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Home My WebLink AboutCDP 2018-0038; SELVIDGE RESIDENCE; PRELIMINARY HYDROLOGY STUDY; 2019-11-21BRIAN ARDOLINO, RCE 71631 DATE I PRELIMINARY HYDROLOGY STUDY I For ALLANSON-SELVIDGE RESIDENCE 5170 CARLSBAD BLVD CARLSBAD, CA 92008 I CDP 2018-0038 DWG 520-4A GR 2019-0036 I I City of Carlsbad, CA I I I 1 I I I I I I I PREPARED FOR: Paula Selvidge 2406 Trona Way Carlsbad, CA 92009 Date: November 21, 2019 PREPARED BY: Pasco Lai:et Suiter & Associates 535 N. 1-Iighwav 101, Suite A Solana Beach, CA 92075 (858) 259-8212 R1ECE llVJD FEB 20 2020 LAND DEVELOPMENT ENGINEERING SECTION 2.0 2.1 2.2 2.3 3.0 3.1 3.2 4.0 5.0 November 2019 TABLE OF CONTENTS Executive Summary Introduction Existing Conditions Proposed Project Summary of Results and Conditions Conclusions References Methodology Introduction County of San Diego Criteria Runoff coefficient determination Hydrologic Analyses Pre-Developed Hydrologic Analysis Post-Developed Hydrologic Analysis Hydraulic Calculations Appendix 'I I I I I I I I I I I I is I I 'I I I I 1 1.0 EXECUTIVE SUMMARY 1 1.1 Introduction This Hydrology Study for a proposed single-family residence project has been prepared to I' analyze the hydrologic and hydraulic characteristics of the existing and proposed project site. This report intends to present both the methodology and the calculations used for determining the runoff from the project site in both the pre-developed (existing) conditions ' and the post-developed (proposed) conditions produced by the 100 year, 6 hour storm event. In addition, this report will propose the sizing of all necessary storm drain facilities and storm drain piping necessary for the storm drain system to safely convey the runoff I from the 100-year rainfall event. 1.2 Existing Conditions I The property is geographically located at N 33007'52.61" W 117°20'03.41". The site is bordered by residential development to the north and south and east. Carlsbad Boulevard is I located directly to the west of the proposed development. The project site is located in the Agua Hedionda Hydrologic Area (904.3) and contains type B soils. ' The existing project site includes 1 residence with an attached garage, a shed, a concrete driveway, and a concrete rear yard patio. The site consists mostly of a gentle slope from the east to west. Drainage from the existing site sheet flows in the westerly direction onto I Carlsbad Boulevard. I 1.3 Proposed Project The intent of the proposed project is to construct a new single family residence with an attached garage, associated hardscape improvements and driveway. The proposed project generally conveys stormwater runoff from impervious areas to landscape areas where it is collected by a series of inlets and conveyed via PVC pipe to a I bioretention BMP basin located on the southwest corner of the property. The proposed bioretention BMP basin will mitigate any increase in stormwater runoff flows resulting from the proposed development which will increase the impervious area of the project site. I Runoff that makes its way to the bioretention basin will pond and infiltrate into the ground with any excess runoff being discharged via an overflow structure to Carlsbad Boulevard, mimicking the existing conditions of the project site. 1 We believe the proposed storm drain system will not adversely affect the downstream system negatively. To address the storm water quality