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HomeMy WebLinkAboutMS 15-02; CARLSBAD LAGOON CUSTOM HOMES; HYDROLOGY STUDY FOR CARLSBAD LAGOON BEACH HOMES; 2016-02-09HYDROLOGY STUDY FOR CARLSBAD LAGOON BEACH HOMES 165 CHINQUAPIN AVENUE Grading Permit / Parcel Map PUD 15-04 / SDP 15-03 I MS 15-02 CITY OF CARLSBAD, CA PREPARED FOR: RINCON REAL ESTATE GROUP, INC. 1520 N. EL CAMINO REAL, UNIT 5 SAN CLEMENTE, CA 92672 (949) 637-3354 PREPARED BY: PASCO LARET SUITER & ASSOCIATES, INC. 535 N. HIGHWAY 101, SUITE A SOLANA BEACH, CA 92075 (858) 259-8212 Prepared: October 23, 2015 Revised: January 15, 2016 Revised: February 9, 2016 LER G. LAWSON, RCE 80356 DATE PLSA 2276-02 I-03 TABLE OF CONTENTS SECTION Executive Summary 1.0 Introduction 1.1 Existing Conditions 1.2 Proposed Project 1.3 Conclusions 1.4 References 1.5 Methodology 2.0 Introduction 2.1 County of San Diego Criteria 2.2 Runoff Coefficient Determination 2.3 Hydrology & Hydraulic Model Output 3.0 Pre-Developed Hydrologic Calculations (100-Year Event) 3.1 Post-Developed Hydrologic Calculations (100-Year Event) 3.2 Appendix 4.0 Isopluvial Maps Intensity Duration Design Charts Runoff Coefficients Overland Flow / Initial Time of Concentration Hydrologic Soil Group - USDA Web Soil Survey Pre-Development Hydrology Node Map Post-Development Hydrology Node Map PLSA 2276-02 1.0 EXECUTIVE SUMMARY 1.0 Introduction This Preliminary Hydrology Study for the proposed development at 165 Chinquapin Avenue has been prepared to 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 2-year, 10-year, and 100-year, 6-hour storm. 1.1 Existing Conditions The subject property is located along Chinquapin Avenue, west of the intersection of Chinquapin Avenue and Garfield Street, in the City of Carlsbad. The site is bound by an existing single family residential development to the west, an existing multi-family residential development to the east of the property, Chinquapin Avenue to the north, and the Agua Hedionda Lagoon to the south of the property. The existing site consists of an existing residence, driveway, and associated improvements. The project site is located in the Agua Hedionda Hydrologic Area, and, more specifically, the Los Monos Hydrologic Sub-Area (904.31). The existing site can be categorized into one drainage basin, and primarily drains from the southeast to the northwest corner of the site and out to Chinquapin Avenue. An existing asphaltic berm and sloping in the front yard along Chinquapin Avenue prevent any offsite drainage from entering the parcel to the north. Existing residential properties to the west and east prevent cross lot drainage from passing through the site. The existing drainage basin has an approximate area of 0.23 acres and is approximately 46% impervious. Per the Web Soil Survey application available through the United States Department of Agriculture, the basin is generally categorized to have group B soils. Based on the existing impervious area, a pre-development runoff coefficient of 0.55 was calculated using the methodology described in section 3.1.2 of the San Diego County Hydrology Manual and the formula provided therein. Using the Rational Method Procedure outlined in the San Diego County Hydrology Manual, a peak flow rate and time of concentration were calculated for a 100-year, 6-hour storm event. For the existing drainage basin, the peak flow rate for the 100-year, 6-hour storm was determined to be 0.83 cfs at the point of discharge from the site with a time of concentration of 5.0 minutes. Refer to pre-development hydrology calculations included in Section 3.1 of this report for a detailed analysis of the existing drainage basin, as well as a pre-development hydrology node map included in the appendix of this report for pre-development drainage basin delineation and discharge locations. 