21176 (2)0)-L 1 -.0
"_ �kNYM�NI
At
F
HYDROLOGY REPORT
L-A- c"icc-k—PbLo ( s
For
DOLEMO RESIDENCE
TENNIS COURT ADDITION
South Half of Lot 14
Tract 21176
Prepared by:
Dudek
75 -150 Sheryl Avenue, Suite C
Palm Desert, California 92260
(760) 341 -6660
February 15, 200$
Project # 5770
HU
�� FEB 2 6 2008 I U
lip
w � � m
it C 69056
* EXP. 06-30- 0 S'
civic. �P
FCAl�F�a
This drainag to wa ep ed under the direction of
Charles Greely, R.C.E.,,40,9656 Exp. 06 -30 -08 Date
PURPOSE:
The following preliminary storm drainage analysis has been prepared to model the 100
,year storm and provide the necessary information for the design of onsite retention basin
for the addition of a tennis court and outdoor kitchen to Lot 14 of Tract 21176 located at
51 -800 Vista Bonita Trail, in the City of La Quinta, California.
The proposed improvements will be designed to retain one - hundred percent of the design
storm on site.
METHODOLOGY:
Criteria for this study is based on methods prescribed by the Riverside County Flood
Control and Water Conservation District's Hydrology Manual.
RESULTS:
Flood Volume:
The total flood volume of the 100 -year storm model was determined to be as follows:
1 -HOUR: 0.078 Acre -Feet
The recessed tennis court will serve as the projects retention basin system, with the
improvements designed to retain 100% of the calculated runoff. Box catch basins will be
installed at the corners of the. tennis court, with 24" diameter perforated HDPE pipe
connecting the basins. This system will allow for percolation of nuisance and small storm
events, while acting as a conveyance system for the full 100 year return interval event.
During the calculated peak storm event, the tennis court will fill with approximately 4.5"
of water.
Project # 5770
Synthetic Unit Hydrograph Results
BASIN SIZING
100 Yr 1 Hr
3391 Cu Ft Controls
3 Hr
2603 Cu Ft
6 Hr
2133 Cu Ft
24 Hr
871 Cu Ft
Site Drainage'Area: 0.64 Ac
Runoff Volume: 0.078 Ac -FT
3,391 ft ^3
RETENTION SYSTEM:
Pipe Storage Capacity:
Dia of Pipe
24 in
24" Sure Lock Pipe Capacity per linear feet
3.14 ft ^3 /ft
Suggested Length
280 ft
Volume of Pipe
879.2 ft ^3 /ft
Total Pipe Storage Capacity:
0.020 Ac -ft
Percolation:
Width of Pipe
2 ft
Length
280 ft
Percolation Surface Area:
560 ft ^2
Percolation Volume:
0.002 Ac -ft
Runoff Volume Required:
0.078 Ac -ft
Storage Capacity of Pipe:
0.020 Ac -ft
Percolation Volume:
0.002 Ac -ft
Total Capacity:
0.022 Ac -ft
Surplus Volume:
0.056 Ac -ft
TENNIS COURT FLOODING:
Area of Tennis Court
6534.27 ft ^2
0.150 ac
surplus volume
0.056 Ac -ft
submerged depth
4.454 inches
FORMULA USED:
Vista Bonita Trail
2/15/2008
Assuming 0 Percolation
0 Ac -ft
0.020 Ac -ft
0.058 Ac -ft
Max. Perc. Rate Allowed = 2 " /hr
Perc. Vol. = 2 " /hr 1 hr
12 " /FT 43560 Sf /AC
Net -Req. Vol.= Runoff Vol - Perc Vol
Submerged = Surplus Vol x 12 in /ft
Tennis Court Area
Page 1 of 1
0.058 Ac -ft
4.625 inches
® r/ ®E K Job # 5770
75 -150 Sheryl Ave - Suite C Date: 2/15J21)l)8
Palm Desert, CA 92211
i
RCFC & WCD - Hydrology Manual
Synthetic Unit Hydrograph - Shortcut Method
Input Data:
Concentration Point:
N/A
Storm Rain Loss Rate
Unit Time:
5.
Min
Area Designation:
N/A
0.89
Storm Frequency:
100
Yr
Drainage Area:
0.64
Ac
Storm Duration:
1
Hr
Longest Watercourse:
0
Miles
Precip Rate:
2
In
L ca:
0 j
Miles
Area Effect:
100
%
Elev at Basin:
0
Feet
Adjusted Storm:
2
In
Elev at Headwater:
0
Feet
Soil Grou: _
A
30
H:
0
Feet
Runoff Index:
32
234.6
Slope:
#DIV /0!
ft/mi
AMC Condition:
2
0.94
Mannings n:
0.0015
9
Infiltration Rate (Fp):
0.74
1.62
Lag:
#DIV /01
Hrs
Impervious Area (Ai):
30
%
2.41
1.54
466.9
Adj Loss Rate (F):
0.54
4.22
0.54
3.68
2.36
Min Loss Rate (Fm):
0.27
16.1
3.86
0.54
3.32
Low Loss Rate:
0.9
60
Output Data: ITotall Volume = 3391 Cubic Ft
Unit Time
Pattern %
Storm Rain Loss Rate
Eff Rain
Flow (CFS)
Volume (Cu Ft)
5
3.7
0.89
0.54
0.35
0.22
67.3
10
4.8
1.15
0.54
0.61
0.39
118.4
15
5.1
1.22
0.54
0.68
0.44
132.4
20
4.9
1.18
0.54
0.64
0.41
123.1
25
6.6
1.58
0.54
1.04
0.67
202.1
30
7.3
1.7,5
0.54
1.21
0.78
234.6
35
8.4
2.02
0.54
1.48
0.94
285.7
40
9
2.16
0.54
1.62
1.04
313.6
45
12.3
2.95
0.54
2.41
1.54
466.9
50
17.6
4.22
0.54
3.68
2.36
713.2
55
16.1
3.86
0.54
3.32
2.13
643.5
60
4.2
1.01
0.54
0.47
0.30
90.6
DUDEK Job #i 5770.
