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HomeMy WebLinkAboutCUP 2018-0014; FIRE STATION NO. 2; DRAINAGE STUDY FOR CARLSBAD FIRE STATION NO.2; 2021-04-01DRAINAGE STUDY for CARLSBAD FIRE STATION NO.2 FOREST A VENUE CARLSBAD, CA 92008 APN: 156-110-84-00 Prepared By: B\VE STRUCTURAL ENGINEERING • CIVIL ENGINEERING • SURVEYING • LAND PLANNING 9449 Balboa Avenue, Suite 270 San Diego, CA 92123 BWE Job #: 13200U Date: April 2021 RE r;-vlVF,"!l APR 2 7 2D21 LAt,ff) DEVcL ·,JPMENT E · SlNEE.f;:;NG Table of Contents 1. Purpose ........................................................................................................................ 2 2. Background ................................................................................................................. 2 3. Existing Condition ...................................................................................................... 2 4. Proposed Improvements .............................................................................................. 2 5. Soil Characteristics ..................................................................................................... 2 6. Methodology ............................................................................................................... 3 7. Calculations ................................................................................................................. 4 a. Impervious and Pervious Areas ............................................................................... 4 Table 7-1 Summary of Areas ...................................................................................... 4 b. Runoff Coefficient ................................................................................................... 4 C. Peak Flow Rates ....................................................................................................... 4 Table 7-2 Existing and Proposed Conditions Peak Flow Rates Summary ................. 5 8. Conclusion .................................................................................................................. 5 9. References ................................................................................................................... 5 Appendices Site Vicinity/Imagery Maps ....................................................... Appendix A Hydrologic Soil Group Map FEMAMap Existing Condition Runoff Coefficient Calculations ........................... Appendix B Existing Condition Hydrology Calculations Existing Condition Hydrology Map Proposed Condition Runoff Coefficient Calculations .......................... Appendix C Proposed Condition Hydrology Calculations Proposed Condition Hydrology Map 1. Purpose This drainage study analyzes the existing and proposed drainage patterns and peak flow rates for the proposed Fire Station No.2 in the City of Carlsbad, California. The proposed development consists of a new fire station building, driveway, permeable pavers, tree wells, and landscaping. To determine the impacts of the proposed development the pre-development and post- development peak flow rates resulting from the 100-year, 6-hour storm event are analyzed using the Rational Method. This report has been prepared in accordance with the requirements of the County of San Diego Hydrology Manual. 2. Background This project is located in Region Number 9, Carlsbad Hydrologic Unit, San Marcos Hydrologic Area, and Batiquitos Subarea (HSA 904.51) as defined in the Regional Water Quality Control Board's (RWQCB) Water Quality Control Plan. The site discharges indirectly to the City of Carlsbad's Storm Drain System on El Camino Real and Arenal Rd, which flows to San Marcos Creek, and ultimately to the Pacific Ocean. The Federal Emergency Management Agency (FEMA) categorizes the project site's Flood Hazard as Zone X, where Zone X is area determined to be outside 500-year floodplain (FIRM Panel 06073C 1032H). Appendix A contains the FEMA floodplain mapping within the vicinity of the project site. 3. Existing Condition The existing site contains an existing fire station building, parking area, pavement, driveway and some vegetation. The existing contours show that the site drains in 2 discharge points: one southeast to Arenal Road (Discharge Point 1) and one southwest to El Camino Real (Discharge Point 2). See Appendix B for the Existing Condition Hydrology