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Home My WebLink AboutCDP 2017-0024; Highland James Subdivision (Highland Drive Portion); Hydrology/Hydraulic Drainage Report; 2020-12-09 HYDROLOGIC/HYDRAULIC DRAINAGE REPORT 100-year Peak Flow in Pre & Post-Development Conditions for: Highland James Subdivision Project ID (CT 08-06) CDP 15-47, 15-48, 15-49, 2017-0024, 2017-0025 Carlsbad, CA, 92008 APN: 207-130-75 to 80 DWG 483-6B, DWG483-6C, & DWG483-6D Prepared by: REC Consultants 2442 Second Avenue San Diego, CA 92010 619-232-9200 ______________________________________________ William O’Gorman, PE, 88286 Date Report Prepared: December 9, 2020WILLIAM M. O'G O RMANCI V I LST A TE OF CA LI F O R N IAREGISTERED P R OFESSION A L ENGINEER12/9/20 R·E·C 1 I Consultants, Inc. Drainage Study Highland James Subdivision REC Consultants, Inc. Page | 1 TABLE OF CONTENTS Introduction ................................................................................................................................ 1 Project Description ..................................................................................................................... 1 Location ..................................................................................................................................................... 1 Description ................................................................................................................................................ 1 Land Use and Zoning ................................................................................................................................ 1 FEMA Considerations ............................................................................................................................... 1 Drainage Aspects ....................................................................................................................... 2 Existing Condition ..................................................................................................................................... 2 Developed Condition ................................................................................................................................. 3 Hydrology ................................................................................................................................... 4 Time of Concentration ............................................................................................................................... 4 Rational Method (per Section 3.1 of the SDCHM) .................................................................................... 4 Modified Rational Method (per Section 3.4 of the SDCHM) ..................................................................... 5 Hydraulics .................................................................................................................................. 6 Catch Basin (Weir) .................................................................................................................................... 6 Graded Trapezoidal Weir .......................................................................................................................... 7 Pipes ......................................................................................................................................................... 7 Conclusions ............................................................................................................................... 