goals established for this development, proposed permanent Best Management Practice (BMP) and treatment methods will be incorporated I into the storm water runoff design. The proposed BMP's include multiple landscape BMP areas, and a dedicated bioretention area which is intended to mitigate peak flows and provide stormwater treatment. I November 2019 1 I 1.4 Summary of Results I Upon performing hydrologic analysis of the project site in both the proposed developed and existing condition the following results were produced. One discharge point was analyzed. In the pre-developed condition one discharge point was analyzed. Outlet point indicates that the 100-year peak flow is 0.45 cfs with a time of concentration of 5 min based on an area of 0.15 AC. In the post-developed condition one discharge point was analyzed. Outlet point indicates that the 100-year peak flow is 0.69 cfs with a time of concentration of 5 min based on an area of 0.15 AC. The increase in peak flow leaving the site is due to the increase in impervious area from existing to proposed condition. The subsequent 183 CF increase in 100-year peak flow attenuation is mitigated by the on-site bioretention BMP basin. See Sections 3.0 and 4.0 for calculations. 1.5 Conclusions The overall peak flow leaving the property is increased by 0.24 cfs due to the increase in impervious area. The existing drainage patterns of the site will not be significantly altered as a result of the proposed development and the existing site runoff points are to be maintained in the post developed site condition. The bioretention BMP basin proposed is adequately designed to treat the runoff from the impervious material and the volume of storage is sized to mitigate the increase in peak runoff from the site. U Based on the discussion in this report it is the professional opinion of Pasco Laret Suiter & Associates, Inc. that the existing drainage system on the corresponding Preliminary Grading I Plan will function to adequately intercept, contain and convey flow to the appropriate points of discharge. See Sections 3.0 and 4.0 for calculations. 1.6 References "San Diego County Hjidrology Manual", revised June 2003, County of San Diego, Department of Public Works, Flood Control Section. "California Regional WaterQualiy Control Board Order No. 2009-0009-D WQ' California Regional Water Control Board, San Diego Region (SDRWQCB). I November 2019 I 2.0 METHODOLOGY 2.1 Introduction The hydrologic model used to perform the hydrologic analysis presented in this report utilizes the Ration Method (RM) equation, Q=CIA. The RM formula estimates the peak rate of runoff based on the variables of area, runoff coefficient, and rainfall intensity. The rainfall intensity (1) is equal to: I = 7.44 x P6 x D °645 Where: I = Intensity (in/hr) P6 = 6-hour precipitation (inches) D = duration (minutes - use Tc) I Using the Time of Concentration (Tc), which is the time required for a given element of water that originates at the most remote point of the basin being analyzed to reach the point at which the runoff from the basin is being analyzed. The RM equation determines the I storm water runoff rate (Q) for a given basin in terms of flow (typically in cubic feet per second (cfs) but sometimes as gallons per minute (gpm)). The RM equation is as follows: I Q=CIA Where: - Q flow (in cfs) I C = runoff coefficient, ratio of rainfall that produces storm water runoff (runoff