About the Tappan Zee Bridge

The existing Governor Malcolm Wilson Tappan Zee toll bridge, usually referred to as Tappan Zee Bridge opened to traffic in 1955 and is an integral component of the regional roadway network that connects South Nyack in Rockland County with Tarrytown in Westchester County in the Lower Hudson Valley.

The total length of the bridge and approaches is 16,013 feet (4,881 m). The cantilever span is 1,212 feet (369 m) providing a maximum clearance of 138 feet (42 m) over the water. The bridge is about 25 miles (40 km) north of midtown Manhattan.

The bridge is part of the New York State Thruway mainline and also designated as Interstate 87 and Interstate 287. The span carries seven lanes of motor traffic. The center lane can be switched between eastbound and westbound traffic depending on the prevalent commuter direction; on weekdays, the center lane is eastbound in the morning and westbound in the evening. The switch is accomplished via a movable center barrier which is moved by a pair of barrier transfer machines. Even with the switchable lane, traffic is frequently very slow. The bridge is one of the primary crossings of the Hudson River north of New York City; it carries much of the traffic between southern New England and points west of the Hudson.

It was designed to carry 100,000 vehicles on a peak day but traffic volumes have grown to approximately 138,000 vehicles per day with a high percentage being intrastate and interstate trucking.

Building of the Existing Tappan Zee Bridge:

Eight underwater concrete caissons, which support about 70 percent of the bridge’s dead weight, are themselves supported by steel piles driven to rock. The caissons incorporate a “buoyant” design that stores pressurized air within small compartments. Water is periodically pumped out of these compartments, which range in number from 8 to 24 in each caisson, to achieve the desired buoyancy. This innovative design saved millions of dollars in construction costs. 

The two largest caissons, which support the two main towers of the bridge, are 100 feet by 190 feet, and weigh 16,000 tons each. The two caissons for the flanking piers are 77 feet by 124.5 feet, and the four smallest caissons are 46 feet by 100 feet. Each caisson is 40 feet high, and has exterior walls that are 34 to 45 inches thick.

The caissons were constructed in a natural clay pit at Grassy Point, Rockland County, which is about 10 miles north of the bridge site. This pit, which is 32 feet below the river’s surface at its deepest point, was the largest natural dry dock in the world. About 350,000 gallons of water were pumped out to permit construction of the caissons. All eight caissons were transported by barge to the bridge site, the first of which arrived on October 13, 1953. 

Once the caissons arrived, they were floated into their exact position by maneuvering them into a fender system built for each pier. Open wells lined with corrugated, galvanized iron were run vertically through the compartmentalized walls of the caissons. The caissons were then filled with water and sunk atop a five-foot blanket of sand and gravel about 42 feet below the river surface.

Between Westchester and Rockland counties, the riverbed of the Hudson River consists of layers of silt hundreds of feet deep. With bedrock more than 300 feet below sea level, engineers found it difficult to lower the caissons. To solve this problem, they drove steel pipe piles, some up to 270 feet long, into the bedrock through the open wells of the caissons. Once the piles were driven, the pipe piles were cleaned out, filled with concrete and then encased by concrete within the walls to pin the caissons permanently in place. 

As construction of the bridge added dead weight to the caissons, water was pumped from them to obtain the desired buoyancy. Two pumps, a 60-gallon-per-minute pump for small amounts of water and a 300-gallon-per-minute pump for larger amounts, were installed at the low point of each caisson. These pumps continue to regulate the buoyancy of each caisson.

In addition to the 42,702 cubic yards of concrete, a total of 1,602,200 feet (303 miles) of timber piles, 330,500 feet (62.5 miles) of steel “H” pile and 33,400 feet (6.3 miles) of 30-inch steel pipe piles filled with concrete were used to construct the foundations.

The original design of the Tappan Zee Bridge included a 1,112-foot steel tied-arch span for the main channel of the Hudson River. As construction progressed on the rest of the span, steel fabricators decided not to bid on the main span because their estimates exceeded that of the chief engineer. Subsequently, engineers selected a more economical cantilever design. The main cantilever span, which was to be 100 feet longer than the originally proposed main steel arch span, was to be the widest of its type. 

Two steel falsework structures, each 16 stories high, were used to construct the main span and the two 293-foot-tall towers. Each falsework structure measured 517 feet long, 93 feet wide and 168 feet high. Derricks atop the falsework were used to build the main towers. Approximately 1,700 tons of steel were used for the falsework, which was constructed at Grassy Point and shipped by barge to the bridge site.

The derrick on each falsework had a 40-ton lifting capacity, and was used in erecting a 100-ton stiff-leg derrick on the main structure. The stiff-leg main structure derrick was used in the erection of the towers, the main span and the side spans.

