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Dam expert to be hired for 40 Mile Creek project

The Town of Banff plans to hire an expert to investigate options to prevent the potential collapse of an aging dam on 40 Mile Creek north of the Banff townsite.

The Town of Banff plans to hire an expert to investigate options to prevent the potential collapse of an aging dam on 40 Mile Creek north of the Banff townsite.

A structural inspection earlier in the summer revealed there was no imminent danger of the dam failing, though officials say it is possible an earthquake could bring down the dam and cause some flooding in the downtown core.

Officials say one of the biggest concerns should the 1946 dam ever fail is the release of a big build-up of sediment, which would wipe out the effective operation of the creek.

“The present condition of the dam is good, and there’s no indication anything would happen, unless there was an earthquake,” said Adrian Field, the Town of Banff’s engineering manager.

“But the first line of defence is to prevent anything from happening. If something did, there is no risk to the highway bridge and there may be minor flooding downtown.”

The Town has set aside $50,000 to remove trees from the crest of the dam in 2013 that have the potential to come down, as well as to hire a consultant to look at options to remove the risk of the structure failing.

Another half a million dollars is earmarked for 2018 for the potential decommissioning of the dam, if they go that route. Parks Canada has indicated a willingness to chip in dollars, but funds have not yet been forthcoming.

There has been no recent modeling done, but a 1972 report states the total capacity is 18,500 cubic metres and, at that time, 7,400 cubic metres of the total volume was occupied with silt.

“We don’t know what the solution is, but we’re hoping to find more innovative, and less expensive, solutions to allow us to keep the dam in place,” said Field.

The 2010 Banff National Park management plan says Parks Canada will work with the Town of Banff to restore 40 Mile Creek through a decommissioning plan for the aging dam between Stoney Squaw and Cascade Mountain.

The dam was built about 1946 and was used as Banff’s drinking water supply. These days, the town’s drinking water is drawn from several deep wells in the area.

The municipality inherited the dam as part of the incorporation agreement.

However, officials say the water has been contaminated with a disease-causing bacteria since before incorporation and the dam could never been used, as suggested in the agreement, as a back-up to the fire water supply as this would result in contamination of the town’s drinking water.

“We’ve never had any beneficial use of this structure,” said Mayor Karen Sorensen. “It could never have been used as backup fire water.”

An inspection last August, completed by EBA Engineering Consultants, revealed there were no serious structural concerns at this time, but they did recommend routine inspections.

The Town of Banff is responsible for inspections every three years, which will aim to identify any concerns and potential measures, including partial draining of the reservoir to reduce sediments.

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