Early Friday morning, about 20 hours after the Marshall Fire ignited, a drone operated by Twitter user WxChasing/Brandon Clement flew over subdivisions that were devastated by the December 30 fire. It found block after block of ash piles, some still smoldering. In many scenes there was scarcely a structure still standing. (Scroll down to see the video.)
All of the reasons why some houses did not burn even though dozens around them were consumed could not be determined from the video, but there was one common feature — the survivors were more distant from the neighboring homes. Many houses in the subdivisions were only 10 to 20 feet apart based on archived imagery in Google Earth.
The fire was driven by very strong winds gusting at 60 to 100 mph, extremely dry conditions after months of drought, and relative humidity in the mid-20s. These are the very worst fire conditions. The weather paired with the nearly back to back structures led to the fire spreading through a continuous human-made fuel bed. When one house burned the convective and radiant heat easily ignited its neighbor, which ignited its neighbor, etc.
The fire in the vegetation and structures lofted burning materials far downwind, creating distant spot fires in the home ignition zone on bone dry lawns, mulch beds around ornamental plants, and on structures. It is unknown at this point how many had been designed and built to be fire resistant, such as the characteristics of the roof, vents, siding, doors, windows, foundation, fences, eaves, and decks. A FEMA publication (13 MB) has excellent detailed recommendations. Headwaters Economics found that the cost of building a fire-resistant home is about the same as a standard home. Local building codes could regulate these features. But if the lot size is so small that residences are only 10 to 20 feet apart, if one becomes fully involved, the neighbors also burn, especially during windy conditions.
So far we have listed some factors that affect the vulnerably of structures during a wildland-urban interface fire: home spacing and lot size, the envelope of the structure itself, fire codes, and the home ignition zone. Others are:
Safety zones where residents can shelter in place;
Road and driveway width, wide enough for large fire trucks;
Turnarounds at the end of roads;
Signage, and;
Emergency water supply.
The video below of the Marshall Fire devastation was shot by WxChasing/Brandon Clement at first light on December 31, 2021, the day after the fire started. Not long after, snow began falling. The National Weather Service in nearby Boulder recorded an accumulation of eight inches.
Jurisdictions need to develop standards for structures, the home ignition zone, and community infrastructure
A neighborhood on Debbie Lane in Paradise, California, before and after the Camp Fire that started November 8, 2018. The homes were 14 to 18 feet apart.
In the weeks after 86 people were killed and over 14,000 homes and businesses were destroyed in the Camp Fire at Paradise, California three influential individuals and organizations urged the consideration of banning or restricting development in areas that are at high risk from wildfires.
First there was the Los Angeles Times Editorial Board on November 24 writing that “To rebuild Paradise as it was, would be land-use malpractice.” The Board continued, “The question facing state and local authorities is whether Paradise — and other towns that have burned — can be rebuilt to withstand the next, inevitable wildfire. If not, how does California relocate communities and restrict new construction while respecting property rights and not worsening the state’s affordable housing crisis? At a minimum, cities should remap fire-prone areas and focus reconstruction in areas with lower risk. “
Then on December 10 the group 1000 Friends of Oregon released “A New Vision for Wildfire Planning” that recommended avoiding development in high risk areas.
Chief Ken Pimlott, March 22, 2016. Photo by Bill Gabbert.
Five days before he retired on December 15 Ken Pimlott, Director of the California Department of Forestry and Fire Protection, was quoted by the Associated Press as saying officials should consider banning home construction in areas vulnerable to wildfires.
Cities, counties, and planning boards (where they exist) are often under pressure to approve new housing developments. They want to expand their tax base. Developers try to fit as many homes into a new subdivision as possible to maximize their investment. This too often results in homes that are 20-feet apart. If one is ignited by a burning ember that may have traveled a quarter of a mile from a fire (or a burning home) the radiant heat alone can ignite the homes on both sides. Then you can have a self-powered conflagration spreading house to house through a city. As long as the structures are that close together, the homeowners have not reduced the fuel in the Home Ignition Zone within 100 feet of the structure, and the home itself is not built to FireWise standards, a massive disaster can be the result.
The NFPA and the FireWise program recommend reducing flammable material within 100 feet of structures, and spacing trees at least 18 feet apart that are within 30 feet of the home. At the 60 to 100-foot distance tree canopies should be at least 6 feet apart. Another house that is 15 to 50 feet away is also fuel and if it ignites will be a serious threat.
If a homeowner wants, or is required, to reduce the flammable material within 100 feet of their residence, what are they expected to do if there is another home 20 feet away that is really a large assembly of flammable material?
