- Location: Diablo Ridge, Pt. 12,505, approx. 1 mile W of Conejos Peak
- State: Colorado
- Date: 2014/03/04
- Summary Description: 1 skier caught, buried, and killed
- Primary Activity: Ski Patroller
- Primary Travel Mode: Ski
- Location Setting: Backcountry
- Caught: 1
- Partially Buried, Non-Critical: 0
- Partially Buried, Critical: 0
- Fully Buried: 1
- Injured: 0
- Killed: 1
- Type: HS
- Trigger: AS - Skier
- Trigger (subcode): u - An unintentional release
- Size - Relative to Path: R3
- Size - Destructive Force: D3
- Sliding Surface: O - Within Old Snow
- Slope Aspect: NW
- Site Elevation: 11700 ft
- Slope Angle: --
- Slope Characteristic: --
The avalanche (HS-ASu-R3-D3-O) was a hard slab, triggered unintentionally by a skier. It was medium sized relative to the path, but destructive enough to bury a car or break trees. It broke on a layer of faceted snow three to five feet below the snow surface, and the crown was about 250 feet wide. It started on a northwest facing slope near treeline. The avalanche ran through a confined gully.
The latter half of February was dry with no snowfall. A three-day storm occurred 2/28-3/2. At the CAIC Wolf Creek Pass Study Plot, approx 16 miles northwest of the accident site, 36" of snow with 3.5" of water content was measured during the storm. Winds were strong from the southwest during the storm.
There was an exceptionally dry period of weather that began before Christmas and extended until the very end of January. During that period, the upper half of the snowpack evolved into faceted snow grains. These became a persistent weak layer when they were buried, first by a long storm cycle at the end of January through the first third of February, and then the storm system prior to the accident, 2/29-3/2/14.
Events Leading to the Avalanche
On March 3, 2014, four ski patrollers from the Wolf Creek Ski Area were transported via helicopter to Pt. 12,505, approximately one mile west of Conejos Peak and approximately 16 miles southeast of the Wolf Creek Ski Area. The patrollers placed explosives to mitigate the avalanche hazard and had no significant results. They made two passes through the terrain observing snow profiles and natural avalanche activity from the last storm. They descended in the trees in the northeast facing side of Canon Diablo and an avalanche path to the southwest of the path that would avalanche on March 4.
On March 4, 2014, the Mountain Manager from the Wolf Creek Pass ski area traveled via helicopter to North Mountain, approximately 11 miles to the east southeast of the ski area. He placed two explosive charges on an east-facing slope. The second released a very large avalanche (R4D3 - large enough to destroy a timber structure or passenger vehicle). This avalanche occurred in the same avalanche path that claimed a life in February 2007. The helicopter and ski area personnel returned to the ski area. They planned to send a group of four ski patrollers to Pt. 12,505 (the area where they had been on March 3rd). This group of four discussed the results of the explosive work on North Mountain, the observations made on March 3rd, the weather forecast, and the CAIC's backcountry avalanche forecast. The avalanche forecast rated the backcountry danger as Considerable (Level 3) above treeline and Moderate (Level 2) near and below treeline. The forecast highlighted Persistent and Deep Persistent Slab avalanche problems, breaking on layers of faceted snow buried 3 to 7 feet below the snowpack surface. The group made their plan and proceeded to the site in groups of two via helicopter.
Patrollers 1 and 2 arrived first and proceeded to the avalanche path the previous day's group had skied. Patrollers 1 and 2 dug two snowpits. They observed no obvious signs of instability until they were about to leave. They triggered a collapse while putting on skis. They waited in a safe location to discuss and share their observations with Patrollers 3 and 4. Patrollers 1 and 2 then skied the avalanche path to the planned helicopter pick up zone.
Patrollers 3 and 4 proceeded farther to skier's right to dig an additional snowpit. Patroller 4 spotted from above while Patroller 3 collected snowpit data.
After finishing the data collection, Patroller 3 told Patroller 4 he would descend the forested terrain on the skier's right of the avalanche path. Patroller 3 instructed Patroller 4 to wait at his spotting location. Patroller 3 would ski to a safe spot and radio Patroller 4 when it was safe to descend. Patroller 3 made three turns, down the hill and to the right. He descended out of sight before the avalanche released. Patroller 4 felt a large collapse and watched the crown break near the snowpit location and spread far to the skier's right. Patroller 4 warned 3 by radio that an avalanche had released, then contacted Patrollers 1 and 2.
Patrollers 1 and 2 heard Patroller 4's radio call reporting the avalanche. They immediately attached climbing skins and ascended towards the avalanche. After several minutes they established communication with the helicopter, which relayed communication to the the ski area, and requested additional resources. They also recommended mobilizing Flight For Life from Durango.
Patroller 4 began a transceiver search as he descended the avalanche path. He acquired a signal about three-fourths of the way down the path. Patrollers 1, 2, and 4 converged on the signal. They located Patroller 3 on the first or second probe strike. Patroller 3 was buried about 5 feet deep, face down, with his head down hill. Rescuers estimate he was buried about 30 minutes. He was pulseless, not breathing, and showed minor signs of trauma. Rescuers began CPR and maintained it for about 2 hours. Additional rescuers and equipment were transported from the ski area to the site via helicopter and began arriving at the burial location during the extrication. Evacuation equipment was dropped at the burial location and Patroller 3 was transported by rescue sled to the helicopter landing zone. From there, Flight for Life transported Patroller 3 to a Durango hospital, where he was pronounced deceased by attending physicians, about 4 hours after the avalanche.
This report is compiled from Patrollers' 1, 2, and 4 written statements provided by the Wolf Creek Ski Area. Supplemental material provided included profile data from the snowpits on March 4th, 3rd, as well as prior visits to the area. CAIC staff visited the avalanche path and debris, but did not investigate the crown of the avalanche or conduct witness interviews.
The snow profile and test results from Patroller 3's snowpit are included below. He conducted an Extended Column Test (ECT) which broke along an interface between two layers of depth hoar. The fracture propagated across the entire column, which suggests unstable conditions. The fracture is notable because it occurred at a depth where the ECT becomes a less effective technique. Patroller 3 did not record shear quality or fracture character, but the test result indicated that fracture propagation was possible along the interface.
Structural indices are another tool to assess fracture potential and propagation from snowpit data. Applying the "yellow flags" to the snow profile, the interface at the top of the depth hoar receives all six flags. Five or six flags indicate the potential for skier triggering of the slope. The interface that broke during the ECT only had three flags. The interface does not get flagged, because there is no difference in grain size, the hardness difference is not great enough, and the layer is deeper than the critical threshold.
Figure 16: Profile done by Patroller 3 prior to the avalanche. Data provided by Wolf Creek Ski Patrol. Plotted by CAIC.