The contractor has been named as the preferred bidder for Hinkley’s tunnelling and marine works package, which will deliver up to 9.5 km of tunnels to form the cooling system for the new reactor.

The four-year package will see three 7 m-wide tunnels bored underneath the surrounding area both onshore and offshore.

The scheme is the second major works package picked up by Balfour Beatty at Hinkley Point C, following its appointment to the power station’s £460m electrical works package in joint venture with NG Bailey in 2015, which is currently on site.

Balfour Beatty’s Major Projects MD Stephen Tarr said: “With our nuclear heritage dating back to the 1950s, reaching preferred bidder status on our second major package of works at Hinkley Point C is testament to both our expert engineering skills and our in-depth market knowledge.

“Hinkley Point C is a project which inspires collaboration by its very nature due to its significant scale and complexity. Our expert engineers will deploy heavy civil engineering skills and extensive knowledge of tunnelling.”

An EDF spokesperson said: “Following a competitive process, the Hinkley Point C project team has awarded preferred bidder status to Balfour Beatty for the contract to construct the cooling water intake and outfall pipes for the station.

“This award extends Balfour Beatty’s role at HPC, as they are already involved in civil and electrical works for the project.”