Diving incident at Eagles Nest Sink

[PfcAJ]

I have a question for the second dive team members. The first team probably went in with a thought that it could be a rescue. The comment months ago after I asked is that the second dive team had no such thoughts. Considering the time of day (night) and the possible fatigue level, was it really prudent to dive when they did?

This dive site appears to be challenging under good conditions. Throw in fatigue and it would seem to raise the risk level.

Go back to the Colgan plane crash in Buffalo. My recollection is that crew fatigue played a factor in that deadly crash.

Are there, and if not, should there be standards on when you make dives like this if there is no reasonable chance of it being a rescue dive?

I was a member of the 2nd team.

The time of day was a factor and we elected to minimize our bottom time because of it.

The initial plan was to search to the end of the mainline and then exit rather than a full search side passages (like Team 1 did upstream).

We encountered the deceased divers very quickly and modified our plan to take notes since the depth was significantly shallower (220ish vs our planned 280ish avg depth). We kept our overall run time similar despite having a longer bottom time than we initially planned.

 

[Kevrumbo]

A summation of known facts on this tragedy was posted to the NSS-CDS site earlier today:
October 2016 Eagles Nest Tragedy, Revisited - NSS CDS

@Dsix36 's explanation seems to be the best general cause and speculative outline of this tragedy based on the above facts:

Ok, I guess I may as well post my guess of what happened in view of my previous experiences there. . .

MY OPINION:

They went through the restriction and did their dive into Revelation Space. Upon their return to the restriction the vis was either not very good or the first diver out mucked it up for the second diver. The second diver had difficulty getting out the restriction either by going on the wrong side of the line or being in too much of a heads up position and his rebreather not clearing the ceiling. After several minutes of trying to get out the diver decided that he must remove his rebreather to get out. Since his Bo is also clipped to the same harness then he effectively becomes no mount at this point. He is buoyant as hell but the ceiling works in his favor. He pushes the rebreather and tank through the restriction and his buddy helps pull them out. by the time the diver is out of the restriction he has probably pretty much used up that entire tank and the visibilty is completely gone in that area and the silt cloud is bellowing into the room of dreams. As the diver trys to locate and get his RB back on his buoyancy takes him on a hell ride to the ceiling with his BO tank and his buddy goes to the rescue with his own BO. As they float at the ceiling they see nothing through the silt below them and decide to exit relying on their BO and staged tanks. I highly doubt that either of them even looked at their deco obligation until this time.

Pick it apart all you want, I have not interest in trying to justify my thoughts. The fact that they were still together until the end tells me that regardless of how things went, they worked together and did everything to the best of their ability, knowledge, and experience to stay alive.

I believe, as others have already said, that the fatal mistake was in not taking the time needed to locate and get back into the rebreather. It is entirely possible that due to the circumstances that this was either not a possibility or was perceived as such in one or both of their minds.

The only thing different from the above conjecture --after interpreting the downloaded runtime and depth data from the victim's dive computers-- is that they attempted to negotiate that now infamous restriction twice (see Don Six's Drawing in the report) but never made it through and down into Revelation Space.

 

[Cowfish Aesthetic]

@Dsix36 's explanation seems to be the best general cause and speculative outline of this tragedy based on the above facts:
The only thing different from the above conjecture --after interpreting the downloaded runtime and depth data from the victim's dive computers-- is that they attempted to negotiate that now infamous restriction twice (see Don Six's Drawing in the report) but never made it through and down into Revelation Space.

My interpretation is that one diver made it through the restriction on the second attempt. It would seem that, when his buddy did not appear, he attempted to return and eventually removed his CCR. It certainly seems likely that he got stuck or was otherwise unable to get back through, thus necessitating the removal.