HomeMy WebLinkAboutCT 14-07; BEACHWALK AT ROOSEVELT; HYDROLOGY STUDY; 2016-06-10HYDROLOGY STUDY
For
BEACHWALK AT ROOSEVELT
CT 14-07
2685, 2687, & 2715 ROOSEVELT STREET
CARLSBAD, CA 92009
City of Carlsbad, CA
PREPARED FOR:
Geoff McComic
Vesta Pacific Development
1818 First Ave, Suite 100
San Diego, California 92131
Date: November 24, 2015
Revised: May 31, 2016
PREPARED BY:
Pasco Laret Suiter & Associates
535 N. Highway 101, Suite A
Solana Beach, CA 92075
REcEIVEID (858) 259-8212
JUN 10 2016
LAND DEVELOPMENT
ENGINEERING
\c3F ESS,5
rn
No. 7165
I
9F CA1.11
BRIAN ARDOLINO, RCE 71651 DATE
CT 1LkJJ—
Beachwalk at Roosevelt
TABLE OF CONTENTS
SECTION
Executive Summary 1.0
Introduction 1.1
Existing Conditions 1.2
Proposed Project 1.3
Summary of Results and Conditions 1.4
Conclusions 1.5
References 1.6
Methodology 2.0
Introduction 2.1
County of San Diego Criteria 2.2
Runoff coefficient determination 2.3
Hydrologic Analyses 3.0
Pre-Developed Hydrologic Analysis 3.1
Post-Developed Hydrologic Analysis 3.2
Hydraulic Calculations 4.0
Appendix 5.0
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1.0 EXECUTIVE SUMMARY
1.1 Introduction
This Hydrology Study for the Roosevelt Street project has been prepared to analyze the
hydrologic and hydraulic characteristics of the existing and proposed project site. This
report intends to present both the methodology and the calculations used for determining
the runoff from the project site in both the pre-developed (existing) conditions and the post-
developed (proposed) conditions produced by the 100 year 6 hour storm. In addition this
report will propose the sizing of all necessary storm drain facilities and storm drain piping
necessary for the storm drain system to safely convey the runoff from the 100-year rainfall
event.
1.2 Existing Conditions
The property is geographically located at N 33°09'44.27" W 117°20'55.26". The site is
bordered by residential development to the north and south and commercial development to
the west. Roosevelt Street is located to the east of the proposed development. The project
site is located in the Buena Vista Creek Hydrologic Area and more specifically, the El Salto
Sub-Area (904.21).
The existing project site includes 4 residences, accessory buildings and associated paving and
hardscape. The site consists mostly of a gentle slope from the east to the west. Drainage
from the existing site sheet flows in the westerly direction onto the adjacent site. The runoff
is then conveyed south along State Street where it is collected in a curb inlet and ultimately
discharges into the Buena Vista Lagoon.
1.3 Proposed Project
The intent of the proposed project is to construct 16 condominium units with associated
hardscape improvements and driveways.
The proposed drainage design conveys runoff from the west to the east to Bioretention
BMP areas for priority storm water treatment. Once treated, the water is discharged into an
existing storm drain system in Roosevelt St flowing north toward Buena Vista Lagoon. The
drainage pattern is altered from the existing condition as the storm drain system in Roosevelt
Street was constructed in 2014 and provides a means to divert water from crossing onto the
western adjacent site.
The proposed 8" PVC outlet drain pipe will be used to convey storm water overflow from
the Bioretention BMP areas to the existing curb inlet along the frontage on Roosevelt Street.
See section 4.0 for hydraulic calculations for the pipe.
We believe the proposed storm drain system will not adversely affect the downstream system
negatively.
1.4 Summary of Results
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Upon performing hydrologic analysis of the project site in both the proposed developed and
existing condition the following results were produced.
In the predeveloped condition two discharge points were analyzed. Outlet point 1.2 indicates
that the 100-year peak flow is 0.82 cfs with a time of concentration of 5.0 min based on an
area of 0.15 AC. Outlet point 2.2 indicates that the 100-year peak flow is 1.89 cfs with a time
of concentration of 8.28 min based on area of 0.66 AC.
I In the postdeveloped condition one discharge point was analyzed. Outlet point 1.2 indicates
that the 100-year peak flow is 2.48 cfs with a time of concentration of 9.95 mm based on an
area of 0.81 AC.
I 1.5 Conclusions
I The overall peak flow leaving the property is decreased by 0.23 cfs. However, the proposed
site plan removes the cross lot drainage point that exists in the existing condition, and
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diverts all flow from the site to the outlet point in Roosevelt Street.
