07-1341 (SFD) Geotechnical Investigation ReportSUPPLEMENTAL GEOTECHNICAL
INVESTIGATION
57-175 PENINSULA LANE
PGA WEST
LA QUINTA, CALIFORNIA
-Prepared By-
Sladden Engineering
77-725 Enfield Lane, Suite 100
Palm.Desert, California 92211 .
(760) 772-3893
Sladden Engineering
77-725 Enfield Lane, Suite 100, Palm Desert, CA 92211 (760) 772-3893 Fax (760) 772-3895
6782 Stanton Ave., Suite A, Buena Park, CA 90621 (714) 523-0952 Fax (714) 523-1369
450 Egan Avenue, Beaumont, CA 92223 (951) 845-7743 Fax (951) 845-8863
15438 Cholame Road, Suite A, Victorville, CA 92392 (760)962-1868 Fax (760) 962-18:78
August 15, 2007 Project No. 544-07138 .
07-08-568
Peter Jacobs Homes
P. O. Box 356
La Quinta, California 92253
Attention: Mr. Peter Jacobs
Project: Taylor Residence
57-175 Peninsula Lane
PGA West
La Quinta, California
Subject: Supplemental Geotechnical Investigation
Presented herewith is the report of our Supplemental Geotechnical Investigation co.zducted for the
proposed single-family residence. to be located at 57-175 Peninsula Lane within the PGA West
development in the, City of La Quinta, California. The investigation was performed to provide
supplemental recommendations for site preparation and to assist in.foundation design for the proposed
residential structure including the subterranean parking level and the related site improve-ments.
This report presents the results of our supplemental field investigation and laboratory tests along with
conclusions and recommendations for foundation design and site preparation. - The recommendations
provided within this report are intended. to supplement the recommendations included within our
geotechnical update dated April 5, 2007 as well as the previously referenced geotechnical reports.
We appreciate the opportunity to provide service to you on this project. If you haute any questions
regarding this report, please contact the undersigned
Respectfully submitted,
SLADDEN ENGINEERING
IVO, C 45A9
z Exp..
Nicholas S. Devlin Brett L. Ander o'�
Project Engineer Principal Engineer
SER/nd
Copies: 6/Peter Jacobs Homes
TABLE OF CONTENTS
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SUPPLEMENTAL GEOTECHNICAL INVESTIGATION
1
TAYLOR RESIDENCE
SCOPEOF WORK............................................................................................................................._....
PROJECTDESCRIPTION....................................:........:..................................................................._:...
57-175 PENINSULA LANE
PGA WEST
LA QUINTA, CALIFORNIA
2
August 15, 2007
TABLE OF CONTENTS
..
INTRODUCTION.............................................................................................................................. _....
1
SCOPEOF WORK............................................................................................................................._....
PROJECTDESCRIPTION....................................:........:..................................................................._:...
1
1
GEOLOGYAND•SEISMICITY.........................................................................:..........................:..._....
2
SUBSURFACE CONDITIONS.............................:...:......................................................................._....
LIQUEFACTION
3
CONCLUSIONS AND RECOMMENDATIONS................................................................................
4
FoundationDesign ................................................. .............................. :..................................... .....
Settlement........................ :................................................................................................................. .....
4
5
LateralDesign...................................::...............................................................................................
5
RetainingWalls...................................:..............................................................................................
ExpansiveSoil............................................................................................................................_.....
5
5
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Concrete Slabs-on-Grade.............................................................................................:............_...:.
6
SolubleSulfates.........................................................................................................................._.....
Shrinkageand Subsidence ............. :.......................................................................................... _.....
6
6
GeneralSite Grading....................................................................:...:......................................... _.....
6
1. Site Clearing................:..........................................................................................................
2. Preparation of Basement Areas ........................................................ ........:..........................
6
6
3. Preparation of Building and Foundation Areas.............:.................................................
7
4. Placement of Compacted Fill...............................................................:.........:.....:...............
5. Preparation of Slab and Pavement Areas...........................................................................
7
7
6. Tests and Inspection ...........................: :
........................................................................._......
GENERAL..............:.........................................
REFERENCES........................................:................................................:........................................_...... 9
APPENDIX A - Site Plan and Bore Logs
Field Exploration
APPENDIX B - Laboratory Tests
Laboratory Test Results
APPENDIX C - 2001 California Building Code with 1997 UBC Seismic Design Criteria
FRISKSP Output Data
August 15, 2007 -1- Project No. 544-07138
07-08-568
INTRODUCTION
This report presents the results of our Supplemental Geotechnical Investigation perform --d to provide
specific recommendations for site preparation and to assist in the design and .construction of the
foundations for the proposed residential structure including the subterranean parking/basement level.
