Because of a change in emphasis from power plant siting to projects principally involving process and facility monitoring and certification of existing structures (dams, pipelines, etc.), geotechnical and groundwater geophysics is in quite a healthy state after some lean years following the demise of nucJear energy construction projects. The orders-of-magnitude jump in the computational capability of geophysicists working in these fields has overshadowed advances in instrumentation (e.g., digital enhancement seismographs), field methods (e.g., cross-boreho!e EM), and interpretive procedures. The advent of powerful, affordable microcomputers has enabled expansion into applications demanding finer resolution and quicker turnaround of results. As aresuit, shallow seismie reflection, seismie and electromagnetic geotomography, and the complementary use of surface and borehole electrical resistivity and seismie data wiJl soon be common if not dominant methods in geotechnical and groundwater investigations.Future trends point to increased emphasis on environmental and economie issues (e.g., toxic wastes or the stability of underground petroleum storage facilities), cross-fertilization with petroleum reservoir engineering (process monitoring and detailed reservoir description), and greater involvement of computers in the planning, data acquisition, and interpretive phases of our projects. As computers take over more of the data collection-processing-interpretation sequence, one of the greatest challenges facing us will be to define the proper role of humans and to use the new technology wisely.
P art 1 of this paper (TLE, August 1989) reviews recent geotechnical investigations conducted at Beaver Dam, Arkansas. The problem addressed was anomalous seepage beneath Dike 1, adjacent to the main embankment dam. The paper presents a summary of the site geology, seepage history, and foundation grouting programs. Figure 17 is a plan map showing the north and south bounding fault zones of a graben structure beneath Dike 1. The foundation is a down-faulted block of severely weathered limestone/dolomite of the Boone formation. Figure 4 of part 1 shows a simplified geologic cross-section through Dike 1 showing the graben structure. Overall objectives of the geotechnical investigations were to assess the anomalous seepage and plan remedial measures to eliminate or significantly abate the seepage. The engineering geophysics investigations discussed in part 1 were designed to detect, map, and monitor anomalous seepage paths and delineate geologic structure beneath Dike 1.In addition to the initial "routine" engineering geophysics phase of the investigation at Beaver Dam, a subsequent "research" phase was conducted. The site was chosen as a major field test site for the Corps' Repair, Evaluation, Maintenance, and Rehabilitation Research (REMR) Program project "
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