COGGON — A dam built on Buffalo Creek to enhance recreation at a Linn County park ironically has become a recreational liability.
“Now we’re trying to find out people’s connections with the dam and get their input on how we can best mitigate the dam’s threat to public safety and its negative impact on the environment,” said Dennis Goemaat, deputy director of the Linn County Conservation Board.
Toward that end, county, state and federal environmental officials will host a public informational meeting from 5:30 to 7:30 p.m. June 19 at the Coggon Center.
Members of Linn County Conservation, the Department of Natural Resources, U.S. Fish and Wildlife Service and the consulting companies of Riverwise Engineering and Shive-Hattery Inc. will be on hand to seek input and answer questions.
The county built the dam in the mid-1960s to create a recreational impoundment for the enjoyment of users of Buffalo Creek County Park. That impoundment, once covering 35 acres, has filled with silt, creating inhospitable habitat for most aquatic life and an unappealing site for human recreation.
The Buffalo’s only dam — positioned about midway along its 53-mile course from its source in Fayette County to its junction with the Wapsipinicon River at Anamosa — also blocks fish passage, which over time has resulted in more species and more representatives of individual species below the dam than above it.
And, as with most of the 177 low-head dams identified on major Iowa rivers, the Coggon dam — with its hydraulic features and recirculating currents — constitutes a safety hazard, especially during high flows.
Though there has never been a drowning at the dam, the Conservation Board worries that the perception of low risk during low flows will result in deadly behavior during high flows.
Goemaat said the county has no preconceived notions of the best mitigation practice, which include removal, partial removal or conversion to a rock arch rapids among other options.
Four reaches of the creek, including those immediately above and below the dam, are included on the state’s impaired waters list.
David Suchan, Buffalo Creek watershed coordinator with the Iowa Department of Agriculture and Land Stewardship, said four factors contribute to the impairment — sedimentation, nutrient load, stream modification and stream alteration.
The dam is part of the problem, as it disrupts connectivity between the upper and lower reaches of the creek, Suchan said.
Water quality above the dam is slowly improving, said Suchan, who coordinates a watershed improvement project on upper and middle portions of the Buffalo, in which farmers get cost-share funding to install terraces, grass waterways, filter strips and other conservation practices intended to reduce the volume of sediment and nutrients entering the stream from farm fields.
By 2015, 60,000 acres of the 97,900-acre watershed above the dam will have been targeted for conservation improvements, Suchan said.
The goal, he said, is to get the Buffalo off the impaired waters list.
Improved fish passage and habitat enhancements as part of the mitigation should improve angling below and above the dam, according to Goemaat.
The county has received a $48,000 state river programs grant to pay half the cost of the project’s study and design phase, he said.
Nate Hoogeveen, the state’s river programs coordinator, said grant funds will be available this fall to help pay for the mitigation work.
Goemaat said the county hopes to be in a position to apply for additional funding by this fall.
Hoogeveen said the U.S. Fish and Wildlife Service has been impressed with efforts to remove Buffalo Creek from the impaired waters list and may be in a position to help fund the dam mitigation.