Workers with a New York City tunnelers union recently celebrated the completion of a project that many thought wouldn’t finish with a tunnel boring machine that flooded out during Superstorm Sandy.

The New York City Harbor Siphons Project completed by a TBM dubbed “Pat” is a 1.8-mile long tunnel between Brooklyn and Staten Island. Subcontractor Tully/OHL USA JV brought in the 12.5-foot TBM, a Caterpillar model, in 2012 to tackle the mix of clays, sands, rocks and boulders running the length of the route. Pat launched from a shaft on Staten Island in August of that year, bound for an exit shaft in Brooklyn.

Then, the unthinkable happened. Superstorm Sandy ripped into the East Coast with 90 mph winds, overcoming concrete barriers designed for 100-year floods. Seawater filled the tunnel submerging Pat, which was just 1,500 feet into its drive.

“Obviously this was our biggest challenge,” said Luis Alonso, Tunnel Manager for OHL. “After that, not many people thought we would be able to finish this tunnel.”

A severely corroded Pat sat idle until July 2013, by which time Caterpillar had announced the closure of its TBM business. OHL looked around for other manufacturers to help, and found The Robbins Company.

“OHL was always determined to finish this project,” Alonso said. “After studying other options, we decided to proceed with the full refurbishment of the TBM with the help of The Robbins Company. The whole crew worked together to achieve that goal.”

Robbins mustered its people in December 2013 to replace all of Pat’s hydraulics and rewire its entire electrical system. The company also removed rear gantries and the belt conveyor for cleaning, evaluation and repair. The crews worked for four months, with much of the refurb being done in the tunnel and under water pressure. Even after the refurb, Robbins field service personnel stayed on the job to offer ongoing maintenance. They helped drive Pats performance up as high as 100 feet per day.

Tunnelers completed the project in January 2015, even powering through difficult glacial geology with excessive water ingress following the rebuild. “The TBM needed more thrust and we decided to implement four additional auxiliary cylinders. Robbins field service helped in developing the size, features and location of the cylinders, which were eventually placed in the lower quadrant of the propulsion system,” Alonso said.

“This tunnel is an important part of a larger project, and we are proud to be doing what we do every day, dealing with troubles as they come up, until we reach the end of the drive,” he added.

Now that tunneling is complete, the stationary and tail shields will be buried at the exit shaft entrance, with the cutterhead and back-up being removed.

The New York City Harbor Siphons Project was managed by the New York City Economic Development Corporation (NYCEDC). It replaces shallower lines, making way for a larger project — the dredging of the Anchorage Channel portion of New York Bay. The channel is a critical waterway for shipping.

The Robbins Company has more than 60 years of experience in underground construction and excavation. For more information, visit