EKFB Completes Chipping Warden Green Tunnel Final Segment

UK – The final precast concrete segment was installed at the Chipping Warden green tunnel on the High Speed 2 (HS2) project in early 2025, completing the 2.5‑kilometre cut‑and‑cover structure. Installation rates more than doubled to an average of 5.5 segments per day during the final phase of construction, according to main works contractor Eiffage‑Kier‑Ferrovial‑Bam Nuttall (EKFB).

What Is the Full Scope of This Project?

The Chipping Warden tunnel is one of five “green tunnels” being built on the HS2 Phase 1 route between London and Birmingham. The 2.5‑km structure is formed inside a pre‑excavated cutting and will be backfilled with earth to blend the railway into the landscape and reduce noise for neighbouring communities. The tunnel is built in an ‘M’ shape, with separate vaults for northbound and southbound tracks. More than two million cubic metres of mudstone were excavated to create the level base; that material is now being compacted back over the tunnel as backfill. With the precast structure complete, work is concentrating on waterproofing, the internal floor slab, emergency walkways and the extensive earthmoving required to bury the tunnel by the end of winter.

Key Project Data

How Does This Compare to Similar Projects?

Specific cost and schedule benchmarks for comparable green tunnels on other high‑speed rail networks were not publicly available at the time of publication. The other two near‑complete HS2 green tunnels – at Burton Green in Warwickshire and Copthall on the London outskirts – are of a similar design but their lengths and costings have not been released. Separately, North American rail freight volumes reached the second‑highest annual total on record in 2025, with intermodal units up 1.5% to 14.06 million and carloads up 1.5% to 11.51 million, signalling continued investment appetite for rail infrastructure globally (Source: Logistics Management, 2025).

Editor’s Analysis

The doubling of segment installation speed at Chipping Warden – from two to 5.5 per day – demonstrates the tangible productivity gains that can be extracted when contractors are given the latitude to trial and refine methods on a dedicated test section. EKFB’s switch to directly delivered logistics, prefabricated reinforcement cages and larger backfilling plant all contribute to cost‑certainty, a critical focus as HS2 Ltd Chief Executive Mark Wild executes a programme‑wide reset. If the same learning curve can be replicated at the Greatworth and Wendover tunnels, the north end of Phase 1 could absorb fewer delays and return meaningful savings against the original baseline.

FAQ

Q: What is the purpose of the Chipping Warden green tunnel?
A: The tunnel is designed to carry the HS2 high‑speed line through a shallow cutting, after which earth is replaced on top to absorb noise, maintain visual screening and reconnect the local landscape. It is one of five such green tunnels on the London–Birmingham section.

Q: When will trains start running through the tunnel?
A: No commissioning date has been confirmed by HS2 Ltd. The structural shell is now complete, but internal fitting‑out, railway systems installation and extensive testing will follow the current earthworks phase.

Q: How many segments make up the tunnel and how were they installed?
A: A total of 5,000 precast concrete segments form the M‑shaped double‑vault structure. They were lifted into position using optimised delivery sequences and trialled offline in a test section, enabling the installation rate to rise from two to 5.5 segments per day.