In a series of cooperative agreements with the U.S. Geological Survey under its Coal Availability program, the Ohio Division of Geological Survey has conducted detailed investigations to estimate the amount of coal resources available for development. Using geographic information system (GIS) methods, these investigations determined original resources, mined-out, and resources restricted to mining because of land-use or technological reasons. Initial investigations assessed all coal resources within a 7.5-minute quadrangle. Coal Availability investigations have been completed for eight 7.5-minute quadrangles in eastern Ohio. Subsequent investigations assessed the resources of individual coals on a regional scale. GIS-derived statewide coal-resource estimates have been completed for the Upper Freeport (No. 7) coal and the Middle Kittanning (No. 6) coal.
METHODS USED TO CALCULATE AVAILABLE COAL RESOURCES
- Only coal in beds greater than or equal to 14 inches thick are included as a resource. Coal in beds less than 14 inches thick are excluded.
- Coal-resource tonnages are reported in thickness increments of either 14 to 28 inches or greater than 28 inches.
- Three overburden categories are reported: <20:1 overburden-to-coal thickness ratio, >20:1 overburden-to-coal thickness ratio, and >1,000 feet. These categories are most representative of Ohio mining practice. The U.S. Geological Survey uses overburden categories of 0 to 200 feet, 200 to 1,000 feet, or >1,000 feet. Coal resources were calculated using both procedures.
- Coal-resource estimates are reported in the following categories of reliability: measured (coal 0 to 0.25 mile from point of thickness measurement), indicated (0.25 to 0.75 mile), inferred (0.75 to 3 miles), and hypothetical (greater than 3 miles).
To perform the resource calculations, a GIS-based computer program combined maps of thickness, overburden, mined areas, and restricted areas to produce maps consisting of areas of these resource classifications. For each resource-classification area, the coal thickness in this area was used to calculate the volume of coal resources, which was converted to tons using a conversion factor of 1,800 short tons per acre-foot. First, original resources were calculated by applying the map of areas of original resources to the map of coal thickness and using the GIS to calculate the volume of coal contained in each resource category. The GIS then subtracted mined-out and lost-in-mining areas from the original resource map to produce the map of remaining resources. The areas of total restricted resources were removed from the map of remaining resources to produce the map of available resources. Restrictions to mining were classified into two types, land use and technological. Land-use restrictions affect surface-mineable coal, whereas technological restrictions affect primarily deep-mineable coal. To determine type of mining most likely to be used, the Coal Geology Group developed a computer program that uses slope, outcrop, coal-elevation, and coal-thickness maps to construct maps that show surface-mineable coal (<20:1 overburden-to-thickness ratio) and deep-mineable coal (>20:1 overburden-to-thickness ratio).