Sunday, April 30, 2017

Muscatine, IA Bridges over the Mississippi River

(1891 Bridge Hunter1972 Bridge HunterJohn A Weeks IIISatellite)

While studying the location of a couple of depots in Muscatine, IA, I noticed the Mississippi River bridge moved. It used to be an extension of Walnut Street.

1938 Aerial Photo from ILHAP
When I first saw pictures of the old bridge, I thought it was just another suspended span cantilevered truss bridge that we have now seen replaced several times. But when I read that it was built in 1891, I dug deeper.

Oscar Grossheim1909  photo from the Musser Public Library
It was built with steel cylindrical piers. But, in 1899, a crew of men and a team of horses pulling a load of logs fell 40 feet with the bridge when a piece of ice slammed into the third pier. All of the piers were rebuilt with stone from Cedar Valley, Iowa. The referenced photo shows the old steel piers. (I wonder if this was a quarry. Nature does not make 90-degree angles. There are three other "water pools" in this area along the shore of Cedar River that were probably quarries.) This 1899 collapse evidently taught engineers that steel piers should not be used in rivers because you now don't see any, even in older pictures.

Oscar Grossheim 1909 photo of the levee and High Bridge from the Musser Public Library
If you look at the Bridges--Muscatine search results, you can seem some pictures during the 1922 flood. All of this levee was covered by water because the water had been on top of the tracks at the left side of the above photo. This is a reminder that a side effect of building the dams to create a 9-foot navigation channel was to reduce the variance of the river level. This Iowa-side photo also has an elevation view of a little over half of the cantilevered span. Historic Bridges has a photo of the Illinois side of the cantilevered span.

When I read in the Bridge Hunter facts that the width of the deck was 18 feet, I checked the width of the Hummer Bridge, which I know is a scary bridge because it is skinny and high. The Hummer is 19.7 feet wide. The new bridge is also just two lanes, but its deck width is 32 feet. So I'll bet the local residents were glad to switch to the new bridge and see the skinny bridge demolished in 1973.

The 1972 Norbert F. Beckey replacement bridge has a through steel truss for the 500-foot wide navigation channel with a clearance of 65 feet. The rest of the spans are steel girders.

John A. Weeks III

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