Air inversion halts USFS slash burning

The job is nearly done, but late last week the Forest Service called a halt to its own burning program.

For the past few weeks, Forest Service employees have been racing the advancing winter weather to finish burning thousands of slash piles.

Most of the slash consists of fallen limbs and small trees cut to thin the forest.

"Last week was a pretty big week for burning, " said Mark Rapp, Assistant Fire Management Officer for the Sisters Ranger District. "We've ceased new ignitions, however, primarily because of the air inversions trapped by the recent cold weather."

Rapp said that fires already burning would be allowed to burn themselves out.

Still, on Friday night, November 17 -- the eve of Oregon's football Civil War -- the nighttime forest along Highway 20 resembled the storied descriptions of army encampments from America's real Civil War.

Hundreds of little blazes could be seen dotting the woods like molten puddles in the darkness.

Of the 1,200 Forest Service acres originally littered with burn piles, Rapp estimated that only 300 acres remain. Further, the acreage with unburned piles has less waste material waiting.

He estimates that 90 percent of the targeted slash is already gone.

What remains is mostly on the north side of the highway, west of town; and most of that is out of sight from the road.

The piles were stacked this past summer by state and county inmates. The program is designed to enhance forest health and reduce the amount of accumulated combustible vegetation along the Highway 20 corridor.

Rapp explained the reason for invoking a pause to the burning.

"The Central Oregon airshed was pretty well loaded up with particulate from smoke and other sources," he said.

He acknowledged that much of the smoke was from Forest Service burns, but pointed out that quite a bit was also coming from private burns, especially south of Sisters.

"We plan to resume burning when conditions start clearing out the airshed," Rapp said. "We'd like a little more moisture, too. Even with a little snow, the ground is still pretty dry, so you end up with a lot of smoldering duff and woody debris."

Duff consists of matted layers of grasses and fallen vegetation on the forest floor.

Three parcels of land totaling about 135 acres were originally slated for "underburning," a process in which everything on the forest floor is burned.

Rapp feels that the window of opportunity for those burns has passed, and they will be rescheduled for next year.

Rapp hopes to avert a smoky Thanksgiving holiday.

The Forest Service's current plan is to wait until after Thursday for the last of the fires to be ignited.