Wilket Creek is a tributary of the Don River that is vulnerable to acute erosion as a result of the influx of uncontrolled urban runoff during storm events. The Wilket Creek valley has sustained significant erosion in recent years resulting in damage to bridges, trails and park amenities as well as impacts on the valleyland ecosystem. The Edwards Gardens/Toronto Botanical Gardens (TBG) parking lot contributed uncontrolled flows into the ravine system, exacerbating erosion and degrading aquatic habitat. The sustainability strategy for the parking lot was aimed at mitigating these impacts, improving both stream stability and water quality. The retrofit design incorporates a full suite of Low Impact Development (LID) technologies that are aimed at encouraging infiltration, reducing runoff rates and arresting the pollutants that are contained within runoff as well as achieving objectives related to energy and water conservation, recycling, alternative transportation and naturalization.
The overall stormwater management strategy combines permeable pavement with a network of biofilters that were installed below landscaped medians within the parking lot to attenuate stormwater run-off, encourage infiltration and enhance water quality. The biofilter system collects water discharged from the parking lot using a combination of permeable pavement and infiltration inlets. Stormwater is directed through to the granular filter system, slowing the rate of discharge of water into Wilket Creek during rainfall events. Commensurate with this function, the granular media filters out contaminants from run-off. Organisms remove substances from the stormwater by processing contaminants and assisting in the degradation of pollutants. Plant material growing over top of the galleries helps to further absorb nitrogen and phosphorus while contributing to a reduction in CO2 and providing shade over the surface of the parking lot.
The reconfigured parking lot includes bicycle parking, as well as linkages to transit and the Don Mills Rail Path to promote the use of alternative modes of transport. The parking lot integrates an improved pedestrian circulation system to enhance visitor safety. Sustainability objectives were achieved throughout the construction process including the re-use of all existing asphalt as sub-base material for the parking lot. Existing trees that were removed were re-used in art installations or chipped to create the ‘Woodland Walk.’ Components of the existing concrete curbs and lighting system were salvaged to save waste and cost. Sculptural structures for bicycle parking were installed as part of a public art component of the project.
The LED lighting system was designed to enable adaptation into a solar-based system in the future. The lights will be energized utilizing electricity captured and stored by a proposed ‘solar arcade’. The project was designed in consultation with the TBG with the objective of positioning the sustainable parking lot as an integral and complementary element within the Edwards Gardens/TBG landscape as well as a key element to support the interpretive and educational programs offered through the TBG.
The transformed Edwards Gardens/ TBG parking lot serves as a prototypical demonstration project in support of Toronto’s Green Development Guidelines and represents a model of sustainable parking lot design to be emulated throughout the City of Toronto.