Detailed Accident Report
Submitted By: CAIC
Place: Steep Gully #1, west of Arapahoe Basin Ski Area
Summary: 1 snowboarder caught, partially buried, and killed
*** OFFICIAL REPORT FROM THE CAIC ***
View report with photos: avalanche.state.co.us
Three snowboarders presumably exited the Arapahoe Basin Ski Area and headed for the Steep Gullies, an out-of-bounds area adjacent to the ski area boundary.
The previous weekend brought new snow. Temperatures had been mild. Winds were not excessive but had cross-loaded the start zones of all the Steep Gullies with available snow and southwest winds. Wind shifted to the northwest prior to the accident.
The snowpack this season can be described as slab over weak facets. It is generally shallow.
EVENTS LEADING TO AVALANCHE
Unknown. The investigator was not able to speak to the survivors for an interview.
There is a convex knob in the middle of the starting zone for Steep Gully #1. The first rider triggered the avalanche as he rode over the knob. The avalanche broke to the ground along the convexity. The snowpack was very shallow, and rescuers estimated the average crown depth about 12 inches, and around 30 inches at the deepest. The initial avalanche released several additional start zones as it ran through the track. The avalanche was the full width of the gully, but left large areas of hangfire.
The rider was caught and carried for most of the avalanche's run. He was stopped by trees in the upper portion of the runout, and partially buried. His partners descended the path and used their snowboards to excavate him before organized rescue arrived. The avalanche broke trees approximately 6 inches in diameter. It took his partners nearly 40 minutes to reach the bottom of the path and to call 911, due to the rugged nature of the terrain.
Out-of-bounds locations next to ski areas, also know as the "side country". They are not patrolled by ski area staff and there is no avalanche hazard mitigation done in these areas. They are backcountry areas that are accessed from an open ski area. The snowpack though frequently skied or ridden, is still considered to be a backcountry snowpack and could be prone to avalanching.
UPDATED: 24 Sept 2015 to correct link to CAIC report.