Proposed changes to a section of seawall at Hinkley Point C have concerned the Environment Agency, which believes the alterations could pose a flood risk.
EDF is proposing to pull a section of the seawall around the nuclear power plant back from the seafront by 7m, over a period of 100m. Doing so would avoid intersecting a graving (dry) dock near the foreshore, which had been excavated during work on Hinkley Point A and filled in with an unknown material.
Recent tests have shown that the material contains asbestos.
“The nature of the contamination includes hydrocarbons and asbestos. Altering the line of the sea wall to avoid intersection of the graving dock would negate the requirement to excavate the contaminated material and potentially expose receptors (human and environmental) to the risks posed by the material,” said EDF in the planning statement.
Historic data about the location of the graving dock was used to inform the current design for the seawall included in the original Development Consent Order (DCO) for Hinkley Point C. It was assumed that the graving dock would be avoided.
But subsequent ground investigations have found that the graving dock is not where originally thought, and the seawall would therefore intercept it. This would cause problems as the current design for the wall assumes the structure rests on solid ground (i.e. rock).
EDF argues that moving a section of the seawall back to avoid the graving dock would mitigate the problems.
But the Environment Agency objects, arguing that the documents detailing the proposed design changes do not adequately address the flood risk from tidal over-topping at the nuclear power plant.
“Whilst the crest height of the proposed sea wall indentation is set at 13.5m AOD [above ordenance datum], as per the original approved DCO, we would ask whether the newly formed indent could cause any increase in tidal over-topping rates from large waves travelling in a west to east direction along the face of the wall e.g. the previously modelled mach-stem wave. Would this pose any additional flood risks to the eastern EPR and/or interim spent fuel storage buildings?” said the Environment Agency in a letter to planning authorities.
The Environment Agency is demanding to know what flood risk assessments have been carried out to accompany the changes, and it warning the changes could require a new Flood Risk Activity Permit.
Planning permission was granted for the power plant in 2013. In August it emerged that an £840M electricity upgrade could be needed to connect Hinkley Point C to the grid.
New Civil Engineer has asked EDF for a comment. The Environment Agency has declined to comment.