SITE INFORMATION AND CORRESPONDENCE

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Role of the Regulatory Agencies As part of the Federal Facility Agreement for DOE/LLNL Site 300,the U.S.EPA and the State of California DTSC and RWQCB provide guidance to DOE/LLNL on the investigation and remediation of contaminants at the GSA. Specifically, the three regulatory agencies review and comment on all CERCLA compliance reports prepared by DOE/LLNL,provide applicable or rel- evant and appropriate requirements (ARARs) for the site, review and evaluate remedial technolo- gies and alternatives, participate in the selection of the final remedy, and provide oversight and enforcement of state and federal environmental regulations. In addition, the regulatory agencies monitor and review public acceptance of the proposed remedy. In doing so, the regulatory agen- cies will actively participate at the public meeting in the Crystal Room at the Tracy Inn for the GSA on April 24, 1996. Site Background The GSA is composed of a cluster of eleven DTSC,and RWQCB in June 1992. Since then, buildings that were constructed in the late 1950s all remedial investigations have been conducted to support Site 300 activities. Undetermined under the guidance of these regulatory agen- quantities of solvents containing trichloroeth- cies. To determine the extent of contamination ylene (TCE), a suspected human carcinogen, in the GSA, DOE/LLNL drilled 75 boreholes and other volatile organic compounds (VOCs) to collect soil samples. Ninety-eight ground were released to the ground as a result of past water monitor wells have been installed for activities in the craft shops,equipment fabrica- water-level measurements and water sample tion and repair facilities in the GSA and are collection. present in the soil/rock and ground water in the Geologic and hydrogeologic data were col- area. For purposes of discussion,the GSA has lected and field parameters were measured dur- been divided into two subareas: the central GSA ing the drilling and installation of monitor wells and eastern GSA, based on.differences in hy- to characterize the subsurface properties of the drogeology, contaminant source areas, and the GSA. As shown in Figure 4, the central GSA location of ground water VOC plumes. Two is underlain by a shallow water-bearing zone primary release sites were identified: 1)a former (aquifer). This shallow water-bearing zone is dry well area located in the central GSA near underlain by a thick, low-permeability layer Building 875, and 2) the debris burial trench (also referred to as an aquitard) that, where area located in the eastern GSA. Four other present, prevents downward migration of wa- release sites have also been identified in the ter to the regional aquifer in this area. In the GSA including a decommissioned drum stor- eastern GSA, the aquitard is not present, and age rack, a steam cleaning/sink area, and two the shallow water-bearing zone directly over- former dry wells. lies the regional aquifer. In 1982, DOE/LLNL discovered the con- tamination at the site and began an investiga- Extent of Soil and Ground Water tion under the guidance of the RWQCB. The Contamination Site 300 Experimental Test Facility was placed The remedial investigation determined that on the EPA National Priority List in August VOC releases in the GSA had affected ground 1990, and DOE entered into a Federal Facility Fater in both the shallow water-bearing zone Agreement with the U.S. EPA Region IX, 4