Draft Overview of HPC Construction - EDF Hinkley Point

infrastructure. In these cases, the connections will be arranged to ensure that thedrainage is managed throughout the transition from temporary to permanentsystems. Parts of the temporary drainage systems within the permanent powerstation site will be in use until relatively late in the construction works and these willremain in place and will be isolated where they do not form part of the permanentinfrastructure.4.1.45 Construction drainage systems located outside the permanent power station footprintwill be removed as part of the construction area clearance and landscaping.However, the Holford Stream culvert will remain and will be integrated into theproposed landscaping scheme.4.2 Construction of the Sea Wall4.2.1 The sea wall will be constructed to provide erosion protection for the Hinkley Point Cpower station platform. It is located approximately along the line of the existing cliffsin front of the permanent power station site and will incorporate return sections ateach end of the wall to prevent erosion from the side.4.2.2 The existing cliff line will be trimmed as necessary to provide space for the wallconstruction. Rock armour will be delivered by sea and temporarily placed seawardof the works to provide protection during construction. A haulage road will be builtparallel to the cliff to provide access and the foundations of the wall will beexcavated.4.2.3 Following concreting of the wall, the area behind the wall will be backfilled with freedrainingmaterial and the rock armour will be moved to its final location at the toe ofthe sea wall to provide scour protection.4.2.4 The return sections at each end of the wall will be constructed of interlocking cast-insituconcrete piles, extending down into the underlying rock.4.2.5 The West Somerset Coast Path will be closed at the start of construction of the seawall and a new path will be constructed immediately behind the completed wall,connecting to the existing coastal path. An access ramp down to the beach will beprovided at the western end of the wall for inspection and maintenance. Accesssteps will be provided at three positions along the length of the wall to allow safeaccess and egress from the beach level.4.3 Construction of Buildings and Infrastructurea) Nuclear Island4.3.1 The nuclear island buildings are constructed of reinforced concrete. The concretewill be mixed on site using a batching plant and will use sand, aggregate and cementimported via the temporary jetty. In some cases, cement substitutes, such aspulverised fuel ash will be used to secure specific concrete properties. Thereinforcement will be with steel reinforcing bars, fabricated into cages appropriate tothe building geometry and strength requirements. Some reinforcement will beprefabricated into assemblies which can be lifted into place. Such pre-fabrication willnormally take place close to the workface to minimise handling issues. Where plantor equipment has subsequently to be attached to the concrete structure, embeddedDRAFT | Overview of HPC Construction | February 2011 23