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Home My WebLink AboutPD 2019-0012; BLOCK RESIDENCE; DRAINAGE STUDY, BLOCK (WARD) RESIDENCE, 3291 HIGHLAND DR.; 2019-10-24Drainage Study BLOC K (Ward)Residence 3291 Highland Drive Carlsbad, CA 92008 Date Prepared: RECORD COPY October 24, 2019 initial Date Prepared for: Brett Ward 7043 Whitewater Street Carlsbad, CA 92011 DWG#: 519-7A GR 2019-0031 Prepared By: Omega Engineering Consultants 4340 Viewridge Ave, Suite B San Diego, CA 92123 Ph: (858) 634-8620 RE'TVED ft4i6 VU Z020 LAN) MENT ENGtr ING Declaration of Responsible Charge: I hereby declare that I am the engineer of work for this project, that I have exercised responsible charge over the design of the project as defined in section 6703 of the business and professions code, and that the design is consistent with current standards. I understand that the check of the project drawings and specifications by the City of Carlsbad is confined to a review only and does not relieve me, as an engineer of work, of my responsibilities for project design. /Patric T. de Boer RCE 83583 Registration Expires 3-31-2021 Omega Engineering Drainage Study Consultants Ward Residence Table of Contents Site& Project Description ....................................................................................................... 1 Methodology............................................................................................................................2 ExistingConditions.................................................................................................................2 DevelopedConditions .............................................................................................................3 ExistingRunoff Analysis .......................................................................................................... 3 ProposedRunoff Analysis........................................................................................................4 Resultsand Conclusions..........................................................................................................4 Weighted"C" Values...............................................................................................................5 85' Percentile Hydrology ........................................................................................................6 100-Year Hydrology Flows.......................................................................................................7 Site '.ticiliit)r Map (Figure 1).....................................................................................................9 Existing Hydrology Exhibit (Figure 2) .................................................................................10 Proposed Hydrology Exhibit (Figure 3) ................................................................................11 Proposed Site Exhibit (Figure 4)............................................................................................12 ConduitSizing........................................................................................................................13 AutodeskSSA Pump Analysis ................................................................................................14 Appendices SoilHydrologic Group Map....................................................................................Appendix 1 100-yr 6-hr Storm Isopluvial Map ...........................................................................Appendix 2 100-yr 24-hr Storm Isopluvial Map..........................................................................Appendix 3 Intensity-Duration Design Chart ...........................................................................Appendix 4 RunoffCoefficient Chart.........................................................................................Appendix 5 Timeof Concentration Charts................................................................................Appendix 6 ReferenceDrawings................................................................................................Appendix 7 PROP. ORSflE 