75 -150 Sheryl Ave - Suite C Date: 2/15/2008
Palm Desert, CA 92211
RCFC & WCD - Hydrology Manual
Synthetic Unit Hydrograph - Shortcut Method
Input Data:
Concentration Point:
N/A
0.41
Unit Time:
10`
Min
Area Designation:
N/A
0.37
Storm Frequency:
100
Yr
Drainage Area:
0.64
Ac
Storm Duration:
3
Hr
Longest Watercourse:
0
Miles
Precip Rate:
2.6
'In
L ca:
0 '
Miles
Area Effect:
100
%
Elev at Basin:
0
Feet
Adjusted Storm:
2.6
In
Elev at Headwater:
0
Feet
Soil Grou:
A
5.3
H:
0
Feet
Runoff Index:
32
0.80
Slope:
##DIV /01
ft/mi
AMC Condition:
2
0.54
Mannings n:
0.0015
5.9
Infiltration Rate (Fp):
0.74
0.38
Lag:
HDIV /01
Hrs
Impervious Area (Ai):
30
%
8.5
1.33
0.54
Adj Loss Rate (F):
0.54
14.1
2.20
0.54
1.66
Min Loss Rate (Fm):
0.27
2.20
0.54
1.66
170
Low Loss Rate:
0.9
0.54
Output Data: Total Volume = 2603 Cubic Ft
Unit Time Pattern % Storm Rain Loss Rate Eff Rain
10
2.6
0.41
0.37
0.04
20
2.6
0.41
0.37
0.04
30
3.3
0.51
0.46
0.05
40
3.3
0.51
0.46
0.05
50
3.3
0.51
0.46
0.05
60
3.4
0.53
0.48
0.05
70
4.4
0.69
0.54
0.15
80
4.2
0.66
0.54
0.12
90
5.3
0.83
0.54
0.29
100
5.1
0.80
0.54
0.26
110
6.4
1.00
0.54
0.46
120
5.9
0.92
0.54
0.38
130
7.3
1.14
0.54
0.60
140
8.5
1.33
0.54
0.79
150
14.1
2.20
0.54
1.66
160
14.1
2.20
0.54
1.66
170
3.8
0.59
0.54
0.05
180
2.4
0.37
0.34
0.04
Flow (CFS) Volume (Cu Ft
0.03
15.7
0.03
15.7
0.03
19.9
0.03
19.9
0.03
19.9
0.03
20.5
0.09
56.6
0.07
44.5
0.18
111.0
0.16
98.9
0.29
177.4
0.24
147.2
0.38
231.8
0.50
304.3
1.06
642.5
1.06
642.5
0.03
20.4
0.02
14.5
DUDEK
Pattern %
Job #
5770
75 -150 Sheryl Ave - Suite C
10
1.1
Date:
2/15/2008
Palm Desert, CA 92211
0.01
7.9
20
1.2
0.22
0.20
0.02
0.01
8.6
RCFC & WCD - Hydrology Manual
1.3
0.24
0.22
Synthetic Unit Hydrograph - Shortcut Method
0.02
9.4
40
Input Data:
0.26
0.23
0.03
0.02
Concentration Point: N/A
50
Unit Time:
10
Min
Area Designation: N/A
0.02
Storm Frequency:
100
Yr
Drainage Area: 0.64
Ac
Storm Duration:
6
Hr
Longest Watercourse: 0
Miles
Precip Rate:
3.1
In
L ca: 0
Miles
Area Effect:
100
%
Elev at Basin: 0
; Feet
Adjusted Storm:
3.1
In
Elev at Headwater: 0
Feet
Soil Grou:
A
0.02
H: 0
Feet
Runoff Index:
32
0.27
Slope: #DIV /01
ft/mi
AMC Condition:
2
1.6
Mannings n: 0.0015
0.27
Infiltration Rate (Fp):
0.74
11.5
Lag: #DIV /0!
Hrs
Impervious Area (Ai):
30
%
0.02
12.2
Adj Loss Rate (F):
0.54
0.32
0.28
0.03
Min Loss Rate (Fm):
0.27
140
1.8
0.33
Low Loss Rate:
0.9
0.02
Output Data:
150
Total Volume =
0.33
2133 Cubic Ft
Unit Time
Pattern %
Storm Rain Loss Rate
Eff Rain
Flow (CFS)
Volume (Cu Ft)
10
1.1
0.20
0.18
0.02
0.01
7.9
20
1.2
0.22
0.20
0.02
0.01
8.6
30
1.3
0.24
0.22
0.02
0.02
9.4
40
1.4
0.26
0.23
0.03
0.02
10.1
50
1.4
.0.26
0.23
0.03
0.02
10.1
60
1.5
0.28
0.25
0.03
0.02
10.8
70
1.6
0.30
0.27
0.03
0.02
11.5
80
1.6
0.30
0.27
0.03
0.02
11.5
90
1.6
0.30
0.27
0.03
0.02
11.5
100
1.6
0.30
0.27
0.03
0.02
11.5
110
1.6
0.30
0.27
0.03
0.02
11.5
120
1.7
0.32
0.28
0.03
0.02
12.2
130
1.7
0.32
0.28
0.03
0.02
12.2
140
1.8
0.33
0.30
D.03
0.02
13.0
150
1.8
0.33
0.30
0.03
0.02
13.0
160
1.8
0.33
0.30
0.03
0.02
13.0
170.
2
0.37
0.33
0.04
0.02
14.4
180
2
0.37
0.33
0.04
0.02
14.4
190
2.1
0.39
0.35
0.04
0.02
15.1
200
2.2
0.41
0.37
0.04
0.03
15.8
210
2.5
0.47
0.42
0.05
0.03
18.0
220
2.8
0.52
0.47
0.05
0.03
20.2
230
3
0.56
0.54
0.02
0.01
6.9
240
3.2
0.60
0.54
0.06
0.04
21.3
250
3.5
0.65
0.54
0.11
0.07
42.9
260
3.9
0.73
0.54
0.19
0.12
71.7
270
4.2
0.78
0.54
0.24
0.15
93.3
280
4.5
0.84
0.54
0.30
0.19
114.9
290
4.8
0.89
0.54
0.35
0.23
136.5
300
5.1
0.95
0.54
0.41
0.26
158.1
310
6.7
1.25
0.54
0.71
0.45
273.4
320
8.1
1.51
0.54
0.97
0.62
374.2
330
10.3
1.92
0.54
1.38
0.88
532.6
340
2.8
0.52
0.47
0.05
0.03
20.2
350
1.1
0.20
0.18
0.02
0.01
7.9
360
0.5
0.09
0.08
0.01
0.01
3.6
D U D E K Job # 5770
75 -150 Sheryl Ave - Suite C Date: 2/15 /2008
Palm Desert, CA 92211
RCFC & WCD - Hydrology Manual
Synthetic Unit Hydrograph - Shortcut Method
Input Data:
Pattern % Storm Rain Loss Rate.
Eff Rain
Flow (CFS)
Volume (Cu Ft)
30
Concentration Point.
