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Sierra Club Water Sentinels

Green Infrastructure

Rain garden

Nationwide, stormwater is a leading source of water pollution. Stormwater runoff transports water carrying contaminants over land into waterways from large urban areas, construction and industrial sites, and municipal sewer systems and is one of the leading causes of water pollution. According to the EPA 13% of U.S. rivers, 18% percent of lakes, 32% of estuaries and 55% of ocean shorelines are classified as impaired by stormwater, which means they are rendered unsafe for swimming or fishing.

In a natural system, rainwater does not travel very far. It soaks into the soil and is taken up by plants. The quick infiltration prevents the water from transporting contaminants and keeps waterways from eroding.

But the concrete and asphalt of the urban setting is anything but natural. Instead of soaking into the ground, rain runs across impervious surfaces, picking up contaminants along the way. By the time it reaches a stream or lake, the runoff can be full of metals, oil, grease, bacteria and other contaminants.

Green Infrastructure is an adaptable term used to describe an array of products, technologies, and practices that use natural systems-or engineered systems that mimic natural processes-to enhance overall environmental quality and provide utility services. As a general principle, Green Infrastructure techniques use soils and vegetation to infiltrate, evapotranspirate, and/or recycle stormwater runoff. When used as components of a stormwater management system, Green Infrastructure practices such as green roofs, porous pavement, rain gardens, vegetated swales and constructed wetlands can produce a variety of environmental benefits. In addition to effectively retaining and infiltrating rainfall, these technologies can simultaneously help filter air pollutants, reduce energy demands, mitigate urban heat islands, and sequester carbon while also providing communities with aesthetic and natural resource benefits.

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