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• S <br /> February 24,2014 <br /> Project: Inundation Mapping for City of Trinidad <br /> Vendor: City of Trinidad,PO Box 880,Trinidad,CO 81082 <br /> Phone: (719)846-9843 <br /> c/o Mr.Tom Acre <br /> Consultant: W.W.Wheeler&Associates, Inc.; 3700 S. Inca Street, Englewood,CO 80110-3405 <br /> Phone: (303)761-4130 <br /> c/o Mr.John Treacy, P.E. <br /> CWCB funding source: Severance Tax Operational Fund <br /> SCOPE OF WORK <br /> W.W.Wheeler, Inc. (Consultant),at the direction of the City of Trinidad (Vendor),will perform a dam <br /> breach modeling study and flood inundation mapping for three dams within the Vendor's system. Two <br /> sets of maps will be generated: (1)Sunny Day dam failure breach inundation maps and (2)spillway <br /> discharge (non-breach) inundation maps. The studies shall be in accordance with the latest Breach <br /> Guidelines published by the Colorado Dam Safety Branch. The level of analysis shall be <br /> "INTERMEDIATE," as defined in Table 1 of the Guidelines for both the breach modeling and flood <br /> inundation mapping. Flood routing models and inundation mapping shall be based on USGS 10-meter <br /> Digital Elevation Model (DEM)or best available topographic mapping. <br /> The three dams to be modeled are the Fisher Peak Detention Dam FPC-1, Fisher Peak Detention Dam <br /> FPC-2,and Pinon Canyon Detention Dam. The downstream limit of the inundation mapping will extend <br /> downstream of the dams to a location on the Purgatoire River where there is no potential for loss of life <br /> and no significant property damage. <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, peak velocities and peak <br /> flood wave depths at critical locations. Roads, highways and critical infrastructure (schools, hospitals, <br /> fire stations,etc.)shall be annotated and any roads expected to be overtopped by the flood wave shall <br /> be identified. 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 dams and route the resulting <br /> outflow hydrographs downstream using an unsteady HEC-RAS model. Breach parameters shall be <br /> estimated in accordance with methodologies recommended by the Office of the State Engineer, Dam <br /> Safety Branch. Also spillway discharge(non-breach) inundation maps shall be prepared showing the <br /> downstream inundation areas associated with full spillway discharge flood events. 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 using the unsteady flow option. A <br /> water surface profile resulting from peak flow rates at various locations shall be generated. Topographic <br />