American Scientist

The New York City metropolitan area is full of traffic bottlenecks, and among the worst is the Tappan Zee Bridge, which carries the state’s Thruway—Interstate 87—across the Hudson River about 25 miles north of New York Bay, into which the Hudson flows. Between the bridge and the bay there is only one other overwater crossing of the river proper, and that is the George Washington Bridge, which connects New Jersey and New York via Interstate 95. The Verrazano-Narrows Bridge, which takes Interstate 278 across the entrance to the upper bay known as the Narrows, joins the New York City boroughs of Staten Island and Brooklyn, which is at the westernmost part of Long Island. Each of these last two crossings was the longest-spanning suspension bridge in the world when completed, the George Washington in 1931 and the Verrazano-Narrows in 1964. They remain today, respectively, the 19th and 8th longest in the world. There are also two vehicular tunnels connecting New Jersey to Manhattan: the Holland Tunnel, which carries Interstate 78 into the city in the vicinity of Canal Street, and the Lincoln Tunnel, which comes in at 39th Street. These few fixed crossings of the Hudson south of the Tappan Zee are critical to the road network that connects New York to points west.

Metropolitan Infrastructure

Transportation problems are nothing new to the city that, until the last years of the 19th century, comprised what are now known as the boroughs of Manhattan and the Bronx, which are separated by the relatively narrow and therefore relatively easily bridged Harlem River. But for a long time the city’s western boundary (the Hudson River, long known as the North River to distinguish it from the South or Delaware River) and its eastern boundary (the inappropriately named East River, which is really a tidal estuary connecting Upper New York Bay with Long Island Sound), were wider than bridge-building technology could span in a single leap. The East River, being about half the width of the Hudson, was the first to be attempted. Proposals were put forth in the early 1800s, and by midcentury there were numerous ideas on the table for connecting Manhattan Island to Brooklyn and Queens, but the achievement did not occur until the Brooklyn Bridge was completed in 1883. With the opening of that bridge, travel between New York and Brooklyn became predictable and reliable. No longer did the ice on the river or fog in the air hamper commuters by interrupting ferry service, so the two separate cities began to function more like a single one. In 1898, just 15 years after the completion of the bridge, the City of Greater New York—consisting of the five boroughs of Manhattan, Brooklyn, Queens, the Bronx and Staten Island—was formed, thus demonstrating the important role that infrastructure can play in government and politics.

With the completion of the Brooklyn Bridge—and the traffic it encouraged between Manhattan and Brooklyn—there was soon a heightened desire and indeed a need for additional fixed crossings of the East River. The unification of the boroughs expedited the political process whereby bridges were planned and funded, so in the first decade of the 20th century three new bridges were opened across the East River: the Williamsburg (1903) and Manhattan (1909) bridges connecting lower Manhattan and Brooklyn, and the Queensboro Bridge (1909) connecting midtown Manhattan and Queens. (The Queensboro is also known as the 59th Street Bridge, after the location of its main approach route in Manhattan.) Today, these centenarian overwater structures, along with the Triborough Bridge (1936), Queens-Midtown Tunnel (1940) and Brooklyn Battery Tunnel (1950), constitute the principal traffic arteries among the boroughs. Except for the Brooklyn, the bridges also carry rapid transit trains over the East River, as do dedicated subway tunnels under it.

On Whose Authority?

Although Manhattan and New Jersey had been joined by Pennsylvania Railroad tunnels by the end of the first decade of the 20th century, the Hudson River remained without a bridge over it or a vehicular tunnel under it until the Holland Tunnel was opened in 1927. (Known during construction as the Canal Street Tunnel, the completed structure was renamed in honor of its chief engineer, Clifford M. Holland, who died just before the first tunnel tube was holed through.) Although a bridge would likely have been less expensive to construct than a tunnel, debates over the limits of bridge technology argued for a tunnel to relieve the congestion of Hudson River ferries, which in the 1920s were carrying about 30 million passengers a year.

It had long been difficult to resolve jurisdictional disputes and coordinate infrastructure planning between New York and New Jersey, so in 1921 the bistate Port of New York Authority was established, with each state’s governor appointing equal numbers of members to the governing board of the port district. Many New Yorkers and New Jerseyites persisted in referring to the agency as the “Port of Authority,” and this malapropism long served as a shibboleth for identifying natives of the area. More than this, it was probably New Jersey’s desire for equal billing that led to the 1972 name change to the Port Authority of New York and New Jersey. Whatever its name, the Port Authority is responsible for the bulk of the region’s transportation infrastructure, which includes tunnels, bridges, airports and seaports within a 25-mile radius of the Statue of Liberty. The Port Authority planned and built the World Trade Center in Lower Manhattan, its originally planned location on the east side of the island moved to the west side so that New Jersey could more readily share in its economic benefits.

