The contractor tasked with excavating the vast underground structure beneath Old Oak Common has completed the work, opening the way for the next phase of HS2’s super-hub station in West London.
It’s taken three years for joint venture Balfour Beatty VINCI SYSTRA’s (BBVS) and its specialist structures contractor, Expanded to excavate the underground box structure, where high speed trains will stop. The man-made cavern is big enough to accommodate the equivalent of 300 Olympic sized swimming pools.
Permanent construction to form the walls of the box began in June 2021. It has a 1.12-mile fibre-reinforced concrete diaphragm wall around it, and 1.3m tonnes of London clay were removed from inside. The honour of the excavation’s final completion went to HS2’s 1,500th apprentice, Miguel Jardim, removing the last of the London clay from the box.
“It is quite an honour to be part of celebrating such a massive excavation milestone – the opportunity came along very unexpectedly,” said Jardim, 19, a civil engineering apprentice who hails from Surrey Quays, in South East London.
“The best thing about my job here at Old Oak Common is all the experience I’m gaining from going out onsite daily, seeing progress coming along. I would 100% encourage others to start working on HS2, as it’s a massive project where you get to work with lots of people with similar goals. There is also a great network of people that you can learn from and connect with.”
More than 1,500 apprentices have now started work on HS2, putting the project on track to meet its target to generate 2,000 apprenticeships.
Steve O’Sullivan, Project Director at BBVS, said: “This achievement is a testament to the dedication and hard work of our team, and in particular the valuable contributions of our apprentices like Miguel.
“The progress here at Old Oak Common moves us one step closer to completing this key transport hub, which will enhance connectivity and drive regeneration in the area. We are excited to move forward to the next phase of construction and continue delivering this transformative project.”
Meeting in the middle
The excavation was completed section by section within the box, starting from the West and the East of the structure and meeting in the middle.
The box is 20m in depth and a reinforced concrete base slab up to 2m in depth is being poured throughout. Furthermore, 32,000 tonnes of steel rebar, assembled by hand on site, has been used in the box alongside 160 reinforced concrete columns that have been installed inside the outer wall to help support the structure.
All steel used was 100% responsibly sourced, BBVS says, and most of the concrete used is produced by the London Concrete batching plant on site, which reuses rainwater in its mixes. Now the box has been fully excavated, the team will be working to pour the final sections of base slab to fully complete the box.
Six 450m platforms will be constructed in the underground box for HS2 services. Above ground, eight further platforms are being built, and will be served by the Elizabeth Line, Great Western Mainline services and the Heathrow Express.
Old Oak Common station is intended to become one of the country’s most vital transport hubs, which will be directly connected on the UK’s railway network to more than 170 destinations.
Sam Clark, head of delivery for HS2 Ltd, said: “The tremendous progress made by our construction team to complete the excavation of the box is an exciting milestone for the project as it signals the next phase of construction where high speed platforms will be built, as well as the station building itself.
“HS2’s Old Oak Common station will be transformational for local and regional connectivity and attract huge investment, development and regeneration to the surrounding area.”
The huge amount of London clay removed in the excavation has been taken away from site by conveyor, reducing lorry movements on local roads. The conveyor, run by the Subcontractor Fairport, took the spoil to the nearby London Logistics Hub, managed by Skanska Costain STRABAG, from where it has been transported by rail to beneficial reuse sites in Kent, Warwickshire, and Cambridgeshire.
Main image: HS2 civil engineering apprentice, Miguel Jardim marks the final excavation of the Old Oak Common underground box
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