TR 28034 Geotechnical Report-PREPARED FOR
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SOUTH VALLEY ESTATES
SS-S234-Pi
JANUARY 11, 1995
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EARTH SYSTEMS CONSULTANTS
0 Earth Systems Consultants Buena Engineers Division
Southern California 79-811 B Country Club Drive
Bermuda Dunes, CA 92201
(619) 345-1588
(619) 328-9131
FAX (619) 345-7315
January ,11, 1995 ` SS-5234-PI
94-12-718
South Valley Estates
41-910 Boardwalk, Suite -A10
Palm Desert, California 92211-
Attention: Neil Kleine
Project: Tract 28034
La Quinta, California
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 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.
PIease" contact the undersigned if there are any questions concerning this report
or the recommendations included herein.
Respectfully submitted,
EARTH SYSTEMS (CONSULTANTS Reviewed and Approved,
Ess
Hogan R. Wright Brett L. Anderson, �. S
Staff . Engineer.:
Daniel C. Schneidereit, CEO 4 NO. E-Ve,�98
rr orvt�.
pc/S ER \c At
Copies: 6/South Valley Estates
1/VTA File -
..� TABLE OF CONTENTS
INTRODUCTION
PURPOSE AND SCOPE OF WORIC .................:..........:....r........:.......... 1
` SITE DESCRIPTION ...:..:.......:....... -
i FIELD EXPLORATION.......................................................2
LABORATORY TESTING, .... .... .. •3
SOIL CONDITIONS.
.� GROUNDWATER.
REGIONAL GEOLOGY........:.......................:.:........................:...........................:3
.......:......:.....................
.....
LOCAL GEOLOGY. ...........:....." ............... .... ........................:....4
+...! GEOLOGIC 1F�AZARDS....... ...............................................................'.4
!.J Primary....4
Secondary.......... .... ............................ •.....••...... ...........5
.Non -Seismic .............::.• .. .... ..•5
CONCLUSIONS AND ••RECOMIVIENDATIONS........................................... 5
.......... ...
SITE DEVELOPMENT AND. GRADING....:........:....................................7
Site Development - Grading ........:............. ,:7
Site Development - General'.:............r......:.....:.....:......:.....:. 8
Excavations.................................
.................................:..8
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Utility Trenches.. :. _
STRUCTURES.......... ...............................................9
Foundations........... .............. ................................9
Slabs on Grade ....... ..............:......... ,,..10
l Settlement Considerations....,..::........................................�.....11
' 1 . ..........
Frictional and Lateral • Coefficients ..... ......:.............. ��•�•�.1 1
' a Retaining Walls.................................. .................�..........11
Slope Stability.................................. ....... ....12
.� Expansion .................
...........:
............ ...............................12
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AdditionalSe"rvices................ .........:...................:..................... 12
LIMITATIONS AND UNIFORMITY. OF CONDITIONS. ................. .',13
REFERENCES ..................................... ... , ...................:..14
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APPENDIX A
I Site and Vicinity Map' ,
Logs of Borings A'
IjC-14 APPENDIX B
Summary of Test Results.
.Table 2
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i... - INTRODU .TION
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This Geotechnical Engineering -Report 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
4 A. It is assumed" that the residential structures will be of relatively
lightweight wood frame construction and will be, supported by 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 proposed
j residential structures.
I. .I C These values were assumed based upon loadings typically associated with
normal wood frame construction. If design -loading is to exceed these
' values, it may be necessary to' reevaluate the given recommendations.
ii D. All. loading is assumed to be dead plus reasonable live load.
I PURPOSE ANDS OP . OF WORK
{ The purpose of our services was to evaluate the site soil conditions, and toprovide conclusions and recommendations relative to the site and the proposed
development., The scope of work ,includes the following:
--i 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.
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.
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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 tabulatedresults of laboratorytests and field studies.
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.
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Not Contained In This Report:
A. Our scope of services did not include any environmental assessment or.
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investigation to determine the presence of hazardous or toxic materials in
the soil, surface water, groundwater or air, on, below or around this site.
DESCRIPTION
The project site is located on the north side of Avenue 58 west of Madison Street
in the City of La Quints, California.
A. The approximately twenty (20) acre site is presently vacant and covered
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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.