Map. 4. Proposed Improvements The proposed development consists of a new fire station building, driveway, permeable pavers, tree wells, and landscaping. The site is designed to maintain the existing drainage pattern to the maximum extent feasible. Proposed permeable pavers and tree wells on the northern side of the building will help mitigate the peak flow rate from the development. See Appendix C for the Proposed Conditions Hydrology Map. 5. Soil Characteristics The NRCS Web Soil Survey indicates that the site consists of Hydrologic Soil Groups "B" and "D". The Soil Map is included in Appendix A. 2 6. Methodology Rational Method: A rational method analysis was utilized to perform hydrologic calculations in this study. Rational Equation: Q = C * I * A Where; Q = Peak discharge, cfs C = Rational method runoff coefficient (unitless) I = Rainfall intensity, Inch/Hour A = Drainage area, Acre The CivilD computer model is used to automate the hydrology analysis. This computer version of the rational method analysis allows user to develop a node-link model of the watershed. CivilD computer program has the capability of performing calculations utilizing mathematical functions. These functions are assigned code numbers, which appear in the printed results. The code numbers and their corresponding functions are described below; Sub-area Hydrologic Processes; Code 1 -INITIAL subarea input, top of stream Code 2 -STREET flow through subarea, includes subarea runoff Code 3 -ADDITION of runoff from subarea to stream Code 4 -STREET INLET + parallel street & pipe flow+ area Code 5 -PIPEFLOW travel time (program estimated pipe size)** Code 6 -PIPEFLOW travel time (user specified pipe size) Code 7 -IMPROVED channel travel time (open or box)** Code 8 -IRREGULAR channel travel time** Code 9 -USER specified entry of data at a point Code 10 -CONFLUENCE at downstream point in current stream Code 11 -CONFLUENCE of mainstreams **NOTE: These options do not include subarea runoff **NOTE:(#) -Required pipe size determined by the hydrology program 3 C C 7. Calculations a. Impervious and Pervious Areas The impervious and pervious areas are calculated for both the existing and proposed site conditions. The proposed development increases the impervious area by less than 0.01 acres as shown in Table 7-1. Table 7-1 Summary of Areas Area (Acres Impervious Pervious Percent Percent Total (Ai) (Ao) Impervious Area Pervious Area Existing 0.33 0.23 0.10 69% 31% Condition ' ' Proposed 0.33 0.23 0. 69% 31% Condition Percentage Change 0% +200% -10% b. Runoff Coefficient The runoff coefficient for the site is calculated by using the following equation provided in Section 3 .1.2 of the County of San Diego Hydrology Manual: C = 0.90 x (%Impervious)+ Cp x (1 - % Impervious) Where, Cp = Pervious Coefficient Runoff Value for the soil type shown in Table 3-1 as Undisturbed Natural Terrain/Permanent Open Space. Cp = 0.35 is used for Soil Type D See Appendices B and C for the runoff coefficient calculations. c. Peak Flow Rates The CivilD computer program, which utilizes the rational method of analysis, is used to determine peak flow rates in this study. The peak flow rates for the 100-year storm, 6-hour event are calculated for both existing as well as proposed conditions and summarized in Table 7-2. The detailed calculations (CivilD results) are located in Appendices Band C for the existing and proposed conditions respectively. 4 Table 7-2 Existing and Proposed Conditions Peak Flow Rates Summary Drainaee Area (acres) 100 Yr, 6 Hr Flow Rate (cfs) Existing Proposed Existing Proposed Change Condition Condition Condition Condition (%) Discharge Point #1 (southeast to Arenal Rd) 0.24 0.29 1.07 1.06 -1% Discharge Point #2 (Southwest to El Camino Real) 0.09 0.04 0.39 0.26 -33% In the proposed condition, the runoff from the 100-year, 6-hour storm event will decrease by 0.14 cfs. See Appendix C for detailed calculations. 8. Conclusion Storm water runoff discharges southeast to Arenal Road and southwest to El Camino Real where it is collected by the City of Carlsbad storm sewer system. The proposed development maintains existing drainage patterns and provides sufficient mitigation to have peak flow rates not exceed existing condition for the 100-yr, 6-hr storm event. Due to this, no adverse downstream impacts are anticipated. 