Based on the discussion in this report it is the professional opinion of Pasco Laret Suiter &
Associates, Inc. that the existing drainage system on the corresponding Tentative Map will
I function to adequately intercept, contain and convey flow to the appropriate points of
discharge.
I 1.6 References
"San Diego Countj Hjdrology Manual", revised June 2003, County of San Diego, Department of
I Public Works, Flood Control Section.
"Calrnia Regional WaterQualitji Control Board Order No. 2009-0009-D W<Q, "California
I Regional Water Control Board, San Diego Region (SDRWQCB).
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2.0 METHODOLOGY
I 2.1 Introduction
The hydrologic model used to perform the hydrologic analysis presented in this report
I utilizes the Ration Method (RM) equation, QCIA. The RM formula estimates the peak
rate of runoff based on the variables of area, runoff coefficient, and rainfall intensity. The
rainfall intensity (I) is equal to:
I I = 7.44 x P6 x D °645
Where:
I = Intensity (in/hr)
I P6 = 6-hour precipitation (inches)
D = duration (minutes - use Tc)
1 Using the Time of Concentration (Tc), which is the time required for a given element of
water that originates at the most remote point of the basin being analyzed to reach the point
at which the runoff from the basin is being analyzed. The RM equation determines the
I storm water runoff rate (Q) for a given basin in terms of flow (typically in cubic feet per
second (cfs) but sometimes as gallons per minute (gprn)). The RM equation is as follows:
I Where:
Q= flow (in cfs)
I C = runoff coefficient, ratio of rainfall that produces storm water
runoff (runoff vs. infiltration/evaporation/absorption/etc)
I = average rainfall intensity for a duration equal to the Tc for the
I area, in inches per hour.
A = drainage area contributing to the basin in acres.
I The RM equation assumes that the storm event being analyzed delivers precipitation to the
entire basin uniformly, and therefore the peak discharge rate will occur when a raindrop falls
at the most remote portion of the basin arrives at the point of analysis. The RM also
I assumes that the fraction of rainfall that becomes runoff or the runoff coefficient C is not
affected by the storm intensity, I, or the precipitation zone number.
I In addition to the above Ration Method assumptions, the conservative assumption that all
runoff coefficients utilized for this report are based on type "D" soils.
I Rational Method calculations were performed using the AES 2010 computer program. To
perform the hydrology routing, the total watershed area is divided into sub-areas which
discharge at designated nodes. The procedure for the sub-area summation model is as
U follows:
Subdivide the watershed into an initial sub-areas and subsequent sub-areas,
which are generally less than 10 acres in size. Assign upstream and downstream
4 node numbers to each sub-area.
Estimate an initial T. by using the appropriate nomograph or overland flow
velocity estimation. The minimum T considered is 5.0 minutes.
1 (3) Using the initial T, determine the corresponding values of I. Then Q = CIA.
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(4) Using Q, estimate the travel time between this node and the next by Manning's
equation as applied to particular channel or conduit linking the two nodes.
Then, repeat the calculation for Q based on the revised intensity (which is a
function of the revised time of concentration)
2.2 County of San Diego Criteria
As defined by the County Hydrology Manual dated June 2003, the rational method is the
preferred equation for determining the hydrologic characteristics of basins up to
approximately one square mile in size. The County of San Diego has developed its own
tables, nomographs, and methodologies for analyzing storm water runoff for areas within
the county. The County has also developed precipitation isopluvial contour maps that show
even lines of rainfall anticipated from a given storm event (i.e. 100-year, 6-hour storm).
One of the variables of the RM equation is the runoff coefficient, C. The runoff coefficient
is dependent only upon land use and soil type and the County of San Diego has developed a
table of Runoff Coefficients for Urban Areas to be applied to basin located within the
County of San Diego. The table categorizes the land use, the associated development
density (dwelling units per acre) and the percentage of impervious area. Each of the
categories listed has an associated runoff coefficient, C, for each soil type class.
The County has also illustrated in detail the methodology for determining the time of
concentration, in particular the initial time of concentration. The County has adopted the
Federal Aviation Agency's (FAA) overland time of flow equation. This equation essentially
limits the flow path length for the initial time of concentration to lengths of 100 feet or less,
and is dependent on land use and slope.
2.3 Runoff Coefficient Determination
As stated in section 2.2, the runoff coefficient is dependent upon land use and soil type and
the County of San Diego has developed a table of Runoff Coefficients for Urban Areas to
be applied to basin located within the County of San Diego. The table, included at the end
of this section, categorizes the land use, the associated development density (dwelling units
per acre) and the percentage of impervious area. Low Density Residential coefficient of 0.41
was used for pervious area, and Commercial/Industrial coefficient of 0.87 was used for
impervious area. Weighted runoff coefficients for onsite areas were calculated using the
existing and proposed impervious area for each basin. See Appendix 5.0 for Coefficient
Table and C Value Calculations on the Pre and Post Development Maps.
