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Former Discovery Chevrolet June 6, 1997 Tracy,California Report of Additional Subsurface Investigation Alameda, California, and was formerly occupied by Discovery Chevrolet and most recently by Tracy Chevrolet. Currently the site is unoccupied. Site facilities include an auto showroom, a sales office, and service bays. We understand from information provided by Winner Ford that two 500-gallon gasoline underground storage tanks (USTs) were removed from a common excavation at the site in April 1993, and that no USTs are known to remain at the site (GeoStrategies Inc., December 7, 1994, Preliminary Environmental Investigation and Evaluation Report for Former Discovery Chevrolet, 1615 11th Street, Tracy, California). Locations of these facilities and other pertinent site features are shown on Figure 2. GcoStrategies (December 7, 1994) indicated that when the two gasoline tanks were removed, four soil samples were collected from the base of the excavation at approximately 9 to 10 feet below surface grade(bsg). These samples were found to contain total petroleum hydrocarbons as gasoline (TPHg) at concentrations ranging from 920 to 4,400 parts per million (ppm). Groundwater was not encountered in the tank excavation. In addition, a t>: =? sample was collected below the dispenser located inside the service bays. Benzene was detected at 0.88 ppm in the sample collected from beneath the dispenser. Historical results are included as Appendix A. GeoStrategies installed three groundwater monitoring wells (MW-1 through MW-3) in September 1994 to evaluate the presence of hydrocarbons in the soil and groundwater. The wells were drilled to approximately 20 feet bsg. TPHg was detected at concentrations of 340 and 240 ppm, respectively, in the soil samples collected from the borings for wells MW- 1 and MW-2 near the former UST excavation, as shown by GeoStratgies (Appendix A, Table 1). The groundwater samples from wells MW-1 and MW-2 were reported to contain concentrations of TPHg up to 17,000 parts per billion (ppb), and benzene up to 3,100 ppb (Appendix A, Table 1). The recent trend has shown a significant decrease in these concentrations as shown on Table 3 (Appendix A) reproduced from a GeoStrategies report. The historical groundwater gradients were found to be approximately 0.003 and consistently '< to the north-northwest. 3001-11.rpt 2 HORIZON ENVIRONMENTAL INC.