05-0665 (SFD) Geotechnical ReportEarth Systems Consultants Buona Enginoors Division
Southern California 79-8118 Country Club Drivo
Bermuda Dunes. CA 92201
(619) 345-1588
(619) 328-9131
FAX (619) 345-7315
January 11. 1995 SS-5234-PI
94-12-719
South Valley Estates
41-910 Boardwalk:' Suite A10
Palm Descrt, California 92211
Attention: Neil Kleine
Project: Tract 28034
La'' Quinta, California
Subject: Geotcchnical. Engineering Report
Presented herewith is our Geotcchnical Engineering Rcport 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- accordance with our agreement.
Other services which may be required, such as ' plan, review and grading
observation are additional services and will be billed according' to the Fee Schedule
in effect at the time services are provided.
Please contact the undersigned if there are any questions concerning this report
or the recommendations included herein.
Respectfully submitted.
EARTH SYSTEMS CONSULTANTS Reviewed and Approved,
Hogan R. Wright Brett L. nderson,
Staff Engineer
No. Co4dM89
Daniel C. Schncidcrcit,_ CEG ExQ 9 30 98
ctvt-
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pc/SER �of cn0F°? i
Copics: 6/South Valley Estates
1/VTA File
TABLE OF CONTENTS
INTRODUCTION............:......:............:.....:.....:...............:................... I
PURPOSE AND SCOPE OF WORK ........................................................ I
SITE DESCRIPTION.. ................ ... ... ....
FIELDEXPLORATION.............:........................................................2
LABORATORY TESTING.................................•.:.................................3
SOIL CONDITIONS................................................... • .... ............3
GROUNDWATER.................................................................... . ..3
REGIONAL GEOLOGI............................................................:...........4
LOCALGEOLOGY...............................................................................4
GEOLOGICHAZARDS... ..................................... .........................4
Primary. .. . ............... ........................4
.... ............ .......... .......
Secondary...........................................................•......................5
Non-S cis m ic............. .................................................................. 5
CONCLUSIONS AND RECOMMENDATIONS..............................................6
SITE DEVELOPMENT AND GRADING..................................................7
SiteDevelopment Grading..........................................................7
Site Development - General.........................................................8
Excavations...........................I..................................................... 8
Utility Trenches............... ..9
STRUCTURES......................................................... .................9
. ... ....... ...... ... ...
Foundations................................................... ............................ 9
Slabson Grade............ ......... ..........:. ............ .:... .........10
SettlementConsiderations ................................ ........................I I
Frictional and Lateral Coefficients ..............:. .............................11
Retaining Walls.............................:.....................................1I
SlopeStability .......... .............. .................... ................................ 12
Expansion. ............. ................ ............................... ...........::.......1 2
Additional Services ................................................................... 12
LIMITATIONS AND UNIFORMITY OF CONDITIONS............................13
REFERENCES................. .................................. ............................... 1 4
APPENDIX A
Site and Vicinity.,Map
Legs, of Borings
APPENDIX B
Summary of Test Results
Table 2
.' January 1 1, 1995 • 1 • SS-5234-PI
94-12.718
,
INTRODUCTION'
This Gcotechnical Engineering Rcport has been prepared for the proposed
residential development to be located on the north side of Avenue 58 in the
City of La Quinta, California.. ..+
f
A. It is .assumed that the residential structures w.i11 be of relatively
` lightweight wood frame construction and will be supported b}; normal
continuous or pad footings.
B. Structuralconsiderations tfor building column loads of up to 20 kills 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 ,proposed `
residential , structures.
C These values' were assumed based upon loading, typically associated' with
normal `wood frame construction. If. 'design .'loading is to exceed these
' values, it may •be ncccssary� to rccvaluatc,,,thc given recommend:+bons.
r _ D. Alt loading is assumed to- be dead, plus* reasonable live load.
PURPOSE AND SCOPE OF WORK
The purpose of our services was. 'to evaluate•` the site soil. conditions, and to
provide conclusions and rccomntendations'-relative to the site and the "proposed
.w.
development. The scope of work*. 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. 4
` D. Review of selected technical literature pertaining to the site.
E. Evaluation 'of field and laboi•ator.y 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 Ares ;
s A. Discussions on regional, and local .geologic and, soil conditions. -
B. Graphic and/or tabulated results of laboratory' tests and field studies.
C. Discussionsand' 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.'
EARTH SYSTEMS CONSULTANTS
January 11, 1995 -2- SS-5234-111.
94-12-718
c
Not Contained In This Report:
A. Our scope of services did not include any environmental assessment or
investigation to determine the presence of hazardous of toxic materials in
the ,soil,' surface water, groundwater or air; on, below or around this site.
SITE DESCRIPTION
The project site is located on the north side of Avenue 58 west ,of Madison' Street
in the City of La Quinta, California.
