Modern miners clean up after themselves
When David Vink prepares for the start of mining at the New Acland coal mine in southern Queensland, he is also planning for the end.
When David Vink prepares for the start of mining at the New Acland coal mine in southern Queensland, he is also planning for the end.
New Hope Group’s general manager for projects and operational improvement maps out where the bulldozers will transport dirt from the active mine site to where they will set it down for future cattle country.
New Acland’s progressive rehabilitation and agribusiness is one of the ambitious projects undertaken by coal-mining companies across Australia, turning pits into pastures.
“We put the same level of effort into planning a final land form as we put into planning where we’re going to mine,” Vink says.
“We pick up the dirt and we put it down once. It’s a smarter way of mining, in that there’s a very close alignment between very high standards of rehabilitation and low cost of operations.”
Resources companies recognise the social and economic benefits that can come with restoring land. They also know effective rehabilitation is a necessity of modern mining practice, in line with their regulatory obligations.
Until a generation ago rehabilitation was not widely considered. Disturbed land was mostly left remediated. Queensland Treasury estimated 91 per cent of the state’s mined land area has not been rehabilitated. Across the coal-rich Bowen Basin the mined area is about 0.9 per cent.
Now the thinking has changed. Miners and environmental scientists are devising ways to rebuild land to ecological function and restore practical uses.
Vink says the mine employs progressive rehabilitation, following the footprint of active extraction: “It’s a specialisation that we’ve worked on to take pastoral land, mine it, and restore it to that pastoral use.”
At the outset, the topsoil is removed and stored. An active pit of about 24 hectares (about 3 per cent of their land area) is mined, surrounded by a 363-ha buffer. Then the dirt is replaced and shaped into contours. Once mining is complete, the topsoil is returned and the area is seeded with a specific program of grasses for optimal pasture. Creepers like the Japanese millet and bisset blue grass hold the soil, then pasture is added: Queensland blue grass, Rhodes and Gatton panic. Finally a legume is added for nitrogen fixation.
Vink says over the 16 years they have worked on New Acland they have determined a gradient of about 20 degrees is ideal — “something that can be graded by cattle” — and regular contours within the slope reduce water and soil runoff.
The operation, under Acland Pastoral Company, breeds and sells about 2000 calves a year.
In NSW’s Hunter Valley, Glencore’s Liddell mine is trailing pastures from mined land in a bid to expand the operations across their other sites.
Since 2012 it has run trials investigating whether cattle on rehabilitated land perform as well as stock on unmined, natural pasture.
Land and property manager, Nigel Charnock, says cattle raised on rehabilitated land put on 30 per cent more weight, due to higher quality protein and energy.
“It provided better feed quality in the pastures compared to unmined paddocks,” he says.
Charnock says significant effort — with an agronomist — goes into reseeding the land by hand, machine or even drone.
“We’re always looking at the seed mix and looking at the species within that mix,” he says. “They have, over a long time, proven to grow well and persist well in our mine rehabilitation areas.”
Across Glencore’s operations, Charnock says post-mining land use is chosen on a case-by-case basis. Some areas are being returned to a native ecology, which in the Hunter Valley means eucalypts, acacia shrubs and native grasses, while other areas are more suited to grazing.
“It’s a site-specific consideration for each of the operations,” he says. “You’ve got to consider the pre-mining environment and the pre-mining capability of the land.”
Glencore had rehabilitated 12,600ha by January 2018 but Charnock says good outcomes “do not just happen”.
“It has got to be underpinned by strong systems and a strong planning regime, and integrated across all the functions,” he says.
In February, Peabody’s Wilkie Creek mine achieved Queensland government certification a 86.67ha land area was “safe, stable, self-sustaining and non-polluting”, recognition of a rehabilitated state.
Peabody president George J Schuller Jr said the company-first certification followed land-shaping works, groundwater management and monitoring since the mine closure in 2013: “We understand that mining plays an important, but temporary role in the life of a region and that the land we mine must remain a community and economic asset long after last coal production.”
While these endeavours have been successful, the University of Queensland’s Sustainable Mining Institute associate professor, Peter Erskine, says Australia lacks an overarching policy to encourage best-practice rehabilitation.
He says there is inconsistency across processes and uncertainty in regulation for filling voids and costing residual risk.
“Without a broader, federally mandated guideline of requirement each state has different outcomes,” he says.
“The companies want the certainty to know what they have done will cost them this much so they can relinquish their mining lease.”
A spokesperson for Queensland’s Department of Environment and Science says a new Progressive Rehabilitation and Closure framework would ensure all current and future large mines would plan and maximise restoration. He says the expectations would be clear.
“This is a significant step forward for the rehabilitation of mined land in Queensland,” he says. “The new laws will compel mining companies to progressively rehabilitate mined land so we don’t leave a legacy of abandoned mines for future generations.”
But Environmental Defenders’ Office chief executive Jo-Anne Bragg says it is yet to be determined whether reforms would have a meaningful impact, dependent on their enforcement.
“The soft approach of requiring industry to backfill only certain voids needs to be addressed,” she says.
Bragg says there remain an estimated 20 mine features posing a serious risk, from 15,000 abandoned mine features. Mining companies have in the past shuttered or sold mines to avoid rehabilitation, she says.
Minerals Council CEO Tania Constable says mine-closure planning and rehabilitation is regulated through the states and federally through environmental laws.
“For a modern mine, planning commences during the assessment and approvals phases for a proposed mining project, well before mining commences,” she says.
“This includes health, safety and environmental aspects, but also social and economic outcomes.”
She says the mining industry employs 10,000 environmental scientists directly and indirectly in these efforts.
“Mining rehabilitation is critical to ongoing community acceptance and a key indicator for corporate reporting,” she says.
“While much progress has been made, the industry is continuing its efforts to improve rehabilitation methods to ensure mining’s compatibility with current and future land uses. The ability to successfully rehabilitate mined areas is fundamental to the industry’s social licence to operate and a foundation for demonstrating the industry’s commitment to operating responsibly.”