HomeMy WebLinkAboutDrainage Report East MU 5.9.18
D:\73452 PA-12 Apts\06 Entitlements\In-house Prelim Reports\Hydrology\PA-12 Drainage 2018 0509.docx
D:\73452 PA-12 Apts\06 Entitlements\In-house Prelim Reports\Hydrology\PA-12 Drainage 2018 0509.docx
TABLE OF CONTENTS
Vicinity Map
1. Scope of Report................................................................................................................... 1
2. Prior Reports ....................................................................................................................... 1
3. Existing Conditions ............................................................................................................. 1
4. Project Description.............................................................................................................. 1
5. Methodology ............................................................................................................................... 1
5.1 Design Criteria .......................................................................................................................................... 1
5.2 Soil Type .................................................................................................................................................... 2
5.3 Runoff Coefficient (C-Factors) .................................................................................................................. 2
5.4 Peak Flow Rates ........................................................................................................................................ 2
5.5 Rainfall ...................................................................................................................................................... 2
5.6 Time of Concentration ............................................................................................................................... 2
6. Inlet Sizing .................................................................................................................................. 3
7. Hydrology ................................................................................................................................... 3
8. Water Surface Profiles ............................................................................................................... 3
9. Conclusion ................................................................................................................................. 4
Proposed Drainage / Node Exhibit ............................................................................... Map Pocket
EXHIBITS
A. Curb Inlet Calculations
B. Hydrology / Civil-D Calculations
C. Water Surface Profiles (WSPG)
APPENDIX
San Diego County June 2003 Hydrology Manual References
City of Chula Vista Subdivision Manual References
D:\73452 PA-12 Apts\06 Entitlements\In-house Prelim Reports\Hydrology\PA-12 Drainage 2018 0509.docx
D:\73452 PA-12 Apts\06 Entitlements\In-house Prelim Reports\Hydrology\PA-12 Drainage 2018 0509.docx 1
1. Scope of Report
The final drainage study is intended to support the construction plans for the backbone storm
drain at the site. A separate Storm Water Quality Management Plan (SWQMP) has been
prepared to document the treatment and Hydromodification Management facilities.
2. Prior Reports
The drainage for the site was addressed is part of the public storm drain system (City of Chula
Vista drawings 03070-15 & 16) in Olympic Parkway and Town Center Drive. These systems
were installed to serve the Planning Area 12 East and West. The mass grading plans and storm
drain profiles for “McMillin Otay Ranch Village 12 – Freeway Commercial” (Rick Engineering)
were completed in 2007.
3. Existing Conditions
The project site is located in the eastern portion of Planning Area 12 of Otay Ranch Village. As
noted above, the site was previously mass graded, with a single a large pad, mildly sloping (2%)
from southeast to northwest, with a temporary sediment basin near the intersection at Olympic
Parkway and Town Center Drive. The pad area is generally located above the adjacent streets,
with a maximum slope height of approximately 10 feet above the intersection.
4. Project Description
The Otay Ranch Planning Area 12 East project is located in the eastern portion of the City of
Chula Vista, at the southeast corner of the intersection of Olympic Parkway and Town Center
Drive. The site is located east of SR-125, west of Eastlake Parkway, and immediately north of
the shopping center (Otay Rach Town Center).
The project will include multi-family residential apartment buildings, along with some retail
commercial along the Town Center frontage. A private driveway will provide access through the
site from Town Center to Olympic Parking, providing surface access to the parking garages.
See Drainage Exhibit located in the Map Pocket.
5. Methodology
5.1 Design Criteria
The public drainage system will be designed in accordance with the City of Chula Vista’s
“Subdivision Manual”, Section 3 and 4. Storm drain is designed to convey 50-year storm event
D:\73452 PA-12 Apts\06 Entitlements\In-house Prelim Reports\Hydrology\PA-12 Drainage 2018 0509.docx 2
runoff, and flow depths in the street gutters shall not exceed the top of curb. (Excerpts from the
Subdivision Manual are included in the Appendix).
5.2 Soil Type
Hydrologic Soils Group D was assumed for the calculations in this report.
5.3 Runoff Coefficient (C-Factors)
The project site is expected to be approximately 85% imperviousness, which corresponds to a
runoff coefficient of C=0.80. This is consistent with a blend of Commercial (C=0.85) and Dense
Residential R2, R3 (C=0.75).