9 APPENDIX A: Maps APPENDIX B: Calculations Drainage Study Highland James Subdivision REC Consultants, Inc. Page | 1 HYDROLOGIC/HYDRAULIC DRAINAGE REPORT 100-year Peak Flow in Pre & Post-Development Conditions for Highland James Subdivision, Carlsbad, CA INTRODUCTION This document summarizes the approach used to analyze and compare the hydrologic and hydraulic volumetric flows of the existing and proposed conditions of a project site in the City of Carlsbad. In accordance with the Carlsbad BMP Design Manual (2016) and the San Diego County Hydrology Manual, this report will show that the proposed condition will mitigate flooding. In addition to flood control, the proposed drainage of the project site must comply with Pollutant Control and Hydromodification Management requirements as mandated by the Carlsbad BMP Design Manual. According to the Carlsbad Watershed Management Area Analysis (WMAA) prepared by Geosyntec & Rick Engineering (Oct 2014), the project site exists within the Hydromodification Exempt area and thus does not require a Hydromodification analysis. Please refer to the “Storm Water Quality Management Plan” (SWQMP)” prepared by Terramar Engineering for further discussion of Pollutant Control requirements. PROJECT DESCRIPTION Location Street Address: 3980 Highland Drive City/County/State/Zip: Carlsbad, County of San Diego, California, 92008 Latitude, Longitude: 33˚09’13” N, 117 ˚19’44” W Description This project consists of a lot subdivision and residential development of 3980 Highland Drive, Carlsbad, CA (See Location Map in Appendix A). The site area is 49,653 sf. The proposed residential development will result in the existing lot subdivided into five (5) smaller lots which will be the location of 5 residences. The total impervious area in the existing and proposed conditions is 4,340 sf and 19,767 sf, respectively. Land Use and Zoning The subject property is the current location of an existing residence and appurtenances (hardscape and landscape). In the proposed condition, all 5 lots will be future locations for residences. Access to lots 4 & 5 (Lots 1 & 2 of Map 16234) are afforded by Highland Avenue to the southwest. Access to lots 1, 2 and 3 (of Map 15082) are afforded by James Drive to the northeast. Each lot will consist of a residential building, connected garage, driveway, sidewalk, and landscaping. Zoning: R-1 (Single-family Residential) APN: 207-130-75 to 207-130-78-00 FEMA Considerations Before proceeding with the calculations, the property was investigated from the Federal Emergency Management Agency (FEMA) point of view, to determine if the property is located totally or partially outside of a flood zone. Community Number: 06073C0764G Drainage Study Highland James Subdivision REC Consultants, Inc. Page | 2 Effective Date: 5/16/12 Zone: X (unshaded) ZONE X (unshaded) is defined as “The areas of minimal flood hazard, which are the areas outside the Special Flood Hazard Area (SFHA) and higher than the elevation of the 0.2-percent-annual-chance flood.” DRAINAGE ASPECTS The project site is the future location of five (5) residences on five (5) individual lots. The cumulative area of the project site is 1.14 acres. The project site generally drains southwest to northeast (Highland Dr to downstream James Dr). A City storm drain curb inlet along James Dr., located near the eastern corner of the project site is considered the point of comparison/compliance (POC). Existing Condition The subject site is a residential parcel located on the easterly side of Highland Drive. The property is located at the top of a rise with the east side of the site fronting James Drive approximately 15 to 20 feet lower than the west side. A 10-foot, approximately 2:1 cut slope extends midway through the site from the south to north. A 2-to-3 feet fill slope is located at the top of the cut on the north end. The property is presently occupied by a one-story single-family residence with a detached garage and driveway. There is a four-foot retaining wall behind the garage and a 3-foot rock retaining wall behind the house. There is a 12-inch public storm drain that conveys stormwater runoff from Highland Drive eastward through the site along its northern perimeter down to James Drive; however the property does not contain any storm drain infrastructure for stormwater generated onsite. Existing topography dictates that stormwater runoff sheet flows