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HomeMy WebLinkAbout56 Development Permit 288 West Knoll Section 2DRAINAGE COMPUTATIONS for A Replat Of Block 3, West Knoll -Section 2 College Station, Brazos County, Texas Prepared for Thomas Properties P.O. Box 10106 College Station, Texas 77845 Prepared by.· Garrett Engineering 4444 Carter Creek Parkway -Suite 108 Bryan, Texas 77802 Telephone: (409) 846-2688 • DRAINAGE COMPUTATIONS for A Replat Of Block 3, West Knoll -Section 2 College Sta tion, Braw s Coun ty , T exas Prepared for Thomas Properties P.O. Box 10106 College Station, Texas 77845 Prepared bv: Garrett Engineering Bryan , Texas 77802 Te lephone: (409) 846 -2688 *April, 1995 * DRAINAGE COMPUTATIONS for A Rep lat of Block 3 West Knoll -Section 2 College Station, Brazos County, Texas * April, 1995 * SUMMARY The project is situated to the north of Soutl1west Parkway between Dexter and Medina drives in tl1e West Knoll Subdivision, College Station, Brazos County, Texas. Block 3 of West Knoll -Section 2 consists of 14 lots being established within the bounds of tlle 3.54 acre tract. The total drainage area tributary to tlle project is 3.54 acres. The pre-development run-off coefficient was estimated to be 0.40, while taking into account typical residential site improvements would result in a post-development run-off coefficient of 0.65. A detention facility will be constructed in U1e soutllem portion of tlle property in keeping witll tl1e existing contours and as designated on tlle plat. The detention pond is designed to facilitate up to and including tlle 100-year stonn event, and discharge at a rate less Ulan tlle current pre-development peak discharge rate. The detention pond will intercept, store and meter run-off from 1.88 acres of tlle project. The run- off generated on tlle remaining 1.66 acres will "free-flow" across tlle project site unmetered off tlle property. These report calculations are sununruized according to tlle following metllodology. Beginning on page 1, based on tlle total tributary drainage area of U1e project (being estimated at 3.54 acres), tlle pre- development run-off coefficient (being assumed at 0.40), and a minimum time of concentration of 10 minutes, U1e relative pre-development peak discharge rate ("Q") was detennined. The Rational Metllod was utilized to compute tlle estimated peak pre-development discharge rates. The equation tllat represents tlle Rational Metllod is as follows: Q = CIA. "Q" is tlle peak discharge rate in cubic feet per second, "C" is tlle run-off coefficient, assumed to be 0.40 in tlle pre-development condition, "I" is tlle storm intensity in inches per hour, ru1d "A" is tlle area of U1e drainage basin in acres. Computations on page 2 are based on tlle tributary area of 3.54 acres, tlle post-development run-off coefficient of 0.65 (being weighted according to tlle relative amounts of pervious and impervious surface area), a minimum time of concentration of 10 minutes, to yield tlle relative pre-development peak discharge rate ("Q") (assuming tlle same minimum time of concentration of 10 minutes). The Rational Metllod was again utilized to compute U1e estimated peak post-development discharge rates. The equation tllat represents tlle Rational Metl1od is as follows: Q = CIA, where; "Q" is tlle peak discharge rate in cubic feet per second. The "C" variable is U1e run-off coefficient. (In the post-development condition "C" is assumed to be 0.65.) "I" represents tlle rainfall intensity in inches per hour, and similarly "A" is tlle area of tlle basin in acres. Comparison of U1e peak pre-development discharge rate to tlle post-development discharge rate is included in tlle report to aid U1e designer in establishing a preliminary "target" of detention volume required. This preliminary estimate is determined as U1e volume difference generated between tlle pre- development and post-development hydrograpbs. (See pages 9-11 for pre-development and post- development hydrographs.) Please note tllat tlle post-development bydrograph shown on tllese same graphs assumes no detention and reflects tlle "worst-case" scenario tllat all run-off is allowed to free-flow. Pa ge s 3 and 4 provide inform a tion con ce rning th e post-developm ent run-off that is not routed through the detention facility ("free-flow") as well as th e pos t-de velopm ent run -off tlrnt is routed throu g h th e de tention facility and re tain ed on site . Page 5 and page 6 are tabulation s of th e pre-de velo pm ent and th e post-d evelopment hydrographs based on the computations perform ed on page 1 and page 2. The post-dev elopment hydrograph as sumes no d e tention to facilitate direct compari son in tb e pre-and post-de velopment conditions . Page 7 and pa ge 8 are tabulation s of th e post-d evelopment hydrograph for run-off directed through the d etention facility and tbe po s t-d e velopm ent hydrograph for "free-flow" from th e proj ect site. Computations on page 4 d e tennine th e actual peak post-d e ve lopment "inflow" ra te suppli ed to the proposed de tenti on facility . From t11i s "inflow" rate and th e tim e of concentration (10 minute s minimum), a hydrograph as tabulated on p age 8 is d erived. The hydrograph is triangular in shape a nd is based on th e standa rd SCS unit hydrograph wit11 tim e to peak se t equal to t11 e time of concentration and th e total time base se t at 3.00 tim es th e tim e of con centra tion. Pl ease note th a t a 30 minute total stonn eve nt duration was utilized e xclu siv ely throu ghout thi s re port du e to th e relati ve small siz e of t11e proj ect. Hav ing deriv ed th e prelim inary volum e requirements and "allowabl e peak" di scharge rate, tt ts now po ss ibl e to des ign th e final de tention facility and outl e t control structure . Pa ge 12 presents a data tabul ation and a de pth versus volum e graph of th e de tention facility. The maximum de pth of th e pond was se t at 2.5 fee t. (With ili e top of berm elev ation at 297.50 ft. less fl o w lin e "out" of outl et control structure at 295 .00 ft.: 297 .5' -2 95.00' = 2 .5' ). Page 13 suppli es a ta bul a ti o n and a ratin g curv e fo r ili e propo sed outl e t control structure . A circular pipe cul vert was ch osen du e to tll e di scharge ratio characte ri sti cs associated with tlle anticipated headw ater de ptll. An ultim ate stora ge de pt11 of 2 .5 is avail abl e du e to th e phy sical ge om etry of tll e pond . Howe ver, even a t 100-year storm condition s, de pt11 s of less tllan 2 fee t are anticip a te d . The pipe diam eter of 8 in ches or 0 .67 fee t was selec ted . Thi s valu e was d e termin ed from th e following e1u a tion for headw ater depth (in fe e t), H = [ [ ( 2 .5204 ( 1 + K)) I D4] + [ ( 466.1 8 n2 L ( 1 + K)) ID 6/3]] x (DI 10 )2. "K" is the entrance lo ss coe ffici ent ( K = 0 .50 for tlli s ca se). "D" is the diam e ter of tll e pipe in feet. "L" is th e l ength of cul ve rt in fee t. "Q" is tll e des ign di scharge rate in cublic fe et per second . "n" is m am1ing's rou g hn ess coefficient (n = 0.012 for con cre te pip e), a nd "H'' is the headw a te r de pti1 in feet which ran ge s fr om 0.00 ft. to a maximum of 2 .00 ft. Page 14 presents a tabulati on of U1 e rela tion ship be tw een di sc harge from t11 e de tenti on facility and th e dim en sionl ess qu antity 2 S/t-O . Al so presente d is a Storage Indication Curve for tll e de tention facility based on tll e afo re mention ed phy sical c harac te ri stic s of tll e de tention pond , stora ge volum e , inflow hydro g raph , and ratin g curve fo r t11 e outle t structure. The storage indicati on curve as shown on pa ge 12 is a graphical soluti o n to t11 e equ a ti o n presente d in th e "Draina ge Policy And Des ign Standard s " as follows : 2s 1 (I 1 + 12) + (--------------- dt 2 s2 -01) = (-----------------+ 02) dt Page 15 tllrou g h page 26 prese nt simul a tion s of th e 2, 5 , 10, 25, 50, and 100 year storm events . The first page of each storm simul a tion re presents t11 e tabulated data fo r th e stonn eve nt. The maximum depth achi e ved in th e de tention p o nd durin g eac h simul ation is shown below a s is tll e tim e at durin g which thi s m ax imum deptll occurs fr om t11 e on se t of til e storm event. Th e calculated peak di sc harge rate corres pondin g to thi s deptil o ver sam e period is al so shown below . Additionally, t11 e maximum water sur face ele vatio n ac hi e ved durin g eac h eve nt and til e m ax imum p eak di sc harge durin g each e ve nt are li s ted below. The sec ond page of each storm simul a tion re presents til e pre-de velopm e nt hydro graph , til e pos t-d e velopm ent hydro graph (witil no d etention), th e po st-d evelopm ent hydro g raph a s routed tilrou g h til e dete ntion pond, and post-d eve lopm ent "free-flow" hydrograph fo r each storm e vent Page 27 through page 32 provide total inflow/outflow hydrographs for U1e 2, 5, 10, 25, 50 and 100-year pre-development and post-development stonn events. It can be detennined from Ulese same hydrographs iliat ilie post-development peak discharge rates have been minutely decreased from Ulose peak pre- development discharge rates due to U1e incorporation of Uw detention facility in ilie post-development condition. Total post-development peak discharge rates from ilie detention pond outlet control structure and project site are kept less Ulan ilie pre-development peak discharge rates due to ilie incorporation of ilie proposed detention facilities. Subsequent peak post-development discharge velocities projected to be wiiliin manageable limits. Determine T otal Pre-Development Peak Storm Water Discharge Rates Tributary Area ("A"): 3.54 Acres Pervious Area : 3.54 Acres Impervious Area: 0.00 Acres Run-Off Co efficient ("C wt"): 0.40 Time Of Con centratio n ("T/c"): W ood la nd s: Low Elevation : High Elevation : Distance (Feet): Slope (%Grade): Velocity ("Vw "): Time : Pa sture s: Low Ele vat ion : High Elevat ion : Distance (Feet): Slope (% Grade): Velocity ("Vp "): Time : Pave ment s: Low Elevation : High Elevation : Distance (Feet): Slope (%Grade): Velocity ("Vpave "): Time : Total Tra vel Time : Hourly Inte nsity Rates ("I"): 2-Year: 6.33 5-Year: 7.6 9 10-Year: 8.63 25-Yea r: 9.86 50-Yea r: 11.15 100-Year: 11.64 Peak Disc harge Rate ("O"): 2-Yea r: 8.96 5-Year : 10 .89 10-Year: 12 .23 25-Year: 13 .96 50-Year : 15 .79 100-Year: 16.48 C= 0.40 C= 0.98 0.00 0.00 0.00 0.00 0.00 Feet I Second 0.00 Minut es 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 0.00 Minutes 1 o.oo Minutes In c hes I Hour Inches I Hour Inches I Hour Inches I Hour Inches I Hour Inches I Hour Cubic Feet I Sec ond Cubic Feet I Second Cubic Feet I Second Cubic Feet I Seco nd Cub ic Feet I Second Cubic Feet I Second Determine Post-development Peak Storm Water Dischar e No Detention Tributary Area ("A"): 3.54 Acres Pervious Ar ea : 1.99 Acres Imp e rvious Area : 1.55 Acres Run-Off Coefficient ("Cwt "): 0.65 Time Of Concentration ("T/c"): 1 O Minu t es (Min) Hourly Inte nsity Rates ("I"): 2-Year: 6.33 5-Yea r: 7.6 9 10-Year: 8.63 25 -Year: 9.86 50-Year: 11 .15 100-Year: 11 .64 C= 0.40 C = 0.98 Inches I Hour Inches I Hour Inches I Hour Inches I Hour Inches I Hour Inches I Hour Peak Disc harge Rate ("Q"): 2-Year: 14 .65 Cubic Feet I Sec on d 5-Year: 17 .81 Cubic Feet I Secon d 10-Year: 19 .99 Cubic Feet I Sec o nd 25-Year: 22.83 Cubic Fe et I Sec ond 50 -Year : 25.81 Cubic Feet I Sec ond 100-Year: 26.94 Cubic Feet I Sec o nd Comparison Of Predevelopment And Post-development Peak Discharge Rates Predeve lopment Post-Dev elopme nt Increase 2-Year: 8.96 Ft3 /sec 14.65 Ft3 /sec 5.69 Ft3 /sec 5-Year: 10 .89 Ft3/sec 17.8 1 Ft3 /sec 6.92 Ft3/se c 10-Year: 12.23 Ft3/sec 19 .99 Ft3 /sec 7.76 Ft3/sec 25-Year: 13 .96 Ft3 /sec 22.83 Ft3/sec 8.87 Ft3 /sec 50-Year: 15.79 Ft 3/sec 25 .81 Ft3 /sec 10 .02 Ft3/sec 100-Year : 16.48 Ft3/sec 26 .94 Ft3/sec 10 .46 Ft3/sec Preliminary Determination Of Dete ntion Po nd Volume 2-Year : 5.69 Ft3/sec x (30 Min. x 60 Sec . I 2 ) = 5,119 Cubic 5-Year: 6 .92 Ft3/sec x (30 Min . x 60 Sec. I 2 ) = 6 ,224 Cubic 10-Year: 7.76 Ft3/sec x (30 Min. x 60 Sec . I 2 ) = 6,98 6 Cubic 25-Year: 8.87 Ft3/sec x (30 Min. x 60 Sec . I 2 ) = 7,979 Cub ic 50-Year: 10.02 Ft3/sec x (30 Min. x 60 Sec. I 2 ) = 9,020 Cubic 100-Year: 10.46 Ft3 /sec x (30 Min . x 60 Sec . I 2 ) = 9,4 17 Cubic 2 Feet Feet Feet Feet Feet Feet Determine Post-Development "Free-Flow" Peak Storm Water Discharge Tributary Area ("A"): 1.66 Acres Pervious Area: 0 .95 Acres Impervious Area : 0 .71 Acres Run-Off Coefficient ("Cwt"): 0 .65 Time Of Concentration ("T/c"): 10 Minutes (Min) Hourly Intensity Rates ("I"): 2-Year: 6 .33 5-Year: 7 .6 9 10-Year: 8.63 25-Year: 9.86 50-Year: 11 .15 100-Year: 11 .64 Peak Discharge Rate ("Q"): 2-Year: 6.81 5-Year: 8.28 10-Year: 9.29 25-Year: 10.61 50-Year: 11.99 100-Year: 12.52 3 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 Flow Into Detention Pond Tributary Area ("A"): 1.88 Acres Pervious Area : 1.06 Acres Impervious Area : 0.82 Acres Run-Off Coefficient ("Cwt"): 0.65 Time Of Concentration ("T/c"): 10 Minutes (Min) Hourly Intensity Rates ("I"): 2-Year: 6.33 5-Year: 7 .69 10-Year: 8.63 25-Year: 9.86 50-Year: 11.15 100-Year: 11 .64 Peak Discharge Rate ("O"): 2-Year: 7 .77 5-Year: 9.44 10-Year: 10.60 25-Year: 12 .11 50-Year: 13 .68 100-Year: 14.29 4 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 Pre-Deve lopmen t Infl ow Hydrograph O rdi na tes (Cubic Feet per Second) Time 2-Year 5-Year 10-Year 25-Yea r 50-Yea r 100-Y ear {Minutes} Storm Storm Storm Storm Storm Storm 0 0.00 0.00 0.00 0.0 0 0.00 0.00 1 0 .90 1.09 1.22 1.40 1.58 1.65 2 1.79 2 .18 2.45 2 .79 3 .16 3 .30 3 2 .69 3 .27 3 .67 4 .19 4.74 4.94 4 3 .58 4 .36 4 .89 5.59 6 .3 1 6 .59 5 4.48 5.45 6 .11 6.98 7 .89 8 .24 6 5.37 6 .54 7 .34 8.38 9.47 9 .89 7 6 .27 7 .63 8 .56 9 .77 11 .05 11 .54 8 7 .17 8 .71 9 .7 8 11 .17 12.63 13.18 9 8 .06 9 .80 11 .00 12 .57 14.2 1 14.83 Peak=> 10 8 .96 10.89 12.23 13.96 15.79 16.48 11 8.51 10.35 11 .62 13.27 15.00 15.66 12 8.06 9 .80 11 .00 12 .57 14.21 14.83 13 7.61 9 .26 10.39 11 .87 13.42 14.01 14 7.17 8 .71 9.78 11.17 12.63 13.18 15 6.72 8 .17 9.17 10.47 11 .84 12 .36 16 6.27 7.63 8 .56 9 .77 11 .05 11 .54 17 5 .82 7 .08 7 .95 9.08 10.26 10.71 18 5.37 6.54 7 .34 8 .38 9.47 9 .89 19 4 .93 5.99 6.72 7 .68 8 .68 9 .06 20 4.48 5.45 6 .11 6.98 7.89 8 .24 21 4.03 4 .90 5 .50 6 .28 7.1 0 7.42 22 3.58 4 .36 4 .89 5 .59 6 .3 1 6 .59 23 3 .14 3 .81 4 .28 4.89 5 .52 5 .77 24 2 .69 3 .27 3 .67 4.19 4.74 4.94 25 2 .24 2 .72 3 .06 3.49 3 .95 4.12 26 1.79 2 .18 2.45 2 .79 3 .16 3.30 27 1.34 1.63 1.83 2 .09 2 .37 2.47 28 0.90 1.09 1.22 1.40 1.58 1.65 29 0.45 0.54 0.61 0 .70 0 .79 0 .82 30 0.00 0 .00 0 .00 0.00 0 .00 0 .00 5 Post-Development Inflow Hydrograph Ordinates (Cubic Feet per Second) 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 1.46 1.78 2 .00 2.28 2.58 2.69 2 2 .93 3 .56 4 .00 4.57 5.16 5.39 3 4 .39 5.34 6.00 6.85 7.74 8.08 4 5 .86 7 .12 8.00 9.13 10.32 10.78 5 7 .32 8.90 9 .99 11 .41 12 .90 13.47 6 8.79 10 .69 11 .99 13 .70 15.48 16.17 7 10 .25 12.47 13.99 15 .98 18 .06 18.86 8 11 .72 14 .25 15 .99 18 .26 20.65 21 .56 9 13 .18 16 .03 17.99 20 .55 23.23 24 .25 Peak=> 10 14 .65 17 .81 19.99 22 .83 25.81 26.94 11 13.91 16 .92 18.99 21 .69 24 .52 25.60 12 13.18 16 .03 17.99 20 .55 23 .23 24 .25 13 12.45 15 .14 16 .99 19.40 21 .94 22 .90 14 11 .72 14 .25 15 .99 18 .26 20 .65 21 .56 15 10.98 13 .36 14.99 17 .12 19 .36 20.21 16 10 .25 12.47 13 .99 15 .98 18.06 18 .86 17 9.52 11 .58 12 .99 14 .84 16.77 17.51 18 8 .79 10.69 11 .99 13 .70 15.48 16 .17 19 8.06 9.79 10 .99 12 .56 14.19 14 .82 20 7.32 8.90 9 .99 11.41 12 .90 13.47 21 6.59 8.01 9 .00 10.27 11.61 12 .13 22 5 .86 7 .12 8.00 9 .13 10 .32 10.78 23 5.13 6.23 7.00 7 .99 9 .03 9.43 24 4.39 5 .34 6.00 6.85 7.74 8.08 25 3.66 4.45 5 .00 5 .71 6.45 6.74 26 2.93 3.56 4 .00 4 .57 5.16 5.39 27 2.20 2.67 3 .00 3.42 3 .87 4 .04 28 1.46 1.78 2.00 2 .28 2.58 2.69 29 0 .73 0 .89 1.00 1.14 1.29 1.35 30 0 .00 0 .00 0 .00 0 .00 0 .00 0.00 6 Post-Development "Free-Flow" Inflow Hydrograph Ordinates (Cubic Feet per Second) 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 0.68 0.83 0.93 1.06 1.20 1.25 2 1.36 1.66 1.86 2.12 2.40 2.50 3 2.04 2.48 2.79 3.18 3.60 3.76 4 2.72 3.31 3.72 4.24 4.80 5.01 5 3.40 4.14 4.64 5.30 6.00 6.26 6 4.08 4.97 5.57 6.37 7.20 7.51 7 4.76 5.79 6.50 7.43 8.39 8.76 8 5.44 6.62 7.43 8.49 9.59 10.02 9 6.13 7.45 8.36 9.55 10.79 11.27 I . Peak=> 10 6.81 8.28 9.29 10.61 11.99 12.52 11 6.47 7.86 8.82 10.08 11.39 11.90 12 6.13 7.45 8.36 9.55 10.79 11.27 13 5.79 7.03 7.90 9.02 10.19 10.64 14 5.44 6.62 7.43 8.49 9.59 10.02 15 5.10 6.21 6.97 7.96 8.99 9.39 16 4.76 5.79 6.50 7.43 8.39 8.76 17 4.42 5.38 6.04 6.90 7.80 8.14 18 4.08 4.97 5.57 6.37 7.20 7.51 19 3.74 4.55 5.11 5.83 6.60 6.89 20 3.40 4.14 4.64 5.30 6.00 6.26 21 3.06 3.72 4.18 4.77 5.40 5.63 22 2.72 3.31 3.72 4.24 4.80 5.01 23 2.38 2.90 3.25 3.71 4.20 4.38 24 2.04 2.48 2.79 3.18 3.60 3.76 25 1.70 2.07 2.32 2.65 3.00 3.13 26 1.36 1.66 1.86 2.12 2.40 2.50 27 1.02 1.24 1.39 1.59 1.80 1.88 28 0.68 0.83 0.93 1.06 1.20 1.25 29 0.34 0.41 0.46 0.53 0.60 0.63 30 0.00 0.00 0.00 0.00 0.00 0.00 7 Post-Development Flow Routed Through Detention Pond Inflow Hydrograph Ordinates (Cubic Feet per Second) 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 0.78 0.94 1.06 1.21 1.37 1.43 2 1.55 1.89 2.12 2.42 2.74 2.86 3 2.33 2.83 3.18 3.63 4.11 4.29 4 3.11 3.78 4.24 4.84 5.47 5.72 5 3.88 4.72 5.30 6.05 6.84 7.14 6 4.66 5.67 6.36 7.26 8.21 8.57 7 5.44 6.61 7.42 8.47 9.58 10.00 8 6.21 7.55 8.48 9.68 10.95 11.43 9 6.99 8.50 9.54 10.90 12.32 12.86 Peak=> r 10 7.77 9.44 10.60 12.11 1i.68 14.29 11 7.38 8.97 10.07 11.50 13.00 13.57 12 6.99 8.50 9.54 10.90 12.32 12.86 13 6.60 8.03 9.01 10.29 11.63 12.15 14 6.21 7.55 8.48 9.68 10.95 11.43 15 5.82 7.08 7.95 9.08 10.26 10.72 16 5.44 6.61 7.42 8.47 9.58 10.00 17 5.05 6.14 6.89 7.87 8.90 9.29 18 4.66 5.67 6.36 7.26 8.21 8.57 19 4.27 5.19 5.83 6.66 7.53 7.86 20 3.88 4.72 5.30 6.05 6.84 7.14 21 3.49 4.25 4.77 5.45 6.16 6.43 22 3.11 3.78 4.24 4.84 5.47 5.72 23 2.72 3.31 3.71 4.24 4.79 5.00 24 2.33 2.83 3.18 3.63 4.11 4.29 25 1.94 2.36 2.65 3.03 3.42 3.57 26 1.55 1.89 2.12 2.42 2.74 2.86 27 1.16 1.42 1.59 1.82 2.05 2.14 28 0.78 0.94 1.06 1.21 1.37 1.43 29 0.39 0.47 0.53 0.61 0.68 0.71 30 0.00 0.00 0.00 0.00 0.00 0.00 8 16.00 14 .00 .... Q) 0.. -12 .00 Q) Q) u.. 0,,...,, 10 .00 ·-'O ..0 c ::I 0 8 .00 u 0 ...... Q) Q) V> 6 .00 Ol .... 0 .s:: 4 .00 0 II) 0 2 .00 0 .00 0 Total Pre-Development Vs. Total Post-Development (No Detention) Peak Discharge Rates 2-Year Storm Event 5 10 15 20 25 Time (Minutes) ----Pre-Development Hydrograph ----Tota l Post-Development Hydrograph 18.00 .... 16 .00 Q) 0.. -14.00 Q) Q) u.. 12 .00 0,,...,, ·-'O 10 .00 ..0 c ::I 0 u 0 8 .00 ...... Q) Q) V> Ol 6 .00 .... 0 .s:: 4 .00 0 II) 0 2 .00 0 .00 0 Tota l Pre-Development Vs. Total Post-Development (No Detention) Peak Discharge Rates 5 -Year Storm Event 5 10 15 20 25 Time (Minutes) Pre-Development Hydrograph ---Post -Development Outflow Hydrograph Without Detention 9 30 30 ... Cl> a.. -Cl> Cl> ..... 0,.... ·-"O .0 c: :> 0 () 0 -Cl> Cl> Cl) 0) ... 0 .c. 0 II) 0 ... Cl> a.. -Cl> Cl> ..... 0,.... ·-"O .0 c: :> 0 () 0 -Cl> Cl> Cl) 0) ... 0 .c. 0 II) 0 20 .00 18 .00 16 .00 14.00 12 .00 10 .00 8 .00 6.00 4 .00 2 .00 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-Development Hydrograph ----Post-Development Outflow Hydrograph Without Detentio n 25.00 20 .00 15 .00 10 .00 5 .00 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 ---Pr e-Develo pment Hydrograph ----Post-De velopment Outflow Hydrograph Wit h o ut Detention 10 30 .00 ... Q) 25 .00 Q. -Q) Q) 20.00 L&.. 0 ....... ·-"O .0 c ::::J 0 15 .00 () 0 ....., Q) Q) <I) O> 10 .00 ... 0 .£: 0 5 .00 <I) i5 0 .00 0 Total Pre-Development Vs. Total Post -Development (No Detention) Peak Discharge Rates 50-Year Storm Ev ent 5 10 15 20 25 Time (Minutes) 30 ---Pre-Deve lopment Hydrograph ----Post-De velopment Outflow Hydrograph Without Detention Total Pre-Development Vs. Total Post-Development (No Detention) Peak Discharge Rates 100 -Year Storm Event O .OO <f'-~~~+-~~~+-~~~+-~~~+-~~~+-~~~ 0 5 10 15 20 25 Time (M inutes) Pr e-Development Hydrograph ----Post-Development Outflow Hydrograph Without Detention 11 30 Detention Pond Depth Vs. Volume Elevation Depth Vol um e (Feet ) (Ft3 ) 295 .00 0.00 0 295 .50 0.50 656 296 .00 1.00 3,46 2 296 .35 1.35 6,8 87 297 .00 2.00 14,34 9 297 .50 2 .50 20 ,53 4 Detention Pond Depth Vs. Volume 2 .50 2 .00 1.50 ........ -Cl> Cl> u.. -.r::. -Q. Cl> a 1.00 0.50 0.00 0 5 ,000 10 ,000 15 ,000 20,000 25 ,000 Detention Pond Volume (Cubic Feet) 12 Rating Curve For Outlet Control Structure Pipe Dia . (Inches): 8 0.67 De th Vs. Volume Pipe Length 38 .00 Feet Elevation Depth Discharge (Feet) Ft3/Sec 295 .00 0 .00 0 .00 295 .50 0 .50 1.05 296 .00 1.00 1.49 296 .35 1.35 1.73 297 .00 2.00 2.10 297 .50 2 .50 2 .35 Rating Curve For Outlet Control Structure Depth Vs. Volume 1.50 --Cl> Cl> LL. -.t::. -Q. Cl> a 1.00 0.00 0.50 1.00 1.50 2.00 2.50 Discharge (Cubic Feet Per Second) 13 I Storage Indication Curve Depth Storage Discharge 2s/t 2s/t+O (Feet) (Ft3) (Ft 3/Sec) (Ft3 /Sec) (Ft3/Sec) 0 .00 0 0 .00 0.00 0.00 0 .50 656 1.05 21 .87 22 .92 1.00 3,462 1.49 115.40 116.89 1.35 6,887 1.73 229 .57 231.30 2.00 14 ,349 2.10 478 .30 480.40 2.50 20 ,534 2 .35 684.47 686.82 Storage Indication Curve 2.50 2.00 ,..... "O c 0 0 Q) Cl) ... 1.50 Q) a.. -Q) Q) LL. 0 :0 ;:, u '"" Q) l.00 O> ... 0 .&: 0 Cl) a 0 .50 0.00 0.00 l 00 .00 200 .00 300 .00 400 .00 500 .00 600 .00 700.00 2s/t+O (Cubic Feet Per Second) 14 Inflow I Outflow Simulation 2-Year Storm Event Time Inflow 11+ 12 2s/t-O 2s/t+O Outflow Depth Elevation (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) 0 0 .00 0.00 0.00 0 .00 0.00 0 .00 295 .00 1 0 .78 0 .78 0 .71 0 .78 0.04 0.00 295.00 2 1.55 2.33 2 .76 3 .04 0 .14 0 .01 295 .01 3 2 .33 3 .88 6 .03 6.64 0 .30 0 .04 295.04 4 3 .11 5.44 10.41 11.47 0 .53 0 .13 295 .13 5 3.88 6 .99 15.81 17.40 0 .80 0 .29 295 .29 6 4 .66 8 .54 22 .23 24 .35 1.06 0 .51 295 .51 7 5.44 10 .10 30 .14 32 .33 1.10 0 .54 295 .54 8 6.21 11.65 39 .51 41 .79 1.14 0 .59 295 .59 9 6.99 13.20 50 .33 52 .71 1.19 0 .64 295 .64 10 7 .77 14.76 62 .59 65 .08 1.25 0 .70 295.70 11 7 .38 15.14 75 .12 77 .73 1.31 0 .77 295 .77 12 6 .99 14.37 86 .77 89.49 1.36 0.84 295.84 13 6.60 13.59 97.54 100.36 1.41 0 .90 295.90 14 6 .21 12 .81 107.43 110.35 1.46 0 .96 295 .96 15 5 .82 12 .04 116.49 119.47 1.49 1.01 296 .01 16 5 .44 11 .26 124.72 127.75 1.51 1.03 296 .03 17 5.05 10.48 132 .16 135.21 1.53 1.05 296 .05 18 4 .66 9 .71 138.78 141 .86 1.54 1.07 296 .07 19 4 .27 8.93 144 .61 147.71 1.55 1.09 296 .09 20 3 .88 8 .15 149 .64 152.76 1.56 1.10 296 .10 21 3.49 7 .38 153.87 157.01 1.57 1.12 296 .12 22 3 .11 6 .60 157.31 160.47 1.58 1.13 296 .13 23 2 .72 5 .82 159.97 163.14 1.59 1.14 296 .14 24 2 .33 5.05 161.83 165.01 1.59 1.14 29..6 .14 25 1.94 4.27 162 .92 166.11 1.59 1.14 296.14 26 1.55 3.49 163.23 166.42 1.59 1.15 296.15 27 1.16 2 .72 162 .77 165.95 1.59 1.14 296 .14 28 0 .78 1.94 161 .53 164.71 1.59 1.14 296.14 29 0 .39 1.16 159 .53 162 .70 1.58 1.13 296 .13 30 0 .00 0.39 156.76 159 .92 1.58 1.13 296 .13 15 Inflow/Outflow Simulation 2-Year Storm Event 16 .00 14 .00 I ' I ' I ' I ' I ' 12.00 I ' ' ' I '"' "O I ' c 0 I ' 0 10.00 Q) Cl) I ' ... ' Q) I a.. ' -' Q) I Q) ' LL. 8 .00 0 ' :.0 ::J u I ' -' ' ~ I / 6 .00 0 • I ' ' E I ' ::J / ....... ' 0 I ' I' ' I ....... ' ' I ....... 