On a walk through two unique streets in the Lakeview neighbourhood of Mississauga, visitors might notice meadow flowers and grasses blowing along the boulevards while at one end of the street, a large patch of Black-eyed Susans beckons.  The only hint that there is something really unique here is a large sign near the Black-eyed Susans proclaiming, “This is a Green Street”.

A “green street’ in the Lakeview neighborhood of Mississauga incorporates permeable paver driveways, curb cuts and bioretention or “rain” gardens to treat rainfall and urban runoff where it falls.

The Lakeview Road Revitalization project (on parts of First and Third Streets) is the first-of-its-kind in Canada, serving as a model province-wide. On these streets, bioretention cells (or “rain gardens”) and permeable driveways replace traditional curb-and-gutters to treat rainfall and urban runoff where it falls.  Such “green streets” prevent stormwater from overwhelming storm sewers during extreme weather events.  They also filter out pollutants before entering streams and rivers which flow to Lake Ontario, the source of drinking water for 8 million people.

Early performance monitoring is proving this.  CVC started monitoring performance at the site in August 2012 from equipment located at the two “green street” sites and at a control site near the same neighborhood.  The monitoring is one way of measuring the impacts of the specific LID practices on both the quality and quantity of water flowing from the site.

Based on observations to date, the Lakeview site is collecting 80 to 95 percent of typical rainfall events in the GTA.  This means that only 5 to 20 percent of the usual amount of rain that falls in the GTA is entering the municipal system at these Lakeview Streets.

This is significant, and very encouraging in these early days.  But it leads to other questions.  Are these results because of one particular LID practice or all?  What will results show during more extreme rainfall events?  How is water quality affected?

Performance monitoring will continue throughout 2013 at this and many other LID sites.  Lessons learned will form the basis of guidance documents that CVC and partners will publish beginning in 2014.