Sunny Corner mine was abandoned a century ago. It’s still a toxic ‘deadly’ mess

Red dirt contrasts sharply with green banks of algae along the creek that trickles through the defunct Sunny Corner silver mine. The abandoned area, 37 kilometres from Bathurst, is eerie. There are hardly any animals. The plants closest to the mine are either dead or an off-grey colour. The air is still; nothing moves. And when it gets dark, the only sound you can hear are gunshots as people hunt in the nearby state forest.

The mine’s surroundings are so toxic that if it were windy, we’d be wearing masks. If it were raining, the sulphur in the dirt would turn to sulphuric acid, damaging our lungs. While some mining shafts have been fenced off, others haven’t been marked – in some cases, trail bike riders have fallen down and injured themselves. There is little to deter people from the area.

While it’s not somewhere you would want to spend much time, the site affords an insight into a problem for governments and industry that is only growing bigger – what do you do with a mine once you’re finished with it? The question is becoming increasingly important as mines and other fossil fuel-intensive projects across Australia wrap up. In the Hunter Valley alone, some 17 coal mines may close in the next 20 years.

The cost of rehabilitation

Coal mining has been fundamental to NSW and can be traced back to Newcastle in the 1790s. This industry is the reason that many small towns exist today. Coal quickly became Australia’s first commodity export, with the first shipment leaving Newcastle for India that decade.

There is little data on how many abandoned mines exist nationwide, but estimates venture about 60,000 sites, with others putting 573 of those in NSW. Each state approaches a legacy mine differently, but in NSW, the government prioritises remediation of sites that are either a risk to public safety, that pose an environmental risk or that offer no further benefits to the industry. It’s expensive work.

However, we’ve moved a long way since the 1790s, and NSW now mines a range of minerals and metals, including gold, copper, silver, nickel, lead, zinc, cobalt, lithium and limestone. The market size of the industry, measured nationally by revenue, was $501.8 billion last year, says market research company IBISWorld.

In the centuries since NSW began mining, rehabilitation conditions have also become more onerous. They are now legally enforceable, and companies must take responsibility for all aspects of the work, even after closure. NSW Natural Resources Minister Courtney Houssos says mining rehabilitation requirements were made more robust in 2021. This included ensuring leaseholders undertook rehabilitation to achieve an approved final land use, and ongoing annual reporting of these efforts.

“We will continue to evaluate if they are fit-for-purpose,” Houssos says of the requirements. “We must protect local communities after the closure of the mine.

“I am keen to explore other opportunities for post-mine options for the land, including for alternative energy and as manufacturing and skills hubs. Rehabilitating mines, which in some cases ceased work more than 120 years ago, is challenging.”

Before mining begins, “companies work with government authorities to develop comprehensive rehabilitation plans”, NSW Minerals Council chief executive Stephen Galilee says. “Rehabilitation of land disturbed by mining commences almost as soon as mining itself takes place.”

Galilee says mining companies must pay a bond that forms part of their legal obligation to rehabilitate the land. This also includes returning the land to the approved land use in line with the rehabilitation plan or development consent set out before mining begins.

The sum of bonds held across the state as of November 2022 was $3.5 billion. This figure has risen steadily over the past 12 years. The bond is only returned to the company once rehabilitation has been achieved. But in 2017, the NSW Audit Office warned that the security deposit – which was then $2.2 billion – did “not include sufficient contingency given the substantial risks and uncertainties associated with mine rehabilitation and closure” of the state’s 450 mines. The system has been in place for several decades. A NSW government spokesperson said there have been instances where the rehabilitation security bonds have been utilised not, however, for a state-significant development mine site.

‘So deadly’

Western Sydney University professor Ian Wright and undergraduate student Holly Nettle bend over the creek at Sunny Corner with blue surgical gloves on, taking samples and discussing the highly toxic water. Groundwater flows through the mine, collecting toxic minerals before they pool and trickle through the landscape.

Previous tests by Wright showed the water contained arsenic that was several hundred times above the recommended guideline, copper that was close to 10,000 times, lead about 100 times and zinc about 3000 times.

“It’s so clear but so deadly,” Nettle says, holding up a small jar of the water. “You think it’s suitable for drinking, but it’s not.”

It wasn’t always like this. More than 100 years ago, Sunny Corner had a population of 5000 and was a wealthy community, mining copper and silver. For a while, the town was one of the most productive in the country. But when the price of silver crashed in 1893, it was no longer viable. For the past few decades, the site has remained untouched, except for trail bikers, hikers and scientists who have been brave enough to walk through the ruins.

