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r REQUEST FOR SITE CLOSURE REPORT Former Beacon Station #610 3300 Waterloo Road, Stockton, California AMV Project No 19042 04 G.D inferred extent of soil containing hydrocarbon constituents have been prepared and are presented on Figures 9 and 10. It appears that a limited volume of soil (probably less than 100 cubic yards) currently in place beneath the site contains petroleum hydrocarbon constituents The average concentrations of TPHg and TPHd in soil, determined using the analytical results from soil samples collected within the areas illustrated on Figures 9 and 10, were calculated to be 187 and 1,970 mg/kg, respectively Based on a sort mass of approximately 2,800 pounds per cubic yard, and average concentrations of 187 mg/kg TPHg and 1,970 mg/kg TPHd, up to 31 pounds (approximately 5 gallons) of TPHg and 327 pounds (approximately 46 gallons) of TPHd remained in the soil as of September 1994. Calculations are provided in Appendix C Current ground water analytical results obtained in October 1994 indicate that detectable concentrations of benzene, TPHg, and TPHd are not present in ground water beneath the site 4.0 DISCUSSION AND RECOMMENDATIONS investigation of the subject site conducted between October 1993 and September 1994 indicated • that detectable concentrations of petroleum hydrocarbon constituents were present in limited areas of soil beneath the site Ground water samples collected from monitoring wells MW -5, MW -6, and MW -7 since April 1993 indicate that ground water beneath the site does not contain petroleum hydrocarbon constituents • Analytical results of the soil samples collected from the overexcavation of the UST basin indicated that soil at the southwest end of the UST basin contained detectable concentrations of petroleum hydrocarbon constituents (Tables 2 and 5) Analytical results from soil borings advanced at the site in September 1994 indicate the vertical and horizontal extent of hydrocarbons in soil beneath the site have been defined Vertically, samples collected at depths exceeding 40 feet below grade did not contain detectable concentrations of petroleum constituents (except for one sample (SB2-12) reported to contain 2 6 mg/kg TPHd) Results of soil bonngs advanced in September 1994 confirmed that the lateral extent of petroleum constituents is confined to the area of the southwest end of the UST basin Analytical results from the Wet DI and TCLP extract tests performed on soil sample SB2-8 indicate that benzene did not readily enter water in contact with this sample Also, as discussed in Section 1 2, state records indicate that only one well (with a total depth of 408 feet below grade) lies within a 1/2 -mile -radius of the site in a direction downgradient from the site (Figure 3) Because ground water sampling indicates that ground water beneath the site does not currently contain petroleum hydrocarbon constituents, it is unlikely that this well is at risk of receiving ground water containing these constituents as a result of activities at the subject site rptli4 mi BQO 11526