Accident Analysis of Guangxi China Cave Divers Accident (according to DIR philosophy)

[WhiteSands]

I posted this question here instead of the accident analysis sub-forum, as I am a believer in the DIR philosophy of diving, and wanted to hear analysis of this accident mainly from that angle to keep things focused.

Please let me know if it is not appropriate to discuss this here.

I'd like to know if the divers did anything wrong in this accident, and if it could have been prevented.

Were their training levels sufficient for the depth and penetration range of dives they did?

How about the quantity of gas carried? Was it conservatively sufficient?

Did they violate any safety rules or guidelines?

Was their choice of deco gas correct?

If this dive had been done by the WKPP team, what would they have done differently, and why?

Would like to learn as much as possible from this incident. I am not cave/tech trained but will do my best to follow the discussion.

Original article by the buddy of the deceased posted here:

http://www.scubaboard.com/forums/ac...-duan-guangxi-china-cave-diving-accident.html

 

[Mike.D]

Interesting question. I look forward to hearing peoples responses

 

[WhiteSands]

The victim was Wang Tao.

According to the link, these are their training credentials.

[FONT=&amp]Divers information:[/FONT]
[FONT=&amp]Wang Tao[/FONT]
[FONT=&amp]Diver level: WUD CAVE 2, UTD CAVE 2, NSSCDS FULL CAVE, GUE T1
cave diving Start Date: 2009[/FONT]
[FONT=&amp]Cave Diving Experience: 200 +[/FONT]
[FONT=&amp]For the first time in cave diving accident Date: 2010[/FONT]
[FONT=&amp]In cave diving accident Views: 15[/FONT]
[FONT=&amp]Once the largest cave diving depth: 122 m[/FONT]
[FONT=&amp]Once the longest crossing Distance: 1000 meters[/FONT]
[FONT=&amp]Cave Diving: China, the Philippines, Mexico, United States[/FONT]

[FONT=&amp]Wang Yuan[/FONT]
[FONT=&amp]Diver level: WUD CAVE 3, PSAI / NSSCDS FULL CAVE, UTD / NACD CAVE DPV, TDI CAVE REBREATHER / ADVANCE TRIMIX
cave diving Start Date: 2008[/FONT]
[FONT=&amp]Cave Diving Experience: 400 +[/FONT]
[FONT=&amp]For the first time in cave diving accident Date: 2010[/FONT]
[FONT=&amp]In cave diving accidents: 15 +[/FONT]
[FONT=&amp]Once the largest cave diving depth: 122 m[/FONT]
[FONT=&amp]Maximum Open Water diving depth: 150 m[/FONT]
[FONT=&amp]Once the longest crossing Distance: 3000 meters[/FONT]
[FONT=&amp]Cave Diving: China, the Philippines, Mexico, the United States, France, Portugal[/FONT]

[FONT=&amp]Zhou Pei[/FONT]
[FONT=&amp]Diver level: WUD CAVE1/TEC DEEP 1[/FONT]
[FONT=&amp]Cave Diving Start Date: 2013[/FONT]
[FONT=&amp]Cave diving experience: 15[/FONT]
[FONT=&amp]For the first time in cave diving accident date: 2013[/FONT]
[FONT=&amp]In cave diving accident Views: 3[/FONT]
[FONT=&amp]Once the largest cave diving depth: 51 meters[/FONT]
[FONT=&amp]Maximum Open Water diving depth: 63 meters[/FONT]
[FONT=&amp]Once the longest crossing Distance: 100 meters[/FONT]
[FONT=&amp]Cave Diving: China, Philippines[/FONT]

For the victim Wang Tao, I could not find anything on WUD Cave 2 Certification and I have not heard of it.