The project site is located at 57-175 Peninsula Lane within the PGA West development in the City of La
Quinta, California. The preliminary plans indicate that the proposed project will include a single-family
residence with a basement level along with various associated site improvements. The associated site
improvements are expected to include.a swimming pool, concrete walkways, patios, driveways, and pool
decking, underground utilities, and landscape areas. This report is intended to supplement the
geotechnical reports previously prepared for the subject lot.as well as the adjacent portions of the PGA
West development.
SCOPE OF WORK
1
The purpose of our supplemental investigation was to determine certain engineering characteristics of the
near surface soil on the site to develop specific recommendations for foundation design. and site
preparation. - Our investigation included previous report review, supplemental field exploration,
laboratory testing, literature review, engineering analysis and the preparation of this report. Evaluation
of hazardous materials or other environmental concerns was not within the scope of ser4ices provided.
Our investigation was performed in accordance with contemporary geotechnical enginee_ing principles
and practice. We do not make other warranty, either express or implied.
PROJECT DESCRIPTION
The project site is located at 57-175 Peninsula Lane within the PGA West development in the City of La
Quinta, California. It is our understanding that the project will consist of a single-family residence along
with various associated site improvements. - It is our understanding that the proposed residential
structure will be of relatively lightweight wood -frame construction with a subterranean/easement level
and will be supported by conventional shallow spread footings and concrete slabs on grade. The
associated improvements will include a swimming pool, concrete walkways, driveways, pool decking,
and patios, landscape areas and various underground utilities.
The subject site is presently vacant and the lot has been previously graded during construction of the
surrounding PGA West residential development and golf course. The ground surface is gEnerally clear of
vegetation and debris. The adjacent lots east and west of the site are currently vacant. '-'he property is
level throughout and is near the elevation of the adjacent properties and roadways. Peninsula Lane is
paved and forms the southeastern site boundary and the existing golf course forms the northwestern site
boundary. There are underground utilities along the existing roadways and servicing the adjacent lots.
Based upon our previous experience with lightweight reinforced concrete, reinforced masonry and wood -
frame structures, we expect that isolated column loads will be less than 50 kips and wall,loading will be
less than to 4.0 kips per linear foot. Grading is expected to include excavation for the subterranean
parking level along with minor cuts and fills to match the nearby elevations to accommodate site
drainage. This does not include removal and re -compaction of the bearing soil within the easement area.
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07-08-568
GEOLOGY AND SEISMICITY
The project site is located within the central Coachella Valley that is part of the broader .3alton Trough
geomorphic province. The Salton Trough is a northwest trending depression that extends• from the Gulf"
of California to the Banning Pass. Structurally the Salton Trough is dominated by several northwest
trending faults, most notable of that is the San Andreas system.
A relatively thick sequence of sedimentary rock has been deposited in the Coachella .Valley portion of the
Salton Trough from Miocene to present times. The sediments are predominately terrestrial in nature with
some lacustrian and minor marine deposits. The mountains surrounding the Coachella Valley are
composed primarily of Precambrian metamorphic and Mesozoic granitic rock.
The Coachella. Valley is situated in one of the more seismically active areas of California. The San
Andreas Fault zone is considered capable of generating a maximum credible earthquake of magnitude 8.0
and because of its proximity to the project site it should be considered in design fault for th` project.
Based on our review of published and unpublished .geotechnical maps and literature pertaining to site,
the San Andreas (Southern) Fault (approximately 12.9 kilometers or 8.0 miles to the north-ast of the site)
would probably generate the most severe site ground motions with an anticipated max<mum moment
magnitude (MW) of 7.4. In addition to. the San Andreas (Southern) Fault, the San Jacinto (Anza) Fault
presents a ground rupture hazard and is located approximately 28.5 kilometers or 17.7 miles. to the
southwest of the site with an anticipated maximum moment magnitude (Mw) of 7.2.
_ A probabilistic seismic hazard analysis (PSHA) was performed to evaluate thelikeli'�ood of future
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earthquake ground motions at the site. The computer program FRISKSP Version 4 was used to perform
the analysis (Blake, 2026). Based upon the results of subsurface characterization at the project site, the
attenuation relationships o ships by Abrahamson and Silva (1997), Sadigh, et al. (1997), Boore, et al. (1997), and
Campbell and Bozorgnia (1997) that is pertinent to shallow crustal earthquakes was used in the PSHA.
