London completes super sewer in fight against river spills

Tideway

A NEW super sewer that will prevent an estimated 95% of spills into the River Thames has been fully connected in London.

After ten years of construction, the final connections of the 25 km-long Thames Tideway Tunnel have been completed, bringing the full system online. Known as a super sewer, the new system features 21 connections to the original Victorian sewers, including at landmark locations at the starting point of the University Boat Race at Putney Embankment, and Blackfriars Bridge in central London.

Since autumn last year, when the super sewer first began being connected, the system has prevented more than 5.5m m³ of sewage from entering the river.

Sewage releases to UK rivers have become a major problem. During periods of heavy rainfall when water entering the system exceeds its capacity, overflows are allowed to divert sewage into rivers to prevent sewage backing up and flooding homes. However, a lack of investment in infrastructure has seen overflows used when there has not been significant rainfall.   

Tideway’s operator predicts the new system will prevent 95% of overflows.

Tideway CEO Andy Mitchell said: “Our next step is to test it in storm conditions – which is why we are keeping a close eye on the weather – and we will do this over the coming months.”

More than 20 deep shafts, some as wide as the dome of St Paul’s Cathedral – were constructed during the project to divert sewage and lower tunnelling machines into the ground.

Engineering firm Amey is now working on the integration of the process control and software systems needed for operation and reporting. This includes connecting existing instrumentation and control assets such as flow meters and level controllers to control centres, including integration with the existing SCADA system used by Thames Water which is set to take full control later this year.

David Black, CEO of water industry regulator Ofwat, said: “By optimising our innovative regulatory models, including learnings from Tideway's financing structure, we will unlock investment for the next generation of major water and wastewater infrastructure projects."

In January, the Environment Agency announced that it had secured an agreement from water industry companies to invest £22.1bn (US$27.9bn) in more than 24,000 interventions over the next five years to meet their legal environmental obligations. A list of the interventions, which include projects to remove nitrate and phosphorous from wastewater and investigating “emerging substances” of concerns including PFAS, are listed in a national dataset here.

The Environment Agency said it would work with other regulators to drive water companies to embrace state-of-the-art technologies and groundbreaking innovations to meet their obligations. It declined a request to discuss this in further detail and instead pointed to case studies submitted by industry. Industry has been asked to make engineers available who could provide more technical detail.

Last year, engineers assembled by the Royal Academy of Engineering published a report on actions to reduce the risk of harmful organisms polluting UK’s waterways and making people sick. This included increasing the capacity of the sewage systems, fixing leaks to the environment, and implementation disinfection processes at storm overflows.