Yellowknife city councillors are again considering options to address the municipality’s ageing drinking water infrastructure.
During a meeting on Monday, representatives of consulting firm AECOM gave a presentation to councillors that updated a 2017 study about where the city’s drinking water could come from.
The city has since published the updated study online.
The initial 2017 study recommended that the city replace an underwater pipeline with a new one so the municipality could continue drawing raw water from the Yellowknife River.
In 2019, the city received nearly $26 million in federal funding to support replacement of the pipeline. At the time, that accounted for 75 percent of the total project costs.
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By early 2023, the estimated cost for the project had ballooned to more than $57 million.
Now, city councillors are being told the overall cost could be more than $100 million.
The City of Yellowknife has used the river as its primary source of drinking water since 1968, largely to avoid possible arsenic contamination in Great Slave Lake from the nearby Giant Mine.
In recent cases where the city has drawn drinking water from the lake’s Yellowknife Bay, Chris Greencorn, the municipality’s director of public works, said on Monday that testing by the NWT health department has indicated the water quality is high.
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Currently, the city transports water from pumphouse two – near the mouth of the river – to pumphouse one, near Yellowknife’s water treatment plant, via an 8.5-km underwater pipeline.
According to Monday’s presentation, diver inspections in 2016 found leaks in the ageing pipeline. Meanwhile, there are concerns about the condition and long-term reliability of both pumphouses. AECOM said pumphouse one is currently “in a state of failure” as its heating system has failed.
The updated study considered four options to address those challenges:
- pumping water from the Yellowknife River through a new submarine pipeline and making major upgrades to both pumphouses;
- pumping water from Yellowknife Bay with a major new treatment process for arsenic removal, making major upgrades to pumphouse one and demolishing pumphouse two;
- sticking with the status quo – continuing to pump water from the river using the existing pipeline and switching to the bay once the pipeline is no longer useable; or
- using a hybrid source by pumping water from Yellowknife Bay with a new arsenic removal process, while using the existing pipeline from the river as a backup source when arsenic levels exceed a concentration that can be removed, along with major upgrades to pumphouse one and minor upgrades to pumphouse two.
Those options were evaluated based on the reliability of the water supply (given a weight of 50 percent among evaluation criteria), susceptibility to raw water quality changes (20 percent), 25-year life cycle cost (15 percent), constructability (10 percent) and ease of operation (five percent).
Based on that scoring method, and as the 2017 study had concluded, the updated study awarded the highest score to replacing the pipeline from the Yellowknife River. However, that option also came with the biggest price tag: $107.7 million in capital costs and a 25-year life cycle cost of $108.8 million.
The report’s authors recommended that the city review the rating criteria and weighting to confirm whether they still accurately reflect the values and priorities of the city.
The authors also recommended that the municipality review the existing pipeline’s condition.
City councillors asked several technical questions about the report on Monday.
City staff are expected to present further information on the matter for discussion among councillors on March 10.
