Sizewell C – Specialist Hydrogeological Services

(SZC) is a new nuclear power station under development on the Suffolk coast, adjacent to the existing Sizewell B site. Located in an environmentally sensitive area and close to the Sizewell Marshes Site of Special Scientific Interest (SSSI), the project demands rigorous hydrogeological assessment and water management planning to support construction, particularly within the Main Construction Area (MCA) and Temporary Construction Area (TCA).

WJ was commissioned to deliver hydrogeological investigations, resource assessments, and technical advisory services to support dewatering, abstraction testing, and groundwater modelling activities.

Project Scope and Challenges

WJ’s role encompassed the full range of specialist hydrogeological services, including:

• Hydrogeological Resource & Risk Assessments: Evaluating groundwater quality, abstraction risks, and potential impacts to local surface water systems.
• Test Pumping Programme: Conducting and analysing step and constant rate pumping tests at both the TCA and MCA sites to assess long-term abstraction viability for water supply and dewatering activities.
• Wellfield and Water Balance Analysis:Assessing impacts of water abstraction on groundwater levels and hydrological connectivity with the surrounding environment, including nearby SSSI areas.
• Geochemical Sampling & Water Quality Analysis: Daily water sampling during testing for laboratory and field-based parameter analysis.
• Surface Water Monitoring: Installation and data collection from multiple stilling wells and sensors to assess potential influence of groundwater abstraction on surface water features.

WJ’s Innovative Approach

WJ delivered a suite of integrated technical solutions:

• Conceptual & Numerical Modelling: Developed detailed 3D groundwater models of the MCA and surrounding catchment, integrating geological mapping and permeability data to inform dewatering design.
• Specialist Geological Analysis: Used to refine the conceptual understanding of site conditions and improve groundwater model accuracy.
• Academic & Technical Expertise: Our in-house hydrogeologists and geologists, with over 130 years of collective experience and over 35 published technical papers, provided advisory support to client teams and regulatory bodies.
• Field Instrumentation & Monitoring:High-resolution data from piezometers and flow meters informed real-time groundwater and surface water interaction assessments.

A Key Contribution to Success

WJ’s involvement enabled SZC to:

• Mitigate environmental risk to adjacent SSSI wetlands by providing robust evidence on groundwater drawdown limits.
• Assisted our client’s team to secure Environment Agency approvals for groundwater abstraction and discharge at the TCA and MCA sites through detailed water quality and impact assessments.
• Optimise the dewatering design for the MCA by using model simulations across various rainfall, permeability, and construction conditions.

The WJ Difference

At WJ, we deliver more than groundwater control we provide science-driven, field-proven solutions. Our work at Sizewell C exemplifies how expert hydrogeological insight and technical excellence underpin sustainable infrastructure development.