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New report maps shows scale of unfilled coal pits in NSW

New report maps shocking scale and legacy of unfilled super-sized coal pits in NSW 
Call to backfill ‘final voids’, which combined are larger than Sydney Harbour

New research quantifies, for the first time ever, the size of coal mine pits or ‘final voids’ which will remain unfilled in NSW once the coal mining boom ends, which combined form an area greater than Sydney Harbour, with at least 45 voids planned or approved for the state, comprising 6,050 hectares.

Key environment groups are calling on the NSW government to require mining companies backfill the voids and properly rehabilitate land, a policy that has existed in the United States since the 1970s.

The research report, “The Hole Truth: the mess coal companies plan to leave in NSW”

  • assesses the toxic legacy of final voids for water, the environment and public safety.
  • examines the rationale used by mining companies to justify leaving the voids unfilled. 
  • explores the failure of the NSW government to properly regulate rehabilitation.

Lock the Gate and the Hunter Central Rivers Alliance have produced a short policy brief with recommendations for the NSW government, to accompany the report. The report was commissioned by the Hunter Communities Network and written by Energy & Resource Insights.

Ms Bev Smiles, spokesperson for the Hunter Central Rivers Alliance, said, “Mining companies have been living the high life. When the party is over, mining multinationals are free to walk away, leaving the public these huge voids, that if left unfilled, will exist for centuries, drawing in and tainting vital groundwater.

“The public would be shocked to realise that the strict regime in the United States which forces mining companies to fill coal pits does not exist in Australia, even though experts support the backfilling of final voids,” Ms Smiles said.

“Big, open mining pits, which can be hundreds of metres deep and kilometres long, are an eyesore for people who live nearby and sterilise the land from productive use.

“The pits, which will eventually become vast, ugly, saline lakes, pose serious risks to local groundwater and the massive high walls compromise public safety.

“Urgent reform is needed before the structural decline of the thermal coal market sees companies abruptly shut up shop, head back overseas, leaving the Australian public holding the can,” Ms Smiles said.

Steve Phillips from the Lock the Gate Alliance said, “The NSW government has already approved the abandonment of 39 open voids from coal mines across the state, and has done so against the advice of experts and the objections of local communities who fear the toxic legacy of these pits will continue for hundreds of years.

“Mining companies are being allowed to leave considerable swathes of NSW polluted and pockmarked.

“Despite the serious damage done by open cut coal mining to farmland, water and bushland, from the Hunter Valley to Western NSW and the Liverpool Plains, the government has never conducted a proper cumulative impact assessment.

“While experts recommend that all pits be backfilled, regulators have caved into the demands of mining companies and allowed them to take the cheapest and most damaging option of leaving the pits unrehabilitated, which will pose environmental risks for decades, even centuries, after a mine closes.

“Multinational mining companies in NSW have made a handsome profit from a public resource, and it is the public that will pay the price when the mining companies are long gone and these pit holes are left behind.

“For the controversial Warkworth expansion project, Rio Tinto recently cried poor, saying it could not afford to pay $2 billion to fill in the pit, which will be the state’s biggest, claiming it would make the mine ‘uneconomic.’

“The basis of the coal industry’s huge profits has been its strategy of shifting their costs and damage onto the community.”

Dr Gavin M Mudd, Head of Environmental Engineering, Monash University and Chair, Mineral Policy Institute writes in his foreword to The Hole Truth, “This report is a clinical and careful examination of the extent of the problem of final voids left after massive scale open cut mining.

“Despite industry and government assurances, there remain many unknowns in the long-term fate and behaviour of such voids – such as hydrology and the effects on surface waters and groundwaters, water quality issues such as salt loads and heavy metals, wall stability in perpetuity, and let alone what all of this means ecologically, socially and economically.”

