Network Rail has been forced to carry out track renewal and engineering work in the Severn Tunnel as salt-water has corroded parts of the tunnel and track over a period of time.
Network Rail will be working around the clock to renew the track which includes 3.2km of old track, alongside 5,200 sleepers.
14,000 tonnes of the supporting ballast will also be replaced.
Track renewal within the tunnel would typically only have to happen every 25 years within a typical tunnelled environment however, the corrosive nature of salt causes issues within the Severn Tunnel, meaning that the life cycle of the track is cut down to 10 years.
The salt-water within the region has caused issues with Network Rail having to replace nearly 3km of track on the Monmouthshire side of the tunnel. In June, the track will also be will be replaced on the South Gloucestershire side of the track.
To combat the corrosion, the sleepers within the Severn Tunnel will be coated in tin to give some protection against the elements. This coating of the sleepers in tin will extend the life of them whilst giving extra support to the supporting stone.
Mark Dix, project manager at Network Rail, said: “Owing to the environmental conditions within the tunnel, we have an enhanced programme of track renewals, which includes replacing worn sections of track every 10 years, as opposed to every 25 years for less challenging environments.
“This renewal is therefore part of an ongoing maintenance schedule which is more cost effective than multiple weekend closures and vital to ensure the continued safe and reliable running of train services along this busy route.”
It is expected that the track will be shut between Friday 9 and Sunday 18 with one final day of closure on Sunday 25.
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