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Home My WebLink AboutDrainage ReportT: D4 a.vn GALINDO ENGINEERS AND PLANNERS, INC. 3833 South Texas Ave., Suite 213 Bryan, Texas 77802 (979) 846-8868 February 27, 2003 Mr. Spencer Thompson Engineering Department City of College Station College Station, TX Subject: Updated Drainage Report University Heights Condominiums College Station, TX Dear Spencer: Pleased find enclosed the referenced report for your review. This report is an update of the original report submitted on November 22, 1999. Sincerely, GALINDO ENGINEERS AND PLANNERS, INC. J �� Christian A. Galindo, P.E., R.P.L.S. President cc: Horizon Homes 0 F tj �'�' l t. HRISTIAN A. GAL I UNIVERSITY HEIGHTS CONDOMINIUMS DRAINAGE REPORT 1. TRACT DESCRIPTION The University Heights Condominiums project covers a 1.3978-acre tract located on the northwest corner of Welch and Nevada Streets. A separate 24"x36" sheet, Site Plan 8: Drainage Plan, is part of this report and will be referred here as Exhibit 1. The adopted Flood Insurance Study does not identify the existence of a 100-flood plain affecting this tract (Map # 48041 C 0143 C, July 2, 1992). 2. STORMWATER RUNOFF All of the runoff from the 1.3978 acres flows in a general southeast direction, as sheet flow, onto Nevada Street. The current site is currently vacant. Exhibit 1 shows the tract, its location and its topography. Topographic data was obtained from city of College Station records. The tract has been defined as one drainage section. Exhibit 2 shows the runoff calculations for 5, 10, 25, 50 and 100-year rainfalls for each of the two sections. Runoff detention computations have been made using the 100-year return period and therefore the maximum allowed runoff after development is 6.51 cfs. In order to mitigate the effect of the increase runoff, a location for a detention facility was defined on the project parking lot. 3. INFLOW HYDROGRAPHS Haestad Methods Quick Tr-55 V. 5.47 was used for the analysis given in Exhibit 3 (in six pages). This Exhibit graphically shows individual hydrographs for all storm frequencies. The estimated required storage for the 100-yr storm is calculated at 0.096 ac-ft. 4. DETENTION FACILITY The pond will be built on the project's parking lot. The weir will consist of a 3.0' long curb cut on the south end of the parking lot. The curb at this location will be 0.8' (9.5" curb) high. The flow elevation is set at 312.8' and the curb elevation is set at 313.6'. This weir will empty onto a 4'-wide concrete flume with an upper flow elevation of 312.8'. This flow will in turn discharge onto Nevada Street at the approximate gutter elevation of 311.5'. Exhibit 4 shows the storage volume calculations based on the proposed grading of the parking tot. 5-03 Page 2 The available storage is calculated at 0.12 ac-ft. Exhibit 5 estimates that the available storage at a maximum allowed peak outflow of 6.51 cfs the storage required will be about 0.1 ac-ft. Thus the available storage is sufficient to pond the excess runoff. Haestad Methods Pondpack V. 5.21 was used in the ponding calculations. Exhibit 6 (in two pages) shows the input data for