On Montreal's St. Catherine Street, a big dream is punctured – and for what?

Is there room on St. Catherine Street for big ideas?

This week, the City of Montreal announced it was cancelling a project for a set of inflatable structures, which were meant to animate the street during a four-year reconstruction.

Designed by the local architecture firm Kanva, the project, Imago, would be a smart temporary intervention in the cityscape – functional, highly visible and a little bizarre. Choosing it was a sign of boldness. Cancelling it will be a sign of something else: a betrayal of Montreal's strong local design culture.

With the decision, the new administration of Mayor Valérie Plante seems to be getting cold feet. That's perhaps understandable. Kanva won a design competition in 2016 with a scheme that is unorthodox: a set of inflatable tunnels.

Luc Ferrandez, the borough mayor for the Plateau-Mont-Royal district and the politician in charge of the St. Catherine rebuild, said this week that the plan had logistical problems: "It was a great idea and it would have been a wonderful project," Mr. Ferrandez said Thursday. However, the project had already been altered in such a way that it "was not reaching the objective sought by the city."

The project was budgeted at $3.8-million. In the original scheme, the tunnels would cover the roadway while it was being rebuilt, protecting the sidewalk; then the reverse, with the inside of the translucent tunnels providing a walking area and event venue while the sidewalks were being rebuilt. In the architects' drawings, it looks like a great place for yoga.

There's no doubt the inflatable tunnels would have been highly visible and would draw people to St. Catherine. Architecture and travel journalists would love them. This sort of place-making through design is a strategy that smart cities around the world are adopting. And Montreal already knows how to do it. It styles itself a design city and has already placed a big bet on being a city of summer festivals with a well-made public realm. The Quartier des Spectacles arts and entertainment district is a real success as an ensemble of architecture and urban design. Everyone benefits from its success, particularly locals.

And yet. Mr. Ferrandez said a risk analysis prepared by city engineers under Denis Coderre's mayoralty suggested Imago would not be practical. Limited clearance for construction equipment could have interfered with the reconstruction work, slowing the project and imperilling the schedule of a planned Metro station rebuild and construction on the city's new LRT.

This, however, is exactly the kind of issue that often crops up as an architectural project gets closer to construction. Kanva, working with a variety of experienced consultants, including structural engineers Blackwell, apparently responded by altering the project to place inflated pavilions along the fringes of the site.

So why kill it now? Mr. Ferrandez offered an aesthetic objection: That in its redesigned form, "it's just a decoration." And when pressed, he suggested that local merchants didn't really want the thing: "They told us, 'We want a quick and fast construction site. We don't want delays.'"

This sort of nuts-and-bolts, get-it-done thinking is what usually drives city politics. Montreal's design competition system has provided a way of changing the conversation and creating public places of the highest design quality. That's of benefit to everyone, including locals.

It's time for the city to call its architects back and figure out how to resurrect Imago – if not now, at least for the second phase of construction on St. Catherine. The city's Projet Montréal government was elected on the winds of change. Here's hoping they won't take the air out of this fanciful and welcome project.