The next time you’re told to pull over at a designated waiting area on a wintry mountain road that’s just been upholstered in snow, look on the bright side. The reason for your stop is likely because a highway avalanche control crew is in action to keep you from getting squashed by a sliding wall of snow.
“There’s no point getting annoyed when you see the barriers come down to close the road,” says Olivia Sofer, a ski guide who divides her time between Canmore, Alta., and an off-grid straw-bale cottage in Golden, B.C., within easy reach of untracked ski terrain. The gates, she explains, are for drivers’ own good. Gates block vehicles from entering places such as Kootenay Pass on B.C.’s Hwy. 3 and Rogers Pass on the Trans-Canada Highway. Both sections of road see some 3,000 cars and trucks move through per day during the week; at Rogers Pass that number rises to 5,000 in winter, 10,000 in summer. They’re also two of the most challenging stretches of highway in the country, thanks to the traffic volume and the frequency of the avalanches. At Kootenay Pass, for instance, there are 47 known avalanche paths (where slides tend to occur), some of which reach the highway. Olivia is philosophical: “Just sit back while the avy control teams do their job. Soon enough, it’s safe to travel through.”
Avalanches come roaring down the mountainsides during periods of heavy snowfall or storm cycles, when the new snow landing on the surface is not bonding to the existing surface, or when the weight of the new snow is more than the existing snowpack can support. Slides can start on slope angles of anywhere from 15° to 45°—as steep or steeper than a double black-diamond ski run. They can be small enough that no one ever notices. But sometimes they attain speeds of up to 300 km/h, ripping trees with them and burying roads and other infrastructure. “Using weather and snowpack data, we can predict and minimize the risk of an avalanche hitting the road and forcing a closure or causing personal injury,” says Robb Andersen, the senior manager of the B.C. Ministry of Transportation and Infrastructure’s Avalanche and Weather Programs. Last winter, a crew of avalanche technicians spent most of the season at their office, a building at the Kootenay Summit, at the highest point (1,775 m) on Hwy. 3, between Salmo and Creston. It has beds, showers, and a kitchen “because you never know how long you’re going to be stuck there for,” explains Andersen. The Pass received nearly 15 metres of snowfall last year, up from the 9.8-metre average (in part due to it being a La Niña year), making for a busier-than-usual season, which lasted into May.
Starting at 6 a.m., the weather technicians tap into the province’s network of 220 remote weather stations and use the collected data to analyze what type (dry and fluffy vs. moist and heavy) and amount of precipitation is coming their way, as well as the temperature of the air and speed and direction of the wind. The team combines this information with snowpack data they gather by digging—by hand, with a shovel—a one- to four-metre deep pit to reveal different layers of snow over the season, noting strata that might have weakened and could give way under fresh snow. Analyzing all of this data allows them to assess the risk of an avalanche, from 1 (low) to 5 (very high). If they find a weak layer in the snowpack and lots of heavy, moisture-laden snow falls on top, there is cause for concern. As soon as they think there’s going to be an avalanche that will affect the highway, they close the road.
“If we can’t fly up there and trigger the slide itself, then we have no other option than to keep the road closed overnight until it is safe to do avalanche control,” explains Andersen. Sometimes, a change in weather—say it gets colder overnight, or if it rains and then freezes—will improve conditions.
When there’s no time to wait for nature to do its thing, Andersen says, “we can try to deliberately trigger avalanches onto the highway during low-traffic periods and have those cleaned up in time for the daytime traffic flow to start.” When they need to trigger a slide, there are a number of ways to do it. First, they sweep the highway by driving the closed stretch to ensure that there are no vehicles on the road. Then Andersen’s team can send up members of their crew in helicopters to drop explosives in the start zone of known avalanche paths, setting off a slide and thus removing the risk. “But this method is limited, because the helicopter can’t fly in low visibility, during a storm, or if it’s dark outside. So the highway stays closed either until conditions improve or it’s daylight, when we can resume control work,” he says.
Once the avalanche has been released, they send in a crew in large loaders and excavators. The cleanup can take anywhere from an hour up to a day or more, depending on the size of the slide.
Another strategy, only in use at the Kootenay Pass since 1993, is a remote avalanche control system, called Gazex, that can trigger slides at optimal times—when there’s less traffic and when timing is critical—or when access is difficult. “Gazex lets us control avalanche risks from anywhere, 24-7,” Andersen explains. With a computer, they set off exploders the team has, in clear weather, placed in the starting zones of the avalanche paths. The detonation triggers a gas explosion—and an avalanche. “It’s like lighting a barbecue with the lid on,” he says. Since Gazex has been in place, it has helped his crew cut closures from 300 hours a year to 100 hours a year.
Over at Rogers Pass in Glacier National Park, avalanche control is run federally, in collaboration between Parks Canada staff and the Canadian Armed Forces, who have a few other weapons in their arsenal. They will sometimes use Gazex and helicopter-dropped explosives, but their primary control method uses two 105-mm Howitzer cannons, each weighing 2,260 kg, about the same as a white rhino. The team can move them to different launch spots along the pass’s 40-km corridor—regardless of weather and visibility—so control work can take place around the clock. They have also installed brand new metal snow nets that, like a catcher’s mitt set perpendicular to the slope high up in the avalanche start zones, trap snow before it can move down the mountain. Rogers Pass is a swath of highway with 134 avalanche paths that meet the road, where a chunk of the 12-m average annual snowfall could tumble down from the surrounding mountains at any moment—a fact that makes road closures look pretty appealing.
There are ways of getting around the delay, though. “I rarely get stuck on the highway waiting for avalanche control,” says Olivia Sofer. She plans ahead, checking the DriveBC and Alberta Motorists Association websites beforehand and at stops on her drive if there’s a cell signal. She also uses InfoEx, a resource that ski guides can get through their association membership. You can get forecasts, photos, and avalanche, snowpack, weather, and incident reports from Avalanche Canada’s Mountain Information Network, a publicly available data-sharing service.
She also suggests the obvious: finding an alternate route. Bypasses for Kootenay Pass exist, but at Rogers Pass, there is no alternative—if you get stuck, you’re stuck. Just in case, Olivia always keeps a warm blanket, extra clothes, food, water, and a shovel in her car, as well as a full tank of gas. “At Rogers Pass, there’s no food or coffee,” she says, “so if you do get stranded, you need to be prepared.”