04-4484 (CSCS) Geotechnical Reportf
99 CENTS ONLY STORES
5010 NORTH PARKWAY CALABASAS, SUITE 200
CALABASAS, CALIFORNIA 91302
GEOTECHNICAL ENGINEERING REPORT
PROPOSED RETAIL
COMMERCIAL DEVELOPMENT
NWC HIGHWAY 111
AND JEFFERSON STREET
LA QUINTA, CALIFORNIA
February 19, 2004
0 2004 Earth Systems Southwest
Unauthorized use or copying of this document is strictly prohibited
without the express written consent of Earth Systems Southwest.
File No.: 09514-01 ..
04-02-755
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�j Earth Systems
�� Southwest 79-811B Country Club Drive
Bermuda Dunes, CA 92201
(760)345-1588
(800)924-7015
FAX (760) 345-7315
February 19, 2004
99 Cents Only Stores
5010 North Parkway Calabasas, Suite 200
Calabasas, California 91302
Attention: Mr. Doug Digison
Project: Proposed Retail Commercial Development
NWC Highway 111 and Jefferson Street
La Quinta, California
Subject: GEOTECHNICAL ENGINEERING REPORT
Dear Mr. Digison:
File No.: 09514-01
04-02-755
We take pleasure in presenting this geotechnical engineering report prepared for the proposed
retail commercial development to be located on the west side of the existing Home Depot off the
northwest corner of the intersection of Highway 111 and Jefferson Street in the City of La
Quinta, California.
This report presents our findings and recommendations for site grading and foundation design,
incorporating the information provided to our office. The site is suitable for the proposed
development, provided the recommendations in this report are followed in design and
construction. In general, the upper soils should be compacted to improve bearing capacity and
reduce settlement. The site is subject to strong ground motion from the San Andreas fault.
Electrical resistivity of the near surface soils indicates a moderate corrosion potential. This
report should stand as a whole and no part of the report should be excerpted or used to the
exclusion of any other part.
This report completes our scope of services in accordance with our agreement dated January 12,
2004. Other services that may be required, such as plan review and grading observation, are
additional services and will be billed according to our Fee Schedule in effect at the time services
are provided. Unless requested in writing, the client is responsible for distributing this report to
the appropriate governing agency or other members of the design team.
We appreciate the opportunity to provide our professional services. Please contact our office if
there are any questions or comments concerning this report or its recommendations.
Respectfully submitted,
EARTH SYSTEMS SOUTHWEST
Shelton L. Stringer
GE 2266
SER/sls/reh
Distribution: 6/99 Cents Only Stores
1/RC File; 2/BD File
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. i
TABLE OF CONTENTS
Page
EXECUTIVESUMMARY................................................................................................ ii
1.0 INTRODUCTION..............................................................................................................1
1.1 Project Description.................................................................................................. 1
1.2 Site Description....................................................................................................... 1
1.3 Purpose and Scope of Work.................................................................................... 2
2.0 METHODS OF INVESTIGATION.................................................................................3
2.1 Field Exploration................................................................................................... 3
" 2.2 Laboratory Testing.................................................................................................. 3
3.0
DISCUSSION.....................................................................................................................4
3.1
Soil Conditions........................................................................................................
4
3.2
Groundwater...........................................................................................................
4
3.3
Geologic Setting......................................................................................................
4
3.4
Geologic Hazards....................................................................................................
5
3.4.1 Seismic Hazards..........................................................................................
5
3.4.2 Secondary Hazards......................................................................................
6
3.4.3 Site Acceleration and Seismic Coefficients ................................................
7
4.0
CONCLUSIONS................................................................................................................9
5.0
RECOMMENDATIONS
.................................................................................................10
5.1
Site Development — Grading.................................................................................
10
5.2
Excavations and Utility Trenches.........................................................................
11
5.3
Slope, Stability of Graded Slopes..........................................................................
11
STRUCTURES.................................................................................................................
12
5.4
Foundations...........................................................................................................12
5.5
Slabs-on-Grade.....................................................................................................
13
5.6
Mitigation of Soil Corrosivity on Concrete..........................................................
14
5.7
Seismic Design Criteria........................................................................................
14
5.8
Retaining Walls and Below -grade Walls...........................:..................................
15
5.9
Pavements.............................................................................................................
16
6.0
LIMITATIONS AND ADDITIONAL SERVICES......................................................17
6.1
Uniformity of Conditions and Limitations...........................................................
17
6.2
Additional Services...............................................................................................
18
REFERENCES................................................................................................................19
APPENDIX A
Site Location Map
Boring Location Map
Table 1 Fault Parameters
2003 International Building Code (IBC) Seismic Parameters
Logs of Borings
APPENDIX B
Laboratory Test Results
EARTH SYSTEMS SOUTHWEST
11
EXECUTIVE SUMMARY
j' Earth Systems Southwest has prepared this executive summary solei
overview of the report. The report itself should be relied upon for yinforpmation about the
findings, conclusions, recommendations, and other concerns.
The site is located on the west side of the existing Home Depot off the northwest corner of the
intersection of Highway 111 and Jefferson Street in the City of La Quinta, California. The
proposed development will consist of a retail commercial development of four attached retail
units. We anticipate that the proposed structures will be wood -frame and stucco const
supported with perimeter wall foundations and concrete slabs -on -grade. ruction
It is our professional opinion that the proposed project may be constructed as planned ro
vided
that the recommendations in this report are 'incorporated In the final design and construction.
Site development will include clearing and grubbing of vegetation, site grading, buildingad
preparation, underground utility installation, drive lanes and parking lot construction,
landscaping, and concrete driveway and sidewalks placement. Based on the non-uniform nature
and hydro -collapse potential of the near surface fill soils, remedial site grading is recommended
to provide uniform support for the foundations.
We consider the most significant geologic hazard to the project to be the potential for moderate
to severe seismic shaking that is likely to occur during the design life of the proposed structures.
The project site is located in the highly seismic Southern California region within the influence
of several fault systems that are considered to be active or potentially active. The site is located
in Seismic Zone 4 of the 2001 California Building Code (CBC). Structures should be designed
in accordance with the values and parameters given within the CBC- The seismic dei n
parameters are presented in the following table and within the report. g
EARTH SYSTEMS SOUTHWEST
111
SUMMARY OF RECOMMENDATIONS
f��Design Item Recommended Parameter Reference Section No.
Foundations
Allowable Bearing Pressure
Continuous wall footings
1 500sf
p
Pad Column footings
2,000. sf
5.4
Foundation Type
Spread Foundations
5.4
Bearin Materials
En ineered fill
Allowable Passive Pressure
250 cf
Active Pressure
30 cf
5.4
At rest Pressure
50 cf
5.8
Allowable Coefficient of Friction5.8
0.35
. Soil Ex ansion Potential
Very low EI<20
5.4
Geolo is and Seismic Hazards
3.1
Liuefaction Potential
Ne li ible
Si nificant Fault and Ma nitude
Fault
San Andreas, M7.7
3.4.2
3.4.3; 5.7
T e
A
Seismic Zone
3.4.3; 5.7
Soil Profile Type
4
3.4.3; 5.7
Near -Source Distance
So
Seismic Coefficient, NA
8.1 km
3.4.3; 5.7
Seismic Coefficient, Nv
1.08
3.4.3; 5.7
Pavement
1.35
3.4.3; 5.7
TI = 4.0 (Auto Parking Areas)
2.5" AC / 4.0" AB
TI = 7.0 (Truck Access
4.0"AC/8.0"AB
5.9
Slabs
5.9
Buildin Floor Slabs
On en ineered fill
5.5
Modulus of Sub rade Reaction
200
Existin Site Conditions
ci
5.5
Existin Fill
2 feet
Soil Corrosivity
low sulfates
3.1
low chlorides
5.6
Groundwater Depth
moderate corrosivi
Presently about 100 feet,
Estimated Fill and Cut
Historic hi h 70 feet
3.2
includes over -excavation
3 feet -fill
5 feet
1.1
- cut
The recommendations contained within this report are subject to the
Section 6 of this report. We
limitations presented in
recommend that all individuals using this report
read the limitations.
EARTH SYSTEMS SOUTHWEST
T February 19, 2004
GEOTECHNICAL ENGINEERING REPORT
PROPOSED RETAIL
COMMERCIAL DEVELOPMENT
NWC HIGHWAY 111 I.
AND JEFFERSON STREET
LA QUINTA, CALIFORNIA
1.0 INTRODUCTION
1.1 Project Description
File No.: 09514-01
04-02-755
This geotechnical engineering report has been prepared for the proposed retail commercial
development to be located on the west side of the existing Home Depot off the northwest corner
of the intersection of Highway 111 and Jefferson Street in the City of La Quinta, California.
The proposed development will include four attached units varying in size from 9,750 to 23,000
square feet. Each unit will be a one-story structure. The two larger units will have loading docks
along the north side of the buildings. We understand that the proposed structures will be of
wood -frame and stucco construction and will be supported by conventional shallow continuous
or pad footings. .
