We probably don’t do this enough but…
Have a dubious natural anchor?
Let’s assume a party of 4.
The goal is to back up the anchor for the first 3 people, and to test the anchor sufficiently so that the last person (usually the anchor builder) can descend with a high degree of confidence.
So let’s give the anchor a good sniff. Look it over carefully, tug on it as hard as possible while being safe.
Let’s back it up. If a super-solid natural anchor is available nearby, run a rope or sling to that and clip it in. Of course, we assume you have a good reason for not using the obvious super-solid anchor in the first place, like it would require 60 feet of sling or the pull is wrong – or something.
How to rig the back up? Well, if you are really doing this “backup and confidence building” exercise, then you want to rig it in such a way that the back up does not take any load unless the primary anchor fails. If the primary fails, you really really want the backup to take the load as quickly as possible (this is known as “no- extension”). Often it is not possible to rig for no-extension, so try to minimize the extension as much as physically possible.
What if no natural anchor is available to use as a back-up?
Use a “sequence” or “human” anchor. No, its not time to do Shane in. Have your team sit down, shut up and hold on. Er, something. Human anchors are made by having humans select an advantageous place to sit and brace themselves in the canyon. Best done with more people. Sometimes the best place is quite a ways back – don’t be shy. And YES you should be very careful that the braced human beings can actually hold the forces generated by the anchor failing.
How to attach the rope to the human anchor? Personally, I think attaching using a “contingency anchor” is the best idea. I put the rope through my rappel device, then wrap it around my hand a few times. Perhaps it is un-generous self-preservation, but my feeling is that given the choice of being pulled over the drop or dropping my partner (in a controlled fashion, of course), I’ll drop my partner.
Chain the other people to the first person. I like clipping a sling into the front person’s belay biner, and leaning back on that.
Who goes first? Well, generally the heaviest persons go first, while there are more people stacked up making a humans anchors. The lightest person gets to go last.
Testing the Anchor – once down, the big burly guy can test the anchor safely from the bottom of the drop. One big guy jumping up and down on the rope equals a lot of confidence in the anchor on my part. Don’t overdo it, and wreck a perfectly good anchor, but do give it a solid test.
How to develop a feel for this? Practice in a safe place.
And this is a good technique to use for short drops. Often every person but one can rappel, then the last person, light and nimble, can downclimb with a high quality spot from below. I did say SHORT drops.
Remember, there is no i in Canyoneeryng.
Tom