0001-163 (SFD) Geotechnical Engineering Report•
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•
GEOTECHNICAL ENGINEERING REPORT
THE ORCHARD
TRACTS 26524 & 26525
LA QUINTA, CALIFORNIA
THIS DOCUMENT WAS ISSUED PREVIOUSLY
MAY NOT REFLECT CURRENT SITE CONDITAND
IONS
AND/OR STANDARDS OF GEOTECHNICAL PRACTICE.
THE CONTENT OF THE DOCUMENT SHOULD NOT BE
USED OR RELIED UPON WITHOUT A REVIEW BY
QUALIFIED PROFESSIONALS.
Init_ (`Date�QV � 9 ZOQ6
EARTH SYSTEMS SOUTHWEST
PREPARED FOR
STROTHER CONSTRUCTION
137-2823-P1 �I ��I C�►I�
DECEMBER 18, 1990
•
BUENA EN INEERS, INCb' 1; t.C&MK4FZe 21/
n
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r- oBuena Engineers, Inc.
Z*o FF AN EARTH SYSTEMS, INC COMPANY
79-811 B COUNTRY CLUB DRIVE • BERMUDA DUNES, CALIFORNIA 92201 • PHONE (619) 345-1588 • FAX (619) 345-7315
December 18, 1990
Strother Construction
• 41-555 Cook Street
Palm Desert, California 92260
Attention: Chuck Strother
Project: The Orchard - Tracts 26524 & 26525
La Quinta, California
137-2823-P 1
90-12-786
Subject: Geotechnical Engineering Report
Presented herewith is our Geotechnical Engineering Report prepared for the
• proposed residential development to be located in the City of La Quinta,
California.
This report incorporates the tentative information supplied to our office and in
accordance with the request, recommendations for general site
development and foundation design are provided.
This report was prepared to stand as a whole, and no part ;of the report
should be excerpted or used to exclusion of any other part.
This report completes our scope of services in accordcnce with our
• agreement. Other services which may be required, such as pron _review and
grading observation are additional services and will be billed according to
the Fee Schedule in effect at the time services are provided.
Please contact the undersigned if there are any questions concerning this
report or the recommendations included herein.
Respectfully submitted,
BUENA ENGINEERS, INC. Reviewed and Approved,
THIS DOCUMENT WAS ISSUED PREVIOUSLY AND
�►+- W/x % MAY NOT REFLECT CU T 1 ON (TIONS
AND/OR STANDARDS 0E.
Hogan R. Wright THE CONTENT OF THE D�� E
Staff Engineer USED OR RELIED UPO I
Q ALIFIEDp,ROFESSIONALS. NOV
R. �ayne pichins
Staff Geologist^'t G� Date.
•
PC EARTH SYSTEMS SOUTHWEST o
HD/SER * _
•
Copies: 6 - Strother Construction
1 - P. S. File
1 - VTA File
BERMUDA DUNES BEAUMONT BAKERSFIELD LANCASTER
!6191345-I.W 171 Al AAr,_oRA� ianr,%'V37.91cn /OAC%^A01too
VENTURA
TABLE OF CONTENTS
INTRODUCTION..........................................................................................................1
PURPOSE AND SCOPE OF WORK.......................................................................1
SITEDESCRIPTION....................................................................................................2
FIELDEXPLORATION ........................ ......................................................... _............... 2
LABORATORYTESTING.............................................................................................3
SOILCONDITIONS....................................................................................._...............3
GROUNDWATER........................................................................................_...............4
REGIONALGEOLOGY..............................................................................................4
LOCALGEOLOGY.....................................................................................................4
GEOLOGICHAZARDS...............................................................................................5
Primary.................................................................................................................5
Secondary.........................................................................................................6
Non -Seismic ...................................................................................... _............... 6
CONCLUSIONS AND RECOMMENDATIONS .. .................................. _............... 6
SITE DEVELOPMENT AND GRADING.....................................................................8
Site Development - Grading ...................................................... _............... 8
Site Development - General ...................................................... _............... 9
Excavations......................................................................................................10
TrafficAreas....................................................:..................................................11
UtilityTrenches..................................................................................................11
STRUCTURES..........:..................................................................................................11
Foundations......................................................................................_.............11
Slabson Grade..............................................................................._.............13
Settlement Considerations............................................................ _............ 13
Frictional and Lateral Coefficients.
RetainingWalls...............................................................................................14
SlopeStability..................................................................................................15
Expansion.........................................................................................................15
AdditionalServices........................................................................................15
LIMITATIONS AND UNIFORMITY OF CONDITIONS...........................................15
REFERENCES..............................................................................................................17
APPENDIX A
Site and Vicinity Map
Logs of Borings THIS DOCUMENT WAS ISSUED PlEVIOUSLY AND
APPENDIX B MAY NOT REFLECT CURRENT SITE CONDITIONS
ANDIOR STANDARDS OF GEOTECHNICAL PRACTICE.
Summary of Test Results THE CONTENT OF THE DOCUMENT SHOULD NOT BE
Table 2 USED OR RELIED UPON WITHOUT A REVIEW BY
QUALIFIED PROFESSIONALS.
APPENDIX C
Init�.iG'�!—Dat���L-� �O6
Standard Grading Specificatie)MTH SYSTEMS SOUTHWEST
RIIFNA FN(:INFFRc Mrl..
M December 18, 1990 -1- 137-2823-P1
90-12-786
INTRODUCTION
This Geotechnical Engineering Report has been prepared for the two (2)
...._proposed residential tracts to be located in the City of La Quinta,
California.
