Pratt Institute | Sustainable Environmental Systems Final Capstone Report | Galvanizing Gowanus by Aishwarya Mukund

GALVANIZING GOWANUS A Policy and Process-based Study toward Net-Zero Combined Sewer Overflow

Aishwarya Mukund

Masters in Sustainable Environmental Systems

flow

Advisors: Leonel Ponce, Ira Stern-Zero Combined Sewer Over

Table Of Contents Abstract

Acknowledgments

1 History & Background 1.1 Gowanus Creek 1.2 Gowanus Canal

First, I would like to thank Amy Motzny, GCC’s watershed planner, for the encouragement, support and her kindness throughout my study. Her letting me explore and innovate for green solutions have led me to truly understand and appreciate GCC’s missions and vision for a better Gowanus Watershed.

1.3 Industry and Urbanization

Secondly, I would also thank my advisor, Leonel Ponce, from Pratt Institute for his persistent push to have me make decisions, understand intersecting systems, and thinking of myself as if I were my own organization, and John Shapiro, for leading me along the right path to assess potential environmental indicators that could potentially be . Also, if not for my my parents’, grandmother’s, friends’ and my partner’s support and input and their trying their best to even marginally understand what I’d been up to for the last 8 months, and the complex problems that I was attempting to understand myself, this study would not be where it is now.

1.7 Gowanus Superfund

Lastly, I would like to thank my dog, Nyquist, for just being the best boy during my exhausting effort to understand, restore, remediate, and help make for a cleaner and healthy Gowanus.

1.4 Water and Sewer Infrastructure 1.5 Gowanus Canal + Combined Sewer Overflow 1.6 Clean Water Act 1.8 Green Infrastructure 1.9 Gowanus Neighborhood Plan

2 CLIENT 2.1 Gowanus Canal Conservancy 2.2 Projects and Initiatives 2.3 Gowanus Lowlands Masterplan 2.3 Net-Zero CSO

3 Project Plan + Analysis 3.1 Project Overview 3.2 Sewershed Analysis 3.3 Zoning Impact Analysis 3.4 Landscape & Terrain Analysis

4 Recommendations + Discussion Appendices A. Example Site Analysis B. Supplementary Maps C. Calculations

ABSTRACT Once a complex system of inter-tidal saltwater marshes and creeks, in what we now know as Central Brooklyn, the Gowanus Canal is one of the nation’s most polluted waterways. This is largely attributable to rapid and unregulated urbanization and industrialization in the areas abutting the Canal since the 1700s by the dredging and bulkheading of the robust stream networks that still lay beneath. The Canal is on the United States Environmental Protection (US E.P.A)’s list of “Impaired Waters” under the Clean Water Act, and is currently undergoing a massive clean-up through the EPA’s Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA or Superfund) due to a legacy of pollutants that have entered its waters from the industries that once surrounded it. The Canal’s cleanup was driven by years of community support and environmental advocacy. The neighborhoods surrounding the Gowanus Canal are being rezoned by the New York City Department of City Planning (DCP) from previous industrial uses to accommodate additional residential populations along the shoreline. The Canal’s Watershed is served by New York City’s aging Combined Sewer System that triggers additional pollutant discharge during rain events through events known as Combined Sewer Overflow (CSO). These events cause street runoff and raw sewage to mix and enter the canal waters, further impairing the water quality. With rain events and storms growing more frequent due to climate stresses, even negligible rainfall causes CSO events. It is imperative to test innovative stormwater management techniques to ensure a clean waterway. The New York City Department of Environmental Protection (DEP) employs techniques to manage and absorb stormwater runoff to reduce the load on the city’s sewer system during rain events (wet weather) through nature-based low impact development installations called “green infrastructure”. However, some of the typologies of green infrastructure employed by DEP may not be applicable in the Gowanus Watershed due to the terrain constraints and the natural water flows. This project presents a framework and an interactive tool toward net-zero combined sewer overflow into the canal in support of a community-based client - Gowanus Canal Conservancy. Through spatial and tabular data analysis of the stormwater and sewer impacts of increased density and development from the rezoning, identifying potential issues that key stakeholders may face, I present alternate reliable methods that can be incorporated into existing drainage models using the NRCS TR-55 Handbook. The study focuses exclusively on nature-based solutions to support the ongoing remediation of the Gowanus Canal, and also proposes siting criteria for innovative nature-based interventions through hydrological analysis and landscape assessment.

1.1 Gowanus Creek The Gowanus Creek was originally part of one of New York City’s tidal estuaries feeding into saltwater marshes. The Creek itself provided power for Brooklyn’s earliest industries, such as Tide Mills. Pre-canal maps indicate that the Creek was once a natural ecosystem composed of complex tributaries and tidal saltmarshes. Salt marshes are widely known to be highly productive ecosystems that . Serving as spawning and shelter areas for many species of aquatic life, diverse invertible fauna, and critically important feeding areas for birds. Records from the early European settlements show that the Gowanus Creek was acknowledged as being one of among the world’s foremost oyster producing beds1. As of the 1600s, it was recorded that a handful of Dutch farmers established themselves along the marshes and engaged in the clamming of big oysters, which became a significant first export to Europe. Brackish water was forced farther into the creek by the 6-foot (1.8 m) tides of Gowanus Bay, providing an environment conducive to the growth of enormous bivalves. For much of the nineteenth century, the Gowanus Creek watershed consisted mostly of farms and mills located on the outskirts of Brooklyn, until the construction of Gowanus Canal in 18402. The creek was one of seven New York waterways with low navigability which was dredged and developed into navigable canals. Despite this limitation, the creek’s proximity to rapidly growing inland urban areas, made the Gowanus Canal was the first fully developed interior waterway in New York3. 1 Hunter Research. Inc, and USACE, 2004, “National Register of Historic Places Eligibility Assessment: Gowanus Canal, Borough of Brooklyn, Kings County, New York”, 2 NYC DEP, 2009, “Gowanus Canal WWFP” 3 Hunter Research. Inc, and USACE, 2004, “National Register of Historic Places Eligibility Assessment: Gowanus Canal, Borough of Brooklyn, Kings County, New York”,

1.2 Gowanus Canal

History & Background

In 1774, the State of New York passed legislation to expand the stream and turn it into a canal, to preserve the watercourse in good condition, and to impose taxes on anyone who lived or worked on land near the creek, in addition to which the marshes were drained and filled1. By 1846, the marshes of the Gowanus Creek were considered “undesirable” for the rapid development needs of New York, and a solution to Brooklyn’s needs for sewage and stormwater. The initial plans for the canal were designed for it to be a glorified sewer, with secondary considerations for commercial barge traffic. The city government quickly realigned the emphasis toward filling the marshes for development and creating a navigable canal that would assumably cleanse itself through tidal flows. As per design standards from those days, it is likely that the streams of Gowanus Creek were curverted and buried in drainage pipes.

1 Martin, Douglas, 1993, “Brooklyn Legends Thrive On Banks of the Gowanus”. https://www.nytimes.com/1993/10/11/nyregion/brooklynlegends-thrive-on-banks-of-the-gowanus.html

Source: New York Public Library

Plan for the drainage of that part of the city of Brooklyn which empties its water into Gowanus Creek, 1848

1.3 Industry, Urbanization and Sewer Issues In the early stages of the canal design, it was assumed that stationary pollution concerns would exist and that a number of flushing methods would be needed, but went unimplemented. The original design that was proposed in 1847 was modified to build several turning basins for incoming barges for the movement of arriving goods. Public improvements made by special commissions often composed of interested landowners, which may have been reflective of the landowners’ resistance to fund a canal without a point of sale to reap the canal’s benefits. According to studies that have been conducted to assess the historic nature of the development around the canal, the landowners probably realized that the need for quick and easy development in areas in South Brooklyn could be potentially be expedited by providing cheap water access for transporting building materials and fuel. The developers proceeded to secure state approval for public and private entities to complete the main canal. The Gowanus Canal became an important area for concentrated heavy industry in Brooklyn, such as coal gas producing plants, oil refineries, machine shops, chemical plants, a cement manufacturer, a sulfur producer, a soap maker, and a tannery all located around the waterway. In the early twentieth century, the rise of this industrial corridor along the banks of the Gowanus Canal brought in new land speculation. The industrial core was surrounded by large working-class residential districts, populated primarily by Irish and Scandinavian families. South Brooklyn’s communities were rapidly expanding, with as many as 700 new buildings being built each year. These new structures required a sewer hookup, which resulted in raw sewage being discharged into the Gowanus Canal1. The major identifiable administrative problem with the work done in this era was the lack of regulatory oversight during the design to fund or build a usable waterway. By the turn of the twentieth century, a combination of industrial pollutants, storm water runoff, and the new sewage system had turned the canal into a repository for various pollutants. The Gowanus/Brooklyn-Queens Expressway eventually led to the Gowanus Canal’s decline in use. The Canal’s construction was followed by truck distribution, and the Army Corps of Engineers stopped dredging the canal on a regular basis in 1955 since it was no longer cost efficient2. The Canal reflected New York’s loss of industrial jobs during this time, and by the late 1970s, it was believed that over half of the property in Gowanus was underused and dilapidated. Seemingly, the Gowanus Canal’s usefulness had passed. The areas surrounding the waterway are still zoned for industrial and manufacturing uses, despite the departure of the manufactured gas plants, and other polluters. The sites with detected pollution have now been identified as brownfield sites.

