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Home My WebLink AboutPUD 16-08; COVE DRIVE CONDOMINIUMS; HYDROLOGY STUDY; 2019-05-06HYDROLOGY STUDY FOR COVE DRIVE CONDOMINIUMS 4547 COVE DRIVE CARLSBAD, CA. MS 04-05 I PUD16-08 DWG 502-7A/ GR 2017-0017 Prepared For: KWD HOLDINGS, LLC. 265 VIA DEL MONTE OCEANSIDE, CA 92058 (619) 733-8379 Prepared By: Florez Engineering, Inc 11440 West Bernardo Ct. San Diego, CA 92131 (858) 229-2493 Original: 10/04/2016 Revised: 03/26/2018 Revised: 05/06/2019 RECEY\TED MAY 22 2313 LAND DEVELOrMENIT ENGINEEkINO r ENGINEER'S CERTIFICATION This Drainage Study has been prepared by Frank Florez, a Registered Civil Engineer in the State of California The Registered Civil Engineer attests to the technical information contained herein and the engineering data upon which recommendations, conclusions, and decisions are based. -—) J—-"---. 5/6/19 "J Dennis Fibman DATE RCE Exp: 12131/2020 1 -4 L L TABLE OF CONTENTS PROJECT DESCRIPTION............................................................................................................1 SCOPEAND PURPOSE ..............................................................................................................1 SITEDESCRIPTION ................................. ... ................................................................................ 1 HYDROLOGIC METHODOLOGY ..................... ........................................................................... I Pre and post development ...........................................................................................3 HYDRAULIC METHODOLOGY .... . ............................................................................................. 1 DetentionBasin ..................................................................................................... .4 OutletPipe .................................................................................................................4 HYDROLOGIC ANALYSIS RESULTS APPENDICES APPENDIX A HYDROLOGIC REFERENCE MATERIAL APPENDIX B HYDRAULIC CALCULATOR APPENDIX C HYDROLOGY MAPS I '.4 PROJECT DISCRIPTION The project proposes the construction of a 3,200 square foot two story two unit residential I condominium with 2-1 car garages on a 0.108 AC (4,676 s.f.) lot. SITE DISCRIPTION The entire site is currently vacant of any structures. The site topographic relief ranges from approximately 12 feet to 13 feet above mean sea level with the lower elevation at the rear of the lot. The site is located at 4547 Cove Drive in Carlsbad California and abuts a navigable canal with direct access to Aqua Hediona Lagoon off the Pacific Ocean. The site drains toward the canal and has rock slope protection along the canal abutting rear property line. SCOPE AND PURPOSE The scope of this study is to determine the post development 100 year storm runoff and to show that this runoff can be safely intercepted and discharied to the abutting canal. HYDROLOGIC METHODOLOGY The small size and short drainage paths of the site makes the time of concentration calculation based on multi-sub-basin drainage paths ineffective. The calculation for the hydrologic runoff is therefore in accordance with the County