Once the snow falls and the ski season starts, there’s a hazard on the hills that’s largely overlooked. Tree wells took the lives of two local snow hounds about this time last year.

Last February, a 29-year-old Burnaby snowboarder in a popular backcountry area near Pemberton fell headfirst into a tree well and suffocated. A 63-year-old West Vancouver man died of similar causes on Whis­tler Mountain the month before.

A tree well is a hole or void that forms around the base of a tree while snow accumulates. A tree-well event, also known as a snow-immersion-suffocation (SIS) incident, occurs when someone falls, usually headfirst, into the depression and becomes immobilized and trapped under the snow. Breathing becomes difficult as loose snow packs in. The more a person struggles, the more entrapped he becomes. Suffocation can result.

“People are drawn to skiing in the trees because everybody loves to ski powder,” explains North Shore Rescue volunteer Jeff Yarnold in a phone interview. “The trees are where people go to find powder; they’re trying to get off the beaten track and are looking for untracked snow. Once we get fresh snow or there’s a big storm coming through, we get a lot of new, unconsolidated snow on the surface, and that’s when tree wells become more of a hazard. Tree wells build quite quickly.”

In many cases, a person can die quickly from suffocation—as fast as someone can drown in water, according to the Tree Well and Snow Immersion Suffocation (SIS) Hazard & Safety Information website developed by Northwest Avalanche Institute director Paul Baugher and Gwyn Howat, operations manager of the Mt. Baker Ski Area.

Evergreen trees, in particular, such as fir and hemlock, can have large, deep tree wells that form when low-hanging branches block snow from filling in around the base of the tree. The voids are often hidden by those low branches, and there’s no easy way to tell if a tree has a dangerous well. That’s why all tree wells should be considered dangerous.

Preventing oneself from falling into a tree well is crucial because the odds of surviving snow immersion are low, the SIS site states. In fact, 90 percent of people involved in tree-well research experiments could not rescue themselves.

“The first thing for us is prevention, and that is avoiding tree wells,” Yarnold says. “You avoid them by skiing within the boundaries on groomed runs. That’s the first step. Once you’re leaving a ski-area boundary and you’re leaving marked runs, you need to be aware of the hazards you’re getting into, and tree wells are definitely one of the hazards. People who head into the backcountry need to be aware of these hazards, and that involves further training.”

Although staying out of the trees is a no-brainer, so is skiing with at least one other person.

“Skiing with a buddy is always important; do not ski by yourself,” says Joffrey Koeman, director of sales and marketing at Cypress Mountain. “Know where each other is. If you can’t see your buddy, that’s when you have to stop and take a look.”

In other words, skiing or riding with a friend does not mean meeting them at the bottom of the hill. The SIS website puts it in no uncertain terms: “Many SIS victims have died while their partners were waiting at the bottom of a lift,” the site says.

“When we get these 40- or 50-centimetre big dumps, everyone’s flocking to get powder in the trees,” Koeman says. “Our terrain doesn’t have a lot of tree-well dangers, but it’s still something that’s of concern, and safety is something we highlight when those conditions arise. We always encourage skiing with a buddy.”

That’s a point that North Shore Rescue can’t emphasize enough.

“You want to be skiing or riding very short pitches so that you’re staying in contact with each other; you can’t just ride off,” Yarnold says. “Break the run into smaller segments and plan to regroup a lot more often so that you’re always in sight of your partner. Most often, it’s where people are way too far away from their partners or riding on their own that we end up with fatalities.

“If you are skiing on your own, you could be down there way too long and hypothermia could set in,” he adds. “We need to stress [that] it’s going to be your partner who will save you. By the time we come looking for people in tree wells, it’s getting a little tough.”

There’s still much more that local snow enthusiasts can do to stay safe. North Shore Rescue urges people to carry a whistle on them, not tucked away in an inside jacket pocket or pants pocket but attached to your zipper at your jacket collar. If you do end up going down a tree well, it will be easily accessible, enabling you to signal for help. Cellphones should be easy to reach too, but the organization stresses that you can’t rely on a cellphone alone to get help, given the notoriously poor battery life of so many devices and the fact that you may be out of cell range.

If you do end up in a situation where you realize you’re headed for a tree well, Yarnold suggests placing an arm in front of your face so that you create an air pocket.

“You want to protect your face as you’re going in, to try and get yourself an air pocket with your arm in front of your face clearing the snow as you’re going in, grabbing the tree if you can,” he explains. “If there’s any way to get feet parallel to your head or lower than your head, that’s what you want to do, because the worst possible position is to have your head down. Then people start to struggle in that position and snow continually falls down and closes up your air pocket. You don’t want to be fighting and kicking in your feet, knocking more snow down on your face.”

If you see your ski or boarding buddy go into a tree well, don’t try to dig them out the same way they went in, as you might knock snow on top of them and cut off their oxygen supply. Rather, experts suggest determining where the person’s head is and tunnelling in from the side.

For those who travel outside of ski-area boundaries, carrying proper safety equipment is a must. That includes essentials such as a light, a navigation tool like a GPS unit, water, extra clothes, and fire starter, among other items, as well as tools like an avalanche transceiver, a probe, and a shovel.