Whitehorn II – Seeing the Light of DayPosted: March 4, 2011
Things at Lake Louise are a far cry from how they were around the new year, when below-average snowfall amounts conspired with weak layers in the snowpack to cause much of our double-black diamond terrain to avalanche, losing most or all of whatever snow had accumulated up to that point. Even after some of the big snowfalls in January, the weak layers persisted and our hearts sank as we watched what looked like a good start slide out to the bottom of the slope. As much as we convinced ourselves that this was a good thing (it is – really!), it doesn’t make it easier.
Why is it a good thing? Well, knowing what we know now about the state of our snowpack, avalanches were the only way of clearing out any weak layers and rain crust that still existed from the early season. The weak layer couldn’t support the weight of new snow on top, and the rain crust from Nov. 9 provided a smooth running surface that allowed snow to avalanche even more easily.
On a typical day in a normal January, avalanche control teams would spend the first part of the morning controlling terrain that had already opened that season so it could open for the day, and would then move on to still-closed slopes so they could the get the attention they needed in order to have their gates cracked eventually as well. This was no normal January, however, as over 150cm of snow fell during the month, making a huge job out of just keeping open the runs that had already been so. This meant that teams weren’t able to spend much time in the steep back side runs. Constant traffic by control teams using ski cuts and explosives is needed, especially in places like Whitehorn II, which is a large, complex piece of terrain that require significant attention to detail in order to safely rule out avalanches being triggered by skiers.
When looking up at Whitehorn II from the Boomerang flats, the gully that comes straight down from the visible top of the Summit Platter is ‘C’ Gully, and this is the first full-length gully that you see looking from left to right. ‘A’ and ‘B’ Gullies start lower and to the left, and are also less complex. It’s common that ‘A’ Gully opens with the rest of Rodney’s Ridge, as was the case this season. Only recently, with the increased ability of control teams to get into the area, have more gullies opened. Last week saw a new fence installed down the rib dividing ‘C’ and ‘D’ Gullies, and both ‘B’ and ‘C’ were opened to the public.
The more laps control teams can do in these areas the better, for a few reasons. Obviously, the more ski cuts and explosives teams can deploy the better for slope stabilization. But increased travel also results in increased confidence, as teams improve their knowledge of each of the many little features that make up a huge piece of real estate, and their big-picture view gradually gets filled in by lots of little pictures.
In a place like Whitehorn II, control teams will use every weapon in their arsenal to give them the confidence they need that the area is safe to open for the public. This includes encouraging other patrollers and trail crew to make laps and cover as much ground as possible, providing valued slope compaction and breaking up any layers that exist in the snow pack. Why wouldn’t we allow just anyone to ski the run and give us the compaction that helps so much? Until avalanche forecasters have the confidence needed to open a run to the public, all traffic must be controlled, and by using staff, we can discuss the routes to be taken and how to travel safely through the terrain, and all staff have radios that can be used for instant communication if needed.
Even with this planned and organized traffic, just because a slope doesn’t avalanche under the weight of one skier doesn’t mean it will hold up when the masses are on it. As one of the last steps in preparing a slope to open, control teams have two related methods of simulating the stress of a large number of skiers on a slope. The first is a “nuke on a stick”, which is two explosive rounds taped together, then attached to the top end of a bamboo placed in the snow, leaving the shots a foot or two above the snow surface. Leaving the shots exposed to the air allows the blast to travel a greater distance and therefore affect more of the slope at once. The other method involves a “Hershey kiss”, which is a shot placed into a bag of ANFO and left on the surface of the snow. The effect is similar to that of the nuke on the stick, but packs more of a punch and can cover a greater distance.
Usually the goal of explosive work is to get the shot deep into the snow, so it can test the stability of weak layers that may be buried in the snow pack. The methods mentioned above do not achieve this goal, but they don’t have to , since that type of control work would have happened much earlier in the life of the slope. Buried weak layers are no longer a concern, so the only purpose of these surface blasts is to simulate the weight of a large group of skiers on a slope.
Control teams have made great progress in the rest of Whitehorn II lately, and their hard work is about to pay off as skiers will soon see the opening of most of the rest of the gullies, over to and including ‘G’ Gully. Conditions are great, especially below the gullies in the fans, where snow is deep and rocks are hard to come by. Once control work is completed, all that remains to do is to install a new fence line to divide ‘G’ and ‘H’ Gullies, and it’ll be good to go.