5.4 Peak Flow Rates
Peak flow rates are estimated using the Rational Method (Q=CIA). Rainfall intensities are
based upon the following formula;
I = 7.44 P6 Tc-.645
Where;
P6 is the local 6-hour rainfall total (inches) for a given storm frequency.
Tc is the time of concentration (minutes) at the design location in the drainage system.
Note: For purpose of calculating intensity, the minimum Tc shall be 5 minutes.
5.5 Rainfall
Rainfall intensities were calculated using the rainfall data form the City Isopluvial Maps, as
follows:
Rainfall Totals
Storm
Duration
100-Year
(in)
50-Year
(in)
10-Year
(in)
2-Year
(in)
6-Hour 2.5 2.2 1.75 1.15
See Appendix for City Rainfall Maps.
5.6 Time of Concentration
The time of concentration is based upon the distance for surface runoff to travel from the most
remote point in the tributary basin to the design location. It is the sum of the overland / sheet
flow (To), gutter flow (Tg) and pipe flow (Tp). Travel times in the gutter and pipe will be
estimated using the gutter flow nomograph and pipe velocities using the adjacent street slopes.
D:\73452 PA-12 Apts\06 Entitlements\In-house Prelim Reports\Hydrology\PA-12 Drainage 2018 0509.docx 3
In accordance with the City of Chula Vista Manual, Overland flow times (To) for urban
conditions may be estimated using the following equation;
3
)1.1(8.1
S
DC-
D = Length of watercourse (feet)
S = Slope (%)
C = Runoff Coefficient
6. Inlet Sizing
The project has several inlets located on the private driveway (Promenade Street). These include
San Diego Regional Standard Drawing curb inlets (Type “B”). The peak flow rates (Q50) used
for curb inlet sizing were estimated using a 5-minute time of concentration for the tributary area.
Copies of the inlet sizing calculations may be found in Exhibit “A”.
7. Hydrology
The project proposes a distributed system of biofiltration basins and private drains. The most
remote hydrologic point is located at the easterly edge of the site (Eastlake Parkway frontage).
The initial overland flow length is relatively short, with a mild slope toward a shallow treatment
basin. Private storm drain will continue along the Olympic Parkway frontage to the private
driveway (Promenade Street) to the HMP storage facility, then along the Town Center Drive to
the existing curb inlet near the Eastlake Parkway intersection.
A Node to Node rational method analysis was prepared to estimate the initial times of
concentration and travel times, and calculate the 50-year peak flow rates. The effect of the
hydromodification storage structure was ignored for the analysis.
The Civil-D analysis is located in Exhibit “B”.
8. Water Surface Profiles
In order to better define the peak flow characteristics, a backwater analysis using Water Surface
Profile Gradient (WSPG) software was prepared to determine the flow depths and velocities. No
attempt was made to model the effect of the hydromodification storage structure.
The WSPG analyses for the storm drain downstream and upstream of the HMP storage are
located in Exhibit “C”.
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9. Conclusion
The project proposes a mix of multifamily residential and retail commercial, consistent with the
original commercial assumptions. The proposed imperviousness is consistent with, and may be
less than, the original commercial land use. On this basis the peak runoff from the site is
expected to be consistent with the original storm drain design. From the site plan and storm
drain layout, the estimated peak flow rate for the project (Q50) is approximately the same design
flow rate shown on the record storm drain plans. Based upon the above information, we do not
anticipate any impacts to the existing storm drain system.
D:\73452 PA-12 Apts\06 Entitlements\In-house Prelim Reports\Hydrology\PA-12 Drainage 2018 0509.docx
Exhibit A
Curb Inlet Calculations
D:\73452 PA-12 Apts\06 Entitlements\In-house Prelim Reports\Hydrology\PA-12 Drainage 2018 0509.docx
Exhibit B
Hydrology / Civil-D Calculations
San Diego County Rational Hydrology Program
CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2014 Version 9.0
Rational method hydrology program based on
San Diego County Flood Control Division 2003 hydrology manual
Rational Hydrology Study Date: 05/03/18
------------------------------------------------------------------------
********* Hydrology Study Control Information **********
------------------------------------------------------------------------
Program License Serial Number 6334
------------------------------------------------------------------------
Rational hydrology study storm event year is 50.0
English (in-lb) input data Units used
Map data precipitation entered:
6 hour, precipitation(inches) = 2.200
24 hour precipitation(inches) = 4.400
P6/P24 = 50.0%
San Diego hydrology manual 'C' values used
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 1.000 to Point/Station 2.000
**** 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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Initial subarea total flow distance = 65.000(Ft.)
