Montreal experiments with urban water features that could protect the St. Lawrence River
'Blue-green alley' will be open to public, providing greenspace with water basins
With both feet sinking into damp dirt, urban planner Pascale Rouillé surveys a narrow strip of land that will soon be used to not only retain runoff, but also be bursting with greenery that the community can enjoy.
Tucked in next to a warehouse known as Bâtiment 7 in the Montreal neighbourhood of Pointe-Saint-Charles, near the intersection of Le Ber and Sainte-Madeleine streets, the terrain will become what has been dubbed a "blue-green alley."
Construction crews have been adding the finishing touches to a retention pond and park features to the 100-metre strip that will serve as a collection basin for the rainwater and snowmelt that would normally flow off the warehouse and into the city's sewer system.
That warehouse, once used for railway maintenance, now houses community groups and there has been a grassroots effort to build an outdoor green space that would help prevent overflow into the St. Lawrence River.
Montreal already has an abundance of "green alleyways" — alleys behind or between homes that have been given new life with plants, gardens and outdoor space to socialize with neighbours.
Green alleyways reduce heat island effects, improve air quality and reduce vehicle traffic, the city says. But green alleyways aren't known for water retention, and that's where the blue-green alley comes in.
Each year, the equivalent of 1,200 Olympic swimming pools overflows the drainage network and ends up in the river, according to the city of Montreal's water service.
"In Quebec, we have thousands of overflows a year, which is really problematic for our natural environments like the St. Lawrence River," said Rouillé, president of Ateliers Ublo and member of the Alliance Ruelles bleues-vertes, which has been pushing for the project.
"We were wondering what our solutions are to limit these overflows."
WATCH | Explore the blue-green alley coming to Montreal:
She said all these overflows not only contaminate rivers, but could eventually lead to flooding, she said.
Over the past year, the warehouse's roof drains were disconnected from the sewer lines so as to direct water to a bioretention area — designed to collect runoff.
Protecting environment with retention
While some bioretention basins may filter water slowly through soil, these have a membrane at the bottom, allowing for the water to be collected and treated to promote the growth of plants known for absorbing large quantities of water.
The collected water can also be routed to gardens for more plant or food production.
"All these elements will eventually reduce the pressure on the municipal network," said Rouillé.
Véronique Houle, responsible for the development and outdoor facilities at the building, said there will be an effort to bring the community closer to water, creating an educational living environment.
"We plan to install a water mill, water boxes and a water tower — a tank with a valve — so that the water can be used to water the plants, for example. The gutters will also be open so that we can see the water flowing from them," she said.
While the borough takes care of the trees, some 3,000 native plants, shrubs and grasses will be planted in June by volunteers.
This distribution of responsibilities is a reflection of the project's inclusive style — each stage, from design to completion, has seen the work divided between the stakeholders.
"It could have happened strictly on the public side or on the private side, but here, the sharing is between the two," said Rouillé.
Soil decontamination slows project
The framework for this project was approved last week at the Sud-Ouest borough council, said Houle, who described the agreed terms as unique because they determine the roles and responsibilities — development, construction, management, maintenance — which fall respectively to Bâtiment 7 and the city.
Instead of delegating most of the project to the public works department, as would have been the custom, the Alliance surrounded itself with organizations such as the Centre d'écologie urbaine de Montréal and the Société d'habitation populaire de l'Est de Montréal.
Houle said the project hit delays due to the pandemic and soil contamination.
Construction was supposed to take three to six months, but it ultimately took more than a year. Now the goal is to open the area up next month.
A similar project, called La Ruelle Turquoise, has been proposed in the borough of Mercier–Hochelaga-Maisonneuve, but the process stalled for lack of sufficient support and funding.
with files from Radio-Canada
