The Upper Prior Lake alum treatment is now complete! The contractor finished the alum application on Wednesday, ahead of schedule. Find more details on the alum treatment website here.

Alum treatments have been identified as a way to address high levels of internal phosphorus stored in the lake bottom sediment on Spring and Upper Prior Lakes. Both lakes are listed by the State of Minnesota as impaired lakes due to the high levels of phosphorus.

While phosphorus is an essential nutrient for plants, too much phosphorus can lead to excessive algae growth in lakes. Excessive algae is not only unsightly and undesirable for recreation, it can also reduce lake oxygen levels leading to fish kills and kill beneficial aquatic plants by blocking sunlight. An alum treatment reduces internal phosphorus by applying aluminum sulfate (alum) to the lake; the alum binds to the phosphorus making it unavailable for algae growth.

Alum treatments are only one of many ways the Prior Lake-Spring Lake Watershed District is working to improve and protect water quality in your local lakes and wetlands. Reducing the incoming sources of phosphorus and nutrients to the lakes is also important.

We’re looking forward to a cleaner lake!