The Thames Tideway Tunnel project will upgrade London’s sewerage system to cope with the demands of 21st Century London.
Starting in west London, the proposed route for the main tunnel generally follows the route of the River Thames to Limehouse, where it then continues north-east to Abbey Mills Pumping Station near Stratford. There it will be connected to the Lee Tunnel, which will transfer the sewage to Beckton Sewage Treatment Works.
The volume and frequency of untreated sewage overflowing into the River Thames is clearly unacceptable and also contravenes the European Urban Wastewater Treatment Directive.
We have worked with the Environment Agency to identify the most polluting combined sewer overflows (CSOs) – the ones that cause unacceptable environmental impacts because of the frequency or volume of the overflow, or because they discharge into an environmentally sensitive part of the river.
The project will address the overflows from these CSOs, either by directly connecting them to the tunnel, or by making other alterations to the sewerage system which will utilise the existing capacity more effectively.
The flows diverted into the tunnel will be stored in the tunnel and pumped out for treatment at Beckton Sewage Treatment Works in east London.
The CSOs will still be needed after the Thames Tideway Tunnel has been built to direct flows to the River Thames in exceptional circumstances when the new tunnel system is full. This is only expected to occur very occasionally.
The Thames Tideway Tunnel will improve the quality of the water in the River Thames, bringing significant benefits to the environment and river users.
We looked at a number of different ways to reduce the amount of untreated sewage that overflows into the River Thames from London’s Victorian sewerage system. For more information see our project information paper Options below.