BRES2015-0085 Geotechnical Engineering ReportEarth Systems Consultants
Southwest 79-811 B Country Club Drive
Bermuda Dunes, CA 93201
(760) 345-158S
(900) 924-7015
FAX (760) 345-7315
September 22, 2000 File No.: 07117-1.0
- " -- 00-09-772
Country Club of. the Desert
P.O. Box 980 _
La Quinta, California 92253
Attention: Ms. Aimee Grana
Project: Country Club of the Desert, Phase I
La Quinta, California
Subject: GEOTECIDNICAL ENGINEERIiNG REPORT
Dear Ms. Grana:
We take pleasure to present this .Geotechnical Engineering Report prepared for the proposed Phase I of
the Country Club of the . Desert to be located between 52nd and 54th Avenues, and Jefferson and
Madison Streets in .the City of La Quina, California-.
This report presents our findings and recommendations for site grading and foundation design,
incorporating the tentative information supplied to our office. This report should stand as a whole, and
no part of the report should be excerpted or used to the exclusion of any other part.
This report completes our scope of services in accordance with our agreement, dated August 22, 2000.
Other services that 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. Unless
requested in writing, the client is responsible to'distribute'this report to the appropriate governing agency
or other members of the design team.
We appreciate the opportunity to provide our professional services. Please contact our office if there are
any questions or comments concerning this report or its recommendations.
Respectfully submitted,
EARTH SYSTEMS CONSULTANTS QFpFESS/p
Southwest N L. STysl2
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Distribution: 6/Country Club of the Desert
I/VTA File
2/BD File
TABLE OF CONTENTS
Page
-Section l
INTRODUCTION' .................... .....................................................................1
1:1
Project Description........'...:.....................:................................................................1.
1.2
Site Description.......:..:................................................_.._._.......................................__1
1.3
Purpose and Scope of Work......................................................................................,
Section 2
METHODS OF IMTJ STIGATION. ............... .................... .......
........4
. 2.1
Field Exploration ... ...........................................................................................4
_.2
Laboratory Testing ............................... ....................
Section3
DISCUSSION.......................................................................................:.................6
3.1
Soil Conditions........................................:.....::.....:...:,.............................................6
3.2
Groundwater........:........................................................:...:......................................6
3.3
Geologic Setting................:...............................................:..........................:...........6
3.4
Geologic Hazards ....................... .. .. ...........................................
.... .. .... ._...................7
3.4.1 Seismic Hazards....::.,.......,.......................................................:...................7
3.42 Secondary Hazards..:.:..................................................................................8
3.4.3 Site Acceleration and UBCSeismic Coefficients :................:......................9
Section 4
CONCLUSIONS. ..................... .... ............................ .............................11.
Section S
RECOMMENDATIONS .....................................................................................12
SITE
DEVELOPMENT AND GRADING..........:.............................................:.............12
5.1
Site Development - Grading..............:.:.................................................................12
5.2
Excavations and Utility Trenches......................................::.....................:............13
5.3
Slope Stability of Graded Slopes ...................
STRUCTURES.........................:_.....................:...............................................................14
5.4
Foundations .............. :................................. .............................................................
1.4
5.5
Slabs-on-Grade..............................:......_...._._...,.......................................................
15
5,6
Retaining Walls...:.........:_...:......................:..._:...._..................................................1.6
5.8
Seismic Design Criteria............................................................................:............17
5.9
Pavements.....:...::.......::...:.....:...................:.....:.........:........:.......................:...........1
S
Section 6
LIMITATIONS AND ADDI'T'IONAL SERVICES, ........................................
20
6.1
Uniformity of Conditions and Limitations...:.........................................................20
6.2
.Additional Services........................................................................:.......................21.
REFERENCES.....:....................................:..........................................................:.........22
APPENDIXA.
Site Location Map
Boring Location Map
Table 1 Fault Parameters
1997 Uniform Building Code Seismic Parameters
2000 International Building,Code Seismic Parameters .
Logs of Borings
APPENDIX )g
Laboratory Test Results
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Section l
INTRODUCTION
1.1 Project Description
This_Geotectu-ucal Engineering Report has been prepared for. the proposed Phase I of the Country
~ Club of the Desert to be located between 52nd and 54th Avenues, and Jefferson and Madison
Streets in the City of La Quinta, California.
The project will ultimately consist of three,' 1 8 -hole golf courses with about 766 residential units
built on prepared pads. A clubhouse with: parking facilities, pool, spa and driving range is
proposed to be constructed at the northwestern portion of the project site. A maintenance facility
will be constructedat the southwest comer of 52nd Avenue to 54th Avenue with three proposed
auto or golf cart under crossings.
Based on preliminary mass grading plans prepared by Dye Designs of Denver, Colorado, dated
May 12, 2000, extensive mass -grading is proposed to.construct the golf courses and "super" pads
for the residential units. Fills as much as 20 feet are proposed at the ends of cul-de-sacs. Cuts as
deep as 20 to 26 feet are proposed to construct several small lakes for the golf courses. Slopes as.
high as 30 to 32 feet with. 2:1 (horizontal:vertical) slopes are proposed. Overall, in excess of
4,000,000 cubic yards of earthwork.i.s anticipated.
The proposed clubhouse and residences are assumed to be one-story structures. We anticipate
that the proposed structures will be of wood -frame construction and will be supported by
conventional shallow continuous or pad footings. Site development will include mass grading,
"super" building pad preparation, underground utility installation, street and parking loi
construction, and golf course development:
We used maximum column loads of 50 kips and a maximum wall loading of 3 kips per linear
foot as a basis for the foundation recommendations for residences and the clubhouse. All loading
is assumed to be dead plus actual live load. If actual structural loading is to exceed these
assumed values, we might need to reevaluate the given recommendations.
1.2 Site Description
The entire project site consists of approximately 900 acres of land consisting of most of Section
9, andthe southern half and the western 80 -acres of the northern half Section 10, Township 6
South, Range 7 East, San Bernardino baseline and meridian (see Figure 1. in Appendix A). The
site is irregular in shape, and generally bounded by Jefferson Street and the Coachella (All
American) Canal to the west, Avenue 52 to the north, agricultural properties and Monroe Street
to the east and Avenue 54 to the south.
The site is a mixture of undeyeloped desert land,, agricultural land, and ranches. The topography
of the site was moderately undulating to flat. Artificial ponds are located in several, portions of
the site. No other significant surface drainage features were observed.. The elevation of the site
ranges from approximately 22 feet above Mean Sea Level (MSL) to 29 feet below MSL.
The project site consists primarily of formerly agricultural and undeveloped land associated with
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former ranches 'on the property. The Fowler Packing Ranch and the vineyards on the Majestic
Property are the only two areas currently in use. for a*ricul.ture as of the date of this report.
