Myself, Craig Newham, Verna van Schaik and Nuno Gomes squeezing out of Vetsgat
These bits of hard clay could range from fine silt to almost tennis ball sized and occasionally even get as big a soccer balls. Imagine our surprise the first time we went there to feel these bits of roof caving in on our helmets and tanks. I can tell you, we had more than a few very scary moments. Eventually we realized that the roof was not actually going to collapse on us (at least not all at once) so we relaxed a bit and came to really enjoy exploring the cave. Still, I remember occasions when we had to beat a hasty retreat when things got a little too uncomfortable to ignore. As you can imagine the decision to withdraw from the cave was always a very individual thing. One guy might tolerate a lot more roof dissolving than another.
Craig Kahn diving Vetsgat (Photo courtesy Nuno Gomes)
Vetsgat bottomed out in a small chamber at just about 50 metres. The problem with this chamber is that it’s really only big enough for one diver. One time my buddy Larry, seemed to have forgotten this fact, and unbeknownst to me, followed me into the chamber! When I turned around, carrying my guideline with me, the visibility had dropped to almost zero and I didn’t see him. I duly followed my line out of the chamber and back into the clear open space. I expected to find Larry waiting for me. You can imagine the uncomfortable feeling in the pit of my stomach when I couldn’t see him anywhere. I waited a few very anxious moments at about 45 metres for him to come poking out of the silt. At this depth I could not wait for more than a few minutes. I was incredibly relieved when Larry’s torch light poked out of the misty brown cloud towards me.
Never take anything for granted
I recall an incident that, although not a cave dive, was at a cave site and clearly illustrates the element of unpredictability that diving can have. Over the years I’ve always told people never to take anything about a dive buddy for granted. I’ve cautioned new divers to always make a point of asking new dive buddies about their qualifications and about verifying signals between different diving organisations. I like to think I never assume anything about people’s diving skills and experience. But one day, I made an assumption (or be it an unconscious one) that could easily have had fatal consequences.
The weekend of the 1st and 2nd of March 2003 turned out to be a very scary learning experience for me. More than that, it was a salutary reminder that diving, even so called sport-diving, has a dangerous side to it which must be respected.
We were at Badgat a site some 300 kilometres north-east of Johannesburg. In addition to being a popular place for more advanced divers because of its 54 metre maximum depth, Badgat is also a favourite site for cave divers. This is because Badgat(or Komatie Springs as its called now) is a disused asbestos mine with a series of tunnels that lead to a shaft that drops to 100 metres. On this occasion our first dive to just twenty metres in open water (for me a dive that should have been routine to the point of boredom), all seemed well - then I turned to check on my group and found only two of the three other divers in my group were visible. I did a quick look around for signs of the missing diver. No sign! – We swam back along our route; in the low visibility she’d probably just fallen behind a bit and would no doubt emerge out of the brown mists surrounding us. A minute that felt like an hour passed - no sign. Look up - no sign. Look down - no sign. The bottom is 54 meters deep here. Do I go down and look? I go to almost 30 metres. Still no sign. The little voice in my head put there by years of training and diving shouted at me lost buddy procedure ... I looked around in a slow circle ascending slowly - so up we go. As we broke the surface I looked around, almost franticly now; still no sign! I could see lots of bubbles around ... A large group of divers passed below us. The little voice in my head hammered away again. Four minutes without oxygen before we see minor brain damage, eight minutes before serious problems … To make everything worse the lost diver was my fiancé on her first real dive in about five years. To keep myself calm and force my mind to think clearly, I decided to assume she’d just got separated from the rest of us and was alive somewhere below us. That gave us twenty minutes or so to find her. I followed procedure again. Looked for bubbles, called for assistance, then I descended down a line of bubbles which I knew should lead me to a diver. Luckily was it the right diver. By sheer grace, I’d chosen the correct set of bubbles and found her at twenty metres. She was fine, but I gave her the briefest shake on the shoulder before proceeding to inflate her BC and guide her up to the surface. She was somewhat taken aback by this unnecessary “rescue”. With hindsight I should have checked her condition more rationally. I’ve always taught people to never assume anything about other divers, but I had done just that. In the briefing before the dive I’d touched on the lost buddy procedure, and everyone sort of nodded, but we did not go into detail. If ever I’m diving with a non-regular buddy again. I will ask them everything in detail and know we speak the same language, not assume we are.
In case you doubt that people can and do die diving at Badgat. Just about two years prior to our dive, three divers went on a night dive. They strayed into one of the many caves in the site and unfortunately all three drowned. Their friends said afterwards that they were just doing a dive they’d practised in the daytime. Of course in the daytime they could see the cave mouth and simple stay out. Tragically, in the dark it was a different story. They were all found in water shallower than ten metres. They were not trained cave divers, so had no idea of how to methodically search for a cave entrance. They did not even have a line with them to do such a search.