the proposed Vertical -Rectangular weir (curb cut). Exhibit 7 (in five pages) shows the routing calculations for a multiple storm. Peak outflows for each frequency do not exceed pre -development conditions. The following is the routing summary in terms of maximum outflow allowed (pre -development conditions) and peak attained: Storm Max. Allowed Peak Attained Max. 2levation 5-year 4.30 4.31 313.42 10-year 4.83 4.67 313.45 25-year 5.51 5.15 313.50 50-year 6.23 5.66 313.54 100-year 6.51 5.85 313.56 Exhibits 8 and 9 of the original report remain unchanged. The above referenced Exhibit 1 shows the location of the pond and depicts the construction details necessary for implementation of this project. 5. CERTIFICATION This report and design conform to the City of College Station Drainage Policy and Design Standards. �4 6 CHRISTIAN A. GALINDO, P.E. # 53425, R.P.L.S. # 4473 February 27, 2003 Page 3 11 m 11 r N N II 11 II � II 11 N II N N O < T 11 tG N N O 11 p 11 Q 11 11 '- 11 N 11 y d T 11 1 0 b N 11 y II N II II r � , a II 11 I M W M m I fp I N f0 w O 1 > 11 II i 1 N 11 II i 0 O ; O O 11 � II C'1 th !D b U II II at 11 II i L 3 ii N ii , O 11 T II Ip )O p II 11 II - O II O II II � 11 11 II i 11 11 T II O II � II 11 II II 11 II y 11 11 i f0 W II N II � OI i � II 11 w II O O 11 11 ZcL X w N it H II I Ol A 0 o Z ~ II II r Q Q z 6 11 R L) O 11 II ^ N y 1- F 11 II m n 0 � ~ N 11 N II O O F 11 II g = w ii II i v iit ; 0 o 0 o J II O II II U w > n D ~ it i 1 O z ii U 11 j D � 11 II II 11 L 11 11 ' � 11 II q G 11 � 11 ; O i O II 11 II ry J 11 11 it II 11 n o O II n N 11 o O i 0 O n > n n n , u n n t o t o II n y II � OJ p) I CO p) 11 II it Q 11 11 it I r- it II II it it 11 � 6 Q 11 � 11 Y 'Op a 11 U IIy N � N EXHIBIT 2 EXHIBIT 3 Quick TR-55 Ver.5.47 SIN: Executed: 14:47:35 02-26-2003 * * * MODIFIED RATIONAL METHOD * ---- Grand Summary For All Storm Frequencies ---- First peak outflow point assumed to occur at Tc hydrograph recession leg. UNIVERSITY HEIGHTS CONDOMINIUMS ............................................................................ Area = 1.40 acres To = 10.00 minutes ............................................................................ VOLUMES Frequency Adjusted Duration Intens. Qpeak Allowable I Inflow Storage (years) ---------------------------------------------- 'C' minutes in/hr cfs cfs I (ac-ft) (ac-ft) 5 0.800 13 6.903 7.72 4.30 --------- 0.138 0.063 10 0.800 13 7.770 8.69 4.83 0.156 0.071 25 0.800 13 8.885 9.94 5.51 0.178 0.081 50 0.800 13 10.056 11.25 6.23 0.201 0.092 100 0.800 13 10.495 11.74 6.51 0.210 0.096 Quick TR-55 Ver.5.47 SIN: Executed: 14:47:35 02-26-2003 F L 0 W c f s MODIFIED RATIONAL METHOD ---- Graphical Summary for Maximum Required Storage ---- First peak outflow point assumed to occur at Tc hydrograph recession leg. UNIVERSITY HEIGHTS CONDOMINIUMS * RETURN FREQUENCY: 5 yr I Allowable Outflow: 4.30 cfs * 'C' Adjustment: 1.000 1 Required Storage: 0.063 ac-ft *--------------------------------------------------------------------* * Peak Inflow: 7.72cfs Inflow .HYD stored: 5IN .HYD Td = 13 minutes I Approx. Duration for Max. Storage ------/ I I Tc= 10.00 minutes 1 I = 7.693 in/hr Q = 