Projects > Doux de Coly 02

The Push Dive

Latest update: March 18, 2004

By Michael Waldbrenner

On Thursday morning, 22nd August 2002, the ring of my Nokia mobile woke me up. It was 5 o’clock in the morning! I stared at the phone in confusion then realized it was the alarm I had set the previous evening.

It slowly dawned on me that this was the morning I was to undertake another dive in one of Europe’s longest underwater caves. We had agreed to start early to have the long bottom-time during the morning hours, when concentration would be at its highest. Even so, we would not be coming out of the cave until after midnight, assuming all went to plan…

I took a shower and drove from Terrasson to La Grande Prade, where most of the others were staying. However, once there it appeared that the team had already gone to the cave. I stepped into Reinhard’s apartment and we had spaghetti bolognese for breakfast. Carbohydrates are good prior to big dives: they keep you warm. Also it had become a habit for us to eat noodles before our big dives. We took magnesium and calcium tablets with some water and each of us took an Imodium: P-valves only solve half of one’s toilet related problems!

After breakfast we drove to the dive-site and briefly checked over our gear before donning the layers of insulation and our drysuits. Everyone respected the fact that we would not be too talkative, but still some jokes were made and the atmosphere was not tense.

I saw the video-team in the water: Paolo and Ian were ready to film our way into the cave. As with last year I was very impressed with the commitment of team-members from different countries willing to contribute to this kind of expedition. We had Dirk and Wido in the water to help us gear up and Tom and Peter and the others providing assistance from the concrete platform. Our heating-shirts were measured for the right impedance and we jumped in the water to get the double-RB80 rebreathers onto our backs.

This year we were using new counterlungs with an improved dump-ratio. This would give us an even greater gas-duration, but at the expense of a higher FO2 drop. Despite having already tested this new set-up on several dives below 100 m (330 ft) depth, we were interested in the pO2-behaviour over the course of such a large dive. For this reason I was using an Oxygauge to log the data for post-dive analysis.

We plugged a 30 cuft aluminium stage of 50/25 (50% O2, 25% He) into the swagelok-connector of the rebreather gas-block and connected a 14 cuft stage of argon to our drysuit. This was additional argon to be used during our descent, conserving the primary back-mounted argon for the remainder of the dive. The argon stage was rigged like any other stage and was to be dropped at the bottom of shaft, ready for use should it be needed during decompression and the habitat entry.

The last few checks were made: the 20Ah-NiCad lights and one last check of the four rebreather units; finally we were ready to go.

A glimpse on my Suunto Vyper showed that it was a few minutes before 7 am, the latest time we wanted to start the dive. We each clipped on a long-tube Gavin-scooter and, with a final wave goodbye to our dudes, we hit the trigger.

Entering the cave it occurred to me that we would have no daylight, fresh-air, wind nor weather for another twenty hours. We scootered side by side along the 300 m (900 ft) to the shaft. At one point during our ride in we were blinded from up front by the 50W HID-lights of the video-team. However, they kept well away from us, knowing that we would not want to be delayed.

On top of the shaft we clipped off our scooters to the permanent line and switched rebreathers for a final test. After making sure everything was fine we descended the shaft to the 21 m (70 ft) stop, briefly stopping off at 9m to check on our habitats. At the 21 m stop there were five 80 cuft aluminium tanks (al80's) hanging on a mountaineering clamp: three contained 50/25 for back-up open-circuit decompression; one contained 17/55 to be used for break-gas during the decompression; the final al80 we wanted to use now. It was marked “60” in large numerals, indicating the maximum operating depth for this gas-mixture in metres. I disconnected the small 50/25 tank from the gas-block and clipped it off, replacing it with the 60 m tank. I could hear the high helium in the mixture making its familiar sound as it was injected into the rebreather while I was purging the loop.

The gas we were breathing now contained twenty-two percent oxygen and seventy percent helium. At the maximum depth encountered on our last dive here this mix would give us a narcotic depth of around ten metres, much less than most sport-divers experience. For such a dive as this we wanted to have as clear a head as possible. As a bonus, keeping the nitrogen content very low helps to provide a more effective decompression in the relatively cold water.

We checked each other to ensure that the right gas was plugged in and continued our descent. We passed the two al80 tanks with 35/35 mix on the way down and a small 40 cuft-tank with 30/40 mix at 42 m. At around 40 m the bottom of the shaft slopes down to 45 m and there we passed our heating-batteries which also provided additional light for the decompression phase: we knew that we only had light for around eleven hours on our primary canister-lights. We carried two Barry Miller backup-lights each and LED-lights as a last line of defence. We also carried a complete spare light-head each in our pockets.

