National Grid has awarded a trio of construction contracts worth £300 million for the connection of the Hinkley Point C nuclear power station to the transmission network.

The 400kV power line will stretch for 57km between substations in Bridgwater and Seabank near Avonmouth. Almost 11km will be buried underground to protect views in the Mendip Hills Area of Outstanding Natural Beauty.

National Grid will remove 67km of 132kV overhead lines owned by Western Power Distribution, including all of the pylons currently crossing the Mendip Hills.

Balfour Beatty has been awarded a contract to build the new T pylons – the winning design from a 2011 competition – that will be used along much of the route.

Siemens will construct a new substation at Sandford, while J Murphy and Sons will install an 132kV underground cable that runs alongside the main 400kV line between Nailsea and Portishead.

Sue Adam, director of the Hinkley connection project at National Grid, said: “The awarding of these contracts marks a major step forward on this vital connection project. It means that we will now be able to gear up to start construction work in earnest.”

She added: “This will see lots of construction work going on at different times and in different places over the next eight years. We and our newly appointed contractors will do everything we can to minimise impacts wherever possible.”

Mark Bullock, chief executive of Balfour Beatty’s rail and utilities business, said: “Our extensive knowledge and unique capability in delivering major complex overhead line schemes, makes us ideally positioned to play a key role in helping to deliver the first nuclear power station to be built in the UK for more than 20 years.

“We look forward to working with National Grid to successfully and safely deliver low-carbon electricity for around six million homes across the UK.”

Ofgem confirmed in July the project would be funded under a new “competition proxy” model, with revenues being set in line with the anticipated outcome if the project had been put out to tender. It expects this to save between £50 million and £100 million compared to funding the project through the RIIO price controls, mainly due to lower financing costs.

The original quote submitted by National Grid was £839 million. When Ofgem announced the competition proxy model as its preferred option at the beginning of 2018, the regulator lowered the estimated cost to £800 million. National Grid criticised the decision, saying the regulator had set the allowed cost of capital too low.

The £800 million price tag includes £150 million of pre-construction costs which Ofgem still expects to be funded through RIIO.

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