The New NY Bridge

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The New NY Bridge

Services: Geotechnical and Structural Engineering Services
Contractors: Tappan Zee Constructors
Owner: New York State Thruway Authority
Designer: Design Build Project
Status: Projected Completion - 2018

Siefert Associates, LLC was selected by Tappan Zee Constructors, LLC., in 2013 to provide various construction engineering services as part of a new $3.9 Billion Tappan-Zee Bridge construction. The 3 mile (16,000 ft.) long bridge spans the Hudson River between the Rockland and Westchester counties in NY and is the single largest bridge construction project in New York’s history.

Scope of services included:

  • Design of 170 ft. long Bulkhead,
  • 1000 ft. long Temporary Trestle Bridge design
  • 90ftx45ft Cofferdams design for the new bridge piers.
  • Selective Demolition of existing spans and analysis of existing structure.
  • Curved Steel Erection analysis and lift plans for 12’-0” deep by 350’-0” long steel girders in spans 3 and 4 of the West and Eastbound structure.
  • Support of Excavation for various utility installation on existing roadway.
  • Design of rigging and analysis of existing bridge structure for demolition of 2,000,000 pound structure in single crane lift.
  • Temporary Storage Platform design to store 2 layers of 12’-0” deep by 350’-0” long steel girders on the Hudson River.
  • Slope stability analysis for new toll booth installation.


Additional engineering services included analysis and retrofit of an existing dock for construction loads, support of excavation, formwork design, utility supports, construction inspection, and precast pier tub lifting apparatus design.