONTROL DEVICES 4 5 EXTENSION AND COMPLETION OF ACCESS WAYS Extension to Boundaries Improvement of Substandard Access Ways 46 PUBLIC AND PRIVATE ACCESS WAYS Public Access Ways Private Access Ways Providing Required Access 47 NAMES IDENTIFICATION AND ADDRESSES FOR PUBLIC AND PRIVATE STREETS Street Names Street Name Signs Street Addresses 4 8 MINIMUM STREET ELEVATIONS 49 GUARDRAILS AND BARRIERS 4 10 TRANSIT AMENITIES 4 11 BICYCLE PARKING 412 STREET CLASSIFICATION AND GEOMETRIC STANDARDS 413 BICYCLE PATHS 414 BICYCLE LANE 4 15 WORK ZONE TRAFFIC CONTROL 4 16 DISABILITY ACCESS 417 GROUNDCOVER WITHIN RIGHTS OF WAY 4 18 SOILS REPORT APPENDIX 4 A
43. Common Name s Remarks Akebia quinata Fiveleaf Akebia Ampelopsis brevipendunulata Porcelain Berry Vine Berberis thunbergii Japanese Barberry Dwarf forms may be acceptable Clematis paniculatus C terniflora Sweet Autumn Clematis Euonymus alata Burning Bush Dwarf forms may be acceptable Euonymus fortunei Wintercreeper Dwarf forms may be acceptable Hedera helix English Ivy Dwarf forms may be acceptable Rhamnus alnus R cathartica Buckthorn Spiraea japonica Japanese spiraea Some varieties may be acceptable Viburnum dilatatum Linden Arrowwood Groundcovers and Grasses Scientific Name s Common Name s Remarks Arundinaria sp Golden Grove Bamboo Contained use may be acceptable Arundo donax Giant Reed Coronilla varia Crownvetch Iris psuedoacorus Yellow Flag Lysimachia nummularia Creeping Jenny Variegated forms may be acceptable Miscanthus sinensis Chinese Silvergrass Some varieties may be acceptable Phalaris arundinacea Reed canarygrass Phyllostachys aurea P nigra Golden Bamboo Black Contained use may be Bamboo acceptable Sasa palmata S pygmaea Dwarf bamboo Contained use may be acceptable Vinca major Bigleaf Periwinkle Contained use may be acceptable Vinca minor Common Periwinkle Contained use and variegated forms may be acceptable 3 2 3 Recommended Native Speci
44. F for technical information TABLE 2 4 INLET COEFFICIENTS Outlet Control Full or Partly Full Entrance head loss Ke v 2g Type of Structure and Design of Entrance Coefficient Pipe Concrete Projecting from fill socket end groove end 0 2 Projecting from fill sq cut end 0 5 Headwall or head wall and wingwalls Socket end of pipe groove end 0 2 Squate edpe te 0 5 Rounded radius 1 12D sess 0 2 Mitered to conform to fill slope 0 7 End section conforming to fill 1 0 5 Beveled edges 33 7 or 45 5 0 2 Side or slope tapered 0 2 Pipe or Pipe Arch Corrugated Metal Projecting from fill no headwall 0 9 Headwall or headwall and wingwalls square edge 0 5 Mitered to conform to fill slope paved or unpaved 0 7 PT End Section conforming to fill 0 5 Beveled edges 33 7 or 45 2 22221 0 2 Side or slope tapered 2 0 2 Box Reinforced Concrete Headwall parallel to embankment no wingwalls Square edge on 3 0 5 Rounded on 3 edges to radius of 1 12 barrel dimension or beveled edges 3 sides 0 2 Wi
45. Include above or below ground facilities designed to collect and detain stormwater runoff and to release the water slowly until the facility is dry 1 e no permanent pool B Retention Facilities Are above ground facilities designed with a permanent pool and additional runoff storage area free board above the permanent pool elevation from which the stored volume of water can be released at a controlled rate C Re use Facilities Above ground or under ground facilities that capture and store stormwater runoff for non potable uses such as non food crop irrigation equipment cooling washing toilet flushing etc c Facility General Design Criteria and Illustrations Appendix 2 D includes design information and illustrations for a variety of stormwater management control devices 2 4 2 Non structural IMP BMP s Non structural IMP BMP s include Low Impact Design practices that minimize alterations to the existing hydrology These practices include minimizing the amount of land area and vegetation disturbance minimizing impervious surface area and eliminating direct storm sewer discharges into receiving streams 2 5 STORMWATER IMPACT STATEMENT AND STORMWATER MANAGEMENT PLAN CRITERIA A Stormwater Impact Statement and Stormwater Management Plan are typically required as part of Zoning Compliance Permit Site Plan Review Preliminary Plat and Special Use Permit applications in accordance with
46. Inlets should be placed at intersections and all low points in the gutter grade to prevent gutter flow from crossing traffic and pedestrian lanes of the intersecting road Refer to Table 2 3 Maximum Allowable Stormwater Spread Inlets are normally placed upstream of pedestrian crossings to intercept the gutter flow before it reaches the crosswalk Where pavement surfaces are warped as at cross streets ramps or transitions between supereleavated and normal sections gutter flow should be diverted into the storm drainage system to prevent water flow across the roadway Where a curbed roadway crosses a bridge gutter flow should be intercepted before it reaches the bridge Runoff from areas adjacent to streets should be intercepted before reaching the pavement This applies to water that would normally run onto the street from side streets or from cut slopes and areas along the edge of pavement A minimum of two inlets double inlet should be placed in the sag of vertical curves The additional inlets provide extra capacity and a safety factor against potential street flooding if the inlets become clogged due to deposition of sediment and debris Inlets on a continuous grade should be spaced to limit the spread of stormwater onto the pavement The spacing of inlets is based on the allowable spread and the inlet capacity The flow bypassing an inlet must be included in the flow arriving at the next inlet 2 6 5 Open Chan
47. Landscaped Island and Median Requirements Landscaped islands in parking lots and medians separating lanes of traffic on public streets and on internal drives should be a minimum of 4 in width measured from the back of curb and sheuld net extend inte the aecessing street right of way If large trees are to be planted in landscape islands or medians these islands or medians should be a minimum of 10 in width measured from the back of curb and include a minimum of 200 sf of soil surface area per large tree landscaped islands and medians shall receive a minimum of 6 of topsoil over finished subgrade and shall be graded to provide adequate drainage Subsurface drainage and irrigation are is recommended for all landscaped islands and medians In some specific situations where site conditions merit automatic irrigation systems may also be recommended In these situations the use of water conserving irrigation systems is encouraged Loading Area Requirements loading areas shall have a minimum width of 12 and be screened from public rights of way and all adjacent properties standards applicable to screening parking lots sheuld be are required of loading area screening except that the screening height shall be a minimum of 6 above existing grade for both right of way and residential screening Utility Service Area Requirements utility service areas should be screened from public rights of way and all
48. Landscaping Standards The screen should be a minimum of 7 in height and should be located directly adjacent to the dumpster pad In some cases the use of plantings alone to screen the dumpser may be acceptable if they are planted at a size that will permit them to reach the required minimum height within one growing season The most common type of screening used is a wooden privacy fence see diagram 5 4 NW Z 7 5 d LN REAR Tees rv 4 X GROUND CONTACT NOTE FENCING MATERIAL TO PRESSURE TREATED LUMBER PRESSURE TREATED A FENCING DETAIL re 8 4 Fi 5000 FSI FORTLAND CEMENT CONCRETE NOTE FENCING MATERIAL TO BE PRESSURE TREATED LUMBER 4 X 4 TO BE GROUND CONTACT PRESSURE TREATED STANDARD DUMPSTER PAD FENCING Figure 8 5 8 2 4 Dumpster Placement and Access The essential element in locating a dumpster is the ability of the refuse collection vehicle to safely and efficiently service the container The Town s front loading refuse collection vehicles are 33 in length and have an inside turning radius 32 5 In the design of developments where driveways and or parking lot drive aisles will be used to access dumpsters a turning radii template should be used to assure that access can be provided without unnecessary backing maneuvers see diagram 6 5 Where refuse collection vehicles will need to turn around to exit a development
49. Method are described below See APPENDIX 2E Design Manual Hydrology Technical Note SCS Method For the SCS Curve Number method peak discharge and volume calculations shall be based on a Type II precipitation distribution and total runoff depth using SCS equations curves and the appropriate depth duration frequency and intensity duration frequency tables provided in Appendix 2 A 1 Hydrologic Soil Group Soils properties influence the relationship between rainfall and runoff by affecting the rate of infiltration Soils have been divided into four hydrologic soil groups based en infiltration rates as noted in Table 2 2 These soil groups are used in conjunction with land use descriptions to determine runoff curve numbers 2 Land Use Types of land use within a given watershed affect hydrology and runoff characteristics Table 2 2 includes land use descriptions used to determine curve numbers CThings Uses such as vegetation water surfaces roads roofs parking lets ete are all types of dand uses whieh relate to hydrology Each affectsthe 3 Curve Numbers Both soil groups and land use determine applicable runoff curve numbers for use in hydrologic modeling Table 2 2 includes runoff curve numbers for different land uses within specific soil groups TABLE 2 2 SCS Runoff Curve Numbers CN LAND USE DESCRIPTIONS HYDROLOGIC SOIL GROUP Cultivated land without conservation treatment with
50. P Manual to develop the required Operations and Maintenance Plan 4 Inspect rain gardens seasonally and after substantial rainfall particularly during the first full year Small maintenance needs include removing trash and other unwanted debris from the garden replacing mulch and pulling weeds 5 See Town Standard Detail SD 5A TABLE 2 D 2 Partial listing of shrubs and trees potentially used in rain garden bio retention areas APPENDIX 2 D P 14 of 21 Latin Name Common Name N C habit Size form Acer negundo Box elder Across N C Small tree Acer rubrum Red maple Across N C Medium tree Aronia arbutifolia Red chokeberry Across N C Medium shrub Cercis Canadensis Redbud Across N C Large shrub Clethra ainifolia Sweet pepperbush Coastal plain piedmont Medium shrub Cornus sericea ssp stolonifera Red osier dogwood Piedmont mountains Medium small shrub Cyrilla racemiflora Ti ti Coastal plain Large shrub semi evergreen Diospyros virginiana Persimmon Piedmont mountains Small medium tree Euonymus Americana Strawberry bush Across N C Small shrub Faxinus pennslyvanica Green ash Piedmont coastal plain Medium tree Hypericum frondosum St John s wort Piedmont coastal plain Ground cover herbaceous vomitoria Dwarf yaupon Coastal plain Small shrub evergreen Juniperus virginiana
51. Rainfall depth can be obtained from Appendix 2 A Shallow concentrated flow After a maximum of 300 feet sheet flow usually becomes shallow concentrated flow average velocity for this flow can be determined from figure 2 B 1 in which average velocity is a function of watercourse slope and type of channel Tillage can affect the direction of shallow flow Flow may not always be directly down the watershed slope if tillage runs across the slope After determining average velocity in figure 2 B 1 use equation 3 1 to estimate travel time for the shallow concentrated flow segment Open channels Open channels are assumed to begin where surveyed cross section information has been obtained where channels are visible on aerial photographs or where blue lines indicating streams appear on United States Geological Survey USGS quadrangle sheets Manning s equation or water surface profile information can be used to estimate average flow velocity Average flow velocity is usually determined for bank full elevation 2 6 7 Manning s equation is V 2149 12 s m Eq 3 4 where V average velocity ft s hydraulic radius ft and is equal to a py cross sectional flow area ft Pw wetted perimeter ft s slope of the hydraulic grade line channel slope ft ft and n Manning s roughness coefficient for open channel flow Manning s n values for open channel flow can be obtained
52. Street Classifications Street Standards Geometric Design Standards SECTION 5 PARKING AND LOADING 5 1 OFF STREET PARKING Geometric Design Pavement Standards Parking Decks Accessible Parking Spaces for the Handicapped 5 2 ON STREET PARKING 53 LOADING SPACE REQUIREMENTS SECTION 6 STREET LIGHTS SIGNS AND MARKINGS 6 1 STREET LIGHTING APPLICABILITY 6 2 STREET LIGHTING PLAN SUBMITTAL REQUIREMENTS 6 3 STREET LIGHTING GUIDELINES 6 4 STREET LIGHT POLE amp FIXTURE STANDARDS FOR RESIDENTIAL STREETS 6 5 STREET LIGHT PLACEMENT STANDARDS FOR RESIDENTIAL STREETS 6 6 STREET SIGNS AND MARKINGS APPLICABILITY 6 7 STREET SIGNS AND MARKINGS PLAN SUBMITTAL REQUIREMENTS 6 8 STREET SIGNS AND MARKINGS STANDARDS SECTION 7 UTILITIES AND EASEMENTS 74 INTERRELATION OF UTILITY LINES 7 2 UNDERGROUND UTILITIES 7 3 SURFACE APPURTENANCES 74 SEWAGE COLLECTION SYSTEM Provision for Future Service Areas Design and Construction Standards and Materials 7 5 WATER DISTRIBUTION SYSTEMS Provisions for Future Service Areas Design and Construction Standards Fire Hydrants Location of Valves 7 6 AUTOMATIC SPRINKLER SYSTEMS Non Residential Multi family Fraternity and Sorority Houses 77 EASEMENTS SECTION 8 SOLID WASTE MANAGEMENT 8 1 RESIDENTIAL COLLECTION Residential Refuse Collection Note 8 2 MULTI FAMILY COMMERCIAL INSTITUTIONAL REFUSE COLLECTION Recyclable Corrugated Cardboard Note Dumpster Pad Design Dumpster Pad Screening Dumpste
53. Town s Public Works Department for additional information about recommended logging mats TOME damage tho troe s tots a d e Und Utility Installat Repair Open trench excavation within the critical eet_zone oftrees_should _be aveided weeks lines Where the eritieal 22 ies 022 is IE this oe 2221 utility line placement should be adjusted and or the affected tree s removed 2 5 pits and no conflictiscantieipatedowith existing utilities and othervegetation oot cane oF a tree the trunk of the tree SECTION 4 ACCESS AND CIRCULATION SECTION 4 ACCESS AND CIRCULATION 41 REQUIRED ACCESS development must provide shall bedecated en a zening tot that _has_vehicular_bicycle and pedestrian aecess access to publicly maintained vehicular bicycle and pedestrian facilities as defined below Vehicular Access abutment on access to a street that is approved by the Town as being in compliance with Town standards and or is currently maintained by the Town or the State of North Carolina Bicycle Access abutment on access to a street or recreation area space containing a bikeway bike lanes bike paths or bike trail or abutment on a street for which bikeways are not required Such streets are presumed to be adequate for combined vehicula
54. adient assume I 1 SA bottom surface area of facility in fe 1 Infiltration Rate Over the life of an infiltration facility the rate of infiltration into the soil f may gradually decrease due to clogging of the surface layer of soil safety factor of 2 shall be applied to the infiltration rate determined from the soil analysis The design soil infiltration rate fy therefore is equal to one half of the actual rate fa 0 5 APPENDIX 2 D P 8 of 21 TABLE 2 D 1 SOIL DEPTH PERMEABILITY RATES SOIL NAME SOIL NAME AND MAP DEPTH PERMEABILITY AND MAP DEPTH PERMEABILITY SYMBOL SYMBOL Inches Inches per hour Inches Inches per hour Altavista 0 6 2 0 6 0 Hiwassee 0 6 0 6 2 0 Aa 6 50 0 6 2 0 HwB HwC 6 79 0 6 2 0 50 80 79 85 Appling 0 11 2 0 6 0 Iredell 0 8 2 0 6 0 ApB ApC 11 48 0 6 2 0 IrB 8 29 0 06 0 2 48 60 29 40 AuC 0 11 2 0 6 0 IuB 0 8 2 0 6 0 Appling part 11 48 0 6 2 0 Iredell part 8 29 0 06 0 2 48 60 29 40 Urban land part 0 4 2 0 6 0 Urban Land part 0 6 0 6 2 0 Cecil 4 46 0 6 2 0 Lignum 6 36 0 06 0 6 CfB CfC 46 61 36 48 0 2 0 6 Chewacla 0 6 0 6 2 0 Louisburg 0 8 6 0 20 Ch 6 52 0 6 2 0 LoC LoF 8 20 6 0 20 52 60 20 60 Congaree 0 7 0 6 6 0 Orange 0 5 0 6 2 0 Cp 7 56 0 6 2 0 Or 5 24 0 06 0 2 56 63 24 42 0 2 0 6 42 45 Creedmore 0 8 2 0 6 0 Pitts 0 5 0 6 2 0 CrB 8 15 0 2 0 6 Pt 5 34 0
55. and Designing Urban BMPs Metropolitan Washington Council of Governments Washington DC Stormwater Best Management Practices 1999 North Carolina Department of Environment and Natural Resources Division of Water Quality Water Quality Section Urbonas Ben and P Stahre 1993 Stormwater Best Management Practices and Detention Prentice Hall Englewood Cliffs NJ SECTION 3 LANDSCAPING AND TREE PROTECTION SECTION 3 LANDSCAPING AND TREE PROTECTION 31 DESIGN STANDARDS 3 1 1 Buffer Requirements The following chart indicates the minimum width and planting requirements for each buffer type established in Section 14 12 5 6 of the Development Ordinance Land Use Management Ordinance The arrangement of plants within each buffer should be integral to the design concept of the project as a whole as well as responsive to the landscapes of adjacent properties The room required for plants to develop their natural form especially large trees should also be considered when determining plant spacing Allowing greater than minimum buffer widths can therefore provide more design flexibility The buffer locations shown in the chart refer to whether the buffer area is adjacent to a street external or adjacent to some other property line internal When developing external buffers large trees may be planted within the public right of way if they are consistent with adjacent street tree plantings and are acceptable to the Town and the Nort
56. and or angle parking is allowed on Town streets However 90 degree perpendicular on street parking is not permitted Time restrictions may be posted for on street parking by means of signs or parking meters to regulate the use of parking spaces Dimensioning of on street parking spaces shall take into account driver sight distance pedestrian patterns and maneuvering area for vehicles For more information please contact the Town of Chapel Hill Engineering Department 5 3 LOADING SPACE REQUIREMENTS Off street loading spaces shall be designed so that a semi trailer truck WB 43 design can use the space by means of one continuous parking maneuver The off street loading space shall have a minimum width of 12 feet minimum length of 55 feet and a vertical clearance of 14 feet above the finished grade SECTION 6 STREET LIGHTS SIGNS AND MARKINGS SECTION6 A STREET LIGHTS SIGNS AND MARKINGS 6 1 STREET LIGHTING APPLICABILITY A developer may be required to install or upgrade street lights within a public right of way as part of the Town s design approval process The two situations in which these street lighting improvements are typically required are 6 1 1 When new public streets are proposed or existing public streets are improved 6 1 2 When significant development is proposed adjacent to a public street within the Downtown Streetscape Study Area where a Street Lighting Master Plan has been ado
