HomeMy WebLinkAbout06-4134 (MFD5) Geotech Report Addendum 2Earth Systems
Southwest -- 79-81113 Country Club Drive
I F—
FE+ I(: �^ I i Bermuda Dunes, CA 92203
(760) 345-1588
(800)924-7015
�y 7 FAX (760) 345-7315
August 9, 2007
Coachella Valley Housing Coalition
45-701 Monroe Street, Plaza 1, Suite G
Indio California 92201
Attention: Mr. Brian Peulicke
E
IY OF LA QUINTA
BUIILDING & SAFETY DEFT.
APPROVED
FOR CONSTRUCTION
File No.: 09571-04
07-08-739
Subject: Addendum 2 — Supplemental Grading Recommendations and Update of the
Geotechnical Engineering Report
Project: Proposed Multi -Family Residential Development
Northwest Corner of Dune Palms Road and Avenue 48
La Quinta, California
References: 1. Earth Systems Southwest, Geotechnical Engineering Report, Proposed Multi -
Family Residential Development, Northwest Corner of Dune Palms Road and
Avenue 48, La Quinta, California, File No.: 09571-04, Document No.: 06-07-
734, dated July 13, 2006.
2. Earth Systems Southwest, Addendum to Geotechnical Engineering Report,
Proposed Multi -Family Residential Development, Northwest Corner of Dune
Palms Road and Avenue 48, La Quinta, California, File No.: 09571-04,
Document No.: 06-08-778, dated August 14, 2006.
Dear Mr. Peulicke:
As requested, we have reviewed the project plans with regards to the currently proposed
construction associated with underground parking facility at the subject site. We understand that
the structure will include two levels above -grade, of wood -frame construction, with one
subterranean level that will be of reinforced concrete construction and will be used for parking.
We understand the anticipated loads will be less than 350 kips. Recommendations are provided
in Reference 2 to over -excavate to a depth of 5 feet below the footing level to a distance of 10
feet beyond the outer edge of the exterior footings. Based on our discussions with the owner
(Coachella Valley Housing Coalition), structural engineer (Grayner Engineering), and general
contractor (Brown Construction, Inc.), the following revised grading recommendations are
offered for your use.
The lateral limits of the recommended over excavation may be reduced to 5 feet; however, the
owner, contractor, and surveyor should take care as to the accuracy of the field staking. ESSW
does not verify line and grade and will rely on the accuracy of work performed by others.
The site soils are predominately poorly graded sands and silty sands with localized areas that
contain higher silt contents. It is feasible to perform a partial over excavation, pre -water the
resulting surface, and compact using loaded scrapers. Therefore, the basement should be
excavated to a depth of two to three feet below the bottom of the proposed footings. The
resulting surface should be moisture conditioned to achieve the optimum moisture content to a
depth of an additional 3 feet. The bottom of the excavation should then be compacted using
loaded scrapers. A series of test pits should be excavated to verify the depth of moisture
�t4
August 9, 2007 2 File No.: 09571-04
07-08-739
penetration, and compaction tests should be taken to verify the effects of the applied compactive
effort. If localized pumping occurs as a result of the presence of silt, localized deepening of the
over excavation will be required to remove the unstable 'soils. We suggest that at least 3 test
strips be prepared as outlined above to verify the effectiveness of this method of treatment. If the
subsurface soils exhibit erratic response, then a physical removal is suggested.
In addition, we have reviewed the referenced geotechnical engineering report as to the
applicability to the currently proposed development. Except as modified in this report, it is our
opinion that the referenced documents are applicable to the proposed development. We make no
representation as to the accuracy of the dimensions, measurements, calculations, or any portion
of the design.
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 take the necessary steps to see 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.
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.
If there are any questions regarding this letter or if additional information is desired, please call
the undersigned at (760) 345-1588.
Respectfully submit
EARTH SYST�
/
Cf. 38234
Craig S. Hill
Exp.03l31/09'
CE 38234
�gfFOF CAL�`p
LTR/csh/aj f
Distribution: 2/Coachella Valley Housing Coalition
2/Interactive Design Group
2/MSA, Inc.
Attention: Ms. Melody Maccarone
1 /RC File
2BD File
EARTH SYSTEMS SOUTHWEST
0Earth Systems
10MR, Southwest 79-811B Country Club Drive
Bermuda Dunes, CA 92203
(760)345-1588
(800)924-7015
FAX (760) 345-7315
August 14, 2006
Coachella Valley Housing Coalition
45-701 Monroe Street, Plaza 1, Suite G
Indio, California 92201
Attention: Mr. Steve Crowell
Subject: Addendum to Geotechnical Engineering Report
Project: Proposed Multi -Family Residential Development
Northwest Corner of Dune Palms Road and Avenue 48
La Quinta, California
File No.: 09571-04
06-08-778
Reference: Earth Systems Southwest, Geotechnical Engineering Report, Proposed Multi -
Family Residential Development, Northwest Corner of Dune Palms Road and
Avenue 48, La Quinta, California, File No.: 09571-04, Document No.: 06-07-734,
dated July 13, 2006.
Dear Mr. Crowell:
As requested by Mr. George Grayner, we present this addendum to the referenced geotechnical
engineering report prepared for the proposed multi -family residential development to be located
on the northwest corner of Dune Palms Road and Avenue 48 in the City of La Quinta, California.
We understand that a three-story concrete parking structure with basement is planned. The
maximum column load is 350 kips and the maximum wall loading is 5 kips per linear foot for
this parking structure. The referenced geotechnical engineering report is applicable for other
buildings and the following grading and foundation recommendations are applicable for this
parking structure.
Grading Recommendations
Soils within the zone of influence include silty sands and sands. Due to this relatively non-
uniform and variable subsurface condition, we recommend over -excavation and recompaction of
soils in the building area to provide a uniform bearing layer below the footings.
The existing surface soils within the building pad and foundation areas should be over -excavated
to a minimum of 5 feet below the footing level. The over -excavation should extend for at least
10 feet beyond the outer edge of exterior footings. The bottom of the sub -excavation should be
scarified, moisture conditioned to near optimum, and recompacted to at least 95% relative
compaction (ASTM D 1557) for an additional depth of 1 foot.
Engineered Fill Soils: The native sandy 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
August 14, 2006 2 File No.: 09571-04
06-08-778
should be placed in maximum 8-inch lifts (loose) and compacted to at least 95% 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 pre -qualified 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.
Foundation Design Recommendations
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 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.
A summary of our design recommendations for spread foundations for columns are as follows:
Design
Allowable
Minimum
Anticipated
Estimated
Column
Bearing
Footing Size
Total Static
Differentia
Load
Pressure
Settlement
1
Settlement
350 kips
4000 psf
9.5 ft x 9.5 ft
1 inch
0.5 inch
Excavations and Utility Trenches
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.
EARTH SYSTEMS SOUTHWEST
August 14, 2006
3
File No.: 09571-04
06-08-778
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
Hongbin uo, Ph.D.
Project Engineer
SER/hh/lk/ajf
Distribution: 3/Coachella Valley Housing
1/RC File
2/BD File
Reviewed by,
44
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Senior Vice -President
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EARTH SYSTEMS SOUTHWEST
COACHELLA VALLEY HOUSING COALITION
45-701 MONROE STREET, PLAZA 1, SUITE G
INDIO, CALIFORNIA 92201
GEOTECHNICAL ENGINEERING REPORT
PROPOSED MULTI -FAMILY
RESIDENTIAL DEVELOPMENT
NORTHWEST CORNER OF
DUNE PALMS ROAD AND AVENUE 48
LA QUINTA, CALIFORNIA
July 13, 2006
0 2006 Earth Systems Southwest
Unauthorized use or copying of this document is strictly prohibited
without the express written consent of Earth Systems Southwest.
