HUNDREDS of fish were killed after Thames Water pumped 'millions of litres' of undiluted sewage into rivers. 

At a hearing at Lewes Crown Court on July 3, the court heard how rivers near Gatwick Airport had turned 'black' and that hundreds of fish died as a result. 

It also heard how Thames Water, which also supplies water to households across Swindon and north Wiltshire, was behind a “significant and lengthy” period of polluting of the Gatwick Stream and River Mole between Crawley, in West Sussex, and Horley, in Surrey, on October 11, 2017.

Thames Water pleaded guilty on February 28 to four charges relating to polluting the rivers and was sentenced to pay a £3.3 million fine on July 4. 

Swindon Advertiser: Dead fish and 'black' water after Thames Water leaked undiluted sewage into a river near Gatwick Airport.Dead fish and 'black' water after Thames Water leaked undiluted sewage into a river near Gatwick Airport. (Image: PA)

On the first day of the hearing, the court heard how a storm pump at Crawley Sewage Treatment Works site was unexpectedly diverting sewage to its storm tank for 21 hours and went “unnoticed”.

From no alarm being raised, prosecutor Sailesh Mehta said the “best estimate” was that untreated sewage was spilling into the river from the tank for six and a half hours.

Eyewitness accounts read in court said how they saw the river turn “black” and “grey”, with “huge numbers of dead fish” visible in the water.

It is understood nearly 1,400 dead fish from the rivers were recovered by Environment Agency officers following the incident.

Mr Mehta said there were “cumulative management deficiencies” at the company and that the sewage spill was an “accident waiting to happen”.

Defending, Lisa Roberts KC said Thames Water expresses its “unreserved and sincere apology” for the incident, adding: “Put bluntly, it shouldn’t have happened and Thames deeply regrets the event.”

However, Ms Roberts rejected previous issues were to blame for the spillage but instead, it was a “faulty switch” in the storm pump that caused the incident which “could not have reasonably been foreseen”.

According to Ms Roberts, a £33-million plan to improve the Crawley site was put in place since the incident with aims to complete it by the end of March 2025.

New systems have also been rolled out across other Thames Water sites to prevent such incidents from happening again.

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However, in the last two years, there have been several leaks at the Haydon Wick pumping station in North Swindon, with multiple instances of undiluted sewage contaminating the nearby River Ray. 

Thames Water has previously racked up £32.4 million in fines for pollution incidents in the Thames Valley and southwest London from other prosecutions brought by the Environment Agency between 2017 and 2021.