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<br />Summary of Revisions to the <br />Preliminary Flood Insurance Study Report and <br />Preliminary Flood Insurance Rate Map <br />Eagle County and Incorporated Areas, Colorado <br />This document summarizes changes that have been made to the Preliminary Flood Insurance Study (FIS) <br />report and Flood Insurance Rate Map (FIRM) for Eagle County, Colorado and Incorporated Areas dated <br />August 28, 2003. In a letter dated November 26, 2003, Mr. Gregg Barrie, Senior Landscape Architect, <br />Town of V ail, expressed concerns regarding the FIRM. The letter contained a list of comments and <br />seven exhibits (A through G) to illustrate the areas in question. Most of the comments pertained to the <br />floodplain delineation along Gore Creek. A copy of this letter is enclosed, and a reply to each comment is <br />shown below. <br /> <br />General Issues <br /> <br />I. The Gore Creek floodplain boundaries have been redelineated based on the referenced geographic <br />information systems (GIS) fIle. This floodplain meets or exceeds tolerance level requirements set by <br />the Department of Homeland Security's Federal Emergency Management Agency's (FEMA' s) <br />Guidelines and Specifications for Flood Hazard Mapping Partners. Because of map scale <br />limitations, some homeowners may need to obtain a Letter of Map Amendment (LOMA). <br /> <br />2. The line types and hatch patterns used on the FIRM are FEMA standard. <br /> <br />3. The current effective flood hazard information for the Town of Vail is based on hydrologic studies <br />that were completed more than 20 years ago. The new study data contains cross sections cut from <br />the topographic mapping provided by the Town of Vail that have been used to develop new <br />water-surface profiles. The Town of Vail contracted with Peak Land Surveying to provide survey <br />data for all crossing structures within the study reaches. <br /> <br />The hydrologic investigations for this study include a review of previous studies and new statistical <br />evaluations of peak-flow data for 20 individual U.S. Geological Survey (USGS) stream gages in the <br />Gore Creek basin and stream gages for other basins in the eastern Eagle County region with similar <br />hydrologic characteristics. Results of analyses of individual stream gages in the basin were adopted <br />for the reaches for which they were applicable. New peak-flow regression equations were developed <br />using the results of the statistical analysis of individual station records and relating them to their <br />drainage areas. These regression equations were then used to develop 10-, 2-, 1-, and <br />0.2-percent-annual-chance discharge frequency values for study reaches without individual stream <br />flow gages. <br /> <br />The results of this information will cause the new study to differ from the current effective FIRM. <br />This includes new Base Flood Elevations (BFEs), changes in minimum channel elevations, and new <br />floodplain boundary delineations. Gore Creek, near the confluence of Buffehr Creek, is shown as an <br />approximate study on the current effective FIRM. In some locations, the revised BFE is higher than <br />the effective BFE; in other places, the opposite is true. In addition, the information on the current <br />effective FIRM is shown in the National Geodetic Vertical Datum of 1929 (NGVD); on the <br />