vs. infiltration/evaporation/absorption/etc) I = average rainfall intensity for a duration equal to the Tc for the area, in inches per hour. A = drainage area contributing to the basin in acres. ' The RM equation assumes that the storm event being analyzed delivers precipitation to the entire basin uniformly, and therefore the peak discharge rate will occur when a raindrop falls at the most remote portion of the basin arrives at the point of analysis. The RM also I assumes that the fraction of rainfall that becomes runoff or the runoff coefficient C is not affected by the storm intensity, I, or the precipitation zone number. I In addition to the above Ration Method assumptions, the conservative assumption that all runoff coefficients utilized for this report are based on type "B" soils. 2.2 County of San Diego Criteria As defined by the County Hydrology Manual dated June 2003, the rational method is the I preferred equation for determining the hydrologic characteristics of basins up to approximately one square mile in size. The County of San Diego has developed its own tables, nomographs, and methodologies for analyzing storm water runoff for areas within I the county. The County has also developed precipitation isopluvial contour maps that show even lines of rainfall anticipated from a given storm event (i.e. 100-year, 6-hour storm). I November 2019 I I 1 I Li I One of the variables of the RM equation is the runoff coefficient, C. The runoff coefficient is dependent only upon land use and soil type and the County of San Diego has developed a I table of Runoff Coefficients for Urban Areas to be applied to basin located within the County of San Diego. The table categorizes the land use, the associated development density (dwelling units per acre) and the percentage of impervious area. Each of the I categories listed has an associated runoff coefficient, C, for each soil type class. The County has also illustrated in detail the methodology for determining the time of concentration, in particular the initial time of concentration. The County has adopted the Federal Aviation Agency's (FAA) overland time of flow equation. This equation essentially limits the flow path length for the initial time of concentration to lengths of 100 feet or less, and is dependent on land use and slope. I 2.3 Runoff Coefficient Determination As stated in section 2.2, the runoff coefficient is dependent upon land use and soil type and the County of San Diego has developed a table of Runoff Coefficients for Urban Areas to be applied to basin located within the County of San Diego. The table, included at the end of this section, categorizes the land use, the associated development density (dwelling units per acre) and the percentage of impervious area. The runoff coefficient can be calculated for I an area based on soil type and impervious percentage using the equation found in section 3.1.2 of the County Hydrology Manual. See Sections 3.0 and 5.0 for Coefficient Table and C Value Calculations on the Pre and Post Development Maps. I E I I I November 2019 I I / 3.0 HYDROLOGIC ANALYSES Rational Method Parameters Runoff Coefficient C= 0.90 x (% Impervious) + Cp (1-% Impervious)* Cp0.25* for existing condition pervious type "B" soils I 100 Year 6 Hour Storm Precipitation (P6) =2.5 in (see rainfall isopluvial*) Tc(11.9L3/tE)0.385 per Figure 3-4 of the County of San Diego Hydrology Manual (L=miles)* Tt=Ti + Tc 1= Intensity in/hr, I7.44xP6xD0.645* I Duration P)= Time of Concentration, Tc QPeak Runoff, QC*I*A (cfs) C= (% IMP x 0.90) + [(1-%IMP) x 0.25] I *From San Diego County Hydrology Manual, June 2003 Revision Section 3 I 3.1 Pre-Developed Hydrologic Model Output A6,660 sf = 0.15 ac ' Impervious area = 2,119 sf % IMP 32.1% - I C= (0.321x 0.90) + [(1-0.321)0.25] C= 0.46 T=(11.9(100/5280)3/3.6)°385 T0.0162 hours 0.97 mm 0.97 min <5 nun T=5 minutes jow Iioo7.44(2.5)(5) -0.645 Ioo=6.59 in/hr Qioo 0.46(6.59 in/hr) 0.15 acres Qioo0.45 cfs 3.2 Post-Developed Hydrologic Model Output A6,660 sf= 0.15 ac Impervious area = 4,500 sf % IMP = 68.2% C (0.682x 0.90) + [(1-0.682)0.25] C= 0.69 Assume T5 minutes 1 IiocF7.44(2.5)(5) -0.645 I006.59 in/hr I November 2019 L r- I Qioo 0.69(6.59 in/hr) 0.15 acres Qioo0.685 cfs I Qioo0.69 cfs Qioo = Qpost - Qpre = 0.69 cfs - 0.45 cfs Qioo = 0.24 cfs I I I I November 2019 i I I I I 4.0 HYDRAULIC CALCULATIONS Detention Volume Sizing Required 100 year Storage Volume per hydrographs included in this report = V100,p0 - V100, Pee ,xV=65Ocf -467cf = 183 cf Required detention = 183 cf Proposed BMP area = 93 sf Ponding Depth = 12 inches (1 ft) Engineered Soil Layer = 33 inches (2.75 ft) Void Ratio Factor = 0.4 Proposed Storage Volume = (93 sfx I ft) + (93 sfx 2.75 ft x 0.4) = 93 cf+ 102 cf = 195 cf of proposed stormwater storage capacity Proposed Storage Volume > Required Storage Volume 195 cf > 183 cf I I I I I November 2019 I Rational Method Hydrograph Calculations Pre Developed Condition 1 5170 Carlsbad Blvd, Carlsbad CA 92008 U 0100= 0.45 cfs Tc= 5 min C= 0.45 #= 72 P506 2.5 in A= 0.151 acres • (744*P6*DA 645) (I-D160) (VI-VO) (A V/A T) (Q=ciA) (Re-ordered) D I VOL AVOL I (INCR) Q VOL ORDINATE I # (MIN) (IN/HR) (IN) (IN) (IN/HR) (CFS) (CF) (CFS) 0 0 0.00 0.00 0.55 6.59 0.45 135 1 5 6.59 0.55 0.15 1.84 0.12 37 0.01 2 10 4.21 0.70 0.11 1.30 0.09 27 0.01 3 15 3.24 0.81 0.09 1.05 0.07 21 0.01 4 20 2.69 0.90 0.07 0.89 0.06 18 0.01 , 5 6 25 30 2.33 2.07 0.97 1.04 0.06 0.06 0.78 0.70 0.05 0.05 16 14 0.01 0.01 7 35 1.88 1.10 0.05 0.64 0.04 13 0.01 8 40 1.72 1.15 0.05 0.59 0.04 12 0.01 I 9 45 1.60 1.20 0.05 0.55 0.04 11 0.01 10 50 1.49 1.24 0.04 0.51 0.03 10 0.01 11 55 1.40 1.29 0.04 0.48 0.03 10 0.01 I 12 60 1.33 1.33 0.04 0.46 0.03 9 0.01 13 65 1.26 1.36 0.04 0.44 0.03 9 0.01 14 70 1.20 1.40 0.03 0.42 0.03 8 0.01 15 75 1.15 1.44 0.03 0.40 0.03 8 0.01 I 16 80 1.10 1.47 0.03 0.38 0.03 8 0.01 17 85 1.06 1.50 0.03 0.37 0.03 8 0.01 I 18 19 90 95 1.02 0.99 1.53 1.56 0.03 0.03 0.36 0.34 0.02 0.02 7 7 0.01 0.01 20 100 0.95 1.59 0.03 0.33 0.02 7 0.01 21 105 0.92 1.62 0.03 0.32 0.02 7 0.01 I 22 110 0.90 1.64 0.03 0.31 0.02 6 0.01 23 115 0.87 1.67 0.03 0.31 0.02 6 0.02 24 120 0.85 1.70 0.02 0.30 0.02 6 0.02 25 125 0.83 1.72 0.02 0.29 0.02 6 0.02 I 26 130 0.81 1.75 0.02 0.28 0.02 6 0.02 27 135 0.79 1.77 0.02 0.28 0.02 6 0.02 28 140 0.77 1.79 0.02 0.27 0.02 5 0.02 I 29 145 0.75 1.81 0.02 0.26 0.02 5 0.02 30 150 0.73 1.84 0.02 0.26 0.02 5 0.02 31 155 0.72 1.86 0.02 0.25 0.02 5 0.02 I 32 160 0.70 1.88 0.02 0.25 0.02 5 0.02 33 165 0.69 1.90 0.02 0.24 0.02 5 0.02 34 170 0.68 1.92 0.02 0.24 0.02 5 0.02 I 35 175 0.66 1.94 0.02 0.23 0.02 5 0.02 36 180 0.65 1.96 0.02 0.23 0.02 5 0.02 37 185 0.64 1.98 0.02 0.23 0.02 5 0.03 38 190 0.63 2.00 0.02 0.22 0.02 5 0.03 I 39 195 0.62 2.02 0.02 0.22 0.01 4 0.03 40 200 0.61 2.03 0.02 0.21 0.01 4 0.03 41 205 0.60 2.05 0.02 0.21 0.01 4 0.03 1 2912 