Water Quality - Sewage Treatment
Update on progress towards a solution to combined sewer overflows affecting water quality in the Thames Tideway and River Lee
Introduction
The sewage systems serving London along the tidal Thames are largely combined systems which collect domestic and industrial sewage and rainwater run-off and convey it to sewage works for treatment. It is normal for such systems to allow excess flows to discharge direct to the water environment during rainfall, primarily to prevent flooding of properties, and sewage treatment works from becoming overloaded.
In February 2005 following a five year study, a report concluded that overflow discharges were having an adverse effect on the tidal Thames. Work on finding a solution has progressed substantially since then. Two short-listed options (PDF 20 KB) were assessed in detail by Thames Water before the decision reached by Government on the solution.
Ian Pearson, Minister of State for Climate Change and the Environment announced in a statement to Parliament on 22 March that he is asking Thames Water progress the chosen solution to planning and financial approval stage.
Proposed solution
The chosen solution, illustrated below, includes an early phase construction of a link tunnel to transfer sewer overflows from Abbey Mills for treatment at Beckton. Once complete, this phase of the overall solution to Tideway overflows will contribute significantly to reducing the volume of sewer overflows, as Abbey Mills pumping station discharges fifty per cent of the annual volume of sewer overflows affecting the tidal Thames.
Further information
The future
Ian Pearson will be writing to Thames Water outlining the next steps. Defra will continue to work closely with Thames Water to see this scheme through the early stages of initiating the work. This will entail six monthly reports on progress and where needed, meetings for example to report problems or issues delaying the delivery timetable.
2012 London Olympic and Paralympic Games
As mentioned above, the early phase work will involve construction of a link tunnel from Abbey Mills to Beckton to collect the large and frequent discharges occurring at Abbey Mills. Thames Water has been asked to proceed with this work quickly to meet the requirements of the Urban Waste Water Treatment Directive as soon as possible.
Consideration has also been given to whether the Abbey Mills to Beckton link tunnel could be completed by the time of the Olympic and Paralympic Games. However this is a large and complex project likely to entail use of established technology but at an unprecedented scale in this field of operation. This carries high risks of delays occurring which could significantly affect planned delivery timetables.
In case a permanent solution to Abbey Mills discharges cannot be in place by the time of the Olympic and Paralympic Games, interim contingency measures to mitigate the effects of the discharge are being investigated in parallel.
Page last modified: 22 March 2007