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HomeMy WebLinkAbout100 Development Permit 457 A Brittan Court AdditionDRAINAGE COMPUTATIONS for A Replat of Block 2 REGENCY SOUTH College Station, Brazos County, Texas Prepa r ed for: E. Douglas & Carolyn Bri 236 Highway 46 West Boerne , Texas 78006 -811 Prepa r ed bv: Garrett Engineering APPROVED FOR ain ~AP 1 7 1997 CONSTR CTIOfi 4444 Carter Creek Parkway -Suite 108 Bryan, Texas 77802 Telephone : (409) 846-2688 * March, 1997* DRAINAGE COMPUTATIONS for A Rep lat Of Block 2 Regency South College Station, Brazos County, Texas *Rev ised March, 1997 * SUMMARY The total drainage area tributary to the project is 2 .82 acres . The pre-development nm-off coefficient was estimated to be 0.40 , while taking into account typical duplex site improvements would result in a post- development weighted run-off coefficient of0.60 . / A detention facility will be constructed in the southwest corner of the property in keeping with the existing contours and as designated on the plat. The detention pond is designed to facilitate up to and including the 100-year stom1 event, and discharge at a rate less than the current 100-year pre- development peak discharge rate. The detention pond will intercept, store and meter run-off from 2 .08 acres (Cwt= 0 .60) of the project . The run-off generated on the remaining 0 .74 acres (Cwt= 0 .60) will "free-flow" across the project site unmetered across the city park to Bee Creek. These report calculations are summarized according to the following methodology . Beginning on page 1, based on the total tributary drainage area of the project (being estimated at 2,82 acres), the pre- development run-off coefficient (being assumed at 0 .40), and a minimum time of concentration of 10 minutes, the relative pre-development peak discharge rate ("Q") was determined. The Rational Method was utilized to compute the estimated peak pre-development discharge rates . The equation that represents the Rational Method is as follows : Q = CIA "Q" is the peak discharge rate in cubic feet per second, "C" is the run-off coefficient, assumed to be 0.40 in the pre-development condition, "I" is the storm intensity in inches per hour, and "A" is the area of the drainage basin in acres. Computations on page 2 are based on the tributary area of 2 .82 acres, the post-development run-off coefficient of 0 .60 (being weighted according to the relative amounts of pervious and impervious surface area), a minimwn time of concentration of 10 minutes to yield the relative pre-development peak discharge rate ("Q") (asswning the sanle minimum time of concentration of 10 minutes). The Rational Method was again utilized to compute the estimated peak post-development discharge rates . The equation that represents the Rational Method is as follows : Q = CIA, where ; "Q" is the peak discharge rate in cubic feet per second. The "C" variable is the run-off coefficient. (In the post-development condition "C" is assumed to be 0 .60.) "I" represents the rainfall intensity in inches per hour, and similarly "A" is the area of the basin in acres . Comparison of the peak pre-development discharge rate to the post-development discharge rate is included in the report to aid the designer in establishing a preliminary "target" of detention volume required. This prelintinary estimate is determined as the volume difference generated between the pre- development and post-development hydrographs . (See pages 9-11 for pre-development and post- development hydrographs.) Please note that the post-development hydrograph shown on these same graphs asswnes no detention and reflects the "worst-case" scenario that all run-off is allowed to free-flow . Pages 3 and 4 provide information concerning the post-development run-off that is not routed through the detention facility ("free-flow") as well as the post-development run-off that is routed through the detention facility and retained on site . Page 5 and page 6 are tabulations of the pre-development and the post-development hydrographs based on the computations performed on page I and page 2 . The post-development hydrograph assumes no detention to facilitate direct comparison in the pre-and post-development conditions. Page 7 and page 8 are tabulations of the post-development hydrograph for run-off directed through the detention facility and the post-development hydrograph for "free-flow" from the project site. Computations on page 4 determine the actual peak post-development "inflow" rate supplied to the proposed detention facility . From this "inflow" rate and the time of concentration (10 minutes minimum), a hydrograph as tabulated on page 8 is derived. The hydrograph is triangular in shape and is based on the standard SCS unit hydrograph with time to peak set equal to the time of concentration and the total time base set at 3 .00 tin1es the time of concentration . Please note that a 30 minute total storm event duration was utilized exclusively throughout