While the large and powerful I Lift NY super crane continues to raise enormous, 410-foot sections of steel above the Hudson River, a far smaller and swifter machine, called a derrick crane, is hard at work on an equally important task – installing hundreds of road deck panels to form the base driving surface of the bridge.
The team’s stiff-leg derrick crane, or derrick, is based on an ancient and amazingly efficient design that utilizes a system of guy wires, winches, counterweights and a mast to raise materials. However, the New NY Bridge project’s derrick includes modern advancements in its hoisting system, which can raise up to 80 tons at once.
While it cannot compare to the 1,900-ton lifting capacity of I Lift NY, the derrick’s real strength is its ability to quickly perform without the need for complex hydraulics and electronics. This makes it energy efficient and a perfect fit for jobs that require frequent lifts into a single area over an extended period of time – such as the project’s road deck operations, particularly on the Westchester approach.
This area of the bridge is located more than 100 feet above the Hudson River – beyond the reach of most project cranes. However, the derrick operates atop a 150-foot blue tower on a mobile barge. The combination of this perch and a 130-foot lifting arm allows the derrick to easily reach both of the bridge’s spans on the Westchester approach. Its mobile barge also allows the project team to move the machine to new areas as road deck construction continues.
The road deck is comprised of nearly 6,000 interlocking concrete panels that are prepared offsite and barged directly to the derrick. After the panels are properly rigged to the derrick’s lifting arm, an operator takes control of the machine from water level. Signal crews, standing at the roadway level, communicate with the operator via radio as the panels are hoisted to their final position. After the panels are safely placed atop the bridge’s structural steel girders, they are connected into a single base surface with steel reinforcement and concrete.
The derrick will continue placing road deck panels on the Westchester approach throughout the year. By next year, it will be moved to the Rockland approach to assist with the bridge’s westbound span.
Those interested in a closer look are invited to view the daily project progress via the project’s webcams and photo gallery as well as by visiting the New NY Bridge construction viewing platforms at Scenic Hudson RiverWalk Park in Tarrytown or at Memorial Park in Nyack.