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Home My WebLink AboutMS 2021-0002; JUNIPER BEACH HOMES; HYDROLOGY STUDY FOR GRADING PERMIT/PARCEL MAP, JUNIPER HOMES - 295 JUNIPER AVENUE; 2021-11-01 HYDROLOGY STUDY FOR GRADING PERMIT / PARCEL MAP JUNIPER HOMES - 295 JUNIPER AVENUE MS 2021-0002 / CDP 2021-0007 / PUD 2021-0002 / SDP 2021-0004 DWG 533-7A CITY OF CARLSBAD, CA PREPARED FOR: RREG INVESTMENTS SERIES, LLC SERIES I039 5315 AVENIDA ENCINAS, SUITE 200 CARLSBAD, CA 92008 PREPARED BY: PASCO LARET SUITER & ASSOCIATES, INC. 535 N. HIGHWAY 101, SUITE A SOLANA BEACH, CA 92075 PH: (858) 259-8212 Prepared: August 2021 Revised: November 2021 __________________________________________________ Bryan Knapp, PE #86542 DATE 11-12-21 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 Pre-Developed vs. Post-Developed Peak Flows (100-Year Event) 3.3 Detention Analysis 3.4 Appendix 4.0 Isopluvial Maps Intensity Duration Design Charts Runoff Coefficients Hydrologic Soil Group - USDA Web Soil Survey Pre-Development Hydrology Node Map Post-Development Hydrology Node Map PLSA 3459-01 Page 1 of 13 1.0 EXECUTIVE SUMMARY 1.1 Introduction This Hydrology Study for the proposed development at 295 Juniper Avenue, known as Juniper Homes, 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 100-year, 6-hour storm. 1.2 Existing Conditions The subject property is located along Juniper Avenue, northeast of the intersection of Juniper Avenue and Garfield Street, in the City of Carlsbad. The site is bound by a combination of existing single-family and multi-family developments to the west, south, and east, as well as Juniper Avenue, a public road, to the north. The existing site consists of a single-family residence, driveway, walkways, landscaping, open space consisting of mostly dirt, and miscellaneous improvements typical of this type of development. The project site is located in the Agua Hedionda Hydrologic Area, and, more specifically, the Los Monos Hydrologic Sub-Area (904.31) of the Carlsbad watershed. The subject property has an approximate area of 0.251 acres and is approximately 54% impervious in the existing condition. Per the Web Soil Survey application available through the United States Department of Agriculture, the basin is generally categorized to have type B hydrologic soils. Based on the existing impervious area and land use type, a pre-development weighted runoff coefficient of 0.60 was calculated for the subject property using the methodology described in section 3.1.2 of the San Diego County Hydrology Manual and the formula provided therein. The existing site can be categorized into one (1) major drainage basin, with one (1) primary discharge location leaving the property. Drainage basin EX-1 consists of the entirety of the project site and primarily drains from the southeast corner of the property to the northwest, discharging to the Juniper Avenue right-of-way by surface and sheet flow methods. Once in the Juniper Avenue right-of-way, runoff leaving the site travels northwest approximately 45 feet toward an existing storm drain inlet. The storm drain inlet is on the north side of Juniper Avenue, which is a superelevated road sloping to the north. Surface flow enters the storm drain inlet ultimately are conveyed south to outlet in the Agua Hedionda Lagoon prior to entering the Pacific Ocean. Using the Rational Method Procedure outlined in the San Diego County Hydrology Manual, a peak flow rate and time of concentration was calculated for the 100-year, 6- hour storm event for the onsite drainage basin. Table 1 below summarizes the results of the Rational Method calculations. PLSA 3459-01 Page 2 of 13 EXISTING DRAINAGE FLOWS DRAINAGE AREA DRAINAGE AREA (ACRES) Q100 (CFS) I100 (IN/HR) EX-1 0.251 1.00 6.59 Table 1. Existing Condition Peak Drainage Flow Rates 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. 