Driving around JBM-HH, you may have noticed gardens planted in depressions and medians. These are examples of bioretention areas, where stormwater runoff flows and slowly settles into the ground instead of being carried directly to stormwater sewers. Stormwater in sewers flows directly to streams and rivers without filters or treatment. As a result, pollutants in the stormwater, including nutrients, chemicals, sediment, bacteria and trash, also end up in our local streams and rivers and ultimately affect water quality in the Chesapeake Bay.
Bioretention areas are specially-designed basins that use plants and soil to filter and absorb stormwater. As it flows into the bioretention area, stormwater runoff is slowed down and drained through a filter bed containing layers of mulch, sand, soil, or other media that is planted with plants and shrubs. Pollutants are left behind or absorbed by plants, and the filtered stormwater then drains to groundwater or flows to the stormwater sewer system.
Stormwater pollutants are captured in bioretention areas in a variety of ways:
Sedimentation - As stormwater runoff slows, sediment particles settle out and add to the soil in bioretention areas.
Absorption - Stormwater runoff containing pollutants is soaked up by soil, rather than entering the stormwater sewer system. Absorption leads to other methods of capturing pollution, including those listed below.
Adsorption- Dissolved pollutants, such as chemicals, nutrients and bacteria, adhere to soil particles, allowing cleaner water to drain to the soil layer below the basin.
Microbes - Bacteria, nutrients and chemicals from stormwater runoff are broken down by microbes in the soil, turning them into less harmful materials.
Volatilization - Some chemicals associated with petroleum, oil or grease, evaporate as stormwater slowly filters through the bioretention area.
Bioretention areas use a combination of parts that work together to remove pollutants. Different layers of soil and gravel promote drainage. Gently sloping, grassy sides slow down stormwater runoff and filter out large particles. The center of the basin is the bioretention area's lowest point and is planted with water-tolerant plants. In times of heavy rain, the center of the basin also stores water that cannot be absorbed immediately. Finally, using native plants in the bioretention area reduces the need for pesticides and fertilizers, because the plants are more suited to the local environment.
You can find JBM-HH's bioretention areas just inside of Wright Gate and next to the Radnor Heights Substation at Fort Myer; outside of the Memorial Chapel at Henderson Hall and behind the fitness center parking lot and Marshall Hall at Fort McNair. Bioretention areas combine form and function to help reduce stormwater pollution as part of a comprehensive stormwater management plan. They are designed to suit local needs and come in many shapes and sizes.
Next time you come across one of JBM-HH's bioretention areas, take a minute to enjoy the scenery and the positive impact they have on the health of the Chesapeake Bay.
To report conditions that could cause stormwater pollution or to get more involved with stormwater activities at JBM-HH, call the Environmental Management Division at 703-696-8055.
Social Sharing