File No.: 09571-04
06-07-734
0Earth Systems
;,� Southwest
July 13, 2006
Coachella Valley Housing Coalition
45-701 Monroe Street, Plaza 1, Suite G
Indio, California 92201
Attention: Mr. Steve Crowell
Subject: Geotechnical Engineering Report
Project: Proposed Multi -Family Residential Development
Northwest Corner of Dune Palms Road and Avenue 48
La Quinta, California
Dear Mr. Crowell:
79-811 B Country Club Drive
Bermuda Dunes, CA 92203
(760)345-1588
(800) 924-7015
FAX (760) 345-7315
File No.: 09571-04
06-07-734
We take pleasure in presenting this geotechnical engineering report prepared for the proposed
multi -family residential development to be located on the northwest corner of the intersection of
Dune Palms Road and Avenue 48 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 the potential for differential settlement. The site is subject to strong ground motion from
regional faults, including the San Andreas fault. 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 February
22, 2006. 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
Hongbin Huo, Ph.D.
Project Engineer
SER/hh/csh/reh
Distribution: 6/Coachella Valley Housing Coalition
1/RC File
2/BD File
Reviewed by,
Craig S. Hill
CE 38234
i
TABLE OF CONTENTS
Page
EXECUTIVE SUMMARY .................................................... ..
Section 1. INTRODUCTION........................................................................................... I
1.1
Project Description............................................................................................1
1.2
Site Description.................................................................................................1
1.3
Purpose and Scope of Work..............................................................................2
Section 2
METHODS OF INVESTIGATION...............................................................3
2.1
Field Exploration...............................................................................................
3
2.2
Laboratory Testing.............................................................................................3
Section3
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
Section 4
CONCLUSIONS..............................................................................................9
Section 5
RECOMMENDATIONS..............................................................................10
SITE
DEVELOPMENT AND GRADING.................................................................10
5.1
Site Development — Grading...........................................................................10
5.2
Excavations and Utility Trenches....................................................................11
5.3
Slope Stability of Graded Slopes.....................................................................
I I
STRUCTURES............................................................................................................12
5.4
Foundations.....................................................................................................12
5.5
Slabs-on-Grade................................................................................................13
5.6
Retaining Walls...............................................................................................14
5.7
Mitigation of Soil Corrosivity on Concrete.....................................................15
5.8
Seismic Design Criteria...................................................................................15
5.9
Pavements........................................................................................................16
Section 6 LIMITATIONS AND ADDITIONAL SERVICES....................................18
6.1 Uniformity of Conditions and Limitations......................................................18
6.2 Additional Services..........................................................................................19
REFERENCES..........................................................................................................20
APPENDIX A
Figure 1 — Site Location Map
Figure 2 — Boring Location Map
Table 1 — Fault Parameters
Terms and Symbols used on Boring Logs
Soil Classification System
Logs of Borings
APPENDIX B
Laboratory Test Results
EARTH SYSTEMS SOUTHWEST
11
EXECUTIVE SUMMARY
Earth Systems Southwest has prepared this executive summary solely to provide a general
overview of the report. The report itself should be relied upon for information about the
findings, conclusions, recommendations, and other concerns.
The site is located on the northwest corner of the intersection of Dune Palms Road and Avenue
48 in the City of La Quinta, California. The proposed development will consist of about 31
multi -unit buildings and a community center with pool and spa. We understand that the
proposed structures will be of wood -frame and stucco construction supported with perimeter wall
foundations and concrete slabs -on -grade.
The proposed project may be constructed as planned, provided the recommendations in this
report are incorporated in the final design and construction. Site development will include
clearing and grubbing of vegetation, site grading, building pad preparation, underground utility
installation, street and parking lot construction, and concrete driveway and sidewalks placement.
Based on the non -uniform nature and hydrocollapse potential of the near surface 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 design
parameters are presented in the following table and within the report.
EARTH SYSTEMS SOUTHWEST
iii
SUMMARY OF RECOMMENDATIONS
Design Item
Recommended Parameter
Reference Section No.
Foundations
Allowable Bearing Pressure
Continuous wall footings
Pad (Column) footings
1,500 psf
2,000 psf
5.4
Foundation Type
Spread Footing
5.4
Bearing Materials
Engineered fill
Allowable Passive Pressure
250 pcf
5.4
Active Pressure
35 pcf
5.6
At -rest Pressure
55 pcf
5.6
Allowable Coefficient of Friction
0.35
5.4
Soil Expansion Potential
Very low (EI < 20)
3.1
and Seismic Hazards
-Geologic
Liquefaction Potential
Negligible
3.4.2
Significant Fault and Magnitude
San Andreas, M7.7
3.4.3; 5.8
Fault Type
A
3.4.3; 5.8
Seismic Zone
4
3.4.3; 5.8
Soil Profile Type
Sp
3.4.3; 5.8
Near -Source Distance
8.9 km
3.4.3; 5.8
Near Source Factor, Na
1.05
3.4.3; 5.8
Near Source Factor, N„
1.29
3.4.3; 5.8
Pavement
TI equal to 4.5
3.0" AC / 4.0" AB
5.9
TI equal to 5.0
3.0" AC / 4.0" AB
5.9
Slabs
Building Floor Slabs
On engineered fill
5.5
Modulus of Subgrade Reaction
200 pci
5.5
Existing Site Conditions
Existin Fill
N/A
Soil Corrosivity
low sulfates
low chlorides
severe resistivity
(protect buried metal pipes)
5.7
Groundwater Depth
> 100 feet
3.2
Estimated Fill and Cut
15 feet
1.1
The recommendations contained within this report are subject to the limitations presented in
Section 6 of this report. We recommend that all individuals using this report read the limitations.
EARTH SYSTEMS SOUTHWEST
July 13, 2006
GEOTECHNICAL ENGINEERING REPORT
PROPOSED MULTI -FAMILY
RESIDENTIAL DEVELOPMENT
NORTHWEST CORNER OF
DUNE PALMS ROAD AND AVENUE 48
LA QUINTA, CALIFORNIA
Section 1
INTRODUCTION
1.1 Project Description
File No.: 09571-04
06-07-734
This geotechnical engineering report has been prepared for the proposed multi -family residential
development to be located on the northwest corner of the intersection of Dune Palms Road and
Avenue 48 in the City of La Quinta, California. We understand that the proposed development
will include about 31 multi -unit buildings and a community center with pool and spa.
The proposed residential development will be single- or multi -story structures. 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, street and parking lot construction, and concrete
driveway and sidewalks placement. The development also consists of underground parking
facilities. Based on existing site topography and ground conditions, site grading is expected to
consist of cuts and fills of about 15 feet.
We used maximum column loads of 20 kips and a maximum wall loading of 2 kips per linear
foot as a basis for the foundation recommendations. All loading is assumed to be dead plus
actual live load. If actual structural loading exceeds these assumed values, we would need to
reevaluate the given recommendations.
1.2 Site Description
The proposed multi -family residential development is to be constructed on the northwest corner
of the intersection of Dune Palms Road and Avenue 48 in the City of La Quinta, California. The
site location is shown on Figure 1 in Appendix A.
The site consists of abandoned agricultural land described as a portion of the southeast quarter of
the southwest quarter of Section 29, Township 5 South, Range 7 East, San Bernardino baseline
and meridian. The history of past use and development of the property was not investigated as
part of our scope of services. The northern portion of the site was previously occupied by
structures assumed to be residential. Remnants of previous concrete foundations, wood, and
other construction debris are present on the site. The southeast corner of the site appears to have
been graded in the past. Grass clippings and clayey soils were observed in the southwest corner
of the site and extend in a northwest direction off -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.
