Home

1 Welcome to ALOHA - DISASTER info DESASTRES

1. aah dis 50 Tue Seu ac 53 Ggonic HM 53 a Chemical eos sea aU da EID UD 54 Reactive chemicals delis tiis unt PEE ed dedita 54 Chemical information in the Text Summary window 55 Chemical Data ict veri Oboe aa his ue ES 27 How to add a chemical to the library 58 How to modify information about a chemical 59 Delete 60 AOS DE 60 User p l meresan 60 Wind speed direction and measurement height 60 Ground Tous iness Ett bb E 63 C TOUL C OVE E E E 66 aes a a con use 66 viral 66 Invetstotr lietb ledit esque 68 4 EETA E inae Ee dota ota 69 IV Ad Olli aD dU MPa SUA 69 Choostfio AnA MN esiti mes sins 69 Transmitting SAM data to ALOHA 70 Using a SAM during an 1 1 2 71 Choosing the correct port for receiving SAM data 71 CHOOSING 4 t dio TrEQUETICY uere e pr ER e 71 Setting up ALOHA when you re using a 12 SANT OU OMS
2. AN eun eode eeu Dus 73 Check the time and date meet T Choosing a Calculate option eeessssseeeeeeeeeeneenenn TT OE E 77 ALOHA uoi o Pe o Pe Pd teet 78 ALOHA reports two release 78 When vou re using d SAM n im o iHe ees 79 DE CU os teresa vee NM dud 79 Describing d direct release a 80 a 80 81 Entering information about a puddle 82 Watch for changing weather conditions ssss 84 lien T ETE KE 84 Pressurtzed gulis iterates mod ens s 85 Tank size and s oe oat 86 CHGS ALS LAG atte 86 IE3quid 88 ee 88 Chemical of unknown state in tank 89 PAPC a ANd type OLGA osi ER pt eb ten p dina 90 Leak height on the tank wall cece ccccccccccceeeeeeeeaeeeeeeeeeeeees 9 Puddle TOMA OM hb e mdi ina ae 92 liio MANU DIMITTO 93 Pipe source 94 Source strength information in the Text Summary 95 COMP UCLA OM all ss eecostasctotosutitius edades uit epe N 95
3. Date amp Time Click Set constant time The scenario date is November 17 2000 so type 11 in the month box 17 in the day box and 2000 in the year box The accident time is 14 30 so type 14 1n the hour box and 30 in the minute box Click OK Date and Time Options You can either use the computer s internal clock for the model s date and time or set a constant date and time 3 Use internal clock i Set constant time Input constant date and time Month Day Year Hour Minute wj tz 2000 1 12 1 31 1900 0 23 0 59 Choose methane from ALOHA s chemical library by selecting Chemical from the SetUp menu Find METHANE in the list quickly type the characters me to go to the section of the list containing methane highlight the name then click Select Chemical Information MAGNESIUM DIAMIDE MAGNESIUM DIPHENYL MECHLORETHAMINE MESITYLENE MESITYL OHIDE METHACROLEIN DIRCETRTE METHACRYLALDEHYOE METHACRYLIC ACID METHACRYLIC ANHYDRIDE METHACRYLONITRILE METHACRYLOYLOHYETHYL ISOCYANATE METHALLYL ALCOHOL METHANESULFONYL FLUORIDE METHANE SULPHONYL CHLORIDE METHORYMETHYL ISOCYANATE METHORYMETHYLPENTANONE 4 METHOHYPHENYLACETIC ACID Chapter S Examples Entering weather information 1 Inthe SetUp menu point to Atmospheric then click User Input Lhemical aeH Atmospheric User Input SAM Station Computational
4. e e D oR Genter value complete 0 10 OR Q enter value medium 0 100 Figure 4 26 The SAM input dialog boxes ALOHA will not allow you to choose items from the Source menu until the SAM has been collecting data for at least 5 minutes 72 Chapter 4 Reference Your SAM will send data to ALOHA every 30 seconds If ALOHA is making calculations that require more than 30 seconds to complete it will miss some of these transmissions ALOHA uses the ast available data transmission to complete its calculations Similarly if you have set up an archive file to save the incoming SAM data see below the data will not be saved for you if ALOHA is busy calculating or drawing SAM Options After you click OK on the Cloud Cover and Humidity dialog box you ll see a new menu SAM Options to the right of ALOHA s Sharing menu You need not choose any items in this menu to use a SAM with ALOHA Instead use them when you want to view or archive weather information collected by the SAM SAM Options Archive Data Processed Data Wind Rose Figure 4 27 ALOHA s SAM Options menu Archive Data Choose Archive Data from the SAM Options menu to create a tab delimited text file containing data from the SAM along with dates and times of transmissions You will be asked to name the archive file Type in a file name then click Save ALOHA then creates this file for you as it receives SAM data adding data each time it receives ne
5. 2 Chapter 3 Learning the Basics 4 Next enter the amount of chlorine present in the tank In the scenario the tank contains 1 ton of chlorine You can enter the amount of chemical into ALOHA in of several ways In this case you know the mass weight of chlorine in the tank so click tons 2 000 Ibs then type 1 in the tank mass box Click OK Liquid ass or lone Enter the mass in the tank OR volume of the liquid pounds The mass in the tank is i tons 000 Ibs O kilograms OF Enter liquid level OR volume The liquid i gallons bic feet 8 O liters i cubic meters full by volume 5 Next describe how the chlorine is escaping from its container In the scenario a half inch diameter valve located at the center of one end of the tank is leaking Check to be sure that Circular opening is selected Click inches then type 0 5 in the opening diameter box Click Short pipe valve then click OK Hrea and Type of Leak Select the shape that best represents the shape of the opening through which the pollutant is exiting with length diameter A Circular opening O Rectangular opening inches feet Opening diameter 5 centimeters i meters Is leak through a hole or short pipevalue C Hole Short pipe valve 28 Chapter 3 Learning the Basics 6 Next indicate the height of the leak above the tank bottom Type in 50 for the
6. Select spreading algorithm If unsure let model decide Let model decide select this if unsure 3 Use Gaussian dispersion only 3 Use Heavy Gas dispersion only Define dose t Dose 0 2 Select Options from the Display menu Display Tile Windows Stack Windows TTT Options es Text Summary Footprint Concentration Dose Source Strength Calculate Calculate Now 3 The LOC for this example is 10 ppm so click Enter value then type 10 into the LOC box Click ppm 4 Check to be sure that Plot on grid and auto scale to fit window is selected Select either English units or Metric units depending on your preference ALOHA s computation results will be displayed in the units that you choose Click OK 130 Chapter 3 Examples mu pisplay Options SSS Select Level of Concern or Output Concentration t Default LOC not set in library IDLH ppm milligrams cubic meter eee value 2 milligrams liter 9 grams cubic meter Select Footprint Output Option amp Plot on grid and auto scale to fit window 9 Use user specified scale Select Output Units amp English units 2 Metric units 5 Choose Footprint from the Display menu to obtain a footprint plot Display Tile Windows Stack Windows Options db Y Text Summary Footprint Concentration Dose Source Strength 6 R
7. 111 Chapter 4 Reference Source Strength Release Rate Figure 4 56 Source strength graph for a pressurized tank release Source strength averaging ALOHA predicts source strength as a series of up to 150 steps These values must be averaged into fewer steps so that dispersion and concentration calculations can be completed quickly The averaged source strengths form a series of up to five steps each of at least 1 minute duration The highest release rate from each of the two series is reported on the Text Summary window The highest release rate from the first series of up to 150 unaveraged rates 1s the maximum computed release rate The highest release rate from the series of up to five averaged rates 1s the maximum averaged release rate The series of averaged steps 1s shown on the Source Strength graph since this 1s the information used to calculate the footprint Calculate some of ALOHA s computations especially its heavy gas concentration and dose calculations may be time consuming on less powerful computers For this reason you can specify when ALOHA calculations will be made and when Footprint Concentration and Dose windows will be updated When you use a SAM Station for Atmospheric Measurement with ALOHA your choice of calculation option affects how SAM data are used by ALOHA see below Calculation options Choose any of three options for deciding when to update ALOHA output windows Automatically update
8. 2 Type 15 in the wind speed box then click Knots Enter SE in the wind direction box Click the left hand button under the Measurement height above ground 18 heading to indicate that the wind speed 1s measured at a height of 3 meters Because the setting of this scenario is a rural road construction site click Open Country ground roughness Since you have little information about this site you may wish to run this scenario a second time this time with Urban or Forest selected Click the cloud cover button for complete cover Click OK Atmospheric Options Wind Speed is H5 amp Knots MPH Meters Sec Wind is from sE Enter degrees true or text e g ESE Measurement Height above ground is feet OR t 3 4l uh enter value l5 Ground Roughness is i Open Country iin OR Input roughness 20 3 0 ape 1 Urban or Forest Select Cloud Cover enter value oO 0 3 complete partly clear 3 Enter 44 for the air temperature then click ALOHA selects stability class D because when the sky 1s completely overcast regardless of the wind speed and the time of day stability class 15 always Since you were not informed that an inversion exists check to be sure that No Inversion is selected Type 78 percent into the relative humidity box Click OK 145 Chapter 5 Examples Atmospheric Options 2 Air Temperature
9. In a small industrial park outside Baton Rouge Louisiana a 500 gallon 4 foot diameter vertical tank contains liquid benzene On August 20 2000 at 10 30 p m local time a security guard discovers that liquid 1s leaking out of the tank through a 6 inch circular hole located 10 inches above the bottom of the tank He also sees that the liquid 1s flowing onto a grassy field west of the industrial park The guard thinks that the tank had just been filled that evening The temperature on scene is 80 F with the wind from the east at 7 knots as measured at a height of 10 meters by a fixed meteorological tower at the site The sky 1s more than half covered by clouds and the humidity is about 75 percent There is no inversion The local emergency planning committee LEPC has indicated that the Level of Concern LOC for this product 1s 10 parts per million ppm In this example scenario we ll determine the downwind distance to this LOC Choosing a location and a chemical 1 Start ALOHA Read the list of ALOHA s limitations click for more details then click OK 2 Choose Location from the SiteData menu SiteData Location 1 Building Type Date amp Time 121 Chapter 5 Examples 3 to quickly move to the section of the list containing names beginning with b then scroll down a little farther until you see BATON ROUGE LOUISIANA Click on this name to highlight it then click Selec
10. atm 3 psi OF Ci Pa C pounds tons 000 Ibs The amount of gas is 0 052 gt kilograms C cu ft at STP C3 cu m at STP Cancel Figure 4 38 Tank pressure amount of gas in a tank Type a value for either the tank pressure or the amount of gas either as mass or as volume at the Standard Temperature and Pressure of 1 atmosphere and 0 C then select units Click OK If you enter a value for tank pressure ALOHA will automatically estimate the mass in the tank Once you have entered values for tank size temperature and either pressure or amount of chemical ALOHA will check to be sure that the chemical is a gas If the tank temperature is below the chemical s normal boiling point or if the tank pressure is high enough to liquefy the chemical ALOHA will warn you that your chemical 15 not a gas If this happens click Cancel to return to the previous dialog box click Tank contains liquid then continue Chemical of unknown state in a tank If you are unsure whether a chemical in a tank is a gas or liquid and you clicked Unknown when asked to identify chemical state you will need a value for the total mass weight of chemical in the tank in order to run ALOHA ALOHA uses this value along with information about the chemical s properties and the temperature in the tank to predict the chemical s state and the amount of chemical that could be released Type in the mass of chemical in the tank then select units o
11. cubic feet cubic meters Select ground type amp Default 9 Concrete G Sandy Moist Input ground temperature Use air temperature selectthis if unknown Ground temperature is oc Input initial puddle temperature Use ground temperature select this if unknown 3 Use air temperature Initial puddle temperature is Is OC Figure 4 34 ALOHA s puddle source dialog boxes Next indicate the type of ground beneath the puddle Ground type influences the amount of heat energy transferred from the ground to an evaporating puddle Ground type 1s most important when the spilled liquid is cryogenic Cryogenic liquids are those such as liquefied natural gas LNG which are stored at low temperatures because they boil at temperatures well below ambient As it estimates heat transfer from ground to puddle ALOHA assumes that the ground does not absorb any of the spilled chemical ALOHA offers you four choices for ground type Default unwetted soil not covered by rock or concrete Concrete concrete cement asphalt or otherwise paved surfaces Sandy sandy dry soil Moist sandy moist soil 83 Chapter 4 Reference ALOHA expects heat to be transferred most readily from default ground or concrete surfaces into a puddle and least readily from sandy ground Next indicate the ground temperature which influences the amount of heat transferred between the ground and the puddle The warmer
12. Dispersion Options Pius nine rei E 96 edd oon MEE ee 97 272817 nie 99 Tile and Stack Wan Ow E 99 ODO 100 Level C OC Elus tenni tn E 100 Footprint options seessessssssssseeeennnnne nennen nennen nnn enses 102 DelecL OUIDUE D PIS uae etis rette diesem tiet 103 E 103 FOO 104 Interpretino 4 TOOLUDETE oro 105 ConcenttatiloDi soe etii Ra DIR pa ovS avete repe doi pei No de vicusit S 105 Designating lOCAION occa 107 Using fixed east west and north south coordinates 107 Using relative downwind and crosswind coordinates 108 DOSE 109 ALOHA definition of 109 Adjusting the dose exponent 110 q dose E pet Gea Ed pee tod 110 SOUC ESENE ITE 110 Constant source SIREN O p Maa eu 111 Variable Source SITETIOLIT 111 Source SU OL May CACO 112 Gri E 112 Ties Torres 115 It msan the SBatimo Meni p os cou 115 Soa mulsum PCT
13. If you already have an earlier version of ALOHA installed on your computer either in Windows or on a Macintosh the ALOHA installer will update your existing ALOHA files as follows B It will not change the ALOHA location library CityLib any location information you have added will be retained B It will replace your out of date chemical library ChemLib with the current version Any chemical information you have added to the library will not be saved You will need to re enter that information into the new library after you have installed ALOHA Because you will not be able to open a previous version of the chemical library using the current version of ALOHA before you install ALOHA be sure that 17 Chapter 2 Installing ALOHA you have a record in some other form of the information you have added to the library Whether or not you have a previous version of ALOHA installed on your computer follow the instructions below to install the current version Installing ALOHA Windows An installer contained on the CAMEO CD ROM disk automatically uncompresses and copies the ALOHA files to your hard drive Making the installation 1 Exit all Windows programs before beginning the installation 2 Insert the compact disk In Windows 95 98 or NT in the Start menu click Run In Windows 3 1 choose Run from the Program Manager s File menu 3 Type D ALOHA Setup exe in the dialog box if D is t
14. 2 8 for the pipe diameter then click inches Type 1000 for the pipe length then click feet This pipe 1s connected to a safety valve but because the valve has been left open the pipe is likely to release methane until the valve can be closed The conservative choice for this example problem is to assume that the pipe 15 connected to a methane source large enough that methane will continue to flow through the pipe at a constant rate Therefore click connected to infinite tank source If the safety valve for the pipe had been closed closed off would have been a better choice The pipe s inner wall is smooth so click Smooth Pipe Click OK fM input E Input pipe diameter Diameter is i inches O cm Input pipelength Chem Pipe length is Gb ft Qyds meters The unbroken end of the pipe is Heip i connected to infinite tank source O closed off Select pipe roughness Heip i Smooth Pipe Rough Pipe Cancel Type 100 for the pipe pressure then click psi The temperature of the pipe is described as ambient so click Unknown assume ambient Click OK Pipe Pressure and Hole Size Input pipe pressure Pressure is psi atm Pa Input pipe temperature Unknown assume ambient Co Temperature is mF OLD Hole size equals pipe diameter The information that you have entered into ALOHA as well as ALOHA s estimates for release rate and duration now appe
15. AlohaSpy a companion program to ALOHA Use it to view results of ALOHA model runs that you have archived as Spy files Installing ALOHA on a Macintosh An installer contained on the CAMEO compact disk automatically uncompresses and copies the ALOHA files to your hard drive Use this installer whether or not your computer has a math coprocessor Making the installation 1 Insert the CAMEO compact disk 2 Double click the ALOHA Installer program icon 19 Chapter 2 Installing ALOHA 3 Read the introductory information then click Install to install ALOHA on your hard drive Your ALOHA files will be placed either in your existing ALOHA Folder if you already have one or in a new ALOHA Folder on the top level of your hard drive or startup volume if you have more than one hard drive If you also are installing CAMEO on your computer we recommend that you place the ALOHA Folder inside your CAMEO Folder You can move the ALOHA Folder to any location on your hard drive but don t remove any ALOHA files from this folder Your new ALOHA Folder will contain the following files ALOHA is the main program ChemLib is ALOHA s chemical library It contains physical and toxicological property values for about 1 000 chemicals B CityLib is ALOHA s location library It contains elevations latitudes and longitudes and other information about many U S cities and a few non U S locations You can add or d
16. Calculate Calculate Now You ll see ALOHA s footprint for this scenario showing that benzene concentrations may exceed 10 ppm as far as about 900 yards downwind of the leaking tank Footprint Window 131 Chapter 5 Examples Check the Text Summary for this release You ll see a note Dispersion model Gaussian indicating that ALOHA made Gaussian dispersion computations even though benzene s molecular weight is greater than that of air This 1s because the concentration of benzene vapors in the air 1s not high enough to make the density of the mixture of benzene vapors and air substantially greater than that of pure air Text Summary SITE DATA INFORMATION Location BATON ROUGE LOUISIANA Building Air Exchanges Per Hour 0 65 iunsheltered single storied Time August 28 2888 amp 2236 hours COT user specified CHEMICAL MFORMAT I OH Chemical Mame BENZENE Molecular Height 78 11 kgrkmol TLV THRH 8 1 ppm IDLH 566 ppm Warning Potential or confirmed human carcinogen Footprint Level of Concern 18 ppm Boiling Point 175 16 F Vapor Pressure at Ambient Temperature 8 13 atm Ambient Saturation Concentration 134 948 ppm or 13 953 ATMOSPHERIC INFORMATION MANUAL INPUT OF DATA Hind knots from at 18 meters Ho Inversion Height Stability Class O Air Temperature 88 Relative Humidity 752 Ground Roughness open country Cloud Cover tenths SOURCE STRENGTH INFORMATION Leak from hole in vertical
17. Pipe hole size Pipe length Pipe pressure Pipe temperature Puddle area Puddle depth Puddle diameter Puddle mass Puddle volume Source height Tank diameter Tank length Tank mass Tank opening Tank pressure Tank temperature Display Dose setting User spec conc User spec scale Must be greater than or equal to 0 01 per hour 1286 ft 392 m 09 09 1 1 0 0 100 73 0 tenths 0 0004 in 0 001 cm 10 ft 3 m 0 2 kts 1 m s 2 3 mph 0 any units 58 50 C 0 4 in 1 cm 0 200 times pipe diameter 2 times ambient pressure boiling point 3 sq in 20 sq cm 0 1 in 0 25 cm 2 in 5 cm 0 22 Ibs 0 1 kg 0 03 gal 1 1 0 0 7 ft 20 cm 1 7 ft 50 cm 0 0 04 in 0 1 cm 1 1 atm 459 F 273 C less than or equal to 60 per hour 28 000 ft 8 535 m 90 180 12 31 23 59 150 F 65 C 10 tenths 78 in 200 cm 5000 ft 1 524 m 100 100 kts 51 m s 115 mph 1 000 000 000 any units 188 F 70 C 32 8 ft 10 m diameter of the pipe 6 2 mi 10 km 680 atm 10 000 psi 2 795 F 1535 C 37 500 sq yd 31 400 sq m 110 yd 100 m 220 yd 200 m 110 tons 100 metric tons 2 640 000 gal 10000 cu m 5000 ft 1 525 m 3 280 ft 1 000 m 3 280 ft 1 000 m 200 000 000 Ibs 90 720 000 kg circular cross sectional area or 1096 of surface area whichever is smallest 68 atm 1 000 psi 19 937 F
18. Y Text Summary ae Footprint Concentration Dose Source Strength 6 Calculate Calculate Now ag Source Strength Release Rate pounds minute Whenever you run ALOHA ask yourself Is ALOHA accurately representing what is actually occurring in this scenario In this case liquid benzene leaks from a tank to form a puddle ALOHA expects that because the puddle is undiked it spreads out to cover a large area and evaporates at a high rate for a short period of time What if the puddle were constrained by small depressions in the ground The puddle would not spread out as far because the liquid flowing away from the tank would fill up the depressions in the grass The puddle would then be smaller in area and deeper It would evaporate at a slower rate and it would take longer to completely evaporate 129 Chapter 5 Examples Because ALOHA assumes that the puddle would spread out to cover a maximum area its release rate estimate may be conservative more likely to be an overestimate than an underestimate At a real accident scene check for terrain features that would constrain the puddle from spreading use this information to estimate the maximum puddle area Choosing a LOC and plotting a footprint First check the computational setting Select Computational from the SetUp menu Check to be sure that Let model decide select this if unsure is selected Click OK Computational Preferences z
19. at 18 meters Ho Inversion Height Stability Class O Air Temperature 28 F Relative Humidity 87 Ground Roughness urban or forest Cloud Cover 18 tenths Describing the release You re now ready to enter information about the release itself Inthe SetUp menu point to Source then click Direct Chemical Atmospheric P Source Direct DS Puddle 3 Lomputational Tank Pipe a amp 2 Inthis example scenario about 500 gallons of chlorine spray from a ruptured pipe and evaporate within about 10 minutes Click gallons as your units of source strength This is a continuous release because it takes longer than minute for the chlorine to escape into the atmosphere so click Continuous source Because the release is continuous you need to enter a rate of release rather than the total amount released Divide 500 gallons the total amount of chlorine released by 10 minutes the release duration to obtain a release rate of 50 gallons per minute Type 50 into the release rate box and 10 into the duration box Click OK 137 Chapter 5 Examples User Input Source Strength Select source strength units of mass or volume grams kilograms i pounds C tons 000 Ibs o cubic meters liters i cubic feet gallons Select an instantaneous or continuous source iw Continuous source C Instantaneous source Enter the amount of pollutant ENTERING THE ATMOS
20. but less accurate than those used in DEGADIS and ALOHA DEGADIS models sources for which the release rate changes over time as a series of short steady releases rather than as a number of individual point source puffs Throughout the creation of ALOHA DEGADIS NOAA worked closely with the original authors of DEGADIS to ensure a faithful representation of DEGADIS model dynamics ALOHA DEGADIS was checked against DEGADIS to ensure that only minor differences existed in results obtained from both models Considering the typical inaccuracies common in emergency response these differences are probably not significant In cases where technical accuracy is required you should obtain the original DEGADIS model and use it to investigate the scenarios of interest ALOHA can choose a dispersion model for you ALOHA can automatically choose whether to predict the dispersion of a chemical as a Gaussian or heavy gas release it bases this choice mainly on molecular weight size of the release and temperature of the gas cloud But sometimes you may want to specify the model to use rather than letting ALOHA choose In particular when a chemical with a molecular weight less than that of air has been stored at a low temperature or under high pressure it can behave like a heavy gas ammonia is an example of such a chemical If you have chosen one of these chemicals depending on how you model its release ALOHA may not have enough information about the rele
21. measurements of average wind speed and direction at a location see Roughness length Index advection 7 air exchange rate estimating 48 air modeling basics of 6 10 air temperature 66 ALOHA basic organization 1 example scenarios 21 37 121 164 installing 17 20 memory and space requirements 17 purpose of 1 ALOHA s menu bar 2 ALOHA limitations of 11 15 AlohaSpy about 20 118 120 menus 119 120 saving Spy files 41 119 ambient saturation concentration 55 56 173 Atmospheric menu item about 60 SAM Station 69 77 User Input 60 atmospheric stability 66 boiling point 174 building shelter 50 Building Type menu item 48 50 Calculate menu item 112 114 Calculate Now menu item 114 CAMEO 115 CAMEO menu 115 116 carcinogens 56 Chemical adding chemicals to ChemLib 58 59 carcinogen warnings 56 chemical index 53 deleting a chemical 60 modifying chemical data 59 166 properties for heavy gas 57 properties needed for ALOHA calculations 57 58 property values in library 57 reactive chemicals 14 54 55 selecting a chemical 54 solutions and mixtures 15 ChemLib 20 53 60 174 CityLib about CityLib 20 43 adding a location 44 47 definition 174 deleting a location 48 modifying a location 47 cloud cover 66 174 combustion byproducts 14 communicating with other programs 115 Computational menu item 95 98 Computer Aided Management of Emergency Operations CAMEO 57 115 116 Concentration definition 174 designating a location 107
22. 115 The MAR PLOT menit ico ne vt e doi 116 Displaying an ALOHA footprint on 116 Usma MARPLO 117 AIONA SPY aiena ERE 118 Exatuple S o 121 FROUDIE S OO CE 165 bI M MM E 171 Co d 173 Chapter 1 Welcome to ALOHA Welcome to ALOHA This chapter contains an overview of ALOHA an explanation of how to use this manual and ALOHA s online help and a discussion of basic air dispersion modeling concepts About ALOHA Program purpose ALOHA Areal Locations of Hazardous Atmospheres is a computer program designed especially for use by people responding to chemical accidents as well as for emergency planning and training ALOHA can predict the rates at which chemical vapors may escape into the atmosphere from broken gas pipes leaking tanks and evaporating puddles It can then predict how a hazardous gas cloud might disperse in the atmosphere after an accidental chemical release ALOHA runs quickly on small computers Windows or Macintosh that are easily transportable and affordable for most people It 1s designed to be easy to use so that you can operate it successfully during high pressure situations Its chemical library contains information about the physical properties of about 1 000 common h
23. 165 Online help in Windows 5 index 4 on a Macintosh 5 using 4 5 21 Open Country 64 Open menu item 39 Options menu item 100 103 overriding stability class 68 patchiness of gas concentration 13 Pipe source option about 92 94 infinite tank source 93 model inputs 94 too short pipe length 166 plume definition of 181 Print menu item 41 PrintAll menu item 41 Printing from ALOHA 41 program organization basic 1 Puddle source option about 81 84 choosing ground type 83 estimating puddle area 82 factors influencing evaporation rate 81 initial puddle temperature 84 puff definition of 181 purpose of ALOHA 1 Quit menu item 42 radioactive particles 15 relative humidity 69 181 release rate 77 95 Response Information Data Sheets RIDS viewing information in 3 roughness elements 64 roughness length Z 65 roughness length Z0 64 SAM choosing a Calculate option 77 113 114 choosing a radio frequency 71 choosing a SAM 69 choosing a serial port 71 minimum transmission duration 166 required data format 70 71 setting up ALOHA for use with 72 73 use during incident 63 71 76 79 84 SAM Options menu about 73 Archive Data 73 74 Processed Data 75 Raw Data 74 75 Wind Rose 75 76 saturation concentration ambient 55 56 save files 40 SetUp menu 2 53 98 Sharing menu 115 120 SiteData menu 43 51 solution definition of 182 Source definition of 182 Direct 79 81 duration limits 78 duration of direct release 80 factors influencing evapora
24. 1s pressurized It treats ammonia and chlorine as special cases however because enough information about these chemicals 15 available to permit the use of more refined source strength calculations When there is only a small amount of chlorine or ammonia in a tank when the hole in the tank is small or when the tank pressure 1s low ALOHA will predict that the chemical will escape as a pure gas rather than as a two phase flow 85 Chapter 4 Reference Tank size and orientation To model the release of a liquid or gas from a storage vessel you must indicate both the size of the tank and its general shape which affects how it will drain Choose the most appropriate of three tank types a horizontal cylinder an upright cylinder B a sphere Next enter the tank s dimensions If it is a cylinder enter any two of the following three values a diameter b length and or c volume If it is a sphere enter either the tank s diameter or its volume ALOHA will compute and display values for the remaining dimensions Volume means the total volume of the tank rather than the volume of chemical within the tank Tank 5ize and Orientation Select tank type and orientation Sphere Vertical cyl inder Horizontal cyl inder o O Enter two of three values aJi ameter diameter feet O meters length volume 752 gallons cu feet Figure 4 35 Tank size and orientation Chemical state You next
25. ALOHA cannot model gas release from a pipe that has broken in the middle and is leaking from both broken ends To describe a pipe release to ALOHA type the pipe diameter and length indicate whether the pipe 1s connected to a reservoir indicate whether the inner pipe surface 1s smooth or rough type pipe pressure and temperature and type the area of the hole if the pipe is of finite length m Pipe Input SS Input pipe diameter Pipe Pressure and Hole Size gt Diameter is i inches 2cm Input pipe pressure Pressure is amp psi Pa Input pipe temperature The unbroken end ofthe pipe is 2 Unknown assume ambient amp connected to infinite tank source amp Temperature is 2 closed off Select pipe roughness Smooth Pipe Rough Pipe Figure 4 43 ALOHA s Pipe input dialog boxes 93 Chapter 4 Reference Pipe source inputs 94 Pipe diameter and length Use the inner diameter of the pipe The pipe length must be at least 200 times the diameter of the pipe Pipe connection Indicate whether the pipe 15 connected at its unbroken end to a large reservoir or 1s closed off Pipe roughness Degree of roughness of the inside wall of the pipe Rough texture causes turbulence which reduces the flow rate of the gas in the pipe A gas will flow more slowly through an older corroded rough pipe than through a newer smooth pipe A rough pipe would be for example a metal pipe with a rusted inner surface or a p
26. ALOHA results that you would like to see and to choose how you would like the information to be displayed Choose to tile or stack ALOHA s windows choose whether to see Chapter 1 Welcome to ALOHA ALOHA s results displayed in English or metric units and indicate when you want computations made and windows updated Select a Level of Concern LOC for the footprint this 1s the threshold concentration of an airborne pollutant usually the concentration above which a hazard may exist ALOHA s footprint represents the zone where the ground level pollutant concentration may exceed your LOC at some time after a release begins Choose to see the footprint either plotted on a grid at a scale automatically selected by ALOHA or displayed at a scale that you specify B Sharing Choose items from this menu to display an ALOHA footprint on a background map using MARPLOT the CAMEO mapping module or b to see detailed information about the chemical you ve selected displayed in CAMEO s Response Information Data Sheets RIDS module Display Sharing Chemical Tile Windows About Shared Menus Atmospheric k Stack Windows Edit Shared Menus Source gt MARPLOT Text Summary Footprint Page Setup Concentration Print Dose Printall source Strength 6 Close save 5 Saue Hs Calculate Calculate Now Figure 1 1 ALOHA s menus on a Macintosh
27. Once you designate a location ALOHA will place a blue crosshair mark amp on the Footprint plot to indicate the location where concentration 1s evaluated If you have plotted the footprint on a map in MARPLOT ALOHA will place the crosshair mark on the map as well I In the Footprint window double click on the location of concern ALOHA will display a concentration graph for any point that you indicate Because it then uses relative downwind and crosswind coordinates to remember your site s position in effect the geographic location of the point then will move if the wind direction changes 2 Choose Concentration from the Display menu Choose Concentration from the Display menu then type in the coordinates of a location either 1n terms of its east west and north south distances or its downwind and crosswind distances from the source Once you have typed in coordinates and clicked OK ALOHA will display a concentration graph for that location Choosing coordinates Your choice of coordinates affects the information that ALOHA presents to you if the wind direction changes whether you re using a SAM station or manually entering a new value as explained below Using fixed east west and north south coordinates Choose this method to see predicted concentrations at a specific geographical location This could be for example a school 100 yards to the west and 400 yards to the north of the spill location Fixed coordinates is the
28. a puddle tank or gas pipeline as a series of up to 150 brief timesteps the Maximum Computed Release Rate is the highest of these release rates ALOHA then averages this series of many release rates into between one and five release rates each averaged over a time period of at least 1 minute the Maximum Average Sustained Release Rate is the highest of these averaged release rates To save calculation time ALOHA uses only the averaged release rate s to make its footprint estimates Text Summary SITE DATA INFORMATION Location SIOUX FALLS SOUTH DAKOTA Building Air Exchanges Per Hour 8 43 unsheltered single storied Time June 25 2868 amp 1438 hours COT user specified CHEMICAL MFORMAT I DH Chemical Mame CHLOR IHE Molecular Height 78 91 kg kmol TLV THR 8 5 ppm IDLH 18 ppm Footprint Level of Concern 18 ppm Boiling Point 28 25 F Vapor Pressure at Ambient Temperature greater than 1 atm Ambient Saturation Concentration 1 866 888 ppm or 166 60 ATMOSPHERIC INFORMATION MANUAL INPUT OF DATA Hind 9 mph fram s at 18 meters Inversion Height Stability Class B Hir Temperature 72 F Relative Humidity 505 Ground Roughness open country Cloud Cover 3 tenths SOURCE STRENGTH HF ORHHRT I OH Leak from short pipe or valve in horizontal cylindrical tank Tank Diameter 2 5 feet Tank Length 5 8 feet Tank volume 258 gallons Tank contains liquid Internal Temperature 72 F Chemical Mass in Tank 1 tons Tank is BSx f
29. after a release begins If ALOHA predicts that a release would last longer than hour you will see a message on the Text Summary window Release Duration ALOHA limited the duration to 1 hour One important reason for the 1 hour duration limit is that the wind changes speed and switches direction frequently Researchers have found that atmospheric conditions change enough to affect ALOHA s predictions on a time scale of about 1 hour Bear in mind that ALOHA assumes that weather conditions remain constant for the duration of any release Another reason is that the calculation methods ALOHA uses are based on the results of experiments In these experiments gases were released into the atmosphere for time periods from 10 minutes to 1 hour the researchers then observed how the dispersing gases behaved Note that this 1 hour limit represents the maximum possible release duration If you are responding to an incident check whether release conditions change substantially before an hour has passed If for example an evaporating pool has substantially changed in area or the wind speed or direction has changed enter new atmospheric and source information into ALOHA and obtain an updated footprint plot ALOHA reports two release rates When you use ALOHA s Puddle Tank or Pipe source options ALOHA reports two release rates in the Text Summary the Maximum Computed Release Rate and the 78 Chapter 4 Reference Maximum Average Sustaine
