Cae Coch Sulphur MIne - CAL Documents

[Dave Tyson]

The enclosed information is for historical interest only as the CAL scheme ended on 20th November 2022. That scheme allowed registered and experienced mine explorers to visit this and other listed mines without fear of prosecution by Natural Resources Wales (NRW). The scheme worked well for 8 years with benefits for both NRW and mine-explorers, so it was hard to understand their change of heart - other than in recent years they have been extremely against any underground exploration in both mines and caves.

Copies of the original documents are listed below. Please note that when the mine was within the agreement then there were some inspections of the in-situ safety lines and these were maintained on an ad-hoc basis. This has not been the case for the last 3 years and so they may have deteriorated and new hazards may be present. Keep safe and keep a low profile.

Mine Notes

Cae Coch Sulphur Mine was worked by pillar and stall techniques, the iron pyrites thus extracted was used as a source of sulphur for the chemical industry. The mine closed at the end of the 19th century but was re-opened during both World Wars to provide material for the manufacture of sulphuric acid.

The mine is quite extensive and consists of many interconnected chambers which slope down following the dip of the mineralisation.

Most of the mine is fairly safe, but there are some areas when timber roof supports have failed and these should be avoided. There are many pools of water in the mine which are very acidic and support various bacterial colonies which live off the sulphurous liquid.

The walls and chamber roof have many multi-coloured formations, some mineral and others bacterial in origin. There are many areas with crystals of gypsum and secondary minerals derived from the oxidation of the iron pyrites.

Lesser Horseshoe Bats are known to use Cae Coch as a winter roost and so there is no access between October and April to avoid disturbance to hibernating bats.

The Mines of the Gwydyr Forest Part 7 by John Bennett and Robert Verson has a full description of the mine and a diagram showing the main passages and adits. Adit 3 collapsed many years ago and its position on the surface has been lost. Adit 4 gradually silted up over the years, but was dug out and a drainage tube inserted by persons unknown some years ago. It may be technically possible to exit via adit 4, but the water depth will be neck deep and quite acidic...

Dave