WA
0.04
Unit Time:
30 •
Min
Area Designation:
N/A
0.06
Storm Frequency:
100
Yr
Drainage Area
0.64
Ac
. Storm Duration:
24
Hr
Longest Watercourse:
0
Miles
Precip Rate:
4
In
L ca:
0
Miles
Area Effect :
100
%
Elev at Basin:
0
Feet
Adjusted Storm:
4
In
Elev at Headwater:
0
Feet
Soil Grou:
A
210
H:
0
Feet
Runoff Index:
32
9.3
Slope:
#DIV /0!
ft1mi .
AMC Condition:
2
0.01
Mannings n:
0.0015
1.3
Infiltration Rate (Fp):
0.74
0.01
Lag:
#DIV /0!
Hrs
Impervious Area (Ai):
.36
%
0.01
0.01
13.9
Adi Loss Rate (F):
0.54
0.10
0.09
0.01
0.01
Min Loss Rate (Fm):
0.27
1.6
0.13
0.12
0.01
Low Loss Rate:
0.9
390
Output Data: ITotal Volume = 871 Cubic Ft
Unit Time
Pattern % Storm Rain Loss Rate.
Eff Rain
Flow (CFS)
Volume (Cu Ft)
30
0.5
0.04
0.04
0.00
0.00
4.6 ,
60
0.7
0.06
0.05
0.01
0.00
6.5
90
0.6
0.05
0.04
0.00
0.00
5.6
120
0.7
0.06
0.05
0.01
0.00
6.5
150
0.8
0.06
0.06
0.01
0.00
7.4
180
1
0.08
0.07
0.01
'0.01
9.3
210
1
0.08
0.07
0.01
0.01
9.3
240
1.1
0.09
0.08
0.01
0.01
10.2
270
1.3
0.10
0.09
0.01
0.01
12.1
300
1.5
0.12
0.11
0.01
0.01
13.9
330
1.3
0.10
0.09
0.01
0.01
12.1
360
1.6
0.13
0.12
0.01
0.01
14.9
390
1.8
0.14
0.13
0.01
0.01
16.7
420
2
0.16
0.14
0.02
0.01
18.6
450
2.1
0.17
0.15
0.02
0.01
19.5
480
2.5
0.20
0.18
0.02
0.01
23.2
510
3
0.24
0.22
0.02
0.02
27.9
540
3.3
0.26
0.24
0.03
0.02
30.7
570
3.9
0.31
0.28
0.03
0.02
36.2
600
4.3
0.34
0.31
0.03
0.02
40.0
630
3
0.24
0.22
0.02
0.02
27.9
660
4
0.32
0.29
0.03
0.02
37.2
690
3.8
0.30
0.27
0.03
0.02
35.3
720
3.5
0.28
0.25
0.03
0.02
32.5
750
5.1
0.41
0.37
0.04
0.03
47.4
780
5.7'
0.46
0.41
0.05
0.03
53.0
810
6.8
0.54
0.54
0.00
0.00
4.4
840
4.6
0.37
0.33
0.04
0.02
42.7
870
5.3
0.42
0.38
0.04
0.03
49.3
900
5.1
0.41
0.37
0.04
0.03
47.4
930
4.7
0.38
0.34
0.04
0.02
43.7
960
3.8
0.30
0.27
0.03
0.02
35.3
996
0.8
0.06
0.06
0.01
0.00
7.4
1020
0.6
0.05
0.04
0.00
0.00
5.6
1050
1
0.08
0.07
0.01
0.01
9.3
1080
0.9
0.07
0.06
0.01
0.00
8.4
1110
0.8
0.06
0.06
0.01
0.00
7.4
1140
0.5
0.04
0.04
0.00
0.00
4.6
1170
0.7
0.06
0.05
0.01
0.00
6.5
1200
0.5
0.04
0.04
0.00
0.00
4.6
1230
0.6
0.05
0.04
0.00
0.00
5.6
1260
0.5
0.04
0.04
0.00
0.00
4.6
1290
0.5
0.04
0.04
0.00
0.00
4.6
1320
0.5
0.04
0.04
0.00
0.00
4.6
1350
0.5
0.04
, 0.04
0.00
0.00
4.6
1380
0.4
0.03
0.03
0.00
0.00
3.7
1410
0.4
0.03
0.03
0.00
0.00
3.7
1440
0.4
0.03
0.03
0.00
0.00
3.7
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RUNOFF INDEX NUMBERS OF HYDROLOGIC SOIL -COVER COMPLEXES FOR PERVIOUS AREAS -AMC II
Quality of
Soil Group
Cover Type (3)
Cover (2)
A
B
C
D
NATURAL COVERS -
Barren
78
86
91
93
(Rockland, eroded and graded land)
Chaparrel, Broadleaf
Poor
53
70
80
85
(Manzonita, ceanothus and scrub oak)
Fair
40
63
75
81
Good
31
57
71
78
Chaparrel, Narrowleaf
Poor
71
82
88
91
(Chamise and redshank)
Fair
55
72
81
86
Grass, Annual or Perennial
Poor
67
78
86
89
Fair
50
69
79
84
Good
38
61
74
80
Meadows or Cienegas
Poor
63
77
85
88
(Areas with seasonally high-water table,
Fair
51
70
80
84
principal vegetation is sod forming grass)
Good
30
58
72
78
Open Brush
Poor
62
76
84
88
(Soft wood shrubs - buckwheat, sage, etc.)
Fair
46
66
77
83
Good
41
63
75
81
Woodland
Poor
45
66
77
83
(Coniferous or broadleaf trees predominate.
Fair
36
60
73
79
Canopy density is at least 50 percent)
Good
28
55
70
77
Woodland, Grass
Poor
57
73
82
86
(Coniferous or broadleaf trees with canopy
Fair
44
65
77
82
density from 20 to 50 percent)
Good
33
58
72
79
URBAN COVERS -
Residential or Commercial Landscaping
Good
32
6
69
75
(Lawn, shrubs, etc.)
Turf
Poor
58
74
83
87
(Irrigated and mowed grass)
Fair
44
65
77
82
Good
33
58
72
'79
AGRICULTURAL COVERS -
Fallow
76
85
90
92
(Land plowed but not tilled or seeded)
R C F C th W C D RUNOFF INDEX NUMBERS
FOR
HYDROLOGY MANUAL
PERVIOUS AREAS
PLATE E -6.1 0 of 2)
i
ACTUAL IMPERVIOUS COVER
Recommended Value
Land Use (1) Range- Percent For Average
Conditions- Percent(2
Natural or Agriculture 0 - 10 0
Single Family Residential: (3)
40,000 S. F. (1 Acre) Lots 10 - 25 20
20,000 S. F. (-t Acre) Lots 30 - 45 40
7,200 - 10,000 S. F. Lots 45 - 55 50
Multiple Family Residential:
Condominiums 45 - 70 65
Apartments 65 - 90 80
Mobile Home Park' 60 - 85 75
Commercial, Downtown- 80 -100 90
Business or Industrial
Notes:
1. Land use should be based on ultimate development of the watershed.
Long range master plans for the County and incorporated cities
should be reviewed to insure reasonable land use assumptions.