Site development will include clearing and grubbing of vegetation, site grading, building pad
preparation, underground utility installation, drive lanes and parking lot construction,
landscaping, and concrete driveway and sidewalks placement. Based on existing site topography
and ground conditions, site grading is expected to consist of fills not exceeding 3 feet and cuts of
about 5 feet (including over -excavation).
We assumed a maximum column load of 40 kips and a maximum wall loading of 3 kips per
linear foot as a basis for the foundation recommendations. All loading is assumed to be dead
plus actual live load. If the actual structural loading exceeds these assumed values, we would
need to reevaluate the given recommendations.
1.2 Site Description
The site of the proposed retail commercial development is located off the northwest corner of the
intersection of Highway 111 and Jefferson Street in the City of La Quinta, California. The site is
currently vacant of structures and consists of previously graded pads. The site is located south of
and adjacent to the Whitewater River Channel. The southern embankment of the channel has
been lined with concrete in the vicinity of the project site. The site location is shown on Figure 1
in Appendix A.
The project site is sparsely vegetated with some shrubs. Evidence of old irrigation pipes was
seen across the site and dumped concrete blocks were observed at the west end of the site. The
history of past use and development of the property was not investigated as part of our scope of
services. Nonetheless, some previous development of the site is possible. Buried remnants such
as old foundations, slabs, or septic systems may exist on the site. There may be underground
utilities near .and within the building area. These utility lines include, but are not limited to,
domestic water, electric, sewer, telephone, cable, and irrigation lines.
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1.3 Purpose and Scope of Work
The purpose for our services was to evaluate the site soil conditions and to provide professional
opinions and recommendations regarding the .proposed development of the site. The scope of
work included the following:.
➢ A general reconnaissance of the site.
➢ Shallow subsurface exploration by drilling six exploratory borings to depths ranging from
19 to 31.5 feet.
➢ Laboratory testing of selected soil samples obtained from the exploratory borings.
➢ A review of selected published technical literature pertaining to the site.
➢ An engineering analysis and evaluation of the acquired data from the exploration and
testing programs.
• ➢ A summary of our findings and recommendations in this written report.
This report contains the following:
➢ Discussions on subsurface soil and groundwater conditions.
➢ Discussions on regional and local geologic conditions.
➢ Discussions on geologic and seismic hazards.
➢ Graphic and tabulated results of laboratory tests and field studies.
➢ Recommendations regarding:
• Site development and grading criteria.
Excavation conditions and buried utility installations.
• Structure foundation type and design.
• Allowable foundation bearing capacity and expected total and differential settlements.
• Concrete slabs -on -grade.
• - Mitigation of the potential corrosivity of site soils to concrete and steel reinforcement.
• Seismic design parameters.
Preliminary pavement structural sections.
Not Contained in This Report: Although available through Earth Systems Southwest, the current
scope of our services does not include:
➢ A corrosive study to determine cathodic protection of concrete or buried pipes.
➢ An environmental assessment.
➢- An investigation for the presence or absence of wetlands, hazardous or toxic materials in
the soil, surface water, groundwater, or air on, below, or adjacent to the subject property.
EARTH SYSTEMS SOUTHWEST
February 19, 2004 3 File No.: 09514-01
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2.0 METHODS OF INVESTIGATION
2.1 Field Exploration
Six exploratory borings were drilled to depths ranging from 19 to 31.5 feet below the existing
ground surface to observe the soil profile and to obtain samples for laboratory testing. The
borings were drilled on January 27, 2004 using 8 -inch outside diameter hollow -stem augers,
powered by a CME 75 truck -mounted drilling rig. The boring locations are shown on the boring
location map, Figure 2, in Appendix A. The- locations shown are approximate, established by
pacing and sighting from existing topographic features.
Samples were obtained within the test borings using a Standard Penetration (SPT) sampler
(ASTM D 1586) and a Modified California (MC) ring sampler (ASTM D 3550 with shoe similar
to ASTM D 1586). The SPT sampler has a 2 -inch outside diameter and a 1.38 -inch inside
diameter. The MC sampler has a 3 -inch outside diameter and a 2.37 -inch inside diameter. The
samples were obtained by driving the sampler with a 140 -pound hammer, manually activated by
rope and cathead, dropping 30 inches in general accordance with ASTM D 1586. Recovered soil
samples were sealed in containers and returned to the laboratory. Bulk samples were also
obtained from auger cuttings, representing a mixture of soils encountered at the depths noted.
The final logs of the borings represent our interpretation of the contents of the field logs and the
results of laboratory testing performed on the samples obtained during the subsurface
exploration. The final logs are included in Appendix A of this report. The stratification lines
represent the approximate boundaries between soil types although the transitions may be
gradational.
2.2 Laboratory Testing
Samples were reviewed along with field logs to select those that would be analyzed further.
Those selected for laboratory testing include soils that would be exposed and used during
grading and those deemed to be within the influence of the proposed structure. Test results are
presented in graphic and tabular form in Appendix B of this report. The tests were conducted in
general accordance with the procedures of the American Society for Testing and Materials
(ASTM) or other standardized methods as referenced below. Our testing program consisted of
the following:
➢ In-situ Moisture Content and Unit Dry Weight for the ring samples (ASTM D 2937).
➢ Maximum density tests to evaluate the moisture -density relationship of typical soils
encountered (ASTM D 1557).
➢ Amount of Material Finer than the No.200 Sieve (ASTM D 1140).
➢ Particle Size- Analysis (ASTM D 422) to classify and evaluate soil composition. The
gradation characteristics of selected samples were made by hydrometer and sieve analysis
procedures.
➢ Consolidation (Collapse Potential) (ASTM D 2435 and D 5333) to evaluate the
compressibility and hydroconsolidation (collapse) potential of the soil.
➢ Chemical Analyses (Soluble Sulfates and Chlorides, pH, and Electrical Resistivity) to
evaluate the potential adverse effects of the soil on concrete and steel.
EARTH SYSTEMS SOUTHWEST
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3.0 DISCUSSION
3.1 Soil Conditions
The field exploration indicates that site soils consist of fill underlain by native soils consisting
generally of'sands, silty sands, and sandy silts with some gravel (Unified Soil Classification
Symbols of SP -SM, SM, and ML). The sands are medium dense to dense and fine- to coarse-
grained in texture. The boring logs provided in Appendix A include more detailed descriptions
of the soils encountered. The soils are visually classified to be in the very low expansion (EI <
20) category in accordance with Table 18A -I -B of the California Building Code.
In arid climatic regions, granular soils may have a potential to collapse upon wetting. Collapse
(hydroconsolidation) may occur when the soluble cements (carbonates) in the soil matrix
dissolve, causing the soil to densify from its loose configuration from deposition. A
consolidation test indicates 1.7% collapse upon inundation and collapse is therefore considered a
slight to moderate site risk. The hydroconsolidation potential is commonly mitigated by
recompaction of a zone beneath building pads.
The site lies within a recognized blow sand hazard area. Fine particulate matter (PM10) can
create an air quality hazard if dust is blowing. Watering the surface, planting grass or
landscaping, or hardscape normally mitigates this hazard.
3.2 Groundwater
Free groundwater was not encountered in the borings during exploration. The depth to
groundwater in the area is believed to be about 100 feet (EI -39) based on a nearby water well's
data in 1986 obtained from USGS WRI Report 91-4142. Historic high groundwater, based on
1961 groundwater contours, was about 70 feet (EI -10) from California Department of Water
Resources Bulletin 108. Groundwater levels may fluctuate with precipitation, irrigation,
drainage, regional pumping from wells, and site grading.
3.3 Geologic Setting
Regional Geology: The site lies within the Coachella Valley, a part of the Colorado Desert
geomorphic province. A significant feature within the Colorado Desert geomorphic province is
the Salton Trough. The Salton Trough is a large northwest -trending structural depression that
extends approximately 180 miles from the San Gorgonio Pass to the Gulf of California. Much of
this depression in the area of the Salton Sea is below sea level.
The Coachella Valley forms the northerly part of the Salton Trough. The Coachella Valley
contains a thick sequence of sedimentary deposits that are Miocene to recent in age. Mountains
surrounding the Coachella Valley include the Little San Bernardino Mountains on the northeast,
foothills of the San Bernardino Mountains on the northwest, and the San Jacinto and Santa Rosa
Mountains on the southwest. These mountains expose primarily Precambrian metamorphic and
Mesozoic granitic rocks. The San Andreas fault zone within the Coachella Valley consists of the
Garnet Hill fault, the Banning fault, and the Mission Creek fault that traverse along the northeast
margin of the valley.
EARTH SYSTEMS SOUTHWEST
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Local Geology: The project site is located approximately adjacent to the Whitewater River
channel and approximately 60 feet above mean sea level in the central part of the Coachella
Valley. The sediments within the valley consist of fine- to coarse-grained sands with
interbedded clays, silts, gravels, and cobbles of aeolian (wind-blown) and alluvial (water -laid)
origin. The depth to crystalline basement rock beneath the site is estimated to be in excess of
2000 feet (Envicom, 1976).
