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New NY Bridge Update: Last of Piles Installed in Riverbed

Safety Week

In related news, more than 50 national and global construction fi rms recently joined forces with Tappan Zee Constructors, LLC (TZC), project team for the New NY Bridge, to participate in an annual, industry-wide education and awareness event: Safety Week. The event, which began on May 2nd, focused on work-related injury prevention, refl ecting the New York State Thruway Authority's commitment to safety and TZC's "Take Zero Chances" motto on the New NY Bridge project.

TZC has worked more than six million hours with a total recordable incident rate well under the national average for a project of this size and scope. "We credit this achievement to the men and women who are focused on safety every day as they work to construct this mega infrastructure project," TZC President Terry Towle said.

Safety Week was sponsored by members of The Construction Industry Safety Initiative (CISI) and the Incident & Injury Free Executive Forum (IIF™). Additional support came from the Alliance Partners, many of which are non-profit associations.

Both the Tappan Zee Bridge and its replacement partially share the same footprint where they approach the shores of the Hudson River, posing a logistical challenge for project engineers. Originally, work on the new bridge's piers in these overlapping areas was planned for late 2017, after the existing bridge's demolition. But thanks to innovative engineering, the project team developed plans to advance foundation construction in these areas. This April, the first such installation was successfully executed near the Rockland shoreline in a bold overnight operation unlike any other on the project. To date, all of the bridge's massive piles have been installed in the riverbed with large cranes and pile hammers, which require a great amount of overhead space. Overcoming the low clearance under the existing bridge at the shoreline — just under 30 feet — was achieved by temporarily removing two panels of the existing Tappan Zee's road deck to establish a ceiling-less work area for crews to install the replacement bridge's 75-foot-tall piles.

The New NY BridgeThe first step was designing a floating frame that would act as a template for the pier's foundations and provide a water-free workspace in which the construction team would operate. The 12-foot-tall steel structure, called a cofferdam, was moved between two of the existing bridge's piers and secured using mooring lines in shallow water near the Rockland shoreline. The cofferdam's hollow, tub-like form was then drained of all water. This dry work area was then prepared for installation of the foundation piles. Since minimizing impacts on Thruway travelers was a key priority, the project team scheduled a single overnight operation when traffic volume would be at a minimum. Work began at 9 p.m., Friday, April 29, when maintenance teams deployed protective barriers, including a specialized barrier truck, on the deck of the bridge to separate traffi c from the work area. Crews then swiftly removed two 50-foot-long portions of the Tappan Zee Bridge's deck to allow cranes to place the foundation piles in the correct locations. The piles were then driven deep into the riverbed. All of the pier's foundation piles were successfully installed and trimmed to the appropriate length by just after 8 a.m. on Saturday, April 30. The deck segments were then reinstalled, the lanes were reopened and traffic flow returned to normal.

New NY Bridge Update: Last of Piles Installed in Riverbed

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