| Two research projects by the Water and Energy Team of the National Energy Technology Laboratory were carried out in collaboration between the US Department of Energy and the University of Pittsburgh. Both projects are related to investigating current and potential impacts of abandoned coal mines on the adjacent populated regions.;The first project was carried out in West Virginia over 14 active and abandoned coal slurry impoundments (Appendix A) in order to remotely investigate their current condition and potential hazards related to the mine-waste pools. Three main scenarios of impoundment failure are overtopping of the impoundment, internal erosion (piping) and entry of unconsolidated material into adjacent mine voids due to subsidence. To characterize these potential hazards, helicopter-mounted electromagnetic (HEM) surveys were completed to identify fluid saturated zones within coal waste and to delineate the paths of filtrate fluid flow. Attempts were also made to identify flooded mine workings underlying the impoundment areas. A total of 431 flight lines were processed, each from 2 to over 4 km in length, in total more than 1300 line-kilometers of HEM survey. Follow-up, ground-based resistivity surveys verified the results of the HEM investigations. The HEM and ground-based geophysical surveys proved to be effective in delineating the phreatic surface, determining seep locations, imaging areas of unconsolidated slurry, locating areas where process water has invaded adjacent aquifers, potentially depicting the possible location of flooded underground mine workings and locating infiltration zones.;The second project took place in southwestern Pennsylvania. In order to image beneath the surface and identify zones of possible gas accumulation and migration routes, reflection seismic surveys were completed in this area. Seismic imaging was successful in identifying regions of subsurface gas accumulation. Because of the urban nature of the survey, it was very challenging to collect and process seismic reflection data. |
