The Brief

Transforming a parking lot into a high-density residential development that will yield long-term environmental benefits in the City of Richmond Hill.

Project Overview

Building for the greener good

Throughout the Greater Toronto Area, many properties are being redeveloped into high-density residential condominiums. What is not obvious to most are the environmental benefits that result from these site redevelopments, particularly with respect to stormwater runoff. A case in point is the redevelopment of the Richmond Hill Country Club main parking lot into a high-density condominium development.

The subject site is a conventional paved parking lot that was built in the late 70s as part of a country club’s facility. Much of the stormwater runoff from the parking lot is collected by catch-basins and conveyed by on-site storm sewers that discharge into the Don River. The remaining runoff from the parking lot simply drains overland directly to the adjacent valley slopes. At the time of the construction of the parking lot, there were no measures put in place to manage the stormwater runoff other than its conveyance to the valley lands and river.

The proposed redevelopment of the parking lot is comprised of two linked residential condominium towers, 20 storeys and 15 storeys in height, respectively. The towers will sit atop a three-level underground parking structure interconnecting the two condominium towers.

RVA was retained to prepare a site servicing, site grading, and stormwater management plan for the development to meet the requirements of the City of Richmond Hill, York Region, and Toronto Region Conservation Authority.

With respect to storm water management, the benefits that will result from the redevelopment include:

Reduced storm runoff

Most of the rain that falls onto conventional paved parking lots converts to runoff. Parking lots are designed with gradients to efficiently shed water, and the pavement itself is not pervious enough to allow rain to penetrate into the ground. The larger the storm event, the greater the volume and rate of runoff that is directed unabated into the environment, leading to flooding and erosion of the receiving water courses.

The redevelopment of the site will result in overall reduction of hard, impervious surfaces through the implementation of naturalized buffers areas adjacent to the valley slopes and the introduction of pervious landscaped surfaces throughout the development such as the green roofs over top of the building structures. While the introduction of these pervious surfaces alone, result in a reduction in the rate and volume of runoff, further measures will also be implemented.

A large tank will be incorporated into the basement of the building to house daily rainfall that is captured by the storm drainage system. The harvested rainwater will be pumped into buried chambers that will allow the rainfall to infiltrate naturally back into the ground. During the summer months, some of the harvested rainwater will be treated and used for irrigation of the landscaped areas on the site as well.

During larger storms, a stormwater tank will fill up and release the captured rainwater into a newly constructed outfall into the Don River at a rate that will reduce erosion.

Improved water quality

Parking lots often accumulate pollutants such as oil, heavy metals, and debris. When it rains, these contaminants are washed into natural environment, degrading water quality.

While there will still be paved driveways to access the redevelopment, the parking requirements will be served by underground parking, which is not exposed to rainfall.  With respect to the surfaces that are exposed to the sky, landscape features act as natural filters. Additionally, all runoff captured within the development will enter a filter-based treatment system to remove pollutants before being discharged to the Don River.

Erosion mitigation

The runoff from the existing paved parking lot that drains directly into the adjacent valley has caused erosion scars along the slopes and the transport of sediments into the river. The stormwater management system and new storm outfall implemented with the redevelopment will mitigate that condition. Additionally, the erosion scars will be repaired by staking Silt-soxx with growing medias, which will restore the current eroded areas and become a stable slope when the project is complete.

Urban heat island mitigation

Other benefits beyond those related to stormwater include mitigating the urban heat island effect. Paved parking lot surfaces in contribute to the urban heat island effect, elevating temperatures compared to surrounding rural areas. Integrating landscaping, shade-providing trees, and reflective surfaces in redevelopments helps to counteract this effect by promoting cooler temperatures. This not only benefits the local environment, but also enhances the overall comfort of urban spaces.

In the face of climate change and urbanization, converting the redevelopment of existing sites such as parking lots into developments that prioritize stormwater management is a proactive and sustainable approach. Beyond meeting regulatory requirements, this transformation offers Richmond Hill an opportunity to create resilient, environmentally friendly spaces that enhance the well-being of its residents while safeguarding the natural environment for future generations.