Estes Design

2005 Pervious concrete and Bioretention/Rain Garden,
Design and Installation, Charlotte, NC

Stormwater BMPs turned demonstration project

Wilmore Walk began as a simple stormwater project, in which EDI was contracted to provide 401/404 and stormwater permitting for a small townhouse project just south of downtown Charlotte, NC.  In order to comply with federal and state regulations, EDI incorporated rain gardens (bioretention cells) as LID devices to control and treat the on-site stormwater.  

The owner of EDI quickly realized that the northern parking area would be ideal for a demonstration of pervious concrete.  A cost sharing agreement was put in place between the developer and the City of Charlotte to turn the project into the first of its kind in North Carolina.

wilmore walk  

Construction of the Pervious Concrete

Estes Design integrated the pervious concrete into the design, managed and supervised construction of the project. Double ring infiltrometer tests were used to directly measure infiltration rates below the carefully designed gravel reservoir. Gravel is added for the reservoir and the pervious concrete is poured on top.   

 perv concrete infiltrometer   stone base  

  perv concrete     

Water truck floods basin, Infiltration rates measured

After construction, the reservoir was filled to the brim via a fire hose to test the reservoir's ability to draw down a full reservoir. As was designed, the water in the reservoir drew down 7.47" of water in 5.57 days, which calculates to 1.34" per day. 

hydro truck  

fire truck graph  

7 years of successful monitoring

Estes Design monitored the pervious concrete reservior for the first year after construction beginning in August 2006.  The City of Charlotte funded an additional two years of monitoring, completed by Department of Earth Science students from UNC Charlotte.  

As designed, the reservoir was sized to accommodate the 2-year storm with a wide safety factor.  Seven years of continuous monitoring has shown that the 18" deep gravel reservoir can easily infiltrate the 50-year storm.

The City of Charlotte has a summary of the project on the Storm Water Services portion of their website here: Wilmore Walk - Pervious Concrete Parking Lot