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<br />. <br /> <br />. <br /> <br />against the levee is based on hydrology which was developed by the Corps of Engineers and used by the <br />Urban Drainage & Flood Control District, FEMA, and CWCB. <br /> <br />In response to the additional concerns which CU has expressed in their June 10, 1997 letter to us <br />regarding the flood hazard evaluation for the subject property, I provide the following responses: <br /> <br />1. CONCERN: Whether the dike should remain in place, and, if so, whether the lower portions of the <br />dike should be raised to a level at least four feet above the base flood elevation. RESPONSE: <br />After reviewing all the technical data which has been presented to the Board, it is the CWCB staff <br />finding that the levee system is a valuable flood mitigation measures and when it is certified by <br />FEMA will provide flood protection to downstream property owners. Providing an additional of <br />freeboard (total = 4 feet) is a good design parameter! <br /> <br />2. CONCERN: Whether the dike currently offers flood protection benefit to the residences to the <br />north of the property? RESPONSE: Yes. <br /> <br />3. CONCERN: Whether you support FEMA recognition of the dike for FEMA mapping purposes? <br />RESPONSE: Yes. Due to the extensive residential development that has occurred downstream of <br />the subject gravel pit, it appears that the dike/levee system is the most feasible flood mitigation <br />measure. This Board does recognize that other types of flood mitigation measures may be workable <br />also. In addition, from the engineering data that have been provided at meetings, hearings, and <br />reports, this Board finds that the subject gravel pit, downstream developments, and roadway systems <br />lie in the historic flow pattern of the South Boulder Creek. Human intervention has changed the <br />natural flow regime many times. Therefore, structural flood mitigation measures or complete <br />relocation of the downstream developments appear to be the only viable means of providing 100, <br />year flood protection to the existing inhabitants of the South Boulder Creek floodplain. <br /> <br />The Board staff will recommend endorsement of a University of Colorado, Boulder request to the CWCB <br />for FEMA levee certification which is based on good engineering and technical backup data. <br /> <br />Should you have additional concerns or questions regarding the CWCB staff findings, I will happy to <br />respond, <br /> <br /> <br />01 and Floodplain Management Section <br /> <br />encl. <br />cc. Leslie Botham, Leonard Rice Water Engr" Inc. <br />John Liou, FEMA <br />Bill DeGroot, UD&FCD <br /> <br />I :/wctranslsecallarry/susobou2.doc <br /> <br />2 <br /> <br />.--.. <br />