30. all visible windows This is ALOHA s default calculation mode Use this option when you wish all visible windows to be updated automatically whenever you modify input data or ALOHA receives weather data from a SAM 112 Chapter 4 Reference Automatically update only front window Select this option if you want only the front window to be updated whenever input values have been modified or SAM data have been received The Footprint Concentration and Dose windows will be greyed out once they are out of date To update an out of date window click on the window to bring it forward Select Calculate Now from the Display menu to update all windows Manual update of all visible windows Select this option if you wish no windows to be updated until you select Calculate Now from the Display menu Consider this option if you wish to make multiple changes to input values before updating footprint concentration and or dose information Whenever you make changes to ALOHA inputs out of date windows will be greyed out until you update them If you re using a SAM station If you have selected Automatically update all visible windows incoming SAM data will be transferred automatically to ALOHA s dispersion modules and the Footprint Concentration and Dose windows will be updated accordingly If you have selected Automatically update only front window incoming SAM data will continue to be archived The front window as well as windows tha
31. as a Gaussian neutrally buoyant or heavy gas release It bases this choice mainly on molecular weight size of the release and temperature of the gas cloud By default Let model decide remains selected unless you choose a different option When Let model decide 15 selected if ALOHA s chemical library does not include values for all physical properties of your selected chemical necessary to make heavy gas dispersion calculations ALOHA will use Gaussian dispersion calculations to predict footprint size When a chemical with a molecular weight less than that of air has been stored at a low temperature or under high pressure it can behave like a heavy gas ammonia 15 an example of such a chemical If you have chosen one of these chemicals and have chosen the Direct source option ALOHA may not have enough information about the release to determine whether a heavy gas could be formed In such a case ALOHA will make Gaussian calculations but will alert you that you should try running the heavy gas model as well Figure 4 46 Chapter 4 Reference Mote This chemical may flash boil and or result in two phase flow Use both dispersion models to Investigate its potential behavior Figure 4 45 ALOHA alerts you when flash boiling or two phase flow may occur Use Gaussian dispersion only Choose this option if you know that the escaping gas cloud is approximately neutrally buoyant about as dense as air ALOHA will use the Gaus
32. as a percentage When relative humidity 1s 50 the air contains one half as much water vapor as it could potentially hold The period of time over which a release occurs ALOHA limits release duration to 1 hour Also Zo A numerical measure of ground roughness An average taken in consecutive overlapping segments e g the average of the first five values then the average of the second through sixth values then the average of the third through seventh values etc See Average Station for Atmospheric Measurements A portable meteorological measurement station that can transmit weather data to ALOHA through a computer s serial port A file containing information about a release scenario that you have entered into ALOHA You can reopen and modify a save file in ALOHA Choose Save from the File menu to create a save file 18 Glossary Serial port Sigma theta Smoke Solution Source Source height Source strength Spy file Stability class Stable Standard deviation 182 A data interface on a computer through which peripheral devices such as a SAM scanner printer or digitizing tablet can be connected ALOHA can receive weather data from a SAM through a serial port The standard deviation of the wind direction A SAM configured for use with ALOHA measures changes 1 wind direction then transmits an estimate of sigma theta ALOHA uses this value for sigma theta and the wind speed to estimate
33. averaged over a very short time period When using a SAM ALOHA recomputes its footprint concentration and dose estimates each time it receives new weather data from a SAM However it does not recompute source strength when it receives new data During prolonged incidents because time of day and weather conditions may have important effects on source strength especially from an evaporating pool be sure to periodically update ALOHA s source strength calculations Direct source Choose Direct from the Source menu if you know the amount of pollutant gas released directly into the atmosphere or if you have too little information about a release to use another source option but feel that you can make a ballpark estimate of the source strength The amount that enters the atmosphere directly as a gas may not equal the amount spilled For example a liquid may spill from a tank at a given rate and then evaporate as a gas into the atmosphere at a much slower rate ALOHA will not calculate evaporation rate or release rate but instead will use your source strength estimate to make its footprint concentration and or dose predictions 79 Chapter 4 Reference User Input Source Strength Select source strength units of mass or volume O grams O kilograms i pounds C tons 000 Ibs O cubic meters liters i cubic feet O gallons Select an instantaneous or continuous source Continuous source i instantaneous sou
34. by contact time yielding a predicted dose of 500 ppm min If you change the exponent to 2 0 ALOHA will estimate dose as concentration squared and multiplied by exposure time For the example above ALOHA would predict dose to be 50 000 ppm2 min Because ALOHA computes dose as a function of concentration and time and because the form of this function changes whenever is changed the exact form of ALOHA s units for dose depends on the value of When 1 0 the default value dose units are displayed in ALOHA as either ppm min parts per million minute or mg cu m min milligrams per cubic meter minute When n is any value other than 1 0 ALOHA displays dose in units of either ppm n min or mg cu m n min The symbol indicates that the concentration has been taken to the power of n 98 Chapter 4 Reference The Display Menu Select items from the Display menu to indicate the ALOHA results that you would like to see and how you would like the information to be displayed Choose Tile or Stack to organize ALOHA s windows on your screen Choose Text Summary Footprint Concentration Dose and or Source Strength to display the corresponding windows Choose Options to select either English or metric units choose the type of footprint display or enter a Level of Concern LOC Choose Calculate to indicate when you want computations made and windows updated Choose Calculate Now to manually update AL
35. cylindrical tank Tank Diameter 4 feet Tank Length 9 32 feet Tank volume SHE gallons Tank contains liquid Internal Temperature 56 Chemical Mass in Tank 1 92 tons Tank is 166 full Circular Opening Diameter inches Opening is 18 inches from tank bottom Soil Tupe Default Ground Temp equal to ambient Puddle Diameter Unknown Release Duration 44 minutes Max Computed Release Rate 96 7 pounds min Max Average Sustained Release Rate 88 5 poundz min averaged over a minute or more Total Amount Released 3 862 pounds Hote The chemical escaped as a liquid and formed an evaporating puddle FOOTPRINT IHFORHHRT I OH Dispersion Module Gaussian User specified LOC 18 ppm Max Threat Zone for LOC 8B yards Threat Zone for IDLH S8 yards 132 Chapter X Examples Example 2 Direct Input Heavy Gas A paper mill located in a highly industrialized section of Columbia South Carolina stores large amounts of liquid chlorine On May 15 2000 at 13 00 a reckless forklift operator breaks open a pipe About 500 gallons of liquid chlorine spray out in a fine mist and evaporate within about 10 minutes The chlorine is normally stored at a temperature of 30 F The paper mill s single storied office building is located about 1 000 yards directly downwind of the accident The building is surrounded by bushes and trees Since the weather for the past few days has been cool most people in the building have kept their windows clo
36. heavy gas dispersion computations Relative humidity is defined as the ratio of the amount of water vapor that the air contains to the maximum amount of water vapor that it could hold at the ambient temperature and pressure Relative humidity 15 expressed as a percentage When relative humidity is 50 percent the air contains one half as much water vapor as it could potentially hold The warmer the air the greater its capacity to contain water vapor Cold air may contain little water vapor but have a high relative humidity because the amount of water vapor in the air 1s near the air s relatively low maximum capacity Enter a relative humidity value in either of two ways either click the button that best represents your relative humidity value or type the relative humidity in percent in the humidity box SAM Station Although you can enter all weather information into ALOHA manually ALOHA also can accept data from an external portable meteorological monitoring station called a Station for Atmospheric Measurement SAM SAM data can be transmitted to ALOHA by either radio frequency or a cable ALOHA can use SAM measurements of wind speed and direction standard deviation of the wind direction and air temperature It cannot accept relative humidity readings made by a SAM you ll need to enter these measurements into ALOHA manually Choosing a SAM A few companies manufacture SAMs for use with ALOHA Before purchasing a SAM to use with ALOHA c
37. indoor concentration 1s predicted to remain much lower than the outdoor concentration as long as the school s door and windows are closed You also can see that ALOHA predicts that outdoor concentration would exceed the LOC for this scenario only briefly and that indoor concentration would not exceed the LOC When you use ALOHA 1n planning or response however you may wish to compare predicted concentrations with other toxic thresholds besides IDLH The IDLH 1s intended to represent hazard to healthy adults you may wish to choose a different value to use as your LOC when you re concerned about hazard to children Be sure that the LOC that you choose reflects the hazard that you are concerned about and 15 conservative enough for the uses to which you re putting your ALOHA results Here s how the Text Summary window should look now that you have completed your work with this example scenario note that depending on the type of computer you use 36 Chapter 3 Learning the Basics some of the numbers that you see on your screen may be slightly different than those in the following figure Text Summary pH SITE DATA INFORMATION Location SIOUX FALLS SOUTH DAKOTA Building Air Exchanges Per Hour 8 43 Cunsheltered single storied Time June 25 2668 amp 1438 hours COT fuser specified CHEMICAL HF ORHMRT ION Chemical Mame CHLORINE Molecular Height 78 91 kg kmol TLY THA 8 5 ppm IDLH 1 amp 8 ppm Footprint Level of Concern 18 pp
38. library and the city name will be removed from the index 45 Chapter 4 Reference Location Information JUPITER FLORIDA KEMMERER WYOMING KENNEWICK WASHINGTON KENT OHIO KENT WASHINGTON KINGMAN ARIZONA KINGS MOUNTAIN NORTH CAROLINA KINGSTON NEW YORK KINSTON NORTH CAROLINA EKN HIILLE TENNESSEE KOKOMO INDIANA LA MESA CALIFORNIA LAFAYETTE LOUISIANA Figure 4 8 Location index with Jupiter Florida Adding a location outside the U S To add a city or town that is not located 1n the U S click Add then type in the name of the location Don t include its country name you ll be asked for that later Click Not in U S Type the location s approximate elevation latitude and longitude then click OK Location Input Enter full location name Is location in a U S state or territory O In 0 5 i Not in U S Enter approximate elevation Elevation is jo ft im Enter approximate location deg min Latitude DN OS Longitude OE w 08 Figure 4 9 Adding Hamilton Bermuda non U S city to library Next you ll see the Foreign Location Input dialog box Figure 4 10 Type the country name then the number of hours that local standard time at the location differs from Greenwich Mean Time GMT This time offset value should be positive if the location 1s 46 Chapter 4 Reference in the western hemisphere North and South America and negative if it s in the eastern hemisphere E
39. need to specify the state and temperature of the chemical in the tank ALOHA needs to know whether the chemical is a liquid or gas in order to estimate the quantity of chemical in the tank and the way in which the chemical may escape from the tank as a pure gas or as a pressurized or unpressurized liquid Click the button corresponding to one of the following options B Tank contains liquid Choose this option if there is any liquid in the tank even if it s just a small amount 86 Chapter 4 Reference Tank contains gas only Choose this option if you know that the tank contains only gas with no liquid present Unknown Choose this option if you don t know the chemical s state Under the heading Enter the temperature within the tank on the Chemical State and Temperature dialog box either B click Chemical stored at ambient temperature if the chemical 15 stored at the temperature of the surrounding air you entered a value for air temperature when you entered atmospheric information or B if the tank is at a different temperature type the storage temperature in the tank temperature box and choose its units Whether a liquid is stored in a tank at a temperature above or below its boiling point greatly affects how it will escape through a tank rupture or leaking valve If the liquid 1s stored below its boiling point it will flow out of the tank pool on the ground and enter the atmosphere by evaporating
40. percent of the way to the top of the tank since the valve 1 located at the center of one end of the tank Click OK Height of the Tank Opening The bottom of the leak is lig level inm above the bottom of the tank OR n of the way to the top of the tank ALOHA then calculates the rate of release of chlorine from the tank the duration of the release and the total amount released You ll see these calculation results 1n the Text Summary window and in the source strength graph 7 Choose Source Strength from the Display menu to see the source strength graph below for this scenario The graph shows the predicted averaged release rate during the hour after the release begins Source Strength Release Rate pounds minute 20 minutes On the graph time since the release started from 0 to 40 minutes 1s shown on the horizontal axis and release rate is shown on the vertical axis You can see from this graph that because the chlorine 1s escaping from a pressurized container ALOHA predicts that release rate starts out high then declines as container pressure drops The highest step on this graph is the Maximum Averaged Sustained Release Rate 29 Chapter 3 Learning the Basics In the Text Summary below under the Source Strength Information heading you can see two release rate estimates the Maximum Computed Release Rate and the Maximum Average Sustained Release Rate ALOHA predicts release rate from
41. predicted indoor and outdoor concentrations downwind of an evaporating puddle of acrolein This graph shows that ALOHA predicts that outdoor concentration starts to increase soon after the release begins exceeding the LOC 2 ppm within about 5 minutes Inside sheltered single story buildings the type selected for this scenario ALOHA predicts that it takes much longer for indoor concentration to increase and that indoor concentration does not reach the LOC until nearly the end of the first hour after the release begins Comparing predicted indoor and outdoor concentrations shown on a Concentration vs Time graph is a way to assess the relative potential hazard associated with remaining indoors versus leaving the area through a dispersing pollutant cloud Note To estimate the rate at which pollutant gas could infiltrate into buildings ALOHA assumes that all doors and windows are closed If doors and or windows are open as they might be on a warm summer day concentrations might increase more rapidly and drop off sooner inside buildings than ALOHA s indoor concentration line indicates 106 Chapter 4 Reference Designating a location You may choose either of two ways to designate a location for which you would like to see a concentration prediction you ll first need to have chosen a chemical and entered information under the source option Double click within the Footprint window Choose Concentration from the Display menu
42. roughness 20 50 O Urban or Forest Station Height above ground is e OR Center val ES enter value a HE i meters Cancel 71 Chapter 4 Reference Setting up ALOHA when you re using a SAM Check to be sure that your SAM is properly connected configured and turned on you ll need to check with the manufacturer if you have questions on how to do this Next in the SetUp menu point to Atmospheric then click SAM Station You ll need to enter some information about environmental conditions Figure 4 26 B Ifan inversion is present type in the height of the inversion layer and select appropriate units If there 1s no inversion be sure that No Inversion is selected Indicate the ground roughness in the area downwind of the release point Specify the station height the height of the instruments above the ground Indicate the amount of cloud cover in tenths Finally enter a value for relative humidity as a percentage Even if your SAM can measure relative humidity you ll need to enter this value manually into ALOHA User Input for 5AM Unit Inversion Height Options are Mo inversion i feet 9 Inversion present Height is meters Ground Roughness is 3 Open Country Qin OR Input roughness 7o Input roughness qox 100 cn amp Urban or Forest Station Height above ground is gf m 977 B enter value a pu i amp meters Select Cloud Cover VANS oA y
43. same format in which it 1s transmitted from the SAM Sam Data 0909 8 32 181 96 6 43 22 44 8 35 182 30 22 44 12 3 2509 E 3 4 Q Q Station ID number Sigma theta degrees gt Mean air temperature gt Instantaneous wind speed meters per second Mean wind direction degrees true gt Instantaneous air temperature gt Remaining SAM battery voltage volts gt Vector mean wind speed meters per second gt Instantaneous wind direction degrees true gt Figure 4 28 Interpreting line of raw SAM data 74 Chapter 4 Reference Processed Data Choose Processed Data from the SAM Options menu to view processed weather data including the most recently transmitted instantaneous readings as well as 5 minute running averaged values 1 a new Processed SAM Data window If ALOHA cannot interpret and process the data that it receives from your SAM it will display an error message in this window Processed Sam Data Meteorological Station ID 999 INSTANTANEOUS Hind Speed 19 6 mph Hind Direction 181 degrees true Temperature 73 Fahrenheit MINUTE RUNNING AVERAGE Mind Speed 15 5 mph Hind Direction 181 degrees true Temperature 72 Fahrenheit Sigma Theta 6 6 degrees Battery Voltage 12 30 valts Figure 4 29 Processed SAM data Several items in the Processed SAM Window need explanation B The Meteorological
44. shifts 12 13 187
45. sometimes can escape together from a ruptured tank as a two phase flow Many substances that are gases under normal pressures and temperatures are stored under pressures high enough to liquefy them For example propane is a gas at normal pressures and temperatures but is often stored under pressure as a liquid When a tank rupture or broken valve causes a sudden pressure loss 1n a tank of liquefied gas the liquid boils violently the tank contents foam up and the tank fills with a mixture of gas and fine liquid droplets called aerosol When such a two phase mixture escapes from storage the release rate can be significantly greater than that for a purely gaseous release When liquefied propane or a similar chemical escapes from storage as a two phase release it can form a heavy gas cloud The cloud 1s heavy in part because it 1s initially cold and therefore dense and also because it consists of a two phase mixture The tiny aerosol droplets mixed into the cloud act to weigh the cloud down and make it more dense and their evaporation acts to cool the cloud When ALOHA predicts that a pressurized liquid will escape as a two phase flow it alerts you with a message on the Text Summary Note The chemical escaped as a mixture of gas and aerosol two phase flow When you use ALOHA to model a release from a tank of a liquefied gas such as propane ALOHA generally will predict that the substance will escape as a two phase flow if the tank
46. stability class A mixture of gases suspended solid particles and vapors resulting from combustion A mixture of two or more compounds Many common solutions are mixtures of soluble chemicals and water Examples include alcohol in water and table salt in water The vessel or pool releasing a hazardous chemical into the atmosphere The distance above the ground at which a chemical is being released The amount of a pollutant gas entering the atmosphere or its rate of entry An archive file containing information about a scenario that you have run in ALOHA including ALOHA computation results which can be opened in AlohaSpy but not in ALOHA see Atmospheric stability The atmosphere is stable when little air turbulence exists so that there is little tendency for air to be mixed into a dispersing pollutant cloud A measure of the degree to which individual values deviate from an average value Computed as the square root of the sum of the squared deviations divided by the number of measurements STP Street canyon Sublimation Terrain steering TLV TWA Threat distance Threat zone Time dependent dispersion Time dependent source Glossary Standard Temperature and Pressure Physical properties such as boiling point are often expressed at standard temperature 0 C and standard pressure 1 atmosphere A street bordered along both sides by high rise buildings that block air movement so that the wi
47. the approximate elevation of Manassas then click feet Type the city s latitude and longitude 38 50 N and 77 30 W Click and W Choose VIRGINIA from the scrolling list of state names Click OK Locatian Input Enter full location name Location MHNRSSRS Is location in a U S state nr territory T m In U S O in U S elect state or territory TEHAS UTAH Elevation 1 ft om UERMONT Enter approximate elevation SS a UDIRGINIA Enter approximate location VIRGIN ISLANDS deg min ISLAND WASHINGTON Latitude 50 0 OS west VIRGINIA WISCONSIN Longitude OE SW yoming The list of locations will be displayed with Manassas Virginia highlighted Click Select Location Information MANASSAS VIRGINIA MANCHESTER IOWA MANCHESTER HAMPSHIRE MANHATTAN KANSAS MANSFIELD MASSACHUSETTS Cancel MANSFIELD OHIO MARIETTA GEORGIA MARQUETTE MICHIGAN MARTINEZ CALIFORNIA MARYSUILLE CALIFORNIA MEMPHIS TENNESSEE Modify MENLO PARK CALIFORNIA MENOMONEE FALLS WISCONSIN MENTOR OHIO MESA ARIZONA MESQUITE TEHRS MIAMI FLORIDA MIAMISBURG OHIO Delete We ll ignore Building Type during this scenario since we re interested only in outdoor concentration Choose Date amp Time from the SiteData menu SiteData Location aeL Building Type Date tr Time Chapter 3 Examples 7 Click Set constant time then enter the month d
48. the Basics indoor concentration and dose at a location of concern In this example the location of concern 1s the Central Valley Elementary School To estimate infiltration rate into a building ALOHA assumes that all doors and windows are closed Choose Building Type from the SiteData menu SiteData Location Building Type 1 Date tr Time 6 The school is a single storied building surrounded mostly by open fields Check to be sure that Single storied building is selected then click Unsheltered surroundings Click OK Infiltration Building Parameters Select building type or enter exchange parameter J Enclosed office building Single storied building Double storied building O No of air changes is per hour Select building surroundings Sheltered surroundings trees bushes etc Unsheltered surroundings 7 Select Date amp Time from the SiteData menu to enter the date and time for the scenario SiteData Location Building Type Date tr Time 8 Click Set constant time The scenario date 15 June 25 2000 so type 6 in the Month box 25 in the Day box and 2000 in the Year box The accident time is 2 30 in the afternoon ALOHA requires time of day in 24 hour time so type 14 in the Hour box 23 Chapter 3 Learning the Basics and 30 in the Minute box click Help to learn how to convert a time value to 24 hour time Click OK Date and T
49. the ground the warmer the puddle and the higher the evaporation rate Type in a value for ground temperature and choose either Fahrenheit or Celsius degrees If you do not know the ground temperature you can choose to guess that it 1s about equal to the air temperature In this case click Use air temperature select this if unknown Air and ground temperatures can be very different in some situations such as in a parking lot on a hot day late 1n the afternoon or on a street during the early morning after a very cold night Be sure to estimate air and ground temperatures carefully in such situations The last piece of information ALOHA needs 1s the initial puddle temperature ALOHA assumes the initial temperature to be the same throughout the depth and width of the puddle Indicate that the initial puddle temperature equals either the ground temperature or the ambient air temperature or enter a value for the initial puddle temperature Click the button that represents your choice If your value for initial puddle temperature 1s above the liquid s normal boiling point ALOHA will alert you and then set the initial puddle temperature to the boiling point 1t assumes that a boiling puddle will quickly cool to its boiling point Watch for changing weather conditions ALOHA doesn t account for changes in atmospheric conditions such as changes in wind speed or air temperature when calculating the rate of evaporation from a puddle Bear in min
50. those units in the Text Summary even if you selected metric output units Text Summary select Text Summary from the Display menu to bring the Text Summary window forward when other ALOHA windows appear in front of it ALOHA s Text Summary contains information about the scenario you are working on Review its contents to see summaries of the information that you have entered into ALOHA some basic properties of the chemical you have selected results of ALOHA s computations messages indicating the information that you still need to enter additional notes describing any special circumstances that may exist Text Summary SITE DATA INFORMATION Location Please select your location Building Sheltered single storied Time April 1995 amp 0946 hours OST Using computer s clack CHEMICAL INFORMATION SELECT CHEMICAL ATMOSPHERIC INFORMATION SELECT ATMOSPHERIC gt Figure 4 49 The Text Summary window The Text Summary window remains open whenever ALOHA is running Review its contents periodically as you prepare a scenario to ensure that you have entered model inputs correctly and to check the results of ALOHA s computations Choose New from 103 Chapter 4 Reference the File menu when you want to clear existing Text Summary information before beginning a new scenario Footprint ALOHA plots a footprint which encompasses the area where the ground level concentration of a pollutant gas is predicte
51. time even at distances far from the release point ALOHA does not account for buildup of high gas concentrations in low lying areas First responders should be aware that very stable atmospheric conditions create a dangerous situation in which models like ALOHA are not very reliable In this situation think about whether the chemical will behave as a heavy gas and look for physical depressions and topographic features that may trap or steer the dispersing cloud Wind shifts and terrain steering effects ALOHA allows you to enter only single values for wind speed and wind direction It then assumes that wind speed and direction remain constant at any given height throughout the area downwind of a chemical release ALOHA also expects the ground below a dispersing cloud to be flat and free of obstacles In reality though the wind typically shifts speed and direction as it flows up or down slopes between hills or down into valleys turning where terrain features turn The way in which land features modify patterns of air flow is called terrain steering Figure 1 10 Wind shifts In urban areas wind flowing around large buildings forms eddies and changes direction and speed significantly altering a cloud s shape and movement Through streets bordered by large buildings can generate a street canyon wind pattern that constrains and funnels a dispersing cloud ALOHA ignores these effects when it produces a footprint plot the 12 C
52. vapor pressure for solutions or mixtures ALOHA s predictions are greatly affected by this and other chemical properties When an incorrect property value is used in ALOHA the model s release rate and dispersion estimates will not be valid lerrain ALOHA expects the ground below a leaking tank or puddle to be flat so that the liquid spreads out evenly in all directions It does not account for pooling within depressions or the flow of liquid across sloping ground 15 Chapter 1 Welcome to ALOHA 16 Chapter 2 Installing ALOHA This chapter describes how to install ALOHA on a computer running Microsoft Windows or on a Macintosh computer Before you install ALOHA Check package contents You should have received a CAMEO compact disk containing an installer for ALOHA and this manual along with installers and manuals for CAMEO MARPLOT Memory and hard disk space requirements In Windows ALOHA runs 1 Microsoft Windows version 3 1 or above It requires at least 1 megabyte of Random Access Memory RAM and about 2 5 megabytes of space on your hard drive On a Macintosh ALOHA runs on any Apple Macintosh with at least megabyte of random access memory RAM and a hard drive You must have 3 megabytes of hard disk space available to load ALOHA ALOHA runs under System 6 7 or 8 but cannot communicate with the current version of MARPLOT in System 6 If you already have a previous version of ALOHA
53. wind speed from environmental clues One knot equals 1 15 miles per hour Meters per International Second Knots Description Specifications Calm Calm smoke rises vertically Light air Direction of wind shown by smoke drift but not by wind vanes Light breeze Wind felt on face leaves rustle ordinary vane moved by wind Gentle breeze Leaves and small twigs in constant motion wind extends light flag Moderate Raises dust loose paper small branches are moved Fresh Small trees in leaf begin to sway crested wavelets form on inland water Strong Large branches in motion whistling heard in telegraph wires umbrellas used with difficulty Near gale Whole trees in motion inconvenience felt walking against wind Gale Breaks twigs off trees generally impedes progress Enter the direction from which the wind 1s blowing using either units of degrees true or one to three letter directional terms For example you can indicate that the wind 1s blowing from the north northeast by entering either NNE or 22 5 degrees Wind directions expressed in degrees and letter terms correspond as follows as 2 4 9 ESE 112 5 WNW 292 5 NW 315 SE 157 5 NNW 337 5 5 5 0 W 270 35 62 Chapter 4 Reference Finally enter the height at which wind speed and direction have been measured ALOHA accounts for the way in which wind speed changes with height in a pattern called a wind profile Close to the ground fricti
54. you ve finished reading the help information if you are using Microsoft Windows when you are ready to go back to using ALOHA close or minimize the Help window If you re using a Macintosh click Cancel to exit from the online help 21 Chapter 3 Learning the Basics Describing the Time and Place Your first tasks are to start ALOHA and then describe the time and place of the scenario 1 Start ALOHA In Windows 95 NT or 98 click the Start button point to Programs 4 5 22 then choose the ALOHA item from the Aloha submenu a Macintosh double click the ALOHA program icon drive In Windows 3 1 click the program icon located in the ALOHA program group in Program Manager Read the list of ALOHA s limitations click to see more details then click OK Select Location from the SiteData menu You ll see a list of the names of cities included in ALOHA s location library SiteData Location Date tr Time Type the characters si to quickly move to SIOUX FALLS SOUTH DAKOTA Check to be sure that this name 1s highlighted then click Select Location Information SHAWNEE OKLAHOMA Cancel SPARKS NEVADA SPARTANBURG SOUTH CAROLINA Modify Delete ST PETERSBURG FLORIDA ALOHA uses information about building type along with other information such as wind speed and air temperature to determine indoor infiltration rate and to estimate Chapter 3 Learning
55. 109 fixed location coordinates 107 graph 105 large values near source 165 patchiness near source 13 relative location coordinates 108 confidence lines wind direction 104 conservative estimates 175 Copy menu item 42 cryogenic liquids evaporation of 83 Date amp Time menu item 50 51 daylight savings time at foreign locations 44 47 daylight savings time definition of 175 daylight savings time setting 44 47 dense gas dispersion 8 10 Design Institute for Physical Properties Data DIPPR 57 diffusion 7 DIPPR database 57 Direct source option 79 8 1 Dispersion basic definition of 6 choice of model 10 choosing a calculation option 96 97 Gaussian 7 heavy gases 8 10 particulates 15 plume rise 14 dispersion modeling 6 10 Display menu 99 114 Dose ALOHA s definition 109 defining dose exponent 97 98 graph 110 Edit menu 2 42 Exit menu item 42 exponential notation 165 176 File menu 2 39 42 Files ALOHA save files 40 archiving scenario results 41 119 opening in Planning Mode 40 opening in Response Mode 40 saving and opening files 39 41 168 Spy files 41 119 168 185 Index flash boiling explanation of 9 Footprint definition 2 display options 102 displaying on a map 116 168 interpreting 104 105 168 setting scale 102 wind direction confidence lines 104 foreign locations indicating daylight savings time at 44 47 freezing point 177 gas definition of 177 Gaussian dispersion 7 Gaussian equation 7 GMT Greenwich Mea
56. 2 3 Grass thin to 50 cm Wheat stubble plain 18 cm Grass with bushes some trees 1 2 m high vegetation Trees 10 15m high Savannah scrub trees grass sand Note How ALOHA interprets your value for Zo depends on whether it uses Gaussian or heavy gas dispersion calculations When ALOHA makes its heavy gas calculations it uses the specific Zo value that you entered unless that value is greater than 10 centimeters In such cases ALOHA assumes Z to be 10 centimeters When Gaussian calculations are made ground roughness must be expressed as either Open Country or Urban or Forest When you enter a Zo value of 20 centimeters or more ALOHA uses Urban or Forest roughness when you enter a 4 0 value of less than 20 centimeters ALOHA uses Open Country roughness 65 Chapter 4 Reference Cloud cover ALOHA needs a value for cloud cover the proportion of the sky that is covered by clouds in order to estimate the amount of incoming solar radiation at the time of an accidental release Solar radiation is an important influence on puddle evaporation rate because heat from the sun can warm a puddle and speed up evaporation Cloud cover 15 usually measured in tenths when the sky is completely covered by clouds cloud cover is 10 tenths when half the sky is covered by clouds it 1s 5 tenths when the sky is completely clear it 15 0 tenths To enter cloud cover either B click the button corresponding to either 0 3 5 7 or 10 t
57. 44 Degrees mF CU Stability Class is On Oc amp n OF Inversion Height Options are 2 Feet No Inversion Inversion Present Height is O Meters select Humidity T y 1 C OR amp enter value LEN medium dry 0 100 The information that you have entered into ALOHA appears in the Text Summary Ignore the air exchange rate estimate you will not estimate indoor methane concentrations in this example Text Summary SITE DATA INFORMATION Location PORTLANDO OREGON Building Air Exchanges Per Hour 1 26 sheltered single storied Time November 17 2868 amp 1438 hours PST user specified CHEHICRL MFORMAT ION Chemical Mame METHANE Molecular Height 15 84 TLY THAS unavail IDLH unavail Default LOC from Library S888 ppm Footprint Level of Concern I8688 ppm Boiling Point 258 58 F Vapor Pressure at Ambient Temperature greater than 1 atm Ambient Saturation Concentration 1 886 888 ppm or 188 8 ATMOSPHERIC INFORMATION MANUAL INPUT OF DATA Mind 19 knots from SE at 3 meters Inversion Height Stability Class D Air Temperature 44 F Relative Humidity 79x Ground Roughness open country Cloud Cover 18 tenths Describing the release 1 Inthe SetUp menu point to Source then click Pipe Lhemical 38H Atmospheric gt Source a Direct Puddle 30 EY Computational Tank Pipe E 146 Chapter S Examples
58. 5503 C 5 1 000 000 ppm 1 1 267 200 169 Chapter 6 Troubleshooting 170 Bibliography American Conference of Governmental Industrial Hygienists ACGIH 1999 1999 TLVs and BEIs Threshold Limit Values for Chemical Substances and Physical Agents Biological Exposure Indices ACGIH pubs acgih org Most recent annual list of threshold limit values TLVs and biological exposure indices BEIs for several hundred chemical substances also discusses how these values were derived and how to interpret them Board on Toxicology and Environmental Health Hazards National Research Council 1986 Criteria and Methods for Preparing Emergency Exposure Guidance Level EEGL Short Term Public Emergency Guidance Level SPEGL and Continuous Exposure Guidance Level CEGL Documents Available from the National Academy Press 800 624 6242 Washington D C Describes short term exposure limits developed for use by the Department of Defense DOD Brutsaert Wilfried 1982 Evaporation into the Atmosphere Theory History and Applications Boston D Reidel Publishing Company Committee on Toxicology National Research Council 1993 Guidelines for Developing Community Emergency Exposure Levels for Hazardous Substances National Academy Press 800 624 6242 Washington D C Available from the Board on Environmental Studies and Toxicology 2101 Constitution Ave N W Washington D C 20418 Describes criteria and methods to use in establ