Pre Hydrograph.xls 11/21/2019 1 Rational Method Hydrograph Calculations Pre Developed Condition 5170 Carlsbad Blvd, Carlsbad CA 92008 42 210 0.59 2.07 0.02 0.21 0.01 4 0.03 43 215 0.58 2.09 0.02 0.21 0.01 4 0.04 44 220 0.57 2.10 0.02 0.20 0.01 4 0.04 45 225 0.57 2.12 0.02 0.20 0.01 4 0.05 46 230 0.56 2.14 0.02 0.20 0.01 4 0.06 47 235 0.55 2.15 0.02 0.19 0.01 4 0.09 48 240 0.54 2.17 0.02 0.19 0.01 4 0.12 49 245 0.54 2.19 0.02 0.19 0.01 4 0.45 50 250 0.53 2.20 0.02 0.19 0.01 4 0.07 51 255 0.52 2.22 0.02 0.18 0.01 4 0.05 52 260 0.52 2.23 0.02 0.18 0.01 4 0.04 53 265 0.51 2.25 0.01 0.18 0.01 4 0.03 54 270 0.50 2.26 0.01 0.18 0.01 4 0.03 55 275 0.50 2.28 0.01 0.18 0.01 4 0.02 56 280 0.49 2.29 0.01 0.17 0.01 4 0.02 57 285 0.49 2.31 0.01 0.17 0.01 3 0.02 58 290 0.48 2.32 0.01 0.17 0.01 3 0.02 59 295 0.47 2.33 0.01 0.17 0.01 3 0.02 60 300 0.47 2.35 0.01 0.17 0.01 3 0.02 61 305 0.46 2.36 0.01 0.16 0.01 3 0.02 62 310 0.46 2.38 0.01 0.16 0.01 3 0.01 63 315 0.46 2.39 0.01 0.16 0.01 3 0.01 64 320 0.45 2.40 0.01 0.16 0.01 3 0.01 65 325 0.45 2.42 0.01 0.16 0.01 3 0.01 66 330 0.44 2.43 0.01 0.16 0.01 3 0.01 67 335 0.44 2.44 0.01 0.15 0.01 3 0.01 68 340 0.43 2.45 0.01 0.15 0.01 3 0.01 69 345 0.43 2.47 0.01 0.15 0.01 3 0.01 70 350 0.43 2.48 0.01 0.15 0.01 3 0.01 71 355 0.42 2.49 0.01 0.15 0.01 3 0.01 72 360 0.42 2.51 0.00 0.00 0.00 0 0.01 SUM= 422 cubic feet 0.01 acre-feet I I I I I I I I I L I 2912 Pre Hydrograph.xls 11/21/2019 I Rational Method Hydrograph Calculations Pre Developed Condition 5170 Carlsbad Blvd, Carlsbad CA 92008 I i 0.50 RM-HYDROGRAPH Project 0.45 0.40 0.35 0.30 0.25 Cy 0.20 0.15 0.10 0.05 0.00 0 50 100 150 200 250 300 350 400 Time (mm) I I 2912 Pre Hydrograph.xls 11/21/2019 S Li I I I I Li I I I Rational Method Hydrograph Calculations Post Developed Condition 5170 Carlsbad Blvd, Carlsbad CA 92008 Q100 069 cfs Tc= 5 min C= 0.69 #= 72 P506= 2.5 in A= 0.151 acres (744*P6*DA 645) (I-D/60) (VI-VO) (A V/il T) (Q=ciA) (Re-ordered) 0 I VOL AVOL I (INCR) Q VOL ORDINATE # (MIN) (IN/HR) (IN) (IN) (IN/HR) (CFS) (CF) (CFS) 0 0 0.00 0.00 0.55 6.59 0.69 207 1 5 6.59 0.55 0.15 1.84 0.19 57 0.02 2 10 4.21 0.70 0.11 1.30 0.14 41 0.02 3 15 3.24 0.81 0.09 1.05 0.11 33 0.02 4 20 2.69 0.90 0.07 0.89 0.09 28 0.02 5 25 2.33 0.97 0.06 0.78 0.08 24 0.02 6 30 2.07 1.04 0.06 0.70 0.07 22 0.02 7 35 1.88 1.10 0.05 0.64 0.07 20 0.02 8 40 1.72 1.15 0.05 0.59 0.06 18 0.02 9 45 1.60 1.20 0.05 0.55 0.06 17 0.02 10 50 1.49 1.24 0.04 0.51 0.05 16 0.02 11 55 1.40 1.29 0.04 0.48 0.05 15 0.02 12 60 1.33 1.33 0.04 0.46 0.05 14 0.02 13 65 1.26 1.36 0.04 0.44 0.05 14 0.02 14 70 1.20 1.40 0.03 0.42 0.04 13 0.02 15 75 1.15 1.44 0.03 0.40 0.04 12 0.02 16 80 1.10 1.47 0.03 0.38 0.04 12 0.02 17 85 1.06 1.50 0.03 0.37 0.04 12 0.02 18 90 1.02 1.53 0.03 0.36 0.04 11 0.02 19 95 0.99 1.56 0.03 0.34 0.04 11 0.02 20 100 0.95 1.59 0.03 0.33 0.03 10 0.02 21 105 0.92 1.62 0.03 0.32 0.03 10 0.02 22 110 0.90 1.64 0.03 0.31 0.03 10 0.02 23 115 0.87 1.67 0.03 0.31 0.03 10 0.02 24 120 0.85 1.70 0.02 0.30 0.03 9 0.02 25 125 0.83 1.72 0.02 0.29 0.03 9 0.02 26 130 0.81 1.75 0.02 0.28 0.03 9 0.02 27 135 0.79 1.77 0.02 0.28 0.03 9 0.03 28 140 0.77 1.79 0.02 0.27 0.03 8 0.03 29 145 0.75 1.81 0.02 0.26 0.03 8 0.03 30 150 0.73 1.84 0.02 0.26 0.03 8 0.03 31 155 0.72 1.86 0.02 0.25 0.03 8 0.03 32 160 0.70 1.88 0.02 0.25 0.03 8 0.03 33 165 0.69 1.90 0.02 0.24 0.03 8 0.03 34 170 0.68 1.92 0.02 0.24 0.02 7 0.03 35 175 0.66 1.94 0.02 0.23 0.02 7 