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SUP 06-12; ROBERTSON RANCH HABITAT CORRIDOR; DRAINAGE STUDY; 2007-02-21
) DRAINAGE STUDY FOR ROBERTSON RANCH HABITAT CORRIDOR GRADING SUP 06-12 Job No. 06-1172/5 February 21, 2007 Prepared by: - - O'DAY CONSULTANTS, INC. 2710 Loker Avenue West Suite 100 Carlsbad, California 92010-6603 Tel: (760) 931-7700 Fax: (760) 931-8680 Keith Hansen RCE 60223 Exp. 06/30/08 Date DRAINAGE STUDY FOR ROBERTSON RANCH HABITAT CORRIDOR GRADING SUP 06-12 Job No.06-1172/5 February 21, 2007 Prepared by: O'DAY CONSULTANTS, INC. 2710 Loker Avenue West Suite 100 Carlsbad, California 92010-6603 Tel: (760) 931-7700 Fax: (760) 931-8680 zoo coy"? iOFESS 60223 Uj 6/30/08 4.1 CML ' OF CAL% 3,4'347 Keith Hfnsen RCE 60223 Date Exp. 06/30/08 TABLE OF CONTENTS SECTION 1 INTRODUCTION Purpose of Study Scope Facilities Proposed in City of Carlsbad Master Plan of Drainage Proposed Detention Basins HYDROLOGY Modified Rational Method Description Program Process CONCLUSION Existing Condition Basin Exhibit Proposed Condition Basin Exhibit SECTION 2 Vicinity Map Runoff Coefficients Isopluvial Maps 100-Year, 6-Hour 100-Year, 24-Hour Intensity-Duration Design Chart - Figure 3-1 Overland Time of Flow Nomograph - Figure 3-3 Maximum Overland Flow Length & Initial Time of Concentration - Table 3-2 Nomograph for Determination of Tc for Natural Watersheds - Figure 3-4 San Diego County Soils Interpretation Study SECTION 3 Hydrology 100 year Analysis Existing Condition SECTION 4 Hydrology 100 year Analysis Proposed Condition SECTION 5 Temporary Desiltation Basins SECTION 6 Hydrologic and Hydraulic Analyses prepared by Chang Consultants POCKET Exhibit A Existing Condition Drainage Map Exhibit B Proposed Condition Drainage Map SECTION 1 INTRODUCTION Purpose of Study This preliminary drainage study was prepared to determine existing and proposed runoff quantities for the Habitat Corridor Grading within the Robertson Ranch West Project, and for the purposes of sizing drainage structures. Scope This study analyzes the 100-year flow for existing and proposed conditions for the western portion of the site. The remaining portion is analyzed for the purpose of sizing drainage structures. Runoff from this project combines with runoff from the larger Agua Hedionda watershed before leaving the site through the 8' x 8' RCB under El Camino Real. Refer to the February 20, 2006 study titled "Hydrologic and Hydraulic Analyses for Robertson's Ranch" prepared by Wayne Chang (Section 6) for pre- and post-developed conditions. Also the 48" pipe to the east of the project was analyzed for adequacy for a commercial development. This calculation is included in Section 4. HYDROLOGY The hydrologic analyses are being performed according to the 2003 San Diego County Hydrology Manual. The overall drainage area is less than one square mile and includes junctions of independent drainage systems; therefore, the Modified Rational Method is being used for the analyses. The Modified Rational Method is applicable to a 6-hour storm duration because the procedure uses Intensity-Duration Design Charts that are based on a 6-hour storm duration. In some cases, the 6-hour precipitation must be adjusted based on the ratio of the 6- to 24-hour precipitation. This will be performed where necessary. Modified Rational Method Description The modified rational method, as described in the 2003 San Diego County Flood Control/Hydrology Manual, is used to estimate surface runoff flows. The basic equation: Q = CIA C = runoff coefficient (varies with surface) I = intensity (varies with time of concentration) A = area in acres For the 100-year design storm, the 6-hour rainfall amount is 2.6 inches and the 24-hour rainfall amount is 4.3 inches. Excel spreadsheets along with the San Diego County Rational-Hydrology Program Package Version 7.4, developed by CivilCADD/CIVILDESIGN Engineering Software © (1991-2004), was used to determine the rainfall amount, times of concentration, corresponding intensities and flows for the various hydrologic basins within this model. The program was then used to route flows through drainage conveyance structures and confluence basins per the modified rational method. Program Process The Rational-Hydrology program is a computer-aided design program where the user develops a node link model of the watershed. Developing independent node link models of each interior watershed and linking these submodels together at confluence points create the node link model. The program has the capability of performing calculations for 11 different hydrologic and hydraulic processes. These processes are assigned and printed in the output. They are as follows: Initial sub-area input, top of stream. Street flow through sub-area, includes sub-area runoff. Addition of runoff from sub-area to stream. Street inlet and parallel street and pipeflow and area. Pipeflow travel time (program estimated pipe size). Pipeflow travel time (user-specified pipe size). Improved channel travel - Area add option. Irregular channel travel time - Area add option. User-specified entry of data at a point. Confluence at downstream point in current stream. Confluence of main streams. CONCLUSION In summary, this analysis shows that the runoff from Basin 1 is slightly decreased by the proposed grading and basin. The existing flow from the site is 42.0 cfs, and the proposed flow is 41.30 cfs. For analysis of the runoff from Basins 2 and 3, please reference the study prepared by ,Chang Consultants in Section 6. Also, the 48" pipe on the east side of the site was analyzed and found to be adequate for the ultimate condition of commercial development. File: g:\011014\hydrology\PA 11-HYD.doc SECTION 2 CITY OF OCEANSIDE fl HIGHWAY ,-,78 _.- 0 3D VLL. SITE CITY TA Cl TY F OF STA AILOMAR NOT TO\ CA S B SAN MARCOS /1Y OF - SCALE 0 y -• PACIFIC OCEAN C/fl' OF ENCIM TA S VICINITY MAP NO SCALE Sac Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 6of26 Table 3-1 RUNOFF COEFFICIENTS FOR URBAN AREAS Rimoff Coefficient "C" NRCS 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. Corn) Commercial/Industrial, (G. Corn) Commercial/Industrial (O.P. Corn) Commercial/Industrial (Limited I.) Soil Type A B C D 0.20 0.25 0.30 0.35 0.27 0.32 0.36 0.41 0.34 0.38 0.42 0.46 038 0.41 0.45 0.49 0.41 0.45 0.48 0.52 0.48 0.51 0.54 0.57 0.52 0.54 0.57 0.60 0.55 0.58 0.60 0.63 0.66 0.67 0.69 0.71 0.76 0.77 0.8 0.79 0.76 - 0.77 0.78 0.79 0.90 0.80 0.81 0.82 0.83 0.84 0.84 0.85 0.83 0.84 0.84 0.85 0.87 0.87 Permanent Open Space 0 Residential, 1.0 DU/A or less 10 Residential, 2.0 DU/A or less 20 Residential, 2.9 DU/A or less 25 Residential, 43 DU/A or less 30 Residential, 7.3 DU/A or less 40 Residential, 10.9 DU/A or less 45 Residential, 14.5 DU/A or less 50 Residential, 24.0 DU/A or less 65 Residential, 43.0 DU/A or less 80 Neighborhood Commercial 80 General Commercial 85 Office Professional/Commercial 90 Limited Industrial 90 *The values associated with 0% impervious may be used for direct calculation of the iunoff coefficient as described in Section 3.12 (representing the pervious runoff coefficient, Cp.for the soil type), or for areas that will remain undisturbed in perpetuity. 