Highest elevation = 636.300(Ft.)
Lowest elevation = 635.650(Ft.)
Elevation difference = 0.650(Ft.) Slope = 1.000 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 65.00 (Ft)
for the top area slope value of 1.00 %, in a development type of
43.0 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 4.50 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.7900)*( 65.000^.5)/( 1.000^(1/3)]= 4.50
Calculated TC of 4.499 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 5.796(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.790
Subarea runoff = 0.366(CFS)
Total initial stream area = 0.080(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 2.000 to Point/Station 3.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Calculated TC of 4.499 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 5.796(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 4.50 min.
Rainfall intensity = 5.796(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 0.379
Subarea runoff = 1.832(CFS) for 0.400(Ac.)
Total runoff = 2.198(CFS) Total area = 0.480(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 2.000 to Point/Station 3.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Calculated TC of 4.499 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 5.796(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 4.50 min.
Rainfall intensity = 5.796(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 0.687
Subarea runoff = 1.786(CFS) for 0.390(Ac.)
Total runoff = 3.984(CFS) Total area = 0.870(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 2.000 to Point/Station 3.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Calculated TC of 4.499 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 5.796(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 4.50 min.
Rainfall intensity = 5.796(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 1.193
Subarea runoff = 2.931(CFS) for 0.640(Ac.)
Total runoff = 6.915(CFS) Total area = 1.510(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 2.000 to Point/Station 3.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Calculated TC of 4.499 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 5.796(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 4.50 min.
Rainfall intensity = 5.796(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 1.390
Subarea runoff = 1.145(CFS) for 0.250(Ac.)
Total runoff = 8.059(CFS) Total area = 1.760(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 2.000 to Point/Station 3.000
**** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________
Upstream point/station elevation = 631.500(Ft.)
Downstream point/station elevation = 622.330(Ft.)
Pipe length = 475.42(Ft.) Slope = 0.0193 Manning's N = 0.011
No. of pipes = 1 Required pipe flow = 8.059(CFS)
Given pipe size = 18.00(In.)
Calculated individual pipe flow = 8.059(CFS)
Normal flow depth in pipe = 8.65(In.)
Flow top width inside pipe = 17.99(In.)
Critical Depth = 13.20(In.)
Pipe flow velocity = 9.59(Ft/s)
Travel time through pipe = 0.83 min.
Time of concentration (TC) = 5.32 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 3.000 to Point/Station 4.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.566(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 5.32 min.
Rainfall intensity = 5.566(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 1.564
Subarea runoff = 0.647(CFS) for 0.220(Ac.)
Total runoff = 8.706(CFS) Total area = 1.980(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 3.000 to Point/Station 4.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.566(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 5.32 min.
Rainfall intensity = 5.566(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 1.849
Subarea runoff = 1.583(CFS) for 0.360(Ac.)
Total runoff = 10.289(CFS) Total area = 2.340(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 3.000 to Point/Station 4.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.566(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 5.32 min.
Rainfall intensity = 5.566(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 2.070
Subarea runoff = 1.231(CFS) for 0.280(Ac.)
Total runoff = 11.520(CFS) Total area = 2.620(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 3.000 to Point/Station 4.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.566(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 5.32 min.
Rainfall intensity = 5.566(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 2.291
Subarea runoff = 1.231(CFS) for 0.280(Ac.)
Total runoff = 12.751(CFS) Total area = 2.900(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 3.000 to Point/Station 4.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.566(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 5.32 min.
Rainfall intensity = 5.566(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 2.386
Subarea runoff = 0.528(CFS) for 0.120(Ac.)
Total runoff = 13.279(CFS) Total area = 3.020(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 3.000 to Point/Station 4.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.566(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 5.32 min.
Rainfall intensity = 5.566(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 3.010
Subarea runoff = 3.474(CFS) for 0.790(Ac.)
Total runoff = 16.752(CFS) Total area = 3.810(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 3.000 to Point/Station 4.000
**** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________
Upstream point/station elevation = 622.000(Ft.)
Downstream point/station elevation = 619.790(Ft.)
Pipe length = 220.93(Ft.) Slope = 0.0100 Manning's N = 0.011
No. of pipes = 1 Required pipe flow = 16.752(CFS)
Given pipe size = 24.00(In.)
Calculated individual pipe flow = 16.752(CFS)
Normal flow depth in pipe = 13.77(In.)
Flow top width inside pipe = 23.74(In.)
Critical Depth = 17.72(In.)
