Press Release

Nothing boring about Hinkley Point C’s latest milestone moment

10 December 2020


Another key milestone has been achieved at the Hinkley Point C construction site in Somerset, with the completion of the first of three off-shore tunnels needed for the power station’s cooling-water system.

The first Tunnel Boring Machine (TBM), named Mary, reached the end of her 3.5km journey under the Bristol Channel to complete intake tunnel 1 on 9 December 2020.

Roger Frost, Balfour Beatty Project Director, said: “This is a significant achievement - one that marks another step towards the successful delivery of the UK’s landmark nuclear power station, Hinkley Point C. The unrivalled expertise of our people, combined with our state-of-the-art offsite manufacturing facility in Avonmouth, has made it possible for us to break through the first of three off-shore tunnels. I am immensely proud of the commitment everyone has shown.”

The 3.5km-long intake tunnel 1 was mined at a depth of 33m below the Bristol Channel, using one of three TBMs needed for the project. The TBM, named Mary after prominent palaeontologist Mary Anning, was effectively a moving factory operating underground.

As Mary advanced forward she installed concrete rings, each made up of six segments. The tunnel comprises more than 2,300 of these rings, with nearly 14,000 segments needed to complete them. After each ring was placed, the crew then filled the gap behind it with grout. Around 12,000m3 of grout was used in total over the full length of the tunnel.

The nuclear-standard precast segments were produced at Balfour Beatty’s purpose-built manufacturing plant in Avonmouth and transported to site. Some 38,000 segments will be needed to complete the three tunnels.

Mary’s cutter head removed around 340,000 tonnes of earth, which was passed along seven different conveyors, both belt conveyors and a ‘bucket’-style vertical conveyor, down the length of the tunnel, up and out of the deep dig. From here it was loaded onto trucks and used for landscaping on site.

Parts of the TBM will now be stripped and installed on another machine, with the remainder immortalised under the Channel as a time capsule to the incredible feat of engineering.

Attention now turns to the two remaining tunnels for the cooling-water system. Emmeline, the largest of the TBMs, has just started on her 1.8km journey mining the outfall tunnel, and Beatrice, supplemented by equipment from Mary and responsible for intake tunnel 2, is set to launch early next year.

Image: TBM passes through 1-kilometre for intake tunnel 1


Media enquiries to:
Vivienne Dunn
Balfour Beatty
+44 (0)203 810 2345 | follow us @balfourbeatty

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Notes to editors:

  • Balfour Beatty (com) is a leading international infrastructure group. With 26,000 employees, we provide innovative and efficient infrastructure that underpins our daily lives, supports communities and enables economic growth. We finance, develop, build and maintain complex infrastructure such as transportation, power and utility systems, social and commercial buildings.
  • Our main geographies are the UK, US and Hong Kong. Over the last 110 years we have created iconic buildings and infrastructure all over the world including the London Olympics’ Aquatic Centre, Hong Kong’s first Zero Carbon building, the National Museum of the Marine Corps in the US and the Channel Tunnel Rail Link.
  • Balfour Beatty’s Major Projects business deliver large-scale, complex infrastructure projects which keep the UK moving and the economy thriving. Employing over 2,000 people, the business operates within three principal markets; Transportation; Energy and Power and Major Infrastructure.
  • To maximise our offering on major infrastructure projects, we partner with the world’s leading international companies in joint ventures such as VINCI, Skanska and Mott MacDonald to complement our construction offering on mega-infrastructure projects.
  • Our current portfolio of major projects include two design and build contracts for High Speed 2 in a joint venture with VINCI, the four-year Hinkley Point C nuclear power station tunnelling and marine works package on behalf of EDF Energy and London’s new major super-sewer through central London, in a joint venture with BAM Nuttall and Morgan Sindall.
  • Iconic projects of the past include Heathrow Airport Terminal 2 departure lounges, the transformation of the iconic former London Olympic Stadium into a multi-purpose sporting venue and in a joint venture with VINCI the South West of England’s first Smart Motorway to improve journey safety and traffic capacity on the M4 and M5.

Vivienne Dunn

Senior Media & PR Manager