Why the L.A. Fires Are Exceptionally Hard to Fight

A fire needs three things to burn: heat, fuel, and oxygen. The first is important: At some point this week, for a reason we have yet to discover and may never will, a piece of flammable material in Los Angeles County got hot enough to ignite. The last is essential: The resulting fires, which have now burned nearly 29,000 acres, are fanned by exceptionally powerful and dry Santa Ana winds.

But in the critical days ahead, it is that central ingredient that will preoccupy fire managers, emergency responders, and the public, who are watching their homes — wood-framed containers full of memories, primary documents, material wealth, sentimental heirlooms — transformed into raw fuel. “Grass is one fuel model; timber is another fuel model; brushes are another — there are dozens of fuel models,” Bobbie Scopa, a veteran firefighter and author of the memoir Both Sides of the Fire Line, told me. “But when a fire goes from the wildland into the urban interface, you’re now burning houses.”

This jump from chaparral shrubland into neighborhoods has frustrated firefighters’ efforts to gain an upper hand over the L.A. County fires. In the remote wilderness, firefighters can cut fire lines with axes, pulaskis, and shovels to contain the blaze. (A fire’s “containment” describes how much firefighters have encircled; 25% containment means a quarter of the fire perimeter is prevented from moving forward by manmade or natural fire breaks.)

Once a fire moves into an urban community and starts spreading house to house, however, as has already happened in Santa Monica, Pasadena, and other suburbs of Los Angeles, those strategies go out the window. A fire break starves a fire by introducing a gap in its fuel; it can be a cleared strip of vegetation, a river, or even a freeway. But you can’t just hack a fire break through a neighborhood. “Now you’re having to use big fire engines and spray lots of water,” Scopa said, compared to the wildlands where “we do a lot of firefighting without water.”

Water has already proven to be a significant issue in Los Angeles, where many hydrants near Palisades, the biggest of the five fires, had already gone dry by 3:00 a.m. Wednesday. “We’re fighting a wildfire with urban water systems, and that is really challenging,” Los Angeles Department of Water and Power CEO Janisse Quiñones explained in a news conference later that same day.

LADWP said it had filled its 114 water storage tanks before the fires started, but the city’s water supply was never intended to stop a 17,000-acre fire. The hydrants are “meant to put out a two-house fire, a one-house fire, or something like that,” Faith Kearns, a water and wildfire researcher at Arizona State University, told me. Additionally, homeowners sometimes leave their sprinklers on in the hopes that it will help protect their house, or try to fight fires with their own hoses. At a certain point, the system — just like the city personnel — becomes overwhelmed by the sheer magnitude of the unfolding disaster.

Making matters worse is the wind, which restricted some of the aerial support firefighters typically employ. As gusts slowed on Thursday, retardant and water drops were able to resume, helping firefighters in their efforts. (The Eaton Fire, while still technically 0% contained because there are no established fire lines, has “significantly stopped” growing, The New York Times reports). Still, firefighters don’t typically “paint” neighborhoods; the drops, which don’t put out fires entirely so much as suppress them enough that firefighters can fight them at close range, are a liability. Kearns, however, told me that “the winds were so high, they weren’t able to do the water drops that they normally do and that are an enormous part of all fire operations,” and that “certainly compounded the problems of the fire hydrants running dry.”

Firefighters’ priority isn’t saving structures, though. “Firefighters save lives first before they have to deal with fire,” Alexander Maranghides, a fire protection engineer at the National Institute of Standards and Technology and the author of an ongoing case study of the 2018 Camp fire in Paradise, California, told me. That can be an enormous and time-consuming task in a dense area like suburban Los Angeles, and counterintuitively lead to more areas burning down. Speaking specifically from his conclusions about the Camp fire, which was similarly a wildland-urban interface, or WUI fire, Maranghides added, “It is very, very challenging because as things deteriorate — you’re talking about downed power lines, smoke obstructing visibility, and you end up with burn-overs,” when a fire moves so quickly that it overtakes people or fire crews. “And now you have to go and rescue those civilians who are caught in those burn-overs.” Sometimes, that requires firefighters to do triage — and let blocks burn to save lives.

Perhaps most ominously, the problems don’t end once the fire is out. When a house burns down, it is often the case that its water pipes burst. (This also adds to the water shortage woes during the event.) But when firefighters are simultaneously pumping water out of other parts of the system, air can be sucked down into those open water pipes. And not just any air. “We’re not talking about forest smoke, which is bad; we’re talking about WUI smoke, which is bad plus,” Maranghides said, again referring to his research in Paradise. “It’s not just wood burning; it’s wood, plastics, heavy metals, computers, cars, batteries, everything. You don’t want to be breathing it, and you don’t want it going into your water system.”

Water infrastructure can be damaged in other ways, as well. Because fires are burning “so much hotter now,” Kearns told me, contamination can occur due to melting PVC piping, which releases benzene, a carcinogen. Watersheds and reservoirs are also in danger of extended contamination, particularly once rains finally do come and wash soot, silt, debris, and potentially toxic flame retardant into nearby streams.

But that’s a problem for the future. In the meantime, Los Angeles — and lots of it — continues to burn.

“I don’t care how many resources you have; when the fires are burning like they do when we have Santa Anas, there’s so little you can do,” Scopa said. “All you can do is try to protect the people and get the people out, and try to keep your firefighters safe.”