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Home My WebLink AboutCDP 14-13; HIRSCHKOFF RESIDENCE; DRAINAGE STUDY FOR HIRSCHKOFF RESIDENCE; 2015-06-12(CDP 14-13/CDP 14-14) RECORD Copy Htia1 Date CITY OF CARLSBAD ENGINEERING DIVISION DRAINAGE STUDY FOR HIRSCHKOFF RESIDENCE Jefferson Street ENGINEER OF WORK VINCENT L. SAMPO - RCE 44,173 \ "CEIVEWD", JUN 8Ol01 LAND DEVELOPMENT PREPARED BY: ENGINEERING SAMPO ENGINEERING, INC. 171 SAXONY ROAD, SUITE 213 ENCINITAS, CA 92024 760-436-0660 Hirschkoff Residence Sampo Engineering, Inc. CDP 14-13/CDP 14-14 6/12/2015 Standard Development Project 1 TABLE OF CONTENTS Criteria Hydrology Introduction Hydrology: Existing Basin 1 Hydrology: Existing Basin 2 5.. Existing Basin 1 & 2 Area Exhibit Hydrology: Existing Basin 3 (Off Site) . Existing Basin 3 (Off Site) Area Exhibit Hydrology: Existing Basin 4 (Off Site) Existing Basin 4 (Off Site) Area Exhibit Hydrology: Proposed-Basin 1 Proposed Basin 1 Area Exhibit Proposed Basin 1 Impervious Area Exhibit Storm Drain Hydraulic Calculations Curb Outlet Pipe Flow Velocity Calculations Hirschkoff Residence Sampo Engineering, Inc. CDP 14-13/CDP 14-14 6/12/2015 Standard Development Project 2 Hydrology Study For: Hirschkoff Residence, APN: 155-180-28 Criteria: Use the current County of San Diego Hydrology Manual "Rational Method". Design for a 100-year frequency storm using the County of San Diego 6 hour and 24 hour precipitation isopluvials. Runoff coefficients are based on soil type "D". "C" factors have been weighted based on the individual "C" factors for different surfaces (i.e. concrete= 0.95), and the areas of the individual surfaces. Times of concentration (Tc) are determined from the urban overland flow formula. Refer to the attached drainage map for basin areas and locations. Hydrology Introduction: The subject property is approximately 0.28 1 gross acres and is located on the northwesterly side of Jefferson Street adjacent to and south west of Interstate 5 in the City of Carlsbad. The property has not been previously developed but there is an existing graded pad. The entire lot currently sheet flows northwesterly to the Buena Vista Lagoon. A small portion of property adjacent to and southwest of the subject property drains onto the subject property. No storm water from Jefferson Street drains on-site. The site contains 2 hydrologic basins: the upper portion (Basin 1) that contains the building pad where all improvement will be located, and the lower sloped area (Basin 2). Basin 1 (Existing. and Proposed) drain northwesterly from the adjacent property at an approximate grade of 4% until reaching the top of a 2:1 slope above the graded pad. Stormwater runoff continues northwesterly down said slope through the existing pad at an approximate slope of 3.6% before reaching the rear top of slope. All improvements and grading will be located within Basin 1. Basin 2 (Existing and Proposed) drain from the top of slope in the rear yard to the northerly property line and ultimately to Buena Vista Lagoon. No improvements or grading are