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On Saturday, May 23, Dr. Reinhard Buchaly and Sandro Madeo dived the Ress= el to search for continuation of the cave. The Ressel is an underwater cave located in southern France in the departement Lot. Probably it is the most dived cave in France and Europe.= Despite the high diving frequency only Olivier Isler had penetrated the cave after a 2 km dive in the year 1990, reaching an air filled room, but= could not check for continuation because diving alone it was too risky to= remove his gear(double semiclosed rebreather RI 2000) and leave the water= =2E Entry of the cave is within the river Cele, where the cave opens in the riverbed at a depth of 6 meters. The first part of the cave is quite shallow, after about 350 meters a shaft gets the divers to the deep part = of the cave which finds the deepest point at 81 meters 1500 meters from the entrance. During a setup dive six alu trimix safety cylinders were placed in the de= ep part between 600 and 1100 meters. Decompression gases on the entry side were placed at 33 meters(Ntx35), at 21 meters( Ntx50) and oxygen at 9 meters. Two habitats were installed 200 meters from the entrance at a dep= th of 9 meters. = The habitats were fastened to the ground and adjusted to depth. Sandro=92= s habitat had a steel frame, which allows entry of the habitat without removing the doubles on the back, and having only the lower part of the l= eg in the water. The other habitat was of a tent style like an huge lifting bag, where it is necessary to remove the gear before entry, and staying i= n this habitat is very comfortable and completely dry. Bottom mix was trimix 15/55. The high helium content makes the dive enjoyable with a clear head, generally we never use a narcosis level deep= er than 30 meters, on high workload dives 20 meters narcosis is even better.= Air was not used as breathing gas at all, only for inflating the habitats= =2E Initially it was planned for both of us to do the dive open circuit. Because I got a Halcyon rebreather in April, we changed the plan to take advantage of the options of the Halcyon. Anyway, if the dive could not be= done open circuit with the necessary setup dives, it may not be a good id= ea to use a rebreather. But the rebreather allowed us to reduce the number o= f setup dives, and I was also able to carry gas for my partner. = Knowing that we had to surface 2 km in the cave, each of us carried two decompression bottles with 50/50 and oxygen. Having a rebreather the amou= nt of decompression gas I carried was way to much at a first glance. But thi= s way I could share some of my nitrox to my partner in case he needed it, a= nd not sure about the gas quality in the cave after surfacing, we had enough= oxygen to breathe at the surface out of the water. = The decompression stops below 21 meters on the far side were done on bott= om mix. = Each of us used a Gavin style scooter and towed a spare scooter. =2E = Conditions in the cave were not optimum, visibility up to 1300 meters was= about 7 meters, after this it increased to more than 10 meters. Water temperature in the cave is 13 deg Celsius. = I carried four alu stage cylinders, one trimix power stage for the rebreather, the two decompression cylinders and another trimix stage for = my partner. The number of cylinders and the heavy decompression gases compar= ed to a trimix fill, reduced the easyness of travel which we normally have o= n our dives, where two decompressions are not necessary. The rebreather was= fitted with two backmounted 18 liter cylinders with bottom mix for redundancy and wing inflation. Suit inflation was argon. 90 minutes after entering the water, we reached 21 meters depth on the other side of the cave. Here we parked the backup-scooters on a plateau, dropped the trimix stages, to proceed along a smaller tunnel for further decompression. The open circuit bubbles from my partner removed a lot of silt from the ceiling, and reduced the visibility drastically. After 3:45= minutes we surfaced on the other side. The air filled room has a horizontal diameter of 10 by 15 meters, about o= ne third of it has water surface. The cave has collapsed in this area. The collapsed part starts under water at a depth of nine meters, and goes uphill from the water surface for another 1,5 meters. The ceiling is approx. 2-3 meters above the water surface and the dry part of the room. = No mud was present near the surface. = The rocks from the collapsed cave have a diameter of approx. one meter maximum. The water cleared quite fast at the nine meter level. This all gives the conclusion that it is probably not possible to work through thi= s collapsed part of the cave. Sandro removed his 20 liter-doubles and left the water to check for dry cave or another sump. We had a mountaineering rope with us in case to secure the gear in the water, because leaving the water with the rebreath= er was not the option. But because he could not find continuing cave, I left= my gear on and after a 40 minute surface interval with a small picknick w= e returned. = Decompression on the entry side started with nitrox 35 at 33 meters after= some deeper stops on the bottom mix, followed by ntx50 from 21 meters, an= d oxygen at 9 meters in the habitat. I had to remove the rebreather at 12 meters, clip on lead, and a safety bottle to enter the habitat. Because w= e were still 200 meters in the cave, it was necessary to get into the rebreather with the doubles again for exit. With the Halcyon rebreather i= t was not much different than diving with doubles only. But removing the ge= ar and putting it on again, has to be done very carefully, especially becaus= e we had no support divers available. The way back was totally 4:55. = The Halcyon worked excellent. Before this dive I had about 20 hours on th= e Halcyon. This rebreather is probably the closest system to open circuit scuba. There is no need to monitor any gauges, no worry about condensatio= n anywhere in the unit, everything can be checked by the breathing characteristics and the sound of discharging and gas addition. There is n= o delay on a scooter dive for monitoring and the concentration is not take= n away from the diving environment. = Time on the Halcyon on this dive was seven hours, the first decompression= was done completely on the rebreather,on the second decompression oxygen was breathed open circuit. There was no sign of breakthrough of the canister with a water temperature of 13 deg C. ----------------------------------------------------------------- Dr. Reinhard Buchaly Germany +49-2858-1576 phone = +49-2064-35286 fax -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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