The contractor has sealed an £8.7m early contractor involvement deal to develop the flagship AMP8 scheme, working with Thames Water and its design team to finalise the design, manage delivery risks and prepare the project for construction.

Maple Lodge Sewage Treatment Works at Maple Cross near Rickmansworth serves almost 500,000 people across west Hertfordshire. The 24-acre site discharges treated wastewater into the Grand Union Canal and River Colne.

The upgrade will increase treatment capacity, add new storm storage and improve the site’s resilience and environmental performance while keeping the treatment works fully operational throughout construction.

Works are expected to include upgraded storm storage, inlet works, screening, primary settlement and biological treatment, together with new final settlement tanks, tertiary treatment and improvements to electrical, control and monitoring systems.

Andy Lingham, managing director for water at Kier, said: “Maple Lodge is a flagship AMP8 scheme and an important example of the type of complex infrastructure programme now underway across the sector.”

The award extends Kier’s long-standing relationship with Thames Water, following major schemes including the Deephams and £66m Mogden sewage treatment works upgrades and the £45m Faringdon to Blunsdon pipeline.