Debris was observed in several portions of the project site. The. debris appeared to consist
primarily of green waste. Most of the debris appeared to be quite old, except for the material in
- the dry pond in the northeastern portion of the site; or the material actively being dumped by Arid
Zone Farms Nursery in the western portion of the site.
The vicinity around the site consists primarily of a mix of undeveloped, residential, and
agricultural properties, with the All American Coachella Canal bordering the site to the
northwest.. Residences were associated with some of the agricultural land.
There are underground and.overhead utilities near and within the development area. These utility
lines include but are not limited to domestic water, electric, sewer, and irrigation lines. Evidence
of an underground irrigation distribution system was observed in several portions of the site,
including both onsite and regional distribution pipelines.
1.3 Purpose and Scope of Wort:
The purpose for our services was to evaluate the site soil conditions anal to provide professional
opinions and recommendations regarding the proposed development of the site. The scope of
work included the following:
r A general reconnaissance of the site.
.Shallow subsurface exploration by drilling 24 exploratory borings and four cone
penetrometer (CPT) soundings to depths ranging from 31.5 to 1-10 feet.
➢ Laboratory testing of selected soil'samples obtained from the exploratory borings.
i Review of selected published technical literature pertaining to the site and previous
geotechnical, reports prepared for prior. conceptual developments for the properties
conducted by Buena Engineers in.,1989 and 1.990.
Engineering analysis and evaluation of the acquired data from the exploration and testing
programs.
A summary of our findin.gs and recommendations in this written report.
This report contains the following:
r Discussions on subsurface soil and groundwater conditions:
i Discussions on.regional and local geologic conditions.
Discussions on geologic and seismic hazards.
%- Graphic and tabulated results of laboratory tests and field studies.
Recommendations regarding:
Site development and gradings criteria,
Excavation conditions and buried utility installations,
Structure foundation type and design,
Allowable foundation bearing capacity and expected total and differential settlenien.ts,
Concrete slabs -on -grade;
Lateral earth pressures and coefficients,
Mitigation of the potential corrosivityof rile soi ls. to concrete and steel reinforcement,
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Seismic design parameters,
a Pavement structural sections.
Not Contained -In This Report: Although available through Earth Systems Consultants
Southwest, the current scope of our services does not include:
A corrosive study to determine cathodic protection of concrete or buried pipes.
An. environmental assessment.
Investigation for the presence or absence of wetlands, hazardous or toxic materials in the
soil, surface water, groundwater, or air on, below, or adjacent to the subject property.
Separate Phase I and Phase IT Environment Site Assessment reports have been prepared.
by Earth Systems`Consultants Southwest in 1998, 1999, and 2000.
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Section 2
METHODS OF INVESTIGATION
2.1 Field Exploration
Soil Borings: Twenty-four exploratory borings were drilled to depths of about 31.5 feet beloxv
the existing ground surface. to observe the soil profile and to obtain samples for laboratory
testing. The borings were drilled on August 18 and .23, Using'S-Inch outside diameter hollow -
stem augers, and powered by a Mobile B61 truck -mounted drilling rig. The boring locations are
shown on the boring location map, Figure 2, in. Appendix A. The locations shown. are
approximate, established by pacing and sighting from existing topographic features.
Samples were obtained within the test borings using a Standard Penetration (SPT) sampler
(ASTM D 1586) and a Modified California (MC) ring sampler (ASTM D 3550 with shoe similar
to ASTM D 1556).. The SPT sampler has a 2 -inch outside diameter and a 1.35 -inch inside
diameter. The MC` sampler has a 3 -inch outside diameter and a 2.37 -inch inside diameter. The
samples were obtained by driving the sampler with a 1.40 -pound -downhole hammer dropping
30 inches in general accordance with ASTM D 1586: Recovered soil samples were sealed in
containers and returned to the laboratory. Bull: samples were also obtained from auger cuttings,
representing a mixture of soils encountered at the depths noted.
The final logs of the borings represent our interpretation of the contents of the field logs and the
results of laboratory testing ' performed on the . samples" obtained during the subsurface
investigation. The final logs are included in Appendix A of this report. The stratification lines
represent the approximate boundaries between soil types although the transitions, however, may
be gradational.
CPT Soundings: Subsurface exploration was supplemented on August 28, 2000, using Fugro,
Inc. of Santa Fe Springs, California to advance, four electric cone penetrometer (CPT) soundings
to an approximate depth of 50 feet. The soundings were made at.the approximate locations
shown on the Site Exploration Plan, Figure 2, in Appendix A.
CPT soundings provide a nearly,continuous profile -of the soil stratigraphy with readings every 5
cm (2 inch) in depth. Direct sampling for visual and physical confirmation of soil properties is
generally"recommended with CPT exploration in large geographical regions. The author of this
report has gen.erally.conf rnzed accuracy of CPT interpretations from extensive work at numerous
Imperial and Coachella Valley sites:
The CPT exploration was conducted by hydraulically advancing an instrument 1.0 cm'- conical
probe into the ground at a ground rate of 2 cm per second using a 23 -ton truck as a reaction mass.
An. electronic data acquisition system recorded a nearly continuous log of the resistance of the
soil against the cone tip (Qc) and soil -friction against the cone sleeNle (Fs) as the probe «vas
advanced. Empirical relationships (Robertson and Campanella, 19S9) Nvere applied to the data to,
give a nearly continuous profile of the soil stratigraphy. Interpretation of CPT data provides
correlations for SPT.blow count, phi (0) angle (soil fiiction angle), ultimate shear strength (Su)
of clays, and soil type.
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b-iterpretive logs of the CPT soundings are - presented in Appendix A of this report. The
strat'f cation lines shown on the subsurface logs represent the approximate boundaries betivecn
the various. strata. However, the transition from one stratum to another may be gr dational.
2.2 Laboratory Testing
Samples were reviewed' 'along with field logs to select those that would be anal�2ed further..
Those selected for laboratory testing include soils that would be exposed and used during
grading, and those deemed to be within the influence of the proposed structure. Test results are
presented in graphic and tabular form in Appendix B of this report. The tests were conducted in
general accordance with the procedures of the, American Society for Testing and. Materials
(ASTM) or other standardized methods asreferenced below. Our testing program consisted of
the following:
i= In-situ Moisture Content and.Unit Dry Weight for the ring samples (ASTM D 2937).
i' Maximum density tests were performed to. evaluate the moisture -density relationship of
typical soils encountered (ASTM D 1:557-91):
r Particle Size Analysis (ASTIvI-D 422) to classify and evaluate soil composition: The
gradation characteristics of selected samples were made by hydrometer and sieve analysis
procedures.
Consolidation (Collapse Potential) (ASTM D 2435 and D5333)). to ..evaluate the
compressibility and hydroconsolidation (collapse) potential of the soil.
