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From 2015 to 2017, UrbanToronto and its sister publication, SkyriseCities, ran an occasional series of articles under the heading Explainer. Each one took a concept from Urban Planning, Architecture, Construction, or other topics that often wind up in our publications, and presented an in depth look at it. It's time to revisit (and update where necessary) those articles for those new to UrbanToronto. While you may already know what some of these terms mean, others may be new to you. We will be (re)publishing Explainer on a weekly basis.
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Cities all over the world are phasing out heavy industrial activities in their urban areas in favour of a safer, more sustainable, mixed-use built form. Consider Pittsburgh, where steel manufacturing was a crucial component of the local economy, and numerous former industrial properties have since been reimagined as vibrant neighbourhoods with a myriad of residential, office, and retail uses. These bygone industrial sites, many of which are characterized by severe soil contamination, are referred to as brownfield lands.
Brownfield sites do not have to be large in scale. Gas station and dry cleaner operations, which can be and often are located outside designated commercial and industrial areas, typically produce a range of subsurface contaminants. Pesticides and heavy metals like lead and mercury, left unobserved, could also pose community safety risks, though the cost of remediating the soil and making it suitable for future development has been a significant barrier for many builders. In an effort to revitalize these derelict properties, government programs in various jurisdictions have been created to help predict or offset the expense of remediation.
Several techniques are used to clean up contaminated land. Soil vapour extraction involves the drilling of wells into soil situated above the water table. Volatile organic compounds are then vacuumed out of the wells in vapour form. Air sparging — pushing contaminated vapours upward from the groundwater via air injection — may also be used in conjunction with this practice. In some cases, specific deep-rooted plant species like sunflowers are introduced to the site, which can help immobilize and degrade the contaminants. Known as phytoremediation, some species also absorb metals in their tissue, and are disposed of as hazardous waste after maturity.
Once sites are cleaner, they are safe for redevelopment into areas that people frequent more commonly. Toronto's Port Lands, some of which appear in the image above, is a prime example of an area that has been primarily industrial, but which will have a mix of uses in the future — including some industrial in some zones — but which will mostly be converted over to new parks, neighbourhoods, and commercial areas, as a way to better connect Toronto with Lake Ontario while providing new places to live, work, shop, dine, and play, all of it close to Toronto's core where local infrastructure can be put to higher and better uses.
In the meantime, do you have other planning terms that you would like to see featured on Explainer? Share your comments and questions in the comments section below!
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Want to read other Explainers? Click on the magenta Explainer box at the top of the page.
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