along the ground surface of the property from west to east and discharge offsite and onto James Drive at the sites eastern edge. In pre-development conditions the entire site may be considered as a single drainage management area with one point of discharge (at its eastern perimeter). Once the runoff discharges onto James Drive it is collected by a curb inlet on James Drive which is part of the municipal separate storm sewer system (MS4) owned and operated by the City of Carlsbad. The City MS4 conveys the runoff further downstream to the Agua Hedionda Lagoon with ultimate discharge into the Pacific Ocean along Carlsbad State Beach (at Tamarack jetties and at the discharge for the Encina Power Station). Drainage Study Highland James Subdivision REC Consultants, Inc. Page | 3 Developed Condition In the proposed condition, the natural drainage pattern of the site is roughly maintained. Ridges and swales divide the site into twelve (12) Drainage Management Areas (DMA). The DMAs are designated N1a, N1b, N1c, N2a, N2b, N2c, N3, N4, N5, N6, N7 and N8. All DMAs discharge into a private storm drain system via catch basins and the private storm drain system terminates at an existing public curb inlet (City MS4). N1a+N1b and N2a+N2b each discharge into a Bioretention Best Management Practice (BMP) for water quality purposes. Higher flows from the BMPs enter a concrete swale which terminates at catch basins and enters the private storm drain system. N3 through N8 flow to catch basins without entering structural BMPs and are treated by Site Design BMPs. See the Water Quality Management Plan prepared by Terramar Engineering for a detail explanation of the methodologies used to design BMPs for Water Quality requirements. The DMAs are described below. • DMA N1a is 0.037-acres (19% impervious) and an area within the public right-of-way along Highland Avenue that flows onto DMA N1b. DMA N1a consists of landscaping and the driveway for Lot 2 of Map 16234 that ties into Highland Avenue. • DMA N1b is 0.274-acres (29.5% impervious) and contains proposed Lot 2 of Map 16234. DMA N1b accepts run-on from DMA N1a. Runoff discharges into a Bioretention BMP for pollutant control. Flows leaving the BMP are managed by infiltration and an overflow weir. The overflow weir conveys flows to DMA N1c. • DMA N1c is 0.014-acres (0% impervious) and contains the western edge of Lot 3 and southern half of the western edge of Lot 2 (i.e. the 6-ft strip of landscaping with drainage swale above the retaining wall). This DMA conveys runoff from DMAs N1a and N1b into the private storm drain system via the proposed riprap drainage swale which terminates at a catch basin. • DMA N2a is 0.039-acres (19% impervious) and an area within the public right-of-way along Highland Avenue that flows onto DMA N2b. DMA N2a consists of landscaping and the driveway for Lot 1 of Map 16234 that ties into Highland Avenue. • DMA N2b is 0.274-acres (30% impervious) and contains proposed Lot 1 of Map 16234. DMA N2b accepts run-on from DMA N2a. Runoff discharges into a Bioretention BMP for pollutant control. Flows leaving the BMP are managed by infiltration and an overflow weir. The overflow weir conveys flows DMA N2c. • DMA N3 is 0.082-acres (62% impervious) and contains the southern half of Lot 3. Runoff from N3 enters the private storm drain system via a catch basin near the northeastern corner of the DMA. • DMA N4 is 0.082-acres (50% impervious) and contains the northern half of Lot 3. Runoff from N4 enters the private storm drain system via a catch basin near the northern edge of the DMA. • DMA N5 is 0.082-acres (65% impervious) and contains the southern half of Lot 2. Runoff from N5 enters the private storm drain system via a catch basin near the northern edge of the DMA. • DMA N6 is 0.082-acres (50% impervious) and contains the northern half of Lot 2. Runoff from N6 enters the private storm drain system via a catch basin near the northern edge of the DMA. • DMA N7 is 