Construction of HS2’s 1.4km Wendover green tunnel in Buckinghamshire has reached a significant milestone, with engineers completing the central structure of the cut-and-cover tunnel designed to reduce noise and visual impact on surrounding communities.
The achievement marks the joining of two separately constructed sections of the tunnel, which is being built in a cutting alongside the A413 to the west of Wendover.
The final precast concrete segment was installed this week, bringing together the two sections and allowing construction teams to focus on completing the tunnel portals, floor slab, internal fitout and surrounding landscaping.
The milestone is another step forward for HS2’s extensive civil engineering programme between London and Birmingham, where five green tunnels are being constructed to help integrate the new high-speed railway into the surrounding landscape.
Precast construction accelerates tunnel delivery
The Wendover tunnel has been designed using an M-shaped cross-section, providing separate enclosed spaces for northbound and southbound trains.
The overall structure incorporates 2,740 precast concrete segments, with the central section constructed from opposite directions to allow excavation, foundation preparation, segment installation and backfilling to progress simultaneously.
This approach has enabled construction teams to work across different parts of the site at the same time, reducing the need to complete each stage sequentially.
The final segment connecting the two sections was installed on Monday, with members of the construction team signing the concrete element before it was lifted into position.
HS2 Ltd Project Manager Umesh Gorasia said: “It’s great to see the two halves of the tunnel linked up for the first time. Once complete, the green tunnel will dramatically reduce disruption from passing trains and blend the railway into the countryside.
“There’s still some way to go, but we’re making good progress and I’d like to thank the team for all their hard work.”
More than 1.2 million cubic metres excavated
The tunnel is being delivered by EKFB, the joint venture comprising Eiffage, Kier, Ferrovial Construction and BAM Nuttall, which is responsible for HS2’s main civil engineering works through Buckinghamshire and into South Warwickshire.
Construction has required the excavation of more than 1.2 million cubic metres of material, predominantly chalk, to create the cutting and establish a level foundation for the structure.
Rather than transporting all the excavated material away from the site, the project has retained it for reuse in the backfilling process.
As completed sections of the tunnel are covered, the material is carefully placed and compacted to distribute loads evenly across the structure.
Once backfilling and landscaping are complete, the tunnel will be covered by earth, helping the railway blend into the surrounding countryside while reducing the impact of passing trains on nearby communities.
The approach demonstrates how major earthworks, structural engineering and environmental mitigation are being combined within the same construction programme.
Specialist machinery used beneath temporary road bridge
One of the more complex engineering challenges involved installing precast segments beneath the temporary Ellesborough Road bridge, which maintains a local road connection while construction continues.
Although most tunnel segments were installed using cranes, the restricted working space beneath the bridge required a different approach.
Engineers deployed a self-propelled modular transporter (SPMT), supported by 16 sets of wheels, to lift and position the concrete elements from underneath.
The specialist equipment allowed the team to manoeuvre heavy segments into place where conventional crane operations would have been constrained by the temporary bridge overhead.
Ellesborough Road, which connects Wendover towards Princes Risborough, will eventually be realigned over the completed tunnel, allowing the temporary arrangement to be removed and the surrounding landscape reinstated.
Lessons shared across HS2 green tunnel programme
Wendover is one of three green tunnels being constructed by EKFB, alongside similar structures at Chipping Warden and Greatworth.
The contractor has been sharing lessons between the sites to improve productivity, construction sequencing and the efficiency of specialist operations.
These improvements include prefabricating reinforcement cages for the base slab, refining concrete delivery arrangements within the tunnels and testing whether larger machinery can safely be used during backfilling operations.
The emphasis on repeatable construction methods is particularly relevant to HS2’s wider efforts to improve delivery efficiency and reduce costs across the remaining programme.
EKFB Project Manager Elton Qafaliaj said: “EKFB installed the first concrete segment in spring 2025, and in less than 18 months, we have lifted more than 2,000 segments to complete the central structure of the Wendover green tunnel. This was a huge undertaking and has required the expertise of a skilled workforce.
“The team has worked together to safely overcome challenges, keeping productivity high and pushing the construction programme forward.
“Seeing the two halves of tunnel finally come together was a proud moment for everyone involved.”
Focus shifts to portals, fitout and reinstatement
With the central structure connected, the remaining work will include completing the portals at both ends, finishing the floor slab and progressing the internal fitout.
Backfilling will continue as the structure is completed, followed by the permanent realignment of Ellesborough Road and the final landscaping works.
Across the London to Birmingham route, HS2 plans to construct approximately 65 miles (105km) of tunnels, including both deep-bored tunnels and five shallower cut-and-cover structures.
The five green tunnels are located at Wendover, Chipping Warden, Greatworth, Burton Green and Copthall in Hillingdon, where construction of the tunnel structure was completed during the summer.
The overall HS2 programme will also involve the excavation of approximately 130 million tonnes of earth.
Progress continues amid wider HS2 programme reset
The Wendover milestone comes as HS2 Ltd continues a comprehensive reset of the project under Chief Executive Mark Wild, with the aim of improving delivery efficiency and bringing the remaining construction programme under tighter cost and schedule control.
While the completion of major civil engineering structures demonstrates progress along the route, significant work remains across the 140-mile railway between London and Birmingham.
Once operational, HS2 is intended to improve connections between London, Birmingham and the North, while releasing capacity for additional local and regional services on the southern section of the West Coast Main Line.
For the wider rail construction industry, Wendover also provides an example of the benefits that can be achieved through repeatable precast designs, coordinated construction activities and the sharing of engineering lessons between major work sites.
As HS2 moves through its next phase of delivery, applying those lessons consistently across the programme will be increasingly important to achieving the productivity improvements and cost reductions now being demanded of Britain’s largest rail infrastructure project.