This tragedy brings me to one of the less obvious attributes in the cave divers I’ve encountered. All of us have taken the time to acquire the very high degree of training in the techniques of cave diving. For example, as I mentioned before, nitrogen narcosis is a very real problem for deep diving. If nitrogen is the problem, then it follows that we need to have less and less nitrogen in the gas we breathe. All deep cave divers need to understand the theory and practise of mixing gases, or gas blending as we call it. As I said earlier, this is not a training manual, but the art of blending gas serves as an example where theory and practise don’t always agree. In such cases, we effectively trust our lives to our practical experience and that of other deep cave divers around the world.
Mix Mysteries – the art of blending gases
Generally when we go deeper than about 50 metres we add helium to the mix. Being a thinner gas it seems to be far less narcotic than nitrogen. The gas mixture is called HeliAir or more commonly Trimix . The only way to get these gases is either to buy it from a suitably equipped filling station or mix it yourself. In South Africa these facilities are few and far between; when we began our explorations there was simply no place to get this gas so the only way we could get these mixes was to prepare them ourselves.
The principles of how to blend gases like Trimix, HeliAir or EANx (sometimes called Nitrox) are not difficult. Neither are the physical steps involved. However, when Nuno Gomes, the leader of the deep diving group at WUC, first started doing mixed gas diving there were no easily available tables for Trimix, nor were there any official blending courses for sport divers. Nuno was only able to learn the rudiments of mixing whilst on a commercial diving course in Simon’s Town (this is a small town built around a naval base near Cape Town proper). He used this knowledge coupled with his own additional research to manually work out his first Trimix tables. By the time I came along we were able to learn from Nuno. Not too many years later we were able to go on courses ourselves. So it was that I became a certified gas blender. In South Africa we’ve found gas blending to be more of an art than a science. Via the internet we’ve seen other people around the world having similar experience. So what are the problems of a procedure that seems on paper to be fairly easy and very accurate indeed?
Firstly, in the early days we did not have such sophisticated devices as portable gas analysers. We had to rely on the physics and mathematics to get it right. I have to say, even after we got analysers
and such tools, we still get the same level of accuracy as ever we did. Today there are a whole range of portable gas analysers available. These devices tell you how much oxygen and helium you have in your tank so you can verify your calculation. But - and here is the thing - even the manufacturers tell us that we can get a 1% error either way on the readings. Add to this the fact that we are diving at altitudes of around 1400 metres above sea level and you can add another 1% error. Then there is the heat, humidity and the speed at which you fill up the various gases. All these factors combine to make gas blending something of an art.
This problem of accuracy of mix is very critical, especially when you are diving as deep as Nuno and Verna were thinking of diving. The extreme pressures they would be diving at meant that even apparently minor impurities in the gas they breathe would be fatal. In my ten years or so experience I’ve seen the gas-mixing problem at least twice, once on a trip with Nuno and once with Verna.
In 2002 during one of the Polish Expeditions to Boesmansgat in South Africa, Nuno and the rest of us had set up a mixing station halfway down the slope of Boesmansgat. Although it was hot weather, probably close to 30º, it was in a relatively well-shaded area. That day Nuno was preparing some Trimix for himself and Leszek Czarnecki, the leader of the polish team that had come to dive at Boesmansgat. Nuno had already mixed one set of tanks for Leszek, and the result had been perfect as usual. We proceeded to the second set, where the process called for a decanting of helium into empty scuba cylinders and then topping off with air. Once the calculation was done, this is exactly what we did. The maths told us we should have got say 50% helium and about 10% oxygen. But when we measured it we got a crazy reading of –20% or some such figure. It could not be correct! We tried another analyser, with a very similar result. This did not make sense. We initially put it down to the heat, and we waited about half an hour then analysed again, but the result was more or less the same. Nuno had a good think, and decided to try something we’d never done before. He stood the tanks up and pushed them back and forth, attempting to manually mix the gas in the tanks. We’d heard some American divers recommending that whenever Trimix was made, one should roll the tanks to make sure the gases mixed properly. But we’d figured why would this be necessary if the gas is going into the tank at 200bar? But lo and behold, this time the agitation of the gases seemed to work and we got within a percent of what we wanted. We still aren’t really sure why this worked, but there you go.
Gareth Lowndes and Derek Hughes in the mixing shed at Boesmansgat (2004)
The next time I saw a funny with the mixing process I was directly involved. It was during Verna’s first world record expedition to Boesmansgat This time, having learned from our experience with Nuno, not just to shake the tanks, but also to set up in a well ventilated area, we set up in a farm shed. The idea was to have a clean, dry place to blend the gases, whilst at the same time affording us some shade.
