Evaluation of the long term impact on domestic and farm groundwater supplies under Pennsylvania longwall mining conditions

Longwall coal mining is a dynamic method of coal extraction that disrupts overlying geologic strata and develops zones of increased permeability. This study was undertaken to determine what long-term effects longwall mining has on overlying domestic and farm water supplies under thick overburden conditions in Pennsylvania. The study region was comprised of the Greene and Washington County area in the southwestern corner of the State where overburden ranges from 700 to 900 ft thick. Investigative methods included analysis of coal company water level monitoring data, interviews with company representatives and State officials, and field contacts with concerned property owners. A new comparative approach for analyzing water level data led to these general conclusions: hilltop and hillside topographic settings tended to lose water supplies, while valley settings gained new ones in the form of springs and increased water well levels. Deeper drilled wells found in higher topographic settings lost water, while shallower ones in the valley settings remained reasonably unaffected. Three parameters, topographic setting, well depth, and overburden thickness, are recognized as the most important aspects for whether a water supply will be affected by longwall mining under these overburden conditions. Though water supplies were affected by mining, coal companies in the area exhibited good success in finding replacement water supplies by drilling new, deeper wells nearby for those affected property owners