Underground coal fires are serious trouble. Because coal deposits contain oxygen, they can keep burning even when there is no air present. This phenomenon is at play in Utah’s Lila Canyon mine where coal has been burning for nearly three months, even after mine operators filled the mine with nitrogen, displacing all oxygen remaining near the fire.
The battle to save the Emery County mine enters a new phase this week when drilling crews start injecting an expanding cavity-filling foam down several new boreholes in the hopes of sealing off the burn area before flooding it with water.
At stake are tens of millions of dollars worth of mining equipment and the fate of Utah’s most productive coal mine, which employs 238 people and supplies three Utah power plants.
These miners have been idled since Sept. 20, when a coal pillar spontaneously combusted deep underground making the extensive underground mine unsafe to enter. It was safely evacuated with no reported injuries, but extinguishing the fire has proven far more tricky.
Under an emergency program authorized Oct. 21 by the Bureau of Land Management, mine operator Emery County Coal Resources (ECCR) has since been drilling round the clock, sinking up to 35 boreholes 1,100 feet into the mine from the top of the Book Cliffs. The plan is to use these holes to seal off the burn zone, then direct millions of gallons of water underground to squelch the fire, according to an environmental assessment.
“It’s unknown how long it may take to extinguish the fire, but other coal fires have burned from a few days to decades,” the assessment states. “It is also difficult to quantify the impact of coal fires on regional air quality because it is not possible to determine how much coal is being combusted, and little is known about criteria and hazardous pollutant emissions from other coal fires to use as a reference.”
Drilling is nearly complete, despite some setbacks, according to Dana Dean, who heads the mining section of the Utah Division of Oil, Gas and Mining, or DOGM.
“The mine is still on fire. They still can’t go underground. Sealing off that area with the foam will advance that, hopefully that will allow them to get underground,” Dean told the Utah oil and gas board at its Dec. 7 meeting.
In the meantime, water is already leaking into the part of Lila that was being actively mined, resulting in another headache for the operator.
(Utah Division of Oil, Gas and Mining) A crew works a mobile drill rig in Utah’s Book Cliffs, pictured on Nov. 23, sinking a borehole into the Lila Canyon coal mine. Mine operator Emery County Coal Resources has been drilling round the clock for weeks, sinking up to 35 boreholes 1,200 feet into the mine where a coal deposit has been burning since Sept. 20. This week, the company plans to inject an expanding foam down the holes in the hopes of sealing off the burning section.
“They’re still trying to save their longwall equipment from the water that’s building up in that area,” Dean said. “They’re fighting against the clock. Longwall equipment is as waterproof as they can make it, but being submerged for a long period of time will not be good.”
Before the fire, Lila Canyon was producing nearly 300,000 tons of high-quality coal a month, most of it going to the Hunter and Huntington power plants, also in Emery County. Returning the mine to service is a top priority for state and local officials, but that could take a long time, even if the fire is extinguished soon.
After the mine is flooded, the operators may still have to wait up to 120 days before entering to make sure the fire is out, according to Jurgen Brune, a professor of mining engineering at the Colorado School of Mines.
“You will continue to monitor gases through these boreholes, monitor the atmosphere in the mine,” said Brune, who is not involved with the fire response. “If you keep getting carbon monoxide levels going down, that indicates the fire eventually goes out.”
Then there is the question of water damage to the longwall components.
“The hydraulic parts can be salvaged,” Brune said, “but anything electrical, the motor, the controls, that kind of stuff once it gets underwater is pretty much junk.”
DOGM will oversee the reclamation of the emergency drilling and boreholes, but it has no authority over the firefighting effort itself, which is being supervised by the federal Mine Safety and Health Administration, or MSHA.
The state agency, however, has been providing public updates in the face of complete silence from the mine’s corporate parent, Ohio-based American Consolidated Natural Resources. The company has yet to respond to any media inquiries since the fire broke out and prompted what is shaping up to be the costliest emergency response associated with a Utah coal mine since the 2007 Crandall Canyon disaster, where collapses claimed the lives six miners and three rescuers.
When asked for comment, MSHA directed questions to the mine operator. “Reopening the mine is the operator’s responsibility,” said a spokesperson.
Coal mines in the Book Cliffs region of Utah and Colorado face a risk of spontaneous combustion because of the chemical composition of the deposits they tap. Several mines in Colorado have closed down because of such fires and some continued to smolder for years.
(Francisco Kjolseth | The Salt Lake Tribune) Coal transportation and rail operations along US-6 in Helper on Tuesday, Dec. 6, 2022. Lila Canyon is Utah’s most productive coal mine, which employs 238 people and supplies three Utah power plants.
In the case of Lila Canyon, the coal deposits contain pyrite, or iron sulfide, according to Charles Kocsis, a University of Utah professor of mining engineering. Pyrite oxidizes in the presence of water and oxygen, resulting in a heat-producing chemical reaction. If the oxidizing pyrite exceeds 110 degrees Fahrenheit, it can ignite surrounding coal.
“Initially, it is smoldering,” he said in a recent phone interview. “There is a lot of smoke generated, but no flame.”
Kocsis, who has been consulted on the fire, has been told it is burning in a part of the mine that was previously abandoned and sealed off.
“There is no human presence. You can’t even go in there,” he said. “The only way is to drill boreholes from the surface.”
Early in the Lila emergency, the operator drilled three holes into the mine, then injected nitrogen, an inert gas that eventually pushed all the oxygen out of the mine, according to the BLM.
Based on data gathered from those initial boreholes, the operator came up with the current fire-fighting plan involving extensive drilling, phenolic foam, water pumping and mine flooding.
Kocsis believes the plan will ultimately be successful because the part of the mine that’s burning has been abandoned and was likely to have been isolated from the rest of the mine before the fire started. The burning area is about two miles southeast of the mine portal at the end of Lila Canyon Road.
“My opinion is this fire will be safely put out. How long it takes, that is a big question. I would say maybe a couple months,” Kocsis said. “It takes time to understand where the fire is. Once it is located it is easier to manage. Each mine site is unique, it has a unique layout. What works at one mine site might not work here.”
In addition to the holes at the entry points, ECCR is drilling three more for monitoring and four others for extracting water from an inactive part of the mine. Over a 12-month period this water would be pumped to the surface, piped overland and sent underground into the burn area.
There is no way to know how much water would be needed, but the BLM’s environmental review said it would likely be hundreds of acre-feet, far too much to be trucked in on rugged roads in winter. Moving just 100 acre-feet — enough to fill 50 Olympic-size pools — would take 6,300 round trips.
By applying water, the goal is to cool the burn area below what is known as the “self-heating temperature of the burning coal, according to Brune. The challenge is to ensure the water submerges the part of the mine that’s on fire.
“It’s a question of whether they have suitable topography,” Brune said. “You can only make a puddle where there’s a depression. Let’s assume they have that. Then there’s a reasonable chance they can flood that part of the mine where the fire is and that might work.”
Either way, the mine operator has lots of work left to do before firm answers emerge from the smoldering mine.
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