A. The approximately twenty (20) acre site is :prescntly vacant and covered
with brush, short grass and weeds.
B. The' site is fairly level with a slight, overall slope ,to 'the south.
C. There are existing overhead _and underground 'utilities along Avenue. 58.
D. The adjacent property to , the cast is presently vacant, there is a date grove
to the west and a residential development to the north of the site.
FIELD EXPLORATION
Exploratory borings were drilled for -observing the soil profile and. obtaining
samples for further analysis.
A-. Three. '(3) . borings were-- excavated for soil ° profiling .and sampling, to a
maximum depth of thirty-six .(36) feet below the. existing ground surface:.
The . borings .were excavated on November- 4, 1994, using eight (8) inch
diameter hollow -stem augers powered . by a CME 45B drilling rig. The
approximate boring locations as indicated on ..the. attached plan in
Appendix. A, - were determined by pacing, and sighting from existing
streets. 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 was, recorded.
Recovered soil samples were .sealed in containers and returned to the
laboratory for further classification and testing.
C. Bulk disturbed samples of the, 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.
I). 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 arc included in the appendix A of this report. The
stratification lines represent the approximate boundaries between soil
types although the, transitions may be gradual.
EARTH SYSTEMS CONSULTANTS
January . 11, .. 1995 -3- SS-5234-PI
94-12-718
s,
LABORATORY TESTING ~
F " After a visual and tactile classification in .the field samples were returned to
the- laboratory, classifications wcrc checked, and a testing program was
established.
'A. Samples. were reviewed aloe with field to s to determine which would be
t P g g
further analyzed. Those' chosen wcrc considered as representative of soil
which would be exposed and/or used in grading and those deemed within
building influence. '
B. In situ , moisture content and unit dry weights for the cord samples wcrc
developed in accordance with ASTM D .2937.
t Y
I 'C The relative strength characteristics of the subsurface soils wcrc '
determined from the results of direct sheartests. Specimens were placed
in contact with water at least twenty=four (24) hours before testing, and
were then sheared under normal loads .ranging from 0.5 to 2.0 kips per
- square foot in general accordance with ASTM D 3080.
D. Classification tests consisted of: Expansion Index (UBC Standard No. 29-2),
Maximum Density -Optimum -Moisture (ASTM D 1557) and Ilydromctcr
Analysis (California Test Method 203). ,
E. Refer to Appendix IJ for tabular 'and graphic representation of the test
results.
.' 5011_. CONDITIONS
As determined by the . borings, site soils were found to consist primarily of
slightly silty very fine to fine grained sands and clayey silty very fine
grained sands. The boring logs in Appendix A contain a more detailed
description of the, soils encountered.
A. The -site soils were found 'to be of ''inconsistent density with samples
indicating relative compaction varying from eighty -.one (81) to one
hundred (100)! percent.
B. The soils were generally found to be dry 'near the surface and moist below
a depth of five (5) feet:
C Clay and silt contents of the soils exhibit low plasticity. Expansion tests
indicate that the majority of the soils' are in the "very low" expansion
category in accordance with Table 2 in Appendix B of this report. Refer
to section . G of the structures section .for_ specific explanations and
requirements dealing with expansive, soil., `
D. Soils should be readily cut by normal grading equipment.
f .
GROUNDWATER
Free groundwater was not encountered An any, of the borings. The depth to
groundwater in the area is generally in excess of forty (40) feet. - Fluctuations
EARTH SYSTEMS CONSULTANTS .7
January 11,- 1995 -4• SS-5234-11I
94-12-719
in groundwater levels may occur duc to variations in rainfall, temperature
1 and other factors.
REGIONAL GEOLOGY
The site is located in the Coachella' Valley,' which -is part of the Colorado Desert
geomorphic province. The dominant feature of the Colorado Desert province is
the Salton Trough, which is 'a large 'northwest -trending structural depression that extends from San Gorgonio Pass, near Palm Springs for about ISO miles to
the head- of the Gulf of California. Much of this depression in the; area cif the
Salton Sea is at an elevation below. sca level.
t The Coachella •Valley forms the northerly portion of the- Salton Sea basin. The
valley contains a thick sequence of sedimentary rocks that arc Miocene to
Recent in age. Mountains surrounding the Coachella Valley include the I..ittle
San Bernardino Mountains on the northeast, foothills of the San Bernardino
Mountains on the west 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 in the upper portion of
the Coachella Valley is composed by the Banning -fault;- the Garnet Hill fault
and the Mission Creek fault, which traverses along the northeast margin of
the valley.
LOCAL GEOLOGY
The proposed development is located in the ,La Quinta area of the Coachella
Valley. The primary. sediments 'encountered were silty sands of acolian and
alluvial - origin. At one time' portions of the subject property may have been
covered by ancient Lake Cahuilla. t.
