Are the Thames and Lee Tunnels really needed?
In March 2007, the Government gave us the go-ahead to design a tunnel solution to substantially reduce the amount of untreated sewage which overflows into the River Thames and River Lee from London’s Victorian sewers. These overflows can occur after as little as 2mm of rainfall. Currently, the overflows occur more than once a week on average, via 57 combined sewer overflows (CSOs), which were designed by Victorian engineer Sir Joseph Bazalgette over 150 years ago. They discharge 39 million tonnes of untreated sewage into the River Thames in an average year, and up to three times more in wetter years. The overflows create health risks to river users, endanger wildlife and release tonnes of ‘sewage-derived litter’ into the river, such as condoms, sanitary products and toilet wipes. In order that the UK complies with the Urban Wastewater Treatment Directive (UWWTD), the frequency of these discharges cannot be allowed to continue at their current rate.
