Document 4Jp9Om6GNVMv7oenKLOBZO5Mx
AR226-2262
ISC Modeling Methodology and Results
Emission Source Information
The ISC3 model was used to calculate ambient ground-level vapor concentrations and deposition rates for year 2000 actual C8 emissions from the Washington Works site. Table 1 shows the stack parameters used in the model for each emission point. Table 2 shows the emission rates used. (The stack parameters and emission rates are identical to those submitted under Consent Order GWR-2001-019). Since the C8 emissions are partitioned between the vapor and particle phases, deposition runs were completed by modeling each phase separately. (Modeling runs to determine ground-level concentrations were based on the total emissions.)
Deposition modeling requires particle size distribution information and scavenging coefficients for each phase of emissions (vapor and particle). The size distribution information used in the modeling for the particle phase was obtained from testing at the Washington Works site. The scavenging coefficients used for the particle phase were obtained from Figure 1-11 of the BPA ISC3 User's Guide. The vapor phase scavenging coefficients used were based on calculations by DuPont which were submitted under the Consent Order. This data shows the calculated vapor scavenging coefficient based on rain intensity. Since only one value of the scavenging coefficient can be entered into the ISC3 model, the largest scavenging coefficient was chosen to ensure that the model predictions were conservative. Table 3 shows the gas and particle data used in the model and, additionally, shows the basis for the vapor scavenging coefficient used in the model.
Modeling Methodology
Dispersion and deposition modeling was performed using the Industrial Source Complex 3 Model (ISC3), version 00101, provided by Lakes Environmental. All modeling was done in accordance with the procedures in EPA's Guideline on air Quality Models (40 CFR Part 51, Appendix W). The EPA regulatory default options and rural dispersion coefficients were used in the model.
The C8 emission sources were evaluated for downwash effects from surrounding buildings. The Lakes Environmental BPIP View model was used to provide wind direction specific building
parameters. AH buildings on the site were evaluated to determine if they could potentially impact the stack by causing building downwash effects. A plot plan showing the location of buildings
included in the model is shown in Figure 1. (The buildings included in the model are identical to the list submitted under Consent Order GWR-2001-019).
A 100-meter grid extending out 4,000 meters from the source was used. In addition, discrete receptors with 100-meter spacing were placed on the plant property line. Terrain elevations were imported from electronic files obtained from the U.S. Geological Survey.
An additional receptor grid was used to determine deposition to the watershed for the Little Hocking wells. A USGS topographical map was used to identify the general area of the
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watershed (Figure 2), and a receptor grid with 100 meter spacing was placed within this watershed (Figure 3).
One year ofon-site meteorological data (1996) was analyzed. The data was processed by Trinity consultants, using Wilmington, Ohio for the upper air data. Missing data and measured wind speeds of less than 1 m/s were treated consistent with the recommendations made in EPA's Onsite Meteorological Program Guidance for Regulatory Modeling. An anemometer height of 10 meters was used for the modeling.
Modeling Results
An averaging time of one year was used to determine the annual average vapor concentrations and annual deposition rates over the entire receptor grid. A contour plot of the annual average vapor concentrations is shown in Figure 4. Contour plots of the total deposition rates for the particle and vapor phases are shown in Figures 5 and 6. The maximum off-site values predicted by the model were:
Maximum Annual Average Ground-Level Concentration = 2.806 ug/m3
Particle Phase: Maximum Dry Deposition Rate = 0.1345 g/n^/yr Maximum Wet Deposition Rate = 0.0479 g/n^/yr Maximum Total Deposition Rate = 0.1824 g/ro /yr
Vapor Phase: Maximum Wet Deposition Rate = 0.0085 g/n^/yr
The maximum ground-level concentration and all of the maximum deposition rates were predicted to occur at the same receptor (442135.47E, 4346899N), which is located on the plant fenceline north of the plant.
Additionally, 9 smaller receptor grid was used to determine the annual deposition rate to the Little Hocking well watershed. The model was run to calculate vapor and particle phase deposition rates for each receptor, which were then imported into a spreadsheet An average
deposition rate was calculated for all of the receptors and multiplied by the receptor grid area (2.57 km2) to get a total deposition per year over the entire watershed. The deposition amounts
calculated were:
Particle Phase:
Total Dry Deposition == 6,966 g/yr Total Wet Deposition = 12,484 g/yr Total Deposition = 19,450 g/yr
Vapor Phase:
Total Wet Deposition = 1642 g/yr
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Table 1 Stack Parameters
1
1823A 815D 815D
T7IME
662
T6IFCE
644
T6IZCE
699
1353A
164-5E
652
Pre-Existing
164-2E
658
614A
163-E-26
231
614A
163-E-11
232
781
163-E-33
216
1953
242
242
2365A
C1FSE
274
Semiworks Application R022EEF6
Semiworks Application R022EEF86
Semiworks Application R022EEF87
Semiworks Application R022EEF89
442025 442Q84 442091
441920 441923 441952 441953 441960 441954 441787 442086 442069 442058 442063
4346847 4346835 4346836
4346767 4346756 4346776 4346766 4346788 4346741 4346744 4346624 4346627 4346634 4346635
150 59 63
70 68 93 81 60 114.5 110 47 49 49 49
1.33 1,5
18-1ft
1,96 1.63 0.67 0.67 1.3 0.5 0,69 2.5 2,0 2.0 2.0
3,349 18,000 180002
9,800 2,800 500 600 2,750 1,250 1,000 8836 . 7540 1885 3770
"Vent ID T61ZCE consists of 18 one-foot diameter vents. The flow rate given is the total for all 18 vents. ''The velocity listed is the velocity calculated for one individual vent.
