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' 45 E Harding Way, Stockton, California September 1, 1993 <br /> Chevron USA Products Company Page 6 <br /> 4.0 SITE CONDITIONS <br /> ' 4.1 HYDROGEOLOGY <br /> ' The site Is located in the northern part of the San Joaquin Valley at an elevation of approximately 12 <br /> feet The valley fill consists of late Mesozoic through Eocene dominantly marine deposits overlain by <br /> late Tertiary and Quaternary dominantly non-marine deposits which usually contain fresh water In <br /> Stockton area, the late Cenozoic deposits are approximately 3,000 feet thick and generally consist of <br /> ' alluvial gravel, sand, silt, and clay Groundwater in these alluvial deposits is usually unconfined to <br /> semiconfined Extensive Pho-Pleistocene lacustrine deposits, including the areally extensive <br /> diatomaceous Corcoran Clay, occur in San Joaquin Valley, south of Stockton The water beneath the <br /> ' clay bed is usually confined <br /> The materials penetrated to a depth of 65 feet during drilling at the site are dominantly clayey silts and <br /> silty clays with lenses of sand Groundwater was encountered during drilling at a depth of approximately <br /> ' 52 feet in MW-12 and 55 feet in MW-13, and was measured at approximately 51 feet below grade in both <br /> wells on July 23, 1993 Groundwater flow direction on July 23 was found to be to the east-northeast at <br /> a gradient of 0 003 (Figure 3) <br /> 4.2 ANALYTICAL RESULTS FOR SOIL <br /> Results of all soil samples analyses are summarized in Table 1 and the laboratory results are enclosed in <br /> ' Appendix D No TPH-G nor BTEX compounds were detected in any of the analyzed samples <br /> 43 ANALYTICAL RESULTS FOR GROUNDWATER <br /> ' Results of all water sample analyses are summarized in Table 2, and the laboratory reports are enclosed <br /> in Appendix D No dissolved hydrocarbons were detected in the groundwater sample from MW-12 <br /> MW-13 contained 730 ppb TPH-G, but did not contain benzene above the MOL The remaining wells <br /> sampled ranged from below the MOL (MW-10) to 680 ppb TPH-G (MW-9) The rinsate sample collected <br /> prior to sampling MW-12 (RBMW12) contained 61 ppb TPH-G However, MW-12 sampled after did not <br /> contain TPH-G above the MOL as previously mentioned ]—� <br /> ;LIFT <br /> GROUNDWATER <br /> 3399EAFt RPT �--� I TECHNOLOGY <br />