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Home My WebLink AboutCDP 2020-0007; TERRA BELLA DEVELOPMENT; PRELIMINARY DRAINAGE STUDY; 2021-02-01PRELIMINARY DRAINAGE REPORT AND STORM WATER STANDARD PROJECT REQUIREMENTS For 6479 Surfside Lane Carlsbad, CA 92011 APN 214-021-11 December, 2020 Revised: February, 2021 Mel Landy, PE PREPARED BY: Jose Sanchez, PE HOWES I WElLER I LANDY PLANNING & ENGINEERING REcrrT MAR 2G 2021 LAND DEVEWr %4 -NT ENGE 2888 LOKER AVENUE EAST, SUITE 217 CARLSBAD, CA 92010 (760) 929-2288 I TABLE OF CONTENTS I Introduction .2 Project Vicinity Map......................................................................2 Existing Drainage Conditions..........................................................3 I Proposed Drainage Conditions........................................................3 Methodology...............................................................................3-6 Drainage Summary ......................................................................6-7 I Storm Water Quality Summary.........................................................7 Conclusions.................................................................................7 References..................................................................................8 I Appendix I i Existing Conditions Calculations - Basin Map 2 Developed Conditions Calculations & Hydraulic Calculations - Basin Map 1 3 Storm Water Standard Project Requirements 4 Maps and Charts, Weighted Runoff Coefficient Calc. I I I] I I I I Page I 1 of 20 DRAINAGE REPORT 1 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I I Introduction I I This Drainage Study for the proposed single-family detached development located at 6479 Surfside Lane, in the city of Carlsbad, APN 214-021-11 has been prepared to analyze the hydrologic and hydraulic characteristics of the existing and proposed project site. This I 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. In addition, this I report will propose the sizing of all necessary storm drain facilities and storm drain piping to safely convey the runoff, based on the 100-year rainfall event, per County of San Diego Hydrology and Storm Drain Design Standards. I PROJECT VICINITY MAP Page 12 of 20 DRAINAGE REPORT 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I I I I I IT I I I I I Existing Drainage Conditions Project site is located approximately 300 feet south west of Island Way and Surfside Lane, on the west side of Surfside Lane. The project side consist of a previously graded pad, which has been graded to surface sheet flow in a westerly direction towards Surfside Lane, where flows enter street flows before being conveyed via gutter in a southerly direction to an existing curb inlet located approximately 55 feet south of the south easterly property corner. Proposed Drainage Conditions The project proposes to create a single-family residence, with new impervious surfaces which consist of rooftop, hardscape and access driveway, along with landscape areas. Since project site has previously been pad graded, no alterations to the project site will be perform. Project site will continue to flow in a easterly direction, towards Surfside Lane. Two 3" storm drain pipes located on the north and south side of the property will collect roof flows and convey them to Surfside Lane via curb under drain, where flows will discharge as surface flows within the existing street gutter, after which they will continue as surface flows via gutter in a southerly direction to an existing curb inlet located approximately 55 feet south of the south easterly property corner. Study Methodology The method of analysis was based on the Rational Method according to the San Diego. Runoff calculations for this study were accomplished by using the Rational Method. The Rational Method is a physically-based numerical method where runoff is assumed to be directly proportional to rainfall and area, less losses for infiltration and depression storage. Flows were computed based on the Rational formula: Q=CIA Where Q = Peak discharge (cfs); C = runoff coefficient, based on land use and soil type = rainfall intensity (in/hr) A = watershed area (acre) (1) Runoff Coefficient, C Table 4-1 lists the estimated coefficients for urban areas. ri Table 4-1 Page 1 3 of 20 DRAINAGE REPORT I 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I I I I I r i Li I I 1 I I I 1 I I El RUNOFF COFflCWNT (%) Hvdro1Dgk SofiTs LND USE (CoinThEiernents) hapelT. A B C D Print open sp-we 020 0.25 030 035 RithI, 1.0'])LJfAcr1s 10 0.27 0.32 036 0.41 :idiI, 20DUA, less 20 0.34 03 ov 04 Rii4 2.9 DIJIA 2.5 '0.3 0.41 0.45 0.49 Resi&zdA 4.3 DUIA,ar Ims 30 0.41 0.45 DAB 052 Ridb47.3DUiAorless 40 10-4 0.51 0.54 057 :Rii1iI, 109DUfAor less . 45 '052 054 057 0.60 RidaI, 145 DUFA or less, 50 055 05 0.60 0.63 :RidrtiI. 24.0 DUA or less 65 '0.66 0.87 0.69 0.71 RidiiI,, 43.0' DUJA or less 0 '0.76 0.77 0.7 0.79 Neboth.odConintiaL 80 016 0.77 0.75 0.79 Cmmff all Cnr11 55 'ORI 020 021 022 OceProfio1fCarncia1 90 0.83 024 024 025 United 1ndushial 90 '023 024 0.84 0.85 Gieia1 ]EihizthaJ 95 '027 0.87 027 027 The runoff coefficient C for this site is calculated as follows pursuant to section 3.1.2 of the County Hydrology Manual. The runoff coefficient (C) represents the ratio of rainfall that runs off the watershed versus the portion that infiltrates to the soil. The runoff coefficient is dependent on the land use coverage and soil type (Table 4-1). Adjustment have been made to accurately represent the existing compacted rough graded condition. See appendix 3, for runoff coefficient calculations, which were prepared based on soil type and impervious percentage using the formula by the San Diego County Hydrology Manual C = 0.90 x (% Impervious) + Cp x (1 - % Impervious) Where: Cp = Pervious Coefficient Runoff Value for the soil type (shown in Table 3-1 as Undisturbed Natural Terrain/Permanent Open Space, 0% Impervious). Soil type can be determined from the soil type map provided in Appendix 4 of