Bioretention is a vegetated stormwater management practice which utilizes shallow temporary ponding in vegetated swales and depressions to capture and treat surface runoff.
"A sample bioretention cell or rain garden. Photo courtesy of WSSI Inc."
Bioretention works as a stormwater quality facility by reducing pollutant loads through filtration, chemical and microbial activity in the soil mixture and mulch media, biological uptake and evapotranspiration by vegetation, and infiltration into the ground. It works as a quantity control by capturing runoff, storing it temporarily and releasing it at slower rates through infiltration into the ground and through stormwater control structures. Depending on the specific design and application, bioretention facilities may be called bioretention basins, bioretention filters, or rain gardens.
Each bioretention area is generally designed to treat small areas and can be easily worked into a parking lot landscape by providing small facilities between parking aisles and around the perimeter. The surface runoff flows from the parking lot through openings in the curb to the bioretention areas. In addition, roof runoff can easily be directed by gutter and downspouts or through stone roof dripline interceptors to bioretention areas.
Detailed design, construction, and maintenance information can be found on the “Virginia Stormwater BMP Clearinghouse” website. The most stringent standard will apply and some state practices may not be permitted in the City of Virginia Beach.
For additional information, click here, or contact Public Works Stormwater Engineering at (757) 385-4131.