The project site is approximately three miles southwest " of the San Andreas
fault (Banning/Mission Creek Fa,ult). Figure 1 shows the. project site in
t relation to. local geology.
GEOLOGIC HAZARDS
A. Primary Seismic Ha ar`
Primary seismic geologic 'hazards that :may affect "any property in the
" seismically active Southern California area , include:
I 1. Fault Rupture:
The project site is not located in any Alquist-Priolo Fault Zones.
Nor are any faults mapped through or adjacent to the project area.
At- the time -of drilling ; no surface expression of faulting was
observed.
Fault'rupture would most likely occur along previously established
traces. . However, fault rupture may `occur at other. locations not
previously mapped.
EARTH SYSTEMS CONSULTANTS ,
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\ r1� , 1y .•CoiOat`Ctd11 Y - �_)
January 11,.-1995 ' .S- - r SS-5234,P41 V
_ r 94-12-718
M
! ' ; 2: Ground Shaking:
Strong ground. niotion 'generated by' nearby earthquakes- can, be
expected to. occur . in , the , lifetime of the proposed development. Bascd
It upon the historical and .'prehistorical . record, the Coachella Valley
segment of the San Andreas fault 'is likely to ... generate an
approximate _magnitude eight (8.0) or greater earthquake within- the
r i` next 50 . years, especially . if it --ruptures with the adjacent San
Bernardino segment. '° This earthquake represents" the strongest -
ground shaking potential on the site. Peak accelerations arc
estimatedto range from 0.6g to .0.7g, 'based on.'which attenuation
curve is used (Boorc,-Joyncr and' Fumcl, 1994, Campbell, 1990)
t The project area is .mapped in . Ground Shaking Zone III. C :as
designated by the County of _Riverside, California. Ground Shaking
l Zoncs, ,arc bascd ' on -distance from causative faults and soil types.
B.' Secondary Seismic Hazards: i j
Scconda`ry' seismic geologic'' hazards. include settlement, ' liquefaction and
y 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 th"e• 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 r to 'liquefy based on grain size.-' No free
�. groundwater was encountered in ,our exploratory borings.
r 3. Ground lurching=y is generally ' associated with fault rupture and -
liquefaction. - Because -of the sites' distance from any known "active'
' fault and it's relatively flat 'nature, , the , possibil.ity of ground
lurching affecting the site is,considered 'low.
4.. Other secondary seismic: geologic hazards - that may result • from a,n r'
+ ' earthquake include ; -::Csunamis (tidal waves) and: seiches (waves
' oscillating in an 'enclosed area, i.e., storage, tanks, lakes). Based on
F the project sites .geologic' location and topography, it . is our opinion-'
F that the probability of the above hazards -affecting the property arc
ncgli-gible. <
C. Non -Seismic Hazards:
Non -seismic geologic. hazards include" Landslides, :subsidence, flooding and
erosion. v _
1. No cvi.dcnce of past .landsliding was observed at the site nor are any
known 'landslides mapped in or 'around the project site The subject
EARTH SYSTEMS CONSULTANTS
= Janunry '11, 1995 y -6- SS-5234-Pl
94-12-719
property is not at the immediate`basc of any steep hills, and is' located
i
on gently sloping ground.
2. At this time there' is no evidence of subsidence .,due to groundwater,
depletion in the southern Coachella Valley. r
3. Flooding and erosion `arc always a consideration , in arid regions.
Increased -fluvial erosion, , may' occur as. a result �of construction
t. ,• -
activity.
The
C_ONLI.1lSIONS AND RECOMMENDATIONS
following is a summary t of our.. conclusions and- professional opinions
based
on the data obtained from a review of '�sctected, technical literature and .
t the .
site investigation. `
A.
The primary geologic hazard relative to - site` development is 'strong,
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 San Andreas fault, zone
would be the most likely cause of significant earthquake • activity at the
'
site within the; estimated design, life of the proposed development.
B.
Settlement due to seismic factors or flooding .i& .a potential hazard in the
Coachella Valley arc a. Adhcrence- to ., the following, grading
recommendations should limit potential settlement problems due to
seismic forces, heavy rainfall, -flooding and - the weight of the intended
structures.
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. , Fluvial and acolian erosion may
affect the_ site during and' after construction., _
D.
Other hazards -including' ground 'rupture, liquefaction,. lurching,
landslides, tsunamis, subsidence and seiches are considered' negligible. '
E.
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
constructed on the site 'be designed by,, a qualified professional who is
aware of <the • project's seismic setting. y
F.
It is our opinion that the 'upper native' soil may not' p_rovide
uniform support for tile` • proposed' .,residential structures
without the recommended sitework. - To ,decrease, , the potential for
consolidation and to provide a more • uniform and firm bearing support
for the proposed structures, ,we recommend.- constructing recompacted soil
mats beneath all ,foundations and • slabs-on=grade. A, -
G.
