Porous Asphalt

Porous asphalt consists of a special open-graded surface course bounded by asphalt cement, followed by a larger stone bed over the subgrade.  It is designed to manage and treat stormwater runoff.  The open-graded section in a typical installation ranges from 3 to 7 inches thick with a void ratio between 15% to 20%.  Common applications for porous asphalt include parking areas, walkways, trails, and roads.  After the water drains through the open-graded section and stone bed, it slowly infiltrates into the soil.

Why use this strategy?

In general, benefits of permeable pavements include recharge of the ground water reserves; less consumed energy and natural resources; low-impact infrastructure and cost-effective method for stormwater mitigation by eliminating the use of drainage structures.

How to use it?

Consider using pervious concrete or porous asphalt on a specially designed permeable pavement structure. Permeable structures are best suited for parking lots or low traffic roads.

Where to learn more and who to contact?

Green Up page on permeable pavement structures:

National Asphalt Pavement Association:

  • Porous Asphalt web page includes links to design guidelines

Federal Highway Administration Tech Brief