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WATERCOURSE DISTANCE IN FEET C C C El 0 OVERLAND FLOW TIME IN MINUTES s ) San Diego County Hydrology Manual Date: June 2003 Section: 3 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 be used in hydrology studies. Initial T1 values based on average C values for the Land Use Element are also included. These values can be used in planning and design applications as described below. Exceptions may be approved by the "Regulating Agency" when submitted with a.. detailed study. Table 3-2 MAXIMUM OVERLAND FLOW LENGTH (LM) & INITIAL TIME OF CONCENTRATION (T Element DUI Acre .5% 1% 2% 3% 5% 10% LmT T1 L T1 L7, Tj Liii Ti . Natural 501 13.2 70112.5 85 10.9 100 10.3 100 8.7 100 6.9 LDR. 1 50112.2 70111.5 85 10.0 100 9.5 100 8.0 100 6.4 LDR. 2 501 11.3 70 10.5 85 9.2 100 8.8 100 7.4 100 5.8 LDR. 12.9 50 10.7 70 10.0 85 8.8 1 95 81 100 7.0 1001 5.6 MDR 4.3 50 10.2 70 9.6 80 8.1 95 7.8 100 6.7 1001 5.3 MDR 7.3 50 9.2 65 8.4 80 7.4 951 7.0 1001 6.0 1001 4.8 MOR 10.9 50 8.7 65 1 7.9 80 1 6.9 901 6.4 1001 5.7 1001 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 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./Corn 501 4.2 601 3.7 70 3.1 801 2.9 90 2.6 100 2.2 Limited!. 50 4.2 60 3.7 701 3.1 80 2.9 2.6 100 2.2 General L 50 3.7 60 3.2 70 2.7 80 2.6 ±90 2.3 100 1.9 See Table 3-1 for more detailed description 3-12 N •• \5 __ '.. Jill 73 -32 'r _ • 41 \ 0 SUIC" ( /N\\ eJ )\\ tjf D \ \ \\ ,ICH Ejç AVE_ \L.( SITE / H ED I 0 N D A c \çLsBAD \/\. '(•''$V 9 h go ns VTN 3.. dLk c-i• )z B ) 3 ( ( -A A \\ - b SECTION 3 EXISTING CONDITIONS BASIN 1 V 1.) Overland flow across Natural Area (node 100 - node 107) C= 0.35 A= 32.64 acres E(CA)= 11.42. L= 1700 feet AE= 127 feet S= 7.5 % v" 100' maximum length per Table 3-2, determine Tfrom Figure 3-3 T= 1.8(1.1-C)D1' 1I3 T = 6.91 minutes for initial 100' travel length From Figure 3-4, for the remaining 1600' It= 6.21 minutes we Total time of Concentration = 13.12 minutes / From Figure 3-1 '6 = 2.6 inches / = 4.3 inches P6/P24 = 60 % = 3.68 inches/hour ' Q=CIA Q= 42.0 cfs .' SECTION 4 PROPOSED CONDITIONS ' BASIN 1.) Overland flow across Natural Area (node 100 - node 107) C= 0.35 A= 27.09 acres E(CA) = 9.48 L= 1700 feet AE = 127 feet S= 7.5 % 100' maximum length per Table 3-2, determine T from Figure 3-3 T = 1.8(1.1-C)D1' 1/3 Ti = 6.91 minutes for initial 100' travel length From Figure 3-4 for the remaining 1600' Tt 6.21 minutes IQ Total time of Concentration = 13.12 minutes From Figure 3-1 = 3.68 inches/hour Q= 34.9 cfs BASIN2 1.) Overland flow across Natural Area (node 101 - node 102) C= 0.35 A= 0.07 acres (CA) = 0.02 L = 100 feet (per Table 3-2) E= 5 feet S= 5.0 % 100' maximum length per Table 3-2, determine T from Figure 3-3 T1 = 1.8(1.1-CD S S1'3 IN T = 7.89 minutes for initial 100' travel length From Figure 3-4, for the remaining 200' (node 102 - node 103) T= 1.41 minutes Total time of Concentration = 9.30 minutes From Figure 3-1 = 4.59 inches/hour Q= 0.1 cfs Channel Flow (node 103 - node 104) and addition of subarea flow C= 0.35 A= 0.92 acres >(CA) = 0.35 L = 375 feet S= 7.87 % Qavg 0.8 cfs n= 0.015 V= 5.94 fps T= 1.05 minutes T= 10.36 minutes From Figure 3-1 = 4.28 inches/hour Q= 1.5 cfs Check Qavg Qavg = 0.1+(1.5.1)/2 = 0.8 OK Channel Flow (node 104 - node 105) plus subarea addition C= 0.35 A = 3.08 acres >(CA)= 1.42 L= 400 feet S=1 % Qavg = 3.2 cfs n= 0.035 V= 1.85 fps T= 3.60 minutes Tc = 13.96 minutes From Figure 3-1 = 3.53. inches/hour Q= 5.0 cfs Check Qavg Qavg = 1.5+(5.0-1.5)/2 = 3.2 OK Add 1.68 acres at node 105 C= 0.35 E(CA) = 2.01 Q= 7.12 cfs Pipe Flow (node 105 - node 106) D= 18 inches S= 0.5 % V = 5.53 fps L= 132 feet l= 0.40 minutes T= 14.36 minutes From Figure 3-1 I = 3.47 inches/hour Q= 7.0 cfs Confluence (basin 1 and basin 2) T1 = 13.12 minutes = 34.9 cfs I = 3.68 inches/hour 12 = 14.36 minutes 02 = 7.0 cfs 12 = 3.47 inches/hour = 41.30 cfs = 39.92 cfs Q= 41.30 T= 13.12 PA11O2.OUT San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software, (c) 1993 Version 3.2 Rational method hydrology program based on San Diego County Flood Control Division 1985 hydrology manual Rational Hydrology Study Date: 10/25/06 ------------------------------------------------------------------------ ROBERTSON RANCH PA 11 - BASIN II BORROW SITE/ INTERIM DRAINAGE G:\ACCTS\011014\PA1102 .OUT ------------------------------------------------------------------------ Hydrology Study Control Information ------------------------------------------------------------------------ O'Day Consultants, San Deigo, California - S/N 10125 ------------------------------------------------------------------------ Rational hydrology study storm event year is 100.0 Map data precipitation entered: 6 hour, precipitation(inches) = 2.600 24 hour precipitation(inches) = 4.300 Adjusted 6 hour precipitation (inches) = 2.600 P6/P24 = 60.5% San Diego hydrology manual 'C' values used Runoff coefficients by rational method ++++++H-++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 201.000 to Point/Station 202.000 INITIAL AREA EVALUATION User specified 'C' value of 0.350 given for subarea Time of concentration computed by the natural watersheds nomograph (App X-A) TC = [11.9*length(Mi)A3)/(elevation change))A.385 *60(min/hr) + 5 mm. (City of Oceanside) Initial subarea flow distance = 100.00(Ft.) Highest elevation = 194.00(Ft.) Lowest elevation = 191.50(Ft.) Elevation difference = 2.50(Ft.) TC=[(11.9*0.0189A3)/( 2.50)]A.385= 1.12 + 5 mm. = 6.12 mm. Rainfall intensity (I) = 6.013 for a 100.0 year storm Effective runoff coefficient used for area (Q=KcIA) is C = 0.350 Subarea runoff = 0.168(CFS) Total initial stream area = 0.080(Ac.) Process from Point/Station 202.000 to Point/Station 203.000 Y1c IRREGULAR CHANNEL FLOW TRAVEL TIME Estimated mean flow rate at midpoint of channel = 0.452(CFS) Depth of flow = 0.086(Ft.), Average velocity = 1.520(Ft/s) Irregular Channel Data ----------------------------------------------------------------- Information entered for subchannel number 1 Point number 'x' coordinate 'Y' coordinate 1 0.00 0.50 2 20.00 0.00 Page 1 PA1102 .OUT 3 40.00 0.50 Manning's 'N' friction factor = 0.040 ----------------------------------------------------------------- Sub-Channel flow = 0.452(CFS) flow top width = 6.901(Ft.) velocity= 1.520(Ft/s) area = 0.298(Sq.Ft) Froude number = 1.290 upstream point elevation = 191.500(Ft.) Downstream point elevation = 176.000(Ft.) Flow length = 140.000(Ft.) Travel time = 1.54 mm. Time of concentration = 7.66 mm. Depth of flow = 0.086(Ft.) Average velocity = 1.520(Ft/s) Total irregular channel flow = 0.452(CFS) Irregular channel normal depth above invert elev. = 0.086(Ft.) Average velocity of channel(s) = 1.520(Ft/s) Sub-Channel No. 1 critical depth = 0.096(Ft.) critical flow top width = 7.656(Ft.) critical flow velocity= 1.235(Ft/s) critical flow area = 0.366(Sq.Ft) Adding area flow to channel user specified 'C' value of 0.350 given for subarea Rainfall intensity = 5.205(In/Hr) for a 100.0 year storm Runoff coefficient used for sub-area, Rational method,Q=KCIA, C = 0.350 Subarea runoff = 0.492(CFS) for 0.270(Ac.) Total runoff = 0.660(CFS) Total area = 0.35(Ac.) +++++++++++++++++++++++++++++++++-f-f+++++++-f+++++++++++++++.f+++++++++++ Process from Point/Station 203.000 to Point/Station 204.000 IRREGULAR CHANNEL FLOW TRAVEL TIME Estimated mean flow rate at midpoint of