9. References • City of Carlsbad Drainage Master Plan, 2008 • City of Carlsbad Engineering Standards, 2016 • County of San Diego Hydrology Manual, 2003 • City of Carlsbad Land Development Engineering Department Standards (http://www.carlsbadca.gov/ services/ depts/landev /landdev .asp) 5 J C APPENDIX A: Site Vicinity/Imagery Maps Hydrologic Soil Group Map FEMA Floodplain map VICINITY CITY Of' OCEANSIDE PACIFIC OCEAN 78 MAP v or N MARCOS IMAGERY MAP 33" 5'42"N 33" 5'39'N Kl ij 0 1ii ij S N A Hydrologic Soil Group-San Diego County Area, California Map Scale: 1:498 if printed on A portrait (8.5" x 11") sheet. ---====------=====Meters 0 5 10 20 JJ ----====--------=======Feet o 20 ~ oo m Map projection: Web Mercator Comer rooolinates: WGS84 Edge tics: LI™ Zone UN WGS84 USDA Natural Resources Web Soil Survey National Cooperative Soil Survey ---Conservation Service 0 Iii ij 4/16/2021 Page 1 of 4 33" 5'42"N 33" SYN Hydrologic Soil Group--,_. fDiego County Area, California MAP LEGEND MAP INFORMATION Area of Interest (AOI) D Area of Interest (AOI) Soils Soil Rating Polygons D A D AID DB D B/D DC D CID DD D Not rated or not available Soll Rating Lines A -AID -B -B/D C CID D ,. -Not rated or not available Soil Rating Points C A D AID ■ B ■ B/D USDA. Natural Resources -EE Conservation Service [] C [] C/D [] D □ Not rated or not available Water Features -Streams and Canals Transportation +-H Rails -.,, Interstate Highways US Routes Major Roads Local Roads Background • Aerial Photography Web Soil Survey National Cooperative Soil Survey The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: San Diego County Area, California Survey Area Data: Version 15, May 27, 2020 Soil map units are labeled (as space allows) for map scales 1 :50,000 or larger. Date(s) aerial images were photographed: Jan 23, 2020-Feb 13,2020 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. 4/16/2021 Page 2 of 4 Hydrologic Soil Group-San Diego County Area, California Hydrologic Soil Group Map unit symbol Map unit name Rating Acres inAOI Percent of AOI Hue Huerhuero-Urban land D 0.6 complex, 2 to 9 percent slopes Totals for Area of Interest 0.6 ~ Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (ND, B/D, and CID). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (ND, 8/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition USDA Natural Resources :iiiiiiiMi Conservation Service Web Soil Survey National Cooperative Soil Survey 100.0% 100.0% 4/16/2021 Page 3 of 4 Hydrologic Soil Group-San Diego County Area, California Component Percent Cutoff: None Specified Tie-break Rule: Higher C C USDA Natural Resources " Conservation Service Web Soil Survey National Cooperative Soil Survey 4/16/2021 Page 4 of 4 Natio I Flood Hazard Layer FIRMet ~ ~FEMA Legend SEE FIS REPORT FOR DETAILED LEGEND ANO INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOOD HAZARD AREAS OTHER AREAS OF FLOOD HAZARD Without Base Flood Elevation (BFE) Zon~ A, V, A99 With BFE or Depth Zorn, AE. AO, AH, VE. AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Area of 1% annual chance flood with average depth less than one foot or with drainag, areas of less than one square mile Zone> Future Conditions 1% Annual Chance Flood Hazard Zone x Area with Reduced Flood Risk due to Levee. See Notes. Zone x Area with Flood Risk due to Levee Zone o NO SCREEN Area of Minimal Flood Hazard Zone X c:::::::J Effective LOMRs OTHER AREAS Area of Undetermined Flood Hazard Zone GENERAL Channel. Culvert, or Storm Sewer STRUCTURES I I I I I I I Levee, Dike, or Floodwall OTHER FEATURES MAP PANELS e Cross Sections with 1% Annual Chance -.1L1 Water Surface Elevation ©---Coastal Transect -su-Base Flood Elevation Line (BFE) = Limit of Study ---Jurisdiction Boundary Coastal Transect Baseline Profile Baseline Hydrographic Feature Digital Data Available N No Digital Data Available Unmapped + The pin displayed on the map is an approximate point selected by the user and does not represe an authoritative property location. This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 12/30/2020 at 4:38 PM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective Information may change or become superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. C C APPENDIXB: Existing Condition Runoff Coefficient Calculations Existing Condition Hydrology Calculations Existing Condition Hydrology Map Runoff Coefficient Calculation (Existing Condition) Project: Carlsbad Fire