Tideway confirms smaller cost hike than previously feared

Tideway’s interim report, published today, confirms that the project cost estimate is £4.2bn and that the estimated £20-£25 annual cost range for Thames Water bill payers remains unchanged.

This represents an approximate 1% increase in costs (£39M).

In July modelling carried out by Tideway had shown that in a worst-case-scenario the cost of the project could rise by an additional £300M to £4.4bn. A second “plausible downside scenario” recorded a 12% increase in remaining costs which would take the total to £4.3bn.

Overall, Tideway remains on track to deliver the project by 2025, following the most substantial review of the programme since 2018.

The review, undertaken collaboratively by Tideway and key stakeholders including its main works contractors and Thames Water, looks at progress made on the project so far, taking into account the impacts of the Covid-19 pandemic, and provides an up-to-date picture of the future schedule.

Key achievements in the period included the completion of shaft excavation on all sites and completion of 9.8km of tunnel secondary lining. Almost 24km of the new tunnel system has now been excavated under the River Thames.

Tideway has also started its process of handing back areas where it has finished work, with a section of land at Hammersmith Pumping Station having been successfully handed back to a residential developer.

With the remaining tunnelling, secondary lining of the tunnels and shafts and the connections to the Thames Water sewer network progressing well, the verified programme provides confidence the project will be completed in 2025.

Tideway chief executive Andy Mitchell said: “Working closely with our contractors and Thames Water has allowed us to look in detail at our progress so far and what we need to do going forward, to complete our project and start tackling sewage pollution in the River Thames as soon as possible.

“This comprehensive review has reaffirmed confidence in our programme as we reach the end of the tunnelling phases and look ahead to the testing and commissioning stage. We are fully focused on delivering the Tideway project safely, at the right quality and to best value.”

Thames Water chief executive Sarah Bentley added: “This joint review of progress is a positive step forward in the delivery of the Thames Tideway Tunnel. Our teams are focused on working together to complete the project and bring the tunnel into service – so that it can do the vital job of improving the health of the river Thames and London’s environment.”

The new sewer is designed to capture more than 95% of the sewage spills that enter the river from London’s Victorian sewer system. It will have a significant impact on the water quality, making it a much healthier environment for wildlife to survive and flourish.

To date, Tideway has transported more than 5M.t of material by river during construction, avoiding more than 600,000 HGV journeys and saving 14,816t of carbon dioxide emissions.

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