The Ranger 3 Deeps exploration decline project has suffered another setback after a collapse during works on a new ventilation shaft last week.
Energy Resources Australian reported that soft ground had “gradually subsided” beneath the top of the vent opening, and that crumbling of material has created a cavity in the shaft wall, about 20 metres below the surface running to the top, which was observed after the completion of drilling by a raise bore.
ERA said this type of crumbling is common, and that ground movement was identified in the development of the raise bore design.
The crumbling, which began midway through last week, created a cavity in the ventilation shaft wall which led to the gradual subsidence of material to the top of the shaft.
The new shaft is three metres wide and 280 metres deep, and was drilled from a side area of the decline, known as a cuddy, up to the surface. Material that has fallen back into the shaft is being removed through the main decline.
Usually the walls of the ventilation shaft would be coated with shotcrete, however this was not carried out prior to the collapse of material.
ERA chief executive Andrea Sutton said all employees, contractors and equipment were removed from the top of the shaft on Friday afternoon.
“The safety of all employees and contractors is always our paramount consideration,” she said.
“Remediation works will now be undertaken to allow work on the ventilation shaft to be completed.”
However, ERA has also stated that underground development and drilling activities are still continuing to plan, and the company does not expect any material impact on the Ranger 3 Deeps schedule and overall project costs.
Underground ventilation will be supplied through two existing air tubes that run down the roof of the decline.
The Australian Conservation Foundation, outraged at the “litany of management and material failures at Ranger”, has called upon ERA to suspend development of the Ranger 3 Deeps project altogether.
“All mine development operations at Ranger should be immediately halted,” said ACF nuclear free campaigner Dave Sweeney.
“The Ranger mine is a dog’s breakfast with eroding shafts, collapsing tanks and the company routinely losing contaminants and credibility,” he said.
“There have been enough warnings, now there needs to be a stop to works and a comprehensive and public assessment of the full impacts of this aging and failing facility.”
In 2021 ERA are legally obliged to end all mining and mineral processing and start the comprehensive clean-up of the existing Ranger site, however in their 2013 report ERA has stated they will not be able to fund the clean-up unless the Ranger 3 Deeps project goes ahead.
Rio Tinto again refused to commit to underwrite the cost of Ranger’s rehabilitation.
The structural failure of a leach tank in December 2013 resulted in the spillage of 1.4 million litres of sulphuric acid and uranium ore, which caused ERA to voluntarily cease operations, bringing attention to the issue of maintenance on site.
This has called into question the issue of regulatory approval for the Ranger 3 Deeps expansion.
“The ultimate cost of rehabilitation is uncertain and whilst ERA has used its best estimate, costs may vary in response to factors such as legal requirements, technological change and market conditions,” the 2013 report reads.
“In addition, if the Ranger 3 Deeps mine is not developed, in the absence of any other successful development, ERA may require an additional source of funding to fully fund the rehabilitation of the Ranger Project Area.
“Any inability to obtain additional capital or to monetise assets would have a financial impact on ERA’s business and financial performance.”
Under the Ranger permit, rehab works must be completed by 2026, which a strategy review has found will cost $603 million.
According to the Sydney Morning Herald, ERA currently holds $357 million, and maintains a trust with the Australian Government worth $63.9 million as of December 2013.
Some rehabilitation of the site has already been completed, including the decommissioning of filtration ponds last year.
Present rehabilitation works include backfilling the open-cut Pit 3, as well as the capping of Pit 1, which is 70 per cent complete.
“The mining giants have made enormous profits at the expense of Mirarr traditional lands and are now holding the Word Heritage listed area to ransom,” O'Brien said.
“ERA is a subsidiary of a much larger company, the responsibility for clean up at Ranger ultimately rests with Rio Tinto.”