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320 PETROLEUM OONVAMINATEO SOILS IEST1MATES FOR HYDROCARBON VAPOR EMISSIONS 321 1V. AIR DISPERSION MODELING stud} Included gradual plume rise,buoyancy-induced dispersion,and stack down- wash The source was assumed to be located in an urban env Ironrnenl IV 7 Model Description The "box model" illustrated in Figure 14 was used to predict conservative ambient cuncenlration estimates for receptors located on the downwind edge of The EPA-recommended Industrial Source Complex (ISC) Model, %,,hich can the area sources considered in this chapter It was assumed that vapors within be used to predict ambient concenirattons from both stack and arca sources for lite box were "well-mixed," and the height of the box, S, was set to be equal receptors located at least 100 m from a sourer, %as used to perform the err dis- to human breathing zone height — 2 in Given the wind speed ,breathing persion modeling For this analysts,a polar-coordinate grid was generated with zone height S, length of emission source parallel to the wind direction L, and receptors located on concentric rings at radii of 100 ni, 300 m, 500 m, 700 m, emissions flux XF,, then the ambient concentration C, ,.b. is and 1000 in from each source Thtrty-six receptors, at 10 degree intervals, wereC ff,L (�4) located on each ring, snaking a total of 180 receptors The ISC model employs iiib r S standard gaussian dispersion algorithms to calculate the hourly concentration at cacti receptor If an entire year of meteorological data Is Input to the model,then IV.2 ISC Model Predictions a full year of hourly concentrations can be calculated for each receptor These hourly values can then be averaged to give an annual average for each receptor, ISC model predictions are summarized in Table 3. Each scenario modeled is or they can be sorted and ranked to give inaxinsnni F. 8-, and 24-h averages, described bredly below For this modeling,irleteorological data from Long Beach,California for the year 1964 was used Other required mtdeoralogical parameters include wind speed Table 3 Air Dispersion Modeling Results and direction, ambient temperature, mixing height, and stability class For area Beene vapor Contvawlons 'l sources, the size and height of the release a% well as the einission flux are re- Reaudpistsncs quired input parameters For stack releases, the Stack height and diameter and Sornarto 0uratim 100 m 300 m 34n m 100 m 100D m sox Model exit-,as velocity and temperature are needed Modeling options selected for this i excaealwrr" 039 0A77 004 OD3 002 24 (70yaveTage) 3d <001101 <0OD01 <00001 <00001 <00001 <001 2 M8vallo11" 015 003 002 001 001 42 170 y average) 341 <00001 <0 DON <0 0001 <O D001 <00001 <001 3 sod pleb 75 is 079 0 S7 041 4110 {TO i average) 3x8 h <0001 <00001 <0 DWI <OA00I <OODD1 <001 4 venting unlreatedvaprs" 66 09 038 02 011 NA r� ^� (701 average) 160 d 045 <0 01 <0 01 <0 01 <0 001 NA � < � 3 venting,unhealed v>Ap e D D8 001 <001 <001 <001 RA (70yaverage) 180d <0WOt <00001 <0 DWI <00001 <OOWl 11A 6 verging lresled%apanc 012 0im 0112 001 <001 NA 1110- {70 y average) 180 d <OOOt <90D1 <0001 <0A001 <O 0001 NA 7 venting healed vapors` <001 <OOOF <0001 <DAol <000i NA (70)average) 1ODd <OODOi <0OD0D1 <OWD01 <00=1 <00DD01 NA 8 trw4quld pumping` <0001 <0 DDI <0001 <0001 <0001 NA (70 y averege) 60d <O D0041 <0 DD001 <0 09001 <0 DOM <OODDOI RA 9 gwohri"eturaled GW puW 060 008 D05 002 <001 NA (70 y emeragel 6 y 007 <11)01 <001 <0 01 <O wl NA 10 1ppm benreneGthfgrirtlp° 00; <001 <001 <DWI <0001 NA 1 (70 y average) 6 y <001 <D 001 <0001 <00001 <0 0001 NA 11 alr4trlppei gas sal Of 12 025 DID 006 0 03 NA 170yavemp) Si 004 002 <0 Of `041 `001 t0A % s>,if;3 x> 12 an stripper I ppm Wrims Gff 007 001 <0 D1 <001 <021 14A t r=y1 .t ry j--+ ; j} {, `c ;, (70 y average) 5 y <001 <0 001 <0001 <O ODI <0001 NA { ` ��i-5` 1 13 boned soilsleflnplaoe 0044 <0 01 <001 `001 <DOi 09� (70yaverage) 70y 0444 <001 <001 <001 <001 094 Contaminated Soil 'peak 24hncetraAfan mak&h caxenrrarron `annual average euncenlral.ort i, Ftgute 14 Bax model schematic 4nrndnmm 1wnq neo M Jnr vIod i nr Md� A unrn.•r Poi qrn ati"111 I-P