of San Diego Hydrology Manual, June 2003, for a small single basin drainage shed utilizing the Rational Method equation. The time of concentration to determine the rainfall intensity index will be the intitial area qualifying time of 5 minutes as required by the County Manual. The drainage shed area is the entire site at 0.108 acres (4,676 s.f.) for the pre-develoted condition and 0.108 acres (4,718 s.f.) for the post developed condition. See exhibit B, appendix A. The slight increase in area for the post developed condition is due to the driveway encroachment into the street parkway. The rainfall intensity (I) index was determined using the equation from the Intensity- Duration I • Design Chart, Figure 3-2, taken from the San Diego County Hydrology Manual: From: I = 7.44P6 D 645 Where: P6 = 6-Hour Precipitation in inches = 2.5 inches as shown for the mainland costal area on the County 100 year isopluvial map. L 0 = Duration in minutes = 5 minutes. I = 6.59 in/hr With the intensity the peak runoff can be calculated with the rational formula: I Q=CIA For the pre-developed condition: C = 0.35 1=6.59 in/hr A0.lO8ac(4676s.f.) Q=O.249cf For the post-developed condition: With 2,888 s.f. of impervious surface and 1,457 s.f. of pervious surface. C = (0.98 x 2,888 + 0.35 x 1,457)14,345 = 0.77 1=6.59 in/hr A = 0.100 ac (4,345 s.f.) Q=O.506cjc HYDRAULIC METHODOLOGY The peak 100 year post development discharge of 0.506 cfs is a 106 percent increase from the pre-development discharge of 0.249 cfs by the use of a bio-filtration basin. Because the site was just: dirt and brush this increase in runoff is reasonable. The project incorporates LID Blo-filtration basins that are sized in the SWQMP, by Florez Engineering dated May 6, 2019, under separate cover, to provide a surface area that can pass and treat 85 percentile storm event through an amended soil medium at an infiltration rate of 5 inches per hour per square foot. Therefore, the minimum square foot area of the basin is set in LID policy including a minimum depth of filtration medium of 1.33 feet plus a 0.5 foot layer of crushded rock. This 1.83 feet of material has a porosity of 40 percent. This void ration will provide a storage volume that will atenuate the developed flows. Just how much the dischare will be attenuated is out of the scope of the study because the project is exempt from the dischare restriction in CEQA. L TABULATED HYDROLOGIC I HYDRAULIC COMPUTATIONAL RESULTS Developed 100 year Condition Effective C Tc (mm.) I in/hr Area (ac) Total Qak (cfs) Total Pre-Development 0.35 5.0 6.59 0.108 0.249 Post Development 0.80 5.0 6.59 0.108 0.506 HYDROLOGIC ANALYSIS RESULTS Even though the peak 100 year discharge has increased by 106 percent it dose not present a danger because there is nothing down stream but the Pacific Ocean. r' The Bio-Filtration basins and pervious payers drain out, through a 4 inch perforated sub drain connected to the basin overflow riser. The overflow outlet must be able to pass the 100 year storm. The riser outlet pipe is a 6 inch HDPE. Outlet pipe Capacity: The calculated flow capacity of the overflow outlet pipe is based on the critical depth of the flow through the entrance Considering