The main cantilever span, which measures 1,212 feet in length, is comprised of cantilever spans of 340 feet and a suspended span of 531 feet. It is flanked by two 602-foot side spans.

The Deck Truss Spans:

 On either side of the main and side cantilever span are nineteen deck truss spans, each measuring 235 to 250 feet long, 93 feet wide and 28 feet deep. Each of the spans, which weighed as much as 900 tons, was shipped by barge from the Grassy Point assembly site, and hoisted into place by four 500-ton jacks. Two sets of falsework were constructed at Grassy Point to enable the workers at the bridge site to work without interruption. The falsework was returned to Grassy Point after each of the truss spans was delivered to the bridge site.

Pier Protection:

Until recently, all eight caissons are protected by an all-around pile fender system. During 2000, workers constructed a new pier protection system: the two main piers are now protected by a new, pre-cast concrete ring structure on steel pipe piles, while the flanking piers are now protected by a new, reinforced timber system designed to current standards. Concrete icebreakers, each of an equilateral, triangular hollow shape and measuring 90 to 110 feet long, are employed at each of the eight caissons. Icebreakers, which are of timber pile cluster construction, are used for the approaches.

The Movable Barrier System:

To maximize roadway efficiency, the seven-lane bridge utilizes a moveable concrete barrier. Tom Caruso of the NYSTA supplied the following information on the bridge’s movable barrier system:

The seven-lane Tappan Zee Bridge, which currently employs a movable barrier system, converted in 1992 from a four-lane southbound, three-lane northbound configuration with Jersey barrier. Prior to 1987, the bridge had a three-lane northbound, three-lane southbound configuration, with a single-lane, wide-open, curb-height median strip.

Under normal circumstances, there are four southbound and three northbound lanes, separated by a jointed, moveable barrier. This configuration is switched from four-lane southbound, three-lane northbound to three-lane southbound, four-lane northbound each day around 2:00 PM for the afternoon rush, and then changed back later in the evening. Each changeover takes about 45 minutes.

The system used is from a company called Barrier Systems, and is similar to that used in a number of road construction sites, with the exception of the actual machine. Each three-foot-long section is made of concrete and is tied together by a metal hinge system. The cross-section of each section looks much like a jersey barrier, except for a “T”-shaped flare at the top. This flare is used by the barrier machine to pick up each section of the wall.

The Barrier Systems web site shows a big gangly orange machine that is typically used in construction, but on the Tappan Zee Bridge, there are three half-lane-width machines that are used two at a time in tandem to move the barrier. (Most likely, this setup causes less traffic congestion than using a single full-lane-width machine.) Moreover, these machines, which are painted “Thruway yellow and blue,” are enclosed for all-weather use.

The first barrier machine starts at one end of the Tappan Zee Bridge, straddles the barrier in a channel that runs through the undercarriage on a curved diagonal, lifts it several inches, slides it over a few feet and sets it down in place. The second machine follows a few yards behind to complete the lane shift. On each machine, there are two operators at either end for steering. These operators follow guide markings painted on the pavement.

Why do we need a Tappan Zee Bridge?

Plans for a trans-Hudson crossing from Westchester County had first arisen in the 1920’s. The trans-Hudson bridge was proposed in conjunction with a circumferential highway that would encircle the New York-New Jersey metropolitan area. After spending many years in limbo, the circumferential highway plan was given serious consideration in the years after World War II, which saw unprecedented demands on the regional highway system.

In 1949, the New York State Thruway Authority (NYSTA) established as its goal the development of a toll superhighway connecting the major cities of New York State. Originally proposed to end in Suffern, Rockland County, the mainline route was extended into New York City after engineering and fiscal experts agreed that the extension would serve as an integral part of the system.

Earlier bridge plans called a crossing between Dobbs Ferry, Westchester County and Piermont, Rockland County (near Tallman Mountain State Park). However, the proposed Dobbs Ferry-Piermont location fell within the 25-mile radius of the Port Authority, which held jurisdictional rights to Hudson River crossings within its jurisdiction. The challenging geography of the lower Rockland County palisades also would have made construction of a connecting east-west roadway difficult.

In 1951, the proposed bridge was relocated to the current Tarrytown-to-Nyack location, incorporating the proposed Thruway extension between Suffern and New York City. This route would connect to (and take maximum advantage of) north-south arteries on both sides of the Hudson River, not only those in Westchester and Rockland counties, but also those existing or under construction in New York City, Connecticut and New Jersey. It also took advantage of the proposed route of the Cross Westchester Expressway (along the Central Westchester Parkway right-of-way), which was to comprise part of the metropolitan beltway

In June 1951, not long after the route of the span had been approved, workers drove the initial test pilings. Construction of the Tappan Zee Bridge, which was delayed by steel shortages brought about by the Korean War, began in March 1952. The engineering firm Madigan-Hyland oversaw construction.

