Contract award

Kier takes £8.7m early role on £265m Thames Water upgrade

By Staff Writer  |  12 August 2026

Kier has signed an early contractor involvement contract worth £8.7m to develop the £265m upgrade of Maple Lodge sewage treatment works in Hertfordshire.

Kier has sealed an £8.7m early contractor involvement deal to develop the upgrade of Maple Lodge sewage treatment works, a scheme valued at £265m. Under the contract it will work with Thames Water and its design team to finalise the design, manage delivery risks and prepare the project for construction.

Maple Lodge, 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 the River Colne.

The £8.7m contract is the early stage. It buys design development and risk management ahead of construction, not the construction itself, and the two should not be confused when reading the figure.

Scope

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

Work is 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.

Maple Lodge is a flagship AMP8 scheme and an important example of the type of complex infrastructure programme now underway.

Andy Lingham, managing director for water, Kier

Building on a live works

The requirement to keep the treatment works operational throughout is the defining constraint. It dictates the construction sequence, the temporary works, and the number of separate tie-in windows the programme must accommodate, each of which is a point at which access disputes commonly arise.

Early contractor involvement exists precisely to surface those constraints before the price is fixed. Where it works, the buildability and sequencing questions are answered while the commercial terms are still open. Where it does not, the same questions arrive later as variations, and the argument is about entitlement rather than method.

The scale of the asset

Maple Lodge serves almost 500,000 people, which places it among the larger treatment works in the Thames Water estate. The 24-acre site discharges treated wastewater into the Grand Union Canal and the River Colne, so the environmental performance of the works is directly observable in two watercourses.

That combination, a large population served and a visible discharge, is why capacity and storm storage sit at the front of the scope. It also explains the requirement to keep the works fully operational throughout: there is no practical option to take it offline.

For the supply chain, an AMP8 scheme of this size implies a long procurement tail of mechanical, electrical, instrumentation and civils packages. The early contractor involvement stage is where the packaging strategy is decided, so it is the point at which the shape of those subcontracts is determined rather than merely priced.