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Drainage ReportG ALIND O E N GINEERS AND PLANNERS, INC. 3833 South Texas Ave., Suite 213 Bryan, Texas 77802 (979) 846-8868 1. TRACT DESCRIPTION HOLLEMAN VILLAGE ADDITION, SECTION TWO DRAINAGE REPORT 18-01 This subdivision covers approximately 4. 5 acres of land located at the southwest corner of the intersection of Holleman Drive and the proposed south extension of Jones-Butler Road. Upon development and deeding of additional right of way to the City the net subdivision area will be about 4.3 acres. The tract is currently vacant and it is traversed by an unlined dirt channel that conveys runoff water from upstream lands as shown on Exhibit 1. These upstream lands are defined as Drainage Area 1 covering approximately 9. 76 acres . Drainage areas 2, 3, 4 and 5 are area within the confines of the subdivision. Exhibit 2, in a larger scale, shows the total drainage basin, of which this subdivision is a part. The basin covers a total area of 69.5 acres. The construction design drawings submitted together with this report constitute a reference document where appropriate. The adopted Flood Insurance Study does not identify the existence of a 100-flood plain affecting this tract (Map # 48041 C 0182 C, July 2, 1992). Exhibit 3 shows the outline of the 100-yr flood plain boundary interpreted by City Staff. 2. STORMWATER RUNOFF Exhibit 4, in two pages, shows the runoff calculations for 5, 10, 25, 50 and 100-year rainfalls for the project area and for the other areas in the basin as shown on Exhibits 1 and 2 before and after development. Five sections are identified in this exhibit: Section 1 is the area that contributes the offsite runoff that traverses through the subject subdivision. Sections 2, 3, 4 and 5 are part of the subdivision itself. In addition, Exhibit 4 shows the overall basin area less Drainage Sections 1, 2, 3, 4 and 5 or an area of 55.47 acres. Runoff form this area remains unchanged when this subdivision goes from pre to post development conditions. 3. ON -SITE DETENTION No onsite detention has been provided for this project due to the proximity of the existing pond across from the extension of Jones-Butler Rd. shown on Exhibit 1. Currently this pond stores runoff from post developed Section 1 and pre developed Sections 2 through 5. Page 1 • 4. STORMWATER SYSTEM The following analysis was made using Qs for a 100-yr storm. 4.1. Runoff from Section 1 currently will drain through an unlined channel traversing the tract subject of this report. The characteristics and capacity of this channel are shown on Exhibit 5. This channel, with a maximum capacity of 78.18 cfs, is capable of handling the 100-yr runoff for Section 1 calculated at 68.16 cfs . 4.2. Runoff from Section 1 will be conveyed into a 33" RCP through a controlled inlet at the entrance of Holleman Village Addition, Section Two. The characteristics of this pipe are given in Exhibit 6. This pipe has a full flow capacity of 89 . 95 cfs , greater than the required 68. 16 cfs . 4.3 A curb inlet at the end of the 33" RCP will connect this pipe with a 42" RCP that will extend to the east side of Jones-Butler Rd. The characteristics of this pipe are given in Exhibit 7. The Q flowing into this pipe comes from Sections 1, 2, 4 and one half 3, or a total of 85.03 cfs. The full flow capacity of this pipe is calculated 92.47 cfs. 4.4. An unlined channel, trapezoidal section, will be cut at the end of this pipe and will be extended to connect with the existing channel that currently drains all runoff to the pond discussed in Paragraph 3 above. The characteristics of this channel are given in Exhibit 9. 