Accident on Southern Cal Oil Rigs Dive

[HalcyonDaze]

I have my pony filled with 30% nitrox, because on my deepest dives these days that's what I put in my main tank. I haven't been an adherent of the 1.4 limit since I got my nitrox cert back in 2005; I treat 1.6 as a never-exceed and try to give myself a little bit of room for error. These days the bottom is at about 135-140 on the deepest site I hit and I haven't gone deeper than 136, which I was probably at for a minute at most.

My rationale was the same as boulderjohn stated - if I'm close to NDL when I need to bug out, I'd rather have a little extra cushion against DCS even if my calculations are factoring in a normal ascent rate and a safety stop. That said, every time I open the valve, test the reg before the dive, and then purge it after shutoff that's taking a little gas out. With air I could just top it off regularly, as opposed to having to completely drain and refill it with nitrox when it goes under par.

I find it unlikely that using 32% for 9 minutes at 130 ft is going to cause someone to pass out. Possible, but unlikely.

I would think 9 minutes was the total time from when he left the surface and not how long he was at depth. When I selected a 19 cf tank as my bailout, it was after I had run the numbers through an Excel spreadsheet provided by a tech diver. Assuming a base SAC of 0.8 cf/min, ascending at 30 ft/min, and taking a 3 min safety stop at 15 ft, coming up from 140 ft would consume about 15.5 cf of gas - roughly 82 percent of the tank's gas, leaving me with a little over 500 psi. That's after 7-8 minutes of ascending or hanging at 15 ft, not remaining at 110-133 ft.

For another example from the near miss section, some time ago a poster put up a video of himself using an underfilled (~2,500 psi) 13 cf pony bottle to dive down and get a weight belt at 85 ft. The descent took about a minute and it was another minute on the bottom before he recovered the belt, after which he had 1,300-1,400 psi left. He then took two minutes to ascend and got back up top with a little under 1,000 psi. Run the numbers and he burned about 4-5 cf of gas in 2 minutes descending to and leveling off almost 50 ft shallower than where the victim in this case was going.

 

[infieldg]

I can imagine me possibly doing the same in the early days, backmounted and without my own pony and green (so very green) hose and secondary cover, maybe borrowing a pony and asked someone to help me get dressed and clip it on, rushing to not hold anyone up, asking where my reg went as it inevitably got tangled and having a helpful hand pass the wrong but same coloured one over, dunno... wouldn't happen now (touch wood).

From that point on everything would look perfect wouldn't it, wrong reg or not you'd still check the main tank's gauge before rolling in and again on the way down where it would have lost a little pressure to the cold, then suddenly nothing. Horrible.

 

[Diving Dubai]

A very interesting thread, with stark conclusions. Thankyou @raftingtigger for posting.

My comments here are based from personal experiences, and I mean no disrespect. Indeed hopefully others can learn from me too.

1. Breathing a Pony down to zero in error:

Yes, I've done this. In my example I'd intentionally switched to my pony to breath it down halfway. The premise behind this, was that our boat pumped Air or 32% The following day we were doign a deeper dive and I wanted a leaner fill. Enjoying the dive, forgot that I was on my pony - not watching my contents. and then felt my reg go tight. Switching regs was no issue but I did admonish myself considerably. My point here being I assume the Diver's main reg was very close. So in reality shouldn't have been more than an embarrassment.

2. Inhaling water

Yes this has happened to me too. I still don't know the cause (the reg came back No fault Found) However while diving I took a wet breath. I immediately purged (exhale) tried again. Nothing. Switched to pony (always on, reg never more than a quick pull away) again nothing. Both SPG's showed in excess of 160bar. Even though my buddy (wife) was only a few metres away taking a pic of something, I headed for the surface. My computer showed I covered 10m in 30 seconds (two ascent alarms) - at 10m I could breath. My epiglottis had shut (natural defence against water ingest) and spasmed shut.

My point with this, is that even if you swallow water and your epiglottis shuts, you still have time to sort out the issue. I can assure everyone, that those 30 seconds heading for the surface seemed like an eternity and I had full clarity of thought - although the incident happened at only 21m.

3. Pony and gas mix.

I realise this is all personal. I happen to chose always to sling. I would always carry a 40cf. it would be filled with 32% if my hard bottom was in the rough MoD range, or 21% if not. Most of the sites I dive, while reef walls and pinnacles have hard bottoms at or below the 100m mark (similar to this rig).

On one dive I was at 30m (with a 21%pony) and a down current hurled us to 57m - just below the MoD for Air. My wife and I had to mountain climb back up the pinnacle and get out of the current - and we incurred some deco. Even though I had a 15L (HP120, and she a 12L HP100 + 30cf pony) we found ourselves well below acceptable minimums near the end of deco. We happend to use gas off other divers in our group to preserve what we had left.

The point of this story, is on dives with a hard bottom below 40m I now drag an 80CF as a pony. While gas planning seems sufficient on the surface, when the SHTF you don't want to be wishing you were carrying more gas.

I still am at a loss while this incident ended this way because it should have been survivable but we'll never truly know.

 

[Hatul]

I suppose, but if you're matching your MOD with the dive how much nitrogen are you really cleaning up? For example a planned dive to 130 ft. at 1.4 ppo2 is what, 28%. Is that extra 7% going to make that much of a difference for the ascent and safety stop? Not trying to be argumentative. Honest question.

Edit to add: Personally, I'd rather not have to think about what is in the pony. I also don't want to be constantly dumping and adding gas for different dives. Fill it with air and forget about it.

I agree. The pony is for situations where things have gone wrong and you don't want an extra issue to worry about. What if he inadvertently descended below the mod either from loss of buoyancy or a downcurrent. Even if the chance of seizure is small if you do have one it's fatal underwater. And a report on this accident suggested he may have had a seizure which is why he could not troubleshoot the problem.

