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FIRM-930315March 15, 1993 Mr. Matthew B. Miller Federal Emergency Management Agency Federal Insurance Administration Office of Risk Assessment 500 C Street, SW, Room 418 Washington, D.C., 20472 RE: Case Number: 92- 06 -124P Community: City of Coppell, Dallas and Denton Counties, Texas Community #: 480170 Revisions to the Flood Insurance Study (FIS) and Flood Insurance Rate Map (FIRM) Dear Mr. Miller: The City of Coppell has received and reviewed the letter submitted on December 18, 1992, concerning the revisions to our FIS and FIRM. The City of Coppell also appreciates the ninety day time frame in which to address the various items that FEMA had concerning our map revisions. Most of the items have been addressed and will be explained in greater detail later in this letter. However, some items could not be addressed and the City of Coppell is aware that the final map may not reflect the changes to the items that have not been addressed. To help assist FEMA in evaluating the requested information, this letter will follow the same format as the letter the City of Coppell received dated December 18, 1992. Each item of concern will be restated in this letter and then a detailed analysis of what the City of Coppell has done to address the concern will follow that section. Corporate Limits Mr. Grin requested that the corporate limits for the City of Coppell shown on the preliminary revised FIRM be annotated to reflect submitted annexation Ordinance Nos. 88410, 88412, 88427, and 89430, and disannexation Ordinance No. 91504. As will be discussed later in this letter, annotations reflecting these corporate limits changes must be made by the City of Coppell on a copy of the December 18, 1991, preliminary revised FIRM and submitted to FEMA. The City of Coppell has adjusted the corporate limits on the December 18, 1991, preliminary revised FIRM, as requested by FEMA. Specifically the changes are as follows: 1) The City of Coppell has adjusted the city limits along State Highway 121 to accurately show the city limits on the southeast side of SH 121 and also has included a section of the City of Coppell that extends on the west side of SH 121 along Denton Creek. 2) The city limits along Belt Line Road, immediately east of Denton Tap, has been revised to accurately show the city limits. 3) The City of Coppell has adjusted the city limits adjacent to Denton Creek, Elm Fork Trinity River and Grapevine Creek along the east side of Coppell. Our city limit map was flown and digitized on a 1" =1000' scale in 1992. We have used that information to show the various streets and subdivisions on the east side of Coppell. In making the subdivisions fit, it was apparent that the location of the creeks themselves were slightly incorrect. Therefore, slight adjustments are necessary to the east city limits along the creeks. The city requests that the changes be incorporated into the final revised FIRM. Street Names and Locations Mr. Grin submitted numerous plat maps and requested that streets be added to and labeled on the preliminary FIRM for the following subdivisions: Oakbend Addition, Shadow Woods Estates, Park Meadows Sections I and II, and Carter Estates. Mr. Griffin also requested that the extension of Parkway Boulevard west of Denton Tap Road be added to the preliminary revised FIRM. These street additions and labels must be made on a copy of the December 18, 1991, preliminary revised FIRM and submitted to us for review, as discussed at the end of this letter. As requested, the City of Coppell has provided street names for the Oakbend Addition, Shadow Woods Estates, Park Meadows Sections I and II and Carter Estates. Also, the section of Parkway Blvd. west of Denton Tap has been shown. The city requests that the changes be incorporated into the final revised FIRM. Flood Hazard Information Denton Creek Rood plain Mr. Griffin submitted "as- built" grading plans for the Gibbs Station and the Lakes of Coppell /Lakewood Estates subdivisions and requested that the 100 -year floodplain for Denton Creek be revised on the preliminary revised FIRM to reflect that information. As discussed later in this letter, these changes to the Denton Creek 100 -year floodplain must be made on a copy of the December 18, 1991, preliminary revised FIRM. The City of Coppell used its 1 " =1000' maps from 1992 to show the subdivisions for the Lakes of Coppell, Lakewood Estates and Gibbs Station along the east side of Coppell, west of Denton Creek. These subdivisions fit generally very well with the FEMA maps. However, as previously stated, to accurately align the subdivisions on the FEMA map will necessitate the realignment of the east city limits as it goes along Denton Creek. As