the San Diego County Hydrology Manual. (2) Rainfall Intensity, I Average rainfall intensity for a duration equal to the Tc for the area, in inches per hour. The storm frequency for this study has a 100-year recurrence interval. The six-hour anticipated precipitation for the project site subject to the design storm frequency. I Page 1 4 of 20 DRAINAGE REPORT I 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I I I El I I I I I I 1 I I I P24 = 4.25 in P6 is in the range of 45% to 65% of P24 and therefore doesn't need to be adjusted. The RM equation assumes that the storm event being analyzed delivers precipitation to the entire basin uniformly, and therefore the peak discharge rate will occur when a raindrop falls at the most remote portion of the basin arrives at the point of analysis. The RM also 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. (1) Time of Concentration, Tc The time of concentration is the time required for runoff to flow from the most remote part of the watershed to the outlet point under consideration. The time of concentration for each sub-area on site, Tc is determined from the following formula (San Diego County Hydrology Manual, dated June 2003) with the initial lengths and times adjusted per Table 3-2 of the Manual for slope and land use. 1 = 1.8(1.1—C)J (For overland time of flow) vs— Where, = Time of Concentration (hours) D = Watercourse Distance (ft) S= Slope (%) C = Runoff Coefficient .O35 (119L' =1 (For natural watersheds) I Where, = Time of Concentration in hours (hours) I L = Watercourse Distance (miles) AE= Change in elevation along effective slope line (It) ' The average rainfall intensity is calculated from the following equation (San Diego County Hydrology Manual, June 2003) 1= 7.44xP xD ° 645 I Where, I = Rainfall Intensity (in/hr) I P = Six hour precipitation (inches) D= Duration (min) There is an illustration of this formula in Figure 2, which is per County 2003 Hydrology ' Manual. Time of concentration (Tc) is composed of two components: The initial time of concentration (Ti), and the travel time (Tt). Page 1 5 of 20 DRAINAGE REPORT 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I I I I I I I I I I U I The maximum overland flow length (LM ) is used from Table 4 in calculating the initial time I of concentration. The source for this chart is the San Diego County Hydrology Manual (Table 3.2), June 2003. Table 4-Maximum Overland Flow Length (L) & Initial Time of Concentration(Ti) Element nu/ Acre 0.50% 10/b 2% 3% 5% 10% LM I Ti LM Tj LM T1 LM T1 LM TL FNatura1 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 7.41100 5:8 LDR 2.9 50 103.0 70 10.0 85 8.8 95 8.1 100 7.0 tOO 5.6 1v.DR 4.3 50 10.2 70 9.6 80 8.1 95 7.8 100 6.7 10015.3 MDR 7350 92 65 84 80 74 95 70 1006010048 JNDR 10.9 50 8.7 65 7.9 80 6.9 90 6.4 100 5.7 100 4.5 MDR 14.5 .50 8.2 65 7.4 80 6.5 90 6.0 1100 5.41100 4.3 BDR 1 24150 1 6.7 1651 6.1175 15.11 90 1 4.914.3 too iII 431 -50 1 5.3 165j4.7 1 751 4.0 1 85 13.8 195 13.4 100 12:7 }N.. Corn. 1 1.50 1 5.3 1 60 1 4.S 17S 1 4.0 1 85 1.3.8 1 95 13.4110012.7 1G. Corn. 1 150 1 4.7 160141175 13.6 195 13.4 190 12.91 t001 2.4 lO.P./Cotn. 150 141.0 16013.7 170 13.1180 12.9 190 12.61 t001 2.2 [L='t'd 1. 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 tOO 2.2 GeneráiI 50 3.7 60 13.2 1 70 2.7 80 1 2.6 90 12.31100 1.9 In addition to the above Ration Method assumptions, the conservative assumption that all runoff coefficients utilized for this report are based on Type "B" The County of San Diego Rational Method program within CivilDesign was utilized in calculating runoff for all basins smaller than 0.5 square miles in size. I Drainage Summary Upon performing hydrologic analysis of the project site in both the proposed developed I and existing condition, the following results were produced: Table I - Summary of existinq conditions BASIN I Node Effective C Tc (mm.) I inlhr Area (ac) Total Qpeak (cfs) Total Al 15 0.25 12.83 3.59 0.106 0.10 Total -- -- -- 0.106 0.10 Page 1 6 of 20 DRAINAGE REPORT I 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I I I I 1 I I 1 I I Table 2 - Summary of develoøed conditions BASIN I Node Effective C Tc (mm.) I in/hr Area (ac) Total Qpeak (cfs) ii Total A/15 0.58 8.13 4.82 0.106 0.30 TOTAL -- -- -- 0.106 0.30 As shown on tables above, there will be an increase in a 100-year storm event in the proposed condition of 0.20 CFS. Such minor increase will not have a detrimental effect on the underground storm drain system located downstream. Storm water Quality Summary This project has been determined to be a "Standard Project" per the City of Carlsbad Storm Water Standards Questionnaire (E-34) and is therefore exempt from priority project requirements. The development proposes to reduce the discharge of pollutants offsite by utilizing source control and Site Design Low Impact Development (LID) BMP's to the maximum extent possible. The project proposed landscaping and ground cover along the perimeter of the property. Roof downspouts will disperse flows within grassy swales located at the north and south property line. The grassy swales will be integrated with the landscape design to provide treatment to storm water runoff generated on-site before discharging runoff in a control manner via curb outlets at the predevelopment discharge point. Conclusions The proposed storm drain system was designed in accordance with the guidelines set by the County of San Diego. During the design of the proposed drainage systems precautions were taken to limit adverse downstream affects and to maintain existing drainage characteristics wherever possible. A summary of the facts and findings associated with this project and the measures addressed by this report is as follows: The project will not significantly alter drainage patterns on the site. The ultimate discharge points will not be changed. Graded areas and slopes will be landscaped to reduce or eliminate sediment discharge. The storm drain system for the project is designed to route and convey all resulting runoff