11211 (CSCS) Geotechnical InvestigationSOIL • FOUNDATION • GEOTECHNICAL ENGINEERING • SOIL TESTING • SITE INVESTIGATION
June 23, 1992 Project No: 92-R214-131
To: MAC & PATTI MacCORMICR
1845 Anaheim Street, #9-B
Costa Mesa, California 92627
Attention: Mr. Mac MacCormick
Subject: GEOTBCHNICAL INVESTIGATION
Proposed "TARE -OUT PIZZA" Building
Lot #9, Blk. #10
78-090 Calle Estado (A.P.N. 771-101-009)
La Quinta, California 92253
INTRODUCTION
This report presents the results of .our geotechnical investigation performed at
the site referenced above. The location of the site is shown on the Site
Location Map, Figure 1.
The purpose of this investigation was to provide information on the soil
' conditions which could impact the development of the site, and develop
recommendations regarding site grading, foundation and retaining wall design,
slab and pavement design, drainage and maintenance considerations, and related
' concerns. The scope of our work included' site reconnaissance; the excavation,
logging, and sampling of two exploratory trenches up to about 15 feet in
depth; laboratory testing of geotechnical properties of representative soil
samples; geotechnical analysis of field and laboratory test data; and the
' preparation of this report presenting our findings, conclusions, and
recommendations.
' For'this investigation of the site, we were provided with a Plot Plan prepared
by AM Custom Builders, La Quinta, California, which was used as the base for
Figure 2, "Location of Exploratory Trenches".
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65-861 PIERSON BLVD. SUITE C & D, DESERT HOT SPRINGS, CA 92240 (619) 329-3588 FAX -(619) 329-3041
MacCORMICR-CALLE ESTADO 92-R214-131
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SITE CONDITIONS AND PROPOSED DEVELOPMENT
Site Conditions
The project site is located in the commercial area in the La Quinta Cove area in
La Quinta, California. The site is on the floor of the Coachella Valley near
the base of the Santa Rosa Mountains. The site is bordered on the south by
Calle Estado, on the north by an existing alley, on the west by a commercial
building, and on the east by a vacant lot.
At the time of our field investigation, the site was undeveloped, relatively
flat, and appeared to have been cleared at some time in the past. Low weedy
vegetation was present on the lot as well as some scattered surficial trash and
debris. The soils exposed at the ground surface appeared to consist primarily of
sandy silts and silty sands. Aerial photographs of the site area dated 1953 and
1975 also show the site undeveloped at those times.
Proposed Development
As shown on the plot plan, the proposed development will consist of an
approximately 1,500 square foot commercial building along with paved parking and
drive areas, landscape planters, etc.
No detailed grading plans or specific structural load information was available
at this time, however we expect that the building to be constructed at the site
would be a one-story wood frame or masonry structure with slab -on -grade floors.
The recommendations in this report are based on the assumption that the
foundation loads are relatively light, as would be typical for this type of
construction. The plot plan prepared by AM Custom Builders does not show the
final grades planned for the project, however, the desired finish grades would
be expected to'be achieved with relatively minor cuts and fills perhaps on the
order of about one or two feet.
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PAGE 2 RUBICON GEOTECHNICAL
' MacCORMICR-CALLE ESTADO 92-R214-131
FIELD AND LABORATORY INVESTIGATIONS
1 Subsurface Investigation
The subsurface soils.at the site were examined by means of two exploratory
backhoe trenches excavated to depths of 14 and 15 feet. During excavation, the
trenches were continuously' logged by our field engineer, who also collected
' representative samples of the soils encountered for further classification and
testing. Field testing was conducted within and adjacent to the trenches to
determine the in-place density and moisture content of the soils. Sampling and
testing procedures are described in Appendix A. Approximate locations of the
trenches are shown on Figure 2. Descriptive logs of the trenches are presented
in Appendix B. After being excavated, sampled, and logged, the trenches were.
infilled with soils from the spoil piles to reduce the hazard of open trenches.
Laboratory Testing
Samples of soils encountered in our exploratory trenches were returned to our
laboratory for further testing. Moisture contents and soil densities are
presented in the trench logs of Appendix B. Maximum density, sand equivalents,
and gradation tests were performed on the samples and the results of this
testing are presented in Appendix C.
PAGE 3 RUBICON GEOTECHNICAL
' MacCORMICR-CALLE ESTADO 92-R214-131
SUMMARY OF GEOTECHNICAL CONDITIONS
Earth Materials
tThe earth materials encountered in the exploratory trenches at the site
consisted of windblown and lake deposits composed of interbedded silty and sandy
materials in varying proportions. These deposits were horizontally stratified,
' dry near the ground surface, and becoming moist at depth. The consistency of
the soils ranged from medium dense at the ground surface to very stiff at depth.
The USDA Soil Conservation Service (SCS) soil survey for the Coachella Valley
area indicates that a variety of soils types are present in the area, including
soils classified as "Myoma fine sand", and "Indio fine sandy loam". The SCS
' indicates that these soils have a low potential for expansion and for corrosion
to concrete, but may be subject to some erosion and/or caving.
Laboratory tests performed on samples of the subsurface soils provided
' quantitative information on soil characteristics. The grain size distribution
tests indicated that the soils had grain sizes which would classify most of the
soils as clean to sandy silts with a wide range of grain sizes. Classification
' tests performed on two samples from the site indicated from 65 to 84 percent of
the soil fraction passing the #200 sieve (0.075mm size). Tests performed on two
samples yielded a sand equivalent of 1 on each test.
' Ground Water
' Ground water in the area of the site is considered to be contained within the
Thermal Subarea in the Indio Subbasin of the Coachella Valley Ground Water Basin
(California Department of Water Resources, 1964).
