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February 16, 2012 <br />Project: Inundation Mapping for The Consolidated Mutual Water Company <br />Vendor: The Consolidated Mutual Water Company; 12700 W. 27th Avenue; Lakewood, CO 80215 <br />Phone: (303) 274-7401 <br />c/o Mr. Mike Queen <br /> <br />Consultant: J&T Consulting; 1400 W. 122nd Avenue, Suite 120; Westminster, CO 80234 <br />Phone: (303) 457-0735 <br />c/o Mr. Jason Murray <br /> <br />CWCB funding source: Severance Tax Trust Fund Operational Account <br /> <br />SCOPE OF WORK <br /> <br />J&T Consulting (Consultant), at the direction of The Consolidated Mutual Water Company (Vendor), will <br />perform a dam breach modeling study and flood inundation mapping for two dams within the Vendor’s <br />system. The study shall be in accordance with the latest Breach Guidelines published by the Colorado <br />Dam Safety Branch. The level of analysis shall be “Simple,” as defined in Table 1 of the Guidelines for <br />both the breach modeling and flood inundation mapping. Flood routing models and inundation <br />mapping shall be based on USGS 10-meter Digital Elevation Model (DEM) or best available topographic <br />mapping. Field measurements of bridges and culverts at critical sections shall be incorporated into the <br />model as necessary. The limits of the dam breach flood mapping shall extend from reservoir/dam, <br />downstream to the location where breach flood impacts become negligible. <br /> <br />The two dams to be modeled are Fairmount Reservoir and Maple Grove Reservoir. The downstream <br />limit of the inundation mapping for both reservoirs is expected to extend to Clear Creek, in the vicinity <br />of the I-70 and US Highway 58 interchange. Preliminary results will determine if additional modeling of <br />Clear Creek is required. <br /> <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 /> <br />PROPOSED METHODOLOGY <br /> <br />The Consultant shall perform a clear day dam failure analysis of each dam and route the resulting <br />outflow hydrographs downstream using HEC-HMS. Breach parameters shall be estimated in accordance <br />with 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