Diving incident at Eagles Nest Sink

[Stoo]

Also, is it common for people to place all their ballast on a rebreather, making themselves so vulnerable to being excessively buoyant if removed (when wearing a dry

The units themselves are quite heavy and likely that was all the "ballast" they had. If I understood properly, they were also carrying LP 95s as BO.

When I dive with twin steels, I don't wear any additional lead, even with my thickest undies on. If I removed those bottles and let go, I'd be gone.

 

[oya]

A diver may last any where from 3 hours to indefinitely before experiencing hypothermia in water between 70 and 80 degrees.

Rereading stuff in some more detail happened to catch this.

Thermoneutral zone for a person in water is closer to 84-88 degrees. And, yes, that narrow a range. As low as 77 is survivable... with a great deal of exercise.

 

[Dan]

We all read this discussion, but are limited by our own inexperience. So when I asked for confirmation that the CCR was dropped outside of a restriction and both divers penetrated further inward, this is not what seems to have happened?...

I don't think so now. I was thinking the same thing, but after reading Dsix36 scenario, who himself has been in that restriction before, it makes more sense that both divers were able to go in with their CCR, especially the restriction visibility was still good before they went in. However, the condition changed on their return due to the silt may have gotten disturbed on their way in and became worse on the way out of the lead Diver1 to the point of near zero visibility, which made it difficult for Diver2 to find the right opening of restriction to enter and forced him to remove his CCR & drag it through the restriction.

Another point why it doesn't make sense for Diver2 to remove his CCR outside of the restriction and penetrate further with 95 bailout bottle is the positive buoyant situation, which will be difficult to maneuver in a big room. He would have floated up to the ceiling of the big Room of Dreams before getting into the restriction.

 

[Capt Tom McCarthy]

@Tmccar1, how about you? Do either of you believe that a side mount rebreather could have been a better choice here?

Just from a maneuverability perspective a sidemount unit would certainly have been a better choice. I know a few folks have been diving that area with them. Now I don't mean that as a casual tern of phrase; I mean that a very small subset of an already small subset of exploration level divers are using them in an area that I personally wouldn't go into without one of them showing me the way first.

Sidemount rebreathers are a great piece of kit for a very specific task, however, a lot of us agree that you need to make sure the person you're training isn't the diving equivalent of giving a 16 year old kid with their learners permit a top fuel drag car.

I think accident analysis is a grim but necessary learning tool. The procedures, equipment, and training that we have today have all been honed and refined at the expense of lives. We can never take those lost lives for granted.

I have a theoretical walkthrough of events that a few other people have agreed with but I feel like it's more appropriate for those who were involved directly to say what they think happened. I'm just a third party but in my personal experience with this kind of thing, it helped to talk it through with outsiders as well.

 

[PfcAJ]

More info from farmerted on cdf, ccr not clipped on the line, now Dsix36's theory seems very plausible (diver 1 goes thru restriction with unit on, viz messed up, diver 2 stuck, removes gear, pushes it in front, all the way out but off the line, zero viz and very buoyant, finds buddy but not the gear, both decide to get out asap instead of looking for ditched unit).
Still curious how they navigated after the light head was disconnected, and why wasn't the scooter clipped to any of the divers when they were found.
Can a rebreather diver speculate why the loop was crushed?

I think that when the light head came unplugged that it was a straw that broke the camels back. One diver had a backup light out of his pocket but still clipped off. I kinda think he was trying to get that light going but it didn't work out.

Scooter might have been unclipped to aid in getting through the pit restriction considering all the crazy that was going on.

My hypothesis is that both divers expired at roughly the same time on the ceiling and Chris then sunk to the floor. With no gas to fire the ADV the loop was squeezed from the pressure. Again total speculation on that and I think it's nearly impossible to know nitty gritty specifics like that based on what we observed.

 

[Dsix36]

Gentle people. I'm seeing a few flashes of emotion in here and hope it does not escalate. It's OK to disagree, but do it gently. None of us were down there. Don and Tom, both of your expertise are really welcome in this discussion. That you both agree to a point on the time line says a lot to me about the probability that this is what happened.

@Dsix36, what is your take away at this point? What lesson can we take away from this?

@Tmccar1, how about you? Do either of you believe that a side mount rebreather could have been a better choice here?

Slow progressive dives to work up both knowledge of a system and your own experience are still the best way to approach this type of dive. Obviously the other thing is to make damn sure to be practicing all of your skills and drills on a regular basis. When was the last time that a seasoned CCR diver actually practiced buddy breathing on OC?

Myself and the other divers that I have ventured into that restriction with have had several in depth discussions on the what ifs of the dive and run all kinds of scenarios before we ever considered doing the dives. things like who rides the scooter if 2 of them fail and who gets towed, not planning to swim out, and who rides the scooter if a scooter and a RB fail on the dive. I know it is not likely to happen but it is better to have a plan before the crap hits the fan at 300' of depth and try to figure it out then. We even plan to use a buddies BO until a restriction so that the bailed out diver has full supplies in case of a slowed exit from the restriction and buddies gas is not available. I also insist on a stage tank outside each restriction, including the pit just to make myself feel better.