The Indio Subbasin encompasses about 400 square miles; this comprises the
majority of the floor of the Coachella Valley. The Indio Subbasin is bordered
on the southwest by the San Jacinto Mountains and Santa Rosa Mountains, and is
' separated from the Mission Creek and Desert Hot Springs Subbasins to the north
by the Banning and San Andreas Faults and the Indio Hills.
t Ground water moves from the northwest part of the subbasin southeastward into
interbedded sands, silts, and clays which underlie the central and southern
parts of the Indio Plain. The ground water within most of the Thermal Subarea
' is confined or semi -confined within the horizontally bedded deposits present in
this area. Water flows to the south out of the Coachella Valley Ground Water
Basin into the Salton Sea. Throughout much of the Coachella Valley, water
levels have been declining since about 1949, however in the Thermal Subarea,
' water levels have risen as a result of imported Colorado River water applied for
irrigation.
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PAGE 4 RUBICON GEOTECHNICAL
' MacCORMICR-CALLE ESTADO 92-R214-131
rGround Water (Con't)'
Information obtained from Mr. Alan Harrell of the Coachella Valley Water
District (C.V.W.D.) indicates that the regional ground water level is at a depth
of 100 feet or more below the ground surface in the area of the site. (Note that
sometimes perched water may be present at shallower depths than the C.V.W.D. well
' data indicates.)
Ground water levels in the area may be expected to vary through time in response
' to seasonal and/or long-term hydrologic influences. Grading of the site would
not be expected to be impacted by ground water, however, deep excavations may
encounter soils becoming increasingly moist with depth.
Geologic Setting
The Coachella Valley (where the site is located) is a portion of the Salton
Trough; a landlocked basin forming the northern extension of the Gulf of
California. The Salton Trough is a structural basin bounded on the northeast by
the San Andreas Fault Zone and on the west and southwest by the San Jacinto and
Elsinore Faults. The basin extends from the area of the San Gorgonio Pass to
the Gulf of California, and it is separated from the gulf by the Colorado River
delta. The basin is underlain by several thousand feet of sediments. These
' sediments were deposited in ancient freshwater lakes which periodically occupied
this part of the Salton Trough. The largest of these, referred to as Lake
Cahuilla, filled to a high point slightly above sea level. The last of these
lakes are believed to have last been present about 500 years ago. Fossils of
' mollusks (mostly small gastropods) which lived in the ancient lakes are abundant
in the southern Coachella Valley area.
' The southern part of the Coachella Valley is bounded by the Santa Rosa Mountains
on the west and the Little San Bernardino Mountains and the Mecca Hills to the
north and east. The site is located in a portion of the valley referred to as
' the Indio Plain (CDWR, 1964). The Indio Plain covers the majority of the
Coachella Valley, extending from the San Gorgonio Pass to the Salton Sea. In
the area south of Indio, the plain forms a fiat valley floor.
The area of the site is underlain by interlayered lake deposits composed of a
random sequence of lenses or beds consisting mostly of silty and sandy materials
(the near -surface soils encountered in the trenches are described in the "Earth
Materials" section of this report).
PAGE 5 RUBICON GEOTECHNICAL
' MacCORMICR-CALLE ESTADO 92-R214-131
1 Seismicity
There are no faults known to traverse the site, and the site is not located
within a State of California "Alquist-Priolo" Special Studies Zone for fault
rupture hazards. However, the site is located within a region which is
seismically very active. A number of active faults are present in the area, and
numerous earthquakes have been recorded originating in and/or near this part of
the Salton Trough. The active or potentially active fault nearest to the site is
the San Andreas Fault, which approaches within about 7 miles on the northeast.
' In the Coachella Valley area, the San Andreas is considered to comprise a fault
zone rather than an isolated, distinct fault. In the northern portions of the
Coachella Valley, the San Andreas Fault Zone is considered to be divided into
' northern and southern branches, known respectively as the Mission Creek Fault
and the Banning Fault. These faults trend northwest/southeast and merge
together near the central part of the Indio Hills. The prominent fault that
extends to the southeast from that area is identified as the San Andreas Fault.
In the southern regions of California, the San Andreas Fault Zone is believed to
be capable of generating an earthquake of up to magnitude 8.3 (the maximum
probable event) somewhere along its trace during the next 100 years. This does
not necessarily imply that an event of this magnitude would occur at a location
on the fault nearest to the site. Considering the fault -site distances and the
high magnitude events it is capable of, ground motions originating on the San
Andreas Fault would overshadow those from other faults in the area, and would be
more likely to have a more significant impact on the site if the M8.3 event did
happen to occur near the site.
The site is located within Seismic Zone 4, as designated by the Uniform Building
Code, and Groundshaking Zone III as designated by the Seismic Safety Element of
the Riverside County Comprehensive General Plan (1987). Therefore, buildings at
the site could be subject to strong ground motions generated by earthquake
activity at some time during their design life.
The potential for liquefaction generally occurs during strong ground shaking
within loose, cohesionless sediments where the ground water is usually less than
about 30 feet. Because of the depth to ground water expected at the site,
liquefaction is considered unlikely at the site.
PAGE 6 RUBICON GEOTECHNICAL
MacCORMICR-CALLE ESTADO
rnMPT.ncT nNC
General Suitability of Site
92-R214-131
Based on the results of our field exploration, laboratory testing, and our
experience and judgement, it is our professional opinion that the site is
suitable for the proposed development from a geotechnical standpoint, providing
that the recommendations of this report are implemented in design and
construction.
