Snowbound: What to do About Avalanches

Each winter, the safety of thousands of drivers traveling over the state’s mountain passes are in the hands of a few skilled pros. These experts spend their days analyzing snow and weather conditions—and deciding when the time and conditions are ripe for avalanches, and what to do about them

One dark night last January, retired Boeing engineer Dan Osborne pulled his van onto I-90 after dropping off his son, a ski instructor, at Snoqualmie Pass for the week. As he began the trek home to Bremerton, he squinted into the pools of light cast by his headlights onto the highway. It was, as Osborne later remembers, “raining cats and dogs, really coming down.” He was just leaving the pass, at about milepost 50, when mixed in with the rain, Osborne’s headlights illuminated a swirl of snow blowing across the road. No stranger to mountain driving, he didn’t view blowing snow as a problem.

But as Osborne approached the plume, his car suddenly slammed into a wall of snow. Before he could register what had happened, his face was in the airbag. Snow, slush and ice exploded through a window in the van. The hood popped open from the impact, and snow and debris packed the engine compartment. The blowing snow turned out to be an avalanche.

Osborne shakily unfastened his seat belt and managed to clamber over the seats to exit via the rear doors of the car—the only ones not blocked by snow. “I didn’t have time to be scared,” remembers Osborne, who escaped safely.

Avalanches, with enormous destructive potential, are among the most serious winter hazards in mountainous terrain. Each year, backcountry skiers and other recreationists are caught in avalanches—death is not an uncommon outcome. They occur when the stresses on a quantity of snow overcome the forces adhering the snow to a slope, which can be caused by changing conditions. Within five seconds of releasing, they can reach 60–80 miles per hour; when the snow finally stops, it immediately sets as densely as concrete.

In Washington, it’s relatively rare for uncontrolled avalanches to tear across the state’s mountain highways, in large part because of the work of avalanche controllers and forecasters who work for the Washington State Department of Transportation (WSDOT). Six of these individuals (two full-time and four seasonal employees) cover the South Central Region that includes I-90 and Chinook Pass, toiling around the clock to keep Mother Nature at bay.

Among them is John Stimberis, an athletic 40-year-old with twinkling eyes and ruddy cheeks; he’s the swing-shift WSDOT avalanche forecasting supervisor for the South Central Region at Snoqualmie Pass.

When Osborne’s van slammed into the avalanche, Stimberis had been working for several days at the pass without going home. All six members of the avalanche control crew had stayed to keep up with the heavy rains and unstable snowpack. After three days, he was finally heading home to Ellensburg. Just as he arrived, he received a call from the Snoqualmie dispatch, reporting that an unusual avalanche of slush, snow, water and debris caused by the high rains had hit I-90, and a van was caught. Still on the phone, Stimberis jumped back in his truck and turned it westward toward the pass.

WSDOT estimates that 27,000 vehicles, 6,500 of which are commercial trucks, pass over Snoqualmie Pass on I-90 and under its avalanche paths every day. The number of vehicles grows at a rate of 2.1 percent per year. The dedicated team of avalanche forecasters and controllers has brought the average number of avalanches hitting the highway unintentionally to fewer than one per year. Even so, when the news comes that an avalanche has reached the road, “It’s the worst feeling you can have,” says Kevin Marston, one of the seasonal employees who works with Stimberis. “You get this sick feeling in your stomach. Our job is to keep any snow off the highway that didn’t fall there naturally.” It’s a tall order.

Between 1992 and 2004, Snoqualmie Pass was closed an average of 120 hours a year for snow control, road conditions and accidents. And those closures don’t come without a cost. Interstate 90—connecting Seattle with Boston—is the longest interstate highway in the nation, and a key conduit for national and international trade. The I-90 closure of January 29–February 2, 2008, caused by high rains that destabilized the snowpack, is blamed for an economic impact of $27.89 million, from lost commercial and personal income, lost jobs and lost tax revenue. It caused Governor Christine Gregoire to issue a state of emergency—not just because of risk to individuals, but because of risk to the economy.

The WSDOT avalanche forecasters and controllers daily walk a precarious tightrope, balancing the need to keep the highways safe for travelers and the pressing requirement to keep the roads open for commerce.

Stimberis heads out to take measurements

No matter the conditions, at the beginning of every night shift Stimberis and one of the seasonal controllers leave their Hyak office and climb into a large Chevy pickup, complete with plow and flashing lights, to drive a “lap,” the section of the highway around the pass most susceptible to avalanches, and observe conditions on the neighboring mountainsides.

