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Home My WebLink AboutMS 15-11; GARFIELD CUSTOM BEACH HOMES; HYDROLOGY STUDY FOR 3806 GARFIELD STREET, CARLSBAD, CA; 2016-04-04v. •' ••r:"U - - lnital Date HYDROLOGY STUDY FOR 3806 Garfield Street, Carlsbad, CA Grading Permit / Parcel Map PUD 15-17 I SDP 15-16 / MS 15-11 / CDP 15-34 .4 CITY OF CARLSBAD, CA PREPARED FOR: RINCON REAL ESTATE GROUP, INC. 1520 N. EL CAM1NO REAL, UNIT 5 SAN CLEMENTE, CA 92672 (949) 637-3354 PREPARED BY: PASCO LARET SUITER & ASSOCIATES, INC. 535 N. HIGHWAY 101, SUITEA SOLANA BEACH, CA 92075 (858) 259-8212 RECEIVED APR 05 2116 LAND DEVELOPMENT ENGINEERING Prepared: January 8, 2016 Revised: February 25, 2016 Revised: April 4, 2016 G. LAWSON, RCE 80356 DATE PLSA Job #2319 535 N. Hwy 101, Suite A Solana Beach, CA 92075 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 Pipe Analysis Results and Discussion 3.3 Appendix 4.0 Isopluvial Maps Intensity Duration Design Charts Runoff Coefficients Overland Flow I Initial Time of Concentration Hydrologic Soil Group - USDA Web Soil Survey Pre-Development Hydrology Node Map Post-Development Hydrology Node Map 6-in PVC Pipe Capacity / Channel Report 3-in PVC Pipe Capacity / Channel Report PLSA Job #2319 535 N. Hwy 101, Suite A Solana Beach, CA 92075 Page 1 of 1.0 EXECUTIVE SUMMARY 1.1 Introduction This Hydrology Study for the proposed development at 3806 Garfield Street 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. 1.2 Existing Conditions The subject property is located along Garfield Street, at the intersection of Garfield Street and Hemlock Avenue, in the City of Carlsbad. The site is bound by existing residential developments to the south and east of the property, Garfield Street to the west, and Hemlock Avenue to the north of the property. The existing site consists of an existing residence, driveways, 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 southwest to the northeast corner of the site and out to Hemlock Avenue. Existing curb, gutter, and sidewalk improvements along Garfield Street and Hemlock Avenue prevent any offsite drainage from entering the parcel to the west and north. Existing residential properties to the south and east prevent cross lot drainage from passing through the site. The existing drainage basin has an approximate area of 0.15 acres and is approximately 25% 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 0.41 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 0.4 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 Appendix A of this report for pre- development drainage basin delineation and discharge locations. 1.3 Proposed Project (Grading Plan 491-5A) The proposed project includes the demolition of all existing onsite improvements and the construction of a 2-unit detached condo map with associated landscaping and hardscape improvements. Site grading along with road, drainage and utility improvements typical PLSA Job #2319 535 N. Hwy 1O1 Suite A Solana Beach, CA 92075 Page 2 of 9 of residential development will also be constructed. The proposed building pad elevations are 61.3 feet for the westerly unit and 58.6 feet for the easterly 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. The proposed site will be graded so that runoff will drain from a high point at the southwest corner of the site to the low point in the northeast corner. Each unit will convey generated runoff through landscaped areas and vegetated swales. Area drains are proposed along the flow path for each unit leading to underground storm drain piping in an effort to remove runoff from the surface during high frequency storm events. 