Kensico Reservoir - Dam Construction

Dam Construction

Before constructing the existing Kensico Dam, the old Kensico Dam had to be removed; this began in 1911. The construction of the 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 1,825 feet (556 m) long. It stands 307 feet (94 m) above its foundation and contains 1 million cubic feet (28,000 m3) of masonry—as much masonry as the Egyptians used to build some of the pyramids. In one month, 2.5 million cubic yards of concrete were poured into blocks, which had to cure for three months before being swung onto the rising hyperbolic pile of dam. The dam is able to hold back about 30 billion US gallons (110,000,000 m3) of water.

Frank E. Winsor was the engineer in charge of construction of Kensico as well as Hillview Reservoir and 32 miles (51 km) of the Catskill Aqueduct.

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. The water supply board created a mounted police force to keep order. Crews were largely made up of Italian immigrants, who began the long task of 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. As the aqueduct neared completion in 1913, the work gangs at Kensico began laying the first of the concrete bricks of which the dam is built.

The tremendous influx of workers provided a period of prosperity for the surrounding area. New stores, rooming houses, hotels, restaurants and saloons met the needs of the workers and their families. Many of the construction families remained in the area after 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 New York City Department of Environmental Protection. Kensico Dam Plaza is a Westchester County Park.