Firefighters on the Decker Fire are using a combination of shovel crews and bulldozers to place direct and indirect lines to contain the fire in places.
Line positions are determined by hotshot crews and wildfire planners. Direct lines are right on the edge of the fire, and indirect lines are near the fire, usually between the fire and a value at risk in a place where crews think the fire can be stopped.
Operations Chief Mark Delmerico said he prefers direct lines a lot of the time, but snags and fire-weakened trees can be very dangerous for hotshot crews, and the Decker Fire has a lot of that sort of material, so going direct poses a hazard.
The operations team does deliberate risk assessments to figure out whether areas are worth going into to put direct lines, Delmerico said.
For example, there’s an area on the northwest corner of the fire that is too rugged and dangerous for crews to apply direct line to, and there is a lot of fuel between that part of the fire and the indirect line placed nearby. That would be a candidate for backburning, he said (more on this later).
Lines can be dug by hand or with heavy equipment such as a bulldozer. The method used depends on terrain and the fire’s behavior. Crews can’t take heavy equipment into wilderness areas, for instance.
Part of building fire lines involves removing “ladder fuel,” public information officer Jonathan Ashford said, which is brush and other possible fuels that can move the fire from the ground into the canopy of a forest, at which point it becomes a lot easier for the fire to move around and jump lines.
Crews remove brush and low-lying branches to make sure the fire stays near the ground in front of the line, which keeps the fire at a low enough intensity to avoid jumping the line.
How wide a fire line is depends on vegetation and fire behavior, Ashford said. He measured one indirect line northwest of the fire at about 25 feet across that had been cleared, plus the dirt road that functioned as the actual line.
The actual lines are where all vegetation has been removed down to “mineral soil,” so the fire can burn all the way up to that point and then stop. A hand line is about 2-3 feet across and a dozer line is as wide as the dozer.
Delmerico said where they put hand lines as opposed to dozer lines depends on topography, time and space. Steeper terrain is usually more suited to a hand line, he said. Fuels play a smaller role in the decision.
When possible, he said, they use a dozer line because it’s less risk to firefighters and faster to make.
For the Decker Fire, Delmerico said it’s really tough to put in hand lines because of the accumulation of fuels such as beetle kill spruce, so they try to use existing trails and roads.
Crews try to use natural features such as a ridgeline or riverbed, Ashford said. He said they try to find places that offer a high probability of success.
A lake or rock outcropping works too – anything that won’t burn, Delmerico said.
The first people through an area are the saws, then, for a hand line, the shovel crew, then a firefighter with a rake who makes sure the line is completely free of fuel.
Fire lines can be used to set lines when backburning. When that happens, one part of the crew uses drip torches and other incendiary devices to burn fuels between the line and the main body of the fire, while another part of the crew monitors the discarded material from making the line to make sure it doesn’t ignite. The material collected from building lines is discarded on the non-fire side of the lines to reduce fuels and fire intensity, Ashford said.
He said there is some possibility for backburning along the Rainbow Trail in the coming days, if weather conditions cooperate. Crews are waiting to see how the moisture predicted for today affects the fire conditions. Crews may not go out at all today if the weather is bad, Ashford said.
After the fire is contained, the last thing a crew will do is cover up a line and otherwise mitigate it so it fits in with the landscape as much as possible and doesn’t erode. Ashford said they don’t want an area that wasn’t supposed to be a trail to suddenly become a trail.
A lot of the decisions on where lines can go fall to the boots on the ground themselves, Delmerico said, because he’s not going to ask someone to do something they aren’t comfortable with.
Everybody has the right to refuse risk, he said.