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D. The adjacent property to the east is presently vacant, there is a date grove
to the west and a residential development tothe north of the site.
kiELD EXPLORATION
Exploratory borings were drilled for observing the soil profile and obtaining
samples for further analysis.
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A. Three (3) borings were excavated for soil profiting 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
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diameter hollow -stem augers .powered by a CME 45B drilling rig. The
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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:
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B. Samples were secured within the borings with a two and one-half (2.5)
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inch inside diameter ring sampler (ASTM D 3550, shoe similar to ASTM D
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1586). The samples were obtainedby 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
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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
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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.
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SYSTEMS CONSULTANTS
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LABORATORY TESTING
+ j After a visual and tactile classification in the field, samples were returned to
.") the laboratory, classifications were checked, and a testing program was
established.
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A. Samples were reviewed along with field logs to determine which would be
further analyzed. Those chosen werc 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 core samples were
developed in accordance with ASTM D 2937.
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C 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) 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 Ind ex " (UBC Standard . No. 29-2),
Maximum Density -Optimum Moisture (ASTM D 1557) and Hydrometer
(( Analysis (California Test Method 203). ,
E. Refer to Appendix B fortabular and graphic representation of the test
r_ results.
SOILC!QNIDI, 'IONS
r-, 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
f 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
j 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
I 1 to section G of the structures section for specific explanations and
requirements dealing ,' with expansive soil.
F1D. Soils should be readily cut by normal grading -equipment.
GROUNDWATER
Free groundwater was not encountered in any of the borings. The depth to
n groundwater in the area is generally in excess of forty (40) feet. Fluctuations
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in groundwater levels may occur due to variations in rainfall, temperature
and other factors.
REGIONALGEOLOGY
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 norihwest-trending
structural depression
that extends from San Gorgonio Pass, near Palm Springs for about 180' miles to
the head of the Gulf of California. Much of this .depression in the area or the
Salton Sea is at an elevation below sea level.
The Coachella Valley forms the, northerly portion of the SalLo'n Sea basin. The
valley contains a thick sequence of sedimentary rocks that are Miocene to
Recent in age. Mountains surrounding the Coachella Valley include the Little
San Bernardino Mountains on the northeast, foothills, of the San Bernardino
Mountains On the west and �the San Jacinto and Santa Rosa Mountains on the
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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
d by the Banning fault, the Garnet. Hill fault
and the Mission Creek fau I L, 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 aeolian and
alluvial origin. At one time.
. portions of the subject property may have been
covered by ancient Lake Cahuilla.
The project site is approximately three 'miles -southwest of the. San Andreas
fault (Banning/Mission "Creek Fault). Figure 1 shows the project site in
relation. to local geology.,
_,.QE!2L0G1C HAZARDS
A.' 'Primary Seismic Hazards:
Primary seismic- geologic hazards that may affect any property in the
seismically active Southern, California area include:
1. Fault Rupture:
The project site is not Iodated in any Alquist-Prioto 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.
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2. Ground Shaking:
Strong ground motion generated by nearby earthquakes can be
expected to occur in the lifetime of the proposed development_ Based
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
next 50 years, especially if it ruptures with the adjacent San
I Bernardino segment. This earthquake represents the strongest
! ground shaking potential on the site: Peak accelerations are
i estimated to, range from 0.6g to 0.7g, based on which attenuation
curve is used -Poore, Joyner and Fumel, 1994, Campbell, 1990)
The project area is mapped in Ground Shaking Zone III C as
designated by the County of Riverside, California. Ground Shaking
Zones arc based on' distance from causative faults and soil types.
B. Secondary Seismic Hazards:
Secondary seismic geologic hazards 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
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episodes of settlement in the' Coachella Valley, area due to seismic
(� forces and/or heavy rain fall , and flooding.
. 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
1 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, lurching 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 possibility of ground
lurching affecting the, site. is considered -low.
4. Other secondary' seismic geologic hazards that may , result from an
' ! earthquake include tsunamis (tidal waves) and seiches (waves
oscillating in an enclosed area, i.e., storage tanks, lakes). Based on
the project sites geologic location , and topography, it' is our opinion
that the probability of the ,above hazards "affecting the property are
negligible;
" C. ' Non -Seismic Hazards:
Non -seismic geologic hazards include landslides, subsidence, flooding and
�.l erosion.
