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Westhaven-CS140207
inKimley-Horn and Associates,Inc. Febuary 7,2014 ■ 12750 Merit Drive Mr.Kenneth M. Griffin,P.E. suite 1000 Director of Engineering and Public Works Dallas,Texas 255 Parkway Boulevard 75251 Coppell,Texas 75019 Re: Response to Comments—January 29,2014 ,Westhaven Residential Development LOMR Denton Creek Dear Mr. Griffin: This letter addresses comments received from Halff Associates, Inc. (Halff), dated January 29, 2014, in regard to the above referenced LOMR. Our responses to the comments are as follows. Comment 1: The as-built project seems to have no significant impact on water surface elevations on Denton Creek for the fully developed watershed condition. No response necessary. Comment 2: The as-built project seems to have no significant impact on the 2-year or 100 year velocities on Denton Creek for the fully developed watershed condition. No response necessary. Comment 3: Valley storage loss on Denton Creek due to the as-built project does not exceed the maximum allowable of 15%. Valley storage reductions for the standard project flood event was not determined since the as-built project modifications have no significant impact on the standard project flood backwater elevation from the Elm Fork of the Trinity River. No response necessary. Comment 4:Be advised that our copy of the LOMR submittal contained two (2) copies of the hydraulic model output for the FEMA post project floodway condition. A copy of the FEMA pre project floodway output was not included. Please correct the omission and resubmit. A copy of the FEMA pre-project floodway output is attached to this letter. Comment 5:Be advised that the water surface elevations shown in Table 3 for both "Pre-Project"and "Post-Project"conditions do not match the hydraulic model output for each condition found in Appendix A. Please revise and resubmit. • TEL 972 770 1300 FAX 972 239 3820 cznKimley-Horn and Associates,Inc. Mr.Ken Griffin,P.E.,February 7,2014 Water surface elevations shown in Table 3 for both the"Pre-Project"and"Post- Project"conditions have been revised and page 8 of the LOMR report containing Table 3 is attached to this letter. Comment 6: The as-built project seems to have no significant impact on water surface elevations on Denton Creek for existing conditions (FEMA). No response necessary. Comment 7: The as-build project does not create any surcharges greater than 1.0 feet or less than 0.0 feet. No response necessary. Comment 8:Be advised that an explanation may need to be included as part of this LOMR submission which explains why the floodway topwidths are greater than the 100 year floodplain topwidths at cross-sections 34950 and 35253. Typically floodway topwidths are less than or equal to the 100 year un-encroached floodplain topwidths. The discrepancy in the floodway and floodplain topwidths is a result of the encroachment placement. Generally, encroachment stations were rounded to nearest foot and were placed outside of the bank stations. As a result, some of the floodway topwidths