Because the East River bridges are wholly within the boundaries of Greater New York City, they are not under the control of the Port Authority. As interborough but intracity bridges, the Brooklyn, Manhattan, Williamsburg and Queensboro are toll-free, thereby obviating any backups due to toll collection. Tolls are collected for the use of other intracity bridges and the tunnels under the East River, but they are collected only from traffic going into Manhattan. This one-way toll collection was an inspired innovation first introduced on a major crossing in 1968 when it was employed on the Golden Gate Bridge. In New York, tolls for all the Hudson River crossings are collected at the New Jersey end, thereby relieving somewhat—but only somewhat—traffic congestion around the bridge and tunnel approaches in Manhattan. Of course, the one-way collection system does nothing to relieve congestion on the New Jersey approaches.

Fracture-Critical

By design, the Tappan Zee Bridge is located just outside the 25-mile radius of influence of the Port Authority of New York and New Jersey. This explains in part why the bridge is located not at a narrow section of the Hudson but rather at one of its widest parts. The bridge, which carries the New York State Thruway between Rockland and Westchester counties, is thus uncommonly long, stretching about three miles from end to end, with its longest span being just over 1,200 feet. Siting a bridge at a wide part of the river may be counterintuitive, but generally where a river is wide it is also relatively shallow. This can reduce the cost of constructing foundations for piers, so there can be many piers relatively close together and hence many modest spans. Drivers and passengers crossing the Tappan Zee Bridge are reminded of this by the regular and frequent sound of tires rolling over road joints atop the piers and between the spans. Unfortunately, poor riverbed conditions complicated foundation design.

The name Tappan Zee derives from the Tappan Indian tribe that lived in the area and the Dutch word zee, meaning “sea,” alluding to the expansive width of the river at the location. In 1950, the Port of New York Authority wished to build a new bridge across the Hudson River at Dobbs Ferry, New York, which was just inside the 25-mile limit of its jurisdiction. Then New York Governor Thomas E. Dewey effectively vetoed the proposal, wishing instead to construct a bridge taking the New York State Thruway across the Hudson and on through Westchester County to connect with the New England Thruway. Dewey prevailed and a proposal to build a bridge at Tarrytown, which is just across the river from Nyack, went forward. This location, being outside the Port Authority’s jurisdiction, meant that toll revenue would go not to the Port Authority but to the New York State Thruway Authority. The structural design called for a 1,200-foot steel-cantilever main span flanked by viaduct-like approach spans. Among the innovative features of the bridge was to be hollow concrete caisson foundations, whose buoyancy would help support the main span and thus reduce costs somewhat. Construction began in 1952 and the bridge was open to traffic near the end of 1955.

Although commonly known by its original name, the Tappan Zee Bridge, and familiarly known as the Tap, since 1994 the official name of the crossing has been the Governor Malcolm Wilson Tappan Zee Bridge, even though Governor Wilson did not play any significant role in the bridge’s history. Appending his name to the Tappan Zee was done to honor him politically on the occasion of the 20th anniversary of his one-year term as governor. In fact, Wilson was never even elected governor; he rose from the position of lieutenant governor to serve out the remainder of Nelson Rockefeller’s term when he resigned for political reasons. In an effort to continue in the governor’s office, Wilson ran for election himself but lost. Perhaps there was among some state employees lingering resentment of his name being attached to the Tappan Zee structure, for when signs bearing the bridge’s new name were unveiled on the Nyack and Tarrytown approaches, it was evident that the governor’s first name was misspelled on them as Malcom. The signs had to be replaced at a cost of $3,000 each.

Today, the Tappan Zee, which has been called “one of the ugliest bridges in the East,” has more serious problems than signs containing misspellings and general lack of aesthetic respect. One infrastructure critic has said that it “is being held together with glue and duct tape.” It would certainly take more than those quick fixes to put the bridge back in mint condition. When it was a brand-new bridge, in 1955, on average about 18,000 vehicles a day used the crossing. Today, there are about 140,000 (and on peak occasions as many as 170,000) vehicles crossing the bridge daily, which means it is suffering the abuse of traffic volume an order of magnitude greater than when the structure was new. At current traffic levels, it serves about 50 million vehicles each year, which collectively pay about $650 million in tolls.

