We completed the first-ever alum treatment in Isanti County on Blue Lake in September. Over a few days, a small barge went back and forth, injecting alum into the water over the deepest parts of the lake. During the application period, the alum sank to the bottom and collected algae and phosphorus as it descended. The alum on the lake's bottom acts as a barrier to prevent more phosphorus from releasing into the lake from the sediments. This treatment comes after years of installing projects near the lake to reduce phosphorus run-off as part of a larger goal to protect Blue Lake. Both phases were partially funded by a Clean Water Fund Grant which is awarded by the Board of Water and Soil Resources (BWSR).
BWSR was one of the many curious visitors that came to see the treatment. While at Blue Lake, they filmed a video about the treatment. BWSR also published a story detailing our current and past work on Blue Lake, how the Clean Water Fund plays a role in our work, and how people came together to make the alum treatment a reality. Click either image below to watch the video or read the story!
What to Expect After Blue Lake Alum Treatment
Blue Lake received its first alum treatment on September 14th to address high phosphorus levels in the lake and protect lake health. Now, you may be wondering what comes next. Boaters were able to resume using the lake as soon as the treatment finished. Since alum collects particles as it sinks to the bottom of the lake, they were able to notice an improvement in water clarity right away! As the years go on Blue Lake will continue to enjoy improved water clarity since it will have lower phosphorus levels preventing algae blooms. In 2024 the second half dose of the alum treatment will be applied.
There are a few things people can expect and do to help the treatment be as effective as possible. Due to the increased water clarity, residents should expect the possibility of higher plant growth in the lake. Lake plants are very good for lake health and fish habitat. However, invasive species including Curly Leaf Pondweed present in Blue Lake will need to be managed so it does not overtake the native plants. The SWCD and the Blue Lake Improvement District are prepared for increased plant growth and have created a vegetation management plan to prevent the possibility of invasive plant overgrowth.
Wake boat users can have an impact on the effectiveness of the alum treatment. The treatment works by forming a barrier on the bottom of the lake, like a blanket, to prevent phosphorus stored in the sediment from being released. Alum was applied in lake depths over 20 feet however, studies suggest wake boats can disturb the lake bottom at depths over 20 feet due to their unique design. Therefore, wake boats are able to disrupt the alum barrier and reduce its effectiveness. If you own a wake boat and enjoy time on Blue Lake, please reduce your wake to protect the lake, or consider visiting other waterbodies.
Interested in hearing what else you can do to protect Blue Lake? There are simple steps anyone can take to protect their lake. Those that visit the lake can prevent the spread of aquatic invasive species, and those living near the lake can take steps to reduce their phosphorus runoff. Blue Lake residents can contact the Isanti SWCD or Blue Lake Improvement District to learn ways to get involved. We all have a part to play to protect our beloved natural resources!
The alum treatment was paid for by a Clean Water Fund Grant, and the Blue Lake Improvement District provided the necessary grant match.'
The Alum Treatment has Begun!
Tuesday September 13th the alum treatment application began. The small barge went back and forth injecting alum into the water over the deepest parts of the lake. During this application period, the alum will sink to the bottom of the lake and collect algae and phosphorus as it sinks. Once on the lake bottom, it will act as a barrier to prevent more phosphorus from entering the lake from the sediments. The alum treatment will do wonders for the health of Blue Lake!
The application will take place Tuesday September 13th through Thursday September 15th. The boat launches on Blue Lake will be closed during that time to ensue the application can work efficiently and effectively. However, pedestrians may stop by to see the application taking place. If you take pictures that you would like to share with us, please email them to
Blue Lake to Receive Alum Treatment this September 2022
The dates have been selected for the Alum Treatment on Blue Lake! The Isanti SWCD has been working to protect the health of Blue Lake. An alum treatment has been selected as the next most logical and cost-effective way to protect it.
The alum treatment will take place from September 12th to the 16th. Both Blue Lake Public Boat Launches will be shut down during the application on the 13th, 14th, and 15th to ensure the application will work as effectively as possible. Residents are also advised to avoid boating on Blue Lake during these dates. Parking will be limited at the Stanford Public Boat Launch on the 12th and the 16th due to the alum equipment set up. If you are planning to use the boat accesses on these days, please consider making other plans. As soon as the application is over, people may resume using the lake as normal!
Diagnostics taken on Blue Lake indicate it is at risk of becoming an impaired water body due to an excess of phosphorus in the lake, which fuels algae blooms. The Isanti SWCD is taking steps to reduce the amount of phosphorus in Blue Lake and assure it does not become impaired. Multiple conservation projects in the area surrounding the lake have already been completed by the Isanti SWCD however, these projects are not enough. Studies on Blue Lake indicate an alum treatment is the best next step to protect the lake.
Alum is a safe and widely studied option for lake treatments to reduce the amount of phosphorus present in the water. It works by forming a fluffy aluminum hydroxide solid called a floc when applied to water. As the floc settles, it removes phosphorus and particulates (including algae) from the water column. Therefore, after the treatment, the water should be noticeably clearer! The floc settles on the sediment where it forms a layer that acts as a blanket for phosphorus, so phosphorus released from the sediments cannot enter the water. The alum treatment will achieve 164% of the phosphorus reduction goal the Isanti SWCD set to keep Blue Lake Healthy!
The Isanti SWCD secured a Clean Water Fund Grant to pay for the alum treatment. The treatment also would not be possible without the Blue Lake Improvement District, which is providing a necessary 25% grant match and has been working with the Isanti SWCD to make this a reality. The first treatment is happening this September and a second treatment will be done in 2024. Regular updates are available on www.isantiswcd.org as well as answers to frequently asked questions.
Blue Lake Alum Treatment Dates Announced!
The alum treatment will be taking place September 12th – 16th.
The actual application will occur on the 13th-15th while the other days shall be used for set up/ take down. We ask that people avoid boating on the lake during the treatment days so that the alum application can work as effectively as possible. It is also possible the Blue Lake Public Boat Launch in Stanford Township will be shut down during the treatment days, in which case this page will be updated and a notice will be provided at the access. Thank you for your understanding.
The Isanti SWCD will be sharing pictures and video footage throughout the treatment!