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<br />-- <br /> <br />'--' <br /> <br />'-' <br /> <br />'"', <br /> <br />significant. The Lower Latham Dam (near Kersey in Weld <br />County) failure in 1973 and the Prospect Dam (also in Weld <br />County) failure in 1981 were by any standards fortunate as <br />to loss of life. The Lawn Lake Reservoir dam failure in <br />Larimer County (classified as a moderate hazard dam) unfor- <br />tunately cost 3 (possibly 4) lives in 1982, but again <br />Coloradans and our visitors were fortunate. National <br />experience has shown that those who live in a potential <br />inundation zone are doing so in some instances at very high <br />risk. Colorado's degree of seismic activity across the <br />State, the old age and design characteristics of many of our <br />2,249 dams and the high probability of flash flooding across <br />the State intensifies this degree of risk, Of these high <br />hazard dams, 26 are currently also ident ified as "unsafe." <br />These dams are unsafe usually because spillways are too <br />small to pass the run off from a probable maximum precipi- <br />tation event. See Annex "B" for a list of unsafe, high and <br />moderate hazard dams. <br /> <br />. <br /> <br />Residents who live "downstream" from a dam may be at <br />significant risk, so that the aggregate problem for exposed <br />communities to prepare safety measures for those at risk is <br />urgent. National experience has shown that a significant <br />number of lives can be saved in event of dam failure if <br />people can be warned and evacuated. People in potential <br />inundation zones must be made aware of the danger, local dam <br />failure warning signals and available evacuation routes. It <br />follows that there is a strong moral as well as legal <br />obI igation to Colorado's governments to develop and test <br />plans which can provide adequate safety measures. <br /> <br />The State Engineer's list of high hazard dams has <br />received wide publicity in Colorado, Every community <br />exposed to possible dam failure should undertake prepared- <br />ness measures with a sense of urgency. Specifically, <br />communities should review their own situations to identify <br />people and property at risk, then take those actions neces- <br />sary to expeditiously prepare warning and evacuation plans <br />for those determined to be at risk. Essential steps for <br />planners are: (1) coordinate with dam owners or staff <br />to determine failure or warning notification procedures for <br />the dam site, (2) obtain or develop worst case estimates of <br />flooding (or inundation maps in some cases where large <br />numbers of people are exposed or when feasible to accomplish <br />by dam owners with significant mapping capability) and (3) <br />obtain flood wave travel times (assuming complete failure) <br />to those people or communities who are in the worst case <br />inundation zone. When these data have been determined, a <br />plan may be formulated, publicized and tested at very low <br />local expense. <br /> <br />. <br /> <br />. <br /> <br />. 24 <br />