3.4 Geologic Hazards
Geologic hazards that may affect the region include seismic hazards (ground shaking, surface
fault rupture, soil liquefaction, and other secondary earthquake -related hazards), slope instability,
flooding, ground subsidence, and erosion. A discussion follows on the specific hazards to this
site.
3.4.1 Seismic Hazards
Seismic Sources: Several active faults or seismic zones lie within 62 miles (100 kilometers) of
the project site as shown on Table 1 in Appendix A. The primary seismic hazard to the site is
strong ground shaking from earthquakes along the San Andreas fault. The Maximum Magnitude
Earthquake (Mm.) listed is from published geologic information available for each fault (Cao et.
al, CGS, 2003). The Mmax corresponds to the maximum earthquake believed to be tectonically
possible.
Surface Fault Rupture: The project site does not lie within a currently delineated State of
California, Alquist-Priolo Earthquake Fault Zone (Hart, 1997). Well -delineated fault lines cross
through this region as shown on California Geological Survey (CGS) maps (Jennings, 1994).
Therefore, active fault rupture is unlikely to occur at the project site. While fault rupture would
most likely occur along previously established fault traces, future fault rupture could occur at
other locations.
Historic Seismicity: Six historic seismic events (5.9 M or greater) have significantly affected the
Coachella Valley in the last 100 years. They are as follows:
• Desert Hot Springs Earthquake — On December 4, 1948, a magnitude 6.5 ML (6.OMW)
earthquake occurred east of Desert Hot Springs. This event was strongly felt in the Palm
Springs area.
• Palm Springs Earthquake — A magnitude 5.9 ML (6.2MW) earthquake occurred on July 8,
1986 in the Painted Hills, causing minor surface creep of the Banning segment of the San
Andreas fault. This event was strongly felt in the Palm Springs area and caused structural
damage, as well as injuries.
• Joshua Tree Earthquake — On April 22, 1992, a magnitude 6.1 ML (6.1MW) earthquake
occurred in the mountains 9 miles east of Desert Hot Springs. Structural damage and minor
injuries occurred in the Palm Springs area as a result of this earthquake.
• Landers and Big Bear Earthquakes — Early on June 28, 1992, a magnitude 7.5 Ms (7.3MW)
earthquake occurred near Landers, the largest seismic event in Southern California for
40 years. Surface rupture occurred just south of the town of Yucca Valley and extended
some 43 miles toward Barstow. About three hours later, a magnitude 6.6 Ms (6.4MW)
EARTH SYSTEMS SOUTHWEST
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earthquake occurred near Big Bear Lake. No significant structural damage from these
earthquakes was reported in the Palm Springs area.
Hector Mine Earthquake — On October 16, 1999, a magnitude 7.1MW earthquake occurred
on the Lavic Lake and Bullion Mountain faults north of Twentynine Palms. While this event
was widely felt, no significant structural damage has been reported in the Coachella Valley.
Seismic Risk: While accurate earthquake predictions are not possible, various agencies have
conducted statistical risk analyses. In 2002, the California Geological Survey (CGS) and the
United States Geological Survey (USGS) completed the latest generation of probabilistic seismic
hazard maps.. We have used these maps in our evaluation of the seismic risk at the site. The
Working Group of California Earthquake Probabilities (WGCEP, 1995) estimated a 22%
conditional probability that a magnitude 7 or greater earthquake may occur between 1994 and
2024 along the Coachella segment of the San Andreas fault.
The primary seismic risk at the site is a potential earthquake along the San Andreas fault.
Geologists believe that the San Andreas fault has characteristic earthquakes that result from
rupture of each fault segment. The estimated characteristic earthquake is magnitude 7.7 for the
Southern Segment of the fault (USGS, 2002). This segment has the longest elapsed time since
rupture of any part of the San Andreas fault. The last rupture occurred about 1690 AD, based on
dating by the USGS near Indio (WGCEP, 1995). This segment has also ruptured on about 1020,
1300, and 1450 AD, with an average recurrence interval of about 220 years. The San Andreas
fault may rupture in multiple segments, producing a higher magnitude earthquake. Recent
paleoseismic studies suggest that the San Bernardino Mountain Segment to the north and the
Coachella Segment may have ruptured together in 1450 and 1690 AD (WGCEP, 1995).
3.4.2 Secondary Hazards
Secondary seismic hazards related to ground shaking include soil liquefaction, ground
subsidence, tsunamis, and seiches. The site is far inland, so the hazard from tsunamis is non-
existent. At the present time, no water storage reservoirs are located in the immediate vicinity of
the site. Therefore, hazards from seiches are considered negligible at this time.
Soil Liquefaction: Liquefaction is the loss of soil strength from sudden shock (usually
earthquake shaking), causing the soil to become a fluid mass. In general, for the effects of
liquefaction to be manifested at the surface, groundwater levels must be within 50 feet of the
ground surface and the soils within the saturated zone must also be susceptible to liquefaction.
The potential for liquefaction to occur at this site is considered negligible because the present
and historic high depth of groundwater beneath the site exceeds 50 feet. No free groundwater
was encountered in our exploratory borings. In addition, the project does lie within the Riverside
County designated low liquefaction hazard susceptibility area, defined as historic high
groundwater between 50 to 100 feet. Surficial expression of liquefaction is not expected.
Ground Subsidence: The potential for seismically induced ground subsidence is considered to be
moderate at the site. Dry sands tend to settle and densify when subjected to strong earthquake
shaking. The amount of subsidence is dependent on relative density of the soil, ground motion,
and earthquake duration. Uncompacted fill areas may be susceptible to seismically induced
settlement. Based on Tokimatsu and Seed methodology, we estimate that about 1.3 inches of
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total ground subsidence may occur in the upper 33 feet of soils for the Design Basis Earthquake
ground motion.
Slope Instability: The site is relatively flat. Therefore, potential hazards from slope instability,
landslides, or debris flows are considered negligible.
Flooding: The project site lies just outside a designated FEMA 100 -year flood plain but within a
500 -year -flood plain. The project site may be in an area where sheet flooding and erosion could
occur. Appropriate project design, construction, and maintenance can minimize the site sheet
flooding potential.
3.4.3 Site Acceleration and Seismic Coefficients
Site Acceleration: The potential intensity of ground motion may be estimated by the horizontal
peak ground acceleration (PGA), measured in "g" forces. Included in Table 1 are deterministic
estimates of site acceleration from possible earthquakes at nearby faults. Ground_ motions are
dependent primarily on the earthquake magnitude and distance to the seismogenic (rupture)
zone. Accelerations are also dependent upon attenuation by rock and soil deposits, direction of
rupture, and type of fault. For these reasons, ground motions may vary considerably in the same
general area. This variability can be expressed statistically by a standard deviation about a mean
relationship.
The PGA alone is an inconsistent scaling factor to compare to the CBC Z factor and is generally
a poor indicator of potential structural damage during an earthquake. Important factors
influencing the structural performance are the duration and frequency of strong ground motion,
local subsurface conditions, soil -structure interaction, and structural details. Due to these factors,
an effective peak acceleration (EPA) is used in structural design.
The following table provides the probabilistic estimate of the PGA taken from the
2002 CGS/USGS seismic hazard maps.
Estimate of PGA from 2002 CGS/USGS
Probabilistic Seismic Hazard Maps
Equivalent Return
Risk Period(years) PGA 19)2-
10% exceedance in 50 years 475 0.60
Notes:
1. Based on a soft rock site, SB/C, and soil amplification factor of 1.0 for Soil Profile Type Sp.
2001 CBC Seismic Coefficients: The California Building Code (CBC) seismic design criteria
are based on a Design Basis Earthquake (DBE) that has an earthquake ground motion with a
10% probability of occurrence in 50 years. The PGA estimate given above is provided for
information on the seismic risk inherent in the CBC design. The seismic and site coefficients
given in Chapter 16 of the 2001 California Building Code are provided below and in Section 5.7
of this report.
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2001 CBC Seismic Coefficients for Chapter 16 Seismic Provisions
Reference
Seismic Zone: 4 Figure 16-2
Seismic Zone Factor, Z: 0.4 Table 16-I
Soil Profile Type: SD Table 16-J
Seismic Source Type: A Table 16-U
Closest Distance to Known Seismic Source: 8.1 km = 5.0 miles (San Andreas fault)
Near Source Factor, Na: 1.08 Table 16-S
Near Source Factor, INv: 1.35 Table 16-T
Seismic Coefficient, Ca: 0.47 = 0.44Na Table 16-Q
Seismic Coefficient, Cv: 0.87 = 0.64Nv Table 16-R
Seismic Hazard Zones: The site does not lie within a landslide or fault rupture hazard area or
zone established by the 2002 Riverside County General Plan. Riverside County has not been
mapped by the California Seismic Hazard Mapping Act (Ca. PRC 2690 to 2699).