 

[EricTheDood]

Understand that when your number is up and its time to go, it doesn't matter what you are doing and how much knowledge and experience you have, a mistake will be made because it is part of the equation. If today was your day to die and you knew you were going to be hit by a truck, you would stay home and think you have beaten death by not going anywhere only to choke on a piece of chicken you fixed yourself for lunch and die. You cannot alter this so I do not believe the guy was careless. In his mind he did check and did have the right regulator in his mouth and was breathing from the correct tank. I apologize to those of you that believe we are in control of our own destiny as I have no intention to offend anyone here. Its just the way I'm wired...

Your post has no place in any sort of accident analysis forum. Save it for the passings/condolences forum. IMO your posts in this thread should be deleted by the mods.

It shouldn't be difficult to understand the difference between self preservation and free will.

 

[EricTheDood]

2. Inhaling water

Yes this has happened to me too. I still don't know the cause (the reg came back No fault Found) However while diving I took a wet breath. I immediately purged (exhale) tried again. Nothing. Switched to pony (always on, reg never more than a quick pull away) again nothing. Both SPG's showed in excess of 160bar. Even though my buddy (wife) was only a few metres away taking a pic of something, I headed for the surface. My computer showed I covered 10m in 30 seconds (two ascent alarms) - at 10m I could breath. My epiglottis had shut (natural defence against water ingest) and spasmed shut.

My point with this, is that even if you swallow water and your epiglottis shuts, you still have time to sort out the issue. I can assure everyone, that those 30 seconds heading for the surface seemed like an eternity and I had full clarity of thought - although the incident happened at only 21m.

This is a great piece of info that never gets mentioned in OW/AOW instruction. Running out of air comes as a shock to the body and mind. Things may not happen the way you'd expect, and may not be as simple as switching a reg.

In your case, it was a wet breath for an unknown reason. In another diver's OOA situation, he could have taken a wet breath in a panic. That's a bad situation to be in at 130 FSW.

I sling a pony in case a reg on my backgas freeflows, not because I wrecklessly suck the backgas down to zero.

 

[EricTheDood]

I still am at a loss while this incident ended this way because it should have been survivable but we'll never truly know.

I think it was the shock and confusion factor. The diver may have also been narc'd.

IMHO, putting in the wrong reg was an excusable error. It's one of the pitfalls of using a backmounted pony. Where it all went wrong was when he looked at his SPG and didn't notice that it wasn't going down with each breath. If he had a digital SPG, he should have caught that error on the boat. If he had a mechanial spg, he should have at least noticed on his way down.

Barring that, I think a lot of people would have ended up in the same situation. "Can't breathe out of the reg - whoops, I'm OOA. Not going to go for the octo because it's OOA as well. Don't need to go to my dive buddy because I have a pony. Still calm at this point, so time to go for the pony. Wait, where is it? Panic."

I would speculate that in that state of panic, the diver never knew he had the pony reg in his mouth before he passed out.

 

[EricTheDood]

As a side note with regards to the SPG, it's one reason why I like to use a digital SPG and also why I like to always dive with a full tank.

Alarm bells should ring if you've been down for even 3 minutes and your pressure's at 3400psi.

 

[HalcyonDaze]

This is a great piece of info that never gets mentioned in OW/AOW instruction. Running out of air comes as a shock to the body and mind. Things may not happen the way you'd expect, and may not be as simple as switching a reg.

In your case, it was a wet breath for an unknown reason. In another diver's OOA situation, he could have taken a wet breath in a panic. That's a bad situation to be in at 130 FSW.

I sling a pony in case a reg on my backgas freeflows, not because I wrecklessly suck the backgas down to zero.

That's the same reason I carry a pony - a pull-the-cord-and-go bailout in case the primary reg/tank suffers a catastrophic malfunction and nobody else is around to donate gas.

I had a similar experience as Diving Dubai in shallow water off Catalina a little over a decade ago - my mask half-flooded and as I was trying to clear it a took a breath (or thought I did) and got nothing. Spat my primary out, grabbed my Air2 ... nothing. At that point my buddy saw I was having issues and signaled to share air, which we did. At that point I got a breath and settled down; we then proceeded to surface and I checked my regs. They were working fine. Turns out I had gotten a slug of nice, cold, Southern-California-in-November seawater up my nose and my breathing reflex had shut down. It's notable that in his case, rather than trying to get the attention of his wife "a few meters away," he initiated an OOA ascent from 21 meters - which indicates that "full clarity of thought" aside, he took a direct route to the surface rather than trying to get to an available air source that was closer.

Just as a note, Power Scuba did post a photo of the victim on the FB announcement for his memorial service back in November; while it was not the photo in the account of him making his entry it was him on the day of the accident gearing up. In light of the posted account, I did notice a couple items. His pony bottle was mounted to his main tank on the right side, and the reg appeared to be a similar if not identical model to his primary second stage. Both hoses (I presume, since the picture was taken from the right front at close range) were over the right arm and secured with the same hose keeper to his left chest D-ring. It appears he also had an air-integrated BC inflator as an alternate air source.

Personally, I keep my primary second stage on a necklace and my alternate on the left chest D-ring (I'd prefer to have the primary on a long hose and the alternate on a necklace, but it's a pain to find a 5-ft hose that works with my primary reg set), while the pony second is on the right chest D-ring. More importantly, both my main primary and alternate second stages are Poseidon Cyklons while the pony is a Scubapro R190 - hard to confuse those two models even blind.

 

[hakuna]

Don't know if anyone else does this, but I use a custom molded mouthpiece on my primary second stage and a generic mouthpiece on my pony second stage. So if its super comfortable it's not my alternate.