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Mansions Phase 1-CS 990706 (3) Federal Emergency Management Agency Washington, D.C. 20472 CERTIFIED MAIL IN REPLY REFER TO: RETURN RECEIPT REQUESTED Case No.: 99-06-831P The Honorable Bobbie J. Mitchell Community: City of Lewisville, Texas Mayor, City of Lewisville Community No.: 480195 P.O. Box 299002 Panel Affected: 48121C0685 E Lewisville, TX 75029-9002 Effective Date of J IJ L 0 ~ ~99 This Revision: 102-D-A Dear Mayor Mitchell: 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 Demon County, Texas 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 February 1, 1999, Mr. Rusty Spiars, P.E., Vice President, Dunaway Associates, Inc., requested that FEMA revise the FIRM and FIS report to show the effects of placement of fill, grading, and excavation of two ponds associated with the Mansions by the Lake development along Denton Creek from approximately 2,570 feet downstream to approximately 540 feet downstream of State Highway 121 (SH121). Expansion and contraction coefficients and ineffective flow areas were added to the hydraulic model for Denton Creek in the vicinity of SH121 to show the effects of the SH121 bridge. In addition, this request included more detailed topographic information from approximately 3,840 feet downstream to just upstream of SH121 and the effects of an existing pond located just downstream of the project. This request follows up on a Conditional Letter of Map Revision issued on February 10, 1998. All data required to complete our review of this request were submitted with letters from Mr. Kenneth M. Griffin, P.E., Director of Engineering and Public Works, City of Coppell; Mr. T. S. Kumar, P.E., Assistant City Engineer and Floodplain Administrator, Department of Community Development, City of Lewisville; and Mr. Splats. 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 1-percent chance of being equaled or exceeded in any given year (base flood) along Denton Creek from SH121 to approximately 1,100 feet upstream. As a result of the modifications, the base flood elevations (BFEs) for Denton Creek and the widths of the Special Flood Hazard Area (SFHA), the area that would be inundated by the base flood, and the regulatory floodway decreased. The modifications are shown on the enclosed annotated copies of FIRM Panel(s) 48121C0685 E; Profile Panel(s) 35P, 36P, and 37P; and affected portions of the Floodway Data Table. The label for Cross Section D shown on the effective Floodway Data Table was changed to Cross Section B to match the effective profile for Denton Creek, and the stationing of Profile Panels 36P and 37P was adjusted so that the water-surface and streambed profiles match those for Denton Creek on Profile Panels 09P and 10P of the effective FIS report for the City of Coppell, Texas. This Letter of Map Revision (LOMR) hereby revises the above-referenced panel(s) of the effective FIRM dated April 2, 1997 and the affected portions of the FIS report dated March 30, 1998. Because this revision request also affects the City of Coppell, a separate LOMR for that community was issued on the same date as this LOMR. The modifications are effective as of the date shown above. The map panel(s) as listed above and as modified by this letter will be used for all flood insurance policies and renewals issued for your community. The following table is a partial listing of existing and modified BFEs: Existing BFE Modified BFE Location (feet)* (feet)* Just upstream of SH 121 468 467 *Referenced to the National Geodetic Vertical Datum, rounded to the nearest whole foot Public notification of the modified BFEs will be giYen in the Lewisville News on or about August 4 and August 11, 1999. A copy of this notification is enclosed. In addition, a notice of changes will be published in the Federal Register. Within 90 days of the second publication in the Lewisville News, a citizen may request that FEMA reconsider the determination made by this LOMR. Any request for reconsideration must be based on scientific or technical data. All interested parties are on notice that, until the 90-day period elapses, the determination to modify the BFEs presented in this LOMR may itself be modified. Because this LOMR will not be printed and distributed to primary users, such as local insurance agents and mortgage lenders, your community will serve as a repository for these new data. We encourage you to disseminate the information reflected by this LOMR throughout the community, so that interested persons, such as property owners, local insurance agents, and mortgage lenders, may benefit from the information. We