59. A gas cloud that 1s denser than the air around it There are several reasons why a gas forms a heavy gas cloud or behaves like a heavy gas 1 because its molecular weight 1s greater than that of air about 29 kilograms kilomole 2 because it is stored cryogenically refrigerated or 3 because aerosols form in sufficient quantity during a release to cause the mixture to behave like a heavy gas Immediately Dangerous to Life or Health A limit originally established for selecting respirators for use in workplaces by the National Institute for Occupational Safety and Health NIOSH IDLH is the default Level of Concern LOC in ALOHA A chemical s IDLH represents the maximum concentration in the air to which a healthy adult worker could be exposed without suffering permanent or escape impairing health effects NIOSH 1997 IDLH values have been established for about one third of the chemicals in ALOHA Infinite tank source Instantaneous source Inversion Level of concern LOC Mass Maximum Average Sustained Release Rate Glossary A case in which a gas pipeline is connected to a reservoir that 15 so large that gas escapes from the broken end of the pipeline at a constant rate for an indefinite period of time A very short term release ALOHA assumes that an instantaneous release lasts minute An atmospheric condition in which an unstable layer of air near the ground lies beneath a very stable layer of air above The h
60. ALOHA AREAL LOCATIONS OF HAZARDOUS ATMOSPHERES User s Manual AUGUST 1999 Chemical Emergency Preparedness and Prevention Office U S ENVIRONMENTAL Washington D C 20460 PROTECTION AGENCY Hazardous Materials Response Division Seattle Washington 98115 NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Contents W elcome to cs 1 ABOUCA L OTEN EE 1 How TO USC tis MANU edades d eee 5 modele cta ripe 6 e Meme dae m ea 17 Leanne ete ive e E 21 ad attt ps 39 TEPISE M sr 39 DIC 39 OD 39 Response Modessa 40 Pianno beads aen omo rera mte bs ata osse auratis 40 CNG NR 40 Dave did SA VS inta DUE EAE 40 ALOHA Say CNC REEL 40 e Ee M TEE 41 and Prnt AM teeta 4 nm b es einen EIE EE LI NEA d 42 The EGEMEN eee E 42 TG SWCD aba MET 43 CACO sea 43 Selects edere gebe E 43 Adding modifying and deleting location information 44 BUNS T 48
61. ALOHA s menus in Windows are nearly identical Getting help Online help is available at any time when ALOHA 1s running If you re using ALOHA in Windows choose About ALOHA from the Control menu Figure 1 2 Move Size Minimize Maximize x Close About ALOHA Figure 1 2 Accessing ALOHA Help in Windows 98 Chapter 1 Welcome to ALOHA If you re using ALOHA on a Macintosh select About ALOHA from the menu to access online help Figure 1 3 About ALOHA Figure 1 3 Accessing ALOHA Help on a Macintosh In Windows or on a Macintosh click Help buttons on ALOHA windows and dialog boxes Figure 1 4 to view information about particular features or required model inputs Infiltration Building Parameters Select building type or enter exchange parameter 9 Enclosed office building 17 i Single storied building 3 Double storied building C3 No of air changes is per hour Select building surroundings Sheltered surroundings trees bushes etc C Unsheltered surroundings Figure 1 4 Clicking an ALOHA Help button on a Macintosh In Windows or on a Macintosh the Help Index that you access from About ALOHA is arranged alphabetically Figure 1 5 ALOHA 5 2 3 Developed jointly by NOt OF x File Edit Bookmark Options Help Contents Search Sack Bim gt Help Indi About help ALOHA Windows ver Add chemical data Add lo
62. Calculate Now menu item becomes available only when you select Automatically update only front window or Manually update all visible windows from the Calculate menu item Otherwise it remains greyed out Choose Calculate Now from ALOHA s Display menu when you wish to update all ALOHA calculations and out of date windows after you have changed input values If you are using a SAM with ALOHA select Calculate Now to effect a transfer of SAM data to ALOHA s dispersion modules and to update ALOHA footprint concentration and dose plots To reset ALOHA to automatically recompute all plots whenever inputs have been changed and to accept all transfers of SAM data choose Calculate from the Display menu then click Automatic update of all visible windows Display Tile Windows Stack Windows Text Summary Footprint Concentration Hpg source Strength Calculate Calculate Now Figure 4 57 The Calculate Now menu item 114 Chapter 4 Reference The Sharing Menu The programs that make up the CAMEO Computer Aided Management of Emergency Operations package work together by means of the Sharing menu Any program that can communicate with ALOHA can install a menu in ALOHA s Sharing menu This menu appears whenever the two programs are run simultaneously A menu installed by another program into the ALOHA Sharing menu belongs to the installing program Likewise ALOHA places a menu in MARPLOT s Sharing menu ALOHA a
63. D conditions heavy gas and Gaussian footprints will be similar in length Define dose ALOHA defines dose as the concentration of pollutant at a specified location to which people may be exposed taken to a power and multiplied by the period of time that it 1s present The exact equation is displayed in the Computational dialog box Figure 4 44 97 Chapter 4 Reference In this equation C represents the concentration of pollutant and t represents the contact time The power to which concentration is taken is called the dose exponent Dose information 1s difficult to interpret because the effects of most toxic chemicals on people are poorly understood If you don t know the appropriate dose exponent to use for a particular chemical or can t consult with a specialist who can advise you on the correct exponent to use and help you to interpret ALOHA s results avoid using ALOHA s dose calculations Instead use information from ALOHA s footprint and concentration plots and your own knowledge of a chemical to make response decisions You can adjust ALOHA s value for the dose exponent to account for the particular effects of a chemical as estimated from toxicological data Consider for example that the concentration of a pollutant is predicted to remain at a constant 100 parts per million ppm for 5 minutes at a particular location If you set the dose exponent to 1 0 ALOHA will calculate dose as concentration multiplied
64. Design Institute for Physical Properties Data DIPPR known as the DIPPR database Design Institute for Physical Property Data 1999 Other values were obtained from the chemical database included in the Computer Aided Management of Emergency Operations CAMEOTM hazardous chemical information system U S Environmental Protection Agency and National Oceanic and Atmospheric Administration 1999 ALOHA uses information from the library to model the physical behavior of a chemical that you have selected For example once ALOHA knows the temperature within a tank it can use library information to estimate the vapor pressure density and other properties of the chemical stored in the tank You need only the name of a chemical and its molecular weight to run the simplest ALOHA scenarios using the Direct source option and Gaussian dispersion module However ALOHA s more complex calculations require information about other properties of the chemical Check Table 4 1 for the property information needed for ALOHA s Tank Puddle or Pipe source options or for its heavy gas calculations You do not need to add values for liquid density or molecular diffusivity because ALOHA estimates both of these properties from other information that you enter However if you have an accurate diffusivity value add it to the library ALOHA then will use your value rather than estimating this property 57 Chapter 4 Reference Table 4 1 Properties needed to us
65. Display menu to view ALOHA s footprint Display Tile Windows Stack Windows Options db Y Text Summary Footprint Concentration Dose Source Strength 6 Calculate Calculate Now You ll see ALOHA s footprint diagram for this scenario On the diagram the shaded oval represents the area where chlorine concentrations are predicted to exceed the LOC in this case the IDLH at some time after the release begins This area 1s predicted to extend for almost a mile downwind of the leaking cylinder 33 Chapter 3 Learning the Basics Footprint Window Dashed lines along both sides of the footprint indicate uncertainty in the wind direction The wind rarely blows constantly from any one direction As it shifts direction it blows a pollutant cloud in a new direction The uncertainty lines around the footprint enclose the region within which about 95 percent of the time the gas cloud is expected to remain 4 Check the Text Summary You ll see the line of text Model Run Heavy Gas informing you that ALOHA used the heavy gas module to make its footprint estimate Because a cloud of chlorine is heavier than air ALOHA models it as a heavy gas rather than as a gas that 1s about the same weight as air Checking Concentrations at a Location of Concern You can use ALOHA not only to estimate the extent of the area that could be at risk 1n an incident that s the footprint but also to obt
66. HA s front window However you cannot close the Text summary window save and Save As Choose Save or Save As from ALOHA s File menu when you want to save the results of your work in a data file You can save a file in either of two formats a as an ALOHA save file which you can reopen later in ALOHA or b as a Spy archive file which you can view in ALOHA s companion application AlohaSpy ALOHA save files Choose this file type if you wish a to prepare in advance for an incident response by creating a set of ALOHA save files or b to be able to rerun a scenario in the future If you modified property information about a selected chemical while setting up a scenario you can save this information in a save file without making a permanent change to the chemical library When you open and use a save file in ALOHA in planning mode all the information in the file will be restored When you open and use a save file in ALOHA in 40 Chapter 4 Reference response mode you ll still need to enter information specific to a particular release such as weather conditions and the amount of material released before you can obtain a source strength estimate or footprint plot Spy files You can archive the results of an ALOHA model run as a Spy file in order to document the results of your work with ALOHA for future reference A Spy file contains all the information from the windows visible in ALOHA at the time the file was saved Once you
67. IPPR data Daylight savings time Density Glossary An estimate that is more likely to result in footprint and downwind concentration estimates that are too large rather than too small Selecting conservative choices for weather conditions low wind speed and a stable atmosphere source strength larger puddle area or higher release rate or LOC a low LOC concentration results in a longer footprint A source that releases gas into the atmosphere at a constant or near constant rate for an extended period of time Perpendicular to the wind Relating to processing or storing substances at very low temperatures For purposes of ALOHA the use and storage of gases liquefied by refrigeration DEnse GAs DISpersion model Havens and Spicer 1990 ALOHA uses a simplified version of this complex computer model developed by researchers at the University of Arkansas to predict the dispersion of a heavy gas A window that ALOHA presents to you in which you enter information or choose options Values for physical properties compiled by the Chemical Engineering Department of the Pennsylvania State University for the Design Institute for Physical Property Data DIPPR of the American Institute of Chemical Engineers DIPPR 1999 These values are included in ALOHA s chemical library ChemLib for more than half of the chemicals in the library At most U S locations daylight savings time 1s put into effect each spring when local standa
68. LH concentration if one has been established and you have not entered a default LOC value will be the default LOC Either the Default Level of Concern button or the IDLH Concentration button will automatically be highlighted If you have not entered a default LOC the Default Level of Concern button will be dimmed and titled Default LOC not set in library If no IDLH exists for the chemical you have selected the IDLH Concentration button will be titled IDLH Not Available 101 Chapter 4 Reference You can use any other concentration as your LOC without permanently adding the value to the library by typing it in the User Specified Conc box To use your own LOC click Enter value then type the value and choose units If no IDLH value exists for your chemical and you have not previously added a default LOC to the library you must enter a LOC in order to obtain a footprint Footprint options You can choose how to view ALOHA s footprint in the Footprint window by clicking the button corresponding to either of two display formats B Plot on grid and auto scale to fit window The footprint is automatically scaled on a grid Use user specified scale The footprint is scaled to your specification on a blank background By default ALOHA automatically scales each footprint to fit within the Footprint window and displays it on a grid but you can change the footprint scale 1f you wish You might want to do this in order to make a
69. LORIDE BENZYL CHLOROFORMATE BIFLUORIDE BIS 2 CHLOROETHOHY METHANE BIS TRICHLOROMETHYL SULFONE BORIC ACID BORON TRIBROMIDE Entering weather information Now that you ve selected the location time and chemical you must provide information about weather conditions and ground roughness 1 Inthe SetUp menu point to Atmospheric then click User Input Atmospheric b User Input 36H Computational 2 OnALOHA s first Atmospheric Options dialog box type 7 into the wind speed box then click Knots Type e into the wind direction box to indicate that the wind is from the east then click the right hand button under the Measurement height above ground 1s heading This button represents a wind measurement height of 10 meters 123 Chapter 5 Examples 124 The benzene is flowing onto a grassy field located to the west of the industrial park Since the wind is blowing from the east we can expect the cloud of benzene vapor to disperse westward across this field An open field fits into the category of Open Country ground roughness so click Open Country If the wind was instead blowing from the west towards the industrial park Urban or Forest would be the most appropriate roughness category Under the Select cloud cover heading click the second button from the left this button represents 7 10 cloud cover Once the dialog box on your screen looks like the one below cli
70. MEO 115 Chapter 4 Reference If you have selected a chemical in ALOHA choose Get RIDS Info to see information about this chemical in CAMEO s RIDS Response Information Data Sheets database Choose Go to CAMEO to start CAMEO or to go to CAMEO if it is already running Sharing About Shared Menus Edit Shared Menus CAMEO MARPLOT Get RIDS Info Go to CAMEO Figure 4 58 The CAMEO menu in ALOHA s Sharing menu The MARPLOT menu The MARPLOT menu in ALOHA s Sharing menu contains two items Choose Help to learn about information sharing between MARPLOT CAMEO s mapping program and ALOHA Choose Go to Map to start MARPLOT or to go to MARPLOT if it is already running Sharing About Shared Menus Edit Shared Menus CAMEO 4 hMARPLOT Ld ta Map Figure 4 59 The MARPLOT menu in ALOHA s Sharing menu Displaying an ALOHA footprint on a map Use MARPLOT with ALOHA to display an ALOHA footprint on an electronic map of your community If you re using ALOHA for Windows you ll need to run ALOHA and MARPLOT simultaneously in Windows If you re using a Macintosh you must be using System 7 or later to use the current version of MARPLOT 116 Chapter 4 Reference MARPLOT can display several different types of maps It was primarily designed to use special maps generated from TIGER Topologically Integrated Geographic Encoding and Referencing files prepared by t
71. OHA s computations Display Tile Windows Stack Windows Options AT Text Summary Footprint Concentration Dose Source Strength Calculate Calculate Now Figure 4 46 The Display menu Tile and Stack Windows The Tile and Stack Windows options allow you to organize the information windows on your computer screen Choose Tile Windows when you wish to see all of ALOHA s open windows at once rather than overlapping each other in a stack Windows will be reduced in size and arranged in rows and columns as necessary to fit on your screen 99 Chapter 4 Reference B Select Stack Windows when you wish to arrange ALOHA s windows on your screen so that each overlaps the next with only the front window fully visible The title bars of the remaining windows will remain visible You may resize or move any ALOHA window after you have chosen either option Options Choose Options from the Display menu when you want to M enter a Level of Concern LOC indicate a Footprint output format preference choose to see ALOHA s output displayed in either English or metric units ES Display Options SSS Select Level of Concern or Output Concentration C3 Default LOC not set in library amp IDLH ppm 2 milligrams cubic meter 3 Enter value 2 milligrams liter 9 grams cubic meter Select Footprint Output Option amp Plot on grid and auto scale to fit window 9 Use user specifi
72. OHA calculates the amount of energy coming into the puddle from the atmosphere and from the ground For example if the sun 1s high in the sky the amount of energy coming into the puddle is greater than it would be in the early morning or late afternoon when the sun 15 lower The more energy coming in the higher the evaporation rate Selecting a location To specify the location where a release 1s occuring select Location from the SiteData menu You ll see a scrolling alphabetical list of cities mostly U S cities and towns You ll need to find the name of your location in this list Scroll through the list to speed your search type the first one or two letters of the city name click on the city name then click Select 43 Chapter 4 Reference Location Information ABERDEEN MARYLAND ABILENE TEXAS AIKEN SOUTH CAROLINA ALAMEDA CALIFORNIA ALBANY NEW YORK ALBANY OREGON ALEXANDRIA BAY NEW YORK ALEXANDRIA LOUIS LANA ALEXANDRIA VIRGINIA ALLEN TEXAS AMBLER PENNSYLVANIA AMES IOWA AMESBURY MASSACHUSETTS ANACONDA MONTANA ANAHEIM CALIFORNIA ANCHORAGE ALASKA ANNAPOLIS MARYLAND Figure 4 5 Choosing a location Adding modifying and deleting location information You can add a new city or other geographic location to ALOHA s library of cities CityLib You can add both U S and non U S locations to the library For a location outside of the U S you must manually change the time setting see below when
73. PHERE 9 gallons sec i qallons min for gallons hr Enter source height feet 0 if ground source meters 3 When you enter the rate of release in volume units you need to describe the physical state of the chemical liquid or gas and its storage temperature so that ALOHA can estimate the mass of material released The chlorine was refrigerated at 30 F The boiling point for chlorine displayed in the Text Summary 15 29 25 F so the chlorine is barely in the liquid phase Click Liquid and Chemical temperature is Type 30 into the chemical temperature box then click F to indicate degrees Fahrenheit Click OK Volume Input Information Is the chemical stored as a gas or liquid Gas i Liquid Enter the temperature at which the chemical is stored o Ambient Temperature i Chemical temperature is 30 degrees OC 4 ALOHA will alert you that the chemical may flash boil and or escape as a two phase flow Mote This chemical may flash boil and or result in two phase flow 138 Chapter 5 Examples Click Help to view background information about flash boiling and two phase flow ALOHA recognizes that because the boiling point of chlorine 1s well below air temperature the chlorine may have been stored as a pressurized liquid If so it may flash boil when released During flash boiling much of the stored liquid would turn instantly to vapor so that a mixture of liquid d
74. Station ID is the identification code of the SAM that is sending data to your computer this ID 1s assigned by the manufacturer Wind Direction in the case of both instantaneous and average values is the direction from which the wind 1s blowing B The standard deviation of the wind direction is called Sigma Theta This value reflects the amount of fluctuation in the wind direction during the last 5 minutes The more the wind switches direction the larger 1s the value of sigma theta ALOHA uses sigma theta along with wind speed cloud cover and time and date to choose the stability class for your scenario The SAM transmits a value of 1 00 for sigma theta until it has been transmitting for 5 minutes Battery Voltage is the remaining voltage of the battery on your SAM 75 Chapter 4 Reference Wind Rose Choose Wind Rose from the SAM Options menu to view a diagram showing the 10 most recent average wind speed and direction values received from the SAM station Each line on the diagram represents a 5 minute running average speed and direction Each line is drawn from the center out towards the direction to which the wind 1s blowing Line length indicates wind speed Wind Rose 15 9 mph Figure 4 30 ALOHA s wind rose The two concentric circles on the diagram represent wind speeds of 10 and 20 miles per hour mph if you have indicated a preference for English units or 5 and 10 meters per second m s if you indic
75. U S Highway 29 211 near the right side of the map PRINCE WILLIAM COUNTY VA Dcus Pt Focus Pt 88947 45 M 773545 45 H 77 36 45 H 1 in 0 07 mi Location of release Location of workmen 9 Inthis example the tank car releases chlorine at the point where the Southern Railway line crosses U S Highway 29 211 To indicate this location choose the arrow tool from MARPLOT s tool palette then click once at this intersection MARPLOT will place a visible crosshair mark or click point at this location 161 Chapter 5 Examples 10 In MARPLOT s Sharing menu point to ALOHA then click Set Source Point Sharing About Sharing ES ALOHA b CAMEO po Set Source Point Set Conc Dose Point Delete ALOHA Objects Go to ALOHA 11 An ALOHA footprint will automatically be drawn on the map RM PRINCE WILLIAM COUNTY UA muni Focus Pt 38747 49 N 7v 38 34 H 1 in 0 08 mi o US Hwy 29 and 211 Roads Major PRINCE WILLIAM COUNTY undivided secondary road Now you ll choose the location for which you d like an ALOHA Concentration by Time graph Find the intersection of Gallerher Road and U S Highway 29 211 this 1s close to the middle of the footprint Be sure that the arrow tool remains selected in the tool palette then click on this location 12 In MARPLOT s Sharing menu point to ALOHA then click Set Conc amp Dose Point Sharing Abou
76. Vertical cyl inder Horizontal cyl inder Q s o Enter two of three values im feet o meters length 3 352 volume d gallons i cu feet diameter 3 benzene is stored in the tank as a liquid notice in the Text Summary that it has a boiling point of 176 16 F well above the ambient temperature Check to be sure that Tank contains liquid and Chemical stored at ambient temperature are selected then click OK Chemical State and Temperature Enter the state of the chemical Tank contains liquid C Tank contains gas only O Unknown Enter the temperature within the tank Chemical stored at ambient temperature O Chemical stored ateo degrees F OU 126 Chapter 5 Examples 4 The security guard thinks the tank was filled in the evening so the most conservative estimate we can make is that the tank is 100 percent full Either 1 type 100 in the full by volume box 2 type 500 in the liquid volume box then click gallons or 3 scroll the liquid level bar to the top of the tank diagram Once you have entered your estimate of the liquid volume ALOHA estimates the mass of the liquid 1 82 tons Click OK Liquid Miass or Volume Enter the mass OR volume of the liquid pounds The mass of liquid is tons 000 Ibs O kilograms Enter volume liquid level The liquid amp gallons bic feet liters O cubic meters full by volum
77. a save file within ALOHA you can choose between two modes Response Mode or Planning Mode 39 Chapter 4 Reference Response Mode Choose this mode when you open a save file in order to use ALOHA during a real emergency As ALOHA opens the file it will restore the information contained in the file that 15 expected to stay the same from day to day This information includes location chemical of concern and the dimensions of existing storage vessels and containment areas You ll need to enter information specific to the particular incident including current weather conditions and the circumstances of the release these could include for example the dimensions and location of a hole in a tank or the area of a puddle of spilled liquid Planning Mode Choose this mode when you need to completely recreate the scenario saved in the ALOHA save file When you open a save file in planning mode all input values will be restored to their state when you saved the file If you were using the computer s clock ALOHA will use the time when the file was saved as the constant time If you were using a portable weather monitoring station the most recent transmission will be entered into ALOHA as user entered atmospheric data save files created from the current version of ALOHA version 5 2 3 are cross platform you can open a save file created in Microsoft Windows on a Macintosh computer and vice versa Close Choose Close to close ALO
78. a two phase mixture of gas and liquid In two phase flow cases your choice of hole type can have an important effect on ALOHA s release rate computations because ALOHA accounts for the friction generated as the gas liquid mixture passes through a constricted passage such as a valve or short pipe ALOHA will predict a higher release rate for a two phase release if you choose the hole option rather than the short pipe valve option Hole type does not make a difference in a pure gas or unpressurized liquid release case 90 Chapter 4 Reference Hrea and Type of Leak Select the shape that best represents the shape of the opening through which the pollutant is exiting Po with length dianeter m C Circular opening i Rectangular opening opening length 5 Steet i i centimeters pening width meler Is leak through a hole or short pipe valve Hole C3 Short pipe valve Figure 4 40 Area and type of tank Leak height on the tank wall If there is liquid in the tank you must tell ALOHA where the leak occurs on the tank Enter a value for the height of the bottom of the leak whether it 1s a hole pipe or valve above the floor of the tank ALOHA uses this value to determine whether the leak 1s above or below the liquid level If an unpressurized liquid 1s stored in the tank and the leak 1s below the liquid level the chemical will spill out and form a puddle on the ground It will stop spilling once the li
79. ain predicted indoor and outdoor concentrations at any location of special concern during the hour after a release begins The Central Valley Elementary School 15 located about 1 500 yards downwind of the treatment plant You have already indicated the school s building type and degree of shelter from the wind Next you ll indicate the location of the school relative to the release point at the treatment plant 34 Chapter 3 Learning the Basics 1 Choose Concentration from the Display menu Display Tile Windows Stack Windows Text Summary Footprint Concentration Dose Source Strength 6 Calculate Calculate Now a 2 Click Relative Coordinates to indicate that you are describing the school s location in terms of its downwind and crosswind distance relative to the release point you otherwise could choose to describe the school s location in terms of geographic north south east west distances Type 1500 in the downwind distance box then click yards Type 0 in the crosswind distance box when you enter a crosswind distance of 0 you re indicating that the wind is blowing the gas cloud directly towards the location of concern so that concentrations will be as high as possible ALOHA s concentration graph then represents the worst case prediction for the location Click OK Concentration and Dose Location Specify the location at which you want to evaluate the concentration and
80. al names appear in alphabetical order in the index with prefixes such as n tert or 1 2 1gnored To navigate quickly through the index type the first one or two letters of the name then scroll up or down until you see the name of the chemical that you wish to select Double click on the name or click once on the name then click Select to select it Once you have selected a chemical you ll see some of its most important properties listed in the Text Summary window Figure 4 18 Reactive chemicals To predict how a pollutant cloud will disperse in the atmosphere ALOHA assumes that the molecules in the cloud do not react with each other or with the gases that make up the atmosphere such as oxygen and water vapor That 15 ALOHA assumes that the molecules that disperse in the atmosphere are the same molecules that originally escaped from a container However some chemicals react with dry or humid air water other chemicals or even themselves Because of these chemical reactions some or all of the molecules that disperse downwind sometimes may be very different from the molecules that originally escaped from containment They may be heavier or lighter than the original molecules may have different properties and behave differently in the atmosphere and may be more or less toxic than the original chemical In some cases these differences may be substantial enough to make ALOHA s dispersion predictions inaccurate ALOHA wil
81. ame items appear in this menu on a Macintosh and in Windows Chemical Select Chemical from the SetUp menu to access an index of the chemicals included in ALOHA s chemical library ChemLib Figure 4 15 Physical property and toxicological data for about 1 000 pure chemicals are included in the library ALOHA uses the information in the library to predict how a particular chemical may escape from a container and disperse in the atmosphere The library does not include any chemical mixtures or solutions chemicals with unstable structures or chemicals of such low volatility and toxicity that they don t represent air dispersion hazards that 1s solids or liquids with very low vapor pressures that present a toxic hazard only when present at high concentrations You can add chemicals to the library or delete chemicals from it and you can modify information about the physical properties of any chemical 53 Chapter 4 Reference Chemical Information ERT BUTVL ACETATE BUTYL ACRYLATE BUTYL ALCOHOL SEC BUTYL ALCOHOL ERT BUTVL ALCOHOL a BUTYLAMINE D Cancel SEC BUTYLAMINE EEE ERT BUTYLAMINE BUTYLANILINE BUTYL BENZENE BUTYL BROMIDE NORMAL BUTYL BUTYRATE BUTYL CHLORIDE BUTYLCHLOROFORMATE SEC BUTYL CHLOROFORMATE ERT BUTYLCYCLOHEHYLCHLOROFORMATE 1 2 BUTVLENE OHIDE BUTYL ETHER Figure 4 15 ALOHA s chemical index Selecting a Chemical To choose a chemical locate its name in the chemical index Figure 4 15 Chemic
82. ameter that you enter as a number only if it is within a specified range These restrictions help to prevent you from inadvertently entering an unrealistic input value If you enter a value outside of the allowable range ALOHA will warn you and tell you what the limits are You must modify your value before ALOHA will continue Check the table in this chapter to see the allowable ranges for ALOHA inputs Check ALOHA s online help topics for more information about ALOHA inputs Chapter 6 Troubleshooting The Text Summary shows a Maximum Computed Release Rate that is much higher than the Maximum Sustained Averaged Release Rate How should I interpret these numbers When I changed some atmospheric conditions ALOHA told me that it is unable to verify the consistency between my new atmospheric data and the source data Then I had to reset the source I think done everything I needed to set up a scenario in ALOHA chosen a location and chemical entered weather conditions and set the source But now I can t choose Footprint from the Display menu it s unavailable I set up a release scenario in ALOHA then started MARPLOT clicked on a location on my map and chose Set Source Point from the ALOHA menu in MARPLOT s Sharing menu But I don t see a footprint on my map What s wrong ALOHA averages the release rate over five steps The maximum computed release rate corresponds to the very highest releas
83. arry the pollutant cloud directly towards the hospital To find this out use ALOHA to obtain a concentration graph for a location a quarter mile directly downwind with a crosswind distance of 0 miles This graph represents the worst case concentrations that could develop at any point one quarter mile downwind of the source should the wind shift to blow the cloud towards that point When you use relative coordinates ALOHA remembers the location of any point you specify in terms of its downwind and crosswind distance to the source Therefore the geographic location of the point that you have specified to ALOHA will move when the wind direction changes A point specified in this manner follows the wind 108 Chapter 4 Reference Concentration and Dose Location Specify the location at which you want to evaluate the concentration and dose over time Relative Coordinates Evaluation Downwind Crosswind Point B Fixed Coordinates Pa Wind direction Q East West North South from the source and V the perpendicular distance from the downwind axis Input the downwind distance x PER feet O yards 0 25 miles Input the crosswind distance jo oO meters kilometers Input the downwind distance Figure 4 53 Entering wind relative coordinates for a location of concern Dose The Dose vs Time graph shows you the predicted dose of chemical to which people might be exposed at a location that yo
84. ars in the Text Summary ALOHA predicts that about 147 Chapter 5 Examples 1 400 pounds of methane will escape from the pipe each minute until the safety valve can be shut off Because the release rate in this example scenario is constant the Maximum Computed Release Rate and Maximum Averaged Sustained Release Rate are equal ALOHA sets release duration to the maximum possible time of 1 hour Text 5ummary SOURCE STRENGTH INFORMATION Pipe Diameter 8 inches Pipe Length 1868 feet Pipe Temperature 44 F Pipe Press 188 Ibs sqd i Pipe Roughness smooth Hole Area 58 3 sq in Unbroken end of the pipe is connected to an infinite source Re lease Duration ALOHA Limited the duration to 1 hour Computed Release Rate 4 438 pounds min Max Average Sustained Release Rate 1 438 pounds min faveraged over a minute or more Total Amount Released 84 565 pounds Choosing a LOC and plotting a footprint 1 First check the computational setting Select Computational from the SetUp menu Check to be sure that Let model decide select this if unsure is selected Click OK 2 Select Options from the Display menu Display Tile Windows Stack Windows Options Text Summary K Footprint Concentration 3R Dose Source Strength 6 Calculate Calculate Now 3 The LOC for this example is 5 000 ppm so click Enter value then type 5000 into the LOC box Click ppm 4 Check to be sure that Pl
85. ase to determine whether a heavy gas could be formed In such a case ALOHA will make Gaussian calculations but will alert you that you should try running the heavy gas model as well In such cases you should re run ALOHA using the heavy gas calculations and compare the two footprint estimates 10 Chapter 1 Welcome to ALOHA ALOHA s limitations Like any model ALOHA cannot be more accurate than the information you give it to work with But even when you provide the best input values possible ALOHA like any model can be unreliable in certain situations and it cannot model some types of releases at all Even when you can provide accurate input information ALOHA s results can be unreliable when the following conditions exist very low wind speeds very stable atmospheric conditions wind shifts and terrain steering effects concentration patchiness particularly near the spill source ALOHA doesn t account for the effects of fires or chemical reactions B particulates topography Very low wind speeds ALOHA s footprint accurately depicts a pollutant cloud s location only 1f the wind direction does not change from the value that you entered Generally wind direction 1s least predictable when wind speed is low To show how much the cloud s position could change if the wind were to shift direction under the particular weather conditions that you enter ALOHA draws two dashed lines one along each side o
86. ated a preference for metric units indicate your units preference by choosing Options from the Display menu The length of each line on the diagram indicates wind speed For example a line drawn from the center of the diagram out to the 10 miles per hour circle represents an average wind speed of 10 miles per hour The most recent average wind value is represented on the diagram by a darker line The most recent 5 minute average wind speed is displayed in the lower left corner of the window Monitoring a long term release You may sometimes use a SAM with ALOHA to monitor weather conditions during a long term release such as a slowly evaporating pool of toxic liquid or a potential spill When you do so bear in mind that although your SAM 15 providing current weather information other ALOHA inputs may become out of date during the course of the response as conditions change At least once each hour assess whether you need to adjust important model inputs that could affect ALOHA s estimates of source strength or cloud dispersion For example you may respond to a release of a liquid from a storage tank originally running the release in ALOHA as a Tank source After an hour or so though the tank may stop leaking but an evaporating puddle may have formed in the meantime 76 Chapter 4 Reference In such a case rerun the scenario in ALOHA as a Puddle source Later if the puddle becomes smaller in size as it evaporates or bec
