Fall '11

From the President

By David G. Barber

An aspect of canal and waterway structure that we often overlook is moveable bridges. I was recently reminded of this while studying the Wabash River in Indiana. The Delaware and Raritan Canal was also noted for its moveable bridges and a few of them survive if you look carefully at them from underneath. The Delaware Canal also had a couple near its southern end at Bristol.

The New York Canals had many in the enlarged era and they are a notable feature of the western end of today’s Erie Canal. There are a couple on the Chambly Canal in Quebec and the Hennepin Canal in Illinois has several of quite different designs. The Fox Wisconsin Waterway in Wisconsin has several including a bascule bridge due for replacement in Eureka and an abandoned railroad swing span, now on a rail trail, in Princeton. There are others in Appleton and Kaukauna. But, two of the larger ones are on active rail lines across lake portions of the route in remote places on the upper Fox River and Lake Wisconsin.

Recently, when reading a guide to the Wabash River, I found a statement that there were three surviving swing bridges from the former steamboat navigation on the lower river. But, looking at Google Earth, I can see there are probably several more. Most of these survivors are railroad bridges as the structures that have been in use for a hundred years still serve today’s trains. This contrasts to highway bridges which have had to be replaced due to the great increase in traffic volume and truck weights in the twentieth century. A search for these structures is helped by the fact that they often go east west and the through truss structure of the bridge shows as a shadow on the water upstream of the bridge. These bridges have multiple truss spans, but careful study will find one that has a round pier, which is the pivot, in the center of a span and the span is continuous across this pier. While you would at first expect the moveable span, and thus the channel to be in the middle of the river, sometimes it is at one end and half of the swing span is actually over the river bank.

I visited one such site this July at Vincennes, IN, where the formerly moveable east span has recently been replaced by a fixed deck girder span, with the round pivot pier in the middle. From the large trees growing in the swing arc, it is very apparent that it was a long time ago that this bridge last moved. Photos are on our web site.

A most unusual example of the swing bridges is in New York State on the Niagara River just south of the Black Rock Lock. There, the now land end of the railroad bridge swings across I-190 (built on the original route of the Erie Canal) while the other end opens to clear the modern channel approaching the lock.

These bridges are also a part of the waterway story, just as locks and aqueducts are.<span class="style13">

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