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3.0 HYDROLOGIC ANALYSES
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****************************************************************************
I RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM PACKAGE
Reference: SAN DIEGO COUNTY FLOOD CONTROL DISTRICT
2003,1985, 1981 HYDROLOGY MANUAL
I
(c) Copyright 1982-2008 Advanced Engineering Software (aes)
Ver. 15.0 Release Date: 04/01/2008 License ID 1452
Analysis prepared by:
I
* * * * * * * * * * * * * * * * * * * * * * * * * * DESCRIPTION OF STUDY * * * * * * * * * * * * * * * * * * * * * * * * * *
* PREDEVELOPED HYDROLOGIC ANALYSIS FOR 100 YEAR STORM EVENT *
* ROOSEVELT STREET *
* PLSA 2110 - 6.10.16 *
FILE NAME: 2110E100.DAT
TIME/DATE OF STUDY: 11:15 06/10/2016 I
USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
I 2003 SAN DIEGO MANUAL CRITERIA
USER SPECIFIED STORM EVENT(YEAR) = 100.00
6-HOUR DURATION PRECIPITATION (INCHES) = 2.600
SPECIFIED MINIMUM PIPE SIZE(INCH) = 3.00 I SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE FOR FRICTION SLOPE = 0.95
SAN DIEGO HYDROLOGY MANUAL "C-VALUES USED FOR RATIONAL METHOD
NOTE: CONSIDER ALL CONFLUENCE STREAM COMBINATIONS
FOR ALL DOWNSTREAM ANALYSES I *USER_DEFINED STREET-SECTIONS FOR COUPLED PIPEFLOW AND STREETFLOW MODEL*
HALF- CROWN TO STREET-CROSSFALL: CURB GUTTER-GEOMETRIES: MANNING
WIDTH CROSSEALL IN- / OUT-/PARK- HEIGHT WIDTH LIP HIKE FACTOR
NO. (FT) (FT) SIDE / SIDE! WAY (FT) (FT) (FT) (FT) I (n)
1 30.0 20.0 0.018/0.018/0.020 0.67 2.00 0.0313 0.167 0.0150
I GLOBAL STREET FLOW-DEPTH CONSTRAINTS:
Relative Flow-Depth = 0.00 FEET
as (Maximum Allowable Street Flow Depth) - (Top-of-Curb)
(Depth)*(Velocity) Constraint = 6.0 (FT*FT/S) '
*SIZE PIPE WITH A FLOW CAPACITY GREATER THAN
OR EQUAL TO THE UPSTREAM TRIBUTARY PIPE.*
****************************************************************************
FLOW PROCESS FROM NODE 1.00 TO NODE 1.10 IS CODE = 21 I ----------------------------------------------------------------------------
>>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
*USER SPECIFIED(SUBAREA): I USER-SPECIFIED RUNOFF COEFFICIENT = .7700
S.C.S. CURVE NUMBER (AMC II) = 0
INITIAL SUBAREA FLOW-LENGTH(FEET) = 70.00
UPSTREAM ELEVATION(FEET) = 39.90 I DOWNSTREAM ELEVATION(FEET) = 38.40
ELEVATION DIFFERENCE(FEET) = 1.50
SUBAREA OVERLAND TIME OF FLOW(MIN.) = 3.855
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100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 6.850
NOTE: RAINFALL INTENSITY IS BASED ON To = 5-MINUTE.
SUBAREA RUNOFF(CFS) = 0.26
I TOTAL AREA(ACRES) = 0.05 TOTAL RUNOFF(CFS) = 0.26
I
FLOW PROCESS FROM NODE 1.10 TO NODE 1.20 IS CODE = 61
>>>>>COMPUTE STREET FLOW TRAVEL TIME THRU SUBAREA<<<<<
>>>>>(STANDARD CURB SECTION USED)<<<<<
I UPSTREAM ELEVATION(FEET) = 38.40 DOWNSTREAM ELEVATION(FEET) = 36.90
STREET LENGTH(FEET) = 100.00 CURB HEIGHT(INCHES) = 6.0
STREET HALFWIDTH(FEET) = 22.00
I DISTANCE FROM CROWN TO CROSSFALL GRADEBREAK(FEET) = 17.00
INSIDE STREET CROSSFALL(DECIMAL) = 0.020
OUTSIDE STREET CROSSFALL(DECIMAL) = 0.020
I SPECIFIED NUMBER OF HALFSTREETS CARRYING RUNOFF = 1
STREET PARKWAY CROSSFALL(DECIMAL) = 0.020
Manning's FRICTION FACTOR for Streetf low Section(curb-to-curb) = 0.0150
I
Manning's FRICTION FACTOR for Back-of-Walk Flow Section = 0.0200
**TRAVEL TIME COMPUTED USING ESTIMATED FLOW(CFS) = 0.54
STREETFLOW MODEL RESULTS USING ESTIMATED FLOW:
STREET FLOW DEPTH(FEET) = 0.20
I HALFSTREET FLOOD WIDTH(FEET) = 3.93
AVERAGE FLOW VELOCITY(FEET/SEC.) = 1.98
PRODUCT OF DEPTH&VELOCITY(FT*FT/SEC.) = 0.41
STREET FLOW TRAVEL TIME(MIN.) = 0.84 Tc(MIN.) = 4.70
I 100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 6.850
NOTE: RAINFALL INTENSITY IS BASED ON To = 5-MINUTE.
