All three recent wildfires near Boulder are now believed to have been caused by people, not lightning or utility equipment, according to ongoing investigations by fire officials.
Since late February, the Bluebell Fire on Feb. 28, a vegetation fire near Enchanted Mesa on April 5 and the Goat Trail Fire on April 8 have all ignited near Boulder’s western edge. While the exact ignition sources have not been publicly identified, officials told Boulder Reporting Lab that natural and electrical causes have been ruled out.
“So you can surmise, most likely, the cause was human,” said Brian Oliver, Boulder Fire-Rescue’s wildland division chief. The exact details, however, remain unknown and may never be fully determined.
The assessment comes as Boulder faces extremely dry vegetation, limited winter moisture and delayed seasonal green-up, conditions that can allow small fires to spread faster than normal.
Wildfires are not unusual around Boulder in the spring. But three in roughly six weeks, combined with the dry conditions, have unsettled local fire officials, who say they may offer an early warning of what could lie ahead if weather patterns do not improve.
“This is kind of like three strikes. It’s a big warning sign,” Boulder City Councilmember Rob Kaplan told Boulder Reporting Lab.
Kaplan, a former captain with Boulder Rural Fire-Rescue, urged the city to move more aggressively on wildfire resilience after the recent blazes.
The Bluebell Fire, the most serious of the three, prompted evacuation warnings for the Chautauqua Cottages and visitors on nearby trails. Weeks later, the Goat Trail Fire led to warnings west of the 200 block of Hawthorne Avenue. Another small vegetation fire near Enchanted Mesa was quickly contained.
Kaplan said the city was fortunate. Hydrants were nearby. Winds were light. Embers did not leap into neighborhoods. Luck, he suggested, is not a strategy.
In a public post on April 8, Kaplan called for three immediate steps: clearer wildfire risk signage at trailheads, patrols on open space trails aimed at preventing human-caused ignitions and expanded buffer zones where open space meets homes and where fire can be far harder to contain. During the Marshall Fire, embers flew ahead of the fire, setting neighborhoods ablaze and rapidly spreading flames.
“This isn’t a critique of OSMP’s current plan,” Kaplan said, referring to the city’s Open Space and Mountain Parks department. “It’s just a recognition that the plan was built for 2016, not 2026, and we need to fund them and move at a much faster speed than a typical budget cycle.”
City officials responded last week that they are already moving on several of those requests.
New “Don’t Spark a Disaster” signs are being installed at popular trails. Fuel mitigation projects, including thinning, grazing and juniper removal, are underway along Boulder’s western perimeter. Patrols are operating through daily morning shifts, trail staff, volunteers and increased coordination with Boulder’s wildland firefighters on high-risk days.
Kaplan also pointed to the large number of junipers on the west edge of the city. Junipers are highly flammable, and planting new ones is now prohibited under the new landscaping code throughout the city.
Concern is also growing because Boulder and its trail system will soon host Sundance visitors, many of whom may be unfamiliar with fire-prone landscapes.
City council is expected to discuss wildfire resilience actions in greater detail on July 30, he said.
Boulder Fire-Rescue officials said the recent cluster of blazes is not necessarily unusual for this time of year. What stands out, they said, is how readily the fires have grown in the current conditions.
“I wouldn’t say we’ve had more fires than normal. We typically have a pretty decent spring fire season pre-green-up,” Oliver said, adding that the size of these fires is larger than typical for this time of year.
Ignitions can stem from anything from lightning to cigarette embers, dragging trailer chains or other sparks. But in a more typical spring, vegetation would hold enough moisture to keep fires smoldering or even extinguish themselves. That buffer is largely absent this spring. Oliver also said seasonal green-up has been delayed, leaving grasses and brush dead and dry later into the spring.
“We did have a rash of three or four [fires] there in a couple of weeks,” Oliver said. “I think that’s attributed not so much to carelessness but to the fact that our fuels are so dry.”
Boulder County officials have been warning of a potentially difficult fire season after limited winter relief. As of April 23, Boulder had received 30.1 inches of total snowfall, around 55 inches below average, according to BoulderCAST.
Read: ‘A really bad fire season’? Boulder County official warns conditions are already in place
Wildfire investigations can be painstaking, according to Oliver. Evidence is often lost to flames or firefighting efforts. Once an origin area is identified, investigators search it by hand.
“You kind of literally, inch by inch, grid out where you think the fire started and you comb through it on your hands and knees,” he said.
If evidence is found, investigators search for potential witnesses. The process is voluntary, and many leads do not go anywhere. “It just takes a really long time to work through all that process,” he added. The lack of clear findings can frustrate residents eager for answers and accountability.
On high-risk days, Boulder Fire-Rescue adds overtime staff to wildland engines “because we know we have to be aggressive in our initial attack,” Oliver said.
He has noticed some exhaustion. “There’s been a lot of extra work. People are tired,” he said. “But it’s what the community pays us to do to manage that risk and keep fires as small as possible. So we just keep trucking.”
For residents, officials said the most important step may be the most obvious: Follow all restrictions on smoking, open fires, campfires, fireworks and anything that could create sparks. The city’s restrictions are often stricter than the county’s. Recreationists should also know how to leave an area in case a fire breaks out.
“Be super diligent and safe. Try to avoid those activities that could create a spark and just recreate responsibly,” Oliver said.
