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Human Health Screening Evaluation Mountain House Development Site#6 January 18,2011 Where: Kd= soil/water partition coefficient, cm 3/g (or L-water/kg-soil) Koc = organic carbon partition coefficient, L/kg or cm 3/g foc = fraction of organic carbon(default= 0.02) 6. SUMMARY AND CONCLUSIONS Condor and SAIC characterized impacts from historical crude-oil pipeline operations to on-site soils under the direction of, and to the satisfaction of, the Central Valley RWQCB during three studies conducted between 2001 and 2010. Forty-nine soil samples were collected from 38 soil borings at depths between 0 and 10 feet bgs. SAIC performed this risk analysis for the BTEX and PAH constituents detected in soil. The Central Valley RWQCB is satisfied that the soil characterization data set adequately describes conditions at the Site; therefore, SAIC calculated EPCs as the UCL of the mean soil concentration for each of the COPCs in soil. SAIC prepared this HHSE at the direction of the Central Valley RWQCB to estimate potential on-site residential risks and hazards under current conditions at the Site. This HHSE was developed with health-protective, conservative reasonable maximum exposure assumptions, using risk and hazard algorithms developed by the DTSC and promulgated in the PEA Guidance Manual for COPCs in soil. 6.1 CANCER RISKS FROM EXPOSURE TO SOILS SAIC estimated potential oral and dermal direct contact exposures to on-site soils; cancer risks for individual COPCs and the summation of risks for all COPCs for these exposure routes are provided in Table 8. SAIC estimated potential indirect inhalation exposures to on-site soils; cancer risks for individual COPCs and the summation of inhalation risks are provided in Table 9. The aggregate risks for oral, dermal, and inhalation cancer risks are provided in Table 10. SAIC estimated the total potential cancer risk to a hypothetical resident from oral, dermal, and inhalation exposures to on-site soils to be 5E-06. This level of risk is above the de minimis level of 1E-06, but at the lower end of the risk management range of 1E-06 and 1E-04. SAIC utilized a residential scenario in this assessment; however, the crude-oil affected soil and groundwater found at the Site are located primarily within and beneath the utility/highway corridor easements and beneath a portion of an adjacent agricultural field(Figure 2). In addition, three borings (SB-21, SB-22, and GP-152) contain the highest PAH concentrations, and thus account for a majority of the risk. These three borings are located in the utility/highway corridor, not on private property. This evaluation indicates an acceptable cancer risk for exposures to on-site soils for a hypothetical resident. 6.2 NON-CANCER HEALTH HAZARDS FROM EXPOSURE TO SOILS SAIC estimated potential oral and dermal non-cancer health hazards from direct contact exposures to on-site soils; the hazards for individual COPCs and the summation of hazards for all COPCs for these routes are provided in Table 11. SAIC estimated potential indirect inhalation exposures to on-site soils; non-cancer health hazards for individual COPCs and the summation of hazards for all COPCs for the inhalation route are provided in Table 12. The 10 FMM sclence to Solvtloas