0.03 36 180 0.65 1.96 0.02 0.23 0.02 7 0.04 37 185 0.64 1.98 0.02 0.23 0.02 7 0.04 38 190 0.63 2.00 0.02 0.22 0.02 7 0.04 39 195 0.62 2.02 0.02 0.22 0.02 7 0.04 40 200 0.61 2.03 0.02 0.21 0.02 7 0.05 41 205 0.60 2.05 0.02 0.21 0.02 7 0.05 2912 Post Hydrograph.xls 11/21/2019 Rational Method Hydrograph Calculations Post Developed Condition 5170 Carlsbad Blvd, Carlsbad CA 92008 42 210 0.59 2.07 0.02 0.21 0.02 7 0.05 43 215 0.58 2.09 0.02 0.21 0.02 6 0.06 44 220 0.57 2.10 0.02 0.20 0.02 6 0.07 45 225 0.57 2.12 0.02 0.20 0.02 6 0.08 46 230 0.56 2.14 0.02 0.20 0.02 6 0.09 47 235 0.55 2.15 0.02 0.19 0.02 6 0.14 48 240 0.54 2.17 0.02 0.19 0.02 6 0.19 49 245 0.54 2.19 0.02 0.19 0.02 6 0.69 50 250 0.53 2.20 0.02 0.19 0.02 6 0.11 51 255 0.52 2.22 0.02 0.18 0.02 6 0.07 52 260 0.52 2.23 0.02 0.18 0.02 6 0.06 53 265 0.51 2.25 0.01 0.18 0.02 6 0.05 54 270 0.50 2.26 0.01 0.18 0.02 6 0.04 55 275 0.50 2.28 0.01 0.18 0.02 5 0.04 56 280 0.49 2.29 0.01 0.17 0.02 5 0.03 57 285 0.49 2.31 0.01 0.17 0.02 5 0.03 58 290 0.48 2.32 0.01 0.17 0.02 5 0.03 59 295 0.47 2.33 0.01 0.17 0.02 5 0.03 60 300 0.47 2.35 0.01 0.17 0.02 5 0.03 61 305 0.46 2.36 0.01 0.16 0.02 5 0.02 62 310 0.46 2.38 0.01 0.16 0.02 5 0.02 63 315 0.46 2.39 0.01 0.16 0.02 5 0.02 64 320 0.45 2.40 0.01 0.16 0.02 5 0.02 65 325 0.45 2.42 0.01 0.16 0.02 5 0.02 66 330 0.44 2.43 0.01 0.16 0.02 5 0.02 67 335 0.44 2.44 0.01 0.15 0.02 5 0.02 68 340 0.43 2.45 0.01 0.15 0.02 5 0.02 69 345 0.43 2.47 0.01 0.15 0.02 5 0.02 70 350 0.43 2.48 0.01 0.15 0.02 5 0.02 71 355 0.42 2.49 0.01 0.15 0.02 5 0.02 72 360 0.42 2.51 0.00 0.00 0.00 0 0.02 SUM= 647 cubic feet 0.01 acre-feet I I I I I 1 2912 Post Hydrograph.xls 11/21/2019 I I I I I I Li I I 1 I Rational Method Hydrograph Calculations Post Developed Condition 5170 Carlsbad Blvd, Carlsbad CA 92008 RM-HYDROGRAPH Project 0.80 0.70 0.60 0.50 0.40 a 0.30 0.20 0.10 I :.:: 0 50 100 150 200 250 300 350 400 Time (mm) 2912 Post Hydrograph.xls 11/21/2019 I 5.0 APPENDIX I I I I I I LI I I I I I I I November 2019 1 t San Diego County Hydrology Manual Date: June 2003 Section: 3 Page: 6of26 Table 3-1 RUNOFF COEFFICIENTS FOR URBAN AREAS Land Use I Runoff Coefficient "C" Soil Type NRCS Elements County Elements I % INTER. 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 0.45 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 County of San Diego Orange I Ii I:T:ii IT iI_::T Hydrology Manual --33*3 -j-Count 33030- -+ - - - + - - - 4- - ' -. - ---4-- - - -* -4- ------4- --• + -'--4- +- - -'---4- -. 4- 4--,--. + _- -+-- - ---- --- Riv-Rivers -'-- -•---'----+- Li DIE lit ___________________ I lIT \i 41 i Rainfall Isopluvials -33'-1-5'-" 33015 lOO Year Rainfall Event -6Hours 2 -- 1 7t -OCEANSIDE - - --*--+ - \ - - 4 -- - - *--'_-4* -•- IsopluviaI(inches) -S .- e+ - + - ' - - - + - - - _5_ -- - 5• + - - - - • - - -CARLSBAD -_. - - -'- ':-7r-.'.------------:s ------'------ -. - + 0 ENCINITAS :: - 451. ______________________ - 3 33 00 - = + 33900 SOLANABEACH - -' S COUND ---------- DEL MAR',- - - -4- 4 4 -i- 4 + - - -4- + () 4 -•- 4- f r+-------, __r_i-_ 4- - if - - Q - - 4- - -- - ------ : /- -/ - ---'- \-- - :--. - - - - -- - - -- - -4- 4- --4 4- V., .- -. -- .. _e' .-. 5. 5. .5,. . .. - 4 - 1• - -. --- ----* +-4----- - _•5+ -,-- -c '- --'-'- •.- - -----------.•. -* - ..- ---- , - 4 --------- - -- - - - -----4 NTEE -• . .--- • --••- . -- V-.--- 4-_ - --- - - -- -+-- --.-...-+--s -'-• - ,. '-+*.----.-.'-- .