1. No evidence of past landsliding was observed at the site nor are any
ry known landslides mapped in or around the project site. The subject
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property is .not at the immediate base of any steep' hills and is located
on gently ,sloping ground.
2. At this time there is no evidence of subsidence due to groundwater
depletion in the southern Coachella Valley.
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3.. Flooding and erosion ' are . always a_ consideration in arid regions.
Increased fluvial erosion, may occur" as-- a result of construction
activity.
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CONCLUSIONS AND RECOMMF.NIiATION4
The following ,is a summary of our conclusions and professional opinions
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based on the data obtained- from a review of selected technical literature -and
the site investigation.'
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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
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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. Adherence to the following grading
recommendations should limit potential settlement problems due to
seismic forces, heavy -rainfall, flooding and the "weight of the intended
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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 aeolian erosion may
affect the site during and . after construction.
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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.
F. It is our -opinion that the upper native soil may not provide
uniform support for the 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.
G. It is recommended that Earth Systems Consultants be retained to provide
Geotechnical Engineering services during project design, site,
development, excavation, grading, and foundation construction phases of
the work. This is to observe compliance . with the design concepts,
specifications and recommendations, and. to allow design changes in the
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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.
91TE DEVEL—OP ENT AND GRADINQ
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 I 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 Systems 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 Ito 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 ovemcavated to a depth of
two (2) feet below existing grade or two (2) feet below the bottom of
footings, whichever 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) percentof maximum density. The intent
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is to have at least three (3)feet of soil compacted to a
minimum of ninety (90). percent of maximum density
compose, the building pad , beneath the footings.
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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 frees -Landing 'or retaining walls
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should have the existing soils beneath the structure processed as .per
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items five and six above. The grading recommendations apply to
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three (3) feet beyond the footings. If plans, for auxiliary structures
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and walls arc provided' for our review, these recommendations may
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be revised.
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8. It is anticipated that during grading a loss of approximately one
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tenth (A) of a foot due to stri in
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fifteen (15) to twenty (20) percent for the upper five (5) feet of soil,
may be used for quantity calculations. This is based on compactive
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effort needed 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
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between one -tenth (A) and two -tenths (.2) of a foot.
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B. Site Development - General
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1. The following general recommendations listed in this section are in
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addition to those listed in the "Grading", section A above.
2. Ail rocks Iarger 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 prequalifed by Earth Systems
Consultants. Comments on the characteristics of import will be given
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after the material is. on the project, either in -place or in stockpiles
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of adequate quantity -to complete the project.
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4. Areas around the. structures should be graded so that drainage is
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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:
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C Excavations
All excavations should be made ,in accordance, with applicable pp cable
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regulations. From our site exploration and knowledge of the general
area, we feel there is a potential -for construction problems
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involving caving of relatively deep site excavations (i.e, utilities,
etc.). Where such - situations are encountered, lateral bracing or
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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, p
equal to the depth of
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the excavation.:
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D. Utility 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.),
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2• Utility trench Backfill within private property should be placed in
strict conformance with the provisions of this report relating to
minimum compaction standards: ' In general, service lines extending
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inside of property. may be backfilled with native soils compacted to a
minimum of ninety (90) percent of maximum density.
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3. Backfill operations --should be observed and tested by Earth Systems
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Consultants, to monitor, compliance with these recommendations.
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STRUCTURES
Based upon the results of this" evaluation, it is our opinion that the structure
foundations can be supported by compacted soils- placed as recommended
above. The recommendations that follow are based on "very low" expansion
category soils.
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A. Foundations
It is. anticipated that foundations will be placed on firm compacted soils as
recomended elsewhere in this report. The recommendations that follow
are based on "very low" :expansion category soils,
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1. Table 2. gives specific recommendations for width, depth and
reinforcing. Other structural consideration may be more stringent
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and would govern in any case. A minimum footing- depth of twelve
_. (12). inches . below lowest adjacent grade for -one (1) -story -structures
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and eighteen (18) inches for two (2) story structures should be
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maintained.