UTD Cave 2 - Max depth 30m, min 6m visibility to enter a cave, Max Penetration 1/3 of gas, but it does not state maximum penetration distance on UTD's website

NSSCDS Full Cave - Max Depth 40m, Max Penetration 1/3 of gas, specifically says no staging or scootering

GUE T1 - Max depth 51m, max deco time 30mins

[FONT=&amp]Cave conditions:[/FONT]
[FONT=&amp]Cave entrance Depth: 18 meters[/FONT]
[FONT=&amp]Maximum depth: over 170 m[/FONT]
[FONT=&amp]Caves form: Ladder[/FONT]
[FONT=&amp]Typically Visibility: 5-10 meters[/FONT]
[FONT=&amp]Visibility date of accident: 2 m[/FONT]
[FONT=&amp]Flow: weak[/FONT]
[FONT=&amp]Water temperature: 19 degrees[/FONT]

On paper it seems this dive was way beyond the level of training for the diver in terms of depth.

 

[Mike.D]

They hadn't even completed a cave dive to within 50m of the planned depth. Talk about jumping in the deep end.

 

[WhiteSands]

[FONT=&amp]

Gas options: stay underwater because time is short, so accepting a slightly higher oxygen partial pressure, to shorten decompression time.

When I saw this I was immediately very curious as to what kind of PPO2 they were doing to shorten deco time.

Further down it says:

[FONT=&amp]Placed ahead of 21/35 at 57 meters, EAN35 at 50 meters (depth of 36 m switch), EAN 50 at 21 meters, O2 at 6 m[/FONT]
[/FONT]

21/35 @ 57m is 1.4 PPO2
EAN35 @ 50m is 2.1 PPO2 (maybe the wording is suspect)
EAN35 @ 36m is 1.6 PPO2
EAN50 @ 21m is 1.55 PPO2
O2 @ 6m is 1.6 PPO2

For deco it seems all were well within limits, except for the EAN35 @ 50m which may/may not be a mis-translation.
If it were a mis-translation and they only switch ed EAN35 at 36m then I don't see any higher than acceptable PPO2 levels for deco?

 

[Diver0001]

I posted this question here instead of the accident analysis sub-forum, as I am a believer in the DIR philosophy of diving, and wanted to hear analysis of this accident mainly from that angle to keep things focused.

Please let me know if it is not appropriate to discuss this here.

I'd like to know if the divers did anything wrong in this accident, and if it could have been prevented.

This accident didn't start in the water. It started, from my reading of it, when the divers agreed that this dive was within their reach. I posted in the A&I forum about why I believe they may have reached this conclusion.

No agency, let alone an agency that teaches in the DIR style, would approve of doing an entirely experimental dive that was pretty clearly outside the envelope of their collective ability, without adequate planning, without adequate experience, and without building up team ability progressively while working toward this goal.

In other words, they were over-reaching from the planning stages onward. This would normally be a question of mis-judging the dive or impatience but in this case I think there may have been something more going on as well that caused them to over estimate their own abilities, none of which has anything to do with the actual diving.

R..

 

[PfcAJ]

A few things:

"Thirds" for a dive like that is WAY too sporty. Its bananas. Its also bonkers to use backgas. When real DIR teams do cave exploration or deep cave dives, the backgas is always completely in reserve (possibly a few exceptions, but few and far between). We'll put in safeties at key points to up the available gas volume, too. This is probably the biggest thing that I see in this accident from a gas management point of view. The divers didn't have enough time in reserve to handle problems like the one they encountered, which greatly compounds the stress of the situation. There's nothing worse than getting hung up or delayed when you KNOW you're running out of gas. Doing the dive on a rebreather is probably safer, in my opinion. I'm a little unclear as to the exact progression of the dive, but handing a diver a half empty stage with nothing else to breath (empty backgas) is not building your house with bricks. The guy's just going to run out twice making the situation worse. This comes back to not using backgas and placing safety tanks.

