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1 I _ 22 November 2006 AGE-NC Project No. 95-0167 Page 14 of 15 i dispenser location and under the building at the site. The plume of impacted soil at the site has an estimated north-south diameter of approximately 30 feet, an west-east diameter of approximately 20 feet and appears to extend downward to approximately 30 feet bsg. The calculated volume of hydrocarbon-impacted soil is approximately 775 cubic yards. The feasibility for soil excavation to effectively address the impacted soil is low to uncertain due to the extent of the impacted soil beneath the building. AGE recommends that SVE be used to remove the contaminated mass in soil. Additionally, soil vapor intrusion will be mitigated with the use of SVE remediation. 8.0. RECOMMENDATIONS FOR REMEDIATION OF HYDROCARBON- rl IMPACTED GROUND WATER i An in-situ remediation method would be more feasible from a cost and operation perspective, over an ex-situ remediation method (i.e. pump and treat) . The in-situ method (air sparging in conjunction with soil vapor extraction) described in this CAP could be effective to remediate the site. Petroleum hydrocarbon-impacted ground water appears to be limited to the area containing wells MW- 1 and MW-2 (Table 3) and grab ground water samples collected from P-5 , P-6, P-7, and P-8. Impacted ground water at the site has an estimated north-south diameter of approximately 45 feet, l_J an east-west diameter of 55 feet and appears to extend downward to a depth of approximately 30 feet bsg (Figure 5). Remediation of impacted ground water in the "core" area should be conducted concurrently with soil remediation to prevent re-contamination of remediated soil In-situ air sparging/vapor extraction appears to be a viable alternative for remediation of both soil and ground water in the vicinity of the former UST location. The system used for soil vapor extraction could also be used for the air sparging/extraction system. i� Combined with SVE, IAS should mechanically strip hydrocarbons without the addition of any chemicals or microbe solution into the environment. It is a well known and widely accepted method of volatilizing hydrocarbons. As IAS has few, if any, adverse environmental effects, it is likely to be more readily approved for implementation by regulatory agencies . A 12- to 24-month remediation period can be expected to reduce concentrations to a level suitable for closure consideration. 9.0. LIMITATIONS I` Our professional services were performed using that degree of care and skill ordinarily exercised by IJ Advanced GcoEnvironnaental, Inc. J