2. Recommended values are based on average conditions which may not
apply to a particular study area. The percentage impervious may
vary greatly even on comparable sized lots due to differences in
dwelling size, improvements, etc. Landscape practices should also
be considered as it is common in some areas to use ornamental grav-
els underlain by impervious plastic materials in place of lawns and
shrubs. A field investigation of a study area should always be made,
and a review of aerial photos, where available may assist in estimat-
ing the percentage of impervious cover in developed areas.
3. For typical horse ranch subdivisions increase impervious area 5 per-
cent over the values recommended in the table above.
RCFC & WCD
rJYDRULJGY MANUAL
IMPERVIOUS COVER
FOR
DEVELOPED AREAS
PLATE E-6.3
Lot 14 TM 21176.XLS
iverside County Hydrology Manual
Calculation of
SYN HYDROGRAPH METHOD
Lag (hr) =
#DIV /0
SHORTCUT METHOD Less an 100 -200 acres & Lag Time < 7 -8 min)
Data Input (boxed is calced)
Concentration Point
0
Soil Group (Sheet 11/ pp 78)
A
Area Designation
Precipitation Rate (PI E5.1 -5.6)
2.0
Area (acres)
0.64
0 sqmi
Area Precip Corr (E5.8 ( %)) 1
100.00
L (miles)
Total Adjusted Storm =
2.00
Lca (miles)
0
Runoff Index (PI E -6.1) I
3
Elev @ Headwater
0
AMC Condition (I, II, or III (Sheet E -8))
2
Elev @ Concentration Point
0
Infiltr Rate for Pery Areas (PI E -6.2) Fp
0.74
H =
0
Devel Area Cover (PI 6.3) 1
r 40%
S (ft/mile)
#DIV /0!
Const Loss Rate, F (3 -6 hr storm)
0.47
n (Ave Mann, Plate E.3)
0.0015
Fm, Min Low Loss 50 -75% of F
0.24
Lag (min)
#DIV /01
Low Loss
Rate Percent 3 &
Storm Frequency (10, 25, 100)
100
oOoResults
La Quinta Zone (1 to 6)
5
3438
Cubic Ft
Duration 1, 3, 6, 24
1 hr
0.08
Acre - Ft
Unit Time
Pattern
Storm
Loss Rates
Effective
Flood
Period
Percent
Rain
Max
Used Rate
Rain
Hydrograph
Volume
Sum Vol
Basin Infil
(min)
(%)
(in /hr)
(in /hr)
(cfs)
(cult)
(cult)
(cuft)
5
3.7
0.89
0.47
0.47
0.41
0.0
0
0
10
4.8
1.15
0.47
0.47
0.68
0.4
130
130
15
5.1
1.22
0.47
0.47
0.75
0.5
144
274
20
4.9
1.18
0.47
0.47
0.70
0.4
135
409
25
6.6
1.58
0.47
0.47
1.11
0.7
213
623
30
7.3
1.75
0.47
0.47
1.28
0.8
245
868
35
8.4
2.02
0.47
0.47
1.54
1.0
-296
1164
40
9.0
2.16
0.47
0.47
1.69
1.1
324
1488
45
12.3
2.95
0.47
0.47
2.48
1.6
476
1964
50
17.6
4.22
0.47
0.47
3.75
2.4
720
2684
55
16.1
3.86
0.47
0.47
3.39
2.2
651
3335
60
4.2
1.01
0.47
0.47
0.53
0.3
103
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00 •
0.00
0.0
0
3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
0
0.0
0.00
0.84
0.00
0.00
0.0
0
0
0.0
0.00
0.84
0.00
0.00
0.0
0
V3438
0
0.0
0.00
0.84
0.00
0.00
0.0
0
0.0
0.00
0.84
0.00
0.00
0.0
0
0.0
0.00
0.84
0.00
0.00
0.0
0
RMi
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RUNOFF INDEX NUMBERS OF HYDROLOGIC SOIL =COVER COMPLEXES FOR PERVIOUS AREAS- AMC.II
Cover Type (3) Quality 0 fj Soil Group
Cover (2); A 1 B I C D
NATURAL COVERS -
Barren
(Rockland; eroded and graded land)
Chaparrel, Broadleaf
(Manzonita, ceanothus and scrub oak)
Chaparrel,. Narrowleaf
(Chamise and redshank)
Grass, Annual or Perennial
Meadows or Cienegas
(Areas with seasonally high water table,
principal vegetation is sod forming grass)
Open Brush
(Soft wood shrubs - buckwheat, sage, etc.)
Woodland
(Coniferous or broadleaf trees predominate.
Canopy density is at least 50 percent)
Woodland, Grass
(Coniferous or broadleaf trees with canopy
density from 20' to 50 percent)
URBAN COVERS -
Residential or Commercial Landscaping
(Lawn, shrubs, etc.).
Turf. .
(Irrigated and mowed grass)
AGRICULTURAL COVERS -
Fallow
(Land plowed but not tilled or seeded)
Poor
Fair
Good
Poor
Fair
Poor
Fair
Good
Poor
Fair
Good
Poor
Fair
Good
Poor
Fair
Good
Poor
Fair
Good
Poor
Fair
Good
RUC & W C p RUNOFF INDEX
r�YDROLOGY' MANUAL FOR
PERVIOUS
78 186 191 193
53 70 80 85
40 63 75 81
31 57 71 78
71 82 88 91
55 .72 81 86
67 78' 86 89
5.0 69 79 84
38 61 74 80
63 77 85 88
51 70 80 84
30 58 72 78
62 76 84= 88
46 66 77 83
41 63 75 81
45 66 77 83
36 60 .73 79
28 55 '70 77
57 73 82 86
44 65 77 82.
33 58 72 79
32 156 169 175
58 174 183 187,.
