Ground-water conditions during coal strip mining in two small watersheds are described as part of an ongoing study of effects of mining on hydrologic systems. Both watersheds were underlain by stratified sedimentary rocks containing two perched aquifers above clay beds which underlaid the major coal seams. Mining involved removing the overburden rocks, including the top aquifer, stripping the coal seam, and recontouring the overburden spoils to the approximate premining shape of the watershed.
Water levels in the top aquifer declined as mining neared the watersheds, but destruction of observation wells precluded a record of any decline during mining in the watersheds. Depletion of the top aquifer was reflected in base flow of streams, which was reduced and more highly mineralized after mining. Initial saturated thickness of replaced overburden spoils ranged from 0 to 4 feet, based on data from observation wells installed immediately after reclamation. Down-hole specific-conductance measurements of water in the spoils suggest the presence of more highly mineralized water than that in the premining top aquifer. No significant effects of mining are evident on ground-water levels or quality beneath the stripped coal.
