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4 <br /> i <br /> noted at the 14 to 16 feet and 32 to 34 feet below grade <br /> intervals, respectively, with extraction volumes ranging <br /> from 14 to 17 cfm. The maximum capture radius recorded at <br /> the 28 to 30 feet below grade interval was 110 feet at <br /> volumetric flow rates of 16 to 24 cfm. Influence was noted <br /> up to 110 and 147 feet between monitoring wells at <br /> extraction volumes ranging from 24 to 26 cfm. <br /> CONCLUSIONS <br /> The results of the Soil Gas Survey indicate that <br />' concentrations of hydrocarbon as vapor are located <br /> predominantly in the vicinity of the former tank cavity. <br /> Concentrations were recorded at depths greater than 28 feet <br />' below grade in this area. The results of the performance <br /> testing indicate that the soil conditions at this site are <br /> suitable for remediation by vacuum extraction. <br /> Based on an extrapolated average vapor concentration of <br /> 10, 000 ppm with a flow rate of 100 cfm, approximately 160 <br /> pounds of petroleum hydrocarbons would be removed daily <br /> during the initial stages of operation. It is estimated <br /> that average soil hydrocarbon vapor concentration would <br /> decrease to less than 6, 000 ppm within several weeks. <br /> Removal would be approximately 96 pounds of petroleum <br />' hydrocarbons per day at this time. <br /> With Exxon's approval, a proposal for a soil remediation <br />' program that includes a site-specific system design will be <br /> developed. <br /> 1 <br /> 1 <br /> 1 <br />