Toronto Waterfront: Building Sustainability with Silva Cells and Soil Volume

One of the most ambitious urban redevelopments in North American history, the multi-phase initiative along the Toronto waterfront features hundreds of healthy trees

Multi-Phase Project Totals

Number of Silva Cells: 10,853 (2x)

Amount of Soil Volume Per Tree: 15 m3 to 35 m3

Number of Trees: 354

Type of Project: Streetscape, Plaza, Municipal, Stormwater

Project Designer: Claude Cormier, DTAH, PFS, West 8

Project Contractor: UCC, CRCE, Eastern Construction, Aldershot

Installation Date of Silva Cells: 2009-2014

Soil Volume and the Toronto Waterfront

From 2009 to 2014, Toronto’s downtown waterfront district underwent one of North America’s largest urban redevelopments ever attempted, with green infrastructure at the forefront: more than 350 new trees were planted along the harbor promenade, plazas, and streetscapes, each one accessing lightly compacted soil in the Silva Cell system (of which nearly 11,000 were installed).

The success of these trees a decade later is a testament to Toronto’s ongoing commitment to sustainability. The city’s Green Standard, implemented in 2010 and rolled out in phases since, ensures that developers prioritize the health of new public-realm trees: the standard at the time of the waterfront projects required 15 cubic meters of accessible soil volume per tree (it has since been raised to 30 cubic meters).

The effects of an ambitious soil-volume mandate are most visible in neighborhood-wide initiatives like the Toronto waterfront, as residents across the area enjoy the benefits of a thriving urban forest and its advantageous canopy coverage. Soil-volume standards are, quite simply, climate action at work: not only do healthy, mature trees sequester carbon and reduce energy costs, but they help mitigate the increasingly dangerous onslaught of global heat and, in paved city environments, the heat island effect. By prioritizing soil on a policy scale, the positive impact is felt at the community level (and is, importantly, equitably distributed).

There is simultaneously an economic boost: responsibly grown urban trees, like those planted in Silva Cells, do not buckle sidewalks with their roots, keeping new infrastructure intact and usable. Likewise, as research has proven, businesses in areas with tree coverage are more successful than those without. Visitors spend more time in welcoming, shady areas, which in turns often revitalizes commerce in the area (much like it’s done in Toronto).

So, how exactly did the DeepRoot Silva Cell system help make this happen?

Silva Cells and the Trees

The multi-phase Toronto waterfront initiative was made up of four primary projects: Sugar Beach, the dockside/ bayside promenade, Sherbourne, and the Queens Quay streetscape — and, with few exceptions, the trees are looking great! DeepRoot was involved with contributing to two of the project’s chief objectives: making the water’s edge along Lake Ontario an accessible public amenity and creating a more sustainably built environment through improving water quality, reducing flooding, and bringing a green presence to parks, streets, and other publics areas. Silva Cells were used on all public-realm sites in the Central Waterfront community as well as along the adjacent street (Queens Quay).

Sugar Beach, the initial phase of the project, began in the fall of 2009 with the site officially opening in August 2010. Landscape architect Claude Cormier specified Silva Cells to meet the city’s 15 cubic-meter standard for soil volume — but he didn’t stop there, granting each of the 33 maple trees access to 35 cubic meters of soil volume.

The designers opted for a two-layer deep Silva Cell system because of the high water table. The layer and amount of Silva Cells (1,500 2X) created 2.5x the required amount of soil. There is 300mm of aggregate cover on top of the Silva Cell decks, and there are sand-set pavers at the surface. Just two years after installation, in 2012, landscape architect Marc Hallé, with Claude Cormier, visited the trees and said:

The trees at Sugar Beach — they look like they are on steroids — phenomenal growth that I have never seen before for an urban tree!

A decade later and trees continue to look remarkable, providing a shady gathering space for waterfront visitors.

Silva Cell installation June 2014 by UCC

Just a year after Silva Cells were installed in Sugar Beach, the construction along the Bayside and Dockside promenade struck ground. Over 117 trees were planted alongside the Bayside and Dockside: 88 Red Maples were planted throughout the fall of 2010 and the other 29 in 2014. Like at Sugar Beach, the amount of soil volume exceeded the city’s requirements. Each tree received 20 cubic meters of volume throughout the promenade. The trees have gone from just a few inches of ABH to close to a foot and created a shady canopy for pedestrians to enjoy the promenade on hot days.

The results over the years are absolutely stunning. DTAH led the design portion of this waterfront project, choosing Silva Cells as the technology that would allow them to meet their design goals of 20 cubic meters of soil volume per tree under hardscape — and the results, much like Sugar Beach, are impressive. These trees have all exhibited strong color, new growth, and overall vigor from the outset, and barring unforeseen pests or damage, their expected outlook continues to be very positive.

Then, in 2014, Queens Quay Blvd. received a green infrastructure revitalization. The street runs parallel to the water, separated by the waterfront projects and other promenades. The Queens Quay is Toronto’s main waterfront street stretching over 1.7 km (1 mile). The Silva Cells are supporting tree planting between Spadina Avenue and Bay Street.

Before the reconstruction, the street was defined by four lanes of vehicle traffic with narrow sidewalks and outdated public transit facilities. Dominated by delivery vehicles and used primarily as a loading zone and for the businesses and condominiums that line the street, it acted as a barrier to the city’s waterfront. The revitalization of Queens Quay has been one of the most complex street reconstruction projects in Toronto’s history and is a key element of the total waterfront transformation, creating an inviting, vibrant landmark and destination for the city.

Landscape architects West 8 and DTAH, in a joint venture, re-envisioned Queens Quay as a defining landscape that serves as a linear park connecting various parts of the city. A key element of the design is the trees that line the street and the Martin Goodman Trail, a multiuse recreational trail that for the first time is continuous along the full length of the city’s waterfront; 134 trees, on the south side of the street, were installed in Silva Cells, used to allow the soil volume to span beneath the Martin Goodman Trail and were essential in meeting and exceeding the city’s target soil volume.

The existing storm system on the street was surcharged and over capacity, and the new integrated system showed important positive impacts on the overall stormwater calculations for the site. On the south side of Queens Quay, surface runoff flowing from the Martin Goodman Trail and boulevard surfaces enters the Silva Cells via custom-designed catch basins that capture and store the first flush of runoff and allow stormwater to enter the Silva Cells through a network of perforated pipes that passively irrigate the trees. In total, 47 percent of surface runoff is being diverted into the Silva Cells; the entire system was designed to handle a 100-year flood event.

In addition to the low-impact features of the site, landscape materials were selected to be sustainable, robust, durable, and timeless. The granite cobbles that pave the street with a maple leaf mosaic hail from Quebec, and the yellow Cedar for the custom wood street light poles is harvested sustainably in British Columbia. Wood benches line the promenade and add a splash of color with their bright red cast aluminum supports that also sport the abstracted maple leaf. The project as a whole comes together as a street that welcomes not only residents of the city, but also visitors from around the country and the world.

The DeepRoot Silva Cells have an impressive history of success in the City of Toronto. The area just north of the waterfront is currently being redeveloped, yet another multi-phase initiative in which green infrastructure is a top priority — and where Silva Cells are being installed throughout the neighborhood. And, with an increased soil-volume mandate (up from 15 cubic meters to 30 cubic meters), we look forward to watching these trees grow even larger and healthier.

Maple trees’ vivid colors shine along the Waterfront Toronto in fall of 2021


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