Laval invests $39M in retention basin after historic flooding in 2024
Last year, on August 9 and 10, 2024, Laval endured one of its costliest climate disasters when more than 160 mm of rain from Storm Debby overwhelmed the city’s aging sewer and stormwater systems, flooding thousands of homes. More than seven months later, the detailed report on what went wrong has yet to be released, despite promises from Mayor Boyer’s administration.
In response to public pressure and mounting criticism over under‑funded infrastructure, the city announced on April 4, 2025, that it will build a 15 000 m³ underground retention basin in the Cartier sector. The facility equivalent to six Olympic‑sized swimming pools aims to capture excess stormwater and sewage overflows during heavy rainfall, reducing discharges into the environment and protecting the Baie du Marigot watershed (City of Laval press release, April 4 2025).
Lessons from Debby
Storm Debby’s deluge was not unique to Laval; much of Quebec suffered flooding during the historic summer of 2024. According to Catastrophe Indices and Quantification via the Insurance Bureau of Canada, insured losses from Debby topped $2.5 billion, making it the province’s most expensive natural disaster on record surpassing the 1998 ice storm
Critics had long warned that Laval’s drainage infrastructure needed at least $500 million in upgrades; yet only $50 million was allocated in 2024. During a heated city council meeting on August 13, residents recalled reporting these vulnerabilities as early as 2017, with little action taken until the crisis struck.
A major investment in resilience
The new basin, budgeted at $39 million, is funded in part by a $23 million grant from the Ministry of Municipal Affairs and Housing under the PRIMEAU program. Mayor Stéphane Boyer emphasized the project’s role in Laval’s broader climate‑adaptation strategy:
“With increasing extreme weather events, Laval must modernize its infrastructure to better manage stormwater and safeguard our natural areas,” he said. Work will begin this spring and continue through 2027, during which the synthetic field at Cartier Park will be reconstructed, including upgraded lighting, seating, a new concession stand, and improved accessibility.
Over the next three years, Laval plans $1.72 billion in water‑related investments, with an additional $100 million earmarked specifically for resilience and stormwater management. Ultimately, the basin will not only control overflows but also support up to 11 000 new housing units by ensuring adequate sewer capacity.
Looking ahead
While the new retention basin marks a major step forward, residents and experts alike await the promised system‑failure report to understand exactly how and why the sewer network collapsed last summer.
As extreme weather events grow more frequent, Laval’s experience serves as a stark reminder that proactive investment in infrastructure is essential to protect communities and the environment.