were greater than the 100-year floodplain topwidths. If requested by FEMA,the floodplain models will be adjusted. Comment 9: The applicant has indicated on MT-2 Form 3 Sections B and C that sediment transport was not considered as part of this project; however, an explanation was not provided. Please correct the omission and resubmit. If requested by FEMA, an explanation of why sediment transport was not considered will be provided. I trust the above responses and the updated attachments are sufficient to address Mr. Erskine's comments. If you have no further comments, please sign the appropriate location on FEMA Form 1 and return it to me. A scanned copy of the signed form is sufficient. If you do have additional questions or comments, please do not hesitate to contact me at(972) 776-1757 or kyle.dickey @kimley-horn.com. Sincerely, KIMLEY-HORN AND ASSOCIATES, INC. Kyle A.Dickey,P.E. cc: Russell P.Erskine,P.E.,CFM;Halff Associates,Inc. Mark Harris,P.E.;Kimley-Horn and Associates,Inc. Attachments: FEMA Pre-Project Floodway Output LOMR Report,Page 8 K:\DAL_Hydro\64447701\LOMR\Docs\Comment Response Letter City.docx DENTON CREEK-WESTHAVEN RESIDENTIAL DEVELOPMENT LOMR SUBMITTAL FEBRUARY 2014 4.9 RESULTS Table 3 summarizes the 100-year water surface elevations in the subject reach. The results show that the post-project improvements do not cause increases in water surface elevations above effective or pre-project conditions. The post-project FEMA tie- in elevations are shaded with a light blue for reference. Table 3: 100-Year FEMA Water Surface Elevation Summary Cross FEMA Duplicate Effective Models Kimley-Horn Models Section HEC-2 HEC-RAS Pre-Project Post-Project Difference _.,_,349+50 463.65 463.70 463.31 463.31 0.00 352+53 463.79 463.79 0.00 356+14 464.54 464.54 0.00 358+38 464.75 464.75 0.00 360+34 464.89 464.88 -0.01 361+97 464.93 464.93 0.00 362+17 465.00 464.97 -0.03 364+65 465.17 465.14 -0.03 365+42 465.18 465.13 -0.05 368+37 465.37 465.24 -0.13 369+90 465.39 465.25 -0.14 372+01 _ 465.49 _ 465.27 -0.22 373+50 465.50 465.28 a -0.22 375+39 465.53 465.30 -0.23 377+02 465.69 465.46 -0.23 377+27 465.73 465.50 -0.23 377+87 465.70 465.53 -0.17 379+69 465.93 465.79 -0.14 381+94 466.10 465.88 -0.22 383+81 466.22 465.98 -0.24 385+73 466.23 466.00 -0.23 _ 387+81 466.25 466.02 -0.23 389+88 466.23 466.03 -0.20 392+81 466.39 466.06 -0.33 394+36 466.77 466.33 -0.44 394+90 466.71 466.72 466.90 466.50 -0.40 4.0 Hydraulics ranKimley-Horn �, 1 and Associates,Inc. K:\DAL_Hydro\64447701\LOMR\Dacs\LOMR Report.docx Copyright©2014 Kimley-Hom and Associates,Inc. HEC-RAS Plan:PreProj FEMA FW River:RIVER-1 Reach:Reach-1 '...Reach River Sta Profile W.S.Elev Prof Delta WS E.G.Elev Top Wdth Act CI Left 'D Charnel CI Right Enc Sta L Ch Sta L Ch Sta R Enc Sta R (0)... (8) (ft) (ft) (cfs) (cfs) (cfs) °(ft) (ft) (ft) (ft) Reach-1 25530 100-Year 453.52 454.25 23567 20600.00 2495.20 2742.67 R88001 '"'25330 earfiW- 454.11 0.59 454.78 240.13 20800.00 2494.00 2495.20 2742.67 274300 Reach-1 25770 100-Year 453.97 454.44 272.69 20600.00 2495.20 2780.00 Reach-1 25770 