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Record set for fewest Idaho 21 avalanche closures

For the second straight winter, a new standard has been set for keeping the state’s notorious "Avalanche Alley" section of Idaho 21 between the Grandjean Junction turnoff and Banner Summit open during the avalanche season.

Not long ago, the highway was routinely closed all winter. Even as recently as a few years ago, closures for 60-plus days each season were common. This winter, there were four closures, totaling nine days. That broke the record of 21 days, set last year.

Undoubtedly, fewer snowflakes falling on the route during the season contributed to the reduced closures. Only 205 inches of snow fell this season, compared to 330 inches the previous winter. But limiting the highway’s “down time” was attributable to more than the mild conditions, said ITD Avalanche Forecast Manager Bill Nicholson.

"We are able to keep the closures to a minimum thanks to a great staff of forecasters and lots of assistance from the Boise National Weather Service office," explained Nicholson.

"Being vigilant and not over-reacting are the keys. We also count on other ITD area crews – particularly from ITD Headquarters, other district offices and the plow crews – to do our jobs effectively."

The corridor, also known as Canyon Creek, has 57 known avalanche chutes (up from the 54 previously thought) and is responsible for about 90 percent of the state's avalanches affecting roadways.

In 2002-03, forecasters were hired to help more accurately predict and/or assess avalanche danger.

Two years ago, ITD expanded its avalanche control measures by adding an experienced avalanche team trained in forecasting avalanches. ITD also added high-tech weather stations and other forecasting equipment, and purchased an Avalauncher to fire explosives into weak snowpacks to bring them down in a controlled manner.

The 2009-2010 season in the Avalanche Alley region unofficially runs from December 1 through April 30 each year. Late November snowstorms are not uncommon, however, and Mother Nature does not hold fast to the spring timeframe either.

This year, for instance, ITD counted 20 inches of snow in November, and called an end to the avalanche season April 25 because of a rapidly diminishing snowpack, "continued warm temperatures and favorable weather forecasts," Nicholson explained.

Idaho 21 was paved in 1969, but was not designed to be open through the winter. As a result, it was constructed adjacent to numerous avalanche slide paths. For safety, it was frequently closed all, or a major portion of each winter. Then-Gov. Cecil D. Andrus verbally decreed in 1986 that Idaho 21 needed to remain longer.

When the road is closed it has a significant impact on the local economy. The cost to the traveling public for having Idaho 21 closed is about $4,000 per day – excluding the cost to the economy when motorists can’t get through. In contrast, the maintenance cost is $3,400 per lane mile to clear it. Another key factor is the time saved – the detour is 82 miles (about another 110 minutes) when the road is closed.

The District 3 team also supported or trained crews on U.S. 12 in the Lochsa area, the Galena Summit area on Idaho 75, U.S. 89 near Montpelier, U.S. 26 through Palisades and U.S. 20 in the Ashton Hill area.