The Thames Tideway Tunnel is a large sewer proposed by Thames Water that will run underneath the Thames through central London that has been dubbed the ‘supersewer’.


Its main purpose is to stop sewer outfalls along the Thames discharging into the river when they overflow (usually during heavy rain), and to discharge into the sewer instead. 57 sewer outfalls do this, and the tunnel will address the 34 worst of these.

The main tunnel will run under the Thames from Hammersmith to Rotherhithe, veering north via the Limehouse Cut and terminating at the Abbey Mills Pumping Station near Stratford. It is to be 7.2 metres in diameter and run from 30 metres below the river in the west to 65 metres below in the east.

Connecting tunnels will run from the main tunnel to existing sewer outfalls along the banks of the Thames and further inland. There will be construction sites and additional permanent infrastructure at 21 of these sites, some involving structures built into the river.


Although the main tunnel will run underneath the River Thames, land will be acquired at each of the 21 surface sites – usually a larger area temporarily for construction, and a smaller area permanently to house various structures. Land will also be acquired underground for the connecting tunnels.

The main effects of the project will be the compulsory acquisition and temporary occupation of land (around 28,000 parcels of land are affected); the environmental effects of construction such as noise, vibration and dust; road closures and other access restrictions; and the environmental effects of operation such as noise and odour. Property values may decrease temporarily or permanently. Thames Water estimate that the construction phase will commence in 2016 and last 6 to 7 years.

The construction of the main tunnel and the larger of the connecting tunnels will cause settlement of the land above. Thames Water are likely to follow the example of Crossrail and offer landowners a ‘settlement deed’ that sets out a protocol for assessing and paying for any damage caused to buildings by the boring of the tunnel.


The Thames Tideway Tunnel has been designated as a Nationally Significant Infrastructure Project and Thames Water’s application for consent to proceed with the project is therefore being considered by the Planning Inspectorate and will be decided by the Secretary of State under the provisions of the Planning Act 2008. The application was made on 28 February 2013.

There is a statutory process for consideration of the application, including opportunities for landowners and other interested parties to make representations, which is likely to start in April and last around nine months. Parties may make written representations and attend ‘open floor hearings’ to put their case forward. If your land is being compulsorily acquired, you may attend and speak at a ‘compulsory acquisition hearing’.

A decision on whether to grant consent will be reached within the six months following that examination period. There will also be issue-specific hearings on particular topics such as noise or traffic impacts.