A It is assumed that the structures will be of lightweight one or two story
construction. It is assumed that the buildings will be supported by
0 normal continuous or pad footings.
B. Structural considerations for building column loads of up to 20 kips
and a maximum wall loading of 2.0 kips per linear foot were used as
a basis for recommendations related to the construction of the
residential buildings.
IA
C. These are estimated values since foundation plans were not
available at the time of production of this report. If design loading is
to exceed these assumed values, it will be necessary to reevaluate
the given recommendations.
D. All loading is assumed to be deadplus reasi�n P �i46 load.
THIS DOCUMENT . WAS ISSUED PRE i0
MAY NOT REFLECT CURRENT
CURRENT SITE CONDITIONS
TX*A p� R6 Q ECHNIC W NOT BE
USED OR RELIED UPON WITHOUT A REVIEW BY
The purpose of ouPW6K MsP*WsEfi§I9*5t t SARA 9cNgitions, and
to provide conclusions and recommer�=lcaW-o e -the" site and
the proposed deveEllopTH SYSTEMS S8&%?� fork includes the following:
A A general reconnaissance of the site.
B. Shallow subsurface exploration by drilling.
C. Laboratory testing of selected soil samples obtained from the
exploratory borings drilled for this project.
0 D. Review of selected technical literature pertaining to the site.
E. Evaluation of field and laboratory data relative to soil conditions.
F. Engineering analysis of the data obtained from the exploration and
testing programs.
G. A summary of our findings and recommendations in written report.
Contained In This Report Are:
A Discussions on regional and local geologic and soil conditions.
B. Graphic and/or tabulated results of laboratory tests and field
studies.
BUENA ENGINEERS, INC.
December 18, 1990 -2- B7 -2823-P1
90-12-786
C. Discussions and recommendations relative to allowable foundation
bearing capacity, recommendations for foundation design,
estimated total and differential settlements, lateral earth pressures,
site grading criteria, geologic and seismic hazards.
Not Contained In This Report:
A Our scope of services did not include any env ronmental
assessment or investigation to determine the presence of
hazardous or toxic materials in the soil, surface water, groundwater
or air, on, below or around this site.
SITE DESCRIPTION
The proposed project is located on the south side of Avenue 50, west of
Jefferson Street in the City of La Quinta, California.
A The majority of the site is in an existing citrus grove.
B. The site is fairly level throughout with the exception of a large sand
dune in the southeast corner of the site.
C. Avenue 50 forms the northern edge of the site.
D. There are under r
underground irri s k§1*g�jke�lal s�Xr l S 50 and
g gC� 6�LIgtf>hr�fifre SIT E CONDITIONS
AND/OR STANDARDS OF GEOTECHNICAL PRACTICE.
a`qp �,�I T SHO LD tyOT BE
E. There are residentia V ,15 �� $���rAs p¢�� /long the
south and west e WEN SSIONALS.
InitCa-=—�QQ6
EAR ST
Exploratory borings .were drilled for observing the soil profile and
obtaining samples for further analysis.
A Six (6) borings were drilled for soil profiling and sampling to a
maximum depth of thirty-six (36) feet below the existing ground
surface. The borings were drilled on November 20 and November.
21, 1990, using an eight (8) inch diameter hollow -stem auger
powered by a CME 45-B drilling rig.. The approximate boring
locations as indicated on the attached plan in Appendix A, were
determined by pacing and sighting from existing sheets and
topographic features. The boring locations should be considered
accurate only to the degree implied by the method used.
B. Samples were secured within the borings with a two and one-half
(2.5) inch inside diameter ring sampler (ASTM D 3550, shoe similar to
ASTM D 1586). The samples were obtained by driving the sampler
with a one hundred forty (140) pound hammer, dropping thirty (30)
inches. The number of blows required to drive the sampler one foot
BUENA ENGINEERS, INC.
December 18, 1990 -3- 1317-2823-P1
90-12-786
was recorded. Recovered soil samples were sealed in containers
and returned to the laboratory for further classification and jesting.
_ ___C....__Bulk...-disturbed.-samples_-of.-Ahe.__soils were obtained from cuttings
developed during excavation of the test borings. The bulk samples
were secured for classification purposes and represent a mixture of
soils within the noted depths.
D. The final logs represent our interpretation of the contents of the field
logs, and the results of the laboratory observations and tests of the
field samples. The final logs are included in the appendix A of this
report. The stratification lines represent the approximate boundaries
between soil types although the transitions may be gradual.
After a visual and tactile classification in the field, samples were returned
to the laboratory, .classifications were checked, and a testing program
was established.
A Samples were reviewed along it ' �RWI61RStAe nine which
would be furttvis T ��II s W%elT=nsldered as
representative T �®p`1 campGs(FdA oTor used in
grading and th 01VI 11Dft0 Tlgfle
�� BY
USED OR RELIED UPON WITH
UT AIW
B. In-situ moisture 00fdI6kP16RfUWMf0vei for the core' samples
were developed in accordance withi Inez_ B� 2 9 2006
C. Settlement and 11&Ws I iq��iHpofiential was evaluated from
the results of consolidation tests performed in accordance with
ASTM 2435.
.D. The relative strength characteristics of the subsurface soils were
determined from the results of direct shear tests. Specimens were
placed in contact with water at least twenty-four (24) hcurs before
testing, and were then sheared under normal loads rangirg from 0.5
to 2.0 kips per square foot in general accordance with ASTM D 3080.
E. Classification tests consisted of: Expansion Index (UBC Standard No.
29-2), Maximum Density -Optimum Moisture (ASTM D 1557) and
Hydrometer Analysis (California Test Method 203).
