London’s water and wastewater system provider, Thames Water, is improving its water quality through a three-stage upgrade. Thames Tideway Tunnel is intended to carry sewerage from 34 of London’s largest combined overflows over a length of 25 km, store and transfer it to Lee Tunnel from 2023 on. The main tunnel will have an internal diameter of 7.2 m and start at a depth of approx. 30 m in Acton. From there the tunnel follows the course of the Thames through and under London’s central business district and terminating at a depth of 70 m at Abbey Mills Pumping Station.