NYC Put Millions Into Green Infrastructure by the Bronx River. Did it Work?

This is part 1 of our 3 part series on green infrastructure in the Bronx. Read part 2 here.

In New York City, no one goes near the rivers after it rains. Even small amounts of stormwater overwhelm the combined sewer system. Raw sewage gushes into the surrounding rivers—enough to fill 45,000 Olympic swimming pools annually.

New Yorkers demanded that the city do something.

The NYC Green Infrastructure Plan was that something.

In 2010, then Mayor Bloomberg announced the city would invest up to $1.5B to build green infrastructure. Over the next 20 years, the city would construct thousands of rain gardens, green roofs, street trees, and more.

Traditional water management solutions include wastewater treatment plants. However, green infrastructure, or GI, promised handsome benefits at lower long-term costs. More street trees would mean more shade. More green spaces to maintain would mean more jobs.

By 2030, the city wanted to manage the equivalent of stormwater generated by one inch of precipitation from 10% of impervious surfaces (sidewalks, roads, etc) within combined sewer areas.

Local environmental advocacy groups celebrated the city’s embrace of green infrastructure. Paul Gallay, President of Riverkeeper, said, “Riverkeeper supports New York City for embracing green infrastructure as an integral part of its plan to reduce sewage pollution of New York City’s waters. We’re counting on the City to work with State regulators and environmental groups to find the right mix of stormwater control techniques for improved water quality and a more livable city.”

Maybe the NYC Green Infrastructure Plan could help a city so tormented by unnatural development rediscover the generosity of nature.

Saving The Bronx River Watershed

The good news could not have come sooner for the communities located along the Bronx River. Over 150 years of industrialization and neglectful city planning had dealt spectacular blows to the 23-mile winding waterway. Reports from the New York State Department of Conservation state the river’s problems plainly:

“Urban stormwater runoff, combined sewer overflows (CSOs), sanitary sewer overflows and illegal (unpermitted) sanitary discharges, as well as the overall industrial use of the waterway are sources of pollutants.”

Bronx River filled with trash and a bird

The NYC Department of Environmental Protection (DEP) agreed the Bronx River watershed was perfect for its initial GI investments. DEP planned to invest $20M in grey infrastructure over the next 20 years. However just using grey infrastructure would not meet federal water quality standards. DEP found there were opportunities to install green infrastructure in nearly half of the watershed area. It also recorded “significant public support” for green infrastructure.

In the Green Infrastructure Plan, DEP projected it would spend $119M on GI in the Bronx River watershed. The capital cost per gallon would be $1.58, compared with a $0.06 capital cost per gallon for its grey infrastructure investments.

DEP justified the higher initial upfront costs, “The significant sustainability benefits of the Green Strategy ‒ which are not available through the Grey Strategy ‒ would begin to accrue immediately and build over time, in contrast to tanks, tunnels, and expansions, which provide only water quality benefits at the end of a decades-long design and construction period.” (Image credit: NYC DEP)

Where Do We Stand Now?

It has been almost 10 years since the announcement of the NYC Green Infrastructure Plan. How has this policy impacted the Bronx River and surrounding communities?

This three-part series is a search for an answer. The story of the Bronx River watershed contains critical lessons for municipalities and communities worldwide.

Testing the Waters with Green Infrastructure

The years after the enactment of NYC Green Infrastructure Plan were dedicated to experimentation. Green infrastructure was, well, green. Very few American cities had green infrastructure plans, and databases of existing projects were just a jumping off point.

Before constructing thousands of GI assets across the city, DEP tested multiple prototype designs. Of the more than 30 pilot projects, several were built in communities along the Bronx River. The pilot project at the Bronx River Houses stood out for its scale and diversity of GI practices used.

The Bronx River Houses Go Green

Ride the 6 train to the Morristown Av/Soundview Station, walk two blocks along 174th Street and you will arrive at the Bronx River Houses. A community of over 3,000 people live in the chromosomal shaped towers managed by the New York City Housing Authority (NYCHA).

A community center sits in the heart of the complex. A team of paid and volunteer staff run programs for children after school, adults and seniors. Soon, the community center would also host green infrastructure projects.

