Cave diver Chris Jewell heads to the Picos de Europa in Spain to take part in two very-different projects, beginning with the ambitious and challenging Ario Caves ProjectPhotographs by Chris Jewell, Mark Burkey and Bartek Biela“ Given the potential for depth, I elected to take a nine-litre cylinder of trimix as my offboard diluent and deep bailout plus another nine litre of EANx 30 to feed my drysuit and for shallow bailout ”The Picos de Europa in Northern Spain is a 20km-long mountain range with peaks reaching over 2,600 metres. The mountains are mostly comprised of limestone which means they contain many caves. Where there are caves, there is usually water, and for me that means cave diving exploration. This summer presented me with the change to take part in two significant cave diving expeditions in the Picos.

Ario Caves Project

The first objective was a sump (water-filled passage) at the bottom of a 900 metre deep cave called Cabeza Muxa, which was located high up on the Ario plateau (1,630 metres altitude) in the western massif of the Picos. That meant that in order to dive the sump, we needed to get everything up a mountain, then down a vertical distance of 900 metres, as well as along a 2km cave passage following a fast-flowing river. Oh… and we also needed to install all the ropes (totalling about 1,300 metres) along with new rock anchors (150 stainless steel bolts) and set-up an underground camp! You can tell I like a challenge…

Cabeza Muxa was last visited by a UK team in 1988, when the downstream sump was dived by Rick Stanton to a depth of 33m using open-circuit scuba gear. It has remained unexplored since then and offers the potential for a significant hydrological connection to other caves in the area.

Given the logistical challenges involved in this project, I was going to have to make some some smart choices about equipment. Firstly, I own some nine-litre carbon composite cylinders which weigh about 9kg out of the water. The problem, of course, is that these require around 6kg of weight to make them negatively buoyant. That weight would need to be carried down the cave, but at least it could be separated from the cylinders and then staged for future expeditions. The weight of everything else would also need to be examined and reduced where possible. At the same time, I’d need sufficient spares and tools to deal with most dive kit eventualities. Finally, everything would need to be dismantled and packed in robust bags and containers for the long trip down the cave.

When I first decided that it would make a good objective for summer 2022, I knew that it would be hard work. We’d need a strong team and anything we could do to make it easier would really help. I couldn’t do much about the cave, but we could get a helicopter to fly the gear into base camp at the mountain ‘refugio’. After the long drive down through France with a fully loaded van, we arrived in the Picos. The next day we drove up into the mountains as far as the track would take us. From here a helicopter did the rest of the work, lifting 900kg of kit into the sky and off to the refugio while we made the two-hour hike up.

The caving began straight away with a sense of urgency and purpose. After five days of hard tiring caving, including three nights where we camped underground, we had the cave ‘rigged’ to the sump so that transporting diving kit was possible. Two days later re-enforcements had arrived on the expedition so a team of six fresh cavers entered the cave with heavy bags of diving equipment each. Then the following day myself and three others (Lisa Wooton, Stu Weston and Mark Burkey) went underground for the main event - to dive the sump.

Did you know?The Picos de Europa National Park contains meadows, lakes, mountains such as the Naranjo de Bulnes, gorges and impressive forests which host large mammals like rod deer, along with grouse and Egyptian vulture.After descending the 600-metre-deep shaft series we reached underground camp before heading off along the 2km stream way which drops 300 metres via 26 roped pitches to the sump, where I would dive. Unfortunately, just over halfway down this section of cave, disaster struck. Our expedition photographer Mark Burkey was approaching one of the roped drops when the rock he was holding on to broke. Mark fell forward on to his face, with his nose taking the impact.

A lot of blood followed, and it was clear he’d broken his nose. Everyone fully expected the trip to be turned then and there, but Mark was determined that the dive would go ahead and that he’d be there to document it. Several hours later we arrived at the sump. I prepped my dive gear aided by Stu and Lisa while Mark prepared to photograph the effort. However, when he unpacked his camera he discovered to his horror that his fall had damaged the case and caused it to leak. The precious camera was flooded, and no more photos would be possible!

I expected the dive to be deep and possibly lengthy, so in the chilly 6 degree C water I would certainly be using a drysuit and it also made sense to take a rebreather for this project.

I’ve been diving a KISS Sidewinder for a couple of years with good results and so that was the obvious choice. Given the potential for depth, I elected to take a nine-litre cylinder of trimix as my offboard diluent and deep bailout plus another nine litre of EANx 30 to feed my drysuit and for shallow bailout. A two-litre bottle of oxygen to run the rebreather and a seven-litre bottle of oxygen staged at 6m depth in the sump completed the setup.

In most cave diving I do, I almost always use a large cylinder as offboard diluent and bailout combined, then a second cylinder acting as suit/ wing inflation and further bailout. As a streamlined rebreather, the KISS Sidewinder tends to be dived like this. By contrast, most other conventional rebreather configurations and therefore training, separate diluent from bailout gas, while separate suit inflation cylinders are also very popular.
The team discussing the forthcoming diveFor me there are several advantages to combining the cylinders. Primarily it allows me to take fewer cylinders into the cave. Most onboard diluent or suit inflation cylinders will be small, making them suitable for one single dive. If cylinders are being carried a long way into a cave, then a single large cylinder being used for multiple purposes makes sense. Similarly, I would rather dive with two large cylinders than several smaller ones, as it makes kitting up and diving much more comfortable and streamlined.

