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1 Introduction
Pages 13-42

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From page 13...
... The City's water supply is managed by the Bureau of Water Supply within the New York City Department of Environmental Protection (NYC DEP)
From page 14...
... They considered extracting water directly from the Hudson River, but water quality was unacceptable due to seasonal and climatic saline intrusion; the "salt line" of the Hudson estuary, varying with season and climate, extends as far north as Troy, New York, 150 miles north of the City. Instead, the New York State Water Supply Act of 1905 created a Board of Water Supply to develop a larger system of reservoirs and aqueducts in the Catskill Mountains north 2  In contrast, parts of Queens and all of Nassau and Suffolk counties on Long Island overlie a sole-source aquifer that provides drinking water to its more than seven million residents.
From page 15...
... INTRODUCTION 15 FIGURE 1-1  Basic elements of the New York City water supply system. SOURCE: Figure courtesy of NYC DEP.
From page 16...
... from Delaware River headwaters 7.5 million 1936 Delaware River system begun   1953 New Jersey v.
From page 17...
... Environmental Protection Agency promulgated Surface Water Treatment Rule requiring water systems to filter or meet filtration avoidance criteria 7.3 million 1990   1993 NYC received first Filtration Avoidance Determination for the Catskill/Delaware supply   1997 Watershed Management Agreement signed SOURCE: Adapted from NRC (2000; Table 2-1)
From page 18...
... permit issued regulating Shandaken Tunnel diversions 2005–2006 Extremely wet weather 2007 Filtration Avoidance Determination issued 2007 SPDES permit issued for discharge of alum into the Catskill Aqueduct and Kensico Reservoir (Catalum SPDES permit) 8.375 million 2010 2010–2011 Extreme weather, including Hurricane Irene, producing the highest discharges in 100 years in some parts of the watershed 2013 Catskill/Delaware ultraviolet disinfection facility completed 2013 Operations Support Tool completed 2013 Consent Order issued requiring NYC to prepare environmental impact statement for proposed modifications to Catalum SPDES permit 2015 Croton filtration plant enters into service 2016 National Academies OST Review begins 2017 New ten-year Flexible Flow Management Program takes effect 2017 Filtration Avoidance Determination issued land protection organizations.
From page 19...
... Twentyfive years after the signing of the first MOA, New York City manages to reliably deliver high-quality drinking water with minimal treatment and without use of filtration, except for the Croton system. Configuration of the System The New York City water supply system of today, depicted in Figure 1-1, is made up of three upstate reservoir systems (the Croton, the Catskill, and the Delaware)
From page 20...
... SOURCE: Figure courtesy of NYC DEP. agency agreement, primarily to achieve environmental goals.
From page 21...
... . These processes include the erosion of glacial lake silt and clay deposits in stream banks and beds as well as slope failures of these deposits during floods and also the re-suspension of silt and clay ­ from stream beds (NYC DEP, 2008a)
From page 22...
... The City's most recent five-year water demand management report shows continuing modest declines in average daily demand from 2013 to 2017 despite an increasing population (NYC DEP, 2018)
From page 24...
... Surface Water Treatment Rule In 1989, EPA promulgated the Surface Water Treatment Rule (SWTR; 40 CFR Part 141, Subpart H) to address public health risks associated with Legionella, Giardia lamblia, and viruses for all public water systems using surface water or groundwater under the direct influence of surface water.
From page 25...
... • A watershed control program must be in place that minimizes the potential for contamination of the source water by Giardia lamblia cysts and viruses. This program must characterize the watershed's hydrology, physical features, land use, source water quality, and operational capabilities.
From page 26...
... To comply with its FAD over the last 25 years, the NYC DEP created the Watershed Protection Program, memorialized in the 1997 Memorandum of Agreement, which includes numerous individual components that target potential sources of contamination to the water supply, including agriculture, stormwater, wastewater, and changes in land use. Under the Watershed Protection Program, New York City has acquired sensitive lands around its reservoirs and their headwaters, upgraded dozens of wastewater treatment and collection systems throughout the watershed, replaced more than 5,000 residential septic systems, restored about 40 miles of streambanks and floodplains, installed thousands of best management practices to improve the quality of runoff from local farms, and reviewed thousands of building projects to ensure that their plans aid in protecting water quality.
From page 27...
