Thames Water has been fined £4 million after untreated sewage flooded Green Lane recreation ground and Hogsmill River.

A court heard dozens of high-priority alarms would have told staff about the incident, but were either missed or ignored, leading to pollution of the popular park, woodland and river, in New Malden. 

The sewage treatment works at Surbiton couldn’t handle the amount of sewage produced by Storm Imogen in the winter of 2016.

On May 26, Judge Francis Sheridan noted the company's new commitment to improving compliance, but said that must be the norm, issuing a warning shot they will be held to this commitment in future cases.

The court was told that around 79m litres of sludge escaped across an area of about 6,500m2.

The Environment Agency reported that it took 30 people a day for almost a month to clean-up sludge that was ankle-deep in places.

Gary Waddup, a land and water officer for the Environment Agency in south London, said: “Like similar incidents in the past few years for which they have been prosecuted, better management overall and on the night by Thames Water could have prevented this catastrophic incident. 

“It wasn’t the first time sewage had escaped from manholes due to problems at the treatment works in Surbiton. Pollution as a result from problems at the site goes back to 2001.

“The Environment Agency’s enforcement action over several years and the pressure it has put on water companies has led to £30bn of investment by the industry in water quality.

"This incident shows Thames Water and the industry have a lot more to do to protect the environment.”

Your Local Guardian: Credit: Environment AgencyCredit: Environment Agency

Thames Water’s equipment at Hogsmill struggled under the pressure of forecast extreme weather one night five years ago.

Instead of the sewage being treated, pumps failed, allowing raw effluent to back up along the sewer network, bursting out of a manhole to cover an area the size of “three football pitches”.

One of Thames Water’s own engineers described finding an “avalanche of foul waste” spread over Green Lane recreation ground.

It was reported that the sewage travelled with such force across the park and into the river, leaving thick sludge, toilet paper and wet wipes covering the riverbank, grass, shrubs and a wooded area. 

An investigation by the Environment Agency found things began to go wrong at the treatment plant just after midnight on February 8 2016.

The park was closed for a month during the clean-up, although some of the toilet paper swept along by the sewage was still visible in the woods months later.

Your Local Guardian: The Environment Agency said there was enough toilet paper to fill 2,500 refuse bags was recovered from the sceneThe Environment Agency said there was enough toilet paper to fill 2,500 refuse bags was recovered from the scene

As untreated sewage built up below ground, almost 50 warning alarms were set off over the next five hours. Every one was left unchecked, said the Environment Agency.

It was reported that an engineer arrived several hours after the incident began. 

It took Thames Water 15 hours to report the incident to the Environment Agency, a legal requirement, and another 12 hours – by now, the morning of February 9– before the company had “any sizeable presence” at the scene.

An Environment Agency investigator found a thick layer of sewage charting a course across the park and into the Hogsmill River. The water’s fast flow had flushed away any evidence before his arrival.

Judge Francis Sheridan fined Thames Water £4m, ordering them to pay the Environment Agency’s costs of £84,669.

Thames Water pleaded guilty to depositing sewage waste at the recreation ground in February 2016.

The court also took into consideration breach of a permit regarding that incident, and discharging into the Hogsmill River in January and October 2018, and an incident in September 2019, when sewage sludge was released from Hogsmill sewage treatment works in error. 

Steve Spencer, Thames Water operations director, said: “We’re very sorry for what happened at Hogsmill sewage works five years ago, and the other three incidents that have been sentenced today.

"It doesn’t reflect how much we care about the environment, our customers and communities, and it’s not how we want to perform.  

“We’ve developed a turnaround plan which focuses on significantly improving our performance, with an unprecedented amount of investment directed towards safeguarding the environment.

"We’re committed to long term, sustainable solutions and we’re already working with partners across our region to enhance and restore the rivers we all share and value.

“We’re pleased the judge recognised this new approach in his comments, and we are determined to deliver on our promises.

"We strongly believe that discharges of untreated sewage are unacceptable, even when they are legally permitted, and we will work with our stakeholders to accelerate work to stop them being necessary.”