proposed in Basin 2 therefore historical drainage patterns will be maintained. The owner proposes to construct a new single-family residence, a permeable paver driveway, flatwork, landscaping, and associated improvements, etc all located within Proposed Basin 1. The project anticipates an increase in runoff due to the increase in impervious surface area from the building footprint. The Proposed Basin 1 storm water runoff will be conveyed by pressure pipe from the lower pad to Jefferson Street via storm drain, flow through planters, and a pump system to the existing curb and gutter in Jefferson St. Hydrologic investigations were done for the northerly curb and gutter capacity of Jefferson Street as well as storm drain capacity calculations for the downstream 18" ACP public storm drain at the intersection on Jefferson St. and Las Flores that discharges to Buena Vista Lagoon. Please see attached calculations for the anticipated flows from the proposed development, storm drain sizing/hydraulic calculations, and curb and gutter capacity calculations. Hirschkoff Residence Sampo Engineering, Inc. CDP 14-13/CDP 14-14 6/12/2015 Standard Development Project 3 DRAINAGE STUDY CALCULATOR JN: 14-107 Hirschkoff DATE: June 12, 2015 EXISTING BASIN # I DESCRIPTION: Northeasterly portion of subject property from Jefferson Street to the rear top of slope. Area = 9,420 SF = 0.216 AC (Pervious)(C0% IMPER) + (lmpeMousXC_, IMPER) (8570 sf)(0.35) + (850 sfX0.95) = = = 0.4 Total Area 9420 sf I = 1.8(1.1-C)(D)112 - 1.8(1.1.35&20)1 = 10.16 (S)"3 - (7.7) MIN ho = 7.44 P8 DT,, -0.045 = 7.44(1.6)(10.16)° = 2.67 IN/HR iso = 7.44 P8 = 7.44(2.1X10.16)5 = 3.50 IN/HR 1100 = 7.44 P6 DTc,° = 7.44(2.5X10.16)45 = 4.17 IN/HR 210 = CIA Q50 = CIA Qioo = CIA * Per San Diego County Hydrology Manual 2003 = (0.40X2.67 INIHR)(0.216 AC) = 0.23 CFS (0.40)(3.50 IN/HRXO.216 AC) = 0.30 CFS = (0.40)(4.17 INIHRXO.216 AC) = 0.36 CFS Hlrschkoff Residence COP 14-13, CDP 14-14 Sampo Engineering, Inc. Standard Development Project 6/1212015 EXISTING BASIN #2 DESCRIPTION: Southwesterly portion of the subject property from top of slope to the rear property line Area = 4,710 SF 0.108 AC C = CI,,ER Natural - (Table 3-1, San Diego County Hydrology Manual) = 0.35 Li = 1.8(1.1-C)(D)" - 1.8(1.1-.35X53)1'3 = - (66)13 2.43<5.00 MINIMUM (S)113 USE 5.00 MIN 110 = 7.44 P6 DT,, -0.845 = 7.44(1.6X5.00)0645 = 4.22 IN/HR 150 = p -0.645 7.44 6DTCI = 7.44(2.1X5.00)°645 = 5.53 IN/HR !ioo = 7.44 P6 DT,, -0.645 = 7.44(2.5X5.00)4645 = 6.59 IN/HR QIO = CIA = (0.35)(4.22 IN/HR)(0.IO8AC) = 0.16 CFS 5o = CIA . = (0.35X5.531N/HR)(0.IOBAC) = 0.21 CFS Qloo = Cl A = (0.35X6.59 IN/HR)(0.I08AC) = 0.25 CFS Hirschkoff Residence COP 14-13, CDP 14-14 Sampo Engineering, Inc. Standard Development Project 6/12/2015 EXISTING BASIN #3 (OFF SITE) DESCRIPTION: Portion of Jefferson St, the hillside to the east and a small portion west of Jefferson St. tributary to the gutter north of the curb inlet at the northeast corner of Jefferson and Las Flores Intersection AREA = 78.410 SF = 1.800 AC = C IMPER. M0R109 DLJIAC w/ Soil Type D (Table 3-1 of San Diego County Hydrology Manual) = 0.6 _C2 = CO%MER (Table 3-1, San Diego County Hydrology Manual) = 0.35 - 1.8(1.1 - C1)(D1)"2 - 1.8(1.1_.60)(100)1 7.14 MIN - - = (S1)113 - T2 - 1.8(1.1 -C2)(D2)112 - 1.8(1.1-.35X40)' - = 2.92 MIN — lI3 (S2, (25)' 10.06 MIN TOTAL Lw = 7.44 P6 D.r ° 645 = 7.44(1.6X10.06)°645 = 2.68 IN/HR ho = -0.645 - 7.44P6 Di1 - 7.44(2.1X10.06).0645 = 3.52 IN/HR 1100 .0.645 oo = - 7.44 Pe DTCI - 7.44(2.5)(10.06)'0645 = 4.20 IN/HR 2 IO = C1 I A = (0.60X2.68 IN/HR)(1 .80 AC) 2.90 CFS = C1 IA = (0.60X3.52lN/HR)(1.BOAC) 3.81 CFS Q 10 = C1 I A = (0.60X4.20 IN/HR)(1 .80 AC) 4.53 CFS Hirschkoff Residence CDP 14-13, COP 14-14 Sampo Engineering, Inc. Standard Development Project 6/12/2015 EXISTING BASIN #4 (OFF SITE) DESCRIPTION: Offsite area tributary to the two curb Inlets at the intersection of Jefferson Street and Las Flores AREA = 164,221 SF = 3.77 AC = C IMPER M0R109 DU!AC wl Soil Type D (Table 3-1 of San Diego County Hydrology Manual) = 0.6 _C2 = Co%I,ER (Table 3-1, San Diego County Hydrology Manual) = 0.35 Overland Flow 1.8(1.1 - C1XD1)1 - 1.8(1.1.60)(50)1 Id = (S1)113 - (1.0)113 = 6.36 MIN 1.8(1.1 - C2XD2)"2 - 1.8(1.1-.35)(30) - .1.2 = (S2)1'3 - (23) - 2.60 MIN Gutter Flow 1.3 = 350 FT x 3.8 FT/S 1 MIN 60S/MIN = 1.50 MIN 10.46 MIN TOTAL !io = .0.645 6 DTC1 = 7.44(1.6)(10.46)4.645 = 2.62 IN/HR 150 = 7.44 P6 DT,, -0.645 = 7.44(2.1X10.46).0645 = 3.44 IN/HR !ioo = 7.44 P6 DT,, -0.645 = 7.44(2.5)(10.46).0645 = 4.09 IN/HR 10 = C1 I A = (0.60X2.62 IN/HR)(3.77 AC) = 5.92 CFS 50 = C1 I A = (0.60X3.44 IN/HR)(3.77 AC) = 7.77 CFS ioo = C1 I A = (0.60X4.09 IN/HRX3.77 AC) = 9.26 CFS Hirschkoff Residence CDP 14-13, COP 14-14 Sampo Engineering, Inc. Standard Development Project 6/12/2015 EX/SIINGHYDROLOGYFOR LU 1 "--60' =60' HIRSCHKOFF RESIDENCE I VACANT PROPERTY ON JEFFERSON ST 0 30 60 120 PROPOSED BASIN #1 DESCRIPTION: Northeasterly portion of subject property from Jefferson Street to the rear top of slope. AREA = 9,420 SF 0.216 AC =(A, pmOJCO% IMPER) + (A1 ImpeMous)(C_1oo,6 IMPER)+ (A3 1mpe,vlojs)(C.3016 IMPER) - Total Area * - (3,102 SF)(0.35) + (3,326 SFXO.95) + (2,992 SF)(0.45) = 059 - 9,420 SF T = 1.8(1.1 - C1)(D1)12 - 1.8(1.1-.35)(120)'12 - (Si)hhi - (4.2)' - 9.19 MIN 110 = ,s D LJ -0.645 = 7.44(1.6)(9.19)° = 2.85 IN/HR Iso = - 645 - 7.44.6DTC1 7.44(2.1)(9.19)0645 = 3.74 IN/HR 1100 = 7.44 P6 D1 °645 = 7.44(2.5)(9.19)4 = 4.45 IN/HR 10 = CIA = (0.59X2.85 IN/HR)(0.216AC) = 0.36 CFS 50 = CIA = (0.59X3.74 IN/HR)(0.216AC) = 0.48 CFS g10 = CIA = (0.59X4.45 lNIHR)(0.216AC) = 0.57 CFS Determine gutter depth of flow on east side of Jefferson Street: Q100 = 4.53 CFS (Existing Basin #3) + 0.57 CFS (Proposed Basin #1) = 5.10 CFS From County of San Diego Gutter and Roadway Discharge-Velocity Chart For gutter slope = 0.5% and Q5.10 CFS, Depth = 0.43 ft From survey data of street cross sectons at 0.43 feet gutter depth the street will flood approximately 5 to 8 feet west of the easterly curb line, which will allow for two lanes of traffic in the flooded condition and will not rise to the crown