1so PATH Omega Engineering Drainage Study Consultants Ward Residence Site & Project Description The project sits on a 0.51 acre parcel located at 3291 Highland Drive. The existing site consists of a one-story single-family residence and other improvements. The site slopes to the west with elevations ranging from approximately 156 feet at the west to approximately 171 feet at the easterly side of the property. In the proposed condition, the project will remodel the existing single family home as well as laterally expanding it to the south-west. To the north-west of the existing residence, a separate building is proposed which will act as a garage on the first floor and an accessory dwelling unit on the second. The project proposes the use of a permeable paver driveway and walkway. The project proposes to eliminate the discharge of runoff to the backyard of the westerly neighbor. This will be accomplished by collecting the runoff at a low point of the site , and using a pump system to convey the runoff uphill to Highland Drive. As this is a diversion of flow, this report includes calculations indicating that the existing public storm drain system has sufficient capacity to handle the increased flow that will be introduced to Highland Drive. Figure 1. Offsite Flow Path Exibit H/c,14 McKINLEY ST. The existing offsite flowpath between the site and the point of discharge will see a decrease in 100- yr flow, while the existing public 12" storm drain and V- ditch will experience an increase. This increase in flow will not overcapacitate these conveyances as is shown in the hydraulics calculations included in this report. The 100-year flow downstream of the point of discharge will see a decrease in 100 year flow. See 'Proposed Analysis' section of this report. See Figure 2 for the existing drainage conditions and Figure 3 for the proposed drainage conditions. Omega Engineering Drainage Study Consultants Ward Residence Methodology This drainage report has been prepared in accordance with current County of San Diego regulations and procedures. The Modified Rational Method was used to compute the anticipated peak runoff flowrates for the existing and proposed conditions. RatHydro was used to generate a hydrograph from the Rational Method results for the basin tributary to the proposed pump system. This hydrograph was touted through a modeled storage element and pump in Autodesk Storm & Sanitary Analysis, a hydraulic modeling program based on EPA SWMM. The resulting peak flowrate from the curb outlet was input back into the Rational Method calculations and confluenced with the other basins. Although pump discharge is intermittent, for conservative purposes the pumps' peak flow rate was used in confluence calculations. Flow confluencing was calculated through addition of flows with no flow reduction for further conservative purposes. The flow rate in the existing 12" storm drain on Highland Drive was taken from the reference drawings located in Appendix 7, referred to as offsite basins "OFF-I" within Table 3 calculations. Basins 1 and 2 were determined by examining the overland flow paths of the surrounding neighborhood, as well as points where the flow entered the public storm drain system. Each basin's flow transition into a pipe or channel has been marked with a nodal number, corresponding to Table 3. Travel times for the basins were based upon a model of assumed berm-side flow, 4" in depth at an average street slope of 0.75%. For conservative purposes, all basin time of concentrations were decreased to the minimum of five minutes, thus maximizing basin discharge. Rational Method Q=CIA Where: Q=peak discharge, in cubic feet per second (cfs) Crunoff coefficient, proportion of the rainfall that runs off the surface (no units) (0.90*(% impervious)+Cp*(1% Impervious)) page 3-5, County Hydrology Manual I =average rainfall intensity for a duration equal to the Tc for the area, (m/hr) = 7.44*P6Fc 0 A = drainage area contributing to the design location, in acres Cp= Pervious Coefficient Runoff Value, County of San Diego Hydrology Manual minimum of 0.35 T= 1.8*(I.1C)*(2)2 50.33 