3 mines · down to 45 m
Mine diving in North Wales
- Mines3
- Max depth45 m
- Water temperature~7 °C
Why come here
In North Wales you dive flooded slate mines full of traces of the mine work: staircases, railed haulage ways, mine carts, tools and even bridges and pump houses, now in dark water. At Glyn Ceiriog, close to Llangollen, Cambrian and Aber Las lie side by side, once one mine and now split by a collapse. According to UKMC, Aber Las is the jewel in the crown of the club, which explored and lined it from 2013. Further west, near the small village of Croesor in Gwynedd, three flooded galleries lie one above the other, from simple shallow circuits to the deepest gallery. Expect cold water (~7 °C at Cambrian), complex navigation and access the proper way: UKMC knows the arrangements.
Don't miss
- Aber Las Slate Mine: two levels at ~8 and ~20 m, joined by the 'Stairway to Heaven', with long railed haulage ways between large chambers; only with permission through UKMC.
- Cambrian Slate Mine: five dive bases, large open chambers, open staircases and mine carts, some still fully laden, at 16 and 29 m.
On a rest day
- Pontcysyllte Aqueduct: Thomas Telford and William Jessop's navigable aqueduct (1805) carries the Llangollen Canal 39 m above the Dee; you can walk across on the towpath. A UNESCO World Heritage Site.
- Castell Dinas Brân: The medieval castle of the princes of Powys Fadog on a hilltop above Llangollen, built on the site of an Iron Age hillfort.
- Llechwedd Slate Caverns: Near Blaenau Ffestiniog, not far from Croesor: the Deep Mine Tour takes you down a steep narrow-gauge railway into the old slate caverns, dry.
- Ffestiniog Railway: A heritage narrow-gauge railway from Porthmadog to Blaenau Ffestiniog, mostly within Snowdonia National Park, opened in 1836 to carry slate to the harbour.
All 3 mines
| Site | Max depth | Type | Certification |
|---|---|---|---|
| Aber Las Slate MinePermission neededSidemount · Full cave | 20 m | Sidemount | Full cave |
| Cambrian Slate MineBackmount · Full cave | 29 m | Backmount | Full cave |
| Croesor Slate MineNot known yet · Full cave | 45 m | Not known yet | Full cave |
Certification requirements, configurations and trimix depths are estimates for planning. Always check them locally and dive within your training.
Map
Practical info: rules, fills and emergency numbers
Emergencies
- 999 or 112. Accident in a mine or cave: call 999, ask for the police and say it is a cave rescue; cave rescue is free in the UK (TDI). In North Wales that is the North Wales Cave Rescue Organisation. Diving accident on land: National Diving Accident Helpline 07831 151 523 (24 h, England and Wales) or the nearest BHA chamber; DAN Europe +39 06 4211 5685.
- Chamber: Hyperbaric Treatment & Training, 2 East Street, Birkenhead CH41 1BY, tel. 0151 648 8000 (24/7; backup 07802 824245), category 1 (~1 h from Llangollen, ~2 h from Croesor; estimate).
Access and rules
- Access: according to TDI all underground sites in the UK have access requirements. Some are open access, some need BCA (British Caving Association) membership with BCA diving insurance, your public liability insurance, and you apply for access in the way the landowner asks. Aber Las: BCA membership and the landowner's permission through UKMC. Cambrian: open according to TDI (2019, updated 2021), with no formal permission. Croesor: no access rule published, and only reachable with a decent 4x4 (UKMC).
Gas and fills
- Gas: our sources name no fill station near Llangollen or Croesor: arrange your gas in advance.
Water and season
- Water and visibility: in Cambrian ~7 °C, with 10–15 m visibility that drops to 2–3 m after rain; in Aber Las visibility is usually very good, except at the dive base and on the way out (TDI).
Safety
- Safety: TDI advises all mine divers to leave a callout time with someone they trust on the surface, who raises the alarm if you are not back on time.
Rest day
- Non-diving day: the Pontcysyllte Aqueduct over the Dee, the castle of Castell Dinas Brân above Llangollen, and near Croesor the Llechwedd Slate Caverns and the Ffestiniog Railway.
Good to know
- Read this first: in North Wales you dive dark, flooded slate mines with complex navigation. UKMC (UK Mine Cave group), a club of mine and cave divers, explored and lined Aber Las and gives its members location maps, access agreements, dive maps and surveys. These pages are not an invitation to go on your own.
News
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