Detailed Accident Report

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Date: 2002-01-27
Submitted By: Doug Chabot, GNFAC
Place: Miller Creek outside of Cooke City
State: MT
Country: USA
Summary: 2 snowmobilers caught, 1 injured.

TWO SNOWMOBILERS CAUGHT, ONE INJURED

IN MONTANA AVALANCHE

January 27th, 2002

On Sunday, January 27th, three snowmobilers triggered an avalanche as they were riding up a slope on the east side of Miller Creek outside of Cooke City. One rider escaped to the side, another was caught briefly, and the third was completely buried, but only suffered a broken tibia. The buried person was found 50 feet below his machine with his head buried 4 feet under the snow surface. Everyone was carrying rescue gear and his partners extricated him within 15 minutes.

The avalanche released on a south-facing slope, at an elevation of 9,650 feet. The slide was 2-4 feet deep, 300 feet wide and ran 400 feet vertical. The slope angle averaged 33 degrees with the crown being 36 degrees. The US Classification of the slide is HS-2-AV-O.

During the previous 3 days, over 30 inches of snow fell with westerly winds averaging 20-40 mph and gusting into the 60s. On the day of the slide it was snowing and blowing 20 mph creating marginal visibility. The starting zone of the avalanche was wind loaded, and the path was cross-loaded, which created hard slabs. These slabs were deposited on top of a 3 cm ice layer capped with 1 cm of small-grained facets (1-1.5 mm). The ice layer, located 90 cm above the ground, provided a good bed surface with the facets being the obvious weak layer.

I was in an adjacent drainage when I was notified via radio (12:25 pm) that there was an avalanche with one person buried. My partner and I rode to the site and were informed that the person was alive, but injured. Once on the scene I was able to assist in the rescue and investigate the incident further. The terrain is a shallow gully with mostly open sides. Two riders were heading down the gully while one person, the victim, was heading up when the avalanche was triggered. The rider furthest up the hill saw the slide release on the south facing side of the hill. Luckily, the slope next to him was a shallow angle and the avalanche moved slowly. This allowed him to ride to the side, jump off his sled and take a few steps uphill to get out of the path. His sled was completely buried under 6 feet of debris. The middle person was caught, but thrown to the side on top of the snow. His sled was found against some trees 100 feet below him. The victim saw the slide approach and tried unsuccessfully to veer away. He tumbled, made swimming motions and tried to clear an air space before the slide stopped. His two partners searched the narrow path with their transceivers, but as they got closer one turned his off and let the other finish the search since he was much faster. They dug up the victim and cleared his airway within 15 minutes. He immediately started breathing and a secondary survey revealed a broken tibia. After splinting, he was evacuated by Cooke City Search and Rescue.

If you have any questions or comments, you can contact me at 406-587-6984 or dchabot@fs.fed.us.

Doug Chabot, Director

Gallatin National Forest Avalanche Center

January 29, 2002