requested, all the changes have been made on the December 18, 1991, preliminary revised FIRM. The city requests that the changes be incorporated into the final revised FIRM. Lakes of Coppell /Villages of Coppell Mr. Griffin requested that the 100 -year floodplain for Denton Creek be revised to reflect the Lakes of Coppell /Villages of Coppell project. A conditional LOMR was issued for this project on September 8, 1992. However, the data necessary to support a revision to the FIRM upon completion of the project, as stated in the conditional LOMR, have not been submitted to FEMA. Therefore, the FIRM for the City of Coppell cannot be revised to reflect this project until the required data are submitted. As requested, the as -built plans for Villages of Coppell Phase III and Phase IVB are being provided with this letter. Based on your letter, this should satisfy the requirement to revise the floodplain in that area. The revisions to the floodplain are shown on the December 18, 1991, preliminary revised FIRM. The city requests that the changes be incorporated into the final revised FIRM. Elm Fork Trinity River Rood lain Mr. Griffin submitted topographic information for the area south of Beldine Road and requested that the area designated as Zone X be included in the 100 -year floodplain for the Elm Fork Trinity River. This revised 100 -year floodplain must be made on a copy of the December 18, 1991, preliminary revised FIRM, as discussed later in this letter. The floodplain south of Belt Line Road has been revised as requested and is shown on the December 18, 1991, preliminary revised FIRM. The city requests that the changes be incorporated into the final revised FIRM. Grapevine Creek Channelization and Drop Structure Mr. Griffin requested that the flood flood hazard information for Grapevine Creek be revised to reflect the channelization and concrete drop structure located downstream of Interstate Highway 635. A LOMR for the City of Coppell was issued to reflect this completed project on August 10, 1992. The effects of this LOMR will be incorporated into the final effective FIRM for the City of Coppell. We understand that a LOMR was issued for this project on August 10, 1992, and that this project will be incorporated into the revised firm. We have shown the revisions on the December 18, 1991, preliminary revised FIRM. Big Cedar Addition Mr. Griffin requested that the flood hazard information for Tributary G -1 of Grapevine Creek be revised to reflect fill associated with the Big Cedar Addition. As stated in our October 16, 1992, letter to you the effects of this project will be incorporated into the final effective FIRM for the City of Coppell. It is our understanding that this project will be incorporated into the final effective FIRM. However, the December 18, 1991, preliminary revised FIRM has the alignment of Grapevine Creek slightly incorrect. We have made the adjustments to the December 18, 1991, preliminary revised FIRM to accurately show the alignment of Grapevine Creek along the Big Cedar Subdivision. By changing the alignment of the creek, there is additional portions of land north of Grapevine Creek that should be included in the floodplain. The additional portions of land in the floodplain was shown on the subdivision that recently platted adjacent to Grapevine Creek. The city requests that the changes be incorporated into the final revised FIRM. Denton Tap Road Bridge Mr. Griffin requested that the flood hazards for Grapevine Creek be revised to reflect the construction of a new bridge at Denton Tap Road. A LOMR request was previously submitted for this project in a November 20, 1990, letter from Mr. John C. Karlsruher, P.E. , of Ginn, Inc. Subsequently, we responded with a January 3, 1991, letter requesting additional data to support this request. We received these data on November 25, 1992. After we evaluate their correctness and completeness, we will notify you in a separate letter whether the effects of the Denton Tap Road bridge can be incorporated into the finalized preliminary revised FIRM. It is our understanding that as of November 25, 1992, all data had been submitted to FEMA for review. It is also our understanding that we will be notified after this information has been evaluated. Depending on the timetable for review, hopefully any revisions to the map concerning the Denton Tap Road Bridge can be incorporated into the final revised FIRM. Creekview Estates Mr. Grin requested that flood hazards for Grapevine Creek also be revised to reflect the Creekview Estates subdivision. A conditional LOMR was issued on July 1, 1988. However, the data necessary to support a revision to the FIRM upon completion of the project, as stated in the conditional LOMR, were never