Diving incident at Eagles Nest Sink

[Dan]

Hindsight is 20/20. Would it help if the CCR BCD is inflated to a neutral or positively buoyant during the push through the restriction?

 

[Capt Tom McCarthy]

Hindsight is 20/20. Would it help if the CCR BCD is inflated to a neutral or positively buoyant during the push through the restriction?

Probably, but you're still talking about being almost 300' deep, in a silt out, while on Open Circuit, in a restriction that just demoralized you to the point where you actually removed your rebreather. I think at that point you're just trying to get out.

 

[mdb]

We will never know what really happened in this tragic accident.

The (mostly) respectful posts-over 400+-have helped all divers at all levels in evaluating risks
and procedures.

The very experienced technical divers have made significant comments that will help newer
divers as they move forward in pursuit of whatever their diving goals are.

 

[KevinNM]

I check the spec of JJ-CCR from A REBREATHER CHOSEN BY DEMANDING DIVERS - JJ-CCR
It has 34.2kg (75lbs) with 2x3L tanks or 19.8kg (44lbs) w/o tanks & soda lime. That's a lot of weight to balance underwater.

The configuration I've seen in person is the GUE setup which has much larger bailouts/off-board dilutent mounted to the (not visible in this picture) rails along the main canister and appeared to be connected together via a high pressure link. It looked enormously heavy. But I didn't mess with someone $12,000+ rebreather.

 

[Bobby]

Thanks clarifying my ignorance about type of CCR out there.

I was referring to your statement:

"... After a few minutes of working too hard to resolve the situation and allowing anxiety rise to an unacceptable level I was close to abandoning the CCR and exiting on OC. This is when I stopped all actions and just told myself to calm down, as long as I had the functioning CCR I had nothing but time"...

Is it not similar to the situation that Diver2 was facing?

Someone here, may be you (I lost track on whom, after 43 pages & 425 posts) mentioned about when you have CCR on, you have time to wait until the silt to settle enough to see a better opening to go through with the CCR on. After all, you were able to get in with the CCR on initially.

The big difference between my experience and this team is that my CCR was setup to be removed in the water during a dive to push smaller SM passage. Back when I did the dive that I was posting about the passage was not large enough to get through with a CCR on my back. I removed it before entering the restriction. It is my understanding that the team was not setup to remove their CCR's and only did so to extricate himself while attempting to exit the restriction. This would make managing the CCR & the BO cylinders very difficult due to the diver being positively buoyant and the rig negative. Once free of the restriction I believe the diver lost control/grip on the unit resulting in it crashing on the floor and the diver shooting to ceiling. Crashing anything near the entrance to the restriction would cause a very bad silt out. The silt in this part of the system is very fluffy and will not settle for a long time.

 

[Bobby]

The statement said that the QC6 offboard connection was found still connected to the final bailout cylinder which was used. Both onboard and offboard 95 were drained. You would have a breathable loop for small period of time, for sure, assuming that you don't have to descend, clear a mask or accidentally purge any loop volume (which in a situation like this is highly possible).

At that point you'd have pure oxygen remaining as the only addition gas. Just based upon the close proximity that the divers were found I would go this route. There is always the possibility that Diver 1 had a hypoxic/hyperoxic event as well but we wont know more until the report is finished.

Again, while sometimes it's an interesting learning exercise to talk about what could have happened, based upon facts we know, at this point it is still pure speculation until ALL the facts are put together. Even then we may not know everything.

It is also possible that the IP for the O2 was tuned down low enough that the diver could not add O2 at the depth they were at. I have my O2 IP turned down to about 100 psi, IIRC the O2 cylinder only had 300 psi, it is possible that diver 1 could not add more O2 due to depth and IP.

 

[Bobby]

Hindsight is 20/20. Would it help if the CCR BCD is inflated to a neutral or positively buoyant during the push through the restriction?

The diver likely would have been neutral if the CCR were on. He still would have had to keep the CCR negative to offset his positive buoyancy while holding onto the CCR. If he lost his grip then it would be game over as the CCR crashes to the floor and he goes to the ceiling. When X wanted to practice removing her doubles in OW we went to a 20 foot platform. She did well until she went to put the unit back on. Her legs got above her body (dry suit) and she became positively buoyant causing one of her fins to blow off her foot. If we were not at the platform which I used to hold us down after grabbing her she would have skyrocketed to the surface. This is without her letting go of her doubles, if she had, I don't know if I could have maintained my grip on her to keep her at the platform.

It is possible a few might jump in that weight should go on the diver. The reality is that at this level of diving the gear is so negative that it becomes self defeating to add weight. Practice controlling your gear, if you are going to remove it, is essential before getting into a situation where you are going to do it on a more demanding dive. It seems that this situation, the plan was to leave the gear on, the decision to remove it was an effort to get out of a bad situation.

 

[thoga00]

From experience I can say that reactions to a cascading event are different between solo and team diving. When solo diving you only need to think about yourself, when team diving the pressure of supporting your team adds a lot of complexity. I have had situations that were not truly a cascade, simply miscommunication, that were handled poorly by everyone in the team due to the pressure, felt by each team member, of supporting the team. Each cascading event is different and none of us know how we are going to react until we are actually there. I have had situations that I have handled without much fanfare and I've had situations that I've not handled properly. From the reports, it seems that this team worked to help each other and did an admirable job in a horribly bad situation.

