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was initiated in November 1990 The SVE system utilized SVE Wells V-1 through gh V-5 and Morutonng Wells MW-3 through MW-6 Many of the groundwater wells at the site went dry during the time period of 1989 to 1991 Drought was thought to be the probable cause Groundwater Technology, Inc. One soil boring was drilled in July 1991 and converted into Monitoring Well MW-9 The well was installed because many of the site wells (MW-1 through MW-8) were dry Nine soil samples were collected from the boring The highest TPH-g concentrations from these samples, collected between 21 and 26 feet bgs, were 560 and 3,900 ppm, respectively Soil samples at 71 feet did not contain detectable TPH-g concentrations Groundwater was found to contain TPH-g and benzene at concentrations of 1,900 and 20 ppb, respectively Three additional soil borings were drilled in May 1992 Two of the borings were developed into monitoring wells (MW-10 and MW-11) These wells were drilled to 75 feet bgs The third boring, converted to an SVE well (V-6) and connected to the existing SVE system, was drilled to a depth of 29 feet bgs Benzene at 0 12 ppm and TPH-g at 730 ppm were detected only at a depth of 30 feet bgs in Well V-6 The SVE system operated continuously from November 1990 through November 1992, except for a 7-month hiatus from February to September 1992 During the SVE system operation the total amount of hydrocarbons removed was approximately 12,000 pounds In June 1993, two soil bonngs were drilled off site to depths of approximately 65 feet bgs in order to install two additional monitoring wells (MW-12 and MW-13) All previous wells were installed on site All soil samples from these wells were non-detect for TPH-g and BTEX compounds In December 1993, three soil borings (SB-1, SB-2, and SB-3) were drilled near the former USTs in order to determine the effectiveness of the SVE system Results of soil analysis from the confirmation soil borings indicated that the bulk of the lighter constituents of gasoline have been removed from the vadose zone by SVE Soil samples collected from Soil Borings SB-2 and SB-3 indicated the bulk of hydrocarbons remained at 25 and 35 feet bgs TPH-g concen- trations at these depths ranged from 8 to 2,000 ppm Well MW-14 was also installed at the tune in El Dorado Avenue to further define the downgradient extent of the dissolved plume While installing another new monitoring well in December 1993, designated MW-2R, to replace MW-2 (which went dry), one more UST was located Spectrum Environmental Services, Inc conducted a geophysical investigation of the former service station in order to locate other unknown USTs Other than the unidentified UST near Well MW-2R, no USTs were found during the geophysical investigations The above mentioned tank and product • 3201337B/1918REV A- 3 Au gust 31, 1995