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Greener tunnelling for London’s super sewer

Thames Tideway montage


02 February 2021

The Thames Tideway Tunnel reached a significant milestone as the final tunnel boring machine (TBM) Selina broke ground to the east of Chambers Wharf on 8 January.

Tunnelling from Chambers Wharf towards Abbey Mills (Stratford) will connect into the Lee Tunnel towards Beckton. The TBM Annie, began tunnelling in Greenwich last December and will bore the connection tunnel into the main Thames Tideway Tunnel at Bermondsey (Chambers Wharf). Both tunnelling machines arrived by sea and Selina travelled up the River Thames, before being lowered into shafts.

Thames Water’s largest infrastructure project investment will install a new urgently needed sewer to protect the tidal River Thames from pollution and to modernise London’s Victorian sewerage network. It is a large complex programme to give the capital city a safer and more environmentally sustainable water infrastructure.

In 2015, Costain was awarded the £605 million contract for the East works package of the Thames Tideway Tunnel in London in Joint Venture (‘JV’) with VINCI Construction Grands Projets and Bachy Soletanche Ltd (‘CVB’). The programme remains on schedule despite the challenges faced in 2020 due to COVID-19 restrictions and the additional safety measures to keep the team safe. The team’s success is underpinned by their maturity in the use of digital technology, including social distancing watches and digital collaboration tools.

“The planning and delivery of these two TBMs is a major engineering and programme management achievement for the project team. Work has been focussed on the safe and efficient deployment of these machines, enabled by digital technology whilst minimising impact on our neighbours. It’s the first project of this scale and size undertaken in such a densely populated area, under the streets of London.”

Neil Grosset, deputy project director in the CVB joint venture

At Chambers Wharf, all tunnel segments are delivered by barge. Once all the gantries and component parts of the TBM are installed, the machine will be approximately 130m long, the same size as the platform at Bermondsey underground station.

Each assembled concrete tunnel ‘ring’ is comprised of seven segments measuring 1.5m in length. The Chambers Wharf Main Tunnel will have 21,413 segments and the Greenwich Connection Tunnel 18,372 segments.

At both tunnel drive sites, the spoil is processed in the slurry treatment plant and the resulting materials removed from site and used in nature reserve restoration projects to provide improved habitats for birds, invertebrates, and swamp vegetation.

As part of our greener programme delivery, we are implementing our More by River Strategy which aims to limit Tideway’s use of the road as much as possible, to increase safety and reduce congestion and air quality impacts around our sites.

As the tunnelling work progresses on the eastern section, there will be a number of barge operations to remove waste:

  • At Chambers Wharf, 1,500 tonne barges will keep over 35,000 lorries off London’s roads and save over 2,030 tonnes of CO2e
  • At Greenwich, Deptford Creek, a tributary of the Thames, will be used to remove tunnel waste by barge. The project has committed to transport 30% of tunnel waste by barge from Greenwich which will keep over 4,500 lorries off London’s roads and save over 280 tonnes of CO2e
  • Tunnel segments for the Chambers Wharf Main Tunnel will be brought to site by barge keeping over 6,000 lorries off London’s roads and saving over 820 tonnes of CO2e.

The joint venture, of which Costain has a 40% share, is expected to complete its programme of works in 2023.



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For press enquiries contact:

Alison O’Donnell, head of content at Costain
[email protected]

Notes to editors
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