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Parking Lots: Letting It Soak In

EPA researchers are experimenting with “green” parking lot designs and permeable pavement as a way to reduce runoff and improve water quality.

Parking lot

This past winter brought a thick blanket of snow to much of the country. Big piles lined our driveways. Gigantic, dirty-white mounds claimed parking spaces from lots in New England to the Mid- Atlantic. But things are starting to warm up.  

The big melt is here.

When the snow that once covered a parking lot or other paved surface melts, the resulting water flows toward the nearest storm drain, entering the local watershed. And as snowmelt and other runoff flows over paved surfaces, it accumulates contaminants such as leaked motor oil, road salt, and hydrocarbons deposited from motor vehicle exhaust.

A team of EPA researchers are exploring how parking lots designed with permeable pavements and rain gardens can help.

To get started, EPA replaced a 43,000-square-foot section of parking lot at the Agency’s research lab and offices in Edison, New Jersey with three different types of permeable pavement, and planted several rain gardens with different types of vegetation.

Over the next decade, EPA researchers will evaluate the effectiveness of each pavement type and the rain gardens in removing pollutants from stormwater. They will also measure how each type of permeable pavement helps water filter back into the ground.

Throughout the project, scientists will compare changes in surface performance with standard parking lot maintenance, and track temperatures under each surface to detect patterns. Monitors will measure the water quality for at least ten years, to establish changes associated with time and seasonal patterns.

The research will be conducted without taking up parking spaces, as the lot will be functional during the study. This way, researchers can accurately evaluate how the different types of pavement handle traffic and vehicle-related pollution.

This is the first real-world experiment to determine if permeable pavement reduces pollutant runoff. The measurements and analysis EPA scientists make will answer some key questions about how effective permeable pavements are at reducing both the volume of stormwater and  the amount of environmental pollutants flowing off parking lots and into nearby streams and rivers. This information will be a big help to municipalities and land managers across the country. 

The project is part of EPA's Aging Water Infrastructure Research Program, which address the nation's critical water infrastructure needs through research and innovation.

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