1.2 Proposed Project The proposed project includes the demolition of all existing onsite improvements and the construction of a 3-unit detached condo map with associated private landscaping and Page 1 of 8 PLSA 2276-02 hardscape improvements, as well as curb, gutter, and sidewalk improvements in the public right-of-way. Site grading along with road, drainage and utility improvements typical of residential developments will also be constructed. The proposed building pad elevations range from 58.2 feet at the easterly unit to 56.6 feet at the westerly unit in an attempt to match the existing sloping terrain. In the resulting post-developed condition, runoff can be categorized into one drainage basin similar to the existing site. Each unit will convey runoff by means of vegetated swales to proposed area drains located along the southern and northern boundaries of the property. Once water is collected in the area drains, PVC under drain pipes will discharge the runoff into the proposed curb and gutter on Chinquapin Avenue. The proposed drainage basin has an approximate area of 0.23 acres and is approximately 44% impervious. As in the existing condition, runoff is prevented from entering the site due to proposed curb, gutter, sidewalk, and driveway improvements along Chinquapin Avenue, and the neighboring residential developments to the west and east. Based on the proposed impervious area, a runoff coefficient of 0.54 was calculated using the methodology described in section 3.1.2 of the San Diego County Hydrology Manual and the formula provided therein. Using the Rational Method Procedure outlined in the San Diego County Hydrology Manual, a peak flow rate and time of concentration were calculated for a 100-year, 6-hour storm event. For the proposed drainage basin, the peak flow rate for the 100-year, 6-hour storm was determined to be 0.81 cfs at the ultimate point of discharge with a time of concentration of 5.0 minutes. A storm drain curb inlet located approximately 150 feet downstream west of the project at the low point of the cul-de-sac on Chinquapin Avenue will then collect runoff from the curb and gutter and direct it to the public storm drain system. Refer to post-development hydrology calculations included in Section 3.2 of this report for detailed analysis of the proposed drainage basin, as well as a post-development hydrology node map included in the appendix of this report for post-development drainage delineation and discharge locations. In an effort to comply with the City of Carlsbad storm water standards, the proposed site has incorporated LID design techniques to optimize the site layout. Runoff from proposed roofs and hardscape areas will be directed to vegetated swales in an effort to disperse drainage to pervious surfaces. The swales will remove sediment and particulate- bound pollutants from storm water and will assist in decreasing peak runoff by slightly increasing the site's overall time of concentration. Site hardscape has been minimized with the addition of pervious paver walkways, driveways, and patios. 