EARTH SYSTEMS SOUTHWEST
July 13, 2006 2 File No.: 09571-04
06-07-734
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 eight exploratory borings to depths ranging
from approximately 19 to 51.5 feet below existing grade.
➢ 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.
• Lateral earth pressures and coefficients.
• 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.
The client did not direct ESSW to provide any service to investigate or detect the presence of
moisture, mold, or other biological contaminates in or around any structure, or any service that
was designed or intended to prevent or lower the risk or the occurrence of the amplification of
the same. Client acknowledges that mold is ubiquitous to the environment, with mold
amplification occurring when building materials are impacted by moisture. Client further
acknowledges that site conditions are outside ofESSW's control and that mold amplification will
likely occur or continue to occur in the presence of moisture. As such, ESS W cannot and shall
not be held responsible for the occurrence or recurrence of mold amplification.
EARTH SYSTEMS SOUTHWEST
July 13, 2006
Section 2
METHODS OF INVESTIGATION
2.1 Field Exploration
3 File No.: 09571-04
06-07-734
Eight exploratory borings were drilled to depths ranging from approximately 19 to 51.5 feet
below the existing ground surface to observe the soil profile and to obtain samples for laboratory
testing. The borings were drilled on May 12 and 16, 2006 using 8-inch outside diameter hollow -
stem augers, powered by a CME 55 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 automatic hammer, 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.
➢ Maximum density tests to evaluate the moisture -density relationship of typical soils
encountered.
➢ Particle Size Analysis to classify and evaluate soil composition. The gradation
characteristics of selected samples were made by hydrometer and sieve analysis
procedures.
➢ Consolidation (Collapse Potential) 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
July 13, 2006 4 File No.: 09571-04
06-07-734
Section 3
DISCUSSION
3.1 Soil Conditions
The field exploration indicates that site soils consist generally of silty sand, poorly graded sand
with silt, and silt (Unified Soils Classification System symbols SM, SP-SM, and ML).
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. Consolidation
testing indicates 2.2% collapse upon inundation and collapse is therefore considered a 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 (PMio) can
create an air quality hazard if dust is blowing. Watering the surface, planting grass or
landscaping, or placing hardscape normally mitigates this hazard.
3.2 Groundwater
Free groundwater was not encountered in the borings during exploration. The depth to
groundwater at the site was evaluated by contacting the Coachella Valley Water District
[CVWD]. Mr. Brad Gummer of the CVWD indicated the average depth to groundwater for
Township 5 South, Range 7 East, Section 29, was 148.84 feet in 2004. The groundwater levels
may fluctuate with precipitation, irrigation, drainage, regional pumping from wells, and site
grading. Groundwater should, not be a factor in design or construction at this site.
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 Miocene to Holocene sedimentary deposits. 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
EARTH SYSTEMS SOUTHWEST
July 13, 2006 5 File No.: 09571-04
06-07-734
Hill fault, the Banning fault, and the Mission Creek fault that traverse along the northeast margin
of the valley.
Local Geology: The project site is located 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),
lacustrine (lake -bed), and alluvial (water -laid) origin. Dune sand is present on the property. 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 and San Jacinto faults. The
Maximum Magnitude Earthquake (MmpX) 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);
however, no active faults are mapped in the immediate vicinity of the site. 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 La Quinta
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 Coachella Valley area and caused structural
damage, as well as injuries.
• Joshua Tree Earthquake — On April 22, 1992, a magnitude 6.1 ML (6.1 Mw) earthquake
occurred in the mountains 9 miles east of Desert Hot Springs. Structural damage and minor
injuries occurred in the Coachella Valley area as a result of this earthquake.
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• 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)
earthquake occurred near Big Bear Lake. No significant structural damage from these
earthquakes was reported in the La Quinta area.
• Hector Mine Earthquake — On October 16, 1999, a magnitude 7.1 Mw 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 site lies within a moderate liquefaction hazard area established by the 2002 Riverside County
General Plan, based on historic high groundwater from 50 to 100 feet and very susceptible
(Holocene) sediments. Quantitative liquefaction analyses are typically not required for general
construction where groundwater depth exceeds 50 feet. The potential for liquefaction to occur at
this site is negligible because the existing depth of groundwater beneath the site exceeds 50 feet
and is not expected to return to levels above 50 feet. Therefore, no special mitigation for soil
liquefaction is warranted for this project.
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Ground Subsidence: The potential for seismically induced ground subsidence is considered to be
low 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.
Slope Instability: The site is relatively flat. Therefore, potential hazards from slope instability,
landslides, or debris flows are considered negligible.
Flooding: The project site does not lie within a designated FEMA 100-year flood plain. The
project site is 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 I 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 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
Prohahilistic Seismic Hazard Mans
Risk
Equivalent Return
Period (years)
PGA () t
10% exceedance in 50 years
1 475
0.56
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 in Section 5.8 of this
report and below.
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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:
Sp
Table 16-J
Seismic Source Type:
A
Table 16-U
Closest Distance to Known Seismic Source:
8.9 km = 5.5 miles
(San Andreas fault)
Near Source Factor, Na:
1.05
Table 16-5
Near Source Factor, Nv:
1.29
Table 16-T
Seismic Coefficient, Ca:
0.46 = 0.44Na
Table 16-Q
Seismic Coefficient, Cv:
0.83 = 0.64Nv
Table 16-R
Seismic Hazard Zones: The site lies within a moderate liquefaction hazard area established by
the 2002 Riverside County General Plan, based on historic high groundwater from 50 to 100 feet
and very susceptible (Holocene) sediments. Quantitative liquefaction analyses are typically not
required for general construction where groundwater depth exceeds 50 feet. The potential for
liquefaction to occur at this site is negligible because the existing depth of groundwater beneath
the site exceeds 50 feet and is not expected to return to levels above 50 feet.
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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.
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 SD, and is about 8.9 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 and hydroconsolidation are potential hazards in
the Coachella Valley area. 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, seismically induced
flooding, and landslides, are considered low or negligible on this site.
➢ The upper soils were found to be relatively loose to medium dense and are unsuitable 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 the potential for differential
settlement from static loading. Soils can be readily cut by normal grading equipment.
➢ The native soils were found to have low sulfate and chloride ion concentrations.
Electrical resistivity testing of the soil suggests that site soils may present a "severe"
potential for metal loss from electrochemical corrosion processes.
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Section 5
RECOMMENDATIONS
SITE DEVELOPMENT AND GRADING
5.1 Site Development — Grading
A representative of Earth Systems Southwest (ESSW) should observe site clearing, grading, and
the bottoms of excavations before placing fill. 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, trees, large roots,
pavements, foundations, 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: Because of the relatively non -uniform and under -compacted nature of
the site soils, we recommend recompaction of soils in the building area. The existing surface
soils within the building pad and foundation areas should be over -excavated to a minimum of
4 feet below existing or finished grade or a minimum of 2 feet below the footing level
(whichever is lower). For the underground parking lots, the over -excavation should be 2 feet
below the footing level. The over -excavation should extend for 5 feet beyond the outer edge of
exterior footings. The bottom of the sub -excavation should be scarified, thoroughly moisture
conditioned, and recompacted to at least 90% relative compaction (ASTM D 1557) for an
additional depth of 1 foot.
Auxiliary Structures Subgrade Preparation: Auxiliary structures such as garden or retaining
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.
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 sandy soil is suitable for use as engineered fill and utility
trench backfrll, provided it is free of significant organic or deleterious matter. The native soil
should be 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.
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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.
Shrinkage: The shrinkage factor for earthwork is expected to range from 5 to 20 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 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).
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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 for
single -story structures and 18 inches below lowest adjacent grade for two-story structures. 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, or as
noted above:
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 3000 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 3000 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 (as specified in the California Building
Code) 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 '/2 inch, expressed in a post -construction angular
distortion ratio of 1:480 or less.