Driving the lap on a night late last winter, Stimberis points out long swaths of smooth, treeless, snow-covered slope above the highway. “There are about 30 avalanche paths we pay attention to,” he explains. “About half a dozen are really active.” Each of these paths has been recognized as an area of concern because of previous slides, or because its slope characteristics include a run-out area affecting the highway. One avalanche path is at the East Snowshed, a tunnel that covers a westbound section of I-90, just east of the pass. Completed in 1950, it is constructed so that an avalanche travels over the snowshed, missing the highway completely. With the multiyear five-mile expansion of I-90 east of Snoqualmie Pass that began last July, engineers are paying special attention to this area, the heaviest slide area on the pass. WSDOT is evaluating two proposals for lane expansion to mitigate the risk of avalanches during the project; the first would channel traffic into two lanes under the existing snowshed until the new snowshed is constructed, and the second would channel traffic 40–60 feet away from the slope with a large construction ditch to catch any falling snow. Both plans involve working closely with the controllers for proactive maintenance of the slope.

Stimberis and his crew have dual specialties—as snow specialists and explosives experts. There’s no formal education path for controllers; they all started out working as ski patrollers, most at Alpental. They share other qualities: a love of the outdoors, snow and skiing. Most are backcountry skiers, well aware of the dangers inherent in their sport. All have had to learn about the extraordinarily complex nature of snow in order to stay safe and, as ski patrollers, to keep others safe as well. They are all trained as avalanche professionals, the same training required of a professional mountain or ski guide. Much of the specific education for forecasting and controlling is learned on the job.

The crew must also know a lot about explosives—the most important tool in avalanche control. Getting those explosives to the right place (the starting zone of an avalanche path) can be challenging. Driving his pickup truck from Denny Creek back to Hyak, Stimberis points out the cables heading up from small shacks above the road. “Those are the closed-loop trams driven by bicycles,” he explains. “There’s a stationary bicycle in each shack. When you attach the explosive load to the cable, you pedal the bicycle to move the package up to the avalanche starting zone.”

In addition to the trams, controllers use a 105-mm recoilless rifle for avalanche control along I-90. It’s permanently mounted on a platform up the mountain, to shoot down snow from specified avalanche paths. Stevens Pass has a Howitzer and two tanks positioned to shoot down slides.

Deciding when to use the explosives requires a broad and deep knowledge of snow, so after driving the nightly lap on the highway, Stimberis and Aaron Opp, a dark-haired 32-year-old who spends summers as a commercial fisherman and winters as a WSDOT seasonal employee, head to the snow plot, located by the old WSDOT office on West Hyak. This small area of land, approximately a quarter acre, holds several instruments used to measure snowpack and snow conditions, including a snow lysimeter, an instrument that detects the movement of water through the snowpack. It is believed that when snowpack is draining water, it is returning to a stable condition.

Stimberis records the data from these checks, and scans data from seven weather stations positioned around Snoqualmie Pass, which take a variety of different measurements. “Because of where they are positioned,” Stimberis explains, “we can literally watch the weather come in from these readings.” As snow accumulates, the forecasting and controlling crew watches for conditions that could lead to avalanches.

Back at the office in Hyak, Opp sits down at his computer to enter the data they have collected, most of which is used for trending. “We work really closely with the guys at Alpental, too,” he says, referring to the ski patrollers whose daily work keeps them in constant touch with snow conditions. “That way we have a good sense of what the snow is doing all through the day.” All of this information goes into complex charts and spreadsheets, and also factors into the judgments of these experts.

After entering the observations, Stimberis, Opp and Marston walk outside to the maintenance shed to brief the maintenance crew. “What did we get?” Stimberis asks Opp about the recent snowfall. “Forty-nine centimeters,” Opp says. “Nineteen inches!” Stimberis translates. “Sixteen in the last eight hours!”

Members of the maintenance crew that drive the snowplows and gravel trucks are up, putting on their vests, waiting for instructions. (Ten to 20 crew members work on any given night—with more called in when heavy snow is forecast.)