from developed conditions to the existing points of discharge. I Page 1 7 of 20 DRAINAGE REPORT I 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I I I I I LI I LI ri Ll Li I I I Li I 1 I References "San Diego County Hydrology Manual", revised June 2003, County of San Diego, I Department of Public Works, Flood Control Section. "California Regional Water Quality Control Board Order No. 2001-07," California Regional I Water Control Board, San Diego Region (SDRWQCB). "City of Carlsbad BMP Design Manual" February 2016, Edition I I 1 I I 11 1 1 I I Page 8of2O DRAINAGE REPORT 1 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 Email. info@HWL-PE.COM 1 I APPENDIX 1 i Existing Conditions Calculations & Drainage Map I I I I I I 1 I 1 1 I Page I9of2O DRAINAGE REPORT 1 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. irifo@HWL-PE.COM I — — — — — — — — MMM mow a. — a. a. a. a. San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software, (c)1991-2018 Version 9.0 Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 02/28/20 ------------------------------------------------------------------------ 6479 Surfside Lane Pre-Development Condition 100-YR Storm Event ------------------------------------------------------------------------ ********* Hydrology Study Control Information ********** ------------------------------------------------------------------------ Program License Serial Number 6446 ------------------------------------------------------------------------ Rational hydrology study storm event year is 100.0 English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 2.500 24 hour precipitation(inches) = 4.250 P6/P24 = 58.8% San Diego hydrology manual IC! values used ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.000 to Point/Station 10.000 INITIAL AREA EVALUATION kk Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [UNDISTURBED NATURAL TERRAIN (Permanent Open Space Impervious value, Ai = 0.000 Sub-Area C Value = 0.250 Initial subarea total flow distance = 50.000 (Ft.) Highest elevation = 69.000(Ft.) Lowest elevation = 68.700(Ft.) Elevation difference = 0.300(Ft.) Slope = 0.600 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 50.00 (Ft) for the top area slope value of 0.60 %, in a development type of Permanent Open Space In Accordance With Figure 3-3 Initial Area Time of Concentration = 12.83 minutes TC = [1.8*(1.1_C)*distance(Ft.)'.5)/(% s1ope'(1/3)J TC = [1.8*(1.1_0.2500)*( 50.000".5)/( 0.600"(1/3)1= 12.83 Rainfall intensity (I) = 3.587(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.250 Subarea runoff = 0.040(CFS) Total initial stream area = 0.045(Ac.) I Page 1 10 of20 DRAINAGE REPORT 1 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I I I I I I I I I I I 1 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 10.000 to Point/Station 15.000 **** SUBAREA FLOW ADDITION **** Rainfall intensity (I) = 3.587(In/Hr) for a 100.0 year storm User specified 'C' value of 0.250 given for subarea Time of concentration = 12.83 mm. Rainfall intensity = 3.587(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.250 CA = 0.026 Subarea runoff = 0.055(CFS) for 0.061(Ac.) Total runoff = 0.095(CFS) Total area = 0.106(Ac.) End of computations, total study area = 0.106 (Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++,++++++++++++++++++++++ Process from Point/Station 15.000 to Point/Station 15.000 CONFLUENCE OF MINOR STREAMS Along Main Stream number: 1 in normal stream number 1 Stream flow area = 0.106(Ac.) Runoff from this stream = 0.095(CFS) Time of concentration = 12.83 mm. Rainfall intensity = 3.587(In/Hr) Summary of stream data: I I I I I I I I Stream Flow rate TC No. (CFS) (mm) 1 0.095 12.83 Qmax(l) = 1.000 * 1.000 * Rainfall Intensity (In/Hr) 3.587 0.095) + = 0.095 I I I I I 7 Total of 1 streams to confluence: Flow rates before confluence point: 0.095 Maximum flow rates at confluence using above data: 0.095 Area of streams before confluence: 0.106 Results of confluence: Total flow rate = 0.095(CFS) Time of concentration = 12.827 mm. Effective stream area after confluence = 0.106(Ac.) End of computations, total study area = 0.106 (Ac.) I I I Li Page Iii of20 DRAINAGE REPORT 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I APPENDIX 2 I Developed Conditions Calculations, Hydraulic Calculations & Drainage Map I Ell I I I I I I F F F F I I Page 112 of 20 DRAINAGE REPORT 6479 Surfside Lane www.HWL-PECOM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I - - - - - - - - - - - - - - - - - - - LEGEND iiA1 SYMBOL BASIN BOUNDARY SUBBA S/N BOUNDARY — — — — DRAINAGE DIRECT/ON BASIN DRAINAGE DESCRIPTION ACRES NODE 62 FL Qioo=O.30cfs SCALE: 10 5 0 10 20 30 SURFSIDE LANE WUON 6479 POST-DEVELOPMENT CONDITION DRAINAGE EXHIBIT HOWES I WEILER I LANDY PLANNING & ENGINEERING TO. 760 929 2288 Fax. 760 929 2287 DATE: I DRAVtING: I 2889 LOKER AVENUE EAST SUITE 217 CIJILSBAD,CA92010 2/28/20 1 SHEET 1 OF 1 APN: 214-021-04 BASIN A.2 SO "ACRES CFS i8 0 BASIN A. I 0.045 \ / IOIL APN: 214-021-12 I I I I San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software, (c)1991-2018 Version 9.0 Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 02/28/20 ------------------------------------------------------------------------ 6479 Surfside Lane Post-Development Condition 100-Year Storm Event ------------------------------------------------------------------------ ********* Hydrology Study Control Information ------------------------------------------------------------------------ Program License Serial Number 6446 ------------------------------------------------------------------------ Rational hydrology study storm event year is 100.0 English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 2.500 24 hour precipitation(inches) = 4.250 P6/P24 = 58.8% San Diego hydrology manual 'C' values used ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.000 to Point/Station 10.000 INITIAL AREA EVALUATION Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [MEDIUM DENSITY RESIDENTIAL I (10.9 DU/A or Less Impervious value, Ai = 0.450 