Diving incident at Eagles Nest Sink

[Kevrumbo]

rough math.
1.5cfm SAC rate, should be about 2x elevated sac rate, but not out of the realm of possibility for a hypercapnia incident.
Assume 300ft for easy math of 10ata
Consumption is 15cfm
2x95's cave filled = 260cf of gas
260/15=17 minutes
17 minutes of kicking at a normal pace of 50fpm=850ft of bailout gas.

EoL at 1200ft puts you in the middle of the Pit if you are going off of those numbers. Have an extra AL80 in that room and that will get you another 250ft into the Ballroom where you have deco bottles staged. Is this thin? Yes if you subscribe to the numbers above being real. It does not give you much time to be in an excited state and stuck in one spot, doesn't give you much time to fix a problem, but few divers ever really plan on that sac rate of 1.5cfm lasting more than a couple of minutes

With a spare DPV they could have expected to be going at least 2x that kick speed out of there, and a 1.5cfm sac rate is about 3x of a normal sac rate when on a dpv and about 2.5x a relaxed kicking sac rate. Is this enough gas? I think in most peoples minds the answer is yes, but what it doesn't account for is sharing gas with anyone. This is same ocean diving where you can't plan on being your buddies lifeline to get out. IMHO leaving the CCR and a full bailout bottle where they did is what ultimately caused the dual fatality. What brought them to leaving full bottles and a functioning CCR back there is something that I doubt we will ever know. My dive buddies and I have discussed this many times, and have a mutual understanding that one is better than none and there is nothing and no one in a cave worth dying for. Harsh reality, but we plan close proximity solo diving because panic can cause too many problems in the water

. . .

Yeah FWIW I figured 22 minutes for two 95's at 10ATA and SAC 30l/min (1.1 cfm) . . .If they could've found that AL80 safety at 270' deep at the bottom of the Pit Restriction, that might have got them via single scooter to the safety tank stash at the Lockwood Tunnel junction.

But leaving that full 95cf tank back at the end-of-the-line/Revelation Restriction left them no more margin for error or adversity -and that was the hypothetical dilemma for them:

Do you spend time and consume gas at the Revelation Restriction 1200ft back looking for that dropped/lost 95cf tank and CCR in a silt-out off the guideline at 300' deep? Or conserve what you have left in the three 95cf cylinders and immediately use the single back-up scooter to tow both of you back to the Pit where you know you stashed that AL80 safety?

An obvious but draconian choice nonetheless -they had to gamble their lives that they would make it back to find that AL80 safety tank. . .

 

[dumpsterDiver]

I would like to apologize if I am being dense, however is the current understanding that the CCR was left in front of the restriction, the divers both penetrated past the restriction and went further into the cave (voluntarily) and they planned to pick up the CCR and use it on the way out? And then there was a problem getting back on the CCR because it was difficult to locate?

This sounds so crazy to me that I am embarrassed to ask. Tell me I am misunderstanding the discussion and I will delete this post.

 

[Kevrumbo]

I would like to apologize if I am being dense, however is the current understanding that the CCR was left in front of the restriction, the divers both penetrated past the restriction and went further into the cave (voluntarily) and they planned to pick up the CCR and use it on the way out? And then there was a problem getting back on the CCR because it was difficult to locate?

This sounds so crazy to me that I am embarrassed to ask. Tell me I am misunderstanding the discussion and I will delete this post.

I now don't think it was an elective option in the original plan to drop the backmount CCR 1200ft inside and purposely explore the rest of the passage into Revelation Space on open circuit sidemount --think about it DD! You can't get farther distance inside the space linearly on open circuit versus CCR at 300' deep!! Does that make sense? They stayed on CCR until one of them determined he couldn't make the Revelation Restriction and d'offed the Rebreather & bailout 95 tank as a contingency either on egress, or maybe on initial ingress with a thumb-the-dive abort & turnaround. . .

Go back and read Dsix36's incident: Diving incident at Eagles Nest Sink

They probably had a similar situation on egress at the Restriction (or sideways along the Crevice). . .

 

[Dan]

Yeah, that's what I speculate from reading the previous posts. It would be helpful to put a small strobe on each of AL80 safety tanks for locating it when silt-out condition occurs.

 

[PfcAJ]

Yeah, that's what I speculate from reading the previous posts. It would be helpful to put a small strobe on each of AL80 safety tanks for locating it when silt-out condition occurs.

Safety tanks get clipped to the line which is what you're following during zero is. A strobe isn't the appropriate tool for finding your scuba tanks in a cave.

 

[CptTightPants21]

I would like to apologize if I am being dense, however is the current understanding that the CCR was left in front of the restriction, the divers both penetrated past the restriction and went further into the cave (voluntarily) and they planned to pick up the CCR and use it on the way out? And then there was a problem getting back on the CCR because it was difficult to locate?

This sounds so crazy to me that I am embarrassed to ask. Tell me I am misunderstanding the discussion and I will delete this post.

No.

CCR and bailout were on the back end (deeper into the cave).

 

[TONY CHANEY]

I mention contaminated gas because its probably the only causal factor which actually demands a speedy examination to avoid future catastrophe to someone else who has gotten fills from the same source recently.

There has been at least one "save" (in FL) by the rapid publication of info about a compressor failure which was detected by a diver's CO monitor.

Not exactly true. Both divers were diving the same rebreathers so it could have been an equipment failure.

 

[cerich]

Bad silt out and you won't see a strobe even feet away.

Yeah, that's what I speculate from reading the previous posts. It would be helpful to put a small strobe on each of AL80 safety tanks for locating it when silt-out condition occurs.

 

[cerich]

Not exactly true. Both divers were diving the same rebreathers so it could have been an equipment failure.

All reports indicate it was not a ccr failure so far.

 

[RainPilot]

His on board dil tank was empty and his offboard bailout was empty. He was the very definition of zero dil and no means of lowering his PO2.

Although, from the description of the location, he was pretty close to one of their safety bottles and then eventually their deco bottles.

Loss of dil is very rarely a major emergency in terms of loop gas composition. Your PPO2 is constantly reducing due to metabolism. Unless you subsequently have a MAJOR descent which you do fast, you should be able to hold a setpoint by not adding O2 (manually or solenoid).

Of course, there are some compications that may arise leading to longer deco if you cant do a dil flush but in an emergency a lack of dil wont give you a PPO2 problem on the ascent usually. Maintaining loop volume in a scenario where you go down to get up would be a lot more difficult to deal with. I wonder if that isnt maybe a part of why the loop was crushed? Towing a very buoyant diver I would instinctively drop my loop volume to minimum to get negative, then when I needed to descend on the way out I may find an unbreathable loop with empty counterlungs. As a new CCR diver and no clue at ALL about cave CCR training, please correct me if this is something that is dealt with in training.

I imagine the only way would be to grab a breath off the OC and then exhale into the loop, I dont think Id have the wherewithal to think of and do that while in a full emergency.

Ive done a lot of SAR for my buddies in the Air Force when they have gone missing. Finding your friends and getting out the bodybags is not something that ever leaves you. Listening to Ken and co, it seems that there are a lot of similarities. However, my personal safety was generally not a huge factor, unlike these brave volunteers. You guys and especially your spouses etc have all my respect and admiration.