04-6175 (SOTB) Geotechnical EngineeringEarth Systems'Consultants
Wr Southwest
w•
GEOTECHNICAL ENGINEERING
AND LIMITED GEOLOGIC REPORT
PROPOSED COMMERCIAL DEVELOPMENT,
NW CORNER OF HWY 111 & WASHINGTON STREET
rLA QUINTA, CALIFORNIA _
r
CITY OF LA QUINTA
1
BUILDING & SAFETY DEPT.
APPROVED
FOR CONSTRUCTION
DATEa
BY
r
j. Consulting Engineers and Geologists
DF"4M COPY
DESERT CITIES DEVELOPMEN'17`
78-600 HIGHWAY 111
LA QUINTA,.CALIFORNIA 92253
1 GEOTECHNICAL ENGINEERING
AND LIMITED GEOLOGIC REPORT
PROPOSED COMMERCIAL DEVELOPMENT
NW CORNER OF HWY 111 & WASHINGTON STREET
LA QUINTA, CALIFORNIA
Q
Earth System Consultants
Southw est
Project:, Proposed Commercial Development
Northwest Corner of Washington Street and Highway 111
La. Quinta, California
It is our pleasure to present this Geotechnical Engineering Report prepared for the proposed
commercial development to be located at the northwest corner of Highway 111 and Washington
Street in the City La Quinta California.
This report presents our findings and recommendations for general site development and
foundation design, incorporating the tentative information supplied to our office. This report
should stand as a whole, and no part of the report should be excerpted or used to "exclusion of any
other part.
This report completes our scope of services in accordance with our agreement dated December 16,
1998. Other services that may be required, such as plan review and grading observation are
additional services and will be billed according to the Fee Schedule in effect at the time services are
provided.
This report was revised to include slope stability discussions and conclusions inadvertently omitted
from the. original report dated March'8, 1999.
We appreciate the opportunity to provide our .professional services. Please contact our office if
1 there are any questions or comments concerning this report or its recommendations.
Respectfully submitted,
EARTH SYSTEMS CONSULTANTS
Southwest PEp
oQ�pFESSI � �� O�
�5 DAVID
t" GOODRICH
No. EG1932
Shelton L. StringerW m 'm David.Goodrich CERTIFIED.
N0.?266 "
GE 2266 LU CEG .1932 ENGINEERING
6,90-M GEOLOGIST
SER/pc �TgEXA TF �CHN��O��`°
Distribution: 6/Desert Cities Deve
OF C.4 1F
1/VTA File
1BD File
1
79-811 B Country Club Drive
Bermuda Dunes, CA 92201
'
(760)345-1588
(800)924-7015
FAX (760) 345-7315
March 8, 1999
File No. 07074-01
Revised 3-2499
99-03-759
Desert Cities Development
78-600 Highway 111
La Quinta, California 92253
Attention:, Mr. Dave Smoley
e
;]
Subject: Geotechnical Engineering Report
Project:, Proposed Commercial Development
Northwest Corner of Washington Street and Highway 111
La. Quinta, California
It is our pleasure to present this Geotechnical Engineering Report prepared for the proposed
commercial development to be located at the northwest corner of Highway 111 and Washington
Street in the City La Quinta California.
This report presents our findings and recommendations for general site development and
foundation design, incorporating the tentative information supplied to our office. This report
should stand as a whole, and no part of the report should be excerpted or used to "exclusion of any
other part.
This report completes our scope of services in accordance with our agreement dated December 16,
1998. Other services that may be required, such as plan review and grading observation are
additional services and will be billed according to the Fee Schedule in effect at the time services are
provided.
This report was revised to include slope stability discussions and conclusions inadvertently omitted
from the. original report dated March'8, 1999.
We appreciate the opportunity to provide our .professional services. Please contact our office if
1 there are any questions or comments concerning this report or its recommendations.
Respectfully submitted,
EARTH SYSTEMS CONSULTANTS
Southwest PEp
oQ�pFESSI � �� O�
�5 DAVID
t" GOODRICH
No. EG1932
Shelton L. StringerW m 'm David.Goodrich CERTIFIED.
N0.?266 "
GE 2266 LU CEG .1932 ENGINEERING
6,90-M GEOLOGIST
SER/pc �TgEXA TF �CHN��O��`°
Distribution: 6/Desert Cities Deve
OF C.4 1F
1/VTA File
1BD File
1
1
1?
i
e
1
TABLE OF CONTENTS
Paae
Section 1
INTRODUCTION ..............................................
1.1
Project Description................................................................
1
1.2
Site Description...................:....................................................
1
1.3
Purpose and Scope of Work .........................................................
1
Section 2
METHODS OF INVESTIGATION ............. ..........................
3
2.1
Field Exploration .................. . ..............................
3
2.2
Laboratory Testing............................................................:.....
3
Section 3
DISCUSSION.....................................................................
4
3.1
Soil Conditions.........:.............................................................
4
3.2
Groundwater ....................................
3.3
*Geologic Setting .........................:............................................
4
3.4
Geologic Hazards.......................................................... ........
4
3.4.1 Seismic Hazards ............................................................
3.4.2 Secondary Hazards ..........................................................
6
3.4.3 Site Acceleration and UBC Seismic Coefficients .......................
7
Section 4
CONCLUSIONS ..............:................................................
9
Section 5
RECOMMENDATIONS.........................................................
10
SITE
DEVELOPMENT AND GRADING
5.1
Site Development-Grading..........................................................
10. .
5.2
Slope Stability of Graded Slopes .....................................................
11
5.3
Excavations and Utility Trenches ......................................................
11
5.4
5.5
Foundations..................................:.......................................
Slabs
12
-on -Grade ........................................... .....................
STRUCTURES
13
5.6
Retaining Walls ..........
14
5.7
................................:.........................
Mitigation of Soil Corrosivity on Concrete .......................................
14
5.8
Seismic Design Criteria...................................................:......:..
16
5.9
Pavements............................................................................
17
Section 6
LIMITATIONS AND ADDITIONAL SERVICES ......................
18
6.1
Uniformity. of Conditions and Limitations ..............................
18
6.2
Additional Services..................................................................
19
REFERENCES ...........................I ....... :............ ..................... .
....
20
APPENDIX A
Figure
Vicinity Map and Boring Location Map ...........................................
1-2
SiteGeologic Map...................................................................
3
Log of Borings
Table 1 - Fault Parameters
APPENDIX B
.
Laboratory Test Results
March 8, 1999 =1- a" File No. 07074-01
Revised 3-24-99 99-03-759
Section 1
INTRODUCTION
j1.1 Project Description
This Geotechnical Engineering Report has been prepared for the proposed commercial
development to be located at the northwest corner of Highway ,111 and Washington Street in the
City of La Quinta, California. �-lL i
Five restaurant buildings, one bank building, once. offiice.building—and—two gas stations are
pronstruopos d_� We anticipate that the proposed structures will be o,yvo_od-_bamea. and stu, cco
cction .and will be supported by conventional shallow continuous or pad footings. Site
development will include site grading, building -pad preparation, underground utility installation,
street and parking lot construction, and concrete driveway and sidewalk placement.
The proposed access driveway from Highway 111 will receive excavation into the existing rock
slope. Design of this. -proposed cutslope has not been completed at this time.
We used structural building column loads of up te_�50 d a maximum wall loading o i s
per linear foot as a basis for the foundation recomme cCn afions. All loading is assumed. to be dead
plus actual live load. If actual loading is to exceed these assumed values, it may be necessary to
reevaluate the given recommendations.
1.2 Site Description
The proposed commercial development is to be constructed on a vacant parcel at the northwest
corner of Highway 111 and Washington Street.
