Diving incident at Eagles Nest Sink

[dumpsterDiver]

Do these types of dives require that each diver carry enough bail-out gas to independently survive the loss of the rebreather? or do they assume they will need to dip into their buddy's bail out to survive a CCR failure?

Do they plan to survive the loss of a scooter AND simultaneously a CCR or is that third scooter a necessity for survival?

 

[KevinNM]

If indeed diver 2's plan was to ditch the CCR at the restriction, one would hope that some type of offset (I.e. weight belt) for the buoyancy of a dry-suit would be place.

Perhaps it wasn't planned, but was carried out when when it seemed to be a practical and reasonable solution to an unexpected issue, and then something went very wrong?

Is it a reasonable assumption that diver 2 would have been carrying one 95 in his hands swimming out?

Would it have been practical for diver 1 to have transported diver 2's second bailout (so he would have been carrying three 95s), so the fact that he didn't further suggests again that they lost contact with the CCR and bailout in some fashion? Or is that reaching?

 

[CptTightPants21]

Each diver has enough bailout for themselves independently. In this cave situation, protocol is to carry at least enough to reach the nearest safety bottle at all points on the dive. 3 95s with all the bottles they had stored should have been enough. The extreme depth, accelerated breathing rate, and delay--caused by viz or buoyancy issues, clearly took a toll.

A diver will also take into account the loss of a scooter. Dive plan would have been adjusted accordingly if they only had one scooter, the fact that they had a back up means the dive plan probably would have relied on that extra scooter being the answer to a scooter failure, rather than carrying more gas and/or limit penetration.

 

[KevinNM]

Do these types of dives require that each diver carry enough bail-out gas to independently survive the loss of the rebreather? or do they assume they will need to dip into their buddy's bail out to survive a CCR failure?

It was stated early in the thread they each had what seemed like a reasonable amount of bailout to make it out themselves, it wasn't a team bailout plan. No idea how one calculates bailout gas needs for this kind of dive, so how far you can be expected to get on two 95s at really deep depth I have no idea on.

 

[catone]

For the record (if it matters to anyone) I do dive a JJ, I am fully trained with both trimix diving as well as cave diving and have dove at Eagles Nest.

The narrative given above leads to some questions as well as some assumptions that can be made on the conditions of the dive. Note that I base this based solely on the narrative on the report PfcAJ quoted from Charlie Robertson.

Diver 2 had just a dry-suit, mask and fins and was noted as positively buoyant. There is no mention if the diver 2 had some type of weight belt built in place to help offset the buoyancy. If indeed diver 2's plan was to ditch the CCR at the restriction, one would hope that some type of offset (I.e. weight belt) for the buoyancy of a dry-suit would be place. Either it was not in place, fell off during the exit (which would contribute to the difficulty of the exit). This is a bit of an assumption on my part.

Without a doubt, diver 2 was in serious difficulties during the exit. With no harness to attach bottles, extreme positive buoyancy of the dry-suit and also with no rig, there would have not been any capability to add gas to the dry-suit. On the way back depths in the tunnel get as high as 220-ish. Having to dip back down to 300' to navigate through the pit with no ability to add gas to the dry-suit must have been very uncomfortable. I think it fair to assume the workload of diver 2 was extremely high

Diver 1 also would have his hands full trying deal with the emergency trying to manage an out of gas diver who is so positively buoyant. Diver 1 may not even have enough negative buoyancy to stabilize the two of them. So I think it fair to say that the workload for diver 1 was extremely high.

It is roughly 600' from the room of dreams back to the pit. In that time two divers (one on CCR) ran through 3 95's of gas plus whatever dilluent was with diver 1. Their breathing and CO2 loading must have been through the roof.

All in all it presents a picture of two divers fighting like hell to get themselves and their buddies out and sadly coming up a bit short. This truly was a deck that was stacked against them.

The one oddity I had from the narrative was diver 1's inhalation loop being crushed while the loop was out of the divers mouth and open. I would have expected if there was a strong enough negative pressure to crush a loop, that it would have equalized by drawing in water through the exhalation once the loop left the divers mouth.

All in all a very sad situation.

