Nelson has added 2.2 million litres of treated drinking water storage at its Mountain Station water treatment facility, providing additional capacity during emergencies like major fires.
The project was identified in the city’s 2017-2027 strategic plan as part of efforts to strengthen Nelson’s water infrastructure.
Community planning manager Chris Johnson told council Tuesday the reservoir is part of the city’s regular water system, storing water after it has been treated and disinfected before being distributed to taps.
He explained that chlorine reacts with organic material as part of the disinfection process. The water needs enough time for that process to take place before it moves into the finished-water reservoir.
“In simple terms, when it contacts organics, they cancel each other out. So by default, if there’s chlorine left over in the water, that means that there’s no organics left, provided you give it a certain amount of contact time,” Johnson said.
The reservoir holds 2,200 cubic metres of treated water, which Johnson said is about half a day’s use during the winter, when outdoor watering is not taking place.
Nelson’s water demand typically sits around 4,000 cubic metres per day during the winter but can climb to about 9,000 cubic metres a day during hot, dry summer weather.
Johnson said the additional storage provides a buffer when demand suddenly increases, such as during a major fire or water main break.
“The finished water reservoir allows for us to store finished water, to increase the capacity in the event that there would be like a large fire or something that would require a lot of water,” he said.
Without enough treated water available, the city could be forced to draw untreated water into its distribution system, potentially triggering a boil-water advisory or order.
“And that would be a very big issue,” Johnson said. “We would have to go through and sanitize our whole system if we drew water through all of it, or at least those pressure zones.”
Construction began in early 2025 and will be fully finished by late 2026. Johnson said the project was tendered multiple times before adjustments helped secure better pricing.
“Finally, we made some adjustments, went out and actually got really good pricing this time around,” he said.
The project also leaves room for potential future filtration beds at the site, should Nelson ever need to draw water from Kootenay Lake and introduce additional filtration.
Johnson also told council the concrete structure is expected to have a lifespan of about 100 years.
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