The lot is currently vacant of structures and is fairly level with some recent improvements having
recently been completed along the Whitewater Channel. These improvements include concrete
armament and an access area along the top of the embankment. Some grading was performed in
the past as a result of the construction of Highway 111 and Washington Street and the along the
drainage channel located at the rear of the lot. As part of the site improvements, a proposed
ingress/egress driveway is to be constructed at the southwest corner of the site. In order to make
room for the proposed driveway, the existing rock outcrop, located along the west side of the site
will require partial excavation and removal. This will result in a cut slope in the bedrock. The
development of the proposed office building may also include the partial removal of bedrock and/or
surface rocks and boulders that may be unstable.
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:
• Geological site reconnaissance.
• Geologic mapping of the site.
• Shallow subsurface exploration by drilling seven exploratory borings to depths ranging
from 6 to 31 feet.
• Laboratory testing of selected soil samples obtained from the exploratory borings.
• Review of selected published technical literature pertaining to the site.
• Evaluation of field and laboratory data.
• 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.
EARTH SYSTEMS CONSULTANT'S SOUTHWEST
March 8, 1999
Revised 3-2499
-2- File No. 07074-01
99-03-759
This report contains the following:
• Discussions on subsurface soil and groundwater conditions.
• Discussions on regional and local geologic conditions.
• Discussions on the stability of adjacent rock slopes.
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.
• lateral earth pressures and coefficients.
• mitigation of the potential corrosivity of site soils to concrete and steel reinforcement.
• seismic design parameters.
• pavement structural sections.. .
Not Contained In This Report: Although available through Earth Systems Consultants 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.
• 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 CONSULTANTS SOUTHWEST
March 8, 1999 -3- ; e _
Fel No 07074 01
Revised 3-24-99 99-03-759
Section 2
METHODS OF INVESTIGATION
2.1 Field Exploration
Seven borings were drilled to maximum depths ranging from 6 to 31 feet below the existing
ground surface to observe the soil profile and.to obtain samples for.laboratory testing. The borings
were drilled on January 21,,-1999, using 6 -inch outside diameter hollow=stem augers, and powered
by a CME 45 truck -mounted drilling rig. The approximate locations of the test borings were
established by pacing and sighting from existing topographic features. The approximate boring
locations are shown on Figure 2.
Samples were obtained within the test borings with a Modified California (M.C.) ring sampler
(ASTM D 3550 with shoe similar to ASTM D 1586). The M.C. 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 downhole hammer dropping 30 inches in accordance with ASTM D 1586. 'Bulk
samples of the soils encountered were also gathered from the auger cuttings.
The final log of the boring represent our interpretation of the contents of the field log and the
results of laboratory testing performed on the samples obtained during the subsurface
investigation. The final logs are included in Appendix A of this report. The stratification lines
represent the approximate boundaries between soil types although the transitions, however, 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 laboratorytesting were considered representative of soils that would be exposedand
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 laboratory testing program consisted of the following tests:
• In-situ Moisture Content and Unit Dry Weight -for the ring samples (ASTM D 2937).
Direct Shear (ASTM D 3080) to evaluate the relative frictional strength of the soils.
Remolded specimens were placed in contact with water at least 24 hours before testing and
were.then sheared under normal loads ranging from 0.5 to 2.0 kips per square foot.
• Maximum density tests were 'performed to evaluate the moisture -density relationship of
typical soil encountered (ASTM D 1557-91). .
• Particle Size Analysis (ASTM D422) to classify and evaluate soil composition. The
gradation characteristics of selected samples were made by hydrometer and sieve analysis
procedures.
• Chemical Analyses (Soluble Sulfates & Chlorides, pH, -.and Electrical Resistivity) to
evaluate the corrosivity of the soil on concrete and steel.,
1 EARTH SYSTEMS CONSULTANTS SOUTHWEST
March 8; 1999 -4- File:No. 07074-01
Revised 3-2499 99-03-759
Section 3
DISCUSSION
3.1 Soil Conditions
The field exploration indicates that site soils consist primarily of medium dense to dense, silty sand
(SM) with gravel. Some sandy silty (MI..) was encountered at depths greater than 7 feet.
Weathered granite was encountered at 28 foot'depth in Boring 5.
The boring logs provided in Appendix A include detailed descriptions of the soils encountered.
Soils should be readily cut by normal grading equipment.
3.2 Groundwater
Free groundwater was not encountered in the borings .during exploration. The depth to
groundwater in the area is believed to be in .excess of 100 feet. Groundwater levels may fluctuate
with precipitation, flow within the Whitewater Stormwater Channel, precipitation, drainage, and
site grading. Groundwater should'not be a factor in design or construction.
1 3.3 Geologic Setting
Regional Geology: The site lies within in 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
from San Gorgonio Pass, approximately 180 miles 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 portion
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.
Local GeoloQ . The project site is located on the south bank of the Whitewater River channel in the
middle portion of the Coachella Valley. The upper sediments. observed onsite consist of fine to
coarse-grained sands with interbedded .clays; silts, gravels, and cobbles of aeolian and alluvial
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 (surface fault rupture, ground
shaking, 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: Our research of regional faulting indicates that 23 known active faults or seismic
zones lie within 47 miles of the project site as shown on Table I in Appendix A. The Maximum
Magnitude Earthquake (M.) listed was taken from published geologic information available for
EARTH SYSTEMS CONSULTANTS SOUTHWEST
1
L
March 8, 1999
Revised 3-24-99
each fault (CDMG, 1996)
tectonically possible.
-5-
File No. 07074-01
99-03-759
The M,,,,x corresponds to the maximum earthquake believed to be
The primary seismic hazard`to the project site is strong groundshaking from earthquakes along the
San Andreas and San Jacinto Faults. A further discussion of site acceleration from groundshaking
follows in Section 3.4.3.
Surface Fault Rupture: The project site does not lie within a currently delineated State of California,
Alquist- Priolo Earthquake Fault Zone..(Hart, 1994). Well -delineated fault lines cross through this
region as shown on California Division of Mines.and Geology (CDMG) 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: Five historic seismic events (5.9 M or greater) have significantly affected the
Coachella Valley this century. They are as follows:
• Desert Hot Springs Earthquake - On December 4, 1948, a magnitude 6.5 ML (6.OM,) earthquake
occurred east of Desert Hot, Springs (Proctor 1968). 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
(USGS 1987). This event was strongly felt in the Palm Springs area and caused structural
damage; as well as injuries
• Desert Hot Springs Earthquake - On April 22, 1992, a magnitude 6.1 ML (6.IMW) earthquake
occurred in the mountains .9 miles east of Desert Hot Springs (OSMS 1992). Structural damage
and minor injuries occurred in the Palm Springs area as a result of this earthquake.
• Landers & Big Bear Earthquakes - Early on .June 28, 1992, a magnitude 7.5 MS (7.3M,,,)
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 (6.4M,,,) earthquake occurred near
Big. Bear Lake. No significant structural damage from these earthquakes was reported in the
Palm Springs area.
Seismic Risk: While accurate earthquake predictions are not possible, various agencies have
published extensive statistical risk analyses. In 1996, the California Division of Mines and
Geology (CDMG) and the United States Geological Survey (USGS) completed the latest
generation of probabilistic seismic hazard maps for use in the 1997 UBC. 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 significant
earthquake would occur between 1994 to. 2024 along the Coachella segment of .the San Andreas
Fault.
The primary seismic risk to the project site is the San Andreas Fault. Geologists believe that the
San Andreas Fault has characteristic earthquakes that rupture each fault segment. The estimated
characteristic earthquake is magnitude 7.4 for the Southern (Coachella) Segment of the fault. This
segment has the longest elapsed time since rupture than any other portion of the San Andreas Fault.
