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Green Infrastructure for Multiple Objectives

Authors:

Matthew Jones - Hazen and Sawyer

Hazen and Sawyer has conducted stormwater monitoring at numerous green infrastructure controls, such as this bioretention area within a park in NYC that discharges to the Bronx River.

This stormwater wetland, part of the Staten Island Bluebelt, was photographed shortly after Superstorm Sandy, where it was subjected to flooding, but quickly recovered without the need for major maintenance.

Drainage improvements and stormwater controls designed by Hazen for the City of Virginia Beach have alleviated coastal flooding during intense storms, and provided water quality benefits to support the MS4 program and Chesapeake Bay TMDL requirements.

Within the City of Richmond (VA), Hazen has designed green alleys with permeable pavement to improve local site conditions and water quality and thereby reduce pollutant loads within the MS4 and to the Chesapeake Bay. The green alleys promote infiltration, groundwater recharge, treatment of stormwater pollutants, and reduce runoff volumes and peak flowrates during rain events.

Green infrastructure offers municipalities several tools they can implement either alone or in concert to capture and treat stormwater runoff amidst a range of site constraints.

This large bioretention within a roadway median in Queens, NY retained nearly all of the runoff it received during 3 years of monitoring, effectively eliminating the water quantity and quality impact of the contributing watershed on the downstream system. Furthermore, infiltration rates within the facility have increased over time as vegetation has become better established through multiple growing seasons.

Green infrastructure offers a broad toolbox to address a range of stormwater management needs, including Municipal Separate Storm Sewer System (MS4) management, TMDL requirements, CSO mitigation, and climate change concerns. This broad toolbox is particularly suited for stormwater retrofits, addressing a variety of site constraints at multiple scales, helping to address water quality goals for existing development while optimizing cost effectiveness and enhancing the quality of life in the community.

With an anticipated increase in the frequency of extreme storm events and impacts from sea level rise, resilience in stormwater controls will become increasingly important in protecting vital resources and managing long-term costs. Incorporation of natural design elements into stormwater control plays a critical role in mitigating flooding, controlling runoff, and removing harmful contaminants from stormwater with systems that can withstand and rebound from extreme storms and changing conditions.

Although some of the most aggressive green infrastructure initiatives have been focused on CSO mitigation, green infrastructure can be a valuable tool in MS4 areas, particularly those subject to TMDLs with requirements to address existing development. Not only can green infrastructure improve water quality through a variety of treatment mechanisms, but can provide substantial pollutant load reductions by infiltrating runoff and reducing the volume discharged to receiving waters.

Once the green infrastructure is implemented, it can then be monitored, yielding valuable information regarding potential CSO reductions and pollutant load reductions.

Whether the challenge is CSOs, MS4 requirements, TMDLs, or climate change impacts, a green infrastructure solution can also be customized to best meet the needs of the community. Permeable pavement, green/blue roofs, and bioretention are all available resources and can be used in numerous configurations and at varied scales, from individual sites to large watershed implementation efforts, providing flexibility in stormwater management.

For more information about these projects, please contact the author at mjones@hazenandsawyer.com.

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Horizons

Horizons Fall 2017 (pdf)

Horizons showcases significant water, wastewater, reuse, and stormwater projects and innovations that help our clients to achieve their goals, and can help you achieve yours. Articles are written by top engineers and process group leaders, demonstrating and explaining the beneficial application of a variety of technologies and tools.

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