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• 41 io r Mr Kyte Christie Project 0805-152 02 August 4, 1995 Page 2 gasoline USTs and the dispenser islands, along the north and west side of the former gasoline tank cavity, and near the southeast comer of the site (RESNA, January 31, 1992, Report No 30041-2, and November 12, 1992, Report No 30041-3) The lateral extent of residual gasoline hydrocarbons in soil was delineated at the site except for the area near the southeast comer of the site Although trace to low concentrations of gasoline hydrocarbons were detected below 70 feet bgs, the vertical extent of residua[ gasoline hydrocarbons in soil appeared to be hmited to a depth between 50 and 70 feet bgs, dependent upon location, and from surface grade to approximately 70 feet bgs beneath the dispenser islands RESNA performed a vapor extraction test at the site on October 14, 1991, using vapor extraction wells VW-1, VW-2, VW-3, and VW-4 (RESNA, January 31, 1992, Report No 30041-2) The results of the test indicated that vapor extraction is a feasible means to remove residual gasoline hydrocarbons from the soil In December 1992, RESNA observed drilling of one soil boring (B-26) and construction of a vapor extraction well Residual gasoline hydrocarbons were detected in soil samples collected from the soil boring (RESNA, March 18, 1993, Report No 30041-4) Groundwater was not encountered in the soil boring The lateral extent of residual gasoline hydrocarbons in soil has not been delineated southeast of the site In August 1993, RESNA researched the water supply well located at the site Results of the investigation indicated the depth to first-encountered groundwater was not indicated on the Department of Water Resources (DWR) driller's log for the water-supply well (June 26, 1969), however, the log does indicate that the depth to groundwater after development was 100 feet bgs RESNA measured static groundwater after pumping the well for 0 25 hour Static groundwater was measured at approximately 58 51 feet below the access plug Based on current vapor extraction wells drilled to 115 feet bgs, RESNA concluded that first-encountered groundwater beneath the site is below 115 feet bgs, groundwater is under confined conditions, and the top of the first saturated unit,based on DWR driller's logs, is most likely 396 feet bgs or deeper SUPPLEMENTAL INVESTIGATION Authorization to access the private property southeast of the site was granted from the property owner during the first quarter 1995 The purpose of this investigation was to further characterize soil southeast of the site and to provide vapor extraction coverage in that area On June 26, 1995, a geologist from EMCON observed Woodward Drilling drill one . soil boring and install one vapor extraction well (VW-18) Vapor extraction well VW-18 was SAC1N 1PJ=805V08051520 2BS-951pas 1