The 20-year history of fires in the Boulder, Colorado area

October 19, 2020   |   5 a.m. MDT 

Colorado fire history Boulder
The history of fires north and west of Boulder, from 2000 to October 18, 2020.

The map shows the history of fires north and west of Boulder, Colorado from 2000 through October 18, 2020. It includes two fires that are currently active, the Lefthand and Calwood Fires.

The fire on the map that is most notable for many Coloradans is likely the 6,200-acre Fourmile Canyon Fire on Labor day of 2010:

  • It burned 169 homes.
  • 12 of those were firefighters’ homes.
  • This was one of the first fires where it became known that private firefighters hired by an insurance company defended homes of policy holders that were valued at more than $1 million.
  • The state of Colorado did not apply for disaster assistance from the Federal Emergency Management Agency to provide help for the property owners that were affected by the fire. If a disaster declaration had been requested and then approved by the President, FEMA may have made assistance available for individuals including temporary housing, disaster losses not covered by insurance, related medical costs, replacement of vehicles and clothing, moving costs, and disaster unemployment insurance.

We covered the Fourmile Canyon Fire extensively.

Is a little pre-fire mitigation around structures better than none?

According to experience from Colorado’s Fourmile Canyon Fire, sometimes the answer is “No”.

When Dave Lasky was leading the effort in the Four Mile Fire Protection District not far from Boulder, Colorado conducting pre-fire mitigation near structures, he and others assumed that doing SOMETHING, cutting trees and building slash piles, would be better than doing nothing. They realized it would not be the total solution in the wildland-urban interface (WUI), but when the Fourmile Canyon Fire started on September 2, 2010 the Fire Protection District found out how wrong they were.

Fourmile fire_map_MODIS_0418_9-8-2010
Map of the Fourmile fire near Boulder, showing heat detected by the MODIS satellite at 4:18 a.m. Sept. 8, 2010. Map by Wildfire Today and NASA.

After the ashes cooled, Dr. Jack Cohen, a U.S. Forest Service fire researcher who has investigated the effects on structures at numerous WUI fires, found what he has seen many times before (more details here). Most of the damaged homes, 83 percent in this case, ignited from airborne fire embers or surface fire spreading to contact the structure; not from high intensity crown fire or direct flame impingement.

The fuel reduction along travel corridors may have helped residents to evacuate, but the unburned slash piles, Mr. Lasky said, could have been a problem:

 In several areas, our crew’s piles were associated with complete stand mortality. We created ladders into the canopy. At best, these unburned piles represented a sad waste of money, and at worst, it is possible that if we hadn’t treated them, these stands might not have carried fire.

Below are excerpts from an article written by Mr. Lasky about what he learned. It first appeared at the website for Fire Adapted Communities Learning Network.

“Doing something is not better than doing nothing.
When the mitigation crew approached residents in the past, they often said, “I didn’t move up here to see my neighbors. I don’t want to cut trees.” In an effort to build momentum, we often performed work that we knew was not reflective of the best science, cutting fewer trees than we should have. This practice was in regard to both defensible space as well as shaded fuel-break projects. The hope was that as communities adjusted to the cosmetic changes, we’d be able to reenter and accomplish more.

“I still hear many colleagues say “let’s just get something done.” I believe this is wrong. We need to do it right or not do it at all. Half measures are proven to fail and engaging in them has great reputational costs. In the current climate of high-profile, catastrophic fires, I am not interested in fear mongering. But I am interested in applying our limited resources to only those communities that are fully committed.

“It’s not just about cutting trees in the wildland-urban interface.
Fuels crews are run by firefighters. Perhaps they should be run by architects. In retrospect, we spent far too much money on fuels reduction and not enough on assisting residents with the installation of fire-resistant building materials and landscaping. Few of the homes lost were directly impacted by crown fire; rather, embers undoubtedly ignited the fine fuels around them, which eventually led to the loss of entire structures. In many instances, residents would have been better served by our crew putting a decorative stone perimeter around the structure. Many residents are capable of cleaning gutters, but less can move tons of gravel. We had chainsaws, and we knew how to use them. We should have picked up our shovels instead.”

Documentary about Colorado’s Fourmile Fire

A documentary that appeared on Colorado Public Television last year about the Fourmile Fire told the story of the fire through the eyes of local residents, including the filmmaker who lived in the area. The fire burned 6,200 acres and destroyed 168 homes west of Boulder, Colorado on Labor Day in 2010.