The. site does lie within a low susceptibility liquefaction hazard zone, based on historic high
groundwater of 50 to 100 feet. However, surficial expression of liquefaction is not expected nor
is the groundwater expected to return to its historic high of 70 feet depth because of the intensive
development of groundwater resource in the La Quinta area. No mitigation of a low potential for
liquefaction is considered warranted for normal risk project.
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4.0 CONCLUSIONS
The following is a summary of our conclusions and professional opinions based on the data
obtained from a review of selected technical literature and the site evaluation.
General:
➢ From a geotechnical perspective, the site is suitable for the proposed development,
provided the recommendations in this report are followed in the design and construction
of this project.
Geotechnical Constraints and Mitigation:
➢ The primary geologic hazard is severe ground shaking from earthquakes originating on
nearby faults. A major earthquake above magnitude 7 originating on the local segment of
the San Andreas fault zone would be the critical seismic event that may affect the site
within the design life of the proposed development. Engineered design and earthquake -
resistant construction increase safety and allow development of seismic areas.
The project site is in seismic Zone 4, is of soil profile Type Sp, and is about 8.1 km from
a Type A seismic source as defined in the California Building Code. A qualified
professional should design any permanent structure constructed on the site. The
minimum seismic design should comply with the 2001 edition of the California Building
Code.
➢ Ground subsidence from seismic events or hydroconsolidation is a potential hazard at this
site. Adherence to the grading and structural recommendations in this report should
reduce potential settlement problems from seismic forces, heavy rainfall or irrigation,
flooding and the weight of the intended structures.
➢ The soils are susceptible to wind and water erosion. Preventative measures to reduce
seasonal flooding and erosion should be incorporated into site grading plans. Dust
control should also be implemented during construction. Site grading should be in strict
compliance with the requirements of the South Coast Air Quality Management District
(SCAQMD).
➢ Other geologic hazards, including fault rupture, liquefaction and landslides, are
considered low or negligible on this site.
➢ The upper fill soils were found to be variable in density and are not considered suitable in
their present condition to support structures, fill, and hardscape. The soils within the
building and structural areas will require moisture conditioning, over -excavation, and
recompaction to improve bearing capacity and reduce settlement from static loading.
,Soils can be readily cut by normal grading equipment.
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5.0 RECOMMENDATIONS
5.1 Site Development — Grading
General: A representative of Earth Systems Southwest (ESSW) should observe site clearing,
grading, and the bottoms of excavations before placing fill. Due to the proximity of the
Whitewater Storm Channel on the north side of the development, we are recommending over -
excavation and recompaction of a 100 -foot wide strip of the site adjacent to the channel
easement. Local variations in soil conditions may warrant increasing the depth of recompaction
and over -excavation.
Clearing and Grubbing: At the start of site grading, existing vegetation, large roots, non -
engineered fill, construction debris, trash, and abandoned underground utilities should be
removed from the proposed building, structural, and pavement areas. The surface should be
stripped of organic growth and removed from the construction area. Areas disturbed during
clearing should be properly backfilled and compacted as described below.
Dust control should also be implemented during construction. Site grading should be in strict
compliance with the requirements of the South Coast Air Quality Management District
(SCAQMD).
Building Pad Preparation: Due to the relatively non-uniform nature of the site soils along the
channel easement of the Whitewater Storm Channel, we recommend over -excavation and
recompaction of soils in the building area. For bidding purposes, we estimate a strip
approximately 100 feet wide as measured from the channel easement may be subject to at least a
5 -foot over -excavation. Areas influenced by subterranean structures, such as a truck loading
ramp, will require an over -excavation to a depth of 2 feet below the bottoms of the footings but
in no case should be shallower than 5 feet below existing grade. Actual depths and extent of
over -excavation in this area should be determined during grading, based on exposed soil
conditions. The remaining soils within the building pad and foundation areas should be over -
excavated to a minimum of 3 feet below existing grade or a minimum of 2 feet below the footing
level (whichever is lower). The over -excavation should extend for 5 feet beyond the outer edge
of exterior footings. The transition between the deeper and shallower over -excavation sections
should be sloped no steeper than 5:1 (horizontal:vertical). The bottom of the sub -excavation
should be scarified, moisture conditioned and recompacted to at least 90% relative compaction
(ASTM D 1557) for an additional depth of 1 foot. Compaction should be verified by testing.
Auxiliary Structures Subgrade Preparation: Auxiliary structures such as retaining or below -
grade walls should have the foundation subgrade prepared similar to the building pad
recommendations given above. The lateral extent of the over -excavation needs to extend only 2
feet beyond the face of the footing. Compaction should be verified by testing.
Subgrade Preparation: In areas to receive fill, pavements, or hardscape, the subgrade should be
scarified, moisture conditioned, and compacted to at least 90% relative compaction
(ASTM D 1557) for a depth of 1 foot below finished subgrades. Compaction should be
verified by testing.
Engineered Fill Soils: The native soil is suitable for use as engineered fill and utility trench
backfill, provided it is free of significant organic or deleterious matter. The native soil should be
EARTH SYSTEMS SOUTHWEST
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placed in maximum 8 -inch lifts (loose) and compacted to at least 90% relative compaction
(ASTM D 1557) near its optimum moisture content. Compaction should be verified by testing.
Imported fill soils (if needed) should be non -expansive, granular soils meeting the
USCS classifications of SM, SP -SM, or SW -SM with a maximum rock size of 3 inches and
5 to 35% passing the No. 200 sieve. The geotechnical engineer should evaluate the import fill
soils before hauling to the site. However, because of the potential variations within the borrow
source, import soil will not be prequalified by ESSW. The imported fill should be placed in lifts
no greater than 8 inches in loose thickness and compacted to at least 90% relative compaction
(ASTM D 1557) near optimum moisture content. Compaction should be verified by testing.
Shrinkage: The shrinkage factor for earthwork is expected to range from 15 to 25 percent for the
upper excavated or scarified site soils. This estimate is based on compactive effort to achieve an
average relative compaction of about 92% and may vary with contractor methods. Subsidence is
estimated to range from 0.1 to 0.2 feet. Losses from site clearing and removal of existing site
improvements may affect earthwork quantity calculations and should be considered.
Site Drainage: Positive drainage should be maintained away from the structures (5% for 5 feet
minimum) to prevent ponding and subsequent saturation of the foundation soils. Gutters and
downspouts should be considered as a means to convey water away from foundations if adequate
drainage is not provided. Drainage should be maintained for paved areas. Water should not
pond on or near paved areas.
5.2 Excavations and Utility Trenches
Excavations: Excavations should be made in accordance with CalOSHA requirements. Our site
exploration and knowledge of the general area indicates there is a potential for caving of site
excavations (utilities, footings, etc.). Excavations within sandy soil should be kept moist, but not
saturated, to reduce the potential of caving or sloughing. Where excavations over 4 feet deep are
planned, lateral bracing or appropriate cut slopes of 1.5:1 (horizontal:vertical) should be
provided. No surcharge loads from stockpiled soils or construction materials should be allowed
within a horizontal distance measured from the top of the excavation slope and equal to the depth
of the excavation.
Utility Trenches: Backfill of utilities within roads or public right-of-ways should be placed in
conformance with the requirements of the governing agency (water district, public works
department, etc.). Utility trench backfill within private property should be placed in
conformance with the provisions of this report. In general, service lines extending inside of
property may be backfilled with native soils compacted to a minimum of 90% relative
compaction. Backfill operations should be observed and tested to monitor compliance with these
recommendations.
5.3 Slope Stability of Graded Slopes ,
Unprotected, permanent graded slopes should not be steeper than 3:1 (horizontal:vertical) 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. Fill
slopes should be overfilled and trimmed back to competent material. Slope stability calculations
are not presented because of the expected minimal slope heights (less than 5 feet).
EARTH SYSTEMS SOUTHWEST
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STRUCTURES
In our professional opinion, structure foundations can be supported on shallow foundations
bearing on -a zone of properly prepared and compacted soils placed as recommended in
Section 5.1. The recommendations that follow are based on very low expansion category soils.
5.4 , Foundations
Footing design of widths, depths, and reinforcing are the responsibility of the Structural
Engineer, considering the structural loading and the geotechnical parameters given in this report.
A minimum footing depth of 12 inches below .lowest adjacent grade should be maintained. A
representative of ESSW should observe foundation excavations before placement of reinforcing
steel or concrete. Loose soil or construction debris should be removed from footing excavations
before placement of concrete.
Conventional Spread Foundations: Allowable soil bearing pressures are given below for
foundations bearing on recompacted soils as described in Section 5.1. Allowable bearing
pressures are net (weight of footing and soil surcharge may be neglected).
➢ Continuous wall foundations, 12 -inch minimum width and 12 inches below grade:
1,500 psf for dead plus design live loads
Allowable increases of 300 psf per each foot of additional footing width and 300 psf for each
additional 0.5 foot of footing depth may be used up to a maximum value of 2500 psf.
➢ Isolated pad foundations, 2 x 2 foot minimum in plan and 18 inches below grade:
2,000 psf for dead plus design live loads
Allowable increases of 200 psf per each foot of additional footing width and 400 psf for each
additional 0.5 foot of footing depth may be used up to a maximum value of 3,000 psf.
