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anticipated contractor personnel will be provided to Navy security representatives to arrange for <br />site access. <br />2.4.2 Tank and Piping Removal <br />The tasks required for the removal of the UST and associated piping include: uncovering <br />tank top; tank and pipe emptying; tank purging; soil excavation; pipe removal; and tank removal. <br />Prior to any excavation, an exclusion zone will be delineated and Photoionization Detection (PID) <br />measurements will be taken to determine the background levels of organic vapors. The zone will <br />be large enough to stockpile excavated soil and provide access for operating equipment and <br />emergency vehicles. <br />Uncover Tank Toa <br />The surface soil covering the top of the tank will be removed and stockpiled on plastic <br />sheeting. This soil will be covered with plastic sheeting once excavation of the tank top is <br />complete. The tank cover soils will be kept separated from the soils removed from the sides and <br />below the tank. <br />w"0 <br />Tank and Pine Emntying <br />Any waste product found in the tank or piping, as well as rinsates generated during tank <br />rinsing activities will be removed with a pump truck and disposed of as hazardous waste. Small <br />quantities of sludge remaining in the tank after pumping will also be transported off-site with <br />the tank under proper manifest by a licensed tank hauler to a permitted disposal site. <br />Tank Purging <br />N�"3o <br />If the tank contains flammable vapors in excess of 10 percent of the lower explosive limit <br />(LEL), solid carbon dioxide (dry ice) will be used to purge the tank. Tank purging will be <br />performed at least 2 hours before tank removal. The tank will be filled with at least 15 pounds <br />of dry ice per 1,000 gallons of tank volume. During purging, the LEL will be measured through <br />the vent pipe opening to determine when explosive vapor levels fall below 10 percent of the LEL. <br />Soil Excavation <br />A backhoe will be used to excavate soil to a distance of approximately 3 feet around the <br />perimeter of the tank and above the associated product lines. Soil and gravel fill material will be <br />11 <br />i <br />