HomeMy WebLinkAbout3676; PALOMAR AIRPORT RD AND EL CAMINO REAL TURN LANES; HYDROLOGY AND HYDRAULICS STUDY; 2000-01-04Hydrology and Hydraulics Study
Palomar Airport Road/El Camino Real Right Turn Lanes Project
City of Carlsbad Project Number 3676
Prepared for:
The City of Carlsbad
Vincent Gn, P.E , Project Manager
2075 Las Palmas Drive
Carlsbad, California 92009-1576
(760)438-11261
Prepared by:
Berryman & Henigar
Mark Risch, P.E , Project Manager
11590 'Nest Bernardo Court, Suite 100
San Diego, California 92127-1624
(858)451-6100
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Mark Risch, P.E DatO
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Introduction and Purpose:
The purpose of this study and report is to validate the existing curb inlet, in its current size and
configuration, at the northeast corner of Palomar Airport Road and El Camino Real. The
methodology for the hydrology and hydraulics calculations are summarized below with the actual
calculations and support map comprising the latter portion of this report.
Hydrology:
The rational method hydrology for a 100 year event was performed in a manner consistent with
the methodology described in the City of Carlsbad "STANDARDS FOR DESIGN AND
CONSTRUCTION OF PUBLIC WORKS IMPROVEMENTS IN THE CITY OF CARLSBAD" dated
April 20, 1993 with slight modification to account for the higher 'C' value resulting in the
construction of this project. The rational method equation
Q = CIA
was used for calculating the final runoff value at the curb inlet. The detailed calculations and
appropriate charts and nomographs can be found on the pages following this descriptive text. A
hydrology map showing the areas can be found in the pocket at the end of this report.
'C' value:
Two areas of distinctly different imperviousness were identified and are depicted on the hydrology
map at the end of this report. The boundaries for these two sub-basins were arrived at by
inspection of the existing topography and the plans for the actual improvements and by assuming
that the curb inlet approximately 800 feet upstream (east) of the subject curb inlet intercepts all
flow (no bypass into the subject basin). By weighting the acreages of these two sub-basins and
appropriate imperviousness values for each of them, a composite 'C' value for the overall
basin was calculated to be 0.92.
Intensity (I):
The calculation for intensity, I, for this basin was arrived at by first calculating the Time of
Concentration, Tc, for the basin using the equation provided on the "Urban Areas Overland Time
of Flow Curves" nomograph. This calculation resulted in a Tc = 5.66. Next the intensity, I, was
calculated using the equation from the County of San Diego nomograph for intensity (Appendix
XI-A), the time of concentration, Tc, and the precipitation value for the area obtained from the
current 6 hour and 24 hour isopluvial tables for a 100 year event. The calculation resulted in an
intensity, I = 6.57.
Final Runoff (Q):
The area for the overall basin was measured and found to be A = 1.31 acreas. Applying the Q =
CIA eqation resulted in the final runoff value of:
Q = CIA = (0.92)(6.57)(1.31) = 7.92 CFS
Hydraulics (Curb Inlet Capacity Calculations):
S
Hydraulics for the capacity of the existing curb inlet was calculated using the equation found in
the City of Carlsbad "STANDARDS FOR DESIGN AND CONSTRUCTION OF PUBLIC WORKS
IMPROVEMENTS IN THE CITY OF CARLSBAD" dated April 20,1993 for a curb inlet on a
continuous grade. Using the slope of the curb just upstream of the curb inlet (1.24%), the
nomograph for depth of flow in a street (County of San Diego AppendixX-D), and a clear opening
in the existing curb inlet of 20 feet, the inlet capacity was found to be 8.91 CFS.
Finding:
The inlet capacity of the existing curb inlet is found to be in excess of the anticipated 100 year
peak flow and therefore the curb inlet requires no modifications and is sufficient in its
current size and configuration.
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Hand Calculations
Charts and Nomographs
and
Hydrology Map
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INTENSITYDUMTION DESIGN CHART
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I Equation: I 744 p6 D 645
1) From precipitation naps determine 6 hr. and
I = Intensity 24 hr. amounts for the selected frequency.
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These maps are printed in the County Hydrology
- ' p6 6 Hr. Precipitation (In.) Manual (10, 50 and 100 yr. maps Included in the
• 'r ' Design and Procedure Manual).
D Duration (Mm.)
4. - • •.• •,: 2) Adjust 6 hr. precipitation (if necessary) so
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3.
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the intensity-duration curve for
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COUNTY OF SAN DIEGO
DEPARTMENT OF SANITATION &
FLOOD CONTROL
45'
100-YEAE 6-HOU1.. PECIITATO
'10.-' ISOPLUVIALS OF 100-YEAR 64OUR
PflECIPFtOal l I TS O LU1 ICR
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U.S. DEPARTMEN 1'(
NATIONAL OCEANIC AND AT. OSI
ITS SPECIAL STUDIES ORANCII. OFFICE OF II DR
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COUNTY OF SAN DIEGO
DEPARTMENT OF SANITATION & 100-YEAR 244101 11 PflECIPITITIO .
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FLOOD CONTROL
'iO.ASOPLUVIALS OF 100 -YEAR 2441DUR
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DISCHARGE (C.FS.)
EXAMPLE:
I Given Q= 10
Char? es Depth = 0.4, Velocity = 4.4 ts.
SAN DIEGO COUNTY GUTTERAND ROADWAY
I DEPARTMENT OF SPECIAL DISTRICT SERVICES DISCHARGE—VELOCITY CHART
DESIGN MA:NUAL:
I APPROVED DATE APPENDIX X-D
I'ItFIIPI!..
0.20 ACRES
C==O.5 0 an
Ii• Cr o -
i_•• - - Elf,= - - - _ - _
ill - 1247 .
--/® --------------------' --±,—_-
H
. EXISTING CURB INLET _ - h1,_.. - - ------ - - - - - ---- - - ELEVATION = 320.0± - - - - __' - - - . - - . - - - - - . - - -. - - . - - - - - - • • ASSUME FULL INTERCEPTION
, • __ _ I.
1.11 ACRES
C = 1.00
L=800'
EXISTING CURB INLET-
ELEVATION = 286.0
CLEAR OPENING = 20'
AIV
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PLAN: PALOMAR AIRPORT ROAD
SCALE: 1" = 40'
SHEET CITY OF CARLSBAD SHEETS1
1 ENGINEERING DEPARTMENT 1
PALOMAR AIRPORT ROAD!
EL CAMINO REAL RIGHT TURNS
11590 W. Bernardo Ct. Suite 100
San Diego, CA 92127 ( )
FAX: (858) 451-2846
APPROVED
CITY ENGINEER PE EXPIRES DATE
__ DWN BY: PROJECT NO. DRAWING NO. 1
RVWD BY:
INITIAL CHKD DATE INITIAL
REVISION DESCRIPTION
DATE INITiAL DATE
_______ ENGINEER OF WORK OTHER APPROVAL CITY APPROVAL