' A one-third ('/3) increase in the bearing pressure may be used when calculating resistance to wind
or seismic loads. The allowable bearing values indicated are based on the anticipated maximum
loads stated - in Section 1.1 of this report. If the anticipated loads exceed these values, the
geotechnical engineer must reevaluate the allowable bearing values and the grading
requirements.
Minimum reinforcement for continuous wall footings should be two No. 4 steel reinforcing bars,
one placed near the top and one placed near the bottom of the footing. This reinforcing is not
intended to supersede any structural requirements provided by the structural engineer.
Expected Settlement: Estimated total static settlement should be less than 1 inch, based on
footings founded on firm soils as recommended. Differential settlement between exterior and
interior bearing members should be less than % inch, expressed in a post -construction angular
distortion ratio of 1:480 or less. Seismically ,induced settlement may be about 1 %2 inches total
and 1 inch differential.
Frictional and Lateral Coefficients: Lateral loads may be resisted by soil friction on the base of
foundations and by passive resistance of the soils acting on foundation walls. An allowable
coefficient of friction of 0.35 of dead load may be used. An allowable passive equivalent fluid
pressure of 250 pcf may also be used. These values include a factor of safety of 1.5. Passive
resistance and frictional resistance may be used in combination if the friction coefficient is
EARTH SYSTEMS SOUTHWEST
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reduced by one-third. A one-third ('/3) increase in the passive pressure may be used when
calculating resistance to wind or seismic loads. Lateral passive resistance is based on the
assumption that backfill next to foundations is properly compacted.
5.5 Slabs -on -Grade
Sub rade: Concrete slabs -on -grade and flatwork should be supported by compacted soil placed
in accordance with Section 5.1 of this report.
Vapor Retarder: In areas of moisture sensitive floor coverings, an appropriate vapor retarder
should be installed to reduce moisture transmission from the subgrade soil to the slab. For these
areas, an impermeable membrane (10 -mil thickness) should underlie the floor slabs. The
membrane should be covered with 2 inches of sand to help protect it during construction and to
aide in concrete curing. The sand should be lightly moistened just prior to placing the concrete.
Low -slump concrete should be used to help reduce the potential for concrete shrinkage. The
effectiveness of the membrane is dependent upon its quality, the method of overlapping, its
protection during construction, and the successful sealing of the membrane around utility lines.
The following minimum slab recommendations are intended to address geotechnical concerns
such as potential variations of the subgrade and are not to be construed as superceding any
structural design.
Slab Thickness and Reinforcement: Slab thickness and reinforcement of slabs -on -grade are
contingent on the recommendations of the structural engineer or architect and the expansion
index of the supporting soil. Based upon our findings, a modulus of subgrade reaction of
approximately 200 pounds per cubic inch can be used in concrete slab design for the expected
very low expansion subgrade.
Concrete slabs and flatwork should be a minimum of 4 inches thick (actual, not nominal). We
suggest that the concrete slabs be reinforced with a minimum of No. 3 rebars at 18 -inch centers,
both horizontal directions, placed at slab mid -height to resist cracking. Concrete floor slabs may
either be monolithically placed with the foundations or doweled after footing placement. The
thickness and reinforcing given are not intended to supersede any structural requirements
provided by the structural engineer. The project architect or geotechnical engineer should
continually observe all reinforcing steel in slabs during placement of concrete to check for proper
location within the slab.
Control Joints: Control joints should be provided in all concrete slabs -on -grade at a maximum
spacing of 36 times the slab thickness (12 feet maximum on -center, each way) as recommended
by American Concrete Institute (ACI) guidelines. All joints should form approximately square
patterns to reduce the potential for randomly oriented, contraction cracks. Contraction joints in
the slabs should be tooled at the time of the pour or saw cut ('/4 of slab depth) within 8 hours of
concrete placement. Construction (cold) joints should consist of thickened butt joints with one-
half inch dowels at 18 -inches on center or a thickened keyed joint to resist vertical deflection at
the joint. All construction joints in exterior flatwork should be sealed to reduce the potential of
moisture or foreign material intrusion. These procedures will reduce the potential for randomly
oriented cracks, but may not prevent them from occurring.
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Curing and Quality Control: The contractor should take precautions to reduce the potential of
curling of slabs in this and desert region using proper batching, placement, and curing methods.
Curing is highly affected by temperature, wind, and humidity. Quality control procedures may
be used, including trial batch mix designs, batch plant inspection, and on-site special inspection
and testing. Typically, for this type of construction and using 2500 -psi concrete, many of these
quality control procedures are not required.
5.6 Mitigation of Soil Corrosivity on Concrete
Chemical Tests: Selected chemical analyses for corrosivity were conducted on a soil sample
from the project site as shown in Appendix B. The native soils were found to have a low sulfate
ion concentration (54 ppm) and a low chloride ion concentration (11 ppm). Sulfate ions can
attack the cementitious material in concrete, causing weakening of the cement matrix and
eventual deterioration by raveling. Chloride ions can cause corrosion of reinforcing steel. The
California Building Code does not require any special provisions for concrete for these low
concentrations as tested. Normal concrete mixes may be used.
A minimum concrete cover of three (3) inches
embedded components exposed to native soil
should be thoroughly vibrated during placement,
should be provided around steel reinforcing or
or landscape water. Additionally, the concrete
Electrical Resistivity Test: Electrical resistivity testing of the soil (4,831 ohm -cm) suggests that
the site soils may present a moderate potential for metal loss from electrochemical corrosion
processes. Corrosion protection of steel can be achieved by using epoxy corrosion inhibitors,
asphalt coatings, cathodic protection, or encapsulating with densely consolidated concrete.
Earth Systems does not practice corrosion engineering. We recommend that a qualified
corrosion engineer evaluate the corrosion potential on metal construction materials and concrete
at the site to provide mitigation of corrosive effects.
5.7 Seismic Design Criteria
This site is subject to strong ground shaking due to potential fault
movements along the
San Andreas fault. Engineered design and earthquake -resistant construction
increase safety and
allow development of seismic areas. The minimum seismic design should comply with the 2001
edition of the California Building Code using the seismic coefficients given in the table below.
2001 CBC Seismic Coefficients for Chapter 16 Seismic Provisions
Reference
Seismic Zone: 4
Figure 16-2
Seismic Zone Factor, Z: 0.4
Table 16-I
Soil Profile Type: SD
Table 16-J
Seismic Source Type: A
Table 16-U
Closest Distance to Known Seismic Source: 8.1 km = 5.0 miles
(San Andreas fault)
Near Source Factor, Na: 1.08
Table 16-5
Near Source Factor, Nv: 1.35
Table 16-T
Seismic Coefficient, Ca: 0.47 = 0.44Na
Table 16-Q
Seismic Coefficient, Cv: 0.87 = 0.64Nv
Table 16-R
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The CBC seismic coefficients are based on scientific knowledge, engineering judgment, and
compromise. If further information on seismic design is needed, a site-specific probabilistic
seismic analysis should be conducted.
The intent of the CBC lateral force requirements is to provide a structural design that will resist
collapse to provide reasonable life safety from a major earthquake, but may experience some
structural and nonstructural damage. A fundamental tenet of seismic design is that inelastic
yielding is allowed to adapt to the seismic demand on the structure. In other words, damage is
allowed. The CBC lateral force requirements should be considered a minimum design. The
owner and the designer should evaluate the level of risk and performance that is acceptable.
Performance based criteria could be set in the design. The design engineer should exercise
special care so that all components of the design are all fully met with attention to providing a
continuous load path. An adequate quality assurance and control program is urged during
project construction to verify that the design plans and good construction practices are followed.
This is especially important for sites lying close to the major seismic sources.
5.8 Retaining Walls and Below -grade Walls
The following table presents lateral earth pressures for use in wall design. The values are given
as equivalent fluid pressures without surcharge loads or hydrostatic pressure.
Lateral Pressures and Sliding Resistance t
Granular Backfill
Passive Pressure
375 pcf - level ground
Active Pressure (cantilever walls)
30 pcf - level ground
Use when wall is permitted to rotate 0.1% of wall height
At -Rest Pressure restrained walls
50 pcf - level ground
Dynamic Lateral Earth Pressure
Acting at 0.5H,
25H psf or 50 pcf
Where H is height of backfill in feet
Base Lateral Sliding Resistance
0.50
Dead load x Coefficient of Friction:
Notes:
1. These values are ultimate values. A factor of safety of 1.5 should be used in stability analysis
except for dynamic earth pressure where a factor of safety of 1.2 is acceptable.
2. Dynamic pressures are based on the Mononobe-Okabe 1929 method, additive to active earth
pressure. Walls retaining less than 6 feet of soil and not supporting inhabitable structures need not
consider this increased pressure (reference: CBC Section 1630A. 1. 1.5).
