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4 t <br /> February 16, 2012 <br /> Project: Inundation Mapping for Farmers High Line Canal and Reservoir Company <br /> Vendor: Farmers High Line Canal and Reservoir Company; 725 Malley Drive; Northglenn, CO 80233 <br /> Phone: (303)451-7604 <br /> c/o Ms. Cynda Lower <br /> Consultant: Deere &Ault Consulting, Inc.; 600 S.Airport Rd, Building A, Suite 205; Longmont, CO 80503 <br /> Phone: (303) 651-1468 <br /> c/o Mr. Mark Severin, P.E. <br /> CWCB funding source: Severance Tax Trust Fund Operational Account <br /> SCOPE OF WORK <br /> Deere &Ault Consulting, Inc. (Consultant), at the direction of Farmers High Line Canal and Reservoir <br /> Company (Vendor), will perform a dam breach modeling study and flood inundation mapping for the <br /> dam at Hyatt Lake. The study shall be in accordance with the latest Breach Guidelines published by the <br /> Colorado Dam Safety Branch. The level of analysis shall be "Simple," as defined in Table 1 of the <br /> Guidelines for both the breach modeling and flood inundation mapping. Flood routing models and <br /> inundation mapping shall be based on USGS 10-meter Digital Elevation Model (DEM) or best available <br /> topographic mapping. Field measurements of bridges and culverts at critical sections shall be <br /> incorporated into the model as necessary. The limits of the dam breach flood mapping shall extend <br /> from reservoir/dam, downstream to the location where breach flood impacts become negligible. <br /> The downstream limit of the inundation mapping for the dam at Hyatt Lake is expected to extend down <br /> an unnamed drainage to Van Bibber Creek and terminate at the confluence with Ralston Creek. <br /> Preliminary results will determine if additional modeling is required. <br /> The inundation limits shall be prepared in UTM coordinates (NAD 83, Zone 13—meters) which shall be <br /> overlaid on base mapping that includes color aerial imagery(2009 or newer). The inundation map shall <br /> be printed in color on a minimum sheet size of 11"x 17". The inundation extents shall be clearly <br /> illustrated and include peak discharge estimates, peak flood wave arrival times and peak flood wave <br /> depths at critical locations. Roads, highways and critical infrastructure (schools, hospitals,fire stations, <br /> etc.) shall be annotated and any roads expected to be overtopped by the flood wave shall be identified. <br /> The map shall include a legend noting the dam, DAMID, north arrow and a graphic scale. <br /> PROPOSED METHODOLOGY <br /> The Consultant shall perform a clear day dam failure analysis of the dam and route the resulting outflow <br /> hydrographs downstream using HEC-HMS. Breach parameters shall be estimated in accordance with <br /> methodologies recommended by the Office of the State Engineer, Dam Safety Branch. Hydraulic <br /> parameters, including width of flow, depth of flow and velocity at critical locations shall be estimated <br /> using the Corps of Engineer's HEC-RAS computer modeling software. A steady-state water surface <br /> profile resulting from peak flow rates at various locations shall be generated. Topographic information <br /> for the floodplains shall be based on USGS 10-meter DEMs from the National Elevation Dataset (NED) <br /> elevation data. <br />