Lake Vyrnwy Dam, Llanwddyn, is a large masonry dam built by the Corporation of Liverpool in 1881-8 to create Vyrnwy reservoir to provide a water supply. The dam is of the gravity type in neo-Baroque style, measuring 358m long and 44m high, and topped with a carriageway of 31 arches. There are groups of four towers at either end of the central arch section, each capped with a pyramidal stone roof. There are two transverse discharge tunnels at the base of the dam. The dam was the first to be constructed with a system of drainage tunnels incorporated to prevent the build up of pressure beneath the base. The dam is depicted under construction on OS County series mapping (1891), with quarries, tramways, workshops and workers housing.
(Source CADW listed buildings database)
J Hill, RCAHMW, 09.10.2003
Associated with: Quarry (nprn 308781), Tramway System (nprn 309728), Straining Tower (nprn 32443).