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Home My WebLink AboutPD 2021-0019; SPEER RESIDENCE; DRAINAGE REPORT; 2021-07-28I I I I I I I I I I I I I I I Drainage Study Speer Residence PD202 1-0019/GR202 l-OO14fDWG 530-9A Lot 3, Map No. 4393 3342 Donna Drive Carlsbad, California 92008 Prepared for: Jeff and Marsha Speer 3342 Donna Drive Carlsbad, CA 92008 Prepared by: Christensen Engineering & Surveying 7888 Silverton Avenue, Suite "J" San Diego, CA 92126 (858) 271-9901 July 28, 2021 IT I Introduction This project involves construction of single-family residence on Lot 3 of Map No. 4393, in the City of Carlsbad. The project is located at 3342 Donna Drive. Other improvements include landscaping to treat runoff, walkways, masonry walls and pool & spa. The attached drainage area map is from a topographic survey prepared by Teas Land Surveying, Inc. dated February 26, 2019. No runoff is tributary to the project parcel, only runoff generated from the site, is the subject of this study. Currently, runoff from the site flows onto Donna Drive. Following construction, the same pattern will persist with runoff flowing onto Donna Drive. Proposed pool and spa area are not included in the analysis. The Rational Method was used to calculate the anticipated flow for the 100-year storm return frequency event. I I I ,id Antony K. Christensen RCE 54021 Exp. 12-31-21 iN A2020-113 I I I I 07.28.21 Date I I I Li I I I I I I Calculation 1. Coefficient Determination For residential area From Table 3-1 Soil Type = B Determine per NRCS web Soil Survey CP = 0.25 Pre-construction Impervious area = 6,722 sf Imperviousness pre-construction = (6,722/11,831)100% = 56.8% Post-construction Impervious area = 6,809 sf Imperviousness post-construction= (6,809/11,831)100% = 57.5% C = 0.90 x (% Impervious) + Cp x (1Ô/oImpervious) Pre-construction C = 0.90 x 0.568 + 0.25(1-0.568) C = 0.619 Post-construction C= 0.90 x 0.575 + 0.25(1-0.575) C= 0.624 I 2. Intensity Calculation (From San Diego County Hydrology Manual, Figure 3-3) I = Tc Time of concentration 1.8(1.1-C)Dist. 1/2 ( S'13 ) I Pre-construction slope over the area with the greatest elevation change is (261'-250.5')/122' = 8.61% over the site and the distance traveled is 122 feet and the runoff coefficient is 0.619 pre-construction. I Post-construction slope over the area with the greatest elevation change is (260-250.8')/161' = 5.71% over the site and the distance traveled is 161 feet and the runoff coefficient is 0.624 post-construction. I Tc = 4.7 minutes pre-construction I Tc =6.1 minutes post-construction I I Ix = 7.44 P6 Duration .0.645 Since D= 4.6 min pre-construction and D = 5.1 min post-construction Ix = 2.74 P6 pre-construction Ix = 2.32 P6 post-construction from: San Diego County Hydrology Manual Rainfall Isopluvial Map for 100-year Rainfall Event —6 Hour P6 (100) = 2.7, P24 (100) = 5.0 Adjusted P6 = 2.7 So: Iioo = 2.74 (P6) 11 o = 2.74 (2.7) Loo = 7.4 inches pre-construction boo= 2.32 (P6) Iioo = 2.32 (2.7) Iioo = 6.3 inches post-construction 3. Volume calculations Q=CIA Areas of Drainage Pre-Construction Area of site flowing to street A = 0.266 