BY TODD McNEAL
When considering all of the responsibilities laden on fire personnel in the wildland urban interface (WUI), the rapid sorting of structures into categories based on defensibility, also known as triage, is arguably one of the most challenging. The goal is to thoughtfully and systematically place each structure into the following categories:
- 1. Stand alone.
- 2. Defensible with improvement or physical presence.
- 3. Indefensible.
Triage is based on the concept of “the greatest good for the greatest number.” By adhering to that concept, firefighters make decisions that, unfortunately, under certain conditions, result in homes being destroyed. By default, this decision process induces stress and potentially initiates the downward spiral of self-doubt or second guessing one’s actions. The resultant stress of triage decisions is associated with a variety of issues that pull at firefighters’ emotions: our sense of duty, our desire to protect, and our unfaltering mission to reduce destruction in the communities where we work and live. In addition, fire agencies are supplying resources requested by incident management teams that are of a magnitude and complexity that historically have not occurred to the extent we see today. This is a direct result of the growing, undeniable fact that more communities are expanding into the wildland, especially fire-prone wildland. All of us know the emotional ties attached to a home: its significance, its history, the amount of irreplaceable possessions. Add to that the fact that we, as firefighters, have pledged to protect people and property. These facts, combined with time compression, make structure triage one of the most vexing duties in the business. To aid in this task, I offer a suggestion that has helped me keep the decision as objective as possible—Top-Down Triage.
Although it sounds simplistic, top-down triage ties together numerous concepts and provides a systematic analysis of the structure and the surrounding ignition zone to aid in the rapid sorting of structures. Triage must be completed without hesitation, as fire progression in the WUI does not often afford us the luxury of time. There is no doubt that the constantly increasing WUI and historic fuel loading are applying pressure on the fire service. We must train in, prepare for, and equip ourselves for this complex task. Much like the acronyms the fire and EMS communities use to help personnel remember their incident-specific priorities and information gathering, the method of top-down triage, hopefully, will speed the process and, more importantly, help ensure that all structures are analyzed on the basis of specific criteria and in a consistent manner in times of stress. All responding personnel should target the basic skills that will enable them to remain objective, rapidly prioritize, recognize threats to firefighters’ safety in the WUI, and make sound decisions. Prior to the approaching fire season, set a goal to increase your efficiency, capabilities, and safe triage decisions for the benefit of the whole. The process works and should be trusted.
|(1) The 2003 Old Fire rapidly advances toward homes in the WUI. (Photos by author.)|
You can gather clues and information about the three-dimensional fire environment by looking up at the sky. Many complex interactions are occurring in the atmosphere even on a “normal” day without the influence of fire in the area. Add a large column to the equation, and you now have a whole new set of interactions firefighters need to read, interpret, and react to. Start by reading the smoke, much as we are trained to do in the structural suppression side of the house; the same skills can be drawn on in the wildland. Observe the color, density, definition, direction, and amount of rise of the smoke column to help you determine the fuel type and atmospheric and wind conditions.
If there is no visible smoke in your area, look to the clouds. With the simple task of observing the weather, cloud shape, and cloud movement, you can begin to estimate the fire’s current potential. Remember the importance of things like upper-level winds and observations of atmospheric stability. Where is the smoke column going? How is it behaving? Where are the embers going to fall? It may seem that these observations are not directly tied to the structure triage process, but how can you safely commit to structure protection, even with defensible space and favorable construction, if the indicators of the fire’s potential obviously place you in the path of the proverbial “freight train”?
At this point, look at the amount of fuels present, not only directly above the structure of question but also the aerial fuels of the surrounding area. Fuel arrangement and continuity in the aerial fuels can be just as much of a problem as fuels on the surface. With the right combination of overhead fuels and a weather forecast that identifies potential fire movement, the house may not be in a safe location. Few homes can survive a direct hit by a sustained crown run, so be able to recognize the potential for that event.
