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Home My WebLink AboutCIP 4608; POINSETTIA COMMUNITY PARK PHASE IV; HYDROLOGY MEMORANDUM - POINSETTIA COMMUNITY PARK PHASE IV; 2020-10-15POINSETTIA COMMUNITY PARK PHASE IV – HYDROLOGY MEMORANDUM OCTOBER 2020 PAGE 2 OF 5 Rainfall Intensity, I: The rainfall intensity is dependent on the time of concentration for a given drainage basin. Given the size of the drainage basins on site (greater than one acre), a time of concentration of 7 minutes has been assumed. Based on isopluvial maps in the Hydrology Manual, the P6 for the 100-year storm is 2.6”. See Attachment 2. Rainfall intensity is determined from the equation given in the Hydrology Manual as: I = 7.44 x P6 x Tc-0.645 = 7.44 x 2.6 x 7.0-0.645 = 5.51 in/hr Basin Area*: The tributary basin area is determined based on existing and proposed topography. The two project work areas are in different basins and drains to different POCs. Both areas exhibit increase in area in proposed conditions. The dog park denoted as Basin A has a minor increase in area from 2.18 ac to 2.21 ac drains to POC A. Basin B, incorporating the parking lot exhibit greater increase in area from 0.70 ac to 1.00 ac drains to POC B. Basin C is an offsite existing park lot, that is not within the limits of work and will not exhibit any development, that drains to POC B. *See attached Existing & Proposed Conditions Hydrology Map Flow Rate, Q: The 100-year peak flowrate of runoff is then calculated as follows: Q100 = C x I100 x A Inlet Capacity: POINSETTIA COMMUNITY PARK PHASE IV – HYDROLOGY MEMORANDUM OCTOBER 2020 PAGE 3 OF 5 HYDROLOGY RESULTS* The table below summarized the hydrology results for the existing and proposed conditions. Basin Condition Runoff Coefficient Intensity in/hr Area ac Q(100) cfs A Existing 0.48 5.51 2.18 5.77 Proposed 0.50 5.51 2.21 6.10 B Existing 0.63 5.51 0.70 2.43 Proposed 0.75 5.51 1.00 4.13 C (Offsite) Existing 0.79 5.51 0.43 1.88 Proposed 0.79 5.51 0.43 1.88 POINSETTIA COMMUNITY PARK PHASE IV – HYDROLOGY MEMORANDUM OCTOBER 2020 PAGE 4 OF 5 Basin A exhibits a slight increase in peak discharge in proposed conditions. Basin A will discharge into existing 24”x24” catch basin denoted POC A. Basin B exhibits a greater increase in peak discharge in proposed conditions. Basin B will discharge into existing 18” RCP through 24”x24” catch basin denoted POC B. Basin C remains unchanged. The following section will address the capacity of the existing storm drain system at POC A and B to illustrate enough capacity is available to convey the proposed flows. *See attached Existing & Proposed Conditions Hydrology Map. Inlet Capacity shown on Proposed Conditions Exhibit HYDRAULICS CALCULATIONS To assess the capacity of the existing drains going into POC A & B, pipe flow calculations were prepared using the FlowMaster program by Bentley Systems. These pipe segments have been identified as SD Pipes A1, A2, B1, B2 on the attached Existing Conditions Hydrology Map. Proposed pipe segments identified as SD Pipes #1, #4, #7, and #8 were also analyzed for this study. A Manning’s n factor of 0.01 was used for PVC pipe and 0.013 for RCP pipe. The normal depth was calculated to ensure that the pipes have adequate capacity for the proposed 100-year