The film is excellent and well worth your time. The story of the first four days of the fire is told almost entirely through interviews with residents, some of whom decided not to evacuate in order to take personal responsibility for protecting their own house. Others found paths around roadblocks and went into the fire area to save their own and other houses. A quartet of men self-described as gay went from house to house putting out fire as it approached homes, keeping about a half dozen from burning. The film also has some very good footage of fire activity.

After it was over, I realized that the film did not show or interview a single professional or volunteer firefighter. I believe it had a photograph of one fire truck. It did have a small amount of audio of firefighters giving a sizeup on the radio during the early stages of the fire. Ms. Michelle Bauer Carpenter, who directed, produced and edited the film told Wildfire Today that she attempted to interview numerous firefighters but they all declined to participate.

We have embedded the documentary below.

Below is the description of the film from YouTube:


Published on YouTube Oct 16, 2012 by Michelle Carpenter

Above the Ashes is an award winning documentary that reveals untold heroes, the strength of mountain communities and the devastation caused by the catastrophic Fourmile fire.

Above the Ashes documents the Fourmile fire through the eyes of Sunshine residents who joined together to fight fire, taking action and saving numerous homes in the Sunshine community. Using haunting visuals Above the Ashes reveals tales of bravery, family, friends, loss and the rebuilding of a community.

A long time Boulder resident Michelle Bauer Carpenter and her family live in the historic mining town site of Sunshine located in the Fourmile fire burn area. “The losses our friends suffered are absolutely heartbreaking. Over half of the homes in our neighborhood were lost to the fire. As soon as we were allowed home I began documenting the devastation”.

Above the Ashes was directed, produced and edited by video artist Michelle Bauer Carpenter, presently assistant professor in Digital Design at the University of Colorado Denver College of Arts and Media.

Above the Ashes features original score by Brandon Vaccaro and closes with the musical piece Smoke and Tears composed by long time Sunshine resident and nationally acclaimed singer/songwriter Rebecca Folsom. The piece features a haunting 5.1 surround sound mix by sound editor and re-recording mixer David Bondelevitch, MPSE, CAS.

Above the Ashes was recently awarded two Heartland Chapter Emmy Awards in the categories of best topical documentary and best program editing. The Heartland Chapter is a chapter in the National Academy of Television Arts & Sciences (NATAS)

and the Emmy Award represents the best in the television industry. The entries were judged by seven chapters from across the county and included San Francisco/Northern California, Miami/Suncoast, Chicago, Michigan, Lone Star, Mid Atlantic, and the Rocky Mountain Southwest chapters.

For more information please visit

Documentary about Fourmile Canyon fire

I wish I had known about it earlier, but last night Colorado Public Television aired a documentary about the Fourmile Canyon fire that burned 6,200 acres and destroyed 168 homes west of Boulder, Colorado on Labor Day in 2010. The documentary tells the story of seven residents who refused to evacuate but fought the fire on their own.

Here is the trailer for the program.

Did anyone see it Tuesday night?

More information about the program.

Articles on Wildfire Today about the Fourmile Canyon fire.

Report released on Colorado’s Fourmile Canyon fire

A draft report has been released about the the Fourmile Canyon fire. The fire started on September 6 and burned 6,200 acres and 168 homes a few miles west of Boulder, Colorado. The fire was devastating to local fire districts within the burned perimeter in several ways, including the facts that a firefighter’s burn pile escaped and started the fire, the homes of 12 firefighters burned, and one fire station and an engine inside it burned. Wildfire Today covered the fire extensively.

Fourmile fire_map_MODIS_0418_9-8-2010
Map of the Fourmile fire near Boulder, showing heat detected by the MODIS satellite at 4:18 a.m. Sept. 8.

One of the interesting findings was that some fuel treatments done before the fire came through actually increased the intensity of the fire, compared with untreated areas. This was primarily due to the more open stands allowing wind to push the surface fires, and the treatment prescriptions’ emphasis on thinning to a target basal area (density of trees) rather than designing a prescription that accounted for fire behavior during dry and windy conditions. In addition, a significant amount of surface fuels remained, including slash piles in some areas that had not been burned after the treatments.

Another finding was that 83% of the homes that burned were ignited by surface fire, rather than a crown fire, which is typical.

The report includes some statistics on the use of aircraft on the fire. I broke out a calculator and did some analysis, arriving at these numbers:

  • $343,082, total cost of the retardant dropped by air tankers (just the retardant).
  • $1.97, cost per gallon of retardant (just the retardant).
  • 174,149, gallons of retardant dropped by air tankers.
  • 86, loads of retardant dropped by air tankers.
  • 47.09, total flight hours by air tankers.
  • 3,698, gallons of retardant dropped per flight hour by air tankers.
  • $3.55, total cost per gallon for the delivery of retardant by air tankers.
  • $619,483, Total cost of the air tankers, including retardant and flight costs.
  • 0.55 hour, the average time for each air tanker drop. (This is extremely low and is due to the fact that the air tankers were reloading at Rocky Mountain Metropolitan Airport near Boulder, Jeffco air tanker base, about 15 air miles from the fire. This helped keep the cost per gallon of delivered retardant lower than on your typical fire, which is normally much more than 15 miles away from the reload base.)

