Plans are moving forward to reconstruct the Coon Rapids Dam to make it a more effective barrier against invasive fish species on the Mississippi River.
Construction on the Anoka County side of the dam is expected to begin next spring, followed by work in Hennepin County during 2014.
The Minnesota Department of Natural Resources (DNR) hosted an open house Nov. 12 at Anoka’s Green Haven Golf Club to update residents on the progress of the project.
Property owners along the river had plenty of questions about both the reconstruction of the dam and how it would affect their shoreline.
According to Jason Boyle, a state dam safety engineer with the DNR, 86 people signed in at Tuesday’s session.
The construction process was outlined at the meeting by Marty Weber, an engineer with Stanley Consultants, the firm hired to design and engineer the reconstruction project.
The current rubber gates will be replaced with a steel system. A new stilling basin will also be constructed on the Anoka County side of the dam, according to Weber.
“The estimated life span is 50 years,” said Weber after being asked how long the reconstruction would be good for. “It has to be maintained during that time. You can’t just walk away from it for 50 years.”
It will be easier for the new gates to handle ice in the spring, because the water passes over, rather than under as it does with the current gate system, he said.
The DNR’s Coon Rapids Dam rehabilitation project is being funded by $16 million from the 2011 state bonding bill, approved by the Minnesota Legislature and signed by Gov. Mark Dayton.
In addition, to make the dam a more effective barrier to the migration of invasive fish species, like Asian carp, the reconstruction will also include the repair of downstream scour damage discovered in 2009.
A $3.5 million contract for the gates has been awarded to the Rodney Hunt Company, while the bid award for construction will likely take place in March.
As part of the long-term management to protect from the migration of invasive species, the six-mile recreational pool above the dam will be left at the summer level year round, reverting to how the dam operated during its first 60 years, said Weber.
That concerns many residents who aren’t sure how their properties will handle the punishing ice break up in the spring.
Karen Rosar of Coon Rapids has lived on the Mississippi River for 20 years. Her property has extensive shoreline work.
“Our concern is the damage that could happen this year with the pool level being left up,” said Rosar.
Dock systems and retaining walls could take a beating during the ice break up next spring when river levels are high.
Rosar’s neighbor Tom Murman is new to the river. He said there has been little bank stabilization done on his property.
“People generally want to do the right thing,” said Murman, who is holding off on doing any work until he sees what happens next spring.
The Anoka Conservation District and Hennepin Conservation District are assessing shoreline stabilization issues along the pool above the dam to develop strategies for public outreach and possible funding for improvements.
The ACD received a $10,0000 grant from the DNR for this project.
In the past, the recreational pool level has been drawn down during construction on the dam. Not this time.
“The pool will remain at the recreational level during construction,” said Weber.
While this does make the project more expensive, it will help to protect against the carp moving upstream, he said.
Low water levels upstream could mean easy access for the high flying fish.
While there has been DNA found upstream of the Coon Rapids Dam, Dale Homuth, senior manager of the DNR’s division of ecology and water resources, said it is still not clear how that DNA got into the water.
According to Homuth, the dam will also act as a barrier to native species, like white bass, that could be damaging to fish populations upstream.
The pool stretches six miles upstream of the dam. It will be maintained through the construction of a coffer dam – an earthen structure designed to hold the water in place.
The contractor will access the dam from 99th Avenue in Coon Rapids on the Anoka County side and from West River Road in Hennepin County, Weber said.
While the reconstruction of the dam being led by the DNR, the dam is owned and operated by the Three Rivers Park District.
“We have maintained the dam for 40 years and we will continue to do that under this agreement with the DNR,” said Margie Dahlof, associate superintendent with Three Rivers Park District, referencing a joint powers agreement that exists between the agencies.
Three Rivers already budgets for maintenance of the dam from funds that largely come from suburban Hennepin County taxpayers.
Construction will impact recreation in the area around the dam, including the closure of the pedestrian walkway in 2013 and 2014. Additionally, a portion of the Anoka County Parks trail system will be closed from April to November of 2013, along with the boat launch near the Anoka County Parks Visitors Center, although the Champlin boat launch is expected to remain open.
For more information and updates on the project, visit coonrapidsdam.net.
Mandy Moran Froemming is at firstname.lastname@example.org