1 Hunter Research. Inc, and USACE, 2004, “National Register of Historic Places Eligibility Assessment: Gowanus Canal, Borough of Brooklyn, Kings County, New York”, https://issuu.com/proteusgowanus/docs/2004-gowanus_usace_historic_resources_report 2 US EPA, 2013, “Record of Decision Gowanus Canal Superfund Site” https://semspub.epa.gov/work/02/692106.pdf

Source: Hunter Research Inc Source: New York Public Library

Gowanus Canal and Flushing Tunnel

Gowanus Canal Flushing Tunnel and Punp Station

1.4 Water and Sewer Infrastructure The existing infrastructure of New York City is composed of an enormous network of approximately 7,400 miles of sewer pipes that collect sanitary sewage and rainwater, as well as 14 Wastewater Resource Recovery Facilities (WRRFs) or Wastewater Treatment Plants (WWTPs) that treat the sewage that has been collected in the system. In addition to being one of the City’s most valuable assets, this network has helped generations of New Yorkers enhance their overall health and well-being. Stormwater runoff, whether from roadways, rooftops, or other impermeable surfaces, is handled together with residential and commercial wastewater by relatively old single-pipe combined sewage systems in many older American cities, particularly in the Northeast and Midwest. A typical CSS collects both domestic sewage and stormwater and discharges it into a publicly owned treatment works (POTW), where the wastewater is treated. When peak storm flows overrun the system’s capacity, these systems often employ a number of outfalls that discharge a mixture of untreated sewage and stormwater runoff. The primary water quality issue in many older U.S. communities that rely on CSS rather than municipal separate stormwater systems is combined sewer overflows (“CSOs”), which are caused by severe rains and the constraints of existing infrastructure1. Combined sewage systems (CSS) are relics of the country’s early infrastructure and are usually found in older cities, such as New York City. It is estimated that about 40% of the system is divided into separately sewered regions, in which sanitary sewers send waste water directly WWTPs and separate storm sewers direct runoff directly to waterbodies.The sewer system in NYC carries both sanitary and storm water flows at about 60% of its capacity. During times of high demand on the sewer system, a diluted mixture of rainwater and sewage is discharged into nearby rivers. This is to referred to in the industry as a combined sewer overflow (CSO) event2. The CSOs in New York City used to include about 30% sanitary trash; now, that proportion has fallen to 12 percent of total garbage. The amount of CSO volume that is reduced varies from watershed to watershed, as does the effect of CSOs on water quality. This is due to the fact that water quality is also affected by other sources of pollution, the strength of tidal flows, and historical dredging, filling, or other alterations to the watershed (“bathymetry”), all of which have an impact on the flow of water and the mixing of surface and deep waters. Many of New York City’s tributaries would fail to meet water quality requirements even if all wastewater facilities stopped discharging completely and all CSOs were removed from the water system entirely3 DEP’s improvements to its plants and sewer systems, as well as the construction of storage tanks, have enabled the agency to capture an increasing proportion of total CSO volume, increasing from approximately 30 percent annually in the 1980s to more than 72 percent today as a result of these improvements. “The CSO outfalls cannot be simply “plugged up;” if they were, the combined flow would destroy elements of the system and would cause even greater discharges over time” - NYC DEP Green Infrastructure Plan

1 Holloway et. al, 2015, “Solving the CSO Conundrum: Green infrastructure and the unfulfilled promise of federal-municipal cooperation” 2 See Appendix A for NYC Sewer System Types and Distribution 3 NYC DEP, 2010, “NYC DEP Green Infrastructure Plan” https://www1.nyc.gov/assets/dep/downloads/pdf/water/stormwater/greeninfrastructure/nyc-green-infrastructure-plan-2010.pdf

1.5 Gowanus Canal + Combined Sewer Overflow In the New York City context, NYS DEC delegates front-line responsibility to NYC DEP for compliance with permits issued pursuant to state and federal law. In the parts of the city where sewer and stormwater systems are separate, DEP’s obligations are specified in a Municipal Separate Storm Sewer System (MS4) permit; in the City’s ten combined sewer areas they are specified in Long Term Control Plans (LTCPs). A codified Consent Order executed by DEC and DEP in 2005 expanded on the obligations for DEP1.The recommendation in the Gowanus Canal LTCP was for the sewage system be upgraded, which would immediately overlap with the superfund cleanup, making cooperation essential in order to optimize the benefits of local and environmental infrastructure improvements. The Gowanus Canal watershed/sewershed is situated under the governmental authority of the Borough of Brooklyn (Brooklyn County, which is part of the New York City metropolitan area). The Owls Head and Red Hook wastewater treatment plants, as well as their related collecting systems, service the watershed. To this day, on practically every wet day 263 million gallons of sewage, along with street water runoff, flows untreated into the Canal’s waters. Although the water is currently circulated through a tunnel by the flushing pump, there is minimal movement in the Canal, and the “summer stink” is generally strong at low tide. This mix of stormwater and sewage backup cause significant contamination; the waterway has tested positive for fecal coliform and dissolved oxygen, which are both deleterious to the aquatic life in the canal as well as NYC DEP Sewer Infrastructure

the water quality. It has been found that the outfall at the canal’s head is the single most significant source

NYC DEP Sewer-shed Drainage Areas

to CSO discharges, the effects of contaminated CSO solids are most apparent at the head end of the canal2. These findings are in accordance with the conclusions reached by the NYCDEP in its 2008 Waterbody/WaterSource: dLand Studio

shed Facility Plan: “Historical discharges by CSOs and stormwater have damaged practically the whole canal bottom.” The NYCDEP determined in that report that “CSOs dominate the loadings of... total suspended solids... to Gowanus Canal,” and that discharges from the canal’s head outfall (RH-034) “dominate the CSO impacts throughout the Canal.”3 Due to variations in infrastructure and population, the amount of precipitation required to trigger an overflow at each outfall varies. 7 of the CSO-sheds overflow during 1.2” rain events. All of them overflow during 2” rain events4.

Combined Sewer Overflow Outfall in Gowanus Source: Pardon Me for Asking

NYC DEP Combined Sewer Overflow Outfalls

Raw Sewage and Toxic Discharge in the Gowanus

1 NYS DEC, 2005, “Order on Consent, In the Matter of Violations of Art. 17 of the ECL and 6 NYRCC pt. 750 et seq, DEC Case No. CO2-20110512-25 (2005). 2 Ibid. 3 NYC DEP, 2009, “Gowanus Canal Watershed Waterbody Facility Plan Report”. https://www1.nyc.gov/assets/dep/downloads/pdf/ water/nyc-waterways/gowanus-canal/gowanus-canal-wwfp.pdf 4 GCC, 2019, “Gowanus Lowlands Draft Master Plan”

1.6 Clean Water Act The Clean Water Act (CWA), also known as the Federal Water Pollution Control Act, is intended to restore and maintain the chemical, physical, and biological integrity of U.S. waters. It regulates point sources of water pollution (i.e., discharges of municipal sewage, industrial wastewater, stormwater; and, the discharge of dredged or fill material into navigable waters and other waters of the U.S.) and non-point source pollution (i.e., runoff from streets, agricultural fields, construction sites, and mining that enter waterbodies, from other than the end of a pipe). In 1972, the E.P.A. passed the Clean Water Act (CWA) with the objective to “restore, maintain the chemical, physical, and biological integrity of the nation’s waters”. The Clean Water Act is one of United States’ first environmental laws, administered with United States Environmental Protection Agency’s (U.S. EPA) oversight. In coordination with state governments and U.S. Army Corps of Engineers (US ACE), the CWA introduced the National Pollutant Discharge Elimination System (NPDES). This permit system is a regulatory measure to control point sources of pollution that include manufacturing, mining, shipping, oil and gas extraction to sewage treatment plants. Under the CWA, point sources may not discharge pollutants to surface waters without a National Pollution Elimination (NPDES) managed by E.P.A. in partnership with state environmental agencies who (NYS DEC, in the case of the Gowanus) issue State Pollution Discharge Permits. The CWA’s regulation of stormwater discharges by the US Environmental Protection Agency (“EPA”) is unique among environmental laws in that the major regulated entities are municipalities (rather than private corporations), and as a result, a large number of taxpayers or ratepayers are required to spend a significant amount of money on stormwater management infrastructure projects. Unlike other basic municipal services like solid waste management, snow removal, policing, and traffic safety, the CWA directly includes the federal government in wastewater management services supplied by local governments1. As of 2012, the Gowanus Canal remains on the 303(d) list. The Gowanus Canal empties into Upper New York Bay, which is currently listed on the USEPA’s 303(d) list of impaired waters due to polychlorinated biphenyls (PCBs) and other toxics such as mercury, dioxins/furans, polycyclic aromatic hydrocarbons (PAHs), pesticides, and other heavy metals. This listing authorizes the EPA to assist states in developing a “Total Maximum Daily Load” or TMDL of contaminants for the waterbody2. The preparation of this TMDL has been paused till after the remedial actions under the Superfund are completed3. The floatables, odors, and oxygen demand associated with urban and storm runoff, as well as CSOs, were/are the reason for the 303(d) listing. Precipitation and CSO discharges are the only significant fresh water flows into the Gowanus Canal. The State of New York has designated the Gowanus Canal as a Class SD waterbody, indicating that its primary use should be for fishing and that the waters should be suitable for fish, shellfish, and wildlife survival. Although the Gowanus Canal is classified as a Class SD waterbody, the NYSDEC has determined that it does not support the designated use of fishing.

