Dol-y-Mynach Dam
Unfinished foundations and the story of the scheme once planned for the Claerwen Valley.
The history of Dol-y-Mynach Dam
Dol-y-Mynach Dam was to be the first of the Claerwen Valley dams and is also known as the unfinished dam.
Dol-y-Mynach, which was planned to be 101 ft (31 metres) high and 938 ft (286 metres) long, was never completed.
It was intended to be the first of three dams in the Claerwen Valley: Dol-y-Mynach, Cil Oerwynt and Pant-y-Beddau.
Due to both world wars, the three dams were never built and Claerwen Dam was built instead.
There is a small tower just upstream of Dol-y-Mynach Dam which marks the entrance to the Dol-y-Mynach Tunnel.
This feeds water from the Claerwen directly into Garreg Ddu Reservoir during droughts.
The tunnel is just over 1 mile long.
Height – 10.7 metres
Total capacity – 150 million gallons