57. and shalt be determined by the Town Manager 4 10 TRANSIT AMENITIES Transit amenities including shelters benches walkways pulloffs etc will be required for areas to be served by the transit system The appropriate Town party Council Planning Board Manager will determine which amenities will be required and where they will be located based upon transit routes street classifications types of development passenger volumes and any other pertinent considerations on a case by case basis However bus pull offs should be provided at bus stops on Collector and Arterial streets with only two travel lanes unless traffic volumes or site conditions indicate that a pull off is not warranted as determined by the Town Manager 4 11 BICYCLE PARKING At new development or redevelopment projects_ shal provide lockable bike rack spaces equalne atleast 5 AER IE Eraternities and Sororities EE students HESS f nro of commercial space automobile pace Government Building i1 9eofthenumberofautomobilespaces 5 10 of the number of automobile spaces Manufacturing Plant 49e ofthenumberofautomobilespaees 5 10 of the number of automobile spaces b Classification of bicycle parking 1 Class I bicycle parking means a locker individually locked enclosure or supervised area within a building providing protection for bicycles therein from theft
58. another in a watershed is a component of time of concentration which is the time for runoff to travel from the hydraulically most distant point of the watershed to a point of interest within the watershed is computed by summing all the travel times for consecutive components of the drainage conveyance system T influences the shape and peak of the runoff hydrograph Urbanization usually decreased thereby increasing the peak discharge But Tc can be increased as a result of a ponding behind small or inadequate drainage systems including storm drain inlets and road culverts or b reduction of land slope through grading Factors affecting time of concentration and travel time Surface roughness One of the most significant effects of urban development on flow velocity is less retardance to flow That is undeveloped areas with very slow and shallow overland flow through vegetation become modified by urban development the flow is then delivered to streets gutters and storm sewers that transport runoff downstream more rapidly Travel time through the watershed is generally decreased Channel shape and flow patterns In small non urban watersheds much of the travel time results from overland flow in upstream areas Typically urbanization reduces overland flow lengths by conveying storm runoff into a channel as soon as possible Since channel designs have efficient hydraulic characteristics runoff flow velocity incr
59. application and practices The asphalt mix specifications should generally include void space aggregate type gradation and quality asphalt cement grade and content in the mix and mixing temperature Coring may be required Permeable Pavestones are interlocking concrete sections that when installed create a porous pavement surface material design APPENDIX 2 D P 19 of 21 standard should meet ASTM 936 Refer to product manufacturers installation recommendation for design details Operations and Maintenance must be carried out on all porous pavement surfaces This includes wet vacuuming on a routine basis and inspection of the observation wells at least quarterly to ensure that draw down is occurring After one year of monitoring the observation well monitoring may be reduced to an annual basis as long as the performance is adequate Cleaning of the surface at least quarterly is required to prevent clogging This may be accomplished with a vacuum cleaning street sweeper followed by high pressure water washing Otherwise porous pavement requires maintenance similar to that of regular pavement During snow and ice events do not utilize sand or other aggregate material that would clog the voids If the voids become fully clogged the only maintenance measure is replacement APPENDIX 2 D P 20 of 21 7 GENERAL DESIGN CRITERIA FOR MANUFACTURED PRODUCTS 1 Manufactured products ma
60. aproprate tina aan sheets and ecorded onthe final plat Unless specificalydesicnated as beine Public a Reserved Storm Drainageway Easement and the facHitiesit protects are consideredto be private withthesoleresponsibHity oftheownerto C EFhe minimumowidth of the Reserved Storm Drainageway Easement shall be 30 feet unless etherwise appreved by the Town Manager DESIGN OF CULVERTS 2 6 DRAINAGE FACILITY DESIGN For the purposes of this section manual drainage facilities include engineered infrastructure designed to safely and effectivelyearry receive convey and discharge stormwater runoff within Town s planning jurisdiction Drainage facilities must be designed to control convey stormwater runoff resulting from all storm events up to and including the design storm and check storm as noted in Table 2 1 2 6 1 Design Storms and Check Storms The 10 year design storm and 25 year check storm shall be used for design of stormwater management infrastructure on Local Streets The 25 year design storm and 50 year check storm shall be used for design of stormwater management infrastructure on Collector and Arterial Streets All streets crossing perennial or intermittent streams must comply with the Land Use Management Ordinance regulations regarding development in the Resource Conservation District 2 6 2 Design Standards The stormwater management and storm draina
61. be acceptable j Reference the N C State University Cooperative Extension Office for further design considerations k For flat areas a Stilling Basin Level Spreader may be used See the Outlet Protection section for design criteria or Appendix 2 F APPENDIX 2 D 2 of 21 EXISTING GRADE DITCH TO BE CUT ALONG IILS x CONTOUR TREATED TIMBER BERM CONSTRUCTED WITH 2 ml E lt OR OTHER SUTABLE mel 3 lt A PERMEABLE MATERIAL lt lt zs 4 pm A S INSTALL WASHED STONE A DEPTH gt OF R OF 6 TO FUNCTION AS FRENCH DRAN Es o SN FOR DITCH WRAFFED WITH NOTE SIAL EEES T PME GEOTEXTLE THE USE OF TREATED TIMBER OR 902 SIMLAR MATERIALS 5 RECOMMENDED pe OTHER DESIGNS BE ACCEPTABLE MIN us wa WITH TOWN ENGINEER AFPROVEL LA REBAR ANCHOR SECTION lt lt TYACAL INFILTRATION LEVEL SPREADER Figure 2 D 1 APPENDIX 2 D 3 of 21 SAMPLE LEVEL SPREADER WITH INFILTRATION DESIGN FOR SINGLE FAMILY LOT RATIONAL RUNOFF CALCULATIONS GROSS LOT AREA PRE CONSTUCTION C PROPOSED IMPERVIOUS AREA POST CONSTUCTION C TIME OF CONCENTRATION TWO YEAR INTENSITY TWENTY FIVE YEAR INTENSITY PRE CONSTRUCTION RUNOFF ONE YEAR 80 OF TWO YEAR TWO YEAR TWENTY FIVE YEAR POST CONSTRUCTION ONE YEAR 80 OF TWO YEAR
62. d make a reasonable effort to avoid damage to landscaping and vegetation within and or adjacent to easements The Town will not be liable for plants trees and other vegetation damaged as a result of work associated with use of utility easements When utilities are located in the public right of way it is desirable for the utilities to be located at the outer edge of the right of way Utility poles should be located as near the right of way lines as practical Utilities crossing under streets should be bored and jacked when practical SECTION 8 SOLID WASTE MANAGEMENT SECTIONS SOLID WASTE MANAGEMENT 8 1 RESIDENTIAL COLLECTION Residential refuse collection is provided by the Town of Chapel Hill Public Works Department for occupants of dwellings with five 5 units or less In order to provide this service the owner or occupant of the residence is required to previde standard metal or plastic refuse receptaeles of thirty twe 32 gallen ecapaeity or less p haye eae lids e Ded use 68 vallon Toll out Containers available 1222 222 Town s Public Works Department Alternatively standard commercially available metal or plastic containers can be used if they have tight fitting lids and do not exceed 32 gallons in size A maximum of two containers will be collected from each residential unit and must be placed at the curb on collection days Residents who cannot bring their containers to
63. description of the proposed erosion and sediment control measures shall be indicated on the Stormwater Management Plan If applicable a phasing schedule for construction and or removal APPENDIX 2 G P 5 of 6 of proposed control devices will also be required to ensure adequate protection for all phases of the development Inspection and approval of the installed devices by the Town or Orange County 1 required III B RESERVED STORM DRAINAGEWAY EASEMENT engineered stormwater facilities intended for management of peak discharges volume or water quality treatment shall be located within easements entitled RESERVED STORM DRAINAGEWAY and shall be indicated on the Stormwater Management Plan Unless specifically designated as being Public these easements and the facilities functions they serve are considered by the Town to be private and the Town assumes no responsibility for necessary inspection operation and or maintenance duties IV STORMWATER MANAGEMENT PLAN FOR SINGLE FAMILY OR TWO FAMILY DWELLINGS A Professional Engineer s Certification and Stormwater Management Plan are required for all Zoning Compliance Permit Building Permit Applications for single or two family development involving more than 5 000 square feet of land disturbance The Stormwater Management Plan shall indicate the Best Management Practices BMP s and or Integrated Management Practices IMP s necessary to manage peak discharge ra
64. ding thirty 30 feet in height where over fifty 50 percent of trees with a diameter at breast height DBH over six 6 inches are hardwoods Rare and specimen trees are defined in Section 5 7 6 of the Town s Land Use Management Ordinance and generally include all trees with a DBH greater than eighteen 18 inches Refer te section H of the Town s Development Ordinance for a comprehensive deseription of which trees to inchide onthe Landscape Protection Plan The critical root zone of a tree is defined as A circular area the radius of which is twelve 12 times the diameter of the tree at breast height measured from the trunk of the tree 1 E v P Ve UR 6 3j lt 2 2 v I2 x DBH DBH DIAMETER BREAST HEIGHT DIAMETER OF TREE 4 FROM GROUND LEVEL CRITICAL ROOT ZONE Figure 3 3 The Landscape Protection Plan should also be overlaid on the proposed grading plan and should identify the construction limit line and should indicate where tree protection fencing will be located In addition the following Tewn standard notes and a detail of the proposed tree protection fencing should be included on all plans EXCAVATION FOR IMPROVEMENT CRITICAL ROOT ZONE ExrEND TO CRITICAL ROOT ZONE Figure 3 4 b Town Standard Tree Protection Notes 1 pre construction conference will be held with the Town s Urban Forester prior to beginning site work
65. e Moderate High Density Residential gt 12 impervious or gt 1 unit acre Values calibrated for the Town of Chapel Hill and based on data from Hartigan 1983 CDM 1989 Haith 1992 and Schueler 1987 In order to perform these loading calculations the land use types and relative acreage must first be determined For example a proposed development contains 100 residential half acre lots moderate APPENDIX 2 G P 4 of 6 density A 20 acre commercial district is also planned The remaining tracts 15 acres will remain undeveloped open space The total nitrogen loading calculations for this proposed development would be as follows Moderate Residential 100 lots x V5 acre isses 50 acres 50 acres x 7 4 370 Ibs yr Commercial 20 acres VEL eee ord abi 264 Ibs yr Undeveloped 15 actes 0 6 9 Ibs yr Total Nitrogen 643 Ib yr II F MAINTENANCE AND OPERATIONS PLAN The Stormwater Impact Statement shall include a Maintenance and Operations Plan This plan shall detail the types and frequency of inspection and maintenance operations major and minor equipment necessary to perform maintenance activities access to the stormwater control facility disposal methods for uncontaminated and contaminated materials and information regarding the facility owner s and party or parties responsible for facility operation and mainte
66. e Department for a eurrent list of approved materials and for information on collection schedules 8 5 1 COMMERCIAL INSTITUTIONAL RECYCLING Commercial institutional development includes all sites zoned for commercial or institutional use that are not used for residential development A Solid Waste Management Plan is required to_be submitted to and approved by the Orange County Solid Waste Department to determine what types of recyclable materials will be generated by all newly proposed commercial or institutional development In order to receive glass and metal container recycling collection service service the owner or occupant of any food beverage service business is required to provide space for Tewn County standard roll carts compatible with semi automated collection vehicles For some small food beverage service businesses typically less than 1 000 square feet of serving floor area roll carts for glass and metal container recycling may not be required dependent upon the collection needs as determined by a Solid Waste Management Plan Reeyelable Corrugated Cardboard Note pee pu DONNE C IDE PEE MUN QD MN Ud be ues service epu 2 pam This must o MC Po contractors are SAN _ for 2 cardboard e a a a nai fae grease OF WAX 12 non corrugated cardboard Hike that used to construet single layer cereal box type cartons may be Pis 5 In additio
67. e appropriate intensity duration frequency table found in Appendix 2 A NOTE For the 1 yr storm use 80 of the 2 year storm peak discharge or the following equation to calculate intensity I g h T where I rainfall intensity in inches per hour G 104 empirically derived constant H 18 empirically derived constant T rainfall duration in minutes or time of concentration in minutes 4 Determine the composite runoff coefficient C using the table found in Appendix 2 5 Apply the Rational Equation for the applicable pre post development condition and storm frequency 2 4 INTEGRATED MANAGEMENT PRACTICES BEST MANAGEMENT PRACTICES IMP BMP S Development applicants shall utilize stormwater Integrated Management Practices and or Best Management Practices IMP BMP s to the extent practicable and as approved by the Town Manager The Town encourages the use of low impact design techniques to manage stormwater runoff as close as possible to its source The selection and use of the IMP BMP s for a specific development will vary depending upon variety of factors including site characteristics public safety spatial requirements soil characteristics hydrologic characteristics slope land use considerations maintenance requirements location within the watershed overlay districts buffer requirements tree protection requirements easements etc The following structu
68. e continuous and accessible to physically disabled users Such facilities should be designed to reasonably accommodate users with physical disabilities that require the use of walkers wheelchairs scooters or other such supplemental mobility devices Pedestrian facilities shall be designed such that they do not include slopes in excess of 1 12 unless flat rest areas are included between steeper segments Intersections between motorized vehicle ways and pedestrian ways shall be at grade or connected by means of a ramp with a slope no steeper than 1 12 Ramps and segments of pedestrian ways at intersections shall include detectable warnings in accordance with the requirements of the Americans with Disabilities Act See Section 5 of this manual for information on Parking Requirements 417 SOILS REPORT The developer shall submit may be required to submit a detailed soils report prepared by a soils testing company te the Tewn Manager to establish the suitability of the existing soils for roadway construction fer all streets This requirement may be waived by the Tewn Manager when his preliminary if the Town Engineering Inspector s site investigation indicates that normal compaction tests would sufficiently guarantee road base suitability In the event that the soil report and or site investigation indicates roadway construction requirements different from the standards described herein the Town Manager may require
69. e developer believes that for certain reasons his development will take more than one year to build out then he should record the final plat for only the phase that will be mest likely expected to be completed within one year H aeeessary tThe Town Manager may extend this deadline te Any failure ef the streets street failures that occurs within ene year of being approved the one year warranty period after acceptance of the street by the Town shall be repaired by the developer I 3n the judgment of the Town Manager the damages to the street surface area is excessive _such_that _patchine would _produce an anacceptable_surface _the _developermaybe ied id neh 1 cd 4 4 TRAFFIC CONTROL DEVICES Where warranted te ensure and as necessary for motorist bicyclist and or pedestrian safety and er te traffic control traffic signals signs and markings shall be provided in accordance with the standards set forth the latest version of the Manual on Uniform Traffic Control Devices for Streets and Highways Installation of all traffic control devices shall be approved by the Town Manager and the North Carolina Department of Transportation where applicable 45 EXTENSION AND COMPLETION OF ACCESS WAYS 4 5 1 Extension to Boundaries Streets bikeways and pedestrian ways to be extended onto adjacent property or into subsequent approved phase s of a single development shall be constructed to the common prope
70. e standards for pole and fixture selection and street light placement as described below are consistent throughout the Town 6 4 STREET LIGHT POLE AND FIXTURE STANDARDS FOR RESIDENTIAL STREETS The Town s standard residential lighting fixture is a 9 500 lumen high pressure sodium economical traditional luminaire mounted 12 black fiberglass This pole and fixture combination is available from Duke Power Company and requires that a supplemental fee reimbursement be provided to the Town prior to installation Comparable pole and fixture combinations are available from other utility providers in areas of Town not served by Duke Power Company Alternatively 9 500 lumen high pressure sodium cut off lens cobra head fixtures mounted on wooden poles at height of 25 may be acceptable in place of the Town standard fixture This pole and fixture combination generally does not require a supplemental fee reimbursement Other fixture and pole combinations including taller fiberglass poles and or ornamental fixtures may be acceptable as long as the developer is responsible for reimbursement of all associated supplemental fees Developers should contact the Public Works Department if an alternative to the Town standard pole and fixture combination is proposed 6 5 STREET LIGHT PLACEMENT STANDARDS FOR RESIDENTIAL STREETS The following standards should be used to determine the placement of street lights
