Project Overview

The £4.2bn Thames Tideway Tunnel project is the largest sewer improvement scheme undertaken in the UK for over a century.

The 25 km tunnel runs beneath the River Thames, connecting 34 existing combined sewer overflows owned and operated by Thames Water.

The Kirtling Street site, located on the south bank of the River Thames, forms part of the central and largest section of the Tideway project (£746m).

Joseph Gallagher Ltd was contracted to construct the launch tunnels for the two Central Section Tunnel Boring Machines.

Scope of Works

The project comprised:

Construction of 2 no. SCL tunnels, each 10 m internal diameter and 37 m long
Construction of 2 no. reinforced concrete portal frames (20 m × 16 m)
Installation incorporating approximately 280 tonnes of steel reinforcement
TBM launch enabling works, including launch rails and shove frames

The enabling works were delivered concurrently with the SCL tunnelling package, providing a significant programme benefit.

Challenges

Key challenges included the delivery of substantial underground structures within a constrained programme, requiring mobilisation of a large workforce operating 24 hours a day, seven days a week, across eight SCL gangs.

The works were constructed deep within the Lambeth Group, presenting highly variable ground conditions and unpredictable water ingress. Robust training, induction, and briefing processes were essential to maintaining safety and quality standards.

Delivery & Outcome

Through careful planning and collaborative working, the project was completed one week early, while maintaining high standards of safety and quality. A strong working relationship with FLO JV supported effective communication and delivery throughout the project lifecycle.

“Joseph Gallagher Site Management were open and honest, providing information and responding well to issues that occurred. They were always in attendance in the daily briefings (days and nights).”
Alan Hughes
FLO H&S Manager