Thames Water: top 13 polluting sites revealed as company faces £104m fine

Thames Water is staring at a £104 million fine over historic sewage spills that have seen treatment works in south Buckinghamshire and Berkshire among its worst polluters.

Ofwat, the industry regulator, has announced proposals to sanction Thames Water and two other companies for a ‘catalogue of failure’ in fixing sewage pollution.   

In a report on Thames Water, the regulator noted sewage treatment works at Little Marlow and Slough were among Thames Waters’ ‘top 13’ worst polluters – out of 354 sites.  

The proposals are set to go out for consultation before being finalised.

Ofwat’s chief executive officer David Black said the ‘catalogue of failures’ at Thames Water – as well as Yorkshire and Northumbrian Water – had caused ‘excessive sewage spills’.

Yorkshire and Northumbrian could be hit with £47 million and £17 million fines under the proposals.

Mr Black added: “Our investigation has shown how they routinely released sewage into our rivers and seas, rather than ensuring that this only happens in exceptional circumstances as the law intends.

“The level of penalties we intend to impose signals both the severity of the failings and our determination to take action to ensure water companies do more to deliver cleaner rivers and seas.”

Ofwat’s investigation into Thames Water, part of the regulator’s largest ever investigation, identified numerous problems with how the company maintained its sewage plants and treated spills.

The report pointed to Thames Water failing to ‘operate and maintain’ its sewage infrastructure, in addition to upgrading when necessary.

Water companies are permitted to release untreated sewage into rivers through Combined Sewer Overflows (CSOs), as a last measure when flooding of a treatment plant is a major risk.

But the report found that Thames had failed to ensure sewage spills ‘only occur in exceptional or unforeseeable cases’.  

And it also criticised management for a ‘lack of adequate oversight’ leaving the company ‘failing to be aware of and/or failing to address’ pollution problems.

Considering the problem treatment works, the report identified the top ‘13’ sites responsible for more than a third all Thames Water’s sewage pollution incidents over the period 2014 to 2021.

These included Slough and Little Marlow.

The Maidenhead treatment plant was in the top 50 for overall pollution risk, and Windsor was identified as 157 sites ‘of concern’ regarding future sewage spills.  

The Slough water treatment works discharges into the Roundmoor Ditch in Eton Wick, a River Thames tributary.

Little Marlow sewage treatment works discharges directly into the Thames.

In 2017, Thames Water forked out more than £20 million over sewage spills from sites including at Little Marlow.

Last month the company announced it only has enough money to last till June 2025.

If Thames Water cannot pay the fine, Ofwat could take it to court to recover the debt with interest.

The regulator could, at its discretion, also allow payments to be made in instalments.

A spokesperson for the Thames Water said: “We take this matter very seriously and have cooperated at every stage of Ofwat’s investigation.

“We regard all untreated discharges as unacceptable, even when they are permitted, and are taking action to improve the health of our rivers as a key area of focus and investment.

They added: “Where appropriate, Ofwat may decide not to issue an enforcement order, or decide to impose a reduced or no financial penalty at the conclusion of the consultation period, in light of a commitment from the company to taking appropriate measures to secure compliance and provide redress for failures identified.”

“We are encouraged that Ofwat recognises that in order to resolve the issues identified any redress needs to be deliverable, affordable and financeable.”