Avalanche
Accident Report
Forest
Service Utah Avalanche Center
December
26, 2008
Little
Water Peak – Four foot burial and miraculous recovery.
Accident
Report by Bruce Tremper
Location:
Northwest
side of Little Water Peak along the Big Cottonwood – Mill Creek
ridgeline. The area is locally known as Shangri-La.
Accident
and Rescue Summary:
A group
of four very experienced, backcountry skiers were out for a tour in very
conservative terrain because the Forest Service Utah Avalanche Center had
issued an avalanche warning for the day and rated the danger as High on most
slopes. Three people (Matt Clevenger, Dan Steenblik and Paul Sharpentier
ran into their acquaintance, Tom Diegel, who was skiing alone. The three suggested that they go to
Shangra-La and Tom accompanied them. They went to terrain with gladed trees
that is almost entirely less than 30 degrees in steepness. On their climbing
track back up, they came to a small opening in the trees that was 29 degrees in
steepness, which is not generally steep enough to slide in most conditions.
Tom was
breaking trail and he noticed that the slope above them was slightly
steeper. So, to be safe, they
decided to cross it one at a time. Tom and Paul crossed the slope and
waited on the other side. When the third person, Matt Clevenger, began to
cross, the entire slope collapsed and it slid, very slowly, down into some trees,
catching both Matt and Dan, who were carried only about 10-15 feet down the
slope where Matt was pushed up against a large fir tree and buried with his head between 4 and 6 feet deep
(6 feet on the uphill side and 4 feet on the downhill side) and Paul was buried
to his knees just a few feet away. Matt was buried upright but hunched
over. The rest of the avalanche went only about 100 feet down slope before
coming to a stop on the gentle terrain.
Luckily,
Tom Diegel regularly practices with his beacon and often practices deep
burials. He located the victim in about two minutes in deep debris piled
up against trees. He probed, hit him and organized the others and they
began to dig. He knew it was a deep burial so two of them dug while
the third helped move snow away from the hole. Since the victim was
pushed up against a large, fir tree, they could not dig in from the downhill
side so they dug straight down from above and they also had trouble digging
through all the branches. They uncovered MattŐs face in about six minutes
but it could have been as long as 10 minutes from the time of burial. Matt
groaned when they uncovered his face, but he was blue-faced and unresponsive.
Tom gave him some rescue breaths and Matt began to breathe again. They
extricated him from the snow and Matt completely recovered but was cold.
He was able to ski out on his own and even climb to the top of the ridge to
descend the other side to the car. It was a miraculous recovery
considering the depth of the burial.
See a video of my interview of three of the four party members two days
after the rescue. (posted
on the Utah Avalanche Center channel at You Tube).
Terrain
Summary:
The
area locally known as Shangri-La is just on the north side of the Big
Cottonwood Canyon – Mill Creek divide and just north of Little Water
Peak. It is an area of gladed aspens and fir with gentle slopes.
ItŐs often a place where backcountry skiers go during high danger
conditions. I investigated the site two days later and Tom Kimbrough, a
retired forecaster for the Utah Avalanche Center investigated the slope the day
after. We both measured the slope
to be northwest facing, about 9200 feet, 29 degrees where their climbing track
crossed the slope but it steepened to an average of 32 degrees at the crown
with a small section of 33 degrees.
The snow on the steeper upper section moved about 100 feet down the
slope and pushed the snow on the lower, gentler section and it was buckled up
like pushing a blanket. Since the
slope was so gentle, the snow did not move very far.
If looking from the bottom, the party crossed the slope from left to right. Matt and Dan stood on the left flank at
the time of the fracture while Tom and Paul stood on the right flank. The crown was about 80 feet above them
and the victims were carried about 15 feet into a tree.
Avalanche
Data:
The
avalanche averaged 4 feet (120 cm) deep and was 100 feet wide. It slid about
400 feet down the slope loosing about 150 vertical feet.
The
slab was composed of snow that fell over the past two weeks. The weak
layer is an extremely fragile layer of faceted snow growing both on top of and
below a prominent rain crust about 30 cm (a foot) above the ground. See snow profile. Widespread avalanche activity had been
occurring on that layer for the past week. An avalanche warning was in
effect and the avalanche danger was rated as High. On my snow profiles along the crown, flanks and adjacent
slopes, it was difficult to isolate a column of snow on the fragile layer. Snow
Profile
Weather
and Avalanche History: (Seasonal
Weather Charts)
Snow
started to pile up in early November but a month of dry weather followed, which
metamorphosed all of the snowpack to very weak, depth hoar. Around
Thanksgiving, rain formed a clear and prominent crust on the snow surface throughout
most of the mountains of northern Utah. As more light density snow fell, finer-grained,
faceted snow formed on top of the rain crust as well. A series of storms
since December 13th began to overload these layers, reaching a
crescendo the day previous to the accident when over a foot of dense snow fell
accompanied by very strong, southwesterly winds and warm temperatures. An
additional foot of light powder fell overnight, which covered up all the older,
denser snow. This Christmas storm initiated a widespread avalanche cycle
on these buried weak layers.
Comments
This story has a happy ending, first because the party was knowledgeable and experienced enough to choose very conservative terrain and carry proper rescue gear, and second, because Tom had been regularly practicing with his beacon using realistic scenarios, such as deep burials with a beacon in a buried pack. He is an accomplished outdoorsman with extensive experience, so he is used to dealing with high-risk situations and training for them. He indicated that his regular practice doing realistic drills with deep burials probably made the critical difference. He did not have to think, and he could quickly spring into action with little wasted effort. In addition, he is one of the most aerobically fit outdoor athletes in Utah and regularly places very high in competitions such as rondenee rally, running and bicycle races. Paul and Dan are also very fit outdoorsmen and contributed significantly to the rescue efforts. In short, because of their training and team effort, one person is alive in a story that could easily have an unhappy ending.
