Reclamation of surface mines in Texas became mandatory in 1978, requiring that overburden removed during surface mining (mine spoils) be emplaced in open mine pits and land surface reshaped to pre-mining topography. The reclaimed land surface then is revegetated to control erosion. Shallow ground-water-flow systems that develop in reclaimed areas have geochemical characteristics substantially different from pre-mining conditions. Because the solutes produced by mine spoils potentially can degrade the quality of ground and surface water, the mining industry has developed methods of spoils emplacement and surface reclamation to mitigate these effects. Comparisons of chemical data from ground water collected from two coal mine reclamation sites in east-central Texas and results of a laboratory-controlled, column-leaching experiment on reclaimed spoil material from the area indicate that large amounts of solutes are mobilized from the spoil material. Increased concentrations of dissolved solids (550 to 6,050 milligrams per liter), dissolved sulfate (73 to 2,800 milligrams per liter), dissolved iron (2,000 to 160,000 micrograms per liter), and dissolved manganese (800 to 13,000 micrograms per liter) and low pH (4.0 to 6.2) in ground water from two reclaimed areas indicate these to be the primary water-quality concerns. However, reclamation practices and establishment of strongly reducing environmentsmore » in shallow ground water inhibit mobilization and transport of trace elements (including radium-226 and uranium-238, which are present in very small amounts in the ground water). Mass-balance models indicate that pyrite oxidation and dissolution of halite, carbonates, amorphous alumina, amorphous silica, and to a lesser extent, gypsum are reaction processes occurring in reclaimed spoils. Sulfate reduction was apparent in the aquifers from detection of sulfide in ground water; however, the magnitude of sulfate reduction was not substantial in mass-balance models.« less
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