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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
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
Subgrade: 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
aid 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 superseding any
structural design. The design engineer and/or project architect should ensure compliance
with SB800 with regards to moisture and moisture vapor.
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
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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
%2-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.
Curing and Quality Control: The contractor should take precautions to reduce the potential of
curling of slabs in this arid 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 Retaining Walls
The following table 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 t
Granular Backfill
Passive Pressure
375 pcf - level ground
Active Pressure (cantilever walls)
Use when wall is permitted to rotate 0.1 % of wall height
35 pcf - level ground
At -Rest Pressure (restrained walls)
55 pcf - level ground
Dynamic Lateral Earth Pressure 2
Acting at 0.6H, where H is height of backfill in feet
50 pcf
Base Lateral Sliding Resistance
Dead load x Coefficient of Friction:
0.50
Notes:
l . 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 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. Waterproofing should be according to the designer's specifications. Water
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should not be allowed to pond near the top of the wall. To accomplish this, the final backfll
grade should be such that all water is diverted away from the retaining wall.
Backfill and Subgrade 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. Foundation subgrade
preparation should be as specified in Section 5.1.
5.7 Mitigation of Soil Corrosivity on Concrete
Selected chemical analyses for corrosivity were conducted on soil samples from the project site
as shown in Appendix B. The native soils were found to have low sulfate ion concentrations (22
to 45 ppm) and low chloride ion concentrations (127 to 144 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 should be provided around steel reinforcing or
embedded components exposed to native soil or landscape water. Additionally, the concrete
should be thoroughly vibrated during placement.
Electrical resistivity testing of the soil suggests that the site soils may present a "severe" 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.
The information provided above should be considered preliminary. These values can potentially
change based on several factors, such as importing soil from another job site and the quality of
construction water used during grading and subsequent landscape irrigation.
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, if further guidance is desired.
5.8 Seismic Design Criteria
This site is subject to strong ground shaking due to potential fault movements along regional
faults, including the San Andreas and San Jacinto faults. 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
seismic coefficients given in the table below.
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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 16-1
Soil Profile Type:
SD
Table 16-J
Seismic Source Type:
A
Table 16-U
Closest Distance to Known Seismic Source:
8.9 km = 5.5 miles
(San Andreas fault)
Near Source Factor, Na:
1.05
Table 16-S
Near Source Factor, Nv:
1.29
Table 16-T
Seismic Coefficient, Ca:
0.46 = 0.44Na
Table 16-Q
Seismic Coefficient, Cv:
0.83 = 0.64Nv
Table 16-R
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 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.
Estimated peak (mean plus one standard deviation) horizontal site accelerations based upon a
probabilistic analysis (10% probability of occurrence in 50 years) is approximately 0.56 g for a
stiff soil site. Actual accelerations may be more or less than estimated. Vertical accelerations are
typically %3 to 2/3 of the horizontal accelerations, but can equal or exceed the horizontal
accelerations, depending upon the local site effects and amplification.
5.9 Pavements
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.
EARTH sYS'rEMS SOUTH WES"r
July 13, 2006
17 File No.: 09571-04
06-07-734
PRELIMINARY RECOMMENDED PAVEMENTS SECTIONS
R-Value Subgrade Soils — 50 (assumed) Design Method — CALTRANS 1995
Flexible Pavements
Rigid Pavements
Asphaltic
Aggregate
Portland
Aggregate
Traffic
Pavement Use
Concrete
Base
Cement
Base
Index
Thickness
Thickness
Concrete
Thickness
(Assumed)
(Inches)
(Inches)
(Inches)
(Inches)
4.5
Auto Parking Areas
3.0
4.0
4.0
4.0
5.0
Residential Streets
3.0
4.0
5.0
4.0
Notes:
1. Asphaltic concrete should be Caltrans, Type B, ''/2-in. or 1/4-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 (3/4 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
July 13, 2006
18 File No.: 09571-04
06-07-734
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 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 geoteehnical 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
EARTH SYSTEMS SOUTHWEST
July 13, 2006 19 File No.: 09571-04
06-07-734
or toxic materials in the soil, surface water, groundwater, or air on, below, or adjacent to the
subject property.
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
July 13, 2006 20 File No.: 09571-04
06-07-734
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), 2004, ACI Manual of Concrete Practice, Parts 1 through 5.
American Society of Civil Engineers (ASCE), 2003, Minimum Design Loads for Buildings and
Other Structures, ASCE 7-02
California Department of Water Resources, 1964, Coachella Valley Investigation, Bulletin No. 108,
146 pp.
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.
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.
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.
Wallace, R. E., 1990, The San Andreas Fault System, California: U.S. Geological Survey
Professional Paper 1515, 283 p.
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 SOUTHWEST
APPENDIX A
Figure 1 — Site Location Map
Figure 2 — Boring Location Map
Table 1 — Fault Parameters
Terms and Symbols used on Boring Logs
Soil Classification System
Logs of Borings
EARTH SYSTEMS SOUTHWEST
116°18'0"W
565000
116017'15"W 116°16'30" 6V 116°15'45"W
566000 567000 568000 569000
0
G
M
M
M
0
0
0
0
M
F
M
MILES
L9
PP
AVENUS
r %
li ? \ ''' U '-i �'r, Ai,"H�T�4, � Trra7h�J,�'�,11•�._a`�; .. ., �• '.>�y:�I ,I `t x
`�•�-°�-te.:pr•: qM-72 - �, ;
+:• i iitt�
it
?If
Li l
. > railer NO •i •,�
i -
Y.
rj
r' '• ;t'.: Ave �'4� Nam{`
•
nue
-
We
'
...SIT
E
r .A, r ,jj{:
+� • '� t' V 33A well
.. � ���'3.1 ` ' 1. "� �� `I• ..,,, `' j ,�; _- � �_.
1
565000
116°18'0"W
666000
116°17'15"W
r•
1 _i U Jd I>t AVENU
_ It
I
Well
7
n
G
0
0
00
N
M <
567000 568000 569000
116°16'30"W 116015 45"W
0 500 1,000 2,000 3,000 4.000 5,000
Feel
Figure 1
LEGEND N Site Location Map
Multi -Family Residential Development
Site Boundary NWC Dune Palms Road & Avenue 48
La Quinta, Riverside County, California
A�Earth Systems
Southwest
Reference: www.terraserverusa.com 07/13/06 1 File No.: 09571-04
v
'^ M
566700
116'16'42"W
566900
567000
567100
0
0
0
rn
N
F
M
ti
R
M
M
O
O
M
04
N
F
M
O
O
a
rn
N
F
M
O
O
N
O
N
M
M
116°l6'42"W
0 50 100 200 300 400
500
R Feet
' Figure 2
LEGEND N Boring Location Map
Approximate Boring Location Multi -Family Residential Development
NWC Dune Palms Road & Avenue 48
La Quinta Riverside County, California
t Site Boundary '
...... : joft Earth Systems
Southwest
Reference: www.globexplorer.com 07/13/06 1 File No.: 09571-04
NWC Dune Palms and Avenue 48, La Quinta, CA 09571-04
Table 1
Fault Parameters
& Deterministic Estimates of Mean Peak Ground Acceleration (PGA)
Fault Name or
Seismic Zone
Distance
from Site
(mi) (km)
Fault
Type
Maximum
Magnitude
Mmax
(Mw)
Avg
Slip
Rate
(mm/yr)
Avg
Return
Period
(yrs)
Fault
Length
(km)
Mean
Site
PGA
W
Reference Notes: I
2
3
(4)
(2(2)_(2)
(5
San Andreas - Southern
5.5
8.9
SS
A
7.7
24
220
199
0.44
San Andreas - Banning Branch
5.9
9.5
SS
A
7.2
10
220
98
0.37
San Andreas - Mission Crk. Branch
5.9
9.5
SS
A
7.2
25
220
95
0.37
Blue Cut
14.3
22.9
SS
C
6.8
1
760
30
0.17
San Jacinto (Hot Spgs - Buck Ridge)
17.1
27.4
SS
C
6.5
2
354
70
0.12
Burnt Mtn.
