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1444 MARIPOSA <br /> WKA No 2307 02 <br /> May 24, 1993 <br /> ' Page 4 <br /> ' Analysis of samples B4-5I, B4-6I and B4-71, obtained from depths of 39 5 to 49 5 feet, revealed <br /> TPH gasoline concentrations ranging from less then 0 50 mg/kg to 0 74 mg/kg and trace <br /> ' concentrations of BTEX <br /> Table 1 contains a summary of laboratory test results, boring logs containing descriptions of the <br /> materials and conditions encountered in the field are shown on Plates 3 through 14 Complete <br /> ' laboratory results and chain-of-custody documentation are appended <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> ' The laboratory results of soil samples obtained from the two angle borings (B2 and B3) and the <br /> two vertical borings (B1 and B4) indicate that the soils beneath the former underground storage <br /> tanks contain relatively low concentrations of TPH gasoline and BTEX to a depth of <br /> approximately 75 feet <br /> Laboratory analysis of samples obtained from borings B3 and B4 at a depth of approximately 45 <br /> feet indicate that relatively Iow concentrations of TPH gasoline and BTEX are present at this <br /> ' depth approximately ten feet westerly and southerly of the excavation Additional analyses of <br /> samples obtained from boring B1 at depths ranging from 415 to 56 5 feet indicate that relatively <br /> ' low levels of TPH gasoline are present approximately five feet easterly of the excavation <br /> ' Analytical results of samples obtained during the November 9, 1992 excavation and the analytical <br /> results of samples obtained from the four soil borings, indicate that the majority of significant <br /> ' gasoline contaminated soil appears to be confined to the central portion of the excavation at <br /> depths ranging from 36 to 50 feet below grade It is our opinion that the depth and extent of the <br /> ' remaining contaminated soil reduces the feasibility of additional excavation, in addition to raising <br /> safety concerns Based on our findings, we recommend that a meeting be convened with San <br /> 16 Joaquin County personnel to discuss future options for the site <br /> o <br /> `�W <br /> WALLACE KUHL <br /> 7te.ckd�atxr &ASSOCIATES INC. <br />