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ST9002-CS 901214 71 Cr~l~pelt, T~:xn.'~ 75019 The Cily With A [~om~lilul I:~1~. 214- 4G2-0022 FAX 214 - 393-0948 December 14, 1990 Mr. Matthew Miller, P.E. Rick Studies Division Federal Insurance Administration Federal Emergency Management Agency 500 C Street, Southwest Washington, D.C. 20472 Re: Request for Conditional Letter of Map Revision for Proposed Structures on Grapevine Creek, Southwestern Blvd. to IH 635 in Coppell, Texas Dear Mr. Miller: Please find enclosed a technical report on existing and proposed floodplain and floodway conditions relative to the reach of Grapevine Creek from Southwestern Boulevard 'to IH-635 in Coppell. This report, prepared by Albert H. Halff Associates, Inc., includes a detailed hydraulic analysis of the existing and proposed channel and overbank conditions. This report also includes the HEC-2 computer printouts, floodplain and floodway maps, and other data required for a Conditional Letter of Map Revision. Attached you will also find a copy of related Corps of Engineers' 404 Permit, dated November 14, 1990. A Conditional Letter of Map Revision dated August 18, 1987, Case No. 86-06-47R already exists for this reach of Grapevine Creek. This report incorporates the previous hydraulic analysis and provides technical data for two additional bridge crossings. We respectfully request a new Conditional Letter of Map Revision, which will include the proposed Southwestern Boulevard improvements and the railroad crossing, as well as, the existing channelization, Freeport Parkway bridge and the previously submitted drop structure. Mr. Ron Morrison of Kimley Horn & Associates has reviewed this report on behalf of the City of Coppell and recommends approval of this project, as submitted. If you have any technical questions on this report, please contact Ms. Jean Hansen of A. H. Halff Associates, Inc., and if you have any administrative questions, please call me at (214) 462-8495. Thank you for your consideration of this request. Sincerely, City of Coppell ~ Acting City Engineer Enclosure cc: Steven G. Goram, Director of Public Works Jean Hansen, Albert H. Halff & Associates Ron Morrison, Kimley-Horn & Associates DEPARTMENT OF THE ARMY FORT WORTH DISTRICT, CORPS OF ENGINEERS p. o. sox NOV FORT WORTH, TEXAS 76102-0300 November 14, 1990 , Operations Division [g~' © ['g fl~.7 I:,~, Of fice Operations Branch SUBJECT: Project Number 198800444 r~l Ms. Jean Hansen Albert H. Halff Associates, Inc. 8616 Northwest Plaza Drive Dallas, Texas 75225 Dear Ms. Hansen: Thank you for your letter of October 23, 1990, concerning construction of bridge crossings and erosion control improvements on Grapevine Creek in Dallas County, Texas. Your project has been assigned Project Number 198800444; all future correspondence concerning your project should include this number. Failure to reference the project number on future correspondence will result in a delay. Your project has been reviewed in accordance with Section 404 of the Clean Water Act under which the U.S. Army Corps of Engineers regulates the discharge of dredged and fill material into waters of the United States including adjacent wetlands. Based on your description of the proposed work and all information available to us, we have determined that your project will involve such discharges and will require prior Department of the Army authorization under Section 404 of the Clean Water Act. Two general permits are applicable to your project. These permits have been issued on a nationwide basis for discharges into waters of the United States. The first nationwide permit authorizes minor road crossing fills including all attendant features, both temporary and permanent, that are part of a single and complete project for crossing of a non-tidal waterbody, provided that the crossing is culverted, bridged or otherwise designed to prevent the restriction of, and to withstand, expected high flows and provided further that discharges into any wetlands adjacent to the waterbody do not extend beyond 100 feet on either side of the ordinary high water mark of that waterbody. A "minor road crossing fill" is defined as a crossing that involves