44 65 77 82
33 58 72 79
76 185 190 192
NUMBERS
AREAS
PLATE E -6.1 0 of 2)
I
ACTUAL IMPERVIOUS COVER
Recommended Value
Land Use. (1) Range- Percent For Average
Conditions- Percent(2
Natural or Agriculture 0 - 10 0
Single Family Residential: (3)
40,000 S. F. (1 Acre) Lots
20,000 S. F. 0i Acre) Lots
7,200 - 10,000 S.. F. Lots
Multiple Family Residential:
Condominiums
Apartments
Mobile Home Park
10 -25
30 - 45
45 - 55 .
45 - 70
65 -90
60 - 85
20
40
50
65
80
75
Commercial; Downtown I 80 -100 I 90
Business or Industrial
Notes:
1. Land use should be based on ultimate development of the watershed.
Long range master plans for the County and incorporated cities
should be reviewed to insure reasonable land use assumptions.
2. Recommended values are based on average conditions which may not
apply to a particular study area. The percentage impervious may
vary greatly even on comparable sized lots due to differences in
dwelling size, improvements, etc. Landscape practices should also
be considered as it is common in some areas to use ornamental grav=
els underlain by impervious plastic materials in place of lawns and
shrubs. A field investigation of a study area should always be made,
and a review of aerial photos, where available may assist in estimat-
ing the percentage of impervious cover.in developed areas.
3. For typical horse ranch subdivisions increase impervious area 5 per-
cent over the values recommended in the table above.
RCFC Ek WCD
HYDROLOGY 1\/JANUAL _
IMPERVIOUS
FOR
DEVELOPED
COVER
AREAS
PLATE E -6.3
Siadden Engineering
77 -723 Enfield Lane, Suitt 100, Palm DeeM CA 92211 (760) 772-3893 Fax (760) 772 -3895
6782 Stanton Avc., Suite A, Buena Park, CA 90621 (714) 523 -0952 Fax (714) 523 -1369
450 Egan Avcnuc, 9.raumont, CA 92223 (951) 845 -7743 Fax (951) 945 -8863
December 7, 2007
Chris McFadden Architect
72 -925 Fred Waring Drive, Suite 204
Palm Desert, California 92260
Project: Proposed Residential Addition
Lot 14 — Bonita Trail — La Quinta Polo Estates
La Quinta, California
Project No. 544 -4345
07 -12 -841
Subject: Geotechnical Update
Ref: Geotechnical Investigation report prepared by Sladden Engineering dated July 2,
2004, Project No 544- 4345, Report No. 04- 06-444
As requested, we have reviewed the referenced geotechnical report as. it relates to the design and
construction of the proposed addition. The project site is located on lot 14 Bonita Trail within the
La. Quinta Polo Estates in the City of La Quinta, California. It is our understanding that the
Proposed structures will be- of relatively lightweight wood -frame construction and will be
supported by conventional shallow spread footings and concrete slabs on grade.
In order to provide adequate and uniform bearing conditions we recommend overexcavation
throughout the proposed addition. The building area should be overexcavated to a depth of least
3 feet below existing grade or 3 feet below the bottom of the footings, whichever is deeper. The
exposed soil should than be scarified to a depth of 1 foot, moisture conditioned and recompacted
to at least 90 percent relative compaction. The excavated material may then be replaced as
engineered fill material as recommended below.
The referenced report includes recommendations pertaining to the construction of structure
foundations. Based upon our review of the referenced report, it is our opinion that the structural
values included in the report remain applicable for the design and construction of the proposed
structure foundations.
,IAN 8 2003
November 28, 2007 -2- Project No. 544-06498
07 -11 -812
The structural values recommended in the referenced geotechnical report remain applicable for
use in foundation design. Conventional shallow spread footings should be bottomed into
properly compacted fill material a minimum of 12 inches below lowest adjacent grade.
Continuous footings should be at least 1.2 inches wide and isolated pad footings should be at least
2 feet wide. Continuous footings and isolated pad footings should be designed utilizing
allowable bearing pressures of 1800 psf and 2000 psf, respectively. The recommended allowable
bearing pressures may be increased by one -third for wind and seismic loading. increases in
allowable bearing pressures may be realized with increased footing size. Allowable increase of
200 psf for each additional 1 foot of width and 250 psf for each additional 6 inches of depth may
be utilized, if desired. The maximum allowable bearing pressure should be 3000 psf.
Resistance to lateral loads can be provided by a combination of friction acting at the base of the
slabs or foundations and passive earth pressure along the sides of the foundations. A coefficient
of friction of 0.43 between soil and concrete may be used with dead load forces only. A passive
earth pressure of 275 pounds per square foot, per foot of depth, may be used .for the sides of
footings that are placed against properly compacted native soils.
Retaining walls /wing walls may be required to accomplish the proposed construction. Cantilever
retaining walls may be designed using "active" pressures. Active pressures may be estimated
using an equivalent fluid weight of 35 pcf for native backfill soil with level free - draining backfill
conditions.
The bearing soil is non - expansive and falls within the "very low' expansion category. in
accordance with Uniform Building Code (USC) classification criteria. Pertinent 2007 Seismic
Design parameters are summarized on the attached data sheet.
if you have questions regarding this report, please contact the undersigned.
Respectfully submitted,
SLADDEBN ENGINEIJ
QppFFSSlp,�
ANp�gl�
Brett L. Anderson v, m
No. C 45359
Principal Engineer W
* Exp. 9- 30.2008
Letter/91
�i-t A -
Copies: 4 /Chris McFadden Architect
Sladden Engineering
November 28, 2007 -3- Project No. 544 -06498
07- 11-812
1997 UNIFORM BUILDING CODE SEISMIC DESIGN INFORMATION
The International Conference of Building Officials 1997 Uniform Building Code contains
substantial revisions and additions to the earthquake engineering section in Chapter 16.
Concepts contained in the code that will be relevant to construction of the proposed structures
are summarized below.
Ground shaking is expected to be the primary hazard most likely to affect the site, based upon
proximity to significant faults capable of generating large earthquakes. Major fault zones
considered to be most likely to create strong ground shaking at the site are listed below.
Fault Zone
Approximate Distance
m i
Fault Type
(1997 UBC)
San Andreas
9.6 km
A
San Jacinto
32.3 km
A
Based on our field observations and understanding of local geologic conditions, the soil profile
type judged applicable to this site is So, generally described as stiff or dense soil. The site is
located within UBC Seismic Zone 4. The following table presents additional coefficients and
factors relevant to seismic mitigation for new construction upon adoption of the 1997 code.
Sla"en Engineering
Near-Source
Near- Source
Seismic
Seismic
Seismic
Acceleration
Velocity
Coefficient
Coefficient
Source
Factor, Na
Factor, Nx
Ca
CV
San Andreas
1.05
1.25
0.44N.
