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Home My WebLink About10500 Stockdale Hwy - Drainage StudyThe Shops at Riverwalk – Phases 2B &3 Drainage Study 2 Background Castle & Cooke California, Inc. has been contracted to prepare drainage study for additional improvements within an existing commercial development. This commercial project, on approximately 16.21 acres, is located on Stockdale Highway between Buena Vista Road and Calloway Drive in the City of Bakersfield, CA. The site, while generally flat in topography, gently slopes to the southwesterly. The project is currently partially developed with vacant pads, paved parking, and several existing restaurants along Stockdale Highway. The proposed layout will alter the current configuration of the parking lot. The existing storm drain lines in the parking lot consist of 18” RCP lines based on the approved plans. Several existing storm drain lines will be protected in place and incorporated as part of the new storm drain system. The analysis will focus on the series of existing and proposed catch basin. There will be four tie-in points which ultimate ties into the mainline paralleling Stockdale Highway. This study will also focus on the watershed contributing to this existing storm drain system. It will also verify the capacity existing storm drain pipes with flows generated from proposed development. Purpose This study will present the findings pertaining to the anticipated storm water runoff for the drainage areas tributary to and generated by the contributing to existing and proposed inlets within the existing commercial development. The study also provides analysis to size inlets and pipes by quantifying the flow to each pipe and analyzing the hydraulic grade lines stays within the existing and proposed storm drain system. Approach The procedure used to determine the design flows are outlined in the City of Bakersfield Subdivision & Engineering Design Manual (hereafter referred to as the Manual). The pertinent steps are as follows: 1. Using a topographical map, the design grades, and the proposed development layout, determine the sub-basin boundaries within the watershed. Record the sub-basin characteristics in a tabular format similar to the one provided in the Manual. 2. Determine the average velocity using the SCS Average Velocity Chart 3. Determine the initial time of concentration, (Tc), based on Section 2.3.2.1 of the Manual by using the roof gutter time and average velocity. 4. Establish the intensity based on the Intensity-Duration curves for a given event using Sheet D-1 in the Manual. 5. Determine the flow to the concentration point. 6. Route the flow to the downstream concentration points and divide the study area into defined subareas that incrementalized all flow contributions to the proposed drainage inlets. 7. Estimate flows utilizing the City’s Rational Method in accordance with the Subdivision Standards The Shops at Riverwalk – Phases 2B &3 Drainage Study 3 Assumptions The following information was assumed to apply: 1. The runoff coefficient of 0.90 is consistent over the commercial zones and a runoff coefficient of 0.15 is applied to landscaped areas. 