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Federal Emergency Management Agency Washington, D.C. 20472 CERTIFIED MAIL RETURN RECEIPT REQUESTED IN REPLY REFER TO: Case No.: 99-08-304P The Honorable James Sullivan Chairman, Douglas County Board of Commissioners 101 Third Street Castle Rock, CO 80104 Community: Douglas County, Colorado Community No.: 080049 Panels Affected: 0170 C and 0188 C E~ective. ~ate of DEe 0 3 1999 ThIS RevIsion: 102-I-C Dear Mr. Sullivan: This responds to a request that the Federal Emergency Management Agency (FEMA) revise the effective Flood Insurance Rate Map (FIRM) for your community in accordance with Part 65 of the National Flood Insurance Program (NFIP) regulations. In a letter dated April 26, 1999, , P.E., Project Engineer, Rocky Mountain Consultants, Inc., requested that FEMA revise the FIRM to show the effects of construction along Tributary B to East Plum Creek (Tributary B) of two 6O-inch-diameter reinforced-concrete pipe culverts (RCPs) under Santa Fe Drive approximately 100 feet upstream of the Atchison, Topeka and Santa Fe Railway (AT &SFR); a detention pond approximately 300 feet upstream of the AT &SFR; a pond inlet drop structure approximately 800 feet upstream of the AT &SFR; three 64-inch-diameter RCPs under Access Road approximately 1,200 feet upstream of the AT &SFR; and two 66-inch-diameter RCPs under Red Hawk Drive approximately 2,200 feet upstream of the AT&SFR. This request also included a detailed hydrologic and hydraulic analysis of the reach of Tributary B from approximately 100 feet downstream to approximately 2,600 feet upstream of the AT&SFR. All data required to complete our review of this request were submitted with letters from Ms. Stepanek. With a letter dated June 21, 1999, Ms. Stepanek provided a corporate limits map that shows that the portion of the area of revision west of the AT &SFR was annexed by the Town of Castle Rock. We have completed our review of the submitted data and the flood data shown on the effective FIRM. We have revised the FIRM to modify the floodplain boundary delineations of the flood having a I-percent chance of being equaled or exceeded in any given year (base flood) along the reach of Tributary B from just downstream to approximately 50 feet upstream of the AT &SFR and from approximately 800 feet downstream to approximately SOO feet downstream of West Wolfenberger Road. As a result of the modifications, the width of the Special Flood Hazard Area (SFHA), the area that would be inundated by the base flood, for the revised reach increased in some areas and decreased in other areas. The increases in SFHA width are a result of the detailed hydrologic and hydraulic analysis for Tributary B. All increases in SFHA width are contained on the requester's property. Please note that Tributary B was previously labeled as Omni Drainageway. The modifications are shown on the enclosed annotated copies of FIRM Panel(s) 0170 C and 0188 C. This Letter of Map Revision (LOMR) hereby revises the above-referenced panel(s) of the effective FIRM dated September 30, 1987. Because this revision request also affects the Town of Castle Rock, a separate LOMR for that community was issued on the same date as this LOMR.