SURVEY OF MINE-RELATED SUBSIDENCE IN THE BYESVILLE, OHIO AREA: POSSIBLE IMPLICATIONS OF USING UNDERGROUND MINE-FED AQUIFERS

The city of Byesville, Ohio recently drilled a water well in the area of the abandoned Ideal coal mine. The well was brought into production during 2006 and takes water from underground min-fed aquifers. High periods of water usage could potentially lower the water table locally which might cause subsidence events. Mining related subsidence has been shown to be caused by several factors including shallow depth of coal, weak overburden, geological discontinuities, rainfall amounts, lowering of groundwater, and earthquakes. In an attempt to determine the potential impact of the water well, we surveyed subsidence events in a 3 km area around the Ideal mine to determine the history and frequency of events in this area.

The study area (794 square kilometers) is underlain by 401 square kilometers of underground mines which were abandoned between 1895 and 1947. The Pennsylvanian Conemaugh Group underlies 74 % of the area and contains the Upper Freeport coal (#7 seam) which averages 5 feet thick in the area. The coal dips slightly to the southeast as determined from depths reported for the mines and from oil well records in the study area. The mines are typically less than 400 feet below the surface and are room and pillar type mines. The maximum depth that sinkhole subsidence can occur has been documented at around 330 feet. The water table was determined using water well records in the study area and was found to be 50 to 100 feet above the elevation of the mines.

Eighteen subsidence events occurred in this area between 1984 and 2008. Three of the events were associated with the Ideal mine occurring in 1985, 2003, and 2007. Subsidence events were correlated with monthly stream flows records for Wills Creek at Cambridge, Ohio located approximately 5 miles northwest of Byesville. Eleven (69 %) of the events occurred during periods of higher stream flow (greater than 500 cfs) indicating that rain may have been the cause of these events. Five of the events including the2007 sinkhole at the Ideal mine occurred during periods of lower stream flow (less than 100 cfs). These events include 3 shallow sags and 2 sinkhole events. The 2007 sinkhole occurred at the edge of the Ideal Mine during an extended period of low stream flow indicating that the lowering of the water table and/or pumping from the mine-fed aquifer may have caused this event.