2 Conventional Foundations:
Estimated bearing values are given beIow for foundations on
recompacted soils, . assuming import fill (if required) to be equal to or-,
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better than site soils:
a. Continuous foundations of one (1) "foot wide and twelve (12)
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inches below grade:
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i. 1500 psf for dead plus reasonable live loads.
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ii. 2000 psf for wind and seismic considerations.
b. Isolated pad foundations 2.', x 2' and bottomed"twelve (12) inches
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below grade:.
i. 1800 psf for dead plus reasonable live loads,
ii. 2400 psf for wind and seismic considerations.
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3. Allowable increases of 200 psf per one (1) foot of additional footing
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width and 300 psf for each additional six (6) inches of footing depth
may be used. The maximum allowable bearing will be 2500 'psf.
The allowable bearing values indicated have been determined based
upon, the anticipated maximum loads indicated in the
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"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.
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4: Although footing reinforcement may not be required per Table 2;
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nominal reinforcement should be considered to reduce the potential
problems related to cracking due to temperature and shrinkage
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stresses and in order , to span surface imperfections. Other
requirements that are, more stringent due to structural loads will
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govern.
Soils ` beneath footings and slabs should be premoistened prior to
placing concrete.
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6. Lateral Goads 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 .
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assumption that- any required backfili adjacent- to foundations and
grade beams is properly compacted.
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7. Foundation excavations should be visually observed by the soil
engineer during excavation and prior to. placement of reinforcing
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steel or concrete. , Local variations in conditions may warrant
deepening of footings.
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8. Allowable bearing values are net (weight of footing and soil
surcharge may be neglected) and are applicable fordead plus
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reasonable live loads.." ,
B. Slabs -on -Grade. -
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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 p
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
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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 lightly, 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
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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 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 in bearing 'members should be
less than one-half (1/2) inch.
2. The majority of settlement` should occur during construction'.
D.' Frictional and Lateral Coefficients
1. 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.
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 (I/3) increase in the quoted passive value may be _used
for wind or seismic loads.
E. Retainine 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 surchar a co 'd d
g nst ere should include the loads from any
structures or temporary ,loads.,that would influence the wail design.
3. A backdrain or an equivalent system of backfill drainage should be
incorporated into the retaining wall design. Our firm 'can provide
construction details when the specific 'application is determined.
Backfill immediately behind the retaining structure should be a
free -draining granular material.
EARTH SYSTEMS CONSULTANTS
I , .
January 11, 1995 -12- SS-5234-P1
94-12-718
i
E
4. Compaction on the retained side of the wall within a horizontal
j
distance equal to one (1) wall height should be performed . by hand-
operated or other light weight compaction equipment. This is
intended "locked
to reduce potential.. -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 the retaining wall.
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.
G. Expansion
_.1
_. .
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
f
added, the expansion index may 'change.
Therefore, the expansion index should be evaluated after the
..I
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 performed
during the final design
_
and construction phases to check compliance
-with .these. recommendations. Maintaining Earth Systems Consultants, as
the soil engineering firm from beginning to end of the project wiII. help
assure continuity of services, Construction monitor;" d t
g an esttng
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:
is Consultation during the final design stages of the project.
2. Review of the building plans to observe that recommendations of our
j� report, have been properly implemented into the design.
(( 3. Observation and testing during site preparation, grading and
placement of engineered fill.
4 Consultation
n as required during construction.
EARTH SYSTEMS CONSULTANTS
3
January
11, 1995 -13-.
SS-5234-PI
...
I
94-12-719
i
L[iViITATIONS AND NIF(b12MiTY
F nRtDrTrnArc
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. T h e
nature
become
and extent of variations between
evident until
the borings may not
evident,
. construction. If
it will be
variations then appear
....;
this report.
necessary to reevaluate
the recommendations of
( I
Findings of this report are valid as of this date., . However, changes in
conditions
of a property can occur with passage of time whether they be due 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 broadening
or 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. ei h n
P g tee (IS) months.
j __.
In the event that any changes in the nature, design or location of the
are planned, the conclusions and
l...i
recommendations contained in this.reportshall not be considered valid unless the changes are reviewed and conclusions
of this report modified or verified in writing.
j
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
f
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
,..5
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 No
practices. other
warranties, either expressed or implied, are made as the professional advice
...
provided under the terms of I this agreement, and I included in the report.
