Is the Thames Tideway Super Sewer Futureproof?

London today is one of the world’s leading metropolitan cities, with 8+ million inhabitants, countless multinational companies, as well as being the official residence of the Royal family.

However, the city hasn’t always been the slick, efficient operation. In 1858, Parliament considered a move to Oxford because of something known as ‘The Great Stink’. Thanks to the lack of a proper sewerage system and the overcrowding that had beset the city, the smell of waste had reached unbearable levels for its residents.

Sir Joseph Balzagette’s ingenuity solved this issue, coming up with the blueprints for the first iteration of a combined rainwater/sewer system we have now used for over a century.

Over Capacity

Overflowing sewer

Fast forward to the present day and there is once more an issue regarding the way London’s wastewater is transported, with the House of Commons again wondering whether to undertake a significant relocation, this time of the waste itself.

It is London’s 57 ‘combined sewer overflow’ sites that are attributed with the problem, due to how much waste their emitting:

  • Hammersmith Pumping Station – 2,200,000 m3
  • Western Pumping Station – 2,040,000m3
  • Greenwich Pumping Station – 3,940,000m3
  • Abbey Mills Pumping Station – 18,820,000m3
  • This equates to a combined overflow of 39,500,000m3.

While they work without issue most of the time, come heavy rainfall the sewers have no other option but to overflow (by design) into the Thames, causing serious pollution issues. These 57 ‘CSOs’ were designed to overflow approximately 12 times when they were created in the 19th century, but today that number has climbed rapidly to on average 60 times a year.

As well as creating nasty smells and pollution problems, the excessive number of overflows also means that London is breaching the EU Urban Waste Water Directive.

The Thames Tideway Solution

Thames Tideway Tunnel

To combat such a problem, the Thames Tideway project was created, requiring years of planning and several more of proposed labour which is currently underway. At a cost of £4.2bn, the 25km, 7.2m diameter super tunnel will be constructed up to 65m below ground. The system will handle both sewage and rainfall, similar to Balzagette’s.

Running from Acton to Stratford, the majority of the tunnel will be located under the Thames (as the name suggests), aiming to collect and redirect the city’s (increasing) sewage output that has been of severe detriment to the environment of late.

The sewer is to be split into three parts: east, central and west. 2,500 people are working on the system, and off the back of the project there will likely be the creation of around 4,500 sustainable jobs once the project concludes in 2022/23.

In fact, some of the world’s biggest contractors have been attached to work on the project, including Laing O’Rourke and Morgan Sindall, and the innovative engineering and planning has meant that the proposed length of the tunnel was reduced to 25 kilometres from 32 kilometres in the design stage, with the total number of required construction sites down from 45 to 24.

Old vs New – see the infographic

Future Capacity

When the Thames Tideway is up and running, the volume of overflow discharge will be significantly reduced, down 94% at a combined overflow of 2,350,000m3.

Projections indicate London’s population will continue to grow at a fast clip, reaching 10 million by the mid 2020s. Fortunately the super tunnel, in all of its size and scope, has always had future-proofing in mind with considerations right down to the quality of concrete used bearing upon the ultimate lifespan. As a result, the Thames Tideway is expected to last at least as long as its predecessor; 120 – 150 years.


As London moves forward in countless industries, it is important that its contribution to the preservation of the environment is not neglected. The Thames Tideway is hoped to be a major step in the right direction, massively reducing the amount of waste that flows into the Thames from our homes and businesses and continuing to protect the River Thames from increasing pollution for decades to come. The financial cost of the project may seem startling, but the reductions in waste and pollution could prove to be priceless.

Want more information?Contact us today on 020 3124 1785

EDS unblocked and repaired over 20,000 drains last year for the residents and businesses of London.

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Category: General News


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