American Society of Civil Engineers


Mapping of Karst Bedrock to Define Groundwater Pathways Underlying an Industrial Facility Using the Electrical Resistivity Imaging Method


by Alan P. Troup, (URS Corporation, 200 Orchard Ridge Dr., Ste. 101, Gaithersburg MD 20878), H. Russell Steele, P.G., (U. S. Steel Corporation, Environmental Engineering, 5700 Valley Rd, Fairfield AL 35064), and Robert Hines, P.G., (URS Corporation, 917 Western America Circle, Ste. 400, Mobile AL 36609-4111)
Section: Field Trip Guide, pp. 717-730, (doi:  http://dx.doi.org/10.1061/40698(2003)66)

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Document type: Conference Proceeding Paper
Part of: Sinkholes and the Engineering and Environmental Impacts of Karst (2003)
Abstract: Two-dimensional Electrical Resistivity Imaging (ERI) methods provide a powerful tool to assess subsurface karst conditions and bedrock fractures acting as primary geologic controls on groundwater movement in lower Paleozoic carbonate bedrock (Ketona Dolomite and Conasauga Formation) underlying parts of the United States Steel Corporation (U. S. Steel) Fairfield Works near Birmingham, Alabama. The strata are structurally complex and have experienced almost total destruction of primary porosity and permeability. Regionally, fractures in the carbonate rocks provide conditions that are conducive to the circulation of groundwater and formation of karst features such as cavities, cavernous porosity and pinnacles. As part of a facility-wide groundwater investigation, karsted bedrock was examined via literature review and aerial photographic analysis to identify features indicative of primary controls on groundwater movement. Targets thus identified were screened and verified by field geologic mapping and by two-dimensional (2-D) Electrical Resistivity Imaging (ERI) methods selected as a particularly flexible tool for deployment over the variety of structural and lithologic settings expected at the facility. The ERI results proved very successful for detecting and delineating karst features in carbonate bedrock including solution enlarged joints, bedrock pinnacles and voids. The success of the 2-D ERI method in detecting water-bearing joints, fractures, and faults is attributed to a large resistivity contrast between the high resistivity carbonate bedrock and the lower resistivity formation water, associated clays, and gouge typically contained within the fractures. The ERI results were used to confirm the subsurface orientation of features at depth and to select the optimum location for emplacement of groundwater monitoring installations.


ASCE Subject Headings:
Bedrock
Cracking
Groundwater flow
Imaging techniques
Industrial facilities
Karst
Mapping