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CHANGES ARE MADE IN DETERMINATIONS OF BASE FLOOD ELEVATIONS FOR THE CITY OF ARVADA AND THE UNINCORPORATED AREAS OF JEFFERSON COUNTY, COLORADO, UNDER THE NATIONAL FLOOD INSURANCE PROGRAM On June 17, 2003, the Department of Homeland Security's Federal Emergency Management Agency identified Special Flood Hazard Areas (SFHAs) in the City of Arvada and in the unincorporated areas of Jefferson County, Colorado, through issuance of a Flood Insurance Rate Map (FIRM). The Mitigation Division has determined that modification of the elevations of the flood having a I-percent chance of being equaled or exceeded in any given year (base flood) for certain locations in these communities is appropriate. The modified Base Flood Elevations (BFEs) revise the FIRM for the communities. The changes are being made pursuant to Section 206 of the Flood Disaster Protection Act of 1973 (Public Law 93-234) and are in accordance with the National Flood Insurance Act of 1968, as amended (Title XIII of the Housing and Urban Development Act of 1968, Public Law 90-448), 42 U.S.C. 4001-4128, and 44 CFR Part 65. A hydraulic analysis was performed to incorporate a new hydrologic analysis and new topographic data for Leyden Creek from the confluence with Ralston Creek to just upstream of Church Ditch and the effects of two culverts located from approximately 900 feet upstream to approximately 1,300 feet upstream of Indiana Street and from approximately 300 feet downstream to approximately 90 feet downstream of Indiana Street, respectively. This has resulted in a revised delineation of the regulatory floodway, increases and decreases in SFHA width, and increased and decreased BFEs for Leyden Creek. In addition, a regulatory floodway was established for Leyden Creek from approximately 300 feet upstream of Indiana Street to approximately 1,520 feet upstream of West 72nd Avenue. The table below indicates existing and modified BFEs for selected locations along the affected lengths of the flooding source(s) cited above. Location Existing BFE (feet) * Modified BFE (feet) * I Approximately 150 feet downstream of Simms Street lApproximately 1,450 upstream of West 72nd Avenue 2Approximately 1,800 feet upstream of West 72nd Avenue 2 Approximately 100 feet downstream of Church Ditch 5,431 5,452 5,455 5,616 5,429 5,447 5,450 5,605 *National Geodetic Vertical Datum, rounded to nearest whole foot lCity of Arvada 2Unincorporated areas of Jefferson County Under the above-mentioned Acts of 1968 and 1973, the Mitigation Division must develop criteria for floodplain management. To participate in the National Flood Insurance Program (NFIP), the community must use the modified BFEs to administer the floodplain management measures of the NFIP. These modified BFEs will also be used to calculate the appropriate flood insurance premium rates for new buildings and their contents and for the second layer of insurance on existing buildings and contents. Upon the second publication of notice of these changes in this newspaper, any person has 90 days in which he or she can request, through the Chief Executive Officer of the community, that the Mitigation Division reconsider the determination. Any request for reconsideration must be based on knowledge of changed conditions or new scientific or technical data. All interested parties are on notice that until the 90-day period elapses, the Mitigation Division's determination to modify the BFEs may itself be changed.