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KLEI NFELDER <br /> 1 <br /> was drilled through the backfilled tank excavation, it is possible that the low and <br /> inconsistent levels of gasoline and benzene detected in the well during the first two <br /> sampling events may have been induced during the drilling and well completion. <br /> ' Kleinfelder recommends that Nor-Cal Beverage seek closure of the site as an <br /> environmental concern, and approval from San Joaquin County Public Health Services to <br /> abandon the well. <br /> Based on the following results, Kleinfelder does not recommend additional ground water <br /> monitoring wells or assessment. <br /> ' The monitoring well was drilled through the approximate center of the backfilled <br /> tank excavation in an area likely to encounter the vertical migration of petroleum <br /> ' hydrocarbons if present. <br /> • Elevated petroleum hydrocarbon concentrations were not detected in the two soil <br /> borings drilled vertically to a depth of 40 feet. These borings were drilled in the <br /> vicinity of elevated petroleum hydrocarbon concentrations remaining• in the <br /> excavation after soil removal. <br /> 1 The bulk of the contaminated soil and source of potential future contamination was <br /> removed during the tank and soil excavation activities. <br /> • Ground water is approximately 70 feet below the ground surface and approximately <br /> SO feet below the remaining two elevated petroleum hydrocarbon areas.detected in <br /> the excavation. The site is currently capped with asphalt, thus reducing the potential <br /> ifor surface water infiltration and the vertical migration of hydrocarbons to the <br /> ground water surface. <br /> 1 Low TPH and benzene concentrations were detected in the first sampling event, but <br /> these concentrations were not consistently detected in the second sampling event <br /> (including the laboratory retained by San Joaquin County). Concentrations were <br /> not detected during the third sampling round conducted by Kleinfelder. <br /> ' Concentrations detected during the first round of sampling may have been induced <br /> during the drilling and construction of the well. <br /> FR1-92-15 Page 19 of 21 <br /> ' Copyright 1992 Mcinfelder,Inc. <br />