Mining legacies: breathing new life into old operations

When a large mine approaches the end of its economic life, concerns loom.

We know today that responsible closure is essential and considerations ranging from environmental and biodiversity to social, Indigenous community impacts and climate change resilience must be taken into account. 

While the closure of a large number of coal mines in support of net zero is expected in the coming years, long operating metal mines are also due to cease. For example, Queensland, Australia, will see the shuttering of the underground Mt Isa copper mines in 2025 after 100 years of operation. 

As investors are increasingly focused on environmental and social matters, how closure is undertaken and legacies managed is important. Here are a few thoughts on legacy management…

Closure is not the end

Most mine closure plans are short-term, with a five-year outlook after which any surplus bond money is paid back to the mining company. The last deep underground coal mine in the UK was shuttered in 2015, but the industry had been in decline since the miners strikes of the mid-1980s. 

In Britain, the Coal Authority manages the after-effects of mining. Operating for 30 years, we are busier than ever dealing with legacies, and new challenges arising from coal and metal mining. We’re also modelling the impacts that climate change may have on old workings going forward. 

The treatment of water to prevent metallic elements entering drinking water aquifers and water courses is not always seen as priority for remote mines, but as water availability becomes more stretched it is becoming increasingly significant. 

In the US,  the National Institutes of Health have reported that Native American communities living by abandoned mine lands are affected by contaminated water and soil. This causes them to experience higher levels of ailments such as diabetes, kidney disease and hypertension. The same could apply to many communities living local to abandoned mine sites around the globe.

To help mitigate against this, the Coal Authority treats 220 billion litres of water per year in the UK to prevent 3,756 tonnes of iron solids entering water courses.

The aim is to use nature-based solutions, such as reed beds and settlement ponds, where possible. In some cases, we have converted abandoned colliery sites into wetland parks where people enjoy leisure and wildlife flourishes.

Reusing land

What to do with former mining land is an important question. Closure plans often focus on restoring the land to its previous use, but this might not be the best solution and community consultation is key.

In Britain, due to land shortages, much of the coalfield has been built over by housing or commercial property developers. This presents both challenges and opportunities. Risks of gas escapes and subsidence from former workings exist. 

The management of historic mining data, locations of underground tunnels and entries is vital to enable developers and home buyers to make informed decisions and when managing issues. In 2023, the Coal Authority carried out over 10,000 mine entry inspections for safety and investigated 770 mining hazard and subsidence claims.  

An opportunity also exists where warmed water in closed underground mine workings occurs – this can be used to provide a self-sustaining, low cost, renewable and low carbon heat source for heat networks.

With a few schemes in operation in Britain, the Coal Authority is working to increase adoption across the coalfield.

Circular economy

The mind set of closure as a burden on the company, to be avoided, if possible, appears to be changing. In the past large mine sites were sold on as they approached resource depletion and, along with them, the management responsibilities.

However, today, companies are increasingly accepting that closure is part of the mining lifecycle and an important part of their social contract with a community. With this mindset, opportunities can be explored, such as uses for treated water.

For instance, Peter Harvey, Managing Director for Closure and Legacy Management at Rio Tinto, said in this Linkedin post: “We see increasing opportunities to partner in re-purposing assets, targeted R&D work on earthmoving, water, waste and social aspects as well as working more closely with local stakeholders and regulators.”

Innovation is also a focus at the Coal Authority, alongside a sustainable and circular economy approach. Having a commitment to zero landfill by 2030, applications are sought for by-products of water treatment. 

For example, the 4,000 tonnes of iron-rich ochre sludge (which has historically been used as a colourant in products such as paints) produced annually from our water treatment schemes, has gone to landfill. 

However, we have recently discovered that ochre can be used in the remediation of polluted land, and it removes the smell and accelerates the bio-mass anaerobic digestion process.

With 50% iron content, the ochre could also be used in steel-making blast furnaces. We are also testing to see if it contains any critical minerals. This will enable us to meet our goal of zero landfill by 2030.

New beginnings 

The ceasing of operations and closure of mines is part of the mining cycle, just as death is an inevitable part of life. 

Mining companies haven’t always wanted to face this reality. But as communities become increasingly empowered to hold corporates to account, and the focus on environmental and social considerations increases, the responsible and effective management of mining legacies is coming more and more to the forefront.

It makes good business sense to embrace and plan for this as early as possible.

Ros Lund is an international mining professional with a passion for environmental and social governance and net zero. She is currently working on strategic projects with the Coal Authority which manages the legacies of mining in Britain. Prior to this, she was Responsible Mining Lead at the UK Government Department for Business and Trade, and a producer of noted mining events. The views expressed here are her own.