Malaga Estates (Plans 1-3) Geotechnical Investigation ReportMwilmoll
S,�
6L�eo-Engineers and Geologist
A :1 W 0.141A a 9,
LANfliiARK
a DBEIMBEISBE Company
May 27, 2005 . I
Mr. Jerry t4reen
RT. Hughes Co. LLC
78-900 Avenue 47, Suite 200
La Quinta,'CA 92253
Geotechnical Investigation
Proposed Coral Mountain Estates
SWC of Avenue 60 and Madison Street
La Quinta. California
LCI Report No. LP05098
780 N. 4th Street
El Centro. CA 92243
"60) "7-0-3000
5.
17601 337-8900 fax
77-948 Wildcat Drive
Palm Desert, CA 922 11
i76M 360-0665
'1760) 360-052� fax
Dear Mr. Green:
This geotechnical report is provided for design' and construction of the proposed Coral Mountain'
Estates residential development located near the southwest comer of Avenue 60 and Madison Street
south of La Quinta, California. Ou r geotechnical. investigation was conducted in response to your
our -soil---engineenng investigation . and-
--far-ou'r-services. The-enclosed-r-eport descri
presents our professional opinions regarding geotechnical conditions at the site to be considered in
the design and construction of the project.
The findings of this study indicate the site is underlain by interbedded silty sands and sandy silts.
The subsurface soils are medium dense to dense in nature. Groundwater was not encountered in the
borings during the time of field exploration.
Elevated sulfate and Chloride levels were not encountered in the soil samples tested for this study.
However the soil is severely corrosive to metal. We recommend a minimum of 2,500 psi concrete of
Type U Portland Cement with a maximum water/cement ratio of 0.60 (by weight) should be used for
concrete placed in contact with native soils of this project.
We did not encounter soil conditions that would preclude implementation of the proposed project
provided the recommendations contained in this report are implemented in the design and
constructionof this project. Our findings, recommendations, and application options are related only
through reading thefull report, and are best evaluated with the active participation of the engineer
of record who developed them.
J
Proposed Coral Mountain Estaies — La Quinta, CA LCI Report No. LP05098
We appreciate the opportunity to provide our findings and professional opinions regarding
geotechnical conditions at the site. If you have any questions of comments regarding our findings,
please call our office at (760) 360-0665.
Respectfully Submitted,
Landmark Consultants, Inc.
�Kel -
Staff Geologist
C
Grey C andra, PE
Prifipal
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Distribution:
Client (4)
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O.0 A.
No. C 34432 1r1r1,
EXPIRES 09-30-05 0
o�'. C M L
hafiquI Alam
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Staff Engineer
Proposed Coral Mountain Estates — La Quinta, CA LCI Repoil No. LP05098
Page
SectionI ............................................ a .............................................................................................. I
INTRODUCTION.......................................................................................................................
I
1. 1 Project Description ............................................................... s ...........................................
I
1.2 Purpose and Scope of Work .............................................................................................
I
1.3 Authorization ....................................................................................................................
2
Section2 ..........................................................................................................................................
3
METHODS OF INVESTIGATION ............................................................................................
3
2.1 Field Exploration ................................................................................................................
3
2.2 Laboratory Testing ............................................................................................................
4
Section3 ..........................................................................................................................................
5
DISCUSSION................. I .............................................................................................................
5
3.1 Site Conditions .................................................................................................................
5
3.2 Geologic Setting ...............................................................................................................
5
3.3 Seismicity and Faulting ....................................................................................................
6
3.4 Site Acceleration and CBC Seismic Coefficients .............................................................
7
3.5 Subsurface Soil .................................................................................................................
8
3.6 Groundwater .................................................................................................. *****"** ... * ...... 8
3.7 Hydroconsolidation ............................................................................................................. 8
3.8 Soil Infiltration Rate .......................................................................................................... 9
Section4 .........................................................................................................................................
10
RECOMMENDATIONS ...........
4.1 Site Preparation ..................... ...................................................................................
10
4.2 Foundations and Settlements ...........................................................................................
12
4.3 Slabs -On -Grade ..............................................................................................................
13
4.4 Concrete Mixes and Corrosivity .....................................................................................
14
4.5 Excavations ...............
15
4.6 Lateral Earth Pressures ....................................................................................................
15
4.7 Seismic Design ................................................................................................................
16
4.8 Pavements .......................................................................................................................
16
Section5 ........................................................................................................................................
18
LIMITATIONS AND ADDITIONAL SERVICES ...................................................................
18
5.1 Limitations ......................................................................................................................
18
5.2 Additional Services .........................................................................................................
19
APPENDIX A: Vicinity and Site Maps
APPENDIX B: Subsurface Soil Logs and Soil Key
APPENDIX C: Laboratory Test Results
APPENDIX D: Summary of Infiltration Testing,
APPENDIX E: References
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Pro2osed Coral Mountain Estates — La Quinta. CA LCI Report No. LP05098
Section 1
INTRODUCTION
1.1 Project Description
4
This report presents the findings of our geotechnical investigation for the proposed Coral Mountain
Estates residential development located on southwest comer of Avenue 60 and Madison Street south
of La Quinta, California (See Vicinity Map, Plate A- 1). The proposed development will consist of
several one to two story single family residential homes on approximately 23 -acres. A site plan for
the proposed development was provided by RT. Hughes Co., LLC of La Quinta, California.
The structures are planned to consist of continuous footing with slabs -on -grade and wood -frame
construction. Footing loads at exterior bearing walls,are estimated at I to .3 kips per, lineal foot.
Column loads are estimated to range from 5 to 15 kips. If structural loads exceed those -stated above,
we should be notified so we may evaluate their impact on foundation settlement and bearing
capacity. Site development will include building pad preparation, underground utility installation,
street construction, and concrete driveway and sidewalk placement.
1.2 Purpose and Scope of Work
The purpose of this geotechnical study was to investigate the upper 51.5 feet of subsurface soil at
selected locations within the site for evaluation of physical/engineering properties. - From the
subsequent field and laboratory data, professional opinions.were developed and are provided in this
report regarding geotechnical conditions at this site and the effect on design and construction. The
scope of our services consisted of the following:
Field exploration and in-situ testing of the site soils at selected locations and depths.
Laboratory testing for physical and/or chemical properties of selected samples.
Review of the available literature and publications pertaining to local geology,
faulting, and seismicity.
Engineering analysis and evaluation of the data collected.
Preparation of this report presenting our findings, professional opinions, and
recommendations for the geotechnical aspects of project design and construction.
NO- In-situ testing of soil infiltration for stormwater retention basin.
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Proposed -Coral Mountain Estates — La Quinta. CA LCI Report No. LP05098
This report addresses the following geotechnical issues:
Subsurface soil and groundwater conditions
Site geology, regional faulting and seismicity, near source factors, and site seismic
accelerations
Aggressive soil conditions to metals -and concrete
Soil infiltration rates of the native soil for stormwat6r retention basins
Professional opinions with regard to the above issues are presented for the following:
Site grading and earthwork
Building pad and foundation subgrade preparation
Allowable soil bearing pressures and expected settlements
Concrete slabs -o n -grade
Lateral earth pressures
Excavation conditions and buried utility installations
Mitigation of the potential effects of salt concentrations in native soil to concrete
mixes and steel reinforcement
Seismic design parameters
Pavement structural sections
Our scope of work for this'repor t did not include an evaluation of the'siie for th6'presefice-of
environmentally hazardous materials or conditions.
1.3 Authorization
Mr. Jerry Green of RT. Hughes Co. LLC provided authorization by written agreement to proceed
with our work on April 13, 2005. We conducted our work according to our written proposal dated
April 13, 2005
't
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Proposed Coral Mountain Estates —.La Quinta. CA LCI Report No. LP05098
Section 2
METHODS OF INVESTIGATION
2.1 Field Exploration
Subsurface exploration was performed on April 22, 2005 using Williams Drilling of Indio, California
to advance three (3) borings to depths of 14.0 to 51.5 feet below existing ground surface. The
borings were advanced with a truck -mounted, CME 55 drill rig using 8 -inch diameter, hollow -stem,
continuous -flight augers. The approximate boring locations were established in the field and plotted
on the.site map by sighting to discernable site features. The boring locations are shown on the Site
and Exploration Plan (Plate A-2).
A staff geologist observed the drilling operations and maintained a log of the soil encountered and
sam pling depths, visually classified the soil encountered during drilling in accordance with the
Unified Soil Classification System, and obtained drive tube and bulk samples of the subsurface
materials at selected intervals. Relatively undisturbed soil samples were retrieved using a 2 -inch
outside diameter (01)) split -spoon sampler or a 3 -inch OD Modified California Split -Barrel (ring)
sampler. The samples were obtained by driving the sampler ahead of the auger tip at selected depths.
The drill rig was equipped with a 140 -pound CME automatic hammer for conducting Standard
Penetration Tests (SPT). The number of blows required to drive the samplers the last 12 inches of an
18'inch drive length into -the soil is recorded on the boring logs as "blows per foot". Blow counts (N
values) reported on the boring logs represent the field blow counts. No corrections have been
applied for effects of overburden pressure, automatic hammer drive energy, drill rod lengths, liners,
and sampler diameter.
After logging and sampling the soil, the exploratory borings were backfilled with the excavated
material. The backfill was loosely placed and was not compacted to the requirements specified for
engineered fill.
