New York City Completes Rehabilitation of 123 Year-old New Croton Aqueduct

Project Marks Key Milestone Towards Reactivation of the Croton Water Supply System, Which Can Provide Between 10 and 30 Percent of the City’s Daily Water Needs

 The New Croton Aqueduct conveys water from the City’s oldest collection of upstate reservoirs in Westchester and Putnam Counties, the Croton watershed, to the in-city drinking water distribution network.  For more than 150 years the system provided unfiltered drinking water to the city, first through the Old Croton Aqueduct, which was built in 1842, and then the New Croton Aqueduct.  However, as population density increased around the Croton reservoirs, water quality in the system diminished and, in the late 1990s, DEP stopped using Croton Water for in-city distribution and began planning the construction of a filtration plant.  With the system taken off-line and the Aqueduct drained of water, DEP conducted an extensive inspection of the tunnel and began plans for repairs.

A major component of the project was the connection of the Aqueduct to the Croton Water Filtration Plant in the Bronx.  A large concrete plug, 58 feet long and 12 feet wide, was built within the Aqueduct to direct the water through a new tunnel to the filtration plant.  Once the water has gone through the filtration process, it travels through a separate tunnel back to the Aqueduct, downstream of the concrete plug, and towards the distribution network.  The filtration and mechanical systems within the Croton Plant are currently being tested with water provided through the New Croton Aqueduct.

The completion of the Croton Filtration Plant and the reactivation of the Croton drinking water supply system will play important roles in the future as DEP repairs leaks in the Delaware Aqueduct, which currently supplies more than 50 percent of the city’s daily water needs.  Last year DEP began building two vertical shafts on opposite sides of the Hudson River in Orange and Ulster Counties.  The shafts will be used by workers to build a bypass tunnel around a leaking portion of the Delaware Aqueduct, roughly 600 feet below ground level.  Once that bypass tunnel has been built, DEP will temporarily shut down the Delaware Aqueduct in 2021 to make the necessary connections.  The Croton system will be critical in ensuring that DEP can continue to meet the city’s drinking water needs during the shutdown of the Delaware Aqueduct.  It will also help to supplement the city’s water supply during future drought conditions.