Men's Journal

By mid-January, Avalanches this winter had already killed 32 people in North America. Photo credit: Natalie Harris

In snow country, the best defense against deadly slides is the blast technician who deliberately sets them off.

By Berit Campion

By mid-January, avalanches this winter had already killed 32 people in North America. While governments and resorts spend millions on avalanche awareness, forecasting, and control, the job of triggering slides to prevent more damage falls to a rare breed of experts: part snow scientists, part explosives specialists, engaged in a war against threats beneath the snow’s pristine surface. Through winter, blasters monitor the snowpack, analyzing the strength of the bonds between layers and identifying weaknesses, eventually bringing down slides to provide safe passage for others. Many do it to conquer fears of close calls or avenge deaths of buried friends. But most do it for the thrill of starting slides. Firemen love fire; avalanche guys love avalanches. When the danger is high, they light the fuse.

Option One: Hand Charges

Alta snow safety director Titus Case is up at 3:30 am. A major storm has dumped snow at the Utah resort, and another is on the way. Before dawn, he and his co-patrollers test stability on all in-bounds slopes before opening to the public. It would be easier if the wind would stop howling and they could actually see. With backpacks full of two-pound explosives, they ski across the High Traverse to Alf’s High Rustler. This black-diamond run was skied the day before, which helped compact the snow, but the Utah Avalanche Center has upgraded the backcountry slide danger to “extreme.” Case yells, “Fire in the hole!” as he lights a charge and tosses it into the run’s 45-degree start zone. Two minutes later it detonates with a whumph! Snow settles around the charge, but no further instability is revealed. They repeat the blast at other susceptible spots, then ski down. The good news is they got first tracks; the bad news is they have other slopes to test. “We go out with prior knowledge of the snowpack and weather and use explosives to test our ideas,” Case says. “But just because we use explosives doesn’t make the slope safe.”

Option Two: Bomb Tram

This fixed cable system delivers larger explosives into known slide zones. Popularized in the Alps, bomb trams ignite charges above pistes, using both air and ground waves to shock the snowpack. Bomb trams are difficult to install and maintain, but they can be used in bad weather, and allow blasters to launch explosives from safe locations. Visibility is nil as Troy Leahey, avalanche forecaster at BC’s Revelstoke Mountain Resort, and co-blaster Gavin Greene climb to the cables across Greely Bowl. They suspend a 27-pound bag of ANFO (ammonium nitrate fuel oil) from the cables, light the fuse, and wheel the explosives out to a distant location they cannot see. Greene checks his watch and covers his ears. The bag explodes: Echoes slam off the rocks, and three feet of snow fractures across the top of the slope and roars downhill. Leahey surveys the damage: a Class 3 slide that would have buried a group of out-of-bounds boarders that he’d warned off the day before. “It’s not a perfect science,” he says, “but we do our best.”

Option Three: Heli-Blasting

As manager of Avalanche and Weather Programs for the BC Ministry of Transportation, Mike Boissonneault and his team control hazards on 1,400 different slide paths affecting more than 700 miles of highway. Their preferred technique is to drop 55-pound bags of primed ANFO out of helicopters. Though limited by weather, heli-blasting is an excellent way to trigger slides in areas otherwise dangerous to access. Boissonneault’s crew collects data in search of snow instability above roads. “We consider terrain and traffic variables, and add a dash of intuition and gut feeling,” he says. Then they send up the A-Star helicopter. Hovering above the slope, the bombardier lights bags of explosives and drops them out the right rear door. The pilot has 140 seconds to maneuver to safety after deploying the first charge. In all but the worst conditions, most avalanche-related road closures are kept to fewer than two hours. “That’s because of the incredible job our crews do,” Boissonneault boasts. “But let’s face it: We’re flying in marginal conditions with the door off. If you like explosives, go join the army. To be an avalanche professional, you need a passion for snow.”

Option Four: Heavy Artillery

If you love 105mm howitzers and massive slides, join the Royal Canadian Horse Artillery and hope to get assigned to Rogers Pass. Located in BC’s Glacier National Park, the narrow pass has deadly slide zones above the Trans-Canada Highway, the country’s main east-west artery — naturally, it’s home to the largest mobile avalanche control program in the world. Its tried-and-true 1950s howitzers have a range of seven miles and work regardless of conditions or visibility. From his desk, which looks up at one of the most dangerous of the 144 slide paths he controls, senior avalanche officer Bruce McMahon pores over data. Team members radio in: The four feet of new storm snow atop the weak faceted layer has slabbed up, producing easy failures all the way down to the early December rain layer. McMahon makes the decision to shut the highway and meets the RCHA crew at a gun platform below a snow bridge on the eastern side of the pass. They sight on the first target: a steep, rocky area 3,500 feet above the valley, near where a grizzly bear hibernates. “We’re aware of him,” McMahon says. “Every spring, he crawls out of his den.” Troops load the round, a high-explosive projectile with a point-detonating fuse, and fire it from the barrel. Seconds later a white cloud erupts in the target zone, then snow rumbles down the slope. After other controlled slides, the highway is smothered — and stays closed for a costly 27 hours. “It’s nice the enemy doesn’t shoot back,” McMahon says. “But you have to be careful.”

How an avalanche starts

Snow accumulates in layers reflecting storm cycles. As in a multitiered cake, some layers are thick and fluffy, others dense and thin. And icing between them can prevent bonding. When a storm deposits heavy snow above a weaker layer, it creates instability that’s magnified by wind, temperature, aspect (slope direction), and terrain. Additional snow or added stress to a 35-to-45-degree slope will cause it to fail. The most dangerous are slab avalanches, which occur when snow fractures across a slope and then gathers mass and velocity as it tumbles downhill, reaching speeds of 120 mph.

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