17.6
28.4
SS
B
6.5
0.6
5000
21
0.12
Eureka Peak
18.5
29.8
SS
B
6.4
0.6
5000
19
0.11
San Jacinto -Anna
21.4
34.4
SS
A
7.2
12
250
91
0.14
San Jacinto -Coyote Creek
21.8
35.1
SS
B
6.8
4
175
41
0.11
Morongo
29.0
46.7
SS
C
6.5
0.6
1170
23
0.07
Pinto Mountain
30.5
49.1
SS
B
7.2
2.5
499
74
0.10
Emerson So. - Copper Mtn.
31.8
51.2
SS
B
7.0
0.6
5000
54
0.09
Landers
32.7
52.7
SS
B
7.3
0.6
5000
83
0.10
Pisgah -Bullion Mtn. -Mesquite Lk
33.8
54.4
SS
B
7.3
0.6
5000
89
0.10
San Jacinto - Borrego
35.1
56.5
SS
B
6.6
4
175
29
0.06
San Jacinto -San Jacinto Valley
36.8
59.3
SS
B
6.9
12
83
43
0.07
North Frontal Fault Zone (East)
38.9
62.6
RV
B
6.7
0.5
1727
27
0.08
Earthquake Valley
40.1
64.5
SS
B
6.5
2
351
20
0.05
Brawley Seismic Zone
41.0
66.1
SS
B
6.4
25
24
42
0.05
Johnson Valley (Northern)
43.5
70.0
SS
B
6.7
0.6
5000
35
0.06
Elsinore -Julian
44.2
71.1
SS
A
7.1
5
340
76
0.07
Calico - Hidalgo
45.2
72.7
SS
B
7.3
0.6
5000
95
0.08
Elsinore -Temecula
48.0
77.2
SS
B
6.8
5
240
43
0.05
Elmore Ranch
49.2
79.2
SS
B
6.6
1
225
29
0.05
Lenwood-Lockhart-Old Woman Sprgs
49.3
79.4
SS
B
7.5
0.6
5000
145
0.08
North Frontal Fault Zone (West)
50.0
80.5
RV
B
7.2
1
1314
50
0.08
Elsinore -Coyote Mountain
51.2
82.4
SS
B
6.8
4
625
39
0.05
Superstition Mtn. (San Jacinto)
53.2
85.6
SS
B
6.6
5
500
24
0.04
Superstition Hills (San Jacinto)
54.0
86.9
SS
B
6.6
4
250
23
0.04
Helendale - S. Lockhardt
57.2
92.1
SS
B
7.3
0.6
5000
97
0.06
San Jacinto -San Bernardino
59.1
95.2
SS
B
6.7
12
100
36
0.04
Elsinore -Glen Ivy
61.7
99.3
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, RV = Reverse, DS = Dip Slip (normal), 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 at; (3) 1997 Campbell, (4) 1997 Abrahamson & Silva
(mean plus sigma values are about 1.5 to 1.6 times higher)
Based on Site Coordinates: 33.704 N Latitude, 116.277 W Longtude and Site Soil Type D
EARTH SYSTEMS SOUTHWEST
DESCRIPTIVE SOIL CLASSIFICATION
Soil classification is based on ASTM Designations D 2487 and D 2488 (Unified Soil Classification System). Information on each boring
log is a compilation of subsurface conditions obtained from the field as well as from laboratory testing of selected samples. The
indicated boundaries between strata on the boring logs are approximate only and may be transitional.
12" 3" 3/4"
SOIL GRAIN SIZE
U.S. STANDARD SIEVE
4 10 40 200
BOULDERS
COBBLES
GRAVEL
I SAND
SILT CLAY
COARSE I FINE
I COARSE I MEDIUM FINE
305 76.2 19.1 4.76 2.00 0.42 0.074
SOIL GRAIN SIZE IN MILLIMETERS
0.002
RELATIVE DENSITY OF GRANULAR SOILS (GRAVELS, SANDS, AND NON -PLASTIC SILTS)
Very Loose
*N=0-4
RD=0-30
Easily push a 1/2-inch reinforcing rod by hand
Loose
N=5-10
RD=30-50
Push a 1/2-inch reinforcing rod by hand
Medium Dense
N=11-30
RD=50-70
Easily drive a 1/2-inch reinforcing rod with hammer
Dense
N=31-50
RD=70-90
Drive a 1/2-inch reinforcing rod 1 foot with difficulty by a hammer
Very Dense
N>50
RD=90-100
Drive a 1/2-inch reinforcing rod a few inches with hammer
*N=Blows per foot in the Standard Penetration Test at 60% theoretical energy. For the 3-inch diameter Modified California sampler,
140-pound weight, multiply the blow count by 0.63 (about 2/3) to estimate N, If automatic hammer is used, multiply a factor of
1.3 to 1.5 to estimate N. RD=Relative Density (%). C=Undrained shear strength (cohesion).
CONSISTENCY OF COHESIVE SOILS (CLAY OR CLAYEY SOILS)
Very Soft
*N=0-1
*C=0-250 psf
Squeezes between fingers
Soft
N=24
C=250-500 psf
Easily molded by finger pressure
Medium Stiff
N=5-8
C=500-1000 psf
Molded by strong finger pressure
Stiff
N=9-15
C=1000-2000 psf
Dented by strong finger pressure
Very Stiff
N=16-30
C=2000-4000 psf
Dented slightly by finger pressure
Hard
N>30
C>4000
Dented slightly by a pencil point or thumbnail
MOISTURE DENSITY
Moisture Condition: An observational term; dry, damp, moist, wet, saturated.
Moisture Content: The weight of water in a sample divided by the weight of dry soil in the soil sample
expressed as a percentage.
Dry Density: The pounds of dry soil in a cubic foot.
MOISTURE CONDITION RELATIVE PROPORTIONS
Dry .....................Absence of moisture, dusty, dry to the touch Trace ............. minor amount (<5%)
Damp................Slight indication of moisture with/some...... significant amount
Moist.................Color change with short period of air exposure (granular soil) modifier/and... sufficient amount to
Below optimum moisture content (cohesive soil) influence material behavior
Wet....................High degree of saturation by visual and touch (granular soil) (Typically >30%)
Above optimum moisture content (cohesive soil)
Saturated .......... Free surface water
LOG KEY SYMBOLS
PLASTICITY
'
Bulk, Bag or Grab Sample
DESCRIPTION
FIELD TEST
Nonplastic
A 1/8 in. (3-mm) thread cannot be rolled
Standard Penetration
Split Spoon Sampler
Low
at any moisture content.
The thread can barely be rolled.
(2' outside diameter)
Medium
The thread is easy to roll and not much
Modified California Sampler
time is required to reach the plastic limit.
'
(3" outside diameter)
High
The thread can be rerolled several times
after reaching the plastic limit.
No Recovery
GROUNDWATER
LEVEL
Water Level (measured or after drilling)
Terms and Symbols used on Boring L
Water Level (during drilling)
GRAPHIC
LETTERSYMBOL
MAJOR DIVISIONS
SYMBOL
TYPICAL DESCRIPTIONS
Well -graded gravels, gravel -sand
CLEAN
GW
mixtures, little or no fines
GRAVELS
rs ri•'rlia raa•�i•
< 5% FINES
GRAVEL AND
GP
Poorly -graded gravels, gravel -sand
GRAVELLY
+�+r: + +�++r+
mixtures. Little or no fines
SOILS
r••r••r,•r••r•r•r••r••
.