0.64N-,
San Jacinto
1.0
1.0
0.44N.
0.64N.,
Sla"en Engineering
November 28, 2007 -4- Project No. 544.06498
07 -11 -812
Based on our field observations and understanding of local geologic conditions, the soil profile
type judged applicable to this site is Sn, generally described as stiff soil. The site is located within
UBC Seismic Zone 4. The following presents additional coefficients and factors relevant to
seismic mitigation for new construction upon adoption of the 2006 code.
The seismic design category for a structure may be determined in accordance with Section 1613
of the 2006 IBC or ASCE7. According to the 2006 18C, Site Class D may be used to estimate
design seismic loading for the proposed structures. The period of the structures should be less
than 14 second. This assumption should be verified by the project structural engineer. The 2006
iBC Seismic Design Parameters are summarized below.
Occupanry. Category (Table 1604.5):11
Site Class (Table 161355): D
Ss (Figure 16135(3)):1.50g
SI (Fiore 16135(4)): 0.60g
Fe (Table 1613:5,3(1)).1.0
Fv (Table 16135.3(2)):1.5
Sms (Equation 16-37 {Fa X Ss)): 1.50g
Sm1(Equation 16-38 (Fv X Si)): 0.908
SDS (Equation 16-39 12/3 X Smsl):1.00g
SDI (Equation 16- 4012/3 X Sm1)): 0.608
Seismic Design Category based on SDS (Table 1613.5.6(1)): D
Seismic Design Category based on SDI (Table 16135.6(2)): D
Sladden Engineedng
Sladden Engineering
6782 Stanton Ave., Suite A, Buena Park, CA 90621 (714) 523-0952 Fax (714) 523 -1369
39-725 Garend Ln., Suite G, Palm Desert, CA 92211 (760) 772 -3893 Fax (760) 772 -3895
July 2, 2004
Sedona Homes
49 -950 Jefferson Street, Suite 134
Indio, California, 92201
Attention: Mr. Lance Alacano
Project: Proposed Single Family Residence
Lot 14 — Bonita Trail - La Quinta Polo Estates
La Quinta, California
Subject: Geotechnical Investigation
Project No. 544.4345
04- 06-444
Presented herewith is the report of our Geotechnical Investigation conducted for the construction of the
proposed single family residence to be located at Lot 14 on Bonita Trail within the La Quinta Polo Estates
development in the City of La Quinta, California. The investigation was performed in order to provide
recommendations for site preparation and- to assist in foundation design for the proposed single family
residence and the related site improvements.
This report presents the results of our field investigation and laboratory testing along with conclusions
and recommendations for foundation design and site preparation. This report completes our initial scope
of services as described in our proposal dated June 17, 2004.
We appreciate the opportunity to provide service to you on this project. If you have any questions
regarding this report, please contact the undersigned
Respectfully submitted,
SLADDEN ENGINEE1
Brett L. Anderson
Principal Engineer
SER/pc
Copies: 6/Sedona Homes
I Ex P. I ,;r06 x
TO -d LTZVLGG 8T6 uI13naisu3 I d o Wd £b:£O 4eeZ- ve -33a
July 2, 2004 -6- Project No. 544 -4,345
0406 -444
Tentative Pavement Design: All paving should be underlain by a minimum compacted fill
thickness of 12 inches (excluding aggregate base). This may be performed as described in the Site
Grading Section of this report. R -Value testing was not conducted during our investigation but
based upon the sandy nature of the surface soils, an R -Value of approximately 50 appears
appropriate for preliminary pavement design. The following preliminary onsite pavement
section is based upon a design R -Value of 50.
Qnsite Pavement (Traffic Index = 5.0)
Use 3.0 inches of asphalt on 4.0 inches of Class 2 base material
Aggregate base should conform to the requirements for Class 2 Aggregate base in Section 26 of
CalTrans Standard Specifications, January 1992. Asphaltic concrete should conform to Section 39
of the CalTrans Standard Specifications. The recommended sections should be provided with a
uniformly compacted subgrade and precise control of thickness and elevations during placement.
Pavement and slab designs are tentative and should be confirmed at the completion of site
grading when the subgrade soils are in- place. This will include sampling and testing of the
actual subgrade soils and an analysis based upon the specific traffic information
Shrinkage and Subsidence: Volumetric shrinkage of the material that is excavated and replaced
as controlled compacted fill should be anticipated. We estimate that this shrinkage could vary
from 20 to 25 percent. Subsidence of the surfaces that are scarified and compacted should be
between 0.1 and 0.3 tenths of a foot. This will vary depending upon the type of equipment used,
the moisture content of the soil at the time of grading and the actual degree of compaction
attained. These values for shrinkage and subsidence are exclusive of losses that will occur due to
the stripping of the organic material from the site and the removal of oversize material.
General Site Grading: All grading should be performed in accordance with the grading
ordinance of the City of La Quinta, California. The following recommendations have been
developed on the basis of um field and laboratory testing and are intended to provide a uniform
compacted mat of soil beneath the building slabs and foundations.
1. Site Clearing: Proper site clearing will be very important. Any existing vegetation,
slabs, foundations, abandoned underground utilities or irrigation lines should be
removed from the proposed building areas and the resulting excavations should be
properly backfilled. Soils that are disturbed during site clearing should be removed and
replaced as controlled compacted fill under the direction of the Suits E, ngineer.
2. Preparation of Building and Foundation Areas: In order to provide adequate and
uniform bearing conditions, we recommend overexcavation throughout the proposed
building areas. The building areas should be overexcavated to a depth of at least 2 feet
below existing grade or 2 feet below the bottom of the footings, whichever is deeper. The
exposed soils should then be scarified to a depth of 1 foot, moisture conditioned and
recompacted to at least 90 percent relative compaction. The excavated material may then
be replaced as engineered fill material as recommended below.
Sladden Eni ineerinz
ZO'd LTZVL96 8T8 uIionN1suo I d 8 Wd ZS: £e )-06L- v-0 -33a
July 2, 2004 -5- Project No. 544 -4345
0406 -444
Lateral Design: Resistance to lateral loads can be provided by a combination of friction acting at
the base of the slabs or foundations and passive earth pressure along the sides of the foundations.
A coefficient of friction of 0.40 between soil and concrete may be used with consideration to dead
load forces only. A passive earth pressure of 250 pounds per square foot, per foot of depth, may
be used for the sides of footings which are poured against properly compacted native or
approved non - expansive import soils. Passive earth pressure should be ignored within the upper
1 foot except where confined (such as beneath a floor slab).
