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DRAFT— FOR INTERNAL REVIEW ONLY <br /> 1.0 HUMAN HEALTH RISK EVALUATION <br /> The potential threat to human health posed by the properties comprising the South Shore <br /> parcels ("the Site"comprised of Areas 2A, 2B, 3, and 4)was assessed in this risk <br /> screening evaluation in accordance with Preliminary Endangerment Assessment(PEA) <br /> requirements (CaUEPA, 1994; updated 1996). The approach to conducting the risk <br /> screening evaluation consists of a compilation of methods, models, and assumptions <br /> typically used by the U.S. Environmental Protection Agency(U.S. EPA) to quantify <br /> noncarcinogenic hazards and carcinogenic risks, which is the basis of guidance provided <br /> in the PEA Guidance Manual (CaUEPA, 1994; updated 1996). <br /> The human health risk evaluation, conducted individually for each of the properties <br /> comprising the South Shore properties, includes four components: selection of chemicals <br /> of concern (COC), exposure assessment,toxicity assessment, and risk characterization as <br /> ' described in the following sections. <br /> 1.1 Selection of Chemicals of Concern <br /> COCs were initially identified by including matrix-specific chemicals that were reported <br /> as detected in subsurface soil and groundwater based on data from the soil and <br /> groundwater investigation of the South Shore properties conducted by Treadwell &Rollo <br /> (1999). Additionally,historical chemical data for soils in Area 2A were included in the <br /> ' chemical evaluation(Treadwell & Rollo (1996). SOMA did not perform an independent <br /> data validation of data provided by others. A summary of COCs and associated chemical <br /> concentrations detected in soil and groundwater for each area is presented in Tables 1-6. <br /> Certain metals were excluded as COCs for this risk evaluation by comparing Site soil <br /> data with background concentrations of metals in California soils (Bradford et al., 1996). <br /> The area-specific geometric means and the log normal 95% upper confidence limits <br /> (UCL) of the geometric means were compared with reported values for background <br />