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1 <br /> 27 December 1996 <br /> AGE-NC Project No 95-0143 <br />' Page 7 of 19 <br />' treatment of soil lying below ground water or within the "smear" zone and ineffective treatment of <br /> longer-chain hydrocarbons (i e , diesel) Ground water remediation may have to be conducted <br /> concurrently with SVE to facilitate remediation of the smear zone <br /> 1 <br /> 515 DURATION <br />' Cleanup periods for soil vapor extraction typically range from several months to several years Based <br /> upon the plume size, high hydrocarbon concentrations and the presence of clay-rich soil, an SVE <br />' cleanup period of 18 to 36 months is estimated <br />' 5 1 6 ESTIMATED COST OF SOIL VAPOR EXTRACTION <br /> The costs for SVE systems varies greatly, depending upon the particular system utilized for <br />' destruction of the extracted hydrocarbon vapors (thermal destruction, carbon adsorption, etc ) fhe <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 nary 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 /> , Y <br /> 52 EX-SITU TREATMENT OF IMPACTED SOIL �. <br /> Hydrocarbon-impacted soil can be excavated and treated on-site or transported off-site for <br /> recycling/disposal On-site treatment alternatives (ex-situ) include aeration, bioremediation, vapor <br /> extraction, and thermal destruction All are feasible methods for above-ground remediation of soil <br /> contaminated with gasoline Off-site disposal generally involves the transportation of the impacted <br /> soil to a licensed treatment/disposal facility <br />' 5 2 1 EXCAVATION <br /> All of the mentioned methods of ex-situ treatment require excavation of the impacted soil, which is <br /> generally the fastest and most effective method for soil remediation Once excavated, the impacted <br /> soil is generally stockpiled on-site for treatment or transported for disposal If soil is treated on-site <br /> and the hydrocarbon concentrations can be reduced to concentrations set by the lead agency or to <br /> non-detectable concentrations, the soil can be used to backfill the excavation If the hydrocarbon- <br /> impacted soil is disposed of off-site, material must be imported to backfill the excavation <br />