channel = 2.829(CFS) Depth of flow = 0.318(Ft.), Average velocity = 2.794(Ft/s) ******* Irregular Channel Data ----------------------------------------------------------------- Information entered for subchannel number 1 Point number 'x' coordinate 'y' coordinate 1 0.00 0.50 2 5.00 0.00 3 10.00 0.50 Manning's 'N' friction factor = 0.040 ----------------------------------------------------------------- Sub-Channel flow = 2.829(CFS) flow top width = 6.365(Ft.) velocity= 2.794(Ft/s) area = 1.013(Sq.Ft) Froude number = 1.234 upstream point elevation = 176.000(Ft.) Downstream point elevation = 141.000(Ft.) Flow length = 530.000(Ft.) Travel time = 3.16 mm. Time of concentration = 10.82 mm. Depth of flow = 0.318(Ft.) Average velocity = 2.794(Ft/s) Total irregular channel flow = 2.829(CFS) Irregular channel normal depth above invert elev. = 0.318(Ft.) Page 2 PA1102 . OUT Average velocity of channel(s) = 2.794(Ft/s) Sub-Channel No. 1 critical depth = 0.346(Ft.) critical flow top width = 6.914(Ft.) critical flow velocity= 2.367(Ft/s) critical flow area = 1.195(sq.Ft) Adding area flow to channel User specified 'C' value of 0.350 given for subarea Rainfall intensity = 4.164(In/Hr) for a 100.0 year storm Runoff coefficient used for sub-area, Rational method,Q=KcIA, C = 0.350 Subarea runoff = 3.352(cFs) for 2.300(Ac.) Total runoff = 4.012(cFs) Total area = 2.65(Ac.) + +++ +++++++ +.+++++ +++ +++++++++++++++ + + ++++++++++ ++++++++ ++++++++++++ + + Process from Point/station 204.000 to Point/Station 205.000 IRREGULAR CHANNEL FLOW TRAVEL TIME Estimated mean flow rate at midpoint of channel = 5.602(CFS) Depth of flow = 0.490(Ft.), Average velocity = 2.337(Ft/s) ******* Irregular Channel Data ----------------------------------------------------------------- Information entered for subchannel number 1 Point number 'x' coordinate 'v' coordinate 1 0.00 0.50 2 5.00 0.00 3 10.00 0.50 Manning's 'N' friction factor = 0.040 - - - Sub-Channel flow = 5.602(CFS) flow top width = 9.793(Ft.) velocity= 2.337(Ft/s) area = 2.398(Sq.Ft) Froude number = 0.832 Upstream point elevation = 141.000(Ft.) Downstream point elevation = 128.000(Ft.) Flow length = 500.000(Ft.) Travel time = 3.57 mm. Time of concentration = 14.38 mm. Depth of flow = 0.490(Ft.) Average velocity = 2.337(Ft/s) Total irregular channel flow = 5.602(CFS) Irregular channel normal depth above invert elev. = 0.490(Ft.) Average velocity of channel(s) = 2.337(Ft/s) Sub-Channel No. 1 critical depth = 0.455(Ft.) critical flow top width = 9.102(Ft.) critical flow velocity= 2.705(Ft/s) critical flow area = 2.071(Sq.Ft) Adding area flow to channel user specified 'C' value of 0.350 given for subarea Rainfall intensity = 3.465(In/Hr) for a 100.0 year storm Runoff coefficient used for sub-area, Rational method,Q=KcIA, C = 0.350 Subarea runoff = 2.547(CFS) for 2.100(Ac.) Total runoff = 6.559(CFs) Total area = 4.75(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 205.000 to Point/Station 206.000 IMPROVED CHANNEL TRAVEL TIME Page 3 PA11O2.OUT upstream point elevation = 128.00(Ft.) Downstream point elevation = 93.50(Ft.) Channel length thru subarea = 210.00(Ft.) Channel base width = 1.000(Ft.) Slope or 'z' of left channel bank = 2.000 Slope or 'Z' of right channel bank = 2.000 Estimated mean flow rate at midpoint of channel = Manning's 'N' = 0.015 Maximum depth of channel = 1.000(Ft.) Flow(q) thru subarea = 7.084(CFS) Depth of flow = 0.309(Ft.), Average velocity = Channel flow top width = 2.235(Ft.) Flow Velocity = 14.18(Ft/5) Travel time = 0.25 mm. Time of concentration = 14.63 mm. Critical depth = 0.742(Ft.) Adding area flow to channel 7. 084(CFS) 14. 178(Ft/s) User specified 'C' value of 0.350 given for subarea Rainfall intensity = 3.427(In/Hr) for a 100.0 year storm Runoff coefficient used for sub-area, Rational method,Q=KCIA, C = 0.350 Subarea runoff = 0.912(CFs) for 0.760(Ac.) Total runoff = 7.471(CFS) Total area = 5.51(Ac.) Process from Point/Station 206.000 to Point/Station 207.000 IRREGULAR CHANNEL FLOW TRAVEL TIME Estimated mean flow rate at midpoint of channel = 8.142(CFS) Depth of flow = 0.621(Ft.), Average velocity = 2.113(Ft/s) Irregular Channel Data ----------------------------------------------------------------- Information entered for subchannel number 1 Point number 'xt coordinate 'v' coordinate 1 0.00 1.00 2 10.00 0.00 3 20.00 1.00 Manning's 'N' friction factor = 0.040 ----------------------------------------------------------------- Sub-Channel flow = 8.142(CFS) flow top width = 12.415(Ft.) velocity= 2.113(Ft/s) area = 3.853(Sq.Ft) Froude number = 0.668 Upstream point elevation = 93.500(Ft.) Downstream point elevation = 90.400(Ft.) Flow length = 200.000(Ft.) Travel time = 1.58 mm. Time of concentration = 16.21 mm. Depth of flow = 0.621(Ft.) Average velocity = 2.113(Ft/s) Total irregular channel flow = 8.142(CFS) Irregular channel normal depth above invert elev. = 0.621(Ft.) Average velocity of channel(s) = 2.113(Ft/s) Sub-Channel No. 1 critical depth = 0.527(Ft.) critical flow top width = 10.547(Ft.) critical flow velocity= 2.928(Ft/s) critical flow area = 2.781(sq.Ft) Adding area flow to channel Page 4 PA11O2.OUT User specified 'C' value of 0.350 given for subarea Rainfall intensity = 3.208(In/Hr) for a 100.0 year storm Runoff coefficient used for sub-area, Rational method,Q=KCIA, C = 0.350 Subarea runoff = 1.112(cFs) for 0.990(Ac.) Total runoff = 8.583(cFs) Total area = 6.50(Ac.) ++ + + + + + +++++++++++++++++++++++++++++++++++++ +++++++++++ +++ +++++++ + Process from Point/Station 207.000 to Point/Station 208.000 **** IRREGULAR CHANNEL FLOW TRAVEL TIME Estimated mean flow rate at midpoint of channel = 8.985(cFS) Depth of flow = 0.586(Ft.), Average velocity = 5.226(Ft/s) Irregular Channel Data Information entered for subchannel number 1 Point number 'x' coordinate 'V' coordinate 1 0.00 1.00 2 5.00 0.00 3 10.00 1.00 Manning's 'N' friction factor = 0.040 -------------------------------------------------------- Sub-Channel flow = 8.985(CFS) flow top width = 5.864(Ft.) velocity= 5.226(Ft/s) area = 1.719(Sq.Ft) Froude number = 1.701 Upstream point elevation = 90.400(Ft.) Downstream point elevation = 68.500(Ft.) Flow length = 210.000(Ft.) Travel time = 0.67 mm. Time of concentration = 16.88 mm. Depth of flow = 0.586(Ft.) Average velocity = 5.226(Ft/s) Total irregular channel flow = 8.985(CFs) Irregular channel normal depth above invert elev. = 0.586(Ft.) Average velocity of channel(s) = 5.226(Ft/s) Sub-Channel No. 1 critical depth = 0.727(Ft.) critical flow top width = 7.266(Ft.) critical flow velocity= 3.404(Ft/s) critical flow area = 2.639(Sq.Ft) Adding area flow to channel User specified 'C' value of 0.350 given for subarea Rainfall intensity = 3.126(In/Hr) for a 100.0 year storm Runoff coefficient used for sub-area, Rational method,Q=KcIA, C = 0.350 Subarea runoff = 0.667(cFS) for 0.610(Ac.) Total runoff = 9.250(cFS) Total area = 7.11(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 208.000 to Point/Station 208.000 SUBAREA FLOW ADDITION 1t User specified 'C' value of 0.350 given for subarea Time of concentration = 16.88 mm. Rainfall intensity = 3.126(In/Hr) for a 100.0 year storm Runoff coefficient used for sub-area, Rational method,Q=KCIA, C = 0.350 Subarea runoff = 4.540(CFs) for 4.150(Ac.) Total runoff = 13.790(cFs) Total area = 11.26(Ac.) Page 5 PA11O2.OUT Process from Point/station 208.000 to Point/station 209.000 PIPEFLOW TRAVEL TIME (User specified size) Upstream point/station elevation = 64.00(Ft.) Downstream point/station elevation = 39.20(Ft.) Pipe length = 350.00(Ft.) Manning's N = 0.013 No. of pipes = 1 Required pipe flow = 13.790(CFS) Given pipe size = 36.00(m.) Calculated individual pipe flow = 13.790(CFs) Normal flow depth in pipe = 6.79(m.) Flow top width inside pipe = 28.16(mn.) Critical Depth = 14.18(m.) Pipe flow velocity = 14.91(Ft/s) Travel time through pipe = 0.39 mm. Time of concentration (TC) = 17.27 mm. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 209.000 to Point/Station 209.000 SUBAREA FLOW ADDITION User specified 'C' value of 0.350 given for subarea Time of concentration = 17.27 mm. Rainfall intensity = 3.080(In/Hr) for a 100.0 year storm Runoff coefficient used for sub-area, Rational method,Q=KCIA, C = 0.350 subarea runoff = 4.635(CFs) for 4.300(Ac.) Total runoff = 18..425(CFs) Total area = 15.56(Ac.) End of computations, total study area = 15.56 (Ac.) Page 6 O'Day Consultants Inc. 2710 Loker Avenue West, Suite 100 . Carlsbad, CA 92008 Tel: (760) 931-7700 Fax: (760) 931-8680 Inside Diameter 48.00 in.) * * * AAAAAAAAAAAAAAAAAA*AA - - A * Water * * * I * * ( 14.82 in.) 1.235 ft.) * * I * * I * V Circular Channel Section ------------------------ Flowrate ..................83.000 CFS Velocity ...................25.166 fps Pipe Diameter .............48.000 inches Depth of Flow .............14.816 inches Depth of Flow .............1.235 feet Critical Depth ............2.754 feet Depth/Diameter (D/d) 0.309 Slope of Pipe ..............7.800 % X-Sectional Area 3.298 sq. ft. Wetted Perimeter 4.712 feet AR(2/3) ..................2.600 Mannings 'n' ..............0.013 Mm. Fric. Slope, 48 inch Pipe Flowing Full 0.334 % O%TIOk) : fbg. 411 ?1 PE ASSLWE. yypi. j (S cS3 c SECTION 5 TEMPORARY DESILTING BASIN CALCULATIONS ROBERTSON RANCH PA 11 Job No. 061172 Prepared: OCTOBER 2006 Prepared by: O'DAY CONSULTANTS,' INC. 2710 Loker Avenue West Suite 100 Carlsbad, California 92010 Tel: (760) 931-7700 Fax: (760) 931-8680 DESILTING BASIN CALCULATIONS SECTION Surface Area Calculations Explanation 2 Soil Loss Calculations Explanation 3 Dewatering Calculation Explanation 4 Basin Sizing, Soil Loss, & Outlet Works Calculation Spreadsheets 5 Exhibits SECTION 1 Surface Area Calcullatona According to the Fact Sheelfor Water Quality-Order 99-08-DWQ issued by the State Water Resources Control Board (SWRCB), sediment basins shall, at a minimum, be designed and maintained as follows: Option 1: Pursuant to local ordinance for sediment basin design and maintenance, provided that the design efficiency is as protective or more protective of water quality than Option 3. Option 2: Sediment basin(s), as measured from the bottom of the basin to the principal outlet, shall have at least a capacity equivalent to 3,600 cubic feet of storage per acre draining into the sediment basin. The length of the basin shall be more than twice the width of the basin. The length is determined by measuring the distance between the inlet and the outlet; and the depth must not be less than three feet nor greater than five feet for safety reasons and for maximum efficiency. OR. Option 3: Sediment basin(s) shall be designed using the standard equation: A= 1.2Q/V5 Where: A. is the minimum surface area for trapping soil particles of a certain size; V is the settling velocity of the design particle size chosen; and Q=CxJxA where Q is the discharge rate measured in cubic feet per second; C is the runoff coefficient; I is the precipitation intensity for the 10-year, 6-hour rain event and A is the area draining into the sediment basin in acres. The design particle size shall be the smallest soil grain size determined by wet sieve analysis, or the fine silt sized (0.01 mm) particle, and the V used shall be 100 percent of the calculated settling velocity. The length is determined by measuring the distance between the inlet and the outlet; the length shall be more than twice the dimension as the width; the depth shall not be less than three feet nor greater than five feet for safety reasons and for maximum efficiency (two feet of storage, two feet of capacity). The basin(s) shall be located on the site where it can be maintained on a year- round basis and shall be maintained on a schedule to retain the two feet of capacity; OR Option 4: The use of an equivalent surface area design or equation, provided that the design efficiency is as protective or more protective of water quality than Option 3. Sediment basins for Carlsbad Oaks were designed to satisfy the requirements of fipao,s 1 using the following parameters: Appendix ll-A-4 of the San Diego County Hydrology Manual gives the precipitation for a 10-year, 6-hour storm as 1.9 inches for this project. (See Exhibit "A") P=1.9inchcs/6hours I = 032 avg. inches/hour (per Goldman et al., p. 8.16) Appendix IX of the San Diego County Hydrology Manual gives the runoff coefficients for this project as C0.35 to C0.45. (See Exhibit "B") Table 8.1 of the Erosion and Sediment Control Handbook (See Exhibit "C") gives the settling velocity for a 0.01 mm sized particle as Vs = 0.00024 feet/second. The San Diego County Soils Interpretation Study gives the soil classification for this project as "B", "C", and "D". (See Exhibit "D") (1 FOR BASIN CALCULA TIONSUMMARYSFREADSHEET SEE SECTION 4 SECTION 2 (1 LENGTH SLOPE AND STEEPNESS FACTOR "LS" SLOPE LENGTH AND STEEPNESS FACTOR "LS" IS CALCULATED USING TABLE 5.5 OF THE EROSION AN SEDIMENT CONTROL HANDBOOK. (SEE EXHIBIT "F") FOR BASIN CALCULATION SUMMARY SEE SECTION 4 VEGETATION COVER FACTOR "C" THE COVER FACTOR TABLE LISTED BELOW IS USED FOR AREA UNDER CONSTRUCTION OR CULTIVATION. TO BE CONSERVATIVE THE HIGHEST VALUE IS ASSUMED. c=110 ?ABLR$. C Vmbm dw 5ma lam Now *3 N.ths v5.tithu 1idIitibs0 % cwow. wood pasm& so mukb St OS W.4 1b iilth. S to .Maw (LI tdh.k with eeedt 0$ .__L_ a.JdØ OS 70 1Jei1.e (3.4 tlbe) tadod down 0$ 4 tuIs (SO Vhs). 4 353 OS tPeOstia. EROSION CONTROL PRACTICE FACTOR "P" THE P VALUES LISTED BELOW ARE GIVEN FOR AREAS UNDER CONSTRUCTION OR CULTIVATION. TO BE CONSERVATIVE, THE HIGHEST VALUE WAS ASSUMED. P=1.3 TALR SI P Facto, far C.erieU.. S6 (%âapt'4 Bran PaL 1*) &,rf c. P uJie - L.a Tráw1hsd aloaq contour- L.2 TeceIL.4 up and dcc,,, clopet as kud,sd at,sw as knsr cut 0.3 LAO" to it-in (30.)depth as 68 tea up and dacm dooft Irc a-fkaked namMal - .- SECTION 5.3 1, PAGES 5.27 TO 5.28 LISTS A STEP BY STEP PROCEDURE FOR USING THE UNIVERSAL SOIL LOSS EQUATION (SEE EXHIBIT "G") FOR SOIL LOSS CALCULATION SUMMARY SPREADSHEET SEE SECTION 4 SECTION 3 (L II I -.. ..j• ..-. - __ . -. p ---Ii' 4 - 10 4 ' •••E - I - - -I - - -- •- . - ------ - - -- - - - -1 6t,.vcy P11L ---------.. - .--..- SECTION 4 StandoiDe Calculations QCxlxA Ic = 10 mm. (see Desilting Basin Tributary Area Exhibit) = 4.38 in/hr. Q = cfs h= Case 1 Q = CPh C = 3.0 P= 4.1 ft d= 1.31 ft Case 2 Q = CA(2gh)"2 C= 0.67 A= 2.29 ft' d= 1.71 ft 24" pipe 4 11 (West Basin) Desiltation Basin Calculations = C tavg x A C= 0.45 = P6/6 hr. P8 = 1.7 in. (per 10 yr.-6 hr. Isopluvial) avg = 0.28 in./hr Pad A= 4.16 ac. Slope A = 0.60 ac. Total A= 4.76 ac. Qavg =[o6cfs A= 1.2QN5 V. = 0.00024 ft/sec mm. A5 = 2999 sf actual A3= 3120 sf .nll Loss Calculations :RxKxLSxCxp R =16.55(p)22 p= 1.3 in. (per 2yr.-6 hr. Isopluvial) R= 29.48 K= 0.24 C= 1.0 P= 1.0 Area Use % Area Length** Slope! Grade LS*** Slope 12.6% 1 1 55 2:1 1 1 13.2 Pad 87.4% 450 2 0.32 = ee Uesilting basin I ributary Area Exhibit = Per Figure 5-5 Avg. LS= 1.94 A = 13.75 tn/yr/ac Soil Loss = 65.4 tn/yr = ,1190 cf Basin Dewatenna Calculations A0 = 3600(T)C(g)112 H= 2 ft T= 40 hr Cd= 0.6 g = 32.2 ft/sec A0 = 0.012727 ft' ,°.1.83 .41n2 StandyiDe Calculations QCxlxA Ic = 10 mm. (see Desilting Basin Tributary Area Exhibit) = 4.38 in./hr. Q14.3 cfs h= 1 ft. Case I Case 2 Q = CPh Q = CA(2gh) C= 3.0 C= 0.67 P = 4.766667 ft A = 2.66 ft' d= 1.52 ft d= 1.84 ft 24" pipe Basin Dewaterina Calculations A. = 3600(T)Cd(g)1'2 H= 2 ft 4 11-(East Basin) Desiltation Basin Calculations Qavg = C X avg X A C = 0.45 avg = P616 hr. P6 = 1.7 in. (per 10 yr.-6 hr. Isopluvial) avg = 0.28 in./hr Pad A = 2.22 ac. Slope A = 1.28 ac. Total A= 3.50 ac. Qavg =O.441 cfs A5 = 1.2QN5 V8 = 0.00024 ft/sec min. A5 = 2205 sf actual A,= 10200 sf il Loss Calculations A=RxKxLSxCxP R =16.55(p)22 p = 1.3 in. (per 2yr.-6 hr. Isopluvial) R = 29.48 K= 0.24 C= 1.0 P= 1.0 Area Use % Area Length** Slope! Grade LS* Slope 36.6% 1 1 45 1 2:1 11.94 Pad 63.4% 300 2 0.28 = See Desilting Basin Tributary Area Exhibit = Per Figure 5-5 Avg. LS = 4.55 A= 32.17 tn/yr/ac 1 Loss = 112.6 tn/yr 2047. cf SECTION 5 (L Q County I 3330 — Riverside Coury k A I T4J H T15 I '--- CARLSBAD ENCIi <7 $OANA BEAD - - 300 Q )EL MAR I' ....... 16 - <T 3245-- H -- \..'. 2R45 OE OR _:i1__ HPERERA __ - - 3230 3230 N- County of San Diego Hydrology Manual Rainfall Isopluvials 2 Year Rainfall Event - 6 Hours -------- sopluvaI (inches) p s- ire N This MAP IS EROSTOED I4THOUT RARP.MOV Of RITA EJIRI EITHER STEREOS -*- C.MOJRI MACIL JR RIB.I. R.d. 7TH IROTROR TMIT .JRTHR IOTA ARMORS R.QOTS E S 3 0 3MiIes County of San Diego - Hydrology Manual 33 9. v Rainfall Isopluvials :w 10 Year Rainfall Event - 6 Hours IsopIuvial (Inches) 1 5DtOUt4r / a IL - \ County of San Diego Hydrology Manual Rainjall Isopluvials 100 Year Rainfall Event - 6 Hours sopIuvia (inches) s—cia R.ia 3 0 3MiIes RUNOFF COEFFICIENTS (RATIONAL METHOD) LAND USE Undeveloped Residential: Rural Single Family Multi-Units Mobile Homes (2) Commercial (2) 80% Impervious Industrial (2) 90% Impervious Coefficient, C Soil Group (J.) .30 .35 .40 .45 .30 .35 .40 .40 .45 .50 .35 .45 .50 .60 .0 .45 .50 .53 .63 .10 .75 .80 .35 .80 as .90 .93 NOTES: Obtain soil group from maps on file with the Department of Sanitation and Flood Control. 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. However, in no case shall the final coefficient be less than 0.50. For example: Consider commercial property on 0 soil group. Actual imperviousness = 50% Tabulated imperviousness = 8000- Revised C = ..g. X 0.35 I 1. (HT "C/ 8.18 Erosion and Sediment Control Handbook Sediment Retention Structi TABLE 8.1 Surface Area Requirements of Sediment Traps and Basins of the peak flow. A aubetar Buxtace area requirements. and basin efficiency is not a Settling velocity, ft' per ft2/eec (m' iier m3/eec Consider a basin designe, Particle size, mm ft/sec (rn/eec) discharge discharge) off rate. The average rainfai 05 (coarse sand) 0.19 (0.050) 5.3 (20.7) storm (Sec. 4.11). On. site 02 (medium sand) 0.087 (0.020) 17.9 (58.7) ideal settling conditions thi 01 (fine sand) 0023 (0.0070) 62.2 (171.0) soil (i.e., 62 percent of the 0.05 (coax.. silt) 0.0082 (0.0019) 193.6 (635.0) particles). 0.0 (medium silt) .0.00091(0.00029) 1,250.0 (4,101.0) If the surface area of tb 0.01 (fine silt) 0.00024 (0.000073) 5,000.0 (18,404.0)' would be roughly 3 time. 0.006 (day) 0.00006 (0.000018) 20,000.0 (65.817.0) Reclamation (10). 25 parcel period (Fig. 4.2). Since the I limetem) per hour,. the pox percent of the 6-hr total. Si ' sight composed of particles in the 0.01- to 0.02-mm range. A surface area 4 . discharge rate (A 1.2W1 times larger would be needed to capture 5 percent more of this soil. time, the average rate (50 A balance between the coat-effectiveness of a certain basin size and the deqire now would be about 3 times to capture fine particles must be achieved. It I. desirable to capture the very sized for the peak flow woul small soil particle. (days and fine silts) because they cause turbidity and other particles with approximate water quality problems. However, Table 8.1 shows that a basin would have to be ci.. Since the 0.02-mm part very large to capture particles smaller than 0.02 mm, particularly clay particles with a settling velocity of 0.005 mm and smaller. Because of the high coat of trapping very small particles, tured. These are approzimi the authors recommend 0.02 as the design particle size for sediment basins Suppose a basin on a sib except In areas with coarse soils, where a larger design particle may be used. The rate. For the purpose of ill 0.02-mm particle is classified as a medium silt by the AASHT() soil classification of the San Francisco Bay I 3Y5tffn1. tides, by weight, greater U . 0.02 mm). A basin with aLa - . tun the 0.01- to 0.02-mm 8.2d Basin Discharge Rate 1 67 percent of the eroded m cent (6/62) by tripling the The peak discharge, calculated by the rational or another approved method, is effective to aim a basin bj used to size the basin riser. During any major storm, a sediment basin should fill basin efficiency will not be with water to the top of its riser and then discharge at the rate of inflow to the basin. A sediment basin is not designed with a large water storage volume an is a reservoir. If the inflow exceeds the design peak flow used to size the riser, the I overflow should discharge down an emergency spillway. 8.2f Settling Depth If a basin is too shallow, w 3.2e Design Runoff Rate settled particles and deere grit-settling chambers at s trolled to prevent particle I equation for surface area of a sediment basin, the discharge rate Q is a grit chamber (2) is: 'e to be chosen by the designer. The above discussion of basin discharge ..e shows that the discharge rate is, to a large extent, equal to the inflow. The iser is sized to handle the peak inflow to the basin. The authors suggest deter. v,, = mining the surface area by the average runoff of a 10.year, 6-hr storm instead I HE .DIONDAt, . Df ? --D----L Cl- .1 - I 4 9 C fiueJJ / \ 06 I + ON lb B&I 6 - AY •. \ 1 CHES TNU . .:. I I: 1A GITE U A * CARLSBAD P. Ilk B ... .. Aau Hedjond - Po ID QAHStLO aI-aostLLo pqsu.o nqjO GiOtWLO JTSLLL0 -dii'O dWSL0 dVVO aostio LflLi'1L0 LSfflLO JX itIr('t cr\r7 tr\ AflI n £ZZ09 :308 N3SNVH M H1i3)I WOOSUOflnSU03I(DP0©I(OPO 099 609L :XDJ :3jy0 6u!1cMns OOLL— L6-09L 6U!ss930Jd 006 D!UJOJID3 poqspo >4OM JO 133NION3 6u!uuDld 6UIJOUI6U UA!3 00 I. 