“Centerville Lake is considered impaired,” said Matt Kocian from the Rice Creek Watershed District. “That means it has too much algae fueled by too much phosphorus, so we’re working to change that.”
Specifically that change is coming in the form of alum treatment on parts of Centerville Lake that are more than 10 feet deep. Kocian is hoping this will make the lake clearer in the future.
“Alum is short for aluminum sulphate,” Kocian said. “What alum does is control internal nutrient loading phosphorus. So phosphorus is algae food. There’s phosphorus that is being recycled inside of Centerville Lake. What this product does – what aluminum phosphorus does – is binds with that phosphorus, kind of cuts off the food source for the algae. Makes the water clearer.”
The treatment is applied by a barge, which has plastic containers on it that are constantly refueled. A shiny tanker truck gets the process started by pumping the liquid into giant alum-filled drums just a few yards from the lakeshore.
“The barge goes out,” Kocian said. “It’s applying aluminum sulfate for maybe half an hour, something like that. It comes back in to refill. Goes back out. That process continues all day long for about a week and a half or two weeks.”
Two-phase project
This is a medium to large size project. Phase one of the Alum treatment began in 2024. Phase two started in late April and should be finished by early May.
“It’s used very commonly across Minnesota and across the United States,” Kocian said. ” It’s been used for many years. Alum almost always works in lakes in terms of making lakes clear and cutting off algae. The trick is really in insuring that it’s going to last a long time. It’s not cheap. This project is costing between $900,000 and about $1 million. So you want to make sure it has a good long life span.”
Kocian believes the treatment will do wonders for the lake.
“We’re really excited about this project,” Kocian said. “I think that there’s a great chance that we can get Centerville Lake off the impaired waters list. Really hopeful that this is going to be a nice lake to recreate on for the next 15 to 20 years.”
Keeping lakes off the impaired waters list requires everyone to chip in and do their part to prevent phosphorus from getting into the water.
“It’s really important that all of us – the watershed district, homeowners, city partners, everybody – continues to work to reduce the amount of phosphorus and nutrients that’s coming off the landscape,” Kocian said.
Centerville Lake is 474 acres in size and the deepest spot is 19 feet.
