Brackish water in unsaturated confining beds at a Texas lignite mine
Deposits of low permeability are hydrologic barriers between reclaimed land and juxtaposed aquifers and should limit the impact of mining on ground-water quality. Claystone and mudstone in argillaceous facies of the Calvert Bluff Formation (lower Eocene, Wilcox Group) function as confining beds in the East Texas Basin. In the subsurface and at the outcrop, water in argillaceous deposits is brackish to saline. Samples of vadose water from the outcrop of confining beds at the Big Brown lignite mine in Freestone County, Texas, have a chloride concentration of up to 3500 mg/l and total dissolved solids of up to 8000 mg/l. Groundwater composition evolved from Eocene sea water by seven- to nine-fold dilution with rain water. Ion exchange, pyrite oxidation, and calcite dissolution further modified water composition. The amount of recharge through the vadose zone where confining layers crop out is probably negligible over an extremely long time. Meteoric flushing in reclaimed land at the surface mine is many times greater than that in unmined mudstone deposits, and the chemical composition of vadose water in reclaimed land is changed by further dilution and water-rock reactions. 31 references, 8 figures, 4 tables.
- Research Organization:
- Texas Univ., Austin
- OSTI ID:
- 6320773
- Journal Information:
- Ground Water; (United States), Journal Name: Ground Water; (United States) Vol. 23:1; ISSN GROWB
- Country of Publication:
- United States
- Language:
- English
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Hydrogeochemistry of the vadose zone in unmined and reclaimed deposits at Big Brown Lignite Mine, East Texas
Hydrogeochemistry of the unsaturated zone at Big Brown lignite mine, East Texas
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