Information for planning caving trips in North Wales. This page is currently a work in progress, please get in contact if you are interested in contributing.

CROESOR-RHOSYDD THROUGH TRIP

^{By Jonty Pine and Aidan Kuhlmann, BSCC, 2022}

The Croesor-Rhosydd Through Trip is a classic North Wales underground trip. It is also the most rescued underground location in North Wales. This is due to a variety of reasons, the foremost of which are route-finding and underestimation of the time it takes to complete the trip. It is very common to get lost on this trip, especially on the Rhosydd side. Part of the reason for this is lack of clear survey or description. This guide aims to address this, improve the quality of trips and reduce the number of rescues.

 

Important Information

The trip takes a minimum of 4-5 hours including the approach and walk back, but it is recommended that you leave at least an 8-hour call out starting from when you leave the car park if this is your first time making the trip. There is good phone signal in either car park but weak or no signal nearer to the mine so be prepared to walk down before cancelling call-out.

There are in-situ ropes for the entirety of the trip, but these have been known to be cut, damaged or in generally poor condition in the past. Use them at your own risk and inspect all rigging and bolts before committing to them. It is strongly recommended that you bring your own rope as a back-up. The ropes may be stiff and not provide a smooth descent.

Midway through the trip it is necessary to cross a flooded chamber on a 2-person canoe. There is a possibility of capsizing or otherwise sinking so it is recommended to bring some form of buoyancy aid.

Recommended Kit

• Standard safety kit – first aid (including major trauma for sharp slate injuries), group shelter, spare lights, food and water
• SRT kits
• 30m Back-up rope
• Buoyancy aids x 2
• Zipwire pulley (not essential)
  
  

The Approach

It is possible to approach this trip from 2 directions. Approaching from Croesor gives a shorter walk in but a longer walk back at the end of the trip. The Tanygrisiau side has a longer walk in but allows for a shorter walk out at the end of the day. Either route will give a total walking time of 2-3 hours depending on group ability.

Entrance
52.9906, -4.0022
SH 65699 45576

Exit
52.9963, -3.99025
SH 66523 46195

From Tanygrisiau
Parking
52.9901, -3.9636
SH 68289 45445

This car park is very busy on weekends, holidays and good weather days so it is recommended to arrive early. It is up a single-track hill with limited turning space when busy so large vehicles may wish to consider this. There is further parking lower down and adds 15 minutes to the walk.

Follow the Snowdonia Slate Trail to Croesor Quarry. You will pass the Rhosydd No. 9 adit, your exit point from the mine, on the way. The route is largely uphill, consisting of flat sections interspersed with steep uphill stretches.

 

From Croesor
Parking
52.98206, -4.03975
SH 63156 44694

This car park can also be very busy but is more likely to have space available and is less committing for large vehicles than Tanygrisiau.

Follow the track from the car park to Croesor Quarry. This route is a constant low gradient uphill walk.

 

Underground

Enter through the grate at the provided pin. Follow the tunnel and continue straight at the fork. The tunnel widens significantly and then splits. In the centre you will see a pool of water, this is the top of a flooded incline. Pass this and continue straight to scramble, using the in-situ hand lines, up over the collapsed winding house. This will bring you to the rising incline where you will see a large yellow pipe on the left-hand side. Follow the incline up, being wary of the airy ledges in the tunnels to the right. Climb 3 levels, scrambling over some boulders, until you reach a metal grate blocking the way upwards. Here, take a left and you will immediately find a traverse line leading to the first pitch.

Pitch 1 – The Chamber of Whispers

It is traditional to avoid loud noises once reaching this pitch to avoid triggering rockfall in the surrounding unstable chambers. The effectiveness of this is in debate but it can’t hurt.

After reaching the bottom, face away from the pitch and go forwards, to come underneath a large overhanging pillar. Continue in the same direction following the polished route as much as you can towards the opposite side of the chamber. Avoid getting too high up to the left as the rock is much looser. As you near the far wall you will see a large opening where the top of the second pitch is. You may also see a traverse rope off to the right, but this is not the way on.