A 2011 DEP press release described the project as a joint effort between DEP and NYCHA to beautify the community, reduce pollution, and help prevent combined sewer overflows into the Bronx River. “In the summer of 2010, DEP and NYCHA project managers met with the residents, local groups, Community Board 6 and the Borough President’s Office and informed them about the benefits of this project and also included the residents’ feedback into the green infrastructure plan built in the complex.”

I spoke with Norma Saunders, long-time resident and current President of the Bronx River Houses Resident Association, about her impression of the project at the time. She said assumed the presidency after the project was already under construction, but was unaware why it was happening.

The city spent $1M to test four types of GI at the Bronx River Houses: a perforated pipe system, stormwater chambers, rain gardens, and a blue roof tray system. Each rain garden cost an estimated to be $40,000, while the perforated pipe system cost an estimated $195,000. DEP describes the cost of a stormwater chamber as comparable to the perforated pipe system; the blue roof is even lower cost. (Image credit: NYP DEP)

Diagram of green infrastructure installations

DEP collected data about water quantity, weather, and water and soil quality for nearly two years. The data would determine whether the systems effectively managed stormwater.

Stormwater Storage Below the Surface

Construction crews descended upon the north and south parking lots to unearth tons of stone and dirt. In their place, the workers installed a perforated pipe system and a stormwater chamber for stormwater detention.

In a perforated pipe system, parallel perforated pipes buried in gravel store stormwater and then release it into the ground. A stormwater chamber, instead, uses open-bottom, perforated plastic chambers surrounded by stone. (Image credit: NYP DEP)

Perforated pipe system

Together, the systems would hopefully create 0.4 greened acres. A greened acre equals the volume of stormwater runoff managed by a GI asset spread out with a 1 inch depth.

DEP used a variety of techniques to characterize how the subsurface systems impacted water quantity and quality, and soil quality. The research team installed flow turbines at inflow and outflow pipes to measure flow rates. They also mounted a rain gauge to measure local precipitation. Lastly, they took water and soil samples to test levels of diesel, metals and other materials.

The monitoring system captured data for 20 months, weathering 5-day long storms and punishing amounts of rain. In a 2012 report, DEP reached a number of positive conclusions. The stormwater chambers frequently retained nearly all runoff it received. The perforated pipes reduced peak flows by more than 60%. Plus, the systems required minimal routine maintenance.

High-Tech Gardens

Autumn Magic Black Chokeberry Shrubs, Wild Hydrangeas, and Christmas Dagger Ferns brought life to five newly constructed rain gardens. Beneath the surface of each garden, an engineered soil layer created a super soaker. The engineered soil made the rain garden capable of managing water from an area twenty times its size. The five gardens, in total, constituted another 0.4 greened acre.

In addition to the monitoring equipment that was used for the subsurface systems, DEP also installed a stage to measure relative water level and conducted soil sampling.

Overall, the rain gardens frequently managed all of the stormwater from a 1-inch storm. Water level and flow data demonstrated that the rain gardens stored water on the surface level, then rapidly drained to store additional runoff.

There were winners and losers among the 20 different species of plants in the gardens. Some plants had over a 75% survival rate after two years, such a Red Twin Dogwood and Golden Groundsel. Other plants like Spiderwort had a less than 30% survival rate.

Compared to the subsurface systems, it was more difficult to maintain the rain gardens. A maintenance team regularly removed litter and leaves from curb cut sumps. However, the team found it challenging to pick up leaves caught in plants. (Image credit: NYP DEP)

Rain garden inlet with litter

Compared to the subsurface systems, it was more difficult to maintain the rain gardens. A maintenance team regularly removed litter and leaves from curb cut sumps. However, the team found it challenging to pick up leaves caught in plants.

The rain gardens were the most visible green infrastructure asset installed. DEP and another source reported the local community was pleased. “With the installation of the rain gardens came a lot more foliage which brightens up the area. People enjoy how it looks. It adds a lot of color,” said David Shuffler, Executive Director of Youth Ministries for Justice and Peace at Truth Out, which is headquartered across the street.