1.3 Proposed Project The proposed project includes the demolition of all existing onsite improvements and the construction of four (4) new condominium units. The project proposes a driveway to provide vehicular access to the proposed garages consisting of pervious pavers. Two private onsite parking stalls interior to the site are also shown for site residents. There are two proposed pad elevations for the 4 proposed structures. The northern structures are to be built on a graded 56.9 pad elevation, and the southern structures are to be built on a graded 57.2 pad elevation. Site grading, drainage and utility improvements typical of this type of multi-family residential development will also be constructed as can be seen on the precise Grading Plan prepared by Pasco, Laret, Suiter & Associates under separate cover. The subject property is approximately 42% impervious in the proposed condition. Based on the proposed impervious area and land use type, a post-development weighted runoff coefficient of 0.52 was calculated for the subject property using the methodology described in section 3.1.2 of the San Diego County Hydrology Manual and the formula provided therein. The proposed site consists of one (1) major drainage basin, with one (1) primary discharge location from the southwest corner of the property similar to the existing condition. Drainage basin PR-1 consists of the entirety of the site and will continue to convey runoff generally from a high point in the southeast corner of the site to the Juniper Avenue right-of-way by means of surface flow and a storm drain conveyance system. Runoff from the northeast side yard will enter a trash capture BMP and will then be routed west to the inlet at the end of the concrete ribbon gutter. A concrete ribbon gutter located at the center of the pervious paver driveway will also serve to capture and convey drainage to the proposed trash capture BMP inlet and then will be routed the final trash capture BMP inlet in the northwest front yard. All runoff will leave the site through a modified D-25 sidewalk underdrain connected to the inlet in the northwest side yard. PLSA 3459-01 Page 3 of 13 Using the Rational Method Procedure outlined in the San Diego County Hydrology Manual, a peak flow rate and time of concentration were calculated for the 100-year, 6- hour storm event for the onsite drainage basin. Table 2 below summarizes the results of the Rational Method calculations in the post-developed condition. PROPOSED DRAINAGE FLOWS DRAINAGE AREA DRAINAGE AREA (ACRES) Q100 (CFS) I100 (IN/HR) PR-1 0.251 0.86 6.59 Table 2. Proposed Condition Peak Drainage Flow Rates Refer to post-development hydrology calculations included in Section 3.2 of this report for a 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 basin 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 new or removed and replaced hardscape areas will be directed to landscaped areas or pervious pavers to disperse drainage to pervious surfaces. The landscaped areas will assist to remove sediment and particulate-bound pollutants from storm water. In addition, the storage layers of the pervious pavers will help to mitigate peak runoff by providing detention volume as well as slightly increasing the site’s overall time of concentration. Refer to Section 3.4 of the report for a static detention analysis showing that the increase in overall volume generated by the slight increase in hardscape is accounted for in the gravel storage layer of the pervious pavers. 