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Home My WebLink AboutCDP 98-01A; La Costa Glen Skilled Nursing Center Expansion; La Costa Glen Skilled Nursing Center Expansion; 2008-01-02PRELIMINARY DRAINAGE STUDY FOR LA COSTA GLEN SKILLED NURSING CENTER EXPANSION S.D.P. 98-01(A) C.U.P. 98-01(A) C.D.P. 98-01(A) V08- Original: January 28, 2008 JN: 021039 Prepared by: O'Day Consultants, Inc. 2710 Loker Avenue West, Suite 100 Carlsbad, CA 92010-6609 Tel: (760)-931-7770 Fax: (760)-931-8680 George RCE 32014 Exp. 12/31/08 Date PRELIMINARY DRAINAGE STUDY LA COSTA GLEN SKILLED NURSING CENTER EXPANSION TABLE OF CONTENTS DECLARATION OF RESPONSIBLE CHARGE 1 1.0 INTRODUCTION 2 1.1 PURPOSE OF STUDY 2 1.2 SITE CHARACTERISTICS 2 1.2.1 Existing Conditions 2 1.2.2 Proposed Conditions 2 1.3 SOIL CLASSIFICATION 3 1.4 SITE VICINITY MAP 3 2.0 RATIONAL METHOD DESCRIPTION 4 3.0 RUNOFF CALCULATIONS 4 3.1 EXISTING CONDITION 4 3.2 PROPOSED CONDITION 5 3.3 EXISTING AND PROPOSED RUNOFF COMPARISON 5 4.0 CONCLUSION 6 5.0 REFERENCES 7 APPENDICES: APPENDIX A - EXHIBITS • EXISTING CONDITION HYDROLOGY MAP • PROPOSED CONDITION HYDROLOGY MAP • HYDROLOGIC SOILS GROUPS APPENDIX B - HYDROLOGY CHARTS • RAINFALL ISOPLUVIALS • INTENSITY DURATION DESIGN CHARTS • NOMOGRAPH FOR DETERMINATION OF TIME OF CONCENTRATION • RUNOFF COEFFICIENTS FOR URBAN AREAS APPENDIX C - CAPACITY CALCULATIONS • EXISTING STORM DRAIN CAPACITIES <$$$^ PRELIMINARY DRAINAGE STUDY LA COSTA GLEN SKILLED NURSING CENTER EXPANSION DECLARATION OF RESPONSIBLE CHARGE I, hereby declare that I am the Civil Engineer of work for this project, that I have exercised responsible charge over the design of the project as defined in section 6703 of the business and professions code, and that the design is consistent with current design. I understand that the check of the project drawings and specifications by the regulating agency is confined to the review only and does not relieve me, as engineer of work, of my responsibilities for project design. _ _ Geqirge O'Day^E 32014 "Date PRELIMINARY DRAINAGE STUDY LA COSTA GLEN SKILLED NURSING CENTER EXPANSION 1.0 INTRODUCTION 1.1 PURPOSE OF STUDY The purpose of this preliminary hydrology study is two-fold: 1) to determine the potential hydrologic impacts of the La Costa Glen Skilled Nursing Center Expansion proposed development; 2) to verify the capacities of the existing drainage facilities to ensure accommodation of the proposed drainage conditions. This report compares the proposed development hydrology condition with the existing hydrology condition using the Rational Method as outlined in the County of San Diego Hydrology Manual, June 2003 (SD County 2003). This report analyzes 100-year six-hour storm event flows for the existing and proposed site conditions. The calculated Q values are used to determine the capacity of existing and proposed drainage structures in accordance with the City of Carlsbad Engineering Standards, 2004 to determine adequacy to accommodate run-off. 1.2 SITE CHARACTERISTICS 1.2.1 Existing Conditions The 4.53 acre