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• <br /> February 14, 1992 �A SMA <br /> . ARCO Service Station No 2130, Stockton, California <br /> and local regulations The asphalt and concrete above the tanks and associate piping will <br /> be removed The contractor will triple-rinse each tank, remove the fluids, and purge the <br /> vapors Triple rinsing is performed to clean the inside of the tanks and remove any <br /> remaining fluids Prior to removal, each tank will be filled with an inert gas, usually carbon <br /> dioxide, to remove oxygen and residual vapors and prevent fire or explosion, this is <br /> commonly achieved by placing dry ice in the tanks <br /> Before the tanks are removed from the ground, the contractor will analyze the atmosphere <br /> inside the tanks for concentrations of combustible vapors and oxygen using a hand-held <br /> combination combustible gas indicator and oxygen meter When combustible vapors and <br /> oxygen have been reduced to acceptable levels, a representative of the local fire department <br /> will approve removal of the tanks The ends of the product pipelines and vent lines will be <br /> sealed The contractor will remove the tanks and product lines and place them on flatbed <br /> trailers for transport to an appropriate facility for disposal <br /> Soil Sampling <br /> The sand or gravel backfill material that was originally placed around the tanks to fill the <br /> tank cavity will be removed from the tank cavity and stockpiled onsite After the tanks are <br /> removed, additional material will be excavated until native soil is exposed on the base and <br /> sides of the tank cavity Two native soil samples will be collected within 2 feet of the base <br /> of each former tank (approximately 12 feet below grade) for laboratory analyses to evaluate <br /> whether gasoline is present in the surrounding native soil Soil samples will also be <br /> collected within 2 feet of the base of the former product lines at 20-foot intervals Soil <br /> samples will be submitted to a State-licensed laboratory and analyzed for appropriate <br /> compounds according to the SJCPHS-EHD guidelines <br /> Tank and Product-Line Installation <br /> Before the new tanks are installed in the tank cavity in which the original tanks were <br /> removed, two vertical 12-inch-diameter plastic casings will be installed between each new <br /> tank extending from approximately 2 feet into the native soil to the ground surface The <br /> casing will allow soil borings to be drilled between the new tanks to continue further <br /> investigation of soil conditions beneath the new tanks, if warranted <br /> Results of laboratory analyses of soil samples collected from the tank cavity and product-line <br /> trenches will be forwarded to the SJCPHS-EHD The data collected from investigations to <br /> date, suggests hydrocarbons will remain in the soil in the tank cavity and product-line <br /> trenches at concentrations that will warrant remediation When authorization to install new <br /> tanks and product lines is requested from the SJCPHS-EHD, we will also request <br /> 30003-4W <br />