1.4 Conclusions Based upon the analysis included in this report, there is a decrease of ~0.14 cfs in peak runoff as a result of the proposed development due to the 1,339 square feet of decreased hardscape in the proposed condition as compared the existing site. Similar to the existing condition, the project will discharge to the northwest and onto the Juniper Avenue right- of-way. Thus, water will not be diverted away from existing drainage patterns, and the runoff produced by the proposed development will not have an adverse effect on the downstream watershed. Although there is no increase is storm water volume, the inherent detention characteristics and storage volume provided in the gravel layers of the pervious pavers will assist to detain and mitigate peak runoff to pre-project conditions. Additionally, the proposed project will be exempt from hydromodification compliance requirements as it does not qualify as a Priority Development Project as defined in the Regional Municipal Separate Storm Sewer System (MS4) Permit and the San Diego County Model BMP Design Manual. PLSA 3459-01 Page 4 of 13 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 September 2014, County of San Diego, Department of Public Works, Flood Control Section “City of Carlsbad Engineering Standards, Volume 5: Carlsbad BMP Design Manual (Post Construction Treatment BMPs)”, revised February 2016 “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 September 2, 2020 PLSA 3459-01 Page 5 of 13 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-0.645 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 3459-01 Page 6 of 13 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 for purposes of calculating rainfall intensity per the County of San Diego Hydrology Manual 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 in the Appendix of this report, categorizes the land use, the associated development density (dwelling units per acre) and the percentage of impervious area. For this study, a weighted runoff coefficient was used for both the pre-project and post- developed site in accordance with the equation provided in Section 3.1.2 of the County of San Diego Hydrology Manual. The weighted runoff coefficient is a function of the total impervious and pervious surface areas in the existing and proposed conditions. PLSA 3459-01 Page 7 of 13 3.0 HYDROLOGY MODEL OUTPUT 3.1 Pre-Developed Hydrologic Model Output (100-Year Event) Pre-Development: Q = CIA *Rational Method Equation P100 = 2.5 *100-Year, 6-Hour Rainfall Precipitation Basin EX-1 Total Area = 10,941 sf ➔ 0.251 Acres Impervious Area = 5,919 sf ➔ 0.136 Acres Pervious Area = 5,022 sf ➔ 0.115 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 5,919 sf + 0.25 x 5,022 sf = 0.60 10,941 sf Tc = 5.0 Min *Minimum Tc for Rainfall Intensity per SDHDM I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation I = 7.44 x 2.5 x 5.0-0.645 ≈ 6.59 in/hr Q100 = 0.60 x 6.59 in/hr x 0.251 Ac = 1.00 cfs PLSA 3459-01 Page 8 of 13 3.2 Post-Developed Hydrologic Model Output (100-Year Event) Post-Development (without considering HMP/BMP treatment): Q = CIA *Rational Method Equation P100 = 2.5 *100-Year, 6-Hour Rainfall Precipitation Basin PR-1 (Total Site) Total Area = 10,941 sf ➔ 0.251 Acres Impervious Area = 4,580 sf ➔ 0.105 Acres Pervious Area = 6,361 sf ➔ 0.146 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 4,580 sf + 0.25 x 6,361 sf = 0.52 10,941 sf Tc = 5.0 Min *Minimum Tc for Rainfall Intensity per SDHDM I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation I = 7.44 x 2.5 x 5.0-0.645 ≈ 6.59 in/hr Q100 = 0.52 x 6.59 in/hr x 0.251 Ac = 0.86 cfs PLSA 3459-01 Page 9 of 13 Basin PR-1.1 (Flow at NW corner outlet) Total area = 2,015 sf ➔ 0.046 Acres Tc = 5.0 Min *Minimum Tc for Rainfall Intensity per SDHDM I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation I = 7.44 x 2.5 x 5.0-0.645 ≈ 6.59 in/hr Q100 = 0.52 x 6.59 in/hr x 0.047 Ac = 0.2 cfs Basin PR-1.2 (Flow at NE corner outlet) Total area = 2,115 sf ➔ 0.049 Acres Tc = 5.0 Min *Minimum Tc for Rainfall Intensity per SDHDM I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation I = 7.44 x 2.5 x 5.0-0.645 ≈ 6.59 in/hr Q100 = 0.52 x 6.59 in/hr x 0.049 Ac = 0.2 cfs Basin PR-1.3 (Flow at NW outlet) Total area = 6,689 sf ➔ 0.154 Acres Tc = 5.0 Min *Minimum Tc for Rainfall Intensity per SDHDM I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation I = 7.44 x 2.5 x 5.0-0.645 ≈ 6.59 in/hr Q100 = 0.52 x 6.59 in/hr x 0.154 Ac = 0.5 cfs 3.2.1 Capacity Check for modified D-25 PVC Sidewalk Underdrain CD-25 = 1.10 cfs** *Capacity of 3” X 1’ drainage channel sloped at 2% QPR1.1 = 0.2 cfs *Peak flow from basin PR-1.1 QPR1.2 = 0.2 cfs *Peak flow from basin PR-1.2 QPR1.3 = 0.5 cfs *Peak flow from basin PR-1.2 PLSA 3459-01 Page 10 of 13 Capacity check for modified D-24 3” x 1’ drainage channel sloped at 2% onto Juniper Avenue for basins PR-1.1, PR-1.2, and PR-1.3. CD-25 - QPR1 - QPR2- QPR3 = 1.10 – 0.2 – 0.2 -0.5 = +0.2 cfs 3” X 1’ drainage channel sidewalk under drain pipes sloped at 2% will sufficiently handle the 100-year storm peak flow rates for PR-1.1 and PR-1.2 **See Appendix for capacity calculations for 3” X 1’ drainage channel sloped at 2% 3.3 Pre-Developed vs. Post-Developed Peak Flows (100-Year Event) Total Pre-Development (Total Discharge Leaving Site) Basin EX-1 Q100 = 1.00 cfs *Discharging from the site at the northwest corner to Juniper Avenue Total Q100 = 1.00 cfs Total Post-Development (Total Discharge Leaving Site) Basin PR-1 Q100 = 0.86 cfs *Discharging from the site at the northwest corner to Juniper Avenue Total Q100 = 0.86 cfs Pre-Development vs. Post-Development (Discharge Leaving Site): Pre-Development Post-Development Delta Q100 = 1.00 cfs Q100 = 0.86 cfs 0.14 cfs decrease 3.4 Detention Analysis The 100-year, 6-hour storm event detention analysis was performed in accordance with Chapter 6 of the San Diego County Hydrology Manual (SDCHM). The results of the analysis provide a static detention requirement by comparing the total volume produced by the 100-year, 6-hour storm in the existing and post-project conditions. The total PLSA 3459-01 Page 11 of 13 volume can be calculated after producing a hydrograph for each event (pre- and post- developed) with the results of the Rational Method analysis. Calculations and results of this analysis can be shown below. The proposed pervious pavement driveway provides mitigation of the 100-year, 6-hour storm event peak flow rate. Underneath the paver units and bedding layer is a 6-inch gravel storage layer that provides sufficient detention volume to offset the increase in total volume generated in the proposed condition due to the increase in overall hardscape. See sections 3.4.1 and 3.4.2 below for the results of these calculations. 