A Not So Blue Roof

Blue roof trays soon decorated the surface of the Bronx River Houses Community Center. The term, blue roof, is a misnomer. If you stood on the roof of the community center, you would see a bunch of dark colored shapes. Some trays were filled with carefully selected rocks that guide water into a storm drain. DEP tested four different configurations of trays, geotextiles, and plastics to determine which combination of elements performed best. The blue roof contributed a small 0.03 greened acre.

To evaluate the blue roof trays’ performance, DEP installed a weather system that captured evaporation, rainfall, wind, relative humidity and solar radiation. The only other monitoring equipment was a stage.

All of the trays performed similarly, although Tray D was best at retention. The report also noted that trays typically drained in less than 24 hours after it rained. Fast drainage avoids nuisance ponding and ensures the trays were ready for another storm. The maintenance team needed to regularly remove debris to maintain the trays’ performance.

All of the trays performed similarly, although Tray D was best at retention. The report also noted that trays typically drained in less than 24 hours after it rained. Fast drainage avoids nuisance ponding and ensures the trays were ready for another storm. The maintenance team needed to regularly remove debris to maintain the trays’ performance. (Image credit: NYP DEP)

Cross section views of tray configurations

A Sign of Things to Come

The pilot at the Bronx River Houses demonstrated the value of green infrastructure in stormwater management. Overall, the systems performed similarly to computational models and effectively managed stormwater from 1-inch precipitation events.

In mid-2012, DEP published Guidelines for the Design and Construction of Stormwater Management Systems to provide NYC developers ways to comply with local stormwater performance standards. The guidelines include photos and insights from the Bronx River Houses and other pilot sites.

Above ground systems, such as the rain garden and blue roof, required a maintenance team. When I spoke with Saunders, she was unsure who is currently responsible for maintenance. The Bronx River Houses property manager and building supervisor at the time of the project no longer work there. She recounted that someone removed the blue roof about four years ago. Saunders once asked a NYCHA representative to clear a buildup of leaves in the rain garden, but the person said it was the city’s responsibility. According to Saunders, the lack of maintenance has turned the rain gardens into an “eyesore.” The ability to maintain green infrastructure is a big test for the city.

The $1M spend created nearly 1 greened acre—a small step towards to city’s ultimate goal of creating 8,000 greened acres. We can assume the actual cost to build green infrastructure was between $600,000-$700,000, and the rest of the budget went to other pilot costs. On the low-end, that projects a cost of $5B at scale. The city would need to get creative to stay within its $1.5B budget.

Up Next: The Struggle to Scale

Flooded area during Hurricane Sandy

As 2012 wound down and the green infrastructure monitoring projects neared their end, New York City met catastrophe: Hurricane Sandy. The lives lost, homes destroyed, and heartbreaking devastation reignited cries for environmental justice and protection.

In an interview with Municipal Water Leader, DEP Deputy Press Secretary Tara Deighan, described the role of green infrastructure in the city’s recovery plans, “In the face of this, and expecting that other storms may bring heavy rains or cloudbursts, we’re separating sewers and building tanks and a ton of green infrastructure all over the place, including rain gardens, permeable paving, and green roofs.” The city said they wanted to put green infrastructure “all over the place,” but it couldn’t build it fast enough.

The Green Infrastructure Plan stipulated that by 2015, green infrastructure would manage the equivalent of stormwater generated by one inch of precipitation from 1.5% of impervious surfaces in combined sewer areas citywide. However at the end of 2015, the city only had enough infrastructure to manage 0.6% of that stormwater. That figure rose to 1% if you isolated the prioritized watersheds with the worst water quality. For example, the city managed 1.1% of qualified runoff in the Bronx River watershed.

My interview with Saunders and other NYC residents highlighted the challenge to educate citizens about GI and its benefits. Saunders was enthusiastic when she said she would welcome any information.

In the series’ next installment, I explore the challenges that DEP is facing implementing the mandate, and how communities around the Bronx River view the progress so far.

Read part 2 here.

To learn more about how to build a green infrastructure monitoring system and foster community engagement around environmental sensor data, check our Temboo’s tutorials or email us at