Station No.2 (Permanent) Basin A-1 Soil Type: D C= 0.90 x (%Impervious)+ Cp x (1-% Impervious) Cp= 0.35 (per table 3-1, County of San Diego Hydrology Manual, Soil Class B) Area Acres) *Composite Total Area Runoff Coeff. **Equivalent Land Use (from Basin# (ac) Imp. Area (Ai) %imp (C) Table 3-1) B-1 0.012 0.000 0.0 0.35 - B-2 0.134 0.134 100.0 0.90 - B-3 0.094 0.052 55.3 0.65 - B-4 0.033 0.033 100.0 0.90 - B-5 0.061 0.010 16.8 0.44 - Total 0.334 0.229 68.7 0.73 HOR, 24.0 DU/A or less Notes: *The composite runoff coefficient (C) is calculated for the site by using the following equation: 0.90 x (% Impervious)+ Cp x (1-% Impervious); where Cp = 0.35 per Table 3-1 of the County of San Diego Hydrology Manual. C San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2012 Version 7.9 Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 04/16/21 13638 Permanent Carlsbad Fire Station Existing to Discharge Point 1 ********* Hydrology Study Control Information********** Program License Serial Number 6116 Rational hydrology study storm event year is English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 2.750 24 hour precipitation(inches) = 4.750 P6/P24 = 57.9% San Diego hydrology manual 'C' values used 100.0 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 101.000 to Point/Station 102.000 **** 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 [UNDISTURBED NATURAL TERRAIN (Permanent Open Space ) Impervious value, Ai= 0.000 Sub-Area C Value= 0.350 Initial subarea total flow distance Highest elevation= 92.000(Ft.) Lowest elevation= 86.900(Ft.) Elevation difference= 5.100(Ft.) ] = 34. 000 ( Ft . ) Slope= 15.000 % This document was created by an application that isn't licensed to use novaPDF. 0, ....... 1-.,....,,..,... ,.. Ii .................... ,1,...., __ ..,.,....,,...,1,...., nnc iii--,a,i+h,.., ,,1, ,1,1,.,.:.,.. ....... ,1.:,.., .... INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 100.00 {Ft) for the top area slope value of 15.00 %, in a development type of Permanent Open Space In Accordance With Figure 3-3 Initial Area Time of Concentration= 5.47 minutes TC= [1.8*{1.l-C)*distance{Ft.)A.5)/(% slopeA{l/3)] TC= [1.8*{1.1-0.3500)*( 100.000A.5)/( 15.000A{l/3)]= 5.47 Rainfall intensity {I)= 6.834{In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.350 Subarea runoff= 0.029{CFS) Total initial stream area= 0.012{Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 102.000 to Point/Station 103.000 **** IRREGULAR CHANNEL FLOW TRAVEL TIME**** Estimated mean flow rate at midpoint of channel= Depth of flow= 0.101{Ft.), Average velocity= ******* Irregular Channel Data*********** Information entered for subchannel number 1 Point number 'X' coordinate 'Y' coordinate 1 0.00 0.25 2 5.00 0.00 3 10.00 0.25 Manning's 'N' friction factor = 0.016 Sub-Channel flow = 0.366{CFS) flow top width= 4.034{Ft.) velocity= 1.799{Ft/s) area= 0.203{Sq.Ft) Froude number= 1.412 Upstream point elevation= Downstream point elevation= Flow length= 119.000{Ft.) Travel time = 1.10 min. 86. 900 { Ft . ) 84. 500{ Ft.) Time of concentration= 6.58 min. Depth of flow= 0.101{Ft.) 0.366{CFS) Average velocity= 1.799{Ft/s) Total irregular channel flow= Irregular channel normal depth Average velocity of channel{s) above invert elev. = = 1. 799{Ft/s) Adding area flow to channel 0.366{CFS) 1.799(Ft/s) 0.101(Ft.) Rainfall intensity {I)= 6.071{In/Hr) for a 100.0 year storm User specified 'C' value of 0.900 given for subarea Rainfall intensity= 6.071{In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area {Q=KCIA) is C = 0.855 CA= 0.125 This document was created by an application that isn't licensed to use novaPDF. :) C Subarea runoff= Total runoff= Depth of flow= 0.729(CFS) for 0.134(Ac.) 0.758(CFS) Total area= 0.146(Ac.) 0.133(Ft.), Average velocity= 2.158(Ft/s) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 103.000 to Point/Station 104.000 **** IRREGULAR CHANNEL FLOW TRAVEL TIME**** Estimated mean flow rate at midpoint of channel= Depth of flow= 0.131(Ft.), Average velocity= ******* Irregular Channel Data*********** Information entered for subchannel number 1 : Point number 'X' coordinate 'Y' coordinate 1 0.00 0.25 2 5.00 0.00 3 10.00 0.25 Manning's 'N' friction factor = 0.016 Sub-Channel flow = 0.959(CFS) flow top width= 5.236(Ft.) velocity= 2.799(Ft/s) area= 0.343(Sq.Ft) Froude number= 1.928 Upstream point elevation= Downstream point elevation= Flow length= 87.000(Ft.) Travel time = 0.52 min. 84.500(Ft.) 81. 