Liquid and Plastic Limits Tests to evaluate the plasticity and expansive nature of clayey
soils.
�= Chemical Analyses (Soluble Sulfates & Chlorides, ply, and Electrical Resi.stivi.ty) to
evaluate the potential adverse effects of the soil on concrete and steel.
EARTH SYSTEMS CONSULTANTS SOUTHWEST
September 22, 2000
Section 3
DISCUSSION
3.1. Soil Conditions
-G-
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The field exploration indicates that site soils consist primarily of an upper layer of silty sand to
sandy silt soils (Unified Soil Classification Symbols of SM and ML). These soils are loose to
medium dense. At depths greater than S feet, layers of clayey silt soils and some layers of sand
were encountered.
The boring and CPT logs provided in Appendix A include more detailed descripfions of the soils
encountered. The upper soils are visually classified to be in the very low expansion category in
accordance` with Table l SA -I -B of the. Uniforin Building Code. Clayey silt soils are expected to
be in the low expansion category.
In and climatic- regions, granular'soils may have a potential to collapse upon wetting. Collapse
(hydroconsolidation) ,may occur when the soluble cements (carbonates) in the soil matrix
dissolve, causing the soil.to densify from'its loose configuration from deposition. Consolidation
tests indicate I to 3% collapse upon inundation and is considered a slight to moderate site risk.
The hydroconsolidation potential is, commonly mitigated by'recompaction. of a zone beneath
building pads.
The site lies within a recognized 'blow sand. hazard arca. Fine particulate matter (PMio) can
create an air quality hazard if dust is blowing. Watering the surface, planting grass or
landscaping, or hardscape normally mitigates this hazard.
3.2 Groundwater
Free groundwater was not encountered in the borings or CPT soundings during exploration. The
depth to groundwater in the area. is believed to be about 69 feet based on 1999 water well. data
obtained for the well near the former Colchest Ranch house from the. Coachella Valley Water
District. Groundwater levels may fluctuate with, irrigation, d.rainage, 'regional pumping from
wells, and site grading.. The development of perched groundwater. is possible over clayey soil
layers with heavy irrigation.
3.3 Geologic Settiug
Regional Geolog The site lies within the Coachella Valley, a part of the Colorado Desert
geomorphic province. A significant feature within the Colorado Desert geomorphic province is
the Salton Trough. The Salton .Trough is a lame northwest -trending structural depression that
extends from San Gorgonio Pass,. approximately 180 miles to the'Gulf of California. Much of,
this depression in the'area of the Salton Sea is below sea Level.
The Coachella Valley forms the northerly portion of the Salton Trough. The Coachella Valley
contains a thiel: sequence of sedimentary deposits 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 northwest, and the San Jacinto and Santa Rosa
Mountains on the southkN,6st. I These mountains expose primarily Precambrian metamorphic and
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Mesozoic granitic rocks. The San Andreas Fault zone within the Coachella Valley consists of
the Garnet Hill Fault, ' the Banning Fault, and the Mission Creek Fault that traverse along the
northeast margin of the valley.
Local Geoloey: The project site is located within the lower portion of the Coachella Valley. The
.upper sediments within the lower valley consist of fine to coarse-grained sands with interbedded
clays and silts, of aeolian (wind-blown), and alluvial (water -laid) origin.
3.4 Geologic Hazards
Geologic hazards" that may affect the region include _ seismic hazards (surface fault rupture,
ground shaking, soil liquefaction, , and other secondary earthquake -related hazards); slope
instability, flooding, ground subsidence, and erosion. A discussion follows on the specific
hazards to this si.te.
3.41 Seismic Hazards
Seismic Sources: Our.research of regional faultina indicates that several active faults or seismic
zones lie within . 62 miles (100 kilometers) of the project site as shown on Table 1 in
Appendix A. The primary seismic hazard to the site is strong groundshaking from earthquakes
along the San Andreas and San Jacinto Faults. The, Maximum Magnitude Earthquake
listed is from published geologic information available for each fault (CDMG, 1996) The Mma,
corresponds to the°maximum. earthquake believed to be tectonically possible.
Surface Fault Rupture: The project site does not lie within a currently delineated State of
California, Alquist-Priolo Earthquake Fault -Zone (Hart, 1994). Well -delineated fault Iines cross
through this region as shown on California Division of Mines and Geology (CDMG) maps
(Jennings, 1994)., Therefore, active fault rupture is unlikely to occur at the project site. While
fault rupture would most likely occur along previously established fault traces, future fault
rupture could occur -at other.locations.
Historic Seismicity: Six historic seismic events (5.9 M or greater) have significantly affected the
Coachella Valley this century:' They are as follows:
• Desert Hol Springs Earthquake On December 4, 1948, a magnitude 6.5 ML (6.OMw) earthquake
occurred east of Desert Hot Springs. This event was strongly felt in the Palm Springs area.
Palin. Springs Earthquake - A magnitude 5.9 ML.(6.2Mw) earthquake occurred on July S, 1986 in the
Painted Ilills causing minor- surface creep of the Banning segment of the San Andreas Fault. This
event was strongly felt in.the Palm Springs area and caused structural damage, as well as injuries.
Joshud Tree Earthquake - On April 22, 1992,•a magnitude 6.1 Mi. (6.1Mw) earthquake occurred in
the mountains 9 miles east of Desert I -lot Springs: Structural damage and minor injuries occurred in
the Palm Springs area as a result of this earthquake.
Landes & Big Bear L•arthquakas-- Early on .lune 28, 1992, a magnitude 7.5 Ibis (7.3&lw) earthquake
occurred near Landers,"the largest seismic event in Southem California for 40 years. Surface rupture
occurred just south of the town of Yucca Valley and extended some 43 miles toward Barstow. About
three hours later, a magnitude 6.6 Ms (6AMw). earthquake occurred near Big. Bear Lake. No
significant structural damaile from these earthquakes was reported in the Palm Springs area.
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Hecto- Mine Earthquake - On October 16, 1999. a magnitude 7.1Mw earthquake occurred on the
Lavic Lake and Bullion Mountain Faults north of 29 Palms. This event while widely felt, no
significant structural damage has been reported in the Coachella Valley.
Seismic Risk: While accurate earthquake predictions are not possible, various agencies have
conducted statistical risk analvses. In 1996, the California Division. of Mines and Geology
(CDMG) and the United States Geological Survey (USGS) completed the latest generation of
probabilistic seismic hazard maps for use in the 1997 UBC. We have used these maps in our
evaluation of the seismic risk at the site. The Working Group of California Earthquake
Probabilities (WGCEP, .1995) estimated a 22% conditional probability that a magnitude 7 or
greater earthquake may occur between 1994 to 2024 along the Coachella segment of the San
Andreas Fault.