F. Refer to Appendix B for tabular and graphic representa-ion of the
test results.
IL CONDITION
As determined by the borings, site soils were found to consist primarily of
fine windblown sands with interbedded clay layers. The boring logs in
Appendix A contain a more detailed description of the soils
encountered.
BUENA ENGINEERS, INC.
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December 18, 1990
in
137-2823-P1
90-12-786
A The soils were found to be fairly loose throughout with blow counts
indicating relative compaction as low as seventy one (71) percent
of maximum density.
B. The soils were found to be moist throughout with the majority of the
deeper clay layers being saturated.
C. Clay and silt contents of the soils exhibit low plasticity. Expansion tests
indicate the surface soils in the "very low" expansion category in
accordance with Table 2 in Appendix B of this report. The clay layers
were found to be in the "medium" expansion category. Refer to
section B of the structures section for specific explanations and
requirements dealing with expansive soil.
D. Soils should be readily cut by normal grading equipmen
ZkO11111MIEUE
Free groundwater was not encountered in any of the borings. The depth
to groundwater in tl r,�a � r�b�IIMOEgxq�;� I0Q*LhDVt'9D(40) feet.
Fluctuations in groun "��' ip�pM ueTl® v��iflit�in rainfall,
temperature and oth QIIMANDARDS OF GEOTECHNICAL PRACTICE.
THE CONTENT OF THE DOCUMENT SHOULD NOT BE
USE D,10UT A REVIEW BY
QUA NOV 2 9 2006
The project site is located in the southeri IC-l"6--Vatl•ey- near the
base of the Santa Ro ftk�y�s Jbg�j�ella Valley is. part of the
tectonically active Sa on assn. his basin is a closed, internally draining
trough that has been filled with a complex series of continental clastic
materials during Pleistocene and Holocene time (Van de Camp, 1973).
The San Andreas rift zone dominates the geology of the Coachella
Valley. The Banning and Mission Creek faults, which are part -z, of the San
Andreas system are responsible for earthquakes recently felt in the
Coachella Valley, Other regional faults that have produced events felt in
the Coachella Valley are the San Jacinto, Imperial and Elsinore faults
(see figures 1 & 2).
Based upon the historical and prehistorical record, the Coachella Valley
segment of the San Andreas fault system is likely to generate a
magnitude seven (7.0) or greater earthquake within the next fifty (50)
years. The potential for a magnitude seven (7.0) earthquake within the
next fifty (50) years is estimated by Seih (1985) as 'High' (50°/-90%).
LOCAL GEOLOGY
The project is in an area that has once been covered by Ancient Lake
Coahuila. Lithologic units observed consist chiefly of Quaternary lake
deposits. The boring logs in Appendix B contain specific descriptions of
the soils encountered on site.
BUENA ENGINEERS, INC.
37•
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THIS DOC MENT WAS ISS PRET f SLi ICN c r
° SO 100 k^ MAY NOT REFLECT CURB CTIC Colit.
AND/OR S DS OF GEO CHN t5•
THE CON1'L14T OF THE DOCUMENT LD N
USED OR RELIED UPON WITHOUT A REVIEW BY
QUALIFIED PROFESSIONALS. NOV 2 9 200-
Init C4 Date___
EARTH SYSTEMS SOUTHWEST
Base map of southern California region with major faults
* From Hileman et al (1973) ,
rontisniec
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1927 (6) \
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1946 (6.3)
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1952(7.7,6.4,6 1,6.1)
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1947 (6.2) _—
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1918 (6.8 }
1933 (6.3) 1937(
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1948 (6.5)
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Date____
EARTH SYSTEMS SOUT ST 1934 (5.5) 1934 (7.1
1915 (7.1) f
1335(6.0) 0
O /OO Mi/es Ensenodo 1956(6.8.6.f,6.3,6.4} �.
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/00 ZOO Kms.
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Earth Ouakes of magnitude 5.9 and
greater in the Southern California
Region, 1912 — 1972 (including the
North Palm Springs Earthquake).
From Hileman et al (1973)
0
December 18, 1990 -5- E7 -2823-P1
90-12-786
The project site is approximately six and eight tenths (6.8) miles southwest
of the San Andreas fault system. Figure 3 shows the project site in relation
to the local geology.
• at __ 1.101060F. • •
Primary seismic geologic hazards that may affect any property in
the seismically active Southern California area include:
1. Fault Rupture:
a. The project site is not located in any Alquist-Priclo special
study zones. Nor are any faults mapped through or
adjacent to the project area. At the time of zirilling no
surface expression of faulting was observed.
b. Fault, rupture would most likely occur along reviously
established trac nn IE Rv`��rirfmd raPft fesk i " �ccur at
other Ioc §z Rp �ud�cRiala 3p c .
AND/OR STANDARDS OF GEO ECHNiCAL Pi,.ACTIC:E.
2. Ground ShakingiE CONTENT OF THE DOCUMENT SHOULL.NOT 3E
USED OR RELIED UPON WITHOUT A REVIEW BY ..%
IF ROFESSIONALS. ��11
a. Strong grc9A ri�gtPion Is the se isr V;j1a� mos�� .ikely to
affect the site during the life. & mended structures.
Using meto Mrzs
� ®li and Idriss (982) and
modified 33''` I�y (1988) the following t:ible was
compiled for -anticipated accelerations which may be
experienced during an earthquake at the project site.