500( Ft.) Time of concentration= 7.09 min. Depth of flow= 0.131(Ft.) 0.959(CFS) Average velocity= 2.799(Ft/s) Total irregular channel flow= Irregular channel normal depth Average velocity of channel(s) above invert elev. = = 2.799(Ft/s) Adding area flow to channel 0.959(CFS) 2.799(Ft/s) 0.131(Ft.) Rainfall intensity (I)= 5.782(In/Hr) for a 100.0 year storm User specified 'C' value of 0.650 given for subarea Rainfall intensity= 5.782(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.775 CA= 0.186 Subarea runoff= 0.317(CFS) for Total runoff= 1.075(CFS) Total Depth of flow= 0.137(Ft.), Average End of computations, total study area 0.094(Ac.) area= 0.240(Ac.) velocity= 2.879(Ft/s) = 0.240 (Ac.) This document was created by an application that isn't licensed to use novaPDF. San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2012 Version 7.9 Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 04/16/21 13638 Permanent Carlsbad Fire Station Existing to DP2 ********* Hydrology Study Control Information********** Program License Serial Number 6116 Rational hydrology study storm event year is English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 2.750 24 hour precipitation(inches) = 4.750 P6/P24 = 57.9% San Diego hydrology manual 'C' values used 100.0 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 201.000 to Point/Station 202.000 **** 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 (General Industrial ) Impervious value, Ai= 0.950 Sub-Area C Value= 0.870 Initial subarea total flow distance = 35.000(Ft.) Highest elevation= 95.800(Ft.) Lowest elevation= 95.300(Ft.) Elevation difference 0.500(Ft.) Slope= 1.429 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 60.00 (Ft) for the top area slope value of 1.43 %, in a development type of General Industrial This document was created by an application that isn't licensed to use novaPDF. n ............................. 1:,.. ............... ,1....., ............................. nnc .r.1,., ....... :,1.1-.. ......... ,1.1,..:,. ......... -1-: ..... .... C C In Accordance With Table 3-2 Initial Area Time of Concentration= 3.20 minutes (for slope value of 1.00 %) Calculated TC of 3.200 minutes is less than 5 minutes, resetting TC to 5.0 minutes for rainfall intensity calculations Rainfall intensity (I)= 7.246(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.870 Subarea runoff= 0.208(CFS) Total initial stream area= 0.033(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 202.000 to Point/Station 203.000 **** IRREGULAR CHANNEL FLOW TRAVEL TIME**** Estimated mean flow rate at midpoint of channel= Depth of flow= 0.151(Ft.), Average velocity= ******* Irregular Channel Data*********** Information entered for subchannel number 1 Point number 'X' coordinate 'Y' coordinate 1 0.00 0.25 2 5.00 0.00 3 10.00 0.25 Manning's 'N' friction factor = 0.050 Sub-Channel flow = 0.324(CFS) flow top width= 6.052(Ft.) velocity= 0.708(Ft/s) area= 0.458(Sq.Ft) Froude number= 0.454 Upstream point elevation= Downstream point elevation= Flow length= 90.000(Ft.) Travel time = 2.12 min. 85.300(Ft.) 83.700(Ft.) Time of concentration= 5.32 min. Depth of flow= 0.151(Ft.) Average velocity= 0.708(Ft/s) Total irregular channel flow= Irregular channel normal depth Average velocity of channel(s) 0.324(CFS) above invert elev. 0.708(Ft/s) Adding area flow to channel 0.324(CFS) 0.708(Ft/s) 0.151(Ft.) Rainfall intensity (I)= 6.963(In/Hr) for a 100.0 year storm User specified 'C' value of 0.440 given for subarea Rainfall intensity= 6.963(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.591 CA= 0.056 Subarea runoff= 0.179(CFS) for Total runoff= 0.387(CFS) Total Depth of flow= 0.162(Ft.), Average End of computations, total study area 0.061(Ac.) area= 0.094(Ac.) velocity= 0.740(Ft/s) = 0.094 (Ac.) 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(~~t}}f2~J> yl<' "-" ()< 1.,\ ~ ~ -SHEET TITLE HYDROLOGY EXHIBIT EXISTING CONDITION SHlEI 1 Of 1 ....,_ ·, ISSUE DATF: DRAWN BY: CHFCKED BY: ' ' BWE JOB NUMBER: CIJEN I JOB NUMBER MUNICIPALITY PROJECT NllMBE8: -----J ' 'Tl " " -....,_-....,___ . ------··-··· --~~---· \1,\ (j'\ ~)> ,o \ ' (j) ·,;·--/ . -' ' ,;,.n\(Y) -----_,.._ "-·-,l!'\? r{:tS~-----·-<:s.\" ·c,·;{""-\ \<>1'·: '. ~-,,, -----.--,cs _\_c ( ----•-··---------.