Coordinated Power for Major NY State Bridge

The Tappan Zee Bridge, a twin cable-stayed bridge spanning the Tappan Zee section of the Hudson River between Tarrytown and Nyack in New York, was decaying and in desperate need of replacement. The bridge’s 8 lanes carry heavy automobile traffic  as part of the New York State Thruway, Interstate 87 and I-287.  The bridge also carries a shared use path for bicycles and pedestrians.

Replacement of the bridge meant installing a new electrical system including coordination between two separate utility jurisdictions. Eaton’s Integrated Power Assembly (IPA) group invited Trachte to be part of the construction team because of an ongoing partnership and successful completion of multiple past projects.

Trachte designed two integrated electrical houses (E-houses) for installation on both ends of the bridge to house critical power, control, and protection equipment for the operation of the bridge’s elaborate electrical scheme. Project challenges included an aggressive construction schedule, DOT travel permitting for the oversized E-houses, and coordination between two different utilities for the power system, each required to support the entire bridge system in the event of failure on either side.

Application Notes

• Two E-houses designed to meet the standards as dictated by two separate local utilities.
• Multi-split buildings: Building #1, 22′-10″ x 55′-0″ x 10′-8″ and Building #2, 24′-4″ x 63′-1″ x 10′-8″.
• Medium voltage switchgear and third-party control and protection equipment with fiber optic interface.
• High level of switchgear interconnect cables for state of the art, automated operating equipment.
• The first E-house was installed using a high-capacity crane.
• The second E-house, which was to be located under the bridge, required a complex jack & slide system to offload and set the building. Unlike cranes, which perform a lift from above with a pulling action, a jack & slide operation lifts objects from below with a pushing action. Hydraulic jacks lifted the building slightly, so the slide and supports could be positioned below the load. The slides then moved the building horizontally to its desired destination.

Solution

Trachte shipped (2) multi-split buildings on time, even after navigating rural delivery routes, restrictive DOT permitting, and heavy traffic at different times of the day. On-time delivery meant a successful connection of medium voltage cables to the switchgear. Trachte’s extensive quality management, including the installation and verification of control terminating points, resulted in zero punch list items during site commissioning.