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HYDROGEOLOGIC CHARACTERIZATION OF FRACTURED ROCK FORMATIONS: A GUIDE FOR GROUNDWATER REMEDIATORS
Citation:
Cohen, A. B. HYDROGEOLOGIC CHARACTERIZATION OF FRACTURED ROCK FORMATIONS: A GUIDE FOR GROUNDWATER REMEDIATORS. U.S. Environmental Protection Agency, Washington, DC, EPA/600/S-96/001, 1996.
Impact/Purpose:
provide information
Description:
A field site was developed in the foothills of the Sierra Nevada, California, to develop and test a multidisciplinary approach to the characterization of groundwater flow and transport in fractured rocks. Nine boreholes were drilled into the granite bedrock, and a wide variety of instruments and methodologies were tested. Fracture properties were measured on outcrops and in boreholes using acoustic televiewer, digital borehole color scanner, and by down-hole camera logs. Conventional geophysical logs were collected. In addition, thermal-pulse and impeller flowmeter logging, fluid replacement and conductivity logging, packer-injection profiling tests, and ordinary open-hole pumping tests were conducted. Transmissive fractures were identified by integrating results from hydrologic and geophysical measurements, and the hydrogeologic structure of the formation was hypothesized. Cross-hole seismic surveys yielded tomograms of inter-borehole rock properties. Visualization software was used in combination with geophysical logs to interpolate inter-boreholes properties, and a detailed 3-D model of the subsurface was constructed. Other referenced work at the site includes cross-hole hydrologic tomography, tracer tests, fracture-specific morphology studies, and development of an automated data acquisition system used to collect data and monitor and control test parameters during borehole testing. A novel aspect of the project report is its guidebook format. A description of each tool and methodology, the strengths and shortcomingof each, how they compare with one another, and suggestions of how best to analyze and integrate data are presented.