Craig Goch

Craig Goch, the highest upstream of the series of dams in the Elan Valley, is often referred to as the ‘top dam’. It is located at a height of 1040 feet (317m) above sea level. As with all the dams, work started with the arrival of the railway line at the site. In the case of the top dam the line had the  farthest to go and a rocky outcrop had to be blasted and dug through on the route to the site.**

Gareg Ddu

Garreg Ddu Dam in the lower Elan Valley serves a dual role. It is a low, completely submerged dam which plays a vital role in maintaining a constant supply of water to Birmingham. It also supports masonry pillars carrying the access roadway to the neighbouring valley of the River Claerwen.**

Pen-Y-Gareg Reservoir

Total capacity 1.320,000,000 gallons. Top area 124 acres. Top water level 945 feet above ordnance datum. Height of dam above river be 123 feet. Depth of foundations below river bed 17 feet. Length of weir 417 feet 6 inches. Thickness of dam at base 115 feet 4 inches. Estimated quantity of masonry 90,372 cubic yards.*

Caban Coch Reservoir

Total capacity 8,000,000,000 gallons. Top water level 822 feet above ordnance datum. Height of dam above river bed 122 feet. Length of the weir 566 feet. Thickness of dam at base 122 feet 6 inches. Estimated quantity of masonry 144,800 cubic yards.

Total area of watershed 45,562 acres.*

Claerwen Reservoir

This mass concrete dam, 240 feet maximum height from foundation to roadway level with facings of masonry and blue brick, was built between September 1946 and October 1952 and forms a reservoir over four miles long with a top water area of 650 acres at 1.210 feet above ordnance datum. The total weight of materials used was 700.00 tons including 43,800 tons of gritstone, 173,000 tons of pit sand, 65,000 tons of cement and 18,000 tons of masonry. *

*info from signboard next to the dam

** info from the Elan Valley website