The subsurface logs are presented on Plates B -I through B-3 in Appendix B. A key to the log
symbols is presented on Plate B-4. The stratification lines shown on the subsurface logs represent
the approximate boundaries between the various strata. However, the transition from one stratum to
another may be gradual over some range of depth.
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2.2 Laboratory Testing
Laboratory tests were conducted on selected bulk and, relatively un�isturbed soil samples to aid in
classification and evaluation of selected engineering properties of the site soils. The tests were
conducted in general conformance to the procedures of the American Society for Testing and
Materials (ASTM) or other standardized methods as referenced below. The laboratory testing
program consisted of the following tests:
Particle Size Analyses (ASTM D�22) — used for soil classification and liquefaction
evaluation.
Unit Dry Densities (ASTM D2937) and Moisture Contents (ASTM D2216) — used for
insitu soil parameters.
0. Collapse Potential (ASTM D5333) — used for hydroconsolidation potential evaluation.
Moisture -Density Relations* (ASTM D1557) —used for soil compaction determinations.
Chemical Analyses (soluble sulfates-& chlorides, pH, and resistivity) (Caltrans Methods) —
used for concrete mix evaluations and corrosion protection requirements.
The laboratory test results are presented on the subsurface logs and on Plates C-1 through C-4 in
Appendix C.
Ll
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Proposed Coral Mountain Estates — La Quinta. CA LCI Report No. LP05098
Section 3
DISCUSSION
3.1 Site Conditions
The 23 -acre project site is relatively flat -lying, triangular in shape and is currently vacant desert land.
Thick vegetation, consisting of mesquite, desert flowers, tall grasses and other large bushes cover the
site' The All American Canal, approximately 30 feet above the surrounding area, is located along the
western boundary of the site. The site is bounded to the north by Avenue 60, a rural dirt road.
Adjacent properties are flat -lying and are approximately at the same elevation with this site. A single
family residence and vacant desert land are located acrossAvenue 60 to the north. To the east is a
single family residential community currently under development.
The project site lies at an elevation of approximately 30 feet below mean sea level (MSL) in the
Coachella Valley region of the California low desert. Annual rainfall in this and region is less than 4
inches per year with four months of average summertime temperatures above 100 OF. Winter
temperatures are mild, seldom reaching freezing.
12''Geologic-Setting
The project site is located in the Coachella Valley portion of the Salton Trough physiographic
province. The Salton Trough is a geologic structural depression resulting from large scale regional
faulting. The trough is bounded on the northeast by the San Andreas Fault and Chocolate Mountains
and the southwest by the Peninsular Range and faults of the San Jacinto Fault Zone. The Salton
Trough represents the northward extension of the Gulf of California, containing both marine and
non -marine sediments since the Miocene Epoch. Tectonic activity that formed the trough continues
at a high rate as evidenced by deformed young sedimentary deposits and high levels of seismicity.
Figure I shows the location of the site in relation to regional faults and physiographic features.
The surrounding regional geology includes the Peninsular Ranges (Santa Rosa and San Jacinto
Mountains) to the south and west, the Salton Basin to the southeast, and the Transverse Ranges
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Proposed Coral Mountain Estates GaOuinta. CA LCI Report No. LP05098
(Little San Bernardino and Orocopla Mountains) to the north and east. Hundreds of feet to several
thousand feet of Quatemary*fluvial, lacustrine,'and aeolian soil deposits underlay the Coachella
Valley.
-1
The southeastern part of the Coachella Valley lies below sea level. In the geologic past, the ancient
Lake Cahuilla submerged the area. Calcareous tufa deposits may be observed along the ancient
shoreline as high as elevation 45 to 50 feet MSL along the Santa Rosa Mountains from La Quinta
southward. Lacustrine .(lake bed) deposits comprise the subsurface soils over much of the eastern
Coachella Valley with alluvial outwash along the flanks of the valley.
3.3 Seismicity and Faulting
Faultinp, and Seismic Sources: We have performed a computer-aided search of known faults or
seismic zones that lie within a 62 mile (100 kilometers) radius of the project site as shown on Figure
I and Table 1. The search identifies known faults within this distance and computes deterministic
ground accelerations at the site based on the maximum credible earthquake expected on each of the
faults and the distance from the fault to the site. The Maximum Magnitude Earthquake (Mmax)
listed was taken from published geologic information available for each fault (CDMG OFR 96-08
and Jennings, 1994).
Seismic Risk: The project site is located in the seismically active Coachella Valley of southern
California and is considered likely to be subjected to moderate to strong ground motion from
earthquakes in the region. The proposed site structures should be designed in'accordance with the
California Building Code for near source factors derived from a "Design Basis Earthquake" (DBE).
The DBE is defined as the motion having a 10 percent probability of being exceeded in 5 0 years.
Seismic Hazards.
o. Groundshaking. The primary seismic hazard at the project site is the potential for strong
groundshaking during earthquakes along the San Andreas Fault. A further discussion of
groundshaking follows in Section 3.4.
o. Surface Rupture. The project site does not lie within a State of California, Alquist-Priolo
Earthquake Fault Zone. Surface fault rupture is considered to be unlikely at the project site because
of the well -delineated fault lines through the Coachella Valley as shown on USGS and CDMG maps.
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Proposed Coral Mountain Estate�'- La Quifita, CA LCI Report No. LP05098
MAP OF REGIONAL FAULTS AND SEISMICITY
34.75
34.50
34.25
34.00
33.75
33.50
33.25
-117.25 -117.00 -116.75 -116.50 -116.25 -116.00 -115.75
Copyright 1997 by Shelton L, Stringer, GE
Faults and Seismic Zones from Jennings (1994), Earthquakes modified from Ellsworth (1990) catalog.
Figure 1. Map of Regional Faults and Seismicity
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Legends to Faults:
BC: Blue Cut
BM: Borrego Mountain
BSZ: . Brawley Seismic Zone
CC: Coyote Creek
CN: Calico -Newberry
EL: Elmore Ranch
ELS: Elsinore
EM -C: Emerson -Copper Mtn.
L EP: Eureka Peak
0
S H: Helendale
HS -13 Hot Springs -Buck Ridge
JV: Johnson Valley
IM:: Imperial
M: Morongo
E -C ML: Mesquite Lake
NF: North Frontal Zone
OWS: Old Woman Springs
6.4 A (92)
7.3 (92) P -B: Pisgah -Bullion
PM Pinto Mtn
Joshu SA: San Andreas
SG -B: San Gorgonio -Banning
SH: Superstition Hills
d
Redlands
SJ: San Jacinto
0 0
6.2 gs 6. ftl(9 2)
Cabaz
6.5 (48)
Pa 9s RIVERSIDE CO.
Sa cinto
Palm Desert
lnd�,'
La (?�W6
A
Project Site. �r
A�lMe
0 0
M5.5+
Sho
A M 5.9-6.4
"�;O�A
DseC%Sh res
6.5 - 6.9
_J
A(18*
A(17)M
M 7.0+
5.. 0(69) Safton
S Iton Sea
alton
16.2 A
-117.25 -117.00 -116.75 -116.50 -116.25 -116.00 -115.75
Copyright 1997 by Shelton L, Stringer, GE
Faults and Seismic Zones from Jennings (1994), Earthquakes modified from Ellsworth (1990) catalog.
Figure 1. Map of Regional Faults and Seismicity
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I , Proposed Coral Mountain Estates-7,La Qqjnta, CA LCI Report No. LP05098
Table I
FAULT PARAMETERS & DETERMINISTIC
ESTIMATES
OF PEAK GROUND ACCELERATION (PGA)
Distance
i
Maximum
Avg
Avg
Data of
Largest
Est
Fault Name or
(mi) & -
Fault 1
Fault
agnit:ude
Slip
I Return
Last
Historic
site
Seismic Zone
Direction
Type Length
�M Mmax
Rate
Period
Rupture
Event
PGA
from site
(km)
(Mw) _ftn�!
(yrs)
(year)
>5.5M
(year)
(9)
Reference Notes: (1) i
1(2)1(3)1
(2)
(4) 1
(3)
1 (3) 1
(3)
(5)
(6)
San Andreas Fault System
- Coachella Valley
8.9
NE
A
A
95
7.4
25
220
1690+/-
6.5
1948
0.32
- San Gorgonio -Banning
12
N .
AIA
98
7.4
10
-
1690+/-
6.2
1986
0.26
- San Bernardino Mtn
31
NW
A
A
107
7.3
.24
433
1812
6.5
1812
0.12
- Whole S. Calif. Zone
8.9
NE
A
A
345
7.9
-
--
1857
7.8
1857
0.41
San Jacinto Fault System
- Hot Spgs-Buck Ridge
13
SSW
BIA
70
6.5
2
354
6.3
1937
0.16
- Anza Segment
16
SSW
A
A
90
7.2
12
250
1918
6.8
1918
0.19
- Coyote Creek
19
SW
B
A
40
6.8
4
175
1968
6.5
1968
0.14
Borrego Mtn
29
S
B
A
29
6.6
4
175
1
6.5
1942
0.09
- San Jacinto Valley
39
W
B
A
42
6.9
12
83
6.8
1899
0.08
- Elmore Ranch
43
'ESE
B
A
29.-
6.6
1
225
1987
5.9
1987
0.06
- Superstition Mtn.
