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<br />. <br /> <br />. <br /> <br />. <br /> <br />acknowledge that the 100, year floodplain downstream of V,S. Highway 36 has not been <br />completely delineated by the existing floodplain studies. <br /> <br />EXAMINATION OF THE DELINEATED FLOOD HAZARD/RISK <br /> <br />. <br /> <br />Floodplain studies which date back to 1969 show that a portion of the Flatiron! Gateway <br />property lies within the limits of the South Boulder Creek 100, year Floodplain. Today's 100- <br />year floodplain is based on the presence of an in'place levee system. The Love study presents <br />an analysis with and without the Flatiron levee system. The engineering analyses show that the <br />levee system reduces the downstream flood hazard. Recently, the owner of the levee system <br />(Flatiron Gravel Company) was notified by FEMA that the levee system does not meet federal <br />design and safety standards. The notification advised the owners and local and state officials <br />that if the levee system is not improved to meet FEMA's levee standards, a new map will be <br />issued which shows portions of the site and downstream areas subject to inundation from a 100, <br />year flood event. <br />Should the existing levee fail during a large event (100, year flood) the hazard to <br />downstream areas could be worse than the pre,mining condition because the lands within the <br />mined areas are up to 12 feet lower than pre,mining operation elevations. This changed <br />condition could initiate a change in the direction of floodwaters during times of high flow and <br />could inundate additional areas along the left overbank not presently in an identified 100, year <br />floodplain. Due to this potential floodplain condition, it appears that it may be in the best <br />interest of the community that the levee system become a permanent floodplain landform. <br />Without the levee system, the Love investigations show that larger flood flows will be <br />experienced at downstream floodplain locations. It should be noted that a delineated downstream <br />floodplain may include numerous homes in the floodplain. The Board staff findings the Love's <br />investigations to be a reasonable assessment of existing conditions. <br /> <br />OVERVIEW OF THE FLOOD MITIGATION MEASURES <br /> <br />With the recent development activities which have occurred upstream and downstream <br />of U.S. Highway 36, there is a need for the implementation of flood mitigation measures for <br />the South Boulder Creek floodplain risks. Some potential flood mitigation measures are: <br /> <br />. <br /> <br />Certification of the Flatiron Levee System ' It appears to us that the community may <br />want to endorse this mitigation measure. The action will assist to lessen the magnitude <br />of the threat to downstream flood prone lands and property. The CWCB has made a <br />request to FEMA not to change the flood insurance maps until after March 15, 1997. <br />This will provide owners and the local communities to make the necessary levee system <br />improvements to obtain FEMA levee certification prior to the 1997 flood season. I <br />understand that FEMA is considering the request. The present Love investigation does <br />not include the required technical data to fully evaluate the levee system for levee <br />certification. <br /> <br />. <br /> <br />5 <br />