Underwater concrete is being poured by specialist divers to protect two railway viaducts in Carlisle which carry the West Coast main line.
The work is being carried out after laser surveys by Network Rail revealed fast-flowing water on the River Eden had caused parts of the riverbed to wash away – posing a risk to the foundations of the viaducts.
Because of the deterioration of the riverbed, trains have been passing over the structures – one Victorian, one built in the 1940s – at just 20mph.
About 900 tonnes of special setting concrete is now being poured by the diving teams to provide a stable platform for the viaducts’ columns or piers.
The work is being carried out on the structures as part of a £1.3 million Great North Rail Project investment.
The divers, from Scour Protection, work in challenging conditions to shore up underwater structures such as bridges and viaducts around the UK and beyond.
As part of the project, more than 2,200 tonnes of rock has also temporarily been put into the river to calm the waters and divert its flow so the divers can work under the surface.
The water visibility in the River Eden is particularly poor, and consequently a lot of the work has to be done by touch alone.
Network Rail’s ecology teams have been working closely with the Environment Agency and Natural England to monitor the river and make sure this work has the least impact possible.
The concrete is made from a mix with ‘zero leach’, meaning it’s wildlife friendly and safe for the environment.
Chris Pye, Network Rail infrastructure director for the North West, said: “It’s not every day you call in diving teams to help improve railway lines, but this work is essential to keep passenger and freight trains moving on the West Coast main line over the River Eden in Carlisle.
“After using the latest laser mapping technology to give detailed scans of the riverbed we brought this work forward so we could secure this crucial rail link between England and Scotland for the winter ready for the second phase of work next summer.”
The second phase of viaduct strengthening will serve as a permanent fix to the riverbed erosion.