site currently consists of a skilled nursing facility building with a footprint of approximately 67,308 square-feet (1.55 acres) and 91 on-grade parking stalls with private driveways along the front and rear of the building. Two separate on-site private drainage systems collect and convey runoff generated on- site to public storm drain systems that ultimately discharge into two separate depollutant basins downstream. See Appendix A for Existing Condition Hydrology Map. 1.2.2 Proposed Conditions The proposed expansion of the skilled nursing facility will increase the current building footprint area to approximately 68,353 square-feet, an increase of 1,045 square-feet. As a result of the larger building footprint, four existing parking stalls will be eliminated, the existing on-site private drainage system will be modified to accommodate expansion and the total impervious surface of the site will have a slight increase. Existing drainage patterns will remain relatively the same except for the said increase of impervious surface. See Appendix A for Proposed Condition Hydrology Map. PRELIMINARY DRAINAGE STUDY LA COSTA GLEN SKILLED NURSING CENTER EXPANSION 1.3 SOIL CLASSIFICATION The Soil Hydrologic Group for this preliminary drainage study is Type 'D' soil as determined by using the County of San Diego Hydrology Manual Soil Hydrologic Groups Map. A full size and project specific copy of the Soils Hydrologic Groups Maps are provided in Appendix A. 1.4 SITE VICINITY MAP CITY OF OCEANSIDE HIGHWAYj CITY OFSAN MARCOS CITY OF ENCINITAS VICINITY MAP NO SCALE PRELIMINARY DRAINAGE STUDY LA COSTA GLEN SKILLED NURSING CENTER EXPANSION 2.0 RATIONAL METHOD DESCRIPTION The rational method, as described in the SD County 2003 manual, was used to generate surface runoff flows, which were then used to size the proposed drainage facilities and to verify the capacity of the existing drainage facilities. Rational equation: Q = CIA Q = peak discharge in cubic feet per second (cfs) C = runoff coefficient (varies with surface) I = intensity (varies with time of concentration) A = Area in acres The design storm for this project is the 100-year event; the corresponding 6-hour rainfall amount (Ps) and 24-hour rainfall amount (P2/0 were found using the Isopluvial Charts in Appendix B. The Pe and Pi4 values are given in the following table. 6-hour and 24-hour Rainfall 2-year 10-year 100-year P6 1.2 1.7 2.7 P24 1.9 3.1 4.5 Pfi/P24(%) 63.2 54.8 60.0 Runoff coefficients for each area were obtained from the table included in Appendix B. For areas with a percentage of impervious area the coefficient was calculated using the formula: C = 0.9(% impervious) + Cp(l-% impervious). Areas (including % impervious) were measured from the hydrology maps shown in Appendix A. 3.0 RUNOFF CALCULATIONS 3.1 EXISTING CONDITION Based on the topography maps the existing site including tributary areas can be subdivided into two drainage areas. The existing drainage areas are illustrated on the Existing Hydrology Map in Appendix A. Corresponding runoff coefficients (C) and rainfall intensity (I) values were derived using the SD County 2003 manual. The table of coefficients and rainfall isopluvials are included in Appendix PRELIMINARY DRAINAGE STUDY LA COSTA GLEN SKILLED NURSING CENTER EXPANSION B. These values were used to calculate the peak flow for the 2-year, 10-year, and 100-year flows (Q) using the Rational Method. The drainage areas and corresponding Q values are summarized below. Existing Drainage Condition Basin No Area C Iioo Qioo Al A2 0.96 acres 1.31 acres 0.74 5.00 in./hr. 0.73 4.67 in./hr. 3.5 cfs 4.5 cfs 3.2 PROPOSED CONDITION The proposed hydrology conditions for the project have been designed to preserve the existing drainage patterns to the maximum extent practicable. The proposed site drainage conditions are shown in Proposed Hydrology Map in Appendix A. The proposed drainage areas, and corresponding Q values are summarized below. Basin No Area C Iioo Qioo Al A2 0.96 acres 1.31 acres 0.75 0.74 5.00 in./hr. 4.91 in./hr. 3.6 cfs 4.7 cfs (1) Area of the proposed site development 3.3 EXISTING AND PROPOSED RUNOFF COMPARISON The difference between the existing and proposed hydrology conditions are shown below. Condition Al A2 QIOO Existing QIOO Proposed Difference 3.5 cfs 3.6 cfs +0.1 cfs 4.5 cfs 4.7 cfs +0.2 cfs Existing Conditions BASIN 1 Overland flow node 100-101 C = A = L = S = 0.49 0.05 40 1.0 Soil Group D acres feet % From Figure 3-3 T= 1.8(1.1-OL" gl/3 Ti = 6.9 minutes From Figure 3-1 P6 = 2.7 inches P24 = 4.5 inches P<i/P24= 60 % Use P6 = 2.7 inches I = 7.44P6D-C I = 5.76 Q = Q = CIA 0.1 inches/hour cfs Pipe Flow (6" PVC @ 1%) node 101-102 ibarea addition = assume Qavg = V = T,= Tc = 1 = A1 = A2= C1 = C2= C = A = Q = 2.4 1.7 8.6 5.00 0.47 0.49 1.00 0.49 ((C1(A1) 0.96 3.5 0.96 acres 245 feet 1.0 % 0.1 cfs fps minutes minutes inches/hour acres (Roof Top) acres (Landscape) acres (Roof Top) acres (Landscape & Hardscape, 30% impervious) +C2(A2))/(A1+A2) = 0.74 acres cfs Existing Conditions BASIN 2 Overland flow node 200-201 Soil Group D C = 0.35 A = 0.05 acres L = 75 feet S = 2.5 % From Figure 3-3 T= 1.8(1.1-CM.1' Q1/3 8.6 minutes From Figure 3-1 P6 = 2.7 inches P24 = 4.5 inches P6/P24= 60 % Use P6 = 2.7 inches I = 7.44P6D-° I = 5.00 Q= Q= CIA 0.1 inches/hour cfs Pipe Flow (6" PVC @ 3.5%) node 201-202 L= 217 feet Savg = 3.5 % assume Qavg= 0.1 cfs V = 3.8 fps T,= Tc = l = A1 = A2= A3= C1 = C2= C3= C = A = Q = 1.0 9.6 4.67 0.41 0.42 0.48 1.00 0.90 0.35 minutes minutes inches/hour acres (Roof Top) acres (AC Pvmt) acres (Landscape) acres (Roof Top) acres (AC Pvmt) acres (Landscape) ((C1 (A1 )+C2(A2)+C3(A3))/(A1 +A2+A3) = 0.73 1.31 4.5 acres cfs Proposed Conditions BASIN 1 Overland flow Soil Group D node 100-101 C = 0.49 A = 0.05 acres L = 40 feet S = 1.0 % From Figure 3-3 T= 1.8(1.1-CM.1* S1'3 T, = 6.9 minutes From Figure 3-1 P6 = 2.7 inches P24 = 4.5 inches P6/P24= 60 % Use P6 = 2.7 inches I = 7.44P6D"0645 I = 5.76 inches/hour Q= CIA Q = 0.1 cfs Pipe Flow (6" PVC @ 1%) node 101-102 subarea addition = 0.96 acres L = 245 feet Savg = 1 -0 % assume