More than $1.2 million in remediation works were spent on the site in 2010 and 2017, a government spokesperson says. That included earthworks aiming to reduce the generation of acid mine water that discharges from underground workings.

But Wright doesn’t believe Sunny Corner can ever be rehabilitated. “These mines operated when we didn’t have planning legislation, and we didn’t have that knowledge of geology and environmental science to manage and reduce that pollution,” he says. “We should learn from this.”

RMIT environmental engineering expert Dr Gavin Mudd says abandoned mines – those that typically closed before 1970 – generally had few rehabilitation requirements. Mines that operated from the 1980s onwards had to adhere to strict regulations, which included security bonds.

Mudd says rehabilitation is yet to occur at a major modern mine, where effects have been monitored for several decades. “All modern mines that have been rehabilitated have been small,” he says. “Look at the scale of the mines in the Hunter Valley. If we are wrong, the scale of risk is so much bigger. We need to make sure we are funding the liability to match the scale. Otherwise, we are leaving a huge hole for the future – one that is just as big as the open-cut mines in Hunter.”

Mudd says rehabilitation plans that work at one site may not apply to others – this makes it even more difficult to get right. “There is a huge liability there, and we are not funding it properly. We need to do better.”

Mudd says that rather than relying on companies to fund their rehabilitation works, or relying on security bonds for the clean-up, it would be better to create a future fund established through an extension of the bond system.

Australia Institute research director Rod Campbell says that while Australia has entered a new mining boom for critical minerals – which are used in renewable energy – it is yet to learn lessons from the previous boom.

“I don’t think we’ve learnt from the last boom on how to tax resources, how to do royalty regimes and certainly not [how] to do clean-up,” he says. “We’ve more or less never rehabilitated a modern mine.”

Campbell says one example of a modern mine undergoing rehabilitation that will prove whether governments and industry are up to the task is the Ranger uranium mine in the Northern Territory. The mine, 250 kilometres from Darwin, shut down production in January 2021, but the rehabilitation costs keep growing and are now expected to be between $1.6 billion and $2.2 billion and to stretch until 2028 due to engineering, technical risks and water treatment. Energy Resources of Australia (ERA) – a subsidiary of mining giant Rio Tinto, which owns the mine – is meant to be finished rehabilitation in 2026 and off the site as required by its legislated conditions.

“The world is watching it,” Campbell says. “Can they do it? Is it even possible to do it? If rehabilitation can’t be done at Ranger, it can’t be done anywhere.”

He adds that cleaning up is complex for mines because often previously agreed-upon rehabilitation plans are no longer in line with community expectations. For example, original rehabilitation plans that call for filling voids with saline water after use are no longer favoured by many communities due to the environmental problems that can occur. This includes draining water from the water table below and polluting the landscape during floods.

Some mines are reconsidering their rehabilitation plans. For example, Mount Arthur coal mine in the state’s Hunter Valley is set to close by 2030. It is exploring what else it could do with its site. Originally, approvals stated that BHP needed to rehabilitate the site to include pastoral land, mining voids and remove infrastructure. “There are many alternatives and possibilities,” BHP NSW energy coal vice president Adam Lancey says. “For example, advanced manufacturing hubs, alternate energy solutions, community recreation areas and high-quality agricultural land.”

“While we are realistic about the challenges that exist with delivering alternate mining land uses post-closure, we are committed to exploring options with stakeholders in the community’s best interests.”

Have we learnt our lessons?

Despite the challenges of rehabilitation upon closure, old and abandoned mines including Sunny Corner offer the best example of what can go wrong if nothing is done. An exploration licence has been issued for Sunny Corner, which means the area could be re-mined in the future. But for now, as Nettle looks out across the mine, she sees it producing a different kind of wealth: knowledge.

Sunny Hill offers a unique opportunity to study the potential of bioremediation – a process by which biological organisms are used to neutralise a pollutant.

Nettle points to the algae blooming along the toxic creek: something is thriving in this hostile environment. With enough research, Nettle believes this could be used to help remediate the environment here and elsewhere.

“There are elements of hope. We need to learn from our mistakes and try and implement ways not to make the same mistakes again,” she says. “We’ve got our work cut out for us ... we will get there. It’s just a matter of time.”

Get to the heart of what’s happening with climate change and the environment. Our fortnightly Environment newsletter brings you the news, the issues and the solutions. Sign up here.