S. La Jolla Canyon Wall Dive Report
Dive Site: South La Jolla Canyon Wall
Location: North from Buoy B off La Jolla Shores Cove
,
Type: Wall - Top 100' / Bottom 400'+
Entry: Shore
Dive Buddy: Roger Bly
Date: 22 Aug 2010
Time: 8:00 am
Swell: 3.9'
Max Depth: 170'
Visibility: 40'
Temp: 52 f
Dil/Bailout Gases: 18/45 & O2
Runtime: 90 min
Equipment: AG- MX 90 mCCR Rebreather / Roger - Twin 130's and 2 deco's Nitrox 50 and O2
DPV: AG- 2 x Sierra's / Roger - CUDA
Gas used: AG - 3 cft of Trimix and 4 cft O2 / Roger 200 cft / 40cft Nitrox 50 and 20 cft O2
Met Roger Bly at La Jolla shores at 8:00 am sunday morning. After unloading, setting up and a brief discussion about the entry and exit, we decided to shuttle in and out. The swell was wrapping around the point and breaking on the beach. Other locals divers and instructors setting up to dive decided to opt out as the swell was too big, but Roger and I felt we could do it as long as we shuttled the gear in. Especially the 3 DPV's, 2 sierra's and a CUDA. Plus Roger is on Open Circuit so he needed to carry 130's (160 lbs and 2 deco's) :) After 20 mins or so scooter ride out to buoy B, we figured it was about 2500' off shore, we descended and headed north until we hit the wall, about 2 mins on the trigger and the we dropped down the wall to the 150'/160' range. Take a look at the contour map I have included for reference but basically we headed west for 20 mins exploring this gorgeous wall. This really is a world class wall, filled with monster vermillion rockfish, treefish, of course all the other usual suspects but most interesting in this site is the orange gorgonian's, the california golden gorgonian, reds and so on and so on, all plastered up on the wall. Just fantastic. I also love the sponges and of course the one "LONE" white plumed Anemone on top of this floating line about 7' off a shelf on the wall. We also both commented on the Rainbow Starfish that was at 168'. This wall is truly covered with life. After returning to the approximately spot we dropped on the wall, roger and I ascended up the wall and then scootered home during the decompression. Surface just outside the cove and shuttled back up the beach. What a fantastic day. After the dive I did manage to jump on my bike and do a nice 40 miles ride followed by a 6 mile run. So all in all this was great day.
, Replies to This Discussion
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Permalink Reply by Unified Team Diving on -
Wasn't needed as the bottom time and depth were within Technical Diver range and a single O2 window is all that is needed in 1:1.
Rainer said:AG, any reason you did not bring 50% for bailout deco gas?
What was the deco plan if you or Roger lost backgas?
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Permalink Reply by Unified Team Diving on
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Rainer said:So if Roger's 50% bottle had exploded, the plan was just to back gas the deco to 20'? Seeing as he used 40cf of 50%, that's a lot of backgas deco...
Yes
Plan was deep stop's of 1 from 75% and then 2's from 50% and then O2 window at 20'. So,
150 1min
up 2 min
110 1min
100 1min
90 1min
80 1min
70 2 min
60 2 min
50 2 min
40 2 min
30 2 min
20 1 gas switch
Then 20 mins of O2.
This would be the minimum deco ascent profile in an emergency as it was not an emergency we scootered back to shore at depth taking our time of 20 mins from 70 to 20' as we followed the contours home rather than direct ascent. But in emergency we could of done a direct ascent up Buoy B line and then surface scootered home if need be.
Total 18 mins at average of 3 ata at breathing rate 0.75 would be right around 40cft needed or 54 cft if using a tech 1 diver abilout breathing rate of 1.0 cft /min
He was carrying 80cft for bailout so ample.
On a side note, even if roger did not have an O2 bottle we still had mine. So we had a ton of O2 bailout too.
AG
in reality 10 mins of
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Permalink Reply by Unified Team Diving on
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Chris
While I certainly understand your question and will take the time to answer it, I wanted to make sure that we keep this positive and a learning experience, not a slugfest.
So to that end, I want to say that diving, like decompression, is very dynamic. Using your experience, training and resources, especially in emergencies, is part of the power of learning the UTD methodologies and most importantly Ratio Deco. With our style of diving we can easily adapt to the resources at hand. So you asked me what happens if Roger's Nitrox 50 bottle "exploded," which I assume is a dramatic way of asking about lost deco gas procedures.