Upward sloping backfill or surcharge loads from nearby footings can create larger lateral
pressures. Should any walls be considered for retaining sloped backfill or placed next to
foundations, our office should be contacted for recommended design parameters. Surcharge
loads should be considered if they exist within a zone between the face of the wall and a plane
projected 45 degrees upward from the base of the wall. The increase in lateral earth pressure
should be taken as 35% of the surcharge load within this zone. Retaining walls subjected to
traffic loads should include a uniform surcharge load equivalent to at least 2 feet of native soil.
Drainage: A back drain or equivalent system of backfill drainage should be incorporated into the
retaining wall design. Our firm can provide construction details when the specific application is
determined. Backfill immediately behind the retaining structure should be a free -draining
EARTH SYSTEMS SOUTHWEST
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granular material. Waterproofing should be according to the designer's specifications. Water
should not be allowed to pond near the top of the wall. To accomplish this, the final backfill
grade should be such that all water is diverted away from the retaining wall.
Backfill and Subgrade Compaction: Compaction on t
horizontal distance equal to one wall height should be
lightweight compaction equipment. This is intended
pressures caused by. compaction with heavy grading
preparation should be as specified in Section 5.1.
5.9 Pavements
he retained side of the wall within a
performed by hand -operated or other
to reduce potential locked -in lateral
equipment. Foundation subgrade
Since no traffic loading was provided by the design engineer or owner, we have assumed traffic
loading for comparative evaluation. The design engineer or owner should decide the appropriate
traffic conditions for the pavements. Maintenance of proper drainage is advised to prolong the
service life of the pavements. Water should not pond on or near paved areas. The following
table provides our preliminary recommendations for pavement sections. Final pavement sections
recommendations should be based on design traffic indices and R -value tests conducted during
grading after actual subgrade soils are exposed.
PRELIMINARY RECOMMENDED PAVEMENTS SECTIONS
R -Value Subgrade Soils - 40 (assumed) Design Method — CALTRANS 1995
Notes:
1. Asphaltic concrete should be Caltrans, Type 13, Y2 -in. or %-in. maximum -medium grading and compacted to a
minimum of 95% of the 75 -blow Marshall density (ASTM D 1559) or equivalent.
2. Aggregate base should be Caltrans Class 2 (% in. maximum) and compacted to a minimum of 95% of ASTM
D1557 maximum dry density near its optimum moisture.
3. All pavements should be placed on 12 inches of moisture -conditioned subgrade, compacted to a minimum of 90%
of ASTM D 1557 maximum dry density near its optimum moisture.
4. Portland cement concrete should have a minimum of 3250 psi compressive strength at 28 days.
5. Equivalent Standard Specifications for Public Works Construction (Greenbook) may be used instead of Caltrans
specifications for asphaltic concrete and aggregate base.
EARTH SYSTEMS SOUTHWEST
Flexible Pavements
Rigid Pavements
Asphaltic
Aggregate
Portland Aggregate
Traffic
Concrete
Base
Cement Base
Index
pavement Use
Thickness
Thickness
Concrete Thickness
Assumed
Inches
Inches
Inches Inches
5.0
Auto Parking Areas
3.0
4.0
4.0 4.0
7.0
Truck Access
4.0
7.0
6.0 6.0
Notes:
1. Asphaltic concrete should be Caltrans, Type 13, Y2 -in. or %-in. maximum -medium grading and compacted to a
minimum of 95% of the 75 -blow Marshall density (ASTM D 1559) or equivalent.
2. Aggregate base should be Caltrans Class 2 (% in. maximum) and compacted to a minimum of 95% of ASTM
D1557 maximum dry density near its optimum moisture.
3. All pavements should be placed on 12 inches of moisture -conditioned subgrade, compacted to a minimum of 90%
of ASTM D 1557 maximum dry density near its optimum moisture.
4. Portland cement concrete should have a minimum of 3250 psi compressive strength at 28 days.
5. Equivalent Standard Specifications for Public Works Construction (Greenbook) may be used instead of Caltrans
specifications for asphaltic concrete and aggregate base.
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6.0 LIMITATIONS AND ADDITIONAL SERVICES
6.1 Uniformity of Conditions and Limitations
Our findings and recommendations in this report are based on selected points of field
exploration, laboratory testing, and our understanding of the proposed project. Furthermore, our
findings and recommendations are based on the assumption that soil conditions do not vary
significantly from those found at specific exploratory locations. Variations in soil or
groundwater conditions could exist between and beyond the exploration points. The nature and
extent of these variations may not become evident until construction. Variations in soil or
groundwater may require additional studies, consultation, and possible revisions to our
recommendations.
Findings of this report are valid as of the issued date of the report. However, changes in
conditions of a property can occur with passage of time, whether they are from natural processes
or works of man, on this or adjoining properties. In addition, changes in applicable standards
occur, whether they result from legislation or broadening of knowledge. Accordingly, findings
of this report may be invalidated wholly or partially by changes outside our control. Therefore,
this report is subject to review and should not be relied upon after a period of one year.
In the event that any changes in the nature, design, or location of structures are planned, the
conclusions and recommendations contained in this report shall not be considered valid unless
the changes are reviewed and the conclusions of this report are modified or verified in writing.
This report is issued with the understanding that the owner or the owner's representative has the
responsibility to bring the information and recommendations contained herein to the attention of
the architect and engineers for the project so that they are incorporated into the plans and
specifications for the project. The owner or the owner's representative also has the responsibility
to verify that the general contractor and all subcontractors follow such recommendations. It is
further understood that the owner or the owner's representative is responsible for submittal of
this report to the appropriate governing agencies.
As the Geotechnical Engineer of Record for this project, Earth Systems Southwest (ESSW) has
striven to provide our services in accordance with generally accepted geotechnical engineering
practices in this locality at this time. No warranty or guarantee is express or implied. This report
was prepared for the exclusive use of the Client and the Client's authorized agents.
ESSW should be provided the opportunity for a general review of final design and specifications
in order that earthwork and foundation recommendations may be properly interpreted and
implemented in the design and specifications. If ESSW is not accorded the privilege of making
this recommended review, we can assume no responsibility for misinterpretation of our
recommendations.
Although available through ESSW, the current scope of our services does not include an
environmental assessment or an investigation for the presence or absence of wetlands, hazardous
or toxic materials in the soil, surface water, groundwater, or air on, below, or adjacent to the
subject property.
EARTH SYSTEMS SOUTHWEST
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6.2 Additional Services
This report is based on the assumption that an adequate program of client consultation,
construction monitoring, and testing will be performed during the final design and construction
phases to check compliance with these recommendations. Maintaining ESSW as the
geotechnical consultant from beginning to end of the project will provide continuity of services.
The geotechnical engineering firm providing tests and observations shall assume the
responsibility of Geotechnical Engineer of Record.
Construction monitoring and testing would be additional services provided by our firm. The .
costs of these services are not included in our present fee arrangements, but can be obtained from
our office. The recommended review, tests, and observations include, but are not necessarily
limited to, the following: '
• Consultation during the final design stages of the project.
• A review of the building and grading plans to observe that recommendations of our report
have been properly implemented into the design.
• Observation and testing during site preparation, grading, and placement of engineered fill
as required by CBC Sections 1701 and 3317 or local grading ordinances.
• Consultation as needed during construction.
•1•
Appendices as cited are attached and complete this report.
EARTH SYSTEMS SOUTHWEST
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" REFERENCES
Abrahamson, N., and Shedlock, K., editors, 1997, Ground motion attenuation relationships:
Seismological Research Letters, v. 68, no. 1, January 1997 special issue, 256 p.
American Concrete Institute (ACI), 1996, ACI Manual of Concrete Practice, Parts 1 through 5.
California Geologic Survey (CGS), 1997, Guidelines for Evaluating and Mitigating Seismic
Hazards in California, Special Publication 117.
Cao, T, Bryant, W.A., Rowhandel, B., Branum. D., and Wills, C., 2003, The Revised 2002
California Probabilistic Seismic Hazard Maps, California Geologic Survey (CGS), June
2003.
California Department of Water Resources, 1964, Coachella Valley Investigation, Bulletin No. 108,
146 pp.
Envicom Corporation and the County of Riverside Planning Department, 1976, Seismic Safety
and Safety General Plan Elements Technical Report, County of Riverside.
Frankel, A.D., et. al, 2002, Documentation for the 2002 Update of the National Seismic Hazard
Maps, USGS Open -File Report 02-420.
Hart, E.W., 1997, Fault -Rupture Hazard Zones in California: California Division of Mines and
Geology Special Publication 42.
International Code Council (ICC), 2002, California Building Code, 2001 Edition.
Jennings, C.W, 1994, Fault Activity Map of California and Adjacent Areas: California Division of
Mines and Geology, Geological Data Map No. 6, scale 1:750,000.
'Petersen, M.D., Bryant, W.A., Cramer, C.H., Cao, T., Reichle, M.S., Frankel, A.D., Leinkaemper,
J.J., McCrory, P.A., and Schwarz, D.P., 1996, Probabilistic Seismic Hazard Assessment for
the State of California: California Division of Mines and Geology Open -File Report 96-08.
