HomeMy WebLinkAboutCT 01-13; LAGUNA POINT; STORM DRAIN REPORT LAGUNA POINT; 2003-07-21STORM DRAIN REPORT
FOR
LAGUNA POINT
Tentative Tract Map CT 01-13
Carlsbad, California
July 21, 2003
DWG No. 409-9A
PROJECT No. CT 01-13 RECEIVIED
JUL 2 5 2003
l»4QINEERING
iSEPARTMENT
Prepared By:
PARTNERS Planning and Engineering
9988 Hibert Street, Suite 212
San Diego, CA 92131
(858) 695-3344
Andrew J. Kann, \P.E.
Registration Expires
RCE 50940
9-30-2005
10 J
TABLE OF CONTENTS
SITE AND PROJECT DESCRIPTION Page 1
METHODOLOGY Page 1
EXISTING CONDITIONS page 1
DEVELOPED CONDITIONS page 1
EXISTING RUNOFF ANALYSIS page 1
DEVELOPED RUNOFF ANALYSIS page 1
CULVERT DESIGN AND ANALYIS page 3
RESULTS AND CONCLUSIONS Page 3
UST OF FIGURES
FIGURE 1: VICINITY MAP page 2
FIGURE 2 A: EXISTING HYDROLOGY MAP attached
FIGURE 2B: PROPOSED HYDROLOGY MAP attached
LIST OF TABLES
TABLE 1 A: EXIST HYDROLOGY/INLET SUMMARY page 4
TABLE IB: DEVELOPED HYDROLOGY/INLET SUMMARY page 5
TABLE 2: HYDROLOGY AND HYDRAULIC CALCS page 6
Appendix 1
Appendix 2
Appendix 3
Appendix 4
LIST OF APPENDICES
RunofF Coefficients
Urban areas Overland Time of Flow Curves
Intensity - Duration Design Chart
Handbook of Hydraulics Tables 7-4 and 7-14
SITE AND PROJECT DESCRIPTION:
This storm drain report has been prepared as part of the Grading Permit submittal
requirements for the development of Laguna Point. The site currently consists of 1.1 acres of
mass graded pad. The site had been previously developed with a single building and
associated parking lot. The project site is located north of Carlsbad Village Drive and west
of Interstate 5. See Figure No. 1 for Vicinity Map.
METHODOLOGY
This drainage report has been prepared in accordance with current City of Carlsbad
regulations and procedures. The proposed catch basin and existing storm drain culverts were
designed to intercept and convey the 50-year storm. The Modified Rational Method was
used to compute the anticipated runoff See Tables 1 and 2 for design calculations. The
following references have been used in preparation of this report:
(1) City of San Diego Drainage Design ManuaL April, 1984.
(2) Handbook of Hvdraulics. E.F. Brater & H.W. King, 6* Ed., 1976.
EXISTING CONDITIONS:
The existing site currently consists of a mass graded pad with an existing curb inlet located
adjacent to the site located at the southeast comer of the intersection of Laguna Drive and
State Street. The majority of the runoff from the existing site sheet flows towards an existing
sump located adjacent to Laguna Drive where it ponds on-site until the water surface
elevation reaches approximately 42.5. Once this occurs, the runoff will then follow the path
of least resistance towards either State Street or Laguna Drive. The remainder of the site
sheet flows towards State Street.
DEVELOPED CONDITIONS:
The proposed site includes the addition of a single building with associated hardscape,
landscaping and parking. The majority of the parking occurs at grade beneath the proposed
building. The improvements include twelve (12) area drains, two (2) trench drains,
approximately 950 lineal feet of storm drain culvert and one (1) CDS Unit to cleanse the
storm water.
EXISTING RUNOFF ANALYSIS:
There is an existing Type 'B' curb inlet adjacent to the site located at the southeast comer of
Laguna Drive and State Street. A mnoflf coefficient of 0.45 would be appropriate for the
existing basin in its current condition. See Table 1A Hydrology / Inlet Summary for a
breakdown ofthe existing basin.
DEVELOPED RUNOFF ANALYSIS:
Project site.
viciNny MAP
NO SCALE
flSo^ A/o. X
The proposed catch basins and storm drain culverts were designed to intercept and convey
the 50-year storm. The mnofif coefiGcients for the site were based on soil group D and the
ultimate improvements for the site. A coefificient of 0.95 was used for all impervious areas
and a coefificient of 0.45 was used for all landscape areas. Runoflf coeflficients were weighted
as necessary for drainage basins. See Table IB, Hydrology / Inlet Summary for a breakdown
for each basin. .
CULVERT DESIGN AND ANALYSIS:
The storm drain culverts were sized using King's handbook (Reference 2) Table 14 to verify
capacity. For circular conduits:
K' = Qn/[d'^(8/3)s'^(l/2)] where
K' = Discharge Factor
Q = Runofif Discharge (cfs)
n = Manning's Coefficient
d = Diameter of Conduit (ft)
s = Pipe Slope (ft/ft)
See Table 2 for Developed Hydrology and Hydraulic Calcs, for culvert sizing.
RESULTS AND CONCLUSIONS
The existing site generates 1.2 cfs with a Time of Concentration of 14.6 minutes and 0.4 cfs
with a Time of Concentration of 7.0 minutes for basins EX-1 and EX-2 respectively. The
developed site generates 3.2 cfs with a Time of Concentration of 6.9 minutes. The increase
in site mnoflf is consistent with the zoning for the site. Although the developed condition
generates additional mnofif, this increase in flow will not be transferred downstream. The
reason for this is due to flood routing. The time of concentration for the developed on-site
basins will be much less than the time of concentration for the entire contributing basins. To
obtain peak flow in the existing culvert located within State Street, the developed mnofif
generated by proposed improvements to Laguna Point will be corrected by a ratio ofthe
overall basin intensity versus the on-site intensity as allowed by the Modified Rational
Method when a junction is reached per the following equation:
Qp = Qa + Qb*(Ia/Ib) where
Qp = Peak Runofif in cfs
Qa = Runofif upstream of Laguna Point connections
Qb = Runofif generated on-site for Laguna Point developed condition
la = Rainfall Intensity for basins upstream of the Laguna Point connections
Ib = Rainfall Intensity for on-site Laguna Point developed condition
The intensity ratio (la/Ib) will reduce the additional flows generated by the developed on-site
conditions to the point where the increase in mnofif from this project will not adversely
impact the existing system.
LAGUNA POINT EXIST HYDROLOGY / INLET SUMMARY 4/22/2003
Basin Area C L H Tc 1 Q Structure Inlet Gutter Flow "A" Inlet Remarks
No. (ac) (weighted) (ft) (ft) (min.) (in/hr) No. Type Slope (ft/ft) Depth (ft) Length
(open)
50-year storm
EXI 0.89 0.48 240 4 14.6 2.80 1.2 ----
EX2 0.25 0.45 110 6.0 7.0 3.70 0.4 1 Exist Inlet ----Exist curb inlet
15220-SDEX
LAGUNA POINT HYDROLOGY / INLET SUMMARY 3/4/2003
Basin
No.
1 -^"L^
Area
(ac)
c
(weighted)
L
(ft)
H
(ft)
Tc
(min.)
1
(in/hr)
Q Structure
No.