---·--~~l\"-' ... _, . \0, '" . \), 'f • (.,\l t;'. . ,,,. <-' ~ ~ --/· ~ ,,, ' ' ~ it,· P. I ' ' ' I I l ·, j,1, ; ' i, . ' . I 'i, L , I . I I, ,,. ' ' ' 1,· '· 1. CD +>-07 'Tl ' '·,,....,_ UI SYM ··n, i;:n, '/ ·;-~') ,;t'\ "'---•.,, ,, ', 'O --->. v-.J ....,__ rn I N -'-' ~ C.D ' 77 ·,,....,__ __ ,,....,_ DESCRIPTION ,,,. --. k'. ,:,· <)'; T\ \'t"\ /,. ( I \ ,·\ .\~--(J \ ,.. .. --• I .. "1 --~.}-•• ✓ \... .. -\ OJ C.D . 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I ID : I 0 I ! r DATE IAl'rR CIVIL• STRUCTURAL• SURVEY• PLANNING 9449 BALBOA AVE, STE 270 SAN DIEGO, CA 92123 619.299,5550 ;1 , APPENDIXC: Proposed Condition Runoff Coefficient Calculations Proposed Condition Hydrology Calculations Proposed Condition Hydrology Runoff Coefficient Calculation (Proposed Condition) Project: Carlsbad Fire Station No.2 (Permanent) Basin A-1 Soil Type: D C= 0.90 x (% Impervious)+ Cp x (1 -% Impervious) Cp= 0.35 (per table 3-1, County of San Diego Hydrology Manual, Soil Class 8) Area Acres) Total Imp. Roofs (Imp. Area for Area) over Runoff *Composite Total Area Imp. Area Pervious Calculations Runoff Coeff. Basin# (ac) (ac) Area (ac) (Ai) %imp (C) B-1 0.018 0.000 0.000 0.000 0.0 0.35 B-2 0.105 0.057 0.009 0.066 63.0 0.70 B-3 0.048 0.036 0.003 0.039 81.7 0.80 B-4 0.012 0.002 0.000 0.002 17.4 0.45 B-5 0.102 0.096 0.000 0.096 94.4 0.87 B-6 0.043 0.036 0.001 0.036 84.7 0.82 B-7 0.008 0.003 0.000 0.003 33.3 0.53 Total 0.334 0.229 0.013 0.242 72.4 0.75 Notes: **Equivalent land Use (from Table 3-1) - - - - - - - HDR, 43.0 DU/A or less *The composite runoff coefficient (C) is calculated for the site by using the following equation: 0.90 x (% Impervious)+ Cp x (1 - % Impervious); where Cp = 0.35 per Table 3-1 of the County of San Diego Hydrology Manual. San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2012 Version 7.9 Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 04/16/21 13638 Permanent Carlsbad Fire Station Proposed Discharge Point 1 ********* Hydrology Study Control Information********** Program License Serial Number 6116 Rational hydrology study storm event year is English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 2.750 24 hour precipitation(inches) = 4.750 P6/P24 = 57.9% San Diego hydrology manual 'C' values used 100.0 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 101.000 to Point/Station 102.000 **** 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 [UNDISTURBED NATURAL TERRAIN ] (Permanent Open Space ) Impervious value, Ai= 0.000 Sub-Area C Value= 0.350 Initial subarea total flow distance = 49.000(Ft.) Highest elevation= 91.800(Ft.) Lowest elevation= 89.500(Ft.) Elevation difference= 2.300(Ft.) Slope= 4.694 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 100.00 (Ft) for the top area slope value of 4.69 %, in a development type of Permanent Open Space This document was created by an application that isn't licensed to use novaPDF. n ............................ 1: ............... ,.. ..,,... .......................... ,.. nnc .,::1 ........••• :,1,1-,, .......... ,1,1,.,,: ................ : .... ,.. In Accordance With Figure 3-3 Initial Area Time of Concentration 8.06 minutes TC= [1.8*(1.l-C)*distance(Ft.)A.5)/(% slopeA(l/3)] TC= [1.8*(1.1-0.3500)*( 100.000A,5)/( 4.694A(l/3)]= 8.06 Rainfall intensity (I)= 5.324(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.350 Subarea runoff= 0.034(CFS) Total initial stream area= 0.018(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 102.000 to Point/Station 103.000 **** IRREGULAR CHANNEL FLOW TRAVEL TIME**** Estimated mean flow rate at midpoint of channel= Depth of flow= 0.074(Ft.), Average velocity= ******* Irregular Channel Data*********** Information entered for subchannel number 1 : Point number 'X' coordinate 'V' coordinate 1 0.00 0.25 2 2.50 0.00 3 5.00 0.25 Manning's 'N' friction factor= 0.012 Sub-Channel flow = 0.177(CFS) flow top width= 1.471(Ft.) velocity= 3.270(Ft/s) area= 0.054(Sq.Ft) Froude number= 3.005 Upstream point elevation= Downstream point elevation= Flow length= 77.000(Ft.) Travel time = 0.39 min. 89.500(Ft.) 85.080(Ft.) Time of concentration= 8.46 min. Depth of flow= 0.074(Ft.) 0.177(CFS) Average velocity= 3.270(Ft/s) Total irregular channel flow= Irregular channel normal depth Average velocity of channel(s) above invert elev. = = 3.270(Ft/s) Adding area flow to channel 0.177(CFS) 3.270(Ft/s) 0.074(Ft.) Rainfall intensity (I)= 5.163(In/Hr) for a 100.0 year storm User specified 'C' value of 0.700 given for subarea Rainfall intensity= 5.163(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.649 CA= 0.080 Subarea runoff= 0.378(CFS) for 0.105(Ac.) Total runoff= 0.412(CFS) Total area= 0.123(Ac.) Depth of flow= 0.101(Ft.), Average velocity= 4.040(Ft/s) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 103.000 to Point/Station 104.000 **** IRREGULAR CHANNEL FLOW TRAVEL TIME**** This document was created by an application that isn't licensed to use novaPDF. n, , ...... i... .... ,... ......... 