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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />1500 <br /> <br />could be relocated. From the map study, it appears the property <br /> <br /> <br />damage would be principally the Highway 666 bridge which may not be <br /> <br /> <br />designed for greater than the 100-year Elood. Without performing <br /> <br /> <br />field investigations to determine channel and flood plain <br /> <br /> <br />characteristics and extent of human habitat and development <br /> <br /> <br />downstream, sufficient information was not available to establish <br /> <br /> <br />the hazard classification and perform a flood analysis in accordance <br /> <br /> <br />with the State Engineer's criteria. Accordingly, the traditional <br /> <br /> <br />governmental method following the Soil Conservation Service (SCS) <br /> <br /> <br />TR-60 was used for the flood hydrOlogy analysis. <br /> <br />Using the SCS TR-60 methodology, dams at the potential study sites <br />were assigned a hazard classification of Class B. Two flood <br />hydrographs were developed for a dam at site 9' <br />o An Inflow Design Flood (IDF) consisting of the runoff from a 100- <br />year rainfall plus 12 percent of the runoff from th~ probable <br />maximum storm (PMP) in excess of the 100-year flood: and <br /> <br />o A Freeboard Design Flood (FDF) consisting of the runoff from a <br />c 10Q-year rainfall plus 40 percent of the difference between the <br />PMF and the lOO-year flood. <br /> <br />Drainage basin physical characteristics were estimated by <br />delineation of the basin on the USGS l:lOO,OOO scale topographic map <br />.cortez, Colo.". The 100-year and PMP rainfall were developed using <br />NOAA Atlas 2, Volume III and the Corps oE Engineers (COE) <br /> <br />25 <br />