Mine Diving in the UK

By Michael Thomas

Saruman:
Moria… You fear to go into those mines. The dwarves delved too greedily and too deep. You know what they awoke in the darkness of Khazad-dum… shadow and flame. – J.J.R. Tolkien

The British Isles has a significant underground history both of natural caves and mine workings. When I walk or swim around some of the extensive disused mine workings it’s not hard to see why the mines have given the imagination and backdrop to many books and films. The mines that we can access and dive are found in all corners of the United Kingdom to Scotland via Wales and all the way down to Cornwall in Southwest England.

I’m not going to list every mine by mine account of location, access and dive descriptions as that would be too long and tedious. Plus, some sites are sensitive to access and should also be protected from over diving. It’s not to say you can’t dive these sites but doing research and gaining permission correctly is half the fun!

Access Arrangements and Cave/Mine rescue.

All underground sites in the UK have access requirements. That means you the diver have to research what is required of you to be able to dive these sites. Some are as simple as having open access (at the time of writing) and require you to do nothing more than take responsibility for yourself when in the mine. The landowner and mineral rights owner have warned you of potential dangers, where the rest is up to you. Some sites require you to hold BCA (British Cave Association) membership and BCA diving insurance. The insurance is your public liability insurance. You must apply for access to the site you wish to dive in the manner the landowner requests. This all sounds a bit difficult but with planning and talking to the correct people it’s actually very easy and very rare for access to be denied if all your paperwork correct. If you are reading this from outside the UK and wish to mine dive here, contact myself or another TDI cave/mine instructor in the UK and they will help.

Venturing underground into mines or caves in the UK or any other place in the world carries some risk. I would advise all mine divers to leave a callout time with someone you trust on the surface. It’s this person that will summon the cavalry if you are not back on time. In the UK we have a fantastic cave rescue organisation that you can summon in an emergency by phoning 999 and ask for police and cave rescue. You will then be contacted by cave rescue for details of your location (please make sure you have your correct location name) and details of the incident. This is a free service in the UK, donations to the cave rescue teams are always appreciated, especially if you have just been rescued.

Here is a sample of some of the mine diving locations in the UK. All the sites that follow are well documented and easy to research in guidebooks or on social media. The others …… well …. let’s not give it all away at once.

Dinas Silica Mine

Access is open, no formal permission required.

Dinas is probably and historically the most well documented and popular mine dive in the UK and many trainee mine divers’ first mine dive. Located in South Wales, it has a walk of around 15 minutes to reach the entrance from the car, initially steep and rocky then a gentle walk over the hill. Good walking boots are recommended and a rucksack to carry your equipment. Once at the entrance a short walk underground of around 80m reaches the dive base. Diving is extensive in six levels down to a depth of 22m in generally very good visibility and water temperatures of 7°C.

Cambrian Slate Mine

Access is open, no formal permission required.

Located near Llangollen in North Wales the impressive entrance to this Slate Mine is down a steep wooded and at times slippery slope. Once inside the mine, a short walk brings you to one of five separate dive bases. It’s possible to dive from any dive base to arrive at another but navigation is complex and several dives would be needed to learn the system. The mine is extensive and has many very good artefacts in situ and in places very large passage, do not lose the line. Open circuit cylinders will get you some good dives but to reach the further reaches at depth a CCR is advisable. Water temperatures around 7°C and visibility varies from 10-15m down to 2-3m depending on the rainfall causing a stream that flows into the mine to increase in volume and change the visibility.

Aber Las Mine

Access BCA Membership and permission required from landowner via UKMC 

Really Aberlas is a continuation of Cambrian mine next door, a collapse in the passage has now separated the mine into two separate dive sites with different entrances. Do not approach the collapse area from either Aber las or Cambrian mine, it is still unstable! Permission is a must to acquire before diving. A steeply inclined shaft that can be walked down for around 80m reaches the dive base. Care is needed as the slate debris you walk on is slippery especially when carrying heavy dive equipment. From the dive base, two passages lead off. One into the deep route at 20m one into the main shallow tunnel at 12m. A round trip dive is possible as is exploring the many side passages and superb mine artefacts that are in situ. It’s possible to dive 588m from dive base. Visibility is generally very good apart from at the dive base where a stream washes slate dust into the pool, which you disturb when getting ready. Your exit will mostly always be in visibility of 1m or less over the last 30m or so, depending on how many divers you have in your team.

Holme Bank Chert Mine

Access is required contact Derbyshire caving association for current access procedures.

The mine was used for extracting chert stone which was used in the pottery industry. The mine is fairly complex but the underwater section fairly short around 200m length total at 5m depth. Visibility is good and the site is now used extensively for overhead training. Still worth a dive on your mine tour of the UK.

Hodge Close Slate Mine

A goodwill fee is payable for parking your car but otherwise, no formal permission is required.

The mine entrance is reached after a walk through a tunnel and climb down a short ladder. An open water Quarry is reached with a maximum depth of 32m. The entrance to the mine is reached at a depth of 24m in the far wall of the quarry. Around 200m of passage can be explored through three chambers reaching a distance of 150m from the dive base. Water temperatures are around 6°C and visibility generally good. The site is 150m above sea level and combined with cold water and exertion of getting to and from the dive base, divers should consider conservative decompression plans. Several accidents have happened here.

Roscobie Mine

No formal permission required.

This is one of the most Northern mines in the UK being found in Fife, Scotland. The mine was used for extracting limestone. Water temperatures vary from 12°C on the surface in summer to the underground constant temperature of 7°C Visibility is sometimes poor in the entrance areas but can increase to 20m further into the system. At the Northern end of the entrance, lake two entrances are found with around 200m of diving possible at a depth of 8-10m, or maybe less. On the Eastern side are several more entrances but the diving here is more serious with the silty passage, old mine debris and complex navigating in poor visibility. This area is currently being re-explored and not suitable for tourist diving.

Noxon Park Iron Mine

A formal access agreement covers all caves and mines in the area, contact Forest of Dean cave conservation and access group permits@fodccag.co.uk or any cave instructor for information. BCA insurance is required.

Evidence exists of mining in the Forest of Dean over 2000 years ago. The mines were worked up until just after World War II when the last operation ceased. Water level varies considerably over the year from summer to winter but on high water times, depths of up to 50m can be found in the mines. The mines are very extensive and some long and deep dives can be conducted here in very good visibility and 7°C water temperatures. Navigating can be complex and great care should be taken. The physical access to the dive base can be challenging and a knowledge of dry caving skills would be an advantage to transport you and your dive equipment through the mine safely. Despite the challenges of this site the quality of diving here is superb.

Bream Iron Mine

This mine is next door to Noxon Park Iron Mine, just along the wooded ridgeline so access requirements are the same as for Noxon Park above.

Reaching the dive base again requires some dry caving skills whilst moving down the steep terrain to the dive base. Visibility is similar to Noxon Park and water temperatures of around 7°C The complex nature of the mine allows the diver some long and challenging dives. Exploration of these mines is still possible with new ground waiting to be rediscovered.

I hope the above has given you a taste of what UK mine diving has to offer, combined with some superb cave diving and a massive amount of shipwreck diving, we have plenty to offer the visiting Technical Diver.

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