This blog series started with asking whether Worthington is losing its greatest natural asset: Lake Okabena. Response from the community indicated deep interest in the future of the lake. In Part 2, I addressed algae, a chief challenge to the use and quality of the lake. Giant summer blooms of pea soup wreak havoc on our enjoyment of the lake and its surrounding parks. We considered whether an algae skimmer may be a solution to this problem.
In my final article in this series, we will talk about dredging—a common inquiry in discussing lake quality.
Defining the Problem
If you’re like me, you nostalgically remember the old dredge, “Shawano.” I vaguely recall seeing it at work on Lake Okabena, and distinctly remember its resting place on West Shore. The dredge provided comfort—we believe something good was being done to the lake below its murky waters.
Should we dredge Okabena again? Dredging will certainly solve one problem: Lake depth. We often wish Lake Okabena was deeper. If you have run your motor into the ground or jumped off into the muck, you will probably agree.
And, Lake Okabena always seems like it’s getting shallower. Lakes serve the purpose of sediment retention ponds, and nature eventually reclaims them. Based on studies conducted on local lakes, we lose an average of 1/20th of an inch of the lake each year. If you saw the inflow of sediment into the lake this spring with the torrential rains, you know it can be more in rainy years and you know all that mud has to go somewhere. Many other lakes and rivers around the world no longer enjoy their full use due to sediment fill. In short, Lake Okabena is slowly, and naturally, filling in.
Would dredging do more than make the lake deeper? Hopefully. A study conducted in 1979 on Fairmont’s Hall Lake, similarly situated to Lake Okabena, indicated that dredging Hall Lake allowed for water thermoclines to mix properly, reducing algae and improving game fish. To achieve this, they recommended dredging to an optimal maximum depth of 24 feet.
A historical anecdote from Wgtn.net indicates that dredging did noticeably improve water quality in Lake Okabena too: “Gradually over the years of dredging, the removal of large amounts of silt and the natural wave action of the lake allowed the lake to cleanse itself and bring a return of clean sand on the shores and a decreased muddy bottom for swimming and lake water sports.” I’ve heard many stories of better water quality during our dredging days, and I would enjoy hearing from more people who knew the lake back then to contribute anecdotally.
Why did Worthington start dredging in the first place? In the 1930s, local philanthropist, E.O. Olson, caught a vision for cleaning up Lake Okabena. He experimentally bought a dredge pump and used it to help build the grade. Due to the success of his experiment, he bought Shawano the dredge in the 1940s off the Mississippi River and gave it to Worthington. The city funded its operational costs.
If we want to dredge again today, turnkey solutions exist with dredge companies—they will do it all from equipment to operations to permitting. Hydraulic dredging costs $4-8 per cubic yard. If we want to take 20 acres of the lake down 2.5 feet, we are looking at a cost of $300,000-500,000.
At that price, we are in the ballpark to consider buying a used dredge for Worthington to own (like these from Dredgebrokers.com). It would certainly be beneficial to have our own dredge for continued use, and naturally there would be incremental operational costs. On the other hand, it would be convenient to hire a flat-rate company to show up and handle the details.
A bigger challenge might be what to do with the sediment. Worthington’s old dredge built most of Olson Park, Centennial Park, and many of the other parks around Lake Okabena. It’s not obvious where the sediment would go, but not insurmountable.
Next time you drive across the grade and pass by Olson Park, give a nod to E.O. Olson. He had the foresight and initiative to envision the future of Worthington and extend the value of Lake Okabena decades forward. His dredging took an estimated six inches of mud out across the entire lake—approximately 17,280,000 cubic feet. The value of that today falls between $2-5 million. Without Olson’s foresight, Lake Okabena today would be considerably shallower. We enjoy Lake Okabena and it’s parks today largely because of his vision.
Lake depth is a problem we will need to confront eventually—maybe even dire several generations from now. Lake depth also may contribute to our other woes, such as the muck and algae blooms. Do we suck it up (pun completely intended), and make the investment to start dredging again? Or, do we stay the course and hope Lake Okabena fills very slowly?