71. eases and travel time decreases Slope Slopes may be increased or decreased by urbanization depending on the extent of site grading or the extend to which storm sewers and street ditches are used in the design of the water management system Slope will tend to increase when channels are straightened and decrease when overland flow is directed through storm sewers street gutters and diversions Computation of travel time and time of concentration Water moves through a watershed as sheet flow shallow concentration flow open channel flow or some combination of these The type that occurs is a function of the conveyance system and is best determined by field inspection Travel time is the ratio of flow length to flow velocity T L 3600 V Eq 3 1 Where travel time hr L flow length ft V average velocity ft s and 3600 conversation factor from seconds to hours Time of concentration is the sum of T values for the various consecutive flow segments 3 2 Where Tc time of concentration hr and m number of flow segments 210 VI TR 55 Second Ed June 1986 rse slope ft ft Wate APPENDIX 2 B iH E Vy So RECHT ee et LELLI ee N R rt EID 0105 03314 PE ETT EZECH HOCH 1
72. ects 7 4 SEWAGE COLLECTION SYSTEM Within the Urban Services Boundary a system of sanitary sewers together with all necessary pumping station and appurtenances shall be provided to serve all parcels of the subdivision or principal building of the development The system shall be designed to accommodate all reasonably anticipated future construction and occupancies The collection system shall conduct the sewage in sewers of adequate capacity to an approved treatment facility For development outside of the Urban Services Boundary Where i sewer is dw eG as by he n Manaager after con h se Wate approval of the lot by the County Health stall be 7 4 1 Provisions for Future Service Areas Where adjacent property is in the same drainage basin as the property being developed lines shall be designed to accommodate development of other properties in the same drainage basin Easements or other right of ways should be consistent with the potential needs for future extensions as well as the project under consideration 7 4 2 Design and Construction Standards and Materials The sewage collection system shall conform to all requirements and minimum standards of OWASA and of the applicable County and State regulatory agencies unless more stringent standards are provided herein Cast iron pipe fer private laterals must be used for taps at to the public sewer and must extend to the property li
73. ed utility provider to determine what types of plantings typically limited to shrubs and small trees are permitted within the easement areas 3 1 2 Parking Lot Requirements a Screening Standards parking lots shall be screened from public rights of way and adjacent properties zoned residential The minimum height of the screening should be 3 above the existing grade of the parking lot edge for right of way screening and 6 above the existing grade for residential screening These minimum heights should be reached within 2 years of planting when vegetation is included to meet the screening standards There should be no gaps in the screen greater than 6 wide b Screening Materials Fences or walls used for screening should be built of materials compatible with the principal building or existing adjacent fences or walls A minimum of 25 of the surface area of all fences and walls should be screened by plant materials within 2 years Whether plantings alone or a combination of plantings and fences or walls are used for screening the screen should be of a density to occupy 75 of a vertical plane of the required height for the peripheral length of the parking lot Plant materials used for screening in lieu of fences or walls shall be evergreen and have a minimum height of 2 when planted for 3 tall screening and 3 when planted for 6 tall screening Earth berms used for screening should have a minimum crown
74. edestrian movements Access points should be located to provide the optimum driver sight distance and least disruption to traffic on the public street system Driveway spacing requirements are provided in the Appendix 4 A in the Access and Circulation Section of this Manual When angle parking abuts a sidewalk it will be necessary for the designer to provide additional clearance between the sidewalk and the parking space to ensure vehicle overhangs would not decease the useable area of the sidewalk to adversely affect the pedestrian and handicap accessible routes See Section 4 11 for bicycle parking requirements 5 1 1 Geometric Design A lot layout schedule is provided in the Town of Chapel Hill Standard Details The lot layout schedule specifies the minimum standard dimensions for parking spaces and drive aisles parking spaces should be identified with pavement markings and or wheel stops Because of the difficulty of controlling the use of parking spaces the designer is encouraged to use standard or larger size spaces If site conditions dictate the necessity of compact spaces the percentage of compact spaces shall not exceed 20 of the total number of spaces Typically no more than 10 parking spaces should be arranged side by side without the provision of a landscaped island The island shall be of sufficient shape and width to provide for landscaping The minimum width for a landscaped parking lo
75. erflow spill way designed for the 100 yr storm event If design depths exceed 3 feet in any location they must include a perimeter safety ledge with a minimum width of 10 feet and maximum depth of 3 feet Must include sediment forebays at all points of discharge into the basin Must include a planting plan that is appropriate for the basin hydrology and design Must include maintenance access Reserved Storm Drainageway Easement and Operations and Maintenance Plan 2 Retention facilities permanent pool shall be designed to meet one or all of the general performance criteria They shall draindown to normal pool level within a period of 2 to 5 days The following general design criteria apply a Must have a minimum depth deepest point of 4 feet b Must be designed to promote sufficient oxygenation via fountains flush or other means c Must be designed to discourage mosquito larvae propagation or per acceptable practices d Must be designed to have appropriate appearance e Must include maintenance access Reserved Storm Drainageway Easement and design f Exposed side slopes shall be 3 1 or flatter g Retaining walls are acceptable in cases where the grades do not allow side slopes 3 Re Use facilities may be used to meet one all of the general performance criteria These facilities may include irrigation systems non potable uses in structures such as mechanical and flush wate
76. erstanding ef inlet losses resulting from the shape and alignment of the entrance to a culvert outlet losses resulting from the change in cross sectional area at the outlet of a culvert and friction losses resulting from resistance to flow within a culvert Culvert design may require the calculation of the hydraulic grade line to ensure surcharge protection 1 The inlet control analysis evaluates the capacity of a culvert is eentrelled at its entrance considering the depth of headwater type of inlet and the entrance shape The headwater depth is the vertical distance from the culvert invert at the entrance to the headwater pool surface The roughness length and outlet conditions of the culvert are not factors in an inlet control analysis 2 The outlet control analysis evaluates the capacity of a culvert is considering all hydraulic factors upstream from the outlet These hydraulic factors include the culvert shape length slope and roughness and the depth of water at the culvert outlet Friction losses are part of the outlet control analysis Culvert End Treatments are intended to provide protection against excessive are an cimportant consideration when designing culverts scour at inlets and outlets Chapel Hit requires that either a End treatments typically include flared end sections and or headwalls Table 2 4 lists inlet coefficients Ke for different entrance conditions and structure types Refer to Appendix 2
77. es This list includes species native to the Southeastern United States that are generally available in the nursery trade and are known to perform well in typical landscape installations in the Chapel Hill area Plants on this list are underutilized in area landscapes and are recommended for inclusion in regulated and non regulated landscape projects within the Town a Trees Scientific Name s Common Name s Remarks Aesculus pavia Red Buckeye Amelanchier laevis Serviceberry Several varieties available Chionanthus virginicus Fringe Tree Halesia Carolina Carolina Silverbell Ilex opaca American Holly Several varieties available Ilex vomitoria Yaupon Holly Several varieties available Magnolia virginiana Sweet Bay Magnolia Nyssa sylvatica Black Gum Prunus caroliniana Cherry Laurel Quercus pagodifolia Cherrybark Oak Very tolerant of heavy soils Quercus laurifolia Laurel Oak Taxodium distichum Bald Cypress Very tolerant of heavy soils b Shrubs and Vines Scientific Name s Common Name s Remarks Bignonia capreolata Crossvine Callicarpa Americana American Beautyberry Calycanthus floridus Sweetshrub Sweet Betsy Gelsemium sempervirens Carolina Jasmine Hydrangea quercifolia Oakleaf Hydrangea Ilex glabra Inkberry Holly Several varieties available Ilex verticillata Winterberry Holly Several varieties available
78. es a joint use agreement between the affected property owners will need to be developed submitted to the Town Attorney for approval and recorded en the apprepriate deeds in the appropriate county Registrar of Deeds Office In addition to this the proposed site plan may need to include an accessible location for a possible future dumpster This may also be required in other situations where the Selid Waste Management Plan indieates that an on site dumpster pad although not initially needed to service the anticipated quantity of refuse may be required in the future On large multi family commercial institutional developments the use of roll off compactors may be preferable to the use of multiple refuse dumpsters Developers can contact the Public Works Department for additional information about roll off compactor capacity collection and site design issues In erder to receive cardboard recycling collection service the owner or occupant of all commercial order to receive collection of food wastes including preparation waste extra portions or plate scrapings the owner or occupant of any food beverage business is required to provide space for food waste collection container s This material is generally collected from barrel type containers from 5 55 gallons in size 8 2 1 Recyclable Corrugated Cardboard Note Since November 1 1995 Town of Chapel Hill ordinance and Orange Regiona
79. evised August 22 2003 I INTRODUCTION Pursuant to the Town of Chapel Hill Land Use Management Ordinance Section 5 4 Stormwater Management all applications for developments or subdivisions and any building some single family or two family dwellings resulting in less than or equal to 5 000 square feet of land disturbance may not be subject to these requirements within the Town of Chapel Hill Planning Jurisdiction must include a Stormwater Impact Statement and a Stormwater Management Plan As authorized by the Chapel Hill Land Use Management Ordinance affirmative exemption to all or part of the requirements of the Stormwater Impact Statement may be granted by the Town Manager STORMWATER IMPACT STATEMENT THE FOLLOWING INFORMATION SHALL PROVIDED UNLESS OTHERWISE NOTED FOR ALL DEVELOPMENT OTHER THAN SINGLE FAMILY OR TWO FAMILY DWELLINGS INVOLVING LESS THAN OR EQUAL TO 5 000 SF OF LAND DISTURBANCE II A SITE ANALYSIS AND NARRATIVE A pre application discussion with the Town Stormwater Management Engineer is encouraged to determine the limits of study and to define study elements required Elements of the analysis should include but are not limited to Land use density impervious surface area and phasing Location topography on site and off site drainage conditions Upstream and or downstream volumes discharges and velocities Backwater impacts effects on existing upstream and or downstream drainage conveyance facilt
80. feet Designing the Overflow Design an overflow to discharge excess water out of the rain garden via a riser or yard inlet type outlet In cases where a turf or other stable gravel cover exists water can flow out of the rain garden on one side through a reinforced weir Rocks or turf reinforcement mats may be used to line the outlet weir For weir outlets adequate drainage down slope must be present Designing in Clay Soils bio retention areas must be designed to include drainage unless the engineer wishes to design using the underlayment soil with permeability rates exceeding 0 5 inch hour There are three principal parts to the rain garden cross section beginning with the bottom section 1 sub surface reservoir and drainage area which is comprised of 4 inch high density black plastic perforated pipe and 57 washed gravel 2 Thesandy loam soil zone 2 4 depth 3 The vegetation zone the visible part of the rain garden APPENDIX 2 D P 11 of 21 4 _ Ground cover may be double shreaded hardwood mulch pinestraw or native grass Do not use pine chips or other floatable materials P Apply Darcey s Law to establish draw down time in soil and Manning s formula for the pipe drainage system It should completely draw down for any design storm from 2 5 days Summary of design criteria parameters for rain gardens Sandy loam Infiltration rate And textural classification
81. from standard textbooks such as Chow 1950 or Linsley et al 1982 After average velocity is computed using equation 3 4 for channel segment can be established using equation 3 1 Reservoirs or lakes Sometimes it is necessary to estimate the velocity of flow through a reservoir or lake at the outlet of a watershed This travel time is normally very small and can be assumed as zero Limitations Manning s kinematic solution should not be used for sheet flow longer than 300 feet Equation 3 3 was developed for use with the four standard rainfall intensity duration relationships In watersheds and storm sewers carefully identify the appropriate hydraulic flow path to estimate Storm sewers generally handle only a small portion of a large event The rest of the peak flow travels by streets lawns and so on to the outlet Consult a standard hydraulics textbook to determine average velocity in pipes for either pressure or nonpressure flow The minimum T used in TR 55 is 0 1 hour A culvert or bridge can act as a reservoir outlet if there is significant storage behind it The procedures in TR 55 can be used to determine the peak flow upstream of the culvert Detailed storage routing procedures should be used to determine the outflow through the culvert 2 P 7 of 7 FIGURE 2 B 2 SCS METHOD FOR ESTIMATING VELOCITY Watershed Characteristics D NENNEN 2 1u
82. ge infrastructure shall be designed such that e Streets will not be flooded as a result of stormwater runoff from the applicable design storm Backwater will not exceed the boundaries of storm drainage easements or rights of Way e Structures and or property located outside of drainage easements or regulatory floodplains will not be flooded e maximum stormwater spread widths allowed in Table 2 3 are not exceeded for the applicable street classification TABLE 2 3 MAXIMUM ALLOWABLE STORMWATER SPREAD ON PAVEMENT STREET CLASSIFICATION MAXIMUM ALLOWABLE SPREAD LOCAL No curb over topping flow spread must leave at least one lane free of water COLLECTOR AND ARTERIAL No curb over topping flow spread must leave at least one lane in each direction free of water Where no curbing exists spread shall not extend outside of the public right of way Reference Wright McLaughlin Engineers e Surface flow and channel velocities do not exceed 4 feet per second for the applicable design storm There is no surcharging in the drainage system for the applicable design storm Hydraulic grade lines or grades must be calculated to demonstrate the efficiency of the storm drain system and as a check to ensure that there is no surcharging in the system a Hydraulic Efficiency Determining the hydraulic efficiency of a culvert requires calculation of three energy losses an und
83. h Carolina Department of Transportation if applicable Plants per 100 Linear Feet Buffer Minimum Location Large Small Shrubs Type Width Trees Trees A 15 External 2 4 6 Internal 2 4 6 15 External 6 8 15 10 Internal 4 7 12 20 External 5 10 36 Internal 4 8 30 D 30 External 6 12 40 Internal 5 10 30 E 100 External 10 15 70 Examples of appropriate varieties of large and small trees and shrubs can be found in the Plant Selection Standards When selecting shrub species a minimum of 5096 of the total number of required shrubs should be evergreen When it is acceptable to the Town existing vegetation can be used to satisfy some or all of the required buffer plantings In these cases the existing vegetation shall be in good health and be protected during the development process In most locations where existing vegetation is retained supplemental plantings of evergreen shrubs along buffer edges will still be needed in order to meet the planting requirements noted above The location of existing or proposed utility easements should be taken into account when determining the location of proposed buffers Consistent with Section 5 6 3 of the Land Use Management Ordinance required buffers cannot overlap utility easements other than in locations where the easements cross these buffers In these locations and where easements exist that may conflict with other landscaping standards applicants should contact the affect
84. hall be placed at the closest intersection to the dead end Also temporary dead end streets expected to be extended in the future shall include a sign located at the temporary dead end stating This Roadway is Subject to Future Extension 4 3 STRUCTURAL STANDARDS streets shall be paved with a minimum of an eight inch 8 compacted thickness crushed rock base and a minimum of a three inch 3 compacted thickness asphaltic concrete surface or equivalent design as approved by the Town Manager Streets to be constructed in areas designated as Type II on the map at the end of this section will require a ten inch 10 compacted thickness crushed rock base unless otherwise approved by the Town Manager Based on the results of soils investigations previously observed conditions and or conditions encountered in the field additional requirements for street construction may include increased pavement and or base thickness dewatering drain systems excavation of unsuitable materials installation of geotextile materials and other enhancements as may be deemed necessary to assure that streets will not experience premature failure The use of the curb and gutter section for street development has been determined to require the least amount of grading clearing right of way and maintenance of all alternative roadway sections Therefore to preserve the natural environment and to minimize erosion and sedimentation the Town will typical