1 Holloway et. al, 2015, “Solving the CSO Conundrum: Green infrastructure and the unfulfilled promise of federal-municipal cooperation” 2 US EPA, “2012 Waterbody Report for Gowanus Canal”, Waterbody Quality Assessment Report, https://ofmpub.epa.gov/waters10/ attains_waterbody.control?p_list_id=NY-1701-0011&p_cycle=2012&p_report_type=T 3 NYS DEC, 2016, “Priority Waterbodies List: Gowanus Canal (1701-0011) Water Quality Problem/Issue Information”. https://www. dec.ny.gov/data/WQP/PWL/1701-0011.pdf

1.7 Gowanus Superfund With assistance from the New York State Department of Environmental Conservation (NYS DEC), the EPA suggested for the canal to be identified as a Superfund cleanup site in March 2009. The EPA first identified nine “Potentially Responsible Parties,” or PRPs, in the instance of Gowanus. The EPA then compeled these polluters to fund the clean-up and remediation of sites under the Superfund program. This initiative was met with opposition from New York City. For the first time, the city proposed to develop a cleanup plan “that would match the effort of a Superfund cleanup but would achieve it faster” by funding the cleanup using state and local public monies, while the EPA would seek money from polluters. As part of the EPA Superfund cleanup, the City will be mandated to construct two CSO holding tanks, each of which will store 8MG and 4MG of CSO during rainy weather and release them slowly to the wastewater treatment facility during dry weather1. Following the EPA designation of the Canal as a Federal Superfund Site in 2010, and Superstorm Sandy in 2012, increased attention and community engagement resulted in two noteworthy efforts: (a) remediate and improve infrastructure in the Gowanus area, and (b) advanced discussions about the Gowanus’ future among members of the community, elected officials, and City, state, and federal officials. The Record of Decision listing the Gowanus Canal as a Superfund site explicitly states, “to ensure continued protection of the canal remedy, future permanent CSO sediment controls are required. The only practicable, costeffective measure for control of this volume of contaminated CSO solids is the use of retention tanks. Scientific literature suggests that it can be assumed that the “first flush” comprises approximately 20% of the total discharge volume and contains between 30% and 60% of the total PAH load of the discharge (Stein, 2006). The first flush phenomenon under urban settings with regard to the discharge of contaminants such as PAHs and metals has been studied in various geographic regions in the U.S. that experience different hydrologic patterns and various levels of urbanization. For example, studies have been performed in an ultra-urban area in Maryland and the District of Columbia, California, Ohio , Florida; and across other countries/continents. These studies demonstrate that first flush phenomenon is observed for various precipitation patterns and different chemical compositions, including those for metals and PAHs. In summary, the findings of these studies across the country are consistent with Stein et al. (2006), which states that “within individual storms, PAHs exhibited a moderate first flush with between 30% and 60% of the total PAH load being discharged in the first 20% of the storm volume.” Therefore, the first flush concept and taking advantage of it for controlling CSO discharges are directly applicable to the CSO controls developed for the Gowanus Canal.”2 The New York State Department of Environmental Conservation (NYSDEC) and the Mayor’s Office of Environmental Remediation (OER) have devised remediation and incentive programs to aid in the investigation and cleanup of Brownfield sites.

1 2

Gowanus Canal Conservancy US EPA, “Record of Decision Gowanus Canal Superfund Site”

Summary The unregulated development of the Gowanus Canal watershed has resulted in decreased infiltration and natural subsurface conveyance, as well as the elimination of all natural streams that were once tributaries to Gowanus Creek, resulting in the absence of any continuous freshwater tributaries to the waterbody. In order to avoid flooding, runoff is carried through the combined and separate sewage systems, which discharge straight into the Gowanus Canal since the wetlands have been removed. It is typical in a balanced ecosystem for runoff from a watershed to reach the receiving waterways via a mix of overland surface flow and subsurface conveyance, often with ponding and other possibilities for retention and infiltration. Because of the presence of tidal marsh regions formerly around Gowanus Creek, wet-weather discharges would have been reduced further still provided had the marshes been preserved1. The Gowanus LTCP has stressed the imminennt need for cooperation crucial in order to optimize the benefits of local and environmental infrastructure improvements2. Additionally, under the Superfund remedial actions, overseen by the U.S. Environmental Protection Agency, the City will be required to install two CSO holding tanks, which will capture a portion of overflows for treatment after a rainstorm ends. This is projected to reduce CSO in the Gowanus Canal by 40%. Since the design and construction of permanent long-term CSO controls for the Superfund remedy might not take place by the time remedial dredging is carried out, interim contaminated CSO solids control measures would need to be developed during the remedial design to control the discharges until the permanent measures are implemented. Under the Superfund and the CWA, the city is required to reduce CSO into the canal through investments in grey and green infrastructure, which will include two large sewage detention tanks, a sewer separation project, upgrades to Souce: Gowanus Canal Conservancy

pumping stations, and approximately 70 curbside rain gardens. Apart from the CSO tanks as required by the Supefund designation, some of New York’s City DEP’s planned improvements for

the

Gowanus

Canal

watershed

include implementation of programmatic controls, modernization of the Gowanus Canal, Flushing Tunnel, reconstruction of the Gowanus Wastewater Pump Station, maintenance, inspections, and cleaning of the sewer elements and installation of

Planned Infrastructure Upgrades

high-level storm sewers.

1.8 Green Infrastructure The ecological consequences of water treatment projects are becoming an increasing source of worry for

The Green Infrastructure Program in New York City was established to aid in the reduction of combined sewer

environmentalists. Disrupting the normal flow of rivers, streams, and groundwater diffusion may have far-

overflow incidents. By collecting rain runoff from typical rain events, green infrastructure mitigates the effects of

reaching implications for the ecological health of a watershed’s ecosystem. When in good health, a fresh-

heavy rainfall. The Department of Environmental Protection (DEP) has developed critical connections with local

water system maintains a condition of dynamic equilibrium, allowing it to provide critical ecological services

agencies and broadened the application of sustainable stormwater management concepts to our streets and

such as habitat, protection from pollutants, nutrient delivery, and filtering activities, among others. Specifically,

public spaces through the Green Infrastructure Program. In accordance with current regulations, such as the NYC

“mechanisms enable the ecosystem to regulate external stressors or disruptions within a specific range of

Green Infrastructure Plan and the OneNYC initiative, improved stormwater management around the City is being

reactions thus preserving a self-sustaining condition” in order to preserve this equilibrium.

implemented. By 2030, the City of New York’s Green Infrastructure Plan, which was announced in September 2010, aims to reduce CSOs by 1.67 billion gallons per year through the deployment of retention and detention

Huge pipe systems are capable of transporting large quantities of water rapidly from one watershed to another. This movement has the potential to cause the groundwater table at the source to decrease, resulting in an imbalance in the system. The disturbance of a watershed’s balance may result in high nutrient and pollutant concentrations in regions that were previously free of these pollutants, reducing the quality of the ecological services that these systems offer. Large-scale water infrastructure projects put a burden on the resilience of these complex watershed systems, making this extremely valuable resource more prone to degradation1.

elements such as forests, floodplains, and wetlands, combined with policies like as infill and redevelopment that lower overall imperviousness in a watershed or ecoregion. Green infrastructure on a local scale consists of site- and neighborhood-specific practices and runoff reduction strategies. Such approaches fundamentally result in runoff reduction and/or habitat area creation by making extensive use of soils, plants, and engineered media rather than typical hardscape collection, conveyance, and storage facilities. Green roofs, trees and tree boxes, pervious pavement, rain gardens, vegetated swales, planters, reforestation, and the conservation and improvement of riparian buffers and floodplains are some examples2. With respect to stormwater management, green infrastructure refers to a wide range of practices at various scales that manage and treat stormwater, maintain, mimic, and restore natural hydrology and ecological

Green Infrastructure Practices for Runoff Reduction (Adapted from NYS Stormwater Design Manual)

Stream Daylighting Form & Function: Where combined sewer overflow (CSO) separation and other upgrades to storm-sewer systems are

Source: American Rivers

Green infrastructure, on a regional scale, is the process of preservation and restoration of natural landscape

measures.

part of a daylighting project, significant water-quality improvements have been determined during wet-weather events. Also, as ultraviolet radiation is one of the most effective ways to eliminate pathogens in water, exposing these streams to sunlight could significantly decrease pathogen counts in the surface water. Note: This practice is not recommended for sites or right-of-way green passages near identified brownfields. Scale: Neighborhood-Wide Recommendation: Where high-level storm sewers are being

Stream Daylighting

planned.