Retaining Walls: Retaining wa may ay be necessary to accomplish the proposed construction.
Lateral pressures for use in retaining wall design can be estimated using an equivalent fluid
weight of 35 pcf for level free- draining native backfill conditions. For walls that are to be
restrained at the top, the equivalent fluid weight should be increased to 55 pcf for level free -
draining native backfill conditions. Backdrains should be provided for the full height of the
walls.
Expansive Soils: Due to the prominence of "very low" expansion category soils near the surface,
the expansion potential of the foundation bearing soils should not be .a controlling factor in
foundation or floor slab design. Expansion potential should be reevaluated subsequent to
grading.
Concrete Slabs -on- Grade: All surfaces to receive concrete slabs -on -grade should be underlain by
a minimum compacted non - expansive fill thickness of 24 inches, placed as described in the Site
Grading Section of this report. Where slabs are to receive moisture sensitive floor coverings or
where dampness of the floor slab is not desired, we recommend the use of an appropriate vapor
barrier or an adequate capillary break. Vapor barriers should be protected by sand in order to
reduce the possibility of puncture and to aid in obtaining uniform concrete curing.
Reinforcement of slabs -on -grade in order to resist expansive soil pressures should not be
necessary. However, reinforcement will have a beneficial effect in containing cracking due to
concrete shrinkage. Temperature and shrinkage related cracking should be anticipated in all
concrete slabs -on- grade. Slab reinforcement and the spacing of control joints should be
determined by the Structural Engineer.
Soluble Sulfates: The soluble sulfate concentrations of the surface soils were determined to be
less than 107 parts per million, which is considered non - corrosive with respect to concrete. The
use of Type V cement and specialized sulfate resistant concrete mix designs should not be
necessary for any concrete in contact with the native soils.
Sladden Engineering
10-d LTZVLQ6 8T8 -ii3nN su3 I d n Wd Ts:£e t00Z- vo -a3a
July 2, 2004 -7- Project No. 544 -4345
04 -06 -444
3. Placement of Compacted milk Within the building pad areas, fill materials should be
spread in thin lifts, and compacted at near optimum moisture content to a minimum of
90 percent relative compaction. Imported fill material shall have an Expansion index not
exceeding 20.
The contractor shall notify the Soils Engineer at least 48 hours in advance of importing
soils in order to provide sufficient time for the evaluation of proposed import materials.
The contractor shall be responsible for delivering material to the site which complies with
the project specifications. Approval by the Soils Engineer will be based upon material
delivered to the site and not the preliminary evaluation of import sources.
'Our observations of the materials encountered during our investigation indicate that
compaction within the native soils will, be most readily obtained by means of heavy
rubber tired equipment and/or sheepsfoot compactors. A uniform and near optimum
moisture content should be maintained during fill placement and compaction.
4. Preparation of Slab and Paving Areas: All surfaces to receive asphalt concrete paving or
exterior concrete slabs -on- grade, should be underlain by a minimum compacted fill
thickness of 12 inches. 'Ibis may be accomplished by a combination of overexcavation,
scarification and recompaction of the surface, and replacement of the excavated material
as controlled compacted fill. Compaction of the slab and pavement areas should be to a
minimum of 90 percent relative compaction.
5. Testing and Inspection: luring grading tests and observations should be performed by
the Soils Engineer or his representative in order to verify that the grading is being
performed in accordance with the project specifications. Field density testing shall be
performed in accordance with applicable ASTM test standards.
The minimum acceptable degree of compaction shall be 90 percent of the maximum dry
density as obtained by the ASTM D1557 -91 test method. Where testing indicates
insufficient density, additional compactive effort shall be applied until retesting indicates
satisfactory compaction.
Madden Enaineerine
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July 2, 2004
4l-
GENERAL
Project No. 544 -4345
04- 06-444
The findings and recommendations presented in this report are based upon an interpolation of the soil
conditions between boring locations and extrapolation of these conditions throughout the proposed
building area. Should conditions encountered during grading appear different than those indicated in
this report, this office should be notified.
This report is considered to be applicable for use by Mr. Lance Alacano for the specific site and project
described herein. The use of this report by other parties or for other projects is not authorized. The
recommendations of this report are contingent upon monitoring of the grading operations by a
representative of Sladden Engineering. All recommendations are considered to be tentative pending our
review of the grading operations and additional testing, if indicated. If others are employed to perform
any soil testing, this office should be notified prior to such testing in order to coordinate any required situ
visits by our representative and to assure indemnification of Sladden Engineering.
We recommend that a pre -job conference be held on the site prior to the initiation of site grading. The
purpose of this meeting will be to assure a complete understanding of the recommendations presented in
this report as they apply to the actual grading performed.
Slgdden Engineering
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GEOTECHNICAL INVESTIGATION
PROPOSED SINGLE FAMILY RESIDENCE
LOT 14 — BONITA TRAIL — LA QUINTA POLO ESTATES
LA QUINTA, CALIFORNIA
July 2, 2004
TABLE OF CONTENTS
INTRODUCTION..................................................................................................... ............................... 1
SCOPEOF WORK .................................................................................................... ............................... 1
PROJECT DESCRIPTION .................... .................................................................................................... 1
GEOLOGYAND SEISMICITY .......................................................:.................. ............................... 2
SUBSURFACE CONDITIONS ....................... .... 2
......................................................... ...............................
LIQUEFACTION................................................................................................... ..........:.................... 3
CONCLUSIONS AND RECOMMENDATIONS ................................................. ............................... 3
FoundationDesign ........................................................................................... ............................... 4
Settlements........................................................ ............................... ............. ............................... 4
LateralDesign ............................................................... ............................... ............................... 5
RetainingWalls .......... .... ............................ . ................................................... ............................... 5
ExpansiveSoils .................................................................................................. ............................... 5
ConcreteSlabs- on- Gradc .................................................................................. ............................... 5
SolubleSulfates ................................................................................................ ............................... 5
TentativePavement Design ............................................................................. ............................... 6
Shrinkage and Subsidence ............................................................................... ............................... 6
GeneralSite Grading ........................................................................................ ............................... 6
1. Site Clearing ........................................................................................... ............................... 6
2. Preparation of Building and Foundation Areas ................................. ............................... 6
3. Placement of Compacted Fill ................................................................ ............................... 7
4. Preparation of Slab and Pavement Areas ........:................................... ............................... 7
5. Testing and Inspection .............................................:........................... ............................... 7
GENERAL.................................. : ............... . ............................... ..............