46
SSE
B
A
23
6*6
5
500
1440+/-
0*06
- Superstition Hills
47
SE
B
A
-22
6.6
4
250
1987
6.5
1987
0.06
- Whole Zone
18
WSW A
A
245
7.5
-
-
0.20
Mojave Faults
Blue Cut
20
N
B
C
30
6.8
1
762
0.13
Eureka Peak
24
N
C
C
19
6.4
0.6
5,000
1992
6.1
1992
0.09
Burnt Mtn
24
NNW
B
C
20
6.4
0.6
5,000
1992
7.3
1992
0.09
Morongo
.35
NW
C
C
23
6.5
0.6
1,172
5.5
1947
0.07
Pinto Mountain
36
NNW
B
6.
73
7.0
2.5
499
0 . 09
Bullion Mtn -Mesquite Lk.
37
NNE
B
C
88
7.0
0.6
5,000
0.09
S. Emerson -Copper Mtn.
38
N
B
C
54
6.9
0.6
5,000
0.08
Landers
39
NNW
B
C
83
7.3
0.6
5,000
1992
7.3
1992
0.10
N. Johnson Valley
49
NNW
B
C
36
6.7
0.6
5,000
0.06
North Frontal Fault Z. (E)
50
NNW
B
C
27
6.7
0.5
1,727
0.07
Notes:
1. Jennings (1994) and CDMG (1996)
2. CDMG (1996), where Type A faults - slip rate >5 mmtyr and well constrained paleoseismic; data
Type B faults - all other faults.
3. WGCEP (1995)
4. CDMG (1996) based on Wells & Coppersmith (1994)
5. Ellsworth Catalog in USGS PP 1515 (1990) and USBR (1976), MW moment magnitude,
6. The deterministic estimates of the Site PGA are based on the attenuation relationship of:
Boore, Joyner, Furnal (1997)
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�roposed Coral Mountain Estaies — La Quinta. CA LCI Report No. LP05098
However, because of the high tectonic activity and deep alluvium of the region, we cannot preclude
the potential for surface rupture on undiscovered or new faults that may underlie the site.
i- Liquefaction. Liquefaction is unlikely to be a potential hazard at the site since the groundwater is
deeper than 50 feet (the maximum depth that liquefaction is known to occur).
Other SecondM Hazards.
o. Landsliding. The hazard of landsliding is unlikely due to the regional planar topography. No
ancient landslides are shown on geologic maps of the region and no indications of landslides were
observed during our site investigation.
o,. Volcanic hazards. The site is not located in proximity to any known volcanically active area and
the risk of volcanic hazards is considered very low.
P. Tsunamis, seiches, and flooding. The site does not lie near any large bodies of water, so the
threat of tsunami, seiches, or other seismically -induced flooding is unlikely. The site is located down
gradient from the All American Canal. If rupture of the canal were to occur due to seismic events,
flooding of the site is possible.
3.4 Site Acceleration and CBC Seismic Coefficients
Site Acceleration: Deterministic horizontal peak ground accelerations (PGA) from maximum
probable earthquakes on regional faults have been estimated and are included in Table 1. Ground
motions are dependent primarily on the earthquake magnitude and distance to the seismogenic
(rupture) zone. Acceleratioris also are dependent upon attenuation by rock and soil deposits,
direction of rupture and type of fault; therefore, ground motions may vary considerably in the same
general area.
We have used the computer program FRISKSP (Blake, 2000) to provide a probabilistic estimate of
the site PGA using the attenuation relationship of Boore, Joyner, and Furnal (1997) Soil (3 10). The
PGA estimate for the project site having a 10% probability of occurrence in 5 0 years (return period
of 475 years) is 0.55g.
CBC Seismic Coefficients: The CBC seismic response coefficients'are calculated from the near -
source factors for Seismic Zone 4. The near -source factors are based on the distance from the fault
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'o. LP05098
Proposed Coral Mountain Estates — La Quinta. CA LCI Report N,
and the seismic source type. The following table lists seismic and site coefficients (near source
factors) determined by Chapter 16 of the 2001 CBC. This site lies within. 14.3 km of a TypeAfault
overlying S, (stiffi soil.
CBC Seismic Coefficients for Chapter 16 Seismic Provisions
3.5 Subsurface Soil
Subsurface soils encountered during the field exploration conducted on April 22, 2005 consist of
medium dense to dense interbedded silty sands and sandy silts. The subsurface logs (Plates B -I
through B-3) depict the stratigraphic relationships of the various soil types.
3.6 Groundwater
Groundwater was not encountered in the borings during the time of exploration and is deeper than 50
feet below ground surface at this site. There is uncertainty in the accuracy of short-term water level
measurements, particularly in fine-grained soil. Groundwater levels may fluctuate with precipitation,
irrigation of adjacent properties, drainage, and site grading. The groundwater level noted should not
be interpreted to represent an accurate or permanent condition.
3.7 Hydroconsotidation
In and climatic regions, granular soils have a potential to collapse upon wetting. This collapse
(hydrocon�olidation) phenomenon is the result of the lubrication of soluble cements (carbonates) in
the soil matrix causing the soil to densify from its loose configuration during deposition.
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Seismic
Distance to
Near Source Factors
Seismic Coefficients
CBC Code
Soil Profile
Source
Critical
Edition
Type
Type
Source
Na
N I v
Ca
C
SD
2001
A
< 14.3 km
1.00
1.03
0.44
0.66
(stiff soil)
Ref. Table
16-J
16-U
---
3.5 Subsurface Soil
Subsurface soils encountered during the field exploration conducted on April 22, 2005 consist of
medium dense to dense interbedded silty sands and sandy silts. The subsurface logs (Plates B -I
through B-3) depict the stratigraphic relationships of the various soil types.
3.6 Groundwater
Groundwater was not encountered in the borings during the time of exploration and is deeper than 50
feet below ground surface at this site. There is uncertainty in the accuracy of short-term water level
measurements, particularly in fine-grained soil. Groundwater levels may fluctuate with precipitation,
irrigation of adjacent properties, drainage, and site grading. The groundwater level noted should not
be interpreted to represent an accurate or permanent condition.
3.7 Hydroconsotidation
In and climatic regions, granular soils have a potential to collapse upon wetting. This collapse
(hydrocon�olidation) phenomenon is the result of the lubrication of soluble cements (carbonates) in
the soil matrix causing the soil to densify from its loose configuration during deposition.
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Proposed Coral Mountain Estates — La Quinta. CA LCI Report No. LP05098
Collapse potential test indicated a slight risk of collapse upon inundation indicating at the project
. . 1,
site. Therefore, building foundations are not required to include provisions for mitigating the
hydroconsolidation caused by soil saturation from landscape irrigation or broken utility lines.
3.8 Soil Infiltration Rate
A total of two (2) infiltration tests were conducted on May 24, 2005 at the proposed location for the
stormwater retention basin as shown on the Site and Exploration Plan (Plate A-2). The tests were
performed using pipes inside 6 -inch diameter hand auger boreholes made to depths of approximately
3 feet below the existing ground surface, corresponding to the anticipated bottom depth of the
stormwater retention basin. The pipes were presoaked and filled with water and successive readings
of drop in water levels were made for a total elapsed time of 360 minutes, until a stabilization drop
was recorded.
A soil infiltration rate of 3-5 gallons per hour per square- foot of bottom area may be used for
infiltration design. An oil/water separator should be installed at inlets to the stormwater retention
basin to prevent sealing of the basin bottom with silt and oil residues.
We recommend additional testing.should. be performed after the completion of rough grading
operations, to verify the soil infiltration rate.
0
Landmark Consultants, Inc. Paoe 9
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�roposed Coral Mountain Estat6s' � La Quinta. CA LCI Report No. LP05098
Section 4
RECOMMENDATIONS
4.1 Site Preparation
Clearing and Grubbing: All surface improvements, debris or vegetation including grass, trees, and
weeds on the site at the time of construction should be removed fTom the construction area. Root
balls should be complVely excavated. Organic strippings should be hauled from the site and not
used as fill. Any trash, construction debris, concrete slabs, old pavement, landfill, and buried
obstructions such as old foundations and utility lines exposed during rough grading should be traced
to the limits of the foreign material by the grading contractor and removed under our supervision.
Any excavations resulting from site clearing should be dish -shaped to the lowest depth of
disturbance and backfilled under the observation'of the geotechnical engineer's representative.
Building Pad Preparation: The existing surface soil within the building pad areas should be removed
to 36 inches below the existing grade or 18 inches below the lowest foundation grade (whichever is
lower) extending five feet beyond all exterior wall/column lines (including adjacent concreted areas).
Exposed subgrade should be scarified to a depth of 12 inches, uniformly moisture conditioned to
2% and recompacted to a minimum of 90% of the maximum density determined in accordance with
ASTM D 1557 Methods.
The native soil is suitable for use as engineered fill provided it is free from concentrations of organic
matter or other deleterious material. The fill soil should be uniformly moisture conditioned by
discing and watering to the limits specified above, placed in maximum 8 -inch lifts (loose), and
compacted to the limits specified above.
Imported fill soil (if required) should be similar to onsite soil or non -expansive, granular soil meeting
the USCS classifications of SM, SP -SM, or SW -SM with a rn�ximum rock size of 3 inches. The
geotechnical engineer should approve imported fill soil sources before hauling material to the site.
Imported granular fill should be placed in lifts no greater than 8 inches in loose thickness and
compacted to a minimum of 90% of ASTM D 1557 maximum dry density at optimum moisture ±2%.
In areas other than the building pad which are to receive area concrete slabs, the ground surface
should be scarified to 12 inches, moisture conditioned to at optimum moisture ±2% and recompacted
to a minimum.of 90% of ASTM D 15 5 7 maximum density just prior to concrete placement.