the discharge of less than 200 cubic yards of fill material below the plane of ordinary high water. The crossing /1, -2- may require a permit from the United States Coast Guard if ].ecated in navigable waters of the United States. District Engineers are authorized, where local circumstances indicate the need, to define the term "expected high flows" for the purpose of establishing applicability of the nationwide permit. The other general permit applicable to your project authorizes discharges of dredged or fill matsrial into non-tidal rivers, streams, dnd their lakes and impoundments, including adjacent wetlands, that are located above the headwaters and other non-tidal waters of the United States, including adjacent wetlands, that are not part of a surface tributary system to , !nterstate waters or navigable waters of the United States (i.e., ~solated waters) provided the activity does not cause the loss or substantial adverse modification of one or more acres of waters of the United States. For discharges which will cause the loss or substantial adverse modification to one or more acres of waters of the United States, written Department of the Army authorization will be required prior to initiation of work. The only requirement in the use of this permit is that the person responsible for the project must ensure that the work is in compliance with the above stated specifications and the conditions, and best management practices listed on the enclosure. Failure to satisfy these conditions invalidates the authorization and may result in a violation of the Clean Water Act. The verification for the construction of an activity under this nationwide permit will be valid until the nationwide permit is modified, reissued, or revoked. All of the nationwide permits are scheduled to be modified, reissued, or revoked prior to January 13, 1992. it is incumbent upon you to remain informed of changes to the nationwide permits. The U.S. Army Corps of Engineers will issue a public notice announcing the changes when they occur. Furthermore, if you commence, or are under contract to commence, this activity before the date that this nationwide permit is modified or revoked, you will have twelve months from the date of the modification or revocation to complete the activity under the present terms and conditions of the nationwide permit. This permit should not be considered as an approval of the design features of any activity authorized or an implication that such construction is considered adequate for the purpose -3- intended. It does not authorize any damage to private property, invasion of private rights, or any infringement of federal, state, or local laws or regulations. Thank you for your interest in our nation's water resources. If you have any additional questions concerning our regulatory program, please contact ~r. Stan Walker at the address above or telephone (817)334-3551. L. M. Hawking, Jr. Chief, Office OPerations Branch, Enclosure Copies Furnished: Mr. Rollin MacRae Texas Parks and Wildlife Department 4200 Smith School Road Austin, Texas 78444 Mr. Robert M. Short U.S. Fish and Wildlife Service Ecological Services Stadium Centre Building, 711 Stadium Drive, East Suite 252, Arlington, Texas 76011 Mr. Jerry Saunders U.S. Environmental Protection Agency Region VI, 1445 Ross Avenue Dallas, Texas 75202 FLOOD PLAIN STUDY ON GRAPEVINE CREEK UTHWESTERN BOULEVARD 7'0 IH-635 FOR c~rv o~ co~~, SEPTEMBER, 1990 ALBERT H. HALFF ASSOCIATES, INC. 8616 NORTHWEST PLAZA DRlVE DALLAS, TEXAS 75225  ALIIERT It. IIALI'I'/\5S()(]1A'1'12;, 1NIl. I;N(;INI;I;RS * S(:II;N'I'IS'I?; ,. SIll [}ALl,AS· ARI.IN{;T(IN · (:III(:A(;(), I'()I~T WIIRTI[ RIiIG NOJiIIIWI-?I t'1AIA Ill,WI - I),%1 [/,'1 ~[ ,:7% /,,:,:,,; :, 4/~.:~,, ,.; September 28, 1990 AVO 10751 M. Shohre Daneshard, P.E. City of Coppell P. O. Box 478 732 Deforest Lane Coppell, Texas 75019 Re: Letter of Map Revision for Proposedd Improvements to Grapevine Creek -- Soothwestern Boulevard to IH-635 Dear Shohre: Please find enclosed tile report entitled "Flood Plain Study on Grapevine Creek Southwestern Boulevard to IH-635 for the City of Coppell, Texas". This report fulfills the require~nents for issuance of a Condilional Letter of Map Revision by the Federal Emergency Management Agency. A draft cover letter for this submission is included in thc report. Technical data has also been supplied to address fully developed watershed conditions as specified by tile City of Coppcll Flood Plain Ordinance No. 87390. Please feel free to call il' you have any ClUCStions. Yours Very Truly, .