Councilwoman: When It Comes to Sidewalks, Is Concrete Always Best?

Jan 22, 2015

Pittsburgh’s city code requires that sidewalks are made out of concrete, but Councilwoman Deborah Gross is questioning whether that’s the best option.

During a post-agenda meeting Thursday, Gross heard from various organizations saying there are better alternatives to concrete, which often times is lifted or cracked from trees and their roots.

Gross said solving this problem could help with Pittsburgh’s issues managing water, which includes flooding and water pollution.

“One small step we can do, which is to try to preserve our tree canopy because we know trees retain rainfall,” Gross said. “And what our topic of conversation is today is what kind of sidewalks help us do that.”

Matthew Erb, director of urban forestry at Tree Pittsburgh, compared sidewalks to plastic wrap over a bowl of food.

“As water condenses on that plastic wrap, or water condenses on the bottom side of the sidewalk, tree roots grow there to take advantage of that water resource,” Erb said. “And so you get tree roots growing directly below the sidewalk, they start to push up that sidewalk, so that’s a part of the issue.”

He said adding a six-inch gravel layer or rigid Styrofoam underneath the sidewalks could help reduce the condensation issues.

Thomas Hylton, president of the nonprofit Save Our Land, Save Our Towns, said they are trying to address the same issue in Pottstown, near Philadelphia.

He suggested two brands of porous pavement that could work as an alternative to concrete: Flexi-Pave and Porous Pave.

“It’s ground-up gravel, and it’s ground-up recycled tires, and it’s mixed together in an epoxy of binder, and you just trowel it out on your sidewalk,” Hylton said. “(It’s) very porous, Flexi-Pave will take about 2,000 per square foot per hour, which is amazing, and it doesn’t clog up because of the rubber.”

Bill Urbanic, Pittsburgh City Council budget director, said the city looked into using tires to make rubber sidewalks years ago, but the price of the rubber pavers at the time did not allow them to move forward with the idea.

“There was an initial investment that needed to be made,” Urbanic said. “The city, going under Act 47, was unable to make any kind of those investments, capital investments — one would be for the machinery to be able to take tires, grind them, or to purchase tires from other areas or have tires donated to the city, grind them up and then process them.”

But he said maybe the city could look into doing this again.