3-inch PVC under drain pipes will discharge runoff entering the underground system into the existing curb and gutter on Hemlock Avenue. A storm drain curb inlet located approximately 150 feet east of the project on Hemlock Avenue will then collect runoff from the curb and gutter and direct it to the public storm drain system. Refer to the project grading plan, drawing 491-5A, for precise grade information and proposed drainage patterns. The proposed drainage basin has an approximate area of 0.15 acres and is approximately 59% impervious. The basin has two discharge locations along Hemlock Avenue and can be further separated into two sub-drainage basins: Basin A with an approximate area of 0.07 acres and Basin B with an approximate area of 0.07 acres. As in the existing condition, runoff is prevented from entering the site due to curb, gutter, and sidewalk improvements along Hemlock Avenue, and the neighboring residential developments to the south and east. Based on the proposed impervious area, a runoff coefficient of 0.64 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 both proposed drainage Basins A and B, the peak flow rate for the 100-year, 6-hour storm was determined to be 0.3 cfs at each discharge location with a time of concentration of 5.0 minutes. The total site runoff generated by sub-drainage Basins A and B was determined to be 0.6 cfs at the ultimate point of discharge from the site on Hemlock Avenue. This flow is calculated before onsite LID Source Control BMP's (SC-BMP's) have been taken into account. Refer to post-development hydrology calculations included in Section 3.2 of this report for detailed analysis of Basins A and B, as well as a post-development hydrology node map included in Appendix A 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 various LID design techniques and site design BMPs to optimize the site layout while mitigating for the proposed increase in impervious area. Runoff from proposed roofs and hardscape areas will be directed to landscaped areas and vegetated swales in an effort to disperse drainage to pervious surfaces. Partial infiltration and evapotranspiration in self-treating yard landscaped areas will assist in slowing runoff discharges and in reducing volume generated during storm events. Proposed swales will PLSA Job #2319 535 N. Hwy 101, Suite A Solana Beach, CA 92075 Page 3 of 9 remove sediment and particulate-bound pollutants from storm water and will assist in decreasing peak runoff velocities by increasing the site's overall time of concentration. 1.4 Conclusions Based upon the analysis included in this report, the proposed onsite increase in peak runoff as a result of the proposed development does not cause additional impacts to downstream properties or existing drainage facilities. The increase in runoff will be mitigated using site design measures outlined in the County of San Diego Model BMP Design Manual. Similar to the existing condition, the post-developed site will ultimately discharge directly into the curb and gutter system on Hemlock Avenue. Once in the gutter, drainage will be conveyed to an existing curb inlet located approximately 150 feet east of the project boundary, and will enter the buried pipe network. Water will not be diverted away from existing drainage patterns. The increase in proposed impervious area and resulting peak runoff will not have an adverse effect on the downstream watershed since it will be mitigated for onsite. The post-developed site will be exempt from hydromodification compliance requirements as it is not a priority development project. 