The URL can be used to link to this page

Home My WebLink AboutMS 15-11; GARFIELD CUSTOM BEACH HOMES; HYDROLOGY STUDY; 2016-04-04I I I I I I I I I I I I HYDROLOGY STUDY FOR 3806 Garfield Street, Carlsbad, CA Grading Permit I Parcel Map PUD 15-17 / SDP 15-16 / MS 15-11 ICDP 15-34 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 RECEIVER APR 05 2016 LAND DEVELOPMENT ENGINEERING PASCO LARET SUITER & ASSOCIATES, INC. 535 N. HIGHWAY 101, SUITE A SOLANA BEACH, CA 92075 (858)259-8212 I I I I I I I Prepared: January 8, 2016 Revised: February 25, 2016 Revised: April 4, 2016 No. r0356 DATE PLSA Job #2319 535 NI. Hwy 101, SueA Solana Beaci, CA 92075 G. LAWSON, RCE 80356 I I I I I I I I I I I I I I I I I I I TABLE OF CONTENTS Executive Summary Introduction Existing Conditions Proposed Project Conclusions References Methodology Introduction County of San Diego Criteria Runoff Coefficient Determination Hydrology & Hydraulic Model Output Pre-Developed Hvcrologic Calculations (100-Year Event) Post-Developed Hydrologic Calculations (100-Year Event) Pipe Analysis Results and Discussion Appendix 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-Developmen: Hydrology Node Map 6-in PVC Pipe Capacity / Channel Report 3-in PVC Pipe Capacity / Channel Report SECTION 1.0 1.1 1.2 1.3 1.4 1.5 2.0 2.1 2.2 2.3 3.0 3.1 3.2 3.3 Mil PLSA Job #2319 535 N. Hwy 101, Suite A Solana Beach, CA 92075 Page 1 of 1.0 EXECUTIVE SUMMARY 1 1.1 Introduction I 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 I 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 1.2 Existing Conditions I 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 I 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 I Sub-Area (904.31). The existing site can be categorized into one drainage basin, and primarily drains from I 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 I 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 I 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 l 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 I 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) I 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 101, Suite A Solana Beach, CA 92075 I Page 2of9 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 I attempt to match the existing sloping terrain. In the resulting post-developed condition, runoff can be categorized into one drainage 1 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 I 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 I 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 I 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. 1 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 I 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 I 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 I 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 I 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 I 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 I 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 I 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 I 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 I Page 3of9 remove sediment and particulate-bound pollutants from storm water and will assist in I decreasing peak runoff velocities by increasing the site's overall time of concentration. 