Sub-Area C Value = 0.540 Initial subarea total flow distance = 50.000(Ft.) Highest elevation = 69.000(Ft.) Lowest elevation = 68.500(Ft.) Elevation difference = 0.500(Ft.) Slope = 1.000 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 65.00 (Ft) for the top area slope value of 1.00 %, in a development type of 10.9 DU/A or Less In Accordance With Figure 3-3 Initial Area Time of Concentration = 8.13 minutes TC = [1.8*(1.1_C)*distance(Ft.).5)/(% slope"(1/3)] TC= [1.8*(1.1_0.5400)*( 65.000".5)/( 1.000"(1/3)1= 8.13 Page 113 of 20 DRAINAGE REPORT I 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. irifo@HWL-PE.COM I I I I I Li I I I I I Li 1 I Rainfall intensity (I) = 4.815(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.540 Subarea runoff = 0.117(CFS) Total initial stream area = 0.045(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 10.000 to Point/Station 15.000 SUBAREA FLOW ADDITION **** Rainfall intensity (I) = 4.815(In/Hr) for a 100.0 year storm User specified 'C' value of 0.610 given for subarea Time of concentration = 8.13 mm. Rainfall intensity = 4.815(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.580 CA = 0.062 Subarea runoff = 0.179(CFS) for 0.061(Ac.) Total runoff = 0.296(CFS) Total area = 0.106(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 15.000 to Point/Station 15.000 CONFLUENCE OF MINOR STREAMS Along Main Stream number: 1 in normal stream number 1 Stream flow area = 0.106(Ac.) Runoff from this stream = 0.296(CFS) Time of concentration = 8.13 mm. Rainfall intensity = 4.815(In/Hr) Summary of stream data: Stream Flow rate TC Rainfall Intensity No. (CFS) (mm) (In/Hr) 1 0.296 8.13 4.815 Qmax(l) = 1.000 * 1.000 * 0.296) + = 0.296 Total of 1 streams to confluence: Flow rates before confluence point: 0.296 Maximum flow rates at confluence using above data: 0.296 Area of streams before confluence: 0.106 Results of confluence: Total flow rate = 0.296(CFS) Time of concentration = 8.127 mm. Effective stream area after confluence = 0.106(Ac.) End of computations, total study area = 0.106 (Ac.) I I Page 114 of 20 DRAINAGE REPORT I 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I I I I- I I I I I I U I I I I Section 1 Reach (ft) I Channel Report I Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. I Surfside 4-inch Storm Drain Circular (Diameter ftjJ 0.3) I Invert Elev(ft) = 1.00 I Slope (%) = 2.00 U N-Value = 0.013 I Calculations Compute by: Q vs Depth No. Increments = 10 I Hi ghlighted Depth (ft) (b (cfs) Area (sqft) Velocity (ft/s) Wetted Perim (ft) Crit Depth, Yc (ft) Top Width (ft) EGL (ft) Tuesday, Feb 162021 = 0.30 C 0.27) = 3.44 = 0.83 = 0.30 = 0.20 = 0.48 Note: Qi 00 being discharged from site = 0.30 cfs per Post-Development Condition Exhibit shown on Appendix 2 of this report, each 4 storm drain has the capacity to discharge 0.28 cfs, therefore the 2 - 4" storm drains shown have the capacity to handle the Q100. I Elev (ft) ii 2.00- - 1.75- -I ii 1.25- - 1.00 — - 1 0.75— I -I -I Ii 1.50— -I ii I I I I I I I I I I I I I I I I I I I Depth Q Area (ft) ç(cfsj'. (sqft) 0.03 0.006 0.004 0.07 0.023 0.012 0.10 0.051 0.022 0.13 0.088 0.032 0.17 0.132 0.043 0.20 0.177 0.054 0.23 0.220 0.064 0.26 0.256 0.073 0.279) 0.081 0.33 0.262 0.086 Hydraflow Express - Surfside 4-inch Storm Drain - 02/16/21 Max Q per 4' pipe 1 I I 1 I I I I I I I I I I I I 1 I I I Veloc WP Yc (ft/s) (ft) (ft) 1.23 0.21 0.04 1.89 0.31 0.09 2.38 0.38 0.13 2.76 0.45 0.17 3.07 0.52 0.21 3.29 0.59 0.24 3.43 0.66 0.27 3.49 0.73 0.29 3.44 0.83 0.30 3.06 1.04 0.29 Hydraflow Express - Surfside 4-inch Storm Drain - 02/16/21 I I I I I I I I I I I I I I I 1 I I I TopWidth Energy (ft) (ft) 0.20 0.06 0.26 0.12 0.30 0.19 0.32 0.25 0.33 0.31 0.32 0.37 0.30 0.41 0.26 0.45 0.20 0.48 0.00 0.48 Hydraflow Express - Surlside 4-inch Storm Drain - 02/16/21 3 1 I I APPENDIX 3 Storm Water Standard Project Requirements I I I 1 I I I I I I I 1 I Page 115 of 20 DRAINAGE REPORT 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I I C-Pty of Carlsbad Development Services Land Development Engineering 1635 Faraday Avenue (760) 602-2750 www.carlsbadca.gov STORM WATER STANDARDS QUESTIONNAIRE E-34 INSTRUCTIONS: - To address post-development pollutants that may be generated from development projects, the city requires that new development and significant redevelopment priority projects incorporate Permanent Storm Water Best Management Practices (BMPs) into the project design per Carlsbad BMP Design Manual (BMP Manual). To view the BMP Manual, refer to the Engineering Standards (Volume 5). This questionnaire must be completed by the applicant in advance of submitting for a development application (subdivision, discretionary permits and/or construction permits). The results of the questionnaire determine the level of storm water standards that must be applied to a proposed development or redevelopment project. Depending on the outcome, your project will either be subject to 'STANDARD PROJECT' requirements or be subject to 'PRIORITY DEVELOPMENT PROJECT' (PDP) requirements. Your responses to the questionnaire represent an initial assessment of the proposed project conditions and impacts. City staff has responsibility for making the final assessment after submission of the development application. If staff determines that the questionnaire was incorrectly filled out and is subject to more stringent storm water standards than initially assessed by you, this will result in the return of the development application as incomplete. In this case, please make the changes to the questionnaire and resubmit to the city. If you are unsure about the meaning of a question or need help in determining how to respond to one or more of the questions, please seek assistance from Land Development Engineering staff. A completed and signed questionnaire must be submitted with each development project application. Only one completed and signed questionnaire is required when multiple development applications for the same project are submitted concurrently. PROJECT INFORMATION PROJECT