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Connection tunnel breakthrough at Carnwath Road

A significant milestone for London’s ‘super sewer’ has been achieved at the Carnwath Road Riverside site in Fulham with the breakthrough of the West main tunnel connection into the Central section.

The breakthrough of the 75m connection tunnel, which has been constructed to join these two sections, brings all three sections of the new Thames Tideway Tunnel together as one.

When a change was needed to the arrival into the Carnwath Road shaft by Tunnel Boring Machine (TBM) Millicent, the teams came together to deliver a solution. Working alongside the West section Joint Venture of Balfour Beatty, Morgan Sindall, and BAM Nuttall, Tideway determined that the best course would be to ‘turn and bury’ the TBM and for a connection tunnel to be constructed from the Carnwath Road shaft to the main tunnel.  

The final connection between the sprayed concrete lined tunnel and the segmental tunnel involved the West section team carefully breaking out the precast tunnel segments and forming an enlargement around the segmental interface ring. Prior to the works starting the team carried out a full scale trial of the connection to ensure that the they could achieve the quality required.

Works on the connection tunnel started in January this year and the breakthrough was achieved in mid-July.

Twenty kilometres of the 25-km 'super sewer' have been constructed with secondary lining underway. Tunnel Boring Machine Selina is tunnelling the final section from Chambers Wharf in Bermondsey to Abbey Mills Pumping Station.