Porous pavement partnership

How do you vacuum debris without also sucking up material placed to hinder weed growth? Louisville’s central business district bark mulch tree surrounds collected cigarette butts, got kicked around by pedestrians, dirtied sidewalks, and washed away in the rain. Over time, the underlying soil compacted to the point where people getting out of cars were stepping down into the tree wells, which presented a potential tripping hazard.

Louisville Metro Public Works replaced bark mulch with pour-in-place paving material that uses rubber recycled from tires and infiltrates 5,800 - 6,300 gallons of water per hour per square foot. Installing Porous Pave XL takes two days: one to remove old material and build a two-inch base of compacted 3/8-to-3/4-inch aggregate; one to mix the product in a standard mortar mixer, place, and finish with hand trowels. Curing takes 24 hours.

To leave space around tree trunks, Louisville Metro Public Works crews cut six-inch-diameter cardboard tubes into six- to eight-inch lengths. “We cut the tube pieces lengthwise, like a hot dog bun, and wrapped them around the trees before installing Porous Pave XL,” says Roads Division Labor Supervisor Kevin Alexander. “We came back the next day after the material cured and removed the cardboard, leaving nice, smooth, round openings around the trunks that give trees room to grow.”

Adjacent to parking spaces on busy downtown streets, the seamless tree surrounds provide a safe, solid surface for pedestrians while protecting tree root systems by eliminating soil compaction from foot traffic. Rainwater and air pass through the permeable paving material to tree roots, and no slippery puddles remain on the surface. Porous Pave conforms to any landscape design and installs on grades up to 30 degrees.

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