S= Slope of drainage course DWater course distance The following references have been used in preparation of this report Handbook of Hydraulics, E.F. Brater & H.W. King, 6th Ed., 1976. Modem Sewer Design, American Iron & Steel Institute, 1st Ed., 1980. County of San Diego Hydrology Manual, 2003 2 Omega Engineering Drainage Study Consultants Ward Residence Existing Conditions The existing site is the location of a single family residence. The ground cover consists of several trees, native brush, brick payers, and bare dirt. The site drains via overland flow to the southwest at a 9% slope to the adjacent property. The site receives runoff from a small sliver of land between the easterly property line and the existing AC berm along Highland Drive. Proposed Conditions The proposed project will increase the footprint of the existing residence as well as include the addition of the unattached garage/accessory dwelling unit. The proposed improvements include a permeable paver access driveway, concrete outer garage parking area, slatted deck, and a private storm drain system to convey runoff to a storm drain lift station.. The site will drain to the western corner of the lot at a slope varying from 33% in the front of the house to 2% in the backyard. Runoff will drain into a 48" round fiberglass pump vault that is 8 feet deep. The lift station contains two Liberty FL70 Effluent pumps, manifolded into a single 3" schedule 40 PVC forcemain that discharges to a 3-foot wide curb outlet in the right-of-way on Highland Drive. Flow from the curb outlet will be conveyed to the adjacent existing Type B concrete inlet which is connected to a 12-inch public storm drain. These conditions will constitute a necessary flow diversion. The diversion is necessary to eliminate cross lot drainage and flooding of the neighboring lot. The public storm drain system will experience an increase in flow, however, the calculations provided in this report indicate that the existing system can accommodate the added flow. Existing Runoff Analysis The Modified Rational Method was used for calculating existing peak flow rates for the 100-year; 6- hour storm. This analysis includes large portions of offsite to establish the current demand on the public storm drain system. The Soil Hydrologic Groups Map from the San Diego Hydrology Manual reflects Group B soil (soil map in Appendix 1). For both basins, a value of 0.45 was used. This value was taken from Table 3-1 of the County of San Diego Hydrology Manual for a land use element of Medium Density Residential. Omega Engineering Drainage Study Consultants Ward Residence Below is a smnmar r of the basin input data: - -- Basin# Area Runoff T (•) Intensity Slope Qioo (cfs) (ac) Coefficient, C (in/hr) E-1 0.70 0.45 5.0 6.85 8.7% 2.16 E-2 2.53 0.45 5.0 6.85 5.2% 7.80 Both existing basins confluence at an offsite point at the the intersection of Basswood Ave and McKinley Street. The confluenced peak flowrate for the 100-year; 6-hr storm at this point is 12.36 cfs. See the attached calculations on Table 3 for details. Proposed Runoff Analysis The Modified Rational Method was used for calculating proposed peak flow rates for the 100-year; 6-hour storm. Analysis of the proposed conditions includes two offsite drainage areas (A-I & A-2) and one onsite area (A-3). RatHydro was used to generate a hydrograph for the flow generated by A-3. This hydrograph was imported into Autodesk Storm and Sanitary Analysis, a hydrology and hydraulics program based on EPA SWMM. The hydrograph was run through a model of the proposed lift station and force main pipe. The resulting peak flowrate was brought back in to the Modified Rational Method calculations and confluenced with the flow generated by the two offsite basins. For conservative purposes, confluence flows were again calculated through addition of flows with no flow reduction, and times of concentration were minimized to five minutes in order to maximize basin discharge. Below is a slinunary of the basin input data: Basin # Area (ac) Runoff Coefficient, C Intensity (in/hr) Slope % Qioo (cfs) A-1 0.69 0.45 6.85 8.7% 2.13 A-2 1.96 