.....:.
....
GM
Silty gravels, gravel -sand -silt
More than 50% of
GRAVELS
mixtures
COARSE
GRAINED SOILS
coarse fraction
FINES WITH
WITH
re i e on No. 4
> FINES
Clayey gravels, gravel -sand -clay
sieve
GC
mixtures
SW
Well -graded sands, gravelly sands,
little or no fines
SAND AND
CLEAN SAND
SANDY SOILS
Little or no fines
< 5%
SP
Poorly -graded sands, gravelly
More than 50% of
sands, little or no fines
material is larger
than No. 200
sieve size
SAND WITH FINE
SM
Silty sands, sand -silt mixtures
More than 50% of
(appreciable
coarse fraction
amount of fines)
passing No. 4 sieve
' 1270
SC
Clayey sands, sand -clay mixtures
Inorganic silts and very fine sands,
ML
rock flour, silty low clayey fine sands
or clayey silts with slight plasticity
LIQUID LIMIT
Inorganic clays of low to medium
FINE-GRAINED
LESS THAN 50
CL
plasticity, gravelly clays, sandy
SOILS
clays, silty clays, lean clays
OL
Organic silts and organic silly
clays of low plasticity
SILTSAND
Inorganic silty, micaceous, or
CLAYS
MH
diatomaceous fine sand or
silty soils
;�
,
,
CH
Inorganic clays of high plasticity,
fat clays
50% or more of
material is smaller
than No. 200
LIQUID LIMIT
GREATER
sieve size
THAN 50
............
OH
Organic clays of medium to high
............
plasticity, organic silts
yyyyyyyyyyy
yyyyyyyyyyyy
Peat, humus, swamp soils with
HIGHLY ORGANIC SOILS
'1y\>'"1yy1y1Vyy\>'
yyyyyyyyyyy
PT
high organic contents
�v\y1y1y1y"\y1y"\Y1>1
VARIOUS SOILS AND MAN MADE MATERIALS
Fill Materials
MAN MADE MATERIALS
Asphalt and concrete
Soil Classification
System
Earth Systems
Southwest
0 Earth Systems
Southwest
79-811 B Country Club Drive, Bermuda Dunes, CA 92203
Phone (760) 345-1588. rax (760) 345-73 15
Boring No: B-1
Drilling Date: May 12, 2006
Project Name: NWC Dune Palms Rd. & Ave. 48, La Quinta, CA
Drilling Method: 8" Hollow Stem Auger
File Number: 09571-04
Drill Type: Williams CME 55 w/Auto Hammer
Boring Location: See Figure 2
Logged By: Dirk Wiggins
v
Sample
Type w
Penetration
_
N
Description of Units Page 1 of 1
F
Resistance
A
°'
o CL
= °
Note: The stratification lines shown represent the
-, o
T
b,
� o
approximate boundary between soil and/or rock types Graphic''rend
p
m N 0
(Blows/6")
q
U
and the transition may be gradational, Blow Count Dry Density
SM
SILTY SAND: pale yellowish brown, very loose,
dry, fine to medium grained
5
4,6,9
92
1
SM
SILTY SAND: pale yellowish brown, medium
dense, dry, fine to medium grained
10
3,5,8
88
4
pale to moderate yellowish brown, damp
15
4,6,10
92
3
SM
SILTY SAND: pale yellowish brown, medium
dense, damp, fine to medium grained
20
5,9,14
89
10
25
Total Depth 21.5 feet
No Groundwater Encountered
30
35
40
45
50
55
cn
% Earth Systems
IVIN Southwest 79.811 B Country Chub Drive, Bemmda Dunes, CA 92203
Phone (760) 345-1588, Fax (760) 345-7315
Boring No: B-2
Drilling Date: May 12, 2006
Project Name: NWC Dune Palms Rd. & Ave. 48, La Quinta, CA
Drilling Method: 8" Hollow Stem Auger
File Number: 09571-04
Drill Type: Williams CME 55 w/Auto Hammer
Boring Location: See Figure 2
Logged By: Dirk Wiggins
Samle
Type w
Penetration
Description of Units Page l of 1
�
�
Resistance
�
�
Q �
•= �
No
Note: The stratification lines shown rep resent the
o
q
�g
� o
approximate boundary between soil and/or rock types Graphic Trend
q
m'
(B1ows/6")
q
U
and the transition may be gradational. Blow Count Dry Density
SP-SM
SAND WITH SILT: pale yellowish brown, loose,
dry, fine to medium grained, with mica
2,4,4
85
2
5
2,3,5
86
6
damp, silty sand lenses
10
4,6,8
88
2
medium dense, dry
15
6,12,20
dense
20
Total Depth 19 feet
No Groundwater Encountered
25
30
35
40
45
50
55
cn
Earth Systems
Southwest 79-811 B Country Club Drive, Bennuda Dunes, CA 92203
Phone (760) 345-1588, Fnx (760) 345-73 15
Boring No: B-3
Drilling Date: May 16, 2006
Project Name: NWC Dune Palms Rd. & Ave. 48, La Quinta, CA
Drilling Method: 8" Hollow Stem Auger
File Number: 09571-04
Drill Type: Williams CME 55 w/Auto Hammer
Boring Location: See Figure 2
Logged By: Dirk Wiggins
v
Sample
Types
Penetration•c
4)'
Description of Units Page I of 1
Resistance
n
U
°'
q Q
0 ,�,
Note: The stratification lines shown represent the
0
44 Q
T
�
�
o
approximate boundary between soil and/or rock types Graphic Trend
q
(IIlows/6")
q
U
and the transition may be gradational. Blow Count Dry Density
SP-SM
SAND WITH SILT: pale yellowish brown, loose,
dry, fine to medium grained
5
2,3,5
92
3
10
3,4,7
90
4
medium dense, damp
15
4,9,10
100
3
dry, trace coarse grained sand
20
6,12,15
92
4
dry to damp, lenses of silty sand
25
7,12,10
92
G
SM
SILTY SAND: pale yellowish brown, medium
dense, damp, fine to medium grained
30
7114,22
97
2
Sp-SM
SAND WITH SILT: pale yellowish brown, dense,
damp, fine to medium grained
35
Total Depth 31.5 feet
No Groundwater Encountered
40
45
50
55
4n
Earth Systems
'�✓ Southwest 79-811 B Country Club Drive, Bermuda Dunes, CA 92203
Phone. (760)345-1588,Fax (760)345-7315
Boring No: B-4
Drilling Date: May 16, 2006
Project Name: NWC Dune Palms Rd, & Ave. 48, La Quinta, CA
Drilling Method: 8" Hollow Stem Auger
File Number: 09571-04
Drill Type: Williams CME 55 w/Auto Hammer
Boring Location: See Figure 2
Logged By: Dirk Wiggins
v
Sample
Type
Penetration
C
a
Description of Units Page 1 of 1
F
a
w
Resistance
N
A a
•o �
Note: The stratification lines shown represent the
Y A
T
o
approximate boundary between soil and/or rock types Graphic Trend
p
m 0
(Blows/6")
N
p
U
and the transition may be gradational. Blow Count Dry Density
SM
SILTY SAND: pale yellowish brown, loose, dry,
fine to medium grained
5
3.4.5
98
1
SP-SM
SAND WITH SILT: pale yellowish brown, loose,
dry, fine to medium grained
10
314,8
97
14
medium dense
IS
6,10,12
87
14
gM
SILTY SAND: pale yellowish brown, medium
dense, damp, fine to medium grained, lenses of
sandy silt
20
8,8,11
85
4
fine grained
25
5,10,13
89
11
1v1L
SANDY SILT: pale yellowish brown, dense, dry,
fine grained, lenses of silty sand
30
4,6,7
SP-SM
SAND WITH SILT: pale yellowish brown, medium
dense, dry, fine to medium grained
35
Total Depth 31.5 feet
No Groundwater Encountered
40
45
50
55
cn
Earth Systems
RSouthwest 79-81 1 B Country Club Drive, Bennuda Dunes, CA 92203
Phone (760) 345-1588, fax (760) 345-7315
Boring No: B-5
Drilling Date: May 16, 2006
Project Name: NWC Dune Palms Rd. & Ave. 48, La Quinta, CA
Drilling Method: 8" Hollow Stem Auger
File Number: 09571-04
Drill Type: Williams CME 55 w/Auto Hammer
Boring Location: See Figure 2
Logged By: Dirk Wiggins
v
Sample
Type
Penetration
'y
� ..
