With just a few feet to spare, the Left Coast Lifter successful squeezed under the 60-year-old Tappan Zee Bridge on Oct. 8 as crews positioned it to begin building a replacement structure.
The $50-million floating crane, with a lifting capacity of 1,750 metric tons, was ballasted with about 2.5 million gallons of water inside its roughly 400-ft-long, 100-ft-wide barge, so it could draft deep enough to clear the bridge. Prior to the move, the crane was upgraded with fresh wire rope on its 1-7/8-in.-dia main hoist line and load-tested with 538 metric tons.
Total wire rope on the crane exceeds nine miles. In addition to the main hoist, the crane runs a 2-in.-dia boom hoist line reeved in 24 parts, a 1-5/16-in.-dia auxiliary hoist line reeved in six parts and a 1-3/16-in.-dia whip hoist line reeved in one part.
Contractor joint-venture Tappan Zee Constructors LLC can now use the rig to begin construction of heavy precast concrete and steel elements: the heaviest of which are estimated to weigh up to 1,000 metric tons.
Each steel module will consist of two or three 12.5-ft-deep plate girders spaced about 24 ft apart and measuring approximately 400 ft long. Conventional girders would be just 100 ft long, requiring much smaller cranes, project officials say.
"It's much safer job to assemble this steel on land and get it out to the job," says Dan Bell, construction manager for TZC. "That way, we've done a lot of the work already on he ground."
The $3.9-billion replacement bridge is expected to finish in 2018. After using it to build the new bridge, TZC will also use the heavy-lifter to dismantle the old structure.