Detail view of room-and-pillar layout of a typical underground mine in Indiana.
The quality and accuracy of this mine information can vary greatly depending on the source, type, and age of the mine. The Indiana Geological Survey, with assistance from the Indiana Department of Natural Resource's Division of Reclamation, has compiled, organized, and digitally archived Indiana's underground coal mine maps. This map information, as well as all other coal mine data, has been consolidated into the Coal Mine Information System (CMIS) using current geographic information system (GIS) software and relational database technology. The CMIS has proven a valuable resource for the mining industry, planners, developers, and the public. To access the interactive coal mine maps, go to the Coal Mine Information System page.
There are numerous reasons why active underground mining may break into old mine works: an old mine may have never been mapped, quite often a mine's location on a map could be off as much as 300 to 500 feet, and in rare instances in the past, mining has gone beyond the extent shown on its map (referred to as "robbing coal"). As is the case in Pennsylvania, the accuracy and correlation of abandoned mine maps may come into question. The incomplete or inaccurate documentation of some abandoned mines can pose hazards to new mining activities in the area. Poorly documented abandoned underground mines also present a potential land subsidence threat to infrastructure and homes unknowingly constructed above these areas. There are numerous examples of subsidence events in Indiana.
Paul Irwin of the Indiana Geological Survey observes a pit created by the collapse of a section of an underground coal mine near Coalmont, Indiana in southwestern Clay County.
Coal in Indiana is located in the southwestern portion of the state. Coal mining in Indiana started in the early 1830s resulting in approximately 2,100 underground mines. Records of these mines have been maintained at the Indiana Geological and Water Survey (IGWS) for more than 100 years. Of these 2,100 mines, approximately 600 have detailed maps and approximately 1,500 of the mines are poorly documented. Information available for mines can be as detailed as an original company mine workings map that shows where the coal was removed or provide just an approximate location point representing the mine entrance.
In 2001, nearly 35 million short tons of coal were mined in Indiana. Although most of this production came from surface (strip) mine operations, there are also seven active underground mines currently operating in the state (two of which are located on the Illinois/Indiana border and have their entrances in Illinois). These mines range in depth from 70 to 1000 feet, with coal thickness ranging from 4 to 7 feet. Because of strict regulatory control and diligence on the part of Indiana's coal industry, the risk of a catastrophic mine flood, such as the accident in Pennsylvania, is relatively low. Through the mine permit process, coal companies are required to locate abandoned mines (often by drilling exploratory bore holes) and keep active mining operations at least 200 feet away from known abandoned mines. Underground mining is a potentially hazardous undertaking that requires miners and company officials to take great care in the development and oversight of their operations. Indiana's mine safety record is high, with no major mining accident reported for decades.