The traffic volume and intensity is taxing the structure’s capacity, not only in number of vehicles but also in structural endurance. Every vehicle, and especially a heavy bus or truck, that crosses any bridge causes the structure’s fabric to flex and creates a situation in which so-called fatigue cracks can be initiated and grow. Every bridge is designed to last a certain number of years, and the intended lifetime for a bridge such as the Tappan Zee when it was on the drawing board was about 50 years. As the bridge approached its golden anniversary in 2005, its owner—the New York State Thruway Authority—reportedly refuted that it was built to last only that long. But a few years later, perhaps because it could smell the federal cash that was likely becoming available for a replacement, the authority began to speak of the bridge as “reaching the conclusion of its useful life.” It was indeed technically considered “functionally obsolete,” in that among other things it did not have roadway shoulders onto which disabled vehicles could pull over and allow the able traffic to continue on its way. Still, the authority’s executive director insisted that the bridge was “perfectly safe” because inspection— intended to catch the development of corrosion and cracks before they become dangerous—was being done regularly. Further, maintenance—designed to arrest any corrosion and cracks that are found—was keeping pace, even if the cumulative cost of those functions had long surpassed the original cost of the structure.

The Tappan Zee also falls into the category of bridges known as fracture-critical, meaning that it does not possess structural redundancy. If an essential part fails—whether because of an unstable fatigue crack or another weakness—there is not another part capable of taking up the slack and the entire bridge is likely to collapse. There are an estimated 18,000 such bridges in the United States. The Interstate-35W bridge over the Mississippi River in Minneapolis was a fracture-critical structure, and when it collapsed without warning under rush-hour traffic in 2007, the incident naturally led to increased scrutiny of all fracture-critical bridges, including the Tappan Zee. Understandably, there were calls for the design and construction of a replacement bridge over the Hudson at Tarrytown. However, advocates for a new bridge wanted more than just something that could carry more cars, buses and trucks with fewer delays; they also wanted the new structure to accommodate mass transit in the form of a dedicated bus lane or a light rail line. Improving the aesthetics of the crossing was also a desirable objective. Even without the complications or additions of such amenities, which could delay design and construction, the bridge was expected to cost at least $5 billion to build. With bus lanes and rail tracks, the price tag could reach $16 billion, according to a Federal Highway Administration estimate.

An Expedited Search

In 2011, the plight of the Tappan Zee Bridge came to the attention of the White House, and that October President Barack Obama announced that the proposed Hudson River crossing would be among 14 major infrastructure projects that would be “fast-tracked” to encourage development and promote job growth for the construction industry, which had been ailing for years. Fast-tracking meant that a federal review of environmental impact studies would go forward on an accelerated schedule and the availability of federal funds for construction would be expedited. As planning and review went forward on a new Tappan Zee bridge, which would have at least eight traffic lanes compared to the existing structure’s seven, newspaper reports began to quote officials that the price tag might rise to $6 billion.

In times past, the next step in the process of acquiring a new bridge would be for the structure to be designed by either state thruway engineers or a specialist consulting firm engaged by the state. When the design was complete, requests for proposals would be announced and published in trade journals of the construction industry. Construction companies interested in bidding on the project would submit their sealed bids by a stated deadline, and they would be ceremoniously opened and the job given to the low bidder, unless other criteria were also to be taken into consideration. That serial process not only took time to progress but also had the potential of sometimes leading to bridges of unremarkable aesthetics, and at other times to protracted legal disputes between the designer and the builder over whether the plans or the construction was at fault when something did not match up or fit properly.

To obviate such disappointments, inefficiencies, disputes and delays a process known as design-build has come increasingly to be adopted in the United States. Design-build has the advantage that designers and builders form a team that bids on a project as an entity and so has responsibility for both the design and the construction of it. Any disputes that might arise will supposedly be resolved quickly and amicably within the team, for otherwise the partners share in any loss associated with delay or dispute. New York state passed a law in December 2011 to allow such contracting, and so the state’s “largest-ever bridge project” was to be among the very first design-build projects to be overseen by New York state employees. State transportation agencies evaluated the qualifications of five teams of engineering firms and construction companies and approved four to be allowed to submit bids. Among the criteria for establishing the short list were accomplishment and reputation in the technical, financial and management spheres.

Only the four qualifying partnerships and joint ventures received formal requests for proposals. The short-listed teams had only about four months to prepare and submit their detailed plans and cost figures. According to one team member, “We’ve had more time on $50 million jobs,” and yet this one had been estimated to be worth about a hundred times as much. The state agencies would have to review and evaluate all four proposals in a similarly short period of time, if a contract were to be offered in time for work to begin before the November 2012 elections, as politicians wished. New York Governor Andrew Cuomo—no doubt along with some politicians in Washington—was said to be especially keen to see that work was started by then.

