Green Infrastructure

What is Green Infrastructure?

Green infrastructure is a term that is used more often these days by a variety of architectural, landscape, and engineering professionals. Initially green infrastructure was used to define a planned network of natural lands, working landscapes, and other open spaces for the purpose of habitat restoration and ecosystem preservation.

Over the past decade, green infrastructure has evolved and been used frequently by the U.S. Environmental Protection Agency (EPA) specifically when referencing neighborhood and site level stormwater management techniques.

The EPA defines green infrastructure as a system that uses vegetation, soil, and natural processes to manage water and create healthier urban environments.

These systems take shape in a variety of different forms, some of which are listed below. All of these types though, are meant to repair the damage created by paving over green spaces in our urban areas, and allow the land to mimic water capture and infiltration functions typically found in nature.


Why Do We Need Green Infrastructure?

In 2007, the EPA issued a court-ordered Consent Decree and Consent Orders with Allegheny County Sanitary Authority (ALCOSAN), the City of Pittsburgh, and 82 municipalities to comply with the 1972 Clean Water Act.

The action by the EPA forced the region to submit a Wet Weather Plan, which would outline a long-term plan to update and enhance its aging storm and sanitary infrastructure. The plan must address the combined sewer system (CSO) overflow issues that occur during dry and wet weather events. Additionally, it has to eliminate all sanitary sewer system (SSO) overflows in separate systems.

The result of this planning process is a more than $2 billion plan, which will be the largest public works project ever completed in Allegheny County. This plan is designed entirely with engineered gray infrastructure solutions (e.g., pipes, holding tanks, tunnels, etc.) that will be buried hundreds of feet beneath the ground. It is imperative to incorporate green infrastructure into the region’s planning process, as there are numerous benefits, including, but not limited to:

1. Increase water quality through the management of stormwater volume

2. Holistic management of water

3. Triple bottom line community and economic development

4. Sustainable and cost-effective wet weather management

5. Provide climate resilient and adaptive approaches

6. Increase community green space and recreational areas


Types of Green Infrastructure

Stormwater Planters – urban rain gardens installed along sidewalks with vertical walls and enclosed or natural filtration bottoms. Stormwater is collected through curbcuts along the street curb and enters the planter, directing any excess water to an overflow pipe.

Bioswales – vegetated linear channels installed street-side or in parking areas with the intention to retain and filter stormwater. Bioswales are designed to hold the stormwater on-site, providing the water a space to slowly infiltrate and filter into the ground.

Green Roofs – vegetation and growing medium on a waterproof membrane that covers the roof of a built structure. Green Roofs allow buildings in dense urban areas to manage stormwater through rooftop infiltration and evapotranspiration.

Permeable Pavement – paved surfaces, such as plazas, sidewalks, parking lots, and streets constructed with materials that allow stormwater to infiltrate and filter into the ground. Materials include permeable concrete, porous asphalt, and other types of structural pervious pavers.

Trees– strategically planted throughout urban areas will contribute to an increased overall canopy cover. The higher the percentage of urban tree canopy, the more stormwater the leaves are able to capture, filter, and infiltrate into the ground.

Rain Garden – shallow vegetated bioretention areas that collect and absorb stormwater from impervious surfaces (roofs, sidewalks, etc.). Rain gardens are designed for stormwater to infiltrate and evapotranspirate, with attention to locations, soils, and climates.

Rain Barrel – stormwater harvesting system designed to collect rooftop runoff through interconnected gutters and downspouts. Rain barrels collect, slow and reduce runoff, retaining the stormwater for later use on site.

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