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<br />.' <br /> <br />CHANGES ARE MADE IN DETERMINATIONS OF BASE FLOOD ELEVATIONS FOR THE CITY <br />OF LONGMONT AND THE UNINCORPORATED AREAS OF BOULDER COUNTY, COLORADO. <br />UNDER THE NATIONAL FLOOD INSURANCE PROGRAM <br /> <br />On June 2, 1995, the Department of Homeland Security's Federal Emergency Management Agency <br />identified Special Flood Hazard Areas (SFHAs) in the in the City of Longmont and in the unincorporated <br />areas of Boulder County, Colorado. through issuance of a Flood Insurance Rate Map (FIRM), The <br />Mitigation Division has determined that modification of the elevations of the flood having a I-percent <br />chance of being equaled or exceeded in any given year (base flood) for certain locations in these <br />communities is appropriate, The modified Base Flood Elevations (BFEs) revise the FIRM for the <br />communities, <br /> <br />The changes are being made pursuant to Section 206 of the Flood Disaster Protection Act of 1973 (Public <br />Law 93-234) and are in accordance with the National Flood Insurance Act of 1968, as amended <br />(Title XlII of the Housing and Urban Development Act of 1968, Public Law 90-448), 42 U,S,C, <br />4001-4128, and 44 CFR Part 65, <br /> <br />A hydraulic analysis was performed to incorporate the effects of channelization, placement of fill, and <br />bridge construction along Lefthand Creek; bridge construction along St. Vrain Creek; and more detailed <br />topographic data for the following streams: Lefthand Creek from the confluence with St. Vrain Creek to <br />just upstream of South Main Street (V,S, Highway 287); St. Vrain Creek from approximately 160 feet <br />upstream to approximately 7,200 feet upstream of I 19th Street; Dry Creek No, I (Old Channel) from the <br />confluence with St. Vrain Creek to just upstream of Ken Pratt Boulevard; and shallow flooding areas <br />from just upstream of Ken Pratt Boulevard to just downstream of South Main Street. <br /> <br />This has resulted in increases and decreases in SFHA width and increased and decreased BFEs for <br />Lefthand Creek from the confluence with St. Vrain Creek to just upstream of South Main Street; increases <br />and decreases in SFHA width and increased BFEs for St. Vrain Creek from approximately 140 feet <br />upstream to just upstream of South Main Street; and decreases in SFHA width and decreased BFEs for <br />Dry Creek No, I (Old Channel) from the confluence with St, Vrain Creek to just upstream of South,Main <br />Street. Portions of the SFHA in the right overbank area (looking downstream) along St. Vrain Creek <br />from just upstream of Ken Pratt Boulevard to just downstream of South Main Street that previously had <br />BFEs determined were redesignated as SFHAs subject to shallow flooding with average depths of 2 feet or <br />3 feet. The table below indicates existing and modified BFEs for selected locations along the affected <br />lengths of the flooding source(s) cited above, <br /> <br />Location <br /> <br />Existing BFE <br />(feet)* <br /> <br />Modified BFE <br />(feet)* <br /> <br />Lefthand Creek: <br />Just upstream of confluence with St. Vrain Creek <br />Just downstream of South Main Street <br /> <br />4,926 <br />4,951 <br /> <br />4,927 <br />4,948 <br /> <br />St. Vrain Creek: <br />Approximately 160 feet upstream of I 19th Street <br />Approximately 3,700 feet upstream of I 19th Street <br /> <br />4,916 <br />4,927 <br /> <br />4,918 <br />4,928 <br /> <br />Dry Creek No, I (Old Channel): <br />Approximately 300 feet upstream of confluence <br />with St. Vrain Creek <br />Just downstream of Ken Pratt Boulevard <br /> <br />4,941 <br />4,944 <br /> <br />4,940 <br />4,942 <br />