Avalanche claims one
Danger is 'considerable'
by Nathaniel Smith
The Times-Independent
Jan 31, 2019 | 2726 views | 0 0 comments | 99 99 recommendations | email to a friend | print
Avalanche
This graphic shows the location of all the snowmobilers in Dark Canyon on the east side of the La Sal Mountains when a fatal avalanche occurred Friday. The number 4 represents the victim, Scott Pehrson, Jr. 		  Photo courtesy of the USFS Utah Avalanche Center
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A massive avalanche in the La Sal Mountains claimed the life of a Monticello man on the afternoon of Friday, Jan. 25. Search and rescue crews were able to recover the body the next day after an exhaustive search that involved using an explosive to trigger another avalanche.

Scott Pehrson, Jr., 39, was snowmobiling in Dark Canyon on the eastern side of the La Sal Mountains when he was buried by the avalanche. He visited the remote yet popular snowmobiling destination with a group of seven other Monticello-area residents.

A report issued by Eric Trenbeath of the Utah Avalanche Center detailed the tragic incident and the ensuing recovery effort. Around 4 p.m. on Friday, one member of the party drove his snowmobile up to a high pass between Mount Mellenthin and a subpeak of Laurel Mountain at an elevation of 11,974 feet. Three other members of the party followed the first rider up the steep slope, with Pehrson taking a straight line up a narrow gully, according to the report.

The lead rider “reported feeling a collapse as he looked down from the pass,” reads the report. He saw a hard slab of snow fail and propagate across the entire northeast aspect of Laurel Mountain. The report estimates that the avalanche was approximately 900 feet wide and ran down the slope for a vertical distance of 1,500 feet. Heading up the gully, Pehrson was met by the full force of the avalanche about 600 feet below where the slide initiated.

Once the avalanche stopped and the party regrouped, they realized a rider was missing. They began to search and were able to locate the destroyed snowmobile and helmet near the toe of the debris, but they could not find Pehrson. According to the report, the group carried “three beacons, two shovels and one probe.” They believed Pehrson was also wearing a beacon and “reported hearing a ‘ping.’” One rider left the scene to call 911. San Juan County dispatched a Classic Air Medical helicopter, but darkness soon fell, and the search had to be called off until the following morning.

The next day, the search brought together various entities to form a sizeable group of professionals and volunteers under the direction of incident commander Alan Freestone, chief deputy for the San Juan County Sheriff’s Office. The San Juan Record reported that approximately 65 residents of Grand and San Juan counties volunteered for the search and rescue effort.

Worried the search effort could cause another avalanche, Trenbeath and Scott Sole of Grand County’s Winter Rescue Team were taken in a Classic Air helicopter to conduct an aerial reconnaissance at 7 a.m. on Saturday morning. They determined “explosives were necessary to make the scene safe,” said Trenbeath. Members from San Juan and Grand County Search and Rescue teams were on site, but they had to wait to commence the ground-level search until the avalanche mitigation work was completed.

The Utah Department of Public Safety provided another helicopter to shuttle people in and out and search the avalanche debris pile from the air, according to Trenbeath. While the DPS helicopter searched using specialized devices that can detect signals from avalanche beacons and RECCO reflecting chips, explosives were being assembled in Salt Lake City.

Trenbeath said that Wasatch Powderbird Guides, a backcountry helicopter skiing operation, donated the first hour of their flight time and carried out all the explosive work. He noted it took only a single two-pound explosive to trigger another giant avalanche, showing the sensitive state of the snowpack. The explosive-triggered avalanche was “almost an identical slide” to the first, said Trenbeath, adding that the second slope’s steepness, elevation and aspect were all similar. “If people go out there right now, they still have to worry about [triggering an avalanche]. We want people to stay off steep, north-facing terrain for a while,” Trenbeath emphasized.

After the bombardier team completed the avalanche mitigation work around 2:30 p.m., professional dog teams from Wasatch Backcountry Rescue, Alta and Park City ski patrols were inserted at the place where Pehrson was last seen. The second dog alerted “near the toe of the debris” at 4:20 p.m., then 15 minutes later there was a positive probe strike. The body was buried beneath two to three feet of snow, about 150 feet uphill from where the snowmobile was found. “He was not wearing a beacon, but had one turned off in his pack,” the report notes. Trenbeath said his La Sal Mountain forecast for the day of the avalanche rated the danger as “considerable,” meaning human-triggered avalanches were likely, particularly on north-facing slopes on mid and upper elevation terrain. His forecast recommended “sticking to wind-sheltered, low-angle terrain and meadows.”

