English

Abstract

Prevention of acid mine drainage (AMD) at surface coal mines in the Appalachian region relies greatly on minimizing ground-water contact with acid- forming materials and maximizing ground-water contact with alkalinity-yielding materials. Acid-forming materials (AFMs) are often selectively handled to minimize or prevent contact with ground water. Controlling ground-water contact with acidic- or alkaline materials depends on accurate forecasting of the level and range of fluctuation of the post-mining water table and preferred ground water flow paths within the backfill. Physical measurements and aquifer testing of more than 120 wells from 18 reclaimed mines in Kentucky, Ohio, Pennsylvania and West Virginia have improved forecasting of the post-mining ground-water flow system. Flow regime influencing factors include spoil lithology and particle size, age of reclamation, spoil thickness, distance to the final highwall, and pit floor dip angle and direction. Hydraulic conductivity (K) exhibits a broad range of 7 orders of magnitude about a mean K of 1.69 x 10 -5 meters/second. Spoil aquifer saturated thickness is related to the thickness of the spoil, spoil lithology, dip of the pit floor and distance to the highwall. Saturated spoil thickness has a 99% confidence interval of 1.86 to 3.97 meters (m) about a mean of 2.91 m. Spoil saturated zone averages 20% of the total thickness.