County Court Bio-Filter Swales

Initiated in 2014, the County Court Bio-Filter Swale project is a demonstration of how Low Impact Development (LID) can be integrated into planned road resurfacing practices and represents the City of Brampton’s first bio-filter swale to be initiated by the municipality. The primary role of the bio-filter swales is to collect and clean storm water run-off from County Court Boulevard before it enters the Etobicoke Creek. The project showcases co-benefits of climate action, as the feature also provides an aesthetic and urban forest enhancement in the public realm. The integrated project was able to access new funding and draw on existing budgets, demonstrating a strategic financing model and interdepartmental coordination.

Located in the City of Brampton’s south end, the bio-filter swales were built on County Court Blvd, within an older neighbourhood that is home to about 5,800 people of diverse backgrounds and cultures. This was initiated as a demonstration project of the County Court Sustainable Neighbourhood Action Plan, part of TRCA’s broader SNAP program. County Court SNAP is a comprehensive environmental improvement plan that integrates local community interests into urban renewal and climate action, with implementation of cross cutting projects and programs underway.

The project included design and construction of two lined bio-filter swales within the road right-of-way of County Court Boulevard, a medium traffic collector road that is adjacent to the large County Court Park, and services residential and institutional areas in the neighbourhood. Project partners include: City of Brampton, Toronto and Region Conservation Authority’s Sustainable Technologies Evaluation Program (STEP), Partners in Project Green (PPG) and Sustainable Neighbourhood Action Program (SNAP), Region of Peel, Ontario Ministry of the Environment, Tree Canada and TD Friends of the Environment Foundation, and Fletchers Creek Senior Public School.

Understanding and Assessing Impacts

The main climatic impact that this project aims to address is increased urban runoff and water quality concerns as a result of increasing precipitation and extreme precipitation events. This climatic impact is exacerbated by the prevalence of impervious surfaces throughout the region and ongoing changes in land-use which converts previously pervious surface to impervious. Increased overland flooding is the main risk associated with heavy precipitation and has many impacts on the local socio-ecological system (e.g., damage to infrastructure and private property, human health and safety concerns, and aquatic ecosystem health concerns). There are also opportunities to achieve co-benefits as part of climate action projects that address water, including improvement of green infrastructure, urban forest and neighbourhood aesthetics. In addressing this issue, the City of Brampton installed its first bio-filter swales along County Court Boulevard as part of planned road resurfacing in 2014. The integrated project was able to access new funding and draw on existing budgets, demonstrating a strategic financing model and interdepartmental coordination. The primary role of the bio-filter swales is to collect and clean storm water run-off from County Court Boulevard before it enters the Etobicoke Creek.

Identifying Actions

In addressing the compounding issues of urban development in regard to the local and regional water balance, a more holistic approach was taken by the Toronto and Region Conservation Authority (TRCA) and other project partners. The project was identified as a demonstration project as part of the County Court SNAP neighbourhood scale analysis. This approach incorporates the use of green infrastructure, which helps to enhance opportunities for infiltration and evapotranspiration of rainfall within urban settings. Green infrastructure is essentially referring to any natural or built system that help to restore the local hydrology while also offering ecological benefits. The construction and planting of the two bio-filter swales which took place between 2014-2016, involved a number of actors but was led by the City of Brampton. The region of Peel provided review of the bioswale design. Fletcher’s Creek Senior Public School was the official planting partner with funding from Tree Canada and TD Friends of the Environment. TRCA’s Sustainable Technologies Evaluation Program (STEP) team undertook a two-year monitoring program to evaluate the performance of the project with funding from Ontario Ministry of Environment and Climate, and TRCA’s Partners in Project Green.

Implementation

This project, with its use of bioswales, is an example of a green infrastructure project that uses low-impact development (LID) as a way of increasing infiltration and reducing the flow and volume of urban runoff. Green infrastructure projects are becoming increasingly popular as nature-based solutions to climate adaptation offer multiple co-benefits that can be realized through the implementation of a single project. Two three-meter wide biofilter swales were implemented on County Court Boulevard, Brampton; one on the east side (70 meters) and one on the west (85 meters). The bioswales service a combined drainage area of 3,095 square meters. Road runoff enters the swales through a series of curb cut inlets along their length. The swales feature herb and grass plantings and river stone cover, thereby creating an attractive landscaped feature that also treats road runoff. Impermeable liners were included in the design to protect the watermain infrastructure located below them from potential impacts of enhanced infiltration of de-icing salt laden stormwater during winter. Stormwater treatment performance of each biofilter swale and effluent temperature was continually monitored for 2 years in parallel with an untreated portion of County Court Blvd. (i.e., control catchment). Observed suspended solids treatment performance was combined with a 50-year life cycle cost estimate, generated using the TRCA Sustainable Technologies’ LID Life Cycle Costing Tool. Results were compared with estimates for other stormwater retrofit practices suited to roadways and infiltration constrained contexts: (i) hydrodynamic separator; and (ii) grass swale.

Design Features of the Bio-filter Swale

Image showing the design features of the bio-filter swale along the roadside. The swales feature herb and grass plantings and river stone cover, thereby creating an attractive landscaped feature that also treats road runoff.

Bio-filter Swales: Curb cut inlets

Image showing how road runoff enters the swales through a series of curb cut inlets along their length. The swales feature herb and grass plantings and river stone cover, thereby creating an attractive landscaped feature that also treats road runoff.

Outcomes and Monitoring Progress

Effectiveness of the biofilter swales retrofit project was examined with respect to the following: Runoff volume and pollutant load reduction; Effects on effluent temperature; Effects of winter operation on treatment performance and maintenance needs; and, Life cycle cost of total suspended solids removal over a 50 year life cycle. Results showed that the biofilter swales have been effective in meeting their design objectives by reducing runoff volumes, attenuating peak flows, removing pollutants, and reducing thermal loading relative to the control catchment. This study demonstrates the viability of filtration-only, lined bioretention swales as a retrofit stormwater source control practice to treat runoff from a medium-traffic road within the climatic context of the Greater Toronto Area. The understanding gained about the performance and cost-effectiveness of biofilter swales helps inform decisions regarding practices to consider as part of future road reconstruction or other linear infrastructure renewal projects.

Planting of the bio-filter swale along the roadside.

Image showing the planting of the bio-filter swale along the roadside.

Group of students from Fletcher’s Creek Senior Public School helping to plant the bio-filter swales.

Image showing a group of students from Fletcher’s Creek Senior Public School helping to plant the bio-filter swales.

Next Steps

The lessons learned, as described in the previous ‘Outcomes and Monitoring Progress’ section, have been applied to other bioswale projects in the City of Brampton.