40,2 169.8 21.2''
54.1 22.4 23,6 28.4 34.5 -106.1 44.6 30.0 40.0 10,0 20.0
Table 2 Emission Information
T7IME
662
T6IFCE
644
- T6IZCE
699
164-5E
652
164-2E
658
163-E-26
231
163-E-ll
232
163-E-33
216
242
242
C1FSE
274
R022EEP6
R022EEP86
R022EEF87
R022EEF89
0 0.54 0.9 0.9 0.9 0.11 0.09
0
0.9 0.03
.1
1 1 1
1
0.46 0.1 0.1 0.1 0.89 0.91
1
0,1 0.97
0 0 0 0
0
13,977 0 33 79
3,541 4,680
0
3,510 5,414
12
0.3 3
0.6
0
0.2010 0
0.0005 0.0011 0.0509 0.0673
0
0.0505 0.0779 1.73E-04 4.32E-06 4.32E-05 8.63E-06
0
0.1086 0
4.27E-04 0.00102 0.00560 0.00606
0
0.0454 0.00234 1.73E-04 4.32E-06 4.32E-05 8.63E-06
Tables Gas & Particle, Data
Particle Phase:
Particle Diameter (microns)
0.2 0.4 0.75 2.0 4.0
Mass Fraction
0.538 0.267 0.035 0.127 0.033
Particle Density (g/cm3)
2.2 2.2 2.2 2.2 2.2
Scavengin ; Coefficients
Liquid
Frozen
Precipitation Precipitation (s^/mm-h1) (s^/mm-h'')
1.2xl0-4
4xl0-3
5X10'5
1.67xl0"3
4xl0"5
1.33x10-^
1.3xl0-4
4.33X10'3
2.8x10-4
9.33X10-3
Vapor Phase:
Liquid Scavenging Coefficient (s'Vmm-h'1) = Frozen Scavenging Coefficient (s^/mm-h'1) =
6.4x10^ 6.4x10'*
Calculations of Vapor Scavenging Coefficient: - vapor scavenging coefficients are presented in the consent order submittal as a list of values for
different rainfall intensities
- the vapor scavenging coefficient that is entered into the ISC model is in units ofs^/mm-h'', therefore the scavenging coefficients shown in the consent order must be adjusted to the proper units and then divided by the rainfall intensity
- to ensure that model predictions would be conservative, the scavenging coefficient based on a 1 mm/hr rain intensity was used, as this gives the largest value for input into the model
2.311xl0-2--x
hr
^.-^"L^riO-6
hr
-= 6.4x10-6
hr 3600s Imm
s-mm
mm-hr
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1346800-1 4346700H
4346S01H iOO
> k
s 1 6
r }
10 8
No rth
r '
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110
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180
0-.1is^aQ
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^ 162/163
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0 r
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0 L-'-
210
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-l-1S^6-8'T^-- OQO
167a,b ,c
r P
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L---3
^3.0^
r'--'^r^--
7'i.^-J
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4y 215a
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22 \
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r^3
C 3"---1
Z
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r-n
^L--^
------------------^--------------------j
441700
441800
441900
442000
442100
442200
Figure 1 -Building Plot Plan
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4348500-1
434800CH
4347500H 434700CH 4346500-1
4346000 441000
11111111 1111 i 1
1
1 1
4- + 4-4-4-4- 4- 4- 4- 4- 4- 4- 4- 4- 4-4-4-4-4-4-4-4-
4- + 4-4-4-4- 4- 4- 4- 4- 4- 4- 4- 4- 4-4-4-4-4-4-4-4-
+ + + + + + 4- 4- 4- 4- 4- 4- 4- 4- 4-4-4-4-4-4-4-4-
4- + + + + 4- 4- 4- 4- 4- 4- 4- 4- 4- 4-4-4-4-4-4-4-4-
+ + + + + + 4- 4- 4- 4- 4- 4- 4- 4- 4-4-4-4-4-4-4-4--4-4-4-4+ + + + + + 4- 4- 4- 4- 4- 4- 4- 4- 4-4-4-4-4-4-4-4--4-4-4-4-
+ + + + 4- + 4- 4- 4- 4- 4- 4- 4- 4- 4-4-4-4-4-4-4-4---1-4-4-4-
+ + + 4- 4- + 4- 4- 4- 4- 4-4-4- 4- 4-4-4-4-4-4-4-4-
+ + 4-4-4-4- 4- 4- 4- 4- 4- 4- 4- 4- 4-4-4-4-4-4-4-4-
+ + 4-4-4-4- 4- 4- 4- 4- 4- 4- 4- 4- 4-4-4-4-4-4-4-4-
^^ ^ -W
i^^ r^ ^
^ --1+-H+4-^--4--+-^--1r.--| r--i-^\ 4-^-t^-
, eb ^----+
-^H^-
441500
442000
442500
443000
443500
444000
Figure 3 Little Hocking Well Watershed Receptors Modeled
444500
4348500
C8 2000 Actual Emissions Annual Average Vapor Concentrations (ug/in3)
4348000-^
434750CH 4347000-1
4346500
4346000-4
440000
440500
441000
441500
442000
442500
443000
443500
444000
444
Figure 4 Maximum Ground-Level Concentrations
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. -.ir t." > I|JM;
Ce ZOOO Wral Erolsslw Fia'lleulatt Pha<-
To]j 0po.tlllan lglin2l'(!
COMC. DBPOS. Dffli.P. WD6 ., RURAL. EI.EV. DFAULT. ORyOPI... WFTnPl.
)tl
-.'t..H.l--; DRPOS
^
WAT,
11,182.1
, g/m"2
-A"i.
msaw.
Figure 5 - Particle Phase Total Deposition Rates
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Figure 6 - Vapor Phase Wet Deposition Rates
