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Mr Michael Walton • • Walton Engineering March 20, 1998 . The approximate 2,000 square-foot convenience store and sales office was located near the eastern edge of the property (Figure 2) The surface of the site was covered predominantly with asphaltic- concrete and concrete with a subordinate area of exposed soil in landscaped planters along the northern boundary of the site The former underground storage tank used to store mid-grade unleaded gasoline, apparently was once used to store diesel fuel (T1 on Figure 2) An abandoned underground product delivery pipeline, which may have supplied diesel fuel to dispenser islands that Once existed parallel to Alpine Avenue was buried beneath the asphaltic concrete along the western side of the site building TANK REMOVAL The fuel dispenser pipelines and underground storage tanks were removed by Walton Engineering, Inc , on November 21, 1997 Prior to removing the tanks from the ground, the tanks were rinsed and emptied by Ramos Environmental of West Sacramento California Approximately 250 pounds of dry ice was placed in each of the 8,000-gallon storage tanks and approximately 300 pounds of dry ice was placed in the 10,000-gallon storage tank The dry ice displaced oxygen (O,) to less than 8% in each of the tanks, while lowering the lower explosive limit(LEL) to less than 10% in each of the tanks After removing the storage tanks from the ground the tanks were inspected and found to be in fair condition The three tanks were hauled from the site by West Coast Equipment of Turlock, California and disposed of at Cal Coast Manufacturing, Inc , of Turlock, California Representatives from San Joaquin County Environmental Health Division (SJCEHD) and City of Stockton Fire . Department were present to supervise the tank removal and soil sampling operation Soil Sample Collection Native soil strata encountered in the tank excavation at the site consisted of interbedded, light brown and gray sandy silts and silts with clay Field evidence for subsurface soil contamination was observed in tank backfill sand and in native soil mainly beneath the north end of the former mid- CY ;rade unleaded gasoline storage tank (T1 on Figure 2) Native soil encountered beneath the north end of storage tank TI had a moderate odor of petroleum-based fuel hydrocarbons and appeared moderately discolored Groundwater was not encountered in the open excavation during the tank removal work After removing sandy tank backfill material from the open excavation, soil samples were collected from beneath each end of the three former underground fuel storage tanks (Figure 2) Native soil samples were collected from beneath each of the tanks at various depths by removing soil from the subsurface using an excavator and then immediately driving a clean sample sleeve into a relatively undisturbed part of the soil contained in the excavator bucket Each individual soil sample was collected by driving the stainless steel sample sleeve into the native soil using a hand-operated,AMS percussion core sampler 0 GRA YLAND ENVIRONMENTAL 7 Gras lurid 022-160 trr