The last rupture occurred about 1690 AD, based on dating of trench surveys 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 along the San
Bernardino Mountain Segment to the north indicates. -that both it and the Southern (Coachella)
Segment may have. both ruptured together in 1450 and 1690 AD (WGCEP, 1995).
EARTH SYSTEMS CONSULTANTS SOUTHWEST
I/
March 8, 1999 -6- ! File No. 07074-01
Revised 3-24-99 99-03-759
3.4.2 Secondary Hazards
Secondary seismic hazards related to ground shaking include soil liquefaction, ground
deformation, areal 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 vicinityof 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 depth of groundwater beneath
the site exceeds 50 feet. No free groundwater was encountered in our exploratory borings. In
addition, the project does not lie within in the Riverside County liquefaction study zone.
Ground Deformation and Subsidence: Non -tectonic ground deformation consists of cracking of the
ground with little to no displacement. This type of deformation is not caused by fault rupture.
Rather it is generally associated with differential shaking of two or more geologic units with
differing engineering characteristics. Liquefaction may also cause ground deformation. As the site
is flat with consistent geologic material, and has a low potential for liquefaction, the potential for
ground deformation is also considered to be low.
The potential for seismically induced ground subsidence is considered to be relatively low at the
site. Dry sands tend to settle and densify when subjected to earthquake shaking. The amount of
settlement is a .function of relative density, groundshaking (cyclic shear strain), and earthquake
duration (number of strain cycles).
Slope Instability: The majority of the site is relatively flat. Therefore, potential hazards from slope
instability, landslides, or debris flows are considered negligible in the eastern flat -lying portion of
the site.
Because of the anticipated high strength of the bedrock materials in the slope at the western end of
the site, this slope is considered grossly stable in its existing condition. However, because of the
potential for high ground accelerations at the site (see the following'section), surficial failures such
as rock -fall and debris flows cannot be precluded in the event of a nearby large earthquake.
No grading plans are currently available showing the configuration of the proposed cut slope in the
southwest corner of the site. As a result, the potential height of this slope is unknown at this time.
However, Figure 2 shows the relationship of the currently proposed entrance roadway to .the
existing slope. Based on this relationship, we assume that an east and southeast facing cut slope
will be required along the northwest side of the entrance roadway. Our geologic mapping shows
that the predominant orientation of significant fractures in this area is dipping steeply to the West.
This orientation is generally favorable for an east to southeast facing cut slope since fracture planes.
dipping out -of -slope would not daylight within the cut slope face:Therefore, .based on this
preliminary mapping, we expect that a fairly steep cut slope, on the order of 3/4:1
(horizontal: vertical) would be grossly stable and would have a relatively low probability of
exposing large unstable blocks or wedges. We estimate that such a 3/4:1. slope would be on the
order of 40 feet high. Smaller loose and unstable blocks may be exposed during grading and, could
require removal or stabilization on an individual basis.
These conclusions will require verification by geologic inspection during excavation of the cut
slope. If unstable blocks' or wedges are identified during slope construction, additional
stabilization mitigation techniques such as scaling, rock bolting, or a rockfall mesh system could be
required.
' EARTH SYSTEMS CONSULTANTS SOUTHWEST
March 8 1999 -7-
File No. 07074-01
Revised 3-2499 99-03-759
The area of the proposed office building, at the northwest corner of the site, is potentially
Lvulnerable to falling rocks in the event of a large earthquake. Therefore, we do not recommend that
spaces where people spend significant amounts of time (patios, etc.) be planned at ground level at
the rear (west side) of this structure. This existing slope is inclined at approximately 1:1. Atthis
inclination, any dislodged_ rocks would be expected to roll, rather than bounce down the slope.
However, some bouncing away from the slope face could occur as a result of impacts with large
rocks on the. slope face. Therefore, second story balconies or similar spaces should. be kept. a
minimum of 10 feet from the slope face. The stability of individual boulders or rock outcroppings
should be evaluated in more detail when building plans are available.
Flooding: The project site does not lie within a designated FEMA 100 -year flood plain. The
project site may .be in an area where sheet flooding and erosion could occur. If significant changes
are proposed for the site, appropriate project design, construction, and maintenance can minirruze
the site sheet flooding potential.
3.4.3 Site Acceleration and UBC Seismic Coefficients
Site Acceleration: To assess. the potential intensity of ground motion, we have estimated the
horizontal peak ground acceleration (PGA). 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. also are
' 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 is an inconsistent scaling factor to compare to the UBC 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. Because of these factors, an effective
peak acceleration (EPA):is used in structural design.
11
' EARTH SYSTEMS CONSULTANTS SOUTHWEST
t
March 8, 1999 -8- { File No. 07074-01
Revised 3-2499 99-03-759
The following table provides the probabilistic estimate of the PGA and EPA taken from the 1996
CDMG/USGS seismic hazard maps. .
Estimate of PGA and EPA from 1996 CDMG/USGS Probabilistic Seismic Hazard
Maus.
Notes:
1 1. Based on soft rock site, Site Class SB _
2. Spectral acceleration (S,,) at period of 0.3 seconds divided by 2.5 factor for 5% damping
as defined by the Structural Engineers Association of California (SEAOC, 1996).
I UBC Seismic Coefficients: The Uniform Building Code (UBC) seismic coefficients are based on
an Design Basis Earthquake (DBE) that has an earthquake ground motion with a 10% probability
of occurrence in 50 years. The UBC seismic force provisions should be regarded as a minimum.
design in that it allows for. inelastic yielding of structures. The UBC design criteria permit
structural damage and possible loss of use after an earthquake. The PGA and EPA estimates given
above are provided -for information on the seismic risk inherent in the UBC design.
The following table lists the relevant seismic and site coefficients given in Chapter 16 of the 1994
and 1997 Uniform Building Code (UBC). The .1997 UBC seismic provisions are more stringent
. for areas less than 10 km (6.2 miles) from major seismic sources.
UBC Seismic Coefficients for Chanter 16 Reicmir Prnvicinnc
UBC
Soil
Equivalent Return
FApproximate
Near Source
Seismic Coefficients
Risk
Period .(years)
PGA ( ) (1)
EPA (g) (2)
Factors
10% exceedance in 50 years 475 0.51 0.46
Notes:
1 1. Based on soft rock site, Site Class SB _
2. Spectral acceleration (S,,) at period of 0.3 seconds divided by 2.5 factor for 5% damping
as defined by the Structural Engineers Association of California (SEAOC, 1996).
I UBC Seismic Coefficients: The Uniform Building Code (UBC) seismic coefficients are based on
an Design Basis Earthquake (DBE) that has an earthquake ground motion with a 10% probability
of occurrence in 50 years. The UBC seismic force provisions should be regarded as a minimum.
design in that it allows for. inelastic yielding of structures. The UBC design criteria permit
structural damage and possible loss of use after an earthquake. The PGA and EPA estimates given
above are provided -for information on the seismic risk inherent in the UBC design.
The following table lists the relevant seismic and site coefficients given in Chapter 16 of the 1994
and 1997 Uniform Building Code (UBC). The .1997 UBC seismic provisions are more stringent
. for areas less than 10 km (6.2 miles) from major seismic sources.
UBC Seismic Coefficients for Chanter 16 Reicmir Prnvicinnc
UBC
Soil
Seismic
Distance
Near Source
Seismic Coefficients
Code
Profile
Source
to Critical
Factors
Edition
Type
Type
Source
Na Nv
Ca
Cv
1994S',
---
---
--- ---
Z = 0.4
Z =0.4
S factor =1.5
Ref. Table
16-J
---
--
--- ---
16-I
16-I
1997
Sp
I
A
8.9 'km
1'.29
0.44Na
0.64Nv
(stiff soil)
11.04
= 0.46 I
= 0.82
Ref. Table
16-J I
16-U
---
16-S I 16-T 1
16-0
16-R
Seismic Zoning: The Seismic Safety Element of the 1984 Riverside County General Plan
establishes groundshaking hazard zones. The project area is mapped in Ground Shaking Zone.
