6/5/2013
Reed Hollinshead
ITD Communication
208-334-8881
reed.hollinshead@itd.idaho.gov
ITD's recent avalanche season was one for the record books
Closed just 8.5 days from November through April - a record low
BOISE - Some records are sacred – Joe DiMaggio’s 56-game hitting streak, Bill Russell’s 11 NBA titles in 13 years, Gone With the Wind’s ticket sales and revenue from 1939.
Some are just begging to be broken – and the Idaho Transportation Department’s southwest Idaho Avalanche Forecast Unit is happy to comply.
Despite 230 inches of snow and 45 individual slides, the road was closed a record-low of just 8.5 days during the recent 2012-13 avalanche season on Idaho 21 in the 12-mile “Avalanche Alley” section.
It’s only the second time in history the road has been closed fewer than 10 days for the entire avalanche season. The 2009-10 season was the other, and the forecasters were on duty then, too.
The notorious stretch of road is home to approximately 60 known avalanche chutes and about 90 percent of all slide activity in the state that reaches the highway. Only 26 of this year's 45 slides reached the road.
Click here for a slide picture from this spring.
For several years now, the district has used a forecasting unit to improve the number and duration of closures.
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.
Another key factor is time savings. The closest detour is 86 miles (approximately another 120 minutes) if the road is closed. It can be almost three times that distance if motorists drive all the way to the closure gates before being forced to turn around. Click here for a picture of the detour.
The numbers speak for themselves – closures reduced by two-thirds, despite about 65 more inches of snowfall per year.
Only 56 lbs. of explosives were used this year to probe or bring down avalanches, much less than usual.
“We usually use around 250 pounds,” said ITD southwest Idaho Lead Avalanche Forecaster Bill Nicholson, “but the rain and warm temperatures made the explosives less effective.”
“The avalanche forecasting this season presented unique challenges as usual,” explained Nicholson.
“Early snow followed by long dry and cold spells produced a weak snowpack. This was followed later in the winter by unusually warm storms, putting greater stress on the weak snowpack.”
"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.
Decades ago, 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.
Future improvements
Nicholson said the forecasters will be working to create an Idaho 21 web page this summer to assist travelers with their plans. This will be on the ITD web page and also linked to the statewide 511 traveler advisory system.
The department’s research partnership with Boise State University is also progressing, as teams work on an infrasonic avalanche-detection system to assist with forecasting, explosive testing and a warning system if forecasters misjudge the extent of a hazard.
Nicholson said the system will provide “avalanche size and distance, as well as shot placement for explosives,” which will combine to “greatly improve safety and reduce closure times.”