SITE INFORMATION AND CORRESPONDENCE

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i No Further Action Required Request Report Tracy Byron Road-Tracy,California December 1,2011 as Appendix B, and analytical results are included as Appendix C. The results of the HHSE are summarized in section 2.1. For investigations performed at the Site, soil analytical results were i compared to the lowest, most conservative united States Environmental Protection Agency (EPA)Preliminary Remediation Goals(PRGs,which have been replaced by Regional Screening Levels [RSLs; EPA, 2008]) and San Francisco Bay RWQCB Environmental Screening Levels (ESLs; San Francisco Bay RWQCB,2008). Similarly, groundwater analytical results were compared to the WQOs and ESLs. Note that the RSLs and ESLs have changed over time,but for delineation purposes as used at Historical Pipeline Portfolio—Bakersfield to Richmond (HPP- BTR) sites, they have always been conservative. 2.1 HUMAN HEALTH SCREENING EVALUATION, 2011 Due to the large lateral extent of the area investigated and the variable land use at the Site, SAIC , divided the Site into Area 1, Area 2, and Area 3 for risk assessment purposes. SAIC evaluated health risks to hypothetical residents and the potential threat to sensitive ecological receptors from exposure to soil in a residential land-use scenario(Areas 1 and 2) and a construction worker ' scenario (Area 3) at the Site. SAIC developed the HHSE using approaches and methodology consistent with those presented in the Preliminary Endangerment Assessment(PEA) Guidance Manual(California Environmental Protection Agency [Cal/EPA] Department of Toxic I Substances Control [DTSC], 1999). SAIC quantitatively evaluated the exposure routes of incidental ingestion of soil and dermal contact with soil, inhalation of wind-blown dust for non-volatile constituents, and inhalation of chemical vapors from soils for volatile constituents. Shallow groundwater is unlikely to be used as a drinking-water source at the Site due to naturally occurring high total dissolved solids(TDS)concentrations; therefore, exposure to groundwater was not evaluated quantitatively in the HHSE. Inhalation of volatiles from groundwater is a potential exposure route; however,benzene,toluene,ethylbenzene, and total xylenes (BTEX) were not detected in groundwater. The volatile organic compounds detected at the Site were at low concentrations in groundwater, indicating that the potential risks associated with this pathway are low. The potential for vapor intrusion of volatile chemicals to indoor air from groundwater was not quantitatively evaluated. All analytes detected in soil in at least one sample between 0 and 10 feet below ground surface (bgs; or approximately 3 meters)were considered COPCs. Metals are not typically considered critical constituents of crude oil at former OVP and TAOC sites; therefore, soil samples from the Site were not analyzed for metals. Benzene and toluene were not detected in any soil samples from Area 1; thus, these analytes are not considered COPCs in Area 1. Finally, benzene, toluene, ethylbenzene, and acenaphthylene were not detected in any samples from Area 3, and are not considered COPCs in Area 3. All COPCs for the Site were evaluated quantitatively in the HHSE. SAIC estimated total potential cancer risk to a hypothetical resident from oral, dermal, and inhalation exposures to on-site soil in Area 1 to be 3E-06,and in Area 2 to be 9E-07. The level of risk in Area 1 is above the de minimis level of I E-06, but at the lower end of the risk management range of 1E-06 and 1E-04. The level of risk for Area 2 is below the de minimis level of 1E-06. 2 SAIC I