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HomeMy WebLinkAboutPIP 05-03; PALOMAR FORUM LOT 6 & 7; HYDROLOGY STUDY; 2005-08-16Prepared by: HYDROLOGY STUDY FOR PALOMAR FORUM LOTS6&7 P.I.P 05-03 Developed Condition Job No. 011010-5 Revised: August 16, 2005 Revised: July 5, 2005 Revised: May 2, 2005 March 1, 2005 O'DAY CONSULTANTS, INC. 2710 Loker A venue West Suite 100 Carlsbad, California 92008-6603 Tel: (760) 931-7700 Fax: (760) 931-8680 Keith Hansen RCE 60223 Exp. 06/30/06 Date V) 0 C) - <S' \t-' i ~ ..:..:. ~ 0 '2 ' ._. I D) E z ........ J) i • SECTIONl SECTION2 • SECTION3 SECTION4 SECTIONS APPENDIX • INTRODUCTION Purpose of Study Scope TABLE OF CONTENTS Hydrologic Analysis HYDROLOGY Modified Rational Method Description Program Process CONCLUSION Vicinity Map Intensity-Duration Design Chart Isopluvial Maps 100-Year, 6-Hour 100-Year, 24-Hour San Diego County Soils Interpretation Study Runoff Coefficients Nomograph for Determination of Tc for Natural Watersheds Urban Areas Overland Time of Flow Curves Hydrology 100 year Analysis Developed Condition Developed Condition Drainage Map Hydrologic Calculations for Existing Conditions w/ Map from "Hydrology and Hydraulic Study for Palomar Forum" dated February 3, 2003 Rancho Carlsbad Channel & Basin Project • INTRODUCTION Purpose of Study This drainage study was prepared to determine proposed runoff quantities for Lots 6 & 7 of Palomar Forum after development. Scope This study analyzes the 100-year flow for developed conditions of the site. Hydrologic Analysis The hydrology of this site for the developed condition is calculated using one basin that outlets into an existing Type 'F' catch basin at node 2000. (See map in section 4) The 100-yr flow at this point is 36.13 cfs with a Tc of 7 .29 min. The existing condition of the site is a mass graded pad per grading plan drawings 399-4A. The existing hydrology was analyzed in a study done by O'Day Consultants titled "Hydrology and Hydraulic Study for Palomar Forum" dated February 3, 2003. That study used C values reflective of a developed site, 0.95.The previously calculated 100-yr ultimate flow at node 2000 (node 118 in said report) is 41.26 cfs with a Tc of 5.79 min. (See Section 5 for calcs) HYDROLOGY The hydrologic analyses are being performed according to the 1985 San Diego County Hydrology Manual. The 1985 manual is being used so that results are consistent with those of the hydrology study for the existing conditions (mass graded pads). Section 1.3 of the June 2003 Hydrology Manual states that the manual must not be used if there is already an established flow. 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 1985 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 3.0 inches and the 24-hour rainfall amount is 5.2 inches. San Diego County Rational-Hydrology Program Package Version 3.2, developed by CivilCADD/CNILDESIGN Engineering Software © (1993), 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: 1. Initial sub-area input, top of stream. 2. Street flow through sub-area, includes sub-area runoff. 3. Addition of runoff from sub-area to stream. 4. Street inlet and parallel street and pipeflow and area. 5. Pipeflow travel time (program estimated pipe size). 6. Pipeflow travel time (user-specified pipe size). 7. Improved channel travel -Area add option. 8. Irregular channel travel time -Area add option. 9. User-specified entry of data at a point. 10. Confluence at downstream point in current stream. 11. Confluence of main streams . Section 2 • • • • • LOT7PR.OUT 0.999 * 1.000 * 1.126) + = 3.002 Qmax(2) = 1.000 * 0.998 * 1.877) + 1.000 * 1.000 * 1.126) + = 3.000 Total of 2 streams to confluence: Flow rates before confluence point: 1.877 1.126 Maximum flow rates at confluence using above data: 3.002 3.000 Area of streams before confluence: 0.250 0.150 Results of confluence: Total flow rate= 3.002(CFS) Time of concentration= 5.008 min. Effective stream area after confluence= 0.400(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1106.000 to Point/Station 1108.000 **** PIPEFLOW TRAVEL TIME (Program estimated size)**** Upstream point/station elevation= 420.70(Ft.) Downstream point/station elevation= 420.20(Ft.) Pipe len~th = 102.85(Ft.) Manning's N = 0.010 No. of pipes= 1 Required pipe flow = 3.002(CFS) Nearest computed pipe diameter = 12.00(In.) calculated individual pipe flow = 3.002(CFS) Normal flow depth in pipe= 9.lS(In.) Flow top width inside pipe= 10.21(In.) critical Depth= 8.92(In.) Pipe flow velocity= 4.67(Ft/s) Travel time through pipe= 0.37 min. Time of concentration (TC)= 5.38 min. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/station 1108.000 to Point/Station 1110.000 **** PIPEFLOW TRAVEL TIME (Program estimated size)**** upstream point/station elevation= 420.20(Ft.) Downstream point/station elevation= 419.85(Ft.) Pipe len~th = 69.0S(Ft.) Manning's N = 0.010 No. of pipes= 1 Required pipe flow = 3.002(CFS) Nearest computed pipe diameter = 12.00(In.) calculated individual pipe flow = 3.002(CFS) Normal flow depth in pipe= 8.99(In.) Flow top width inside pipe= 10.41(In.) critical Depth= 8.92(In.) Pipe flow velocity= 4.76(Ft/s) Travel time through pipe= 0.24 min. Time of concentration (TC)= 5.62 min. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1110.000 to Point/Station 1116.000 tn'<** PIPEFLOW TRAVEL TIME (Program estimated size) inH-t, upstream point/station elevation= 419.85(Ft.) Downstream point/station elevation= 419.69(Ft.) Pipe len~th = 30.75(Ft.) ~anning's N = 0.010 No. of pipes= 1 Required pipe flow ~ 3.002(CFS) Nearest computed pipe diameter = 12.00(In.) Page 3 ( ·• LOT7PR.OUT ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1130.000 to Point/Station 1140.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** Upstream point/station elevation= 412.90(Ft.) Downstream point/station elevation= 412.68(Ft.) Pipe lenijth = 19.25(Ft.) Manning's N = 0.010 No. of pipes= 1 Required pipe flow = 13.737(CFS) Nearest computed pipe diameter = 18.00(rn.) calculated individual pipe flow = 13.737(CFS) Normal flow depth in pipe= 13.88(In.) Flow top width inside pipe= 15.13(In.) critical Depth= 16.SO(In.) Pipe flow velocity= 9.39(Ft/s) Travel time through pipe= 0.03 min. Time of concentration (TC)= 6.70 min. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1130.000 to Point/Station 1140.000 **** CONFLUENCE OF MINOR STREAMS**** Along Main Stream number: 1 in normal stream number 1 stream flow area= 2.020(Ac.) Runoff from this stream= 13.737(CFS) Time of concentration= 6.70 min. Rainfall intensity= 6.547(In/Hr) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1143.000 to Point/station 1142.000 **** INITIAL AREA EVALUATION ***-* Decimal fraction soil group A= 0.000 Decimal fraction soil group B = 0.000 Decimal fraction soil group c = 0.000 Decimal fraction soil group D = 1.000 [INDUSTRIAL area type ] Initial subarea flow distance = 234.00(Ft.) Highest elevation= 426.00(Ft.) Lowest elevation= 418.30(Ft.) Elevation difference= 7.70(Ft.) Time of concentration calculated by the urban areas overland flow method (App X-C) = 2.78 min. TC= [1.8*(1.l-C)*distanceA.5)/(% slopeA(l/3)] TC= [1.8*(1.1-0.9500)*(234.00A.5)/( 3.29A(l/3)]= 2.78 setting time of concentration to 5 minutes Rainfall intensity (I)= 7.904 for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is c = 0.950 subarea runoff= 3.679(CFS) Total initial stream area= 0.490(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1142.000 to Point/Station 1140.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** upstream point/station elevation= 415.30(Ft.) Downstream point/station elevation~ 413.lO(Ft.) Pipe len9th = 10.00(Ft.) Manning's N = 0.010 No. of pipes= 1 Required pipe flow = 3.679(CFS) ~earest computed pipe diameter ~ 6.00(rn.) Pdge 14 • LOT7PR.OUT Process from Point/Station 1158.000 to Point/station 1152.000 **** CONFLUENCE OF MINOR STREAMS**** Along Main stream number: 2 in normal stream number 1 Stream flow area= 1.0lO(Ac.) Runoff from this stream= 6.371(CFS) Time of concentration= 6.81 min. Rainfall intensity= 6.474(In/Hr) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1156.000 to Point/Station 1154.000 **** INITIAL AREA