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. Mr Harlin Knoll June 5, 1998 Page 2 In-Situ Bioremediation The design of an in-situ soil bioremediation system typically includes provisions for the injection of air, water and nutrients into the plume for the purpose of enhancing the biological growth of naturally occurring microorganisms The proximity of the plume beneath the site,which contacts the groundwater surface, poses risks associated with the injection of water for bioremediation The leaching of hydrocarbons to groundwater would likely occur and would necessitate a groundwater treatment system to contain and treat leached hydrocarbons Groundwater treatment would result in the withdrawal of dissolved hydrocarbons from beneath the site and would result in prohibitively expensive treatment and disposal costs The risks and prohibitive cost of in-situ bioremediation,estimated at approximately$200,000,eliminates this option from further consideration Soil Vapor Extraction Vapor extraction pilot test data indicates that SVE has the potential to remove approximately 216 pounds of hydrocarbons per day SVE has been proven to be an effective method to decontaminate impacted soil,both from a technical and economic perspective The cost to design, install and operate a 100 cubic foot per minute SVE system for a period of one year is approximately$100,000 As such, SVE is clearly the most economic and technically sound remedial option for hydrocarbon source removal at the subject site AIR SPARGING FOR GROUNDWATER TREATMENT Due to the increases in groundwater elevation beneath the site in the last 4 years, some of the wells originally installed between 1990 and 1994, currently have well screens that are completely submerged below groundwater A review of the construction log for existing well MW-1 indicates that the upper well screen is approximately 27 feet below groundwater More importantly, the well/borehole seal is also submerged approximately 23 feet below the groundwater surface Based on the configuration of well MW-1 as compared to the current groundwater depth,well MW-I can be utilized as an air sparge well The advantages of adding air sparging via well MW-1 areas follows a The construction of a new well is not necessary a Well MW-1 is located within the area of highest groundwater impact a Air sparge off-gas from the saturated zone will be contained by the SVE system a Air sparging will effect the removal of dissolved gasoline and BTEX while promoting saturated zone biodegradation via dissolved oxygen increases Therefore, Ramage Environmental proposes the inclusion of air sparging using existing well MW-1 as an air injection well The design effort for the SVE system will be expanded to include I)the addition of an air compressor to deliver pressurized air to the saturated zone, 2) subsurface piping from the treatment compound to the MW-1 wellhead and 3)process control provisions to manage the pressure and flowrate of sparge air