5.7. SR 12-06-2010 - Laserfiche WebLink

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• Structure: Coon Rapids Dam. • Location: River Mile 866.2. • Dam Width: 2,150 Feet Overall, 1,000 Foot Longest Structure. • River Elevation (Pool): 823 Feet. • River Elevation g 10 Feet. (Outflow): • Water Fall: 13 Feet. • Date Opened: Built 1913, Rebuilt 1997. The original dam at this location was built in 1913. It was constructed as an earth and concrete structure resting on wood and steel piles. Demand for hydro power dropped in the 1960s, and the dam was abandoned on December 31, 1966. The dam was taken over by the county park districts to be used as a regional recreation area. The dam and the overhead pedestrian bridge was removed and rebuilt over a two year period from 1995 to 1997. The old dam had 33 gates. The replacement dam has 10 gates, but they are much larger gates than were found on the old dam. Five of the gates are crest gates, which means that water flows over the gate, and the gate can lift up to stop the flow of water. Four of these crest gates have inflatable rubber bladders. The bladders can be inflated to hold back more water and raise the level of the dam pool. The Coon Rapids Dam is the largest dam in the world to use these inflatable rubber bladder gates. The Coon Rapids dam does not have a lock system for navigation traffic. That means that this is the true head of navigation for the great river. All dams south of this point have locks and are primarily for navigation, with the Keokuk Power Dam being the notable exception of having a large powerplant. The Coon Rapids dam is primary for recreation to maintain a constant pool depth. Dams north of here were installed for a variety of reasons from flood control and reservoir management to hydro power and logging. The photo above is looking east across the main river channel structure. The photo was taken during a period of high water. The noise and power of the water flowing through this dam is nothing short of amazing. The photo below is looking east towards the walkway that runs across the top of the main dam structure. This walkway is open to the public and is heavily used by pedestrians, bikers, and rollerbladers.