The END was probably super high (didn't do the math). Like they said though, HPNS is a thing at those depths, so I don't have a good solution. Option 1, probably (don't dive). I also read that the ppo2 of the bottom gas was a bit high to try and reduce deco time. Not for me. If you're gunna do the crime (the dive), you gotta do the time (the deco). The things guys do when going much past 350-400 gets weird and I have zero experience with it.

35% at 50m is probably 50m IN the cave, not depth.

On to support. Solo support is a no-go, even though the support diver was the real hero that day. Might not have ended so well without him. Imo, for a dive like that you need multiple shifts of support guys to check on the divers including topside management and an evac plan firmly in place.

Over all, the plan seems a bit monkey see monkey do without a lot of real thought put into it. Tragic.

 

[jethrocramp]

[FONT=&amp]
For deco it seems all were well within limits, except for the EAN35 @ 50m which may/may not be a mis-translation.
If it were a mis-translation and they only switch ed EAN35 at 36m then I don't see any higher than acceptable PPO2 levels for deco?

You are correct. It's a poor translation. The line is giving a mixture of where the bottles are placed and where they will switch. So the EAN50 is placed at 50m, but they planned to switch to it at 36m.

 

[WhiteSands]

AJ,
Thanks for the analysis, it's very informative. Sorry for the late reply, been diving.

I totally agree with what you said, that having to solve problems while you know your gas is running out is scary. My skin was crawling as I was reading that part of the account.

A couple of questions:

- You mentioned using rule of "thirds" is not suitable for a dive like this. What kind of gas plan does GUE use for a case like this? How much gas needs to be carried, and how much placed in reserve safety bottles along the line?

- When you say they should not use "backgas" do you mean they should be using rebreather on this dive?

Thanks.

A few things:

"Thirds" for a dive like that is WAY too sporty. Its bananas. Its also bonkers to use backgas. When real DIR teams do cave exploration or deep cave dives, the backgas is always completely in reserve (possibly a few exceptions, but few and far between). We'll put in safeties at key points to up the available gas volume, too. This is probably the biggest thing that I see in this accident from a gas management point of view. The divers didn't have enough time in reserve to handle problems like the one they encountered, which greatly compounds the stress of the situation. There's nothing worse than getting hung up or delayed when you KNOW you're running out of gas. Doing the dive on a rebreather is probably safer, in my opinion. I'm a little unclear as to the exact progression of the dive, but handing a diver a half empty stage with nothing else to breath (empty backgas) is not building your house with bricks. The guy's just going to run out twice making the situation worse. This comes back to not using backgas and placing safety tanks.

The END was probably super high (didn't do the math). Like they said though, HPNS is a thing at those depths, so I don't have a good solution. Option 1, probably (don't dive). I also read that the ppo2 of the bottom gas was a bit high to try and reduce deco time. Not for me. If you're gunna do the crime (the dive), you gotta do the time (the deco). The things guys do when going much past 350-400 gets weird and I have zero experience with it.

35% at 50m is probably 50m IN the cave, not depth.

On to support. Solo support is a no-go, even though the support diver was the real hero that day. Might not have ended so well without him. Imo, for a dive like that you need multiple shifts of support guys to check on the divers including topside management and an evac plan firmly in place.

Over all, the plan seems a bit monkey see monkey do without a lot of real thought put into it. Tragic.

 

[TSandM]

I think most GUE teams would do a dive like this with at least an SCR (semi-closed rebreather). But that wasn't what AJ was talking about.

When GUE divers do a dive with a stage, they set aside a reserve of gas in the tanks on their back, to account for the possibility of either losing the stage, or coming back and finding it empty. By the time you are doing a dive with three stages, you are reserving essentially ALL the gas in the tanks on your back for those contingencies. In such extreme dives, the gas in the doubles you are wearing is purely emergency gas; everything else is in stages or, often, in safeties, which are tanks you have placed during preparation dives, so that they will be available in the event of something untoward during the main dive.

Dives of this magnitude require a great deal of forethought and preparation. Mishaps on this type of dive require an extreme degree of sang-froid to survive.