Public Support for a New Tappan Zee Bridge:

“The Tappan Zee Bridge is a vital part of our state and region’s infrastructure. The Tappan Zee Bridge project improves a key component of our state and nation’s infrastructure, and at the same time puts tens of thousands of New Yorkers back to work.”

– Governor Andrew M. Cuomo 

• “The Tappan Zee Bridge is a vital project for the area, the region and the nation. While its economic effects are widespread, the immediate effect is on the people of Rockland and Westchester Counties. The Department of Transportation is performing a great service in holding public hearings in both counties to allow these people to have their say in the rebuilding of the bridge.”
— Eliot Engel – Congressman

• “Governor Cuomo knows that the reconstruction of the Tappan Zee Bridge is vital to New York’s economy and he has taken the necessary steps to ensure that the project progresses as rapidly as possible. The new bridge will reduce congestion, provide greater safety and will include an immediate dedicated express lane, making the new bridge fully transit capable. Under the Governor’s time line, it is clear that the new bridge will continue to be a crucial artery between Westchester and Rockland counties. I look forward to continuing my work with Governor Cuomo and putting New Yorkers back to work.”
— Nan Hayworth – Congresswoman

• “Rebuilding the Tappan Zee Bridge is critical for enhancing the safety of motorists, creating well-paying jobs, and meeting the transportation needs of our growing region. I am pleased President Obama expedited permitting and environmental review for the new bridge, and I stand ready to work with Governor Cuomo and the Congressional delegation to ensure the federal government continues to do its part to facilitate this important project.”
— Nita Lowey – Congresswoman

• “I thank the Governor for taking on the Tappan Zee Bridge project, which had gone stale from endless discussions, and turning it into a reality through decisive leadership. Fast-tracking the replacement of the Tappan Zee Bridge after years of planning will provide New Yorkers with much needed jobs and bring economic growth for our region and beyond. With an immediate dedicated express lane, New Yorkers can look forward to full transit capability and I look forward to breaking ground on the new Tappan Zee Bridge with Governor Cuomo.”
— David Carlucci – State Senator

• “Replacing the aging Tappan Zee Bridge is long overdue, and Governor Cuomo is right to take advantage of this opportunity to expedite construction and secure federal funding for this much-needed project. Building the new bridge will create thousands of jobs in our area, restore a critical component of our infrastructure and provide a structure wide enough to accommodate future mass transit. I share the Governor’s commitment to develop a viable off-site plan for mass transit while construction of the new bridge moves forward.”
— Suzi Oppenheimer – State Senator

• “The momentum for the new Tappan Zee Bridge is moving forward, and President Obama and Governor Cuomo have made it a priority for our nation and state. The critical issue of adding mass transit to the bridge in the future remains, and I will continue to advocate for it. But there is no doubt that this project will create thousands of much needed jobs in our region and help make our infrastructure safer and more stable. At this crucial stage, the public needs to remain involved, so I encourage all who wish to weigh in to attend this Thursday’s public hearing.”
— Andrea Stewart-Cousins – Senator

• “In the interest of public safety, our best option is to move forward with the Tappan Zee Bridge construction as soon as possible, allowing for all the legal steps for review. Without this new bridge, there will be no mass transit and I am confident that when the state’s economy improves there will be opportunity to provide an additional full bus rapid transit system or other transportation options that will go through Rockland and Westchester counties.”
— Ellen Jaffe – Assemblywoman

• “The public hearings on the new Tappan Zee Bridge demonstrate that we are moving full steam ahead with the goal of breaking ground later this year. I applaud the Governor’s commitment to ensure that the new bridge project is fast tracked and has the full capacity of mass transit for the future. This project is critical to our aging infrastructure and will invigorate our regional economy by creating thousands of jobs.”
— Kenneth P. Zebrowski – Assemblyman

• “Governor Cuomo has presented a practical plan for the construction of a new Tappan Zee Bridge as he puts New York back on the road to recovery, creating thousands of jobs along the way. With its continuing deterioration, this essential corridor in the Hudson Valley is in dire need of help. The Governor’s proposal will build a new, safer structure for thousands of motorists in a cost-effective timeline by building a sturdy bridge and dedicating a lane for mass transit to be added in the near future. I applaud Governor Cuomo for making the Tappan Zee Bridge and the Hudson Valley communities a priority among his initiatives to rebuild the state’s economy and infrastructure.”
— George Latimer – Assemblyman