NAME: 6479 Surfside Lane PROJECT ID: ADDRESS: 6479 Surfside Lane, Carlsbad CA, 92011 APN: 201-021-11-00 The project is (check one): 11 New Development El Redevelopment The total proposed disturbed area is: 4,617 ft2 (_0.106 ) acres The total proposed newly created and/or replaced impervious area is: 2,352 ft2 (_0.053 ) acres If your project is covered by an approved SWQMP as part of a larger development project, provide the project ID and the SWQMP # of the larger development project: Project ID SWQMP #: Then, go to Step 1 and follow the instructions. When completed, sign the form at the end and submit this with your application to the city. E-34 Page 1 of 4 REV 02/16 I I I I I I I I I I I .1 I I I I I STEP I TO BE COMPLETED FOR ALL PROJECTS To determine if your project is a "development project", please answer the following question: YES NO Is your project LIMITED TO routine maintenance activity and/or repair/improvements to an existing building El N or structure that do not alter the size (See Section 1.3 of the BMP Design Manual for guidance)? If you answered "yes" to the above question, provide justification below then go to Step 5, mark the third box stating "my project is not a 'development project' and not subject to the requirements of the BMP manual" and complete applicant information. Justification/discussion: (e.g. the project includes only interior remodels within an existing building): If you answered "no" to the above question, the project is a 'development project', go to Step 2. STEP 2 TO BE COMPLETED FOR ALL DEVELOPMENT PROJECTS To determine if your project is exempt from PDP requirements pursuant to MS4 Permit Provision E.3.b.(3), please answer the following questions: Is your project LIMITED to one or more of the following: YES NO 1. Constructing new or retrofitting paved sidewalks, bicycle lanes or trails that meet the following criteria: Designed and constructed to direct storm water runoff to adjacent vegetated areas, or other non- erodible permeable areas; El El Designed and constructed to be hydraulically disconnected from paved streets or roads; Designed and constructed with permeable pavements or surfaces in accordance with USEPA Green Streets guidance? 2. Retrofitting or redeveloping existing paved alleys, streets, or roads that are designed and constructed in accordance with the USEPA Green Streets guidance? 3. Ground Mounted Solar Array that meets the criteria provided in section 1.4.2 of the BMP manual? E] 191 If you answered "yes" to one or more of the above questions, provide discussion/justification below, then go to Step 5, mark the second box stating "my project is EXEMPT from PDP .....and complete applicant information. Discussion to justify exemption ( e.g. the project redeveloping existing road designed and constructed in accordance with the USEPA Green Street guidance): If you answered "no" to the above questions, your project is not exempt from PDP, go to Step 3. E-34 Page 2 of 4 REV 04/17 I El I I I I I I H I I I I I I I Li I STEP 3 TO BE COMPLETED FOR ALL NEW OR REDEVELOPMENT PROJECTS To determine if your project is a PDP, please answer the following questions (MS4 Permit Provision E.3.b.(1)): - YES NO Is your project a new development that creates 10,000 square feet or more of impervious surfaces collectively over the entire project site? This includes commercial, industrial, residential, mixed-use, El IXI and public development projects on public or private land. Is your project a redevelopment project creating and/or replacing 5,000 square feet or more of impervious surface collectively over the entire project site on an existing site of 10,000 square feet or El FX_1 more of impervious surface? This includes commercial, industrial, residential, mixed-use, and public development projects on public or private land. Is your project a new or redevelopment project that creates and/or replaces 5,000 square feet or more of impervious surface collectively over the entire project site and supports a restaurant? A restaurant is a facility that sells prepared foods and drinks for consumption, including stationary lunch counters and El El refreshment stands selling prepared foods and drinks for immediate consumption (Standard Industrial Classification (SIC) code 5812). Is your project a new or redevelopment project that creates 5,000 square feet or more of impervious surface collectively over the entire project site and supports a hillside development project? A hillside El M development project includes development on any natural slope that is twenty-five percent or greater. Is your project a new or redevelopment project that creates and/or replaces 5,000 square feet or more of impervious surface collectively over the entire project site and supports a parking lot? A parking lot is a land area or facility for the temporary parking or storage of motor vehicles used personally for business or for commerce. Is your project a new or redevelopment project that creates and/or replaces 5,000 square feet or more of impervious street, road, highway, freeway or driveway surface collectively over the entire project El M site? A street, road, highway, freeway or driveway is any paved impervious surface used for the transportation of automobiles, vehicles. _trucks, _motorcycles, _and _other Is your project a new or redevelopment project that creates and/or replaces 2,500 square feet or more of impervious surface collectively over the entire site, and discharges directly to an Environmentally Sensitive Area (ESA)? "Discharging Directly to" includes flow that is conveyed overland a distance of LI I1 200 feet or less from the project to the ESA, or conveyed in a pipe or open channel any distance as an isolated flow from the project to the ESA (i.e. not commingled with flows from adjacent lands).