Green Design at Evergreen Brick Works: Brownfield Remediation
Background image: DTAH
Brownfields are abandoned or underused industrial sites or commercial spaces—often in urban communities—where redevelopment is complicated by contamination. The large-scale project to revitalize Evergreen Brick Works is just one example of how these sites, which are found throughout the country, can be reclaimed and redeveloped.
Helping the Water Flow
We wanted to improve water flow on site, but the challenge of soil and groundwater contamination was immense. Much of the surface had to remain impervious to keep the toxins from seeping through. In addition, the roofs catch a lot of water, and we needed to divert this volume into eavestroughs and channel it away. A multi-layered design helps direct, cleanse and conserve water on site.
The Don Valley floodplain floods several centimetres on a regular basis. During rare storms, such as Hurricane Hazel in 1954, several metres of water can rise across the industrial site.
We’ve designed the site to withstand these events. The concrete ground floor space is essentially waterproof and mold resistant, and major mechanical systems are placed above the height of even the most severe flood. The likelihood of flooding did eliminate some of our ideas including composting toilets and other innovative technology.
A central storm water management pond collects water from the central parking lot, greenways and other hard surfaces on site and allows sediment within the water to be filtered before it is released into the Don River.
Rainwater running off the buildings’ rooftops is stored in fifteen 20,000-litre cisterns for reuse in gardening and toilets. This, combined with water-conserving toilets and faucets and waterless urinals, reduces water use by more than 60 percent.
Greenways set between the site’s buildings have been planted with grasses and shrubs that slow rainwater down, trap sediment and release oxygen. These swales clean the water and channel it into the stormwater management pond at the southern edge of the site. Lined with a geotextile material, these greenways also prevent rainwater from seeping into the contaminated ground. They remain dry for a good portion of the year but can accommodate large and sudden storms.
Emergency Sewage Cistern
During normal operations, waste from washrooms is pumped via a pumping station on the west end of the site up to a main sanitary line in North Rosedale.
During a flood, the pumping station will shut down. In the event that we are unable to evacuate the site, this building is the refuge centre. We need a way to deal with the sewage generated during that time. A cistern in The Kilns building will contain this sewage, and prevent any contamination of the groundwater.
The soil under the Commons and east parking lot was not contaminated and did not contain heritage artifacts. Here, a combination of concrete unit pavers and pervious concrete absorbs rainwater and recharges the water table. The concrete surface in the east parking lot contains less sand and 20–25% more air than normal mixtures, making it significantly more porous. This means that rainwater percolates through and into the soil, where it is naturally filtered and helps replenish the groundwater supply.
In heavy rains, any runoff is channeled via the swale along Bayview Avenue into the stormwater management pond.
Impervious surfaces help prevent rainwater from carrying metals and other toxins into the water system.
As well, they preserve heritage artifacts, discovered under the central parking lot during construction, for future exploration. Hard paving protects these from water damage, and from being crushed by the weight of vehicles.
Demonstration mounds containing native plants showcase different themes or habitats such as a butterfly garden and a water garden.
The raised beds are lined with geotextile to keep contaminated soil below and clean soil and plants above. They provide a natural habitat that is safe for growing plants, playing in the garden and for wildlife.
This site is adjacent to the Weston Family Quarry Garden, and at the hub of several well-used ravine trails. The former factory quarry was redeveloped with the help of volunteers and donors in the mid-1990s.
Designed as a natural ecology park, it has three storm water management ponds and eight landscape units. These include meadows and wetlands, which dominate the low-lying areas, and a Carolinian plant community native to southern Ontario, including redbud, sassafras, swamp white oak, sycamore and tulip trees.
Due to restoration efforts, natural habitats are being re-established. Species living in and around the site include blue heron, red-winged blackbirds, nighthawks, grackles, song sparrows, barn swallows, chimney swifts, raccoons, muskrats, beaver, deer, squirrels, eastern garter snake, brown snake, snapping turtle, midland painted turtle, leopard frogs, green frogs, spring peepers, and countless insects.