The primary seismic risk at the site is a potential earthquake along the San Andreas Fault.
Geologists believe that the San Andreas Fault has characteristic earthquakes that result from
rupture of each fault segment. The estimated characteristic earthquake is magnitude 7.4 for the
Southern Segment of the fault. This segment has the longest elapsed time since rupture than any
other portion of the San Andreas Fault. The last rupture occurred about 1690 AD, based on
dating by the USGS near Indio (WGCEP, 1995). This segment has also ruptured on about 1020,
1300, and 1450 AD, with. an average recurrence interval of about 220 years. The San Andreas
Fault may rupture in. multiple segments producing a higher magnitude earthquake. Recent
paleoseismic studies suggest that the San Bernardino Mountain Segment to the north and the
Coachella Segment may have both ruptured together in 1450 and 1690 AD (WGCEP, 1995).
3.4.2 Secondary Hazards
Secondary seismic hazards related to ground shaking include soil liquefaction, ground
deformation, areal subsidence; tsunamis, and seiches. The site is far inland so the hazard from
tsunamis is non-existent. At the present lime, no water storage reservoirs are located in the
immediate vicinity of the site. Therefore, hazards from seiches are considered negligible at this
time.
Soil Liquefaction: Liquefaction is the loss of soil strength from. sudden shock (usually
earthquake shaking), causing the soil to become a fluid mass. In general, for the effects of
liquefaction to be manifested at the surface, groundwater levels must be within 50 feet of the
ground surface and the soils within the saturated zone must also be susceptible to liquefaction.
The potential for liquefaction to occur at this site is considered low because the depth of
groundwater beneath the site exceeds 50 feet. No free groundwater was encountered in. our
exploratory borings or CPT Soundings. Only the extreme southeastern part of the Phase 1 area
lies within the Riverside County liquefaction. study zone.
Ground Deformation and Subsidence: Non -tectonic ground deformation consists of cracking of
the ground Nwith little to no displacement. This type of deformation is generally associated with
differential shaking of two or more geologic units with differing engineering characteristics.
Ground deforniation may also be caused by liquefaction. As the site is relatively flat with
consistent geologic material, and has a low potential for liquefaction, the potential for ground
deformation is also considered to be low.
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The potential for seismically induced ground subsidence is considered to be moderate at the site.
Dry sands tend to settle and densify when subjected to strong earthquake shaking.. The amount of
subsidence is dependent on relative density of the soil, groundshaking (cyclic shear strain), and
earthquake duration (number of strain cycles). Uncompacted. fill areas may be susceptible to
sei.smicall.y induced settlement.
Slope Llstability: The site is currently relatively flat. Mass -grading will reshape the topography
so that slopes, are as high as 20 to 30 feet with up to 2:1 (horizontal:vertical) inclination will
exist. Therefore, potential hazards from slope instability, landslides, or debris flows are
considered negligible to low.
Flooding: The project site does not lie within a designated FEMA 100 -year flood plane. The
project site may be in an area where sheet flooding and erosion (especially on slopes) could
occur. Significant grade changes are proposed for the site. Appropriate project design,
construction, and maintenance can minimize the site sheet flooding potential.
3.4.3 Site Acceleration and UBC Seismic Coefficients
Site Acceleration: The potential intensity of ground motion may be estimated the horizontal
peal: ground acceleration (PGA), measured in "g" forces., hicluded in Table 1 are deterministic
estimates of site acceleration from possible earthquakes at nearby faults. Ground motions are
dependent primarily on the earthquake magnitude and distance to the seismogenic (rupture) zone.
Accelerations_ also are dependent upon attenuation by rock and soil. deposits, direction. of rupture,
and type of fault. For these reasoris, ground motions may vary considerably in the same general
area. This variability can be expressed statistically by a standard deviation about a mean
relationship,.
The PGA is an inconsistent, scaling factor to compare to the UBC Z factor and is jenerally a poor
indicator of potential structural damage during an earthquake. hnportant factors influencing the
structural performance are the duration and frequency of strong ground motion, local subsurface
conditions, soil-stnieture interaction, and structural details. Because of these factors, an effective
peal: acceleration (EPA.) is used in structural design.
The following table provides the probabilistic estimate of the PGA and EPA taken from the
1996 CDMG/USGS seismic hazard maps.
EARTH SYSTEMS CONSULTANTS SOUTHWEST
September 22, 2000
-10-
Estimate of PGA and EPA from 1996 CDM'G/USGS
Prnhnhifictic fieismic Hazard Mans
File No.: 07117-10
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Risk
Equivalent Return
Period (years) .
PGA (g) 1
Approximate
EPA g) '"
1.
10% exceedan.ce in 50 years
1 475
0.49
0.45
Notes:
1. Based on a soft rock site, SB/c and soil amplification factor of 1.0 for Soil Profile Type So -
2. Spectral acceleration (SA) at period of 0.3 seconds divided by 2.5 for 5% damping, as defined by
the Structural _Engineers Association of California (SEAOC, 1996).
1997 UBC Seismic Coefficients: The Uniform Building Code (UBC) seismic design are based
on a Design Basis Earthquake (DBE) that has an. earthquake ground motion with a
10% probability of occurrence in 50 years. The PGA and EPA estimates given above are
provided for information on the seismic risk inherent in the UBC design. The following lists the
seismic and site coefficients given in Chapter 16 of the 1997 Uniform Building Code (UBC).
1997 UBC Seismic Coefficients for Chapter 16 Seismic Provisions
Seismic Zonin : The Seismic Safety Element of the 1984 Riverside County General Plan
establishes groundshaking-hazard zones. The majority of the project area is mapped in Ground
Shaking Zone IIB. Ground Shaking Zones are based on distance from causative faults and
underlying soil types. The site does not lie within the Liquefaction. Hazard area established by
this Seismic Safety Element. These groundshaking hazard zones are used in deciding suitability
of land use.
2000 IBC Seismic Coefficients:. For comparative purposes, the newly released 2000
International Building Code (IBC) seismic and site coefficients are given in Appendix A. As of
the issuance of this report, we are unaware when goveming jurisdictions may adopt or modify the.
IBC provisions.
EARTH SYSTEMS CONSULTANTS SOUTHWEST
Reference
Seismic Zone:
4
Figure 1672
Seismic Zone Factor, Z:
0.4
Table 16-I
Soil Profile Type:
So .
Table 16-J
Seismic Source Type:
A
Table 16-U
Closest Distance to Known Seismic Source:
9.8 km = 6.1 miles
(San Andreas Fault).
