Southern Water risked “significant adverse effects on human health” while pumping colossal amounts of raw sewage into coastal waters, a court heard.

A total of 9-10 thousand oysters, potentially contaminated with E-coli, were harvested as the private company dumped untreated effluent into Kent, Sussex and Hampshire waters for six years.

Southern awaits sentencing after admitting 51 violations of pollution law in the Environment Agency’s biggest investigation to date, between 2010-2015.

Canterbury Crown Court heard the utility giant illegally discharged raw sewage into north Kent oyster beds, prompting the agency to launch Operation Garden, after shellfish were found deteriorating with high levels of faecal matter.

“Polluting material was noxious, widespread or pervasive with significant adverse effects on human health or quality of life.

“Whilst not usually life threatening, norovirus infection can result in death in a few extreme cases of vulnerable people,” prosecutor Andrew Marshall said.

“The assessment of risk cannot be confined to the non-vulnerable but must look at the whole cohort that might be exposed to the risk - there is a risk.”

Although there were no official cases of poisoning linked to the sewage, Mr Marshall added people may have become unwell but not associated their illness with pollution.

“It cannot be said the defendant only created a risk to human health," he said.

Outbreaks triggered by contaminated shellfish consumption may be a “seed” for wider community illness, the court heard.

It is unknown what happened to the 9 - 10 thousand shellfish harvested after the raw sewage was pumped through the oyster beds.

Norovirus is caused by ingesting small amounts of feces or fluids, causing diarrhoea, vomiting, nausea, fever and body pains.

“Polluting material was noxious, widespread or pervasive with significant adverse effects on human health or quality of life..."

The firm dumped sewage into The Swale affecting Sheppey, Whitstable and Herne Bay, where waters are heavily protected to help maintain marine life and ecosystem.

Raw sewage was also spilled into The Solent’s protected waters, between Southampton and Chichister.

Whole oyster beds in both rivers were made unfit for human consumption and withdrawn from the market. However, there are 9-10 thousand oysters which were harvested before the pollution was discovered and it is unknown where they ended up.

“(Raw sewage) discharge to coastal waters is itself environmental harm,” Mr Marshall continued.

“However, it contaminates shellfish and therefore either inhibits or prevents their economic harvesting.

“Or, instead the contaminated shellfish are harvested and enter the human food chain where they may cause serious harm to humans.”

Southern was not only aware of dumping billions of litres of raw sewage out to sea but did so to boost profits, Mr Marshall added.

Failing to treat the sewage, while charging millions of customers as if it were performing properly, was intended to “create financial gain,” he said.

Southern Water, which turned over £878m with a £213m profit in 2019/20, pleaded guilty last year to 51 counts of dumping poisonous, noxious substances including raw sewage, after a criminal investigation.

It polluted The Swale, The Solent and Beaulieu River in the South Downs for 61,714 hours, the court heard.

Millbrook, a sewage works near Southampton, discharged almost one billion litres of untreated waste, the equivalent of 371 Olympic sized swimming pools, the court heard.

But the Environment Agency was unable to source the cause of the pollution after Southern Water reported legal levels of discharge on its network, prompting the agency to turn its attention to other potential causes - agricultural pollution for example.

And yet the agency would later discover effluent discharged from storm tanks across 17 treatment plants during Operation Garden.

It found 10,741 discharges with 78% illegal, totalling 6,971 unlawful sewage dumps.

Storm tanks at many sites were being used as an everyday convenience rather than emergency measures, where raw sewage, sometimes septic, was diverted into the sea rather than being treated at the plant.

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• Southern Water committed more than 6,000 sewage breaches

Mr Marshall said: “All could have been avoided since the causes were known but deliberately avoided… there was a general unwillingness by the company, despite knowledge of its failed systems, to fund the necessary staff, maintenance and upgrades that would make the company compliant.”

Richard Matthews QC, for Southern Water, apologised on behalf of the new board of directors and chief executive Ian McAulay, for “serious failures in its wastewater treatment.”

He explained the firm pleaded guilty at an early opportunity and remedial changes have since been put in place.

Opening the defence’s case, Mr Matthews said he will tomorrow address the issues of culpability and harm, starting with the Eastchurch site on the Isle of Sheppey.

Presided over by Mr Justice Jeremy Johnson, the sentencing hearing is expected to last until the end of the week.

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