Mississauga road low-impact development stormwater pilot project

In the Region of Peel, ON, extreme rainfall events have caused flooding that has impacted residents and municipal infrastructure. With climate change, these occurrences are expected to become more frequent and severe. Temperature increases intensify the environmental impacts, making the receiving streams more vulnerable to a rise in water temperature.

A key strategy in addressing this issue is the region’s expanding network of roadways, whose drainage systems contribute to the flow of stormwater into the watershed. The Region of Peel completed an innovative project to reconstruct the storm drainage system using a low-impact development (LID) approach that mimics the natural movement of water through the environment on a six-lane regional road - Mississauga Road. The project was funded through a grant from FCM’s Municipalities for Climate Innovation Program (MCIP).

In 2014, Peel’s regional council made plans to pilot low-impact development principles as part of a watershed approach to stormwater management. The aim is to take the health of the whole watershed into consideration, while reducing infrastructure life cycle costs and maintaining high service levels.

Low-impact development uses existing landscape features and construction techniques to infiltrate, filter and absorb rainwater upstream, where it falls. It’s a cost-effective way to reduce stormwater runoff, improve its quality and prevent temperature changes in receiving waterways.

The Mississauga Road project is the first instance in the Greater Toronto Area (GTA) of this green infrastructure approach to stormwater management and could be a model for future road projects. The region installed a bioswale - linear channels designed to concentrate stormwater runoff while removing debris and pollution - in the centre median of the roadway, made up of granular material and native plants. A pipe diverts stormwater from the road drainage system into the median, where it passes over weirs to prevent erosion and subsequently, irrigates the plants. The vegetation filters and cools the water before it re-enters the drainage system.

The region plans to begin monitoring the system in 2020. This will include automated water quality sampling and the monitoring of flow and water levels.

Project details

• Project: Mississauga Road low-impact development stormwater pilot project
• Sector: Water
• Grant amount: $925,600
• Lead entity: Department of Public Works

Primary objectives

• Reduce the vulnerability of both new and existing municipal assets to climate change impacts such as flooding.
• Mitigate increases in stream water temperature in the Credit River.
• Reduce the number of overflow events.
• Avoid costly upgrades to conventional infrastructure.
• Reduce infrastructure life cycle costs and extend the life of municipal infrastructure.
• Reduce erosion in receiving watercourses, which in turn reduces hazards, protects property and reduces municipal costs related to erosion protection.
• Improve watershed health.
• Maintain high levels of service.
• Reduce water consumption.

By the numbers

• 25mm of precipitation of each rain event treated, covering 90% of all rain events
• 10–36% reduction in runoff volumes
• $1,560,000 anticipated reduction in capital expenditures
• $3400 anticipated reduction in maintenance/repair costs (existing stormwater management pond)
• $83,400 anticipated reduction in maintenance/repair costs (erosion control)
• 5.63 hectare drainage area with imperviousness of 67.7%

Project activities

• Prepare the site and remove existing materials, including asphalt pavement, impressed concrete, concrete curb and gutter, existing median planters and temporary asphalt curb and gutter.
• Install a storm sewer network and components, including an oil and grit separator to capture oils and sediments from stormwater runoff.
• Install concrete weirs, a bioswale and a planting bed.
• Complete remediation of the roadway and surfaces, including a concrete curb, gutter, median and splash pad.
• Complete the landscaping by installing a jute mat, plantings and accessories.

"On a watershed basis, regional roads represent a major contributor to watershed flow through storm drainage networks discharging to local watercourses. Over the past decade, the Region of Peel has experienced several severe weather events that have resulted in significant impacts to municipal infrastructure systems and services. The Mississauga Road LID project has significant environmental, social and economic benefits that will help to create a more sustainable community in West Brampton by reducing, cleaning and cooling stormwater before it enters the natural environment and providing a gateway feature for the community."

— Samantha Paquette, Project Manager, Infrastructure Programming and Studies, Transportation, Public Works, Region of Peel

Resources 

• Mississauga Road Low Impact Development Infrastructure Performance and Risk Assessment