8.60 cfs .I. I - Required Storage I -- 0.063 ac-ft I I I I x x x x x x xIx x x x x x x x x x x I Return Freq: 5 yr C adj.factor: 1.00 Area (ac): 1.40 Weighted C: 0.80 Adjusted C: 0.80 Td= 13 minutes I = 6.903 in/hr Q = 7.72 cfs x x 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Q= 4.30 cfs x o I• Ix (Allow.Outflow) 0 1 x o 1 NOT TO SCALE I x o--------- I 0 1 x ----------------------- 1----------------------------- I------------ 15.00 minutes 17.43 minutes Quick TR-55 Ver.5.47 SIN: Executed: 14:47:35 02-26-2003 F L O W c f s MODIFIED RATIONAL METHOD ---- Graphical Summary for Maximum Required Storage ---- First peak outflow point assumed to occur at Tc hydrograph recession leg. UNIVERSITY HEIGHTS CONDOMINIUMS * RETURN FREQUENCY: 10 yr I Allowable Outflow: 4.83 cfs * 'C' Adjustment: 1.000 Required Storage: 0.071 ac-ft *--------------------------------------------------------------------* * Peak Inflow: 8.69 cfs Inflow .HYD stored: LOIN HYD Td = 13 minutes I Return Freq: 10 yr /------- Approx. Duration for Max. Storage ------/ C adj.factor: 1.00 I I To= 10.00 minutes I = 8.635 in/hr Q = 9.66 cfs •I• I • I Required Storage I .-- 0.071 ac-ft I I I I x x x x x x xIx x x x x x x x x x x I x 0 0 0 0 0 0 x o 0 x 0 0 I • ------------------I---------- 15.00 minutes Area (ac): 1.40 Weighted C: 0.80 Adjusted C: 0.80 Td= 13 minutes I = 7.770 in/hr Q = 8.69 cfs x 0 0 0 0 0 0 0 0 0 o Q= 4.83 cfs Ix (Allow.Outflow) I NOT TO SCALE I x x ------------------- I ------------ 17.44 minutes Quick TR-55 Ver.5.47 SIN: Executed: 14:47:35 02-26-2003 F L 0 W c f s MODIFIED RATIONAL METHOD ---- Graphical Summary for Maximum Required Storage ---- First peak outflow point assumed to occur at Tc hydrograph recession leg. UNIVERSITY HEIGHTS CONDOMINIUMS * RETURN FREQUENCY: 25 yr I Allowable Outflow: 5.51 cfs * 'C' Adjustment: 1.000 1 Required Storage: 0.081 ac-ft *--------------------------------------------------------------------* * Peak Inflow: 9.94 cfs Inflow .HYD stored: 25IN .HYD Td = 13 minutes /------- Approx. Duration for Max. Storage 10.00 minutes 9.861 in/hr 11.03 cfs Required Storage I Return Freq: 25 yr -/ C adj.factor: 1.00 I -- 0.081 ac-ft f I x x x I I x x x xIx x I x x x x I x x x x x Area (ac): 1.40 Weighted C: 0.80 Adjusted C: 0.80 Td= 13 minutes I = 8.885 in/hr Q = 9.94 cfs x x 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Q= 5.51 cfs x 0 Ix (Allow.Outflow) 0 1 x 0 NOT TO SCALE I x o ___________= I 1 0 1 x ------------------------ I ----------------------------- I ------------ 15.00 minutes 17.45 minutes Quick TR-55 Ver.5.47 SIN: Executed: 14:47:35 02-26-2003 F L 0 W c f s MODIFIED RATIONAL METHOD ---- Graphical Summary for Maximum Required Storage ---- First peak outflow point assumed to occur at To hydrograph recession leg. UNIVERSITY HEIGHTS CONDOMINIUMS * RETURN FREQUENCY: 50 yr I Allowable Outflow: 6.23 cfs * 'C' Adjustment: 1.000 1 Required Storage: 0.092 ac-ft *--------------------------------------------------------------------* * Peak Inflow: 11.25 cfs Inflow .HYD stored: 50IN .HYD Td = 13 minutes Approx. Duration for Max. Storage ------/ I I To= 10.00 minutes I = 11.148 in/hr Q = 12.47 cfs •I• I • I