Document pBJkgMmVae3kGnrbX8E5pwDoD

AR226-2623 Draft: Prepared at the Request of Council AR226-2623 Data and Modeling Procedures Dispersion modeling was performed using the U.S. EPA's Screen3 model. This model is a screening tool which gives predictions of ambient ground level concentrations for a single stack. Due to the assumptions made in the model, particularly those regarding meteorological conditions, these predictions will always be more conservative than predictions made by the ISC3 model. There is one source of APFO emissions on the Circleville site....describe emission source. The following parameters for this source were used in the model: Stack Height: 65 feet Diameter: 15.5 inches Temperature: 303F Flow Rate: 1927 acfm C8 Emission Rate: 130 kg/yr The C8 emission rate is based on mass balance estimates provided by the site. To determine the impacts of building downwash on dispersion from the stack, the Screen3 model uses only the dominant downwash structure as an input to the model. The dominant downwash structure can be found by first locating all buildings which have an area of influence encompassing the stack. The area of influence is defined by EPA as a distance of five times the lesser of the height or the maximum projected width of the building. Once all of the potential downwash structures are located, the dominant downwash structure is determined by calculating the GEP (Good Engineering Practice) stack height for each building. The building with the greatest GEP stack height is the building that should be included in the Screen3 model. The GEP stack height is calculated according to the following formula: H = h + 1.5L where H = GEP stack height h = building height L = lesser of the building height or maximum projected width The following table shows the buildings that were included in the downwash analysis and their respective GEP's: Max Projected Height Length Width Width GEP Building (ft) (ft) (ft) (ft) (ft) Coating 52 92 62 111 Powerhouse 35 67 25 72 EP* 60 50 50 71 Building 3 35 150 150 212 "This building has the highest GEP and was used in the model. Modeling Results 130 87.5 150 87.5 Using the above data the Screen3 model predicted a maximum off-site ground level concentration of 1.306 |ig/m3at a distance of 1500 feet from the source. This concentration is based on a 1-hour averaging time. To convert a Screen3 model result to an annual average, EPA guidance directs the user to multiply the predicted Screen3 concentration by a value of 0.05. This gives an annual average concentration of 0.065 (ig/m3. A copy of the Screen3 model output is attached. Draft: Prepared at the Request of Council 07/23/2004 *** SCREEN3 MODEL RUN *** *** VERSION DATED 96043 *** 13:25:05 CIRCLEVILLE APFO EMISSIONS ** 0 SIMPLE TERRAIN INPUTS: SOURCE TYPE = EMISSION RATE (G/S) = STACK HEIGHT (M) = STK INSIDE DIAM (M) = STK EXIT VELOCITY (M/S) = STK GAS EXIT TEMP (K) = AMBIENT AIR TEMP (K) = RECEPTOR HEIGHT (M) = URBAN/RURAL OPTION = BUILDING HEIGHT (M) = MIN HORIZ BLDG DIM (M) = MAX HORIZ BLDG DIM (M) - POINT 0.412200E- 19.8120 0.3937 7.4706 423.7056 293.0000 0.0000 RURAL 18.2880 15.2400 15.2400 THE REGULATORY (DEFAULT) MIXING HEIGHT OPTION WAS SELECTED. THE REGULATORY (DEFAULT) ANEMOMETER HEIGHT OF 10.0 METERS WAS ENTERED. STACK EXIT VELOCITY WAS CALCULATED FROM VOLUME FLOW RATE = 0.90944278 (M**3/S) BUOY. FLUX = 0.876 M**4/S**3; MOM. FLUX = 1.495 M**4/S**2. . *** FULL METEOROLOGY *** ********************************** *** SCREEN AUTOMATED DISTANCES *** ********************************** TERRAIN HEIGHT OF 0. M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES DIST (M) CONC U10M USTK MIX HT PLUME SIGMA SIGMA (UG/M**3) STAB (M/S) (M/S) (M) HT (M) Y (M) Z (M) DWASH 457. 500. 600. 700. 800. 900. 1000. 1100. 1200. 1300. 1400. 1500. 1.306 1.213 1.042 0.9144 0.8110 0.7331 0.6687 0.6146 0.5685 0.5286 0.4937 0.4629 6 1.0 1.5 10000.0 24.01 16.55 19.46 SS 6 1.0 1.5 10000.0 24.01 17.97 19.77 SS 6 1.0 1.5 10000.0 24.01 21.24 20.48 SS 6 1.0 1.5 10000.0 24.01 24.46 21.18 SS 6 1.0 1.5 10000.0 24.01 27.63 21.34 SS 6 1.0 1.5 10000.0 24.01 30.78 21.97 SS 6 1.0 1.5 10000.0 24.01 33.88 22.55 SS 6 1.0 - 1.5 10000.0 24.01 36.96 23.11 SS 6 1.0 1.5 10000.0 24.01 40.01 23.66 SS 6 1.0 1.5 10000.0 24.01 43.04 24.20 SS 6 1.0 1.5 10000.0 24.01 46.05 24.73 SS 6 1.0 1.5 10000.0 24.01 49.03 25.26 SS LXIMUM 1-HR CONCENTRATION AT OR BEYOND 457. M: 457. 1.306 6 1.0 1.5 10000.0 24.01 16.55 19.46 SS DWASH= MEANS NO CALC MADE (CONC = 0.0) DWASH=NO MEANS NO BUILDING DOWNWASH USED DWASH=HS MEANS HUBER-SNYDER DOWNWASH USED DWASH=SS MEANS SCHULMAN-SCIRE DOWNWASH USED DWASH=NA MEANS DOWNWASH NOT APPLICABLE, X<3*LB **************************************** . *** REGULATORY (Default) *** PERFORMING CAVITY CALCULATIONS WITH ORIGINAL SCREEN CAVITY MODEL (BRODE, 1988) Draft: Prepared at the Request of Council ** CAVITY CALCULATION _ *** CONC (UG/M**3) = 9.860 CRIT WS @10M (M/S) = 1.00 CRIT WS @ HS (M/S) = 1.15 DILUTION WS (M/S) = 1.00 CAVITY HT (M) = 28.19 CAVITY LENGTH (M) 25.71 ALONGWIND DIM (M) = 15.24 *** CAVITY CALCULATION _ 2 *** CONC (UG/M**3) = 9.860 CRIT WS @10M (M/S) = 1.00 CRIT WS @ HS (M/S) = 1.15 DILUTION WS (M/S) = 1.00 CAVITY HT (M) 28.19 CAVITY LENGTH (M) = 25.71 ALONGWIND DIM (M) = 15.24 **************************************** END OF CAVITY CALCULATIONS **************************************** *************************************** *** SUMMARY OF SCREEN MODEL RESULTS *** ************************** ************* CALCULATION PROCEDURE SIMPLE TERRAIN BLDG. CAVITY-1 BLDG. CAVITY-2 MAX CONC (UG/M**3) 1.306 9.860 9.860 DIST TO MAX (M) 457. 26. 26. TERRAIN HT (M) 0. -- DIST = CAVITY LENGTH) -- (DIST = CAVITY LENGTH) Note: The off-site concentration referenced in the report is the concentration shown for simple terrain. Although the model predicted a building cavity concentration that is higher than the predicted value for simple terrain, this concentration will occur on site and is not applicable for this analysis.