 

[Capt Tom McCarthy]

Ok, because all the facts are out and i've seen those involved in the recovery posting their opinions as well, i'm going to share what I consider a consolidated theory of events.

NOTE: none of this is proven or factual, it is a loosely based theory of what COULD have happened and is in no way an official position of anyone involved in the incident. It is pure speculation and nothing else. If this steps on anyones toes or offends anyone i'll gladly remove the post.

Eagle’s Nest Double Fatality Theory

Diver 2- No Rebreather on when found
Diver 1- Rebreather on when found

Both divers scootered to the end of the Room of Dreams and proceeded to drop scooters and make their way through the restriction towards Revelation Space.


Diver 2 (and Possibly 1) made their way through the restriction, silted out the cave, one of them then decided to turn the dive. At this point diver 2 had difficulty exited through the restriction. Diver 1 was wearing a backmounted JJ with two LP95’s sidemounted. At this point diver 2 proceeded to switch to OC bailout, remove the rebreather and push it though the restriction (possibly with assistance from Diver 1).


Once on the other side of the restriction Diver 2 became extremely positively buoyant, due to a lack of rebreather as weight, and rose to the ceiling while carrying a single LP95 as bailout. It is possible that the area surrounding their rebreather was in a complete silt out. For whatever reason, Diver 2 was not able to re-don their rebreather. (Due to difficulty locating it or difficulty donning it)


At this point it would appear that diver 1 towed diver 2 for roughly 700’. During this tow diver 2 was likely hand carrying a steel LP95 while holding onto diver 1’s crotch strap. It is unknown how positively buoyant diver 2 was; it is doubtful that neutral buoyancy would have been possible.


At some time during the tow it is likely that diver 2 either entirely switched bailout cylinders with diver 1; or that diver 2 continued to hold a cylinder for ballast while breathing from diver 2’s clipped off sidemount cylinder.


At some point prior to the restriction two LP95’s were dropped (possibly to accelerate the exit through the restriction at the Pit). Diver 1 then handed the only remaining sidemount cylinder to diver 2. At this point they may have also been thinking that there would be a full al 80 bailout on the other side of the restriction as well.


While passing through the restriction area, or shortly after, diver 1’s primary light head may have become caught on a rock which pulled apart the EO cord connection. This was the only light source being utilized at the time (diver 2’s was on the dropped rebreather). In a total blackout, diver 1 unclipped and turned off his scooter (this also could have been before the restriction and pushed through). Diver 2 began to deploy their backup light.

At this point diver 2 fully emptied the single LP95 remaining before they could find the aluminum 80 stashed off the line. At this point diver 2 likely ran out of breathable gas. Diver 1, however, now had a completely drained onboard diluent cylinder because the LP95 diver 2 was breathing from was still connected to the rebreather via an offboard QC6. It would only take a simple mask clearing or accidental venting of the loop contents to then make it impossible for the diver to take a breath. There would be no more diluent to add via ADV. (This assumes that the QC was manifolded to the onboard diluent cylinder)

Edit: Switched diver numbers to correspond with previous posts

 

[Ron Lee]

Ok, because all the facts are out and i've seen those involved in the recovery posting their opinions as well, i'm going to share what I consider a consolidated theory of events.

I think that you switch Diver 1 and 2 from previous discussions where Diver 2 ditched his rebreather.

 

[Capt Tom McCarthy]

I think that you switch Diver 1 and 2 from previous discussions where Diver 2 ditched his rebreather.

They were arbitrarily assigned, in my post, and have been changed.

 

[CuzzA]

So earlier in the thread (revealing a little ignorance to cave diving) I questioned if it's common to tether your rig to yourself when you push through a restriction, but it sounds like the proper procedure would be to clip it to the line and push it through? Am I right about that?

It would seem to me that anything worth keeping in a cave should be clipped to the line to facilitate recovery from a no viz situation.

I'm a stickler for tethering gear to me, mostly because I'm too cheap to risk loosing it and having to buy it again. Dive knife, EMT scissors, flash light, you name it, I use a simple coiled lanyard in open water, but in a cave, I would think it would be even more important to clip essential gear to yourself or the line.

Am I missing something? It seems the fatal error here was "freely" pushing your life support through the restriction increasing the possibility it becomes lost in the silt. If it were clipped to the line, diver 1, in the blind, could have followed the line by feel and retrieved the breather for diver 2 who was stuck on the ceiling. I know this is all hindsight Monday morning quarterbacking, but I'm really curious to know if there are standard procedures for passing restrictions while doffing gear since there's a higher probability of reduced viz.