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S ECOR • Minimum detected concentration; t • Maximum detected concentration; and f • 95% UCL of the arithmetic mean (for the reasonable maximum exposure[RMEJ case). t When COPCs were not detected in samples, half of the SQL was used in the statistical calculations_ (Typically, SQLs that are more than 2,times the detected concentrations in non-detected samples were eliminated from the relevant datasets to avoid cases in which the 95% UCL is higher than the maximum detected concentration, which is not used at this Site). The results of the statistical analysis for soil and groundwater data are presented in Tables 1 and 2, respectively. It should be noted that the calculations of 95% UCL based on the entire soil dataset, given the presence of isolated hotspots (ND4 and SD4); is very conservative. More representative EPC concentrations can include the use of area-weighted average calculations (Cal-EPA, 1992), which should provide numerical estimates that are lower than the 95% UCLs.. Pro-UCL results for COPCs in soil and groundwater are presented in Appendix D. 5.3 SELECTION OF SCREENING LEVELS As discussed above, initial SLs for the Site groundwater are the California primary and secondary MCLs (California Office of Administrative Law, 2006) for the ingestion pathway—to satisfy the RWQCB's water quality objectives. In addition, the RWQCB San Francisco Region's ESLs for protection of the indoor air inhalation pathway for the on-site commercial/industrial workers were also identified as groundwater SLs. ESLs based on protection of chronic freshwater aquatic habitat and ceiling values (odor.and taste) are also listed for references. The applicable SLs for the residual shallow soil at the Site (excluding samples in the removed soil mass) are the USEPA Region 9 PRGs (for commercial/industrial workers)7(U SEPA, ".cam, �,► 2004a) and the RWQCB San Francisco Region's ESLs for :protection of direct contact (fors^"' commercial/industrial and utility/construction workers) and indoor air inhalation pathways. Irl'addition, ESLs for protection of drinking water source and ceiling values based on odor and taste are also used. To be conservative, residential ESL values are also presented(RWQCB,2005): The USEPA Region 9 has developed medium-specific and land use-specific PRGs as screening values (USEPA, 2004a). Soil PRGs are based on-the soil ingestion, dermal contact to soil, inhalation of soil particulates, and inhalation of VOCs pathways. Similarly, the RWQCB San Francisco Region has also developed pathway- and land use-specific ESLs based on the methodology used in the derivation of USEPA Region 9's PRGs. The ESLs were calculated using Cal-EPA toxicological data and incorporate inhalation of vapors from soil gas, groundwater, or soil and a factor for multi-chemical exposures not included in the PRGs. The ESLs were evaluated by the Cal-EPA OEHHA along with other health-based screening levels from different EPA regions; the State of California, and agencies in other states. The OEHHA found that based on the methodology used to develop the ESLs, they provide a more stringent evaluation of risk than levels used by other agencies (Cal-EPA, 2004). In general, chemical-specific PRGs, CHHSLs, and ESLs based on carcinogenic effects reflect a target ECR value of 1E-06. While chemical-specific PRGs and CHHSLs based on noncarcinogenic effects ; i ` I