The owners of the NWT’s Diavik Diamond Mine are hoping to join the fight to return Yellowknife’s Frame Lake to its former glory.
Many Yellowknifers today know Frame Lake as a “dead lake” where fish don’t live and it’s not safe to swim or harvest nearby edible plants – but that wasn’t always the case.
The lake at the heart of the city was once a favourite swimming locale, home to McNiven beach, where families would hold picnics on the sandy shore and there was even a lifeguard on duty.
The lake was also a popular fishing spot. Traditionally known as Enaàtì, it was the site of a Yellowknives Dene fishing camp.
“Frame Lake is really important to Yellowknife,” said Sean Sinclair, project lead for Rio Tinto, which operates and part-owns Diavik.
“It just seems like a really good opportunity for us to have a positive impact on the city where so many of us live.”
Rio Tinto is required to perform fish habitat compensation work as a condition of operating the mine. Sinclair said the federal Department of Fisheries and Oceans suggested revitalizing Frame Lake, a goal many organizations have been working on for years.
Dr Tim Patterson, a Carleton University earth sciences professor who has overseen research on Frame Lake, says there are two main problems: high arsenic levels and nutrient buildup.
While in production, the city’s Giant and Con gold mines released toxic arsenic trioxide that fell on nearby land and water. Patterson said arsenic “keeps bubbling up toward the surface” of Frame Lake.
Research indicates the lake became rich in nutrients as a result of urban runoff, use of the lake as a winter snow dump and, potentially, dumping.
Urbanization around Frame Lake, particularly the building of the causeway in 1975, slowed the flow of the lake, further causing nutrients to build up with nowhere to go. That led to an increased growth of plants.
“The bottom is almost completely covered with very luxuriant plant growth, and I mean luxuriant, it’s just like a thicket,” Patterson described.
He explained that those plants release carbon dioxide and consume oxygen when they die and rot in the winter. That has led to oxygen levels so low that even by the 1970s, the lake could no longer support fish. Without fish as predators, the lake became overrun with leeches.
“This lake began to just have one problem after another and began to get mucky from this rotting vegetation every year,” Patterson said.
“There was a story, I guess in the 1970s some time, about some young girl who supposedly went in and came out completely covered with leeches. And that kind-of was the end.”
Yellowknife Mayor Rebecca Alty has fond memories of swimming at McNiven beach as a kid in the 1990s.
“We would stop off at the gas station and pick up little salt packets so that we could get the leeches off at the end of our swim,” she said. “When you’re little and you don’t have a car to get out to the main beach, Frame Lake was a great place to go to the summer and cool off and swim.”
What was once a thriving beach has now been taken over by a thicket of willows. Signs installed around the lake in 2017 warn of high arsenic levels.
Yet the lake remains an attraction for locals and tourists alike, even if they can’t take a dip or drop a line.
Frame Lake offers an extensive walking trail, while its shores boast the Legislative Assembly, Prince of Wales Northern Heritage Centre, and Yellowknife City Hall.
What’s the solution?
Rio Tinto is proposing to install an aerator in Frame Lake – which would add oxygen to the water – then reintroduce fish from nearby lakes.
Sinclair said the aerator is designed so that it won’t affect ice thickness, meaning people will still be able to skate, ski and snowmobile over the lake in the winter.
That was one of the recommendations from research into the lake. Patterson said an aerator would both allow fish to breathe and cause plant material to break down more rapidly.
Other suggestions researchers have proposed include installing stormwater management ponds – which would allow greater water flow, flushing out nutrients – and dredging the sediment at the bottom of the lake.
One study found that at least 180,000 cubic metres of sediment, much of it contaminated by arsenic, has been introduced to Frame Lake since around 1962. Core samples even showed ash in the sediment from when Christmas trees were burned on the lake between 1968 and 1971.
Sinclair said the project team looked into dredging but it’s not an option Rio Tinto plans to pursue.
“It’s just a lot less practical. It would be a huge effort. You’d end up disturbing and resuspending sediment,” he said.
“I think there are quite a lot more challenges and risks associated with that option rather than this aerator, which is a lot less intrusive.”
Overall, Patterson said he’s pleased the project is moving forward.
“Up until now, there hasn’t been much action taken to try and recover this wonderful, natural resource which is sitting right in the middle of Yellowknife,” he said.
“I’m quite heartened to hear that Diavik is going to be making efforts now to attempt to clean the lake up.
“If we can make some contribution to helping recover places like Frame Lake and put them back the way they were, everybody in the whole community would benefit.”
Mayor Alty is also supportive of the project.
“I think it would be great to see this lake, in the middle of Yellowknife, have fish and some more activity with it,” she said.
Rio Tinto’s project is in its early stages. The company has met with groups like the City of Yellowknife and Yellowknives Dene First Nation to discuss the project, and now plans to submit an application to the Department of Fisheries and Oceans.
Sinclair hopes local organizations can take over the project in the longer term.
The Yellowknives Dene First Nation declined a request for comment regarding the project and the lake’s cultural significance.