Landmark Consultants, Inc. Pa -e 10
�roposed Coral Mountain Estates — La Quinta. CA LCI Report No. LP05098
Trench Backfill: On-site soil free of debris, vegetation, and other deleterious matter may be suitable
for use as utility trench backfill. Backfill soil within roadways should be placed in layers not more
than 6 inches in thickness and mechanically compacted to a minimum of 90% of the ASTM D 1557
maximum dry density except for the top 12 inches of the trench which shall be compacted to at least
90%. Native backfill should only be placed and compacted after encapsulating buried pipes with.
suitable bedding and pipe envelope material. Pipe envelope/bedding should either be clean sand
(Sand Equivalent SE>30) or crushed rock when encountering groundwater. A geotextile filter fabric
(Mirafi 140N or equivalent) should be used to encapsulate the crushed rock to reduce the potential
for in -washing of fines into the gravel void space. Precautions should be taken in the compaction of
the backfill to avoid damage to the pipes and structures.
Moisture Control and Drainape: The moisture condition of the building pad should be maintained
during trenching and utility installation until concrete is placed or should be rewetted before
initiating delayed construction.
Adequate site drainage is essential to future performance of the project. Infiltration of excess
irrigation water and storm waters can adversely affect the performance of the subsurface soil at the
site. Positive drainage should be maintained away from all structures (5% for 5 feet minimum across
unpaved areas) to prevent ponding and subsequent saturation of the native clay soil. Gutters and
downspouts may be considered as a means to convey water -away from foundations. If landscape
irrigation is allowed next to the building, drip irrigation systems or lined planter boxes should be
used'. The subgrade soil should be maintained in a moist, but not saturated state, and not allowed to
dry out., Drainage should be maintained without ponding.
Observation and Densi!y Testing: All site pieparation and fill placement should be continuously
observed and tested by a representative of a qualified geotechnical engineering firm. Full-time
observation services during the excavation and scarification process is necessary to detect
undesirable materials or conditions and soft areas that may be encountered in the construction area.
The geotechnical firm that provides observation and testing during construction shall assume the
responsibility of "geotechnical engineer ofrecord' and, as such, shall perform additional tests and
investigation as necessary to satisfy themselves as to the site conditions and the recommendations for
site development.
Landmark Consultants, Inc. Page I I
Proposed Coral Mountain Estates — La Quinta, CA LCI Report No. LP05098
AuxiliM Structures Foundation Preparation: Auxiliary structures such as free standing or retaining
walls should have the existing soil beneath the structure foundation prepared in the manner
recommended for the building pad except the preparation needed only to extend 18 inches below and
beyond the footing.
4.2 Foundations and Settlements
Shallow spread footings and continuous wall footings are suitable to support the structures provided
they are structurally tied with grade -beams to resist differential movement. Footings shall be
founded on a layer of properly prepared and compacted soil as described in Section 4. 1. The
foundations may be designed using an allowable soil bearing pressure of 1,500 psf. The allowable
soil pressure may be increased by 20% for each foot of embedment depth in excess of 18 inches and
by one-third for short term loads induced by winds or seismic events. The maximum allowable soil
pressure at increased embedment depths shall not exceed 2,500 psf.
All exterior and interior foundations should be embedded a minimum of 18 inches below the
building support pad or lowest adjacent final grade, whichever is deeper. Interior footings may be 12
inches deep. Continuous wall footings should have a minimum width of 12 inches. Spread footings
should have a minimum dimension of 24 inches. Recommended concrete reinforcement and sizing
for all footings should be provided by the structural engineer.
Resistance to horizontal loads will be developed by passive earth pressure on the sides of footmigs
and frictional resistance developed along the bases of footings and concrete slabs. Passive resistance
to lateral earth pressure may be calculated using an equivalent fluid pressure of 300 pcf for sands to
resist lateral loadings. The top one foot of embedment should not be considered in computing
passive resistance unless the adjacent area is confined by a stab or pavement. An allowable friction
coefficient of 0.35 for sands may also be used at the Lse of the footings to resist lateral loading.
Foundation movement under the estimated static (non-seisn-tic) loadings and static site conditions are
estimated to not exceed '/4inch with differential movement of about two-thirds of total movement for
the loading assumptions stated above when the subgrade preparation guidelines given above are
followed.
Landmark Consultants, Inc. Page 122
Rro2osed Coral Mountain Estates — La Quinta. CA LCI Report No. LP05098
4.3 Slabs -On -Grade
Concrete slabs and flatwork should be a minimum of 4 inches thick. Concrete floor slabs may either
be monolithically placed with the foundation or dowelled after footing placement. The concrete
slabs may be placed on granular subgrade that has been compacted at least 90% relative compaction
(ASTM D 1557) and moistened to near optimum moisture just before the concrete placement
To provide protection against vapor or water transmission through the slabs, we recommend that the
slabs -on -grade be underlain by a layer of clean concrete sand at least 4 inches thick. To provide
additional protection against water vapor transmission through the slab in areas where vinyl or other
moisture -sensitive floor covering is planned, we recommend that a I 0 -mil thick impermeable plastic
membrane (visqueen) be placed at mid -height within the sand layer. The vapor inhibitor should be
installed in accordance with the manufacturer's instructions. We recommend that at least a 2 -foot
lap be provided at the membrane edges or that the edges be sealed.
Concrete slab and flatwork reinforcement should consist of chaired rebar slab reinforcement
(minimum of No. 4 bars at 18 -inch centers, both horizontal directions) placed at slab mid -height to
resist potential swell forces and cracking. Slab thickness and steel reinforcement are minimums only
and should be verified by the structural engineer/designer knowing the actual project loadings. All
steel components of the foundation system should be protected from corrosion by.maintaining a. 3-
..........
inch rainimurn concrete cover of densely consolidated concrete at footings (by use of a vibrator).
The construction joint between the foundation and any mowstrips/sidewalks placed adjacent to
foundations should be sealed with a polyurethane based non -hardening sealant to prevent moisture
migration between thejoiht. Epoxy coated embedded steel components or permanent waterproofing
membranes placed at the exterior footing sidewall may also be used to mitigate the corrosion
potential of concrete placed in contact with native soil.
Control joints should be provided in all concrete slabs -on -grade at a maximum spacing (in feet) of 2
to 3 times the slab thickness (in inches) as recommended by American Concrete Institute (ACI)
guidelines. All joints should form approximately square patterns to reduce randomly oriented
contraction cracks. Contraction joints in the slabs should be tooled at the time of the pour or sawcut
(V4 of slab dep th) within 6 to 8 hours of concrete placement. Construction (cold) joints in
foundations and area flatwork should either be thickened butt -joints with dowels or a thickened
keyed -joint designed to resist vertical deflection at the joint. All joints in flatwork should be sealed
Landmark Consultants, Inc. Pacye 13
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Proposed Coral Mountain Estates — La Quinta. CA LCI Report No. LP05098
to prevent moisture, vermin, or foreign material intrusion. Precautions should be taken to prevent
curling of slabs in this and desert region (refer to ACI guidelines).
All independent flatwork (sidewalks, driveways, patios) should be underlain by 2 inches of concrete
sand or aggregate base, dowelled to the perimeter foundations where adjacent to the building and
sloped 2% or more away from the building. A minimum of 24 inches of moisture conditioned (2%
minimum above optimum) and compacted subgrade (90%) and a 10 -mil (minimum) polyethylene
separation should underlie the flatwork containing steel reinforcing (except wire mesh). All flatwork
should be j ointed in square patterns and at irregularities in shape at a maximum spacing of 10 -feet or
the least width of the sidewalk. Driveway slabs should have a thickened edge extending a minimum
of 4 inches below a 4 -inch sand or aggregate base course which should be compacted to a minimum
of 90% of ASTM D 155 7 maximum density.
4.4 Concrete Mixes and Corrosivity
Selected chemical analyses for corrosivity were conducted on bulk samples of the near surface soil
from the project site (Plate C-4). The native soils have low level of sulfate ion concentration (212
ppm). Sulfate ions in high concentrations can attack the cementitious material in concrete, causing
weakening of the cement matrix and eventual deterioration by raveling ------
A minimum of 2,500 psi concrete of Type 11 Portland Cement with a maximum water/cement ratio
of 0.60 (by weight) should be used for concrete placed in contact with native soil on this project
(sitework including streets, sidewalks, driveways, patios, and foundations).
The native soil has moderate level of chloride ion concentration (260 ppm). Chloride ions can cause
corrosion of reinforcing steel, anchor bolts and other buried metallic conduits. Resistivity
determinations on the soil indicate severe potential for metal loss because of electrochemical
corrosion processes. Mitigation of the corrosion of steel can be achieved by using steel pipes coated
with epoxy corrosion inhibitors, asphaltic and epoxy coatings, cathodic. protection or by
encapsulating the portion of the pipe lying above groundwater with a minimum of 3 inches of
densely consolidated concrete. No metallic pipes or conduits should be placed belowfoundations.-
Landmark Consultants, Inc. Page 14
Proposed Coral Mountain Estates — La Quinta.. CA LCI Report No. LP05098
Foundation designs shall provide a minimum concrete cover of three (3) inches around steel
reinforcing or embedded components (anchor bolts, hold-downs, etc.) exposed to native soil or
landscape water (to 18 inches above grade). If the 3 -inch concrete edge distance cannot be achieved,
all embedded steel components (anchor bolts, hold-downs, etc.) shall be epoxy dipped for corrosion
protection or a corrosion inhibitor and a permanent waterproofing membrane shall be placed along
the exterior face of the exterior footings. Additionally, the concrete should be thoroughly vibrated at
footings during placement to decrease the permeability of the concrete.
