"To prevent pollution of the River Thames and increase its community relationship with Londoners" is a strong driver for the success of Tideway explained Roger Bailey, Chief Technical Officer of Tideway, at the IET Central London Network evening lecture webinar, hosted by David Tabor IET Central London Chair.

In 1858 the Thames had high levels of pollution to which parliament decided to introduce a sewer pumping network, this became known as the Bazalgette System after its creator. In 1860 London had 2 million people, in 1920 had 4 million, in 2019 had 8.8 million and by 2160 its population is expecting to have 16 million. Currently, during high rain flow, flat valves allow water to overflow into the river where 40 million raw cubic meter of sewage contaminates the river creating ecological harm - that is filling up Wembley Stadium 40 times explained Roger.

The Tideway project is set to change that by upgrading sewage tunnels at a cost of £4.1 billion whose operations will be run by joint controller companies on project end. This new tunnel has its own 'Tideway Route Map', up to 66 meters deep and 7.2-meter-wide tunnels with a 1.6 million cubic meter peak capacity where the 25km long tunnel will be ready to take overflow from major storms. The tunnel is designed to prevent the build up of air-pockets as the water overflow runs through the vortex chamber - which has been designed with innovative hydraulic modeling methods. The collective tunnel spans from west London to east London and currently tunneling is expected to end in 2022, followed by System commissioning in 2023 and final handover in 2025 to controlling entities - currently the project has used 21 million work hours! Interestingly, the international 'Green Bond Market' has generated investments as this is a sustainable project that has long term community considerations such as;

· Environment: Lower carbon footprint methods to promote air quality considerations during and after project end.

· Health, Safety & Wellbeing: Creation of an 'Induction Center' that focuses on medical health issues.

· Economy: Community based projects.

· People: Collaborating with 'MatesInMind' who are a known construction industry mental health charity.

· Place: Public realm enhancements.

River jetties were used that allowed reduction in the number of road-side vehicles by 150,000. This then increased river freight traffic so the 'Thames Skills Academy' was created to ensure river standards can be met by the project. This also allowed skills to be enhanced as the project mandated that 1 in 50 staff should be apprentices. In total, 40,000 hours of STEM activity have been volunteered to date including visiting schools to explaining how 'engineering' is making a real difference across London, or explaining how for the first time the UK is using 900 tonne tunnel boring machines (TBM).

This lecture was packed with engineering facts that demonstrated the breadth and depth of technical expertise required to design a system expected to have a shelf life of 120 years. Incidentally, Roger explained that the old sewer is still in core use - this project just accommodates for overflow!

Re-watch the entire lecture here on our YouTube channel and listen to the QnA session to find out what happens with fatbergs, air quality and what is going to happen with the TBM's once the project is over (in 2025).

In 2017 Dr Sian Thomas, Head of Asset Management at the Thames Tideway Tunnel presented her updates which also covered control-systems and her update can be read here.


Robert Heaton