this report due to the relative small size of the project. Having derived the preliminary v olume requirements and "allowable peak" discharge rate, it is now possible to design the final detention facili ty and outlet control structure. Page 12 presents a data tabulation and a depth versus v olume graph of the detention facility . The max imum depth of the pond was set at 3.15 feet . (With the top of berm elevation at 263 .50 ft . less flow line "out" of outlet control structure at 260.35 ft .: 263 .50' -260 .3 5' = 3.15' ). Page 13 supplies a tabulation and a rating curve for the proposed outlet control structure. A 15" diameter R.C .P . was chosen as the outlet "metering" device due to depth verses discharge ratio characteristics associated wi th the anticipated shallow headwate r depth as well as ease of installation . An ultimate storage depth of 3.15 feet is available due to the physical geometry of the pond. However, at 100-year storm conditions, depths of less than 3 .15 feet are anticipated. "H" is the headwater depth in feet and ranges from 0 ft . to a maximum of 3.15 ft .(This includes required 0 .50 foot free-board) Page 14 presents a tabulation of the relationship between discharge from the detention facility and the dimensionless quantity 2S/t-O. Also presented is a Storage Indication Curve for the detention facility based on the aforementioned phy sical characteristics of the detention pond, storage volume, inflow hydrograph, and rating curve for the outlet structure. The storage indication curve as shown on page 12 is a graphical solution to the equation presented as follows : 2s 1 (I l + 12) + (----------------01) dt 2s2 (-----------------+ 02) dt Page 15 through page 26 present simulations of the 2 , 5, 10 , 25 , 50, and 100 year storm events. The first page of each storm simulation represents the tabulated data for the storm event. The maximum depth achieved in the detention pond during each simulation is shown below as is the time at during which this maximwn depth occurs from the onset of tlle storm event. The calculated peak discharge rate corresponding to this depth over same period is also shown below . Additionally , the maximum water surface elevation achieved during each event and the maximum peak discharge during each event are listed below . The second page of each storm simulation represents the pre-development hydrograph, the post-deve lopment hydrograph (wi th no detention), the post-development hydrograph as routed through the detention pond, and post-aevelopiiient "free-flow" hydrograph for each storm event. 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 eve nts . It can be detennined from these same hydrographs that the post-development peak discharge rates have been minutely decreased from thos e peak pre- deve lopment discharge rates due to the incorporation of the detention facility in the post-deve lopment condition . Total post-development peak discharge rates for the 2, 5, 10 , 25 , 50 ,and 100-year storm from the detention pond outlet control structure and project site are kept at or less than the pre-deve lopment peak discharge rates due to the incorporation of the proposed detention faciliti es. Subsequent peak post- development discharge vel ocities are projected to be within manageable limits . Determine Total Pre-Development Peak Storm Water Discharge Rates Tributary Area ("A"): 2.82 Acres Pervious Area : 2.82 Acres Impervious Area : 0.00 Acres Run-Off Coefficient ("Cwt"): 0.40 Time Of Concentration ("T/c"): Woodlands: Low Elevation : High Elevation : Distance (Feet): Slope (%Grade): Velocity ("Vw "): Time : Pastures: Low Elevation: High Elevation : Distance (Feet): Slope (%Grade): Velocity ("Vp"): Time : Pavements: Low Elevation : High Elevation: Distance (Feet): Slope (%Grade): Velocity ("Vpave"): Time : Total Travel Time: Hourly Intensity Rates ("I"): 2-Year: 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: 7.14 5-Year: 8.68 10-Year: 9.74 25-Year: 11 .12 50-Year: 12.57 100-Year: 13 .13 1 c = 0.40 C= 0.98 0.00 0.00 0.00 0.00 0.00 Feet I Second 0.00 Minutes 0.00 0.00 0.00 0.00 0.00 Feet I Second 0.00 Minutes 0.00 0.00 0.00 0.00 0.00 Feet I Second 0.00 Minutes 10 .00 Minutes Inches I Hour Inches I Hour Inches I Hour Inches I Hour Inches I Hour Inches I Hour Cubic Feet I Second Cubic Feet I Second Cubic Feet I Second Cubic Feet /Second / Cubic Feet I Second Cubic Feet I Second Determine Post-development Peak Storm Water Discharge (No Detention) Tributary Area ("A"): 2 .82 Acres Run-Off Coefficient ("Cwt"): 0.60 Time Of Concentration ("T/c "): 10 Minutes (Min) Hourly Intensity Rates ("I "): 2-Year: 6.33 Inches I Hour 5-Year : 7.69 Inches I Hour 10-Year: 8.63 Inches I Hour 25-Year: 9.86 Inches I Hour 50-Year: 11.15 Inches I Hour 100-Year: 11 .64 Inches I Hour Peak Discharge Rate ("Q "): 2-Year : 10.70 Cubic Feet I Second 5-Year : 13.02 Cubic Feet I Second 10-Year: 14.61 Cubic Feet I Second 25 -Year : 16.69 Cubic Feet I Second 50-Year: 18 .86 Cubic Feet I Second I 100-Year : 19.69 Cubic Feet I Second Comparison Of Predevelopment And Post-development Peak Discharge Rates Predevelopment Post-Development Increase 2-Year: 7 .14 Ft3 /sec 10.70 Ft3/sec 3 .57 Ft3/sec 5-Year: 8.68 Ft3 /se c 13.02 Ft3/sec 4.34 Ft3/sec 10-Year : 9.74 Ft3 /sec 14 .61 Ft3 /sec 4 .87 Ft3/sec 25-Year: 11 .12 Ft3 /sec 16 .69 Ft3 /sec 5.56 Ft3/sec 50-Year: 12 .57 Ft3 /sec 18.86 Ft3/sec 6.29 Ft3/sec 100-Year: 13 .13 Ft3/s ec 19.69 Ft3 /sec 6.56 Ft3/sec Preliminary Determination Of Detention Pond Volume -~ .. , .. 