We used magnitude weighting to derive the peak ground acceleration as recommended: by Martin and
Lew of SCEC (1999) and consistent with the recommendations by NCEER (Youd and 1driss, 1997) for
liquefaction analysis. According to our PSHA, the site could be subjected to peak ground acceleration on
the order of 0.548 for an earthquake having a 10 percent probability of exceeded in 50 years (475 -year
return period).
The site is not located in any Earthquake Fault zones as designated by the State but is mapped in the
County's Liquefaction and Ground Shaking Hazard Zone V: Several significant seismic events have
occurred within the Coachella Valleyduring the past 50 years. The events include Dese-t Hot Springs -
1948 (6.5 Magnitude), Palm Springs - 1986 (5.9 Magnitude), Desert Hot Springs - 1992 (5.1 Magnitude),
Landers - 1992 (7.5 Magnitude) and Big Bear'- 1992 (6.6 Magnitude).
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August 15, 2007
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SUBSURFACE CONDITIONS
Project No. 544-07138
07-08-568
The soil underlying the site consists primarily of a generally thin layer of engineered fill soil overlying
native fine-grained silty sand with several prominent sandy silt layers and scattered clay layers. The
surface soil consists of engineered fill material up to 8 feet in depth that was placed during the initial
rough grading of the building pads and adjacent golf course. Silty sand was the most prominent soil
encountered within our exploratory bores but several prominent sandy silt layers were also encountered.
The engineered fill encountered near the existing ground surface appeared dense but the underlying
native silty sand and sandy silt layers appeared somewhat loose. Relatively undisturbed samples
indicated dry density varying from 79.8 to 127.2 pounds' per cubic foot. (pcf). Sampler penetration
resistance (as measured by field blowcounts) indicates that density generally varied with depth and soil
type. The site soil was dry on the surface and moist below a depth of approximately 5 feet and the silty
and clayey layers were typically moist and in some cases wet. Laboratory tests indicated moisture
content varying from 1.5 to 39.0 percent.
Laboratory tests indicate that the surface soil consists primarily of silty sand and sandy silt. Expansion
tests indicate that the surface silty 'sand is generally non -expansive and is classified as "very low"
expansion category soil in accordance with Table 18 -I -B of the 1997 Uniform Building Code.
Groundwater was not encountered within our bores that extended to depths of approximately 31 feet
below the existing ground surface. Groundwater should not be a factor in design and construction.
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LIQUEFACTION
Liquefaction occurs with sudden loss of soil strength because of rapid increases in pore pressures within
cohesionless soil as a result of repeated cyclic loading during seismic events. Several conditions must be
present for liquefaction to occur including; the" presence of relatively shallow groundwater, generally
loose soil conditions, the susceptibility of soil to liquefaction based upon grain -size characteristics and the
generation of significant and repeated seismically induced ground accelerations. Liquefaction affects
primarily loose, uniform grained cohesionless sand with low relative densities.
In the case of this project site, several of the factors required for liquefaction to occur are absent. As
previously indicated, groundwater was not encountered within our exploratory bores that extended to a
maximum depth of approximately 31 feet below the existing ground surface on the site. Because of the
surface -to -groundwater depth, specific liquefaction analyses were not performed. Based upon the
surface-to=groundwater depth, the potential for liquefaction and related surficial affects of liquefaction
impacting the site are considered negligible.
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August 15, 2007 -4- Project No. 544-07138
07-08-568
CONCLUSIONS AND RECOMMENDATIONS
Based upon our field investigation and laboratory tests, it is our opinion that the proposed single-family
residence (including the subterranean basement level) is feasible from a soil mechanics standpoint
.� provided that the recommendations included in this report are considered in building foundation design
and site preparation. Because the lot has been previously rough graded, the remedial grading
recommended .at this time expected to be is limited. except for the subterranean basement level.. We
recommend that remedial grading within the basement level that extends through the previous
engineered. fill soil include overexcavation and recompaction of the bearing soil. The rerr.edial grading
recommended for the remainder of the 'at -grade building areas is limited to the processing and
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recompaction of the weathered surface soil. Specific recommendations for site preparation are presented in the Site on
section of this report.
