History in Structure

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The Big Arch

A Grade II Listed Building in Abersychan, Torfaen

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Latitude: 51.7253 / 51°43'30"N

Longitude: -3.0728 / 3°4'21"W

OS Eastings: 325999

OS Northings: 203495

OS Grid: SO259034

Mapcode National: GBR J2.2HST

Mapcode Global: VH79K.PWDS

Plus Code: 9C3RPWGG+4V

Entry Name: The Big Arch

Listing Date: 13 September 1994

Last Amended: 28 July 1997

Grade: II

Source: Cadw

Source ID: 14871

Building Class: Transport

Location: Located next to the B4246 and carries a disused railway embankment across a disused railway line now a track. The arch forms the visual and actual gateway to the former British Ironworks area.

County: Torfaen

Town: Pontypool

Community: Abersychan

Community: Abersychan

Locality: The British

Built-Up Area: Abersychan

Traditional County: Monmouthshire

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The 'Big Arch' was constructed in 1879 to carry the Monmouthshire Railway to a junction with the London and North-Western Railway Blaenavon branch. The junction was immediately north of this bridge and led to a jointly owned stretch of line running through Abersychan and Talywain station to Garndiffaith junction. A low level branch of the Monmouthshire Railway left the line south east of the junction to serve the main level of the British Ironworks, which operated from 1827 -1883. This branch crossed back under the Monmouthshire Railway's embankment which made the construction of this tunnel necessary. The height of the embankment, which was the result of the already existing London and North-Western line, meant the construction of this unusually long arch and tall revetment walls. The Talywain branch was opened from Pontnewynydd on 18/9/1879. It was built by the Monmouthshire Railway and Canal Company but was worked from the start by the Great Western Railway and the companies were formally amalgamated 1/8/1880. It was closed to traffic on 3/5/1980.


Constructed of sandstone and brick. The bridge has a semi-circular arch 11m wide of five rings of engineering brick. The arch is 36m long and was constructed as a cut-and-cover tunnel. The revetment walls forming the portals are of bull-nosed sandstone on an unusual L-plan to support the embankment, which is on a skew to the arch. The corners of the L's are rounded and the walls are slightly battered. They slope steeply to the ground from apexes near the track bed level.

Reasons for Listing

Included for its historical interest, as a good example of railway engineering, and for its group value with the former British Ironworks offices and workshops, and the pumping Engine house of British Colliery.

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