a 6 inch (0.50 feet) diameter pipe with an entrance flow of 0.506 cfs the critical depth is 0.38 feet and the critical velocity is 3 52 f/s See critical depth calculator in appendix C. The head water build up in the overflow riser to push the required flow into the pipe is: G From the velocity head equation; Assuming an entrance loss k = 0.2 Headwater buildup in riser: Vh = kV2 /29 Vh =12 (3.52)2 / 64.4 = 0.23 feet. HW=Vh+ Dc=0.61 feet Therefore for this flow, as long as the 6 inch outlet pipe has a slope that is steeper than the I critical slope of 1.20 percent the pipe will exhibit entrance control and the headwater will not Li exceed 0.61 feet; See critical slope calculator in exhibit C. I I P F APPENDIX A i HYDROLOGY REFERENCE MATERIAL ii. IL IA VICINITY MAP CITY OF OCEANSIDE .4 project CITY OF VISTA CITY OF SAN MARCOS CITY OF ENCINITAS .4 -J FL U - c C777 c C-7 I= San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 6 of 26 Tabie3-I RUNOFF COEFFICIENTS FOR URBAN AREAS Land Use I Runoff Coefficient "C" Soil Type NRCS Elements County Elements I % IMPER A B C D Undisturbed Natural Terrain (Natural) Permanent Open Space 0* 0.20 0.25 0.30 0.35 Low Density Residential (LDR) Residential. 1.0 DU/A or less tO 0.27 0.32 0.36 0.41 Low Density Residential (LDR) Residential, 2.0 DU/A or less 20 0.34 0.38 0.42 0.46 Low Density Residential (LDR) Residential, 2.9 DU/A or less 25 0.38 0.41 0.45 0.49 Medium Density Residential (IvffR) Residential, 4.3 DU/A or less 30 0.41 P0.45 0.48 0.52 Medium Density Residential (N')R) Residential. 7.3 DU/A or less 40 0.48 0.51 0.54 0.57 Medium Density Residential (MDR) Residential, 1.0.9 DU/A or less 45 0.52 0.54 0.57 0.60 Medium Density Residential (MDR) Residential. 14.5 DU/A or less 50 0.55 0.58 0.60 0.63 High Density Residential (HDR) Residential. 24.0 DU/A or less 65 0.66 0.67 0.69 0.71 High Density Residential (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77 0.78 0.79 Commercial/Industrial ('. Corn) Neighborhood Commercial 80 0.76 0.77 0.78 0.79 Commercial/Industrial (G. Corn) General Commercial 85 0.80 0.80 0.81 0.82 Commercial/Industrial (O.P. Corn) Office Professional/Commercial 90 0.83 0.84 0.84 0.85 Commercial/Industrial (Limited I.) Limited Industrial 90 0.83 0.84 0.84 0.85 Commercial/Industrial (General I.) General Industrial 95 0.87 0.87 0.87 0.87 *The values associated with 0% impervious may be used for direct calculation of the runoff coefficient as described in Section 3.1.2 (representing the pervious runoff coefficient. Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. Justification must be given that the area will remain natural forever (e.g., the area is located in Cleveland National Forest). DU/A = dwelling units per acre NRCS National Resources Conservation Service 3-6 MAXIMUM OVERLAND FLOW LENGTH (LM) & INITIAL TiME OF CONCENTRATION (T Element* DU/ Acre .5% 1% 2% 3% 5% 10% LM Tj LM Ti LM T. LM T. LM Ti L. T Natural 50 13.2 70 12.5 85 10.9 100 10,3 100 8.7 100 6.9 LDR 1 1 50 12.2 1 70 11.5 1 85 10.0 100 9.5 1 100 8.0 100 6.4 LDR 2 50 11.3 70 10.5 1 85 9.21 100 8.8 100 7.4 100 5.8 LDR 2.9 50 10.7 70 10.0 85 8.8 95 8.1 100 7.0 100 5.6 MDR 4.3 50 .10.2 70 9.6 80 8.1 95 7.8 100 6.7 100 5.3 MDR 7.3 50 9.21 65 8.4 80 7.4 95 7.0 100 6.0 100 4.8 MDR 10.9 50 8.71 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 6.0 100 5.4 100 4.3 HDR 24 50 6.7 65 6.1 75 5.1 90 4.9 95 4.3 100 3.5 HDR 43 50 5.3 65 4.7 75 4.0 85 3.8 95 3.4 100 2.7 N. Corn 50 5.3 1 60 4.5 75 4.0 85 3.8 95 3.4 100 2.7 G. Corn 50 4.7 60 4.1 75 3.6 85 3.4 90 2.9 100 2.4 O.P./Coni 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2 Limited I. 