Thames Tideway Tunnel: purpose, overview, delivery model and financing

Fully operational in August 2025, the £4.6 billion Thames Tideway Tunnel project is one of the largest and most complex civil engineering schemes in the world. The project is a deep-level collect, store and transfer tunnel system for combined sewer overflow control in London, UK, to improve the health of the tidal River Thames. This paper reports on the purpose of the scheme, an overview of technical solutions, the delivery model used and how the project was financed.