Near Source Factor, Na:
1.01
Table 16-S
Near Source Factor, Nv:
1.22
Table 16-T
Seismic Coefficient, Ca:
0.44 = 0.44Na
Table 16-Q
Seismic Coefficient, Cv:
0.78 = 0.64Nv
Table 16-R
Seismic Zonin : The Seismic Safety Element of the 1984 Riverside County General Plan
establishes groundshaking-hazard zones. The majority of the project area is mapped in Ground
Shaking Zone IIB. Ground Shaking Zones are based on distance from causative faults and
underlying soil types. The site does not lie within the Liquefaction. Hazard area established by
this Seismic Safety Element. These groundshaking hazard zones are used in deciding suitability
of land use.
2000 IBC Seismic Coefficients:. For comparative purposes, the newly released 2000
International Building Code (IBC) seismic and site coefficients are given in Appendix A. As of
the issuance of this report, we are unaware when goveming jurisdictions may adopt or modify the.
IBC provisions.
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Section 4
CONCLUSIONS
The .following is a summary of our "conclusions and professional opinions based on the data
obtained from a review of selected technical Iiterature and the site evaluation.
The prunary geologic hazard relative to site development is severe ground shaking from
earthquakes originating on nearby faults. In our .opinion, a major seismic event
originating on the local segment of the San Andreas Fault zone would be the most likely
cause of significant earthquake -activity at the site within the estimated design life of the
proposed development.
i The project site is in. seismic Zone 4 as defined in the Uniform Building Code. A
qualified professional who 'is aware of the site seismic setting should design any
permanent structure constructed on the site.
:- Ground subsidence from seismic events or hydroconsolidation is a potential hazard in the
Coachella Valley area. Adherence to the following grading and structural
recommendations should reduce" potential settlement problems from seismic forces, heavy
rainfall or irrigation, flooding, and the weight of the intended structures.
The soils are susceptible to wind and water. erosion. Preventative measures to minimize
seasonal flooding and erosion should be incorporated into site grading plans. Dust
control should also be implemented during construction.
Other geologic hazards 'including ground rupture, liquefaction, seismically induced
flooding; and landslides are considered low orrnegligible on this site.
The upper soils were found to be relatively loose to medium dense silty sand to sandy silt
overlying layers of clayey soils. In our. opinion, the soils within building and structural
areas will require over excavation and recompaction to improve bearing capacity' and
reduce settlement from static loading. Soils should be readily cut by normal grading
equipment.
Earth. Systems Consultants Southwest (ESCSW)should 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 event that
subsurface conditions differ from those anticipated prior to the start of construction.
Plans and specifications should be provided to ESCSW prior to grading. Plans should
include the "grading plans, foundation, plans, and foundation details. .Preferably, structural
loads should be shown on the foundation plans.
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Section a"
RECOMMENDATIONS
SITE DEVELOPMENT AND GRADING
5.1: Site Development - Grading
A representative of ESCSW should observe site grading and the bottom of excavationsprior to
placing fill. Local variations in soil conditions may warrant increasing the depth of recompacti.on
and over -excavation.
Clearing and. Grubbing: Prior to site grading existing vegetation, trees, large roots, old structure,
foundations, uncompacted fill, construction debris, trash, and. abandoned underground utilities
should be removed from theproposed building, structural, and pavement areas. The. surface
should be stripped of organic growth and removed from the construction area. Areas disturbed
during demolition and clearing should be properly backfilled and compacted as described below.
Non-structural (golf course) areas may be used as disposal areas for resulting debris as
designated clearly on grading plans and approved by project owner, engineers and governing
jurisdictions.
Building Pad Preparation: Because of the non-uniform andunder-compacted nature of the site
soils, we recommend recompaction of soils 'in the building' and structural areas. The existing
surface soils within the building pad and. structural areas should be over -excavated to 30 inches
below existing grade or a minimum of 24 inches below the footing level (whichever is lower).
The over -excavation should extend for 5 feet beyond .the outer edge of exterior footings. The
bottom of the sub -excavation should be scarified; moisture conditioned, and recoknpacted to at
least 90 °iii relative compaction (ASTM D 1557) for an additional depth of 12 inches. Moisture
penetration to near optimum moisture should extend at Ieast 5 feet below existing grade and be
verified by testing. These recom.mendati.ons are intended to provide a minimum of 48 and 36
inches of moisture conditioned and compacted _soil beneath the floor slabs and footings,
respectively.
Auxiliary Structure Subgrade Preparation: Auxiliary structures such as'garden or retaining walls
should have the subgrade prepared. sinular to the building pad preparation reconuiiendation given
above. Except the lateral extent of the overexcavation need only to extend 2 feet beyond the face
of the footing:
Settlement Monitors: In areas. where.fill depths are greater than 10 feet above existing grade, we
recommend the placement of settlement monitors (one for each general area) to monitor the post -
grading settlement of the fill and underlying soils. Compression,of the deep seated clayey soil
may occur after grading, but is expected to stabilize relatively soon the Monitoring allows
the geotechnical engineer to .evaluate the movement (if any) and its potential impact on
construction.
Sub, --rade Preparation.: Lr areas ` to'receive, non-structural fi11, pavements, or hardscape, the
ground surface should be scarified;. moisture conditioned, and compacted to at least 90% relative
compaction (ASTM D 1557) for a. depth of 24 inches below subgrade. Compaction. should. be
verified by testing.
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Enzineered Fill Soils: The native sand, silty, sand, and sandy silt soil is suitable for use as
engineered f 11 and utility trench backfill. The native. soil should be placed in maximum 8 -inch
lifts (loose) and compacted , to at feast 90% relative compaction. (ASTM: D 1557) near. its
optimum moisture content. Compaction should be verified by testing.
Clayey silt soils where encountered at depths generally below 8 -foot depth are less desirable soils
and should not be. placed- witlun. the' upper 3 feet of finished' subgrades for building pads or
streets.
Imported fill. soils .(if required) should be, non -expansive, granular soils meeting the
USCS classifications of SM; SP -SM, or SW -SM with a maximum rock size of 3 inches and
5 to 35% passing the No. 200 sieve. The geotechnical. engineer should evaluate- the import fill
soils before hauling to the site.. However, because of the potential variations within the borrow
source, import soil will not prequalified by ESCSW. The imported fill should be placed in lifts
no greater than 8 inches in loose thickness and compacted to at least 90% relative compaction
(ASTM D 1557) near optimum moisture content:
Shrinkage: The shrinkage factor for earthwork is expected to variably range from 5 to 20 percent
for the majority of the excavated or scarified soils, but in the clayey soils and upper 4 feet of
some areas it may range from,2_i1Q 501/. This estimate is based on compactive effort to achieve
an average relative compaction of about 92% and may vary with contractor methods. Subsidence
is estimated to range from 0.1 to 0.3 feet. Losses from site clearing and removal of existing site
improvements may affect earthwork quantity calculations. and should be considered.