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UP, 06-12 EXISTING HYVROL CONDITION OGY MAP FOR ROBERTSON RANCH HA BITA T CORRIDOR GRADING - . \ - \.. \X S low - CITY OF OCEANSIDE HIGHWAY 78 VILL. SITE CITY OF WSTA CA SBAD NOT TO CITYOF SCALE 3O SAN AIARCOS PACIFIC \\ COS1 AVE OCEAN : /0 CITY OF ENCIMTAS V/C/Mi)' MAP NO SCALE . . .: ••• •. EL LEGEND FE/IA / 0607300768F AND 0766F FE/IA ROOD ZONE (ExIST/NC PER - - ____- ____- FE/IA MAP, PANEL 768 OF 2375, EFFEC11frE 1/UNE 19, 1997) EXIS11NG FLOOD ZONE (EXIST/NC PER - --------- CHANC SW Y, DA lED FEB. 20, 2006; ASSUMING B12, MELROSE AND FARADA Y DE TEN liON BASINS BU/L1 COLLEGE & CANNON GRADED) PROPOSED FLOOD ZONE (PROPOSED PER CHANG SW Y, DATED FEB. 20, 2006; ASSUMING BiB, MELROSE AND FARADAY DETENT/ON BASINS BUlL 1 COLLEGE & CANNON GRADED, 84 STORM DRAIN BUILT, AND PA 22 GRADED) BASIN 1/NE EASEM&%'1Y PER PRELIMINARY huE REPCYi'T BY FiRST AMER/CAN 111ZE INSURANCE C0MPAN1 NO. 1173037-6, DATED APRIL 27, 2001 AND AMENDMEJITS DA To MAY 17, 2001. EASEMENTSOF RECORD NO PURPOSE OWNER DOCUMENT REC. DATE DISPOSITION 3 PUBLIC 1/I7L/77ES & INCIDENTALS O.M. WD, BK 1796/PG 142 OF DEEDS 7-11-1930 QUITCLAIM 4 SLOPES CARLSBAD BK 521/PG 230 OR 6-12-1936 TO REMAIN *5 UT/LIliES & INCIDENTALS WS KELLY, L.J KELLY BK 1843/PG 398 OR 3-31-1945 TO REMAIN 6A UTiLITY S.D.G. & £ BK 4874/PC 143 OR 6-1-1953 TO REMAIN 7 UTiLITY SD.G. & £ BK 4874/PG 148 O.R. 6-1-1953 TO REMAIN 10 PIPELINES C/I. WI.?, FiLE Na 96185 0. R. 6-6-1961 QUIT CLAIM 13 UTiLITY S.D. C & E fiLE NO. 98887 0. R. 1 6-16-19661 TO REMAIN 14 SLOPE/DRAINAGE CARLSBAD FiLE NO. 44687 O.R. 3-72-1970 1 TO REMAIN 50' 200' I- 100' SCALE: 1" = 200' 55,5. DATE REkiSED: FEBRUARY 20, 2007 * LOCA liON CAN NOT BE DETERMINED BY RECORD 01%W4 12 DRAWN DESIGNED BY: S.K. BY: B.B. DATE: MAY 2006 SCALE: AS SHOWN PROJECT MGR.: K.H. JOB NO.:01-1014 CONSULTANT 2710 Loker Avenue W. Suite 100 Civil Engineering Planning ENGINEER OF WORK Carlsbad, California 92010 Processing 760-931-7700 Fax: 760-931-8680 Surveying DATE: KEITH W. HANSEN RCE: 60223 Oday@Odayconsultants.com ©2006 O'Day Consultants, Inc. G:\011014\0114SHYD03.dwg Feb 23, 2007 2:29pm Xrefs 0114sGRD 0114BSTR 0114BUTL 01147UTL 0114GUTL 0114BMAP 0114GSTR 0114MAP 0114TP—Q 0114shyd 0114fema 0114bgrd SHEET 1 OF 1 SHEETS H.D.P. 06-4 S. U.P. 16-12 PROPOSED C H17DROL OGY A. FOR ROBERTSON RANCH HA RITA CORRIDOR GRADING I C/fl' OF OCEANSIDE HIGHWAY '. ck SITE CITY OF ViSTA C/fl' Of- SAN MARCOS PACIFIC OCEAN CITY OF ENCIM TA S VICINITY MAP NO SCALE IGEND iTAlA / 0607300768F AND 0766F FEMA FLOOD ZONE (EXIST/NO PER - -____- ____- - FLAI14 MAP, PANEL 768 OF 2375, EFFEC111'E JUNE 19, 1997) EXISTING FLOOD ZONE (EXIS11NG PER - - - - - - - - - - CHANG S70Y, DATED iTS. 20, 2006; ASSUMING 88, UELROSE, AND FARADAY DE TEN 71ON BASINS BY/L1 COLLEGE & CANNON GRADED) PROPOSED FLOOD ZONE (PROPOSED PER - -. - - - - CHANO SWY, DATED FEB. 20, 2006; ASSUMING BiB, AIELROSE AND FARADAY DETEN110N BASINS BUILT, COLLEGE & CANM2N GRADED, 84 STORM DRAIN BUILT, AND PA 22 GRADED) EASEMENTS PER PREJJM/NARY huE REPC+?T BY FiRST AMERICAN 111ZE INSURANCE COMPANY, NO. /173037-6, DATED APRIL 27, 2001 AND AMENDMENTS DA lED MAY 17, 2001. 50' 200' I - 100' 400' SCALE: 1" = 200' EASEMENTS OF RECORD NO PURPOSE OWNER DOCUMENT REC. DATE DISPOSITION 3 PUBLIC (JilL/liES & INCIDENTALS 0./I. WD. BK 1796/PG 142 OF DEEDS 7-11-1930 QUITCLAIM 4 SLOPES CARLSBAD BK 521/PG 230 OR 6-12-1936 TO REMAIN *5 (JilL/i/ES & INCIDENTALS WS KELLY, L.J KELLY BK 1843/PG 395 OR 3-31-1945 TO REMAIN 64 U17U1Y S.D.G. & £ BK 4874/PG 143 O.R. 6-1-1953 TO REMAIN 7 U17UTY SD .G & £ BK 4874/PG 148 O.R. 6-1-1953 TO REMAIN 10 PIPELINES CM WD. fiLE NO. 96185 OR 6-6-1961 QUIT CLAIM 13 UT/LI?',' S.D.C. & £ FiLE NO. 98887 O.R. 6-16-1966 TO REMAIN 14 SLOPE/DRAINAGE CARLSBAD fiLE NO. 446870.1?. 3-12-1970 TO REMAIN DATE REI4SED. OCTOBER 25 2006 * LOCA 1/ON CAN NOT BE DETERV/NED BY RECORD 0 DESIGNED BY: S.K. DRAWN BY: B.B. DATE: MAY 2006 SCALE: AS SHOWN PROJECT MGR.:K.H. JOB NO.: 01-1014 CONSULT N T S 2710 Laker Avenue W. Suite 100 Civil Engineering Planning ENGINEER OF WORK Carlsbad, California 92010 Processing 760-931-7700 Fax: 760-931-8680 Surveying DATE. KEITH W. HANSEN RCE: 60223 oday©odayconsultants.com ©2006 O'Day Consultants, Inc. C:\011014\0114SHYD02.dwg Feb 23, 2007 2:37pm Xrefs 0114sGRD 0114BSTR 0114BUTL 01147UTL 0114CUTL, 0114BMAP 0114GSTR 0114MAP 0114TP—Q 0114shyd 0114fema 0114bgrd SECTION 6 HYDROLOGIC AND HYDRAULIC ANALYSES FOR ROBERTSON'S RANCH February 20, 2006 No. 46548c, Exp. 6/30/07 CF Wayne W. Chang, MS, PE chanowmimn Civil Engineering Hydrology Hydraulics Sedimentation P.O. Box 9496 Rancho Santa Fe, CA 92067 (858) 692-0760 -TABLE OF CONTENTS - ( Introduction................................................................................................................................... 1 DetentionBasin BIB Ponding......................................................................................................2 CalaveraCreek Floodplain ............................................................................................................ 3 ParkSite Ponding .......................................................................................................................... 5 Conclusion....................................................................................................................................6 APPENDIX 100-Year HEC-1 Analyses and Work Map 100-Year HEC-RAS Analyses 100-Year WSPGW Analysis and HEC-1 Assuming 8'x8' RCB Open MAP POCKET ( 100-Year Floodplain and Ponding Exhibit WY OF OCEANSIDE HIGHWAY 78 \' N MAR rr'ii INTRODUCTION Robertson's Ranch is a proposed project by Calavera Hills II, LLC located in the city of Carlsbad (see Vicinity Map). The easterly portion of Robertson's Ranch is named the East Village. The East Village is immediately north of the Rancho Carlsbad Mobile Home Park (RCMHP) and west of College Boulevard. Cannon Road follows an east-west alignment near the southerly boundary of the East Village. The area north of Cannon Road will be developed with single- and multi-family residential units. The area south of Cannon Road (Planning Area 22) will contain an approximately 4.4 acre pad developed with residential units. Finally, a park site and 5:1 slope grading (for a wildlife corridor) will be constructed within a portion of Robertson's Ranch West Village, which is just west of the East Village, north of Cannon Road, and east of El Camino Real. SITE I aff or wsr OF:ROA - CAJ3BAD go COsT AVE CITY or ENCINI TA S Figure 1. Vicinity Map The following paragraphs outline the pre- and post-development storm runoff patterns associated with Robertson's Ranch. Under both conditions, the upper Calavera Creek watershed is tributary to Detention Basin BJB, which is immediately east of the East Village. However, the pre- and post-developed conditions have different methods of conveying flow downstream of Detention Basin BJB. Under pre-developed conditions, storm runoff from the East Village footprint and tributary areas flows in a southerly direction towards the lower reach of Calavera Creek, which is located along the boundary of the East Village and RCMHP. A free-standing masonry wall exists along this boundary. A weir has been constructed within the easterly portion of the wall to regulate Calavera Creek flow along the north and south sides of the wall. In general, creek flow south of the wall is conveyed westerly to a confluence with Agua Hedionda Creek within RCMHP, and then continues westerly to Agua Hedionda Lagoon. Creek flow north of the wall is conveyed westerly, passes through culverts under Cannon Road and El Camino Real, and then enters Agua Hedionda Lagoon. The base of the wall contains several semi-circular openings along much of its length, which allows some flow migration between either side of