The Croesor-Rhosydd mine through trip.

(Apologies for the quality of the smaller, video captured stills - mouseover the images for descriptions, and click the pics to see larger versions)

I'll get this straight from the start, this article is not at all bouldering-related…so what's it doing here?

Well, I don't know about where you live, but around here the weather has been consistently appalling for about the last two months, and very little bouldering has been occurring at all. Also, some of the ukb crew enjoy wriggling about underground of an evening, rather than hanging out down the woody hurting their tips, so we thought we'd share this little adventure with you.

In our defence, the proximity of this trip to the fantastic bouldering areas of North Wales also makes this trip a viable rest-day/rainy-day activity for bored boulderers looking for something silly to do.

Croesor and Rhosydd are old slate mines, situated northeast of the tiny village of Croesor, which in turn is about eight miles from Tremadog. They are both set high up on the slopes of the Moelwyns near Bwlch Cwmorthin, a high pass separating the valleys of Cwm Croesor and Cwm Orthin. Both mine enterances are at an altitude of approximately fifteen hundred feet, and set in beautiful, rugged mountain scenery, albeit in one of the highest areas of rainfall in Wales.

Although not the biggest of the Welsh slate mines, these certainly aren't tiddlers either - the spoil tip at Rhosydd alone contains over two million tons of rock. Croesor mine is almost all underground, was worked from the late nineteenth century until nineteen-thirty, and consists of seven levels, the bottom three of which are flooded.

Rhosydd is the largest underground slate mine in Wales bar the big Ffestiniog mines. It consists of one hundred and seventy chambers on fourteen levels, but again, all levels below level nine are now flooded. Work commenced in eighteen-forty, and, like Croesor, ended in nineteen-thirty, due to the continuing decline of the Welsh slate industry.

There have been several large collapses in Rhosydd over the years, but the through trip between the mines is still possible. The link between the two was originally made to settle a dispute regarding their respective boundaries, and we can only speculate that it was not sealed off again in order to provide an alternative exit from either mine in case that ever became necessary. There is actually the remains of a wall across the route of the connection at the Rhosydd end, but it's hard to tell when it was built and for what purpose.

Ok, history lesson over - but that should give you some idea of the creaky old age of the place, which you'll be desperately trying to forget as you tip-toe beneath the poised blocks above your head.

Sun 2nd June, 2002

sorting the gear at Eric's campsite
Following the previous evening's sunny bouldering session at Utopia in the Pass, it almost seemed odd to be going underground, but the weather wasn't looking too hot, and anyway, this was the real objective of the weekend and so, after a lardy breakfast in Eric's café we started to pack the tackle bags….and pack, and pack….. we took a lot of kit. In fact, we probably took too much kit, but as we couldn't contact anyone who'd done the trip recently, we thought it better to be over-prepared rather than to travel light, and were carrying many extras such as a bolt-kit, a small climbing rack and some dynamic rope.

There were four of us - Mike, Sam, Jim, and John. Sel & Mel were not enthused about the trip and so were going to hook up with us back at the campsite later on…..much later on as it happened. We loaded the car and set off to the mines, stopping off on the way to pick up Pete, the fifth member of our party, who lived nearby and was the only one of us who had done the trip before, back in nineteen ninety-four.

the approach march


Sam drove the poor, overloaded car as far up Cwm Croesor as he could, and we stumbled out and started off uphill on the long walk in, with Jim setting a brutal pace right from the off.

Soon, the inevitable rain started, and by the time we arrived at the mine my clothes were soaked from the inside by sweat, and from the outside by drizzle. The walk in was longer than I expected, and took about an hour, although it seemed worse than it really was due to the heavy bags and the fact that I was not yet fully awake.

the entrance
looking down the entrance adit
We got changed in the rain under the bemused gaze of a bunch of cagouled walkers, who seemed puzzled by our desire to go through the mountain, rather than up it. They didn't seem to be past a bit of voyeurism though, and asked if Sam "would get changed like that in front of them again, as they missed it properly the first time…." Then out of the blue appeared three blokes with helmets glancing knowingly at our tackle-bags - it turns out they'd been around to Rhosydd, to look at the other end of the trip, but were stopped at a big lake…my anticipation grew.

The entrance adit was gained by squeezing through a gap in the bars - we all clambered in, glad to be out of the rain, and stashed our now wet clothes just inside. Lamps on, and the super-torch was unleashed. It shone away down the half kilometre entrance passage; an eerie sight as there was still blackness beckoning, even beyond the range of the considerable beam of the super-torch.

