New Croton Dam

The New Croton Dam is a massive masonry gravity dam located in New York. It sits across the Croton River near Croton-on-Hudson. This structure forms the New Croton Reservoir, which is a vital part of the New York City water supply system. A masonry gravity dam is a structure built from stone or concrete. It uses its immense weight to resist the pressure of the water pushing against it.

To build such a large structure, engineers had to change how the river flowed. They could not build the dam while the river was running through the site. First, workers dug a crescent-shaped canal into a hill on the north side of the river. They secured this canal with a masonry retaining wall. They also built temporary dams to direct the water elsewhere. This allowed them to pump the riverbed dry so construction could begin on the actual site.

This dam was designed by Alphonse Fteley, who lived from 1837 to 1903. Construction officially began in 1892 at a site owned by A.B. Cornell. This site was downstream from the original Croton Dam, which was eventually submerged by the new reservoir. The project was a huge undertaking that lasted many years. Initial construction took eight years, but repairs and modifications continued for another six. By the time it was completed in 1906, it was the tallest dam in the world.

The workforce required to complete this project was very diverse. The crew included laborers and stonemasons who had worked on the original dam built decades earlier. John B. Goldsborough served as the superintendent of excavations and hiring. He even recruited skilled stonemasons from southern Italy to move to New York for the job. Building the dam was not always easy, as workers faced difficult conditions. In 1900, a silent film called The Croton Dam Strike was released to show the labor and management problems occurring at the site.

The physical scale of the New Croton Dam is truly impressive. The structure contains 650,000 cubic yards of masonry. Its foundation is built to extend below the bed of the river for stability. The dam and its spillway together reach a total length of 1,100 feet. The spillway itself is 500 feet long. When full, the reservoir can impound up to 7 billion gallons of water. While this is a large amount, it is only a small fraction of the total New York City water storage capacity of 11 billion gallons.

Engineers also monitor how much water moves through the dam during heavy weather. The dam features a spillway to manage excess water. For example, during Hurricane Ida in 2021, the dam saw water over the spillway. The average daily discharge during that event was 10,100 cubic feet per second. The highest recorded discharge since 1933 occurred on October 16, 1955. During that time, dual hurricanes named Connie and Diane caused a discharge of 33,000 cubic feet per second.

Today, the area around the dam serves many different purposes. The reservoir supplies water through a new aqueduct to the Jerome Park Reservoir in the north Bronx. The dam also provides space for recreation and nature. People can visit the Teatown Lake Reservation or Croton Point Park nearby. Hikers and bikers use the Old Croton Trail, which follows the route of the Old Croton Aqueduct. The trail has an endpoint located near the base of the dam.