As previously stated, groundwater was not encountered within our bores and groundwater is in excess of
30 feet below the existing ground surface in the vicinity of the site. Because of t_ie surface -to -
groundwater depth, specific liquefaction analyses were not performed. Based upon the surface -to -
groundwater depth, the potential for. liquefaction and related surficial affects of liquefaction impacting
the site are considered negligible.
The site is located in one of the more seismically active areas in California. Design professionals should
be aware of the site setting and the potential for earthquake activity during the anticipated life of the
structure should be acknowledged. The accelerations that may be experienced on the site (as previously
discussed) should be considered in design. The seismic provisions included in the Uniform Building
Code for Seismic Zone 4 should be considered the minimum design criteria. Pertinent 1957 UBC Seismic
Design Criteria is summarized in Appendix C.
Caving did occur within our bores and the potential for caving should be expected within deeper
excavations. All excavations should be constructed in accordance with the normal CalOSHA excavation
criteria. On the basis of our observations of the materials encountered, we anticipate that the near surface
silty sand will be classified by CalOSHA as Type C. Soil conditions should be verified in the field by a
"Competent person" employed by the Contractor.
The near surface soil encountered during our investigation was found to be non -expansive. Laboratory
tests indicated Expansion Indices of 0 and 2 for the surface silty sand that corresponds with the "very
low" expansion category in accordance with UBC Table 18 -I -B.
The followingrecommendations resent more detailed desi n criteria that have been develo ed on the
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basis of our field and laboratory investigation. The recommendations are based upon non -expansive soil
�. criteria.
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Foundation Design: The results of our investigation indicate that either conventional shallow
continuous footings or isolated pad footings that are supported upon properly compacted soil,
may be expected to provide adequate support for the proposedresidential structure foundations.
Building pad grading should be performed as described in the Site Grading Section of this report
to provide for uniform and firm bearing conditions for the structure foundations.
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August 15, 2007
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Project No. 544-07138
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Footings should extend at least 12 inches beneath lowest adjacent grade. Isolated square or
rectangular footings should be at least two feet square and continuous footings shculd be at least
12 inches wide. Continuous footings may be designed using an allowable bearing value of 1300
pounds per square foot.(psf) and isolated pad footings may be designed using an allowable
bearing pressure of 1800 psf. Allowable increases of 100 psf for each additional 1 foot of width
and 150 psf for each additional 6 inches of depth may be. utilized if desired. The maximum
allowable bearing pressure should be 3000 psf. The allowable bearing pressures are applicable to
dead and frequently applied live loads. The allowable bearing pressures may be increased by 1/3
to resist wind and seismic loading. Care should be taken to see that bearing or subgrade soil is
not allowed to become saturated from the ponding of rainwater or irrigation. Drainage from the
building area should be rapid and complete.
The recommendations provided in the preceding paragraph are based on the assumption that all
footings will be supported upon properly compacted engineered fill soil. All grading should be
performed under the tests and inspection of the Soil Engineer or his representative. Prior to the
placement of concrete, we recommend that the footing excavations be insp€cted to verify
extension into compacted soil and the absence of loose and disturbed materials.
Settlement: Settlement resulting from the anticipated foundation loads shouild be minimal
provided that the recommendations included in this report are considered in foundation design
and construction. The estimated ultimate settlement is calculated to be approximately 1 inch
when using the recommended bearing values. As a practical matter, differential settlement
between footings can be assumed as one-half of the total settlement.
Lateral Design: Resistance to lateral loads can be provided by a combination of f=iction acting at
the base of the slabs or foundations and passive earth pressure along the sides of the foundations.
A coefficient of friction of 0.40 between soil and concrete may. be used with consiceration to dead
load forces only. A passive earth pressure of 250 pounds per square foot, per foct of depth, may
be used for the sides of footings that are poured against properly compacted native or approved
non -expansive import soil. Passive earth..pressure.:should be.. ignored within the upper 1 foot
except where confined (such as beneath a floor slab). . .
Retaining Walls: Retaining walls may be necessary to accomplish the proposed construction.
Lateral pressures for use in retaining wall design can be estimated using an equivalent fluid
weight of 35 pcf for level free -draining native backfill conditions. For wallE that are to be
restrained at the top such as the basement walls, the equivalent fluid weight should be increased
to 55 pcf for level free -draining native backfill conditions. Backdrains should be -provided for the
full height of the walls.