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2 General 1. 50 3.7 60 3.2 70 2.7 80 2.6 90 2.3 100 1.9 ii If I San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 12 of 26 Note that the Initial Time of Concentration should be reflective of the general land-use at the upstream end of a drainage basin. A single lot with an area of two or less acres does not have a significant effect where the drainage basin area is 20 to 600 acres. Table 3-2 provides limits of the length (Maximum Length (LM)) of sheet flow to he used in hydrology studies. Initial T1 values based on average C values for the Land Use Element are I also included. These values can be used in planning and design applications as described below. Exceptions may he approved by the "Regulating Agency" when submitted with a II detailed study. -f t Table 3-2 *See Table 3-1 for more detailed description I, 3-12 - - - - - - - - - - - - - - - - - - - 100 30 (1) W w I- w z U 0 20 w z— w C) z I-C,) w 0 -J C,) LL 10 0 cr a:: LU w I- > 0 0 EXAMPLE: Given: Watercourse Distance (D) = 70 Feet Slope (s) =1.3% 1.8(1.1-C)\[i5 Runoff Coefficient (C) 0.41 T = 3v- Overland Flow Time (T) = 9.5 Minutes SOURCE: Airport Drainage, Federal Aviation Administration, 1965 FIGURE Rational Formula - Overland Time of Flow Nomograph 3-3 2.0 F III T - -- -I----- _i --•- --t ---Th- County of San Diego cit:L 33 0 , Hydrology Manual 14 le Rainfall Isopluvials I I, P \ ' . 1OO Yew RInfail Event -6Kours t4--t 1 L1T :IPF NOD I- - -i tT 4 4_Ei ____ - - •-rn - - IeopIuvIa (inches) U Location -TT4i ii±fT ___ __ : •cç- 'fl1iH I tt tuiTT - - - - ---------- -:f -- -•---j- • i 4T - -- - I ' Li J - I __________ 3T4 7,7 ITJ+ DPW.L - • '- st -'MGIS SanGta I T N I - 1 t.J L. ± - I Thu_ ft" NO Nff *S 77 1 --- --f ---• I ---- - - --- -ri- --•- ---- I I Hi fL - ____ ____ - - :.: i to t - H 1J 3 I •1•• TI Ii _______ -. co I ii!Hydrology Manual ng County of San Diego e1 - I ±* C0J H jJj±I HLLLtH -4t'rerstde eOtJnL' H I L IN r4poftew us" we -Ar Ltji \ -1 Rain all kop&Wals lOO Year lialnfajl Event 24 Hours fFL F •-i I \ Ji&J.. 1 -- Iscpuv3(ncho.) Je 6i 100 I _______ ecq - 33 M, fog .•' . I ____ -LI c' rn J I-- JLTT' •I .t ' \ \4 4T!1 ffl!?t: —L' - - 17. _ H -1H'm _ I 3945 I _________________________________ ___________ ___________ • - - I ______________ LLTT DPW t14- GIS1 - : --- .