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Costain selected by Thames Water to upgrade key treatment sites

9 May 2024

  • Upgrade to sewage treatment works will transform the lives of local communities in Sandhurst and Selborne. 

Costain, the infrastructure solutions company, has been awarded a design and build contract with Thames Water to upgrade two strategic treatment assets in Sandhurst, Berkshire and Selborne, Hampshire.  

The award, valued at more than £5m for the two sites, will see Costain support Thames Water’s upgrading of wastewater treatment assets as part of its Wastewater Asset Assurance Programme (WAAP). The schemes are the first that have been awarded to Costain as part of a wider investment programme for sewage treatment sites (STWs). This could see up to 25 similar projects allocated to Costain to create cost-efficient infrastructure solutions for Thames Water.  

The planned construction will involve implementing flow monitoring technology to validate flow-to-full treatment for wastewater before it is discharged, upgrading the existing screening operations at the inlet station, improving storage tank capacity and revising the storm return pumping systems. The work will improve the ability of both sewage treatment works to treat the increasing volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The schemes are due to complete in 2025.  

Thames Water is currently undertaking its largest ever upgrade of sewers and STWs, with plans to improve more than 250 sites in the coming years as part of a £1.12bn investment in its wastewater sites.  

Gerard Shore, water director at Costain, commented: Thames Water is investing in river health and has a clear plan to upgrade hundreds of treatment plants across the region. This will have a transformative impact on the lives of residents and local communities. We know we can add considerable value by identifying further opportunities at the outline design stage to maximise efficiencies for the upgraded treatment infrastructure. This will help ensure that these assets are fit for purpose for the long term.”  

Andrew Popple, director of delivery at Thames Water, added: “We have an excellent track record of working with Costain and we are looking forward to collaborating with them once again for this work.  

We operate in a changing environment, with a population that is growing in many areas, so we continually monitor the potential need for upgrades at our STWs.”  

The news follows Costain’s appointment by Northumbrian Water to its AMP8 strategic infrastructure framework that could see contracts with the potential value of £670m awarded to Costain over the 12-year period.  In 2023, Costain extended into AMP8 its Managed Service Provider contract with United Utilities and its consultancy work with Yorkshire Water. Costain has also won funding from Ofwat to support innovation projects.   




Media enquiries: George Parrett [email protected]  

Notes to editors 

About Costain 

Costain helps to improve people’s lives by creating connected, sustainable infrastructure that enables people and the planet thrive. We shape, create, and deliver pioneering solutions that transform the performance of the infrastructure ecosystem across the UK’s energy, water, transportation, and defence markets. 

We are organised around our customers anticipating and solving their challenges and helping to improve performance. By bringing together our unique mix of construction, consulting, and digital experts we engineer and deliver sustainable, efficient, and practical solutions.  

About Thames Water    

  • Thames Water is the UK’s biggest water and wastewater services provider. Our key workers provide essential services around the clock to c.16 million customers across London, the Thames Valley, and surrounding areas.       
  • For an average of just over £1 a day for our households, we provide 2.7 billion litres of drinking water and safely remove 4.6 billion litres of wastewater every day.       
  • We invested £1.8 billion in 2022/23, and we will continue to spend wisely on improving resilience, service, and efficiency, as well as provide more support for customers in vulnerable circumstances.        
  • We also have additional responsibilities to society and the natural environment. What we do and how we do it delivers significant public value, which is why we have ambitious plans to self-generate more of our own power, reduce our carbon emissions and increase biodiversity across our sites.