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!

The first ever alum treatment on Upper Prior Lake will start Tuesday, May 26. The treatment should take 8-11 days to complete, depending on weather conditions. The contractor cannot apply the alum if it is too windy. The Upper Prior Lake alum treatment is largely funded by grant from the Minnesota Board of Water & Soil Resources (BWSR).

There are no restrictions on recreation on and in the lake during treatment. However, please give the alum barge room to work. The barge applies the alum following computerized tracks across the lake to precisely apply the correct amount of alum to each area of the lake. You can help by moving out of the barge’s way during alum application. The project will be staged out of the lot just north of Charlie’s.

Aluminum sulfate (alum) is used to improve water clarity and reduce algae blooms by reducing phosphorus levels in the lake. Phosphorus is a nutrient naturally found in lakes, however due to development and runoff, excess amounts of phosphorus feed algae blooms. Alum treatments bind phosphorus making it unavailable for algae growth.

Landowners can also do their part to improve water quality:  reduce the amount of turf grass and add native plants to your yard which minimizes your use of fertilizer and improves infiltration. Visit the ‘Get Involved’ section of our website for more information and ideas. We look forward to enjoying a cleaner lake!

For more information and project updates visit the alum treatment project page on our website and the Upper Prior alum treatment website. Contact Jaime Rockney with project questions at jrockney@plslwd.org.