0.45 6.85 5.2% 6.04 A-3 0.57 0.48 1 6.85 1 5.0% 1 0.20* *Note: Flow from basin A-3 is regulated by the pump system. The pump discharge will increase the runoff to the 12" storm drain in Highland Drive by 0.20 cfs. The conduit sizing calculations included in this report show that even with the added flow, the 12" pipe will have a flow depth/diameter ratio of 0.36, and the 18" circular ditch will have a flow depth/diameter ratio of 0.28. Runoff to the westerly neighbor's back yard will be eliminated. All of the proposed basins confluence at an offsite point at the the Intersection of Basswood Ave and McKinley Street. The confluenced peak flowrate for the 100-year; 6-hr storm at this point is 10.77 cfs. This is a reduction of 1.59 cfs. See the attached calculations on Table 3 for details. 4 Omega Engineering Drainage Study Consultants Ward Residence Results and Conclusions The redevelopment of the site will result in a decrease in runoff flowrates at the offsite point of discharge. It will eliminate cross lot drainage to the neighboring lot. It will increase runoff to the portion of the public storm drain system between the site and the offsite discharge point, but the increase will not exceed the capacity of any of the existing conveyance system. The project does not propose to discharge fill or dredged materials to the Waters of the State, therefore no CWA 401 or 404 permit is required. It is the opinion of Omega Engineering Consultants that the project will not cause adverse effects to the downstream facilities or receiving waters as a result of increase 100-year; 6-hour storm peak flowrates. Ward Resid 10/24/2019 Rational Method Calculations (Table No. 3) Sub- Basin AREA Ac. ,CII Overland flow length Concentrated S(%) Ti Flow Length, (ft) (avg.) mins Tt mins T mins I In/hr Q cfs Q tot cfs NOTES 100-year, 6 hr storm (mitigated) E-1 0.70 0.45 0.0 225.0 8.7% 5.3 1.06 5.0 6.85 2.16 2.16 JP(6) 2.6 Node 1 to 2 Surface Flow OFF-i Per Reference Drawing 445-3 2.40 2.40 Node 3 to 4 Pipe Flow OFF-i Per Reference Drawing 445-3 2.40 2.40 Node 4 to 2 Channel Flow 4.56 Node 2 Confluence. No flow reduction calculated, for conservative purposes. E-2 2.53 0.45 100.0 480.0 5.2% 6.7 2.25 5.0 6.85 7.80 7.80 Node 4 to 3 Surface Flow 12.36 Node 3 Confluence. No flow reduction calculated, for conservative purposes. Existing Flow at Point of Discharge 12.36 A-3 0.57 0.48 95.0 150.0 5.0% 6.7 0.00 5.0 6.85 1.87 1.87 Node 5to1 0.20 Pump flow from SSA analysis, see Appendix OFF-i Per Reference Drawing 445-3 2.40 2.40 Node - to 1 2.60 Node 1 Confluence. No flow reduction calculated, for conservative purposes. OFF-i Per Reference Drawing 445-3 2.60 2.60 Node 1 to 2 Pipe Flow OFF-i Per Reference Drawing 445-3 2.60 2.60 2 to 4 Channel Flow A-i 0.69 0.45 0.0 225.0 8.7% 5.3 1.06 5.0 6.85 2.13 2.13 Node 3 to 4 Surface Flow 4.73 Node 4 Confluence. No flow reduction calculated, for conservative purposes. A-2 1.96 0.45 100.0 480.0 5.2% 6.7 2.63 5.0 6.85 6.04 6.04 Node 6 to 7 Surface Flow 10.77 Node 7 Confluence. No flow reduction calculated, for conservative purposes. Proposed Flow at Point of Discharge 10.77 0548-H&H NEW DRAINAGE BASIN DATA BASIN / AREA (A C) C—VALUE 7. (MINS) /loo (IN/HR) oloo (CFS) E-1 0.70 0.45 5.0 6.85 216 E-2 2.53 0.45 5.0 6.85 780 GRAPH/CAL SCALE: 1" 80' 0 40 80 160 WARD RESIDENCE EXISTING HYDROLOGY EXHIBIT FIGURE 2 aMEGA, O=12.36 LEGEND BASIN NUMBER (E-1) DRAINAGE BASIN LIMITS OVERLAND FLOW PATH. STORM DRAIN (EX) PROJECT AREA CIRCULAR DITCH (Ex) .................= = = NODE........ 'zrj V' EX 12" 5D 1.0% LX 10 LONG) / Q B—INLET / /EXPROJECTS/TE EX12"SD2.6Z SURFACE DRAINS / O,=2. 4CFS V=8. 5FPS / TO SOUTHERLY PER DWG 445-3 / NEIGHBOR 7 1 I I T L CONCENTRA TED L=480' / McKINLEY ST. EX. 1 2. 5 6% / 4CFS V=& 50FPS PER OWG 445-3 I\. (A- ' ''II Nç 1 L I CONG lED L4 ------------ McKINLEY ST. AV SDRSi9 D-25 OUIZET / Ck 1O'LOC ' B-IN/FT EE) PROP PROJECT SITE SUP/ACE DRAINS TO PC/HP 4 T S/W CORNER AND IS PUMPED UP TO HIGHLAND OR! VE POINT OF DISC Oioo 10.77 CFS LEGEND BASIN NUMBER DRAINAGE BASIN LI,W/1S ............. .. ___ - - ___ OI(RLAND FLOW PA TH. ............... S/ORb! DRAIN (ix) PROJECT AREA CIRCULAR DITCH (ix) NODE...................,. () DRAINAGE BASIN DATA BASIN / AREA (Ac) C- VALUE T (MINS) I,OO (/N/HR) 0/0.0 (CFS) A-i 0.69 0.45 5.0 6.85 2.13 4 -2 1.96 0.45 50 6.85 6.04 4 -3 0.57 0.48 50 6,85 0.20* *OUTFLOW PA 7E FROM A-J GOVERNED BY PUMP SYSTEM CRAP/-I/CAL SCALE 1" - 0 40 80 160 WARD RESIDENCE PROPOSED HYDROLOGY EXHIBIT FIGURE 3 M E (`-ol A Project Description File Name . 