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404 WEST FREMONT STREET <br /> ` { WKA No 1628 02 <br /> September 2, 1994 <br /> Page 5 <br /> Hydrogeologic Setting <br />' The 1966 California Division of Mmes and Geology Geologic Map of California, San Jose Sheet <br /> shows the site to be underlain by Quaternary Basin Deposits These deposits consist primarily of <br /> "semi-consolidated gravels, sands and silts" that are the remnants of older alluvial terraces and <br /> 1 r dissected alluvial fans The thickness of the Quaternary Basin Deposits is variable but is likely to <br /> be over one hundred feet thick beneath the site The soils observed during the tank removal and <br /> subsequent site investigations were brown and gray sands and silts <br />' The site lies within the San Joaquin Valley Ground Water Basin (California Department of Water <br /> Resources, 1986) The upper ground water table is unconfined and approximately 25 feet below <br /> 1 { grade, based on the Spring, 1990 Ground Water Elevation Contour Map published by San <br /> i <br /> Joaquin FIood Control and Water Conservation District The regional ground water flow <br /> direction is reported to be easterly, ground water depths have been observed to fluctuate between <br /> 16 to 27 feet below grade <br /> FIELD INVESTIGATION <br /> To evaluate the extent of gasoline observed in soil and ground water beneath the site, two soil <br />' [ borings (MW5 and MW6) were drilled on the site at the locations shown on Plate 2 The <br /> l borings were drilled to a depth of 40 feet using a Mobile B61 drill rig provided by Westex <br />' Drilling and subsequently converted into four-inch diameter monitoring wells <br />' A total of six soil boring samples and six ground water samples were collected from the new <br /> wells and the existing wells MW2 through MW4 The samples were analyzed for TPH-g, using <br /> modified EPA method 8015 and BTEX, using EPA method 8020 Soil boring logs and well <br /> construction diagrams for wells MW5 and MW6 are provided on Plates 3 and 4, a detailed <br /> description of drilling, sampling and well construction procedures is contained in Appendix A <br /> L <br /> WALLACE•KUHL <br /> + Rcc cicdpap,r &ASSOCIATES INC <br />