*USER SPECIFIED(SUBAREA):
USER-SPECIFIED RUNOFF COEFFICIENT = .8100
I S.C.S. CURVE NUMBER (AMC II) = 0
AREA-AVERAGE RUNOFF COEFFICIENT = 0.797
SUBAREA AREA(ACRES) = 0.10 SUBAREA RUNOFF(CFS) = 0.55
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TOTAL AREA(ACRES) = 0.2 PEAK FLOW RATE(CFS) = 0.82
END OF SUBAREA STREET FLOW HYDRAULICS:
DEPTH(FEET) = 0.23 HALFSTREET FLOOD WIDTH(FEET) = 5.23
FLOW VELOCITY(FEET/SEC.) = 2.09 DEPTII*VELOCITY(FT*FT/SEC.) = 0.48
I LONGEST FLOWPATH FROM NODE 1.00 TO NODE 1.20 = 170.00 FEET.
+ --------------------------------------------------------------------------+
END OF BASIN 1 I I
I BEGIN BASIN 2
+ --------------------------------------------------------------------------+
I FLOW PROCESS FROM NODE 2.00 TO NODE 2.10 IS CODE = 21
I >>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
*USER SPECIFIED(SUBAREA):
USER-SPECIFIED RUNOFF COEFFICIENT = .7000
S.C.S. CURVE NUMBER (AMC II) = 0 I INITIAL SUBAREA FLOW-LENGTH(FEET) = 70.00
UPSTREAM ELEVATION(FEET) = 39.90
DOWNSTREAM ELEVATION(FEET) = 39.00
ELEVATION DIFFERENCE(FEET) = 0.90
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SUBAREA OVERLAND TIME OF FLOW(MIN.) = 5.512
WARNING: INITIAL SUBAREA FLOW PATH LENGTH IS GREATER THAN
THE MAXIMUM OVERLAND FLOW LENGTH = 69.29
(Reference: Table 3-1B of Hydrology Manual)
THE MAXIMUM OVERLAND FLOW LENGTH IS USED IN Tc CALCULATION!
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 6.433
SUBAREA RUNOFF(CFS) 0.09
TOTAL AREA(ACRES) = 0.02 TOTAL RUNOFF(CFS) = 0.09
****************************************************************************
FLOW PROCESS FROM NODE 2.10 TO NODE 2.10 IS CODE 7 ----------------------------------------------------------------------------
>>>>>USER SPECIFIED HYDROLOGY INFORMATION AT NODE<<<<<
-----------------
USER-SPECIFIED VALUES ARE AS FOLLOWS:
TC(MIN) = 6.65 RAIN INTENSITY(INCH/HOUR) = 5.70
TOTAL AREA(ACRES) = 0.02 TOTAL RUNOFF(CFS) = 0.10
FLOW PROCESS FROM NODE 2.10 TO NODE 2.20 IS CODE = 52 ----------------------------------------------------------------------------
>>>>>COMPUTE NATURAL VALLEY CHANNEL FLOW<<<<<
>>>>>TRAVELTIME THRU SUBAREA<<<<<
ELEVATION DATA: UPSTREAM(FEET) = 39.00 DOWNSTREAM(FEET) = 36.80
CHANNEL LENGTH THRU SUBAREA(FEET) = 168.00 CHANNEL SLOPE = 0.0131
NOTE: CHANNEL FLOW OF 1. CFS WAS ASSUMED IN VELOCITY ESTIMATION
CHANNEL FLOW THRU SUBAREA(CFS) = 0.10
FLOW VELOCITY(FEET/SEC) = 1.72 (PER LACFCD/RCFC&WCD HYDROLOGY MANUAL)
TRAVEL TIME(MIN.) = 1.63 Tc(MIN.) = 8.28
LONGEST FLOWPATH FROM NODE 2.00 TO NODE 2.20 = 238.00 FEET.