KMDs speculation makes a lot of sense. Still some things that seem off: diver 2's rig and bailout were found "just outside the restriction to Revelation Space in the Room of Dreams", to me that means on the exit side. Why would he take his rig off after passing through the restriction, if indeed he went that way? More likely it was removed prior to going in and not found on the way back due to heavy silting. Why not come back for it once back on the line, I guess they thought it would be best to exit and take a chance with the available gas (D1 still having a fully functioning unit, bailout for D2).
Apparently diver 1 light head was found in 270ffw, yet they made it to 220ffw, D1 with backup lights stowed and D2 with a backup dangling from his pocket. Was that the source of light? Or did they have helmet lights?
Scooter was not clipped on and turned off, was it done to navigate the restriction? But they were found on the exit side of the restriction, why not clip it back on and go for the exit/safety bottle?
Crushed loop. Did they fight for the last source of gas? How easy is to crush the loop, anyway? Could it have crashed after the ordeal was over?
Hopefully, the dive profiles from computers and maybe available footage will provide more answers.

 

[Dan]

Revised Scenario tying in the observations above:

Low visibility egress from Revelation, Diver2 trailing behind never sees Diver1 successfully negotiate the restriction ahead in normal CCR backmount & bailout tanks configuration. Diver2 goes open circuit on his bailout 95cf cylinder, decides to d'off his CCR and the other bailout 95cf tank in order to pass the restriction, has problems managing his extreme positive buoyancy, and in a zero visibility silt-out loses sight & contact with his dropped CCR & 95cf bailout tank. Diver1 finds him on the guideline exiting above out past the restriction, and they make the difficult decision to abort a search down in the silt cloud for the dropped 95cf bailout cylinder. (Per Charlie Roberson's statement #11 above, the Recovery Team found the CCR in apparent operational order with the loop closed, and a full 95cf bailout cylinder at the Restriction to Revelation in the Room of Dreams).

Towed via the single back-up scooter, they make it back with difficulty because of Diver2's very positive buoyancy, through the Downstream Tunnel to the vertical shaft leading up to the Pit Restriction, with three 95cf cylinders clipped to Diver1, two of which are nearly exhausted supplying open circuit gas to Diver2. As last resort they look for the AL80 safety at 270ffw, "but was not easily seen on the way out" (per Charlie Roberson's statement #8) and don't find it. They ascend the narrow vertical shaft and exit at the far end of the Pit Restriction and drop the two empty 95cf bailout cylinders (found later by the Recovery Team, see statement #9 above).

They now have only one remaining 95cf cylinder which is likely at half tank pressure at best, which Diver2 breathes open circuit on the long hose, and Diver1 has already plugged into via QC6 (see statement #6) as offboard diluent supply -his own onboard diluent cylinder long ago emptied during the stressful extended return through the Downstream Tunnel. They have five minutes of gas left to negotiate the massive broken Boulder Field of the Pit Restriction, before scootering onward to find the AL80 safety tanks just before the Lockwood Tunnel jump . . .but ultimately get delayed or lost with deteriorating visibility & silt-out and tragically they perish.

Map:
EAGLE'S NEST - Association of Underwater Explorers

It sounds like the straw that breaks the camel's back is Diver2 removal of his CCR. When the area silted out, he should have thumbed the dive & waited for Diver1 to come back & find him near the entrance of the restriction with his CCR still on his back, rather than doffing the CCR & making the silt out conditition worse with positive buoyancy without the CCR on.

 

[mdb]

It sounds like the straw that breaks the camel's back is Diver2 removal of his CCR. When the area silted out, he should have thumbed the dive & waited for Diver1 to come back & find him near the entrance of the restriction with his CCR still on his back, rather than doffing the CCR & making the silt out conditition worse with positive buoyancy without the CCR on.

We will, of course, never know what really happened.

The discourse has now turned in a less fractious manner. The theories and thoughts can help in future planning.

Discussing the "what ifs" has merit.

 

[tbone1004]

Do these types of dives require that each diver carry enough bail-out gas to independently survive the loss of the rebreather? or do they assume they will need to dip into their buddy's bail out to survive a CCR failure?

Do they plan to survive the loss of a scooter AND simultaneously a CCR or is that third scooter a necessity for survival?

there are a couple schools of thought on CCR and DPV bailout planning, but it appears they planned for independent bailout instead of team bailout. Requires more bottles, but is a lot more conservative. In this scenario, you should not have to dip into your buddies bailout unless you also suffer a gas loss out of one of the bottles but you don't plan for that.

