Thames Sewer

Resist the Thames super sewer


As the Planning Inspector begins a consultation into the ‘Thames Tideway Tunnel’, Leonie Nimmo discovers that the battle for sustainable water systems in London has hit a crucial stage.


39 million tonnes of sewage are estimated to pollute the Thames each year.(1) But this isn’t just sewage, it’s sewage and rainwater. 

Heavy rainfall causes heavy leakage into the Thames, because London’s Victorian-era sewerage system combines both storm water drainage and the sewage system. Thames Water, the company responsible for the lion’s share of London’s sewage, admits that the root of the problem is this combined system. (2)

But its plans for the future involve the construction of a mega-project which will be exactly that – a 25 kilometre ‘super sewer’, known as the Thames Tideway Tunnel, which again combine the sewage and rainwater drainage systems. This is in contravention of European regulations which are designed to encourage separate systems. 

Campaigners point out that some countries have outlawed combined systems and in more modern areas of London, segregated sewers and stormwater drainage are already in place.

The green alternative Green stormwater infrastructure, as pioneered by the American city of Philadelphia, is a tried and tested alternative to the super sewer. This would involve smaller scale water management, intercepting stormwater and allowing it to be utilised, evaporate, or infiltrate the ground and rivers. This month the European Commission followed the lead taken by the United States and adopted a Green Infrastructure Strategy. A financing facility to pay for such infrastructure is to be established in 2014.

Thames Water has published a study which it claims indicates that such alternatives are too costly and impractical. There are, however serious question marks over this study. In a letter to DEFRA in December 2012, Lord Berkleley called for a new study to be conducted, using correct data and by an independent team.



Picking up the tab for the Thames super sewer 

Thames Water customers, which make up a quarter of the population of the UK, are likely to see their wastewater bills rise permanently by approximately 57% to pay for the sewer.(3)

In 2007, when the construction costs were projected to be £2-£2.5bn, the Consumer Council for Water estimated that nearly 50% of households with children in inner London could be in water poverty by 2017 due to rising water bills.

Moreover, with project costs now at £4.1bn, the Super Sewer would add to the already huge debts of Thames Water. This will be financed by a mixture of debt and equity. The company has failed to build up capital reserves to pay for the project, choosing instead to pay out big dividends to shareholders. 

Thanks to the Water Industry (Financial Assistance) Bill, passed by the coalition government last year, if the super sewer goes ahead British taxpayers will underwrite the un-insurable project, shouldering all the financial risks and receiving nothing in the event it should prove a success.



European pressure

Thames Water have argued that the Tideway Tunnel is necessary for compliance with the European Urban Waste Water Directive. But when advisers of the community organisation Thamesbank met with officials from the European Commission in March 2012, they learned that the opposite was closer to the truth and that, in the Commission’s view, the purpose of the Directive is to require sewage and stormwater to be separated at source. The Tideway Tunnel “is understood by the Commission to be antithetical to the spirit of the Directive”.(5)

Furthermore, the Tunnel is not expected to be operational for another ten years, during which time sewage will continue to flood the Thames and the country will be racking up fines for failing to comply with European pollution regulations.

Clean Thames Now and Always Thames Water gives the impression that construction of the Tideway Tunnel is a done deal, but in fact the government will not make a final decision until September 2014.

A campaign against the Tideway Tunnel is being run by Clean Thames Now and Always, who have a 38 Degrees petition against the project. They demand a clean Thames, delivered as soon as possible, at a cost affordable to all, in the most sustainable way and using intelligent, 21st Century green infrastructure.




[accessed 3rd June 2013]
2‘Project information paper’, Thames Water, Autumn 2011. Available from 
4 People in water poverty are defined as households with water charges in excess of 3% of disposable income after housing costs. 
5‘Legal Status of the Thames Tunnel Proposal in relation to the Urban Waste Water Directive’, Dr Benjamin Pontin, Environmental Law Unit, University of the West of England