COMPLIANCE INFO_FILE 9 - Laserfiche WebLink

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Supplemental Information The 834-DlU1 tank system was installed in 1960 and is located south of Building 834B. The tank supplies diesel fuel to an emergency generator that serves the Building 834 Complex. The tank system consists of a 1,000-gallon, single-walled, carbon steel underground storage tank (UST), associated fill pipe, vent pipe, and fuel supply and fuel return piping. Piping within and beneath concrete will be closed in place. All other accessible piping will be removed. It is not known if a concrete anchor pad is present beneath the tank. If a concrete anchor pad is present, it will be removed if it is feasible to do so. The system was registered with the State Water Resources Control Board on June 27, 1984, as 834-11D and has subsequently been renamed 834-D1U1. Figure 1 (see Appendix B) shows the location of the 834-D1U1 tank system in relation to the Lawrence Livermore National Laboratory (LLNL), Site 300. Figure 2 (see Appendix B) shows a plan view of the 834-DlU1 tank system in relation to Building 834A. Historic tank integrity testing confirms the integrity of UST 834-D1U1 and indicates that the tank has not leaked. The results of the most recent integrity test performed on January 21, 1994, are included in Appendix C. These results confirm that UST 834-DlU1 and associated piping are leak tight. Eighteen ground water monitor wells located in the vicinity of UST 834-DlU1 monitor a shallow (99 ft) perched ground water-bearing zone beneath the Building 834 Complex. Water levels and ground water samples have been collected from these wells since 1983. Ground water samples from monitor well W-834-D8, located 15 ft southwest of 834-D1U1, as well as from several monitor wells located immediately east and south of the tank have been analyzed for diesel (Modified EPA 8015 TPH-D) and volatile organic compounds (VOCs) (EPA 601/602). The VOC trichloroethylene (TCE) has been most frequently detected, at concentrations up to 800,000 ug/L (ppb); while diesel has only been detected in a selected number of wells (5600 ug/L [ppb] at W-834-138 on Dec. 15, 1993). The nature and extent of TCE and diesel contamination is described in detail in the Site Wide Remedial Investigation Report (Webster-Scholten et al., 1994) and the Draft Feasibility Study for the Building 834 Operable Unit Lawrence Livermore National Laboratory (Landgraf and Miner, 1994). Based on the findings of the remedial investigation report as well as the historic tank integrity test results, it is likely that the diesel ground water contamination is the result of periodic overfilling of UST 834-D1U1. TCE was used in the Building 834 complex as a heat transfer fluid. A silicon- based oil, tetra 2-ethyl butyl ortho-silicate (T-BOS), was used as an additive in the 1970s. TCE and T-BOS were not stored or contained at the closure site but may be present due to migration into the site.