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30% of Thames Water Outfalls Are Discharging Raw Sewage Into Rivers This Week

Published on: 11 Jan, 2023
Updated on: 11 Jan, 2023

By Hugh Coakley

Around 30 per cent of Thames Water outfalls have been spilling raw sewage into rivers over the last 48 hours since January 9, including into the River Wey in Guildford, a new interactive map of real-time discharges shows.

A warning on the map where there are raw sewage spills, including at Slyfield and Ripley, states: “This means there could be sewage in this section of the watercourse.”

Thames Water real-time interactive map shows around 30 per cent of their outfalls had raw sewage discharges into rivers this week (commencing January 9 2023). The red symbol shows discharge happening now and the amber shows spills within the last two days.

The Slyfield plant discharged untreated sewage for three and a half hours directly into the River Wey at Stoke Lock on Monday, January 9 between 7:30 pm and 11pm. There was a 30 minutes discharge also into the Wey at Ripley.

Just north of the M25 at Cobham, raw sewage has continued to flow into the River Mole for over 20 hours since Tuesday evening at the time of writing. At Leatherhead, the sewage discharge, again into the Mole, had been going on for over 94 hours since last Saturday, January 7.

Guildford sewage treatment works at Slyfield.

Thames Water has published the data in response to pressure from campaigners and the public about polluted rivers and in the expectation that the government is likely to make publication mandatory

Water Rangers, organised through Zero Carbon Guildford, have been testing water quality in the Wey every month since March 2022. Within the first three months, they showed nitrate levels were three times higher downstream of the Slyfield sewage treatment works than upstream.

Thames Water CEO, Sarah Bentley, said discharging untreated sewage into rivers was “unacceptable”.

The discharges, even though they are legally allowed in exceptional circumstances, would now appear to be normal practice and have been described as illegal.

Details of the raw sewage discharges from Slyfield sewage treatment works on January 9.

There are frequent raw sewage discharges into the Wey at Slyfield. The sewer overspilled into the river 27 times for 346 hours in 2020 and 11 times for a total of 98 hours in 2021. Data for 2022 was not available but the Thames Water map said there had been no spills from Slyfield since April 2022.

Professor Dieter Helm, University of Oxford, said: “Thirty-two years after water privatisation, rivers in England and Wales are not improving, leakage levels are unacceptable, and massive financial engineering has not added to the resilience of the system or the ability to finance the large-scale investment we now need. It cannot and should not be allowed to go on like this.”

Ofwat said poor performance by some firms including Thames Water was embedded in the way they served customers and ran the system. 

Thames Water has committed to reducing raw sewage spills by 50 per cent by 2030 and by 80 per cent in “sensitive catchments”.

A Thames Water spokesperson said: “Taking action to improve the health of rivers is a key focus for us, but we also need to explain what is happening, and why. After a successful trial in the Oxford area, we have decided to provide close to real-time information about storm discharges from all of our 468 permitted locations.

“We are absolutely committed to protecting and enhancing our rivers and the communities who love them, and we want to make these discharges of diluted sewage unnecessary as quickly as possible … the alerts will be available through an open data platform for third parties, such as swimming and environmental groups, to use.”

See Feature: The Challenge Of Processing Guildford’s Human Waste (December 2022)

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test 2 Responses to 30% of Thames Water Outfalls Are Discharging Raw Sewage Into Rivers This Week

  1. Anthony Mallard Reply

    January 12, 2023 at 10:41 am

    From time to time I read the comments that the sewage works at Slyfield are operating well beyond their designed capacity. Those comments often relate to and are closely associated with planning applications for further dwellings.

    It is usually remarked that until the facility is updated and capacity increased additional housing would put further strain on these already overstretched works.

    If those comments are accurate and the reason for the sewage discharge into the River Wey is the inadequacy of the sewage works to process the present volume of sewage and, possibly, surface water, then surely the environmental harm should and must be a significant material factor for serious consideration before further planning applications are approved.

  2. Dave Fielding Reply

    January 14, 2023 at 11:43 pm

    I agree with Mr Mallard but surely there must be a question of Thames Water’s investment in its treatment plants. Maybe it’s more cost effective to pollute our rivers, rather than improving the infrastructure.

    This is the sort of thing I would like our MP to follow up on.

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