He feared being stung by wasps and accidentally started California’s biggest fire

All he wanted to do was plug up a wasp nest because he’s allergic to bees and worried about being stung.

It was a hot day. The rancher in the Northern California hamlet of Potter Valley walked into a bed of waist-high cured grassland, driving a stake into the ground. That created a spark that grew into the largest wildfire in state history.

The blaze grew larger by the second and the man’s attempts to smother it with dirt were futile. Authorities this week released their findings on the cause of the Ranch fire, the largest of the two blazes in the massive Mendocino Complex that began last summer and was not contained until January. In all, 459,123 acres and more than 280 structures were burned. One firefighter was killed and three injured.

Investigators released a harrowing narrative of how the monster fire happened that experts say underscores how easy it is for fires to explode during hot, dry conditions in California.

“In the middle of summer, when we see rolling hills golden, which the gold is dry grass, it can look picturesque,� said Seth Brown, battalion chief for the California Department of Forestry and Fire Protection’s Fresno and Kings county division. “But what firefighters are thinking is, ‘That’s fuel.’�

While utility malfunctions have been the cause of some of California’s most destructive fires in recent years — including Paradise and wine country — officials say human causes like the rancher’s stake are by far the most common.

“What we’ve seen in the past is people wait too long to call because they think they can extinguish it themselves. And instead of being a 10-by-20-foot fire it’s an acre. Then fast forward ... and now it’s 5 acres,� Brown said. “We don’t expect the person who doesn’t have experience to fully understand the potential. But we’re always trying to educate.�

Cal Fire investigators did not name the Potter Valley rancher, and he is not expected to face any charges because the blaze was ruled an accident.

Officials said that once the fire started, he shuffled through the waist-high grass and grabbed his trampoline and a rug, then threw those onto the flames, hoping they’d do the trick.

Instead, the trampoline caught fire, and the flames spread to a 60-by-12-foot shade cloth on the ground and ignited the bed of grass it was on. The flames wrapped around his water tank and moved 25 feet downhill toward Highway 20.

He turned to a black polyurethane tube connected to the water tank, but the fire burned it until it kinked, cutting off the connection.

In desperation, he broke off a PVC line also connected to the water tank and tried to squeeze the flow toward the flames, but the PVC hole was too wide, his thumb too small and the fire was too far for the water to reach it.

So the rancher tried one last thing — he disconnected his trailer from his four-wheel-drive truck then drove to the front of the fire, which was now racing up hill toward his second water tank, and hit the gas so his tires would kick up dirt to knock down the flames.

But his tires lost traction and he lost control of the vehicle. The rancher bailed out before the truck rolled down into an embankment.

Out of options and his cellphone lost somewhere in the field, the rancher sprinted 200 yards back down to his home and called 911.

Over the following weeks, the fire vanquished every attempt to stop it. In its first 12 days, it jumped at least four creeks, a major road and a bulldozer-cut firebreak, all of which have traditionally served as defensive fronts in firefighting.

But feeding on tinder-dry vegetation and driven by winds that produced flames up to 300 feet high, the fire’s heat created paths all around it, pre-heating grass and shrubs so they could burn a moment later. It spread in all directions and reached into four counties before it was out. Repeated fires without enough years in between to recover can also replace native vegetation with invasive species, which are even worse in fire.

Many of the country’s biggest fires start off as grass fires. According to the National Interagency Fire Center based in Idaho, two of the three biggest “mega fires� in the last 20 years were grass fires — the East Amarillo Complex fire in Texas in 2006 that torched 907,245 acres of land and the Northwest Oklahoma Complex fire in 2017 that charred 779,292 acres.

Recent human-caused fires in California include the Carr fire, which killed eight people last year and was started by a trailer creating sparks on the highway, and the Wildomar fire, which burned almost 900 acres in the Cleveland National Forest in 2017, and was started by a dirt biker crashing into a tree.

Other common causes are lawnmower blades or metal weed whackers striking rocks, creating sparks, experts say.

Grass is the fastest burning fuel type in the state. Brown estimated that grass — which is even more plentiful this year after one of the wettest winters in a decade — can burn across 20 feet in a second amid light wind.

“California was just one of those places that was designed to burn,� said Thomas Welle, who manages the National Fire Protection Assn.’s field office in Denver, on the rim of the Great Plains.

Welle said that based on his experiences with grass fires, the rancher in Potter Valley didn’t have much of a chance to stop the Ranch fire before it was uncontrollable.

In 2002, Welle was part of a prescribed fire in Colorado. He used a drip torch to ignite a patch of grass, about the size of two 50-cent pieces side by side, then stomped it out. A moment later, the grass reignited.

“It took me about six times before I finally got that small patch of grass out where that resilient heat in the clump of grass wouldn’t reignite,� he said.