Effects of Longwall Mine Subsidence on Overlying Aquifers in Western Pennsylvania

摘要

Ground Water levels and subsidence were monitored over a longwall panel of a deep coal mining operation located in western Pennsylvania. The monitoring network includes 11 ground water monitoring wells completed to measure water level changes in separate shallow and deep aquifer zones and 50-ft surveyed subsidence stations parallel and perpendicular to the panel centerline. Monthly monitoring data were collected during the premining, mining, and postmining time periods. Aquifer testing and borehole geophysical logging were conducted during premining and postmining conditions to document any changes in aquifer properties and ground water flow patterns. Results indicate ground water declines were located with respect to the mining face and mined longwall panel. Dewatering of the deep aquifer zone caused a significant water level decline in deep wells; however, the shallow aquifer zone was isolated from major impacts by an aquitardal layer during the 1-yr period. Transmissivity data were greatly impacted by fracturing in the highly anisotropic aquifer system. Borehole geophysical logging indicated changes in ground water flow patterns and zones of increased fracturing from subsidence.