TABLE 1
* Richter Magnitude, Maximum Probable
*" Ploessel & Slosson 1974
b. Because of the alluvial sedimentary nature of the soils on
site,. ground shaking characteristics are expected to
include low frequency vibration with relatively high
amplitudes. Duration of shaking could be from fifteen (15)
to thirty-six (36) seconds. The project area is snapped in
Ground Shaking Zone III C as designated by tl-e County.
of Riverside, California. Ground Shaking Zones are based
on distance from causative faults and soil types.
BUENA ENGINEERS, INC.
Estimated
Maximum
Maximum
Repeatable Approximate
Design' Acceleration
Acceleration
Ground"
Distance to
Fault Earthquake in Rock
'n it
Accelerations
P oject Site
San Andreas 7.5 48g
.37g
.24g
6.8 mi.
San Jacinto 6.5 .18g
.15g
10g
18.5 mi.
* Richter Magnitude, Maximum Probable
*" Ploessel & Slosson 1974
b. Because of the alluvial sedimentary nature of the soils on
site,. ground shaking characteristics are expected to
include low frequency vibration with relatively high
amplitudes. Duration of shaking could be from fifteen (15)
to thirty-six (36) seconds. The project area is snapped in
Ground Shaking Zone III C as designated by tl-e County.
of Riverside, California. Ground Shaking Zones are based
on distance from causative faults and soil types.
BUENA ENGINEERS, INC.
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December 18, 1990
c. The project
Liquefaction
observed in
1.1
E7 -2823-P1
90-12-786
is mapped near the Riverside County
Study Zone, however, no groundwater was
our borings.
Secondary seismic geologic hazards that may affect the project
site area include settlement, liquefaction and ground lurching.
1. Settlement, whether seismically related or not, is considered a
potential hazard in this area. Historic records report significant
episodes of settlement in the Coachella Valley area due to
seismic forces and/or heavy rain fall and flooding.
2. Liquefaction is the loss of soil strength as a result of an increase in
pore water pressure due to cyclic seismic loading. Conditions
for liquefaction include relatively high water table (within 40' of
surface), low relative densities of the saturated soils and
susceptibility of the soil to liquefy based on grain size. No free
groundwater was encountered in our exploratory borings.
3. Ground lurchi �o�b@9 *fti lJtYr ure and
liquefaction. a At�R�ta�n�ecK��hTI�R� known
"active" faults, P0�rlir8� cui�l�f� the site
is considered Idi,� CONTENT OF TIS DOCUME
USED OR RELIED UPON WITHOUT A REVIEW BY
SIO LS. "I
4. Other secondd4��s�Fs�N�WS9i�oglc�azar hate t� �m
an earthquake include tsunamis' sec es
(waves oscilla�ing,r,��t} �����a, i.e., storage tanks,
lakes). Base 41 " rfooject sites geologic locction and
topography, it is our opinion that the probability of the above
hazards affecting the property are negligible.
C. Non -Seismic Hazards:
Other geologic hazards that could affect the project site include
landslides, flooding and erosion.
1. No evidence. of past landsliding was observed at the site nor
are any known landslides mapped in or around the project site.
The subject property is not at the immediate base of any steep
.hills and is located on relatively flat ground.
2. Flooding and erosion are always a consideration in and
regions. The properties flat topography suggests this is an area
of deposition. No gullies or areas of active erosion were
observed on site. Increased erosion, either fluvial or aeolian,
may occur as a result of construction activity.
CONCLUSIONS AND RECOMMENDATIONS
Based on a review of selected technical literature and the site
investigation, it is our opinion that the site is suitable for the intended
development provided it is designed around the noted geologic
BIJFNA FNrINFFR.q Mr,
December 18, 1990
-7-
B7-2823-P1
90-12-786
hazards. The following is a summary of our conclusions and professional
opinions based on the data obtained. Recompaction of soil is
recommended to limit settlement and improve bearing capacity.
A The primary geologic hazard relative to site development is severe
ground shaking from earthquakes originating on nearby faults. The
site is located in Southern California which is an active seismic area.
In our opinion, a major seismic event originating on the Sin Andreas
fault zone would be the most likely cause of significant earthquake
activity at the site within the estimated design life of the proposed
development.
B. Settlement due to seismic factors or flooding is a potential hazard in
the Coachella Valley area.
C. Areas of alluvial soils may be susceptible to erosion. Preventative
measures to minimize seasonal flooding and erosion should be
incorporated into site grading plans.
D. Fluvial erosion may affect the site during construction.
E. Other hazards includi-[iq W�n, lurching, landslides, tsunamis
and seiches are cons e're N _ CU RENTD SITE CONDI AND
AND/OR STANDARDS OF. G T TIONS
F. It is our opinion that t rrtitcD"w� ��b AVU form or
adequate support �'t7�t r
RPV m�mf vs klPjprksl t the
recommended sitM . P€l�k Base the pc enfiial for
consolidation and to provide a more cif r apa
firm bearing
support for the pro ,. ctture9, we recomm nd' 4&06
recompacted soil mats"b99�`� W MUatlons and slabs -on -
grade.
G. The project site is in seismic Zone 4 as defined in Section 2312 (d) 2. of
the Uniform Building Code. It is recommended that any permanent
structure be designed according to the current addi-ions of the
Uniform Building Code and Standards.
H. It is further recommended that any permanent structure constructed
on the site be designed to accommodate expected repeatable
ground accelerations resulting from the predicted maximum
probable earthquake as stated in Table 1 on page 5 of this report.
I. Adherence to the following grading recommendations should limit
potential settlement problems due to seismic forces, heavy rainfall,
flooding and the weight of the intended structure.
