One of Idaho's popular recreation routes soon will have fewer road closures resulting from avalanches.
ITD received a special use permit from the U.S. Forest Service to use explosives to reduce avalanche hazards along Idaho 21 between Grandjean Junction and Banner Summit. The department expects to begin using hand-placed explosives on a limited basis as part of its avalanche management program this winter.
Once the department obtains necessary equipment, further explosive work will be used next winter.
ITD contracted with a respected avalanche specialist from Alberta, Canada, to determine possible control options and has used those recommendations to develop a Winter Operating Plan. The plan includes the use of an Avalauncher to send explosives into avalanche chutes and "heli-bombing" to drop explosives in avalanche-prone areas by helicopter.
The explosive charges are designed to bring down snow in the chutes, reducing avalanche hazards and allowing ITD crews to safely clear snow from the roadway.
"Our primary goal is to increase safety for motorists and for our winter maintenance crews," said ITD Regional Engineer Shawna King. "The expanded program will also provide more reliable access to winter recreation areas along this highway."
Idaho 21 is an important regional route between Stanley and the Treasure Valley. It also provides a vital transportation link with other parts of the state. The 11-mile section of Idaho 21 between Banner Summit and Grandjean, called Canyon Creek, has 54 avalanche chutes and experiences about 90 percent of the state's avalanches annually. It is closed an average of 60 days per year.
ITD uses several tools to manage avalanche danger. Information is gathered using technology such as weather stations and snow density testing to determine when avalanches are likely. Crews then clear the slides from the roadway when conditions are safe.
"Our agencies have worked together closely to ensure natural resources in this area are protected in the development of a long-term avalanche control program in Canyon Creek," said Neil Bosworth of the U.S. Forest Service's Lowman Ranger District.
The Forest Service issued a special use permit following a public review process that ended in November.
ITD also will purchase an additional weather station and a new variable message sign at the Idaho 75 junction near Challis, to provide the best possible weather-related information for both avalanche forecasters and motorists.
Canyon Creek is located in the Boise National Forest.