Fourteen quadrangles in five separate areas of the Western Kentucky Coal Field were studied to determine what factors affect the availability of coal for mining. Each study area consisted of at least two adjacent 7.5-minute quadrangles in order to account for the geologic variability across broad distances in western Kentucky, and determine how this variability affects availability. Areas both north and south of the Rough Creek Fault System were selected to measure the effect of different geologic, structural, and overburden settings on coal availability. The study emphasized the coals occurring stratigraphically between the Springfield and the Baker.
About 90 percent of western Kentucky coal resources is associated with only six beds, and one bed, the Springfield (W. Ky. No. 9), constitutes 25 percent of the entire estimate. Seventy percent of the resource is greater than 56 in. thick. Most mining in the Western Kentucky Coal Field is currently by underground methods; only 25 percent is by surface mining.
A geographic information system (GIS) was used to estimate tonnages. Point data were obtained from over 5,000 drill-hole and geophysical-log descriptions, and included coal thickness, parting thickness, elevation, and stratigraphic position. Outcrops were digitized from U.S. Geological Survey (USGS) 7.5-minute geologic quadrangle maps, and land-use restrictions from USGS 7.5-minute topographic quadrangle maps. Mined-out areas were obtained from the Kentucky Department of Mines and Minerals, and locations of oil and gas wells from the Kentucky Geological Survey. A digital elevation model was obtained from the U.S. Geological Survey.
Land-use restrictions can apply to both surface and deep mining. Technological restrictions in this study generally apply only to deep mining, and include barriers around existing mines, mining within 40 vertical feet of a seam, active oil and gas wells, coal too thin for current underground mining methods (less than 28 in.), and small mine blocks. Many technological restrictions in western Kentucky could be overcome if the relatively low profit margins in the region increased.
Tonnage estimates for each bed are reported by categories of coal thickness, overburden thickness, and reliability of the estimate. Thickness categories used in this study are 14 to 28 in., 28 to 42 in., and greater than 42. in. Overburden categories are surface-mineable, deep-mineable, and too deep to mine with current technology. Reliability categories, based on distance from coal-thickness measurements, are measured (within % mi of a data point), indicated (between % and % mi), inferred (between % and 3 mi), and hypothetical (beyond 3 mi).
Total original resources for the assessed coals in the 14 studied quadrangles are estimated at 5.55 billion tons (BT). Almost half this total is accounted for by the Springfield coal, and nearly a quarter by the Baker. About 77 percent of the coal is considered deep-mineable.
A total of 1.084 BT, or 20 percent of he original resource, has been mined out or lost to mining. Thus, 4 BT, or 80 percent of original resources, remain.
The average amount of restricted coal is 26 percent of original resources, and 88 percent of this restricted amount is by technological factors. The most important technological restriction was coal too thin to mine. Small interburden thickness between two mineable seams is a key factor in some areas; other locally important factors are mine barriers and small mine blocks.
The average availability of coal in the 14 studied quadrangles is 54 percent. The results by quadrangle range from 9 to 91 percent, which confirms the necessity of studying larger areas.
Deep-mineable coal between 28 and 42 in. thick and surface-mineable coal between 14 and 28 in. thick is considered available, but uneconomic. The uneconomic resources account for 14 percent of the original resource, leaving 40 percent of the coal that is both available and economic.
Report of Investigations 8
Digital Object Identifier (DOI)
Weisenfluh, Gerald A.; Andrews, William M. Jr.; Andrews, Robert E.; and Hiett, John K., "Coal Availability in Western Kentucky" (2001). Kentucky Geological Survey Report of Investigations. 11.