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Published on Sep 13, 2010
London's Victorian sewerage system was designed to overflow into the River Thames during extreme weather when the sewers reached capacity, to prevent homes and streets from flooding.
The system is struggling to cope with the demands of 21st century London, and discharges are now happening much more frequently - around once a week on average. In an average year, 39 million tonnes of sewage is currently discharged into the River Thames.
Thames Water has developed three major engineering schemes to help stop sewer overflows and improve water quality in the River Thames. Two of these schemes are already under way - including the £675m upgrade of London's five major sewage works and the construction of the £635m Lee Tunnel, which will help prevent 16 million tonnes of sewage annually overflowing into the River Lee. The final and most challenging of the three schemes is the proposed Thames Tunnel.