Metro

Span-tastic voyage today

COEYMANS, NY — Bridge ahoy!

The brand-new $600 million Willis Avenue Bridge is getting its sea legs this morning when it’s rafted down the Hudson River from the sleepy Albany County town where it was built to its new home in the Big Apple.

The 350-foot-long swing span was rolled onto two massive barges docked in Coeymans yesterday, ready to begin its 110-mile journey to the city today.

“It’s spectacular,” said Karen Moreau, spokeswoman for the Port of Coeymans, which leased the building site to the city.

“It’s an exercise of precision engineering and physics to be able to move a 2,400-ton bridge over 500 feet onto barges on water.”

The 30-hour trip will include a picturesque passage under the George Washington Bridge before it docks in Bayonne.

At the end of the month, it will be towed to the East River, just south of the old Willis Avenue Bridge, which about 70,000 vehicles cross daily.

Construction of the steel marvel began in March 2009, requiring 55 construction workers to weld it together using 75,000 bolts.

Like its predecessor, the swing bridge will connect First Avenue at East 124th Street in Harlem to Willis Avenue at East 134th Street in The Bronx.

New amenities will include bike lanes, shoulders, and a direct connection from the FDR to the northbound Major Deegan Expressway.

When it opened in 1901, the Willis Avenue Bridge cost only $2.5 million.

The new bridge’s price tag of over $612 million makes it the most expensive the city’s Department of Transportation has ever built. The state is covering part of the cost.

Before the original bridge is scrapped, a portion will be preserved in Harlem River Park.

Installation of the new bridge is scheduled to begin Aug. 2. Removal of the existing span is set for Sept. 20.

The Port of Coeymans, a former brick factory about 14 miles south of Albany, has a history of building and shipping structures for the city.

The 145th Street Bridge, which also connects Manhattan and The Bronx, was completed and shipped from the port in 2008. The port has also provided materials for the renovation of the Brooklyn Bridge and for the revamped runway at JFK Airport.

reuven.fenton@nypost.com