Detailed Accident Report
Submitted By: Snowbird Snow Safety
Place: American Fork Twins, backcountry terrain.
Summary: Close call...1 patroller caught, carried, partially buried, and injured.
Avalanche Accident Report
Snowbird Ski Patrol
Feb 18, 2002
January was a below average snow month; the most significant feature formed was a rime crust that was deposited Jan. 6. This feature along with wide spread upper level weaknesses developed during the periods of light snowfall and cold weather led to a wide spread avalanche cycle following the Jan. 28-29 storm. Most of these avalanches ran on top of or below the rime crust with faceted snow as a weak layer. Activity continued in the backcountry with the last reported avalanche on Feb. 9. On Feb 14 we had 1" of new snow and strong North winds; there was no activity in the ski area, and nothing reported in the backcountry.
On Feb 17 touring off the Twins at Snowbird had been open for 5 of the last 6 days; only minor avalanche activity had been reported in the Wasatch backcountry since Feb 9. The weather overnight had been clear and winds had been light. Two experienced ski patrollers went up the Twins to check out conditions before opening, these same two patrollers had been up the Twins on Friday Feb. 15, had made an evaluation of conditions and had decided to open access to the ski area boundary. After an eighteen minute hike up the Twins on Sun Feb. 17 the two made a decision to ski the upper slopes in Mary Ellen Gulch. One patrolman traversed down the ridge to the left staying high on the slope, the other patroller skied a couple of turns down the slope that his partner had just traversed when the slope fractured sweeping him over a 150' cliff and onto the slope below. The patroller not caught radioed Hidden Peak within seconds of the release. On Hidden Peak the ski patrol was finishing its morning meeting when the call came in, the time was 8:20am. A hasty search party of four ski patrollers was dispatched by 8:23 they used the boot track to the Twins, an 800 foot climb, as their safe route. Life Flight was notified at 08:25 and had a ship in the canyon by 8:46. The victim was quickly located on the surface of the debris and was in stable condition, but suffering from several injuries. A second party of three ski patrollers with medical gear was dispatched at 08:30; they carried oxygen, backboard, and a SKED. They were dispatched up the Twins on foot; at the time the arrival of the helicopter was uncertain. The hasty search party arrived at the scene at 8:42 followed closely by the second team with medical gear. The victim was treated for possible internal injuries, shock, and broken arms. The helicopter was directed to the accident scene and landed 200' below the site at 8:52. The victim was placed on a backboard, loaded into the SKED, and transported to the LZ arriving at 9:06. By 9:13 the ship was in the air bound to LDS Hospital.
The avalanche HS-AS-3 was in two parts, the first part being the upper slope that caught the patroller, and a second slope that was below and slightly left of the rockband. The snow coming over the rockband triggered this lower slope. The starting elevation was 11,400 feet and had an aspect of 130 deg. and an angle of 35-42 deg. The upper slope had a crown of 1'-4' deep, was 120' wide and had a vertical fall of 600'. This avalanche ran on top of the rime crust from Jan. 6 and had a weak layer of small facets. The slab was one finger in hardness. Several interesting facts were observed. There had been a new layer of wind slab up to 18" deep deposited during the north wind event of Feb. 14. The bed surface; the old rime crust, was no longer icy but very slick and smooth. The faceted weak layer was deceptively thin and didn't appear all that weak. Looking at this profile we were wondering why this slope avalanched.
This was a very ugly avalanche; the size of the slide and the cliffs it runs over make it unlikely anyone caught by this avalanche would survive. The victim was extremely lucky. The party was very experienced and used good procedures the entire time. Maybe high angle slopes over rock bands should be avoided in the backcountry. Considering the remote location of the accident the rescue was very quick and efficient. The main lesson to learn is that people traveling in avalanche terrain should always expect and plan for the unexpected.