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Caerhowel Bridge
River Severn, west of Caerhowel, Powys, Wales, UK
Caerhowel Bridge
associated engineer
Thomas Penson jnr
date  1858
era  Victorian  |  category  Bridge  |  reference  SO195981
ICE reference number  HEW 851
photo  © John Haynes and licensed for reuse under this Creative Commons Licence
Caerhowel Bridge, the third cast iron bridge to be constructed in Montgomeryshire, is the most recent in a series of bridges over the River Severn near this spot. An earlier suspension bridge collapsed, with loss of life. The present Victorian-era bridge has been refurbished and carries one lane of signal-controlled road traffic on the B4385.
The first bridge across the River Severn at Caerhowel is likely to have been built about 1250, and was called Baldwin’s Bridge. It was destroyed probably sometime in the late 13th century but by around 1600 there are records of another bridge, known as Montgomery Bridge, Severn Bridge or New Bridge. These structures would have been of timber.
In 1852, a flood destroyed the timber bridge then standing. The Montgomeryshire County Surveyor Thomas Penson junior (1790-1859) recommended the council authorise construction of a single arch iron bridge as a replacement.
Against his advice, a suspension bridge designed by James Dredge senior (1794-1863) was constructed instead. It opened in 1854 and was designed on the taper-chain principle patented by Dredge in 1836. Chains rather than cables supported its continuous deck. In 1858, it collapsed — reportedly under the weight of three loaded wagons of lime from Garthmyl wharf — and one man was killed.
Penson designed the replacement — a two-span cast iron superstructure with a central masonry river pier, and abutments. The base of the pier extends out on the upstream (east) side, forming a low-level cutwater. The generally vertical abutment and pier walls have small raked sections where they meet the arch springings.
At 6.6m wide, Caerhowel Bridge is broader than the first two cast iron bridges in the county — Penson’s single span structures at Llandinam and Abermule. The latter is located 4.4km upstream of Caehowel. All three follow the design ideas of Thomas Telford (1757-1834). Like Abermule, Caerhowel’s ironwork was also cast near Wrexham, by Brymbo Company Iron Founders, established in 1796 by John Wilkinson (1728-1808).
The bridge's two symmetrical arches have equal spans of 22.1m. They consist of five parallel X lattice ribs, 760mm deep, each of five segments. Rectangular diaphragms at the segment joints and circular tie bars at the segment centres provide lateral stiffening, while cruciform-section bars link adjacent ribs with diagonal bracing. The spandrels contain radiating struts between the ribs and the deck.
The original deck was constructed using cast iron plates with an asphalt surfacing. The 6.1m wide roadway had two lanes, without a footway. Cast iron railing on both sides ran between square-section stone pillars on the central pier and abutments.
In March 1983, the bridge was Grade II listed. However, by 1997, the bridge was unable to take modern traffic loading and a Bailey bridge was installed nearby to take the diverted vehicles. In 2004, strengthening works were completed that brought the original bridge to full highway loading. A new concrete deck has been constructed on rolled steel beams, inserted discreetly inside the cast iron arches. The original railings have been replaced, though are now separate from the arches. Traffic lights at either end control a single lane of traffic, with two footpaths for pedestrians.
Ironwork: Brymbo Ironworks, Wrexham
Contractor: David Davies of Llandinam
Contractor (strengthening 2004): Alun Griffiths Contractors Ltd of Abergavenny
Research: ECPK
"Powys" by Richard Haslam, Pevsner Architectural Guides, Yale University Press, January 1979
reference sources   CEH Wales

Caerhowel Bridge