4.00 I I ....... ' ' ....... ' ' 2 .00 0.00 0 5 10 15 20 25 30 Time (Minutes) Pre -----Post -Post -- - - - -• Post - Developme De velopme Developme De velopme nt nt Outflow nt Outflow nt "Free- Hydrograph Hydrograph With Flow· Wi th out Detention Detenti o n 16 Inflow I Ou tfl ow Simulat ion 5-Y ear Storm Event Time Inflow 11+ 12 2s/t-0 2s/t+O Outflow Depth Elevation (Minutes) (Ft3/Sec) (Ft3 /Sec) (Feet) 0 0 .00 0.00 0.00 0 .00 0.00 0 .00 295 .00 1 0 .94 0.94 0.86 0.94 0.04 0 .0 0 295 .00 2 1.89 2.83 3 .35 3.69 0.17 0.01 2 95 .0 1 3 2 .83 4.72 7.33 8.07 0 .37 0.06 295 .06 4 3 .78 6.61 12 .66 13.94 0 .64 0.19 295.19 5 4 .72 8.50 19.22 21.16 0.97 0.43 295.43 6 5 .67 10.39 27.44 29.61 1.08 0 .53 295.53 7 6.61 12 .28 37.46 39 .72 1.13 0.58 295 .58 8 7 .55 14.17 49.25 51 .62 1.19 0 .63 295 .63 9 8.50 16 .05 62 .81 65 .31 1.25 0 .70 295 .70 10 9 .44 17.94 78 .11 80 .75 1.32 0 .79 295 .79 11 8 .97 18.42 93 .74 96 .53 1.39 0.88 295 .88 12 8 .50 17.47 108 .29 111 .21 1.46 0.96 295 .96 13 8 .03 16.53 121 .80 124.81 1.50 1.02 296 .02 14 7.55 15.58 134.32 137.39 1.53 1.06 296 .06 15 7 .08 14.64 145.85 148.96 1.56 1.09 296 .0 9 16 6 .61 13.69 156.39 159.54 1.58 1.12 296 .12 17 6 .14 12 .75 165.94 169 .14 1.60 1.15 296 .15 18 5 .67 11 .80 174.51 177.74 1.62 1.18 296.18 19 5 .19 10.86 182 .11 185.37 1.63 1.20 296.20 20 4.72 9.92 188.73 192.02 1.65 1.22 296.22 21 4 .25 8.97 194.39 197.70 1.66 1.24 296 .24 22 3 .78 8.03 199 .08 202.41 1.67 1.26 296 .26 23 3 .31 7.08 202 .81 206 .16 1.68 1.2 7 296 .27 24 2 .83 6.14 205.58 208 .95 1.68 1.2 8 296.28 25 2 .36 5.19 207.41 210.78 1.69 1.28 296 .28 26 1 .89 4 .25 208 .28 211 .66 1.69 1.29 296 .29 27 1.42 3 .31 208 .2 1 211 .59 1.69 1.29 296 .29 28 0 .94 2.36 207.20 210.57 1.69 1.28 296 .28 29 0 .47 1.42 205 .26 208 .62 1.68 1.28 296 .28 30 0 .00 0.47 202 .38 205 .73 1.68 1.27 296 .27 17 Inflow/Outflow Simulation 5-Year Storm Event 18.00 'I\. I ' ' I ' 16.00 . I ' I ... I ' . ' 14 .00 I . ' I ' I ' ........ "O 12.00 c 0 0 I ' I " I ' Q) U) ... Q) a.. 10.00 -Q) Q) u.. 0 :0 8.00 ::> u -~ 0 E 6.00 ::> 0 4.00 2.00 I " / ~ ' I ' I ~ ... I ' , , I ' I ' ' ! ......... . ' . ~ " I ' . ' ' • ' ' ' ' I ' ' ' ' I ' v . ' . ' "' I . ' ' . .··I . ' ~ ' ' . ' " ' . ' . . ' ' " ·/: """~ ' . ' . I "\ I ' '' . I .. ' '" . . · .. , . '' ' '_,/ .....- "' -~ 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 Detention Detention 18 Inflow I Outflow Simulation 10-Year Storm Event Time Inflow 11+ 12 2s/t-0 2slt+O Outflow Depth Elevation (Minutes) (Ft3/Sec) (Ft3 /Sec) (Feet) 0 0 .00 0 .00 0.00 0.00 0 .00 0 .00 295 .00 1 1.06 1.06 0 .96 1.06 0.05 0 .00 295 .00 2 2.12 3 .18 3 .76 4 .14 0.19 0 .02 295 .02 3 3 .18 5 .30 8.23 9 .06 0.42 0 .08 295.08 4 4.24 7.42 14.21 15.65 0.72 0 .23 295 .23 5 5 .30 9 .54 21 .64 23 .75 1.06 0 .50 295 .50 6 6.36 11.66 31 .10 33.30 1.10 0 .55 295.55 7 7.42 13.78 42.57 44 .88 1.15 0 .60 295.60 8 8.48 15.90 56 .04 58.47 1.22 0 .67 295.67 9 9.54 18.02 71.48 74 .06 1.29 0 .75 295 .75 10 10.60 20.14 88.88 91 .62 1.37 0 .85 295 .85 11 10.07 20.67 106.64 109.54 1.45 0.95 295 .95 12 9.54 19 .61 123.23 126 .25 1.51 1.03 296 .03 13 9.01 18.55 138.70 141 .78 1.54 1.07 296 .07 14 8.48 17.49 153.05 156.19 1.57 1.11 296 .11 15 7 .95 16.43 166.28 169.48 1.60 1.15 296.15 16 7 .42 15.37 178.40 181 .65 1.62 1.19 296 .19 17 6 .89 14.31 189.41 192 .71 1.65 1.23 296 .23 18 6 .36 13.25 199 .33 202 .66 1.67 1.26 296 .26 19 5 .83 12.19 208 .14 211.52 1.69 1.29 296.29 20 5 .30 11.13 215 .87 219.27 1.70 1.31 296 .31 21 4.77 10.07 222 .50 225.93 1.72 1.33 296.33 22 4 .24 9.01 228 .05 231.51 1.73 1.35 296 .35 23 3.71 7.95 232.53 236 .00 1.74 1.36 296 .36 24 3 .18 6 .89 235 .94 239.42 1.74 1.37 296.37 25 2 .65 5 .83 238 .28 241 .77 1.74 1.37 296 .37 26 2 .12 4.77 239 .55 243 .05 1.75 1.38 296 .38 27 1.59 3.71 239 .77 243 .26 1.75 1.38 296.38 28 1.06 2 .65 238 .93 242.42 1.75 1.38 296 .38 29 0 .53 1.59 237.03 240.52 1.74 1.37 296 .37 30 0 .00 0.53 234 .09 237.56 1.74 1.36 296 .36 19 Inflow/Outflow Simulation 10-Year Storm Event 20.00 I ' I .. I ' 18.00 . I ' ' I ' 16.00 I ' I ' I ' I ~ -14 .00 "O c: 0 I ' I - ' I .. 0 I ' CD (/) 12 .00 -CD Q.. -CD CD 10 .00 u.. 0 :.0 :::J u -8 .00 ~ 0 == :::J 0 6.00 4.00 I I\. .. I I ~ ' I ' I ' ' I "" I' I . ' I . ' ' "" ' . ' I . ' . ' . ' /./ ' ' "· .. ~ I ' ' ' ' I .. ' I . . // . '. ·~ . ' . ' . ', ' . ' ' ' ' // ' ·----"" ' .. ' I ' ~\ . '' I l' . .. , ', .. ~ ' ',' 2 .00 0.00 0 5 10 15 20 25 30 Time (Minutes) Pre-----Post-Post --. -...... Pos t - Develo pm e Developme Developme De ve lopme nt nt Outflow nt Outfl ow nt "Free- Hydrograph Hyd ro grap h With Flow" With out De tention Det ention 20 Inflow I Outflow Simulation 25-Year Storm Event Time Inflow 11+ 12 2s/t-0 2s/t+O Outflow Depth Elevation (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) 0 0 .00 0 .00 0 .00 0 .00 0 .00 0 .00 295.00 1 1.21 1.21 1.10 1.21 0 .06 0.00 295 .00 2 2.42 3.63 4 .30 4 .73 0 .22 0.02 295 .02 3 3 .63 6 .05 9.40 10.35 0.48 0.10 295 .10 4 4 .84 8.47 16.23 17.87 0 .82 0.30 295.30 5 6.05 10.90 24.98 27 .13 1.07 0.52 295 .52 6 7.26 13.32 36.05 38 .30 1.12 0.57 295 .57 7 8 .47 15.74 49.42 51.79 1.19 0 .64 295 .64 8 9.68 18.16 65.06 67.58 1.26 0.72 295.72 9 10.90 20.58 82 .95 85 .64 1.34 0.81 295 .81 10 12.11 23 .00 103.08 105.96 1.44 0 .93 295 .93 11 11 .50 23.61 123.67 126.69 1.51 1.03 296 .03 12 10.90 22.40 142 .97 146.07 1.55 1.08 296 .08 13 10.29 21.19 160.98 164.15 1.59 1.14 296 .14 14 9 .68 19.97 177.71 180.95 1.62 1.19 296 .19 15 9 .08 18.76 193.16 196.47 1.66 1.24 296 .24 16 8.47 17.55 207.34 210 .71 1.69 1.28 296 .28 17 7 .87 16.34 220 .26 223 .69 1.71 1.33 296 .33 18 7 .26 15.13 231 .92 235 .39 1.74 1.36 296 .36 19 6 .66 13.92 242 .34 245 .84 1.75 1.38 296 .38 20 6.05 12 .71 251 .52 255 .05 1.76 1.41 296.41 21 5.45 11 .50 259.47 263 .02 1.78 1.43 296.43 22 4 .84 10.29 266 .19 269 .76 1.79 1.44 296.44 23 4 .24 9 .08 271 .68 275.27 1.80 1.46 296.46 24 3 .63 7 .87 275 .94 279.55 1.80 1.47 296.47 25 3 .03 6.66 278 .99 282 .60 1.81 1.47 296.47 26 2.42 5.45 280 .82 284.44 1.81 1.48 296.48 27 1 .82 4 .24 281.43 285 .05 1.81 1.48 296.48 28 1.21 3.03 280 .84 284.46 1.81 1.48 296.48 29 0 .61 1.82 279 .05 282 .66 1.81 1.47 296.47 30 0 .00 0 .61 276 .05 279 .65 1.80 1.47 296.47 21 ,, c 0 0 Q) 25 .00 20 .00 (/) 15 .00 Q; Q., Qi Q) u.. 0 :0 ::::J (j ; 10.00 0 == ::::J 0 5 .00 0 .00 Inflow/Outflow Simulation 25-Year Storm Event 0 5 Pre--- Developme nt Hydrog raph I I I - I I - I I I ' I I I 10 ' .... ' ' ' ' ' ' ' 15 20 Time (Minutes) Post-Post - Developme Developme nt Outflow nt Outflow Hydrograph With Without Detention Detention 22 25 .............. 30 Post- Developme nt "Free- Flow· Inflow I Outflow Simulation 50-Year Storm Event T ime Inflow 11+ 12 2s/t-O 2s/t+O Outflow Depth Elevation (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) 0 0 .00 0 .00 0 .00 0.00 0 .00 0.00 295.00 1.37 1.37 1.24 1.37 0 .06 0.00 295 .00 2 2 .74 4 .11 4 .86 5.35 0 .25 0.03 295 .03 3 4.11 6.84 10.63 11.70 0 .54 0.13 295.13 4 5.47 9 .58 18.35 20 .20 0 .93 0 .39 295 .39 5 6.84 12.32 28.49 30 .67 1.09 0.53 295.53 6 8.21 15.05 41 .25 43 .54 1.15 0 .60 295.60 7 9.58 17.79 56.60 59.04 1.22 0.67 295.67 8 10.95 20 .53 74 .52 77.13 1.30 0 .77 295.77 9 12 .32 23.26 94 .98 97 .78 1.40 0.88 295.88 10 13.68 26 .00 117.99 120.99 1.50 1.01 296 .01 11 13.00 26 .69 141 .58 144.68 1.55 1.08 296.08 12 12 .32 25.32 163.71 166 .90 1.59 1.15 296 .15 13 11 .63 23 .95 184.39 187.66 1.64 1 .21 296 .21 14 10.95 22 .58 203 .61 206.97 1.68 1.27 296 .27 15 10.26 21 .21 221 .39 224 .83 1.72 1.33 296 .33 16 9.58 19.84 237.75 241 .24 1.74 1.37 296.37 17 8 .90 18.47 252 .69 256 .22 1.77 1.41 296.41 18 8.21 17.11 266 .22 269 .80 1.79 1.44 296.44 19 7 .53 15.74 278 .35 281 .96 1.81 1.47 296.47 20 6 .84 14.37 289 .08 292 .72 1.82 1 .50 296 .50 21 6 .16 13.00 298.41 302 .08 1.84 1.52 296 .52 22 5.47 11 .63 306 .34 310 .04 1.85 1.54 296 .54 23 4.79 10.26 312 .89 316 .61 1.86 1.56 296 .56 24 4.11 8 .90 318 .06 321 .79 1.87 1.57 296 .57 25 3.42 7.53 321 .84 325 .58 1.87 1.58 296 .58 26 2 .74 6 .16 324 .25 328 .00 1.87 1.59 296 .59 27 2 .05 4.79 325 .29 329 .04 1.88 1.59 296 .59 28 1.37 3.42 324 .96 328 .71 1.88 1.59 296 .59 29 0 .68 2 .05 323 .26 327 .01 1.87 1.58 296 .58 30 0 .00 0 .68 320 .21 323 .95 1.87 1.58 296 .58 23 30.00 25 .00 ,..... -g 20.00 0 0 Q) Cl) <D Q. Qi .!. 15 .00 0 :0 :::J (.) ...... ~ 0 E :::J 10 .00 0 5 .00 0 .00 Inflow/Outflow Simulation 50-Year Storm Event I • I I I ... I I I I I I 0 5 10 15 20 25 30 Time (Minutes) Pre-----Post -Post-........ Post- Developme Developme Developme Developme nt nt Outflow nt Outflow nt "Free- Hydrog raph Hydr o graph With Flow" Without Detention Detention 24 Inflow I Outflow Simulation 100-Year Storm Event Time Inflow 11+ 12 2s/t-O 2s/t+O Outflow Depth Elevation (Minutes) (Ft3 /Sec) (Ft3/Sec) (Feet) 0 0.00 0 .00 0.00 0 .00 0 .00 0 .00 295 .00 1 1.43 1.43 1.30 1.43 0 .07 0 .00 295 .00 2 2 .86 4 .29 5.07 5.58 0.26 0 .03 295 .03 3 4 .29 7 .14 11 .09 12.22 0.56 0 .14 295 .14 4 5.72 10.00 19.16 21.10 0.97 0.42 295.42 5 7.14 12 .86 29 .83 32 .02 1.09 0 .54 295 .54 6 8 .57 15.72 43 .23 45 .55 1.16 0 .60 295 .60 7 10.00 18.57 59 .34 61 .81 1.23 0 .69 295.69 8 11.43 21.43 78 .13 80 .77 1.32 0 .79 295 .79 9 12 .86 24 .29 99 .58 102.42 1.42 0.91 295 .91 10 14.29 27 .15 123.71 126.73 1.51 1.03 296 .03 11 13.57 27 .86 148.45 151 .57 1.56 1.10 296 .10 12 12 .86 26.43 171 .66 174.88 1.61 1.17 296 .17 13 12.15 25.00 193.36 196.67 1.66 1.24 296 .24 14 11.43 23 .58 213.54 216 .93 1.70 1.30 296.30 15 10.72 22 .15 232.21 235 .68 1.74 1.36 296 .36 16 10.00 20 .72 249.41 252 .93 1.76 1.40 296.40 17 9.29 19 .29 265 .12 268 .70 1.79 1.44 296.44 18 8.57 17.86 279 .37 282 .98 1.81 1.47 296 .47 19 7.86 16.43 292.15 295.80 1.83 1.51 296 .51 20 7.14 15.00 303.47 307 .15 1.84 1.53 296 .53 21 6.43 13.57 313 .32 317 .04 1.86 1.56 296 .56 22 5 .72 12.15 321.73 325.47 1.87 1.58 296 .58 23 5 .00 10.72 328.68 332.44 1.88 1.60 296 .60 24 4 .29 9 .29 334 .19 337.97 1.89 1.61 296 .61 25 3.57 7.86 338 .26 342.05 1.90 1.62 296.62 26 2 .86 6.43 340.89 344 .69 1.90 1.63 296 .63 27 2 .14 5 .00 342 .08 345.89 1.90 1.63 296 .63 28 1.43 3 .57 341.85 345 .66 1.90 1.63 296 .63 29 0.71 2 .14 340 .20 344 .00 1.90 1.63 296 .63 30 0.00 0 .71 337 .12 340 .91 1.89 1.62 296 .62 25 Inflow/Outflow Simulation 100-Year Storm Event 30 .00 A' • " 25 .00 " -" • " • " I " I " I " ....... "O 20 .00 c 0 0 Cl> I " - I " • " Ch I " ... Cl> I " 0.. -Cl> Cl> 15 .00 u.. 0 :0 ::J u .._, ~ 0 == 10 .00 ::J 0 5 .00 • " I "" " • " . ~ " I " l ' I " . ' ' ~ " I . ' . ' . " . ' I . ' . ' " • . ' v . ' ---~ -I . ' " I . ' ' . ' " :'/ . ~--. ' ', ~ . ' " I • ' . ' ... , ... """" " ll : ', ~", ' . . . . . -~ ', ~ 0.00 0 5 10 15 20 25 30 Time (Minutes) Pr e-----Post -Post-........ Post - Develo pme Developme Devel opm e Developme nt nt O utflow nt Outflow nt "Free- Hyd ro g raph Hydrograph With Fl ow· With o ut Detentio n Det enti o n 26 Inflow/Outflow Simulation 2-Year Storm Event 9 .00 8 .00 7.00 B 6 .00 c: 0 0 Q) Cl) ... Q) 5 .00 Q.. -Q) Q) u.. 0 :0 4 .00 ::::J () -~ 0 == ::::J 0 3.00 2.00 1.00 0.00 0 5 10 15 20 25 30 Time (Minutes) ---Pre-Developm e nt Hydrograph ----Total Post -Develo pm ent Hydrograph 27 Inflow/Outflow Simulation 5-Year Storm Event 12 .00 10 .00 -8.00 "O c 0 0 Q) (/) ... Q) Q., -Q) Q) 6 .00 u.. 0 :0 :J u -~ 0 E :J 0 4 .00 2.00 0 .00 0 5 10 15 20 25 30 Time (Minutes) Pre-Development Hydrograph ----Total Pos t-Development Hydrograph 28 Inflow/Outflow Simulation 10-Year Storm Event 14 .00 12 .00 10.00 -"O c: 0 0 Cl> (/) ... 8 .00 Cl> 0... -Cl> Cl> LL. 0 :a :l 0 6.00 ....., ~ 0 = :l 0 4.00 2.00 0.00 0 5 10 15 20 25 30 Time (Minutes) Pre-Development Hydrograph ----To t a l Post-Development Hydrograph 29 Inflow/Outflow Simulation 25-Year Storm Event 14 .00 12.00 10 .00 ........ "O c 0 0 Q) (f) ... 8.00 Q) Q., -Q) Q) u.. 0 :0 ;:, u 6.00 -~ 0 E ;:, 0 4.00 2.00 0 .00 0 5 10 15 20 25 30 Time (Minutes) Pre-Development Hydrograph ----Total Post-Develo pment Hydrograph 30 Inflow/Outflow Simulation 50-Year Storm Event 16.00 14 .00 12.00 ....... "O c: 0 10.00 0 Cl> (f) ... Cl> a.. -Cl> Cl> 8.00 LL. 0 :.0 ::J u -~ 0 6.00 E ::J 0 4.00 2.00 0.00 0 5 10 15 20 25 30 Time (Minutes) Pre-Development Hydrograph ----Total Post-Development Hydrograph 31 Inflow/Outflow Simulation 100-Year Storm Event 18.00 16.00 14 .00 " 12.00 "O c: 0 0 Cl> (/) ... Cl> 10 .00 0... -Cl> Cl> LL. 0 :0 8.00 :::I u -3'; 0 E :::I 0 6 .00 4.00 2.00 0 .00 0 5 10 15 20 25 30 Time (Minutes) ----Pr e-Development Hydrograph ----Total Post-Development Hydrograph 32 Detention Pond Storage Volumes as Percent of Maximum Volume 100% 90% 80% C1> 70% E :J 0 > 60% E :J E ')( 50% 0 :E -0 -40% c C1> 0 .... C1> Q.. 30% 20% 10°/o O°lo 2-year 5-year 10-year 25-year 50-year 100-year Design Storm Storm Simulation Synopsis 2-ear 5-ear 10-ear 25-ear Storm Depth 1.15 1.29 1.38 1.48 Storm Elevation j 296 .29 296 .38 296.48 296.63 Storm Volume 4882 6263 7212 8374 9641 10138 Maximum Capacity 20534 20534 20534 20534 20534 20534 Percent of Capacity 24% 30% 35% 41% 47% 49% 33 ,._ From: Shirley Volk To: City of College Station.City Hall(JDUNN, NTHOMAS, ... Date: 11/7/95 4:41pm Subject: West Knoll Duplexes -Reply -Reply -Reply -Reply -Reply -Reply -Reply -Reply We met on this today and Steve & Veronica worked out an agreement with the Thomas Bros., and I got the c.o. for a duplex issued while they were here. The agreement reached was that no matter if they build more duplexes in this subdivision or not, all drainage facilities will be totally complete by May 30, 1996. I would say that we can continue to issue building permits and c.o.'s for units up until that date. At that point, an inspection must be done on the detention facility because we have a large letter of credit which expires the first part of June anyway. The problem has been addressed with an agreement reached and a handwritten note is now in the file. Charles T. also has a copy of that note. >>> Steve Homeyer 11/07/95 09:07am >>> I just spoke to Charles Thomas about the CO for 1609-1611 Dexter. He is not too happy about this. He said that we intentionaly sat on this co so that we could force his hand. He said that the detention pond was not needed for this site and we knew it. He went on to say that what they did was correct by sending the water to the front of the buildings rather than keeping it to the back as designed by Garrett. He stated that he was close friends to ALL of the Council members and that he would visit with all of them if necessary. To put it nicely, he said this was a bunch of crap and he was ticked off. Veronica, he will be coming in to visit with the two of us because he feels you are wrong. >>> Shirley Volk 11/02/95 02:22pm >>> Who will be contacting the contractor about this? >>> Steve Homeyer 11/02/95 12:14pm >>> I just inspected the detention facility (11-2-95) and it DID NOT pass. They need to grade the existing duplexes to route through the pond and to bring the back side of each roof to the back so that it will flow to the pond. As it stands, some of the water in the back appears to be coming to the front (the streets) which is not the wa it was designed. The existing grading will not suffice. Also, the pond's outlet structure is (1) nonexistent or (2) very silted up, it is not working. If you have any questions let me know. >>> Natalie Thomas 11/02/95 12:01pm >>> I don't know much on this one except that Veronica and I prepared those punchlists that are in the file for issuance of a C.O. and filing the plat. The plat has already been filed. So, Veronica or Deborah should be able to tell you if we have a letter of acceptance on the detention pond, etc. >>> Shirley Volk 11/02/95 11:40am >>> Sorry, Joey, I've sort of been out of the loop on this one, but I'll forward it to Nat. Hopefully she'll be able to answer your questions. Nat, let me know the answer, too, if you have one. >>> Joey Dunn 11/02/95 10:19am >>> The c.o. I have is for 1609-1611 Dexter Drive. I believe you and I went out there a few months ago when I had to check on their pkg./landscaping. I imagine the other duplexes will co'd pretty soon. Shirley, have you been in the loop on this? I have a c.o. ready to sign. >>> Steve Homeyer 11/02/95 09:54am >>> No Sir. I got side tracked the other day and jsut forgot about it since. What are the addresses for these duplexes? I know that in this general area, there is not a pond at the present time. >>> Joey Dunn 11/02/95 09:29am >>> Steve, did you get a chance to check on the detention pond? I need to get back with the Thomas Bros. about their c.o. CC: KLaza, JKee,JCallaway Ill ,,,.,, ......... ......... ......... :z:::z:::z:: 111111111 WEST KNOLL SECTION TWO CROSS SECTIONS DDP #288 CROSS SECTIONS TAKEN ON 11-10-95 BY: VERNON WRIGHT JERRY JONES . ~gg CROSS SECTIONS PLOTTED ON 11-13-95 BY: STEVE HOMEYER -N ---~ ~ ~ BASE LINE FOR PLOTTING IS THE DEXTER DRIVE ROW LINE. ~I STATION 0+00 IS THE COMMON LINE BETWEEN LOTS 19 AND 20 . ' I -1-- . I 0-0--N . N ~ ~ Z.95 0 50 100 lxXTEiC rcow "STA )-0- 0--c ' 0 ~ IV) 'SD 200 o+-oo A. AMPAD (J --9 d) (!" N Z.!50 m€[)1NA. IC.D~ 22-141 50 SHEETS 22-142 100 SHEETS 22-144 200 SHEETS ' • 305 3DD N "' N N ~ r. l"I 0 ("1 cg {VI ~ (\/) Z.95 0 5b 100 1:::£~ ~CA.A) CSIA N N -9 -. (\I ('J 0 0 M f") . 150 Zoe 0+75 ft . AM PAD N 0 er Ir"" N 250 m~l=>INA i<..()..J,,) 22-141 50 SHEETS 22-142 100 SHEETS 22-144 200 SHEETS t---+~+---+~+---+~+---+~+---+-~t---+-~+--+~+--+~+--+~+--+~+--+~+--+~+--+~+--+~+--+~+--+~+--+~+---1 • I "305 ~co --N -:r J ~ ,Q 2.°15 0 SD "Ctx'1C'JZ.. ~ \() N i-~ 0 M 100 ~-,A. 1+50 150 zoo z.so a . AM PAD 22-141 50 SHEETS 22-142 100 SHEETS 22-144 200 SHEETS so5 3co \o Vl IT' fVl . . J" J 0 f), rJ) 'Z.'15 0 /00 ~~ E._1)L.0 ~~ "' \.Cl r !"'> rvi· ("l 0 0 f'/) iv> 1'5'0 Ztx:::> Z"\-ZS' a . AM PAD 0 r: 11"" ~ 250 m~NA ·Ro...J 22-141 50 SHEETS 22-142 100 SHEETS 22-144 200 SHEETS 50-0 ~ IV\ N \j) ")- ~ 0 M Z.95 0 100 7:c~ e()(...) STA z+C?o ~ ~ ('I) ISO 2cx:::> ~. AMPAD a) 0 4 2sz:> l'f}c-r:yNA K.o-J 22-141 50 SHEETS 22-142 100 SHEETS 22-144 200 SHEETS DEVELOPMENT PERMIT PERMIT NO. #288 FOR AREAS OUTSIDE THE SPECIAL FLOOD HAZARD AREA RE: CHAPTER 13 OF THE COLLEGE STATION CITY CODE SITE LEGAL DESCRIPTION: West Knoll -Section 2, Block 3 SITE ADDRESS: Located on the north of Southwest Parkway between Medina and Dexter OWNER: Thomas Properties DRAINAGE BASIN: Bee Creek TYPE OF DEVELOPMENT: This permit is valid for all clearing and grading as per the approved plans for West Knoll - Section 2. The Contractor shall take all necessary precautions to prevent silt and debris from leaving the immediate construction site in accordance with the approved erosion control plan as well as the City of College Station Drainage Policy and Design Criteria. Contractor shall assure that all disturbed areas are sodden and establishment of vegetation occurs prior to removal of any silt fencing of hay bales used for temporary erosion control. Contractor shall also insure that any disturbed vegetation be returned to its original condition, placement and state. Contractor shall be responsible for any damage to adjacent properties, city streets or infrastructure due to heavy machinery and/or equipment as well as erosion, siltation or sedimentation resulting from the permitted work. This permit expires six months from the date of issuance. In accordance with Chapter 13 of the Code of Ordinances of the City of College Station, measures shall be taken to insure that debris from construction, erosion, and sedimentation shall not be deposited in city streets, or existing drainage facilities . I hereby grant this permit for development of an area outside the special flood hazard area. All development shall be in accordance with the plans and specifications submitted to and approved by the City Engineer in the development permit application for the above named project and all of the codes and ordinances of the City of College Station that apply . Administrator/Representative Date Contractor Date Owner/ Agent Date ·---------·--~---·--~--~----------~-~~- -~~------------"~ ---~--~ ---1----11------'·1---· ----~--------::------------~-L-------!.!..' 4 '41;~/ I \/'\~ TO: GARRETT ENGINEERlNG COllSUL TlllG EllGUlfERIHG & LAND SURVfYIHG 4444CARTER CR£EK PARKWAY, SUITE 1111 -BRYAH, TEXAS 17102 -(401) 14S-2111 -(409) 14'-lot4 <-. J ~ n £ Co)\ ( a o(:} , S-kJ H'i hi\ , A \-ht ·-~ \-4 S I uw\n.'S k:_( Dace: :SW \1\-e <?< 1 \ q qs We Are Sending You: __i}_ Herewith __ Under Separate Cover The Following: Copies Date Description 1-$ " -- _\_ Rem arks: By: cc: Re ce ived I3 y: August 1, 1995 Charles & Glen Thomas Thomas Properties P.O. Box 10106 College Station, TX 77845 Dear Mr. Thomas, I am writing this letter to provide you with a punch list of items remaining on two of your projects in College Station. In addition to the building code requirements , the following items must be taken care of prior to issuance of a certificate of occupancy or releasing the guarantee bond. EASTMARK SUBDIVISION It ems remaining prior to issuance of a C.O .: The existing utilities for all five lots must be relocated according to the approved relocation plan . These relocations must be inspected by the City. The existing transformer boxes along Colgate Drive must be adequately screened from the right-of-way. Items remaining prior to releasing the guarantee bond: Streetscape elements must be installed along Colgate and Cypress Drives . These elements must also be installed at the comer of Cypress Drive and Kalanchoe Court to screen the proposed parking areas so that they are not visible from Colgate Drive . Submit a plan addressing this requirement to be reviewed and approved by staff prior to installation. Provide a sidewalk along Colgate Drive to connect with the existing sidewalk along Cypress Drive. Submit the construction documents for the required sidewalk to be reviewed and approved by staff prior to installation . The sidewalk must be inspected during construction. II' . "\ Thoma s Properties West Knoll & Eastmark Page 2 of2 WEST KNOLL II Items remaining prior to issuance of a C. 0 .: Screen the parking areas from Dexter and Medina Drives . The detention pond must be completed in accordance with the approved plans . If utility service lines are currently in place , submit a utility relocation plan for all lots showing the location of the existing service lines and how they will be relocated to serve the subject lots . All utilities must be completed, inspected and accepted by the City . It ems remaining prior to releasing the guarantee bond: Streetscape elements must be installed along the frontage of Southwest Parkway. Submit a plan addressing this requirement to be reviewed and approved by staff prior to installation . Provide sidewalks along Dexter and Medina Drives . Submit the construction documents for the required sidewalks to be reviewed and approved by staff prior to installation. The sidewalks must be inspected during construction . I hope this punch list is helpful in identifying any possible delays in issuing the certificates of occupancy. If you have any questions pertaining to the above mentioned requirements, please contact me at (409) 764-3570 . Sincerely, Natalie Thomas Planning Technician / \ .f \ Figure XII-1 Application Form Development Permit For Areas Outside · Flood Hazard Areas City of College Station, Texas (re: Ordinance No. ) --- Site Legal Description: f?I p U:::. 