At 45 m we picked up three scooters each and started our journey. We were twenty three minutes into our dive. The entry into the deep section makes for a fun fast scooter ride with a long corner curving down and to the right. However, being on an exploration dive we were a little cautious not to risk anything like a ripped suit. We stayed on the trigger, but kept pretty close to each other, and far away from the walls.

To begin with the visibility was around 20 m (70 ft) and we were delighted. I wondered what Götz and Thomas had been talking about. They had apparently encountered “crap vis” some distance into the deep section on their support dive the previous day. This looked like very, very good visibility to me!

A little way in we stopped and dropped our argon stages. “Don’t forget to plug in the other argon-hose!” I thought. It might have been a little wet and cold otherwise, when pushing the suit-inflator. Some hours away, this would be our last stop on the journey out before reaching the deco tanks and heating tubes.

I was not cold at all as we scootered along the deep tunnel. Water temperature was 12 degrees Celsius (54 degrees Fahrenheit). After around 1 km (3000 ft) the visibility started to get bad. The water took on a white milk-like appearance reducing the visibility to as low as 2 m (6 ft). We stayed very close, knowing that if we were not able to see each other the dive would have to be called. I remembered the heavy rainshower two days earlier and thought that it might explain the bad vis. I just hoped that we would be able to see the scooters, stages, and reels deposited at around 1750 m. I was concerned because in this part of the cave there are typically more than four lines. It is often the same: divers think that they need to “lay some line” and they do it of course in the near sections of caves, where existing lines are still in place. In my opinion this just creates problems. Hopefully we were scootering along the right line. If the scooters had been placed on one of the other lines, we would have to double back and search for them.

Suddenly I saw something shiny through the milky water: it was one of our stages. We had found our stuff and could continue the journey.

Now we had a total of five Magnum Gavin scooters each, four towed and one towing.

Now we had a total of five Magnum Gavin scooters each, four towed and one towing. Each scooter had a burntime of almost two and a half hours. We were also carrying one reel each and three al80 stages: two stages with the 60 m gas and one with a 110 m gas containing 16% oxygen and 80% helium. The same mix filled our back-mounted twin 20l tanks, but this was reserved for bailout purposes only. The three stages would be enough for the maximum allowed bottom-time of eleven hours. As mentioned earlier, this maximum was due to the duration of the primary lights. We had targeted for nine hours and so we had two hours for unexpected delays. Any longer bottom time would require use of the secondary lights and the backgas reserve.

Scootering in the bad visibility was not fun, but the new light head reflectors, built and finished by Reinhard just a week before, produced a perfect beam and considerably improved the visible distance. The longer reflector-baffle seemed to substantially reduce the glare from back-scattered light. We concentrated on keeping our light beams parallel and visible at all times; only adding gas to the suit or wing, or pinching the nose made a light disappear for a few seconds, so there was never a need to stop. Good light-discipline was essential for a smooth ride and good average speed, especially given the poor conditions.

At 108 minutes I recognized the “pit” where last year we had discovered the broken line. From here the depth decreases somewhat and the visibility started to improve back to around 15 m. This started to match with the report made by Goetz and Thomas (they had reported the bad vis to be at around 1600 m and we saw it around 1000 m). So fortunately the bad visibility was localised and travelling with the flow. I concluded that it would arrive at the pool the following evening, possibly interfering with the clean-up dives.

As planned, we dropped the first scooter at this point in the shallow section and continued on into the system.

As only three people had ever dived this far into the Doux de Coly there was now only one line to follow. Abruptly the visibility turned bad again, but only down to around 5 m (15 ft) this time. We dropped another scooter when we reachend the previous end–of–the–line at 4300 m.

The Vyper, in gauge mode, showed exactly 3 hours at that point. We were now following the line we had laid last year. It wasn’t long before we were descending into the second deep section of the cave. At 60 m depth we stopped and plugged in our 110 m stage, dropping the 60 m stage. Last year, not expecting the cave to drop deep a second time, we had called the dive at 65 m having reached the MOD of our drive gas.

When we reached the end of our line at 5000 m Reinhard handed me his backup-scooter and using the large exploration reel he tied onto the end of the old line. I was now towing two scooters. We had expected the cave to go much deeper, but around the next corner it stayed around the mid-sixties! I knew what Reinhard was thinking: ”Shit, why did we not go further last year?”

I was lighting ahead for tie-offs. Reinhard, being faster, passed me and headed to the next tie-off. While he was stationary I moved back up-front, lighting his tie-off while staying on the trigger. We repeated the procedure in this way, making good progress.

