While the focus for most Calgarians is currently on the repairs set to begin anew on the Bearspaw water feeder main, the City of Calgary is readying to protect against a different set of conditions at the water treatment plant.

Although it’s in a way that can seem contradictory on the surface; addressing drought conditions in the Bow River by preventing a build-up of ice.

As the water levels ebb in the winter in the Bow River, especially from drought, the potential for buildup of frazzle ice—a slushy form of ice that forms from turbulent water and very cold air conditions—has threatened the raw water intake for Calgary’s water supply in the north.

“What happens is… that frazzle ice gets sucked into the intake. It can stick to the infrastructure, stick to the screens, and get into the pumps, and that reduces the amount of water that we can bring into the plant,” said Sandy Davis, River Engineering Team Lead with the City of Calgary.

“When that happens, we compensate. This is something that we have been dealing with for years, since the the [Bearspaw] Raw Two intake was constructed in the ’80s. So we compensate by bringing in more water from our other intake, from the Raw One intake, or from the Glenmore water treatment plant, and taking more water off the Elbow River.”

The city has looked at various ways of preventing the ice buildup over the years, but funding provided through the Government of Alberta’s Food and Drought Mitigation Program will allow a new and potentially more effective method at the plant.

Davis said that they are currently looking to install a buoy system in the river during the winter in front of the intakes, with a suspended net below the buoys to collect and divert the slushy ice—conceptually like a sieve for the frazzle ice.

Fix good value for taxpayers to increase water system resilience

Previous methods used by the city have included rotating screens to collect the ice (used to limited the effect, said Davis), along with aerators to bubble the ice water to prevent buildup, and heating the ice water.

“We’ve had various studies over there looking at how can we improve the situation. Because really, our goal is to maintain maximum flexibility in how we’re getting that clean water to the city, and our city’s water supply through the winter. So, if we can keep the capacity of Raw Two higher in the winter when these frazzle issues occur, that’s our goal,” Davis said.

The issue facing the raw water intake was identified in a 2011 climate change risk assessment report produced for the City of Calgary by Associated Engineering.

“Bearspaw WTP Raw No. 2 intake continues to lose capacity and the ability to function from the impacts of frazil ice,” said the report.

“Similarly, as populations increase, the load on the facilities, which can be compounded with the projected increase in temperature and dry days, the limited drawdown capacity of the Glenmore Reservoir and available withdrawal rights on the Bow River may present a vulnerability to the overall production capacity.”

Davis said that the project is expected to cost $1 million, with the Government of Alberta picking up about 70 per cent of cost through the grant program.

The remaining $300,000, she said, was a good value for Calgary taxpayers to improve resiliency of the city’s water system.

The City of Calgary was among the first recipients of the grants, which were revealed by the province on Aug. 6.

“It’s fantastic to have that support of the province when we do these types of projects. Similarly, on our flood mitigation and flood resilience strategy, we were lucky enough to get a lot of support from the province. It really does make a difference, and we’re looking for those partnerships wherever we can,” said Davis.

She said that a final design process would take place later this year, with a design and build of the ice sieve to go to a request for proposal after that stage is complete.

“If we can get all the pieces in place… we’ll go through a final design process and verify the effectiveness once we get a design. Looking at, specifically with our river conditions, what would this have to look like and how effective would it be,” Davis said.

“We’d have to get the regulatory approvals, and then if all of that is approved, we would move forward into having it fabricated to our certain specifications for our conditions, and then have it installed likely next fall—so fall 2025—so that it would be in place for the following winter.”