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FS8901-CS 901130Federal Emergency Management Washington, D.C. 20z~72 tqov 30 }111'©11 QWg,?i i, The Honorable Mark Wolfe Mayor of the City of Coppell P.O. Box 478 Coppell, Texas 75019 Dear Mayor Wolfe: IN REPLY REFER TO: (65-DR2) Case Nos.: 6-89-236 and 6-90-152 Community: City of Coppell, Dallas and Denton Counties, Texas Community No.: 480170 This is in reference to a request for a revision to the Flood Insurance Study and National Flood Insurance Program maps for your community. Information pertinent to this revision request is listed below: Requestor: Mr. Russell R. Doyle, P.E., City Engineer and Ms. M. Shohre Daneshmand, P.E., Acting City Engineer Flooding sources: Denton Creek, Cottonwood Branch, Grapevine Creek, and Elm Fork of the Trinity River Project name or area of revision: Kimley-Horn Associates, Inc., restudy of all streams and Elm Fork floodway revisions at the HRWS Tract Map Panels affected: Flood Insurance Rate Map number 480170, panel 0005 Our previous letter to you indicated that additional information might be required to complete our evaluation of the request. We have reviewed the data submitted and have determined that additional and/or revised data are required to complete our evaluation. The enclosed list outlines the information required. A representative of Dewberry & Davis, our technical evaluation contractor, will be calling the requestor to discuss the required information. Please submit the information specified on the enclosed list directly to our Technical Evaluation Contractor, Dewberry & Davis, 8401 Arlington Boulevard, Fairfax, Virginia 22031, to the attention of Mr. Joseph Chapman, Management Engineering and Technical Services Division. If the information is not received within 30 days, we will issue a letter of final determination and publish the September 22, 1988 preliminary FIRM in its final effective form. If the information is submitted after 30 days, then we will prepare another physical map revision to incorporate the Kimley-Horn Associates, Inc., analyses. The case nu~nber referenced above should be included on any further corre- spondence regarding this request. Our review cannot proceed until the required additional data are received. After receiving the data, we will continue our evaluation of the request. If additional information is required to complete our evaluation, we will inform you. Should you have any questions or if additional time is required to provide the required data. please contact Matthew B. Miller of my staff at (202) 646-3461~ Sincerely, J~h~ L. Matticks Chef, Risk Studies Division Federal Insurance Administration Ms. M. Shohre Daneshmand ~ Mr. James C. Graham, P.E., Chief, F.P.M.S., U.S. Army Corps of Engineers, Fort Worth District Mr. Ronald W. Morrison, P.E., Kimley-Horn Associates, Inc. Mr. Erv A. Meyer, Nathan D. Maier Consulting Engineers, Inc. FILE COPY Case Nos.: 6-89-236 and 6-90-152 Community: City of Coppell, Dallas and Denton Counties, Texas Community No.: 480170 ADDITIONAL DATA REQUIRED TO SUPPORT A REVISION TO THE FLOOD INSURANCE STUDY AND NATIONAL FLOOD INSURANCE PROGRAM MAP Requestor: Mr. Russell R. Doyle, P.E. and Ms. M. Shohre Daneshmand, P.E. Date: NOV S 0 The issues listed below must be addressed in order to process this revision request: In our September 18, 1990 letter concerning this revision, we recommended that the City of Coppell coordinate with Kimley-Horn Associates, Inc. (KHA), and Nathan D. Maier Consulting Engineers, Inc. (NDM), to determine a single floodway configuration of the Elm Fork of the Trinity River in the area of the HRWS Tract just upstream of the St. Louis and Southwestern Railroad. With a November 2, 1990 letter, Mr. Ronald Morrison, P.E., of KHA submitted revised technical data in an undated technical report entitled Flood Study of the Elm Fork of the Trinity River Through the City of Coppell, Texas. In this report, it is stated that the floodway at the HRWS Tract was revised to match the NDM floodway at this location. However, our review of the submitted HEC-2 models submitted by KHA indicates that cross-section data at Section 89050 was not changed to match the NDM model. The NDM model contained revised GR points at Section 89050 to more accurately reflect the upstream ineffective flow area due to the St. Louis and Southwestern Railroad embankment. Our review of the NDM data indicates that it better represents existing flow conditions. The HEC-2 models for the Elm Fork of the Trinity River should be revised to reflect these changes. Before the Federal Emergency Management Agency (FEMA) can revise the Flood Insurance Study (FIS) and Flood Insurance Rate Map (FIRM) for the City of Coppell, plotted water-surface profiles for the 10-, 50-, 100-, and 500-year floods for Denton Creek, Cottonwood Branch and Grapevine Creek must be submitted. No profiles were received with the latest models for these streams submitted with a May 4, 1990 letter by Ms. M. Shohre Daneshmand, P.E., Acting City Engineer for the City of Coppell. In addition, the profile for the Elm Fork of the Trinity River submitted by Mr. Morrison with his November 2, 1990 letter is at a horizontal scale of 1 inch equals 5,000 feet, which is inappropriate for use in revising the Coppell FIS. Plotted profiles of the 10-, 50-, 100-, and 500-year floods for each stream studied in detail should be submitted at the following scales consistent with the effective FIS: Vertical Horizontal Stream Scale Scale Elm Fork of the Trinity River 1"~10' Grapevine Creek 1"=5' Denton Creek 1"~10' Cottonwood Branch 1"=10' 1"~1,000' 1"~1,000' 1"=1,000' 1"~500' In our September 18, 1990 letter, we stated that a written statement from the Fort Worth District of the U.S. Army Corps of Engineers (COE) concerning the appropriate hydrologic analysis to be used for FIS purposes must be submitted. The technical report submitted by Mr. Morrison with his November 2, 1990 letter, contained portions of the hydrologic analysis for the COE recon- naissance study of the Elm Fork of the Trinity River. However, no statement from the COE concerning this analysis was submitted. Before utilizing these discharges to revise the Coppell FIS, a statement concerning their appropriateness for FIS purposes must be received. o ~ <~ o >~ >