London’s Sewers and the Thames Tideway Tunnel, St Albans

23 February, 2017 | 18:00 - 20:00

Victoria Embankment shaft.
Victoria Embankment shaft.

About this event

As chief engineer to London's Metropolitan Board of Works in the mid-19th century, Joseph Bazalgette had a significant impact both on London's appearance and, through his design of an efficient sewage system, on the health of its inhabitants.

In the 19th century, London suffered from recurring epidemics of cholera - 1831, 1848/49, 1854/55 (that of 1854/1855 killed more than 10,000 Londoners). The 'Great Stink of London' on the 30th June 1858, focused the minds of the occupants of Parliament to the challenge. The resulting legislation enabled the Metropolitan Board to begin work on sewers and street improvements. By 1871, with the completion of the sewers in the Chelsea and Victoria and Albert Embankments, most of London was connected to the sewer network devised by Bazalgette and at a cost of £4.6 m.

150 years on London's sewers are no longer big enough to cope. While they were built to serve London's population of the day of 2 million there was a built-in designed capacity to serve 4 million. The system of sewers now serves a resident population of 8 million (with a temporary working weekday additional transient population of perhaps 5 million). The under-capacity of the sewerage system results in an average of 40 million tonnes of raw sewage being discharged annually into the river.

Swere outlet into the Thames River.
Sewer outlet into the Thames River.

The 25 km Thames Tideway Tunnel now being constructed below the heart of London is the main feature of the infrastructure designed to tackle this urgent sewage pollution. The main tunnel's inner diameter will measure 7.2 metres. It will have a storage volume of 1.6 million cubic metres and will run up to 65 metres beneath the River Thames, largely following the course of the river. In joining up with the Lee Tunnel, already operational, it will transfer the excess sewage to Beckton Sewage Treatment Works. The upgrading of five sewage treatment works on the tidal Thames (by Thames Water) will deal with the demand for increased treatment capacity, while the Lee Tunnel and the Thames Tideway Tunnel will relieve the pressures on the trunk sewer system.

Tideway is the company delivering the Thames Tideway Tunnel.

Construction started in 2015 following confirmation of independent investors to finance and deliver the scheme. The scheme is scheduled for completion and commissioning in late 2023/early 2024.

The talk will provide a brief history of Bazalgette's work and be followed by an update of the talk given by Nick Butler in September 2014 on the TTT scheme together with an overview of current progress. As well as some of the engineering, stakeholder engagement and other challenges encountered the talk will discuss employment creation, gender equality, apprenticeships, educational opportunities particularly for STEM subject students and the creation of public land next to the Thames.


For further information please contact:

Andy Palmer
t: 01727 535764

Event materials

The following materials are available for download:


Ken Weeks

Ken Weeks

Retired, Fellow of ICE, formerly Director of Thames Water Drainage Services responsible for the sewerage network and associated sewerage pumping stations over the Thames Water plc area from 1982 to 1996.

Roles in Thames Water Authority: Reservoir Inspection, Project Management of Thames Tidal Defences, north bank. Flood Alleviation Schemes, Engineer to the contract for decommissioning sewage works at Heathrow 5th Terminal Site, past member Environment Agency Flood Defence Committee.

Previously with Port of London and Peter Fraenkel and Partners on Docks and Harbours works.

Nick Butler

Nick Butler

(TTT Project Sponsor - East): Nick is a Chartered Civil Engineer and Fellow of the Institute of Materials, Minerals and Mining with 15 years of tunnelling experience; he joined Tideway in September 2014.

Prior to this he worked on tunnels and major civil engineering works on mines in Australia, Channel Tunnel Rail Link (High Speed 1), Kings Cross Redevelopment project, Lee Tunnel and Deephams STW Upgrade project. Nick was responsible for the enabling works, obtaining planning permission, securing funding, procuring the main works contractor and relevant project insurances for Lee Tunnel before taking up a senior role during the construction phase of the project.