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 "City of Carlsbad Standard Urban Storm Water Mitigation Plan " adopted January 14, 2011, City of Carlsbad, Engineering Department "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 PLSA Job #2319 535 N. Hwy 101, Suite A Solana Beach, CA 92075 Page 4 of 9 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 0645 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 Where: 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. PLSA Job #2319 I 535 N. Hwy 101, Suite Solana Beach, CA 92075 Page 5 of 9 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. PLSA Job #2319 535 N. Hwy 101, Suite A Solana Beach, CA 92075 Page 6 of 9 3.0 HYDROLOGY MODEL OUTPUT 3.1 Pre-Developed Hydrologic Model Output (100-Year Event) Pre-Development: Q=CIA P2=1.2 Pio1.7 Pioo=2.5 Basin 1 Total Area = 6,319 sf 4 0.145 Acres Impervious Area = 1,594 sf3 0.037 Acres Pervious Area = 4,725 sf 4 0.108 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 1,594 sf+ 0.25 x 4,725 sf= 0.41 6,319 sf Ic = 5.0 Mm (minimum for small areas) P6 = 2.5 I = 7.44 X P6 x D 05 I = 7.44 x 2.5 x 5.0 0.645 = 6.59 in/hr Iwo 6.59 in/hr I2 3.16 in/hr Iio 4.48 in/hr Q2 = 0.41 x 3.16 in/hr x 0.145 Ac = 0.19 cfs Qio = 0.41 x 4.48 in/hr x 0.145 Ac = 0.27 cfs Qioo = 0.41 x 6.59 in/hr x 0.145 Ac = 0.39 cfs PLSA Job #2319 535 N. Hwy 101, Suite A Solana Beach, CA 92075 Page 7 of 9 3.2 Post-Developed Hydrologic Model Output (100-Year Event) Post-Development (without considering LID treatment): Q=CIA P2=1.2 Pio=1.7 Pioo=2.5 Total Area = 6,319 sf4 0.145 Acres Impervious Area = 3,773 sf 4 0.086 Acres Pervious Area = 2,546 sf 4 0.059 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 3,773 sf+ 0.25 x 2,546 sf= 0.64 6,319 sf Ic =5.0 Mm (mm. for small areas) P6 = 2.5 I = 7.44 X P6 x D 05 I = 7.44 x 2.5 x 6.59 in/hr Iioo 6.59 in/hr I2 3.16 in/hr Iio 4.48 in/hr Basin A (House #1 - Runoff at Node 200.3) Q2 = 0.64 x 3.16 in/hr x 0.073 Ac = 0.15 cfs Qio = 0.64 x 4.48 in/hr x 0.073 Ac = 0.21 cfs Qioe = 0.64 x 6.59 in/hr x 0.073 Ac = 0.31 cfs *At discharge point 1 on Hemlock Avenue PLSA Job #2319 535 N. Hwy 101, Suite A Solana Beach, CA 92075 Page 8 of 9 Basin B (House #2 - Runoff at Node 300.3) Q2 = 0.64 x 3.16 in/hr x 0.073 Ac = 0.15 cfs Qio = 0.64 x 4.48 in/hr x 0.073 Ac = 0.21 cfs Qioo = 0.64 x 6.59 in/hr x 0.073 Ac = 0.31 cfs *At discharge point 2 on Hemlock Avenue Pre-Development vs. Post-Development (Total Runoff) Pre-Development Post-Development Delta Qioo = 0.4 cfs Qioo = 0.6 cfs 0.2 cfs 3.3 Pipe Analysis The project proposes private storm drain piping and catch basins onsite to remove water from the surface during storm events. The pipe analysis to appropriately size onsite storm drains was performed using Autodesk's Civil3D Hydraflow Extension software. The Hydraflow Extension software has the ability to calculate pipe capacity for open channel flow, assuming the pipe is completely full, for a given pipe size, material, roughness coefficient, and slope. The peak flow generated by the 100-year, 6-hour storm event for each onsite sub-drainage basin was calculated in section 3.2 of this report, and was determined to be 0.31 cfs at each discharge location. The onsite storm drain piping for this project i&76-inch PVC ipe sloped at a minimum of 1.0%. 