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Human Health Screening Evaluation <br /> Former Vernalis Pump Station September 2,2010 <br /> Emission Rate for VOCs <br /> SAIC-Benham calculated the emission rates from soils to ambient air for VOCs (Table 18) using <br /> the following equation(PEA Guidance Manual, Figure 2.6): <br /> 1.6 X 105XDiX H° XCi <br /> Ei 0.023 d <br /> 0.284 + 0.046 x K d <br /> H, <br /> Where: <br /> Ei =average emission rate of contaminant i over the residential lot during the exposure <br /> interval, mg/sec <br /> Di=diffusivity in air for compound i, cm2/sec <br /> He =Henry's Law constant, atm-m3/mole <br /> Kd= soil-water partition coefficient, cm 3/g <br /> Ci=bulk soil concentration of contaminant i(chemical concentration in soil, <br /> mg/kg x [10"6 kg/mg]) <br /> The above equation is valid for calculating Ei only if the soil concentration of a VOC is less than <br /> or equal to the soil saturation concentration for that compound. SAIL-Benham compared the <br /> maximum detected soil concentrations of the VOCs listed above to soil saturation concentrations <br /> provided in Table 18 (Emission Rate for VOCs), based on Equation 2.5 (as modified per Item 3 <br /> of the Errata Sheet) and parameters presented in the PEA Guidance Manual. The maximum soil <br /> concentrations are all below the respective soil saturation concentration. <br /> Soil/Water Partition Coefficient <br /> SAIC-Benham used the soil/water partition coefficient(Kd) of a chemical in the calculation of Ei <br /> (Table 19) using the following equation(PEA Guidance Manual, Figure 2.5): <br /> Kd =Kocxfoc <br /> Where: <br /> Kd= soil/water partition coefficient, cm 3/g (or L-water/kg-soil) <br /> Koc = organic carbon partition coefficient, L/kg or cin 3/g <br /> foc = fraction of organic carbon(default= 0.02) <br /> 6. SUMMARY AND CONCLUSIONS <br /> Impacts from historic crude-oil pipeline operations to on-site soils were characterized under the <br /> direction, and to the satisfaction, of the Central Valley RWQCB during studies conducted in <br /> previous investigations. Sixty-seven soil samples were collected from 33 soil borings at depths <br /> between 0 and 10 feet bgs. All soil samples were analyzed for BTEX and PAHs. However, four <br /> 10 ftf a The Benham Companies,LLC <br /> ,..frt j`® A Wholly Owned Subsidiary <br /> From&mxe to Solanoss <br />