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YELLOWKNIFE — The Diavik Diamond Mine in the Northwest Territories says 450 million litres of wastewater spilled due to a broken pipeline. 

The spill took place on Feb. 7 but wasn't reported to the Northwest Territories government until late last week.

The territorial government says pipeline operators did not initially believe it needed to be reported as the wastewater leaked into a containment pond that was its final destination. 

The government says its inspectors have confirmed the spill is within the pond and none has been released into the environment. 

Mine owner Rio Tinto says the pipeline contained groundwater mixed with a small quantity of water used for dust suppression and drilling. 

The company says the mine was designed to mitigate the environmental risk of pipeline failures through routes away from Lac de Gras to containment facilities.

The Northwest Territories government says it has requested that Diavik divert and repair the pipeline and that the company is addressing the issue appropriately. 

Rio Tinto says until extreme weather ends and it establishes safe access to repair the pipeline, flow will continue from an alternative location within the North Inlet Facility.

"We are taking this situation seriously and will ensure such incidents get reported within the required time frames," the company said in a statement. 

The mine is roughly 300 kilometres northeast of Yellowknife. Rio Tinto is a global mining giant that has head offices in the United Kingdom and Australia. 

This report by The Canadian Press was first published March 21, 2023. 

The Canadian Press

Note to readers: This is a corrected story; A previous version, based on a spill report listing what wastewater could contain, said the water contained sewage and mine tailings.