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considered, the forecast of a 200-year coal supply for the United States is overly optimistic. Although some attempts have been made to quantify available coal, none have used a comprehensive geologic data base and considered all of the restrictions now placed on coal mining.
A new methodology is necessary to determine coal actually available for mining. This methodology must be specific enough to consider the key factors that would limit coal mining but flexible enough to be applied in any coal region in the United States. The USGS is currently developing such a methodology, which relies on cooperative efforts with State geological surveys to develop a comprehensive geologic data base. The National Coal Resource Data Base (NCRDS) is the repository for all data, in digital form, and these data can be manipulated to eliminate restricted coal and quantify that which is available for mining.
To test this methodology, a pilot study, in cooperation with the Kentucky Geological Survey, was conducted on the Matewan quadrangle, Pike County, in eastern Kentucky (fig. 3). Restrictions that limit the availability of coal for surface and underground mining have been defined and mapped, and all data were entered in the NCRDS. For surface mining, environmentrelated restrictions are surface features that cannot be moved and generally required that barriers be left. These restrictions include (1) major powerlines and pipelines, (2) town and public buildings, (3) Federal highways, (4) cemeteries, (5) oil and gas wells, (6) railroads, and (7) environmentally sensitive areas, such as endangered species habitats, protected rivers, game lands, and parks. In addition, surface mining is restricted by economic factors,
which are indicated by the limiting strip ratio that can be achieved and still make a profit.
Restrictions on underground mining are primarily economic and technological, and a coal bed will not be mined when (1) it is too shallow or too deep, (2) it is within a certain distance above or below an abandoned mine or a coal bed that is more likely to be mined, (3) it is located in highly folded or faulted areas or areas where roof conditions would be too problematic, or (4) it is too thin to be mined by conventional technology. Coal quality also may restrict coal availability if it does not meet compliance standards for sulfur or if it does not meet user specifications.
An accurate geologic base upon which to apply these restrictions is vital to the study. For the Matewan quadrangle, the most recent geologic maps and data were supplied by Kentucky Geological Survey geologists familiar with the geology of the area. Coal map data in computerized form and sampling and drilling data were entered in the NCRDS, which supplemented data already in the system for this quadrangle. By combining these data with a computerized USGS digital elevation model for the quadrangle, original and remaining coal resources were mapped and calculated for the 22 major coal beds. Figure 4A shows the original extent of occurrence of one coal bed, the Elkhorn No. 2. Restrictions to surface and (or) deep mining were then delineated on the basis of local environmental regulations and mining practices. By mapping these restrictions and applying them to maps of remaining coal resources, available coal was mapped and quantified for each of the coal beds. Figure 4B shows the coal available for surface and deep mining in the Upper Elkhorn No. 2 bed after restrictions were applied.
Calculations for the Upper Elkhorn No. 2 coal bed indicate that of the 92 million short tons of total coal resource remaining after subtracting what has already been mined, only 30 percent, or 28 million tons, is actually available for future mining (table 1). If recovery factors are applied to future mining of this remaining available resource, the available coal would be fur
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POWELCompton şayerswille Paints Harrodsburg
WOLFEN Springfield BO
1 MONROE MARION
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WHITLEY Pine Harian > CUNTON
ther reduced. Additional studies will indicate whether these preliminary calculations are representative of this coal region. If so, these results could dispel some of the optimism that is commonly engendered by coal resource forecasts that are expressed in billions and trillions of tons.
The data developed for a portion of Pike County may be extrapolated some distance provided the geologic conditions, the topography, and the general coal economy are relatively uniform. Coals are found in a variety of geologic settings, and it will therefore be necessary that similar studies be done in the other major coal-producing areas where coal characteristics differ significantly from those in the area of the pilot study. Parts of southern West Virginia and
western Virginia may be well represented
Figure 4A. Original occurrence of the Upper Elkhorn No. 2 coal seam (colored area), Matewan quadrangle, Kentucky, before mining