This time we were blending Nitrox, specifically one of the easier mixes you can make, 50% Nitrox. This means the end mix must have 50% oxygen in it. Verna and I did the calculations, checked them and proceeded to decant the required amount of oxygen into the tanks. As usual we let them cool a bit and then topped them up with air from the compressor. Yup, you guessed it, the process and calculations that we’d used many times in the past did not work this time. This time the analysers gave us way too high oxygen readings. On paper it was not possible. Again we let them cool for about half an hour, again not much change. It is indicative of our level of confidence that we thought, ‘we must have made a mistake’. We went so far as to dump the gas and try again, and again got a wrong reading. At this point we were getting a little irritated and short with each other so we called in the most experienced two people on the trip, Craig Khan and Craig Newham. The Craigs decided to wait till after dinner because it was already late and it would give all the equipment time to cool. After the usual excellent dinner prepared by the owners Debbie and Andries van Zyl, we all trouped back to the shed. Craig and Craig duly did exactly, or as near as damn-it to exactly what we’d done. Would you believe, their mix came out perfectly? Even thinking about it I still shake my head. Chalk another one up to experience. What I do now is make sure that the ambient temperature is as cool as I can get it and I fill as slowly as I can. Of course we always double-check our calculations. In fact, most of us use computer software now anyway.
The final characteristic of cave divers I’d like to touch on is a relatively high level of understanding of computer technology as applied to the diving environment. We don’t call it ‘technical diving’ for nothing. As we progressed in our explorations and understanding of deep cave diving so the equipment at our disposal had to become more and more complex. This was reflected internationally as divers around the world came to rely more and more on computer programs to work out custom decompression tables and wrist mounted submersible dive computers for real-time dive planning. But as with most things the more one learns about how something works, the more one also learns about its limitations. With experience came the realization that no matter how clever a tool may seem, it will have limits and situations when it’s inappropriate to rely on them entirely. In my opinion it is folly to trust one’s life to a device designed by fallible people and more importantly, powered by batteries.
When computers lie
Given the nature of modern deep cave exploration, cave divers have to be prepared to place a large amount of confidence in electronic devices. Almost every cave diver I know carries two or more computers on any given dive. Anybody who has done any exploration type diving will attest to the fact that these devices have really expanded the range of dives we can do. But, like every other electronic piece of equipment, they can and do fail. I know this from personal experience on at least two occasions.
The first time I was diving with my newly acquired Nitrox computer and had begun my ascent from 50 metres maximum depth to decompress on Nitrox36. When I looked to my new computer for my first stop it was giving me a much longer stop than my trusty air computer was. This was completely incorrect.
When one decompresses on Nitrox your stops are shorter, not longer. I now found myself faced with a very serious dilemma, should I ignore the newer computer and follow the older one that showed a shorter decompression? Should I risk it being wrong and possibly getting the bends? Should I follow the newer one that was showing an irrationally long decompression, especially since I was going to breathe Nitrox? Edging my way up to the first stop, I turned the alternatives and their consequences over in my head. In the end I decided to follow my training, my experience and my instinct and do what the older machine was telling me. Just to be safe I still did the decompression on Nitrox.
Turns out I was right and the newer machine had a very, very conservative decompression algorithm built in. So conservative in fact that by choosing a mere 10% safety margin over and above the built in safety, I was choosing a model that made deep diving practically impossible. I later sent this machine back to the manufacturers to have its software upgraded to a version more suited to the real world of technical diving. I still use that computer today and its never given another moment’s trouble.
The second time, I was diving with Mike Beresford (a regular buddy of mine with many, many years more diving experience than me). We were returning from yet another dive to 50 metres and had four dive computers between us. At about our second stop Mike indicated that one of his computers was giving him a very, very,very long stop. We knew from experience with manual tables that this could not be. We thought it was not a problem. We had three other computers to complete the dive with. Pretty soon one of my computers showed an erratic reading as well and then Mike’s other one went blank. By the time we reached our last stop we had only one working computer, which happened to be one of mine. The other three had failed for various reasons. So now you know why we always have someone check our calculations and verify our final mixes. And why we always have table back-ups on our dee
p dives. Quite literally, our lives are at stake.
To my mind there are three things that make the use of decompression computers safe. The first is to carry at least two computers per diver. The second is to plan before hand for the failure of all the computers by carrying submersible tables as well. On deeper dives I’ll always carry a waterproof copy of my planned decompression schedule. Finally, I recommend using the appropriate gas for the dive to ensure that you can think clearly in the event of the computers failing.
Under the guidance of Nuno Gomes and the rest of the cave diving group at WUC, I was able to build up experience in small manageable bits. In retrospect, I believe this approach was a very sensible one. My experiences at Wondergat, Bobbejaansgat, Vetsgat and Badgat prepared me very well for the eventual expeditions to Boesmansgat because they all had elements of the remote and largely unexplored cave. An expedition to Boesmansgat was, and still is, a complex exercise, requiring months of planning, a fair amount of financial resources, disciplined execution, most importantly, strong leadership and a dedicated team.
Into The Deepest And Darkest Page 3