1: ......... -....... -1-.................. ,., .............. nnc .r:1 .......••• :,a... .... ,,,.. ,1.1,..: ......... ,...,1.: ......... Estimated mean flow rate at midpoint of channel= Depth of flow= 0.114(Ft.), Average velocity= ******* Irregular Channel Data*********** Information entered for subchannel number 1 : Point number 'X' coordinate 'V' coordinate 1 0.00 0.25 2 2.50 0.00 3 5.00 0.25 Manning's 'N' friction factor = 0.012 Sub-Channel flow 0.492(CFS) flow top width= 2.271(Ft.) velocity= 3.821(Ft/s) area= 0.129(Sq.Ft) Froude number= 2.826 Upstream point elevation= Downstream point elevation= Flow length= 28.000(Ft.) Travel time = 0.12 min. 85.080(Ft.) 83.850(Ft.) Time of concentration= 8.58 min. Depth of flow= 0.114(Ft.) 0.492(CFS) Average velocity= 3.821(Ft/s) Total irregular channel flow= Irregular channel normal depth Average velocity of channel(s) above invert elev. = = 3.821(Ft/s) Adding area flow to channel 0.492(CFS) 3.821(Ft/s) 0.114(Ft.) Rainfall intensity (I)= 5.116(In/Hr) for a 100.0 year storm User specified 'C' value of 0.800 given for subarea Rainfall intensity= 5.116(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.691 CA= 0.118 Subarea runoff= 0.193(CFS) for 0.048(Ac.) Total runoff= 0.605(CFS) Total area= 0.171(Ac.) Depth of flow= 0.123(Ft.), Average velocity= 4.022(Ft/s) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 104.000 to Point/Station 105.000 **** IRREGULAR CHANNEL FLOW TRAVEL TIME**** Estimated mean flow rate at midpoint of channel= Depth of flow= 0.129(Ft.), Average velocity= ******* Irregular Channel Data*********** Information entered for subchannel number 1 : Point number 'X' coordinate 'Y' coordinate 1 0.00 0.25 2 2.50 0.00 3 5.00 0.25 Manning's 'N' friction factor 0.012 Sub-Channel flow 0.626(CFS) This document was created by an application that isn't licensed to use novaPDF. n ............................. 1:,.,. ................ , ................. ,.. ............. nnc ♦o1 .......••• : .............. , ,1.1-.: ........ ,..,: .... .... 0.626(CFS) 3.763(Ft/s) flow top width= 2.579(Ft.) velocity= 3.763(Ft/s) area= 0.166(Sq.Ft) Froude number= 2.612 Upstream point elevation= Downstream point elevation= Flow length= 47.000(Ft.) Travel time = 0.21 min. 83.850(Ft.) 82.160(Ft.) Time of concentration= 8.79 min. Depth of flow= 0.129(Ft.) Average velocity= 3.763(Ft/s) Total irregular channel flow= Irregular channel normal depth Average velocity of channel(s) 0.626(CFS) above invert elev. = 3.763(Ft/s) Adding area flow to channel 0.129(Ft.) Rainfall intensity (I)= 5.037(In/Hr) for a 100.0 year storm User specified 'C' value of 0.450 given for subarea Rainfall intensity= 5.037(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.675 CA= 0.124 Subarea runoff= 0.018(CFS) for 0.012(Ac.) Total runoff= 0.623(CFS) Total area= 0.183(Ac.) Depth of flow= 0.129(Ft.), Average velocity= 3.758(Ft/s) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 105.000 to Point/Station 106.000 **** IRREGULAR CHANNEL FLOW TRAVEL TIME**** Estimated mean flow rate at midpoint of channel Depth of flow= 0.150(Ft.), Average velocity= ******* Irregular Channel Data*********** Information entered for subchannel number 1 Point number 'X' coordinate 'Y' coordinate 1 0.00 0.25 2 2.50 0.00 3 5.00 0.25 Manning's 'N' friction factor = 0.012 Sub-Channel flow 0.796(CFS) flow top width= 2.992(Ft.) velocity= 3.556(Ft/s) area= 0.224(Sq.Ft) Froude number= 2.291 Upstream point elevation= Downstream point elevation= 82.160(Ft.) 81. 370(Ft.) Flow length= 30.000(Ft.) Travel time = 0.14 min. Time of concentration= 8.93 Depth of flow= 0.150(Ft.) Average velocity= 3.556(Ft/s) Total irregular channel flow= min. 0.796(CFS) This document was created by an application that isn't licensed to use novaPDF. 