The Sistema Cueto-Coventosa, on the west side of the Ason gorge near Arredondo (Cantabria, N. Spain), is one of the great caves in Europe. At the time of the connection of the two caves (1979) it became the deepest through-trip in the world (815m deep).
Cueva Coventosa, whose entrance is a short distance up the hillside from the roadside resurgence cave (Cueva Cuvera) was explored in the 1960's by French cavers, particularly the "Speleo Club Dijon". Prospecting of the mountain ridge above led to the discovery of the small entrance of Sima del Cueto, in 1966. A short distance inside, the first pitch was not descended but measured at 193m. That summer a winch was used to descend the pitch, the 193m "bottom" was discovered to be a small ledge - the actual depth was 302m. The continuing series of shafts were explored over the following years, eventually meeting the main horizontal series of Cueto at a depth of -501m. The system has now been explored to a length of over 28km, and extends to close to Cueva Canuela near Bustablado.
In the summer of 1996 a permit for the cave was obtained for a week by the Derbyshire Caving club. Three teams were able to carry out the through trip, the last consisting of Phil Pappard, Steve Oppenshaw and myself. We left a car near the resurgence, below Ason village, then were given a lift up to the settlement of Socueva. From here a mule path winds up through the cliffs on the western side of the gorge. After several attempts to find the correct route and a slightly bizarre encounter with an elderly Asian gentleman from Epsom, we had a rest from the sun in the shade of a barn. From here a route through high pastures eventually leads to a vague track leading up through lapias on the ridge - the highest point hereabouts is 1347m. The walk up takes about two hours - dependant on the heat and amount of gear we carry - we kept the latter to a minimum.
The insignificant looking entrance passage slopes down to the head of the Pozo de Juhue, the 302m pitch. This was rigged with 9mm rope down to the ledge at -193m, then an 8mm rope to the bottom. We were to use the 8mm rope to pull through on, leaving the 9mm to be pulled up the following day. The alternative is to use a rope of about 50m to pull through from the top, using fixed chains at intervals down the shaft.
I volunteered to go first, to overcome last minute nerves, and clipped on to the insitu traverse lines. Expecting that it would be quite hard to pull up enough of 200m of rope to clip on my stop, it was a surprise to find this next to impossible. Cautiously peering over the edge, a tiny light could be seen far below. This turned to be one of a group from Santander pirating the system using our ropes. They were doing the trip over two days, their amigos coming in the following day with a boat for the lakes.
The rope was soon free and Steve descended, followed by myself. At -303m Steve came across a large and full DCC rope bag, which was to prove a great hindrance as we really had to take through as far as the lakes, rather than abandon it. Steve used this rope to descend the next pitch, Pozo del Algodon (55m), while waiting for Phil to descend from the ledge using the 8mm rope. This latter nearly proved to be disastrous, as this long rope proved very prone to tangling and catching. He nearly ended up totally stuck on one of the intermediate belay chains, with the rope snagged below. After over an hour he was able to reach the bottom with the rope safely retrieved.
After the second pitch, we found most pitches left permanently rigged with ropes of various condition and indeterminate age. Only one pitch, starting off after a pendulum off onto a bridge over a blind shaft, required a pull through. At the bottom the way on is a few metres up the wall, over a pile of old telephone cable. The last pitch, after a squeeze down through a chaos of house size blocks held open by a grotty bit of rope, drops into a large and well decorated passage, Galeria de Juhue, at -581m. This is unfortunately marred by piles of spent carbide and other rubbish. At this point I caught up with the Spaniards, who carried on into the distance while I waited for Steve and Phil.
The large passage is followed to Sala de Las 11 Horas, where it turns west and enlarges for the next Kilometre - Galeria del Chicarron. This is often upto 60 - 80 m wide and high, even with a good T3, it was difficult to make out the walls and roof, total confusion only being avoided by strategically placed reflective markers. The going consists of endless scrambling up and down immense mountains of rubble. Towards the end is El Oasis - a quick stop for a drink at some drippy avens. Eventually we reached Pozo de las Navidades, a pitch down where we again met the Spaniards, who were having doubts over the in situ rigging.
From here the fun really starts - the next 3km consists of crawls, rifts and numerous short pitches up and down, with many sections being exposed, awkward, loose and confusing, often all combined (rather like the cottage on a Saturday night ! Ed..) The sense of commitment certainly helps one push one along through all of this. Towards the end the draft becomes concentrated into one passable route, eventually roaring down la Turbina, a short constricted pitch. This was tight enough for Phil, that he had to remove his SRT kit halfway down.
This really marked the end of the difficulties, but there are still several Km to the end, and tiredness was beginning to tell. A short section of walking leads to a bigger passage, and a descent through boulders to the Coventosa river passage. Following this downstream leads to the lakes where great care is required - buoyancy of some sort, ideally a boat is essential. My option of being towed through in dry gear, with a dry bag and a Daren drum for buoyancy was only just sufficient, and the water is cold. After the lakes the entrance series is eventually reached. In this area the river is left near some large gours. A series of short pitches and a traverse on steel hawsers are followed, in which area we could not locate the way on for about an hour, due to not being able to see a rope up, it being the same colour as the rock.
Eventually the roar of the draft in the (quite large) entrance passage could be heard, and soon we were out , with rapidly failing lights all round, just in time to witness a beautiful sunrise over the mountains. We took around 15 hours to do this trip; one of the other groups managed it in 8 hours (without having to derig the entrance pitch), while another party a few weeks later took 25 hours, having major problems pulling through on the entrance shaft - caught ropes, a descender disintegrating and other epics.