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Station No. 492, 470 N. Main St. , Manteca, - Interim Remediation Plan <br /> Performance Test/Feasibility Study <br /> A Performance Test was conducted concurrently to determine the <br /> feasibility of using vacuum extraction at this site. The performance <br /> test simulates operating characteristics of a vacuum extraction system <br /> using temporary vacuum connections to the existing monitoring wells. <br /> Extraction volumes from the wells tested ranged from 15.0 to 25.0 <br /> standard cubic feet per minute (scfm) . The applied vacuums ranged from <br /> 2.5 to 7.8 inches of mercury. Influence vacuums ranged from 0.075 to <br /> >0.25 inches of water. Favorable influence was measured at a distance of <br /> 30 feet. The results of the performance test indicated that soil <br /> conditions are suitable to remediation using vacuum extraction. <br /> INITIAL PHASE OF REMEDIATION <br /> A successful vapor extraction system comprised of the four vapor recovery <br /> wells (VW-4, VW-5, VW-6, VW-7) and one monitoring well (MW-1) operated at <br /> this site from 13 October 1989 to 17 November 1989. An internal <br /> combustion engine was used for vapor abatement during this period. The <br /> unit operated continuously 24 hours per day. <br /> Approximately 2,250 pounds of hydrocarbons were removed from the soil <br /> during this operation. Influent hydrocarbon concentrations decreased 91% <br /> from a start-up condition of 23,150 ppm to 1,970 ppm at the final <br /> monitoring. Data from this phase of remediation is summarized in Table <br /> 11 and also in Appendix B. <br /> TABLE I1 - INITIAL AND FINAL VAPOR CONCENTRATIONS <br /> Soil Vapor Extraction System <br /> Beacon Station #492 <br /> 470 North Main Street, Manteca <br /> 13 October to 17 November 1989 <br /> I <br /> f Extraction Hydrocarbon Vapor Concentration mv). <br /> Point Initial (10/13/89) Final (11/17/89) <br /> VW-4 26,600 875 <br /> VW-6 7,250 145 <br /> VW-7 8,600 795 <br /> VW-5 12,425 2,550 <br /> MW-1 11,850 725 <br /> System Total 23,150 1,970 <br /> - 3 - <br /> r <br />