1. Description of Project
1) Project Title: Green Infrastructure: Integrating Stormwater Capture into NYC’s Flood-Prone Neighborhoods
2) Brief Description: This project includes sixteen stormwater greenstreets in New York City. Each site provides flood mitigation through stormwater management. The sites were built in seven target neighborhoods primarily based on the City’s priority watersheds and volume of calls for significant flood-related complaints to NYC’s 311 hotline.
Each site was designed to capture runoff from the 95th percentile storm, while remaining between a 3:1 and a 10:1 ratio of drainage area to site area. In total, the sites transformed roughly 55,000 square feet of impervious surface to pervious surface, and capture on average approximately 5.6 million gallons of stormwater each year.
3) Location: New York City
The sites located in the Bronx River Watershed in Bronx County are as follows:
a. Bronx Park East and Pelham Parkway North / b. Metcalf Avenue, Watson Avenue, and Soundview Avenue / c. Metcalf Avenue and Gleason Avenue/ d. Oak Tree Place between Arthur Avenue and Hughes Street
The sites located in the Jamacia Bay Watershed in Queens County are as follows:
a. Camp Road and Fernside Place / b. Frisco Avenue, Elvira Avenue, and Oak Drive c. Seagirt Boulevard between Beach 19th Street and Beach 20th Street / d. Westbourne Avenue and Bay 25th Street
The sites located in the Thurston Basin Watershed in Queens County are as follows:
a. Colfax Street, Murdock Avenue, and 221st Street / b. Francis Lewis Boulevard between 120th Avenue and 219th Street / c. Nashville Boulevard between 116th Avenue and 209th Street / d. Springfield Boulevard, Merrick Boulevard, and 133rd Road / e. Alley Pond Park – non-site, research control point to provide baseline data
The sites located in the Upper Bay Watershed in Richmond County are as follows:
a. Bay Street and Swan Street / b. Hylan Boulevard and Colton Street / c. Targee Avenue and Van Duzer Street / d. Victory Boulvard and St. Pauls Avenue
4) Area: 1.26 acres (16 sites)
5) Type of GI: Stormwater greenstreets
6) Project Objectives: Stormwater capture, reduce air pollutants, lower ambient air temperature, provide habitat for local wildlife, contribute to native plant diversity
7) Background, History, Procedure: This project was made possible through federal funding received in the form of an American Recovery and Reinvestment Act (ARRA) state grant. Each site was reviewed at several phases by the New York State Environmental Facilities Corporation (NYS EFC), providing guidelines for design as well as feedback on submissions. The City of New York Department of Parks & Recreation, Green Infrastructure Unit designed and managed the construction of these sites. The design team consisted of landscape designers and an environmental engineer; each performed design, estimating, and construction project management for the project. The major collaborators include Drexel University, College of Engineering. They assisted in the design of the monitoring equipment and are currently monitoring the performance of several sites. Additionally, various city agencies also collaborated on this project and were instrumental in the design approval process
2. Performance Criteria and Assessment
1) Primary Function: As a whole, these sites work to protect the environment by reducing stormwater runoff, mitigating localized flooding, and creating green space. Much of New York City operates on a combined sewer system. During periods of wet weather, stormwater runoff and sanitary sewer flow overwhelm the system leading to combined sewer overflows (CSO) into our waterways. We located more than half of the sites in this project in areas serviced by a combined sewer system, in an effort to collect runoff in planting areas and replenish underground aquifers. Each site was designed to capture runoff from the 95th percentile storm, while remaining between a 3:1 and a 10:1 ratio of drainage area to site area. In total, the sites transformed roughly 55,000 square feet of impervious surface to pervious surface, and capture on average approximately 5 million gallons of stormwater each year, the equivalent of filling 7.5 Olympic size swimming pools. The sites also work to provide flood mitigation. We identified the locations in seven target neighborhoods based on the volume of significant flood related complaints to New York City’s 311 hotline.
2) Interdisciplinary Collaboration: This project was integral in the creation of a partnership between the City of New York Department of Parks & Recreation (NYC DPR) and Drexel University. We chose to collaborate on this project so that we could quantify the benefits of green infrastructure in New York City. Over the last ten years we have seen an influx in stormwater management designs and green infrastructure, but few have provided quantifiable data to support further implementation of green infrastructure systems. Through this partnership with Drexel, we have been able to design to accommodate live data tracking.
Graduate students from Drexel University, College of Engineering provided supervision for the installation of all monitoring equipment. Further, several students have worked over the years on monitoring these systems both in the field and remotely from Drexel University labs. This real world experience is helping contribute to the students’ education while training them to advance and promote this level of innovation, collaboration, and sustainability in their careers.
3) Building Cost: On average the stormwater greenstreets had a construction cost of $115,000.
3. Multiple Benefits
1) Water: We have gathered a significant and unprecedented amount of data on the performance of these sites. The majority of our research has been on the stormwater greenstreet located on Nashville Boulevard between 116th Avenue and 209th Street (Nashville). Our pre-installation baseline data is zero percent capture, with 100% of stormwater runoff entering local catch basins and ultimately the combined sewer system. Over our 2012 monitoring season (April – November), we found that 21 out of 24 storm events were 100% retained within our site at Nashville. During only three storm events, ponding inside the greenstreet caused brief overflows to the local catch basin. On an annual basis, the site’s performance suggests 74% – 86% retention of all stormwater presented to it, this percentage is dependent upon annual precipitation amounts. Further, our data suggests Nashville can retain 100% of the flow directed to it during all storms less than 1.6 inch depth.
