Effects of longwall coal mining on rural water supplies and stress relief fracture flow systems

The response of 174 domestic water supplies to longwall mining of the Pittsburgh coal seam was compared to various physical parameters. Sixty-four percent of domestic water supplies returned to service without the need for intervention, while thirty six percent required intervention to reestablish a suitable water supply. Domestic well response is strongly correlated with the topographic setting. Valley wells showed the least effect while hilltop wells showed the greatest effect. Well response was also found to be correlated to the location of the well above the mining with greater effects observed in zones of surface tension and compression, and fewer effects in zones which are stress neutral. Ground water supplies remained unaffected or were reestablished at 149 of 150 sites, indicating that ground water resources remain available to domestic wells after mining. This paper reports that results of this study support the stress-relief model of ground water flow in the Northern Appalachian Basin. Longwall mining's effect on this system is to locally increase fracture connectivity in the near surface zone