-_ - —•• - I-!a +44 Srn l)1Lgc ( o red' I I t I ThNd F4t JT'4JL+H• t ii± 1hi1-k- 303 MIs IT lI • II t 4 4• /';i:;iiftii ,' I \ 1 T ' I ) 4 Age j ori Al \ / ] OCEANSID S.. PROJECT LOCATION I SOIL GROUP "C" .. I CARLSBAD ' I .1 1• It I k I HYDROLOGIC SOIL GROUP '1 -, Soil Groups Group A Group B Group C Group D Undetermined ______ Data Unavailable APPENDIX B HYDRAULIC REFERENCE MATERIAL El A 10/4/2016 Critical depth in a circular culvert or pipe. Victor Miguel Ponce, San Diego State University on11nechanne107.php: Critical depth in a circular culvert or pipe Formulas 9 = 2 cos [1 - 2 (y/ D) A = (D'/S) (8 - sinO) \V 3) " INPUT DATA: INTERMEDIATE CALCS: OUTPUT: Select: Relative depth Yc / D: Critical depth yc: Sl units (metric) 0.769 0.384 ft U.S. Customary units Angle 6: 245.3° Critical velocity Vc Pipe diameter 0 : 3.520 fps .5ft Flow area A: 0.162 ft2 Discharge I Q :0.506 cfs Top width T: 0.420 ft FrOude number F: 1.000 Calculate =es Your request was processed at 09:07:39 am on October 4th, 2016 161004 09:07:39]. Thank you for running onhinechannel_07. Please call again. [140618] 113 CIRCULAR PIPE GIVEN Inches Feet Dia. = 6 0.25 = Radius Depth= 4.70 0.39 n = 0.013 S = 0.012 CALC'ED Spring Angle = 249.04 degrees A = 0.165 Sf R = 0.152 Q = 0.506cfs V = 3.573 f/s APPENDIX D HYDROLOGY 'MAPS I li LEGEND €)NORTH SCALE: 1" = 10' DIRECTION OF DRAINAGE - — — - DRAINAGE BOUNDARY Cb ul EXISTING BUILDING fl, // Xiz N 4259'19"E CONC WALKWAY 117.03' X/)j <1 , C 00 5\ I \ ' • •'-' '2' T-' / J7 .H< I — I, - + '-.- + EN 77RE'%T.DRA INS TO THE ROCK4SLOPE PRUTC170N. - - - - - - EXIS T1NBA SIN: 4676 SF. =.> 0.108 AC 5 I - Th=50MINUTES 1 '-J'T . -, -• —, —, -' ' - -, ( N ' I ' -__--I s(• + A -- -'- _- \. %J ) \' CUNC WALKWAY N 42°59'53"E 17.03' \ I; 1 -- I' ---- ,_SJ •' -W-ii PER DWG 4-i, I EXISTING BUILDING '1 ' Florez Engineering, Inc. Civil Engineering £ Planning 10732 clIARBONO TERRACE SAN DIEGO CA, 92131 (858) 229-2493 r)ARL IN TON HOUSE PRE DEVEL OPED HYDROLOGY MAP LEGEND B ETENhION BASIN (I ....____ DIRECTION OF DRAINAGE - - - <— - ---'f - - DRAINAGE SWALE DRAINAGE BOUNDARY I) n NORTH SCALE: 1" = 10' D Florez Engineering, Inc. Civil Engineering & Planning 10732 CHAR8ONU TERRACE SAND/EGO CA, 92131 (8581229-2493 DA'L /N TON HOUSE POS T DE VEL OPED 1-/YDROL OG YMAP - PER VIOUS PA VERS SUB-DRAIN TIGH fl /NE 810-INFIL TM Td ' TOB/O-INF/LTRA TION BASIN#1 - BAN# -: ---- - ---- -- - . BIO-/NFILTR4TION . . - 1" -- CONNECT/ONTO- , BAS/1y#1 BAS/N#RISER N. N42°591$"E \ 117.OY :. -+ -- - -~- --i--- -- + UY U LLLL - LtL LLLLL ------------- -. _L IJL LLLLLLLLLLaL ENTIRE HALF LODR4/NS-TO 810-INF/L 1R4 TION BASIN #1: LLLL 2173 SF -'0DAC .S . LLLLLLLELLLL 'h IMPERWWSAREA=1,444SF ='J-- L L L L L L L L L L LI LL L '-PER PERVIOUS PA VERS SUB . - L..ANOSCAPE AREA = 729 SF(' C = 0.35. lilt I ,gk III fit '. L L L L TO BIO-INF/L TM TION BASIN# 1 / ,- • , 77 - - 'SYL.flflIL LI - + - Tc=5.0 MINUTES. -: - + r -; LLLLLLLULLLLLLL :LLLLLLLLLLLLLLLL LLLILLLLLLLLLLLL LLLLLLLLLLLLLLL LL'LLLLLLLLLLLL -- - LLELLLLLLLL L LLLLL LLLLLLLLLLLLLL --- I I I I I I I - L ,/-PERVIOUS PAVERS SUB-DRAIN ' L t- L L TO 8/0-INFIL TRA 7/ON BASIN #2 I )LLLLLLiLLL L LLILLLL44LLL LLLLLLLLLbLLL L iI L '7 41 ENTIRE HALF LOTDAA INS TO 810-WFIL TM TION84SIN#2 . 2359 SF =- 0.054 AC. p--: -. IMPERVIOUS AREA 1,444 SF t C = 0.98. Th n t LANOSCAPEAREA 729 SF C 0.35. \.........- OVERALL C 0.77. .: LLL Tc-50M/NUTES. i-/ - ) LLL. . I LLL. .-:.-- .--'-..•.. .- ..---.•. - .. 'I'll > ._,.).__. I_I ..IIt_1_IIIIIlIII-III-III-II1I1IitI,iiiII 7/1BRLTRA TION Z. CONNECTION TO B - !-. SAS/N#2RISER BIO-/NFIL TM TION BASIN #2 OL/TLETPIPE I I -4- I..4 PER DWG 134-9 TO 8/0-INFIL TM 7/ON BASIN #2