In their natural state, the soils at the site may have a potential for
moisture -induced settlements to occur. Some earthwork should therefore be
performed in the areas to support structures and pavements to process and
compact the soils as controlled engineered fill in order to provide uniform,
adequate bearing capacity and reduce the potential for post -construction
settlements to occur. The site should be prepared in the normal manner by
clearing and removing trash, debris, and any undocumented fill or buried
structures, then thoroughly prewatering. Construction of the zone of fill soil
can then be achieved by overexcavating and recompacting the on-site soils as
described in the recommendations section of the report.
No free ground water was encountered in the exploratory trenches, and the
regional ground water level is believed to be on the order of 180 feet or more
below the ground surface. Therefore, ground water is not expected to present a
problem during construction, and dewatering of excavations or related measures
will not be required.
Based on their classifications and non -plastic nature, the on-site soils are
expected to be low in expansion potential. Infiltration of water to the
subsurface soils after construction can be expected to cause consolidation and
result in settlement of the structure. Therefore, precautions should be taken
to reduce the infiltration of surface water into the foundations near the
proposed commercial building.
Earthwork at the site would be expected to be accomplished with conventional
earthmoving equipment. Excavations may be subject to caving. Deep excavations
should be sloped or adequately shored to provide stable conditions in the
excavations.
The existing soils will undergo a reduction in volume when watered and compacted
as engineered fill. Calculation of shrinkage factors based on field density
test results, laboratory maximum dry densities and an estimated average relative
compaction of about 93 percent results in from about 10 to 18 percent shrinkage.
Our experience has been that for the silty, sandy soils in this area, a
shrinkage factor on the order of about 25 percent might be a more reasonable
estimate. In addition, a subsidence of 0.30 feet is also considered typical
for silty desert soils such as these due to preparation of areas to receive
fill, prewatering, and equipment operations. Additional volume losses may also
result from the clearing and removals of vegetation, buried structures, etc.
Because shrinkage and subsidence are difficult to predict with a high degree of
accuracy, we suggest that if possible, a balance area be allowed for in the
grading pians, or alternately, that schedules for importing or exporting soils
to or from the site be kept sufficiently flexible so as.to provide the
appropriate volumes for earthwork construction.
PAGE 7 RUBICON GEOTECHNICAL
MacCORMICR-CALLE ESTADO 92-R214-131
Geologic/Seismic Considerations
No faults are known to traverse the site. Although the site will most likely be
subject to ground accelerations generated by local earthquakes at some time
during the life of the project, the probability of ground rupture is remote and
the site is not expected to be vulnerable to secondary seismic hazards, with the
possible exception of seismically induced settlements. Other considerations for
construction at the site include the use of flexible utility connections to allow
for differential movements between soils and structures, and the use of structural
floor slabs, which would be more resistant to seismically indused settlements
Seismic induced settlements are generally an area -wide occurence and are
considered less likely to cause differential settlements of structures.
The site is located within Seismic Zone 4 as designated by the Uniform Building
Code (UBC). According to UBC Standard 23-1 (1985), Seismic Zone 4 can be
related to an "effective" peak acceleration of 0.4g, or a peak acceleration of
0.60g. Due to the proximity of the San Andreas Fault, the current UBC standards
may underestimate the high acceleration levels that could be experienced at the
site during the design life of the project. If further information on seismic
design criteria is desired, a site-specific probabilistic seismic analysis
should be performed.
PAGE 8 RUBICON GEOTECHNICAL
MacCORMICR-CALLE ESTADO 92-R214-131
RECOtRMMATIONS FOR DESIGN AND CONSTRUCTION
Site Grading and Earthwork
All grading should be performed in accordance with the Recommended General
Earthwork and Grading Specifications (Appendix D), except as modified in the
text of this report.
All trash, vegetation, and debris should be fully removed and properly disposed
of prior to the commencement of earthwork construction. This should include the
removal of vegetation, root balls and additional picking of roots and oversize
rocks, continuing as needed throughout the excavation and grading operations.
Clearing and grubbing should be verified by the geotechnical consultant. Any
soils which may contain more than one percent (by weight) of organic matter or
other decomposable material could be used in non-structural areas, but should
not be used in fill to be placed beneath or adjacent to building or paved areas.
The site should be thoroughly prewatered prior to the commencement of earthwork
construction.
Any other existing facilities (surface or subsurface) which may be discovered
during clearing, grading, etc., should be similarly traced out and fully removed
under the direction of the geotechnical consultant. The excavations created
should be backfilled with properly compacted fill to achieve the desired grades.
Should any zones of clay or heavy silt be encountered, these soils should be
exported from the site, or alternatively, could be thoroughly blended with the
more granular soils on the site under the observation of the geotechnical
consultant. Otherwise, they might be placed selectively in non-structural areas
as advised during grading by the geotechnical consultant.
• Preparation of Building Areas: After clearing and prewatering, the ground
should be excavated, scarified, and compacted so that a minimum of 90
percent relative compaction (based on ASTM D1557) is achieved to a depth
of at least 36 inches below the existing or final grade, whichever is
lower. This might be achieved by overexcavating the site soils to a depth
of 24 to 30 inches, then scarifying and recompacting an additional 6 to 12
inches below the excavation bottom. The zone of compacted soil should
extend a minimum of 5 feet beyond the building/footing lines.
• Preparation of Pavement Areas: After clearing and prewatering, the
ground should be excavated to a depth of at least 12 inches below the
existing or final grade, whichever is lower. The excavation bottoms
should be scarified, watered and recompacted to achieve a minimum of 90%
relative compaction (based on ASTM D1557) to a depth of 6 to 12 inches
below. The upper 12 inches of subgrade soils should be compacted to at
least 95% relative compaction.
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MacCORMICR-CALLE ESTADO
Site Grading and Earthwork (Con't)
92-R214-131
Excavation in addition to that described above will be required in any areas to
support structures or pavements where undocumented fill, loose or disturbed
soils, zones of heavy silts or clays, buried structures or debris, etc., are
encountered.
