EDF Energy has announced that two large vessels have arrived off the coast of Somerset, UK, as offshore works commence at the final phase of the Hinkley Point C power station.

The jack-up vessels, dubbed Neptune and Sea Challenger, will install important components for the UK’s latest nuclear power station’s cooling water system.

They will install six vertical shafts at a depth of more than 20m, which represents the next stage in connecting the six miles of tunnels with the seabed.

Upon completion of the installation, miners will dig a horizontal connection between the bottom of the shaft and the tunnel, the first part of linking the intake and outfall heads with the tunnels.

The cranes of the platforms, which are often used to build offshore wind farms, will have a combined lifting capacity of 1,500 tonnes.

Each vessel will use its four legs to elevate itself above sea level, to operate safely without being impacted by waves and currents, said the electric utility.

EDF UK area delivery director Jonathan Smith said: “This is one of the final stages of our offshore operations, which will see teams from EDF, Balfour Beatty and New Wave Solutions working together to deliver yet another incredible feat of engineering.

“The cooling water system is critical to the power station – which will help Britain fight climate change and achieve stronger energy security.”

Last year, Balfour Beatty, together with EDF, lowered the last of six head structures 25m to the bottom of the Bristol Channel.

The concrete structures, weighing 5,000 tonnes, were lowered onto the seabed to meet two floating heavy lift cranes Gulliver and Rambiz, with a combined lifting capacity of 7,300 tonnes.

The six head structures, which will help supply Hinkley Point C’s two nuclear reactors with cooling water, were manufactured by Balfour Beatty.

Earlier this year, EDF increased the cost estimate for the Hinkley Point C nuclear project to almost $40bn (£33bn), saying inflation increased the costs.

Balfour Beatty project director Roger Frost said: “The arrival of Neptune and Sea Challenger marks another significant step forward in the successful delivery of the first new nuclear power station in the UK for over 20 years.

“We now look forward to utilising our unique capability and unrivalled expertise to continue with the linking up of the six miles of tunnels which are buried below the Bristol Channel – this is another important chapter in the offshore works required for Hinkley Point C’s critical water-cooling system.”