Central Parkway Case Study

Central Parkway East is a low impact development (LID) retrofit streetscape project in Mississauga, Ontario. The project utilizes Silva Cells as an underground bioretention system to manage and treat stormwater runoff while simultaneously providing the uncompacted soil volume necessary to grow large trees.

The City of Mississauga partnered with DeepRoot, TD Friends of the Environment Foundation, and Credit Valley Conservation to install the Silva Cell system, as well as monitoring t equipment in order to assess site performance, including water quality and quantity.

Stormwater treatment has become an increasingly important issue to the City of Mississauga and other municipalities in the Greater Toronto Area over the past several years as urban populations continue to rise spurring development. At the same time, the area has experienced more frequent, high intensity storms potentially due to climate change. Polluted runoff from storm events flows from hardscapes and enters the regions creeks and rivers and ultimately into Lake Ontario, negatively affecting water quality, causing erosion, and harming the local ecosystem.

The Silva Cell system at Central Parkway East acts as an underground bioretention system, removing pollutants and controlling runoff volume before stormwater discharges to Cooksville Creek. Runoff from over 784m2 of surrounding impervious surfaces is directed into existing catchbasins and then throughout the system via two distribution pipes. The bioretention soil acts as a filter to remove nutrients, and excess water is discharged to a storm sewer through an underdrain at the base of the system.

Performance results from 2016 indicated a 98% average stormwater volume reduction and a 99% peak flow reduction as well as helping to replicate a natural water balance in an urban setting, contributing to erosion control, improved water quality, and protection of natural aquatic habitat. Contaminant concentration reduction calculations for a sample event shows overall reductions of TSS, phosphorus, nitrogen and iron.

The integrated approach also contributes aesthetic value by way of six salt-resistant Chanticleer pear trees that are planted in the median to provide green canopy cover along the roadway. The six trees have access to 17.5 m3 of soil each from the Silva Cells plus the soil in the planter. The total soil volume (planter and Silva Cells) available is 105m³.

Installation Summary
Average soil volume per tree: 17.5 m³
Number of Trees: 6
Total Silva Cells: 140 Frames, 70 Decks
Installation Date: 2015
Project Type: Transit
Installation type: Integrated – Trees and Stormwater
Project Site: Municipal/government
Project Designer: City of Mississauga
Contractors: Pacific Paving Inc.