2-Year: 3.57 Ft3/sec x (30 Min . x 60 Sec . I 2 ) = 3,211 Cubic Feet 5-Year: 4 .34 Ft3/sec x (30 Min . x 60 Sec. I 2 ) = 3 ,905 Cubic Feet 10-Year: 4.87 Ft3/sec x (30 Min. x 60 Sec . I 2 ) = 4 ,383 Cubic Feet 25-Year: 5.56 Ft3/sec x (30 Min . x 60 Sec. I 2 ) = 5,006 Cubic Feet 50-Year: 6.29 Ft3/sec x (30 Min . x 60 Sec. I 2 ) = 5,659 Cubic Feet 100-Year: 6.56 Ft3/sec x (30 Min. x 60 Sec . I 2 ) = 5,908 Cubic Fee t 2 Determine Post-Development "Free-Flow" Peak Storm Water Discharge Tributary Area ("A"): 0.74 Acres Run-Off Coefficient ("Cwt "): 0.60 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 ("O "): 2-Year: 2.81 5-Year: 3.42 10-Year: 3.83 25-Year: 4 .38 50-Year : 4 .95 100-Year: 5.17 3 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"): 2 .08 Acres Run-Off Coefficient ("Cwt"): 0.60 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: 7.90 5-Year: 9.60 10-Year: 10 .78 25-Year: 12.31 50-Year: 13 .91 100-Year: 14.53 4 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 0.71 0.87 0.97 1.11 1.26 1.31 2 1.43 1.74 1.95 2.22 2.51 2.63 3 2.14 2.60 2.92 3.34 3.77 3.94 4 2.85 3.47 3.90 4.45 5.03 5.25 5 3.57 4.34 4.87 5.56 6.29 6.56 6 4.28 5.21 5.84 6.67 7.54 7.88 7 5.00 6.07 6.82 7.79 8.80 9.19 8 5.71 6.94 7.79 8.90 10.06 10.50 9 6.42 7.81 8.77 10.01 11.32 11.82 Peak=> I 10 7.14 8.68 9.74 11.12 12.57 13.13 11 6.78 8.24 9.25 10.57 11.95 12.47 12 6.42 7.81 8.77 10.01 11.32 11.82 13 6.07 7.38 8.28 9.46 10.69 11.16 14 5.71 6.94 7.79 8.90 10.06 10.50 15 5.35 6.51 7.30 8.34 9.43 9.85 16 5.00 6.07 6.82 7.79 8.80 9.19 17 4.64 5.64 6.33 7.23 8.17 8.53 18 4.28 5.21 5.84 6.67 7.54 7.88 19 3.92 4.77 5.36 6.12 6.92 7.22 20 3.57 4.34 4.87 5.56 6.29 6.56 21 3.21 3.90 4.38 5.01 5.66 5.91 22 2.85 3.47 3.90 4.45 5.03 5.25 23 2.50 3.04 3.41 3.89 4.40 4.60 24 2.14 2.60 2.92 3.34 3.77 3.94 25 1.78 2.17 2.43 2.78 3.14 3.28 26 1.43 1.74 1.95 2.22 2.51 2.63 27 1.07 1.30 1.46 1.67 1.89 1.97 28 0.71 0.87 0.97 1.11 1.26 1.31 29 0.36 0.43 0.49 0.56 0.63 0.66 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 r (Minutes) Storm Storm Storm Storm Storm Storm 0 0.00 0.00 0.00 0.00 0.00 0.00 1 1.07 1.30 1.46 1.67 1.89 1.97 2 2.14 2.60 2.92 3.34 3 .77 3.94 3 3 .21 3 .90 4 .38 5.01 5.66 5 .91 4 4 .28 5.21 5 .84 6.67 7 .54 7 .88 5 5.35 6.51 7 .30 8.34 9.43 9.85 6 6.42 7.81 8.77 10.01 11 .32 11.82 7 7.49 9.11 10.23 11 .68 13.20 13 .79 8 8.56 10 .41 11 .69 13.35 15.09 15.75 9 9.63 11.71 13 .15 15 .02 16 .98 17 .72 Peak=> 10 10.70 13.02 14 .61 16.69 18.86 19.69 11 10.17 12 .37 13.88 15 .85 17 .92 18.71 12 9.63 11 .71 13 .15 15 .02 16 .98 17.72 13 9.10 11.06 12.42 14 .18 16 .03 16.74 14 8.56 10.41 11 .69 13 .35 15 .09 15 .75 15 8.03 9.76 10.96 12.51 14 .15 14.77 16 7.49 9.11 10.23 11 .68 13 .20 13 .79 17 6.96 8.46 9.50 10.85 12 .26 12 .80 18 6.42 7.81 8.77 10 .01 11 .32 11 .82 19 5 .89 7 .16 8.04 9.18 10.37 10 .83 20 5 .35 6.51 7 .30 8.34 9.43 9 .85 21 4.82 5 .86 6.57 7 .51 8.49 8.86 22 4.28 5.21 5.84 6.67 7 .54 7.88 23 3 .75 4.56 5.11 5 .84 6.60 6.89 24 3 .21 3 .90 4.38 5 .01 5 .66 5.91 25 2.68 3 .25 3 .65 4.17 4.72 4 .92 26 2 .14 2 .60 2 .92 3 .34 3 .77 3 .94 27 1.61 1.95 2 .19 2.50 2.83 2 .95 28 1.07 1.30 1.46 1.67 1.89 1.97 29 0 .54 0.65 0.73 0.83 0 .94 0 .98 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 0.28 0.34 0.38 0.44 0.49 0.52 2 0.56 0.68 0.77 0.88 0.99 1.03 3 0.84 1.02 1.15 1.31 1.48 1.55 4 1.12 1.37 1.53 1.75 1.98 2.07 5 1.40 1.71 1.92 2.19 2.47 2.58 6 1.69 2.05 2.30 2.63 2.97 3.10 7 1.97 2.39 2.68 3.06 3.46 3.62 8 2.25 2.73 3.07 3.50 3.96 4.13 9 2.53 3.07 3.45 3.94 4.45 4.65 Peak=> I 10 2.81 3.42 3.83 4.38 4.95 5.17 11 2.67 3.24 3.64 4.16 4.70 4.91 12 2.53 3.07 3.45 3.94 4.45 4.65 13 2.39 2.90 3.26 3.72 4.21 4.39 14 2.25 2.73 3.07 3.50 3.96 4.13 15 2.11 2.56 2.88 3.28 3.71 3.88 16 1.97 2.39 2.68 3.06 3.46 3.62 17 1.83 2.22 2.49 2.85 3.22 3.36 18 1.69 2.05 2.30 2.63 2.97 3.10 19 1.54 1.88 2.11 2.41 2.72 2.84 20 1.40 1.71 1.92 2.19 2.47 2.58 21 1.26 1.54 1.73 1.97 2.23 2.33 22 1.12 1.37 1.53 1.75 1.98 2.07 23 0.98 1.20 1.34 1.53 1.73 1.81 24 0.84 1.02 1.15 1.31 1.48 1.55 25 0.70 0.85 0.96 1.09 1.24 1.29 26 0.56 0.68 0.77 0.88 0.99 1.03 27 0.42 0.51 0.58 0.66 0.74 0.78 28 0.28 0.34 0.38 0.44 0.49 0.52 29 0.14 0.17 0.19 0.22 0.25 0.26 30 0.00 0.00 0.00 0.00 0.00 0.00 - 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 0.79 0.96 1.08 1.23 1.39 1.45 2 1.58 1.92 2.16 2.46 2.78 2.91 3 2.37 2.88 3.23 3.69 4.17 4.36 4 3.16 3.84 4.31 4.92 5.56 5.81 5 3.95 4.80 5.39 6.15 6.96 7.26 6 4.74 5.76 6.47 7.38 