Precedent

natural vegetative features. The capacity of green infrastructure to mitigate the effects of severe precipitation

Tibbetts Brook flows into the Broadway sewer at a rate

and increase in temperatures is largely regarded to be one of the most important climate adaption benefits.

of 4 to 5 million gallons per day from the southern edge

Better storm-water management, fewer combined storm and sewer overflows (CSOs), water capture and

of Van Cortlandt Lake, on a dry day. The Wards Island

conservation, flood prevention, storm-surge protection, defense against sea-level rise, accommodation of

Stormwater Treatment Plant then treats this water for no

natural hazards (e.g., relocating out of floodplains), and reduced ambient temperatures are just a few of the

apparent purpose. When it rains, sewage, street runoff,

advantages of green infrastructure. Additionally, the United States Environmental Protection Agency (EPA) has

and water from the brook all join the combined sewer,

identified green infrastructure as a contributor to improved human health and air quality, lower energy demand,

bypassing the treatment facility and going straight into

reduced capital cost savings, increased carbon storage, additional wildlife habitat and recreational space, and

the Harlem River. WI-056, a linked CSO to the Broadway

even higher land values of up to 30 percent3.

sewer, accounts for more over half of the CSO water entering the Harlem River. Daylighting will assist to remove

Source: NYC DPR

function through infiltration, evapotranspiration, stormwater capture and reuse, and the establishment of

Tibbet’s Brook Project Location

this clean water from the sewer, reducing CSOs on the Harlem River and flooding problems along Broadway and 1 Living Future, 2011, “Toward Net Zero Water” 2 NYS DEC, 2015, “New York State Stormwater Design Manual Chapter 3: Stormwater Management Planning” 3 Center for Clean Air Policy, 2011, “The Value of Green Infrastructure for Urban Climate Adaptation”. http://ccap.org/assets/The-Value-ofGreen-Infrastructure-for-Urban-Climate-Adaptation_CCAP-Feb-2011.pdf

other parts of the Tibbetts Brook Watershed1.

Van Cortlandt Park Alliance, https://vancortlandt.org/programsoverview/daylighting-tibbetts-brook/

Disconnection of Rooftop Runoff

Green Roofs soil installed on top of a conventional flat or sloped roof. The rooftop vegetation allows evaporation and evapotranspiration processes to reduce volume and discharge rate of runoff

and upland overland runoff flow to designated pervious areas to reduce runoff volumes and rates. Scale: Development Site Recommendation: Sites that are not covered by NYC DEP’’s

entering conveyance system.

Unified Stormwater Rule and to landscaped areas along

Scale: Development Site

terrain-based channel networks.

Greenpoint Community Environmental Fund’s Kingsland

Form & Function: Manage and treat small volumes of storm-

Wildflowers at Broadway Stages initiative aims to increase

water runoff using a conditioned planting soil bed and plant-

natural habitat and green corridors for bird and animal

ing materials to filter runoff stored within a shallow depres-

structure that supports New York City wildlife, improves water quality by capturing stormwater, and high-quality

ships with local businesses, community voices, and wildlife

Stormwater Planters devices that can be designed as infiltration or filtering practices. Stormwater planters use soil infiltration and biogeochemical processes to decrease stormwater quantity and improve

Form & Function: Natural drainage paths, or properly de-

water quality.

ing underground storm sewers or concrete open channels to increase time of concentration, reduce the peak discharge, and provide infiltration. Scale: Rights-of-Way Recommendation: Right-of-Way sidewalks and medians in

Rain Barrels and /Cisterns Form & Function: Capture and store stormwater runoff to be contact activities.

Bioswale

Scale: Development Site

Permeable Pavements

Tree Planting/Tree Pits Source: GCC

an alternative to conventional paved surfaces, designed to infiltrate rainfall through the surface, thereby reducing stormwater runoff from a site and providing some pollutant uptake in the underlying soils

Source: NYC DEP

Form & Function: Pervious types of pavements that provide

Form & Function: Plant or conserve trees to reduce stormwa-

Scale: Rights-of-Way

Parking Stormwater Planters

used for irrigation systems or filtered and reused for non-

areas with elevation over 16ft along terrain-based channel

areas and erosion and sediment control.

Scale: Development Site

Source: NYC DEP

Source: NYCDEP

signed vegetated channels, can be used instead of construct-

ing, stormwater management practice areas, conservation

Source: California DOT

Form & Function: Small landscaped stormwater treatment

Vegetated Swale

zation. Trees can be used for applications such as landscap-

Recommendation: Right-of-Way sidewalks and medians in networks and well-drained soils

1 Newtown Creek Alliance, http://www.newtowncreekalliance.org/fieldday-fridays-at-kingsland-wildflowers-art-and-nature-series/

ter runoff, increase nutrient uptake, and provide bank stabili-

Scale: Rights-of-Way

Kingsland Wildflowers

experts1.

networks.

sion.

areas with elevation over 16ft along terrain-based channel

educational programming focused on sustainable conservation practices and wildlife protection, thanks to partner-

Source: NYC DEP

Rain Gardens

Source: NCA

Precedent

populations. Greenpoint will get a living and growing infra-

Form & Function: Direct runoff from residential rooftop areas Source: USEPA

Source USEPA

Form & Function: Capture runoff by a layer of vegetation and

Scale: Development Site

1.9 Gowanus Neighborhood Plan

Policy Highlight: Unified Stormwater Rule (USWR)

Zoning is a major factor in the growth and buliding of New York City; it

Chaptevr 19.1 revisions required to package the USWR modifications.Sites that disrupt 20,000 square feet

controls the density, bulk, height and other related measuements for

or more of soil or increase impervious surfaces by 5,000 square feet or more will be required to manage the

setbacks and yards, to name a few. Residences (R), commercial (C),

Water Quality Volume (WQv) which, under New York State’s 90th percentile rainfall event number for the study

and manufacturing (M) zoning districts are the three major types of

area is a 1.5” rain storm These sites will now be “Covered Development Sites” under the USWR. This policy is

zoning districts in the city (M). The maximum permissible floor area

also expected to be accompanied by a new Stormwater Management Manual that will give clear guidance on

ratio determines the maximum size of a building that may be con-

requirements and design alternatives and prioritized vegetated retention green infrastructure practices over

structed on a lot in any district (FAR). The FAR, on the other hand, does not dictate where the building’s foot-

detention.

print should be located. There are specific regulations for yards, building height and setback, as well as parking

Source: NYC DCP

The New York City Council enacted Intro No. 1851 in August 2020, allowing the DEP to proceed with the

in each zoning district1.

DEP is now upgrading on-site stormwater management regulations after ten years of implementing the NYC Green Infrastructure Program to incorporate lessons learned in designing, locating, and installing over 10,000

Over the years, it has grown more difficult to accommodate Brooklyn’s growth without increasing residential

green infrastructure projects. As part of a Unified Stormwater Rule, the DEP proposed changes to Chapters

capacity and creating additional employment space. Locally, the city’s high demand for housing has resulted

31 and 19.1 of Title 15 of the Rules of the City of New York (RCNY). The Unified Stormwater Rule (USWR),

in pricing increases and a reduction in housing alternatives for low-income people. Simultaneously, the City’s

which will be implemented citywide, will update and integrate Chapter 31 stormwater quantity and flow rate

economy has grown rapidly and diversified during the previous several decades. Along with long-term artists

criteria with Chapter 19.1 water quality criteria of the Construction/Post-Construction Permitting Program.

and a limited number of residual industrial tenants, the number of commercial enterprises, offices, and other

Furthermore, as amended by Chapter 31, the USWR raises the quantity of stormwater that must be handled

uses that support the adjacent residential neighborhoods has expanded. The investments in and reactivation

on-site and regulates release rates for all new and redevelopment projects that need a DEP House or Site

of historic loft buildings for a range of commercial office and artist spaces indicates an increasing need for

Connection Proposal (HCP/SCP)2 . These sites are referred to by the DEP as “Covered Development Sites”.

new office and other workplaces in the area2.

