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Clean Water Partnership focuses on dredging, carp control for Lake Okabena

Kids take photos of the beautiful fall colors from a dock in Worthington's Centennial Park in this Oct. 9, 2022

Posted on December 19, 2022

The clarity and health of Lake Okabena was the focus of Friday’s meeting of the Okabena-Ocheda-Bella Clean Water Partnership Joint Powers Board.

The board was established in 1996 to allow the city of Worthington and the Okabena-Ocheda Watershed District to cooperate on projects outside the city that affect Lake Okabena’s water quality.

A report the watershed district commissioned from Carp Solutions revealed this fall that the lake’s carp count is below the critical threshold, meaning the carp are likely not the biggest cause of the lake’s water quality issues.

Multiple elements may be combining to stir up sediment and impact water clarity, particularly given how shallow Lake Okabena is. Natural wind can have a significant effect, as can boat traffic.

Worthington City Councilman Chad Cummings said any boat coming off a boat lift is initially at a depth of four feet or less, and will stir up some sediment even at very gentle speeds.

Though buffalo fish generally do not root around like carp and previously were not believed to be part of the problem, it’s possible that in such a shallow lake they too could be contributing to poorer water quality, said Rolf Mahlberg, president of the watershed board.

The watershed district will continue its efforts to keep the carp population down.


The group also talked about the possibility of dredging, discussing a tour of the Lake Redwood project several of them had taken last summer. The dredging project turned the 2-foot depths in the lake into 22-foot depths, and several boglike islands disappeared entirely.

It took 13 years to get the project permits.

Regarding Lake Okabena, the primary focus for dredging would be Sunset Bay, which functions as a stormwater pond for the rest of the lake, and has gradually been filling up with sediment over time.

Mahlberg cited the long-term history of the lake, pointing out that it didn’t make sense to dredge before taking measures to stop as much sediment as possible from reaching the lake in the first place, as it would simply fill back up again over time.

The pond project on District 518 property near the Intermediate School is one of those measures, and the watershed district was awarded a grant for it this week from the state.

Cummings said many people seemed to think the whole lake should be dredged.

“The reality of what it would cost to do the lake is unrealistic,” he said. “But people don’t realize that.”

Other groups that have opted to dredge whole lakes and river bottoms have massive dedicated funding sources, and spent 15 to 20 years on the projects.

“It is costing (them) millions and millions of dollars. We have dedicated, through the local option sales tax, a few million dollars,” Cummings said. “It is a priority and a discussion that a few million dollars will go to restoration or quality improvement of the lake, but the focus has always primarily been to Sunset Bay.”

He suggested getting the permitting process started soon, since it takes so long to finish.

“This is a long-term process,” said Steve Schnieder, city engineer and Public Works director for the city of Worthington.


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