The New York City Department of Environmental Protection (DEP) recently announced that it had completed yet another major leg of its Catskill Aqueduct repair and rehabilitation project right on schedule. From November 10 to January 23, DEP workers at dozens of locations in Ulster, Orange, Putnam and Westchester counties were diligently cleaning and repairing sections of the aqueduct.

The work on the Catskill Aqueduct is necessary for multiple reasons. For starters, the aqueduct is one of the biggest water sources for New York City, conveying up to 590 million gallons of drinking water every day (about 40 percent of the city’s total water supply); the other two major sources are the Delaware Aqueduct, which delivers over 600 million gallons per day (roughly 50 percent of the city’s supply) and the Croton Aqueduct, which carries about 300 million gallons per day. That said, maintaining clean and efficient conditions in this particular aqueduct is key to ensuring millions of New Yorkers aren’t left high and dry, literally and metaphorically.

To that end, the DEP coordinated with over 20 municipalities that utilize the aqueduct to organize a shutdown, allowing workers to access the tunnel while also ensuring the municipalities had backup water sources prepared. Then, over 200 DEP workers were deployed to various locations to replace valves, grout cracks, and scrape organic film from the tunnel’s surface that has built up over the course of decades of service.

This isn’t just routine maintenance, however. The Catskill Aqueduct needs to be in tip-top shape in preparation for the 2022 shutdown of the larger Delaware Aqueduct, which is undergoing some serious repairs of its own. The Delaware Aqueduct has suffered for decades now from two major leaks, located in the towns of Wawarsing and Newburgh.

The Wawarsing leaks are rather small and can be fixed with grouting, but the Newburgh section is leaking a whopping 20+ million gallons of water per day and needs a serious overhaul. The DEP has already bored out a 2.5-mile tunnel underneath the Hudson River, parallel to the existing section of the Delaware Aqueduct that connects Newburgh and Wappingers.

In 2022, the DEP will need to shut down the Delaware Aqueduct and drain it of water for five to eight months in order to connect this new section of tunnel to the existing aqueduct. During that time, the Catskill and Croton aqueducts will be working overtime, which is why the repair and rehab efforts on the Catskill Aqueduct are so important.

The DEP workers tackling the Catskill Aqueduct project certainly had their work cut out for them. Workers focused on the 74 northernmost miles of the 92-mile-long aqueduct, the section extending from the Kensico Reservoir in Valhalla to the Ashokan Reservoir. In addition to replacing aging shutdown valves and drilling a total of 14,036 linear feet of holes for the purposes of crack repair via grouting, the team also cleaned a collective 32.5 miles of tunnel. This cleaning does more than improve the water’s quality, the 800 tons of organic film removed from the aqueduct’s walls also reduce friction in the tunnel, allowing for an additional 40 million gallons of water to pass through each day.

“This complex project to rehabilitate the Catskill Aqueduct has required more coordination and flexible planning than perhaps any in the history of our water supply,” said DEP Commissioner Vincent Sapienza. “I want to thank the laborers who worked around the clock for ten consecutive weeks, the communities north of the city who prepared and activated their backup water supplies while the aqueduct was out of service, and our DEP engineers and planners who coordinated activities during the shutdown. While we are pleased with the significant progress that was made this year, much work remains to complete the project and ensure this critical aqueduct can serve New Yorkers for generations to come.”