Lifecycle of Green Infrastructure - 5 Years of Monitoring and Post-Construction Evaluations
- Matthew Jones PhD, PE - Hazen and Sawyer
As one of the first initiatives of an expansive green infrastructure program, New York City Environmental Protection implemented dozens of green infrastructure retrofits to evaluate the feasibility and performance of these controls. These pilots, constructed from 2010-2013, include multiple bioretention configurations, permeable pavement, rooftop controls, and subsurface detention and infiltration systems. Green infrastructure was installed in locations ranging from ultra-urban residential areas to forested parks and large highway medians.
Detailed monitoring evaluations conducted over at least 2 years utilized a combination of site visits and remote data loggers to examine quantitative performance regarding runoff retention and water quality, as well as aspects like community acceptance, maintenance requirements, and triple bottom line co-benefits. These evaluations have yielded valuable insight into the design and functionality of green infrastructure and validated its ability to provide substantial runoff retention. Among many of the lessons learned was the observation that infiltration performance improved at a bioretention area densely vegetated with native vegetation over the course of 3 years of monitoring as the root structure matured.
To build upon the several years of detailed post-construction monitoring efforts and gain insight into long-term performance, site evaluations were conducted to compare the present condition of green infrastructure pilots, many now in place for more than 5 years, against as-built conditions and other prior assessments. These evaluations noted substantial changes in appearance and vegetation coverage and composition over time. There was little evidence of poor bioretention drainage, with blockage of curb cuts the most substantial issue related to performance. Maintenance of the pilots and their condition appeared to correlate with local site conditions and the background of staff performing maintenance. While opportunities for individual site improvements were observed, the evaluations generally indicated the resilient nature of green infrastructure controls and their ability to support long-term stormwater management efforts.
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