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HomeMy WebLinkAboutPUD 2018-0008; THREE ON CHERRY; PRELIMINARY DRAINAGE STUDY; 2019-02-04Preliminary Drainage Study Three on Cherry Lot G, Block 1 of Map No, 1777 160 Cherry Avenue Carlsbad, California Prepared for: CHERRY KMA, LLC 6026 WENRICH PLACE SAN DIEGO , CA 92120 Prepared by: Christensen Engineering & Surveying 7888 Silverton Avenue, Suite "J " San Diego, CA 92126 (858) 271-9901 February 4, 2019 RECEIVr- FEB 2 7 20 19 CITY OF CARL::::,R PLANNING DI V'' Introduction This project involves removal of the existing single-family residence and appurtenances from the parcel at 160 Cherry Avenue, in the City of Carlsbad. Following its removal, a 3 unit multi-family residential project will be constructed, including landscaping and pervious paving and walkways. The attached drainage area map is from a topographic survey by Teas Land Surveying, Inc., dated November 23, 2017 and revised January 29 , 2019. No runoff is tributary to the project parcel and so only runoff generated on site, it the subject of this study. Prior to construction the site drains northwest to a neighboring property. Following construction site runoff will be conveyed to Cherry Avenue. Runoff will not flow over neighboring properties . The Rational Method was used to calculate the anticipated flow for the 100-year storm return frequency event. The drain system was tested and found adequate to convey anticipated runoff. Antony K. Christensen RCE 54021 Exp . 12-31-1 9 JNA2018-119 02-04-19 Date -----1. --------------------- --2. ------- Calculations Intensity Calculation (From San Diego County Hydrology Manual, Figure 3-3) Tc= Time of concentration = 1.8(1.1-C)Dist. 112 ( S 1/3 ) Since the slope over the area with the greatest elevation change is (3.7'/150') 2.5% over the site and the distance traveled is 150 ft and the runoff coefficient is 0.45 (29.1 % pre-construction). Post- construction flow is 170' @ 2%, C= 0.61 (51.8% imperviousness post-construction). Tc= 10.6 minutes (pre) Ix = 7.44 P6 Duration -0·645 Since D = 10.6 Ix= 1.62 P6 Tc= 9.1 minutes (post) Ix = 7.44 P6 Duration -0·645 Since D = 9.1 Ix= 1.79 P6 from: San Diego County Hydrology Manual Rainfall lsopluvial Map for 100 year Rainfall Event -6 Hour P6 (100) = 2.6 The six-hour storm is selected over the 24-hour storm due to its closer approximation to the site's time of concentration. So: l100 = 1.62 (P6) 1100 = 1.62 (2.6) 1100 = 4.21 inches (pre) Coefficient Determination For residential area From Table 3-1 hoo = 1.79 (P6) 1100 = 1. 