EVALUATION**** Decimal fraction soil group A= 0.000 Decimal fraction soil group B = 0.000 Decimal fraction soil group c = 0.000 Decimal fraction soil group D = 1.000 [INDUSTRIAL area type ] Initial subarea flow distance = 86.00(Ft.) Highest elevation= 418.SO(Ft.) Lowest elevation= 416.lO(Ft.) Elevation difference= 2.70(Ft.) Time of concentration calculated by the urban areas overland flow method (App x-c) = 1.71 min. TC= [1.8*(1.l-C)*distanceA.5)/(% slopeA(l/3)] TC= [1.8*(1.1-0.9500)*( 86.00A.5)/( 3.l4A(l/3)]= 1.71 setting time of concentration to 5 minutes Rainfall intensity (I)= 7.904 for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is c = 0.950 subarea runoff= 1.577(CFS) Total initial stream area= 0.210(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1154.000 to Point/Station 1152.000 "'*** PIPEFLOW TRAVEL TIME (Program estimated size) **** upstream point/station elevation= 414.lO(Ft.) Downstream point/station elevation= 411.26(Ft.) Pipe len~th = 20.SO(Ft.) Manning's N = 0.010 No. of pipes= 1 Required pipe flow = 1.577(CFS) Nearest computed pipe diameter = 6.00(In.) calculated individual pipe flow = 1.577(CFS) Normal flow depth in pipe= 3.28(In.) Flow top width inside pipe= 5.97(In.) critical depth could not be calculated. Pipe flow velocity= 14.34(Ft/s) Travel time through pipe= 0.02 min. Time of concentration (TC)= 5.02 min. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1154.000 to Point/Station 1152.000 "'*** CONFLUENCE OF MINOR STREAMS u** ~long Main stream number: 2 in normal stream number 2 Stream flow area= 0.210(Ac.) Runoff from this stream= 1.577(CFS) Time of concentration~ 5.02 min. Rainfall intensity= 7.880(In/Hr) summary of stream data: Page 18 •• • ·• LOT7PR.OUT ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1150.000 to Point/station 1170.000 **** PIPEFLOW T~VEL TIME (Program estimated size) **** upstream point/station elevation= 410.67(Ft.) Downstream point/station elevation= 410.Sl(Ft.) Pipe length = 19.97(Ft.) Manning's N = 0.010 No. of pipes= 1 Required pipe flow = 25.537(CFS) Nearest computed pipe diameter = 24.00(In.) calculated individual pipe flow = 25.537(CFS) Normal flow depth in pipe= 19.0S(In.) Flow top width inside pipe= 19.41(In.) critical Depth= 21.30(In.) Pipe flow velocity= 9.55(Ft/s) Travel time through pipe= 0.03 min. Time of concentration (TC)= 7.03 min. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/station 1150.000 to Point/Station 1170.000 **** CONFLUENCE OF MINOR STREAMS**** Along Main stream number: 1 in normal stream number 1 stream flow area= 3.920(Ac.) Runoff from this stream= 25.537(CFS) Time of concentration= 7.03 min. Rainfall intensity= 6.345(In/Hr) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/station 1174.000 to Point/Station 1172.000 **** INITIAL AREA EVALUATION**** Decimal fraction soil group A= 0.000 Decimal fraction soil group B = 0.000 Decimal fraction soil group c = 0.000 Decimal fraction soil group D = 1.000 [INDUSTRIAL area type ] Initial subarea flow distance = 100.00(Ft.) Highest elevation= 419.70(Ft.) Lowest elevation= 415.SO(Ft.) Elevation difference= 3.90(Ft.) Time of concentration calculated by the urban areas overland flow method (App x-c) = 1.72 min. TC= [1.8*(1.l-C)*distanceA.5)/(% slopeA(l/3)] TC= [l.8*(1.1-0.9500)*(100.00A.5)/( 3.90A(l/3)]= 1.72 setting time of concentration to 5 minutes Rainfall intensity (I)= 7.904 for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is c = 0.950 subarea runoff= 0.60l(CFS) Total initial stream area= 0.080(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1172.000 to Point/station 1170.000 ~,*'/:1, PIPEFLOW TRAVEL TIME (Program estimated size) >'r:'r1r* upstream point/station elevation~ 412.SO(Ft.) Downstream point/station elevation= 411.lS(Ft.) Pipe length = 5.00(Ft.) ~anning's N = 0.010 ~o. of pipes= 1 Required pipe flow = 0.601(CFS) r'age 21 Section.5 • • • LOT7PR.OUT Total initial stream· area= 0.760(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/station 1190.000 to Point/station 1192.