Weir Wood Reservoir

 In 1952, the wooded valley surrounding the River Medway, East Sussex, was dammed by the Weir Wood Water Board in order to create a 5.6 million m3 surface water reservoir, providing a sustainable water resource to ever-growing nearby communities. 

Recreationally, the reservoir also provides entertainment activities, such as sailing and angling. 

Working in conjunction with our design partner, Capita, Pell Frischmann has been commissioned by Trant Engineering to undertake process option selection and the detailed design of a new 13 MLD water treatment facility for Southern Water at the site of the existing treatment works.  

Following the submission of outline designs and the planning application in spring 2022, detailed design will commence in early summer 2022, with construction also scheduled to begin in summer 2022. The project will be completed and provide wholesome water into service by the end of 2023. 

What we are doing

The Weir Wood Reservoir scheme epitomises our collaborative approach to delivery and our multi-disciplinary expertise, bringing in specialists from across our business. Working in partnership with Capita, Pell Frischmann is responsible for process design and all aspects of Civil, Structural, and Geotechnical Engineering including ground investigation.  

The site is within an Area of Outstanding Natural Beauty (AONB) and adjacent to a Site of Special Scientific Interest (SSSI). Careful consideration of all environmental impacts has been key to ensuring a promotable scheme and a smooth planning application process. 

The process includes Clarification (DAF), RGF, GAC and Chlorination. All plant and equipment will be housed in a purpose-built main process building covering c.1000m2and two other ancillary pump houses. 


Weir Wood Reservoir redevelopment is a key part of Southern Water’s wider drought plan, ensuring sufficient water supply is delivered to the surrounding communities. This requirement has been intensified due to increased climate change risks and future drought resilience. 

Local councils are aiming to increase population in towns Horsham and Crawley, both of which are supplied with water from Weir Wood Reservoir. Thus, improvements to the reservoir, and maintaining the sanitation of the water itself, are fundamental in keeping existing communities and families safe. 

Left Arrow Right Arrow Arrow Down Cross Quote Search Icon