RootCells Perform at North America’s Tallest Tower

By Kristyn M. Levis

The latest project by Citygreen® in Toronto, Canada is proof of the encompassing nature of their product range.

The main goal for the revitalization project of the existing CN Tower Public Realm, in the heart of the Entertainment District in Toronto, was to redo the space and clarify pedestrian movement patterns to the tower’s main entrance from Front Street and Bremner Boulevard.

Trevor McIntyre, Director of Landscape Architecture and Urban Design, for IBI Group was the design lead and Chris Calabrese, landscape designer for IBI Group was the design/construction coordinator. IBI Group’s involvement included Landscape Architecture, Architecture, Urban Design and public placemaking.

“This is a critical destination for tourists and visitors to Toronto, and has been neglected for several decades; Canada Lands Corporation took the lead on initiating and delivering the project on the basis of a Design-Build competition, with a fast track delivery,” Trevor said.

IBI Group was awarded the project in February 2012 after a fast track Design/Build proposal process. The construction began in late May 2012 and “substantial completion” was met by May 2013 with an overall budget of around $16 million.

The project included three major components – the Landscape Architectural design and construction of the public realm, Architectural work including a new vertical circulation system with glass elevators, stairs, a 15 metre high canopy to provide weather protection, and a new signage component of a 35 square metre electronic media sign.

As part of the renovation at the base of the tower, a new amphitheater was designed by the IBI Group. Although Citygreen’s RootCells® were not used in this case for street trees, RootCells were successfully used as spacers in the renovation of the CN Tower lower plaza.

“The Citygreen system provided the flexibility and functionality necessary in order to work within the confines of the existing site conditions without exceeding the structural roof slab loading capacity,” said Chris.

He added that since Citygreen’s RootCells module is smaller than most pre-manufactured soil structure systems on the market, it offered the required height in order to fill in the gap from the structural roof slab below and the ‘fixed’ paver finished grade height necessary to tie into adjacent elevations and utilize existing drainage structures.

Aside from using the 98mm RootCells, 25mm Gravelrings were placed upside down to increase the overall fill depth to a height of 123mm as necessary for this application.

Jeremy Bailey, Citygreen consultant to the Landscape Architect says, the project utilised RootCells as a spacer to reduce the weight above a building structure, and although they had previously used Styrofoam this system had many disadvantages.

“The Citygreen RootCell system was necessary to allow the paving surface to be permeable. The existing Styrofoam fill on the lower plaza space was unable to properly drain and caused the existing pavers to heave over the years. This made the hardscape surface aesthetically unpleasing and increased safety concerns throughout the pedestrian plaza,” Chris notes.

After using the Citygreen system, the resulting public space is a more dramatic gathering area oriented around the base of the tower, with a series of paving rings designed to appear as “ripples in the water” when viewed from the glass floor at the top of the tower.

With its competitive pricing compared to other manufacturers and ease of installation, the Citygreen system helped control construction costs.

“The installation was straightforward and the product’s flexibility minimized any potential unknown issues to arise during construction. There were several ‘surprises’ when uncovering the materials and identifying the construction methods that were used over the years at the base of the tower through previous renovation efforts. All along, the solution was simple. Citygreen’s RootCell system replaced the previous renovation materials/methods and has proven to be effective,” Chris says.

He added that the Citygreen RootCells, Gravelrings and Filter Grid were easy to work with and could easily be modified or cut to accommodate the necessary angles and grade limitations for the project.

“On-site construction mobilization for Citygreen’s materials did not require extensive equipment in this very busy public area. As a result, access to the tourist attraction was not hampered by the lower plaza RootCell system installation,” he says.

The most challenging issue during the project was maintaining site accessibility and allowing an open door to Canada’s greatest attraction through strategic hoarding placement and a detailed construction schedule.

“This was the portion of work that required most attention. There was no back door access and closing the attraction was not an option,” Chris adds.

After the project was completed, the system was a “perfect fit given the existing site conditions, drainage objectives and high level aesthetic qualities of the site”.

Because of the product and construction experience, Chris says they would recommend the Citygreen system to other design consultants and contractors. There have been no issues since the project was completed. After a recent visit by Jeremy, he confirmed that the location “looks like the day it went in”.

Supplier Contact: Citygreen Urban, info.na@citygreen.com/ – www.citygreen.com/