EA 2014-1002 La Quinta Square - Geotechnical Engineering ReportEarth Systems
Southwest
Geotechnical Engineering Report
for Proposed Retail Development
Former Simons Motors Site
Southwest Corner
Highway 111 & Simon Drive
La Quinta, California
Consulting Engineers and Geologists
Earth Systems
'mm7F Southwest
September 4, 2014
ACM La Quinta IV-B LLC
1800 Avenue of the Stars, Suite 105
Los Angeles, California 90067
Attention: Mr. Billy Yeung
Project: Proposed Retail Development (Former Simons Motors Site)
Southwest Corner of Hwy 111 & Simon Drive
La Quinta, California
Subject: Geotechnical Engineering Report
79-811B Country Club Drive
Bermuda Dunes, CA 92203
(760)345-1588
(800)924-7015
FAX (760) 345-7315
File No.: 12287-01
Doc. No.: 14-09-703
Earth Systems Southwest [Earth Systems] is pleased to submit this geotechnical engineering
report for the proposed Retail Development located in the city of La Quinta, California. The
intent of this report is to provide geotechnical information with respect to newly proposed
commercial construction. It is our opinion that it is geotechnically feasible to construct the
proposed retail development at the site as long as the recommendations of this report are
followed in design and construction.
This report completes our scope of services in accordance with our agreement (SWP-13-157R2)
dated September 9, 2013 and revised July 2, 2014. Other services that may be required, such as
plan reviews, responses to agency inquiries, and grading observation are additional services and
will be billed according to the agreed upon Fee Schedule in affect at the time services are
provided. Unless requested in writing, the client is responsible to distribute the report to the
appropriate governing agency and 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 SOUTHWEST O�go
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No. 60302 m
Exp. 61,t.21
Anthony Colarossi, CE 60302
Project Engineer ClVlt \�
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Distribution: 6/ACM La Quinta IV-B LLC
1/BD File
I
TABLE OF CONTENTS
Page
Section1 INTRODUCTION...........................................................................................1
1.1 Background and Project Information............................................................... 1
1.2 Site Description................................................................................................. 2
1.3 Purpose and Scope of Services......................................................................... 2
Section 2 METHODS OF EXPLORATION AND TESTING..................................................5
2.1 Field Exploration............................................................................................... 5
2.2 Laboratory Testing............................................................................................ 6
Section3 DISCUSSION.................................................................................................7
3.1 Geologic Setting................................................................................................ 7
3.2 Expansive Soils................................................................................................ 10
3.3 Groundwater...................................................................................................10
3.4 Geologic Hazards............................................................................................ 10
3.4.1 Seismic Hazards............................................................................................... 10
3.4.2 Secondary Hazards.......................................................................................... 12
3.4.3 Seismic Coefficients........................................................................................ 13
3.5 Retention Basin Infiltration Testing................................................................ 14
Section4 CONCLUSIONS............................................................................................16
Section 5 RECOMMENDATIONS................................................................................18
5.1 Site Development — Grading........................................................................... 18
5.2 Excavations, and Utilities................................................................................ 21
5.3 Foundations.................................................................................................... 22
5.4 Slabs-on-Grade................................................................................................23
f5.5 Corrosive Soils................................................................................................. 25
l 5.6 Retaining Walls and Lateral Earth Pressures .................................................. 25
5.7 Slope Construction.......................................................................................... 27
5.7.1 Surficial Slope Failures.................................................................................... 227
7
5.8 Site Drainage and Maintenance......................................................................
5.9 Streets, Driveways and Parking Areas............................................................ 28
Section 6 LIMITATIONS AND ADDITIONAL SERVICES.................................................32
l 6.1 Uniformity of Conditions and Limitations...................................................... 32
6.
Additional Services.....................................................................................
RE 33
REFERENCES. .35
APPENDIX A
L Plate 1—Site Location Map
Plate 2 — Boring Location Map
Terms and Symbols Used on Boring Logs
Soil Classification System
Logs of Borings (5 pages)
Site Class Estimator (2 pages)
L Settlement Calculations (1 pages)
Seismic Settlement Calculation (5 pages)
APPENDIX B
LLaboratory Test Results
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Table of Contents, continued
APPENDIX C
Figures 2-4 from Earth Systems Past 2002 Report
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September 4, 2014
Section 1
INTRODUCTION
1
Geotechnical Engineering Report
for Proposed Retail Development
Former Simon Motors Site
Southwest Corner
Highway 111 and Simon Drive
La Quinta, California
1.1 Background and Project Information
File No.: 12287-01
Doc. No.: 14-09-703
This Geotechnical Engineering Report has been prepared for the proposed Retail Development
to be located on a currently developed lot located west of Simon Drive and south of the
Highway 111 in the city of La Quinta, Riverside County, California. The purpose of this report is
to summarize the geotechnical conditions of the property and provide geotechnical
recommendations for site development, including recommendations for site grading and
foundation design.