* Is your project a new development or redevelopment project that creates and/or replaces 5,000 square feet or more of impervious surface that supports an automotive repair shop? An automotive repair shop is a facility that is categorized in any one of the following Standard Industrial Classification (SIC) codes: 5013, 5014, 5541, 7532-7534, or 7536-7539. Is your project a new development or redevelopment project that creates and/or replaces 5,000 square feet or more of impervious area that supports a retail gasoline outlet (RGO)? This category includes El R1 RGO's that meet the following criteria: (a) 5,000 square feet or more or (b) a project Average Daily Traffic (AD T) of 100 or more vehicles per day. Is your project a new or redevelopment project that results in the disturbance of one or more acres of land El X and are expected to generate pollutants post construction? Is your project located within 200 feet of the Pacific Ocean and (1) creates 2,500 square feet or more of impervious surface or (2) increases impervious surface on the property by more than 10%? (CMC LI FI 21.203.040) If you answered "yes" to one or more of the above questions, your project is a POP. If your project is a redevelopment project, go to step 4. If your project is a new project, go to step 5, check the first box stating "My project is a PDP and complete applicant information. If you answered "no" to all of the above questions, your project is a 'STANDARD PROJECT.' Go to step 5, check the second box stating "My project is a 'STANDARD PROJECT'.....and complete applicant information. I I E-34 Page 3 of 4 REV 04/17 I I I I I I I i I I I 1 I I I Li STEP 4 TO BE COMPLETED FOR REDEVELOPMENT PROJECTS THAT ARE PRIORITY DEVELOPMENT PROJECTS (PDP) ONLY Complete the questions below regarding your redevelopment project (MS4 Permit Provision E.3.b.(2)): YES NO Does the redevelopment project result in the creation or replacement of impervious surface in an amount of less than 50% of the surface area of the previously existing development? Complete the percent impervious calculation below: Existing impervious area (A) = sq. ft. El 0 Total proposed newly created or replaced impervious area (B) = sq. ft. Percent impervious area created or replaced (B/A )* 100 =% If you answered "yes", the structural BMPs required for PDP apply only to the creation or replacement of impervious surface and not the entire development. Go to step 5, check the first box stating "My project is a POP ..." and complete applicant information. If you answered "no," the structural BMP's required for PDP apply to the entire development. Go to step 5, check the check the first box stating "My project is a PDP and complete applicant information. STEP 5 CHECK THE APPROPRIATE BOX AND COMPLETE APPLICANT INFORMATION Fj My project is a PDP and must comply with PDP stormwater requirements of the BMP Manual. I understand I must prepare a Storm Water Quality Management Plan (SWQMP) for submittal at time of application. Xl My project is a 'STANDARD PROJECT' OR EXEMPT from PDP and must only comply with 'STANDARD PROJECT' stormwater requirements of the BMP Manual. As part of these requirements, I will submit a "Standard Project Requirement Checklist Form E-36" and incorporate low impact development strategies throughout my project. Note: For projects that are close to meeting the PDP threshold, staff may require detailed impervious area calculations and exhibits to verify if 'STANDARD PROJECT' stormwater requirements apply. LI My Project is NOT a 'development project' and is not subject to the requirements of the BMP Manual. Applicant Information and Signature Box Applicant Name: Mellor Landy Applicant Title: Civil Engineer Applicant Signature: 7'-' Date: 2/28/20 nvironmentaiiy sensitive Areas include but are not limited to all Liean Water Act section 3U3(a) impaired water bodies; areas designated as Areas ot special Biological Significance by the State Water Resources control Board (Water Quality control Plan for the San Diego Basin (1994) and amendments); water bodies designated with the RARE beneficial use by the State Water Resources control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments); areas designated as preserves or their equivalent under the Multi Species Conservation Program within the Cities and County of San Diego; Habitat Management Plan; and any other equivalent environmentally sensitive areas which have been identified by the City. This Box for City Use On/v City Concurrence: YES NO LI LI By: Date: Project ID: E-34 Page 4 of 4 REV 04/17 I I I I n- I I I I I I I 1 I I I I I Project Information Project Name: 6479 Surfside Lane Project ID: DWG No. or Building Permit No.: Source Control BMPs All development projects must implement source control BMPs SC-1 through SC-6 where applicable and feasible. See Chapter 4 and Appendix E.1 of the BMP Design Manual (Volume 5 of City Engineering Standards) for information to implement source control BMPs shown in this checklist. Answer each category below pursuant to the following. Yes" means the project will implement the source control BMP as described in Chapter 4 and/or Appendix E.1 of the Model BMP Design Manual. Discussion/justification is not required. 'No" means the BMP is applicable to the project but it is not feasible to implement. Discussion/justification must be provided. Please add attachments if more space is needed. N/A" means the BMP is not applicable at the project site because the project does not include the feature that is addressed by the BMP (e.g., the project has no outdoor materials storage areas). Discussion/justification may be provided. Source Control Requirement Applied? SC-1 Prevention of Illicit Discharges into the MS4 Ii Yes U No LI N/A Discussion/justification if SC-1 not implemented: SC-2 Storm Drain Stenciling or Signage 0 Yes LI No N/A Discussion/justification if SC-2 not implemented: No storm drain inlets or catch basins are being proposed, only providing small area drains. SC-3 Protect Outdoor Materials Storage Areas from Rainfall, Run-On, Runoff, and Wind III Yes 0 No 0 N/A Dispersal Discussion/justification if SC-3 not implemented: E-36 Page 1 of 4 Revised 09/16 I I I I I I I I I I I I I 1 I I I I I City of Carlsbad STANDARD