Detailed Accident Report

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Date: 1999-04-02
Submitted By: B. Engelhard, UAFC-Logan
Place: Wood Camp Hollow, Logan Canyon
State: UT
Country: USA
Summary: 1 skier caught

Accident Report -Utah Avalanche Forecast Center-Logan

Ham Hollow Avalanche Incident

Friday April 2nd, 1999

Bear River Range, Wasatch-Cache National Forest

Report Submitted by: B. Engelhard, UAFC-Logan

Avalanche Location: Wood Camp Hollow, Logan Canyon, Utah

Date: 04/02/99

Time: 16:30

Type: WS

Crown Height: 7 inches

Crown Width: 25 feet

Size (width): 90 feet

Maximum Debris Depth: 9 feet

Aspect: 205 degrees (SSW)

Vertical Drop: 900 feet

Starting Zone Elevation: 8000 feet

Starting Zone Slope Angle: 38 degrees

Bed Surface: M/F crust (from mid March sustained high pressure)

Weak Layer: Saturated interface of wet slab with old M/F crust

Trigger: Human (skier)

Accident Summary

Events Leading up to the Accident:

From the March 10th through March 26th, 1999 the mountains in northern Utah received no snow and maintained constant melt/freeze cycles that created ideal corn conditions. Supportable crusts were found on east, south, and west aspects. The snowpack had consolidated very well. Then from March 26th to April 2nd the mountains received at least 32 inches of new snow with 1.7 inches of water weight. The snow came in two separate storm cycles, one dropping 9 inches in three days and the other dropping 23 inches in two days. These storm totals were registered at the UAFC-Logan, Beaver Mt. Study Plot; the amounts from this study plot usually reflect up to 80% of the total snowfall found in the highest precipitation locations in the Bear River Range. Throughout these two events the weather remained unseasonably cool with mostly cloudy skies. Both events came in with the old snow surface frozen solid and the interface with the new snow did not show good signs of bonding. Significant greenhouse warming occurred during the afternoon of the 1st settling the new snow from the previous day and that snow settled to 3 inches of spongy melt/freeze material. Then overnight it snowed another 8 inches of 7% density snow. The morning of the incident was mostly cloudy with high thick clouds that were not allowing greenhouse warming till 11:30 hours. The party skied one lap on the suspect slope at 10:45 hours, only going 2/3 way up the 1400 foot mostly SW facing slope called Ham Hollow in the Wood Camp Hollow Drainage. The snow at that time was cold powder snow on a slick supportable M/F crust with the spongy M/F from the solar heating from the 1st acting as an interface at the old M/F crust; but upon returning up their skin ascent and continuing up the slope, the sun came out intensely at 11:30 hours and the snow immediately became damp. Three members of the party skied the same slope from the upper reaches down to the top of their first run and the ventured back up the skin ascent. The other member of the party elected to ski an east-northeast slope on the other side of the ridge to avoid the damp snow. The party reunited and continued up the ridge, skied another north-northeast slope before returning to the original slope. Upon returning to the initial slope the party descended slopes above the slope of incident making tracks in very wet snow that had received on and off sunshine for the past three hours. At the top of the slope of incident the group commented that the snow was very wet and that the party should be careful on steep roll overs as the slick crust would surely work as a good bed surface. They noticed that there was someone down on the old skin track ascending and the group waited to ski until the unidentified person was clear of the intended gully. The first skier skied down to the first obvious rollover and traversed slightly to his left out of the incident gully, then proceeded to ski for 400 vertical feet on a minor nose type ridge line. He stopped and noticed that he had released a small wet point release that was gaining momentum. He immediately asked the unidentified climber if she was alone, and after her positive response the two watched the wet slide continue past them and go another 400 feet below in the gully to skiers left. The three remaining persons on the ridge acknowledged that he was ok and then the victim proceeded to ski. The first skier communicated at least twice that he was ok, but before he got a noticeable response he heard the victim shouting he was in a slide.

Accident Account: After making 6 turns the victim noticed the snow he was on was moving all around him and that his skis were being overtaken and unmanageable. The victim proceeded to be swept off his feet. The victim struggled to stay in control only to be taken faster in the quickening debris flow. After sliding 150 feet the victim came into view 100 feet above the first skier(who was on a sub ridge to skiers left of the gully. He and the victim communicated by yelling, and he told the victim to move to his left. The victim swam and scooted (with skis on) to his left banging into a tree on the left flank of the slide, this slowed his momentum greatly and he was then able to get out of the slide another 50 feet lower.

Rescue: Self

Other Pertinent Information: Bed surface was very slick and hard prior to the slide and actually got glazed and harder with the motion of the slide. It was very critical that the victim was experienced and strong enough to fight his way out of the slide. A large 7 foot secondary wave came moments after the victim got out of the slide.

Victim(s): White male, 38 years old, very experienced back country skier.

Other Party Members: One very experienced white male in early 40s and two other back country skiers both white males in 30's with moderate back country training and experience

Condition of the Victim:

Very good, considering circumstances, 3 inch laceration to the left cheek, blood blister on jaw and a little cut inside his mouth, victim skied out under his own power without a problem.

Avalanche Danger from the UAFC-Logan Advisory:

Considerable hazard of avalanches on slopes steeper than 35 degrees affected by solar heating.

Actual Weather Conditions:

Partly cloudy, highs at 8000 feet in the mid 20's, no significant winds, excellent conditions for greenhouse radiation of all slopes, aspects and elevations except northerly slopes with slope angles 30 degrees and greater, minimal direct solar radiation but with the seasonal intensity of the sun solar warming was a factor.

Avalanche Path Characteristics:

Known wet avalanche gully with walls at least 10 feet higher on the sides, gully 120' in width throughout it's upper length funneling in between two large rock formations and fanning out into lower angle terrain.