Frame Lake fish reintroduction will be delayed, Diavik says

Fish won’t be reintroduced to Yellowknife’s Frame Lake this summer, as originally planned, because data from an aerator installed to improve lake health is still being reviewed.

Representatives of the project team provided an update on the aerator’s first two years at a conference last week.

Frame Lake is considered a dead lake after decades of dumping, arsenic dust from nearby mining and nutrient buildup. Diavik installed the aerator in a bid to help the lake and as a means of meeting regulatory requirements to offset the mine’s impact on Lac de Gras at Diavik itself.

“Most people looked forward to Frame Lake being turned into more usable habitat,” said Mark Nelson, superintendent of environment and closure at Diavik.

“It’s not a great place to go swimming, paddling. You wouldn’t want your dog to spend a lot of time in there.”

Nelson and Nathan Lawko, an engineer in training at Diavik, spoke at the Northwest Territories and Nunavut Association of Professional Engineers and Geoscientists annual professional development symposium, which took place in Yellowknife from May 13-14.

Along with researching if Frame Lake could be oxygenated year-round and if the aerator would prevent arsenic in the soil from entering the water column during the winter, Diavik was also hoping to re-introduce fish as early as 2026.

Because Diavik is still reviewing data from the first two years, fish will not be re-introduced into the lake this summer. Nelson said he hopes to provide another update on the project in the fall, this time with data.

The project has not been without its challenges, said Lawko.

He said in spring 2025, drifting ice caused the aerator’s anchors to release and allowed the device to tilt over. Water entered the aerator’s head, damaging electrical components and the team couldn’t replace the parts until the ice had melted.

Lawko said this is when Diavik discovered the aerator didn’t have a back-up system to locally store the data it was collecting. The aerator was sending data wirelessly up until that point. Lawko said only a few months of data was lost.

Nelson said the mine was happy to collaborate with the Great Slave Snowmobile Association to confirm the aerator wouldn’t degrade ice conditions. Nelson said aerators are usually designed in a way that ice builds up around the head, making ice less reliable around the device. The model Diavik chose was specifically designed not to do this.

“Choosing a system that wasn’t going to degrade the ice was really, really important to us,” said Nelson.

He said the snowmobile association did extra ice thickness testing near the device in its first winter, and confirmed “there’s no issues with the aerator decreasing the ice thickness near the aerator.”

Nelson said there are a lot of small lakes close to Yellowknife that are experiencing a similar problem, and that this project could be used to re-oxygenate those lakes if it is successful.