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Alwen Dam

A Grade II Listed Building in Cerrigydrudion, Conwy

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Latitude: 53.0636 / 53°3'48"N

Longitude: -3.5599 / 3°33'35"W

OS Eastings: 295565

OS Northings: 352950

OS Grid: SH955529

Mapcode National: GBR 6F.C5R4

Mapcode Global: WH66F.9817

Entry Name: Alwen Dam

Listing Date: 17 February 1998

Last Amended: 17 February 1998

Grade: II

Source: Cadw

Source ID: 19351

Building Class: Water Supply and Drainage

Location: The dam is placed across the valley of the Afon Alwen, approximately 4km N of Cerrigydrudion.

County: Conwy

Town: Cerrigydrudion

Community: Cerrigydrudion

Community: Cerrigydrudion

Locality: Alwen Reservoir

Traditional County: Denbighshire

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The dam was constructed for the Corporation of Birkenhead as its only water supply, the first stone being laid on 3 October 1911. The engineers were Sir Alex Binnie, Son and Deacon, and the contractors Sir Robert McAlpine and Son. Associated works continued until 1921. At the time of inspection (Aug 1997) the dam was supplying 50million litres per day, still ducted by the original underground pipe as far as the major filtration plant at Shotton.


Built of in-situ reinforced concrete and rock-faced concrete blockwork. Distinctively curved on plan, and approximately 157m long, the face battered and swept out at the foot, with a spillway against the SW face discharging into a rectangular basin, with an iron weir on its outfall. The top of the dam has 12 arches on rusticated concrete piers rising from the dam face, and carrying a reinforced concrete footway, and extending up to provide piers for a pipe handrail with cast iron stanchions. The arches are divided after the eighth open arch from the SW by a tall open-arched Italianate style tower, the voussoired arches set back below the corner piers, which rise to a wide cornice, 3 bold guttae in the rusticated recess between the end piers. The arches on the outer and inner face of the tower have balconies of reinforced concrete. At the foot of the dam, immediately below the tower, the turbine house with a recessed rusticated front under a moulded arch, spanning between battered end piers, all crowned by a shouldered gable. Central pair of timber doors. Sheet plastic roofing.

Reasons for Listing

Included as a fine work of early C20 engineering, displaying confidence in its bold handling of concrete detailing; the major element of the dedicated water system for Birkenhead.

Other nearby listed buildings

  • II Pont-yr-Alwen
    The bridge is located on a bend of the old road from Cerrigydrudion to Llyn Brenig and Denbigh, at the crossing of the Afon Brenig.

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