21012

 

II  

Designated  

23/12/1998  

23/12/1998  

Abercarn Aqueduct and Bridge (partly in Abercarn Community)  

 

Caerphilly  

Abercarn  

 

Cwmcarn  

321974  

193063  

 

At the S end of Cwmcarn village, on the community boundary with Abercarn, at the N end of the surviving length of canal, crossing Nant Carn.  

Transport  

 

In 1790s a consortium of coalowners and industrialists sought Parliamentary approval to build canals through the Eastern and Western Valleys of Monmouthshire to link the industrial areas in the N with Newport on the Usk estuary, the canals in turn to link with a system of feeder tramroads. Bill received assent in 1792 and Monmouthshire Canal Navigation company was formed. The Western Valley Canal, also known as The Crumlin Arm, was constructed from Crumlin to join the Eastern Valley Canal just N of Newport, completed c 1797. Engineer Thomas Dadford. Reservoirs to feed canal constructed to E, including one in the Carn valley. Thomas Dadford's map of 1792 shows the canal crossing the Nant Carn and this structure was apparently built for this purpose. First edition OS map shows site of canal reservoir in Cwm Carn. This failed in 1875, creating a destructive flood. Illustrated London News July 1875 has an engraving which shows total destruction of main arch and text states ' a clean breach was made, a gap being left of about 40 yards wide'. Penny Illustrated Paper for July 24 refers to a former 'large arch...to allow the flow of a small brook and a portion of the overflow from the pond'. Thus the abutments, especially to N, are likely to be part of the original structure but the central section including the W arch has apparently been rebuilt in reduced size though probably using much of the original masonry. It is likely that the extension of the canal abutment to S and the E portal date from later post-flood repair, strengthening and road improvement works; the boundary stone on the road bridge is dated 1880. Within the tunnel a definite straight joint is visible between the masonry of the repaired aqueduct and this later work. Tithe Map of 1846 shows the canal and road separate with a cottage between. This and other nearby buildings, including a flannel factory between aqueduct and river, were demolished in the flood and in the restoration the aqueduct and road bridge were abutted. Area was formerly known as 'Factory Trip'.  

The aqueduct and bridge carry both the canal and adjacent road across the Carn valley. The structure comprises a high abutment to W with a relatively small tunnel for the stream; to S is a further extension of the abutment in different later masonry, both sections rising to form a low parapet beside the W side of the canal; on the E side, also of the later period masonry, is the E tunnel portal, the surrounding masonry not continuous with the higher roadside parapet. The aqueduct masonry to W is mostly narrow coursed rubble creating a massive retaining wall with ashlar voussoirs and tooled quoins. Segmental arched portal; on either side the walls project slightly leaving the central section including arch recessed. Walls curve outwards, with a sharper curve end left (N). Right end (S) returns sharply with a change in masonry to rockfaced stone. The parapets at canal level also differ though are mostly ivy covered. On E side the portal is round arched with deep narrow rockfaced voussoirs; angled abutments with heavy capstone, incomplete to left, are built against the archway, the masonry bonded at impost level. Above is the roadside parapet of rubble with rockfaced coping and boundary stone 'Mynyddislwyn Highway District MR 1880'.  

 

Listed as an important early C19 canal structure with later modifications of historic interest.