- - •+- ----------------------------- -,-,- N -—--• -++ - Q 4 - + -- - -e- - ---v'------- -'--'-- - - - - - -32°45' - '5 .. .' .• II :. 32045 - ?ii: I 7,T 4GE - ON DPW 4- - / 44r4+ '+ H+ir Sin Diego ( ct rd' - -------------------------- --- -CUA --------- - N THIS MAP IS PROVIDED WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS ORIMPUEINCLUDG, BUT NOT LARTEDTO, THE IMPUEDWARRARTIES FOR A PARTICULAR PURPOSE - - - IMPERIAL BEACII - 4- - - - - H, - - 11.HHI Ill H+Tl III 11 :MIle+X 1::: + - m products may contain informationfrom the SANDAG Regional cannot b0 reproduced without the WE Information System which written permission of SANDAG. - - - This product may contain information which has been reproduced with ____________________________ - -32 - 030' -- + ----- __________________________ - 4- - __________________________ granted by Thomas Brothers Maps. Y - 32°30' - S ----------- permission 30 3MiIes ZD I I I I I I I .1 I I I I [1 1 I I I 1 I Hydrologic Soil Group—San Diego County Area California K 4€8803 If. -.- 4 f. 45&M 4IfKV 405749 33 753"N r , 33 7 53 N k ril% If :• 4" Aw 1. IC . . k .. 33 731 N V lid it III 751 N 468754 4686X3 454545 12 418 454824 468833 468833 414042 448 Map Scale: 1:277 if printed onA landscape (11 x8.5) sheet. Meters K N 0 4 8 16 24 Feet 0 10 20 40 60 Map projection Web Mercator Corner coordinates: WGS84 Edge tics UTM Zone uN WGS84 t.Is Natural Resources Web Soil Survey 8/6/2018 Conservation Service National Cooperative Soil Survey Page 1 of 4 Hydrologic Soil Group—San Diego County Area, California MAP LEGEND MAP INFORMATION DC dID o Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography Area of Interest (AOl) Area of Interest (AOl) Soils Soil Rating Polygons A/D B/D EIIC do Not rated or not available Soil Rating Lines A -- A/D ,.... B B/D -- C -- C/D ..01 D . Not rated or not available Soil Rating Points o A A/D B • B/D The soil surveys that comprise your AOl were mapped at 1 24,000 Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements Source of Map Natural Resources Conservation Service Web Soil Survey URL Coordinate System Web Mercator (EPSG.3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area San Diego County Area, California Survey Area Data: Version 12, Sep 13, 2017 Soil map units are labeled (as space allows) for map scales 1 50.000 or larger. Date(s) aerial images were photographed: Nov 3, 2014—Nov 22, 2014 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps As a result, some minor shifting of map unit boundaries may be evident. Natural Resources Web Soil Survey 8/6/2018 Conservation Service National Cooperative Soil Survey Page 2 of 4 Hydrologic Soil Group—San Diego County Area, California Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOl Percent of AOl MIC Marina loamy coarse sand, 2 to 9 percent slopes B 0.2 100.0% Totals for Area of Interest 0.2 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (AID, BID, and CID). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (AID, BID, or CID), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition USDA Natural Resources Web Soil Survey 8/6/2018 Conservation Service National Cooperative Soil Survey Page 3 of 4 Hydrologic Soil Group—San Diego County Area, California Component Percent Cutoff: None Specified I Tie-break Rule: Higher I I I L Li] I I I [I I I I [11 I 1 USiJA Natural Resources Web Soil Survey 8/6/2018 Conservation Service National Cooperative Soil Survey Page 4 of 4 I