Third HS2 Tunnelling Machine Completes its Drive Beneath London

Skanska Costain STRABAG Joint Venture (SCS JV) has reached another key milestone on HS2’s London section, as tunnel boring machine (TBM) Emily completed its 3.4-mile drive beneath west London. The machine, designed for soft ground conditions and built by Herrenknecht in Germany, is one of four working on the 8.4-mile Northolt Tunnel—currently the second longest on the high-speed rail project. Excavation began in early 2024 and has involved continuous operation to remove 775,000 tonnes of London Clay while lining the tunnel with over 17,500 concrete segments.

TBM Emily's arrival at Green Park Way marks the third successful breakthrough on this stretch of HS2 infrastructure. The SCS JV team is now progressing with follow-on works, including the construction of cross passages, ventilation shafts, and final tunnel preparations to accommodate rail systems installation. The high-speed route will eventually connect Old Oak Common station to outer London, providing a critical link in the UK’s future rail network.

Dave Hannon, Project Director for Tunnels & Routeway at SCS JV, described the milestone as a “significant achievement,” highlighting the technical expertise and collaboration behind the project. With one TBM remaining on the Northolt Tunnel, full tunnelling for this section is expected to complete later this year.

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