Shaken But Not Stirred
by Peter Shelton
Jan 14, 2010 | 1884 views | 0 0 comments | 18 18 recommendations | email to a friend | print
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On Friday, January 8, 2010, Helitrax dropped a group of skiers off on the shoulder of Pilot Knob for a run into Waterfall Canyon. It was a placid day: blue sky, very little wind. The powder was old and settled, wind-affected in places; it hadn’t snowed in a while.

Long-time Ophirian Mark Rikkers was the guide. He decided, along with the other guides and the dispatcher, to ski Poster Pitch. His would be the first commercial group down that run this season. But it was not the first time it had been skied. In fact, earlier that morning, a cadre of “heli-hitchers,” including Helitrax founding members Mike Friedman and Mark Frankmann, had dug a snow pit there, before themselves skiing down Poster Pitch and thence to Ophir. Their pit revealed “moderate” weakness in the snowpack, a totally expectable, if typically ambiguous hazard rating for the San Juans in January.

Using standard protocol, Rikkers had his clients ski the first pitch one at a time. One of them, an Australian man, stopped off to the side to take a picture of his wife skiing by. Hers was the eighth track marking the hill. Then, as she passed him, 30 feet away, the snow above and all around the man fractured to the ground and swept him down the fall line.

Rikkers was moving almost as soon as the Aussi man was. “I was watching him the whole way, skiing and talking on the radio. He was never buried. He was never under the snow. He lost both skis, but he ended up on top. I did help him dig one arm out.”

Rikkers called in the helicopter and stomped out a landing pad below the debris, which was littered with La-Z-Boy-sized chunks of hard slab. They flew the man down to Telluride, where he was treated for a slight ankle injury, perhaps an Achilles strain. In classic Aussi good humor, he declared himself “shaken but not stirred.”

Everybody at Helitrax was shaken. Theirs is an exemplary safety record over 28 years of skiing in arguably the trickiest snowpack in North America. In fact, their only serious accident happened in 1994, and it didn’t involve an avalanche. That was the infamous Christie Brinkley crash, when the helicopter with Mrs. Billy Joel aboard went down, mysteriously and hard, on Pilot Knob just the other side of the ridge from Poster Pitch.

Only two clients have ever tangled with avalanches. The first incident happened up in Hope Lake Basin on a run they now call Lucky Bob’s, after a customer who triggered a slide but managed to ski safely out to the side. Poster Pitch is the second, and the only time someone has taken a ride.

Helitrax director Aaron Rodriguez sent email word out to the snow-and-avalanche community that same night, with photos of the scene, and Rikkers later put together detailed diagrams and analysis. They cancelled skiing for the next day and flew up to do a fracture-line profile on the slide. They also threw 24 three-pound explosives into likely start zones with no results whatsoever.

It was clear at the site that the avalanche had been triggered remotely. That is, the pressure of a ski turn (the wife’s) in softer snow off to the side, had caused the nearby hard slab, where her husband was standing, to break free. She wasn’t caught, nor did the snow she was skiing in move.

Senior guide Speed Miller, who has been out on skis almost every winter day these last 28 years, had never seen an avalanche that high on the pitch before. The slope angle at the fracture line was only 29 degrees. Steep enough to slide, obviously, but significantly shallower than the “most common” failure angle of 38 degrees.

“We knew there were little pockets of tension in the snow,” Miller told me. They had, in fact, bombed this very slope a week previous, with a five-pounder, without results. Hard slabs, which form from densely-compacted, wind-driven snow, are notoriously difficult to gauge. They may be hidden under layers of softer snow. They may be stable enough to support Hannibal’s elephants. They may be as brittle as a hair trigger. And they may, as in this case, lurk on only a small portion of a large terrain feature.

“That was one of the lessons we took from the ‘post mortem,’” Rikkers said. “That spatial variability – the idea that you may have a completely different snowpack 20 feet away – is a reality. The other thing is the idea of persistent weaknesses [the slide ran on a layer of old, fragile, faceted grains near the ground]; they are just that, persistent.”

“We were lucky,” Speed mused. “We didn’t get somebody severely injured or buried. Eventually, someone would have hit that sweet spot” – and the results might have been worse.

“Yeah, we dodged a bullet,” Friedman told me. (An occasional guest guide and consultant, Mike is no longer a Helitrax principal.) “It was the perfect wake-up call. It’s a reminder of how complex and amazing snow is. And snow is the most complex element in nature – that is not an understatement. It’s incredibly tricky: A soft slab can propagate into and cause a knife-hard slab to fracture! It continues to teach us lessons.

“One lesson is, history repeats itself. If you’re in the game long enough, it will come around again with the same sense of awe and surprise.”

Peter Shelton's blog is peterhshelton.wordpress.com
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