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Jacobs: Thames Tideway Tunnel

The Thames Tideway Tunnel infrastructure project focuses on upgrading the section of London’s sewer system that runs under the tidally influenced reaches of the River Thames and Inner London.

Jump to:
  • What we know
  • What we’re doing
  • What it’s worth

What we know

London’s sewer system is 150 years old and was originally built for a population less than half its current size. Despite being planned for population growth, the system’s capacity has been exceeded to the point where even light rain risks untreated sewer overflows to the River Thames [source]. This has led to an average of 39 million tonnes of untreated sewage being discharged into the Thames each year [source].

The Tideway project aims to upgrade and modernise the system to meet both modern demands and future-proof the system for at least the next hundred years. This will involve constructing a tunnel 25 km long and over 65 m deep, providing a 94% reduction in sewage pollution alongside other sewage network upgrades, once complete [source].

Image credits: Tideway

What we’re doing

Tideway embraces numerous approaches involving lean construction, collaborative planning and continuous improvement. Construction materials and excavated spoil are primarily being moved by barge, reducing road congestion and protecting vulnerable road users.

The project is also operating within the context of policy drivers. This includes London’s target to reduce carbon emissions by 78% by 2035 [source] and goals within the construction and infrastructure sector, such as reaching net zero emissions for steel manufacture by 2035, for cement by 2040, and largely decarbonising all construction material manufacture by 2040.

By working to ambitious carbon budgets and using clear reporting parameters the project is being undertaken sensitively to address the challenges of global climate change and demonstrating good practice in reducing the project carbon footprint. The objective is to capture, store and convey almost all the raw sewage and rainwater that currently overflows into the estuary. To optimise outcomes, the scheme employed industry-leading and innovative approaches to project planning and management.

Image credits: Tideway

illustration of three birds in navy

What it’s worth

Various initiatives within the planning and management of Tideway’s construction are estimated to have generated considerable carbon reductions. Careful selection of an optimal, shortest possible route for the tunnel led to a 19% reduction in material use with an estimated saving of 199,000 tCO2e.

The decision to transport materials primarily by river avoided an estimated 23+ million HGV kms to date, equivalent to a reduction of 14,500 tCO2e as well as 240 tonnes of nitrogen oxides. Reducing the thickness of the secondary lining in the tunnel’s central area alone resulted in 16,000 m3 less concrete being needed, saving 7,300 tCO2e by the end of March 2021.

Tideway is also working to support local communities through investment, job creation and new public spaces along the Thames. It was named Infrastructure Project of the Year at edie 2021 Sustainability Leaders Awards [source].

Image credits: Tideway