The third DPV in this case is a convenience thing. They had ample bailout to kick out from what it sounds like, but the deco penalty of kicking out vs. scootering out is severe. DPV's will move you anywhere from 2x-5x as fast as you kick *depending on how fast you kick, and how fast you choose to go on the DPV*. Cruise speed is typically 2-3x as fast as kick speed depending on your particular scooter and particular kick speed. On my UV26, with my slow 50fpm kick speed, it's 3x. My buddy kicks faster than I do when he's alone, and cruise is just over 2x as fast as his kick speed. We typically exit the caves around 200fpm *limited by my UV26, and crotch comfort*, so 4x my kick speed.
In this case, if a CCR failed, they would be both exiting on their own DPV's, one diver on CCR, the other on OC. If a DPV failed, but didn't flood, then whoever had a dead dpv, would stow it between their legs, grab the fresh one *either between their legs, or their buddies legs*, and they would finish the exit as normal. Tow scooter is mainly a convenience thing to either limit the amount of bailout you have to carry with you because of the speed thing which is compounded by increased deco time, and/or to limit the scenarios where you have to tow the other diver out. It isn't particularly difficult, but it's annoying compared to diving on your own *think towing a trailer vs. just driving your vehicle*.

In an OC scenario, if one of the divers suffered catastrophic loss of gas and was exiting on the other guys air, then he would be towed out because of safety and practicality of two divers trying to DPV while tethered to each other with an air hose, and in that case the DPV's will typically slow down to about cruise speed for practicality of navigating the cave with a trailer behind you as well as thrust limitations.

From what has been said, it sounds like they planned for each to have a CCR failure, and for one of the DPV's to fail. For that dive it is more conservative than many similar dive plans I have seen where they only plan for one CCR and one DPV, or one CCR and no dpv.

 

[wgw04024]

I'm sure these guys are far better on air than I myself am, but it still doesn't seem like 2 95's at 220-250' is very much time to continue into a cave, and get back to the ccr that was dropped.

 

[Bobby]

Many years ago I lived close to EN and had the opportunity to dive it regularly. I have been past the restriction past the EOL and had an event back there myself. My CCR is modified to allow me to take it off at depth, go back on the loop, and push it through restrictions. The dive that I had an issue I had a setup that did not give me solid buoyancy control of the CCR with changing depth. Brett and I had a discussion after this dive where he gave me some ideas that resulted in vastly improving my setup, thanks Brett. I also have dual O2 cylinders on my CCR with my dil plugged in from off board. At the time I changed O2 cylinder size pending depth & penetration planning without placing additional O2 for deco. The O2 cylinders can be easily removed and clipped off in the event that the CCR floods and it is ditched to ease exiting.

On this dive, after entering the restriction, buoyancy control of the CCR was lost resulting in a complete silt out. 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. Eventually I properly oriented myself and exited the restriction, put the CCR back on, and exited the system. This situation nearly doubled my planned decompression time.

My configuration has the CCR clip in on top of my SM rig with not changes needed to my SM cylinders or rig. I simply plug and play using my BO cylinders as off board dil. At the time removing the CCR changed buoyancy considerably, today the CCR remains neutral and the SM wing controls my buoyancy which makes removal/replacement of the CCR much easier.

I learned from this dive that when negotiating restrictions with the CCR that separate O2 will be brought in for decompression in the event that the CCR needs to be ditched for whatever reason. I also plan OC decompression gas volume for having a lengthy delay. On that dive if I had left the CCR I would not have had enough decompression gas to complete my obligation. Due to the remoteness of EN & that I was diving solo with no surface support (an entirely different discussion) I likely would not have survived even if I would have gotten myself out of the water.

After reading the reports, multiple times, from the recovery divers it seems that the team was close to getting out. One, of a number of things, could have possibly turned this situation. There was BO gas left all the way back to where one of the CCR's were located at the entrance to the restriction past the EOL. The experience/ability level required to do this dive is on the extreme end of the scale. I know Andy and a few others have made comments regarding things being easy. An easy dive is relative and they have much more extreme and difficult dives in their experience/ability bag. These dives are well beyond any training agency's certification ability. At this level problems compound very quickly and the difference between more experience and tragedy can be razor thin.