0548-SSA.SPF 'roject Options Flow Units.............................................................................CFS Elevation Type ............................................... .......................Elevation Hydrology Method .................................................................EPA SWMM EPA SWMM Infiltration Method ...........................................Horton Link Routing Method .............................................................Hydrodynamic Enable Overflow Ponding at Nodes ......................................YES Skip Steady State Analysis Time Periods ............................NO Analysis Options Start Analysis On ..................................................................Jul 15, 2019 00:00:00 End Analysis On ...................................................................Jul 15,2019 08:00:00 Start Reporting On ................................................................Jul 15,2019 00:00:00 Antecedent Dry Days ............................................................0 days Runoff (Dry Weather) Time Step ..........................................0 0000:10 days hh:mm:ss Runoff (Wet Weather) Time Step ........................................000:00:10 days hh:mm:ss Reporting Time Step ............................................................0 00:00:10 days hh:mm:ss Routing Time Step ................................................................1 seconds Number of Elements aty RainGages ...........................................................................0 Subbasins.............................................................................. 0 Nodes.................................................................................... 3 Junctions...................................................................... Outfells.........................................................................1 FlowDiversions...........................................................0 Inlets............................................................................0 Storage Nodes .............................................................1 Links......................................................................................3 Channels......................................................................0 Pipes............................................................................ Pumps..........................................................................2 Ottflces.........................................................................0 Wehs............................................................................0 Outlets..........................................................................0 Pollutants..............................................................................0 LandUses ............................................................................0 Node Summary SN Element Element Invert Ground/Rim Initial Surcharge Ponded Peak Max HGL Max Min Time of Total Total Time ID Type Elevation (Max) Water Elevation Area Inflow Elevation Surcharge Freeboard Peak Flooded Flooded Elevation Elevation Attained Depth Attained Flooding Volume Attained Occurrence (if) (if) (if) (if) (if') (cfs) (It) (It) (if) (days hh:mm) (ac-in) (mm) 1 Jun-01 Junction 152.30 159.80 0.00 1000.00 0.00 0.22 212.30 52.50 0.00 0 00:00 0.00 0.00 2 D-25_ curb _outlet Outran 174.40 0.20 174.65 3 Pump_Vault Storage Node 151.80 160.33 151.80 0.00 1.87 160.09 0.00 0.00 Link Summary SN Element Elomeot From To (Oue length Intel Oi$Jet Average Diameter or Mannmg Peak Desn Flow Peak Flow! Peak Flow Peak Flow Peak Flow Total The Reported ID Type Oleo Node lived Invert Slope Height Rougtmess Flow Capac4y Desn Flow Veby Depth DoptKl Surthaiged