4.5 Excavations
All site excavations should conform to CalOSHA requirements for Type C soil. The contractor is
solely responsible for the safety of workers entering trenches. Temporary excavations with depths of
4 feet or less may be cut nearly vertical for short duration. Temporary slopes should be no steeper
than 1.5:1 (horizontal:vertical). Sandy soil slopes should be kept moist, but not saturated, to reduce
the potential of raveling or sloughing.
Excavations deeper than 4 feet will require shoring or slope inclinations in conformance to
CAL/OSHA regulations for Type C soil. Surcharge loads of stockpiled soil or construction materials
should be, set back from thl�jop of the slope a minim distance equal to the.heigbt of the slo e. All
Urn T
permanent slopes should not be steeper than 3:1 to reduce wind and rain erosion. Protected slopes
with ground cover may be as steep as 2: 1. However, maintenance with motorized equipment may
not be possible at this inclination.
4.6 Lateral Earth Pressures
Earth retaining, structures, such as retaining walls, should be designed to resist the soil pressure
imposed by the retained soil mass: Walls with granular drained backfill may be designed for an
assumed static earth pressure equivalent to that exerted by a fluid weighing 3 5 pcf for unrestrained
(active) conditions (able to rotate 0. 1 % of wall height), and 5 5 pcf for restrained (at -rest) conditions.
These values should be verified at the actual wall locations during construction.
Landmark Consultants, -Inc. Page 15
Z__
P.ro2osed Coral Mountain Estates — La Quinta. CA LCI Report No. LP05098
When applicable seismic earth pressure on walls may be assumed to exert a uniform pressure
distribution of 7.5H psf against the back of the wall, where H is the height of the backfill. The total
seismic load is assumed to act as a point load at 0.6H above the base of the wall.
Surcharge loads should be considered if loads are applied within a zone between the face of the wall
and a plane projected behind the wall 45 degrees upward from the base of the wall. The increase in
lateral earth pressure acting uniformly against the back of the wall should be taken as 50% of the
surcharge load within this zone. Areas of the retaining wall subjected to traffic loads should be
designed for a uniform surcharge load equivalent to two feet of native soil.
Walls should be provided with backdrains to reduce the potential for the buildup of hydrostatic
pressure. The drainage system should consist of a composite HDPE drainage panel or a 2 -foot wide
zone of free draining crushed rock placed adjacent to the wall* and extending 2/3 the height of the
wall. The gravel should be completely enclosed in an approved filter fabric to separate the gravel
and backfill soil. A perforated pipe should be placed perforations down at the base of the permeable
material at least six inches below finished floor elevations. The pipe should be sloped to drain to an
appropriate outlet that is protected against erosion. Walls should be properly waterproofed. The
project geotechnical engineer should approve any alternative drain system.
4.7 Seismic Design
This site is located in the seismically active southern California area and the site structures are
subject to strong ground shaking due to potential fault movements along the San Andreas Fault.
Engineered design and earthquake -resistant construction are the common solutions to increase safety
and development of seismic areas. Designs should comply with the latest edition of the CBC for
Seismic Zone 4 using the seismic coefficients given in Section 3.4 of this report. This site lies
within 14.3 kin of a Type A fault overlying S,, (stiffi soil.
4.8 Pavements
Pavements should be designed according to CALTRANS or other acceptable methods. Traffic
indices were not provided by the project engineer or owner; therefore, we have provided structural
Landmark Consultants, Inc. Page 16
Proposed Coral Mountain Estates — La Quinta. CA LCI Report No. LP05098
sections for several traffic indices for comparative evaluation. The public agency or design engineer
should decide the'appropriate traffic index for the site. - Maintenance of proper drainage is necessary
to prolong the service life of the pavements. Based on the current State of California CALTRANS
method, an estimated R -value of 40 for the subgrade soil and assumed traffic indices, the following
table provides our estimates for asphaltic concrete (AC) pavement sections.
RECOMMENDED PAVEMENTS SECTIONS
R -Value of Subgrade Soil - 40 (estimated) Design Method - CALTRANS 1990
Traffic
Flexible Pavements
Asphaltic
Aggregate
Index
Concrete
Base
(assumed)
Thickness
Thickness
5-0
3.0
4.5
6.0
3.5
6.0
7.0
4.5
6.5
8.0
.5.0
8.5
Notes:
1) Asphaltic concrete shall be Ciltrans, Type B, 3/4inch maximum medium grading, (Y2inch for
parking areas) compacted to a minimum of 95% of the 50-blo.W Marshall density (ASTM
D1559).
2) Aggregate base shall conform to Caltrans Class 2 (3/4 in. maximum), compacted to a
minimum of 95% of ASTM D1557 maximum dry density.
3) Place pavements on 8 inches of moisture conditioned (minimum 4% above optimum) native
soil compacted. to a minimum of 90% of the maximum dry density determined by ASTM
D1557.
Final recommended section may need to be based on sampling and R-Value.testing during grading
operations when actual subgrade soils will be exposed.
Landmark Consultants, Inc. Page 17
Pro2osed Coral Mountain Estates - La Quinta. CA -LCI Report No. LP05098
Section 5
LIMITATIONS AND ADDITIONAL SERVICES
5.1 Limitations
The recommendations and conclusions within this report are based on current informati . on regarding
the proposed Coral Mountain Estates residential development located near the southwest comer of
Avenue 60 and Madison Street south of La Quinta, California. The conclusions and
rfcommendations of this report are invalid if.
Structural loads change from those stated or the struct ures are relocated.
The Additional Services section of this report is not followed.
This report is used for adjacent or other property.
Changes of grade or groundwater occur between the i ' ssuance of this report and
construction other than those anticipated in this report.
Any other change that materially alters the project from that proposed at the time this
report was prepared.
Findings and recommendations in this report are based on selected points'of field exploration,
geologic literature, laboratory testing, and our understanding of the proposed project. Our analysis of
data and recommendations presented herein are based on the assumption that soil conditions do not
vary significantly from those found at specific exploratory locations. Variations in soil conditions
can exist between and beyond the exploration points or groundwater elevations may change. If
detected, these conditions -may require additional studies, consultation, and possible design revisions.
Th is report contains information th at may be useful in th e preparation of contract specifications.
However, the report is not worded is such a manner that we recommend its use as a construction
specification document without proper modification. The use of information contained in this
reportfor bidding purposes should be done at the contractor's option and risk
This report was prepared according to the generally accepted geotechnical engin eering standards of
practice that existed in Riverside County at the time the report was prepared. No express or implied
warranties are made in connection with our services. This report should be considered invalid for
periods after two years from the report date without a review of the validity of the findings and
recommendations by our firm, because of potential changes in the Geotechnical Engineering
Standards of Practice.
Landmark Consultants, Inc. Page 18
Proposed Coral Mountain Estates — La Quinta. CA LCI Report No. LP05098
The client has responsibility to see that all parties to the project including, designer, contractor, and
subcontractor are made aware of this entire report. The use of information contained in this report
for bidding purposes should be done at- the contractor's option and risk.
5.2 Additional Services
We recommend that Landmark Consultants, Inc. be retained as the geotechnical consultant to
provide the tests and observations services during construction. If Landmark Consultants does not
provide such services then the geotechnical engineeringfirm providing such tests and observations
shall become the geotechnical engineer of record and assume responsibilityfor the project.
The recommendations presented in this report are based on the assumption that:
Consultation during development of design and construction documents to check that the
geotechnical recommendations are appropriate for ' -the'proposed project and that the
geotechnical recommendations are properly interpreted and incorporated into the
documents.
Landmark Consultants will have the opportunity to review and comment on the plans and
specifications for the project prior to the issuance of such for bidding.
Continuous observation, inspection, and testing by'the geotechnical consultant of record
d -site clearing,- grading, excavation, placement of fills,"building ''pad and su*bg* r a*de'
preparation, and backfilling of utility trenches.
Observation of foundation excavations and reinforcing steel before concrete placement.
-Other consultation as necessary during design and construction.
We emphasize our -review of the project plans and specifications to check for compatibility with our
recommendations and conclusions. Additional information concerning the scope and cost of these
services can be obtained from our office.
Landmark Consultants, Inc.
Page 19
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CH, CL
(�T
..it CL
CH, 01.
A-7
A-7
A-4
A-4
A-4
A-4
A-2. A-3
A-2
A -3, A A
A4
A-2., A-4
A-2, A-4
k-2, A-3
�-4
A -7
L-6 A--7
L-4, A -7
0 1 7�5-100
o 1 1100
0 100
0
100
100
RIVERSIDE (COUNI-Y.
CATAFOIRNIA
7")-S-5
go -loo
A
ezmd
too
go -100
Frn.w
P
T, Lw- t�
limit.
100,
110-80
NY p
100
95--100
70-85
4G-55
N P-5
96-100
.......
NP
loo
too
70A5
40-55
--30
"P -5
too
too
It
100
95-100 i
50-60 l..
