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<br />. <br /> <br />. <br /> <br />2 <br /> <br />Option 1 would appear to result in an overestimate of the extent of the base floodplain. The BFEs <br />determined for the FHAD consider that all of the flow would be contained along South Boulder Creek by <br />the embankment. If the embankment does not provide protection from the base flood, FEMA would <br />determine BFEs for the landward side of the embankment based on a hydraulic analysis of South Boulder <br />Creek considering that the levee did not exist. The BFEs resulting from such an analysis would likely be <br />lower than those computed for the FHAD and may result in a different delineation of the base floodplain <br />boundaries than that shown on the work map you submitted labeled "Attachment IV. " <br /> <br />Option 2 would also result in a FIRM that does not represent existing conditions. Because the FHAD was <br />based on revised hydrologic and hydraulic analyses and not merely based on consideration of the effects <br />of the embankment along South Boulder Creek, it would not be appropriate to ignore all of the information <br />developed for the FHAD and republish the information from the 1979 FIRM. <br /> <br />., <br /> <br />Upon receipt of hydraulic analyses of existing conditions along South Boulder Creek, including an <br />evaluation of the effects of the levee and an assessment of the quantity of flow splitting from the main <br />channel downstream of the levee, we will make a determination on revising the FIRM for Boulder County, <br />Colorado and Incorporated Areas. In the interim, please keep in mind that any community may adopt more <br />stringent floodplain management criteria than the minimum NFIP criteria in accordance with Section 60.1 <br />of the NFIP regulations. <br /> <br />In your letter, you also requested that FEMA withhold certification of the existing embankment as <br />providing protection from the base flood. Any determination by FEMA related to how the effects of a <br />levee system will be reflected on an NFIP map will be made based on an evaluation of whether the levee <br />system satisfies the requirements of Section 65.10 of the NFIP regulations. <br /> <br />We trust that we have addressed your concerns. If you have any questions regarding this matter, please <br />contact Mr. John Magnotti of our staff in Washington, DC, either by telephone at (202) 646-3932 or by <br />facsimile at (202) 646,4596. <br /> <br />Sincerely, <br /> <br />'--.~ tj-S\\~ <br /> <br />Frederick H, Sharrocks, Jr., Chief <br />Hazard Mitigation Branch <br />Mitigation Directorate <br /> <br />cc, Mr. Curt Parker, P.E. <br />Water Resources Engineer <br />Boulder County Transportation Department <br /> <br />Mr. Larry F. Lang <br />Chief, Flood Control and Floodplain <br />Management Section <br />Colorado Water Conservation Board <br /> <br />Mr. Bill DeGroot <br />Chief, Floodplain Management Section <br />Urban Drainage and Flood Control District <br />