Behind the Scenes: Hanging From a Rock Face for Avalanche Safety

The Ministry of Transportation and Infrastructure Avalanche and Weather Program is changing the landscape of avalanche control in Canada.

Dropping explosives from a helicopter has traditionally been our weapon of choice for triggering controlled avalanches. But some challenging terrain on Yellowhead Highway 16, between Terrace and Prince Rupert, has compelled our avalanche team to try harnessing snow and ice rather than letting it loose.

In fall 2014, crews completed Canada’s second ever avalanche fencing installation at the 35 Mile avalanche area, located 56.4 kilometres west of Terrace (the first installation was completed as part of the Kicking Horse Canyon Project).

So, why install fencing at 35 Mile before one of the other 1,388 avalanche paths above provincial highways?

Avalanche Control in a Tight Space

Well, not all avalanche paths are created equal. Nor do they all appear as obvious scars across a mountainous treed landscape.

You may not even notice the 35 Mile avalanche path, which is the most challenging of all 44 avalanche paths between Terrace and Prince Rupert. The 35 Mile avalanche path begins 400 metres above a narrow stretch of two-lane highway, with a steep granite wall on one side and the CN rail line on the other.

avalanche fencing

CN railway on one side, towering granite wall on the other.

Talk about a tight space.

Removing snow and ice from this section is difficult because of the narrowness of the highway and lack of ditches. There simply isn’t much room for falling snow and ice to go, except pushed further down the highway where space opens up.

The area is also the most demanding location to forecast in the ministry’s Northwest Avalanche Program, which covers:

  • Highway 16 (Terrace – Prince Rupert).
  • Highway 113 (Greenville – Kincolith).
  • Highway 37 north of Meziadin (Snowbank-Ningunsaw).
    • Highway 51 into Telegraph Creek.
    • Select areas just south of the Yukon border, including the access road into Cassiar.
  • Babine Lake Road north of Smithers
  • Shames Mountain access road near Terrace

The 35 Mile avalanche area causes about 80 per cent of closure time between Terrace and Prince Rupert, and we want a permanent solution to eliminate the need to forecast and to do avalanche control work. The avalanche fencing installation is part of a trial to determine if it is an effective alternative.

How Avalanche Fencing Works

Avalanche fencing stabilizes the snow in the avalanche path start zone throughout winter so the snow can never be released. The start zone is the location where snow in an avalanche path fails and results in additional amounts of snow flowing downslope. As long as snow in the start zone cannot release, there will be no avalanche. The nets are designed to hold the maximum amounts of snow that may accumulate in the start zone. The method of control is referred to as “permanent,” as it is always in place, does not need anyone or anything to initiate it, and represents a permanent solution to the concerns of avalanches. The snow eventually melts when temperatures increase.

Getting It Done

It took 75 hours of flying to transport a 7-person crew and 82 metres of steel mesh fence 325 metres above the highway (in the video, you can spot the helicopter landing pad to the right of the worksite). The crew was flown to the helicopter pad at the beginning of each day from a nearby gravel pit, and flown out again at the end of the day.

That’s quite the commute, eh?

Working on a steep rock face requires a level head and a comprehensive safety regime. All crew members were roped in at all times and trained in rope rescue. Pre-installation rock scaling and tree falling made the area safer for installation activities. The helicopter pilots had approximately 9,000 hours flying time with extensive longline experience.

Fencing 2

Descending 35 Mile avalanche path, high above the Skeena River.

The ministry is always looking for ways to improve traveller safety across BC. Successful avalanche fencing will not only protect travellers from falling snow and ice, it will also improve the highway’s reliability. According to the ministry’s Pacific Gateway Branch, CN rail traffic to the Port of Prince Rupert is expected to increase from 12-16 trains to 36-40 trains per day by 2020. Highway traffic is also expected to increase.­­­

The avalanche team is monitoring the Mile 35 avalanche fencing through winter 2014-15. If successful, the ministry will look at doing future avalanche fencing along BC highways.

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7 Responses to Behind the Scenes: Hanging From a Rock Face for Avalanche Safety

  1. Brian Lang on February 16, 2015 at 12:05 pm

    How do the fences prevent avalanches? Wouldn’t they just collect snow & ice and any debris pushed down by an avalanche until they give way from the weight of it all?

    • tranbceditor on February 16, 2015 at 12:48 pm

      Good question, Brian. The fencing stabilizes the snow in the avalanche path start zone throughout winter so the snow can never be released. The start zone is the location where snow in an avalanche path fails and results in additional amounts of snow flowing downslope. As long as snow in the start zone cannot release, there will be no avalanche. The nets are designed to hold the maximum amounts of snow that may accumulate in the start zone. The method of control is referred to as “permanent,” as it is always in place, does not need anyone or anything to initiate it, and represents a permanent solution to the concerns of avalanches. The snow eventually melts when temperatures increase.

      We’ll add this explanation to the blog, too.

  2. Steve Brushey on February 16, 2015 at 7:07 pm

    Nicely done TranBC.

    • tranbceditor on February 17, 2015 at 9:29 am

      Thanks for the positive feedback Steve! 🙂

  3. Nicholas Thomas on February 21, 2015 at 7:16 am

    It would be nice if some sort of permanent avalanche control could be done at Three Valley on the Trans-Canada. Closures here probably cost business and non-commercial travelers more than anywhere else in the Province. This winter we had a two day closure because it wasn’t possible to do avalanche control by helicopter one day because of the weather (winds and icing). We often get overnight closures (which usually last at least until mid-day by the time avalanche control and clean up is finished). Perhaps a combination of snow fences on the smaller paths and gas-ex exploders on the bigger paths?

    Or do we have to wait a couple of decades for this to get fixed (perhaps by rerouting or snowsheds) when you finally get round to delivering on the Kamloops to Alberta 4 laning promise?

  4. C on March 24, 2016 at 12:09 pm

    My hubby worked on this project. There is a very cool video of the install. https://www.youtube.com/watch?v=EzLeXAhNdYg

    • tranbceditor on March 24, 2016 at 1:51 pm

      Hi Carli,

      That looks very much like the same video here in this blog. It was a very neat project indeed!

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