United Utilities opens £600m tender race for £3.7bn Windermere clean-up

United Utilities has launched a tender worth up to £600m for a design and integration partner to drive its proposed £3.7bn Windermere clean-up, with submissions due by 2pm on 30 November.

The contract anchors one of the water sector's biggest emerging construction programmes. An initial four-year development phase is expected to be worth £60m-£100m. Extensions covering design and integration during construction could take the appointment to £600m over 13 years.

The fee structure splits clearly. Up to £500m covers detailed design and system integration during delivery. A narrower integration-only role would be worth around £100m beyond the initial development phase.

What will the winning partner actually do?

The water company wants a partner to turn its Only Rainwater into Windermere proposals into a consented construction programme spanning tunnels, sewers, pumping stations and treatment infrastructure.

The scope is broad:

• outline design, planning and consent applications
• environmental assessments
• ground investigations
• early contractor involvement

The partner will also help shape how the huge programme is delivered, because United Utilities is still weighing up its construction model. Options include supporting a prime contractor or joining an integrated enterprise that brings together the client, designers and delivery contractors under shared incentives.

That decision matters for bidders. The choice between a prime-contractor structure and an integrated enterprise determines who carries design risk, who controls the supply chain and where the remaining fee pool sits.

How will consent be secured?

United Utilities intends to seek development consent for the main infrastructure as a Nationally Significant Infrastructure Project, subject to approval from Defra to use that route. NSIP status would route the programme through the Planning Inspectorate rather than local planning authorities, compressing a consenting timeline that conventional applications could stretch for years.

What did the feasibility work establish?

Earlier feasibility work by Jacobs and Mott MacDonald narrowed more than 70 options to two preferred solutions. Both involve intercepting wastewater entering the lake catchment and transferring it through underground pipelines for advanced treatment.

The wider proposals carry hard numbers:

• up to 138km of new sewers
• around 35km of highway runoff interception
• 37 hectares of sustainable drainage

Thousands of properties using private treatment systems could be connected to public sewers, with remote treatment provided where connections are impractical.

What is the timeline?

United Utilities previously estimated construction would take around seven years once design, planning and regulatory approvals are secured. Combined with the 13-year span of the integration appointment, the programme sets a delivery horizon well into the 2040s.

Tender submissions are due by 2pm on 30 November. An award decision is expected on 1 April 2027, with the appointment starting on 15 April. Bidders now face roughly two years of evaluation before a partner takes control of the consenting phase — and, with it, the shape of one of the largest water infrastructure builds in England.