100-Year FW 454.51 0.54 454.95 276.63 2060000 2495.00 2495.20 278000 278000 Reach-1 26830 ` 100-Year 454.69 455.09 1199.31 18283.48 3016.52 2619.58 3100.00 Reach-1 26830 100-Year FW 455.08 0.39 45564 438.78 2102002 279.98 2619.58 261058 310000 320000 Reach-1 26880 100-Year 454.73 455.19 1176.84 20749.39 550.61 1012.00 1585.00 Reach-1 26880 100YearFW 455.38 0.64 455.73 1313.48 19816.44 1483.56 1012.00 1012.00 158500 2668.71 Reach-1 [27165 100-Year 455.28 455.39 1419.85 6965.46 14334.54 985.00 1308.00 Reach-1 27165 100-Year FW 455.80 0.52 455.89 1428.82 6509.42 14790.58 985.00 985.00 130800 2610.10 Reach-1 27449 100-Year 455.39 455.47 1555.66 6419.42 14880.58 1014.00 1534.00 Reach-1 'i 27449 100-Year FW 455.89 0.50 455.95 160116 5824.66 1547534 1014.00 1014.00 1534.00 2736.39 Readrl 27748 100-Year 455.46 455.53 1447.43 6706.69 14593.30 1071.00 1606.00 Reach-1 27748 100-Year FW 455.95 049 456.00 1464.74 6312.80 14987.20 107100 107100 1606.00 2767.54 Reach-1 ' 27992 100-Year' 455.52 455.59 1345.58 8426.28 12873.72 1041.00 1543.00 Reach-1 27992 100-Year FW 45509 0.48 456.06 1356.82 8052.04 13247.96 1041.00 1041.00 154100 2589.88 Reach-1 28168 100-Year 455.57 455.63 1315.15 5893.23 15406.77 1021.00 1419.00 Reach-1 28168 100-Year FW 456.03 047 456.09 1333.02 561168 15686.32 102100 102100 141900 247091 Reach-1 28492 100-Year 455.61 455.68 1221.75 6072.76 15227.24 1215.00 1605.00 Reach-1 28492 100-Year FW '' 456.07 046 456.13 123806 579634 1550126 121500 1215.00 1605.00 2578.64 Reach-1 28720 100-Year 455.65 455.74 1097.10 7311.87 13988.33 1280.00 1689.00 Reach-1 28720 `100-Year FW 456.11 046 456.19 1108.80 7044.44 1425556 128000 128000 168000 2516.67 Reach-1 28890 100-Year 455.68 455.82 1078.60 9318.20 11981.80 1289.00 1696.00 _ Reach-1 28890 100-Year FW 456.13 045 456.25 1091.66 8841.01 12458.99 128000 1289.00 169600 2526.00 Reach-1 29124,JJ 100-Year 455.74 456.06 985.50 16484.94 4815.06 1264.00 1620.00 Reach-1 29124 100-YearFW 456.19 0.45 456.46 993.65 15732.74 5567.26 1264.00 1264.00 1620.00 2359.22 Reach-1 " 29651°a 100-Year 456.27 456.42 1022.10 11716.66 9583.34 1168.00 1615.00 Reach-1 29651" 100-YearFW 456.62 0.36 456.76 1047.34 11377.59 9922.41 1168.00 1168.00 1615.00 2590.89 Reach-1`.` 29831 100-Year 456.36 456.50 858.42 9984.44 11315.56 1147.00 1570.00 Reach-1 29831 100-YearFW 456.70 0.34 456.83 867.63 9791.72 11508.28 1147.00 1147.00 1570.00 2421.32 Reach-1 30027 100-Year 456.40 456.69 682.58 13523.32 7776.68 1128.00 1525.00 Reach-1 30027 100-YearFW 456.74 0.34 457.00 700.68 13205.58 8094.42 1128.00 1128.00 1525.00 2140.64 Reach-1 30384 100-Year 456.77 457.34 430.35 17092.23 4207.77 1045.00 1447.00 Reach-1 30384 100-YearFW 457.07 0.30 457.60 442.02 17010.47 4289.53 1045.00 1045.00 1447.00 1994.78 Reach-i 30604 100-Year 457.44 457.82 827.03 14964.81 6335.19 1014.00 1350.00 Reach-1 30604 100-Year FW 457.69 0.25 458.04 834.37 14755.51 6544.49 1014.00 1014.00 1350.00 2149.69 Reach-1 30958 100-Year 457.94 458.06 1142.51 3537.64 17762.36 1048.00 1285.00 Reach-1 30958 100-YearFW 458.15 0.21 458.26 1146.63 3471.23 17828.77 1048.00 