4 | NATIONAL RECREATION AND PARK ASSOCIATION COMMON GREEN STORMWATER INFRASTRUCTURE PRACTICES FOR PARK SETTINGS Common green stormwater infrastructure practices are defined below as adapted from the U.S. Environmental Protection Agency Green Infrastructure website.5 BIORETENTION is a versatile stormwater treatment system that collects, filters, and infiltrates stormwater runoff from impervious surfaces during small storm events and allows it to infiltrate into subsurface soils and evapotranspirate, the movement of water from the land to the atmosphere by evaporation and by transpiration from plants. Bioretention areas are depressed, flat-bottomed cells of various shapes and configurations that include plants and an engineered soil mix and may include an underdrain. Their flexible design features, relatively small footprint, and ability to be adjusted to accommodate utilities and other conflicts allow them to easily fit into community landscapes. Common variants include rain gardens, micro-bioretention areas, stormwater planters, and tree box filters. Bioswales are another variant detailed below. BIOSWALES are bioretention channels that collect runoff from small drainage areas. Bioswales differ from other bioretention practices in that they are designed to be conveyance treatment devices, not storage devices. Water does not pond and slowly infiltrate in bioswales. Instead, treatment and retention is provided as stormwater moves from one place to another. As linear features, they are particularly well suited to being placed along streets, sidewalks, and parking lots. CONSTRUCTED WETLANDSmimic the functions of natural wetlands to capture runoff, improve water quality, and provide wildlife habitat. Constructed wetlands filter stormwater by slowing down water flow and trapping sediments and pollutants. Plants unique to wetland habitats take up pollutants and foster the growth of microorganisms that remove pollutants from water. Wetlands can be a costeffective, practical approach to treating polluted runoff. However, they can generally only be built on uplands and outside floodplains to avoid damaging natural aquatic ecosystems.6 IMPERVIOUS SURFACE DISCONNECTIONS involve directing runoff from rooftops or other small impervious areas (such as a hard turf area, a small parking lot, or section of roadway) into a pervious area or another stormwater best management practice that infiltrates, filters, and/or captures the runoff. Disconnecting downspouts from the storm drain system is a simple, effective green infrastructure practice that is applicable to a wide variety of site conditions and development designs. GREEN STORMWATER INFRASTRUCTURE Montgomery County Department of Environmental Protection Steven Vance Low Impact Development Center, Inc.
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