Ground Shaking Zones are based on distance from causative, faults and underlying soil types.
These groundshaking hazard zones are.used in deciding suitability of land use.
EARTH SYSTEMS CONSULTANTS SOUTHWEST
March 8, 1999 -9- File No. 07074-01
Revised 3-24-99 99-03-759
Section 4
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.
' The primary geologic hazard. relative to site development is severeround shaking from
g g
earthquakes originating on nearby faults. In our opinion, a major seismic event. originating on
the local segment of the San Andreas fault zone would be the most likely cause of significant
earthquake activity at the site within the estimated design life of the proposed development.
• The project site is in seismic Zone 4 as defined in the Uniform Building Code. A qualified
professional who is aware of the site . seismic setting should design any permanent structure
constructed on the site. -
• Ground subsidence from seismic events or hydroconsolidation is a potential hazard in the
Coachella Valley area. Adherence to the following. grading and structural recommendations
should limit potential settlement problems from seismic forces, heavy rainfall or irrigation,
1 flooding, and the weight of the intended structures.
• The soils are susceptible to wind and water erosion. Preventative measures to minimize
seasonal flooding and erosion should be incorporated into site grading plans. Dust control
should also be implemented during construction.
• For planning purposes, the anticipated cut slope along the northwest side of the entrance
roadway are expected to be grossly stable at an inclination of 3/4:1 (horizontal:vertical). This
conclusion is tentative pending review of final grading plans showing the orientation and height
of the proposed slope. Further confirmation will be required using geologic mapping during
slope construction. Additional stabilization could be required based on the findings during
slope construction.
• The proposed office building at the northwest corner of the site is potentially vulnerable to
falling rocks during a large earthquake.
' • , Other geologic hazards including ground rupture, liquefaction, seismically induced flooding,
and landslides are considered low or negligible on this site.
• The upper soils were found to be relatively dense. In our opinion, the soils within the building
area will require minimal compaction to improve bearing capacity and limit settlement from
static loading.
We recommend that Earth Systems Consultants Southwest (ESCSW) be retained to provide
Geotechnical Engineering services during project design, site development, excavation,
grading, and foundation construction phases of the work. This is to observe compliance with
the design concepts, specifications and recommendations, and.to allow design changes in the
.event that subsurface conditions differ from.those anticipated prior to the start of construction.
Plans and specifications should be provided to ESCSW prior to grading. Plans should include
the grading plans, foundation plans, and foundation details. Preferably, structural loads
should be shown on the foundation plans.
IEARTH SYSTEMS CONSULTANTS SOUTHWEST
March 8 1999 -10- -
File N o 07074 01
R2vised 3-24-99 99-03-759
Section 5
RECOMMENDATIONS
' SITE DEVELOPMENT AND GRADING
5.1 Site Development - Grading
A representative of ESCSW prior to placing fill should observe site grading and the bottom of all
excavations.. Local variations in soil conditions -may. warrant increasing the depth of recompaction
and/or over -excavation.
Clearing�and Grubbing; Prior to site grading any existing vegetation, trees, large roots, pavements,
1 foundations, uncompacted fill, construction debris, trash, and any abandoned underground utilities
should be removed from the proposed building and pavement areas. The surface should be
stripped of organic growth along with other debris and removed from the construction area. Any
areas disturbed during demolition and clearing should be properly backfilled and compacted as
described below.
Building Pad Preparation: Because of the relatively dense nature of the majority of the site soils,
we recommend minor regrading the upper soils in the building area. The existing surface soils
within the building pad areas should be over -excavated to 12 inches below existing grade or to the
footing level (whichever is lower). The over -excavation should extend for 5 feet beyond the
outer edge of exterior footings. The bottom of the sub -excavation should be scarified, moisture
conditioned, and recompacted to at least 90% relative compaction (ASTM D1557) for a depth of 12
inches.
Subgrade Preparation: In areas to receive pavements or hardscape, the ground surface should be
scarified, moisture conditioned, and compacted to at least 90% relative compaction (ASTM D1557)
' for a depth of 12 inches below finished subgrades. Compaction should be verified by
testing.
Engineered Fill Soils: The native granular soil is suitable for use as engineered fill and utility trench
backfill. The native soil should be placed in maximum 8 -inch lifts (loose) and compacted at least
90% relative compaction (ASTM D1557) near optimum moisture. Compaction should be
verified by, testing. All rocks larger than 6 inches in greatest dimension should be removed
' from fill or backfill material.
All imported fill soils. (if required) 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 20%
'
passing -the No. 200 sieve. The geotechnical engineer should evaluate the import fill soils before
hauling to the site. However, import soil will not be prequalified by ESCSW. 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 D1557) at optimum moisture ± 2 percent.
Shrinkage: The shrinkage. factor for earthwork is expected to range from 5 to 15% 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 be. about less than 0.1 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
' EARTH SYSTEMS CONSULTANTS SOUTHWEST
March 8 1999 -11-
File No. 07074-01
Rtvised 3-24-99 99-03-759
drainage is not provided. Drainage should be maintained for paved areas. Water should not pond
on or near paved areas
5.2 Slope Stability of Graded Slopes
All unprotected' permanent graded soil .slopes should not be steeper than 3:1 to reduce wind and
rain erosion. Soil .slopes protected with. ground cover may be as steep as 2:1. However,
maintenance with motorized equipment may not.be possible at this inclination.
Slope stability calculations were not performed for soil slopes because of the expected minimal
slope height (less than 5 feet). If soil slope heights exceed 5 feet, engineering calculations should
beperformed to evaluate the stability of 2 to 1, horizontal to vertical, slopes. Fill'slopes should be
' overfilled and trimmed back to competent material.
Cut slopes in bedrock materials can be tentatively planned at an inclination of 3/4:1. The stability
of these slopes should be further evaluated after completion of grading plans showing slope
heights and orientations.
5.3 Excavations and Utility Trenches
All excavationshou
sld be made in strict accordance with CaIOSHA requirements. From our site
exploration and knowledge of the general area, we'believe 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 deep 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, equal to the depth of the
excavation.
Utility Trenches: Backfill of utilities within road or public right-of-ways should be placed in
conformance with the requirements of the governing agency (water district, road department, etc.)
Utility trench backfill within private property should be placed in conformance with the provisions
of this.report relating to minimum compaction standards. 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 by ESCSW to monitor compliance with these
recommendations.
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' EARTH SYSTEMS CONSULTANTS SOUTHWEST
March 8, 1999 -12- File No. 07074-01
' Revised 3-24-99 99-03-759
STRUCTURES
In our professional opinion, the structure foundation 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.
1 5.4 Foundations
Footing design widths, depths,. and reinforcing are the responsibility of the Structural Engineer.
Footings should be design for structural considerations .and the geotechnical conditions described
in this report.' A minimum footing depth' of '12 inches below lowest adjacent .grade should be
maintained.
' 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:
1800 psf for dead plus reasonable live loads.✓y
2400 psf for wind and seismic considerations.VV/`
Wall foundations should be 15 -inches wide and embedded 18 inches below grade for two-story
structures.
• Isolated pad foundations, 2 x 2 foot minimum in. plan and 18 inches below grade:
' 2000 psf for dead plus. reasonable live loads.✓/
2650 psf for wind and seismic considerations. t/
Allowable increases of 200 psf per each foot of additional, footing width and 300 psf for each
additional foot of footing depth may be used. The maximum allowable bearing pressure should
limited to 3000=psf. The allowable bearing values mac icated have been determined based upon the
anticipated maximum loads indicated in Section 1.1 of this report. If the indicated loading is
' exceeded then 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,
split between the top and the bottom of the footing. This reinforcing is not intended to supersede
any structural requirements provided by the structural engineer.