87. ause it 15 being cleaned up or diked enter new values for its area and its volume mass or depth then rerun your Puddle scenario Check the time and date Whenever you use a SAM with ALOHA make sure that your computer s internal clock is set to the time and date of the release that you are modeling ALOHA uses time and date along with wind speed and cloud cover to choose stability class Choosing a Calculate option You can set ALOHA to any Calculate option when you use a SAM station with ALOHA check the Display menu chapter to learn more about these options If you wish to see footprint concentration and dose windows updated as weather conditions change choose Calculate from the Display menu then click Automatically update all windows this is the model s default setting If you instead click Manual update of all visible windows meteorological data will continue to be tracked and archived as you specify However SAM data will be transferred to ALOHA s dispersion modules only when you select Calculate Now from the Display menu After each data transfer footprint concentration and dose plots will be updated Source In an ALOHA scenario the source is the vessel or pool releasing a hazardous chemical into the atmosphere and the source strength is the rate of release of the chemical into the air A chemical may escape into the atmosphere very quickly so that source strength is high as when a pressurized container is
88. ave not entered a different value for the LOC the LOC line represents the IDLH In this example this is the LOC recommended by the safety officer If she had instead recommended a different value you would have needed to choose Options from the Display menu and type that value into the LOC box Concentration Window minutez 140 Chapter 3 Examples You can see from the graph that the chlorine cloud passes by the office building within the first 15 minutes after the release begins After that time the predicted outdoor concentration drops back to zero while the predicted indoor concentration persists for much longer Check the Text Summary to see ALOHA s estimates of maximum indoor and outdoor concentration You also can see that ALOHA made heavy gas rather than Gaussian calculations for this release look just under the FOOTPRINT INFORMATION heading to see this Text 5ummary SITE DATA INFORMATION Location COLUMBIA SOUTH CAROLINA Building Air Exchanges Per Hour 8 45 sheltered single storied Time May 15 2886 amp 1388 hours EDT user specified CHEMICAL INFORMAT I OH Chemical CHLORIME Molecular Height 78 91 kg kmal TLY TWA 8 5 ppm IDLH 18 ppm Footprint Level of Concern 18 ppm Boiling Point 29 25 F Vapor Pressure at Ambient Temperature greater than 1 atm Ambient Saturation Concentration 1 888 868 ppm or 188 8 ATMOSPHERIC INFORMATION MANUAL INPUT OF DATA Mind 18 knots from at 18 me
89. ay year hour and minute of this accident as shown below Click OK Date and Time Options You can either use the computer s internal clack for the model s date and time or set a constant date and time Use internal clock i amp Set constant time Input constant date and time Month Day Year s 200 1 12 1 31 1900 0 23 0 59 Minute 8 Choose Chemical from the SetUp menu 36H Chemical Atmospheric Source tompuinationaL 9 Use the scroll bar or quickly type the characters ch to find CHLORINE Double click on this name or click once on it then click Select Chemical Information CARBON DIOHIDE CARBON MONOHIDE CARBON TETRABROMIDE CARBON TETRACHLORIDE CARBONYL FLUORIDE CARBONYL SULFIDE CHLOROBENZENE Entering weather information 1 Inthe SetUp menu point to Atmospheric then click User Input Chemical 36H Atmospheric User input Computational 153 Chapter 5 Examples 2 Type a wind speed of 12 knots and a wind direction of ENE Under the Measurement height above ground is heading click the left hand button to indicate that the wind speed 1s measured at a height of 3 meters The area between the derailed tank car and the injured workmen 1s flat and free of obstacles so click Open Country ground roughness Click the fourth cloud cover button from the left to indicate that cloud cover is 3 tenths Click OK Atmo
90. azardous chemicals Its computations represent a compromise between accuracy and speed it has been designed to produce good results quickly enough to be of use to responders ALOHA 15 designed to minimize operator error It checks information that you enter and warns you when you make a mistake ALOHA s online help offers you quick access to explanations of ALOHA s features and computations as well as background information to help you interpret its output Basic program organization To use ALOHA you ll typically perform several basic steps indicate the city where an accidental chemical release is occurring and the time and date of the accident choose the chemical of concern from ALOHA s library of chemical information enter information about current weather conditions M describe how the chemical is escaping from containment Chapter 1 Welcome to ALOHA B request ALOHA to display a footprint showing the area where chemical concentrations in the air may become high enough to pose a hazard to people ALOHA can display this footprint on an electronic map of your city You can also view graphs showing predicted indoor and outdoor chemical concentrations at any location of special concern downwind of a release such as a school or hospital and the dose of chemical to which people at that location may be exposed You can save ALOHA results as archive files and you can copy and paste graphs plots and text information fro
91. best method to choose if you want to monitor potential concentration at the school and you are using a SAM station to track wind speed and direction in ALOHA If the wind shifts direction the concentration graph displayed by 107 Chapter 4 Reference ALOHA may change depending on whether or not the shift in wind direction moves the cloud closer to the school or farther away from it Concentration and Dose Location Specify the location at which you want to evaluate the concentration and dose over time Relative Coordinates Evaluation Downwind Crosswind Paint Fined Coordinates ne East West North South v Input the east west distance from the source and the Source y north south distance from the source feet yards i miles O kilometers Figure 4 52 Entering fixed coordinates for a location of concern Using relative downwind and crosswind coordinates Choose this method when you wish to know the concentration expected at a position best described in terms of its downwind and crosswind distance from the source For example suppose that you have estimated the straight line distance between the site of a spill and a nearby hospital to be a quarter mile At the moment the wind is not blowing the chemical cloud directly towards the hospital but the wind 1s shifting direction You might want to know the worst case concentration you could expect if the wind were to shift to c
92. ble storied buildings and within unsheltered than sheltered buildings To estimate indoor pollutant concentration ALOHA first estimates the building s air exchange rate the number of times per hour that the volume of air within the building 15 completely replaced by new outdoor air when doors and windows are closed This rate 1s less than 1 0 if it takes more than an hour to completely change the air within the building You also can choose to enter a value for air exchange rate rather than specifying a building type if you have this information To estimate infiltration rate into a building ALOHA assumes that all doors and windows are closed Whether you specify building type to be a a single or double storied building or b an enclosed office building makes a big difference in how ALOHA chooses an exchange rate value For single and double storied buildings ALOHA accounts for the effects of wind speed and temperature to compute air exchange rate ALOHA expects a building s air exchange rate to increase if the wind speed increases because a faster wind exerts more force to push air through the small openings in a building s walls The degree of difference between indoor and outdoor air temperature also affects ALOHA s air 48 Chapter 4 Reference exchange rate estimate ALOHA assumes the temperature within the building to be 68 F or 20 C The greater the temperature difference the higher the air exchange rate regardless of whe
93. by step procedures for hazards analysis recommends and discusses use of one tenth of the IDLH as the Level of Concern for Extremely Hazardous Substances in emergency planning Spicer Tom and Jerry Havens 1989 User s Guide for the DEGADIS 2 1 Dense Gas Dispersion Model EPA 450 4 89 019 Cincinnati U S Environmental Protection Agency Turner D Bruce 1994 Workbook of Atmospheric Dispersion Estimates An Introduction to Dispersion Modeling Second edition Boca Raton Florida Lewis Publishers Turner D Bruce and Lucille W Bender 1986 Description of UNAMAP Version 6 Springfield Virginia National Technical Information Service Wilson D J 1987 Stay indoors or evacuate to avoid exposure to toxic gas Emergency Preparedness Digest 14 1 19 24 172 Glossary ALOHA Aerosol Air dispersion model Air exchange rate AlohaSpy Ambient saturation concentration Anhydrous Areal Locations of Hazardous Atmospheres The air dispersion model described in this manual ALOHA is a trademark of the U S Government Fine liquid droplets or solid particles suspended in a gas A computer model such as ALOHA that predicts the movement and dispersion of a gas in the atmosphere The number of times that the outdoor air replaces the volume of air in a building per unit time Usually expressed as number of air changes per hour A companion application to ALOHA Use AlohaSpy to view or print archived Spy files The maxi
94. called the inversion height An inversion can trap pollutant gases below the inversion height causing ground level concentrations of a pollutant to reach higher levels than would otherwise be expected The type of inversion of concern for dispersion modeling 1s a low level inversion that could trap a pollutant cloud near the ground Sea smoke and low ground fog are good indicators of the presence of this type of inversion A low level inversion is different from the inversion that causes smog That type of inversion is typically thousands of feet above the ground much too high to affect a dispersing gas cloud 68 Chapter 4 Reference ALOHA s Gaussian dispersion model accounts for inversions but the heavy gas model does not even when you ve indicated that an inversion exists A low level inversion may significantly increase ground level concentrations of a neutrally buoyant gas Molecules of such gases disperse upwards and outwards as they are transported downwind and are reflected from an inversion layer back towards the ground A heavy gas cloud in contrast remains close to the ground as it disperses and 1s not normally affected even by low level inversions If an inversion is present type in the height of the inversion layer and select units If there 1 no inversion be sure that No Inversion 15 selected Humidity ALOHA takes relative humidity into account when it estimates the rate of evaporation from a puddle and when it makes
95. cation data Air temperature ALOHA Limitations AlohaSpy Ambient saturation concentratio Amount of chemical unknown st Amount of gas in tank ALOHA 5 2 3 Help Index Developed jointly by NOAA and EPA About help ALOHA Windows version About hel ALOHA Macintosh version Add chemical data Add location data Air temperature ALOHA Limitations AlohaSpy Ambient saturation concentration Amount of chemical unknown state in tank Amount of gas in tank Amount of liquid in tank Amount of pollutant entering atmosphere Atmospheric BitPlot ALOHA Windows version only Boiling point Bugs Building shelter Figure 1 5 ALOHA Help Index on a Macintosh background and in Windows 98 foreground Chapter 1 Welcome to ALOHA In Windows Click any topic name to view a discussion of that topic When you ve finished reading about that topic click Contents to return to the Help Index When you are ready to go back to using ALOHA close or minimize the Help window On a Macintosh Highlight a topic name then click Select to view a discussion of that topic When you ve finished reading the topic discussion click either Topics or Cancel to return to the Help index to select another topic Print to print the Help screen or Copy to copy the discussion text to the clipboard ALOHA S LIMITATIONS ALOHA cannot be more accurate than the information you give it to work with But even when you provide the best i
96. ce 155 Chapter 5 Examples ALOHA will display the warning shown below Mote This chemical may flash boil and or result in two phase flow It recognizes that because the boiling point of chlorine is well below air temperature the chemical may have been stored as a pressurized liquid If so it may flash boil when released through a tank hole During flash boiling much of the stored liquid would turn instantly to vapor so that a mixture of liquid droplets and vapor a two phase flow would be released to the atmosphere ALOHA s Tank release calculations account for these processes but the Direct Source option does not Since we don t have the necessary information to run the Tank option we ll use the Direct Source calculations as the best approximation that we can make recognizing that the model will treat this release as a steady flow of gas from the tank instead of a two phase release Click OK Check the Text Summary to be sure that you correctly entered information about the release Text Summary SOURCE STRENGTH INFORMAT ION Direct Source 4000 pounds hr Source Height 0 Release Duration 60 minutes Release Hate 66 7 poundz min Total Amount Released 4 000 pounds Hote This chemical may flash boil and or result in two phase flow Choosing a LOC and plotting a footprint 1 First check the computational setting Select Computational from the SetUp menu Check to be sure that Let model decid
97. ch a two phase mixture escapes from storage the release rate can be significantly greater than that for a release of pure gas When liquefied propane or a similar chemical escapes from storage as a two phase release it can form a heavy gas cloud The cloud is heavy in part because it 1s initially cold and therefore dense and also because it consists of a two phase mixture The tiny aerosol droplets mixed into the cloud act to weigh the cloud down and make it more dense and their evaporation acts to cool the cloud ALOHA s heavy gas calculations The heavy gas dispersion calculations that are used in ALOHA are based on those used in the DEGADIS model Spicer and Havens 1989 one of several well known heavy gas models This model was selected because of its general acceptance and the extensive Chapter 1 Welcome to ALOHA testing that was carried out by its authors In order to speed up the computational procedures and reduce the requirement for input data that would typically be difficult to obtain during an accidental release a few simplifications were introduced into ALOHA DEGADIS making it different from the DEGADIS model These simplifications include ALOHA does not use the Ooms model for elevated sources to account for the initial momentum of a jet release ALOHA DEGADIS assumes that all heavy gas releases originate at ground level the mathematical approximation procedures used for solving the model s equations are faster
98. ck OK Atmospheric Options Wind Speed is Knots OMPH Meters Sec Wind is from le Enter degrees true or text e g ESE Measurement Height above ground is feet EE OF enter value al O meters Ground Roughness is Open Countr in oe j OR O Input roughness 20 5 0 9 O Urban or Forest e cm Select Cloud Cover Help T ie es enter value Cu JR complete partly clear On ALOHA s second Atmospheric Options dialog box type 80 into the air temperature box then click F to indicate that this temperature is 1n degrees Fahrenheit ALOHA uses the wind speed cloud cover and date and time information that you ve entered to automatically select atmospheric stability class D Check to be sure that No inversion 15 selected then click the second relative humidity button from the left which represents 75 percent relative humidity Once the dialog box on your screen looks like the one below click OK Chapter 3 Examples Himospheric Options 2 Air Temperature is 8 Degrees mF Stability Class is O8 OB Ge D OF OF Inversion Height Options are Feet No inversion Inversion Present Height is O Meters select Humidity ES enter value 75 x medium dry 0 100 The information that you have entered into ALOHA appears in the Text Summary Ignore ALOHA s estimate of building exchange rate since we are not cons
99. companion program to ALOHA Use it to view or print archived Spy files that you have previously saved from within ALOHA You may wish to create a Spy file whenever you have run an ALOHA scenario and would like to save your results for later viewing An archived Spy file contains the information from all the windows visible in ALOHA at the time the file was saved 118 Chapter 4 Reference Whenever you d like to create a Spy file first check that all of the windows that you d like to archive are visible in ALOHA Then select Save As from ALOHA s File menu Click Spy on the Save As Options dialog type in a file name and click OK Double click on the AlohaSpy icon or choose the AlohaSpy menu item from the Start menu in Windows 95 98 NT when you wish to use the program to view or print Spy files Each menu item available in AlohaSpy 1s described below Note Spy files can be opened only with AlohaSpy File menu pen Window Archive Close Window Archive Page Setup Print PrintHll Open Window Archive opens a Spy archive file that has been created in ALOHA If you are currently viewing a Spy archive file selecting a new archive file to open will close the current file Close Window Archive closes an open Spy archive file Close closes the front window of the current archive display Page Setup allows you to adjust page printing settings Print prints the contents of the front window Print All p
100. cted rate of release of the chemical to the atmosphere not the rate at which a liquid is predicted to spill from a tank B Total amount released This is the amount of chemical that ALOHA predicts will be released into the atmosphere during the hour after a release begins not the amount of liquid that spills from a tank during that time Review the information you have entered as it appears in the Text Summary to be sure that you made no errors when entering information Review the source type predicted release rate duration and total amount released to be sure that this information seems reasonable to you If it does not try to obtain more information about the release in order to more accurately model it Computational Choose Computational from the SetUp menu to either a select the type of dispersion calculation you wish ALOHA to make or b change the exponent in the equation that ALOHA uses to calculate dose 92 Chapter 4 Reference Computational Preferences Select spreading algorithm If unsure let model decide iw Let model decide select this if unsure O Use Gaussian dispersion only O Use Heavy Gas dispersion only Define dose 1 Dose 0 Figure 4 44 Computational options Dispersion options You can choose from among three dispersion calculation options 96 Let model decide When you select this option ALOHA automatically chooses whether to predict the dispersion of a chemical
101. cular weight Neutrally buoyant gas Open country Parts per billion ppb Parts per million ppm Particulates 180 ALOHA computes release rate from a puddle tank or gas pipeline as a series of up to 150 timesteps it then averages these rates together to obtain a smaller series of averaged rates to use in making its footprint estimates The Maximum Computed Release Rate is the highest in this series of release rates This rate may last anywhere from a fraction of a second in the case of a highly pressurized release in which release rate drops very quickly as container pressure drops to a few minutes in the case of a slowly evaporating puddle The process by which air 1s mixed into a pollutant gas cloud This includes both mechanical induced by the wind passing over rough ground and thermal induced by surface heating mixing Amount of a substance containing 6 02 x 1025 molecules The molecular weight of a chemical is the mass of 1 mole of that chemical The sum of the atomic weights of all the atoms in the molecule the weight of one molecule of the chemical A gas that 15 about as dense as air and neither positively nor negatively buoyant neither rises nor sinks in air An area of low ground roughness such as a parking lot or open field Units of gas or vapor concentration in air parts of gas per billion parts of air ALOHA uses parts per million ppm 1 ppm 1 ppb x 1 000 Units of gas or vapor c
102. d Release Rate ALOHA computes release rate from a puddle tank or gas pipeline as a series of up to 150 timesteps Each timestep represents a rate of release that is maintained for a particular amount of time timesteps are short if release rate 15 changing rapidly and longer if release rate is nearly constant The Maximum Computed Release Rate is the highest of these release rates This rate may last anywhere from a second or two in the case of a highly pressurized release in which release rate drops very quickly as container pressure drops to a few minutes in the case of a slowly evaporating puddle ALOHA then averages this series of many release rates into between one and five release rates that are each averaged over a time period of at least 1 minute Choose Source Strength from the Display menu to see a graph of these averaged release rate s for a particular scenario To save calculation time ALOHA uses these averaged release rate s to make its footprint estimates The Maximum Average Sustained Release Rate 1s the highest of these averaged release rates It 1s represented by the tallest timestep on the source Strength graph When a gas or liquid escapes from a pressurized container the release rate may drop very quickly even within a second or two as the pressure within the container drops In such cases the Maximum Computed Release Rate may be much higher than the Maximum Average Sustained Release Rate because it represents a rate
103. d that wind speed and air temperature are important influences on evaporation rate If these conditions change after ALOHA has estimated an evaporation rate enter the new values and rerun ALOHA Tank Choose Tank from the Source menu to model releases of pressurized or unpressurized liquids or gases from tanks or drums You can choose to model releases from three types of tanks a cylindrical tank lying on its side a cylindrical tank standing on its end or a spherical tank ALOHA assumes any tank to be on level ground If the tank contains pressurized gas or liquid ALOHA estimates the change over time in pressure and temperature as well as liquid volume inside the tank as it leaks If the tank 84 Chapter 4 Reference contains unpressurized liquid ALOHA assumes that gravity will drain the tank and that a puddle will form on the ground below the tank you then need to enter information about the puddle and its environment ALOHA cannot model a release in which there 1s both a pre existing puddle on the ground and liquid continuing to leak from a tank into the puddle If you encounter this situation and the puddle is still spreading choose Tank from the Source menu to model the release as a tank leak case If the puddle has reached or is about to reach its maximum size choose Puddle from the Source menu to treat the release as a pre existing puddle evaporation case Pressurized liquids Both the liquid and gas phases of a chemical
104. d to complex models that require massive amounts of input data and powerful computers The type of model appropriate for a particular use depends on the scale of the problem the level of detail available for input and required for output the background of the intended user and the time available to wait for the model computations to be completed ALOHA was designed with first responders in mind It 15 intended to be used for predicting the extent of the area downwind of a short duration chemical accident where people may be at risk of exposure to hazardous concentrations of a toxic gas It 1s not intended for use with accidents involving radioactive chemicals Nor 15 ALOHA intended to be used for permitting of stack gas or modeling chronic low level fugitive emissions Other models are designed to address larger scale and or air quality issues Turner and Bender 1986 Since most first responders do not have dispersion modeling backgrounds ALOHA has been designed to require input data that are either easily obtained or estimated at the scene of an accident ALOHA s online help can assist you in choosing inputs Chapter 1 Welcome to ALOHA What is dispersion Dispersion is a term used by modelers to include advection moving and diffusion spreading A dispersing vapor cloud will generally move advect in a downwind direction and spread diffuse in a crosswind and vertical direction crosswind 15 the direction perpendicular to the
105. d to exceed your Level of Concern LOC at some time after a release begins On ALOHA s footprint plot the shaded area represents the footprint itself Dashed lines along both sides of the footprint the wind direction confidence lines indicate the amount of uncertainty in the wind direction The wind direction is affected by wind speed and stability class The wind rarely blows constantly from any one direction When it shifts direction it blows a pollutant cloud in a new direction The wind direction confidence lines around the footprint enclose the region within which about 19 times out of 20 the gas cloud 15 expected to remain The lower the wind speed the more the wind changes direction so as wind speed decreases the confidence lines become farther apart They form a circle when wind speed 15 very low A curved dashed line leads from the end of one confidence line across the tip of the footprint to the end of the other confidence line It represents the farthest downwind extent of the footprint if the wind were to shift to rotate the footprint towards either confidence line FOOTPRINT area where predicted gas concentrations gt Level of Concern Footprint Window WIND DIRECTION CONFIDENCE LINES bound area in which gas cloud is 95 likely to remain given expected amount of fluctuation in wind direction Figure 4 50 An ALOHA footprint 104 Chapter 4 Reference Once you have entered all necessary infor
106. direction as well as the height at which the wind speed and direction are measured The wind direction determines which way a 60 Chapter 4 Reference pollutant cloud will drift The wind speed affects not only how fast the cloud will travel downwind but also how much it moves about in the crosswind and vertical directions When the wind 15 slower the cloud meanders more Atmospheric Options Wind Speed is I Knots amp MPH Meters Ser Wind is from jw Enter degrees true or text e g ESE Measurement Height above ground is feet F OF t lue 8 4l C wh O enter value 3 Sanctum Ground Roughness is Open Countr in dnd S OR C Input roughness Zo a cm Urban or Forest Select Cloud Cover ao X5 enter value Or nO a E complete Atmospheric Options 2 Air Temperature is 65 Degrees mF OC Stability Class is O8 Ot O8 OF OF Inversion Height Options are Feet No inversion Inversion Present Height is i Meters Select Humidity Ay a OR Center value o medium dry 0 100 Figure 4 21 The User Input dialog boxes Use Table 4 2 below when you need to estimate the wind speed from environmental clues For example when the wind speed is 12 knots you would expect to see small branches of trees and bushes moving slightly and dust and loose paper blowing along the ground 61 Chapter 4 Reference Table 4 2 Estimating
107. divided by n For example the mean of 2 2 4 and 6 is 2 2 4 6 4 which equals 3 5 The maximum temperature at which a substance s liquid phase can exist in equilibrium with its vapor phase Above the boiling point a liquid vaporizes completely The boiling point is also the temperature at which the vapor pressure of a liquid equals the atmospheric pressure The boiling point depends on a chemical s composition and on the pressure As pressure increases a substance s boiling point also increases The normal boiling point is the temperature at which a liquid under 1 atmosphere of pressure boils ALOHA s library of chemical information ChemLib contains values for physical properties and toxic thresholds for about 1 000 chemicals ALOHA s location library It contains elevations latitudes and longitudes and other information about many U S cities and a few non U S locations You can add or delete cities from CityLib definition The fraction of the sky that is obscured by clouds ALOHA uses a scale in which cloud cover is measured in tenths for example when half the sky is covered by clouds the cloud cover 1s 5 tenths The amount of a chemical present in a given weight or volume of air In ALOHA concentration of a gas in air 1s expressed in units such as parts per million by volume or milligrams per cubic meter Conservative Continuous source Crosswind Cryogenic DEGADIS Dialog box D
108. dose over time ws Relative Coordinates Exial stion Downwind Crosswind Point B Fined Coordinates b Wind direction East West North South Input the downwind distance d from the source and the perpendicular distance from the downwind auis feet ards Input the downwind distance Sy miles i meters Input Y the crosswind distance O kilometers Cancel 3 ALOHA then displays a graph of predicted chlorine concentrations at the school during the hour after the release begins The horizontal axis of this graph represents 35 Chapter 3 Learning the Basics time from 0 to 60 minutes after the release start and the vertical axis represents concentration at the location Three lines are visible on this graph The solid red line represents the predicted outdoor ground level concentration The dashed blue line represents predicted concentration inside a building of the type you selected using the Building Type menu item in the SiteData menu To draw this line ALOHA assumes that the building s doors and windows are closed and that its ventilation system is off The wider horizontal green line represents the LOC Concentration Window minutez ALOHA predicts that the cloud of chlorine would arrive at the school 1n about 4 minutes that s when the outdoor concentration line begins to rise steeply on the graph under the conditions of this scenario You also can see that the
109. e The office building is single storied Since the building has windows that open the air exchange rate 1s probably not controlled so Single storied building is the most appropriate building type Because the building 1s landscaped with trees and bushes that break the wind click Sheltered surroundings Click OK Infiltration Building Parameters Select building type or enter exchange parameter Enclosed office building Single storied building Double storied building 3 Nn of air changes is per hour Select building surroundings Sheltered surroundings trees bushes etc 5 Unsheltered surroundings Choose Date amp Time from the SiteData menu SiteData Location aeL Building Type Date tr Time Chapter 3 Examples 7 Click Set constant time then enter the month day year hour and minute when this incident begins Click OK Date and Time Options You can either use the computer s internal clock for the model s date and time or set a constant date and time 9 Use internal clock Set constant time Input constant date and time Month Day Year Hour Minute is ts mo fo 1 12 1 31 1900 0 23 0 59 8 Choose CHLORINE from ALOHA s chemical library Select Chemical from the SetUp menu Find chlorine 1 the list quickly type the characters ch to locate chlorine in the list clic
110. e 5 Describe how the benzene is escaping from the tank Click Circular opening enter 6 for the hole diameter then click inches Click Hole since the benzene is not escaping through a pipe or valve then click OK Area and Type of Leak Select the shape that best represents the shape of the opening through which the pollutant is exiting Po with length diameter 3 e i Circular opening O Rectangular opening inches feet Opening diameter 6 centimeters i meters Is leak through a hole or short piper valve Hole O Short pipe valve Cancel 127 Chapter 5 Examples 6 Indicate the height of the leak above the tank bottom Under the The bottom of the leak 1s heading type 10 then click in inches Click OK Height of the Tank Opening 4 The bottom of the leak is moin oft cm C m above the bottom of the tank OF of the way to the top of the tank 7 The liquid benzene is flowing onto a grassy field Click Default ground type Since you have no information about the ground temperature click Use air temperature Because the product 15 flowing into a field 1 15 probably not contained by a dike Under the Input maximum puddle diameter heading click Unknown Click OK Puddle Parameters Select ground type Default gt Concrete 5 Sandy 3 Moist Input ground temperature i Use air temperature select this if unknown C Gro
111. e select this if unsure is selected Click OK 2 Choose Options from the Display menu Display Tile Windows Stack Windows Text Summary Footprint Concentration 36H Bese Source Strength 6 Calculate f NOU Ns 156 Chapter 3 Examples 3 The IDLH of chlorine 10 ppm is the LOC for this example Check to be sure that IDLH Concentration is selected 4 Check to be sure that Plot on grid and auto scale to fit window is selected Select either English units or Metric units depending on your preference Click OK Dig pti nsS Emu select Lepel of Concern or Dutput Concentration LOD nof eet in Horarg i IDLH Concentration m Enter value IMEEM nn t milligrams cubic meter Select Footprint Output Option i Plot on grid and auto scale to fit window O Use user specified scale Select Output Units i English units O Metric units 5 Choose Footprint from the Display menu Tile Windows Stack Windows Text Summary Footprint Concentration 3R 80s Source Strength 6 Calculate NOU Sis 157 Chapter 5 Examples Check the Text Summary to see the maximum length of the footprint the Maximum Threat Zone ALOHA expects the footprint to extend at least 800 yards downwind Text Summary SITE DATA INFORMATION Location MANASSAS VIRGINIA Building Air Exchanges Per Hour 8 97 s
112. e each ALOHA source and dispersion option Property Gaussian Heavy Gas Direct Puddle Tank Pipe Direct Puddle Tank Pipe Chemical Name Molecular Weight Normal Boiling Point Critical Pressure Critical Temperature Gas Density Normal Freezing Point Gas Heat Capacity Liquid Heat Capacity Vapor Pressure Required property value Required if release rate or amount is expressed in volume units gallons liters or cubic meters Required if vapor pressure not entered Required if critical temperature and critical pressure not entered Adding modifying or deleting chemicals You can add a new chemical modify information about a chemical already included in ALOHA s chemical library ChemLib or delete a chemical from the library Changes that you make to the chemical library from within ALOHA will be saved note that this is a change from previous versions How to add a chemical to the library Choose Chemical from the SetUp menu then click Add Type the chemical s name in the Chemical Name box Next type its molecular weight in grams per mole in the molecular weight box Then add values for all other properties that you ll need to run ALOHA check Table 4 1 to see which properties are necessary for ALOHA s various source and dispersion options To enter additional property values click on the name of each property in the scrolling list of property names or click Next Field until the property name is highlighted Type prop
113. e rate possible for the given scenario The maximum sustained averaged release rate 1s averaged over at least a minute If these values are significantly different the maximum release rate was sustained for less than a minute This is most common in the case of pressurized releases ALOHA s Puddle Tank and Pipe source strength calculations are affected by atmospheric conditions ALOHA recomputes source strength whenever possible after you have modifed atmospheric information In some cases however it cannot so it asks you to reenter information about the source For example by increasing air temperature you may cause a tank to be filled to more than 100 percent of capacity or a puddle s temperature to increase above its boiling point In such cases you must enter new source information to resolve the problem You need to enter a Level of Concern LOC for your scenario IDLH Immediately Dangerous to Life and Health is the default LOC in ALOHA but only for chemicals for which an IDLH value has been established To learn about LOCs and see some LOC values that might be appropriate for your scenario check the LOC page at http response restoration noaa gov cameo locs LOCpage html Before ALOHA can place a footprint on your MARPLOT map a footprint plot needs to be displayed in ALOHA To solve your problem in ALOHA choose Footprint from the Display menu then return to MARPLOT You should now see the footprint on yo
114. e taken up by a gas depends on the pressure exerted on it Examples of gases include oxygen air a mixture of nitrogen oxygen and trace amounts of other gases chlorine and carbon dioxide 177 Glossary Gaussian Ground roughness Ground temperature Ground type Heavy gas IDLH 178 A Gaussian curve 1s a bell shaped or normal probability curve named after a famous mathematician ALOHA uses a Gaussian distribution to describe the movement and spreading of a gas that is neutrally buoyant about as dense as air The roughness of the ground over which a pollutant cloud is moving Degree of ground roughness depends on the size and number of roughness elements which can range in size from blades of grass to buildings Ground roughness generates air turbulence which acts to mix air into the pollutant cloud and dilute the pollutant gas When all else 1s equal a footprint will be smaller when you choose a larger ground roughness value The temperature of the ground beneath an evaporating puddle ALOHA uses your value for ground temperature to estimate the amount of heat that 1s transferred from the ground to an evaporating puddle The physical composition of the ground beneath a puddle The ground type is especially important when a refrigerated liquid spills to form a boiling puddle In such cases often more of the heat required for puddle evaporation 1s supplied by the ground rather than the atmosphere
