House to House
A groundbreaking NIST study takes a close look at the devastating Waldo Canyon Fire, and offers recommendations for wildland/urban interface preparedness
BY JESSE ROMAN
Late in the afternoon on June 26, 2012, the Waldo Canyon Fire crossed a mountain peak and descended a ridge to begin its assault on the Colorado Springs neighborhood of Mountain Shadows. By the time the fire front reached the community, firefighters had difficulty seeing the hoods of their vehicles through the thick smoke. For the next five-plus hours, the fire tore through the neighborhood, destroying 344 homes—more than a home a minute—and damaging about 100 more. The fire killed an elderly couple, and caused an estimated $454 million in insured losses.
“Think of the fire moving through the community as water rolling downhill—it finds the path of least resistance, in this case ignition vulnerabilities,” said Alexander Maranghides, a fire protection engineer at the National Institute of Standards and Technology (NIST). “In the aftermath, what we saw was the result of a combination of exposures, ignition vulnerabilities, and defensive actions.”
That Maranghides reflexively distills the fire into a series of cause and effect variables is to be expected. He and four NIST colleagues spent two years documenting exactly how that combination of factors shaped the fire’s path through Mountain Shadows, and recently released a 227-page case study of the fire. The study, “A Case Study of a Community Affected by the Waldo Fire—Event Timeline and Defensive Actions,” is likely the most comprehensive examination of a wildland/urban interface (WUI) fire ever, according to NIST, and one of the first based on quantitative analysis.
The NIST team spent almost a year in Mountain Shadows conducting about 250 interviews with witnesses and first responders. They cross-referenced those accounts with radio logs, time-stamped photographs, satellite images, and city records to meticulously piece together how the wildfire moved through time and space. In doing so, they tried to determine how factors such as topography, weather, building density, ignition vulnerabilities, and first responder actions affected the fire’s path.
Time and planning are critical
NIST’s WUI fire investigation project actually began in the aftermath of the 2007 Witch Fire, a blaze near San Diego that destroyed more than 1,000 residences. The scope of the fire proved to be “prohibitively large” to study with the rigor later spent on Waldo Canyon, Maranghides said, but the challenge led to innovation. Investigators on scene in San Diego developed new post-fire data collection methodologies and devised a way to quantify a structure’s wildfire exposure based on weather, topography, and other variables during the fire event. In the years that followed, NIST refined the WUI investigation methods pioneered in San Diego, and tested them with success while investigating a wildfire in Amarillo, Texas, in 2011.
Following the Waldo Canyon Fire, officials in Colorado asked if NIST would be interested in conducting a similar investigation there. NIST dispatched a team to Colorado Springs to determine if enough data existed to conduct a meaningful analysis; seven months later, NIST formally launched its study, according to Maranghides.
A NIST map of the study zone. Red areas indicate structures that were destroyed. Click to enlarge.
Key findings from NIST's Waldo Canyon case study
» Defensive actions were effective in suppressing burning structures and containing the Waldo Canyon Fire.
» Pre-fire planning is essential to enabling safe, effective, and rapid deployment of firefighting resources in wildland/urban interface (WUI) fires. Effective pre-fire planning requires a better understanding of exposure and vulnerabilities. This is necessary because of the very rapid development of WUI fires.
» Current concepts of defensible space do not account for hazards of burning primary structures, hazards presented by embers, and the hazards outside of the home ignition zone.
» During and/or shortly after an incident, with limited damage assessment resources available, the collection of structure damage data will enable the identification of structure ignition vulnerabilities.
The study revealed a lot about WUI first response. As with structural firefighting, time is of the essence in battling a WUI blaze, and firefighters’ defensive actions can make a big difference in the outcome of a fire incident, the study found. In the first hour of the Waldo Canyon Fire’s descent into Mountain Shadows, it was “relatively contained,” with 100 structure ignitions, the report said. But once the fire started rolling, it found additional fuel and quickly escalated, especially in neighborhoods with a high density of structures, in this case residential homes. Burning vegetation ignited structures, structures ignited other structures which in turn ignited more vegetation, and so on. “There were all of these different paths the fire took across the community,” Maranghides said.
