Turcot Interchange – Dynamic and smart stormwater management

Located in the heart of Montreal, the Turcot interchange was built more than 50 years ago. Some 300,000+ vehicles rely on it per day and the structures were nearing the end of their useful life. WSP was awarded the detailed design, including the stormwater management for the project. Consequently, construction of numerous water management structures was planned, including surface retention ponds, line retention, flow controllers and two pump stations.

The Turcot interchange drainage network relies on the City of Montreal's rainwater collection and domestic water collection system, and more specifically on the Saint-Pierre high and low level sewer network (combined sewer network). This raised several challenges related to the hydraulic capacity of the City of Montreal's collection system, the control of overflows (particularly from the combined sewer) to the St. Lawrence River, and the impact of flooding in neighboring areas. In particular, WSP had to ensure that the planned Turcot interchange stormwater management system met the environmental and municipal stormsewer network requirements, in terms of peak water flows and piezometric level to the collectors and annual report.

During stormwater management design it was identified that it would be beneficial to incorporate the two planned Turcot project pumping stations (SP-01 and SP-02) into the city’s intelligent sewer management system. On the island of Montreal, the intelligent sewer management system operates all interception works based on precipitation forecasts, to optimize the use of available retention and minimize overflows to the river. Thus, by integrating the two pumping stations with the city’s automated dynamic management system, it was possible to optimize the available retention volume for overflow control and reduce overflows to the river.

The goal of the dynamic pump station management is to optimize stormwater management structures to protect highway and municipal infrastructure while reducing the volume of overflow discharged into the Saint Lawrence river.

Two outlets were planned for the pump stations: the Saint-Pierre collector and a future artificial wetland. Water would be pumped to the wetland to maintain its balance. An overflow pipe was planned from the wetland toward the Saint-Pierre sewer network. When the wetland is saturated, an automated diversion chamber (part of the pump station dynamic management system) diverts the water to the outlet into the Saint-Pierre sewer network.

For successful, smart management of the pump stations, several specific installations were necessary:

• The pump stations were integrated with the city’s automated dynamic management system, thereby enabling control of the stations based on weather forecasts;
• Level sensors were installed inside the pump stations, the stormsewer and the wetland in order to provide real-time information on water levels in the retention structures and receiving environments;
• 4 high-flow pumps were installed at each pump station;
• 2 low-flow pumps were installed at the SP-01 station to pump water into the wetland.

Together, these installations allow a smart system to be created for dynamic pump station management. For example, this system makes it possible to increase the discharge flow rate to the stormsewer when the latter is not at full capacity, in order to free up unused volumes in the water retention pond ahead of heavy rainfalls. Conversely, it is possible to retain water in the water retention ponds when the collector is full.