Bonnington Traverse

Bonnington traverse Feb 2-6 trip report. TL:DR – 10/10 snow, 1/10 trail breaking, we brought too much food and booze for the slog, lots of signs of instability, no big slides noted, it is full winter up there, and tarrifs suck. A motley crew of Canadians and Americans from the Coast and PNW completed the Bonnington traverse over the past few days from Feb 2-6. Dubbed the Anti Tariff Traverse, we were the first group through after the last storm cycle. HS ranged from 190cms at Grassy hut to 300 cms plus at Copper. 10-20 cms of fist density snow from the past few nights of convective activity sits on 30-80 cms 4 finger storm/soft slab, depending on elevation/aspect. Daily test pits showed a significant crust facet interface down 20-40 cms on south/west slopes at treeline, and varied crust/hoar interfaces down 40-80cms on N and E slopes at and below treeline. Temperatures were moderate, ranging from -5 on Weds the 5 afternoon to -15 overnight. Serial compression tests revealed easy to moderate failures, mostly sudden collapse, on the aforementioned interfaces. There was significant whoomphing and cracking underfoot on wind affected ridge lines above treeline, and even more significant evidence of instability in clearings below treeline, where the surface hoar was the most significant. We had shooting cracks out 20-30 meters from us, especially on the NW aspect of Copper mtn. A careful ski from the summit, on supported terrain features, however, was stellar! We had planned to ski some of the steeper lines on Siwash and Commonwealth, but elected to keep it mellower and enjoy the absolutely stellar tree skiing. Snow quality was all time, with a few cms of cold smoke nightly on top of the previous, now well settled storm snow. Other than isolated point releases on steep solar aspects, we saw no natural avalanche activity until Feb 5, when we noted a size 1.5 natural off of the NW aspect of Commonwealth, soft slab in wind loaded bowl, that stopped in the middle of the path with no step down. Travel however, was challenging due to the amount of snow. S and W aspects were the best for travel, with ski pen of 10-20 cms on a supportive crust, and only needed ski crampons for the last steep ridgeline of Commonwealth. Ski pen below treeline was often 50 cms plus, and the travel was slow as a result. The Colonly/Empire/Territory ridgeline was significantly wind loaded, rimed up, icy and sketchy and required some creative excavation and tunnelling thought a large cornice to make it safe to travel with heavy packs, as well as crossing steep windloaded slopes, with ice and rime on S aspects and wind slab on N aspects. Allow extra time for this, move carefully and perhaps throw in a lightweight ice axe if you are not comfortable with a few low 5th class moves on snow/ice with some moderate exposure. This was the first day we saw anyone else, with some heli ski parties skiing the S slopes Commonweath. The ski down to Lost lake hut from Commonwealth was all time, and on the ski out from Lost lake we chose to exit from the summit ridge of Commonwealth down a line on the SSE aspect to a pronounced gully feature that feeds into the secondary FSR. This was the best run of the trip, with lighter packs and over the head blower snow below treeline and much improved stability. Overall a excellent wintery week; while this is a shorter traverse with no glacier travel, do not underestimate it, especially with high hazard. There is some significant route-finding required in complex terrain, challenging ridgeline travel and trailbreaking in deep snow makes the days much longer than one might anticipate if solely looking and length in kms. Final notes: Copper and Steed hut require propane – we left a half full green can in each for the lanterns, but bring your own if you want to use the stove. Lots of firewood left. Huge thanks to KMC for the absolutely stellar hut network. Lost lake hut is 10/10! Peace love and no tarrif