0.796(CFS) 3.556(Ft/s) Irregular channel normal depth above invert elev. = 0.150(Ft.) Average velocity of channel(s) = 3.556(Ft/s) Adding area flow to channel Rainfall intensity (I)= 4.986(In/Hr) for a 100.0 year storm User specified 'C' value of 0.870 given for subarea Rainfall intensity= 4.986(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.745 CA= 0.212 Subarea runoff= 0.436(CFS) for Total runoff= 1.059(CFS) Total Depth of flow= 0.167(Ft.), Average End of computations, total study area 0.102(Ac.) area= 0.285(Ac.) velocity 3.819(Ft/s) 0.285 (Ac.) This document was created by an application that isn't licensed to use novaPDF. n, , ...... a... ................ 1:,.. ....................................................... nn~ .i:1 ........ ···="'-'--· ·• •i...: ............ i: ..... ..... 7.9 2 San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software, (c)1991-2012 Version Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 04/16/21 13638 Permanent Carlsbad Fire Station Proposed Discharge Point ********* Hydrology Study Control Information********** Program License Serial Number 6116 Rational hydrology study storm event year is English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 2.750 24 hour precipitation(inches) = 4.750 P6/P24 = 57.9% San Diego hydrology manual 'C' values used 100.0 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++ Process from Point/Station 201.000 to Point/Station 203.000 of **** 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 [COMMERCIAL area type (General Commercial ) Impervious value, Ai = 0.850 Sub-Area C Value = 0.820 Initial subarea total flow distance 77.000(Ft.) Highest elevation= 85.000(Ft.) Lowest elevation= 84.300(Ft.) Elevation difference 0.700(Ft.) Slope= 0.909 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 60.00 (Ft) for the top area slope value of 0.91 %, in a development type General Commercial In Accordance With Figure 3-3 Initial Area Time of Concentration 4.03 minutes This document was created by an application that isn't licensed to use novaPDF. n ......... 1,.,. ........ ,.. .... 1: .......................................................... nnc-r.1 ........... :1-1,.. .... , ,.., ,1.1-..: ................ : .... .... TC= [l.8*(1.l-C)*distance(Ft.)A.5)/(% slopeA(l/3)] TC= [l.8*(1.1-0.8200)*( 60.000A.5)/( 0.909A(l/3)]= 4.03 Calculated TC of 4.030 minutes is less than 5 minutes, resetting TC to 5.0 minutes for rainfall intensity calculations Rainfall intensity (I) = 7.246(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C 0.820 Subarea runoff= 0.255(CFS) Total initial stream area= 0. 043 (Ac.) +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++ Process from Point/Station 201.000 to Point/Station 203.000 **** CONFLUENCE OF MAIN STREAMS**** The following data inside Main Stream is listed: In Main Stream number: 1 Stream flow area= 0.043(Ac.) Runoff from this stream 0.255(CFS) Time of concentration= 4.03 min. Rainfall intensity= 7.246(In/Hr) Program is now starting with Main Stream No. 2 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++ Process from Point/Station 203.000 202.000 to Point/Station of storm 0.520 **** INITIAL AREA EVALUATION Decimal fraction soil group A Decimal fraction soil group B Decimal fraction soil group C Decimal fraction soil group D [MEDIUM DENSITY RESIDENTIAL (4.3 DU/A or Less ) Impervious value, Ai= 0.300 Sub-Area C Value= 0.520 **** 0.000 0.000 0.000 1.000 Initial subarea total flow distance 75.000(Ft.) Highest elevation= 84.800(Ft.) Lowest elevation= 84.200(Ft.) Elevation difference 0.600(Ft.) Slope= 0.800 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 70.00 (Ft) for the top area slope value of 0.80 %, in a development type 4.3 DU/A or Less In Accordance With Figure 3-3 Initial Area Time of Concentration 9.41 minutes TC= [l.8*(1.l-C)*distance(Ft.)A.5)/(% slopeA(l/3)] TC = [ 1 . 8 * ( 1 . 1-0 . 5 2 0 0) * ( 7 0 . 0 0 0 A . 5) / ( 0 . 8 0 0 A ( 1 /3) ] = 9 . 41 Rainfall intensity (I) = 4.819(In/Hr) for a 100.0 year Effective runoff coefficient used for area (Q=KCIA) is C Subarea runoff= 0.020(CFS) Total initial stream area= 0.00B(Ac.) End of computations, total study area= 0. 051 (Ac.) This document was created by an application that isn't licensed to use novaPDF. n ......... 1-..,... ............. 1: ........................... ,.. ................... ,1, .... nnc .i:1 ........... :,1.1-.. ......... ,1.1,.,.: ................ : .... .... 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