ARCHIVED REPORTS HUMAN HEALTH SCREENING EVALUATION

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' Human Health Screening Evaluation Surland Homes--Brittle Creek February 12,2009 Ci =bulk soil concentration of contaminant i (chemical concentration in soil, mg/kg x [10-6 kg/mg]) The above equation is valid for calculating Ei only if the soil concentration of a VOC is less than or equal to the soil saturation concentration for the VOC. The UCL soil concentrations of the seven VOCs listed above were compared to soil saturation concentrations presented in the EPA ' Region 9 Preliminary Remediation Goal (PRG) documentation (EPA, 2004). On comparison, the concentrations of the VOCs were found to be below the listed soil saturation concentrations. ' Soil/Water Partition Coefficient The soil/water partition coefficient (Kd) of a chemical is used in the calculation of Ei and is ' calculated (Table 23) using the following equation (PEA Guidance Manual, Figure 2.5): Kd = Koc x foe ' Where: Kd= soil/water partition coefficient, cm 31g (or L-water/kg-soil) Koc = organic carbon partition coefficient, L/kg or cm.3/g foe =fraction of organic carbon (default=0.02) 6. SUMMARY AND CONCLUSIONS Impacts from historic crude-oil pipeline operations to on-site soils were characterized during two ' studies conducted in 1998 and 1999. An additional investigation was performed in 2007 to collect additional soil samples for this HHSE. Twenty-three soil samples were collected from 15 soil borings at depths from 1 foot to 12 feet bgs. Samples were analyzed for BTEX and ' PAHs, and for metals during the 2007 investigation. EPCs were calculated as the UCL of the mean soil concentration for the detected BTEX and PAH COPCs. EPCs for metals were also calculated as the UCL of the mean soil concentration. ' This HHSE was prepared at the request of the DTSC to estimate future on-site residential risks and hazards under current site conditions. The HHSE was developed using health protective, ' conservative reasonable maximum-exposure assumptions, using risk and hazard algorithms developed by DTSC and promulgated in the PEA Guidance Manual. 6.1 RESIDENTIAL SCENARIO 6.1.1 Cancer Risks from Soils Future potential oral and dermal cancer risks from direct contact exposures to on-site soils were estimated, and the cancer risks associated with the individual COPCs and the summation of ' cancer risks associated with all COPCs for these exposure routes are provided in Table 8. Potential future indirect inhalation exposures to on-site soils and cancer risks were also estimated, and the risk associated with 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. Total potential cancer risk to a hypothetical future resident from oral, 1 11 --w a MR From Science to Solutions