0.082-acres (65% impervious) and contains the southern half of Lot 1. Runoff from N4 enters the private storm drain system via a catch basin near the northern edge of the DMA. Drainage Study Highland James Subdivision REC Consultants, Inc. Page | 4 • DMA N8 is 0.082-acres (49% impervious) and contains the northern half of Lot 1. Runoff from N4 enters the private storm drain system via a catch basin near the northern edge of the DMA. N8 also contains a 12-inch public storm drain with a 5-ft easement along its northern perimeter that conveys flows from Highland through the site and into storm drain under James Drive (the project does not contribute runoff to this pipeline). N1a, N1b, and N1c will be evaluated as one collective DMA since these DMAs all drain to one point. N2a, N2b, and N2c will also be evaluated as one collective DMA since these DMAs all drain to one point. See Appendix A to see the existing and proposed site layout. HYDROLOGY The methodology for this drainage report follows analyses found within Section 3.1 of the San Diego County Hydrology Manual (hereafter referred to as the “Hydrology Manual”). See Appendix B for the detailed calculations described in the section. Time of Concentration The time of concentration (tc) is used to determine the peak flow during a storm event. The value represents the time it takes for the entire area to contribute to runoff and is a function of flow path length, slope, and surface roughness. An iterative process was used to determine tc. First, the initial time of concentration for the initial 100 feet of flow path distance was determined using the following equation. 𝑡𝑐𝑐= 1.8 ∗(1.1 − 𝐶)∗𝐿0.5𝑆13 Equation 1 Where: tci = initial time of concentration in minutes C = unitless runoff coefficient of the initial area = 0.9*ai + Cp*(1-ai) Cp = unitless runoff coefficient of the natural soil (Soil Type B for this site) = 0.25 ai = unitless impervious fraction = impervious area / total area L = initial flow path length in feet (maximum 100 ft) S = initial slope of the longest flow path as a percent (%) With the initial tci evaluated, the subsequent flow velocity of the concentrated flow will be determined. A final velocity of the channel flow will be estimated and used to estimate the travel time (tt), which represents the time it takes for the concentrated flow to channelize. Summing tci and tt yields the total time of concentration (tc). With tc, the outlet volumetric flow Q and flow velocity v can be determined. The equations for Q are described in sections “Rational Method” and “Hydraulics” (Manning’s Equation). The estimated final velocity is then iterated until the value converges on the calculated final velocity. The iteration process will yield the true travel time between the initial area evaluation point (i.e. 100-ft along the longest flowpath) and the DMA outlet. Subsequently, the process with yield the correct tc and Q. Table 1 in the next section outlines the times of concentration for each DMA (existing and proposed). Rational Method (per Section 3.1 of the SDCHM) To determine the 100-yr runoff for each drainage area, the following equation was used. 𝑄=𝐶𝐶𝐶 Equation 2 Where: Q = runoff in cubic feet per second (cfs) C = unitless runoff coefficient of the initial area Drainage Study Highland James Subdivision REC Consultants, Inc. Page | 5 I = rainfall intensity in in/hr (see below for equation) A = contributing area in acres We evaluated the rainfall intensity for each DMA using the following equation (from Figure 3-1 in the Hydrology Manual). 𝐶= 7.44𝑃6𝐷−0.645 Equation 3 Where: I= rainfall intensity in in/hr P6 = cumulative precipitation during the most intense 6 hours of the design storm D = duration in minutes To determine the 100-yr runoff (Q100) of each DMA, we used P6 for the 100-yr event and the times of concentration for the 100-yr event (analyzed in the previous section) for the duration to determine the 100-yr peak rainfall intensity. The following table outlines the results from the Rational Method analysis. Table 1. 