|Emergency Swing Dam||Truss||None||Algoma District, ON||Sault Ste Marie||Sault Canal (St. Marys River)|
This Emergency Swing Dam has global significance as the last remaining structure of its kind in the world, a bridge-like dam that can swing out over the water, and lower wickets and shutters down into the water to reduce the flow of water. Although this bridge has only been called into service once, the bridge proved that one time to be a valuable asset. If a boat breaks the locks and releases torrents of water, this dam allows for a temporary slowing of that water flow so that the locks can be repaired and closed once again. I took a photo of a sign near the bridge, which has a description of the history and operation of the bridge, as well as a historic photo and diagram.
This is not a bridge in the sense that it was not built to facilitate the crossing of something. However, that is where the dissociation with the word "bridge" ends. This structure is in terms of design a swing truss bridge, and for that reason it appears on this website as one of the finest and most unusual examples of the structure type I have seen. It was built in 1896 by the Dominion Bridge Company, which was based in Lachine, which is part of Montreal, Quebec. This company also built the nearby stationary spans of the International Railroad Bridge, according to builder plaques on that structure. As a result, it is quite possible that they also built the swing span for the International Railroad Bridge. There are some striking similarities between that railroad bridge and this swing dam. The main thing is the shape of the bridge, which is an unusual combination of a camelback design like this one, while also having very long sections of straight top chords, reducing the curved appearance of the bridge to make it seem more like this bridge.
The Emergency Swing Dam features a Baltimore style truss configuration. Most connections are pinned, although some are riveted. There is v-lacing and lattice all over this bridge! I noted an unusually large number of different steel mill stamps on this bridge. I found Carnegie stamps, Burbach stamps, Consett stamps, and finally, I spotted what looked like A.H.A.V. 1891 to me. the 1891 might refer to some sort of patent date. The bridge itself was built in 1896.
The bridge retains a high degree of historic integrity, with some exceptions. The deck beams are huge on this bridge and are likely not original. Nor is the shed/garage present on the bridge, which probably houses the motor and other machinery. Also, some steel beams were run perpendicular to the deck beams, and steel was welded to them and to some rollers below that handle the chain. This apparently was to strengthen the rollers. There is a weird i-beam that runs the length of the east side of the bridge and is attached to a weird arrangement of bracing in front of the portal bracing. All of this is riveted, but it does not look like it fits in although I think it is probably original anyway. It is definitely old, with rivets and all, and plus I can see it in a 1909 historic photograph. The bridge has been maintained very well, and I noted no major structural detonation. It is good to see this wonderful structure being maintained for future generations. The informative sign near the bridge shows that Ontario is indeed recognizing the historic nature of it and wants to help educate the public about this bridges fascinating history and operation.
This bridge was only used once, way back in 1909. Below is an except from an article about the incident that happened on June 9th. This excerpt was retrieved online here: http://www.pc.gc.ca/apprendre-learn/prof/itm2-crp-trc/htm/accidentcanal_e.asp
The Accident at the Canadian Canal, Sault Ste. Marie, Ontario, 1909
There was a major accident on June 9, 1909 at the
Sault Canal. Downbound from Lake Superior, the Canadian passenger vessel
Assiniboia was waiting in the lock at the Sault to be lowered to the
Lake Huron level of the St. Marys River. Behind the Assiniboia, the
Pittsburg Steamship Company’s steamer Crescent City was just entering
the lock. Captain Frank Rice was asked to lock down with the Canadian
Pacific passenger vessel Assiniboia.
Above: View of the damage to the locks.
Above: View of the swing dam in operation.
Excerpts taken from: