HomeMy WebLinkAboutCT 00-02; CALAVERA HILLS PHASE 2; TEMPORARY DESILTING BASIN REPORT; 2003-11-20CALAVERA HILLS
PHASE II
TEMPORARY DESILTING BASIN REPORT
JOB NO. 98-1020
PREPARED: NOVEMBER 20, 2003
~~o
- Z~~ /-m~- I
KEITH HANSEN RCE 60223
EXP. 06/30/04
C60223
EX /J4/a,12
ii/2afr3
DATE
O'DAY CONSULTANTS, INC.
2710 LOKER AVENUE WEST, SUITE 100
CARLSBAD, CALIFORNIA 92008-6603
TEL: (760) 931-7700
FAX: (760) 931-8680
CO NSULTA N T S
TRANSMITTAL LETTER
To: Cim' (fieLss&b Date: If 20103 JobNo.: __________
Project: V?J4
Re: -
Attn: J09= 1ACMAA100 T. M.:
DWG.:
We are enclosing blueline sepias original drawings
or
O For your files DFor your proposal
0 For your review and approval 0
DPer your request DTransmitted via OMeil
O For information OParcel Post
oPlease sign__copies and return to our office DPick up by
OFAX
Remarks: oOelivered by
3 401P/C5 ALA v(Z4 I/ILLS 7_CM,00,C49r
53(L77Ne 54,) £E4'
RECEIVED
ENOV 20031
CITY O CARIS RAt) ENGINIEffl(; DEPARTMENT
Z_ I tALa5ueL 7t''i LAA e c&
2'rJt Mi7ZL-j
By:
2710 Loker Avenue West
Suite 100
Carlsbad, California 92008-6603
760.931.7700
Fax: 760.931.8680
E-mail: oday@odayconsultants.com
Civil Engineering
Planning
Processing
Surveying
INTRODUCTION
During the construction phase of Calavera Hills Phase II, desilting basins are used
throughout the site to minimize the amount of sediment that could leave the site in the
event of rain. Enclosed are the calculations to determine the necessary sizes of the
desilting basins in order to function in accordance with California Regional Water
Quality Control Board and local standards. On November 18, 2003 O'Day Consultants
conducted a field survey to verify that the desilting basins were constructed, at a
minimum, to the sizes calculated.
DESILTING BASIN SIZING
As = 1.2 Q/Vs (OPTION 3 REGIONAL WATER QUALITY CONTROL BOARD
FACT SHEET)
DESIGN PARTICLE SIZE = 0.01 MM 10 Vs = 0.00024 FT/SEC
USING A 10 YR, 6 HOUR STORM EVENT
QIOAVG = CIAVG A
C = 0.45 (LARGE PARCEL> 2 AC)
IAVG = P6/6 = 1.7 IN/6 HR = 0.28 IN/HR
Q = (.45)(.28)A = 0.13A
SURFACE AREA NEEDED = As = 1.2Q/VS = 650 SF/AC
VOLUME = RUNOFF FROM 1" 24 HOUR STORM PER CITY OF CARLSBAD
FOR BARREN LAND WITH SOIL TYPE D CN =93
DIRECT RUNOFF FROM A 1" STORM = 0.45 IN = 0.375 FT
VOLUME = (0.375)(43,560 SF/AC) = 1634 CF/AC
1634 CF WITH 650 SF GIVES A BASIN HEIGHT = 2.5'
FOR BASINS DEEPER THAN 2.5'
650 SF/AC WILL DETERMINE BASIN SIZE
Option 2: Sediment basin(s), as measured from the bottom of the basin to the
principal outlet, shall have at least a capacity equivalent to 3,600 cubic feet
of storage per acre draining into the sediment basin. The length of the
basin shall be more than twice the width of the basin. The length is
determined by measuring the distance between the inlet and the outlet; and
the depth must not be less than three feet nor greater than five feet for
safety reasons and for maximum efficiency.
I OR
Option 3: Sediment basin(s) shall be designed using the standard equation:
As=1.2Q/Vs
Where: As is the minimum surface area for trapping soil particles of a
certain size; Vs is the settling velocity of the design particle size chosen;
and Q=C x I x A where Q is the discharge rate measured in cubic feet per
second; C is the runoff coefficient; I is the precipitation intensity for the
10-year, 6-hour rain event and A is the area draining into the sediment
basin in acres The design particle size shall be the smallest soil grain size
determined by wet sieve analysis, or the fine silt sized (0.01mm) particle,
and the Vs used shall be 100 percent of the calculated settling velocity.
The length is determined by measuring the distance between the inlet and
the outlet; the length shall be more than twice the dimension as the width;
the depth shall not be less than three feet nor greater than five feet for
safety reasons and for maximum efficiency. (two feet of storage, two feet
of capacity). The basin(s) shall be located on the site where it can be
maintained on a year-round basis and shall be maintained on a schedule to
retain the two feet of capacity;
I OR
Option 4: The use of an equivalent surface area design or equation, provided that the
I design efficiency is as protective or more protective of water quality than
Option 3.
I A sediment basin shall have a means for dew atering within 7-calendar days following a
storm event. Sediment basins may be fenced if safety (worker or public) is a concern.
I The outflow from a sediment basin that discharges into a natural drainage shall be
provided with outlet protection to prevent erosion and scour of the embankment and
i
channel.
I
I .. 15
I
I
I
p
I
I
I
- - - - - - - - - -- -- - --
COUNTY OF SAN DIEGO 10-YEAR 6-HOUR PRECIPITATION DEPARTMENT OF SANITATION FLOOD CONTROL e-16- IS5?LUVfLS CF 10-VEi1 0-01
N 45
F
PRECIPITATIO Ifi EMTIIS OF MI ICII
4 74
30
t'
'L SAN Cl t.l 22 NT[
23.
ç2 -'2r '28
22
330 \ ./)4 \t2 ~
14 :35
28
CAP 451
—
22
;dby
USDEPARTMEI COMMERCE I
-
J NATIOrAt. OCEANIC AND Al 051 IIERIC ADMINISTRATION
I I SPECIAL STUDIES ORA'4CI( OFFICL.. OF I VDROLOGY, NATIONAL WEATHER SERVICE
SM "If
30' 0
16182024 24222 1 20 20
. 1.
15' 1I6 1)80 45' 30' 15' 1170 45' 30' 1
I RUNOFF CURVE NUMBERS FOR HYDROLOGIC SOIL-COVER COMPLEXES (C N)
TABLE I-A-I
I AMC 2
Ia=O.2S I ..
Cover . Hydrologic
Soil Groups I .
Treatment Use HydroIogi Land or Practice3 Condition' A B C 0
Water Surfaces I (during floods) 97 98 99 99
I ..
Urban
Commercial-industrial 89 90 91 92
I High density residential 75 82 88 90
Medium density residential 73 80. 86 88
I Low density residential
- 70 .. 78 84 . 87
Barren . . 78 86 91
row 76 85 Fa1la Straight 90 92.
I
Vineyards (see accompanying land-use-description)
disked 76 85 90 92
I .
. annual grass or Poor 65 78 85 89 legume cover
Fair 50 69 79 84
I . Good 38 61 .4 80
Roads (hard surface) . 74 8k 90 92 I (dirt)
.
72 . 82 87 89
I Row crops Straight row Poor 72 81 88 91
Good . 67 78 85 89
I Contoured Poor 70 79 84 88
Good 65 75 82 86 I Narrowleaf Poor 82 88 chaparral 71 91
1 .
-
Fair 55 72 81 86
.
. . I-A-5
I
(LLAGE K OgSTJ
TRIBUTARY AREA
= 6.41 AC
DESIGN AREA = 6.41 (650) = 4.167 SF
BASIN IS 55' WIDE x 85' LONG x 4' DEEP
SURFACE AREA = 4,675 SF
BASIN IS ADEQUATELY SIZED
H
I TRIBUTARY AREA = 2.86 AC
DESIGN AREA = 2.86 (650) = 1,859 SF
DESIGN VOLUME = 2.86 (1634) = 4,673 CF
I MCMILL1N TO RAISE OUTLET PIPE 1.5', ADD 2 COURSES OF SAND BAGS,
AND EXTEND OUTLET TO DOWNSTREAM OUTLET TO TAMARACK ON
11-20-03. ONCE COMPLETE:
BASIN AREA = 55'x 75' = 4,125 SF AVG DEPTH = 1.25' VOLUME = 5,156 CF
I
BASIN IS ADEQUATELY SIZED
[VILLAGE K (EAST) J I TRIBUTARY AREA = 6.03 AC'
DESIGN AREA = 6.03 (650) = 3,920 SF
I PAVING IS IMMINENT
SHOULD THERE BE A THREAT OF RAIN BEFORE PAVING OCCURS, A
40' WIDE x 100' LONG x 3' DEEP BASIN SHALL BE BUILT USING SAND BAGS
IN THE CUL-DE-SAC
I yLLAoEU]
TRIBUTARY AREA = 12.26 AC
DESIGN AREA = 12.26 (650) = 7,969 SF
I BASIN IS 50' WIDE x 165' LONG x 6' DEEP
SURFACE AREA = 8,250 SF
I BASIN IS ADEQUATELY SIZED
I
I
I
I
I
VILLAGE X
I
TRIBUTARY AREA = 7.66 + 22.98 = 30.64 AC
DESIGN AREA = 30.64 (650) = 19,916 SF
BASIN IS 200' WIDE x 150' LONG x 3' DEEP (AVG)
I SURFACE AREA = 30,000 SF
BASIN IS ADEQUATELY SIZED
I TRIBUTARY AREA = 7.84 AC
DESIGN AREA = 7.84 (650) = 5,096 SF
BASIN IS 35' WIDE x 150' LONG x 5' DEEP
I SURFACE AREA = 5,250 SF
BASIN IS ADEQUATELY SIZED
I
____
IANG
I TRIBUTARY AREA (WORST CASE)
COLLEGE BLVD = 5,000'x 120'= 13.77 AC
I
:VILLAGE U=12.26AC
VILLAGE Y = 7.66 AC
VILLAGE X = 22.98 AC
VILLAGE W (SOUTH) =15.24 AC
I TRIANGLE = 8.16 AC
TOTAL = 80.07 AC
I
DESIGN AREA = 80.07 (650) = 52,046 SF
DESIGN VOLUME = 80.07 (1634) = 130,834 CF
BASIN IS 140' x 500' x 2' DEEP (AVG)
SURFACE AREA = 70,000 SF
I VOLUME = 140,000 CF
BASIN IS ADEQUATELY SIZED
I
I
I
I