85. he Fosse provide clearance toratt abere the conductors should_be removed fom a troe during routine line clearanece pranmae Foppine and hedgetke timmine oflarce trees to maintaintine clearance should not Maximum clearances around utHity ines should be as foHows Secondary conductors service loops communication conductors and street lightine conductors Side under and over clearance 3 Side under and over clearance 3 3 4 TREE PROTECTION STANDARDS 3 4 1 Tree Protection Ordinance Requirements development activities on non exempt sites that involve disturbance to trees or to the soil within the critical root zone of any tree should conform to the provisions of a Landscape Protection Plan submitted to the Town for approval a Landscape Protection Plan A Landscape Protection Plan should be prepared showing existing site conditions and areas to be protected during construction Existing conditions to be shown on the plan include vegetatien areas of significant tree stands and other signifieant notable landscape elements of the development site as well as and sheuld identify the critical root zones of all rare and specimen trees that will be affected by construction Significant trees stands are defined in Section 5 7 7 of the Town s Land Use Management Ordinance and generally include all wooded areas greater than 1000 square feet in size with a continuous canopy excee
86. her factor considered is whether impervious areas outlet directly to the drainage system connected or whether the flow spreads over pervious areas before entering the drainage system unconnected Table 2 A 1 is provided to aid in selecting the appropriate figure or table for determining curve numbers APPENDIX 2 2 7 in table 2 2 a to d represent average antecedent runoff condition for urban cultivated agricultural other agricultural and arid and semiarid rangeland uses Table 2 2 assumes impervious areas are directly connected The following sections explain how to determine CN s and how to modify then for urban conditions Hydrologic soil groups Infiltration rates of soils vary widely and are affected by subsurface permeability as well as surface intake rates Soils are classified into four HSG s A B C and D according to their minimum infiltration rate which 1 obtained for bare soil after prolonged wetting Appendix A defines the four groups and provides a list of most of the soils in the United States and their group classification The soils the area of interest may be identified from a soil survey report which can be obtained from local SCS offices or soil and waer conservation district offices Most urban areas are only partially covered by impervious surfaces the soil remains an important factor in runoff estimates Urbanization has a greater effect on runoff in whatersheds with soils having high inf
87. hould be placed over the critical root zone 3 33 Planting Requirements a Planting Seasons Trees and shrubs should be planted prior to May 15 and after September 15 Delayed plantings of required buffers and or other landscaping can be accommodated with the acceptance of a letter of credit submitted to and approved by the Town Planning Department b Weather Conditions Digging and planting operations should be performed only when the soil temperature at each planting area and of all backfill materials is above 32 degrees F Following a period of precipitation planting operations should resume only when the full epth of the planting pits tep twelve has satisfactorily drained c Handling Plant Materials Shade and water should be provided to all delivered material during dry weather and B amp B materials should be mulched if they are to remain unplanted for over 24 hours d Excavating Planting Pits planting pits should be excavated to a depth equal to or slightly less than the height of the planting ball The sides of the planting pits shoud be loosened and Toughened to facilitate the movement of roots into the surrounding soil and grax placedan he planting pit unle drainage outletis provided Setting Balled and Burlapped and Container Plants The top of the plant root ball should be set so that it will be level with the finished grade after settlement Generally large plants should be installed fro
88. icapped shall be on hard or paved surfaces and shall be indicated by pavement markings or other suitable means The spaces shall be identified with above ground signs as specified in the General Statutes 20 37 6 and 136 30 and the Manual on Uniform Traffic Control Devices Standard handicapped accessible parking spaces shall have a 96 inch minimum width and an access aisle adjacent to the space with a minimum width of 60 inches Van accessible parking spaces shall have a 96 inch minimum width and an access aisle 96 inches wide TOTAL NUMBER OF MINIMUM NUMBER OF SPACES IN LOT ACCESSIBLE SPACES 1 to 25 T 26 to 50 2 511075 3 76 to 100 4 101 to 150 5 151 to 200 6 201 to 300 7 301 to 400 8 401 to 500 9 501 to 1 000 two percent 2 of total 1 001 and over 20 plus 1 for each 100 over 1 000 Source North Carolina Building Code 5 2 ON STREET PARKING The designer must design on street parking to provide safe and orderly traffic flow on the street The primary use of the street 15 the movement of vehicles On street parking is considered secondary use of street space as are other uses such as truck loading zones Parking prohibitions can be warranted on the basis of statues traffic capacity or accident hazard Statutory prohibitions also apply to on street parking spaces near fire hydrants crosswalks and approaches to intersections Parallel
89. ies 5 Ability of natural drainage channel to convey additional volume discharges and velocities 6 Potential mitigation measures and 7 Delineation of the Resource Conservation District RCD for perennial and intermittent streams as determined by the Town jurisdictional wetlands soil series and regulatory FEMA Special Flood Hazard Areas po Note If it is believed that an intermittent or perennial stream may be on or within 150 feet of the property to be developed the applicant should submit a request for a stream determination to be performed by Town staff APPENDIX 2 G P 2 of 6 RELEASE RATE MANAGEMENT Accepted engineering practices will be required for determining both pre development and post development stormwater peak discharge data Hydrographs may be required on a site specific basis The peak discharge rate for the post development conditions shall be no greater than the peak discharge rate for the pre development conditions for the local 1 year 24 hour duration 2 year 24 hour duration and the 25 year 24 hour duration return period storms Acceptable methodologies for computing peak flow rates include the Rational Method HEC 1 or HEC HMS methods USDA TR 55 or other methods subject to approval by the Town Stormwater Management Engineer Depending on the development site location size area and the condition of the existing conveyance system and associated lands the Manager may waive or change the
90. iltration rates sands and gravels than in watersheds predominantely of silts and clays which generally have low infiltration rates Any disturbance of a soil profile can significantly change its infiltration characteristics With urbanization native soil profiles may be mixed or removed or fill material from other areas may be introducted Therefore a method based on soil texture is given in appendix A for determining the HSG classification for disturbed soils Cover type Table 2 2 addresses most cover types such as vegetation bare soil and impervious surfaces There are a number of methods for determining cover type The most common are field reconnaissance aerial photographs and land use maps Treatment Treatment is a cover type modifier used only in table 2 2b to describe the management of cultivated agricultural lands It includes mechanical practices such as contouring terracing and management practices such as crop rotations and reduced or not tillage Hydrologic condition Hydrologic condition indicates the effects of cover type and treatment on infiltration and runoff and is generally estimated from density of plant and residue cover on sample areas Good hydrologic condition indicates that the soil usually has a low runoff potential for that specific hydrologic soil group Cover type and treatment Some factors to consider in estimating the effect of cover on infiltration and runoff are a canopy or density of
91. ind each dumpster to protect the adjacent screening materials These bollards should be set in concrete footings a minimum of 2 in depth see diagram 4 3 Diagram 1 Standard Typical single dumpster pad with screening fence erected adjacent to pad TYHCAL DUMPSTER PAD SEE KENE E MIN Figure 8 1 Diagram 2 Standard Typical double dumpster pad with screening fence erected adjacent to pad 20 MIN E QNM E 22 MIN MERE TYHCAL DOUBLE DUMPSTER PAD D a a aa Figure 8 2 Diagram 3 Steel pipe bollard typical to be concrete filled and erected behind dumpster 5000 FORTLAND CEMENT V2 STEEL HFE AT 1007 Figure 8 3 8 2 5 Dumpster Pad Screening dumpsters are required to be screened on three sides Typically this includes screening the full width of the rear of the pad and 10 along either side If gates are proposed to screen the front of the dumpster s they should be installed with retainers to keep the gates in the open position during servicing and the use of this hardware should be noted on the development plans All gates should be dimensioned to provide a minimum clear width of 12 to service each dumpster Screening can consist of stone block brick wood or a combination of these materials The screen should be designed and planted areund landscaped so that it is consistent with the Town s
92. ing plan approval by the Town staff The use of the listed plants is also strongly discouraged in non regulated landscaping projects within the Town a Trees Scientific Name s Common Remarks Ailanthus altissima Tree of Heaven Albizia julibrissin Mimosa Morus alba White Mulberry Paulownia tomentosa Princess Tree Shrubs and Vines Scientific Name s Common Remarks Celastrus orbiculatus Oriental Bittersweet Vine Eleagnus angustifolia E pungens E umbellate Russian Olive Silverleaf Ipomoea purpurea Tricolor Common Morningglory Reseeding annual Ligustrum lucidum Waxleaf Privet Ligustrum sinense Chinese Privet Includes variegated type Ligustrum vulgare Common Privet Lonicera japonica Japanese Honeysuckle Lonicera maackii L Bush Honeysuckle morrowii L tatarica Rosa multiflora Multiflora Rose Wisteria floribunda Japanese Wisteria Wisteria sinensis Chinese Wisteria Groundcovers and Grasses Scientific Name s Common Remarks Fallopia cuspidatum Polygonum cuspidatum Japanese Knotweed Lythrum salicaria Purple Loosestrife Polygonum perfoliatum P sachalinense Giant Knotweed 3 2 20 Restricted Species This following list includes exotic species that may be available in the nursery trade and have
93. iods for determining design storm and check storm discharges for different types of facilities ia Chapel HiH The check storm analysis should indicate that surcharge or overflow discharges will be conveyed in a controlled manner that will not cause a public health or safety risk TABLE 2 1 DESIGN and CHECK STORMS Land Use Facility Design Storm Check Storm SCS 24 hour duration SCS 24 hour duration ee 77 Bridges Box Culverts Stream 50 yr 100 yr Crossings Detention Retention Infiltration 1 yr 2 yr and 50 25 yr 100 yr Facilities Buildings tty tg 2 For Regulatory Floodways the Design Storm is the 100 year return period and the Resource Conservation District provisions must be met Facilities may be designed to meet multiple stormwater management performance criteria Note Where conflicts exist between applicable State and Town design storm requirements the more restrictive of the two shall govern 2 3 1 Hydrologic Methodology RNC UR Hydrologic methodology includes estimating peak runoff rates volumes and time distributions discharge per unit of time as a result of precipitation The most commonly recognized methods for determining the relationship between rainfall and runoff are the SCS Method and the Rational Method Other analytical tools may be approved by the Town Manager if properly substantiated The SCS Method and Rational
94. ion of all proposed street markings centerlines stop bars crosswalks etc This plan should also include the following Town standard notes where applicable 6 7 1 Prior to the installation of any street signs or markings the developer will contact the Town s Public Works Department for an on site approval of the final design and placement 6 7 2 All pavement markings within the public right of way will be installed using a thermoplastic material with a minimum thickness of 125 mils 6 7 3 The developer will be responsible for installation of all required street signs and markings and for any repairs to these signs and markings that are necessary prior to the final acceptance of a new or improved public street for Town maintenance 6 8 STREET SIGNS AND MARKINGS STANDARDS Where warranted by the need to ensure motorist bicyclist or pedestrian safety and or to control vehicular bicycle and pedestrian traffic traffic signs and markings should be provided in accordance with the standards set forth in the most current edition of the Manual on Uniform Traffic Control Devices for Streets and Highways proposed street signs and markings plans should reflect the standards for sign and marking design and placement as set forth in this manual and should be approved by the Town Manager and where applicable NCDOT during the Town s design review process Developers can contact the Town s Public Works Departmen
95. ions and maintenance Where underground utility lines are to be located within a street right of way lateral lines shall be provided from the trunk lines to the right of way line for all lots and or development sites along the street and shall be installed concurrent with the installation of the trunk line to minimize cutting and repairing of street subsurfaces base courses and paving Lateral lines shall be installed as close to a 90 degree angle to the trunk line as possible and should not cross into or along the street frontage of abutting lots The minimum desirable horizontal separation between water sanitary sewer and stormwater drainage pipes installed in a common easement is ten feet Prior to a Certificate of Occupancy as built drawings shall be provided for all development for which a Zoning Compliance Permit or Engineering Construction Permit was required In addition to providing the depth of the installation and horizontal location the as built drawing shall call out the type of utility size and materials used for the installation Where trench compaction using standard procedures is impractical or if time constraints so dictate the Town will require the use of flowable fill material 73 SURFACE APPURTENANCES Surface appurtenances such as pump stations transformer boxes pedestal mounted thermal boxes and meter cabinets shall be located so as to minimize safety hazards visual impact and noise eff
96. ith the standards set forth in the Manual on Uniform Traffic Control Devices for Street and Highways 4 7 3 Street Addresses Street addresses are assigned to properties by the Town Manager Street identification siens shal inclide assiened bloclk numbers in addition to street names 4 8 MINIMUM STREET ELEVATIONS Minimum Elevations for crown of majer and miner arterial street pavements shall be two 2 feet above the one hundred 100 year flood elevation as shown in the HUD Flood Insurance Study Flood Boundary and Floodway Maps and Flood Insurance Report Streets bridges and other similar transportation facilities are permitted in the Resource Conservation District only upon approval of a Special Use Permit or a Subdivision application by the Town Council or by a variance granted by the Board of Adjustment 4 9 GUARDRAILS amp BARRIERS Guardrail shall be constructed within the right of way wherever the Town Manager determines that guardrails are necessary fer the preteetien ef the pubhe Generally guardrails will be required if a fill slope is steeper than 3 1 with a fill height greater than eight feet or as necessary adjacent to bridges and large culverts Reflectorized barriers shall be installed at the end of pavement on all streets or drives which are temporarily dead ended or when a T turnaround is installed The type s of barrier s required will be as necessary fer public safety
97. jects Following this list is a list of plants species that are discouraged due to their potential to become invasive and a third list of native plant species that are specifically encouraged as substitutions for more commonly planted non native species In addition to the information provided in the following lists of plants landscape designers are encouraged to research their plant selections carefully to assure that they are providing a diverse mix of species that will perform well on a specific project site For additional information about local plant adaptability landscape designers can contact the North Carolina Botanical Garden and the J C Raulston Arboretum Consistent with these Town landscaping objectives landscape designers are discouraged from planting large numbers of a single species in any given project and from utilizing plant varieties such as red tip photinia and leyland cypress that are prone to insect and disease problems in the Chapel Hill area For additional information about susceptible plant species landscape designers can contact the North Carolina County Extension Service Ne trees which by the nature of their fruit root system brittleness ofwood or Finke biloba Ginl ne A tt Walnut fuas Salix babylonica Weeping Willow The follewing tree species should not be plantedowithin25 feet of any s
98. l Landfill policy prohibit the disposal of recyclable corrugated cardboard from any business institution multi family or construction activity into any bulk waste refuse container Dumpsters found to contain recyclable corrugated cardboard may be refused service and or assessed a monetary penalty This material must be recycled Private contractors are available locally for cardboard recycling containers and collection services Some businesses may use public recycling drop off sites for corrugated cardboard recycling depending on quantity produced Non recyclable corrugated cardboard such as that which has been contaminated with food grease oil paint or wax and or non corrugated cardboard like that used to construct single layer cereal box type cartons may be thrown in the refuse container without penalty 8 2 2 Dumpster Pad Design Dumpster pads should be constructed of concrete with a compressive strength of 3500 psi For a typical single dumpster the pad should be 12 wide and 20 deep see diagram 1 For two dumpsters the pad should be 22 wide and 20 deep see diagram 2 The pad apron should be a minimum of 8 inches thick 3nereasing to 8 inches in thickness in the vieinity of the front wheels_of the service vehicle and tapering to a minimum of 4 inches in thickness direetly below the container see diagram 3 Two concrete filled 6 I D steel pipe bollards should be installed 4 apart and 1 from the rear edge of the pad beh
