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<br />DETERMINATION OF THE BASE SAFETY CONDITION <br /> <br />The Base Safety Condition (BSC) is defined in the "Guidelines" "s follows: <br />"The Base Safety Condition (BSC) is the small,ost design inflow flood event for <br />",hleh there will be no significant increment in loss of life or economic <br />consequences from dam failure I compared to thj~ dam passing the BSC flood safely <br />with safety modifications in place," If failure always results in a significant <br />i.ncrease in losses, regardless of the :inflow event., the design flood event chosen <br />for safety modification design purposes should be the PMF." <br /> <br />Flood routings were completed for "wi,th" and "'without darn failure 11 <br /> <br />conditions for the following design storm/dam modification combinations: (1) 63 <br /> <br /> <br />percent PMF with the existing dam and spillway; (2) 80 percent PMF with a <br /> <br />200-foot concrete chute spillway and the exist:Lng spill,.ay; and (3) 100 percent <br /> <br />PMF with a 390-foot concrete chute spillway and che existing spillway, The <br /> <br />concrete chute spillway concept modifications 1lTill be discussed subsequently in <br /> <br />PLAN FORMULATION AND EVALUATION. <br /> <br />As shown on table 8, failure of the dam ,always results in a considerably <br /> <br /> <br />larger peak outflow than under nonfailure conditions. Figure 1 il.J.uscraces the <br /> <br />significant economic losses incurred with dam failure compared to the economic <br /> <br />losses without dam failure and the safety modification in place. This <br /> <br /> <br />significant loss is consistent from 25 percent of the PMF to 100 percent of the <br /> <br />"fully developed condition" PMF. The.-efore, l:he ESC for Cherry Creek Lake Dam <br /> <br />is 100 percent of the PMF, <br /> <br />29 <br />