Monday, November 6, 2017

AA Bridge and Argo Dam on Huron River in Ann Arbor, MI

(Bridge Hunter3D Satellite)

What caught my eye is that you generally don't see control gates, Tainter in this case, on low head dams. It is also kinda rare to see all of the hoppers in a grain train looking the same. When I have seen it, the cars look new.
Mark Hinsdale posted
"Huron River Crossing"
A southbound Ann Arbor Railroad grain train, consisting entirely of Norfolk Southern power and equipment, crosses the curving bridge over the Huron River in Ann Arbor MI. 3-22-16
I saved the satellite image because it captured just the two middle gates open. Mark's photo captures the eastern two gates open some and the middle gates opened wider.
Then I noticed the structure upstream of the dam on the right. So I zoomed out. It appears to be a canoe bypass around the dam. For the bypass to remain open, it requires a precise pool level so that just the right amount of water flows through the canoe channels. (I have yet to see the bypass around the dam in Aurora be open.) Did they add the Tainter gates when they built the bypass or could they build the bypass because the pool level was already controllable? Did this bypass use to be a millrace that got repurposed as a bypass?

Update: Bridge Hunter indicates that the concrete-pier bridge was built in 1904. Probably after this steel-pier bridge had a boo-boo. I doubt if the Argo Dam existed before 1904 because the current bridge doesn't have enough clearance above the water to hold all of those cars under the bridge and above the water.
Carl Venzke posted
Huron Valley Bridge collapse of 1904 - Ann Arbor MI
Pat Slade Ray Bennets work

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