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Table 3 Calculation of Risk-Based Screening Levels for Ground Water <br /> (Industrial Worker Scenario) <br /> 1325 and 1515 West Weber Avenue,Stockton, California <br /> Target Level Screening <br /> Constituent H' Da Dw Deff(cap) Deff(soil) Deff(ws) Wwamb in Air Level <br /> (dimensionless) cm2 cm2 cm2 cm2 cmz mg/rn.-air (Industrial) (Industrial) <br /> sec sec sec sec sec mg/1-water {ug/m3) (µg/1) <br /> Benzene 2.00E-01 8.80E-02 9.80E-06 2.09E-05 6.87E-03 4.76E-04 2.60E-05 1.43E-01 5,5E+03 <br /> Toluene 3.00E-01 9.00E-02 9.00E-06 1.75E-05 7.02E-03 4.02E-04 3.30E-05 5.62E+02 1.7E+07 <br /> Ethylbenzene 3.00E-01 7.50E-02 7.80E-06 1.47E-05 5.85E-03 3.39E-04 2.78E-05 1.48E+03 5.3E+07 <br /> Xylenes 3.00E-01 7.00E-02 7.80E-06 1.41E-05 5.46E-03 3.24E-04 2.66E-05 1.02E+03 3.8E+07 <br /> 1,2-DCA 4.00E-02 1.00E-01 1.00E-05 6.15E-05 7.81E-03 1.27E-03 1.39E-05 2.04E-01 1.5E+04 <br /> 1,3,5-TMB 3.00E-01 7.50E-02 7.10E-06 1.43E-05 5.85E-03 3.30E-04 2.70E-05 8.69E+00 3.2E+05 <br /> 1,2,4-TMB 2.00E-01 7.50E-02 7.10E-06 1.66E-05 5.85E-03 3.79E-04 2.07E-05 8.69E+00 4.2E+05 <br /> Model Parameters <br /> volumetic air content(capillary fringe) oacap= 3.80E-02 (dimensionless) (ASTM,1996) <br /> volumetic air content(vadose zone) eas= 2.60E-01 (dimensionless) (ASTM,1996) <br /> total soil porosity stotai= 3.80E-01 (dimensionless) (ASTM,1996) <br /> volumetric water content(capillary fringe) owcap= 3.42E-01 (dimensionless) (ASTM,1996) <br /> volumetic water content(foundation cracks) ewcrack= 1.20E-01 (dimensionless) (ASTM,1996) <br /> volumetic water content(vadose zone) ows= 1.20E-01 (dimensionless) (ASTM,1996) <br /> thickness of capillary fringe heap= 5.00E+00 cnt (ASTM,1996) <br /> thickness of vadose zone by= 1.17E+fl2 cm (site-specific,based on a Lgw of 122 cm and heap=5 cm)_ <br /> _ _ .. <br /> ' " tli""" a to ound water= <br /> `- <br /> flea +by - L `-'- _ "�"-1.22E+02 " - cul �-" (site-s e - <br /> cific based on a Lgw of 4 feet) <br /> Henry's Law Constant(dimensionless form) H'= chemical specific (ASTM,1996;tlSEPA Region 9,1999) <br /> Diffusion coefficient(air) Da chemical specificA_STM,1996;USEPA Region 9,1999) <br /> x .. <br /> Diffusion coefficient(water) _-` Dw- chemical specific (ASTM,1996;USEPA Region 9,1999) Ic <br /> Deff(cap)=[Da x(oacap3')/(ototae)]+[Dw x(I/H')x(ewcap3'33)/(ototae)] (ASTM,1996) <br /> Deff(soil)=(Da x(oas3')/(ototal2))+[Dw x(1/H')x(ews7)/(Ptotal2)] (ASTM,1996) <br /> Deff(ws)_(heap+hv)/[(heap/Deff(cap))+(hv/Deff(soil))] (ASTM,1996) <br /> VFwamb-(H'x 10001/m3)/[1+[(225 cm x 200 cm x Lgw)/(1500 cm x Deff(ws))]] (ASTM,1996) <br /> Target level in air: from Table 2 <br /> Screening level=target level in air/Vfwamb (ASTM,1996) <br /> Notes: <br /> 1. Screening level=risk-based screening level for ground water <br /> 2. 1,2-DCA-I,2-dichloroethane <br /> 3. 1,3,5-TMB-1,3,5-trimethylbenzene <br /> 4. 1,2,4-TMB-1,2,4-trimethylbenzene <br />