by Stacy James, Water Resources Scientist

For every inch of rain that falls, about a half-gallon of stormwater runoff is produced from one square foot of roof or pavement. That’s a lot of water, and most of it eventually winds up in our waterways. Along the way, the stormwater picks up oil, trash, bird droppings, pesticides, and other pollutants from the ground.

Since stormwater is dirty, certain construction sites, industrial developments, and municipalities are required to have a permit for the stormwater they shed. The Illinois Environmental Protection Agency (IEPA) is responsible for issuing these permits, which allow stormwater to be discharged with little or no treatment into sewer systems and rivers. Historically, regulated entities have managed stormwater on their properties via “gray infrastructure” (e.g., gutters, pipes, storm drains) and detention or retention ponds. These systems do little to purify stormwater. But now people realize that infiltrating stormwater into the ground keeps pollution out of waterways and reduces flooding. Subsequently, a suite of practices known as “green infrastructure” has been developed to trap and soak up water where it falls. Examples of green infrastructure include porous pavement and rain gardens.

Green infrastructure is not very widespread, but could become required by permits, local ordinances, or even state law. To better understand green infrastructure’s potential to manage stormwater, IEPA has funded a report that should be completed in 2010. One of the recipients of the funding is Chicago’s Center for Neighborhood Technology, a PRN partner organization. For our part, we will be working with the report writers and IEPA during and after the completion of the report, and advocating that Illinois take significant steps to promote on-site infiltration and green infrastructure.