3.4.1 Static (No Routing) Detention Calculation Pre-Development: 100-Year Event (Basin EX-1) Volume = C*P6*A *Equation 6-1 of SDCHM Volume = 0.60 * (2.5 in * 1 ft / 12 in) * (10,941 SF) = 1,368 CF Post-Development: 100-Year Event (Basin PR-1) Volume = C*P6*A *Equation 6-1 of SDCHM Volume = 0.52 * (2.5 in * 1 ft / 12 in) * (10,941 SF) = 1,185 CF Required Detention Volume = Total Post-Development – Total Pre-Development = Basin PR-1 – Basin EX-1 = 1,185 CF – 1,368 CF = -183 CF* *The proposed project produces less storm water volume that volume produced by the existing conditions. This is primarily due to the decrease in proposed impervious area and the implementation of pervious pavers. 3.4.2 Pervious Pavement Drive Aisle – Storage Detention Volume Provided = Driveway Area x 6” Gravel Layer x 40% Voids = 2,295 SF * (6 in * 1 ft / 12 in) * 0.40 = 459 CF PLSA 3459-01 Page 12 of 13 459 CF of storage in gravel layers under pervious paver driveway. **As stated previously, the potential storage of storm water is not required but provided in the site design, by pervious pavers, for improved runoff mitigation. PLSA 3459-01 Page 13 of 13 4.0 APPENDIX 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 TypeNRCS Elements County Elements % IMPER. A B C D Undisturbed Natural Terrain (Natural) Permanent Open Space 0* 0.200.250.300.35Low 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. Com) General Commercial 85 0.80 0.80 0.81 0.82 Commercial/Industrial (O.P. Com) 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 Hydrologic Soil Group—San Diego County Area, California Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/29/2021 Page 1 of 436680173668026366803536680443668053366806236680713668080366808936680173668026366803536680443668053366806236680713668080467866467875467884467893467902467911467920 467866 467875 467884 467893 467902 467911 467920 33° 9' 3'' N 117° 20' 40'' W33° 9' 3'' N117° 20' 38'' W33° 9' 1'' N 117° 20' 40'' W33° 9' 1'' N 117° 20' 38'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 11N WGS84 0 15 30 60 90 Feet 0 5 10 20 30 Meters Map Scale: 1:357 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI 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 15, May 27, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jan 24, 2020—Feb 12, 2020 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. Hydrologic Soil Group—San Diego County Area, California Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/29/2021 Page 2 of 4 Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI MlC Marina loamy coarse sand, 2 to 9 percent slopes B 0.3 100.0% Totals for Area of Interest 0.3 100.0% 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 (A/D, B/D, and C/D). 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 (A/D, B/D, 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 Hydrologic Soil Group—San Diego County Area, California Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/29/2021 Page 3 of 4 Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—San Diego County Area, California Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/29/2021 Page 4 of 4 XX EXISTING 1 STORY BUILDINGEXISTING 1 STORY BUILDING13"TD16"TC12"TDXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXOEOEOEOEOEOEOEOEOEOEOEOEOEOEOEOE OE OE OE OE OE OE OE OE OE OE OE OE OE OE OE OE OE OE OEOEOEOEOEOEOEE E E GW OEOEOEOEOEOEX X X X X X X XXXXXXXXXXXXXXXXX57575757575656 