8.35 8.72 7 5.53 6.72 7.54 8.61 9.74 10.17 8 6.32 7.68 8.62 9.85 11.13 11.62 9 7.11 8.64 9.70 11.08 12.52 13.07 Peak=> r 10 7.90 9.60 10.78 12.31 13.91 14.53 11 7.50 9.12 10.24 11.69 13.22 13.80 12 7.11 8.64 9.70 11.08 12.52 13.07 13 6.71 8.16 9.16 10.46 11.83 12.35 14 6.32 7.68 8.62 9.85 11.13 11.62 15 5.92 7.20 8.08 9.23 10.43 10.89 16 5.53 6.72 7.54 8.61 9.74 10.17 17 5.13 6.24 7.00 8.00 9.04 9.44 18 4.74 5.76 6.47 7.38 8.35 8.72 19 4.34 5.28 5.93 6.77 7.65 7.99 20 3.95 4.80 5.39 6.15 6.96 7.26 21 3.55 4.32 4.85 5.54 6.26 6.54 22 3.16 3.84 4.31 4.92 5.56 5.81 23 2.76 3.36 3.77 4.31 4.87 5.08 24 2.37 2.88 3.23 3.69 4.17 4.36 25 1.97 2.40 2.69 3.08 3.48 3.63 26 1.58 1.92 2.16 2.46 2.78 2.91 27 1.18 1.44 1.62 1.85 2.09 2.18 28 0.79 0.96 1.08 1.23 1.39 1.45 29 0.39 0.48 0.54 0.62 0.70 0.73 30 0.00 0.00 0.00 0.00 0.00 0.00 8 y y 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 2-Year Storm Event 5 10 15 20 25 Time (Minutes) 30 ---Pre-Development Hydrograph ---Total Post -Development Hydrograph Total Pre-Development Vs. Total Post-Development (No Detention) Peak Discharge Rates 5-Year Storm Event 14 .00 ------.-------,,------.------.----,-------, 12.00 -----+-----#--1r--_,_---+------+----+----------i 10 .00 +-----+--_,_--l------"""-!----+------+-----1 8 .00 +-----+--1----r--t--=~---+--~.,---+-----+-----j 4.00 +--~'-----:;A------+------1f-----f""-..,---~-+------l 2 .00 +---f-:.,,C---+-----+-----+-----+---~-...::-''-:--~ 0.00 ~---+-----+-----+-----+-----+---..;;11111 0 5 10 Pre-Development Hydrograph 15 20 25 30 Time (Minutes) 9 ---Post-De velopment Outflow Hydrograph Wit hout Detention y y I 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 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 25-Year Storm Event 5 10 Pre-Development Hydrograph 15 20 25 30 Time (Minutes) ---Post-Development Outflow Hydrograph Without Detentio n 10 20.00 18 .00 16.00 14.00 12.00 y 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 50-Year Storm Event 5 10 15 20 25 Time (Minutes) 30 ---Pre-Development Hydrograph ---Post-Development Outflow Hydrograph Without Detention 20.00 18.00 16 .00 14.00 12 .00 y 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 100-Year Storm Event 5 10 15 20 25 Time (Minutes) 30 ---Pre-Development Hydrograph ---Post-Development Outflow Hydrograph Without Detention 11 Detention Pond Depth Vs. Volume Elevation Depth Volume (Feet) (Ft3) 260 .35 0.00 0 261.00 0.65 678 261 .50 1.15 1,826 262.00 1.65 3,185 262.50 2 .15 6,581 263.50 3 .15 8,642 Detention Pond Depth Vs. Volume 3.50 y / I / / .--L/ / _,,,,.... v ~ / v I / I 3.00 2.5 0 2.00 1.50 l.00 0 .50 0.00 0 1,000 2 ,000 3 ,000 4 ,000 5 ,000 6 ,000 7 ,000 8 ,000 9 ,000 Detention Pond Volume (Cubic Feet) 12 Rating Curve For Outlet Control Structure Pipe Diameter (ft): 1.25 15 inches Depth Vs. Volume Pipe Length (ft): 230.00 c: 0.013 Slope(%): 2.48 U .S . FL : 2 60 .35 D .S . FL: 255.00 5.35 Ce : 0.50 Elevation Depth Discharge (Feet) Ft3/Sec 260.35 0 .00 0.00 261 .00 0.65 3 .03 261.50 1.15 4 .04 262 .00 1.65 4 .83 262 .50 2.15 5 .52 263 .50 3 .15 6 .68 Rating Curve For Outlet Control Structure Depth Vs. Discharge y 0.00 1.00 2 .00 3 .00 4 .00 5.00 6.00 7.00 Discharge (Cubic Feet Per Second) 13 !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 0.65 678 3.03 22 .60 25.63 1.15 1,826 4.04 60.87 64.90 1.65 3 ,185 4 .83 106 .17 111 .00 2.15 6,581 5.52 219 .37 224.88 3 .15 8,642 6.68 288.07 294 .75 Storage Indication Curve 7.00 6 .00 5 .00 4 .00 y 3.00 2 .00 l.00 0.00 0.00 50.00 100 .00 150 .00 200.00 250 .00 300.00 2s/t+O (Cubic Feet Per Second) 14 Inflow I Outflow Simulation 2-Year Storm Event Time Inflow 11+ 12 2s/t-0 2s/t+O Outflow Depth Elevation Velocity (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) (Ft/Sec) 0 0.00 0.00 0.00 0.00 0.00 0.00 260.35 0.00 1 0.79 0.79 0.60 0.79 0.09 0.00 260.35 0.08 2 1.58 2.37 2.27 2.97 0.35 0.01 260.36 0.29 3 2.37 3.95 4.74 6.22 0.74 0.04 260.39 0.60 4 3.16 5.53 7.84 10.27 1.22 0.10 260.45 0.99 5 3.95 7.11 11.41 14.95 1.77 0.22 260.57 1.44 6 4.74 8.69 15.34 20.09 2.38 0.40 260.75 1.94 7 5.53 10.26 19.54 25.60 3.03 0.65 261.00 2.47 8 6.32 11.84 25.02 31.38 3.18 0.71 261.06 2.59 9 7.11 13.42 31.72 38.44 3.36 0.80 261.15 2.74 10 7.90 15.00 39.58 46.72 3.57 0.90 261.25 2.91 11 7.50 15.40 47.41 54.98 3.78 1.01 261.36 3.08 12 7.11 14.61 54.09 62.02 3.96 1.11 261.46 3.23 13 6.71 13.82 59.73 67.91 4.09 1.18 261.53 3.33 14 6.32 13.03 64.42 72.76 4.17 1.23 261.58 3.40 15 5.92 12.24 68.18 76.66 4.24 1.27 261.62 3.45 16 5.53 11.45 71.04 79.63 4.29 1.30 261.65 3.50 17 5.13 10.66 73.05 81.70 4.33 1.32 261.67 3.53 18 4.74 9.87 74.22 82.92 4.35 1.33 261.68 3.54 19 4.34 9.08 74.59 83.30 4.35 1.34 261.69 3.55 20 3.95 8.29 74.19 82.88 4.35 1.33 261.68 3.54 21 3.55 7.50 73.04 81.69 4.33 1.32 261.67 3.53 22 3.16 6.71 71.16 79.75 4.29 1.30 261.65 3.50 23 2.76 5.92 68.59 77.08 4.25 1.27 261.62 3.46 24 2.37 5.13 65.35 73.72 4.19 1.24 261.59 3.41 25 1.97 4.34 61.45 69.69 4.12 1.20 261.55 3.36 26 1.58 3.55 56.93 65.00 4.04 1.15 261.50 3.29 27 1.18 2.76 51.89 59.69 3.90 1.08 261.43 3.18 28 0.79 1.97 46.35 53.86 3.75 1.00 261.35 3.06 29 0.39 1.18 40.35 47.54 3.59 0.91 261.26 2.93 30 0.00 0.39 33.91 40.75 3.42 0.83 261.18 2.79 15 Inflow/Outflow Simulation 2-Year Storm Event 12 .00 " , " 10 .00 " " , " , " , " , " , " 8.00 I " • " , " , " , " , " y 6.00 " , " , " , " ' , 4.00 , , , , , , ....... / ....... ' ....... " / ' ..... 