--? / / Jean Hansen Jt t/lilY ellclosure cc: Mr. Mike Tucker, Premiss Propcrlics Ltd., lllc. September 28, 1990 AVO 10751 XGO1 Federal Emergency Management Agency 1725 I. Street N. Washington, D.C. 20472 Attn: Mr. Matt Miller Re: Request for Conditional Letter of Map Revision for Proposed Structures on Grapevine Creek in Coppell, Texas Dear Mr. Miller: · Please find, enclosed a technical report on ex/sting and proposed flood plain and floodway conditions relative to the reach of Grapevine Creek from Southwesteru Boulevard to IH-635 in Coppell. This report, prepared by Albert H. Halff Associates, Inc., includes a detailed hydraulic analysis of the existing and proposed channel and overbank conditions. This report also includes the HEC-2 computer printouts, flood plain and floodway maps, and other data required for a Conditional Letter of Map Revision. A Conditional Letter of Map Revision dated A%mst 18, 1987, Case No. 86-06-47R already exists for this reach of Grapevine Creek. This report incorporates the previous hydraulic analysis and provides technical data for two additional bridge crossing. We request a new Conditional Letter of Map Revision which will include thc proposed Southwestern Boulevard improvements and the railroad crossing, as well as, the existing channe '~lization, Freeport Parkway bridge and the previously submitted drop structure. If you have any questions on this report, please contact Ms. Shohre Daneshmand, P.E. at the City of Coppell (214/462-8495). Thank you for your consideration of this request. Yours Very Truly, City of Coppcll M. Shohre Dancslmaand, P.E. Enclosure cc: Ms. Jean Hansen, Albert H. Halff Associates, Inc. TABLE OF CONTENTS I. PURPOSE ................................................... 1 II. PROCEDURES ............................................... 1 III. DESCRIPTION OF IMPROVEMENTS ............................. 3 IV. RESULTS .................................................... 4 V. CONCLUSIONS ............................................... 6 LIST O F TAB LES Table 1 Description of Existing and Proposed Improvements .................................... 4 Table 2 Comparison of August 1978 }PIS and May 1990 FIS update ................................... 5 'Fable 3 Valley Storage Comparison .................................. 5 Table 4 Comparison of Ex/sting and Proposed Flood Plain Conditions - FIS Discharges ........................................... 7 Table 5 Floodway Comparison ...................................... 8 Table 6 Comparison of Existing and Proposed Flood Plain Conditions - Fully Developed Discharges .................................. 9 LIST OF FIGURES Figure 1 Vicinity Map Figure 2 IH-635 Bridge Cross Section from F.1.S. update Figure 3 Modified IH-635 Bridge Cross Section Figure 4 Proposed Rail Road Bridge Cross Section Figure 5 Proposed Southwestern Boulevard Cross Section Figure 6 Water Sur£ace Profiles with Proposed Improvements Figure 7 Flood Plain and Floodway APPENDICES Appendix A Conditional Letter of Map Revision, Case No. 86-06-47P, Appendix B F.I.S. Existing Conditions Flood Plain HEC-2 model Appendix C F.I.S. Existing Conditions Floodway HEC-2 model Appendix D Revised Existing Conditions Flood Plain HEC-2 model Appendix E Revised Existing Conditions Floodway HEC-2 model Appendix F Proposed Conditions Flood Plain HEC-2 model Appendix G Proposed Conditions Floodway HEC-2 model Appendix H Existing Conditions/Ultimate Discharges HEC-2 model Appendix I Actual Existing Conditions/Ultimate Discharges HEC-2 model Appendix J Proposed Conditions/Ultimate Discharges HEC-2 model GRAI'EVIN E CREEK SOUTIIWESTERN BOULEVARD TO IH-635 I. PURPOSE This study on Grapevine Creek in Coppell, Texas was undertaken to provide thc necessary technical data for issuance of a FEMA Conditional Letter of Map Revision and a Flood