Aquifer tests of surface coal mine spoil indicate two distinctly different groundwater hydrologic characteristics exist. Slug tests empirically indicate the presence of discrete conduits within the spoil. Groundwater flow within conduits is pseudokarst, and flow between conduits is porous media. Under transient or stress conditions, pseudokarst groundwater flow in the spoil becomes prominent; under steady-state conditions, porous media flow dominates. Tracer testing indicates the average linear velocity of groundwater through spoil is close to pure porous media and significantly lower than true karst flow.