Reichard, E.G. and Mead, J.K., 1991, Evaluation of a Groundwater Flow and Transport Model of
the Upper Coachella Valley, California, U.S.G.S. Open -File Report 91-4142.
Riverside County Planning Department, 2002, Geotechnical Element of the Riverside County
General Plan — Hearing Draft.
Rogers, T.H., 1966, Geologic Map of California - Santa Ana Sheet, California Division of Mines
and Geology Regional Map Series, scale 1:250,000.
Tokimatsu, K, and Seed, H.B., 1987, Evaluation of Settlements in Sands Due To Earthquake
Shaking, ASCE, Journal of Geotechnical Engineering, Vol. 113, No. 8, August 1987.
Working Group on California Earthquake Probabilities, 1995, Seismic Hazards in Southern
California: Probable Earthquakes, 1994-2024: Bulletin of the Seismological Society of
America, Vol. 85, No. 2, pp. 379-439.
Wallace, R. E., 1990, The San Andreas Fault System, California: U.S. Geological Survey
Professional Paper 1515, 283 p.
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.. anl'ytore k t: �=
' BF:. F� i. T �y • J� f S
� (('� s.,�s pQ .�'��_` � t� -. ✓ /1 ,�„� � .fir F'b] '�S
. � V
2,
e�a ail .. �'..
' Y#
#_-�_` a a W [
#£'=iJ.�G+....., r�..'a;�..i"'
{ii¢,�
h%
s 1 �
(rJE
U. . 4 P
LEGEND
Approximate Boring Locations
N Approximate Scale: 1" = 100'
0 100' 20C
Figure 2
Boring Location Map
99 Cent Only Store
La Quinta, California
O9 Earth Systems
Southwest
02/19/04 File No.: 09514-01
Jefferson Plaza
Table 1
Fault Parameters
& Deterministic Estimates of Mean Peak Ground Acceleration PGA
09514-01
Fault Name or
Seismic Zone
Distance
from Site
(m1) (km)
Fault
Type
Maximum
Magnitude
Mmax
(Mw)
Avg
Slip
Rate
(mm/yr)
Avg
Return
Period
(yrs)
Fault
Length
(km)
Mean
Site
PGA
(g)
Reference Notes: 1
2
3
4
2
2
2
5
San Andreas - Southern
5.0
8.1
SS
A
7.7
24
220
199
0.48
San Andreas - Mission Crk. Branch
5.5
8.8
SS
A
7.2
25
220
95
0.39
San Andreas - Banning Branch
5.5
8.8
SS
A
7.2
10
220
98
0.39
Blue Cut
13.9
22.3
SS
C
6.8
1
760
30
0.17
Burnt Mtn.
17.4
28.0
SS
B
6.5
0.6
5000
21
0.11
San Jacinto (Hot Spgs - Buck Ridge)
17.5
28.2
SS
C
6.5
2
354
70
0.11
Eureka Peak
18.2
29.4
SS
B
6.4
0.6
5000
19
0.10
San Jacinto-Anza
21.9
35.2
SS
A
7.2
12
250
91
0.14
San Jacinto -Coyote Creek
22.3
35.8
SS
B
6.8
4
175
41
0.11
Morongo
28.9
46.6
SS
C
6.5
0.6
1170
23
0.07
Pinto Mountain
30.4
48.9
SS
B
7.2
2.5
499
74
0.10
Emerson So. - Copper Mtn.
31.4
50.5
SS
B
7.0
0.6
5000
54
0.09
Landers
32.5
52.2
SS
B
7.3
0.6
5000
83
0.10
Pisgah -Bullion Mtn. -Mesquite Lk
33.3
53.6
SS
B
7.3
0.6
5000
89
0.10
San Jacinto - Borrego
35.4
57.0
SS
B
6.6
4
175
29
0.06
San Jacinto -San Jacinto Valley
37.1
59.7
SS
B
6.9
12
83
43
0.07
North Frontal Fault Zone (East)
38.7
62.3
DS
B
6.7
0.5
1727
27
0.07
Earthquake Valley
40.5
65.2
SS
B
6.5
2
351
20
0.05
Brawley Seismic Zone
41.0
66.0
SS
B
6.4
25
24
42
0.04
Johnson Valley (Northern)
43.2
69.6
SS
B
6.7
0.6
5000
35
0.05
Elsinore -Julian
44.6
71.9
SS
A
7.1
5
340
76
0.06
Calico - Hidalgo
44.8
72.2
SS
B
7.3
0.6
5000
95
0.07
Elsinore -Temecula
48.4
71.9
SS
B
6.8
5
240
43
0.05
Lenwood-Lockhart-Old Woman Sprgs
49.2
79.1
SS
B
7.5
0.6
5000
145
0.07
Elmore Ranch
49.21
79.1
SS
B
6.6
1
225
29
0.04
North Frontal Fault Zone (West)
50.0
80.4
DS
B
7.2
1
1314
50
0.07
Elsinore -Coyote Mountain
51.6
83.1
SS
B
6.8
4
625
39
0.04
Superstition Mtn. (San Jacinto)
53.4
85.9
SS
B
6.6
5
500
24
0.04
Superstition Hills (San Jacinto)
54.2
87.1
SS
B
6.6
4
250
23
0.04
Helendale - S. Lockhardt
57.1
91.9
SS
B
7.3
0.6
5000
97
0.05
San Jacinto -San Bernardino
59.3'
95.4
SS
B
6.7
12
100
36
0.04
Elsinore -Glen Ivy
62.0
99.8
SS
B
6.8
5
340
36
0.04
Notes:
1. Jennings (1994) and California Geologic Survey (CGS) (2003)
2. CGS (2003), SS = Strike -Slip, DS = Dip Slip, BT = Blind Thrust
3. 2001 CBC, where Type A faults: Mmax > 7 & slip rate >5 mm/yr & Type C faults: Mmax <6.5 & slip rate < 2 mm/yr
4. CGS (2003)
5. The estimates of the mean Site PGA are based on the following attenuation relationships:
Average of: (1) 1997 Boore, Joyner & Fumal; (2) 1997 Sadigh et al; (3) 1997 Campbell, (4) 1.997 Abrahamson & Silva
(mean plus sigma values are about 1.5 to 1.6 times higher)
Based on Site Coordinates: 33.709 N Latitude, 116.272 W Longtude and Site Soil Type D
EARTH SYSTEMS SOUTHWEST
i
Earth Systems
'q19 -Southwest 79.81113 Country Club Drive, Bermuda Dunes, CA
Boring No: B-1
Project Name: 99 Cent Only Store, La Quinta, CA
File Number: 09514-01
SILTY SAND: moderately brown, dry to damp, fine
Boring Location: See Figure 2
Sample
Type
Penetration.,
0
grained, some gravel
3
Resistance
q
(Blows/6")
ri
Av
�j
SM
- 5 .
-10
- 15
- 20
- 25
- 30
- 35
- 40
rnone tiou) J47-Uba, rax (/OU) J43 -U13
Drilling Date: January 27, 2004
Drilling Method: 8" Hollow Stem Auger
Drill Type: CME 75 w/rope & cathead
Logged By: Dirk Wiggins
Description of Units IPage 1 of 1
Note: The stratification lines shown represent the
approximate boundary between soil and/or rock types Graphic Trend
and the transition may be gradational. Blow Count Dry Density
SM
SILTY SAND: moderately brown, dry to damp, fine
grained, some gravel
(FILL)
SILTY SAND: moderately brown, dense, damp,
SM
encountered some fill and gravels
50/3"
87 2
(FILL)
SP -SM
SAND WITH SILT: light brown, medium dense,
damp, fine to medium grained
9,10,12
102 l
8,9,11
SP -SM
SAND WITH SILT: pale yellowish brown, medium
dense to dense, dry
9,15,18
Boring completed at 21.5 feet
No groundwater encountered
s
Backfilled with cuttings
Earth Systems
22,50/5"
;. Southwest
sM
102 2
79-811B Country Club Drive, Bermuda Dunes, CA
Phone(760)345-1588, Fax 760) 345-7315
SAND WITH SILT: light brown, dense, dry, fine
Boring No: B-2
grained
Drilling Date: January 27, 2004
Project Name: 99 Cent Only Store, La Quinta, CA
15,23,30
Drilling Method: 8" Hollow Stem Auger
85 1
File Number: 09514-01
Drill Type: CME 75 w/rope & cathead
Boring Location: See Figure 2
Logged By: Dirk Wiggins
~'
Sample
Type 4
Penetration
_
10,12,17
°'
Description of Units iPage 1 of 1
more grayish orange
�a
(3
Resistance
A
N
°'
A"
g
«.