1.3 Conclusions Based upon the analysis included in this report, there is a slight decrease in peak runoff as a result of the proposed development, minimizing additional impacts to downstream - properties and existing drainage facilities. Similar to the existing condition, the post- developed site will discharge onto Chinquapin Avenue into the proposed curb and gutter - system. Once in the gutter, drainage will be conveyed to an existing curb inlet located Page 2 of 8 PLSA 2276-02 approximately 150 feet west of the project boundary, and will enter the buried pipe network. Water will not be diverted away from existing drainage patterns, and the decrease in proposed impervious area and resulting peak runoff will not have an adverse effect on the downstream watershed. The post-developed site will be exempt from hydromodification compliance requirements as it does not qualify as a Priority Development Project as defined in the San Diego County Model BMP Design Manual. Additional analysis and design will be required to verify that the proposed project is in compliance with current stormwater quality regulations. 1.5 References "San Diego County Hydrology Manual ", revised June 2003, County of San Diego, Department of Public Works, Flood Control Section. "San Diego County Hydraulic Design Manual", revised October 2012, County of San Diego, Department of Public Works, Flood Control Section "Model BMP Design Manual San Diego Region ", adopted June 27, 2015, San Diego Region "Low Impact Development Handbook - Stormwater Management Strategies", revised July 2014, County of San Diego, Department of Public Works Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov. Accessed July 20, 2015 Page 3 of 8 PLSA 2276-02 2.0 METHODOLOGY 2.1 Introduction The hydrologic model used to perform the hydrologic analysis presented in this report utilizes the Rational 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 (I) is equal to: I = 7.44 x P6 x D 045 -. Where: I = Intensity (in/hr) P6 = 6-hour precipitation (inches) D = duration (minutes - use Tc) 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 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: Q=CIA VAJ T,473 Q= flow (in cfs) 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 that falls at the most remote portion of the basin arrives at the point of analysis. The RM also 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. Page 4 of 8 PLSA 2276-02 2.2 County of San Diego Criteria As defined by the County Hydrology Manual dated June 2003, the rational method is the 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 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). 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 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 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 under - 100 feet, and is dependent on land use and slope. The time of concentration minimum is 5 minutes per the County of San Diego requirements. 2.3 Runoff Coefficient Determination As stated in section 2.2, the runoff coefficient is dependent only 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. Page 5 of 8 PLSA 2276-02 3.0 HYDROLOGY MODEL OUTPUT 3.1 Pre-Developed Hydrologic Model Output (100-Year Event) Pre-Development: Q=CIA P2=1.2 P101.7 - P1002.5 Basin 1 Total Area = 9,972 sf 4 0.229 Acres Impervious Area = 4,586 sf 4 0.11 Acres Pervious Area = 5,386 sf 4 0.12 Acres Cn, Weighted Runoff Coefficient - 0.25, Cn value for natural ground, Type B soils * Per San Diego Hydrology Design Manual (SDHDM) Section 3.1.2 - 0.9, C value for developed / impervious surface * Per SDHDM Section 3.1.2 Cn = 0.9 x 4,586 sf+ 0.25 x 5,386 sf= 0.55 9,972 sf Tc =.5.0 Mm (minimum for small areas) P6 = 2.5 I = 7.44 x P6 D 045 I = 7.44 x 2.5 x 6.59 Iwo 6.59 in/hr 1 I23.16 in/hr Iio 4.48 in/hr Q2 = 0.55 x 3.16 in/hr x 0.229 