Paved parking lots and driveways often create an easy pathway for pollutants to reach underground water sources and change the natural flow of water back into the ground. Today, EPA announced a study that will investigate ways to reduce pollution that can run off paved surfaces and improve how water filters back into the ground.

EPA is testing a variety of permeable pavement materials and rain gardens in the parking lot at the agency’s Edison, NJ facility, which houses offices and its laboratory. Most major sources of pollution going into waterways are well-controlled, but pollution runoff from hard surfaces remains a complicated problem.

Stormwater runoff is generated when precipitation from rain and snow flows over land or impervious surfaces and does not readily flow back into the ground. As the runoff flows over the land or impervious surfaces, it accumulates debris, chemicals, sediment, or other pollutants that could adversely affect water quality if the runoff discharged is not properly treated.

Over the summer, EPA replaced a 43,000-square-foot section of the parking lot with three types of permeable pavement and planted several rain gardens with varying vegetation. For the next decade, EPA will evaluate the effectiveness of each pavement type and the rain gardens in removing pollutants from stormwater, and how they help water filter back into the ground. The parking lot will remain functional during the study to accurately evaluate how the different types of pavement handle traffic and vehicle-related pollution like leaking oil.

While the installation of permeable pavement systems has become more prevalent, there is a lack of full-scale, outdoor, real-world permeable pavement research projects. Similarly with rain garden systems, relatively few studies have quantified the ability of the gardens to allow the ground to better absorb and filter stormwater, which reduces peak flows.