Plumes

of smoke rise from the top of Fortification

Mountain near White Pine Ski Area around

11 a.m. on June 12. Slowly, the fire expands

and moves down the slope. Flames lick slash

piles of dead timber and fir trees explode like

match sticks.

This was not an out-of-control wildfire,

but a carefully planned prescribed burn.

Bridger-Teton National Forest public information

officer and burn boss Paul Swenson

said that prescribed burns take years to plan

and are cooperative efforts between different

agencies.

On Wednesday, 30 firefighters from the

national forest, Sublette County Unified

Fire, Grand Teton National Park and the

High Desert BLM District worked their way

down the ridge. The firefighters were split

into an “ignition” group and a “holding”

group, Swenson said.

Swenson was in charge of the ignition

crews who worked to set slash piles and

selected trees on fire. Firefighters used drip

torches and sometimes tossed incendiary devices

they called “hand grenades” into difficult

to reach or unsafe areas.

The holding team makes sure the flames

stay within the perimeter of the prescribed

burn.

On Wednesday, the holding team remained

in constant radio contact with the

ignition team to coordinate the movement of

the fire.

Two fire engines and a helicopter in Kelly

Park and a BLM brush rig at the top of the

ridge stood ready “for immediate containment

of hot spots and slop” that might escape

the fire lines, Swenson said. The helicopter

was also on call to evacuate injured personnel

out of the fire zone.

Thankfully, no one had to be evacuated

on Wednesday. The ignition went as planned

and the fire slowly snaked down the mountain

“controlled by humans, not nature,” said

Swenson. Weather reports came in every

hour to keep the teams up to speed on any

changing conditions.

The prescribed burn was a partnership between

BTNF the Wyoming Game and Fish.

The 190-acre site was carefully preselected

because it contained potentially dangerous

fuels that needed to be cleared, Swenson

said.

“The ultimate objective of a prescribed

burn is to reduce fuel loading in an area,” Swenson

said. “This will allow for a better response

from firefighters (if a wildfire breaks

out) so they are not out there in a jungle of

dead trees and other flammable material.”

Ignition crews target slash piles of deadfall

and certain trees that are more flammable

than others. For example, thick pockets of

what Swenson called “sub alpine firs” that

had invaded the aspen groves along the ridge

were lit up. These firs are “extremely vulnerable

to fire,” Swenson said. Douglas firs, on

the other hand, with 2-inch thick bark that

have withstood wildfires for hundreds of

years, were left untouched by crews.

Prescribed burns create healthier forests,

Swenson said. In addition to removing deadfall

and some of the firs, older aspen trees

were burned to make more room for saplings

to grow, Swenson said. The healthy aspens

and Douglas Firs left behind after the prescribed

burn will generate better forage for

wildlife, he added.

Late spring is the optimal time for prescribed

burns, Swenson said, although prescribed

burns also take place in the fall.

Prescribed fires in the fall require more

“holding resources” to contain the flames,

however, as fuel tends to be dryer (a problem

during the Roosevelt Fire).

In spring, the ground is full of moisture to

absorb any embers that escape the perimeter,

Swenson explained. During the spring “green

up,” grasses and shrubs are not as flammable

as they are later in the summer, he continued.

The site on Fortification Ridge was selected

because the conifer forests on both

sides of the aspen grove were thinned and

piled by forest crews last fall. With a reduced

canopy and no flammable fuels left on

the forest floor, the conifer forests provided

a natural “holding line” for the prescribed

burn.

The perfect conditions converged for

the forest service to “burn with utmost

confidence and a low risk of spotting,” said

Swenson.

Late Wednesday afternoon, the ignition

teams finished its project. On Wednesday,

Swenson said that ignition crews might need

to return to do any “touch up.” Otherwise,

the prescribed burn was turned over to the

holding crews.

Crews will remain in Pinedale for days,

possibly weeks (depending on weather), to

ensure that all hotspots are put out and no

smoke remains.