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C' of Stockton - Van Buskirk Park Golf Course TL 394-007¢01 <br /> July 29, 1994 Page 3 <br /> 3.2.2 H drolo <br /> Sediments containing fresh groundwater are largely unconsolidated silts and sands derived <br /> from river channel, flood plain, and alluvial fan deposits of Pliocene to Recent age (Davis <br /> and others, 1959). <br /> Sediments containing fresh groundwater are largely unconsolidated silts and sands derived <br /> from river channel, flood plain, and alluvial fan deposits of Pliocene to Recent age (Davis <br /> and others, 1959). <br /> First encountered groundwater in the site vicinity occurs under unconfined (water table) <br /> iconditions at a depth of approximately 15 feet BSG and generally flows to the east(Personal <br /> Communication with Mr. John Fukumoto, City of Stockton Public Works Department). <br /> Local groundwater flow may be influenced by pumping of water wells and recharge from <br /> various sources. The effect of these influences on groundwater beneath the site is beyond <br /> the scope of this investigation. <br /> 3.3 Project Histo <br /> Twining understands that a 550-gallon gasoline UST was removed from the SM in April <br /> 1991 and that analysis of a soil sample collected from four feet BSG in the vicinity of the <br /> former dispenser detected 350 milligrams per kilogram (mg/kg) TPH-G and 7,200 mg/kg <br /> TPH-D. Twining also understands that a 1,000-gallon diesel UST was removed in January <br /> 1994. Analysis of a soil sample collected from 11 feet BSG at the west end of the <br /> excavation detected 135 mg/kg TPH-D, 435 mg/kg TPH-G, 5.8 mg/kg benzene, 29 mg/kg <br /> toluene, 8.2 mg/kg ethylbenzene, and 44 mg/kg total xylenes. The diesel UST pit was open <br /> at the time of Twining's field activities. <br /> r <br /> 4.0 FIELD PROCEDURES <br /> Field activities are summarized in the following subsections. Standard operating procedures <br /> (SOPS) for relevant field activities are described in Appendix A. <br /> 4.1 Soil Borings and Sampling <br /> Twining drilled three soil borings to a depth of approximately 30 feet BSG using a CME-75 <br /> truck-mounted drill rig equipped with 7-5/8-inch diameter hollow-stem augers. Soil boring <br /> MW3 was drilled near the approximate center of soils reported to contain PPCs. Soil boring <br /> ' MW1 was placed to the east to assess the downgradient groundwater conditions, and soil <br /> boring MW2 was placed to the northwest (MW2) to assess the upgradient groundwater <br /> conditions (Drawing 2). Soil boring logs are presented in Appendix B. <br /> I <br /> 1 tl <br /> l <br />