What could have been a huge disaster on Lake Carlos – erosion that led to a breach in the dam near the mouth of the Long Prairie River – is on the mend.

The dam, which is technically a weir, according to the Lake Carlos Area Association, is on the north end of Lake Carlos. The weir is a fixed iron barrier that helps to control the water level on Lake Carlos and because of the lake being part of the chain, can affect the levels of all lakes on the chain.

Last month, the earth on one end of the barrier gave way causing water to rapidly flow out of Lake Carlos and into the Long Prairie River.

David Holtz, a board member of the Lake Carlos Lake Association, said the association became aware of the problem last summer. He said it was temporarily fixed, but that the fix didn’t hold.

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Holtz said another board member, Alan Grundei has been a leader on this project and has been working with the Minnesota Department of Natural Resources to remedy the problem.

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The problem was that the earth on the west side of the weir started to erode creating a by-pass channel, which then widened and caused the barrier to shift.

The permanent fix? The construction of a rock arch rapids, which was set to be built this spring. The project was pushed up and work began on Wednesday, March 3. Funding for it was provided by the Midwest Glacial Lakes Partnership and Outdoor Heritage Fund, created as part of the Clean Water, Land and Legacy Amendment, according to Amanda Hillman, restoration coordinator with the DNR's River Ecology Unit.

Hillman said the construction will take about a month to complete, depending on weather and site conditions.

She also said the dam modification project will address scouring and bank erosion by adding a rock arch rapids to the existing dam on the south end of Lake Carlos. A rock arch rapids is a long, gradual rock ramp consisting of arches of large boulders that spread out the vertical water drop at the dam face and gradually step down water levels. It will not affect water levels on Lake Carlos.

Hillman also noted other benefits of the project, which include reducing dam maintenance and repair requirements, improving safety at the site and reducing downstream erosion.

“We are hopeful and supportive of the plan,” Holtz said.

Holtz said that the lake association had contacted Emily Siira, a hydrologist with the DNR who works out of the Glenwood office, and that she has been great to work with. He said within a week of contacting her that the project was moved up and construction had started.

“The response has been wonderful,” he said.

According to information posted on the Lake Carlos Area Association’s Facebook page, the rock arch rapids will help not only help maintain the lake level, but it will also address the bank erosion issues and improve fish habitat by providing spawning areas, to name a few.

The dam on the Long Prairie River near Lake Carlos consists of metal retaining walls on the river banks with an iron beam across the river. The area that washed out was on the far side and is currently plugged with sandbags. The dam is intended to keep water levels in Lake Carlos at consistent levels. (Lowell Anderson / Echo Press)
The dam on the Long Prairie River near Lake Carlos consists of metal retaining walls on the river banks with an iron beam across the river. The area that washed out was on the far side and is currently plugged with sandbags. The dam is intended to keep water levels in Lake Carlos at consistent levels. (Lowell Anderson / Echo Press)

Additionally, the rock arch rapids will be placed in such a way that it will provide a passable route for people who tube down the river, canoe or kayak.

Although preliminary work has begun, the bulk of the work or the main construction will take place next week.

According to information on the Lake Carlos State Park page on the DNR website, visitors are asked to use extra caution when driving through the area. There will be trucks hauling material and large pieces of equipment in the area and visitors are asked to allow those working to complete their work in a timely manner and not get in their way.

Sandbags on the edge of the dam are currently holding back the water that was flowing unchecked. (Lowell Anderson / Echo Press)
Sandbags on the edge of the dam are currently holding back the water that was flowing unchecked. (Lowell Anderson / Echo Press)

In addition, the Long Prairie River Dam parking lot is closed to the public until further notice.