Nyc Innovation Sees Century-Old Bridge Replaced Currently $93M Under Budget, Without Stopping Trains

Nyc Innovation Sees Century-Old Bridge Replaced Currently $93M Under Budget, Without Stopping Trains

New York City had to replace a 132-year-old railway line along Park Avenue, and the contractor’s innovative approach has saved taxpayers millions.

Confusingly called the Park Avenue Viaduct, the same name as the historic automobile viaduct at Pershing Square, the aging structure carried some 750 Metro-North trains into Grand Central Station every day.

The city’s Metropolitan Transport Authority contracted Halmar International to lead the design and building process, which is to be done in several stages from October 2023, to summer of 2027. Halmar is so far working $93 million under budget, and a staggering 51 months ahead of schedule.

For Phase 1, Halmar brought in an enormous hydraulic gantry system to remove the old concrete and steel superstructure and replace it with brand new pre-fabricated elements, each weighing 190,000 lbs. and coming already assembled with track fasteners, third rail fasteners, guardrails, and walkways

According to Engineering News Record, GNN’s favored source for feats of engineering, it took crews 19 weekends to perform the first 128 installations between East 115th Street and East 123rd Street along Park Avenue in Upper Manhattan. They installed 8,240 feet of the track on the new bridge.

A gantry crane system allows operators to quickly lift, move, and lower heavy materials into place. Gantry cranes differ from normal cranes because they perch over the work site rather than beside it.

A typical gantry consists of four legs mounted either on rails or wheels. Atop and across each pair of legs is a long sturdy beam that supports the crane mechanism. Utilizing either hydraulic legs, or hydraulic crane components, the gantry lowers until the building element is secured, then raises it up above the work site, and moves along the rails or the road to the spot where the element is to be lowered into position.

A favorite for loading and unloading boxcars trains or container ships at port, Halmar contacted the gantry manufacturer MiJack, which produced the largest gantry it had ever made to perch completely over the viaduct. This allowed Metro-North service to continue on two of the four rail while the other two were being replaced.

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Crews could cut away the aging concrete of the rail bridge in large segments, which the gantry could quickly pick up and lower onto a flatbed which drove it away. Then, the gantry could lay the new sections down like planks on a footbridge.

The first stretch was finished 21 months early, despite a constrained urban environment with sidewalks and crossings that had to remain open. The second stretch began in March 2024, from East 127th Street to East 132nd Street.

Work is expected to conclude next April.

WATCH a time-lapse video of the work in progress…