–The 37,280 square meters that make up the Mississauga City Hall plaza were transformed in 2011.
– The square added 30 trees in raised gardens and by design brought two previously separated areas together.
– Ten years later and the Autumn Blaze Maples (Acer × freemanii) have grown exponentially since they were installed. The $40 million infrastructure project included 1,010 1X Silva Cells to support the soil. The trees sit on a roof deck, above the parking garage, and needed the extra support.
Mississauga Civic Centre is a 37,280 square meter complex that houses the Mississauga City Hall, a towering monument of post-modern architecture designed by Edward Jones and Michael Kirkland that opened in 1987. Although it received numerous accolades, the surrounding campus and Civic Square suffered from mid-century design perspectives on public spaces, catering toward keeping people (and thus problems) out of the space. In fact, it was essentially two squares in one: Civic Square in front of City Hall and Library Square in front of the library. The spaces rested at different grade levels and were separated by Civic Centre Drive.
In light of significant residential growth in the surrounding area in the early 2000s, as well as a desire to revitalize and update the public space, the City Council endeavored to revamp the Civic Square, bringing separate squares together and calling for the creation of a large open lawn with raised gardens containing 16 new trees in front of City Hall.
Planning for the redesign of the Civic Square began in 2009 and was guided by the council’s desire to create a multifunctional, flexible, hard-surface civic space scaled for daily life as well as special events. The $40 million project evolved to become the city’s largest public infrastructure stimulus project, with costs split equally among the city, provincial, and federal governments. The first major step for the design was to bring the two squares to nearly the same grade, thus enabling a unified square to be formed via the temporary closure of Civic Centre Drive for large events. For the raised gardens on the Civic Square specifically, the objective of the design was to knit together the landscaped qualities of the intimate Jubilee Gardens, an English walled garden that was dedicated by the Duke and Duchess of York in 1987, into the Civic Square. The introduction of raised gardens to the Civic Square would create a strong green edge for a friendlier Civic Square and serve as a more open and public passageway into the Jubilee Gardens.
Because the Civic Square was located on top of a parking garage, a soil delivery system was needed that would be capable of providing a sufficient volume of soil to guarantee a long life for the trees and that could also support the weight of the pavement and the increased pedestrian traffic on the site from daily use as well as special events. The designers, Janet Rosenberg & Studio, selected Silva Cell, which has since been used on 25 other projects with Janet Rosenberg & Studio.
The roof deck was retrofitted to support the added loads of the soil, trees, and Silva Cell system, and, as with most on-structure applications of Silva Cells, a drainboard was used to provide drainage at the roof deck level. High-density foam was also laid on top of the concrete roof of the parking garage to act as a lightweight fill to bring up the grade difference between the existing roof and the plaza elevations, and was installed in variable thicknesses based on the contour of the existing space. Unlike conventional installations, stakes were not needed to affix the frames to the foam. In some areas, a concrete cap was poured over the top of the foam, and screws and washers were used to attach the frames to the subgrade concrete. In other areas, wood spacers were used between the frames to lodge them in place.
In total, 1,010 1X Silva Cells were installed across the plaza square on top of the parking garage. Because the design criteria specified pedestrian-only, the pavement section over the Silva Cells was able to be reduced from what is normally required to meet H-20 standards and a thinner pavement was used. Finally, 30 Autumn Blaze maples were planted on the square. They have since seen a dramatic amount of growth, creating a majestic tree canopy that serves to knit together the Civic Square and the adjacent Jubilee Gardens, creating a space more welcoming to both everyday and celebratory use by residents and visitors.
Since the project’s completion, the plaza has been named Celebration Square. It is a welcoming space that the mayor of Mississauga, Hazel McCallion, reflected on just a few years after installation: “Every city has a heart, and this is ours.”
Celebration Square continues to benefit residents and visitors with art exhibitions, farmers’ markets, and a seasonal ice rink. It is the site of the annual Canada Day celebration for the city, and this year features a popup dance studio.
Number of Silva Cells: 1010 1X in foam
Amount of soil volume per tree: 17.8 m3 (631.25 ft3)
Number of trees and type: 30
Type of project: Integrated trees, stormwater
Project designer: Janet Rosenberg & Studio
Project contractor: Pave-Al Limited
Installation date of Silva Cells: November 2011
Project timeline: 2010–2012