The site address is 78-611 Highway 111 and includes Parcels 1, 2, and 3 of APN 643-220-001
having an area of approximately 3.9 acres. An existing, abandoned automobile dealership and
repair facility currently occupies the site. Due to a request from the client for the urgent
preparation of this geotechnical report, our services were performed prior to demolition of the
existing dealership. We understand the dealership structures, sidewalks, and utility tie-ins will
be demolished as part of redevelopment activities. We have assumed existing structure
footings are on the order of 24 inches deep maximum and a maximum upper three feet will be
disturbed during demolition. Research of 2002 subsurface investigation showed, within the
Main Repair Area, hydraulic car lifts with possible depths of 8 feet below the ground surface
(See Plates 2-4 in Appendix C for approximate locations). Three new retail buildings are
proposed, as shown on Plate 2. The new total building area is approximately 30,250 square feet
with 183 parking spaces and associated drive areas. We assume the proposed structures will be
single story light wood framed or metal stud buildings constructed on concrete slabs with
shallow footings, and will have no below grade levels. Foundation loads are assumed to have a
maximum column load of 30 kips, and a maximum wall loading of 2 kips per linear foot. As the
basis for the foundation recommendations, all loading is assumed to be dead plus actual live
load. No preliminary design loading was provided by the structural engineer. If actual structural
loading exceeds these assumed values, we will need to reevaluate the given recommendations.
Appurtenant construction is anticipated to consist of asphalt concrete paved drives and parking
and underground utilities. Minimal site grading, excluding remedial grading, is anticipated. We
understand below ground drainage structures (drywells) as well as detention basins are
proposed to control storm water. We have assumed underground structures and basins will be
on the order of 60 and 3 feet below grades, respectively. Drywell evaluation is presented by
Earth Systems under separate cover.
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1.2 Site Description
The approximately 3.9 acre site is identified as Assessor's Parcel Map (APN) 643-220-001,
Parcels 1, 2, and 3. The site is located at an approximate latitude and longitude of 33.7125°N
and 116.2930*W, respectively. The site vicinity is shown on Plate 1. The property boundaries
are defined by a Highway 111 to the north, Simon Drive to the east and south, and existing
retail to the west. Topographically, the site is generally flat and level with an elevation of
approximately 75 feet above mean sea level. Drainage of the parking lot is by sheet flow to
Highway 111 and Simon Drive.
At the time of our field exploration, the site consisted of existing constructed Simon Motors
with curb and gutter. Domestic trees and plants, part of the commercial site landscaping, are
spaced within the parking lot. Based on aerial images, the site was graded as part of the overall
commercial site development. The exterior of existing structures appeared in overall decent
condition with minor stucco cracking and minor signs of post -construction settlement; however
concrete slabs for parking and drive areas was settled appreciably with large settlement cracks
and differential settlement offset indicating likely poor compaction control.
It is assumed that underground utilities exist within or immediately adjacent to the proposed
building pad. These utility lines may include but are not limited to domestic water, electric,
sewer, and irrigation lines. Underground storage tanks were noted onsite, with solution voids
and settlement of surrounding backfill noted. Drywells were not observed but are typically used
in the project area.
1.3 Purpose and Scope of Services
The purpose for our services was to evaluate the site soil and groundwater conditions and to
provide professional opinions and recommendations regarding the proposed development.
The scope of services included:
➢ Surficial site conditions were visually assessed and selected published reports were
reviewed, including prior reports by Earth Systems.
➢ Near -surface soil conditions were explored by means of drilling five exploratory borings at
the site. Exploratory borings were accomplished using a truck -mounted drilling rig equipped
with hollow -stem augers and extended to a maximum depth of approximately 50 feet
below the ground surface. The borings were backfilled with soil derived from the drilling.
The boring locations were pre -marked and cleared for underground utilities by
Underground Service Alert. The exposed soil profile were observed relative to soil and
groundwater (if encountered) conditions. Samples of the surface and subsurface materials
were collected at various intervals, logged by our representative, and returned to our
laboratory.
➢ Laboratory testing was performed on selected soil samples obtained from the exploratory
borings. Such testing included unit densities, moisture content, particle size analysis,
collapse potential, expansion potential, moisture -density relationship, R-Value for
pavement evaluation, and soil chemical analyses. These test results aided in the
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classification and evaluation of the pertinent engineering properties of the various soils
encountered.
➢ Engineering analysis of the data generated from this study was performed and this written
report prepared to present our findings and recommendations, including the following:
• A description of the proposed project including a site plan showing the approximate
boring locations;
• A description of the surface and subsurface site conditions including groundwater
conditions, as encountered in our field exploration;
• A description of the site geologic setting and possible associated geology -related
hazards, including a liquefaction, subsidence, and seismic settlement analysis;
• A discussion of regional geology and site seismicity;
• A description of local and regional active faults, their distances from the site, their
potential for future earthquakes;
• A discussion of other geologic hazards such as ground shaking, landslides, flooding, and
tsunamis;
• A discussion of site conditions, including the geotechnical suitability of the site for the
general type of construction proposed;
• Recommendations for geotechnical seismic design coefficients in accordance with the
2013 California Building Code;
• Recommendations for imported fill (if required) for use in compacted fills;
• Recommendations for foundation design including parameters for shallow foundations,
and subgrade preparation;
• Anticipated total and differential settlements for the recommended foundation
system;
• Recommendations for site preparation, earthwork, and fill compaction specifications
Iconsidering the demolition of the existing structures;
L
• Discussion of anticipated excavation conditions;
• Recommendations for underground utility trench backfill;
• Recommendations for slabs -on -grade, including recommendations for reducing the
potential for moisture transmission through interior slabs.
