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SITE CLOSURE REOUESr REPORT <br /> Former Exxon Service Station No 7-3330 <br />� . 3128 West Benjamin Bolt Drive <br /> Stockton,California <br /> Delta Project No. D093-810 <br /> Page 7 <br /> former tank basin area was excavated to a depth of 14.5 feet bsg. The former product line area was <br /> excavated to approximately 14 feet bsg. <br /> Soil samples collected at the limits of the overexcavation in the area of the former used oil tank were <br /> analyzed for chromium, nickel, and lead (EPA Method 60101200.7 ICP) and total oil and grease <br /> (SM 5520). Soil sample analytical results for these samples are summarized in Table 5. The final depth <br /> of the excavation in the area of the used oil tank was 11 feet bsg. Details of the additional excavation <br /> and sampling activities are included in a report entitled Soil Remediation Report, dated July 1992 prepared <br /> by Artesian. <br /> 2.8 Additional Soil Borings <br /> In July 1993, Delta supervised the drilling of eight soil borings (SB-1 through SB-8) to a depth of <br /> approximately ten feet bsg. The borings were advanced to assess the lateral and vertical extent of <br /> ipossible residual petroleum hydrocarbons in soil in the eastern portion of the site. Soil boring locations <br /> are shown in Figure 3. Soil samples were collected for laboratory analysis of BTEX and TPH as gasoline <br /> (EPA Methods 8020 and 8015 Modified, respectively). Soil sample analytical results for samples collected <br /> from the soil boring activities are summarized in Table 1. Details of the drilling and sampling activities <br /> are included in Delta's report entitled Soil Investigation Report, dated September 14, 1993. Soil beneath <br /> the site consists of clay with intermittent sand lenses. <br /> Geologic cross-sections were prepared using the soil boring data collected at the site. A cross-section <br /> location map is presented in Figure 6 and cross-sections A-A' and B-B' are presented in Figures 7 and 8, <br /> respectively. <br /> 2.9 Ground Water Monitorin <br /> Quarterly ground water monitoring has been performed since March 1991 to assess fluctuations in the <br /> depth to ground water, ground water flow direction, and dissolved concentrations of petroleum <br /> hydrocarbons beneath the site. <br /> AD <br /> RPT001.810 <br />