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139 South Center Street, Stockton, California June 28, 1994 <br /> Chevron USA Products Company Page 5 <br /> 4.0 RESULTS OF ADDITIONAL ASSESSMENT <br /> 4.1 Hydrogeology <br /> The materials logged to a depth of 44 feet during drilling at the site consist of fill material (broken <br /> concrete, brick, and chunks of wood) in a silty clay to a depth of approximately 10 feet BGS, silty sandy <br /> clay to 25 feet BGS, and bluish gray silty clay to the base of the borings. Groundwater was encountered <br /> while drilling SB-3 at a depth of 43 feet BGS, in a dark bluish gray clayey silt. <br /> 4.2 Results of Soil Sample Analyses <br /> Results of all soil sample analyses are summarized in Table 1. Soil from SB-4 at 43 feet BGS had <br /> highest hydrocarbon concentrations at 160 parts per million (ppm) benzene and 15,000 ppm TPH-G. <br /> Low concentrations (<5ppm) of benzene and TPH-G were in the 40-foot BGS sample collected from <br /> SB-3. Low benzene concentrations (<0.1 ppm) were detected in the 40 and 43-foot BGS samples from <br /> SB-1. Soil samples with detectable concentrations of hydrocarbons are listed on Figure 2. <br /> Results of soil from SB-5 containing CAM-17 metals are summarized in Table 2. Metals detected at low <br /> concentrations were arsenic, barium, cobalt, copper, nickel, and vanadium. Copies of the laboratory <br /> analyses reports and chain-of-custody manifests are included in Appendix E. <br /> GROUNDWATER <br /> 5039SUM.gpr _ ._ TECHNOLOGY <br />