Plain Development permit iii accordance with the City's Flood Plain Management Ordinance No. 87390. Grapevine Creek is a tributary of the Elm Fork of the Trinity R/ver. The creek enters the City of Coppell from the south at IH-635 (LBJ Freeway ) and flows in an easterly direction for 6.0 miles to it's confluence with the Ehn Fork on the Coppell/Irving corporate boundary. The study area which is the focus of this report is located in the upstream reach of Grapevine Creek, from the IH-635 bridge crossing to the ex/sting Southwestern Boulevard crossing, Figure 1. A "Belief Letter" for this reach of Grapevine Creek, Case No. 86-06-47R, was issued on August 18, 1987 which included the existing channelization, the Freeport Parkway bridge and a proposed drop structure. This study incorporates the hydraulic analyses for these existing and proposed improvements into the design models for proposed Southwestern Boulevard and the railroad crossing. IL PROCEDURES A. Hydrology - Discharges for the ex/sting land use condition 10-, 50-, 100- and 500-year frequencies used in this report are from the Corps of Engineers' hydraulic models for the Dallas County Flood Insurance Study, August 1978, updated by Kimley-Horn and Associates, May 1990. The flood plain/floodway for the existing and proposed conditions was evaluated based on these discharges, in accordance with FEMA criteria. The City of Coppell Flood Plain Ordinance also requires the evaluation of the hydraulic impacts on the ultimate 2 and 100 year flood plains. The discharges used in these models are from the City of Coppell's "Master Drainage Study" performed by Kimley-Horn and Associates in January 1990. These discharges are based on fully developed land uses. B. Hydraulics ~ The Corps of Engineers' HEC-2 program, September, 1988 PC version, updated June 1990, was utilized to perform the required hydraulic analysis. The following nine computer models were utilized and printouts from each are included in the Appendices of this report. 1. F.I.S. F_~xisting Conditions Model (Appendix B) - This is the existing conditions, F.I.S. hydraulic model for the 10-, 50-, 100-, and 500-year floods. This model was obtained from Kimley-Horn and Associates and is thc F.I.S. update model submitted to FEMA, May 1990. 2. FEMA Existing Conditions Floodway Model (Appendix C) - This is the ex/sting conditions floodway model, May 1990 as referenced in Number 1. 3. Revised Existing Conditions Model (Al'~pcndix D) - This is thc F.I.S. existing conditions model (No.'l), modified as follows: a. Cross sections 383+80 through 386+70, the IH-635 bridge sections, has the left and right banks marked at the small pilot channel in the center of the cross section (see Figure 2). Examination of on-site conditions suggests that what can physically be considered the channel area extends to the edge of thc concrete side slopes. The revised bank stations have been set at thc foot of thc concrete side slopes. The overbank 'n' wfiues have been set at 0.01.5 to represent the concrete side slopes. b. The elevations of the bridge encroachments tX3 10) at cross sections 383+80 through 386+70 were set for the low point of the right overbank area and not for the minimum top of road to silnulate weir flow. Consequently, the original F.I.S. model carried significant amounts of flow in the right overbank areas downstream and upstream of the IH-635 bridges. However, given the elevation of the minimum top of road, flow over the highway is not possible. This has been corrected by adjusting the X3 card to confine all flows to the bridge openings. These corrections were also made to the previous F.I.S. model, August 1.978 in the course of obtaining the conditional letter of map revision referenced in Section I. The May, 1990 F.I.S. update confines thc flow to the bridge opening and changes the 'n' value through the bridge for the eastbound (upstream) IH-635 bridge only. The bank stations are not corrected. A comparison of this hydraulic model with the revised base model is included in Table 2. The modified cross section of the iH-635 bridge is shown on Figure 3. 4. Revised Existing Conditions Floodway Model (Appendix E) - This is this May, 1990 F.I.S. floodway model, modified as noted in No.3. 