New York City plans $1.2B tunnel project at Kensico Reservoir

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Kensico Dam/Wikipedia Commons
Kensico Dam/Wikipedia Commons

The New York City Department of Environmental Protection (DEP) says it is planning a $1.2 billion tunnel project starting at Kensico Reservoir.

The DEP plans to dig a roughly two-mile-long tunnel from the Kensico Reservoir to a water treatment facility in Eastview. The project is expected to improve operational flexibility between the two facilities, which help provide the drinking water supply for more than 9 million people in New York City and Westchester, the DEP says in a news release.

The project will require a series of environmental reviews and permit approvals from federal, state, county, city and local agencies. According to DEP officials, the first part of the tunnel construction will start in about five years. Work on the tunnel is expected to begin around 2025, with an estimated completion of 2035.

The work could create hundreds of jobs for local laborers, according to the announcement from the DEP.

Construction on the first elements of the project is expected to start in approximately five years.

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 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 Kensico-Eastview Connection is a critical investment in the long-term resiliency of New York City’s water supply system,” DEP Commissioner Vincent Sapienza said in a statement. “By providing an additional connection between Kensico Reservoir and our treatment facilities to the south, this new tunnel will further guarantee the reliable delivery of water to New York City and population centers in Westchester County, including New Rochelle, White Plains and Yonkers. We look forward to working with our neighbors in Westchester County to ensure that the City’s waterworks continue to supply high-quality drinking water to more than 9.6 million New Yorkers every day.”

“This is an example of how government can work effectively when we all work together,” Westchester County Executive George Latimer said. “Westchester has long enjoyed some of the best drinking water in the country and this is an important step to make sure future generations will enjoy fresh, clean water. Along with preserving this great resource, I am also pleased to see that this project will create local jobs while providing helpful redundancy to the infrastructure that our communities depend on. This is a ‘win-win’ for all involved.”

The KEC project will include construction of the new tunnel, facilities to draw water from Kensico Reservoir and move water into the ultraviolet plant, and other infrastructure work. In 2017, DEP collected soil and bedrock samples from the area to support the design of the project, which has already begun. Construction on the first portions of the KEC project are expected to start in approximately five years; work on the tunnel itself is expected to begin around 2025. DEP expects to finish the project around 2035.

The tunnel will stretch approximately two miles from an intake chamber on the western side of Kensico Reservoir to a connection point at the ultraviolet disinfection facility. DEP expects the finished tunnel to measure approximately 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. An interconnection for the Town of Mount Pleasant water supply will also be incorporated into the screen chamber. 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 and utility improvements.

In addition to the work at Kensico Reservoir, DEP will also build a connection chamber at the ultraviolet plant to receive water from the new tunnel. The chamber will connect to a number of existing pipes at the ultraviolet facility that were installed at the time of its construction. Work at this site will also include a number of projects related to drainage, stormwater and utility improvements.

During the next several years, DEP will work toward completing the design of the tunnel and the facilities that will connect it to the reservoir and ultraviolet plant. It will also start the process of environmental review and obtaining dozens of permits from federal, state, county, city and local agencies. DEP will keep the public apprised of all opportunities for input as work on the KEC project continues.

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.

Kensico Reservoir is a vital component of the Catskill-Delaware System. The reservoir stores approximately 30 billion gallons of water at full capacity. DEP draws about one 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.

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