Green Infrastructure. NYC Rain Garden sign. CurrentWater.CO

Green Infrastructure in NYC

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Revised: September 23, 2018

February 28, 2019

Green Infrastructure adoption in NYC–what is the back story?

Prior to 2010 the city of New York had been managing flood control with a primarily grey-infrastructure based system. Consent decrees had been filed against NYC in 1992 and 1996 and an order was issued again in 2005 to address numerous violations. These violations included discharging untreated domestic sewage into waters of the state. A change was needed.

The choice? Green Infrastructure. 

Adopting Green Infrastructure (GI) would both save the city billions of dollars and offer many additional benefits. In addition to saving money, GIs will save large tracts of natural areas, beautify neighborhoods, reduce sewer overflows, improve air quality, increase wildlife nesting and foraging areas, increase shading, increase property values and improve the streetscapes. 

In 2010 the city introduced the Green Infrastructure Plan outlining a program to complement then-Mayor Bloomberg’s PlaNYC program.  The New York State Department of Conservation (DEC) and the Department of Environmental Protection (DEP) signed an agreement in 2012 in which DEP committed to building GI that would manage one inch of stormwater from 10% of impervious surfaces by 2030.

This move was anticipated to save the city billions of dollars by avoiding the construction of additional hard infrastructure (new sewer lines and treatment plants) and focus instead on the use of GI. 

Mayor Bloomberg committed to spend an estimated $1.4 billion on public GI investments by 2030. As of Fiscal Year 17 $410,691,296 has been spent or promised with the remaining balance budgeted through Fiscal Year 27.

Combined Sewer Overflows (CSOs)

Common to many older east-coast cities, NYC uses a combined sewer system that carries both stormwater and domestic sewage in shared pipes. Approximately 60% of the city’s sewers are combined, or 3,337 miles of combined pipes.

The current treatment plants are designed to treat and disinfect twice the dry-weather flow but overflows occur when heavy storms exceed the system’s capacity. These overflows pour into New York Harbor and violate the terms of the Clean Water Act. 

Consent Decree Timetable

The Consent Decree requires that NYC manage one inch of stormwater runoff from 10% of impervious surfaces in combined sewer areas on the following scale: 1.5% coverage by 2015, 4% by 2020, 7% by 2025 and 10% by 2030.

It’s a tall order for a city with 72% impervious surfaces. The city acknowledges that this will be a long-term effort requiring the retrofitting of both public and privately-owned properties. To assist in covering the costs of converting private properties to GI, the city has grant money available through the Grant Program.

Did NYC meet the 2015 goal?

DEP announced early in 2015 that it would likely be unable to meet the 1.5% target goal. The actual number achieved in 2015 was .6%. DEP had run into a series of obstacles during the course of evaluating sites that prevented meeting the goal on time: high groundwater and bedrock, space limitations in right-of-ways, conflicting capital projects, environmental conditions and other limitations that prevented the installation of GIs.  

DEP began working on a contingency plan which was to be submitted by June 2016. The plan was completed and accepted as DEP was able to show that it had used “best efforts” to achieve its goal and had met the requirement of $187 million investment in GI.

What types of Green Infrastructure are being built?

The initial plan to meet the 1.5% goal was to be achieved primarily through the installation of right-of-way (ROW) bioswales, rain gardens, and green streets. Other methods could also include green and blue roofs, permeable pavement, cisterns, rain barrels and subsurface detention systems.

By the end of 2017 an anticipated 4,376 GIs have been installed and thousands more are in the planning process.

Where is Green Infrastructure being installed?

DEP evaluated locations requiring remediation using the following criteria: areas experiencing high volumes of CSO flooding, high frequency overflows, high likelihood for success, and locations near outfalls that directly affect the public.

The initial locations selected were identified as “Priority CSO Tributary Areas” and are located in Brooklyn, Queens and the Bronx. The map shown below is dated February 2018 but is updated monthly. Visit the link shown at the bottom of this article for a current version.

ArcGIS map showing Green Infrastruture assets around the city of New York. February 2018. Updated monthly. CurrentWater.CO
ArcGIS map showing Green Infrastruture assets around the city of New York. February 2018. Updated monthly. See link at bottom of page.


Please come back and join me for more Current Water.

Jennifer Croft


ArcGIS Green Infrastructure Map, click here

2012 Consent Order Modification, click here

GI Metrics Report, 2016, click here

EPA National Enforcement Initiative on CSO’s, click here

NYC Parks, click here

Rain barrel program, click here

Past Coverage on Green Infrastructure from CurrentWater.CO:

Seattle, click here

Milwaukee, click here