79 (2.6) 1100 = 4.65 inches (post) C=O.45 pre-construction (B soil, 29.1 % imperviousness) ------3. -- ---------------4. --- ------ ,. -- C= 0.61 post-construction (8 soil, 51.8% imperviousness) Volume calculations O=CIA Areas of Drainage Pre-Construction Area of site (no runon) Post-Construction Area of site flowing to Outlet 0-1 (entire site) O100(A) = (0.45) (4.21) (0.160) 0100 (PCA) = (0.61) (4.65) (0.160) 0100 (A)= 0.30 cfs 0100 (PCA) = 0 .45 cfs Discussion A= 0.160 Acres PCA = 0.160 Acres Pre-construction the site runoff flows northwesterly across the neighboring properties. Following development, the site will convey its runoff to Cherry Avenue through three sidewalk underdrains. There is a calculated increase of 0.15 cfs for the 100-yr return frequency event following development, and is conveyed to the same public storm drain, located in Carlsbad Boulevard, as it was pre-construction. --- • ------------.. -- ---------.. -.. .. - -.. - 5. Test for Adequacy The attached program was used to test for adequacy of the sidewalk underdrains. They were found to be adequate to convey the runoff. ,IYpe of conueyance is a: Each Sidewalk underdrain ianeter of conueyance equals .25 Feet 9lope of conueyance equals 2 % Roughness equals .01 -low quantity equals .1500091 CFS Jllfrea equals .0407641 Square Feet Velocity equals 3.679709 FPS --epth of flow equals .2330002 Feet ------------------.. -.. --------.. --- -----APPENDIX ---- .. ---------.... --- ---- • -- • --.. ---------.. --- ------------ -.. .. -------- Feet 5000 4000 Tc Tc L ..6.E = = = = EQUATION (1~f)°·385 Time of concentration (hours) Watercourse Distance (miles) Change in elevation along effective slope line (See Figure 3-S)(feet) .6. E 3000 2000 1000 0 0 0 6' ' 500 '\. 400 300 200 100 30 20 10 5 ' ' '~ ,~~ ~'$ ' ' ' ' ' ' SOURCE: California Division of Highways (1941) and Kirpich (1940) ' L MIies Feet ' '1 0.5 L 3000 ' 2000 1800 1600 1400 1200 1000 900 800 700 600 500 300 200 ' Nomograph for Determination of ' ' Tc Hours Minutes 4 3 2 ' ' ' Tc 50 40 30 20 18 16 14 12 10 9 8 7 6 5 4 3 Time of Concentration (Tc) or Travel Time (Tt) for Natural watersheds FIGURE ~ 10.0 9.0 8.0 7.0 :i 0 .c -;;; Q) .c 6.0 5.0 4.0 3.0 2.0 .s 1.0 ;:o.9 ~0.8 Q) ~0.7 0.6 0.5 0.4 0.3 0. 0. ' N'i---. 1--1--- N. I 'K t--.1 l'h. .... 'r-,. l' r-,..1',. ~ I I'..: j'..., r--."'- I I I ' ,_ C--L--- I I I ' ' ' 5 6 ' "'"-!',I.., .... r--.1. .., .......... I N. 't-,., 'I'-rt--"'' I', r-,_ .., ... r--.w-"' r,.,.,.., .,,.., ""',.., I "-' 'r--. I'~ I: '"' I' I', r,-. ~~ "' .... ~ ..... J'} " l'o!'o ~ t-,., ... ~~,., ~I r,. 