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On January 30, 1991, WaterWork Corp published a Problem Assessment Report for Investigation of Petroleum Hydrocarbon Contamination Their scope of work included the installation of four soil borings (SB-1, SB-2, SB-3 and SB-4) and one groundwater monitoring well (MW-1) The monitoring well MW-1 was positioned over the center of the former UST excavation Results of the soil and groundwater sampling indicated that groundwater had been impacted by gasoline hydrocarbons but that the majority of the hydrocarbon mass was concentrated in soil between 10 and 20 feet bgs The soil sample collected at 16 feet below ground surface (bgs) from MW-1 contained 12,000 mg/kg of TPH-as-Gasoline and 26 mg/kg of benzene The groundwater sample collected from MW-1 contained 140 micrograms per liter (ug/1) of TPH-as-Gasoline and 25 gg/I of benzene On July 9, 1992, Resna published their Summary Report—Assessment of Petroleum Hydrocarbon Contamination of the Groundwater Their scope of work included the installation and sampling of two additional groundwater monitoring wells (MW-2 and MW-3) The highest concentrations of gasoline hydrocarbons in groundwater(1,100 µg/I of TPH-as-Gasoline and 120 gg/I of benzene) were detected in MW-3, approximately 30 feet north and downgradient of the former USTs From May 8, 1992 to April 27, 1994, the three monitoring wells were monitored and sampled on three different occasions In general, the concentrations of gasoline hydrocarbons in these wells declined, However, by April 27, 1994, the static groundwater level had risen above the top of the screen interval in all three wells This condition likely compromises the accuracy of groundwater table monitoring and sampling results On July 8, 1994, Resna published Summary Report/Additional Groundwater Investigation This report documented the installation of two additional groundwater monitoring wells (MW4 and MW-5) Gasoline hydrocarbons were not detected in groundwater collected from these two new wells The direction of groundwater flow remained north-northeast On June 29, 1995, Groundwater Technology, Inc (GTI) published their Environmental Assessment Report documenting the installation of two vapor extraction well nests (VW-1 and VW-2) and two single vapor extraction wells (VW-3 and VW4) and the pilot testing and modeling of soil vapor extraction According to GTI, results of this work indicated that an area of approximately 2,055 square feet of soil is impacted by gasoline hydrocarbons to a depth of approximately 70 feet bgs Soil vapor extraction testing indicated an achievable radius of influence of 59 to 75 feet and an effective coverage of 80 percent of the impacted soil plume Based on these findings GTI recommended that the site be remediated by soil vapor extraction plus air sparging from MW-1 This active remedial work was never implemented 4 t