:................ ............................... 8
REFERENCES................ ...................................................................................... ............................... 8
APPENDIX A - Site Plan and Boring Logs
Field Exploration
APPENDIX B - Laboratory Testing
Laboratory Test Results
APPENDIX C - 1997 UBC Seismic Design Criteria
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C
July 2, 2004 -1- Project No. 544 -4345
04 -06-444
INTRODUCTION
This report presents the results of our' Geotechnical investigation performed in order to provide
recommendations for site preparation and the design and construction of the foundations for the
proposed single family residence. The project site is located at Lot 14 on Bonita Trail within the La
Quinta Polo Estates in the City of La Quinta, California. The preliminary plans indicate that the proposed
project will include a single - family residence along with various associated site improvements.
Associated improvements will include paved roadways, concrete driveways and patios, underground
utilities, and landscape areas.
SCOPE OF WORK
The purpose of our investigation was to determine certain engineering characteristics of the near surface
soils on the site in order to develop recommendations for foundation design and site preparation. Our
investigation included field exploration, laboratory testing, literature review, engineering analysis and
the preparation of this report. Evaluation of hazardous materials or other environmental concerns was
not within the scope of services provided. Our investigation was performed in accordance with
contemporary geotechnical engineering principles and practice. We make no other warranty, either
express or implied.
PROJECT DESCRIPTION
The site is located at Lot 14 on Bonita Trail within the La Quinta Polo Estates in the City of La Quinta,
C:alifomia. It is our understanding that the project will consist of a single - family residence along with
various associated site improvements. It is our understanding that the proposed residence will be of
relatively lightweight. wood -frame construction and will be supported by conventional shallow spread
footings and concrete. slabs on grade. The associated improvements will include concrete walkways,
patios, driveways, landscape areas and various underground utilities.
The majority of the subject site Is presently vacant and the ground surface is cleared of vegetation. The
lot to the south of the site remains vacant and there are existing residences to the west of the site across
Bonita Trail. The site appears to have been leveled in conjunction with the initial development of the La
Quinta Polo Estates project.
Based upon our previous experience with lightweight residential structures, we expect that isolated
column loads will be less than' 20 kips and wall loading will be less than to 2.0 kips per linear foot.
Grading is expected to include minor cuts and fills to match the nearby elevations and to construct
slightly elevated building pads to accommodate site drainage. This does not include removal and
recompaction of the bearing soils within the building area. if the anticipated foundation loading or site
grading varies substantially from that assumed the recommendations included in this report should be
reevaluated.
Slddden F.nrins"imp
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July 2, 2004 =2- Project No. 544 -4345
04 -06 -444
GEOLOGY AND SEISMICITY
The project site is located within the central Coachella Valley that is part of the broader Salton Trough
geomorphic province. The Salton Trough is a northwest trending depression that extends from the Cuff
of California to the Banning Pass. Structurally the Salton Trough is dominated by several northwest
trending faults, most notable of which is the San Andreas system.
A relatively thick sequence of sedimentary rocks has been deposited in the Coachella Valley portion of
the Salton Trough from Miocene to present times. These sediments are predominately terrestrial in
nature with some lacustrian and minor marine deposits. The mountains surrounding the Coachella
Valley are composed primarily of Precambrian metamorphic and Mesozoic granitic rock.
The Coachella Valley is situated in one of the more seismically active areas of California. The San
Andreas fault zone is considered capable of generating a maximum credible earthquake of magnitude 8.0
and due to its proximity to the project site the distance of approximately 9.6 kilometers should be
considered in design fault for the project.
Seismic activity along the nearby faults continues to affect the area and the Coachella Valley is considered
one of the more seismically active regions in California. A computer program and pertinent geologic
literature were utilized to compile data related to earthquake fault zones in the region and previous
seismic activity that may have affected the site. E.Q. Fault Version 3.00 (Blake) provides a compilation of
data related to earthquake faults in the region. The program searches available databases and provides
both distances to causative faults and the corresponding accelerations that may be experienced on the site
due to earthquake activity along these faults. The attenuation relationship utilized for this project was
based upon Joyner & Boore (1987) attenuation curves. The information generated was utilized in our
liquefaction evaluation
The site is not located in any Earthquake Fault zones as designated by the State but is mapped in the
County's Liquefaction and Ground Shaking Hazard Zone V. Several significant seismic events have
occurred within the Coachella Valley during the past 50 years. The events include Desert Hot Springs -
1948 (6.5 Magnitude), Palm Springs - 1986 (5.9 Magnitude), Desert Hot Springs - 1992 (6.1 Magnitude),
Landers -1992 (7.5 Magnitude) and Big Bear -1992 (6.6 Magnitude).
SUBSURFACE CONDITIONS
The soils underlying the site consist primarily of fine grained silty sands with scattered generally thin
sandy clayey silt layers. As is typical for the area, the silty sand and thin sandy silt layers are interbedded
and vary in thickness. Silty sands were the most prominent soils within our exploratory borings but
several prominent sandy silt and clayey silt layers were also encountered.
The silty sands encountered near the existing ground surface appeared somewhat loose but the deeper
silty sand and sandy silt layers appeared relatively firm. Sampler penetration resistance, (as measured by
field blowcounts) indicate that density generally increases with depth. The site soils were dry on the
surface but moist below a depth of approximately 5 feet.
Sladden Engineering
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I.t.d Deaig- Raafronc'e to Lateral load. on b, provided by . comol-don d fnM_ ,c l.,; .t
the bas of de.l,b. or loved. -inns and p.wly, oaM Pxaux along dw aldw of the fowdosimu.
A tecffkwd of friction of 0.40 bee+een q4 and cvnoee may be used with cor-Id -tion m dead
W W F— unly. A p.eive -.h pnmux of 170 Paul. m qu- Ions Par go. d d.ptt may
b, used for the aide of 1---P whk h .w Pomxd allam" P"P-ly c°°Ip..d rhadw m
.pp r. v nwn,.p.nlve import . ib. Past. ca+th phvwx Yhould be Ignored w.I*dn the ppar
I foot a'acMi when cmnfirrd lath o beneath a Door -1-4
Reeking wall&. Re -ining walls may be r.KV%wy W ao,omplM the propo.ed -usual-.
Latest! preeswo h- uw m nn&" wall decip m be estimated uting an equtv.imt fluid
wriBht of 37 pd for 1_4 be",.Wng nadw b.duill tondltarha Da wall. eNt w t0 b.
rclmalnd at the top. Ih, qur,.ent fluid wd9tn should b. i-.wd m 55 pct fur level has
draining native baddill condttose. Bar4d*rinc should be provided for the fun hrght of th,
ralL.