“What’re you going to shoot?” maintenance manager Gary Mankus asks Stimberis. “East shed,” Stimberis replies. “Didn’t see any naturals at all on the lap today,” he says, referring to avalanches occurring without an artificial trigger. They are the clearest sign of avalanche danger, both for WSDOT and backcountry travelers, as they indicate instability of the snow even without artificial triggers. The data from their lap and measurements suggest that the snowpack is stable, but with the high volume of snow falling they want to take every precaution. They will shoot the East Snowshed, the area most susceptible to avalanche, just to be safe.

This tool measures the hardness of the snow

Stimberis, Opp and Marston all wear avalanche beacons all day, every day. These are small, paperback-book-sized transmitters that people heading into the backcountry wear strapped around their torsos. Should one of them be buried in an avalanche, the beacon will help rescuers locate him.

Soon they climb into the snowcat, a small tracked vehicle made for climbing steep hillsides covered in deep snow, and head up the mountain on Forest Service roads. Marston drives. Stimberis and Opp, along with Tippy—Opp’s dog—are along for the ride. High above I-90, Marston brings the snowcat to a halt, and they step into thigh-high snow. In the moonlight a ladder is visible against a tree, with three cables heading down the mountain in different directions.

Below, headlights and taillights on I-90 snake around a curve. The constellation Orion glitters in the night sky behind thin, drifting clouds. The wind, usually blowing 40–50 miles per hour, is calm.

Marston brings up three green plastic “bags,” as the explosive packages are called. Though they are about the size of a 5-pound bag of oranges, each has 25 pounds of explosives in it. Opp attaches a thin pink detonation cord to each bag, which will burn at the rate of 25,000 feet per second. Because these are gravity trams, the explosives easily deploy down the cable.

Meanwhile, on I-90, Mankus and his maintenance crew have been stopping traffic in both directions. Stimberis gets on the radio to talk to Mankus. “You guys ready down there?” When the snow releases it could vault over the snowshed and onto the eastbound highway. Clean-up crews are on site, ready to clear the roads and open them as soon as possible to the night traffic. The radio crackles in the clear darkness. “Ready down here, John.”

Opp attaches the shooter, a piece of metal with shotgun primer and a firing pin, to another piece of cord, called the shock tube, which attaches to the detonation cord. The men put on ear protection. “Fire in the hole!” Opp yells, and almost concurrently a BOOM! explodes through the forest. Snow dumps from the trees. The sound reverberates through the wide valley. The smell of rusted metal, residue from the explosives, hangs in the cold night air. Stimberis and Opp hike over to the slope to see if snow has released. “Looks like about a 2-inch slab,” Opp notes, referring to the depth of snow breaking from the snow pack to slide. Mankus reports on the radio that the slide did not reach the highway. The State Patrol opens both lanes, and traffic flows again. It is a successful mission: The explosives have released instabilities that the control and forecasting crew identified from their observations, and the snowpack is stable once again. With clear night skies and no extreme weather forecast, I-90 is safe for the rest of the night.

Despite the years of training, experience and deep expertise of these controllers, avalanche control is “not an exact science,” Stimberis says. “No matter how well we consider the indicators, sometimes things happen you don’t expect.

“Even a little bit of snow can be incredibly dangerous. We had a really small slide a couple of years ago which left just a bit of snow on the road,” he remembers, “and a semi thought he could blow through it. It almost ripped the cab apart.”

Fortunately, WSDOT mitigates most of the risk for those of us traversing the passes—and the crews’ work protecting the public and commerce during storms in recent years has not gone unnoticed. On February 20, 2009, the Washington State Legislature issued Senate Resolution 8634 commending “the employees of the Washington State Department of Transportation on their work to maintain our state’s transportation corridors during and after the storms of 2007, 2008, and 2009.”

While appreciating the accolades, snow professionals understand the unpredictability of mountain conditions and know that accidents will still happen. Living in the Northwest and the mountains inspires both awe of the beauty of soaring peaks, rushing rivers and silent forests, and humility in realizing that nature’s power is ultimately transcendent.

After Dan Osborne escaped his vehicle unscathed last January, avalanche controller Opp was on the scene as quickly as he could drive from Hyak, along with the State Patrol. They conducted interviews with people in cars ahead of and behind the avalanche—standard procedure to be sure no other vehicles were buried. State Patrol closed the highway. Mankus’ maintenance crew made its way through the stopped traffic to begin clearing the road. For Osborne, the incident was a strong warning. “I’m a lot more watchful. I never take anything for granted anymore.”


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