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0 <br />G <br />i <br />11 <br />C <br />C <br />f' <br />C <br />r <br />C <br />C <br />0 <br />0 <br />n <br />11 <br />Mr. Michael Walton <br />Walton Engineering <br />December 20, 1996 <br />TANK REMOVAL <br />The former fuel dispensers and underground storage tanks were unearthed and removed by Walton <br />Engineering, Inc., on November 18 and 19, 1996, respectively. One fuel island containing a total <br />of three fuel dispensers was removed from the area immediately adjacent to the eastern edge of the <br />former tank excavation. Prior to removing the tanks from the ground, the tanks were rinsed and <br />pumped dry by Erickson, Inc., of Richmond, California. Approximately 350 pounds of dry ice was <br />placed in the 8,000 -gallon gasoline storage tank, 300 pounds of dry ice was placed in the 10,000 - <br />gallon diesel fuel storage tank, and 450 pounds of dry ice was placed in the 12,000 -gallon gasoline <br />storage tank. The dry ice displaced oxygen (02) to less than or equal to 8% in each of the tanks. <br />After removing the storage tanks from the ground, the tanks were inspected and found to be in good <br />condition with no apparent perforations. The three tanks were hauled from the site and disposed of <br />by Erickson, Inc. Representatives from San Joaquin County Environmental Health Division <br />(SJCEHD) and San Joaquin County Fire Prevention Bureau were present to supervise the tank <br />removal and soil sampling operation. <br />Native soil strata encountered in the tank excavation at the site consisted of light brown and gray <br />sandy silt with some clay overlying sand. Field evidence for subsurface soil contamination was <br />observed in tank backfill material and to a lesser extent in native sandy silt mainly beneath the fill <br />end of the former 12,000 -gallon storage tank. Tank backfill material encountered in the tank <br />excavation had a slight odor of petroleum-based fuel hydrocarbons and appeared slightly discolored. <br />Groundwater was not encountered in the open excavation. <br />Soil samples were collected from beneath each end of the three former underground fuel storage <br />tanks and from beneath each end of the former fuel dispenser island (Figure 2). An additional soil <br />sample was collected from beneath the middle of the former 12,000 -gallon underground storage <br />tank. After removing tank and trench backfill material with an excavator, native soil was removed <br />from beneath each of the former tanks to depths ranging from approximately 13 to 21 feet below <br />ground surface using the excavator. Soil samples were collected from the bucket of the excavator <br />immediately after removing the soil from the subsurface. Soil was collected in situ beneath each of <br />the former fuel dispensers from approximately 3 feet below ground surface (Figure 2). Each <br />individual soil sample was collected by driving a clean stainless steel sleeve in to the freshly exposed <br />or removed native soil using a hand -operated, ATM percussion core sampler containing a clean <br />stainless steel sample sleeve. <br />Soil and backfill material removed from the open excavation was stockpiled on the north side of the <br />convenience store (Figure 2). Grayland collected a total of three soil sample composites from the <br />soil stockpile. Each individual soil sample was collected using the percussion core sampler by first <br />removing approximately 1 foot of soil/backfill material from the surface of the pile and then driving <br />a clean stainless steel sleeve into the freshly exposed surface of the pile. A total of four individual <br />GRA YLAND ENVIRONMENTAL <br />Grayland 022-130.ta 2 <br />