also encourage you to prepare a related article for publication in your community's local newspaper. This article should describe the assistance that officials of your community will give to interested persons by providing these data and interpreting the NFIP maps. We will not physically revise and republish the FIRM and FIS report for your community to reflect the modifications made by this LOMR at this time. When changes to the previously cited FIRM panel(s) and FIS report warrant physical revision and republication in the future, we will incorporate the modifications made by this LOMR at that time. The floodway is provided to your community as a tool to regulate floodplain development. Therefore, the floodway modifications described in this LOMR, while acceptable to FEMA, must also be acceptable to your community and adopted by appropriate community action, as specified in Paragraph 60.3(d) of the NFIP regulations. This LOMR is based on minimum floodplain management criteria established under the NFIP. Your community is responsible for approving all floodplain development, and for ensuring all necessary permits required by Federal or State law have been received. State, county, and community officials, based on knowledge of local conditions and in the interest of safety, may set higher standards for construction in the SFHA. If the State, county, or community has adopted more restrictive or comprehensive floodplain management criteria, these criteria take precedence over the minimum NFIP criteria. The basis of this LOMR is, in whole or in part, a channel-modification project. NFIP regulations, as cited in Paragraph 60.3(b)(7), require that communities ensure that the flood-carrying capacity within the altered or relocated portion of any watercourse is maintained. This provision is incorporated into your community's existing floodplain management regulations. Consequently, the ultimate responsibility for maintenance of the modified channel rests with your community. This determination has been made pursuant to Section 206 of the Flood Disaster Protection Act of 1973 (Public Law 93-234) and is 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 U.S.C. 3 4001-4128, and 44 CFR Part 65. Pursuant to Section 1361 of the National Flood Insurance Act of 1968, as amended, communities participating in the NFIP are required to adopt and enforce floodplain management regulations that meet or exceed NFIP criteria. These criteria are the minimum requirements and do not supersede any State or local requirements of a more stringent nature. This includes adoption of the effective FIRM and FIS report to which the regulations apply and the modifications described in this LOMR. FEMA makes flood insurance available in participating communities; in addition, we encourage communities to develop their own loss reduction and prevention programs. Our Project Impact initiative, developed by FEMA Director James Lee Witt, seeks to focus the energy of businesses, citizens, and communities in the United States on the importance of reducing their susceptibility to the impact of all natural disasters, including floods, hurricanes, severe storms, earthquakes, and wildfires. Natural hazard mitigation is most effective when it is planned for arid implemented at the local level, by the entities who are most knowledgeable of local conditions and whose economic stability and safety are at stake. For your information, we are enclosing a Project Impact Fact Sheet. For additional information on Project Impact, please visit our Web site at www.fema._vov. If you have any questions regarding floodplain management regulations for your community or the NFIP in general, please contact the Consultation Coordination Officer (CCO) for your community. Information on the CCO for your community may be obtained by contacting the Director, Mitigation Division of FEMA in Denton, Texas, at (940) 898-5127. If you have any technical questions regarding this LOMR, please contact Mr. Alan Johnson of our staff in Washington, DC, either by telephone at (202) 646-3403 or by facsimile at (202) 6464596. Sincerely, Alan A. lohnson, P.E., Project Engineer For: Matthew B. Miller, P.E., Chief Hazards Study Branch "-~/,'~ Hazards Study Branch Mitigation Directorate Mitigation Directorate Enclosure(s) cc: The Honorable Candy Sheehan ~/~ Mayor, City of Coppell Mr. Kenneth M. Griffin, P.E. Director of Engineering and Public Works City of Coppell Mr. T. S. Kumar Assistant City Engineer Floodplain Administrator Depatiment of Community Development City of Lewisville Mr. Rusty Spiars, P.E. Vice President Dunaway Associates, Inc.