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OfINICI_�_[fRGI Mr. Charles Leubner 10 October 1991 Page 7 Three remediation alternatives are presented Alternative 1 is an in-situ method relying on vapor extraction to remove the petroleum hydrocarbons that are present. Alternatives 2 and 3 involve the excavation of soil with offsite disposal at a facility permitted for petroleum hydrocarbon wastes (Alternative 2) or transport of the contaminated soil to the District's Corporation Yard for treatment utilizing an aboveground vapor extraction system (Alternative 3). A breakdown of the estimated costs for the three alternatives is presented on Table 2. The assumptions used in developing these costs are also presented in Table 2. Alternative 1 - In-situ Vapor Extraction Because the volume of soil requiring remediation is relatively small (18 feet by 20 feet by 18 feet), an in-situ vapor extraction system comprised of a number of vapor extraction wells is a viable in-situ alternative. The proposed vapor extraction system consists of 9 vapor extraction wells connected to a blower. The wells would be screened between a depth of 5 feet and 20 feet. The suction side of the blower would be connected to the wells and the exhaust gas from the blower would pass through carbon canisters to capture hydrocarbon vapors prior to discharge to the atmosphere. Since the site is a school yard, the permitting process for obtaining air emissions permits would be more extensive than would normally be required for commercial sites and would include parental notification and possibly a public hearing. The estimated cost for this alternative is $48,000, excluding costs for notifying the public and conducting a public meeting. Alternative 2 - Excavation and Offsite Disposal This alternative entails the excavation and offsite disposal of contaminated soil at a permitted treatment or disposal facility. Based on the results of soil boring B-1, the maximum depth of excavation is anticipated to be between 15 to 20 feet below the ground surface. Excavation will continue until that are no indications of petroleum hydrocarbons such as stains, odors or organic vapors above 100 ppm by headspace analysis. Soil samples will then be collected from the bottom and sidewalls of the excavation to confirm the results of field monitoring. The excavated soil will be disposed of at a facility which is permitted for hydrocarbon wastes. The estimated cost for this alternative is $60,000. Alternative 3 - Excavation and Aboveground Vapor Extraction Excavation procedures will follow those described for Alternative 2, however, instead of disposing of the soil at a permitted facility, the soil will be treated by vapor extraction at the District's Corporation Yard. This will be accomplished by placing the soil on a liner, embedding perforated plastic pipe in the soil and covering the soil with plastic