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1 <br />' 18 February 1997 <br /> AGE-NC Project No 95-0104 <br /> tPage 9 of 22 <br />' 615 DURATION <br /> Cleanup periods for soil vapor extraction typically range from several months to several years Based <br />' upon the volume of impacted soil, hydrocarbon concentrations and the presence of finer-grained soils <br /> (silts and clays), we estimate a 12 to 24 cleanup period <br /> MM' S <br /> 6 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 ) 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 range <br />' from $12,000 00 to $30,000 00 annually Costs for installation, operation and maintenance are <br /> dependant upon the type of SVE unit utilized and the cleanup goals established <br /> 10 6 2 EX-SITU TREATMENT OF IMPACTED SOIL <br />' Hydrocarbon-impacted soil can be excavated and treated on-site or transported offsite 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 Incensed treatment/disposal facility <br />' 6 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 /> Iand the hydrocarbon concentrations can be reduced to concentrations set by the Iead 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 offsite, material must be imported to backfill the excavation <br /> I6 2 2 FEASIBILITY OF EXCAVATION <br /> Excavation of impacted soil, followed by ex-situ treatment and/or disposal is a very effective method <br /> Iof remediation Theoretically, all or at least the majority of the impacted soil is removed However, <br />