When Network Rail needed to repair the vent shafts of the historic Sough tunnel in Lancashire, it had to use a helicopter to deliver the materials it needed.
Sough tunnel is 1,843 metres long and was opened in 1847. It carries the single-track railway between Clitheroe and Manchester through a hillside under Cranberry Moors, just south of Darwen in Lancashire.
Two vent shafts protrude from the moors. In the days of steam, these let the steam and soot out of the tunnel, making life easier for the driver and fireman on the locomotive’s footplate as well as the passengers.
In fact, when the tunnel was first built, the method employed was to drive 13 vertical shafts into the hill, their depths ranging from 40 feet to 260 feet (12 to 80 metres). Miners then worked at the bottom of these shafts, digging the tunnel in short sections which were then joined up.
The resultant tunnel is slightly curved and on an uphill grade, rising from the northern, Darwen end southwards towards Entwistle.
The whole process took three years and five tunnellers lost their lives. Once the tunnel was complete, the 13 access shafts were filled in.
Conditions in the tunnel were never good. However, in 1903, when the Lancashire & Yorkshire Railway began running express trains through it, something had to be done. Two of the original vertical shafts were reopened, forming the vents that are still there.
Today, those vents serve to relieve the air pressure build-up inside the tunnel as diesel trains speed through, while at the same time helping to flush out the diesel exhaust fumes.
Network Rail contractor J Murphy & Sons needed to maintain the two vent shafts, repairing the brickwork inside the vents and fitting steel grilles to keep unwanted items, including trespassers, out of the tunnel.
Due to its location, access by traditional means was almost impossible. A specialist helicopter team was therefore employed to transport five tonnes of bricks and materials to build a new 2.6-metre-diameter metallic grille on top of the shafts.
Network Rail scheme project manager Mark E Smith said: “We’ve invested £150,000 to make Sough tunnel safer and reliable for trains carrying East Lancashire residents between Clitheroe and Manchester via Blackburn and Darwen.
“While we were unable to access the site from the surrounding fields, we used a helicopter to help complete the safety repairs.
“It proved a cost-effective solution as we did not have to pay any landowner costs and, with the wet weather we have experienced, it meant there was much less damage to the local area building access roads for heavy goods vehicles.”
Murphy’s senior contracts manager, Alistair Weir, added: “It was a great collaborative team effort and we are delighted to use our skills to play our part in keeping Sough Tunnel safe and reliable.”
Work commenced in February 2020 and was completed this spring.
Trains that use the tunnel are Northern services between Clitheroe and Rochdale. There was no disruption to services while the work was carried out.
For more information on the construction of Sough tunnel, see Eric Leaver’s article in the Lancashire Telegraph.