HS2 launches third TBM under capital building the Northolt Tunnel

HS2’s London tunnels programme passed a major milestone as the third tunnel boring machine (TBM) being used as part of the project was launched on 25 February 2024.

TBM Emily, named after Emily Sophia Taylor who helped establish the Perivale Maternity Hospital in 1937 before becoming Ealing’s first female mayor in 1938, will be used to dig almost half of the 8.4-mile Northolt Tunnel. She will bore 3.4 miles under Ealing from Victoria Road Crossover Box, near HS2’s new Old Oak Common station, to Greenpark Way in Greenford.

HS2’s London Tunnels contractor, Skanska Costain STRABAG joint venture, assembled the TBM underground at the Victoria Road site after being lifted in parts and lowered into a shaft. Manufactured by world-leading tunnelling experts, Herrenknecht in Germany, TBM Emily weighs 1,700 tonnes and has a 9.11 m diameter cutterhead. The TBM is an earth pressure balance machine, which is designed specifically for the soft London clay that will be extracted from the ground.

The Northolt Tunnel will carry HS2 trains in and out of London – extending between the new Old Oak Common superhub and the outskirts of the capital at West Ruislip. The twin-bore tunnel is being built in two sections. Two TBMs, named Sushila and Caroline, are already constructing it eastward between West Ruislip and Greenford. Another two – Emily and Anne – are being used to dig the tunnel in the opposite direction from Victoria Road Crossover Box to Greenford.  

Emily and Anne’s tunnel drive will cover 3.4 miles of the tunnel in total – slightly less than those being used on the other section. Emily was launched today and Anne – the fourth and final Northolt TBM – will launch next month. The quartet of TBMs are all set to complete their journeys in 2025, when they will be extracted from the ground through giant shafts at Greenpark Way.

The London Clay, that will be extracted to build the tunnel, will be taken away from Victoria Road Crossover Box by conveyor, and taken to the London Logistics Hub at Willesden Euro Terminal. From there, it will be taken by rail and reused at sites in Cambridgeshire, Kent and Rugby.

HS2 is also making progress on preparations on the separate tunnel between Old Oak Common and Euston – the line’s ultimate central London terminus. The Atlas Road Logistics Tunnel breakthrough in January. The logistics tunnel is runs from the Old Oak Common Station box to Atlas Road logistics site and will facilitate the tunnelling operation to construct the Euston Tunnel.

Two further TBMs will be delivered to Old Oak Common later this year, and placed into the underground box, ready to begin boring the Euston Tunnel. Following the Government’s Network North announcement in October last year, the funding and delivery arrangements for the Euston Tunnel are being reviewed.