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Table I I <br /> Calculation of Rtsk-Based Screening Levels for Ground Water <br /> (CommerctaWndustrial Worker Scenario) <br /> Former Heinz Facility <br /> Tracy, California <br /> Target Level Screening <br /> Constituent H' Da Dw Deff(cap) Deff(soil) Deff(ws) VFwamb in Air Level <br /> (dimensionless) cm2 cm2 cm2 cm2 cm2 m m3-alr (Industrial) (Industrial) <br /> sec sec sec sec sec mg/1-water (µg/m) (µg/I) <br /> Benzene 2 OOE-01 8 80E-02 9 8013-06 2 09E-05 6 87E-03 5 30E-04 2 58E-05 143E-01 5 5E+03 <br /> Toluene 3 OOE-01 9 OOE-02 9 OOE-06 1 75E-05 7 02E-03 4 49E-04 3 28E-05 562E+02 17E+07 <br /> Ethylbenzene 3 OOE-01 7 50E-02 7 80E-06 147E-05 5 85E-03 3 79E-04 2 7613-05 148E+03 5 4E+07 <br /> Xylenes 3 OOE-01 7 OOE-02 7 80E-06 141E-05 5 46E-03 3 62E-04 2 64E-05 102E+03 3 9E+07 <br /> Model Parameters <br /> volumetric air content(capillary fringe) oacap= 3 801:02 (dimensionless) (ASTM,1996) <br /> volumetric air content(vadose zone) gas= 2 601-01 (dimensionless) (ASTM,1996) <br /> total soil porosity ototal= 3 80E-01 (dimensionless) (ASTM,1996) <br /> volumetric water content(capillary fringe) Owcap= 3 42E-01 (dimensionless) (ASTM,1996) <br /> volumetric water content(foundation cracks) owcrack= 1 20E-01 (dimensionless) (ASTM,1996) <br /> volumetric water content(vadose zone) ews= 120E-01 (dimensionless) (ASTM,1996) <br /> thickness of capillary fringe hcap= 5 ODE+00 cm (ASTM,1996) <br /> tluckness of vadose zone by= 132E+02 cm (site-specific,based on a Lgw of 137 cm and hcap=5 cm) <br /> depth to ground water(=hcap+hv) Lgw= 137E+02 cm (site-specific,based on a Lgw of 4 5 feet) <br /> Henry's Law Constant(dimensionless form) H1= chemical specific (ASTM,1996,USEPA Region 9,1999) <br /> diffusion coefficient(air) Da= chemical specific (ASTM,1996,USEPA Region 9,1999) <br /> diffusion coefficient(water) Dw= chemical specific (ASTM,1996,USEPA Region 9,1999) <br /> Deff(cap)= [Da x(oacap")/(ototal)] + [Dw x(1/H')x(owcap")/(ototal)] (ASTM,1996) <br /> Deff(soil)=(Da x(oas3-"-)1(ototal'))+[Dw x(1/H')x(ows333)/(ototal2)] (ASTM,1996) <br /> Deff(ws)_(hcap+hv)/[(hcap/Deff(cap))+(hv/Deff(soil))] (ASTM,1996) <br /> VFwamb w(H'x 10001/m3)/11 +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 />