Document 3LzgqX2R6yB3vr7j98gJ2yzJ

AR226-2655 -& 01 AR226-2655 ISC Modeling Methodology and Results Introduction This report summarizes dispersion modeling that was completed for the DuPont Washington Works facility to demonstrate that the emission limits included in the form R13 permits (815E, 1353B, 1953B, and 2365C) comply with the C-8 assessment oftoxicity (CAT) recommended airborne screening level of 1.0 ug/m3 at the property line fence. Compared to the modeling report submitted in October, 2003, this report incorporates several revisions to stack parameters that were the result of stack testing, and the refinement ofUTM coordinates. Emission Source Information Table 1 shows the stack parameters used in the model as well as the locations and emission rates for each emission point. Note that two emission points from previous modeling (242 and 232) have been removed from the model and emission point 231 has been relocated. Modeling Methodology Dispersion and deposition modeling was performed using EPA's Industrial Source Complex 3 Model (ISC3), version 02035. 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 selected in the model. The APFO emission sources were evaluated for downwash effects from surrounding buildings. EPA's Building Profile and Input Program (BPIP) was used to provide wind direction specific building parameters. All buildings on the site were evaluated to determine if they could potentially impact the stack by causing building downwash effects. Plot plans showing the location of buildings included in the model are shown in Figures 1 and 2. (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 using the "highest" method to assign an elevation to each receptor. One year ofon-site meteorological data (1996) was analyzed. Concurrent upper air data from Wilmington, OH was used to calculate twice daily mixing depths. Missing data and measured wind speeds of 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. C:\c8\pennits\2004 Permit Ammendments.doc Modeling Results An averaging tim^ofone year was used to determine the annual average ground level concentrations over the entire receptor grid. A contour plot of these concentrations is shown in Figure 3. The maximum annual average ground-level concentration predicted by the model was 0.521 |lg/m3. This concentration occurred at a receptor located on the plant fenceline north of the plant. Electronic Files This report and the following electronic files were transmitted by email to Chris Arrington at WVDAQ on April 30, 2004: ISC Input file ISC Output file BPIP Input file BPIP Output file Meteorological Data file newjpermit_2004.dat new_permit_2004.1st new_permit_2004.bpi new_permit_2004.bpo pkbiln96.asc Permit Vent ID T61ZCE T61XE T61YE T5HGE T5HIE C2DTE C1FSE C1FKE C3HP Table 1 Stack Parameters Reg 29 Reg 29 Zone 17 Unit ID TIV, E&F TIV TIF THG THI CDT CFS CFK CHP Vent ID 699 697 694 658 652 231 274 268 276 UTM-E 442098 442128 442101 441928 441926 441941 441790 441774 441842 UTM-N 4346843 4346829 4346815 4346757 4346758 4346758 4346744 4346753 4346772 Stack Diameter ft 4 2.25 1.67 1.5 0.88 1.00 0.65 0.27 1.5 Stack Height ft Stack Flow ACFM Stack Velocity ft/sec Stack Temp F 170 45 45 63 64 100 110 72.5 75 12,000 2,000 344 6,478 4,031 1,200 . 667 100 5,000 15.9 8.4 2.6 61.1 111.7 25.5 33.5 28.7 47.2 124 176 112 142 139 53 min 41 min 110 amb Permit Annual C-8 Emission Ib/yr 3,258 3 3 94 71 2,753 1,327 300 0.16 R022EEF6 R022EEF86 R022EEF87 R022EEF89 (Research) (Research) (Research) (Research) 442086 4346624 2.5 442069 4346627 2 442058 4346634 2 442063 4346635 2 47 8836 49 7540 49 1885 49 3770 80 12 80 0.3 80 3 80 0.6 4346900-^ 4346800-^ 4346700-^ 4346600-^ 4346500441600 441700 441800 441900 442000 Figure I - Building Plot Plan 442100 4346850 4346800---- 4346750---- 4346700 441850 441900 441950 442000 442050 Figure 2 Building 162/163 Detail Figure 3 Predicted Annual Average Concentrations (p,g/m3)