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19 June 2000 AGE-NC Project No 96-0232 Page 20 of 35 814 Feasibility Based on depth to ground water measurements collected at the site between July 1996 and May 2000 (Table 5), ground water levels have fluctuated anywhere between 3 and 15 feet bsg, therefore, the majority of adsorbed petroleum-impact is submerged beneath the water table Based on review of boring logs (Appendix A) generated during site investigation activities and geotechnical analysis of three shallow soil samples(Appendix D), soil beneath the former UST area has a relatively high silty sand, sandy silt and sandy clay content in the upper thirty-five feet, potentially making SVE an ineffective remedial method in the vadose zone Another negative aspect of SVE is that not all contaminated zones of soil are remediated effectively or at the same rate For example, a sandy soil zone will cleanup more quickly than a silty one SVE is not usually effective in soil with high clay content Other drawbacks of SVE include ineffective treatment of soil lying below ground water or within the capillary fringe or "smear" zone and ineffective treatment of longer-chain hydrocarbons Ground water remediation may have to be conducted concurrently with SVE to facilitate remediation of the smear zone 815 Duration Cleanup penods for soil vapor extraction typically range from several months to several years Based upon the volume of impacted soil at the site(estimated 3,337 cubic yards) and the likelihood that in- situ air sparging would be required assist in mechanically stripping submerged adsorbed hydrocarbons to finer-grained soils(silty sands,sandy silts and sandy clays),a 36 to 48 month period is estimated for the duration of remediation 8 16 Estimated Cost Of Soil Vapor Extraction The costs for installation,operation and general maintenance of SVE systems vanes,depending upon the particular system utilized for destruction of the extracted hydrocarbon vapors (then-nal destruction,carbon adsorption, etc ) and the established cleanup goals Installation of SVE wells at the site could cost between $20,000 and $30,000 The total cost to operate, sustain, monitor and sample an SVE system at this site could vary between $40,000 00 and $50,000 00 per year Based on the estimated 36 to 48 month period of remediation, total cost for SVE should range between $140,000 and $230,000 00 and does not include remediation of ground water Advanced GeoEn%tronmcntal,Inc