' Foundation excavations should be observed by the geotechnical engineer during excavation and
prior to placement of reinforcing steel or concrete.. Local variations in conditions may require
deepening of footings
' Expected Settlement: Estimated total static settlement,- based on footings founded on firm soils as
recommended, should be less than 1 inch. Differential settlement between exterior and interior
bearing members should be less than 1/2 -inch.
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 stem walls. Lateral capacity
is based partially on the assumption that any required backfill adjacent to foundations and grade
beams is properly compacted.
An allowable coefficient of friction of 0.40 may be used for dead load forces. An allowable
equivalent fluid pressure of 300 pcf may included for resistance to lateral loading. These values
' EARTH SYSTEMS CONSULTANTS SOUTHWEST
March 8, 1999 -13- File No. 07074-01
Revised_ 3-2499 99-03-759
include a factor of safety of 1.5. Passive resistance and frictional resistance may be combined in
determining the total lateral resistance. However, the friction factor should be reduced to 0.28 of
dead load forces. A one-third (1/3) increase in the passive pressure may be used when calculating
resistance to wind or seismic loads.
1 5.5 Slabs=on-Grade
Subgrade: Concrete slabs -on -grade and flatwork should .be supported by compacted soil placed in
accordance with Section 5.1: of this report.
Vapor Barrier: In areas.of moisture sensitive floor coverings, an appropriate vapor barrier should
' be installed in order to minimize .moisture transmission from 'the subgrade soil to the slab. We
recommend that an impermeable membrane (6 -mil visqueen) 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 minimize shrinkage.
Slab thickness and reinforcement: Slab thickness and reinforcement of slab -on -grade are contingent
upon the structural engineer's or .architect's recommendations 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.
Concrete slabs and flatwork should be a minimum of 4 inches thick. We suggest that a minimum
reinforcement for concrete slabs consist of a minimum of No. '3 rebars at 187 -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 x 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 randomly oriented contraction cracks. Contraction joints in the slabs should be
tooled at the time of the pour or saw cut (1/4 of slab depth) within 8 hours of concrete placement.
Construction (cold) joints should either be thickened buttjoints with one-half inch dowels at 24 -
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 prevent moisture or foreign material intrusion.
Precautions should be taken to prevent curling of slabs in this and desert region.
EARTH SYSTEMS CONSULTANTS SOUTHWEST
March 8, 1999
Revised 3-24-99
I5.6 Retaining Walls
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File No. 07074-01
99-03-759
The table below presents lateral earth pressures for use in retaining wall design. The values are
given as equivalent fluid pressures without surcharge loads or hydrostatic pressure.
Lateral Pressures and Sliding Resistance (1) .
Granular Backfill
Passive Pressure
450 pcf
Active .Pressure (cantilever walls)
33 pcf .
able to rotate 0.1% of structure height
At -Rest Pressure (restrained walls)
55 pcf
Dynamic Lateral Earth Pressure (2)
acting at mid height of structure,
20H psf
where H is height of backfill in feet
Base Lateral Sliding Resistance
Dead load X Coefficient of Friction:
0.55
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 need not consider this increased pressure.
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 loads are applied within a zone from 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 2 feet of native soil.
Drainage: A backdrain or an 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 granular
material. 'In this case the native soils are considered free draining. Waterproofing should be per
the Architect's specifications.. Water should riot 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 Compaction: Compaction on. the retained side of the wall within a horizontal distance equal
to one wall ' height should be performed by hand -operated or other lightweight compaction
equipment. This is intended to reduce potential "locked -in" lateral pressures caused by compaction
with heavy grading equipment.
' 5.7 Mitigation of Soil Corrosivity on Concrete
Selected chemical analyses for corrosivity were conducted on samples at the project site The native
soils were found to have low sulfate ion concentration (0.001%) and low chloride ion
concentrations (0.003%). 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 Uniform Building Code requires that increased quantities of
Type II Portland Cement be used at a low water/cement ratio when concrete is subjected to
moderate sulfate concentration.
' EARTH SYSTEMS CONSULTANTS SOUTHWEST
March 8 1999 -15- File No. 07074-01
4O1
' Revised 3-24-99 99-03-759
A minimum concrete cover of'3 inches should be provided around steel reinforcing_ or embedded
' components exposed to native soil or landscape water (to 18 inches above grade). Additionally,
the concrete should be thoroughly vibrated during placement.
' Laboratorytesting of the soil suggests that the site soils may present a severe potential for metal
loss from electrochemical corrosion processes. Corrosion protection of steel pipes can be achieved
by using epoxy corrosion inhibitors, .asphalt coatings,. cathodic protection, or encapsulating with
' densely consolidated concrete. A qualified corrosion engineer should be consulted regarding
mitigation of the corrosive effects of.site.soils on metals.
M1
EARTH SYSTEMS CONSULTANTS SOUTHWEST
March 8, 1999 -16 File No. 07074-01
Revised 3-2499 99-03-759
5.8 Seismic Design Criteria
This site is subject to strong ground shaking due to.potential fault movements along the San
Andreas and San Jacinto Faults. Engineered design and earthquake -resistant construction are the
common solutions to increase safety and development of seismic areas. The minimum seismic
design should comply with . the latest edition of the. Uniform Building Code for Seismic Zone 4
using the seismic coefficients given in Section .3.4.3 of this report. the table below. The 1997
UBC seismic provisions are more stringent for sites lying close to major faults.
The UBC . seismic coefficients are based on scientific knowledge, engineering judgment, and
compromise. Factors that play an important .role in dynamic structural performance are: (1)
' effective peak acceleration (EPA), .(2) duration and predominant frequency of strong ground
motion, (3) the period of the structure, (4) soil -structure. interaction, (5) total resistance capacity of
the system, (6) redundancies, (7) inelastic load -deformation behavior, and (8) the modification of
damping and effective- period as structures behave inelastically. Factors S. to 8 are accounted by the
' structural ductility factor (R) used in deriving a reduced value for design base shear. If further
information on seismic design is needed, a site-specific probabilistic seismic analysis should be
conducted. '
The intent of the UBC 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 UBC lateral force requirements. should be considered as a minimum design criteria.
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 has the responsibility to
interpret and adapt the.'principles of seismic behavior and design to each structure using experience
and sound judgment. 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.
' EARTH SYSTEMS CONSULTANTS SOUTHWEST
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March 8, 1999 -17- File No. 07074-01
Devised 3-24-99 99.-03-759
5.9 Pavements
Since no traffic loading were 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 necessary to prolong the
service life of the pavements. The following table provides our recommendations for pavement
sections.
RECOMMENDED PAVEMENTS SECTIONS
R -Value Subgrade Soils - 50 (assumed) Design Method - CALTRANS.1990
Notes:
1. Asphaltic concrete should be Caltrans, Type B, 1/2 in. maximum -medium grading, compacted to a
minimum of 95% of the.75-blow Marshall density (ASTM.D1559).
2. Aggregate base should be Caltrans Class 2 (3/4 in. maximum), compacted to a minimum of 95% of ASTM
D1557 maximum dry. density.
3. All pavements should be placed on 12 inches of moisture conditioned subgrade, compacted to a minimum
of 90% of ASTM D1557 maximum dry density.
4. Portland cement concrete should have a minimum of 3250 psi compressive strength @ 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 CONSULTANTS SOUTHWEST
Flexible
Pavements
Rigid Pavements
Asphaltic
Aggregate
Portland
Aggregate
Traffic
Concrete
Base
Cement
Base
Index
Pavement Use
Thickness
Thickness
Concrete
Thickness
(assumed).