2.00 ....... " ....... ....... ..... ....... ....... ....... ..... ..... 0.00 0 5 10 15 20 25 30 Time (Minutes) Pre-• Post-Post---- - -Post- Development Development Development Development Hydrograph Outflow Outflow With "Free-F low· Hydrograph Detention Without Detention 16 Inflow I Outflow Simulation 5-Year Storm Event Time Inflow 11+ 12 2s/t-0 2s/t+O Outflow Depth Elevation Velocity (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) (Ft/Sec) 0 0.00 0 .00 0 .00 0.00 0.00 0 .00 260.35 0.00 0.96 0.96 0 .73 0.96 0 .11 0 .00 260 .35 0.09 2 1.92 2.88 2.76 3.61 0.43 0 .01 260 .36 0.35 3 2.88 4 .80 5.77 7 .56 0.89 0 .06 260.41 0 .73 4 3 .84 6.72 9.53 12.49 1.48 0 .15 260 .50 1.20 5 4 .80 8 .64 13.87 18 .17 2.15 0.33 260.68 1.75 6 5.76 10.56 18 .65 24.43 2.89 0 .59 260.94 2.36 7 6.72 12.48 24 .78 31.13 3 .17 0.71 261.06 2 .59 8 7 .68 14.40 32.42 39 .18 3 .38 0 .81 261 .16 2.75 9 8.64 16.32 41.50 48.74 3.62 0.93 261 .28 2 .95 10 9 .60 18.24 51 .93 59 .74 3 .90 1.08 261.43 3.18 11 9 .12 18 .72 62 .38 70 .65 4 .14 1.21 261 .56 3.37 12 8 .64 17.76 71 .54 80 .14 4.30 1.31 261 .66 3.50 13 8.16 16 .80 79.46 88 .34 4.44 1.39 261 .74 3 .62 14 7.68 15 .84 86 .18 95 .30 4.56 1.47 261 .82 3 .72 15 7 .20 14 .88 91 .73 101 .06 4 .66 1.53 261 .88 3.80 16 6.72 13 .92 96 .17 105.65 4 .74 1.59 261 .94 3.86 17 6.24 12 .96 99 .53 109 .13 4.80 1.63 261 .98 3 .91 18 5.76 12 .00 101 .85 111 .53 4 .84 1.65 262 .00 3 .94 19 5 .28 11 .04 103 .20 112.89 4.85 1.66 262 .01 3 .95 20 4 .80 10 .08 103 .59 113.28 4.85 1.66 262 .01 3.95 21 4 .32 9.12 103 .02 112 .71 4 .84 1.66 262 .01 3 .95 22 3 .84 8.16 101 .51 111 .18 4 .84 1.65 262.00 3.94 23 3.36 7 .20 99 .12 108.71 4 .79 1.62 261 .97 3.91 24 2.88 6.24 95 .89 105.36 4 .74 1.58 261 .93 3 .86 25 2.40 5.28 91.84 101.17 4 .66 1.54 261.89 3 .80 26 1.92 4.32 87 .01 96.16 4 .58 1.48 261 .83 3 .73 27 1.44 3.36 81.41 90 .37 4.48 1.42 261 .77 3 .65 28 0.96 2.40 75 .09 83 .81 4.36 1.34 261 .69 3 .56 29 0.48 1.44 68 .05 76 .53 4 .24 1.27 261 .62 3.45 30 0 .00 0.48 60 .34 68 .53 4.10 1.19 261.54 3.34 17 y - Inflow/Outflow Simulation 5-Year Storm Event 14.00 12.00 10.00 8 .00 6.00 4 .00 2.00 0 .00 0 5 ---Pre- Development Hydrograph • • • • • • • • • ' . ' 10 ' ' ' ' ' ' 15 20 25 30 Time (Minutes) ----Post-- - ---- -Po st-• Post- Development Outflow Hydrograph Without Detention Development Development Outflow With "Free-Flow· Detention 18 Inflow I Outflow Simulation 10-Year Storm Event Time Inflow 11+ 12 2s/t-O 2s/t+O Outflow Depth Elevation Velocity (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) (Ft/Sec) 0 0.00 0.00 0.00 0.00 0.00 0.00 260.35 0.00 1 1.08 1.08 0.82 1.08 0.13 0.00 260.35 0.10 2 2 .16 3.23 3 .10 4.06 0.48 0.02 260.37 0.39 3 3.23 5.39 6.48 8.48 1.00 0.07 260.42 0.82 4 4.31 7 .54 10 .70 14 .02 1.66 0.19 260 .54 1.35 5 5.39 9.70 15.57 20.40 2.41 0.41 260 .76 1.97 6 6.47 11 .85 21 .26 27.42 3 .08 0.67 261 .02 2 .51 7 7.54 14 .01 28 .71 35 .27 3 .28 0.76 261 .11 2.67 8 8.62 16 .16 37 .83 44.88 3.52 0.88 261 .23 2.87 9 9.70 18.32 48.52 56 .14 3 .81 1.03 261 .38 3 .11 10 10.78 20.47 60.78 68 .99 4.11 1.19 261 .54 3.35 11 10.24 21 .01 73 .14 81 .79 4 .33 1.32 261 .67 3.53 12 9 .70 19 .94 84 .03 93.07 4 .52 1.44 261 .79 3.69 13 9.16 18 .86 93 .50 102 .88 4 .69 1.56 261 .91 3 .82 14 8.62 17.78 101 .60 111 .28 4 .84 1.65 262 .00 3.94 15 8.08 16 .70 108.55 118.31 4.88 1.68 262 .03 3.97 16 7.54 15 .63 114.35 124.18 4.91 1.70 262 .05 4.00 17 7 .00 14 .55 119 .01 128.90 4.94 1.72 262.07 4.03 18 6.47 13.47 122 .56 132.48 4.96 1.74 262 .09 4.04 19 5 .93 12 .39 124.99 134.95 4.98 1.75 262 .10 4.06 20 5.39 11 .31 126.34 136.31 4.99 1.76 262.11 4.06 21 4.85 10.24 126 .60 136.57 4.99 1.76 262 .11 4 .06 22 4 .31 9 .16 125 .79 135 .76 4.98 1.75 262 .10 4.06 23 3 .77 8.08 123.93 133.87 4.97 1.75 262 .10 4 .05 24 3 .23 7.00 121.03 130.93 4.95 1.73 262 .08 4.04 25 2.69 5.93 117.09 126.95 4.93 1.72 262.07 4.02 26 2.16 4.85 112 .14 121 .94 4.90 1.70 262 .05 3 .99 27 1.62 3 .77 106 .19 115.91 4 .86 1.67 262 .02 3.96 28 1.08 2.69 99 .29 108.88 4 .80 1.63 261.98 3.91 29 0.54 1.62 91 .58 100.90 4.66 1.53 261.88 3 .80 30 0.00 0.54 83 .11 92 .12 4 .51 1.43 261.78 3.67 .. Inflow/Outflow Simulation 10-Year Storm Event 16 .00 14 .00 12 .00 10 .00 y 8.00 6.00 4 .00 2 .00 0.00 0 ---Pre- Development Hydrograph • I I I 5 I I I I ' I 10 15 20 25 30 Time (Minutes) • Post- Development Outflow Hydrograph Without Detention ----Post-- - -----Post- Development Development Outflow With "Free -Flow" Detention 20 Inflow I Outflow Simulation 25-Year Storm Event Time Inflow 11+ 12 2s/t-0 2s/t+O Outflow Depth Elevation Velocity (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) (Ft/Sec) 0 0.00 0.00 0.00 0.00 0.00 0.00 260.35 0.00 1 1.23 1.23 0.94 1.23 0.15 0.00 260.35 0.12 2 2.46 3.69 3.54 4.63 0.55 0.02 260 .37 0.45 3 3.69 6.15 7 .40 9 .69 1.15 0 .09 260.44 0.93 4 4.92 8.61 12 .22 16.01 1.90 0 .25 260.60 1.54 5 6.15 11.08 17.78 23.30 2.76 0.54 260.89 2.25 6 7.38 13.54 24 .96 31 .32 3.18 0 .71 261 .06 2.59 7 8.61 16 .00 34 .11 40.96 3.43 0.83 261.18 2.79 8 9.85 18.46 45 .13 52.57 3 .72 0.98 261.33 3 .03 9 11.08 20 .92 57 .94 66.05 4.06 1.16 261 .51 3.30 10 12 .31 23 .38 72.68 81 .32 4.32 1.32 261 .67 3 .52 11 11.69 24.00 87.51 96 .68 4 .59 1.49 261 .84 3 .74 12 11 .08 22 .77 100.63 110.28 4 .82 1.64 261.99 3 .93 13 10.46 21.54 112 .37 122.17 4.90 1.70 262 .05 3.99 14 9.85 20 .31 122.75 132.68 4.96 1.74 262 .09 4.05 15 9.23 19.08 131.78 141.82 5.02 1.78 262.13 4.09 16 8.61 17 .85 139 .50 149.63 5.07 1.81 262 .16 4 .13 17 8.00 16 .61 145.90 156.11 5.11 1.84 262.19 4 .16 18 7 .38 15 .38 151.01 161 .29 5.14 1.86 262.21 4 .19 19 6.77 14.15 154.85 165.17 5 .16 1.88 262.23 4.20 20 6.15 12 .92 157.42 167.77 5.18 1.89 262 .24 4.22 21 5.54 11 .69 158.75 H39.11 5.18 1.90 262.25 4 .22 22 4.92 10.46 158.84 169.21 5.18 1.90 262 .25 4 .22 23 4.31 9.23 157.72 168.07 5 .18 1.89 262 .24 4.22 24 3 .69 8.00 155 .39 165.71 5 .16 1.88 262.23 4.21 25 3 .08 6.77 151 .88 162 .16 5.14 1.87 262 .22 4.19 26 2.46 5.54 147.19 157.41 5 .11 1.85 262.20 4 .17 27 1.85 4.31 141 .34 151.50 5.08 1.82 262.17 4.14 28 1.23 3 .08 134.35 144.42 5 .03 1.79 262 .14 4.10 29 0.62 1.85 126.22 136.19 4 .99 1.75 262.10 4.06 30 0.00 0.62 116.98 126.84 4.93 1.72 262 .07 4.02 21 - y - Inflow/Outflow Simulation 25-Year Storm Event 18 .00 16 .00 14 .00 12.00 10 .00 8 .00 6 .00 4 .00 2 .00 0 .00 0 5 ---Pre- Development Hydrograph • I I I I I ' ' I ' ' I ' .. ' ' ' 10 15 20 25 30 Time (Minutes) ---· Post-- - -- - - -Post-• Post- Development Outflow Hydrograph Without Detention Development Development Outflow With "Free-Flow" Detention 22 Inflow I Outflow Simulation 50-Year Storm Event Time Inflow 11+ 12 2s/t-0 2s/t+O Outflow Depth Elevation Velocity (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) (Ft/Sec) 0 0.00 0 .00 0 .00 0 .00 0.00 0 .00 260 .35 0.00 1 1.39 1.39 1.06 1.39 0.16 0.00 260 .35 0 .13 2 2 .78 4 .17 4 .00 5 .24 0 .62 0 .03 260.38 0.50 3 4 .17 6.96 8.36 10 .95 1.30 0.12 260.47 1.06 4 5 .56 9 .74 13 .81 18 .10 2.14 0.32 260 .67 1.75 5 6.96 12.52 20 .23 26 .33 3.05 0.66 261 .01 2.49 6 8.35 15 .30 28 .96 35 .53 3 .29 0.76 261 .11 2 .68 7 9.74 18 .09 39 .89 47 .05 3.58 0 .91 261.26 2.92 8 11.13 20 .87 52 .89 60 .75 3.93 1.09 261.44 3 .20 9 12.52 23 .65 68.07 76.55 4.24 1.27 261 .62 3.45 10 13 .91 26.43 85.41 94.50 4.55 1.46 261 .81 3 .71 11 13 .22 27 .13 102.85 112.54 4.84 1.66 262 .01 3.95 12 12.52 25 .74 118.71 128.59 4 .94 1.72 262.07 4 .03 13 11.83 24.35 133.00 143.05 5 .03 1.78 262 .13 4 .10 14 11 .13 22 .96 145.75 155.96 5.10 1.84 262 .19 4 .16 15 10.43 21.56 156.97 167.31 5.17 1.89 262.24 4 .21 16 9.74 20 .17 166 .68 177.14 5.23 1.93 262 .28 4.26 17 9.04 18 .78 174.90 185.46 5.28 1.97 262 .32 4.30 18 8.35 17 .39 181.64 192.29 5.32 2 .00 262 .35 4 .34 19 7 .65 16 .00 186.93 197.64 5.35 2.02 262.37 4.36 20 6.96 14 .61 190.78 201 .54 5 .38 2.04 262 .39 4 .38 21 6.26 13.22 193.21 204.00 5 .39 2.05 262.40 4.39 22 5 .56 11 .83 194 .24 205 .04 5.40 2.06 262.41 4.40 23 4 .87 10.43 193.88 204 .68 5.40 2.06 262.41 4.40 24 4 .17 9.04 192 .15 202 .92 5 .39 2 .05 262.40 4.39 25 3.48 7.65 189 .07 199.80 5 .37 2.03 262.38 4 .37 26 2.78 6.26 184.65 195.33 5.34 2 .01 262 .36 4.35 27 2.09 4 .87 178.91 189.52 5.31 1.99 262.34 4 .32 28 1.39 3.48 171 .86 182.38 5.26 1.96 262 .31 4 .29 29 0 .70 2.09 163.52 173.94 5 .21 1.92 262.27 4.25 30 0 .00 0 .70 153 .91 164.22 5 .15 1.88 262 .23 4.20 23 Inflow/Outflow Simulation 50-Year Storm Event 20 .00 ' ' 18.00 • -• ' • ' • ' 16.00 • ' ' I ' • ' I ' 14.00 . I ' I .... I ' 11\... . 12.00 y 10 .00 : I ~ ' I .. I ' I ' . 8.00 1• I I I I I I I I J // :! j / , , !/ 6.00 4.00 2.00 0.00 0 5 ---Pre- Development Hydrograph "\ ' ~ ' ' ' ""' ' ' ' ' ' ' - ' ~ ' - ~ ;;--, ~ .......... ' . . ""' . . . . . . ' . . """, . . . . . . . . . ... ·-.. ~ .. .... .. .. ' ........ lO 15 20 25 30 Time (Minutes) • Post- Development Outflow Hydrograph Without Detention ---Post--- ---- -Post- Development Development Outflow With 'Free-Flow· Detention 24 Inflow I Outflow Simulation 100-Year Storm Event Time Inflow 11+ 12 2s/t-0 2s/t+O Outflow Depth Elevation Velocity (Minutes) (Ft3/Sec) (Ft3/Sec) (Feet) (Ft/Sec) 0 0 .00 0.00 0.00 0.00 0 .00 0 .00 260 .35 0.00 1 1.45 1.45 1.11 1.45 0.17 0 .00 260 .35 0 .14 2 2.91 4.36 4 .17 5.47 0.65 0.03 260.38 0.53 3 4.36 7.26 8 .73 11.44 1.35 0.13 260.48 1.10 4 5.81 10.17 14.42 18 .90 2.24 0.35 260 .70 1.82 5 7 .26 13 .07 21 .33 27 .50 3.08 0.67 261 .02 2.51 6 8.72 15.98 30 .65 37.31 3 .33 0 .78 261.13 2.72 7 10.17 18 .88 42 .24 49.53 3 .64 0.94 261 .29 2.97 8 11 .62 21 .79 56 .00 64.03 4.01 1.14 261.49 3.27 9 13 .07 24 .69 72 .08 80.70 4.31 1.31 