J. It is recommended that Buena' Engineers, Inc. be retained to
provide Geotechnical Engineering services during site
development; excavation, grading, and foundation construction
phases of the work. This is to observe compliance witr the design
concepts, specifications and recommendations, and to allow
design changes in the event that subsurface condition=s differ from
those anticipated prior to the start of construction.
BUENA ENGINEERS, INC.
December 18, 1990 -8- 137-2823-P1
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K. Plans and specifications should be provided to Buena Engineers,
Inc. prior to grading. Plans should include the gracing plans,
foundation plans, and foundation details. Preferably, structural loads
should be shown on the foundation plans.
SITE DEVELOPMENT AND GRADING
Prior to any construction operations, areas to be graded should be
cleaned of vegetation and other deleterious materials. Appendix C,
"Standard Grading Specifications" contains specific suggestions for
removal and disposal of deleterious substances and, as such, forms a
part of these Site Development and Grading Recommendations.
A. Site Development - Grading
Site grading and the bottom of all excavations should be observed
by a representative of Buena Engineers, Inc. prior to placement of
fill. Local variations in soil conditions may warrant increasing. the
depth of recompaction and/or overexcavation.
1. Because the majority of the site is in an existing ci-rus grove,
proper clearing is very important. Prior to site grading any
existing structures, stumps, roots, foundations, pavements,
leachfields, uncompacted fill, trash piles, and any abandoned
underground utilities should be removed from the proposed
building and paving areas. The top surface should be stripped
'of all organic growth and non -complying fill which, along with
other debris, should be removed from the site.
2. Depressior�fii§eiAbipgE flprojp*.(p§pjmrrtLWI(DudioLAdDhave debris
and looswgoitia)emewedreCI&FbeTfigOd WMITJ9li tle fill soils
compact6do/d§ 4"hit� � T AJ CO pacted fill
should b sl�c�thy�lv�c� has been
observed A MQD4air jilc. NC V 2 9 200F;
3. In order to help minimize problems
associateg)(4%gWWgt qJ%q! on a non-uniforr-) thickness
of compacted fill, Buena Engineers, Inc. should be consulted
for site grading recommendations relative to backfilling large
and/or deep depressions resulting from removal t-nder item
one above. In general, all proposed construction should be
supported by a uniform thickness of compacted soil.
4. Testing showed the surface soils are loose and susceptible to
settlements due to the introduction of water and the additional
loading of structures. In addition the inevitable presence of
roots may dictate the actual depth of overexcavation
deemed necessary. To control differential settlement and to
produce a more uniform bearing condition we re--ommend
that the structure be supported by a recompacted soil mat.
Compaction is to be verified by testing.
5. Building areas should be overexcavated to a depth of two (2)
feet below original grade or the bottom of footings whichever
BUENA ENGINEERS, INC.
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December 18, 1990
137-2623'-P1
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is greater. The exposed surface should be scarified, moisture
conditioned and compacted so that a minimum of ninety (90)
percent of maximum density is obtained to a depth of one (1)
foot. The previously removed soil and any .fill material should
then be placed in eight (8) inch layers in a loose condition at a
near optimum moisture and compacted to a minimum of
ninety (90) percent of maximum density. The intent is to have at
least three (3) feet of soil compacted to a minimum of ninety
percent of maximum density compose the building pad
beneath the footings. Compaction is to be verified by testing.
6. Due to the granular nature of the site soils in the area of the
large sand dune, it may be possible to obtain compaction to
a depth of three (3) or four (4) feet by watering and
compacting from the surface. Regardless of the method used
in the area, the recommended depth of compaction as
indicated in item five should be attained.
7. These grading recommendations apply to building areas and
at least five (5) feet beyond building limits.
8. Auxiliary structures including freestanding or retaining walls should
have the existing soils beneath the structure processed as per
items five (5) and six (6), above. The grading requirements
apply to three (3) feet beyond the face of the walls. If plans for
auxiliary structures and walls are provided for our review, these
recommendations may be revised.
9. It is anticipated that during grading a loss of approximately one
tenth (.1) of a foot due to stripping, and a shrinkage factor of
about fifteen (15) to twenty (20) percent for the upper three (3)
feet of soil, may be used for quantity calculations. This is based
on compactive effort needed to produce an average
degree of compaction of approximately ninety-three (93) to
ninety-four (94) percent and may vary depending on
contractor��Sl�e
boUMEN$LA19 DispaafiroatladAbDtween one -
tenths (.1)CONDITIONS
AND/OR STANDARDS I F GEOTECHNICAL PRACTICE.
TIE CO EN OF THE DOCUMENT SHOULD NOT BE
Site Developmt,-,ersi, UPON WITHOUT A REVIEW BYNOV 6
� g 200E
QUALIFIED PROFESSIONALS.
1. The following general recom en a Delisted in this section
are in addition to those listed in In sec Ion A above.
.EARTH SYSTEMS SOUTHWEST
2. All rocks larger than eight (8) inches in greatest dimension should
be removed from fill or backfill material.
3. Import soil used to raise site grades should be equal to or
better than on-site soil in strength, expansion, and
compressibility characteristics. Import soil will not be prequalified
by Buena Engineers, Inc. Comments on the characteristics of
import will be given after the material is on the project, either in-
place or in stockpiles of adequate quantity to complete the
project.
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4. Areas around the structures should be graded so that drainage
is positive and away from the structures. Gutters and down
...._..spouts_should.h.e considered_as._a way to convey water out of
the foundation area. Water should not be allowed tc pond on
or near pavement sections.