The trenches excavated for our subsurface exploration were up to 15 feet deep,
approximately 13 feet long and 4 feet wide. After logging and sampling, they
were loosely backfilled. During site grading and earthwork, the trenches should
be re -excavated to a depth of at least 36 inches below grade as described above,
scarified, flooded and soaked with water, and backfilled with properly
controlled compacted fill.
Compacted Fill
The on-site soils, cleared of any organic material and debris, are suitable for
use in compacted fills. If imported soils are to be used as fill, they should
be tested and approved by the geotechnical consultant prior to being transported
to the site. Further requirements for import soils can be given if desired
should such become necessary. Should zones of extremely silty soils be
encountered during site grading, they should be placed in non-structural areas
or may be thoroughly blended with sandier soils at the direction of the
geotechnical consultant to facilitate moisture -conditioning and compaction.
Should any clayey soils be encountered during the site grading, they should be
disposed of off-site or, alternatively could be blended with other site soils
and placed outside of building or pavement areas under the direction of the
geotechnical consultant. Fill should be placed in thin lifts, moisture -
conditioned, and compacted to at least 90 percent relative compaction based
on ASTM D1557. Fill should generally be placed and compacted in uniform, near
horizontal lifts not exceeding 8 inches thick prior to compaction. Field
density testing of the soils should be performed as the lifts are placed and
compacted.
Placement and compaction of fill should be performed in accordance with local
grading ordinances, Chapter 70 of the most recent Uniform Building Code, and
this report under the direction of the geotechnical consultant. Additionally,
we recommend that the contract between the owner and the earthwork contractor be
worded such that it is the responsibility of the contractor to place the fill
soils to the required minimums of 90 or 95 percent relative compaction as
described in this report, since the observation and testing performed by the
geotechnical consultant does not relieve the contractor of the primary
responsibility to perform all work in accordance with the project specifications
and regulations of the governing agencies.
PAGE 10 RUBICON GEOTECHNICAL
' MacCORMICR-CALLE ESTADO 92-R214-131
Foundation/Footing Design
' After site preparation as recommended, the use of continuous or isolated spread
footings is feasible for the support of the structure. Footings should be
founded 12 inches below the lowest adjacent final grade and should be a minimum
of 12 inches wide. All footings must be founded on dense, properly compacted
r soils. If any footings are to be founded at a depth greater than 18 inches or
exceed 2 feet in width, a greater depth of compacted soils may be required below
' the footings. The geotechnical engineer should be given the opportunity to
determine this based on a review of the final grading and foundation plans. The
depth of the footings should be measured from the lowest adjacent firm grade. A
maximum allowable bearing value of 1800 pounds per square foot(psf) may be used
for footings designed and constructed as described. This value may be increased
by one-third for transient loads such as those imposed by wind or seismic
forces. The footings should be reinforced with at least one No. 4 rebar at the
' top and bottom, properly lapped and tied at corners, intersections, etc.
Additional reinforcement may be recommended by the structural engineer based on
structural requirements, and/or for increased resistance to seismic forces.
Resistance to lateral loads can be developed by frictional resistance on the
footing bottoms and passive earth pressure on the sides of the footings, and
embedded portions of other structures. The frictional resistance can be
' computed using a frictional coefficient of 0.30. An allowable lateral bearing
value of 200 pounds per square foot per foot of depth may be used in calculating
the resistance of properly compacted fill to lateral forces. The top one foot
' of embedment should not be considered when computing passive pressure unless the
area adjacent to the foundations is confined by a slab or pavement. A combination
of frictional resistance and lateral bearing may be used, providing the latter
' value is reduced by one-third.
The bearing values indicated above are for the total dead load and frequently
applied live loads. If normal code requirements are applied for design, the
' above vertical bearing values may be increased by a factor of two for short
duration loadings, such as those due to the effect of wind or earthquake forces.
' It is important to minimize the infiltration of water into the foundation soils
after construction to reduce the potential for adverse amounts of settlement.
Heavy watering of planter areas, ponding next to structures or leaking
utilities, etc. may create a potential for adverse amounts of post -construction
' settlements, seepage through the floor slabs, etc. Positive drainage should
therefore be provided and maintained as described in the Site Maintenance
section of this report.
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PAGE 11 RUBICON GEOTECHNICAL
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MacCORMICR-CALLE ESTADO 92-R214-131
Temporary Construction Excavations
Temporary construction excavations should be designed in accordance with the
requirements of Cal/OSHA. Caving should be expected to occur in excavations at
' the site, especially those penetrating dry granular soils. Excavations made in
dry sandy soils at the site should be expected to cave and ravel continuously,
regardless of their depth. Laying back or shoring of any such deep excavations
' will be an important consideration. Sandy soils exposed in temporary
construction excavations should be kept moist but not saturated to retard
ravelling and sloughing. Temporary excavations.in moistened soils may stand for
' short intervals if designed in accordance with the Cal/OSHA requirements and
care is taken during the construction process. Cal/OSHA requires that the
contractor provide and maintain safe working conditions during construction.
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' PAGE 12 RUBICON GEOTECHNICAL
MacCORMICR-CALLE ESTADO
Concrete
92-R214-131
Slab subgrade and footing excavations should be properly moistened prior to the
placement of concrete. In general, Type II cement is expected to be suitable
for use in contact with the types of soils at the site. At the completion of
grading, test could be performed on the soils exposed in the subgrades and
footing excavations to evaluate the possible need for Type V (sulfate resistant)
cement in concrete for use at the site. Concrete with a low water:cement ratio
and low slump (preferably 4 inches or less) will have'a low potential for
shrinkage cracking when properly placed, vibrated, and cured.
