New York City is building a massive, decades-long lifeline deep beneath its busy streets

Countries & Cities · Published 15 October 2026 Swipe more like this →

In short: Since 1970, New York City has been boring a colossal water tunnel to secure its future. This engineering feat will finally allow the city to inspect and repair its aging infrastructure, which has been in continuous, uninterrupted service for over a century, while providing a vital, modern backup water supply.

New York City relies on two primary water tunnels, commissioned in 1917 and 1936, to deliver its drinking water. Because these tunnels have never been shut down for maintenance in their entire history, the Department of Environmental Protection initiated the construction of City Water Tunnel No. 3. This project, which began in 1970, is designed to provide an alternative route for water delivery, granting the city the unprecedented ability to perform necessary repairs on the original infrastructure.

The project is divided into four distinct stages. The first stage, completed at a cost of approximately $1 billion, runs from the Hillview Reservoir in Yonkers through Manhattan and into Queens. Subsequent stages expand this network through Brooklyn, Staten Island, and the Bronx. While the initial phase relied on traditional drilling and blasting, later sections utilized tunnel boring machines to improve efficiency and safety. The entire endeavor is a massive undertaking, spanning over 60 miles in total length.

The project has faced significant challenges and evolution over its long timeline. While early estimates placed the total cost at around $5 billion, more recent assessments suggest the final figure will exceed $6 billion. The construction process has also seen shifts in scope, with some segments being reclassified as separate projects, such as the Kensico-City Tunnel. Despite the complexity and the long duration of the work, the completed system will eventually ensure that the city's water supply remains resilient and reliable for future generations.

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