Document 82xLvGaZ0myVyYOMqENVZ95Xd

AR226-2281 4/ 17/02 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 used are those that were available as o f 12/17/01, and are identical to those submitted pursuant to 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 o f the EPA 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 CFRPart 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. All buildings on the sit were evaluated to determine if they could potentially impact the stack by causing building downwash effects. A plot plan showing the location o f 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 Water Association well field. A USGS topographical map was used to identify the EID676755 4/ 17/02 general area of the watershed (Figure 2), and a receptor grid with 100 meter spacing was placed within this watershed (Figure 3). One year of on-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 o f less than 1 m/s were treated consistent with the recommendations made in EPA's On site Meteorological Program Guidance for Regulatory Modeling. An anemometer height of 10 meters was used for the modeling. Modeling Results An averaging time o f 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 pg/m3 Particle Phase: Maximum Dry Deposition Rate = 0.1345 g/m2/yr Maximum Wet Deposition Rate = 0.0479 g/m2/yr Maximum Total Deposition Rate = 0.1824 g/m2/yr Vapor Phase: Maximum Wet Deposition Rate = 0.0085 g/m2/yr The maximum ground-level concentration and all o f the maximum deposition rates were predicted to occur at the same receptor (442135.47E, 4346899N), which is located on the plant fenceline north o f the plant. The maximum annual ground-level concentration predicted to occur in areas where people may reside in the community is approximately 0.8 pg/m3. Additionally, a 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 rates 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 EID676756 4/ 17/02 E ID 676757 1823A 815D 815D 1353A Pre-Existing 614A 614A 781 1953 2365A Semiworks Application Semiworks Application Semiworks Application Semiworks Application T7IME T6IFCE T6IZCE 164-5E 164-2E 163-E-26 163-E-ll 163-E-33 242 C1FSE R022EEF6 R022EEF86 R022EEF87 R022EEF89 Table 1 Stack Parameters 1. VjfiS ti^ l -:Zfne:.l-.7;:;,l;i;lBllli i i-iemh: I.Vmtetcr ' W m . ,\ `7 --*4-Vf S ticky ^ l a c k :J | ^iTM Vei&C'ty' 'Temperature' m 662 442025 4346847 150 1.33 3,349 40.2 644 442084 4346835 59 1.5 18,000 169.8 699 442091 4346836 63 18-1 ft 18000" 21,2b 652 441920 4346767 70 1.96 9,800 54.1 658 441923 4346756 68 1.63 2,800 22.4 231 441952 4346776 93 0.67 500 23.6 232 441953 4346766 81 0.67 600 28.4 216 441960 4346788 60 1.3 2,750 34.5 242 441954 4346741 114.5 0.5 1,250 106.1 274 441787 4346744 110 0.69 1,000 44.6 442086 4346624 47 2.5 8836 30.0 442069 4346627 49 2.0 7540 40.0 442058 4346634 . 49 2.0 1885 10.0 442063 4346635 49 2.0 3770 20.0 172 111 111 200 300 130 130 158 200 255 80 80 80 80 "Vent ID T61ZCE consists of 18 one-foot diameter vents. The flow rate given is the total for all 18 vents. bThe velocity listed is the velocity calculated for one individual vent. EID676758 4/ 17/02 ' " T>*SrHtrtl4it li S ll T7IME T6EFCE ,, T6IZCE 164-5E 164-2E 163-E-26 163-E-ll 163-E-33 242 C1FSE R022EEF6 R022EEF86 R022EEF87 R022EEF89 662 644 699 652 658 231 232 216 242 274 Table 2 Emission Information ii 'illiiililillii 111! fiBsHilHrl 0i 0.54 0.46 0.9 0.1 0.9 0.1 0.9 0.1 0.11 0.89 0.09 0.91 01 0.9 0.1 0.03 0.97 10 10 10 10 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 0 0.0925 0 4.75E-05 1.14E-04 0.0453 .0.0613 0 0.00505 0.0755 0 0 0 O' V a t/ Table 3 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/cm0 2.2 . 2.2 2.2 2.2 2.2 Scavengin i Coefficients Liquid Frozen Precipitation Precipitation (s'Vmm-h'1) (s'Vmm-h'1) 1.2x10"* ixTff5 5x10'S 1.67x10'3 4x10_i 1.33xl0's 1.3x1O'4 4.33X10* 2.8X10-4 9.33x10'* Vapor Phase: Liquid Scavenging Coefficient (s'Vmm-h'1) = 6.4x10*6 Frozen Scavenging Coefficient (s'Vmm-h1) = 6.4x10 s Calculations of Vapor Scavenging Coefficient: - vapor scavenging coefficients are presented in the consent order submittal as a list o f values for different rainfall intensities - the vapor scavenging coefficient that is entered into the ISC model is in units o f s'Vtnm-h'1, 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 ------x - ^ --= 6.4x10_s -- = 6.4xl(Ts -- - hr 3600s 1mm smm m m hr E I D 676759 EID676760 E ID 676761 4/ 17/02 Figure 1 - Building Plot Plan i I TcO o to EID676762 //7/02 4/ 17/02 EID676763 4348500 C8 2000 Actual Emissions Annual Average Vapor Concentrations (ug/m3) 4/ 17/02 EID676764 4348000- 4347500 4347000- 4346501 4346000 440000 440500 441000 441500 442000 442500 443000 443500 Figure 4 Maximum Ground-Level Concentrations 444000 444500 **.fel- ' IAMil CT5ot2al00D0eApocstutlaial oEmigttems2,loiynta\Partteutaie PftMt* & u I i t j i IS S /.' S* 3*1 Figure 5 - Particle Phase Total Deposition Rates v . [ 4/ 17/02 EID676765 ''uF'r.V.'"'*'K ; CONC. OSPOS. DDP. WDKP, ' RURAL. ELCV. DPAULT. ! ORYOPL, WJTTDPL ! :-162 DCPOS WAA 0.1824 ' >Iti ` j g/m*`2 1/19/200? ' P P O -B C T N A M G . C8 2000 Actual Em issions Vnpor Phase Wet Deposition (g/m2/yr) 4/ 17/02 EID676766 W CCUISO OPTICNS CONC, WDEP, RURAL, ELEV, DFAULT, WETDPL j | ngCCP'-ORS 4629 CKilPvjVTYPf WDEP M AX 0.00845 j .li> i j g/m,42 `SC'A S flM O O Vi liy Scttwa OAT 6 1/19/2002 Ofc^ _j0.5km PKCJC :>noT no r. \iaovtpW;VWAhlNGT::iN VVOHK?-,AC''W I'jvAN'X'-OAi.t.. Figure 6 - Vapor Phase Wet Deposition Rates