# Kensico Reservoir

The Kensico Reservoir is a reservoir spanning the towns of North Castle and Mount Pleasant, New York. It was formed by the Kensico Dam in 1885, which impounded waters from the Bronx and Byram rivers.
The reservoir mainly serves to store waters received from the Catskill Mountains. Along with the West Branch Reservoir and Boyds Corner Reservoir, it is one of four reservoirs within the Catskill/Delaware system. The dam is 1,843 feet (562 m) long, stands 307 feet (94 m) above its foundation, and is able to hold back about 30 billion US gallons (110,000,000 m$^3$) of water.

## History

The first use of water from Westchester County came from the Old Croton Dam, which was completed in 1842. During the 1880s, New York faced increased demands for water and sought to enlarge the Croton Reservoir to meet that need. The enlargement was completed in 1906 as a part of a system of reservoirs designed to attract water from Putnam and Westchester Counties (the Croton Watershed) to New York City.
In 1885, the old Kensico Dam was built south of the village of Kensico as an additional source of water for New York City. The dam formed a small lake with water from the Bronx River and the Byram River, but it was not enough for New York's increasing population. A reservoir was needed to act as a holding tank for distribution to New York City. Kensico was surrounded by hills that came to a natural V-shape, making it an ideal area to hold a vast amount of water. To the south of Kensico was two ponds (Rye Pond and Little Rye Pond) in Harrison, New York, which would eventually form part of the new reservoir. A nearby quarry in Harrison bordering Cranberry Lake provided the necessary materials for building the new dam.
In 1905, New York State passed legislation to allow fundraising for the construction of Kensico Reservoir. The following year, final planning by the state was approved, and preliminary surveys were started. A seventeen-mile railroad spur and a small network of highways were built to carry materials from quarries at nearby Cranberry and Silver Lakes to the dam site. A camp for the workers and their families was also constructed, along with public facilities for their children.
To prepare for the dam construction, each individual lot of land was condemned and appraised, and the owner was paid a "fair value" for the land. Many of the families had to move to the surrounding communities of Armonk, Harrison, Valhalla, and White Plains. The village of Kensico was then flooded to make way for the reservoir.
On July 12, 2018, the New York City Department of Environmental Protection (DEP) press office announced plans for a Kensico-Eastview Connection Project. The project mainly involves constructing an approximately 2-mile long tunnel between the Kensico Reservoir and the nearby Catskill/Delaware Ultraviolet Light Disinfection (CDUV) Facility.

## Dam construction

Before constructing the new Kensico Dam, the old one had to be removed (Demolition began in 1911). The construction of the new dam began in 1913 and was concluded in 1917—three years ahead of schedule—at a cost of more than $15,000,000.
The dam is 1,843 feet (562 m) long, stands 307 feet (94 m) above its foundation, and is able to hold back about 30 billion US gallons (110,000,000 m$^3$) of water. It contains 1 million cubic feet (28,000 m$^3$) of masonry.
Frank E. Winsor was the engineer in charge of construction at Kensico. New York City's main contractor built a work camp at nearby Valhalla for the 1,500 men who worked on the dam at the height of construction, and the water supply board created a mounted police force to keep order. Crews were largely made up of Italian immigrants, who were tasked with digging straight down to a depth of 110 feet (34 m) to reach solid rock with no water-bearing seams. This entailed months of blasting and a number of fatal accidents.
The tremendous influx of workers and their families provided a period of growth for the surrounding area, spurring new stores, rooming houses, hotels, restaurants and saloons. Many of the worker's families remained in the area after the completion of the dam, contributing to the growth and character of Valhalla and its environs. The Kensico Reservoir was acquired as parkland in 1963 from the New York City Watershed Commission and remains the property of the DEP.

## Water sources

The reservoir is the collecting point for the Ashokan Reservoir, the Cannonsville Reservoir, the Neversink Reservoir, the Pepacton Reservoir, the Rondout Reservoir, and the Schoharie Reservoir. It also receives water from the Boyds Corner Reservoir and the West Branch Reservoir through the Delaware aqueduct. Through the use of pumping stations along the Delaware Aqueduct, it is possible to supply Kensico reservoir with water from the Cross River Reservoir and Croton Falls Reservoir (and indirectly, the reservoirs upstream of Croton Falls) as well as the Hudson River, however these connections are rarely in use.
The resulting body of water has a drainage basin of 13 square miles (34 km$^2$) and holds 30.6 billion US gallons (116,000,000 m$^3$) of water at full capacity. The reservoir's watershed provides only 2% of New York City's water supply, while the rest comes from the reservoirs to which it connects. There are two outlets that provide water to parts of Westchester County, the Catskill Aqueduct or the Delaware Aqueduct. After leaving Kensico, the water is treated with ultraviolet light at the New York City Department of Environmental Protection's Eastview facility, then continues on to Hillview Reservoir. At Hillview the water enters the three city tunnels that distribute water throughout the boroughs of New York City.

## Fishing

Kensico Reservoir sustains an active population of gamefish including brown trout, lake trout, smallmouth bass, largemouth bass, perch, and grass pickerel. The size and depth of the reservoir allow lake trout in particular to thrive. Shore fishing is practiced in many areas, and boating is restricted to Department of Environmental Conservation licensed and inspected aluminum rowboats. No motorboats or recreational watercraft are permitted on the reservoir. In April 2020, the reservoir was stocked with 7,360 brown trout fingerlings. The reservoir was formerly stocked with lake trout, however this program was discontinued after it was determined they had established a sustainable breeding population.

## Kensico Dam Plaza

The Kensico Dam plaza is a plaza located at the foot of the dam. Historically, Westchester County's Department of Parks has hosted several community-wide events at the plaza, including outdoor screenings throughout the summer and early autumn, and a Fourth of July celebration with fireworks, food trucks, and live music. Amidst the COVID-19 pandemic, it also began sponsoring "Winter Wonderland," a winter holiday-themed drive-through light experience. The plaza also provides recreational activities, including a playground, a large lawn, gravel paths for walking and biking, and a hiking trail running from the plaza level to the top of the dam. Placards posted throughout the plaza encompass its history.
The plaza is also home to The Rising, a memorial dedicated to victims of the 9/11 terrorist attacks who were from Westchester County. This memorial displays the names of the victims on the granite surrounding the main structure. The main structure of the memorial is made of steel rods that come together and point towards the sky.