2. These calculations are based on the current precise grading plans. Summary of Results There will be four separate drainage areas with four separate tie-in points located on the site (see table below). A few drainage areas (Areas 1a, 3a, and 3b) included the landscaping sloping towards the proposed parking lot. These areas used a composite coefficient to calculate the proposed runoff. It was assumed that most of the proposed commercial buildings would drain to the back. A roof to gutter time of 10 minutes was used for these drainage areas. The revised drainage system will consist of existing and proposed storm drain ranging in size from 12” to 18” in diameter. The proposed on-site pipes were sized to have enough capacity for the generated flows. The following table will summarize the results of the hydrology calculations at tie-in points. Refer to the Hydrology Calculations for the complete results. Tie-in Point Area (acres) Tc (mins) Proposed Q10 (cfs) 1 2.94 18.34 3.25 2 3.78 13.44 5.44 3 6.76 26.93 5.67 4 2.73 12.01 4.14 Civil 3d Hydraflow Express uses the slope, size, and, known/proposed discharge to determine pipe capacity. This program was used for verifying the capacity of the existing pipes located just downstream of the tie-in points. These calculations show there’s sufficient capacity to handle the proposed flows (see appendix). The sizes, lengths, and slopes of these existing pipes can be viewed on the Drainage Exhibit. There are 2’x2’ Christy Box Inlets proposed onsite which was sized using the Hydraflow software (see appendix). These inlets will be able to handle 8.25 cfs with a maximum depth of 1 foot and a radial spread of 53 feet. The new inlet locations will be spread out throughout the site as shown on the Precise Grading Plan. The Shops at Riverwalk – Phases 2B &3 Drainage Study 4 Vicinity Map Not to Scale@ The Shops at Riverwalk The Shops at Riverwalk – Phases 2B &3 Drainage Study 5 ATTACHMENTS · HYDROLOGY CALCULATIONS · PIPE CAPACITY CALCULATIONS · INLET SIZING CALCULATIONS · DRAINAGE EXHIBIT CITY OF BAKERSFIELD RATIONAL METHOD (In accordance with City of Bakersfield Standards) TABLE OF RUNOFF COEFFICIENTS R-1, 6000 SF 0.42 JOB TITLE:THE SHOPS AT RIVERWALK - PHASES 2B/3R-1, 7500 SF 0.38 DATE:R-1, 10000 SF 0.34 REVISION DATE:R-1, 15000 SF 0.27 Rational Values:R-2 0.55 Event:10YEAR Values: 5, 10, 50R-3, R-4, M-H 0.8 M.A.P.6 in./yr. Values: 6, 10, 15, 20, 25, 30Commercial 0.9 Industrial 0.8 Curve Values Parks 0.15 a:2.38I=a+bTc (Tc<20min.)Grasslands, Type A Soil0.15 b:-0.058Grasslands, Type B Soil0.25 P60:0.550I=K1*(6.02*Tc)^(0.17*LN(p60/K1)Grasslands, Type C Soil0.35 K1:40.00 (Tc>=20min.)Grasslands, Type D Soil0.45 Pavement, drives & roofs0.95 Backyards 0.05 Lawn-landscape 2% slope0.100.17 Lawn-landscape 2-7% slope0.150.22 Lawn-landscape 7% slope 0.20 0.35 SUBAREACIARslt TcLdHQV Trial Tc Roof toTmD NAMERunoff Intensity TotalTimeLengthElev.FlowVel.MIN.GutterTravelPipe Coef.(in./hr.)Area Conc.Feet Diff.Slope CFS FPS Time Time Dia. AC.MIN.Feet%MIN.MIN.In. PIPE SIZING CALCULATIONS Area 1a 0.791.651.5112.552752.10.75%1.96 1.8012.5510 2.55 Pipe 1 332.50 0.2212 12.76 Pipe 2 0.791.641.51222 1.94 1.1012.76 3.3618 16.13 Pipe 3 0.791.441.51129 1.71 0.9716.13 2.2218 18.34 Area 1b 0.901.801.4310.001803.31.84%2.32 2.7010.000 1.11 Pipe 4 162.95 0.0918 10.09 Tie-In Point 1 0.841.312.94 3.25 18.34 Area 2a 0.901.751.2010.931613.42.14%1.89 2.9010.9310 0.93 Pipe 5 0.901.751.2086 1.89 1.0710.93 1.3418 12.27 Area 2b 0.901.760.6610.611102.62.35%1.05 3.0010.6110 0.61 Pipe 6 1871.33 2.3312 12.95 Area 2c 0.901.741.9211.001753.82.19%3.01 2.9111.0010 1.00 Pipe 7 0.901.632.58142 3.78 4.8112.95 0.4912 13.44 Tie-In Point 2 0.901.603.78 5.44 13.44 January 27, 2014 Q:\PROJECTS\680693\studies\Drainage -Phases 2&3\Calculations\35769271.xls Page 1 SUBAREACIARslt TcLdHQV Trial Tc Roof toTmD NAMERunoff Intensity TotalTimeLengthElev.FlowVel.MIN.GutterTravelPipe Coef.