The Cub Creek 2 Fire investigation showed extreme heat in the origin area.
Rigorous process defines each investigation
After a fire, everything is charred black or deep in ash, with burned remnants of grass and other vegetation. But investigators find vital clues amid all that destruction — minuscule bits of metal, fuel canisters and marks left on rocks or pavement.
Marc Titus and Bruce Long, senior wildland fire investigators for the Washington Department of Natural Resources (DNR), have been investigating fires for decades. Determining what actually caused a fire is a complex, painstaking process that involves a detailed inspection of the ground.
Specialized techniques help uncover evidence and narrow down a set of hypotheses to isolate a cause. Investigators look for the angle of char — the scorch pattern created as a fire burns across the ground and on standing fuels. They study the overall area, use aerial photographs, and interview eyewitnesses and others with relevant information.
After identifying the first fuels to ignite and an ignition source, investigators create a sequence of events that would propagate a fire to identify a small origin area, generally 10 by 10 feet or smaller, Titus said.
It’s part of a seven-step scientific method set out in the National Fire Protection Association principles, which go from gathering data and evidence through testing hypotheses. Investigators consider nine categories of fire causes, including lightning, debris burning, children and equipment use, each with its own detailed checklist.
Investigators documented items from the Cub Creek 2 Fire.
DNR investigates all human-caused wildfires within its jurisdiction. By law, DNR must recover suppression costs on the state or private land it protects if the fires were determined to have been caused by negligence or criminal intent. Completed investigation reports are available to the public upon request.
Specialized training
Some fire investigators have a law enforcement background, but most are wildland firefighters with specialized training. Fire investigators get down on their hands and knees to narrow down the ignition point. Tools of the trade include magnifying glasses, magnets and metal detectors.
They conduct interviews with eye-witnesses and others in the fire area. They also get clues from technology, including cell phones, home-surveillance cameras, and government cameras on roads.
While all of the large fires currently burning in and around Okanogan County were started by lightning, the vast majority of fires — about 85% — are human-caused, according to DNR.
Fires have just two natural causes — lightning and volcanos. If those circumstances aren’t present, investigators go step by step, testing hypotheses to rule out categories until there’s only one hypothesis they can’t disprove, Titus said.
Sometimes, investigators are unable to rule out all possible causes and a fire is deemed “undetermined.” In some cases, they can narrow down the potential causes to just a few, Titus said.
Unfortunately, “It’s not that difficult to get an ignition in wildland fuels,” Titus said.The ignition point for grasses and fine fuels is just 400 degrees — easily reached by barbecues, sparks and car mufflers.
Fires started by vehicles are quite common. Dragging tow chains, driving on wheel rims with a flat tire, and worn brakes can all throw sparks. A catalytic converter can heat up to 2,000 degrees. If you’ve been driving and park your car on dry grass, there’s a high probability of ignition.
Lawn mower blades can hit a rock and spark, and even a string trimmer can propel a rock so it bounces off another rock, causing a spark and starting a fire. “Ask me how I know,” Titus said.
While cigarettes pose a fire risk, it actually requires fairly specific conditions, including fine, dry fuels, temperatures above 80 degrees, and humidity below 20%, to ignite a fire with a cigarette — particularly if tossed from a car window. Still, people need to dispose of cigarettes and vape pens properly because they can and do start blazes, Long said.
Methow Valley investigations
DNR has investigated numerous large and small fires in the Methow Valley in recent years. Some fires were controlled before they caused significant damage, while others burned houses or tens of thousands of acres.
The Frazer Crossing Fire progressed from a power pole.
A fire on Rendezvous Road in 2019 was determined to have been caused when a property owner burned debris in a metal garbage can in a dry flower bed. The investigator quickly ruled out railroads, equipment use, incendiary devices and a campfire and asked the property owner if anyone had been smoking and if there’d been children in the area. That eliminated all categories but lightning and debris burning, he wrote.
In the investigation report, the investigator described how he moved laterally across the advancing fire vector and then in a serpentine pattern to identify fire indicators, which he flagged. Following the flags led him to the flower bed.
An investigation into the 2014 Rising Eagle Road Fire concluded that the fire had started when a wheel on a utility trailer stopped rotating and dragged on the pavement, sending superheated metal flakes onto the side of the road, where they ignited extremely dry vegetation. The fire burned 579 acres and destroyed 24 structures, including 10 houses.
The investigator, who arrived about four hours after the fire began, located a single tiny shard of metal near each of the ignition points. He determined the shards had come from the ground-down wheel. He also found abrasion marks on the highway that he determined had been caused by the grinding of the wheel.
