Thames Tideway Tunnel
Sewage system being created for London, England / From Wikipedia, the free encyclopedia
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The Thames Tideway Tunnel is a 25 km (16 mi) combined sewer running mostly under the tidal section (estuary) of the River Thames across Inner London intended to capture, store and convey almost all the raw sewage and rainwater that currently overflows into the estuary. These events occur when rainfall volumes exceed the capacity of Bazalgette's and other engineers' London sewerage system. The tunnelling phase of the project was completed in April 2022;[3] construction ended in March 2024 ahead of a testing and handover phase expected to conclude in 2025.[4]
Overview | |
---|---|
Location | Greater London |
Status | Completed |
Start | Acton, London |
End | Lee Tunnel, Abbey Mills, between Hackney and Stratford, London |
Operation | |
Work begun | 2016[1] |
Constructed | Various (see article) |
Opens | 2025[2] |
Owner |
|
Operator | Bazalgette Tunnel Ltd |
Character | Combined sewer |
Technical | |
Design engineer | Various (see article) |
Length | 25 km (16 mi) |
Highest elevation | −30 m (−98 ft) at Acton |
Lowest elevation | −70 m (−230 ft) at Abbey Mills |
Width | 7.2 m (24 ft) |
CSOs intercepted | 34 |
Cost | £5 billion (2024 estimate) |
Bazalgette Tunnel Limited (BTL) is the licensed infrastructure provider for its finance, building, maintenance and operation. It has as investors: Allianz, Amber Infrastructure, Dalmore Capital and DIF. Since the licence award, it also trades as Tideway. On 3 November 2015, the award was made by Ofwat, ensuring the start of the project.[5]
Started in 2016, the project was due to be completed by 2024.[1][6][7] The COVID-19 pandemic delayed this to early 2025.[2] The main tunnel has an internal diameter of 7.2 m (24 ft) and runs from −30 m (−98 ft) at Acton in the west of London for over 25 km (16 mi) across the full width of Inner London finally reaching −70 m (−230 ft) at Abbey Mills in the east.
This tunnel will drain 34 of the most polluting combined sewer overflows (CSOs) and has been forecast to lead to the overflows operating for 3.7% of the time on a maximum of four days per year at the time of commissioning.
The tunnel will transfer the combined sewers water to the Stratford to East Ham Lee Tunnel for onward delivery to Beckton Sewage Treatment Works. Following treatment the water will then be released into the Thames Estuary.
The estimated capital cost – excluding financing, operations and maintenance – was £3.8bn with an additional £1.1bn for preparatory works.[8] Due to the COVID-19 pandemic, additional costs of £233m were incurred.[2] The 2021-22 annual report gave an updated cost of £4.3bn.[9] The final cost was £5bn.[4] It is set to become fully operational in 2025.[4][10]
Its outfall, the Lee Tunnel, runs deep under the London Borough of Newham to Beckton Sewage Treatment Works.