Utah's biggest coal field, the Kaiparowits Plateau field in Kane and Garfield counties, is estimated to have 62 billion tons in place, according to a circular issued by the Utah Geological Survey in 1997. Of this, the mineable portion is 22.7 billion tons, though not all of that could be extracted economically.

"We estimate recoverable reserves at 9.1 billion tons," Vanden Berg said. That amounts to more than 61 percent of the total in the state.

But most of the Kaiparowits coal won't be mined soon, if ever. It is within Grand Staircase-Escalante National Monument, designated by then-President Bill Clinton in 1996.

The word "reserves" does not mean any amount of coal, located anywhere and in any type of seam, according to Kohler. Reserves must be suitable for economical extraction at the present. "If you can't mine it at a profit at the time of determination, it's not a reserve," he said.

Considerations that go into deciding what's a profitable reserve include how thick the coal bed is, the quality of the coal, the depth of the overburden (a "very, very significant" factor), geologic conditions such as whether seams are connected, and whether the coal block is big enough to justify the investment.

Still, Kohler said, Utah coal that is easily accessible and not too far from present production facilities should last 40 to 45 years at today's rate of mining.

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A four-day Deseret Morning News series examines Utah's energy future:

Today: A look at coal reserves in Utah.
Monday: Conventional oil, natural gas, oil sands and oil shale.
Tuesday: Wind and solar power
Wednesday: Uranium-nuclear power

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E-mail: bau@desnews.com