Slabs -on -Grade
Concrete floor slabs should be at least 4 inches thick and should be reinforced
in accordance with code requirements and structural considerations. We recommend
that as a minimum, slabs -on -grade be reinforced by either wire mesh (6x6-10/10 WWF)
or No. 3 rebars spaced 18 inches on center in perpendicular directions, installed
at midheight in the slabs. If portions of the floor slabs are to have coverings
placed on them which would be susceptible to moisture damage (vinyl tiles,
carpeting, etc.), the floor slabs should be carefully moisture -proofed. This
may include installation of a vapor barrier below the slabs consisting of a 6 -mil
polyethylene sheet. openings in the barrier should be sealed and the vapor
barrier should be carefully installed to avoid puncturing it and reducing its
effectiveness. A 2 inch thick layer of clean sand should be placed above and
below the vapor barrier to protect it and to aid in the curing of the concrete.
Tentative Pavement Section Design
Asphaltic concrete should conform to Section 203 of the most recent edition of
' the "Standard Specifications for Public Works Construction" (SSPWC). Base
course material should be Crushed Aggregate Base, Crushed Miscellaneous Base, or
Processed Miscellaneous Base conforming to Sections 200-2.2 and 200-2.4 or
t 200-2.5 of the SSPWC. The base course and A.C. should be placed in accordance
with Sections 301-2 and 302-5 of the SSPWC. Pavement subgrade areas should be
prepared as described in the "Site Preparation" section of this report. In all
areas to support pavements, the upper 12 inches of subgrade materials below the
' pavement section should be compacted to at least 95 percent relative compaction
based on ASTM Test Method D1557.
' Maintenance of proper drainage in paved areas and minimizing the flow of water
over pavement areas will prolong pavement life. Concrete aprons or thickened
pavement sections should be considered in areas which may be subjected to heavy
wheel loads, such as loading zones, the areas in front of trash enclosures, etc.
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PAGE 13 RUBICON GEOTECHNICAL
MacCORMICR-CALLE ESTADO 92-R214-131
Tentative Pavement Section Design (con't)
Based on their classification and properties, we would expect the near -surface
soils at the site to have an R -value on the order of about'25 or more.
Considering this, a tentative pavement section consisting of 2k inches of AC
over a 6 inch thick base course would be suitable for a Traffic Index of 4.0
(light service conditions, passenger car parking, etc.). A Traffic Index of 5.5
(reflecting moderate truck traffic, etc.) would result in a pavement section of
3 inches of AC over an 8 inch thick base course. Other pavement sections could
also be considered based on the expected loading conditions, etc.
If desired, other loading conditions or alternative pavement sections including
full -depth A.C. pavements, could also be evaluated for use at the site.
This pavement evaluation was based on assumed Traffic Index values and the
physical properties of the near -surface soils encountered on the project site.
These recommendations should reviewed if site conditions during construction
appear to be different from the soils observed during this investigation. If
import soils are used or finer grained materials are exposed in the pavement
subgrades, or if the traffic loading conditions vary from those assumed as
described above, the pavement sections should be revised based on review of the
conditions encountered and further testing.
Site Maintenance and Drainage
Heavy landscape watering, ponding next to structures, leaking utilities, etc.
could create a potential for post -construction settlements to occur in the silty
and sandy soils at the site. It is important therefore to provide and maintain
positive drainage to direct surface waters away from foundations, slabs, and
pavements. Planting areas at grade should be provided with adequate positive
drainage directed away from building. Drainage devices should be properly
maintained at all times so that water is not allowed to pond in areas adjacent
to structures. Maintenance of proper drainage in paved areas will prolong
pavement life. Asphalt responds poorly to prolonged exposures to water, and if
surface waters pond up or are concentrated and directed over asphalt surfaces,
the asphalt will deteriorate, weaken and break up under wheel loads much more
quickly than it would otherwise. In addition, in wet areas, the subgrade soils
may become saturated and softened, which may then cause further break up of the
pavements due to a loss of subgrade support to the pavement section.
Landscape watering should be kept to the minimum required to maintain plant
vigor, and consideration should be given to the use of native or drought
tolerant vegetation. Eave gutters and downspouts should be installed on the
buildings in a manner suitable to direct roof runoff away from foundations.
PAGE 14 RUBICON GEOTECHNICAL
MacCORMICR-CALLE ESTADO
Site Maintenance and Drainage (con't)
92-R214-131
Some routine site maintenance should be expected to be required at intervals
during the life of the structures at the site. This may include maintaining
grades to drain away from the structures, restoring soil removed from foundation
areas by animal activity, wind or water erosion, etc. The facility manager and
maintenance crews should be informed of these considerations and the possible
consequences of heavy landscape watering, altering the grades to create a
ponding effect, etc.
Observation and Testing During Construction
The recommendations provided in this report are based on preliminary design
information and subsurface conditions observed in the exploratory trenches at
the site. Geotechnical observations and testing during construction are the
continuation of this geotechnical investigation and not separate unique
functions. Field review during site grading allows for evaluation of the
exposed soil conditions and confirmation or revision of the assumptions and
extrapolations made in formulating the design parameters and recommendations
presented in this report. Because of our experience and familiarity with the
project, maintaining Rubicon Geotechnical as the geotechnical consultant during
planning, design, and construction phases of the project will provide continuity
of services. Any other subsequent geotechnical consultant of record must assume
responsibility for all phases (design and construction) of the project which is
within the purview of the geotechnical engineer, and should so notify the owner,
project designers, the appropriate regulatory agencies, and this office.
Notification should indicate they have reviewed this report and any subsequent
addenda and either agree with the conclusions and recommendations or will
provide new recommendations. Final project plans should be reviewed by the
geotechnical engineer prior to excavation or construction to check that the
recommendations provided in this report have been incorporated into the project
plans.
