Rio Tinto aims for ‘something not many others have done’: successfully closing a NWT mine

Rio Tinto is still two years away from ending production at its Diavik diamond mine in the NWT, but there are already signs that nature could restore East Island to its former glory in the years ahead.

During a media tour last Friday, fireweed and flowers were seen growing near the mine’s main building, and green plant life was visible in some places along the gravel roads.

“The proposal was to make the site not attractive or intimidating, but neutral, for wildlife,” said Gord Stephenson, Diavik’s manager of surface operations and closures, referring to the engagement with neighbouring indigenous communities over the mine’s closure.

He said the company was still working with partners to figure out what to plant and where, if anything, to go next. Part of that process, he said, was actually testing in designated areas to see what could grow back in crushed granite and tillage.

“We can return the land to a state where it can be used by wildlife and people in the future,” said Matt Breen, Diavik’s chief operating officer. “Hopefully, when people come across this a hundred, 200 years from now, it will just look like part of the landscape.”

Dixter Wedawin, a man from Tłı̨chǫ who works in the mine and drove a bus during the media tour, hopes this will happen in the near future.

“I hope that someday my children and grandchildren will come to this place… and that my family will come here to hunt and fish too.”

What does Diavik’s closure look like?

The Wek’eezhii Land and Water Board has not yet approved Rio Tinto’s final closure and remediation plan, but mine officials say they have been working on the closure since before production began at Diavik in 2003 and have a good idea of ​​what it will look like once the last buildings are demolished.

Breen said open pit mining has already ended. The A154 and A21 pits are still being mined underground, he said, while the A418 pit has been fully mined and is now being used to store processed kimberlite.

Stephenson said the plan is to fill Diavik’s three wells with water from Lac de Gras in the fall of 2026. The process will be done with pipes and will be slow — it is expected to take six to eight months. Then, once the water meets criteria yet to be determined, the dikes holding back the lake will be perforated.

Large, mobile equipment that is not being used is already being moved off site, he said. Hazardous materials are also being moved off site. Material from demolished buildings is being taken to the site’s landfill and then covered with 15 feet of rock, Stephenson said.

Diavik also hopes that some of the infrastructure can be saved or reused.

“We’ve got a great camp, it’s in great shape. We’ve got a great airstrip that we think is well-placed to support future road development, if that were to happen,” Stephenson said. But the time to get that all in order is getting shorter.

“We hope to have answers by the end of 2025,” he said.

A 2022 version of the closure and remediation plan states that some areas – the processed kimberlite storage facility (PKC) and the waste rock storage areas – will remain “significant landscape features” after the site is closed.

On Friday, officials reported that the PKC was already 67 percent covered with granite, while the closure of the North Country Rock Pile (one of the waste rock storage areas) was 97 percent complete and had become a place of pride after a herd of caribou used it as a sleeping area in the spring.

“They were there for a couple of weeks, sort of grazing and going up and down the slope,” Stephenson said. “It shows what can be done and shows that the wildlife that lives here is comfortable in the environment.”

Which parts of the plan still need to be worked out?

While there is enough certainty about what the closure will look like for Rio Tinto to create a 3D model of the site after 2030, there are aspects of the plan that have not yet been worked out, officials said.

First, a solar farm just became operational on the mine site this year. The company hopes it can be redeployed elsewhere if it closes, but has not yet said where that will be.

The water retention ponds around the site will eventually be flooded using the same process as the open wells, but water quality criteria have not yet been established, Stephenson said.

“We need to set those criteria in a way that we can create a path to distance, which is not there now. That is the biggest challenge,” he said.

Breen said the company is “really finding its feet in this process, in a process that is not well defined.” Successfully relinquishing a mine is “something that not many others have been able to do,” he said.

Breen said he wants to consult with the territorial government and the Wek’eezhii Land and Water Board to make sure everyone is on the same page.

“If we have separate conversations, we come to separate conclusions and then we have a (closure plan) that is not right for everyone.”

Stephenson said it is also unclear at this point exactly how long scientific and traditional monitoring will continue after the site is abandoned. He said it could be between 10 and 20 years, but that has not been decided either.

He hopes Diavik will be remembered as the first successfully closed mine in the NWT