In 2017, Dakota County completed a lake water quality assessment of the Lebanon Hills Regional Park chain of lakes system to study the increasing levels of phosphorous, a nutrient that supports plant growth.
When too much phosphorous gets into our lakes, it causes problems such as algae growth, low levels of oxygen for aquatic life, and murky water which makes it difficult for aquatic plants to grow.
The water quality assessment identified lake bottom sediments within Schulze Lake are high in phosphorus and that an alum treatment would achieve 70 percent of the water quality goal established for Schulze Lake. Dakota County has received a Clean Water Fund grant to address the remaining 30 percent of the water quality goal from upstream runoff sources.
Dakota County applied aluminum sulfate (alum) treatments to Schulze Lake in fall 2019. Alum binds to phosphorus, making it unavailable to algae, limiting algae growth. Water quality continues to be monitored. If phosphorus levels increase, an additional alum treatment could be considered.
Project funding was provided by watershed-based funding through the Board of Water and Soil Resources and the Eagan-Inver Grove Heights Watershed Management Organization with additional support from Dakota County.
Alum is safe for aquatic life and humans
Scientific studies show that alum is safe for fish, invertebrates and humans. Alum is used for treating drinking water as well as in food and cosmetics. Alum treatments have safely and successfully improved clarity within several ponds and lakes within Eagan in recent years and throughout greater Minnesota.