Alum Applications at Three Mile Lake, Prairie Rose Lake, and Green Valley Lake

High nutrient loading in Iowa lakes, particularly from phosphorus, has accelerated eutrophication and subsequently degraded water quality, impaired ecological health, and reduced recreational opportunities. As a result, many Iowa lakes experience frequent and widespread algal blooms, diminished water clarity, unpleasant odors, oxygen depletion, and fish kills, which have become common occurrences during the open-water season. The Lake Restoration Program (LRP) has been working to develop new tools for managing phosphorus in lakes over the past five years, particularly those that are effective at treating internal phosphorus recycling. The LRP first worked with researchers from Iowa State University and the University of Wisconsin – Madison to better understand mechanisms for internal loading in Iowa Lakes (2020-2023 study) and develop strategies for managing different pathways of internal loading. In 2023, the LRP hired Barr Engineering to investigate the utility of alum as a tool in nine Iowa Lakes, and has since initiated alum application programs at two of the study lakes: Green Valley Lake (Union County) and Prairie Rose Lake (Shelby). This contract builds on work previously completed by continuing the application schedule for the in-lake silt basis at these two lakes and starting an alum application program for Lake of Three Fires. All lakes being treated as a part of this effort are high priorities for the program, and were determined to be good candidates for alum applications, as each exhibited high rates of phosphorus release from the sediments and exhibited favorable conditions for an alum application program. Additionally, water quality modeling showed that phosphorus would be reduced substantially with alum at each of these lakes. Initial applications reduced phosphorus concentrations substantially, however; additional doses of alum are needed to inactivate the remaining internal load in each lake. Vendors are required to submit their bids through IMPACTS at the following link: https://bids.sciquest.com/apps/Router/PublicEvent?CustomerOrg=DASIowa. ISSUING OFFICER: Colton Lullmann CONTACT: (515) 361-0743 or colton.lullmann@dnr.iowa.gov BID CLOSING DATE AND TIME: 10/01/2025 at 11:00 AM CST