It . is recommended that Earth Systems - Consultants be retained to provide
Geotechnical Engineering services during• project design, s-ite..
development, excavation, grading; and foundation construction phases of
the work... This is to observe compliance' 'with• the design concepts,
specifications and recommendations. and to allowdesign changes. in the
EARTH SYSTEMS CONSULTANTS
January 11. 1995
-7-
SS-5234-PI
94-12-719
event, that subsurface conditions differ from those anticipated prior to
the start of construction.
H. Plans and specifications should be provided to Earth Systems Consultants
prior to grading. Plans should include the grading plans, foundation
plans, and -foundation details. Preferably, structural loads should be
shown on the foundation plans.
Prior to any construction operations, areas to ' be graded should be cleaned- of
vegetation and other deleterious materials.
A. Site Development Grading
Site grading and the bottom of all excavations should be observed by a
representative of Earth Systems. Consultants prior to placement of fill.
Local variations in soil conditions may warrant increasing the depth of
overexcavation.
1. Prior to site grading" any stumps, roots, uncompacted fill, trash piles
and any abandoned underground utilities should be removed from
the proposed building and paving areas. The surface should be
stripped of all organic growth and non -complying fill which, along
with other . debris, should be removed from the site. Of particular
significance will . be the roots associated. with existing and previously
removed date palms.
2. Depressions resulting from these removals should have debris and
loose soil removed and be filled with suitable fill soils compacted as
recommended herein.. No compacted fill should be placed unless the
underlying soil has been observed by Earth Systcros Consultants
3. In order to help minimize potential settlement problems associated
with structures supported on a non -uniform thickness of compacted
fill, Earth. Systems Consultants should be consulted for site grading
recommendations relative to backfilling, large and/or deep
depressions resulting from removal under item one above. In
general, all proposed construction should be supported by a uniform
thickness of compacted soil.
4. Due to the inconsistent density of the near surface soils, we
recommend recompaction of the soils within the proposed building
areas.
5. As a minimum building areas should be overcxcavatcd to a depth of
two (2) feet below existing grade or two (2) feet below the bottom of
footings, whi:hever is deeper. 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 soils and fill material should then
be placed in thin layers at near optimum moisture and compacted to
a minimum of ninety (90) percent of maximum density. The intent
EARTH SYSTt";PAS CONSULTANTS
January 11. 1995 - -8- SS-5234-PI
94-12-718
is to have at least three (3) fee of soil completed to a
minimum " of ninety (90) percent of maximum density
compose the building pa.d beneath the footings.
Compaction should be verified by testing..
6. These grading recommendations apply to building areas and to areas
at least five -(5) feet -beyond building limits.
7. Auxiliary .structures- including freestanding or retaining walls
should have the existing soils beneath the structure processed as per
items five and six above. ' The grading recommendations apply to
three (3) . feet beyond the footings. If plans for auxiliary structures
and walls arc ,'provided for our review, these . recommendations may
be revised.
8. 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 'five (5) feet of soil,
may be used for quantity calculations,.. This is based on cornpactive
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. methods. Subsidence is estimated
between one -tenth (1) and two -tenths (.2) of a foot.
B. Site Development General
1. The following general recommendations listed in.` this section arc in
addition `to those listed in the "-Grading" section ., A above.
2. All rocks larger than •:eight (8) inches in greatest dimension should
be removedfrom 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 Earth Systems
Consultants 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.
4. Areas around the 'structures should be graded so that drainage is
positive and away from the structures. Gutters and down spouts
should be considered ' as a way 'to convey water„ out of the foundation
area. Water should. not :be"allowed to pond on or near pavement
sections.
C_ Excavations
1. All excavations should be made in accordance with applicable
regulations. ?rpm our site exploration °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 arc ,encountered, lateral bracing or
appropriate cttt slopes should be provided.
EARTH SYSTEMS CONSULTANTS
January
11, 1995 -9- SS 5234 PI.
94-12-7.18
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. tility
Trenches '}
1.
•Backfill of utilities within, road right-of-way should be placed in
strict conformance with the requirements of ,the governing aecncy
(Water District, Road Department, etc.).
2.
Utility trench backfill within private property should he placed in
strict conformance, with the provisions of this report relating to
minimum compaction standards. In general, service lines extending
inside of property may be backfilled with native soils compacted to a
minimum of ninety (90) percent of maximum density.
3.
Backfill operations should be observed and tested by Earth Systems
Consultants, to, monitor, compliance with these recommendations.
- y
Based .uvon
- -STRUCTURES'
the results or, this. evaluation, it is our opinion that the structure
foundations can be supported by compacted soilsplaced as recommended
above.
-The recommendations that follow are based on "very low" expansion
category
soils. - y
A. Foundations
It
is anticipated that foundations. will be placed on firm compacted soils as
recommended elsewhere in, this report. The recommendations that follow
i are
based on "very low"' expansion category soils.
