The sewage spill that cost a water company boss £1m
Environment Agency/HS2
A water company boss was denied his annual bonus worth more than a million pounds after thousands of tonnes of raw sewage ended up in a river.
The BBC can reveal that almost 3,500 tonnes of untreated sewage entered the River Mardyke in Grays, Essex, on 25 August 2025, killing at least 4,723 fish.
Anglian Water confirmed its chief executive Mark Thurston’s £1.05m bonus was withheld for the 2025-26 financial year over the spill, following new government legislation designed to improve accountability and the performance of water companies.
Anglian Water said it could not comment on the pollution incident itself due to an ongoing investigation.
The spill was deemed a Category 1 incident by the Environment Agency, which is its highest classification for pollution events and indicates major environmental harm.
Investigation reports and correspondence obtained under the Environmental Information Regulations revealed the alarm sounding from the Corran Way pumping station in Stifford, Thurrock, was ignored after an oversight meant that operators were instructed to disregard alerts from the site.
The alarm was triggered when a valve controlling the flow of sewage automatically shut when it should not have, which sent the untreated sewage into the river.
Investigators noted that the total number of fish deaths was likely to be <a href="https://industrymovement.com/flu-activity-higher-than-last-four-years-in-september-warns-ukhsa/” title=”Flu activity higher than last four years in September, warns UKHSA”>higher than 4,723, because parts of the watercourse could not be searched effectively due to vegetation and access constraints.
Among the aquatic life killed were European eel, a critically endangered species, pike, perch, roach, gudgeon, three spined sticklebacks and carp.
Environment Agency
The Environment Agency estimated the sewage was discharged at an average rate of 55 litres per second over at least 18 hours.
Elevated ammonia levels were detected several kilometres downstream from where the sewage entered the river and there were depleted oxygen levels across a long reach.
The ecological effects were visible up to about 5km (3.1 miles) from the discharge point, one of the reports noted.
Readings for so-called suspended solids – which can include faeces and related matter – was more than five times the permitted limit in one location.
Environment Agency
Under the Water (Special Measures) Act 2025, the government gave powers to the Water Services Regulation Authority (Ofwat) to ban the payment of bonuses to water bosses if they failed to meet standards to protect the environment, their consumers and their company’s finances.
In July 2025 Thurston received what was described as a “retention payment” of £500,000. In the same financial year he also received a Medium Term Alignment Plan (MTAP) payment of £451,440.
Anglian Water said MTAP and retention awards were not linked to the company’s performance and were permitted under the regulations and not funded by customers.
The company’s previous chief executive was also denied a bonus under the Water Act, following an alleged pollution incident that resulted in 900 fish dying at King’s Dyke, near Peterborough, in September 2024.
The Environment Agency said it was prosecuting Anglian Water in relation to the incident.
Environment Agency
Amy Fairman, from the campaign group River Action, said she welcomed the Environment Agency’s investigation into “this serious, shocking and illegal pollution incident” in Essex.
She added: “The principle is simple: when a water company’s failures cause environmental damage, the polluter should never profit.”
She described the additional payments that Thurston received as “a worrying pattern of water company executives receiving increases to their basic pay as restrictions on bonuses have tightened”.
In January the government published a white paper setting out its plans to “overhaul the water system” in England and Wales.
An Anglian Water spokesperson said: “Customers have been very clear that they expect executive pay and bonuses to be linked to performance, and we agree. No performance bonus was paid to our chief executive in 2025/26.”
They added: “Our shareholders decided to fund targeted, time-limited retention arrangements to maintain leadership continuity. These temporary arrangements do not replace bonuses and are not paid for by Anglian Water Services or customers.”
The Environment Agency said that it had ensured Anglian Water took “swift action” to reduce the impact of the Mardyke pollution incident, and its investigation was ongoing.
“We will continue to rigorously regulate the water industry, investigate incidents and permit breaches, and take action against companies that fail to meet their environmental obligations” an Environment Agency spokesperson added.
An Ofwat spokesperson said: “Rebuilding public trust in the water sector is vital and central to our rules on executive pay – last year alone, companies were prohibited from paying approximately £4m in potential bonuses.”
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