Tamarack Lake, part of Tamarack Nature Center, is a shallow lake that is listed as impaired for nutrients. Alum (aluminum sulfate) treatments help reduce algae growth and improve water clarity and quality. In turn, this allows native aquatic plants and wildlife to thrive.
This project is financed through VLAWMO capital improvement funds.
Tamarack Lake is a shallow lake with a maximum depth of 10 feet. Pre-project, the lake had limited levels of native aquatic vegetation. It is listed by the MPCA as impaired for high nutrient levels, primarily due to internal loading. This refers to the process of phosphorus being released from lake sediments over time, spurring further algae growth in the lake.
Alum treatments have been used by water resource professionals since the 1970s as a method for reducing phosphorus levels. A feasibility study conducted with Barr Engineering in 2023 determined that an alum treatment would be the best means for working to improve water quality in Tamarack Lake. Alum (aluminum sulfate) treatments help lower phosphorus levels in a water body by binding to phosphorus. This helps boost overall water quality.
Rigorous review of water quality monitoring data preceded project implementation. An in-lake alum treatment was recommended as the best means to work toward meeting water quality goals moving forward.
When alum enters water, it reacts and forms a substance known as floc. Floc binds to phosphorus as it sinks to the bottom of the lake. Settled floc helps keep phosphorus in place, preventing it from contributing to further algae growth.
Partnership is key to this project. Ramsey County Parks and Recreation and Ramsey County Soil and Water Conservation Division have provided a temporary access agreement to allow the project to occur. Tamarack Nature Center provides coordination, collaboration, and assistance with logistics during applications.
The first phase of the alum treatment on Tamarack Lake was applied in spring 2025. The project will move into its fourth phase in spring 2026. When the fourth phase is completed, the project will transition into monitoring and maintenance.
This project is ongoing. Check back for project updates.
