Idaho 21 avalanche closure, clean up unusual but not unprecedented
The recent Idaho 21 avalanche closure, in the 12-mile stretch from Grandjean Junction to Banner Summit, was one of a kind, but also not completely unprecedented.
The highway was closed the afternoon of March 3 for avalanche threat. The first of multiple slides occurred March 6, and the road was closed until Sunday afternoon, March 16, in the aftermath of the avalanche activity.
"We just kept pushing snow out of the way with loaders and the bulldozer, and used the excavators and dozer to sort through the snow for trees and rocks," said Stuart Wilson, Idaho City maintenance foreman. "Once we cleared out the other material, we could use the big rotary to blow out the snow."
The length of the closure, 13 days (March 3-16), made for the longest closure of the highway in at least the past six years. Until about 1986, this stretch of road was closed for the entire winter every winter as a concession to the avalanche threat. Avalanche has been the reason for eight of the nine longest highway closures in the state since the beginning of 2008.
ITD¹s response to the closure cost approximately $20,000 from ITD¹s maintenance budget, involved more than a dozen maintenance personnel and avalanche technicians, utilized deicer, and the following equipment:
There were 20 observed avalanches during the closure. The area has experienced nearly 100 slides so far this winter, with 46 of them reaching the road surface.
ITD maintenance crews from the Idaho City and Lowman sheds, with help from Special Crew, used excavators, loaders, bulldozers and a big rotary snowplow to clear tons of snow and debris and open the route.
(Top and above) Idaho 21 is choked off by one last winter avalanche. (Below) Crews work to clear debris and restore traffic flow to this avalanche-prone highway.