Qavg= 0.1 cfs V = 2.4 fps T, = 1.7 minutes Tc = 8.6 minutes I = 5.00 inches/hour A1= 0.48 acres (Roof Top) A2= 0.48 acres (Landscape) C1= 1.00 acres (Roof Top) C2= 0.49 acres (Landscape & Hardscape, 30% impervious) C = ((C1 (A1 )+C2(A2))/(A1 +A2) = 0.75 A = 0.96 acres Q = 3.6 cfs Proposed Conditions BASIN 2 Overland flow Soil Group D node 200-201 C = 0.35 A = 0.05 acres L = 30 feet S = 1.0 % From Figure 3-3 T, = 7.4 minutes From Figure 3-1 P6 = 2.7 inches P24 = 4.5 inches P6/P24= 60 % Use P6 = 2.7 inches I = 7.44P6D-°645 I = 5.53 inches/hour Q= CIA Q= 0.1 cfs Pipe Flow (6" PVC & 1%) node 201-202 L = 78 feet savg= 1.0 % assume Qaug= 0.1 cfs V = 2.4 fps TM = 0.5 minutes Pipe Flow (6" PVC 3 3.5%) node 202-203 L= 217 feet SaVg = 3.5 % assume Qaug= 0.1 cfs V = 3.8 fps Tc = 1.0 minutes Tc = 8.9 minutes I = 4.91 inches/hour A1= 0.43 acres (Roof Top) A2= 0.41 acres (AC Pvmt) A3= 0.47 acres (Landscape) C1= 1.00 acres (Roof Top) C2= 0.90 acres (AC Pvmt) C3= 0.35 acres (Landscape) C= ((C1(A1)+C2(A2)+C3(A3))/(A1+A2+A3) = 0.74 A = 1.31 acres Q = 4.7 cfs t***************************************************************** * O'Day Consultants, Inc. * * 2710 Loker Avenue West, Suite 100 * * Carlsbad, CA 92008 * * Tel: 760-931-7700 Fax: 760-931-8680 * Inside Diameter ( 6.00 in.) * * * * * Water * ( 1.57 in.) ( 0.131 ft.) | | * v Circular Channel Section Flowrate 0.100 CFS Velocity 2.438 fps Pipe Diameter 6.000 inches Depth of Flow 1.572 inches Depth of Flow 0.131 feet Critical Depth 0.156 feet Depth/Diameter (D/d) 0.262 Slope of Pipe 1.000 % X-Sectional Area 0.041 sq. ft, Wetted Perimeter 0.537 feet ARA(2/3) 0.007 Mannings 'n' 0.011 Min. Fric. Slope, 6 inch Pipe Flowing Full 0.023 % *****************************************i *************************** O'Day Consultants, Inc. 2710 Loker Avenue West, Suite 100 Carlsbad, CA 92008 Tel: 760-931-7700 Fax: 760-931-8680 Inside Diameter ( 6.00 in.) Water * ( 1.15 in.) ( 0.096 ft.) v Circular Channel Section Flowrate 0.100 CFS Velocity 3 .789 fps Pipe Diameter 6.000 inches Depth of Flow 1.153 inches Depth of Flow 0.096 feet Critical Depth 0 .157 feet Depth/Diameter (D/d) 0.192 Slope of Pipe 3 .500 % X-Sectional Area 0.026 sq. ft Wetted Perimeter 0.454 feet AR* (2/3) 0.004 Mannings 'n' 0.011 Min. Fric. Slope, 6 inch Pipe Flowing Full 0.023 % PRELIMINARY DRAINAGE STUDY LA COSTA GLEN SKILLED NURSING CENTER EXPANSION 4.0 CONCLUSION The net increase in storm water run-off due to the proposed building expansion is approximately 0.1 cfs for Basin Al and 0.2 cfs for Basin A2. Capacity calculations shown in Appendix C, for the existing drainage structures show that the downstream drainage structures are adequate to accommodate the net increase in the 100-year flow. PRELIMINARY DRAINAGE STUDY LA COSTA GLEN SKILLED NURSING CENTER EXPANSION 5.0 REFERENCES City of Carlsbad, Engineering Standards, 2004. San Diego County Hydrology Manual, County of San Diego Department of Public Works Flood Control Section, 2003. APPENDIX A PRELIMINARY DRAINAGE STUDY LA COSTA GLEN OFFICES APPENDIX A - EXHIBITS • EXISTING CONDITION HYDROLOGY MAP • PROPOSED CONDITION HYDROLOGY MAP • HYDROLOGIC SOILS GROUPS APPENDIX B PRELIMINARY DRAINAGE STUDY LA COSTA GLEN OFFICES APPENDIX B - HYDROLOGY CHARTS • RAINFALL ISOPLUVIALS • INTENSITY DURATION DESIGN CHARTS • NOMOGRAPH FOR DETERMINATION OF TIME OF CONCENTRATION • RUNOFF COEFFICIENTS FOR URBAN AREAS 33*30- 331 32'3ff 32-30- County of San Diego Hydrology Manual Rainfall Isopluvials 2 Year Rainfall Event - 6 Hours Isopluvtal (Inches) DPW CIS VW: HAXV San l^tc^ f ^JVCTC :33*30t 32-30-3T301 County of San Diego Hydrology Manual Rainfall Isoplnvials 2 Year Rainfall Event - 24 Hours IsopkwU (Inches) CIS 303 Mile* 33-00- 32M51 32-30-32*30- County of San Diego Hydrology Manual Rainfall Isopluviab 10 Year Rainfall Event - 6 Hours hopluvlal (Inches) DPW CIS 303 Miles 33-30 32°30' County of San Diego Hydrology Manual Rainfall Isopluviab 10 Year Rainfall Event - 24 Hours •— !K>pluvW(lnchS8) GIS .33W saw 32M51 32-301 County of San Diego Hydrology Manual Rainfall Isoplwiais 100 Year RainfaH Event - 6 Hours topluvW (Inches) D CIS 32*30' County of San Diego Hydrology Manual Rainfall Isopluvials 100 Year RainfiUl Event - 24 Hours IsopluvM (Inches) GIS- 303 Mites san-diego.ca.us/dpw/watersheds/pubs/susmp_85precfp.pdf - Micros Favorites Tools Help met Explorer 4=*Back " ». > •'$j^Favorites AQUA HEDIONDA LAGOON * BAHQUFFOSLAGOON RESERVOIR < 48x36 in TP"" H KK jj | Address jSj http: jjwww. co. san-diego, ca. us/dpw/watersheds/pubs/susmp_85precip. pdf cjDone H **!• f Autodesk Land D...| jgtotodeskLandD...} 0 Wmdcm Media... } ^http!//www.carb., ||@l>ttp://wiTOi.co.... Internet iT 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 "C" th.o -0.9 gO.8 fo.7 0.6 0.5 0.4 0.3 0.2 ^^ ^ S s ^ >, s, s ^ ^ t ^ r^, V Ss, I i ^ ^ ^ S % S <s s ^V S s^ V s V ^ \ i \ ^ ^ s, s \ ss s . s / V; % w S s s V > ^ s V, t S s ^ \ > s sfc ^1SN l\'VsX S S . * . ' , ' ^ i!l. :!::,::!:: : i 1 = 3.2 iii/hr ^ " n , * ' k ' ' ' ' J1 \ ^ s ^ S ^ » Sj i 1 \ N. \ \ N '>». '''• , ' ' s^'^'x'1'1- '''' ^:;x"- I NX-/":: |: ''*!1 f it ^^;;;;;;:: , t , . . if. — 20 min ! 1 \ ' EQ 1 = 7.44 ^ P6= 6-Houi N«,|'' '•• r SS |'i. ;•"''' ' : >SK x'N :oS 's '' ' ""S N ''''., '^SS *» ••, I1' ^ '' ' ' i ^ Ssi ' fl ^k -j "s J s ''•' , f r ^s 'i ;;;;:;;;:; b Si: == = | _ •- ^ J | — — — T ... [. . • • • f '" f f : 1 i ; JATION 6D-0.645 ity(in/hr) r Precipitation (in on(min) s" «s ^ S, s,1" s ^^ s ^ 1 ? h ^ ^ 1 ' 1 ^ N ' fc * *«l , J> J ' 1 1 h ' '*M r>, N,T I1', *ss ». * > ^ ;====;=;; . . . . -S , It . . •4— 4 5 6 7 8 9 10 15 20 30 40 50 1 2 34 Minutes HoursDuration Dlraett • • • (1)Ffoi fort Cou in ir (2)Adji the aoo _ (3) piot . (4} Dr» (5) This ber on* for A tiprecipitz hesetecto nty Hydro! le Design jst 6 hr pr range of A licapleto Shrprec walinetH > line is th< \Q analyze I! Application For g (a) Selected freq I (b)P6S j 60 j <c)Adji C R fiJ 5.0 1 (d>*ic" 4-5 ? (e) I = 4-0 13-5 ~ Note: T 30 C ITUI1 «*91 ' , j F6 _^ ' ' : [ ^ j I.T 10• 1 5 15 : : .| 20 • • • ! 