Major HS2 milestone reached as final section of Northamptonshire green tunnel installed
The construction of one of the longest 'green tunnels' on the HS2 project has reached a major milestone after the final reinforced concrete segment was installed in Northamptonshire.
The 1.5-mile (2.5km) tunnel, designed to reduce noise and help the railway blend into the landscape, is being built using a "cut and cover" method, with earth eventually placed back over the structure.
The final of 5,020 precast concrete segments was lifted into position this week, completing the tunnel's main structure.
Built in an 'M' shape, the tunnel has separate sections for northbound and southbound trains. Construction was carried out in two phases to speed up delivery, with excavation, tunnel assembly and backfilling taking place simultaneously where possible.
More than two million cubic metres of material were excavated to create the tunnel. The earth is now being replaced before the site is landscaped with trees and restored hedgerows.
Sam Arrowsmith, senior project manager at HS2 Ltd, said: "It's great to see the final segment slotted into position at Chipping Warden.
"We've still got a long way to go, but with the tunnel structure complete, we can now focus on finishing the interior works and the landscaping that will blend the railway into the surrounding countryside."
Work will now continue on waterproofing, floor slabs, emergency walkways and internal finishing before the tunnel is buried by the end of winter.
The Chipping Warden tunnel is one of three being built in the area by HS2's contractor EKFB, with lessons learned helping to speed up construction on other sections of the high-speed rail project between London and Birmingham.