City on Montreal's South Shore finally finds source of stink plaguing neighbourhood

At the corner of Collège Street and Kimber Boulevard in Longueuil, Que., it has smelled like excrement for years.

"It smells like diarrhea," said resident Francine Morissette. "It's special, really special, and not enjoyable at all."

CBC News has verified Morissette's testimony. The stink is impossible to miss. Neighbours have been demanding answers and the city has made at least two attempts to dampen the odour.

In 2022, the city redid the streets and sidewalks, but residents said that made the smell worse. In 2023, carbon filters were installed in the sewers. Still, the smell lingered.

So the city hired an engineering team last winter, and Longueuil officials called a meeting Thursday night to unveil the source of the stench.

It's coming from roof vents on houses that are connected to the sewage system, and it's unlike anything they have seen before.

"We thought about the obvious, which was that the odours could come out of the manhole connected to the sewage system," said Longueuil city spokesperson Louis-Pascal Cyr.

"But further investigation proved to us that that was not the case. It came out of the venting, the vents on the roofs of a lot of houses around the sector. So that's why this is a situation that we're not used to seeing."

The sewage system in this area sits lower than the surrounding neighbourhood, officials explained. This causes waste to slow down as it moves through. As a result, odours get trapped. With nowhere else to go, the smell rises up and escapes through rooftop vents, spreading the fermented fragrance throughout the area.

Longueuil's plan is to build an odour treatment unit that will purify the air in the surrounding area.

"So basically, we will have a depressurized system," Cyr said. "We will catch the bad air and then treat it in an area outside of the residential area with [charcoal], and then basically get 99.9 per cent of the bad air out."

Construction is set to begin this fall. But some people are upset with the timeline because it means another nostril-assaulting summer.

"The thing is, we're going to be stuck again for another 10, 11 months with the same problem," said resident Serge Rancourt. "It's not fun. Not fun. Seems like it got worse lately. Why? I don't know. I mean, right now it's basically 24 hours a day."

Rancourt said the smell was a problem before he moved into the neighbourhood in 2021. Working with his neighbour, he has been pushing the city for a solution. He said it's disappointing that it took so long for the city to thoroughly investigate and take action.

Things finally started to move when neighbours increased pressure and the media got involved, he said. Now there's a solution that is "supposed to work. But what if it doesn't work? What's next?"

The purification unit will be installed outside the storm water pumping station located along a bicycle path. The city says it will cost about $538,0000.