peak flows. In cases where pipes exceed capacity through normal depth calculation, head calculation was used to analyze the capacity of the pipes. Existing conditions indicate a 100-year peak flow rate over capacity for SD Pipe A1 so head calculation approach was used. SD Pipe A1 with the existing peak flow rate of 5.77 cfs shows 1.55 feet of head at the upstream end. The catch basin at this end is buried roughly 3’ below ground, so flow is still contained within the pipe at the preceding pipe, SD Pipe A2 running at 20.9% slope. For the proposed condition, the flow rate increased to 6.10 cfs at SD Pipe A which brings the head at the upstream end to 1.72 feet. This head is still contained within the capacity of the preceding pipe, SD Pipe A2. Existing conditions indicate a 100-year peak flow rate for SD Pipe B1(18” RCP) and B2 (8” PVC) to be within capacity, with normal depth values of 6.19 in and 3.34 in, respectively. Proposed conditions indicate increase in peak flow rates for both existing pipes. Proposed SD Pipe #8 (12” PVC) will replace part of existing SD pipe B2 (8” PVC) to ensure pipe capacity to be adequate for the increased flow rates. Proposed conditions indicated a normal depth of 3.73” within proposed SD Pipe #8 and 7.41” within existing SD Pipe B1. Both values are within capacity of their pipe size. Results of the hydraulic calculations are included in Attachment 5. SD Pipe B1 will easily convey the proposed flow rate without becoming pressurized. SD Pipe A1 will be pressurized under proposed conditions. However, the proposed Hydraulic Grade Line of 152.82 at the upstream end of the pipe is more than 1 foot below the proposed flow line of the nearest inlet of 163.48. Therefore, the proposed flow rates will not cause flooding or overflow within both basins. CONCLUSION While the proposed Poinsettia Community Park Phase IV project will slightly increase runoff from existing conditions in Basin A, the proposed development indicate proper storm drain installments to ensure 100-year peak flow is within the capacity of the existing and proposed storm drain system. POINSETTIA COMMUNITY PARK PHASE IV – HYDROLOGY MEMORANDUM OCTOBER 2020 PAGE 5 OF 5 ATTACHMENTS Attachment 1 Soil Group Map Attachment 2 Isopluvial Map Attachment 3 Existing Conditions Hydrology Map Attachment 4 Proposed Conditions Hydrology Map Attachment 5 FlowMaster Hydraulics Calculations BASIN A C = 0.48 AREA = 2.18 AC Q(100) = 5.77 CFS BASIN B C = 0.63 AREA = 0.70 AC Q(100) = 2.43 CFS BASIN CC = 0.79AREA = 0.43 ACQ(100) = 1.88 CFSPOINSETTIA COMMUNITY PARK PHASE IV EXISTING CONDITIONS HYDROLOGY EXHIBIT GNIREENEIGN 6390 Greenwich Dr., Suite 170, San Diego, California 92122 tel 858.554.1500 fax 858.597.0335 www.fuscoe.com SDG PROJECT NO: 15-406 PLT DATE: 11/16/16 2 h n iLc.AC www.sc peeltho A o 4 NV ,219 idtesgn.c 1-632}91 138, im {e d 6 319 f elimisca Z 3 m 62 4 98-632}716{9 2 xS11i 9DeAvenu,San iego,CAth 2101iSute005,11 LEGEND EXISTING CONTOUR EXISTING STORM DRAIN HYDROLOGY BASIN FLOW DIRECTION HYDROLOGY CALCULATIONS Q=C*I*A SOIL TYPE D Tc= 7 MIN, P6= 2.6 IN => I= 5.51 IN/HR X X X pervious definitionpervious concrete problemsprevious weatherpervious vs permeable XXXXXXXXXX X X X X KEY MAP N.T.S. XXXXXXXXXXEV CHARGING ONLY EV CHARGINGONLY EV