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Thames Tideway Tunnel

The Thames Tideway Tunnel will clean up one of London’s greatest natural assets, the iconic River Thames, protect it for generations to come and improve the quality of life for all Londoners.

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Worker standing in a sewer tunnel before operation.

Image credit: Tideway

At 25-kilometers long and at its deepest 70-meters below ground, Thames Tideway Tunnel is the largest water infrastructure project ever undertaken in the U.K.

The tunnel runs from east to west London and will modernize the city’s 150-year-old sewer system, originally built for a population less than half its current size, reducing untreated discharges into the River Thames by tens of millions of tons per year. 

The tunnel is now operational and has begun protection of the Thames. Data published in one day alone, when London saw heavy rainfall on September 23rd 2024, showed 589,000 cubic meters were captured by the London Tideway Tunnel with just the first connections activated.   

Teams are now working to bring the system into full operation, with the project on track for completion in 2025. Once complete, the new super sewer 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 100 years. The new system will have a capacity equivalent to 640 Olympic-sized swimming pools.  

Jacobs has been the program manager for the Thames Tideway Tunnel since 2008, building on our record of delivering major urban wastewater treatment projects globally. The Thames Tideway Tunnel is the kind of highly 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.

The Thames Tideway Tunnel project
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  • 42 M

    U.S. tons (39M tonnes) – the average amount of untreated sewage currently discharged into the tidal River Thames each year.

  • 100

    Providing additional sewer capacity to ensure the city has a sewerage system fit for at least the next 100 years.

  • 25 km

    Constructing the deepest continuous tunnel in Europe - over 25km long and over 65m deep.

  • 95 %

    reduction in sewage pollution when the super sewer is in operation, alongside other sewage network upgrades.

Creating a cleaner, healthier River Thames

The Thames Tideway Tunnel is one of the most significant infrastructure projects being undertaken in London.

Once complete, the sewer relief tunnel will create a cleaner, healthier River Thames and will enable the capital’s sewer system to continue to serve London for at least the next 100 years. Running from Acton to the Abbey Mills Pumping Station in Stratford, it will help treat tens of millions of tonnes of sewage that is discharged into the tidal Thames each year.

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

Our water and tunneling experts are helping deliver one of the most challenging wastewater projects in Europe. New sewer relief tunnels will intercept 24 of the most polluting combined sewer overflows (CSOs) where untreated sewage is being discharged into the tidal Thames. Pollution will be reduced by 95% when the super sewer is in operation, alongside other sewage network upgrades. 

With over 30km of new sewer, up to 65m below street-level, the tunnel will run beneath London’s complex network of utilities and London Underground lines. We interface with all the 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 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 sectorfor strategic, regulated assets. These arrangements are key to make Tideway’s risk profile similar to that of an established U.K. regulated water company.

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 led the planning and writing of the 125,000-page DCO submittal and the 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, in procurement and in the final stages of release. We used value engineering techniques throughout planning and design, and our continued drive for efficiencies and cost savings has 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 continue to use lean construction, collaborative planning and continuous improvement techniques to deliver to schedule and reduce costs.

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

Andy Alder

Andy Alder

Program Director

Delivering social value on Thames Tideway

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

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Tideway: You're all part of an underground movement
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Tideway: You're all part of an underground movement

A thriving community and environmental asset

Sustainability lies at the core of Tideway’s values and mission with their investment in local communities, education, training and the supply chain ensuring that the legacy of the Tideway project will be 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 Crossrail. 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.

The Thames Tideway Tunnel will not only create a sewer network that will serve London’s growing population for at least the next 100 years, it will also provide a much-needed boost to 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. Seven new public spaces with a total of more than three hectares of new land will be built along the river. This includes the extension of London’s iconic embankments.

More than 90% of the excavated spoil removed to create the tunnels was removed 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, the Thames Tideway Tunnel 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.

The Tideway project is due to be complete in 2025, following secondary lining, construction of the connections to the Thames Water sewer network, and testing and commissioning works. To date, the Tideway project has seen the creation of more than 4,000 sustainable jobs and more than 100 apprenticeships across the U.K.

“It’s so exciting to be this early in my career and gain invaluable experience in creating a significant part of London’s infrastructure. Tideway puts trust in all of their apprentices which encourages me to work with confidence on such a large-scale project. Not only is Tideway creating a cleaner River Thames, but it is shaping the next generation of construction professionals.”

Tom Clayton in blue jumper

Tom Clayton

Commercial Apprentice

Awards

Featured articles

Engineering News-Record: Thames Tunnel Seeks to Turn the Tide on Pollution

Infrastructure Intelligence: Huge step forward for London’s 25km super sewer as tunnelling begins

Tunnel Business Magazine: London’s Super Sewer Becomes ‘Longest Tunnel Under the Thames’

Infrastructure Intelligence: Delivering safe and efficient infrastructure for Thames Tideway