(in./hr.)Area Conc.Feet Diff.Slope CFS FPS Time Time Dia. AC.MIN.Feet%MIN.MIN.In. Area 3a 0.771.352.0917.672952.30.79%2.18 1.8417.6715 2.67 Pipe 8 331.23 0.4518 18.12 Pipe 9 0.771.332.09195 2.14 1.2118.12 2.6918 20.81 Pipe 10 0.771.182.0989 1.90 1.0820.81 1.3718 22.18 Area 3b 0.881.721.6411.301952.91.49%2.49 2.5011.3010 1.30 Pipe 11 261.41 0.3018 11.60 Pipe 12 0.821.133.7345 3.45 1.9522.18 0.3818 22.56 Pipe 13 0.821.123.7376 3.41 1.9322.56 0.6518 23.21 Area 3c 0.901.740.2511.051823.82.09%0.39 2.9011.0510 1.05 Pipe 14 150.22 1.1318 12.17 Pipe 15 0.821.093.98254 3.58 2.0323.21 2.0918 25.31 Pipe 16 0.821.033.9810.00116 3.36 1.9025.31 1.0118 26.32 Area 3d 0.901.730.7711.211461.61.11%1.20 2.0011.2110 1.21 Pipe 17 1260.68 3.1018 14.32 Area 3e 0.901.711.0611.531832.11.13%1.63 2.0011.5310 1.53 Pipe 18 0.851.005.81101 4.91 2.7826.32 0.6118 26.93 Area 3f 0.901.800.9510.002053.91.90%1.54 2.7210.000 1.26 Pipe 19 990.87 1.9018 11.90 Tie-In Point 3 0.850.986.76 5.67 26.93 Area 4a 0.901.761.2310.761342.92.16%1.94 2.9310.7610 0.76 Pipe 20 882.47 0.5912 Pipe 21 0.901.761.23112 1.94 2.4710.76 0.7512 11.52 Area 4b 0.901.681.5012.012703.31.24%2.27 2.2412.0110 2.01 Pipe 22 592.89 0.3412 Tie-In Point 4 0.901.682.73 4.14 12.01 Q:\PROJECTS\680693\studies\Drainage -Phases 2&3\Calculations\35769271.xls Page 2 Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Tuesday, Jan 28 2014 Exist 18" Pipe Downstream of Point #1 Circular Diameter (ft)= 1.50 Invert Elev (ft)= 1.00 Slope (%)= 0.24 N-Value= 0.013 Calculations Compute by:Known Q Known Q (cfs)= 3.25 Highlighted Depth (ft)= 0.87 Q (cfs)= 3.250 Area (sqft)= 1.07 Velocity (ft/s)= 3.05 Wetted Perim (ft)= 2.60 Crit Depth, Yc (ft)= 0.69 Top Width (ft)= 1.48 EGL (ft)= 1.01 0 1 2 3 Elev (ft)Section 0.50 1.00 1.50 2.00 2.50 3.00 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Tuesday, Jan 28 2014 Exist 18" Pipe Downstream of Point #2 Circular Diameter (ft)= 1.50 Invert Elev (ft)= 1.00 Slope (%)= 0.80 N-Value= 0.013 Calculations Compute by:Known Q Known Q (cfs)= 5.44 Highlighted Depth (ft)= 0.82 Q (cfs)= 5.440 Area (sqft)= 0.99 Velocity (ft/s)= 5.50 Wetted Perim (ft)= 2.50 Crit Depth, Yc (ft)= 0.90 Top Width (ft)= 1.49 EGL (ft)= 1.29 0 1 2 3 Elev (ft)Section 0.50 1.00 1.50 2.00 2.50 3.00 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Tuesday, Jan 28 2014 Exist 18" Pipe Downstream of Point #3 Circular Diameter (ft)= 1.50 Invert Elev (ft)= 1.00 Slope (%)= 0.45 N-Value= 0.013 Calculations Compute by:Known Q Known Q (cfs)= 5.67 Highlighted Depth (ft)= 1.02 Q (cfs)= 5.670 Area (sqft)= 1.28 Velocity (ft/s)= 4.43 Wetted Perim (ft)= 2.91 Crit Depth, Yc (ft)= 0.92 Top Width (ft)= 1.40 EGL (ft)= 1.32 0 1 2 3 Elev (ft)Section 0.50 1.00 1.50 2.00 2.50 3.00 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Tuesday, Jan 28 2014 Exist 18" Pipe Downstream of Point #4 Circular Diameter (ft)= 1.50 Invert Elev (ft)= 1.00 Slope (%)= 0.36 N-Value= 0.013 Calculations Compute by:Known Q Known Q (cfs)= 4.14 Highlighted Depth (ft)= 0.89 Q (cfs)= 4.140 Area (sqft)= 1.09 Velocity (ft/s)= 3.78 Wetted Perim (ft)= 2.64 Crit Depth, Yc (ft)= 0.78 Top Width (ft)= 1.47 EGL (ft)= 1.11 0 1 2 3 Elev (ft)Section 0.50 1.00 1.50 2.00 2.50 3.00 Reach (ft) Inlet Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Thursday, Jan 23 2014 50% Clogging Factor - 2'x2' Inlet Drop Grate Inlet Location= Sag Curb Length (ft)= -0- Throat Height (in)= -0- Grate Area (sqft)= 1.50 Grate Width (ft)= 2.00 Grate Length (ft)= 2.00 Gutter Slope, Sw (ft/ft)= 0.020 Slope, Sx (ft/ft)= 0.020 Local Depr (in)= -0- Gutter Width (ft)= 2.00 Gutter Slope (%)= -0- Gutter n-value= -0- Calculations Compute by:Q vs Depth Max Depth (in)= 12 Highlighted Q Total (cfs)= 8.25 Q Capt (cfs)= 8.25 Q Bypass (cfs)= -0- Depth at Inlet (in)= 12.57 Efficiency (%)= 100 Gutter Spread (ft)= 106.77 Gutter Vel (ft/s)= -0- Bypass Spread (ft)= -0- Bypass Depth (in)= -0-