27CRDLWBMBALM-0001 - Alum Applications at Casey Lake (Tama Co.)

Objective: This contract will include alum application for Silver Lake (Delaware County), a priority restoration lake in Iowa, to reduce phosphorus concentrations in the lake and thereby decrease the frequency and intensity of algal blooms. Background information: 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 2020, the LRP hired Shive Hattery and Limnotech to investigate restoration alternatives at Silver Lake, a small natural lake located in Delaware County, including a dredging feasibility study and modelling effort to show how different restoration practices (including an alum application) would reduce phosphorus concentrations in the lake. As a part of this study, sediment cores were collected from the lake bottom to estimate the portion of the total phosphorus load that was attributed to internal loading. Additionally, a watershed model was utilized to determine the amount of phosphorus coming to the lake from the watershed. Silver Lake is a high priority for restoration, and the LRP has been working with the local community over 10 years to stabilize water levels in the lake and implement watershed best management practices to reduce phosphorus loads from the watershed. The study determined that an alum application program was the most cost effective and lowest risk restoration alternative for improving water quality. Silver Lake was re-cored in late 2025 to confirm alum and sodium aluminate quantities needed to develop an accurate dose for inactivating phosphorus being released from the sediments at Silver Lake. This alum application program, spread over two doses, will help inactivate phosphorus being released from the sediments at Silver Lake and improve overall water clarity and quality. Internet website where contract terms and conditions are posted: http://www.iowadnr.gov/InsideDNR/RFPBidLettings.aspx It is advised to "Save Progress" often and especially after uploading documents. NOTE: Anytime the Respondent opens their bid after the initial submission, they MUST certify and resubmit. No information will be lost from the initial submission. NOTE: Respondent must approve and resubmit their Proposal after an amendment has been posted by the Issuing Officer. If the Proposal was submitted before the amendment, all information will be saved. The Respondent only needs to read and acknowledge the amendment. Instructions for Amendments: Answer the newly posted question in the Questions Section, and CERTIFY and SUBMIT your proposal again (if previously submitted).