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5265 Ronald Reagan Blvd.,Suite 210 <br /> Johnstown,CO 80534 <br /> G Al owa 970.800.3300•GallowayUS.com Memorandum <br /> y <br /> To: Alan Overton, PE, and Robert Graves (Fort Morgan Farms, LLC) <br /> From: Suleyman Akalin, PE, PhD, CFM (Galloway, Inc.) <br /> Date: April 16, 2021 <br /> Re: Delta Reservoir West Cell Preliminary and East Cell Conceptual <br /> Design (GAL Project No. FMF00001.25) <br /> Introduction <br /> This memorandum describes the preliminary design for the Delta Reservoir West Cell (Cell 1) <br /> and the conceptual design for the East Cell (Cell 2) storages located directly east of Weld <br /> County Road (WCR) 47 in Greeley, CO. The hydraulic analyses of the influence on the <br /> Cache La Poudre River(CLPR) and South Platte River (SPR) floodways due to each design <br /> and the effect of flows from the 1-percent annual chance (1-PAC, a.k.a. 100-year)) flooding of <br /> the CLPR and SPR on the reservoir structure were evaluated in one-dimensional (1 D) <br /> hydraulic models and compared with the best available data. The designs for both West Cell <br /> and East Cell were developed from a two-dimensional unsteady hydraulic model of the 1- <br /> PAC flood. <br /> Project Area Description <br /> The project area is generally located approximately 5 miles east of the City of Greeley, CO. It <br /> extends along the southern bank of Poudre River and northern bank of South Platte River <br /> immediately downstream of WCR 47, and upstream of the Poudre River and South Platte <br /> River confluence. All locations and elevations are referenced geospatially to Colorado State <br /> Plane North US feet and North American Vertical Datum (NAVD88). <br /> In addition to the 1-percent annual chance (1-PAC) and 0.2-PAC floodplains, the regulatory <br /> floodways have been delineated for both the CLPR and SPR. A portion of the project area is <br /> located within the 1-PAC and floodway boundaries. The regulatory floodway is defined by <br /> Weld county as channel of a river or other watercourse and the adjacent land areas that must <br /> be reserved in order to discharge the base flood without cumulatively increasing the water <br /> surface elevation more than 0.5 feet. The Federal Emergency Management Agency (FEMA) <br /> National Flood Insurance Program (NIFP) "prohibit encroachments including fill, new <br /> construction... and other development" in the regulatory floodplain "unless the proposed <br /> encroachment would not result in an increase in the flood levels" in accordance with 44 CFR <br /> 60.3(d)(3). <br /> Hydrologic Information <br /> Steady Uniform Flow <br /> The hydrology utilized as part of the steady 1 D hydraulic analysis of the CLPR was <br /> determined by Anderson Consulting Engineers, Inc. (ACE) COCWCB25 CLPR Hydrology <br /> F M F_Tech M ern o-20210416.d ocx <br /> Page 1 of 7 0 <br />