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Home My WebLink AboutCDP 2016-0006; PERLIMINARY HYDROLOGY CALCULATIONS; 2017-09-15Victor Rodriguez-Fernandez, PE. 1283 E Main St., Ste 109, El Cajon, CA, 92021 engineervictorrfaoI .com PH: (760) 357-2434 PRELIMINARY HYDROLOGY CALCULATIONS for 2637 JEFFERSON ST., CARLSBAD CDP 2016-0006 3, U\ C353)) Victor Rodriguez-Femandez, RCE 35373 OF, CA September 15, 2017 RE C \E'I JAN 112018 LAND DEV1LOPVNT ENGINaEJNG Description Existing property is a flat 0.25 Acre residential lot draining with about a 1% slope towards the West towards an existing multi-family development that is accepting the existing flows with an exisitng retaining wall. Existing structures and pool to be demolished. No offsite drainage flows were observed. The project proposes 4 Apartment Units structure with permeable payers driveway and landscaping. There will be an increase of 742 SF of impermeable surface (from 4152 SF to 4894 SF). The drainage proposed will be directed towards the same west property line. There will be no increase of flows by mitigating the imperviousness surfaces increase by providing permeable payers to increase the Time of Concentration of the flows and decrease the peak flow for the south side and a proposed 3" Landscape pond to provide sheet flow as before over the north side tributary area. The expected proposed conditions maximum runoff for the north side of 0.15 CFS will be less than the existing conditions runoff of 0.25 CFS, for the south side proposed 0.09 CFS will be less than existing of 0.23 CFS. For the previous existing pool concrete areas draining to the back of the property, similar conditions are proposed with similar 0.01 Acre tributary areas. In summary, the proposed project proposes to simulate existing conditions and increase of runoff will not be expected. The portion of ground between the existing retaining wall and the property line will receive the same or less peak runoff from the site as before. CALCULATIONS: EXISTING CONDITIONS NORTH AREA C = 0.55 (Per Table 2 for Single Family) L=150' S = (58.3-56.8)/150'= 1% Al =0.11 Ac. 1/2 1.8x(1.1-C)x(L) Tc= ----------------------------(Fig. 3-3) 1/3 S 1/2 1.8 x (1.1-0.55) x (150) Tc= ----------------------------= 12.1 Min > I=4.2(Fig.3-l) Q 100 = CIA = 0.55 x 4.2 x 0.11 = 0.25 CFS over 25'> 0.01 CFS/FT Sheet Flow SOUTH AREA C = 0.55 (Per Table 2 for Single Family) L=190' S = (58.0-56.8)/190'= 0.6% A20.12Ac. 1/2 1.8 x (1.1-0.55) x (190) Tc= ----------------------------= 16.2Mm > I=3.46(Fig.3-1) 1/3 (0.6) ) 100 = CIA = 0.55 x 3.46 x 0.12 = 0.23 CFS CENTER AREA A3 = 0.01 Ac Assume 1=7.0 in/hr (highest chart value for P=2.8) Q 100 = CIA = 0.95 x 7.0 x 0.01 = 0.07 CFS sheet flow PROPOSED CONDITIONS Total Tributary Area = 0.25 Ac C = 0.70 (Per Table 2 for Multi-Units) NORTH AREA A3 = 0.07Ac LO=20' S=3% To = 6.41(90/20) = 1.4 mm. (used value per Table 3-2 for MDR 14.5 DU/Ac) L1 =110' 5 = (57.7-57.0)1110 = 0.6% 1/2 1.8x(0.40)x (110) Tc1= ----------------------------= 15.7 Min (Fig. 3-3) 1/3 (0.6) Tc2 = Time to fill 3" Landscape pond Assuming Tc = 18.4 mm. > Intensity = 3.18 in/hr (Fig. 3-1) Landscape Pond storage Area = (50+30)/2 x 0.3= 12 CF Q3 = CIA = 0.70 x 3.18 x 0.07 = 0.156 CFS Tc2 = 12CF/ 0.156 CFS = 77 Sec. = 1.3 mm Total Tc = 1.4 + 15.7 + 1.3 = 18.4 mm. > Intensity = 3.18 in/hr (Fig. 3-1) Q100 CIA 0.70x3.18x0.07 = 0.15 CFS > 0.15/15' = 0.01 Sheet Flow over proposed Landscape Pond = 0.01 (existing) OK SOUTH AREA The initial AO=0.014 Ac, To = 6.4/(90/30) = 2.1 mm. (used value per Table 3-2 for MDR 14.5 DU/Ac) Assuming Tc = 200 mm. > Intensity = 0.68 in/hr (Fig. 3-1) Payers Storage Area = 3,738 SF x 0.67'x 0.4= 1002 CF AO+A1=0.18Ac. Q = CIA = 0.70 x 0.68 x 0.18 = 0.086 CFS Time to fill Payers subase Ti = 1002CF / 0.086 CFS = 11,651 Sec. = 194.2 mm Total Tc = 2.1 +194.2 = 196.3 mm. 100 yr maximum peak flow AO+A1+A2=0.19Ac. Q 100 = CIA = 0.70 x 0.68 x 0.19 = 0.09 CFS CENTRAL WEST AREA A3 = 0.01 Ac Assume 1=7.0 in/hr (highest chart value for P=2.8) Q 100 = CIA = 0.95 x 7.0 x 0.01 = 0.07 CFS sheet flow VICINITY MAP Jp38m ) BUENA VISTA LAGOON BUENA VISTA WAY 1 BUENA VISTA WAY BUENA PL CYNTHIA LN KNOWLES AV Uj ( -s STRATFORD LN lIE 4 LACUNA DR - - -- - L AW-WOrS 1=001 - 0—___ A A1 0.11 Ac. . - A2 0.12 Ac 190 57,72 -•- U, aarwo,, 00 t0000 tO / S1=(58.3_56.8)/1501.0% S2 = (58.0-56.8)/190 = 0.6% EXISTING TOTAl. TRIBUTARY AREA 11,100 SF = 0.25 ACRES SHEETS FLOWS TOWARDS THE WEST VICINITY MAP LEGEND sT1NGrrgus DESCRIPTION SYMBOL ! 