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<br />Cross section geometries were determined from a map provided by UCC <br />through Intermountain Technical Services, Inc., of Grand Junction, <br />Colorado. The map scale of 1" = 200" and a 2 foot contour interval <br />provided sufficient detail to plot th"irty-two cross sections on the <br />main river channel and six croSS sections on the Atkinson Creek <br />tributary. Field data on the county truss bridge across the San <br />Miguel near Atkinson Creek and the reinforced concrete state highway <br />bridge across Atkinson Creek was provided by UCC personnel. Field <br />verified cross sectional data in the mill area and the Main Street <br />bridge details were provided by MSM. <br /> <br />3.3.3 HEC-2 Program Results <br /> <br />The results of the flood flow analyses for the 10, 50, 100 and SOO <br />year events are listed in the Appendix and also on Drawings 244-2049 <br />through 244-2055. <br /> <br />In the Club Ranch Ponds reach, the 500 year flood crest is contained <br />within the San Miguel channel. The plan, profile and cross sections <br />indicate that no UCC structureS are directly affected by the flood <br />flows. All floods except the 10 year event would ir.lpact the county <br />truss bridge at Station 21+70. This bridge would probably not sur- <br />vive any of these floods. <br /> <br />The backwater effects of the San Miguel channel on Atkinson Creek are <br />minimal. A review of the Atkinson Creek profile on Drawing 244-2049 <br />indicates that the flood parallels the creek bottom after Section 7.4. <br />The flood flows would pass under the structure in various combinations <br />of pressure flow and low flow. <br /> <br />11 <br />