Rainwater running off of a concrete or asphalt parking lot carries oil and other contaminants into storm drains, fouling waterways. New “permeable pavement” designs from North Carolina State University could make parking lots less polluting.

Construction proceeds in layers. A water-permeable polymer fabric is laid over a gravel base. Then heavy-duty interlocking plastic rings are embedded in sand layered over the fabric. More sand tops the whole structure. Rain filters down through the lot rather than running off of it; pollutants are carried into shallow ground water where microbes break them down. Researchers have been studying a city-owned lot in Kinston, NC, for two years and plan to construct another in Wilmington, NC. Bill Hunt, a North Carolina State water management engineer working on the projects, says that the design should be less prone to potholes than earlier efforts with porous asphalt. Although not durable enough for busy parking lots (think McDonald’s), the new pavement could serve well in daily or long-term lots like those at airports. Hunt says other local governments, as well as homeowners, have expressed interest.