Nashville was closely monitored during both Hurricane Irene and Superstorm Sandy. In both scenarios inflow from the street was approximately 31 times direct precipitation on the site. This site was only designed for a 5:1 ratio rather than a 31:1 ratio. We believe this increased ratio occurred because the site is located at a low point in the neighborhood and catch basins clogged upslope contributed additional runoff. In short, approximately 40,000 gallons of water deposited by Superstorm Sandy either infiltrated into the site or evaporated.
This data suggests that as a whole, in our sixteen sites we are capturing and redirecting approximately 4,500,000 – 5,300,000 gallons of water annually and preventing it from entering our sewers.
2) Land & Habitat: Collectively the sites contribute to the creation of 1.26 acres of active stormwater capture planting area distributed across the city that will lower ambient air temperature, sequester carbon, and reduce air pollutants. This created space provides habitat for local wildlife as well as promoting plant species native to the Eastern United States. Over half of the plants used are native, those that are not native are non-invasive and mostly naturalized. Some non-native species were used given the nature of the project being low-maintenance spaces in the challenging urban environment of New York City. Native Plants include the following:
Canopy Trees (37): Acer rubrum (7), Nyssa sylvatica (6), Quercus bicolor (2), Quercus coccinea (1), Quercus palustris (3), Cercis canadensis (4), Liquidambar styraciflua (9), and Taxodium distichum (5).
Ornamental & Flowering Trees (56): Crataegus viridis (11), Amelanchier spp. (17), Juniperus virginiana (3), Magnolia spp. (12), and Picea spp. (13).
Shurbs (836): Aronia arbutifolia ‘Brilliantissima’ (206), Clethra alnifolia ‘Hummingbird’ (34), Clethra alnifolia ‘Ruby Spice’ (43), Cornus sercia ‘Baileyi’ (32), Cornus sercia ‘Cardinal’ (3), Hamamelis virginiana (9), Hydrangea quercifolia (15), Hydrangea quercifolia ‘Alice’ (36), Ilex glabra ‘Shamrock’ (83), Ilex verticillata ‘Jim Dandy’ (5), Ilex verticillata ‘Red Sprite’ (64), Itea virginica ‘Henry’s Garnet’ (133), Fothergilla gardenii (24), Myrica pennsylvanica (10), Yucca filamentosa ‘Color Guard’ (95), and Yucca filamentosa ‘Variegata’ (44).
Grasses (2202): Andropogon virginicus (35), Carex pennsylvanica (135), Carex platyphylla (94), Carex stricta (15), Juncus effusus (848), Panicum virgatum (68), Panicum virgatum “Shenandoah” (350), Panicum virgatum “Heavy Metal” (582), and Panicum virgatum ‘Northwind’ (75).
Perennials (1495): Asclepias incarnata (160), Asclepias tuberosa (111), Aster cordifolius ‘Avondale’ (71), Aster ‘Wood’s Pink’ (156), Echinacea purpurea ‘Kim’s Knees’ (79), Echinacea purpurea ‘Red Knee High’ (65), Echinacea purpurea ‘Ruby Giant’ (65), Echinacea purpurea ‘Virgin’ (65), Monarda spp. (30), Rudbeckia spp. (222), Sedum ‘Autumn Joy’ (56), Solidago ‘Little Lemon’ (88), Symphyotrichum novae-angliae (148), and Iris versicolor (179).
3) Social: This project provided social benefits by its visibility, increasing awareness of how natural systems can provide benefits and address urban infrastructure problems. Communities that witnessed flooding prior to the installation of these sites can see how replacing asphalt with green space to capture and store stormwater can provide a multitude of benefits. Many of our sites are located in underserved, low income neighborhoods, providing these often overlooked communities with trees and other vegetation. These sites also provide an educational tool for local schools. The stormwater greenstreet located at Westbourne Avenue and Bay 25th Street is neighboring Public School 104. We worked with the principal to insure a safe environment while creating an educational opportunity. Furthermore, these sites contribute to an overall increase in green space to New York City.
Additionally, several of the sites are outfitted with monitoring equipment included but not limited to an inlet flume (to monitor flow rates of stormwater runoff), a climate station (to measure precipitation, wind speed and direction, solar radiation, and relative humidity), a monitoring well (to quantify fluctuations in the water table), a weighing lysimeter (to measure evapotranspiration and soil moisture), a water quality sampler (to determine pollutant removal efficiency), and a shallow well (to measure ponding depth in planting beds). This equipment is highly visible within the sites. NYC DPR and our research partners are frequently visiting the site to observe conditions and gather data from monitoring equipment. Our continued interaction with the sites allows local homeowners to discuss the project with our staff and partners.
4) Materials and Waste: Our contract for this project included a Buy America provision requiring that all manufactured goods shall be produced in the United States. This reduced transportation energy and contributed to our local economy.