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Station No. 492, 470 N. Main St. , Manteca, - Interim Remediation Plan <br /> borings and the installation of monitoring wells in the boreholes. <br /> Analyses of soil and water samples have indicated the presence of <br /> hydrocarbon contamination at the site. <br /> SITE CHARACTERIZATION <br /> A Soil Gas Survey and a Performance Test were conducted by EVAX <br /> Technologies, Inc. , at the subject site on 25 July 1989. Four existing <br /> vapor recovery wells were used in the subsurface investigation. These <br /> are shown in Figure 1. <br /> Soil Gas Survey <br /> Soil gases were extracted and analyzed for total volatile hydrocarbons <br /> (TVH) during the Soil Gas Survey to screen for the presence of <br /> hydrocarbons and to delineate the extent of TVH impacted soils at the <br /> site. Four existing 2" diameter vapor recovery wells (VW-4, VW-5, VW-6 <br /> and VW-7) were used in the investigation. <br /> A vacuum was applied to each well to extract soil gas. The extracted <br /> soil gas was analyzed using a Beckman Model 400 Total Hydrocarbon <br /> Analyzer equipped with a Flame Ionization Detector (FID) . The analyzer <br /> was calibrated using certified hydrocarbon standards. <br /> Hydrocarbon vapor concentrations as high as 27,000 ppmv were recorded <br /> during the Soil Gas Survey. The results are presented in Table I. <br /> TABLE I - SOIL GAS SURVEY RESULTS <br /> Beacon Station #492 <br /> 470 North Main Street, Manteca <br /> July 25, 1989 <br /> Vapor Recovery Well Concentration (Rpm. <br /> VW-7 1,200 <br /> VW-4 7,000 <br /> VW-5 27,000 <br /> VW-6 25,500 <br /> PPmv - parts per million on a volume to volume basis (200C, 760mm Hg) <br /> - 2 - <br />