The secondary lining works in the western section started in March 2021 and have required more than 800 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 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.

The main drive of the 6.9m internal diameter, 7km tunnel was completed by TBM Rachel in late 2020 and the site is now being prepared to undertake the secondary lining of the main shaft at Carnwath Road Riverside.

Six TBMs bored the 25km sewer, which will be operational in 2025.