25 3fl! i{ 40: : •1-° so 90 120 150 180 56 300 360 istedP6<2 r , **Jr-~ ID Tits chart urvesuse pplieation: rtion maps determi <J frequency. Thes ogy Manual (10, 50 arid Procedure Mi acipitatfon(ifnece «% to 65% of the Desert). Dilation on the rig rough the point pa 9 intensity-duratior id. n: jency 10 yea in..P.4= 3.1 )- A? in. nin. ./hr. replaces the Inten d since 1965. I ne 6 hr and 24 hr amounts a maps are included in the , and 100 yr maps included •tnual). ssary) so that it is within 24 hr precipitation (not it side of the chart, irallel to the plotted lines. i curve for the location r D_§. = *><}. & %w P24 sity-Duration-Frequency i _i I . _ i. . .': .. i L '-. i.f 1 ;14>i i I i 2.63 !3.95 2Tl2J3.liH 1 30 '195 1.08 jl.62 6.93 11.40 083 lfJS4' 6.69 li.03 0.60 [0.90 0.41 0.61 034 !0~Si 029 16.44 0^6 16.39 OJ22 • 6.331 0.19 6.28. 6.17 iO.25 2 j 2.5 3 : iSi ' 1 1 i i 1 JS|JJ*J7J»'?J? L3.37HT21 (S.05tpO 2.59 1 124 i 3 89 f 4^4iittSMiaasJirr 1.66iiL07i2.49i2.9o] 1.19 i 1.49 '1.79 i! 2.09 1J»!1.33TiLS9iii6 6.82! iiOJt'ijBil 43 0.68 -aSS 11.021 1.19i 0.591 0.73- 0.88 '; 1.03: 6.52 j 6.65 : 0.78] 6.91 6.43! 6.54 i6.85i6.76] bi38i6.47 OJ56j6.iS6 6.3316.42 6.50)0.58 4 < 4.S ' S I £5 ! 6i i I i i i i i i 10.54s 1 1.86M3.171 14.49 15.81 8.481 9.54 iiOJSOl 11.66 '12.72 £L74r7.58 i 8.421 8L27ll6.il 5 19 1 5.84 5 649 1 7 13 ^779 4.31 j 4.85 j 5.39 \ 5.93 i 6.46 3.73 I 4.20 ! 4.67 [ 5.13 f 5.60 3.32 f 3.73J 4.15 ! 4.56 I 4.98 2.76 T 3.10 i 3.45 1 179 ; 4.13 2.39 i 2.69 '. 2.98 > 3.28 > 3.58 2.12 1 2.39 | 2.65 > 2.92 1 3.18 1 63 1 1 84 (2.04 ' 2.25 > 245 l!36 ! 1.53 i 1.70 i .87 1 2.04 i.isT] 1.32T 1.47: .62 ; 1.761.04 1 i.18'1 1.31 ; .44 i 1.57 087 [6.98! 1.08 : .19 [1.30 6.75 I 6.85! 6.94 .03' 1.13 0.67 i 6.75 ! 6.84 : 6.92 '• 1.00 FIGURE Intensity-Duration Design Chart - Example 3-2 EQUATION 7,44 PQ Q-0.645 I - Intensity (in/hr) P6* 6-Hour Precipitation (in) D = Duration (min) 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 applicapte to Desert). (3) Plot 6 hr precipitation on me right side of the chart. (4) Draw a line through me point parallel to the plotted lines. (5) This line is the intensity-duration curve for the location being analyzed. Application Form: (a) Selected frequency (6) Pg = .../'2-.. in., P24 (c) Adjusted P6<2> = /•! in. (d) ^ = ^ min. (e) I * 2,1- in./hr. Note: This chart replaces the Intensity-Duration-Frequency curves used since 1965. i 1 1145 pf 12J5"' T'n t J t~i "i > i ] &Sf-r VI ~n~in'i''M « "M ~p ""90 180- 300" 2.63 , 3.18 1-66J.2J53 T30Tt.95 0.93 11.40 0.83 ,'i.w 0.69 ilXO OedTaaO; 0,34 10.51 0.29J0.44 OJ22 '6;jJ3 &27T&58! 3.37 7.90 i 9.22 6.36 7.42 3.89j 2.15; 2,69 J3L23 t~.87r2.33'few' 1.6Si2J>7F2.49 2.90 3.77 357 i.ue i.9aii.saii.8e OJKflJBjlJBiixB 6:68 ;O85i 1.02] 1.19 1064^1^61 i 15.81 7.58' 6.19 _3.73 _ 6.49. 7.13 1739"'"— - , 4.20 ! 4j7T5."l3"! 15.60'" " 2.39 j 2.69 i 2.98 ! p2 r£38 fzM'l p|tl|i|$ If ^lOSfl"}^^ I"l.w1"t!;3l"t' o^i_^IS-iwjaTOijJwjawJ.t.pe| ; 4.56.! 3.28 2.92 ZS& 0.47^0.56! 0.66 i 0.75 ) 0.85 ! 0.94 at? i6J2s?o^33f6>K;ai50las8Toi67 T O/TS 1 a84 1.44 1J9 1.03 0.92 ! 4.13 I 3.58r3.i8 ! 2,45 1 2.04 i 1.76r'l-s? ! 