An engineered, planted area in the median on Sandy Forks Road that collects and cleans stormwater runoff when it rains

Sandy Forks Road has three bioretention basins including one in the median.  

Roadway Bioretention Areas

Green Stormwater Infrastructure Along Raleigh Roadways

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What is a Bioretention Area Why we Install Them How They Work Bioretention Areas at Work

What is a Bioretention Area

A bioretention area is a planted area that collects and cleans stormwater runoff from paved surfaces, like roads and sidewalks. The plants and soil in the area slow down the water and filter out pollution before it reaches a storm drain or creek.

Why we Install Them

When we install new sidewalks, bike paths, and widen streets, we place more impervious surfaces throughout Raleigh. More impervious surfaces can lead to more pollution. We strive to keep Raleigh green but also give the people of Raleigh a safe multi-modal transportation system. That is why we try and incorporate green stormwater infrastructure into our projects.

How They Work

Water is directed from the roadways and sidewalks into areas that have been engineered to remove pollutants from the runoff before it enters the stormwater system.

  1. Cutouts in the curb, drains, or small channels direct the water into the bioretention area. 
  2. The water slowly seeps through layers of mulch, dirt, sand, and stone before entering the stormwater system. 
  3. The plantings in these areas also play a large part in removing pollutants, as plant roots help clean the water. 

These systems are engineered so that water can use the roadway to move some of the water to the storm drain system so as not to overburden the bioretention area during heavy rain events. Bioretention areas stay dry when it is not raining.

Bioretention Areas at Work

Coming Soon:




Roadway Design and Construction

Division Manager
Sylvester Percival, PE

Stormwater Management

Heather Dutra
Water Quality Supervisor

Engineering Services
Service Categories:
StormwaterRoadway Design and Construction
Related Services:
Green Stormwater Infrastructure Initiatives