Barmouth Viaduct

BARMOUTH VIADUCT RESTORATION

Griffiths were appointed by Network Rail in February 2021 to undertake the design, fabrication and construction of a new steel viaduct to replace the existing. Recognising the historic significance of the viaduct, the new structure is a like-for-like replica of the existing structure. The viaduct is a Grade II* listed structure which carries the single line Cambrian Coast railway from Dovey Junction to Pwllheli line, and incorporates a pedestrian footway over the Mawddach estuary. Construction of the original viaduct commenced in 1864 and was eventually opened in 1867.

The viaduct consists of two primary forms of construction, a timber section comprising 113 spans (renewal was completed in 2021) and a metallic section, the element that is being delivered as part of this contract.

The metallic element of the viaduct consists of 5 individual spans. Spans 1-3 (UB41) comprise hog back lattice girders braced overhead with underslung cross girders and rail bearer troughs, spans 4 & 5 (UB42) comprise simply supported lattice truss girders with underslung cross girders and rail bearer troughs.

Over the years, the metallic structure has experienced severe corrosion causing loss of section to numerous elements, particularly the hog back girder, and generally widespread paintwork breakdown.

The works are in two distinct phases, strengthening and refurbishment of the substructure, followed by the replacement of the overlying bridge structure, and includes:

• Replacement of the life expired diagonal bracing
• Replacement of the existing paint system

To replace the overlying bridge, an innovative method of construction is being deployed, and in summary is as follows:

• The new bridge girders are transported on rail trailers to the estuary location and are supported inside the existing bridge girders
• The new structure is used to support the old structure as it is being demolished
• Once the old structure is removed, hydraulic jacks are used to jack the new girders apart to the required width
• The new bridge deck is then transported to the viaducts’ location where it is then lifted up to the underside of the girders and fixed to the bottom flange
• Finally, the newly completed structure is lowered down onto newly installed bridge bearings

Work was safely and successfully completed, on schedule, with the bridge reopened to rail services and pedestrians on Saturday 2 December 2023.

For further information please visit the Network Rail project website:

https://www.networkrail.co.uk/running-the-railway/our-routes/wales/restoring-barmouth-viaduct/

If you have any additional questions or concerns about this work, please contact Network Rail directly by calling Network Rail’s dedicated 24-hour national helpline on: 03457 11 41 41 or email crwales@networkrail.co.uk