Inlet
Type
Gutter
Slope (ftm)
Flow
Depth (ft)
"A" Inlet
Length
(open)
50-year storm
A 0.09 0.75 5.0 4.20 0.28 1 Area Drain ----Landscape Drain
B 0.11 0.78 5.0 4.20 0.36 2 Area Drain ----Landscape Drain
C 0.02 0.45 5.0 4,20 0.04 3 Area Drain ----Landscape Drain
D 0.08 0.95 5.0 4.20 0.32 4 Trench Drain ----Trench Drain
E 0.14 0.95 5.0 4.20 0.56 5 Trench Drain ----Trench Drain
F 0.03 0.45 5.0 4.20 0.06 6 Area Drain ----Landscape Drain
G 0.03 0.45 5.0 4.20 0.06 7 Area Drain ----Landscape Drain
H 0.04 0.70 5.0 4.20 0.12 8 Area Drain ----12" Square Grate
1 0.06 0.83 5.0 4.20 0.21 9 Area Drain ----12" Square Grate
J 0.19 0.95 5.0 4.20 0.76 10 Area Drain ----IZ' Square Grate
K 0.03 0.88 5.0 4.20 0.11 11 Area Drain ----Landscape Drain
L 0.11 0.90 5.0 4.20 0.42 12 Area Drain ----Landscape Drain
M 0.05 0.78 5.0 4.20 0.16 13 Area Drain ----Landscape Drain
N 0.05 0.78 5.0 4.20 0.16 14 Area Drain ----Landscape Drain
15220-SD
.fflRNA^!RNTfl?DRHf)GlfflSD /4/I
Confl. Sub-AREA "C" CA Sum L(ft) S (%) Ti Tt Tc I Q L(ft) S (%) Dia. K' D\d Ca V NOTES
Point Ac. CA (Ovrlnd) (min) (min) mm. in/hr cfs (Pipe) (Pipe) (in) (fps) 50 - yr event
A 0.09 0.75 0.07 0.07 --5.0 0.0 5.0 4.20 0.3 84.00 1.00 6 0.2340 0.50 0.3930 2.9
B 0.11 0.78 0.09 0.15 5.0 0.5 5.5 4.00 0.6 65.00 1.00 8 0.2350 0.50 0.3930 3.5
C 0.02 0.45 0.01 0.16 5.5 0.3 5.8 3.95 0.6 45.00 1.00 8 0.2457 0.52 0.4130 3.5
D 0.08 0.95 0.08 0.24 5.8 0.2 6.0 3.90 0.9 70.00 1.00 8 0.3562 0.66 0.5500 3.8
E 0.14 0.95 0.13 0.37 6.0 0.3 6.3 3.90 1.4 55.00 1.00 12 0.1882 0.45 0.3428 4.2
F 0.03 0.45 0.01 0.38 6.3 0.2 6.5 3.85 1.5 67.00 1.00 12 0.1926 0.45 0.3428 4.3
G 0.03 0.45 0.01 0.40 6.5 0.3 6.8 3.80 1.5 29.00 9.10 12 0.0652 0.26 0.1623 9.3
H 0.04 0.70 0.03 0.03 5.0 0.0 5.0 4.20 0.1 44.00 1.00 4 0.2862 0.57 0.4620 2.3
I 0.06 0.83 0.05 0.08 5.0 0.3 5.3 4.10 0.3 64.00 1.00 6 0.2633 0.54 0.4330 2.9
J 0.19 0.95 0.18 0.26 5.3 0.4 5.7 4.00 1.0 71.00 1.00 8 0.3960 0.71 0.5960 3.9
K 0.03 0.88 0.03 0.28 5.7 0.3 6.0 3.90 1.1 126.00 1.00 8 0.4256 0.76 0.6400 3.9
L 0.11 0.90 0.10 0.38 6.0 0.5 6.5 3.85 1.5 46.00 1.00 12 0.1920 0.45 0.3428 4.3
M 0.05 0.78 0.04 0.42 6.5 0.2 6.7 3.85 1.6 52.00 1.00 12 0.2116 0.48 0.3727 4.4
N 0.05 0.78 0.04 0.46 6.7 0.2 6.9 3.75 1.7 12.00 29.50 12 0.0414 0.20 0.1118 15.5
A 0.86 6.9 0.0 6.9 3.75 3.2 17.00 9.10 12 0.1390 0.38 0.2739 11.8 confluence basins
AthruN
1 1 1
15220-sdpipe
APPENDIX
TABLE 2
RUNOFF COEFFICIENTS (RATIONAL METHOD)
DEVELOPED AREAS (URBAN)
Land Use Coefficient. C
Soil Type (1)
Residential: D
Single Family .55
Multi-Units .70
Mobile Homes .65
Rural (lots greater than 1/2 acre)
Commercial (2)
80% Irnpervious .85
Industrial (2)
90% Impervious .95
NOTES:
(1) Type D soil to be used for all areas.
(2) Where actual _ conditions deviate significantly from the tabulated
imperviousness values of 80% or 90%, the values given for coefficient C,
may be revised by multiplying 80% or 90% by the ratio of actual
imperviousness to the tabulated imperviousness. However, in no case shall
the. final coefficient be Jess than 0.50. For example: Consider commercial
property on D soil.