3 wt:.'5T 'b,1'):>L.L -"St.L=noN. 2. Site Address: Located in: :Bt;.£ c.J2 EF:.K ORA.\ t-JA.~~ BA~\ N Watershed Architect/ Engineer: C;p r<.g tt Er~~l oe f fln.J Contractor: Date Application Filed: Application is hereby made for the f ollowing development: W£.ST K t...\OLL. -5.e-L.\.ioO . 2.. Attached as part of this application: lo/\02 .00 Application Fee .7 .( Drainage Plan with supporting documentation: 1;WO copies of each J Other:· DL2A1NAC£. g,,t;PoRT ,,... o,,pt>ro lJ.fo1 · Pt ~ thL Cf~. ACKNOWLEDGEMENTS: ~+ ki ~ O\,U\'\.U" , as ~. hereby acknowledge or affirm that: The above Drainage Plan and supporting documents complies with the requirements of Ordinance No. .:SU.vvwe 5 , ' 5 q 5 Date 98 .:."' : .. ·• • ... '!'. . . . , . .. ' . GARRETT ENGINEERING PH . 409-846-2688 4444 CARTER CREEK PKWY . SUITE 108 BRYAN , TEXAS 77802 ----=-6 _-_._[ __ 19 9 .5' 1398 1 88 -257 /1 1 I OQ PAY ~ ~ I TO THE f!t ('.../--...,f- ORDE R OF ~ '1-~---------------_J o~-~ ~ ~7rour------------=o~RS (00. $ VICTORIA BANK & TRUST 3000 BRIARCREST • BRYAN, TEXAS 77802 MEMBER: V ICTORI A BA NKSHAR ES . I NC./FDIC 83 5 FOR{J~~-~ p~ n•o • :l gaau• 1: •• :l •o 2 5 78•: 365228 -:---;-Jr--;~----.-=:._+-=-+---. 19 q {L CITY OF COLLEGE ST A TION $ 100°~ RECEIVED OF ____ __.,6~.Ll!.~~___!~J-4~'f--'-:JJ~{_b.t!fl~--------- FOR _~~~~~---,-....--~:::;::-~r-~~~~-_JL.'.__~~~~~~~- THANK ~·~,-CITY OF C~L~E~~ STATION ~ EngmeermgD1V1s10n ~·~ r CITY OF C~L~E<:J~ STATION ~ Engmeenng D1vis10n «> Co~t ove,. 8" PVC o~tf el fff e f s o.,jy b '' wi /'1 °'-siJe ""°' //c ove!' i J. " P'fe. l,,.,.Jl sp~e.;f;,J o .. f"J ~ I~ ,,/~.s ''° J. c Ofl~sro~~ i.1 JI. -I-le p/,.., s. • p,._ ~ •• )op ..... l Dts<~•'7• f,._ JLe re/wJ olo no~ con·~10.,.p(_ -J.o J he. J/s,l1a.r7c Ok 4he ptev,'ou~ r~f1"rJ.. .· 'I . .· .. t) I ' '. ·' . ~.~ ' ,. . . I · ,. r . ·.; ~ . . ~ .. r: .. .. . ,'\' <, \ ... ....... -· .. ; > -. . . . . ,.; ... ... . ~ ... .. ·1 GARRETT ENGINEERlNG COlfSUL TD~ ENGDIEERlllG & LAND SURVEVI~ 4444 CARTER CREEK PARXWAY, SUITE 1DI. BRYAN, TEXAS 71102 . (401) 14'-2111 • (4119) 141-lot4 TO: ( 'i bj of co1A-e ~ S k rh\b \.J . Dace: Atl{nb'on " >2\-r ic'j s I OJ..Oir'I SlGt RE: W£ s t llvl n ~ \ O retH)CL~ .e._, Com ,pcdCL4-l u''(\..,S. Ke plcd of 6\ .aL ~ We<>+ VCYLo ~ \ -\-,e c h D n '2.. We Are Sending You : _j__ Herewith __ Under Scparace Cover The Following: Copies Dace Description ~ Lt {2-Rr \) 1<pw Ow~ . '2-~0 r+ ... I ~ o n'u~Y\ov\ 0~1~-(_, (Le.,Q ort--.. wi'±ki ef'd 11·11 -e s b u.+ c c,,,J,,\ By : cc: ReceivedDy~ ~ · CITY OF COi l~EGE STATION Post Office Box 9960 1101 Texas Avenue March 18, 1996 Thomas Properties P.O. Box 10106 College Station, Texas 77845 College Station, Texas 77842-9960 RE: Detention Facility for Block 3, West Knoll -Section 2 (DDP #288) Dear Sirs: ~~ As per your request, I made an inspection of your detention facilities at the above referenced location on Friday, March 15, 1996. From my inspection, I found the items indicated in my February 12, 1996 correspondence to be completed, therefore, I will ask the Building nepaitment to remove the hold currently placed on Lots Rl, R2 and R3, Block 3 ofWest Knoll -Section 2. In addition, I will make a final inspection, at the time you request your last Certificate of Occupancy, to determine compliance with the approved drainage report. As always, if you have any questions or comments, feel free to contact me at 764-3570. Steve Homeyer Graduate Engineer cc: Kent Laza, City Engineer Veronica Morgan, Asst. City Engineer Sabine Kuenzel, Senior Planner Shirley Volle, Development Coordinator David Dobbs, Quality Assurance Inspector Carl Warren, Plans Examiner Home of Texas A&M University PAGE 01 08/17/1 995 15:41 409-590-7118 BEN CHMARK/THOMAS PRP ft- WlnFax PRO Cover Page v (;(( DN ~LI\. - ~+4~"'2J ~ A (ef-fcR '(o!2_!je>O(( (:leS QoN Ce'.v-N~N~ c__/Q '.s 1 ooK wcs-f-k'Nul1 ?v-c:)~.t I '?IE*s~ CA t1 /v.t ('1 Jti u ~uc A-NJ ~ucs~;~ - OY. Phone: ... Fmc ~ rant.r :OX eaqO-ff/ 7 ram :OS PAGE 02 08/1711995 15:41 40g-5g0-7118 BENCHMARK/THOMAS PRP -AuglJlt 17, 1995 Ml. V.aicafllbga1 ~~ils.r.lcm City d CoUlgl 8lllltien P.0.lk»l 9880 College Station, Teas 77845 Ow'""'"" •. ~.-.-.n11 FAX: .___,,,. Yau mnd "JOI dlpn1M *If hmve t..'I molt helpfuJI to Thoma Propettiee cUing the ~ and CD1ltnJctian af the the proiect on W9lt Knoll, 1h8nk you Wirf much. M deaJ111d in ya1oflice~o•181h, we pl91 to r9qU99t mm CertiftClltea d ~on mt lwt ecrne d the ~ et on I 1 r :le• and Da&ilr" Fridlly, Augult 18, 1995. In a Mitter' from [)~ Natie Thcma dDd w 1, 1995 it .. brought to my att9ntion that the psking .... from -},?" Oexler' and Madina would need ID be 1a eenad. In tt.t the heat index i• OY« 100 we f9el it would be betlar ID p&.m the l9qUir9d ,,.._ in w1y fall ndhel" than now. I twve r9q1 iMted ., -*itia 1111 $4800.00 i.tl9r' dad be eent ID the City from Victoria 88'k & Trust tD CXJY9f' the aaeening upenae. We wm complete pining in October or November. The Only utility wvice lines we c:Nl lg9d on the West Knoll project WM the Electrical main .net sec:aldaly l8rVic:el. Water & sewer remained the 11me. Aa ID the dM9i ltion pond, • we dilCUaed, we have signed cor rb eds to cxxnptete an llddltiona six (6) ~i • by~ 1, 1998 far lit'. Jllnea Wiison, { Same owner u first eight.) We NNe ~ in the pond and fMI it ii doing wtWit it WU dnigned to do. 0.Vid Dobbe ha ii llp8d9d It and 1-t• we h8ve not cnated and cntnage problems. We would llke to DOltDOrle the completion d the pond '61til the <DTl>letion d the nut lix units. Fin.tly, • to lide W111ka and dri'IWJ9)'8 on Mmdena; due to the natural eiev.aon d the land 9tld the leek d foot tr.rr.c we fMI it woMd be ui n l90llt•'Y for the city ID 9Y9f consider the utentian d a aic:tftc91k an Ml ttei ia. Mlder ia is a dead end street. For this ruaon we will be making .. • .aio ...w.. for a vmi.nol not to inltafl a aide walk on the Madena side af the Welt Knoll prqect. If you t.. and qi .oor. or fltT'J feel there are other items we should consider pl .... cont8Ct me. -~ ~~ -~'! $1;~. ~~~ June 24, 1996 Thomas Properties P .O . Box 10106 College Station, Texas 778 45 CI TY OF COLLEGE STATION Pos t Offlce BoJC 9960 i 101 fe>.as Avenue College Stati on , Texas 77842-9960 ( 40 9 ) 764-3500 RE: Dete ntion Facility for Block 3, West Knoll -Section 2 (DDP #288) Dear Sirs : At the last City Council meeting on June 13 , 1996 , a citizen indicated that the detention pond at your site was not functioning properly during storm events . As in all situations brought before Council, staff will investigate the concern . On Thursday, June 20 , I made an inspection of your pond and found what I understand to be the concern . The three duplexes situated on Lots RI, R2 and R3, Block 3, West Knoll -Section 2 are not complete and therefo re the final grading has not occurred. Please rememb er that the final grading must be compl ete prior to the issuance of a Certificate of Occupancy for any of these structures . If you would like for someone to inspect the grading prior to placing sod and installing the irrigation system, pleas e feel free to contact me and I will schedule a time that is convenient for you . As always , if you have any questions or comments , do not hesitate to contact me at 764-3570 . Sincerely, ~~ Graduate Engineer cc : Tom Brymer, Asst. Ci ty Manager Jim Callaway, Acting Dir. of Developm en t Services Kent Laza, City Engineer Veronica Morgan, Asst. City Engineer Shirley Volk, Development Coordinator Drainage Permit File No . 288 Home of Tex.as AlrM Unlver.,it.:, DRAINAGE COMPUTATIONS for A Replat Of Block 3, West Knoll -Section 2 College Station, Brazos Cou11ty, Texas Prepared for Thomas Properties P.O. Box 10106 College Station, Texas 77845 Prepared bv: Garrett Engineering 4444 Carter Creek Parkway -Suite 108 Bryan, Texas 77802 Telephone: (409) 846-2688 *April, 1995 * DRAINAGE COMPUTATIONS for A Replat Of Block 3, West Knoll -Section 2 College Station, Brazos County, Texas Pr ep ared for Thomas Properties P.O. Box 10106 College Station, Texas 77845 Pr epare d by: Garrett Engineering 4444 Carter Creek Parkway -Suite 108 Bryan, Texas 77802 Telephone: (409) 846-2688 * April, 1995 * DRAINAGE COMPUTATIONS fo r A R e pl a t of Block 3 Wes t Knoll -Section 2 College Station , Brazos County, Texas * April , 1995 * SUMMARY The project is situ a ted lo th e north of Southwest Parkway between Dexter and Medina drives in the West Knoll Subdivision, College Station, Brazos County, Texas. Bl ock 3 of Wes t Knoll -Section 2 consists of 14 lots being established within th e bounds of th e 3.54 acre tract. The tota l drain age area tributary to lh e proj ect is 3.54 acres. The pre-devel op ment run-off coefficient was estimated to be 0.40, whil e taking into account typical res id en tial site improve ments would result in a pos t-developm ent run-off coefficient of 0.65. A detention facility will be constructed in th e so uth ern portion of U1 e properly in keepin g with th e existing contours and as desig na ted on th e plat. T he de te ntion pond is designed to faci litate up to and including th e 100-year stonn event, and di sc harge a t a rate less th a n U1 e current pre-d evelopme nt peak di sc harge rate. The de te ntion pond will intercept, store and meter run-off from 1.88 ac res of th e proj ect. The run- off generated on lh e remainin g 1.66 acres will "free-flow" across the project site unm ete red off th e prope rty. Th ese report calculations are s ummarized according to th e following me thodology. Begi nning on page 1, based on the total tributary drain age area of th e proj ec t (being estimated at 3.54 acres), the pre- development run-off coeffici ent (b e ing ass um ed at 0.40), and a minimum Lime of concentration of 10 minutes, the relativ e pre-developme nt peak di sc harge rate ("Q") was de tennined. The Rational M ethod was utili zed to compute th e esti mated peak pre-develo pm ent di scharge rates. The e qu a ti o n th at rep resents th e Rational Method is as follow s : Q = C IA . "Q" is U1 e peak discharge rate in cubic feet per second, "C" is th e run-off coefficient, assumed to be 0.40 in th e pre-development condition, "I" is th e storm inte ns ity in inch es per ho ur, and "A" is th e area of th e drain age basin in ac res . Computations on page 2 are based on th e tributary area of 3.5 4 acres , the pos t-d evelo pm ent run-off coefficient of 0.65 (being weighted according to th e re la tiv e amounts of perv ious and imp erviou s surface area), a minimum lime of concentration of 10 minutes, to yield lhe re la tive pre-d evelopment peak di sc harge rate ("Q") (ass uming U1 e same minimum time of concentration of 10 minutes). The Rational Me thod was again utilized to compute lh e es timated peak po st-d evelopm e nt discharge rates. The equation th at represents t11 e Rational Method is as follows: Q = CIA, where; "Q" is lh e peak discharge rate in cubic feet per second. The "C" variable is U1 e run-off coefficient. (I n the pos t-d evelopment condition "C" is ass um ed to be 0.65.) "I" represents lhe rainfall intensity in in ches per hour, and s imil arly "A" is the area of th e bas in in acres. Comparison of th e peak pre-development di scharge rate to t11 e pos t-d evelopment discharge rate is included in lh e re port lo aid t11 e design er in establi s hin g a preliminary "ta rget" of dete nti on volume req uire d. Thi s preliminary es tim ate is determin ed as t11 e volwne differenc e generated between th e pre- d evelopment and pos t-d evelopm ent hydro graph s. (See pages 9-11 for pre-developm ent and post- development h yd ro graphs.) Please note tliat th e pos t-d evelo pm ent bydro graph shown on th ese same grap hs assumes no dete ntion and re fl ects t11 e "w o rs t-case " scenario that all run-off is allowed to free-flow. Pages 3 and 4 provid e infonn a ti o n co ncernin g th e pos t-developm ent run-off th at is not route d throu g h the de tention facility ("fr ee-flow ") as well as th e pos t-development run-off th a t is routed throu g h th e de te ntion facility and re tain e d on s ite . Page 5 and page 6 are tabulation s of tll e pre-de velopme nt and th e post-deve lo pm ent hydrograph s based on the computation s perfonn ed on page 1 a nd page 2 . Th e pos t-developm e nt hydro graph ass umes no de te ntion to facilita te direct compari so n in th e pre -and po st-d e velopment conditions . Page 7 and page 8 are tabul a tion s of th e pos t-develo pm ent hydrograph for run-off dire cted through th e de tention facility and th e pos t-d e vel opm ent hydrog raph for "free-flow" from th e proj ec t s ite. Computa tions on page 4 de tennine th e actual peak pos t-development "inflow" rate supplied to th e proposed de tenti o n facility. From t11i s "inflow" rate a nd t11 e tim e of concentration (10 minutes min imum), a hydrog raph a s tabulated on page 8 is d eriv ed . The hydro gra ph is trian gular in shape and is based on th e standard SCS unit hydro graph with tim e to peak set e qual to t11 e time of con centration a nd th e total tim e base set at 3 .00 tim es th e tim e of co ncentra tion . Pl ease note th a t a 30 minute total sto rm event duration was utili zed exclu s ively throu g ho ut thi s report du e to th e re la ti ve small s ize o f th e proj ect. H av in g derived U1 e pre liminary volum e re quire me n ts a nd "al lowable peak" di scharge rate, 1t 1s now po ss ibl e to des ign U1 e fin a l de tention fa cility a nd outl e t co ntrol structure. Page 12 presents a da ta tabul ati o n and a de pth versu s volum e graph of th e de te ntion fac ility. The m a ximum de pUl o f the pond was set a t 2.5 fee t. (With th e to p of berm elevati o n a t 29 7 .50 ft. less fl ow lin e "out" of outl e t control stru cture at 295.00 ft.: 297 .5' -29 5 .00' = 2 .5' ). Page 13 s uppli es a tabul ation a nd a ra tin g curv e fo r th e prop osed outl e t control s tru cture . A circular pipe cul ve rt was chosen du e to t11 e di sc harge ratio characte ri s ti cs associated with th e a nticip a ted headwater de pUl . An ultim ate stora ge de pU1 of 2.5 is avail abl e du e to Ul e phys ical geometry of t11 e po nd . Howe ver, even a t 100-year s to rm cond iti o ns, de pt11 s of less tl rnn 2 fee t are anticip ated . The pipe di ame ter of 8 in c hes or 0.67 fee t was se lec ted . Thi s val ue was de termin e d fr om th e foll ow in g e qu ati on for headw ater de pUl (in fe e t), H = [ [ ( 2.5 204 ( 1 + K )) I D4] + [ ( 466 .18 n 2 L ( 1 + K)) I D16/3 ]] x (DI 10 )2. "K" is th e entra nce loss coe ffi cient ( K = 0 .50 for Uii s case). "D " is tl1 e diame ter of tl1 e pipe in feet. "L" is th e len g Ul of cul ve rt in feet. "Q" is Ul e d es ign di scharge ra te in cublic fee t pe r second. "n" is m annin g's rou g hn es s co e ffi cient (n = 0.01 2 for co ncrete pip e), and "H'' is Ul e headw a ter de pth in fee t whi c h ranges from 0 .00 ft. to a maximum of 2.00 ft. Page 14 presents a tabulati o n of th e rela tion s hip be tw ee n di scharge from U1 e de tenti on facility and tl1 e dim e ns ionl ess qu antity 2S/t-O. Al so presented is a Storage Indica tion Curve for t11 e d e tention facility based on th e afo remention ed phys ical char ac teri s ti cs of Ul e de tention p ond, sto rage vo lum e , inflow hyd rog raph, and ra tin g c urv e fo r t11 e o utl e t s tru c ture . Th e s torage indic a ti o n c urv e a s sh o wn on pag e 12 is a g raphica l soluti on to t11 e equ a ti o n presente d in th e "Dra in age Po li c y And D es ign Stcmd ard s " as fo ll o ws: 2 s 1 (I 1 + I2) + (--------------- dt 2 s 2 -01) = (-----------------+ 0 2) dt Page 15 t11rou g h page 26 present s imul a tion s of th e 2 , 5, 10, 2 5, 50, and 100 year storm events . The fir s t p age of e ach s to rm s imul a ti o n re presents Ul e tabul a ted da ta fo r t11 e stonn e ve nt. The m ax imum de pUl achi eved in th e de te ntion po nd durin g each s imul a ti o n is shown below as is th e tim e at durin g which thi s m ax imum de pt11 occurs fr o m t11 e o nse t of th e s to rm event. The calculated peak di sc harge rate co rres pondin g to thi s de pth over sam e peri od is also shown below. Ad d iti o nally, th e m ax imum wa ter s ur face ele vati o n ac hi eved durin g each event a nd th e max imum peak d isc harge durin g each event are li s ted be low. The seco nd page of each s torm s imul a tio n re presen ts tl1 e pre-develo pm e nt hydrogra ph, th e post-d e ve lopm ent hyd rogra ph (with n o d ete nti on), th e po s t-d e velopm e nt hydrog raph as routed throu g h th e detenti on pond, and pos t-d evel o pm e nt "free-fl o w " hydro g raph fo r each stonn e ve nt. Page 27 through page 32 provide total inflow/outflow hydrographs for the 2, 5, 10, 25, 50 and 100-year pre-development and post-development storm events. It can be determined from these same hydrographs that the post-development peak discharge rates have been minutely decreased from those peak pre- development discharge rates due to t11e incorporation of the detention facility in tlle post-development condition . Total post-development peak discharge rates from the detention pond outlet control structure and project site are kept less than the pre-development peak discharge rates due to the incorporation of the proposed detention facilities. Subsequent peak post-development discharge velocities projected to be within manageable limits. Determine Total Pre -Development Peak Storm Water Di scharQe Rates _ Tributary Area ("A"): 3 .54 Acres Pervious A rea: 3 .54 Acres Im pervious A rea: 0.00 Acres Run -Off Coefficient ("Cwt"): 0.40 Ti m e Of Conc entration ("T/c"): Woo dla nds: Low Elevation: High Elevat ion : D istance (Feet): Slope (%Grade): Velocity ("Vw"): Time: Pastu res: Low Elevation: H igh Elevatio n: Distance (Feet): Slope (% Grade): V elocity ("Vp"): Time: Pave m ents: Low Elevation: H igh Elevat ion : D istance (Fee t): Slope (% G rade): V elocity ("Vpave"): T ime : Total T rave l T ime: Hourly Intensity Rates ("I"): 2-Year: 6.33 5-Yea r: 7.6 9 10-Year: 8 .63 25-Year: 9.86 5 0-Yea r: 11 . 15 100-Year: 11 .64 Peak Discha rge Rate ("Q"): 2-Year: 8.96 5-Year: 10.89 10-Year: 12 .23 25-Year: 13 .96 50-Yea r: 15.79 100-Year: 16.48 C = 0.40 C= 0 .98 0.00 0.00 0 .00 0 .00 0 .00 0 .00 0.00 0.00 0.00 0 .00 0 .00 0.0 0 0 .00 0 .00 0 .00 0.00 Feet I Second M inutes Feet I Second Minutes 0 .00 Feet I Sec on d o.oo M inutes 10.00 M inutes Inches I Hour In ches I Ho u r Inches I Ho ur Inches I Hour In ches I Ho ur Inches I Ho ur C ubic Feet I Seco nd Cubic Fee t I Secon d Cubic Feet I Second C ubic Feet I Seco nd C ubic Feet I Second C ubic Feet I Second {" t)U \.'\d, ~ -W'-\.:)~\ ~\){. ~\S \o \a<. ~\(j""-\-Vj ~ ~ \t ~ -Y.M.t k> Qg. v.:>I V\Q\\A_I~ ~J\YLj -C'rovvv Ct. ~.f_dQM0~ ~l r .\.o c...:. Pl'(J< c..u l\J..l.K-t-. -,-i, esc t-1 uM bers. 01re o(;fft:tt:...I .Jt~., -J-lie f;,sJ refo,..J. 1 b.A .J.~e s"~e ofuf Pi is vs~J? Determine Post-development Peak Storm Water Dischar e No Detention Tributary Area ("A"): 3.54 Acres Pervious Area : 1.99 Acres Impervious Area: 1.55 Acres Run-Off Coefficient ("Cwt"): 0.65 Time Of Concent ration ("T/c"): 1 O Minutes (Min) Hourly Intensity Rates ("I"): 2-Year: 6.33 5-Year: 7.69 10-Year: 8.63 25-Year: 9.86 50-Year: 11.15 100-Year: 11 .64 Peak Discharge Rate ("O"): 2-Year: 14 .65 5-Year: 17 .81 10-Year: 19 .99 25-Year: 22 .83 50-Year: 25.81 100-Year: 26.94 Comparison Of Predevelopment And Post -development Peak Dischar e Rates c = 0.4 0 C= 0.98 Inches I Ho ur Inches I Hour Inches I Ho ur Inches I Hour Inches I Hour Inches I Hour Cubic Feet I Second Cubic Fee t I Second Cubic Fee t I Second Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second Predevelopment Post-Development 2-Year: 8.96 Ft3/sec 14 .65 Ft3/sec 5-Year: 10.89 Ft3/sec 17 .81 Ft3/sec 10-Year: 12.23 Ft3/sec 25-Year: 13.96 Ft3/sec 50-Year: 15.79 Ft3/sec 100-Year: 16.48 Ft3/sec 19 .99 Ft3/sec 22.83 Ft3/sec 25 .81 Ft3/sec 26 .94 Ft3 /sec J r-t3/sec 8.87 Ft3/sec 10.02 Ft3/sec 10.46 Ft3/sec Prel iminary De termination Of Detent ion Pond Volume 2-Year : 5.69 Ft3/sec x (30 Min . x 60 Sec . I 2 ) = 5 ,119 Cubic Feet 5-Year: 6.92 Ft3/sec x (30 Min . x 60 Sec. I 2 ) = 6,224 Cubic Feet 10-Year: 7.76 Ft3/sec x (30 Min . x 60 Sec . I 2 ) = 6,986 Cubic Feet 25-Year: 8.87 Ft3/sec x (30 Min. x 60 Sec . I 2 ) = 7 ,979 Cubic Feet 50-Year: 10.02 Ft3/sec x (30 Min . x 60 Sec. I 2 ) = 9,020 Cubic Feet 100-Year: 10.46 Ft3/sec x (30 Min . x 60 Sec. I 2 ) = 9,417 Cubic Feet 2 Determine Post-Development "Free-Flow" Peak Storm Water Discharge Tributary Area ("A"): 1.66 Acres Pervious Area : 0.95 Acres Impervious Area : 0 .71 Acres Run-Off Coefficient ("Cwt"): 0 .65 Time Of Concentration ("Tic "): 1 O Minutes (Min) Hourly Intensity Rates ("I"): 2-Year: 6.33 5-Year: 7.69 10 -Year: 8.63 25-Year: 9.86 50-Year: 11 .15 100-Year: 11 .64 Peak Discharge Rate ("Q"): 2-Year: 6 .81 5-Year: 8 .28 10-Year: 9.29 25-Year: 10.61 50-Year: 11 .99 100-Year: 12.52 3 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 Flow Into Detention Pond Tributary Area ("A"): 1.88 Acres Pervious Area : 1.06 Acres Impervious Area : 0 .82 Acres Run-Off Coefficient ("Cwt"): 0 .65 Time Of Concentration ("T/c"): 1 O Minutes (Min) Hourly Intensity Rates ("I"): 2-Year: 6.33 5-Year: 7 .69 10-Year: 8.63 25-Year: 9 .86 50-Year: 11 .15 100-Year: 11 .64 Peak Discharge Rate ("Q"): 2-Year: 7 .77 5-Year: 9.44 10-Year: 10.60 25-Year: 12.11 50-Year: 13.68 100-Year: 14.29 4 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 • Pre-Development Inflow Hydrograph Ordinates (Cubic Feet per Second) 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 0.90 1.09 1.22 1.40 1.58 1.65 2 1.79 2.18 2.45 2.79 3.16 3.30 3 2.69 3.27 3.67 4.19 4.74 4.94 4 3.58 4.36 4.89 5.59 6.31 6.59 5 4.48 5.45 6.11 6.98 7.89 8.24 6 5.37 6.54 7.34 8.38 9.47 9.89 7 6.27 7.63 8.56 9.77 11.05 11.54 8 7.17 8.71 9.78 11.17 12.63 13.18 9 8.06 9.80 11.00 12.57 14.21 14.83 Peak=> r 10 8.96 10.89 12.23 13.96 15.79 16.48 11 8.51 10.35 11.62 13.27 15.00 15.66 12 8.06 9.80 11.00 12.57 14.21 14.83 13 7.61 9.26 10.39 11.87 13.42 14.01 14 7.17 8.71 9.78 11.17 12.63 13.18 15 6.72 8.17 9.17 10.47 11.84 12.36 16 6.27 7.63 8.56 9.77 11.05 11.54 17 5.82 7.08 7.95 9.08 10.26 10.71 18 5.37 6.54 7.34 8.38 9.47 9.89 19 4.93 5.99 6.72 7.68 8.68 9.06 20 4.48 5.45 6.11 6.98 7.89 8.24 21 4.03 4.90 5.50 6.28 7.10 7.42 22 3.58 4.36 4.89 5.59 6.31 6.59 23 3.14 3.81 4.28 4.89 5.52 5.77 24 2.69 3.27 3.67 4.19 4.74 4.94 25 2.24 2.72 3.06 3.49 3.95 4.12 26 1.79 2.18 2.45 2.79 3.16 3.30 27 1.34 1.63 1.83 2.09 2.37 2.47 28 0.90 1.09 1.22 1.40 1.58 1.65 29 0.45 0.54 0.61 0.70 0.79 0.82 30 0.00 0.00 0.00 0.00 0.00 0.00 5 Post-Development Inflow Hydrograph Ordinates (Cubic Feet per Second) 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 1.46 1.78 2.00 2.28 2.58 2.69 2 2 .93 3 .56 4 .00 4 .57 5.16 5 .39 3 4.39 5.34 6.00 6.85 7 .74 8 .08 4 5 .86 7.12 8.00 9 .13 10.32 10.78 5 7 .32 8.90 9 .99 11.41 12 .90 13.47 6 8.79 10 .69 11 .99 13 .70 15.48 16 .17 7 10.25 12.47 13 .99 15 .98 18.06 18.86 8 11.72 14 .25 15 .99 18.26 20 .65 21 .56 9 13.18 16.03 17 .99 20.55 23 .23 24 .25 Peak=> 10 14.65 17.81 19 .99 22.83 25.81 26.94 11 13.91 16 .92 18.99 21 .69 24 .52 25 .60 12 13 .18 16 .03 17 .99 20 .55 23 .23 24 .25 13 12.45 15 .14 16.99 19.40 21 .94 22 .90 14 11 .72 14 .25 15 .99 18.26 20.65 21 .56 15 10.98 13 .36 14 .99 17 .12 19 .36 20 .21 16 10.25 12.47 13 .99 15 .98 18.06 18 .86 17 9.52 11 .58 12 .99 14.84 16 .77 17.51 18 8.79 10.69 11 .99 13.70 15.48 16 .17 19 8.06 9 .79 10 .99 12.56 14.19 14.82 20 7.32 8.90 9 .99 11.41 12 .90 13.47 21 6.59 8.01 9 .00 10 .27 11 .61 12 .13 22 5.86 7.12 8.00 9 .13 10 .32 10.78 23 5 .13 6.23 7 .00 7.99 9 .03 9.43 24 4.39 5.34 6.00 6 .85 7.74 8.08 25 3 .66 4.45 5.00 5 .71 6.45 6.74 26 2.93 3.56 4 .00 4 .57 5 .16 5 .39 27 2.20 2.67 3 .00 3.42 3 .87 4 .04 28 1.46 1.78 2 .00 2.28 2.58 2 .69 29 0.73 0 .89 1.00 1.14 1.29 1.35 30 0 .00 0.00 0 .00 0 .00 0 .00 0.00 6 Post-Development "Free-Flow" Inflow Hydrograph Ordinates (Cubic Feet per Second) 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 0.68 0.83 0.93 1.06 1.20 1.25 2 1.36 1.66 1.86 2.12 2.40 2.50 3 2.04 2.48 2.79 3.18 3.60 3.76 4 2.72 3.31 3.72 4.24 4.80 5.01 5 3.40 4.14 4.64 5.30 6.00 6.26 6 4.08 4.97 5.57 6.37 7.20 7.51 7 4.76 5.79 6.50 7.43 8.39 8.76 8 5.44 6.62 7.43 8.49 9.59 10.02 9 6.13 7.45 8.36 9.55 10.79 11.27 Peak=> c 10: 6.81 8.2$ 9.29 10.61 11.99 12.52 11 6.47 7.86 8.82 10.08 11.39 11.90 12 6.13 7.45 8.36 9.55 10.79 11.27 13 5.79 7.03 7.90 9.02 10.19 10.64 14 5.44 6.62 7.43 8.49 9.59 10.02 15 5.10 6.21 6.97 7.96 8.99 9.39 16 4.76 5.79 6.50 7.43 8.39 8.76 17 4.42 5.38 6.04 6.90 7.80 8.14 18 4.08 4.97 5.57 6.37 7.20 7.51 19 3.74 4.55 5.11 5.83 6.60 6.89 20 3.40 4.14 4.64 5.30 6.00 6.26 21 3.06 3.72 4.18 4.77 5.40 5.63 22 2.72 3.31 3.72 4.24 4.80 5.01 23 2.38 2.90 3.25 3.71 4.20 4.38 24 2.04 2.48 2.79 3.18 3.60 3.76 25 1.70 2.07 2.32 2.65 3.00 3.13 26 1.36 1.66 1.86 2.12 2.40 2.50 27 1.02 1.24 1.39 1.59 1.80 1.88 28 0.68 0.83 0.93 1.06 1.20 1.25 29 0.34 0.41 0.46 0.53 0.60 0.63 30 0.00 0.00 0.00 0.00 0.00 0.00 7 Post-Development Flow Routed Through Detention Pond Inflow Hydrograph Ordinates (Cubic Feet per Second) 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 0.78 0.94 1.06 1.21 1.37 1.43 2 1.55 1.89 2.12 2.42 2.74 2.86 3 2.33 2.83 3.18 3.63 4.11 4.29 4 3.11 3.78 4.24 4.84 5.47 5.72 5 3.88 4.72 5.30 6.05 6.84 7.14 6 4.66 5.67 6.36 7.26 8.21 8.57 7 5.44 6.61 7.42 8.47 9.58 10.00 8 6.21 7.55 8.48 9.68 10.95 11.43 9 6.99 8.50 9.54 10.90 12.32 12.86 Peak=> ' 10 7.77 9.44 10.60 12.11 13.68 14.29 11 7.38 8.97 10.07 11.50 13.00 13.57 12 6.99 8.50 9.54 10.90 12.32 12.86 13 6.60 8.03 9.01 10.29 11.63 12.15 14 6.21 7.55 8.48 9.68 10.95 11.43 15 5.82 7.08 7.95 9.08 10.26 10.72 16 5.44 6.61 7.42 8.47 9.58 10.00 17 5.05 6.14 6.89 7.87 8.90 9.29 18 4.66 5.67 6.36 7.26 8.21 8.57 19 4.27 5.19 5.83 6.66 7.53 7.86 20 3.88 4.72 5.30 6.05 6.84 7.14 21 3.49 4.25 4.77 5.45 6.16 6.43 22 3.11 3.78 4.24 4.84 5.47 5.72 23 2.72 3.31 3.71 4.24 4.79 5.00 24 2.33 2.83 3.18 3.63 4.11 4.29 25 1.94 2.36 2.65 3.03 3.42 3.57 26 1.55 1.89 2.12 2.42 2.74 2.86 27 1.16 1.42 1.59 1.82 2.05 2.14 28 0.78 0.94 1.06 1.21 1.37 1.43 29 0.39 0.47 0.53 0.61 0.68 0.71 30 0.00 0.00 0.00 0.00 0.00 0.00 8 16 .00 14.00 ... Q) Q.. -12 .00 Q) Q) u.. 0,...,, 10.00 ·-"O ..0 c: J 0 8 .00 u 0 ....,, Q) Q) Cl) 6 .00 ()) ... 0 ..c 4 .00 0 V) 0 2.00 0 .00 0 Total Pre-Development Vs. Total Post-Development (No Detention) Peak Discharge Rates 2-Year Storm Even t 5 10 15 20 25 Time (Minutes) ----Pre-Development Hydr ograph ----Tota l Po st-Develo pment Hydrograph ... Q) Q.. -Q) Q) u.. 0,...,, ·-"O ..0 c: J 0 u 0 ....,, Q) Q) (/) ()) ... 0 ..c 0 V) 0 18.00 16.00 14 .00 12 .00 10 .00 8.00 6 .00 4.00 2.00 0 .00 0 Total Pre-Development Vs. Total Post-Development (No Detention) Peak Discharge Rates 5-Year Storm Event 5 10 15 20 25 Time (Minutes) ---Pre-Developm ent Hydrograph ---Post -Develo pment Outfl ow Hydrograph Without Detention 9 30 30 ... Cl> 0... -Cl> Cl> ..... 0 ........ ·-"C ..0 c ::::J 0 () 0 .._, Cl> Cl> Cl) 0) ... 0 .s::. 0 II) a ... Cl> 0... -Cl> Cl> ..... 0 ........ ·-"C ..0 c ::::J 0 () 0 .._, Cl> Cl> (f) 0) ... 0 .s::. 0 II) a 20 .00 18 .00 16 .00 14.00 12.00 10.00 8 .00 6 .00 4 .00 2 .00 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-Development Hydrograph ----Post-Development Outflow Hydrograph Without Detention 25 .00 20 .00 15.00 10.00 5 .00 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-D evelopment Outflow Hydrograph Without Detention 10 30 .00 .... G> 25.00 a.. -G> G> 20 .00 LI.. 0 ....... ·-"O .0 c: :J 0 15.00 u 0 ......, G> G> Cl) O'> 10.00 .... 0 ~ 0 V> 5.00 0 0 .00 0 Total Pre-Development Vs. Total Post -Development (No Detention) Peak Discharge Rates 50-Year Storm Eve nt 5 10 15 20 25 Time (Minutes) 30 ---Pre-Development Hydrograph Post-Development Outflow Hydrograph Without Detention .... G> a.. -G> G> LI.. 0 ....... ·-"O .0 c: :J 0 u 0 ......, G> G> Cl) O'> .... 0 ~ 0 V> 0 30 .00 25.00 20 .00 15.0 0 10 .00 5.0 0 0 .00 0 Total Pre-Development Vs. Total Post-Development (No Detention) Peak Discharge Rates 100-Year Storm Eve nt 5 10 15 20 25 Ti me (Minutes) ---Pre-De v el o pment Hydrograph ----Post-Development Outflow Hydrograph Without Detention 11 30 Detention Pond De th Vs. Volume Elevation Depth Volume (Feet) (Ft3) 295 .00 0.00 0 295 .50 0.50 656 296 .00 1.00 3,462 296 .35 1.35 6 ,887 297.00 2 .00 14,349 297.50 2.50 20,534 Detention Pond Depth Vs. Volume 2.50 2.00 1.50 " -Q) Q) LL. ..... .s::. -a. Q) 0 1.00 0.50 0.00 0 5,000 10 ,000 15 ,000 20 ,000 25 ,000 Detention Pond Volume (Cubic Feet) 12 [ ·s~O/ ~\.t fD~f QA l...i,1 Rating Curve For Outlet Control Structure Pipe Di a . (Inches): De pth Vs . Volume ~\.).. CA.~ ':. '"9f"'rt.d-'. ""th I'> vcu.\ \M.. \l\.<:4. c; Y;).u."\I'\ 3©. ~e.xJ. ~ Pipe Le ngt h Elevat ion Depth Discha rge (Feet ) Ft3/Sec 295 .00 0.00 0 .0 0 295.50 0 .50 1.27 296 .00 1.00 1.79 296 .35 1.35 2.08 297 .00 2.00 2.5 3 297 .50 2.50 2.83 Rating Curve For Outlet Control Structure Deptl Volume 11,-t °'"""'"'; .. , s~ows .f~1's /~~ 4o be. dos~ io '67'? :f s }~~ slof't! t>f i~ pipe cXf'~sseJ. ei",Y ""4'K i~ +L~se CPi1'.~lc..~io111i 2 .50 ----~---~---~---~---~--~ 2.00 -+------+-----+-----+---- .£: 0.. Q> Cl l .00 -+------+-----t----+----l--t------1-------i 0 .00 0 .50 l .00 l.50 2 .00 2 .50 3 .00 Dis charge (Cubic Feet Per Second) 13 I Storage Indication Curve Depth Storage Discharge 2s/t 2s/t+O (Feet) (Ft3} (Ft3/Sec) (Ft3/Sec) (Ft3/Sec) 0.00 0 0.00 0.00 0.00 0.50 656 1.27 21.87 23.13 1.00 3,462 1.79 115.40 117.19 1.35 6 ,887 2.08 229 .57 231 .65 2 .00 14 ,349 2.53 478 .30 480.83 2.50 20 ,534 2.83 684.47 687.30 Storage Indication Curve 3.00 2.50 ....... "O c 0 2.00 0 Cl> (/) -Cl> Q.. -Cl> Cl> LL. 1.50 0 :.0 ::I u ....., Cl> O> -0 1.00 .t: 0 VI 0 0 .50 0.00 0.00 100 .00 200 .00 300 .00 400 .00 500 .00 600.00 700 .00 2s/t+O (Cubic Feet Per Second) 14 Inflow I Outflow Simulation 2-Y ear Storm Event Time Inflow 11+ 12 2s/t-0 2s l t+O Outf low De pt h Elev at ion (M inutes) (Ft3/Sec) (Ft3/Sec) (Fe et) 0 0 .00 0.00 0.0 0 0.0 0 0.00 0 .00 295.00 1 0 .78 0 .78 0 .69 0 .7 8 0.04 0 .00 295 .00 2 1.55 2 .33 2.69 3 .02 0.1 7 0 .0 1 295 .01 3 2 .33 3 .88 5 .85 6.57 0 .36 0.04 295 .04 4 3 .11 5.44 10.05 11 .29 0 .62 0.12 295 .12 5 3 .88 6 .99 15.18 17.04 0.93 0 .27 295 .27 6 4 .66 8.54 21 .18 23 .72 1.27 0 .50 295.50 7 5.44 10.10 28 .65 31 .27 1.31 0.54 295 .54 8 6 .21 11 .65 37.57 40 .3 0 1.36 0 .58 295 .58 9 6 .99 13 .20 47 .93 50 .7 8 1.42 0.63 295 .63 10 7 .77 14 .76 59 .71 62.69 1.49 0 .69 295 .69 11 7 .38 15.14 71 .75 74 .86 1.56 0.75 295 .75 12 6 .99 14 .37 82 .88 86 .12 1.62 0.82 295.82 13 6 .60 13 .59 93 .12 96.47 1.68 0 .88 295.8 8 14 6 .21 12 .81 102.47 105.93 1.73 0 .93 295.93 15 5 .82 12 .04 110.96 114.5 1 1.78 0 .98 295 .98 16 5.44 1 1.26 118 .61 122 .22 1.80 1.01 296.0 1 17 5 .05 10.48 125.45 129 .10 1.82 1.03 296 .03 18 4 .66 9.71 131.48 135.16 1.84 1.05 296 .05 19 4.27 8 .93 136.7 1 140.42 1.85 1.07 296 .07 20 3.88 8.15 141 .14 144 .87 1.86 1.08 296.08 21 3.49 7 .38 144.78 148 .52 1.87 1.09 296 .0 9 22 3 .11 6 .60 147.62 151.38 1.88 1.1 0 296 .10 23 2 .72 5 .82 149.68 153.45 1.88 1.11 296.11 24 2 .33 5.05 150.96 154 .73 1.89 1.11 296 .11 25 1.94 4 .27 151.45 155.23 1 .89 1.1 1 296.11 26 1.55 3.49 151.17 154.95 1 .89 1.11 296 .11 27 1.16 2 .72 150.12 153 .89 1.88 1.11 296 .11 28 0 .78 1.94 148.30 152.06 1.88 1.10 296 .10 29 0 .39 1.16 145.72 149.47 1.87 1.09 296 .0 9 30 0 .00 0 .39 142.38 146.11 1.87 1.08 296 .08 15 Inflow/Outflow Simulation 2-Year Storm Event 16.00 14 .00 I ' I . ' I ' I ' I ' 12 .00 I ' . ' ' I ....... "O c ' I ' 0 I ' 0 10 .00 Cl) • .. (/) I ' -Cl) I ' Q., -Cl) Cl) 8 .00 LA.. 0 :.0 ::J () .._, ~ 6.00 0 E ::J 0 4 .00 2 .00 I ~ ' . ' I ' . /,. ~ ' I ' j ' I ' ' "' ' ' I ' '-" • /,/ ' ~-,~ ' ..... I -,, ' I ' I ' I I I ''· "" ' ·)' ...... '~ ' ~ I ' • ... I ' I ', I'\. ' r · I ·,~ '/ , -, ' -, . ' ' 0.00 0 5 10 15 20 25 30 Time (Minutes) Pre-----Post-Post --• -• -· Post - De ve lopme De velopme Developme Developme nt nt Outflow nt O utfl ow nt "Fr ee- Hydrograph Hydrograph Wit h Flow" Without Det ent ion Detenti o n 16 Inflow I Outflow Simulation 5-Year Storm Event Time Inflow 11+ 12 2s/t -0 2s/t+O Outflow Depth Elevation (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) 0 0 .00 0 .00 0.00 0 .00 0.00 0 .00 295 .00 1 0 .94 0.94 0.84 0 .94 0 .05 0 .00 295 .00 2 1.89 2.83 3.27 3 .67 0.20 0 .01 295 .01 3 2 .83 4 .72 7 .12 7 .99 0.44 0 .06 295.06 4 3 .78 6.61 12.22 13.73 0.75 0 .18 295 .18 5 4 .72 8.50 18.45 20 .72 1.14 0.40 295.40 6 5 .67 10.39 26.24 28 .84 1.30 0 .53 295 .53 7 6 .61 12.28 35.81 38 .52 1.35 0 .57 295 .57 8 7 .55 14.17 47 .15 49 .98 1.42 0 .63 295 .63 9 8.50 16.05 60 .22 63 .20 1.49 0 .69 295.69 10 9.44 17.94 75 .01 78 .16 1 .57 0 .77 295 .77 11 8 .97 18.42 90 .11 93.43 1.66 0 .86 295 .86 12 8 .50 17.47 104.11 107.58 1.74 0 .94 295 .94 13 8.03 16.53 117.03 120.63 1.80 1.01 296.01 14 7 .55 15.58 128.95 132 .61 1.83 1.04 296 .04 15 7 .08 14 .64 139 .87 143 .59 1 .86 1.08 296.08 16 6 .61 13.69 149 .80 153.56 1.88 1.11 296 .11 17 6 .14 12.75 158 .73 162 .54 1 .91 1.13 296 .13 18 5 .67 11 .80 166.68 170.54 1.93 1.16 296.16 19 5 .19 10.86 173.65 177.54 1.94 1.18 296.18 20 4 .72 9 .92 179.65 183.57 1.96 1.20 296.20 21 4 .25 8.97 184.67 188.62 1.97 1.21 296.21 22 3 .78 8.03 188.73 192 .70 1.98 1.23 296 .23 23 3 .31 7 .08 191 .83 195.82 1.99 1.23 296 .23 24 2 .83 6.14 193.98 197.97 2 .00 1.24 296 .24 25 2.36 5 .19 195.17 199.17 2 .00 1 .25 296.25 26 1.89 4 .25 195.42 199.42 2 .00 1.25 296 .25 27 1.42 3 .31 194.73 198.73 2 .00 1.24 296 .24 28 0 .94 2.36 193.10 197.09 1 .99 1.24 296 .24 29 0.47 1.42 190.54 194.52 1.99 1.23 296 .23 30 0 .00 0.47 187.06 191.02 1.98 1.22 296 .22 17 Inflow/Outflow Simulation 5-Year Storm Event 18.00 j~ • ' ' • ' 16.00 . - • ' • -• ' . ' 14 .00 I ' ' • ' I ' " "O 12.00 c 0 0 I " • ' I ' Q) (/) -Q) a.. 10 .00 -Q) Q) u.. 0 :0 8 .00 ::J () ....., ~ 0 = 6 .00 ::J 0 4 .00 2 .00 I ' I J ~ ' ; ' I ~ .. • " ' • ' • ' ' / ......... . ' . ~ " I ' . ' ' • ' ' ' ' I ' ' ' ' I ' I , ' ' "' I , ' ' , ' .