261.66 3.51 10 14.53 27 .60 90.40 99.68 4 .64 1.52 261 .87 3.78 11 13.80 28 .33 108.97 118.73 4 .88 1.68 262 .03 3.98 12 13.07 26.87 125 .87 135.84 4 .98 1.75 262 .10 4.06 13 12 .35 25.42 141 .14 151.29 5 .08 1.82 262 .17 4.14 14 11.62 23.97 154.79 165.11 5.16 1.88 262 .23 4.20 15 10.89 22 .51 166 .84 177.30 5.23 1.93 262.28 4 .26 16 10.17 21 .06 177.31 187.90 5.30 1.98 262 .33 4.32 17 9.44 19 .61 186.22 196.92 5 .35 2.02 262 .37 4.36 18 8.72 18.16 193 .59 204 .38 5.40 2.06 262.41 4.40 19 7 .99 16 .70 199.43 210 .29 5.43 2.08 262.43 4.43 20 7 .26 15 .25 203 .77 214 .68 5.46 2 .10 262.45 4.45 21 6.54 13 .80 206 .62 217 .57 5.47 2.12 262.47 4.46 22 5.81 12 .35 208 .00 218 .96 5.48 2.12 262.47 4.47 23 5.08 10 .89 207 .93 218 .89 5.48 2 .12 262.47 4.47 24 4.36 9.44 206.42 217 .37 5.47 2 .11 262.46 4.46 25 3 .63 7.99 203.50 214.41 5.46 2.10 262.45 4.45 26 2.91 6.54 199 .18 210.04 5.43 2.08 262 .43 4.42 27 2.18 5 .08 193.48 204 .27 5 .39 2 .05 262.40 4.40 28 1.45 3 .63 186.41 197.11 5.35 2 .02 262 .37 4 .36 29 0 .73 2.18 177.98 188.58 5.30 1.98 262 .33 4 .32 30 0 .00 0 .73 168 .23 178 .71 5.24 1.94 262.29 4.27 25 Inflow/Outflow Simulation 100-Year Storm Event 20 .00 1 ' I "' "' 18.00 I "' I & I "' I .. 16 .00 I "' • "' "' I ' I "' 14 .00 I - I "' 12.00 y 10 .00 8.00 I "" "' I I "' . "' I ~ .. I "' I .. I "' I I ~ "' I "' "' I "' • I/ ~ "' I "' I "' I I ~ "' // ' - ,, ~ ~' ~ ---"' -. . 6 .00 . ./ j / -. '\ -. "' -. . . . I\\ 4 .00 ' !/ 2 .00 0 .00 0 5 ---Pr e- Dev elopme nt Hy drograph ' . . --. . . . ........... .. ~ ·-' ......... --. 10 15 20 25 30 Time (Minutes) • Post- Developm e nt O utflow Hydrograph With o ut Detention ----Post-• • • • • • • Post- Devel o pm ent Develo pme nt O utflo w With "Fre e-Flow" Detentio n 26 Inflow/Outflow Simulation 2-Year Storm Event 8 .00 7.00 6 .00 5 .00 y 4.00 3 .00 2 .00 1.00 0 .00 0 5 10 15 20 25 30 Time (Minutes) ---Pre-Development Hydr o graph ---Tota l Post-Development Hydrograph 27 Inflow/Outflow Simulation 5-Year Storm Event 9 .00 8 .00 7 .00 6 .00 5.00 y 4 .00 3.00 2.00 l.00 0 .00 0 5 10 15 20 25 30 Time (Minutes) ---Pre-Devel opment Hydrograph ---Tota l Post-De velopm ent Hydrograph 28 Inflow/Outflow Simulation 10-Year Storm Event 10.00 9 .00 6 .00 3.00 2.00 l.00 0 .00 0 5 10 15 20 25 30 Time (Minutes) Pre-De velopment Hydrograph ---Tota l Po st-Development Hydrograph 29 Inflow/Outflow Simulation 25-Year Storm Event 12.00 8.00 y 6 .00 4 .00 0 5 10 15 20 25 30 Time (Minutes) Pr e-Development Hydrograph ---Total Post -Developm ent Hydrograph 30 Inflow/Outflow Simulation 50-Year Storm Event 14.00 12 .00 10 .00 8.00 y 6 .00 4 .00 2 .00 0 .00 0 5 10 15 20 25 30 Time (Minutes) Pre-Development Hydrog raph ---Tot a l Post-Development Hydrograph 31 Inflow/Outflow Simulation 100-Year Storm Event 14.00 12 .00 10.00 8 .00 y 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-Deve lopm ent Hydrograph 32 Detention Pond Storage Volumes as Percent of Maximum Volume 100% 90% 80% 70% 60% y 50% 40% 30% 20% 10% 0% 2-year 5-year 10-year 25-year 50-year 100-year Design Storm Storm Simulation Synopsis 2-year 5-year 10-year 25-year 50-year 100-year Storm Depth 1.34 1.66 1.76 1.90 2.06 2.12 Storm Elevation 261 .69 262.01 262 .11 262.25 262.41 262.47 Storm Volume 2339 3210 3908 4865 5957 6393 Maximum Capacity 8642 8642 8642 8642 8642 8642 Percent of Capacity 27% 37 % 45% 56% 69% 74% 33 CHECK FULL FLOW CAPACITY OF BRITTAIN COURT (112 Street Section @ Given 2.00% Grade) The flow capacity can be calculated from the following equation: Where; 1.486 Q = x (A) x (R2/3) x (S 112) n Q = Flow capacity (in cubic feet per second) n = Roughness coefficient (0.021) A = Flow Sectional Area (2.07 square feet) R = Hydraulic radius (0.21 feet) S = Slope (0.020 feet per foot) Q = 8.42 cubic feet per second (1/2 street capacity) Please note that 8.42 cubic feet per second is greater than the anticipated peak discharge rate generated by the 100-year stonn event, therefore, the street" carries" the design peak flow rate and actually exceeds that peak flow rate as supplied by the 100-year stonn event Q 8.42 cfs Velocity = A = ---------------------= 4.07 feet per second 2.07 square feet "Size" curb leave-out at end of Brittain Court; (2-year) 7.90 cfs For inlet box in sag: Where; (5-year) 9.60 cfs Supplied Run-Off (From Areas "A", "B" & "C") (10-year) 10.78 cfs (25-year) 12.31 cfs Q = CLH3/2 (50-year) 13.91 cfs Q = Inlet capacity in cubic feet per second C = Entrance Coefficient L = Length of inlet opening in feet H = Headwater depth in feet (100-year) 14 .53 cfs The maximum available headwater depth (H) is 5 inches (0.42 feet), the supplied length of inlet opening (L) is 17 .5 feet For given 2-year through 100-year peak discharge rates the following headwater depths (H) are required : (2-year) 0.28 feet (5-year) 0.32 feet (10-year) 0.34 feet (25-year) 0.37 feet (50-year) 0.40 feet (100-year) 0.42 feet From the above computations it can be seen that the inlet opening is adequately sized to convey the anticipated peak