Saturday, November 13, 2010

The Bridge Is Over

Carroll Street Bridge.  Aerial photo via Google Maps.

In our old neighborhood, crossing the Gowanus Canal, stands the oldest retractile bridge in the United States.  Built in 1889 and restored a hundred years later, the Carroll Street Bridge stands out for its unique operating mechanism (a sliding bridge?!) and its trapezoidal shape.  I'm no historian, but if I had to guess, it seems clear why they designed such a bridge here in the 1880s: at the design presentation to the Community Board, the residents of the luxury waterfront condos objected to their views being obstructed by a drawbridge.  Actually, while it takes up a great deal of space in plan--it requires a docking platform at least the size of the bridge--it allows vertically unobstructed passage for the entire width of the clear space.

On another note, not once in the half an hour I spent on the bridge last weekend did I catch so much as a glimpse of a six-legged dog or a fish with three eyes.  Progress on the Gowanus cleanup front!

View across bridge to West
Detail of steel tension rod connection

In the photo below, you can see the tracks upon which the trapezoidal bridge slides onto the bank of the canal.  

View of bridge to East

At the risk of stating the obvious--the bridge breaks free at the (what looks to be 45-degree) line separating the cobblestone from the wood planks:

Looking across bridge to East
Wood decking
Pedestrian path
Steel Guide Tracks
The point of departure (West end of bridge)
Local Gowanians dismayed by the absence of Sludgie.
West side of bridge: gate in the open position
Mechanical pulley system on concrete pads
Bridge control house

Here's a clip from YouTube of the bridge in operation:

For further reading, see this New York Times article from 1989 discussing the restoration and designation of the bridge as a landmark, and this post from a blog dedicated to NYC area bridges.


  1. Cool post. Any idea on the actual reason for the mechanism?

  2. I can't seem to find a direct answer, but from what I have read, I would guess it was done this way for a couple of reasons: cost and simplicity. Compared to a bascule bridge*, it seems that the engineering would be less complex, and less material would be used. As I mentioned in the post, the disadvantage is that this type of bridge requires a huge amount of space adjacent to the bridge to accommodate the open position. In the descriptions I've seen of retractile bridges, another advantage might be that there would be no vertical obstruction for the entire width of the passageway, as opposed to a drawbridge, a lift bridge or a bascule bridge. However, this wouldn't seem to be the case with the Carroll Street Bridge, where the permanent segments partially extend out into the canal.

    * Funny little animated GIFs of moveable bridges can be found on wikipedia.