The New York City Department of Environmental Protection (DEP) has started tunneling for the Delaware Aqueduct Bypass Tunnel, the largest repair project in the 175-year history of the city’s drinking water supply. The $1 billion project will repair two areas of leakage within the 85-mile Delaware Aqueduct, the longest tunnel in the world. The primary leak will be eliminated through the construction of a 2.5-mile bypass tunnel, which will be drilled 600 feet below the Hudson River from Newburgh to Wappinger.
The tunnel will be driven by one of the world’s most advanced tunnel boring machines. The machine—which measures more than 470 feet long and weighs upwards of 2.7 million pounds—was dedicated in honor of Nora Stanton Blatch Deforest Barney, a noted suffragist and the first woman in the United States to earn a college degree in civil engineering. Barney, who worked as a draftsman on the City’s first reservoir and aqueduct in the Catskill Mountains, was also the first female member of the American Society of Civil Engineers.
“The start of tunneling to repair the Delaware Aqueduct is a major milestone in the history of New York City’s water supply system,” DEP Acting Commissioner Vincent Sapienza said. “While the City has added new facilities to its water supply over the past century, repairs approaching this magnitude have been few and far between. The effort to fix the Delaware Aqueduct is by far the most complex DEP has undertaken, and it highlights the absolute need to keep our public works in a state of good repair.”
The next phase of construction includes the lowering of the $30 million tunnel boring machine into a subsurface chamber that is located 845 feet below the ground. The machine is currently being stored in 22 pieces and will take workers approximately 4 months to assemble.
Once assembled, DEP expects the tunnel boring machine to drive about 50 feet of tunnel per day. Work on the tunnel will continue 24 hours a day, five days a week, with tunneling expected to take 20 months to complete.
The finished bypass tunnel will be reinforced by 9,200 linear feet of steel and a second layer of concrete after the tunnel boring machine is finished driving its path beneath the river. Once those are in place, DEP will shut down the Delaware Aqueduct to connect the bypass tunnel to the existing aqueduct. The approximately 6-month shutdown is planned for October 2022. The project is expected to be finished in 2023.