Detailed Accident Report

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Date: 2003-03-09
Submitted By: CAIC; Dale Atkins
Place: Ptarmigan Lake, Cottonwood Pass, Sawatch Range
State: CO
Country: USA
Fatalities: 1
Summary: 1 Snowmobiler Caught, Buried and Killed

Ptarmigan Lake, Cottonwood Pass, Sawatch Range,

March 9, 2003

1 Snowmobiler Caught, Buried and Killed

A 42-year-old Manitou Springs man was buried and killed in a medium- to large-sized avalanche at "Upper" Ptarmigan Lake near Cottonwood Pass. The avalanche was triggered at about 10:00 Sunday morning. At 10:48 the Chaffee County Sheriff's Office received the report of the accident. The man and his wife were riding at the lake by themselves while many other riders were in the Cottonwood Pass area. Around 16:00 the victim was found dead under 6 feet of debris by an avalanche rescue dog.

Ptarmigan Lake is located high in the Sawatch Range about 3.5 miles south-southeast of Cottonwood Pass.

Avalanche Summary

This avalanche was classified as HS-AV-3-G/O [This is a downgrade in size from earlier reports. The size rating is a function of the volume of snow relative to the avalanche path.] The avalanche was a classic hard slab with the debris field looking like a rocky scree pile. The slide released about 1100 feet across a shallow bowl. The fracture line ranged in depth from 1.5 to 10 feet, with the deeper portions (south side) averaging 8 feet and right above where the snowmobiler triggered the avalanche. The avalanche was triggered on an east aspect but fractures propagated to north and released the southeast aspect too. The top of the fracture line was at 12,800 feet, and the avalanche fell 560 vertical feet. The slope angle in the starting zone ranged from 34 to 39 degrees.

At the same time this avalanche was triggered the adjacent slope to the north on Jones Mountain also released sympathetically. This hard-slab avalanche was about 3,000 feet across.

Comments

We have not yet spoken the victim's wife--the only witness to this avalanche, so there is still uncertainty to where her husband was when the slide released and to what clues of avalanche danger where spotted or missed.

In many accidents there are usually clues of avalanche danger present, but they are too often missed or ignored. At this site there was evidence of a sizable natural avalanche on the adjacent slope to the south. A soft slab avalanche released on the northeast-facing slope sometime earlier in the week, perhaps Wednesday or Thursday. This is a guesstimate given recent snowfall and winds, inspection of the debris, and observation of the fracture line. The victim's route likely traveled within 50-75 feet of this debris.

While the above description may make the avalanche seem obvious and the rider oblivious, the untrained- and unaware-avalanche person could easily miss the slide. Little of the fracture line was visibile as recent strong winds and blowing snow filled back in the starting zone. The best sign was the irregular-shaped mounds of debris at the bottom of the slope. Though the winds had smoothed over the debris, it stood slightly taller compared to the smooth, flat adjacent slope.

Often in avalanche programs instructors state the best clue to avalanche danger is a recent avalanche and then show a sharp photograph or two of a well-defined avalanche. A recent avalanche is certainly the best clue, but defining "recent" is tricky and too often new snows and winds will hide or partly obsure recent avalanches. In this case the natural avalanche occurred 3 or 4 days earlier, but that can still be though of as "recent" because the weather conditions had not changed. Persistant strong winds causing blowing snow continued to contribute to the avalanche danger.

Take time to stomp around in avalanche debris and revisit debris piles to see how they change over time. This will help you learn to estimate the age of slides and to spot old and new avalanches, too.

This is the fourth Colorado avalanche death of the season, and the third in Chaffee County in just over 2 weeks.

We will post additional information when it becomes available.

Report from Brad Sawtell (CAIC Summit County Avalanche Office observer/forecaster) and Dale Atkins.

Atkins, 3/9; updated 3/13, Atkins