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The firing table gravels and associated debris are contaminated primarily with depleted uranium, lead, beryllium and trace amounts of high explosives. On some occasions in the past, natural uranium and thorium may have been used. Little or no tritium experimenta- tion has been carried out in this pit since it opened in 1961. No liquid wastes are known to have been disposed into this landfill, either. The gravels and the debris were collected after shots and buried in designated disposal areas within Site 300. Monitoring data shows no evidence that Pit 1 has released any contaminants into the groundwater. One major fault, the Elk Ravine Fault, crosses the East Firing Area. A branch of this fault, passes beneath Pit 1. An investigation was conducted in November 1988 that showed no evidence of movement of the fault within Holocene time. Pit 7 DESCRIPTION Pit 7 is about 6,250 square yards or about one -and -a -half acres containing a volume of 31,111 cubic yards of mixed wastes. The start-up date for this unit was 1979 and ceased operating on November 8, 1988. Similar to Pit 1, the wastes disposed here were generated from the hydrodynamic test of non-nuclear explosives. The wastes are contaminated with depleted uranium, lead, beryllium and trace amounts of high explosives. Little tritium experimentation has been carried out since it opened in 1979. Most if not all occasional uses of natural uranium or thorium ended prior to the opening of Pit 7. No major earthquake fault has been discovered underneath the Pit 7 complex. III. SITE GEOLOGY AND GROUNDWATER SITUATION Since the proposed closure leaves waste in place, the geology of the area is particularly important because the rate and direction of the ground water flow is generally dependent on the geology of the site. LLNL is in a remote location in the Altamont Hills between the Livermore and San Joaquin valleys. The site is underlain by interbedded sands, silts and clay with occasional gravel and cobble lenses generally ranging from three to 30 feet in thickness. This alluvial fill is underlain by bedrock formation called the Neroly Formation which is up to 450 feet thick. It is made up of sandstone and sandy siltstone, coarse conglomerate of pebbles and cobbles and interbedded volcanic shales. This formation is yet underlain by another thick rock formation call the Cierbo which has an average thickness of 300 feet. The geological structure is complex, as several major folds and minor faults exist beneath the site. A recently discovered branch of the Carnegie Fault at the Southern boundary of Site 300 exhibits evidence of Holocene displacement. This fault is approximately three miles south of Pits 1 and 7. However, no faults showing evidence of Holocene displace- ment are present within or in the vicinity of Pits 1 and 7. (Any movement during the Holocene period, which is within the recent 11,000 years span, means that movement will more likely to reoccur.)