Ground-breaking bridge lift
Black Bridge on the Cambrian line in Wales is standing tall after being raised by one meter to lift it out of rising river waters. The project is genuinely innovative and the first time it’s been done in Wales on the railway.
The bridge near Machynlleth was repeatedly hit by severe floods and closures for emergency repair work. Over the last decade the bridge has been closed 30 times with 10 of those in 2020 alone. The project was fast-tracked using Network Rail’s ‘Project Acceleration in a Controlled Environment’ (PACE) concept to prevent greater passenger upheaval over the winter months.
Adding to the challenge, the railway line which runs between Machynlleth and Shrewsbury travels over the River Dulas in Powys, which is a fish spawning river. This means we had a limited time period to carry out the resilience work to make sure we protected the environment as well as bringing it forward.
With nine months from concept to completion, we knew from the outset that it was going to be difficult to deliver this scheme in such a short timescale. We worked together with Network Rail and our supply chain to develop the design and programme in tandem to progress the project.
Work started on Saturday May 15 2021 with a total of 360 engineers’ working day and night and 32,000 hours reopening the line after just six weeks on Monday June 28 2021.
To maintain the stability of the structure and to prevent twisting and buckling we decided to use traditional methods lifting the 80-tonne bridge manually, rather than using hydraulics. We applied eight, 20 tonne chains in total raising the bridge 10 millimetres for every 10 meters of chain pulled.
This methodical approach meant that our teams pulled more than 12,800 metres of chain taking a lot of manual strength and dedication. In addition to the painstaking and labour intensive work heavy rain caused the river levels to rise at the end of May. Water levels hit the closure mark of the bridge so we had to stop work.
Despite this setback, we all worked together to recoup the lost time and work to raise the bridge and re-profile the track completed on time as planned.
Richard Compton, project manager for Network Rail Wales and Borders, said:
Andy Crowley, Operations Director Wales and Western at AmcoGiffen, commented: