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HomeMy WebLinkAbout3 Development Permit 554 Glenhave Ph 10·/ ' I~ I' DRAINAGE COMPUTATIONS For Glenhaven Eatates -Phase IX College Station, Brazos County, Texas Prepared For: Mr. Steve Arden Brazosland Properties, Inc. 4103 South Texas Avenue su· .. -~ . ·' Determine Total Pre-Development Peak Storm Water Dischar e Rates Tributary Area ("A"): 17 .35 Acres Pervious Area: 17.35 Acres Impervious Area : 0 .00 Acres Run-Off Coefficient ("Cwt"): 0.40 Time Of Concentration ("T/c"): Woodlands: Low Elevation : High Elevation : Distance (Feet): Slope (%Grade): Velocity ("Vw"): Time: Pastures: Low Elevation : High Elevation : Distance (Feet): Slope (%Grade): Velocity ("Vp"): Time : Pavements: Low Elevation : High Elevation : Distance (Feet): Slope (% Grade): Velocity ("Vpave"): Time : Total Travel Time: Hourly Intensity Rates ("I"): 2-Year: 5.20 5-Year: 7 .69 10-Year: 8.63 25-Year: 9.86 50-Year: 11 .15 100-Year: 12 .60 Peak Discharge Rate ("Q"): 2-Year: 36.09 5-Year: 53.39 10-Year: 59 .92 25-Year: 68.44 50-Year: 77 .36 100-Year: 87.44 c = 0.40 C= 0.98 0.00 0 .00 0.00 0.00 0.00 Feet I Second 0 .00 Minutes 0.00 0.00 0 .00 0.00 0 .00 Feet I Second 10 .00 Minutes 0.00 0.00 0.00 0 .00 0.00 Feet I Second 0 .00 Minutes 10.00 Minutes Inches I Hour Inches I Hour Inches I Hour Inches I Hour Inches I Hour Inches I Hour Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second I Determine Post-development Peak Storm Water Dischar e No Detention T ributary A rea ("A"): 17.35 Acres Pervio us Area : 11.50 Acres c = 0 .4 0 C= 0.98 Imperv ious A rea: 5.85 Acres Run-Off Co efficient ("Cwt"): 0.60 T ime Of Co ncentration ("T/c"): 1 O Minutes (Min) Hourly Int e nsity Rates ("I"): 2-Yea r: 5 .20 Inches I Hour 5-Yea r: 7.7 0 Inc hes I Hour 10-Yea r: 8.60 Inc hes I Hour 25-Year: 9.9 0 Inc hes I Hour 50-Year: 1 1.20 Inche s I Hour 100-Y ear: 12.6 0 Inche s I Hour Peak Discharge Rate ("Q "): 2-Year: 53 .73 Cubic Feet I Seco nd 5-Year: 79.56 Cubic Feet I Seco nd 10-Year: 88.86 Cubic Feet I Second 25-Year: 102 .3 0 Cubic Feet I Second 50-Year: 115.73 Cubi c Feet I Seco nd 100-Year: 130.20 Cubic Feet I Second Comparison Of Predevelopment And Post-development Peak Discharge Rates Prede velopment Post -Develop me nt In crease 2-Year: 36.09 Ft3/sec 53 .73 Ft3/sec 17.64 Ft3/se c 5-Year: 53 .39 Ft3/sec 79.56 Ft3/sec 26 .18 Ft3/sec 10-Year: 59 .92 Ft3/sec 88 .86 Ft3/sec 28.94 Ft3/sec 25-Year: 68.44 Ft3/sec 102.30 Ft3/sec 33.86 Ft3/sec 50-Year: 77 .36 Ft3/sec 115.73 Ft3/se c 38 .36 Ft3/sec 100-Year: 87.44 Ft3/sec 130.20 Ft3/se c 42.7 5 Ft3/sec Preliminary Determination Of Detention Pond Volume 2-Year: 17.64 Ft3/sec x (26 .7 Min. x 60 Sec. I 2 ) = 14, 133 Cubic 5-Year: 26 .18 Ft3/sec x (26.7 Min. x 60 Sec . I 2 ) = 20 ,967 Cubic 10-Year: 28.94 Ft 3/sec x (26 .7 Min . x 60 Sec. I 2 ) = 23 ,181 Cubic 25-Year: 33.86 Ft3/sec x (26 .7 Min . x 60 Sec . I 2 ) = 27,12 0 Cubic 50-Year: 38.36 Ft3/sec x (26 .7 M in . x 60 Sec . I 2 ) = 30,73 0 Cubic 100-Year: 42 .75 Ft3/sec x (26 .7 Min. x 60 Sec. I 2 ) = 34 ,244 Cubic Feet Feet Feet Feet Feet Feet Determine Post-Development Flow Into Detention Pond Tributary Area ("A"): 11 .16 Acres Pervious Area: 7 .30 Acres Impervious Area : 3 .86 Acres Run-Off Coefficient ("Cwt"): 0 .60 Time Of Concentration ("T/c "): 1 O Minutes (Min) Hourly Intensity Rates ("I"): 2-Year: 5 .20 5-Year: 7 .70 10-Year: 8 .60 25-Year: 9.90 50-Year: 11 .20 100-Year: 12 .60 Peak Discharge Rate ("Q"): 2-Year: 34 .85 5-Year: 51 .61 10-Year: 57 .64 25-Year: 66 .36 50-Year: 75.07 100-Year: 84.46 C= 0.40 C= 0.98 Inches I Hour Inches I Hour Inches I Hour Inches I Hour Inches I Hour Inches I Hour Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second Determine Post-Development "Free-Flow" Peak Storm Water DischarQe Tributary Area ("A"): 6 .19 Acres Pervious Area : 4 .10 Acres Impervious Area : 2 .09 Acres Run-Off Coefficient ("Cwt"): 0 .60 Time Of Concentration ("T/c"): 10 Minutes (Min) Hourly Intensity Rates ("I "): 2-Year: 5 .2 0 5-Year: 7.70 10-Year: 8 .6 0 25-Year: 9.90 50-Year: 11 .20 100-Year: 12 .6 0 Peak Discharge Rate ("Q"): 2-Year: 19 .18 5-Year: 28.40 10-Year: 31 .72 25-Year: 36 .51 50-Year: 41 .31 100-Year: 46.47 c = 0.40 C= 0.98 Inches I Hour Inches I Hour Inches I Hour Inches I Hour Inches I Hour Inches I Hour Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second Detention Pond De th Vs; Volume Elevation Depth Volume (Feet) (Ft3) 0.00 0.00 0 1.00 1.00 8,841 2.00 2.00 19,251 3 .00 3.00 31,356 3 .50 3 .50 38 ,084 4.00 4.00 45,285 Detention Pond Depth Vs. Volume 4 .00 3.50 3.00 2.50 --Cl> Cl> LI.. ~ 2.00 -a. C1> a 1.50 1.00 0 .50 0.00 0 10 ,000 20 ,000 30 ,000 40,000 50 ,000 Detention Pond Volume (Cubic Feet) Rating Curve For Outlet Control Structu r e W eir Lengt h(L): 1 .66 Depth Vs . Volume 4 .00 3.5 0 3.00 2.50 ~ Q) Q) ..... ;; 2.00 a. Cl> 0 1.50 1.00 0.5 0 0 .00 Elevation Depth Discharge (Feet) Ft3/Sec 0 .00 0.0 0 0 .00 1.00 1.00 5.12 2.00 2 .00 14.49 3 .00 3.00 26 .63 3 .50 3 .50 33.5 5 4 .00 4.00 41 .00 Rating Curve For Outlet Control Structure Depth Vs. Volume ~ v~ / / / ~ / / / / I 0 .00 5 .00 10 .00 15 .00 20 .00 25 .00 30 .00 35 .00 40 .00 45.00 Dis c harge (C ubic Feet Pe r Secon d ) I Storage Indication Curve 45 .00 40 .00 u 35.00 c 0 0 ~ 30.00 Q) Q.. a; 25 .00 Cl> LL. 0 :g 20.00 u -Cl> ~ 15 .00 s:. 0 I/) a lo.oo 5.00 0.00 Depth (Feet) 0 .00 1.00 2.00 3 .00 3 .50 4.00 / / ,, Storage Discharge 2s/t 2s/t+O (Ft3) (Ft3/Sec) (Ft3/Sec) (Ft3/Sec) 0 0.00 0 .00 0 .00 8 ,841 5.12 294.70 299 .82 19,251 14.49 641 .70 656 .19 31,356 26.63 1,045.20 1 ,071 .83 38,084 33 .55 1,269.47 1,303.02 45,285 41.00 1 ,509 .50 1 ,550 .50 Storage Indication Curve ~ ~ / ~/ / / / ir / v / 0 .00 200.00 400.00 600.00 800.00 l ,000.00 1.200 .00 l .400.00 1.600 .00 2s/t+O (Cubic Feet Per Second) Pre-Development Storm Intensity Rates (Inches Per Hour) Time 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year (Minutes) Storm Storm Storm Storm Storm Storm 0 0 .00 0 .00 0.00 0 .00 0 .00 0 .00 1 3.61 5.34 5.99 6.84 7 .74 8.74 2 7 .22 10.68 11 .98 13.69 15 .47 17.49 3 10.83 16.02 17.98 20.53 23 .21 26 .23 4 14.44 21 .36 23 .97 27 .38 30 .95 34 .98 5 18.04 26.69 29 .96 34 .22 38 .68 43 .72 6 21 .65 32 .03 35 .95 41 .06 46.42 52 .47 7 25 .26 37 .37 41.95 4 7.91 54.16 61 .21 8 28 .87 42.71 47 .94 54 .75 61 .89 69.96 9 32.48 48 .05 53 .93 61.59 69 .63 78 .70 Peak=> 10 36 .09 53 .39 59 .92 68.44 77.36 87.44 11 33 .93 50 .19 56 .34 64 .34 72 .73 82 .21 12 31 .77 46 .99 52 .75 60.24 68 .10 76.97 13 29 .61 43 .80 49 .16 56 .14 63.47 71 .74 14 27.44 40 .60 45 .57 52.05 58.83 66 .50 15 25 .28 37.40 41 .98 47 .95 54.20 61.26 16 23 .12 34 .21 38 .39 43 .85 49.57 56 .03 17 20 .96 31 .01 34 .81 39 .75 44 .94 50.79 18 18.80 27 .81 31 .22 35.65 40.30 45 .55 19 16.64 24 .62 27 .63 31.56 35.67 40.32 20 14.48 21.42 24.04 27.46 31.04 35 .08 21 12 .32 18.22 20.45 23 .36 26.41 29 .85 22 10.16 15.03 16 .86 19 .26 21.77 24 .61 23 8.00 11 .83 13 .28 15.16 17.14 19.37 24 5 .83 8.63 9.69 11 .06 12 .51 14 .14 25 3 .67 5.43 6 .10 6.97 7.88 8.90 26 1.51 2 .24 2 .51 2 .87 3 .24 3 .67 27 0 .00 0 .00 0 .00 0.00 0.00 0 .00 Post-Development Storm Intensity Rates (Inches Per Hour) Time 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year (Minutes) Storm Storm Storm Storm Storm Storm 0 0 .00 0 .00 0 .00 0 .00 0 .00 0 .00 1 5.37 7 .96 8 .89 10.23 11 .57 13.02 2 10.75 15.91 17.77 20 .46 23 .15 26.04 3 16.12 23 .87 26 .66 30 .69 34 .72 39 .06 4 21 .4 9 31 .83 35 .55 40 .92 46 .29 52 .08 5 26 .87 39 .78 44.43 51.15 57.86 65 .10 6 32 .24 47 .74 53 .32 61.38 69.44 78 .12 7 37 .61 55.69 62 .20 71.61 81 .01 91 .14 8 42 .99 63 .65 71 .09 