Positive and negative impacts of longwall mine subsidence on a sandstone aquifer |
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Authors: | C J Booth E D Spande C T Pattee J D Miller L P Bertsch |
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Institution: | (1) Department of Geology, Northern Illinois University, DeKalb, Illinois 60115 USA Tel: +1 815 753 1943 Fax: +1 815 753 1945, US |
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Abstract: | Subsidence due to longwall underground coal mining changes the hydraulic properties, heads, yields, and in some cases the
groundwater chemistry of overlying bedrock aquifers. A 7-year study of a sandstone aquifer overlying an active longwall mine
in Illinois has supported a comprehensive model of these impacts. Subsidence caused increases in permeability and storativity
over the longwall panel. These changes initially caused a major decline in water levels in the sandstone, but the aquifer
recovered slightly within a few months and fully within several years after mining. The enhanced hydraulic properties combined
with potentiometric recovery resulted in a zone of greater well yield. However, at sites with very poor transmissivity and
inadequate recharge pathways, recovery may not occur. Also, at the study site, the physical enhancement was accompanied by
a deterioration in groundwater quality from slightly brackish, sodium bicarbonate water to more brackish water with increased
sulfate levels.
Received: 17 March 1997 · Accepted: 9 September 1997 |
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Keywords: | Aquifer properties Mining Subsidence |
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