The roof of a structure in the WUI is its first line of defense. Specifically, what are the roofing materials? Wood shake asphalt shingles, tiles, metal, and so on—all of these roofing materials have advantages and disadvantages when considering the impact of fire. As research and personal experience have shown the fire service during major interface incidents, it is not the direct flaming front that impacts and destroys the homes but the ember shower the fire produces. Embers transported to and deposited in distant locations remain undetected and then grow to consume structures.
|(2) The fuel accumulation and the construction materials of homes can make them more susceptible to fire’s approach.|
Although roofing material type is the most critical element to visualize, also take a moment to observe the shape of the roof. Note the number of valleys and steepness of the pitch. Try to determine the amount of dead and dry vegetation debris present and where it accumulates. As wind currents flow over and around structures, natural eddies form, and they are responsible for depositing materials in certain locations. Embers will also be deposited in these locations. How convenient that as embers arrive from their journey, in some cases from great distances, a receptive bed of dry fuels is there to welcome them.
The skylight is another roof feature that has to be identified: How many skylights are there, and where are they located? Depending on the skylight’s construction materials and the fire’s approach, you may potentially identify the weakest point in the roof assembly. If the plastic skylight fails because of radiant or convective heat loading, or direct impingement in some cases, the breach in the roof assembly will often result in a fatal blow to the structure.
Determine the significance of the contribution that gutters, or specifically the amount of vegetation material they harbor, will make to the potential threat to structures you are evaluating. I am not a proponent of emergency gutter cleaning to defend a structure, as I do not think this is a wise use of an engine company that has numerous structures to protect with little time. However, I have witnessed tile roof houses without mortar end caps succumb to fire. The primary reason for this loss is direct exposure of the sub-roof assembly to fire that originated as an ember landing in the gutter in a receptive fuel bed. Even though the fire will be relatively small, its direct access to the vulnerable dry and preheated sub-roof materials, combined with the natural chimney effect created by the tile channels to the venting ridge cap, spell probable disaster. Fire can quickly become seated in the prime location of a gutter and burn undetected until it involves most of the roof and attic. You will be surprised at how effective just a couple of short bursts of water, literally a few gallons above the gutters, will be in dampening the fuels present there and changing them from receptive to unreceptive.
The Eaves and Soffits
Like the gutters that provide access to the vulnerable portion of the sub-roof, the eaves are significant heat traps and a collection point for ember turbulence during a fire’s approach to a house. Once again, what pathway is usually present there? The attic vent! The open attic vent is no more protection against fire entering the house than a screen door is against a burglar. The attic, that perfect location of tinder dryness and concealment that fire loves to find and spread in, is directly entered through the vents located between rafters. As embers are blown in, it is nearly impossible to detect the presence of fire in the attic because of drift smoke until the fire is well established. Despite this challenge, engine companies can use technology present in the cab, like a thermal imaging camera, to aid in detecting heat both inside and outside of the attic. Much like the screens that are now required to be placed over the intakes of our fire apparatus to protect them from ingesting embers, the presence of enclosed soffits, or small-diameter screens over vents, can greatly improve the structure’s survivability.
This phase of analysis is similar to that used for the roof in that determining the construction materials is very important. Wall construction is also directly tied to the pathway immediately above in the eaves and soffits. Like the roof, the materials present have different strengths and weaknesses. The more likely it is that fire will walk up the siding, the lower the chances for the structure to survive alone. When personnel are observing this area, they must diligently note the amount, placement, construction materials, and privacy coverings of windows and doors within the various walls. Much as the presence of skylights is a weakness to the roof, the presence of windows and doors means weaknesses to the walls. Once these features fail, fire will enter the structure and quickly involve interior contents—again a fatal blow.
Another component of this phase of top-down triage is noting heat traps and vegetation debris deposits around the structure. These are the places where the embers will land, unite, and lay subtle siege to the home unattended. Decks and exposed crawl spaces are other construction features that fall into the problematic heat-trap category. These areas, much like the attic, can become perfect areas for trapping embers, which, with the fuel available, create hidden fires that usually are not discovered until they have grown into a deep-seated house fire.
I am not an advocate of entering structures. However, I believe it is warranted if you observe open windows and doors. Make a note in the unit log you use for daily operations of the time you entered, for what purpose, with whom, and the time you exited. Once you have entered for that purpose, take the time to mitigate the light flashy window coverings that could potentially ignite from radiant heat alone, or close the resistant shades.