submitted to FEMA. The FIRM for the City of Coppell cannot be revised to reflect this project until the required data is submitted. It is our understanding that the as -built plans for Creekview Estates were recently submitted to FEMA. We have revised the December 18, 1991, preliminary revised FIRM to show the effects of the as -built plans for Creekview Estates. The City of Coppell requests that the as -built plans be reviewed and that the final FIRM for the City of Coppell be revised to reflect the as -built plans for Creekview Estates. Villages of Cottonwood Creek Mr. Griffin submitted "as- built" grading plans and requested that the 100 - yearfloodplain and FEMA - designated floodway for Cottonwood Branch be revised to reflect the Villages of Cottonwood Creek project. Additional data are necessary to incorporate this information, as discussed later in this letter. Your letter requested additional HEC -2 models for Cottonwood branch along the Villages of Cottonwood Creek. It is our understanding that FEMA issued a letter on May 23, 1986, concerning this project and that the letter served as a LOMR. This has been discussed with Mr. Jerry Sparks, of Dewberry and Davis. Mr. Sparks has stated that the May 23, 1986, letter was sufficient and that there was no need for any additional HEC -2 data. The City of Coppell has made the changes as reflected in the May 23, 1986, letter on the December 18, 1991, preliminary revised FIRM. The City of Coppell requests that the changes be incorporated into the final FIRM. MacArthur Boulevard Bridge Mr. Grin submitted "as- built" plans for the MacArthur Boulevard bridge that crosses Denton Creek and requested that the flood hazard information for Denton Creek be revised to reflect this completed project. As discussed later in this letter, additional data are necessary to reflect the effects of the bridge at MacArthur Boulevard. The City of Coppell worked closely with Mr. Deaton, of Carter and Burgess, to obtain the information that FEMA requested. Mr. Deaton was sent a letter on February 22, 1993, detailing all information required by FEMA. I spoke with Mr. Deaton on March 12, 1993, concerning the project. Mr. Deaton was unable to generate the information for the submittal to FEMA. Therefore, the City has been unable to provide the information as requested by FEMA for the revision of the map in this area. Mr. Deaton has been informed that the property most likely will be shown in the floodplain and that to develop the property at some future date there would still need to be a floodplain study approved by both the City of Coppell and FEMA. Northlake Woodlands East No. 12 Mr. Griffin submitted a floodplain study for this subdivision and requested that the FIRM be revised as appropriate to reflect this information. We have reviewed this information and determined that the Northlake Woodlands East No. 12 subdivision is outside the 100= year floodplain for Grapevine Creek as shown on the preliminary revised FIRM. Thus, a revision to the FIRM is not required for this subdivision. It is our understanding that Northlake Woodlands East No. 12 is outside the 100 - year floodplain and therefore we are not required to take any action on the item. Redelineation of Floodplain Boundaries for all Streams In an October 23, 1992, letter, Mr. Griffin requested that the floodplains be redelineated for each .stream within the community utilizing topographic mapping provided by the City of Coppell. With this letter, Mr. Griffin submitted draft street and topographic maps at a scale of 1 " =600' with a contour interval of 10 feet. The City of Coppell submitted a final set of topographic maps at a scale of 1 " =200' with a contour interval of 2 feet on November 25, 1992. As discussed below, FEMA will not perform the work to revise the floodplain delineations based on this topographic information. This work must be performed by the city. The City of Coppell has chosen to use topographic information to revise the floodplain in only one area. The area is generally bounded by Sandy Lake, MacArthur, Belt Line and the east city limits. Because of the revision, the December 18, 1991, preliminary revised FIRM has been revised and certified by a registered professional engineer. Also, the topographic maps used to revise the floodplain have been certified by a registered professional engineer. The city regrets that it is unable to revise the entire floodplain within the city limits at this time. Additional Data Required by FEMA Because the City of Coppell contracted KHA to prepare the data used to support the December 18, 1991, preliminary revised FIS and FIRM, it is inappropriate for the City of Coppell to request that FEMA correct the deficiencies resulting from the KHA analyses. In essence, the city is appealing its own study and is requesting that FEMA perform the necessary work at the expense of flood insurance policy holders nationwide. Nevertheless, one of FEMA's goals is to assure that the most accurate flood hazard information possible is presented on the FIRM for your community; thus, we will suspend processing of the preliminary revised FIS and FIRM for 90 days in order for your community to prepare the required data listed below. 