Ac = 0.40 cfs Qio = 0.55 x 4.48 in/hr x 0.229 Ac = 0.56 cfs - Qioo = 0.55 x 6.59 in/hr x 0.229 Ac = 0.83 cfs Page 6 of 8 PLSA 2276-02 3.2 Post-Developed Hydrologic Model Output (100-Year Event) Post-Development (without considerin2 HMP/BMP treatment): Q=CIA P2=1.2 P10=1.7 P100=2.5 Basin A Total Area = 9,972 sf 4 0.229 Acres Impervious Area = 4,376 sf4 0.10 Acres Pervious Area = 5,595 sf4 0.13 Acres Cn, Weighted Runoff Coefficient - 0.25, Cn value for natural ground, Type B soils * Per San Diego Hydrology Design Manual (SDHDM) Section 3.1.2 - 0.9, C value for developed / impervious surface * Per SDHDM Section 3.1.2 - Cn = 0.9 x 4,376 sf+ 0.25 x 5,595 sf= 0.54 9,972 sf Tc =.5.0 Mm (mm. for small areas) P6 = 2.5 I = 7.44 x P6 D.0645 I = 7.44 x 2.5 x s.O-° 6.59 in/hr Iioo 6.59 in/hr I2 3.16 in/hr Iio 4.48 in/hr *At northwest corner under drain Ai = 7,779 sf 4 0.18 Acres Q2 = 0.54 x 3.16 in/hr x 0.18 Ac = 0.31 cfs Qio = 0.54 x 4.48 in/hr x 0.18 Ac = 0.44 cfs Qioo = 0.54 x 6.59 in/hr x 0.18 Ac = 0.64 cfs Page 7 of 8 PLSA 2276-02 *At sidewalk under drain A2 = 1,080 sf 4 0.02 Acres Q2 = 0.54 x 3.16 in/hr x 0.025 Ac = 0.04 cfs Qio = 0.54 x 4.48 in/hr x 0.025 Ac = 0.06 cfs Qioo = 0.54 x 6.59 in/hr x 0.025 Ac = 0.08 cfs *At sidewalk under drain A.3 = 1,102 sf 4 0.03 Acres Q2 = 0.54 x 3.16 in/hr x 0.03 Ac = 0.05 cfs Qio = 0.54 x 4.48 in/hr x 0.03 Ac = 0.07 cfs Qioo = 0.54 x 6.59 in/hr x 0.03 Ac = 0.09 cfs *Total leaving site at ultimate discharge point Qioo = 0.54 x 6.59 in/hr x 0.229 Ac = 0.81 cfs Pre-Development vs. Post-Development (Discharge Leaving Site): Pre-Development Post-Development Delta Qioo = 0.83 cfs Qioo = 0.81 cfs -0.02 cfs Page 8 of 8 PLSA 2276-02 4.0 APPENDIX PLSA 2276-02 EQUATION __________________________ 11111111 uitW'' 11111111 Intensity (in/hr) kN It, U1,111- P6 = 6-Hour Precipitation (in) rtion H Iii"i*i ••••v•ii•u•i IiIII5I IIb'Ih iii IdIi. $111111111111111 Hill 1111111H 11111111111 iIlI1IUi!!Ili !!III!I II 'lIIIIII IIIIIIIIIIIllIllhIllhIIlI H14,11101HURINN1,100, III IIlli!!!G I! !iII1II I1IIIlIIIII1I1IIII IIIIiiiiIIIlIII! 1111111111 ffl'iIIIii lull 1111111111111 111111111HiH!!111111 1111111!i! 11111 Ill. 01111 fisou !11'. MEN •iiiuuiiiuiiii U•UII•IIiIiihui ulllllh;'lllhllulllIll MEMO MEN milli II,II uulIuuullIlIuuIll IlIluIulIllIllIll IlIlIllIllIl1011 IllIllIllIlIllIll flhIIOhIDIllhIIIfIIIllhI1IIHHIHI1II1IIIffli!iHhIIlli!!llHII1i .u.uuiIuuIISuIIuIIuI..U•IUIuIuIiI;IIIuIIIIIIuIII •h •IUU1IUh'fl _ ..n..fl.uU usu.,.,,II.SShSUtSItIuuuIIul$lIulluInSa 2. 1flS.'flflUSII• ...• ...nn.., u,...,u,IflS.uueulu.IuuIIIulIIIUIIluIa UkUUBUJIR!IIIIIl ••• .....n..I I.IIIuII,uuS..It..SU.IuuIIlIIIIIuuItuI a.•.bI•JI• .,.u.n ••UUIIUII uIIliuiHIUU•IlIII.IIIIIuIuIIIIIluIII UUI'on NEON" U;411 sill Ill INIIIIlII : ...uI.uuI;uhIII,lII4 u1 1 511111111111111113 1111011 JuhuJIIIuuII,IIuHhlII ....0 11M Uu4 1 Ub'fl1 I1 11 CZ I•uuluI•IIuIuIuIIII••IUIuIuu•IIuIuIuIfluuuuI Il U•UUURI•iuu111uIIft •••••••• ..•uiuiuuiiiiiuiiuii.uuuuuuuiuuiuiliniiiuuli II ...URU.U.IU.IIIIIUIIH .• ••.amu.IIIIiuuu uluulIIIUIIlIIIIluullullll,IIuuuIuluulIIIuIIuIuIIIII1IIu t•m•u•iu•iiuinuunuiiupiin IN R11, it•••.uiUiiiuiuuutiiiuiiuiu IIuIuuIuuIuIIfflIHIIIuIIIuI•••RI••ICuIIuIUI1IIIIIth .u.•.iuuuuuiiL'T'iui ItmIunuhIJunuHIIIIlmIuIIIluu.IIuIuuuuuuuInuIluIH ••mauuauiuiii. .i..uulIIIIIIIIIIII But Uflh1IIIIIIIIIIIIIIIIISU mammon puppy Winn .