Firefighters’ eyes generally first gravitate toward native and ornamental fuels directly adjacent to the structure during triage. This almost automatic response is logical in that these are the fuels that provide fire the best access to the structure and where we fight it. This is also the circle of ignition potential around the structure we observe to determine the classic idea of defensible space. Defensible space and, hopefully, its location around structures, are essential; it assists firefighters by increasing their safety while protecting them. In spite of the lure of seemingly perfect defensible space, fire suppression personnel must be disciplined enough to complete the analysis of all of the fuels surrounding the structure both in the immediate area and in the greater circle. Don’t forget the simple things like the locations of out buildings, fuel storage, fences, or landscaping features that provide flammable pathways to the house.
Some of the key considerations when looking at surface fuels are fuel arrangement, continuity, moisture content, size, class, volatility, age, native or ornamental, loading, density, and the all-too-familiar “yard accumulation.” The composition and volume of accumulation vary with geographic region and various other demographics, but the point remains the same: If this accumulation is present in significant quantities, protecting a structure becomes more challenging. Yard accumulation is a serious threat to structures because of its ability to grab fire brands, hide them, provide fuels of unique composition, and ultimately yield problematic fire behavior with possible impingement of the structure. This hazard comes in many shapes and sizes and, in some instances, can be mitigated with enough time and resources. However, emergency property cleanup with a time constraint when you have multiple other houses to triage is not a wise allocation of your efforts. You might have to decide to move on to the next threatened structure.
Placement in the Topography
Of all the areas to be considered during top-down triage, the structure’s location in the greater topography needs the most thoughtful analysis. Regardless of whether all the previous steps in the top-down triage have had unanimous positive outcomes, if the structure is in a location where the fire’s intense approach will decimate it, it is no place to stay. Recognizing the greater topography is possibly the most difficult area of consideration because firefighters may be unfamiliar with local factors—they may have traveled from out of the area, may be operating at night, have had little sleep, have been given limited briefing information, may be in rapid initial attack, or may even have political pressure being applied from agencies or the public. Despite all the mounting distractions, you must be responsible for your safety and that of your crew and remain part of the solution to the problem you have been called to resolve. Examine the surrounding topography. Determine if the topographic influences combined with other fire environmental factors like fuels and weather will come into alignment and target your structure protection assignment. There are numerous sources of topographic information, from briefing maps to aerial photos to the Internet, that are literally at your fingertips in our electronically connected culture. The time you spend pursuing this information could save your life.
(3) Topographic placement of structures, even with vegetation clearance, can make structure protection dangerous for firefighters.
The top-down triage technique in the WUI is an easy tool to aid in the trying assignment of protecting structures. Although there is no easy remedy to the very real problems facing the fire service with regard to the dangerous complexity of WUI operations, we can, as a fire community, identify tools that work. As our confidence in the use of these tools grows, we can make the smart, safe, and effective decisions that protect the greatest number of structures. As we all know, when responding to fires in the WUI, time is critical, distractions are numerous, and protection of life and property is the objective. Use whatever method works for you and your company, but find a system that allows for the rapid and systematic triage of structures and ultimately assists you in making the safest decision.
TODD McNEAL, a 19-year veteran of the fire service, has a diverse background in wildland and structural fire management and suppression. He is a captain with the Sonora (CA) Fire Department and has been serving as the wildland training officer as well as a division/group supervisor on a Federal Type II Incident Management Team for the past five years. McNeal’s career began with the National Park Service, for which he worked between California and Montana. He worked for a brief time for special districts and local land management agencies before returning to federal service as the fire cache manager for Glacier National Park, where he coordinated and delivered wildland and structural fire operations courses. He later worked as an engine captain with the Stanislaus National Forest (CA) and supervised an Interagency Fire Engine Module between Yosemite National Park and the Stanislaus. An active instructor for the past decade, he has numerous ICS qualifications in wildland operations, is a registered instructor with CA State Fire Training, and is a CA fire officer. He has a bachelor’s degree in natural resource management.
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