Description of Units Page 1 of I
P ��
u
Resistance
_
°
.A
U
Cn
°'
q n,
H ,e
Note: The stratification lines shown represent the
To
approximate boundary between soil and/or rock types Graphic Trend
q
0
(Blows/6")
q
U
and the transition may be gradational. Blow Count Dry Density
SP-SM
SAND WITH SILT: loose, dry, no recovery
2,4,5
5
2,5,6
medium dense, no recovery
10
4,6,8
96
1
pale yellowish brown, medium dense, dry
ML
SANDY SILT: moderate yellowish brown, medium
dense, dry to damp, fine to medium grained
15
3,7,11
97
12
20
5,10,12
85
18
moist
25
6,6,8
damp, with fine grained sand
30
4,5,7
damp
35
3,9,9
pale to moderate yellowish brown, with fine to medium
grained sand
40
5 9,9
SP-SM
SAND WITH SILT: pale yellowish brown, medium
dense, dry, fine to medium grained
45
❑
4 7 g
SM
SILTY SAND: pale to moderate yellowish brown,
medium dense, dry, fine to medium grained
50
9 16 )g
SP-SM
SAND WITH SILT: pale yellowish brown, dense,
dry, fine to medium grained
55
Total Depth 51.5 feet
No Groundwater Encountered
Gn
0Earth Systems
2OR; Southwest 79-811 B Country Club Drive, Bermuda Dunes, CA 92203
Phone (760) 345-1588• Fax (760) 345-7315
Boring No: B-6
Drilling Date: May 16, 2006
Project Name: NWC Dune Palms Rd. & Ave. 48, La Quinta, CA
Drilling Method: 8" Hollow Stem Auger
File Number: 09571-04
Drill Type: Williams CME 55 w/Auto Hammer
Boring Location: See Figure 2
Logged By: Dirk Wiggins
k
Sample
Type
Penetration
Description of Units Page 1 of I
a
Resistance
0
U
0 chi
p
y r-
Note: The stratification lines shown represent the
:D
�`
o c
approximate bounds between soil and/or rock types Graphic Trend
pP boundary Yp p
Ca
m °vi 5
(Blows/6"
rn
p
o
U
and the transition may be gradational. Blow Count Dry Density
SP-SM
SAND WITH SILT: pale yellowish brown, loose,
dry, tine to medium grained
2,4,4
-
I
5
3,6,8
82
3
medium dense
10
5,6,10
88
4
SM
SILTY SAND: pale yellowish brown, medium
15
dense, dry, fine grained
5,10,12
90
2
dry to damp, sand with silt lenses
20
5,9,16
94
13
moist, poor recovery
25
1 t,14,►8
99
2
sP-sM
SAND WITH SILT: pale yellowish brown, dense,
30
dry, fine to medium grained
5,7,8
medium dense
35
❑
5,7,8
40
Total Depth 39 feet
No Groundwater Encountered
45
50
55
Earth Systems
WN-1 Southwest 79-811 B Country Club Drive, Bennuda Duties, CA 92203
Phone (760) 345-1588. Fax (760) 345-7315
Boring No: B-7
Drilling Date: May 16, 2006
Project Name: NWC Dune Palms Rd. & Ave. 48, La Quinia, CA
Drilling Method: 8" Hollow Stem Auger
File Number: 09571-04
Drill Type: Williams CME 55 w/Auto Hammer
Boring Location: See Figure 2
Logged By: Dirk Wiggins
Sample
Type..,
Penetration
7'
Description of Units Page I of t
L _
n
u
Resistance
q a
.o
Note: The stratification lines shown represent the
A
T
q
�v
o
approximate boundary between soil and/or rock types Graphic Trend
q
(Blows/6")
q
U
and the transition may be gradational. Blow Count Dry Density
sP
SAND WITH SILT: pale yellowish brown, medium
dense, dry, fine to medium grained
2,4,6
92
1
5
90
1
10
5,10,14
S2
3
SM
SILTY SAND: pale yellowish brown, medium
15
dense, dry, fine grained
10,14,16
86
2
20
6,11.12
91
2
25
7,11,11
SP-SM
SAND WITH SILT: pale yellowish brown, medium
dense to dense, dry, fine to medium grained
30
9,14,15
SM
SILTY SAND: pale yellowish brown, dense, dry,
fine to medium grained, trace coarse grained
35
7,13,15
40
T.
7,12,10
45
4,10,12
T.
fine grained
50
'total Depth 49 feet
No Groundwater Encountered
55
�n
Earth Systems
`O, Southwest 79-811 B Country Club Drive, Bermuda Dunes, CA 92203
Phone (760) 345-1588. Fax (760) 345-7315
Boring No: B-8
Drilling Date: May 16, 2006
Project Name NWC Dune Palms Rd. & Ave. 48, La Quinta, CA
Drilling Method: 8" Hollow Stem Auger
File Number: 09571-04
Drill Type: Williams CME 55 w/Auto Hammer
Boring Location: See Figure 2
Logged By: Dirk Wiggins
v
Sample
Type,,:
Penetration
'�
�'
Description of Units Page 1 of I
a
Resistance
o
�
rUn
°'
q Q
o „
Note: The stratification lines shown represent the
�v
c
o
approximate bounds between soil and/or rock es Graphic Trend
boundary bP P
q
0
Blows/6"
( )
0)
q
U
and
and the transition may be gradational. Blow Count Dry Density
SP-SM
SAND WITH SILT: pale yellowish brown, medium
dense, dry, fine to medium grained
5
316,8
93
2
10
3,6,7
86
7
15
5,10,11
88
1
20
7,10,12
89
2
SM
SILTY SAND: pale yellowish brown, medium
dense, dry, very fine to fine grained
25
11,17,22
93
1
SM
SILTY SAND: pale yellowish brown, dense, dry,
fine to medium grained
30
7,18,17
35
5,10,13
T.
