Lessons learned from staged wildfire burn

Last Thursday we witnessed the stunning speed and heat of a wildfire.
   Granted, our fire consumed just one old shed and spread no farther than 20 feet around it. But I’ll no longer scoff when witnesses report seeing a fire “explode” into a blaze.
   PEMCO teamed up with Kittitas County Fire District 7 to stage a controlled burn at a residence east of Cle Elum, literally on the perimeter of the 2012 Taylor Bridge fire. The owner had asked KCFD7 if it would burn an old wood shed he no longer wanted.
   The timing was perfect, since we sought a burn structure to show the news media how fast wildfire can spread if rural homeowners don’t prepare their property to resist it.
   I had no idea a controlled demonstration could depict wildfire danger so vividly.
   Weather forecasts called for light winds from the southwest. An army of KCFD7 volunteers, led by Chief Russ Hobbs, surrounded the shed with hoses fed by large tanker trucks.
   A fireman lit a thick layer of pine needles near the shed, simulating property that had not been prepared using Firewise principles. Small flames sputtered for a few minutes, and we joked they’d never ignite the shed. After a few minutes a fireman lit a parched pine branch and placed it next to the shed, hastening the process.
   Within seconds, the branch ignited an old canvas tarp. The tarp ignited the wood, and soon we had a real fire.
   Then the wind shifted from out of the east. With stunning swiftness the fire raged. “Exploded” is not hyperbole. Huge flames licked out from under the eaves, billowing gray smoke soon turned black, and heat swathed our faces, making us retreat several yards.
   That all transpired in about 30 seconds.
   I’ll admit I got worried when long flames, fanned by east winds, ignited a tall pine tree behind the shed.
   Firefighters quickly blasted it with their hoses, but not before I briefly witnessed the flames climb upward, intent on consuming the crown. So that’s what’s meant by “ladder fuel,” and why a key Firewise step calls for removing all tree limbs within 15 feet off the ground.
   KCFD7’s firefighters doused the shed to slow the burn, and we watched it collapse and diminish into a burning wood pile.
   I later asked Chief Hobbs what we had witnessed, why the fire escalated so quickly. He said the hotter fire gets, it grows exponentially, and at 1,200 degrees things really change. What had been a wood fire essentially became a gas fire as solids like resin in the wood vaporize. The shifting wind, plus winds created by the fire itself as it surges and heats, fanned the flames to where we had to back away, and to where the pine branches ignited.
   Our staged burn not only demonstrated the need to follow Firewise precautions, it ended up being a very real and practical training exercise for the KCFD7 crew.

by  Jon Osterberg

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