ABSTRACT: Geologic Constraints on the Development of Coal Resources in West-Central Illinois

TREWORGY, COLIN G., GAYLA K. COATS, and MARGARET H. BARGH, Illinois State Geological Survey, Champaign, IL

Billions of tons of coal resources underlie the west-central mining district of Illinois. A study supported by the U.S. Geological Survey was conducted to identify the nature and magnitude of geologic constraints on the mining and recovery of these resources. The Middletown Quadrangle, located 12 mi north of the city of Springfield was chosen as a sample area representative of the conditions found in many parts of the west-central district. In-depth interviews were conducted with mining companies familiar with conditions in the area and with the state agency responsible for permitting mines. Geologic constraints on mining identified in these interviews included thick glacial deposits overlying thin bedrock cover, weak underclay, unsupportable geologic strata directly above the coal, a d clay dikes. Based on these and other constraints on mining we calculated that approximately 60% of the coal resources in the quadrangle are available for mining. Furthermore, if mining is restricted to room and pillar methods (a likely scenario because of the weak floor, potential for water seepage into the mine, and difficulty of obtaining subsidence rights), only about 25% of the resources can be recovered. Though these geologic constraints limit the recovery of a large quantity of resources, there remain billions of tons of available, recoverable coal resources in the west-central mining district. However, this study shows that these geologic constraints should be considered when putting together a mine block in order to avoid acquiring large amounts of unrecoverable coal.

AAPG Search and Discovery Article #91013©1992 AAPG Eastern Section Meeting, Champaign, Illinois, September 20-22, 1992 (2009)