Thames Water’s plans for a tunnel to reduce the amount of raw sewage discharged into the River Thames have been given the support of UK environment secretary Caroline Spelman.
The core of London’s sewage network was designed in the late 19th century and was intended to overflow at times of heavy rainfall to ensure that sewage did not back up into houses and streets. Combined Sewer Overflows (CSOs) were intended to discharge the raw sewage into the Thames in the event of extremely heavy rain.
Increasing populations and changes to land use in London have led to this occurring around 50 times a year. With further population growth and projected climate change, this figure is expected to increase in coming decades and spills could occur when there is very little rain. This also creates problems for the UK’s continued compliance with EU wastewater treatment regulations.
On 22 March 2007, the then minister for climate change and the environment announced his support for a tunnel to solve the problem in the Thames and asked Thames Water to take forward the design process for the Thames Tideway Project, which includes the Thames Tunnel.
Thames Water estimates that the proposed tunnel will cost £3.6bn, which could result in increases of around £60-65 a year in the bills of Thames Water’s customers.
Caroline Spelman said: ’A tunnel continues to offer by far the most cost-effective solution to the unacceptable problem of raw sewage being regularly discharged into the Thames. This is a large and complex project and I recognise that it comes at a significant cost. I will ensure that Defra and Ofwat continue to scrutinise the costs and options to ensure that Thames Water’s proposals represent proper value for money.’
Thames Water will shortly launch a consultation exercise on the need for the tunnel, the route and the sites needed to construct and operate the project. Defra carried out an Impact Assessment in 2007 and will update this before publishing the revised version of the document on the Defra website.