discharge rates generated by the 2-year through the 100-year storm events. Check full flow capacity of the proposed 4' wide reinforced concrete flume at the end of Brittain Court: (given 2.00 % grade) The flow capacity can be calculated from the following equation: Q= Where; Velocity = 1.486 n Q = Flow capacity (in cubic feet per second) n = Roughness coefficient (0 .013) A = Flow Sectional Area (2.333 square feet) R = Hydraulic radius (0.465 feet) S = Slope (0.020 feet per foot) Q = 22.56 cubic feet per second Q A 22.56 cfs = ---------------------= 9.67 feet per second 2 .333 square feet Pl ease note that the full flow capacity of the 4' wide reinforced concrete flume located at the end of Brittain Court exceeds the anticipated discharge as generated by the 100-year storm event DEVELOPMENT PERMIT PERMIT NO . 457-A BRITTAIN COURT ADDITION FOR AREAS INSIDE THE SPECIAL FLOOD HAZARD AREA RE : CHAPTER 13 OF THE COLLEGE STATION CITY CODE SITE LEGAL DESCRIPTION: Replat of Block 2, Regency South being Brittain Court Addition SITE ADDRESS: Not addressed OWNER: E . Douglas Brittain 236 Highway 46 West Boerne, Texas 78006 (210)249-9331 DRAINAGE BASIN: Bee Creek Tributary "A", Segment II TYPE OF DEVELOPMENT: This permit is valid for all site construction as shown on the approved plans. The contractor shall prevent silt and debris from leaving the site in accordance with the City of College Station Drainage Policy and Design Standards . The owner and/or contractor shall be responsible for any damage to existing city streets or infrastructure due to heavy machinery and/or equipment. · 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 inside 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 proje and a of the codes and ordinances of the City of College Station that apply. Date ~ h ~21 y7 Date ~7 Contractor Date .. Figure XII Application Form Development Permit Inside/Outside &tablished Flood Hazard Areas City of College Station, Texas (re: Ordinance No. 1728) 1;2e~L-~'\ c::>F ec....oc..1e. 'Z I \2ec:::;:eJC..'l ~-n-1 'SStJ4 Site Legal Description: -e:e.11Tb..tU C.oV(??r Aoo1TIC:1'-i ~~ eJ~ll-:J~~ Architect/ lfll-' (' ( ~ ~-es-<-~w;\-\ Engineer: ~l-n:' \D4b Contractorr--kB'c::n.....J · Co0~c.;:ooA....l Date Application Filed : ___ '3""'-'J"-~~l.__/_9'_,_J_.__ _____ Approved : ----------- / J Attached as part of this application: 'i5('Application Fee ro S igned Certificate O Site and Construction Plans, with supporting documentation: two (2) copies of each O Other:------------------ ACKNOWLEDGEMENTS: I, i:::. frx,ACL.A:S 'E£..s1Jl'rtt...), as owner, hereby acknowledge or affirm that : The above Drainage Pl an a nd supporting documents c o mplies wiht the require ments of Ordina nc e No. 1728, and Da te ) ~· -sfa1/iz Date ~~ Contractor Da te Page 1of 2 ·- Figure XII Continued CERTIFICATIONS: A. I, certify that any nonresidential structure on or proposed to be on this site as part of this application meets flood-proofing requirements as set out in Section of Ordinance No. 1728 Architect/Engineer Date B. I, certify that the finished floor level of the lowest floor, including any basement, of any residential structure as part of this application is or proposed to be at or above the base flood elevation as established in the latest Federal Insurance Administration flood hazard study and maps, as amended . Architect/Engineer Date Floodplain Administrator Date · APPROVAL: Special conditions or comments as part of a pproval :----------- DEVELOPMENT PERMIT PERMIT NO. 457 BRITTAIN COURT ADDITION FOR AREAS INSIDE THE SPECIAL FLOOD HAZARD AREA RE: CHAPTER 13 OF THE COLLEGE STATION CITY CODE SITE LEGAL DESCRIPTION: Replat of Block 2, Regency South being Brittain Court Addition SITE ADDRESS: Not addressed OWNER: E . Douglas Brittain 236 Highway 46 West Boerne, Texas 78006 (210)249-9331 DRAINAGE BASIN: Bee Creek Tributary "A", Segment II TYPE OF DEVELOPMENT: This permit is valid for site clearing and grubbing operations ONLY. Any work that does not conform to this description shall be considered unauthorized and will be subject to code enforcement as defined in the City's Drainage Policy and Design Standards. The contractor shall prevent silt and debris from leaving the site in accordance with the City of College Station Drainage Policy and Design Standards. The owner and/or contractor shall be responsible for any damage to existing city streets or infrastructure due to heavy machinery and/or equipment. 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 inside 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 pr.oject and al of the codes and ordinances of the City of College Station that apply. Contractor Daff I z=6!9l Date r Date 't LEGACY CONSTRUCTION 4475 HICKS LANE t.i ~ COLLEGE STATION , TEXAS n845 J (409) 776-6111 FIRST AMERICAN BANK P.O. BOX 1033 BRYAN, TX 77805 (409) 268-7575 THIS CHECK IS IN PAYMENT OF THE FOLLOWING DESCRIPTION ";z.gz._4 4402 88-2 32/1131 CHECK AMOUNT 383040 -..r----t----=-~-0~3:::.......!-.1 ' 19Cf1-