In ‘landmark’ moment, Diavik’s final closure plan is approved

Regulators have approved a final closure and reclamation plan for the NWT’s Diavik diamond mine, a moment described as a territorial and global first.

Though Diavik is by no means the first mine in the NWT to close, experts describe it as the first to do so according to a predetermined schedule and with a full closure plan in place.

Commercial operations are set to end later this month. Active closure work will take until roughly 2029, followed by monitoring that could last into the 2040s.

In a letter last week approving Diavik’s plan, Wek’èezhìi Land and Water Board chair Mason Mantla said the regulator was “proud to see Diavik be the first mine to close as planned” in the region.

“This is a landmark,” land and water board executive director Ryan Fequet told Cabin Radio.

Fequet said Diavik is “setting a new standard of closure around the world,” adding that Rio Tinto, the mine’s owner, is treating the mine as a showcase for responsible closure in a jurisdiction with high environmental standards and Indigenous participation.

“All we really should care about is the end land use,” Fequet said.

“Will this area be available for the owners of the land, who have traditionally used it for those practices like fishing and hunting, and the caribou migration that goes through the area?”

A Rio Tinto spokesperson called the approval “an important milestone” and said the company is committed to continuing to work with the board and Indigenous partners through the closure process.

Areas where work is needed

While the board approved most of the plan’s objectives and criteria, it still ordered 31 revisions and requested upgrades to several parts of the plan.

The most prominent gap is Diavik’s revegetation strategy.

The board said the plan does not contain the level of detail expected in a final plan and compared it unfavourably to the approach approved for the now-closed Snap Lake mine. The board ordered a significantly revised plan within six months that includes species native to the mine’s location, such as willows, blueberry and cranberry.

The board endorsed the concept of making an independent expert available to Indigenous groups to help advance the revegetation plan, an idea originally put forward by the Tłı̨chǫ Government. The Tłı̨chǫ Government also offered nine Elder recommendations on vegetation, though Diavik said they were received too late to be incorporated into this version.

The board ordered a specific plan for the closure of Diavik’s North Inlet, a body of water the mine used during operations. The original plan was to fully reconnect the inlet to Lac de Gras, allowing fish to move freely in and out.

Instead, the board approved a shift to what is called a hydraulic-only reconnection – a structure that would allow water to circulate but block fish from entering. That approach was supported by the Tłı̨chǫ Government.

Elders who visited the site in the summer of 2025 said a fish barrier would help build confidence about the safety of fishing in Lac de Gras itself, even if water quality standards are met.

The board told Diavik to confirm with Environment and Climate Change Canada that the approach complies with federal mining effluent regulations. A detailed plan is due within six months.

A third area flagged by the board is the processed kimberlite containment facility, where fine kimberlite slurry must freeze before a rock cover can be placed on top.

If the slurry does not freeze on schedule, it could delay the closure timeline and raise questions about wildlife safety. (This part of Diavik has already been under scrutiny lately, as a remotely operated bulldozer fell into some of this material in December and couldn’t be recovered.)

Fequet said the time taken by this planned freeze is in some ways “the driver of how long Diavik will be on site,” adding that the mine anticipates completing active closure within three years but uncertainties remain.

The board agreed with the view of some groups that five years of thermal monitoring is likely not enough to evaluate the facility’s long-term performance.

‘Still far from ready’

While the regulator broadly praised Diavik’s approach, the Environmental Monitoring Advisory Board – the independent body that monitors the mine’s environmental performance – was more critical.

Emab said in its submissions that the mine’s plan was “still far from ready for approval.”

The board acknowledged parts of the plan were not yet ready but decided those could be addressed through revisions without delaying the start of closure work.

More: Diavik’s full closure plan and comments from other groups

Fequet said the process of working through the entire closure planning process for the first time under the territory’s co-management system had been “very enlightening for everybody,” with lessons learned on all sides.

Diavik has been central to the NWT economy for more than 20 years. In 2024, the mine reported spending roughly $285 million through northern businesses, of which $131 million was with northern Indigenous businesses.

Staffing is expected to drop from about 900 to between 200 and 300 once closure work begins, falling further to between 100 and 250 through 2029.

More: A quick guide to the end of Diavik

The closure plan decision came as the Tłı̨chǫ Government and Rio Tinto signed a separate closure agreement in Behchokǫ̀. The North Slave Métis Alliance signed its own closure deal with Diavik in December.

The NWT’s other two diamond mines face uncertain futures.

Gahcho Kué paused a key project last month – one that would have extended the mine’s life – and said it had begun engaging with about five percent of its staff about redundancies.

Ekati received a $115-million federal loan late last year after laying off hundreds of workers.

Diavik is the first of the three to reach the point of planned closure. How that now proceeds is expected to set a benchmark.

Diavik’s existing licence requires that the territorial government hold $184.77 million provided by the mine in security for its closure, according to the plan approved last week.

That figure should dwindle over time as parts of the closure plan are completed.