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0 0 CLOSURE REPORT FOR UNDERGROUND STORAGE TANK 814-D1 U1 BACKGROUND The underground storage tank (UST) identified as UST 814-D1 U1, was located north of Building 814, at the Lawrence Livermore National Laboratory (LLNL) Site 300, south of Tracy, California, see Figures 1 and 2 (Appendix A). A copy of the UST 814-D1 U1 Approved Application for Underground Storage Tank Closure Permit is included as Appendix B. The cylindrical 300-gallon tank had an approximate diameter of 45 inches, a length of 42 inches, and was constructed of single-walled, carbon steel. UST 814-D1 U1 contained diesel fuel to supply a standby emergency generator for Building 814, and was installed in 1972. The most recent precision tank test results for UST 814-D1 U1, from Gary Peters Enterprises in 1987, using the Tank Audit Leak Computer, showed the tank system to be leak tight, see the UST 814-D1 U1 Closure Plan. After the tank test, the tank was emptied and decontaminated. Between May 6, 1993 and October 14, 1993, UST 814-D1 U1 was monitored weekly using manual stick readings. UST 814-D1 U1 was closed because it was no longer in service. SOIL EXCAVATION AND TANK REMOVAL Soil excavation and tank removal were performed by the LLNL Labor Shop on October 15, 1993. The tank disposal site for this project was Erickson Enterprises in Richmond, California. A representative of the San Joaquin County Public Health Services, Environmental Health Division (PHS-EHD), Mr. Bill Snavely, was present during tank removal activities. Oxygen displacement using dry ice was the method used to inert the tank. The oxygen level within the tank was measured at 2.9 parts per million (ppm) by a LLNL Health and Safety Technician and Bill Snavely gave permission to remove the tank from the excavation, see Photograph 3 (Appendix C). The tank and piping showed no holes, cracks, corrosion, or other signs of failure. The UST had a tar coating that was relatively undamaged, see Photographs 5 and 6 (Appendix C). Figure 3 (Appendix A) shows the tank excavation, which measured 8 feet by 9 feet by 8.5 feet deep, and the soil sample collection points. Excavated soil was stored on and covered with sheets of polyethylene. The LLNL Heavy Equipment Group Leader, Mr. Stan Pereira, determined that no shoring of the excavation was necessary. A summary of the soil types within the excavation is as follows: • 0-8.5 foot - Cobbly, brown clay Petroleum product odors were not detected in the fill material, in the tank excavation, or in the native soil where the piping entered the concrete standby emergency generator pad. The fuel supply and return lines in the concrete generator pad were cut and capped below ground. UST 814 CLOSURE REPORT -1-