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March 20, 1992 AWAVA <br /> ARCO Station No 6100, Tracy, California <br /> Vapor-Extraction Test <br /> RESNA performed a vapor-extraction test at the site on October 14, 1991, using vapor- <br /> extraction wells VW-1, VW-2, VW-3, and VW-4 The test was conducted to collect site <br /> specific data and evaluate the feasibility of vapor extraction as a soil remediation alternative <br /> and to evaluate the off-gas treatment alternatives, if applicable (RESNA, January 31, 1992, <br /> Report 30041-2) <br /> The highest observed vacuum reading was recorded at 10 inches of water from well VW-2 g� <br /> while well VW-3 was undergoing an air flowrate of 98 cubic feet per minute (cfm) at a ' 1,10 <br /> vacuum of 43 inches of water The vacuum measurements obtained from this vapor- <br /> extraction test are sufficient for use in evaluating vapor-extraction system feasibility The <br /> results of laboratory analyses of the vapor samples indicated that the influent TPHg <br /> concentrations ranged from 130,000 milligrams per cubic meter (mg/m3) from wells VW-1 <br /> and VW-3 to 160,000 (mg/m3) from well VW-4 (RESNA, January 31, 1992, Report No <br /> 30041-2) Based upon the VET data, RESNA concludes that vapor extraction is a feasible <br /> method of remediating soil at this site <br />. SUMMARY <br /> Objectives of our investigation were to evaluate the lateral and vertical extent of gasoline <br /> hydrocarbons previously detected at the limits of the old and new tank cavity excavations, <br /> beneath the product pipelines, beneath the dispenser islands, and to evaluate whether vapor- <br /> extraction was a feasible method for removing hydrocarbons from the soil <br /> Data from borings drilled during this and previous investigations were used to achieve <br /> delineate of the vertical and lateral extent of gasoline hydrocarbons in soil beneath the site, <br /> with the exception of areas to the west and south of the tanks and fuel islands Vapor- <br /> extraction wells VW-1 through V-9 were installed and field pilot testing was performed to <br /> evaluate the feasibility of using vapor-extraction to remediate the soil affected by <br /> hydrocarbons <br /> CONCLUSIONS <br /> Based on our investigation, we conclude the following <br /> o The highest concentrations of gasoline hydrocarbons are beneath and near the east <br /> side of the dispenser islands <br /> 10 30041-2 <br />