Detailed Accident Report

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Date: 2001-04-04
Submitted By: Ron Johnson; GNFAC
Place: Truman Gulch West side of Bridger Range
State: MT
Country: USA
Summary: 2 skiers caught, carried, partially buried. 1 injured.

TRUMAN GULCH AVALANCHE ACCIDENT

SYNOPSIS:

Two skiers were caught in an avalanche on the west side of the Bridger

Range north of Bozeman, Montana. The incident resulted in one skier

being seriously injured and required that he be evacuated by helicopter.

The avalanche released on a wind loaded slope with a northwest aspect

and a slope angle of 37 degrees. The crown was 2 ? 3 feet deep and 500

feet in width. The avalanche ran approximately 1000 vertical feet with

an a-angle of 28 degrees. US classification of the avalanche is

SS-4-AS-O.

WEATHER:

During the 10 days prior to the avalanche, approximately 4.3 inches of

water fell in the Bridger Range. Most the snow was deposited in smaller

increments, however 9 inches of new snow at 14% density (1.3? water)

fell at Bridger Bowl Ski Area during the early hours of April 3. Ridge

top winds averaged 20 mph with gusts to 40 out the southwest the day of

the storm. Many natural avalanches occurred on steep wind loaded slopes

on April 3, but all were confined to the new snow.

AVALANCHE:

On the afternoon of April 4th, 21-year-old Mike Nujent and his partner

Nick Baldwin exited the Bridger Bowl Ski Area and proceeded to a

northwest-facing slope with plans to film some ski footage. The slope is

comprised of two broad gullies, the tops of which had been wind loaded

by southerly winds from the previous two days. Nick skied first and

triggered a small avalanche approximately 1 foot deep and 50 feet wide

as he crossed into the northern most gully. He then proceeded to ski

approximately 500 vertical feet and stopped on the small, thinly treed

ridge that divides the two gullies. At this point, Nick removed his ski

gear and set up a camera and tripod, preparing to film Mike as he skied

the southern gully. Mike entered the gully on the wind-loaded southern

flank. This released an avalanche approximately 18 inches deep and 100

ft wide. Within a short distance, the weight of this slide caused the

avalanche to step down through two more layers to its full depth of

approximately 3 feet. This full depth fracture propagated across the

ridge and into the gully that Nick had already skied.

Realizing he was in an avalanche, Mike pointed his skies down the fall

line in an attempt to outrun the slide. He was overtaken and knocked off

his feet at which point he was enveloped in the flow. Approximately 800

vertical feet from where he initiated the avalanche, Mike struck a tree

and came to a stop. The avalanche continued on, leaving him only

partially buried. The collision fractured the femur and pelvis of his

right leg.

Nick saw the avalanche develop through the viewfinder of his camera and

grabbed a tree just uphill of his location. He was able to hang on as

the avalanche passed over him and ended up unburied. He quickly located

Mike and then ? having lost all his gear in the avalanche ? started the

long boot back to the ridge in an effort to locate help. Approximately 2

hours after the slide was triggered, Nick was able to make contact with

the Bridger Bowl Ski Patrol.

RESCUE:

The Bridger Ski Patrol received notification of the incident at

approximately 1700 hours. Two members of the patrol were dispatched to

an equipment cache on the ridge above the avalanche site to provide

rescue gear and a communications relay. Two other patrollers descended

the avalanche path to assist in the extraction. A fifth patroller was

flown directly to the site by helicopter in order to stabilize the

injured party and assess equipment needs. Rescue gear was long-lined to

the site by helicopter. The patient was packaged and short hauled to a

waiting ambulance at the Bridger Bowl staging area.

SNOWPACK:

The wind blown snow from April 3rd was deposited on a thin layer of

low-density snow that had fallen the previous day. The added weight of a

skier was enough to trigger a slide in this upper layer wind slab. By

itself, this would not have been a particularly large avalanche, but

continuous loading from the past 10 days had added enough weight to the

snowpack to activate a layer of near-surface-facets buried 3 feet deep

and sitting on an ice crust. The initial avalanche slid approximately

200 ft before stepping down to the full-depth running surface.

If you have questions about this incident please feel free to email me at: sschmidt@fs.fed.us.

Scott Schmidt, Avalanche Specialist

Gallatin National Forest Avalanche Center