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some people will not begin to evacuate ~he flood plain until they feel threatened and that some individuals will not make an effort to evacuate the area at all. In the estimation of LOL, the following assumptions were made. It was assumed that persons would not lose tbeir lives in less than 2 feet of water. All persons attempting to evacuate the flood plain could do so with a warning time of at least 3 hours; that is assuming that the warning and evacuation systems were on target. Persons belonging to one or more of the following groups would require extra time evacuating the flood plain but should still be able to escape with 3 hours warning time; perso~s 5 years and under, persons 65 years and older, and inmates of institutions. YITHOUT DAM ANALYSIS The without dam alternative was de~eloped in order to justify retaining and modifying Cherry Creek Dam, The following analysis in table 12 displays the large amount of benefits associated with retaining and modifying the dam by raising the dam crest. Included in the benefit analysis are those benefits derived from flood control and recreation. Included in tbe cost analysis is the annual operation and maintenance cost at Cherry Creek La~e. This analysis indicates the existing project should be retained and the without dam alternative should be eliminated from consideration. Table 12 Economic Analysis for Witbout Dam Alternative Annual Benefits of Continuing Existing Project Total Benefits $21,020.000 5.725.700 $26,745,700 EAD Recreation Annual Costs IS-ft. Dam Raise Modification (50 yrs. @ 8.625%) $ 628,800 Annual Operations and Maintenance Total Costs Benefit-Cost Ratio Net Benefits 525.000 $ 1,153.800 23/1 $25,591,900 38