99. l meet all applicable standards Provision for their continued maintenance shall be approved by the Town Manager and recorded with the County Register of Deeds in a legally valid and binding instrument that describes the properties which the private access way serves and which runs with the land The maintenance agreement shall apply to all properties which the private access ways serve It shall contain a provision that at any such time that the private access way is no longer maintained to applicable standards the Town of Chapel Hill the County or the State of North Carolina as appropriate may provide such maintenance with the total costs of required maintenance assessed to those properties subject to the agreement 4 7 NAMES IDENTIFICATION AND ADDRESSES FOR PUBLIC AND PRIVATE STREETS 4 7 1 Street Names Names of streets shall reflect the continuity of streets 1 that a proposed street obviously in alignment with an existing street or planned as a continuation of a existing street be given the same name as the existing street and shall be neither wholly or partially duplicative nor phonetically similar to the name of an existing street within Chapel Hill Township 4 7 2 Street Identification Name Signs Street identification name signs shall be provided at all street intersections as part of street construction location and design of street identification name signs shall be approved by the Town Manager as in accord w
100. l supports should be removed after one year unless tree is excessively weak 3 3 4 General Pruning Requirements Pruning should consist of the removal of dead dying diseased interfering obstructing and weak branches and selective thinning to lessen wind resistance and improve the appearance of trees and shrubs Fhe folowing specifications should apply Pruning Specifications All cuts should be made close to the trunk or parent limb without leaving a protruding stub and without cutting into the branch collar or the branch bark ridge Clean cuts should be made at all times Trees limbs too heavy to handle by hand should be precut above the final cut to prevent splitting or peeling of the bark Where necessary to prevent tree or property damage branches should be lowered to the ground with ropes or equipment Treatment of cuts and wounds with tree wound dressing is discouraged except for cosmetic purposes in highly visible areas If such treatment is made materials non toxic to the cambium layer must be used and care should be taken to treat only the exposed wood with a thin coat of dressing diluted ih d OF ios idee 55 Me between trees where there is known danger of transmitting the disease on tools Climbing spurs should not be used unless the tree is dead or is to be removed Line Clearance Pruning 2 bees ied OF E greund utility lines t
101. lan must be prepared by a licensed professional The following pollutant removal credit will be given for level spreaders and filter strips that meet the previously described design criteria 40 TSS removal for filters strips that are primarily natural woody vegetation 30 TSS removal for filters strips that are planted with primarily woody vegetation 25 TSS removal for filter strips that are planted in grass or legumes APPENDIX 2 P 6 of 21 3 GENERAL DESIGN CRITERIA FOR INFILTRATION DEVICES 1 Infiltration facilities receive and temporarily impound stormwater runoff and discharge exfiltrate it into the surrounding soil 2 Infiltration devices are primarily used for 85 TSS removal water quality enhancement and volume management up to the two year design storm Infiltration practices that capture all of the 2 year 24 hour volume increase may utilize additional storage if necessary to provide sufficient reductions to the 1 and 2 year peak discharge as required by the general performance criteria 3 Infiltration devices shall be constructed after the site work is completed and stabilization measures have been implemented 4 Infiltration devices must be protected until their contributing drainage areas have been adequately stabilized 5 Requires engineered drainage perforated pipe system with outlet to ensure full draw down if underlayment soils permeability rate is less than 0 5
102. lectric Safety Code to allow 18 feet clearance over all public streets and over private driveways subject to truck traffic If a dumpster pad is proposed to be located in an area that requires the refuse collection vehicle to drive under wires the development plans should indicate that the wires will meet this standard In addition if refuse collection vehicles must drive below awnings canopies or other structures to access a dumpster these structures should also be a minimum of 16 14 6 in height In the immediate vicinity of the dumpster pad the minimum height clearance is 24 see diagram 8 7 Overhead clearance required for refuse collection vehicle directly above the container REFUSE TRUCK OVERHEAD CLEARANCE Figure 8 8 Multi family Commercial Institutional Refuse Collection Note Certain refuse yard waste white goods bulky items paint corrugated cardboard medical waste etc eaanet will not be collected from standard dumpsters Owners occupants of developments receiving dumpster collection service are advised to contact the Town of Chapel Hill Public Works Department for additional information about refuse requiring special handling and refuse collection schedules 8 3 RESIDENTIAL RECYCLING Residential recyclables collection is provided by Chapel HilPs Orance Community Recycling the Orange County Solid Waste Department for occupants of dwellings with five 5 units or less In erderto provide this service the owner
103. ly require the use of curb and gutter roadway section except as noted in the paragraph below In areas where poor subsoil drainage and periodic flooding is determined to be a problem by the Town Manager or in established neighborhoods without curb and gutter streets the developer may be required to use a roadside swale type street construction If curb and gutter 15 deleted additional right of way may be required The design of the swales shall be such that no significant erosion will occur from a ten 10 year storm rate of discharge Shoulders on arterials shall be paved On all other roads shoulders shall be constructed of at least 5096 gravel and at most 50 soil material Rell type curbs maybe considered andercertain condHions ontocal streets subject to submittal eftechnical support date_and justification for approval by the Town Manager 4 3 1 Phased Completion of Streets The developer shall synchronize the probable completion of houses or other building construction with the completion of the utilities fire hydrants and streets serving those buildings The intent is to prevent unreasonable inconvenience to the building occupants from dust mud or hazardous conditions and also to avoid unsightly appearance along the access to these buildings Therefore the developer shall complete the at a minimum the base course paving of all streets within the development within one year of the recording ef the final plat If th
104. m 3 4 above grade to allow for settlement plant material greater than 3 feet in height should be set plumb regardless of the slope of finished grade Plants smaller than 3 feet in height may be set perpendicular to finished grade on sloping sites the slope For container grown plants carefully remove the container and cut any container bound circling roots For balled and burlapped plants cut burlap away from the top of the root ball For plants in wire baskets set plant in planting pit then cut and remove wire that will remain exposed after backfilling along with the burlap from the top of the root ball Place and tamp backfill around root ball in 6 to 8 inch layers up to the level of the finished grade Avoid bruising or breaking roots when tamping the soil Remove all protective wrapping from trunks and branches and thoroughly settle plantings with water Place a minimum of 3 inches of mulch over plant ball and pit area taking care to keep material a minimum of 2 inches from the trunk of tree f Staking Trees Support should be provided only for al trees greater than 8 10 feet in height planted in exposed locations Trees should be secured using vertical stakes driven into the ground outside the planting pit with constraining lines made of webbing hose protected wire or other material that will not abrade or become embedded in trunk Slack should be provided in each constraining line to allow for some trunk movement and al
105. ment on all streets which are temporarily dead ended or where T turnarounds are constructed 4 2 7 Intersections Intersections of streets should be designed to minimize the number of potential conflicts among vehicular movements to give preference to the heaviest and fastest traffic flows to coordinate the location and alignment of driveways to discourage dangerous vehicular movements to avoid multiple and compound merging and diverging maneuvers and to provide adequate sight distances 4 2 8 Sight Line Triangles at Intersections Sight line triangles at intersections should be designed to assure adequate visibility for vehicles and pedestrian using the intersection Signs trees shrubs etc should not interfere with these sight lines The property owner shall dedicate sight line easements as necessary 4 2 9 Dead End Streets Street to be Pernan Aky dra end shall terminate in a paved circular cul de sac with a minimum of forty feet pod the center of the turnaround to the back of the curb Streets designed to be dead end temporarily such as in a phased development or where a street is to be extended can terminate in a paved circular turnaround or a paved T turnaround of adequate size to accommodate vehicles expected to use the street Under special circumstances a T turnaround may be acceptable as a permanent improvement A separate post mounted Dead End sign s
106. n one side of new streets where that side clearly cannot be developed and where there are no existing or anticipated uses that would generate pedestrian trips APPENDIX 4 A P 4 of 5 Where there are service roads the sidewalk adjacent to the main road may be eliminated and replaced by a sidewalk adjacent to the service road on the side away from the main road For rural roads likely to serve development a shoulder of at least 4 feet in width preferably 8 feet on primary highways should be provided Surface material should provide a stable mud free walking surface GSeurce Fhe National Safety Council and The Federal Highway Administration 1989 WalkAlert _National Pedestrian Safety Program Guide p 59 Recommendations forculde saes determined by Town staf APPENDIX 4 P 5 of 5 TABLE 4 A 2 GEOMETRIC DESIGN STANDARDS FOR STREETS AND INTERSECTIONS Level Roll Level Roll Level Roll Hilly Terrain Type 8 15 8 15 8 15 gt 15 Grade Vertical Curve K 2 45 40 40 28 20 28 2 15 Value Crest Sag 45 40 45 35 20 35 20 Street Grade 96 12 1 1 1 15 1 Max Min Min Horizontal Street SA 300 250 200 200 bd 100 Center line Radius ft 400 350 300 250 175 100 Super elevated Unsuper elevated Typical Shoulder 4 Width for Streets Without Curb and Gutter or Sidewalk ft 15 20 Minimum Street Corner Radius at Intersections ft Minimum Street and See T
107. nalte cardboard and containerrecycling the developer of al newly propesed commercial 2 interior OF a RS service areas to additi lali e eee 22222 20 generate more than 200 wooden pallets per week the development plans should alse include dedicated space of atleast 25 square feet for the storage reuse return _and or recychne of the pallets em 6 MAIN MMN Ks MAIN TYACAL SINGLE VVITH ROLLOUT CARTS Figure 8 9 Seale 4 F REDUCE SIZE AND WRAP TEXT Dineran 10 9 double dumpster pacaath teteartirea tor teesetubles and sereenine terce 1 2 1 eee AN Rr 41 ST M oi no PM M HB 24 MIN TYHCAL DOUBLE WITH ROLLOUT CARTS Figure 8 10 Note Pad width is 2 wider than standard double dumpster pad to allow rollcart access 8 5 2 Service Area Design Design requirements for dumpster pads for cardboard only dumpsters are identical to the requirements for refuse dumpsters For food beverage service businesses utilizing roll carts for glass and metal container recycling a combination refuse dumpster and roll cart area is recommended see previous diagrams 9 8 and 109 Service Area Access In order to provide recyclables collection all service areas must be accessible to
108. nance The Town will require a maintenance plan and may require that a perpetual maintenance bond be posted STORMWATER MANAGEMENT PLAN SEE SECTION IV FOR FURTHER INSTRUCTIONS REGARDING SINGLE FAMILY OR TWO FAMILY DWELLINGS A preliminary Stormwater Management Plan shall be submitted with the Stormwater Impact Statement detailing site location existing and proposed stormdrainage system s stormwater detention structure s BMP s IMP s grading landscaping erosion control features and Resource Conservation District location s The plan must present the existing and proposed conditions and features at a scale and quality suitable to include all impacted areas on site and off site For certain applications a pre application discussion with the Town Stormwater Management Engineer is suggested to discuss alternatives A final Stormwater Management Plan shall be submitted prior to issuance of a Zoning Compliance Permit III A EROSION AND SEDIMENT MANAGEMENT Any development causing the disturbance of more than 5000 sf of land area requires erosion and sedimentation control measures For disturbance greater than 20 000 sf of land area an Erosion Control Permit is required by Orange County For development causing one 1 acre or more of land disturbance the applicant must also submit an erosion control performance guarantee or bond with the Town Contact the Engineering Department for the required dollar value of this guarantee A general
109. ne within S of the servicedlocation The 5 building stub eut shall be of the same material 7 5 WATER DISTRIBUTION SYSTEM A water distribution system providing potable water from an approved treatment facility shall be provided to serve all parcels of the subdivision or principal buildings of the development The pipes shall be sized to provide fire protection and an adequate supply of domestic water for all reasonably anticipated construction and occupancies 7 5 1 Provisions for Future Service Areas Developers may be required to install additional linear footage of water mains and or of larger size to provide for water service to property outside the project under consideration Easements and rights of ways should be provided for lines installed by the developer and provisions shall be available for extensions to other adjacent properties 7 5 2 Design and Construction Standards The water distribution system shall conform to all requirements and minimum standards of OWASA and of the applicable State and County regulatory agencies unless more stringent standards are established herein Materials that are used by OWASA for piping are ductile and C 900 PVC If a developer deviates from this type of pipe it must be approved by the Town Manager after consultation with OWASA The piping for fire protection shall provide a minimum residual pressure of at least 20 psi when the following gallons per minute of fi
110. nels Ditches For maintenance and stability reasons the maximum side slope for open channels is 3 1 The channel protection required to prevent erosion is determined by computing the velocity in the channel at the design discharge and comparing that velocity with the permissible value for the type of channel lining used 2 6 6 Curb amp Gutter Standard 30 inch curb and gutter is required in all cases unless an alternative is approved by the Town Manager The minimum longitudinal grade for curb amp gutter is 2 Spot grades or profiles shall be provided in cul de sacs to ensure positive drainage 2 6 7 Subsurface Drainage The installation of subsurface drainage measures may be required to protect against inundation of subgrade materials when landscaped and or irrigated areas are constructed adjacent to streets or sidewalks See the following illustration of typical subsurface drain that may be required ae Department Stermwater Desien Ha additional and speeificcinformation regarding a variety of design issues concerning stormwater management and drainage Copies_of this handbool are avadablein the Chapel Hil Engineering Department SS Y uk S a 5446 YTE U Bree Oz i 155 y 2 5 OF 501 s Q 2 SG 2 une amp Ag ZO Rese 93 V r u
111. ng 3 1 2 feet from sidewalks and other paved pedestrian surfaces except where urban conditions would prohibit any planting 10 feet from all buildings 15 feet from street lights utility poles and above ground utility wires 10 feet from all underground utilities and 10 feet from utility vaults and ground level utility structures 2 Small Trees All trees reaching a mature height of less than 35 feet should be planted a minimum of 3 feet from back of curb edge of street pavement and driveways allow for any proposed future widening 2 feet from sidewalks and other paved pedestrian surfaces except where urban conditions would prohibit any planting 5 feet from all buildings 10 feet from street lights and utility poles 5 feet from all underground utilities and 5 feet from utility vaults and ground level utility structures 10 feet from door side 32 PLANT SELECTION STANDARDS The Town encourages the use of diverse plantings of native and well adapted non native species in all landscaping projects Because some species of plants have the potential to become invasive however there is a need for all landscape designers to carefully consider the risk of unintentional environmental damage when specifying exotic plant materials on planting plans Accordingly the Town provides here a list of plants that are known to be invasive the Chapel Hill area and are thereby prohibited from being used on Town regulate planting pro
112. ngwalls at 30 to 75 to barrel Square edge at crown essere 0 4 Crown edge rounded to radius of 1 12 barrel dimension or beveled top edge 0 2 Wingwall at 10 to 25 to barrel Square edged at crown 0 5 Wingwalls parallel extension of sides Square edged at 0 7 Side or slope tapered 0 2 Note End Section conforming to fill slope made of either metal or concrete 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 Outlet Protection must be provided as necessary to dissipate energy and to create diffuse flow at the outlet ends of conveyance structures Outlet protection measures include installation of rock reinforced aprons stilling basins level spreaders sump or other approved methods Refer to APPENDIX 2 F for further information Evaluation of flow conditions scour potential and channel erosion should be included in standard design analyses The initial protection against channel erosion should be sufficient to minimize the impacts of a single storm event Stilling basin and level spreader installations are preferred means of energy dissipation The use of local rock is preferred in lieu of quarried rip rap for the construction of energ
113. o determine their suitability for landscape use topsoil mixes should contain a minimum 2 organic matter range in pH from 4 5 5 0 7 0 and be free of herbicide and pesticide residues prior to the addition of amendments topsoil mixes should be amended as recommended by soil test results and be loose and friable at the time of planting c Backfill for Planting Pits Soil dug from the planting pit should be used for backfilling in order to avoid creating soil interfaces at the edge of the planting pit The backfill may be amended to contain a maximum of 10 added organic matter The backfill should be loose and friable at the time of planting d Mulch Mulch should consist of pine bark leaf mold or well aged wood chips or a combination of these three components On sloped sites where pine bark may float well aged wood chips should be used 3 3 2 Soil Preparation a Tilling of Areas to be Landscaped Existing compacted topsoils that are to receive plants or seed and subsoils that are to be overlaid with topsoil should be tilled to a minimum depth of 6 b Placing Topsoil in Areas to be Landscaped areas that are to be planted with turf shrubs or trees should receive a minimum of 4 6 of topsoil over finished subgrade Within the critical root zones of rare and specimen trees no remaining soil should be disturbed and provided that no change in grade occurs at the tree s trunk no more than 6 of topsoil s
