HomeMy WebLinkAboutCDP 06-25; Hagey Residence; Drainage Study; 2009-02-23N
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w i^E Sampo Engineering. Inc.
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fiST £±23-
Initial Date
DRAINAGE STUDY
FOR
HAGEY RESIDENCE
CDP 06-25, GRADING PLAN No. 458-3A
A PORTION OF TRACT NO. 3,
LACUNA MESA TRACTS, MAP NO. 1719
CARLSBAD, CA
APN: 155-140-37,38
February 23, 2009
j.n. 03-127
1034 Second Street * Encinitas, CA 92024 * phone: 760-436-0660 » fax: 760-436-0659
info@sampoengineering.com
CD
Z)
CO
DC
j.n. 03-127
February 23,2009
CDP 06-25, GRADING PLAN 458-3A
DRAINAGE STUDY FOR; A PORTION OF TRACT NO. 3, LAGUNA MESA
TRACTS, MAP NO. 1719, CARLSBAD, CA
APN: 155-140-37, 38
Criteria:
1. Use the current County of San Diego Hydrology Manual "Rational Method".
2. Design for a 100-year frequency storm using the County of San Diego 6 hour and
24 hour precipitation isopluvials.
3. Runoff coefficients are based on soil type "D". "C" factors have been weighted
based on the individual "C" factors for different surfaces (i.e. concrete= 0.95), and
the areas of the individual surfaces.
4. Times of concentration (Tc) are determined from the urban overland flow
formula.
5. Refer to the attached drainage map for basin areas and locations.
1034 Second Street » Encinitas, CA 92024 V phone: 760-436-0660 » fax: 760-436-0659
info@sampoengineering.com
introduction:
1. The subject property is located on the westerly side of Jefferson Street, just south
of the intersection with Las Flores Drive, in the City of Carlsbad. The property is
currently vacant; however, there is evidence that a structure occupied the property
in the past. The majority of the property descends from Jefferson Street to the
west and northwest at an approximate grade of 25 percent. A small easterly
portion of the site currently drains to Jefferson Street.
2. The project proposes to redevelop the property by constructing a new residence
and attached garage. The project site have been designed to minimize grading by
proposing 30% of the total area is disturbed. Permeable pavers are proposed at the
new driveway for permanent BMP's.
3. The existing storm water runoff consists of two drainage patterns where 0.045
acres drains to Jefferson St and 0.411 acres is flowing to the west & northwest.
The proposed drainage pattern mimics the existing drainage where 0.048 acres is
directed to Jefferson St and 0.408 acres is flowing west and northwest.
4. The intent of the design is to maintain the existing drainage patterns, where
approximately 90% of the run-off drains to the westly end of property and
approximately 10% drains toward Jefferson Street.
5. The design provides a terraced grass swale, rip-rap energy dissipator and
permeable driveway pavers, all for permanent Best Management Practice
measures.
6. The project proposes a slight increase in storm water discharge (Q) of 0.12 CFS
between pre & post conditions; however no significant impact is expected
downstream due to the project design and permanent BMP's proposed.
1034 Second Street * Encinitas, CA 92024 * phone: 760-436-0660 » fax: 760-436-0659
info@sampoengineering.com
DRAINAGE STUDY CALCULATOR
JN: 03-127
HAGEY
DATE: February 23,2009
EXISTING BASIN '1-E1
DESCRIPTION: Easterly portion of the subject property tributary to Jefferson Street
AREA =
C =
1,980 SF = 0.045 AC.
0.35
TC1 = 1.8(1.1-.35M22)A(1/2)
(5.5)A(1/3)
6.33
1.77 3.59 MINUTES < 5.0
USE 5.0 MINUTES PER S.D. COUNTY MANUAL
1100 =7.44(2.5)(5.0)A(-.645)6.59 IN/HR
QlOQ= (0.35)(6.59 IN/HR)(0.045 AC)0.10 CFS
EXISTING BASIN '2-E1
DESCRIPTION: Northerly portion of subject property tributary to northwesterly property line
AREA =
C =
11,372 SF =
0.35
0.261 AC.
Tc1 = 1.8(1.1-.35) (170)" (1/2)
(27.8)A(1/3)
hoo= 7.44(2.5) (5.81 )A(-.645) =
17.60
3.03
5.98 IN/HR
5.81 MINUTES
(0.35)(5.98 IN/HR)(0.261 AC)0.55 CFS
EXISTING BASIN '3-E1
DESCRIPTION: Southerly portion of subject property tributary to west
AREA =6,530 SF= 0.150 AC.
c =0.35
Tc1 = 1.8f1.1-.35)(153r(1/2)
(26.8)A(1/3)
16.70
2.99 5.58 MINUTES
hop =7.44(2.5)(5.58n-.645) = 6.14 IN/HR
(0.35)(6.14IN/HR)(0.15AC)0.32 CFS
JN: 03-127
HAGEY
DATE: January 22, 2009
PROPOSED BASIN # 1
DESCRIPTION: Easterly portion of the subject property tributary to Jefferson Strret
AREA =
C =
Tc1 =
2,090 SF =0.048 AC.
