- Date released
- 30 July 2024
- Request number
- 202407001
- Release of information under
-
Environmental Information Regulations (EIR)
Information requested
My request is to see if the ONR can provide me with any information you have regarding the measures to prevent coastal erosion around the [HPC] site, and whether I may be able to interview/discuss with someone from the ONR (online or in person) regarding the use of these defences and any other information around it, such as cost or other geographical survey documents that may be of use to me when researching the defences used to protect the site from coastal erosion.
Information released
We confirm that we hold the information you have requested.
The coastline immediately around Hinkley Point comprises cliffs to the frontage and westwards, and a low shingle barrier beach eastwards. Without the addition of coastal protection, as is being implemented on the Hinkley Point C (HPC) site frontage, continued cliff recession would occur.
At HPC, the site platform is set at 14m Ordnance Datum (OD), with a small area to the south of the site raised to 20m Ordnance Datum (OD). The coastal flooding design basis at HPC is the Reference High Sea Level (RHSL) of 12.92 m OD. As there is a margin of 1.08m OD between the RHSL (12.92m OD) and the site platform (14m OD), NNB GenCo (HPC) Ltd considers that the platform height is appropriate to withstand the design basis coastal flooding event.
A sea wall is being constructed around the HPC site to protect the land platform from erosion. The sea wall consists of the main wall, crest wall (wave-return wall) and two walls located at the eastern and western end of the main wall to prevent outflanking of the sea wall through cliff erosion over the lifetime of HPC and avoid the loss of fill from the sea wall. The wave-return wall has a curved geometry with a concave front and rounded top to provide resistance to wave impact and provide a degree of protection from scour on the upper revetment.
The sea wall is designed to prevent coastal erosion affecting the stability of the site platform or any other safety classified structures. The sea wall is designed to protect the site against coastal erosion (platform undercutting) for 100 years. As coastal erosion is a slow process that can be monitored, it is not considered as a coastal flooding hazard initiator by NNB GenCo (HPC) Ltd.
Further information
For further guidance on ONR’s expectations, please see:
- ONR Safety Assessment Principles, 2014 Edition, Revision 1 – SAP EHA.12 and ECE.23;
- NS-TAST-GD-013 Annex 3 – Coastal Flood Hazards;
- Principles for Flood and Coastal Erosion Risk Management, Revision 2, July 2022; and,
- Use of UK Climate Projections 2018 (UKCP18) Position Statement
References
- HPC Material Change Application EIA Scoping Report
- Hinkley Point C Pre-Construction Safety Report 3
- NNB Genco: Hinkley Point C Pre-Construction Safety Report 2012 – Assessment Report for Work Stream B7 External Hazards
We also note your request to interview/discuss the points raised in your request with ONR but hope the above response and references address the points raised regarding the measures to prevent coastal erosion around the HPC site.
Exemptions applied
N/A
PIT (Public Interest Test) if applicable
N/A