Construction should be observed by the geotechnical engineer at the following
stages:i
• During site clearing, removal of surface or buried structures, and
excavation of building and pavement areas.
s
• During all stages of grading and earthwork operations, including
scarification, recompaction, backfilling of utility trenches, etc.
• Prior to paving or placement of construction materials (steel, concrete,
etc.) into footing excavations or over other areas where fill soils or
backfills are present.
• Any time that unusual soil conditions are encountered during grading.
No site clearing or excavation should be begun without the presence of the
geotechnical consultant's representatives. A final report should be prepared
upon completion of the construction summarizing the compliance with the
recommendations of this report and geotechnical observations during grading.
PAGE 15 RIIBICON GEOTECHNICAL
MacCORMICR-CALLE ESTADO
t
92-R214-131
I
CLOSURE
This report has been prepared to aid in the evaluation of the site and to assist
' in the design of the structure and site improvements. It is recommended that this
office be provided the opportunity to review the project drawings and specifications
to check that the recommendations and intent of this report have been implemented.
If the nature of the project changes so as to differ. significantly from that
described in this report, further geotechnical evaluation would be required to
determine if revisions to this report are necessary.
The conclusions and recommendations contained herein are based on the findings
and observations made at the time of our site reconnaissance and subsurface
exploration. If, at a later time, the conditions appear to be different from
' those observed in our field investigation, this office should be notified to
consider the possible need for modifications to the geotechnical recommendations
presented in this report.
' This report has been prepared exclusively for the use of the addressee for the
project described in the text. It is not to be transferred to or used by other
parties without the express consent of Rubicon Geotechnical. Rubicon Geotechnical
t will not be responsible for, or liable for, unauthorized changes or uses of this
report or the recommendations contained herein. All changes to this report must
be in written form and must be approved by this office.
' We appreciate this opportunity to be of service. If you have any questions
regarding this report, or have further requirements, please do not hesitate to
contact this office.
' Respectfully submitted,
' RUBICON GEOTECHNICAL
0,4, 6'.
' Douglas E. Stephenson Brent J. Inghram, R.C.E. 40264
� I
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DES/BJI/amf
BRENT J.
� INGHRAM
CM
No. 40264 M
Exp.94-
s CIVIL
OF A
IPAGE 16 RUBICON GEOTECHNICAL
MacCORMICK-CALLE ESTADO 92-R214-131
FIGURES AND APPENDICES
Figure 1: SITE LOCATION MAP
Figure 2: LOCATION OF EXPLORATORY TRENCHES
Appendix A:: SAMPLING AND TESTING PROCEDURES
Appendix B: LOGS OF EXPLORATORY TRENCHES
Appendix C:• LABORATORY TEST DATA
Appendix D: RECOMMENDED GENERAL EARTHWORK AND GRADING SPECIFICATIONS
Appendix E: REFERENCES
DISTRIBUTION
5 copies Mac & Patti MacCormick
1845 Anaheim Street, #9-B
Costa Mesa, California 92627
PAGE 17 RUBICON GEOTECHNICAL
92-R214-13
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PROPOSED COMMERCIAL BUILDING -
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"PEIMIX A
MacCORMICR-CALLE ESTADO
APPIMIZ A
SAMPLING AND TEST PROCEDURES
Sampling Procedures
92-R214-131
Backhoe Trenches: Trenches were excavated with a Ford 555 rubber -tire
backhoe with "Extendahoe" arm. The exploratory trenches were logged by our
field representatives at the time of their excavation. Representative bulk
samples were bagged and transported to our laboratory for classification
and testing. In-place density and moisture tests were performed at various
depths in the trenches as well as selected locations outside the trenches
on the existing ground surface. In-place densities and moisture contents
of the soils encountered were determined in accordance with the nuclear
densometer method, per ASTM Test Methods D2922 and D3017. Locations in the
field were estimated by means of pacing distances, sighting from known
features and locations, etc., and should therefore be considered accurate
only to the degree implied by the methods used.
Sample Storage: Soil samples presently stored in our laboratory will be
discarded 30 days after the date of this report unless this office receives
a specific written request to retain the samples for a longer period.
Laboratory Testing Procedures
Classification Tests: Typical materials were subjected to mechanical
' grain -size analysis by wet sieving with U.S. Standard brass screens. The
data was used to evaluate the classification of the materials. Graphical
presentations of the grain -size distribution are presented in the test data
and the Unified Soil Classification of the soil types are presented in both
the test data and the trench logs.
Maximum Density Tests: The maximum dry density and optimum moisture
content of typical materials were determined in accordance with ASTM D1557.
This method uses a 10 pound hammer with an 18 inch drop, with 25 blows on
each of 5 lifts in the 1/30 cubic foot mold.
' Sand Equivalents: The sand equivalents of typical samples were determined
in accordance with ASTM D2419. Sand equivalents provide an empirical
' measure of the granularity of a sample.
� I
PAGE A-1 RUBICON GEOTECHNICAL
S %IQNgddii
GEOTECHNICAL LOG — TRENCH NO. T-1
Project Name MacCORMICK Location See Figure 2 Equipment F555 Backhoe
Project Number 92-R214-131 Elevation Top Sidewalk±6"Logged by -,DES
' Date 6-10-92 Reference Top Sidewalk -Calle Estado!