In over 20 years of diving and teaching I've never seen a bottle "explode." or be lost But if his Nitrox 50 regulator or valve failed, or the bottle was lost or accidently emptied, as I said we would simply ascend to the next available deco gas using deep stops. This is NOT a "we'll bang up to 20' and deco there philosophy". This is an emergency strategy that we (I) have used for over 15 years of decompression diving.
Simply put, if we were in an situation where Roger lost his Nitrox 50 and was using backgas to ascend we would use deep stops to the next available deco gas. 1's, 2's, 3's, 5's depending on if you are at 75%, 50% or 35% of your avg depth. Simple "Deep Stop" strategy. Yes, we could easily do a few extra minutes at 30' and 40' using an exponential curve from "Strict" Ratio Deco, as Roger had a ton of bailout gas - remember he is saving RB for two divers and in this case he is only one diver - but in reality it is smarter to simply accelerate those few extra minutes and do them on the O2 window. In this scenario we are only talking about 5 minutes and those would be more effective at 20' than doing an exponential curve from 70' to 20'.
Now keep in mind the reason that we carry the 50% bottle in OC diving is that we do not carry enough bailout on our backgas for two people to get from the bottom at 150' to 20'. Which is the main reason we teach in OC to carry Nitrox 50% - not for better decompression but for better gas management. In this case, we had ample backgas to bailout to get to 20' to do the deco. If Roger simply lost his 50%, he would use his own backgas to get to 20'. If Roger lost his backgas, I would provide my backgas to his 50% bottle and if he lost his backgas and also his 50%, I still had enough bailout (80cft) to make his O2 bottle. If I lost my breather, I would use my own backgas, or if I lost my breather and backgas, I would use Roger's backgas to the 20'. Now, If I lost my breather and my backgas and Roger lost his Nitrox 50% then we would be short on his backgas, but I am pretty sure we would of still got to the O2. :) I can go on and on with the unlikely scenarios but the fact is that we had more than ample gas for bailout. The other important part of our diving philosophy is we plan for one catastrophic failure. Although it is possible for failures to compound, and we train for multiple failures, it is unlikely an unlikely scenario. A solid, thinking diver will be flexible enough to manage multiple failures, but our focus is returning safely to the surface following one major failure.
Now, to address you last statement, Roger and I dove absolutely seamlessly. That was the beauty of this dive. We had great awareness of each other and, more importantly, of our environment such as the little critters on the dive we both saw like the starfish and so on. We had seamless skills, cohesive mindset, incredible team work especially in the cove where the viz was 3 ft, perfect deco, and so on and so on. The most important thing we had was a ton of FUN. The only difference was that I was carrying 70lbs less of gear and used 3cft of trimix as opposed to his 200cft of trimx.
I hope this helps explain things a little better.
Andrew
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Permalink Reply by Unified Team Diving on
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Chris
As I tried to explain earlier 1:1 ratio deco is based on "One" O2 window. So, in Tech 1 we do that window at 20'/6m on O2 as the rock bottom from 130' and shallower is feasible. As you go deeper we need a 70'/21m bottle so as not to make Rock Bottom too large and therefore we might as well make that the O2 window. So we use a 50% bottle for that O2 window as taught in Tech 2. Of course that 50% bottle become negligible in the shallows and and therefore we added a Technical Gold rating to add an O2 bottle to further increase effectiveness of the shallow decompression and help with the slow tissue off gas. All in all the Technical diver program covers use of O2 or Nitrox 50% and gives a diver after 25 dives of technical diving experience and some more education the tools to improve their technical diving by adding a second deco bottle without adding risk.
Andrew
Rainer said:If UTD is teaching that 50% is being added only (mainly?) for min gas reasons and not for accelerated decompression, then I guess we're at an impasse.
Unified Team Diving said:Which is the main reason we teach in OC to carry Nitrox 50% - not for better decompression but for better gas management. In this case, we had ample backgas to bailout to get to 20' to do the deco.
Andrew
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Permalink Reply by Nick Ambrose on -
Chris, you are a smart guy, where do you think the usage by (say) GUE of 50% might come from(even if these days they may be reluctant to discuss that topic) ? AG is not comparing 50% to BG deco here, he is saying the reason to choose 50% over 100% for basic T2 dives is due to lower RB, not necessarily better deco (given an appropriate ascent profile)
On an OC UTD Tech2 profile, both 50% OR100% O2 can be used to accelerate deco and give very similar runtimes with as effective deco. 50% has some additional benefits (lower RB, isolation from choppy surface conditions etc. etc.)
