A hole big enough to be seen from aircraft flying overhead is just a tiny part of Calgary’s flood mitigation work.
The 13-metre diameter hole along 10 Street N.W. is big enough to lower a bus into it and goes 20 metres underground. A boring machine will make its way to 7 Street N.W. and Memorial Drive, creating a tunnel to connect with the Bow River.
Ward 7 Coun. Terry Wong said the upper plateau separation is designed to redirect stormwater from higher elevations directly into the river.
“It basically separates the storm sewer water from the upper part (north of Hillhurst/Sunnyside) and not having any overflow into the lower area,” Wong said.
The chair of the Hillhurst Sunnyside Community Association’s flood committee said it’s one of the most important flood mitigation projects for Sunnyside.
Charlie London described it as an “expressway” for water.
“It will take the water directly into the river rather than flowing through Sunnyside, because when the river is even a little bit high and the river gates are closed, that water in the past — and even today — backs up into Sunnyside,” he told Global News.
A resident of the area since 2005, London said water from the North Hill backing up into Sunnyside has been a frequent challenge.
He said the city looked at a variety of options to relieve the problem.
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“They looked at all kinds of alternatives that did not involve this level of engineering, and nothing else worked,” London said. “This is where we’ve ended up because this is the best solution.”
The work is taking up one lane of 10 Street N.W. near 5 Avenue and the sidewalk, and Wong said there’s been minimal impact on the surrounding community.
The river pathway near 7 Street has also been diverted.
“Certainly, the cyclists going up and down the hill are having to navigate around the construction site. But again, they’ve protected the area so the cyclists are protected from the roadway,” the area councillor said.
In June 2013, floods caused more than $400 million in damage to city infrastructure and $5 billion in damages provincewide.
A 2019 Public Safety Canada report found that flood mitigation efforts yielded a 1-to-7 to 1-to-10 return for post-flood recovery costs.
“We are on budget – it’s a $48-million project – and we… definitely will be on time,” Wong said.