BOULDER, Colo. — State crews are in the final stages of the mitigation project on the Lewis Mine Fire burning underground southeast of Boulder. The fire, which has been burning for more than 50 years, has received more public attention following the devastating Marshall Fire in late 2021.
Crews for the Colorado Division of Reclamation, Mining, and Safety (DRMS) began excavating the Lewis Mine site January 25, 2024. While they found no active flames during their excavations, they regularly encountered smoldering coal at temperatures up to 650 degrees, underscoring the importance of the mitigation effort. An estimated 10,500 cubic yards of coal, soil, and rock have been excavated through the mitigation process, which entails mixing the smoldering coal with soil and rock until it reaches a temperature of 90 degrees or lower.
“And that cools it down very rapidly,” explained Jeremy Reinke, the DRMS project manager for Lewis Mine. “Typically, we can go from 400-500 degrees out of the ground to below 90 degrees in a matter of five to ten minutes.”
Underground mine fires are not uncommon.
Officials know of at least 38 in Colorado alone, and more than 250 were reported nationwide as of September 2021. However, the Lewis Mine fire and the nearby Marshall Coal mine fire have garnered a great deal of attention locally in recent years, following the devastating Marshall Fire. While officials do not believe the coal mine fires contributed — the Boulder County Sheriff announced last year that findings that the Marshall Fire was likely caused by a downed Xcel power line and embers from an earlier fire on private property — concern has grown for risk of future ground fires as more cracking and venting at Lewis Mine have been observed.
That concern was a key reason for the decision to begin mitigation, said Jeff Graves, the director of the Office of Active and Inactive Mines.
“It’s a significant reduction in the risk of future wildfire ignition in this area, which I think is a huge benefit obviously to the community here,” Graves said.
Thanks to cooperative weather and a smaller-than-anticipated excavation required, mitigation efforts are ending roughly two months ahead of schedule. The project’s cost is estimated at roughly $300,000, with funding coming from the Bipartisan Infrastructure Law signed by President Biden in 2021. The state of Colorado is set to receive $10 million each year for 15 years to deal with underground mine fires, Graves said.
Lewis Mine is not alone in the noticeable increase in underground fire activity. State officials are observing similar trends at sites statewide. Drought and drier soil conditions are believed to be the cause, which is why DRMS is looking to begin similar mitigation projects at other sites as soon as this year.
With fire mitigation at the Lewis Mine site now reaching completion, crews will re-contour the area in harmony with the surrounding open space in Boulder County.
Editor's note: An earlier version of this article said that the Lewis Mine Fire was initially suspected in the 2021 Marshall Fire blaze. It was actually the nearby Marshall Coal Mine Fire that was initially suspected. Officials do not believe either contributed.
