An environmental project to protect the St. Lawrence River
Did you know that the shore of the St. Lawrence River in the sector of the Bonaventure Expressway used to be a landfill site for industrial and household waste? The Corporation conducted an innovative environmental project in this area to protect the St. Lawrence River from groundwater contaminants.
Together, the federal, provincial and municipal authorities responsible for this land are investing in restoring its ecological balance. The Corporation has spearheaded these historic partnerships to identify an integrated solution to this environmental problem for the entire site.
The west sector includes the land along the Bonaventure Expressway facing Île des Sœurs at the approach of the Champlain Bridge. In this area, groundwater analyses indicated the presence of ammonia nitrogen, polycyclic aromatic hydrocarbons (PAH), and dissolved metals.
The environmental project in the west sector has been in place since September 2017. In this sector, we installed a groundwater containment and treatment system. The water is contained by a hydraulic barrier of 32 pumping wells that capture contaminated groundwater and direct it to a building for treatment before it is discharged back into the river. Every 10 days, the system cleans the equivalent of an Olympic-sized swimming pool of contaminated water, which it will continue to do for the next 15 years.
This very promising project is being conducted in partnership with Quebec’s Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques (MDDELCC).
The east sector includes the section of the Bonaventure Expressway between the Clément Bridge and Victoria Bridge. Here, testing detected free-phase petroleum hydrocarbons (diesel) contaminated with polychlorinated biphenyls (PCBs). These hydrocarbons float at the top of groundwater.
In this sector, the Corporation built a retaining wall that is 1.2 kilometres long and 8 metres deep using an innovative method called deep soil mixing—a first in Quebec—to contain and capture PCB-contaminated hydrocarbons. Every month, 127 wells retain and pump approximately 10,000 litres of contaminated water that contain an average of 160 litres of diesel with a PCB concentration of 250 ug/L, which is 4 million times above the standard for water discharged into the river. At the site, two pumping stations at each end of the wall collect the contaminants, which are then disposed of safely as per the applicable legislation.
The site has been operational since spring 2018.
A medium to grow a biofilm with approximately the same density as water to allow bacteria to develop so that they perform nitrification in 2 phases:
- Phase 1: Ammonia is converted into nitrite (nitrosation).
- Phase 2: Nitrite is converted into nitrate (nitratation).
For more information about rehabilitation in the area of the Pointe-Saint-Charles industrial park (a property of the Ville de Montréal), visit the Ville de Montréal’s website.