The work follows a 10-week closure last summer, during which engineers cleaned soot from the tunnel lining, carried out detailed surveys and replaced thousands of bricks to stop water leaking into the tunnel and damaging the railway.
Services that normally run through the tunnel will be diverted via other routes during the 10 weeks.
The work is needed because the one-mile-long tunnel, which opened in 1849, is prone to leaks and water damage. The tunnel’s brickwork is affected by the freezing and thawing of rainwater which filters through the ground into the tunnel. While the tunnel is safe, the leaks and very wet conditions inside it damage track and electrical equipment, causing delays and speed restrictions.
Over the last year, faults in the tunnel have been the cause of around 1,000 minutes of delay to Southeastern passengers.
David Davidson, Network Rail’s Kent route director, said:
“We know there’s never a good time to close the railway, and that changes to services for a 10-week period is a long time.
“We are carrying out the repairs over a series of 10-week closures because working in cramped and narrow tunnels is incredibly difficult. If traditional weekend working was used engineers would spend at least 50% of a weekend bringing materials and plant in and out of the tunnel, leaving limited time for actual work.
“We are sorry for the inconvenience caused by the closure, but this is a long-term project and this will be the last closure until we are back in to finish over summer 2027.
“When the tunnel is repaired with water damaged infrastructure replaced and the tunnel waterproofed, passengers will benefit from fewer delays, fewer speed restrictions and improved reliability.”
Scott Brightwell, Southeastern’s operations and safety director said:
“We are working ever closer with our Alliance partner Network Rail to deliver better journeys, and these essential repairs will improve the safety and operation of the tunnel.
“I want to thank customers for bearing with us during the closure and there are a number of alternative travel options.
“We are running extra services on Woolwich line for connections to the Docklands Light Railway and the Elizabeth line.
“There are also extra services on the Bexleyheath line and your rail tickets can be used at no extra cost on some local bus routes. Full details are available on our website.”
