Document wKyrzzwwnoQvjK3ErJ1JJJoK6
AR226-2616
Draft: Prepared at the Request of Council
AR226-2616
Screening level modeling report which was superceded bv ISC modeling report Data and Modeling Procedures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.
Although there are several different sources of C8 emissions in the Telomers area at the Washington Works site, these emission points are all headered together into a common stack. The following parameters for this stack were used in the model:
Stack Height: 85 feet Diameter: 1.5 feet Temperature: 68F Velocity: 47 ft/s C8 Emission Rate: 0.16 Ib/yr (1.83x10'5 Ib/hr)
The C8 emission rate is based on the maximum production rate for the Telomers area. The basis for the emission calculations is shown in the attached document titled "Calculation of Emissions from the Telomers Process."
To determine the impacts of building downwash on dispersion from the stack, the Sereen3 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:
Building
Max Height Length Width PrWojiedcthted GEP
(ft) (ft) (ft) (ft) (ft)
164 44 90 90 125
180 184*
64 96
70 195
12250
75 230
'This building has the highest GEP and was used in the model.
Modeling Results
110 160 240
Using the above data the Screen3 model predicted a maximum off-site ground level concentration of 0tim.0e0.2T3opgco/mnv3eartt aa dSicsrtaenecne3 omfo2d8e9l freeestuflrtotomatnheansnouuarclea.vTehraisgeco, nEcPeAntgrautiidoannicsebdaisreedctsonthae 1u-sheorutroamveurlatipgliyng
Draft: Prepared at the Request of Council
the predicted Screen3 concentration by a value of 0.05. This gives an annual average concentration of 1.15x1O'4 pg/m3. This concentration is four orders of magnitude below the recommended ambient air concentration level in the community. A copy of the Screen3 model output is attached.
Draft: Prepared at the Request of Council
08/01/03
*** SCREEN3r MODEL RUN *** *** VERSION DATED 96043 *** '
13:17:07
WASHINGTON WORKS TELOMERS 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 .230576E 25.9080
.4572 14.3256 293.1500 293.0000
.0000 RURAL 29.2608 36.5760 59.4360
THE REGULATORY (DEFAULT) MIXING HEIGHT OPTION WAS SELECTED. THE REGULATORY (DEFAULT) ANEMOMETER HEIGHT OF 10.0 METERS WAS ENTERED.
BUOY. FLUX =
.004 M**4/S**3; MOM. FLUX = 10.719 M**4/S**2.
*** FULL METEOROLOGY ***
**********************************
*** SCREEN AUTOMATED DISTANCES *** **********************************
*** TERRAIN HEIGHT OF ***
0. M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES
DI ST (M)
CONC
U10M USTK MIX HT PLUME
(UG/M**3) STAB (M/S) (M/S)
(M) HT (M)
10. 100. 200. 300. 400. 500. 600. 700. 800. 900. 1000. 1100. 1200. 1300. 1400. 1500. 1600. 1700.
.0000 .2091E-02 .1291E-02 .8797E-03 .6730E-03 .5466E-03 .4609E-03 .3988E-03 .3517E-03 .3147E-03 .2848E-03 .2601E-03 .2394E-03 .2217E-03 .2065E-03 .1932E-03 .1815E-03 .1711E-03
0 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6
.0 .0
.0 .00
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
1.0 1.7 10000.0 26.21
SIGMA Y (M)
.00 4.07 7.73 11.23 14.64 17.97 21.24 24.46 27.63 30.78 33.88 36.96 40.01 43.04 46.05 49.03 51.99 54.94
SIGMA Z (M) DWASH
.00 18.28 24.04 30.17 30.53 30.89 31.25 31.60 31.95 32.29 32.63 32.96 33.29 33.62 33.94 34.26 34.57 34.89
NA SS SS ss ss ss ss ss ss
ssss ss ss ss ss ss ss ss
Draft: Prepared at the Request of Council
1800. 1900. 2000.
.1618E-03 .1534E-03 .1459E-03
6 6 6
1.0 1.7 10000.0 26.21 1.0 1.7 10000.0 26.21 1.0 1.7 10000.0 26.21
MAXIMUM 1-HR CONCENTRATION AT OR BEYOND 10. M:
88. .2254E-02
6
1.0 1.7 10000.0 26.21
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) ****************************************
57.87 60.78 63.68
3.65
35.20 35.50 35.80
17.65
SS SS SS
SS
CAVITY CALCULATION - ^ ***
CONC (UG/M**3)
= .8839E-03
CRIT WS @10M (M/S) =
1.27
CRIT WS @ HS (M/S) =
1.54
DILUTION WS (M/S) =
1.00
CAVITY HT (M)
= 38.48
CAVITY LENGTH (M) = 67.12
ALONGWIND DIM (M) = 36.58
*** CAVITY CALCULATION - 2 ***
CONC (UG/M**3)
= .1001E
CRIT WS @10M (M/S) =
2.37
CRIT WS @ HS (M/S) =
2.87
DILUTION WS (M/S) =
1.44
CAVITY HT (M)
= 32.60
CAVITY LENGTH (M) = 48.77
ALONGWIND DIM (M) = 59.44
****************************************
* * * * * * E*N*D* * O*F* * C* A* V* I* T* Y* * *C*A*L*C*U*L*A*T*I*O*N*S* * * * * * * *
***************************************
*** SUMMARY OF SCREEN MODEL RESULTS *** ***************************************
CALCULATION PROCEDURE
SIMPLE TERRAIN
BLDG. CAVITY-1
BLDG. CAVITY-2
MAX CONC (UG/M**3)
.2254E-02
.8839E-03
.1001E-02
DIST TO MAX (M)
88.
67.
49.
TERRAIN HT (M)
. o. -- (DIST = CAVITY LENGTH)
-- (DIST = CAVITY LENGTH)
*************************************************** ** REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS ** ***************************************************
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