As a comparison, on September 9 there were three large Type 1 helicopters dropping water:

  • $99,284, Total cost for the three Type 1 helicopters on September 9.
  • 71,950, gallons of water dropped by the three helicopters.
  • 12.9, hours flown by the three helicopters.
  • 5,577, gallons of water dropped per flight hour by three Type 1 helicopters on September 9.
  • $1.38, cost per gallon of water delivered.
  • (?) the number of loads of water delivered was not specified.

A decision about using helicopters vs. air tankers should be based on more than just the above numbers. Retardant, sometimes known as “long-term retardant”, slows the spread of a fire more effectively and for a longer period of time than plain water. And helicopters cruise at a much slower speed than an air tanker, so depending on their location at the time of initial dispatch, it can take much longer to arrive at the fire.

Scroll down to see a map showing the location of every drop by a large air tanker on the fire.

Moving on to the rest of the report, here are some excerpts:


Fuel Treatments

  • Thinning trees to a specified density (residual basal area) or spacing was the prescription often negotiated with land owners. In addition, the treatments were often focused on improving the health of the forest (removing diseased and malformed trees, i.e., dwarf mistletoe) rather than modifying fire behavior.
  • Pervasive spotting observed during the Fourmile Canyon Fire easily breached the narrow fuel treatment units and rendered them of limited value to containment efforts.
  • The abundance of grasses, forbs, shrubs, and often branches and twigs that could have been removed through judicious surface treatments (e.g., prescribed fire) occurring within the areas where the fuels had been treated contributed to the high fire intensities and fire spread rate observed.
  • Post-fire satellite imagery clearly shows the absence of changes in stand condition inside treated areas compared to neighboring untreated stands. In some cases, treated stands appeared to burn more intensely than adjacent untreated stands, perhaps because of additional surface fuels present as a result of the thinning. One clear example of this comes from near Gold Hill where the piles of slash were scattered in the understory of a thinned stand but had not been burned.

Smoke from Fourmile fire provides bonanza for researchers, bad news for firefighters and the public

smoke in Moscow
A woman wears a mask in central Moscow to "protect" herself from smoke from fires outside the city. August, 2010. Photograph: Mikhail Voskresensky/Reuters

When the Fourmile Canyon fire was burning west of Boulder, Colorado in September, 2010, Jim Roberts, a chemist with NOAA’s Earth System Research Laboratory, was surrounded by something he had previously studied at the U.S. Forest Service’s Missoula Fire Science Laboratory in Montana — smoke, and lots of it. In Missoula he used a new instrument they had built, a custom mass spectrometer, to examine the levels of isocyanic acid in the atmosphere and in smoke. Isocyanic acid has been difficult to detect with conventional measurement techniques. At Missoula, he measured the levels of the chemical in smoke generated when the researchers burned vegetation in the lab and in cigarette smoke.

When the Fourmile Canyon fire started, Roberts had the mass spectrometer at the University of Colorado at Boulder’s Cooperative Institute for Research in Environmental Sciences.

Here is an excerpt from the Daily Camera:

Isocyanic acid easily dissolves in water, which makes it possible for the acid to also dissolve into moist tissues in the body, including the lungs. The full health effects of exposure to isocyanic acid in the air aren’t fully understood, but the chemical has been linked to cataracts, cardiovascular disease and rheumatoid arthritis.

Last September, the researchers had the opportunity to measure the presence of the acid in a real wildfire. On Labor Day, the Fourmile Fire began burning in the foothills west of Boulder, just a few miles upwind of the state-of-the-art atmospheric instruments housed at NOAA’s campus on Broadway.

“Boulder has a world-class atmospheric chemistry building and only once in its lifetime is it going to have a full-on hit from a wildfire,” said Joost de Gouw, a co-author of the study and a researcher at the Cooperative Institute for Research in the Environmental Science. “So just everyone in that building turned on their instruments.”

CIRES is a joint institute of the University of Colorado and NOAA.

The sensitive new spectrometer used in Missoula also picked up the isocyanic acid in the plume of smoke from the Fourmile Fire.

More information

Fourmile fire near Boulder
Smoke from the Fourmile fire as imaged by the MODIS satellite on September 6, 2010.