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IDMERIM PROBLEM ASSESSMENT REPORT/MrERIM REMMIAL ACTION PLAN Former Beacon Station No. 494, 2185 East Fremont Street -$ Stockton, CA--AMV Project No. 19005.07 Ground water samples Collected ollected from each monitoring well in July 1993 contained petroleum constituents. Dissolved benzene concentrations in samples ranged from 26 µg/1 in the sample collected from monitoring well MW-4 to 2,300 µg/i in the sample collected from monitoring well MW-3. TPHg concentrations ranged from 190µg/l in monitoring well MW-4 to 7,000µg/ll in monitoring well MW-3. Table 3 includes the ground water sample results from this sampling ' event. Figure 6 illustrates the inferred distribution of dissolved benzene beneath the site using the analytical data from the July 1993 sampling. The ground water sample collected from monitoring well MW-2 did not contain detectable ' concentrations of chlorinated hydrocarbons. The results for the ground water sample collected from monitoring well MW-5, however, indicates the presence of 1,2-dichloroethane (DCA) ' (0.18 µg11) and trichloroethene (0.13 µg/i). Appendix K contains copies of the certified analytical report for all of the July 1993 ground water samples. ' 5.0 SUMMARY OF RESULTS 5.1 Subsurface Soil Conditions and Distribution of Petroleum Constituents in Soil Soil boring logs indicate that soils beneath the site consist of silty clay, sandy silt, clayey silt, ' silty sand, sand, silt, clayey sand, and sandy clay. Soil units do not appear to be laterally continuous across the site. Of the 61 soil samples submitted for Iaboratory analysis from the borings for MW-1 through MW-5, B-1 and B-2, and VW-1 through VW-4, only 9 results contained TPHg at concentrations exceeding 100 mg/kg TPHg. Eight of those nine soil samples were collected from the soil ' borings for monitoring/extraction wells MW-3, VW-1, and VW-2. The remaining soil sample was collected from 40 feet below grade in the boring for extraction well VW-4. In six other samples analyzed from the VW-4 boring, the highest TPHg result was 1.1 ppm. In samples from the tank basin and piping trenches, laboratory analysis detected TPHg in only one of the 10 samples collected. This sample contained TPHg at a concentration of 0.92 mg/kg. ' This sample was collected from the southwest corner of the tank basin, closest to monitoring well MW-3 and vapor extraction well VW-2. �toos.