An unprecedented project to clean up the Thames and make it fit for the 21st century was today announced by Environment Minister Ian Pearson.
A single 30km long tunnel is planned to intercept sewage and rain water discharges along the length of the river and transport the waste water for treatment in East London. It would be the largest such project ever undertaken in this country.
London's current sewer network, which was built by Joseph Bazalgette in the second half of the 19th century, was hailed as a major engineering achievement in its day and collects sewage and rainwater runoff together.
Today, with the climate changing and the city expanding, the system is under pressure and 52 million cubic metres of untreated sewage and rainwater pollute the Rivers Thames and Lee each year - enough to fill the Albert Hall about 525 times. Of this, 32 million cubic metres comes from sewer network overflows, which provide the only safety valve to prevent the overloaded system from backing up and flooding homes and streets.
The discharges kill fish, create a higher health hazard for users of the river and damage the aesthetic appeal of the Thames, reducing its attractiveness to tourists.
Commenting on the project, which is estimated to cost at least £2bn, Ian Pearson said:
"I think most Londoners would be shocked to hear that, because of an historic but increasingly outdated sewer network, a huge amount of untreated sewage and rainwater is spilling into the Thames at least once week. This is unacceptable.
"This tunnel is the right solution for London and for the environment. It will give us a 21st century River Thames that we can all be proud of."
Today's announcement follows six years of detailed work by a range of specialists. In particular, the reports by the Thames Tideway Strategic Study, the independent review by consultants Jacobs Babtie, and the reports recently completed by Thames Water have been instrumental in helping determine the solution. All recommended a major tunnel under the Thames.
The project is expected to be delivered by 2019/20. The economic regulator Ofwat will be tasked with ensuring that it is delivered cost effectively. It is estimated that it will add around £37 to Thames Water sewerage bills by 2017.
Work will now go ahead on further detailed design, planning and funding.
Ian Pearson added:
"We haven't reached this decision in a vacuum. A wide range of players have been instrumental in getting us to this point and I thank them all.
"Of course this is only the beginning of a long and challenging project and I have every confidence that this co-operation will provide a solid foundation as we now work towards delivering the new tunnel for London.
"This will inevitably mean some extra costs for customers, but it will deliver tangible benefits for London in the long-term."
In addition to improving the environmental quality of the Thames, the scheme will also help meet European obligations on sewage treatment.