****************************************************************************
FLOW PROCESS FROM NODE 2.20 TO NODE 2.20 IS CODE = 81
---------------------------------------------------
>>>>>ADDITION OF SUBAREA TO MAINLINE PEAK FLOW<<<<<
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 4.947
I *USER SPECIFIED(SUBAREA):
USER-SPECIFIED RUNOFF COEFFICIENT = .5700
S.C.S. CURVE NUMBER (AMC II) = 0
AREA-AVERAGE RUNOFF COEFFICIENT = 0.5793
I SUBAREA AREA(ACRES) = 0.64 SUBAREA RUNOFF(CFS) = 1.80
TOTAL AREA(ACRES) = 0.7 TOTAL RUNOFF(CFS) = 1.89
TC(MIN.) = 8.28
I END OF STUDY SUMMARY:
TOTAL AREA(ACRES) = 0.7 TC(MIN.) = 8.28
PEAK FLOW RATE(CFS) = 1.89
END OF RATIONAL METHOD ANALYSIS
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****************************************************************************
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM PACKAGE
Reference: SAN DIEGO COUNTY FLOOD CONTROL DISTRICT
2003,1985,1981 HYDROLOGY MANUAL
(c) Copyright 1982-2008 Advanced Engineering Software (aes)
Ver. 15.0 Release Date: 04/01/2008 License ID 1452
Analysis prepared by:
* * * * * * * * * * * * * * * * * * * * * * * * * * DESCRIPTION OF STUDY * * * * * * * * * * * * * * * * * * * * * * * * * *
* POSTDEVELOPED HYDROLOGIC ANALYSIS FOR 100 YEAR STORM EVENT *
* ROOSEVELT STREET *
* PLSA 2110 - 6.10.16 *
**************************************************************************
FILE NAME: 2110P100.DAT
I TIME/DATE OF STUDY: 11:19 06/10/2016
USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
I 2003 SAN DIEGO MANUAL CRITERIA
USER SPECIFIED STORM EVENT(YEAR) = 100.00
6-HOUR DURATION PRECIPITATION (INCHES) = 2.600
I SPECIFIED MINIMUM PIPE SIZE(INCH) = 3.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE FOR FRICTION SLOPE = 0.95
SAN DIEGO HYDROLOGY MANUAL "C"-VALUES USED FOR RATIONAL METHOD
NOTE: CONSIDER ALL CONFLUENCE STREAM COMBINATIONS
I FOR ALL DOWNSTREAM ANALYSES
*USER_DEFINED STREET-SECTIONS FOR COUPLED PIPEFLOW AND STREETFLOW MODEL*
HALF- CROWN TO STREET-CROSSFALL: CURB GUTTER-GEOMETRIES: MANNING
WIDTH CROSSFALL IN- / OUT-/PARK- HEIGHT WIDTH LIP HIKE FACTOR
I NO. (FT) (FT) SIDE / SIDE/ WAY (FT) (FT) (FT) (FT) (n)
1 30.0 20.0 0.018/0.018/0.020 0.67 2.00 0.0313 0.167 0.0150
I GLOBAL STREET FLOW-DEPTH CONSTRAINTS:
Relative Flow-Depth = 0.00 FEET
as (Maximum Allowable Street Flow Depth) - (Top-of-Curb)
(Depth)*(Velocity) Constraint = 6.0 (FT*FT/S)
I *SIZE PIPE WITH A FLOW CAPACITY GREATER THAN
OR EQUAL TO THE UPSTREAM TRIBUTARY PIPE.*
****************************************************************************
I FLOW PROCESS FROM NODE 1.00 TO NODE 1.10 IS CODE = 21 ----------------------------------------------------------------------------
>>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
I
------------------------
*USER SPECIFIED(SUBAREA):
USER-SPECIFIED RUNOFF COEFFICIENT = .6300
S.O.S. CURVE NUMBER (AMC II) = 0
INITIAL SUBAREA FLOW-LENGTH(FEET) = 85.00
I UPSTREAM ELEVATION(FEET) = 40.00
DOWNSTREAM ELEVATION(FEET) = 39.00
ELEVATION DIFFERENCE(FEET) = 1.00
SUBAREA OVERLAND TIME OF FLOW(MIN.) = 6.548
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WARNING: INITIAL SUBAREA FLOW PATH LENGTH IS GREATER THAN
THE MAXIMUM OVERLAND FLOW LENGTH = 66.76
(Reference: Table 3-1B of Hydrology Manual) I THE MAXIMUM OVERLAND FLOW LENGTH IS USED IN Tc CALCULATION!