This point is easily missed and perhaps one of the most important ones to understand. The divers were likely in a total silt out with zero vis. So communication was likely done through limited visual and touch communication at the crucial stage were Diver 1 lost his rig and Diver 2 likely came to help. No one knows how each diver interpreted the event and reacted accordingly. It is probably that Diver 2 had no idea whether Diver 2 dropped his rig outside of the restriction or within it. All he likely knew was that his buddy was without his rig, pinned to the ceiling, moments away from exhausting his resources. Diver 1, in Zero Vis had limited means to communicate with his buddy and was likely significantly stressed with heavy breathing on his BOB. It is no doubt these divers did their best with the information available and in the situation they found themselves. Diver 2 did not cut and run, but apparently consciously sacrificed himself to try to save his buddy, he deserves massive respect as do they both.

It is also possible that the IP for the O2 was tuned down low enough that the diver could not add O2 at the depth they were at. I have my O2 IP turned down to about 100 psi, IIRC the O2 cylinder only had 300 psi, it is possible that diver 1 could not add more O2 due to depth and IP.

That was what I was just about to suggest. With onboard Dil exhausted and O2 at 300psi there might have not been enough IP to allow injection of O2. Frankly I didn't know you could reduce it so much. By the way there was a AL13 inflation cylinder. I imagine this was Argon and not a breathable gas. But if it were...

It can take substantial time for clay siltouts to clear. I've been to this particular restriction 24-48 hours after another team had a silt out there. It was still cloudy with only 1-3' of visibility.

I understand that the system was reopened the day following the recovery, I wonder what the viz was at that time.

I would like to make another point may not be self-evident. Besides, learning from incidents, divers such as most of us, even baby Intro Cave Divers such as myself are turned to by our acquaintances for either explanations or accusation since many know that we dive in Caves. Understanding the system as well as the incident help us to be able to properly and accurately speak to the events to the best of our ability. Thanks once again to the Rescue Divers who have provided information, Experts and professionals who have provided interpretation and explanation.

 

[dumpsterDiver]

I have a hard time finding the discussion topics applicable to my diving.. with the exception of the diver being excessively buoyant without wearing the scuba unit. I would feel very vulnerable if I wore a scuba rig which would not facilitate easy removal and replacement.

It is for this reason that I don't agree with divers wearing all there lead integrated on their recreational bcs. It seems short sighted to not put enough ballast on the diver to allow them to safely removal and replace their scuba unit... even in open water in a recreational setting. Do others see some parallels? Or relevance?

 

[tbone1004]

@dumpsterDiver the problem with putting lead on the diver is that in technical diving it is very rare to ever need to add ballast to the rig and if you do, it isn't enough to matter. I.e. if I'm diving in real cold water in a drysuit, I may put my SS plate on instead of the kydex plate that I normally use. I don't have to use the steel, but it allows me to put more air into the suit on deco so it makes me happier. The 4lb delta in weight is certainly not going to do me any good if I have to remove the rig. Even using light tanks like LP121's that float a little bit when empty, you still have ~4lbs of bands, ~8lbs of regulators, valves, etc. I can't move all of that ballast to a weight belt because then I would be dangerously overweighted.
For me diving sidemount *no backplate, no bands, no crossbar*, I don't wear any lead with any of my sidemount tanks in a drysuit.

The warmer the water, the worse it becomes and Florida cave diving *warm ish, fresh water* is notorious for having the complete inability to dive a balanced rig. We have to dive dry because the water is just cold enough to cause serious problems with the run times, but not so cold that you can dive with the suit inflated the whole time. The gas and equipment requirements far outweigh the ballast requirements for the suit so you are usually trying to shed as much ballast as possible. With rebreathers it is usually a bit better than doubles since the units are less negative, but even then, with a SS backplate, you are neutral and 4-6lbs on a belt isn't going to help that much in a drysuit. It unfortunately is not practical, safe, or realistically even possible to put all or most of your ballast on the diver and separate it from the rig.

What @Bobby mentioned earlier is important though. These divers likely did not intend to remove their rig, and removal of backmounted rigs whether doubles or CCR is VERY rare. The guys that I know that do plan for this, dive a rig similar to Bobby. You are in a sidemount rig, and the rebreather is designed to lift off of that rig to be pushed in front of you. When this happens, there is essentially no buoyancy change to the diver because they have the ballast on their sidemount unit and aren't going "naked" through any passage. They will usually have a very small wing attached to their rig *similar to those that do true no mount diving where a small travel wing will be strapped to the sidemount tank so it will become neutral to push through*, and the rig is neutral, the diver is neutral, and you can move around. I know of maybe 4 guys that do this on a somewhat regular basis? They're crazy in my opinion, but that was before sidemount ccr's were available and certainly before they were exploration worthy. I think all but one of them is using a sidemount ccr for that type of diving now so they don't have to remove a backmount unit.