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i Former Discovery Chevrolet March 13, 1997 Tracy,California Work Plan deep. These samples were found to contain total petroleum hydrocarbons as gasoline (TPHg) at 'I concentrations ranging from 920 to 4,400 parts per million (ppm), as shown on Table 1 from the I GeoStrategies report, attached as Appendix B. Groundwater was not encountered in the tank It i excavation. In addition a sample was collected below the dispenser located inside the service II bays. Benzene was detected at 0.88 ppm in the sample collected from beneath the dispenser. Results are shown on the Table 1 included in Appendix B. Three groundwater monitoring wells (MW-1 through MW-3) were drilled to approximately 20 I, feet below surface grade (bsg) in September 1994 to evaluate the presence of hydrocarbons in the soil and groundwater. 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 in Table 2 (Appendix B). The groundwater from wells MW-1 and MW-2 have been found to contain concentrations of TPHg up to 17,000 parts per billion (ppb), and benzene up to 3,100 ppb, but the recent trend has shown a significant decrease in these concentrations as shown on Table 3 (Appendix B) reproduced from a GeoStrategies report. The groundwater gradient was found to be approximately 0.003 and consistently to the north-northwest. The soil underlying the site was found to be predominantly clay and silt to the groundwater interface at about 10 to I 1 feet bsg. Below this depth, sandy silt to silty sand was encountered. Gravel was encountered in the first 8 feet of the boring for MW-1, indicating that this well was located at least partially in UST pit backfill. 3001-1 1 b.wp 3 HORIZON ENVIRONMENTAL INC.