elevation of the street in a 100 yr event (See attached chart). Existing basins 2-4 are outside of this proposed project area or offsite. Therefore, the existing basins hydrology Is to remain in the same existing condition. Per San Diego County Hydrology Manual 2003 Hirschkoff Residence CDP 14-13, CDP 14-14 Sampo Engineering, Inc. Standard Development Project 6/12/2015 STORM DRAIN HYDRAULIC CALCULATION DESCRIPTION: MAXIMUM STORM DRAIN CAPACITY & HEIGHT CALCULATIONS FOR 18" ACP PUBLIC STORM DRAIN AT THE INTERSECTION OF JEFFERSON STREET AND LAS FLORES. THE PIPE DISCHARGES DIRECTLY TO BUENA VISTA LAGOON. 100 = 9.26(Q 100 Ex. Basin 4) + 0.57 (Q 100 Proposed) = 9.83 CFS Maximum Storm Drain Slope = 3.6% (see attached As-Builts) Maximum Capacity for 18" SD (ä 3.6% QMAX = 1.49 ARmSIt2 .QMAX = 1.49 (1.77) (0.376) w (0.036)1,2 = 20.05 CFS 0.013 Q'oo<Qmax OKAY Maximum Water Height in SDMH Q CA /2 g (H - d/2 + Val2g)1'2 9.83 = (0. 62)(1. 77)i 2(32. 2)(H - 0.75) 8.96 = / 2(32.2) (H - 0.75) 1.12 = H-O.75 = 1.87 FT Hirschkoff Residence CDP 14-13, CDP 14-14 Sampo Engineering, Inc. Standard Development Project • 6/12/2015 SAMPD .° P4BINECRSNQ. INC. I ... PIPE FLOW VELOCITY CALCULATOR Calculations show the anticipated velocity In the 4" and 6" stormdraln pipe that convey storm water from the pressure/gravity cleanout to the existing curb and gutter In Jefferson Street. The exsiting curb and JN. 14-107 gutter in Jefferson Street is 0.63' high in the area of 40 storm drain curb outlet connection. Hirschkoff DATE: June 12, 2015 6" PVC PIPE = 0.57 CFS = 0.570 CFS = 6.00 IN = 0.500 FT = 1.00 % = 0.01 = 0.011 (Roughness Coefficient for PVC) = 0.011 K' - Q - (0.57)(0.011) - 040 - - d S112 - (0.5)A8/3(0.01)1/2 - For the K' value found above, the corresponding Did value can be found In Table 7-14 of King's Handbook Did = 0.720 (Per Table 7-14) D = (0.72)(0.5) = 0.360 FT For the Did value found above, the corresponding Ca value can be found In Table 7-4 of King's Handbook a = 0.605 (Per Table 7-4) A Ca d2 = (0.605X0.5)A2 = 0.151 FT V = Q = 0.57 = 3.77 FTiS - A 0.15 411 PVC PIPE (0.63' HIGH CURB IN JEFFERSON STREET) = 0.5713 CFS = 0.190 CFS = 4.00 IN = 0.33 FT = 1.00 % = 0.01 n = 0.011 (Roughness Coefficient for PVC) = 0.011 - - an - (0.19X0.011) - - 0.389 d°'3 S' - (0.334)8I3(0.01)A1/2 For the K' value found above, the corresponding Did value can be found In Table 7-14 of King's Handbook Did = 0.710 (Per Table 7-14) 'I. D = (0.71 )(0.334) = 0.237 FT For the Did value found above, the corresponding Ca value can be found in Table 7-4 of King's Handbook _Ca = 0.605 (Per Table 7-4 A = C.d2 = (0.605)(0.334)A2 = 0.067 FT - a - 0.57/3 - - 2.82 F T iS -. A - 0.07 Hirschkoft Residence COP 14-13, COP 14-14 Sampo Engineering, Inc. Standard Development Project 6/1212015 ______________________________I(ViIiJ 1111111 I' 1iIJiiiiIiItijIIi1II:Iq;I///"///JII1;II;ffllj/,1;111111 11111 I IiIii!iil!IIi1;!uii:' iIIIIIIIII1IlIIIIIIIIIIIII!! _____ 1IIIIRJi!iIIIiIII!IIIIiiillI/ll'iii///II!ii!Ifl!i!/1;/j;/:;;j! 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