2008 Avalanche News

Mountain News: Telluride brings in big guns
November 19, 2008

TELLURIDE, Colo. – Telluride’s new ski terrain in Prospect Bowl is so big and steep that the U.S. Forest Service has authorized a pair of 105-mm howitzer cannons to provoke avalanches before skiers get there. Only a handful of ski areas in the United States are permitted such howitzers.

“Not every ski area needs them,” says the U.S. Forest Service National Avalanche Center, which is located in Ketchum, Idaho. “They’re expensive, and the U.S. Army and Forest Service require extensive gunner training and adherence to security procedures.”

But howitzers do have range, precision, and military punch, making them effective in certain terrain conditions. Those ski areas that use them are: Aleyeska; in Alaska; Taos, in New Mexico; Jackson Hole, in Wyoming; Mammoth Mountain and Alpine Meadows, in California; and Snowbird, in Utah.

Oregon’s Mt. Hood Meadows also got permission to use howitzers this winter, to reduce the danger to ski patrollers.

Avalaunchers are a common tool for controlling avalanches at ski areas. A device patterned after baseball pitching machines, it uses pressurized nitrogen to propel projectiles onto snow-laden slopes. However, Avalaunchers are notoriously imprecise, especially in storms, precisely when they are most needed. “They get blown around in the wind,” says Ken Kowynia, the Forest Service winter sports program manager in Colorado, speaking of the projectiles.

Also, their range is only a few hundred metres. As such they’re more useful for smaller areas.

The 105-mm howitzers, in contrast, can be fired up to 10 miles with enough accuracy that holes could be dug into the mountainside with repeat shelling. That makes them effective in targeting the “sweet spot” of slopes most likely to result in avalanches.

In addition, less than 1 per cent of howitzer shells are duds, compared to 38 per cent for Avalauncher projectiles.

Another common technique for abating avalanche threat is to dispatch ski patrollers to throw explosives by hand from ridges and other areas near the starting zones of snow slides. Hand-delivery of explosives can be dangerous, says Kowynia. He has experience with avalanche control at Colorado’s Arapahoe Basin, where the throwing of charges on the resort’s rocky and steep East Wall sometimes took six hours. That terrain is also exposed, he says, and the work is cold and dangerous.

Because of similar threats to ski patrollers at Telluride, the Forest Service decided, the new terrain warrants the use of howitzers. The howitzers also give ski area managers a higher confidence that they have reduced the threat of avalanches to an acceptable level.

“It’s really what Telluride needed,” said Kowynia. “Because the terrain has so many starting zones, with so many slide paths, we concluded that the most efficient system is a military weapons program.”

The U.S. Army controls howitzers, limiting their use to ski areas administered by the U.S. Forest Service or to programs administered by state governments. For example, Colorado uses howitzers to control avalanches on Berthoud, Loveland, and Red Mountain, among other passes.

The 105mm howitzers were manufactured beginning in 1941, with most now in use built in the 1950s. Several other ski areas use 105 mm and 75 mm recoilless rifles, which are different but still large ammo. They are: Alpenthal, in Washington, Kirkwood in California, and Alta, in Utah. Montana’s Bridger Bowl also continues to use the 75 mm recoilless, but is ending use in January.

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