81 .84 92.58 104 .16 9 48 .36 71 .61 79.98 92 .07 104 .16 117.18 Peak=> 10 53 .73 79 .56 88.86 102.30 115.73 130.20 11 50.51 74 .80 83 .54 96 .17 108.80 122.40 12 47 .30 70 .04 78 .22 90.05 101 .87 114.60 13 44 .08 65 .27 72 .90 83 .92 94 .94 106.81 14 40 .86 60 .51 67 .58 77 .79 88 .01 99 .01 ,, 15 37.64 55 .74 62 .26 71 .67 81 .08 91 .22 16 34.43 50 .98 56 .94 65 .54 74 .15 83.42 17 31.21 46 .21 51 .62 59.42 67 .22 75 .62 18 27.99 41.45 46 .29 53 .29 60 .29 67 .83 19 24 .77 36 .69 40 .97 47.17 53 .36 60 .03 20 21 .56 31 .92 35 .65 41.04 46.43 52 .23 21 18.34 27 .16 30 .33 34 .92 39 .50 44.44 22 15 .12 22 .39 25 .01 28 .79 32 .57 36.64 23 11 .90 17.63 19 .69 22 .66 25 .64 28.85 24 8.69 12 .86 14.37 16 .54 18.71 21 .05 25 5.47 8 .10 9 .05 10.41 11 .78 13.25 26 2 .25 3 .34 3.72 4.29 4 .85 5.46 27 0 .00 0 .00 0 .00 0 .00 0 .00 0 .00 Post-Development Flow Routed Through Detention Pond Storm Intensity Rates (Inches Per Hour) Time 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year (Minutes) Storm Storm Storm Storm Storm Storm 0 0.00 0 .00 0.00 0 .00 0 .00 0 .00 1 3.49 5.16 5.76 6.64 7 .51 8.45 2 6.97 10 .32 11 .53 13 .27 15 .01 16.89 3 10.46 15.48 17.29 19 .91 22.52 25.34 4 13.94 20 .64 23 .06 26 .54 30 .03 33.78 5 17.43 25 .81 28 .82 3 3.18 37.54 42 .23 6 20 .91 30 .97 34 .59 39 .81 45.04 50 .67 7 24.40 36 .13 40 .35 46.45 52 .55 59.12 8 27 .88 41 .29 46.12 53 .09 60 .06 67.56 9 31 .37 46.45 51 .88 59 .72 67 .56 76 .01 Peak=> 10 34.85 51.61 57 .64 66 .36 75.07 84.46 11 32 .77 26 .70 29.82 34 .33 38 .83 43 .69 12 30 .68 25 .00 27 .92 32 .14 36 .36 40.91 13 28 .59 23 .30 26 .02 29 .95 33 .89 38.12 14 26 .51 21 .60 24.12 27 .77 31.41 35 .34 15 24.42 19 .90 22 .22 25 .58 28 .94 32.56 16 22 .33 18 .20 20 .32 23 .39 26.47 29 .78 17 20 .24 16 .50 18.42 21 .21 23 .99 26 .99 18 18.16 14.79 16.52 19.02 21 .52 24 .21 19 16.07 13 .09 14 .62 16.84 19.05 21.43 20 13 .98 11.39 12 .73 14.65 16 .57 18.64 21 11.90 9.69 10 .83 12.46 14 .10 15.86 22 9.81 7 .99 8 .93 10.28 11 .63 13 .08 23 7 .72 6 .29 7 .03 8 .09 9 .15 10.30 24 5.64 4.59 5 .13 5 .90 6 .68 7.51 25 3 .55 2 .89 3 .23 3.72 4 .20 4 .73 26 1.46 1.19 1.33 1.53 1.73 1.95 27 0 .00 0 .00 0 .00 0.00 0 .00 0 .00 Post-Development "Free-Flow" Storm Intensity Rates (Inches Per Hour) Time 2-Year 5-Year 10-Year 25-Year 50-Yaar 100-Year (Minutes) Storm Storm Storm Storm Storm Storm 0 0 .00 0.00 0 .00 0 .00 0.00 0.00 1 1.92 2 .84 3 .17 3 .65 4 .13 4 .65 2 3 .84 5 .68 6 .34 7 .30 8.26 9 .29 3 5 .75 8.52 9 .52 10 .95 12 .39 13.94 4 7.67 11 .36 12 .69 14 .61 16.52 18 .59 5 9 .59 14.20 15.86 18.26 20 .65 23.24 6 11 .51 17 .04 19 .03 21.91 24 .78 27 .88 7 13.43 19.88 22 .20 25.56 28 .92 32 .53 8 15.34 22 .72 25 .37 29.21 33.05 37.18 9 17.26 25.56 28 .55 32.86 37.18 41.82 Peak=> 10 19 .18 28.40 31 .72 36.51 41.31 46.47 11 18 .03 26 .70 29.82 34 .33 38 .83 43 .69 12 16.88 25 .00 27 .92 32 .14 36.36 40 .91 13 15.73 23 .30 26 .02 29 .95 33.89 38.12 14 14.58 21.60 24 .12 27.77 31.41 35.34 15 13.44 19 .90 22 .22 25 .58 28 .94 32 .56 16 12 .29 18 .20 20 .32 23 .39 26.47 29 .78 17 11 .14 16.50 18.42 21.21 23 .99 26.99 18 9.99 14.79 16.52 19.02 21 .52 24.21 19 8.84 13.09 14.62 16.84 19 .05 21.43 20 7 .69 11.39 12 .73 14.65 16.57 18.64 21 6.55 9 .69 10.83 12.46 14.10 15.86 22 5.40 7 .99 8 .93 10.28 11.63 13.08 23 4 .25 6.29 7 .03 8 .09 9 .15 10.30 24 3 .10 4 .59 5 .13 5 .90 6 .68 7.51 25 1.95 2 .89 3 .23 3 .72 4.20 4 .73 26 0 .80 1.19 1.33 1.53 1.73 1.95 27 0.00 0 .00 0.00 0.00 0 .00 0 .00 Inflow I Outflow Simulation 2 -Year Storm Event Time Inflow 11+ 12 2s/t-0 2s/t+O Outflow Depth Elevation Velocity (Minutes) (Ft3 /Sec) (Ft3 /Sec) (Feet) (FVSec) 0 0 .00 0 .00 0 .00 0.00 0 .00 0 .00 0.00 0 .00 1 3.49 3.49 3 .37 3.49 0 .06 0.05 0.05 0.70 2 6.97 10.46 13.35 13.82 0.24 0.13 0.13 1.11 3 10.46 17.43 29 .73 30 .78 0.53 0 .22 0.22 1.45 4 13.94 24.40 52 .27 54 .12 0.93 0 .32 0.32 1.74 5 17.43 31 .37 80.78 83.64 1.43 0.43 0.43 2 .02 6 20.91 38 .34 115 .05 119 .12 2 .04 0.54 0 .54 2.27 7 24.40 45 .31 154.88 160 .36 2 .74 0.66 0 .66 2.51 8 27 .88 52 .28 200 .08 2 07.16 3 .54 0 .78 0 .78 2 .73 9 31 .37 59 .25 250.47 259 .33 4.43 0 .91 0 .91 2.94 10 34 .85 66 .22 305 .56 316.69 5 .57 1.06 1.06 3.17 11 32 .77 67.62 359 .07 373 .18 7 .05 1.24 1.24 3.43 12 30.68 63.45 405.82 422 .52 8 .35 1.38 1.38 3 .63 13 28 .59 59 .27 446 .15 465 .09 9.47 1.51 1.51 3.79 14 26.51 55.10 480.41 501 .25 10.42 1.61 1.61 3 .91 15 24.42 50.93 508.92 531.34 11 .21 1.69 1.69 4.01 16 22.33 46.75 531 .96 555.67 11 .85 1.75 1.75 4.08 17 20.24 42 .58 549 .85 574 .54 12.35 1.80 1 .80 4.14 18 18 .16 38.40 562 .83 588 .25 12.71 1.83 1 .83 4 .18 19 16 .07 34 .23 571 .18 597 .06 12 .94 1.85 1.85 4 .20 20 13.98 30.05 575 .14 601.24 13.05 1.86 1.86 4 .22 21 11 .90 25 .88 574 .93 601 .02 13.04 1.86 1.86 4 .21 22 9 .81 21 .71 570 .78 596 .64 12 .93 1.85 1.85 4 .20 23 7 .72 17.53 562 .90 588 .31 12 .71 1.83 1.83 4 .18 24 5 .64 13 .36 551.47 576.25 12.39 1.80 1.80 4 .14 25 3 .55 9.18 536 .69 560.65 11 .98 1.76 1 .76 4.10 26 1.46 5 .01 518 .73 541 .70 11.48 1.71 1.71 4.04 27 0 .00 1.46 498 .35 520 .19 10.92 1.66 1.66 3 .97 28 0 .00 0 .00 477 .67 498 .35 10.34 1.60 1.60 3 .90 29 0 .00 0 .00 458 .06 477 .67 9 .80 1.54 1.54 3 .83 30 0 .00 0 .00 439 .50 458 .06 9 .28 1.49 1.49 3 .76 Inflow/Outflow Simulation 2-Year Storm Event 60.00 ' 50.00 I ' I I ' ' -I "O ' c .. ' 0 I ._ 0 40 .00 Q) I ' Cl) I ... Q) I ' Q. -I ' Q) Q) ' LL. 30.00 ' 0 ' :0 ' ::::J u ' ...... 3'; I 0 20 .00 === ,, I / ...... ' ::::J , 0 • / ...... ' / ..... , 10 .00 0 .00 0 5 10 15 20 25 30 Time (Minutes) Pre-----Post-Post -- - -• -• Post- Developme Developme Developme Developme nt nt Outflow nt Outflow nt "Free- Hydrograph Hydrograph Wit h Flow" Without Det ention Detention Inflow I Outflow Simulation 5-Year Storm Event Time Inflow 11+ 12 2s/t-0 2s/t+O Outflow Depth Elevation Velocity (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) (FVSec) 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1 5.16 5.16 4.98 5.16 0.09 0.07 0.07 0.80 2 10.32 15.48 19.77 20.47 0.35 0.17 0.17 1.26 3 15.48 25.81 44.02 45.57 0.78 0.28 0.28 1.65 4 20.64 36.13 77.40 80.14 1.37 0.41 0.41 1.99 5 25.81 46.45 119.62 123.86 2.12 0.55 0.55 2.30 6 30.97 56.77 170.36 176.39 3.01 0.70 0.70 2.59 7 36.13 67.10 229.34 237.46 4.06 0.86 0.86 2.86 8 41.29 77.42 296.15 306.76 5.31 1.02 1.02 3.12 9 46.45 87.74 369.22 383.89 7.33 1.27 1.27 3.48 10 51.61 98.06 448.22 467.28 9.53 1.51 1.51 3.80 11 26.70 78.31 504.36 526.53 11.09 1.67 1.67 3.99 12 25.00 51.70 532.34 556.06 11.86 1.75 1.75 4.08 13 23.30 48.30 555.62 580.63 12.51 1.81 1.81 4.16 14 21.60 44.89 574.45 600'.51 13.03 1.86 1.86 4.21 15 19.90 41.49 589.08 615.95 13.44 1.90 1.90 4.26 16 18.20 38.09 599.71 627.17 13.73 1.93 1.93 4.29 17 16.50 34.69 606.55 634.40 13.92 1.95 1.95 4.31 18 14.79 31.29 609.82 637.84 14.01 1.96 1.96 4.32 19 13.09 27.89 609.69 637.71 14.01 1.96 1.96 4.32 20 11.39 24.49 606.35 634.18 13.92 1.95 1.95 4.31 21 9.69 21.09 599.96 627.44 13.74 1.93 1.93 4.29 22 7.99 17.69 590.69 617.65 13.48 1.91 1.91 4.26 23 6.29 14.28 578.68 604.97 13.15 1.87 1.87 4.23 24 4.59 10.88 564.08 589.56 12.74 1.84 1.84 4.18 25 2.89 7.48 547.02 571.56 12.27 1.79 1.79 4.13 26 1.19 4.08 527.64 551.10 11.73 1.74 1.74 4.07 27 0.00 1.19 506.54 528.83 11.15 1.68 1.68 4.00 28 0.00 0.00 485.42 506.54 10.56 1.62 1.62 3.93 29 0.00 0.00 465.41 485.42 10.00 1.56 1.56 3.86 30 0.00 0.00 446.46 465.41 9.48 1.51 1.51 3.79 Inflow/Outflow Simulation 5-Year Storm Event 80.00 I ' I • ' 70 .00 I ' I " • ' ....... 60.00 "O c I I ' 0 • 0 ' Cl> (/) 50 .00 ... Cl> Q. -Cl> Cl> 40.00 ...... 0 :0 ::I u 30.00 -?; 0 == ::I 0 20 .00 10 .00 0.00 0 5 10 15 20 25 30 Ti me (Minutes) Pre-----Post-Post--------· Post- Developme Developme Developme De velopme nt nt Outflow nt Outflow nt "Free- Hydrograph Hydr ogra ph With Flow· With out Det ention Detention Inflow I Outflow Simulation 10-Year Storm Ev ent Time Inflow 11+ 12 2s/t -O 2s/t+O Outflow Depth Elevation Velocity (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) (FVSec) 0 0 .00 0.00 0 .00 0.00 0 .00 0 .00 0 .00 0.00 5 .76 5.76 5.57 5.76 0 .10 0 .07 0.07 0.83 2 11 .53 17.29 22 .08 22 .86 0 .39 0.18 0 .18 1.31 3 17.29 28.82 49.16 50 .90 0 .87 0.31 0.31 1.71 4 23 .06 40 .35 8 6.45 89 .51 1.53 0.45 0.45 2 .06 5 28.82 51 .88 133.60 138 .33 2 .36 0.60 0 .60 2 .39 6 34.59 63.41 190.28 197 .01 3 .37 0.76 0.76 2.68 7 40 .35 74 .94 256 .15 265 .21 4.53 0.92 0 .92 2 .96 8 46.12 86.47 330.12 342 .62 6 .25 1.14 1.14 3 .30 9 51.88 97 .99 411.12 428 .11 8.50 1.40 1.40 3.65 10 57 .64 109 .52 498 .78 520 .64 10.93 1.66 1.66 3.97 11 29 .82 87.46 560 .93 586 .24 12 .65 1.83 1.83 4.17 12 27.92 57.74 591 .66 618 .67 13 .51 1.91 1.91 4 .26 13 26 .02 53 .94 617 .17 645 .60 14.22 1.97 1 .97 4 .34 14 24.12 50 .14 637 .67 667 .31 14.82 2 .03 2 .03 4.40 15 22.22 46 .34 653 .4 0 684 .02 15.31 2 .07 2 .07 4 .45 16 20 .32 42 .54 664 .64 695 .95 15.65 2 .11 2.11 4.48 17 18.42 38 .75 671.64 703.38 15.87 2 .12 2.12 4 .50 18 16.52 34 .95 674 .66 706 .59 15.97 2.13 2 .13 4 .51 19 14.62 31.15 673.92 705 .81 15.94 2 .13 2.13 4 .51 20 12 .73 27 .35 669 .65 701 .27 15.81 2.12 2 .12 4.49 21 10.83 23 .55 662 .05 693 .20 15.57 2 .10 2 .10 4.47 22 8 .93 19.75 651 .32 681 .81 15.24 2.07 2.07 4.44 23 7.03 15.95 637 .64 667 .28 14.82 2 .03 2 .03 4.40 24 5 .13 12 .16 621 .15 649 .80 14.33 1.98 1.98 4 .35 25 3.23 8.36 601 .92 629 .50 13.79 1.93 1.93 4 .29 26 1.33 4 .56 580 .10 606.48 13.19 1.88 1.88 4 .23 27 0 .00 1.33 556 .38 581.43 12 .53 1.81 1.81 4 .16 28 0 .00 0 .00 532 .64 556 .38 11.87 1.75 1.75 4 .08 29 0 .00 0 .00 510 .15 53 2.64 11 .25 1.69 1.69 4.0 1 30 0.00 0.00 488 .84 510 .15 10.65 1.63 1.63 3.94 :0-c 0 90 .00 80 .00 70 .00 ~ 60 .00 (I) ... CD Q., Q; 50 .00 CD LL. 0 :0 40 .00 :J u ...... ~ 30 .00 == :J 0 20 .00 10 .00 0 .00 Inflow/Outflow Simulation 10-Year Storm Event " I ' I ' • ,. , ' , ' ' , , .. , ' , ~ I ~ ' , . , ' I . I ~ ' I . ' I I'\. "' I v "" ' , I ' , ' ' ,''/ . ' ' ""' ' , , ' ' , ' ' ' , , . ' . ' I\. ' , ' , -./...-, ' ' -"'-, ' ' ' , ' -~ ' ' "'' ' ' ~ t ·' __,/' '"", ...... "'\, ,' , ' ' ~ , ' .~ 0 5 10 15 20 25 30 Time (Minutes) Pre-----Post-Pos t -·····--· Post- De velopme Developme Developme Developme nt nt Outflow nt Outflow nt "Free- Hydrograph Hydrograph With Flow· Without Detention Detentio n Inflow I Outflow Simulation 25-Year Storm Event Time Inflow 11+ 12 2s/t -O 2s/t+O Outflow Depth Elevation Velocity (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) (Ft/Sec) 0 0 .00 0 .00 0 .00 0.00 0 .00 0 .00 0 .00 0 .00 1 6.64 6 .64 6.41 6.64 0.11 0.08 0 .08 0.87 2 13.27 19 .91 25.42 26.32 0.45 0 .20 0 .20 1 .37 3 19 .91 33 .18 56 .59 5 8 .60 1 .00 0.34 0 .34 1.79 4 26 .54 46.45 99 .52 103 .04 1 .76 0.49 0.49 2 .16 5 33 .18 59 .72 153.80 159 .24 2 .72 0.66 0 .66 2 .50 6 39 .81 72.99 219 .04 226 .79 3 .88 0 .83 0 .83 2 .81 7 46.45 86 .27 294 .77 305 .31 5.27 1.02 1 .02 3 .12 8 53.09 99 .54 379.09 394 .30 7 .61 1.30 1 .30 3 .52 9 59 .72 112 .81 471 .55 491.90 10.17 1.58 1.58 3 .88 10 66.36 126.08 571.72 597 .63 12 .95 1 .86 1.86 4.21 11 34.33 100.68 642.47 672.40 14.97 2.04 2 .04 4.41 12 32 .14 66.47 676 .87 708.94 16.03 2 .14 2 .14 4 .52 13 29 .95 62 .09 705 .14 738 .96 16 .91 2 .22 2 .22 4 .60 14 27.77 57 .72 727 .65 762 .86 17.61 2 .28 2 .28 4.66 15 25 .58 53.35 744 .72 781.00 18.14 2 .32 2 .32 4.70 16 23 .39 48 .98 756 .68 793 .70 18.51 2 .35 2 .35 4.74 17 21 .21 44 .60 763.83 801.28 18.73 2 .37 2 .37 4.76 18 19 .02 40 .23 76 6.4 3 804 .06 18.81 2.38 2 .38 4 .76 19 16.84 35 .86 764 .77 802 .29 18 .76 2 .38 2 .38 4 .76 20 14.65 31.48 759 .09 796 .26 18.58 2 .36 2 .36 4 .74 21 12.46 27 .11 749 .63 786 .20 18.29 2 .34 2 .34 4.72 22 10.28 22 .74 736 .59 772 .36 17.89 2 .30 2 .30 4.68 23 8.09 18.37 720 .21 754.96 17.38 2.26 2 .26 4.64 24 5 .90 13 .99 700 .66 734 .20 16.77 2 .20 2 .20 4 .58 25 3 .72 9 .62 678 .13 710 .28 16.07 2 .14 2 .14 4 .52 26 1.53 5 .25 652 .80 683 .38 15.29 2 .07 2 .07 4.44 27 0 .00 1.53 625.44 6 54 .33 14.45 2 .00 2 .00 4 .36 28 0 .00 0 .00 598 .07 62 5.44 13.69 1.92 1.92 4 .28 29 0.00 0 .00 57 2 .14 598 .07 12 .97 1.86 1.86 4.21 30 0 .00 0 .00 547 .57 572 .14 12 .28 1.79 1.79 4 .13 ~ c 0 120 .00 100 .00 ~ 80 .00 (/) a; CL. -; £ 60.00 0 :0 :::> (.) ...., 0 .00 Inflow/Outflow Simulation 25-Year Storm Event I I I I 0 5 Pre ---- - De velopme nt Hydrograph I I I ' 10 ' ' ' 15 20 nme (Minutes) Post-Post - De velopme De velo pme nt Outflow nt Outflow Hydr ograph With Without Det ention Detention ' ' 25 30 ........ -Post- Developme nt 'Free- Fl ow' Inflow I Outflow Simulation 50-Year Storm Event Time Inflow 11+ 12 2s/t-O 2s/t+O Outflow Depth Elevation Velocity (Minutes) (Ft3/Sec) (Ft3 /Sec) (Feet) (FVSec) 0 0 .00 0.00 0 .00 0.00 0.00 0 .00 0.00 0.00 1 7.51 7 .51 7 .25 7 .51 0.13 0 .09 0.09 0.90 2 15.01 22.52 28 .75 29.77 0 .51 0 .21 0 .21 1.43 3 22.52 37 .54 64 .02 66 .29 1.13 0 .37 0 .37 1.87 4 30 .03 52 .55 112 .59 116.57 1.99 0 .53 0 .53 2.25 5 37 .54 67 .56 174 .00 180.15 3 .08 0 .71 0 .71 2.60 6 45 .04 82 .58 247 .80 2 56 .57 4 .39 0.90 0 .90 2 .93 7 52 .55 97 .59 332 .75 345.40 6 .32 1.15 1.15 3 .31 8 60.06 112 .61 427.46 445 .36 8.95 1.45 1.45 3 .72 9 67 .56 127 .62 531.41 555.08 11.84 1.75 1.75 4.08 10 75 .07 142 .64 644.01 674.04 15.02 2 .05 2 .05 4.42 11 38.83 113.91 722 .99 757.92 17.46 2 .26 2 .26 4 .65 12 36 .36 75.20 760 .91 798.19 18 .64 2 .37 2.37 4 .75 13 33 .89 70 .25 791 .95 831 .16 19 .60 2.45 2.45 4 .83 14 31.41 65 .30 816 .53 857 .25 20.36 2 .51 2 .51 4 .89 15 28 .94 60 .35 835 .01 876 .88 20 .94 2 .56 2.56 4 .94 16 26.47 55.41 847 .75 890.41 21 .33 2.59 2 .59 4.97 17 23 .99 50.46 855 .09 898 .21 21 .56 2 .61 2 .61 4 .98 18 21 .52 45 .51 857 .35 900 .61 21 .63 2 .61 2 .61 4.99 19 19.05 40 .57 854 .81 897 .91 21 .55 2 .61 2 .61 4 .98 20 16.57 35 .62 847 .77 890.43 21.33 2.59 2 .59 4 .97 21 14.10 30 .67 836.48 878.44 20 .98 2.56 2 .56 4.94 22 11 .63 25 .72 821 .19 862 .20 20.51 2 .52 2 .52 4 .90 23 9.15 20 .78 802 .13 841 .96 19 .92 2.47 2.47 4 .85 24 6 .68 15.83 779 .53 817 .96 19 .22 2.41 2.41 4 .80 25 4 .20 10.88 753 .59 790.41 18.41 2 .35 2 .35 4.73 26 1.73 5.9 4 724.50 759 .52 17.51 2 .27 2.27 4 .65 27 0 .00 1.73 693 .16 726 .23 16 .54 2 .18 2 .18 4 .56 28 0 .00 0 .00 662.01 693 .16 15 .57 2 .10 2 .10 4.47 29 0 .00 0.00 632 .68 662 .01 14.66 2 .02 2.02 4 .38 30 0 .00 0 .00 604 .93 632 .68 13 .88 1.94 1.94 4 .30 • • 1J c 0 120 .00 100 .00 g 80 .00 (/) ... Q) 0.. Q; :£. 60.00 0 :0 ::::J (.) -~ 40.00 E ::::J 0 20.00 0 .00 Inflow/Outflow Simulation 50-Year Storm Event I I I I 0 5 Pre----- Developme nt Hydrograph I ' I ' I 10 " " ' " ' 15 20 Time (Minutes) Post-Post- Devel opme Developme nt Outflow nt Outflow Hydrograph With Without Detentio n Detentio n 25 30 --··----Post- Develo pme nt "Free- Flow" Inflow I Outflow Simulation 100-Year Storm Event Time Inflow 11 + 12 2s /t -O 2s/t+O Outflow Depth Elevation Velocity (Minutes) (Ft3 /Sec) (Ft3 /Sec) (Feet) (FVSec) 0 0 .00 0 .00 0 .00 0.00 0 .00 0 .00 0.00 0.00 1 8.45 8.45 8.16 8.45 0 .14 0.09 0 .09 0.94 2 16 .89 25 .34 32 .35 33.49 0.57 0.23 0 .23 1.49 3 25 .34 42 .23 72 .03 74.58 1.27 0.40 0.40 1.94 4 33 .78 59 .12 126 .66 131.15 2 .24 0 .58 0.58 2 .34 5 42 .23 76 .01 195 .74 202 .67 3.46 0 .77 0 .77 2 .71 6 50 .67 92 .90 278 .78 288 .65 4.93 0 .97 0 .97 3 .05 7 59 .12 109.79 373.66 388 .57 7.46 1.28 1.28 3 .50 8 67 .56 126 .68 479 .55 500 .34 10.40 1 .60 1.60 3 .91 9 76 .01 143.57 595 .87 623.12 13.62 1.92 1.92 4 .28 10 84.46 160.47 721 .50 756.34 17.42 2.26 2 .26 4.64 11 43 .69 128.14 809 .36 849 .64 20 .14 2.49 2.49 4 .87 12 40.91 84.59 851 .09 893 .96 21.43 2 .60 2 .60 4.97 13 38 .12 79 .03 885 .14 930.12 22.49 2 .68 2 .68 5 .05 14 35 .34 73.46 911 .95 958 .60 23 .32 2 .75 2 .75 5.12 15 32 .56 67 .90 931 .97 979 .85 23 .94 2 .79 2 .79 5.16 16 29 .78 62 .33 945 .57 994 .30 24 .36 2.83 2.83 5.19 17 26 .99 56 .77 953 .14 1002 .34 24 .60 2 .85 2 .85 5.21 18 24 .21 51 .20 955 .03 1004.34 24 .66 2.85 2 .85 5.21 19 21 .4 3 45.64 951 .57 1000.67 24 .55 2 .84 2 .84 5 .20 20 18.64 40.07 943 .07 99 1.64 24 .29 2 .82 2 .82 5.19 21 15 .86 34 .51 929 .82 977 .57 23 .88 2 .79 2.79 5 .16 22 13 .08 28 .94 912 .11 958 .76 23 .33 2 .75 2 .75 5 .12 23 10.30 23 .37 890 .19 935.48 22 .65 2.69 2.69 5.07 24 7 .51 17.81 864 .31 908 .00 21 .84 2 .63 2 .63 5.01 25 4 .73 12 .24 834 .70 876 .55 20.93 2.55 2 .55 4.93 26 1.95 6 .68 801 .58 84 1.38 19 .90 2.47 2.47 4 .85 27 0 .00 1.95 765 .93 803 .52 18 .79 2 .38 2 .38 4 .76 28 0 .00 0 .00 730 .54 76 5.93 17.70 2 .28 2 .28 4 .67 29 0 .00 0 .00 697 .21 73 0.54 16 .66 2 .19 2 .19 4 .57 30 0.00 0.00 66 5.83 69 7 .21 15 .69 2 .11 2 .11 4.48 • • 140 .00 120 .00 ~ 5 100 .00 0 Q) Cl) Qi 0... 80 .00 a; Q) LL. 0 :a ::::J u -~ 0 E ::::J 0 60.00 40.00 20 .00 0 .00 Inflow/Outflow Simulation 100-Year Storm Event I I I I 0 5 Pre --- -- Developm e nt Hydrograph ' I ' I ' ' ' 10 15 20 Time (Minutes) Post-Post - De velopme Developme nt Outflow nt Outflow Hydrograp h With Without Detention Detention ' ' 25 -....... 30 Post- De velopme nt "Free- Flow" • 80 .00 ... Q) 70 .00 0... -Q) 60 .00 Q) u.. .2 ~ 50.00 ..0 c 8 8 40.00 -Q) 8, (I) 30.00 ... 20 .00 0 .l: 0 10 .00 Cl) 0 0 .00 0 Total Pre-Development Hydrograph Vs. Total Post- Development Hydrograph For 2-Year Storm Event 0 .00 ~---ol~---+----+----+---~~:=i.---4 0 5 10 15 20 25 Time (Minutes) Pre-Development Hydrograph ---Total Post-Development Hydrogra ph Total Pre-Development Vs. Total Post-Development (No Detention) Peak Discharge Rates 5-Year Storm Event 5 10 15 20 25 Time (Minutes) 30 3( ---Pre-Development Hydrograph ---Post-Development Outflow Hydrograph Without Detention 90.00 ..... G> 80.00 a.. -G> 70 .00 G> ~ ...... 60.00 ·-"O .g c 50.00 u 0 40.00 '"' 0 G> ~ 30 .00 0) ..... 0 20.00 .c 0 I/) 10 .00 i5 0 .00 0 Total Pre-Development Vs. Total Post-Development (No Detention) Peak Discharge Rates 10-Year Storm Event 5 10 15 20 25 Time (Minutes) 30 ---Pre-Deve lopment Hydrograph ----Post-Developme nt Out flo w Hydrograph Without Detention 120 .00 ..... G> a.. 100.00 -G> G> LI.. 80.00 0 ...... ·-"O .0 c :J 0 60.00 u 0 '"' G> G> (/) 40.00 0) ..... 0 ..c 20 .00 0 I/) i5 0 .00 0 Total Pre-Development Vs. Total Post-Development (No Detention) Peak Discharge Rates 25-Year Storm Event 5 10 15 20 25 Time (Minutes) 30 ----Pre-Development Hydrograph ----Post -Developm e nt Outflow Hydrograph With out Detention • 120.00 .... Q) 0.. 100 .00 -Q) Q) u.. 80.00 0 ...... ·-"O .0 c :J 0 60 .00 u 0 ....... Q) Q) (f) 4 0 .00 O> .... 0 .&:. 20 .00 0 II) i5 0 .00 0 Total Pre -Development Vs . Total Post-Development (No Detention) Peak Discharge Rates 50-Year Storm Even t 5 10 15 20 25 Time (Minutes) 30 ---Pre-Development Hydrograph ---Post-Developm e nt Outflow Hydrograph Wi th out Detention 140.00 .... Q) 0.. 120 .00 -Q) Q) 100.00 u.. 0 ...... ·-"O 80 .00 .0 c :J 0 u 0 60.00 ....... Q) Q) (f) O> 4 0 .00 .... 0 .&:. 0 20 .00 II) i5 0 .00 0 Total Pre -Development Vs. Tota l Post -Development (No Detention) Peak Discharge Rates 100-Year Storm Event 5 10 15 20 25 Time (M inutes) 30 ---Pre-Development Hydrograph Post -Development Outflow Hydro g rap h Without Detention Inflow/Outflow Simulation 2-Year Storm Event 40.00 35 .00 30 .00 ,..... "O c 0 0 Cl> 25 .00 V> ... Cl> ll.. -Cl> Cl> 20.00 u.. 0 :0 :J (.) -~ 15.00 0 E :J 0 10.00 5 .00 0 .00 0 5 10 15 20 25 30 Time (Minutes) ----Pre-Development Hy drograph ----Total Post-Development Hydrograph • Inflow/Outflow Simulation 5-Year Storm Event 60.00 50.00 -"O c 0 40.00 0 Cl> (/) ... Cl> 0.. -Cl> Cl> 30.00 LL. 0 :.0 :::> u ....., ~ 0 20.00 E :::> 0 10.00 0 .00 0 5 10 15 20 25 30 Time (Minutes) ---Pre-D evel opment Hydrograph ----Total Post-Development Hydrograph • Inflow/Outflow Simulation 10-Year Storm Event 60.00 50.00 ,.... "O c 0 40.00 0 Q) (I) .... Q) Q.. -Q) Q) 30.00 u.. 0 :0 :J u ........ ~ 0 20 .00 E :J 0 10 .00 0 .00 0 5 10 15 20 25 30 Time (Minutes) Pr e-Development Hydrograph ----Total Post-D evelopme nt Hydrograph Inflow/Outflow Simulation 25-Year Storm Event 70.00 60.00 £)' 50 .00 c 0 0 Cl> (/) .... Cl> 40 .00 0.. -Cl> Cl> LL. 0 :0 :J 30 .00 u ....., ~ 0 E :J 0 20 .00 10.00 0 .00 0 5 10 15 20 25 30 Ti me (Minutes) ---Pre-Development Hydrograph ----To tal Post-Development Hydrograph 1J c 0 0 80 .00 70 .00 60.00 ~ 50.00 ... Cl) a.. Q) i2 40.00 0 :0 :J ~ ~ 30.00 0 E :J 0 20.00 10.00 0 .00 0 Inflow/Outflow Simulation 50-Year Storm Event 5 10 15 20 25 30 Time (Minutes) Pre-Developm ent Hydrograph ---·Total Post-De velopm en t Hydrograph r Inflow/Outflow Simulation 100-Year Storm Event 90 .00 80 .00 70 .00 """ "O c 0 60.00 0 Q) IJ) .... Q) 0.. 50.00 -Q) Q) LL. 0 :c 40.00 :J 0 -~ 0 30.00 s: :J 0 20 .00 10.00 0.00 0 5 10 15 20 25 30 Time (Minutes) Pre-Development Hydrograph ----Total Post-Development Hydrograph otz:J ~ ep M t£:<0T pdl-('...( I f , G.L~ 1-Hl votU IO Impact Study Glenhaven Estates Phase IX College Station, Texas 7 Jul 1992 Prepared By: GAr<RFrr Ei',Gli',EEr<li''G 4444 Carter Creek Parkway Bryan, Texas 77802 Phone: 409.846 .2688 RECEIVED SEP 2 3 1992 Impact Study Glenhaven Estates Phase IX College Station, Texas 7 Jul 1992 .This impact srudy is supplemental to works submitted on behalf of the de velopers of earlier phases of · Glenhaven Estates and prepared by Riley Engineering Co. Its purpose is to bring up to date the actual impact of Glenhaven Estates Phase IX on the City of College Station infastrucrure based on revisions to the proposed development plans and previous construction. In the previous impact srudy it was shown that the Electrical Department of the City of College Station has no problems servicing this subdivision as a whole. Lone Star Gas has also indicated that providing service to the proposed lots will not be a problem. The Water, Sanitary Sewer, Drainage and Traffic flows are discussed following this general discussion. It is shown in this document that no adverse impact will result from the construction of this phase of Glenhaven Estates. Drainage Impact Study Glenhaven Estates Phase IX College Station, Texas 7 Jul 1992 This impact study is supplemental to works submined on behalf of the developers of earlier phases of Glenhaven Estates and prepared by Riley Engineering Co. Its purpose is to bring up to date the actual impact on the drainage panem based on revisions to the proposed development plans and previous construction. In the previous impact study it was shown that small frequency rains would pass through the existing 2- 48 inch RCPs at Dominik Drive but that larger frequency rains would spill over the roadway. Phase VIII was constructed with a det~ntion facility at the downstream end of the subdivision to reduce and anenuate the flow rate leaving tflat are of improvement. Phase IX will likewise be constructed in accordance with the City of College Station's Drainage Control Ordinance by detaining water on-site such that the proposed peak flow rate from the site will not be increased over the projected unimproved peak flow rate for the site . This detention facility will be constructed at the southwest comer of proposed Phase IX of the subdivision. -----f'n,,£ -?osr ~VVMS~s ~ !.L.-o.-.J .:Au '1 o ..._ J-.,,, o~ ;+ ~/ /( ../, t- ___,J-lo..,..::J h,·::5 ( o...re.-..._ ......;_. ~~) )5 -f'l,<._ -f;_c.; u~. ,.,,ee_pfs +o .be-~,~~ ~J-/;~ -1-Ae.- µ>,4..+ /_:$ -H-t<...-~~ ~c..::>...--. ~G(c.. ·~( +(j << 2 ~ , en , Ir <---f,' { /h'e.5. pl~(::~ ;.~f.~ae:~~=t= >7~1t~:o; '25 ~ cS..._~oP; ~~/ ~-~<:::>~~~~¥~~ tle...._e ,-... 4-p $-?.ok=>; (5 I 0 ~ °" .,,+ "'""?I~ ~~~ .hL~ l~-i;<-5 (~1'-!~t~ • ? rs ~o-r-v--5~e.,...---OY-~V"'~ rv--Of=>CO~ cl' l~ ~c:::12 1-n---~ c-c:._ c:s.-.--+s <;? 2 o ' 01J2 ~ ~ o-<..l .:5 ~ ""'+-<--< rl-L ..... o Ff== ) r0~ *' <> 1~ ~ ~ b' ~ ~ us; ~ _.,l-.~ ~ --r ~ -r~r d~ °""' -:s -k }( p---t-o -~ ~·:s ~ --D~~a Water Impact Study Glenhaven Estates Phase IX College Station, Texas 7 Jul 1992 This impact study is supplemental to works submiued on behalf of the developers of earlier phases of Glenhaven F..states and prepared by Riley Engineering Co. Its purpose is to bring up to date the actual impact on the water system based on revisions to the proposed development plans and previous construction. In the previous impact study it was shown that the existing eight inch (8") line on Glenhaven Drive (when connected to the eight inch (8") line on Dominik Drive during the construction of Phase IV) will provide adequate fire protection and normal flow delivery of water. This analysis was performed a based on the previous proposed layout. The current proposed layout has reduced the lot density (and therefore the tocal lot count) as well as the actual length of lines and number of service connections. The head loss through the shorter pipe is less as well as reduced demand and lower node elevations therefore the previous analysis is very conservative (i.e., our lessor requirements will cause no further impact). _.I.__ _____________ -- I Sanitary Sewer Impact Study Glenhaven Estates Phase IX College Station, Texas 7 Jul 1992 This impact study is supplemental to works submitted on behalf of the developers of earlier phases of Glenhaven Estates and prepared by Riley Engineering Co. Its purpose is to bring up to date the actual impact on the sanitary sewer system based on revisions to the proposed development plans and previous construction. In the previous impact study it was shown that the existing eight inch (8") line at the southwest boundary of the subject tract has a capacity of approximately 300 gallons /minute. The eight inch (8") line flows into a ten inch (10") line at a manhole aooroximatelv ~00 feet northwest of the intersection of Dominik Drive . "' .. and Merry Oaks Drive. There arc currently no other collection lines flowing into this manhole. The capacity of the ten inch (10'') sanitary sewer line can be computed as follows: 1.486 2/ J/ Q • --AR/3 s7z n n • 0.013 S • 0.003 feet/feet A • 0.5454 sq-ft WP • 2.618 feet A R=- WP R = 0. 5454 sq -ft 2.618 feet R • 0.2083 feet Q· i.436 (o.5454Xo .2083)K(o.003)Yz 0.013 Q • 1.200 cubic feet/second Q • 539 gallons/minute The flow in the existing eight inch (8") line is from Carters Grove and adjacent areas was shown to be 160 gallons /minute at Merry Oaks and Carol Street by the previous impact study. Page 1 The Glenhaven Esrates Phase VIII development added 10 lots to the flow into the existing eight inch (8") line. These 10 lots contribute 19% of the proposed toral flow shown in the computations prepared by Rile y Engineering Co . or an additional flow of 8 gallons/minute. This flow added to the pre vio us 160 gallons /minute accounts for a total flow of 168 gallons/minute in the eight inch (8") line at Me rry Oaks and Carol Street. The proposed Glenhaven Estates Phase IX addition 42 additional lots will be serviced . Assume a density of 4 persons/lot and an average flow of 100 gallons/capita/day . Assume that the peak flow rate is equal to three times the average flow rate. Using these assumptions the flow from these proposed lots can be computed as follows: Average Flow: (42 lots)(4 persons/lotXlOO gallons/capita/day),. 16800 gallons I day ( 16800 gallons I day ) . Peak Flow: 3 = 35 gallons I nunute 1440 gallons I minute Adding this proposed flow of 35 gallons/minute to the existing flow of 168 in the eight inch (8") line at Meny Oaks and Carol Street equals a total flow rate of 203 gallons/minute . The total flow rate of 203 gallons/minute is less than the 300 gallons/minute capacity of the eight inch (8") line and considerably less than the 539 gallons/minute capacity of the ten inch (10") line . The above computations clearly show that the existing sanitary sewer capacity in this area is more than adequate to handle the flow from the proposed development of Glenhaven Estates Phase IX. Page 2 Traffic Impact Study Glenhaven Estates Phase IX College Station, Texas 7 Jul 1992 This impact study is supplemental to works submitted on behalf of the deve lopers of earlier phases of Glenhaven Estates and prepared by Riley Engineering Co. Its purpose is to bring up to date the actual impact on the traffic flows based on revisions to the proposed development plans and previous construction. In the previous impact study it was shown that the traffic flows projected for this subdivision had only a small impact and that no renovations or installation of traffic control devices would be required. University Drive has been upgraded since this study and provides easier turning movements that further lessen the impact of the additional small traffic flow. ------------------- I I I / ~ ..,,,,--__ _ I I Goo I PARK . ~·" wet-I-a-<.·. . I \ ·· :: boo " .... -·· "•. ~ ... . ' --------·-----I ·1 I i / I ~ Impact Study Glenhaven Estates Phase IX College Station, Texas Appendix A , f I I, IMPACT STUDIES REVISED MASTER PRELIMINARY PLAT GLENHAVEN ESTATES 14.935 ACRES COLLEGE STATION, TEXAS SANITARY SEWER MASTER PRELIMINARY PLAT GLENHAVEN ESTATES COLLEGE STATION, TEXAS THE development of the 14.935 acres tract in single family residences on the lot sizes shown on the Revised Master Preliminary Plat that has been submitted to the City of College Station for approval, will not create any problems in the sanitary sewer system serving the area. In 1983, during the planning for the development of the entire 91 acres tract, discussions were held with the Water and Sewer Department, specifically Bennie Luedke, to work out a solution to any problems that might exist. The existing 8-inch line that is generally southwest of the property in the Carters Grove Subdivision was not adequate to ~andle the sanitary sewerage expected to be generated from the subdivision. A plan was worked out whereby a new 8-inch line would be constructed starting at the existing manhole on Francis Drive and continuing along the new Francis Drive to Glenhaven Drive and then to University Drive and along Un~versity Drive to the East Bypass and eventually northwesterly along the Bypass to the existing outfall line along Carter Creek. This line would have increases in size to accomodate all flow expected from northwest two- thirds of the subdivision. The existing line leaving out of the manhole on Francis Drive was plugged. This would allow the southwest corner of the subdivision to be sewered into the existing 8-inch line that flowed in a south- easterly direction toward Dominik Drive. At the time this agreement was made, it was expected that there would be approximately 110 residential lots to be serviced by this 1 in e . The 1 in e w·a s ad e qua t e t o h an d 1 e the f 1 ow from the s e 1 o t s . Since that time, part of the area has been given as park land and an 11 acres tract has been sold as a church site. The lot sizes in the remaining area have been increased resulting in approximately 53 lots to be serviced at this time. Therefore, there will be no problems connected with sewering this area in the existing line and no overload problems will ©'.ccur. ( SEE EXHIBIT 1 ) 12 " LINE PHASE EI 4 .370 ACRES A ·P SANITARY SEWER c -1 /5.226AC. STATE HIGHWAY NO. 6 MASTER PLAT GLENHAVEN ESTATES COLLEGE STATION BRAZOS COUNTY, TEXAS CHURCH TRAC r (SOLO) CARTERS GROVE, 2nd I• LINE .... I Q: RILEY ENG!NEERiNG CO. BRYAN TEXAS WATER LINES MASTER PRELIMINARY PLAT GLENHAVEN ESTATES COLLEGE STATION, TEXAS The development of the 14.935 acres tract in single family residences on the lot sizes shown on the Revised Master Preliminary ~lat that has been submitted to the City of College Station for approval will not create any problems in the water system that is now existing or to be constructed in the future. There is a 12-inch water main along University Drive and along the frontage road of the East Bypass. The 8-inch lines constructed during the earlier phases of the Subdivision have been connected to the 12-inch line. There is a 10-inch line along Dominik Drive that will be tapped when Glenhaven Drive is extended and the proposed 8-inch line is constructed. When all construction is complete, a looped system will exist that will be capable of proviruing for residential needs as well a fire needs. There are fire hydrants existing in the subdivision and additional hydrants will he added as construction progresses to provide a maximum distance of 300 feet to a hydrant in all instances. The Citu Water Department has indicated that there will be no problems providing for the need of the subdivision. ( See Exhibit 2 N "' ! .... . ~ POST OAK FOREST WATER LINES c., . 16.226AC . STATE HIGHWAY NO. 6 12"l1NE I I I I o I 1 8! I lt I I ~I IN I ; i " ( I \ / ..., .... POST OAK ADDI TIO.N CAR~RS GROVE, 2nd I . I I MASTER PLAT GLENHAVEN ESTATES COLLEGE STATION BRAZOS COUNTY, TEXAS CHURCH TRACT (SOLO) DRIVE PR-OPOSED II" LINE I I ~I ig I I~ I I ~I I~ I { o I J" J f 114.9l5 oc. i I . { ~\ (CD\ \ I . \._,I CARTERS GROVE, 2nd RILEY ENG!NEERiNG CO. BRYAN TEXAS B-/4-86 TRAFFIC MASTER PRELIMINARY PLAT GLENHAVEN ESTATES COLLEGE STATION, TEXAS The development of the 14.935 acres tract in single family residences on the lot sizes indicated (approximately 53 lots) on the Revised Master Preliminary Plat will not create an unusual traffic pattern different from that observed in other subdivisions of comparative size. This areais, or will be when construction of the Extension of Glenhaven Drive is completed, served with an unusual number of collector streets to provide for access to the major thoroughfares. Glenhaven Drive will connect Dominik Drive with University Drive and will provide an excellent east/west access to the major streets. Also, Brazoswood Drive will provide excellent access to the frontage road on the East Bypass. Francis Drive will provide access to the schools and other areas to the southwest of the property. There will not be a large volume of traffic generated in the area due to the fact that it is a residential area and has no large traffic volume generators planned or for that matter, sites provided for such generators. The close proximity of the Richard Carter Park and the proposed Church Site will limit the traffic generated in the area during times of peak travel. The volume of traffic generated in this area will not require the installation of any traffic control devices other than stop signs and speed limit signs. The exact number of vehicles per day cannot be determined at this time due to the fact that the dwelling size, income range and family size cannot be determined. Later evaluation of the site after construction is complete will give a better feel for the traffic volumes generated. ( SEE EXHIBIT 3 ) POST OAK FOR £ST i MASTER PLAT .·.I· TRAFFIC GLENHAVEN ESTATES COLLEGE STATION BRAZOS COUNTY, TEXAS • c -1 . 16.226AC. POST OAK ADDI TIO _N STAT£ HIGHWAY NO. 6 I I I I I a I . 81 I :t I I ~I I ... , )i~ . I I I \ I ":'- ci:: CAR~RS GROVE 1 2nd Q Ill ~.__~_M_E_R-RY~O-AK-S~DR-1-VE~~~~~-C~ CHURCH TR4c r .... (SOLO) I Q:: ti ~ tr) t;: ...: . GLENHAVEN DRIVE -I -I.., I /~I 1~1 1g1 ~' I !: I I~, I~ I u (o I o4i I :i I J ~/14.SESS l: . )> I )!~ 1 ..:\ r~l I \· I \. _, I \. _:1 CARTERS GROVE, 2nd ~I 5~ -AKS DRIV ~,-----'----'-'--~~--~ RILEY ENG!NEERiNG CO. BRYAN ·TEXAS 8-/4-86 ~ C2 Q ,~, ...... ~ Q NATURAL GAS MASTER PRELIMINARY PLAT GLENHAVEN ESTATES COLLEGE STATION, TEXAS Lone Star Gas Company has an existing line at the end of the existing Glenhaven Drive. Representatives of the Gas Company have indicated that there will be no problems serving the area. ELECTRICAL DEMAND MASTER PRELIMINARY PLAT GLENHAVEN ESTATES COLLEGE STATION, TE XAS The Electrical Distribution Department of College Station has indicated there will be no problems providing service to the area. There will be no large volume users or other demands for high e ~ectrical capacity. The electrical lines wtll possibly be under g round which will necessitate the coordination with the Electrical Department. Otherwise, no problems are evident. DRAINAGE ANALYSIS REVISED MASTER PRELIMINARY PLAT GLENHAVEN ESTATES 14.935 ACRES COLLEGE STATION, TEXAS cf:/ c;-h .°7 0 I -- _55 .£ c(... "2: .9.4 ·o I ~ '57 lb lS Oob t:" £' "L. 2 (.'_S Z l. .<c £""" h-~ e ~o .b, I 2 p "£'. L '? ·p.~ .h0 "(.2 JI 'S ( l:'"J-:>) ( <;3-=>) :;;e ~ ;;er$'. S??I? f;:I .. DRAINAGE ANALYSIS REVISED MASTER PRELIMINARY PLAT GLENHAVEN ESTATES 14.935 ACRES COLLEGE STATION, TEXAS ( 7 Th ~i :a;e Analysis dated September, 1986 and December, 1987, were prepared for the Extension of Glenhaven Drive and were intended to give the runoff quantities needed to design the storm sewer and inlets on the proposed street. The September, 1986 calculations were based on a 5-year frequency. The December, 1987 calculations were based on a 25-year fnequency. These drainage calculations can be used to give the total runoff entering the 14.935 acres tract with the exception of the portion of Glenhaven Estates, Phase II, that lies northwest of this tract and drains into the tract along the small creek. The nunoff from this area of 5.10 acres is calculated in the same manner as the other figures for a total of 25.49 cfs. This figure, when added to the runoff totals from the Drainage Analysis attached give a total runoff entering the 14.935 acres tract of 139.78 cfs. The runoff from the 14.935 acres tract can be calculated in the same manner to give a total of 74.?5 cfs. This figure, when added to the runoff of 139.78 cfs from outside the tract, give a total runoff at the 2-48" RCP under Dominik Drive of 214 ~43 cfs. The.re is a small creek that enters ·t~perty from the southwest that contributes approximately 100 cfs fo~ear frequency. Adding all the runoff figures together gives a total at Dominik 0 Drive of 314.43 cfs. The capacity of the 2-48" RCP on a 1.00% grade would be approximately 310 cfs. From this, we can see that the pipes are adequate for a small frequency rainfall but would not be adequate for a larger frequency rainfall. In this event, the water would spill over the roadway and into the creek downstream. More detailed analysis of the area at Dominik Drive would be needed when the time arises and the construction of the streets and storm sewer begins. AD IJ ITI ONl\L DI SC Tf? USS J ON Nt\""~ AFFI C .: 'i:.R PREL I MTN/I R "LE · Y PL!