By: The Water Quality Action Team
Established by Congress in 1972, the Clean Water Act (CWA) is the cornerstone of surface water quality protection in the United States. The CWA made it unlawful to discharge any pollutant from a point source into navigable waters, unless authorized by a permit. Point sources are conveyances such as pipes or man-made ditches that discharge into surface waters. The CWA is administered by the Environmental Protection Agency. Pollutants include soil particles, fertilizers, pesticides, grease, and oil from cars, trucks, and road salts.
Natural systems such as wetlands do a great job of filtering pollutants from water by several methods: As water from a stream channel or surface runoff enters a wetland, the water spreads out and flows through dense vegetation. The velocity of the flow is reduced, allowing suspended material in the water to settle to the wetland surface. The roots of wetland plants can then bind the accumulated sediments, nutrients, and chemicals. Over time, chemicals are broken down and clean water is discharged into surface waters or recharge ground water.
Green Infrastructure is an attempt to mimic natural systems such as wetlands to reduce stormwater runoff and improve water quality. The EPA defines Green Infrastructure as “…the range of measures that use plant or soil systems, permeable pavement or other permeable surfaces or substrates, stormwater harvest and reuse, or landscaping to store, infiltrate, or evapotranspirate stormwater and reduce flows to sewer systems or to surface waters.”
Green Infrastructure is a cost-effective, resilient approach to managing wet weather impacts that provides many community benefits. While single-purpose gray stormwater infrastructure—conventional piped drainage and water treatment systems—is designed to move urban stormwater away from the built environment, green infrastructure reduces and treats stormwater at its source while delivering environmental, social, and economic benefits. Green Infrastructure comes in many forms such as rain gardens, green roofs, vegetated swales, stormwater wetlands, and bioinfiltration basins. Some systems are simple such as a rain garden and others are complex, such as a bioinfiltration basin which has multiple layers of planting media, gravel, and plants to filter stormwater, infiltrate it into the ground, and uses plants to transpire water into the atmosphere. If well thought out, constructed, and maintained, Green Infrastructure can be aesthetically pleasing while providing wildlife habitat and keeping our surface waters clean.