As many as 100 barges and 30 cranes will fill the Hudson River between Nyack and Tarrytown by the middle of next year, as construction of the new Tappan Zee Bridge moves into high gear, engineers said during a boat tour of the site with journalists on Tuesday.

Brian Conybeare, special adviser to Gov. Andrew M. Cuomo on the project, said early work on the new bridge has gone smoothly and that the project is gaining momentum.

"Preconstruction work is well under way on this project," said Conybeare, speaking at a waterside staging area in Grand View-on-Hudson, just south of the existing bridge's western terminus in South Nyack. "This project is progressing, and you are going to see it ramp up over the next couple of months."

The two-hour tour on the Tappan Zee II, a 48-foot-long tugboat, was an opportunity for the New York State Thruway Authority, the agency that would own the new bridge, and Tappan Zee Constructors, the consortium building it, to show off their progress.

The Thruway has spent $154 million on the megaproject since signing a contract with Tappan Zee Constructors in December, said Dan Weiller, a Thruway Authority spokesman.

On Tuesday -- a crystal clear, sunny day that was perfect for a ride around the site -- there didn't appear to be a lot of activity. But engineers and state officials said the calm was deceptive. A handful of river barges were moored in the shadow of the 3.1-mile crossing on the eastern side, ready for active roles in coming weeks, engineers said; while on the Westchester shore, a crane and crew of perhaps a dozen men were building a trestle -- or temporary platform -- that will serve as a worksite near the bridge landing in Tarrytown.

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A Tappan Zee Constructors engineer on the tour -- who asked that he not be quoted directly -- said about 36 union workers were on the river Tuesday, while some 200 engineers and designers were at work on land. The same engineer said manufacturers in the Hudson River Valley are now producing steel supports and other materials that will eventually become part of the new bridge, or help in the construction process.

"The beginning of the positive economic effects of this bridge are starting to be felt," Conybeare said.



Workers recently completed tests of the soil and sediments on the river bottom, to gauge the resistance that can be expected when pile driving for the permanent bridge structure begins in the fall, said Conybeare.

Next developments:

• In July, Tappan Zee Constructors will drive test piles as a dry run for work on the permanent piles.

• In August, when the spawning season of the Atlantic sturgeon is over and protective measures have lapsed, the consortium will begin dredging the river bottom, to clear a path for the barges that will serve as foundations for most of the heavy construction work.

• In October, the heavy pile driving for permanent piles will begin.

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The big challenge of the moment, according to the engineer with Tappan Zee Constructors, is coordination of final touches on the bridge design with the preparations for heavy construction. At the same time -- adding to the complexity of the undertaking -- the consortium needs to think about reducing the impact of construction on riverside homeowners, the engineer added.

The Tappan Zee II lingered in the vicinity of the Tarrytown trestle for 20 minutes as a "vibrating hammer" pushed a pile into the river bottom with little ruckus. The device is much quieter than a traditional pile driver, according to the Tappan Zee Constructors engineer.

"The vibrating hammer is a big victory for local residents, who don't have to hear as much pile driving," said Conybeare.

He said only two complaints about noise on the river have arisen so far, both from Tarrytown residents, in connection with operations on the trestle; but then cautioned that neither the state nor the consortium can control every sound on the river.

On this beautiful day in summer, the workers on the trestle were in a good mood.

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"Some of you guys with Life magazine?" one workman yelled, laughing, as the Tappan Zee II pulled away.