Houses in the burn area of the Marshall Fire, which was in part caused by embers from a slash pile burn, can be seen under construction in winter 2023. Credit: Don Kohlbauer

After the revelation that one cause of the Marshall Fire was embers from a slash burn started on a residential property six days before the disaster, some have questioned the place of slash burning in Boulder County. 

Should it even be allowed with such costly downsides? Especially as climate change dries the landscape and raises the risk of a spark bringing another Marshall Fire?

Seth McKinney, fire management officer in the Boulder County Sheriff’s Office, said he believes what’s needed isn’t a ban on Boulder County residents burning slash. Instead, the county needs to inform residents of safety guidelines — some of which have been updated since the Marshall Fire — and improve communication between fire departments. 

Boulder County regulations, for instance, still do not prohibit slash burns — and McKinney said he hopes that doesn’t change.

But since the Marshall Fire, residents are now required to notify the county and get a permit to burn slash, something they weren’t required to do before. 

Even before the Marshall Fire, however, the county open burn ordinance defined slash as only “woody material less than six inches in diameter consisting of limbs, branches, and stems that are free of dirt.” No “tree stumps, roots, or any other material” were allowed. Lumber — like fencing — or any forms of junk were not explicitly prohibited. But among fire personnel it is understood — or it should be, McKinney said — that these have no place in slash piles. Lumber and junk seem to fall under “other materials.”

Meanwhile, the county’s Guide to Open Burning for residents states clearly that lumber, trash and garbage (among other things) “cannot be burned” — “with or without a permit.” Treated wood releases toxic chemicals when burned. So does trash and garbage.

The slash pile that found new life to help spread disaster on Dec. 30, 2021, began on a property owned by the Twelve Tribes community and included “old fencing material” and “junk,” according to an 18-month investigation led by the Boulder County Sheriff’s Office and District Attorney’s Office. The investigators suggested the reawakened embers were an unfortunate accident. What about the fire that caused them? Was it illegal? Should it have been?

Ryan Day, the senior deputy district attorney, told Boulder Reporting Lab that the ordinance in place at the time not only “did not require permits or notification for ‘slash burns,’” it also “did not penalize ‘slash burns’ that included materials like junk or fence posts.” Because junk and fence posts were not explicitly prohibited.

The new open burn ordinance still doesn’t explicitly prohibit junk or lumber from being burned as “it would be very hard to use terms like those in a meaningful way,” according to Day.

Without explicit legal prohibitions, it’s important Boulder County residents — and firefighters — understand the rules of open burning. McKinney said education is the most important factor for this understanding.

‘Nothing other than natural vegetation’ – ‘certainly no trash, and certainly no junk or treated lumber’

On Dec 24, 2021, firefighters from Mountain View Fire District, a deputy from the Boulder County Sheriff’s Office and a Boulder Open Space and Mountain Parks Ranger visited 5325 Eldorado Springs Drive, the property owned by the Twelve Tribes community. 

According to the investigation, residents of the property had started the fire “to dispose of old fencing material, tree branches, discarded pallets and other junk.”

Residents of 5325 Eldorado Springs Drive told fire personnel they planned to let the fire burn down before covering it with dirt using a backhoe on the property. According to the investigation, since the Marshall Fire, Boulder County has updated its burn guidelines to instruct residents explicitly to use water to extinguish fires. But “this guidance was not available on December 24, 2021.”

On scene fire personnel were reassured by the promises made by the Eldorado Springs Drive residents, the report said — despite seeing “lumber and larger pieces of wood,” in the fire. The larger the piece of wood, the longer it takes to burn, and the longer it holds heat if buried.

Six days later, hurricane-force winds uncovered and breathed new life into the previously buried embers. Without being doused by water, embers can smolder underground for weeks or months. Having only rested for six days, these embers were still very much alive and soon threw sparks westward. Sparks thrown from the reawakened embers of the Twelve Tribes slash fire found welcome hosts in dry vegetation and a wooden shed, turning to flames before racing across open space towards Superior and Louisville to consume more than 1,100 structures.

