Porous Asphalt - part 1
Posted by Jesse Willoughby on Mon, May 18, 2009 @ 12:01 PM
Porous asphalt pavements are of great interest to site planners and public-works departments. With the proper design
and installation, porous asphalt can provide cost-effective, attractive pavements with a life span of more than twenty
years, and at the same time provide storm-water management systems that promote infiltration, improve water quality,
and many times eliminate the need for a detention basin. The performance of porous asphalt pavements is similar to that
of other asphalt pavements. And, like other asphalt pavements, they can be designed for many situations.
How does it work?
The technology is really quite simple. The secret to success is to provide the water with a place to go, usually in the form
of an underlying, open-graded stone bed. As the water drains through the porous asphalt and into the stone bed, it slowly
infiltrates into the soil. The stone bed size and depth must be designed so that the water level never rises into the
asphalt. This stone bed, often 18 to 36 inches in depth, provides a tremendous subbase for the asphalt paving.
What does it cost?
Special features such as the underlying stone bed are more expensive than conventional construction, but these costs
are more than offset by the elimination of many elements of standard storm-water management systems. On those jobs
where unit costs have been compared, a porous asphalt pavement is generally the less-expensive option. The cost
advantage is even more dramatic when the value of land that might have been used for a detention basin or other stormwater
management features is considered.