••miiiiiiiui IflhIHIflUIIIIIIHhIIIIIfllHhIIIH1tIHhIIIIIIIUIlIlIIIIltIIUllhIU1I1] San Diego County Hydrology Manual Section: 3 Date: June 2003 - Page: 6 of 26 Table 3-1 RUNOFF COEFFICIENTS FOR URBAN AREAS Land Use Runoff Coefficient "C" Soil Type NRCS Elements County Elements % 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 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 (FLDR) 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. Com) 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 1.) 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 San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: I2of26 Note that the Initial Time of Concentration should be reflective of the general land-use at the upstream end of a drainage basin. A single lot with an area of two or less acres does not have a significant effect where the drainage basin area is 20 to 600 acres. Table 3-2 provides limits of the length (Maximum Length (LM)) of sheet flow to be used in hydrology studies. Initial Ti values based on average C values for the Land Use Element are also included. These values can be used in planning and design applications as described below. Exceptions may be approved by the "Regulating Agency" when submitted with a detailed study. Table 3-2 MAXIMUM OVERLAND FLOW LENGTH (LM) -' & INITIAL TIME OF CONCENTRATION (T Element* DU/ Acre .5% 1% 2% 3% 5% 10% LM T1 LM T1 LM Tj LM T1 LM T, LM Ii Natural 50 13.2 70 12.5 85 10.9 100 10.3 100 8.7 100 6.9 LDR 1 50 12.2 70 11.5 1 85 10.0 100 9.5 100 8.0 1 100 6.4 LDR 2 50 11.3 70 10.5 85 1 9.2 100 8.8 100 7.41 100 1 5.8 LDR 2.9 50 1 10.7 70 10.0 85 8.8 95 8.1 100 7.0 100 5.6 MDR 4.3 50 10.2 70 9.6 80 8.1 95 7.8 100 6.7 100 5.3 MDR 7.3 50 9.2 65 1 8.41 80 7.4 95 7.0 100 6.0 100 4.8 MDR 10.9 50 8.7 65 7.91 801 6.9 90 6.4 100 5.71 100 4.5 MDR 14.5 50 8.2 65 7.41 80 6.5 1 90 6.0 100 5.4 100 4.3 HDR 124 50 1 6.7 65 6.1 75 5.1 90 4.9 95 4.3 100 3.5 HDR 43 50 5.3 65 4.7 75 4.0 85 3.8 1 95 3.4 100 2.7 N. Corn 50 5.3 60 4.5 75 4.0 85 3.8 95 3.4 100 2.7 G. Corn 50 4.7 60 4.1 1 75 3.6 85 3.4 90 2.9 100 2.4 O.P./Corn 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2 Limited 1. 50 4.2 60 3.7 70 3.1 80 2.9 90 1 2.6 1 100 2.2 General I. 50 3.7 60 3.2 70 2.7 80 2.6 90 2.3 100 1.9 *See Table 3-1 for more detailed description 3-12 Hydrologic Soil Group—San Diego County Area, California 33 851"N %. Hydrologic Soil Group—San Diego County Area, California Hydrologic Soil Group Hydrologic Siil Group— Summary by Map Unit - San Diego County Area, California (CA38) Map unit symbol,,Map unit name Rating Acres In AOl Percent of AOl MIC Marina loamy coarse sand, 2 to percent slopes B 1.8 82.1% TeF Terrace escarpments 0.4 17.9% Totals for Area of Interest 2.2 100.0% 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 C/D), 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 usn Natural Resources Web Soil Survey 10/21/2015 Conservation Service National Cooperative Soil Survey Page 3 of 4 Hydrologic Soil Group—San Diego County Area, California Component Percent Cutoff. None Specified Tie-break Rule: Higher usn Natural Resources Web Soil Survey 10/21/2015 Conservation Service National Cooperative Soil Survey Page 4 of 4 Tuesday, Jan 12 2016 Highlighted Depth (ft) = 0.25 Q(cfs) = 0.125 Area (sqft) = 0.05 Velocity (ft/s) = 2.54 Wetted Perim (ft) = 0.79 Crit Depth, Yc (ft) = 0.22 Top Width (ft) = 0.00 EGL(ft) = 0.35 0 1 Elev (ft) 55.00 54.75 54.25 54.00 Channel Report Hydraflow Express Extension for Autodeslø8) AutoCAD® CiI 3D® by Autodesk, Inc. 3-in PVC Drain Pipe @ 2% (QIOO) Circular Diameter (ft) = 0.25 Invert Elev (ft) = 54.60 Slope (%) = 2.00 N-Value = 0.013 Calculations Compute by: Known Depth Known Depth (ft) = 0.25 You created this POF from an application that is not licensed to print to novaPDF printer (http:I/www.novapdf.cQrn)