Alum Treatment on Forest Lake 2025
The Comfort Lake – Forest Lake Watershed District (CLFLWD) will be conducting an alum treatment on Forest Lake to treat excessive levels of phosphorous beginning on September 30th. The application will be focused on the second basin of Forest Lake and in water depths greater than 15 feet.
Alum treatments have been used since the late 1960s to treat high levels of phosphorus in lakes. Excessive phosphorous is the leading cause of nuisance algae blooms; in fact, one pound of phosphorus can produce 500 pounds of algae. Alum effectively binds to the phosphorous in the water and then sinks to the bottom of the lake where it is no longer available for the algae. This is the second phase of the alum treatment for Forest Lake. The first phase was in fall of 2023. Since then, CLFLWD has been monitoring the water quality to determine the effectiveness of the initial treatment and calibrate the dosage for the second treatment. The data indicates the first treatment was successful, and the upcoming second treatment will further reduce the phosphorus, and algae, levels in Forest Lake.
Boating, fishing, and other recreational activities will not be restricted during the alum treatment, but the CLFLWD is asking boaters to give the application barge some room to maneuver as it applies the alum.
If you have any questions about the alum treatment, feel free to reach out to CLFLWD Project Manager Blayne Eineichner at 651-395-5857 or by email.