I.'
Table 2 gives" specific recommendations for width, depth and
reinforcing. Other structural consideration may be more stringent
'
and would govern in any case. Aminimum footing depth of twelve
t
(12) inches below lowest adjacent grade for one (1) story structures .
and eighteen (18) inches , for two (2) story structures should be
f
maintained.
2.
Conventional Foundations: ;
Estimated bearing , values are , given below. for foundations on ;
i
recompacted soils, assuming import fill (if required) to be equal to or,
'
better than site soils:
►
a. Continuous foundations of one 0) foot wide and twelve (12)
4 inches below grade;
is 1500 .psf for dead plus reasonable live loads.
ii.. 2000, psf for' wind -and 'seismic considerations.
'
b. Isolated . pad foundations 2' x 2' and ,bottomed twelve (12) inches
below grade:
.
i. 1800 psf' for dead plus reasonable live loads.
ii. 2400 psf for wind and seismic considerations.
EARTH SYSTEMS CONSULTANTS
January
11, 1995 -10 SS-5234-Pi
9a-12 7IH
t
3.
Allowable increases of 200 psf per one (1) foot of additional footing
width and 300 psf for each additional six (6) inches of footing; depth
may be used. The maximum allowable hearing will he 2500 psf.
The allowable hearing values indicated have been dctermined hasccl
upon the anticipated maximum loads indicated in the
"Introduction" section of this report. If the indicated loading
is exceeded then the allowable bearing values and the grading
requirements must be reevaluated by the soil engineer.
4.
Although footing rcinforccnicnt may not be required per Tablc 2;
nominal reinforcement should be considered to reduce the potential
problems related to cracking. due" to . temperature and shrinkage
stresses and in order to span surface imperfections. Other
requirements that arc more stringent due to structural loads will
govern.
5.
Soils beneath footings and slabs should be prcmoistcncd 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 conditions may warrant
deepening of footings.
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 an impermeable membrane. The membrane
should "be covered with two (2) inches of sand to help protect it
during_ construction. The sand should be Tightly moistened just prior
to placing the concrete. Low -slump concrete should be used to help
minimize shrinkage.
3.
Reinforcement of slabs -on -grade is contingent upon the structural
engineers :recommendations and, the expansion index of the
supporting soil. Since the mixing of fill soil with native soil could
change the expansion index, additional tests should be conducted
EARTH SYSTEMS CONSULTANTS
January
.1 1, 1995 -I I- SS-5234-PT
-
94.12=718
-
during rough. grading to determine .the . expansion index of the
s
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 ;
i
structural engineer. ,
4.
It is recommended 'that the, proposed perimeter slabs. (sidewalks.
patios, c(c.) " be . designed . relatively independent of foundation stems
4
(free-floating) to help mitigate cracking . 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
Icss: than one-half, (1/2) inch.
2..
The majority of settlement- should occur during "construction.
D. Frictional.
and ' Lateral Coefficients
Resistance, to' lateral loading may be provided by friction acting on
the base of foundations,. a coefficient, of friction of .45 may be used
for dead load forces.
1
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.
i 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.
t 4.
A one-third (1/3) increase in the` quoted passive value may be ,, used
for wind or seismic. loads.
E. Retaining Walls -
1.
For cantilever retaining walls backfilled with compacted native
soils. it is . recommended that an equivalent fluid pressure , of thirty-
five (35) pcf be .used for well drained level backfill conditions.
2.
The lateral earth pressure to be resisted by 'the retaining walls or
similar structures should be increased to allow for surcharge, loads..
The surcharge considered should 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 he
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. �-
EARTH SYSTEMS CONSULTANTS
January. 11, 1995' _ 17- SS-5234-111
94-12-71$
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 -in" 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 grade should be such that all water
is diverted away from` •thc retaining wall.
F. Slope Stability
•
j Slope `stability calculations were not performed due to the anticipated
minimal slope height (less that . 5') Af .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.
G. Eansion .f .
t.
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. However, 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 on the assumption that an .adequate program of client
consultation, construction - monitoring . and testing will be perfo►mcd
during . the final design and construction phases to 'check compliance
k with these recommendations. Maintaining Earth Systems Consultants,;c 'as
the soil engineering firm, from beginning to. end 'of the project will help
assure' continuity of services.. 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. The
! recommended .tests and observations include". but ° are. not necessarily
limited to the following:
1: Consultation during the final design,stages of the , project.
2. Review of the: building plans to observe that recommendations - of, our
report " have been properly implemented into "the design.