(in.)
(in.).
(in.)
(in.)
4.0
Auto Parking Areas
2.5
4.0
4.0
4.0
5.0
Driveways
3.0
4.0
5.0
To
10.0
Hwy 111 or
6
8
---
---
Washington St
Notes:
1. Asphaltic concrete should be Caltrans, Type B, 1/2 in. maximum -medium grading, compacted to a
minimum of 95% of the.75-blow Marshall density (ASTM.D1559).
2. Aggregate base should be Caltrans Class 2 (3/4 in. maximum), compacted to a minimum of 95% of ASTM
D1557 maximum dry. density.
3. All pavements should be placed on 12 inches of moisture conditioned subgrade, compacted to a minimum
of 90% of ASTM D1557 maximum dry density.
4. Portland cement concrete should have a minimum of 3250 psi compressive strength @ 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 CONSULTANTS SOUTHWEST
March 8, 1999 -18- File No. 07074=01
Revised 3-24-99 99-03-759
Section 6
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 or appropriate
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 .the building are planned, the
conclusions and recommendations contained in this report shall not be considered valid unless the
changes are reviewed and conclusions of this report are modified or verified in writing.
This report is issued with the understanding that the owner, or his . representative, has the
responsibility .that the information and recommendations contained Herein are brought to the
attention of the architectand engineers for the project and are incorporated into the plans and
specifications for the project. The owner, or his representative, also has the responsibility to take
the necessary steps to see that the general contractor and all subcontractors carry out such
recommendations in the field. It is further understood that the owner or 'his representative is'
responsible for submittal of this report to the appropriate governing agencies.
As the Geotechnical Engineer of Record for this project, ESCSW 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 their authorized agents
ESCSW 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 ESCSW is not accorded the privilege of making
this recommended review, we can assume no responsibility for misinterpretation of our
recommendations.
EARTH SYSTEMS CONSULTANTS SOUTHWEST
' March 8 1999 _19- 9 File No. 07074-01
rtevised 3-2499 99-03-759
Although available through Earth Systems Consultants Southwest, the current scope of our
' services does not include an environmental assessment; or 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. Prior. to purchase or development of this site, we- suggest that
an environmental assessment be conducted which addresses environmental concerns.
' 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 ESCSW 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..
• Review of the building plans to observe that recommendations of our report have been
properly implemente& into the design.
' •' Observation and testing during site .preparation, grading and placement of engineered fill as
required by UBC Sections 1.701 and 3317.or local grading ordinances.
' Consultation as required during construction
-000-
Appendices as cited are attached and complete this report
' EARTH SYSTEMS CONSULTANTS SOUTHWEST
March 8, 1999 -20- '. File No. 07074-01
Revised M4799 99-03-759
REFERENCES
Blake, B.F., 1989-1998, EQSEARCH, v.2, A.Computer Program for the Estimation of Peak
Horizontal Acceleration from California Historical Earthquake Catalogs, Users Manual,
104 p.
Blake, B.F., 1998a, FRISKSP v. 3.01b, A Computer Program for the Probabilistic Estimation of
Peak Acceleration and Uniform Hazard Spectra Using 3-D Faults as Earthquake Sources,
User's Manual, 191 p.
Blake, B.F., 1998b, Preliminary. Fault -Data for EQFAULT and FRISKSP; 71 p.
Boore, -D.M., Joyner, W.B., and Fumal, T.E., 1993, Estimation of Response Spectra and Peak
Accelerations from Western North American Earthquakes: An Interim Report; U.S.
Geological Survey Open -File Report 93-509, 15p.
Boore,. D.M., Joyner, W.B., and Fumal, T.E., 1994, Estimation of Response Spectra and Peak
'Acceleration from Western North American Earthquakes: An Interim Report, Part. 2,; U.S.
Geological Survey Open -File Report 94-127.
California Department of Conservation, Division of Mines and Geology: Guidelines for
Evaluating and Mitigating Seismic Hazards in California, Special Publication 117, WWW
Version.
Campbell, K.W., .1990, Empirical Prediction of Near -Source Soil and Soft -Rock Ground Motion for
' the Diablo Canyon Power Plant Site, San Luis Obispo County; California, Consultant Report
Prepared by Dames & Moore for the Texas Low -Level Radioactive Waste Disposal Authority,
Dated September 1990, 110_ p.
Envicom, Riverside County, 1976, Seismic Safety Element.
Hart, E.W. 1994 rev., Fault -Rupture Hazard Zones in California: California Division of Mines
and Geology Special Publication 42, 34 p.
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.
Joyner, W.B., and Boore„ D.M., 1994, Prediction of Ground Motion in North America, in
Proceedings of ATC -35 Seminar on New. Developments in Earthquake Ground Motion
Estimation and Implications for Engineering Design Practice, Applied Technology Council,
1994.
Kramer, S..L., 1996, Geotechnical Earthquake Engineering: Prentice Hall, 651 p.
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, 59.p.
Pyke, R., Seed, H. B. And Chan, C. K. (1975). Settlement of Sands Under Multidirectional.
Shaking, ASCE, Journal of Geotechnical Engineering, Vol. 101, No. 4, April, 1975.
' Rogers, T.H., 1966, Geologic Map of California - Santa Ana Sheet; California Division of Mines
and.Geology Regional Map Series, scale 1:250,000.
' EARTH SYSTEMS CONSULTANTS SOUTHWEST
March 8, 1999 -21- File No. 07074=01
Revised 3-2499 99-03-759
Seed, H. B. and Idriss, I. M., 1982, Ground Motions and Soil'Liquefaction During Earthquakes.
Seed, H. B., and Silver, M. L. (1972). Settlement of Dry Sands During Earthquakes, ASCE,
Journal of Geotechnical Engineering, Vol. 98, No. 4, April, 1972.
Sieh, K., Stuiver, M., and Brillinger, D„ 1989, A.,More Precise Chronology of Earthquakes
Produced by the San Andreas Fault in Southern California: Journal of Geophysical
Research, vola 94, no.. B 1, January 10, 1989, pp. 603-623.
Seih, Kerry, .1985, "Earthquake Potentials Along The San Andreas Fault' Minutes of The
National Earthquake Prediction Evaluation Council, March 29-30, 1985, USGS Open File
Report 85-507.
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.
Van de Kamp, P. C., "Holocene Continental Sedimentation in the Salton Basin, California: A
Reconnaissance". Geological Society of America, Vol: 84, March 1973.
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..
EARTH SYSTEMS CONSULTANTS SOUTHWEST
J i<c•. DAR Y RYJA0.. •1 1111
' Water • . /. ., .. ��• • 1 /
L c
Trailer
7! `
ndian Welts' �'''� �'' - Project Site
PP LL
.a Ys uee.•
• — = C!�R. N .EL, .•-� _ ::. / � • • �,ti%':Viii`;•.;. QOw � •.-
•
• O O
' � `� � i ••� !. ' N � 872 � � ..; ,
tp• • 30 D '2T. al
0tZO .� • 1 ra ih
10
,��1 1 i ,_- m evef 4 J •,
• r1
Reference: La Quinta 7.5 min. USGS Quadrangle (photorevised 1980)
Figure 1 Vicinity Map
' Project Name: Hwy 111 and Washington Development
Project No.:07074-01
' Scale: 1" = 2,000' ' Earth Systems Consultants
0 2,000 4,000 Southwest
in
INEWOm.11 Vt
:nAM.r.