100-yr Hydrology DMA Tc Q min cfs E1 7.1 1.92 N1a+N1b+N1c 5.2 0.92 N2a+N2b+N2c 5.4 0.91 N3 6.5 0.31 N4 9.7 0.21 N5 6.6 0.32 N6 10.1 0.21 N7 8.3 0.26 N8 8.9 0.22 Modified Rational Method (per Section 3.4 of the SDCHM) The runoff values in the previous section represent the flows leaving each DMA. Each flow will enter the private storm drain system via a catch basin and confluence before leaving the site and entering the City MS4. To quantify the confluence flow, we used the process outlined in Section 3.4 of the Hydrology Manual. At each confluence point, the times of concentration and runoff values were used in combination with the following set of equations to determine the resulting flow. 𝐽𝐽𝐽𝐽𝑡𝐽𝐽𝐽 𝐸𝐸𝐽𝐸𝑡𝐽𝐽𝐽:𝑇1 <𝑇2 <𝑇3 𝑄𝑇1 =𝑄1 +𝑇1𝑇2 𝑄2 +𝑇1𝑇3 𝑄3 𝑄𝑇2 =𝑄2 +𝐼2𝐼1 𝑄1 +𝑇2𝑇3 𝑄3 𝑄𝑇3 =𝑄3 +𝐶3𝐶1 𝑄1 +𝐶3𝐶2 𝑄2 The greatest value of QT1, QT2, and QT3 will be accepted as the resulting flow with the corresponding time of concentration (e.g. if QT2 was greatest, Tc = T2). This is a conservative approach, because friction losses were not considered in the confluence. Friction losses would reduce flow velocity, thus reducing volumetric flow. Drainage Study Highland James Subdivision REC Consultants, Inc. Page | 6 HYDRAULICS See Appendix B for the detailed calculations described in the section. Catch Basin (Weir) Runoff from each DMA will enter the private storm drain system through a catch basin. Each catch basin will have a grate of dimension 1’x1’, thus providing a weir length of 4’. The available head for the catch basins is either a maximum 3”. To determine the flow capacity of the curb inlet, the following equation was used. 𝑄𝑤=𝐶𝑤𝐿𝐻1.5 Equation 4 Where: Qw = volumetric flow of weir in cfs Cw = unitless discharge coefficient of weir = 3.1 (typical) L = length of weir = 4 ft H = available weir head = 3” The flow capacity for the weir was determined to be 1.55 cfs. The maximum 100-yr runoff flowing to a catch basin is 0.92 cfs. Therefore, the weirs are sufficiently sized to convey the 100- yr runoff flows for their respective DMAs. See Appendix B for the detailed analysis. Drainage Study Highland James Subdivision REC Consultants, Inc. Page | 7 Graded Trapezoidal Weir DMAs N1 and N2’s runoff collect in Bioretention BMPs. Lower flows will infiltrate into the soil, while larger flows will overflow into a concrete channel via a trapezoidal weir graded into the sloped sides of the Bioretention basin. The concrete channel will convey flow to a catch basin; the analysis for determining the flow capacity of the catch basin was described in the previous section. To determine the flow capacity of the weir, the weir equation from the previous section (Equation 4) was used. The graded weir was designed as a Cipoletti weir (i.e. 4:1 side slopes), with available head of 3”, and bottom (crest) width of 3’ (used as weir length). The discharge coefficient C will be 3.367 as per Equation 7-7 of the USBR Water Measurement Manual (1997). With this information and equation 4, the flow capacity of the graded trapezoidal weir was determined to be 1.26 cfs, which is greater than both N1 and N2’s 100-yr runoff flow of 0.92 and 0.91 cfs, respectively. Therefore, the graded weirs are sufficiently sized. Pipes The flows within pipes must be evaluated for both the private and public storm drain systems to ensure that the system is sufficiently sized for the 100-yr storm event. To determine the flow capacities of the storm drain pipes, Manning’s Equation (shown below) was used. 