Watershed district aims to keep new retention pond clean with new technology
WORTHINGTON -- The Okabena-Ocheda Watershed District plans to test a Minnesota-made product this spring that is touted to improve water quality by removing excess nutrients from ponds and lakes.
Midwest Floating Island LLC, (www.midwestfloatingisland.com) based in St. Paul, markets a plastic mesh made of recycled pop bottles and milk jugs that serves as a base for wetland grasses, reeds and sedge plantings. Plugs, or young plants, are placed into the mesh, which is anchored in place on a pond or lake. The plants then feed off the nutrients in the water, producing root systems that can provide habitat and a food source for fish and above-water plants that attract insects and birds.
Okabena-Ocheda Watershed District Administrator Dan Livdahl said the district plans to purchase a 100-square-foot floating wetland, which will be tested in the new Olson Regional Stormwater Pond on Minnesota West Community and Technical College's Worthington campus.
The eight-inch-thick Biohaven, combined with the plants, will cost the district approximately $4,500. Livdahl hopes it can be installed in the pond by late April or early May.
There are a couple of reasons the watershed district is installing the floating island.
"The stormwater pond is there to remove sediment and nutrients, and this will do a better job," Livdahl said. "Also, it's a test. If these do well in a sheltered situation, we may want to try them on Lake Okabena."
One square foot of the Biohaven material is, if well maintained, the equivalent of 18 square feet of natural wetland.
"They're very good at removing pollution from water once they're established," Livdahl said.
The floating island will contain about three plants per square foot.
"The plant roots get a biofilm on it and bacteria starts to grow on it," Livdahl explained. "That uses phosphorus as it grows and that bacteria becomes food for insects, which become food for small fish, which become food for game fish. It's kind of recycling that nutrient from the water and storing it in fish, if everything works out right."
The idea of testing the Biohaven floating island locally came about six weeks ago, when Livdahl and OOWD board member Casey Ingenthron attended the Minnesota Association of Watershed Districts conference.
"It sounds like it does a really good job of initially cleaning the water, along with providing habitat," Ingenthron said.
With concerns about testing the product on a larger body of water like Lake Okabena because of the wave action and ice issues, both Ingenthron and Livdahl said the regional stormwater retention pond makes for a good trial.
"It's small enough where we can justify a small island and evaluate its effectiveness before going out in a bigger body of water," Ingenthron said.
Gordon Heitkamp, Minnesota West maintenance and building supervisor, said the college is "very excited" about having the floating island in the regional stormwater pond.
"We believe that, aesthetically, it's going to add a lot to the appearance of the pond," Heitkamp said. "From our point of view it's a win-win aesthetically and environmentally."
With work nearly complete on the stormwater pond -- some grass seeding will need to be done in the spring -- the floating island will be able to be installed before classes end in the spring.
"Some of the ag classes and environmental science classes will be very much involved in not only the planting, but also of learning how the ponds work and how the plants on the island work," Heitkamp said. "Ongoing, we will be involved in the maintenance and the care of the pond."
Heitkamp is already talking about having a larger Biohaven project on the pond.
"We may have some money left over that the other partners may be willing to put toward that yet (to make it larger)," Heitkamp said. "We don't even have the final cost numbers on the pond done yet."
As for the Biohaven the watershed district is purchasing, Livdahl said it will likely be two separate kidney bean-shaped islands.
"If this works well, I could see us going to the Olson Trust and saying, 'Let's put a few other islands in this pond, and let's try some in Sunset Bay,'" Livdahl said. "If that works, maybe we put some in Slater Park, which is where we have the last submergent vegetation in Lake Okabena.
"It needs to be away from boat traffic and ... it needs to be a fairly sheltered location," he added. "If we want to do these on Lake Okabena, we want the public to see them and agree that it's a good idea."
While there are anticipated challenges with using the floating islands on Lake Okabena, Livdahl said he is also concerned about potential challenges with the floating islands in the retention pond.
"The biggest challenge this year will be if we have low water levels," he said. "You need to have at least three feet of water to put them in."
Other challenges include keeping geese from destroying the young plants secured in the Biohaven. Livdahl said they will need to install some type of fencing around the floating island to prevent geese from accessing the plants.
Daily Globe Reporter Julie Buntjer may be reached at 376-7330.