‘Fire in the Hole!’
By David Nyman
TNews Contributor
For more than 40 years, two state agencies have kept a good record of avalanche forecasting, control and detection along Turnagain Arm and in the mountains above Alaska Railroad corridor to Seward.
While avalanche control has relied on military surplus 105 mm howitzer artillery—big, booming cannons shooting at a snow pace—ammunition has become five times more expensive and harder to find.
Now, state agencies are exploring new technology to shear a dangerous snowpack before it becomes a dangerous and massive avalanche.
How About Those Howitzers?
More than Seventy-five years ago, use of artillery firepower to release avalanches was pioneered at Alta Ski Resort.
“When a gentleman named Monty Atwater started shooting military artillery for avalanche mitigation in Little Cottonwood Canyon, it was state of the art and was unheard of,” said Dave Richards, director of the Alta Avalanche Office.
In 1969, the Alaska DOT entered an agreement with the US Forest Service to lease a 75mm recoilless rifle from the U.S. Army for highway avalanche control work.
As use of military artillery became more prevalent at ski areas, Girdwood’s Alyeska Resort followed suit. Alyeska Resort used a 75mm recoilless rifle until around 1973 when it switched to the 105mm recoilless rifle. These were eventually replaced with a more powerful 105mm howitzer in the 1990s because recoilless ammunition and weapons were exhausted.
Additionally, the railroad and transportation department began to use 105mm howitzer artillery to fire from fixed and mobile locations to release snow from starting zones in the mountains.
But seven years ago Army officials notified all users that artillery for avalanche control will be phased out over a 15-30 year period and urged the state to come up with new methods of avalanche control.
Drones and Remote Detonations
Drone Amplified used for avalanche mitigation. (Photo courtesy of AKRR/AK DOT&PF)
Drone Use for Avalanche Control
In a test conducted earlier this year, a drone carrying two explosive rounds buzzed up to a remote mountain snowpack south of Turnagain Arm and released its cargo. The system was a success and, now, pending federal approval, the railroad and transportation departments plan to use drones to fill the gap where other new types of control are not feasible or economical.
In addition to exploring use of drones to deliver explosives, the Railroad and Alaska DOT have made significant investments in equipment, state-of-the-art technology, research and expertise to mitigate avalanche risk with “Remote Avalanche Control Systems”, or RACS, particularly along slide-prone areas between Anchorage and Seward.
RACS have been used more widely as the vendor provided systems have evolved. Efforts to lessen the need to rely on control efforts dependent on military artillery by the ARRC includes installation of avalanche “blaster boxes” and “hanging charge avalanche towers.” Alaska DOT is planning installation of avalanche towers and avalanche detection systems at multiple sites.
Hanging charge Avalanche Towers. lean out over the starting zone and are designed to lower and detonate explosives above the target snowfield to trigger avalanches via deployment of remote-controlled hanging charges. ARRC and Alaska DOT intend on replacing the existing 105mm artillery avalanche control with RACS where possible.
As some motorists recall witnessing a VW microbus wrapped around a tree in one of the Bird Ridge avalanche paths, Turnagain Arm residents and tourists are fortunate that ARRC and the Alaska DOT are working every year to enhance risk mitigation efforts through continuous improvements to their avalanche programs.
(Story updated on Dec. 3, 5:30 p.m. with correct artillery information.)