41 1 oH 1'I PROJECT ADDRESS AREA DATA 592020022090:020 Iottt 9. Ut St ASSESSOR PARCEL NUMBER LEGAL DESCRIPTION OUT 520120 SLOT I 02210(9519009,95 Slit 200(901 9002003.290091.1059509 II 0200090025 BOT 5* BO210IC 0L 09 00200(02(020 0229003.01*102020210923. G 100110.3. 0*1 BENCHMAR OWNE 22(0 955000593.01*3. 3.22 2 CA SUt GRAPHIC SCALE; 1= to. 93. a corn.. CA 22021 050109 5QJYr-rUtl22290Z 0010 4-UNITS APARMENT COMPLEX JEFFO50 STr 11 3D, BENCH MARK SOURCE CONTROL REQUIREMENT AND SITE DESIGN BMPSz j NOTES: BOIBOt I100Rt *4BO BOlWS NO InCTEBO rESInS h 1)01 InOINO 11010100 100000 1 00 V -'- SI 0101 101001 II 101101 01. 0010011111 PERMANENT BMPS El 0111000500 0110111 IS 0.B 7000 50.0711000010100 Ci) 000507011 5070 (6070) 700000701001110410) IICSCALE FEET) 0 - " —— I _ d V _ :1;: .:v ; )- WW0B1 t001 701 1140 .0 174.14 / - - -7 , LEGAL DESCRIPTION VICINITY MAP poor 010001 10107 I 0075014570010710001005017417 ------------------------------- 011011232711241. 011010,, 010500510 S CT 0 11 1000001 ____ PRCOJECT ADDRESS - b5 LEGEND masmG fl2WS I : DEECBIPT(00 DWG.NO. SYMBOL 20 0 0114)----------------------------- = 000400001 7.- 14035005110500--------------------------------- ------------- l0104. LEGEND PROPOSED rr000 S : r DESCRIPTION SYMBOL - O0E404I00----------------------------------- ---- -.57______ —.01 3)00 4010 0010710----------------------------_2.60 W •- - - - U - 00BO01050IS ----------------------- -0010 0000 01000001 ----------------------E747t0 I 001201 4.4010 I I 4 SECTION B—B 1000 SECTION A—A CITY OF CARLSBAD AREA DATA IPROPOSED CONDITIONS 100564 0004 . .10 0) 10100 00141001. 40750 TABLE 2 RUNOFF COEFFICIENTS (RATIONAL METHOD) DEVELOPED AREAS (URBAN) Land Use Residential: Single Family Multi-Units Mobile Homes Rural (lots greater than 1/2 acre) Commercial (2) 80% Impervious Industrial 2) 9096 Impervious Coefficient C Soil Type D EXISTING PROPOSED. .65 .t5 .85 .95 NOTES Type 0 soil to be used for all areas. Where actual conditions deviate significantly from the tabulated imperviousness values of 80% or 90%, the values given for coefficient C, may be revised by multiplying 80% or 90% by the ratio of actual imperviousness to the tabulated imperviousness. -Jowever, in no case shah the final coefficient be less than D.50. For example Consider commercial property on 0 soil.' Actual imperviousness 50% Tabulated imperviousness = 80% Revised C = 50 x 0.85 = 0.53 so 82 & INITIAL TIME I E1ement I DU/ I J 1% Acre LNI I Tj Lj.. .IL_ Lsi !.L_ ._ _J_ Natural RU 13.2 70 12.R 8R [0.9 100 10.3 100 8.7 100 6.9 LDo I RU 12.2 70 11.R 8R lu.O 'i.R 100 8.0 100 6.4 1Db 2 11.11 70 10.. P, 8R 9.2 PJO 8.8 100 7.4 100 R8 LDo 2.9 RU 10.7 70 10.0 8R 8.8 9R 8.1 100 7.0 100 R6 MDo 4.3 RU 10.2 70 9.6 80 X J1 9R 7.8 100 6.71 100 R3 9.2 6R 8.4 80 7.4 9R 7.0 100 60 100 _4,8 MDo 10.9 RU 8.7 6R 7.9 80 6.9 90 6.4 100 97 100 4.R MDo 14.R RU 8.2 6R 7.4 80 6.R 90 6.0 100 R4 100 4.3 HDo 24 P0 7 6R 6.1 7R RI 90 4.9 9R 4.3 100 3.R HDo 43 RU R3 6R 4.7 7R 4.0 SR 3.8 9R 3.4 100 2.7 R 60 4.R 7R 4.0 8R 3.8 9R 3.4 100 2.7 d Curn RU 4.7 t, 60 4.1 7R 3.6 8R 3.4 90 2.9 100 2.4 I .P..om RU +'Zl 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2 Limited 1. RD 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 12.2 denerall. RD 3.7 t 60 3.2 70 2.7 80 2.6 1 90 2.3 100 1.9 See Table 3- for more detailed description RatIona' FounuIaQverIand TirneofRow Nomogrph