The Thames Tideway Tunnel (Tideway) is a new investment in the London sewer network, which will carry sewage and storm water discharges from the existing sewerage network.

Thames Tideway-sml.jpg
Thames Tideway-sml.jpg
Financial close
Concession term


A 25km long, 7.2m diameter tunnel running up to 65 metres below the river Thames, replacing the Thames as a "sewer of last resort”. The Thames Tideway Tunnel will transport overflow sewage to a pumping station located at Abbey Mills (East London) before final treatment in Beckton Sewage Treatment Works.

The tunnel will be built under three separate construction contracts, each covering a distinct physical section of the network. Construction activities are expected to complete in 2024. The tunnel will cost £3.8bn to complete, and an additional £1.1bn has already been spent by Thames Water for preparatory works.


Length of sewer


Diameter of new tunnel



Project highlights include: 

  • A yielding investment through both construction and operating periods
  • A fully RPI-linked revenue stream
  • An investment grade rated entity that will be regulated by Ofwat
  • Strong protections to mitigate construction risks, including:

    • Experienced management team, project manager and construction contractors
    • Significant incentive arrangements under the construction contracts, Licence and stakeholder arrangement
    • A government support package which provides significant mitigation to the risks of construction
    • Limited operational risks.

More details can be found on Tideway's website