Thames and Tideway Tunnel 

London’s outdated largely 19th century sewerage system combines rainwater and foul sewerage into a single pipe. As a result of London’s expanding population and buildings, the system can no longer cope and it overflows into the Thames at times of heavy rainfall. Some fifty “combined sewer outfalls” carry this discharge. In order to provide for at least another century, Thames Water designed a tunnel to run from their Sewage Treatment Works at Becton in East London to connect with their Storm Water plant in Acton. This is intended to intercept 34 of those most offending outfalls and the diverted flows will be stored in the tunnel until pumped out for treatment at the Becton works.

The first stage of this massive structure (hardly less than the diameter of the Channel Tunnel) was launched at Becton in Feb 2012 and is currently boring its way under the Lee Valley. The line (mainly under the Thames) of the remainder is under consideration by the Planning Inspectorate, whose approval is awaited by Autumn 2014. If that is given, then it is intended that main tunnelling will begin in 2016 for completion in 2023.

A major contention has been the location of the construction shafts down which the plant materials and machinery will be lowered and operated and the excavated spoil removed. The preferred sites have been identified mostly near to the river where barges will deliver materials and into which liquefied spoil will be pumped for discharge down river. Our nearest outfall, which is south of the eastern tip of Chiswick Eyot, will be intercepted at source in Acton and may only ever discharge again in very extreme conditions.

There were originally six Tunnel Boring Machines working on the three tunnel sections, two of these have now finished including TBM Rachel. She crossed under our foreshore to run 80 ft beneath Eyot Gardens mid summer and has now reached her final destination in Acton. The work on linings and fitting out is (Dec 2020) in progress. Some rumblings at surface level have been reported probably due the installed railway delivering engineers, plant and equipment.

OCPS has been in touch with Thames Water about this project since inception and will continue so to do. For further information, contact Tony Taylor through this website.