Stanlow Oil Refinery Accused of Repeated Toxic Spills into Mersey Estuary and Local Waterways

One of Britain's largest oil refineries has been found to have exceeded legal pollution limits on numerous occasions over a two-year period, according to internal documents obtained by investigative journalists. The Stanlow refinery in Ellesmere Port, Cheshire, which is operated by EET Fuels, is alleged to have released toxic chemicals and oil into local rivers and the Mersey Estuary dozens of times during 2023 and 2024. The Environment Agency has confirmed it is investigating the breaches, which could amount to criminal offences.

Stanlow is the second-largest refinery in the UK and one of only four still operating in the country. It processes approximately 10 million tonnes of crude oil annually, supplying roughly 18% of the nation's fuel for road transport, including cars and trucks. EET Fuels, formerly known as Essar, purchased the site from Shell in 2011 for £842 million and holds a permit allowing it to discharge controlled quantities of oil and chemicals into the air and waterways, provided it takes steps to minimise environmental harm and risks to human health.

However, reports compiled by the Environment Agency and uncovered by environmental journalists at SourceMaterial indicate that permitted chemical release levels were exceeded hundreds of times between 2023 and 2024. The regulator determined that EET Fuels breached its permit conditions 58 times during that period. Among the pollutants released were cyanide, benzene, and heavy oils, which entered the air and local waterways including Thornton Brook and the River Gowy, both of which flow into the River Mersey Estuary.

The Mersey Estuary is designated a Site of Special Scientific Interest and supports endangered species such as dolphins, as well as serving as a breeding ground for rare birds. Charlotte Harris, chief executive of Cheshire Wildlife Trust, emphasised the ecological importance of the area. She noted that species including dunlin, black-tailed godwit, and redshank travel from around the world to feed and roost in the land around the River Mersey. Harris explained that this wildlife presence has only been possible because organisations like the Wildlife Trusts have spent years cleaning up pollution left by legacy industries in the region.

Harris also highlighted that Atlantic salmon have returned to the river, and the critically endangered European eel migrates up the Mersey and into the River Gowy to breed each year. She warned that chemical pollution does not remain contained to a single location. "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," she said.

The Environment Agency documents detail specific instances where pollutants were released at levels far beyond what the permit allows. Sulphur dioxide was emitted into the air at seven times the permitted concentration, cyanide entered waterways such as the Gowy at more than eight times the allowed level, and oil was discharged at more than thirteen times the permitted amount.

One notable incident occurred in July 2023, when rainwater containing oil leaked from the Stanlow site. The Environment Agency classified the event as "significant." Its report noted a considerable number of complaints from local residents about odours, and further investigations indicated that the oil had contaminated groundwater supplies. In response, EET Fuels told the BBC that the quantity of oil lost was on a "low scale" and "was strictly localised to two boreholes, all well within the Stanlow site itself."

A more serious spill took place on 12 September 2024, when oil was again released from the facility. Over a 36-hour period, more than a tonne of oil flowed into Thornton Brook and eventually reached the Mersey Estuary. Although EET Fuels reported the incident to authorities, the company took nearly two weeks to provide an estimate of the volume spilled. This delay constituted another breach of regulations, which require such estimates to be submitted within 24 hours.

An emergency response team was assembled, including the Environment Agency, Natural England, local port authorities, and the Fisheries Authority, according to meeting records. Natural England, which regulates Sites of Special Scientific Interest, stated during one meeting that the pollution would likely impact vegetation and salt marsh, and that there remained a risk of ingestion by birds. A drone survey was deployed to assess the extent of the damage, revealing that oil had spread more than a mile down the river, with brown discolouration observed around the reedbed. Footage captured wading birds, including the red-listed dunlin, in the affected area.

The Mersey Estuary hosts the largest group of protected dunlins in the UK, underscoring the significance of the contamination. The documents obtained by SourceMaterial paint a picture of repeated regulatory failures at a facility that plays a critical role in the UK's energy infrastructure. EET Fuels has stated that it "takes its environmental responsibilities extremely seriously." The company pleaded guilty earlier this year to 12 charges of breaching environmental law between 2018 and 2020. The Environment Agency's ongoing investigation into the more recent breaches could lead to further legal consequences for the refinery operator.

The case raises broader questions about oversight of ageing industrial sites and the adequacy of self-reporting mechanisms. It also highlights the tension between maintaining domestic fuel production and protecting vulnerable ecosystems. For communities living near Stanlow, the repeated spills and the presence of toxic substances in local waterways and groundwater are likely to intensify concerns about long-term health and environmental impacts. As the Environment Agency continues its investigation, the full extent of the damage to the Mersey Estuary and its wildlife may not be known for some time.