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, ? Federal Emergency Management Agency Washington, D.C. 20472 CERTIFIED MAIL RETURN RECEIPT REQUESTED IN REPLY REFER TO: Case No.: 97-08-394P The Honorable Ron Stewart Chairman, Boulder County Board of Commissioners P.O. Box 471 Boulder, CO 80306-0471 Community: Boulder County, Colorado Community No.: 080023 Panel Affected: 08013C0269 F E~ectivepate of MAY 1" 1999 ThIs ReVISIOn: 102-I-A-C Dear Mr. Stewart: This responds to a request that the Federal Emergency Management Agency (FEMA) revise the effective Flood Insurance Rate Map (FIRM) and Flood Insurance Study (FIS) report for Boulder County, Colorado and Incorporated Areas (the effective FIRM and FIS report for your community), in accordance with Part 65 of the National Flood Insurance Program (NFIP) regulations. In a letter dated August 26, 1997, Mr. Steven G. Smith, P.E., Project Engineer, QCI Development Services Group, Inc., requested that FEMA revise the FIRM and FIS report to show the effects of a revised hydraulic analysis along Lefthand Creek. The revised analysis incorporated updated topographic information and revised bridge modeling at the State Highway 119 (SHI19) and Burlington Northern Railroad (BNRR) bridges. The revised analysis defined two channels along the overflow area shown on the effective FIRM. Lefthand Creek North Overflow Channel is created by floodwater that leaves the main channel just upstream of the southbound lane of SH 119. Lefthand Creek South Overflow Channel is created by floodwater that leaves the main channel between the northbound lane of SH119 and the BNRR. Both overflow channels rejoin the main channel just upstream of South Hover Road. All data required to complete our review of this request were submitted with letters from Mr. Peter Swift, P.E., Project Manager, Swift and Associates, and Mr. Smith. We have completed our review of the submitted data and the flood data shown on the effective FIRM and FIS report. We have revised the FIRM and FIS report to modify the elevations and floodplain boundary delineations of the flood having a I-percent chance of being equaled or exceeded in any given year (base flood) along both overflow channels and the main channel of Lefthand Creek from just upstream of South Hover Road to just downstream of North 87th Street. As a result of the modifications, the base flood elevations (BFEs) for the revised reach increased in some areas and decreased in other areas, and the width of the Special Flood Hazard Area (SFHA), the area that would be inundated by the base flood, increased in some areas and decreased in other areas. The modifications are shown on the enclosed annotated copy of FIRM Panel(s) 08013C0269 F and ProfIle Panel(s) 211P. This Letter of Map Revision (LOMR) hereby revises the above-referenced panel(s) of the effective FIRM and the affected portions of the FIS report, both dated June 2, 1995.