Laserfiche WebLink
Human Health Screening Evaluation <br /> Mountain House Development Site#6 January 18,2011 <br /> Where: <br /> Ca= ambient air concentration, mg/m3 <br /> Ei=total emission rate for compound i (mg/second) <br /> Air concentrations of the following volatile chemicals (PEA Guidance Manual)were estimated <br /> using this equation (Table 15): <br /> • Benzene <br /> • Ethylbenzene <br /> • Xylenes <br /> • Acenaphthene <br /> • Anthracene <br /> • Fluorene <br /> • Naphthalene <br /> Emission Rate for VOCs <br /> SAIC calculated the emission rates from soils to ambient air for VOCs (Table 16) using the <br /> following equation(PEA Guidance Manual, Figure 2.6): <br /> 1-6 x 10" xDixHcx C, <br /> Ei — d <br /> 0.023 <br /> Di x <br /> 0.284 + 0.046 x K e <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, cm3/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. The maximum detected soil <br /> concentrations of the VOCs listed above were compared to soil saturation concentrations <br /> presented in Table 16 (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 (Cal/EPA, 1999). <br /> The maximum soil concentrations are all below their respective soil saturation concentration. <br /> Soil/Water Partition Coefficient <br /> The soil/water partition coefficient(Kd) of a chemical is used in the calculation of Ei and is <br /> calculated(Table 17)using the following equation(PEA Guidance Manual, Figure 2.5): <br /> Kd=Koe x foe <br /> from sukin?to Solvtioas <br />