USGS Groundwater Information: Hydrogeophysics Branch
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John H. Williams,
U. S. Geological Survey, Troy, NY
Pierre J. Lacombe,
U. S. Geological Survey, West Trenton, NJ
Carole D. Johnson,
U. S. Geological Survey, Storrs, CT
Cross-borehole flow tests provided insights into hydraulic connections in fractured and dipping mudstone and sandstone that were consistent with the lithostratigraphic and structural framework of a VOC-contaminated bedrock research site in west-central New Jersey. Two cross-borehole flow tests were completed. Each test involved measurement and analysis of transient flow in a newly installed deep corehole with a long open interval during short-term pumping and recovery in an adjacent shallow well with a short open interval. The cross-borehole flow test in the mudstone identified a hydraulic connection through a dipping fractured bed between the pumped interval in the well and a flow zone at an intermediate depth in the corehole. The presence of a hydraulic connection between the pumped well and the corehole was not obvious because the water-level response in the corehole was dominated by a shallow zone of high transmissivity, which was hydraulically isolated from the pumped interval. In the sandstone, the cross-borehole flow test identified a hydraulic connection along dipping fractured beds as well as a connection to a deep high-angle fracture that cuts across bedding. These results suggest that application of cross-borehole flow tests at other contaminated fractured-bedrock sites could provide insights into hydraulic connections useful the design and implementation of monitoring and remediation programs.
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Final copy as submitted to SAGEEP for publication as: Williams, J.H., Lacombe, P.J., Johnson, C.D., and Paillet, F.L., 2007, Cross-borehole flow tests and insights into hydraulic connections in fractured mudstone and sandstone, in Symposium on the Application of Geophysics to Engineering and Environmental Problems, April 1-5, 2007, Denver, Colorado, Proceedings 2007: Denver, Colorado, Environmental and Engineering Geophysical Society, CD-ROM, p. 1140-1152.