Welsh Water admits illegally spilling sewage for years

Welsh Water has admitted illegally spilling untreated sewage at dozens of treatment plants for years.

The admission came after the BBC presented the water company with analysis of its own data.

One of their worst performing plants is in Cardigan in west Wales.

The company has been spilling untreated sewage there into an environmentally protected area near a rare dolphin habitat for at least a decade.

Welsh Water says it is working to tackle the problems and does not dispute the analysis, which was shared with BBC News by mathematician and former University College London professor Peter Hammond from campaign group Windrush Against Sewage Pollution (WASP).

Most of the UK has a combined sewerage system, meaning that both rainwater and wastewater – from toilets, bathrooms and kitchens – are carried in the same pipes. Usually, all the waste is carried to a sewage treatment works.

During heavy rain, to prevent a plant becoming overwhelmed, it is allowed to discharge untreated sewage. But releasing any before a plant reaches the overflow level stipulated on its permit is an illegal breach.

Prof Hammond requested data on 11 Welsh treatment plants and found that 10 had been releasing untreated sewage at times when they should have been treating it.

Cardigan was particularly bad, spilling for more than 200 days each year from 2019-2022.

The data provided to Prof Hammond showed that Cardigan almost never treated the amount of sewage it was supposed to.

According to its permit it has to treat 88 litres a second before spilling – but had illegally spilled untreated sewage for a cumulative total of 1,146 days from the start of 2018 to the end of May 2023.

“This is the worst sewage works I’ve come across in terms of illegal discharges,” he said.

When presented with the findings Welsh Water admitted it has between 40 and 50 wastewater treatment plants currently operating in breach of their permits. It said decisions on which plants to improve were taken with customer bills in mind, and that because there is “no measurable environmental impact” of the Cardigan estuary spills, these have been a low priority.

The outflow point from the Cardigan treatment plant spills into the Teifi estuary and Welsh Water points to Poppit Sands, a designated bathing beach two miles away, that has water quality consistently rated as “excellent”.

Environmental groups say testing at Poppit Sands only takes place from May to September and there is no regular monitoring of the impact of sewage discharges in the River Teifi. It is designated as a Special Area of Conservation (SAC) and is home to lamprey, Atlantic salmon and otters. The Teifi flows into Cardigan Bay, home to one of Europe’s largest populations of bottlenose dolphins.

“Untreated sewage causes a host of problems on our rivers,” says Gail Davies-Walsh of rivers campaign group Afonydd Cymru.

“High nutrient levels coming from sewage lead to algal blooms that lead to the depletion of oxygen in our rivers. And that clearly has knock-on impacts to our fish populations and to other species.”

The regulator, Natural Resources Wales, said that it has been aware of the issues at Cardigan for eight years and has issued enforcement notices but no fines. It says it is now looking at data from 101 treatment plants run by Welsh Water that have been spilling before they reach their permit capacity.

Welsh Water, a not-for-profit company, said in a follow-up email that it was not under “formal investigation”, that NRW’s figures are “inaccurate,” and that it stands by its total of about 45 treatment plants currently breaking their permits.

Cardigan’s problems date back to 2004 when Welsh Water installed a wastewater treatment system which filters sewage through a membrane. That is not how most sewage plants work.

The sewage network in Cardigan is old and leaky and during Spring tides saltwater gets into the pipes and the treatment plant.

The saltwater causes bacteria to release an enzyme that blocks the membrane. That has meant the plant regularly fails to treat the right amount of sewage and spills untreated sewage.

“We’re not proud of this at all,” Steve Wilson, managing director for wastewater services at Welsh Water said. “It’s a very uncomfortable position to be in – but it’s not for the want of trying. We have been trying to fix this.”

Those fixes have not worked. In 2025 work is due to begin on a new treatment plant for Cardigan, at a cost of £20m.

For Gail Davies-Walsh of Afonydd Cymru there are questions now for both the water company and the regulator, Natural Resources Wales, which is responsible for enforcing permits and, if necessary, issuing penalties.

“Fundamentally this site [Cardigan] has been discharging raw sewage for possibly 10 years and no action has been taken,” she says.

NRW provided the BBC with a timeline of their responses which shows a number of enforcement notices – but no prosecutions or fines. In the last five years the NRW has made no prosecutions anywhere in Wales for illegal sewage spills of this type.

“We have prosecuted Welsh Water on a number of instances for pollution events, just not for low flow spills as is the case here,” Huwel Manley, NRW’s head of operations for south west Wales. said. “But we are working with trying to set national guidance along with England so that we have a more standardised approach as to how and when we take that prosecution route.”

Welsh Conservative, Plaid Cymru and Welsh Liberal Democrats opposition parties called on Wales’ Labour government to take tougher action on sewage dumping.

A Welsh Government spokesperson said: “We expect water companies in Wales to continuously improve services to customers and address any areas of concern.”

Regulators in England are also looking at flow rates through treatment plants as part of what they say is their largest ever criminal investigation into potentially illegal spilling.