ANFO in Whitehorn II

Another beautiful sunny day at Lake Louise today, and the avalanche control team made use of the good visibility to try and get some results in E, F, & G Gullies of Whitehorn II. Previous attempts to get results with our regular 1kg and 2kg shots were unsuccessful, so we decided to pull out the big guns – ANFO, that is.

ANFO stands for ammonium nitrate and fuel oil, and comes in large bags. It looks like lawn fertilizer, and can be used to make custom size shots to fit the needs of the control team. In this case, three 7kg bombs were made by placing the ANFO in separate bags, then inserting a 1kg shot with fuse and igniter.

We loaded the lift around 8:30 and arrived at mid-station just as the sun was beginning to peek over the mountaintops. By the time we got to the top of Summit, Whitehorn II and the rest of the backside was bathed in a beautiful early-morning light. I travelled around to Shoulder Roll on Boomerang so I could get some photos of the action (if there was going to be any). The first two shots were used in E and F Gullies, and both produced very minor results – just a little surface snow around the shot placement.

The shot in G Gully was a different story. As shown in the photos below, as soon as the bomb went off, fracture lines appeared along almost the entire vertical length of the run, and the slope avalanched down to the bottom and up the other side of the terrain slump that runs along most of the bottom of Whitehorn II. This was a size three avalanche, enough to bury or destroy a car. One patroller was asked why Whitehorn II hadn’t been open yet, and the reply was, “Go ski Boomerang, then look up to your right and you’ll get your answer”.

 

The yellow cloud of ANFO appears at the top of G Gully.

The yellow cloud of ANFO, and fracture lines appear at lowerl left.

 

Fracture lines start to appear around the shot and in lower left corner of photo.

Fracture lines continue downslope as snow begins to move.

 

Snow is on the move.

Snow is on the move.

 

Avalanche widens lower on the slope.

Avalanche widens lower on the slope.

 

Snow comes to a stop.

Snow comes to a stop.

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4 Comments on “ANFO in Whitehorn II”

  1. Mooch says:

    So because there was little results in E an F gullies, does that mean the snow is more stable than G ? Or is there other contributing factors as to why there was little results in E an F ? Thanks !! Great stuff !!

    • lakelouiselowdown says:

      Mooch,

      The snow in E & F is not likely more stable than that of G, since all are very similar slopes – same aspect, elevation, length, and slope angle. The different results could be due to where the shots were placed with respect to specific weak spots on the slope, and they may have hit a sweet spot on G Gully but not on E or F. If there’s suspicion about the stability of one particular slope, then that suspicion will also exist for neighbouring and similar slopes. The lack of a result does not necessarily remove that suspicion.

      It’s hard to watch a slope get cleaned out, expecially when you’ve been waiting patiently for it to get to the point where it could be opened. At the same time, this cloud has a silver lining since getting a big result like today’s gets rid of the instability and the slope has a chance to start over and hopefully build with a more stable and trustworthy snowpack.

  2. Mooch says:

    That makes a lot of sense. Thanks. I’m sure it’s a little bitter sweet when the snow you’ve been waiting for needs to be avalanched, but I see that’s what needs to be done in order to make that terrain eventually ski-able.

    The count down is on, 19 days…….can’t wait.

  3. Mooch says:

    A question regarding the warmer weather as of late.

    Is the snow melting a little in the afternoon and then forming a crust overnight? If so would this form a definite barrier between old snow and any new snow?


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