A spectacular bridge for the 21st Century

A spectacular bridge for the 21st Century

By the time it is finished, 400 engineers will have had a hand in the new bridge construction

A spectacular bridge for the 21st Century

David Capobianco was a toddler in 1964 when the Verrazano-Narrows Bridge slowly soared over his Brooklyn neighbourhood and tethered it to Staten Island. As he grew up, the improbable notion of assembling something so big and of such gossamer design propelled him to become a civil engineer.

Now, after years of public argument and indecision, the first new colossal steel bridge in the New York area since the Verrazano is finally beginning to rise over one of the most spacious stretches of the Hudson River, a replacement for the decaying Tappan Zee, the longest bridge in the state, and Capobianco, 51, is its project manager. “All other projects I’ve worked on are dwarfed by this - the size of the equipment involved, the enormity of what we’re doing, the number of people involved,” he said.

From a small boat on the gunmetal waters of the Hudson, weaving among an archipelago of stout barges and giraffe-like cranes, the scale of the work in progress is impressive. The eight-lane bridge - actually two parallel spans - that will stretch across a 3.1-mile breadth of the river between Tarrytown in Westchester County and West Nyack in Rockland County will by some measures be the widest in the world. By Christmas, dock builders on floating barges had used hydraulically driven vibrating hammers to pound 28 piles - steel tubes up to 6 feet in diameter and up to 300 feet long - into the bottom of the Hudson River, some drilled into bedrock, others held by the sheer density of the riverbed muck.

A thousand piles will eventually be needed, so workers are hustling at a pace of eight piles every two weeks, although they have been slowed by the recent bitter cold. To make sure the piles can hold the weight of the daily traffic - 138,000 cars a day - workers delicately set a barge on top of the piles, fill it with water until it weighs 7 million pounds, adjust that force with hydraulic jacks, then test the piles for several days to see if any shifting takes place. For each of the four towers that anchor the cables holding up the bridge decks, more than 60 piles will be needed, clustered together like sticks of spaghetti in a cellophane package.

For those who like to keep track of bridge terminology, the current Tappan Zee is a cantilever truss bridge; the new bridge will be a “cable stay” bridge: Cables anchored by midriver towers will support the weight of the roadway rather than cables anchored to land on both ends.

Yet with an environmental consciousness that was far less evident when the Verrazano (a suspension bridge) was built, the workers are under firm instructions to respect marine life. To soften the underwater sound waves emitted by pile-driving, strong enough to kill fish, workers surround each pile with a “bubble curtain,” a square enclosure fitted with a compressor that produces sound-dampening bubbles. Dredging to enable barges and other craft to enter the relatively shallow waterway was allowed only until Nov. 1 to protect the feeding grounds of the Atlantic and shortnose sturgeon. “Three sturgeons have been found dead in the bridge’s vicinity, but that’s not atypical,” said Hayley Carlock, environmental advocacy attorney for the nonprofit conservation group Scenic Hudson.

The two graceful spans that will take the place of the current deteriorating bridge will be supported by four angled towers, each shaped like a giant harp. The timetable calls for the first 96-foot-wide span, whose piles are rising just north of the current bridge, to open in December 2016. Two months later it is to accommodate eight lanes, four in each direction. Then the current bridge will be torn down and, by summer 2018, a parallel span - 87 feet wide - is scheduled to take its place just 40 feet south of the first span.

Engineering challenges

Each span will then be reconfigured to accommodate four lanes of cars, with traffic on the northern span heading to Rockland and traffic on the other to Westchester. Each span will also have an express bus lane and emergency shoulders, and the northern span will have a special lane for cyclists and pedestrians.

The project presented major engineering challenges. A single span would have required too great a width to stretch for 3.1 miles, according to officials of New York State Thruway Authority, which owns the bridge, so two spans had to be built. Plans for a commuter rail line, a dream of mass-transit advocates, were shelved as too costly for now. Should the will ever crystallize, officials say a rail span could be squeezed between the two automobile spans.

Construction is being handled by a consortium of companies experienced in building bridges that have banded together under the name Tappan Zee Constructors. To direct the project, the authority has hired Peter Sanderson, 65, the engineer who oversaw the speedy replacement of the Interstate 35 bridge in Minneapolis that collapsed in 2007, killing 13 people. Capobianco, the project manager, is his deputy. 

By the time it is finished, 400 engineers will have had a hand in the new bridge, with workers putting in 6 million hours of construction. Thruway officials say Tappan Zee Constructors will bear most of the risk for cost overruns, a result of legislation Gov. Andrew M. Cuomo signed in December 2011.

The builders are calling on the Left Coast Lifter, one of the world’s largest floating cranes, with a hoisting power of 1,750 metric tons (or as the Thruway authorities like to say, 12 Statues of Liberty). It left Oakland, Calif., just before Christmas, passed through the Panama Canal last week and will take a few weeks to travel up the East Coast.The span of the new bridge will slope about half as steeply as the current bridge; the Tappan Zee’s incline is believed to contribute to fender-benders as trucks slow. The bridge will also have all-electronic toll collection, eliminating backups at tollbooths.

Bottlenecks may not end entirely, Thruway officials concede. Two miles beyond the bridge in Rockland County, there is an uphill slope where the Thruway slims to three lanes from four, a constriction that could occasionally back traffic up to the bridge.

The new bridge still has yet to be named. It may remain the Tappan Zee. The Thruway Authority’s website talks about a generic “New New York Bridge,” but officials admit that the name is up for grabs. The question will be mulled by a task force that is studying the bridge’s financing, looking at tolls - at $5, the Tappan Zee’s are less than half that of the George Washington Bridge - and other revenue sources. They could recommend selling the naming rights.

One caution for anyone wanting to buy the name: The current bridge is officially known as the Gov. Malcolm Wilson Tappan Zee Bridge, after the 50th governor of New York, who served only one year. But few drivers invoke his name when giving directions or calling home to explain why they are late.

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