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J <br /> 139 South Center Street, Stockton, California January 21, 1994 <br /> Chevron U.S.A. Products Company Page 6 -c <br /> 4.0 SITE CONDITIONS <br /> 4.1 Hydrogeology <br /> The materials encountered during drilling consisted of silty clay, clayey silt, and fine sand. <br /> Groundwater was encountered at a depth of approximately 44 feet BGS in a 7-foot-thick fine-sand <br /> layer. <br /> Water table elevations were anv r <br /> a e age of 0.42 foot lower than those recorded on August 17, 1993. <br /> Depth to water in site-related wells ranged from 42 to 44 feet BGS. Historical and recent <br /> groundwater monitoring data are summarized in Table 1. Estimated groundwater flow is to the <br /> southeast at a gradient of 0.002 to 0.003 (Figure 3). <br /> 4.2 Analytical Results for Soil <br /> All soil samples analyzed were below method detection limits MDL for benzene eth lbenzen <br /> (MDL) y e and <br /> TPH-G. The 10 and 20 feet BGS sample from MW-6 contained low concentrations of toluene and <br /> xylenes. Analyzed soil samples that were collected below 25 feet were below the MDL for BTEX and <br /> TPH-G (Table 2). Copies of the laboratory analyses reports and chain-of-custody manifests are <br /> included in Appendix D. <br /> 4.3 Analytical Results for Groundwater <br /> The sample collected from the new well (MW-6) on November 22, 1993 contained 9 parts per billion <br /> (ppb) benzene and 980 ppb TPH-G. Dissolved hydrocarbons were detected in all of the site-related <br /> monitoring wells except MW-4. Benzene concentrations ranged from below the MDL up to 170 ppb <br /> (MW-2). Dissolved TPH-G concentrations ranged from below the MDL to 3,600 ppb. Historical and <br /> recent laboratory analytical results are summarized in Table 1. Copies of the laboratory analytical <br /> reports and chain-of-custody manifests are included in Appendix D. <br /> GROUNDWATER <br /> TECHNOLOGY <br />