35624
Llyn (Lake) Cwmorthin in the Moelwyn Mountains above the village of Tanygrisiau, in Gwynedd, North Wales.
The lake was used by Cwmorthin Slate Mine to feed a water wheel, which powered the dressing machinery needed for the mining work.
The quaries in this area were run by several different companies as a venture in its own right during the late 1800's. The earlier underground workings started at "Lake Level" by the Cwmorthin Slate Company Ltd, 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 in 1884 and the end of that company, which failed to recover, in 1888.
A new company (The New Welsh Slate Company Ltd, freshly evicted from Oakeley) 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 closing in 1900 due to financial difficulties, despite phenomenal extraction for just a 12 year stay and only ever using traditional hand-drilling methods. The mine came up for sale and the neighbouring Oakeley Quarry bought the rights to it, though they didn't attempt to work the lower floors initially and let it fill with water (some work was done on A and B in the Old Vein, and a new attempt was made to open up the "North Vein", previously unworked at Cwmorthin).
The lower floors flooded up to Lake Level in the Back Vein and up to C floor in the Old Vein, obviously containing an immense amount of water hundreds of feet deep, which remained until the early 1930's. Oakeley 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 was drained out under controlled conditions.
After the water was cleared, the mines were connected in several places and Oakeley actually re-opened some of Cwmorthin's Back Vein workings and put men to work in them on floor E. The Back Vein Incline was re-equipped and even a whole new incline was driven down another 90 vertical feet to open some more chambers on a whole new floor - Level G. The Old Vein and North Vein were abandoned.
Cwmorthin operated essentially as just another district of Oakeley right up until 1970 when Oakeley itself closed, unable to pay to keep the massive pumps running that kept the whole sprawling labyrinth dry. This marked the end of the mine's working life as a major concern, and ownership of Oakeley and Cwmorthin was once again split. Throughout the 1980's and early 1990's Cwmorthin was working on a limited scale by a small team of local men. Extraction occurred in a few chambers on Lake Level and Level 2. This endeavour too came to an end, with some unsuccessful attempts to untop the ancient Cwmorthin Slate Company workings around the year 2000 by Mcalpines PLC.
Information gained from www.cwmorthin.org/about_cwmorthin.asp
35624
Llyn (Lake) Cwmorthin in the Moelwyn Mountains above the village of Tanygrisiau, in Gwynedd, North Wales.
The lake was used by Cwmorthin Slate Mine to feed a water wheel, which powered the dressing machinery needed for the mining work.
The quaries in this area were run by several different companies as a venture in its own right during the late 1800's. The earlier underground workings started at "Lake Level" by the Cwmorthin Slate Company Ltd, 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 in 1884 and the end of that company, which failed to recover, in 1888.
A new company (The New Welsh Slate Company Ltd, freshly evicted from Oakeley) 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 closing in 1900 due to financial difficulties, despite phenomenal extraction for just a 12 year stay and only ever using traditional hand-drilling methods. The mine came up for sale and the neighbouring Oakeley Quarry bought the rights to it, though they didn't attempt to work the lower floors initially and let it fill with water (some work was done on A and B in the Old Vein, and a new attempt was made to open up the "North Vein", previously unworked at Cwmorthin).
The lower floors flooded up to Lake Level in the Back Vein and up to C floor in the Old Vein, obviously containing an immense amount of water hundreds of feet deep, which remained until the early 1930's. Oakeley 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 was drained out under controlled conditions.
After the water was cleared, the mines were connected in several places and Oakeley actually re-opened some of Cwmorthin's Back Vein workings and put men to work in them on floor E. The Back Vein Incline was re-equipped and even a whole new incline was driven down another 90 vertical feet to open some more chambers on a whole new floor - Level G. The Old Vein and North Vein were abandoned.
Cwmorthin operated essentially as just another district of Oakeley right up until 1970 when Oakeley itself closed, unable to pay to keep the massive pumps running that kept the whole sprawling labyrinth dry. This marked the end of the mine's working life as a major concern, and ownership of Oakeley and Cwmorthin was once again split. Throughout the 1980's and early 1990's Cwmorthin was working on a limited scale by a small team of local men. Extraction occurred in a few chambers on Lake Level and Level 2. This endeavour too came to an end, with some unsuccessful attempts to untop the ancient Cwmorthin Slate Company workings around the year 2000 by Mcalpines PLC.
Information gained from www.cwmorthin.org/about_cwmorthin.asp