Avalanche Details
- Location: South of Arapaho Lakes, west of Rollinsville
- State: Colorado
- Date: 2010/02/26
- Time:
8:30 AM
(Estimated)
- Summary Description: 1 skier caught, fully buried
- Primary Activity: Backcountry Tourer
- Primary Travel Mode: Ski
- Location Setting: Backcountry
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Number
- Caught: 1
- Partially Buried, Non-Critical: 0
- Partially Buried, Critical: 0
- Fully Buried: 1
- Injured: 0
- Killed: 0
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Avalanche
- Type: SS
- Trigger: AS - Skier
- Trigger (subcode): u - An unintentional release
- Size - Relative to Path: R2
- Size - Destructive Force: D2
- Sliding Surface: S - Within Storm Snow
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Site
- Slope Aspect: E
- Site Elevation: 10940 ft
- Slope Angle: 48 °
- Slope Characteristic: Concave Slope
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Avalanche Comments
There may have been two separate avalanches that caught riders around 2/26. One party (RP, the reporting party) reported their incident to the CAIC, which formed the basis of our report. RP spoke with a ranger at the trailhead. The ranger also sent information to the CAIC. Dale Atkins, former CAIC forecaster, visited the site on 2/28. The dimensions he found were smaller than RP described. It is very common to over-estimate avalanche dimensions, especially after a close call, and we assumed that was the case here. Dale may actually have found a second human-triggered avalanche with a partial or full burial. Dimensions listed are for the avalanche Dale measured.
Accident Summary
Three skiers approached fairly steep slope near treeline. The slope was an east-southeast aspect, with a very steep convex roll, and 300-400 vertical feet. The party saw no evidence of previous avalanches, or signs of instability like cracking or whumpfs. They skinned up the face, "testing snow conditions along the way." At the top they dug a pit about 8 feet deep. There was a "distinct layer at 3 feet," assuming up from the ground, with moderate compression tests results but "no distinct sliding." From Dale's visit, only heavily drifted areas would have that deep of a snowpack.
The group skied 1 run "cautiously...making ski cuts at the top with no problems." They ascended and made another run. The slope avalanched on the third skier, during the second run. "As the third was nearing the bottom of the face, the entire slope fractured and gave way." The third skier was not buried, but one of the first two skiers was caught and fully buried.
The two unburied skiers began a beacon search. Less than a minute into the search, the buried skier "was able to punch an arm through the snow and was immediately spotted." The two rescuers were able to clear the buried skier's face in about 3 minutes, and had the skier out about 10 minutes later with "no substantial injuries."
Comments
Dale measured the avalanche and found it much wider but shallower than initially reported. The crown averaged 45 cm (1.5 feet). From below, one drifted spot above the crown appeared to be deeper. The crown broke along a convex roll, where the slope abruptly steepened from about 25 to 48 degrees. The weak layer was soft (4f) new snow, with somewhat harder (1F) drifted snow above. The slide did not run to the ground, but did expose some rock outcrops.
The avalanche debris split into two lobes. The party gave coordinates for the south lobe, an hour-glass shaped debris pile. Dale found most the debris to be less than 1.25 meters deep.
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