a hypothetical for discussion

[BabyDuck]

ok - you and your familiar, similarly experienced full-cave buddy with similar sac rate plan a circuit. you are at a system very much like peacock (and with the same names and same relative distances) but either it is deeper or the distances between openings are longer or your sac is not as good as it is.

you set up one side by going up the peanut tunnel & putting in a jump at crossover in your usual manner. you go up crossover to somewhere in the middle, hit thirds, drop your cookie(s), and turn the dive. you exit without incident and have a surface interval.

you both now go up the pothole/olsen line and put in the jump to crossover. just as you get to your cookie (which might be a hair past thirds in a theoretical way that can't be measured, but is at thirds by the tolerance of your spg), there's some disasterous happening & one of you loses your gas.

you quickly & smoothly start air-sharing, right at 2/3 gas. viz is intact, the line is fine.

do you:

1) keep going to complete your circuit. it is verified line, and shallower than turning around, but will be at the ragged edge of your gas.

2) turn around and go back out the way you came. it is also verified line, but a bit deeper, and might be past your available gas. you could possibly go out pothole. that line is unverified.

3) turn around and head for olsen. you would go back over your jump then turn left instead of right. you have been to olsen before, but not on this trip/not for several months. it is a closer exit by far, but the line is unverified by you recently.

what would you do? assume a small amount of time/gas lost for discussion, but not more than a couple of minutes.

would it matter if as your team was getting in, another was getting out talking about a nice dive to olsen? or not?

would it matter if you had each put a tank of o2 for deco in the cavern?

aaand...go!

[stairman]

Id definetely head for the pothole jump and evaluate from there weather to surface in Olsen or continue toward pothole depending on remaining gas and stress levels.

[cavediver256]

I would turn and attempt exit at Olsen......if exit from Olsen wasn't possible, then Pothole would be my second choice. I would want to get to the nearest exit as cleanly and quickly as possible. End of story !!!

[RN]

None of the above. I don't push my gas management that much. The most I'll push anything is 1/3s + 100. So if I start with 3600, my turn pressure is 2500 leaving me 1100 for exit and 1400 for emergencies. I do this in systems like JB or Devil's. In a system like Peacock, Twin, Hole in the Wall, I dive 1/3s + 200...3600 starting, 2600 turn, 1000 for exit, 1600 for emergencies. If it's a new system or involves advanced stuff, like really tight sidemount passage, I dive 1/4s. This is also what I teach my students because of the possibility of something like what you describe in your scenario. If you need more gas to do the dive, then get larger cylinders or bring a stage.

[Mark Vlahos]

Given your hypothetical I would head for Olsen. If we were unable to surface at Olsen, next would be Pot Hole. If Pot Hole didn't work out I would head for my deco bottle, but usually that is around 30 feet so it is pretty close to the surface. Getting on O2 means the luxury of a safety stop, but if I was still on back gas the safety stop would likely not happen since we would probably be SOL by that time.

All of the diving would be near the ceiling to take whatever advantages there are from being even a few feet shallower with regards to Boyle's Law.

Your hypothetical is pretty specific, so I'll keep my answer limited to your scenario.

Mark Vlahos

[netmage]

1) keep going to complete your circuit. it is verified line, and shallower than turning around, but will be at the ragged edge of your gas.

2) turn around and go back out the way you came. it is also verified line, but a bit deeper, and might be past your available gas. you could possibly go out pothole. that line is unverified.

3) turn around and head for olsen. you would go back over your jump then turn left instead of right. you have been to olsen before, but not on this trip/not for several months. it is a closer exit by far, but the line is unverified by you recently.

would it matter if as your team was getting in, another was getting out talking about a nice dive to olsen? or not?

would it matter if you had each put a tank of o2 for deco in the cavern?

aaand...go!

I don't agree with, or understand the "might be past your available gas" comment.... 3rds is 3rds is 3rds...

I havn't been to Olsen lately - last time I recalled - I thought the sink was visible from the Crossover jump... so from that perspective - I would consider it verified and egress there. Knowledge of the cave comes to bear here. I may have to look tomorrow - on the map it looks further...

I'm also w/ Rob - when calc'ing gas we round down, so there is always a little gravy.

On points #1 & #2 - 3rds is 3rds is 3rds... The only parameter shifting balance towards Peanut as being preferred - is if deco gas is not in the basin... If you do NOT have deco gas - you will want the final shallow exit the Peanut profile provides (say that 3 times fast...)....

But I'm also leaning heavily towards path of most recently known egress...

[tecterri]

Marcie,

Tim (netmage) and I had a rousing discussion about this, we just did a 3 hour dive in Peacock today . . . it continues to put the "what do we do if" scenarios as part of our dive planning. Thanks for the post !!

My gut reaction to the scenario is our training tells us to return to the known/verified/gas requirement exit.

My real world response (only because we dive this cave so often) would be to get to Olsen, if Olsen was not available, get to Pot Hole.

[Tegg]

switch to the other tank and exit.

[tecterri]

switch to the other tank and exit.

Tim says I can do this ~

[RN]

I don't agree with, or understand the "might be past your available gas" comment.... 3rds is 3rds is 3rds...

I havn't been to Olsen lately - last time I recalled - I thought the sink was visible from the Crossover jump... so from that perspective - I would consider it verified and egress there. Knowledge of the cave comes to bear here. I may have to look tomorrow - on the map it looks further...

I'm also w/ Rob - when calc'ing gas we round down, so there is always a little gravy.

On points #1 & #2 - 3rds is 3rds is 3rds... The only parameter shifting balance towards Peanut as being preferred - is if deco gas is not in the basin... If you do NOT have deco gas - you will want the final shallow exit the Peanut profile provides (say that 3 times fast...)....

But I'm also leaning heavily towards path of most recently known egress...

Olsen is about 100' from the Crossover jump and I've never been able to see it from there.

switch to the other tank and exit.

Gotta love sidemount!