5. Proposed Conditions Model (Appendix F) 10-, 50-, 100-, and 500-year floods - This is the existing conditions model modified to reflect the existing and proposed improvements, as approved in the Conditional Letter Case No. 86-06-47R Southwestern Boulevard and railroad proposed bridge crossings are also incorporated. Figure 4 and Figure 5 show the cross sections for these two proposed structures. The water surface profile for this run is displayed on Figure 6. 2 6. Proposed Conditions Floodway Model (AppendLx G) - This is the floodway model modified to reflect the existing and proposed improvements, as discussed in Number 5. 7. Existing Coudition Model with Ultimate Discharges (Appendix H - Detailed output not included) - This is the existing condition model with discharges representing fully developed land use within the watershed, as included in the report entitled "Coppell Master Drainage Plan" by Kimley-Horn and Associates, January 1990. 8. Actual Existing Conditions with Ultimate Discharges (Appendix I - Detailed output not included) - This is the actual existing conditions model with fully developed discharges. This model includes the channelization and Freeport Parkway bridge, as they exist today. "['his is the hydraulic model utilized for the Coppell "Storm Water Management Study." Other modifications made to this model are downstream of the study area and include Denton Tap Road and the Creekview Addition encroachment. 9. Proposed Conditions with Ultimate Discharges (Appendix J - Detailed ~. output not included) - This model includes the existing improvements i discussed in Number 8, the drop structure approved in 1987 and the proposed bridge structures at Southwestern Boulevard and the railroad crossing. III. DESCRIPTION OF IMPROVEMENTS The proposed improvements to Grapevine Creek in Coppell, Texas consist of dual bridges at Southwestern Boulevard, Stream Station 314+70 through 315+48 and a proposed railroad bridge at Stream Station 337+45, approximately 2200 feet upstream of Southwestern Boulevard. The proposed condition hydraulic models also incorporated the existing 200 foot bottom width channel, existing Freeport Parkway and a proposed drop structure immediately downstream of IH-635 as described in the report entitled "Conditional Letter of Map Revision Request for Grapevine Creek in Coppell, Texas," June :1985. Table 1. gives a detailed reach by reach description of these improvements. Table 1 Description of Existing and Proposed Improvements Reach Improvements 31.470 to 31548 Proposed Southwestern Boulevard - dual bridges 31548 to 33737 Existing Earthen Channel, 200-foot bottom width 33737 to 33752 Proposed Rail Road Bridge 33752 to 35450 Existing Earthen Channel, 200-foot bottom width 35450 to 35750 Existing Freeport Parkway Bridge 35750 to 35970 Existing Earthen Channel, 200-foot bottom width 35970 to 38260 Proposed Transition to 70-foot bottom width earthen channel 38260 to 38360 Begin Proposed Reinforced Concrete Drop Structure, provide erosion protection downstream with rip-rap 38360 to 38420 End Proposed Concrete Drop Structure, provide erosion protection upstream with rip-rap, end improvements. As noted in Table 1, the channelization and Freeport Parkway bridge have been built. A Letter of Map Revision for these existing improvements, only was requested previously and denied due to unstable channel conditions between Freeport Parkway and the IH-635 bridge. However, a Conditional Letter of Map Revision, Case No. 86-06-47R was issued by FEMA for the existing improvements with a proposed drop structure to create stable channel conditions during flood events. A copy of this "Belief Letter" is included in Appendix A of this report. This structure has not been constructed to date but property owners within the reach of Grapevine Creek from Southwestern Boulevard to IH-635 are aware of the fact that a final Letter of Map Revision can not be issued until the project is completed. This report requests issuance of a Conditional Letter for the Southwestern Boulevard improvements and a proposed rail bridge in combination with the previously approved channelization and drop