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CHANGES ARE MADE IN DETERMINATIONS OF BASE FLOOD ELEVATIONS FOR THE TOWN OF LYONS AND BOULDER COUNTY, COLORADO, UNDER THE NATIONAL FLOOD INSURANCE PROGRAM On June 2, 1995, the Department of Homeland Security's Federal Emergency Management Agency identified Special Flood Hazard Areas (SFHAs) in the Town of Lyons and in Boulder 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 this community is appropriate. The modified Base Flood Elevations (BFEs) revise the FIRM for the community. 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 US.c. 4001-4128, and 44 CFR Part 65. A hydraulic analysis was performed to incorporate a new hydrologic analysis and new topographic data for North St. Vrain Creek from approximately 1,700 feet downstream to approximately 8,700 feet upstream of Fifth Avenue and for St. Vrain Creek from approximately 6,740 feet downstream to approximately 400 feet upstream of Second Avenue. This has resulted in a revised delineation of the regulatory floodway, increases and decreases in SFHA width, and increased and decreased BFEs for both flooding sources. In addition, a regulatory floodway and BFEs were established for North 8t. Vrain Creek from approximately 300 feet upstream to approximately 2,600 feet upstream of US. Highway 36 and for St. Vrain Creek from just downstream to approximately 3,040 feet upstream of U.S. Highway 36. 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) * North St Vrain Creek: 1 Approximately 1,270 feet downstream of Fifth Avenue 1,2 Approximately 300 feet upstream of US. Highway 36 2 Approximately 2,600 feet upstream of US. Highway 36 5,326 5,396 None 5,325 5,397 5,419 St. Vrain Creek: 1,2 Approximately 3,000 feet downstream of Second Avenue 1,2 Approximately 700 feet downstream of Second Avenue 2 Approximately 50 feet upstream of U.S. Highway 36 5,297 5,314 None 5,294 5,312 5,265 *National Geodetic Vertical Datum, rounded to nearest whole foot ITown of Lyons 2Unincorporated areas of Boulder 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.