3. Observation . ind , testing during `..site`, preparation, grading and
placement of 'engineered fill.
f
4. Consultation as required during 'construction:
EARTH SYSTEMS CONSULTANTS
January 11. 1995 -13 SS-5234-I'J
94-11-719
LIMITATIONS AND UNIFORMITY OF CONDITIONS
.The analysis and . recommendations submitted in this report are based in part
upon the data obtained from the three (3) .borings excavated on the site. The
nature and extent of variations between the borings may not
1)econfe evident until construction. If variations then appear
evident, it will be necessary to reevaluate the recommendations of
this report.
Finding-, of this report arc valid as of this date. llowcvcr, changes in
conditions of a property can occur with passage of. time whether they be duc' to.
natural processes or works . of man on this or adjacent properties. In addition,
changes in applicable or appropriate standards occur whether they result
from legislation or broadening of knowledge. Accordingly, findings of this
report may be invalidated wholly or partially by . changes outside our control.
Therefore, this, report is subject to .review and should not be relied
upon after a period of, eighteen (18) months.
In the event that any changes in the nature, design or location of the building
arc planned, the conclusions and recommendations contained in this report
shall not be considered valid unless the changes arc 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 arc called to the attention of the
architect and engineers for the project and arc 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 sec
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.
Earth Systems Consultants, has prepared this- report for the exclusive use of
the client and authorized agents. This report has been prepared in accordance
with generally accepted soil and foundation engineering practices. No other
warranties, either ,expressed or implied, are made 'as the professional advice
provided under the terms of this agreement, and included -in the report.
It is - recommended that Earth Systems Consultants, 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 Earth Systems Consultants, 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, grounJwatcr 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 OFTEXT
Appendices
EARTH SYSTEMS CONSULTANTS
• January 11, 1995 -14- .. SS-5234-11I
94-12-718
REFERENCES i.
1.
Envicom, Riverside County," 1976, Seismic. Safety Element.
2.
Grecnsfeldcr, Roger W., 1974, Maximum Credible Rock Acccicrations from
'
Earthquakes in California, C,DMG,'Mnp Shcct.23
3.•
f
Krinitzsky; E.L., Chang, F.K., Magnitude-Relatcd' Earthquake Ground
Motions, Bulletin of the Association of Engineering '`Geologists Vol. XXV,
No. 4, 1988, Pgs. 399-423.
4.
Plocssel, M. R. and Slosson, J. E., "Repeatable High Ground Acccicrations
from Earthquakes",, 1974 California, Geology, Vol. 27, No. 9, Pgs. 195-199.
f 5.
'Seed. H. B. and Idriss, 'I.• M., 1982, Ground Motions -and Soil, Liquefaction
During Earthquakes. `
6.
Seih, Kerry, • "Earthquake Potentials' Along The' San Andreas Fault",
.1985,
` "Minutes of The National Earthquake Prediction Evaluation Council, March
29-30. 1985, USGS Open. File Report 85-507.
7.
Van de Kamp; P. C., "Holocene Continental Scdimcntation in the Salton
Basin, , California: A Reconnaissance". Geological Society of America. Vol
84, March 1973
EARTH SYSTEMS CONSULTANTS
7EH A71vE TR ac
MAP b0. 2a0006
E-AsTn.e-DATE Glori
A .t ra..r a y��. a.0 .. a 1
1
' � I I• ..» s.1 ...r `-fe � I ,\ la.r ra\i. \" :. •ems Y .- � - .
W
An
iff Is
In III
co
ty ^ ti
to 11�
PFaVArE
I' au.~.• .w= mr1. \ am 21 v.•. 1)""a\'`�
aw_mi.
\.. \•\ + e
VA
` TRACT 28034
- APPROXIMATE BORING LOCATIONS LA OUINTA. CALIFORNIA
APPROXIMATE PERCOLATION TEST LOCATIONS EARTH SYSTEMS CONSULTANTS
DATE: 11/15/94 FILE SS-5234.-Pt
Tract 28034
Date: -11/4/94 Location: Per Plan BORING NO. 1 File No. SS-5234-Pt .
a d
0
3
DESCRIPTION
o
M4
C
m a
REMARKS
o
0,
°C o
�n
0
0
A 1 Pale gray slightly silty
SM/SPIT
very fine to fine .
27
grained sand
100:2 .
1.4
92
5
17
; IL
1
99.9..
' 1.6.
91.
10
18
1, 1t
aN"
87.7
6.4
80
A3: Yellow brown slightly
SM
clayey silty very fine
,
15
045
to fine grained sand
113.0
11.0
100
f
20
r`
23
N 11
N
93.7
5.2
.83
A2: Yellow brown silty .
SM
-
very clayey very fine
-
to find grained sand
A 3: Yellow, brown., slightly
SM
1-02.3
13.1
90
25
31
clayey silty very tine
to fine grained sand
3-0
25
11 N
N
107.6
17.4
95
_
Al with medium
35
40
and coarse rained sand
Al:
SM/SP
110.7
153
-
- Relatively undisturbed
Total Depth = 36'
_
ring sample
t
No Free Water
No Bedrock
40
45
Note: The stratification .