1.30 ; 1.13 J1.00 FIGURE Intensity-Duration Design Chart • Example 3-2 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 i5 1 P-9 "§0.8 |07 0.6 0.5 0.4 0.3 0.2 0.1i \ ^^^! ^^^J SvfSsJ^ s^ ! *S< s-^sIsJ^ rO !xj | ^ S^L |^ ! I I \ 1 ! ! 1 I : 1 ' i • \ I \ •i ! ^L „„., !_!,„;. - . -H-H ; . ; |~ K, "X .... f i- .sl**s», Sx sh s ^"^> I Ss . S _ I j !\I ... : ' s, 's k . ^, —i 1 sHi•v ^•s « ^ > s s, N s \ \ ~i-i 1 ~i ~ % ^ * || Jgj id St'Ml *i{ ''is 5'*' s'is Sj'Hl,; Si' fj'ir ' lUlJto '"v ! « T ' S j] T I lil - *N«J j- tJJ IT i t T I f T TJ T • T* t-f _l T--T — •• 'f •;! —~i j f t ~""T f IT t ! ^ ^ • 1 E 1 = 7.44 P6 = 64k n, D = Dun> ' > , B ;•'!>!! 'ij t"k'v\:'':'|: :J * v ^ ( '''•,,'" S r ^ L ^ifr- :kI T ''-., B Sx.,, " % 1 N - l-t - L I r • . i" :t t ' \ ! (1 :T T ! V -' QUATION P6 0-0.645 isity (in/hr) Hir Precipitation (in) rtton (min) s N 1 S s 1 s •> 11 N i'vs>>^ \ ssN s N* s: * . s \h > s *s "V_ * s - > 6 7 8 9 10 15 20 30 40 50 1 2 Minutes Duration I „ ::|:i;:; > *s «i „ -, '«,*2 '"'> ' >, > , ''«,•S><-(1| T _ . - it . 1 I 3 4 Hours p«4TrmJ IT Directions for Application: . . . IL H\ From precipitation maps determine 6 hr and 24 hr amounts ., , 1 for the selected frequency. These maps are included in the | County Hydrology Manual (10, 50. and 100 yr maps included • jjr in the Design and Procedure Manual). , |L (2) Adjust 6 hr precipitation (if necessary) so that it is within I the range of 45% to 65% of the 24 hr precipitation (not < jfj- applicaple to Desert). iJI (3) Plot 6 hr precipitation on the right side of the chart i i illl IA\ Draw a HnA thmtinh thA rmlnt ftnrallc*! to tK@ olottfid lines |L (5) This line is the intensity-duration curve for the location j[j being analyzed. JT Application Form: || ^ (a) Selected frequency ,,'^;:-." year 1 i 1 1 60 t (c> Adjusted P6<2> = P7- in. '! BL55 ^ C' -,..".'"'-'• '"'••' i HI 3,0 3 « ii.T.T- ^ ^ j * , i, ,y- III, I.4'5]? (e)l= ^M jn./hr. ... ~) ., ' ' I lil Note: This chart replaces the Intensity-Duration-Frequency 11 I Hr 3 ° curves used since 1 965. flB 2.5 ; • : : : ; ' • ' < , [{T P6 1 i tiS ! 2 i SUi : 3 i *34> 1 4 i 4.5 : 5 i S.S 6NlU Duwiton t i i i ; 1 ; i i i j ; i ; i s i i 1(11 5 i'.eS 3.95' S'i?' 6.59 7.90i9.22i 10.54 11.86; 13.17 14.49 15.81 I i If 7 2.12 ]a.i8i4JSn 5^10 '6.36: 7.42'T 8.48 1 9.64 i 10.60i 11.66 12.72 : : ffl 10 1.68 ;2.53T3.37 i 4.21 r5X)Si5.90[ 6.74 j 7.58 1 8.42 I 9.27 10.1 1 • rnr 1 5 15 1 30 1 95^259 3T24'389 4541 5 19 584 : 649 7 13 778 •• • IT & 1-CB ;-t.62iai5] 2i69li2l3"'3l77T4.31 1 4.85 i &39' f 5.93 6.46 •• • ffl 25 0.93 1.40 j 1.87, 2.33 2.80 3J27! 3.73 i 4.20 i 4.67 i 5.13 5.60 ! ! if 30 6J3 i li24! 1.66! 2.07 > 2.49 i 2.90! 3.32 3,73 U.15 ' 4.56 4.96 . I i If 1'° 50 6.60 6.90! 1.19: 1.49 • 1.79:2.09; 2.39 ; 2.69 1 2.98 3.28 3.58 • • • • jjl 60 6.53 0.80' 1.06 i 1.33 1.59 1.861 2.12 i 2.39 • 2.65 : 2.92 3.18 " ' f m 90 6.41 ;0.61f0.82 1.02'; 1.23; »-43i 1.63 1.84 i 2.04 2.25 2.45 ' ". ffl 120 6.34 i0.51|a68:6.iS5' 1.6211.19; 1.36 i 1.53 i 1.70 : 1.87 2.04 U ISO 059 !0.44!0.59ia73 0.88i1.03i 1.18 i 1.32 I 1.47 1.62 1.76 i" U li» 6i26 ;6.39i6"i52 ! 