City council has voted to support the idea of building a flood diversion tunnel linking the Glenmore Reservoir with the Bow River.
The tunnel is a key recommendation in a feasibility report prepared by the city's flood mitigation panel.
Last week a city committee endorsed the proposal to construct a tunnel under Heritage Drive a potential cost of $500 million.
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With Monday’s vote, council is putting the issue of major flood-prevention projects on the province's plate.
Council is recommending the provincial government compare tunnel idea with two other expensive proposals being considered — water storage projects outside the city on the Elbow River.
They include a dry dam at McLean Creek and an off-stream storage site near Springbank Road.
The head of the city's flood panel, Wolf Keller, said any two of the three projects would likely give the city adequate protection against flooding on the Elbow.
But the cost of any two of those projects would reach hundreds of millions of dollars, he said.
The city is also expecting another report later this year on possible berms and dykes which could be built at selected sites along the Bow River to provide additional protection.
The overall plan for Bow River mitigation also calls on the province to work with TransAlta on the operations of its dams upstream from Calgary to minimize future flooding.