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<br />. <br /> <br />. <br /> <br />September 4, 1997 <br /> <br />FEMA Action Requested <br /> <br />The City is approaching FEMA with a number of important issues that need to be addressed <br />regarding the South Boulder Creek floodplain and the G&O study. In order to provide a framework <br />to adequately resolve these issues, the City of Boulder is requesting that FEMA: <br /> <br />1. Suspend use of the 1986 G&O South Boulder Creek floodplain study pending a detailed <br />analysis and investigation of the accuracy and representations made by the study. This <br />investigation needs to include a complete identification and analysis ofthe impacts created <br />by physical changes in the South Boulder Creek floodplain and any required measures to <br />mitigate adverse impacts on the historic floodplain. <br /> <br />2. Reinstate use of the R.W. Beck and Associates, 1973 South Boulder Creek floodplain study <br />for regulatory purposes, as adopted by the 1978 FIS and 1979 FIRM, replacing the 1988, <br />1990, and 1995 FIRMs for that reach. This study would provide the last adopted accurate <br />floodplain map based on complete engineering data, and reestablishes the base conditions <br />for evaluating the upstream and downstream impacts associated with the Flatiron Property <br />berm and gravel mine prior to the implementation of physical changes in the floodplain. Use <br />of the Beck study would provide an interim measure for floodplain regulatory purposes until <br />a revised floodplain study can be completed by local governmental agencies. <br /> <br />3. Require the Colorado Department of Transportation (CDOT) to perform and submit a <br />detailed impact analysis of the U.S. 36 median crash barrier, and mitigate any adverse <br />floodplain impacts that increase water surface elevations or negatively affect downstream <br />lands. The barrier currently obstructs and deepens flood waters overflowing the highway, <br />and we are unaware of any floodplain analyses or federal approvals for installation of this <br />flood barrier. <br /> <br />4. Require the Flatiron Property gravel mining operator and property owner to perform and <br />submit a detailed impact analysis ofthe earthen berm and gravel mining pit with respect to <br />pre-berm and pre-mining conditions and grades using the R.W. Beck study as a baseline. In <br />addition, FEMA would require mitigation of any adverse floodplain impacts that increase <br />water surface elevations and flood velocities, or negatively affect downstream lands. <br /> <br />5. <br /> <br />Withhold any certification of the existing Flatiron Property embankment as a FEMA flood <br />protection levee, pending the resolution of the G&O floodplain study, a complete review of <br />upstream and downstream impacts associated with the berm and gravel mine, completion of <br />local master planning efforts to evaluate alternative mitigation measures for the South <br />Boulder Creek corridor, and subject to the due public review and permitting processes of the <br />local jurisdictions and affected land owners. <br /> <br />I, <br />I' <br /> <br />3 <br />