\T u , NII J\ VEN ESTi\TES CO LLEGE STA TION, TEXA S As pr evi ously t t d h 4 . into a . s a e ' t e l .935 acres tr a ct will be divided Th ~pro xima tely 53 lots for Single Fa mil y Res idential Develo ment f e price of t~e homes is exp ec ted to b e $130,000 -$150,000. ~ost · O th~ homes will be one-store y with a few two-storey models seen 0 CC : a s l o n a 11 y . The average fa mi 1 y w i 11 be o f up per mi d d l e inc 0 me and wil~ have at least two car~. The families will have an average of 2 children of school age which will probab ly add another car to the total in the years ahead. Some homes will be purchased by older couples ~~ithout ·children at home. On the average, we feel that each lot will have 2.5 cars and that approximately one-half of the families will have two working adults. These projections lead to the assumption that there will be an average of 6 round trips or 12 vehicle trips generated from each lot each day. The bulk of t hese trips will occur in the m6rning (7:30 k.M. to 8:30 A.M.) and .in the evening (5:00 P.M. to 6:00 P.M.). Base on the above assumptions, we find that approximately 636 . · vehicle trips per day will be generated by the subdivision as a whole. Approximately one-half of the trips will be down Glenhaven to Univ-e rs i t y D c i v c a 11 d tow u rd Tex a .s f\ & M • Approx i ma t e 1 y 0 n e -.six th of the trips will be down Brazoswood Drive to the Frontage Road and south toward Post Oak Mall. One-sixth of the trips will be down Glenhaven Drive to Francis Drive and west toward the school. The other one-sixth will be .down Glenhaven Drive to Dominik Drive and down Dominik Drive to the shopping areas. This gives the following: ( 1) ( 2) ( 3 ) ( 4 ) Intersection of Glenhaven and University ... 318 vehicle tri p Intersection of Glenhaven and Francis ...... 53 ,, Intersection of Brazoswood and Frontage Rd. 53 II Intersection of Glenhaven and Dominik ...... 53 " " The Texas Departmc ~t of Highways and Public Transportation made traffic counts in 1989 un Merry Oaks Street both north and south of Dominik Drive. North of Dominik the count was 320 vehicle trips. ·south of Dominik the count was 910 vehicle trips. These figures would indicate that the assumptions made above wre valid when compa~ed with the number of homes in the area and the probable routes taken by t~e homeowners. The addition of the 318 vehicle trips per day to 1 the total at the intersection of Glenhaven and University !~rive will pro·bably merit the installation of a traffic signal at this intersection at some time ~in the future. The signal would not be necessary ~trictly because of the traffic volume but would be needed as a safety device for traffic tur.ninp, left onto TJniv c-~r.s i ty Dr.i.v e . If nnci when the Frontnr,e R o ad i s m n cl c o n c -w <l y , t h c ;ul cl i t i o , , o f ;i t r n f f i c s i. r, n a .l w o u 1 d d r. f i. n i t c 1 y be needed. ' I j I If and when the Frontage Road is made one-way (p robabl y south ) the volume of traffic G ;i Brazoswood Drive would be approximately the same for outbound traffic <ind woul<l <lccrcu.se .some for the inbound traffic. As mentioned above, the Glenhuven/University Drive inter- section would expect a lar ge r volume of traffic if this change is made. The probability t ·hat a large volume of traffic would be entering the subdivision along Glenhaven Drive from Dominik Drive is very small. The density •of the housing and the fact that it would be "goi n g out of the way" would probably prohibit such and o ccurence. The effect on Dominik Drive would be greatest at the far e n d at Texas Avenue where a proble already exists. But the majority of the traffic would probalily exit Dominik Drive before reaching Texas Avenue. The overall effe~t of the subd!v!~!~~ ~!g~~!sa~r~~~ ~~i!~~~gwould be to increase traffic volumes ~o t that major renovations or intersections but ~ot t0f thf~ ex e~rol devices would be required . installation :of maJor tra ic con · I I . , If and when the Frontage Road is made one-wa y (p robabl y south ) the volume of traffic 0n Brazoswood Dri v e would be a pp r ox imately the same for outbound traffic and would dccrcuse some for the inbound traffic. As mentioned above, the Glenhuven/University Drive inter- section would expect a larger volume of traffic if this change is made. The probability t •hat a lar ge volume of traffic would be entering the subdivision along Glenhaven Drive from Dominik Drive is very small. The density •of the housing and the fact that it would be "going out of the way" would probably pro hi bit such and o ccurence. The effect on Dominik Drive would be greatest at the far end at Texas Avenue where a proble already exists. But the majority of 1 the traffic would probaltly exit Dominik Drive before reaching Texas !, Avenue. -' .:_-1 . -·;_ ·; -. ; . :;· . ·{ -~-' l ' , '. ;i .1 ·• The overall effect of the subdivision of this tract of land would be to increase traffic volumes to a small degree at the existing intersections but not t0 the extent that major renovations or install~tion :of major traffic control devices would be required. POST OA K FOREST c -1 . 15.226AC. FOSTOAK ADDI T/ON . . STATE HIGHWAY NO. 6 ~ CAR~RS GROVE, 2nd Cl .,, ~'--~~~~~~~~~---.,.~~--'~ .., /,IERR"f OAXS DRIVE ~I . .i : MASTER PLAT ·:·,··1 . GLENHAVEN :ESTATES , . COLLEGESTAT~ON _BRAZOS COUNTY, TEXAS CHURCH rRAc r (SOLO) • Gl.ENHAVEH DRIVE CARTCRS GROVE, 2nd -. I Q:: I AD :l ITIO NJ\L DISCUSSION TRAFFIC MAS ~R PRELIMI NARY PLJ\T ~LENHAV EN ESTATES COLLEGE STATION , TEXAS As previously stated, the 14.9 35 acres tract will be divided into approximately 53 lots for Sing le Family Residential Development. The price of the home s is expe c te d to b e $130,000 -$150,000. Most of the homes will be one-storey wi t h a few two-storey models seen occ.asionally. The average family wi ll be ..;f upper middle income and will have at least two c ars . The families will have an average of 2 children of school age which will probably add another car to the total in the years ahearu. Some homes will be purchased by older couples ~~ithout . children at home. On the avera g e, we feel that each lot will have 2.5 cars and that ap~r oximately one-half of the families will have two working adults. These projections lead to th~ assumption that there will be an average of 6 round trip~ or 12 vehicle trips g enerated from each lot each day. The bulk of ~hese trips will occur in the morning (7:30 k.M. to 8:30 A.M.) and in the evenin g (5:00 P.M. to 6:00 P.M.). Base on the above assumptions, we find that approximately 636 . · vehicle trips per day will be ge nerated by the subdivision as a whole. Approximately one-half of the trips will be down Glenhaven to Univ- ersity Drlve and toward Texas A & M. ApproximatelyOne-sixth of the trips will be down Brazoswood Drive to the Frontage Road and south towar d Post Oak Mall. One-sixth of the trips wiJl be down Glenhaven Drive ·to Francis Drive and west toward the school. The other one-sixth will be down Glenhaven Drive to Dominik Driv e and down Dominik Drive to the shopping areas. This gives the following: ( 1) ( 2 ) ( 3 ) ( 4 ) Intersection of Gle~haven and University ... 318 vehicle tri p Intersection of Glenhaven and Francis ...... 53 IJ It Intersect :on of Brazoswood and Frontage Rd. 53 Intersection of Glenhaven and Dominik ...... 