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Y I I t I � i04 March 1996 AGE-NC Project No 95-0144 Page 9 of 18 ' hydrocarbons Nova od r ex,traQ11Q fea �1tytest was performed at the sit However, data from the sparging test may-be useful in determining a theoretical e ectrve radius of influence A drawback of SVE is that not all contamrnated,zones of soil are remediated effectively or at the same rate For instance, a sandy soil will clean-up more quickly than a silt, SVE is not usually effective in soils with high clay content Other drawbacks of SVE include ineffective treatment of soil , lying below ground water or within'the "smear" zone and ineffective treatment of longer-chain hydrocarbons Ground water remediation would need to be conducted concurrently with SVE to facilitate remediation of the smear zone 6 1 5 ESTIMATED COST OF SOIL VAPOR EXTRACTION The costs for vapor extraction systems varies greatly, depending upon the particular system utilized for destruction of the extracted hydrocarbon vapors (thermal destruction, carbon adsorption, 'etc ) The cost to operate,'maintain, monitor and sample an SVE system could vary from as low as $40,000 00 for carbon canister system to $100,000 00 per year for an internal combustion/thermal destruction system Maintenance costs can vary significantly, depending upon the specific unit utilized _ i 62 EX-SITU TREATMENT OF IMPACTED SOIL - Hydrocarbon-impacted soil can be excavated and treated on-site or transported of-site for disposal On-site treatment alternatives (ex-situ) include aeration, bioremediation„vapor extraction, and ' themial destruction All are feasible methods for remediating sandy soil contaminated with gasoline However, increasing clay content limits the effect rveness'of each method Offsite disposal generally involves the transportation of the impacted soil to a licensed treatment/disposal facility I 6 2 1 EXCAVATION All of the mentioned methods of ex-situ treatment require excavation of the impacted soil, which is generally the fastest and most effective method for soil remediation Impacted soil extends to a depth ' of less than 20 feet bsg in the vicinity of former UST No 1 Solvent odors were detected during the installation of probulgs neat former UST No 8 However, laboratory analysis of soil samples did not detect petroleum hydrocarbons at the reporting limits The lateral extent of impacted soil in the 4 ' vicinity of former US T Nos 1 and 8 is also limited, making excavation a viable alternative } Once excavated, the impacted soil is generally stockpiled on-site for treatment or transported for disposal If soil is treated on-site and the hydrocarbon concentrations can be reduced to