1,,... t. I ""t-,., , I = 3.2 in/hr "r-. ~ ~ .... " ~ ~ I" I ... ..... --r-.. "~ ~ ~ ,.,. l'o..._ l ..,~ r-.,.. ~ 'I" ~,.., 'r--. I "" 'I'- ,,,.., "-1..,1' "" ~ ... !'or,. I I I I --I c.... ----~,__ 1--------.. tc = 20 min I I I I l I 1111 I I I 111111 I ' ' ' 7 8 9 10 15 20 30 Minutes ~ ~ r/'r r I rr ~ I ~ ~~ ~ ~~ ~ I ~ ~ :-."' ~~ I ~ "'~ n ~ I I I ~" "' --. 40 50 Duration I I l II I I I I I 11 ! I I I I 11 I I I 1 I I I 11 I EQUATION I I = ?.44 P5 D-0.645 I = Intensity (in/hr) P5 = 6-Hour Precipitation (in) D = Duration (min) I I I I r-... ~ r--.,.,. I 1". '"'1' I I I " "'r-...r-... ........ r-., ! 1, ' . ~ ~ '" ' " ... r I rniR I l 1,r-... r-... 1• "r-i ,.,, r-.. r !'o" r I ~ JI r-... ~ ' I • ' I', "N-LI I! ~ I ' "l'o... I i"'" l I I 1' I II t-.... .. '• ~,..,u I ,~ I "'' I',~ I rt I: r~ I I • I I' I'-.... , ~ 1~ ' ' ~N. r I I •.,_ 1~ I I " r---1' 4~ I I r-.. I ' -· ' ~ ' I I I "4 I I I I ' . . -· -· __ ,_ -I--I----.. I I I I I I I 9' I 0 !:; lJ cil (') 6.0 "§: 5.5 ![ 5.0 g· 4.5 '§' (') 4.0 ffi 3,5 !!!, 3.0 2.5 2.0 1.5 ,-1.0 2 3 4 5 6 Hours Intensity-Duration Design Chart -Example Directions for Application: (1) From precipitation maps determine 6 hr and 24 hr amounts for the selected frequency. These maps are included in the County Hydrology Manual (10, 50, and 100 yr maps included in the Design and Procedure Manual). (2) Adjust 6 hr precipitation (if necessary) so that it is within the range of 45% to 65% of the 24 hr precipitation (not applicaple to Desert). (3) Plot 6 hr precipitation on the right side of the chart. (4) Draw a line through the point parallel to the plotted lines. (5) This line is the intensity-duration curve for the location being analyzed. Application Form: (a) Selected frequency~ year p (b) p6 = _3_ in., P24 = ~ .~ = ~ %(2) 24 (c) Adjusted p6{2) = _3 __ in. (d) Ix = ~ min. (e) I = ~ in./hr. Note: This chart replaces the Intensity-Duration-Frequency curves used since 1965. ! I P6 . 1 1.s j·2 · fs : 3:·_: __ J.s:j _4 ~-s _ s · s.J I 6 Duration I I I i I I • I • I I I I f I I , t ·s 2.63 ,3.9515.21 6.s9 • 1.90,9.22110.54 11 .86 13.11, 14.49 15.81 _t 2.12 'f1s, <i.24 ! 53Qj6.36;1.42; 8.48 ; 9.54 : 10.60 1 : 11.66i 1i?2 10 t.68 . 2.53_: 3.37_! _4.21_; 5.:.0.?! 5._9..Q!.§,?4_ J 58_,_!lc4?._, 9.27 I 10.11 1~ 1}_0_. L9~!.E.:?~±'1.!3-·_89)4~54_! 5.19 _ 5.8._~L§:49 i 701_3 Lu e_ 20 1.08 _ 1.62, 2.15 ; 2,69 ! ~.23 :.~-77. 4.31 4.85 I 5.39 L ~-~~ I ~46 25 0.93 ,t.40, 1.87:2:33!2.80,3.27j 3.73 ! 4.20 j 4.67 ; 5.13 : 5.60 30 0.83 1.24.1.66 2.07,2.49,2.901 3.32 3.73 · 4.15 . 4.56 · 4.98 40 0.69 : 1.Q311.38 : 1.12: 2.07'. 2.4i i 2.76 j 3.10 ; 3.45 '. 3.79 : 4.13 50 0.60 : 0.90! 1.19 . 1.49 : 1. 7~, 2.091 2.39 '. 2.69 g.98 : 3,28 ! 3.58 60 0.53 . 0.80! 1.06, 1.33: 1,59. 1.86 t 2.12 : 2.39 2.65 J 2.92 I 3.18 9.Q 0.41 ,0.6\ 0.82 . 1._02 '. 1.23, 1.~31 1.63 , 1.84 2.04 ! 