View all projects

Cleaning up the River Thames through the UK’s largest ever water infrastructure program

The Thames Tideway Tunnel, delivered by Tideway, is cleaning up one of London’s greatest natural assets, the iconic River Thames, protecting it from sewage pollution for generations to come — and improving the quality of life for all Londoners
Worker standing in a sewer tunnel before operation.
Water

At 25 kilometers long and at its deepest 70 meters below ground, Tideway is the largest water infrastructure program ever undertaken in the U.K. It has consistently operated within the cost parameters defined over a decade ago and remains on track for full completion ahead of the regulated 2027 date.

The tunnel runs from west to east beneath London and has extended and modernized the city’s 150-year-old sewer system, originally built to serve a population less than half its current size.  The new infrastructure reduces untreated discharges into the River Thames by 95% — virtually eliminating the harmful effects of sewage pollution in the Thames through central London. 

As of February 2025, the tunnel is fully operational and protecting of the Thames.

The team is now working to thoroughly test the completed system, with the program on track for completion in the coming few months, weather permitting. The new super sewer has a storage capacity of 1.6 million cubic meters — equivalent to 640 Olympic size swimming pools — and will dramatically reduce sewage pollution, creating a cleaner, healthier River Thames and enabling the capital’s sewer system to continue to serve London for at least the next 120 years. 

Jacobs has been the program manager for Tideway since 2008, building on our record of delivering major urban wastewater collection and treatment programs and projects globally. The work we are undertaking with Tideway is the kind of complex program that Jacobs enjoys tackling, with multi-site delivery and significant challenges demanding innovation and better ways of working to achieve the best outcomes. It is a great example of where we have been able to provide our full suite of expertise across the program life cycle — from the early planning and feasibility phase, through to design, delivery and handover into operations.

42M

U.S. tons (39M tonnes) – historically, the average yearly amount of untreated sewage discharged into the tidal River Thames.

120

Providing additional sewer capacity to ensure the city has a sewerage system fit for at least the next 120 years.

95%

Combined with the Lee Tunnel and upgrades to sewage treatment plants, this is the reduction in the volume of sewage pollution spilling into the Thames.

Creating a cleaner, healthier River Thames

Tideway is one of the most significant infrastructure programs being undertaken in London.

Running from Acton to the Abbey Mills Pumping Station in Stratford, it intercepts tens of millions of tons of sewage that have historically discharged into the tidal Thames each year.

Jacobs has been the program manager, working collaboratively as part of an embedded team, alongside our client Tideway and wider supply chain. We have coordinated the implementation of market-leading program management functions through all phases, including planning consents, preliminary and final design, construction oversight, change and risk management, project control, contract management, commissioning and start-up of new facilities.

Our water and tunneling experts helped deliver one of the most challenging wastewater programs in Europe. New sewer relief tunnels intercept the most polluting combined sewer overflows (CSOs), where untreated sewage is being discharged into the tidal Thames. The super sewer will reduce sewer pollution by 95%, alongside other sewage network and treatment upgrades.

With over 25km of new sewer, up to 70m below street-level, the tunnel runs beneath London’s complex network of utilities and London Underground lines. As part of the program, we interfaced with major stakeholders in London, including Transport for London, the Environment Agency, the Port of London Authority, Historic England and the Marine Management Organisation, as well as the numerous London boroughs through which the scheme passes.

Innovative thinking by Tideway at the outset led to a unique business delivery model. Privately financed and delivered by an independent infrastructure provider, regulated by Ofwat, this was the first time that this financing model had been used in the U.K. water sector for strategic, regulated assets. These arrangements are key to make Tideway’s risk profile similar to that of an established U.K. regulated water company. Jacobs’ advisory team played an important role in developing the right financial model for success.

Construction of the tunnel started in 2016, following the successful Development Consent Order (DCO) application. This was commonly recognized as the largest and most complex DCO delivered at that time. We program managed the process, which comprised the planning and writing of the 125,000-page DCO submittal, and stakeholder engagement and communications activities (including 48 public hearings), to achieve DCO approval in September 2014.

Given the complexity of this program, some of the greatest challenges faced were controlling costs and delivering to the regulatory schedule. At the outset, we gave the highest priority to developing robust and appropriate contracts. We used value engineering techniques throughout the planning and outline design phases — our continued drive for efficiencies and cost savings resulted in significant savings by adjusting the tunnel alignment and designing the hydraulic system to control overflows to the River Thames without needing to construct at every overflow point. This has minimized disturbance to local residents, while increasing confidence and reducing cost. Throughout the construction phase, we continued to use lean construction, collaborative planning and continuous improvement techniques to deliver to schedule and reduce costs.

  • The scale of Tideway and its place at the heart of one of the world’s greatest cities mean we have a historic opportunity to leave a lasting legacy for London. The primary purpose of Tideway is to reduce sewage overflows into the River Thames and improve its water quality. But beyond that, Tideway’s vision to reconnect London with the River Thames is an ambitious statement of intent and reflects the desire to deliver wider benefits to London for years to come.
    Jim Avant
    Program Director

Delivering social value on Thames Tideway

Leaving a positive legacy for local communities and the industry required an innovative approach to skills and employment across the Tideway.

Read more about how we're supporting Tideway

A thriving community and environmental asset

Sustainability lies at the core of Tideway’s values and mission, with the program’s investment in local communities, education, training and the supply chain. This ensures that the legacy of the program is profound and long-lasting not only for London, but for the U.K. as a whole.

We have worked with our client to develop a transformational health and safety approach to Tideway construction, building upon best practices learned from the London 2012 Olympic and Paralympic Games and from The Elizabeth Line. We supported the development of leading-edge activities such as Tideway’s Project Employer Induction Center (EPIC) and Mates in Mind, which has had a positive impact on our industry’s health, safety and wellbeing record.

Tideway not only creates a sewer network that will serve London’s growing population for at least the next 120 years, it also supports the city’s economy by providing thousands of skilled jobs and hundreds of apprenticeship opportunities. Once completed, the water quality of the tidal River Thames will be greatly improved, making it one of the cleanest rivers in Europe and enabling communities to enjoy the river for recreational and business activities. As part of this, seven new public spaces with a total of more than three acres of new land has been reclaimed from the river. This includes the extension of London’s iconic embankments. As a result of these efforts, wildlife too will start to benefit from the cleaner river.

More than 90% of the excavated spoil removed to create the tunnels was carried from site by barge, keeping lorries off the road and providing substantial environmental benefits when compared to the HGV (heavy goods vehicle) equivalent.

With London’s growing population expected to increase to 10 million by 2030, Tideway will play a vital role in laying the foundations for human progress in the city. City-wide, Jacobs is tackling a variety of complex infrastructure challenges and is proud to be playing a part in ensuring London remains one of the world’s most competitive cities through a world-class infrastructure network that continues to bring social and economic benefits.

To date, Tideway has seen the creation of more than 4,000 sustainable jobs and more than 100 apprenticeships across the U.K.

 

Awards