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FS9903-CS 990422Morrison Hydrology EngineerinS lnc. 210 Arnold A~ Arlin~on, T_,~r~ 76010 Maro (817) 461-0~21 Fax (81~) 274-1~8 E-Mail: ronmor 7 777~aoL com April 22, 1999 Mr. Kenneth M. Grimn; P.E. Assistant City Manager and City Engineer City of Coppell 255 Parkway Blvd. P.O. Box 478 Coppell, Texas 75019 Oif214-304-3679 Metre 214471-2251 Fax 214-304 3673 Flood Study of the Elm Fork of the Trinity River For a 10 and 48 Acre Parcel of Land South of Sandy Lake Road And East of MacArthur Road in Coppell, Texas We assume you received the information from Ms. Laura Bittner CEmail attached) regardin4 the methodology for submitting a Conditional Letter of Map Revision (CLOMR) and Conditional Letter of Map Revision based on Fill (CLOMR-F) requests. As we understand it, a CLOMR submittal must use "best available d~_t_~" which means that the alyproved existing condition from the latest CLOMR (or LOMR) approved by FEMA must be used as base conditions. We were aware of this requirement. What we were not aware of is that this does not apply to a CLOIvlR-F. For a CLOMR-F you must use the effective model whether it has been modified by a CLOMR or not. This particular site shows on the FEMA FIRM map as being at elevation 446 +/-. The existing condition from the latest approved CLOMR shows an elevation of ~.~.~. +/-. The Co~ps HECRAS model (which has been reviewed by FEMA's technical consultant and approved, but has not been through the FEMA approval process) shows an elevation of 442 +/-. In conversations with FEMA and the FEMA technical consultant we understand that this last model will be official soon (probably this year). So by the time the project is finished we will be required to use the Corps HECRAS model for ashtilt conditions. If we wait until the Corps HECRAS is officially approved the property can be removed from the floodplain by filling to 442 +/-. Naturally, the city will require fill to one foot above the ultimate condition as per OrdinanCe. The problem with waiting for this final FEMA approval of the tiECRAg model is that we do not know within a reasonable period when this will happen, and the timing of this project is critical. ff we use the CLOMR-F procedure with an elevation of 446 +/- the cost of the extra ~H is excossive and we are not sure that there is sufficient storage Cempensation forthis elovalion. Morrison Hydrology Engineering, ln~ 10 and 48 Acre Parcel of Land South of Sandy Lake Road And East of MacArtkur Road in Coppe!l, Twcas Page -2- So to correct the problem we are preparing a CLOMR submittal for the project. We discussed this with The most pressing concern at this point is time. ff this revised submittal must be reviewed by your floodplain review consultant it will delay the project to a point that the developer tells us that it puts the completion of the project in question. Please let me know what you will require. Thank you for your attention in this matter, Sincerely, ~Ro~d W.t~Mo~n, P.E., C.F.M Senior Hydrologist Mr. Dayton Macat~ Engineering EMnil Subj: City of Coppert, TX - Ken Griffin Date: 99-04-19 12:31:29EDT From: LBrFrNEl~fi~akercorp.com (Laura Bittner) To: RONMOR7777~aol.com Ron, I just spoke to Ken Caiffin and I think I was unclear about what we discussed regarding CLOMRs in Laredo. As we talked about, previously issued CLOMR existing conditions models should be used as base models (or as the 'effective model") in new requests for LOMRs/CLOMRs because this information acts as the best available dam in the area. However, we cannot do LOMR-Fs, CLOMR-Fs, or LOMAs Imsed on existing condition CLOMR models. LOMR-Fs, CLOMR-Fs, and LOMAs can only be issued b~sed on effective BFEs. (Unless the area is in Zone A where no effective BFEs exist.) The same is tree for prelil,inary maps. Preliminary maps can be used as best available data for floodplain management but will not be used for insurance purposes anti they become effective. I apologize if this has created some confusion. Please call me at (703) 317-6292 or eraall me if you would like to discuss this further. Ken Griffin - E0u LieboWitz P~dpe~ S6~th. Of ~an'~ly L~ke R~d~Tr~r~it~'Fl~d~j~l~iri ........................ Page 1 ~ From: To: Date: Subject: <RONMOR7777@aol .com> Ken Griffin <kgriffin@ci.coppell.tx.us> 4/21/99 5:17PM Lou Liebowitz Property South of Sandy Lake Rood, Trinity Floodplain Ken: I assume you recieved the information from Laura Bittner regarding the methodology for submitting CLOMR and CLOMR-F requests. As I understand it, a CLOMR submittal must use "best available data" which moons the approved existing condition from the latest CLOMR (or LOMR) appmved by FEMA. This part I knew. What I didn't know was that this does not apply to a CLOMR-F. For a CLOMR-F you must use the effective model whether it has been modified by a CLOMR or not. This particular site shows on the map as being at elevation 446 +/-. The existing condition from the latest approved CLOMR shows an elevation of 444 +/-. The Corps model (which has been reviewed by FEMA's technical consultant and approved, but has not been through the FEMA approval process) shows an elevation of 442 +/-. This last model will be official soon (probably this year). So by the time we finish the subject project we will be required to use the HECRAS model for as-built conditions. It seems rather extreme to fill to 446 +/- when most everyone agrees the correct elevation is 442 +/-, and the FEMA approved (CLOMR) elevation is 444 +/-. I am not sure that there is sufficient storage compensation for an elevation of 446. So to correct the problem we are reworking the CLOMR-F submittal we sent to you. It will now be submitted as a CLOMR. I discussed this with Laura Bittner and she informed me that FEMA would accept this project for review as a CLOMR submittal. We will redo the report as a CLOMR and provide it to you Monday. The most pressing concorn at this point is time. If this revised submittal must go through the Kimley Horn review process, it will delay the project to a point that the developer tells us that it puts the completion of the project in question. Please let me know what yuo will require. Sincerely Ron Mordson CC: Allegro5.Hub 05("macatee@mindspring.com","lbittner...