··I , ' ~ ' ' ' ' ' , " , ' ' ~ ·// "·"~ " , " , I ~\ ' I ' ' ' I~ "·\( -'' ' ', ' '', 0.00 0 5 10 15 20 25 30 Time (Minutes) Pre-Post-Post -............ Post- Developme Developme Deve lopme Developme nt nt Outflow nt Outflow nt "Free- Hydrograph Hyd rograph With Flow" Wi t hout Detention Detention 18 Inflow I Outflow Simulation 10-Year Storm Event Time Inflow 11+ 12 2s/t-0 2s/t+O Outflow Depth Elevation (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) 0 0.00 0 .00 0.00 0 .00 0.00 0 .00 295 .00 1 1.06 1.06 0.94 1.06 0 .06 0.00 295.00 2 2 .12 3 .18 3.67 4 .12 0.23 0 .02 295.02 3 3 .18 5 .30 7.99 8 .97 0.49 0 .08 295.08 4 4.24 7.42 13.72 15.41 0.84 0 .22 295 .22 5 5.30 9 .54 20.73 23.26 1.27 0 .50 295.50 6 6.36 11 .66 29 .75 32 .38 1.32 0 .54 295.54 7 7.42 13.78 40 .77 43.53 1.38 0.59 295.59 8 8.48 15.90 53.76 56 .67 1.45 0 .66 295.66 9 9 .54 18.02 68 .70 71 .78 1.54 0.74 295 .74 10 10.60 20.14 85.57 88 .84 1.63 0.83 295 .83 11 10.07 20.67 102.78 106.24 1.73 0.93 295.93 12 9 .54 19.61 118.78 122.39 1.81 1.01 296 .01 13 9 .01 18.55 133.64 137.33 1.84 1.06 296 .06 14 8.48 17.49 147.38 151 .13 1.88 1.10 296.10 15 7 .95 16.43 159.99 163.81 1.91 1 .14 296.14 16 7.42 15.37 171.48 175.36 1.94 1.17 296.17 17 6.89 14.31 181 .86 185.79 1.97 1.20 296 .20 18 6.36 13.25 191.13 195.10 1.99 1 .23 296.23 19 5 .83 12 .19 199 .30 203 .32 2.01 1.26 296 .26 20 5.30 11 .13 206.37 210.43 2 .03 1.28 296 .28 21 4.77 10.07 212 .35 216.44 2.04 1.30 296 .30 22 4 .24 9.01 217.25 221 .36 2 .06 1.32 296 .32 23 3 .71 7 .95 221 .07 225 .20 2.07 1.33 296 .33 24 3 .18 6.89 223 .81 227 .96 2 .07 1.34 296 .34 25 2 .65 5 .83 225.49 229 .64 2.08 1.34 296.34 26 2 .12 4.77 226 .10 230 .26 2 .08 1.35 296 .35 27 1.59 3 .71 225 .66 229 .81 2 .08 1.34 296 .34 28 1.06 2.65 224 .16 228.31 2.07 1.34 296.34 29 0.53 1.59 221 .62 225 .75 2.07 1.33 296.33 30 0 .00 0.53 218.03 222 .15 2 .06 1.32 296 .32 19 Inflow/Outflow Simulation 10-Year Storm Event 20 .00 I ' I ... I ' 18.00 .. - '\ I '\ I '\ 16 .00 I ' • ' I '\ I • ....... 14 .00 "O c: 0 I ' I '\ I ... 0 I '\ Q) (/) 12.00 .... Q) 0.. -Q) Q) 10 .00 ...... 0 :a :::> u ........ 8 .00 ?; 0 E :::> 0 6 .00 4.00 I .. I I ~ '\ I ' I '\ '\ I "\ ' I ' I . ' "" '\ . ' ' I . ' . ' . ' /../ ' ' ··."~ I ' ' ' ' I " '\ I . .. // . ' -~" . ' . ' . ' ' ', ' ' !/ ' ',,,"' '\ : '\ ' "\ I ' . ', I I/ .. , ', " ' ',' 2 .00 0 .00 0 5 10 15 20 25 30 Time (Minutes) Pre-----Post -Post ---------Post- Developm e Developm e Develo pme Devel o p m e nt nt O utfl ow nt Outflow nt "Fr ee- Hydrog ra ph Hyd ro graph Wit h Fl ow" Without Det e ntion Detention 20 Inf low I Outflow Simulation 25-Y ear Storm Ev ent Time Inflow 11+ 12 2s/t-0 2s /t+O Outflo w Depth Elevation (Minutes) (Ft 3/Sec) (Ft3/Sec) (Feet ) 0 0 .00 0 .00 0.00 0 .00 0 .0 0 0 .00 295 .00 1 1.21 1.21 1.08 1.21 0 .07 0 .00 295 .00 2 2.42 3.63 4 .19 4.7 1 0 .26 0 .02 295.02 3 3 .63 6 .05 9.12 10.25 0 .56 0 .10 295 .10 4 4 .84 8.47 15.67 17.60 0 .96 0.29 295.29 5 6.05 10.90 23 .99 26 .57 1.29 0 .52 295 .52 6 7 .26 13.32 34 .62 37.31 1.35 0 .56 295 .56 7 8.47 15.74 47 .52 50 .36 1.42 0 .63 295 .63 8 9.68 18.16 62.67 65.68 1.50 0.7 0 295 .70 9 10.90 20 .58 80 .04 83.25 1.60 0.8 0 295 .80 10 12.11 23 .00 99 .62 103 .04 1.71 0.91 295 .9 1 11 11 .50 23 .61 119 .61 123 .23 1.81 1.02 296 .0 2 12 10.90 22.40 138.30 142.01 1.85 1.07 296 .07 13 10.29 21 .19 155.68 159.48 1 .90 1.12 296.12 14 9 .68 19 .97 171.78 175.66 1.94 1.17 296.17 15 9.08 18.76 186.59 190.54 1 .98 1.22 296 .22 16 8.47 17.55 200 .12 204 .14 2 .01 1.26 296 .26 17 7 .87 16.34 212 .37 216.46 2 .04 1.30 296 .3 0 18 7 .26 15 .13 223 .36 227.51 2 .07 1.34 296 .34 19 6.66 13 .92 233 .10 237 .28 2 .09 1.36 296 .36 20 6.05 12 .7 1 241 .60 245 .81 2.1 1 1.38 296 .3 8 21 5.45 11.50 248.86 253 .10 2.12 1.40 296.4 0 22 4 .84 10 .29 254 .88 259 .15 2.13 1.42 296.42 23 4 .24 9.08 259.68 263 .96 2 .14 1.43 296.43 24 3 .63 7 .87 263 .25 267 .55 2 .15 1.44 296.44 25 3 .03 6 .66 265 .61 269 .91 2 .15 1.44 296.44 26 2 .4 2 5.45 266 .75 271 .06 2 .15 1.44 296.44 27 1.82 4 .24 266 .68 270 .99 2 .15 1.44 296.44 28 1.21 3.03 2 65.41 269 .71 2 .15 1.44 296.44 29 0 .61 1.82 262.93 267 .22 2 .15 1.44 296.44 30 0 .00 0 .61 259 .25 263 .53 2 .14 1.43 296.43 21 :c-c 0 0 Q) 25 .00 20 .00 Cl') 15 .00 ~ 0... -; Q) LL. 0 :0 ::J u ; 10.00 0 :E ::J 0 5.00 0.00 Inflow/Outflow Simulation 25-Year Storm Event I I I I I I I 0 5 Pre----- Developme nt Hydrograph I I I I ' 10 ' ... ' ' ' ' ' ' 15 20 Time (Minutes) Post-Post- Developme Deve lopme nt Outflow nt O utfl ow Hydrograph With Without Detention Detention 22 25 -------- 30 Post- Developme nt "Fr ee- Flow" Inflow I Outflow Simulation 50-Year Storm Event Time Inflow 11+ 12 2s/t-0 2s!t+O Outflow Depth Elevation (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) 0 0.00 0 .00 0.00 0 .00 0 .00 0 .00 295.00 1.37 1.37 1.22 1.37 0 .07 0 .00 295.00 2 2 .74 4 .11 4.74 5 .32 0.29 0 .03 295 .03 3 4 .11 6.84 10.31 11 .58 0.63 0 .13 295.13 4 5.47 9 .58 17.71 19 .89 1.09 0 .37 295 .37 5 6.84 12.32 27.42 30 .03 1.31 0 .53 295.53 6 8.21 15.05 39.72 42.47 1.37 0.59 295 .59 7 9.58 17.79 54 .60 57.51 1.46 0.66 295.66 8 10.95 20.53 72.01 75 .12 1.56 0.76 295.76 9 12.32 23 .26 91 .93 95 .27 1.67 0 .87 295.87 10 13.68 26.00 114.35 117.94 1.79 1.00 296.00 11 13.00 26 .69 137.33 141.03 1.85 1.07 296 .07 12 12.32 25.32 158.83 162 .65 1.91 1.13 296.13 13 11 .63 23.95 178.86 182.78 1.96 1.19 296 .19 14 10.95 22 .58 197.43 201.44 2.01 1.25 296 .25 15 10.26 21 .21 214 .55 218 .64 2 .05 1.31 296.31 16 9.58 19.84 230 .22 234.39 2.09 1.36 296 .36 17 8.90 18.47 244.46 248.69 2.11 1.39 296.39 18 8.21 17.11 257 .30 261.57 2.14 1.42 296.42 19 7 .53 15.74 268 .72 273 .04 2 .16 1.45 296.45 20 6.84 14.37 278 .74 283 .09 2.18 1.47 296.47 21 6.16 13.00 287.36 291 .74 2.19 1.50 296 .50 22 5.47 11 .63 294 .58 298 .99 2.20 1.51 296 .51 23 4 .79 10.26 300.42 304.85 2 .21 1 .53 296 .53 24 4 .11 8.90 304.87 309 .31 2 .22 1.54 296 .54 25 3.42 7 .53 307.94 312 .39 2 .23 1.55 296 .55 26 2.74 6.16 309 .63 314 .09 2.23 1.55 296.55 27 2 .05 4.79 309.96 314.42 2.23 1 .55 296.55 28 1.37 3.42 308 .92 313 .38 2.23 1.55 296 .55 29 0 .68 2 .05 306 .52 310 .97 2.23 1.54 296.54 30 0 .00 0 .68 302 .76 307.20 2 .22 1.53 296 .53 23 30.00 25.00 ....... -g 20 .00 0 0 Q) (/) Q; Q.. Qi .2 15.00 0 :0 ::> u ....... ~ 0 ~ 10.00 0 5.00 0 .00 Inflow/Outflow Simulation 50-Year Storm Event ' ' I ' • ' I ' I ' I ... I I ' I ' I ' 0 5 10 15 20 25 30 nme (Minutes) Pre----. Post-Post---------Post- Developme Developme Developme Developme nt nt Outflow nt Outflow nt 'Free- Hydrograph Hydrograph With Flow ' Without Detention Detention 24 Inflow I Outflow Simulation 100-Year Storm Event Time Inflow 11+ 12 2s/t-O 2s/t+O Outflow Depth Elevation (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) 0 0.00 0.00 0.00 0 .00 0 .00 0.00 295 .00 1.43 1.43 1.27 1.43 0.08 0 .00 295 .00 2 2 .86 4 .29 4 .95 5 .56 0 .30 0.03 295 .03 3 4 .29 7.14 10.77 12.09 0.66 0.14 295 .14 4 5 .72 10.00 18.50 20 .77 1.14 0.40 295.40 5 7 .14 12.86 28 .73 31 .36 1.31 0 .54 295 .54 6 8.57 15.72 41 .67 44.45 1.39 0 .60 295 .60 7 10.00 18.57 57 .30 60.25 1.47 0 .68 295.68 8 11.43 21.43 75 .58 78 .73 1.58 0 .77 295.77 9 12.86 24 .29 96.48 99 .87 1.70 0 .90 295 .90 10 14.29 27 .15 120 .01 123.63 1.81 1.02 296 .02 11 13.57 27 .86 144 .13 147.87 1.87 1.09 296 .09 12 12.86 26.43 166 .71 170.57 1.93 1.16 296 .16 13 12.15 25 .00 187.75 191 .72 1.98 1.22 296 .22 14 11.43 23 .58 207.27 211 .33 2 .03 1.28 296 .28 15 10.72 22.15 225 .26 229.42 2 .08 1.34 296.34 16 10.00 20.72 241 .77 245 .98 2 .11 1.38 296 .38 17 9 .29 19.29 256 .78 261 .05 2 .14 1.42 296.42 18 8.57 17.86 270 .32 274 .64 2.16 1.45 296.45 19 7 .86 16.43 282 .39 286.76 2 .18 1.48 296.48 20 7 .14 15.00 292 .99 297 .39 2 .20 1.51 296 .51 21 6.43 13.57 302 .13 306.57 2.22 1.53 296 .53 22 5.72 12 .15 309 .81 314 .27 2 .23 1.55 296 .55 23 5 .00 10.72 316 .04 320 .53 2 .24 1.57 296 .57 24 4 .29 9.29 320.82 325.33 2 .25 1.58 296.58 25 3 .57 7 .86 324 .17 328 .68 2 .26 1.59 296 .59 26 2 .86 6.43 326.07 330 .60 2.26 1.59 296 .59 27 2 .14 5.00 326.55 331 .07 2 .26 1.59 296.59 28 1.43 3 .57 325 .60 330.12 2 .26 1.59 296 .59 29 0.71 2.14 323 .23 327 .74 2.26 1.59 296.59 30 0 .00 0.71 319.45 323 .95 2 .25 1.58 296.58 25 30 .00 25 .00 £}' c: 20 .00 0 0 (J) (I) Qi 0.. -(J) :i!. 15 .00 0 :.0 :J u -?; 0 ~ 10 .00 0 5.00 0 .00 Inflow /Outflow Simulation 100-Year Storm Event I I I I • I I 0 5 Pre----- Developme nt Hydrograph I ' ... • 10 " ... ... " " " " 15 " " " " ... 20 Time (Minutes) Post-Post- Developme Developme nt Outflow nt Outflow Hydrograph With Without Detention Detention 26 25 30 .... -... Post- Developme nt "Free- Flow " Inflow/Outflow Simulation 2-Year Storm Event 9 .00 8 .00 7 .00 B 6 .00 c 0 0 Cl> (I) ... Cl> 5 .00 Q.. -Cl> Cl> LL. 0 :0 ::::J 4.00 (.) -~ 0 E ::::J 0 3 .00 2 .00 1.00 0 .00 0 5 10 15 20 25 30 Time (Minutes) ---Pre -Development Hydrograph ----Tota l Post-Development Hydrograph 27 Inflow/Outflow Simulation 5-Year Storm Event 12 .00 ------,--------,,------,...--.r~----~~-----~~~---~-i 10 .00 0 ........ 8.00 "O c 0 0 Cl> Cl) .... Cl> Q.. -Cl> Cl> 6 .00 u.. 0 :0 j () ......, 3'; c:}.,\'\\.~ 0 E ~~~~I j 0 4.00 ~~""''j ~. ~c.P~ ~ 2.00 0.00 0 5 10 15 20 25 30 Time (Minutes) ---Pre-Development Hydrograph ---Total Post-Deve lopment Hydr ograph 28 Inflow/Outflow Simulation 10-Year Storm Event 14 .00 12 .00 10 .00 ....... "O c 0 0 CJ) (/) ... 8 .00 CJ) Q.. -CJ) CJ) u.. 0 :.0 :::J u 6.00 ........ :: 0 E :::J 0 4.00 2 .00 0.00 0 5 10 15 20 25 30 Time (Minutes) Pre-Development Hydr ograph ----Total Post-Development Hydrograph 29 Inflow/Outflow Simulation 25-Year Storm Event 10 .00 "'"" "O c 0 0 Q) V'> ... 8 .00 Q) Q.. -Q) Q) LA- 0 :.0 ::> u 6 .00 -~ 0 E ::> 0 4 .00 0 5 10 15 20 25 30 Time (Minutes) ----Pre-Development Hydrograph ----Total Post-Development Hydrograph 30 Inflow/Outflow Simulation 50-Year Storm Event 16 .00 14.00 12 .00 ...... "O c 0 10 .00 0 Q) (f) ... Q) 0.... -Q) Q) 8 .00 u.. 0 :0 ::::J () -~ 0 6 .00 E ::::J 0 4 .00 2 .00 0 .00 0 5 10 15 20 25 30 Time (Minutes) ---Pr e-Developm e nt Hyd rogra p h ----Tot a l Post-Develo pme nt Hyd ro g raph 31 Inflow/Outflow Simulation 100-Year Storm Event 18.00 16 .00 14 .00 ....... 12.00 "O c 0 0 Cl> (/) ... Cl> 10.00 n. -Cl> Cl> LL. 0 :.0 8 .00 ::> u ........ ~ 0 :E ::> 0 6 .00 4 .00 2.00 0.00 0 5 10 15 20 25 30 Time (Minutes) ---Pre-Development Hydrograph ----To t a l Post-Development Hydrograph 32 Detention Pond Storage Volumes as Percent of Maxim um Volume 100% 90% 80% 70% Q) E :J 0 60% > E :J E ')( 50% 0 ::E -0 -40% c Q) 0 ... Q) Q.. 30% 20% 10% 0% 2-year 5-year 10-year 25-year 50-year 100 -year Desi gn Sto rm Storm Simulati on Synop s is 2-ear 5-ear 10-ear 25-ear 100-ear Storm Depth 1.11 1.25 1.35 1.44 1.59 Stor m Elevation 296.11 296 .25 296 .35 296.44 296 .59 Storm Volume 4543 5871 6842 7970 9204 9689 Maximum Capacity 20534 20534 20534 20534 20534 20534 Percent of Capacity 22 % 29 % 33 % 39 % 45 % 47% 33