115. ed scale 5elect Output Units amp English units C9 Metric units Figure 4 47 Display options Level of Concern A Level of Concern LOC 15 a threshold concentration of an airborne pollutant gas usually the concentration above which a hazard may exist ALOHA plots a footprint which represents the zone where the ground level pollutant concentration 1s predicted to exceed your LOC at some time after a release begins The Immediately Dangerous to Life or Health IDLH level a limit originally established for selecting respirators for use in workplaces by the National Institute for Occupational Safety and Health NIOSH is the default LOC in ALOHA A chemical s IDLH is an estimate of the maximum concentration in the air to which a healthy worker could be exposed without suffering permanent or escape impairing health effects IDLH values have been established for about one third of the chemicals in ALOHA They were 100 Chapter 4 Reference revised and updated in 1994 these updated values are contained in ALOHA s chemical library If an IDLH has been established for a chemical you have selected ALOHA will automatically use it as the LOC for all release scenarios unless you enter a different value Although ALOHA makes it easy for you to use the IDLH as your LOC don t just accept this value without thought Another exposure limit may be the best LOC for your purpose The IDLH was not designed to be an exposure limit fo
116. eight of the abrupt change of atmospheric stability is called the inversion height An inversion can trap pollutant gases below the inversion height This may cause ground level concentrations of a pollutant to reach higher levels than would otherwise be expected A threshold concentration of an airborne pollutant usually the concentration above which a hazard may exist ALOHA plots a footprint which represents the zone where the ground level pollutant concentration may exceed your LOC at some time after a release begins Mass is a physical property related to weight Mass is a measure of the amount of a substance that occupies a given space While the weight of a given amount of a substance is a measure of the force by which it 1s attracted by gravity and 1s less on the moon than on the earth the substance s mass is independent of gravity ALOHA computes release rate from a puddle tank or gas pipeline as a series of up to 150 brief timesteps It then averages this series of many release rates into between one and five release rates that are each averaged over a time period of at least 1 minute To save calculation time ALOHA uses these averaged release rate s to make its footprint estimates The Maximum Average Sustained Release Rate 1s the highest of these averaged release rates It is represented by the tallest timestep on the Source Strength graph 179 Glossary Maximum Computed Release Rate Mixing Mole Mole
117. elete cities from CityLib B AlohaSpy is a companion program to ALOHA Use it to view results of ALOHA model runs that you have archived as Spy files Your ALOHA folder also should contain four other files which ALOHA uses to perform various tasks ALOHA uses the ChemLib idx and CityLib idx files to keep track of the information in those two libraries The ALOHA prf file contains your preferences for measurement units for information displayed in ALOHA If you delete this file ALOHA will automatically regenerate a new copy However do not delete the CHEMLIB wrn file it contains information about carcinogens and reactive chemicals in the chemical library Sj ALOHA Folder E ES H items 5 9 available ALOHA ALOHA prf gr AlohaS py M CHEMLIB IDY CHEMLIB WRN A5 CITYLIB EITYLIB idx 20 Chapter 3 Learning the Basics This chapter contains a step by step example ALOHA scenario describing a chlorine release at a fictional treatment plant in South Dakota Follow along using your own copy of ALOHA Windows or Macintosh in order to familiarize yourself with its menus and features For more information about any aspect of ALOHA check the Reference chapter Guided tour The Central Water Facility treatment plant 1s located in a rural area about 2 miles from Sioux Falls South Dakota The plant uses 1 ton containers of chlorine in the water treatment process these tanks are 2 5
118. ells me that the length must be at least 200 times the diameter of the pipe What should I do Iam using a SAM with ALOHA I have set the SAM options using the Atmospheric menu but the Source menu is not available I can t set my source ALOHA tells me that the input value I just entered is not within allowable limits 166 These properties are estimated by ALOHA from other information in its chemical library To use different property values add a new chemical use name such as CHLORINE 2 then enter new property values If the pipe is too short relative to its diameter and its diameter 1s greater than about 8 inches 20 centimeters use the Tank option instead selecting the configuration of a horizontal tank If the pipe is less than 1 meter long and connected to a tank you also can use the Tank option in this case select Short pipe valve as the type of leak Either of these methods should produce a conservative estimate of downwind dispersion Either the SAM has not yet been collecting data for 5 minutes or ALOHA has not received valid data Before ALOHA can estimate atmospheric stability it must have received data from the SAM for at least 5 minutes Check the Text Summary window for a message alerting you that either the SAM has not been transmitting for 5 minutes or the transmitted data are not valid ALOHA will accept a numeric input value that is a value such as puddle area or tank hole di
119. enths type a whole number between 0 and 10 in the box for cloud cover in tenths for example type 6 1f cloud cover is 6 tenths Air temperature ALOHA requires a value for the air temperature in the vicinity of an accidental release You can enter a value in either degrees Fahrenheit F or degrees Celsius C Air temperature influences ALOHA s estimate of the evaporation rate from a puddle surface the higher the air temperature the more the puddle 1s warmed by the air above it the higher 1s the liquid s vapor pressure and the faster the substance evaporates Because several physical processes involved in a chemical release are affected by temperature use as accurate a value as possible Stability class Depending on the amount of incoming solar radiation as well as other factors the atmosphere may be more or less turbulent at any given time Meteorologists have defined six atmospheric stability classes each representing a different degree of turbulence in the atmosphere When moderate to strong incoming solar radiation heats air near the ground causing it to rise and generating large eddies the atmosphere 1s considered unstable or relatively turbulent Unstable conditions are associated with atmospheric stability classes A and B When solar radiation is relatively weak or absent air near the surface has a reduced tendency to rise and less turbulence develops In this case the atmosphere 1s considered stable or less tu
120. erty values in the appropriate boxes then choose units You must add a reference temperature and pressure for all properties which change their values when temperature and or pressure change For example assume that methyl ethyl 58 Chapter 4 Reference death has a gas heat capacity of 1500 joules per kilogram Kelvin at a temperature of 320 Kelvin and a pressure of 101 325 pascals You would enter these values as shown in Figure 4 19 if you were adding this fictional chemical into the library Input Available Information Chemical Name Methyl Ethyl Death Boiling Point normal Critical Pressure Critical Temperature Ji kg K vw Default Level of Concern Heat Cap gcp Value Density gas Heat tgcp Temperature Diffusivity molecular Em reezing normal XR ype QU INN nct n iX E 7 dt t 0onst press Heat Cap gop Pressure 101435 Heat Cap liq const press IDLH E Figure 4 19 Entering gas heat capacity of methyl ethyl death Once you have entered all information about a new chemical click OK to permanently add your new chemical to ALOHA s chemical library Click Select to select the chemical that you ve just added Click Cancel if you decide not to permanently add the chemical to the library How to modify information about a chemical To modify information about a chemical first choose Chemical from the SetUp menu Click on the name o
121. ever time at the location switches between daylight savings and standard time Be as accurate as you can when entering information about a location ALOHA uses your values for elevation latitude and longitude to calculate solar radiation and air pressure However small errors in location information don t affect the accuracy of ALOHA s predictions An estimate is accurate enough if it is within a degree or so in latitude and longitude and a few hundred feet 1n elevation of the actual site Adding information about a U S city Choose Location from the SiteData menu to access the index of locations Type the location s name approximate latitude and longitude and elevation then click on the name of its state or territory in the scrolling list of U S states and trust territories on the righthand side of the window click anywhere within the list then type the first letter of the state name to quickly move to that letter s location in the list ALOHA checks that the information you have entered 1s within the range of reasonable values for the state or territory that you select If you have entered a value that 1s not in this range ALOHA will tell you which value 15 out of range you must correct your value before continuing Click OK 44 Chapter 4 Reference Location Input Enter full location name Location is Is location in a U S state or territory v me In 0 5 C Not in 0 5 elect state or territory Enter approximate elevat
122. ew the Dose vs Time graph first enter a dose exponent appropriate for the chemical you have selected Next select Concentration from the Display menu to enter the coordinates of the location of concern you also can indicate a location by double clicking on a point within the Footprint window or by selecting a location on a map displayed in MARPLOT ALOHA will display the Concentration vs Time graph for the location Then choose Dose from the Display menu to view the Dose vs Time graph for the same location For more information about choosing a location check the Concentration section above Two lines are visible on the graph They represent the accumulated dose that ALOHA predicts people might receive depending on whether they are outside or inside a building at the chosen location You can choose the type of building used to predict indoor concentration and dose by selecting Building Type from the SiteData menu The solid red line represents the dose predicted to be received by people outdoors and the dashed blue line represents the dose predicted to be received by people within a building given the building type that you specified and assuming that doors and windows remain closed amp Dose Win d w c l E LL LL minutes Figure 4 54 A Dose vs Time graph Source Strength Choose Source Strength from the Display menu when you want to see how rapidly or slowly a chemical mi
123. f pounds kilograms or short tons 1 short ton equals 2 000 pounds 89 Chapter 4 Reference Mass of Chemical In Tank For a chemical of unknown state the chemical mass is required The amount of O pounds chemical in DENN i tons 000 Ibs 3 kilograms Cancel Figure 4 39 Mass of unknown chemical in tank Area and type of leak You must indicate the shape rectangular or circular and size of the opening in the tank before ALOHA can calculate the rate of release of the tank s contents You also must specify whether the release 1s through a a simple hole in the tank wall or b a short pipe or broken valve A hole 15 any kind of break in the tank wall such as a puncture or crack The area of an opening 1s important to ALOHA but its shape 1s used only to compute area ALOHA predicts identical release rates through circular and rectangular openings if they have the same area If your scenario 1 a release of pure gas from the tank when you click OK ALOHA will estimate the rate of release of gas from the tank You will see a summary of the information that you entered and the source strength results calculated by ALOHA If at least some liquid is present in the tank you will need to enter some more information before ALOHA can estimate source strength If the chemical 1s stored as a pressurized liquid a liquid at a temperature above its boiling point ALOHA may expect it to escape from the tank under pressure as
124. f the chemical in the chemical index then click Modify Click on the name of each property that you are adding or modifying in the scrolling list or click Next Field until you ve highlighted the property name Type property values in the corresponding boxes or modify existing values and modify units 1f necessary You ll find that you cannot modify all property values for ALOHA chemicals already included in the library Values that you cannot modify and their units appear dimmed These are values that ALOHA calculates internally using either values for the chemical s critical properties molecular weight boiling point critical temperature and critical pressure or information from the DIPPR database If you would like to use your own property values for an ALOHA chemical add the chemical using a slightly different name such as CHLORINE 2 and type your own values in the new property boxes When you re finished making your modifications click OK to add them permanently to ALOHA s library To avoid making permanent changes to the library click Cancel 59 Chapter 4 Reference How to delete a chemical To permanently delete a chemical from ALOHA s library choose Chemical from the SetUp menu click the name of the chemical in the chemical index then click Delete Click OK to delete the chemical permanently from ALOHA s library Click Cancel to avoid deleting the chemical Atmospheric You can enter information about c
125. f the footprint ALOHA predicts that about 95 percent of the time the wind will not shift direction enough to steadily blow the pollutant cloud outside of either line The wider the zone between the lines the less predictable is the wind direction and the more likely it is to change substantially At the lowest wind speeds acceptable to ALOHA about 2 knots or 1 meter per second at a height of 10 meters these lines form a circle to indicate that the wind could blow from any direction Very stable atmospheric conditions Under the most stable atmospheric conditions most common late at night or very early in the morning there is usually very little wind and almost no mixing of the pollutant cloud with the surrounding air Gas concentrations within the cloud can remain high far from the source The accidental release of methyl isocyanate gas at Bhopal India 1 1984 is an example of what can happen under very stable atmospheric conditions Thousands of people died including many who were far from the release In a very stable atmosphere a chemical cloud will spread out in the same manner as cream poured into a coffee cup 11 Chapter 1 Welcome to ALOHA The cream will dilute and spread slowly into the coffee but until you stir it will take a very long time to mix completely into the coffee Similarly the cloud will spread slowly and high gas concentrations may build up in small valleys or depressions and remain for long periods of
126. f to obtain the radius square the radius then multiply it by pi 3 14 to obtain the area If the diameter 1s 1n units of feet then the area will be in units of square feet 1f the diameter is in meters the area will be in square meters and so on Chapter 4 Reference Source strength information in the Text Summary Regardless of the source option you choose once you have entered all necessary inputs and clicked OK on the last source strength dialog box ALOHA estimates source strength It then displays the source input values you entered as well as the following information in the Text Summary Source type A brief description of the type of source modeled for example Leak from hole in horizontal cylindrical tank selected B Release duration The length of time in minutes during which the chemical is predicted continued to escape into the atmosphere If ALOHA predicts the release to continue for more than an hour you ll see the message Release Duration ALOHA limited the duration to 1 hour B Release rate ALOHA reports two predicted release rates in the Text Summary the Maximum Computed Release Rate this is the very fastest rate at which ALOHA predicts the chemical to escape to the atmosphere it may be sustained for just a few moments and the Maximum Average Sustained Release Rate this 15 the fastest rate once release rate has been averaged over a time period of at least a minute Both values represent the predi
127. feet in diameter and 6 8 feet long The highest risk operation at the plant 1s the changing of chlorine tanks This operation 1s done only during daytime hours We ll use ALOHA to assess the potential hazard from one of many possible accident scenarios In this exercise we ll assume that while being moved into the building a single container begins to leak through a valve located in the center of one end this valve 1s one half inch in diameter The tank contains 1 ton of chlorine when it begins to leak The date and time of the accident are assumed to be June 25 2000 at 2 30 p m Local meteorologists have provided a description of typical weather conditions at Sioux Falls These conditions are a wind speed of 5 miles per hour from the south measured at a height of 10 meters partly cloudy skies air temperature of 72 F and 50 percent relative humidity We ll use ALOHA to see E the footprint representing the area downwind of the release that may be at risk predicted chlorine concentrations at the Central Valley Elementary School located about 1 500 yards downwind of the treatment plant Note As you use ALOHA you ll enter information on a series of dialog boxes to describe your scenario On each dialog box you ll see at least one Help button which you can use to access online help Click any of these buttons at any time to view an explanation of the ALOHA feature you re using or input value that you must enter into the model Once
128. from the puddle surface If the liquid 1s stored above its boiling point the pressure within the tank will be greater than atmospheric pressure When such a tank is punctured the pressurized liquid contents may escape as a two phase mixture of gas and aerosol The rate of release can be significantly greater than the rate of release of an unpressurized liquid You may know that tank temperature is near the boiling point but not be sure whether it is above or below the boiling point If this is the case try running your scenario twice first with tank temperature set to just below boiling and again with temperature set just above boiling Compare the two sets of results produced by ALOHA to find the range of release rates possible for your scenario Running a liquid release scenario at a temperature above boiling will give you the highest release rate and largest footprint Chemical State and Temperature Enter the state of the chemical Tank contains liquid C Tank contains gas only O Unknown Enter the temperature within the tank i Chemical stored at ambient temperature Chemical stored atl 5 degrees OC 87 Chapter 4 Reference Figure 4 36 State and temperature of chemical in tank Liquid in a tank Whenever you indicate to ALOHA that a tank contains liquid by clicking Tank contains liquid when you are asked to identify chemical state you will need to identify the amount of chemical in the tank in any
129. ght be escaping into the atmosphere When you choose this menu 110 Chapter 4 Reference item ALOHA displays a graph showing the predicted rate of release of your chemical the source strength predicted for the first hour after a spill begins ALOHA produces two main types of source strength estimates depending on the type of release that you have chosen Source strength graphs for the two types of estimates differ in appearance Constant source strength Release rate for a Direct source whether it s instantaneous or continuous will remain constant for the duration of the release ALOHA expects an instantaneous release to last for 1 minute and a continuous release to last for up to 1 hour Graphs of either type of Direct release look like the plots shown below Source Strength Release Rate Source Strength Release Rate i i E a un m a a a minutes seconds Figure 4 55 Source strength graphs for a continuous background and an instantaneous foreground Direct release Variable source strength Source strength predicted by the Puddle Tank or Pipe source options can change over time For example consider the rate of release of a pressurized gas from a tank rupture Initially the chemical escapes rapidly through the rupture As the tank pressure drops the rate of release slows If you model such a release using ALOHA you ll see a line that descends in steps on the source strength graph
130. hapter 1 Welcome to ALOHA footprint will appear to go right over or through obstacles such as buildings Consider the effects of terrain on wind flow whenever you are interpreting ALOHA results Figure 1 11 Small scale variations in wind direction Because the wind is likely to shift in direction and change speed over both distance and time limits have been placed ALOHA s output ALOHA will not make predictions for more than an hour after a release begins or for distances more than 10 kilometers 6 2 miles from the release point it truncates footprints that are longer than 10 kilometers ALOHA s 1 hour time cutoff exists because wind shifts direction and changes speed frequently One reason for the 10 kilometer cutoff for ALOHA footprint length is that we don t know what the wind speed and direction are 10 kilometers away and can t assume that they are the same as those we re experiencing at the point where a pollutant is being released If ALOHA has incorrect values for wind speed and direction it can t correctly estimate footprint size or location Concentration patchiness No one can predict gas concentrations at any particular instant downwind of a release with certainty because they result partly from random chance Instead ALOHA shows you concentrations that represent averages for time periods of several minutes it uses the laws of probability as well as meteorologists knowledge of the atmosphere to do th
131. hat be ALOHA displays its results in exponential notation whenever numbers are too large to display in decimal notation Exponential notation is a way of displaying a number as a digital number multiplied by a power of 10 In the number 5e3 for example 5 1s the digital number and 3 is the power to which 10 1s taken Interpret 5e3 as 5 times the quantity 10 taken to the power of 3 which equals 5 000 in decimal notation Likewise interpret 5e 3 as 5 times the quantity 10 taken to the power of 3 which equals 0 005 in decimal notation Interpret 5 2e8 as 5 2 times 10 taken to the power of 8 or 520 000 000 You have asked for a concentration estimate for a point very close to the source ALOHA knows that concentrations of a pollutant are extremely high right at the point of release and drop off as you move downwind It uses equations to approximate what happens in reality Modelers call ALOHA a far field model because these equations much more accurately predict events at distances of more than a few yards from the source than very near the source According to these equations in fact concentration is infinite at the point of release 165 Chapter 6 Troubleshooting I want to modify a chemical either from within ALOHA or by using ChemManager but I can t change some properties they appear grey I am trying to model the release of gas from a gas pipeline but ALOHA says the pipe is too short It t
132. have created and saved a Spy file you cannot modify it or reopen it in ALOHA You can view and print Spy files in ALOHA s companion application AlohaSpy Saving files To create an ALOHA save file choose either Save or Save As from the File menu When you choose Save you need only name the file then click OK When you choose Save As click ALOHA mn the Save As Options dialog box type in a file name then click OK If you enter additional information about the scenario into ALOHA just choose Save to update this file Before creating a Spy file check that all windows you d like to archive are visible Then choose Save As from the File menu click Spy in the Save As Options dialog box type in a file name then click OK Use AlohaSpy to open view and print the new Spy file Save As Options Select save format ALOHA save file Archive windows to display from Alohaspy Figure 4 2 The Save As Options dialog box Print Choose Print to print the contents of the front ALOHA window Print All Choose Print All to print the contents of all visible ALOHA windows 41 Chapter 4 Reference Quit or Exit Choose Quit on a Macintosh or Exit in Windows to quit from ALOHA To save or archive the scenario you have been working with select Save or Save As from the File menu before quitting from the program The Edit Menu nio oo x Puis Figure 4 3 ALOHA s Edit menu The same items appear in thi
133. he U S Census Bureau from U S Geological Survey base maps TIGER files are computer readable geographic data bases for all U S states territories and possessions They include digital descriptions of features such as political boundaries water bodies transportation routes and address ranges for street segments MARPLOT readable maps incorporating this TIGER information can be downloaded from the RTK Net web site http rtk net landview Check your MARPLOT manual for more information about obtaining and using maps When ALOHA and MARPLOT are running simultaneously in Windows or on a Macintosh ALOHA automatically installs a menu in MARPLOT s Sharing menu You can choose items from this menu to indicate the location of a release display an ALOHA footprint on a MARPLOT map or indicate a location for which you would like concentration or dose information Using MARPLOT When ALOHA and MARPLOT are running together ALOHA installs an ALOHA submenu in MARPLOT s Sharing menu Choose from among the following items contained in the ALOHA submenu Help Choose Help to view a description of how to use MARPLOT with ALOHA Set Source Point First click once on the location of an accidental chemical release on your MARPLOT map this is the source point Next choose Set Source Point ALOHA will place a pink cross symbol at the source location Once a footprint has been displayed in ALOHA ALOHA s footprint as well as the wind direc
134. he letter representing your computer s CD ROM drive If your CD ROM drive 15 represented by a different letter use that letter in place of D Click OK peo Type the name of a program folder document or Internet resource and Windows will open it for Oper D YALOHAS Setup exe Cancel Browse 4 Follow the instructions on your screen to install ALOHA In Windows 95 98 and NT the installer creates an Aloha submenu folder in the Start menu s Programs file containing ALOHA AlohaSpy Readme and Uninstall ALOHA menu items In Windows 3 1 the installer creates an ALOHA program group in the Program Manager and places all executable files in that group 18 Chapter 2 Installing ALOHA New Aloha submenu folder and menu items installed in Start menu Windows 95 98 NT 4 Windows Update Accessories d Aloha ea Favorites l Grome 2 AlohaS py E Intemet Explorer d i Readme tet LL Documents Online Services 8 Uninstall ALOHA StartUp sb settings Find MS DOS Prompt y windows Explorer Q x New ALOHA program group in Windows 3 1 ALOHA Alohas py Your new program group or Aloha menu will include B ALOHA the main ALOHA program To run ALOHA in Windows 95 98 or NT in the Start menu point to Programs then Aloha then click Aloha In Windows 3 1 double click the ALOHA program icon to run ALOHA
135. heck with its manufacturer to be sure that it is designed to work with ALOHA and to learn how to connect the station to your computer so that it can transmit 69 Chapter 4 Reference data to ALOHA Before using a station not specifically designed for ALOHA be sure that it transmits data in a format that ALOHA can accept this format is described below Transmitting SAM data to ALOHA For use with ALOHA a SAM must meet several design criteria The SAM should sample wind speed and direction at a rate of at least one sample every 2 seconds It must transmit wind speed and direction and air temperature readings every 30 seconds Because air temperature does not change quickly over time it may be sampled less frequently than wind speed and direction Data transmitted from your SAM to ALOHA must be in the following free field comma delimited format ALOHA displays unprocessed SAM data in the same format cr It ID VS WD SD TA SP DI TI B CHK where lt cr gt acarriage return ASCII character code 13 lt l gt feed ASCII character code 10 ID the station identification number VS the vector mean wind speed averaged over 5 minutes in meters per second WD the mean wind direction averaged over 5 minutes in degrees true SD the standard deviation of the wind direction sigma theta in degrees TA the mean air temperature averaged over 5 minutes in degrees Celsius SP the instantaneous wind s
136. heltered single storied Time June 4 26668 amp 1588 hours EDT fuser specified CHEMICAL HF ORHRT I OH Chemical Mame CHLORINE Molecular Height 78 91 TLV THRH 6 5 ppm IDLH 18 ppm Footprint Level of Concern 18 ppm Boiling Point 28 25 F Mapor Pressure at Ambient Temperature greater than 1 atm Ambient Saturation Concentration 1 888 888 ppm or 166 0 ATMOSPHERIC INFORMATION MANUAL INPUT OF DATA Hind 12 knots from ene at 3 meters Mo Inversion Height Stability Class D Air Temperature 72 Relative Humidity Sms Ground Roughness open country Cloud Cover 3 tenths SOURCE STRENGTH MFORMATION Direct Source 4888 pounds he Source Height B Release Duration 68 minutes Release Rate 66 7 pounds min Total Amount Released 4 888 pounds Note This chemical may flash boil and or result in two phase flow FOOTPRINT INFO RHRT I OH Model Run Heavy Gas User specified LOC equals IDLH 18 ppm Threat Zone for LOC 815 yards Using MARPLOT 1 158 You re now ready to plot this footprint on a map of the area in MARPLOT and to obtain a concentration estimate for the workmen s location Select Go to Map from the MARPLOT submenu under ALOHA s Sharing menu to bring MARPLOT forward Sharing About Shared Menus Edit Shared Menus CAMEO MRRPLOT d to If this is the first time you ve used MARPLOT the PRINCE WILLIAM COUNTY VA map should a
137. hese source options below Source height The source height is the height of the location of a chemical release above the ground Source height is zero if the chemical is released at ground level Enter a source height greater than zero to model a release from an elevated source only if ALOHA is making Gaussian dispersion calculations ALOHA does not account for any substantial upward or 80 Chapter 4 Reference downward movement of a gas cloud in the atmosphere Enter a non zero source height only when the released chemical disperses passively away from the release point without rising substantially upwards as a gas emitted from a heated or burning source may do or slumping downward towards the ground as a heavy gas may do If you enter a source height greater than zero but your selected chemical is a heavy gas ALOHA will alert you that it must use a source height of zero to model the release Although the source height that you entered appears in the Text Summary ALOHA assumes the height to be zero when making its dispersion computations If you are not sure of the source height bear in mind that a ground level release 1s a more conservative choice than an elevated release ALOHA will predict a longer footprint for a ground level release Puddle Choose Puddle to model evaporation from a puddle that has already formed on the ground and 15 not changing in area If liquid is continuing to leak from a tank and spill into a puddle
138. hifted direction but the footprint hasn t changed at all What s wrong I thought I knew what an ALOHA There are two possible explanations depending footprint looks like But on my on your scenario If your source is a puddle of current footprint plot I see a big spilled liquid and if it s large in diameter shaded circle around my source relative to the size of the footprint you may be point What is it seeing it on the footprint plot You may also have a heavy gas footprint If a heavy gas is escaping into the atmosphere at a fast enough rate it will form a large blanket of gas over the source point before it moves downwind If the blanket is big enough ALOHA will show it on your footprint plot We have two computers in our office Individual computers can come up with that sometimes give different answers different answers when they make the same for the same ALOHA scenario calculations In particular different computers can round off numbers differently as they make their calculations This can have a visible effect on ALOHA s source and dispersion estimates 168 Chapter 6 Troubleshooting Allowable Input Input Value Time amp Location Air exchange rate Elevation Latitude Longitude Month Day Hour Minute Meteorological Air temperature Cloud cover Ground roughness Inversion height Relative humidity Wind speed Source Input Release amount Direct Ground temperature Pipe diameter
139. hness 20 3 0 5 Urban or Forest e cm Select Claud Cover 8 enter value 3 Ci C C OF in 10 camplete partly 25 Chapter 3 Learning the Basics 3 On the second Atmospheric Options dialog box type 72 in the air temperature box then click F to indicate that temperature is in degrees Fahrenheit ALOHA uses the wind speed cloud cover and date and time information that you ve entered to automatically select atmospheric stability class B stability 15 a measure of the amount of turbulence in the atmosphere the more turbulent the air the more quickly a pollutant cloud is diluted B is a relatively less stable that 15 more turbulent stability class Check to be sure that No inversion is selected then click the button representing medium 50 percent relative humidity Once the dialog box on your screen looks like the one below click OK Atmospheric Options 2 Air Temperature is 2 Degrees mF Stability Class is O8 OS OF Inversion Height Options are iw Feet No inversion Inversion Present Height is C Meters select Humidity ws QR enter value o medium dry 0 100 Describing the Release You re now ready to enter information about the release itself that is to set the source for this scenario 1 Since the chlorine at the Central Water Facility treatment plant is stored in tanks this scenar
140. idering infiltration into buildings Text Summary SITE DATA INFORMATION Location BATON ROUGE LOUISIANA Building Air Exchanges Per Hour 8 55 unsheltered single storied Time August 28 2666 amp 2238 hours COT user specified CHEMICAL INFORMATION Chemical Mame BEMZENE Molecular Weight 78 11 kg kmol TLV THH 8 1 ppm IDLH S88 ppm Harning Potential or confirmed human carcinogen Footprint Level of Concern S88 ppm Boiling Point 175 15 F Vapor Pressure at Ambient Temperature B 13 atm Ambient Saturation Concentration 134 948 ppm or 13 92 ATMOSPHERIC INFORMATION MANUAL IHPLT OF DATA Mind knots from at 18 meters Ho Inversion Height Stability Class D Air Temperature 58 Relative Humidity 79x Ground Roughness open country Cloud Cover tenthz Describing the release You re now ready to enter information about the release itself 1 Since the benzene is leaking from a tank this scenario should be modeled as a Tank source In the SetUp menu point to Source then click Tank Chemical Atmospheric k Source id Direct Computational a T Pipe ab 125 Chapter 5 Examples 2 Click Vertical Cylinder then enter 500 gallons for the volume and 4 feet for the diameter of the tank Once you have entered the volume and diameter ALOHA calculates the correct length Click OK Tank 5ize and Orientation Select tank type and orientation
141. ime Options You can either use the computer s internal clock for the model s date and time or set a constant date and time 39 Use internal clock Set constant time Input constant date and time Month Day Year Hour Minute e 25 2000 1 12 1 31 1900 0 23 0 59 Choosing a Chemical As you build your ALOHA scenario your next task 1s to choose the chemical that 1s being released 1 24 To choose chlorine from ALOHA s chemical library select Chemical from the SetUp menu Find CHLORINE in the list quickly type the characters ch to locate chlorine more rapidly in the list click on this name then click Select Chemical Information BUTYRYL CHLORIDE CAMPHENE CARBON BISULFIDE CARBON DIOXIDE CARBON MONOXIDE CARBON TETRABROMIDE CARBON TETRACHLORIDE CARBONYL FLUORIDE CARBONYL SULFIDE CARENE CHLORINE DIOXIDE HYDRATE CHLORINE PENTAFLUORIDE CHLORINE TRIFLUORIDE CHLOROACETALDEHYDE CHLOROACETONITRILE CHLOROACETYL CHLORIDE CHLOROANILINE Chapter 3 Learning the Basics Describing the Weather You next must describe the current weather conditions and ground roughness a measure of the roughness of the terrain over which the gas cloud passes The weather conditions for this scenario are a wind speed of 5 miles per hour mph from the south measured at a height of 10 meters About 3 tenths of the sky 1s covered by clouds the air temperature is 72 F and relative humidity is ab
