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<br />" <br /> <br />" <br /> <br />To summarize, a hazard classification system was adopted to prioritize <br />Colorado's 2000 plus darns based upon the degree of damage, which results from <br />failure of the structure under normal operating conditions. After classifying <br />darns in Colorado, the Darn Safety Branch of the Office of the State Engineer <br /> <br />was able to prioritize their workload and establish the frequency and <br />thorouglmess of routine inspections. <br />Assumptions <br />The hazard classification system is based on the following general assumptions: <br />1. The darn fails by erosion of embankment materials initiated <br /> <br />by piping, embankment slides, or deterioration of the <br /> <br />c I "\" - ., <br />. I.'..... - , .' <br /> <br />outlet works. <br /> <br />- )". <br /> <br />2. At the time of failure, the water level in the reservoir is <br />at the ~elevation of the emergency spillway. <br />This assumption is the worst case situation because when <br />water is stored significantly below spillway crest <br />elevation the resulting flood and impact downstream is <br />reduced. 1 <br /> <br />""---.--- ", <br />-' r> j;'..A/, ,(.! <br /> <br />3. The darn fails at its maximum section. <br /> <br />Again, a degree of conservatism is introduced for this <br />worst case assumption. Darns can fail at smaller sections <br />of the embankment with only partial release of water in <br />the reservoir and correspondingly reduced impact <br />downstreaml. <br /> <br />For reservoirs with several distinct dams, a separate hazard classification <br /> <br />for each darn may be established. <br /> <br />1 Prospect Dam failed with the water surface one foot below the crest of <br /> <br />the spillway and at a point where the dam height was only 18 feet. The <br /> <br />darn has a maximum height of 42 feet. <br /> <br />2 <br />