Required Storage -- 0.092 ac-ft • I I I x x x x x x xlx x x x x x x x x x x I Return Freq: 50 yr C adj.factor: 1.00 Area (ac): 1.40 Weighted C: 0.80 Adjusted C: 0.80 Td= 13 minutes I = 10.056 in/hr Q = 11.25 cfs x x 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Q= 6.23 cfs x o Ix (Allow.Outflow) 0 1 x 0 NOT TO SCALE I x o 0 x ----------------------- I ----------------------------- I ------------ 15.00 minutes 17.46 minutes Quick TR-55 Ver.5.47 SIN: Executed: 14:47:35 02-26-2003 F L 0 W c f s MODIFIED RATIONAL METHOD ---- Graphical Summary for Maximum Required Storage - First peak outflow point assumed to occur at Tc hydrograph recession leg. UNIVERSITY HEIGHTS CONDOMINIUMS * RETURN FREQUENCY: 100 yr I Allowable Outflow: 6.51 cfs * 'C' Adjustment: 1.000 1 Required Storage: 0.096 ac-ft *-------------------------------------------------------------------* * Peak Inflow: 11.74 cfs Inflow .HYD stored: 100IN HYD I I I I I I I I I I I I I I I x o o Td = 13 minutes Approx. Duration for Max. Storage ------/ I I Tc= 10.00 minutes I = 11.639 in/hr Q = 13.02 cfs I •I• I • I • Required Storage -- 0.096 ac-ft • I I I x x x x x x xIx x x x x x x x x x x I x 0 Return Freq: 100 yr C adj.factor: 1.00 Area (ac): 1.40 Weighted C: 0.80 Adjusted C: 0.80 Td= 13 minutes I = 10.495 in/hr Q = 11.74 cfs x x 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 o Q= 6.51 cfs o Ix (Allow.Outflow) 0 1 NOT TO SCALE I x x ------------ I ----------------------------- I ------------ 15.00 minutes 17.45 minutes POND-2 Version: 5.21 SIN: UNIVERSITY HEIGHTS CONDOMINIUMS CALCULATED 02-26-2003 15:00:36 DISK FILE: c:\ldata\data2003\5-03\pond\5-03 .VOL Planimeter scale: 1 inch = 1 ft. Elevation Planimeter (ft) (sq.in.) ---------------------- 312.80 0.00 312.90 200.00 313.25 7,300.00 313.60 16,900.00 Area Al+A2+sgr(A1*A2 (acres) -------------------------- (acres) 0.00 0.00 0.00 0.00 0.17 0.20 0.39 0.81 EXHIBIT 4 * Volume Volume Sum (acre-ft) --------------------- (acre-ft) 0.00 0.00 0.00 0.00 0.02 0.02 0.09 0.12 * Incremental volume computed by the Conic Method for Reservoir Volumes. Volume = (1/3) * (EL2-EL1) * (Areal + Area2 + sq.rt.(Areal*Areal)) where: EL1, EL2 = Lower and upper elevations of the increment Areal,Area2 = Areas computed for EL1, E12, respectively Volume = Incremental volume between EL1 and EL2 POND-2 Version: 5.21 SIN: EXHIBIT _5 »»> OUTFLOW HYDROGRAPH ESTIMATOR ««< Inflow Hydrograph: c:\ldata\data2003\5-03\pond\100IN .HYD Qpeak = 11.7 cfs Estimated Outflow: c:\ldata\data2003\5-03\pond\ESTIMATE.EST Qpeak = 6.5 cfs Approximate Storage Volume (computed from t= 0.00 to 0.29 hrs) 0.1 acre-ft Outlet Structure File: 5-03 .SIR POND-2 Version: 5.21 SIN: Date Executed: Time Executed: UNIVERSITY HEIGHTS CONDOMINIUMS ***** COMPOSITE OUTFLOW SUMMARY **** Elevation (ft) Q (cfs) Contributing Structures 312.80 0.0 1 313.00 0.8 1 313.20 2.3 1 313.40 4.1 1 313.60 6.3 1 Outlet Structure File: 5-03 .SIR POND-2 Version: 5.21 SIN: Date Executed: Time Executed: UNIVERSITY HEIGHTS CONDOMINIUMS Outlet Structure File: c:\ldata\data2003\5-03\pond\5-03 .STR Planimeter Input File: c:\ldata\data2003\5-03\pond\5-03 .VOL Rating Table Output File: c:\ldata\data2003\5-03\pond\5-03 PND Min. Elev.