5. Added moisture within previously compacted fill could result in a
number of reactions at the surface depending upon the
amount of moisture increase, the in-place density of the soil, in-
situ moisture content and soil type. Although the sol could in
reality be expanding, collapsing, moving laterally due to the
phenomenon "creep", the result is usually movement and will
most likely manifest itself visually in structural slabs cnd street
areas as cracks, (horizontal, lateral or vertical displacement).
6. The apparent cure to the problem is to not introduce excess
moisture into fill material once in place. To help minimize
increased moisture into the fill material, site draimge and
landscape is critical. Site drainage should be in the fo,, m of roof
gutter, concrete brow ditcher, ribbon gutters and gutters, storm
drain and other drainage devices. Landscaping should be
such that water is not allowed to pond. Additionally, care
should be taken so as not to over water landscaped areas.
7. The Recommended Grading Specifications included in
Appendix C are general guidelines onl a Sao not be
included dir tI 5 jEtp,EproP8tI i �f I� _ out first
incorporating 1::w -ained in
the Site Develop Q@two f tjVM6hapter
70 of the Unifo �i ��ei4<i� erations
for grading an �, Lqjr�i agxVisof�V:
genercq yu' illi :
,nit Date
8. It is recommended that Buena E��n�ag�iin_e rs, Inc., be retained to
provide soil et EMk61&6s�+MA%g construction of the
grading, excavation, and foundation phases of the work. This is
to observe compliance with the design concepts,
specifications or recommendations and to allow design
changes in the event that subsurface conditions differ from
those anticipated prior to start of construction.
C. Excavations
1. All excavations should be made in . accordance with
applicable regulations. From our site explora-ion and
knowledge of the general area, we feel there is a potential for
construction problems involving caving of relatively deep site
excavations (i.e. utilities, etc.). Where such situations are
encountered, lateral bracing or appropriate cut slopes should
be provided.
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2. No surcharge loads should be allowed within a horizontal
distance measured from the top of the excavation slope,
equal to the depth of the excavation.
D. Traffic Areas
1. Curbs and streets should be provided with one (1) foot of
subgrade compacted to ninety (90) percent of maximum
density.
2. On-site parking should be provided with one (1) foot of
subgrade compacted to ninety (90) percent of maximum
density.
3. Final preparation of subgrade will depend on paving section
designs.
4. Sidewalks should be provided with one (1) foot of subgrade
compacted to ninety (90) percent of maximum density.
E. Utilily Trenches
1. Backfill of utilities within road right-of-way should be placed in
strict conformance with the requirements of the governing
agency (Water District, Road Department, etc.).
2. Utility trench bcq ilb) b- Rf-V I e aced in
strict conformcmjOeNgi =f01110U I� ting to
minimum co 0"TAMVMOrdSGEdTE(�I� mEvA�( Lce lines
extending insilC F 6Uft1Jk1$lF�ULWiMT)Wive soils
compacted t I WLffetc�PE& ftaximum
density. �s.
Init �� Date NOV 9 2006
3. Backfill operatLqR4-j4t9gj4and tested by Buena
Engineers, Inc., to monitor compliance with these
recommendations.
STRUCTURES
Based upon the results of this evaluation, it is our opinion that the structure
foundation can be supported by compacted soils placed as
recommended above. The recommendations that follow are based
on "very low" expansion category soils.
It is anticipated that foundations will be placed on firm compacted
soils as recommended elsewhere in this report. The
recommendations that follow are based on "very low° expansion
category soils.
1. Table 2 gives specific recommendations for width, depth and
reinforcing. Other structural considerations. may be more
BUENA ENGINEERS, INC.
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December 18, 1990
-12-
stringent and would govern in any
depth of twelve (12) inches below
one (1) story structures and eighteen
#could-be-fnaintained.------ -
2. Conventional Foundations:
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90-12-786
case. A minimum footing
lowest adjacent grade for
(18) inches for two (2) story
Estimated bearing values are given below for foundotions on
recompacted soils, assuming import fill (if required) to be equal
to or better than.site soils:
a. Continuous foundations of .one (1) foot wide and twelve
(12) inches below grade:
i. 1300 psf for dead plus reasonable live loads.
ii. 1700 psf for wind and seismic considerations.
b:. Isolated pad foundations 2'x 2' and bottomed twelve (12)
inches below grade:
i. 1500 psf for dead plus reasonable live loads.
ii. 2000 psf for wind and seismic consideratbns.
3. Allowable increasesrM W&Gmtpewmes%OEfcRW'OC)00ititMal
footing width and 3@&ps0ToKRftW Sof
footing depth may P9
will be 2000 psf. Th: � g R%VM 1. have
been determined . LAAO E0PQ0FE�h¢ttga►r�ed aximum loads
indicated in the "Introduction" sectionln f r� �x-F.NQ t ie 200fi
indicated loading is exceeded then the owa Fir- earing
values and the gradiAgTFeW &M15 to tYYF_5-e reevaluated by
the soil engineer.
4. Although footing reinforcement may not be required per Table
2; nominal reinforcement should be considered to reduce the
potential for cracking due to temperature and shrinkage
stresses and in order to span surface imperfections. Other
requirements that are more stringent due to structural loads will
govern.
5. Soils beneath footings and slabs should be premoistened prior
to placing concrete.
6. Lateral loads may be resisted by soil friction on floor slabs and
foundations and by passive resistance of the soils acting on
foundation stem walls. Lateral capacity is based partially on
the assumption that any required backfill adjacent to
foundations and grade beams is properly compacted.
7. Foundation excavations should be visually observed by the soil
engineer .during excavation and prior to placement of
reinforcing steel or concrete. Local variations in condRions may
warrant deepening of footings.