PROJECT REQUIREMENT CHECKLIST E-36 Development Services Land Development Engineering 1635 Faraday Avenue (760) 602-2750 www.carlsbadca.gov I I I I I I I I I I 1 I I I I I I I I Source Control Requirement (continued) Applied? SC-4 Protect Materials Stored in Outdoor Work Areas from Rainfall Run-On Runoff, and Wind Dispersal El Yes El No It N/A Discussion/justification if SC-4 not implemented: SC-5 Protect Trash Storage Areas from Rainfall, Run-On, Runoff, and Wind Dispersal El Yes El No it N/A Discussion/justification if SC-5 not implemented: Single Family residence will have, standard trash enclosure bins. SC-6 Additional BMPs based on Potential Sources of Runoff Pollutants must answer for each source listed below and identify additional BMPs. (See Table in Appendix E.1 of BMP Manual for guidance). El On-site storm drain inlets D Yes El No lii N/A El Interior floor drains and elevator shaft sump pumps 0 Yes El No Ill N/A El Interior parking garages El Yes El No ii N/A It Need for future indoor & structural pest control Ill Yes El No El N/A It Landscape/Outdoor Pesticide Use !l Yes El No El N/A El Pools, spas, ponds, decorative fountains, and other water features El Yes El No III N/A El Food service El Yes El No il N/A El Refuse areas El Yes El No It N/A El Industrial processes El Yes 0 No !] N/A El Outdoor equipment materials _storage _of_ _or 0 Yes El No It N/A El Vehicle and Equipment Cleaning 0 Yes El No It N/A El Vehicle/Equipment Repair and Maintenance 0 Yes El No it N/A El Fuel Dispensing Areas 0 Yes El No It N/A El Loading Docks El Yes El No it N/A El Fire Sprinkler Test Water 0 Yes El No It N/A El Miscellaneous Drain or Wash Water El Yes El No It N/A El Plazas, sidewalks, and parking lots It Yes El No El N/A For "Yes" answers, identify the additional BMP per Appendix El. Provide justification for "No' answers. -Residence design features will discourage entry of pest, provide integrated pest management information to owners, lessees. -Pest-resistance plants, maintain landscape using minimal or no pesticides. -Trash cans to be located inside residence an only taken out during trash day. E-36 Page 2 of 4 Revised 09/16 E-36 Page 3 of 4 Revised 09/16 Site Design BMPs All development projects must implement site design BMPs SD-1 through SD-8 where applicable and feasible. See Chapter 4 and Appendix E.2 thru E.6 of the BMP Design Manual (Volume 5 of City Engineering Standards) for information to implement site design BMPs shown in this checklist. Answer each category below pursuant to the following. 'Yes" means the project will implement the site design BMPs as described in Chapter 4 and/or Appendix E.2 thru E.6 of the Model BMP Design Manual. Discussion /justification is not required. 'No" means the BMPs is applicable to the project but it is not feasible to implement. Discussion/justification must be provided. Please add attachments if more space is needed. N/A' means the BMPs is not applicable at the project site because the project does not include the feature that is addressed by the BMPs (e.g., the project site has no existing natural areas to conserve). Discussion/justification may be provided. Site Design Requirement Applied? SD-I Maintain Natural Drainage Pathways and Hydrologic Features Lii Yes I El No I El N/A Discussion/justification if SD-1 not implemented: SD-2 Conserve Natural Areas, Soils, and Vegetation [:]Yes El No lii N/A Discussion/justification if SD-2 not implemented: SD-3 Minimize Impervious Area I Lii Yes I El No El N/A Discussion/justification if SD-3 not implemented: SD-4 Minimize Soil Compaction I iii Yes I El No I El N/A Discussion/justification if SD-4 not implemented: SD-5 Impervious Area Dispersion 9 Yes El No El N/A Discussion/justification if SD-5 not implemented: I LI I I I P1 I I I [1 I I I I I Site Design Requirement (continued) - Applied? SD-6 Runoff Collection Ii Yes D No E N/A Discussion/justification if SD-6 not implemented: SD-7 Landscaping with Native or Drought Tolerant Species T —9 —yes [I No U N/A Discussion/justification if SD-7 not implemented: SD-8 Harvesting and Using Precipitation I El Yes D No I J N/A Discussion/justification if SD-8 not implemented: I I I I Li ii 1 I I I E-36 Page 4 of 4 Revised 09/16 I I 1 I I I 1 ri I I I I I APPENDIX 4 Maps and Charts I I I I] I I 11 1 I I I] I I Page 116 of 20 DRAINAGE REPORT 1 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I I I I I I I I I 1 I I I I 1 I I I I 6479 Surfside Lane 2/28/2020 Pre-Project Drainage Total Pervious Impervious Weighted Total Area - Soil Area - Soil Weighted Runoff Area Type B (sq Type B Runoff Coeff Coef Basin ID (ac) ft) (sq-ft) % Impervious % Pervious C: C: A.1 1 0.045 1 1964 1 0 1 100% 1 0% 0.25 0.25 A.2 1 0.061 1 2666 1 0 1 100% 1 0% 0.25 Total 0.106 AC Runoff Coefficient Table Soil Type B Impervious 0.90 Pervious (landscape) 0.25 Post-Project Drainage Total Pervious Impervious Weighted Total Area - Soil Area - Soil Weighted Runoff Area Type B (sq Type B Runoff Coef Coef Basin ID (ac) ft) (sq-ft) % Impervious % Pervious C: C: A.1 0.045 1 1077 887 55% 45% 0.54 0.58 A.2 0.061 1201 1465 45% 55% 0.61 Total 0.106 AC S:\PROJECTS\6479 Su rfside\CIVI L\REPORTS\HYDROLOGY\Appendix 4 - Weighted Runoff Coefficient\Surfside Lane drn calcs.xlsx Orange range .--. (.ounty ( OCEM4S IDE HROJECT SITE H -o ENCINITAS -U- SCLNNA BEACH C) DEL MAR (2 0 33 5 3300 3245 County of San Diego hydrology Manual :cL 'd;• Rainfall Isopluvials 100 Year Rainfall Event -6 Hours ISopIuviI (Inches) 3230 IMPERIAL BEACH LI GIS '. N 0 0 In - 3230 S 3 0 3MiIes -- 0 - - - P 333O Riverside County I 1 7 18 - 4-8 '4 'o :: I *0 33'15- ------------ ----- ----- ..--- •- .... / ¶3 ------------- -------------- 4' ....................... i I -'- _7- p .4 *0 CD "-'S..- '. '--.•'-- '--V'-- ANIEErY .19 ------------ 3245 so ..........-- ...K / A MeXICO P 32'30' 40 3245' 323O CORONAJ 3330 )raiìqo .-- County L. - *. \_ 331b ~-,,OCEA1JSrOt ••. 