These “Covered Development Sites” will be required to “Housing New York”, the Mayor’s plan to build and preserve affordable housing throughout New York City in

Source: NYC DEP

install green infrastructure for stormwater management that for the stormwater credits that may be accrued for sites that meet the Stormwater Quantity and Flow Rate requirements and the Water Quality Requirements under the Unified Stormwater Rule. The Water Quality

coordination with strategic infrastructure investments to foster a more equitable and livable New York City, was unveiled in May 2014 after an extensive community engagement process. Housing New York is the result of an extensive community engagement process. As part of the Housing New York 2.0 initiative, which was launched in 2018, a report documenting progress and updates since 2014 on the building and maintenance of affordable housing in New York City was published. Housing Additional York has called for neighborhood studies to be

Volume or WQv is measured with the intent to capture and treat runoff from small, frequent storms that tend

conducted in areas across the five boroughs that have the potential to accommodate new affordable housing

to lead to higher amounts of pollutant in the water.

developments.

In New York, it is defined as “the volume of runoff

Prior planning efforts undertaken by the community over the past decade, including previous NYC DCP studies

generated from the entire 90th percentile rain event”,

in 2009 and Bridging Gowanus from 2013 to 2015, which was led by local elected officials and aimed to establish

which means that a practice sized using the WQv will

shared goals and priorities for the area’s future development, led to the selection of Gowanus. Gowanus has

capture and treat 90% of all 24-hour rain events3. The

unique assets and features that could be leveraged to achieve many local and citywide goals, including the

WQv is entirely dependent on the impervious cover

remediation of contaminated land and the development of housing. These assets and features include a

generated by re-development or new development

significant amount of permanently affordable housing, new commercial and industrial space, services, jobs, and

projects. Key thresholds under the USWR are governed

open space in an area with excellent public transportation access3.

by parcel/lot sizes that govern the soil distubance threshold for water quality volume requirements and existing impervious surface that determine the water quantity volume.

Unified Stormwater Rule GI Heirarchy

NYS DEC, 2015, “New York State Stormwater Design Manual Chapter 4: Unified Stormwater Sizing Criteria”

NYC DDC, “Sustainable Site Design”

Process Highlight: City Environmental Quality Review (CEQR) industrial usage have declined in the bulk of areas adjacent to the Canal. Enthusiasm to live and work in older industrial neighborhoods, like areas surrounding the Gowanus Canal, has returned, in keeping with Citywide trends over the last three decades.

Act, CEQR is the process New York City agencies employ to determine the effect of a project may have on the environment. It must be noted that CEQR is a disclosure process and not an approval

NYC Department of City Planning, in collaboration with other City agencies, developed “Gowanus: A Framework for a Sustainable, Inclusive, Mixed-use Neighborhood” (the “Framework”), a comprehensive framework of goals and strategies, including recommended land use changes that would be developed into a comprehensive rezoning proposal and implemented as part of an overall Gowanus plan. Key elements of the Framework include the provision of deeply affodable housing, the ceration of the Gowanus Special District (GSD), a Waterrfont Access Plan (WAP). In June of 2018, the Framework was made public.

Mandated by the New York State Environmental Quality Review

Source: MOEC

While a small portion of the region surrounding the Canal has retained industrial character, manufacturing and

process in and of itself. Completion of an Environmental Review supports other decisions made by agencies such as rezoning approvals, variance applications, etc. In the case of the Gowanus Rezoning, the New York City Planning Commission (CPC) approved the rezoning to move it forward in the revision of land use. The Mayoral Office that coordinates the environmental review

The Proposed Actions are the result of years of planning by local residents, elected officials, and City agencies

process in the city is the Mayor’s Office of Environmental Coordina-

in and around Gowanus, and reflect DCP’s ongoing engagement process with community boards, residents,

tion (MOEC). The MOEC aids all the city agencies in fulfilling their

business owners, community-based organizations, elected officials, and other stakeholders to achieve landuse

environmental review responsibilities and maintains a centralized

objectives centered around economic development, affordable housing, creation of new waterfront open space

repository of City Environmental Quality Review documents.

and nieghborhood parks along the canal through the establishment of a Waterfront Access Plan (WAP) and the

Projects that require governmental approvals are

remediation of brownfields by imposing (E) designations on contaminated sites in the area1.

the State Environmental Quality Review Act (SEQRA) and its

NYC DCP, 2021, “Gowanus Neighborhood Rezoning and Related Actions Final Scope of Work for an Environmental Impact Statement”.

New York

City

implementing

program,

City

subject to Environmental

Quality Review (CEQR), and if they are deemed to have the potential for significant environmental impact will require the preparation of an environmental impact statement (EIS).

The

Draft Environmental Impact Statement that is prepared under the

NYC DCP Projected Development Sites

CEQR process analyzes the sites based on the build-out year. In the case of the Gowanus Rezoning, the build-year has been determined to be 20351. Environmental Impact Statements are highly complex and technical documents that analyze the impacts of proposed actions under two scenarios - with the proposed zoning actions (“With Action”) and without the proposed zoning actions (“No Action” condition). The standard analytical framework used in an EIS measures the impacts of the proposed zoning actions under Reasonable Worst Case Development Scenario (RWCDS), which is crafted to measure the highest level of environmental impacts from the propsoed actions, and ensure that they will be no worse than those evaluated. The RWCDS sites can be sub-divided into two categories: Projected Development sites i.e. sites with planned development, and Potential Development Sites or “soft-sites” i.e. sites with potential Existing Zoning District Types

NYC DCP Proposed Zoning District Types

for development by the build-out year of 2035.

NYC DCP Potential Development Sites

1 NYC DCP, 2021, “Gowanus Neighborhood Plan Final Scope of Wotk” https://zap-api-production.herokuapp.com/document/artifact/sites/nycdcppfs/dcp_ artifacts/2018K0382%20-%20Final%20Scope%20of%20Work%20-%201_8F041C1C8AA7 EB11B1AC001DD804B33C/19DCP157K_Final_Scope_Of_Work_04192021.pdf

Recently analyzed rezonings under the CEQR process in the City have demonstrated “the failure of the City to predict the type and scale of new development that its zoning changes will stimulate, and studies the resulting impacts on open space, transit congestion, school seats, and other measures of livability”1. Water and sewer infrastructure play an extremely important role, more so in the case of the Gowanus Canal given the ongoing Superfund cleanup process and the unique tidal nature of the underground creek.

1 Municipal Art Society of New York, 2018, “A Tale of Two Rezonings: Taking a Harder Look at CEQR”. https://www.mas.org/wp-content/ uploads/2018/11/ceqr-report-2018.pdf

Policy Highlight: Waterfront Access Plan (WAP) The Proposed Rezoning Actions involve developing a Waterfront Access Plan (WAP) for blocks contiguous to the Gowanus Canal. The WAP would establish the locations of required shore public walkways, supplemental public access areas, upland connections, and visual corridors to ensure Canal access from surrounding neighborhoods and to address the Canal’s varied lot configurations and conditions, in conjunction with the proposed zoning districts and Special Gowanus Mixed-Use District (GSD). The WAP would modify public access requirements and standards, such as dimension and grading requirements, permitted obstructions, and design standards, to permit and encourage unique design solutions that would be impossible to achieve under common waterfront public access areas (WPAA) regulations, such as flood-resistant esplanades. All waterfront projects, enlargements, and land-use changes will require to comply with the shoreline zoning amendments1. The City’s waterfront zoning, implemented specifically in Gowanus in 2009, completes the zoning jigsaw for Gowanus. The 1993 citywide zoning ordinance mandates waterfront facilities along lots with no industrial or water-dependent uses. The essential features are continuous, 40’ wide, publicly accessible beachfront esplanades, upland connections, and view corridors. The purpose of the zoning is to provide an active, engaging, publicly accessible waterfront that supports commercial and recreational activities while preserving industrial and waterdependent uses. When the rules were implemented in 2009 in Gowanus, they complimented the planned rezoning by requiring any residential or commercial construction along the waterfront to offer access to the Canal. While waterfront zoning protects industrial and water-dependent activities, others believe it is overly simplistic to address the area’s desired economic development. When the rules were implemented in 2009 in Gowanus, they complimented the planned rezoning by requiring any residential or commercial construction along the waterfront, offering the community access to the Canal. The necessary facilities were not a barrier to Whole Foods Market, a national big-box retailer whose new location is viewed as out of place by some. On the other hand, the required construction was unaffordable to a resident film company seeking to acquire and enhance facilities along lots with no industrial or water-dependent