"
lines represent the
approximate boundaries
'
between the soil types; the
'
transitions may be gradual."
50
1:11oary 11. 1995
B 1
SS--Pi-Pi
94-12-718
BORING/DEPTH
TEST RESULTS
1 @ 21-25'
2 @ 10-15'
I @ 0-5'
USCS
SM/Sp
SM .
'SM
SOIL DESIGNATION
A l
-A 2
A 3
MAXIMUM
DENSITY (pcf)
IU9.3
---
113.5
OPTIMUM MOISTURE (%)
13.0
- - -
13.1
ANGLE OF INT. FRI
31 °
- - -
280
COHESION (psf)
100
-"-
130
EXPANSION INDEX.
0
GRAIN SIZE DISTRIBUTION (%)
GRAVEL
0.0
0.0
0.0
'SAND
79.7
45.8
58.7
SILT
12.7
22.2
26.9
CLAY
7.6
32.0
14.4
SOIL DESCRIPTIONS:
A1: Pale gray slightly silty
very fine to
fine "grained
sand (SM/SP)
A2: Yellow brown silty very clayey very
fine to fine
grained sand (SM)
A3: Yellow brown slightly
clayey silty very
fine to fine grained sand (SM)
EARTH SYSTEMS CONSULTANTS
January, 11, 1995
I3 2
SS-5234-1'1
94-12-718
IN -PLACE DENSITIES
RELATIVE
BORING & DEPTH
DRY DENSITY' .% MOISTURE
COMPACTION
1 @ 2.0
100.2 1.4
92%
5.0
99.9 1,6
91 %
10.0
87.7 6.4
80%
15.0
113.0 11.0
100%
20.0
93.7 . 5.2
83 %
25.0
102.3 13.1
90 %
30.0
107.E 17.4
95 %
35.0
110.7 15.7
- - -
2 @ 2.0
93.2 . 2.4
85 %
5.0
101.2 6.8
93%
10.0
90.8 4.2
8 3 %
15.0
92.6 21.7
85%
3@2.0
98.4" 15
--
5.0
89.9 . 2.1
- - -
10.0
92.3 7.61
81 %
15.0
98.6 5.8
87%
EARTH SYSTEMS CONSULTANTS
Y
It
LA
LL 109
U
m
U
Q
W
a
U
0
z 108
O
a
Z
Uz
W �
107
Q
0
SS-5234-P1
t• -
MOISTURE CONTENT IN PERCENT OF DRY WEIGHT
METHOD OF COMPACTION
ASTM D-1557-78, METHOD A or C
SOIL TYPE MAXIMUM DENSITY OPTIMUM MOISTURE
Al 109.3 pci 13.0
Boring 1 @ 0 - 5'
MAXIMUM DENSITY OPTIMUM MOISTURE CURVE
It
LA
LL 109
U
m
U
Q
W
a
U
0
z 108
O
a
Z
Uz
W �
107
Q
0
SS-5234-P1
t• -
MOISTURE CONTENT IN PERCENT OF DRY WEIGHT
METHOD OF COMPACTION
ASTM D-1557-78, METHOD A or C
SOIL TYPE MAXIMUM DENSITY OPTIMUM MOISTURE
Al 109.3 pci 13.0
Boring 1 @ 0 - 5'
MAXIMUM DENSITY OPTIMUM MOISTURE CURVE
8
LL 114
U.
o]
D
. U y
cr-
W
a
cn
- o
z 113
O
a
z
z w
o -1.12
1
SS-5234-P 1
4.0,
3.5
N�
f'
p
3.0
LL
a
'
- Y
- 2.5
cn
2.0
N
Z
a
1.5
w
U
1.0
0.5
0.5 " 1.0 . V. 5 2.0 2 : 5 3.0 . , 3.5
♦ NORMAL LOAD (KIPS / FOOT ) .
DIRECT SHEAR DATA
Soil type:* Al
Baring and ,depth: 1 ® 0 5'
Angle . of internal friction: 31 °
Cohesion: 100 Vsf
® Samples remolded fo 90 % of maximum density
❑ Samples relatively undisturbed -
r SS-5234.P I
-
4.0
y
3.5
N�
0
3.0.
LL
cn
Y
'2.5
- cn
in
w
CC
2 .0
in
Q
1 '. 5
w
Cn
•1.0
0.5
0.5 1.0 1.5 2.0 2.5 3.0 3.5
{ . 'NORMAL LOAD (KIPS / F001-) F
DIRECT SHEAR DATA
3
1
Soil type: A3
Boring and depth: 2 0 10 - .15'
Angle of internal, friction: 28° '
Cohesion: 130 `si
Samples remolded td. 90 %- of ~maximum density
Samples relatively undisturbed
MINIMUM FOUNDATI REQUIREMENTS_
(1) (10)
Foundations
for Slab and Raised floor Systems
(4) (8)
Concrete Slabs
,
.�
o
"'
o
d
z
�
,u
5
•s
.d
,o
8
u.