1.4 Conclusions 1 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 I 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 I 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 I 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. I 1.5 References "San Diego County Hydrology Manual ", revised June 2003, County of San Diego, I Department of Public Works, Flood Control Section. "San Diego County Hydraulic Design Manual", revised October 2012, County of San I Diego, Department of Public Works, Flood Control Section "City of Carlsbad Standard Urban Storm Water Mitigation Plan ", adopted January 14, I 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 I Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov. Accessed July 20, 2015 I I I PLSA Job #2319 535 N. Hwy 101, Suite A Solana Beach, CA 92075 I I I I I I 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, QCIA. 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 °645 Where: I 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 elemer of water that originates at the most remote point of the basin being analyzed to reach the I 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 (:ypically in cubic feet per second (cfs) but sometimes as gallons per minute (gpm)). The RM equation is as I follows: Q=CIA 1 "Where: I Q= flow (in cfs) C = runoff coefficient, ratio of rainfall that produces storm water runoff (runoff vs. infiltration/evaporation/absorption/etc) I I = average rainfall intensity for a duration equal to the Tc for th area, in inches per hour. I 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 I 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. I PLSA Job #2319 535 N. Hwy 101, Suite A 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. I I I 1 I PLSA Job #2319 535 N. Hwy 101, Suite A I Solana Beach, CA 92075 I I I I I I I I I I I I F 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 Pio=1.7 Pioo2.5 Basin 1 Total Area= 6,319 sf4 0.145 Acres Impervious Area = 1,594 sf4 0.037 Acres Pervious Area = 4,725 sf4 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 I impervious surface * Per SDHDM Section 3.1.2 Cn = 0.9 x 1,594 sf+ 0.25 x 4,725 sf= 0.41 6,319sf Tc = 5.0 Mm (minimum for small areas Po=2.5 I = 7.44 x P6 x I = 7.44 x 2.5 x 5.00645 z 6.59 in/hr boo 6.59 in/hr 12z 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 535N. 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 Pioo2.5 Total Area = 6,319 sf4 0.145 Acres Impervious Area = 3,773 sf4 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 Tc = 5.0 Mm (mm. for small areas P6 = 2.5 I = 7.44 x P6 x D 0645 I = 7.44 x 2.5 x 5.00645 z 6.59 in/hr liooz 6.59 in/hr 12z 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 Qioo = 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. H; 101, Suite A Solana Beach, CA 92075 I I I I I I I I I I I I I I I I I I I I Page 8 of 9 I Delta 0.2 cfs Pre-Development Qioo = 0.4 cfs Post-Development Qioo = 0.6 cfs 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 (Tolal Runoff) I 3.3 Pipe Analysis The project proposes private storm drain piping and c:at:h basins c--.site to remove water from the surface during storm events. The nipe analysis to apropriately size onsite storm drains was performed using Autodesk's Civil31) Hydraflow Extension software. The Hydraflow Extension software has the ability to calculate pipe capacity for ooen channel flow, assuming the pipe is completely full, for a given pipe size, material, roughness coefficient, and slope. The peak flow generated by the 1 GO-year, 6-hour storm event for each onsite sub-drainage basin was calcula:ed in section 3.2 of this report, and was determined to be 0.31 cfs at each discharge locatbn. The onsite storm drain piping for this project is 6-inch PVC pipe sbped at a minimum of 1.0%. 