114. on residential streets 5 1 Street lights should be located approximately 220 feet apart 6 5 2 Street lights should be located at all public street intersections and at the end of all cul de sacs and T turnarounds 6 5 3 Where possible all street lights that are not located at an intersection should be located on or adjacent to a property corner 6 5 4 Street lights should be located within the public right of way a minimum of 3 behind the curb or edge of pavement 6 5 5 On streets with sidewalks on only one side street lights should be located on the same side of the street as the sidewalk On all other streets street lights should be staggered on both sides of the street 6 5 6 On streets where street lights are proposed adjacent to sidewalks they should be located behind the sidewalk unless a tree lawn is provided that permits all parts of the poles to be located a minimum of 3 behind the curb 6 6 STREET SIGNS AND MARKINGS APPLICABILITY A developer may be required to install or upgrade street signs and markings within a public right of way as part of the design review process if the proposed project includes the improvement to or construction of new public streets 6 7 STREET SIGNS AND MARKINGS PLAN SUBMITTAL REQIREMENTS A street signs and markings plan should show the type and location of all proposed street signs stop signs speed limit signs etc and the locat
115. onvey approximately 10 times the maximum inflow Q from soil layer High density 4 perforated black plastic pipe network with clean out at end APPENDIX 2 D P 12 of 21 PARKING LOT STONE DIAPHRAGM BERM lt GRASS FILTER TRF UNDE RDRAIN COLLECTION 4 p 7 gt n VA EN oo fl E Xx 1 M eren Basin jii z MP Nig i Z UE S0 0 WT IRS L Al S SYSTEM 1 SEES RT LUNG UE UN 2 S S niis DAS BR ZA SA Rs I Nn 9 lt P S 1 1 SS 11 CSS m 2 am 2 TOT UNU WASHED STONE CURTAIN DRAIN OPTIONAL SAND ALTER LAYER E B c gt d j Z FILTER FABRIC 22 2 A 2 3 PERFORATED RFE 57 WASHED STONE SECTION AA RAIN GARDEN Figure 2 D 4 APPENDIX 2 D P 13 of 21 Landscaping Bio retention areas are specifically intended not to be wetlands They are designed so that water does not regularly saturate or inundate the garden for long periods The vegetation must be able to withstand brief periods of inundation Neither obligate wetland nor obligate upland vegetation is appropriate for rain gardens The following table lists several trees and shrubs that can be grown in bio retention areas Their Latin name common name habitat and size are given This table is not a complete list More
116. over certain plants listed are primarily found in either the eastern or western portions of North Carolina Other references include the NCDWQ BMP manual Two published references are Manual of Woody Landscape Plants by M Dirr and Carolina Landscape Plants by G Halfacre It is very important to select trees and shrubs that do not have overly aggressive roots Plants like willows can quickly send roots into drainage pipes Another plant to avoid is any type of cherry tree Aesthetics play an important role in plant selection especially for the homeowner Several plants have attractive blooms Evergreen species should also be selected to maintain color in the rain garden during the winter Consult your nursery or landscape professional to help select material that suits your situation Native grasses evergreens deciduous trees and shrubs and herbaceous species can be planted in a rain garden Note 1 very important that the watershed draining into the rain garden be tabilized before construction of the rain garden The site may be used as a sediment trap during site construction and converted after site stabilization occurs and the Erosion Control Officer approves 2 The Town Engineer must approve the sandy loam soil for permeability and texture prior to installation 3 These facilities must be maintained according to the submitted and approved Operations and Maintenance Plan See the NCDWQ BM
117. peak discharge rate criteria in part or in whole if based on an approved Stormwater Impact Statement it is demonstrated that detention would intensify existing peak discharges or might otherwise create problems on abutting and or downstream properties II C VOLUME MANAGEMENT Not applicable for single family and two family lots existing prior to January 27 2003 Using USDA Soil Conservations Service Curve Number CN method for total run off volume or other approved method the increase in volume from pre development conditions to post development conditions for the 2 year 24 hour storm where P 3 6 shall be managed on site using infiltration re use or other approved BMP IMP methods II D WATER QUALITY MANAGEMENT The applicant shall utilize stormwater Integrated Management Practices IMP s and or Best Management Practices BMP s as approved by the Manager to treat stormwater runoff from all disturbed built upon and impervious areas associated with the development The IMP BMP shall be minimally designed to remove 85 average annual total suspended solids TSS from post development stormwater runoff The IMP BMP may also be used to provide for volume management and release rate management as approved by the Manager Further information regarding the IMP BMP practices will be made available in the Town Design Manual Submit proposal s for IMP s BMP s to the Town Stormwater Management Engineer for review assumed TSS remo
118. pended solids pollutants Infiltration Detention Facility A variable depth engineered facility typically including a forebay to intercept waterborne sediment Release rate 15 controlled to facilitate water infiltration into the surrounding soils Soil Amendment includes tilling and amending existing soil with sandy loam to increase permeability Porous Pavement Asphalt concrete pavement specifically designed and placed with a high void ratio to create permeable surface Base materials are typically engineered to provide both support and storage capacity for water passing through the porous pavement Mix designs and placement guidelines are available although the Carolina Ready Mix Concrete Association the U S D O T Federal Highway Administration and the Asphalt Institute among others NOTE For Rational Method runoff coefficient c use 0 10 for SCS runoff Curve Number use 50 IMFPERUOUS ASPHALT dues PAVING IMPERVIOUS ENDS WATERSTOP 6 7 CHOKER COURSE 57 WASHED STONE GRADE BASE COURSE NCDOT 4 40 VOIDS 3 RVERIACKS FEFMOUS ASPHALT OR CONCRETE PERF HDFE ALONG BOT NON WOVEN GEOTEXTILE GRATE Figure 2 3 G Green Roofs Roof areas covered with soil material and vegetation intended to absorb rainfall and re use it to support the rooftop vegetation 3 Detention Retention and Re use Facilities A Detention Facilities
119. pplicable on the same side of an arterial street as the site Fire hydrants shall be located on loop main line systems with two 2 sources of flow when reasonably possible as determined by the Town Manager after consultation with OWASA 7 5 4 Location of Valves All intersections of lines shall be adequately valved as determined by the Town Manager in consultation with OWASA 7 6 AUTOMATIC SPRINKLER SYSTEMS 7 6 1 Non Residential An automatic fire sprinkler system meeting the requirements of National Fire Protection Association NFPA Standard 13 is required to be installed in non residential construction as follows a In new non residential structures if 1 the building has more than 6 000 square feet of floor area or 2 20 or more of the total floor area is more than 200 feet of travel distance from the nearest access point for a fire truck or 3 the building exceeds two stories or 24 feet in height from the height from the average grade of the lot to the windows on the topmost occupied floor In addition all connections shall be located on the street side of each building and activation of the sprinkler system shall activate both a local building alarm and a supervisory alarm at a twenty four 24 hour certified and licensed alarm monitoring service Upon the occupancy of any new renovated or expanded structure subject to this Section no person shall shut off or disable such automatic fire sprinkler system
120. pted that calls for the incremental replacement of existing light poles and fixtures Less commonly where development is proposed adjacent to inadequately lighted public streets incremental street lighting improvements may also be required If there are questions about a specific site the developer can contact the Town s Public Works Department 6 2 STREET LIGHTING PLAN SUBMITTAL REQUIREMENTS Developers should consult with the appropriate utility provider in the development of proposed street lighting plans Typically a street lighting plan will include the following information 6 2 1 The proposed location of street lights and the underground utility lines and or conduits that will be installed to service them If work is proposed within the Downtown Streetscape Study Area the developer should utilize the standard downtown conduit detail included in the Town s Standard Details 6 2 2 The location of street edge of pavement and or curb and gutter sidewalks and all property lines in the area where street lighting is proposed If other improvements such as benches or bus stops are proposed within the public right of way these should also be shown on the plan 6 2 3 A description and or detail of the proposed light pole and fixture Most commonly selected street light poles and fixtures require that a supplemental fee be paid to the utility provider prior to installation Where these poles and fix
121. r BaySaver Separation System CrystalStream Stormwater Treatment Device Stormwater _ Management Inc Stormgate Separator etc b Filtering Structures includes a filter medium to capture pollutants They generally include a primary settling chamber to remove solids and a series of filters or cartridges to remove other pollutants such as hydrocarbons and heavy metals Filter media is selected based on the target pollutant to remove Products include but are not limited to Stormfilter StormTreat System CDS Technologies or Continuous Deflective Separation Stormwater Management Inc Stormfilter and Stormscreen etc 4 General volume control devices include products that serve as a sub surface reservoir in lieu of stone Products include Presto Geoweb ADS perforated pipe Invisible Structures Inc Gravelpave Grasspave and Rainstore etc APPENDIX 2 D P 21 of 21 HYDRODYNAMIC STRUCTURE Figure 2 D 7 APPENDIX 2 P 1 of 1 DESIGN MANUAL HYDROLOGY TECHNICAL NOTE The section describing hydrologic methodology describes that the SCS Method the Rational Method HEC 1 HEC HMS TR 55 and other methods are acceptable for calculating peak discharge and volume For volume calculations the acceptable method is the SCS Curve Number Method For peak discharge calculations either the generation of hydrographs Type II or the Rational Method is acceptable for smaller catchments We are s
122. r Placement and Access Overhead Clearance 8 3 RESIDENTIAL RECYCLING Residential Recycling Note 8 4 MULTI FAMILY RECYCLING Service Area Design Service Area Access 8 5 COMMERCIAL INSTITUTIONAL RECYCLING Service Area Design SECTION 9 APPEALS SECTION 10 DESIGN MANUAL SUPPLEMENT END SECTION 1 INTRODUCTION SECTION 1 INTRODUCTION 1 1 PURPOSE These standards are meant to interpret and clarify the Develepment Ordinanee Land Use Management Ordinance and Design Guidelines of the Town of Chapel Hill The Town s land use and development policies as embodied in the Comprehensive Plan are necessarily discussed in such broad terms as livability Ppublic Ssafety and variety of housing mix The Comprehensive Plan contains community wide goals and objectives which emphasize the existing character of the Town and its neighborhoods The Develepment Ordinanee Land Use Management Ordinance and Design Guidelines deal with the more specific concepts such as types of use lot sizes parking requirements and the like However even these more specific terms can be interpreted in a variety of ways especially where a specific development in a specific location is being considered Therefore the Town of Chapel Hill Design Manual has been prepared to help people involved with land development in Chapel Hill and its planning jurisdiction to understand before they begin what will most likely be acceptable in this jurisdiction These standards
123. r and other uses APPENDIX 2 D P 16 of 21 DETENTION BASIN GRASSED BERM SEDIMENT FOREBAY YEAR EMERGENCY WEIR o SM uw X vg d J gt R ae Figure 2 D 5 APPENDIX 2 D P 17 of 21 00 VEAREMERCENCY UATE SEE cay we NET VEGETATON GRASSED BERM GEA OU OUTLET 2 E pum IN k 1 E m a Stra Jy SANDY LOAM SOL PERFORATED pre WASHED STONE SECTION AA DETENTION BASIN SECTION Figure 2 D 6 APPENDIX 2 D P 18 of 21 6 GENERAL DESIGN CRITERIA FOR POROUS PAVEMENT 1 Porous pavement may be used to the water quality and volume standards of the general performance criteria The general design criteria for the porous pavement stone reservoir drainage design and the underlaying soils are the same as for infiltration devices Additional design is required for determining the porous pavement thickness Pavement design is based on the underlayment soil strength projected traffic intensities and the storage capacity of the reservoir and base 2 A thorough examination of the site is of primary importance to the proper design functioning of porous pavement The following represents a general list of design elements that should be considered in any porous pavement design a Anticipated traffic intensities or average daily equivalent axle load
124. r bicycle traffic Pedestrian Access abutment on access to a street or publicly dedicated recreation area space containing a pedestrian way sidewalks or pedestrian trail or abutment on a street for which sidewalks are not required Such streets and or shoulder areas are presumed to be adequate for pedestrian traffic Nothing in the above definition of access shall be deemed to preclude the Town s authority to require improvement of substandard access ways to applicable standards At a minimum access ways shall have an engineered all weather surface that will reasonably accommodate routine service vehicles and emergency vehicles 4 2 GENERAL STANDARDS 4 2 1 Relationship to Town Plans Streets including associated bikeways sidewalks trails and transit amenities shall be arranged designed and located in conformance with the Land Use Plan Thoroughfare Plan Street Classification Plan Bikeways Plan Sidewalk Plan Entranceways Plan and Transit Plan 4 2 2 Relationship to Surrounding Access Ways Streets including associated bikeways sidewalks trails and transit amenities shall be appropriately related to and coordinated with surrounding existing and proposed roadways bikeways pedestrian ways and transportation patterns Roadways bikeways and pedestrian ways shall connect where necessary to permit the convenient and safe movement of traffic While street connections are encouraged leeal connecto
125. r connections to local streets should be designed to minimize their use by through traffic To provide convenient access for pedestrians each new development should 1 Provide walkways with direct access to adjacent developments neighborhoods parks bus stops and street sidewalks or an alternative pedestrian system 2 Investigate the possibility of using utility easements as connecting trails 3 Preserve existing trails unless superior alternative is provided 4 Install pedestrian signals at major intersections and pedestrian islands on roads wider than four lanes when warranted 5 Provide walkways from parking areas to buildings other than the parking lot itself 6 Submit written plan clearly identifying the party responsible for ongoing maintenance of pedestrian facilites 7 Construct walkways along all public streets unless environmental conditions dictate otherwise 8 All crosswalks should be clearly marked with paint or contrasting surface material in compliance with The Manual On Uniform Traffic Control Devices 9 Provide bicycle access to adjacent greenways If the scale of new improvements is small in relation to the amount of surrounding existing develepment improvements new improvements should be designed to blend with existing eenditiens improvements wherever possible unless existing improvements are inadequate 4 2 3 Appropriate Speed Local streets should be designed in order to
126. r other vegetation and some method to spread the stormwater runoff into a thin sheet Another type of vegetative practice is the buffer zone or buffer strip which is a strip of vegetation that has not been disturbed during development or has been planted along a stream or other area to be protected Filter strips with level spreaders are not generally a sufficient means by themselves to reach the 85 TSS removal requirement but they can be used in a series of BMPs that when combined will provide sufficient protection to surface waters Note The following design requirements apply to buffers and filter strips Design Requirements Filter strips must be 50 feet in width measured along the direction of flow for filter strips up to 5 slope Filter strips must be 50 feet plus 4 feet in width measured along the direction of flow for every 1 increase in slope up to a maximum of 15 Width of filter perpendicular to flow must be 100 feet for each acre of drainage area Velocity of flow must be under 2 fps for the maximum flow resulting from a 10 year storm Design must include a device such as a level spreader to allow runoff to enter the filter strip as sheet flow Maximum drainage areas flowing to individual filters shall be less than or equal to 5 acres B If the filter strip will be used during construction the area must be stabilized within 14 days T A grading and vegetation p
127. ral and non structural stormwater management practices may be used individually or in combination to meet the performance criteria established by the Town Other stormwater management practices and facilities will be considered on a site specific basis subject to approval by the Manager 2 4 1 Structural IMP BMP s a Functional Techniques Structural IMP BMP s are commonly used to meet stormwater runoff volume peak discharge and water quality performance criteria following information describes functional techniques typically associated with structural IMP BMP s 1 Diffuse Flow describes stormwater runoff that is conveyed in shallow un concentrated flow at velocities that do not cause scour Diffuse flow is typically created by uniformly and moderately sloped surfaces often in conjunction with the installation of a level spreader device to evenly disperse concentrated runoff flows Diffuse flow through a vegetated buffer such as wooded areas will often achieve significant removal of suspended solids TOP ELEVATION OF STRIP ON AE m SAME CONTOUR AND DIRECTLY dene d V ABUTS LEVEL SPREADER FORESTED ALTER STRIP LEVEL SPREADER Sen GRASS FILTER STRP SLOFE OF L TOWARD STREAM Figure 2 1 Filter Strip 2 Infiltration refers to the process whereby stormwater enters the soil typicall converting from surface flow runoff to sub surface flow Infiltra
