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March 20, 1992 <br />• ARCO Station No 6100, Tracy, California <br /> o The lateral extent of gasoline hydrocarbons in soil beneath the site has been <br /> delineated north, northeast, and east of the former and new tank cavities, and <br /> southwest, west, and northwest of the dispenser islands <br /> o The lateral extent of residual gasoline hydrocarbons in soil has not been delineated <br /> near the northeast corner of the station building and southeast of the dispenser <br /> islands Plate 44 shows our evaluation of the lateral extent of residual gasoline <br /> hydrocarbons in soil beneath the site <br /> o Results of the vapor-extraction test indicate an effective radius of influence of <br /> approximately 35 feet Based upon the test data, RESNA concludes that vapor <br /> extraction is a feasible method of remediating soil at this site <br /> o Additional vapor-extraction wells are required to remediate soil affected by gasoline <br /> hydrocarbons from surface grade to 30 feet below surface grade near portions of the <br /> dispenser islands and product pipelines, and from approximately 10 feet to 30 feet <br /> below surface grade near borings B-2 and B-7 <br /> RECOMMENDATIONS <br /> Based on the results of this and previous work, we recommend <br /> o Drilling two borings south of the dispenser islands to delineate the lateral extent of <br /> residual gasoline hydrocarbons in soil in this area <br /> o Drilling one boring near the northeast corner of the station building to delineate the <br /> lateral extent of residual gasoline hydrocarbons near the northwest corner of the <br /> former tank cavity <br /> o Drilling one boring near boring B-7 to install a vapor-extraction well to remediate <br /> soil near borings B-1 and B-7 affected by gasoline hydrocarbons <br /> o Installing a vapor-extraction well in the boring near the northeast corner of the <br /> station building to remediate possible gasoline hydrocarbons in soil between this <br /> boring and boring B-2 <br /> o Installing a vapor-extraction well in a boring near B-9 and B-11 to remediate gasoline <br /> hydrocarbons in soil from surface grade to 30 feet below grade <br />�. <br /> 0129Lcar <br /> 301141-2 $ <br /> I <br />