Bioinfiltration/Bioretention

Bioinfiltration and bioretention stormwater management practices (SMPs), often referred to as rain gardens, are vegetated depressions or basins that use surface storage, vegetation, planting soil, outlet controls, and other components to treat, detain, and retain stormwater runoff. Bioinfiltration and bioretention SMPs represent the highest level of preference in Philadelphia Water's (PWD’s) SMP Hierarchy by providing high-performance and cost-effective stormwater management, green space, and triple bottom line benefits. Both types of SMPs reduce stormwater volume and pollution by filtering runoff through a vegetated soil medium that promotes evapotranspiration. Bioinfiltration SMPs remove stormwater via infiltration into the surrounding soils while bioretention SMPs attenuate runoff with flow-regulating underdrains. Bioinfiltration/bioretention SMPs can be found in a variety of configurations from relatively large and open vegetated basins to small-scale SMPs contained within flow-through planter boxes. These SMPs can be combined with other SMPs in series to meet the PWD Stormwater Regulations (Stormwater Regulations). Bioinfiltration/bioretention SMPs can be used to manage stormwater on small and large sites. For example, bioinfiltration/bioretention may be integrated into smaller sites using flow-through planter boxes or integrated into larger sites by using multiple bioinfiltration/bioretention basins throughout the project area.

Bioinfiltration/bioretention SMPs are also suitable for many types and sizes of development, from single-family residential to high-density commercial projects, and are viewed as an integral part of a development’s landscape design during site layout, doubling as both a landscape amenity and stormwater management feature.

At commercial, industrial, and institutional sites, areas for stormwater management and green space are often limited. At these sites, bioinfiltration/bioretention SMPs serve multiple purposes of stormwater management and landscaping by managing runoff from impervious site areas such as parking lots, sidewalks, and rooftops.

A parking lot is an ideal location for bioinfiltration/bioretention SMPs. These SMPs can be incorporated as an island, median, or along the perimeter of the parking area. Bioinfiltration/bioretention SMPs can enhance the aesthetics of a parking lot while managing stormwater from the site.