It is recommended that Earth- Systems Consultants, be provided - the opportunity
for
i
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.
(-7
1
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
I
assessment be conducted which addresses environmental concerns.
FNDOFTE}CT
Appendices -
(�
EARTH SYSTEMS CONSULTANTS,
January 11, 1995 -14- SS-5234-P1
94=12-718
REFERENCES
1. Envicom; Riverside County, , 1976, Seismic Safety Element.
2. Greensfelder, Roger W., 1974, Maximum Credible Rock 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, 1. E., "Repeatable High Ground Accelerations
from Earthquakes", ,1974 California Geology, Vol. 27, No. 9, Pgs. 195-I99.
5. Seed, H. B. and Idriss, L' M., 1.982, Ground Motions and Soil Liquefaction
During Earthquakes.
6. Seib, Kerry, 1985, "Earthquake Potentials Along The San Andreas Fault",
Minutes of The National Earthquake Prediction Evaluation Council, March
29-30, 1985. USGS Open File Report 85-507.
7. Van de, Kamp, P. C., '"Holocene Continental Sedimentation in the Salton
Basin, California: A Reconnaissance". Geological Society of America, Vol
84, March 1973
EARTH SYSTEMS CONSULTANTS
EARTH SYSTEMS CONSULTANTS
TENTATIVE TRACT,
MAP' (Mo.
ElasnNO DATE CROVE
II ' ww � rmar +,r mm :e:r �nm two•
I ne � ` as e� \`:$ '.n'i .?..� `� \ w': Ia.,^ ! , nb.•�^
L11
tarlu tm� B :.\ ••+r rtr.? Star,,T
a71lw A II \
I .:ram \ram . ,��^ m o _a a .m. :. 5 y �<• ..
'e'` j � o�' ar w • t �w`a�` a ; cs � �. a � \ \: •• i � I\ � .
. I.I rmot � 9� wr rua\ rnor• , �\ rmm \� `\
w PRIVATE =a. —RES.
I um .•am ,rea? �w � � ,am
_ .. -- •- VACANT^ ..
.. PARCEL NO. _6924
�. Z ..
TRACT 28034
APPROXIMATE BORING LOCATIONS
- LA OUINTA, CALIFORNIA
APPROXIMATE -PERCOLATION TEST LOCATIONS EARTH SYSTEMS CONS
ULTANTS
DATE: 11/15/94 FILE SS-5234-P1
Tract 28834 `
Date: 11/4/94 Location: Per Plan BORING NO. 1 File No. SS-5234-P1
a m
o
E
m
3
` DESCRIPTION :
n
z
a�
E
mo
> �.
a
,
'' REMARKS
�.
o
_
a
U)
..
(�
v
O
o
O U
_
Al Pale gray slightly- silty
SM/SP
very fine to fine
-
-
27
grained sand
100.2
i.4�
92
;
5
-91
17
ff
ff
99.9
1.6'
10
18
.. �f
�f.
87.7
6.4
80
-
A3: Yellow brown. slightly
SM
,
15
clayey 'silty very.fine
45
to fine grained, sand
113.0
1'1.0
100
20
23
•93.7
5.2
83
-
A2: Yellow brown silty `.
SM
-
very 'clayey very fine'_
-
to fine grained sand
r
25
_
31
f
A3: Yellow brown slightly
SM
102.3
13.,1
90
-
clayey silty very fine
-
to fine grained sand°
30
-
25
107. 6`
h
17. 41'
95 •
35Ai
with medium
Al:A 1=
SM/SP
110.7
15.7
- - -
40 •
and coarse arained.sand
Relatively undisturbed.
J1
Total Depth = 36'
-
ring sample
` .
No Free Water
«
No Bedrock
40
45
-
-
-
Note:. The stratification
lines represent the
-
^
approximate boundaries
-
*
the soil types, the
50
_between
transitions may be gradual.
Tract 28034
Date; 11/4/94 Location: Per Plan BORING NO. 2 File No. SS-5234-PI
i..1
CD
Q
m
0
-. `
.. M
DESCRIPTION
Q
o
j
• C
> O
a
-
-
REMARKS
a)E
o'
m
I
o
0
o U
'
A1:Pale gray slightly silty
SM/SP
.
