4/29/2010
Reed Hollinshead
ITD Communication
208-334-8881
reed.hollinshead@itd.idaho.gov
RECORD SET: Idaho 21 avalanche closures fall dramatically; mitigation efforts credited
BOISE - Records
are meant to be broken, and the Idaho Transportation Department's Avalanche Forecast Office is gladly
complying. For the second straight winter, a new standard has been set for
keeping the notorious "Avalanche Alley" section of Idaho State
Highway 21 between the Grandjean Junction turnoff and Banner Summit open as
much as possible.
Historically, the highway was routinely closed all winter. As recently as a few years ago, closures for 60 or more days each winter season
were commonplace. This winter, there were four closures, totaling nine days.
That broke the record of 21 days, set last year.
Undoubtedly, fewer snowflakes have had something to do with
it. This winter 205 inches of snowfall were recorded in the area, compared to 330
inches the previous winter. But their success owes to much more, said Bill
Nicholson, avalanche forecast manager.
"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."
The corridor, also known as Canyon Creek, has 57 known
avalanche chutes and is responsible for
about 90 percent of the state's avalanches affecting roadways.
Although
the Southwest Idaho team is located in Lowman, it operates statewide and is not
limited to Idaho 21. The crew also has given support and/or training for crews
on U.S. 12 in the Lochsa area, the Galena Summit area on Idaho 75, U.S. 89 in
Montpelier, U.S. 26 through Palisades and U.S. 20 in the Ashton Hill area. Some
routes are more critical than others, so based on greatest priority, the crew goes where needed.
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. Also added were high-tech weather stations, additional forecasting equipment and
purchased an avalauncher to fire explosives into weak snowpacks, thereby
bringing avalanches down in a controlled manner.
The winter season in the Avalanche Alley region unofficially
runs from Dec. 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, ITD counted 20 inches of snow in
November, and called an end to the avalanche season April 25 due to 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 built right against numerous
avalanche slide paths. For safety, it was frequently closed all or most of each winter. Then-Gov. Andrus verbally decreed in 1986 that Idaho 21
needed to remain open more often.
When the road remains closed it impacts the public financially.
The cost to the traveling public for having Idaho 21 closed is about
$4,000 per day - and that's not counting 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 time savings. The closest detour is 82
miles (about another 110 minutes) if the road is closed.