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Sewer Overflows (River Thames)

Volume 458: debated on Thursday 22 March 2007

Since 2000 this Department has been involved in the development of options to improve the water quality of the tidal Thames by addressing the environmental impact of large volumes of sewage overflow discharges. The overflows, which are made up of sewage and run-off rainwater, are an integral part of the sewer network, originally designed by the Victorian engineer Sir Joseph Bazalgette, to convey sewage to east London, where it now receives treatment at Beckton and Crossness.

It is estimated that annual overflow discharges from the sewers and the sewage treatment works to the tidal Thames and River Lee amount to around 52 million cubic metres. This would be enough to fill the Albert Hall 525 times. Of this 32 million cubic metres is discharged from the sewer network overflows, and 20 million cubic metres from the sewage treatment works (Crossness and Mogden).

These overflows are having an adverse effect on the environmental quality of the Thames. It has been found that the frequent overflows (on average once a week), and the large quantities of untreated discharges are causing:

adverse environmental impacts on fish species;

unacceptable aesthetic issues; and

elevated health risks for recreational users of the Thames.

The Department has already been involved in decisions to significantly increase the secondary treatment capacity at Beckton, Crossness and Mogden sewage treatment works. The expenditure is planned through Thames Water’s existing (2005-10) and assumed (2010-15) investment programme, and the schemes are expected to be completed by March 2012 (Beckton and Mogden), and by March 2014 (Crossness). But this does not address the fundamental problem of discharge overflows into the River Thames and River Lee.

On 27 July 2006 I wrote to Thames Water, the sewerage service provider for London, requesting a detailed assessment of two short-listed options to tackle sewer overflows to the tidal Thames and River Lee.

The two options assessed were: 1) a single tunnel, over 30 km long, to intercept discharges from unsatisfactory overflows along the length of the tidal Thames and to the River Lee; 2) two separate shorter tunnels in West and East London to intercept overflow discharges along those stretches of the river. Both options were to convey the collected sewage for treatment in East London.

I have carefully considered the reports Thames Water submitted to me at the end of 2006, and met with stakeholders, who were involved in this work, to hear their views. A Regulatory Impact Assessment has been completed and is available on the DEFRA website.

Today I am announcing the Government decision for an option 1 type solution. As part of the overall scheme I am asking Thames Water to limit overflow discharges from Abbey Mills Pumping Station in East London first, as it is responsible for around 50 per cent. of the total volume of overflow discharges.

This approach is needed to provide a River Thames fit for London in the 21st century and to meet the statutory requirements of the Urban Waste Water Treatment (England and Wales) Regulations 1994. Construction of such a major infrastructure scheme may well cost at least £2 billion, which will be funded through the bills of Thames Water customers and take until 2019-20 to deliver. Depending on how the planning and funding applications progress, indications are that customers bills for this project will start to increase from 2010. It is estimated by the Water Services Regulation Authority that the peak impact on average customer bills could be £37 in 2017.

Thames Water, the Environment Agency, the Water Services Regulation Authority and others will be taking this forward for planning and funding applications. Government will be closely following this detailed work as it develops.