Unexpected hydrologic perturbation in an abandoned underground coal mine: Response to surface reclamation? |
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| Authors: | Denver Harper Greg A Olyphant Edwin J Hartke |
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| Institution: | (1) Indiana Geological Survey, 47405 Bloomington, Indiana, USA;(2) Department of Geology, Indiana University, 47405 Bloomington, Indiana, USA;(3) Indiana Geological Survey, 47405 Bloomington, Indiana, USA |
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| Abstract: | A reclamation project at the abandoned Blackhawk Mine site near Terre Haute, Indiana, lasted about four months and involved the burial of coarse mine refuse in shallow (less than 9 m) pits excavated into loess and till in an area of about 16 ha. An abandoned flooded underground coal mine underlies the reclamation site at a depth of about 38 m; the total area underlain by the mine is about 10 km2. The potentiometric levels associated with the mine indicate a significant (2.7 m) and prolonged perturbation of the deeper confined groundwater system; 14 months after completing reclamation, the levels began to rise linearly (at an average rate of 0.85 cm/d) for 11 months, then fell exponentially for 25 months, and are now nearly stable. Prominent subsidence features exist near the reclamation site. Subsidence-related fractures were observed in cores from the site, and such fractures may have provided a connection between the shallower and deeper groundwater systems. |
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