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 5.756
SUBAREA RUNOFF(CFS) = 0.15
I TOTAL AREA(ACRES) 0.04 TOTAL RUNOFF(CFS) = 0.15
****************************************************************************
FLOW PROCESS FROM NODE 1.10 TO NODE 1.20 IS CODE = 52
I ----------------------------------------------------------------------------
>>>>>COMPUTE NATURAL VALLEY CHANNEL FLOW<<<<<
>>>>>TRAVELTIME THRU SUBAREA<<<<<
I ELEVATION DATA: UPSTREAM(FEET) = 39.00 DOWNSTREAM(FEET) = 36.90
CHANNEL LENGTH THRU SUBAREA(FEET) = 270.00 CHANNEL SLOPE = 0.0078
NOTE: CHANNEL FLOW OF 1. CFS WAS ASSUMED IN VELOCITY ESTIMATION
CHANNEL FLOW THRU SUBAREA(CFS) = 0.15
FLOW VELOCITY(FEET/SEC) = 1.32 (PER LACFCD/RCFC&WCD HYDROLOGY MANUAL) I TRAVEL TIME(MIN.) = 3.40 Tc(MIN.) = 9.95
LONGEST FLOWPATH FROM NODE 1.00 TO NODE 1.20 = 355.00 FEET.
I ****************************************************************************
FLOW PROCESS FROM NODE 1.20 TO NODE 1.20 IS CODE = 81
>>>>>ADDITION OF SUBAREA TO MAINLINE PEAK FLOW<<<<<
I 100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 4.395
*USER SPECIFIED(SUBAREA):
USER-SPECIFIED RUNOFF COEFFICIENT = .7000
S.O.S. CURVE NUMBER (AMC II) = 0 I AREA-AVERAGE RUNOFF COEFFICIENT = 0.6965
SUBAREA AREA(ACRES) = 0.77 SUBAREA RUNOFF(CFS) = 2.37
TOTAL AREA(ACRES) = 0.8 TOTAL RUNOFF(CFS) = 2.48
I TC(MIN.) = 9.95
END OF STUDY SUMMARY:
TOTAL AREA(ACRES) = 0.8 TC(MIN.) 9.95
PEAK FLOW RATE(CFS) = 2.48 -----------------
END OF RATIONAL METHOD ANALYSIS
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4.0 HYDRAULIC CALCULATIONS
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Proposed Outlet Pipe Calculations
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Section
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.
8 INCH PVC OUTLET PIPE
I Circular
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Diameter (ft) = 0.83
Invert Elev(ft) = 511.00
Slope (%) = 2.00
N-Value = 0.009
I Calculations
Compute by: Known Depth
Known Depth (ft) = 0.83
I Elev (ft)
512.00
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i 511.75
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511.50
511.25
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511.00
1 510.75
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0
Highlighted
Depth (ft)
Q (cfs)
Area (sqft)
Velocity (ft/s)
Wetted Perim (ft)
Crit Depth, Yc (ft)
Top Width (ft)
EGL (ft)
Thursday, Jun 11 2015
= 0.83
= 4.426
= 0.54
= 8.18
= 2.61
= 0.81
= 0.00
= 1.87
Reach (ft)
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Detention Basin Sizing:
LID BMP Sizing Requirement
LID BMP area required is equal to 3% of the impervious are being removed and replaced or
added
Required BMP = 0.03 (15,764 so
473 SF
Proposed BMP Area = 589 SF
Proposed BMP Area> Required BMP Area
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5.0 APPENDIX
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San Diego County Hydrology Manual Section: 3
Date: June 2003 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 Tj 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 (Ti
Element* DU/
Acre
.5% 1% 2% 3% 5% 10%
LM T1 LM T1 LM Tj LM T LM Ti LM T
Natural 50 13.2 70 12.5 85 10.9 100 10.3 100 8.7 100 6.9
LDR 1 50 12.2 70 11.5 j 85 10.0 100 9.5 100 8.0 100 6.4
LDR 2 50 11.3 70 10.5 1 85 9.2 100 8.8 100 7.4 100 5.8
LDR 2.9 50
50
10.7
10.2
70
70
10.0
9.6
85 8.8 95 8.1 100 7.0 1 100 5.6
MDR 4.3 80 8.1 95 7.8 100 6.7 100 5.3
MDR 7.3 50 1 9.2 65 8.4 80 7.4 95 7.0 100 6.0 100 4.8
MDR. 10.9 50 8.7 65 7.9 80 6.9 90 6.4 100 5.7 100 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.Com 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./Com 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2
Limited I. 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2
General 1. 50 3.7 60 3.2 1 70 2.7 80 2.6 90 2.3 100 1.9
*See Table 3-1 for more detailed description
3-12
intensity-Duration Design Chart - Template
F I C U R
LL
- - - - - - - - - - - - - - - - - - -
Directions for Application: I I
70i'J (1)R precipthition determine deteine 6 hr and 24 hr amounts
for the selected frequency. These maps are included in the
I ______ 1 EQUATION County Hydrology Manual (1O 50 arid 100 vrmaps rictuded
6 744 PC, D in the Design and Procedure Manual) - T
I = Intensity (in/hr) - Adjust 6 hr precipitation ( necessary) so that it is within
- _________ -
6HourPcpitaton the range of 45% to 65% of the 24 hr precipitation (not
4,0 D = Duration (min) applicaple to Desert).
