Preventing rainwater runoff with permeable pavers

Toronto is one of the densest cities in North America which has both negative and positive consequences. One of the negative consequences to all of the concrete, glass and steel is the lack of porous or permeable land to absorb rainwater which means it runs off into the sewer system. In older areas of Toronto the sewers are combined, meaning they carry both water run off from the streets and untreated sewage.  In torrential downpours the sewers and treatment plants can’t always handle the heavy loads and untreated water can back up and end up in the local streams and watersheds, Lake Ontario or even your basement. In addition to sewage, the water picks up any contaminants that have been left on the ground when it’s not raining and these contaminants also end up polluting local watersheds. Contaminants could be things like motor oil leaked onto the road, effluents from electronics left outside for garbage pickup, and hazardous liquid waste such as paint thinners that have been poured down the sewer instead of being disposed properly.

If more water could be diverted away from the sewer system less contaminated water would enter lakes and streams better protecting local wildlife and watersheds.

In certain wards in Toronto, mandatory downspout disconnection was passed as a by-law in 2007. Residents in the affected wards have been given three years to disconnect their downspouts. Click here to find out if you’re in one of the affected wards. There are instructions (with pictures) showing how to disconnect the downspout here.

As water issues have come to the forefront, methods and materials for diverting rainwater from sewers and to help replenish groundwater systems have become more popular. When it comes to landscaping there are many opportunities to help keep water on your land and avoid sending it into the sewer.

Driveways, pathways and patios all tend to be  hard surfaces and they typically are the areas that increase water run-off.  These areas are part of the “hardscaping” side of landscaping. However, there are materials that can be used to help prevent water from entering the sewer system.

Permeable pavers: Permeable pavers are specifically designed interlocking concrete blocks that are set farther apart than regular pavers. The pavers are specifically designed to maintain space between them so that water can drain between them. Unilock makes several different styles of permeable pavers. They are meant to be used with Unilock’s crushed stone aggregate (filler between the pavers) to promote maximum absorption of rainwater under the heaviest of conditions. The blocks themselves are designed so that there is a distinct gap between each block, while the porous aggregate fills in between the blocks. They can be used for patios and walkways too. Making sure as much water as possible stays on your property promotes ground water replenishment, keeps your lawn and plants healthy and will ease pressure on our aging sewer system.  See the list of  Unilock dealers here. 

One note about using permeable pavers. There is a certain amount of maintenance involved. They should be swept on a regular basis or organic matter will build up in the crevasses. Eventually seeds can settle and germinate causing plant growth between the blocks.