Client

purposes. The essential features are continuous, 40’ wide, publicly accessible beachfront esplanades, upland connections, and view corridors. The purpose of the zoning is to provide an active, engaging, publicly accessible waterfront that supports commercial and recreational activities while preserving industrial and waterdependent uses2 1 NYC DCP, 2021, “Gowanus Neighborhood Rezoning and Related ActionsFinal Scope of Work for an Environmental Impact Statement” file:///Users/aishwaryamukund/Downloads/19DCP157K_Final_Scope_Of_Work_04192021%20(1).pdf 2 Friends of Brooklyn Community Board 6, 2014, P.33, “Gowanus Canal Brownfield Opportunity Area Study” https://www1.nyc.gov/assets/brooklyncb6/downloads/pdf/gowanus-boa-step-II-nomination-study-report.pdf

2.1 Client: Gowanus Canal Conservancy for neighborhoods surrounding the Gowanus Canal since 2006, leading grassroots volunteer and stewardship projects, educating students on environmental issues, and working with key stakeholders to advocate for

Bioswale Stewardship: GCC builds and stewards green infrastructure in the Gowanus Watershed – a 1700-acre area that contributes to 377 million gallons of combined sewer overflow into the Gowanus canal per year. GCC

and build innovative green infrastructure around the Gowanus Canal. GCC

maintains and monitors a set of 11 bioswales completed

advocates and cares for ecologically sustainable parks and public spaces in

in 2014 that reduce CSO and provides the community with

the Gowanus Lowlands while empowering a robust community of stewards.

much needed greening.

Additonally, GCC, as a part of the Gowanus Superfund Community Advisory Group (CAG) also advocates for

The Conservancy is the only non-profit in NYC to have

water quality controls in the Gowanus watershed with their partners - Riverkeeper and SWIM Coalition.

Masterplan is a vision of a connected network of Source: Gowanus Canal Conservancy

BioBlitz: Gowanus Canal Conservancy conducts a yearly “BioBlitz” that integrates experts, volunteers, and students in an event to document the biodiversity thriving in and around the Gowanus Canal. On foot and canoe, the team traverses the area for a set period documenting` their findings using iNaturalist, a citizen science mapping application. These annual events provide yearly species inventories at a time when the canal and its banks are rapidly changing with the Superfund clean-up and new development. Bioblitz

parks and public spaces that bridges the Gowanus Canal to the surrounding watershed. It prioritizes access for everyone, while bringing to light the Canal’s history and beauty against a backdrop of a healthy and safe environment. At the heart of the Gowanus Lowlands plan lies a clean and thriving waterway brimming with aquatic life, community activity, and a bustling industry . The plan is built on years of collaborative effort with various stakeholders: the surrounding community, landowners, elected officials, and local agency

Botanical Garden, Macaulay Honors College, Greenwood Cemetery

Gowanus Lowlands Blueprint

representatives2

is composed of block associations and neighbors who get help and technical assistance in caring for street trees, enlarging tree beds, planting perennials, and installing tree guards1. GCC works with neighbors from 13 blocks across the Gowanus Tree Management Area to work together to build a healthy urban forest. The Gowanus Tree Network comprises of 27 Tree Ambassadors who have worked on 33 tree bed expansions and installed 75 tree guards since

Source: Gowanus Canal Conservancy

Gowanus Tree Network: The Gowanus Tree Network

2018. In 2019, GCC expanded the Tree Network activities

Bioswale Stewardship

Source: Gowanus Canal Conservancy

Gowanus Lowlands: The Gowanus Lowlands

2.2 Projects and Initiatives

Partners: Gowanus Dredgers, Brooklyn Bird Club, New York

procured a maintenance contract with NYC DEP1 .

Source: Gowanus Canal Conservancy

Source: GCC

Gowanus Canal Conservancy (GCC) has served as an environmental steward

In addition to environmental stewardship, GCC also has designated ecosystemspecific planting zones based on elevation to support the ongoing remedial efforts. Partners: The New York Community Trust, SCAPE, Langan Engineering, ARUP

Gowanus Tree Network

to include a pilot Monitoring Program led by volunteers from the surrounding blocks to install six soil moisture sensors in tree beds to assess absorption rates of polluted rainwater before it enters the Canal2.

Gowanus Lowlands Ecosystem Planting Zones

Partners: US Forest Service, Department of Agriculture, NYC Department of Parks and Recreation, NYS Department of Environmental Conservation (NYS DEC), The Nature Conservancy, TreeKIT 1 Gowanus Canal Conservancy, 2018, “Gowanus Lowlands Draft Master Plan” 2 Gowanus Canal Conservancy. www.gowanuscanalconservancy.org”

1 New Yorkers for Parks, 2017, “Meet a New Yorker for Parks: Andrea Parker, Gowanus Canal Conservancy”. http://www. ny4p.org/news/andrea-parker-gowanus-canal-conservancy 2 Gowanus Canal Conservancy

2.3 GCC + Gowanus Neighborhood Plan Source: Gowanus Canal Conservancy

GCC is advocating for a Net Zero CSO rezoning to guarantee that new development does not contribute to pollution. With

portion of the CSO being adressed by the planned CSO tanks under the Superfund, it still leaves the canal experiencing nearly 115 million gallons of oveflow annually. GCC is advocating for

net-zero increase in CSO Gowanus rezoning, with var-

i -

ous options presented in their Lowlands Draft Master Plan. As required by the rezoning, the City’s Environmental Impact Statement (EIS) will investigate the effects of development on the current system and verify that enough regulations and

Annual Combined Sewer Overflow to Canal

infrastructure improvements are in place to manage stormwater and minimize CSO1. GCC believes that, if done right, a district-wide rezoning of a more equitable and environmentally resilient community. After over a decade of real estate speculation and property acquisition in the neighborhood, additional development is expected - regardless of the district-wide rezoning. If these procedures proceed without a comprehensive Environmental Impact Statement (EIS) and rezoning, individual owners will seek land use changes through private applications. This reduces the possibility of community participation and benefit2. As the community’s environmental steward, GCC plays a critical role in determining the result of planned Rezoning actions, making them a “Interested Agency” in the rezoning processes as a whole. GCC has also expressed concerns concerning implementation constraints of the siting green infrastructure practices under the USWR. Additionally, GCC believes that the siting of these elements associated with the rezoning must be executed with great care around

Source: Gowanus Canal Conservancy

Gowanus offers an opportunity to make progress toward

03 Project + Analysis

sites with contaminated soils to ensure no additional pollutants of concern entering the waterbody. With the City presently working on the USWR to enhance stormwater management on new development sites around the city, it may result in Net Zero CSO in Gowanus, but a complete hydrological study is required to confirm that this plan achieves the aim.

Zoning Impacts on Combined Sewer System

1 Gowanus Canal Conservancy, 2020, “Our Position on the Gowanus Rezoning”. https://gowanuscanalconservancy.org/wp-content/ uploads/2018/01/Our-Position-on-the-Gowanus-Rezoning-2.pdf 2 Ibid.

3.1. Project Overview Project Goal:

3.2 Sewershed Drainage Area Analysis The Red Hook and Owls Head Wastewater Treatment Plants (WWTPs) are designed for dry weather capacities of 60 and 120 million gallons, respectively. The sewer-shed drainage areas associated with these WWTPs measure

Create an interactive tool with analysis conducted for the Gowanus Rezoning study area with additional land-

3,643 and 13,135 acres, respectively, with 100% of the Red Hook drainage area and 99% of the Owls Head served

scape and terrain analyses conducted using hydrology models from raster imagery.

by the combined sewer system.

Study Design

I proceeded to establish a baseline design storm of 1.2”, seeing as the Canal experiences overflow events during storms of similar depths or more, using the CEQR analytical approach of calculating residential wastewater

I reverse-engineered the CEQR analytical process for water and sewer infrastructure to identify indicators to as-

volumes from residential units (data from NYC DCP MapPluto Version 21v1), and the specified wastewater gen-

sess the existing conditions for both the sewer-shed drainage areas. Instead of using census data to calculate

eration rates provided in Table 13-2 of the CEQR Technical Manual. Wet weather flows to the WWTPs were then

the residential population in a sewer-shed, I used tax-lot data to achieve a higher degree of accuracy. Owing to

calculated for stormwater and wastewater volumes from the matrices provided in the Technical Manual. The

the legacy of polluted waters in the Gowanus Canal, this study intends to go beyond the analysis scenarios pre-

corresponding wastewater volumes were 49.8 million gallons flowing to the Red Hook treatment plant and 124

scribed by the CEQR Technical Manual in analyzing both the Projected and the Potential Development Sites.

million gallons flowing to the Owls head treatment plant during wet weather.

