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
25953
Building Number
Grade
II*
Status
Designated
Date of Designation
04/12/2001
Date of Amendment
20/12/2002
Name of Property
Canal Aqueduct over Afon Twrch, including weir
Address
Location
Unitary Authority
Powys
Community
Ystradgynlais
Town
Swansea
Locality
Ynyscedwyn
Easting
277270
Northing
209240
Street Side
Location
Situated some 50m N of Twrch Bridge between Ystradgynlais community and Ystalyfera community, reached by footpath along river from Gurnos Road.
Description
Broad Class
Transport
Period
History
Canal aqueduct carrying former Swansea Canal over the Afon Twrch, 1794-8 by Thomas Sheasby, engineer, the largest aqueduct on the canal. This was the first aqueduct to use hydraulic lime for waterproofing. The aqueduct stands on a 4m high stone-faced weir which diverted water into a canal feeder. The 16-mile Swansea Canal was opened in 1798 to Hen Neuadd, Abercraf, declined after the railway opened in 1852 and closed in 1931. The course of the canal around Ystradgynlais is substantially lost under the bypass. The aqueduct was restored 1993-4.
Exterior
Canal aqueduct of 21 m span, 9 m broad, squared rubble stone with 3 broad low arches, each of 7m span, 2.7 m height, the arch soffits and voussoirs rendered over. String course under deep walling to canal sides and later C19 rock-faced stone coping. Downstream side has 2 small triangular cutwaters carried up as triangular piers with 2 offsets. Upstream side has been reinforced in C19 with 2 big stepped rounded stone piers covering earlier cutwaters. This side has a concrete spillway in centre, and parapet top courses in red brick. Under E abutment is circular tunnel for the tailrace of a former mill, with stone voussoirs to entries.
Canal channel 3.35 m wide and 1.25 m deep, has tow-path on S side, canal bed concreted in restoration, canal sides rubble stone, probably rebuilt in 1993-4. There is a cast-iron mounting for a small emptying sluice on the N side and the broad concrete overflow to centre has slots for sluice gates each side.
Interior
Reason for designation
Included as the principal surviving engineered structure of the Swansea Canal.
Scheduled Ancient Monument GM 396(NEP).
Cadw : Full Report for Listed Buildings [ Records 1 of 1 ]
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