The City of Boulder is taking action to address a coal fire that has been burning for more than a century under the Marshall Mesa trailhead. This fire came under scrutiny after the , and while investigators found it unlikely to have caused the blaze, they couldn鈥檛 completely rule it out.
Starting this fall, all smoldering coal and any coal that could ignite in the future will be excavated, extinguished and reburied at the intersection of highways 170 and 93. Then the trailhead and parking lot will be renovated and expanded, and a 20,000-gallon cistern installed to improve fire resilience for nearby homes.
The Board of County Commissioners earlier this month to do the project. Though the land is owned by the City of Boulder, it is technically in unincorporated Boulder County, and the impacts will be substantial. The mitigation project is expected to take three to four months. The expanded trailhead and parking lot, which will increase from 46 spaces to 76, is slated for completion by fall 2025. The project is a collaboration between the city鈥檚 Open Space and Mountain Parks Department, Mountain View Fire Protection District and Colorado鈥檚 Department of Natural Resources Division of Reclamation, Mining and Safety.
This isn鈥檛 the first attempt to address the coal fire under Marshall Mesa. In 2005, a vent caused surface temperatures of 375 degrees, igniting nearby vegetation. In response, the Colorado mine safety division covered the vents with hundreds of tons of aggregate. Officials said this was never meant to be a permanent solution.
A decade later, the state tried to cut off the coal鈥檚 oxygen supply with a surface seal. Now, with funding from the federal Infrastructure Investment and Jobs Act, there are resources to extinguish the mine fire.
鈥淭his is an attempt to completely excavate and extinguish all areas where we鈥檝e seen previous fire activity, and where there鈥檚 additional coal that鈥檚 unburned,鈥� said Jeff Graves, a program manager with the mine safety division.
鈥淚t鈥檚 in an area that has high risk to infrastructure, and is one of those fires that鈥檚 relatively easy to attack and hopefully extinguish,鈥� Graves added.
Map of Marshall Mesa project area. Courtesy of City of Boulder Marshall Mesa project area. Courtesy of City of Boulder Colorado has around 40 underground coal fires. Tara Tafi, a mine reclamation manager with the mine safety division, said the fires could have started from miners鈥� practices in the 1800s, such as smoking or lighting fires underground for warmth. 鈥淭his was long before safety standards,鈥� Tafi said. Lightning strikes, wildfires and spontaneous combustion can also ignite shallow coal seams. Regardless of how the coal under Marshall Mesa started burning, it will require excavation to extinguish.
Excavators will dig 30 feet to the bottom of the coal seam in sections, bringing smoldering coal to the surface to be extinguished before being put back in the ground. No material will be moved offsite. An estimated 364,000 cubic yards of earth will be disturbed. Once the Marshall Mesa coal fire is extinguished, Boulder County will have no underground coal fires, as the Department of Natural Resources recently completed a similar project near the intersection of Cherryvale and Marshall roads.
Graves said community concern following the 2021 Marshall Fire is another reason to address the Marshall Mesa coal fire. The fire destroyed more than a thousand homes and upended thousands of lives. An by the Boulder County Sheriff鈥檚 Office and District Attorney鈥檚 Office determined one of the Marshall Fire鈥檚 ignitions was likely caused by an unmoored Xcel Energy power line near the Marshall Mesa trailhead. Yet, investigators couldn鈥檛 entirely rule out the underground coal fire, something Xcel is leaning on in its legal defense.
Effect of the uderground coal fire can be seen on snow at Marshall Mesa, circled in blue. Courtesy of Colorado Department of Natural Resources Xcel faces a for its alleged ignition of one of two fires that became the Marshall Fire, a claim it denies. In one of its legal filings, ,鈥� Xcel instead implicates several other entities, including the City of Boulder, for allegedly failing to mitigate the known risk in the coal seam under the Marshall Trailhead.
鈥淭he City of Boulder and its agents/representatives were wholly or partially at fault for the injuries and damages claimed by plaintiffs [against Xcel], and the comparative fault of the City of Boulder should be considered by a jury,鈥� the amended designation reads.
At the July county commissioners meeting approving the mitigation project, the commissioners attached a few caveats to their approval, the most noteworthy regarding a cistern to be installed as part of the project. The 20,000-gallon, $200,000 firefighting cistern will provide water for the Mountain View Fire Protection District. Mountain View is paying for and will maintain the cistern.