Acres Area of site flowing to neighboring area B = 0.006 Acres Impervious ROW area C = 0.004 Acres. Qioo (A) = (0.619) (7.4) (0.266) = 1.218 cfs Qioo (B) = (0.619) (7.4) (0.006) = 0.027 cfs Qioo (c) = (0.90) (7.4) (0.004) = 0.027 cfs Qioo = 1.272 cfs pre-construction Qioo flowing to Donna drive = 1.282 - 0.027 = 1.245 cfs I I Post-Construction Area of site flowing to sidewalk underdrain 1 Area of site flowing to sidewalk underdrain 2 Area of site flowing to the street Area of site flowing to trench drain Area of site flowing to neighboring property Area of site flowing to the street Area of pool and spa (retained) Impervious ROW area Qioo (PCA) = (0.624) (6.3) (0.108) = 0.424 cfs Qioo (PCB) = (0.624) (6.3) (0.101) = 0.397 cfs Qioo (PCC) = (0.624) (6.3) (0.020) = 0.079 cfs Qioo (PCD) = (0.624) (6.3) (0.012) = 0.047 cfs Qioo (PCE) = (0.624) (6.3) (0.006) = 0.024 cfs Qioo (PCF) = (0.624) (6.3) (0.014) = 0.055 cfs Qioo (PCP) = (0.624) (6.3) (0.011) = 0.043 cfs Qioo (PCR) = (0.90) (6.3) (0.008) = 0.045 cfs Total Qioo = 1.114 cfs post-construction PCA= 0.108 Acres PCB = 0.10 1 Acres PCC = 0.020 Acres PCD = 0.012 Acres PCE = 0.006 Acres PCF = 0.014 Acres PCP = 0.011 Acres PCR = 0.008 Acres LI] I I I I I I I I I Vioo (PCP) = 0.043 cfs x 6.1 minutes (time of concentration) x 60 = 15.74 cf The pool will have a minimum 3" freeboard. Pool capacity = 566 sfx 3/12' = 141.5 cf> 15.74 cf Therefore, the expected addition of 15.74 cf will be retained. Qioo flowing to Donna drive = 1.114 - 0.024 = 1.09 cfs 1 4. Discussion I The site drains to Donna Drive before and after development except small area flowing to neighboring area. There is a calculated decrease of 0.131 cfs (from 1.245 cfs to 1.114 cfs) for the 100-yr return frequency I event following development. This is due to the increase of time of concentration. 1 5. Tesl for Adequacy The sidewalk underdrain is tested for adequacy and found capable of I conveying the expected volume of runoff. See attached printouts. I I The proposed system on maintenance area requires the use a pump to convey 0.047 cfs (100 year storm) of runoff from 2424 catch basin onto the landscape. The pump will need to be capable of conveying 0.058 cfs onto the landscape. The pump needs to overcome head loss from elevation changes, friction and small bends. Entrance and exit losses are ignored since they are insignificant. The pumps in this system will deliver flow through a 4" PVC drain to the landscape area, changing from 2" outlet from the pumps in a manifold to the 4" PVC drain. The sum of the head losses results in the Total Dynamic Head. The total elevation change is 10'. I To determine other head losses, the velocity in each pipe must be known. To provide conservative values for each head loss it will be assumed that the flow from the pump is at the approximate TDH value. I For the 1/3 HP Goulds pump the maximum flow for a static head of 20 feet is 30 gpm. This is equivalent to 0.067 cfs. I I V=Q/A A=itr2 For a 4" pipe; r = .165 A =it (0.165)2 A= 0.085 ft2 V= 0.245/0.085 V2.88fps The friction loss for the length of pipe can be calculated using the following Hazen - Williams formula: hr= 3.02LD 167 (V/Ch)'85 for a 4" pipe L = 12 ft (from catch basin to landscape) D=4"= 0.33' V = 2.88 Ch = 140 (plastic pipe) hf = 3.02(12)(0.33)''67 (2.88/140)1.85 hf= 0.10' Therefore, the elevation and frictional headloss is TDH= 10+0.10=10.1' Since the Q = 0.047 cfs = 7.48 gal/ft3(0.047 ft3/sec) (60sec/min) =21 gpm Therefore, pump must be capable of conveying 21 gpm with a total dynamic head of 10.1 feet. 1/3 hp Goulds pump is capable of conveying 30 gpm at a head of 20 feet and is therefore adequate. Even assuming some loss for the manifold in the system the pumps will be adequate. The pump will be placed in a storm drain cleanout and an alarm system will be needed to alert the development owner to the failure of the pump. A check valve will be needed to keep the runoff from flowing back into the catch basin, once the pumps shuts off. 0 1 1 249.00 249.25 Elev (ft) 250.00 249.75 249.50 I I I I I I I I I I I I I I I I I I I Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Jul 292021 <Name> Circular Highlighted Diameter (ft) = 0.25 Depth (ft) = 0.20 Q(cfs) = 0.140 Area (sqft) = 0.04 Invert Elev (ft) = 249.54 Velocity (ftls) = 3.32 Slope (%) = 2.00 Wetted Perim (ft) = 0.55 N-Value = 0.011 Grit Depth, Yc(ft) = 0.23 Top Width (ft) = 0.20 Calculations EGL (ft) = 0.37 Compute by: Known Q Known Q(cfs) = 0.14 Elev (if) 250.00 249.75 249.50 249.25 249.00 248.75 Section 0 1 Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. <Name> Circular Highlighted Diameter (if) = 0.25 Depth (if) Q (cfs) Area (sqft) Invert Elev (if) = 249.07 Velocity (ft/s) Slope (%) = 2.00 Wetted Perim (ft) N-Value = 0.011 Crit Depth, Yc (ft) Top Width (if) Calculations EGL (ft) Compute by: Known Q Known Q (cfs) = 0.13 Thursday, Jul 29 2021 = 0.19 = 0.132 = 0.04 = 3.29 = 0.53 = 0.22 = 0.21 = 0.36 Reach (if) Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Jul 29 2021 <Name> Circular Highlighted Diameter (ft) = 0.25 Depth (ft) = 0.18 I Q(cfs) = 0.126 Area (sqft) = 0.04 I Invert Elev (ft) = 251.00 Velocity (ft/s) = 3.32 Slope (%) = 2.00 Wetted Perim (if) = 0.51 N-Value = 0.011 Crit Depth, Yc (ft) = 0.22 I Top Width (if) = 0.22 Calculations EGL (if) = 0.35 Compute by: Known Q Known Q (cfs) = 0.13 I Elev (if) Section 252.00— I I 251.75 251.50 I U 251.25 251.00 I I 250.75 0 1 I Reach (if) - - - - - - - - - - - - - - - - - - - 2.50% slope OOF 2.0- 100 30 w co F- W U- ________ 20 I Cl) W 0 0 —090 -J Cl) -0 95 U.. 10 o 0 _0l• _____ ______ -J W W > 0 EXAMPLE: Given: Watercourse Distance (D) = 70 Feet Slope (s)=1.3% 1.8 (1.1-C) Vi5 = Runoff Coefficient (C) = 0.41 3 VS Overland Flow Time (1) = 9.5 Minutes SOURCE: Airport Drainage, Federal Aviation Administration, 1965 FIGURE Rational Formula - Overland Time of Flow Nomograph 6.1 Directions for Application: From precipitation maps determine 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). 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). Plot 6 hr precipitation on the right side of the chart. Draw a line through the point parallel to the plotted lines. This line is the intensity-duration curve for the location being analyzed. Application Form: (a) Selected frequency 50 year ; (b) P6 = 3 in., P24 = 5.5 P6 54.5 %(2) 6.0 : (c) Adjusted p6(2) = 3 in. 5.5 a,1I s (d) t = min. 4.5 (e) I = 3.2 in./hr. 4.0 3.541 Note: This chart replaces the Intensity-Duration-Frequency 310 curves used since 1965. 