Emergency Swing Dam

Most Recent Visit: May 14, 2006

Key Facts

Bridge Name	Type	Road	Location	City	Crossing
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.

The Canadian canal was fourteen years old in September 1909, having been officially opened on September 7, 1895. The lock was built between 1888 and 1895.

On June 9, 1909, the Perry G. Walker, owned by the Gilchrist Transportation Co. of Cleveland, Ohio, proceeded up the St. Marys River intent on locking through the American canal. Captain Moshier was impatient. He could see several vessels ahead of him also awaiting upbound passage. He began moving his vessel towards the Canadian canal, intent on a quick lockage. The vessel continued up the lower approach. The master, ignoring previous instructions to moor at the southeast pier to await passage, kept moving upwards.

Finally the order to reverse engines was sounded. The Captain made an effort to reverse the engine but there was a misunderstanding of the signals and the engineer did not reverse the engine. It was too late to stop the vessel which was moving at eight or nine kilometres per hour and was within 70 metres of the lock gates.

The Walker struck the south main gate, forcing it back and allowing the force of water to push the north main gate over. The rush of water threw the Walker back, her bow swinging to the south. The Assiniboia was carried down against the Walker, striking the starboard side.

The Crescent City dropped onto the upper wall carrying away the timber work. Leaving the lock, she surged ahead. Suddenly the Assiniboia dropped her anchor, swinging her stern over towards the north pier and the Walker. Immediately Captain Rice called for full speed astern. Slowly the Crescent City responded, swinging her stern to starboard at the last moment. She struck her starboard beam on the Assiniboia and avoided the Perry Walker.

Either the Assiniboia or the Crescent City in their downward drop struck the south main gate, breaking it diagonally in two. Surprisingly no one was hurt during this accident.

With the gates being swept away, it was necessary to bring the Emergency Swing Bridge Dam into operation. This was the first time the structure was required in an emergency situation. The emergency swing bridge dam stopped the flood of water, allowing repairs to be done on the canal and the lock.

There was extensive damage to the valves, the wooden gates, the stonework and the timber on the lock floor. All of the repair work was completed by June 21, 1909, and the canal was reopened.

The canal had been closed for repairs for a total of twelve days. Considering the damage done, the repairs were made in a short period of time thanks to the successful operation of the Emergency Swing Bridge Dam.

Above: View of the damage to the locks.

Above: View of the swing dam in operation.

Excerpts taken from:

Harrison, R. “The Break at the Canadian Canal, Sault Ste. Marie, Ontario, 1909". Inland Seas. Volume 34, No. 2, Summer, 1979. pgs 104-109.