'
very fine to fine
� . -
27
grained sand
-
932
2.4'
85
_
101.2
6.8
93
}
10
d.
90.8
4.2
83
A3; Yellow brown slightly
SM�
'
_
clayey silty very fine
15
to fine grained sand
_
2-0
. - ..
92.6
21.7
05
Scattered thin silt layers
Relatively undisturbed
Total Depth = 16'
I...�
ring sample
No Free Water
_
,
.
No Bedrock
20
25
_
30
f
i
3 5
t w
40
45
? l
Note: The stratification
lines represent the
approximate boundaries
between the soil types; the
50
transitions may be gradual.
' � v
Tract 28034
i
Date: 11/4/94 ' Location: Per Plan BORING NO. 3 File No: SS-5234•P1
o
e-
a
a
y_
m o
s=
E
ID
3'
DESCRBPTION
FT
? 41
IC
�4 U
REMARKS'
O C
fA
p
a:C
'
0
A2: Yellow brown silty,
SM
'
-
very clayey very, fine
,
25
Ito fine grained sand
r
_
98.4i
1.5
--
r ,
89.9
2.1
A3: Yellow brown slightly
SMV
-
clayey silty very fine
Y
10
16
to fine grained sand ,
92,'3
7.6
81
-
.i
+ ! V .P '
�}t•.
.
yr. .
{+' ' • r,rF _ .. •
' `
<
-
38
�� <�
98.6
5.8
87
Relatively undisturbed
_ �' •
Total Depth = 16' ,
ring -sample-,
,
No Free Water. "
2.0
r
; :
No Bedrock
25
30
,
35
40
+Y '
�'
f `•
45
-
-
Note: ' The stratification
lines represent the
approximate boundaries
-
between the soil types; the
5-0
transitions may be gradual.
January 11, 1995
B-1
SS-5234-Pi
i
94-12-718
TEST RESULTS
I {
BORING/DEPTH
1 @ 0-5'
1 @ 21-25'
2 @ 10-15'
USCS
SM/SP
SM"
SM
. i
SOIL DESIGNATION
Al
A2
A
MAXIMUM
j I
DENSITY (pcf)
109.3
--
113.5
OPTIMUM MOISTURE (%)
13.0
- - -
13.1
ANGLE OF INT. FRI
310
280
f.�
COHESION (Psfl
1.00
- - -
.130
1:..,
.171
EXPANSION INDEX
0
GRAIN SIZE DISTRIBUTION (%)
GRAVEL
0:0
OA
0.0
SAND
79.7
45.8
'58.7
1
SILT
12.71
22.2 .
26.9
CLAY
7.6
32.0
14.4
SOIL DESCRIPTIONS:
Al: 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)
j
A3: Yellow brown slightly clayey
silty, very fine to fine grained sand (SM)
U
EARTH SYSTEMS CONSULTANTS
- _
January 11. 1995
B-2
SS-5234-PI
L
94-12-718
IN -PLACE DENSITIES
1
BORING &DEPTH
DRY DENSITY
% MOiSTUR_F
RELATIVE
COMPACTION
1 @ 2.0
100.2
1.4
92%
5.0
99.9 .
2.6
91
r...?
10.0
87.17
6.4
80%
15.0
113.0
11.0
100%
i
20.0
93.7
5.2
83 °l0
..i
25.0
102.3
13.1
90%
30.0
107.6
17.4
95%
.. ;
35.0
110.7
15.7,
---
•
2o .
@ z.
93.2
2.4:
85 %
5.0
1013
6.8
93%
f
10.0
90.8
4.2 :
8 3 %
L..)
15.0
92.6 .
21.7
85 %
..I
3 @ 2.0
98.411.5
,...!
5.0
89.9
2.1
- --
10.0
92.3
-7.6,
81%
�.. I
I_
15:0
98.,6 ...
5.8
8 7 %
'EARTH i
SYS EMS CONSULTANTS-
U
169
I f]
•
r
�
•
co
0
�_.
a
108
p
IL
a
C0
107
i
r
'
r
s
.t
..
4.0
,.
•. 3n5•
r _
NF—
r.T
t
p '
3.0
(L
2.5
f p
W
w.
t.
2.0
Cn
mot.
