NEW YORK  — The New York City Department of Environmental Protection (DEP) announced a schedule change for planned work on the Delaware Aqueduct this week. 

The project, which calls for a portion of the aqueduct to be shut down in order to attach a bypass tunnel under the Hudson River, was originally scheduled to begin in October of this year. It was to last up to eight months, but has been pushed back to October of 2024.

According to the DEP, the pushback in schedule is “necessary to allow additional pumps, as well as related drainage infrastructure and electrical support, to be installed to keep the construction zone dry and ensure worker safety during the complex repair of decades-old leaks.”

The 85-mile-long Delaware Aqueduct is the longest tunnel in the world and it delivers about half of New York City’s water supply. The Aqueduct carries water of about 600 million gallons a day from four Catskill Mountain region reservoirs. Two reservoirs in the eastern Catskills are sources of water that the Catskill Aqueduct provides to the city. They will be heavily relied upon for water sources during the Delaware Aqueduct shutdown. 

New York City announced a $1 billion plan to repair the aqueduct in 2010. The plan called for connecting a 2.5-mile-long bypass tunnel around known leaks that were discovered in the 1990s - one in the town of Newburgh and the other in the town of Wawarsing in Ulster County. 

The new bypass will be connected 700 feet under the Hudson River and is the first tunnel to be built under the Hudson since 1957. That year, the south tube of the Lincoln Tunnel was completed. 

“This is the largest-ever capital repair project in the history of the City’s water supply and worker safety is paramount for DEP,” said DEP Commissioner Rohit T. Aggarwala. “This schedule change will in no way impact the safety or supply of New York City’s drinking water.”

The aqueduct was temporarily shut down and partially drained in March for two weeks as part of a planned test. The DEP collected data during the shutdown, which showed that groundwater was infiltrating the aqueduct faster than originally projected when the tunnel was not at full capacity. DEP will be securing and installing additional equipment to account for the additional infiltration. Normal operations will resume for the DEP as of now, which includes routine downstream releases from reservoirs.