2.25_ I 2.45 120 0.34 i0.51;0,68 J0,85 ;1,02. 1.19J 1.36 , _1.53 1.JO ! 1.87 . 2.04 150 0.29 !0.44>0.59 0.73 10.88!1.031 1.18 1.32 1.47 1 1.62 1.76 100 ·0:26 fo.3s[o:~2_;0.6s f_o.10;9.s1 ; 1.04_: 1_.18 (~1 : 1.44 1.s1 _ 2~0 0.22 ,o.33!9.:.4:3. o.5~ ,9.6510.16. Q.87 _ o.98 1.oa : 1_:1_9 _1.30 300 0.19 :0.28,0.38! 0.47 ;0,56J0.66( 0.75 1 0.:.85 O.J4 , !_,_03 1.1_3 360 0, 17 [0.251 Q.33J 0.42 !0.50 0.581 0.67 I 0.75 0.84 0.92 1.00 FIGURE ~ San Diego County Hydrology Manual Date: June 2003 Table 3-1 Section: Page: RUNOFF COEFFICIENTS FOR URBAN AREAS Land Use I Runoff Coefficient "C" Soil Type NRCS Elements Coun Elements % IMPER. A B Undisturbed Natural Terrain (Natural) Permanent Open Space O* 0.20 0.25 Low Density Residential (LDR) Residential, 1.0 DU/A or less 10 0.27 0.32 Low Density Residential (LOR) Residential, 2.0 DU/A or less 20 0.34 0.38 Low Density Residential (LOR) Residential, 2.9 DU/A or less 25 0.38 0.41 Medium Density Residential (MOR) Residential, 4.3 DU/A or less 30 0.41 0.45 Medium Density Residential (MOR) Residential, 7.3 DU/A or less 40 0.48 0.51 Medium Density Residential (MOR) Residential, 10.9 DU/A or less 45 0.52 0.54 Medium Density Residential (MOR) Residential, 14.5 DU/A or less 50 0.55 0.58 High Density Residential (HOR) Residential, 24.0 DU/A or less 65 0.66 0.67 High Density Residential (HOR) Residential, 43.0 DU/A or less 80 0.76 0.77 Commercial/Industrial (N. Com) Neighborhood Commercial 80 0.76 0.77 Commercial/Industrial (G. Corn) General Commercial 85 0.80 0.80 Conunercial/Tndustrial (O.P. Com) Office Professional/Commercial 90 0.83 0.84 Commercial/Industrial (Limited I.) Limited Industrial 90 0.83 0.84 Commercial/Industrial (General I.} General Industrial 95 0.87 0.87 C 0.30 0.36 0.42 0.45 0.48 0.54 0.57 0.60 0.69 0.78 0.78 0.81 0.84 0.84 0.87 3 6 of26 D 0.35 0.41 0.46 0.49 0.52 0.57 0.60 0.63 0.71 0.79 0.79 0.82 0.85 0.85 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 nmoff 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 g !:: ~ c:: 8 ~ in .. ~ g ~ ~ ~ Orange I .. 33'30' 33'30' ·' . 11 · County (:) . :: .. $·)< / t-· ::•··-~·:····f~.s .. .1:·.::·.·:::: .. / .. /.'.:.·.·.:-:'.····l _ ... ··· Riverside County ~ •···3.o:•····:~:::<;.:.·/; •... ··•• t .. 33•15 I ~. ,··r; Ci••···<~:::•:: ; <\;~ j . . ~ ..... ·'} p~:' ! ,. ' I ' ~ M',S' .. .. • .· • • ~~f • \ \ \ > V \, •• "',.".c-L-__. ••. 'l..'..·r·-1< ·"" · -\'•.·,;•&8, I ·1 ~....,_ \. :, t .•. 'f .••. . :;:::~:-}.;;:;) ···--·· -0 C)) Cl --· -ENCII 33•00 I --· ~,.. . r I /"; ~-1\rJ·':c:::::._ I : Cl •~ ....... ~ · . y . 1,. :A .· 0 Cl ~ C)) -:, tr> ·········1 ·······~:6· ··. ··· ... \ ·. . .. ... '· · . . 