142. io should be modeled as a Tank source in the SetUp menu point to Source then click Tank Chemical Atmospheric 4 Source 1 Direct Puddle 0 e Computational Tank Pipe ab 26 Chapter 3 Learning the Basics 2 Next describe the tank s general shape orientation and dimensions The chlorine 1s stored in standard 1 containers First click Horizontal cylinder Type 2 5 in the diameter box then click feet Type 6 8 in the length box ALOHA automatically calculates the tank volume Click OK Tank 5ize and Orientation Select tank type and orientation Mer tical cul inder Horizontal cyl inder T o o Enter two of three values ength diameter volume feet o meters iw gallons c cu feet Ese 3 Next describe how much chlorine is stored in the tank and indicate its physical state gas or liquid Chlorine is a gas at ambient temperatures but it s usually stored as a pressurized liquid so click Tank contains liquid Check to be sure that Chemical stored at ambient temperature is selected the tank 1s not refrigerated in this scenario then click OK Chemical State and Temperature Enter the state of the chemical Tank contains liquid O Tank contains gas only O Unknown Enter the temperature within the tank Chemical stored at ambient temperature O Chemical stored at 2 degrees OC
143. ion Elevation is mft Om Enter approximate location deg min CONNECTICUT Latitude 57 N OS DELAWARE DIST OF COLUMBIA Longitude OE Figure 4 6 Adding Jupiter Florida to the location list Unless the location is in a state with multiple time zones such as Indiana ALOHA automatically recognizes the location s time zone and also adjusts time of day for daylight savings when necessary ALOHA knows which states are located in each U S time zone However 11 U S states extend across more than one time zone When you add a new city in any of these states to ALOHA s city library you may need to indicate the time zone in which the city is located if it is close to a boundary between time zones If the city 1s not located near a time zone boundary ALOHA will not display this dialog box States with multiple time zones are Idaho Indiana Kansas Kentucky Michigan Nebraska North Dakota Oregon South Dakota Tennessee and Texas Lentral or Eastern Time Zone Select time zone for city Central Eastern Cancel Figure 4 7 ALOHA may ask for a city s time zone if it is in a multiple time zone state Once you ve clicked OK the name of the new location should appear highlighted in the location index To save your information and select the location from the list click Select If you click Cancel now the information about the location that you just entered will not be added to the location
144. ion of concern such as a flammable or explosive limit Threshold Limit Value Time Weighted Average TLV TWA and Immediately Dangerous to Life or Health IDLH TLV TWA and IDLH are Levels of Concern LOCs A LOC is a threshold concentration of an airborne pollutant usually the concentration above which a hazard may exist ALOHA s footprint represents the zone where the ground level pollutant concentration may exceed a specified LOC at some time after a release begins The IDLH level 1s the default LOC in ALOHA An IDLH has been established for about one third of the chemicals in ALOHA If a value is available for the chemical you select ALOHA will display it in the text summary Benzene s IDLH of 500 ppm is shown in the Text Summary below You may choose to use either the IDLH when a value 15 available as your LOC or another threshold concentration Besides the IDLH and TLV TWA a variety of LOCs have been established by several organizations Text Summary SITE DATA INFORMAT I OM Location WASHINGTON DIST OF COLUPMEIR Building Air Exchanges Fer Hour 0 45 Sheltered single storied Time 2 1995 amp 1341 hours EDT Using computer s clock CHEMICAL MFORMAT I OH Chemical Mame BENZENE Molecular Height 79 11 kg kmal TLU THH 0 1 ppm IDLH S00 ppm Warning Potential or confirmed human carcinogen Footprint Level of Concern 300 ppm Boiling Point 176 16 Pressure at Ambient Temperature 0 12 atm Ambie
145. ipe that has been corroded on the inside by the chemicals it carries A smooth pipe would be for example a new metal glass or plastic pipe Pipe pressure If the pipeline is connected to a very large infinite reservoir use the pressure within the reservoir as your value for pipe pressure If gas 1s escaping from a closed off section of pipeline type the pressure within that pipe section Pipe temperature Indicate the temperature of the pipe contents in either of two ways a click Unknown assume ambient if you do not know the temperature ALOHA will then use the ambient air temperature or b type the temperature of the pipe s contents in the pipe temperature box then choose units either degrees Fahrenheit or Celsius Hole size If the pipeline is connected to a very large infinite reservoir ALOHA assumes that the pipe has been completely sheared off so that the hole diameter equals the pipe diameter If only a closed off length of the pipeline 15 leaking you can choose to a enter a value for the area of the hole 1f the hole 1s smaller in area than the pipe diameter or b allow ALOHA to use the pipe diameter as its value for the hole diameter In the case of a leak from a finite length of pipeline either type a value for the hole area and choose units or click Use pipe diameter ALOHA assumes that the hole in the pipe is circular If you know the diameter of the pipe hole but not its area divide the diameter in hal
146. is ALOHA predicts that average concentrations will be highest near the release point and along the centerline of any pollutant cloud and will drop off smoothly and gradually in the downwind and crosswind directions However especially near the source of a release wind eddies push a cloud unpredictably about causing gas concentrations at any moment to be high in one location and low in another This kind of movement is familiar to 13 Chapter 1 Welcome to ALOHA anyone who has tried to toast marshmallows over a campfire no matter where you sit the smoke from the fire always seems to come straight towards you Meanwhile the average concentrations are likely to behave approximately as ALOHA predicts As the cloud moves downwind from the release point these eddies shift and spread the cloud evening out concentrations within the cloud so that they become more similar to ALOHA s predictions Figure 1 12 Concentration patchiness close to the source ALOHA does not account for the effects of fires or chemical reactions The smoke from a fire because it has been heated rises rapidly before it begins to move downwind ALOHA doesn t account for this initial rise It also doesn t account for the by products of combustion or for chemical reactions of any kind ALOHA assumes that a dispersing chemical cloud does not react with the gases that make up the atmosphere such as oxygen and water vapor However many chemicals react
147. ishing community emergency exposure levels CEELs for extremely hazardous substances EHSs Design Institute for Physical Property Data 1999 DIPPR Data Compilation of Pure Compound Properties Electronic Version Described at www aiche org docs pubcat dipprprods asp Havens Jerry University of Arkansas Fayetteville NOAA DEGADIS evaluation report memorandum to Jerry Galt NOAA 1990 Havens Jerry and Tom Spicer 1990 LNG Vapor Dispersion Prediction with the DEGADIS Dense Gas Dispersion Model Topical Report April 1988 July 1990 Chicago Gas Research Institute 171 Bibliography National Institute for Occupational Health and Safety NIOSH U S Department of Health and Human Services DHHS 1997 NIOSH Pocket Guide to Chemical Hazards DHHS NIOSH Publication No 97 140 http www cdc gov niosh npg npg html online version and ordering information Lists TL Vs permissible exposure limits PELs and IDLH values as well as general industrial hygeine information for 677 chemical substances U S Environmental Protection Agency EPA the Federal Emergency Management Agency FEMA and the U S Department of Transportation DOT 1987 Technical Guidance for Hazards Analysis Emergency Planning for Extremely Hazardous Substances 1987 To request a copy call the Emergency Planning and Community Right to Know Hotline 800 535 0202 or 703 412 9877 or fax 703 413 3333 8 30 a m to 7 30 p m Mon Fri Describes step
148. k Windows Options ag v Text Summary Footprint Concentration Dose Source Strength 6 Calculate Calculate Now 2 The LOC for this scenario 1s chlorine s Immediately Dangerous to Life and Health IDLH level IDLH values have been established for many toxic chemicals the IDLH for chlorine is 10 ppm A chemical s IDLH is an estimate of the maximum concentration in the air to which a healthy worker could be exposed without suffering permanent or escape impairing health effects Many other toxic thresholds besides IDLH exist Click the topmost Help button on the Display Options dialog box to learn more about choosing an LOC Check to be sure that IDLH Concentration as well as Plot on grid and auto scale to fit window are selected Select either English units or Metric units depending on your preference ALOHA s computation results will be displayed in the units that you choose English units have been selected for this example Click OK 32 Chapter 3 Learning the Basics EEEE DD ptions Select Level of Concern or Output Concentration J BSefasit GC nai ept Hbrar IDLH Concentration Enter value i ppm O milligrams cubic meter Select Footprint Gutput Option Plot on grid and auto scale to fit window i Use user specified scale Select Gutput Units English units C3 Metric units 3 Choose Footprint from the
149. k on its name to highlight it then click Select Chemical Information CHLOROACETYL CHLORIDE CHLOROANILINE CHLOROBENZENE Entering weather information 1 Inthe SetUp menu point to Atmospheric then click User Input Lhemical Atmospheric User input 3A Computational 135 Chapter 5 Examples 2 Type 10 in the wind speed box then click Knots Type either 360 or into the wind direction box to indicate that the wind 1s from the north then click the right hand button under the Measurement height above ground 1s heading to indicate a wind measurement height of 10 meters Since the accident 1s in an industrialized area click Urban or Forest ground roughness Under the Select cloud cover heading click the left most button this button represents complete cloud cover Click OK Atmospheric Options Wind Speed is Knots oMPH Meters Sec Wind is from Enter degrees true or text e g ESE Measurement Height above ground is feet T C a 9 enter value jo melos Ground Roughness is Open Countr in ae j OR O input roughness 20 100 Urban or Forest n cm Select Cloud Cover RES as mH 4 enter value complete partly clear 3 70 into the air temperature box then click to indicate that this temperature is in degrees Fahrenheit ALOHA uses the wind speed cloud cover and da
150. l allow you to model any reactive chemical but will warn you that it may not be able to produce accurate results When you select an air or water reactive chemical ALOHA will alert you that the chemical 1s reactive and will describe the type of reaction and reaction products to expect Figure 4 16 54 Chapter 4 Reference 5 Stop PHOSPHORUS TRICHLORIDE reacts with any water it contacts to produce hydrochloric acid phosphoric acid and heat ALOHA does model chemically reactive substances and cannot accurately predict the air hazard from the release of this substance if it comes in contact with water Do you wish to continue and model this chemical as if it a non reactive chemical Figure 4 16 ALOHA alerts you when you select a reactive chemical If you choose to model the chemical ALOHA will place a similar warning in the Text summary window as an additional reminder Figure 4 17 Text Summary CHEMICAL INFORMATION Warning PHOSPHORUS TRICHLORIDE reacts with anu water it contacts to produce hydrochloric acid phosphoric acid and heat ALOHA does not model chemically reactive substances and cannot accurately predict the air hazard from the release af this substance if it comes in contact with water Chemical PHOSPHORUS TRICHLOR IDE Molecular Height 137 33 kgrkmol TLU THH 0 2 ppm IDLH 25 ppm Footprint Level of Concern 25 ppm Boiling Point 168 838 F Mapor Pressure at Ambient Tem
151. lop just as they would in the water next to a riverbank The rougher the ground surface the greater the ground roughness and the greater the turbulence that develops Ground roughness is determined by number and size of roughness elements present in an area A roughness element is a surface feature that disturbs the flow of air but is small relative to the size of a pollutant cloud To indicate the ground roughness downwind of a release either a choose one of two roughness classes Open Country low roughness low turbulence or Urban or Forest high roughness much turbulence or b enter your own value for roughness length Z9 a term used by meteorologists to describe ground roughness Click Open Country if there are only small or few roughness elements in the area Examples of open country include farmland grassland and large parking lots A cloud generally travels farther across open country than over an urban area or a forest and remains narrower because it encounters fewer smaller roughness elements to create turbulence or slow its crosswind spread ALOHA s footprint will be longer when you choose Open Country rather than Urban or Forest ground roughness B Click Urban or Forest if the area has many friction generating roughness elements such as trees or small buildings Examples of this category are residential housing developments industrial areas and forests GROUND ROUGHNESS Urban or forest pen country g
152. ly overcast air temperature 1s 44 F and relative humidity is 78 percent The wind is from the southeast at 15 knots measured at a height of 3 meters with a portable weather station Although methane is relatively non toxic the lower explosive limit LEL is about 5 percent or 50 000 parts per million ppm We will use ALOHA to help determine the downwind distance to 10 percent of the explosive concentration or 5 000 ppm Choosing a location and a chemical 1 start ALOHA read the list of ALOHA s limitations then click OK If ALOHA is already running choose New from the File menu to begin a new scenario 2 Choose Location from the SiteData menu SiteData 3 Quickly type the characters to move to the part of the city list containing Portland Oregon Click to highlight PORTLAND OREGON then click Select Location Information POCATELLO IDAHO POMONA CALIFORNIA POMPANO BEACH FLORIDA PONTIAC MICHIGAN PORT ARTHUR TEHAS Cancel PORT HURON MICHIGAN PORTLAND MAINE PORTLAND OREGON PORTSMOUTH NEW HAMPSHIRE PORTSMOUTH VIRGINIA PRESCOTT ARIZONA a Modify PRINCETON JERSEY a PROVIDENCE RHODE ISLAND PROVO UTAH QUINCY CALIFORNIA QUINCY ILLINOIS RACINE WISCONSIN RAHWAY JERSEY Delete 143 Chapter 5 Examples 4 6 144 Select Date amp Time from the SiteData menu to enter the date and time of the accident SiteData Location Building Type
153. m Boiling Point 28 25 F Vapor Pressure at Ambient Temperature greater than 1 atm Ambient Saturation Concentration 1 886 688 ppm or 148 8 ATMOSPHERIC INFORMATION MANUAL INPUT OF DATA Hind 3 mph from at 18 meters Mo Inversion Height Stabilitu Class B Air Temperature 72 Relative Humidity 30 Ground Roughness open country Cloud Cover 3 tenths SOURCE STRENGTH I MFORMATION Leak from short pipe or valve in horizontal cylindrical tank Tank Diameter 2 5 feet Tank Length 6 8 feet Tank Yolume 258 gallons Tank contains liquid Internal Temperature 72 Chemical Mass in Tank 1 tons Tank iz 68 full Circular Opening Diameter 9 inches Opening is 1 29 feet from tank bottom Release Duration 31 minutes Computed Release Rate 178 pounds min Average Sustained Release Rate 169 pounds min averaged over a minute or more Total Amount Released 827 pounds Hote The chemical escaped as a mixture of gas and aerosol twa phase flow FOOTPRINT IHFORHRT I Ol Model Run Heavy Gas User specified LOC equals IDLH 18 ppm Threat Zone for LOC 1 944 yards TIME DEFENDENT INFORMATION Concentration Estimates at the point Downwind 1564 feet Off Centerline B feet Concentration Outdoor 95 7 ppm Indoor 2 94 ppm Hote Indoor graph is shown with a dotted Line ALOHA also can estimate the dose of chlorine to which people at the elementary school may be exposed However don t use ALOHA s dose calc
154. m ALOHA into documents or reports in word processing or graphics programs ALOHA s menu bar Perform basic ALOHA operations by moving left to right through the six menus in its menu bar B File and Edit Choose items from these two menus to perform basic Macintosh and Microsoft Windows M operations such as opening closing and saving files printing the contents of ALOHA s windows and copying text and graphics displayed in ALOHA B SiteData Choose items from the SiteData menu to enter information about a the date and time and b location of an accidental release and c the type of buildings downwind of the release SetUp Choose items from the SetUp menu to a select a chemical from ALOHA s chemical library or to add a chemical to the library if you need to b indicate weather conditions you can do this either manually or by connecting your computer to a portable meteorological station c set the source describe how the chemical is escaping from containment into the atmosphere d choose the type of dispersion calculations for ALOHA to make ALOHA can predict the movement of either neutrally buoyant clouds that are about as dense as air and heavy gas clouds which are denser than air and e adjust the exponent in ALOHA s dose equation dose is the accumulated amount of the chemical to which a person is exposed at a particular location Display Choose items from the Display menu to indicate the
155. mation about a release and chosen a LOC and ALOHA has estimated source strength choose Footprint from the Display menu If the Footprint menu item 1s unavailable ALOHA requires more information from you to make its computations Check the Text Summary to see what s missing Interpreting a footprint ALOHA s footprint represents its best guess of what will happen downwind of a chemical release It s not an exact prediction of just where the gas cloud will travel and how large it will be As you examine any footprint plot remember the many uncertainties involved in trying to predict the effects of a chemical release When you enter information into ALOHA you often have to guess at some of the necessary inputs B Many things that happen by chance such as unexpected changes in wind speed or direction during a release can influence how a gas cloud disperses but are not accounted for in ALOHA s computations Although ALOHA is a relatively complex computer program it contains thousands of lines of computer code reality is much more complex ALOHA makes simplifying assumptions in order to make its predictions Try to identify ways in which reality may be different from what ALOHA assumes For example ALOHA expects the terrain under a dispersing gas cloud to be flat and free of obstacles but in the real world that s rarely the case Treat any footprint plot as a ballpark estimate and always use it along with
156. minutes past that hour 00 to 59 Each day begins at midnight 0000 and the last minute of each day 1s 2359 Under this system 6 00 am 1s 0600 and 2 30 pm 15 1430 Date and Time Options You can either use the computer s internal clock for the model s date and time or set a constant date and time Use internal clock amp Set constant time Input constant date and time Month Day Year Hour Minute 4 hs 1 12 1 31 1900 0 23 0 59 cancel Figure 4 14 Setting constant time 5 Chapter 4 Reference 52 Chapter 4 Reference The SetUp Menu As you enter information into ALOHA about a release scenario after you ve completed your work with the SiteData menu you ll move on to the SetUp menu Choose items from this menu to select a chemical from ALOHA s chemical library describe weather conditions and explain how the chemical is escaping from containment You also can specify how you want ALOHA to predict the dispersion of the pollutant cloud in the atmosphere and the dose of chemical to which people downwind might be exposed Select items from the SetUp menu in descending order as you describe a scenario first select Chemical then Atmospheric and finally Source Chemical 36H Chemical 36H Atmospheric a User Input A Atmospheric be or SAM Station Source i Computational Source Computational Figure 4 14 The SetUp menu The s
157. mum concentration of vapor that could be attained in the air in a closed space above a liquid at ambient temperature and pressure If a spilled liquid has a high ambient saturation concentration it has a strong ability to displace air and the concentration of vapor in the air above it will be high If it has a low ambient saturation concentration the vapor concentration will be low This property changes with temperature a liquid at a higher temperature will have a higher ambient saturation concentration A chemical that 15 a gas at ambient temperature and pressure has an ambient saturation concentration of 100 1 000 000 ppm Without water A chemical shipped or stored without water rather than in solution is in anhydrous form anhydrous ammonia is a common example 173 Glossary Atmospheric stability Average Boiling point ChemLib CityLib Cloud cover Concentration 174 A measure of the tendency of air to move upward or downward within the atmosphere generating turbulence Meteorologists have defined six atmospheric stability classes from A to F each representing a different degree of turbulence in the atmosphere A represents the most unstable conditions air has a strong tendency to move up or down and the atmosphere is more turbulent and F represents the most stable conditions air has little tendency to be displaced up or down and the atmosphere 1 less turbulent Mean The sum of n values
158. n Time 177 Greenwich Mean Time GMT 177 ground roughness 63 65 choosing a category 64 ground type 83 178 Heavy gas definition 178 doesn t account for inversion 69 doesn t account for source height 81 properties needed 57 heavy gas dispersion 8 10 Help online Help Index 4 in Windows 5 on a Macintosh 5 using 4 5 21 humidity relative 69 181 IDLH Immediately Dangerous to Life and Health 56 100 101 Immediately Dangerous to Life and Health IDLH 56 100 101 indoor air infiltration estimating 48 inputs allowable limits 166 169 Installing ALOHA before you begin 17 18 if you have a previous version 17 in Windows 18 19 memory and space requirements 17 on a Macintosh 19 20 inversion height 68 69 inversion definition of 179 Level of Concern LOC 3 100 102 Level of Concern LOC adding your own value 101 limitations of ALOHA 11 15 LOC Level of Concern 3 100 102 LOC Level of Concern adding your own value 101 Location menu item 43 location selection 43 186 maps and ALOHA 116 MARPLOT ALOHA menu in 117 118 and ALOHA 116 Macintosh and Windows versions 117 118 168 MARPLOT menu 116 Maximum Average Sustained Release Rate 79 95 112 167 Maximum Computed Release Rate 78 95 112 167 melting point 177 menu bar ALOHA s 2 meteorological station portable 60 63 69 77 mixing definition of 180 molecular weight 180 near field patchiness 13 neutrally buoyant gases 7 New menu item 39 numbers entering into ALOHA
159. n either use the computer s internal clock for the model s date and time or set a constant date and time i Use internal clock Set constant time Internal Clock Time is Tue May 2 13 26 00 1995 Cancel Figure 4 13 Date and time options The starting time of a scenario affects ALOHA s calculations in two ways 1 ALOHA uses the scenario start time to determine whether it is night or day when choosing a stability class and 2 ALOHA uses the position of the sun at the scenario start time to 50 Chapter 4 Reference estimate incoming solar radiation Solar radiation can be an important influence on puddle evaporation Whenever you use your computer s clock the scenario starting time will be updated to the current time whenever you enter atmospheric information change location or choose the Date and Time menu item To specify date and time choose Date amp Time from the SiteData menu then click either Use internal clock to use your computer s internal clock Set constant time to set a specific time when you want a scenario to begin This option is useful for contingency planning or training exercises because you can set up scenarios to run at different times of the day and or year and therefore under different atmospheric conditions ALOHA uses the 24 hour time system in which time of day is indicated by four digits The first two digits indicate the hour 00 to 23 and the last two indicate the number of
160. nal 2 Check to be sure that Let model decide select this if unsure is selected Click OK Computational Preferences Select spreading algorithm If unsure let model decide i Let model decide select this if unsure O Use Gaussian dispersion only O Use Heavy Gas dispersion only Define dose t Dose evar 0 Choosing a Level of Concern and Plotting a Footprint To obtain a footprint estimate you first must choose a Level of Concern LOC An LOC is a threshold concentration of a pollutant gas usually the concentration above which a hazard 15 believed to exist ALOHA plots a footprint which represents the zone where the ground level pollutant concentration may exceed your LOC at some time after a release begins 31 Chapter 3 Learning the Basics Note No LOC represents an exact line between hazardous and non hazardous conditions because people differ in their sensitivity to chemicals for example old sick or very young people may be more sensitive to chemicals than healthy adults An LOC that s appropriate for one person may be too high for somebody else When you use an LOC in ALOHA familiarize yourself with its definition to be sure it s appropriate for the work that you re doing and the population that you re concerned about Treat ALOHA s footprint as a rough estimate of the true hazard zone for an accidental release 1 Choose Options from the Display menu Display Tile Windows Stac
161. nd and any dispersing pollutant cloud are channeled down the street A frozen substance sublimates when it passes directly into the gas phase without first becoming liquid The way in which land features such as hills and valleys modify the speed and direction of air flow Threshold Limit Value Time Weighted Average The maximum airborne concentration of a given hazardous chemical to which nearly all workers can be exposed during normal 8 hour workdays and 40 hour workweeks for an indefinite number of weeks without adverse effects Set by the American Conference of Governmental Industrial Hygienists ACGIH The downwind distance along the centerline of a chemical cloud out to the level of concern that you set ALOHA s footprint length reported in the Text Summary window 15 a threat distance The area downwind of the source of an escaping pollutant within which concentrations of pollutant may become high enough to threaten people ALOHA s footprint is a diagram of a predicted threat zone A time dependent value 15 something that changes over time ALOHA s dispersion predictions account for release rates that change over time in this sense these predictions are time dependent However ALOHA does NOT account for changing atmospheric conditions when predicting dispersion in this sense its predictions are not time dependent A release rate that changes over time For example release rate from a pressurized tank decline
162. never instead of your own judgment experience and observations when you make response or planning decisions Concentration Once you have checked ALOHA s footprint to see how far a dispersing chemical cloud may spread you may want to find out about the concentration of chemical to which people at a particular location might be exposed This location could be for example a hospital school or large office building in the path of the dispersing cloud ALOHA displays a Concentration vs Time graph showing predicted concentrations for the first hour after the start of a release at a location that you have specified You ll see three lines on the graph 105 Chapter 4 Reference BI The solid red line represents the outdoor ground level concentration B The dashed blue line represents concentration within a building of the type you selected using the Building Type menu item in the SiteData menu The wider horizontal green line represents the LOC Concentration Window minutes Figure 4 51 A Concentration vs Time graph In reality gas concentrations can fluctuate greatly over time periods of several seconds ALOHA s concentration predictions represent values that have been averaged over a time period of several minutes so the maximum peak concentration that could be attained in reality may significantly exceed the predicted maximum averaged concentration shown on the graph The graph above Figure 4 51 shows
163. nput values possible ALOHA like any model can be unreliable in certain situations and it cannot model some types of releases at all ALUHA s results can be unreliable when the following conditions exist a Very low wind speeds ALDHA s footprint accurately depicts a pollutant Cloud s location only if the wind direction does not change from the value that you entered Generally wind direction is least predictable when wind speed is low To show how much the claud s position could change if the wind were to shift direction under the particular weather conditions that You enter draws two dashed lines ane along each side of the footprint ALOHA predicts that about 95 percent of the time the wind will Figure 1 6 Sample Help text on a Macintosh How to use this manual This manual includes six chapters Begin here in Chapter 1 by reviewing a discussion of basic air modeling concepts Turn to Chapter 2 for instructions on installing ALOHA and to Chapter 3 for a step by step ALOHA tutorial Chapter 4 contains descriptions of the main features of ALOHA Sections in this chapter include explanations of each of ALOHA s menus along with background information to help you to better understand ALOHA s computations Turn to Chapter 5 for some ALOHA example problems and to Chapter 6 for trouble shooting advice At the back of the manual you ll find a bibliography a glossary of air modeling terms and an index Chapter 1 Welcome
164. nt Saturation Concentration 118 572 ppm or 11 9 Figure 4 18 Information about benzene in the Text Summary window ALOHA sometimes places either of two notes in the Text Summary 56 When you select a chemical such as benzene which has been identified as a confirmed potential or suspected carcinogen a notation Note Potential or suspected human carcinogen will appear on the Text Summary as in the example above Chapter 4 Reference When you select a chemical for which little information is available ALOHA displays the following note in the Text Summary Not enough chemical information to use the Heavy Gas option This note alerts you that although the chemical s molecular weight is heavier than 29 kilograms per kilomole the average molecular weight of air so that it may behave like a heavy gas ALOHA will have to use Gaussian dispersion calculations to model its behavior in the atmosphere unless you add additional property information Chemical Data The chemical library includes information about the physical properties of each ALOHA chemical It also includes values for IDLH and TLV TWA You can add your own default LOC for any chemical to ALOHA s chemical library ALOHA then will automatically use your LOC rather than the IDLH for the selected chemical The ALOHA library contains information from two sources When available physical property values were obtained from a chemical database compiled by the
165. ntration at the workmen s location could have been higher or lower than ALOHA s estimate If the chlorine was stored as a pressurized liquid its initial release rate was probably greater than ALOHA predicted Downwind concentrations then would have been initially higher too but also might have dropped below the LOC much sooner than ALOHA predicted in this example If you were to respond to a real event similar to this example you might wish to obtain values for the tank car s dimensions the amount of chlorine it contained the size and location of 163 Chapter 5 Examples the hole and other information that you d need to run ALOHA s more realistic Tank source option 13 When you ve finished this example problem simply choose Exit in Windows or Quit on a Macintosh from MARPLOT s File menu ALOHA s footprint will then be deleted from the map 164 Chapter 6 Troubleshooting Often when you encounter difficulties while running ALOHA it will alert you of the problem and suggest a solution At other times you may encounter a problem and not know how to solve it Below are some of these cases For more ALOHA information check the ALOHA Page at http response restoration noaa gov cameo aloha html In the Text Summary I see tank volume estimated to be 5 2e8 gallons How many gallons is that ALOHA gave me an outdoor concentration estimate that s greater than 1 million parts per million how can t
166. ocal time setting and 47 Chapter 4 Reference the GMT offset if it s a non U S location To change information that you ve already entered for a location click on its name in the location index then click Modify Figure 4 5 You will see the information about that location that 15 currently in the location library Delete the information that you wish to change then type in the new value Deleting a location To remove a location from the index click to highlight its name in the index then click Delete Click Cancel to avoid deleting the location click OK to delete the location from the list If you accidentally click OK to delete the wrong city once you re returned to the Location dialog box click Cancel If you instead click Select to close this dialog box the city will be deleted Building Type ALOHA can estimate the pollutant gas concentration within buildings downwind of an accidental chemical release You first must specify the building type of concern which could be either the type of building that is most common in the area downwind of the release point or the type that you are most concerned about Indicate whether the building 15 single or double storied or 15 an enclosed office building You also must indicate whether it 1s relatively sheltered or unsheltered from the wind by trees buildings or other obstacles to the wind ALOHA expects pollutant concentrations to build up faster within single storied than dou
167. of four ways mass of chemical liquid volume percent full by volume or height of liquid level in the tank Choose to type the mass of the chemical in the tank this should be the total mass of the liquid and its vapor in the tank type the volume of the liquid in the tank if you have this information type your best estimate of the percent of the tank volume that is taken up by liquid as full by volume or BI use the scroll bar next to the tank diagram to indicate the approximate height of the liquid level in the tank Scroll up or down to position the horizontal bar on the diagram to indicate the liquid height In a real response checking for a condensation line on the outer tank wall may allow you to estimate the liquid level in the tank Liquid Mass or Volume Enter the mass in the tank OR volume of the liquid pounds The mass in the tank is tons 2 000 Ibs O kilograms Enter liquid level OR volume The liquid a gallons volume is cubic feet liters i cubic meters 55 full by volume Figure 4 37 Liquid in tank Gas in a tank Whenever you indicate to ALOHA that a tank contains only gas by clicking Tank contains gas only when you are asked to identify chemical state you will need to type either the tank pressure or the amount of gas 1 the tank 88 Chapter 4 Reference Mass ar Pressure of Gas Enter either tank pressure OR amount of gas C mmHg The tank pressure Is
168. of the spill There are two ways using either fixed or relative coordinates to describe a concentration location to ALOHA Click Help to view an explanation of both methods Check to be sure that Relative Coordinates is selected you ll describe the location in terms of downwind and crosswind distances from the release point Type 1000 into the downwind distance box and 0 into the crosswind distance box Click yards then click OK Concentration and Dose Location Specify the location at which you want to evaluate the concentration and dose over time e Relative Coordinates Evaluation Downwind Crosswind Point Fixed Coordinates 1 P wind direction East West North South E X Input the downwind distance from the source and V the perpendicular distance fram the downwind axis feet ards Input the downwind distance e miles Input the crosswind distance jo Meters kilometers 4 ALOHA displays a Concentration by Time graph showing the indoor and outdoor concentrations predicted at the office building s location during the first hour after the release begins The solid red line represents the outdoor ground level concentration The dashed blue line represents concentration within the office building as long as doors and windows are closed The wider horizontal green line represents the LOC Because chlorine s IDLH 10 ppm is stored in ALOHA s chemical library and you h
169. on slows the wind At higher elevations the wind speed is faster High enough up typically a few hundred yards or meters or higher the wind speed reaches a maximum because it is no longer affected by friction ELEVATION WIND SPEED Figure 4 22 A wind profile Indicate the wind measurement height under the Measurement height above ground 1s heading Choose one of the following three options to indicate the height SAMs typically are mounted on a 3 meter 9 8 foot stand so the wind reference height for readings from a SAM 1s likely to be 3 meters Click the leftmost measurement height button to indicate a height of 3 meters this is ALOHA s default measurement height B The National Weather Service usually reports wind speed measured at a height of 10 meters about 33 feet Click the middle button to indicate a height of 10 meters B Ifyou know that your wind speed value is being measured at a different height type that height in the measurement height box then choose units Ground roughness The degree of atmospheric turbulence influences how quickly a pollutant cloud moving downwind will mix with the air around it and be diluted below your LOC This affects the size of the cloud s footprint in ALOHA Friction between the ground and air passing 63 Chapter 4 Reference over it is one cause of atmospheric turbulence Because the air nearest the ground is slowed the most eddies deve