Expansive Soil: Because of the prominence of "very low" expansion category soil near the
surface, the expansion potential of the foundation bearing soil should not be a controlling factor
in foundation or floor slab design. Expansion potential should be reevaluated subsequent to
grading.
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August. 15, 2007
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Project No. 544-07138
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Concrete Slabs -on -Grade: All surfaces to receive concrete slabs -on -grade should b� underlain by
a minimum compacted non -expansive fill thickness of 24 inches, placed as described in the Site
Grading Section of this report. Where slabs are to receive moisture sensitive floor coverings or
where dampness of the floor slab, is not desired, we recommend the use of an appropriate vapor
retarder or an adequate capillary break. Vapor retarders should be protected by 2 inches of sand
on top and bottom to reduce the. possibility of puncture and to aid in obtaining uniform concrete
curing.
` Reinforcement of slabs -on -grade in order to resist expansive soil pressures should not be
necessary. However, reinforcement will have a beneficial effect in containing cracking because of
concrete shrinkage. Temperature and.shrinkage related cracking should be an=icipated in all.
concrete slabs -on -grade. Slab reinforcement and the spacing of control joints should be
determined by the Structural Engineer.
Soluble Sulfates: The soluble sulfate concentrations of the surface soil have been determined to
be less than 100 ppm that is generally considered to be non -corrosive with resp=ct to concrete.
The use of Type V cement and specialized sulfate resistant concrete mix designE should not be
necessary for concrete in contact with the native soil.
Shrinkage and Subsidence: Volumetric shrinkage of the material that is excavated and replaced
as controlled compacted fill should be anticipated. Because the surface soil consists of compact
engineered fill, we expect that shrinkage should be less than 5 percent. Subsidence of the
surfaces that are scarified and compacted should be less than 1 tenth of a foot. This will vary
depending upon the type of .equipment used, the moisture content of the soil at the time of
grading and the actual degree of compaction attained. The values for shrinkage and subsidence
are exclusive of losses that will occur because of -the stripping of the organic material from the
surface and the removal of unsuitable material.
General Site Grading. All grading should be performed in accordance w-th the grading
ordinance of the City of La Quinta, California. The following recommendations have been
developed on the basis of our field and laboratory tests and are intended to provide'a uniform
compacted mat of soil beneath the building slabs and foundations.
�\ 1. Site Clearing: Proper site clearing will be very important.
The existing vegetation
abandoned irrigation lines should be removed from the proposed building areas and the
resulting excavations should be properly backfilled. Soil that is distu-bed during site
clearing should be removed and replaced as controlled compacted fill under the direction
of the Soil Engineer.
2. Preparation of Basement. Areas: In order torovide adequate and uniform bearing
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conditions, we recommend overexcavation and recompaction throughcut the basement
areas. The basement areas should be overexcavated to a depth of at least 3 -feet below the
bottom of the footings. The exposed soil should then be scarified to a depth of at least 1
foot, moisture conditioned and recompacted to at least 90 percent relative compaction.
The excavated material may then be replaced as engineered fill material as recommended
in item 4. below.
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August 15, 2007 -7- Project No. 544-07138
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3. Preparation of at Grade Building and Foundation Areas: The weathered surface soil
should be scarified to a depth of at least 1 foot moisture conditioned and recompacted to
at least 90 percent relative compaction. The excavated material may then be replaced as
engineered fill material as recommended below.
4.. Placement of Compacted Fill:' Within the building pad areas, any new fill material
should be spread in thin lifts, at near optimum moisture content and'compacted to a
minimum of 90 percent relative compaction. Imported fill material shall have an
Expansion Index not exceeding 20.
The contractor shall notify the Soil Engineer at least 48 hours in advance of importing soil
in order to provide sufficient time for the evaluation of proposed import materials. The
contractor shall be responsible for delivering material to the site that complies with the
project. specifications. Approval by the Soil Engineer will be based upon material
delivered to the site and not the preliminary evaluation of import sources.
Our observations of the materials encountered during our investigation indicate that .
compaction within the native soil will be most readily obtained by means of heavy
rubber tired equipment and/or sheepsfoot compactors. The moisture content of the near
surface soils was somewhat inconsistent within our bores. In general, the sandy soil is
dry and well below optimum moisture content but some of the deeper silt layers were
wet. It is likely that wet silt/clay layers will.be encountered during grading particularly
in irrigated areas where deep cuts are planned. A uniform and near optimum moisture
content should be maintained during fill placement and compaction.