Commissioner Claire Levy asked that the cistern always be filled as a requirement for project approval, after several residents voiced a similar request during public comment.
Megan Monroe, a Marshall Fire survivor who lost her home near Marshall Mesa, spoke at the meeting, highlighting the need for a filled cistern on the property. She said if there had been one on Dec. 30, 2021, when the fire ignited, things might have been different. Two smaller cisterns were located near the site but were nonfunctional at the time of the fire, according to fire officials.
鈥淭he lack of emergency water, I will always feel, could have prevented this from blowing into the disaster that it was,鈥� Monroe said.
Brian Fuentes, another Marshall survivor, also spoke in favor of a full cistern, saying, 鈥淭he towns of Superior and Louisville could probably sleep better at night knowing this [the Marshall Fire] would never happen again.鈥�
Yet fire officials are wary of the idea that any step, like a cistern, could prevent a wildfire like Marshall, which was spread by hurricane-force winds of up to 100 miles per hour.
鈥淣ature can always provide a circumstance where it will outdo any response plan,鈥� said Jeff Webb, a deputy chief with Mountain View Fire Rescue. 鈥淢aybe you can plan for handling a fire in 30-mile-an-hour winds, or handle a fire in 50-mile-an-hour winds. But nature will always find a way to beat us.鈥�
Webb explained that the Marshall Mesa cistern could be used to fight a slower-moving wildfire that started farther west, allowing firefighters to set up to stop it. But the cistern鈥檚 main benefactors will likely be people affected by more stagnant fires. 鈥淐isterns are great for fires that are occurring in one place,鈥� he said. 鈥淎 house fire is where a cistern really comes into play.鈥�
Even if there had been a filled cistern at the Marshall Mesa trailhead on the day of the Marshall Fire, Webb said it wouldn鈥檛 have made a difference. Because of the fierce winds, by the time firefighters were able to tap the cistern, the fire would have been a half-mile downrange.
Design for the new trailhead at Marshall Mesa. Courtesy of City of Boulder 鈥淭here is always a condition in nature that can overrun whatever water source you have,鈥� Webb said. 鈥淚f [a fire] is moving in a 100-mile-an-hour wind, no amount of planning can deal with that sort of thing.鈥�
The commissioners鈥� approval of the coal remediation and trailhead update included several other conditions: consideration of the Preble鈥檚 Meadow Jumping Mouse, caution around unearthing hot material on days with Red Flag Warnings, and a protected crosswalk from the RTD parking lot to the future trailhead. Commissioner Ashley Stolzmann also asked that the city contact Xcel Energy to explore the possibility of undergrounding nearby power lines while the area is disturbed, a solution outlined in the utility鈥檚 recent wildfire mitigation plan.
鈥淚 was wanting a 鈥榖est efforts鈥� statement that鈥檚 not completely binding 鈥� that the city use best efforts to coordinate with Xcel on undergrounding their line,鈥� Stolzmann said.
While the project is underway, residents will not be able to access the Marshall Mesa trail system from the intersection of Highway 93 and Marshall Road. Alternative access points include the Community Ditch Trail starting from Doudy Draw Trailhead; Greenbelt Plateau Trail starting from Greenbelt Plateau Trailhead or Flatirons Vista Trailhead; Mayhoffer-Singletree Trail starting from 66th Street; the Marshall Valley Trail off Marshall Road; and the Coalton Trail starting from Boulder County Parks & Open Space鈥檚 Coalton Trailhead.
Speaking at the commissioners鈥� meeting, Wendy Sweet, executive director of the Boulder Mountainbike Alliance, asked commissioners to develop another access point closer to the closed trailhead to keep cyclists from riding long distances on highways to get on trails. She specifically cited youth groups like Boulder鈥檚 high school mountain bike teams and Boulder Junior Cycling that often bike from town to the mesa.
鈥淚 urge you to look at a space somewhere very near that Marshall Road intersection and the RTD lot to add a safe crosswalk during the project that leads directly to a trail, so we don鈥檛 have kids cycling on 170 to access Mayhoffer-Singletree or any of the farther trailheads,鈥� Sweet said.
Tim Drugan is a reporter for the Boulder Reporting Lab. His work frequently appears on-air at KUNC 91.5 FM and online at KUNC.org. Contact Tim at tim@boulderreportinglab.org.