Trenbeath’s report said, “We aim to learn from accidents like this and in no way intend to point fingers at victims.” There are numerous lessons to be gleaned from this awful incident. Trenbeath said he and his colleagues at the avalanche center “want people to know that they can have fun in the backcountry,” but preparedness and knowledge of avalanche safety procedures are essential. “There are times that you can go big, and there are times that you need to dial it back… in terms of how steep of slope that you’re willing to play on,” Trenbeath said. He acknowledged how leaving the flats to get on steep slopes appeals to experienced skiers and snowmobilers but stressed that extra caution must be exercised.

“Avalanche terrain is anything steeper than 30 degrees,” Trenbeath pointed out, adding that “prime slope angle for an avalanche is 35 degrees,” which is about the average steepness of an “expert or black diamond run at a ski resort.”

For those interested in exploring the backcountry, Trenbeath recommended the avalanche center’s Backcountry 101 avalanche course scheduled for Feb. 8 and 9.

The course costs $150 and includes “a three-hour classroom session at night and a full day out in the field the next day,” Trenbeath said. Participants will learn vital skills such as how to recognize avalanche terrain, identify avalanche problem types and use rescue equipment. They will also practice digging a pit in the snow to analyze its stability. Learning to notice signs of instability like “cracking in the snow surface, ‘whumphing’ or collapsing, and heavy wind loading” would be another element of the course, said Trenbeath.

The course will be non-motorized because snowmobilers and skiers move at such different paces. Trenbeath said the avalanche center “would love” to organize a class for motorized users, if there is enough interest in the area.

Having the necessary avalanche safety equipment like beacons and probes is only the first step in preparedness. One must also “know how to use it,” said Trenbeath. Fortunately, there is a beacon training park at the Geyser Pass trailhead where people can practice finding beacons before they end up in an emergency situation.

There is also the necessity to check the forecast before heading into the backcountry, explained Trenbeath. The Utah Avalanche Center regularly provides a detailed forecast that will help backcountry travelers figure out which slopes are safe for traversal given the current conditions. Forecasts for the La Sal Mountains can be found at https://utahavalanchecenter.org/forecast/moab.

Trenbeath described how the snow conditions of the La Sal Mountains led to the avalanche. A large amount of snow fell in October, which then sat on the ground and crusted over. More snow fell in early December, followed by three dry weeks. During the dry period, the December snow “turned into a loose, weak, sugary layer” that is referred to as a “persistent weak layer,” said Trenbeath. “Since Christmas Eve, several storms have placed more than four feet of snow on top of that persistent weak layer,” he added.

Avalanches in the La Sal Mountains have been breaking three to four feet down to the persistent weak layer and sliding, said Trenbeath. The fatal avalanche on Friday fit that description exactly. He explained, “You get a big load of new snow and it collapses that weak layer underneath. If that happens on a steep slope, it slides off.”

The conditions led to “two widespread natural avalanche cycles, prompted two avalanche warnings and the danger has been considerable almost for the entire month [of January],” said Trenbeath. Avalanche warnings are when danger is the highest and “widespread natural avalanche activity is occurring and storm intensity is the greatest… the pack underneath is groaning under the stress of the new snow stacking on top,” Trenbeath said. However, that does not mean avalanches cannot happen at other times, as Friday’s tragedy proved. While “considerable” is only in the third of the five avalanche danger ratings, it should still be taken as a warning. “Unfortunately, because ‘considerable’ is right in the middle, people are starting to get the impression that is not that dangerous… but [it means] human-triggered avalanches are likely,” Trenbeath lamented.

The tragedy resulted in an immediate outpouring of support. “Our deepest sympathies continue to go out to the family and friends of local Monticello resident, Scott Pehrson, Jr. who was killed in the accident,” said the Utah Avalanche Center.

“Pehrson is survived by his wife Lashaye, four children, four siblings, parents Scott and Colleen Pehrson and a large extended group of grieving family and friends,” reported the San Juan Record. A Go Fund Me campaign has been established for Pehrson’s family, and it can be found at https://www.gofundme.com/in-memory-of-scott-pehrson.


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