Green Infrastructure – More than Meets the Eye
Green infrastructure (GI) is a network of decentralized stormwater management practices, designed to reduce loads on traditional grey infrastructure. In a landscape, it often appears to center around plant selection, water features and hardscapes, but there is more than meets the eye.
Engineered Aspects
Many components are highly engineered design elements that work together to become functional pieces of stormwater management. These elements take form in the landscape through the integration of green roofs, bioretention (rain gardens), bioswales, planter boxes, constructed wetlands, urban trees, rainwater harvesting and permeable pavement, and more.
Why does it matter?
Grey infrastructure frequently utilizes combined sewer systems to collect sanitary and storm water in a centralized manner. Most combined sewer systems in the country were installed in the late 1800s. At the time, these systems were the more affordable and preferred option in urban areas because less pipe was needed to transport both stormwater and wastewater. By the end of the 19th century, most cities with centralized wastewater management had combined systems.
During heavy rainfall events, there can be too much rain for the ground to absorb. In a combined sewer system, this runoff water is directed to a network of pipes where the stormwater and wastewater are transported to an off-site wastewater treatment plant. When the combined sewer system becomes overwhelmed by the volume of water, the wastewater is discharged back into the environment through a combined sewer outfall instead of backing up into the pipe network. The result is an estimated 850 billion gallons of untreated wastewater and stormwater discharging into U.S. waterways annually from combined sewer overflows, according to a 2005 EPA report.
Green Infrastructure
Each green infrastructure element functions differently and needs to be properly designed and sized for the site it serves to capture and infiltrate rain where it falls on-site. Proper design reduces stormwater runoff, limits strain on combined sewer systems and improves the health of surrounding waterways. This is typically accomplished by designing a landscape that uses terrain, soils and plants to slow down, capture, and filter stormwater. Pretreatment areas of green infrastructure designs filter pollutants such as sediment, heavy metals, and nutrients before they enter waterways.
Example of Green Infrastructure
One example is the Merriman Constructed Stormwater Wetland. The project was designed and constructed to improve the water quality of stormwater runoff by using plants, rocks, and site specific-design techniques. Water enters the site through rainfall, runoff or an inlet that opens into a forebay. The stormwater then filters through the forebay before entering a micro pool with an outlet catch basin for rain events that may overwhelm the wetland. The stormwater wetland provides additional benefits of a natural wetland, such as a habitat for birds and flowers for butterflies as a result of plant selection. The GI landscape requires basic routine maintenance and inspection to ensure the aesthetic and functional pieces of the infrastructure operate as intended to manage the excess stormwater.
Discover EDG’s Green Infrastructure Services
Through innovative and sustainable approaches to design and implementation, Green Infrastructure can provide valuable environmental, aesthetic and economic benefit for any community. Learn more about EDG’s Green Infrastructure Services.