2 Spills from Combined Sewer Overflows (CSOs) along the Thames degrade water quality and the environment of the tidal reaches of the Thames (the Tideway). In 1991, the European Union adopted the Urban Waste Water Treatment Directive (the Directive), aiming to protect the environment from waste water discharges, with member state compliance expected for large cities by 2000. The Directive does not specify thresholds for, or provide detailed guidance on, compliance for CSOs. In 2006, the European Commission issued a 'reasoned opinion' stating that the UK was failing to comply with the Directive's requirements for London. In 2010, the Commission started legal proceedings with the Court of Justice of the European Union, which in 2012 found the UK to be in breach owing to the frequency of spills from CSOs along the River Thames. This has meant that the UK was, and still is, at risk of infraction fines if the problem is not addressed.
3 The Department for Environment, Food & Rural Affairs (the Department) has overall policy responsibility for water and sewerage in England, and overseeing the English regions' compliance with European environmental directives.
4 Work has been ongoing since 2000, in part, aimed at achieving compliance with the Directive. Thames Water, a privately-owned company, is responsible for sewerage infrastructure in London, and for developing a solution to the problem of overflows. In 2000, it began funding research into a solution which reported in 2005. Because of implications for public policy, the Department developed strategic objectives for a solution: to secure compliance with the Directive, and to improve the environmental quality of the Tideway by reducing sewage overflows. The Department announced support for the Tunnel as a solution in 2007. In 2014, the Department added a third objective: to ensure sufficient strategic sewer capacity to accommodate London's growth for at least the next hundred years.
5 The Department intends that the project will be delivered and financed privately, although it has made a contingent financial support package available to secure this. Thames Water has planned the Tunnel and proposed its initial design; its customers will meet the costs through their water bills. Since our report in 2014:
• a specially-created private company, Bazalgette Tunnel Limited (Bazalgette) - trading as 'Tideway' - has successfully bid to design, build, own, maintain and finance the Tunnel;
• a regulatory framework has been established covering Bazalgette;
• the government has provided a package of contingent financial support - the Government Support Package (GSP);
• the project has received development consent; and
• Bazalgette started work on various sites during 2016. The Department expects tunnelling to be completed by 2021, and fully operational in 2024 at the latest.