CASPER, Wyo. — Two avalanche slides near Teton Pass on Thursday, Jan. 9 have closed WY 22 between Wilson and the Idaho state line.
That brings the total number of avalanches in the area since 2020 began to seven, according to a Bridger-Teton Avalanche Center map.
One vehicle was caught in the first avalanche on Thursday, but the driver of that vehicle was able to walk out unharmed.
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Since the area is prone to avalanches, the Wyoming Department of Transportation utilizes a number of avalanche mitigation approaches.
“The Wyoming Department of Transportation (WYDOT) has used artillery for avalanche reduction on highways near Jackson, WY since 1972,” WYDOT Public Relations Specialist Stephanie Harsha says. “As demands on the transportation system have changed, new technology and strategies have been implemented to improve the efficiency of avalanche reduction operations.”
Those include active and passive avalanche mitigation techniques on three highway corrdiors:
- Wyoming State Route 22 over Teton Pass where Thursday’s avalanches occurred
- US 89/191/189/26 through Snake River Canyon south of Jackson
- US 191/189 through Hoback River Canyon
On WY 22 over Teton Pass, “Gazex” and “Avalanche Guard” systems are in place. Those active avalanche control systems and infrasonic avalanche detection technology are in place on the Glory Bowl and Twin Slides paths, Harsha says.
In Snake River Canyon, WYDOT uses snow supporting structures for “passive avalanche defense in the milepost 151 avalanche path.”
In the Hoback River Canyone, two “Obellx” gas exploders are used to actively control avalanches. Those are in place at the “Cow” and “Calf of the Woods” avalanche paths, Harsha says.
“In each terrain, avalanche conditions, environmental impacts, and highway concerns are considered with the implementation of a certain infrastructure tool,” she adds. “With continued capital improvements and the realization of a long term strategy of implementing avalanche forecasting and mitigation technology, WYDOT is moving towards the end of artillery (Howitzer gun) while reducing highway avalanche closures and their durations.”
In addition to the technologies WYDOT employs two avalanche technicians who work to forecast and control slides.
“Controlled avalanches are initiated throughout the winter season, as needed when an emanate slide has emerged through forecasting,” Harsha says. “These guys work out of the Jackson office in the maintenance department.”
“There are several ways in which avalanches can be controlled. They range from simple snow sails and reinforced snow fences that prevent wide accumulations, to rare helicopter bombings that bring down entire slides.”
The technicians are members of the “Avalanche Artillery Users of North America,” Harsha says.
They are “trained and certified to fire artillery guns like the Howitzer M-102 and M-101 in order to bring down the snowpack in controlled situations. They also utilize GazEx Control Systems, which are controlled surface explosions initiated remotely in common avalanche areas like Teton Pass,” she adds.
Avalanches can occur under certain snowpack conditions.
“Weather systems can create a layer of sugary-like snow with a weak crust on the top, with a heavy load of new, wet snow or rain on the top and usually the snowpack can’t adjust to the heavy load,” Harsha explains. “The snowpack gives and an avalanche is born. Under ideal conditions, the snowpack builds continuously and slowly, like adding weight to a backpack.”
“If you wearing a backpack and someone added 5 pounds a little at a time, you could probably carry a lot of weight. But if someone tried to drop 50 pounds in your backpack at once, your knees would buckle.”
No highway fatalities have been recorded due to avalanche slides since WYDOT implemented their mitigation program in 1972, Harsha says.
“The only recorded fatality in WYDOT’s avalanche history came in 1956 when a man was killed at Crater Lake by a large Glory Bowl slide,” she adds.
WYDOT shared this video explaining mitigation efforts in 2018: