Bad Planning.... could kill you.

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Superlyte27

Banned
Scuba Instructor
Messages
4,727
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Location
Florida
# of dives
5000 - ∞
So there was another death at Ginnie this week. Which sucks. Given what I've heard from some of the recovery team, it appears to me that this was a case of poor planning. But that's just rumor. Rumor or not, I've seen a lot of poor planning when it comes to cave diving. Unfortunately, my dive buddy and someone I consider a close friend is probably the worst I've seen.


In planning a dive to the end of the line at manatee last week, I was told that my buddy only plans for one catastrophic emergency. So I gotta ask. What do you plan for? I've heard Jim Wyatt state that if you are going to plan for EVERY emergency, then you might as well not even get out of bed. But where do you draw the line? One catastrophic event, 2, 10?


Here's what I do... Let's use the dive at Manatee as an example.
Assume I'm diving to 10,000' for easy math. At max penetration my rebreather dies. ONE CATASTROPHIC EVENT. At 150 feet per minute on the scooter it should take me 67 minutes to reach open water. That's if I can stay on the trigger the whole time, there's no delays due to lost visibility or other issues like tangled lines, restrictions, etc. I'd guess that the average depth is 3.5ata. So, if my resting SAC rate is .5cfm, can we safely assume that when the crap has hit the fan, it might be elevated to .75 or .80. Let's be conservative at .75. 67 minutes at .75cfm x 3.5ata = 175 cubic feet of gas. Now, bear in mind. That's the gas you need to exit the cave with just ONE CATASTROPHIC ISSUE. So, what's it say about my buddy that wanted to do this dive with just 2 LP46 bottles for bailout. If you pumped them up to 4000psi, you'd have 139cu' of gas. Remember that if everything went right, we'd need 175cu' of gas.


But, that's for one emergency. Any idea why people carry 3 lights into a cave? Because two lights have been known to fail in a dive. Hell, 3 lights have been known to fail. In the event that your primary light failed, could you still maintain 150fpm exit speed. Could you still maintain .75 SAC. I hope so, because if you carried 175cu' of gas, you'd get to live if nothing else changed.


But what happens if the scooter fails. You're not going to exit the cave at 150fpm. You might be able to exit at half that. But for argument sake, let's say you could swim out consistently at 100fpm without increasing your SAC rate above .75. What do you need to get out?
10,000' / 100fpm = 100 minutes x .75 sac x 3.5ata = 262cu' of gas. And you want to bring 139cu'?


Guys, do you understand that when you plan so skinny on bailout gas, that all it takes is a SECOND issue to equal your death? Just one more issue, no matter how minor, and you're dead. Two things in a row happen all the time. Ever had two tires blow in the same week? A tire shouldn't ever blow. But they do.


Are you really going to risk your life just to save the hassle of carrying a couple of extra bailout bottles?


So, to answer the questions I asked earlier... How many events do I plan for? I plan on my rebreather dying, my scooter breaking, my dive buddy not noticing and scootering away from me, and I have to swim myself out.


10,000 feet back in a cave. I'm taking 100 minutes x .6 x 3.5 = 210cu' x 1.5 = 315cu' of gas. And it's not just me. Talk to the big names pushing long lines like Bret, Andy, Beckner, Draker, etc, and ask them if they're planning skinny bailout. I promise you they are not. And neither should you be.
 
In reality, I'm good for at least 2 failures before I have to get creative.

I can lose 2 regs and still share with my buddy. Or lose my RB and a reg (even then I have my buddy's longhose in a pinch). I could lose a scooter and my buddy could tow out, or swim out if 2 fail if we're not towing a backup. On multi scooter dives, we could lose 3 and still have propulsion. I can lose deco gases and share if on OC, or plug in my buddy's to drive the 'breather.

In my opinion, this is a big strength of diving in a cohesive buddy team where everyone has the same gear, the same plan, and the same reactions to situations. Your resources are doubled.
 
I've swam out twice because my buddy didn't realize my scooter died.
I've lost my rebreather once. My dive buddy couldn't do anything to help, because he couldn't find me in the zero vis.

In the two serious issues I had, my dive buddy was completely unaware and gone. Yes, I know, should find better buddies. :)
I truly believe you can't count on anyone but yourself for survival. I'm happy to have the help, but don't count on it.
 
I can get out without them no prob, but I've also NEVER had a buddy leave me, its just not on the table for the folks I dive with.

See above about cohesive team.
 
I probably dive with A LOT more people than you do. But, Either path is fine by me. I don't count on my buddies, and I have more of them. You do count on your buddies, and because your circle is much smaller, you can trust them more (I guess).

Either way probably works.
 
Stupid wreck diver here. Isn't 10,000 feet back a massive push? Like a 400 foot deep dive? Sure, you can do it solo or with a buddy you don't rely on (same thing in my book), but to me, you are at expedition situation here. This is a team that might carry a spare rebreather, enough team bailout to get a couple of divers out, spare dpvs etc. etc. Does anyone wake up in the morning and say "I'm bored, I think I'll push 10,000 at my favorite cave?"
 
The problem that occurs is what planning and what testing? How often do you see a couple people that have met over the internet forums joining up in the parking lot for a "lets got to the Hinkle" dive. We have two divers (won't call them a team) 3000ft back who never did an S drill, never thought about dissimilar tanks, did some math that said they could make it out on an AL80 with never testing it, never discussed towing in case of a DPV failure, possible rally points if there is separation etc etc etc.... nope, nothing could go wrong here.
 
Stupid wreck diver here. Isn't 10,000 feet back a massive push? Like a 400 foot deep dive? Sure, you can do it solo or with a buddy you don't rely on (same thing in my book), but to me, you are at expedition situation here. This is a team that might carry a spare rebreather, enough team bailout to get a couple of divers out, spare dpvs etc. etc. Does anyone wake up in the morning and say "I'm bored, I think I'll push 10,000 at my favorite cave?"
Frank,
With modern scooters and rebreathers a dive to 10,000 feet at Manatee is just a matter of 90 minutes of trigger time. It is very easy if NOTHING goes wrong. This is the problem; once you have done it a few times it is easy to say "I don't really want to deal with all those bailout tanks that i never need" Peter's post is very relevant to all divers; just because it has worked for you in the past does not make it a good plan.

Thanks for for this post Peter, and dive safe out there.
Mark
 
Frank,
With modern scooters and rebreathers a dive to 10,000 feet at Manatee is just a matter of 90 minutes of trigger time. It is very easy if NOTHING goes wrong. This is the problem; once you have done it a few times it is easy to say "I don't really want to deal with all those bailout tanks that i never need" Peter's post is very relevant to all divers; just because it has worked for you in the past does not make it a good plan.

Thanks for for this post Peter, and dive safe out there.
Mark

Aye, and I wasn't being crappy at all, it was an honest question. A dive to 400 feet is same. I've done bounces on the Wilkes to 250 feet and never incurred a deco obligation. That doesn't mean that I didn't have full backgas, shallow and deep deco gas, and plenty of each. In fact, it wasn't meant to be a bounce, but did you know it's cold at 250 feet?

Anyway, it isn't the 90 minute run time or the deco or scooter, it's 10,000 feet frickin back in a cave. When I first started diving, that would be a major expedition with months of wintertime planning, teams of 20 supporters to support 2 divers, with staged gas all along the route, etc. etc. Kind of like a dive to the Britannic. Sure, I could dive to the Britannic, I have the certs, and the knowledge, and the gas and the .... and I know enough folks that maybe I could even get an invitation, probably not though. But, we'd have a staged deco platform and lots of gas at 100 feet and a drift plan and a large team and support divers and on and on and on. I've read the dive plan for that dive. It's 20something pages long. Maybe a 10,000 foot push isn't loke going 400 feet deep. I happen to think a 400 foot dive would be a walk in the park compared to a 10,000 foot penetration, but as I said, stupid wreck diver here. I don't enjoy wet rocks.

I happen to agree with Mr. Wyatt in this case. You can only plan for one catastrophic failure in this (or any case). Actually, it's one equipment failure and one failure to do the right thing about it. Any more than that and the possibilities are too numerous and complex to calculate.
 
This post has nothing to do with the recent incident, I know none of the details and will not speculate.

The issue, IMHO, lies with planning for the perfect failure. Lets use BO gas as an example, it doesn't matter if the dive is OC or CCR both still need BO gas. Diving to full 1/3's is taking the reserves or BO to the skinny edge. It assumes that if there is a gas issue that breathing rates will be matched and stay the same all the way out. The same is true of assuming an average RMV for CCR BO. At the least I hold a couple of hundred psi above thirds and more if I don't know the teammate very well. With CCR I calculate a 1.5 RMV to handle a CO2 hit or anything else that may raise my RMV. When things go bad they tend to cascade & create other issues so I plan on having some cushion with all contingencies & back ups.

It works the same for lights. If I'm doing a 5 hour dive I have a light capable of doing double that time along with back up lights and/or I carry more back ups. That way if there is an issue I have every opportunity of getting out of the system with a working light which helps keep a failure from cascading into more problems on a bad dive.

Planning for everything to go well on a dive and planning that a failure will be handled perfectly & smoothly are plans that will fail when tested IMO.
 
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