Tracks through the 180-year-old Summit tunnel between Rochdale and Hebden Bridge will be upgraded in October.
A total of more than 3km of track will be replaced inside the tunnel from both lines during a nine-day closure between 23 October and 31 October 2021.
During this time, replacement buses will serve the route. At weekends, buses will also replace trains between Manchester and Rochdale as well as between Hebden Bridge, Burnley Manchester Road and Accrington stations.
Karen Hornby, Network Rail’s north west head of performance and customer relationship, said: “We appreciate passengers’ patience while we carry out these vital improvements to Summit tunnel as part of the Great North Rail Project. The work will mean fewer train delays on the Calder valley line and make tracks inside the Victorian-built structure fit for the 21st century.
“However, replacing track like this means we have no choice but to close the line for old sections to be ripped up and replaced with new. I’d urge anyone planning to travel over the nine-day railway closure to check National Rail Enquiries to they know exactly what to expect from their journeys.”
Network Rail is also working with the Environment Agency, which will be upgrading a culvert beneath the railway lines as part of a wider flood defence project in the area.
Nick Pearson, senior flood risk advisor with the Environment Agency, said: “Working in partnership with Network Rail as part of the proposed £56m Rochdale and Littleborough Flood Risk Management Scheme will make a huge difference to rail passengers, residents and the local economy.
“This project, one of the biggest flood alleviation schemes in the north of England, will play a crucial role in better protecting the community from the risk of flooding and we are pleased to see it progress.”