2.5 2.0 1.5 20 1.08 !1.6?2.i5?.693,23.774.31 .45 25 003 140 18712331200 3r374204cfl613ic60 30 0.83 1.24 2.07 2.492.90! 3.32 3.73 4j 4.564.98 40 069 103 138 1.72!_2.07; 241 i 270 1 310 345 k379 413 i 3.28 _0 03:o.00 loG 1,30i1Z,1.0G 2.12 2.39 2.0 2.92010 0.4 0,610.82 i.02!1.23- 1.431 1.63 t.84 2.04 2.25 2.45 120 0.34 0.510.68 0.85i1,02 1.191 1.36 31.531 1.70 1.87 2.04 150 0.29 i0.440.59 0.730.8&1.03i 1.18 t32 1 1.471 1.82 1.76 180 0.26 10.30lO,52.:0.650.7810.01, 1.04 1.18 1.31 1.44 1,57 240 0.22 O.3310.43i 54.!0.6$ 0.76087 0.98 1.08 11.19 r 1.30 300 0.10jO.28102& 0.47 0560.6 0.75 0.85 I 0.04 C 1.03 1.13 360 0.17 10.2510.33 0.42 O.500.581 0.67 0.76! 0.841 0.92 1.00 1.0 25,,3 35 4 45 5 1 55 '6 ilti C 6.59 7.90:9.22110.5411.86 13.17! 14.49 15.81 6.3016.3617.42! 8.48 9.54 10.60i11.6612.72 - - - - - - - - - - - - - - - - - - - 2.1 0.1 0. %flhIUhIIHllllH1ItHHuhIIHIllIllhIUhtllllll1llUIIlI$I1IflflIHhIHflflMh1 EQUATION IIIII _ii'Intensity P6 6-Hour _11111111 I_Duration I IuIh!Ihh4hhRg!h1Ih.. 4Ii'hih I II II II I iuniiirn IIIIIIIIIIIIUU .....uani.nal UUII1IIIIIIIII RR5UUHUl IIIIiiiiilIHIll! Rill llllllllllluhlul III !IIUIIIIIHIIIIR!JIHIIJlil IHIHhIIIb 1 II1!!Hi I IRIIIIUIIIIUIIIII IIIIlIh!IllhIIIIIllhIIiIIIlHIllllffl lflhiII liii !Ifi IN I IIIIIII•IIIIIUII uulllnhll Ih;ani;!1 lIllIllIlUhlIllI IIIIllhIU1llllllhIII!!I 11111 111101110 III!iIIllhlll1!!R I IIIHhI1IIIIIIIII IIIIIINIIllhIIIllh1I !!flIHhIII11UMII!iIh!!Uhi!!0hi! I IIIIIII1I1IHOII HIIIOIIIII011hIIIIllIHI1III !OIIIIiIOIIhi!hi!'i I IIIIIIIIIIIIIHII IIIlluhIffluIHh1IllllhI1IllhIIIIlHMfllli!iOIIiIIffl!!llflI1IIi I In Ian i• UUR a*1I UflalI Ii ,i..uIIUl O M ua *N UUSlUlU uuauiui,uu.u1UUU .mUWUUUlIl N.'UItIIIItUU nN•IUI IIIIIIUhtIflflhlfflII5I1I1IU uImuvIuuuiuNWUIu1III2'IIUU a.UIII .... IuIIIIIrnilummu.IuInI iiiiiiuiiuiiiai ..imiiiiiuiuih. I8# IluUflUhIllffltItllUhIHIflhIflhlIIlflhIIIf!lINIlllIlIUIIflflhlIIl auuur- FRI UUlNURUlftHIfthIflIIIIIIPIUIIIIIluhIlIIuIIIIIUIIIIIIlUIUIIIllIIJII1 IllIllhIllllfth1HIIUIIIIIlluhIIUuhIIllhI I I 5 6 78910 15 20 30 40 O 1 2 3 4 5 6 Minutes Hours Duration 4.( 3.1 FIGURE Intensity-Duration Design Chart - Example 34 - - - - - - - - - - - - - - - - - - - San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 6 of 26 Table 3-1 RUNOFF COEFFICIENTS FOR URBAN AREAS Land Use I Runoff Coefficient "C" Soil Type NRCS Elements County Elements % IMPER. A B C D Undisturbed Natural Terrain (Natural) Permanent Open Space 0.20 0.25 0.30 0.35 Low Density Residential (LDR) Residential, 1.0 DU/A or less 10 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 (MDR) Residential, 4.3 DU/A or less 30 0.41 0.45 0.48 0.52 Medium Density Residential (MDR) Residential, 7.3 DU/A or less 40 0.48 0.51 0.54 0.57 Medium Density Residential (MDR) Residential, 10.9 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 (N. Corn) Neighborhood Commercial 80 0.76 0.77 0.78 0.79 Commercial/Industrial (Ci. 