Residents of Yellowknife’s Niven Lake enjoyed temporary relief from a winter-long foul smell as officials raced to fix citywide leaks believed to be the cause.

The “Niven Smell” drifted away several days ago, but is forecast to return in a few weeks as the lake thaws.

The smell has been a feature of the neighbourhood, which is built around an old sewage lagoon, for years. It is caused by anaerobic respiration in the sediment, sludge, and sewage gathered at the lake bottom (which produces gases like methane and ammonia) and is most prevalent during the churn of spring thaw and the fall.

Unusually, the smell remained resolutely in place throughout the past winter – putting noses out of joint at a public meeting on Thursday evening.

“The fact it has sustained over the winter, we’re really paying attention to this now,” said Sheila Bassi-Kellett, the City’s senior administrator. “We know that something’s different and it really does warrant full attention.”

Where did the smell go?

A constant flow of water through Niven Lake and into Yellowknife’s Back Bay has been identified as the culprit keeping the smell going. However, tracing the reason for that flow has proved a challenge.

“This is an entire system issue. It’s very hard to track things back to the exact problem occurring,” engineering manager Wendy Alexander told around 25 residents at the City Hall gathering.

Alexander said “leaks throughout the city” were being identified and fixed on an ongoing basis, the most recently discovered being a leak on the water line leading to the Chateau Nova hotel. The smell’s disappearance in recent days led city councillor Adrian Bell, a meeting attendee, to conclude the City may have found the leak – but Alexander sounded less sure.

“It may just be the warmer temperatures are helping. I couldn’t tell you the exact leak we fixed that helped relieve part of the issue,” she said.

“The Nova leak determined in the last week or so is most likely part of the problem. We’re not sure how much that’s contributing. We’re still trying to determine all the leaks contributing to this issue.”

‘Secondary issue’

Concerns expressed on Thursday did not stop with the smell, though Bassi-Kellett acknowledged reports of at least one Niven Lake resident experiencing “severe headaches” related to the odour.

Aileen Stevens, who has lived in the area for five years, said: “Aside from the smell, there has been significant ground movement under my house this year.

“Does that have anything to do with the fact that the lake level has increased and permeated the soil? There’s a secondary issue there.”

Other residents questioned the City about a long-term solution to eradicate the smell, but were told not to get their hopes up in the near future – not least because the gases are a natural feature of any wetland area like the Niven Lake environment.

“We probably will be looking for a long-term solution but at this point we’re trying to address what’s been in front of us today,” said Alexander.

Meanwhile, staff acknowledged Yellowknife’s widespread leak problem extends to the City’s coffers, which must make up the deficit when heated and treated water is lost.

Bassi-Kellett is asking colleagues to compare the volume of water treated monthly with the volume of water for which residents are billed, to give a rough indication of the water being lost through leaks and its value.