3-inch PVC sidewalk under drains per SDRSD D-27 sloped at a minimum of 2.09/o are also proposed at the point of discharge for each drainage basin. The Hydrafl.cw Extension software was run for each of these scenarios to de-.ermine 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.G%, 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-develco--nent peak flow generated by the 100-year, 6-hour storm event. Two 3-inch PVC sidewa1: 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 irom 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 Solana Beach, CA 92075 I I I L I I I Li L I I I I I - i I Page 9of9 4.0 APPENDIX I I LI I I I I I I LI I I I I I PLSA Job #2319 535 N. Hwy 101, Suite A Solana Beach, CA 92075 Rainfall Isopluvials 2 Riverside County - / —- 33'15'--I 0 315 33'301--- Orange County k County of San Diego Hydrology Manual 2 Year Rainfall Event - 6 Hours IsopIuvial (inches) CARLSBA // ;: U wrere4 I S --------------- - - - L I F- % ENCINITAS I _5 :--• 7 -' : -_ - SOLANA BEACH - — -.5- -0:l— ow4 --- -:--- •--• s 6 C)UNTY S 1 2 ---33°OO DEL MAR s — - :EiIr L / 00 E - AND ILC 2 N LA LE GROVE; ORONA SO IMPERIAL BEACH CIS, , 33°OO' 32°45' 32°30 0 Cs) N- S1GIS \ h 'a ( I I N THIS MAP IS PROVIDED WITHOUT WARRANTY OF ANY HIND, EITHER EXPRESS * OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE Copyright SanGIS WI Rights Resemed This products rniay contain information from the SANDAG Regional E Irrforimatiorr Systemwhich cannot be reproduced without the written permission of SANDAD This product Pray contain inforrrration which has been reproduced wrth permission granted by Thomas Brothers Maps S 3 0 3MiIes Rainfall Isopluvials 32°30 C If) a a ) C - Ca) CD 323O DOUN Ty w t ; 1 / L \\\\ I I ---I. 1< C>_a_\J H. ) \H oTcAuv** uvreu AN D)E L CAJ N r LAM SAN'- 3245 — LE GROVE - ORONA - ..J F ' SD ISTA , I - IMPERIAL BEACH x I c 32°45' 33°OO SOLANA BE Q DEL () If) a co 33'30' Orange County C C Riverside County \ I J f 7 N Y) County of San Diego Hydrology Manual 333O 33°15' ---- - - -------------- OCEAN J - 14 DIDO U -- CARLSBAD 10 Year Rainfall Event — 6 Hours IsopIuvial (inches) I W\V/ 1 W GIS S G IS THIS MAP IS PROVIDED WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS * OR IMPLIED, INCLIJDlNO, BUT NOT LIMITED TO. THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE Copyright SarrGIS WI Rights Reserved This products may contain information from the SANOAG Regional VV F Information System which cannot be reproduced without the written permission of SANDAG This product may contain nforrnabon which has been reproduced with permission granted by Thomas Brothers Maps S 3 0 3MiIes bLO o b b 0 Co 32°30 32030 330 0 co o - Orange ------------- IC) b IC) b 0 Ce) 33030r County of San Diego Hydrology Manual Rainfall Isopluvials 33°15 - -- -. 33015 ---------------- 100 Year Rainfall Event - 6 Hours IsopIuvial (inches) OCEANSIDE CAR LSBAD l• - - 33000 33°00 0 ENCINITAS SOLANA BEACH Q DEL MAR () I / GIS SaiGls HUS infl( rd! X T Ti-ItS MAPS PROVtDED WITHOUT WAPRANTY OF ANY KIND, EITHER EXPRESS * OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE Copyright SanGIS WI Rights ReServed, This products may contain information from the SANOAG Regional E Information System which cannot be reproduced without the written permission of SANDAG This product may contain information which has been reproduced erA permission granted by Thomas Brothers Maps S 3 0 3MiIes 3245 32°45 CIO === mm == == mm == - - == - - San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 6 of 26 Table 3-1 RUNOFF COEFFICIENTS FOR URBAN AREAS Land I Re Runoff Coefficient "C" Soil Type NRCS Elements County Elements % PAPER. A B C D Undisturbed Natural Terrain (Natural) Permanent Open Space 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 tvkdiuiii 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 Mcdium Density Residential (MDR) Residential, 10.9 DLJ/A or less 45 0.52 0.54 0.57 00 Medium Density Rsidcntial (MDR) Rsideiitial, 14.j DU/A or less 50 0.55 0.58 0.60 0.63 Fligh Density Residential (HDR) Residential, 240 DLJ/.A or less 65 0.66 0.67 0.69 0.71 High Density Residential (1IDR) Residential, 43.0 DU/A ui less 80 0.76 0.77 0.78 0.79 Commcrcial/Industuial (N. Corn) Neighborhood Coiiiiiieieial 80 0.76 0.77 0.78 0.79 Comrnei'cial/lndusli idi (C Corn) G-11t9 HI Commercial 85 0.80 0.80 0.81 0.82 Commercial/Industrial (QJ.Com) Office Professional/Commercial 90 0.83 0.84 094 085 Commercial/Industrial (Limited 1.) 