structure. Fully developed conditions are also addressed as specified by the City of Coppell Flood Plain Ordinance. I¥. RES ULTS Tables 4, 5, and 6 show the results of the various HEC-2 models evaluated in this study. Table 4 is a comparison of the resulting 100-year water surface elevations and velocities for the previously existing and proposed flood plain conditions. Table 5 is the comparison of the floodway water surface elevations for these conditions. The elevations shown in these two tables are based on existing land use discharges and hydraulic models supplied by Kiinley-Horn and Associates from the May 1990 F.I.S. update. The computed water surface elevation at the downstream face of existing Southwestern Boulevard differs by only 0.09 feet as compared to the August 1978 F.I.S., as shown in Table 2. Table 2 Comparison of August 1978 F.I.S. to May 1990 Update August 1978 May 1990 F.I.S. F.I.S. Section CWSEL CWSEL 31480 506.53 506.44 Since this is not a significant change in existing conditions, the existing "Belief Letter" should still be valid. However, this study, based on the May 1990 F.I.S. update, incorporates all existing and proposed improvements and requests a new Conditional Letter of Map Revision for the reach of Grapevine Creek from Southwestern Boulevard to IH-635. The proposed flood plain/floodway is shown on Figure 7. Table 6 contains a comparison of previous, actual and proposed channel conditions for this reach of Grapevine Creek based on discharges developed by Kimley-Horn and Associates for a fully dcvelopcd watershed. As can be seen from this table, velocities upstream of Freeport Parkway with the actual channel conditions range frorn 13 to 16 feet per second. Continuation of the existing channel with the proposed drop structure lowers these velocities and controls the unstable channel conditions. The improvements to Southwestern Boulevard and the proposed rail bridge do not cause an increase in water surface elevation nor do they cause erosive velocities. A comparison of the natural valley storage characteristics of this reach of Grapevine Creek for actual channel conditions versus the flood plain with the two new proposed bridge structures is shown in Table 3. Table 3 Valley Storage Comparison Cross Actual Channel Proposed Bridges Section Volume (ac.ft.) Volume (ac.ft.) "G REXULT 1 .... SGRPROPU" 31310 1.7[)6.8 1706.8 38380 1987.4 1974.4 This comparison shows a loss of 13 ac. feet of storage, approximately 4.5 percent. This loss is primarily due to widening the cham~el immediately downstream of the proposed drop structure. 5 V. CONCLUSIONS The Southwestern Boulcwtrd bridge improvements and proposed rail crossing do not cause any increases in computed water surface elevations, nor do they ca'use erosive velocities within thc channel. Thc prcvitmsly approved proposed drop structure between Freeport Parkway and 114-635 is required to control unstable channel conditions within this reach. Rip-rap erosion control upstream and downstream of this proposed structure is required. Overall this project meets the requirements for issuance of a FEMA Conditional Letter of Map Revision and satisfies the criteria specified in the City of Coppell Flood Plain Ordinance. This ordinance requires that minimum finished floor elevations be set at 2 foot above the F.I.S. base flood (100- year) elevation or 1 foot above the design base flood elevation (100-year Ultimate), whichever is higher. Review of the Proposed Condition water surface elevations, Tables 4 and 6 show that the 2 foot F.I.S. criterion controls. It is recommended that minimum finished floor elevations be set 2 feet above the base flood elevations shown on Figure 7. 6 TABLE 4 COMPARISON OF EXISTING AND PROPOSED FLOOD PLAIN CONDITIONS GRAPEVINE CREEK, 100-YEAR FLOOD-FIS DISCHARGES COE/K~A EXISTING ] REVISED BASE ~PROPOSED CONDITIONSll C.O.E./ A.H.H. I 100 YR C~{ANNEL CHANNEL I CHANNEL K.H.A. I DISCHARGE WSEL VELOCITY WSEL VELOCITY I WSEL VELOCITY X-SECT X-SECT I DESCRIPTION (cfs) (ft) (fps) (ft) (fps) I (ft) (fps) 30250 30250 10500 504.02 8.19 504.02 8.19 I 504.02 8.19 31310 31310 10500 506.15 7.34 506.15 7.34 ~ 506.15 7.34 31420 BEGIN SECTIONS FOR 10500 I[ 506.22 6.73 31464 PROPOSED SOUTHWESTERN 10500 506.27 6.70 31470 D.S. 