London’s water and wastewater system provider, Thames Water, is improving its water quality through a three-stage upgrade. After redeveloping its clarification plants and opening the Lee Tunnel, a combined facility for storage and the conveyance of sewage mixed with rainwater in the east of the city, now the Thames Tideway Tunnel is being tackled. It is the biggest project, entailing investments of ca. 4.2 billion pounds sterling. As from 2023, it is intended to carry sewage from 34 of London’s largest combined sewer overflows over a length of 25 km, store and transfer it to Lee Tunnel. The article in tunnel 8/2016 describes the main construction measures and special features of the Thames Tideway Tunnel, particularly the West Section.