the wall. Under developed conditions, the East Village will construct the 84-inch reinforced concrete pipe (RCP) in Cannon Road as well as the Planning'Area 22 grading. The 84-inch RCP is intended to convey the majority of the East Village runoff as well as flow directed north of the masonry wall by the weir. The 84-inch RCP will outlet on the north site of Cannon Road just east of El Camino Real. Flow outletting the pipe will not re-enter Calavera Creek. This report contains hydrologic and hydraulic analyses of three areas associated with Robertson's Ranch. First, the 100-year ponding within Detention Basin BJB is analyzed. A recent hydrologic analysis prepared for the city of Carlsbad determined ponding based on upstream improvements that are planned, but not yet constructed. This report revises the analysis to determine the ponding elevation based on current, rather than future, improvements. Next, Calavera Creek below Detention Basin BJB is analyzed to determine the benefits from Robertson's Ranch. Since the proposed 84-inch RCP will reduce flow entering Calavera Creek, the East Village will lower water surface elevations and reduce potential flood inundation in the RCMHP. Finally, the impact of the West Village's park site and 5:1 slope grading in the area north of the El Camino Real and Cannon Road intersection is assessed. The park site and slope grading will place fill in this area, which will reduce its storage capacity. DETENTION BASIN BJB PONDING Rick Engineering Company's (REC) December 13, 2004 report, Rancho Carlsbad Mobile Home Park, Alternative Analysis for Aqua Hedionda Channel Maintenance, contains their latest hydrologic and hydraulic analyses of Agua Hedionda and Calavera Creek. The analyses are based on full implementation of all the improvements associated with the city of Carlsbad's ultimate regional flood control solution for RCMHP, i.e., four detention basins (BJ, BIB, Faraday, Melrose), the aforementioned weir, increased storage capacity in Lake Calavera (with associated modifications to Basin BJB), and channel improvements within Agua Hedionda Creek. As of the date of this Robertson's Ranch report, Detention Basin BJB (without 2 ( modifications), the Faraday Basin, the Melrose Basin and the weir are components of the regional solution that either have been or are nearing completion. The Lake Calavera improvements and Detention Basin BJB modifications have not yet been constructed. In order to more accurately determine the existing ponding in Detention Basin BIB, these two improvements were revised in REC's HEC-1 hydrologic analysis to reflect existing conditions. The existing conditions within Lake Calavera and Detention Basin BIB were obtained from previous studies by REC. The revised HEC-1 analysis is included in Appendix A and shows that the 100-year ponded water surface elevation in Detention Basin BIB will be 77.1 feet. The ponding limits have been delineated on the exhibit in the map pocket. The ponding elevation is slightly higher (less than one foot) than the adjacent ground at the southerly end of the basin. As a result, shallow sheet flow can occur over this area during a 100-year event. In comparison, the ponded water surface elevation based on REC's ultimate condition analysis is 75.2 feet. Once the ultimate improvements are implemented by the city, Detention Basin BIB will provide at least one foot of freeboard over the 100-year ponding limits. CALAVERA CREEK FLOODPLAIN In order to assess the East Village's impact on Calavera Creek, hydrologic analyses were performed to determine pre- and post-development 100-year flow rates. The analyses were based on the latest HEC-1 analysis in REC's December 2004 report. To model pre-East Village conditions, REC's HEC-1 analysis was modified to reflect completion of only the ( aforementioned four regional solution components that have been or are nearing completion. This modified HEC-1 analysis and work map is included in Appendix A (see the first REC-1 analysis in Appendix A), and indicates that the combined 100-year flow rate in Calavera Creek near Agua Hedionda Creek is approximately 1,552 cubic feet per second (571 cfs north of the wall and 981 cfs south of the wall). The 84-inch RCP constructed by the East Village is intended to accomplish essentially the same 100-year flow split as the weir wall under ultimate conditions, i.e., approximately 500 cfs. However, there will be some differences during lower flows. The REC report indicates that 300 cfs will flow south of the wall before the weir begins to split flow north of the wall. On the other hand, the 84-inch RCP will begin to split flow when it reaches approximately 75 cfs. This will provide an overall benefit to RCMHP because more of the lower flows will be directed to the 84- inch RCP rather than Calavera Creek. A HEC-1 analysis based on this post-development condition is included in Appendix A (see the second HEC-1 analysis in Appendix A), and indicates that the 100-year flow rate in Calavera Creek near Agua Hedionda Creek is approximately 905 cfs. Next, pre- and post-development hydraulic analyses using the revised flow rates were performed to determine the 100-year water surface elevations in Calavera Creek prior to and after construction of the 84-inch RCP and Planning Area 22. The analyses were based on existing Agua Hedionda and Calavera Creek cross-sectional channel geometries from REC's December 2004 report. Future channel improvements proposed by the regional solution were not modeled since these will be constructed at a later date. REC's report contains an existing condition HEC- RAS analysis based on field surveys of Calavera Creek in December 2001, field surveys of Agua Hedionda Creek in May 2002, and updated field surveys downstream of Cannon Road in June 91 ( 2004. The analyses herein use the same basic information (roughness coefficients, cross-section locations/numbering, reach lengths, etc.) as the REC model, and REC's Agua Hedionda Creek cross-sections were not altered. On the other hand, the Calavera Creek cross-sections were modified as discussed next. REC's analysis of Calavera Creek assumed that the mobile home park wall prevents Calavera Creek flow from passing north of the wall. However, pursuant to discussions with the city of Carlsbad, the analyses in this report assume no wall along Calavera Creek because the existing wall has openings and is not FEMA-certified. The area north of the wall. was modeled using May 12, 2005 topographic mapping provided by O'Day Consultants. This report's analyses also assume that the Calavera Creek flow is encroached by the homes along the south creek bank since these homes define the southerly effective flow area. A baseline HEC-RAS hydraulic analysis was performed first. This analysis uses the HEC-1 100- year flow rates with the weir and is representative of the pre-Robertson's Ranch condition. Under this baseline, the total Calavera Creek 100-year flow rate below the weir (1,552 cfs) is distributed both north and south of the wall, i.e., there is no differential water surface north and south of the wall in Calavera Creek. The HEC-RAS flow rates assume that flow will be conveyed by the Cannon Road culverts as modeled in the HEC-1 analysis. The HEC-RAS results are included in