Light at the End of the Tunnel: Balfour Beatty Breaks Through its Final Onshore Tunnel at Hinkley Point C

Balfour Beatty, alongside EDF, has celebrated a major milestone on its Hinkley Point C tunnelling and marine project, as the team successfully completed the breakthrough of the longest and final onshore cooling-water tunnel, at the UK’s landmark nuclear power station.

This momentous milestone marks the completion of Balfour Beatty’s sprayed concrete lining works at Hinkley Point C; a well-established method for large diameter tunnel construction using mechanical excavation and the application of sprayed concrete to provide ground support. 

Excavating through 600 metres of ground to create the tunnels, the team worked safely and swiftly to spray the ground with 9000m³ of concrete in order to stabilise the recently formed underground structures. In total, the process required over 1.6 million hours across the tunnels, with the programme of works completed to schedule.

The five onshore tunnels will now undergo secondary lining works, installing a number of reinforced rebar concrete structures to further stabilise the sprayed concrete.

In total, the team have successfully completed all five onshore tunnels which will play an essential role in the critical cooling water system for the nuclear power station, responsible for transferring over 120,000 litres of water per second to Hinkley Point C from the Bristol Channel. 

The same team have prepared three portals to facilitate the launch of the Tunnel Boring Machines (TBM) which will excavate the tunnels for the main cooling water system. The first TBM has already set off on its journey, having travelled over 2.5 kilometres, 33 metres under the Bristol Channel.

Alistair Geddes, Balfour Beatty Project Director for Hinkley Point C’s tunneling and marine project, said: “This is a significant step forward in the successful delivery of the first new nuclear power station in the UK for over 20 years. Achieving this incredible milestone is testament to Balfour Beatty’s unrivaled expertise in delivering projects of this scale and complexity.”

On completion, Hinkley Point C will supply safe, secure, low carbon electricity to around six million homes.

Balfour Beatty is contracted to three major packages of works at Hinkley Point C. It was first appointed to deliver the electrical package in a joint venture in 2015, the tunneling and marine package in 2017 and most recently the 400kV overhead line project on behalf of National Grid in 2019.