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Compensation Basin at Pontsticill Water Treatment Works

A Grade II Listed Building in Vaynor, Merthyr Tydfil

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Latitude: 51.7963 / 51°47'46"N

Longitude: -3.3637 / 3°21'49"W

OS Eastings: 306049

OS Northings: 211724

OS Grid: SO060117

Mapcode National: GBR YQ.Y27T

Mapcode Global: VH6CR.N32T

Plus Code: 9C3RQJWP+GG

Entry Name: Compensation Basin at Pontsticill Water Treatment Works

Listing Date: 19 May 1999

Last Amended: 19 May 1999

Grade: II

Source: Cadw

Source ID: 21731

Building Class: Water Supply and Drainage

Location: Beneath the dam of Pontsticill Reservoir on the W side of the Water Treatment Works.

County: Merthyr Tydfil

Community: Vaynor (Y Faenor)

Community: Vaynor

Locality: Pontsticill

Traditional County: Brecknockshire

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Pont Sticill


Compensation basin created as part of Ponsticill Reservoir development 1923 to provide a continuing flow of water in the Taf Fechan river after the valleys of Cwm Taf Fechan had been dammed. This massive water engineering project, involving an extensive network of piping to the urban areas of S and SE Wales, was termed 'The Two Million Scheme' involving a 2 shilling (10 pence) rate on local taxes and was carried out by the Taf Fechan Water Corporation, this latter body being contributed to by each local council. 3400 million gallons (15456 million litres) of water per day passed through the treatment plant. Official opening commemorated on the plaque was in 1927 by Lord Buckland; this records resident engineer FV Stillingfleet, engineers Sir Alex Binnie and Deacon and Thos F Harvey.


Comprises the portal of a tunnel, the walls, piers and steps of the curved basin and the weir. The tunnel is brick lined and the portal is of large blocks of coursed rock-faced stone with massive granite voussoirs with diamond ends and keystone and a frieze of dentil moulding; flanking piers rise to a cornice of giant blocks which incorporates in a pedimented surround a bronze plaque. On each side, walls of coursed rockfaced stone border the basin and flights of steps with giant rock-faced coping descend to water level facing the portal. The weir incorporating 4 sluices with piers to the walls on each side marks the end of the basin and the return to the river.

Reasons for Listing

Listed as an important and decorative part of this major water engineering project; group value with the Turbine House and the Filter House.

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