We made quick progress down the long adit, passing small roof breakdowns, flooded sections, and a strange old brick room branching off from one side of the tunnel, which was apparently where a certain major chemical company used to store their explosives - nothing left there now though, unfortunately.

sam, with the super-torch, baulking at the size of the place We reached the end of the tunnel with no obvious way on - to the right was a short tunnel leading to a huge water-filled chamber. All of the chambers in this place turned out to be vast; although most of them not very wide, they are high and very long, with parallel roofs and floors, inclined at about thirty degrees to the horizontal. Since the mine is flooded below the level of the entrance adit, the particular chambers here had deep water for a floor, and although they have been crossed (guide line still in place), this was off our chosen route, so we didn't investigate any further than shouting into them to hear the gloomy and boomy echos bounce back at us. We stopped this after we'd seen the state of the ceilings - the less provocation aimed at those pointy, shed-sized blocks the better.

The way on was now up an old incline to the site of the old furnace. This was an easy scramble up, following a huge old clay flue pipe on the floor of the passage until another junction was reached. To the right is a high-level window into the same flooded chambers just mentioned, and to the left was our way on, or rather down, via an abseil into another vast chamber.

john rigging the first pitch
There was some old fixed rope in place, but this didn't look so hot, so the triple-bolt belay was re-rigged with an old static rope we'd brought along for this very purpose. The abseil was only about seventy feet, but I found it quite worrying due to the scale of the chamber we were lowering into, the rub-points over slate edges, and the big loose flakes on the way down. I abbed at a snails-pace to prevent rope-bounce, but this was really not necessary as I later noticed on the second abseil that the rub points had mostly been polished down by the passage of other parties.

At the bottom, we found ourselves in a another huge room, the floor (and ceiling) of which consisted of large, sharp, loose blocks. We picked our way across the chamber to a vague window in the other side, to find the next abseil point. This time, there were no bolt belays, but just ropes belayed around boulders with rope-protectors for the sharp edges of the blocks. Again, the existing rope was junked in place of one of ours, and we tentatively made our way down into yes, you've guessed it, another huge space. I was starting to feel a bit more at home in the place now, but still hadn't got over the size of everything which was way beyond the scale of most things I've come across during our usual forays underground.

The old route from this chamber to the next was a hard to find squeeze down through boulders in the floor, which dropped into a tunnel and from there into the next chamber.

pumping up one of the tyres at the start of the first lake
sam sets off across the first lake
jim exits the first lake
A few years previously, there had been a roof collapse, and this way on was now completely blocked. Luckily, at the bottom of the chamber there was another window, the only problem being the fact that to get over to it was going to mean somehow crossing the water-filled bottom section of the chamber.

In such a gloomy and intimidating place as this old mine, it was a revelation to find that the lake was actually quite beautiful; the water was deep, but crystal clear and it sparkled emerald green under our lights.

In order to cross the wet bits, we'd brought along two front wheel inner tubes, kindly donated by helpful farmer back in Derbyshire, which were then tied into the middle of a long piece of baling twine so that they could easily be pulled to and fro across the lakes. As we put the amateur looking kit together and pumped away at the tyres, we giggled like fools at the strangeness of the situation. The place was exhilarating, oppressive and impressive at the same time.

Sam was first off to test the tyres, and all was going swimmingly until he neared the 'far shore' and the twine became tangled - he was now in full-on paddling mode and wasn't stopping, driven on by the cold and the thoughts of that deep water below. Luckily, soon the tangle was sorted and he clambered out on the other side, an easy scramble up into another tunnel.

After ferrying across the tackle bags, and then ourselves, we discovered that the tunnel was only about ten feet long and led straight to another lake. The same tactics were used to cross this one, the only difference being that we had to lower ourselves down an old bit of chain to get into the water (this might be tricky if you ever need to reverse this bit, so check the state of the chain on your way through). By the time we'd all crossed, I was freezing - that water is cold, and the mine draughts hard in places. I danced about on the crunchy slate floor - feeling foolish, but keeping toastie.

We took a moment to look about at our surroundings, once more unleashing the super-torch. Old, high-level passages were spotted, and in one place a rusty old ladder about 80ft high was dangling temptingly down into the chamber. Well, not that temptingly really, one step on it would probably bring it down on your head, along with whatever it was attached to - we'll leave that one for the moment, thanks.

sam rigging the bag haul line on the first bridge
sam unwisely standing in the middle of the bridge!
pete heads off on the tyrolean traverse
watching john rigging the scary second bridge
john on the second bridge
So, onwards we went through big, echoey chambers along old cart tracks, with rails still in-situ in many places, until we arrived at the first old bridge. The route continues at a window on the other side of the chamber, the floor of which is a lake with vertical sides, twenty feet below. The bridges are simple - at the halfway point, old, rusted metal beams hang from the roof, each holding one end of a timber cross-member in place, and the bridge is simply laid across this support to reach each side of the chamber.

