Meet Nora, the TBM that will help to repair the world’s longest tunnel

This is Nora.

The Robbins Company, based in Ohio, recently completed the manufacture and testing of a $30 million tunnel boring machine (TBM) that will be used to repair New York City’s Delaware Aqueduct — the world’s longest tunnel.

The machine is currently being dismantled and shipped in pieces to our construction site in Newburgh, NY. All parts of the TBM are expected to arrive by early summer. We expect to begin using it this fall to drive the bypass tunnel that will eventually convey water around the leaking portion of the Delaware Aqueduct in Newburgh. The bypass tunnel will be 2.5 miles long, and it will be located about 600 feet below the Hudson River, stretching from Newburgh to Wappinger.

The machine will be named after Nora Stanton Blatch Deforest Barney, noted suffragist and the first woman in the United States to earn a civil engineering degree. Nora, 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.

Footage of Nora in Solon, Ohio, during factory acceptance testing.

Some interesting facts about Nora, the TBM:

• The main body, which includes its cutter head, is 21.5 feet in diameter, 42.6 feet long, and weighs 2.2 million pounds.
• The trailing gear—which processes tunnel muck and positions pre-case concrete liners—is an additional 426.5 feet long and weighs 520,000 pounds.
• That means the entire machine stretches nearly 470 feet and weighs more than 2.7 million pounds.
• Nora was built to withstand 30 bar of pressure—believed to be the most of any TBM every manufactured. That’s about 11 times the amount of pressure that comes out of a garden hose. The machine was built to withstand that much pressure because workers encountered huge inflows of water under immense head pressure when the aqueduct was first built more than 70 years ago.
• To deal with groundwater inflows, Nora also has a dewatering system that can pump out 2,500 gallons per minute.
• Nora will be pushing into a very porous formation of limestone. To ensure this rock is sound for drilling, it will first need to be hardened. To do this, Nora includes three drills that can drill ahead in 30 different positions to inject grout into the porous rock, making it one hard mass.
• The entire machine is so large that it will need to be shipped on several trucks. The first half of the trailing system should be shipped around the end of March, wish several other shipments to follow in May and June.