In the case of the dive described here, omitting the 50% bottle given AG's and rogers large Rock Bottom reserves and Rogers double deco gas was a safe choice. In other scenarios bringing the 50% bottle on the RB in addition may make more sense.
Rainer said:If UTD is teaching that 50% is being added only (mainly?) for min gas reasons and not for accelerated decompression, then I guess we're at an impasse.
Unified Team Diving said:Which is the main reason we teach in OC to carry Nitrox 50% - not for better decompression but for better gas management. In this case, we had ample backgas to bailout to get to 20' to do the deco.
Andrew
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Permalink Reply by Jeff Seckendorf on -
Chris,
Please keep this thread on track. You were not asking about planning a dive, you were asking about an emergency decompression profile in the case of a catastrophic failure (Nitorx 50 bottle "exploding"). All of the responses here reflect the deco for that emergency situation, not for a normal deco ascent with no failures.
Jeff
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Permalink Reply by Nick Ambrose on
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Not to continue this derailment too far :)
Deco planner (20/85)
150 for 30 (omitting the He)
with 100% O2, Runtime 70 mins, deco 37
With just 50%:: Runtime 68 mins, deco 35 mins
VPM+2 (21/35)
100% O2 Runtime 69 mins
50% RT 64 mins
So in the "best" case you save 6 mins on a VPM profile compared to worse case Buhlman of 70 mins
Even if I put the correct He into DecoPlanner its very similar runtimes
and yes, one could do the exact same OC bailout just by bringing a 50% bottle in addition. Lots of options open on the RB.
Rainer said:Nick, have you bothered to compare both profiles (50% vs O2) for such a dive? Just because AG says that they're the same (that you only need one "Oxygen Window" for a T1 dive) doesn't mean that's based on any science.
That some here think 170' dives should be *planned* just bringing O2 (regardless of rock bottom reserves) just shows how far away UTD is starting to get from what most would find to be "DIR" principles.
Nick Ambrose said:Chris, you are a smart guy, where do you think the usage by (say) GUE of 50% might come from(even if these days they may be reluctant to discuss that topic) ? AG is not comparing 50% to BG deco here, he is saying the reason to choose 50% over 100% for basic T2 dives is due to lower RB, not necessarily better deco (given an appropriate ascent profile)
On an OC UTD Tech2 profile, both 50% OR100% O2 can be used to accelerate deco and give very similar runtimes with as effective deco. 50% has some additional benefits (lower RB, isolation from choppy surface conditions etc. etc.)
In the case of the dive described here, omitting the 50% bottle given AG's and rogers large Rock Bottom reserves and Rogers double deco gas was a safe choice. In other scenarios bringing the 50% bottle on the RB in addition may make more sense.
Rainer said:If UTD is teaching that 50% is being added only (mainly?) for min gas reasons and not for accelerated decompression, then I guess we're at an impasse.
Unified Team Diving said:Which is the main reason we teach in OC to carry Nitrox 50% - not for better decompression but for better gas management. In this case, we had ample backgas to bailout to get to 20' to do the deco.
Andrew
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Permalink Reply by Nick Ambrose on
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So if you dive 18/45 or 15/55 to 150 do you adjust your deco ?
Rainer said:Nick, here's what I get in VPM+2 (with 18/45, the gas they actually used):
O2 Runtime: 79 minutse
50% Runtime: 66 minutes
That's rather substantial, IMO. That's almost 40% more deco time!
Nick Ambrose said:Not to continue this derailment too far :)
Deco planner (20/85) 150 for 30 (omitting the He)
with 100% O2, Runtime 70 mins, deco 37
With just 50%:: Runtime 68 mins, deco 35 mins
VPM+2 (21/35)
100% O2 Runtime 69 mins
50% RT 64 mins
So in the "best" case you save 6 mins on a VPM profile compared to worse case Buhlman of 70 mins
Even if I put the correct He into DecoPlanner its very similar runtimes
and yes, one could do the exact same OC bailout just by bringing a 50% bottle in addition. Lots of options open on the RB.
Rainer said:Nick, have you bothered to compare both profiles (50% vs O2) for such a dive? Just because AG says that they're the same (that you only need one "Oxygen Window" for a T1 dive) doesn't mean that's based on any science.
