116 3rd St SE
Cedar Rapids, Iowa 52401
COGGON — Water dances around the rocks and ice in Buffalo Creek not far from Coggon.
Where once stood a roughly 10-feet-tall concrete wall — one of the state's more than 200 dangerous low-head dams — a stretch of rock arch rapids remains, providing safe passage to recreationists and wildlife alike.
With the repositioning of a few boulders at the former dam's site and a final walk-through in late November, officials with Linn County Conservation declared the approximately three-year dam mitigation project complete.
With the Buffalo Creek Dam gone, the county now is shifting focus to possible modification or mitigation of Pinicon Ridge Dam near Central City.
Entities statewide have been working to reduce Iowa's stock of low-head dams, which have been deemed unsafe and damaging to the environment and various wildlife.
'When (low-head dams) were put in, people didn't understand how detrimental to both safety and ecology of the river they were. Over time we've learned that,' said Daniel Gibbins, deputy director with Linn County Conservation. 'Around the state, there have been quite a few deaths from these dams.'
More than 160 deaths
The Iowa Department of Natural Resources has logged more than 200 low-head dams across the state. Many of the those dams were built decades ago to create water recreation areas, provide some level of water management or to generate power. Many are nearing the end of their life span, forcing communities to take on costly upgrades or mitigate the structure completely.
Nicknamed roller dams for the powerful recirculating hydraulics created by the dam's design, low-head dams are dangerous to boaters, swimmers and tubers. Since 1900, low-head dams have caused more than 160 fatalities across the state.
'When water pours over a wall across a river, it kind of jumps back up and creates a mound of water downstream and water flows off that mound of water and back toward the face of the dam,' said Nate Hoogeveen, river programs coordinator with the Iowa Department of Natural Resources. 'It's common and predictable, as far as a hazard goes. The problem is that it's difficult to educate the public well on that — it doesn't always look so dangerous.'
In 2008 — following a year that saw six low-head dam-related fatalities — the Iowa Legislature instructed the Department of Natural Resources to create a low-head dam public hazard program, which included planning and an opportunity for funding local projects.
'The reason our program was really established had to do with drownings that were and to an extent still are happening around the state,' Hoogeveen said.
In addition to being dangerous, low-head dams also block wildlife passage, which is bad for fish and some of the state's endangered mussel species. Low-head dams also block a river's natural siltation process, causing a buildup of silt in the river.
Hoogeveen said the natural resources department tries to leverage state funds — approved annually by the Iowa Legislature — with various federal sources, like the U.S. Fish and Wildlife Service, to provide financial aid to communities trying to address their low-head dam woes.
Since it began in 2008, the program has helped fund mitigation or modification efforts on 21 low-head dams across the state. Several more projects are in the planning stages.
In Linn County, the Pinicon Ridge Dam project has received preliminary approval of a $50,000 grant to begin exploring dam modification. Gibbins said the total design process is expected to cost about $160,000 and other grant opportunities are possible.
Discussion on the Central City dam on the Wapsipinicon River began close to two years ago with a public meeting to gather information.
Gibbins said the county hopes to put out a Request for Qualifications this winter to acquire an engineer tasked with designing the dam modification project. A design could take upward of a year to complete, he added.
Each project is different
While the Buffalo Creek Dam was completely dismantled and replaced by rock arch rapids, Gibbins said each project is approached individually. It's likely the Pinicon Ridge Dam will not go through the same type of project.
'At some point you're either going to notch part of the dam to allow flow through and transportation through, but you've got to keep the pool level for the most part,' Gibbins said.
To help communities afford costly mitigation projects — the Buffalo Creek project has been estimated at nearly $1 million — the state Legislature appropriates funds on an annual basis.
This year the state allocated $500,000 to the Iowa Department of Natural Resource's low-head dam and water trails program. Hoogeveen said funding changes annually, but the program has received as much as $2 million in a year.
In addition to Linn County Conservation's dam projects, the Troy Mills Dam Association also is working to mitigate the Troy Mills Dam — located upstream from Central City on the Wapsipinicon River.
Paul Berland, associate director with Northeast Iowa Resource Conservation and Development, the organization taking point on the Troy Mills Dam mitigation project, said he hopes to start construction on the project Feb. 1, water conditions permitting.
The project has been estimated at around $400,000
'If conditions are right, I would think we could be done in a couple of months with that project,' Berland said.
When complete, the Troy Mills Dam, which was the site of a drowning in 2014, will be replaced by rock arch rapids.
What are rock arch rapids?
Rock arch rapids are man made structures created to replace low-head dams. The dam is partially removed, then rocks are placed in the river to create gently sloping pools and small falls that mimic natural rivers.
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