S. Preparation of Slab and Paving Areas: All surfaces to receive asphalt concrete paving or
exterior concrete slabs -on -grade, should be underlain by a. minimum compacted fill
thickness of 12 inches. This may be accomplished by a combination of overexcavation,
scarification and recompaction of the surface, and replacement of the excavated material
as controlled compacted fill. Compaction of. the slab and pavement areas should be to a .
minimum of 90 percent relative compaction.
6. Tests and Inspection:' During grading tests and observations should be performed by
the Soil Engineer or his representative to verify that the grading is being performed in
accordance with the project specifications. Field density tests shall be performed in
accordance with applicable ASTM test standards.
The minimum acceptable degree of compaction shall be 90 percent of the maximum dry
density as obtained by the ASTM D1557-02 test method. Where tests indicate insufficient
density, additional compactive effort shall be applied until retests indicate satisfactory
compaction.
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August 15, 2007 -8- Project No. 544-07138
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GENERAL
The findings .and recommendations presented in this report are based upon an interpolation of the soil
conditions between bore locations and extrapolation of the conditions throughout the proposed building
area. Should conditions encountered during grading appear different than those indicated in this report,
this office should be notified.
This report is considered to be applicable for use by Peter Jacobs Homes for the specific site and project
described herein. The use of -.this report by other parties or for other projects is not authorized. The
recommendations of this report are contingent upon monitoring of the grading operations by a
representative of Sladden Engineering. All recommendations are considered to be tentative pending our
review of the grading operations and additional tests, if indicated. If others are employed to perform any
soil tests, this office should be notified prior to such tests in order to coordinate any required site visits by
our representative and to assure indemnification of Sladden Engineering.
We recommend that a pre -job conference be held on the site prior to the initiation of site grading: The
purpose of this meeting will be to assure a complete understanding of the recommendations presented in
this report as they apply to the actual grading performed.
Sladden Engineering
August 15, 2007 -9- Project No. 544-07138
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REFERENCES
ASCE Journal of Geotechnical Engineering Division, April 1974.
Boore, Joyner and Fumal (1994) Estimation of Response Spectra and Peak Accelerations from North American
Earthquakes, U. S. Geological Survey, Open File Reports 94-127 and 93-509.
Finn- W. E. Liam; (1996) Evaluation of Liquefaction Potential for Different Earthquake Magnitudes and Site
Conditions; National Center for Earthquake Engineering Research Committee.
Joyner and Boore, (1988) Measurements, Characterization and Prediction of Strong Ground Motion, ASCE
Journal of Geotechnical Engineering, Special Publication No. 20.
Lee & Albaisa (1974) "Earthquake Induced Settlement in Saturated Sands".
Seed and Idriss (1982) Ground Motions and Soil Liquefaction During Earthquakes, Earthquake Engineering
Research Institute Monograph.
Seed, Tokimatsu, Harder and Chung, (1985), Influence of SPT Procedures in Soil Liquefaction Resistance
Evaluations, ASCE Journal of Geotechnical Engineering, Volume 1.11, No. 12, December.
Rogers, Thomas H., Geologic Map of California, Santa Ana Map Sheet.
Riverside County, 1984, Seismic Safety Element of the Riverside County General Plan
Sladden Engineering
APPENDIX A
Site Plan
Bore Logs
APPENDIX A
FIELD EXPLORATION
For our field investigation,.4 exploratory bores were excavated on August 1, 2007 using a truckmounted
hollow stem auger rig (Mobile B-61) in the approximate locations indicated on the site plan included 'in
this appendix. Continuous logs of the materials encounteredwere prepared on the site by a
' representative of Sladden Engineering. Bore logs are included in this appendix.
�\ Representative undisturbed samples were obtained within our bores by driving a thin-walled steel
penetration sampler (California split spoon sampler) or a Standard Penetration Test (SPT) sampler with a
140 pound hammer dropping approximately 30 inches (ASTM D1586). The number of blows required to .
.drive the samplers 18 inches was recorded (generally in 6 inch increments). Blowcounts are indicated on
the bore logs.
.The California samplers are 3.0 inches in diameter, carrying brass sample rings having inner diameters of
�! 2.5 inches. The standard penetration samplers are 2.0 inches in diameter with an inner diameter of 1.5
inches. Undisturbed samples were removed from the sampler and placed in moisture sealed containers
in order to preserve the natural soil moisture content. Bulk samples were obtained from the excavation
spoils and samples were then transported to our laboratory for further observations and tests.
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