Green Infrastructure

Green infrastructure uses natural processes such as infiltration, plant transpiration, and evaporation to manage stormwater near where it falls in urban and suburban environments, significantly easing the strain on sewer systems and providing a host of other benefits. Controls such as rain gardens, constructed wetlands, bioretention areas and swales, and blue and green roofs can serve as valuable additions to a community’s stormwater management toolbox, controlling the quantity and quality of stormwater runoff, while also improving air quality, reducing the urban heat island effect, reducing chemical and energy demands at wastewater treatment plants, improving property values, and more.

This interactive graphic outlines four common green infrastructure solutions: bioretention, permeable pavement, blue and green roofs, and pocket wetlands.

Right of Way Bioswales (ROWBs) are simple green infrastructure practices that capture stormwater runoff from the public right of way and infiltrate/evapotraspire the water, reducing the flow into the sewer system. Hazen and Sawyer is working with New York City Department of Environmental Protection, New York City Department of Design and Construction, and New York City Economic Development Corporation to plan, design and construct ROWBs and other green infrastructure practices for over 6,100 acres in New York City.

Bioswale curb cut depressions enhance stormwater runoff capture.

Green infrastructure can often replace the need for expensive storm sewers, providing natural treatment of stormwater, groundwater replenishment, and a beautiful wetland habitat for native flora and fauna.

Constructed wetlands throughout the Staten Island Bluebelt provide water quality improvement, aesthetic enhancement, and community benefits.

Porous pavement at the Bradley Avenue Water Treatment Plant prevents stormwater runoff and replenishes groundwater.

Bioretention sites typically consist of a shallow, vegetated basin layered on top of an engineered sandy soil mixture, stone drainage, and an underdrain system.

Hazen and Sawyer designed the LEED Silver-eligible, 3-million gallon Manayunk CSO detention facility on Venice Island, a sensitive area requiring careful consideration of neighborhood impacts.

A green roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane.

Blue roofs are non-vegetated source controls that detain stormwater, either releasing it more gradually to the sewer system or storing it for beneficial reuse.

Bioswale bump-out intercepts direct flow path along gutters and incorporate pretreatment cell.

Hazen and Sawyer has helped dozens of municipalities across the nation – including several ultra-urban environments – deal with the challenges presented by stormwater runoff and combined sewer overflows (CSOs) using a toolkit that includes many green infrastructure solutions, such as bioretention, subsurface infiltration, blue and green roofs, permeable pavement, and rainwater harvesting, tailoring solutions to best fit each municipality’s goals and opportunities.

While it would not be realistic to attempt to manage 100% of watershed runoff through green infrastructure solutions, Hazen and Sawyer has helped plan and implement strategies for clients who have the potential for 75% mitigation through green stormwater practices.

The goal of green infrastructure is often to capture a storm’s “first flush.” This refers to an initial depth of rainfall that often – depending on how long it has been since the last storm – picks up high concentrations of pollutants and sediment as it washes impervious surfaces like roads, sidewalk, and parking lots, and frequently represents a large portion of the total annual rainfall. Using green infrastructure source controls to send this runoff through natural treatment processes significantly eases the strain on a sewer system and on a facility’s treatment process.

Green infrastructure offers a multitude of advantages to a municipality. The implementation costs for green infrastructure source controls can be comparable to traditional grey infrastructure strategies. But unlike many grey infrastructure approaches, design and construction of green infrastructure can be implemented in phased or distributed approaches, enabling implementation to progress as funding becomes available. Communities often rally around the aesthetic appeal of green infrastructure and leverage the educational opportunities that the highly visible source controls provide. The green infrastructure improvements to the community stand as an obvious demonstration of a city’s commitment to sustainable protection of public health and the environment.

For inquiries contact:
Sandeep Mehrotra