128. range woven plastic or fabric with a height of four 4 feet installed on metal posts set a maximum of ten 10 feet apart as shown in the following typical detail EE ET ESI ERR EM ag FEX EM ET gt TREE FENCING Figure 3 5 In some situations where silt fence is required to be installed along the construction limit lines the silt fence is considered to function in lieu of the standard tree protection fencing and therefore the standard tree protection fencing is not required In other limited situations where construction impact 15 anticipated to be minimal a continuous line of survey flagging may be acceptable to delineate the construction limit lines Developers should contact the Public Works Department if there are questions about when these tree protection fence alternatives can be utilized d Site Work Guidelines 1 Root Pruning Existing Rare and Specimen Trees Root pruning is recommended prior to construction if digging trenching or grading operations are to occur within the critical root zone of a rare or specimen tree Root pruning is especially beneficial when undertaken during a tree s dormant season If root pruning is indicated on the Landscape Protection Plan it should be done with a root pruning or pavement cutting machine or by trenching with a ditch witch and cleanly severing all large roots 2 Clearing and Grubbing Trees and brush
129. re flow is withdrawn from any hydrant Single Family 750 1000 gpm Multifamily 1500 2500 gpm Commercial 2500 12 000 gpm Final determination of required fire flow rate s ql be determined by the Town Fite Chief based on size tecation use ete_of each propesed development Prior to issuance of a Zoning Compliance Permit a fire flow report shall be submitted to the Town Manager for approval The report must call out the gallons per minute that would be available at the applicable hydrant s state if the available fire flow will comply with the Town s standards and be sealed by an engineer registered in North Carolina A typical report would include an OWASA flow test that was conducted less than a year prior to submission of the report with supporting calculations If the required flows cannot be obtained from the existing OWASA systems it is the developer s responsibility to make improvements to the system with OWASA approval as necessary to comply with Town fire flow requirements 7 5 3 Fire Hydrants Fire hydrants shall be placed on lines eight 8 inches or larger in diameter unless approved otherwise by the Town Manager and OWASA They shall also be spaced so that the farthest portion of all principal buildings divisions thereof or dwelling units therein and all building areas of site plan and parcels within five hundred feet as a fire hose would normally be deployed of a hydrant and if a
130. recyclables collection vehicles These vehicles are comparable in size to refuse dumpster collection vehicles and the access standards described in the multi family commercial institutional refuse collection section of this manual for driveway and drive aisle design also apply here In addition to providing accessible service areas the developer of any new commercial institutional development should contact the Fewrs County s Solid Waste Department to complete a Solid Waste Management Plan addressing construction waste management and the use of materials with recycled content during construction and space planning for storage and collection of refuse and recyclables This plan will also need to address the storage and management of all regulated and potentially regulated wastes Commereialdnsttauen Reexeline Note Chape Hill Solid Waste Department for additional information on recyelable materials and for information on colection schedules SECTION 9 APPEALS SECTION 9 APPEALS Any decision of the Town Manager made in the administration of the provisions of this Manual may be appealed to the Board of Adjustment in accord with the provisions of Article 24 Section 24 2 of the Chapel HH Development Ordinance 4 10 of the Land Use Management Ordinance SECTION 10 DESIGN MANUAL SUPPLEMENT
131. rty line or phase boundary Where necessary to facilitate traffic flow or accommodate emergency vehicles a temporary turnaround may be required at the end of a street pending its extension Extension beyond the boundaries may be required where right of way exists to create connectivity 4 5 2 Improvement of Substandard Access Ways Where a development impacts abuts or contains an existing street bikeway or pedestrian way that provides required access but does not meet the standards contained herein improvement of such access way to applicable standards may be required if the development is expected to increase traffic volume and or affect the capacity of the existing facility This may involve improvement of the access way off site Partial width access ways shall be prohibited and abutting existing partial width access ways shall be completed to applicable standards 4 6 PUBLIC AND PRIVATE ACCESS WAYS 4 6 1 Public Access Ways Public access ways are streets bikeways and pedestrian ways located within publicly dedicated rights of way or easements and accepted for maintenance by the Town of Chapel Hill or the State of North Carolina Public access ways shall not be accepted for maintenance unless they meet all applicable standards 4 6 2 Private Access Ways Providing Required Access Private access ways are streets bikeways and pedestrian ways other than the above Where private access ways provide required access they shal
132. sable such automatic fire sprinkler system and no owner or resident of such building shall fail to prevent the shutting off or disabling of such a system Provided however that a sprinkler system may be shut off in order to perform maintenance work on the system during the time that qualified maintenance personnel are on the premises performing necessary maintenance work Such maintenance work shall only be conducted after notice to and approval by the Town Fire Department 7 6 3 Automatie Fire Sprinklersan Fraternity and Sorority Houses An automatic fire sprinkler system meeting the requirements of NFPA Standard 13 or 13R is required to be installed in each fraternity and sorority house in accord with the compliance deadlines in Seetion 7 42 of the Town s Develepment Ordinanee Land Use Management Ordinance In addition all connections shall be located on the street side of each building and activation of the sprinkler system shall activate both a local building alarm and a supervisory alarm at a twenty four 24 hour certified and licensed alarm monitoring service 7 7 EASEMENTS Public utilities are installed in either dedicated easements or public right of ways The standard utility easement width is thirty feet wide Easements for more than one utility typically are increased ten feet in width for each additional underground utility to provide for adequate separation between utility lines The contractor or utility company shoul
133. t for additional information about the specific design and size requirements for required street signs Signs that do not meet these design and size requirements will require replacement with approved signs prior to the acceptance of any new or improved public street for Town maintenance All pavement markings within the public right of way should be installed using a thermoplastic material with a minimum thickness of 125 mils Pavement markings that do not meet this standard will require replacement with approved markings prior to the acceptance of any new or improved public street for Town maintenance SECTION 7 UTILITIES AND EASEMENTS SECTION 7 UTILITIES AND EASEMENTS 7 1 INTERRELATION OF UTILITY LINES The installation and location of any utility line shall be integrated with that of all other utility lines in the vicinity so as to avoid cross connections minimize trenching and tunneling and keep incompatible systems separate Not withstanding sufficient preparation shall be provided as possible to minimize digging that would result in customer service interruption and to minimize adverse operating environments for other utilities 7 2 UNDERGROUND UTILITIES Where underground utility lines are to be provided beneath street roadways sidewalks or other paved access ways all such lines shall be consolidated where practical in a contiguous area so as to optimize excavation for installation consistent with good operat
134. t island is 10 feet of pervious soil 5 1 2 Pavement Standards The minimum standard pavement design for parking lot drive aisles shall be 8 inches of stone base with a 2 inch asphalt surface course A heavy duty pavement section will be required in locations determined to be necessary for service vehicle access The minimum heavy duty section shall be 10 inches of stone base and 3 inches of asphalt surface course An alternative design may be required if geotechnical information or projected traffic patterns dictate a different design The pavement design for parking space areas must provide an all weather dust free surface The pavement design shall be based on traffic patterns frequency of use soil conditions and stormwater drainage Curbing may be required for stormwater control or as wheel stops to prevent vehicle overhang into landscaped areas or walkways Wheel stops are required when other means for identifying parking spaces are not practical 5 1 3 Parking Decks The use of structured parking facilities is encouraged to minimize the amount of land necessary to accommodate cars Generally the geometric requirements for parking decks are the same as for surface parking However the designer may provide an alternative design based on accepted practices and subject to the approval of the Town Manager 5 1 4 Accessible Parking Spaces for Handicapped Parking spaces and access aisles for the hand
135. te to provide 85 total suspended solids TSS removal and if applicable to provide volume management All design submittals shall be sealed by a professional engineer licensed in the State of North Carolina The Stormwater Management Plan shall include all applicable stormwater impact calculations in lieu of a separate Stormwater Impact Statement Erosion control measures and a Stormwater Operations and Maintenance Plan are required for all development disturbing more than 5 000 square feet of land area Prior to issuance of a Certificate of Occupancy CO a P E Certification must be submitted certifying that the stormwater management measures were installed as shown on the approved Stormwater Management Plan and the agreed upon stormwater easement s and covenant s must be recorded with the appropriate County Register of Deeds V BEST MANAGEMENT PRACTICES AND INTEGRATED MANAGEMENT PRACTICES If applicable where the post development peak discharge rate or volume of runoff exceeds the pre development rate or volume and to achieve average annual 85 total suspended solids removal BMP IMP s will be required These practices may include structural or non structural measures Structural measures may include but are not limited to level spreaders curb cuts or diffuse flow grassed swales wet or dry detention basins wet retention basins extended dry detention basins bioretention areas pervious pavement and other infiltration practices Non
136. the Town Council prior to January 27 2003 This criterion can be achieved by hydrologic abstraction recycling reuse or any other accepted scientific method 2 2 3 Rate The post development stormwater runoff rate leaving the site shall not exceed the pre development existing conditions stormwater runoff rate leaving the site for the local 1 year 2 year and 25 year 24 hour storm events 2 2 4 Land Disturbance Disturbance of any stream channel shall be prohibited unless explicitly authorized by issuance of a Zoning Compliance Permit after demonstration of the necessity for the disturbance If stream channel disturbance 15 authorized it shall be minimized to the extent practicable 2 3 HYDROLOGIC DESIGN Hydrologic design includes evaluation of the impacts that development has on stormwater runoff The evaluation involves selecting the required design storm Table 2 1 and using accepted hydrologic methodology to design storm drainage infrastructure stream crossings detention retention facilities etc as necessary to meet applicable requirements and the performance standards of the Town s Land Use Management Ordinance adjaeent te some faeilities during times of peal runoff Designers must evaluate the impacts of sueh temporary impeundmen proposed stormwater management practices both on site and on nearby adjacent properties structures and roadways Table 2 1 lists return per
137. the above parking requirements commercial developments should provide shower and locker facilities Please refer to SECTION 10 DESIGN MANUAL SUPPLEMENT 412 STREET CLASSIFICATIONS AND GEOMETRIC STANDARDS Street classifications and geometric design standards are outlined in the fellewing Table l and Fable Appendix 4 A Information regarding existing streets and their classifications is available in the Chapel Hill Engineering Department streets within the Town limits are classified primarily by functional and or operational characteristics rather than by specific geometric criteria The street design standards represent specific interpretations of the general intentions embodied in the Town of Chapel Hill Develepment Land Use Management Ordinance and Design Guidelines Because the terrain of Chapel Hill varies from level to hilly the standards have been written as broadly as possible The notion of limiting cut and fill within the limits of public safety has been important in developing these standards The conscientious designer may occasionally find that street design in specific areas could be better accomplished in a manner which does not coincide with every standard in Appendix 4A at the end of this section In such cases the Town Manager will consider justification that strict adherence to all standards would create significantly undesirable conditions and or that deviation from the standards would produce a significan
138. the curb for health or age reasons can contact the Public Works Department and apply for an exemption allowing them to receive side or rear yard collection services underground orinside a garage shed or other enclosed area wherethecolHectormusttransportrefuseupordowrsteps wherethe colHector musttransportrefuse up or down driveways or walkways with a grad exceeding 15 in excess of 150 feet fromthe curbline of a publ street In newly proposed residential developments all streets are required to be built to Town standards to assure that refuse collection vehicles will have adequate access Developers should refer to the Town of Chapel Hill Engineering Department s Standard Details for vertical and horizontal curves pavement sections street widths and the dimensions of cul dez sacs and T turnarounds for this he refase erade R any ne if an 22 5 can Be that edd ies ded ies collection 8 1 1 Residential Refuse Collection Note Certain refuse yard waste paint medical waste etc cannot be collected from standard refuse receptacles Residents are advised to contact the Town of Chapel Hill Public Works Department for additional information about refuse requiring special handling and refuse yard waste leaf and white good collection schedules 8 2 MULTI FAMILY COMMERCIAL INSTITUTIONAL REFUSE COLLECTION Multi family development includes all sites zoned for m
139. the the Land Use Management Ordinance Stormwater Impact Statement Guidelines can be found in Appendix 2 G These guidelines provide specific information regarding preparation and submittal of Stormwater Impact Statements 2 5 1 Application Submittal Checklist The following information shall be submitted to the Town for review and approval prior to issuance of a Zoning Compliance Permit or Special Use Permit Stormwater Impact Statement Stormwater Management Plan Storm Drainageway Easements on plat and plan Certificate of Occupancy Engineer s Certification and as built Operations amp Maintenance Plan Recorded Deed dar locaton onion of ext ge inlcr and sacan Conservation District and regulatory A b Peak discharge ealeulations 1 yr amp 50 yr 24 heur duration stoerm event using aecepted hydrologie methodologyineluding but notHimitedto Rational Method USDA TR 55 e Polatanoading ealeulatiensdrecordaneecdthi Fable Guidelines ites Hed Reserced Sterm DramaeesemcEesemenc Here apcdecelepmentduehoceul ebstaetercenstoret stormwater from or aeross the property nternal collection d 5 Dedicated and shall be reserved from effective conveyance and control of B The ReservedStorm Drainageway shal be defined onthe a
140. theft 3 Parking should be located in close proximity to the building s entrance 4 Parking facilities should be located in highly visible well lighted areas to minimize theft and vandalism 5 Bicycle parking facilities shall not impede pedestrian or vehicular circulation and should be harmonious with their environment both in color and design Parking facilities should be incorporated whenever possible into building design or street furniture 6 Each bicycle parking space shall accommodate a bicycle at least six feet long by two feet wide Racks must not be placed close enough to a wall or other obstruction so as to make use difficult There must be at least 24 inches beside each parked bicycle that slows access Adjacent bicycles may share this access An aisle or other space shall be provided for bicycles to enter and leave the facility This aisle shall have a width of at least six feet to the front or rear of a bicycle parked in the facility 7 Paving is preferred not required Well draining gravel is the minimum surface reatment in order to avoid mud and dust 8 Bicycle parking facilities within auto parking areas shall be separated by a physical barrier such as curbs wheel stops poles or other similar features to protect bicycles from damage by cars 9 Ideally bicycle parking should be under cover to protect bicycles from damaging sun and foul weather In addition to
141. tion n Smooth surfaces concrete asphalt gravel or bare 0 011 0 05 Cultivated soils S20 seein 0 06 Residue COMER 0 17 Grass PARI oett EA eta adus mre ete t tad 0 15 eise 5566 coss ADM LT Mec fnt 0 24 tea 0 41 Range MAUI Aly La dec 0 13 Woods eese see abe atte d iei det ai ed 0 40 Denise o o uen e ne ur e e Maca ess sles e eda 0 80 The n values a composite of information compiled by Engman 1986 Includes species such as weeping lovegrass bluegrass buffalo grass blue grama grass and native grass mixtures When selecting n consider cover to a height of about 0 1 ft This is the only part of the plant cover that will obstruct sheet flow where T travel time hr n Manning s roughness coefficient APPENDIX 2 B P 5 of 7 L flow length ft P2 2 year 24 hour rainfall in and s slope of hydraulic grade line land slope ft ft This simplified form of the Manning s kinematic solution is based on the following 1 shallow steady uniform flow 2 constant intensity of rainfall excess than part of a rain available for runoff 3 rainfall duration of 24 hours and 4 minor effect of infiltration on travel time