𝑄𝑝=1.486𝑛∗𝐴53𝑃23 ∗ 𝑆 12 Equation 5 Where: Qp = volumetric flow in the pipe in cfs n = unitless Manning’s roughness coefficient = 0.013 (typical for public pipes) A = cross-section area of flow in ft2 P = wetted perimeter of flow in ft S = slope of pipe in ft/ft For the private storm drain system, the flows per pipe were first determined using the Modified Rational Method described in a previous section. Once the flows for each section of pipe were determined, Manning’s Equation was used to check that the pipes would flow as open channels (no pressure head) during the 100-yr storm event. See Appendix A for the layout of the private storm drain pipes. The following table summarizes the flow depth in each conduit. Table 2: Private Storm Drain Pipe Hydraulics Pipe L S d h Ax P n Q100 Qfull ft % in ft ft2 ft cfs cfs P1 116.5 2.30% 6 0.41 0.15 1.00 0.011 0.92 1.01 P2 45.6 1.80% 4 0.21 0.06 0.61 0.011 0.22 0.30 P3 16.8 1.96% 8 0.40 0.20 1.13 0.011 1.21 2.00 P4 41.9 1.58% 8 0.45 0.23 1.23 0.011 1.32 1.80 P5 17.4 1.44% 8 0.54 0.28 1.40 0.011 1.57 1.71 P6 117.0 3.65% 6 0.36 0.13 0.92 0.011 0.92 1.27 P7 38.6 0.40% 10 0.56 0.36 1.52 0.011 1.17 1.64 P8 11.7 0.70% 12 0.76 0.59 2.00 0.012 2.74 3.23 For Table 2: L = pipe length S = pipe slope Q100 = 100-yr flow going to pipe as determined by the Modified Rational Method d = pipe diameter Ax = cross-sectional area of flow within pipe P = wetted perimeter of flow within pipe Drainage Study Highland James Subdivision REC Consultants, Inc. Page | 8 h = depth of flow within pipe n = Manning’s roughness coefficient = 0.011 for PVC or 0.012 for RCP Qfull = full conduit flow The following table outlines the results from the hydraulics analysis for the public pipes (City MS4). Table 3. Pipe Hydraulics d 18 48 in A 1.8 12.6 ft2 P 4.7 12.6 ft n 0.013 0.013 S 0.245 0.01 ft/ft Qf 52.0 143.6 cfs Qm 56.2 155.1 cfs Qe/Qm 3.4% 1.2% Qn/Qm 5.3% 1.9% ΔQ/Qm 1.9% 0.7% For Table 3: d = pipe diameter in inches A = full pipe cross-section in ft2 = πd2/4 P = full pipe perimeter in ft = πd Qf = full pipe volumetric flow in cfs Qm = max pipe volumetric flow in cfs = 1.08Qf Qe = 100-yr runoff for the existing conditions = 1.92 cfs Qn = 100-yr runoff for the proposed condition = 2.74 cfs ΔQ = increase in runoff = 1.07 cfs The slopes and dimensions of the city storm drain pipes are referenced from Project No. 2-13 (Plans & Profiles for the Sewer, Water, & Storm Drain Improvements in Holiday Manor), Drawing No. 135-5, dated 09/06/1962. Drainage Study Highland James Subdivision REC Consultants, Inc. Page | 9 CONCLUSIONS This report quantifies a 0.82 cfs increase in peak flow discharge rates associated with the proposed development of the subject property (pre-development peak flow rate = 1.92 cfs, post- development peak flow rate = 2.74 cfs). This increase constitutes a 1.9% and 0.7% increase in the flow in the downstream 18” and 48” diameter storm drain pipes, respectively, which should not have a significant impact on the City storm drain infrastructure. “I hereby declare that I am the engineer of work for this project. That I have exercised responsible charge over the design of the project as defined in section 6703 of Business and Professions code and that the design is consistent with current standards. I understand that the check of project drawings and specifications by the City of Carlsbad is confined to a review only and does not relieve me, as engineer of work, my responsibilities for project design. This Hydrologic/Hydraulic Drainage Report of the Highland James Subdivision in Carlsbad, CA was prepared by me (or under my supervision) in accordance with the criteria established by the San Diego County Hydrology Manual, the Carlsbad BMP Design Manual and in accordance with standard practices”. Drainage Study Highland James Subdivision APPENDIX A Pre-Development Conditions Exhibit (with Location Map) Post-Development Conditions Exhibit ) L_ /I I / I ) I I --,---\ I -/ I I / LEGEND (E) : EXISTING , (N) : NEW/ PROPOSED --- ---(E) PROPERTY LINE - ---(E) MAJOR CONTOUR - --(E) MINOR CONTOUR ====== (E)CURB&GUTTER - -12" SD -(E) 12" RCP STORM DRAIN PIPE - -18" SD -(E) 18" RCP STORM DRAIN PIPE - -48" SD-(E) 48" RCP STORM DRAIN PIPE El (E) STORM DRAIN INLET -~~~-~ (E)RETAININGWALL c=J-(E)ACPAVEMENT ~---(E)BUILDING • • -(E) CONCRETE □---(E)VEGETATION ---DRAINAGE DIRECTION --DMA BOUNDARY @ DMALABEL C