pervious asphalt
Good: Pervious asphalt, note the coarse

Pervious Pavement

Pervious pavement allows water to pass through it and soak into the ground, reducing runoff and mimicking the natural hydraulic cycle.  Pervious pavement typically is a layer of specially formulated concrete or asphalt on top of a thick layer of gravel (8-24 inches).  As water passes through the pavement and gravel, contaminants are filtered out.  The water is stored in the gravel layer until it can soak into the ground.  Pervious pavement requires regular maintenance to allow water to pass freely. 

Maintenance sheets

Permeable pavement  (includes pervious concrete/pavement, porous asphalt, permeable pavers, open-celled paving grid with gravel or grass)

Maintenance is needed if you see these signs  

pervisou concrete problem with standing water
Problem: This pervious concrete needs
maintenance; there should be no standing

Standing water during or after rainfall (see photo)

Visible debris or sediment on pavement surface

Moss growth inhibits infiltration or poses a slip safety hazard




Tips for fixing problems and general maintenance

Vacuum and sweep pavement frequently, preferably at least twice a year.

Wash pavement using high pressure water at least once a year.  Protect nearby storm drains from wash water.

Do not allow dirt or landscaped areas to drain or erode onto pervious pavement.

Repair and patch pervious pavement with similar pervious material and gravel layer.

Report Spills

Chemical spills such as oil, gasoline, paint or herbicides/pesticides may cause harm to surface or groundwater.  Spills MUST be reported to the Washington State Department of Ecology and your local city or county.  DO NOT attempt to rinse away the spill until it's been checked.  

Washington Department of Ecology 24-hour Spill Response Number: (360) 407-6300