Idaho 21 avalanche closure, clean up unusual but not unprecedented
The clean up effort along Highway 21. Image by Idaho Transportation Department
The Idaho Transportation Department said on Monday that 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 on March 3 due to threat of avalanche. Multiple slides occurred, closing the highway from March 6 to March 16.
The ITD observed twenty avalanches during the closure. The area has experienced nearly 100 slides so far this winter with 46 of them reaching the road surface.
“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 Idaho City maintenance foreman Stuart Wilson. “Once we cleared out the other material, we could use the big rotary to blow out the snow. “
The length of the closure (thirteen days) made for the longest closure of the highway in the last six years.
“Until about 1986, however, 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,” said ITD officials.
ITD’s response to the closure cost approximately $20,000 from ITD’s maintenance budget, involved more than a dozen maintenance personnel, utilized deicer, and included several types of heavy equipment.
ITD Maintenance crews from the Idaho City and Lowman sheds, with help from a special crew, used excavators, loaders, bulldozers and a big rotary snowplow to clear tons of snow and debris and open the route.