Tappan Zee Bridge

Information and Findings From Pennsylvania's Historic Bridge Inventory

Discussion of Bridge

The Tappan Zee Bridge was constructed between 1952 and 1955. Captain Emil H. Praeger, U.S. Navy Retired (1882-1973), served as chief engineer for Madigan-Hyland, the designers of the bridge. The bridge is 3.1-mile-long structure supported by a substructure consisting of abutments and 198 piers. It is the longest bridge in the state and one of the longest in the country. It also has the world's ninth longest cantilever span, at 1,212 feet. It has been determined eligible for National Register listing for its significance in the areas of transportation and engineering. The Tappan Zee Bridge is not designated as a National Historic Landmark.  

The Tappan Zee Bridge (NR-eligible) was determined eligible for the NR in 2003 under Criteria A and C. The bridge carries the New York State Thruway over the Hudson River from Rockland to Westchester County. Rockland County officials began to advocate for the construction of a bridge across the river to Westchester County near the present-day location of the Tappan Zee Bridge during the early 20th century. Studies were undertaken at that time which indicated the depth of bedrock under the river bed was too great to permit bridge construction. However, the concept for a Hudson River crossing between the counties was explored again roughly 15 years later due to the creation of NYSTA in 1950 and the Federal Interstate Highway System in 1954, which illustrated a pressing need for a Hudson River crossing between the two counties. In response to this need, the Tappan Zee Bridge was constructed between 1952 and 1955. 

Captain Emil H. Praeger, U.S. Navy Retired (1882-1973), served as chief engineer for Madigan-Hyland, designers of the bridge. To solve the depth to bedrock problem identified in the 1930s, Praeger- who also designed Shea and Dodger Stadiums, the Nebraska State Capitol, and the world's largest telescope in Arecibo, Puerto Rico- developed an innovative system in which eight buoyant caissons were constructed north of the crossing site in a natural clay pit in Grassy Point, the world's largest natural dry dock. Upon their completion, the clay pit was flooded and the caissons were floated downriver into place.

The completed bridge is a 3.2-mile-long structure supported by a substructure consisting of abutments and 197 piers. The piers are erected upon four types of foundations, including river-based timber piles and the eight buoyant caissons. Piers in the river are protected by upstream and downstream ice breakers, and the caissons are also protected by a fender system. In the mid-1980s, notable deterioration of the Tappan Zee Bridge was recorded, after which an extensive repair program was commenced. Targeted repairs were undertaken through the mid-1990s, including repairs to the concrete deck, steelwork, bearings, columns, and piles. Due to the high rate of deterioration, major rehabilitation of the deck bearings, barriers, steelwork, and concrete were again initiated in September 2007.  

The Tappan Zee Bridge is the longest bridge in the state and one of the longest in the country. It also has the world's ninth longest cantilever span, at 1,212 feet. It has been determined eligible for NR listing under Criterion A for its significance in the area of transportation and Criterion C for its significance in the area of engineering. Character-defining features identified in the 2003 SHPO resource evaluation include the bridge's unique caisson support system, the length of its cantilever span, and the total bridge length.

Information From American Bridge Company

American Bridge was prime superstructure contractor for the 7,300' (2,225m) deep-water portion of this 16,000' (4,900m) crossing of the Hudson River above New York City. The three-span channel unit is a 2,415' (736m) cantilevered truss that was constructed by erecting the anchor (flanking) spans on falsework trusses and cantilevering the 1,212' (370m) mainspan from both directions. The 20 deck truss approach spans were constructed at an on-land yard facility and floated into place. Each span was about 250' long by 64' wide by 26' deep (76m by 20m by 8m), and weighed 830 tons (753mt).

Bridge History From Wikipedia (CC-BY-SA 3.0)

With the increasing demands for commuter travel taxing the existing bridges and tunnels, the Port Authority of New York and New Jersey had plans in 1950 to construct a bridge across the Hudson near Dobbs Ferry, New York. The proposal was overridden by New York State Governor Thomas E. Dewey, who wanted to construct a bridge to connect the New York State Thruway across Westchester to the New England Thruway. The Port Authority promised its bondholders that it would not allow any other entity to construct a river crossing within its jurisdiction, which reached to a point one mile (1.6 km) south of Nyack on the western shore of the Hudson River and across to Tarrytown[8] on the eastern shore.

A May 10, 1950, editorial in The New York Times suggested that a site in southern Dobbs Ferry or northern Hastings-on-Hudson, where the Hudson narrowed considerably from its three-mile (5 km) width at Tappan Zee, would be a more appropriate site, and suggested that Governor Dewey work with his counterpart, Governor of New Jersey Alfred E. Driscoll, to craft a compromise that would offer Thruway customers a discounted bridge fare at a more southerly crossing.[9] Two days later, Governor Dewey announced that the Port Authority had dropped its plans to construct a bridge of its own. The location would be close to the Tarrytown-Nyack line just outside the Port Authority's jurisdiction. Dewey stated that World War II military technology would be used in the bridge's construction.[10]

The site of the bridge, at the Hudson River's second-widest point, added to construction costs. The site was chosen to be as close as possible to New York City, while staying out of the 25-mile (40 km) range of the Port Authority's influence, thus ensuring that revenue from collected tolls would go to the newly created New York State Thruway Authority, and not the Port Authority.[11][12][13] A unique aspect about the design of the bridge is that the main span is supported by eight hollow concrete caissons. Their buoyancy supports some of the loads and helped to reduce costs.[14]

Construction started in March 1952 and the bridge opened for traffic on December 15, 1955, along with a 27-mile (43 km) long section of the New York State Thruway from Suffern to Yonkers.[15][16] New York State Governor W. Averell Harriman signed a bill on February 28, 1956, to name the structure officially the Tappan Zee Bridge.[17] In 1994, the name of Malcolm Wilson was added to the bridge's name upon the 20th anniversary of his leaving the governor's office in December 1974, though it is almost never used when the bridge is spoken about colloquially.[18]