These advantages, of course, need to be balanced against the downsides. A mix suitable for diluent and bailout has to be selected, there is less redundancy in the system (partially mitigated with the inclusion of a Y-valve) and gas safety calculations need to factor in that bailout gas is being consumed as diluent or for buoyancy.

Once these considerations are understood then hose routing and a system for plugging in the offboard diluent needs to be worked out. Ideally a single offboard connection to the rebreather should feed both the ADV and the MAV simultaneously. Many rebreathers boast the capability to plug in offboard diluent, but very few do so without needing the diver to disable the ADV and only add diluent manually.

While the team kept warm in a storm shelter making hot drinks, I entered the water and began my underwater exploration. The excellent visibility that I had expected was reduced by the sediment that my kitting up had disturbed, however, I could still easily see a good five metres. At 6m depth, I dropped off the bailout oxygen and began spooling out dive line. The 2.5mm thin white cord was marked every ten metres with a small piece of yellow tape featuring a handwritten distance number. I’d carefully prepared the line weeks ago at home and wound all 600 metres of line on to one of my ‘homemade’ line reels. As I progressed further into the cave, the visibility improved. Large calcite mineral deposits hung to the walls in lumps and with little else to attach the dive line to, I wrapped the string around these, sending little puffs of sediment into the water.

Helicopter to deliver supplies“ Taking it nice and slow, I reached the surface where a neverseen-before tall slim passage led away from a circular sump pool ”The winter floods in the Picos are known to be ferocious and I’d not expected to find Rick’s line from 1988 in good condition. Preferably the line would have been completely washed away, but instead the floor and walls of the sump were strewn with old dive line, creating a hazard if I was unwary. In places I cut the old line free and elsewhere dodged around it.

At 30m depth I pushed into new territory. Visibility got better again but the way on wasn’t obvious as the passage twisted and turned, going up then back down again. There were now precious few places to belay the line in the clean, washed passage. After about 150 metres total distance, the sump then began to trend upwards. After passing under an arch I found myself at 15m depth in the bottom of a steeply ascending shaft. With nothing to secure the line to, I spooled out while rising upwards. At 8m depth, the reflective surface above became visible. Taking it nice and slow, I reached the surface where a never-seen-before tall slim passage led away from a circular sump pool.

I’ve been lucky enough to successfully pass sumps and find dry passage on a number of occasions, but the thrill is still just as great. There is excitement at the unknown and relief at the respite a dry chamber represents, all tinged with the apprehension and doubt about the return journey.

My first priority was to secure the dive line which represented my safe route home. Then after dekitting, I headed along the newly discovered cave passage. However only 15 metres from the sump pool, the next obstacle was found. A short vertical drop with the whole streamway crashing down filled the passage. Although the drop wasn’t more than two metres, the floor and walls were smooth and slippery with a calcite deposit and there were absolutely no foot or hand holds.

I was diving solo, something I’m very used to doing. In this case the rationale was driven by simple necessity. Portering diving equipment for one diver would be difficult enough, double the equipment wasn’t feasible given the time constraints. As a solo diver it’s important to be completely self-sufficient and all of your equipment, configuration and gas planning choices take this into consideration. While this made sense underwater, back in the dry cave being on my own was much less ideal. If I climbed down the drop and couldn’t get back up, I would be waiting a very long time for rescue without anyone to help me up. There were other divers on the expedition but there was no other diving kit in the cave and it would be many days before anyone could come to look for me. Knowing there was no safe way down and that the risks couldn’t be justified, I turned back.

Prepping for the diveNow I had one final but vital task - to survey the new cave passage I had found. Although new technology has introduced more options of cave mapping, the basic principle remains unchanged. To produce an underwater survey requires measuring the distance between two points connected by a straight line. At each point the diver needs to record the depth and the compass bearing to the next point. For manual surveying, a well-tagged dive line provides the distance between the two points, a compass the bearing and dive computer the depth. With this data entered into a surveying programme, trigonometry calculations can provide a map of the underwater passage. So, swimming slowly back through the sump I took careful measurements at each belay and every corner where the line changed direction. Back on the surface, my scrawled wet notes and the video of the dive were now my most-precious possessions! It had taken many months of planning and organising as well as the physical effort to enable this dive. Now the results of all that effort and the entire record of my exploration was contained on some sheets of paper and a memory card.

While I’d been diving, the rest of the team had kept warm and well fed but everyone was getting tired at the end of a long day. After packing everything away, the team finally left the bottom of the cave at midnight. A very, very slow return to camp with heavy bags was made, with myself and Mark reaching camp at 4.30am, and Stu and Lisa at 6.30am. The following day no one wanted to get up early, but by midday we were awake and eating breakfast in our sleeping bags. The underground radio link we had with the surface meant we knew that that four cavers were coming in and so we planned our exit. Many slow hours of prusikking up ropes later, the surface was reached. Food and, of course, a welldeserved beer was not far away!

Next issue, Chris joins the team on the Treviso Caves Project in the eastern massif of the Picos de Europa.

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