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OBJECTIVES The objectives of the proposed scope of work are to: 1) conduct a remediation feasibility study to assess a feasible and appropriate remedial method to reduce the potential for vapor intrusion of benzene into the Site building, and; 2) to present the procedures for conducting appropriate pilot testing of the recommended remedial method(s). FEASIBILITY STUDY Based on an initial screening of various remedial methods, which consider known geologic and hydrogeologic conditions and petroleum hydrocarbon distribution in soil and groundwater beneath the Site, the most practical, cost effective remedial alternative for the reduction of petroleum hydrocarbon constituents in vadose zone soils for the purpose of reducing potential vapor intrusion risk is vapor extraction. Based on a review of the boring log for soil borings B 1 and VW-1 (Appendix C) and soil sample laboratory analytical data for boring B 1 (Appendix B), it appears that the elevated concentrations of volatile petroleum hydrocarbons in the vadose zone beneath the Site are due to petroleum hydrocarbon impacted soils between approximately 5 and 15 feet bgs in the vicinity of the former fuel UST. The vadose zone soils reportedly consist of a sandy silt to at least 10 feet bgs, which transitions to a silty clay between 10 and 15 feet bgs. First-penetrated groundwater occurs at approximately 15 feet bgs. The sandy silt present in the vadose zone in the former source area should be amenable to vapor extraction. It is possible that additional active remedial method(s) in addition to vapor extraction may be required should vapor extraction not adequately mitigate vapor intrusion risk. Off-gassing of volatile petroleum hydrocarbons from groundwater and/or the silty clay layer that occurs just above first-encountered groundwater could continue to contribute to vapor intrusion risk following implementation of vapor extraction remediation. In this case, additional remedial methods, such as air sparging or in-situ chemical injection may be warranted to further reduce petroleum hydrocarbon concentrations in soil and groundwater. It is also possible that engineering controls, such as increased building ventilation, indoor air treatment, sub-slab depressurization, etc. may be recommended in lieu of, or in addition to active remediation, to mitigate vapor intrusion risk. DISCOUNTED REMEDIAL METHODS Several additional remedial alternatives exist for reduction of petroleum hydrocarbon constituents in soil to mitigate vapor intrusion risk. These alternatives include, but are not limited to, no action/natural attenuation, bioventing and soil excavation. These methods were not retained as remedial options at the Site for the reasons provided below. No Action/Natural Attenuation No action / natural attenuation has not been considered as a remedial alternative due to the relatively long time required to meet remedial objectives. Since a vapor intrusion risk to the Site building appears to require mitigation now, no action/natural attenuation is not a reasonable remedial alternative.