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Mitigation approved for creeks

Three more mountain creeks in the town of Canmore will see short-term flood mitigation work completed before next spring. Council approved $2.

Three more mountain creeks in the town of Canmore will see short-term flood mitigation work completed before next spring.

Council approved $2.7 million for work on Three Sisters Creek, $350,000 on Stone Creek and $350,000 on Stoneworks Creek at its Tuesday (Nov. 19) meeting.

Manager of engineering Andy Esarte said the new projects are an extension of the forensic analysis conducted by BGC Engineering after the June flood, and follow $14 million in short-term flood mitigation work on Cougar Creek.

“Tonight’s recommendation is for short-term mitigation for the next three priority creeks,” Esarte said. “There is a possibility that before next June we will come back and look at approvals for other creeks, but long-term mitigation will come after detailed hazard assessments are complete.”

The total of $3.35 million in work is also expected to be funded through provincial grants and $609,400 from Three Sisters Mountain Village, as the work on that creek would be on the developer’s property.

Esarte said during the flood crews focused work at the lower end of the creek where it goes under Three Sisters Parkway, as it was the only road connection out of the community after the Trans-Canada Highway flooded.

“What we were not aware of is what was happening upstream,” he said.

Upstream, a pond for the undeveloped golf course filled with 15,000 to 20,000 cubic metres of sediment, which prevented that material from coming downstream and affecting the roadway. Even further upstream, said Esarte, the bottom of the channel and the top of the bank were quite close.

“That suggests the creek came close to leaving the channel and flowing over the fan,” he said. “If the creek was to leave the channel at that point it would flow down into a development area.”

Mitigation for Three Sisters Creek is expected to include removing debris from the pond, excavating the channel to re-establish its capacity, putting in a berm to protect the developed area if the creek leaves its channel or possibly raising the bank of the creek and putting in additional armouring.

Flooding of Stone Creek caused $7.5 million in damages to the Pinnacle building and adjacent properties in June. Esarte said several recommendations for short-term mitigation are being considered, including increasing the capacity of the existing channel between the fan apex and Stonecreek Road and replacing the crossing at the road with a ford rather than a culvert. He also said a small berm could be established on the east bank to prevent water and debris from flowing toward the condo building.

Meanwhile Stoneworks Creek will likely see re-establishment of its flow pattern prior to June’s flood event and two deflection berms. One berm would direct water towards the visitor information centre, while the other would protect Cross Z Ranch.

“Stoneworks Creek contributed to impacts around Palliser, which cost $100,000 to clean up, and the water then ponded into the storm system.

“It also combined with water coming from Silvertip and then crossed the highway over to the hospital area and contributed to flooding around the hospital and the Bow Valley Trail area.”

When it comes to long-term mitigation on Stoneworks, Esarte said it is going to be challenging because there is no development now, but the creek is upstream from a lot of parcels slated for development. He said a hazard and risk assessment is needed to understand what that means and what mitigations might be needed in future.

With Canmore taking the lead in flood mitigation design and construction, council had some concerns the municipality would hold all the liability if the mitigations don’t work.

“I have a whole lot of confidence we are doing the best that can be done with the resources we have,” said Councillor Sean Krausert. “I also think it is a good thing the Town is taking the lead to move these things forward because I think this is the only way we will get these things done.

“My concern is that we as the Town are taking the lead and going onto private property or provincial property and doing the work and that should not absolve the owner of that property from the responsibilities they have.”

Krausert proposed a successful motion to direct administration to take steps to protect the municipality from liability as advised by legal counsel.


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