This first one's not too bad, at least the two main beams are in reasonable nick, but I've heard of someone who had to be cave-rescued from here when they fell through the old planks in the middle of the walkway, and couldn't get back off their rope, so the whole thing still needs to be treated with respect. Anyway, a rope was rigged in addition to the existing handlines so that we could haul the heaviest bags across, it would be poor to end up in the water below wearing a heavy tackle bag. The lake below was a horrible dank pond with no easy way out, so we carefully tiptoed across the slimy beam across to the next bit of solid passage.

After a short distance, an identical room to the first one appeared, but the bridge here had completely collapsed into the water. Old explorers were forced to make a traverse around the chamber, following a small ledge to a tiny beach, then swinging back across old fixed-ropes to gain the window at the other side of the room. Luckily, some enterprising folks had rigged a tyrolean cable straight across the void making it easy work to just zip across on a pulley…

…and then came the third and final 'bridge' crossing. The state of this bridge is appalling - two bendy old rails, just resting on rotten wood and unsecured at each end, span the gap to the support in the middle of the room. Although there are fixed lines here, it's pretty scary shuffling across these rails, especially when they're flexing alarmingly, and you realise that most of the fixed ropes are attached to the centre support. The support beam rocks gently to and fro, and this is where I was trying hard to forget about the age of the rusty supports driven into the roof, and holding everything up. The pool underneath is green and gloomy, and full of old bits of bridge, and other crap - most uninspiring to say the least.

From the centre support, an eight mill bolt in the roof supports another little tyrolean wire, so the second half of the crossing is fine, and certainly better than the original way on which was to 'a cheval' across a rotting beam of wood full of sharp, rusty nails. People have fallen into the water from this beam, and I'm sure glad this didn't happen to any of our party. Once across this obstacle, I knew the main difficulties were over and despite enjoying myself intensely, I was freezing again and was looking forward to the way out.

One last obstacle remained, the third and final lake crossing. This last lake is much wider and deeper than the others, and there is a forty-foot drop just to get to the water. As we were starting to get the tyres rigged up again, somebody pulled on the long bit of twine attached to the abseil point and…..across the water came a dinghy, fully inflated and looking far more inviting than our little tyres. There was much rejoicing at this point, as we knew we wouldn't have to get wet again. It was unforgettable as I dropped off the rope into the dinghy and the others pulled me across the lake. I just lay on my back and watched the huge cavern roof glide silently by above my head.

the shrine at the end of the difficulties
sam looking mental
jim looking happy to still be alive
the first site of daylight
heading up the long exit scree-slope
nearly out now
A quick climb up a fixed rope at the other side of the lake and we had reached the end of the trip - we were now in Rhosydd mine and in celebration of this fact, previous parties had built a bizarre 'shrine' to the crossing. Ok, really this was in fact a heap of junk, but it was really funny to find it there, with such things as a badminton racket, a coffee machine, a stylish (!) old red handbag, etc. We had nothing left but a nutrigrain bar, so that was added to the pile.

Things aren't quite over here however, as you still have to get out of Rhosydd, but fortunately this was fine and, after a few wrong turns through the now much smaller tunnels, passing some interesting old mining artifacts, we suddenly arrived in a vast cavern where daylight could be seen shining in from above. The exit chambers were truly breathtaking, and with the light pouring in ahead, the climb out from the darkness was amazing.

Once out, we paused for a team photo and then proceeded to get completely disorientated in the mist on the mountain top. Sam's compass, although it looked like something you'd get out of a Christmas cracker, saved the day and we picked our way back around and down the hill to the Croesor entrance.

jim trying to look fresh
mike looking like he's just encountered satan in the mine
team photo
and going back in time...
By the time we'd got back at the car, our "three to five" hour trip had stretched into over eight hours, and I for one was very happy to get back to Eric's campsite and a chance to get back into normal clothes and to see Selina, who was a bit worried by the fact that we'd got to within half an hour of our cave rescue callout time.

So, all in all a great trip, very different to anything I've done before and I'd definitely do it again……but maybe not just quite yet.

As an aside, if you knew the two fixed ropes at the start were in good nick, then maybe the best, and quickest way to do it would be by wearing wetsuits, carrying buoyant waterproof bags, and just swimming the lakes.

Mike.



Other accounts of the trip:

Pete's great article
Chris Cowdery's trip
Subwales.co.uk
Some older and scarier pics (from Chris Cowdery's site again)