... NYS DOH, NYS DEC, and the EPA approved the Phase III Implementation Plan in late 2010. o ­ ccurs at aqueducts, reservoirs, streams, and wastewater treatment plants, is essential to operating and managing the system to provide the best possible water at all times, to identify water quality trends, and to focus watershed management efforts.
From page 28...
... The product of these 1972 amendments became known as the CWA, expanding the original Federal Water Pollution Control Act by: • creating the basic structure for regulating pollutant discharges into U.S. waters; • authorizing EPA to set wastewater standards for industry; • furthering existing requirements to set water quality standards for all contaminants in surface waters; • requiring permits for all pollutant discharges from point sources into navigable waters; • funding construction of wastewater treatment plants; and • beginning to characterize and address nonpoint source pollution.
From page 29...
... The purpose of alum addition is to enhance the deposition in Kensico Reservoir of turbiditycausing suspended solids from the Catskill Aqueduct source water. NYS DEC required NYC DEP to apply for a SPDES permit because the state agency determined that alum addition was violating the narrative standard for suspended and settleable solids in Kensico Reservoir.
From page 30...
... In addition to using alum for water entering the Kensico Reservoir from the Catskill system, the NYC DEP also dealt with the turbidity problem by releasing highly turbid Ashokan Reser­ voir waters to the Lower Esopus Creek. The response from those living downstream of Ashokan along the Lower Esopus was very negative, which placed increased critical inquiry on the release strategies and the terms of the ­ PDES permit.
From page 31...
... In late 2006, the Catskill Mountains plaintiffs challenged the Shandaken ­ Tunnel SPDES permit again, claiming it contained unlawful exemptions and there was insufficient public participation in its review and approval of turbidity control measures. After further litigation, the court decided that a water quality variance was required.
From page 32...
... Supreme Court Decree that settled an interstate water dispute between New York State and New York City and the lower Delaware River Basin states. The states of New York, Pennsylvania, New Jersey, Delaware, and New York City recently approved a new Flexible Flow Management Program (FFMP)
From page 33...
... The reservoir system is also managed to reliably meet water quality standards. In the event that contaminants in the water rise to unacceptable concentrations, appropriate physical and/or chemical treatment strategies are undertaken.
From page 34...
... Drinking Water Treatment The City meets drinking water requirements using many watershed management practices and programs followed by appropriate disinfection practices. Among the distinctive features of New York City's water supply is its avoidance of the need to filter the raw water to remove suspended sediment and other contaminants coming from the Catskill and Delaware watersheds.
From page 35...
... Turbidity Control The principal sources of the silt and clay that constitute the extremely high turbidity in the eastern Catskills are the ice-age deposits created in "pro-glacial" lakes that formed at the southern margin of the glaciers that repeatedly covered this region over the last 1.6 million years (NYC DEP, 2008a)
From page 36...
... The FAD continues to be renewed, allowing the City to deliver unfiltered water from the Catskill/Delaware portion of the supply. Because the 2007 FAD calls for the NYC DEP to further examine its control of turbidity in the Catskill portion of the water supply, the NYC DEP has been studying alternatives to minimize the use of alum prior to water reaching Kensico Reservoir to control turbidity, including both structural
From page 37...
... By running OST, system operators can account for changing environmental conditions and streamflow forecasts, allowing for modification of reservoir operations, if required. In contrast to NYC DEP's past practice of single-point hydrologic forecasts and "spreadsheet" analysis of impacts of alternative operational strategies, OST is intended to be a forecast-driven simulation and analysis tool that will provide City operators and managers with probabilistic predictions of future system status based on simulation scenarios.
From page 38...
... This kind of analytical tool has great value in the operations of such a highly complex water resources system as the New York City water supply. In its efforts to manage this complex system at a high level of reliability and quality and meet its many regulatory requirements and operational constraints, NYC DEP has sought outside expert review as it developed new tools or improved on existing methods.
From page 39...
... Chapter 3 addresses the Catskill Turbidity Control Program, particularly metrics that could be used to determine the performance of measures undertaken as part of the program. Chapter 4 considers the City's plan to use OST as it develops an EIS for modifications to the Catalum SPDES permit.
From page 40...
... 2014. Opportunities to Protect Drinking Water Sources and Advance Watershed Goals Through the Clean Water Act: A Toolkit for State, Interstate, Tribal and Federal Water Program Managers.
From page 41...
... NYC DEP. 2014 Water Demand Management Report Update.


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