Some of the homes in Paradise, California that burned were less than 20 feet apart. According to measurements using Google Earth, the structures in the photo at the top of this article were 14 to 18 feet from each other.
Photo: Anchor Point Group, Boulder, CO
The National Institute of Standards and Technology released a report on the Waldo Canyon Fire that burned 344 homes and killed two people in Colorado Springs, Colorado in June, 2012. They concluded that current concepts of defensible space did not account for hazards of burning primary structures, hazards presented by embers, and the hazards outside of the home ignition zone. In addition, NIST recommended:
High-density structure-to-structure spacing in a community should be identified and considered in [Wildland Urban Interface] fire response plans. In the Waldo Canyon fire, the majority of homes destroyed were ignited by fire and embers coming from other nearby residences already on fire. Based on this observation, the researchers concluded that structure spatial arrangements in a community must be a major consideration when planning for WUI fires.
After studying the Carr Fire that destroyed 1,079 residences at Redding, California earlier this year, retired CAL FIRE Battalion Chief Royal Burnett reached similar conclusions.
It was easy to figure out why the houses on the rim burned — they were looking right down the barrel of a blowtorch. Even though they had fire resistant construction, many had loaded their patios with flammable lawn furniture, tiki bars and flammable ornamental plants. Palm trees became flaming pillars, shredded bark became the fuse, junipers became napalm bombs. Under current standards houses are build 6 to an acre; 10 feet to the property line and only 20 feet between houses. Once one house ignited, radiant heat could easily torch the next one.
We have to learn to live with fire
Reducing the chances that a fire in a populated area will turn into a disaster that burns thousands of homes involves at least three categories of factors, in addition to weather:
Envelope of the structure itself: characteristics of the roof, vents, siding, doors, windows, foundation, fences, eaves, and decks. A FEMA publication (13 MB) has excellent detailed recommendations. Headwaters Economics found that the cost of building a fire-resistant home is about the same as a standard home.
Home Ignition Zone, as described above — topography and fuel within 100 feet.
Community infrastructure and planning: distance to nearby structures, evacuation capability, safety zones, road and driveway width, turnarounds at the end of roads, signage, and emergency water supply. Again, the FEMA document has great recommendations.
Someone asked me recently what needs to be done to keep from repeating disasters like we have seen within the last year at Paradise, Redding, and the Napa Valley. I told him that there is no one thing that needs to be done, such as raking or “forest management”, it requires a comprehensive holistic approach.
The items we have listed here only apply within communities. There is of course much that can be done surrounding the places where people live that would reduce the vegetation or fuel and decrease the intensity and ember generation potential of a fire as it approaches an urban area. Large scale fuel management including fuel breaks and prescribed fire programs are usually conducted by state and federal agencies.
The weakest link in the chain principle applies here. If one of these categories is sub-par, the individual structures and the entire community in a fire-prone environment is at risk. And if a homeowner does not do their part, it can endanger their neighbors.
The warming climate is demonstrating that wildfires are becoming increasingly perilous. It is unlikely that local governments or states are going to ban development in fire-prone environments, but it is their responsibility to protect their citizens by enacting sensible standards.
El Paso County, Colorado is home to the state’s most destructive fires. In 2012, the Waldo Canyon Fire burned more than 18,000 acres, destroyed 347 homes in Colorado Springs and killed two people. Almost exactly a year later, the Black Forest Fire ignited east of the city and burned more than 15,000 acres, 486 homes and killed two people.
Ryan Maye Handy wrote an article in the Colorado Springs Gazette that looks at some of the proposals being considered, and in some cases rejected, that could enhance the area’s ability to live with the inevitable fires still to come. Below is an excerpt.
…While El Paso County has taken some steps to address wildfire risk, land use experts say officials could do much more.
Unlike the city of Colorado Springs, which heavily regulates building in wildfire zones, the county has no universal fire code standard. Instead, it has a patchwork of fire codes and land use regulations that vary between more than 26 fire districts. New subdivisions in wildfire zones must meet special wildfire criteria, but individual homes do not have to be built with fire resistant material or have mitigated properties. County master plans for development, while offering guidelines, are years and in some cases decades out of date and make no mention of wildfire.
Ultimately, economic and logistical concerns have kept the El Paso County commissioners from issuing broad regulations for building in wildfire zones, and the result is that many homeowners and areas remain vulnerable to fire.
[…]
While refraining from adopting county-wide fire codes might spare El Paso County residents economic hardship, the decision doesn’t take into account the economic consequences of managing a wildfire, experts say. Wildfires cost money to fight, typically taxpayer money, and the U.S. Forest Service spends a third of its budget defending homes in wildfire zones….
