From the base of the site's drop-shaft, some 41m below ground, the team used a sprayed concrete lining method to dig the tunnel. This technique involves spraying the excavated ground with concrete to form the primary lining.
At 250m, this is the longest connection tunnel on the project built using this method, and the final connection from a shaft base to the main tunnel on the central section.
Once the system is operational, raw sewage that has been dropped to the base of the shaft will run through the connection tunnel and into the new super sewer, where it will travel east to Beckton Sewage Treatment Works.
A concrete secondary lining will now be cast on top of the sprayed concrete lining to protect the tunnel against erosion when sewage passes through it.