Permeable pavement offers designers a surface that permits the free flow of water through pavement, contrary to conventionally designed pavement, which conveys flow off the surface and into catch basins.
"It's extremely popular with folks who are into stormwater management," says David Hein, principal engineer with ARA Transportation.However, popular, permeable interlocking pavers are often abused, neutralizing the effectiveness of carefully selected aggregate packed between paving stones. Hein offers a list of five terrible things that owners do to reduce the effectiveness of their pavers.
1. Use winter sand
"Winter sand made of sand and ice and used to provide traction on road surfaces packs into the spaces between the pavers, clogging them," he says. "Permeable pavers are actually heat sinks and tend not to freeze up quickly and they also tend to thaw faster than conventional pavement. Municipalities need to leave roads using permeable pavers off their winter salt list."
2. Dump construction dirt on permeable pavers
"You're filling up the voids with soil," he says. "You also want to maintain the stability of any dirt upslope with vegetation, for example. That will also help to protect the pavement from any construction work occurring upslope."
3. Permit heavy vehicles to drive over permeable pavers
"Permeable pavers don't mind cars, but buses and trucks are a no-no," he says. "Also, vehicles that leak oils and other chemicals should stay off them."
4. Direct more water to the pavers than they're capable of infiltrating
"Typically, you can direct water representing twice the surface area of the permeable pavement onto that pavement," he says. "You should also avoid high rates of water flow."
5. Aggressively clean and vacuum permeable pavers
"Street sweepers and vacuums can actually remove the aggregate between pavers, rendering them ineffective," he says. "Putting aggregate back is a low-tech endeavor — you need to sweep aggregate into the spaces with a broom."