Out of blue we arrived at a junction. This was the first real junction beyond the small oxbow just inside the entrance to the cave, and we were quite taken aback. We decided to turn right as that way looked a little bit bigger: in general the cave was now getting smaller. We were both considering the possibility that the cave could end soon, but nevertheless it continued on.

Suddenly I noticed the sound of bubbles

Suddenly I noticed the sound of bubbles. It was coming from the right and, so I thought, behind. I was on the right rebreather and it was breathing perfectly. I inhaled a bit and stopped to hear if one of the second-stages was creeping. I heard the bubbling again after a while, but it was now too loud to be a simple creep. Reinhard had just passed me and I saw the 640 m tape-flag on the line. I eventually discovered that the bubbles were coming from one of the hoses at the Swagelok block. I hoped it was not an overpressure valve, unlikely as we had adjusted them just a few weeks earlier. I closed the valves one by one while scootering after Reinhard and finally all was quiet. I grabbed my gauge and it showed around 180 bar. “Still OK “ I thought: I still had two working rebreathers, owing to the fact that each had two injectors. Even so, prudence seemed to be the better course and I decided to call the dive at the next tie-off.

I signalled Reinhard and showed him the turn around signal. He stopped for a second and I knew that he was thinking ”Why is he wanting to call the dive??” but of course he agreed and we turned around after one last look down the tunnel. There was still enough cave left for another day!

I did not tell Reinhard the reason why I had called the dive because everything was still working: sometimes you just need a reason to turn around...

Reinhard took out the compass and wetnotes and started to write down the first tape-flag 660 m, so we had laid between 660 and 680 m of new line. Later we measured the remaining line and found that 675 meters of new line had been added. He was measuring heading, depth, distance and time of the dive and I was pushing the marker-button on the Vyper. I pushed the button at 238 minutes, a short while after calling the dive. Some minutes later we arrived at our dropped 60 m stage and switching rebreathers I plugged it in.

Now began the long trek homewards. We passed back through the restriction into the shallow section and picked up the dropped scooters. We travelled back through the bad visibility and picked up all of our stuff we had clipped to the line. We also retrieved an ancient reel, which had been forgotten or lost. It was empty anyway so it needed sending back for a refill! When we reached the end of the shallow section we picked up the last pair of scooters and now we were fully geared up again.

We dropped down into the “milky passage” and carefully scootered back eventually reaching the clear visibility. It was some time later when we saw the dropped argon stages and realised that we were almost home.

Decompression schedule
Depth (m)	Time (min)	Gas
42	8	tx 30/40
39	17
36	24	tx 35/35
33	11
30	12
27	18
24	18
21	15	Break (OC) tx 15/55
21	31	tx 50/25
18	36
15	48
12	71
12	15	Break (OC) tx 15/55
9	180	Habitat (OC): oxygen & breaks (tx 17/55)

Hitting the ramp out of the deep section, we executed deep-stops all the way up to the 45 m point and used the time to clip off all scooters, reels and unneeded stages. I grabbed my small cylinder of 30/40 and plugged it into the rebreather. After purging the loop I watched Reinhard doing the same and we took a big gulp out of the deposited Platypus drinking bags. They had bitter-lemon in them, just to have a different colour and flavour from the cave-water! I connected the heating-tube and waited until I felt the welcome warmth of the heating-wire. That felt good!

From two hours after we had first set off, support teams had been making hourly dives to the shaft to check for our return. I had a look at my Vyper and it now showed 498 minutes into the dive; it would be a little while before a team discovered us.

We moved up to the 36 m stop and plugged in the 35/35 gas. We knew that we had to hover in the shaft for several hours with the double rebreathers on our back. Initially we had considered getting out of them at the bottom of the shaft and putting on another smaller rebreather-rig. However, we had decided against it as the deeper stops were too short. Anyway, we were now happy just to relax and take care of ourselves…

Then the first support guys arrived and came down to us. They asked the predictable questions: “How far? Everything OK? What do you want?”; and I wrote: “ask Reinhard”, “Yes” and “Ice cream” (at that moment I only knew it was more than 640 m). It was a shame that everyone thought the “Ice cream” was meant as a joke! Of course I expected it to be delivered to the habitat, so I made a note to have a serious talk with our support dudes at the next meeting :-)

I had switched on my LED light and it was now hanging down from the mountaineering clamp; Reinhard had switched on the light connected to his heating-tube. We had turned off our primary 18W HID lights to save some light for the way out later that night.

The next team arrived and they had brought some tea. That tasted much better than the condensation water from the loop or the cave-water. Of course we had tested the cave-water for drinking quality prior to the dive.

