Chartered Institute of Building Magazine of the Chartered Institute of Building


Balfour Beatty breaks through on final Hinkley onshore tunnel

7 October 2020

Balfour Beatty has completed the breakthrough of the longest and final onshore-cooling water tunnel at new nuclear power plant Hinkley Point C.

The milestone marks the completion of Balfour Beatty’s sprayed concrete linking works at the plant – a method for large-diameter tunnel construction using mechanical excavation and the application of sprayed concrete to provide ground support.

Balfour excavated through 600m of ground to create the tunnels, spraying 9,000m3 of concrete.

A total of 1.6m working hours were spent on the five onshore tunnels, which will now undergo secondary lining works and the installation of a number of reinforced rebar concrete structures.

When complete, the tunnels will transfer over 120,000 litres of water per second to Hinkley Point C from the Bristol Channel. 

The same Balfour team has 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 tunnelling 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.”

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 tunnelling and marine package in 2017 and most recently the 400kV overhead line project on behalf of National Grid in 2019.

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