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Incident: Webbing anchor failure in Cerberus canyon, DEVA

Discussion in 'Accidents and Near Misses' started by hank moon, Feb 27, 2017.

  1. hank moon

    hank moon lovely ligatures

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    RopeWiki reference: http://ropewiki.com/Incidents:Webbing_failure_in_Cerberus

    There is a discussion on this incident on the Southwestern Canyoneering Facebook group (not a public group, but easily joined if you have a FB account).


    Excerpts:

    A group that ran this canyon in December 2015 recall they may have replaced this anchor. It was a color they were using that day. If that were the case, this webbing was only one year and two months old. Given this anchor was roughly in the watercourse, it may indicate chemical, rather than UV factors at work.


    Summary
    A webbing anchor tore free, causing a canyoneer on rappel to fall 15 feet. He landed in wet sand.

    • Incident Time: 12:40pm
    • Rappel: 16 of 29.
    • Patient: Male, ~25 years old, 235 lb+ with backpack
    • Group size: 9
    Cerberus is a lengthy technical canyon, even for advanced groups with many years of experience. The frequency and length of rappels, anchoring challenges, and advanced down-climbing make for an arduous day in hostile conditions. Those who participate in this difficult, potentially dangerous trip are richly rewarded by teamwork, accomplishing the extraordinary, and experiencing a part of death valley few have ever seen.

    Rappel 16 was a "deadman" anchor with the base rock being about 2 to 2.5 feet in diameter. The base rock was set into the soil and was not movable, it had several smaller rocks stacked on top of it. The existing webbing was 1" tubular webbing tied in a loop with a water knot, the loop went around the base of the rock and the knot was at the back of the rock. Front side angle of the webbing was approximately 30 to 40 degrees. The anchor rocks and webbing was inspected prior to using it. The webbing was visually inspected all the way around and there was no significant wear or discoloration. A single (9mm low stretch) rope rappel thru the quick-link and blocked the rope with a Figure 8 Block. This anchor was backed up with a meat anchor with the station attendant attached to the "pull" side of the rope. The rappel consisted of a two stage drop, an initial drop sloped 15' down to a 10' ledge, which terminated in another 15' vertical drop, the anchor was set 10' back from the initial drop.
    Last edited: Feb 27, 2017
    Kevin and Ram like this.
  2. Scott Patterson

    Scott Patterson

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    If it was chemical and the webbing actually dissolved or was weakened, wouldn't there be more discoloration around the break?
  3. Tom Collins

    Tom Collins

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    Something similar happened to the group I was in the same weekend in Mosaic. It was on the big drop and I was first down, and about halfway down one of the guys up top happened to look down at the webbing and saw two tears in it and a 3rd one formed as he was looking at it. We had inspected the webbing and while it did look a little sun bleached it was nice and supple still so we thought it was fine. Fortunately they were able to back up the anchor before it failed, and of course I was oblivious to all of this happening until the 2nd guy came down (I was getting a little impatient waiting since it took forever for him to come).
  4. townsend

    townsend

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    Wow. That is a scary story! It was pure luck that the webbing didn't just completely blow out at once, but instead deteriorated in stages.

    The take-home is that inspection (both visual and tactile) is necessary but not sufficient. I'm confused about how to avoid these accidents, other than replace every single webbing anchor, which would be overkill.
  5. Kuenn

    Kuenn

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    ...the most annoying person goes first (MAPF). ;)

    @Tom Collins scenario, their due diligence was exemplary; inspect before AND during the rappel, then be prepared to act immediately. Or maybe yet, what's the harm in attaching that spare sling or clipster or quick-draw or whatever, as a quick backup plan - especially on the big drops - of course remove prior to LPAR (make him earn his keep).

    Peace of mind is a priceless thing.
    gajslk, hank moon and townsend like this.
  6. gajslk

    gajslk

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    My rule of thumb has always been that ANY visible sun-fading is grounds for replacement.

    Gordon
    dakotabelliston and townsend like this.
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