The secondary lining on the 7km western section of London’s new super sewer has been completed, marking a significant milestone for the Tideway project.

Secondary lining is required to provide additional strength to the super sewer and to create a smooth surface over which flows will travel once the sewer is operational in 2025.

Primary lining is created by placing precast concrete segments into place to form a ‘ring’; but secondary lining is poured wet, in situ, around a huge machine called a ‘shutter’.

The secondary lining works in the western section started in March 2021 and have required more than 800 individual concrete pours to make the journey from Acton to Fulham in south-west London.

The concrete was batched on site at the Carnwath Road Riverside site in Fulham and delivered to the six shutters by concrete trains known as bullets to a pump located on a logistics crossing within the tunnel.

Around 48,000m³ of concrete was used to create the secondary lining in this section of tunnel.

Project Director Sally Cox said “This is fantastic achievement for everyone involved.  I am in awe of the endless spirit and perseverance from the team to overcome challenges to deliver this phase of work. It is amazing what you can achieve when you have such a brilliant team.”

The main drive of the 6.9m internal diameter, 7km tunnel was completed by tunnel boring machine Rachel in late 2020 and the team are now preparing the site to undertake the secondary lining of the main shaft at Carnwath Road Riverside.