That some here think 170' dives should be *planned* just bringing O2 (regardless of rock bottom reserves) just shows how far away UTD is starting to get from what most would find to be "DIR" principles. Nick Ambrose said:Chris, you are a smart guy, where do you think the usage by (say) GUE of 50% might come from(even if these days they may be reluctant to discuss that topic) ? AG is not comparing 50% to BG deco here, he is saying the reason to choose 50% over 100% for basic T2 dives is due to lower RB, not necessarily better deco (given an appropriate ascent profile)
On an OC UTD Tech2 profile, both 50% OR100% O2 can be used to accelerate deco and give very similar runtimes with as effective deco. 50% has some additional benefits (lower RB, isolation from choppy surface conditions etc. etc.)
In the case of the dive described here, omitting the 50% bottle given AG's and rogers large Rock Bottom reserves and Rogers double deco gas was a safe choice. In other scenarios bringing the 50% bottle on the RB in addition may make more sense.
Rainer said:If UTD is teaching that 50% is being added only (mainly?) for min gas reasons and not for accelerated decompression, then I guess we're at an impasse.
Unified Team Diving said:Which is the main reason we teach in OC to carry Nitrox 50% - not for better decompression but for better gas management. In this case, we had ample backgas to bailout to get to 20' to do the deco.
Andrew
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Permalink Reply by Unified Team Diving on
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Chris
Again, this has become a "slugfest". As I clearly stated, I want to keep things educational and not destructive.
As Nick A pointed out with his post, you clearly do not understand bailout, decompression, contingencies or diving mixed teams (OC/CC).
You stated that it is a "DIR" stipulation that a diver carries Nitrox 50% for the Tech diving ranges - Reality is the only true covenant is "Reserve enough backgas to get you and your buddy back to your next available gas, wether it be the surface or a deco bottle or even a stage bottle depending on logistics.
You stated that O2 and Nitrox 50% deco times for this dive are not the same runtimes. Again Nick A showed you differently in a later post from two different "Tested" sources. The reality is they are one O2 window giving similar runtimes.
You stated, as seen below, that if two divers where carrying the same deco gas and one was to EXPLODE then they would do the same deco plan as if they were both deco'ing on the Nitrox 50%. Again this is completely inaccurate. You cannot and do not do the same decompression shape or profile as if both of you are deco'ing on Nitrox 50. As we do not carry a second regulator on the deco bottle the contingency plan is dependent on the dive conditions and environments and decisions get made accordingly. One choice is the diver with the EXPLODED bottle could just do all backgas deco doing a exponential profile doing twice the originally planned time (different profile from if both are using Nitrox 50%) , another choice might be to share the nitrox 50% where it counts (again a different profile than if both of you had Nitrox 50%) another choice might be...I can go on on with the choices but all will not look like the original plan and are always based on the environment and conditions. Decompression here is not the danger, it is getting the diver calm and home and we had ample gas to do this.
I understand that DIR, Technical diving, Rebreather Diving and more importantly mixed team diving is all new to you, and others. UTD is definitely forging new ground by bringing UTD/DIR configurations into the fully closed circuit rebreather world and into the reality of Mixed Team (oc/cc) Diving. I ask we keep an open mind and see where our future goes with this. As far as both Roger and I were concerned this dive was conservative and safe, as we were surrounded by a ton of bailout gas and a choice of multiple deco gases. Roger was taking advantage of his UTD training, in that he was diving in the Technical Range but was able to carry and use two decompression gases rather than one, as prescribed by others. That made it not only safer for him but more fun because he always knew in his mind that if we had a failure we were well covered.
Anyways, I think we have beaten this to death and I would gladly meet in person and discuss the in's and out's in person vs. a keyboard.
Andrew
Rainer said:Why you would contingency plan a completely different ascent profile for a single lost bottle versus what you'd do in a non-emergency is beyond me (giving up on bubble models and just accepting a pure Buhlmann schedule). All this could *easily* be addressed by having all divers bring the same deco gases. How is that not the DIR answer?
Jeff Seckendorf said:Chris,
Please keep this thread on track. You were not asking about planning a dive, you were asking about an emergency decompression profile in the case of a catastrophic failure (Nitorx 50 bottle "exploding"). All of the responses here reflect the deco for that emergency situation, not for a normal deco ascent with no failures.
Jeff
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