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Sewerage System (London)

Volume 450: debated on Wednesday 11 October 2006

To ask the Secretary of State for Environment, Food and Rural Affairs (1) what representations he has received, and when, from the Mayor of London regarding investment to modernise London’s sewerage system; (91812)

(2) when he expects to reach a decision regarding the proposed Tideway sewerage scheme;

(3) how much sewage has entered the River Thames via storm overflows in each month since 2003;

(4) what measures are in place to assess the amount of sewage entering the River Thames via storm overflows.

The Department has received two letters (15 November 2004 and 20 June 2006) from the Mayor of London which raised the issue of funding for the London sewerage system.

I expect to decide on a scheme to limit pollution from some of the sewer overflows in early 2007. This will then be taken forward for planning and funding applications.

The Department has already been involved in decisions to address the issue of storm overflows at three London sewage treatment works. As a result, several major schemes, involving substantial expenditure, are planned through Thames Water over the next eight years, to significantly increase the secondary treatment capacity of these works (Beckton, Crossness and Mogden). These schemes will reduce overflow discharges, thereby protecting the fish species and environment of the River Thames.

It is estimated that the total annual overflow discharges from the sewers and the sewage treatment works are around 50 million cubic metres. It is calculated that 32 million cubic metres is discharged from the sewer overflows, and 20 million cubic metres from the sewage treatment works (Crossness and Mogden). As aforementioned, work is in hand to significantly reduce overflow discharges from these sewage treatment works.

For the monthly calculated volumes of untreated sewage discharged to the Thames from the sewer overflows from January 2001 to October 2004, I refer the hon. Member to the answer given on 15 December 2004, Official Report, column 1112W. The calculated monthly volumes of untreated sewage discharged to the Thames Tideway from sewer overflows from 2004 to October 2006 are as follows. It is estimated that these volumes represent 60 per cent. of the total discharged from London’s combined drainage system at these times.

Monthly discharges from storm water overflows to the estuarine Thames from 2004 to October 2006

Cubic metres

2004

2005

2006

January

9,281,000

288,200

1,289,002

February

3,240,000

300,024

2,252,695

March

44,000

1,933,298

841,200

April

3,665,000

1,203,959

497,881

May

3,268,000

n/a

4,570,477

June

3,047,000

1,453,368

1,780,518

July

1,260,000

744,100

n/a

August

4,945,000

1,669,002

1,688,862

September

446,000

1,918,585

4,993,643

October

4,290,000

4,227,192

815,329

November

268,000

200,250

n/a

December

4,437,960

2,581,888

n/a

For January to October 2004 the volumes in the table are as in the answer given on 15 December 2004, Official Report, column 1112W. November 2004 in the table represents a more up-to-date figure than that given in the answer of 15 December 2004.

Volumes are calculated from the pumping records of the five largest pumping stations during wet weather. The calculation is the duration of spill events multiplied by the pumping rate of each of the pumping stations.

Overflow discharges from the sewers are calculated from wet weather pumping records of the five largest pumping stations, and an estimate of the wet weather discharges from the other overflows. Flow monitoring at the sewage treatment works provide measurements of their overflow discharges.

To ask the Secretary of State for Environment, Food and Rural Affairs (1) what assessment his Department has made of the public health risk posed by sewage entering the River Thames; (92112)

(2) what recent estimates his Department has made of the number of fish killed by sewage entering the River Thames; and what assessment the Department has made of the broader environmental impact of such sewage.

Public health risk, fish kills and the broader environmental impacts of overflow discharges of sewage entering the Thames have been assessed by the Environment Agency in the development of the objectives for the Thames Tideway Strategic Study. The Steering Group Report, published in February 2005, provides the information and is available from the Thames Tideway Strategic Study website at www.thamestidewaystrategicstudy.co.uk

The Environment Agency continues to consider and assess these issues as part of the options assessment work, led by Thames Water, that I announced on 27 July 2006.