33'00' .t:-.. \ .... ··"•: ~ l <:·:;\ ..... ! 1~··· ::::!. :::i.'.:t::<>-.. ~ .. ·· .... ···.·.~:....... ~ ,r.. I ~·····~··· I V ' .. ··,~ )\\\;\\ • , -;'; ( ,_, . ...... .. --11·····: =.. . -..... ~ .. . .... .: i .· .... I . ,, 1 • / / /~ f •·• ......... '.:• ... 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(':::::•:::::,-· I •~\·· .. "' 32'30' ~ County of San Diego Hydrology Manual • Rainfall lsopluvials 100 Year Rainfall Event -24 Hours lsopluvial (Inches) DPW *GIS ~ S~GIS ~1'1'\dt" ..... ---\\i-'c H:ivc S:,n l>it.y, C:cwcrcd.! N ?1411Wl'll~wmotrW""'1Wlf'VCIIH(IQHD,Dn«f1Uf'fil(S& 4 ClftW\SO,l'CI.UDIIG.alfHOTI.MttOfO,TMIMIUlOW-"'MHTlU OI-IIVlCtWffMUTYANOr!TNtPFOR4P~~ (Ql¥W'll&e,,ad.M...,__........,_ s Tw. ....... .., .................. INC)AG ....... E ...... ~ ...... ---_._..,_ ... _____ ,,,,~ n...~..,.....,.....,_....__.._~...,_ ..-~or..__.._..,.. 3 0 3 Miles ~ ----DRAINAGE AREA MAPS --------------------... -.. ---------- --- ------------------ -------... --.. .. - PRE-DEVELOPMENT DRAINAGE AREA MAP ~ ~ --------............. --'-.. -" I §] l ~ --,,,/ ,,,/ "- ----\ s--\ 'OOM@TI'O©!m :, :, ! RI r.'O@ r ~rc5 ~"' ~I ~~ ii L_______ "-" " \ \ \ \ \ ~~~ '-- AREA•A• £© 0.180AC FLOWS TO NW CORNER THEN TO NEl8HBORIN PROPERTY I L -lsUIJ~U l2l~. -PR&CONSTRUCTION DRAINAGE AREA MAP -----------..,. \ \ l I ~[Q)@@&@[g ~~rn lOTID I ~W&!!J1, I ~------------..... ---- (iJ ~'ij~ lO~~~ ~ s:> ~~~ ' \ \ \ \ \ I\ : \ I \ I I I _______ ] r-- 1 "- I "- 1 I @©©l I (---..,. I J / ........_J ~--- ~; ~1 ~@ (\!:;i)~ w ~ /"-2 :! I > a: I a: /" I W " :I I \I 0 I --- '..J l<l---30.QQ l07r~ IBILOCK1 PAllSADES HE~GH!l'S MAfP' NO. 1T17 m®'TI' &I?~~OOTr ~-\ .---r-.. \ @~ \ \ \ \ \ \ 4 -- -------------------------------- - POST-DEVELOPMENT DRAINAGE AREA MAP ----------........... ,__ '-.. ld~ --------"' "-"-"' '\ '\ \ \ \ j i -POS~CQNSTRUCTION DRAINAGE AREA MAP ------ LANDSCAPE l07rD \ \ ~l ii LANDSCAPE EXISTBLDG. 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I; ~-~ -en---------= :_ -fJl_ -_.--/ --r:-----~ • -•:•rt,::,·~;:•~:•.~(;•~ .. _.:,:_.,:.- ------~ -------...------------------------------------------/ ---------1-..::=----:::: 1 •::','->~·~;~.;~ :'~ ... :.::.~·:~:t ,:. --. -----_..,._ __ --__ .-----...-------~ ---___. ...... ' -.. . ... . , '. -~ ~-=--_---~ --r"'-=~~?,--,,-.. ---::::: ----------~--~___::-----_-:--_,;~ --------. . . . J ..... , ••• - .-~ ~ ~~ --~~~~~4~~~ AREA •PCA• 0.180AC FLOWS TO CAT~llAslN AND TI-IEN IS PUMPED TO A GRAVITY CATCH BASIN AN TI-IEN TO SIDEWALK UNDERDRAJNS ON CHERR' AVENUE IL.OT~ IBlOCK i PAIIJSAIDIES !HHE~GH7rS IMAP NO. 1717 ' 5' WOOD FENCE -\ \ EXIST APARTMENT BLDG. \ \ \ \ GRASS \ \ \ \ \ \ \ \~ "-