Would an Iron-Enhanced Sand Filter Help Fix Eagle Lake’s Phosphorus and Sediment Problems?
It looks promising.
Eagle Lake’s fundamental challenges – excessive weed growth, poor water quality/algae blooms, and gradual sedimentation of the lake bottom over time – stem from too much phosphorus and sediment entering the lake from the two inlet streams (Eagle Creek and Oakcrest Creek). The Eagle Lake Watershed Task Force, which is jointly sponsored by the Eagle Lake Improvement Association and the Eagle Lake Management District, has been grappling with how to improve the situation.
These challenges have been worsening for decades and are not easy to fix.
As the Task Force has explored the implementation of the Oakcrest Creek Project, we have learned an unfortunate but important truth. The original Oakcrest Creek project plan focused on improving drainage, reducing sedimentation, and some degree of phosphorus reduction. An underlying assumption was that the water entering the Creek was already lower in phosphorus due to the creation of wetlands and the establishment of buffers at the edges of the farmers’ fields. Our recent data gathering has shown, however, that the phosphorus level in the water entering the Creek is much higher than we thought. The Task Force is therefore looking for ways to accomplish major phosphorus reduction as well.
Enter the concept of the “Iron-Enhanced Sand Filter” (IESF).
This is a relatively new idea that is starting to be used more extensively in lake watersheds in Minnesota. Phosphorus reacts with iron, and under the right conditions this reaction can reduce the phosphorus levels in the water. Laboratory and field experiments conducted through the University of Minnesota have shown that the level of phosphorus in water (e.g. Eagle Lake’s inlet streams) can be reduced by one-half to two-thirds by running the water through a mixture of sand and iron filings. The Task Force recently welcomed an expert from the University of Minnesota to Eagle lake. He spent a day getting to know Eagle Lake, assessing the Oakcrest Creek and Eagle Creek areas, and dialoguing with Task Force members about how we might implement IESF(s) in the Oakcrest Creek area.
The Task Force is aggressively considering using an IESF as the project continues to gain traction in 2018. We invite you to visit our website throughout the summer for updates on this important project.
Brian Younger – Chair – Eagle Lake Watershed Task Force