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PREVIOUS WORK <br /> Because of a suspected release of petroleum hydrocarbons to the subsurface during previous site <br /> operations, a single monitoring well was installed at the site on December 5, 1990 The well was <br /> developed and sampled on December 7, 1990 The groundwater sample was analyzed for total <br /> petroleum hydrocarbons as gasoline (TPHg) and for the associated volatile constituents benzene, <br /> toluene, ethylbenzene, and total xylenes (BTEX) The results of these analyses indicated that the <br /> groundwater beneath the site was impacted with petroleum hydrocarbons The laboratory detected <br /> 200 parts per million (ppm) TPHg, 31 ppm benzene, 1 I ppm toluene, 1 9 ppm ethylbenzene, and <br /> 5 2 ppm total xylenes in the groundwater sample (Table 1) <br /> I <br /> TABLE 1 <br /> SOIL AND GROUNDWATER SAMPLE RESULTS <br /> 1766 MONTE DIABLO AVENUE <br /> STOCKTON, CALIFORNIA <br /> Sample TPHg Benzene Toluene Ethyl- Total TPHd <br /> Number benzene Xylenes <br /> Soil <br /> S-9 5-B1 34 0 13 0 035 0 63 14 NA <br /> S-15-BI <1 0 0 040 0 013 0 006 0 023 NA <br /> • S-20-BI 15 026 057 027 10 NA <br /> Groundwater <br /> W-22-MW 1 200 31 11 19 5 2 NA <br /> Laboratory analyses performed by Matrix Environmental Laboratories <br /> Laboratory results reported in mg/kg (parts per million) <br /> TPHg = Total Petroleum Hydrocarbons as gasoline <br /> TPHd — Total Petroleum Hydrocarbons as diesel fuel <br /> <1 0 = Less than the laboratory method detection limits <br /> NA = Not Analyzed <br /> Jim Thorpe Oil of Stockton, California removed one 550-gal waste oil, two 4,000-gal unleaded <br /> gasoline, and two $,000-gal unleaded gasoline underground storage tanks, and product delivery <br /> lines on August 4, 1993 Three additional sand-filled tanks with smaller capacities were <br /> discovered and removed during the tank removal operation A total of six soil samples were <br /> collected from beneath the gasoline storage tanks at depths of 13 and 14 ft by Walsh under the <br /> direction of Ms Pamela Violett of San Joaquin County Environmental Health Division(SCEHD), <br /> additionally, two soil samples were collected from beneath the waste oil tank and pipeline at <br /> depths of 7 and 2 ft, respectively (Figure 2) <br /> 9114/93 2 1685-030 sew <br /> & Associates, Inc <br /> Environmental Scientists and Engineers <br /> t <br /> t <br />