Ground-water conditions before, during, and after surface mining of a small watershed are described as part of a study to determine the effects of mining on hydrologic systems. The watershed was underlain by stratified sedimentary rocks containing three aquifers. The top and middle aquifers were perched above clay beds that underlay the major coal seams; the lowermost aquifer is part of a regional aquifer system and neither water levels nor water quality have been affected by mining. Replacement of the top aquifer by spoils during mining has caused many changes in the land surface, recharge rates, discharge rates, saturated thickness, water-table gradient, hydraulic conductivity, storage, and water quality. Changes in the middle aquifer include: the amount of recharge from precipitation, amount of leakage through the overlying clay bed, and water quality in some areas. Resaturation of the mining spoils during postmining has been slow and irregular, however, water levels in wells in the middle aquifer have remained virtually unchanged. The water quality in the mining spoils is significantly poorer than water in the original aquifer. Specific conductance concentration of water in the spoils is 2 ,020 micromhos per centimeter and sulfate is 940 milligrams per liter. Water levels and water quality in the deep aquifer have not been affected by mining. (USGS)
