October 12, 2021
DEP has temporarily shut down the Catskill Aqueduct this month for the fourth and final year of an all-important rehabilitation project. Over the past decade, we have worked on several projects to ensure New York City will have a reliable supply of drinking water when we enter the last phase of a $1 billion project to repair the longest tunnel in the world—the Delaware Aqueduct. The rehabilitation work on the Catskill Aqueduct is key to those efforts.
While the Catskill Aqueduct is out of service for the next 15 weeks, New York City will rely on additional water from our other two water supply systems: the Delaware System and the Croton System. These changes might cause some New Yorkers to notice that their drinking water tastes different. The change in smell or taste might be unpleasant, but DEP can assure you that it is temporary, seasonal, and 100 percent harmless.
DEP scientists test your water about 2,000 times each day, and our engineers are continually optimizing treatment processes to deliver the best quality water to our customers while we rehabilitate one of the most complex aqueducts in the world. The temporary change in taste that some New Yorkers might experience will go away once DEP is finished with this year’s work, and access to the full flexibility of our reservoir system is restored.
We understand that we deliver your most critical utility each day—clean, safe, and reliable water. Thank you for your patience while we complete these big infrastructure projects.
New York City gets its drinking water from large reservoirs in the Hudson Valley and Catskills. Some New Yorkers might notice that their water smells earthy or musty during the late fall and early winter. That change is caused by two naturally occurring organic compounds called MIB and geosmin. The compound MIB (short for methylisoborneol) is most prevalent in our reservoirs.
These naturally occurring compounds are commonly found in soil, and they are produced as plants and microorganisms grow. MIB and geosmin get into our water late in the year as aquatic plants and microorganisms living in our reservoirs begin to die until the next growing season. This happens around the same time the leaves begin to fall each autumn.
Human noses and taste buds can detect MIB at ultra-low concentrations. In fact, people who are sensitive to these compounds can detect them at concentrations as low as 10 parts per trillion—a concentration equal to 10 grains of sand in an Olympic swimming pool. What’s more, these compounds cannot be removed completely from water through normal treatment and filtration processes. Their taste-and-odor effects can take several months to disappear. Although they make our water taste unpleasant, these organic compounds are harmless to human health.
In a normal year, DEP would solve this challenge by simply switching the source of your water to one of our other 19 reservoirs. But right now, we are working on projects to repair and rehabilitate our two largest aqueducts that carry water from the Catskills to the city. The water supply’s flexibility is limited while these critical infrastructure projects are happening. We cannot simply turn off the water from one source and switch to a different one.
So we need the help of all New Yorkers to get through these essential aqueduct rehabilitation projects that will guarantee the delivery of your high-quality water for the next 100 years.
Please continue to call 311 or fill in this online form if you notice a change in your water quality. Because we test New York City’s water about 2,000 times each day, we know which neighborhoods across the city are experiencing this change in taste, but we still want to hear from our customers and be responsive to your concerns.
If you are experiencing this specific change in your water, it’s important to understand that pitcher filters and faucet filters will not help. To improve the taste, there are two small things that you can do:
We are finishing our rehabilitation of the Catskill Aqueduct, which requires it to be shut down for 15 weeks this fall. That work will prepare the water supply system for shutting down the Delaware Aqueduct for 5–8 months in 2022–2023.
The Catskill Aqueduct is a 92-mile conduit that carries drinking water from Ashokan Reservoir in Ulster County to Hillview Reservoir in Yonkers. The aqueduct conveys about 40 percent of New York City’s drinking water on an average day.
Skilled workers are currently replacing century-old valves, repairing minor leaks, and rehabilitating other structures connected to the aqueduct to ensure it can deliver water from the Catskills to New York City after 106 years in service. Ensuring that the Catskill Aqueduct is in a good state of repair will enable us to rely on it in 2022, when we shut down the Delaware Aqueduct.
The 85-mile-long Delaware Aqueduct is the longest tunnel in the world. It begins at Rondout Reservoir in Ulster County and conveys about 50 percent of New York City’s drinking water every day.
We are currently working on a $1 billion project to repair two areas of leakage from the Delaware Aqueduct. The primary leak will be eliminated through the construction of a 2.5-mile bypass tunnel built 600 feet under the Hudson River from Newburgh to Wappinger. The bypass tunnel was completed in 2019 and will be connected to structurally sound portions of the existing Delaware Aqueduct next year to convey water around the leak. DEP must shut down the Delaware Aqueduct for 5–8 months to finish the connections on either side of the Hudson River. The leaking section of the existing aqueduct will be plugged and taken out of service forever. This is the largest repair project in the 179-year history of the New York City water supply system.