Pinicon Ridge Park Dam Modification Project
Pinicon Ridge Park Dam
The Linn County Conservation Board owns 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 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 studied the issue for several years, held public input sessions, including providing online materials during the Covid-19 pandemic from staff and professionals in the field about possible concepts to address the priorities of this modification. The Conservation Board accepted a bid on a dam modification project, which began in December, 2022.
- The dam was not removed, but rather lowered 12-18 inches from the top.
- Boulders and other engineered materials were placed downstream to allow fish and paddle sport passage.
- The "swirling water" effect which traps debris and people below a roller dam has been eliminated.
- Due to low water levels along the Wapsipinicon River during the spring and summer, the dam modification project was completed in June of 2023 ahead of schedule.
The dam caused an ecological blockade of aquatic life along the Wapsipinicon River, including the endangered Higgins eye mussel. Fish and mussels may move along the Wapsipinicon River with the newly created "fish ladders" on the west side of the river. The U.S. Fish and Wildlife Service recently stocked the river below the project site and at the Wakpicada Natural Area with over 3,000 smallmouth bass with glochidia (mussel) larvae attached for future growth. Additionally, over 21,000 walleye have been stocked by the Iowa DNR in this area during 2023.
Splash pools on the east side of the river enhances opportunities for anglers with additional fish habitat. Although this area is not a white water park, these new splash pools now allow for kayaks to venture downstream past the new river features. Paddlers may also choose to come to shore and down the walk to access the river past the features. All visitors should respect the river by continuing to keep safety in mind, observe safety signage, and proceed with any water activity with caution.
The project was designed in a way that would not result in higher water elevations upstream or downstream to cause a detrimental impact to Pinicon Ridge Park or the City of Central City. However, the park may still be prone to flooding from excessive rains and/or high river levels upstream, or lower water levels due to drought conditions. Linn County Conservation and its engineering team's goal was to lower the dam while keeping adequate river pool depth upstream.
WHKS & Co. was selected for engineering and design and Boomerang Construction of Anamosa was awarded the $3.4 million contract. The project is funded through Iowa Department of Natural Resources low-head dam/fish habitat, U.S Fish and Wildlife, and Linn County Water and Land Legacy Bonds.
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.