6.65; 6.78! 0.91 T 1.04; 1.18 h. 31 1.44 1.57 "i"""1 240 6.22 ;0.33|6.43] 6.54 0.65;6.76T 6.87 i 6.981 1.08 1.19 1.305 6 300 6.19 j6^d!6.38i 6.47; 6.56 i 6^66; 6.75 ! 0.85 i 0.94 1.03 1.13 360 0.17 ' ;0is' 6.33i 6.42* 0.50 i 6.58: a67r 6.7510.84 6.92 1.00 FIGURE Intensity-Duration Design Chart - Template 3-1 San Diego County Hydrology Manual Date: June 2003 Section: Page: 3 6 of 26 Table 3-1 RUNOFF COEFFICIENTS FOR URBAN AREAS Land NRCS Elements Undisturbed Natural Terrain (Natural) Low Density Residential (LDR) Low Density Residential (LDR) Low Density Residential (LDR) Medium Density Residential (MDR) Medium Density Residential (MDR) Medium Density Residential (MDR) Medium Density Residential (MDR) High Density Residential (HDR) High Density Residential (HDR) Commercial/Industrial (N. Com) Commercial/Industrial (G. Com) Commercial/Industrial (O.P. Com) Commercial/Industrial (Limited I.) Commercial/Industrial (General I.) Use County Elements Permanent Open Space Residential, 1.0 DU/A or less Residential, 2.0 DU/A or less Residential, 2.9 DU/A or less Residential, 4.3 DU/A or less Residential, 7.3 DU/A or less Residential, 10.9 DU/A or less Residential, 14.5 DU/A or less Residential, 24.0 DU/A or less Residential, 43.0 DU/A or less Neighborhood Commercial General Commercial Office Professional/Commercial Limited Industrial General Industrial Runoff Coefficient "C" % IMPER. 0* 10 20 25 30 40 45 50 65 80 80 85 90 90 95 A 0.20 0.27 0.34 0.38 0.41 0.48 0.52 0.55 0.66 0.76 0.76 0.80 0.83 0.83 0.87 Soil Type B 0.25 0.32 0.38 0.41 0.45 0.51 0.54 0.58 0.67 0.77 0.77 0.80 0.84 0.84 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 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>**"*"""'"'*<''. C 0.85/ 0.85 0.87 The values associated with 0% impervious may be used for direct calculation of the coefficient, Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. is located in Cleveland National Forest). DU/A = dwelling units per acre NRCS = National Resources Conservation Service runoff coefficient as described in Section 3.1.2 (representing the pervious runoff Justification must be given that the area will remain natural forever (e.g., the area 3-6 APPENDIX C PRELIMINARY DRAINAGE STUDY LA COSTA GLEN OFFICES APPENDIX C - CAPACITY CALCULATIONS • EXISTING STORM DRAIN CAPACITIES ****************************************** O'Day Consultants, Inc. * 2710 Loker Avenue West, Suite 100 * Carlsbad, CA 92008 * Tel: 760-931-7700 Fax: 760-931-8680 * Inside Diameter ( 18.00 in.) Water * ( 16.88 in.) ( 1.407 ft.) v Circular Channel Section Flowrate Velocity Pipe Diameter Depth of Flow Depth of Flow 24 . 910 14.468 18 . 000 16 . 884 1 .407 CFS fps inches inches feet Critical Depth ............ Greater than Pipe Diameter Depth/Diameter (D/d) ..... 0.938 Slope of Pipe ............. 4 . 860 % X-Sectional Area .......... 1.722 sq. ft. Wetted Perimeter .......... 3 . 951 feet AR*(2/3) .................. 0.989 Mannings 'n1 .............. 0.013 Min. Fric . Slope, 18 inch Pipe Flowing Full ...... 5.624 % (St.*