CHARGINGONLY VAN ACCESSIBLE EV CHARGING ONLY HDHDWH BASIN A C= 0.50 AREA= 2.21 AC Q(100)= 6.1 CFS BASIN B C = 0.75 AREA = 1.00 AC Q(100) = 4.13 CFS BASIN CC = 0.79AREA = 0.43 ACQ(100) = 1.88 CFSPOINSETTIA COMMUNITY PARK PHASE IV PROPOSED CONDITIONS HYDROLOGY EXHIBIT GNIREENEIGN 6390 Greenwich Dr., Suite 170, San Diego, California 92122 tel 858.554.1500 fax 858.597.0335 www.fuscoe.com SDG PROJECT NO: 15-406 PLT DATE: 11/14/17 E C E 2 h n iLc.AC www.sc peeltho CHs T DD NAABL W HTI MI N A o 4 NV ,219 idtesgn.c 1-632}91 138, im {e d 6 319 f elimisca Z 3 m 62 4 G T N GN A R TIS OR N M E S NI N V I G I ,PU I PX R E S S I S E N S I T R CI TA O E L 98-632}716{9 2 G . I N D E S I Y C O N IV IT N xS11i 9DeAvenu,San iego,CAth 2101iSute005,11 LEGEND EXISTING CONTOUR PROPOSED CONTOUR EXISTING STORM DRAIN PROPOSED STORM DRAIN HYDROLOGY BASIN FLOW DIRECTION INLET BOUNDARY HYDROLOGY CALCULATIONS Q=C*I*A SOIL TYPE D Tc= 7 MIN, P6= 2.6 IN => I= 5.51 IN/HR X X X pervious definitionpervious concrete problemsprevious weatherpervious vs permeable XXXXXXXXXX X X X X KEY MAP N.T.S. Project Description Friction Method Manning Formula Solve For Normal Depth Input Data Roughness Coefficient 0.010 Channel Slope 0.50 % Diameter 8.00 in Discharge 0.36 ft³/s Results Normal Depth 3.13 in Flow Area 0.13 ft² Wetted Perimeter 0.90 ft Hydraulic Radius 1.69 in Top Width 0.65 ft Critical Depth 0.28 ft Percent Full 39.1 % Critical Slope 0.00393 ft/ft Velocity 2.84 ft/s Velocity Head 0.13 ft Specific Energy 0.39 ft Froude Number 1.14 Maximum Discharge 1.19 ft³/s Discharge Full 1.11 ft³/s Slope Full 0.00053 ft/ft Flow Type SuperCritical GVF Input Data Downstream Depth 0.00 in Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 in Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Normal Depth Over Rise 39.12 % Downstream Velocity Infinity ft/s PIPE #4 - PROPOSED 10/15/2020 4:41:03 PM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page GVF Output Data Upstream Velocity Infinity ft/s Normal Depth 3.13 in Critical Depth 0.28 ft Channel Slope 0.50 % Critical Slope 0.00393 ft/ft PIPE #4 - PROPOSED 10/15/2020 4:41:03 PM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of2Page Project Description Friction Method Manning Formula Solve For Normal Depth Input Data Roughness Coefficient 0.010 Channel Slope 1.20 % Diameter 8.00 in Discharge 1.83 ft³/s Results Normal Depth 7.16 in Flow Area 0.33 ft² Wetted Perimeter 1.66 ft Hydraulic Radius 2.39 in Top Width 0.41 ft Critical Depth 0.61 ft Percent Full 89.6 % Critical Slope 0.01179 ft/ft Velocity 5.55 ft/s Velocity Head 0.48 ft Specific Energy 1.08 ft Froude Number 1.09 Maximum Discharge 1.85 ft³/s Discharge Full 1.72 ft³/s Slope Full 0.01357 ft/ft Flow Type SuperCritical GVF Input Data Downstream Depth 0.00 in Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 in Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Normal Depth Over Rise 89.55 % Downstream Velocity Infinity ft/s PIPE #7 - PROPOSED 10/15/2020 4:39:13 PM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page GVF Output Data Upstream Velocity Infinity ft/s Normal Depth 7.16 in Critical Depth 0.61 ft Channel Slope 1.20 % Critical Slope 0.01179 ft/ft PIPE #7 - PROPOSED 10/15/2020 4:39:13 PM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of2Page