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Estates DC-CS021112IN REPLY REFER TO: The Honorable Candy Sheehan Case Number: 02- 06 -827R Mayor, City of Coppell 255 Parkway Boulevard Community: City of Coppell, Coppell, TX 75019 Dallas County, Texas Community No.: 480170 Dear Mayor Sheehan: 4 Federal Emergency Management Agency Washington, D.C. 20472 Lv Nl e_ NOV 12 2002 104 This is in reference to a letter, dated January 31, 2002, from Michael H. Boyd, P.E., of Nathan D. Maier Consulting Engineers, Inc., requesting a Conditional Letter of Map Revision (CLOMR) from the Federal Emergency Management Agency (FEMA) for the proposed Estates of Denton Creek. The proposed project will be located along Denton Creek from approximately 5,200 feet upstream of the confluence of Denton Creek with Elm Fork of Trinity River to approximately 8,800 feet upstream of the confluence, and will consist of the placement of fill in the 1% annual chance (100 -year) floodplain for Denton Creek and Elm Fork of Trinity River. Backwater effects from the Elm Fork of Trinity River affect the water surface elevations along Denton Creek at the project site; therefore, it is included in this analysis. The area of the proposed project is shown on Flood Insurance Rate Map (FIRM) number 48113C0155 J, dated August 23, 2001. We received the following data, prepared by Mr. Boyd, in support of this request: a HEC -RAS hydraulic model, dated October 17, 2000, of the 10 2 1 and 0.2% (10 -year, 50 -year, 100 -year, and 500 -year, respectively) annual chance floods and floodway, duplicating the effective conditions for Elm Fork of Trinity River; a HEC -RAS hydraulic model, dated August 22, 2002, of the 10 2 1 and 0.2% annual chance floods and floodway, representing the proposed conditions for Elm Fork of Trinity River; a certified topographic work map, dated August 2, 2002, titled FEMA Post Project Floodplain Work Map, at a scale of 1 inch 100 feet, with a contour interval of 1 foot, representing the proposed conditions for Denton Creek and Elm Fork of Trinity River; a report, dated January 2001, titled Estates of Denton Creek FEMA CLOMR Request, prepared by Nathan D. Maier Consulting Engineers, Inc.; KC-4s h4. G 2 a portion of the Dallas County, Texas and Incorporated Areas FIRM number 48113C0155 J, dated August 23, 2001, annotated to reflect proposed conditions; and completed application/certification forms, including community concurrence with the proposed project. We received all of the data required to perform a technical review of the CLOMR request as of October 10, 2002. We have reviewed the submitted data and determined that the proposed project meets the minimum floodplain management criteria of the National Flood Insurance Program (NFIP). If the project is built as proposed, a revision to the Flood Insurance Study (FIS) and FIRM for your community will be warranted. This revision will show the following effects, as shown by the data submitted to support the request: 1% Annual Chance Water Surface Elevations When the proposed conditions were compared to the effective conditions, it was determined that no changes would occur in the 1% annual chance water surface elevations. 1% Annual Chance Floodplain When the proposed conditions were compared to the effective conditions, it was determined that a maximum decrease of 520 feet in the 1% annual chance floodplain would occur approximately 6,400 feet upstream of the confluence of Denton Creek with Elm Fork of Trinity River. Floodway When the proposed conditions were compared to the effective conditions, it was determined that a maximum decrease of 520 feet in the floodway would occur approximately 6,400 feet upstream of the confluence of Denton Creek with Elm Fork of Trinity River. Future revisions to the FIS and FIRM, or restudies of the flood hazards in this area, could modify this determination. We based this determination on the 1% annual chance discharges computed in the FIS for your community without considering subsequent changes in watershed characteristics that could have increased discharges. Additionally, future development of projects upstream may increase discharges, which may increase flood hazards. A comprehensive restudy of your community's flood hazards would consider the cumulative effects of development on discharges subsequent to the publication of the FIS for your community and, therefore, could establish greater flood hazards in this area. Your community must approve all proposed floodplain development, including this proposed project, and ensure that permits required by other Federal agencies and/or State and local 3 agencies have been obtained. State and/or community officials may set standards for construction that are more restrictive than the minimum NFIP standards or may limit development in floodplains, based on knowledge of local conditions and in the interest of safety. If the State and/or the community have adopted more restrictive or comprehensive floodplain management criteria, those criteria take precedence over the minimum NFIP requirements. When your community requests a map revision to reflect the effects of the completed project, you must submit either a copy of a public notice stating the community's intent to revise the floodway on the FIRM or a statement by the community that it has notified all affected property owners and affected jurisdictions of the revision to the floodway, in compliance with NFIP regulations Subparagraph 65.7(b)(1). If fill is placed in your community to raise the ground surface to or above the Base (1% annual chance) Flood Elevation, your community must meet the criteria of NFIP regulations Sections 60.3 and 65.6, which require that the community's NFIP permit official certify that proposed or existing structures to be removed from the Special Flood Hazard Area (SFHA) be "reasonably safe from flooding." "Reasonably safe from flooding" means base flood waters will not inundate the land or damage structures to be removed from the SFHA and that any subsurface waters related to the base flood will not damage existing or proposed buildings. The community and engineers should review and use FEMA Technical Bulletin 10 -01, Ensuring that Structures Built on Fill In or Near Special Flood Hazard Areas are Reasonably Safe From Flooding, which may be downloaded directly from the FEMA website at http:// www .fema.gov /pdf /fima/tb1001.pdf. Upon completion of the proposed project, your community must request a revision to the FIS and FIRM, per NFIP regulations Section 65.3. The revision request should include the data listed below. 1. Evidence of compliance with NFIP regulations Paragraph 65.4(b), which states that "all requests for changes to effective maps...must be made in writing by the community's Chief Executive Officer (CEO) or an official designated by the CEO." 2. The detailed application and certification forms may be required if as-built conditions differ from the preliminary plans. If required, please submit new forms or annotated copies of the previously submitted forms showing the revised information. 3. As -built plans of all relevant project elements or a statement declaring that the project was built as proposed, either of which must be certified by a Professional Engineer. 4. Hydraulic analyses, for as -built conditions, of the 10 2 1 and 0.2% annual chance floods and floodway for Elm Fork of Trinity River. 5. A certified topographic map delineating the 1% and 0.2% annual chance floodplains and floodway for Denton Creek and Elm Fork of Trinity River, including the locations and alignments of the cross sections and flow lines used in the hydraulic model, representing as -built conditions. 4 a. Please show this information on a map of suitable scale and topographic definition to provide reasonable accuracy. b. Please label all items for easy cross referencing to the hydraulic model and summary data. c. Submit this information in paper and, if available, electronic format. 6. A copy of the Dallas County, Texas and Incorporated Areas FIRM number 48113C0155 J, dated August 23, 2001, annotated to reflect the as-built conditions. 7. Please submit a letter stating that your community will adopt and enforce the modified floodway. 8. Documentation showing compliance with NFIP regulations Subparagraph 65.6(a)(14) regarding fill placement and Subparagraph 65.7(b)(1) regarding floodway revisions. If the project is built as proposed in the data submitted in support of this request, you do not have to resubmit items 2, 4, 5, and 6 listed above; otherwise, please resubmit them. We have enclosed a copy of our application/certification forms for your reference. The application/certification forms package may be downloaded directly from the FEMA website at http: /www.fema.gov /mit/tsd/en_main.htm or copies may be obtained by contacting the FEMA Map Assistance Center, toll free, at 1- 877 -FEMA MAP (1- 877 336 2627). Typically, we do not require all of these forms if the project is completed as proposed in the data submitted in support of this request. The enclosed document, titled Requirements for Submitting Application/ Certification Forms to Support Requests for NFIP Map Revisions, describes in detail the circumstances under which the forms are required. The NFIP is primarily funded by policyholders, not taxes. We recover costs associated with reviewing and processing requests for modifications to published FIS and FIRM, to minimize the financial burden on the policyholders. The fee for an as -built Letter of Map Revision request in follow -up to this CLOMR is $3,800, which we must receive before we can begin processing. This fee represents the fee schedule effective September 1, 2002. However, the fee schedule is subject to change, and the requester is required to submit the fee in effect at the time of the submission. Your payment must be a check or money order made payable to the National Flood Insurance Program and should be forwarded to: Federal Emergency Management Agency Fee Charge System Administrator P.O. Box 3173 Merrifield, Virginia 22216 Once we receive the processing fee and the items listed above, complete our review, and verify that the completed project meets all applicable NFIP standards; we will revise your community's FIS and FIRM to incorporate the effects of the completed project, as appropriate. 5 Part 65 of the enclosed NFIP regulations further describes the data needed to support a request to revise the FIS and FIRM. Your compliance with the criteria outlined in the NFIP regulations will streamline our review, allowing us to expeditiously revise your community's FIS and FIRM. If you have any questions regarding this CLOMR, please contact the FEMA Map Assistance Center, toll free, at 1- 877 -FEMA MAP (1- 877 336- 2627). Sincerely, Lloyd A. ake, Project Engineer Hazards Study Branch Federal Insurance and Mitigation Administration Enclosures cc: For: Matthew B. Miller, P.E., Chief Hazards Study Branch Federal Insurance and Mitigation Administration Ken Griffin, P.E., Director of Engineering, City of Coppell Michael H. Boyd, P.E., Nathan D. Maier Consulting Engineers, Inc.