'FACE SOUTHWESTERN W. 10500 506.17 7.37 31480 10500 506.44 8.07 506.44 8.07 31500 10500 506.60 8.07 506.60 8.07 31503 U.S. FACE SOUTHWESTERN W. 10500 506.19 '7.46 31509 10500 506.32 6.97 31515 D.S. FACE SOUTHWESTERN E. 10500 506.25 7.45 31548 U.S. FACE SOUTHWESTERN E. 10500 506.27 7.54 31550 10500 507.48 6.31 507.48 6.31 31554 10500 506.36 7.22 31750 10500 I 507.12 3.77 32740 10500 I I 507.67 4.09 Il 33537 10500 { } 508.28 4.54 33727 1o50o I II 508.49 4.44 33737 D.S. FACE PROPOSED RR 10500 {{ {{ 508.42 5.53 33752 U.S. FACE PROPOSED RR 10500 I II 508.50 5.48 33762 10500 { {~ 500.75 4.32 34o45 1050o I II 509.01 4.14 {I 34330 10500 I II 509.21 5.33 34730 10500 513.73 11.02 I 513.73 11.02 {} 34870 ~0500 { I1 5i0.22 5.0i 35450 JD.S. FACE FREEPORT 10500 I} 511.50 5.82 35570 U.S. FACE FREEPORT 10500 511.78 5.62 37100 11200 520.72 7.90 520.72 7.90 35770 11200 512.00 7.53 35970 11200 512.60 7.52 36140 11200 512.80 8.23 36360 11200 513.26 8.17 38200 11200 522.57 4.63 [~ 522.55 4.61 38285 11200 [[ 513.24 9.60 38290 11200 II 513.25 9.59 38340 BOTTOM OF DROP 11200 I{ 512.84 11.52 38360 TOP OF DROP 11200 {{ 517.52 12.41 38380 38380 ID.S.W. IH635 11200 522.54 8.87 II 522.38 6.17 518.94 11.77 38420 38420 U.S.W. IH-635 11200 522.57 9.58 {] 522.41 6.23 519.35 10.95 38500 38500 BETWEEN BRIDGES 11200 522.63 3.39 I{ 522.58 6.35 I{ 520.84 8.54 38580 38500 D.S.E. IH-635 11200 522.59 3.65 I 522.74 6.60 ~1 521.35 8.37 38620 38620 U.S.E. IH~635 11200 522.65 3.67 I 522.79 6.65 [[ 521.47 8.35 38670 38670 50' U.S. OF IH-635 11200 522.67 3.72 { 522.99 7.35 II 521.91 8.61 39720 39720 11200 523.98 15.13 I 526.06 7.61 II 526.04 7.65 41180 41180 7900 528.83 3.66 I 528.68 3.87 II 528.67 3.87 41950 41950 7900 529.69 8.94 { 529.66 9.04 {I 529.66 9.03 42050 42050 7900 531.11 9.53 II 531.09 9.62 {{ 531.09 9.65 42090 42090 7900 535.42 1.75 {~ 535.41 1'.75 {[ 535.40 1.76 42170 42170 7900 535.43 1.34 II 535.42 1.34 {I 535.42 1.34 44200 44200 7900 535.58 2.83 {I 535.57 2.84 I1 535.57 2.84 TABLE 5 FLOODWAY COMPARISON - GRAPEVINE CREEK COE/IGLR ~ISTING ICOE/KHA REVISED BASE PROPOSED CONDITIONS "SGRENC" C.O.E./[A.H.H. Z...A. I X-SECT IX-SECT DESCRIPTION ....... I ................................ I ........ I ........ II ............................. I ............. 30250 30250 10500 504.0 504.4 0.4 II 504.0 504.4 0.4 504.0 504.4 0.4 31310 31310 10500 506.2 506.6 0.4 Il 506.2 506.6 0.4 506.2 506.6 0.4 31420 BEGIN SECTIONS FOR 10500 I~ 506.2 506.7 0.5 31464 PROPOSED SOU~STERN 10500 t~ 506.3 506.8 0.5 31470 D.S. FACE SOUTI~WESTERN W. 10500 506.2 506.7 0.5 31480 10500 506.4 506.9 0.5 506.4 506.9 0.5 31500 10500 506.6 507.1 0.5 506.6 507,1 0.5 31503 U.S. FACE SOUTHWESTERN W. 10500 506.2 506.7 0.5 31509 10500 506.3 506.8 0.5 31515 D.S. FACE SO~fHWESTERN E. 10500 506.2 506.7 0.5 31548 U.S. FACE SOUTHWESTERN E. 10500 506.3 506.8 0.5 31550 10500 507.5 507.9 0.4 507.5 507.9 0.4 31554 10500 II 506.4 506.9 0.5 31750 ]0500 507.1 507.5 0.4 32740 10500 507.7 508.1 0,4 33537 10500 508.3 508.6 0.3 33727 10500 508.5 508.8 0.3 33737 D.S. FACE PROPOSED RR 10500 508.4 508.7 0.3 33752 U.S. FACE PROPOSED Ri{ 10500 508.5 508.8 0.3 33762 10500 508.8 509.1 0.3 34045 10500 509.0 509.2 0.2 34330 10500 509.2 509.4 0.2 34730 10500 513.7 514.2 0.5 513.7 514.2 0.5 34870 10500 510.2 510.3 0.1 35450 D.S. FACE FREEPORT 10500 511.5 511.6 0.1 35570 U.S. FACE FREEPORT 10500 511.8 511.9 0.1 37100 11200 520.7 520.9 0.2 520.7 520,9 0.2 35770 11200 ~1 512.1 512.2 0.1 35970 11200 512.6 512.6 0.0 36140 11200 512.8 512,8 0.0 36360 11200 513.3 513.3 0.0 38200 11200 522.6 522.5 I-0.1 522.6 522.5 -0.1 38285 11200 513.2 513.2 0.0 38290 11200 513.3 513.3 0.0 38340 BOOM OF DROP 11200 512.8 512.8 0.0 38360 TOP OF DROP 11200 517.5 517.5 0.0 38380 38380 D.S. W. IH635 11200 522.5 523.2 0.7 522.4 523.2 0.8 518.9 518.9 0.0 38420 38420 11200 522.6 523.3 0.7 522.4 523.2 0.8 519.4 519.4 0.0 38500 38500 11200 522.6 523.3 0.7 522.6 523.2 0.6 II 520.8 520.8 0.0 38580 38580 11200 522.6 523.3 0.7 522.8 523.3 0.5 521.4 521.4 0.0 38620 38620 11200 522.7 523.3 0.6 522.8 523.3 0.5 521.5 521.5 0.0 38670 38670 11200 522.7 523.3 0.6 523.0 523.3 0.3 521.9 521.9 0.0 39720 39720 11200 524.0 