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1 <br /> • Drill one additional soil boring to a depth of 20 feet bgs and install <br /> a shallow vapor extraction well, <br /> • Collect soil samples at various intervals from the ground surface <br /> i <br /> ' to 75 feet bgs Analyze selected soil samples for total petroleum <br /> hydrocarbons (TPH) quantitated against gasoline and diesel <br /> standards, benzene, toluene, ethylbenzene and total xylenes <br /> (BTEX) and for total lead using EPA methods 8015, 8020 and <br /> 7421, respectively, <br /> ' • Purge and sample groundwater from each of the three installed <br /> monitoring wells Analyze groundwater samples for TPH, BTEX <br /> and total lead using EPA methods 8015, 8020 and 7421, <br /> ' respectively, <br /> • Survey wells for relative elevation and measure depth to <br /> ' groundwater to evaluate groundwater flow direction and hydraulic <br /> gradient, <br /> ' • Conduct a vapor extraction treatability test on six wells on site <br /> Collect and analyze vapor samples for TPH and BTEX, and <br /> • Prepare this additional site characterization report presenting <br /> Park's findings, conclusions and recommendations <br /> 3.0 BACKGROUND <br /> ' 3.1 Facility Description <br /> The USA Petroleum service station is located on the southeast corner of the intersection of East <br /> Manposa Avenue and Farmington Road in Stockton, California (Figure 1 of Appendix A) The <br /> station has four underground storage tanks (USTs), of which three are 12,000 gallon gasoline <br /> ' tanks and one is a 3,000 gallon diesel fuel tank (Figure 2 of Appendix A) All four tanks appear <br /> to be located in the same tank pit excavation near the front of the property <br /> ' 3.2 Site History <br /> Two phases of site assessment have been performed at this facility The fust, as part of a pre- <br /> purchase due diligence by Pacific Environmental Group in March 1987, consisted of the drilling <br /> and sampling of four soil borings (S-1, S-A, S-B and S-C), one of which was completed as a <br /> groundwater monitoring well (S-1) Groundwater was present at about 45 feet bgs Soil <br /> ' boring S-A was drilled to 45 feet bgs, S-B to 20 feet bgs and S-C to 20 feet bgs Field notes <br /> from these soil borings did not indicate any TPH odor These qualitative results suggest a <br /> S 112531 RPT 2 <br />