BLAKE, RICHARD G., ROBERT W. BAINER, and BERN J. QUALHEIM, Lawrence Livermore National Laboratory, Livermore, CA
ABSTRACT: An Overview of the Geology and Environment Restoration at Lawrence Livermore National Laboratory
This paper presents an overview of the relationship between the geologic setting at Lawrence Livermore National Laboratory (LLNL) and the subsurface conditions that control contaminant distribution, migration, and remediation. The contaminated strata that underlie the site are comprised of 300-400 ft of nonmarine fluvial sediments containing 19 contaminants in concentrations exceeding regulatory standards. The most widespread contaminants are volatile organic compounds that cover an area about 1.4 mi2. These contaminants are dispersed throughout heterogeneous sediments that were deposited as a system of braided and meandering streams and associated coarse-grained (sand and gravel) channel fills and silty-clay levee deposits.
Subsurface geology is key to our understanding of contaminant flow patterns and has played the principal part in our remedial design. The primary migration paths of these contaminants are within high-permeability, coarse-grained channel deposits. Delineation of the channels and associated deposits has been achieved by combining several subsurface methods, such as, borehole lithology, geophysical well log correlation, shallow high-resolution two-dimensional and three-dimensional (3-D) seismic reflection data, and 3-D computer modeling, as well as aerial photographic interpretation, geomorphology, and geologic field mapping.
LLNL is a Superfund site and was added to the National Priorities List in 1987. In July 1992, LLNL was the first active Department of Energy facility to have its sitewide Record of Decision (ROD) signed by regulatory agencies. The ROD outlines selected remedial technologies for the site. Groundwater pump and treat was the chosen technology to contain and remediate the groundwater plume. Locating buried channels by applying the geological characterization methods described in this paper has been instrumental in strategically locating extraction wells and is essential for the implementation of pump and treat technology.
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Discovery Article #90992©1993 AAPG Pacific Section Meeting, Long Beach,
California, May 5-7, 1993.