Selkirk’s Award-Winning Streetscape Projects Go Green with Silva Cells

“[Silva Cells] are a double bonus. You get the cooling effects of the trees – you get all the services trees provide. But you also aren’t wasting the water. It’s just so forward looking.” – Erna Buffie, Trees Please Winnipeg

Overview

In tandem with a downtown utility upgrade, officials in Selkirk — a Manitoban city located approximately 40 minutes north of Winnipeg — chose to retrofit some of the town’s most-trafficked thoroughfares with safe, pedestrian-friendly features. Green infrastructure was an important feature from the outset of this multi-phase initiative, including dozens of new street trees. Manitoba Avenue was the first phase to be completed (in 2019), utilizing Silva Cells for their ability to grow large, healthy trees in the built environment — in this case, those planted along the widened sidewalks. Eveline Street was the next phase: a more ambitious (and award-winning) retrofit in the summer of 2022 that embraced the dual functionality of Silva Cells, tasking the system with LID stormwater treatment in addition to soil-volume benefits. Project planners at HTFC and JR Cousins are likewise installing Silva Cells in the third leg of Selkirk’s streetscape improvement plan, taking place along Main Street in the spring of 2024.

Installation Summary

Number of Silva Cells: 864 (2x)

Number of Trees: 60

Type of Project: Streetscape, Stormwater

Project Designer/Engineer: Phase 1: WSP Group, Phase 2/3: HTFC and JR Cousins

Project Contractor: Phase 1/2: JC Paving, Phase 3: Pending

Installation Date of Silva Cells: Phase 1: Fall 2019, Phase 2: Summer 2022, Phase 3: Spring 2024

The First Stage: Manitoba Avenue

It’d been nearly three decades since the utility network in Downtown Selkirk received an upgrade — an improvement necessity that presented city planners with an opportunity for a more ambitious streetscape redevelopment plan. Why simply repair the aging pipe system when you could simultaneously retrofit the entire district with safer and more accessible streets? Envisioning a revitalized public space, officials sought to improve the pedestrian-friendly usability of the downtown district — and thus rejuvenate local commerce and community engagement.

The City of Selkirk in 2016 adopted the Downtown Selkirk Renewal Strategy, laying out the vision for a “vibrant, safe and attractive downtown core.” The following year, they were granted provincial and federal funding for the first phase: Manitoba Avenue East. The project, which broke ground in 2019, featured a number of concurrent priorities:

Enhanced pedestrian and active transportation facilities
Redesigned parking strategy
Two pocket parks
Public art and activity space
Seasonal patio locations
New street trees

This final objective led city planners and WSP Group to the Silva Cell system: the perfect strategy for supporting the growth and health of new street trees — something Selkirk was seriously lacking, according to the renewal strategy which cites a “noticeable lack of public street trees [and] the ill health of those street trees that do exist.” The lightly compacted soil contained in the Silva Cells’ void space will allow the trees along the newly designed Manitoba Avenue to flourish well into maturity.

The next phase of the Selkirk revitalization project, led by the teams at HTFC Landscape Architecture and JR Cousins Engineering Consulting, took place along Eveline Street in 2022 — and the Silva Cells played an even more important role in this larger-scale effort.

The Award-Winning Eveline Street

Running perpendicular to Manitoba Avenue along the western shoreline of the Red River, Eveline Street received a $7.2 million facelift in 2022. “This is a huge project,” observed Duane Nicol, Selkirk’s Chief Administrative Officer. “We’re rebuilding seven city blocks of road, sidewalk and boulevard all at once. It’s the largest single city street rebuild in Selkirk in decades — if not ever.”

Like Manitoba Avenue, the Eveline Street project sought to improve accessibility and safety with delineated lanes for cars, bikes, and pedestrians — while providing upgraded lighting, seating, and crossing zones. Also mirroring Manitoba Avenue (but on a larger scale), street trees were planted along the length of the renovated roadway: a total of 44 of them accessing uncompacted soil thanks to Silva Cells. A 2x configuration was utilized for most of Selkirk’s seven blocks, though a 3x depth was installed around the tree itself (allowing immediate access to an impressive bank of loamy soil as the roots begin to expand).

Having used the system on Manitoba Avenue, city planners were certainly familiar with Silva Cells’ ability to grow large trees. But an additional benefit was realized on Eveline Street: DeepRoot General Manager and project lead Mike James helped officials realize the multi-purpose functionality of Silva Cells, in this case assisting in on-site stormwater management in addition to growing a healthy urban forest.

One of the chief objectives in implementing a stormwater element with the Silva Cells was to provide natural irrigation to the trees without utilizing city water. At the same time, however, the system is able to treat stormwater runoff on location — this both reduces the reliance on gray infrastructure (and thus potential flooding during major storm events) and removes pollutants from the runoff before it drains into local watersheds: two advantages that fit nicely into Selkirk’s climate adaptation strategy. This strategy is going to be utilized once again in the next phase of the project: Main Street, being worked on in the spring of 2024.

Silva Cells: The “Piece de Resistance”

The Eveline Street phase of Selkirk’s streetscape redesigns is receiving praise across The Prairies, in addition to being the recipient of two 2023 awards (the TAC Achievement Award and ACEC Excellence in Transportation Award). Silva Cells were an integral part of the project success, helping city officials simultaneously achieve a number of their goals, as identified by multiple project planners.

Matt Fisher of JR Cousins refers to Silva Cells as the project’s “piece de resistance”: a “modular suspended pavement system that uses soil volumes to support large tree growth and provide stormwater management.” Kaili Brown, landscape architect at HTFC, likewise praises the way Silva Cells helped adhere to the street design as well as Selkirk’s climate change adaptation strategy:

“We’re talking about Silva Cells, which are basically building blocks beneath the sidewalk that are filled with soil. So, we’re able to get our ideal soil volume for these trees to ensure that they grow beautifully — and they stay a long time. And there will be certain aspects of the street where we’re able to incorporate some stormwater runoff capture. What we’re going to do is take that stormwater runoff and store it, which will eventually water the trees.”

Local tree advocates echo the importance of prioritizing urban forestry and the critical role played by Silva Cells. Erna Buffie of Trees Please Winnipeg states:

“Selkirk’s new tree policy is that it’s treating trees as an essential part of the city’s infrastructure, and [Silva Cells] are a double bonus. You get the cooling effects of the trees — you get all the services trees provide. But you also aren’t wasting the water. It’s just so forward looking.”

Everybody is excited with the new Manitoba Avenue and Eveline Street redevelopment, with an eye toward continuing these sustainably focused and safe, accessible retrofits across Downtown Selkirk.