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SALT LAKE CITY (AP) -- Utah's Tower mine, the deepest coal mine in the United States, was closed Friday because of safety problems.
UtahAmerican Energy Inc. was forced to close the mine because of "unexpected and unusual stress" in mine pillars that threatened the safety of miners, chief executive P. Bruce Hill said.
The company wanted to relocate a longwall mining machine inside Tower but found the conditions unsafe. Changes ordered by federal regulators contributed to the mine's closing, Hill said.
The Murray Energy Corp. subsidiary closed the mine for several weeks last summer as engineers tested its ability to withstand seismic shocks that plagued the company's Crandall Canyon mine near Huntington, Utah, where nine people died in two cave-ins.
The Tower mine, seven miles north of Price, Utah, reopened in late January.
The company's statement didn't specify whether the Tower mine, previously known as the Aberdeen mine, was being permanently shut down. It is the same mine that was slapped with $420,000 in fines for "flagrant" safety violations on March 20.
It was also unclear how many people work at the mine.
William Pariseau, a professor of mining engineering at the University of Utah, said the Tower mine follows a coal seam 2,750 feet.
Pariseau is part of a team of university researchers that presented findings about the dangers of deep coal mining Thursday at a conference at the federal Bureau of Land Management in Salt Lake City.
Pariseau determined the solid coal barriers at Tower were sufficiently large to support the mine, but his analysis did not take into account geologic conditions that could contribute to cave-ins.
"If these operators say they're seeing things that trouble them, and they won't continue their operation because its not safe, I believe them," said Kim McCarter, chairman of the university's Department of Mining Engineering.
"It's not spent out. It's just deep," he said. "This should be a very disturbing to people if they're not comfortable mining at this depth. All of our remaining reserves are that deep."
UtahAmerican said Tower is the deepest operating coal mine in the United States. At that depth, the mountain is bearing down on the mine with a force of 3,025 pounds per square inch, McCarter said.
(Copyright 2008 by The Associated Press. All Rights Reserved.)