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' Spill discharges from the main channel of South Boulder Creek were identified using the <br /> split flow option in the HEC-2 model. The split flow control line was located at the <br /> highest ground point between the Flatiron Property and South Boulder Creek. To <br /> establish the sensitivity of the magnitude of the spill discharge to the assumed 2.6 weir <br /> ' coefficient, the coefficient was varied in the models to try and determine if more waters <br /> remained in the South Boulder Creek main channel section or if more waters were <br /> ' spilling between the main channel and the eastern edge of the Flatiron Property along the <br /> berm. It was determined that the magnitude of the spills from South Boulder Creek <br /> twould decrease by about 15 percent with the coefficient of 2.0 and increase less than 2 <br /> percent with a coefficient of 3.0. Thus, the weir coefficient of 2.6 appears reasonable for <br /> these models. This weir coefficient is a function of the HEC-2 split flow model and is <br /> required in order to complete the HEC-2 model. <br /> ' The starting water surface elevation was obtained from the regulatory model at Cross <br /> Section 20180 upstream of South Boulder Road. The discharge at this Cross Section in <br /> the regulatory model equals the total regulatory 100-year discharge of 6,160 cfs. <br /> Because the main channel spills upstream of Cross Section 20180, it is likely that a <br /> ' discharge lower than 6,160 cfs would be realized at the Cross Section during a 100-year <br /> event. However, identifying the discharge would require identifying the direction and <br /> ' path of the spills north of U.S. 36, which exceed the scope of this study. <br /> An estimate of the sensitivity of the two models to starting water surface elevation was <br /> made. As a result of this analysis, it was decided to use Cross Section 20180 as the <br /> ' starting section but recognize spill discharges could change with additional revisions to <br /> the regulatory HEC-2 downstream of U.S. 36. <br /> Since it was determined that the berm surrounding the Flatiron Property was not a FEMA <br /> ' certified levee, Love & Associates, Inc. developed 100-year floodplain models for the <br /> Flatiron Property based on two conditions. Condition 1 assumed that the site perimeter <br /> berm was did not exist and a model was set up entitled "100-Year Floodplain - No Levee <br /> with 200-foot Wide Channel'. The 200-foot wide interior interceptor channel was <br /> -13- <br />