Saint-Hyacinthe, Que., is trying to fix its smelly water treatment plant problem — and it's costly

The City of Saint-Hyacinthe, Que., is putting a moratorium on all new construction near its water treatment plant in an effort to spare potential future residents from the foul odour that's been emanating from the plant for years.

Alain Leclerc, who lives a few hundred metres from the plant likens it to rotten eggs. Others are more blunt; it smells like excrement, especially on hot summer days.

"Everyone in this area learned a new word: H2S," says Leclerc, referring to hydrogen sulfide, a gas produced by the degradation of organic matter such as sewage.

Leclerc says the odour doesn't always reach the house by the Yamaska River where he lives with his wife. 

"But on days when the wind is [blowing] in our direction, it's really disturbing. We almost can't go outside, it's really not pleasant," he says.

City officials revealed at a public meeting on Sept. 10 that the concentration of hydrogen sulfide in the area surrounding the plant is 10 times higher than what is permitted by Quebec's Environment Ministry which is 4.3 parts per billion (ppb)  over a period of four minutes.

Coun. Claire Gagné doesn't want any more residents to be inconvenienced by the odour, she told Radio-Canada.

She said around 700 residents already live in the affected area.

Gas emissions not toxic, says public health doctor

Although hydrogen sulfide can be toxic at high concentrations, public health officials say that's not what's happening in Saint-Hyacinthe.

"This is really a situation where people are dealing with a nuisance and not toxic effects on their health," public health specialist Dr. Julien Michaud-Tétreault told Radio-Canada.

He specializes in environmental health and health risks, and his team was called on by the City of Saint-Hyacinthe to analyze its gas emissions.

"Some may experience stress, fatigue, nausea, stomach aches. Some might complain about experiencing perturbed sleep so it's not benign either as repercussion," he said.

Hydrogen sulfide starts generating serious health risks at a concentration of 100,000 ppb becoming deadly over 500,000 ppb, according to the US Occupational Safety and Health Administration.

Developer suing the city

The suspension of new commercial and residential development is in place until the end of 2027, as the city upgrades its water treatment facility, expands its capacity and hopefully solves its infamous odour issue.

A real estate development company, Robin Immobilier Inc., is suing the city, asking for $7 million in compensation. It says the moratorium gets in the way of its plans to develop 1,000 homes on the land it owns next to the plant.

Construction work on the plant is expected to begin in the winter of 2025.

Leclerc says the city should have upgraded the nearly 40-year-old plant a long time ago. He was a city councillor himself from 2009 until 2017 for the Bois-Joli district, which houses the plant. 

He says this was an issue he brought up during his time in office, but that he'd always receive the same answers: that the plant was experiencing technical difficulties and was operating at capacity. 

"But [the odour] was coming back every month, every week and now it's every day," he says.

The deputy director-general for technical services at the City of Saint-Hyacinthe, Charles Laliberté, says that when the plant was inaugurated in 1987, there weren't really any systems in place for odour mitigation.

"The rule on air quality came out a bit later so we're really adapting to that rule," he says.

He says the city only became aware of the plant's elevated hydrogen sulfide emissions in 2018 after an external firm carried out a sample analysis of the water basins around the plant. The city then commissioned two more studies in 2022 and 2023, the results of which were shared in the September meeting.

In total, the cost of upgrading the facility will amount to $110 million, according to the city —  $80 million over the original estimate made in 2020. Laliberté says that at least $5 million will go toward odour management.

Leclerc says that price tag and its impact on municipal taxes has him concerned, but says their options are limited.

"We have no choice," he says. "We want to save the river."