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00071685GALIND O ENGINEERS AND PLANNERS, INC. 3833 South Texas Ave., Suite 213 Bryan, Texas 77802 (979) 846-8868 October 25, 2001 Spencer G. Thompson, Jr. Development Services City of College Station 1101 South Texas Avenue College Station, TX 77840 Subject: Drainage Report Skypala Fourplexes College Station, TX Please find enclosed the referenced report for your review. This analysis covers the Skypala Fourplexes, a 0.9511-acre tract bound by Wellborn Road, Maple Street and First Street, in the W. C. Boyett Estate Partition, college Station, TX. Sincerely, GALINDO ENGINEERS AND PLANNERS, INC. a . Galindo, P.E., R.P.L.S. President cc: Greg Et Cindy Skypala 2700 West 16th, Apt. 313 Amarillo, TX 79102 0 F 7-4141. •...ea• .....................v...... •C3.' 53425 C'. F e r4 ~ ~~'c h ~SC'i L, Lam. A I. GALINDO ENGINEERS AND PLANNERS, INC. 3833 South Texas Ave., Suite 213 Bryan, Texas 77802 (979) 846-8868 SKYPALA FOURPLEXES DRAINAGE REPORT 29-01 1. TRACT DESCRIPTION This project encompasses six 2-story fourplexes on Lots 1, 2, 3, 18, 19 and 20, Block 15, W. C. Boyett Estate Partition, for a total of 0.9511 acre. The attached 24" x 36" Site Plan is part of this report and is herein referred to as Exhibit 1. This exhibit depicts the proposed improvements and grading plan for the project. No field work was performed by the undersigned. All surveying data was provided by the Client or obtained from City of College Station public records. The adopted Flood Insurance Study does not identify the existence of a 100-year flood plain affecting this tract (Map # 48041 C 0143 C, July 2, 1992). 2. PURPOSE OF THIS ANALYSIS The purpose of this report was to estimate the pre and post development runoff and determine the performance of the proposed grading and of the proposed outlet structure. 3. RESULTS This tract is relatively flat, currently vacant, clear of ground cover and subjected to considerable amounts of vehicular traffic. This is reflected on the runoff coefficient of 0.45 given in Exhibit 2. This exhibit shows the runoff calculations for the 5, 10, 25, 50 and 100-year storms for the only drainage section defined. The resulting calculated runoff for the 100-yr storm is 4.66 cfs, for Pre Development, and 7.19 cfs for Post Development conditions, or an increase of 50%. Exhibit 3 (in 2 pages) depicts the flow characteristics of the proposed outlet structure to be located at the southeast end of the parking lot. A 2.5' curb cut (in a 0.5' high curb) will allow a flow of 4.66 cfs at a velocity of 5.24 fps with water rising 0.36'. The same curb cut will allow a flow of 7.19 cfs at a velocity of 6.06 fps with water rising 0.47'. Therefore this outlet will provide a degree of runoff mitigation. This analysis has been prepared in conformance with the City of College Station standards. CHRISTIAN A. GALINDO, P.E. # 53425, R.P.L.S. # 4473 October 25, 2000 14 4trI Q, . ~F~. • 'S'' ' . uHPUST.IA I A. GAL.INDO 53+25 to aNAI.~e~'11`a, EXHIBIT 2 II 11 11 N II aa11 II ~ II II II II 11 II II II ` II O 11 N II G tl II t0 II N II N II ~ II d In 11 II II N 11 N II O II II II II > II " II a y II d O II N II II 5 II II U N O II II II 0) II N II II II t.. II d T II C II ~ II N II II L II II 3 O II I it ° it n n u u u II u n u II - a' it II ~ II II I II II - to II II N II II It II II ~ 11 " 11 II - T II 2 II II ~ 11 II W II II II II J a 11 Z II II 0 u M it F II It LL LL C? ~Qx N II Z to D Z h O X IyJI Il C J II F a .E W 1-' W II c II F- z a N 11 O M I I Q J 0 a o U u m II ~ it U LL W LL 5 0 II t I LL a W II Of II 0 -j Z Y J 11 C 0 d) K N U U ii J it II 11 II O p, II II 7 It u u u u u u II N II II I a U II it a II II II 11 - ~ 11 a U 1i N N II I u c u it II ~ II m o p u U u 7 a r n a a m m m c) (p to V V co c) (3) (n r ~ 00 co co CR rn in O O (D (D M M M M to u) r 0 n 0 ^ n co co rn 0 v to Q v O m O W ro n r m Lr) M ro QI r O r N 'n N O N 0 U-) rn O O r O M O lf~ M N S 0 rn rn O , O ~ E CL d l9 t o d O d , ~ 4 Q > d ~ a N o r N a r 0 O O O a ~ o 0 0 tb O N O T O r to O O O 00 N tT O 'O O to O T O r N n 0i o 00 N CO O (MO O T O n lli 0O W O co It It o ~ o ~ j O r to to O O 00 O , C N > O 00 O N to O o0 O (D N C lt1 O U 0 C N O N U m Rectangular Channel Analysis & Design Open Channel - Uniform flow Worksheet Name: SKYPALA FOURPLEXES Comment: PARKING LOT OUTFALL - Q100 PRE DEVELOPMENT Solve For Depth Given Input Data: Bottom Width..... Manning's n...... Channel Slope.... Discharge........ Computed Results: Depth............ Velocity......... Flow Area........ Flow Top Width... Wetted Perimeter. Critical Depth... Critical Slope... Froude Number.... 2.50 ft 0.014 0.0135 ft/ft 4.66 cfs 0.36 ft 5.24 fps 0.89 sf 2.50 ft 3.21 ft 0.48 ft 0.0056 ft/ft 1.55 (flow is Supercritical) EXHIBIT 3 Open Channel Flow Module, Version 3.21 (c) 1990 Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708 Rectangular Channel Analysis & Design Open Channel - Uniform flow Worksheet Name: SKYPALA FOURPLEXES Comment: PARKING LOT OUTFALL - Q100 POST DEVELOPMENT Solve For Depth Given Input Data: Bottom Width..... Manning's n...... Channel Slope.... Discharge........ 2.50 ft 0.014 0.0135 ft/ft 7.19 cfs Computed Results: Depth............ Velocity......... Flow Area........ Flow Top Width... Wetted Perimeter. Critical Depth... Critical Slope... Froude Number.... 0.47 ft 6.06 fps 1.19 sf 2.50 ft 3.45 ft 0.64 ft 0.0058 ft/ft 1.55 (flow is Supercritical) Open Channel Flow Module, Version 3.21 (c) 1990 Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708