53 The Texas Departmc: ·!t of Highways and Public Transportation made traffic counts in 1989 0n Merry Oaks Street both north and south of Dominik Drive. North of Dominik the count was 320 vehicle trips. ·south of Dominik the count was 910 vehicle trips. These figures would indicate that the assumptions made above wre valid when compa~ed with the number of homes in the are a and the probable routes taken by t~e homeowners. The addition of the 318 vehicle trips per day to i the total at the intersection of Glenhaven and University J•rive will probably merit II the installation of a traffic signal at t!lis intersection at some time ;.in the future. The signal would not be necessary ~trictly because of the traffic volume but would be needed as a safety device for t r a f f i c t u r n i n g 1 e f t o n t o TJ n i. v c-~ r s i t y D r i . v e . I f i1 n d w h e n t h e F r o n t n p, e R o a d i s m n cl c o n c -w n y , t h c n d d i t i o ' , o f il t r<1 f f i c s j_ r, n n l w o u 1 d d c f j_ n i t c 1 y be needed. If and when the Frontage Road is made one-way (probably south) the volume of traffic 0;; Brazoswood Drive would be approximately the same for outbound traffic ;incl woul<l <lccrease some for the inboun<l traffic. As mentioned above, the Glenhaven/Universit y Drive inter- section would expect a lar ge r volume of traffic if ·this change is made. The probability t •hat a lar ge volum e of traffic would be entering the subdivision along Glenhav en Drive from Dominik Drive is very small. The density •of the housing and th e fact that it would be "going out of the way" would probably prohibit su ch <i nd occurence. The effect on Dominik Driv e would be er eatest at the far end at Texas Avenue where a proble already exists. But the majority of the traffic would proba~ly exit Dominik Drive before reaching Texas .-~ Avenue. '; I : ' The overall effect of the subdivision of this tract of land would be to increase traffic volumes to a small degree at the existing intersections but not t ~ the extent that major renovations or installation :of major traffic control devices would be required. P OS T OA K FOR EST c -1 . 16.226 AC. POS T OA K A DDI TJO _N STATE HIGHWAY NO. 6 I I I I Io I . g I I lt I I ~I ... , I ~ )"'~ I I \ I ."'::'_,,,. CA R~RS GROVE, 2nd •. L MASTER PLAT ·.·,:.I· GLEN HAVEN :ESTATES .. COLLEGE STA7)0!1 BRAZOS COUNTY, TEXAS CHURCH TRAC T (SOLO) , GLF:NHAVF:H l>R I V F: I !.., I ~I I~ I I ~; IM I I '. !. ' I (' I ~ I u ,·I I ~I I ~I I I ~I . . (~,14.985~l · I :> )~~. ~~HJ\ Vi ~¥,n.:t /~y · \-. I ...J EU~ EO CARTERS GROVE 1 2nd ~ ...... ' ' :::-I ....... ~ . I I Cl RILEY ENG!NEERiNG CO: ·aRYAN ·TEXAS . · !. • . B-/4-86 ......... .; ADDITIONAL DISCUSSION WATER SYSTEM MAS TE R PRELIMINARY PLAT GLENHAVEN ESTATES COLLEGE STA TION, TEXAS In 1 98 3, a Network Analysis was perfo rm ed on the proposed water distribution sys ~e m in the Glenhaven Estates Subdivision. Part of the water distribution system has been constructed in Phase I, Phase II, Phase III, Phase IV, Phase V a~d Phase VI. The only portion of the system that remains to be constructed is the tie-in between the 8" line on Glenhaven Drive and the existing 8" line on Dominik Drive. This portion will be constructed when Glenhaven Drive is ext{ended. The analysis was made assuming Normal Demand, One Fire Demand and Two Fire Demands. The Network and the Fire Flows and Demands are shown on the attached copies of the analysis. The pipe numbers and the node numbers are shown on the attached sketch which also shows what has been completed and what remains to be constructed. From the analysis, we can see that the pressures and flows are adequate to meet the standards. In addition, the City has completed the 16" line around the perimeter of the Subdivision on the northwest and nor the as t sides. The internal sys tern was tied to the 16" line at the points shown on the sketch. These tie-ins will enhance the int erna 1 system and pr 1,v ide for more and better service. I ' CITY OF COI .. LEGE STATION Post Office Box 9960 1101 Texas Avenue July 22, 1993 Urban Design Group 909 Southwest Pkwy, Ste E College Station , TX 77840 attn: Deborah Keating RE: Glenhaven X Drainage Dear Debbie, Coll ege Station, Texas 77842-0960 (409) 764-3500 My review of the information from FEMA and Walton agrees with your letter of 7/14/93. Considering the scale of the graphic and accuracy of the assumptions, I believe decimal readings less than .5 foot of elevation are not reasonably possible. I would therefore recommend e levations of 267.5 a nd 271.5. Storm water flow control in this basin is required for the difference between 100 year existing and 100 year propos ed. Similar control of the greater frequency storms is also required. The objective "i s no more risk with flood damage after development than existed before." Sincerely, Home of Texas A&M University ~m Urban Design Group July 14, 1993 Veronica Morgan Asst. to the City Engineer City of College Station P .O. Box 9960 College Station, Texas 77842 Re : Glenhaven X Development Dear Veronica, As per our discussion, July 13 , 1993 , I am forwarding the results of our review of existing drainage studies pertaining to the Glenhaven X area. We have reviewed three drainage studies known to us . The following table lists the flood elevations determined in each study . The flood elevation listed from the Garrett Study was taken from the preliminary plan submitted by Garrett Engineering. No supporting information was submitted in their report to reflect that elevation . Drainage Study Garrett Engineering 1986 Walton & Associates 1992FEMA Dominik 277 267 .1 W. Frontage Rd 263 .0 Hwy 30 Crossing 255 .7 255 .0 600' DS Hwy 30 255 .4 254 .0 No flood elevations were determined in the FEMA study in the vicinity of the proposed Glenhaven project. Because the Walton study and the FEMA study are comparable in flood elevations for the cross sections downstream of Glenhaven, we believe the flood elevations determined in the Walton Study are accurate and sufficient to use for the location of the floodplain for this project. Walton's elevations are slightly higher and more conservative . Using those flood elevations, no existing 100 year floodplain encroaches within the limits of the proposed Glenhaven development (elev 267 .1) Additionally, no 100 year flood elevations occur within the property (elev 271.2). We would verify the location with field surveys of the elevations . Should fa;ld surveys indicate ultimate 100 year floodplain encroaches within the limits of the property, we would include the 100 year ultimate floodplain on the plat along with required minimum floor elevations . Since no existing 100 year floodplain encroaches on the property, the finished floor elevation requirement of 0 .5' above the 100 year ultimate storm, will apply . We would include the detention area in a dedicated easement that is built at or above City standards . We understand the detention requirements for this development are more stringent, i .e. the 100 year ultimate development. We interpret the ordinance's System's Policies Section to require storage capacity necessary to detain the difference in existing development and ultimate development, of the entire upstream drainage basin, for the 100 year storm . This requirement is above the standard detention requirement (existing vs . proposed). c :\winword\glenhav\veronica RECE\VED JUL 1 4 1993 Po s t Office Box 10153 C o I I e g e S t a t i o n, T e x a s 7 7 8 4 2 • 4 0 9 • 6 9 6 · 9 6 5 3 page 2 letter to Veronica Because this floodplain determination is dramatically different from the previously submitted and approved preliminary plan, we are seeking the City's input. Therefore, after review of this information, a written response from the City Engineer's office either supporting this information or disputing it, is desired . Thank you for the time devoted to review of this project. Answers to these questions are necessary for us to proceed with the project. Sincerely, ~:::::g~~ Urban Design Group cc : David Pullen, City Engineer Myrad Real Estate c :\winword\glenhav\veronica