1. A copy of the December 18, 1991, preliminary revised FIRM annotated to depict the revised corporate limits, added streets and street names, and revised 100- and 500- year floodplain boundaries and floodways. All changes to floodplain boundaries must be supported by topographic information certified by a registered professional engineer or licensed land surveyor. This annotated FIRM must also be certified by a registered professional engineer. Please note that if the floodplain boundaries are completely redelineated based on the City of Coppell's new topographic map at a scale of 1'=200', as requested in Mr. Griffin's October 23, 1992, letter, these topographic maps must also be submitted and certified by a registered professional engineer. As previously stated, we have made various changes to the corporate city limits, we have added streets, street names and revised the 100 -year floodplain boundaries and floodways in various locations. There has also been some changes to the floodplain boundaries based on topographic information. All changes have been made on a mylar copy of the December 18, 1991, preliminary revised FIRM. Also, the city made a blueline copy and color coded it with all the changes. The mylar and the blueline copy was certified by Kenneth M. Griffin, P.E., City Engineer / Foodplain Administrator. The topographic maps were certified by Mr. Gary Teague of Teague Nall & Perkins, Inc. 2. HEC -2 models for Denton Creek reflecting the 10-, 50-, 100- and 500 -year floods and floodway revised to reflect the "as- built" MacArthur Boulevard bridge. Annotated FIS report flood proflles and the floodway data table for Denton Creek to reflect this revised modeling must also be submitted. Also, the revised 100 - and 500- year floodplain boundaries and floodway for Denton Creek must be included on the annotated FIRM, as discussed previously. As previously stated, we were unable to provide the information for the MacArthur Boulevard bridge changes. 3. HEC -2 models for Cottonwood Branch reflecting the 10L, 50-, 100- and 500- year floods and floodway revised to reflect the Villages of Cottonwood Creek. Annotated FIS report flood profiles and the floodway data table for Cottonwood Branch to reflect this revised modeling must also be submitted. Also, the revised 100- and 500- year floodplain boundaries and floodway for Cottonwood Branch must be included on the annotated FIRM, as discussed previously. As previously stated, it is our understanding, based on a conversation with Jerry Sparks, of Dewberry and Davis, that a LOMR was issued for this project and that no additional information is required for processing this request to change the maps in this area. 4. For the Creekview Estates subdivision, all data requirements of Part 65 of the NFIP regulations (copy enclosed), as indicated in the July 1, 1988, conditional LOMR (copy enclosed). As previously stated, the as -built plans have been submitted for Creekview Estates. The City of Coppell requests that the as -built plans be reviewed and incorporated into the final FIRM for the City of Coppell. 5. For the Denton Tap Road bridge, all data requested in our January 3, 1991, letter to the City of Coppell. It is our understanding that all necessary documentation for the Denton Tap Road Bridge was submitted on November 17, 1992. The City of Coppell requests that the data be reviewed and any changes to the map based on the review be incorporated into the final FIRM for the City of Coppell. Again, the City of Coppell appreciates the opportunity to take an additional ninety days to resolve some of the issues so that a map can be generated that more accurately reflects the floodplain in the City of Coppell. Because we were unable to obtain all of the information, we also understand that there still might be areas on the map that may be shown incorrectly on the final FIRM. However, the final FIRM as a whole will be essentially 90 -95 % correct in regards to the floodplain in the City of Coppell. If you should have any questions concerning the submittal of this information please contact me at (214) 393 -1016. Sincerely, 1� Kenneth M. Griffin P.E. City Engineer / F000dplain Administrator CC: Alan D. Ratliff, City Manager Shohre Daneshmand, P.E., Civil Engineer file /fema393