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~ Federal Emergency Management Agency Washington, D.C. 20472 FEB 23 2000 CERTIFIED MAIL RETURN RECEIPT REQUESTED IN REPLY REFER TO: Case No.: 99-0841OP The Honorable Steve Ward Chairman Arapahoe County Board of Commissioners 5334 South Prince Street Littleton, CO 80166 Community: Arapahoe County, Colorado Community No.: 080011 Panels Affected: 08005C0455 J and 0460 J ~c~:~i~~: of JU N 2 9 2000 102-I-A-C Dear Mr. Ward: This responds to a request that the Federal Emergency Management Agency (FEMA) revise the effective Flood Insurance Rate Map (FIRM) and Flood Insurance Study (PIS) report for Arapahoe County, Colorado and Incorporated Areas (the effective FIRM and PIS report for your community), in accordance with Part 65 of the National Flood Insurance Program (NFIP) regulations. In a letter dated August 18, 1999, Mr. Bill DeGroot, P.E., Chief, Floodplain Management Program, Urban Drainage and Flood Control District, requested that FEMA revise the FIRM and FIS report to show the effects of construction along Big Dry Creek of major drainageway features that consist of bank protection, grade-control structures, crossing structures, and detention facilities, including Pond 10 just upstream of South University Boulevard, and revised hydrologic and hydraulic analyses for Big Dry Creek Tributary A (Tributary A) and Big Dry Creek Tributary C. All data required to complete our review of this request were submitted with letters from Mr. DeGroot and Mr. Alan J. Leak, P.E., Project Manager, WRC Engineering, Inc. 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 and floodway boundary delineations of the flood having a I-percent chance of being equaled or exceeded in any given year (base flood) along Big Dry Creek from approximately 150 feet upstream to approximately 750 feet upstream of West Littleton Boulevard and from just upstream of Orchard Road to just downstream of County Line Road. We also have revised the FIRM and FIS report to modify the elevations and floodplain boundary delineations, and to add floodway boundary delineations, of the base flood along the entire reach of Tributary A. As a result of the modifications, the base flood elevations (BFEs) for Big Dry Creek decreased, and the widths of the Special Flood Hazard Area (SFHA), the area that would be inundated by the base flood, and the regulatory floodway increas,ed in some areas and decreased in other areas. Also as a result of the modifications, the BFEs for Tributary A increased, the width of the SFHA increased in some areas and decreased in other areas, and a regulatory floodway was established. The modifications are shown on the enclosed annotated copies of FIRM Panel(s) 08005C0455 J and 08005C0460 J, Profile Panel(s) 06P through l8P, and affected portions of the Summary of Discharges Table and Floodway Data Table. This Letter of Map Revision (LOMR) hereby revises the above-referenced panel(s) of the effective PIRM and the affected portions of the PIS report, both dated August 16, 1995.