Appendix B and summarized in Table 1. Appendix B contains tabular output for both Agua Hedionda and Calavera Creeks and cross-section plots for Calavera Creek. The HEC- RAS cross-sections are shown on the exhibit in the map pocket. Next, a HEC-RAS analysis was performed based on O'Day Consultants' Planning Area 22 grading and the reduced Calavera Creek 100-year flow rate (905 cfs) resulting from construction of the 84-inch RCP. This analysis assumes that the flow will not be conveyed to the Cannon Road culverts, and represents the post-development condition. The HEC-RAS results are included in Appendix B and summarized in Table 1. A comparison of the HEC-RAS results indicates that the East Village will reduce water surface elevations throughout much of Calavera Creek. Therefore, flood inundation in RCMHP will also be reduced. It should be noted that the water surface elevations in the lower reach of Calavera Creek are affected by backwater near the confluence with Agua Hedionda Creek. The HEC-RAS analyses indicate that the 100-year flow will overtop El Camino Real under the current channel geometry. As a result, the floodplain extends over a portion of El Camino Real and Cannon Road. The pre- and post-Robertson's Ranch floodplains are delineated on the exhibit in the map pocket. This exhibit includes a portion of the floodplain exhibit from REC's December 2004 report. REC's exhibit delineates several floodplains based on various scenarios they modeled. The solid green line from REC's exhibit corresponds to the analyses in this report. Consequently, the floodplains developed in this report tie-into the green line on the exhibit. 4 LIEC-RAS Cross-section Elevation without East Village, ft. Elevation with East Village, 84"RCP & PA-22 Grading, ft. Difference, ft. - 50.11 49.6 49.5 -0. 310 49.6 49.5 -0. - 400 49.6 49.5 -0. - 580 49.6 49.5 -0. - 750 49.6 49.6 0 1000 49.6 49.6 0 1230 49.6 49.6 0 1470 49.6 49.6 0 1810 50.8 50.0 -0.8 2100 53.3 51.5 . -1.8 2420 56.2 54.5 -1.7 2700 57.2 55.3 -1.9 2980 58.0 56.1 -1.9 3170 59.8 57.3 -2.5 Table 1. Comparison of 100-Year Water Surface Elevations PARK SITE PONDING REC's HEC-1 analysis did not model the storage that can occur in the area north of the intersection of Cannon Road and El Camino Real. This area currently supports a nursery. The West Village development proposes to fill a portion of the area to create a park site and a 5:1 slope area for a wildlife corridor. In order to assess the park's impact on 100-year ponding in this area, the area's storage-outflow characteristics were added to the HEC-1 analyses. The existing storage volume was included in the HEC-1 analysis modeling the weir wall (see first HEC-1 analysis in Appendix A), while the reduced storage volume resulting from the park site and 5:1 slope area was included in the HEC-1 analysis modeling the 84-inch RCP (see the second HEC-1 analysis in Appendix A). Furthermore, a third analysis (see the third HEC-1 analysis in Appendix A) was performed assuming completion of the East Village development (84-inch RCP and Planning Area 22), but no grading for the park site or 5:1 slope area. The existing storage volume was determined from May 12, 2005, 2-foot contour interval topographic mapping provided by O'Day Consultants, while the proposed storage volume was determined from the topographic mapping and O'Day Consultants' park and 5:1 slope grading plans. Flow leaves the area through a culvert under El Camino Real. REC's report indicates that the culvert is an 8-foot by 8-foot reinforced concrete box (RCB). However, a February 16, 2006 field measurement revealed that sediment had deposited in the culvert reducing the height of the opening to 5 feet. The RCB was modeled in the three analyses based on the reduced height. The HEC-1 results indicate that Robertson's Ranch with the East and West Village development will cause a 0.1 foot increase in the ponded 100-year water surface elevation (41.3 feet pre- development versus 41.4 feet post-development). Both ponding limits are included on the exhibit in the map pocket. The ponding extends slightly into El Camino Real; however, this area 5 (.. ( experiences greater inundation from the Agua Hedionda Creek floodplain. The results also indicate that Robertson's Ranch with only the East, and not West, Village developed will reduce the ponding to an elevation of 41.1 feet. A WSPGW analysis was performed to determine the 100-year flow velocity in the silted El Camino Real culvert (see Appendix Q. The analysis indicates that the velocity can be over 13 feet per second. At this rate, it is possible that accumulated silt will wash out of the RCB. An additional HEC-1 analysis was performed to determine the ponded water surface elevation assuming that Robertson's Ranch was developed and the RCB contained no silt. The analysis is included in Appendix C and indicates that the ponding elevation drops to 35.6 feet, which is several feet lower than the low point in El Camino Real (41.7 feet). CONCLUSION Hydrologic and hydraulic analyses have been performed to determine the ponding in Detention Basin BIB, the 100-year water surface elevations in Calavera Creek, and the ponding in the area north of the El Camino Real and Cannon Road intersection. The analyses assumed completion of only those city of Carlsbad regional solution components that have been, or are currently being, constructed. The remaining components were not modeled since they have yet to be implemented. The results are summarized in Table 2. 100-Year 100-Year Water 100-Year Ponding NE Ponding in Surface Elevation In of El Camino Real Basin BJB, ft. Calavera Creek, ft. and Cannon Rd., ft Exist Conditions 77.1 49.6-59.8 41.3 With East Village (84" RCP, PA-22, and 3' of 77.1 49.5-57.3 41.1 Silt in RCB) With East Village, Park Site, and 5:1 Slope Area 77.1 49.5-57.3 41.4 (3' of Silt in RCB) With East Village, Park Site, and 5:1 Slope Area 77.1 49.5-57.3 35.6 (No Silt in RCB) Table 2. Summary of Results The results show that Robertson's Ranch East Village will reduce flood inundation in some areas. The following findings have been made for this development: The proposed development pads including Planning Area 22 will be above the 100-year floodplain. Portions of six existing mobile homes in RCMHP will be removed from the 100-year floodplain based on the analyses in this report. The floodplain areas that will be eliminated by the East Village have been shaded on the exhibit in the map pocket The project will incrementally decrease ponding in the area north of El Camino Real and Cannon Road. The results also indicate that the park and 5:1 slope area, to be constructed by the West Village, could slightly increase 100-year ponding onto El Camino Real with the 8'x8' RCB silted to it's current level. On the -other hand, it is possible that some silt will be removed as the flow approaches the 100-year magnitude and the velocity increases. In this case, the culvert's capacity would increase, which would prevent ponding onto El Camino Real. Maintenance to remove silt in the culvert would also eliminate 100-year ponding onto the road. 7 APPENDIX A 100-YEAR HEC-1 ANALYSES AND WORK MAP 0 - uj co uiZUi U- [INOH CINIV DC Sy '41610, a I I -r -:- SMMM 'K. At :IwATt 1: '1 'A'4: • I d I IIi 00 Jim -v i •' i.-