170. oncentration in air parts of gas per million parts of air ALOHA ppm 15 by volume not by weight Solid particles so small that they can disperse in the air like gases however unlike gases particulates eventually rainout or fall to the ground ALOHA does NOT model particulate dispersion Patchiness Pipe Plume Plume rise Puff Relative humidity Release duration Roughness length Running average SAM Save file Glossary Distribution of a pollutant gas as patches of high and low concentration Especially near the source of a release wind eddies push a pollutant cloud unpredictably about causing gas concentrations at any moment to be high in one location and low in another ALOHA does not account for patchiness near the point of a release For purposes of ALOHA a pipeline carrying pressurized gas ALOHA does not model releases from liquid pipelines A cloud of pollutant gas dispersing from a continuous source A typical plume is a long cigar shaped gas cloud The upward transport of a gas plume such as smokestack gases which rise because they have been heated ALOHA does not account for plume rise A cloud of pollutant gas dispersing from an instantaneous source A typical puff 1s a short round gas cloud The ratio of the amount of water vapor that the air contains to the maximum amount of water vapor that it could hold at the ambient temperature and pressure Relative humidity 15 expressed
171. ot on grid and auto scale to fit window is selected Select either English units or Metric units depending on your preference Click OK Display Options E Select Level of Concern or Output Concentration Default LOC not set in library gt IDLH not available amp ppm 6 Enter value S000 QO milligrams cubic meter Q milligrams liter Q grams cubic meter Select Footprint Output Option Plot on grid and auto scale to fit window Q Use user specified scale Select Output Units amp English units Q Metric units 148 Chapter 3 Examples 5 Choose Footprint from the Display menu Display Tile Windows Stack Windows Options Text Summary Footprint Concentration Bose Source Strength 6 Calculate taiculate Nou ALOHA predicts that the concentration of methane may exceed 5 000 ppm for up to about 190 yards downwind of the leaking pipe Footprint Window Your Text Summary should now look like the one below Text Summary SITE DATA MFORMATION Location PORTLAND OREGON Building Air Exchanges Per Hour 1 26 sheltered single storied Time Movember 17 2868 amp 1438 hours PST user specified CHENICAL INFORMAT ION Chemical METHANE Molecular Height 15 84 kg kmal TLV THH unavail IDLH unavail Default LOC from Library 306060 ppm Footprint Level of Concern 5808 ppm Boiling Point 258 68 F Vapor Pres
172. out 50 percent Ground roughness is Open Country because this 15 a rural farming area containing open fields with few trees and buildings 1 You must choose one of two options from ALOHA s Atmospheric menu depending on whether you wish to enter weather information manually or from a portable monitoring station called a SAM Station In this example you ll enter information manually In the SetUp menu point to Atmospheric then click User Input Chemical Atmospheric P User Input 3A Serene b SAM Station Computational 2 On the first Atmospheric Options dialog box type 5 in the wind speed box then click MPH Type S in the wind direction box to indicate that the wind is from the south then click the righthand button under the Measurement height above ground is heading This button represents a wind measurement height of 10 meters Check to be sure that Open Country ground roughness is selected Under the Select Cloud Cover heading click the fourth button from the left it represents 3 tenths cloud cover Once the dialog box on your screen looks like the one below click OK Atmospheric Options Wind Speed is Is Knots amp MPH Meters Sec Wind is from ls Enter degrees true or text e g ESE Measurement Height above ground is feet OF t lue AT ES O enter value o S mete Ground Roughness is Open Countr in Op OR O Input roug
173. pe and initial puddle temperature Emitted radiation o Evaporative heat loss radiation conduction Figure 4 33 Factors influencing ALOHA s puddle evaporation estimates Entering information about a puddle When you choose the Puddle option first type either the area or diameter of the puddle Puddle area strongly influences evaporation rate When all else is equal the larger the area of a puddle the higher is its evaporation rate If the puddle is roughly circular type its approximate diameter ALOHA then will estimate its area If the puddle is roughly square or rectangular in shape its area equals its length multiplied by its width If the length and width are in units of feet then the area will be in units of square feet if the diameter or the length and width are in meters the area will be in square meters and so on Next enter the amount of chemical contained in the puddle Specify the amount of liquid contained in the puddle by clicking B Volume of puddle Average depth of puddle or Mass of puddle 82 Chapter 4 Reference to indicate how you are specifying the amount of liquid Type a volume depth or mass value in the corresponding box and select units Puddle Input i feet area is square yards 9 diameter 3 meters 5elect one and enter appropriate data amp Volume of puddle 9 Average depth of puddle Mass of puddle Volumeis 25d amp gallons Q liters
174. peed in meters per second DI the instantaneous wind direction in degrees true TI the instantaneous air temperature in degrees Celsius B instantaneous SAM battery voltage in volts and CHK a checksum computed by summing the ASCII values of all preceding characters in the data line including the carriage return and line feed characters but not the final comma character ec 99 During the first 5 minutes of data collection the SAM should transmit as its value for SD sigma theta Although a station ID number must be included in each data transmission ALOHA does not use this value Wind direction should be the direction from which the wind is blowing If the SAM checks automatically for invalid data and finds an erroneous value it should transmit a data line that includes in place of that value either no value the data line would then contain two successive commas with no value between them or a word such as error as its value for an invalid datum the data line would then contain 70 Chapter 4 Reference error Because ALOHA does not check SAM data transmissions for unacceptable values the SAM should not transmit a numeric value such as 999 in place of an erroneous value Using a SAM during an incident When you use a SAM with ALOHA during incident response place your SAM so that its readings will be as representative as possible of the whole area through which the pollutant cloud may tra
175. perature 0 15 atm Ambient Saturation Concentration 130 564 ppm or 15 1 Figure 4 17 Information about a reactive chemical in the Text Summary Chemical information in the Text Summary window Review the Text Summary for information about the chemical you ve selected For example values for some properties of benzene appear in the text summary below Figure 4 18 You can see for example that benzene s boiling point 15 well above most ambient temperatures so you can expect to encounter it as a liquid Some items in the chemical information summary need some explanation Ambient Saturation Concentration Within a confined space such as a cargo hold or warehouse at a given temperature the ambient saturation concentration is the maximum concentration in the air that the vapor evaporating from a liquid pool may reach If a chemical has a high ambient saturation concentration it has a strong ability 35 Chapter 4 Reference to displace air and the concentration of the chemical s vapor in the air above the liquid will be high If it s low the vapor concentration will be low This property changes with temperature a liquid at a higher temperature will have a higher ambient saturation concentration The ambient saturation concentration of a gas is 1 000 000 parts per million or 100 percent ALOHA displays ambient saturation concentration because it can sometimes be useful to you to compare it with a threshold concentrat
176. por Pressure at Ambient Temperature greater than 1 atm Ambient Saturation Concentration 1 866 868 ppm or 166 6 ATMOSPHERIC INFORMATION MANUAL INPUT OF DATA Mind 12 knots from ene at 3 meters Ho Inversion Height Stability Class O Air Temperature 72 Relative Humidity Sms Ground Roughness open country Cloud Cover 3 tenths Describing the release Thisisa release from a tank car but you don t have all the information that you would need to model the release with ALOHA s Tank source option You can model this release as a Direct Source however In the SetUp menu point to Source then click Direct Chemical 36H Atmospheric gt Source 4 Direct D Puddle 3U Computational Tank Pipe 1 2 You know that about 4 000 pounds of chlorine were released so click pounds The chlorine was released over the course of an hour Click Continuous source then type 4000 as the release amount Click pounds hour Leave the source height as 0 then click OK User Input Source Strength Select source strength units of mass or volume grams C kilograms pounds 4 tons 000 Ibs cubic meters liters cubic feet 3 gallons Select an instantaneous or continuous source i Continuous source C Instantaneous source Enter the amount of pollutant ENTERING THE ATMOSPHERE pounds sec 4000 pounds min for pounds hr Enter source height 0 if ground sour
177. quid level falls below the bottom of the leak If the leak 15 above the liquid level and an unpressurized liquid 1 stored in the tank ALOHA will report that no chemical 1s released Regardless of the height of the leak however if the stored chemical is a liquid stored under high enough pressure ALOHA may predict that it will escape directly into the atmosphere without forming a puddle as a two phase flow of gas and aerosol To indicate the height of the leak above the tank bottom either type the height of the leak in distance units type the leak location as a percentage of the total distance from the bottom to the top of the tank For example 90 means that the leak is 90 of the way to the top of the tank BI use the scroll bar to the right of the tank diagram to indicate the height of the leak on the tank wall 91 Chapter 4 Reference Height of the Tank Opening fF The bottom of the leak is liq level D in amp ft com iom above the bottom of the tank of the way to the top of the tank Figure 4 41 Height of leak in tank Puddle formation If the chemical is stored as a non pressurized liquid a puddle may be formed ALOHA then will ask you for information about the area where the puddle will form You will need to enter ground type and ground temperature just as you would if you had selected the Puddle source option however in a Tank release case ALOHA computes initial puddle tempera
178. r 1 Welcome to ALOHA Figure 1 9 Cloud spread as a result of gravity Classification of heavy gases A gas that has a molecular weight greater than that of air the average molecular weight of air is about 29 kilograms per kilomole will form a heavy gas cloud if enough is released Gases such as anhydrous ammonia that are lighter than air at room temperature but that are stored in a cryogenic low temperature state can also form heavy gas clouds If the density of a gas cloud is substantially greater than the density of the air the density of air 1s about 1 1 kilograms per cubic meter ALOHA considers the gas to be heavy These gases form heavy gas clouds because they are very cold and therefore dense at the time of their release Flash boiling and two phase flow Many substances that are gases under normal pressures and temperatures are stored under high enough pressures to liquefy them For example propane is a gas at normal pressures and temperatures but 1s often stored under pressure as a liquid When a tank rupture or broken valve causes a sudden pressure loss in a tank of liquefied gas the liquid boils violently the tank contents foam up and the tank fills with a mixture of gas and fine liquid droplets called aerosol Flash boiling 1s the sudden vaporization of a liquid caused by a loss of pressure When the liquid and gas phases of a chemical escape together from a ruptured tank the release 1s called a two phase flow When su
179. r the general population It does not take into account the greater sensitivity of some people such as children sick people and the elderly Do not use IDLH values to definitively identify safe or hazardous conditions You may choose to use either the IDLH when a value is available as your LOC or another threshold concentration Besides the IDLH a variety of toxic thresholds have been established by several organizations To learn more about choosing and using LOCs in ALOHA check the references in this manual s bibliography or the LOC information at response restoration noaa gov cameo aloha html You can add your own default LOC for any chemical to ALOHA s chemical library ALOHA then will use your LOC by default rather than the IDLH for the selected chemical To permanently add your own default LOC for a chemical to ALOHA s chemical library choose Chemical from the SetUp menu click to highlight the name of the chemical in the index then click Modify In the list of physical properties click Default Level of Concern then type your LOC value in the Default LOC Value box Choose the correct units either parts per million or milligrams per cubic meter then click OK then Select Once you have chosen Options from the Display menu you can choose between the following LOC options Once you choose a chemical either the default LOC of your choice if you have entered a value into the chemical library or the chemical s ID
180. rbulent the wind 1s weak and the stability class would be E or F Stability classes D and C represent conditions of more neutral stability or moderate turbulence Neutral conditions are associated with relatively strong wind speeds and moderate solar radiation 66 Chapter 4 Reference UNSTABLE NEUTRAL STABLE Figure 4 24 Effects of solar radiation on atmospheric stability Stability class has a big effect on the size of a footprint predicted by ALOHA Under unstable conditions a dispersing gas mixes rapidly with the air around it ALOHA expects that the cloud will not extend as far downwind as it would under more stable conditions because the pollutant is soon diluted to below your LOC UNSTABLE NEUTRAL STABLE gt gt gt gt gt gt winds strong winds weak winds SUNSHINE NIGHTTIME STRONG HEATING QE MUCH TURBULENT i MIXING n rare cases stronger winds may be associated with F stability Figure 4 25 Stability class and mixing of a pollutant cloud ALOHA uses the Table 4 4 below to choose the stability class that best represents the weather conditions that you enter If more than one stability class fits the conditions that you indicate ALOHA selects the most stable of these classes For example if both A and B fit the conditions ALOHA selects B However you can click A if you believe this 67 Chapter 4 Reference class to be more appropriate Buttons for stability cla
181. rce Enter the amount of pollutant ENTERING THE ATMOSPHERE pounds ser pounds min for O pounds hr Enter source height feet 0 if ground source meters Figure 4 32 Direct input of source strength Describing a direct release Indicate whether the release 1s continuous lasting more than a minute or instantaneous lasting only a minute If a release is continuous and lasts for more than 1 minute and less than 1 hour type its duration in minutes Type either the amount of pollutant entering the atmosphere or the rate of entry You can use units of either weight or volume If you use volume units you must specify whether the chemical 1s a gas or liquid and enter its storage temperature ALOHA then converts volume to mass to make its source strength computations If you must estimate or guess the amount or rate of release try entering the largest likely amount or rate as well the smallest likely amount or rate into ALOHA then check to see how the size of the footprint changes when your amount estimate changes Note If a chemical escapes from pressurized storage in a tank or pipe its release rate may decline rapidly as storage pressure drops Since you can enter only a constant rate of release when you use the direct source option you may not be able to obtain an accurate footprint estimate for such a release Choose either the Tank or Pipe option for such releases if you possibly can see the descriptions of t
182. rd time 1s advanced by 1 hour the time is moved back 1 hour in the fall to become standard time again When you select a U S location ALOHA automatically switches between standard to daylight savings time for you when necessary depending on the date that you enter You must manually make this switch for locations outside the U S The ratio of the mass weight of a substance to the volume it occupies For example if 1 cubic foot of a substance weighs 10 pounds its density is 10 pounds per cubic foot 175 Glossary Direct Source Dispersion Dose Dusts Eddies Entrainment Exponential notation 176 Choose this source option when you know or can estimate either the amount of pollutant gas entering the atmosphere or its rate of entry For ALOHA s purposes the process by which a cloud of pollutant gas spreads out into the atmosphere mixing with the air and eventually becoming diluted to below hazardous levels The concentration of pollutant to which people are exposed taken to a power multiplied by the period of time that it 1s present Some researchers refer to this quantity as toxic load Fine solid particles at rest or suspended in a gas usually air These may have damaging effects on the environment may be dangerous by inhalation or contact and frequently constitute an explosion hazard when dispersed in air Parcels of air of various sizes that leave their normal position within an othe
183. reen looks like the one below click Search Search Criteria search for objects that have names that start with GALL Layer s to search Map s to search Individual Layer Cancel replace previous collection T 6 The search collection will include three roads Click once on Gallerher Road to highlight it then click Intersections Search Collection Number of objects in collection 3 Object Name Place Map Ballerher Road PRINCE WILLIAM COUNTY WA 4 Galley Ct Lake Ridge CDP Gallop Lane PRINCE WILLIAM COUNTY V Save Collection Show All on Map Load Collection Show on tr zoom Help 160 Chapter 5 Examples 7 There are three intersections along Gallerher Road Click to highlight US Hwy 29 and 211 in the list then click Show on Map amp Zoom Intersections Intersections for object Gallerher Road on layer Roads of map PRINCE WILLIAM COUNTY Intersect with all layers Number of intersections found 3 Object Name Layer Place Map State Hwy 55 Roads Major PRINCE WILLIAM COUNTY US Hwy 29 and 211 Roads Major PRINCE w ILLIAPT COUNTY untitled Roads PRINCE WILLIAM ul Show on Show on t 8 Your map should look like the one below U S Highway 29 211 crosses map as a Straight line from the lower left to the upper right of the map The Southern Railroad crosses the map horizontally and intersects with
184. rints the contents of all open windows 119 Chapter 4 Reference Quit or Exit allows you to exit quit from AlohaSpy Edit menu ndis HEA Copy RH Pipa Copy copies the contents of the front window to paste into another program The Undo Cut Paste and Clear menu items are not available in Aloha Spy Windows menu Windows Text Summary Footprint Window Concentration Window Dose Window Source Strength Release Rate Tile allows you to view all of the open archive windows simultaneously on the screen with the windows arranged side by side and fit to the screen Stack layers all of the open archive windows on top of each other so that only the title bars from the back windows along with the entire front window are visible Menu items displayed below the Stack menu item represent the individual window names To open a closed window or bring a window forward choose the desired window name from this list A check mark is placed next to the name of the current front window 120 Chapter 5 Examples This chapter contains four step by step example ALOHA scenarios You can complete the first three scenarios using only ALOHA To complete the fourth scenario you ll need the electronic mapping application MARPLOT as well as the sample map of Prince William County supplied with MARPLOT You can complete all four example problems either in Windows or on a Macintosh Example 1 A Tank Source
185. roplets and vapor a two phase flow would be released to the atmosphere ALOHA s Tank release calculations account for these processes but the Direct Source option does not Since we don t have the necessary information to run the Tank option we ll use the Direct Source calculations as the best approximation that we can make recognizing that ALOHA will treat this release as a steady flow of gas from the tank instead of a two phase release Click OK The source strength information that you have entered into ALOHA and the results of ALOHA s computations of release rate in mass units and total mass released appear in the Text Summary Text Summary SOURCE STRENGTH MFORMAT Direct Source 50 gallonz min Source Height Source State Liquid Source Temperature 30 F Release Duration 10 minutes Release Rate 651 pounds min Total Amount Released 6 506 pounds Hote This chemical may flash Boll and or result in two phase flow Checking concentration 1 First check the computational setting Select Computational from the SetUp menu Check to be sure that Let model decide select this if unsure is selected Click OK 2 Select Concentration from the Display menu Display Tile Windows Stack Windows Text Summary Footprint Concentration Dose Source Strength Calculate Calculate Now 139 Chapter 5 Examples 3 The paper mill s office building is about 1 000 yards directly downwind
186. ruptured or more slowly over a longer period of time so that source strength is low as when a puddle evaporates ALOHA can model four types of sources Choose la Direct when you know the rate at which a pollutant gas is entering directly into the atmosphere as well as the duration of the release B Puddle when the chemical has formed a liquid pool and is evaporating into the atmosphere la 7ank when the chemical is escaping from a storage tank either as a gas or as a pressurized or unpressurized liquid la Pipe when the chemical is a pressurized gas escaping from a ruptured gas pipeline 71 Chapter 4 Reference Chemical Atmospheric 4 Source d Direct p UR Puddle Computational Tank Pipe Figure 4 31 Choose the type of source to model from the Source menu When you choose one of the four source options you will need to enter information about the release on a series of dialog boxes Once you click OK on the last dialog box ALOHA will make its source strength calculations and you ll be able to review the results of the source calculations predicted release duration release rates total amount released and other information in a text summary and a graph ALOHA s duration limits ALOHA places minimum and maximum limits on the duration of any release ALOHA expects a release to continue for at least 1 minute and it estimates source strength release rate for no more than 1 hour
187. rwise orderly smooth flow For example air that encounters an obstacle must go over or around it This change in the direction of air flow often causes swirls of air or eddies to tumble off the back of the obstacle Impediments to airflow ranging from simple friction grass to larger obstacles buildings can cause eddies in a variety of sizes to form The mixing of environmental air into a current of gas or air so that the environmental air becomes part of the current For example as air is mixed into a moving toxic cloud the pure gas cloud becomes a gas air mixture ALOHA displays its results in exponential notation whenever numbers are too large to display in decimal notation Exponential notation 1s a way of displaying a number as a digital number multiplied by a power of 10 In the number 5e3 for example 5 1s the digital number and 3 is the power to which 10 is taken Interpret 5e3 as 5 times the quantity 10 taken to the power of 3 which equals 5 000 in decimal notation Flash boil Footprint Freezing point Fumes GMT Gas es Glossary The sudden vaporization of a liquid This occurs most often when a chemical is a gas at standard temperature and pressure but is stored as a liquid under pressure If the storage container ruptures the sudden reduction in pressure leaves the material 1n a superheated state causes it to be ina liquid state above its boiling point so that it will flash boil as it leave
188. s Figure 4 23 ALOHA s two roughness categories Urban or Forest and Open Country Choose the dominant category of ground roughness in the area where the pollutant cloud may travel For example 1 70 of the area is urban or forest and 30 15 open country click Urban or Forest If you can t easily determine the dominant category run ALOHA once with each category selected to get an idea of the possible range in footprint size 64 Chapter 4 Reference If something such as a tall building is very large relative to the pollutant cloud it is likely to be an obstacle that diverts a pollutant cloud rather than a roughness element that generates turbulence For example 1 a downtown area on a Sunday morning with no cars on the streets the best ground roughness category for a small release may be Open Country In this case the buildings are obstacles and the street is the roughness the pollutant cloud will experience If you prefer to type in a value for roughness length Zo you can refer to Table 4 3 below Note that roughness length 1s not a simple function of the height of the roughness elements in an area Table 4 3 Zo equivalences From Brutsaert 1982 surface description Mud flats 1ce 0 001 Smooth tarmac airport runway 0 002 Large water surfaces average 0 01 0 06 Grass lawn to 1 cm high 0 1 Grass airport 0 45 Grass prairie 0 64 Grass artificial 7 5 cm high Grass thick to 10 cm high
189. s menu on a Macintosh and in Windows Copy Choose Copy to copy pictures or selected text from the front window to the clipboard You can then paste copied items into a word processing or graphics application The Undo Cut Paste and Clear menu items are not available in ALOHA 42 Chapter 4 Reference The SiteData Menu The SiteData menu is the first menu in ALOHA that you use to enter information about a release scenario Use the three items in this menu to enter information about the geographic location of the accidental chemical release the type of buildings in the area downwind of the release BI the date and time of the release 5Sitellata Location Building Type Date tr Time Figure 4 4 The SiteData menu 15 the same in Windows and on a Macintosh Location Choose this item to specify the geographical location of a release ALOHA uses the latitude longitude elevation and time zone of the location of a chemical release in some of its computations This information for many cities and towns where ALOHA users reside 15 already included in ALOHA s location library CityLib You can add descriptions of other locations ALOHA uses location information to estimate sun angle ALOHA uses latitude longitude and time of day for this calculation atmospheric pressure determined by the location s elevation The angle of the sun 1s important when a chemical has formed a puddle on the ground AL
190. s over time as tank pressure drops 183 Glossary Two phase flow Unstable Urban or Forest Vapor Vapor pressure Volatility Wind direction Wind rose Zo 184 Both the liquid and gas phases of a chemical sometimes can escape together from a ruptured pressurized tank as a two phase flow Many substances that are gases under normal pressures and temperatures are stored under high enough pressures to liquefy them When a tank rupture or broken valve causes a sudden pressure loss in a tank of liquefied gas the liquid boils violently the tank contents foam up and the tank fills with a mixture of gas and fine liquid droplets called aerosol When such a two phase mixture escapes from storage the release rate can be significantly greater than that for a purely gaseous release The atmosphere is unstable when substantial air turbulence exists so that there is a strong tendency for air to be mixed into a dispersing pollutant cloud An area of relatively high ground roughness such as residential areas or forests The gas produced by the evaporation of a liquid or sublimation of a solid For example the gas produced when liquid water evaporates is water vapor The pressure of a vapor in equilibrium with its liquid or solid form at a given temperature The tendency of a liquid or solid to form a vapor The direction from which the wind 1s blowing For ALOHA s purposes a diagram displaying recent
191. s the container ALOHA s footprint represents an overhead view of the area where the ground level pollutant concentration 1s predicted to exceed your Level of Concern at some time after a release begins Also melting point The temperature at which the solid and liquid phases of a substance exist in equilibrium The freezing point depends on the chemical composition and the applied pressure The normal freezing point is defined at a pressure of 1 atmosphere For example the normal freezing point of water 1s 0 C 32 F Dense smoke like vapors given off by fuming materials such as very reactive liquids gases or molten metals for example concentrated hydrochloric acid or sulfur monochloride Fuming corrosive materials produce dense choking smoke like clouds on contact with the moisture in air Some liquefied gases that react with water when they evaporate such as anhydrous hydrogen fluoride and anhydrous hydrogen chloride also produce fumes Fumes from hot or molten metals may not have a dense smoke like appearance but are hazardous usually by inhalation Greenwich Mean Time or Coordinated Universal Time The reference time along the prime meridian 0 longitude which passes through Greenwich England Evenly dispersed molecules of a material at a temperature above its boiling point A gas unlike solids and liquids does not have an independent shape or volume a gas expands to fill available space and the volum
192. sed At the time of the spill the sky was completely overcast the air temperature was 70 F and the wind was from 360 at 10 knots measured at a height of 10 meters The relative humidity was 67 percent The safety officer at the paper mill has recommended chlorine s IDLH of 10 ppm as the LOC for this chemical We will use ALOHA to predict the indoor concentration of chlorine within the paper mill s office building Choosing a location building type and chemical 1 Start ALOHA or if ALOHA 1s already running choose New from the File menu to begin a new scenario you will be asked whether you wish to save your previous work as a save file 2 Select Location from SiteData menu SiteData Location 1 Building Type Date amp Time 3 Type c then scroll down a little farther until you see COLUMBIA SOUTH CAROLINA Click on this name to highlight it then click Select 133 Chapter 5 Examples 6 134 COLUMBIA MARYLAND C COLUMBUS OHIO CONCORD CALIFORNIA CONCORD MASSACHUSETTS CONCORD NEW HAMPSHIRE CONROE TEXAS CONWAY NEW HAMPSHIRE COOPERSTOWN NEW YORK CORAOPOLIS PENNSYLVANIA CORNING NEW YORK CORONA CALIFORNIA CORPUS CHRISTI TEXAS CORVALLIS OREGON CRESTON IOWA CULBERTSON MONTANA CUMBERLAND MARYLAND SiteData Location Information Choose Building Type from the SiteData menu Location Building Type Date tr Tim
193. sian equation discussed in Chapter 1 to predict the spread of the cloud Avoid using ALOHA s Gaussian model to predict how a large heavy gas cloud will disperse Large gas clouds that are denser than air heavy gases disperse in a very different way than this model would predict They are affected by gravity and other forces besides wind and turbulence As they move downwind they remain much lower to the ground than neutrally buoyant clouds and flow like water Ground level concentrations within such clouds may reach much higher levels at some locations than the Gaussian model would predict Use Heavy Gas dispersion only Choose this option if you know that the cloud is heavier or denser than air You will be alerted if ALOHA does not have enough property information to make heavy gas calculations for your selected chemical To see a list of the properties needed for heavy gas calculations check Table 4 1 To view the property values in the library for your selected chemical choose Chemical from the SetUp menu then click Modify When you choose Use Heavy Gas dispersion only ALOHA will predict the dispersion of the pollutant using the heavy gas computations discussed in Chapter 1 Typically when the atmosphere is most unstable stability classes A and B heavy gas footprints will be longer than Gaussian footprints when the atmosphere is most stable stability classes E and F Gaussian footprints will be longer Under neutral C and
194. so that the puddle s area and volume are increasing choose Tank instead ALOHA can model evaporation from puddles that are either boiling or that are cooler than the boiling point of the liquid that they contain It cannot estimate sublimation rate for a frozen puddle a frozen substance sublimes when it passes directly to the gas state without first becoming liquid To model evaporation from a puddle ALOHA accounts for the effects of wind speed atmospheric turbulence air temperature and pressure viscosity and other properties of the spilled chemical It accounts for the effects on pool temperature of solar heating evaporative cooling and several other ways in which heat 1s exchanged between a pool and its environment For example on a sunny day ALOHA will expect heat energy from the sun to warm the puddle It expects pool temperature to directly influence evaporation rate so that the higher the puddle temperature the faster the evaporation rate It accounts for changes in pool temperature and hence in evaporation rate over time The types of heat transfer that ALOHA expects to affect puddle temperature fall into the following three categories incoming solar radiation affected by location time and date and cloud cover heat transfer with the air affected by air temperature humidity and initial puddle temperature 81 Chapter 4 Reference heat transfer with the ground affected by ground temperature ground ty
195. spheric Options Wind Speed is Knots OMPH Meters Sec Wind is from ENE Enter degrees true or text e g ESE Measurement Height above ground is feet jT enter value H 2 wh w meters Ground Roughness is Open Countr in UR OR O Input roughness 20 3 0 O Urban or Forest cm Select Cloud Cover i G 4 enter value monty E complete partly clear 3 Type an air temperature of 72 degrees ALOHA has selected stability class D Click No inversion since you have no indication that an inversion exists Type 80 percent into the relative humidity box Click OK Atmospheric Options 2 Air Temperature 22 Degrees mF OC Stability Class is O8 O8 Ot OF OF Inversion Height Options are e Feet ee inversion Inversion Present Height is Meters Select Humidity fiy H OQ OR amp enter value ao medium dry 0 100 Check the information in the Text Summary to be sure that you have entered all data correctly 154 Chapter 3 Examples Text summary SITE INFORMATION Location MANASSAS VIRGINIA Building Air Exchanges Per Hour 97 sheltered single storied Time June 4 2888 amp 1588 hours EDT fuser specified CHEMICAL 1HF O RHRT ION Chemical CHLOR IHE Molecular Height 78 91 1 TLV THH B 5 ppm IDLH 18 ppm Footprint Level of Concern 18 ppm Boiling Point 29 25 F Va
196. sses inappropriate for those conditions are unavailable for selection Table 4 4 Stability class and wind speed Wind Speed Day Night meters per knots miles per Incoming Solar Radiation Cloud Cover second hour Strong Moderate SlightS gt 50 lt 50 4 5 4 5 6 7 6 7 11 2 11 2 13 4 213 4 Stability is D for completely overcast conditions during day or night Wind reference height 10 meters i Strong solar radiation corresponds to clear skies with the sun high in the sky solar angle greater than 60 degrees Slight solar radiation corresponds to clear skies with the sun low in the sky solar angle between 15 and 35 degrees You can click Override to override ALOHA s stability class choices and choose any of the six stability classes You should do this however only if you are sure that a special circumstance causes the best choice for stability class to be different from the choice s made by ALOHA For example the atmosphere over a large body of water is typically more stable than would be expected for a given combination of wind speed cloud cover and time of day If you are modeling a release over water then you might want to choose a more stable class than ALOHA chooses for you Inversion height An inversion is an atmospheric condition in which an unstable layer of air near the ground lies beneath a very stable layer of air above The height of the abrupt change of atmospheric stability is
