Hydrologic Characterization and Modeling of a Heterogeneous Acid- producing Surface Coal Mine Spoil, Upshur County, West Virginia.
Previous hydrologic investigations of surface coal mine spoils have shown that classic water-table conditions may not exist, even in spoils that exhibit continuous, year-round flow from one or more discharges. Groundwater flow through the spoil may occur largely through preferred zones or channels of relatively high hydraulic conductivity rather than as diffuse intergranular flow. These preferred flow zones may be an artifact of the backfilling process or can be created by piping through the spoil and have been described as pseudokarst. In an attempt to characterize the effects, if any, of pseudokarst hydrology on acid mine drainage characteristics from heterogeneous strip mine spoil, the U.S. Bureau of Mines has monitored an 8-acre reclaimed mine site in Upshur County, West Virginia, for several years. Current data indicate that porous media flow dominates the hydrology of this site under steady-state conditions. Under steady-state conditions, permeability and recharge sources are the main controlling factors on the groundwater flow regime. Pseudokarst components are observed and become significant under transient flow conditions. Observed flow components related to pseudokarst hydrology are groundwater flow direction changes, increased water table gradients, temporary artesian conditions, and the existence of a stream sink and resurgent spring connected by a subsurface conduit. Aquifer tests (slug withdrawal) were performed in the wells to define the spatial variability of hydraulic conductivity and permeability within the saturated zone of the spoil. The slug test results
Proc 1990 Symp. on Mining, Lexington, Kentucky, May 14-18, 1990. Univ. Kentucky, 1990, PP. 43-52