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 I I I I I I I I I I I I I I I I I I I San Diego County Hydrology Manual Section: 3 Date: June 2003 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 Tj 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 L 1 T1 LM TiLM Ti LM Ti LM T 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 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 10.2 70 9.6 80 8.1 95 7.8 100 6.7 100 5.3 MDR 7.3 50 9.2 65 8.4 80 7.4 95 7.0 100 6.0 100 4.8 MDR 10.9 50 8.7 65 7.9 80 6.9 90 6.4 100 5.7 100 4.5 MDR 14.5 50 1 8.2 65 1 7.4 80 1 6.5 90 1 6.0 100 1 5.4 100 1 4.3 HDR 24 50 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 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 75 3.6 85 3.4 90 2.9 100 2.4 O.P./Corn 1 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 1 100 2.2 Limited I. 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 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 17 77(i) 467780 46768 417820 4678417 ( 7(11 487q6 487870 467940 417711717 41773817 ('N T'1iJ 39 VO 'NO 18 '4 I 17 , ; : .AM W. Ilk I - . "- LJ@ _ 33 56'N 3 3 33 7 Sb N 4(7717) 4(7/80 467803 467820 467840 46/860 467980 467030 1' 467940 467960 467980 74 74 Ma)) S(ale: 1: 1,070 if printed on A landscape (11 x 85) sheet. Meters N 0 15 30 60 90 Feet 0 50 100 200 300 Ma)) projection: Web Mertator Corner coordinat: WGS84 Edge tics: UTM Zone uN WGS84 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 MAP LEGEND MAP INFORMATION E3 C J3 C/D 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 Area of Interest (AOl) Area of Interest (AOl) Soils Soil Rating Polygons AID BID EIIC C/D Not rated or not available Soil Rating Lines , A — AID ..- B BID -- C -- CID ,.- D - Not rated or not available Soil Rating Points 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. http //websoilsurvey nrcs.usda.gov 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 8, Sep 17, 2014 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. tl)A Natural Resources Web Soil Survey 7/20/2015 ilam Conservation Service National Cooperative Soil Survey Page 2 of 4 Hydrologic Soil Group—San Diego County Area, California I Hydrologic Soil Group Hydrologic Soil Group— Summary by Map Unit - San Diegc County Area, California (CA638) Map unit symbol Map unit name Rating Acres in AOl Percent of AOl MIC Marina loamy coarse sand, 2 to 9 percent B slopes 3.8 100.0% 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 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 Ihave 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 (ND, 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 Component Percent Cutoff: None Specified USDA Natural Resources Web Soil Survey 7/20/2015 Conservation Service National Cooperative Soil SL:rvey Page 3 of 4 I Hydrologic Soil Group—San Diego County Area, California I Tie-break Rule: Higher I - I I I I I I I I I I I I 1 I I USDA Natural Resources 21111111111111 Conservation Service I We: So-1 Euriey 7/20/2015 National Cooperat ie So -I Suria', Page 4 of 4 LEGEND AREA l'o",LCULATIONS - - PROPERTY LINE / BASIN BOUNDARY SUB BASIN BOUNDARY EXISTING CONTOUR LINE ____________ • PROPOSED FLOWLINE PROPOSED DIREC17ON OF FLOW — RETAINING WALL o PROPOSED AREA DRAIN = = = = = PROPOSED PRIVATE STORM DRAIN mmq:jA 0 -1111 _ ONSITE IMPERVIOUS AREA 3,772 SF ONSITE PER V1OUS AREA 2,547 SF Z ONSITE IMPERViOUS AREA 59.77. WEIGHTED RUNOFF COEFFICIENT (Cn) 0.64 F53 11 / FS62.9 / - Fse328 TC3$41 / 1062Q5 / ç \•\ \ HEMLOCK A VENUE 7 K N N FS56,5 I N N N / N I / N \ N. / - NflflF 21Y) 9— / / I FS55,13 / FS.5 :' • - rNODE 300.3 \ / (FL=56.3) \ 0100 = 0.31 CFS NODE 200.3 TG=60.2 \ ' / IE=59.2 \ / / FC..5,23 1063.48 /FS63.31/ / / / / TCS26g / -TC57.01 NODE 300.2. .. TG=57.4 IE5.4z .......................... 