Site Drainage: Positive drainage should be maintained away from the structures (5% for5 feet
minimum) to prevent ponding and subsequent saturation of the foundation soils. Gutters and
downspouts should be considered as a meang. to'convey water away from foundations if adequate
drainage is not provided.' : Drainage should, be maintained for paved. areas. Water should not
pond on or near paved areas.
5.2 Excavations and Utility Trenches
Excavations should'be made in accordance with CalOSHA requirements. Our site exploration
and knowledae of the general area indicates there is a potential for caving of site excavations
(utilities, footings, etc.). Excavations within sandy soil should be kept inoist, but not saturated,
to reduce the potential of caving or sloughing. Where deep. excavations over 4 feet deep are
planned, lateral bracing or appropriate cut slopes of 1.5:1 (horizontal: vertical) should be
provided. No surcharge loads from stockpiled soils or construction materials should be allowed
within a horizontal distance measured froni the top of the excavation slope, equal to the depth of
the excavation.
Utility Trenches: Backfill of utilities within road or public right -of ways should be placed in
conformance with the requirements of the governing agency (water district, public works
department, etc.) Utility trench backfill within private property should be placed in conformance
with the provisions of this report. -In general, service lines extending inside of property may be
backfilled with native soils compacted to a minimum of 901/o relative compaction., Backfill
operations should be observed and tested to monitor compliance with these recommendations.
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5.3 Slope. Stability- of Graded Slopes
Unprotected; permanent graded slopes should not be steeper than 3:1 (horizontal: vertical) to
reduce wind and rain erosion. Protected 'slopes with ground cover may be as steep as 2:1.
However, maintenance with motorized equipment may not be possible at this inclination. Fill
slopes should be overfilled and trimmed back. to competent material. Where slopes heights
exceed 20 feet, with 2:1. (horizontal: vertical) slopes, post -construction. engineering calculations
should. be performed to evaluate the stability -using shear strength values obtained from soils
composing the slopes. Erosion control measures should be considered for slopes steeper than 3:1.
until the final ground cover (i.e., grass turf) is established.
STRUCTURES
In our professional. opinion, the structure foundation can be supported on shallow foundations
bearing on a zone of properly prepared an.d compacted' soils placed as recommended in
Section 5.1. The recommendations that follow are based on very.low expansion category soils
with the upper 3 feet of subgrade.
5.4 Foundations
Footing design of widths, depths, and reinforcing are the responsibility of the Structural
Engineer, considering the structural loading and the geotechnical parameters given in this report.
A min.imtim footing depth of 12 inches below lowest adjacent grade should be maintained. A
representative of ESCSW should observe foundation excavations prior to placement of
reinforcing steel or concrete. Any loose soil or construction debris should be removed from
footing excavations prior to placement of concrete.
Conventional Spread Foundations: Allowable soil bearing pressures are given below for
foundations bearing on recompacted soils as described in Section 5.1. Allowable bearing
pressures are net (weight of footing and soil surcharge may be neglected).
Continuous wall foundations, 12 -=inch i`imun widthland T2=inches_belo_w>grade:
1-500psf for dead. plus design live loads
Allowable increases of 30.0 psf per each foot of additional footing width and 300 psf for each
additional 0.5 foot of footing depth may be used up to a maximum value -of -'3-M psf
Isolated pad foundations, 2-x 2-foot-niinimrim)in plan and 1-8-inches_15eloN grade:
200_0 p for dead plus design live loads
Allowable increases of 200 psf per each foot of additional footing width and 400 psf for each
additional 0.5 foot of footing depth may be used up to a ma—x niumwalvE-o-f_-3:000-psf..
A one-third (1/3) increase in the bearing pressure may be used when calculating resistance to
wind or seismic loads. The allowable bearing values indicated .are based on the anticipated
maximum loads stated in. Section 1.1 of this report. If the anticipated loads exceed these values,
the geotecluuical engineer must reevaluate the allowable bearing values and the grading
requirements.
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Minimum reinforcement for continuous wall.footinas should be two, No. 4 steel reinforcing bars,
placed near the top and the bottom of the footing. This reinforcing is not intended to supersede
any structural requirements provided by the structural engineer.
Expected Settlement: Estimated total static settlement, based on•footings founded on finu soils
as recommended, should be less than i inch. Differential settlement between exterior and
interior bearing members should be less than 1/2 -inch. .
Frictional and Lateral Coefficients: Lateral loads may be resisted by soil fiction on the base of
foundations and by passive resistance of the soils acting on foundation walls. An allowable
coefficient of friction of 0.35 of dead load may. be used. An allowable passive equivalent fluid
pressure of 250 pcf may also be used. These values include a factor of safety of 1.5. Passive
resistance and frictional resistance may be used in combination .if the friction coefficient is
reduced to 0.23 of dead load forces. A one-third (1/3) increase in the passive pressure may be
used when calculating resistance to wind or seismic loads. Lateral passive resistance is based on
the assumption that any required backfill adjacent to foundations is properly compacted.
5.5 Slabs -on -Grade
Sub -grade: Concrete slabs -on -grade and flatwork should be supported by compacted soil placed
in accordance with Section 5.1 of this report.
Voor Barrier: In areas of moisture sensitive floor coverings, an appropriate vapor barrier should
be installed to reduce moisture transmission from the subgrade soil. to the slab. For these areas
an impermeable rimennbrane (10 -mil moisture barrier) should. underlie the floor slabs. The
membrane should be covered with 2 inches of sand to help protect it during construction and to
aide in concrete curing. The sand should be lightly moistened just prior to placing the concrete.
Low -slump concrete should be used to help reduce the potential for concrete shrinkage. The
effectiveness" of the moisture barrier is dependent upon its quality, method of overlapping, its
protection during construction, and the successful sealing of the barrier around utility lines.
Slab thickness and reinforcement: Slab thickness and reinforcement of slab -on -grade are
contingent on the recommendations of the structural engineer or architect and the expansion
index of the supporting soil. Based upon our findings, a modulus of subgrade reaction of
approximately 200 pounds per cubic inch can be used in concrete slab design for the expected
very low expansion. subgrade.
Concrete slabs and flatwork should be a mininiu_nz of 4= iiiclies-thick. We suggest that the
concrete slabs ie reinforced, as specifiedby the project structural engineer, to resist cracking.
Concrete floor 'slabs may either be monolithically placed with the foundations or doweled after
footing placement. The thickness and reinforcing given are not inten.ded to supersede any
structural requirements provided by the structural engineer. The project architect or geotechnical
engineer should observe all reinforcing steel in slabs during ,placement of concrete to check for
proper location within the slab. .
