October 25, 2023

New tunnel will improve flexibility between vital water-supply facilities that serve more than 9 million people in New York City and Westchester County

The Final Environmental Impact Statement for the project is available here

The New York City Department of Environmental Protection (DEP) announced the completion of the Final Environmental Impact Statement for the $1.9 billion Kensico to Eastview tunneling and facilities upgrade project in Westchester County that will improve operational flexibility between facilities that are vital to the drinking water supply for more than 9 million people in the City and Westchester. The project will be New York City’s largest water-supply tunneling effort in Westchester County since the 1940s, and its construction will create hundreds of jobs for local laborers.

The centerpiece of the project—known as the Kensico-Eastview Connection (KEC)—will be a 2-mile-long tunnel between Kensico Reservoir and the Catskill-Delaware Ultraviolet Light Disinfection Facility (CDUV) in Eastview. The new aqueduct will provide an additional conveyance between these vital components of the water supply, giving DEP the ability to take other facilities out of service for periodic maintenance and inspection.

The first phase of construction includes site preparation at DEP campuses at the Kensico Reservoir and Eastview, as well as relocation of Westlake Drive at the Kensico campus. Construction work is anticipated to begin in early 2024. All phases of the project are expected to span an approximately ten-year period.

“The Kensico-Eastview Connection project is an essential investment in securing the long-term resilience of New York City’s water supply system,” DEP Commissioner Rohit T. Aggarwala said. “By creating this vital link between Kensico Reservoir and our UV treatment facilities, this new tunnel strengthens our commitment to providing consistent and reliable water delivery to New York City and the growing population centers in Westchester County. We are eager to collaborate with our neighbors in Westchester County to ensure that the City’s waterworks continue to reliably deliver high-quality drinking water to nearly 10 million New Yorkers every day.”

The tunnel will stretch approximately 2 miles from an intake chamber on the western side of Kensico Reservoir to the ultraviolet disinfection facility. The finished tunnel will be 27 feet in diameter and run 400-500 feet below ground. The tunnel will be large enough to carry a maximum of 2.6 billion gallons of water each day. Its design accounts for future growth in the City and Westchester County, the potential addition of treatment facilities, and the need to periodically take other aqueducts out of service for maintenance or inspection.

The project also includes new facilities and site work at Kensico Reservoir and the ultraviolet treatment plant. A century-old intake chamber at Kensico Reservoir will be upgraded and enlarged to draw water into the new tunnel. The reservoir’s shoreline around that intake chamber will also be improved to prevent sediment from getting into the new tunnel. A new screen chamber to remove debris from the water will be constructed just north of DEP’s main campus at the reservoir, near Columbus Avenue in Valhalla. The chemical feed systems at Kensico Reservoir will be upgraded to provide the proper treatment of drinking water in the new tunnel and existing ones. The work at Kensico Reservoir will also include a range of grading, drainage, stormwater management and utility improvements.

In addition to the work at Kensico Reservoir, DEP will also build a connection chamber at the ultraviolet plant in Eastview to receive water from the new tunnel. Work at this site will also include a number of projects related to drainage, stormwater and utility improvements.

Although the project is located in Westchester County, its work centers on the delivery and treatment of pristine drinking water that comes from six reservoirs in the Catskill Mountains. Kensico Reservoir was built in 1915 as part of New York City’s Catskill Water Supply System. Kensico was later modified in the 1940s to receive water from the City’s Delaware Water Supply System, also in the Catskills. Those two systems—collectively referred to as the Catskill-Delaware System—comprise the largest unfiltered water supply in the United States.

The KEC Project (including the environmental review) must be completed prior to the construction of a cover over the Hillview Reservoir in Yonkers. The KEC Project is required by, and must be constructed in accordance with, the terms of the Hillview Consent Decree and Judgment entered by the United States District Court of the Eastern District of New York on May 15, 2019. Completion of the KEC Project would increase flow to the CDUV Facility and improve DEP’s ability to maintain Hillview Reservoir’s water surface levels within normal operating limits during single basin operations at the Hillview Reservoir.

Kensico Reservoir north of White Plains is a vital component of the Catskill-Delaware System. The reservoir stores approximately 30 billion gallons of water at full capacity. DEP draws about 1 billion gallons of drinking water from Kensico Reservoir each day to meet the demand of 8.6 million people in the five boroughs of New York City and approximately 500,000 residents of Westchester County whose communities are connected to the City’s system at Kensico Reservoir or facilities to the south.

As it moves toward the City, drinking water that leaves Kensico Reservoir is treated at the Catskill-Delaware Ultraviolet Light Disinfection Facility, which opened in 2012. The facility in Eastview is the largest ultraviolet treatment plant in the world. The plant provides treatment specifically for Cryptosporidium and Giardia, naturally occurring microorganisms that can be found in surface waters and can cause gastrointestinal ailments in humans. As drinking water passes through the facility it is exposed to UV light that alters the genetic structure of the microorganisms, rendering them unable to reproduce or cause infection. The facility has 56 UV units, each of which contain 210 lamps, for a total of 11,760 UV bulbs.

The Final EIS is available from the Town Halls in Towns of Mount Pleasant, Greenburgh & North Castle; the Town of Mount Pleasant Library; the NYC DEP Offices and online.

DEP manages New York City’s water supply, providing approximately 1 billion gallons of high-quality drinking water each day to nearly 10 million residents, including 8.5 million in New York City. The water is delivered from a watershed that extends more than 125 miles from the city, comprising 19 reservoirs and three controlled lakes. Approximately 7,000 miles of water mains, tunnels and aqueducts bring water to homes and businesses throughout the five boroughs, and 7,500 miles of sewer lines and 96 pump stations take wastewater to 14 in-city treatment plants. DEP also protects the health and safety of New Yorkers by enforcing the Air and Noise Codes and asbestos rules. DEP has a robust capital program, with a planned $31.3 billion in investments over the next 10 years. For more information, visit nyc.gov/dep, like us on Facebook, or follow us on X, formerly known as Twitter.