Through trip


This trip is dangerous, in fact, it's the most dangerous thing I've ever done. I've never before been so acutely aware how little my life hangs upon. Especially hanging by a piece of rusty 100 year old steel 20 metres above a lake 100 metres deep, with every possiblility of many tonnes of wood and iron coming in with you for a swim if you cock up. It's not recommended, but after a few beers you'll agree to anything!.

Some pictures of the trip are here


It all started some time ago when a friend of mine found a magazine article which described a dodgy through trip three blokes had made through a mountain, starting in one mine, and coming out of another. We'd all read this article, and agreed that it sounded like fun?. However, sensibly, the article didn't name either the participants, or the location, as it was so dangerous, and they didn't want anyone else doing it. In the back of our minds however, we'd remembered parts of the description, and mentally compared any mines we visited with it.

Over the time we spent at University in North Wales, we spent a fair bit of time exploring anything that looked remotely like a mine. We also knew from a survey we had of Rhosydd that it connected with Croesor, but initial exploration had indicated that the roof had fallen and the way was blocked.

On a sunny weekend in early September this year, I persuaded James to go back with me to Rhosydd as I was determined to make this through trip. I still had the idea that it was relatively straightforward, as the distance is only about 1km on the surface. We went back into Rhosydd, and explored further, and finally found the way into Croesor. The miners had broken into the other mine mostly by mistake, and for surveying purposes. However, our way was blocked by a 20ft drop into a lake, the other side of the chamber we couldn't see. There were however the remains of a bridge hanging eerily from the ceiling!. We decided to call it a day at this point, and try to do it from Croesor the next day.

Next morning we arrived at Croesor, having never been there before. We spent a little time finding the entrance adit, and proceeded to stroll in. We soon reached the end of the adit, at which point James started to recognise some of the features of the magazine article we'd read. Using our hazy memory, we spent an hour or so making a careful examination of the incline for the way into the chamber to the left, poking about in shaky roof falls and the like. We finally settled on the 20 metre drop at the top of the incline, and tied the rope off to an old rail, weighed down with rocks. James wouldn't go first, so I dropped over the edge and descended down to the floor of the chamber. The drop was dodgy enough, with the unstable wall to push against. James soon followed, and we found ourselves in a chamber with garage sized boulders scattered around the floor. The chamber is so big, that if you stand at one side, you cannot see any of the other sides, and you can only just see the ceiling. We poked around this chamber, and found another drop out of it into another chamber, with some existing rope, obviously left by the previous adventurers.

At this point, we decided that we had definitely found a viable through trip, but what we needed was more equipment. So we called it a day, and went home.

During the week, we contacted two more sporting cavers, who we knew would be keen to have a go. James also got very excited when he re-read the article as he'd had an enthusiasm for doing that trip for some time. This was good as it meant that we both had to do the trip nomatter how dangerous.

The following weekend

The following weekend, we grouped in Bangor, and then drove down to the mine entrance, suitably equipped with camera, lights, rope, metalwork, inner-tubes, armbands, lifejacket, SRT equipment to mention some of it. We quickly retraced our steps to the second pitch (vertical drop) that we'd reached last time. Now the adventure begins......

A test of the existing rope proved that it was still strong enough for us to use, so we proceeded to drop down into the second chamber. It's worth imagining at this point the shape of the chambers, as it makes the understanding clearer. Imagine a cuboid, 200ft long, 60ft high, and 60ft wide, inclined along the long axis at about 25 degrees to the horizontal. A mine is made of a series of these parallel chambers connected by tunnels at roof level. The tunnels are connected by bridges. The water level is about 20feet lower than the tunnels we were about to use, thus meaning that we had to cross each chamber at about 20feet above water level. Anyway, back to the adventure.

We crossed this chamber at floor level, and dropped 10 feet into a tunnel which is the start of the level we used. So far so good!. The first few chambers hadn't been dug out fully, so the need for a bridge hadn't yet arisen, so we could cross on foot. Soon we reached the first obstacle: a nearly complete bridge, unfortunately severely rotten. The basic design of these bridges is simple, hang a pair of steel poles from the ceiling, and put a large piece of timber between the two at the bottom. Then lay two more large pieces of timber across the chamber, resting on the ceiling supported piece. Then put down some sleepers, and presto, a bridge. Wait 100 years for much rot to set in, and then try crossing!, bearing in mind the 20ft drop to a bottomless lake, with sheer sides and no shoreline / beach!.

Fortunately only the sleepers had rotted, and the main supports were not too bad. Very careful walking / sitting enabled that bridge to be crossed with relative ease, although adrenalin had started to flow by now. A couple of easy chambers followed that we walked through, only to meet another deep chamber with no bridge at all. Oh dear!. Luckily we could traverse around the first wall onto a beachlike part of the chamber to cross to the other side. All that meant was another traverse to get into the exit tunnel. The snag here is the total lack of footholds / handholds.

Luckily for us, and God knows how they did it, the previous adventurers had left a rope, which we could attach to, and haul ourselves horizontally along it to the exit tunnel. All going well so far.

A couple more easy chambers followed, and then horror!, another collapsed bridge, with only the central support and a couple of old narrow rails connecting the first side to the middle with nothing on the other half!. No chance of traversing here either. Again luckily for us our precursors had fixed a rope going horizontally across the bridge. Cop out I hear you say, but no, because it was tied to the central bridge support. No problem there, but if the bridge comes down, which is very possible, it takes the rope with it, and hence you as you are firmy attached to it to prevent falling. That thought while hanging off a single rope 20ft over deep water is really scary!. It also makes armbands a little pointless.

After a lot of very careful manoevering, we all crossed this little obstacle, to be confronted with another one, a chamber too wide to see across, flooded, with bridge remains hanging eerily from the ceiling!. If you've read the Rhosydd description it should ring a few bells. This was where the lilo and inner tubes really came in handy. Again, there was a 20ft drop straight into the water, no beach here. So we abseiled down to just above the water, and then slowly lowered ourself onto an inner tube (with slow puncture) or lilo, and paddled like fury in hopefully the right direction across the lake. Fortunately there was a small beach on the other side, and a convenient rope to climb to get up out of the chamber into the tunnel. This was good, as we'd been here before, from the Rhosydd side.

All that remained now was to get out into the open air, and find our way back across the mountain in the dark with failing lights, soaked to the skin, at about midnight on a cold Septembers evening, with the fog coming down!. Not the best thing to be doing, especially as we hadn't even recce'd the route back beforehand. Needless to say we found the car, and got home in one piece.

In conclusion

That through trip had to be done, for a number of reasons, mainly it'd been bugging me big time since I'd found out about it's existence. I'll probably find myself doing the trip again at some point in the future, although at the time, the fear factor told me that I'd never be so foolish again, afterall, being petrified for an hour is not actually much fun. But the buzz afterwards, down the pub after a few beers in front of a nice fire is unbeatable, which is probably why I do it!.


I've done it three times since then, and visited Croesor and Rhosydd in isolation more times as well. There has been a collapse in Croesor so the exit from the chamber the second abseil takes you into is closed. You have to boat / swim to a second tunnel through the pillar. And then boat back again to regain the route. One time we spent quite a while adding extra bolting points on the way, and making it a bit safer. It took 10 hours that time!. And we have done a photographic trip.

It is interesting to note that there has been a major collapse in both Rhosydd and Croesor since this trip was undertaken the first time.

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Last modified on: 25th August 2017 by email the webmaster

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