Dennis Ave. Medical Center Bio Retention Area

The stormwater systems described below were removed as part of a redevelopment project.

Montgomery County Dept. of Environmental Protection (DEP) identified two locations in the Sligo watershed where they plan to demonstrate ways to manage stormwater runoff less invasively than traditional methods like gutters, pipes and holding ponds.

The Dennis Ave. Health Center site (installed in 2005) uses three bio-retention systems which have water-loving vegetation and a special mix of soil to reduce pollutants as water filters through the area. The system acts like a giant sponge. Since this area is designed to hold standing water for only four to six hours, and mosquito eggs need three days in water to hatch, there is no chance the rain gardens will become breeding grounds for the West Nile Virus. Collecting stormwater in multiple locations closer to its source has several advantages compared to the large stormwater water pond systems that are being used at the Dennis Ave. (Wheaton Stormwater Ponds) and University Boulevard sites. To begin with the smaller amount of water you collect at one location is easier to manage than a massive amount of water collected at the ponds. The stormwater collected at large stormwater ponds also do not protect the creek upstream of the ponds. Rain gardens also help recharge the ground water.

The project was made possible by a grant from the U.S. Environmental Protection Agency and matching grants from Montgomery and Prince George's counties to build and study low-impact development projects in the Anacostia watershed. University of Maryland researcher, Dr. Davis, published a study that included the performance of the bioretention system in reducing pollution and runoff.

See for article about the project.

The Dennis Ave. Health Center Project also included the installation of a Filterra bioretention tree box. The tree box which looks like a storm drain with a small tree or shrub growing from it uses the same principals of bioretention to retain and cleanse stormwater runoff. For more information on how this system works, click here and click on the launch button on the sidebar to see an automation on how the process works.

Water quality monitoring station at the inlet to one of the bio retention systems

One of the bio retention systems with the outlet water quality monitoring shown in the background

A swale leading to one of the bio retention systems

Excavation of Bioretention Cell #3

Underdrain Installed with Underdrain Gravel Surrounding the Pipe

Cell Being Planted with Native Plants