Cwmorthin Slate Quarry is a substantial disused slate mine found on the shores of Llyn Cwmorthin above the town of Blaenau Ffestiniog, North Wales. It is one of a number of slate mines that circle the town, most of which were enormous enterprises in their day. It has a long and complex history beginning in the early 1800's, with heavy underground development starting around 1860*.
It was run by several different companies as a venture in its own right during the 1800's. The earlier underground workings started at "Lake Level", so called due to the entrance being just above the surface of the nearby Llyn Cwmorthin, and ascended upwards in the mountain ultimately for 8 floors in both the Old and Back Vein. Poor working practices and reckless engineering decisions ultimately led to a substantial collapse and the end of that company.
A new company took the mine on afterwards and reused Lake Level but sealed off the shattered and dangerous upper floors. Instead, they developed new workings below, going down into the mountain. Ultimately this company sunk five floors on both veins, before itself being being forcibly closed in 1901 due to a legal dispute.
The now abandoned lower floors flooded up to Lake Level, containing an immense amount of water hundreds of feet deep, which remained until the early 1930's. The neighbouring mine (Oakeley Quarries) were at this time driving underneath the old Cwmorthin workings and were uneasy about having such a huge volume of water above them, so decided to drain it out. Special diamond-drilled bore holes were driven through into the deepest parts of Cwmorthin from Oakeley and the water drained out under controlled conditions.
When the water level reached the bottom, the mines were connected in several places by full-size tunnels and Oakeley (who'd taken over the ownership of Cwmorthin) actually re-opened some of Cwmorthin and put men to work in it. The Back Vein Incline was re-equipped and even a new incline was driven down another 90 vertical feet to open some more chambers.
Cwmorthin then operated essentially as just another part of Oakeley right up until 1970 when Oakeley itself closed. This marked the end of the mine's working life as a major concern, however, throughout the 1980's and early 1990's the mine was working on a limited scale by a small team of local men. Extraction occurred in a few chambers on Lake Level and Level 1, with the underground transport being provided by a Series 2 Land Rover 88".
The final twitch occurred in the late 1990's when deep bore-holes were sunk from the surface to near the long abandoned upper floors, filled with explosive and fired, in an attempt to break open the rock to make it suitable for untopping. Little was achieved in this venture however, other than creating massive damage to the already fractured early upper workings.
Today, almost all of the earlier upper workings in both the Back Vein and Old Vein are inaccessible and damaged. It is likely that large tracts of these workings deep in the hill remain in reasonable condition, but are cut off from our reach.
Most of the workings in the lower five floors of both the Back Vein and Old Vein can be accessed today. The Back Vein workings are in excellent shape in structurally good rock, almost all of it is still available to explore. The Old Vein workings however are in a much poorer condition due to the weaker, more fractured rock in which they were driven. Most of it can still be gotten into one way or another, but there have been many wall and roof failures and numerous chambers have collapsed entirely.
What's left to us to see today still comprises of many miles of tunnel and hundreds of enormous chambers. Within these workings can be found artefacts ranging from powder horns to timber stairways, from winches to wagons, and from cranes to bridges. Many days can be spent enjoying this exciting and awe-inspiring environment that will always remain a significant monument to the world famous Welsh Slate industry
the few pics we did take
And a few taken with my android phone on way in as im afraid on way back it was raining and i wasnt getting my dslr wet