- Date released
- 16 February 2023
- Request number
- 202301047
- Release of information under
- Freedom of Information Act 2000 (FOIA)
Information requested
At a recent ONR/NGO forum the Chief Nuclear Inspector indicated there was a need to co-ordinate between the ONR and EA in understanding the design and oversight of the cut-off wall surrounding Sizewell C nuclear platform. There appears, from the NGO perspective, to be a misunderstanding by the ONR of the critical role of this wall approx. 60 metres total height, which will not only enable dewatering of the site but will also form a barrier against coastal and fluvial flooding and groundwater movement generally around the site until it is fully decommissioned, whilst retaining the full construction weight of the two reactors and other buildings including the dry fuel store.
An indication of the importance of the ground anchor trials is given in 1) the press article photograph attached to this message and 2) a description of the work to be carried out by Atkins. These issues were first raised through ONR reference F01202102068 April 2021 and subsequently followed by other enquiries including under ONR reference HPGE202211058.
After the DCO planning inquiry finished, an application was made by the developer to East Suffolk Council under Planning Application DC/22/0078/FUL with the ground anchor trials described as vital and critical by the developer in its application. Many respondents questioned why this was not part of the DCO process
It is quite clear that the technique is difficult and according to Atkins chief engineer at a British Geotechnical Association Conference, is incomplete. Others in the Civil Engineering field have described the techniques at this depth as difficult and unique. It is also clear that a proper understanding of the likelihood that the ground anchors will enable the cut-off wall to be constructed safely, is essential for the well-being of the site’s construction workers.
We note that the project now proposed requires a site substantially more than the 32 ha that was scoped into the project and is nearer to the sea than initially proposed.
The developer appears to have ignored the planning line imposed at the Layfield inquiry and in a subsequent Royal Haskoning scoping report 2008, which was introduced due to the need to protect Sizewell A and B frontages.
Action requested
- We would like confirmation from both the ONR and East Suffolk Council that they will be attending the site during the ground anchor trials to ensure the trials and the subsequent results are independently monitored.
- Please can the ONR send us a fully scaled OS grid referenced plan of the proposed Sizewell C site as typically required for the site licencing.
- We wish to understand the relationship between the cut-off wall and the site’s perimeter walls so we also request a copy of a fully scaled OS grid referenced plan showing the proposed location of the cut-off wall together with the location of the sea defences and other protective walls intended to be constructed around the perimeter of the entire site.
Information released
We confirm that under s.1 of the FOIA, we hold some of the information relevant to your request.
We would firstly like to acknowledge your points above with regards to groundwater and the cut-off wall at Sizewell C. You are correct that there are effects on the permanent groundwater conditions from the existence of the cut-off wall.
As the detailed design of the cut-off wall continues to develop, the effects on the permanent groundwater conditions are being updated and considered in groundwater modelling studies; an aspect ONR continues to engage on. However, the cut-off wall does not have safety claims for protection against coastal and fluvial flooding, nor does it provide any safety claims in relation to support of the reactor buildings or other structures.
We have carefully considered your additional action points and have set out our responses below which we hope you will find useful.
Action 1
In response to action point one, which asks for confirmation that we, alongside East Suffolk Council, will be attending the site during the ground anchor trials; the ground anchor trials are being undertaken to provide further information on design development (trial of an engineering design to gain further performance data) and we will continue to engage with the licence applicant on this matter to seek the necessary regulatory confidence in the overall design of the cut-off wall. This may include attendance at site to observe part of the trials. However, we would like to note that responsibility for planning, conducting, quality assuring and validating the trials sits with the licence applicant, rather than with us.
Ultimately, our focus will be on ensuring that the design the cut-off wall, when developed, is adequately underpinned by performance data.
Action 2
In response to action point two, which asks for a fully scaled OS grid referenced plan of the proposed Sizewell C site as typically required for the site licencing; we do not hold a fully scaled OS map, however you may find a copy of a reproduced OS site map under a previous FOI release on our website at: FOI202108016 useful.
Action 3
In response to action point three, which requests a fully scaled OS grid referenced plan showing proposed location of the cut-off wall together with the location of the sea defences and other protective walls intended to be constructed around the perimeter of the entire site; we are unable to provide this to you as we do not hold this information at this stage. Design development of the cut-off wall is ongoing and will not be complete prior to the potential granting of a nuclear site licence.
Included in the information published by the licence applicant in relation to its application for a Development Consent Order is a construction method statement, which on pages 98 and 99 include drawings of the cut-off wall and its position in relation to the site perimeter, as well as the positioning of the site platform support wall. The cross section on pages 98 and 101 also show the positioning of the cut-off wall compared to the sea defence. Please note that these are outline plans and are therefore subject to change as the design continues to be developed.
The specific timescale for completion of this design development work is a matter for the licence applicant. If a nuclear site licence is granted, we would use the powers within the licence to require that the licensee requests our permission for starting nuclear safety related construction. Similarly, they will be required to seek our permission to proceed to key construction and commissioning stages up to the start of commercial operation and beyond.
Right to appeal
Should you not be content with the above response, you have the right to ask for an internal review to be conducted. This is done in writing and within two calendar months of this dated letter quoting the above reference FOI202301047.
If you are then not content with the outcome of the internal review, you have the right to apply directly to the Information Commissioner for a decision. The Information Commissioner can be contacted at:
Website: FOI and EIR complaints | ICO
Exemptions applied
N/A
PIT (Public Interest Test) if applicable
N/A