The state Department of Natural Resources has determined that tree branches 'chafing' a live power line sparked the Aug. 19th, 2015 wildfire near Twisp that claimed the lives of three U.S. Forest Service members and severely injured another.
The investigative report said light winds caused the branches to sway and touch an uninsulated, energized power line conductor. The conductor was hot enough it caught those branches on fire, which then fell to the ground and lit the fuels below.
A combination of hot temperatures, lack of ground moisture (which were magnified by the extreme drought last year) coupled with the tree branches touching the live conductor created a perfect storm scenario for the Twisp River Fire to start. The probability of fuels igniting was calculated by U.S. Forest Service behavior experts to be greater than 85-percent that day, according to the report.