Acidic waste rock and a leaking dam at a massive Northern Territory mine could have a devastating impact on a remote Indigenous community and the local environment, a report has found.
Sacred Indigenous sites and a river system near the McArthur River Mine face irreversible cultural and ecological damage if mining operations by Glencore Australia continue unchecked, researchers say.
The independent monitoring system set up to protect the environmental and cultural interests of the area is toothless, according to Sydney's Global Water Institute at the University of NSW and the NT Environmental Centre.
Environmental engineer Fiona Johnson says the findings, which are based on publicly released information, are disheartening.
Especially given the NT government recently approved a further expansion of the zinc, silver and lead operation, which is about 800km southeast of Darwin.
"It's hard to understand why the McArthur River Mine has been given a green light when it hadn't proved itself capable of dealing with the problems arising from its current mining practices," she said on Monday.
Some of the problems identified in the report include waste rock, which the mine assessed as unlikely to produce metals, and acid if mixed with water or air despite the independent monitor in 2008 suggesting it could've been misclassified.
It started emitting sulphur dioxide plumes in 2014, forcing the mine to submit an environmental impact statement to the NT mining regulator, which then took a further six years to approve the proposal to fix the problem.
Researchers also identified potential long-term risks to the groundwater and the McArthur River system from metal and acid contamination from a seeping tailings dam.
Prof Johnson said mine operator Glencore Australia had tried to stop the leaks by installing barriers and recovery bores but they failed to stop the seepage.
"If the water becomes more acidic, it will be able to carry toxic metals into the groundwater and river systems and poses risks to the river ecology and Indigenous communities downstream who depend on it," she said.
The report also listed 22 Indigenous sacred sites that it said were potentially under threat from the mining operations, including the Djirrinmini waterhole, which is believed to be a breeding site for critically endangered sawfish.
It concluded there had been extended delays between the independent monitor reporting issues and the mine taking action to address them, which exacerbated the problems.
"The regulatory process has failed to protect the interests of the environment and the community," Prof Johnson said.
"This pattern of delayed reporting and delayed response needs to be overhauled."
The researchers said there also needs to be more meaningful engagement with communities in Borroloola and surrounding districts.
The report is based on publicly available data on water-related issues arising from the McArthur River Mine's operations and expansion from 2007 to 2018.
Glencore said it had complied with NT and federal law and the requirements of the Aboriginal Areas Protection Authority, which protects sacred sites.
"Our current mining management plan was approved after an extensive environmental approval process, with the independent Environment Protection Authority finding that the McArthur River is healthy, water quality is good and fish are safe to eat," the company said in a statement.
"McArthur River Mine is committed to operating a safe, responsible and environmentally sustainable mining operation."
The Department of Industry Tourism and Trade said the NT has a robust regulatory regime, which includes strict and transparent independent monitoring processes.