Details of the three massive tunnels Costain is to build for the £18bn Hinkley Point C nuclear power station in Somerset have been revealed, as the contractor gears up to start manufacturing the concrete lining segments.
The information about the plant is some of the first to emerge from the mega-project regarding its construction. Just the work of the plant alone gives an indication of the enormity of the job.
A total of 38,000 concrete segments need to be made for the three Hinkley tunnels, amounting to 83,000m³ of concrete. Two of the three tunnels will supply the water for cooling the reactor and the third is the water outlet.
To build the segments, Costain has applied for planning permission to build a temporary precast concrete batching facility at Avonmouth Docks, further up the Severn Estuary from Hinkley. It will be used for four years. A decision on the application will be taken by Bristol City Council’s development control committee tomorrow (Wednesday).
Hinkley precast concrete facility
The tunnels will be 20m below the seabed, according to information in the main committee report. The two intake tunnels will be 3.4km and 3.5km long and 6m in diameter. The outlet tunnel will be 1.8km long and 7m in diameter. The plant will need to operate on a 24 hour basis, producing 600 segments a week at peak production. Segments will weigh 4.8t or 4.2t depending on where in the tunnel they are used.
The plant will also make the six head units for the tunnels.
The Health & Safety Executive (HSE) has expressed concern about the facility. It says the facility’s location will put people are within too short a distance of neighbouring sites which can store hazardous substances. Although the sites concerned do have consent to store hazardous substances, two have been demolished and the other three have not stored such substances for four years.
The HSE also says the development has a low probability of a major accident involving explosives close to shipping berths which have explosives handling licences. The Council wants the port authority to adapt its explosives management policies. Solutions being put forward include evacuating the precast facility while boats carrying explosives in the berths are being unloaded.
Council planning executives are advising the committee to approve it, saying conditions for planning permission should overcome the HSE’s concerns.