Control Joints: Control joints should be provided in all concrete slabs -on -grade at a maximum
`. spacing of 36 times the slab thickness (12 feet maximum on -center, each way) as recommended
by American Concrete Institute (ACI) guidelines. All joInts should form approximately square
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patterns to reduce the potential for randomly oriented, contraction cracks. Contraction joints in
the slabs should be tooled at the time of the pour or saw cut (1/4 of slab depth) within S hours of
concrete placement. Construction (cold) joints should consist of thickened butt joints with one-
half inch dowels at 1$ -inches on center or a thickened keyed .joint to resist vertical deflection at
the joint. All construction joints in exterior flag>>ork should be sealed to reduce the potential of
moisture or foreign material intrusion. These procedures will reduce the potential for randomly
oriented cracks, but may not prevent them from occurring.
Curing and Ouality Control: The contractor should take precautions to reduce the potential of
curling of slabs in this and desert region using proper batching, placement, and curing methods.
Curing is highly effected by temperature, wind, and humidity. Quality control procedures in y be
used including trial batch mix designs, batch plant inspection, and on-site special inspection and
testing. Typically, for this type of construction and using 2500 -psi concrete, many of these
quality control procedures are not required.
5.6 Retaining Walls
The following table presents lateral earth pressures for use in retaining wall design. The values
are given as equivalent fluid pressures without surcharge loads or hydrostatic pressure.
Lateral Pressures and Sliding Resistance t
Granular Backfill
Passive Pressure
375 pcf -level ground
Active Pressure (cantilever walls)
35 pcf - level ground
Able to rotate 0.1 % of structure height
At -Rest Pressure (restrained walls)
55 pcf -_level ground
Dynamic Lateral Earth Pressure'
Acting at mid height of structure,
25H psf.
Where H is height of backfill in feet
Base Lateral Sliding Resistance
Dead load x Coefficient of Friction:
0.50
Notes:
1. These values are ultimate values. A factor of safety of 1.5 should be used in stability analysis except
for dynamic earth pressure where a factor of safety of 1.2 is acceptable.
2. Dynamic pressures are based on the Mononobe-Okabe 1929 method, additive to active earth pressure.
Walls retaining less than 6 feet of soil need not consider this increased pressure.
Upward sloping backfill or surcharge loads from nearby footings can create larger lateral
pressures. Should any walls be considered .for retaining sloped backfill or placed next to
foundations, our office should be contacted for recommended design parameters. . Surcharge
loads should be considered if they exist within a zone between the face of the wall and a plane
projected 45 degrees upward from the base of the wall. The increase in lateral earth pressure
should be taken as 350io of the surcharge load within this zone. Retaining walls subjected to
traffic loads should include a uniform surcharge load equivalent to at least 2 .Feet of native soil.
Draina_e: A back -drain or an equivalent system of: backfill drainage should be incorporated into
the retaining wall design. Our f rm can provide construction details when the specific application
,i.s determined. Backfill immediately behind the retaining structure should be a free- drain.i.ng
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granular material. Waterproofing should be according to the Architect's specifications. 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 retainingwall.
Back -fill Compaction: Compaction on, the retained side of the wall within a horizontal distance
equal to one wall height should be performed by hand -operated or other lightweight compaction
equipment. This is intended to reduce potential. locked -in lateral pressures caused by compaction
with heavy grading equipment.
Footing Sub -grade Preparation: The subgrade for footings should be prepared according to the
auxiliary structure subj ade preparation given in Section 5.1..
5.7 Mitigation of Soil Corrosivity on Concrete
Selected chemical analyses for corrosivity were conducted on samples at the low chloride ion
concentration. Sulfate ions can. attack the cementitious material in concrete, causing weakening
of the cement matrix and eventual deterioration by raveling. Chloride ions can cause corrosion
of reinforcing steel. The Uniform Building Code does not require any special provisions for
concrete for these low concentrations as tested. However, excavated soils from mass -grading
may have higher sulfate and'chloride ion concentrations. Additional soil chemical testing should
be conducted on the building pad soils after mass -grading.
A minimum concrete cover of three (3) inches should be provided around steel reinforcing or
embedded components exposed to native soil or landscape water (to 18 inches above grade).
Additionally, the concrete should be thoroughly vibrated during placement.
Electrical resistivity testing of the soil suggests that the site soils may present a moderately severe
potential for metal loss from electrochemical corrosion processes. Corrosion protection of steel
can be achieved by using_ epoxy corrosion inhibitors, asphalt coatings, cathodic protection, or
encapsulating with .densely consolidated. concrete. A qualified corrosion engineer should be
consulted regarding mitigation of the corrosive effects of site soils on metals.
5.8 Seismic .Design Criteria
This site is. subject to strong ground shaking due to. potential fault movements along the
San Andreas and San Jacinto Faults. Engineered design and earthquake -resistant construction
increase safety and allow development of seismic` areas. The m.iniinu'in seismic design should
comply with the latest edition of the Uniform Buil.ding Code for Seismic Zone 4 using the
seismic coefficients given in Section 3.4.3 of this report.
The.UBC seismic coefficients are based on scientific kno,,vledge; engineeringjudgrilent, and
compromise. Factors that play an important role in dynamic structural perfoniIiance are:
(1) Effective peal: accelerati.oii (EPA),
(2) Duration and predominant frequency of strong ground motion,
(3) Period of motion of the structure,
(4) Soil -structure interaction,
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(5) Total resistance capacity of the system,
(6) .Redundancies,
(7) Inelastic load -deformation behavior, and
(8) Modification of damping and effective period as structures behave inelastically.
Factors 5 to 8 are included in the structural ductility factor (R) that is used in deriving a reduced
value for design base shear. If further information on seismic design is needed, a site-specific
probabilistic seismic analysis should be conducted.
The intent of the UBC lateral Torce'requirements is to provide a structural design that will resist
collapse to provide reasonable life safety from a major earthquake, but may experience some
structural and nonstructural ' damage: A fundamental tenet of seismic design is that inelastic
yielding is allowed to adapt to the seismic demand 'on the structure. In other words, daniage is
a11014red. I The -UBC lateral forcerequirements should be considered a minimum design.. The
owner and the designer should evaluate the level of risk and performance that is acceptable.
Performance based criteria- could be set.in the design. The design engineer has the responsibility
to interpret and adapt the principles of seismic behavior and design to each structure using
experience and sound judgment. The design engineer should exercise special care so that all
components of the design are all fully met ivith attention to providing a continuous load. path. An
adequate'quality assurance and control program is urged during project construction.to verify that
the design plans and good. construction 'practices are followed. This is especially important for
sites lying close to the major seismic sources.
5.9 Pavements
Since no traffic loading were provided by the. design engineer or owner, we have assumed traffic
loading for comparative evaluation. The design engineer or owner should decide the appropriate
traffic conditions for the pavements. Maintenance of proper drainage is necessary to prolong the
service life of the pavements'. Water should not pond on or near paved areas. The following
table provides our recommendations for pavement sections.