McKinney said the investigation indicated that the firefighters who okayed the Tribes’ plan to extinguish their Dec. 24 fire were maybe not as discerning as they could have been. Maybe there wasn’t enough legally to cite the Twelve Tribes for their burning. But there were things in their fire that shouldn’t have been. The firefighters who visited the property should have known that, and maybe had the residents put the fire out, with water. 

“I don’t want to take away from [the firefighters’] knowledge or discretion,” McKinney said. “But I think there was probably a lack of understanding about the open burn permitting system and what is allowed and what isn’t. I’ve always understood the open burn policy to be fairly clear. Nothing other than natural vegetation should be [burned]. Certainly no trash, and certainly no junk or treated lumber.”

‘We’ve all got to work better to be on the same page’

McKinney said one challenge Boulder County faces is the large number of fire districts operating here. Twenty-three different districts have a claim to some area of the county, in addition to the U.S. Forest Service, the Bureau of Land Management and the National Park Service. With all these different entities, there’s “a lot of new faces” always working in the county — new faces who might not always be up to speed on guidelines in place.

“We’ve got to train the fire districts so they’re giving out good information,” McKinney said. “We’ve all got to work better to be on the same page.”

McKinney said he hopes no change comes to the burn program that also governs prescribed and agricultural burns — because fire is a cost-effective and useful tool for getting rid of vegetative waste when treated with respect.

“But with that there’s certainly a responsibility,” he said.

“There’s a lot of good that comes from the county’s burn program,” he added. “We still want to encourage people to burn, but we need to ensure they know how to do it safely.”

And one of the ways to burn slash safely is to ensure the fire is out when you’re done, with water. 

“I think it’s pretty common sense you want to go through and make sure all the heat is extinguished,” McKinney said. “I think in the guide to open burning, we’ve always had it as, ‘If you have water available, the best way to extinguish a fire is to add water and stir.”

The county ordinance dating back to 2014 — the only one Boulder Reporting Lab could find with a definition for “extinguished” — defines it as, “no visible flame, smoke, or emissions exist.” There’s no mention of water or checking for heat. And according to the District Attorney’s office, despite the open burn ordinance being updated, there’s still no Boulder County ordinance in place requiring the use of water to extinguish a slash pile burn. 

The firefighters who visited 5325 Eldorado Springs Drive were reassured by an above-ground pool on the property and its ample water supply, according to the investigation. It’s unfortunate the property’s residents didn’t use some of that water on the embers before burying them. But according to the county’s definition at the time, the fire was extinguished.

County is working on a new burn permitting process

McKinney said the county is working to release a new burn program permitting process to provide an extra level of protection against unsafe burns. One problem with the current permitting system, he said, is that residents apply for a burn permit, but they don’t have to say when they’re going to burn or when they’re done burning. 

And as it currently stands, while the sheriff’s office approves the burn from a public safety standpoint and the Colorado Department of Public Health approves it from a public health standpoint, there’s no mandate for the fire department to approve the burn as well. 

With the new plan “we’re trying to at least loop in the fire districts,” McKinney said. 

“If fire management and public health approves a permit, a notification will be sent to a fire department so they know they have a resident applying for a burn permit.”

The next step would be a public-facing website where the resident conducting a burn would be able to let all nearby fire managers — and their curious neighbors — know when they’re burning and when they’re done. Currently, there’s a site that shows where permits have been approved, but the goal is to imbue it with real-time information.

McKinney added that the system would encourage residents to work with their local fire department to ensure they understand all the rules and regulations for the safest burn possible.

“Because there’s so many different fire districts and everybody’s got their own set of rules.”

Tim Drugan is the climate and environment reporter for Boulder Reporting Lab, covering wildfires, water and other climate-related issues for Boulder with a focus on explanatory and solutions journalism. He also is the lead writer of BRL Today, our morning newsletter. Tim grew up in New Hampshire and graduated from UNH with a degree in English/Journalism. Email:

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