(ft) = 312.8 Max. Elev.(ft) = 313.6 Incr.(ft) _ .2 Additional elevations (ft) to be included in table: SYSTEM CONNECTIVITY Structure No. Q Table Q Table WEIR-VR 1 -> 1 Outflow rating table summary was stored in file: c:\ldata\data2003\5-03\pond\5-03 .PND Outlet Structure File: 5-03 .STR POND-2 Version: 5.21 SIN: Date Executed: Time Executed: ******************************* UNIVERSITY HEIGHTS CONDOMINIUMS ******************************* »»» Structure No. 1 ««« (Input Data) WEIR-VR Weir - Vertical Rectangular El elev.(ft)? 312.8 E2 elev.(ft)? 313.601 Weir coefficient? 3.087 Weir elev.(ft)? 312.8 Length (ft)? 3.00 Contracted/Suppressed (C/S)? C Outlet Structure File: 5-03 .SIR POND-2 Version: 5.21 SIN: Date Executed: Time Executed: ******************************* UNIVERSITY HEIGHTS CONDOMINIUMS Outflow Rating Table for Structure #1 WEIR-VR Weir - Vertical Rectangular ***** INLET CONTROL ASSUMED ***** Elevation (ft) Q (cfs) Computation Messages --------------------- ------------------------ 312.80 0.0 H =0.0 313.00 0.8 H =.2 313.20 2.3 H =.4 313.40 4.1 H =.6 313.60 6.3 H =.8 C = 3.087 L (ft) = 3 H (ft) = Table elev. - Invert elev. ( 312.8 ft ) Q (cfs) = C * (L-.2H) * (H**1.5) -- Contracted Weir POND-2 Version: 5.21 SIN: Page 1 EXECUTED: 02-26-2003 15:03:19 STORM # 1 Return Freq: 5 years * * * UNIVERSITY HEIGHTS CONDOMINIUMS * * * * ****************** SUMMARY OF ROUTING COMPUTATIONS ****************** Pond File: c:\ldata\data2003\5-03\pond\5-03 .PND Inflow Hydrograph: c:\ldata\data2003\5-03\pond\5IN HYD Outflow Hydrograph: c:\ldata\data2003\5-03\pond\5 OUT HYD Starting Pond W.S. Elevation = 312.80 ft ***** Summary of Peak Outflow and Peak Elevation ***** Peak Inflow = 7.72 cfs Peak Outflow = 4.31 cfs Peak Elevation = 313.42 ft ***** Summary of Approximate Peak Storage ***** Initial Storage = 0.00 ac-ft Peak Storage From Storm = 0.06 ac-ft --------------- Total Storage in Pond = 0.06 ac-ft STORM # 1 Return Freq: 5 years Pond File: c:\ldata\data2003\5-03\pond\5-03 PND Inflow Hydrograph: c:\ldata\data2003\5-03\pond\5IN HYD Outflow Hydrograph: c:\ldata\data2003\5-03\pond\5 OUT HYD EXECUTED: 02-26-2003 Peak Inflow = 7.72 cfs 15:03:19 Peak Outflow = 4.31 cfs Peak Elevation = 313.42 ft POND-2 Version: 5.21 SIN: Page 2 EXECUTED: 02-26-2003 15:03:19 STORM # 2 Return Freq: 10 years * * * UNIVERSITY HEIGHTS CONDOMINIUMS * * * * ****************** SUMMARY OF ROUTING COMPUTATIONS ****************** Pond File: c:\ldata\data2003\5-03\pond\5-03 .PND Inflow Hydrograph: c:\ldata\data2003\5-03\pond\LOIN HYD Outflow Hydrograph: c:\ldata\data2003\5-03\pond\10 OUT HYD Starting Pond W.S. Elevation = 312.80 ft ***** Summary of Peak Outflow and Peak Elevation ***** Peak Inflow = 8.69 cfs Peak Outflow = 4.67 cfs Peak Elevation = 313.45 ft ***** Summary of Approximate Peak Storage ***** Initial Storage = 0.00 ac-ft Peak Storage From Storm = 0.07 ac-ft --------------- Total Storage in Pond = 0.07 ac-ft STORM # 2 Return Freq: 10 years Pond File: c:\ldata\data2003\5-03\pond\5-03 PND Inflow Hydrograph: c:\ldata\data2003\5-03\pond\10IN HYD Outflow Hydrograph: c:\ldata\data2003\5-03\pond\10 OUT .HYD EXECUTED: 