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London's £4.5bn Tideway super sewer now complete

  • London's £4.5bn Tideway super sewer now complete
    Credit: Tideway

The construction of London's Thames Tideway, a state-of-the-art sewer system costing £4.5 billion (US$5.6 billion), has reached its conclusion, Tideway announced last week. The final milestone was marked by the installation of a massive 1,200-ton concrete lid, sealing the deepest shaft of the project.

The Thames Tideway Tunnel is a 25km-long sewage tunnel designed to dramatically reduce sewage pollution in the central London River Thames. 

In a typical year, tens of millions of tonnes of storm sewage spill into the River Thames. Once fully operational, the new infrastructure will reduce those spills almost completely.  

Tideway, the company building the super sewer, has now built the full 25km, 7.2m-wide main tunnel, a 4.5km connection tunnel in south-east London, and a 1.1km tunnel in south-west London.  

Andy Mitchell, CEO of Tideway, said: “This is the moment we’ve all been waiting for. The underground civil engineering on the Tideway project is now complete following eight years of dedicated hard work from all our teams working in the capital.  

The final milestone was marked by the installation of a massive 1,200-ton concrete lid, sealing the deepest shaft of the project

“There is still work to do – we need to finish some above-ground structures and, crucially, test the system – but this nonetheless marks an absolutely critical milestone for the Tideway project and for London.” 

The tunnel, descending up to 67 meters underground, spans from Acton in the west to the Abbey Mills Pumping Station in Stratford to the east.

Over 30 combined sewer overflows (CSOs) will be rerouted from the sewerage network into the primary tunnel, directing the flow to the Tideway Pumping Station for eventual transport to Beckton sewage treatment works. Utilizing tunnel boring machines (TBMs), the main tunnel construction comprised four drives from three primary sites, with primary tunnelling concluding in April 2022.

The eastern section of the project has been managed by a collaboration between Costain, Vinci Construction Grands Projets, and Bachy Soletanche. In the central section, Flo, a joint venture between Ferrovial and Laing O’Rourke, has led the efforts. The oversight of the western section has been under the responsibility of BMB, a joint venture between Bam Nuttall, Morgan Sindall, and Balfour Beatty.

Tideway will now begin the process of ‘commissioning’ the system – ensuring the new infrastructure functions as designed – before looking ahead to bringing it into full operation in 2025.  

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