Concerns Rise Over Risks from UK’s Largest Opencast Mine Waste

Significant worries have emerged regarding the stability of three large spoil tips poised to remain above Merthyr Tydfil after the cessation of the UK’s final opencast coal mine.

A geotechnical assessment commissioned by the local council indicates a “substantial risk of slope instability” related to the Ffos-y-Fran site, while activists describe the intent to retain the tips as “astonishing”.

Emails acquired by media outlets reveal that the Welsh government is contemplating intervening to assume control over the final planning decisions.

Merthyr South Wales Ltd (MSW), the mining company, contends that equating the “engineered structures” with the dangers presented by historical coal tips is “inaccurate and misleading”.

Ongoing Uncertainty Following Mine Closure

Two years have elapsed since operations ceased at Ffos-y-Fran, yet there remains significant ambiguity surrounding the contentious project’s trajectory.

Initially approved in 2005, the UK’s largest opencast mine was designated as a “land reclamation initiative”.

This classification mandated that a portion of the revenue generated from the sale of 11 million tonnes of coal during a 15-year period be allocated for site cleanup, aiming to restore the area to a green hillside for community use.

Chris Austin, a local resident, remarked, “The intention was to enhance public amenities, restoring rights of way and agricultural land. Now, I fear we are left with a hazardous void and unusable areas.”

His wife, Alyson Austin, echoed these concerns, stating, “We were compelled to accept this opencast operation, and now we face a situation that is far more perilous than what we had at the outset.”

Local Anger and Legal Actions

The current developers, MSW, have incited local outrage and legal disputes after exceeding their mining permissions by over a year to extract and sell coal.

They have since proposed a new, more economical restoration plan, citing a lack of adequate funds to accomplish previous commitments.

Under earlier plans, the substantial spoil tips accumulated over time were intended to fill the central mining void, which reaches a depth of 175 meters (574 feet).

These mounds, referred to as overburden, contain 37 million cubic meters of material excavated during the mine’s operation.

The company now seeks to lower one mound’s height while leaving the other two intact, asserting that they are stable long-term structures and that the mining void would evolve into a “natural lake”.

Geotechnical Report Raises Alarms

The proposal is currently under review by planners at Merthyr Tydfil council, who engaged engineering firm WSP for a geotechnical analysis.

This report concludes that the tips were created as “temporary earthworks” and suggests that the current plans do not instill confidence in their stability, posing ongoing risks to local residents and potential financial liabilities for the council.

WSP’s consultants also pointed out that climate change effects were seemingly overlooked, with some risks dismissed without sufficient evidence.

Moreover, they highlighted that one of the tips, known as OB1, which stands around 170 meters above a major road beside Ffos-y-Fran, had already experienced a landslide in 2022.

The report referenced a troubling trend of tip failures in South Wales due to excessive rainfall.

Political Responses and Future Oversight

Delyth Jewell, Plaid Cymru’s climate spokesperson, cautioned that Merthyr Tydfil residents might have to endure the aftermath of “poor restoration”, expressing that retaining the tips would be both “staggering” and “unconscionable”.

“Coal tips collapsing is not a theoretical risk,” she asserted.

The Welsh government has recently established a new Disused Tips Authority for Wales, which will be located in Merthyr Tydfil, following rising concerns regarding coal tips across the nation.

Haf Elgar, director of Friends of the Earth Cymru, warned that the Ffos-y-Fran overburden mounds could soon be added to the list of monitored sites, creating an additional burden for public authorities that is “entirely unacceptable”.

Controversy Over Stability Assessments

In correspondence to the council, consultants representing MSW expressed “serious concerns” about the geotechnical report, labeling it merely a “desktop evaluation”.

In response, they commissioned a separate assessment from James Associates, a geological and mining consultancy, which contradicts WSP’s findings regarding the mounds’ stability.

This analysis claims that the overburden mounds were built according to an approved design and have been overseen by a specialist.

It asserted that the landslide at OB1 resulted from excavation activities and that future risks could be “substantially minimized” through proper engineering.

Comparing recent landslides from older colliery tips to the situation at Ffos-y-Fran was described as akin to comparing “apples and oranges,” as colliery tips are generally situated on steeper inclines, whereas the overburden mounds are on gentler gradients.

Financial Considerations and Future Steps

The company contends that its new restoration proposals are more sustainable, aiming to reduce carbon emissions and air pollution associated with heavy machinery while fostering a more biodiverse landscape.

Estimates regarding the cost of removing the tips and filling the void vary widely, ranging from £50 million to £175 million.

Recent financial disclosures indicate that the company’s accounts, as of March 2025, allocated approximately £91.2 million to fulfill the approved restoration requirements.

However, reliance appears to be growing on a £15 million fund established jointly with the council as a contingency in case of the firm’s financial failure.

MSW’s consultants stated that detailed cost assessments are currently being finalized.

Calls for Intervention

Last year, the environment committee of the Senedd criticized the oversight of the Ffos-y-Fran coalmine as a “case of epic mismanagement”, warning that it could leave a “permanent scar” on the landscape above Merthyr Tydfil.

Activists have urged the Welsh government to assume control over the decision-making process.

In internal communications, officials highlighted the potential consequences of such actions, including the risk of site abandonment.

In August, they requested additional information from the council.

“Given the level of risk, we must ensure we provide a solid evidence base for the Welsh ministers to support any courses of action they may wish to consider,” the email stated.

Ms. Jewell, a member of the Senedd representing South East Wales, emphasized that the Welsh government bears a “moral duty to safeguard the residents of Merthyr Tydfil” and should take action.

In a statement, Merthyr South Wales Ltd expressed disappointment over Ms. Jewell’s remarks, asserting that they could jeopardize trust in the planning process by introducing political influences into what should be an evidence-driven determination.

“Merthyr South Wales Ltd is fully dedicated to collaborating with the planning authority and has confidence that the application will be resolved lawfully, fairly, and based on verified facts, records, and recommendations,” the company stated.

The council indicated it would conduct further consultations once additional information is received from the developer.

The Welsh government reiterated its commitment to working with the council and other stakeholders to ensure an optimal outcome for the local community, noting that the case remains “actively under consideration for ministerial review.”