Jasper Avenue in Downtown Edmonton Embraces Silva Cells for Stormwater and Soil-Volume Benefits

Project planners embraced LID solutions for area stormwater treatment, using Silva Cells to meet peak-flow requirements

Overview

One phase in a multi-stage initiative to upgrade Jasper Avenue in Downtown Edmonton, the 109 to 114 Street improvement project commenced in 2020. A number of goals were identified by project planners at ISL Engineering, including making the road more pedestrian-friendly. Street trees were also incorporated into the upgrades with nearly 100 new plantings found along this stretch of Jasper Avenue. The DeepRoot Silva Cell system was tasked with not only helping these trees grow — by meeting the 17 cubic-meter soil volume city mandate — but also to assist with treatment of area stormwater, with a focus on reducing peak flows during major rain events.

Installation Summary

Number of Silva Cells: 1,392 (3x)

Amount of Soil Volume Per Tree: 17 m³

Total Soil Volume: 1,615 m³

Number of Trees: 95

Type of Project: Streetscape, Municipal, Stormwater

Project Designer: ISL Engineering

Project Contractor: PCL Construction

Installation Date of Silva Cells: Summer 2020

The Project

A community-led vision to upgrade a major corridor in Downtown Edmonton, the Imagine Jasper Avenue project set out “to not only just remove and replace the infrastructure as it currently exists, but to use the reconstruction as an opportunity to enhance the avenue with an innovative, vibrant and relevant streetscape.” Initial plans for the multi-phase project were drawn up in the fall of 2015.

One of the primary objectives of the initiative was to improve the design of the streetscape itself, making it more inviting and pedestrian-friendly. This included widened sidewalks and improved sightlines (for both pedestrians and motorists) — and amphitheater-style seating was incorporated into the new plaza found at 110 Street. “Increasing the green” was also a Jasper Avenue priority. Nearly a hundred new street trees were planted along the downtown thoroughfare, each one accessing 17 cubic meters of soil volume (per Edmonton city requirement).

Finally, the underground utilities themselves needed improvement, with the storm drain system getting particular attention. In addition to upgrading the gray infrastructure, project planners wanted to incorporate green elements to assist in managing 100-year storm events. Epcor, the local stormwater utility, offered funding for LID solutions that would reduce peak flows in their existing infrastructure. DeepRoot was the perfect partner, as the Silva Cell system not only provided adequate soil volume to the new tree plantings, but also assisted in treatment of stormwater runoff in the area — including helping to achieve peak-flow reductions.

DeepRoot Silva Cell Success

A total of 1,392 (3x) Silva Cells were installed along the five-block stretch of Jasper Avenue in the summer of 2020. The system provided 1,615 cubic meters of total uncompacted soil volume, allowing each of the 95 new trees access to at least 17 cubic meters of soil (as required by Edmonton city mandate). One of the early stated goals of the Imagine Jasper Avenue project was to “ensure trees that will be planted… along Jasper Avenue have adequate soil support and can withstand the harsh urban conditions.” By creating a healthy soil atmosphere where the roots have the space capacity (and soil quality) to appropriately grow, the trees themselves become stronger, healthier, and more resistant to weather and environmental challenges.

Managing stormwater runoff was another important feature of this project. Already installed for their soil-volume benefits, the Silva Cells offered planners an affordable simultaneous advantage when the DeepRoot team suggested a second stormwater application for the system. By reserving 300 milliliters of volume at the top of the Silva Cell for ponding space (as opposed to soil), the system functions as a short-term storage facility for area runoff. This helped solve one of the primary concerns of project planners: addressing peak-flow concerns during major storm events. The ponding space in the Silva Cells slows the surge of rainwater into the sewer system, as the water gradually seeps into the soil (where it’s cleaned of pollutants) before exiting the system. The ponding space works like a swale in a daylighted bioretention pond.

This stretch of Jasper Avenue is now not only more inviting and pedestrian-friendly, but also more functional: green LID solutions are assisting in mitigating the obstacles faced during heavy storm events. DeepRoot is likewise excited to continue monitoring the growth of the 95 trees in the coming years.

Additional Resources

Check out other DeepRoot projects in the Edmonton area with our case studies found here, here, and here.