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.
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, P.E., at email@example.com