Pipe flow velocity = 8.99(Ft/s)
Travel time through pipe = 0.41 min.
Time of concentration (TC) = 5.73 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 4.000 to Point/Station 5.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.306(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
The area added to the existing stream causes a
a lower flow rate of Q = 16.389(CFS)
therefore the upstream flow rate of Q = 16.752(CFS) is being used
Time of concentration = 5.73 min.
Rainfall intensity = 5.306(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 3.089
Subarea runoff = 0.000(CFS) for 0.100(Ac.)
Total runoff = 16.752(CFS) Total area = 3.910(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 4.000 to Point/Station 5.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.306(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 5.73 min.
Rainfall intensity = 5.306(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 3.365
Subarea runoff = 1.104(CFS) for 0.350(Ac.)
Total runoff = 17.856(CFS) Total area = 4.260(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 4.000 to Point/Station 5.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.306(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 5.73 min.
Rainfall intensity = 5.306(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 3.437
Subarea runoff = 0.377(CFS) for 0.090(Ac.)
Total runoff = 18.234(CFS) Total area = 4.350(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 4.000 to Point/Station 5.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.306(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 5.73 min.
Rainfall intensity = 5.306(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 3.547
Subarea runoff = 0.587(CFS) for 0.140(Ac.)
Total runoff = 18.820(CFS) Total area = 4.490(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 4.000 to Point/Station 5.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.306(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 5.73 min.
Rainfall intensity = 5.306(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 3.681
Subarea runoff = 0.713(CFS) for 0.170(Ac.)
Total runoff = 19.533(CFS) Total area = 4.660(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 4.000 to Point/Station 5.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.306(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 5.73 min.
Rainfall intensity = 5.306(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 3.855
Subarea runoff = 0.922(CFS) for 0.220(Ac.)
Total runoff = 20.455(CFS) Total area = 4.880(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 4.000 to Point/Station 5.000
**** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________
Upstream point/station elevation = 619.460(Ft.)
Downstream point/station elevation = 617.870(Ft.)
Pipe length = 226.70(Ft.) Slope = 0.0070 Manning's N = 0.011
No. of pipes = 1 Required pipe flow = 20.455(CFS)
Given pipe size = 24.00(In.)
Calculated individual pipe flow = 20.455(CFS)
Normal flow depth in pipe = 18.02(In.)
Flow top width inside pipe = 20.76(In.)
Critical Depth = 19.48(In.)
Pipe flow velocity = 8.08(Ft/s)
Travel time through pipe = 0.47 min.
Time of concentration (TC) = 6.20 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 5.000 to Point/Station 6.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.044(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
The area added to the existing stream causes a
a lower flow rate of Q = 19.885(CFS)
therefore the upstream flow rate of Q = 20.455(CFS) is being used
Time of concentration = 6.20 min.
Rainfall intensity = 5.044(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 3.942
Subarea runoff = 0.000(CFS) for 0.110(Ac.)
Total runoff = 20.455(CFS) Total area = 4.990(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 5.000 to Point/Station 6.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.044(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 6.20 min.
Rainfall intensity = 5.044(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 4.061
Subarea runoff = 0.028(CFS) for 0.150(Ac.)
Total runoff = 20.483(CFS) Total area = 5.140(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 5.000 to Point/Station 6.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.044(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 6.20 min.
Rainfall intensity = 5.044(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 5.254
Subarea runoff = 6.017(CFS) for 1.510(Ac.)
Total runoff = 26.500(CFS) Total area = 6.650(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 5.000 to Point/Station 6.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 5.044(In/Hr) for a 50.0 year storm
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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 6.20 min.
Rainfall intensity = 5.044(In/Hr) for a 50.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 5.443
Subarea runoff = 0.956(CFS) for 0.240(Ac.)
Total runoff = 27.456(CFS) Total area = 6.890(Ac.)
End of computations, total study area = 6.890 (Ac.)
D:\73452 PA-12 Apts\06 Entitlements\In-house Prelim Reports\Hydrology\PA-12 Drainage 2018 0509.docx
Exhibit C
Water Surface Profiles (WSPG)
D:\73452 PA-12 Apts\06 Entitlements\In-house Prelim Reports\Hydrology\PA-12 Drainage 2018 0509.docx
Appendix
San Diego County June 2003 Hydrology Manual References
City of Chula Vista Subdivision Manual References
Isopluvial Rainfall Maps 50-year, 6-hour duration
Coefficient of Runoff Table