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GEOTECHNICAL DESCRIPTION
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Sandy Silt : Very -6e to Fine grojined, sti;f, becomes moist
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10
15
Bottom of Trench @ 15' Depth
No Free Ground Water Encountered
Trend► 6ackfi l led
GRAPHIC
LOG
North Wall,
Scale 1"=5'
"KEY TO TEST AND
SAMPLE TYPES
B Bulk sample
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SC Sand cone
ND Nuclear densometer
GS Grain size
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I GEOTECHNICAL LOG — TRENCH NO. T_2
Project Name MacCORMICK
Location
See
Figure 2 Equipment -F555 Backhoe
Project Number 92-8214-131
Elevation
Top
Sidewalk-6"Logged by. DES;
Date 6-10-92
Reference
Top
Sidewalk -Calle Estado
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Bottom of Trench @ 14" Depth
II
No Free Ground 1"Iater Encoun•�v�ed
Trenci� BciciC-�i�leci
GRAPHIC
LOG
East Wall Scale 1"=5•
*KEY TO TEST AND
SAMPLE TYPES
a . Bulk sample
a.
.
R . Ring sample
SC . Sand cone
• _.,_' ,
ND : Nuclear densometer
GS . Grain size
•,� -
. l
-- �
SE Sand equivalent
MacCORMICR-CALLE ESTADO 92-R214-131
Sample Location
T-1, Bulk 1 @ 2'
T-2, Bulk 1 C 2'
APPENDIX C
LABORATORY TEST DATA
MAXIMUM DENSITY TEST RESULTS
(performed per ASTM Test Method D1557)
Soil Description
SILTY SAND/SANDY SILT: light
gray, very fine to medium
grained
SANDY SILT: light brown,
very fine to fine grained
Optimum Moisture Maximum Dry
Content Density
14.0% 116.0 pcf
17.5% 106.0 pcf
SAND EQUIVALENT TEST RESULTS
(performed per ASTM Test Method D2419)
Sample Location Soil Description
T-1, Bulk 2 @ 4.5' SANDY SILT: gray -brown,
very fine to fine grained
T-2, Bulk 1 C 2' SANDY SILT:ylight brown,
very fine to fine grained
Sand Equivalent
1.0
1.0
PAGE C-1 RUBICON GEOTECHNICAL
Q %IQN3ddV
APPENDIX D
RECOMMENDED GENERAL EARTHWORK AND GRADING SPECIFICATIONS
1.0 General Intent
These specifications present general procedures and requirements for
grading and earthwork as shown on the approved grading plans,
including preparation of areas to be filled, placement of fill,
installation of subdrains, and excavations. The recommendations
contained in the text of the geotechnical report are a part of the
earthwork and grading specifications and shall supersede the
provisions contained hereinafter in the case of conflict. Evaluations
performed by the geotechnical consultant during the course of grading
may result in new recommendations which could supersede these
recommendations or the recommendations of the geotechnical report.
2.0 Earthwork Observation and Testing
Prior to the commencement of grading, a qualified geotechnical
consultant (soils engineer and/or engineering geologist, and their
representatives) shall be employed for the purpose of observing
earthwork procedures and testing the fills for conformance with the
recommendations of the geotechnical report and these specifications.
It will be necessary that the consultant provide adequate testing and
observation so that he may provide an opinion that the work was or was
not accomplished as specified. It shall be the responsibility of the
contractor to assist the consultant and keep him apprised of work
schedules and changes so that he may schedule his personnel
accordingly.
It shall be the sole responsibility of the contractor to provide
adequate equipment and methods to accomplish the work in accordance
with applicable grading codes or agency ordinances, these
specifications and the approved grading plans. If, in the opinion of
the consultant, unsatisfactory conditions, such as questionable soils,
poor moisture condition, inadequate compaction, adverse weather, etc.,
are resulting in a quality of work less than required in these
specifications, the consultant will be empowered to reject the work
and recommend that construction be stopped until the conditions are
rectified.
Maximum dry density tests used to determine the degree of compaction
will be performed in accordance with the American Society for Testing
and Materials test method ASTM D1557 (Modified Proctor method). All
field density tests shall be expressed in terms of relative compaction
based on ASTM D1557.
3.0 Preparation of Areas to be Filled
3.1 Clearing and Grubbing: All brush, vegetation and debris shall
be removed or piled and otherwise disposed of. Any abandoned
structures encountered must be totally removed. This includes
I I
PAGE D-1 RUBICON GEOTECHNICAL
foundations, septic tanks, leach fields, drywells, storm drains
and other buried structures. Existing wells or utility lines to
be abandoned should be brought to the attention of the
consultant, who will provide recommendations for their
treatment.
3.2 Processing: The existing ground which is determined to be
satisfactory for support of fill shall be scarified to a minimum
depth of six inches. Existing ground which is not satisfactory
shall be overexcavated as specified in the following sections.
Scarification shall continue until the soils are broken down and
free of large clay lumps or clods and until the working surface
is reasonably uniform and free of uneven features which would
inhibit uniform compaction
3.3 Overexcavation: Soft, dry, spongy, highly fractured, or
otherwise unsuitable ground, extending to such a depth that
surface processing cannot adequately improve the conditions,
shall be overexcavated down to firm ground, as approved by the
consultant.
3.4 Moisture Conditioning: Overexcavated and processed soils
extending to such a depth that surface processing cannot
adequately improve the conditions shall be watered, dried -back,
blended, and/or mixed, as required to attain a uniform moisture
content near optimum.
3.5 Recompaction: Overexcavated and processed soils which have been
properly mixed and moisture -conditioned shall be recompacted to
a minimum relative compaction of 90 percent.
3.6 Benching: Where fills are to be placed on ground with slopes
steeper than 5:1 (horizontal to vertical units), the ground
shall be stepped or benched. The lowest bench shall be a
minimum of 15 feet wide, shall be at least two feet deep, shall
expose firm material, and shall be approved by the consultant.
Other benches shall be excavated in firm material for a minimum
width of four feet. Ground sloping flatter than 5:1 shall be
benched or otherwise overexcavated when considered necessary by
the consultant.
3.7 Approval: All areas to receive fill, including processed areas,
removal areas and toe -of -fill benches shall be approved by the
consultant prior to fill placement.
