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1 <br /> June 25, 1992 <br /> ARCO Service Station No. 2076, Lodi, California <br /> 1 <br /> Also on December 11, 1991, Mr Steve Schneider of the SJCPHS-EHD verbally authorized <br /> installation of new product lines and subgrade piping and backfilling of the former tank <br /> cavity with the stockpiled soil collected from the former tank and pipe-line excavations <br /> These tasks were approved with the understanding that future environmental work <br /> conducted at the site would include delineating residual hydrocarbons in soil and installing <br /> a vapor-extraction system <br /> I <br /> CONCLUSIONS <br /> Based on the data from subsurface investigations to date, RESNA concludes <br /> i <br /> o Soil with residual hydrocarbons are delineated laterally to the north,west, and <br /> south of the former gasoline tank cavity by borings B-1, B-2 and B-3 <br /> o Soil with residual gasoline hydrocarbons (quantified as TPHg and BTEX) <br /> remains in place at approximately 14 feet below grade in the former gasoline <br /> cavity at concentrations up to 17,000 ppm and in the eastern side wall <br /> adjacent to the station building at concentrations up to 24,000 ppm <br /> o Soil with residual gasoline hydrocarbons quantified as TPHg and BTEX <br /> remains in place below the former product and vapor-return lines at <br /> concentrations up to 28,000 ppm <br /> o Residual hydrocarbons were not detected in soil samples collected from the <br /> base or sidewall of the new tank cavity <br /> o Pursuant to our Work Plan, soil excavated from the former tank cavity was <br /> placed back into the tank cavity This soil contained concentrations of TPHg <br /> and BTEX to 8,500 ppm <br /> o Vapor extraction is a feasible remedial alternative at the site <br /> o Further work is warranted to delineate the vertical limits of residual <br /> hydrocarbons in the former tank cavity and around the dispenser islands <br />• 3M-3 8 <br />