Actual imperviousness = 50%
Tabulated imperviousness = 80%
Revised C = |^ x 0.85 = 0.53
Al
UtibAM UVLKLANU
T\ML OF FLOW CURVES
100
700
MO
300
jiff ^^^'AT-{ FUl-irzr^-. ^
^2ff r
j-| |-*7^r Use Formulo For
tT-tii; [F Of 800 Feef. :
- 400
2 •<
300
200
too
4f -f--.— -!-rH + rH-r rr- ••!!•! -Hr:
H(I.I-C)VD f-Trtqlt
If .t • -r I • • r I • f • - -
:.i;rf-ti .h-r:: TI-KI,^!-..,.
:.L4lu:r
I . , J Ll _ 1 [il
80
70
60
50
*0 ±
30
20
10
Surfac* Flow 1\m» CurvM
BXAKAPLE. :
GDIVEM uBMGTH op FLow ^ Aao FT.
86
ELEV FACTOR
0-1500 100
r500-300O 1.23
3000-4000 1.42
4 000 — 5000 1.60
5 000-6000 1.70
DESERT 1.25
To oblain comet Inlinilly,
molllply Int«nii1f on chort
bt foctof for dtlign
• If V 01l 0n.
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H O
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M I N UT E S
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D URATI.O N
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2
o
m
o
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z H m
in
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o c
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1.0
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z O.B
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Z u 0.6 — z 0.6
0.5
0.4
0. 3
0.2
lO 2 0
MINUTES
DURATION
HANDBOOK OF HYDRAULICS
for the Solution of
Hydraulic Engineering Problems
Table 7-14. Vahios of K' for Circular Chaimels in thc: Furnuila
71
D = dcptli of water d = diaiiii-ler of cliaiiuel
D
d .00 .01 .02 .03 .04 .05 .00 .07 .08 .09
.0 .00007 .00031 .00074 .00138 .00222 .00328 .004 55 .00004 .00775
.1 .00907 .0118 .0142 .0107 .0195 .0225 .02.'>7 .0291 .0327 .03C.i;
.2 .0400 .0448 .0492 .0037 .0585 .0034 .0080 .0738 .079i$ .0819
.3 .0907 .O'JGG .1027 .1089 .1153 .1218 .1284 .1352 .1420 .1490
.4 .1501 .1033 .1705 .1779 .1854 .1929 .2005 .2082 .2100 .2238
.5 .232 .23'.) .247 .2.->5 .203 .271 .279 .287 .295 .303
.0 .311 .310 .327 .335 .343 .350 .3.08 .300 .373 .380
.7 .388 .305 .402 .409 .410 .422 .429 .435 .111 .447
.8 .453 .4.08 .403 .4 08 .473 .477 .481 .4 85 .4 88 .-191
.y .494 .400 .407 .498 .498 .498 .490 .494 .4 89 .483
1.0 .403
STE.VDV U.NII-OUM FLOW IN OPEN CII.XNXELS
Tabic 7-4. For Determining thc Area a of thc Cross Seclion of a
Circular Conduit Flowing I'art Full
, __il£P_tli^.of :!:jii£I_ _ :5and C = the tubulate.1 value. Then a = Cu-i-.
diameter of channel ti
D .00 .01 .02 .03 .04
d
.0 .OOOO .0013 .0037 .0009 .0105
.1 .0409 .0470 .0534 .0000 .0008
.2 .1118 .1199 .1281 .1305 .1449
.3 .1982 .2074 .2107 .2260 .2355
.4 .2934 .3032 .3130 .3229 .3328
.5 .393 .403 .413 .423 .433
.0 .402 .502 .512 .521 .531
,7 .587 .590 .005 .014 .023
.8 .674 .081 .089 .0"J7 .704
.9 .745 .750 .750 .701 .700
.05
.0147
.0739
.1535
.2450
.3428
.443
.540
.032
.712
.771
.00
.0192
.08.11
.1023
.254 0
.3527
.4.03
.550
.0-10
.719
.775
.0242
.0885
.1711
.2042
.3027
.402
.559
.049
.725
.779
.08
.0294
.0901
.181.10
.2739
.3727
.472
.509
.057
.732
.782
.00
.03.50
.i039
.1890
.2830
.3827
.4.H2
.578
.OOf.
.738
.784
A4