Subsidence impacts on ground and surface water at a western coal mine

Effects of longwall mine subsidence and overburden deformation on water resources were evaluated at a western coal mine. A deep groundwater monitoring well and a subalpine stream were monitored for water level and flow variation as longwall panels were extracted. The well was completed in a confined water-bearing zone 250 m above the mine level. Daily monitoring of the well showed a dramatic rise in the water level as mining progressed, with a subsequent return to near premining levels within 8 months after undermining. The stream flows over a series of longwall panels where the minimum overburden thickness was 180 m. Stream flow data collected weekly during mining coupled with surface deformation measurements showed minor zones of tension and compression developed across the stream, but flow was not altered by the surface movement.