“Silva Cells were used for their ability to achieve water quality treatment goals as well as to grow large and mature trees. Nature-based system are, by far, the best ones available to us.”
Beginning in 2012, Downtown Edmonton broke ground on the first phase of The Quarters redevelopment project, which included a complete redesign of 96 Street — transforming it from a vehicle-first thoroughfare into a pedestrian-friendly “green” street now known as The Armature. Sustainability was one of the primary goals for the design team at ISL Engineering, utilizing the five-block stretch as a welcoming, walkable green space with 90 new trees while also managing at-source stormwater before feeding runoff into the North Saskatchewan River. The DeepRoot Silva Cells assisted in providing both adequate soil volume access for flourishing root growth and by serving as an underground bioretention tool for rainwater management.
Number of Silva Cells: 4,380
Amount of Soil Volume Per Tree: 15 m3
Number of Trees: 90
Type of Project: Municipal, Government, Streetscape, Stormwater
Project Designer: ISL Engineering
Installation Date of Silva Cells: 2013
An ambitious revitalization project of Downtown Edmonton began in 2012, centered around the bold transformation of 96 Street. Now named The Armature, the five-block stretch from 103A Avenue to North Saskatchewan River Valley is the city’s first government-planned “green” street: a pedestrian-first corridor, complete with all-season parks, urban plazas, shopping, eating, and entertainment.
This new downtown focal point runs through The Quarters, a four-quadrant neighbourhood totaling 100 acres of urban land. One of the chief priorities for ISL Engineering was embracing sustainable technology in this revitalization project, which included a stormwater treatment element: assisting in the cleansing and peak-flow drainage reduction of stormwater before entering the North Saskatchewan River. Additionally, street trees were integrated into the design plans as a way of providing locals with inviting, public-use green space along The Armature.
As both a support system for the healthy growth of 90 new trees and as a method of assisting in the management of at-source stormwater, project planners turned to the DeepRoot Silva Cells.
Both sides of The Armature featured Silva Cell installations, a total of 4,380 providing 1,238 cubic meters (43,740 cubic feet) of uncompacted soil volume to the newly planted street trees. The Silva Cells also provide stormwater management along the east side of The Armature through interception and evapotranspiration — the cells have the capacity to handle 25mm of stormwater runoff, equivalent to a two-year, four-hour storm event.
“Silva Cells were used for their ability to achieve water quality treatment goals as well as to grow large and mature trees,” notes Russell Barth, senior water resources engineer at ISL Engineering. “Nature-based system are, by far, the best ones available to us.”
Runoff is collected in catch basins where sediments settle and are cleaned out throughout the year. The water then flows through perforated pipes along the upper layer of the Silva Cells to provide water for the trees above. Excess water is collected by a second perforated pipe along the base of the Silva Cells and is led to a downstream sewer.
City staff is monitoring both hydrology and water quality as well as how winter snow and ice removal practices are impacting trees and soil. The single largest monitored event thus far occurred on July 15, 2016, during which peak flow and volume reduction were 72% and 35%, respectively.
Today, Downtown Edmonton is a rejuvenated area with the “green” Armature as its neighbourhood focal point, a favorite among locals and visitors alike and, after the completion of its multi-phase improvement plans, a 2018 Award of Merit winner.