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After the on-site gasoline and used oil USTs were removed from the site by Blame in February 1988, EA installed monitoring wells on site Six, 4-inch diameter, monitoring wells were installed in November 1988, designated Wells MW-I through MW-6 Soil samples collected from the soil borings were found to contain concentrations of total petroleum hydrocarbons calculated as gasoline (TPH-g) up to 3,300 ppm Groundwater samples were collected and analyzed by EPA Method 8015 for TPH-g and BTEX compounds Petroleum hydrocarbons were not detected in Well MW-1, the apparent upgradient well The highest concentrations were measured in the two wells closest to the backfilled UST pit, Wells MW-3 and MW4 Well MW-3 contained 9,300 parts per billion (ppb) TPH-g, with 2,700 ppb benzene, 360 ppb toluene, 2,800 ppb ethylbenzene, and 2,000 ppb xylenes The hydrocarbon concentrations appeared to decline with distance from the backfilled fuel pit as seen in Wells MW-2, MW-5, and MW-6 Depth to groundwater was found to be 35 to 37 feet bgs In November 1988, while installing Well MW-5, an unknown, 550-gallon UST was found and accidentally punctured After analyzing a sample from the tank, it was found to contain "old product," probably gasoline The hole in the tank was covered during its removal During this tank's excavation, product piping was uncovered leading to two additional unknown tanks These tanks were 4,000 and 3,000 gallons in capacity and had been abandoned by tearing holes in their tops and filling them with sand All three of the tanks were constructed of steel No hydrocarbons were detected in the air above or within these tanks by the organic f vapor monitor The three tanks were removed in December 1988 by Blaine They performed UST removal and soil sampling associated with the removal of the three additional USTs from beneath the site One sod sample was taken from the 550-gallon UST pit The soil sample taken from the pit was analyzed for the presence of high boiling point hydrocarbons, BTEX compounds, organic lead, and ethylene dibromide Laboratory analysis of the soil sample taken from the pat revealed non-detectable amounts of all constituents analyzed One soil sample was taken from the bottom of the 3,000- and 4,000-gallon UST excavation The sample was analyzed for the presence of lugh boiling point hydrocarbons, BTEX compounds, organic lead, and ethylene dibromide Laboratory analysis of the soil sample taken from the 3,000- and 4,000-gallon UST pit revealed non-detectable amounts of all constituents analyzed Groundwater monitoring indicated the groundwater flow to be to the northeast at an approximate gradient of 0 002 foot per foot EA drilled seven soil borings in January 1989 Due to the high TPH contamination in the soils at depths of 31 feet bgs, in-situ remediation was selected Five of the soil borings were completed as soil vapor extraction (SVE) wells (V-1 through V-5), while the remaining two borings were developed into groundwater monitoring wells (MW-7 and MW-8) The site was found to be well suited for vapor extraction as a remediation treatment, and an SVE system 3201337BI1918REV A- 2 August 31, 1995