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r U - October 25, 1995 Former Discovery Chevrolet Work Plan Tracy,California ranging from 920 to 4,400 parts per million (ppm), as shown on Table 1 from the GeoStrategies report, attached as Appendix B. Groundwater was not encountered in the tank excavation. Three groundwater monitoring wells (MW-1 through MW-3)were drilled to approximately 20 feet deep in September 1994 to evaluate the presence of hydrocarbons in the soil and groundwater. TPHg was 1.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 was sampled three separate times and found to contain concentrations of TPHg ranging from 100 to 7,600 parts per billion(ppb), and benzene ranging from 35 to 730 ppb, as shown on Table 3 (Appendix B)reproduced from a June 27, 1995 Geo Strategies report for which no complete reference is currently available. The groundwater gradient was found to be approximately 0.003 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 15 feet deep. Below this depth, sandy silt to silty sand was encountered.`Gravel was , i encountered in the first 8 feet of the boring for MW-1, indicating that this well was located at least partially in tank pit backfill. j SCOPE OF WORK The following work is proposed to remediate gasoline-impacted soil in the area of the former USTs laterally and to groundwater, and to further evaluate the extent of impacted groundwater. Methods are described in detail in Appendix A. Based on the relatively shallow depth to groundwater(10 feet) with respect to the depth of the UST excavation, it is our opinion that the gasoline hydrocarbons would have migrated to the groundwater with a minimal amount of lateral movement. Therefore we believe excavation will be the most cost effective method of remediating the soils in the former gasoline UST area. 3001-11.wp 3 HORIZON ENVIRONMENTAL INC.