Full Report for Listed Buildings
The list description is not intended to be a complete inventory of what is listed: it is principally intended to aid identification. By law, the definition of a listed building includes the entire building (i) and any structure or object that is fixed to the said building and ancillary to it and (ii) any other structure or object that forms part of the land and has done so since before 1 July 1948, and was within the curtilage of the building, and ancillary to it, on the date on which said building was first included in the list, or on 1 January 1969, whichever was later.
Summary Description
Reference Number
87591
Building Number
Grade
II
Status
Designated
Date of Designation
24/07/2009
Date of Amendment
Name of Property
Llanishen Reservoir Dam
Address
Location
Unitary Authority
Cardiff
Community
Llanishen
Town
Locality
Llanishen
Easting
318632
Northing
181464
Street Side
Location
To the east of Llanishen, accessed via a track running SE from the B4562, some 0.5km east of Llanishen station.
Description
Broad Class
Water Supply and Drainage
Period
History
Llanishen Reservoir forms part of the nineteenth century water-supply system for Cardiff. Supply was first in the hands of a private waterworks company who constructed a reservoir at Lisvane in the 1860s, but the Cardiff Borough Council assumed responsibility for the growing town's water supply in 1878, and commissioned a survey by its own engineer, John Avery Williams, to identify a suitable and sufficient water supply for the town. His report was presented in 1881, and the Taff Fawr scheme was the option favoured by the council. Early plans for Llanishen reservoir (also by J.A.Williams) pre-dated adoption of the scheme, but construction went ahead on the basis that it would be an integral part of it, as a storage reservoir receiving water impounded in the upper Taff valley. Llanishen was the first of the four reservoirs which comprised the scheme to be built, and construction began in 1884. It served as the primary source of water for Cardiff during construction of the Taff Fawr reservoirs, then began receiving water from the first of these in 1891.
Exterior
The flat lowland site of the Llanishen reservoir necessitated a continuous encircling dam, enclosing an area of 238,000 square metres, almost a mile in length. Like the other reservoir dams of the scheme (Cantref, Beacons and Llwyn Onn), it uses a clay core and mass earth bund construction with sloping embankments. The inner embankment is faced in pitched stone, and the other embankment is turfed.
The inlet gauge chamber from the Taff Fawr and the outflow control valve platform are faced in rusticated ashlar with heavily dressed plinths, string courses and copings. Similar dressed stone is used on the Nant Fawr by wash channel and spillway, the culvert exits, the stepped weir and scour tunnel exit.
Interior
Reason for designation
Listed as an integral part of the nineteenth century water-supply system for Cardiff. Together with structures associated with the impounding reservoirs in the upper Taff, the Llanishen Reservoir represents a major Welsh civic engineering scheme which has survived virtually intact.
Cadw : Full Report for Listed Buildings [ Records 1 of 1 ]
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