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** Upstream point/station elevation= 413.lO(Ft.) Downstream point/station elevation= 412.SS(Ft.) Pipe lenQth = 27.89(Ft.) Manning's N = 0.010 No. of pipes= 1 Required pipe flow = S.707(CFS) Nearest computed pipe diameter = 12.00(In.) calculated individual pipe flow = S.707(CFS) Normal flow depth i.n pipe = 8. 92(In.) Flow top width inside pipe= 10.49(In.) critical Depth= ll.35(In.) Pipe flow velocity= 9.12(Ft/s) Travel time through pipe= 0.05 min. Time of concentration (TC)= 5.05 min. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/station 1192.000 to Point/station 1194.000 **** PIPEFLOW TRAVEL TIME (Program estimated size)**** upstream point/station elevation= 412.SS(Ft.) Downstream point/station elevation= 409.87(Ft.) Pipe lenQth = 161.47(Ft.) Manning's N = 0.010 No. of pipes= 1 Required pipe flow = 5.707(CFS) Nearest computed pipe diameter = 12.00(rn.) calculated individual pipe flow = 5.707(CFS) Normal flow depth in pipe= 9.35(In.) Flow top width inside pipe= 9.95(In.) critical Depth= 11.35(In.) Pipe flow velocity= 8.69(Ft/s) Travel time through pipe= 0.31 min. Time of concentration (TC)= 5.36 min. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/station 1192.000 to Point/Station 1194.000 **** CONFLUENCE OF MINOR STREAMS**** Along Main Stream number: 2 in normal stream number 1 stream flow area= 0.760(Ac.) Runoff from this stream= 5.707(CFS) Time of concentration= 5.36 min. Rainfall intensity= 7.557(In/Hr) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/station 1195.000 to Point/station 1196.000 **'~* INITIAL AREA EVALUATION **** Decimal fraction soil group A= 0.000 Decimal fraction soil group B = 0.000 Decimal fraction soil group c = 0.000 Decimal fraction soil group D = 1.000 [INDUSTRIAL area type ] Initial subarea flow distance = 152.00(Ft.) Highest elevation= 420.40(Ft.) Lowest elevation= 418.00(Ft.) Elevation difference= 2.40(Ft.) Page 25 Section 4 • • Appendix • • 1 • Preliminary designs were performed for each proposed detention facility to determine the outlet works reqm.red to achieve max1rnu.m detentwn, while mamtammg the height and storage volume below DSOD jurisdictional limits. The preliminary design of each detention facility and the results for each detention facility design are described below. The most upstream proposed detention facility in Agua Hedionda Creek is at Melrose Drive. This facility will be a flow-through detention basin. Melrose Drive runs north-south and currently ends just south of Aspen Way near the Carlsbad Corporate boundary. Future plans call for the extension of Melrose Drive to Palomar Airport Road. An existing reinforced concrete box (RCB) culvert conveys flow under Melrose Drive and is l O feet wide by 7 feet high. The existing Melrose Drive embankment provides minimal detention because of the RCB's large capacity. Hydrologic calculations show that a 36-inch diameter opening at this location will detain the peak flow discharge ( .m approximately 450 cubic feet per second (cfs) to 180 cfs. There are two alternatives for creating the 36-inch opening. One is to replace the existing culvert with a 36-inch RCP and the other is to construct a concrete barrier at the inlet with a 36-inch diameter opening. The resultant storage volume and ponded water surface elevation (WSEL) with the new outlet works will be approximately 41 acre-feet and 329 feet~ respectively. This will create an inundation area of approximately seven acres. The estimated outlet velocities for the first and second alternative will be 25 and 13 feet per second (fps), respectively. The velocity under the first alternative is greater than the maximum desired velocity of 20 fps. The velocity calculation assumed that the proposed 36-inch RCP was constructed at the slope of the existing culvert, which is one percent. If this alternative is selected, the final culvert design should analyze methods for red_ucing the outlet velocity, such as placing the culvert at a flatter slope or using multiple small diameter culverts. A \. Prepared By: Rick Engineering Company -Water Resources Division 8 DCB;MDL:cmn/R.eport/1-13182.00 I 07/01/98