New boat launch, water treatment facility on horizon for Giant Mine site

Team members with the Giant Mine Remediation Project gave an annual presentation at the City of Yellowknife's governance and priorities meeting on Monday, outlining what can be expected in the near future at the contaminated site.

Remediation of the Giant Mine site began in 2021. It's expected to continue until 2038, after which work will shift to a post-care framework, including ongoing water management. The $4-billion project addresses the long-term containment and management of the 237,000 tonnes of arsenic trioxide waste that remained on site after the mine closed, the demolition and removal of buildings, and remediation of surface areas including the tailings ponds.

The deputy director of the remediation project, Natalie Plato, says this year the mill will be demolished.

"The big remaining structures to the mill, those reprocessing plants you see from the highway, most of the big buildings. The contract has been awarded" for their demolition, said Plato.

Work to demolish additional buildings will continue into 2026.

City councillors question water spill risks 

Presenters at Monday's meeting said there's been progress on building a new water treatment plant at the site; the exterior is well underway and now they're working on the interior. It's expected to be operational in 2026.

Currently, contaminated water at Giant Mine is pumped then stored in its northwest pond prior to treatment. 

A catastrophic spill at the pond is one of the biggest risks for water contaminating Yellowknife Bay, which was identified in a recent report to the city.

City councillors have been weighing whether to continue taking the city's drinking water from the Yellowknife River or from Yellowknife Bay — a cheaper option but one that comes with historic concerns about arsenic contamination from Giant Mine operations.

Plato said actively pumping water into the pond will stop next year once the new water treatment plant is ready for use.

"We will stop pumping to the northwest pond in 2026. Then we will pump that down and then it will have to dry out," said Plato.

She added that the treatment plant will run continuously, 365 days a year, and it will go "indefinitely into perpetuity or until it's no longer needed and the water doesn't need treatment."

City Coun. Tom McLennan asked Plato if the remediation team could present on specific spill risks identified in the report. Plato agreed, saying thorough risk assessments have already being done, and offered to prepare a presentation.

New boat launch to be built for 2031

As part of the cleanup and remediation, the nearby boat launch and sailing club will need to close, which has been a contentious issue for years. But the project team says it will first build a new boat launch that residents can use while the remediation is taking place.

Erika Nyyssonen, the territorial government's senior advisor for the remediation project, said the government is responsible for the public use area and sub-leases it to the Great Slave Sailing Club and the Yellowknife Historical Society. 

Nyyssonen said the existing boat launch will remain as is until 2029, when they start building the new dock. Then things will get busier as they replace soil and construct the new boat launch and floating dock nearby.

She added that the new boat launch will be comparable in size to the existing one, and the design will include parking on site. 

Nyyssonen recognized that people will probably have questions about the change.

"That is the responsibility of [the Government of N.W.T.] and I'm working closely with our [Department of] Lands admin folks to make sure that we can plan accordingly and make it less hectic than it needs to be," said Nyyssonen.

When the new boat launch opens in 2031, access to the existing boat launch and parking will be restricted due to the ongoing work in the area.

Nyyssonen noted that the schedule is subject to change. It's not yet clear if the new boat launch will remain open once work is complete and the existing boat launch reopens.