02-26-2003 Peak Inflow = 8.69 cfs 15:03:19 Peak Outflow = 4.67 cfs Peak Elevation = 313.45 ft POND-2 Version: 5.21 SIN: Page 3 EXECUTED: 02-26-2003 15:03:19 STORM # 3 Return Freq: 25 years ************************************* * * UNIVERSITY HEIGHTS CONDOMINIUMS * * ****************** SUMMARY OF ROUTING COMPUTATIONS ****************** Pond File: c:\ldata\data2003\5-03\pond\5-03 .PND Inflow Hydrograph: c:\ldata\data2003\5-03\pond\25IN .HYD Outflow Hydrograph: c:\ldata\data2003\5-03\pond\25 OUT HYD Starting Pond W.S. Elevation = 312.80 ft ***** Summary of Peak Outflow and Peak Elevation ***** Peak Inflow = 9.94 cfs Peak Outflow = 5.15 cfs Peak Elevation = 313.50 ft ***** Summary of Approximate Peak Storage ***** Initial Storage = 0.00 ac-ft Peak Storage From Storm = 0.08 ac-ft -------------- Total Storage in Pond = 0.08 ac-ft STORM # 3 Return Freq: 25 years Pond File: c:\ldata\data2003\5-03\pond\5-03 PND Inflow Hydrograph: c:\ldata\data2003\5-03\pond\25IN HYD Outflow Hydrograph: c:\ldata\data2003\5-03\pond\25 OUT HYD EXECUTED: 02-26-2003 Peak Inflow = 9.94 cfs 15:03:19 Peak Outflow = 5.15 cfs Peak Elevation = 313.50 ft POND-2 Version: 5.21 SIN: Page 4 EXECUTED: 02-26-2003 15:03:19 STORM # 4 Return Freq: 50 years * UNIVERSITY HEIGHTS CONDOMINIUMS * * * * ****************** SUMMARY OF ROUTING COMPUTATIONS ****************** Pond File: c:\ldata\data2003\5-03\pond\5-03 .PND Inflow Hydrograph: c:\ldata\data2003\5-03\pond\50IN .HYD Outflow Hydrograph: c:\ldata\data2003\5-03\pond\50 OUT .HYD Starting Pond W.S. Elevation = 312.80 ft ***** Summary of Peak Outflow and Peak Elevation ***** Peak Inflow = 11.25 cfs Peak Outflow = 5.66 cfs Peak Elevation = 313.54 ft ***** Summary of Approximate Peak Storage ***** Initial Storage = 0.00 ac-ft Peak Storage From Storm = 0.10 ac-ft --------------- Total Storage in Pond = 0.10 ac-ft STORM # 4 Return Freq: 50 years Pond File: c:\ldata\data2003\5-03\pond\5-03 PND Inflow Hydrograph: c:\ldata\data2003\5-03\pond\50IN HYD Outflow Hydrograph: c:\ldata\data2003\5-03\pond\50 OUT HYD EXECUTED: 02-26-2003 Peak Inflow = 11.25 cfs 15:03:19 Peak Outflow = 5.66 cfs Peak Elevation = 313.54 ft POND-2 Version: 5.21 SIN: Page 5 EXECUTED: 02-26-2003 15:03:19 STORM # 5 Return Freq: 100 years * * * UNIVERSITY HEIGHTS CONDOMINIUMS * * * * ****************** SUMMARY OF ROUTING COMPUTATIONS ****************** Pond File: c:\ldata\data2003\5-03\pond\5-03 .PND Inflow Hydrograph: c:\ldata\data2003\5-03\pond\100IN HYD Outflow Hydrograph: c:\ldata\data2003\5-03\pond\100 OUT .HYD Starting Pond W.S. Elevation = 312.80 ft ***** Summary of Peak Outflow and Peak Elevation ***** Peak Inflow = 11.74 cfs Peak Outflow = 5.85 cfs Peak Elevation = 313.56 £t ***** Summary of Approximate Peak Storage ***** Initial Storage = 0.00 ac-ft Peak Storage From Storm = 0.11 ac-ft --------------- Total Storage in Pond = 0.11 ac-ft STORM # 5 Return Freq: 100 years Pond File: c:\ldata\data2003\5-03\pond\5-03 .PND Inflow Hydrograph: c:\ldata\data2003\5-03\pond\100IN .HYD Outflow Hydrograph: c:\ldata\data2003\5-03\pond\100 OUT .HYD EXECUTED: 02-26-2003 Peak Inflow = 11.74 cfs 15:03:19 Peak Outflow = 5.85 cfs Peak Elevation = 313.56 ft