Costain is using a unique walking jack up barge to construct the 490m long jetty in the Bristol Channel, which will be used to import aggregate for the construction of the £18bn Hinkley Point C nuclear power plant.
Costain is designing and constructing the three cooling tunnels for Hinkley, almost 9km in total length, to take in water from the Severn Estuary for the nuclear reactor before it is cleansed, recycled and returned. The work is for client EDF Energy.
The eight-legged 32m by 32m barge, called WaveWalker 1, has been specially designed for use in seas and rougher waters where there are difficulties using a self-elevating platform. These barges can “walk” on the foreshore and general construction area in different directions at a rate of up to 40m per hour, compared to a traditional jack up which would take six hours to relocate and cannot install the piles closest to the cliffs.
The Jetty will be used to bring in aggregate from ships which will then be transported via a conveyor system to the Hinkley construction site. The aggregate is for the four batching plants which will make the nuclear grade concrete.
CGI of Hinkley Point C jetty
“The new jetty is being built in a very challenging environment, as the Bristol Channel has one of the highest tidal ranges in the world, together with very fast tidal currents,” Costain’s contract lead on the jetty Paul Howells told New Civil Engineer.
“It is also a very exposed location, so wind is having a significant impact on the offshore construction activities. We are, however, now making good progress, with the two jack up barges working 24/7 to install the piles and steelwork for the jetty roadway, together with the 3.6m diameter, 140t fender piles.”
The jetty will be constructed from 80 steel tubular piles, which are up to 3.6m wide. The piles are 36m long and weigh around 140t.
Costain has also received planning permission to build a temporary precast concrete batching facility at Avonmouth Docks, further up the Severn Estuary from Hinkley. It will make 38,000 segments for the tunnels.