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NMI Lake Decatur Watershed Management Plan—Scope of Services&Budget <br /> Task 10: Lake Sediment Planning and Analysis <br /> Spheros will work with Berrini and Associates as a subconsultant in order to support the City with Lake Sediment <br /> Planning and Management. The following activities are proposed: <br /> 1. Sustainable sediment management alternatives and preliminary analysis <br /> o Identify and outline sustainable sediment management alternatives, including options such as <br /> strategic sluice gate operations,Water Injection Dredging(WID), and sediment bypass solutions. <br /> o Conduct preliminary research and technical and feasibility analysis of identified alternatives. <br /> o Evaluate potential environmental, social, regulatory, and economic considerations. <br /> o Hold coordination meeting with the Illinois EPA and U.S.Army Corps of Engineers to discuss regulatory <br /> and permitting implications. <br /> o Provide recommendations for alternatives to advance into detailed assessment. <br /> 2. Lake sediment analysis <br /> o If needed to further evaluate sustainable sediment management alternatives, a lake sediment <br /> sampling plan will be developed based on findings of the above activity. <br /> o Sediment samples will be collected using an Ekman dredge or core and submitted to laboratories for <br /> parameters important for informing and guiding sediment management alternatives, including <br /> strategic dredging/disposal. <br /> ■ note:our team will be working with the University of Illinois and Illinois State Water Survey in <br /> the fall of 2025 to collect sediment cores for phosphorus research for another project. We <br /> intend to use this opportunity to analyze additional data from these cores using the current PO. <br /> 3. Lake sediment transport dynamics <br /> o Analyze sediment transport dynamics during up to two significant storm events in 2026/2027. <br /> o Collect ACDP cross-sections in key lake basins (Sangamon River, Big/Long Creek, and Sand Creek) to <br /> map 2D velocities and relative sediment concentrations. <br /> o Collect isokinetic, depth-integrated sediment samples during storm events to support calibration of <br /> ADCP-derived sediment analyses. <br /> o Use results to characterize the dynamics of sediment transport through the lake in order inform <br /> sustainable sediment management solutions and guide future reservoir management strategies. <br /> 4. Bathymetric surveying (planned for 2027) <br /> o Conduct a resurvey of three sediment trap areas and selected lake cross-sections (to be determined) <br /> using a motorized boat,XYLEM SonTek M9 Acoustic Doppler Profiler, and GPS receiver. <br /> SPHER#S <br /> ENVIRONMENTAL <br />