523.3 -0.7 526.1 523.8 I-2.3 526.0 526.2 0.2 41180 41180 7900 528.8 527.6 -1.2 528.7 527.6 I-l.1 528.7 529.3 0.6 41950 41950 7900 529.7 529.9 0.2 529.7 529.9 42050 42050 7900 533.1 531.0 -0.1 531.1 531,0 I-0.1 531.1 531.0 I-0.1 42090 42090 7900 535.4 535.2 -0.2 535.4 535.3 I-0.1 535.4 535.2 I-0.2 42170 42170 7900 535.4 535.3 -0.1 535.4 535.4 44200 44200 7900 535.6 535.8 0.2 535.6 535.8 TABLE 6 COMPARISON OF EXISTING AND PROPOSED FLOOD PLAIN CONDITIONS GRAPEVINE CREEK, 100 YEAR FLOOD-FULLY DEVELOPED DISCHARGES KI1A EXISTING [[ ACTUAL CItANNEL PROPOSED CONDITIONS "~GREXUI,T" I [ "SGIIGLT]" "SGRPROPU" 100 YR CHANNEL II CHANNEL CHANNEL K.H.A. A.II.}{. D1SCDARGE WSEL VELOCITY WSEL VELOCITY WSEL VELOCITY X-SECT X-SECT DESCRIPTION (cfs) (ft) (fps) (ft) (fps) (ft) (fps] 30250 30250 11250 504.54 8.21 504.59 8.15 504.59 8.14 31310 31310 11250 506.59 7.33 506.75 7.14 506.61 7.30 31420 11700 506.60 7.26 31464 11700 506.65 7.22 31470 D.S. FACE SOUTHWESTERN W. 11700 506.54 7.94 31480 11700 506.74 8.99 506.85 8.99 31500 11700 506.94 8.99 507.05 8.99 31503 U.S. FACE SOUTh"WESTERN W. 11700 506.56 8.03 31509 11700 506.71 7.50 31515 D.S. FACE SOUTHWESTERN E. 11700 506.63 8.01 31548 U.S. FACE SOUTHWESTERN E. 11700 II 506.65 8.11 31550 11700 508.10 6.35 508.22 6.22 31554 11700 506.75 7.75 31750 11700 508.48 3.75 507.63 4.02 32740 11700 508.97 4.05 508.23 4.33 33537 11700 508.88 4.75 33727 11700 509.09 4.65 33737 D.S. FACE PROPOSED RR 11700 509.01 5.79 33752 U.S. FACE PROPOSED RR 11700 509.10 5.73 33762 11700 509.37 4.51 34045 11700 509.84 4.25 509.64 4.33 34330 11700 510.03 5.35 509.84 5.48 34730 11700 514.13 11.19 34870 1].700 510.95 5.87 510.82 5.97 35450 D.S. FACE FREEPORT 11700 512.14 5.98 512.07 6.03 35570 U.S. FACE FREEPORT 11700 512.43 5.76 512.36 5.81 37100 11700 520.97 7.83 35770 11700 512.77 7.07 512.71 7.14 35970 11700 513.14 13.33 513.13 7.43 36140 11700 514.99 15.22 513.31 8.13 36360 150' D.S. OF DROP 11700 519.25 16.10 513.74 8.11 38200 11700 522.76 4.68 38285 11700 513.71 9.50 38290 11700 513.72 9.49 38340 BOT~M OF DROP 11700 513.32 11.40 38360 TOP OF DROP 11700 517.68 12.52 38380 38380 D.S.W. IH635 11700 522.75 8.76 522.61 6.23 519.08 11.90 38420 38420 U.~. W. IH635 11700 522.78 9.72 522.65 6.28 38500 38500 BETWEEN BRIDGES 11700 522.84 3.43 522.81 6.41 38580 38580 D.S.E. IH635 11700 522.80 3.68 522.97 6.65 38620 38620 U.S.E. IH635 11700 522.86 3.70 523.02 6.71 38670 38670 50' U.S. OF IH635 11700 522.88 3.75 523.22 7.45 39720 39720 11700 524.07 15.26 41180 41180 6150 528.71 2.98 41950 41950 6150 529.28 7.90 42o5o 42o5o 6~0 5~0.63 9.37 42090 42090 6150 533.82 2.25 I 533.84 2.23 II 533.85 2.22 42170 42170 6150 533.84 1.53 44200 44200 6150 534.10 4.15 -' U ~ I cc c ! ._1 ~ a_ ! © ! C) ~ f'T' ..-" I -r '" / :'5 0 o '~BE R z ,<1;: F- ,<l:j rr rr ...J O )JECT LL I- D F W AIRPORT LLJ N FIGURE 1 I._i VICINITY MAP !11 SCALE IN FEET ,i l'l'/ i Jl i / / i i ~. IRWIN. TOP OF ROAD ! ~ ~TOP OF B~NK ~/ STATIONS,ALSO LOCATION FOR X~ CARD. CORPS OF ENGINEERS FIGURE 2 SECTTON ~8620 .0:!504 0~.5 U.S. =ACE OF -. BOUND I.H. 635 570 .- ' 56O 550 ! ~ x "xx t \ ' ARTIFICIA- LEVEES (~3 CARD) ~O PREVEN OUTSIDE I~RIDGE OP NING 520 5~6.30 FT '~ BANK STAT ONS MOVED 5~.2.30 MZN ' ! ~ 3000 4000 5000 ~nn vnnn nn -~000 0 1000 2000 9-25-~990 STATION v,~I t nAT FIGURE 3 520 SECTION 33737 .000 D.S. iFACE PRO!OSED RA LROAD BR D6E 515 I I I 1 I 510 ~--' -~ -~ \, 5O5 5OO 495 / v :~m ' t 4::,, 5~ i O0 RI6HTI 493. 485 1 950 1000 ~050 1100 1150 1~00 ~50 ~SO0 1350 1400 g-25-1990 STATION XPLT ~. DAT FIGURE 4 520 SECTION 3~470 ! .065 .025 .0~65 PROPOSED SOUTHWi!STERN Bi: IDSE SE(: rlON 515: l 510 oZ 505 , H 50O 495 490 FIGURE 5 ' PROI)OSED BRIIpGE 510.00 RZGHT CR )SS-SECTI N 4~5 iO00 1200 1400 1600 1800 2000 22u0 2400 2600 280C 7-1 l- i 990 STAT I ON s~bridge.x 0 0 0 0 o ~ o o St. Louis S ISW ~ ~ ~ roposed South,,testern 327+4 ~' I~ ~o~ose~ Spur .... V oN TN FEET (NGVD) .qo 0 o 0 0 0 o o- 2 o o ~ o = I*30 ~= ECU ~ _ ~ . ~s C SW RR - reposed Southwestern L ~ 0 -e: ft . Ii Proposed RR Spur i o - \ o_- \ - Freeport Pkwy. - 355+70 ~ - I - 0 o- ~ - ' Propos op St ucture - w - i-685 - ~ _ 386+?0 _ 0 ~ - 0 ........ I I ~ ! ! .... --- - '--' ' - ~'-'~ ~ ' ' ' : ..... a 0 0 0 0 0 0 0 0 0 0 0 ~'~