The Siphon Bridge in Manistique, Michigan
The Mackinac Bridge is heralded as one of the great engineering feats of its time and still stands as a definitive icon of the upper peninsula of Michigan. The upper peninsula has seen a long list of engineering marvels created during the lumber and mining booms of previous centuries. One that is unique, perhaps in the world, was the Siphon Bridge in Manistique, Michigan.
In the early 1900's, the Manistique Pulp and Paper Company had overcome tremendous obstacles to harness the power of the Manistique River for their manufacturing facility. In doing so, they built a reinforced dam, a mill and a canal to confine the river. The canal is over 1/2 mile long with concrete walls rising above the river. While the canal worked perfectly to deliver 650,000 gallons of water per hour to the mill wheel, the height of the sides made it nearly impossible to raise bridges across. The fantastic solution was the Siphon Bridge near the Water Tower.
The Siphon Bridge was built in 1919 and the roadway itself was as much as 4 feet BELOW the water level. The bridge was supported by water that was forced under it via atmospheric pressure. The feed flume was 3,000 feet long and 200 feet wide. This whole project was about like carrying the bridge across the river in a half-cylinder set in the water of the canal.