Are the London Tideway Tunnels really needed?
The two proposed tunnels are needed to substantially reduce the amount of untreated sewage overflowing into the River Thames from the capital’s Victorian sewers after rainfall. Currently the overflows occur more than once a week on average, via 57 ‘Combined Sewer Overflows’ (CSOs), which were designed as an integral part of the capital’s original network by Sir Joseph Bazalgette over 150 years ago. Annually, they now discharge an estimated 32 million cubic metres of untreated sewage into the river, enough to fill The O2 arena 15 times. They can occur after as little as 2mm of rainfall. The overflows create health risks to river users, endanger wildlife and release tones of ‘sewage-derived litter’ into the river. The CSOs were an integral feature of the way the sewer system was designed 150 years ago. At that time the River Thames was almost entirely ‘dead’. There were also much fewer people in London using less water per head. Additionally there was more green space available to soak u
