operating mines. Similarly, some states use industry data to prepare coal reserve estimates on unmined reserves for tax purposes, but these data are not publicly available.

The Keystone Coal Industry Manual is a private publication for the coal industry that has been published annually since 1918. It contains descriptions of the coal resources and geology of coal fields for each coal-producing state, describing coal bed geology, stratigraphy, thickness, quality, rank, mining methods, and identified resources (measured, indicated, and inferred). The state sections of the Keystone Coal Industry Manual are updated on an irregular basis, generally by state geological survey geologists.

U.S. COAL RESOURCE AND RESERVE ESTIMATES

The current estimates of total U.S. coal resources and reserves reported by the EIA are shown in Table 3.1. The ERR (Figure 3.2)—approximately 54 percent of the DRB—is calculated based on accessibility factors (by coal-producing region) and recoverability factors at existing mines. ERR and DRB estimates by state and mining method are presented in Appendix D; a subset of these data for the 15 states containing the largest reserves is shown in Table 3.2.

Limitations of Existing Coal Resource and Reserve Estimates

Old and Out-of-Date Data. By definition, the DRB does not represent all of the coal in the ground (EIA, 2006b). It represents coal that has been mapped, that meets DRB reliability and minability criteria, and for which the data either are publicly available or have been provided by companies under confidentiality provisions. The DRB was initiated in the 1970s, and consequently the majority of DRB data were compiled based on the geological knowledge and mining technology available more than 30 years ago. Although the DRB has been updated in 1989, 1993, 1996, and 1999 to incorporate reserve depletion data and limited more recent reserve data (EIA, 1999), the underpinning data remain those of the original 1974 study. The data on Identified Resources and Total Resources

TABLE 3.1 U.S. Coal Resources and Reserves in 2005

Category

Amount (billion short tons)

Recoverable Reserves at Active Mines

19

Estimated Recoverable Reserves

270

Demonstrated Reserve Base

490

Identified Resources (from Averitt, 1975)

1,700

Total Resources (above plus undiscovered resources)

4,000

NOTE: The relationships between these categories are depicted in Figures 3.1 and 3.2.



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