VICINITY MAP NTS 0 20 40 80 160 ~~--1-----------11 SCALE: 1" = 40 FEET PRE-DEVELOPMENT CONDITION DRAINAGE AREA MAP POST-DEVELOPMENT CONDITION DRAINAGE AREA MAP DMA EXHIBIT NOTES: 1. ENTIRE SITE IS UNDERLAIN WITH HYDROLOGIC SOIL GROUP B 2. THE APPROXIMATE DEPTH TO GROUNDWATER IS GREATER THAN 15 FT 3. THE SITE DOES NOT CONTAIN ANY EXISTING NATURAL HYDROLOGIC FEATURES (WATERCOURSES, SEEPS, SPRINGS, WETLANDS) 4. THE SITE DOES NOT CONTAIN ANY CRITICAL COARSE SEDIMENT YIELD AREAS TO BE PROTECTED 5. PROPOSED DESIGN FEATURES AND SURFACE TREATMENTS USED TO MINIMIZE IMPERVIOUSNESS INCLUDE TREE WELLS (BMP SD-1) AND IMPERVIOUS AREA DISPERSION (BMP SD-5) SUCH THAT EACH OF THE DMAs N3 THOURGH N8 MAY BE CONSIDERED SELF RETAINING AREAS VIA QUALIFYING SITE DESIGN BMPS 6. STRUCTURAL BMPS WERE INCORPORATED TO MEET WATER QUALITY REQUIREMENTS FOR DMAs N1 & N2. 0 SCALE: 1" =FEET 40 4020 80 160 40 ) ) I / l ◊ EX :=~~~~~=:=====£~~~====:i==:::::::=;::::====-□WY -s I / I I l LEGEND (E): EXISTING, (N) : NEW/ PROPOSED ------(E) PROPERTY LINE (E) MAJOR CONTOUR (E) MINOR CONTOUR (N) MAJOR CONTOUR (N) MINOR CONTOUR ====== (E) CURB&GUTTER ------(E) RETAINING WALL ------(N) RETAINING WALL ' • r:, _ (E) CONCRETE 111----(N) BIORETENTION BMP ~-(N) BUILDING ~ (N) HARDSCAPE ------(E) 12" RCP STORM DRAIN PIPE ------(E) 18" RCP STORM DRAIN PIPE ------(E) 48" RCP STORM DRAIN PIPE E3 (E) STORM DRAIN INLET ------(N) EARTHEN SWALE FLOWLINE ~ 59151 @!z:1 (N)RIPRAPSWALE LOCAL DEPRESSION Cl (N) SD CATCH BASIN 9F' (N)BMPSIGN (N) TREE WELL 10' CANOPY (N) TREE WELL 5' CANOPY --m••· ---1,,,.,__ --II•"•· DRAINAGE DIRECTION .,. • .,,,,.,,,.,..,,..,,,,,.,.,..,., •• ,,,,.,,,.,,,,, OMA BOUNDARY GD OMA LABEL ~ OMA AREA (SF) TYPE/NOTES N1a 1,625 SF DRAINS TO STRUCTURAL BMP -BIORETENTION BASIN PR-1A N1b 11,917 SF DRAINS TO STRUCTURAL BMP -BIORETENTION BASIN PR-1A N1c 605SF SELF-MITIGATING AREA (SMA-1) N2a 1,678 SF DRAINS TO STRUCTURAL BMP -BIORETENTION BASIN PR-1B N2b 11,917SF DRAINS TO STRUCTURAL BMP -BIORETENTION BASIN PR-1B N2c 484SF SELF-MITIGATING AREA (SMA-2) N3 3,571 SF SELF-RETAINING AREA VIA QUALIFYING SITE DESIGN BMPs (SRA-1) N4 3,571 SF SELF-RETAINING AREA VIA QUALIFYING SITE DESIGN BMPs (SRA-2) N5 3,571 SF SELF-RETAINING AREA VIA QUALIFYING SITE DESIGN BMPs (SRA-3) N6 3,571 SF SELF-RETAINING AREA VIA QUALIFYING SITE DESIGN BMPs (SRA-4) N7 3,571 SF SELF-RETAINING AREA VIA QUALIFYING SITE DESIGN BMPs (SRA-5) N8 3,571 SF SELF-RETAINING AREA VIA QUALIFYING SITE DESIGN BMPs (SRA-6) Drainage Study Highland James Subdivision APPENDIX B NRCS Web Soil Survey Hydraulic Soil Group Hydrology Calculations Hydraulics Calculations Hydrologic Soil Group—San Diego County Area, California Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/7/2016 Page 1 of 436683103668320366833036683403668350366836036683703668380366839036684003668310366832036683303668340366835036683603668370366838036683903668400469240469250469260469270469280469290469300469310469320469330469340469350469360469370469380469390 469240 469250 469260 469270 469280 469290 469300 469310 469320 469330 469340 469350 469360 469370 469380 469390 33° 9' 14'' N 117° 19' 47'' W33° 9' 14'' N117° 19' 41'' W33° 9' 11'' N 117° 19' 47'' W33° 9' 11'' N 117° 19' 41'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 11N WGS84 0 35 70 140 210Feet 0 10 20 40 60Meters Map Scale: 1:739 if printed on A landscape (11" x 8.5") sheet. USDA - Hydrologic Soil Group Hydrologic Soil Group— Summary by Map Unit — San Diego County Area, California (CA638) Map unit symbol Map unit name Rating Acres in AOI Percent of AOI CbE Carlsbad gravelly loamy sand, 15 to 30 percent slopes B 0.2 21.4% MlC Marina loamy coarse sand, 2 to 9 percent slopes B 0.5 40.7% MlE Marina loamy coarse sand, 9 to 30 percent slopes B 0.4 37.9% Totals for Area of Interest 1.1 100.0% 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 (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. Hydrologic Soil Group—San Diego County