3-inch PVC sidewalk under drains per SDRSD D-27 sloped at a minimum of 2.0% are also proposed at the point of discharge for each drainage basin. The Hydraflow Extension software was run for each of these scenarios to determine maximum capacity when the pipe is full. For 6-inch PVC sloped at 1.0%, the pipe capacity was determined to be 0.56 cfs, and for 3-inch PVC sloped at 2.0%, the pipe capacity was determined to be 0.13 cfs. Refer to the Appendix of this report for results of the Hydraflow Extension analysis performed for a 6-inch PVC pipe at 1.0% slope and a 3-inch PVC pipe at 2.0% slope. Based on the results of the Hydraflow Extension analysis, a 6-inch PVC drain pipe at a minimum slope of 1.0% is sufficient to route the post-development peak flow generated by the 100-year, 6-hour storm event. Two 3-inch PVC sidewalk under drain pipes are sized to discharge up to the 10-year storm event at each discharge location leaving the site. The site has been designed to maintain positive drainage from the southwest corner of each unit to each outlet location so that, in larger storm events, water will flow on the surface away from proposed structures toward Hemlock Avenue, bypassing the sidewalk under drain pipes. PLSA Job #2319 535 N. Hwy 101, Suite A Solana Beach, CA 92075 Page 9 of 9 4.0 APPENDIX PLSA Job #2319 535 N. Hwy 101, Suite A Solana Beach, CA 92075 kn%99 111111,0011hS INS 29111111111111111111111111 Jill 111111 EQUATION ______________________11111111 Intensity (in/hr) IIIIIII PIS 6-Hour Precipitation ________________________________ oil ___ ' Duration UUh'III il*i i uihIIh!lthuuI'huhL iIII1!IIi!!IIi h!IIIiI!!IIli monommmalzamn Nonni N.. IN!!IIIIIifl 111111II1 m1III4I!1llH!I1ImIm1ll !IIIIIIIllhII 1111111 IIIIIIIIIiii!!! 11111 jIii IllI ilillItH WUD •••uuiuuuuuuuuuu III P1111111111111111,09111111 Eb2qM .i..uuuuuuiuuuui UU•IUUIIIuuIIIIUI IllIllIllIlIllIll IIIIHIIIIIIIIIIIIIlI!!llhIIIIIIIIIIIII!!IIIIII!iIIiIII!!Uhi!!! 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Uul I 'ri1111 uuuuuuiiiiiiiitiiiiiiiimuuuuuuuuuuiu 111111111110 ...........I.IuI uuu,uuiiiliulililliiuUiilifluiiililiiiiililiiuUu•UiiiiliuiiluliHullllD ••uu•uuuuuiuiii Iu.luuulllllllulll,IIiuIuIuuuIIIIIIIIIuhIIIIil..u•u.l,..uonhlllullllll n Ucin rtrnn - iFnwamnim San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 6of26 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 (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77 0.78 0.79 Commercial/Industrial (N. Com) 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 San Diego County Hydrology Manual Date: June 2003 Section: 3 Page: 12 of 26 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 T1 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 Tj LM Ti LM TiLM TI LM Tj LM T Natural 50 13.2 70 12.5 85 10.9 100 10.3 100 8.7 100 6.9 LDR 1 1 50 12.2 1 70 11.5 85 10.0 100 9.5 100 8.0 100 6.4 LDR 2 50 11.3 70 10.5 85 9.2 100 8.8 100 7.4 100 5.8 LDR 2.9 50 10.7 70 10.0 85 8.8 95 8.1 100 7.0 100 5.6 MDR 4.3 50 1 10.2 701 9.6 80 8.1 95 7.8 100 6.7 100 5.3 MDR 7.3 50 9.2 65 8.4 80 1 7.4 95 1 7.0 1001 6.0 1001 4.8 MDR 10.9 50 8.7 65 7.9 80 6.9 90 6.4 1001 5.7 100 4.5 MDR 14.5 50 8.2 65 7.4 80 6.5 90 6.0 100 5.4 100 4.3 HDR 24 50 6.7 65 6.1 1 75 5.1 1 90 4.91 95 4.3 100 3.5 HDR 43 50 5.3 65 4.7 75 4.0 85 3.8 95 3.4 1 100 2.7 N. Corn 50 5.3 1 60 4.5 75 4.0 85 3.8 95 3.4 100 2.7 G. Com 50 4.7 60 4.1 75 3.6 85 3.4 90 2.9 100 2.4 O.P./Com 50 4.2 60 3.7 70 3.1 1 80 2.9 90 2.6 100 2.2 Limited I. 50 4.2 60 3.71 70 3.1 80 2.9 1 90 2.6 100 General 1. 50 3.7 60 3.2 70 2.7 80 2.6 90 2.3 100 t19 *See Table 3-1 for more detailed description 3-12 Hydrologic Soil Group—San Diego County Area, California 467760 467786 4678(XJ 467820 4c794( 407860 4F7Q 467920 467940 467960 167060 330 9 331N AL 5$Ad R R I * 6 6 4, 01*1 12 INIII Oil 331 56'N 331 8'56'N ' 0--k iu 401/80 /8bu 46, , 467980 8: Map Scale: 1:1,070if printed onA landscape (11"x8.5")sheet. 