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�W I Illp�ll� II�I-■�I��W- -- III <br /> SAFEWAY MEAT PACKING FACILITY, STOCKTON, CALIFORNIA <br /> TIER 11 RISK BASED CORRECTIVE ACTION <br /> FEBRUARY 26, 1996 <br /> PAGE 4 - 1 <br /> 4.0 SITE CONDITIONS AND CALCULATIONS OF THE SSTLs <br /> The SSTL are soil and groundwater concentrations associated with a given risk level SSTLs <br /> integrate information on site conditions, physical/chemical properties of the COIs, characteristics <br /> of the potentially exposed population, and toxicity of the COIs At the conceptual level, an <br /> SSTL (in either mg/kg or mg/L) is estimated by <br /> SSTL = Acceptable Risk/(VF * EF * SF or 1/RM) <br /> where <br /> VF = volatilization factor <br /> EF — exposure factors <br /> SF = carcinogemc slope factor <br /> RM = Risk Reference Dose <br /> Volatilization factors are based on fate and transport modeling and are used to estimate the <br /> relationship between the subsurface soil (or groundwater) and the environmental medium that is <br /> contacted (ambient au, indoor air, or druikmg water) The equations used to calculate the SSTLs <br /> and the values used for the exposure modeling are reviewed in Sections 4 1 to 4 3 Exposure <br /> factors are human and environmental characteristics that are used to estimate the daily dose (or <br /> exposure) to a chemical and are discussed to Section 4 2 SF and RfD have been described in <br /> Section 2 0 <br /> 0131CDS1 <br />