SM
SILTY SAND: pale yellowish brown, dense, dry,
fine to medium grained
40
❑
6,11,9
45
Total Depth 41.5 feet
No Groundwater Encountered
50
55
4n
A
APPENDIX B
Laboratory Test Results
EARTH SYSTEMS SOUTHWEST
File No.: 09571-04 July 13, 2006
Lab No.: 06-0281
UNIT DENSITIES AND MOISTURE CONTENT ASTM D2937 & D2216
Job Name: NWC Dune Palms & Ave 48, LQ, CA
Sample
Location
Depth
(feet)
Unit
Dry
Density (pco
Moisture
Content
(%)
USCS
Group
Symbol
B1
5
--
1
SM
B 1
10
88
4
SM
B 1
15
92
3
SM
B 1
20
89
10
SM
B2
2.5
85
2
SP-SM
B2
7.5
86
6
SP-SM
B2
12.5
88
2
SP-SM
B3
5
92
3
SP-SM
B3
10
90
4
SP-SM
B3
15
100
3
SP-SM
B3
20
92
4
SP-SM
B3
25
92
6
SM
B3
30
97
2
SP-SM
B4
5
98
1
SP-SM
B4
10
97
14
SP-SM
B4
15
87
14
SM
B4
20
85
4
SM
B4
25
89
11
ML
B5
10
96
1
SP-SM
B5
15
97
12
ML
B5
20
85
18
ML
EARTH SYSTEMS SOUTHWEST
File No.: 09571-04 July 13, 2006
Lab No.: 06-0281
UNIT DENSITIES AND MOISTURE CONTENT ASTM D2937 & D2216
Job Name: NWC Dune Palms & Ave 48, LQ, CA
Sample
Location
Depth
(feet)
Unit
Dry
Density (pcf)
Moisture
Content
(%)
USCS
Group
Symbol
B6
2.5
--
I
SP-SM
B6
7.5
82
3
SP-SM
B6
12.5
88
4
SM
B6
17.5
90
2
SM
B6
22.5
94
13
SM
B6
27.5
99
2
SP-SM
B7
2.5
92
1
SP
B7
7.5
90
1
SP
B7
12.5
82
3
SM
B7
17.5
86
2
SM
B7
22.5
91
2
SM
B8
5
93
2
SP-SM
B8
10
86
7
SP-SM
B8
15
88
1
SP-SM
B8
20
89
2
SM
B8
25
93
1
SM
EARTH SYSTEMS SOUTHWEST
File No.: 09571-04 July 13, 2006
Job Name: NWC Dune Palms & Ave 48, LQ, CA
Lab Number: 06-0281
AMOUNT PASSING NO.200 SIEVE ASTM D 1140
Fines
USCS
Sample
Depth
Content
Group
Location
(feet)
(%)
Symbol
B1
15
21
SM
B4
25
67
ML
B5
15
70
ML
B6
12.5
46
SM
B7
2.5-
4
SP
B8
20
42
SM
EARTH SYSTEMS SOUTHWEST
File No.: 09571-04 July 13, 2006
Lab No.: 06-0281
PARTICLE SIZE ANALYSIS ASTM D-422
Job Name: NWC Dune Palms & Ave 48, LQ, CA
Sample ID: B1 @ 1-4 Feet
Description: Brown Silty Sand (SM)
100
90
80
70
°�° 60
° 50
C
L
40
30
20
10
0
100
Sieve Percent
Size
Passing
1- 1/2
100
1"
100
3/4"
100
1 /2"
100
3/8"
100
#4
100
#8
100
#16
99
#30
98
#50
94
#100
73
#200
41
% Gravel: 0
% Sand: 59
% Silt: 31
% Clay (3 micron): 10
(Clay content by short hydrometer method)
t
10 1 0.1
Particle Size ( mm)
0.01 0.001
EARTH SYSTEMS SOUTHWEST
File No.: 09571-04 July 13, 2006
Lab No.: 06-0281
PARTICLE SIZE ANALYSIS ASTM D-422
Job Name: NWC Dune Palms & Ave 48, LQ, CA
Sample 1D: B4 @ 1-4 Feet
Description: Brown Silty Sand (SM)
100
90
80
70
60
50
a 40
30
20
10
0
Sieve Percent
Size
Passing
1-1/2"
100
111
100
3/411
100
1 /2"
100
3/8"
100
#4
100
#8
100
#16
100
#30
100
#50
93
#100
57
#200
19
% Gravel: 0
% Sand: 81
% Silt: 14
% Clay (3 micron): S
(Clay content by short hydrometer method)
�
•I �; _�
it
;
i
I I
i
t'
4-
100 10 1 0.1
Particle Size ( mm)
0.01 0.001
EARTH SYSTEMS SOUTHWEST
File No.: 09571-04
Lab No.: 06-0281
July 13, 2006
CONSOLIDATION TEST ASTM D 2435 & D 5333
NWC Dune Palms & Ave 48, LQ, CA
B-6 @ 2.5 feet
Silty F Sand (SM)
Ring Sample
2
1
0
-1
-2
Initial Dry Density: 77.9 pcf
Initial Moisture, %: 1.0%
Specific Gravity (assumed): 2.67
Initial Void Ratio: 1.140
Hydrocollapse: 2.2% @ 2,0 ksf
% Change in Height vs Normal Presssure Diagram
Saturation , ter'---a-Hydrocollapse
■ After Saturation ---)I—Rebound -
1.0
Vertical Effective Stress, ksf
10.0
EARTH SYSTEMS SOUTHWEST
File No.: 09571-04 July 13, 2006
Lab No.: 06-0281
MAXIMUM DENSITY / OPTIMUM MOISTURE ASTM D 1557-91 (Modified)
Job Name: NWC Dune Palms & Ave 48, LQ, CA Procedure Used: A
Sample ID: 1 Preparation Method: Moist
Location: B 1 @ 1-4' Feet Rammer Type: Mechanical
Description: Brown Silty Sand (SM) Lab Numbe 06-0281
Sieve Size % Retained
Maximum Density: 109 pcf 3/4" 0.0
Optimum Moisture: 14% 3/8" 0.0
#4 0.1
140
135
130
110 •
105
100
\ate■
0 5 10 15 20 25 30 35
Moisture Content, percent
EARTH SYSTEMS SOUTHWEST
File No.: 09571-04 July 13, 2006
Lab No,: 06-0281
MAXIMUM DENSITY / OPTIMUM MOISTURE ASTM D 1557-91 (Modified)
Job Name: NWC Dune Palms & Ave 48, LQ, CA Procedure Used: A
Sample ID: 2 Preparation Method: Moist
Location: B4 @ 1-4 Feet Rammer Type: Mechanical
Description: Brown Silty Sand (SM) Lab Numbe 06-0281
Sieve Size % Retained
Maximum Density: 106 pef 3/4" 0.0
Optimum Moisture: 14% 3/8" 0.0
#4 0.0
140
135
130
125 .
110
105
I
1-4
I3
I
1
�
'
I
I
}
Zero Air Voids Lines,3
-i
sg =2.65, 2,70, 2,75
--;
}-
-i-
1
I
'
I 1
.
--
f
0 5 10 15 20 25 30 35
Moisture Content, percent
EARTH SYSTEMS SOUTHWEST
File No.: 09571-04
July 13, 2006
Lab No.: 06-0281
SOIL CHEMICAL ANALYSES
Job Name: NWC Dune Palms
& Ave 48, LQ, CA
Job No.: 09571-04
Sample ID: B1
B4
Sample Depth, feet: 1-4'
1-4'
DF RL
Sulfate, mg/Kg (ppm): 45
22
1 0.50
Chloride, mg/Kg (ppm): 144
127
1 0.20
pH, (pH Units): 7.90
7.70
I 0.41
Resistivity, (ohm -cm): 1,650
1,490
N/A N/A
Conductivity, (µmhos -cm):
I 2.00
Note: Tests performed by Subcontract Laboratory:
Surabian AG Laboratory DF: Dilution Factor
105 Tesori Drive RL: Reporting Limit
Palm Desert, California 92211 Tel: (760) 200-4498
General Guidelines for Soil Corrosivity
Chemical A ent
Amount in Soil
Degree of Corrosivity
Soluble
0 -1000 mg/Kg (ppm) [ 0-.1%]
Low
Sulfates
1000 - 2000 mg/Kg (ppm) [0.1-0.2%]
Moderate
2000 - 20,000 mg/Kg (ppm) [0.2-2.0%]
Severe
> 20,000 mg/Kg (ppm) [>2.0%]
Very Severe
Resistivity
1-1000 ohm -cm
Very Severe
1000-2000 ohm -cm
Severe
2000-10,000 ohm -cm
Moderate
10,000+ ohm -cm
Low
EARTH SYSTEMS SOUTHWEST