Porous Asphalt


Porous asphalt is an environmentally friendly tool for stormwater management.
In the natural environment, rainfall sinks into soil, filters through it, and eventually finds its way to streams, ponds, lakes, and underground aquifers. This is different from the way the built environment seals the surface. Rainwater and snowmelt become runoff which may contribute to flooding. Contaminants are washed from surfaces directly into waterways without undergoing the filtration that nature intended.

Stormwater management tools can mitigate the impact of the built environment on natural hydrology. Unfortunately, however, they also can lead to unsound solutions such as cutting down stands of trees in order to build detention ponds. Porous asphalt pavements allow for land development plans that are more thoughtful, harmonious with natural processes, and sustainable. They conserve water, reduce runoff, promote infiltration which cleanses stormwater, replenish aquifers, and protect streams.

A typical porous pavement has an open-graded surface over an underlying stone recharge bed. The water drains through the porous asphalt and into the stone bed, then, slowly, infiltrates into the soil. If contaminants were on the surface at the time of the storm, they are swept along with the rainfall through the stone bed. From there they infiltrate into the sub-base so that they are subjected to the natural processes that cleanse water.

Porous asphalt pavements are being used successfully throughout the United States, in every type of climate and geography. They are recognized by the Environmental Protection Agency as a best management practice for stormwater management.


This Web site is designed to offer a broad range of informational resources on porous asphalt. For further detail, FHWA has released a TechBrief providing an overview of the benefits, limitations and applications of porous asphalt pavements with stone reservoirs, as well as considerations for design, construction, and maintenance. Additional resources and publications covering structural design, construction, and maintenance of porous asphalt pavements can be found on the Publications page.