- -
25�45
N p
VJ-20
Im 1
go -too
7 0-M 1
20-430
NP -5
too
so -loo
50-60
NP
100
Igo
too
50-70
-1.5-45
100
50-70
Zi -45
95 -IW
9- too
TGlq5
13-30
NP -5
95-400
9b -100
80-100 1
50-70
15-30
NP -6
too
95 --too
-1-9
-65
1.5 --30
0
9& -loo
95-100
80-100 i
550w-701
15-30
73-00
50- LOO
5-35
NP
1.00
80-100
65-W
24"5
NP
go-ltx)
75-95
5 --is
....
N'P
0
IGO
100
75-tGO
95-100
*-95
5-15
--70 -'
. . .. 2&--V5
NP
n
0(34-100
100
100
50-W.)
95-100
90-05
..........
45-70
25-45
100
loo
60�40
30--50
15-25
NP --a
0
75-85
65-7 5
0
NP -8
0 1 7�5-100
o 1 1100
0 100
0
100
100
5-35
40-50
73-0.5
75--9.5
15-30
35-60
305-60
30--w
NP
5-10
25-35
1 i -M
25-35
too
'100
7")-S-5
go -loo
95-100
too
go -100
5-35
40-50
73-0.5
75--9.5
15-30
35-60
305-60
30--w
NP
5-10
25-35
1 i -M
25-35
71
SONWA�
So D_
Twnorvheata:
TO -:
Torriorthen tz part-
Rot�k outcrop, Part..
SOIL SURVM
DA3 i Wbo swd
M63 I Vwy Amy wwL owy ;AWy wnd, v�-;-y
q
Sol
Variubts".
(UnWHV Gamy
1 loamy Inc sand..._
r I
A X
j
q PMM-U4
i AW 110251
. . . . . ..............
Gp' SP
Sol,
ENE
A --�
AQ
A -i
W1
A 41
A -I
A-2, A-4
This mapping; unit W made up of two or awre daminant kinds of soiL See mappi-rig unit d4.,sc-ri-ptxci for the Commah;or.
behavior of Uhe whole mapping -unit.
naoisture density, mechanical analyses., liquid Unnit and
plasticity indes,
*In th 'stu
I e nwi or compaction test, a sample
of the W material is connj_-,.ct(?d several ti.nes witin a
C�nnstant C".)T"'�'active effort.. e'.'Ich time at a successively
ligher im,xistare cf-maent. ' "Ihe inoisture content in-
creases until the optinvurn moisture content is reache?
After bat the density decreases mith incm,,ase in
inoisture content. The highest density WAWA in the
compaction test is ternned �4-maxirnurn density"
Moisture-densi'Qty data are impaftant in construction,
for is a rule, optirnum is obt,-..xined if the soil is
compacted to About the m.axiruUm dry deasity wilen it
is at appro.ximatelly the ordiniurn nnoisture contenL
Physical and cherytical properties
Table 11 shows estirnated values for sevenal soil
characteristics ancl features that affe'ct I.-jehai'vior of
soils in er'.,�6neerjng use& These (shmaks are given
for each major horizoli, t1hic,, depths indicated, in the
typi,m) pedon of each so�ijl_ The estimiates are based on
Aeld observations and on Wt d9a for these and' si.milar
so i is.
WrnzeahiRtv is edhnawd on the basis of known re-
lationships aawng the schl characteristics observed in
the field.
particularly soll soudum, porosity, and gra-
dation Of teXtMe, that induence the downward move-
m�ent of walter in, the sail. The eslimates are for vertkal
water nanvernent vhen the ioil is saturatecL blot corp
sidered in the esthnates is lateral ��eepag-e or sue""i
transient soil feabires as Qwpans and surface crusts.
Pernieai)ility r M
. .f the soil ,an i 1portant factor to be
considered in QnWng an.d designiag drainage s- s -
y,
tem -3, in e-vall—atirig tile "n"ftentiai of sails for -_eptic.
tank systems and Kher waste S
systont and in
many otht.,r asppcts of hund ime and roanagernent.
A!7aihable frater va-pat!ity is rabeii (),,i the basis d,` ji.
soil characteristics that ijifhAence the abiMov of L. A0
soil to hold ovater and make it availabip to MlantL`
iniportant charac-teristics are content of Organic Mat�
ter, suit texture, ar,.6 soil �Arutture. Shallow-roo d'
.
plants are not likely to use the avaih% water fm j
the deeI*,r soil hnrizons. Available water capacity is OR':
opa b�
i-niportant factor in the choice of plants or cr to
:rrown and in the desig�m of irrigation sys-terins,
Sail reaction. is expressed as a mnge in pli
The range in pli of each major horizon is based on
rnany fie id checks. For many soils, the vjue_,3 have.:1,
been verified 'uy I-aboratory anaiyAes. Soii reaction L--i-�
hmportant in seMeting the ertips, ornamenbW plad) "
or ather plants to )e grown; in evaluating wh wnendl
raents for fertility and stabilization; and in evalaatinj,..-!.J:'
the corrosivity of soils.
Sa-Unity is expressed -is the elertrical conductivit�,
of the saturation extract. in NOW, per cenhineber
at 2-7) degreps C. Estiinates are based on field and-,
laboratory nneasurernents at rppreseritntive sites of v6e:i
noni.rr-igated Wis. The sal. -nit- r gated j
y of indlividual ir i.
-fields is affecte� by the qualitty, of the. irrigation Nvater,
and by the f�requeney off water 'LPP1iC1tifM. HEr.Ce;.
the sahnity of individual fieWs can e.iffrer greatly from
the value given. in table 11. SUinity afferts the suitr'
ability of a W fW cTGp prad-tuctian.. its stalbil-ity who
used as a constnuction material, and its potential to
corrode rnrefml and <,i-)nerete.
poteah'al de.pends mainly unon f -he
s 'J'
amomit and kfir!d of ckiy in dhe soi!. L.-kborat�ry mea-
surements of the swAling of undi.-sturbed clo(Lq were
mnd,� for niany soils. For others the s,;%'relling W-a—Z
e.-.ztiTY..au-,.d an the hasis of the kind and aninuat of My
in the W and on of* sinvular swils. The
size of the loai-1 and the niagn.._ud(-! of the (.--,hange in
_V: C LIP 'A
RIVE.r NT - A i �)XN I
204L
4f;' -tX1
love numn"
us
_V: C LIP 'A
RIVE.r NT - A i �)XN I
7nuw
' I
ioil nmoi3t-,'rrr- content also influence At swelling of
soils- Shrinkin-g� and sweliing of :-;orne soils can. cau*e
damage to budding foundations, %valls, ro-'ads,
and ot',
ki-3.r unless special deMgns are used.
A high srhriii,* -swpll potential indicates that special
desi,m added expenm? may be required if the
' t� '..ole"nte large �'Qlunje
plan"'PA, u -se of -�e SWI VAU not
changm,
Risk of corrxipu pertains to potential soMindwad
01
�VAIOTI
steel or con-cr'Ae. The rate, of (�orms;on o�** un(.,Qat;,d.
steel is related to soil rnois_t.ur�-, par6.-,1eiiz.,--, distrin-u-
tion, WO xcidity, and electrical conductivity ")� tl�'P
moil material, The isk: of corrosinn of c-o-nerete is
ba:3ed -nainly- on the sulfate content textur, and add-
ity of the soil. Protective rneasures for steel or more
resistant coneryte help to a%iniel or Wage
resul-ting from the corrosion. Uncoated steel inter-
secting soil bounda.rics or sod horizorn, is ri-ore sns-
cept'Me to corrasion than an KAW-Lation thatt is
entirely xithiin ore kind �,,f �*oii or within one M
Wzon'
Was% 1040r,3 RI -e LiZed tr: p-redict thie ero-r.libil.-ity
of a soil and its ltolerivtce to evosicn in relation th
3pecific, kinds of land use and tr-c—atment. "I"he soil
erodibilky factor (K) is a nneasiure (af the suweptHhMQ
of the sail to erosion by water, Soils having the hiNheg
it values are the most erodible K values range frorn
110 tv 011 To esti-mate annuM 301 loss per acre, the
K value of a sail is modified hy L�actw;.-s representing
plant mveq grade and length of slope. management
prMes. and Mtzk. The sail -lass folerance factor
(T) W Te maximuni rate of soD erosion, whether
finnn WOO or sail Iflowins, "I.-ii.A ca.n onicu--.- "A-ithout
reducing crop produnhon or winviraninental qualRy
6085
NP
NP
NP
The. r��te js e.-.ilprk�ssedl in von,-, of s.oill loss per acre per
YOM
Wi'd
-are .-nade up of soits that
have
in-611ar prupei:ties ih..at afffect their res-Litance to
soil blovoing U m4fvaWd. The gToups are used to
predkt t1he susc,,�ptibil.ity soil to -blowing and the
an,
of s.-.)il lost as a result of Wowing. Soils are
t.-,, Mhe following distinctions.
Sand, camse swids, fine sands, and viery fine sands.
These -are -;Fntremely en-Jible? so vegetation is
diOlcult to establ-.-�5h, They ar, generally �65't iditAble
f,ir crops,
Lo;?,my sands, loamy We sarnidst and loamy veq, Ane
sands These soil-;- are very highly erodible, but crops
can be grown if measures to cont-rol Soil
blowltr are used.
Sandly loanis, ro;?irse. sandy Iloams, fine s4indy loams,
and very fine sandy Warns. The,,e soils. are highly erod-
ible. but cropef Can be groam if intensive rneasures to
conhyl sAl Wawing are used.