BUENA ENGINEERS. INC
Sieve Size Percent Passing
3/4" 90-_100
No.4 0-10
THIS QW.L$ NT WAS ISSUED PFWV19USLY AND
MAY NOT REFLECT CURRENT SITE CONDITIONS
/OR STANDAR;W %1If a membri N�be used
to help mitI9nk6RShEIn�WON amourould
be
covered witA IEM)'W;@§1 ift&nd help protect it during
construction. The sand should b% i, hellitened just prior to
placing the concrete. NOV a 9 200h
EARTH SYSTEMS SOUTHWEST
3. Reinforcement of .slab -on -grade is contingent upon the..
structural engineers recommendations and the expansion
index of the supporting soil. Since the mixing of fill sol with native
soil could change the expansion index, additional tests should
be conducted during rough grading to determine the
expansion index of the subgrade soil. Additional reinforcement
due to the expansion index of the site soil should be provided
as recommended in ' section G below. Additional
reinforcement may also be required by the structural engineer.
4. It is recommended that the proposed perimeter slabs
(sidewalks, patios, etc.) be designed relatively independent of
foundation stems (free-floating) to help mitigate cmcking due
to foundation settlement and/or expansion.
C. Settlement Considerations
1. Estimated settlement, based on footings founded on firm soils
as recommended, should be less than one (1) inch Differential
settlement between exterior and interior bearing members
should be less than one-half (1/2) inch.
2. The majority of settlement should occur during construction.
BUENA ENGINEERS, INC.
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8. Allowable bearing values are net (weight of footing and soil
surcharge may be neglected) and are applicable for dead
plus reasonable live loads.
B. Slabs -on -Grade
1. Concrete slabs -on -grade should be supported by
compacted structural fill placed in accordance with
applicable sections of this report.
2. In areas of moisture sensitive floor coverings, an appropriate
vapor barrier should be installed in order to minimize vapor
transmission from the subgrade soil to the slab. We would
suggest that the floor slabs be underlain by a four (4) inch thick
layer of gravel or by. an impermeable memtrane as a
capillary break. A suggested gradation for the gravel layer
would be as follows:
Sieve Size Percent Passing
3/4" 90-_100
No.4 0-10
THIS QW.L$ NT WAS ISSUED PFWV19USLY AND
MAY NOT REFLECT CURRENT SITE CONDITIONS
/OR STANDAR;W %1If a membri N�be used
to help mitI9nk6RShEIn�WON amourould
be
covered witA IEM)'W;@§1 ift&nd help protect it during
construction. The sand should b% i, hellitened just prior to
placing the concrete. NOV a 9 200h
EARTH SYSTEMS SOUTHWEST
3. Reinforcement of .slab -on -grade is contingent upon the..
structural engineers recommendations and the expansion
index of the supporting soil. Since the mixing of fill sol with native
soil could change the expansion index, additional tests should
be conducted during rough grading to determine the
expansion index of the subgrade soil. Additional reinforcement
due to the expansion index of the site soil should be provided
as recommended in ' section G below. Additional
reinforcement may also be required by the structural engineer.
4. It is recommended that the proposed perimeter slabs
(sidewalks, patios, etc.) be designed relatively independent of
foundation stems (free-floating) to help mitigate cmcking due
to foundation settlement and/or expansion.
C. Settlement Considerations
1. Estimated settlement, based on footings founded on firm soils
as recommended, should be less than one (1) inch Differential
settlement between exterior and interior bearing members
should be less than one-half (1/2) inch.
2. The majority of settlement should occur during construction.
BUENA ENGINEERS, INC.
•1
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D. Frictional and Lateral Coefficients
_ ..___.___1.. Res_istance_fo___l.at_e_ralJ.oa.ding._may. be provided by friction
acting on the base of foundations, a coefficient of friction of .46
may be used for dead load forces.
2. Passive resistance acting on the sides of foundation stems
equal to 300 pcf of equivalent fluid weight, may be included for
resistance to lateral loading.
3. Passive resistance of soils against grade beams and the
frictional resistance between the floor slabs and the supporting
• soils may be combined in determining the total lateral
resistance, however the friction factor should be reduced to' .33
of dead load forces.
4. A one-third (1/3) increase in the quoted passive value may be
used for wind or seismic loads.
j- •711TATIR
1. For cantileveFHRt9i D IEY��I�Al t�k. a11�d ftIMMMt
ed native
soils, it is re%ggnr n IREImitm u8y�e I I ressure of
thirty-five (36)DipITfi1i9�Rf *PFf I` TYHAN Mo I backfill
conditions. THE CONTENT OF THE D�CqU&
USED OR RELIED UPON -WITHOUT A REVIE1 0p Y2 1006
Q LIFTED PROFESSIONALS.
2. The lateral ear�� pressure to be resist retaining walls or
similar structuresshouldbe incrd�rsu�a M mor surcharge
loads. The st g4)WgVSq@Mg(jo i0Wwmld include the loads from
any structures or temporary loads that would influence the wall
design.
3. A backdrain or an equivalent system of backfill drainage should
be incorporated into the retaining wall design. Backfill
immediately behind the retaining structure should be a 'fee -
draining granular material. Alternately, the back of the wall
could be lined with a geodrain system.
4. Compaction on the retained side of the wall within a horizontal
distance equal to one (1) wall height should be performed by
.hand -operated or other light weight compaction equipment.
This is intended to reduce potential "locked -inn lateral pressures
caused by compaction with heavy grading equipment.
