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11 Februa <br /> • rY 2003 <br /> AGE-NC Project No. 98-0520 <br /> Page 9 of 21 <br /> ' 6.2.3. Monitoring Activities <br /> Monitoring of vapor extraction systems involves weekly measurement of vapor concentrations at <br /> ' the inlet to the destruction unit and periodic service and repair.-Systems can be equipped with an <br /> automatie'telecommunication system to alert the operator of system malfunction or failure. Vapor <br /> samples should be collected monthly for laboratory analysis to monitor the efficiency of the <br /> ' remediation program. When the,concentrations of extracted vapor have decreased and stabilized ' <br /> after a certain period of operation, confirmation borings are drilled to collect soil samples for <br /> quantitative analysis in the laboratory to document the degree of cleanup obtained. <br /> 6.2.4. Feasibility. <br /> 1 Generally,a vacuum of at least 0.10 inches f r ' <br /> s o Ovate is 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 0.1 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 /> lieobtained during the.installation of soil borings and.monitoring 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 implement an SVE system. <br /> ' One drawback of SVE is that not all contaminated zones of soil are remediated effectively or at the <br /> same rate. For instance, a sandy soil 'zone will clean up 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-chain hydrocarbons (i.e., diesel, motor oil). <br /> ' Ground water remediation should be conducted concurrently with SVE to facilitate remediation-of <br /> the smear zone. <br /> 6.2.5. Duration <br /> Cleanup periods for soil vapor extraction typically range from several months to several <br /> years. <br /> Based upon the plume size and the presence of clay-rich soil, an SVE cleanup period of 18 to 24 <br /> months is estimated. <br /> 1 <br /> Advanced CeoEnvironmental,Inc. <br />