Chileareous loamy iodis the ,ire less Hhan 35 percent
clay and mart? than 5 pervent finely divided calcium
carlmnate, Tlbiesk, soils are erodible. but crops can he
wrown if intenziv. rr.v;A.;ures to control soil blowing
,Ire use'd.
Clays, My clays, clay loarns, and Edity clay loams
flia', are more than 3. pereent clay- Thesse soils are
inoderMely erodible, but errqps can be grow -n if Yrea.-
sures to cantro! soil blowing are used.
I
L��amy soils that are less tiian *18 percent -y an.'
le.zs than 5 walm f-.n:ejy- divided calciurn Carbonate
and sandy clay loams s—andy clays that -Ire less
th-an 5 percent finellv divided ��_alciurn carbonate. These
sails ar ,a siighttl,; ei cdilwe, but croj.�;s can gro-wn
pnea�7jures to� C�mtru'l R�4L� used.
LAwny scills Hn;at ar,,- 1,� to _.115 percent day and less
love numn"
25
NP
i.5
36 A01
axe)
15"5
7nuw
' I
ioil nmoi3t-,'rrr- content also influence At swelling of
soils- Shrinkin-g� and sweliing of :-;orne soils can. cau*e
damage to budding foundations, %valls, ro-'ads,
and ot',
ki-3.r unless special deMgns are used.
A high srhriii,* -swpll potential indicates that special
desi,m added expenm? may be required if the
' t� '..ole"nte large �'Qlunje
plan"'PA, u -se of -�e SWI VAU not
changm,
Risk of corrxipu pertains to potential soMindwad
01
�VAIOTI
steel or con-cr'Ae. The rate, of (�orms;on o�** un(.,Qat;,d.
steel is related to soil rnois_t.ur�-, par6.-,1eiiz.,--, distrin-u-
tion, WO xcidity, and electrical conductivity ")� tl�'P
moil material, The isk: of corrosinn of c-o-nerete is
ba:3ed -nainly- on the sulfate content textur, and add-
ity of the soil. Protective rneasures for steel or more
resistant coneryte help to a%iniel or Wage
resul-ting from the corrosion. Uncoated steel inter-
secting soil bounda.rics or sod horizorn, is ri-ore sns-
cept'Me to corrasion than an KAW-Lation thatt is
entirely xithiin ore kind �,,f �*oii or within one M
Wzon'
Was% 1040r,3 RI -e LiZed tr: p-redict thie ero-r.libil.-ity
of a soil and its ltolerivtce to evosicn in relation th
3pecific, kinds of land use and tr-c—atment. "I"he soil
erodibilky factor (K) is a nneasiure (af the suweptHhMQ
of the sail to erosion by water, Soils having the hiNheg
it values are the most erodible K values range frorn
110 tv 011 To esti-mate annuM 301 loss per acre, the
K value of a sail is modified hy L�actw;.-s representing
plant mveq grade and length of slope. management
prMes. and Mtzk. The sail -lass folerance factor
(T) W Te maximuni rate of soD erosion, whether
finnn WOO or sail Iflowins, "I.-ii.A ca.n onicu--.- "A-ithout
reducing crop produnhon or winviraninental qualRy
6085
NP
NP
NP
The. r��te js e.-.ilprk�ssedl in von,-, of s.oill loss per acre per
YOM
Wi'd
-are .-nade up of soits that
have
in-611ar prupei:ties ih..at afffect their res-Litance to
soil blovoing U m4fvaWd. The gToups are used to
predkt t1he susc,,�ptibil.ity soil to -blowing and the
an,
of s.-.)il lost as a result of Wowing. Soils are
t.-,, Mhe following distinctions.
Sand, camse swids, fine sands, and viery fine sands.
These -are -;Fntremely en-Jible? so vegetation is
diOlcult to establ-.-�5h, They ar, generally �65't iditAble
f,ir crops,
Lo;?,my sands, loamy We sarnidst and loamy veq, Ane
sands These soil-;- are very highly erodible, but crops
can be grown if measures to cont-rol Soil
blowltr are used.
Sandly loanis, ro;?irse. sandy Iloams, fine s4indy loams,
and very fine sandy Warns. The,,e soils. are highly erod-
ible. but cropef Can be groam if intensive rneasures to
conhyl sAl Wawing are used.
Chileareous loamy iodis the ,ire less Hhan 35 percent
clay and mart? than 5 pervent finely divided calcium
carlmnate, Tlbiesk, soils are erodible. but crops can he
wrown if intenziv. rr.v;A.;ures to control soil blowing
,Ire use'd.
Clays, My clays, clay loarns, and Edity clay loams
flia', are more than 3. pereent clay- Thesse soils are
inoderMely erodible, but errqps can be grow -n if Yrea.-
sures to cantro! soil blowing are used.
I
L��amy soils that are less tiian *18 percent -y an.'
le.zs than 5 walm f-.n:ejy- divided calciurn Carbonate
and sandy clay loams s—andy clays that -Ire less
th-an 5 percent finellv divided ��_alciurn carbonate. These
sails ar ,a siighttl,; ei cdilwe, but croj.�;s can gro-wn
pnea�7jures to� C�mtru'l R�4L� used.
LAwny scills Hn;at ar,,- 1,� to _.115 percent day and less
34
Reference: USGS Topographic Map Site Coordinates
La Quinta, CA Quadrangle Lat: 33.612N
Scale 1:25,000 Long: 116.251W
LANWARK
Plate
IL Project No.: LP05046 Topographic Map A-4
I
R
A YCNUF�'.
Projed Site
2a
A
i
t
34
Reference: USGS Topographic Map Site Coordinates
La Quinta, CA Quadrangle Lat: 33.612N
Scale 1:25,000 Long: 116.251W
LANWARK
Plate
IL Project No.: LP05046 Topographic Map A-4
I
CLIENT: RT. Hughes Co., LLC METHOD OF DRILLING: CME 55 w/autohammer
PROJECT� Proposed Coral Mountain Estates - La Quinta, CA DATE OBSERVED: 04/22/05
LOCATION: See Site and Exploration Plan LOGGED BY: TB
LOG OF -BORING B-1 1
U)
It
x
W
UJ
UJ
Z
0 UJ
0
0
�2
Z
UJ
SHEET 1 OF 1
Z
q
LU W
a
Z
U.
S2
W
U)
U.
CL
LU
DESCRIPTION OF MATERIAL
U,
U)
u- Lu
Z CC
Z
(L
LU
U)
15 <
(a
2
(0
0
SURFACE ELEV.
1z
Z
0 0
0 CL
L) 2
Z 0
Cl)
5
CL
U)
<
(L
SILTY SAND (SM): Brown, humid, fine grained.
23
5-
15
medium dense
1.8
92.9
10-
17
SANDY SILT (ML): Brown, medium dense, damp.
3.2
90.4
15-
24
SILTY SAND/SANDY SILT (SM/ML)-. Brown, medium
1.0
98.2
MR
dense, humid, fine grained.
20-
19
-25-
11'
1�
17
-30-
- -
17
SANDY'SILT (ML): Olive brown, medium dense, damp.
-35-
24
SILTY SAND (SM)-. Brown, medium dense, damp,
fine grained.
-40-
22
45-
32
SANDY SILT (ML): Brown, dense, moist.
-50-
34
SILTY SAND (SM): Brown, dense, moist, fine grained.
End of Boring at 51.5 ft
-55-
4 No Groundwater Encountered
Blows not corrected for overburden pressure, sampler
size or increase drive energy for automatic hammers.
Project No:
LANI)MARK
Plate
LP05098
Geo -Engineers cnd Geologists
B-1
&'DArE/MaE/S'W 60"WWW
CLIENT: RT. Hughes Co., LLC METHOD OF DRILLING: CME 55 w/autohammer
PROJECT: Proposed Coral Mountain Estates - La Quinta, CA DATE OBSERVED: 04/22/05
LOCATION: See Site and Exploration Plan LOGGED BY: TB
I
LOG OF BORING B-2
i
x
W
W
0
(L
it:
0
0
2�
U1
CL
SHEET 1 OF 1
75
(L
UJ
U)
LU
DESCR I PT ION OF MATERIAL.
Z
a
W
E5
P
U1
P
0 Z
0
SURFACE ELEV.
(L
(L
SILTY SAND (SM): Brown, damp, fine grained, trace
of gravel.
17
med ium dense
5 -
13
_10-
I
N1
-15-
-20-
-25-
_30-
-35-
-40-
End of Boring at 14.0 ft
No Groundwater Encountered
Blows not corrected for overburden pressure, sampler
size or increase drive energy for automatic hammers.
Project No:
LANDMABK
Plate
LP05098
B-2
a DOZIMSEISBE C—p—y
CLIENT: RT. Hughes Co., LLC METHOD OF DRILLING: CME 55 w/autohammer
PROJECT: Proposed Coral Mountain Estates - La Quinta, CA DATE OBSERVED: 04/22/05
LOCATION: See Site and Exploration Plan LOGGED BY: TB
Z
LOG OF BORING B-3
U)
x i
LU
x
0
L)
0
0
W
0.
SHEET 1 OF 1
Z (a
it:
=
U1
DESCRIPTION OF MATERIAL
LU
a:
Z Cr
Z
us
U)
5
0
0
Z
00
n
>-
Ir
0 (L
L) 2
Z 0
co
cr 5
0
(a
co
a.
SURFACE ELEV.
20
0
0
CL
SILTY SAND (SM): Brown, damp, fine grained.
