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10 June 1999 <br /> . AGE-NC Project No 97-0290 <br />' Page 25 of 26 <br /> concentrations is present from 45 and 60 feet <br /> Excavation of all petroleum hydrocarbon-impacted soil within the vadose zone would require the <br />' removal of a large volume of overburden soil, extensive shoring and special equipment, and is not <br /> logistically feasible at the site Furthermore,excavation of shallow impacted soil would not facilitate <br /> remediation of hydrocarbon-impacted ground water Therefore,an in-situ method of remediation will <br />' be more effective at the site <br /> Natural attenuation is not recommended due to the high concentrations of hydrocarbons present and <br />' the anticipated lengthy time for remediation The pilot test performed at the site indicated that soil <br /> vapor extraction described in this CAP would be effective to remediate the site Soil remediation <br /> methods, estimated durations and associated costs are summarized on Table 10 <br />' AGE recommends the following actions for remediation of hydrocarbon-impacted soil at the site <br />' • Preparation of a Remedial Action Work Plan (RAWP)detailing the proposed SVE system <br /> • Design and installation of an SVE system <br /> I . Assessment of the IC unit should be performed every 6 months of operation to evaluate <br /> progress If necessary, an activated carbon SVE system should be installed to continue the <br /> remediation to acceptable levels Operation of the SVE system at the site should remove <br /> between 80 and 90 percent of volatile contaminant by volume <br /> 92 REMEDIATION OF HYDROCARBON-IMPACTED GROUND WATER <br /> Based upon limited regulatory acceptance and uncertain monitoring requirements, in-situ <br /> bioremediation of ground water may not be the most cost-effective remedial alternative for the site <br /> Natural attenuation is not recommended due to the potential for spreading of the contaminant plume <br /> and long-term ground water monitoring which would be required <br /> Air sparging/soil vapor extraction and"pump and treat"methods could be effective to remediate the <br /> site Remediation of impacted ground water in.the"core"area should be conducted concurrently with <br /> soil remediation to prevent re-contamination of remediated soil <br /> . Ground water remediation alternatives, estimated durations and associated costs for the site are <br /> summarized on Table 10 <br /> In summary, AGE recommends the following aciaons for remediation of hydrocarbon-impacted <br /> ground water at the site <br /> Advanced CeoEnvironmental,inc <br />