0�
Note: The stratification lines shown represent the
P
A
(Blows/6)
W
2 o
approximate boundary between soil and/or rock types Graphic Trend
m V -y
AU
Boring completed at 29 feet
and the transition may be gradational. Blow Count Dry DensitEn
5
10
15
20
25
30
35
40
22,50/5"
sM
102 2
SILTY SAND: moderately brown, very dense, dry
to damp, fine grained
SP -SM
SAND WITH SILT: light brown, dense, dry, fine
grained
15,23,30
85 1
7,10,15
very pale orange, medium dense, damp, fine grained
10,12,17
more grayish orange
11,12,14
10,12,13
moderately brown
Boring completed at 29 feet
No groundwater encountered
Backfilled with cuttings
AEarth Systems
~� Southwest 79-811B Country Club Drive, Bermuda Dunes, CA
5
10
15
20
25
t
30
35
-40
t•none (M) 345-1358, rax (76U) 345-7315
Boring No: B-3
SM
SAND: moderately brown, very dense, dry to damp,
fine grained
Drilling Date: January 27, 2004
Project Name: 99 Cent Only Store, La Quinta, CA
SP -SM
Drilling Method: 8" Hollow Stem Auger
File Number: 09514-01
Drill Type: CME 75 w/rope & cathead
Boring Location: See Figure 2
dense to dense, dry to damp, fine grained
Logged By: Dirk Wiggins
-°
v
Sample
a
Type
Penetration
�
�
°'
Description of Units Page 1 of 1
aResistance
q a
Note: The stratification lines shown represent the
q
l" o
(Blows/6")
rn
o
approximate boundary between soil and/or rock types Graphic Trend
0
n
99 3
q
U
and the transition may be gradational. Blow Count Dry Density
5
10
15
20
25
t
30
35
-40
SM
SAND: moderately brown, very dense, dry to damp,
fine grained
SP -SM
SAND WITH SILT: moderately brown, medium
dense to dense, dry to damp, fine grained
94 1
4,7,7
9,12,26
99 3
6,8,10
8,12,13
Boring completed at 21.5 feet
No groundwater encountered
Backfilled with cuttings
Earth Systems
Southwest 79-811B Country Club Drive, Bermuda Dunes, CA
Boring No: B-4
Project Name: 99 Cent Only Store, La Quinta, CA
File Number: 09514-01
Boring Location: See Figure 2
w
Sample
Type
Penetration
0
a
dense, dry to damp, fine grained
Resistance
N
A g
g
q
s
(Blows/6")
On
q
A
v
ti
5
10
,15
o
20
25
30
35
140
rnone kiou) w-uaa, rax soul J43 -/J u
Drilling Date: January 27, 2004
Drilling Method: 8" Hollow Stem Auger
Drill Type: CME 75 whope & cathead
Logged By: Dirk Wiggins
Description of Units Page 1 of 1
Note: The stratification lines shown represent the
approximate boundary between soil and/or rock types Graphic Trend
and the transition may be gradational. Blow Count Dry Density
SM
SILTY SAND: moderately brown, loose to medium
dense, dry to damp, fine grained
SM
SILTY SAND: moderately brown to light brown,
very dense, dry to damp, fine grained
9,35,35/1"
102
2
13,20,27
101
1
pale yellowish brown to moderately brown, medium
dense to dense
ML
SILT: moderate brown to light brown, stiff, dry,
6,9,14
some fine sand
6,9,14
pale yellowish brown
Boring completed at 19 feet
No groundwater encountered
Backfilled with cuttings
9Earth Systems
``� Southwest 79-811B Country Club Drive, Bermuda Dunes, CA
5
10
15
20
25
30
35
140
rnone (M) 345-1585, hax (760) 345-7315
Boring NO: B-5
SP -SM
SAND WITH SILT: light brown to moderately
Drilling Date: January 27, 2004
Project Name: 99 Cent Only Store,
La Quinta, CA
Drilling Method: 8" Hollow Stem Auger
File Number: 09514-01
brown, medium dense, dry to damp, fine grained
Drill Type: CME 75 w/rope & cathead
Boring Location: See Figure 2
Logged By: Dirk Wiggins
v
Sample
Type
Penetration
aDescription
of Units Page 1 of 1
a
Resistance
D
U
A
11�
Note: The stratification lines shown represent the
q
q,
(Blows/6")
rn
c
approximate boundary between soil and/or rock types Graphic Trend
ti
grained
A
U
and the transition may be gradational. Blow Count Dry Density
5
10
15
20
25
30
35
140
SP -SM
SAND WITH SILT: light brown to moderately
brown, medium dense, dry to damp, fine grained
SM/ML
SILTY SAND/SANDY SILT: light brown to
moderately brown, medium dense, dry to damp, fine
6,10
91 6
grained
SP -SM
SAND WITH SILT: light brown to moderately
brown, medium dense, dry, fine grained
5,6,7
7,7,8
ML
SANDY SILT: moderately brown, medium dense,
damp, fine grained
10,14,24
92 12
Boring completed at 21.5 feet
No groundwater encountered
Backfilled with cuttings
t
Earth Systems
~�
Southwest79-81IB Country Club Drive, Bermuda Dunes, CA
rnone(/ou)345-158a, Pax /ou 345.7ji5
Boring No: B-6 Drilling Date: January 27, 2004
Project Name: 99 Cent Only Store, La Quinta, CA Drilling Method: 8" Hollow Stem Auger
File Number: 09514-01 Drill Type: CME 75 w/rope & cathead
Boring Location: See Figure 2 Logged By: Dirk Wiggins
Sample Pa
Type Penetration Description of Units Page 1 of 1
o Resistance q .O Note: The stratification lines shown represent the
�, C approximate boundary between soil and/or rock types Graphic Trend
A (Blows/6") W A (� . and the transition may be gradational. Blow Count Dry Density
5
10
15
20
25
30
35
h
40
sP-SM
SAND WITH SILT: moderately brown, medium
'dense, damp, fine grained, some medium grained
7,12,16
96
1
4,5,6
5,7,11
light brown, some silt
SM/ML
SILTY SAND TO SANDY SILT: dense, fine to
12,18,29
99
6
medium grained
Boring completed at 31.5 feet
No groundwater encountered
Backfilled with cuttings
F.
File No.: 09514-01 February 19, 2004
UNIT DENSITIES AND MOISTURE CONTENT ASTM D2937 & D2216
Job Name: 99 Cents Only Stores
B 1
5
87
Unit
Moisture
USCS
10
102
Sample
Depth
Dry
Content
Group
2
SM
Location
(feet)
Density (pcf)
%)
Symbol
B3
B 1
5
87
2
SM
B 1
10
102
1
SP -SM
B2
2.5
102
2
SM
B2
7.5
85
1
SP -SM
B3
5
94
1
SP -SM
B3
10
99
3
SP -SM
B4
5
102
2
SM
B4
7.5
101
1
SM
• B5
5
91
6
SM/ML
135
20
92
12
ML
B6
5
96
1
SP -SM
B6
30
99
6
SM/ML
4
EARTH SYSTEMS SOUTHWEST
0
File No.: 09514-01 February 19, 2004
Job Name: 99 Cents Only Stores
r
AMOUNT PASSING NO. 200 SIEVE ASTM D 1140
131
Fines
USCS
Sample Depth
Content
Group
Location feet)
N
Symbol
131
10
8
SP -SM
B2
22.5
10
SP -SM
EARTH SYSTEMS SOUTHWEST
File No.: 09514-01 February 19, 2004
PARTICLE SIZE ANALYSIS ASTM D-422
Job Name: 99 Cents Only Stores
Sample ID: B1 @ 1-4' Feet
Description: Silty Sand: F w/ Gravel (SM)
Sieve Percent
Size Passing
1-1/2" 100
1" 100
3/4" 98
1/2" 96
3/8" 95
#4 92
#8 89-
#16
9.#16 88 % Gravel: 8
#30 84 % Sand: 67
#50 68 % Silt: 19
#100 42 % Clay (3 micron): 5
#200 24 (Clay content by short hydrometer method)
100
90
80 I --�. ------
70
--70
e 60—
so- - --- --- --
a 40--
i
30 - - —
20 - --- - — - --- - -
10
0-
100 10 1 Particle Size( mmg.1 0.01 0.001
EARTH SYSTEMS SOUTHWEST
k
M f,
File No.: 09!' 14=01 February 19, 2004
CONSOLED"'�`,'TION TEST ASTM D 2435 & D 5333
99 Cents Only'Stores� Initial Dry Density: 92.0 pcf
133 @ 5' Feet .k Initial Moisture, %: 0.7%
Sand: F (SP-SM) Specific Gravity (assumed): 2.67
Ring Sample Initial Void Ratio: 0.813
Hydrocollapse: 1.7% @ 2.0 ksf
% Change in Height vs Normal Presssure Diagram
—8 Before Saturation ,m"„�°� °Hydrocollapse
■ After Saturation —SIE--Rebound
2
i
0
-2 -- - --
a-3 - - — - --
bn i
-a — — -- - - - - - --
C _5
AL
a-6 -- - - - — - -
v
a
a -7
-8 --
-9 - id+
-10 -------
0.110.0
..-- ii--- -- — ---
-12
0.tVertical Effective Stress, ksf 10.0
a
EARTH SYSTEMS SOUTHWEST