NYCDEP delays Delaware Aqueduct shutdown and repairs until October 2024

The New York City Department of Environmental Protection announced on Wednesday that it was once again postponing plans to shut down and repair the leaky Delaware Aqueduct, with work now scheduled to begin in October 2024.

In June 2022, the DEP paused a planned aqueduct fix for a year, saying it needed more time to prepare for the monthslong closure. In a series of public meetings this spring, DEP representatives said they would make a go/no-go decision as the shutdown, planned for October, drew closer.

However, DEP spokesman John Milgrim said on Wednesday that new revelations altered the course of the department’s plans.

He noted that the aqueduct was temporarily shut down and partially drained for two weeks in March as part of a planned test.

“Data collected during that timeframe revealed that seepage from groundwater aquifers was infiltrating the aqueduct deep underground at more substantial rates than originally anticipated,” he said.

“After further analysis, engineers feel that these revised infiltration projections are much closer to what can be expected during a full shutdown,” he continued. “Therefore, additional dewatering equipment will be required to ensure a successful repair.” 

Instead of the full shutdown that had been planned for the fall, the DEP will now conduct a dewatering test for a longer duration than what was done in March, he said.

“This will facilitate the collection of even more detailed data to better understand the groundwater infiltration rates,” Milgrim added. “This shift is necessary to allow for additional dewatering pumps, related drainage infrastructure, and augmented electrical support to be installed and constructed to keep the work area in the city water tunnel dry during the complex repair.”

The dewatering test will take place in the fall though a specific timetable has not been set, he said. 

[Read more: NYCDEP recovers from fumbled community outreach about Delaware Aqueduct shutdown]

At a cost of $1 billion, fixing the 85-mile-long tunnel (the longest in the world) represents the largest and most complex repair project in the 180-year history of New York City’s municipal water supply system.

The DEP commissioner, Rohit T. Aggarwala, said the shift in scheduling was being made “to ensure that the men and women working 700 feet underground will be safe as they help us protect New York City’s high-quality drinking water for generations to come.”

He added that the delay in the work will not affect the safety or supply of New York City’s drinking water.

The Delaware Aqueduct delivers about half of New York City’s water supply — typically about 600 million gallons a day — using only gravity to carry the water from four Catskill Mountain region reservoirs.

For decades, the DEP has known about leaks in the Delaware Aqueduct that are leading to the loss of as much as 30 million gallons of water per day.

In 2010, the DEP announced plans to repair the aqueduct by connecting a 2.5-mile-long bypass tunnel around the areas known to be leaking — one in the Town of Newburgh in Orange County and the other in the Town of Wawarsing in Ulster County.

The new bypass, being connected 700 feet beneath the Hudson River, is the first tunnel built under the Hudson River since 1957, when the south tube of the Lincoln Tunnel was completed.

The DEP had planned to create a 30 percent void in the reservoirs ahead of the planned shutdown to address local residents’ concerns about potential flooding. However, the DEP said it will now resume normal operations, including routine downstream releases from the reservoirs, this week.