TORONTO (miningweekly.com) – Arch Coal expects that the longwall at its Dugout Canyon underground mine in Utah will be idled for at least another 30 days, and has warned customers that shipments are likely to suffer.

Production was halted at Dugout Canyon on June 22, after an “ignition event”, the firm said.

All underground employees at the mine were evacuated at the time, and Arch has since been working with the Mine Safety and Health Administration to assess the conditions at the mine.

Workers re-entered the mine to install a remote monitoring system, and atmospheric readings to date seem to be consistent with levels before June 22, and “show no signs of active combustion”, Arch senior vice-president of operations Paul Lang said.

“Nevertheless, for added precaution, we plan to temporarily seal the active longwall panel in order to render the atmosphere behind the seals inert.”

The company now expects the mine will be out of production for longer than initially estimated, “and consequently has advised customers that shipments are likely to be adversely impacted”, Arch said.

The Dugout Canyon mine, which employs 275 people, produced 200 000 t/m of low-sulphur bituminous coal in the first quarter of 2010, about 2% of Arch's total output.

The mine was temporarily halted earlier this year, on April 29, because of an increase in carbon monoxide levels.

Safety and air quality in underground coal mines is a a hot issue in the US, after 29 workers were killed in an explosion in April at Massey Energy's Upper Big Branch mine.

Shares in Arch Coal slid 6,12% on Monday, to $20,71 apiece by 14:15 in New York.

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