4. 5. All runoff from the whole basin accumulates in the pond highlighted in Exhibit 10. This runoff is estimated at 193. 55+68.16+12.45 = 274.16 cfs (Exhibit 4). After development this figure increases to 193.55+68.16+28.59 = 290.30 cfs, or 5.89%. Exhibit 10 indicates the pond level will rise 0.85', to about 31 O', due to the additional run off, a figure which is still within the maximum pond elevation of 311 '. 5. GRIDIRON DRIVE The following analysis was made using Qs for a 10-yr storm. Runoff flow on Gridiron Dr. is calculated in Exhibits 11 and 12. Exhibit 11 shows the performance of the right lane of showing a water depth of 0.41' at the location of a 3-section (15' long) curb inlet. The left lane at this location, Exhibit 12, will have water to a depth of 0.22'. That is, at the location of the proposed curb inlet there will be a strip of dry asphalt nearly 10' wide. The 10-yr flow on the right side of Gridiron Lane (Section 2), at the south end of Section 2, is calculated at 8. 96 cfs. A3-section , 4" depressed, curb inlet installed at this location, with a capacity of 10. 56 cfs, Exhibit 13, will remove all this runoff. Page 2 6. CERTIFICATION This report and design meets the City of College Station Drainage Policy and Design Standards. ~#4473 November 14, 2000 ""'"''"'''''' __ .,., ~ t 0 F r '~•-; '\ \'-... ·····. ····· c ../': Wff1. : ~ .... ··· * ...... :tll ''i ; *.: ···* ~ '*-' ~*l '!"!: .........••.•...•.•.••.••••••.•• : .••... I, ~CHRISTIAN A. GALINool ~·······:························ .. ············-1 ~"'() .... 53425 /Q;-/1 ~ ~ 'e'1J(' <;) .' 4,/ ,& "IM .... A',· ...... GtsTc~~ ... ~~ -'1/J ;f· .. _ • .. .,:: I l:-••• Q• ,, .... .:J:' II, •.• , ·~,= •••• .,Q>' ..,. ·.,eio:: '.~/{ ... :::AL t:..~ ~qa,-- " \. ........ ·.~· . ·. ~ ') ... 'f;."a'l:t.-..~9!b~ ... ~ -~-.... Page 3 EXHIBIT 1 "1 \ I ) \// EXHIBIT 2 •'"' ·"'' • .vu (") I-m :::c >< w Job: Date: Section 18--01 09-Nov-01 Soil Type A Acres Pre-development of thhis Project c RUNOFF CALCULATIONS -RATIONAL METHOD HOLLEMAN VILLAGE ADDITION, SCTION TWO COLLEGE STATION, TEXAS (County: Brazos) Veloc. Length T cone. in min. fps ft Cale. Used 5 yrs 10 yrs OFF-SITE RUN-OFF Tc = 10.0 25 yrs 50yrs 100yrs when the calculated value is less than 10.0 Q 5yrs Q 10 yrs Q 25 yrs Q 50yrs Page 1 Q 100yrs ·----------------------------------------------------------- --------------------------------------- Nat. Woodlands Post-development of this Project Residential Pre-development 2 3 4 5 Total Nat. Woodlands Nat. Woodlands Nat. Woodlands Nat. Woodlands Post-development 2 3 4 5 Total Residential Residential Residential Residential County: Brazos 9.760 9.760 1.730 0.820 0.310 1.420 4.280 1.730 0.820 0.310 1.420 4.280 0.600 0.600 0.250 0.250 0.250 0.250 0.600 0.550 0.600 0.550 5.000 5.000 1.000 1.000 1.000 1.000 4.000 2.500 5.000 2.500 1,600 1,600 500 250 550 550 600 250 520 550 5.3 10.0 5.3 10.0 ON-SITE RUN-OFF 8.3 4.2 9.2 9.2 2.5 1.7 1.7 3.7 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 7.693 7.693 7.693 7.693 7.693 7.693 7.693 7.693 7.693 7.693 Constants for use in formula: l=b/(t+d)Ae b e d 2-yr 5-yr 10-yr 25-yr 65.000 76.000 0.806 0.785 8.000 8.500 80.000 0.763 8.500 89.000 0.754 8.500 8.635 8.635 8.635 8.635 8.635 8.635 8.635 8.635 8.635 8.635 50-yr 98.000 0.745 8.500 9.861 9.861 9.861 9.861 9.861 9.861 9.861 9.861 9.861 9.861 100-yr 96.000 0.730 8.000 11 .148 11 .148 11 .148 11 .148 11 .148 11 .148 11 .148 11.148 11 .148 11 .148 11.639 11.639 11.639 11.639 11 .639 11 .639 11.639 11 .639 11 .639 11 .639 45.05 45.05 3.33 1.58 0.60 2.73 8.23 7.99 3.47 1.43 6.01 18.89 50.56 50.56 3.73 1.77 0.67 3.07 9.24 8.96 3.89 1.61 6.74 21.21 57.75 57.75 4.27 2.02 0.76 3.50 10.55 10.24 4.45 1.83 7.70 24.22 65.28 65.28 4.82 2.29 0.86 3.96 11 .93 11 .57 5.03 2.07 8.71 27.38 68.16 68.16 5.03 2.39 0.90 4.13 12.45 12.08 5.25 . 2.16 9.09 28.59 Job: Date: Section 18--01 09-Nov-01 Soil Type Pre-development of this project Rem. Residential Total A Acres 55.470 55.470 Post-development of this Project Rem. Residential 55.470 Total 55.470 County: Brazos c 0.550 0.550 RUNOFF CALCULATIONS -RATIONAL METHOD HOLLEMAN VILLAGE ADDITION, SCTION TWO COLLEGE STATION, TEXAS (County: Brazos) Veloc. Length T cone. in min. fps ft Cale. Used 5 yrs 10 yrs TOTAL BASIN LESS SECTIONS 1, 2, 3, 4 AND 5 2.500 5,000 33.3 33.3 4.054 4.633 2.500 5,000 33.3 33.3 4.054 4.633 Constants for use in formula: l=b/(t+d)Ae 2-yr 5-yr 10-yr 25-yr 50-yr ---------------------------------------------- b 65.000 76.000 80.000 89.000 98.000 e 0.806 0.785 0.763 0.754 0.745 d 8.000 8.500 8.500 8.500 8.500 Tc= 10.0 25 yrs 50yrs 100yrs 5.330 6.070 6.344 5.330 6.070 6.344 100-yr ------------- 96.000 0.730 8.000 when the calculated value is less than 10.0 Q 5yrs 123.69 123.69 123.69 123.69 Q 10 yrs 141.35 141 .35 141 .35 141.35 a 25 yrs 162.62 162.62 162.62 162.62 a 50yrs 185.19 185.19 185.19 185.19 Page 2 Q 100yrs 193.55 193.55 193.55 193.55 Trapezoidal Channel Analysis & Design Open Channel -Uniform flow Worksheet Name: HOLLEMAN VILLAGE Comment: DOUBLETREE CONDOS CHANNEL CAPACITY Solve For Discharge Given Input Data: Bottom Width ..... Left Side Slope .. Right Side Slope. Manning's n ..... . Channel Slope ... . Depth ........... . Computed Results: Discharge ....... . Velocity ........ . Flow Area ....... . Flow Top Width .. . Wetted Perimeter. Critical Depth .. . Critical Slope .. . Froude Number ... . 2.00 ft 3.00:1 (H:V) 3.00:1 (H:V) 0.060 0.0050 ft/ft 3.00 ft 78.18 cfs 2.37 fps 33.00 sf 20.00 ft 20.97 ft 1.81 ft 0.0549 ft/ft FULL Open Channel Flow Module, Version 3.21 (c) 1990 EXHIBIT .5 Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708 Circular Channel Analysis & Design Solved with Manning's Equation Open Channel -Uniform flow Worksheet Name: HOLLEMAN VILLAGE Comment: 33" RCP FROM DOUBLETREE TO GRIDIRON LANE Solve For Full Flow Capacity Given Input Data: Diameter ......... . Slope ............ . Manning's n ...... . Discharge ........ . Computed Results: Full Flow Capacity .... . Full Flow Depth ....... . Velocity ......... . Flow Area ........ . Critical Depth ... . Critical Slope ... . Percent Full ..... . Full Capacity .... . QMAX @.94D ....... . Froude Number .... . 2.75 ft 0.0250 ft/ft 0.013 83.62 cfs 83.62 cfs 2.75 ft 14.08 fps 5.94 sf 2.67 ft 0.0220 ft/ft 100.00 % 83.62 cfs 89.95 cfs FULL Open Channel Flow Module, Version 3.21 (c) 1990 EXHIBIT 6 Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708 Circular Channel Analysis & Design Solved with Manning's Equation Open Channel -Uniform flow Worksheet Name: HOLLEMAN VILLAGE Comment: 42 11 RCP FROM GRIDIRON LANE TO JONES BUTLER Solve For Full Flow Capacity Given Input Data: Diameter ......... . Slope ............ . Manning's n ...... . Discharge ........ . Computed Results: Full Flow Capacity .... . Full Flow Depth ....... . Velocity ......... . Flow Area ........ . Critical Depth ... . Critical Slope ... . Percent Full ..... . Full Capacity .... . QMAX @.94D ....... . Froude Number .... . 