Thames Water has appointed Costain to upgrade strategic treatment assets in Markyate and Brickendon in Hertfordshire.

The award, totalling £6.6 million across the two sites, relates to Thames Water's upgrade of wastewater treatment assets as part of its Wastewater Asset Assurance Programme (WAAP). Earlier this year Costain was selected to conduct upgrades to treatment assets at Thames Water sites in Sandhurst, Berkshire, and Selborne, Hampshire.

Thames Water is undertaking its biggest ever upgrade of sewers and sewage treatment works, with improvements planned at over 250 sites as part of a £1.12bn investment.


The planned construction across both sites will improve Thames Water’s ability to manage incoming wastewater. This will include modernising operations at inlet stations, whilst storm tanks will undergo repairs, modifications and upgrades. At Markyate, the work will be taking place alongside Thames Water’s ongoing investigations into the impact of groundwater on the sewer network that is informing long-term planning. Both projects are expected to be completed in 2026.

Graham Sugrue, framework director at Costain, commented: "We're looking forward to applying our breadth of experience to drive these important upgrades to the water infrastructure that will improve the quality of life for local residents and communities.

"We'll work closely with Thames Water to apply our skills and expertise to deliver a successful and efficient upgrade of the Markyate and Brickendon sites."