Croesor Rhosydd Through Trip CRTT
23rd September 2022. Leader: Richard
I read about the CRTT a few years ago and was amazed. Therefore this was not just on my ‘must do’ list, but was what inspired me to join an underground exploration club, hence the PCG! Since I read the article, proper permanent lines have been installed, but it still needs propper SRT training and full equipment. Also, you need someone who already knows the way as it is very easy to not only not find your way through, but to get properly lost. Also there are a couple of long descents, which are not what you want if you are not experienced or equipped and have to turn back. One of the most frequent call-outs for North Wales Underground Rescue, has been to retrieve people from Croesor and Rhosydd.
The Croesor and Rhosydd slate mines exploit adjacent parts of the same thick slate vein which runs SW/NE through Moelwyn Mawr on the SE side of the Croesor Valley through to the head of the Cwmorthin Valley. The vein dips to the NW at around 40 degrees, nearly parallel to and deep in from the SE side of the Croesor Valley.
As part of our 2022 Autumn North Wales trip, we met and changed in the Croesor car park and made our way up a mile and a half of steep track to the Croesor Quarry surface workings. Here we got into our SRT gear and then headed in through the 440 yards main adit. Here we encounter the vein and a couple of chambers following it upward. Below here, the chambers are flooded. We scramble up the scree of one of these chambers and then round to one side, go through the wall of the chamber, and enter high up above the floor of the next. Here, although there is a rope rigged in place, being cautious, Richard rigs our own rope to abseil down 80 feet. We each descend, cross a huge cavern, climb a boulder scree, where we go through the next wall into the next chamber. Again, Richard rigs our own rope and we descend 80 feet again.
We then make our way through a series of chambers, crossing one on a wire rope bridge and another via a zipline, both near water level.
Then on a bridge with 2 beams remaining (and a safety wire!) (The Bridge of Doom?)
The Bridge of Death…
This is a single ricketty beam, with a loosely spliced break at one end. However, here again there is a safety wire at head height and also a foot wire to traverse as an alternative to the beam.
The Chamber of Horrors!
We emerge from a tunnel above a lake which spans 2 caverns width, with the intervening wall partly quarried away. Fragments of a suspended tramway bridge dangle from the ceiling, offering no hope of help. The only way across is about 30 feet down the sheer edge to the water, across the water and up the sheer face on the other side. Fortunately, kind souls before us have installed ropes at each side and provided a broad beamed canoe on a continuous cord to get across with.
I get volunteered to be 2nd to abseil down. I have to land carefully in the back of the canoe, which I had to help manoeuvre beneath me as I hovered the last few feet above it. The rope being thick, meant I could not disengage my Petzl Stop, except by sitting and leaning hard back into the canoe to get enough extra length when I sat up again. Unfortunately, I ended up sitting and travelling backwards in the canoe. At the other side, I made my first mistake of trying to climb the smooth slope up the chamber, only realising at the top of a slab, that I needed to be at its base at the front of the canoe. At this point, my fellow canoe traveller dropped his iPhone in the water, where luckily it landed on a gravelly ledge a couple of feet below the surface. He retrieved it, still working! Next I prussicked up the rope on the far wall, but had to traverse to my left to reach the continuation of the tunnel. Here I made my second mistake, being first up, I clipped a cowstail to the traverse line, but was too high to get my ascenders off. I fussed around for a while and eventually sussed how I needed to down prussic a bit, get my ascenders off and shimmy round to the tunnel.
From here, once the rest of the party had got across, we headed a short way round a couple of turns and came to the wall that used to be the emergency escape from one quarry to the other (or the “Let’s knock of early and take a shortcut home” route, which is why it was eventually blocked, only to be knocked through in emergencies.) It being now open again, the passage continued, now intersecting the chambers of the Rhosydd mine, until it was blocked by a fall, where we had to climb up the scree of a chamber, cross over a couple until we came to one that opened to the sky (in the West Twll or hole) and carefully clamber down the scree to the main access level, where soon we picked up a long, broad adit out to the daylight.
Here we stopped for a group photo, made our way back ’overland’ to the Croesor entrance, where Richard and one other had gone back in to derig our ropes, and from here, we headed back downhill.
An epic, magnificent trip! Thank you to Laura Milroy for the first and last photos and to Craig Holdstock for all the others.