�
u,
All perimeter
footings
(S)
Interior footings
for slab and
Wised floors (S)
Rcinforccm_n!
for continuous
footings
(2) (6)
3 1/2 " Minimum
_ Thickness
Weighted,
g
expansion
Index
Prcmoistcning
control for soils
under footings,
piers and slabs
(4) (5)
Piers under
raised floors
Reinforcement
. (3)
Total
thickness
of sand
(1(1)
Depth below nntunl surface
P
of ground and (inish'gr:►dc
INCHES
0-20
Very Low
'(Non -fix-
passive)
1
2
3
G
8
10
.12
IS
iR
G
7
8
12
18
24
12 t
1R
24
1-114 top
and bottom
6x6-
10/10
WWf
2"
Moistening or,
ground,prior to
placing concrete
recommended
Piers .tllowcd,
for single
floor loads
only
21.50
Low�
1
2
3
G
8
10
12
15
18
G
7
R
1S
19
24
12
18
24
1-114 top
and bottom
Gx6-
10/10
WWf
4"
120% of optimun
moisture content
to a depth of 21 "
below lowest
adjacent grade.
fliers :!flowed
for single
floor loads
only
Testis , Rc uirccl
51.9(1
Mccli►ntt
'
1
2
3
G
8
10
12
12
15
G
8
R
21
21
24 -
12
IK
24
1-114 top
and bottom
6x6-
t,/h WWI
or 113
@ 24" e.w.
4"
130%n of optimmi
moisture content
to n depth of 27"
bclow lowest
adjacent grule.
Testing Required
Piers not
:tllci%vcd
II rtrs < < ut ext. footing
and bent T into slnh (7)
Tiers not
allrnvccl
91.11tf
1
2
a
G
8
1(l
12
12
15
G
R
8
27
27
27
12
18
" ' ��I
1-115 top
and bottom
6x6-
6/6 W\VF
or 11.1
(� 24" e.w.
4
140% of optimut
moisture content
ton depth of 33"
I)Clow lowest
I lil:h
adjacent oracle.
'Testing Itec u'I rcd
I
113 bars (p 2,1" in cxt, footing
rind bent 1' into slab (7)
Akwc
Vc-i v I I I--h
special Desil;n I,y 1.1rrnsed l:ni;inner/i\rchitrct
' Ilrl�r� I�� iil•XI pale I��u li�i��iu��r•• t I I �lu�ni��,li i Illi
r
FOOTNOTES TO TABLE 2
1. Premoistening is required where specified in Table 2 in order to achieve
maximum and uniform expansion of soils prior to construction and thus
limit structural .distress caused by uneven expansion and shrinkage.
Other systems which do not include pre -moistening may be approved by
the Building 'Official when such alternatives are, shown to provide
equivalent safeguards against adverse effects of expansive soils.
2. Underfloor access crawl holes shall be provided with curbs extending not
less than six (6) inches - above adjacent grade to prevent surface water
from, entering the .foundation area.
3. Reinforcement for ,continuous foundations shall be placed not less than
three (3) inches above the bottom of the footings and not less than three
(3) inches below the top of the stem.
4. Reinforcement shall be placed. :at mid -depth of slab.
5. After premoistening, the specified moisture content of soils shall be
maintained until concrete is placed. Required moisture content shall be
verified by an approved testing laboratory not more than twenty-four
(24) hours prior -to placement. of concrete.
6. Crswl spaces under raised floors need not be" premoistened except under
interior footings. Interior footings which , are not enclosed by a
continuous perimeter, foundation system or equivalent concrete or.
masonry moisture barrier complying with UBC Section 2907 (b) shall be
designed and constructed as specified for perimeter footings in Table 2.
7. A grade beam not less than twelve (12) inches by twelve (12) 'inches in
cross section, reinforced as specified for continuous foundations in Table
2 shall be provided at garage door openings.
8. Foundation stem walls which exceed .a height of three (3) times the ,..stem .
thickness above lowest adjacent grade, shall be reinforced in accordance
with . Sections 2418 and 2614 in the UBC or as required by engineering
design, whichever is more restrictive. -
9. Bent reinforcing bars, between exterior footing and slab shall be omitted
when floor is -designed as an independent, • "floating" slab.
10. Fireplace footings shall. be � reinforced with a horizontal grid located three
(3) inches, above the bottom of the footing and consisting of not less than
number four (#4) bars at twelve (12) inches on center each way. Vertical
chimney reinforcing bars shall be hooked under the grid. .
EARTH SYSTEMS CONSULTANTS