Barmouth Bridge Restoration

A Grade II listed timber railway viaduct, Barmouth Bridge spans over the Afon Mawddach estuary in Wales. At over 150 years old, it is one of the oldest viaducts of its type still in regular use, carrying trains and pedestrians over the 860-metre distance. Due to the bridge’s age and exposure to coastal elements, decay and corrosion affected many of the timber and metal components. We worked on the restoration project with Alun Griffiths on an innovative bridge lifting technique. The new technique helps to minimise disruption and save time, contributing to a safer and more efficient construction process.

Project Overview

Sector

Infrastructure

Location

Barmouth Bridge, Wales

The Challenge

Bridge required to be lifted off piers

Led by civil engineering contractor Alun Griffiths, the project required the bridge to be lifted off of its piers, enabling the 24 damaged crossheads to be individually removed and replaced.

Site constraints

Barmouth Bridge featured a pedestrian bridge parallel to the rail tracks, and required a design to include a a bespoke cantilevered edge as part of the lifting frame, in order to allow for this site constraint. The tidal estuary and lack of a foundation meant access to the underneath of the bridge was difficult which was an restriction of the project.

Minimal disruption and limited time allocation

An additional challenge on the project was the time constraints, with the work taking place during an 18-day closure of the railway. This was

Our Solution

To minimize disruption on live infrastructure, we developed an innovative lifting system with Alun Griffiths, Cass Hayward, and Network Rail IP Engineering. This system uses steel supports and jacks, built off-site and transported to position, allowing work on crossheads and piers without removing the track and deck structures. It also enables quick relocation along the bridge for further time savings.

Given the Barmouth Bridge’s parallel pedestrian bridge, we designed a custom cantilevered lifting frame. This allowed jacking from the top side, lifting the structure off its piers while avoiding the challenges of the tidal estuary and limited underside access.

The project faced tight time constraints, with only an 18-day railway closure to complete the work. To meet this deadline, we deployed two custom jacking systems, operating from both ends of the bridge and meeting in the middle, significantly accelerating the process. Our team of steel erectors were on site 24/7 to ensure the lifts went smoothly and each jacking system operating from either end of the bridge, before meeting in the middle, we were able to complete the works at a far faster rate while Alun Griffiths completed the crosshead repair and replacement work.
This project won "Conservations & Regeneration Award" and "Civils Project of the Year Award" at Constructing Excellence in Wales in 2022.

Disclaimer: This project was completed by MH International’s parent company using shared personnel, under an intra group informal licence

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The system worked well, with the crossheads being replaced in 12-14 hours without requiring removal of the track and walkway. Also, the full scale testing carried out by MH International assisted enormously.

Steve Richardson

Engineering Manager at Alun Griffiths