HS2 Completes 880m Cut-and-Cover Green Tunnel in London

LONDON – HS2 Ltd has structurally completed the Copthall Tunnel, an 880-metre green tunnel on the western outskirts of London, the first of five such cut-and-cover tunnels on the London–West Midlands high-speed route to be fully backfilled. The single-tube tunnel reused all 1.2 million m³ of excavated material from the nearby Northolt twin-tube tunnel project, avoiding roughly 100,000 lorry movements. No separate contract value for the Copthall Tunnel was disclosed.

What Is the Full Scope of This Project?

The Copthall Tunnel is the only single-tube structure on the 225-km HS2 corridor, positioned between the Northolt Tunnel and the completed Colne Valley Viaduct — the UK’s longest railway bridge. Designed to withstand forces from trains at 200 mph (320 km/h), the tunnel is over 800 metres long, approximately 12 metres high, and up to 16 metres wide inside, fitted with five natural ventilation shafts. The SCS consortium — Skanska, Costain, and Strabag — delivered the civil engineering works as part of the southern section of HS2.

Key Project Data

How Does This Compare to Similar Projects?

In 2023, Poland’s Budimex secured a €34 million contract to prepare for the drilling of a 4-km high-speed rail tunnel in Łódź, as part of the Warsaw–Łódź high-speed line. Unlike the cut-and-cover Copthall Tunnel, the Łódź tunnel will be bored, a method typically associated with greater cost and longer construction timelines. While the Copthall costs remain undisclosed, Budimex’s deal covers preparatory works only and gives a benchmark for a bored tunnel roughly 4.5 times longer. Poland’s CPK delivery body aims to develop 2,000 km of high-speed rail, and 19 firms bid for the Warsaw–Łódź line contracts, signalling comparable European competition for HS2’s contractor pool. (Source: Global Construction Review, 2023)

Editor’s Analysis

Copthall’s completion is a small but telling marker of HS2’s attempt to align on-site engineering with Whitehall’s cost-cutting mandate. The Department for Transport estimates that design simplification across the programme could yield up to £2.5 billion in savings and shave about one year off construction, and the full reuse of spoil — which eliminated 100,000 truck trips — directly supports that goal. However, Poland’s accelerating high-speed rail procurement may pull specialist resources away from UK projects, tightening the market for the remaining four green tunnels and future HS2 phases. (Source: Department for Transport, as reported by HS2 Ltd; Global Construction Review, 2023)

FAQ

Q: How long is the Copthall Tunnel and what speed is it built for?
A: The tunnel is 880 metres long and engineered to handle trains travelling at up to 200 mph (320 km/h). It is the only single-tube tunnel on the HS2 route.

Q: Will the tunnel be visible after the project is finished?
A: No. Over the next two years, the surface will be planted with trees, shrubs, and vegetation to integrate the structure into the natural landscape and reduce visual impact.

Q: What was saved by using cut-and-cover instead of the original open-cut method?
A: The cut-and-cover approach allowed all 1.2 million cubic metres of excavated material from the Northolt Tunnel to be reused on site, eliminating approximately 100,000 truck trips that would have been needed for off-site disposal.