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Chevron Environmental Management Company Soil and Groundwater Investigation Report Tracy Byron Road Project groundwater sample GW-8-13. When samples were analyzed following a silica gel cleanup preparation, concentrations of TPHd in the samples were reduced to below laboratory detection limits in 10 of the 15 samples. Concentrations of TPHd in the split samples collected by the RWQCB [GW-34-19 (280 µg/L) and GW-3 5-18 (110 µg/L)] were less than the concentrations reported for the respective samples submitted by SAIC. Concentrations of BTEX compounds were not detected at or above the laboratory reporting limits in the grab groundwater samples. PAHs were not detected at or above the laboratory reporting limits in 10 of the 15 samples analyzed. The highest concentration of PAHs was reported in water sample GW-34-19 collected from a Hydropunch "companion"boring advanced adjacent to SB-34. In GW-34-19 the following PAHs were detected: acenaphthene (1.4 µg/L), anthracene (0.4 µg/L), fluorene (0.5 µg/L),naphthalene (1.4µg/L), phenanthrene (0.4 µg/L), and pyrene (0.2 µg/L). Groundwater chemical analytical results are summarized in Tables 3 and 4. Maps presenting dissolved petroleum constituents in groundwater are attached as Figures 4a and 4b. A table submitted to ChevronTexaco by the RWQCB summarizing the analytical results from their split samples is included as Appendix E. Six grab groundwater samples were analyzed for total dissolved solids (TDS). Concentrations of TDS in the water samples ranged from 1,200 milligrams per liter(mg/L) (GW-31-17)to 2,100 mg/L(GW-24-15 and GW-33-17). The State of California Department of Health Services (CA DHS) secondary maximum contaminant level (MCL) for TDS ranges from 500 mg/L(recommended)to 1,500 mg/L(short term). All six grab groundwater samples exceeded the recommended MCL concentrations. A copy of the laboratory analytical report with chain-of-custody documentation is included in Appendix D. 5.2.2 Water Supply Well Sampling Analytical Results In cooperation with the RWQCB, SAIC sampled groundwater from 12 water supply wells located at residences and businesses along the West Byron Road corridor selected by the RWQCB. The RWQCB and SAIC proceeded with sampling the water supply wells at the selected properties after the RWQCB obtained permission from the property owners. The sample identification assigned to each sample corresponds with the street address of the respective property. The RWQCB and SAIC collected split samples from each water supply well sampled. The water supply well samples were collected after allowing water to flow from the line for approximately 5 minutes. When possible the water samples were collected from a spigot at the pump house,between the pressure tank and the residence. Otherwise, water samples were collected from a spigot located outside the residence. Immediately upon collection,the samples were labeled and placed in an ice-cooled chest pending laboratory analysis. Water supply well samples collected by SAIC were submitted to F&B under SAIC chain of custody. All water supply well samples collected by SAIC were analyzed for BTEX by EPA Method 8021 B,TPHd by EPA Method 8015 Modified, and PAHs by EPA Method 8270 C SIM. Concentrations of BTEX,TPHd, or PAHs were not detected at or above the laboratory detection limits for all the water supply well samples submitted by SAIC. Analytical results are presented in Table 5. Split samples collected by the RWQCB were submitted to a separate analytical laboratory under RWQCB chain of custody. The RWQCB samples were analyzed for BTEX, TPHd, and TPH quantified as gasoline (TPHg),TDS,methyl tertiary butyl ether(MtBE), metals, and other water quality analytes. Petroleum constituents were not detected at or above the laboratory reporting limits in 11 of the 12 samples submitted by the RWQCB. Analytical results for sample number 3190 collected from the residence at 3190 West Byron Road reported 5 8 µg/L of TPHd. The laboratory analytical report noted that the sample exhibited"an atypical weathered hydrocarbon"chromatographic pattern. A copy of the laboratory analytical report with chain-of-custody documentation submitted by SAIC is included in Appendix D. Water supply well and Hydropunch groundwater analytical data tabulated by the RWQCB is included in Appendix E. 7