197. sure at Ambient Temperature greater than 1 atm Ambient Saturation Concentration 1 888 888 ppm or 166 6 ATMOSPHERIC INFORMATION MANUAL INPUT OF DATA Hind 15 knots from SE at 3 meters Ho Inversion Height Stability Class D Air Temperature 44 F Relative Humidity 792 Ground Roughness open country Cloud Cover 18 tenths SOURCE STRENGTH INFORMATION Fipe Diameter 5 inches Fipe Length 1888 feet Pipe Temperature 44 F Pipe Press 188 Lbs sq in Pipe Roughness smooth Hole Area 358 3 sq in Unbroken end of the pipe is connected to an infinite source Release Duration ALOHA Limited the duration to 1 hour Max Computed Release Rate 4 438 poundz min Max Average Sustained Release Rate 1 438 pournds min averaged over a minute or more Total Amount Released 4 555 pounds FOOTPRINT I HFORHRT ION Dispersion Module Gaussian UWser specified LOCI S888 ppm Threat Zone for LOCI 198 yards 149 Chapter 5 Examples 150 Chapter S Examples Example 4 Using ALOHA and a MARPLOT map On June 4 2000 a train traveling on the Southern Railway near Manassas Virginia collided with a stalled truck at U S Highway 29 this highway is also numbered 211 During the hour from 15 00 to 16 00 about 4 000 pounds of chlorine gas were released from a derailed tank car At the time of the release winds were out of the east northeast ENE at about 12 knots measured at a height of 3 meters One third of the sky was covered by clouds
198. t Location Information BAKERSFIELD CALIFORNIA BALTIMORE MARYLAND BISMARCK NORTH DAKOTA BLOOMFIELD INDIANA In this example we will not enter building type information because we will not assess concentration at specific locations 4 Choose Date amp Time from the SiteData menu to enter the date and time of the accident SiteData Location 1 Building Type Date amp Time E 5 Click Set constant time then enter the month day year hour and minute for this scenario press TAB to move from one box to the next as in the example below The accident time of 10 30 p m equals 22 30 in 24 hour time Click OK Date and Time Options You can either use the computer s internal clock for the model s date and time or set a constant date and time 9 Use internal clock Set constant time Input constant date and time Month Day Year Hour Minute 1 12 1 31 1900 0 23 0 59 122 Chapter 5 Examples 6 Select Chemical from the SetUp menu Chemical H Atmospheric p Source b Computational 7 Find BENZENE in the list type the character b to go to the section of the list containing benzene click on its name to highlight it then click Select Chemical Information ARGON ARSENIC TRICHLORIDE BENZENE PHOSPHORUS DICHLORIDE BENZENE PHOSPHORUS THIODICHLORIDE BENZENE SULFONYL CHLORIDE BENZU UNITRILE BENZDTHIFLUORIDE BENZYL BROMIDE BENZYL CH
199. t Sharing CAMEO gt Set Source Point Set Conc Dose Point gee ee Delete ALOHA Objects Go to ALOHA 162 Chapter 5 Examples ALOHA will display a Concentration by Time graph for this location Review the graph and the Text Summary ALOHA estimated that the workmen were exposed to an outdoor concentration of more than 40 parts per million about four times the IDLH value for chlorine for about an hour after the start of the release a Concentration Window minutez Don t be concerned if the numbers that you see on your screen differ slightly from those shown on the Text Summary ALOHA s estimates are affected by exactly where on the map you click The purpose of running this scenario in ALOHA and MARPLOT was to get an estimate of the concentration of chlorine to which the workmen were exposed Text Summary TINE DEPEHDEHT INFORMATION Concentration Estimates at the point West 332 yards South 126 yards Max Concentration Outdoor 43 3 ppm Indoor 26 7 ppm Hate Indoor graph is shown with a dotted line ALOHA was designed to give you ballpark estimates of source strength and dispersion It cannot give you completely accurate predictions for a real release because no model can account for every uncertainty For example ALOHA predicted that the workmen were exposed to a steady concentration of about 40 ppm of chlorine However if the wind shifted during the course of the release the conce
200. t display SAM data the Wind Rose Processed SAM Data and Raw SAM Data windows will be updated automatically when new data are received The Footprint Concentration and Dose windows unless one of these 1s the front window will be greyed out as soon as new data are received to indicate that they are out of date Footprint concentration and dose information will be removed from the Text Summary window However up to date wind and temperature information will be displayed in this window Select Calculate Now from the Display menu to update all out of date windows If you have selected Manually update all visible windows new SAM data will be archived normally and windows that display SAM data will be updated automatically each time ALOHA receives new SAM data You ll need to choose Calculate Now from the Display menu to update the Footprint Concentration and Dose windows The label Information 15 not current will appear in each of these windows to remind you to re select Calculate Now whenever you wish to see current information Wind and temperature information displayed in the Text Summary window will be updated only when you choose Calculate Now Regardless of the update mode you have selected any SAM data received while Footprint Concentration and Dose windows are being updated will not be used or archived by ALOHA even if you have selected Archive Data from the SAM menu 113 Chapter 4 Reference Calculate Now The
201. te and time information that you ve entered to automatically select atmospheric stability class D representing conditions of neutral atmospheric stability Check to be sure that No inversion is selected then under the Select Humidity heading type 67 percent into the relative humidity box Click OK Atmospheric Options 2 Air Temperature is 70 Degrees mF Stability Class is O8 O8 Of OD OF OF Inversion Height Options are ees ee amp No Inversion Inversion Present Height is Meters Select Humidity T Se ue O 08 enter value 6 wet dry 0 100 136 Chapter 3 Examples The information that you have entered into ALOHA now appears in the Text summary Check under the SITE DATA INFORMATION heading to see the air exchange rate ALOHA will use to predict indoor chlorine concentration 0 45 air changes per hour Text summary SITE IHFORHRT I OH Location COLUMBIA SOUTH CAROLINA Building Air Exchanges Per Hour 8 45 sheltered single storied Time 15 28868 amp 1388 hours EDT user specified CHEHICRL MFORMATIOW Chemical CHLORI HE Molecular Height 78 901 kg kmol TLY THA B 5 ppm IDLH 18 ppm Footprint Level of Concern 18 ppm Boiling Foint 28 25 F Vapor Pressure at Ambient Temperature greater than 1 atm Ambient Saturation Concentration 1 668 668 ppm or 1858 83 ATMOSPHERIC INFORMATION MANUAL INPUT OF DATA Hind 18 knots from
202. ters Ho Inversion Height Stability Class D Air Temperature 74 F Relative Humidity Ground Roughness urban or forest Cloud Cover 18 tenths SOURCE STRENGTH INFORMATION Direct Source 58 qallons min Source Height B Source State Liquid Source Temperature 36 F Release Duration 18 minutes Release Rate 651 pounds min Total Amount Released 6 586 pounds Hote This chemical may flash boil and or result in two phase flow FOOTPRINT INFORMATION Model Bun Heavy Gaz User specified LOC equals IDLH 18 ppm Threat Zone for LOC 1 6 miles TIME DEFENDENT MFORMATION Concentration Estimates at the point Dowr i red 1 yards Off Centerline B yards Concentration Outdoor 78 5 ppm Indoor 3 85 ppm 141 Chapter 5 Examples When IDLH is the LOC ALOHA s footprint for this scenario is shown below choose Footprint from the Display menu to see this footprint Footprint Window 142 Chapter S Examples Example 3 A Pipe Source At a rural road construction site near Portland Oregon a heavy equipment operator accidentally cuts open a methane pipe on November 17 2000 at 14 30 The pipe runs 1 000 feet to the emergency shutoff valve but the valve has been left open The inside diameter of the pipe is 8 inches The inner wall of the pipe is smooth The methane in the pipe is at ambient temperature and the pressure 1s 100 pounds per square inch At the accident site the sky is complete
203. the humidity was about 80 and the air temperature was 72 F The land between the tank car and the intersection of Gallerher Road with U S Highway 29 is flat with no obstructions Two workmen repairing potholes at this intersection were overcome by fumes and treated at a local hospital for chlorine gas inhalation To what approximate concentration of chlorine might the workmen have been exposed You ll evaluate this scenario first by using ALOHA to obtain a source strength estimate and a footprint then by plotting the footprint on a MARPLOT map in order to obtain a concentration estimate for the location where the workmen were injured Choosing a location and a chemical 1 start ALOHA read the list of ALOHA s limitations then click OK If ALOHA is already running choose New from the File menu to begin a new scenario 2 You ll need to add Manassas Virginia to ALOHA s city library Choose Location from the SiteData menu SiteData Location Building Type 3 Click Add Location Information ABERDEEN MARYLAND ABILENE TEHAS AIKEN SOUTH CAROLINA ALAMEDA CALIFORNIA Cancel YORK ALEXANDRIA LOUISIANA ALEXANDRIA HIRGINIR Modify AMESBURY MASSACHUSETTS ANACONDA MONTANA ANAHEIM CALIFORNIA ANCHORAGE ALASKA ANN ARBOR MICHIGAN ANNAPOLIS MARYLAND Delete 151 Chapter 5 Examples 5 6 152 Type Manassas in the location name box Click In U S Type 200
204. ther the air within the building is warmer or cooler than the outside air this 1s because air masses of different temperatures have different pressures and pressure differences stimulate air movement The higher a building s air exchange rate the faster the concentration of a toxic gas 1s predicted to rise within the building To estimate exchange rate ALOHA assumes that single and double storied buildings are about as leaky as typical North American houses that have been studied by researchers Wilson 1987 For enclosed office buildings ALOHA uses a constant air exchange rate of 0 5 regardless of wind speed and air temperature This 1s because the environment within a large modern enclosed building 15 controlled and kept nearly constant regardless of weather conditions using a heating ventilating and air conditioning HVAC system The American Society of Heating Refrigerating and Air Conditioning Engineers ASHRAE recommends that air exchange rates for buildings be kept within the range of 0 5 to 1 0 complete changes per hour to maintain air quality Infiltration Building Parameters Select building type or enter exchange parameter O Enclosed office building Single storied building Double storied building O No of air changes is EE per hour select building surroundings Sheltered surroundings trees bushes etc Cancel O Unsheltered surroundings Figure 4 12 Building parameters If you know a b
205. tion confidence lines around it will automatically be drawn on the map in MARPLOT If you already designated a concentration dose location in ALOHA that location will be marked by a blue crosshair symbol on the map in MARPLOT Set Conc amp Dose Point First click the location on your MARPLOT map for which you wish to see concentration and or dose information Next choose Set Conc amp Dose Point to tell ALOHA the concentration dose location ALOHA will place a blue crosshair symbol C at that location then will display a Concentration by Time graph for that location ALOHA will use fixed east west north south coordinates to remember the point s position check the Concentration section to learn about location coordinates 117 Chapter 4 Reference B Delete ALOHA Objects Choose this item to remove all objects placed on the map by ALOHA ALOHA then will no longer update the map every time it generates new information Goto ALOHA Choose this item to bring ALOHA forward Concentration Dose Location Footprint gal la Huic gut ear ge Source Point Wind Direction Confidence Line Figure 4 60 Components of an ALOHA footprint shown on a map in MARPLOT You can plot an ALOHA for Windows footprint on a map in MARPLOT 2 0 a DOS program that is no longer distributed but that was part of CAMEO DOS You ll find instructions in ALOHA s Using MARPLOT DOS help topic AlohaSpy AlohaSpy is a
206. tion rate 81 height of direct release 81 information in Text Summary 94 95 Pipe 92 94 pressurized liquid release 85 Puddle 81 84 release rate averaging 79 112 release rate reporting 78 79 source strength graph 111 112 Tank 84 92 source strength 77 95 Spy files 41 Stability atmospheric about 66 68 classes 66 68 effects on footprint size 67 overriding class choice 68 very stable conditions 11 Stack Windows 100 Station for Atmospheric Measurement SAM 69 77 STP Standard Temperature and Pressure 183 street canyon 12 183 Index sublimation 183 Tank source option about 84 92 area and type of leak 90 leak height on tank 91 92 liquid in tank 86 pressurized liquid release 85 puddle formation state of chemical in tank 86 90 tank size and orientation 86 Temperature initial puddle 84 of the air 66 within a pipe 94 within a tank 87 88 terrain steering 12 13 terrain effects on puddle spreading 15 Text Summary 103 Threshold Limit Value Time Weighted Average TLV TWA 56 183 Tile Windows 99 TLV TWA Threshold Limit Value Time Weighted Average 56 183 troubleshooting 165 two phase flow explanation of 9 85 units choosing English or metric 103 updating ALOHA windows 112 114 Urban or Forest 64 weather information entering 60 77 Wind entering wind direction 62 estimating wind speed 62 low wind speeds 11 measurement 60 63 measurement height 63 wind direction confidence lines 104 wind profile 63 wind rose 75 76 wind
207. to ALOHA Introduction to air modeling ALOHA is an air dispersion model which you can use as a tool for predicting the movement and dispersion of gases It predicts pollutant concentrations downwind from the source of a spill taking into consideration the physical characteristics of the spilled material ALOHA also accounts for some of the physical characteristics of the release site weather conditions and the circumstances of the release Like many computer programs it can solve problems rapidly and provide results in a graphic easy to use format This can be helpful during an emergency response or planning for such a response Keep in mind that ALOHA is only a tool Its usefulness depends on your accurate interpretation of the data ALOHA originated as a tool to aid in emergency response It has evolved over the years into a tool used for a wide range of response planning and academic purposes However you must still rely on your own common sense and experience when deciding how to respond to a particular incident There are some features that would be useful in a dispersion model for example equations accounting for site topography that have not been included in ALOHA because they would require extensive input and computational time ALOHA s most important limitations are discussed in the following pages Dispersion modeling Many different types of air dispersion models exist They range from simple equations that can be solved by han
208. transparency of the footprint plot to use as an overlay on a paper map of the area where a release 1s occurring If you choose to specify the scale you will be asked to type a scale and select its units Figure 4 48 To enter a display scale indicate the real world distance to be represented by 1 inch or centimeter cm in the Footprint window For example To view the footprint at a scale of 1 inch to 1 000 feet proceeding left to right in the User Specified Plot Scale dialog box click Inch then type 1000 in the scale box then click Feet To view the footprint at a scale of 1 5 000 click Inch type S000 in the scale box then click Inches User Specified Plot Scale Please Input User Scale G inches miles ae 1 1 screen equals CO cem q C feet C meters yards kilometers Cancel Figure 4 48 The user specified plot scale dialog box 102 Chapter 4 Reference Select Output Units You can choose to have ALOHA output displayed in either B English units such as pounds yards and miles metric units such as grams kilograms meters and kilometers Click either English units or Metric units ALOHA will display its predictions 1 the type of units English or metric that you choose It will display input values in the units that you selected when you entered the values For example if you entered wind speed in miles per hour an English unit you will see wind speed displayed in
209. ture for you You must also enter a value for maximum puddle area or diameter If there are no barriers to prevent a puddle from spreading click Unknown If there is a barrier to liquid flow such as a containment or diked area then type the approximate diameter of the barrier or area that it encloses Select units then click OK Puddle Parameters Select ground type amp Default Concrete 2 Sandy Input ground temperature Use air temperature select this if unknown 9 Ground temperature is deg WF OC Input maximum puddle diameter or area Unknown O Maximum diameter is I yds Maximum area 2 meters Figure 4 42 Puddle input 92 Chapter 4 Reference Pipe Choose Pipe from the Source submenu under the SetUp menu when you wish to use ALOHA to model the release of gas from a leaking gas pipeline The pipe must contain only gas ALOHA cannot model the release of liquid from a pipeline You can use ALOHA to model two kinds of gas pipeline leak scenarios a pipeline connected to a very large infinite tank source reservoir so that gas escapes from the broken end of the pipeline at a constant rate for an indefinite period of time A section of pipeline is closed off at the unbroken end for example by a shut off valve The pressure within this section of pipe drops as gas 15 released the release rate slows over time and the release continues only until the finite length of pipe 1s emptied
210. u specify during the hour after a chemical release begins Dose information is difficult to interpret because the effects of most toxic chemicals on people are poorly understood Avoid using this graph if you don t know the dose exponent to use for a particular chemical or can t consult with a specialist who can advise you on the correct exponent to use and help you to interpret ALOHA s results Instead use information from ALOHA s footprint and concentration plots and your own knowledge of a chemical to make response decisions ALOHA s definition of dose ALOHA defines dose as the concentration of pollutant gas at a given location to which people may be exposed taken to a power multiplied by the period of time that the pollutant 15 present Some researchers refer to this quantity as toxic load The exact equation used in ALOHA 15 dose 0 where C is the concentration computed by ALOHA is the period of exposure and n is the dose exponent The power n to which the concentration is taken is intended to account for the particular effects of a chemical as estimated from toxicological data When 7 is 1 0 the result 1s equivalent to what many people call exposure 109 Chapter 4 Reference Adjusting the dose exponent To adjust ALOHA s dose exponent n choose Computational from the SetUp menu check the section on the Computational menu item to learn more about this Obtaining a dose graph To vi
211. uilding s air exchange rate the number of times per hour that the total air volume within the building is replaced type this number next to No of air changes You also can adjust this number to compare the effects of different air exchange rates on indoor infiltration of a pollutant gas 49 Chapter 4 Reference When you specify single or double storied building type you also must indicate whether the building is sheltered or unsheltered Pollutant gases infiltrate more slowly into sheltered than unsheltered buildings of the same type Below is a decision aid for choosing between sheltered or unsheltered surroundings If the buildings Click surrounded by trees or Sheltered surroundings other buildings in the direction from which the chemical cloud will be coming re in an open space with Unsheltered surroundings nothing near them 1f you are unsure Unsheltered surroundings Date amp Time Choose Date amp Time from the SiteData menu to specify the date and time for ALOHA to use as the starting time of your scenario You may choose either to enter a specific time or to have ALOHA take the time from your computer s internal clock Set your computer s clock to the local time where a release has occurred when you use the internal clock option For example if you are running ALOHA in Seattle for an incident taking place in Miami set your clock to the current Miami time Date and Time Options You ca
212. ulations unless you are trained in toxicology or can ask a toxicologist to assist you Exiting Quitting ALOHA 1 When you ve completed your work with ALOHA just choose Exit from the File menu if you re using Windows or Quit from the File menu if you re using a Macintosh You can also first save any ALOHA scenario either in an archive format or as a file you can reopen later in ALOHA check the section of the Reference chapter describing the File menu to learn how to do this 37 Chapter 3 Learning the Basics 38 Chapter 4 Reference Refer to this chapter for detailed explanations of ALOHA program operation features and menu items The sections of this chapter correspond to ALOHA s menus The File and Edit menus With several important exceptions described below the File and Edit menus work the same way in ALOHA as they do in other programs The File Menu Close Save Save As Close sare db ave Hs Print Print All Page Setup Print Setup Print Printall Figure 4 1 ALOHA s File menu in Windows left and on a Macintosh right New Choose New to clear all information about a scenario from ALOHA before beginning a new scenario When you choose this menu item you have the option of saving your old scenario before clearing ALOHA Open Choose Open to open an ALOHA save file which you previously created using the Save or Save As menu item see below Whenever you open
213. ull Circular Opening Diameter inches Opening iz 1 29 feet from tank bottom Release Duration 31 minutes Computed Release Rate 178 pounds min Average Sustained Release Rate 169 pounds min averaged over a minute or more Total Amount Released 827 pounds Hote The chemical escaped as a mixture of gas and aerosol twa phase flow 8 The Text Summary window 15 like a blackboard you can check its contents at any time to verify that you ve entered correct values into ALOHA or to review ALOHA s results If your Text Summary window doesn t look like the one above revise any incorrect information by choosing the appropriate menu item then modifying the information that you entered For example if you indicated that the building is sheltered rather than unsheltered choose Building Type from the SiteData menu again click Unsheltered surroundings then click OK When you are sure that the Text Summary information 1s correct you re ready to move on to the next steps 30 Chapter 3 Learning the Basics Checking the Computational Setting Unless you specifically change its default setting ALOHA uses information about the properties of the chemical and the amount of chemical released to choose whether to make Gaussian or heavy gas dispersion computations Check to be sure that ALOHA is set to this default Select Computational from the SetUp menu Chemical Atmospheric P SOurce Computatio
214. und temperature is deg amp F OC Input maximum puddle diameter i Unknown O Maximum diameter is aft yds O meters Cancel The source strength information that you have entered and the results of ALOHA s source strength calculations appear in the Text Summary ALOHA estimates that the release of vapor into the atmosphere lasts for about 44 minutes and that the maximum amount of vapor released at any one time is about 91 pounds per minute this is the Maximum Computed Release Rate Expect the maximum computed release rate to correspond to the time when the benzene puddle surface is the greatest 128 Chapter 5 Examples Text Summary SOURCE STRENGTH INFORMATION Leak from hole in vertical cylindrical tank Tank Diameter 4 feet Tank Length 3 32 feet Tank Yolume 500 gal loans Tank contains liquid Internal Temperature 80 F Chemical Mass in Tank 1 22 tons Tank iz 100 full Circular Opening Diameter inches Opening is 10 inches from tank bottom Soil Type Default Ground Temp equal to ambient Puddle Diameter Unknown Release Duration 44 minutes Max Computed Release Rate 90 7 pounds min Average Sustained Release Rate 80 5 pounds min Caveraged over a minute or mare Total Amount Released 3 062 pounds Mote The chemical escaped as a liquid and formed an evaporating puddle 8 Toview the source strength graph select Source Strength from the Display menu Display Tile Windows Stack Windows
215. ur map 167 Chapter 6 Troubleshooting My computer crashed while I had an delete a footprint remaining on a map after a ALOHA footprint plotted on a map crash delete the entire ALOHA layer open the in MARPLOT Windows or map again in MARPLOT choose Layer List Macintosh Now whenever reopen from MARPLOT s List menu click on the the map I see the old footprint on the lock icon for the ALOHA layer to unlock the map and I can t delete it layer then click Delete while the ALOHA MARPLOT tells me that the ALOHA layer 15 highlighted in the layer list A new layer is locked ALOHA layer will be added next time you plot a footprint on the map When I save an ALOHA file in the Spy files can only be opened by AlohaSpy Spy format I can t open it from ALOHA can t open or use these files they re ALOHA meant to serve as archive files Save scenarios that you wish to reopen in ALOHA as ALOHA save files check the section of this manual describing the File menu to learn more about saving files Pm running MARPLOT with Whenever you bring MARPLOT forward so ALOHA in Windows or on a that its windows are in front of ALOHA s Macintosh while I respond to a spill windows you ll halt data transmission from I m also using a SAM station to the SAM to ALOHA Bring ALOHA forward collect weather data had a to update the weather data and footprint footprint displayed in MARPLOT for the last half hour I know the wind has s
216. urope Africa and Asia Click the appropriate button to indicate whether standard or daylight savings time is currently in effect at this location ALOHA automatically switches the time setting for U S cities from Standard to Daylight Savings Time using the date on your computer s clock but it does not automatically make this change for locations outside the U S Be sure to change the time setting manually whenever time at a non U S location switches between daylight savings and standard time m Foreign Location Input E Country name Offset from local STANDARD time to GMT hours Is current model time standard or daylight savings time 2 Standard Time Daylight Savings Time Figure 4 10 Adding a foreign country Once you have entered all necessary information about a new location click OK Click Select to add the location to the library Click Cancel only if you decide not to add the location to the library In the example below Hamilton Bermuda has been added to the location index Location Information HAMILTON BERMUDA e HAMLIN TEHAS a Select HAMMOND INDIANA i Figure 4 11 Location index with a non U S city Modifying a location You can modify the description of a city or other location in the city library You can modify the location name its approximate latitude and longitude its average elevation above sea level the state territory or country where it exists the l
217. urrent weather conditions into ALOHA either manually by typing in values for wind speed air temperature and other weather factors or by connecting your computer to a portable meteorological station called a Station for Atmospheric Measurement or SAM ALOHA uses the information that you enter to account for the main processes that move and disperse a pollutant cloud within the atmosphere These include atmospheric heating and mechanical stirring low level inversions wind speed and direction ground roughness and air temperature Lhemical Atmospheric b Source 2 Computational Figure 4 20 ALOHA s Atmospheric menu User Input 35H SAM Station User Input In the SetUp menu point to Atmospheric then click User Input to manually enter the following information about conditions in the vicinity of an accidental release wind speed and direction wind measurement height ground roughness cloud cover air temperature atmospheric stability class inversion height if an inversion exists and relative humidity ALOHA assumes that weather conditions remain constant throughout the area downwind of a chemical release through which the pollutant cloud may travel For this reason use values that best represent conditions throughout this area If weather conditions change update this information and run ALOHA again Wind speed direction and measurement height ALOHA needs to know the wind speed and
218. utomatically be displayed If it 1s not then select Go to View from MARPLOT s View menu Chapter S Examples Go to View Go to Previous View Save Current View 3U Edit Views Set Reference View Show Reference View zoom In 96 Zoom Out 3 Center On Focus Point 3T Marked Point Set Scale 388 to Lat Long 3 Click to highlight entire map PRINCE WILLIAM COUNTY VA then click Go To View E bn tn E Find Find Mani shared sips sentire map gt PRINCE WILLIAM COUNTY V sort by name 3 sort by map XE resize map window to fit view The PRINCE WILLIAM COUNTY map will then be displayed PRINCE WILLIAM COUNT E B DIZ Focus Pt 38 50 S4 M 7v 35 22 H l in 5 9 mi z 159 Chapter 5 Examples 4 Now you ll search on the map for the location where the accident occurred Choose Search from the List menu Show Search Collection 3G Copy fo Search Caled tion Layer List aeL Map List 36M 5 To search for Gallerher Road 1 type GALL in the have names that start with box Make sure that 2 Individual Layer has been selected in the menu just below the Layer s to search heading then 3 select Roads from the menu below that Check 4 to be sure that Maps in View is selected in the menu below the Map s to search heading When the dialog box on your sc
219. utomatically saves menus that other programs have placed in its Sharing menu These menus automatically appear in ALOHA s Sharing menu the next time ALOHA is run When you choose an item from a menu that belongs to a program that is not currently running ALOHA will start that program so that it can carry out the specified action You can delete a menu from the Sharing menu if you wish you might want to do so if you remove a program from your hard drive To do this choose Edit Shared Menus from the Sharing menu select the menu that you wish to delete then click Delete ALOHA automatically installs menus for the Macintosh and Windows versions of CAMEO and the CAMEO mapping program MARPLOT in the Sharing menu Items in the Sharing Menu Two items always appear in the Sharing menu whether or not ALOHA is sharing information with another program Choose About Shared Menus to view online help information about information sharing between ALOHA and other programs Choose Edit Shared Menus to delete a program s menu from the Sharing menu you might want to delete a program s menu if you have removed that program from your hard drive Select the menu that you wish to delete then click Delete The CAMEO menu When CAMEO is running on a Macintosh or in Windows a CAMEO menu appears in ALOHA s Sharing menu The CAMEO menu in ALOHA s Sharing menu contains three items Choose Help to learn about information sharing between ALOHA and CA
220. ve high in the center where concentration 1s highest and lower on the sides where concentration 1s lower Right at the point of a release the pollutant gas concentration 1s very high and the gas has not diffused very far in the crosswind and upward directions so a graph of concentration 1n a crosswind slice of the cloud close to the source looks like a spike As the pollutant cloud drifts farther downwind it spreads out and the bell shape becomes wider and flatter Chapter 1 Welcome to ALOHA 100 80 60 40 CONCENTRATION ppm 20 0 CROSSWIND DISTANCE Figure 1 7 Gaussian distribution K owt CONCENTRATION CROSSWIND SOURCE of SPILL Figure 1 8 Gaussian spread Heavy gases When a gas that is heavier than air 15 released it initially behaves very differently from a neutrally buoyant gas The heavy gas will first slump or sink because it is heavier than the surrounding air As the gas cloud moves downwind gravity makes it spread this can cause some of the vapor to travel upwind of its release point Farther downwind as the cloud becomes more diluted and its density approaches that of air 1t begins behaving like a neutrally buoyant gas This takes place when the concentration of heavy gas in the surrounding air drops below about 1 percent For many small releases this will occur in the first few yards meters For large releases this may happen much further downwind Chapte
221. vel Be sure to place it at a location such as an open field parking lot or clearing where the wind is not affected by obstacles such as trees buildings hills or other obstacles Avoid placing a SAM the lee of buildings vehicles or other obstacles to wind flow where wind speed and direction may be very different from the rest of the area Place the SAM upwind of the source of a pollutant gas release so that you will not need to decontaminate it after use Choosing the correct port for receiving SAM data SAM data 1s transmitted to ALOHA through your computer s serial port On an Windows computer this is the COMI COM2 port On a Macintosh computer this is the modem port labeled with a telephone handset icon Choosing a radio frequency If you are using ALOHA within the U S you ll find that the rules for assigning and using radio frequencies are specific to your locality no national guidelines exist Check with the manufacturer of your SAM or with the government authority in your area that assigns radio frequencies if you want to be assigned a frequency that you can use to transmit SAM information to ALOHA This authority could be a local state or Federal agency depending on your location User Input for SH Unit Inversion Height Options are Mn inversion feet O Inversion present Height is C meters Ground Roughness is Open Country Coin Input roughness 20 5 0 input
222. w information from the SAM However any data received while ALOHA makes source strength and dispersion computations will be lost ALOHA does not place a limit on the amount of data you may archive To stop data archiving choose End Archive Data from the SAM Options menu You can then open and view the file in any word processing program To view the most recently transmitted SAM data without interrupting data archiving select either Raw Data or Processed Data from the SAM Options menu Data are arranged in columns and rows within the archive file The first three lines in the file contain an explanation of units and the date and time when the data were collected The fourth line contains the column headings as follows Hr Min Sec ID mW S mDir SigTh mTemp 1W S iDir 1Temp BatVol 73 Chapter 4 Reference where Hr hours Min minutes Sec seconds ID station ID mW S vector mean wind speed in meters per second mDir mean direction in degrees true Sigh theta standard deviation of the wind direction in degrees mTemp mean air temperature in degrees Celsius 1W S instantaneous wind speed in meters per second iDir instantaneous direction in degrees true ilemp instantaneous temperature in degrees Celsius BatVol instantaneous SAM battery voltage in volts Raw Data Choose Raw Data from the SAM Options menu to examine the most recently transmitted unprocessed SAM data ALOHA displays unprocessed SAM data in the
223. wind A cloud of gas that is denser or heavier than air called a heavy gas can also spread upwind to a small extent ALOHA models the dispersion of a cloud of pollutant gas in the atmosphere and displays a diagram that shows an overhead view of the area in which it predicts that gas concentrations will reach hazardous levels This diagram is called the cloud s footprint To obtain a footprint plot you first must identify a threshold concentration of an airborne pollutant usually the concentration above which the gas may pose a hazard to people This value 1s called the Level of Concern The footprint represents the area within which the ground level concentration of a pollutant gas 1s predicted to exceed your Level of Concern LOC at some time after a release begins There are really two separate dispersion models in ALOHA Gaussian and heavy gas The Gaussian equation ALOHA uses the Gaussian model to predict how gases that are about as buoyant as air will disperse 1n the atmosphere Such neutrally buoyant gases have about the same density as air According to this model wind and atmospheric turbulence are the forces that move the molecules of a released gas through the air so as an escaped cloud is blown downwind turbulent mixing causes it to spread out in the crosswind and upward directions According to the Gaussian model a graph of gas concentration within any crosswind slice of a moving pollutant cloud looks like a bell shaped cur
224. with dry or humid air water other chemicals or even themselves Because of these chemical reactions the chemical that disperses downwind might be very different from the chemical that originally escaped from containment In some cases this difference may be substantial enough to make ALOHA s dispersion predictions inaccurate For example if aluminum phosphide escapes from containment and comes in contact with water the reaction between the water and aluminum phosphide produces phosphine gas It is the phosphine 14 Chapter 1 Welcome to ALOHA rather than the aluminum phosphide that escapes into the atmosphere If you respond to such an accident and wish to use ALOHA to obtain a footprint estimate you need to estimate how rapidly phosphine 15 being generated from the reaction between water and aluminum phosphide and you need to model the incident in ALOHA as a release of phosphine rather than aluminum phosphide particulates ALOHA does not account for the processes that affect dispersion of particulates including radioactive particles Solutions and mixtures ALOHA is designed to model the release and dispersion of pure chemicals only the property information in its chemical library is not valid for chemicals in solution or for mixtures of chemicals It s difficult for any model to correctly predict the behavior of a solution or a mixture of chemicals because it s difficult to accurately predict chemical properties such as

1 Welcome to ALOHA - DISASTER info DESASTRES

Contents

Download Pdf Manuals

Related Search

Related Contents