Isanti Soil & Water Conservation District
Final Alum Treatment on Blue Lake Completed
What to Expect During and After the Blue Lake Alum Treatment
Blue Lake will get its second alum treatment from September 11th - 14th, 2024, to address phosphorus in the lake. Here is what residents and lake users can expect during and after the treatments. Please reach out to us at the Isanti SWCD if you have any questions at 763-689-3271. This article can also be downloaded as a PDF.
During: September 11th - 14th
Both boat accesses on Blue Lake will be closed during the alum treatment. Residents are also advised to avoid boating on the lake to ensure the alum settles properly on the lake's bottom.
To apply the treatment, a small barge will apply the alum by injecting it directly into the water targeting the deeper portions of the lake. This process will involve multiple trips around the treatment area, with occasional stops to refill the barge. The boat accesses will be open to foot traffic, so you are welcome to stop by to see it. Please just give the contractors space to work.
The treatment is scheduled for September 11th - 14th, with most of the work occurring on the 12th and 13th. However, the dates may shift if weather conditions are unfavorable. Continue to watch our website for updates.
After: September 15th - on
Once the treatment is over, people may resume using the lake as usual! Alum is safe for humans and wildlife, so you don’t have to waste any time getting back in the water.
You should expect to see an improvement in water clarity once the treatment is done. After the treatment in 2022, there was a noticeable improvement in water clarity after just one day! The Isanti SWCD and BLID will continue to monitor the lake’s water quality for years to come to track improvement.
Excessive wakes, such as those caused by wake boats, have the potential to reduce the efficiency of an alum treatment. Alum works best by acting as a blanket on the lake bottom to trap phosphorus coming from the sediment, so when the lake bottom gets stirred up that blanket is torn. Please be mindful of your wake to help protect the lake.
The Isanti SWCD and BLID are continuing their work to protect Blue Lake by helping landowners around the lake install conservation projects. Please contact the Isanti SWCD if you are interested.
Blue Lake to Receive Alum Treatment this September
Blue Lake will receive its second and final alum treatment this September. The Isanti Soil and Water Conservation District and the Blue Lake Improvement District have been working in partnership to protect the health of Blue Lake. Their work has culminated in an alum treatment to greatly reduce phosphorus in the lake and improve clarity. The treatment was applied to the lake in two doses, the first applied in 2022 and the second to be applied this fall.
The alum treatment will take place from September 11th to the 14th. The Stanford and Stanchfield Blue Lake Public Boat Launches will be shut down during the treatment on the 12th and 13th 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 Blue Lake public boat launches on the 11th and the 14th due to the alum equipment set up. If you are planning to use the boat access 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 indicated an alum treatment is the best next step to protect the lake. It was decided to spilt the alum treatment into two half doses to improve effectiveness and longevity. The first dose, applied in the fall of 2022, was greatly successful and significantly improved the lake’s water clarity.
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 gets 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. Regular updates are available on www.isantiswcd.org as well as answers to frequently asked questions.
Clean Water Fund leads to Blue Lake's Alum Treatment Success
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.'
