Whitehorse weighing move to multi‑ barrier drinking water treatment

By ES&E Staff

The City of Whitehorse’s water experts say additional treatment processes and disinfection are necessary for their drinking water as its quality has slowly degraded due to the influence of surface water over time. But the upgrade is estimated to cost $39 million and Whitehorse has no funding in place for the project, which would need to be undertaken within the next five years, prior to the renewal of the city’s water license.

The city withdraws and chlorinates all of its drinking water from the Selkirk Aquifer’s seven production wells. Currently, the city is only equipped to treat and distribute groundwater.

According to a staff report, over the past few years, the city has detected changes in the quality of the groundwater source. The changes observed indicate that the Selkirk Aquifer is likely under the influence of groundwater under the direct influence of surface water (GUDI).

Based on regulations under the Yukon’s Public Health and Safety Act, if a drinking water source is in contact with groundwater, then additional treatment processes, as well as disinfection, are required.

“The risk of not proceeding with the project could adversely impact the ability of the city to provide safe and quality drinking water to its customers,” continues the staff report. “Boil water advisories could become prevalent and trying to implement a rushed solution would be costlier and more challenging than implementing a proactive solution.”

Council had a number of questions for city staff about the recency and certainty of “live hit” findings of contamination. They wondered if more research should be completed to confirm the need for additional treatment barriers.

Mike Firlotte, the city’s water and wastewater services manager, told council that the husk of a Giardia cell was found in 2018, but may not be related to surface water contamination. The groundwater could also be experiencing different pH, ions or metals due to contact with surface water, he said.

“We see a fingerprint of groundwater and we see a fingerprint of surface water, and when we see that blending that means there could be evidence of infiltration,” Firlotte told council.

In 2022, Whitehorse staff completed a pre-design report to identify potential upgrades to the current groundwater treatment system at the Selkirk Pumphouse. A multi-barrier treatment system was recommended.

A staff report before the city’s corporate services committee states that completion of the recommended upgrades would provide the ability to withdraw water from both the Selkirk Aquifer and Schwatka Lake, allowing the City of Whitehorse to have a “robust supply of drinking water”.

City staff said they “simplified” their recommendations based on current regulations. For instance, they are now suggesting a level two instead of level four environmental operators’ certification for the plant. The system would be easier to operate, and simplify the hiring process for operators. Also, existing city operators with level one certification would transition more easily into the required level two for the upgraded treatment plant, the staff report stated.

The additional treatment processes would also raise annual operation and maintenance costs by $1.2 million over the current $2.1 million, and a rate increase would be required once the facility is in operation. The current design budget for the new treatment is $2 million and funding has been approved for design.

City staff were asked to come back to council and provide additional information about some of the potential risks to the current system.

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