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SITE CLOSURE REQUEST REPORT Former Exxon Service Station No.7-3330 � . 3128 West Benjamin Holt Drive Stockton,California Delta Project No. D093-810 Page 5 feet below surface grade (bsg). Depth to ground water was measured in monitoring wells MW-1 through MW-3 and ranged from 12 to 13.5 feet bsg. Cumulative ground water level measurements are presented in Table 2. Initial ground water samples collected in March 1991 from monitoring wells MW-1 through MW-3 were analyzed for BTEX and TPH as gasoline using EPA Methods 8020 and 418.1, respectively. Detectable concentrations of BTEX were reported in samples collected from MW-2. Cumulative ground water analytical results are summarized in Table 3. In June 1991, Artesian Environmental Consultants, Inc. (Artesian) conducted a Phase II Subsurface Investigation at the site to evaluate the vertical and lateral extent of hydrocarbons detected in soil during the previous investigation and evaluate the lateral extent of hydrocarbons in ground water. Seven soil borings (13-1 through B-7) were advanced at the site (Figure 3). Soil borings B-1, B-2, and B-3 were converted into ground water monitoring wells MW-4, MW-5, and MW-6, respectively. Soil samples were collected from each of the borings advanced at the site and submitted for laboratory analysis of BTEX and TPH as gasoline using EPA Methods 8020 and 8015 Modified, respectively. Ground water samples were also collected from the newly installed wells and- analyzed for the same analytes using similar methods. Soil sample depths and analytical results are summarized in Table 1 and ground water analytical results are summarized in Table 3. The work conducted by Artesian is presented in their report entitled Phase II Subsurface Investigation, dated July 1991. 2.6 Tank Removal Activities Three gasoline USTs (one 6,000, one 8,000, and one 10,000-gallon capacity), the associated product distribution lines, and one underground used oil storage tank(1,000-gallon capacity) were removed from the site on October 9, 1991. Details of the tank removal activities are included in Artesian's report entitled Tank Removal Report, dated December 1991. Each tank was inspected after removal. No holes, significant corrosion, or broken seams were observed. 1, 18 RPT001.810