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Stockton 99 Speedway <br /> Preliminary Endangerment Assessment Workplan April 92,2007 <br /> established, or in cases where metal concentrations exceeded background levels, a comparison to <br /> regulatory screening levels will be made. <br /> For the risk-based screening evaluation, CHHSLs developed by the Office of Environmental Hazard <br /> Assessment; (CaIEPA, 2005) will be used. The CHHSLs address direct exposure to soil for nonvolatile <br /> chemicals and potential vapor intrusion into buildings for volatile chemicals. CHHSLs are based on <br /> exposure pathways (i.e., incidental ingestion of soil, dermal contact with soil, and inhalation of <br /> dust/vapors) for specific land-use conditions (i.e., residential or commercial). Soil CHHSLs are not <br /> available for VOCs or TPH mixtures. Therefore, in the absence of appropriate CHHSLs, the California <br /> Regional Water Quality Control Board-San Francisco Bay Region's (CRWQCB) Environmental <br /> Screening Levels (ESLs; CRWQCB, 2005) will be used. The CHHSLs and ESLs represent conservative <br /> screening values below which adverse effects on human health are not expected to occur. <br /> PEAw lan.Rnal.doo 3-$ <br /> The Source Group,Inc. <br /> 1 <br />