1048.00 1285.00 2300.64 Reach-1 31335 100-Year 457.85 458.50 1022.59 11103.58 10196.42 1037.00 1204.00 Reach-1 31335 100-YearFW 458.09 024 458.65 1059.11 10606.36 10693.64 1037.00 1037.00 1204.00 2171.32 Reach-1 32150 100-Year 457.93 459.66 380.46 20406.50 893.49 3400.00 3525.00 Reach-1 32150 '100-YearFW 458.13 0.20 459.79 329.27 20334.69 965.31 3040.00 3400.00 3525.00 4400.00 Reach-1 32200 100-Year 457.72 460.37 166.12 19800.23 1499.77 3390.50 3539.50 Reach-1 32200 100-Year FW 457.93 0.21 460.48 168.19 19764.76 1535.24 3050.00 3390.50 3539.50 4440.00 Reach-1 32215 BRD 100-Year 457.72 460.37 166.13 19800.18 1499.82 3390.50 3539.50 Reach-1 32215 BRD 100-YearFW: 457.93 0.21 460.48 168.19 19764.73 1535.27 3050.00 3390.50 3539.50 4440.00 Reach-1 32215 BR U 100-Year 457.89 460.46 167.84 19770.58 1529.42 3390.50 3539.50 Reach-1 32215.BR U 100-YearFW 458.08 0.19 460.56 169.75 19730.53 1569.47 3050.00 3390.50 3539.50 4440.00 Reach-1 32230 100-Year - 457.90 460.46 167.86 19770.30 1529.70 3390.50 3539.50 Reach-1 32230 `100-Year FW 458.09 0.19 46056 16077 1973025 1569.75 3050.00 3390.50 3539.50 444000 Reach-1 32250 100-Year 460.30 460.68 1261.48 115.99 11917.86 2866.14 3400.00 3525.00 Reach-1 32250 100-Year FW 460.35 0.05 460.76 998.98 129.29 1233442 2436.29 3040.00 340000 3525.00 440000 Reach-1 32305 100-Year 460.14 460.85 501.99 11158.19 3741.81 2110.00 2325.00 Reach-1 ` 32305 100-YearFW 460.16 0.02 460.95 473.50 11687.15 3212.85 1825.00 2110.00 2325.00 3316.00 Reach-1 32725 100-Year 461.24 461.34 2160.04 5099.99 6439.27 3360.74 1940.00 2150.00 Reach-1 32725 100-YearFW 461.38 0.14 461.51 1619.88 4470.44 7052.10, 3377.46 1634.00 1940.00 2150.00 3632.00 Reach-1 33145 100-Year 461.44 461.67 499.95 57.90 14842.10 1390.00 1960.00 Reach-1 33145 100-YearFW 461.62 0.18 461.84 427.77 14900.00 1390.00 1390.00 1960.00 1960.00 HEC-RAS Plan:PreProLFEMA FW River:RIVER-1 Reach:Reach-1(Continued) Reach River Sta Profile W.S.Elev Prof Delta WS E.G.Elev Top Wdth Act O Left O Channel' O Right Enc Sta L Ch Sta L Ch Sta R Enc Sta R (ft) (ft) (9) (ft) (cts) (cfs) (cfs) (ft) (it) (ft) (ft) :.. Reach-1 33470 100-Year 461.74 462.08 560.81 376.09 14523.91 1135.00 1603.00 Res e44.4 33470 - 100 ..✓141.1,*R- 461.91 0.17 462.25 403.02 14900.00 1135.00 1135.00 1603.00 1603.00 Reach-1 34260 100-Year 462.59 462.75 598.55 1.92 14898.08 868.00 1520.00 Reach-1 34260 100-Year FW 462.76 0.17 462.91 597.61 14900.00 868.00 868.00 1520.00 1480.00 Reach1 34850 100-Year 462.61 463.72 177.97 14900.00 1310.00 1533.00 Reach-1 34850 100-YearFW 462.77 0.16 463.84 180.02 14900.00 660.00 1310.00 1533.00 1500.00 Reach-1' 34950 + 100-Year 463.31 463.98 555.42 1293.37 13601.37 5.27 -133.00 44.00 Reach-1 34950 100-Year FW 463.46 0.15 464.09 556.70 1500.86 13391.96 7.18 -555.00 -133.00 44.00 63.00 Reach-1 35253 100-Year 463.79 464.50 430.58 256.60 14643.40 -144.00 116.00 Reach-1 5 35253 100-Year FW 463.91 0.11 464.59 438.37 282.58 14617.42 -575.54 -144.00 116.00 115.29 Reach-1 i 35814 100-Year 464.54 464.92 1059.50 1157.75 12911.87 830.37 -95.21 71.00 Reach-1 35814 100-Year FW 464.57 903 465.02 