I I Plot 6 hr precipitation on the right side of the chart. fti Drawaline through the point parallel to the platted lines.
This line is the intensity-duration curve for the location
4ITt j
,,
being analyzed.
2 Application Form:
(a) Selected frequency year
24
(c)AdjustoP6(2) in
6.0
L. - j
fl''4'N
5:,
so (d)t _min.
_L4JLL._i 4 " (e)1 in/hr
_LL 3,5
4.0
Noc This ella-i replaces the Intens lv Di..ration requenc7
1965 curves used since
__- I _ ___ 2.5
33.5443 5 5.5 6
'J 2.0
I I 1 1 I
2,113 395 1 35' - 9.221554 11.6313,17 19 1581
21 15 0 ... 2 618 95' 1060 166 122 03 •
- _
L
*
-
5
7
- _i ' ..:'-'.::'::'":::'':-', : ':,' .•:.i .L;'c' . 10 i3:,::7' •0,9e 8.74 1,56 6.42 27 10.11
7- ... 1:. . C 1->22-25 ?1 1 '5 ,63
7
u
15
20
16 21 q 7 13
01
,-------------.--.-..--.---..-
25
300'l2
2.3 1,40 1.87 233 73 327 724.615,132,50
-1i.63207'1"2,3,'. 34154564.98
- J 40
50
u' 4 's 310 3.46 329 4.13
j 1.19 1' 2 q 28 328 3i8
....................... ............................. .............J, ,,,•.I............ I I 60O.13308051"'6 2.12229265292318
00 1,49
- IT'' .1 .......................
- - 90
120
0,41 01 01' 1 354 15-. 204 225 24
0.34 0,51 0 2 '921.15 1,26 154 70 1,87 2.04
1 I I-hI
..I.........i"TiiiI'T
I i'ii
150 02 0. 0 9 086 103 1,18 1 2 147 162 176
039 0.3 0.65 0780.93 1.04 1.12 :,.1.. 1,7 ,,3s
0.1 I . . . ' _____.1_. 1 --
i
,
5 5 7 910 15 20 31)
.
40 50
---i------l--
1 2 3 4 5
~8O0.26
0.22 0,33 0.'30.64 0630.76 0.87 'Th .08 1,19 1,30
Moutes Hours
'023 0.38 019 bA7 0.%5056 0.73 06 0.94 1.83 113
017 0250.33 042_0.600,38' 057 0,76 - 0.124 0.92 1.00
Duraihon
- - - - - - - - - - - - - - - - - - -
San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 6of26
Table 3-1
RUNOFF COEFFICIENTS FOR URBAN AREAS
Land Use I Runoff Coefficient "C"
Soil Type
NRCS Elements County Elements % IMPER. A B C D
Undisturbed Natural Terrain (Natural) Permanent Open Space 0* 0.20 0.25 0.30 0.35
Low Density Residential (LDR) Residential, 1.0 DU/A or less 10 0.27 0.32 0.36 0.41
Low Density Residential (LDR) Residential. 2.0 DU/A or less 20 0.34 0.38 0.42 0.46
Low Density Residential (LDR) Residential, 2.9 DU/A or less 25 0.38 0.41 0.45 0.49
Medium Density Residential (MDR) Residential, 4.3 'DU/A or less 30 0.41 0.45 0.48 0.52
Medium Density Residential (MDR) Residential, 7.3 DU/A or less 40 0.48 0.51 0.54 0.57
Medium Density Residential (NR) Residential. 10.9 DU/A or less 45 0.52 0.54 0.57 0.60
Medium Density Residential (MDR) Residential, 14.5 DU/A or less 50 0.55 0.58 0.60 0.63
High Density Residential (HDR) Residential, 24.0 DU/A or less 65 0.66 0.67 0.69 0.71
High Density Residential (MR) Residential, 43.0 DU/A or less 80 0.76 0.77 0.78 0.79
Commercial/Industrial (N. Corn) Neighborhood Commercial 80 0.76 0.77 0.78 0.79
Commercial/Industrial (G. Corn) General Commercial 85 0.80 0.80 0.81 0.82
Commercial/industrial (O.P. Corn) Office Professional/Commercial 90 0.83 0.84 0.84 0.85
Commercial/Industrial (Limited I.) Limited Industrial 90 0.83 0.84 0.84 0.85
Commercial/Industrial (General I.) General Industrial 95 0.87 0.87 0.87 0.87
*'The values associated with 0% impervious may be used for direct calculation of the runoff coefficient as described in Section 3.1.2 (representing the pervious runoff
coefficient, Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. Justification must be given that the area will remain natural forever (e.g., the area
is located in Cleveland National Forest).
