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5. Other criteria can be applied at a later time if it is determined that optimizing the Diversion Channel is justified with this initial evaluation. 6. The 100 and 500-year events for the Red River peak flood event will be analyzed. 7. Peak discharge values from the current Phase 6 unsteady model will be used, which is also being applied to the bridge analysis (MFR-001) currently being updated by the USACE. II. Conduct an Impact Analysis using the HEC-RAS unsteady state software for the most favorable alternatives identified in Task 1. 1. The 100 and 500-year events for the Red River peak flood event will be analyzed using the latest Phase 6 unsteady flow model. 2. River impacts will focus only on the Red River upstream, downstream, and throughout Fargo-Moorhead. Impacts will be compared to those determined in Phase 4 and Phase 5, which may require that the gate operations may be modified to obtain similar impacts. 3. Additional impacts can be further evaluated at a later time if it is determined that optimizing the Diversion Channel is justified with this initial evaluation. III. Develop a preliminary cost estimate for the most favorable alternative identified for optimizing the Diversion Channel. 1. Quantify the cost savings based on unit-cost savings using the Feasibility Study unit prices, focusing primarily on costs associated with earth work and at the Maple River Hydraulic Structure. 2. Additional cost detail can be further evaluated at a later time if it is determined that optimizing the Diversion Channel is justified with this initial evaluation. IV. Prepare a Technical Memorandum (TM) summarizing whether the size of the Diversion Channel warrants additional and more detailed study. V. Evaluate the Diversion Channel upstream of the Maple River to determine the most cost effective channel size. Work includes: 1. Develop the existing ground profiles along the right and left banks of the Diversion Channel upstream of the Maple River aqueduct. 2. Update the 1% and 0.2% chance flood event profiles in the Diversion. Determine the minimum bottom width such that the 1% chance flood event is generally below existing ground. Conduct sensitivity analysis to evaluate water surface profiles and comparing to the original bridge MFR flows and Phase 7.1 flows. 3. Calculate flood inundation flow rates at the Red and Wild Rice River control structures to establish an extreme event flow rate in the Diversion Channel. 4. Evaluation project operations during extreme events, and determine how diversion channel size upstream of the Maple River aqueduct affects the Inflow Design Flood (IDF) event and the corresponding staging area. 5. Provide opinion of optimal channel width based on capital, operational, and maintenance costs along with project operation goals. HMG_TO9-A13_Long.docx 3 DR A F T 3/6 / 2 0 1 5