GZA GeoEnvironmental, Inc.

Scope Of Work

The New NY Bridge (Tappan Zee Bridge Replacement) is a Design-Build project with the New York State Thruway Authority.  The project consists of the design and construction of two new 3-mile long multiple span structures that carry I-87/287 across the Hudson River between Rockland and Westchester Counties.  The twin bridges each include approximately 2 miles of approach spans over water and a ¾-mile main span cable stayed bridge.  The new bridges are located immediately to the north of the existing bridge.  The new alignment parallels the existing alignment through the center of the crossing and then ties into the existing alignment shortly past the shoreline at both ends.

The main span towers and anchor piers of the bridge are designed to be supported on 6-ft diameter, open-ended steel pipe piles bearing on either glacial till or sedimentary or metamorphic bedrock at depths of up to 270 feet below the Hudson River. The nominal resistance of these piles is up to 31,135 KN (7,000 kips). The remaining portions of the bridge are designed to be supported on 3-ft and 4-ft diameter, open-ended steel pipe piles, about half of which are friction piles in the deep glacial lake varved clay deposit. The required nominal resistance of the friction piles is up to 19,125 KN (4,300 kips), the higher capacity of any friction piles in these soils. 

GZA served as the Lead Geotechnical Engineer for the Design-Build team and provided geotechnical engineering and foundation design support for all aspects of the design for the new bridge.  The innovative foundation design for this project advanced the state of the practice in geotechnical and foundation engineering relative to the behavior of long, large diameter piles in soft soils that engineers and Owners will benefit from on other projects.

GZA was also responsible for the assessment and handling of all potential environmental hazards during construction.  This engagement represents one of the largest endeavors ever undertaken by GZA.  2017 ACEC Grand Award for the Foundation Design.

Tappan Zee Constructors, LLC (TZC), the Design-Builder for the New NY (Tappan Zee) Bridge. TZC consists of Fluor Enterprises, Granite Construction, Traylor Brothers and American Bridge.

The prime designer for the project is HDR, Inc. major specialty subconsultants include Buckland and Taylor, URS and GZA GeoEnvironmental of New York.

The Owner of the project is the New York State Thruway Authority.

Photo Credit:  New York State Thruway Authority