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RE COMMENDED PAVEMENTS SECTIONS
R -Value Sub -rade Soils -.,40 (assumed) Desi mi Method — CALTRANS 1995
Traffic
Index
(Assumed)
Pavement Use J
Flexible Pavements
F i.id Pavements
Asphaltic. Aggregate'
Concrete. Base
Thickness Thickness'
(Inches) . (Inches)
Portland Aggregate
Cement Base'
Concrete. Thickness
(Inches) (Inches)
4.0
Auto Parking Areas
2.5
4.0
4.0
4.0
5.0
Residential Streets
3.0
4.0'
5.0
4.0
6.5
Collector Road
3.5
6.5
---
---
-7.5
Secondary Road
4.5
7.0
---
---
Notes:
1. Asphaltic concrete should be Caltrans, Type B,'1/2 -in. or 3/4 -in. maximum -medium grading and
compacted to a, minimum of 95% of the 75 -blow Marshall density (ASTM D 1559) or equivalent.
2. Aggregate base should be Caltrans Class 2'(3/4 in.. maximum) and compacted to a minimum of
95% of ASTM D 1557 maximum dry density near its optimum moisture.
3. All pavements should be,placed on 12 inches ofm.oisture-conditioned subs ade, compacted to a
minimum of 90% of ASTM D 1557 maximum dry density near its optimum moisture.
4. Portland cement concrete should have a minimum of 3250 psi compressive strength @ 28 days.
5.. Equivalent Standard Specifications for Public Works Construction (Greenbook) may be used
instead of Caltrans specifications for asphaltic concrete and aggregate base_
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Section f
LIMITATIONS ANIS ADDITIONAL SERVICES
6.1 Uniformity, of Conditions and Limitations
Our findings and recommendations in this report are based on selected points of field
exploration, laboratory testing, and our understanding of the proposed project. Furthermore, out-
findings
urfindings and recommendations are based on the assumption that soil conditions do not vary
significantly from those found at specific exploratory locations. Variations in soil or
groundwater conditions could exist between mid beyond the exploration points. The nature and
extent of these variations may not become evident until construction. Variations in soil or
groundwater may. require additional studies, consultation, and possible revisions to our
recommendations.
Findings of this report are valid as of the issued date of the report. . However, changes in
conditions of a property can occur with passage of time whether they are fi.om natural processes
or works of man on this or adjoining properties. In. addition, changes in applicable standards
occur whether they result from legislation or broadening of knowledge. Accordingly, findings of
this report may be invalidated wholly or partially by changes outside our control. Therefore, this.
report is subject to review and should not be relied upon after a period of one year.
hl the event that any changes in the nature, design, or location of structures are plarined, the
conclusions and recommendations contained in this report shall not be considered valid unless
the changes are reviewed and conclusions of this report are modified or verified in writing.
This report is issued with the understanding that the owner, or the owner's representative, has the
responsibility to bring the information and recommendations contained herein to the attention of
the architect and engineers for the project so that they are incorporated into the plans and
specifications for the project. The owner, or the owner's representative, also has the
responsibility to take the necessary steps to see that the general contractor and all subcontractors
follow such recommendations. It is further 'understood that the owner or the owner's
representative is responsible for submittal. of this report to the appropriate governing agencies.
As the Geotechnical Engineer of Record for this project, Earth Systems Consultants Southwest
(ESCSW) has striven to provide our services in accordance with generally accepted geoteclinical
engineering practices in this locality at this time. No warranty or guarantee, is express or implied.
This report was prepared for the exclusive use of the Client and the Client's authorized agents.
ESCSW should be provided the opportunity for a general review of .final design and
specifications in order that earthwork and foundation recommendations may be properly
interpreted and implemented in the design, and specifications. if ESCSW is not accorded the
privilege of making this recommended review, we can assume no responsibility for
misinterpretation of our recommendations.
Although available tlUough ESCSW, the current scope of our services does not include an
environmental assessment, or investigation for the presence or absence of wetlands, hazardous or
toxic materials in the soil, surface water, groundwater or air on, below, or adjacent to the subject
property.
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6.2 Additional Services
This report is based ' on the assumption that an adequate. program ;of client consultation,
construction monitoring, arid' testing, will be perfonned during the final. design and construction.
phases to check compliance 'With these recommendations. Maintaining ESCSW as the
geotechnical consultant from beginning to end of the project will provide; continuity of se.n-ices.
The geotechnical engineering f,71171' providing tests and ' observations shall assione the
responsibiliti-of Geotechnical Engineer of Recorcl.
Construction monitoring and testing•-would 'be additional services provided by our firm. The
costs of these services are not included in our present fee arrangements, but can be obtained fi-onr
our office. The recommended review, `tests, and observations 'include, but are not necessarily
limited to the following:
6 Consultation during the final.design stages of.the project.
e Review of the building anal 'gradingplans to observe that recommendations of our report
havebeen properly implemented into the design.
® Observation and testing during site preparation, grading and placement of engineered fill
as required by UBC Sections •1:701 and-31.7 or local grading ordinances.
® .:Consultation as required during con_struction. .
-000—
Appendices as cited are attached and complete this report.
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REFERENCES
Abrahamson, N., and Shedlock. K.; editors, 1997, Ground motion attenuation relationships:
Seismological Research Letters, v. 68, no. 1., January 1.997 special issue, 256 p.
Blake, B.F., 1998x, FP.ISKSP v. 3.01b, A Computer Program .for the Probabilistic Estimation of
Peak Acceleration and Uniform Hazard Spectra Using 3-D Faults as Earthquake Sources,
Users Manual, 191. p.
Blake, B.F., 1998b, Preliminary Fault -Data for EQFAULT and FP.ISKSP, 71 p.
Boore, D.M., Joyner; W.B., and Fuinal, T.E.; '1993, Estimation -of Response Spectra and Peal:
Accelerations from Western North American Earthquakes: An, Interim Report; U.S.
Geological Survey Open -File Report 93-509,15 p.
Boore, D.M., Joyner, W.B.; and Fuimal; T.E., 1994, Estimation of Response . Spectra and Peak
Acceleration from Western North Ariierican Earthquakes: An Interim .Report, Part2,
U.S. Geological Survey Open -File Report 94-1.27.
California Department of. Conservation, Division of Mines and Geology: Guidelines for Evaluating
and Mitigating Seismic Hazards in California, Special Publication 117, and WWW Version.
Envicom, Riverside County, 1976, Seismic Safety Element.
Ellsworth, W.L., 1.990, "Earthquake History- 1769-1989" in: The San Andreas Fault System,
California: U.S. Geological Survey Professional Paper 15152,1283 p.
Hart, E.W.,'.and 1994 rev., .Fault -Rupture Hazard Zones in California: California Division of Mines
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