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Mr. Kyle Christie Project 0805-152.03 June 14, 1995 Page 2 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 corner of the site. Although trace to low concentrations of gasoline hydrocarbons were detected below 70 feet bgs, the vertical extent of residual gasoline hydrocarbons in soil appeared to be limited 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. Authorization to access the private property southeast of the site was granted from the property owner during the fust quarter 1995. In August 1993, RESNA researched the water supply well located at the site. Results of the investigation indicated the depth to first-encountered water was not indicated on the Department of Water Resources driller's log for the water-supply well (June 26, 1969); however, the log does indicate that the depth to water after development was 100 feet below surface grade (bsg). RESNA measured static groundwater after pumping the well for 0.25 hour. Static groundwater was rneasured at approximately 58.51 feet below the access plug. Based on current vapor extraction wells drilled to 115 feet bsg, RESNA concluded that first- encountered groundwater beneath the site is below 115 feet bsg, groundwater is under confined conditions, and the top of the first saturated unit is most likely 396 feet bsg or deeper. SCOPE OF WORK Field work will be conducted using Tri-Regional Guidelines and EMCON's Health and Safety Plan. Field procedures are presented in Attachment A. EMCON will conduct the following. SACAN:\P10\0805\08051520.3AL-94Wd :I