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a <br /> 28 February 1997 <br /> AGE-NC Project No 95-0144 <br /> r , <br /> Page 7 of 20 - <br /> remediation program When the concentrations of extracted vapor have decreased and stabilized after <br /> a certain period of operation, confirmation borings are drilled to collect soil samples for quantitative <br /> analysis in the laboratory to document the degree of cleanup obtained <br /> 1 „ <br /> 514 FEASIBILITY _ <br /> Generallyinc , <br /> ,a vacuum of at least 0 10 hes of water required to successfully volatilize subsurface <br /> hydrocarbons The radius of influence is often considered to be the distance from the extraction well <br /> ' at which a vacuum of at least 0 l inches of water is observed (EPA`- A guide for Corrective Action - <br /> Plan Reviewers) A vapor extraction feasibility test has not been performed at the site, however, data <br /> obtained during the installation of soil borings and nionitoring wells may be useful in determining <br /> a theoretical effective radius of influence Installation of extraction,wells would be required at the , <br /> site to ir'riplement an SVE system <br /> ' One drawback of SVE is that not all contaminated zones of soil are remediated effectively of at the <br /> same rate For instance, a sandy soil zone will cleanup more quickly than a silty one SVE is not <br /> usually effective in soil with high clay content Other drawbacks of SVE include ineffective <br /> treatment of soil lying below ground water or within the "smear" zone and ineffective treatment of <br /> longer-chane hydrocarbons(i e , diesel motor oil) Ground water remediation should be conducted <br /> concurrently with SVE to facilitate iemediation of the smear zone <br /> ` , r <br /> 515 DURATION <br /> Cleanup"periods for soil vapor extraction typically range from several months to several years Baged <br /> ' upon the plume size and the presence of clay-rich soil, an SVE cleanup period of 12 to 18 months <br /> is estimated <br /> 5 1 6 ESTIMATED COST OF SOIL VAPOR,EXTRACTION <br /> } f <br /> ' The costs for SVE systems vary greatly„ depending upon the particular system utilized for <br /> destruction of the extracted hydrocarbon'vapor (thermal destruction, carbon adsorption, etc ) The <br /> cost to operate, maintain, monitor and sample an SVE system could vary from $40,000 00 to <br /> $100,000 00 per year Maintenance costs can vary significantly, depending upon the specific unit <br /> utilized However, periodic costs (including maintenance, electricity and supplemental fuel) can <br /> range from-$12,000 00 to'$30,000 00 annually <br /> i <br /> 1 <br /> k . <br /> r <br /> i ' <br />