5. Water should not be allowed to pond near the top of the wall.
To accomplish this the final backfill site grade should be such
that all water is diverted away from the retaining wall.
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F. Slope Stability
Slope stability calculations were not performed due to the
anticipated minimal slope height (less that 5'). If slopes exceed five
(5) feet, engineering calculations should be performed to
substantiate the stability of slopes steeper than 2 to 1. Fill slopes
should be overfilled and trimmed back to competent material.
The design of foundations should be based on the weighted
expansion index (UBC Standard No. 29-2) of the soil. As stated in the
soil properties section, the expansion index of the surface soil is in
the very low (0-20) classification. During site preparation.,, if the soil is
thoroughly mixed and additional fill is added, the expansion index
may change. Therefore, the expansion index should be evaluated
after the site preparation has been completed, and the final
foundation design adjusted accordingly.
H. Additional Services
This report is based cm1Jhg0@�iDtl� t t an adequate program
of client consultatiofWA, 'C* tria cnT P Ott MODvill be
performed during thl ( MS ran�� A(� Wcheck
compliance with thq� ddfl tJw411�vir ALT
Engineers, Inc., as the n 4F S IitAU�e�gkHVMt ,end of
the project will help assure con In n'f se ices. Construction
monitoring and testing would be additie rvmi@s 00Wbe aPy
our firm. The costs offAhaq% j n cluded Inou resent
fee arrangements. The and observations
include, but are not necessarily limited to the following:
I. Consultation during the final design stages of the proiect.
2. Review of the building plans to observe that recommendations
of our report have been properly implemented into the design.
3. Observation and testing during site preparation, grading and
placement of engineered fill.
4. Consultation as required during construction.
LIMITATIONS AND UNIFORMITY OF CONDITIONS
The analysis and recommendations submitted in this report cre based in
part upon the data obtained from the six (6) borings performed on the
site. The nature and extent of variations between the borings may not
become evident until construction. If variations then appear evident, it
will be necessary to reevaluate the recommendations of this report.
Findings of this report are valid as of this date. However, changes in
conditions of a property can occur with passage of time wether they
be due to natural processes or works of man on this cr adjacent
properties. In addition, changes in applicable or appropriate standards
occur whether they result from legislation or broadening of krowledge.
BUENA ENGINEERS, INC.
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Accordingly, findings of this report may be invalidated wholly or partially
9 by changes outside our control. Therefore, this report is subject to review
and should not be relied upon after a period of eighteen (18) months.
In the event that any changes in the nature, design or location of the
building are planned, the conclusions and recommendations
contained in this report shall not be considered valid unless the changes
• are reviewed and conclusions of this report modified or verified in writing.
This report is issued with the understanding that it is the responsibility of the
owner, or of his representative, to insure that the information and
recommendations contained herein are called to the attention of the
architect and engineers for the project and are incorporated into the
plans and specifications for the project. It is also the owners responsibility,
or his representative, to insure that the necessary steps are taken to see
that the general contractor and all subcontractors carry out such
recommendations in the field. It is further understood that the owner or his
representative is responsible for submittal of this report to the appropriate
governing agencies.
Buena Engineers, Inc., has pre df§cD is fpW for the exclusive use of
the client and authorized ag rifs N-MsRm aerpdi?qred in
accordance with generally ac> pi Ts`b�I MC n110
practices. No other warranties,Q§ithe& ECI6 �•�
the professional advice provi8Wdifled �y@Rigs
and included in the report. IONALS. EVIEW By
Inii
It is recommended that BSER i�, c.,UU—pt 9t 6
opportunity for a general review of final de I��bW speclfcatio lin
order that earthwork and foundation recommendations may be
properly interpreted and implemented in the design and specifications.
If Buena Engineers, Inc., is not accorded the privilege of making this
recommended review, we can assume no responsibility for
misinterpretation of our recommendations.
Our scope of services did not include any environmental assessment or
investigation to determine the presence of hazardous or toxic materials
in the soil, surface water, groundwater or air, on, below or around this site.
Prior to purchase or development of this site, we suggest that an
environmental assessment be conducted which addresses
environmental concerns.
END OF TEXT
Appendices
RIJFNA FNMNEERS. INC
December 18, 1990 -17- B7 -2823-P1
90-12-786
1. Envicom, Riverside County, 1976, Seismic Safety Element.
2. Greensfelder, Roger W., 1974, Maximum Credible Rock
0 Accelerations from Earthquakes in California, CDMG Map Sheet 23.
3. Krinitzsky, E.L., Chang, F.K., Magnitude -Related Earthquake Ground
Motions, Bulletin of the Association of Engineering Geologists Vol. XXV,
No. 4, 1988, Pgs. 399-423.
4. Ploessel, M. R. and Slosson, J. E., "Repeatable High Ground
Accelerations from Earthquakes", 1974 California Geology, Vol. 27,
No. 9, Pgs. 195-199.
5. Seed, H. B. and Idriss, I. M1982 Ground Motio,)s and Soil
S
Do,�
• Liquefaction During Earthquake�io7
I)R S ` =Uf=p PF—r-v c
6.' Seih,, Kerry, 1985, "Earthq ,�ke-QRgtet�tials - AIonc`` _ e�66. 10 rJ� psi
Fault , Minutes of The Nc�onaParthqudke 13Ce, >vl�l
Council, March 29-30, 1985, USG`s pen glg� rt;8�1l',: �Lv No.r s .
S. A REVIEW E
8Y
EARTN,SYSTEMS SO IngNOfv�V 4 920
uTHWEST �-- 06
Ll
BUENA ENGINEERS, INC.