142. tion of stormwater may occur naturally and or via devices that supplement and enhance the natural infiltration process 3 Detention involves the temporary storage and slow release of stormwater runoff The slow release shouldoccur over a period of 2 to 5 days with 3 days 72 hours recommended Detention facilities shall be designed to fully drain to a normally dry condition 4 Retention involves both permanent and temporary storage of stormwater runoff Retention facilities include a permanent pool with an additional area volume available to temporarily store stormwater runoff The temporary storage area should be designed to slowly release its stored volume over a period of 2 to 5 days Retention facilities shall be designed to release only the temporary storage volume and to retain the permanent pool volume 5 Re use involves capturing stormwater runoff and using it for appropriate non potable purposes such as non food crop irrigation equipment cooling washing toilet flushing etc b Facility Types and Descriptions 1 Diffuse flow A Level spreaders Constructed devices designed to convert concentrated flow to diverse flow B Uniformly graded moderately sloped conveyances Designed to minimize concentration of runoff flow C Vegetated buffers Natural or planted areas that will spread and reduce velocity of overland flow 2 Infiltration A Dry
143. tly better improvement Similarly the Town Manager may not allow the use of a every standard if public safety considerations dictate otherwise under specific conditions 1 OQ regarding alternative design_standards which_may_be conside d in certain situations on local Streets The standards in Appendix 4A are presumptive They are intended to be valid in most cases but it is understood that the public good may be better served in certain unique situations by allowing some flexibility in the standards New streets should be designed in a manner that balances functional and safety needs with the objective of preserving as much of the existing terrain and vegetation as is practicable 4 13 BICYCLE PATHS A bicycle path is a bikeway physically separated from motorized vehicular traffic by an open space or barrier and within the street right of way an independent right of way or an easement Bicycle paths provide recreational opportunities and serve as extensions of the transportation system The designer must use accepted design criteria to provide a safe bicycle facility Width and Clearance The minimum paved width for all two directional bicycle paths is ten 10 feet In some cases it may be necessary to increase the width of the path due to significant number of pedestrians using the path or when the path is designed with a horizontal radius less than 95 feet For horizontal clearance
144. tormwater or ce ip Mates Salixspp WHows Ulmus spp Elms Recommended Species Fhe folowing istHneludes trees and shrubs hardyn the Chape Hit area q x 9 x 9 appropriately sited and the Town encourages their use Whatever plants are selected seources for the plants should be located during the design process to assure that when a plan lized Fhetistis broken down into three sections targe trees smal trees and shrubs _that correlate dubahlie eateseries dJeundamthe Tosen badter requirement Hn senera tree ees ate alse gt list o near buildings and in undersized planters Inthe shrubs these plants preceded with an asterisk_ are evergreens_that routinely will reach six feet in_heicht within twe erewine Shrubs listed with two asterisks 248 appropriate components of a planting 1 are typicaly somewhat smaller are generally plan te fulfill the Town s sereening requirement a partof required buffers when planted along with larger materials Large Trees 3 2 1 Prohibited Invasive Exotic Species The following list includes exotic species that may be available in the nursery trade and are known to be invasive in the Chapel Hill area Plants on this list cannot be specified for use on landscaping plans for development applications requiring plant
145. ts to streams Level spreaders are one method of converting concentrated flow to diffuse flow Level spreaders may also be designed to provide for infiltration The following general design criteria apply to level spreaders a The entire system must be designed to safely pass the 10 yr storm event without causing scour rills gulleys or other failure b If diffuse flow 15 not attainable or otherwise will not cause improved conditions other methods should be used c Level spreaders shall be located in areas where land disturbances are already planned and unless it can be shown that alternative BMP s are not practical the removal of trees or the disturbance of soil solely for the purpose of level spreader construction is prohibited d Minimum length is 15 feet e The overflow lip must be level and stabilized with timber rock pipe or other hardened material unless the devise is designed to not overtop up to the 25 yr storm event where a grass berm is acceptable f For grass or thick ground cover buffer or filter strip the level spreader shall be 13 feet in length for every 1 cfs and slopes less than or equal to 8 g For woody vegetation buffer or filter strip the level spreader shall be 100 feet in length for every 1 cfs and slopes less than or equal to 6 h For steeper slopes structural level spreaders shall be followed by a grass berm level spreader of the same length i Manufactured level spreaders may
146. tures are placed within the public right of way utility providers require that this supplemental fee be paid through the Town as a one time up front cost Accordingly the following note 1 required to be included on all street lighting plans The developer will be responsible for reimbursing the Town for any and all supplemental fees assessed by the utility provider prior to installation of the proposed light fixtures For information about the relative supplemental fees assessed for different types of street light poles and fixtures developers should contact the utility provider directly 6 3 STREET LIGHTING GUIDELINES The type of street light pole and fixture selected and the recommended placement of the poles and fixtures will depend on a number of site specific variables In the Downtown Streetscape Study Area several different custom poles and fixtures that provide pedestrian level lighting as well as street lighting are recommended Developers can contact the Public Works Department for information about the specific lighting requirements included in the Street Lighting Master Plan for this area In other areas within the Town street lighting design is based on street classification and on the uses of adjacent properties Because these factors vary from site to site developers should contact the Public Works Department when proposing street lighting in non residential areas In residential neighborhoods th
147. uggesting that the Rational Method be used for catchments up to 25 acres in size unless routing the discharge through engineered facilities is required or deemed necessary thereby generating a hydrograph The Rational Method considers time of concentration for the selection of the storm duration and the rainfall intensity Jt cannot be used with a prescribed duration of 24 hours The result will be inaccurate and much less peak discharge generation for both pre and post development conditions will result which will lead to poor design practices The Land Use Management Ordinance states that for the 1 2 and 25 year peak discharges the 24 hour duration event must be considered This statement was assuming that the method to generate the peak discharges was the SCS Method not the Rational Method The Rational Method is a proven and reliable method to predict discharges in small catchments It is quick and easy to use and review Used correctly it is a good tool for the development community and the Town Therefore the Town should continue to accept the Rational Method however it must be used in accordance with acceptable engineering practices This will require that the time of concentration be calculated and used for the storm duration consideration not necessarily the 24 hour duration Most storm events in small catchments cause a peak discharge in a much less time frame than 24 hours such as 5 or 10 minutes
148. ulti family use with apartment buildings townhouses or condominiums with six 6 or more units This includes complexes or groups of buildings that may individually have less than six 6 units but which are located on a single zoning lot or have either shared driveways or common parking areas Commercial and institutional development includes all sites zoned for commercial or institutional use that are not used for residential development Multi family commercial institutional refuse collection service is provided by the Town of Chapel Hill Public Works Department at all sites that meet Town standards for receptacle design and access In order to provide refuse collection service the owner or occupant of all multi family commercial and institutional properties is required to provide standard front loading six 6 er eight 8 eubie yard dumpsters For all newly proposed development a Seld Waste Management Plan is required te applicants should contact the Public Works Department for assistance in determining the number and type of receptacle s necessary For some small developments typically non food service businesses with less than 5000 c feet of floor area alternatives to dumpster refuse collection an may be acceptable Coentaet the Toswn of Plan For some other commercial and institutional developments it may be possible to share the use of an existing or proposed dumpster pad on an adjacent property In these cas
149. ut are not limited to site applicability public safety spatial requirements soil characteristics hydrologic benefits slope existing land use conditions maintenance requirements location within the watershed overlay districts buffer requirements tree protection easements etc As a part of the development permit application process conceptual methods and designs outlined in the Stormwater Management Plan and accompanying Stormwater Impact Statement Appendix 2 G must be submitted to the Town for comprehensive review evaluation optimization and approval Revisions in the plan may be necessary to obtain Town approval B H PROLOGIC 2 2 PERFORMANCE CRITERIA 2 2 1 Total Suspended Solids Stormwater treatment shall be designed to achieve average annual 85 Total Suspended Solids TSS removal and must apply to the volume of post development runoff resulting from the first l inch of precipitation Alternative treatment methods to achieve 85 average annual TSS removal may be acceptable 2 2 2 Volume post development stormwater runoff volume leaving the site shall not exceed the pre development existing conditions stormwater runoff volume leaving the site for the local 2 year frequency 24 hour duration storm event for all development except single family and two family dwellings on lots existing as of January 27 2003 or on lots created pursuant to a Preliminary Plat that was approved by
150. val efficiencies for properly designed IMP s BMP s are as follows Retention Basins 8596 Sand Filters 8596 Bioretention Areas 85 Grassed Swales 100 linear ft per drained acre 35 APPENDIX 2 P 3 of 6 Detention Basins 50 Filter Strips 25 40 Infiltration Devices 85 Level Spreaders amp Buffers 50 minimum length 40 Manufactured Products Varies Single devices may be used or devices may be used in combination to achieve the required pollutant removal of 85 average annual TSS As experience grows in the use and effectiveness of the devices and methods other IMP s BMP s and or other specifications may be considered for use in Chapel Hill The NCDWQ and the Town of Chapel Hill will continue to review and modify both design and removal efficiencies as appropriate NUTRIENT LOADING CALCULATIONS Not applicable for development involving less than 1 acre of land disturbance Nutrient loading calculations shall be included with the Stormwater Impact Statement Yearly loads are calculated by multiplying the area of each land use by the appropriate loading coefficient as provided in Table 1 Required calculations shall include the pollutant loading of total nitrogen and total phosphorus Treating stormwater for nutrient loads is not currently required by the Town TABLE 2 G 1 Chapel Hill Pollutant Loading Coefficients Ibs acre yr LAND USE TYPE Low Density Residential lt 12 impervious or lt 1 unit acr
151. vandalism and weather 2 Class II is a stationary rack to which a bicycle can be secured with the user supplying both lock and cable or chain Racks must be easily usable with both U locks and cable locks Example is inverted U rack Racks that support a bicycle primarily by a wheel only and not the frame such as typical disk racks are damaging to wheels and are not acceptable The following table provides general guideline TABLE 4 1 LAND USE NUMBER OF SPACES CLASSIFICATION Industrial and Office 10 of auto spaces 80 Class 1 20 Class Commercial Retail 10 of auto spaces 20 Class 1 80 Class Multi Family Residential 1 space per unit plus 10 of 9096 Class I Garages or secure auto spaces accessible indoor areas count 10 Class II Recreation 25 of auto spaces 10 Class 1 90 Class II School 1 space per 3 students plus 1 90 Class space per 10 faculty staff 10 Class I Park and Ride Lot 10 of auto spaces 80 Class 1 20 Class Transit Center b Location and design of bicycle parking areas 1 Parking facilities shall support bicycles in a stable position without damage to wheels frame or other components and so that a bicycle if bumped will not fall or roll down 2 Parking facilities shall be securely anchored to the lot surface so they cannot easily be removed and shall be of sufficient strength to resist vandalism and
152. width of 2 maximum slopes of 3 1 and be covered with approved vegetation to provide a screen of the required height Figure 3 1 c interior Plantings and Parking Lot Shading Standards In addition to the screening requirements all parking lots are required to be landscaped and should provide vegetation to achieve at least 35 shading at maturity One large tree and 4 shrubs per 2 000 sf of paved surface planted within 10 of the parking lot edge will satisfy this requirement if the plants are spaced appropriately Typically no parking space should be farther than 50 from the trunk of a large tree or farther than 75 from 2 large trees D Xy NU Me Lewes A My 2 yr PARKING LOT EXAMPLE PLANTING 592 SIS Figure 3 2 When it is acceptable to the Town existing vegetation can be used to satisfy some or all of the required interior plantings In these cases the existing vegetation should be in good health and be protected during the development process Trees and shrubs required for interior plantings can be planted within buffer zones where parking lots abut these buffers These plants hewever cannot be counted te meet both buffer and interior planting requirements If plants are to be installed in landscaped islands these islands shall be designed and constructed to Town standards
153. y be used to meet the water quality or volume element of the general performance criteria These products are used generally in highly urbanized areas where surface facilities are not feasible These are flow through structures where they perform pollutant removal in a treatment chamber based on a design flow When the design flow is exceeded a by pass coveys the flow through the structure 2 The design flow and performance shall be based on the removal of 85 average annual total suspended solids TSS This may be determined with modeling using the manufactures approved software or by calculating the appropriate design discharge Pollutant removal efficiencies are very variable however and highly dependant on storm frequency or size influent pollutant concentration and type and rainfall intensity Additional design criteria information may become available and included in this manual 3 There are two 2 general types of manufactured systems for water quality a Hydrodynamic Structures that are based on a vortex or gravity system to remove pollutants through settling or separation of pollutants from the stormwater runoff They either consist of chambered separation structures relaying on settling of particles or they act as vortex swirl systems creating tangential inflow within a cylindrical chamber Products include but are not limited to Stormceptor Vortechs Stormwater Treatment System Downstream Defende
154. y dissipating rock aprons and stilling basins This Design Manual provides the minimum dimensions for rock aprons and stilling basins at storm drainage outlets However existing conditions at the outlet and scour potential may dictate the installation of outlet protect measures in excess of the minimum requirements 2 6 3 Storm Drainage Pipe The following criteria apply to storm drainage pipes under public streets within public rights of way and or within public drainage easements e storm drainage pipes shall be Class or greater reinforced concrete pipe The minimum pipe size is 15 inch inside diameter e Flared end sections may be used with pipes 36 inch or less in diameter e walls shall be provided for pipes with diameters larger than 36 inches unless alternative end treatments are approved by the Town Manager e The minimum cover for drainage pipes is 2 feet unless otherwise approved by the Town Manager The minimum pipe grade is 2 for storm drainage pipes 36 inches or less in diameter Flatter grades may be accepted by the Town for larger diameter pipe provided that it can be demonstrated that the design pipe grade provides for a self cleaning velocity of 3 feet per second when the pipe is flowing half full The maximum pipe length without installation of a catch basin curb inlet or junction box is 400 feet 2 6 4 Inlet Location and Spacing
155. ypical Section See Typical Section See Typical Section Right of Way Widths Detail Drawings Detail Drawings Detail Drawings TABLE 4 A 2 REFERENCE NOTES 1 Vertical Curve Value Used in computing the minimum length of vertical curve from the formula L KA where L Length of Vertical Curve 100 ft Design Constant Algebraic Difference of Connected Grades 2 Street and right of way widths will vary depending on specific combinations of utility requirements sidewalks traffic lanes turn lanes parking lanes bike lanes bus pull offs etc See typical street cross section drawings for more details 3 streets with centerline or one way crowns should be designed with a 2 cross slope This does not apply to superelevation designs on curves 4 ntersecting streets should be designed to create 90 intersection angles The minimum allowable angle of intersection is 75 under special conditions 5 Intersection sight distance criteria and other related information are shown in the standard details 6 Unless specified herein the American Association of State Highway and Transportation Officials AASHTO guidelines and standards will apply where appropriate SECTION 5 PARKING AND LOADING SECTION 5 PARKING AND LOADING S 1 OFF STREET PARKING The designer must design off street parking facilities to provide safe convenient ingress and egress for vehicular traffic and to minimize conflict with p

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