0L
Bat D
i
i�
>A '
B-3
61t reap j
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FPK.B r• �
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T'19
IDC1
pv r, B-7
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rat.�mo
RAwneum
. 1 I
Base Maps: Preliminary Boundary Map, prepared by Dudek and Associates, dated Nov. 1998
and untitled and undated preliminary'site plan provided -by client
I
LEGEND
Approximate Boring Location
Approximate Scale: 1" = 100'
MM s
0 100 200
Figure 2 -Site Map
Proposed Commercial Development
N W Corner Highway 111 and Washington Street
` La Quinta, California
Project No.: 07074-01
I
Earth Systems Consultants
Southwest
LEGEND
® Approximate Boring Location
64,V Orientation of Joint in Bedrock
cam/ Orientation of Quartz Dike in Bedrock
Surficial Units
Qal Quaternary Alluvium
Bedrock Units
Granite
"I's
W
Gabbro
♦l J,J la'
• ffri
Approximate Scale: 1" = 50'
®s
N 0 50 100
Monzonite
Base Map: Preliminary Boundary Map, prepared
by Dudek and Associates, dated November 1998
Figure 3 - Site Geologic Map
Proposed Commercial Development
NW Corner Highway 111 and Washington Street
La Quinta, California
Project No.: 07074-01
Earth Systems Consultants
'.�.,'�•� Southwest
Earth Systems Consultants
�`/v Southwest
79-811B Country Club Drive, B—i da Dunes, CA 92201
Phone.(760) 345-1588 FAX (760) 345-7315
$bring No: B1
Drilling Date: January 21, 1999
Project Name: Desert Cities Development at
Hwy I
l I and Washington Street Drilling Method: 6 -in. Hollow Stem Auger
Project Number: 07074-01
Drill Type: CME 45
Boring Location: See Boring Location Plan
Logged By:' Cliff Batten
'
Sample
Penetration
Descriptiontion Of Units Page I of I
Type
�.
Resistance
o
.0
E
N
U
En
y
Note: The stratification lines shown represent the
(Blows/6")
Q
o c
approximate boundary between soil and/or rock types Graphic Trend
A
o
A
U
and the transition may be gradational. Blow Count Dry Density
0
. SM
SILTY SAND: Tan, dense, fine to coarse grained
21/41
--
'0.5
with fine gravel, dry
'
5
16/34
86.2
1.9
NI
SANDY SILT: Tan, medium dense to dense, dry
10
12/22
89.8
3.4
15
30/42
90.8
2.8
Total Depth: 16 feet
•
No groundwater or rock encountered
20
25
30
35
40
,
45
Earth Systems Consultants
Southwest 79-811B Country Club Drive, Bermuda Dunes, CA 92201
Phone (760) 345-1588 FAX (760) 345-7315
Boring No: B2 Drilling Date: January 21, 1999
Project Name: Desert Cities Development at Hwy 11`1 and Washington Street Drilling Method: 6 -in. Hollow. Stem Auger
Project Number: 07074-01 Drill Type: CME 45
Boring Location: See Boring Location Plan Logged By: Cliff Batten
rSample
penetration
Description of Units Page 1 of 1
w
iResistance
Type w
o
E
N
A
Note: The stratification lines shown represent the
n
E» A
(Blows/6")
. ,
o
ro-
approximate boundary between soil and/or rock types Graphic Trend
d)
)
ti o
A
and the transition may be gradational. Blow Count Dry Density
0
SILTY SAND: Tan, dense, fine to very fine grained,
■
21/36
100.9
O.S
I.
(try
22/37
105.2
'2.6
'
5
n.
15/27
90.9
2.3
Total Depth: 6 feet
No groundwater or rock encountered
10
15
20
25
.
30
,
0 Earth Systems Conssitltants
' `/ SouthwP,St 79-811B Country. Club Drive, Bermuda Dunes, CA 92201
Phone (760) 345-1588 PAX (760) 345-7315
Mring No: B3
Drilling.Date: January 21, 1999
'
Project Name: Desert Cities Development at Hwy 11 l and Washington Street
. Drilling Method: 6 -in. Hollow Stem Auger
Project Number: 07074-01
Drill Type: CME 45
Boring Location: See Boring Location Plan
Logged By: Cliff Batten
Sample
a
Description of Units Pae 1 of ]
TypePenetration
o
Resistance E
U
CO)a
A
,�
Note: The stratification lines shown represent the
A
(Blows/6") rn
a
. ,
o a
approximate boundary between soil and/or rock types. Graphic Trend
A
A.
U
and the transition may be gradational. Blow Count Dry Density -
0
:.
SM
SILTY SAND:.Tan, very, dense to medium dense,
'
50/2^
__
1 •p
fine to very fine grained, dry
5
14/17
94.2
1.9
10
27/21
95.5
5.3- .
- with some clay layers
'
15
20
■
32/50
84.9
3.6
'
Total Depth: 21 feet
No groundwater or rock encountered
25
30
r
,
'
35
'
40
45
,
0Earth Systems ConpAvltants-
`� Southwest
79-811B Country Club Drive, Bermuda Dunes, CA 92201
Phone (760) 345-1588 FAX (760) 345-7315
Bouin,; No: B4
Drilling Date: January 21, 1999
Project Name: Desert Cities Development at
Hwy 11
l and Washington Street
Drilling Method: 6 -in. Hollow Stem Auger
Project Number: 07074-01
Drill Type: CME 45
Boring
Location: See Boring Location Plan
Logged By: Cliff Batten
Sample
Page 1 1'
Penetration
�.
o
Description Of Units
p
of
Type
Resistance
o
E
N
U
H
a[i
C
Note: The stratification lines shown represent the.
a
(Blows/6")
A a
.Q
approximate boundary between soil and/or rock types Graphic Trend
be
A
A
U
and the transition may gradational. Blow Count Dry Density
0
SM
1
37/50 for 2"
95.9
1.5
SILTY SAND: Tan,. very dense, fine to very fine
grained, dry
5
34/50
93.2
1.8
iSANDY
SILT: Tan to gray, very dense, dry, with
10
24/50
88,8
2,9
silty clay layers
1
.
15
20
50 for 3"
2.0
Total Depth: 20.3 feet
No or rock encountered
25
groundwater
30
35
40
1
45
•
1
0 Earth Systems Consyltants
' `/Southwp—st
19-811 B Country Club Drive, Bermuda Dunes, CA 92201
Phone (760) 345-1588 FAX (760) 345-7315
Boring Noi B5
Drilling Date: January 21, 1999
.
Project Name: Desert Cities Development at.Hwy
111
and Washington Street
Drilling Method: 6 -in. Hollow Stem Auger
Project Number: 07074-01
Drill Type: CME 45
Boring Location: See Boring Location Plan
Logged By: Cliff Batten
Sample
Page 1 of 1
..
Type
Penetration
o
y
o
0
Description of Units
p
iResistance
19
p
E
U
�.
so
A a
. c
Note: The stratification lines shown represent the
a .
U
o
(Blows/6")
a,
o
approximate boundary between soil and/or rock types Graphic Trend
A
m'
A
U
and the transition may be gradational. Blow Count Dry Density
0
.SM
SILTY SAND: Tan,very dense; fine to very fine
grained, dry
5
30/50
90.1
1.6
•
] 0
■ 22/50
1550
for 5"
92.9
2.8
•
X.
20
50 for 5"
No groundwater encountered
25
YA • U
WEATHERED GRANITE
30
50 for 2"
Total Depth: 30.2 feet
'
35
.
'
40
'
45
' 0 Earth Systems Conskltants
Southwest ' 79-811B Country Club Drive, Bermuda Dunes, CA 92701
Phone (760) 345-1588 FAX (760) 345-7315
goring No: B6
Drilling Date: January 21, 1999
Project Name: Desert Cities Development at Hwy I 1 I and Washington. Street
Drilling Method: 6 -in. Hollow Stem Auger.
