Where in the ADK Wednesday: The Hadley Parabolic Bridge
Nerd alert: It’s the only surviving iron semi-deck lenticular truss bridge in New York State.
This week’s “Where in the ADK?” is the Bow Bridge in the Town of Hadley. It is the only remaining example of a semi (or half) deck Lenticular Truss bridge. Bridge nerds Many astute bridge aficionados believe that the Bow Bridge is only one of three iron semi-deck lenticular truss bridges ever built.
Constructed in 1885, this, like other lenticular truss bridges built by Berlin Iron Bridge Co., is made of wrought iron and is pin connected.
The lenticular truss bridge design was developed by engineer William O. Douglas of Binghamton, who patented it in 1878. He then assigned the patent to the Berlin Iron Bridge Company in Connecticut, where he had gone to work as an agent, and patented an improved design in 1885.
Berlin manufactured hundreds of these bridges throughout the late 19th century, most of which were installed in New York and New England, and interestingly in San Antonio, TX.
The Hadley bridge was placed on the National Register of Historic Places in 1977. However, in the following years the bridge would fall into serious disrepair. With the help of federal and state grants, the bridge was restored and resumed operations in 2006.
Aside from its unique main truss, the approach span is notable for its small 3-panel design, which makes it look much more like the original patented "elliptical" truss from which the lenticular design is derived.
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