Derby Fire chars more than 200,000 acres in southern Montana

PHOTO COURTESY WALLY BENNETT’S TYPE 1 IMT The Derby Fire destroyed 26 homes and 20 outbuildings in an overnight fire siege on Aug. 30.

Big Sky Country was filled with smoke as wildfires ravaged Montana throughout September. One fire in particular, the Derby Fire, charred more than 200,000 acres and destroyed 26 homes in an area about 15 miles south of Big Timber. Burning in both the Gallatin and Custer national forests, the fire moved through rugged, inaccessible terrain, complicating containment efforts. At the height of the incident, resources included 10 Type 1 hotshot crews, nine Type 2 hand crews, 94 engines, 12 dozers, nine helicopters, four SEATs and four water tenders, for a total of 1,007 personnel. As of press time, the fire was 95 percent contained.

A Quick Start
Lightning ignited the Derby Fire on Aug. 22. The U.S. Forest Service (USFS) and local volunteer departments quickly responded to the area, sending in smokejumpers and a helicopter. Within two days, the fire charred 12,000 acres of dense timber and grassland. The substantial fire growth was primarily the result of high winds and low humidity from a passing cold front.

A Type II incident management team (IMT), led by Incident Commander Glen McNitt, took command of the fire on Aug. 24. As the fire pushed north, east and southeast, crews worked to reinforce lines built on the south flank, and dozers built line on the north and east flanks. The fire then began moving north into roadless, steep areas, making short runs in the grass areas and on slopes with active fire backing down into several drainages. By Aug. 29, approximately 400 personnel battled the blaze, which was now 40 percent contained. But that was all about to change.

Raging Back
On Aug. 30, the Derby Fire made a major run, burning an additional 60,000 acres and destroying 26 structures and 20 outbuildings. As the fire expanded to the north and northeast during the night, volunteer fire crews from Stillwater, Sweet Grass and surrounding counties joined with crews assigned to the fire to provide structure protection. The increased fire activity triggered the pull back of line crews and equipment to safer areas, and a Type I IMT was ordered.

Nancy Guerrero, a fire information officer with Wally Bennett’s IMT, which took over the following day, says the fire siege actually advanced on the incident command post, forcing personnel to temporarily evacuate.

Guerrero notes that the increased fire activity was caused by a cold front that moved through the area, bringing with it erratic 80-mph winds. “Unfortunately, it was during this time that we lost the 26 homes,” she says. Twenty-three of those homes were in Stillwater County and three were in Sweet Grass County.

Guerrero explains that a fire siege like this was possible because of the low moisture content in area fuels. “Dried timber normally has a 17 percent moisture content,” she says. “Fuels on the ground of this fire had between 5 and 12 percent moisture content.” Further, she says, Montana is especially vulnerable: “They’ve been in a drought for eight years now. The rest of the West has been in a drought for five years. The additional three years makes a huge difference.”

Guerrero adds that the fire was so big, there were two fire camps, each housing more than 200 people. The fire quickly became the No. 1 firefighting priority in the country,  burning approximately 160,000 acres in less than two weeks.

PHOTO COURTESY BRANDON SHEEHAN/USFS Crews conduct a burnout along a dozer line in the Gallatin National Forest on Sept. 6.

Moving West
With the fire now only 20 percent contained, winds pushed it west, prompting fire officials to move a significant number of resources to the west side of the fire. According to an IMT incident report from Sept. 3, spotting up to 100 yards, torching and short-running ground fires in ungrazed terrain carried the fire over some ridges.

Additionally, the stronger winds forced the fire into even higher elevations, making access difficult for firefighters. “The terrain was treacherous,” Guerrero says. “It was very difficult to get our crews in there.” As such, fire officials relied on aircraft to help slow the fire’s progress. On Sept. 3 alone, helicopters dropped 220,000 gallons of water and airtankers dropped 23,000 gallons of retardant.

Guerrero says aerial resources played an active role, cooling the fire’s perimeter as crews built line; however, on Sept. 5, heavy smoke grounded aircraft, creating a temporary setback for firefighting efforts. Air attacks resumed the following day, and crews were finally making progress again. Containment was soon back up to 45 percent.

Over the next week and a half, crews on the western flank battled the fire on the ground and from the air, while crews on the north, east and south side continued mop up and patrol, ensuring the fire didn’t escape containment lines. Dozer line was reinforced, and skidders and feller-bunchers were used to complete contingency line along the still-active southwest flank.

Finally, on Sept. 15, rain soaked the area, providing much-need relief from the dry heat. The same day, Chuck Stanich’s Type I IMT took command of the Derby Fire, which was now 80 percent contained, as well as the 30,000-acre Jungle Fire, burning just a few miles away.

Waiting for Snow
Over the next couple of weeks, crews completed handlines, performed mop up, removed hose and equipment and performed rehabilitation. On Sept. 22, Tim Reid’s Type II IMT took command of both fires.

Gary Hoshide, a fire information officer for Reid’s team, says more than 200 people continued to work on both fires in late September. He adds that the fires likely won’t be 100 percent contained until snow falls in November. 

The Derby Fire ultimately burned 208,000 acres over 323 square miles, destroyed 26 homes and 20 outbuildings and cost approximately $15 million to fight. But it could have been worse. “The day the fire blew up, the winds were so erratic, the fire could have done anything,” Guerrero says. “We were so fortunate that we didn’t lose any lives.”

Janelle Foskett is an associate editor of Wildland Firefighter magazine.