Pinicon Ridge Park Dam Modification Project

Pinicon Ridge Park Dam

The Linn County Conservation Board ownPinicon Ridge Park Dam looking west, intertube swirling in the middles the low-head dam in Central City. The dam was built in 1967 on the Wapsipinicon River downstream from Pinicon Ridge Park, just east of Highway 13. The dam has surpassed its expected 50-year life.

Initiatives to modify low-head dams have been taking place throughout Iowa to not only improve the water quality of rivers and streams, but to improve safety, increase the environmental health and population of aquatic life in the river, and to provide recreational opportunities. 

Linn County Conservation has been studying the issue for several years, held public input sessions, including providing online materials from staff and professionals in the field about possible concepts to address the priorities of this modification. The Conservation Board accepted a bid on the modification project to begin after October 15, 2022.

The existing dam will not be removed

...but rather modified through the lowering of the top of the dam 12-18 inches, and placement of boulders and other engineered materials downstream to allow fish and paddle sport passage. The “swirling water” effect which can trap debris and endanger anyone caught will be eliminated. Fish and mussel passage through a “fish ladder” on the west side of the river will eliminate the current ecological block and promote healthier populations of these species north of the dam. Splash pools on the east side of the river will promote both safe paddle sport passage and enhance opportunities for anglers through additional fish habitat. The project features a no-rise design not resulting in higher water elevations upstream or downstream that would cause a detrimental impact to Pinicon Ridge Park or the City of Central City. Linn County Conservation Deputy Director Daniel Gibbins stated: “The park areas, such as the campgrounds and watercraft concession may still be prone to flooding from excessive rains and high river levels upstream, but not as a result of this dam project design. We worked hard to find the right balance of lowering the dam while keeping adequate river pool depth upstream for park and river recreation along the Wapsi,”

Read on....

Dual Design

Pinicon Ridge Park dam low-head dam dual function conceptThe design addresses the goal of improving safety, fish passage, and recreational opportunities such as fishing and paddling.

Dam Modification site plan 

Additional Resources

Dam Safety

Numerous river rescues have taken place around the state at low-head dams (including two deaths over time at the Pinicon Ridge Park dam). These structures pose a risk to swimmers, boaters, and anglers, due in part to the recirculating current below the dam that can trap victims. Iowa Department of Natural Resources River Programs coordinator Nate Hoogeveen discusses the improvements to safety that dam modification projects create.

Dam Safety - Iowa Department of Natural Resources (Video)

Fish and Mussel Passage

The Wapsipinicon River is abundant in over 800 aquatic species, and the dam structure is currently an impediment to passage upstream. Data has been collected from successful migration patterns after other dam modification projects in eastern Iowa. Paul Sleeper, Fisheries Biologist for the Iowa Department of Natural Resources, explains the negative impacts a low-head dam has to aquatic life and the environmental health of the river.  

Fish Passage - Iowa Department of Natural Resources   (Video)

Fish passage is critical for mussel passage along the Wapsipinicon River. Efforts continue to restore the mussel population, including the endangered species Higgins eye pearlymussel. Louise Mauldin, Fisheries Biologist from the U.S. Fish and Wildlife Service and her team, detail the importance of freshwater mussels. 

Mussel Community and Importance of Fish Passage at the Dam Site - U.S. Fish and Wildlife Service (Video)

The Reproductive Cycle and Importance of Freshwater Mussels - U.S. Fish and Wildlife Service (Video)