Up and under

Out in the Bristol Channel, two incredible vessels are helping to connect Hinkley Point C’s three cooling water tunnels to the six concrete intake head structures that were installed on the seabed last year. They’re rising above the sea to carry out huge feats of engineering.

What is a jack-up vessel?
There are two jack-up vessels called Sea Challenger and Neptune and they are fantastic feats of engineering. They can extend their legs onto the seabed to create a stable platform. Cranes are operated from this platform and it’s also used to install components on the seabed.

Why are they needed?
The Bristol Channel has such a high wide tidal range that it can limit time when work at sea is possible. The jack-up vessels help to avoid some of the challenging offshore conditions by standing on the seabed and rising up above the waves.

What do they do?
Each vessel has its own role. Neptune will stay offshore for the duration of the work, while Sea Challenger brings the equipment out. Combined, the two vessels will install casings and liners to create shafts from the concrete head structures and into the seabed. Once the casings are installed, an enormous drill bit is lowered by Neptune through the casing to create holes of over 20 metres deep, into which steel liners are lifted and grouted into place to form the shafts. This will be repeated six times and it is a vital step in bringing in the water needed to cool the operational power station.

Sea Challenger
  • 132.4m long
  • Weighing 25,000 tonnes
  • 900 tonnes – the lifting capacity of its main crane (there are five smaller ones on board)
  • 39m wide


  • 60.25m long
  • Weighing 8,500 tonnes
  • 600 tonnes – the lifting capacity of its main crane’
  • 38m wide




Posted by Hinkley Point C media team

The Hinkley Point C team brings you news, updates, blogs and information on the Hinkley Point C project.


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