8: N 0 15 30 60 90 Feet ,\\ 0 50 100 200 300 Map projection: Web Memator Corner coordinates: WGS84 Edge tics: (JIM Zone 1 1 WG584 USDA Natural Resources Web Soil Survey 7/20/2015 Conservation Service National Cooperative Soil Survey Page 1 of 4 Hydrologic Soil Group—San Diego County Area, California Hydrologic Soil Group Hydrologic Soil Group— Summary by Map Unit - San Diego County Area, California (CA638) Map unit symbol Map unit name Rating Acres in AOl Percent of AOl MlC Marina loamy coarse B 3.8 100.0% sand, 2 to 9 percent slopes Totals for Area of Interest 3.8 100.0% 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 0) and three dual classes (ND, 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 Component Percent Cutoff: None Specified IJSD Natural Resources Web Soil Survey . 7/20/2015 Conservation Service National Cooperative Soil Survey . . Page 3 of 4 Hydrologic Soil Group—San Diego County Area, California Tie-break Rule: Higher USDA Natural Resources Web Soil Survey 7/20/2015 21111111111 Conservation Service National Cooperative Soil Survey Page 4 of 4 DE VEL OFMEN T HYDROLOGY AREA CALCULATIONS - - PROPERTY LINE / BASIN BOUNDARY EXISTING CONTOUR LINE ___________ • EXISTING FLOWLINE EXISTING DIRECTION OF FLOW 3806 GARFIELD STREET ONSITE IMPERVIOUS AREA 1,594 SF ONSITE PER'iIOUS AREA 4,725 SF Z ONSITE IMPERWOUS AREA 25.2% TC'62.9O / / / / / / / FS=62,9& / / FS3,2 IC63.48 FS53.31/ TC62.22 •••;K 1;::/T / 00 4 / I' H / C7 , I H. ,. ,.. TG/627 FS58,25 APN 204270-0500 TC83.27 TC3.10....... / / . / / /4 PRE-DEVELOPMENT NODE MAP I "-10' GRAPHIC SCALE 119 =10' - 10 0 10 20 30 & ASSOCIATES CIVIL ENGINEERING + LAND PLANNING + LAND SURVEYING 535 North Highway 101, Ste A, Solana Beach, CA 92075 ph 858.259.8212 1 ft 858.259.4812 1 plsaengineering.com TC$2.05 ' I \\ \, \HEMLOCK AVENUE NODE 200.3. / ' • £.'.# '. £. \ .5. TG=60.2 \ S IE=59.2 LEGEND POST DEVEL OPMENT HYDROLOGY AREA CALCULATIONS ONSITE IMPERVIOUS AREA 3,772 SF 38 06 GARFIELD STREE T ONSITE PERVIOUS AREA 2,547 SF ZONSITE IMPERVIOUS AREA 59.7% WEIGHTED RUNOFF COEFFICIENT (Cn) 0.64 - - PROPERTY LINE / BASIN BOUNDARY SUB BASIN BOUNDARY EXIS77NG CONTOUR LINE • PROPOSED FLOWLINE PROPOSED DIRECTION OF FLOW - — — — - RETAINING WALL o PROPOSED AREA DRAIN = = = = = PROPOSED PRIVATE STORM DRAIN 5/ , .rTC/1 1/ 51/ N - ,—NODE 300.3 I (FL=56.3) \ .7 Q100 = 0.31 CFTS TC55,$3 TC2.62. APN 204m2700.500 3? c.i I TC"63,27 .7, '/ //,'/ •j//! .7 // •' 1 '7 / 1/ ," / .1/. • ." " ,',' / POST-DEVELOPMENT NODE MAP 1 "=10' GRAPHIC SCALE 1"=1O' 10 0 10 20 30 PASCO LARET SUITER & ASSOCIATES CIVIL ENGINEERING + LAND PLANNING + LAND SURVEYING 535 North Highway 101, Ste A, Solana Beach, CA 92075 ph 858.259.8212 I ft 858.259.4812 I plsaengineering.com PLSA 2319 Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 31341) by Autodesk, Inc. 6-in PVC @1.0% Circular Highlighted Diameter (ft) = 0.50 Depth (ft) Q (cfs) Area (sqft) Invert Elev (ft) = 59.20 Velocity (ft/s) Slope (%) = 1.00 Wetted Perim (ft) N-Value = 0.013 Grit Depth, Yc (ft) Top Width (ft) Calculations EGL (ft) Compute by: Known Depth Known Depth (ft) = 0.50 Tuesday, Dec 29 2015 = 0.50 = 0.561 = 0.20 = 2.86 = 1.57 = 0.39 = 0.00 = 0.63 Elev (ft) Section 60.00 59.75 59.50 59.25 59.00 58.75 0 1 Reach (ft) 0 1. [4.1SIs 54.75 54.50 54.25 54.00 Channel Report Hydraflow Express Extension for Autodesl) AutoCAD® Civil 3D® by Autodesk, Inc. Tuesday, Jan 122016 3-in PVC Drain Pipe @ 2% (QIOO) Circular Highlighted Diameter (ft) = 0.25 Depth (if) = 0.25 Q(cfs) = 0.125 Area (sqif) = 0.05 Invert Elev (if) = 54.60 Velocity (if/s) = 2.54 Slope (%) = 2.00 Wetted Perim (if) = 0.79 N-Value = 0.013 Grit Depth, Yc (if) = 0.22 Top Width (if) = 0.00 Calculations EGL (if) = 0.35 Compute by: Known Depth Known Depth (if) = 0.25 Elev (if) ei.... Dr ....... ei...e ....e u;...........,1 4... .....;...e e... .......e.... ii..ee....i,...................0