Of the 36 open-cut operations now operating in NSW: 16 are located in the Hunter Coalfield, 9 in the Western Coalfield, 6 in the Gunnedah Coalfield, 3 in the Newcastle Coalfield and 2 in the Gloucester Coalfield. The largest open-cut mines by production volume are located in the Hunter, with a few other large operations situated in the Western (Wilpinjong and Moolarben) and Gunnedah coalfields (Boggabri and Maules Creek).


For comment:
Adam Walters, report author and Principal Researcher, Energy & Resource Insights (currently in the UK)  email [email protected]
Bev Smiles, The Hunter Central Rivers Alliance* 0428 817 282
Steve Phillips, The Lock the Gate Alliance, 0437 275 119
Dr Gavin Mudd, Head of Environmental Engineering, Monash University and Chair, Mineral Policy Institute, 0419 117 494

*The Hunter and Central Rivers Alliance represents 40 community groups across the coalfields of the Hunter and Central Coast.


High res photos of final voids, with credit requirements, can be downloaded here.

Aerial footage of Hunter Valley, Mount Thorley Warkworth and Maules Creek available here:

Download Memes and Info Graphics Zip

Executive Summary

The size of the mess left by open cut coal mines in NSW
Booming demand for coal exports in recent decades has seen the proliferation of huge open cut mines across NSW. In the last five years, 36 open-cut coal mines have been active in the state. In Australia, when mines cease production their owners are not required to fill in the pit that remains. These “final voids” may be hundreds of metres deep and kilometres in length and their impact and scale is poorly understood.

For the first time, this report provides an audit of the total size of final voids in NSW. There are at least 45 voids with a total of 6,050ha of voids either planned or approved, covering a total area greater than all of Sydney Harbour.

The legacy of toxic “final voids”
Modern coal mines have pits that may extend 150 metres or more below the natural water table. This means water impacts are a key issue with final voids. In most cases, lakes will form in the voids. These will draw down local groundwater and take significant periods of time to fill with water, often centuries. Water quality in these final void lakes is typically poor and will worsen over time. The lakes will become increasingly saline. A scientific study estimated that at one large void in the Hunter Valley may contain approximately 1 million tonnes of salt after a period of 500 years. Should these lakes overfill, the flooding of this water onto surrounding land would have a detrimental impact.

The full extent of this toxic legacy is poorly understood. Groundwater assessments for mining approvals often address final void water chemistry very poorly. In addition, there are significant variations in both the quality and nature of predictions contained in environmental impact assessments.

Most companies plan to close their operations when the last mining is occurring at the deepest point they consider is economical. At this point, the highwall is therefore at its greatest - potentially hundreds of metres tall. These highwalls are often unstable over long time periods. This can present a safety risk, with land slips endangering nearby people, animals and structures.


No requirement to backfill final voids in Australia
Backfilling final voids can mitigate many of their social and environmental risks, and presents the opportunity to return land to a form that supports pre-mine use. In the United States, filling in coal mine final voids has been required by law since the 1970s. Yet, in Australia, this is still not the case.

An incremental approach to project approvals prevails in NSW, where mining companies routinely revise project plans after initial approval is granted. The current paradigm does not force mining companies to plan for mine closure in such a way to achieve the best outcome at the least cost. This can only be achieved by embedding major closure requirements into mining plans from their outset.

Mining companies usually present cost as a critical factor in their decision to not backfill final voids and avoid it if possible. Or point to the possibility of mining at a future date. However, retrospectively filling in voids after mining is finished is the most expensive option. If, as in the United States, a mine was planned on the basis that all voids must be filled, the associated costs would be lower.

Regulatory failure leaves an expensive mess for future generations
One responsibility of regulators is long term custodianship for the land, yet they have allowed mining companies to leave a polluting and pockmarked landscape for future generations. Continued regulatory failure and flawed assessment processes are permitting considerable swathes of NSW to be rendered into ugly, vast, saline lakes.

For years the NSW Government has been letting coal companies off the hook on the question of filling in the huge holes created by open cut coal mining. Now, for the first time, the scale and cost of that failure is revealed in all its ugliness. The hole truth is, we've got a big problem.

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