Crews to start cooling a smoldering, underground coal mine in Boulder County

BOULDER COUNTY, Colo. — Colorado’s Division of Reclamation Mining and Safety is set to begin work next week to cool an underground coal mine near the Marshall Mesa in Boulder County.

That mine closed roughly 100 years ago but still holds areas of hot, smoldering coal, registering below-ground temperatures of more than 200 degrees, according to the state.

“There weren’t any regulations at the time that governed how these mines were supposed to be left and at the time,” said Jeff Graves. “Once they were done, they just moved on.”

Graves is the program director for the Colorado Inactive Mine Reclamation Program, which is spearheading the work at the Marshall Mesa.

He said while the risk posed by the coal mine remains low, there are a handful of areas of steam that are regularly seen at the surface.

“If you were to have a collapse that exposed that smoldering coal and it got additional oxygen, there’s a potential for that coal to ignite and then ignite vegetation on the surface with that wildfire ignition,” Graves said.

Beginning Monday, crews will start excavating the old mine, with hopes to cool the coal inside down to roughly 80 degrees.

Graves said they’ll dig down roughly 30 feet, and bring the hot coal to the surface, where it will be mixed with other soil and water.

That material will then be placed back into the earth, and trails will be rebuilt on top. Graves said they’ll be taking significant precautions to make sure the work doesn’t pose any additional fire risk.

“It’s certainly a concern when you’re exposing hot material at the surface with dry conditions, or windy conditions,” Graves said. ”We’ve taken some pretty extensive precautions to ensure that we don’t have any kind of potential for wildfire ignition in that area by having a significant amount of water on site specifically dedicated for fire control if we were to have that, and then also ensuring that we’re not working under extremely windy conditions with the likelihood of moving any of that hot coal material off site.”

The trailhead is expected to be closed for about a year as the work commences.

The coal mine was not found to be a significant factor in the Marshall Fire but has not been completely ruled out as a source of the second fire, which started near the Marshall Mesa Trailhead.