565655555555 545454EXISTING 1 STORY BUILDINGSSSSSSSSSSSSSSSSSSSSSSSCMU WALLCMU WALLASPHALTCONC.CONC.CONC.CONC.CONC.CONC.CONC.CONC.CONC.CONC.CONC.CONC.CONCRETE/PAVER COURTYARDBLOCK WALL 6' HIGH WOOD FENCE CAR PORT 6' HIGH WOOD FENCE6' HIGH WOOD FENCE 6' HIGH VINYL FENCECMU WALLBLOCK WALL 4' HIGH CHAIN LINK FENCE STORAGEDIRT/GRAVELPARKING53.7654.7254.9355.1153.8455.5455.6655.8055.9456.2956.1855.7556.0954.6256.8256.8056.2956.2356.7557.0657.2057.1354.3753.3953.3953.1953.1857.4257.4256.7756.3957.2957.3857.0957.2157.1357.0857.0157.5857.0857.0457.7356.8956.6654.5055.1455.8455.9955.8356.3955.4555.1556.0456.2556.4956.4856.6056.5555.0956.7457.0556.9053.5055.4155.4054.8955.6355.1155.0755.5255.2856.0955.7157.09TW=59.14TW=59.16TW=59.20TW=60.03TW=56.82TW=56.96TW=57.23TW=57.67TW=58.70TW=58.52TW=58.28TW=58.24TW=57.73TW=57.70TW=57.81TW=59.55FF=58.25FF=57.66FF=58.36FF=56.97RF=67.6RF=68.1XXXXWALL/SIDINGWALL/CORRUGATED METAL SIDING N 34°01'13" W 124.95' N 34°00'55" W 125.00'N 56°00'25" E87.54'N 55°58'43" E87.55'JUNIPER AVENODE EX-100 (57.6 EG) NODE EX-101(57.6 EG) Q100=1.00 CFS (57.5 EG)(56.9 FG) (55.6 FG) (55.4 EG) (57.0 TW) (56.5 TW@EG)(56.4 BW@EG) (57.25 TW)(57.1 TW@EG) (56.7 BW@EG) (57.0 EG) (57.1 EG) (57.5 EG) (57.4 EG) (57.3 EG) (57.2 EG) (57.1 EG) (56.1 EG) (56.1 EG) (55.5 EG) (54.4 EG) (54.1 EG) (55.2 EG) (55.7 EG) (56.4 EG) (53.6 FS) (54.3 FS) (55.6 FS) 30' 17' 13' BASIN EX-1 AREA = 10,941 SF (0.251 AC) Cn = 0.60 5 10 15 GRAPHIC SCALE 1" = 5' 05 LEGEND PROPERTY BOUNDARY CENTERLINE OF ROAD ADJACENT PROPERTY LINE PUBLIC RIGHT-OF-WAY BASIN BOUNDARY FLOW LINE IMPERVIOUS AREA EXISTING HYDROLOGY EXIHIBT 295 JUNIPER AVE CARLSBAD, CA 92008 BASIN EX-1 - AREA CALCULATIONS TOTAL SITE AREA 10,941 SF (0.251 AC) BASIN EX-1 TOTAL AREA 10,941 SF (0.251 AC) BASIN EX-1 IMPERVIOUS AREA 5,919 SF (0.136 AC)BASIN EX-1 PERVIOUS AREA 5,022 SF (0.115 AC) % IMPERVIOUS 54% Cn 0.60 TIME OF CONCENTRATION 5.0 MINUTES (PER SDCHM) Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Thursday, Mar 17 2022 <Name> Circular Diameter (ft) = 0.50 Invert Elev (ft) = 100.00 Slope (%) = 1.00 N-Value = 0.013 Calculations Compute by: Known Depth Known Depth (ft) = 0.50 Highlighted Depth (ft) = 0.50 Q (cfs) = 0.561 Area (sqft) = 0.20 Velocity (ft/s) = 2.86 Wetted Perim (ft) = 1.57 Crit Depth, Yc (ft) = 0.39 Top Width (ft) = 0.00 EGL (ft) = 0.63 0 1 Elev (ft)Section 99.75 100.00 100.25 100.50 100.75 101.00 Reach (ft) 6" PVC @ 1% Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Thursday, Mar 17 2022 <Name> Circular Diameter (ft) = 0.50 Invert Elev (ft) = 100.00 Slope (%) = 2.00 N-Value = 0.013 Calculations Compute by: Known Depth Known Depth (ft) = 0.50 Highlighted Depth (ft) = 0.50 Q (cfs) = 0.793 Area (sqft) = 0.20 Velocity (ft/s) = 4.04 Wetted Perim (ft) = 1.57 Crit Depth, Yc (ft) = 0.45 Top Width (ft) = 0.00 EGL (ft) = 0.75 0 1 Elev (ft)Section 99.75 100.00 100.25 100.50 100.75 101.00 Reach (ft) 6" PVC @ 2% Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Thursday, Mar 17 2022 <Name> Rectangular Bottom Width (ft) = 1.00 Total Depth (ft) = 0.25 Invert Elev (ft) = 100.00 Slope (%) = 2.00 N-Value = 0.015 Calculations Compute by: Known Depth Known Depth (ft) = 0.25 Highlighted Depth (ft) = 0.25 Q (cfs) = 1.060 Area (sqft) = 0.25 Velocity (ft/s) = 4.24 Wetted Perim (ft) = 1.50 Crit Depth, Yc (ft) = 0.25 Top Width (ft) = 1.00 EGL (ft) = 0.53 0 .25 .5 .75 1 1.25 1.5 Elev (ft)Depth (ft)Section 99.75 -0.25 100.00 0.00 100.25 0.25 100.50 0.50 100.75 0.75 101.00 1.00 Reach (ft) Modified D-25 capacity @ 2.0 %