The 2021 Cub Creek 2 Fire, which burned more than 70,000 acres, was caused when a property owner used a propane torch to repair an irrigation pipe during hot, dry and windy conditions, DNR investigators concluded.
The investigator arrived at the Cub Creek 2 Fire a little more than an hour after the blaze started. He interviewed the individual determined to have caused the fire and obtained a brief, voluntary written statement.
To preserve evidence, a DNR technician flagged off a large area believed to contain the origin point, and firefighters combating the blaze were not allowed into that area.
Not all investigations are conclusive. Investigators on the 2024 Frazer Crossing Fire found clear fire-pattern indicators showing the fire had progressed from a power pole in one direction, but progression was less clear in other directions. In the end, the investigator couldn’t reach a definitive conclusion. “I could find no evidence based on the recent weather or equipment in place that the power pole could have caused the fire. All equipment appeared to be in working order,” he said.
Use common sense
Determining a cause can help Washington recover firefighting costs for taxpayers. It can also serve as the basis for fire-prevention education. There’s a national campaign warning people about the dangers of dragging vehicle chains, Titus said.
The state doesn’t always pursue restitution, but property owners who sustained damage can seek restitution through their insurance companies; sometimes insurers pursue it themselves.
The vast majority of fires are caused by people. Even when it was an accident — that is, it wasn’t arson — there could be negligence involved, Long said. Many people cause fires but don’t realize that conditions of terrain and fuels made their activity dangerous, he said.
This year, as of Aug. 12, there have been 1,222 fires on DNR-protected land, which burned almost 800,000 acres. The most common cause was debris burning — 168 of all fires. Equipment and vehicles caused 70 fires; fireworks, 48; and celebrations, 62. There have been 84 natural fires (lightning); and 157 are still undetermined.
Even activities intended to reduce fire risk can ignite fires if they’re done in the wrong conditions. Mowing the lawn on a hot, dry afternoon when the wind is blowing is dangerous — if the mower hits a rock, it’s easy to trigger a spark.
If you’re going to mow the lawn, you need to do it really early in the morning, when it’s still cool and damp — in the 50s or 60s, with at least 40% humidity, Bruce said.
Investigating fires turns up many examples of careless behavior. “There are a lot of stupid people out there, who decide, ‘I’m going to use this propane-powered weed torch and burn the weeds that are annoying me,’” Long said. People need to do fire-prevention work in the fall, winter and spring — not during fire season, he said.
Long and Titus have seen people do target shooting on a hot, windy afternoon, aiming into concrete cinderblocks, a rocky hillside, or a rusty cast-iron pan nailed to a tree — all at high risk of ignition.
Fireworks should be an obvious no-no, but this July, people setting off fireworks started a fire in Yakima. To Long, that one and a half seconds of fun turned into a fire that cost $1.5 million to put out.
They stress the importance of personal responsibility and common sense. Knowing the burn ban is going into effect tomorrow doesn’t mean that’s the time to ignite the big pile of brush you’ve accumulated all year, they said.
Even having a burn permit doesn’t mean it’s safe. Long recalled a situation where people had planned Firewise projects — cutting trees, clearing brush, and burning the piles — but conditions were too hazardous and their efforts at prevention ended up incinerating 700 acres, he said.
They thought it was OK because they had a permit. Still, you have to use your head, Long said. “It was the middle of July. It was hot, dry and windy. Terrible time to burn,” he said.
People from other areas don’t always have the same awareness about fire as those in eastern Washington. Long recalled a group of campers from western Washington who’d done their research and gotten the approved type of liquid-fuel camp stove. But they set it on a dry fuel bed, starting a 30,000-acre fire. “They followed all the rules, but not common sense,” he said.
Over and over again, Titus and Long have seen situations where people burning a pile of vegetation thought their fire was out and walked away. “Well, that doesn’t take you off the hook. You can still be held negligent, because you didn’t use your common sense,” he said.
Fire prevention tips
• Clear brush, pine needles and anything flammable from your home, gutters and other structures to create a green space of about 30 feet.
• Screen vents and eaves so embers can’t pass through them.
• Use lawn mowers and similar equipment early in the morning, when it’s still cool and relative humidity is higher.
• Make sure you complete FireWise activities before fire season.
Lithium battery safety
• Lithium-ion batteries, which power everything from phones to lawn mowers to cars, store a lot of energy in a small space and can be a fire risk.
• Make sure you use only the battery, charger and cord made for the device.
• Plug it into a wall outlet, not a power strip or extension cord, and place the items on a hard, stable surface — not a bed or couch.
• Disconnect right away once it’s fully charged.
• Take batteries to a recycling center for disposal.
• Store the batteries at room temperature.
