Sainte-Marthe-sur-le-Lac was warned 2 years ago dike could break
Report commissioned by city officials found 2017 spring floods weakened dike structure
The city of Sainte-Marthe-sur-le-Lac, heavily damaged by floods this spring after a dike was breached, commissioned a report two years earlier that noted dike's fragility and warned of potential disaster.
The Axio Environnement report, obtained by Radio-Canada, was commissioned by city officials after the 2017 spring floods. It found that the dike's structure had been weakened by strong waves and that it could breach during flooding, which could "affect the entire area."
But the city's mayor, Sonia Paulus, says the report didn't stress an urgency to act.
"Nowhere in the report does it indicate an emergency," Paulus said in an interview.
On April 28, the dike that was supposed to protect Sainte-Marthe-sur-le-Lac residents from flooding failed, forcing the evacuation of 2,500 homes — 6,000 people or about one third of the city's population.
In a chapter entitled "anticipated disaster," the near 70-page document said "the force of the waves [from the 2017 floods] created large erosion zones." In the case of a 100-year flood, it warned that close to 1,400 buildings — mostly homes — could be affected.
"Homes could be heavily damaged and materials such as drywall, mineral wool, carpets, etc. could be contaminated … mould could grow due to humidity, which represents a potential health risk for residents," the report said.
The report also warned the administration of the risk of major psycho-social impacts brought on by flooding, such as "depression, anxiety, alcohol abuse, post-traumatic stress disorder, sleeping disorder."
'We were about to do it'
The report made three key recommendations:
- Raise the height of the dike
- Add stones to prevent erosion
- Monitor and maintain vegetation (trees, roots) to prevent the structure from crumbling
The mayor insisted the city was already planning to have the dike built up. "We knew very well what had to be done and we were about to do it," Paulus said.
But no call for tenders for the heightening of the dike was ever launched. The city says it was waiting for authorization from Quebec's Environment Ministry at the time of the breach.
"We followed deadlines, ordered the Axio report, and after that, we began talks with the Environment Ministry. They asked us for additional documents," said the mayor. "The process was done by the book; no one slept on the job."
Paulus also ensured the city completed the stone work suggested by the report. "We put sandbags and we added stone in some places," she said.
The report also recommended cutting trees if needed, and to clear the dike by eliminating big roots. It's unclear if the city did so.
Looking for answers
The city administration said it still doesn't know how the dike failed. An investigation is underway.
Paulus said the report didn't identify the part of the dike that breached this year as a vulnerable area.
"Honestly, we could not have predicted it at that spot," she said.
Paulus said she wants to reassure the population that more work will be done on the dike. She said it will be solidified as of 2020, well before the 2021 deadline given by the province.
"We will have a secure dike; we will go with the best technology," Paulus said.
"People should be able to tell themselves that everything will be perfect after the dike gets elevated. As for me, when the dike will be in place, I will feel safe in the area."
Meanwhile there is a request for a class action lawsuit on behalf of Sainte-Marthe-sur-le-Lac residents before the Quebec Superior Court. It targets the city of Sainte-Marthe-sur-le-Lac, the MRC of Deux Montagnes and the province.
Based on a report by Radio-Canada's Julie Marceau