676.00 387.90 13644.28 867.82 -479.00 -95.21 71.00 197.00 Reach-1 35838 100-Year 464.75 465.05 1202.97 1463.99 12997.27 438.74 -107.01 74.00 Reach-1 35838 - 100-Year FW 464.79 0.05 465.16 560.00 624.70 13891.19 384.11 -393.00 -107.01 74.00 167.00 Reach-1 36034 100-Year 464.89 465.13 149818 1466.54 12686.43 747.03 -60.28 122.00 Reach-1 38034; 100-Year FW 464.98 0.10 465.25 669.00 981.90 13170.69 747.41 -448.00 -60.28 122.00 221.00 Reach-1 36197 100-Year 464.93 465.21 1525.55 2338.02 9535.23 3026.76 -102.20 79.00 Reach-1 36197- 100-Year FW 464.96 0.03 465.38 779.13 771.13 10933.76 3195.11 -469.00 -102.20 79.00 337.00 Reach-1 36217 100-Year 465.00 465.23 1549.83 2947.08 8773.65 3179.27 -104.36 95.00 Reach-1 '`36217 100-YearFW 465.01 0.01 465.40 779.07 1188.16 10721.67 2990.17 -480.00 -104.36 95.00 320.00 Reach-1 36465 100-Year 465.17 465.34 1292.43 1329.16 11260.69 3010.15 -178.99 56.00 Reach-1 36465° 100-Year FW 465.38 0.20 465.55 1026.46 1407.81 11392.50 279970 -617.00 -178.99 56.00 445.00 Reach-1 36542 100-Year 465.18 465.39 1434.63 1201.12 10660.12 3738.76 -164.62 44.00 Reach-1 ' 36542 100-YearFW 465.38 0.20 465.60 1141.00 1305.06 10892.45 3402.49 -625.00 -164.62 44.00 516.00 Reach-1 36837. 100-Year 465.37 465.50 1469.38 692.39 10809.76 4097.85 -100.45 209.00 Reach-1 36837 100-Year FW 465.57 0.20 465.71 1231.00 741.95 11084.85 3773.20 -441.00 -100.45 209.00 790.00 Reach-1 36990 100-Year 465.39 465.58 1388.07 726.47 10941.93 3931.60 -62.58 199.00 Reach-1 -'.-36990 100-Year FW 465.60 0.21 465.77 1230.00 746.32 10887.25 3966.43 -335.00 -62.58 199.00 895.00 Reach-1 37201 100-Year 465.49 465.68 1156.31 1008.98 11041.46 3549.56 -41.04 233.00 Reach-1 37201 100-Year FW 465.69 0.20 465.87 1124.42 101059 10896.30 3693.11 -259.00 -41.04 233.00 92900 Reach-1 37350 100-Year 465.50 465.79 1179.28 362.13 10520.04 4717.82 -50.27 95.00 Reach-1 37350 100-Year FW 465.70 0.20 465.97 1119.00 350.95 10308.77 4940.28 -218.00 -50.27 95.00 901.00 Reach-1 37539 100-Year 465.53 465.90 1299.19 812.91 10650.74 4136.36 -62.63 33.00 Reach-1 37539 -` 100-Year FW 465.71 0.18 466.08 100900 494.31 10721.82 4383.87 -210.00 -62.63 33.00 79900 Reach-1 37702 100-Year 465.69 465.99 1331.32 1309.49 10184.42 4106.09 -139.14 30.02 Reach-1 37702 100-Year FW 465.82 0.13 466.17 995.00 487.71 10789.72 4322.58 -315.00 -139.14 30.02 680.00 Reach-1 37727 100-Year 465.73 466.01 1332.92 1444.06 9934.31 4221.64 -162.03 30.02 Reach-1 37727 100-Year FW 465.83 0.10 466.19 978.00 397.69 10886.68 4315.62 -331.00 -162.03 30.02 647.00 Reach-1 37787 100-Year 465.70 466.10 1277.78 2502.61 11143.72 1953.68 -55.91 47.00 Reach-1 37787 100-Year FW 465.77 0.07 466.31 900.00 1138.91 12387.49 2073.60 -333.00 -55.91 47.00 567.00 Reach-1 37969 ` 100-Year 465.93 466.21 867.97 1480.70 9305.59 4813.71 -79.74 56.00 Reach-1 37969 100-Year FW 466.07 0.14 466.46 511.96 361.20 10673.29 4565.52 -357.00 -79.74 56.00 226.00 Reach-1 38194 100-Year 466.10 466.31 90926 1774.45 7777.94 6047.61 -60.55 75.00 Reach-1 38194 100-Year FW 466.27 0.16 466.58 557.28 607.11 9517.79 5475.11 -322.00 -60.55 75.00 306.00 Reach-1 38381 100-Year 466.22 466.36 888.14 1388.29 7894.80 6316.91 -65.26 67.00 Reach-1 ' 38381"- 100-Year FW 466.47 0.25 466.66 621.83 571.61 8937.43 6090.96 -312.00 -65.26 67.00 362.00 Reach-1 38573 100-Year 466.23 466.42 875.58 1381.42 7006.89 7211.69 -93.00 73.00 Reach-1 `' 38573 ".... 