HomeMy WebLinkAboutMS 08-01; BLUE CONDOMINIUMS; PRELIMINARY DRAINAGE REPORT FOR BLUE CONDOMINIUMS PROPOSED MINOR SUBDIVISION; 2011-11-09R1C761i70
'1 10 2011
LAND DEvELOPMENT
N• L t 4\ M
ENGINEERING
DRAINAGE REPORT
FOR
BLUE CONDOMINIUMS
PROPOSED MINOR SUBDIVISION
MS-08-01
APN 204-231-10
PREPARED FOR
Barry and Mary Blue
2950 Ocean Street
Carlsbad, CA 92008
PREPARED BY
Robert 0. Sukup
4322 Sea Bright Place
Carlsbad, CA 92008
760-720-0098
November 9, 2011
The proposed project is to subdivide an existing lot with a total gross acreage of
.16 acres into a 1 Lot, 2 Unit Condominium Subdivision. There are presently 2
detached rental homes on the site. The density of the project will remain the
same but the use will be greater from a drainage standpoint.
The attached hydrology calculations show a small increase of drainage waters
from the proposed project. This is due to the increase in impervious surface.
Basically all of the storm water is intended to flow to the subterranean parking
driveway where it will first flow into a grate catch basin with a filter insert, then to
a detention pipe, and finally to a sump pump to be pumped up to the street.
The detention [storage] pipe has been designed to hold back the projected
increase.in flow [.21 cfs] for a minimum of 5 minutes. The 5 minutes is the Time
of Concentration I used in my calculations for the anticipated Peak Hydrology
Event for this lot. The amount of flow coming out of the detention pipe will be
restricted by a 6" outlet pipe [.56 cfs] and will not allow more than the pre
development flow [.60 cfs] to be released. The detention pipe as presently
shown on the plans has more capacity than needed and may be reduced in size
in the final design.
The discharge from the sump pump basin will go up to a proposed "dispersion
box", then down a gravel swale [to promote a little bit of infiltration and velocity
reduction] to a concrete apron that discharges into a proposed 0-25 outlet to
Cherry Avenue. Cherry Avenue is the project frontage street where all the site's
water presently goes. Once in Cherry Avenue, the water flows westward in the
existing curb and gutter for about 200' or so until it enters the City's storm drain
system in Carlsbad Boulevard. From there it ultimately makes its way to the
Pacific Ocean via the City's storm drain system.
The supporting hydrology and hydraulic calculations, hydrology map, and
discharge schematic all follow.
In my professional opinion, the drainage concept I have proposed will work very
well and not cause any offsite siltation, erosion, or flooding. Adequate room for
modification in final design has been allowed for.
F.H
SITE CARLSBAD
LOCATION MAP
NO SCALE
THOM. BROS. PG. 1106 E-6
IYDROLO3Y CALCS
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MECH ROOM UNIT 9 GARAGE
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W< I[E REQUIRED jW_rm- RESTRICTION
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UNIT A GARAGE IIII:: S. SEE
!4- ci FOR CO NECTION
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EQUIPMENT RM
WASH RM
FOR SURFACE
DRAINS
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SEE SHT 3
STORAGE J
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1 _1-9 37. __ = e. 36% quuI.J
OWL r?7r—1 '
__________________ S
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- PI( K UP NOTE: FACE OF WALL F.. u FOR STORM S S
0 ON BOUNDARY LINE. jr
_30' LONG X 36" HDPE WATER
FROh AE30VE (DUAL PUMP SYSTEM
1-0 CONCREETE DETENTION AREA
0 (ryp) PAVERS TOP OF PIPE=38.0 W/ ALARM BELL)
SUMP PUMP BASIN
\ (4' X 4' BASIN) J '- CONC OW(t
COLOR TO MATCH
PAVERS IN PVT
—
B C PROPERTY
MAP
M 09 Oi
S J .
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. CA 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 10 027 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 (MDR) 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 '4 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 (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77 0.78 0.79 Commercial/Industrial (N. Corn) Neighborhood Commercial 8Q..?u 0.76-t 0.77 0.78 0.79 bSr .1 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 1.) 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 coeffici
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