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Fort Morgan Farms,LLC <br /> Delta Reservoir—West Cell Preliminary and East Cell Conceptual Design <br /> April 16,2021 <br /> The preliminary/conceptual design was developed to reduce bank protection measures and <br /> to increase storage volume while not negatively impacting the floodplain elevation of the <br /> existing condition. The elevation of the proposed berms ranged between 4606.0 and 4611.5 <br /> feet, and an inflow spillway for the West Cell was designed to direct and control flows <br /> entering the reservoir from the CLPR during the 1-PAC flood as well as to increase storage <br /> volume. An unsteady 2D hydraulic analysis of the proposed design was conducted and <br /> evaluated to meet the design criteria. The preliminary design of the West Cell includes an <br /> inflow and outflow spillways located at 4602 feet crest elevation accompanied by two fuse <br /> plugs at each spillway designed to fail when the water surface elevation upstream of the <br /> spillways reaches 4607 feet elevation. This design allows for additional potential storage of <br /> 355 AF from the maximum reliable storage of 4,207.15 AF. The outflow spillway for the East <br /> Cell extends almost the entire southeast edge along the SPR to allow for blending of the <br /> flows from both CLPR and SPR, and prevent any increase in base flood elevations of the <br /> SPR. <br /> References <br /> 1) AECOM, CHAMP Study of the South Platte River, HEC-RAS Hydraulic Model Version <br /> 5.0.3. Obtained from AECOM upon request, September 2017. <br /> 2) AECOM, Risk MAP Study of the Cache La Poudre River, HEC-RAS Hydraulic Model <br /> Version 5.0.5. Obtained from AECOM upon request, January 2019. <br /> 3) Anderson Consulting Engineers, Detailed Hydraulic Evaluation and Floodplain <br /> Mapping for Cache La Poudre River, Boxelder Creek and Indian Creek as part of the <br /> FEMA Risk MAP Cache La Poudre River Watershed Study, ACE Project No. <br /> COCWCB25, August 2017. <br /> 4) AECOM, Hydraulic Analysis Technical Support Data Notebook for the South Platte <br /> River, prepared for Colorado Water Conservation Board (CWCB) as part of the <br /> Colorado Hazard Mapping Program, CWCB Contract#CT 2016-1452, March 2018. <br /> 5) Federal Emergency Management Agency, Letter of Map Revision (LOMR) Weld <br /> County Road 47 Bridge, Weld County Unincorporated Areas, Colorado, Case No.: 16- <br /> 08-0665P, June 2017. <br /> 6) Urban Drainage and Flood Control District, Urban Storm Drainage Criteria Manual <br /> Volume 1, January 2016. <br /> 7) URS, South Platte River Watershed Phase 2 Hydrologic Evaluation, Post September <br /> 2013 Flood Event. Prepare for CDOT Region 4 Flood Recovery Office, Draft. <br /> Appendices <br /> Appendix 1 — Figures <br /> Appendix 2 — Modeling/Calculation Results <br /> cc: Chris Pauley, PE, CFM (Galloway) <br /> F M F_TechMemo-20210416.docx <br /> Galloway&Company,Inc. Page 7 of 7 <br />