The Grade II listed bridge carries passenger and freight trains over the River Wye between South Wales and the West Country, Midlands and north of England. Network Rail is upgrading the bridge as part of a wider package of work on the Severn Estuary rail line.
Steelwork repairs, waterproofing and masonry repairs will be carried out, as well as strengthening and reconstruction of the abutments.
The viaduct was designed by Isambard Kingdom Brunel and opened in 1852. Although the majority of the structure has since been changed, Brunel’s original tubular supports are still in place. The structure became the basis of design for the Royal Albert Bridge, which links Devon and Cornwall.
Lee Ackerman, scheme project manager at Network Rail, said: “It’s a privilege to be upgrading a historic piece of railway engineering. This bridge has played an important role in linking Wales and England for more than 150 years, and we plan on ensuring that it can continue to do that for many more to come.”