The balance intended to achieve with this study is relatively straightforward: if the proposed zoning actions and

The next step in the sewer-shed analysis was to calculate the stormwater flows to the WWTPs. With data from

related policies do not meet the requirements of net-zero increase in combined sewer overflow, then it will not

NYC DEP’s Citywide Parcel-based Impervious Surface Study, I calculated the stormwater flows in the established

satisfy the needs of Gowanus Canal Conservancy and their partners.

baseline storm for wet weather. Five hundred twenty-nine million gallons of stormwater runoff is directed to the Red Hook wastewater treatment plant, whereas nearly 1,909 million gallons is directed toward the Owls Head

Once completed, I proceeded to identify sites that would be covered under DEP’s Unified Stormwater rule, and

plant in a 1.2” baseline design storm from impervious surfaces on tax lots exclusively. This analysis does not

key challenges that stakeholders may face in complying with the updated policy given the landscape con-

include stormwater runoff from streets and sidewalks that account for 30% of the wet weather flows during

straints and the DEP’s preference of siting vegetated retention practices. Next, I moved on to assessing the

rainfall events.

spatial requirements as stated in the NYC Zoning Regulation for the Gowanus Waterfront Access Plan (WAP) to identify sites and specific measurements required from the same, and streetscape improvements by analyzing the benefits of new street tree plantings as per the Gowanus Rezoning Text Amendment. Within the aegis of DCP’s Waterfront Access Plan, I also incorporated the specific elevation-based ecosystem planting zones as stated in GCC’s Gowanus Draft Master Plan. The secondary section employs spatial analysis to delineate the watershed from bare-earth digital elevation models to identify features and attributes that could contribute to restoring and repairing the ecosystem that

In total, the Red Hook WWTP experiences 578.8 million gallons, and Owls Head over 2 billion gallons of mixed stormwater and wastewater during a baseline design storm of 1.2”. This leaves much room for improvement of the existing water and sewer infrastructure, given the design capacity of the wastewater treatment plants. An additional layer of information analyzed were the 311 complaints lodged between 2010 and 2014 for the following: •

Clogged Catchbasins,

improved water management through preliminary hydrological and terrain analysis.

•

Sewer Backups,

The tools utilized include tabular and spatial (vector and raster) analysis to understand the existing water and

•

Street Flooding, and

•

Basement Flooding

thrives in the study area. The aim is to provide a tool and framework to site BMPs geared toward innovative and

sewer infrastructure within the context of the rezoning to analyze the potential impacts of additional residential population. In addition to analyzing the impacts of proposed zoning actions, I document the benefits and pitfalls of the associated policies and eventually delineate the Gowanus drainage basins as a whole using raster spatial modeling to identify terrain-based drainage networks to site additional green infrastructure along the public right-of-way. Additionally, with NRCS’ TR-55 manual (“Urban Hydrology for Small Watersheds”), I used the widely applied and recommended SCS Curve Number method to identify key zones for GI implementation based on the underlying soil structure, the stormwater volume capture capacity for future planning efforts.

Red Hook SewerIndicator

Weather

shed Drainage Area

Owls Head Sewershed Drainage Area

3.3 Zoning Impact Analysis The Gowanus Rezoning study area is entirely within New York City’s combined sewer system, intersecting Boerum Hill and Prospect Heights to the north, Park Slope and Gowanus to the east, and sections of Caroll

60 Million Gallons per

120 Million Gallons per

Gardens to the east in South Brooklyn. With eight active combined sewer overflow outfalls in the study area

Day

- two of which will be supplemented by the CSO tanks under the Superfund - the study area is served by the

Area

3643.55 Acres

13,135.13 Acres

Residential Population

105,944,700

2,654,650

Capacity

Residential Wastewater Volume in Gallons per Day (@100 GPD/person) Wastewater Volume in a 1.2” Storm from Tax Parcels Stormwater Volume in a 1.2” Storm from Tax Parcels

Red Hook and Owls Head Wastewater Treatment Plants. The Red Hook Sewershed drainage area is a hundred percent combined, and the Owl’s head sewer-shed drainage area is ninety-nine percent combined1. Additional residential development from the proposed rezoning actions is expected to impact all the combined sewer overflow drainage areas to some degree, leading to increased frequency of combined sewer overflow

Dry

discharged into the canal. The Proposed Zoning actions, in turn, overload the combined sewer system by 2.88 million gallons in the

Wet

49.88 Million Gallons 529.48 Million Gallons

124.96 Million Gallons

1,909.32 Million Gallons

established baseline design storm of 1.2”.

Indicator

A: Existing Stormwater Volume in a 1.2”

NYC 311 Complaints from 2010 - 2014

Storm 311 Clogged Catch-basin Complaints

706

3570

311 Sewer Backup Complaints

1,129

5,042

311 Street Flooding Complaints

133

747

311 Basement Flooding Complaints

247

285

Weather

With-Action Projected Development Sites

With-Action Potential Development Sites

Wet

1.45 Million Gallons

0.83 Million Gallons

Wet

1.15 Million Gallons

0.44 Million Gallons

Wet

0.13 Million Gallons

B: Unified Stormwater Rule Covered Stormwater Volume in a 1.5” Storm (NYS 90th Percentile Storm) C: Existing Wastewater Volume in a 1.2” Design Storm With-Action Proposed Residential Population With Action Proposed Residential Wastewater Volume in Gallons per Day (@ 100GPD/person)

Dry

27,995

17,430

2.79 Million Gallons/

1.74 Million Gallons/

Day

D: With-Action Proposed Residential

Wet 1.32 Million Gallons Wastewater Volume in a 1.2” Storm Gowanus Neighborhood Rezoning Impacts Summarized

0.82 Million Gallons

Proposed Wet Weather Volumes to Combined Sewer System = A - B + C + D = (1.45 + 0.83) - (1.15 + 0.44) + (0.13) + (1.32 + 0.82)

= 2.88 Million Gallons of Combined Sewer Overflow in a 1.2” Baseline Design storm 40

Data Sources: Gowanus Neighborhood Plan Final Scope of Work, NYC DCP MapPluto 21v1, GCC

Data Sources: NYC DEP Citywide Parcel-based Impervious Surface Study, GCC

43 42

Wastewater Analysis Stormwater Analysis

Streetscape Improvements Waterfront Access Plan

44 Data Sources: NYC DCP Tax Lot Face, Bytes of the Big Apple, NYC DCP Digital City Map and Street Centerline

Data Sources: NYC DCP MapPluto 21v1, NYC DoITT Planimetrics: Shoreline, NRCS Soils, Gowanus Neighborhood Plan Zoning Text Amendment

Gowanus Rezoning Study: Streetscape Improvements Gowanus Rezoning Study: Waterfront Access Plan

Waterfront Access Plan + Gowanus Lowlands Ecosystem Zones

3.4 Landscape and Terrain Analysis In our increasingly urbanized world, it is not often visible that there is a natural drainage system, other than management, either through the addition of vegetated areas to absorb, retain, and filter runoff, the use of permeable pavement or green and blue roofs to delay runoff, or the installation of detention tanks. Green Infrastructure and other stormwater management systems have successfully managed the rainfall events for which they are intended. However, due to space limits, standard green infrastructure is not intended to handle high rain events. As the frequency of severe rain events in New York City continues to rise, exceeding the capacity of the current green infrastructure systems, we may witness an increase in combined sewer overflows and flooding. This can largely be attributed to the terrain and groundwater recharge capacity. I used high-resolution topobathymetric data to delineate the surrounding drainage basins, identify connected

GIS Clearinghouse

Data Source: Bare Earth 1ft Topobathymetric Data, NYS

what can be observed running into the local storm drain. Every site has the ability to improve its stormwater

channel networks and 1-foot terrain-based contours. I proceeded to use the recommended hydroogic method prescribed by NRCS’ TR-55 Urban Hydrology for Small Watersheds using the SCS Curve Number method to provide an example site analysis strategy that can integrate history with hydrology for better site design and deploy the right green infrastructure techniques for runoff reduction practices.

Precedent: NYC Cloudburst Resiliency Planning Study DEP and the City of Copenhagen signed a

Zoning Impact Analysis: Summarized Findings

Source: NYC DEP

three-year agreement in September 2015 to learn from one other and create creative ways to prepare for greater and heavier downpours, or cloudbursts, as a result of climate change. The Gowanus Neighborhood Plan will cause an influx of over 45,000 residents, in turn adding 2.14 million

This collaboration has now been expanded, with

gallons of wastewater to the combined sewer system in a 1.2” baseline design storm. The existing stormwater

the goal of improving stormwater management

volumes from the RWCDS Projected and Potential Development sites contribute to a sum of 2.28 million

and resiliency through storage and surface flow

gallons of stormwater in the same design storm to the combined sewer system, out of which 1.59 million

conveyance, as well as creating an inspiring

gallons will be managed by NYC DEP’s Unified Stormwater Rule. This leaves a remainder of over 2.8 million

urban environment with advantages for citizens,

gallons of combined sewer overflow into the systems during wet weather events of 1.2” and higher.

local businesses, and both communities. New

Additionally, from the streetscape improvement requirements stipulated in NYC zoning regulations, the Plan will require planting over 11,500 trees in the study area which will contribute to treating over 1 million gallons of stormwater in any given rain event. The Waterfront Access Plan will also contribute to managing over 0.67 million gallons of stormwater in rain events of 1.2” and higher.

In summary, the Plan will not achieve net-zero CSO, as it will create an addition of over 1.2 million gallons of combined sewer overflow during wet weather events of 1.2” storms and higher.

York City hopes to benefit from Copenhagen’s

NYC Cloudburst Resiliency Study

experience coping with urban flooding by implementing green infrastructure to handle heavy storms and more effectively target high-risk regions through this relationship1.DEP began a pilot study phase for Copenhagen’s Cloudburst Management Plan as part of this agreement. Recognizing that New York City is vastly different from Copenhagen in terms of scale, the project concentrated on a small section of the city in Southeast Queens, an area plagued by flooding and where the city is supplementing new storm sewer construction with site-specific green infrastructure to reduce flooding2 1 NYC DEP, “NYC DEP Cloudburst Study” 2 Ibid.

History + Hydrology

Model Set-up

Step 1: Filled DEM

Clipped and Filled Digital Elevation Model

High Level Storm Sewers

Step 2: Delineated Topographic Drainage Basins

Gowanus Ghost Streams + Planimetric Sidewalks

Source: Ate Atema

Daylit Sidewalk Street Creeks

Step 3: Topographic Drainage Channel Networks

Topographic Drainage Networks

Zoning Zoning

Recommendations + Discussion

Green Solutions

CEQR requires only Projected Development impacts of the Proposed zoning actions to be studied. With nearly 36 acres of land considered as With-Action Potential Development sites (“soft sites”), a thorough DEIS is mandated considering the inadequacy of the existing sewer infrastructure in the Study Area. Additionally, the CEQR analytical process for wet weather volume calculations requires assessment of the proposed zoning actions under three design storms (0.4”, 1.2” and 2.5”). A sustainable long-term planning approach must also assess the yearly impacts of development on based on NOAA’s updated rainfall data.

In the unusal case where a GI project requires a discretionary approval within the ambit of a SEQRA/CEQR analysis, it’s lack of environmental impact analysis would generally make it eligible for a negative declaration meaning that no EIS would be required. If the GI project is performed in conjunction with a project that will otherwise require a SEQRA/CEQR study, it may make a negative declaration more likely because it may mitigate negative impacts of projects to which it is attached. This study has found that the Proposed Zoning Actions will add over 1.2 million gallons of combined sewer overflow into the canal in a baseline design storm of 1.2” storm alone. A thorough analysis is required to support the ongoing remedial actions under the Superfund as well as conform with the LTCP processes under the Clean Water Act.

City agencies must be implored to recognize Green Infrastructure as an integral infrastructure asset. Sidewalks and medians along the public right-of-way allow for excellent opportunity zones to install and test innovative green practices that have also been studied to provide multiple social, economic, and environmental co-benefits, and aid in adaptive resilience against the changing climate.

Green Solutions

Green Infrastructure is a robust technique used to restore and mimic natural hydrological processes. The topographic drainage basins in the Gowanus area provide ample opportunity for innovative pilot programs such as the Sponge Park, but existing infrastructure and modeling efforts must be upgraded to support additional pilot programs to achieve no-net increase in combined sewer overflow into the Canal. The Runoff Reduction Method as per NRCS’ TR-55 Urban Hydrology for Small Watersheds must be employed to design appropriate Green Infrastructure practices that can be implemented in the Gowanus watershed.

Green Solutions

An additional layer of information while siting Green Infrastructure practices along the public right-of-way must include studying the underlying soils. This data can predict the practice’s performance and the potential groundwater recharge capacity.

In NYC DEP’s InfoWorks Citywide Recalibration Report, DEP explicitly states that changes made to their Long Term Control Planning (LTCP) modeling approach will be minor based on “initial review of the Gowanus Canal Tributary Area”. I have attempted to bulid a preliminary hydrological model that can be integrated for the watershed’s drainage basins surrounding the Gowanus Rezoning Study Area to better understand flow connectivity networks (channel networks) to plan, build, and manage stormwater management streets and connected pathways. Furthermore, the CSO drainage areas that are being used by DEP to site and install green infrastructure must be updated to match the topographic drainage basins for more innovative pilot programs to manage and alleviate the impacts of stormwater flooding using naturebased green solutions

Appendices

A. Example Site Analysis Precedent: Urban Waterscape, Potzdamer Platz Source: Living Future Challenge

Urban Waterscape, a component of DaimlerChrysler vPotzdamer Platz, was completed in 1998 and serves as a demonstration of rainwater collection at the urban redevelopment scale. The project was created in order to solve floods caused by sewage overflows, water conservation, and urban heatv islands, among other things. It is possible to collect rainwater from the roofs of 19 buildings, which Data Sources: NYS GIS Clearinghosue, NYPL Map Warper, GCC, NRCS

have a combined catchment area of 50,000 m2. It is estimated about 6 million gallons of rainwater collected yearly would be utilized for landscape irrigation, as well as for the pools and canals on the construction site. The rest is used to flush toilets and urinals in the buildings, as well as to provide power for fire suppression equipment. Rainwater covers an average of 80 percent of the yearly water use for toilet and urinal fixtures, according to the EPA. A total of five enormous underground cisterns are used to collect rainwater, with each one being large enough to accommodate additional storage in the case of very heavy rains. Water is pumped from the cisterns into a network of canals built on the south side of the building complex. 60% of the catchment’s rooftops are covered with green roofs that provide a variety of purposes. Water draining off the roofs create microclimates that help to minimize urban heat islands, decreasing temperatures by as much as 2 degrees Celsius during the summer months and lowering the total cooling needs of the buildings in the process, according to research. The canal project in Potsdamer Platz has contributed to the square’s status as one of Berlin’s most popular tourist destinations, highlighting the need of sustainable water usage while also providing a recreational waterscape for the city’s residents and tourists. The vegetation in the canals acts as a natural filter, removing impurities from the water before it is discharged into a nearby river.

Example Site Analysis Technique: Gowanus Green/Public Place + Gowanus Lowlands Ecosystem Planting Zones Source: Living Future Challenge

Urban Waterscape, Potzdamer Platz

B. Supplementary Maps

Green Solutions

SCS Curve Number Method: Stormwater Runoff in 1.2” Baseline Design Storm

C. Calculations Source: Living Future Challenge

Water Quality Volume Calculations The Water Quality Volume (denoted as the W Qv) is intended to improve water quality by capturing and treating runoff from small, frequent storm events that tend to contain higher pollutant levels. New York has defined the W Qv as the volume of runoff generated from the entire 90th percentile rain event. Essentially what this means is that a practice sized using the W Qv will capture and treat 90% of all 24 hour rain events. The W Qv is directly related to the amount of impervious cover constructed at a site.

SCS Curve Number Calculations The SCS curve number method is a simple, widely used and efficient method for determining the approximate amount of runoff from a rainfall even in a particular area. Although the method is designed for a single storm event, it can be scaled to find average annual runoff values. The curve number is based on the area's hydrologic soil group, land use , treatment and hydrologic conditions.

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Step 1 Calculate Curve Number using TR55 SCS Curve Number Method and NLCD Land Cover Data

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Step 2 Calculate Potential Maximum Retention after Runoff Begins and Initial Abstractions

S = (1000/CN) − 10 where S = Potential Maximum Retention after Runoff begins

Ia = 0.05S for highly urbanized watersheds Hawkins et. al. 2002 where,

90th percentile Rainfall Event in New York State NYS DEC, 2013

Ia = Initial Abstractions

W Qv = (P ∗ Rv ∗ A)/12 Source: Living Future Challenge

where,

W Qv = Water Quality Volume in Acre-Feet P = 90% Rainfall Event Number 1.5" in the case of the Gowanus Rezoning Area)

Rv = 0.05 + 0.009(I) where I is Percent Impervious Cover (from DEP's Citywide Parcel-based Impervious Cover Study)

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Step 3 Calculate Approximate Amount of Runoff from a Rainfall event in a Particular Area

Q = (P − Ia)2 /(P − Ia) + S where,

A = the site area in Acres

Water Quality Volume Calculations

CN = Runoff Curve Number

Q = Runoff in inches

SCS Curve Number Calculations