IN Brief:
- Planning approval covers an Avonmouth facility manufacturing 38,500 precast segments for three Sizewell C marine tunnels.
- Early works are under way, with 55 Civil Works Alliance employees and 86 supply chain workers active.
- Production is expected from 2028, with finished components transported to Suffolk by rail and sea.
Sizewell C has secured planning permission for a major production facility at Avonmouth that will manufacture precast concrete components for the nuclear project’s marine tunnels. The facility, around 10km north-west of Bristol city centre, will produce tunnel segments and heads before they are transported to Suffolk by rail and sea.
The development reuses the location and infrastructure associated with the tunnel production operation established for Hinkley Point C. Sizewell C intends to transfer manufacturing experience from the Somerset project into its own construction programme while retaining specialist capability in the South West rather than recreating the production system beside the Suffolk site.
The Avonmouth works will include temporary infrastructure supporting the manufacturing operation, including concrete batching plants, cranes, offices, welfare facilities, storage areas and parking. Early activity is already under way. Sizewell C says 55 people are currently employed at the location through its Civil Works Alliance, with a further 86 supply chain workers active on site.
Subject to the planning conditions being discharged, production of the tunnel components is expected to start in 2028. The factory is intended to manufacture 38,500 precast segments for three marine tunnels, turning Avonmouth into an off-site production base for one of the more specialised civil engineering packages on the Suffolk programme.
The Civil Works Alliance brings Sizewell C together with Balfour Beatty, Laing O’Rourke and Bouygues Travaux Publics in a single delivery organisation for the main civil works. Its scope includes enabling and earthworks, marine and tunnelling, the principal nuclear and conventional island structures, ancillary works, and permanent roads and networks. The marine package includes three undersea tunnels of around 3km each.
Manufacturing the tunnel segments at Avonmouth also forms part of the project’s wider logistics strategy. Sizewell C has committed to move at least 60% of construction materials by rail or sea, reducing the volume of heavy goods traffic using local roads. The project recently brought its purpose-built Green Rail Route into commercial operation, with its first full train carrying more than 1,000 tonnes of material to site.
The Avonmouth arrangement combines factory production with long-distance rail and marine logistics. Precast components can be produced in a controlled environment, while the transport system moves the finished units to the main construction programme without requiring their manufacture within an increasingly congested Suffolk site.
Factory-built elements are appearing elsewhere in Sizewell C’s supporting infrastructure. A separate worker accommodation package is using bathroom pods manufactured off site in Hull, distributing another part of the construction programme away from the main project location.
The Avonmouth workforce plan also extends beyond the immediate production requirement. The Civil Works Alliance is working with local authorities, education providers and industry partners on apprenticeships, work experience, internships, graduate routes and vocational training. Sizewell C says most of the workforce at the facility is expected to come from the local area, retaining skills developed around Hinkley Point C and transferring them to the new programme.
The Civil Works Alliance contractors are all involved at Hinkley Point C, giving Sizewell C access to established engineering approaches, specialist suppliers and construction experience. At Avonmouth, that replication strategy is physical as well as procedural: an existing industrial location is being adapted for another large precast production run rather than treated as a one-project asset.
Sizewell C says almost £5bn has already been invested with more than 1,000 UK suppliers, including around £1bn with businesses in Suffolk. Independent analysis commissioned by the project estimates that construction will generate £26bn of gross value added across the UK. The Avonmouth facility is one example of how that expenditure extends well beyond the nuclear site itself.
Planning approval now moves the facility into its preparation phase ahead of the proposed 2028 production start. The intervening programme will cover site works, batching and handling infrastructure, workforce development and production readiness before the first tunnel segments begin moving from Avonmouth towards the Suffolk coast.
