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The Croton Water Filtration Plant Project

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The Croton System is the oldest of City’s three systems (Croton, Catskill and Delaware) that provide drinking water to the City and upstate communities. Although it was once the only reservoir system supplying water from outside the City, the Croton System is now the smallest of the three systems. The Croton watershed is a series of interconnected reservoirs and lakes in northern Westchester and Putnam Counties. The Jerome Park Reservoir, a distribution reservoir, is located at the downstream end of the Croton System and is the point at which Croton water enters City’s water distribution system. The Croton System provides an average of approximately 10 percent of the City’s average daily demand. During droughts, the Croton System provides up to 30 percent of in-City consumption. Croton water is primarily used in low-lying areas of the Bronx and Manhattan, where the water can be conveyed by gravity. Two pump stations, the Jerome Avenue Pump Station and the Mosholu Pump Station, can supply additional Croton water to the Intermediate and High Level service areas, normally served by the Catskill and Delaware Systems.

The project is being proposed to meet the public water supply and public health needs of the City, and to comply with State and federal drinking water standards and regulations.

Ornamental wall at Jerome Avenue

The New York State Department of Health (NYSDOH) and the United States Environmental Protection Agency (USEPA) have mandated the filtration and disinfection of the Croton water supply to comply with standards set forth in sub-part 5.1 of Chapter 1, New York State Sanitary Code, and the USEPA Surface Water Treatment Rule (SWTR), a National Primary Drinking Water Regulation promulgated under the Safe Drinking Water Act (SDWA), 1974. The City did not apply for Filtration Avoidance for Croton water discharged into the New Croton Aqueduct (NCA) in 1991 under the SWTR because DEP believed that Croton water would require filtration. Instead, in 1992 the City entered into a Stipulation Agreement with NYSDOH for filtration of Croton water. Subsequently, in 1993, USEPA issued a determination pursuant to the SWTR, requiring the City to filter the Croton water supply. More recently, these two regulatory agencies, USEPA and NYSDOH sought a federal court order to obligate the City to construct a Croton filtration plant according to a specified schedule.

The Croton System has provided high quality water to consumers for many years. Although Croton water currently meets all existing health-based water quality regulations, it frequently violates the aesthetic standard for color. Water quality problems have resulted in the Croton System being removed from service on numerous occasions, typically during the summer and fall months (in four of the last several years – 1992, 1993, 1994 and 1998). The entire system was shut down for most of 2000-2001 because of contaminants that leaked into the NCA.

While the USEPA distinguishes between health-based (primary) and aesthetic (secondary) standards with respect to mandatory compliance, NYSDOH considers all standards on an equal basis. Croton water consistently is more colored than the Catskill and Delaware Systems. The raw water, is above the color standard of 15 scu (standard color units), but the chlorination of the raw water generally bleaches the color and brings it into compliance in the distribution system before it reaches the consumer. The City’s goal is to provide equally high quality water to all its users while minimizing the risks associated with the use of chemicals.

The 1996 SDWA Amendments and the rules and regulations that were promulgated subsequent to the SDWA Amendments placed further regulatory burdens on the Croton System. The Interim Enhanced Surface Water Treatment Rule (1998) increased required protection from microorganisms, lowered the turbidity standard, and required the covering of all new treated water reservoirs. One of the SDWA Amendments, the Disinfectants and Disinfection Byproducts Rule has rendered the filtration of Croton water a necessity. Stage 1 of this Rule limits certain by-products of chlorination. These disinfection byproducts have been implicated as a factor in bladder, colon and rectal cancers as well as congenital fetal defects and miscarriages. Stage 2 of this will require measuring the disinfection byproducts as a quarterly running average and to change the points of measurement in the distribution system. As a result of these regulatory changes, without filtration the Croton water is not predicted to consistently meet the Stage 2 Disinfectants and Disinfection Byproducts Rule. Recently Croton water has violated turbidity in 2002, requiring the notification of all users that the water exceeded standards.

The proposed project is designed to meet all current and anticipated future water quality regulations and goals. In addition, the project is intended to allow the City to maximize the use of Croton water that can be conveyed down the NCA.

This project is required to provide filtration and disinfection of the Croton System to: 1) allow DEP to continue to provide drinking water of the highest quality; 2) prevent the periodic shutdown of the Croton System, particularly at times of the year when the City water demand is at its highest; 3) meet the requirements of existing and future regulations; 4) augment the effective yield and operational flexibility of the City’s overall water supply system, and 5) provide additional protection from contamination of the treated water in the water conveyances by pressurizing the treated water conveyances.

Facility Monitoring Committee Meeting Minutes

More Information

NYC Department of Environmental Protection
Public Affairs

59-17 Junction Boulevard
19th Floor
Flushing, NY 11373

(718) 595-6600