Ccinti8on Node Elevation Elevation Ratio Total Depth Ratio (%) (ni) () () (lines) (9) (mio) 1 3 _brch_forcemaia Pipe Jcoi0I D-25anb_oullel 174.00 152.30 174.40 -12.1000 3.000 0.0130 010 0.17 1.19 4.09 0.25 1.00 145.00 SURCHARGED 2Pump-01 Pwrip Pump_Vau9 JLm01 151.80 152.30 012 3Pump.02 Pup Pump_Vauft JLm01 151.80 152.30 0.10 1 Pipe SN Flap No. of Gate Barrels as 1 Pipe Results SN Element Peak Time of Design Flow Peak Flow! Peak Flow Travel Peak Flow Peak Flow Total Time Froude Reported ID Flow Peak Flow Capacity Design Flow Velocity Time Depth Depth! Surcharged Number Condition Occurrence Ratio Total Depth Ratio (cfs) (days hh:mm) (cfs) (ft/sac) (mm) (ft) (mm) 1 3_inch2orcemaln 0.20 0 05:59 0.17 1.19 4.09 0.71 0.25 1.00 145.00 0.25 SURCHARGED Storage Nodes Storage Node: Pump_Vault Input Data mviii Elevation (It) ...............................................151.80 Max (Rn) Elevation (ft) ........................................180.33 Max (Ran) Offset (It) .............................................8.53 Initial Water Elevation (It) .....................................151.80 Initial Water Depth (It) ..........................................0.00 Ponded Area (It ......0.00 Evaporation Loss ..................................................0.00 Storage Area Volume Curves Storage Curve: 48vau8 Stage Storage Storage Area volume (ft) (ft' (It') 0 12.57 0.000 8 12.57 100.56 8.01 2300 112.12 8.33 2300 848.12 All storage volume above 8 ft is surface ponding in the yard. There is an available 6" of ponding across the entire backyard. Storage Node: Pump_Vault (continued) Output Summary Results Peak Inflow (cfs) ...................................................1.87 Peak Lateral Inflow (es) .......................................1.87 Peek Outflow (cfs) ................................................0.22 Peak Exfiftratlon Flow Rate (dm) .........................0.00 Max HGL Elevation Attained (It) ...........................160.09 Max HGL Depth Attained (It) ................................8.29 Average HGL Elevation Attained (It) ....................154.70 Average HGL Depth Attained (ft) .........................2.9 Time of Max HGL Occurrence (days hh:mm) ......0 04:20 Total ExfSration Volume (1000-It') .......................0.000 Total Flooded Volume (ac-in) ...............................0 Total Time Flooded (mm) .....................................0 Total Retention Time (sac) ...................................0.00 Omega Engineering Drainage Study Consultants Ward Residence Appendices Omega Engineering Drainage Study Consultants Ward Residence Appendix 1 Soil Hydrologic Group Map County of San Diego I 3303g. Orange Hydrology Manual Counts 33030 V • Riverside County V V V IOIEC ) r p , l E V V V V V Soil Hydrologic Groups ___________________________________________________________________ V 33°15_________________ - - : V -- V V V V Vt 33°15 I PROJECT SITEL E GROUP 'B' V i - •V VVV A V ____ Legend Soul Groups - Group A CARLSBAD •T.-V .. f • - V V 4 V V V - .• Group B _____ _____ Group C 0 ENCINITAS I , Group 0 33000 - •• .' •VVV V' V d_4VIV V V V V - S.D.COUNTY 6 - 3300 Undetermined Data Unavailable C) SOLANA BEACH V•' 0 DEL MAR JV V 01 y V;. V V V - — N CD NTEE ' DIE LC N - 32045 V . V V•V V_32045 . OR 4 opt XXI DPW GIS StGIS __ AM C STA V • . Ha San l)ILgLI ( / - IMPERIAL BEACH - -TI—r I. • V M e - I N THIS MAP IS PROVIDED WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE CoWIgMS.nGISAIRIgEtoRe.oed. This poduclo rosy osrisUr Infrorosyror honr Be SANDAG RgIon E wAS., p mA.