HomeMy WebLinkAboutCDP 00-26; Mullins Residence; Hydrology Report; 2001-05-22HYDROLOGY REPORT
FOR
WALLACE MULLINS
JEFFERSON STREET
CARLSBAD, CALIFORNIA
760-434-7444
PREPARED BY:
South Valley Engineering, Inc.
P. O. Box 130879
Carlsbad, Ca 92013-0879
760-931-1792, 760-931-1892 Fax
Email: nservin@earthlink.net
DATE: August 4, 2000
Revised: May 22, 2001
CJTiC
INTRODUCTION:
The site is located along Jefferson Street north of the
intersection of Las Flores & Jefferson Street bounded along
the east by Interstate 5 Freeway. No address has been
assigned to this parcel and is known as APN: 155-180-20.
The project site consists of building on a finished pad with
some removal of an existing bank along the frontage of
Jefferson Street to create sight distance for the new single
family dwelling.
The run off from the site will drain away from the structure
and a portion will be collected into an area drain along the
south west corner of the side yard, the balance will be
conveyed by sheet flow over the driveway drainage along the
driveway onto Jefferson Street. At this location, Jefferson
Street is a high point which does not have much drainage
tributary collecting to it. The water will be drained in the
same historical direction with the exception that drainage
will be place onto the street gutter. At the corner of Las
Flores and Jefferson a curb inlet exists that empties into
other drainage systems.
This report will determine the amount of runoff from the
site. The capacity of the pipes will be computed for proper
pipe sizing and drainage into the gutter.
Page 1 of 5
RATIONAL METHOD:
Q = C I A
Where:
Q = peak discharge (cubic feet/sec, Cfs)
C = run off coefficient
I = rain fall intensity (in/hr)
A = tributary area (Acres)
References:
County of San Diego Hydrology Manual, April 1993.
Bureau of Public Roads.
"Greenbook" Standard Specifications for
Public Works Construction, 1997 edition.
San Diego Regional Standard Drawings, March
1997.
HYDROLOGY
1. Soil classification = D
2. Runoff Coefficient (single family) C = 0.80 adjusted for
imperious areas)
3. Time of concentration Tc = 6 min. (see attached)
Page 2 of 5
SITE DATA:
(single family)~ 0.80
I = 3.75 in/hr. (10 year) (7A4P6D~0645 )
TRIBUTARY AREA
Al
AREA(ft2)
4,200
C
0.80
I (in/hr)
3.75
Tc
(min)
6
TOTAL
Q(cfs)
0.26
0.26
Since the drains divides the site flow, Q=0.26 cfs will be used for pipe
sizing.
Page 3 of 5
ANALYSIS AND RESULTS
STORM DRAIN CAPACITY
STORM DRAIN
SD1
TRIBUTARY AREA
Al
Q
cfs
0.26
SIZE
3" PVC
SLOPE
4.0%
CAPACITY
cfs
0.21/ea
The 3" pipe has a capacity of 0.21 cfs. Therefore, two (2) pipes
will have the combined capacity of 0.42 cfs, which is more than
adequate for the site.
SUMMARY
The designed concrete driveways and earthen swales are
sufficient to convey the run off from the site. The drain inlet
and the 2-3" PVC storm drain are adequate to collect and
dissipate the energy resulting from the concentrated flows.
Page 4 of 5
ATTACHMENTS
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SAN DIEGO COUNTY
DEPARTMENT OF SPECIAL DISTRICT SERVICES
DESIGN MANUAL
'.DP:
URBAN AREAS OVERLAND TIME
OF FLOW CURVES
<'[)'y Y -C
Urban
Commercial-Industrial - Commercial industrial complex where 90-95 per-
cent of lot area is covered by structures, roads, sidewalks and paved
parking areas.
_ High density residential - Multiple-family residential zoning with an
average of 1,500 square feet of lot required per unit, and commercial
zoning with 7,500 square feet per lot. Fifty percent to 75 percent of
the lot area Is covered by structures, sidewalks and driveways.
^ Medium density residential - Single-family residential zoning with 6,000
to 10,000 square feet per lot and light Industry zoning with 7»500 square
feet per lot. Twenty-one percent to 27 percent of the lot area is covered
by structures, sidewalks and driveways.
Low density residential <- Single-family residential zoning with 15|000
to 20,000 square feet per lot. Fifteen percent to 18 percent of lot area
Is covered by structures, sidewalks and driveways.
Vineyards - As with orchards, ground cover and land condition must be considered
In estimating CN numbers. Use CN number which applies to the land use or the
kind and condition of cover during storm periods: for example, use annual
grass CN number for land with this ground cover. CN numbers for "disked" and
"annual grass" cover crops are two examples tabulated.
As with orchards, the quality of the cover must also be considered. See Tables
I-A-2 and I-A-3 for appropriate hydrologic conditions.
Woodland-grass - Areas with an open cover of broadleaf or coniferous trees,
usually live oak and pines, with the intervening ground space occupied by
annual grasses or weeds. The trees may occur single or in small clumps. Canopy
density, the amount of ground surface shaded at high noon, is from 20 to 50
percent.
I-A-13
PIPE CAPACITY
Worksheet for Circular Channel
Project Description
Project File c:\haestad\fmw\mullins1.fm2
Worksheet PIPE DRAIN TO CURB FROM PAD
Flow Element Circular Channel
Method Manning's Formula
Solve For Discharge
Input Data
Mannings Coefficient
Channel Slope
Depth
Diameter
0.011
0.040000 ft/ft
0.25 ft
3.00 in
Results
Discharge
Flow Area
Wetted Perimeter
Top Width
Critical Depth
Percent Full
Critical Slope
Velocity
Velocity Head
Specific Energy
Froude Number
Maximum Discharge
Full Flow Capacity
Full Flow Slope
Flow is subcritical.
0.21 cfs -=s=
0.05 ft2
0.79 ft
0.75e-8 ft
0.24 ft
100.00
0.035228 ft/ft
4.25 ft/s
0.28 ft
0.53 ft
0.296-3
0.22 cfs — =£—
0.21 cfs **=-
0.040000 ft/ft
05/24/01
12:28:46 PM Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 (203)755-1666
FlowMaster v5.15
Page 1 of 1
COUNTY OF SAN DIEGO .
DEPARTMENT OF SANITATION
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