DU/A .dwelling units per acre
NRCS = National Resources Conservation Service
3-6
V
o .
.---------,--
0
- -
to V to C) (•1 0
323O
County of San Diego
Hydrology Manual
Rainfall Isopluvials
100 Year Rainfall Event — 6 .Hou
IsopIuvial (inches)
r. 33 c' 44"
ao' 56'
N T'IIS (•VAI IS PROVIOFO WIThOUT WARRANT( OF ANY KIND, EITHER EXPRESS
OR IMPLIED, INCLUOiNO,BUT NOT UMITED TO, ThE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR APARTICIJLAR PURPOSE
CopyllyhI So'IC'IS. t4l Ri5hto Rooerved.
*
This pso4os1s may contain Nrornlolisn Irorn If. SANDAG Roginois
E InronowSon Syslero whlth ceonci be rpmdc~el without U'S
Wrryeo n,mlsoro or LANDAG
Thopctnroycootwn Ir4omroiion oPiUr iren boor- roprorlr.cnd with
permission gisnind by Thor-iwo Er-roPers Maps
S
3 0 3Mifes
V r.- -;' -- --• - -. -. -..
' (
33'16
25
OCI-Al45 fl
- I - I-. : •4 V,• -'--- --V -. - - P • - - e. - - - 0' CA"* SBAD
cb p / 11
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---'- --I ----- •V - - --V - - - --S
El N1FA I
- I : • -- -. 1' •-' 33OO ---- -___ -- --- -. -:---_ SOLANA BEACII V :s ccouv -- - .- • -- - -
4 DEC MAR' -
•' • - - : : --
A" I
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t
32045 - - -'-- ;\ - -'--- - _.••i.________ - -- - —' V / -. - • - - I 1 -- - - : •- -. _ -
-
-
3 - MS.
- - - -.
Q. &-•- -'-- .- -- .-. -- • .- V
_-_,I- •-f -•' --, -- - ;:-.--°-'ç/ /
IMPERIAL BEACH ---- • -' - - - • - -22' -' -
32°30 ..........rn-----------
HYDROLOGIC NODE MAP
ROOSEVELT STREET
PRE-DEVELOPMENT MAP
NODE 2.0
EL =39.9
"C" CALCULATIONS
C= (ZIMPERVIOUS x 0.87) + ((l-XIMPERVIOUS)xo .41)
SUB-AREA Al'
C= (0.87x0.87) + (0.13x0.41)
C=0.81
SUB-AREA 'A2'
C=(0.79x0.87) + (0.21x0.41)
C=0.77
SUB-AREA BI'
C=(0.64x0.87) + (0.36x0.41)
C=0.70
SUB-AREA 82'
C=(0.35x0.87) + (0.65x0.41)
C=0.57
SCALE: 111=20'
... -...... '., . .
. _.a • __ /....
BOUNDARY -
EA BOUNDARY -
IERVI0 AREA 16.376 = (10.608 ONSITE)+ (5,768 SF OFFSITE)I
SCALE: 111=20'
BASIN AREA =35,415 SF = 0.81 AC
OUTLET' 12
/ EL=36.9
../ 0100=2.46 CFS
HYDROLOGIC NODE MAP
ROOSEVELT STREET
POST-DEVELOPMENT MAP
"C" CALCULATIONS
C- (ZIMPERVIOUS x 0.87) + ((l-ZIMPERVIOUS)xo .41)
SUB-AREA Al '
C=(0.48x0.87) + (0.52x0.41)
C=0.63
SUB-AREA A2
C=(0.62x0.87) + (0.38x0.41)
C=0.70
AI=1.726 SF=0.04 AC
C-0.63
LEGEND
BASIN BOUNDARY
SUB-AREA BOUNDARY -
FLOWLINE
IMPERVIOUS AREA 21.707 SF= (15.764 SF ONSITE)+ (5.943 SF