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Carter Ph 1 FS-CS 980603 Federal Emergency Management Agency - Washington, D.C. 20472 JUN 0 3 1998 ( L_ 0 CERTIFIED MAIL IN REPLY REFER TO: RETURN RECEIPT REQUESTED Case No.: 98-06-1223R The Honorable Candy Sheehan Community: City of Coppell, Texas Mayor, City of Coppell Community No.: 480170 255 Parkway Boulevard Coppell, Texas 75019 104 Dear Mayor Sheehan: This responds to a request that the Federal Emergency Management Agency (FEMA) comment on the effects that a proposed project would have on the effective Flood Insurance Rate Map (FIRM) and Flood Insurance Study (FIS) report for your community in accordance with Part 65 of the National Flood Insurance Program (NFIP) regulations. In a letter dated May 6, 1998, Mr. Robert L. Wright, P.E., Senior Vice President, Needham Wright Engineers, Inc., requested that FEMA evaluate the effects that proposed placement of fill in the floodway fringe along Grapevine Creek from approximately 110 feet upstream to approximately 1,385 feet upstream of Moore Road and excavation in the floodway along Grapevine Creek from approximately 485 feet upstream to approximately 1,100 feet upstream of Moore Road would have on the flood hazard information shown on the effective FIRM and FIS report. In addition, this request - included a more detailed hydraulic analysis that incorporated more detailed topographic information to reflect existing watershed conditions along Grapevine Creek from Moore Road to approximately 3,175 feet upstream. All data required to complete our review of this request for a Conditional Letter of Map Revision (CLOMR) were submitted with letters from Mr. Kenneth Griffin, P.E., Director of Public Works, City of Coppell, and Mr. Wright. We have completed our review of the submitted dam and the flood data used to prepare the effective FIRM for your community. The submitted existing conditions HEC-2 hydraulic computer model for Grapevine Creek, dated January 4, 1997, based on updated topographic information, ,,vas used as the base conditions model in our review of the proposed conditions model for this CLOMR request. We believe that. if the proposed project is constructed as shown on the submitted plans entitled "Flood Plain Reclamation Study Carter Addition," and as described in the submitted report entitled "The Carter Addition," both prepared by Jerry Parche Consulting Engineers and dated January 1997, and the data listed below are received, a revision to the FIRM would be warranted. The submitted existing conditions hydraulic model incorporated more detailed topographic information to reflect existing watershed conditions along Grapevine Creek. The elevations of the flood having a l-percent chance of being equaled or exceeded in any given year (base flood) increased and decreased compared to the effective base flood elevations (BFEs). The maximum increase in BFE, 0.4 foot, occurred approximately 1,035 feet upstream of Moore Road. The maximum decrease in BFE, 0.12 foot. occurred just upstream of Moore Road. 2 As a result of the proposed project, the BFEs along Grapevine Creek will increase and decrease compared to those computed in the existing conditions analysis. The maximum increase in BFE, 0.02 foot, will occur approximately 135 feet upstream of Moore Road. The maximum decrease in BFE, 0.07 foot. will occur - approximately 1,147 feet upstream of Moore Road. As a result of the proposed project and more detailed topographic information, the BFEs along Grapevine Creek will increase and decrease compared to the effective BFEs. The maximum increase in BFE, 0.4 foot, will occur approximately 1,035 feet upstream of Moore Road. The maximum decrease in BFE, 0.18 foot, will occur approximately 135 feet upstream of Moore Road. The width of the Special Flood Hazard Area (SFHA), the area that would be inundated by the base flood, will decrease compared to the effective SFHA width. Upon completion of the project, your community may submit the data listed below and request that we make a final determination on revising the effective FIS report and FIRM. · Effective October 1, 1996, FEMA revised the fee schedule for reviewing and processing requests for conditional and final modifications to published flood information and maps. FEMA established flat review and processing fees for most types of requests. Effective March 10, 1997, FEMA modified the fee schedule that became effective on October 1. In accordance with this schedule, the fee for your map revision request will be S2.300 and must be received before we can begin processing your request. Payment of this fee shall be made in the form of a check or money order, made payable in U.S. funds to the - National Flood Insurance Program, or by credit card. Ihe payment must be forwarded to the following address: Federal Emergency Management Agency Fee-Collection System Administrator P.O. Box 3173 Merrifield, VA 22116-3173 · As-built plans, certified by a registered professional engineer, of all proposed project elements · Community acknowledgment of the map revision request · Certification that all fill placed in the currently effective base floodplain and below the proposed BFE is compacted to 95 percent of the maximum density obtainable with the Standard Proctor Test method issued by the American Society for Testing and Materials (ASTM Standard D-698) or an acceptable equivalent method for all areas to be removed from the base floodplain · Hydraulic analyses, for as-built conditions, of the base flood, the flood having a 0.2-percent chance of being equaled or exceeded in any given year. and the regulatory floodway if they differ from the proposed conditions models _.. After receiving appropriate documentation to show that the project has been completed, FEMA will initiate a revision to the FIRM and FIS report. The basis of this CLOMR is, in whole or in part, a channel-modification project. NFIP regulations, as cited in Paragraph 60.3(b)(7), require that communities assure 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 CLOMR 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. 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 CLOMR, please contact Mr. Alan Johnson of our staff in Washington, DC, either by telephone at (202) 646-3403 or by facsimile at (202) 646-4596. Sincerely, _ Alan A. Jc~I{son For: Matthew B. Miller, P.E. Project Edg4neer, Hazards Study Branch Chief. Hazards Study Branch Mitigation Directorate Mitigation Directorate cc: Mr. Kenneth Griffin, P.E. ,~ Director of Public Works City of Coppell Mr. Robert I~. Wright, P.E. Senior Vice President Needham Wright Engineers, Inc.