$Ion of SANOAG 32-30' This product may ASrodn InfomretIo.r w+dctr flee been reproduced with Brothers Mupe. - b Cn - - Ln Cn 32°30' S 3 0 3Miles Omega Engineering Drainage Study Consultants Ward Residence Appendix 2 100-Year; 6-Hour Storm Isopluvial Map Omega Engineering Drainage Study Consultants Ward Residence Appendix 3 100-Year; 24-Storm Isopluvial Map Omega Engineering Drainage Study Consultants Ward Residence Appendix 4 Intensity-Duration Design Chart IIIIIIIIIIIIllhIIIIIIIIIIIIIIIllHIIIIIIUIllIIIIIIIIIIIflhIllhIII 'ks EQUATION __________________________ 11111111 _ IIIIII Intensity (in/hr) MONSOON'" q ji4mij g~1111111tii 111111111111 jjj~ ~ 11111111 ' Duration IIIIIIIIIIIIIIIIIIIIIIIIIIIIIII .1111115111101111 ilk lk!4 I IN 11,111-1kill 11 10, 11111111111111111k11111ihifi 111111111111 IIIII PI !W IIIuuIuIIIIuuuuuIIllnhIIIIIIllhIIIIII;!!IIuhIlIIIIIIIII:!IIIIII MIN :Ifli;!!Uhi!!j 4441 IN 111111111111111111111111111111111111111 iii" 1111111111111111111 111 Ifil 1-111111 MIR1111kill III IIIII IN MIN Hill HY111 i1h,1111 IN IIIIIIIIIIIIIIIIIIIIIIIIUflhIIIHIllhIIIIIIIUIIUhIIIIHh IIi !!IIII Il IiI!!!I Ih I111111 IIi .....m..u..u..uuuhIII,,,..u..u.uIuu,u,u,uI,uIIIuluII ......u..IIuu u,.IulI -----c 111 s . 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UtII ....u...u.iuuiii.i,uii,....uuii.uuuunh,,,uuiuiiiii ..UU.UIU.0 U1I1U11 ........u...uIullII,uIu,....UUUU.U.u.,IIIIIuuuuI,I,I •••U 'UUIUIU UIWII •111111 ___________. 1111111 ___________. •• ••••uuuuiuuuuuuiiii,iipi1u1 no: uu1111u1u1u111111i111111 m•UUu•IuuuuIuuU .;9,lI ___________• •Nu••u••IuluuuuuIFliuuIuuIuuuuuuiuuIiiiiuiuiuuiuiuIii •UUU.•JUuUuIIllliIb , UU••UU•I•IuIuuuuuIIIIuuIIuUUUUuuuIIuuuIIIIuuIuulIIIIII •NUU•IuuuuIuuuuIIIlI ••u••u•u uuuiiuiuuuiiuuuiiiiuuiuuuuuuu MIN iuiiiuiuuuiuiuiiiauuuuuuuuuiuuuiuuu 111111 MMOMMMMMMOME uuiu uuuiuiuuui 11111111111111111111 IiIHIiIiiiiiIIliI••••• IllIlIlIlIll 111111! •••••••uu•uuuuuuuuiuuuu iuuiuuiuuuiuimi . .. uu•uuii"iiuiiuuuiiiiii •••••••••••• milli 111111111111111111111111111111 1111111 uuu••uuuuuiuuuiiuiuiuiiuuiiiiiiiiiiiiuiiuuuiiuiiitiiiiiiiiiiiiii••u•uiuuiuiiiuiuiuuiuiiiiii uuu•uuuuuiiuuuiuuuuiiuuuiiiiiiiiiiiiiuiiuiuuiiiiiiiiiiiiiiiiiiii•uuuuuuiuuiiiuuuiuiuuiiiiii fl F Omega Engineering Drainage Study Consultants Ward Residence Appendix 5 Runoff Ceofficients Chart San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 6of26 Table 3-1 RUNOFF COEFFICIENTS FOR URBAN AREAS Land Use Soil Type NRCS Elements County Elements I % IMPER. A B C D Undisturbed Natural Terrain (Natural) Permanent Open Space 0* 0.20 0.25 0.30 0.35 Low Density Residential (LDR) Residential, 1.0 DU/A or less 10 0.27 0.32 0.36 0.41 Low Density Residential (LDR) Residential, 2.0 DU/A or less 20 0.34 0.38 0.42 0.46 Low Density Residential (LDR) Residential, 2.9 DU/A or less 25 0.38 0.41 0.45 0.49 Medium Density Residential (MDR) Residential, 4.3 DU/A or less 30 0.41 I 0.45 I 0.48 0.52 Medium Density Residential (MDR) Residential, 7.3 DU/A or less 40 0.48 0.51 0.54 0.57 Medium Density Residential (MDR) Residential, 10.9 DU/A or less 45 0.52 0.54 0.57 0.60 Medium Density Residential (MDR) Residential, 14.5 DU/A or less 50 0.55 0.58 0.60 0.63 High Density Residential (HDR) Residential, 24.0 DU/A or less 65 0.66 0.67 0.69 0.71 High Density Residential (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77 0.78 0.79 Commercial/Industrial (N. Corn) Neighborhood Commercial 80 0.76 0.77 0.78 0.79 Commercial/Industrial (G. Corn) General Commercial 85 0.80 0.80 0.81 0.82 Commercial/Industrial (O.P. Corn) Office Professional/Commercial 90 0.83 0.84 0.84 0.85 Commercial/Industrial (Limited I.) Limited Industrial 90 0.83 0.84 0.84 0.85 Commercial/Industrial (General I.) General Industrial 95 0.87 0.87 0.87 0.87 The values associated with 0% impervious may be used for direct calculation of the runoff coefficient as described in Section 3.1.2 (representing the pervious runoff coefficient, Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. Justification must be given that the area will remain natural forever (e.g., the area is located in Cleveland National Forest). DU/A = dwelling units per acre NRCS = National Resources Conservation Service 3-6 Omega Engineering Drainage Study Consultants Ward Residence Appendix 6 Overland Time of Flow Nomograph 100 30 I- (6) LU LU z U- a 20 z U - w z 0 -J Ui (I, U- 10 0 Ui LU 0 EXAMPLE: Given: Watercourse Distance (0) = 70 Feet Slope (s) = 1.3% = T 1.8 (1. 1-C) Vii Runoff Coefficient (C) = 0.41 Overland Flow Time (T) = 9.5 Minutes SOURCE: Airport Drainage, Federal Aviation Administration, 1965 FIGURE Rational Formula - Overland Time of Flow Nomograph 34 ir w/W9, L ii I Fllzo 0 0 Omega Engineering Drainage Study Consultants Ward Residence Appendix 7 Reference Drawings