7 ._----FS5$,03 / 77 - 7 / //•./ 'TC=62. 7 AFN 204270-05---80 FS63.2, TC56.27 FS5$.25 GS56.87 / •1 •./ / / I / / / ,.- / / / / 7 / / FS6.38 TC63.27 TC63. 10 / / A / A ./•//// ///////,/ ///// t'// //// / /// ./ POST—DEVELOPMENT NODE MAP 1 "=10' GRAPHIC SCALE 1"=lO' 1-7771 - 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 1 ft 858.259.4812 1 plsaengineering.com I TC5348 TC6$74 -- LEGEND CA AREA LCULATIONS mp - — — I £J :: ftTAvJF L'A j; J •iij} Y-1II I . -- Z1II ONSITE IMPERVIOUS AREA 1,594 SF ONSITE PERVIOUS AREA 4,725 SF Z ONSITE IMPERViOUS AREA 25.2% — — PROPERTY LINE / BASIN BOUNDARY EXISTING CONTOUR LINE 'lu . • EXISTING FLOWLINE EXISTING DIRECTiON OF FLOW / T;"'=56,411 'S / S.-... ..............................................5-.........................................................................-5S. ............................................ .- / 1 TC62<05 FSS ss 13 / F&-539 HEMLOCK AVENUE ___ \\ VnI N / FS-0068 0 C6 6 // 1 T686 / / 2 TCC511 / -60 95 I I - C ' N S.- - - - _ - * ---- ..-............ -/ . ...........l....I.1 ... ........I.l..i......l --..-.---- - ___ _____ AI G m58,96 4 05-63 a- v.- NODE 100.2 -' GS6 71 '758 94 05-57 34 (FG=58 7) /01 --------------- / 5 V -. 5 * * 4.......-.- / / / ------------- , FS6 03 ,' / / / / GS55 82 'I /,.A '/! // ' \ / H sh1 S-63 V........FS56,25 APN2O4-27OQ$OO --------W I 62 TZ4 ion NODE 1001 ... 856'oo'oB'w ... 12593' / (FG-63.5) / GS62.84 •--- --.- GS6 4 ., $3 GS58 76 L \ 7 7 7 'I - r-3Q.o FS-x56,38 TC63,27 TC63, 10.... PRE-'DEVELOPMENT NODE MAP 1 "=10' GRAPHIC SCALE 111=10' 1C= 7771 10 0 10 20 30 PASCO LARET SUITER 1 & 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 ..--..-------.----.--------.-------.. ...................-.----.—.------.. ....--------..---------.--.---.-.. ..................................... .. -.. - --- .... -..7.-.----. . ..__...____.._...._. .: ..... i --'---- ______________— ...___________________- ... .:• . __ .. _________ .._....._________________ .-. ..-.----_._____.___.__...__.__.._.____..___ .. --------... ... r------------------ 0 1 1 Channel Report I Hydraflow Express Extension for Autodesk® AutoCAD® Civi 3D® by Autodesk, Inc. Tuesday, Dec 292015 6-in PVC @1.O% I Circular Highlighted Diameter (ft) = 0.50 Depth (ft) = 0.50 I Q (cfs) = 0.561 Area (sqft) = 0.20 Invert Elev (ft) = 59.20 Velocity (ft/s) = 2.86 I Slope (%) = 1.00 Wetted Perim (ft) = 1.57 N-Value = 0.013 Crit Depth, Yc (ft) = 0.39 Top Width (ft) = 0.00 EGL(ft) = 0.63 Known Depth = 0.50 I Calculations Compute by: Known Depth (ft) Elev (ft) I 1 60.00 I 59.75 I 1 59.50 I 1 59.25 I 59.00 I I 58.75 I Section Reach (ft) I Channel Report I Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Tuesday, Jan 12 2016 3-in PVC Drain Pipe @ 2% (QIOO) I Circular Highlighted Diameter (if) = 0.25 Depth (ft) = 0.25 I Q(cfs) = 0.125 Area (sqif) = 0.05 Invert Elev (if) = 54.60 Velocity (ft/s) = 2.54 I Slope (%) = 2.00 Wetted Perim (if) = 0.79 N-Value = 0.013 Crit Depth, Yc (if) = 0.22 Top Width (if) = 0.00 I Calculations EGL (if) = 0.35 Compute by: Known Depth Known Depth (if) = 0.25 I Elev (if) I 55.00- 54.75 - IIIIIIIIIIIII I 54.50- 1 I 54.25- I I 54.00 0 1 1 '.1.-.. -.1..--1 -.... OnC7;....., 41-..-4 .-.-.4 I 4.. .......,4 1.... - (I1.4... ...... -.,...\