3300• County of San Diego Hydrology Manual Rainfall Jsopluviais 100 Year Rainfall Event -24 hours IsopIuviI (inches) DPW 4 c,yr54S.O1S Al #MR. S 3 0 3MiIes Hydrologic Soil Group—San Diego County Area, California U ilO- 451135 45 ee 045 _ .5 Soil Map may not he valid. at this scale - 33 6'39 N 1-434 Map Scale: 1:241 if printed on A landscape (lix 8.5') sheet. Meters N 0 3 7 14 21 A Feet 0 •10: 20 :40 : W Map projection Web Mercator Corner coordinates: WGS84 Edge tics UTM Zone UN WG584 LJSI)A Natural Resources Web Soil Survey Conservation Service National Cooperative Soil Survey I - 454554 451455 475034 5: 2/26/2020 Page 1 of 4 Hydrologic Soil Group—San Diego County Area, California I IT, T2JCIIi] Area of Interest (AOl) Area of Interest (AOl) Soils Soil Rating Polygons AID BID CID Not rated or not available Soil Rating Lines A A/D — B B/D # C CID .- 0 - Not rated or not available Soil Rating Points D A D AID • B • B/D D C The soil surveys that comprise your AOl were mapped at 1:24,000, o • D Warning: Soil Map may not be valid at this scale. o Not rated or not available Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil Water Features line placement The maps do not show the small areas of Streams and Canals contrasting soils that could have been shown at a more detailed scale. Transportation 4-I--I Rails Please rely on the bar scale on each map sheet for map Interstate Highways measurements. US Routes Source of Map Natural Resources Conservation Service Web Soil Survey URL Major Roads Coordinate System: Web Mercator (EPSG:3857) Local Roads Maps from the Web Soil Survey are based on the Web Mercator Background projection, which preserves direction and shape but distorts distance and area A projection that preserves area such as the Aerial Photography 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 14, Sep 16, 2019 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 USDA Natural Resources Web Soil Survey 2/26/2020 Conservation Service National Cooperative Soil Survey Page 2 of 4 Hydrologic Soil Group—San Diego County Area, California Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOl Percent of AOl MIC Marina loamy coarse sand, 2 to 9 percent slopes B 0.1 100.0% Totals for Area of Interest 0.1 100.0% 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 O/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 (AID, BID, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition I USDA Natural Resources Web Soil Survey 2/26/2020 Conservation Service National Cooperative Soil Survey Page 3 of 4 11 I I H I I LI I I I Lj U I I 1 1 I Hydrologic Soil Group—San Diego County Area, California U Component Percent Cutoff None Specified I Tie-break Rule: Higher I rj I U U U U LI I 1 I n USDA Natural Resources Web Soil Survey 2/26/2020 Conservation Service National Cooperative Soil Survey Page 4 of 4 I I I I I I I I I I I I I I I I I I I I Watershed Divide / cosloin Pin zT Watershed Divide AE I 7tfftec.6ve 916peLrne (Watershed Outlet) 5frern Profile I Area 'A = Area RB" SOURCE Caffornia Dvon of I-{ays (1941) and (irpii (149) F I C U R E Computation of Effetive Slope for Natural Watershed 3-5 39 Page I 1/ ot 2U DRAINAGE REPORT 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM SiflNIVl NJ 3WI1 MOH ONV1AO 0 0 0 C qM 0 - III = - - 0 0I 01 0 0 1334 N133 NV1SI0 SW1O3iVM ICU 1_ 1 I I I 'I I I I I 1 I 1 I I 1 I I I 'I Page 1 18 of 20 DRAINAGE REPORT 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I I I Manning's n Values for Overland Flow" I The BMP Design Manuals within the county of San Diego allow for a land surface description other than short prairie grass to be used for hydromodification BMP design only if documentation provided is consistent with Table A.6 of the SWMM 5 User's Manual. I In January 2016, the EPA released the SWMM Reference Manual Volume I - Hydrology (SWMM Hydrology Reference Manual). The SWMM Hydrology Reference Manual complements the SWMM 5 User's Manual by providing an in-depth description of the program's hydrologic components. Table 3-5 I of the SWMM Hydrology Reference Manual expounds upon Table A.6 of the SWMM S User's Manual by providing Manning's n values for additional overland flow surfaces. Therefore, in order to provide SWMM users with a wider range of land surfaces suitable for local application and to provide Copermittees with confidence in the design parameters, we recommend using the values published by I Yen and Chow in Table 3-5 of the EPA SWMM Reference Manual Volume I - Hydrology. The values are provided in the table below: Overland Surface Manning value (n) Smooth asphalt pavement 0.010 Smooth impervious surface 0.011 Tar and sand pavement 0.012 Concrete pavement 0.014 Rough impervious surface 0.015 Smooth bare packed soil 0.017 Moderate bare packed soil 0.025 Rough bare packed soil 0.032 Gravel soil 0.025 Mowed poor grass 0.030 Average grass, closely dipped sod 0.040 Pasture 0.040 Timberland 0.060 Dense grass 0.060 Shrubs and bushes 0.080 Land Use Business 0.014 Semibusiness 0.022 Industrial 0.020 Dense residential 0.025 Suburban residential 0.030 Parks and lawns 0.040 I 'Content summarized from Improving Accuracy in Continuous Simulation Modeling: Guidance for Selecting Pervious Overland Flow Manning's n Values in the San Diego Region (TRWE, 2015). I Page 119 of 20 DRAINAGE REPORT 1 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM I I [1 ii 10 AE I re Catforra Dils*on c( l and Kpch (1040) F I G UR P Homograph for Deteirminahon of lime of Cocicorthafion (Ic) or Travel Time (fl) for Natural Watersheds 34 2 Page 1 20 of 20 DRAINAGE REPORT 6479 Surfside Lane www.HWL-PE.COM 2888 Loker Avenue East, Suite 217, Carlsbad, CA 92010 I Tel. 760.929.2288 I Email. info@HWL-PE.COM EQUATION E N 9L3 Y385 Ft Ic Ls000 To • Time oconcenlraUon(houto) L = Wa COUVSO Dstarce lmlleo) T-4MO AE Chg IOwa 1- efIocth* slop. fine (So. Fure 3-3)IleeU To F I$0ur5J Minulas 4 40 3 180 I, I I I I I I I I I I I I I 1 I I I —1000 000 000 WD 400 4' —300 4' 4' —200 4' L \ ILkooFeet 4' 4' —100 i.4000 20 1-' 18 3000 1I 50 1- 14 \ 40 I2000 12 1-1600 1-1600 4' 10 311 1-1400 0 F 1200 A 20 I—i000 I-900 F—sOc 6 • 1—mo 5 2 -I-120 I:ioo ETC I 60 —50 —40 1-30