Stanlow Refinery Accused of Repeated Toxic Spills into Mersey Estuary, Documents Reveal

One of Britain's largest oil refineries has been implicated in dozens of pollution incidents over a two-year period, according to internal documents that suggest toxic chemicals and oil repeatedly escaped into local waterways and the Mersey Estuary. The findings, shared exclusively with the BBC, raise fresh questions about environmental oversight at the Stanlow refinery in Ellesmere Port, Cheshire.

The documents were obtained by investigative journalists at SourceMaterial and indicate that EET Fuels, the company formerly known as Essar that operates the site, exceeded permitted pollution limits on numerous occasions during 2023 and 2024. The Environment Agency (EA) has confirmed it is investigating the breaches and has determined that the company violated its permit conditions 58 times across the two-year span—a figure that could constitute criminal offences.

Stanlow is the second-largest refinery in the UK and one of only four remaining in the country. It processes approximately 10 million tonnes of crude oil annually, accounting for roughly 18% of the nation's fuel supply for road transport, including cars and trucks. EET Fuels purchased the refinery from Shell in 2011 for £842 million and holds a permit allowing controlled discharges of oil and chemicals into the air and waterways, provided the company takes steps to limit environmental harm and risks to human health.

However, EA reports uncovered by SourceMaterial describe permitted chemical release levels being surpassed hundreds of times. Among the pollutants cited are cyanide, benzene, and heavy oils, which entered the air and local waterways including Thornton Brook and the River Gowy, both of which feed into the River Mersey Estuary. In some instances, sulphur dioxide was released into the air at seven times the permitted level, cyanide into waterways at more than eight times the allowed concentration, and oil at more than thirteen times the permitted threshold.

The Mersey Estuary is designated a Site of Special Scientific Interest (SSSI), a protected status recognising its ecological importance. It supports endangered species such as dolphins and serves as a breeding ground for rare birds. Charlotte Harris, chief executive of Cheshire Wildlife Trust, emphasised the estuary's international significance, noting that species including dunlin, black-tailed godwit, and redshank travel from around the world to feed and roost in the surrounding land. She attributed the estuary's recovery to years of pollution cleanup efforts by organisations like the Wildlife Trusts, and highlighted the return of Atlantic salmon and the critically endangered European eel, which migrates up the Mersey and into the River Gowy to breed annually.

One particularly serious incident occurred in July 2023, when rainwater containing oil leaked from the Stanlow site. The EA classified the event as "significant" and reported a substantial number of complaints from local residents about odours. Subsequent investigations indicated that 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 second major spill took place on 12 September 2024, when more than a tonne of oil was released into Thornton Brook over a 36-hour period, eventually spreading into the Mersey Estuary. Although EET Fuels reported the incident to authorities, the company took nearly two weeks to provide an estimate of the spill volume—a delay that itself constituted a breach of regulations requiring such information within 24 hours. An emergency response team was assembled, including the EA, Natural England, local port authorities, and the Fisheries Authority, according to meeting documents.

Natural England, which regulates SSSIs, warned in one meeting that the pollution would likely affect vegetation and salt marsh, with a continued risk of ingestion by birds. A drone survey revealed that oil had travelled more than a mile down the river, leaving brown discolouration around the reedbed. The footage captured wading birds, including the red-listed dunlin, in the affected area.

Harris stressed that chemical pollution in river systems is not 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. This dynamic underscores the potential for incidents at Stanlow to have consequences well beyond the immediate vicinity of the refinery.

The revelations add to a troubled environmental record for the company. Earlier this year, EET Fuels pleaded guilty to 12 charges of breaching environmental law between 2018 and 2020—a separate case that predates the incidents described in the newly obtained documents. The company maintains that it "takes its environmental responsibilities extremely seriously," but the frequency and severity of the breaches outlined in the EA reports suggest a pattern of regulatory non-compliance that has persisted in recent years.

The Environment Agency's ongoing investigation will determine whether further enforcement action is warranted. For local communities and conservation groups, the documents raise concerns about the adequacy of oversight at a facility vital to the UK's fuel supply. The tension between industrial necessity and environmental protection is particularly acute at Stanlow, where the refinery's output supports a significant portion of the nation's transport network while its operations border sensitive habitats of international ecological importance.

As the investigation continues, the case highlights broader questions about how effectively pollution limits are monitored and enforced at major industrial sites. The EA's finding of 58 permit breaches over two years suggests that self-reporting and regulatory inspection may not be sufficient to prevent repeated violations. For the Mersey Estuary and the wildlife that depends on it, the consequences of those breaches may be felt for years to come.