• “I congratulate Governor Cuomo on his swift action to secure the funds to start the construction of a new and improved Tappan Zee Bridge. I know he shares my concern that we do not build a bridge that is obsolete upon completion, but rather a bridge to sustain us in the coming decades, and accommodate the need for mass-transit and heavy rail. While it would be nice to have all these at once, the reality of potential revenue sources requires us, after fifteen years of discussion, to take some action, and get New Yorkers back to work. I applaud his continued commitment to do so in a prudent, yet expeditious manner.”
— Robert J. Castelli – Assemblyman

• “We need to start construction of a new community friendly Tappan Zee Bridge as soon as possible.”
— Thomas Abinanti – Assemblyman

• “After more than a decade of debate that has led nowhere, Governor Cuomo stepped in with a sensible plan for a new Tappan Zee Bridge, proposing to build a bridge for the future by using the resources available today. The new Tappan Zee Bridge will be built with a dedicated express bus lane so that it will be able to accommodate future mass transit options when our government has the money. Furthermore, the Governor’s plan will generate thousands of jobs and much-needed economic activity. We can start planning the implementation of a mass transit system, but I am eager to see construction of the bridge begin now.”
— Ken Jenkins – Chairman, Westchester County Board of Legislators

• “A new river crossing that addresses and corrects the substandard structural, operational, mobility, safety and security features of the existing bridge is essential for the future economic well-being of Rockland and the lower Hudson Valley. Governor Cuomo found a way to jump start and accelerate the bridge project. I look forward to working with him to ensure a bridge that is not only visually beautiful, but also maximizes the public investment by planning for mass transit when funds become available.”
— Harriet Cornell – Chairwoman, Rockland County Legislature

• “After years of inaction, Governor Cuomo has made real progress towards replacing this deteriorating piece of infrastructure with a stronger, safer and more efficient Tappan Zee Bridge. The Governor’s accelerated plan demonstrates his commitment to creating jobs and sustainable economic development opportunities that will greatly benefit local communities in the Hudson Valley, as well as preserving this crucial artery for New Yorkers. I congratulate the Governor on this significant progress and am eager to help him complete the next steps in building the new bridge.”
— Mayor Mike Spano – Yonkers

• “I commend the cooperative effort of Governor Cuomo, the New York State Department of Transportation, New York State Thruway Authority, and the Federal Highway Administration as they work together to expedite the rebuilding of one of the region’s most important infrastructures the Tappan Zee Bridge.”
— Mayor Robert Williams – Village of Elmsford

• “This is a vital project not only for New York State, but a project of regional and national significance. The existing traffic choked bridge is near the end of its useful life. A new bridge will assure regional mobility, mitigate traffic congestion and enhance the safety for the traveling public. We commend Governor Cuomo, for moving this critical project forward in an expedited fashion, and making replacement of this outdated bridge a priority for quick action.”
— John A. Corlett – Legislative Committee Chair, AAA New York State Inc.

• “Based on the assessment of the project’s limited funding opportunities for the foreseeable future, the decision to exclude the complete build out of a mass transit program was a wise decision. Based on the reality of the funding that is now available, the new Tappan Zee Hudson River Crossing Project will not preclude the planning, design, construction or consideration of future transit modes through the Tappan Zee corridor.”
— Al Samuels – Rockland County Business Association President

• “The bridge and corridor process stalled last year due to one critical impediment – the lack of 17 billion dollars of funding. Last fall, federal seed money was identified, and bridge construction can now fast track, with the stipulation that the construction cost will not exceed $5 to $6 billion; and mass transit would be implemented at a later date. It is ironic that many who initially opposed mass transit are now threatening to thwart the construction process unless a rail element will operate immediately upon ribbon cutting of the new span. In response, the public has now received further assurances from Governor Andrew Cuomo: from the outset, the proposed bridge will be structurally engineered to accommodate future rail transit, which can then more easily be implemented once all environmental and funding issues along the 30-mile corridor will have been resolved.”
— Jan Degenshein – Chair, Rockland County Business Association, architect and planner

• “We are pleased that the primary focus of this project will address the immediate need for a new bridge to carry passenger and commercial vehicles across the Hudson River. This is a main thoroughfare for the trucking industry, providing a vital economic link between New England, New York City and Long Island and the rest of the northeast. We applaud the State of New York for their decision to proceed with the critical bridge replacement, while still preserving the ability to address the needs of other modes of transportation in the future.”
— Kendra Adams – Motor Truck Association

Some property information provided by CoStar, Loopnet, HGAR, Yelp, Rand Commercial Services and other public sources.