Of course, it costs time and money to come up with a design and cost estimate and to prepare a proposal in response to any request. In the case of the Tappan Zee project, each qualified proposing team reportedly was to receive a stipend of $2.5 million for its efforts. Whether any such stipend ever covers the actual cost of preparing a proposal is a debated topic, and it surely depends on how much free rein the bidders are allowed. In the case of the Tappan Zee Bridge Hudson River Crossing Project—to use its official name—among the constraints placed on the bidders by the state were that the bridge be located just a few hundred feet north of and beside the existing bridge and that it consist of two separate but equal structures, one carrying eastbound and the other westbound traffic. Each structure was to accommodate four lanes of traffic, have a left and right breakdown lane or shoulder, and have a lane dedicated to pedestrians and cyclists. It seemed likely that all four qualified teams would go forward and produce a document endeavoring to convince those reviewing it that it will give the state the best deal. However, one of the teams did not meet the July 27 bid deadline. The lowest of the three bids was not necessarily expected to win the contract, for in addition to bottom-line price each proposal was to be evaluated on the basis of the maintainability of the proposed bridge and on its “architectural iconism,” which effectively allowed aesthetic judgment and current structural fashion to enter into the evaluation.

In the meantime, after failing earlier in the year to secure a federal loan for about $2 billion, New York state had reapplied to Washington, this time for a $2.9 billion loan. And in mid-September 2012 Governor Cuomo announced the formation of a “selection review team,” which included a sculptor and the director of the Metropolitan Museum of Art. This group was to review the aesthetics of the proposed designs and assist a larger review team, which included technical experts and local community leaders, to choose the proposal that would give the “best value” and “ensure the new bridge is the best choice and fit for the region.” In addition to evaluating the foundation and structural design, construction plan and projected life span of the bridge, selection criteria for choosing the winning team were to take into account future transportation options, environmental requirements and how the design-build team planned to work with a broad range of stakeholders. The review team had the option of recommending to the governor that he accept one of the proposals as written or that he authorize negotiations with selected bidders or that he initiate a call for “a best and final offer” from one or more of the bidders.

For at least a decade, and even as the proposals were being evaluated, other facets of the new bridge had been under scrutiny, including how its construction would affect the Atlantic and shortnose sturgeon that populate the river. Activists and public-interest advocates complained that the request for proposals was issued before the deadline for public comment on the project, thus not taking fully into account alternatives to a new bridge and what ordinary people considered important. Among the things that continue to interest area residents is what will happen to the old bridge when the new one is in place. There are those who would like to save the $150 million it could cost to demolish the old structure and use the money to convert it into a 30-acre park that would stretch along the three miles of the crossing. Advocates of this route point to the Walkway Over the Hudson project, which converted an abandoned railway bridge upriver at Poughkeepsie to a scenic and highly successful and popular pedestrian and cycle way (see this column from May–June 2010). High Line Park, a mile-long elevated urban greenway developed atop an abandoned New York Central Railroad viaduct on Manhattan’s West Side, has also been held up as an example of what could be done with an obsolete and, as is hoped by many, soon-to-be-redundant major piece of infrastructure.

The three proposals for a new Tappan Zee crossing were kept secret while contract negotiations took place with the apparent front-runner. In early December, the three designs and their costs were unveiled. It was little surprise to bridge watchers that all three proposals were for cable-stayed structures, in which the longest spans are supported from cables running directly from the towers to the roadway. The genre allows for wide variations in cable arrangements and tower geometry. One design was described in the popular press as resembling “pairs of tuning forks,” another as a “crowd of sailboats” in a regatta and the other as a “cream-colored version” of the Golden Gate, even though that iconic span is a conventional suspension and not a cable-stayed bridge. In revealing the competitors, the advisory committee described how long each option would take to construct, which ranged from just over five years to almost six; the amount of dredging that would be required, from just under 1 million to just under 2 million cubic yards; and the price, which ranged from a high of about $4 billion for the last two to just over $3 billion for the first. That all the bids came in under the $5 billion estimate reflected the depressed state of the construction industry. Companies would rather risk a financial loss on a big job than be without work.

Just before the end of the year it was announced that the team of Tappan Zee Constructors, a consortium headed by the international construction company Fluor, won a $3.14 billion contract for the tuning-fork design. Construction management, which could add as much as $800 million to the cost of the job, will be handled by HNTB Corp. The State of New York signed off on the contract early this year, and everything seemed in place except the financing. The federal loan was still pending, as was the issuance of bonds to be covered by toll revenue, but groundbreaking for the projected five-year project was expected to occur with or without the money in place.

Acknowledgments

This column is based on reports that have appeared in a wide variety of newspapers and trade journals, including the New York Times and Engineering News- Record . I am grateful to my sister, Marianne Petroski, for sending me clippings from the Rockland County Journal News, which has continued to cover the ongoing story of the bridge from a very interested local perspective.