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139 South Center Street, Stockton, California January 25, 1993 <br />Chevron U.S.A. Products Company Page 6 <br />4.0 SITE CONDITIONS <br />4.1 Hydrogeology <br />The materials encountered during drilling consisted primarily of brown to gray silty clays, fine to <br />medium sands, and silty, sandy clays. Groundwater was encountered at a depth of approximately 47 <br />feet below grade surface In a silty fine to medium sand layer. At a depth of approximately 57 feet, <br />flowing fine sands were encountered that prevented further drilling beyond 60 feet. <br />Based on the groundwater monitoring data observed November 10, 1992, the groundwater flow <br />direction was estimated to be to the southeast at a gradient of between 0.0033 and 0.002 (f=igure 3). <br />4.2 Analytical Results for Soil <br />Results of all soil sample analyses are summarized in Table 1 and the laboratory results are enclosed <br />in Appendix D. All three samples analyzed were below laboratory detection limits for all constituents. <br />4.3 Analytical Results for Groundwater <br />Results of all water sample analyses are summarized in Table 2 and the laboratory reports are <br />enclosed in Appendix D. The new well MW -5 was below laboratory detection limits for all analyzed <br />constituents. The remaining wells (MW -1, 2, 3, and 4) contained levels of TPH-G ranging from 2,300 <br />parts per billion (ppb) in MW -2, to non-detectable (ND) in MW -4. Benzene concentrations in the wells <br />ranged from 3.0 ppb in MW -2 to ND in MW4 and MW -5. <br />C4 GROUNDWATER <br />TECHNOLOGY <br />