Pitch 2 and Zipline

Continue to stay quiet at this point if you have decided to follow this guide’s instructions. The pitch rope is anchored in many places but check the rope over anyway, especially where the failure of one strand would be catastrophic. There is a very awkward deviation near the top on a rusty old carabiner that can be very difficult to open. As it is at the pitch head, it is possible to provide assistance from the top while remaining clipped in. On the way down there are 4 rope protectors on the wall. Take care to run the rope over these as you descend and avoid swinging on the rope.
At the bottom of the pitch, facing away, turn left and scramble down a short distance until you see a cable zipline running across a pool, parallel to a wire bridge. At this point you can cross using either.
CAUTION – THE ZIPLINE IS VERY FAST, KEEP HOLD OF THE BRAKING ROPE

After the zipline, cross a ladder bridge. There are a few passages leading from this chamber. The route onwards is the first tunnel in the left wall, coming away from the ladder bridge. It will soon come to a fork – take either one, they converge not far after – above a pool of blue-tinged water. In the next chamber is a double-beamed bridge crossing. Cross this and the following bridges and traverses, progressing in a straight line, until you reach the Chamber of Horrors.

 

Boat Crossing

You will see a pulley anchored to the roof with two strands of blue polypropylene rope travelling down from it. Pull on one of these to retrieve the 2-person canoe. The other side of the rope if pulled on will send it back to the other side.

It is recommended to wear buoyancy aids and remove any extra metal from harnesses before entering the boat as falling into the water in full kit could be lethal. Do not wear bags on your backs as these would drag you down. It is also worth scanning the chamber for exit points from the water before committing yourself.

Abseiling into the canoe is easier when it is alongside the wall rather than at right angles. It is advisable to remain attached to the rope until you are comfortable and stable. There is a chain on the wall that can be held to keep the boat steady as a second party member descends in. Once the boat is loaded with 2 people, pull on the appropriate side of the blue rope attached to the front of the boat to propel yourselves across to the far side. You can then leave your buoyancy aids in the canoe for remaining party members to pull back.

After exiting the boat there is a small pitch up with an in-situ SRT rope, roughly 4 metres. There is a bolt climb here intended for emergency use, but this is difficult to ascend, and the top out is largely unprotected. If it is necessary to use this, it is recommended that the first person up belays following members.

At the top of the pitch, continue forwards and pass through a half-collapsed wall. Scramble up the low-roofed slab to the right in the second chamber. At the time of writing some metal rail propped up at the base of the chamber makes this easier. Emerge at the top and, taking a left, follow the level along. Soon you will see a staircase going up on your right-hand side. Ignore this and look straight ahead to see a wall spanning the width of the tunnel with enough space at the top to climb over. This is the boundary between Croesor and Rhosydd.

Rhosydd

On the other side of the wall is one of the Rhosydd inclines, where you can still see the old rail turntables. Cross over these and follow the tracks to where they disappear under a pile of rubble. Scrambling over here reveals the tracks again on the other side. Continue to follow them for another couple of chambers until the tunnel ahead appears blocked by more rubble. As you get closer you will see a crawlspace over the top of the rubble. The way onwards is directly ahead of you, in the opposite tunnel, behind all the rubble and a wall. This is not directly accessible but can be reached by going up a level and down on the other side: to reach it, go through the crawlspace and turn right, scrambling up the slate tip. Take extreme care as some of the large pieces are very sharp. After a short distance turn left and pass underneath the overhanging wall before descending to the floor level on the other side.

If it is still daylight outside there will be light coming in from a large opening further above you. Continue along the level, with daylight above you to your right, until you pass a ruined wooden bridge. In the next chamber the tunnel onwards is blocked and is impassable. Turn left down a low-roofed scramble over loose slate. Almost immediately a tunnel is visible in the right-hand wall, leading to another Rhosydd incline.

Follow the incline to the bottom, take a right-hand turn and then continue forwards. The tunnel bends slightly to the left and then continues dead-straight all the way out to the surface. Daylight can be seen a few hundred metres ahead if the sun has not yet set.