3.50 ft 0.0073 ft/ft 0.013 85.96 cfs 85.96 cfs 3.50 ft 8.93 fps 9.62 sf 2.89 ft 0.0072 ft/ft 100.00 % 85.96 cfs 92.47 cfs FULL Open Channel Flow Module, Version 3.21 (c) 1990 EXHIBIT i Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708 Trapezoidal Channel Analysis & Design Open Channel -Uniform flow Worksheet Name: HOLLEMAN VILLAGE Comment: CHANNEL FROM JONES BUTLER TO PARK POND Solve For Discharge Given Input Data: Bottom Width ..... Left Side Slope .. Right Side Slope. Manning's n ..... . Channel Slope ... . Depth ........... . Computed Results: Discharge ....... . Velocity ........ . Flow Area ....... . Flow Top Width .. . Wetted Perimeter. Critical Depth .. . Critical Slope .. . Froude Number ... . 3.00 ft 3.00:1 (H:V) 3.00:1 (H:V) 0.050 0.0050 ft/ft 3.00 ft 105.14 cfs 2.92 fps 36.00 sf 21.00 ft 21.97 ft 1.94 ft 0.0366 ft/ft FULL Open Channel Flow Module, Version 3.21 (c) 1990 EXHIBIT 8 Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708 316.7 x WS 309.2 EXHIBIT 9 SCALE: 80' 1no 1 310.1 x 301 x • Trapezoidal Channel Analysis & Design Open Channel -Uniform flow Worksheet Name: HOLLEMAN VILLAGE Comment: PARK POND Solve For Depth Given Input Data: Bottom Width ..... Left Side Slope .. Right Side Slope. Manning's n ..... . Channel Slope ... . Discharge ....... . Computed Results: Depth ........... . Velocity ........ . Flow Area ....... . Flow Top Width .. . Wetted Perimeter. Critical Depth .. . Critical Slope .. . Froude Number ... . 20.00 ft 5.00:1 (H:V) 9.00:1 (H:V) 0.100 0.0040 ft/ft 16.14 cfs 0.85 ft 0.73 fps 22.03 sf 31.89 ft 32.02 ft 0.26 ft 0.2341 ft/ft 0.16 (flow is Subcritical) Open Channel Flow Module, Version 3.21 (c) 1990 EXHIBIT 10 Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708 • Triangular Channel Analysis & Design Op en Cha nnel -Uniform flow Worksheet Name: HOLLEMAN VILLAGE Comment: GRIDIRON LANE CAPACITY, QlO -RIGHT SIDE Solve For Depth Given Input Data: Left Side Slope .. Right Side Slope. Manning's n ..... . Channel Slope ... . Discharge ....... . Computed Results: Depth ........... . Velocity ........ . Flow Area ....... . Flow Top Width .. . Wetted Perimeter. Critical Depth .. . Critical Slope .. . Froude Number ... . 0 .00:1 (H:V) 26.00:1 (H:V) 0.013 0.0112 ft/ft 8.96 cfs 0.41 ft 4.10 fps 2.19 sf 10.66 ft 11.08 ft 0.49 ft 0.0041 ft/ft 1.60 (flow is Supercritical) Open Channel Flow Module, Version 3.21 (c) 1990 . EXHIBIT 11 Haestad Methods, Inc . * 37 Brookside Rd * Waterbury, Ct 06708 • Triangular Channel Analysis & Design Open Channel -Uniform flow Worksheet Name: HOLLEMAN VILLAGE Comment: GRIDIRON LANE CAPACITY, QlO -LEFT SIDE Solve For Depth Given Input Data: Left Side Slope .. Right Side Slope. Manning's n ..... . Channel Slope ... . Discharge ....... . Computed Results: Depth ........... . Velocity ........ . Flow Area ....... . Flow Top Width .. . Wetted Perimeter. Critical Depth .. . Critical Slope .. . Froude Number ... . 0.00:1 (H:V) 26.00:1 (H:V) 0.013 0.0112 ft/ft 1.61 cfs 0.22 ft 2.67 fps 0.60 sf 5.60 ft 5.82 ft 0.25 ft 0.0052 ft/ft 1.43 (flow is Supercritical) Open Channel Flow Module, Version 3.21 (c) 1990 EXHIBIT 12 Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708 ~ .-. 18-01 s E c T I 0 N 2 2 2 3 I 3 3 HOLLEMAN VILLAGE DEPRESSED INLETS QL = 0.7*(1/(H1-H2))*(H1"5/2-H2"5/2) D E I p D N R E L E p E s T T s H H1 H2 ft in ft ft ft . 5 3 0.41 0.66 0.25 5 4 0.41 0.74 0.33 5 5 0.41 0.83 0.42 10 3 0.41 0.66 0.25 10 4 0.41 0.74 0.33 10 5 0.41 0.83 0.42 15 3 0.41 0.66 0.25 15 4 0.41 0.74 0.33 15 5 0.41 0.83 0.42 INLET - 1, 2 OR 3 SECTIONS DEPRESSION -GUTTER DEPPRS. INCHES DEPTH -FLOW IN APPROACH GUTTER QL -FLOW CAPACITY 2.44 2.44 2.44 2.44 2.44 2.44 2.44 2.44 2.44 EXHIBIT 13 11/09/01 Capture QL Capac. cfs cfs 0.32 0.55 2.75 0.41 0.70 3.52 0.51 0.87 4.35 0.32 0.55 5.51 0.41 0.70 7.04 0.51 0.87 8.69 0.32 0.55 8.26 0.41 0.70 10.56 I 0.51 0.87 13.04