Project Number: 07074-01
Drill Type: CME 45
Boring Location: See.Boring Location Plan
Logged By: Cliff Batten
Sample
o
Page ] of l
Penetration .
y
• 4 ;� s
Description of Units
w
Type w
a
Resistance
o
.0
E
N
U
. �
0 U E •'
0 A .y
Note: The stratification lines shown represent the
P
i
U
(Blows/6")
a,
rn
.., o y
approximate. boundary between soil and/or rock types Graphic Trend
A
0
A U
and the transition may be gradational. Blow Count Dry Density
LLL
0
- sm.
SILTY SAND: Light brown; very dense, fine
'
50 for 2"
grainedl, dry
5
50 for 4"
100.2 0.7
sH
SILTY SAND: Light brown, very dense, fine
10
50 for 6"
113.3 2.1
grainedl, dry to moist, with clay layers
T.
84.4 34.1
15 '
50 for 5"
96.4 4.2
91.1 22.3
Total Depth: 15.4 feet
No groundwater or rock encountered
20
25
30'
0t
t
1
i
r
Earth Systems_"sultants
Southwest 79-811 B Country Club Drive, Bermuda Dunes, CA 92201
` Phone (760) 345-1588 FAX (760) 345-7315
Bo+rine No: B7 Drilling Date: January 21, 1999
Project Name: Desert Cities Development at Hwy 111 and Washington Street Drilling Method: 6 -in.'. Hollow Stem Auger
Project Number: 07074-01 Drill Type: CME 45
Boring Location: See Boring Location Plan Logged By: Cliff Batten
Sample o Description of Units Page 1 of 1
Type w Penetration o H by j1
U aGi Note: The stratification lines shown represent the
Resistance !? rn a
a Q ti o c approximate boundary between soil and/or rock types Graphic Trend
A (Blows/6") O U and the transition may be gradational. Blow Count Dry Density
5
10
15
20
25
30
35.
40
45
rDesert Cities Development Protect No: 07074-01
' Table 1 ^
FAULT PARAMETERS &
Notes:
1. Jennings (1994) and CDMG (1996)
2. CDMG (1996), where Type A faults, Mmax > 7 and slip rate >5 mm/yr,
Type C faults, Mmax <6.5 and slip rate < 2 mm/yr.
' 3. WGCEP (1995), where: A - Type A (Characteristic), B - Type B, C- Type C
4. CDMG (1996) based on Wells & Coppersmith (1994)
5. Ellsworth Catalog in USGS PP 1515 (1990) and USER (1976), Mw = moment magnitude,
6. The estimates of the mean Site PGA are based on the attenuation relationship of:
Weighted average of Campbell & Bozorgnia; Boore, Joyner & Fumal; and Sadigh (1994)
(mean plus sigma values are about 1.6 times higher)
EARTH SYSTEMS CONSULTANTS SOUTHWEST
'
07074-01
Feb 12, 1999
PARTICLE SIZE ANALYSIS
ASTM D-422
Job Name: Desert Cities
Sample ID: Boring #1 @ 0 - 5'
Soil Description Silty F to C Sand with Gravel to 3/4"
(SM)
Particle Shape: Sub -Angular
SIEVE. SIZE
% PASSING
1-1/2"
100
1"
100
3/4"
97
1/2"
93
3/8"
91
'
#4
87
#8
82
'
#16
80
#30
77
#50
68
#100
46
#200
27
% Gravel:
13
% Sand:
59
% Silt:
22
% Clay (3 micron):
5
I I - -1 - M
nun uu
dYIIAIIo�:�i
100
10
1 0.1
Particle Size ( mm)
0.01
U.UU l I
,07074=01 Feb. 12, 1999
DIRECT SHEAR ASTM D.3080-90 (modified for unconsolidated, undrained conditions)
,Desert Cities
Boring #1 @ 0-5' Initial Dry Density: 106.9 pcf
Silty F to C Sand (SM) Initial Mosture Content: 10.5 %
Remolded @ 90% Peak Friction Angle (0): 340
' Cohesion (c): 0.019 Kg/cm^2 (38 psf)
SHEAR vs. NORMAL STRESS
1.4 .
1.2
].0
< --
b�00-0
o 0-00
a — - - — -
0.6
C4_ —... ---- - -- -- --- - - - --_ .— -- -- - - — - -- -.-.._ ._._.__ .-._...- - -- — _
— — --- — — r'
— — -=0.954_
0.2 - —
0.0
0.0
0.2 0.4 0:6 0.8 1.0
.NORMAL STRESS, Kg/cm.^2
EARTH SYSTEMS CONSULTANTS SOUTHWEST
1.2 1.4
t07074-01 Feb -12,1999
DIRECT SHEAR continued ASTM'D 3080-90 (modified for. unconsolidated, undrained conditions)
1
SATURATION, %
1.4
1.2
u
1.0
I
0.8
0.6
a
0.4
0.2
0.0
0.0000
111.6 110.9 111.6 111.2 111.3
Desert Cities
Boring #1 @ 0=5'
Silty. F to C Sand (SM)
Remolded @ 90%
SPECIFIC GRAVITY:
2.67 (assumed)
SAMPLE NO.:
1
2
3
4
AVERAGE
INITIAL.
7
WATER CONTENT, '%
10.5
10.5
10.5
10.5
10.5
'
■
DRY DENSITY, pcf
106.9
106.9
106.9
106.9
106.9
'
SATURATION, % .
50.2
50.2
.50.2
50.2
50.2
VOID RATIO
0.558
0.558
0.558
0.558
0.558
DIAMETER; inches
2.40.
2.40
2.40
2.40
0.000
0.00
0.00
0.00
0.00
AT TEST
WATER CONTENT, %
23.3
23.2
23.3
23.3
23.3
SATURATION, %
1.4
1.2
u
1.0
I
0.8
0.6
a
0.4
0.2
0.0
0.0000
111.6 110.9 111.6 111.2 111.3
0.0500 0.1000. 0.1500
HORIZONTAL DEFORMATION, inches
EARTH SYSTEMS CONSULTANTS SOUTHWEST
0.2000
®
®
■11
■
■
A♦
•
•
0.0500 0.1000. 0.1500
HORIZONTAL DEFORMATION, inches
EARTH SYSTEMS CONSULTANTS SOUTHWEST
0.2000
7074 -01 -
MAXIMUM DENSITY / OPTIMUM MOIS'
ebb Name: Desert Cities
ample ID: Boring #1 @ 0-5'
cation: Native
Description: Olive Brown Silty F to C Sand with
raximum Density:
ptimum Moisture:
140
135
' 130 ,
125
120
b
A
115
110-
105
100
Feb 12, 1999
ASTM D 1557-91
Procedure Used: A
Prep. Method: Moist
Rammer Type: Mechanical
Specific Gravity: 2.67 (assumed)
Sieve Size % Retained
119 pcf 3/4"
2.0
10.5% 3/8"
6.1
#4
9.8
5 10 15 20 25
Moisture Content, percent
EARTH SYSTEMS CONSULTANTS SOUTHWEST
30
i- i i• i ii. i. i i i i, i i i i i i Vi i.
SOIL & PLANT LABORATORY SOIL ANALYSIS
and CONSULTANTS, Inc.
79-607 Country.Club Drive for: Earth'Systems Consultants.Southwest
Suite 7
Bermuda Dunes, CA 92201 report.date: 2-2-9.9 -
760=772-79.95
inv.%lab#:. 87
Ohms -cm ppm meq/L ppm mg/Kg
No. Description Sat./ pH Res NO -.N PO4P K Ca +. Mg Na Cl SO4
07074-01 Desert Cities
B#1 0-5' 8.0 385 265 128