J Z
Q r •
1.5
' M
1.0,
.0.5
SS-5234—Pl
0.5 11.0 1.,5 —2.0 2.5 30 3.5
NORMAL LOAD (KIPS / FOOT')
DIRECT SMEAR DATA
. ti i f �' Y' � 1..•k _ n
Soil type: Al
•� . • , i
. ,-Boring and depth: 1 0 _ 5,
-Angle of internal friction:'31 °
Cohesion:
® Samples remoldedtog0 % of -maximu !density.-,t m -
❑ Samples relatively undisturbed F
�.
�
,i
..
f---•-: 1
L—J---
MINIMUM Fly-jNDAT10N Rl'•OLITRT= -- _-..._...:. ._._...
Mf
(1) 00) -
'
Foundations for Slab and Raised Floor Systems (4) (8)
Concrete Slabs
All perimeter
footings
interior footings
Reinforcement
3 112 " Minimum
'
Weighted
Premoistening
'
for slab and
forcontinuous
Thickness
control for soils
Piers under-
Expansinn
u
A
'J
.d
1
' (5)
raised floors (S)
footings
under footings,
"raised floors
Index
g
u
3
(2) (6) ' -
Reinforcement
Tom]
piers and slabs
Depth below nntural surrucC.
O
to
d
(3)
thickness.
(4)
z
N
.
g
,b
g
• 2r arOUnd and f inish grade
of sand
INCHES'
w
�.
0-20
1
6
12
6
12
12 -
I-11,1 top
r Gx6- t
Moistening or
Picrs;allowcd
Very Low
2
8
15
` 7,
`18"
.�. , I $ •'
- `and bottom
1011U
ground prior to
for single
(Non-l:x-
3
10
111
8
24 -
s 24
WWr-
2"
placing concrete
Moor loads
i
r
r.
'. : ' .
.`
recommended
only
1
6
12
6
15 r .
12
.1=114 top'
6x6-
120% oroptimur►
Piers allowed
7
IR'
tinct bottom
-10/10 _
moisture c_ontcnt
forsinl,lc
21.50
;3
10
18
8
211,
2/1
WWF
4" 'r
to :t depth or
floor toasts
t-rlw
-
'
-
i
below lowest
only
�
adjaccl►l grtcic:.
•
-
'estin � Re aired.
1,
6
12
6
21
12 y
1-114110
6x6- .
130%n of OP6111u(1►
2
8
12
8
21 ^
111
and bottom
6/6 INW1:
mtisture cc►ntcnt
51-90
3
10
15
8
24
24, .
� Qr113
10 it (leplh Or27"
l•
I ICfS 1101
Mccliunl
n 24-- .w.
4"
below lowest
allowed
_
1
adjacent grade.
1! tars ( .i ext. luoling
•
'
ac� d 1►ent 3' into slah (7)
Testing Required
1
6
12
6
27
12
r►
•1-115 top
6x6-
_
140% of optimui
2
1t
12
'R
27
18
and bottom
6/6 W W F
moisture content
- 91=130
3
10
15
It
27,
• 24
or 113
to a cicptli of 33"
Piers not
I liglr
_
24" e.w. 1
4" `
below lowest
allowed
adjacent grade.
z
113 bars (to 24" in ext. Coming
and bent 3' into slap (7)
'Testing Required
rUnirr 1311
Vrrr 1 li::ll
Special Design by Lirrnscil 1:n1;inecr/Archilect
'Rr1'rt In urxt Ical;C Iclr li3ulul1tr'.t I t il�rnucl� i 1t11
,yK
l.. i
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 premoistening may be approved by
1 J
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.
�..t
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
ii
(3) inches below the top of the stem.
4.
Reinforcement - shall be placed at mid -depth of, slab.
�.i
S.
After premoistening, the- specified moisture content of soils shall be
LA
maintained until concrete is placed. Required moisture content shall be
verified by an approved testing laboratory not more than twenty-four
I,
(24) hours prior to placement of concrete..
6.
Crawl 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.
7.
designed and constructed as 'specified for perimeter footings in Table 2.
!...I
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
I
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 footing
of the and consisting of not less than
number four (#4) bars at twelve (12) inches on center each way. Vertical
nchimney
reinforcing bars shall be hooked under the. grid..
f...l
EARTH SYSTEMS CONSULTANTS .