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 CominercialJlndustrial (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 0 . - County of San Diego Hydrology Manual 3330 / ... - / / .-- .-. --.. --. . :. -. •'. •--. .-. ..- -.' .- ' ( cce - L - - •- -- - - '-- - -- U) RainfaflIsopIui ia/s 335 .- -, — 331 \ 100 Year Rainfall Event 6 hours VsTk zt SIT E 5y I - ( IsopluvIal (inches) — CARLSAD -- - ------- ENC!NIT;S — 3300 - - - 0 SO.ANftBACFI' - - ( - .-• 300 o U - - V. -- -. -----------. -- -. -. ..- . -. ) ) J U) -J -Cj -' - ..• . -- ---------- % - - - SAN DIE — C' L CAJC 3245 L GROVE . -. .•_—_.. -- - - - GIS saTiGIS '3H CorL - tt) C-) -- - -f rqCW(TADtYAa rf..YfrN,Apfrcrwff-Jr-n _%L aE .- .--3 3230 ---- - -- - a - - - --.- - ------ - ,,-_I- S 3 0 3Miles 0 DArEE . -;--:---- - ...: - . 7 ..-...---- ............ — ( 0 -4,b ....- -------. ....-............. r .: ,- ..- -.--......... ' B / \' ,J 3d ..............-.-..... . ... . . -t A I - ...... - I 3245--------- 3230 ---------- -- -------------- b N- - 323O LiS 0 U) c-S - 5' 5' I b 0 b r tn -OUflV - 3330' 3330 -. 0 Iv ?- •.- -- •'.-'.-' .. .- .. .. . ..., .... .-.... -.. -. 3315 OCEANSFOS '3.W' -. - County of San Diego Hydrology Manual 5% Raiiifi// fxoplui ia/s 100 Year Rainfall Event -24 Hours soptuvial (inches) 3300' ----- ---- -- CARLSBAD ENCNFTAS CC SOLANA BEACH DEL WAR Ci ..-------------- . . .- -... . --.. .- •.:- -. - - .- - - -. 0 CO r- 7 -i - A 0 7c1 ......0 I - 3 0 3 Miles DRAINAGE AREA MAPS I I I I I I I I I I I - ............. 110.43 -,------ N612256E - -.--- - PRE-CONSTRUCTION DRAINAGE AREA MAP - NJ1 IMPERVIOUS 0.154 AC (BLI FLOW PATH A= 0.266 AC (GREEN) FLOWS TO DONNA DR POC QULT = 1.245 CFS w 0 z z 0 0 ! ().004 AC (RED) OW IMP. AREA LOWS TO DONNA DRIVE POST-DEVELOPMENT DRAINAGE AREA MAP I I I I I I I I I I '3)3" PIPE SID AL JNDERDRAIN I00 = 0.397 C —1 = 0.132C$/EAf CB = 0.100 AC (MAG FLOWS TO DONNA DR HRU SIDEWALI JNDERDRAIN 2 cn H PCRI 0.008 AC tBLUE) OW IMPERVIOUfS ARE QIOO = 0.16CFS1 OFF AREA CONVEY BY SIDEWALK UNDERDRAIN 1 ONTO DONNA DRIVE / AREA = 0.108 AC RUNOFF AREA CONVEY BY SIDEWALK UNDERDRAIN 2 Fzle, ONTO DONNA DRIVE A=0.101AC 7777 RUNOFF AREA CONVEY ONTO DONNA DRIVE A=0.O2OAC RUNOFF AREA CONVEY ONTO TRENCH DRAIN, TO 2424 CATCH BASIN' PUMPED TO PCC (GREEN) A= 0.012 AC OTHER RUNOFF AREA CONVE ONTO DONNA DRIVE A= 0.014 AC RUNOFF AREA FLOWS TO NEIGHBORING AREA A= 0.006 AC POOL AND SPA A = 0.012 AC H9ULT. = 1.09 1212 CATCH BASIN (1W. DOWNSPOUT N66°2700E 110.00 7 ROW IMP. AREA CONVEY ONTO DONNA DRIVE A= 0.012AC (I) PCC =0.020A (GREEN) FLOWS TO DO NA DR cn PROPOSED 2424 CATCH B4SIN WITH 113 HP PMP H TRENCH DIMIN J QIOO = 0.424 = 0.141 CFS/EA [ju PIPE IDEWAL UNDERDR4IN PCF = 014 AC RANGE) LowS O DON A DR CP = 0.011 AC (POOL & SPA) II 11 RUNOFF WILL BE RETAINED LTh—AREA/DECK DRAIN (TYP.)! PCE = 0.006 AC (YELLOW) FLOWS TO NEIGHBORING PROPERTY P - I FLOW PATH (RED) I N61c2256E 110.43 0+14.64-- SPLASH P \ PCD = 0.012 AC (RED) (TYP) FLOWS TO TRENCH DRAIN PUMPED TO PCC POST—CONSTRUCTION DRAINAGE APFA MAP 4 -611 PVC DRAIN PIPE (TYP.) PCA = 0.108 AC (CYAN) FLOWS TO DONNA DRIVE THRU SIDEWALK UNDERDRAIN 1 0