Moody Lake is a 34-acre lake near Chisago City, MN with an average depth of 14 feet and a maximum depth of 48 feet. The lake is eutrophic, experiences excessive summer algae blooms, and has poor water quality (high phosphorus concentrations, large amounts of algae, low water clarity). Moody is listed as impaired for excess nutrients by the Minnesota Pollution Control Agency and has total phosphorus concentrations well above the standard for Minnesota. A substantial amount of phosphorus has accumulated in the lakebed sediments over the years. The sediments release the phosphorus when oxygen levels decrease at the lake bottom. This leaching of phosphorus from the lakebed is called “internal loading” and ultimately increases the amount of phosphorus available for algal uptake and growth. Samples from the bottom of Moody Lake confirmed that phosphorus was very high in the sediments and available for release into the overlying water column.
HAB Aquatic Solutions will conduct the first of two planned buffered alum applications over a 2 day period in October. The application produces a “floc” that settles to the bottom of the lake. The floc has areas where phosphorus in the sediment becomes bound as it leaches from the bottom. The floc effectively intercepts and binds the phosphorus, which makes it unavailable for the algae to use for growth. The goals of the project are to dramatically reduce the internal loading of phosphorus from the sediments, lower the amount of phosphorus in the water column, reduce the amount of algae and improve the recreational opportunities for lake users.
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