100-Year FW 466.48 0.25 466.73 602.53 528.85 8202.18 6868.97 -300.00 -93.00 73.00 357.00 Reach-1 38781 100-Year 466.25 466.51 976.06 1650.42 9853.32 4096.26 -45.45 75.00 Reach-1 38781 100-Year FW 466.43 0.19 466.90 613.18 862.91 12226.08 2511.01 -311.00 -45.45 75.00 306.00 Reach-1 38988 100-Year 466.23 466.69 762.23 1554.76 13233.66 811.58 -76.37 74.00 Reach-1 38988 100-Year FW 466.53 0.30 467.07 502.57 594.94 14226.05 779.01 -314.00 -76.37 74.00 289.00 Reach-1 39281 100-Year. 466.39 467.02 626.49 856.24 13420.49 1323.28 -63.78 72.00 Reach-1 39281 - 100-Year FW 466.63 0.25 467.54 359.70 190.05 15314.42 95.53 -203.00 -63.78 72.00 336.00 Reach-1 39436 J 100-Year 466.77 467.21 630.06 715.16 10843.27 4041.57 -48.68 49.00 Reach-1 39436 " 100-Year FW 467.39 0.63 467.82 430.00 885.88 10907.38 3806.73 -161.00 -48.68 49.00 269.00 Reach-1 39490 100-Year 466.90 467.28 408.20 885.18 14714.82 4030.00 4310.00 Reach-1 39490 100-Year FW 467.56 0.66 467.89 413.94 993.83 14606.17 3887.80 4030.00 4310.00 4447.80 HEC-RAS Plan:PreProLFEMA FW River:RIVER-1 Reach:Reach-I(Continued) Reach River Sta Profile W.S.Elev Prof Delta WS E.G.Den Top Wdth Act a Left a Charnel 'a Right Enc Sta L Ch Sta L Ch Ste R Enc Sta R (ft) (ft) (ft) (ft). ,f(cis) (cfs) (ds) : (ft) (ft) (0) -(ft) Reach-1 39540 100-Year 466.80 467.49 614.48 778.86 12474.23 2146.91 4040.00 4150.00 Reac(nt-:: .30510- 100YeerfW=i,-` 467.37 0.56 468.20 420.67 155.61 13618.34 1626.06 3589.26 4040.00 4150.00 4466.40 Reach-1 39940 100-Year 467.39 468.03 619.56 1846.33 11174.29 2379.38 1420.00 1500.00 Reach-1 39940 - 100-Year FW 468.06 0.67 468.77 400.00 1532.49 11842.02 2025.49 1280.00 1420.00 1500.00 1680.00 Reach-1 40650 100-Year 468.40 468.63 834.11 1315.26 6939.61 1945.13 4730.00 4815.00 Reach-1 40650 100-Year FW ". 469.11 0.72 469.36 499.00 1083.75 7283.90 1832.35 4546.90 4730.00 4815.00 5045.90 Reach-1 48000 100-Year 470.80 470.88 1549.10 3548.18 4176.81 2075.01 2370.00 2445.00 Reach-1 48000 100-Year FW:" 471.37 0.57 471.45 1300.00 3593.81 4141.35 2064.83 1739.00 2370.00 2445.00 3039.00 Reach-1 51350 100-Year 472.05 472.13 1442.62 2876.96 6518.44 4.61 4160.00 4515.00 Reach-1 ''51350 100-YearFW 472.61 0.57 472.76 600.00 713.29 8686.71 3915.00 4160.00 4515.00 4515.00 Reach-1 53350 100-Year 472.60 472.72 2228.55 3214.39 6118.86 66.74 5570.00 5670.00 Reach-1 53350 100-YearFW 473.37 0.77 473.52 902.12 2504.18 6895.82 4470.00 5570.00 5670.00 5670.00 Reach-1 55590 100-Year 473.27 473.69 1417.53 1897.50 7480.64 21.87 4250.00 4340.00 Reach-1 55590 100-Year FW` 474.14 0.87 474.64 598.41 1131.51 8268.49 3590.00 4250.00 4340.00 4340.00 Reach-1 56840 '. 100-Year. 474.51 474.80 1474.32 2741.29 6631.03 27.68 4335.00 441500 Reach-1 58940 a 100-Year FW 475.44 0.93 475.74 637.88 2416.16 6983.84 3665.00 4335.00 4415.00 4415.00