In areas where the fire department could safely engage, its tactics were very effective. Structure by structure, the NIST study found that 75 percent of the fire department’s attempts to extinguish ignited structures were successful, and 79 percent of the time defensive actions kept the fire from spreading beyond the structure. It suggests, of course, that fire service response planning and coordination are crucial.
Citing these findings, the NIST study advocates for a national standard for WUI response times, similar to what exists for structural firefighting. It also calls for a national standard or guide for WUI pre-incident planning. While many states, communities, and fire departments do have extensive WUI incident preplans, others do not and may not know where to begin, which is where NFPA can help provide guidance, Maranghides said.
“Conceptually, I see us going to a national framework on how to preplan for a WUI event, a methodology,” he said. “Different communities will have to apply it to their local conditions, identify hazards, and figure out where resources need to be deployed.”
Maranghides also believes that a guide for WUI firefighting tactics would be useful for many departments. NFPA is in the early stages of developing NFPA 1700, Guide to Structural Firefighting, and Maranghides said a similar guide focused on WUI firefighting could be useful. “I see that aligning perfectly with NFPA and historically what NFPA has done with structural firefighting,” he said.
NFPA hasn’t received any new standard requests related to WUI fire preplanning or response, said Ken Willette, NFPA’s Division Manager of Public Fire. “If we did receive such a request it would be consistent with what we’ve done in other areas, but it’s incumbent on stakeholders to tell us that’s what they want,” Willette said.
If NFPA was to undertake a WUI standard or guide, it would be a complicated challenge, said Faith Berry, a wildfire management expert in NFPA’s Wildland Operations Division. Preplanning is crucial, she said, but so is flexibility. “In a wildfire, response depends a lot on what you are looking at when you size up a fire, just like sizing up a house fire,” she said. “You consider where homes are in relation to fire—are they mid-slope? Are they near a canyon? Weather is a big thing, and so are details like the dryness of the vegetation.”
‘A big opportunity’
Making WUI communities more resilient was also a primary aim of the study. In earthquake-prone California, building codes ensure that structures are built to withstand tremors. But in the fire-prone WUI, where more than 120 million Americans live, there are few commensurate codes to help homes withstand wildfire. NFPA documents designed to mitigate potential impacts of WUI fires include NFPA 1141, Fire Protection Infrastructure for Land Development in Wildland, Rural, and Suburban Areas, which offers guidance for assessing how land use changes might impact a community’s ability to respond effectively to a wildfire incident, and NFPA 1144, Reducing Structure Ignition Hazards From Wildland Fire, which provides methodology for assessing wildland fire ignition hazards around structures.
Greater structural resiliency in the WUI is the goal, but our current knowledge is insufficient to achieve it, Maranghides said. He hopes that efforts like the NIST study will lead to breakthroughs that can help builders design and site structures so they are much more resistant to wildfire. It’s a sizable challenge, because wildfire events are complex, with many more variables than other natural disasters. “On the other hand, wildfires are one of the few disasters where we can control the intensity,” he said. “We cannot change the intensity of a tornado, but with different construction materials and with a careful response we can alter a WUI fire. There is a big opportunity here—if we can develop test methods, we can figure out how to reliably harden structures.”
NIST has been working toward developing methods to quantitatively measure a host of wildfire vulnerability factors in both structures and the surrounding environment to produce exposure scores for structures. Landscape features such as topography and fuel loads in the environment; community factors such as the density of structures in a neighborhood; and parcel-specific factors like a home’s building materials, would all need to be considered in assessing exposure. A much better understanding of how wildfire moves through a landscape and how embers—which cause an estimated half of WUI ignitions—travel and promulgate are also needed, Maranghides said.
The NIST work will continue. While no specific projects are planned, Maranghides figures the next wildfire investigation is just around the corner. Despite the enormous effort, it’s worth it and necessary, he said. “It’s laborious and complicated and multi-disciplinary and slow, and there is no shortcut, but it has enabled us to begin to understand this very complex phenomenon,” he said of the Mountain Shadows work. “You have to go through that long process, because without that due diligence, it’s very easy to come up with wrong conclusions.”