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Subsurface brine detection and monitoring in West Point, Kentucky, with 2D electrical resistivity tomography

Rory D. Henderson, U.S. Geological Survey, Office of Ground Water, Branch of Geophysics and University of Connecticut, Storrs, CT

Mike D. Unthank, U.S. Geological Survey, Kentucky Water Science Center, Louisville, KY

Doug D. Zettwoch, U.S. Geological Survey, Kentucky Water Science Center, Louisville, KY

John W. Lane, Jr., U.S. Geological Survey, Office of Ground Water, Branch of Geophysics, Storrs, CT

Abstract

Ongoing investigations of the Fort Knox public water supply well field in West Point, Kentucky revealed an increase in chloride concentrations within the aquifer system due to improperly abandoned natural gas exploration wells. The site and regional geology consists of unconsolidated glacial outwash approximately 30- to 40-m thick, underlain by shale and porous limestone. Drill logs show that the natural gas wells were completed to the shale and porous limestone formation depths. Brine is believed to flow vertically from the underlying formations to the unconsolidated aquifer through damaged or leaky well casings. Pumping of the water supply wells enhances subsurface migration of contaminated ground water by increasing the hydraulic gradient between the contamination source and the potable wells. Here, we define the subsurface distribution of contaminated ground water by performing 2D electrical resistivity tomography (ERT) surveys. Inversion results were constrained by EM borehole logs recorded near the survey lines. Results from this work have initiated a periodic, geophysical monitoring program at the Fort Knox site to monitor brine migration mitigation strategies.


Final copy as submitted to Environmental and Engineering Geophysical Society for publication as: Henderson, R.D., Unthank, M.D., Zettwoch, D.D., and Lane, J.W., Jr., 2009, Subsurface brine detection and monitoring in West Point, Kentucky, with 2D electrical resistivity tomography [abs.]: in Symposium on the Application of Geophysics to Engineering and Environmental Problems, March 29 - April 2, 2009, Fort Worth, Texas, Proceedings: Denver, Colorado, Environmental and Engineering Geophysical Society.

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