A street that’s lined with beautiful, tall trees is a street that’s very desired in Calgary. Unfortunately, those tall trees can come with their own challenges (and we’re not just talking about raking leaves!). Big trees mean big roots and sometimes big problems, with pathway cracks that turn into tripping hazards and occasionally sidewalks that become impassible.
No existing solutions are perfect –
Remove the root: there is a risk that the tree could lose stability and become unhealthy.
Grind the sidewalk down: the root will continue to grow and make the hazard reappear (about 1 cm each year!).
Remove the sidewalk and replace with black asphalt: the hot black asphalt may kill the root with heat (and is an eyesore), or the same cracked sidewalk reappears as the root continues to grow.
Chris Oshust, Senior Leader of Concrete with the City of Calgary, thinks he has found the solution to the sidewalk vs root war – recycled tire rubber. It’s a product that’s gaining popularity, with companies promoting it as a solution for backyard pads, patios and even playgrounds.
Other municipalities in Canada, including Calgary, have used rubber mats for similar purposes, but it is believed that Calgary is the first municipality to use poured-in-place rubber for sidewalks. Through a pilot project, Oshust’s team is testing different applications of recycled rubber for sidewalk use.
“We think it’s a really innovative product that has potential for multiple applications within our city,” says Oshust. “The rubber is less expensive than concrete, non-slip, easily repaired, can withstand extreme temperatures (even our Calgary winters), is flexible and a breeze for snow clearing.”
In this application, the sidewalk is removed around the tree root and replaced with pour-in-place rubber. As a tree root keeps growing, the rubber flexes and prevents trip hazards that typically reappear every few years with concrete sidewalks. As an added bonus, the rubber material is permeable and isn’t hot like asphalt, so the tree gets all the water it needs and installation doesn’t damage the root.
The rubber is poured in place the same way as concrete. Black rubber is used to complete the bottom layer of the sidewalk, as it is more cost efficient, and the top layer is made in a grey to match the existing surrounding sidewalk. They even stamp the sidewalk with the date, the same way they traditionally do with concrete sidewalks.
“With the two test sites we have, the results are promising,” says Oshust. “Homeowners have told us that snow clearing is easier, and joggers have told us they like how it feels to run on because it’s softer than concrete. Because of the initial success of this pilot, the City Roads group is looking at doing other pilot projects with Calgary Parks. Some ideas that may be popping up around the city soon are a pathway built with rubber concrete and using rubber to fill tree wells instead of metal grates to make sidewalks wider and more accessible.
“As we move through and expand this pilot project, we look forward to seeing how we can use rubber to not only save trees and improve sidewalks, but to save money with this cost efficient product,” says Oshust.
City of Calgary