Colorado crews planning mitigation of second underground coal mine fire near Marshall Fire's origin - CBS News

State mining safety crews are moving forward with plans to unearth a second active underground fire later this year in the area where the most destructive wildfire in Colorado history was ignited.

The Marshall Fire destroyed more than 1,000 homes on Dec. 30, 2021. It was pushed by 100 mph winds across open space and into the communities of Superior and Louisville. Two residents there were killed.

A view of the Marshall Fire in Louisville on Dec. 30, 2021. Marc Piscotty/Getty Images

Authorities, after an 18-month investigation, determined there were two ignition points - the first a smoldering wood pile on private property, the second below power lines. The latter is a point of contention, with Xcel Energy disagreeing with investigators' conclusions. The company is fighting litigation blaming its lines for at least partially causing the blaze.

The investigation did not rule out the possibility that coal burning below ground for decades contributed to the fire. Winds as strong as those experienced during the Marshall Fire could conceivably draw heat from the underground coal fires to the surface.

One such site contains the Lewis Mines that were abandoned and buried in 1946. A surface vent emitting heat measured at 120 degrees was discovered in 2018.

Colorado Division of Reclamation, Mining, and Safety

Crews from Colorado's Division of Reclamation, Mining and Safety started an overhaul of the Lewis Mine site in January. Excavators carefully extracted land adjacent to the Davidson Ditch, alternately digging and filling 10-foot "fingers" of steaming ground to keep the concrete irrigation channel from collapsing.

Crews dug 30 feet deep and encountered temperatures as high as 600 degrees. Where readings were greater than 90 degrees, crews mixed the heated soil with cool soil and rock until temperatures fell below that mark.

The project wrapped up in early April ahead of schedule.

Crews are now planning to turn ground 2,000 feet away above the Marshall Mines, a DRMS spokesman confirmed. The department is currently in the permitting process with Boulder County since the project, slated to start later this summer or fall, will affect access to county open space at the Marshall Mesa trailhead.

It will be the second time mitigation efforts have occurred at the Marshall Mines. A vent from the mines there was blamed for starting a small brush fire in 2005. Three years later, 275 tons of rock was dumped on the site, raising its surface 18 inches.

The recent Lewis Mines mitigation cost $316,002, according to the department's spokesman, Chris Arend. The Marshall mitigation will be done now that additional federal money has been received by the department to address coal mine fires throughout the state.

In a 2018 DRMS study, there are 1,736 know abandoned coal mines in Colorado. A contractor hired by the state to examine them found 38 were actively burning or were dormant and extinguished after previously burning.

Logan Smith

Logan Smith is an assignment desk editor at CBS Colorado in Denver with more than 30 years of journalism experience in digital, television and print media.

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