Area, California Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/7/2016 Page 3 of 4 USDA ,., Appendix B.2 Page 1 of 1 Speck Carlsbad 100-yr Hydrology Calculations Site Parameters C,soil_B 0.25 P6 2.60 in Existing 100-yr Hydrology DMA A A A,imp a,imp C n S L1 T1 I1 A1 Q1 z1 h1 Ax1 v1 L L2 v2 T2 Tc I Q z2 h2 Ax2 v2f sf ac sf ft/ft ft min in/hr ac cfs ft ft ft/s ft ft ft/s min min in/hr cfs ft ft ft/s E1 49653 1.14 4340 0.09 0.31 0.020 0.11 100 6.42 5.83 0.17 0.30 50 0.05 0.14 2.2 344 244 4.1 0.65 7.07 5.48 1.92 25 0.137 0.47 4.1 Proposed 100-yr Hydrology DMA A A A,imp a,imp C n S L L1 T1 I1 A1 Q1 z1 h1 Ax1 v1 L2 v2 T2 Tc I Q z2 h2 Ax2 v2f sf ac sf ft/ft ft ft min in/hr ac cfs ft ft ft/s ft ft/s min min in/hr cfs ft ft ft/s N1a 1625 0.037 312 0.19 N1b 11917 0.274 3521 0.30 N1c 605 0.014 0 0.00 0.325 3833 0.27 0.43 0.014 0.135 195 100 5.09 6.77 0.166 0.48 50 0.053 0.14 3.5 95 8.0 0.14 5.2 6.65 0.92 3 0.196 0.12 8.0 N2a 1678 0.039 324 0.19 ` N2b 11917 0.274 3582 0.30 N2c 484 0.011 0 0.000.323 3906 0.28 0.43 0.014 0.121 194 100 5.25 6.64 0.323 0.92 50 0.069 0.24 3.9 94 7.7 0.14 5.4 6.53 0.91 3 0.199 0.12 7.7 N3 3571 0.082 2202 0.62 0.65 0.013 0.018 97 97 6.55 5.76 0.082 0.31 50 0.063 0.20 1.5 N4 3571 0.082 1782 0.50 0.57 0.013 0.010 143 100 9.46 4.54 0.047 0.12 50 0.050 0.13 1.0 43 1.7 0.27 9.7 4.46 0.21 10 0.112 0.13 1.7 N5 3571 0.082 2309 0.65 0.67 0.013 0.014 90 90 6.56 5.75 0.082 0.32 50 0.067 0.22 1.4 N6 3571 0.082 1798 0.50 0.58 0.013 0.008 118 100 9.97 4.39 0.051 0.13 50 0.053 0.14 0.9 18 1.6 0.12 10.1 4.35 0.21 10 0.115 0.13 1.6 N7 3571 0.082 2172 0.61 0.65 0.013 0.010 123 100 8.18 4.99 0.043 0.14 50 0.052 0.14 1.0 23 1.8 0.14 8.3 4.93 0.26 10 0.122 0.15 1.8 N8 3571 0.082 1765 0.49 0.57 0.013 0.013 139 100 8.72 4.79 0.057 0.16 50 0.052 0.14 1.1 39 1.9 0.22 8.9 4.71 0.22 10 0.109 0.12 1.9 49652 1.14 19767 N1a + N1b + N1c N2a + N2b + N2c I I I I I I I I I I I I I I I I I I I I I I I I I I Appendix B.3 Page 1 of 1 Speck Carlsbad 100-yr Hydraulics Calculations Confluence SchematicN2a+ N2b +N2c P1 N7 QT1 P3 N8 P2 N6 QT2 P4 N5 QT3 P5 N4 QT5 P8 Out N1a+N1 b+N1c P6 QT4 P7 N3 Proposed Hydraulics Pipe Contributing L S Tc I Q v d α h Ax P n Q Qfull Q-Q Areas ft %min in/hr cfs fps in deg ft ft2 ft cfs cfs =0 P1 N2a, N2b, N2c 116.5 2.30%5.23 6.65 0.92 6.2 6 229 0.35 0.15 1.00 0.011 0.92 1.01 -0.001 P2 N8 45.6 1.80%8.94 4.71 0.22 3.8 4 211 0.21 0.06 0.61 0.011 0.22 0.30 0.000 P3 N2a, N2b, N2c, N7, N8 16.8 1.96%5.23 6.65 1.21 6.0 8 194 0.37 0.20 1.13 0.011 1.21 2.00 0.000 P4 N2a, N2b, N2c, N6, N7, N8 41.9 1.58%5.23 6.65 1.32 5.6 8 212 0.43 0.23 1.23 0.011 1.32 1.80 0.000 P5 N2a, N2b, N2c, N5, N6, N7, N8 17.4 1.44%5.23 6.65 1.57 5.6 8 241 0.50 0.28 1.40 0.011 1.57 1.71 0.000 P6 N1a, N1b, N1c 117.0 3.65%5.23 6.65 0.92 7.0 6 211 0.32 0.13 0.92 0.011 0.92 1.27 0.000 P7 N1a, N1b, N1c, N3 38.6 0.40%5.23 6.65 1.17 3.3 10 209 0.52 0.36 1.52 0.011 1.17 1.64 0.000 P8 All 11.7 0.70%5.23 6.65 2.74 4.6 12 229 0.71 0.59 2.00 0.012 2.74 3.23 0.000 Confluence Analyses DMA Tc I Q QTn DMA Tc I Q QTn DMA Tc I Q QTn min in/hr cfs cfs min in/hr cfs cfs min in/hr cfs cfs N2a + N2b + N2c 5.23 6.65 0.92 1.21 QT1 5.23 6.65 1.21 1.32 QT2 5.23 6.65 1.32 1.57 N7 8.32 4.93 0.26 1.15 N6 10.1 4.35 0.21 1.00 N5 6.56 5.75 0.32 1.46 N8 8.94 4.71 0.22 1.12 QT2 1.32 cfs QT3 1.57 cfs QT1 1.21 cfs Tc 5.23 min Tc 5.23 min Tc 5.23 min DMA Tc I Q QTn DMA Tc I Q QTn min in/hr cfs cfs min in/hr cfs cfs N1a + N1b + N1c 5.23 6.65 0.92 1.17 QT4 5.23 6.65 1.17 2.74 N3 6.55 5.76 0.31 1.10 QT3 5.23 6.65 1.57 2.74 QT4 1.17 cfs QT5 2.74 cfs Tc 5.23 min Tc 5.23 min Weir Hydraulics Public Pipe Hydraulics Pipe Hydraulics for Minor SD Pipes Cw 3.1 3.367 d 18 48 in N3 N6 N8 L 4 3 ft A 1.8 12.6 ft2 Qn 0.31 0.21 0.22 H 3 3 in P 4.7 12.6 ft d 6 4 4 Qw 1.55 1.26 cfs n 0.013 0.013 A 0.2 0.1 0.1 Qn 0.92 0.92 cfs S 0.245 0.01 ft/ft P 1.6 1.0 1.0 Qw/Qn 168%137%Qf 52.0 143.6 cfs n 0.011 0.011 0.011 Qm 56.2 155.1 cfs S 0.005 0.058 0.005 Qe/Qm 3.4%1.2%Qf 0.47 0.54 0.16 Qn/Qm 5.3%1.9%Qm 0.51 0.59 0.17 ΔQ/Qm 1.9%0.7%