0.35(390 SF) + 0.45(1700 SR
2,090 SF
1.8(1.1-.45U20)Af1/2l
lioo= 7.44(2.5) (5.00)A(-.645)
5.23
1.06
0.43
4.92
USE 5.00
MINUTES < 5.0
MINUTES
6.59 IN/HR
100 =(0.43)(6.59 IN/HR)(0.048 AC)0.14 CFS
Note: Increase in Q100 to Jefferson equals 0.14 cfs - 0.10 cfs = 0.04 cfs
PROPOSED BASIN #2
DESCRIPTION: Northerly portion of subject property tributary to northwesterly property line
AREA =9,852 SF =0.226 AC.
C= 0.35(7.822 SF) + 0.95(2.030 SF)
9,852 SF
Tc1 = 1.8(1.1 -.35) (210)A (1/2)
(24.8)A(1/3)
Il00= 7.44(2.5)(6.71)A(-.645) =
0.47
19.56
2.92
5.45 IN/HR
6.71 MINUTES
(0.47)(5.47 IN/HR)(0.226 AC)0.58 CFS
Note: Increase in Q100 to northwesterly portion site equals 0.58 cfs - 0.55 cfs = 0.03 cfs
PROPOSED BASIN # 3
DESCRIPTION: Southerly portion of subject property tributary to west
AREA =7,940 SF =0.182 AC.
C_= 0.35(6.990 SF) + 0.95(950 SF)
7,940 SF
Tc1 = 1.8(1.1-.35H190m/2)
(28.3)A(1/3)
18.61
3.05
0.42
6.11 MINUTES
hop =7.44(2.5)(6.1ir(-.645) = 5.79 IN/HR
(0.42)(5.79 IN/HR)(0.182 AC)0.45 CFS
Note: Increase in Q100 to westerly portion site equals 0.45 cfs - 0.32 cfs = 0.13 cfs
COQ.
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F ,',
.2
2D OR 2.W (min.)Endwoll (typical)
PLAN
BEST ORIGINAL
Concrete
Channel
D min.
3 (min.)
SECTION B-B
Design Velocity
m/sec (ft/sec)*
1.8-3
(6-10)
3-3.7
(10-12)
3.7-4.3
(12-14) ,/
4.3-4.9
(14-16)
4.9-5.5
(16-18)
Rock
Classification
No. 2 Backing
220 kg
(1/4 ton)
450 kg
(1/2 ton) /
900 kg
(1 ton)
1.8 tonne
(2 ton)
T (min)
320mm (1.1ft)
823mm (2.7ft)
1.1m (3.5ft)v
1.3m (4.4ft)
1.6m (5.4ft)
*over 5.5 mps (18 fps) requires special design
D = Pipe Diameter
W = Bottom Width of Channel
.5T (min.)
f 13 (#4) Bars Flow
152mm (6")
Rlter Blanket
Sill, Class
249kg/rr? -C-13Mpa (420-C-2000)
Concrete
SECTION A-A
NOTES
1.
2.
3.
4.
5.
Plans shall specify:
A} Rock Class and thickness (T).
B) Rlter material, number of layers and thickness.
Rip rap shall be either quarry stone or broken
concrete (if shown on the plans.) Cobbles
are not acceptable.
Rip rap shall be placed over filter blanket which may
be either granular material or filter fabric (woven filter
slit film fabric shall not be used).
See Regional Supplement Amendments for selection
of filter blanket.
Rip rap energy dissipators shall be designated as either
Type 1 or Type 2. Type 1 shall be with concrete sill;
Type 2 shall be without sill.
IMtic
By Approved
Kercheval 12/75
T. Stonton
S. Brady
Dote
03/03
04/06
SAN STANDARD
RIP RAP
ENERGY DISSIPATOR
RECOMMENDED BY THE SAN DIEGO
REGIONAL STANDARDS COMMITTEE
Chairperson R.C.E. 19246 Dote
DRAWING
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Bon maps determine 6 hr and 24 hr amounts
} frequency. These maps are included in the
>gy Manual (10, 50, and 100 yr maps included
and Procedure Manual}.
jcipitation (if necessary) so that it is within
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F I G U R B
Intensity-Duration De«^qn Chart - Template
! * 1 I 1
1-1
EXAMPLE:
Given: Watercourse Distance (D) = 70 Feet
Stops Is)" 1.3%
ftunoff Goefficient (C)« 0.41
Overland Flow Time (T) = 9,5 Minutes
SOURCE: Airport Drainage, Federal Aviation Administration. 1965
Rational Formula - Overland Time of Flow Nomograph
F I G U R E
3-3
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BEST ORIGINAL
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Hydrology Manual
Rainfall Isopluvials
100 Year Rainfall Event - 24 Hours
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Hydrology Manual
Rainfall Isopluvials
100 Year Rainfall Event - 6 Hours
Isopluvial (inches)
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