Relatório do Acidente ocorrido no Incêndio Florestal de Yarnel Hill

One might view traveling through an escape route to a safety zone as making educated guesses
as to the route and anticipated travel speed while running to a specific point. The educated
guess is that the crew can reach the safety zone before the fire reaches them. There are many
variables involved in this equation but perhaps the most important one is speed. If the fire can
travel at a faster rate than the firefighters, they will lose the race. If they can travel faster than
the fire, they will win the race. In order for the educated guess to prove out, the firefighters
must predict three things with some degree of accuracy: how fast the fire will travel, which
direction the fire will travel, and how fast they will travel. It is possible to misestimate all these
factors and suffer no consequences, for example if the firefighters misestimate the fire’s
direction of travel but it moves away from their position. However, misestimating any of these
variables could cause serious trouble and firefighters misestimating them all may pay the
ultimate price.
Unfortunately, all three of these variables are difficult to estimate accurately. Estimating how
fast a fire will travel, along with its direction of travel, involves making an accurate fire behavior
prediction while also doing a number of other things. Even in hindsight, knowing what the fire
actually did and using the best available hardware and software, fire behavior analysts can still
only approximate how a fire behaved in a blowup situation. Firefighters in the field must use
available information and their own sensemaking to estimate both what the fire is likely to do,
and what it could do under a worst-case scenario. Estimates of how fast firefighters can travel
can also be problematic. A crew can only move as fast as its slowest member, and unexpected
barriers in the route of travel such as rocks, thick vegetation or cliffs, can significantly change
the amount of time required to cover a piece of ground.
This points to a key dilemma of wildland firefighting: firefighters on a fire are one educated
guess away from potential entrapment. Increased mobility increases the tolerable margin of
error; decreased mobility decreases it in terms of how fast a person can travel versus how fast
the fire can travel. Firefighters on foot are perhaps the most vulnerable, but many firefighters
have become entrapped in vehicles as well.
Wildland firefighters often discuss the need to have multiple safety zones; many firefighters also
identify multiple escape routes to the same safety zone, if they exist, although this can require
extensive scouting. In hindsight, we know that the Granite Mountain IHC might have arrived at
the Boulder Springs Ranch if they had stayed on the two-track road, although it is unclear
whether the crew knew that, or how long it might have taken to get there. This highlights
another problem posed by limited mobility: because the Granite Mountain IHC was on foot,
their ability to scout potential escape routes was limited.
Lookouts
Lookouts, Communications, Escape Routes, and Safety Zones (LCES) is an interconnected
system approach to fireline safety, so it is difficult to discuss safety zones and escape routes
without also addressing lookouts. The Granite Mountain IHC had a designated lookout for most
of the day, until the advancing fire threatened the lookout’s location and forced him to
Yarnell Hill Fire Serious Accident Investigation 53