4.0 Fill Material
4.1 General: Material to be placed as fill shall be free of organic
matter and other deleterious substances, and shall be approved
by the consultant. Soils of poor gradation, expansion, or
strength of characteristics shall be placed in areas designated
by the consultant or shall be mixed with other soils to serve as
satisfactory fill material.
IPAGE D-2 RUBICON GEOTECHNICAL
� I
4.2 Oversize: Oversize material defined as rock, or other approved
irreducible material with a maximum dimension greater than 8
inches, shall not be buried or placed in fills, unless the
location, materials, and disposal methods are specifically
approved by the consultant. Oversize disposal operations shall
be such that nesting of oversize material does not occur, and
such that the oversize material is completely surrounded by
compacted or densified fill. Oversize material shall not be
placed within ten feet vertically of finished grade or within
the range of future utilities or underground construction,
unless specifically approved by the consultant.
4.3 Import: If importing of fill material is required for grading,
the import material shall meet the requirements of Section 4.1.
5.0 Fill Placement and Compaction
' 5.1 Fill Lifts: Approved fill material shall be placed in areas
prepared to receive fill in near -horizontal layers not exceeding
' eight inches in compacted thickness. The consultant may approve
thicker lifts if testing indicates the grading procedures are
such that adequate compaction is being achieved with lifts of
igreater thickness. Each layer shall be spread evenly and shall
be thoroughly mixed during spreading to attain uniformity of
material and moisture in each layer.
5.2 Fill Moisture: Fill layers at a moisture content less than
' optimum shall be watered and mixed, and wet fill layers shall be
aerated by scarification or shall be blended with drier
' material. Moisture -conditioning and mixing of fill layers
continue until the fill material is at a uniform moisture
content at or near optimum moisture content.
5.3 Compaction of Fill: After each layer has been evenly spread,
moisture -conditioned, and mixed, it shall be uniformly compacted
to not less than 90 percent of maximum dry density. Compaction
equipment shall be adequately sized and shall be either
specifically designed for soil compaction or of proven
reliability to efficiently achieve the specified degree of
compaction.
5.4 Fill Slopes: Compacting of slopes shall be accomplished, in
addition to normal compaction procedures by backrolling of
slopes with sheepsfoot rollers at frequent increments of two to
three feet in fill elevation gain, or by other methods producing
satisfactory results. At the completion of grading, the
relative compaction of the slope out to the slope face shall be
at least 90 percent.
PAGE D-3 RUBICON GEOTECHNICAL
1
t5.5 Compaction Testing: Field tests to check the fill moisture and
degree of compaction will be performed by the consultant. The
' location and frequency of tests shall be at the consultant's
discretion. In general, the tests will be taken at an interval
not exceeding two feet in vertical rise and/or 1,000 cubic yards
' of embankment. In addition, on slope faces, at least one test
shall be taken for each 5,000 square feet of slope face and/or
each ten feet of vertical height of slope.
' 6.0 Rxcavation
Excavations and cut slopes will be examined during grading. If
' directed by the consultant, further excavation or overexcavation and
refilling of cut areas shall be performed, and/or remedial grading of
cut slopes shall be performed. Where fill -over -cut slopes are to be
graded, unless otherwise approved, the cut portion of the slope shall
' be made and approved by the consultant prior to placement
of materials for construction of the fill portion of the slope.
it
� I
� I
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PAGE D-4 RUBICON GEOTECHNICAL
MacCORMICR-CALLE ESTADO 92-R214-131
APPBADIZ B
REFERENCES
Building News, Inc., 1991, "Standard Specifications for Public Works
Construction", 1991.
California Department of Water Resources, 1964, "Coachella Valley
Investigation", Bulletin 108
California Division of Mines and Geology, 1974, Indio 7.5' Special Studies
Zone Quadrangle, Scale 1:24,000.
Coachella Valley Water District, personal communication with Alan Harrell,
June, 1992.
Carter, M., and Bentley, S.P., 1991, "Correlations of Soil Properties", Pentech
Press, London, 130 pp.
Hart, E.W., 1990, "Fault Rupture Hazard Zones in California", California
Division of Mines and Geology Special Publication No. 42.
International Conference of Building Officials, 1988, "Uniform Building Code",
1988 edition, 926 pp.
Leighton and Associates, Inc., 1986, "Geotechnical Investigation, Proposed Bank
Building, Northeast Corner of Avenida Bermudas and Calle Estado, La Quinta,
California", Project No. 5861289-01, report dated August 13, 1986.
Riverside County Planning Department, 1984, Comprehensive General Plan,
dated March 1984, amended version through December, 1987.
Rogers, T.H., 1965, Geologic Map of California, Santa Ana Sheet: California
Division of Mines and Geology, 1:250,000 scale.
Rubicon Geotechnical, 1991, "Geotechnical Investigation, Three -Lot Commercial
Development, West Side of Jackson Street Between Emerald Avenue and Market
Street, Indio, California", Project No. 91-R205-132, report dated June 1, 1991.
Rubicon Geotechnical, 1992, "Geotechnical Investigation, Proposed Employment
Development Department Building, Southeast Corner of Dr. Carreon Boulevard and
Calhoun Street, Indio, California", Project No. 92-R216-113, report dated
April 30, 1992.
U.S. Department of Agriculture, Soil Conservation Service, 1979, "Soil Survey of
Riverside County, California - Coachella -Valley Area", 89 pp and 17 Orthophoto
quad map sheets (Scale 1:24,000).
U.S. Geologic Survey, 1959b, (Photorevised 1980), 7.5' Quadrangle, La Quinta,
California, Scale 1:24,000.
PAGE E-1 RUBICON GEOTECHNICAL