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Table 12 <br /> Calculation of Risk-Based Screening Levels far Ground Water <br /> (Construction 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 Cruz MSIM3-air (Construction) (Construction) <br /> sec sec sec sec sec mg/1-water (Win ) (µg/1) <br /> Benzene 2 OOE-01 8 80E-02 9 80E-06 2 09E-05 6 87E-03 125E-04 2 74E-05 179E+02 6 5E+06 <br /> Toluene 3 OOE-01 9 00&02 9 OOE-06 1 75E-05 7 02E-03 1 05E-04 3 45E-05 281E+04 8 2E+08 <br /> Ethylbenzene 3 DOE-01 7 50E-02 7 80E-06 147E-05 5 85E-03 8 87E-05 2 91 E-05 7 41 E+04 2 5E+09 <br /> Xylenes 3 OOE-01 7 OOE-02 7 80E-06 141&05 5 46E-03 8 48E-05 2 78E-05 511E+04 18E+09 <br /> Model Parameters <br /> volumetric air content(capillary fringe) oacap= 3 80E-02 (dimensionless) (ASTM,1996) <br /> volumetric air content(vadose zone) oas= 2 601x01 (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= 120E-01 (dimensionless) (ASTM,1996) <br /> volumetric water content(vadose zone) ows= 120E-01 (dimensionless) (ASTM,1996) <br /> thickness of capillary fringe hcap= 500E+00 cm (ASTM,1996) <br /> thickness of vadose zone by= 2 55E+01 cm (site-specific,based on a Lgw of 30 5 cm and hcap=5 cm) <br /> depth to ground water(=hcap+hv) Lgw= 3 05E+01 cm (site-specific,based on a Lgw of 1 foot) <br /> Henry's Law Constant(dimensionless form) H'= 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(oacap333)/(ototal)]+[Dw x(1/H')x(owcap3 3)/(ototal')] (ASTM,1996) <br /> Deff(soil)=(Da x(oas")/(ototal))+[Dw x(1/H')x(ows3n/(ototal2)] (ASTM,1996) <br /> Deff(ws)_(hcap+hv)/[(hcap/Deff(cap))+(hv/Deff(soil))] (ASTM,1996) <br /> VFwamb=(H'x 10001/m)/[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 />