Quick Tree Lessons From AK

Going to a Fire in Alaska?

Check out these lessons from two tree strike incidents that occurred in the Fairbanks area.

Pat Creek Fire Tree Strike (2010)

August 8, 2010. Bucking and swamping was in progress when a gust of wind blew over a black spruce a couple tree lengths away, which then struck a second tree while on the way down, which struck a third tree causing it also to fall. Tree #3 which was approximately 8” dbh, struck the firefighter with its top section. The sawyer was bucking with the saw and the swampers busy moving fuel to the bone-pile, so the falling domino trees were seen only by the CRWB(t) observing the operation some distance away.

AK_hardHat

Hardhat of Firefighter struck by tree

  • Key Factor: Trees in permafrost conditions develop shallow root systems. Fires burning deeply into the organic layer containing those root systems frequently result in consumed roots and unstable trees.
  • Mitigation: Hazard trees need to be evaluated and felled prior to mop-up activities. Mop-up crews cannot assume that prior snagging operations mitigated all hazard trees. Increasing winds in burned-over timber, as well as recently observed wind-throw, should act as watchout triggers to have one eye looking up, or designating a snag look-out for each working group. Good spacing between swampers or other crewmembers involved in mop-up is also key. The working area of this allotment was snagged again after this incident.

Hastings Fire Tree Incident (2011)

At approximately 1820 hours (ADST) on June 16, 2011 while conducting mop-up
operations on the Hastings Fire, near Fairbanks, Alaska, a member of the ZigZag
IHC was struck by a tree. A medium helicopter already working the fire was
quickly staffed with medical personnel and used to extract the injured crew
member from a rapidly improved sling spot near the injury location. The injured
crew member was then flown directly to Fairbanks Memorial Hospital.

AKtree

Portion of the tree that struck firefighter

  • This tree strike occurred in a mixed timber stand comprised of 8-10 inch aspen and 12-24 inch white spruce.
  • A predominate shallow duff layer allowed the fire to penetrate down to mineral soil.
  • The tree that impacted the IHC member had a very shallow root system that had not been impacted by any other activities other than the fire.

 


 

They aren’t lessons if you don’t use ’em!

3 thoughts on “Quick Tree Lessons From AK

  1. Working next to a shot crew in 2015 outside of Fairbanks. Trees had been falling every minute or so but people were able to mitigate the risk until thunder cells passed over the area. Strong outflow winds increased the number of trees falling to every few seconds. I informed my TFL that I was pulling my crew back and into the green. About a minute later, a tree came down right on a shot crew member, breaking her arm. Two minutes later the TFL (a member of the shot crew) calls me to tell us to back off and seek refuge in the green. Great idea.
    Trees in permafrost don’t make a sound when they fall due to fire damage. Especially when the needles have burnt off. The spruce forest in that area grows very dense and I don’t exaggerate about the frequency of falling trees even without the influence of wind. It’s not just the shallow root system that is an issue. What little roots these trees have is anchored into muskeg. It’s just moss.
    Point is: when a strong wind is blowing, you might want to get your people out of the black.

    Liked by 1 person

  2. Be heads up in the bogs in the lower 48 too ( R1 Lolo, in my slide ). They have trees that are just as silent and MUCH larger. Of course treat any thing of any size above your height as the hazard it is.
    I ran a skidgine thru one of these and trees were toppling over behind the machine as it went. They fell inward toward the machines path on either side and essentially closed the egress as it drove across the bog. This, along with a tree falling over almost every time the wind kicked up, created a good slide for a R5 guy. It turned into a no work zone shortly thereafter.

    Like

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