I was writing down (in my wetnotes) my experiences as they came to my mind and I looked over to Reinhard quite often, knowing that during deco I must not lose my attention to details and especially to my buddy. I smiled because I saw that at the same time Reinhard was watching over me.

Oops, it was time to move to the next stop. Now the stops were getting longer. The next team brought soup, but I did not like the taste. I pushed myself to drink some of it anyway but wrote “I want tea!” in my wetnotes. Wetnotes are the coolest method for communicating underwater. I wondered how divers could get along without this great and cheap tool during their dives. I thought back to my dives in the warm water of the Similan islands in Thailand where I was during April; even there I used wetnotes!

We moved up to the 24 m stop and I made a long break on my backgas in anticipation of the high 1,6 pO2 from the 50/25 mix at 21 metres. We switched to the 50/25 mix using the small tank we had used on the ride in so many hours previously. The three al80’s of the same 50/25 mix were here just in case we needed to perform an open-circuit bailout. From this point on I performed all my gas-breaks on open circuit, just to have a different mouthpiece in my mouth every now and again. Other than that, at no point during the entire dive did I feel any urge to go to open-circuit; the rebreathers worked flawlessly, as usual.

I noticed Reinhard watching me again and we exchanged OK-signs. Now the stops really started to get boring; I threw small pieces of rock down the shaft and watched them disappear. I left some tanks behind at the lower clamp and moved the rest upwards. The Vyper showed 664 minutes when we finally left the 21m (70 ft) stop. I was really looking forward to getting into the habitat and actually eating something of substance. I sucked the rest of my carbohydrate-gel out of its tube. Tanja's spaghetti had tasted a whole lot better that morning, although thinking about it was a bad idea: the loop was in danger of being flooded by my Pavlovian response!

Support-divers came and went. They asked us when we wanted to get into the habitat and we figured out the time. The surface manager coordinated all these duties and it was relaxing knowing that all our people were squared away and knew exactly how things were to proceed.

We approached the 12 m stop and were asked who wanted to get into the habitat first. We decided on Reinhard, because his heating-suit had failed and he was by this time a bit colder than I.

Seventy minutes later I shrugged out of my rebreather and entered the habitat. There was already too much gas in it and I had to struggle to get the seat up, but finally I managed it. The depth shown was 8.8 m (30 ft) and the temperature soon raised to a warm 20 degree Celcius (68 Fahrenheit). A wetnote was handed to me: Reinhard wanted the nasal-spray, so I handed it over via a support-diver. Then at last the food-tube arrived. The food was damned hot. ”Noodles again” I thought, but divers are like small children, they all like noodles! At least it was a Chinese noodle dish and it actually tasted OK. But there was another soup to drink! Bah, I decided to accompany the noodles with cave-water instead.

Now the waiting started, only made bearable by three hours of joking around with “humorous” wetnotes. We spent 12 minutes on oxygen followed by 8 minutes on trimix 17/55. The trimix was needed not only as a break from the oxygen but also to keep the fO2 in the habitat low, so there was a chance of recovery from a possible O2 CNS-hit and the associated convulsions. Thankfully, we made it through the decompression without that particular excitement!

This year the habitats were facing towards each other so I could see Reinhard’s window; sometimes we signalled each other with our lights. After a very long three hours we were finally ready to leave the habitats. As Reinhard was the first to enter his habitat, he was the first to leave. We were each accompanied to the top of the shaft where we struggled back into the double rebreathers. Donning them under water in a cave after such a long dive was not fun, but we were soon making our way out to the entrance pool, surrounded by our final team of support-divers.

Suddenly we were out of the cave and in open water. Here I suddenly started to get really cold. However we still wanted to finish the dive with a three minute per meter ascent rate and so it took quite a while to ascend the final 6m. Then finally we broke the surface of the pool.

The rest of the team were gathered on the platform cheering (quietly, as it was 1 am!)

The rest of the team were gathered on the platform cheering (quietly, as it was 1 am!) and we were helped out of the rebreathers for the last time. Like last year, Tanja poured the champagne.

All of our gear was deposited in a separate box and kept near by, ready to go in case of any problems. We had decided to stay in the water for some time before climbing out, just to be cautious, but another chilly ten minutes convinced me that I really should get out. There was no sign of any decompression problems and I climbed out. Next year I will pull the heating tube all the way to the cave entrance!

With my feet back on the ground, my first thought was that there was no way I was ever doing this dive again no matter how much more line there was to lay…

…But by the next morning we were all discussing how to improve things for the dive next year!