Thames Water has been handed a £3.3 million fine for a “reckless” incident in which “millions of litres” of undiluted sewage was pumped into rivers near Gatwick Airport in 2017.
A two-day sentencing hearing at Lewes Crown Court was told there was a “significant and lengthy” period of polluting the Gatwick Stream and River Mole between Crawley in West Sussex and Horley in Surrey on October 11, 2017.
Eyewitness accounts read in court recalled how the river turned '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.
Judge Christine Laing KC said on Tuesday that said she believed Thames Water had shown a “deliberate attempt” to mislead the Environment Agency over the incident, such as by omitting water readings and submitting a report to the regulator denying responsibility.
Thames Water had pleaded guilty on February 28 to four charges relating to illegally discharging waste in October 2017.
The court case comes as the water company faces concerns over its future amid mounting debt.
Throughout the hearing, the court was told of how a storm pump at Crawley Sewage Treatment Works site was unexpectedly diverting sewage to its storm tank for 21 hours and went 'unnoticed'.
Prosecuting, Sailesh Mehta said the 'best estimate' was that untreated sewage was spilling into the river from the tank for six and a half hours, after no alarm was raised.
He said the sewage spill was an 'accident waiting to happen'.
"The public expect high standards of a company such as this, simply because they are trusted to protect our environment," Mr Mehta said.
"It's a heavy burden, they should be heavy and it's common ground they failed in carrying that out in this case."
Defending, Lisa Roberts KC said Thames Water expresses its 'unreserved and sincere apology', 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'.
Thames Water's chief executive Sarah Bentley stepped down with immediate effect last week after she gave up her bonus due to the company's environmental performance.
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 happening again.
Ms Bentley, whose leadership of the company began in 2020, in a statement said the eight-year plan was no 'quick fix' but hoped to counter prior 'poor management decisions, aggressive cost-cutting and decades of under-investment'.
Thames Water also gave 'voluntary reparation' to the South East Rivers Trust amounting to £1 million.
Thames Water has previously racked up £32.4 million in fines for pollution incidents in the Thames Valley and south west London from other prosecutions brought by the Environment Agency between 2017 and 2021.
