Stanlow Oil Refinery Repeatedly Exceeded Toxic Pollution Limits, Leaked Documents Show

One of the UK's largest oil refineries has repeatedly discharged dangerous pollutants into the air, rivers and the Mersey Estuary, according to internal documents obtained by investigative journalists and shared with the BBC. The records point to dozens of breaches of environmental regulations at the Stanlow refinery in Ellesmere Port, Cheshire, during 2023 and 2024, raising fresh concerns about oversight of Britain's shrinking refining industry.

The documents were uncovered by SourceMaterial, a team of environmental investigative journalists, and indicate that the refinery spilled toxic chemicals and oil into local waterways and even groundwater on numerous occasions. The Environment Agency (EA), the regulator responsible for enforcing environmental permits in England, has confirmed it is investigating the breaches.

Stanlow is operated by EET Fuels, a company formerly known as Essar. The firm already pleaded guilty this year to 12 charges of breaching environmental law between 2018 and 2020. The newly revealed documents suggest that problems at the site continued well beyond that period. EET Fuels said in response that it "takes its environmental responsibilities extremely seriously".

The refinery is one of only four remaining in the UK and plays a significant role in national fuel supply. It processes around 10 million tonnes of crude oil every year, producing roughly 18% of the fuel used for road transport in the country, including petrol for cars and diesel for trucks.

EET Fuels bought the site from Shell in 2011 for £842m and holds a permit allowing it to release controlled amounts of oil and chemicals into the air and waterways. Under the terms of that permit, the company is also required to take steps to limit pollution and any harm to human health. However, EA reports examined by SourceMaterial show that permitted chemical release levels were exceeded hundreds of times across 2023 and 2024.

The regulator concluded that these exceedances amounted to 58 breaches of permit conditions over the two-year period, each of which could constitute an illegal offence. Among the pollutants were toxic substances including cyanide and benzene, as well as heavy oils, released into both the air and local waterways such as Thornton Brook and the River Gowy, which flow into the River Mersey Estuary.

The scale of some releases was stark. EA documents describe sulphur dioxide being emitted into the air at seven times the permitted level, cyanide entering waterways including the Gowy at more than eight times the allowed limit, and oil discharged at more than thirteen times the permitted concentration.

The Mersey Estuary is designated a Site of Special Scientific Interest, a status reserved for the country's most important natural habitats. It supports endangered species including dolphins and serves as a breeding ground for rare birds. Charlotte Harris, chief executive of Cheshire Wildlife Trust, explained that species such as dunlin, black-tailed godwit and redshank travel from around the world to feed and roost on the land around the river.

Harris said those populations had only recovered because organisations including the Wildlife Trusts have spent years cleaning up pollution left behind by the region's industrial past. She noted that Atlantic salmon have returned to the river, and that the critically endangered European eel still makes its way up the Mersey and into the River Gowy to breed each year. "Where we have chemical pollution the impact isn't just localised," Harris said. "When it enters the river system, that system is highly dynamic and high energy, which means that pollution spreads far and wide really, really quickly."

One incident in July 2023 was classified by the EA as "significant" after rainwater containing oil leaked from the site. The agency's report noted a significant number of complaints from local residents about the smell, and further investigations indicated the oil had contaminated groundwater supplies. EET Fuels told the BBC that the oil lost was on a "low scale" and "was strictly localised to two boreholes, all well within the Stanlow site itself".

A second major incident occurred on 12 September 2024, when oil was again spilled from the site. According to an EA report, more than a tonne of oil was released into Thornton Brook over a 36-hour period and spread into the Mersey Estuary. Although EET Fuels reported the incident to the authorities, it took nearly two weeks for the company to provide an estimate of how much oil had been spilled, which itself breached regulations requiring such information within 24 hours.

Meeting documents show that an emergency response team was assembled, bringing together the EA, Natural England, local port authorities and the Fisheries Authority. Natural England, which oversees SSSIs, warned in one meeting that whatever had entered the water would have some impact on vegetation and salt marsh, and that there was probably still a risk of birds ingesting the pollution.

A drone was deployed to survey the damage. The footage revealed that oil had travelled more than a mile down the river and that there was brown discolouration around the reedbed. It also showed wading birds, including the red-listed dunlin, in the affected area.

The revelations come at a sensitive time for the UK's refining sector, which has been contracting for years as older sites close or convert to other uses. Stanlow's status as one of only four remaining refineries means its environmental performance carries national significance, both for fuel security and for the communities living near its sprawling industrial footprint.

For residents around Ellesmere Port, the documents add to a long history of concerns about pollution from heavy industry in the region. Environmental groups argue that the case highlights weaknesses in how permits are monitored and enforced, particularly when exceedances occur repeatedly rather than as isolated events.

The Environment Agency has not indicated what enforcement action, if any, might follow its investigation. EET Fuels maintains that it is committed to its environmental obligations, but the documentary record assembled by SourceMaterial suggests that, for at least two years, the refinery's operations regularly pushed beyond the limits set to protect the air, water and wildlife of the Mersey Estuary.