13
medium dense, humid
1.2
111.9
-5-
- -
17
1.1
103.3
-10-
All
N
18
-15-
- -
11-1-19.1
NI
15
-20-
-25-
-30-
-35-
-40-
End of Boring at 16.'5 ft
No Groundwater Encountered
**Blov�s not corrected for overburden pressure, sampler
size or increase drive energy for automatic hammers.
Project No:
LANDMARK
Plate
LP05098
B-3
DOEMBEISBE C�p—y
DEFINITION
OF TERMS
PRIMARY DIVISIONS
04
Loose
F
SECONDARY DIVISIONS
Coarse grained soils
More than half of
Gravels
More than half
of
coarse fraction
is
larger than No.
4 sieve
30-50
ro o cl
LE
[G7W
Well graded gravels, gravel -sand mixtures, little or no fines
Poorly graded gravels, or gravel -sand mixtures, little or n:.:f:in:es:::]
Gravel
with fines
8-16
FGM]J
Silty gravels, gravel -sand -silt mixtures, non -plastic fines
MF
GC]
Clayey gravels, gravel -sand -clay mixtures, plastic fines
material is larger
than No. 200 sieve
Sands
More than half
of coarse
fraction
s sma er than
No. 4 sieve
EFs—wll
Well graded sands, gravelly sands,, little or no fines
Poorly graded sands or gravelly sands. little or no fines
[IMFSMfl
I
Silty sands, sand -silt mixtures, non -plastic fines
Clayey sands, sand -day mixtures, plastic fines
Fine grained soils
More than half of
Silts and clays
Liquid limit is
less than 50%
MFm—L
11
Inorganic silts, clayey silts with slight plasticity
BF—ull
Inorganic clays of low to medium plasticity, gravely, sandy, or lean clays
OFOL11
Organic silts and organic clays of low plasticity
material is smalle
than No. 200 sieve
Silts and clays
Liquid limit is
more than 50%
M[MH]l
Inorganic silts. micaceous or diatomaceous silty soils, elastic silts
MCH]
Inorganic clays of high plasticity, fat clays
FoH]
0 anic; clays of medium to high plasticity, organic silts
Highly organic soifs
IME1
Peat and other highly organic soils
GRAIN
SIZES
Silts an��F
Sand
I Fine . medium coarse]l
Gravel
F
Fine
bl
200 4 10 4
US Sta ndard Series Sieve
ISands, Gravels, e
Very Loose
04
Loose
4-10
Medium Dense
10-30
Dense
30-50
Very Dense
Over 50
3/4" 3' 12"
Clear Square Openings
Clays & Plastic Sil&7
Blows/ft.
Very Soft
0-0.25
0-2
Soft
0.25-0.5
24
Firm
0.5-1.0
4-8
Stiff
1.0-2.0
8-16
Very Stiff
2.0-4.0
16-32
Hard
Over 4.0
Over IL__Jl
11
Number of blows of 140 lb. hammer falling 30 inches to drive a 2 inch O.D. (11 318 in. I.D.) split spoon (ASTM D1 586).
Unconfined compressive strength in tons/s.f. as determined by laboratory testing or approximated by the Standard
Penetration Test (ASTM D1 586). Pocket Penetrometer, Torvane, or visual observation.
Type of Samples:
Ring Sample Standard Penetration Test Shelby Tube 0 Bulk (Bag) Sample
Drilling Notes:
1. Sampling and Blow Counts
Ring Sampler - Number of blows per foot of a 140 lb. hammer failing 30 inches.
Standard Penetration Test - Number of blows per foot.
Shelby Tube - Three (3) inch nominal diameter tube hydraulically pushed.
2. P. P. = Pocket Penetrometer (tons/s.f.).
3. NR =No recovery.
4. GWT Ground Water Table observed @ specified time.
LANDMARK
C. -P. -Y Plate
Project No: LP05098 Key to Logs B-4
- - f-X'VF'
SIEVE ANALYSIS HYDROMETER ANALYSIS
Gravel
I Sand Silt and Clay Fraction
Coarse I Fine
I Coarse Medium Fine
100 10 1 0.1 0.01
Particle Size (mm)
100
)0
50
70 IM
Z
60
50
U)
40
30
20
10.
—� 0
0.001
LANDMARK
L- Geo -Engineers and Geologists
a DBEMB&SBE Co-pany Plate
Project No.: LP05098 Grain Size Analysis C-1
ICOLLAPSE POTENTIAL TEST (ASTM D53
2
Po
0
-2
-3
-4 Water
Added
co"agise,
Potel ia 0.51/6 (Slight)
LM
(D
-5
(D
CD
-6
-7
a)
0
(D
(L -8
-9
--10
-12 –
Silty Sand (SM)
B-1 @ 5.0 ft
-13 —
-14 1
0.1 11
10
100
Pressure (ksfl
Results of Test:
Initial
Final—
Dry Density, pcf:
92.9
99.2
Water Content, %:
1.8
25.3
Void Ratio, e:
0.782
0.670
Saturation, %:
6
100
LANDMARK
Geo -Engineers and Geologists
a DOEIMBEISBE Camp&" v
Collapse Potential
Plate
Project No: LP05098
Test Results
C-2
I L=
WI
1�_!9
145
140
135
130
12 5
Client:
RT Hughes Co., LLC
Project: Proposed Coral Mountain Estates
Project No:
LP05098
Date:
05/25/05
SUMMARY OF TEST RESULTS
D c
Description:
Silty Sand (SM)
Se
as
m
Sample Location:
B-1 @ 0-5 ft.
Test Method:
ASTM D 1 557A
Maximum Dry
Density (pc�:
121.5
0
Optimum Moisture
Content .
10.5
.... ---- - ------
120
115
110
105
I �Wfl
0 5 10 20 25 30
Moisture Content (%)
LANDMABK,
Geo -Engineers and Geologists
. a DBEIMBEISSE co—P.-Y Plate
Project No: LP05098 Moisture Density Relationihip C-3
LANDMARK CONSULTANTS, INC.
CLIENT: RT Hughes Co, LLC
PROJECT: Coral Mountain Estates, La Quinta, CA
JOB NO: LP05098
DATE: 05/26/05
CHEMICAL ANALYSES
Boring: B-2
CalTrans
Sample Depth, ft 0-5
Method
pH- 6.82
643
Resistivity (ohm -cm): 1,500
643
Chloride (Cl), ppm-. 260,
422
Sulfate (SO4), ppm-. 212
417
General Guidelines for Soil Corrosivity
Material Chemical Amount in
Degree of
Affected Agent Soil (Ppm�_
Corrosivitv
Concrete.-... -Soluble 0-1000
Low
Sulfates 1000-2000
Moderate
2000-20000
Severe
> 20000
Very Severe
Normal Soluble 0-200
Low
Grade Chlorides 200-700
Moderate
Steel 700-1500
Severe
> 1500
Very Severe
Normal Resistivity 1-1000
Very Severe
+
Grade 1000-2000
Severe
Steel 2000-10,000,
Moderate
10,000+
Low
LANDMARK
Geo -Engineers and Geologists I i Selected Chemical Plate
a DOEIMS-EISRH COMPO"y
Project No: LP05098 Analyses Results C
SUMMARY OF INFILTRATION TESTING
Client: RT. Hughes Co, LLC. Date Excavated: 04/22/05
Project: Proposed Coral Mountain Estates Technician: JB
Job No.: LP05098 Location: See Site and Exploration Plan
Date: 05/24/05 Soil Type: Silty Sand (SM)
Test Hole -No.: 1-1 Total Depth of Test Hole: . 3 ft.
11
Total
Initial
Final
Fall
Reading
Time
Elapsed
Water
Water
in Water
Stabilized
Rate
0.
Time
Interval
Time
Level
Level
Level
Drop
(min)
(min)
(in.)
(in.)
(in.)
(min/in)
gal/hr/sft
1
15
5
0.00
1.00.
.1.00
2
15
30
0.00
1.50
1.50
3
15
45
0.00
1.00
1.00
4
15
60
0.00
1.50
-1.50
5
30
90
0.00
3.00
3.00
6
30
120
0.00
3.50
3.50
7
60
180
0.00
5.00
5.00
8
60
240
0.00
4.75
4.75
9
60
300
0.00
4.75
4.75
10
60
360
0.00
4.75
4.75
12.47
3.00
SUMMARY OF INFILTRATION TESTING
Client: RT. Hughes Co, LLC.
Project: Proposed Coral Mountain Estates
Job No.: LP05098
Date: 05/24/o5
Test Hole No.: 1-2
Date Excavated: 04/22/05
Technician: JB
Location:' See Site and Exploration Plan
Soil Type: Silty Sand (SM)
Total Depth of Test Hole: 3 ft.
Total
Initial
Final
Fall
Reading
Time
Elapsed
Water
Water
in Water
Stabilized
Rate
No.
Time
Interval
Time
Level.
'(in.)
Level
Level
Drop
I (min)
(min)
I
I (in.)
(in.)
(min/in)
gal/hr/sft
1
15
15,
0.00
2.75
2.75
2,
15
30
0.00
2.75
2.75
3
15
45
0.00
2.50
2.50
4
15
60
0.00
2.50
2.50
5
30
90
0.00
5.00
5.00
6
30
0.00
5.25
5.25
7
60
180'
0.00
8.00
8.00
8
60
240
0.00
8.00
8.00
9
60
300
0.00
8.50
8.50
10
60
360
0.00
8.00
8.00
7.38
5.07
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tdquir�inents and commentary.
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