• Recommendations for collapsible or expansive soils (if applicable).
• Preliminary recommendations for parking and drive Asphalt Concrete and Portland
cement concrete pavement.
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• A discussion of the corrosion potential of the near -surface soils encountered during our
field exploration.
• An appendix, which will include a summary of the field exploration and laboratory
testing program.
Infiltration Testing for Storm Water Detention Basins
In general accordance with the guidelines of the city of La Quinta, the scope of services for the
infiltration testing for storm water retention consisted of the following:
➢ Three borings were drilled at the proposed location of three of the retention basins and
backfilled with perforated PVC pipe. The borings were pre -saturated with potable water the
day before testing.
➢ Field percolation testing of the borings was performed using the falling -head test method at
depth of 3 to 5 feet below existing grades (assumed approximate basin bottom elevation).
The data was organized and evaluated to identify subsurface site characteristics and site -
specific infiltration rates for storm water disposal at the elevation of the bottom of the
retention basins. The results of this evaluation will be presented therein.
Not Contained in This Report: Although available through Earth Systems, the current scope of
our services does not include:
➢ An environmental assessment.
➢ A study 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.
The client did not direct Earth Systems to provide any service to study or detect the presence of
moisture, mold, or other biological contaminates in or around any structure, or any service that
was designed or intended to prevent or lower the risk or the occurrence of the amplification of
the same. Client is hereby informed that mold is ubiquitous to the environment, with mold
amplification occurring when building materials are impacted by moisture. Site conditions are
outside of Earth Systems' control, and mold amplification will likely occur or continue to occur
in the presence of moisture. As such, Earth Systems cannot and shall not be held responsible
for the occurrence or recurrence of mold.
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Section 2
METHODS OF EXPLORATION AND TESTING
2.1 Field Exploration
Five exploratory borings were drilled to depths ranging from about 30 to 51%2 feet below the
existing ground surface to observe soil profiles and obtain samples for laboratory testing. The
borings were drilled on August 4, 2014 using 8-inch outside diameter hollow -stem augers,
powered by a Mobile B61 truck -mounted drill rig operated by Cal Pac Drilling of Calimesa,
California, under subcontract to Earth Systems Southwest. In addition to the geotechnical
borings, two borings were drilled for a previous report by Earth Systems Southwest (2014),
Evaluation of Drywell Percolation Rates Proposed Retail Development SWC Highway 111 &
Simon Drive La Quinta, California, File No. 12287-01, Document No. 14-08-742.
The boring locations are shown on the Boring Location Map, Plate 2, in Appendix A. The
locations shown are approximate, established by consumer grade Global Positioning System
(GPS) accurate to approximately 15 feet in conjunction with pacing based upon the control
provided.
A representative from Earth Systems maintained a log of the subsurface conditions
encountered and obtained samples for visual observation, classification and laboratory testing.
Soils were logged in general accordance with the Unified Soil Classification System. Our typical
sampling interval within the borings was approximately every 2% to 5 feet to the full depth
explored; however, sampling intervals were adjusted depending on the materials encountered
onsite. Samples were obtained within the test borings using a Standard Penetration [SPTJ
sampler (ASTM D 1586) and a Modified California [MC] ring sampler (ASTM D 3550 with those
similar to ASTM D 1586). The SPT sampler has a 2-inch outside diameter and a 1.38-inch inside
diameter. The MC sampler has a 3-inch outside diameter and a 2.4-inch inside diameter.
Samplers were mounted to the end of screwed drill rod and were driven using a 140 pound
automatic hammer falling 30 inches.
Design parameters provided by Earth Systems in this report have considered an estimated 70%
hammer efficiency. The number of blows necessary to drive either a SPT sampler or a MC type
ring sampler within the borings was recorded. Since the MC sampler was used in our field
exploration to collect ring samples, the N-values using the California sampler can be roughly
correlated to SPT N-values using a conversion factor that may vary from about 0.5 to 0.7. In
general, a conversion factor of approximately 0.63 from a study at the Port of Los Angeles
(Zueger and McNeilan, 1998) is considered satisfactory. A value of 0.63 was applied in our
calculations for this project.
Bulk samples of the soil materials were obtained from the drill auger cuttings, representing a
mixture of soils encountered at the depths noted. Following drilling, sampling, and logging the
borings were backfilled with native cuttings and tamped upon completion.
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
exploration. The final logs are included in Appendix A of this report. The stratification lines
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represent the approximate boundaries between soil types, although the transitions may be
gradational. In reviewing the boring logs and legend, the reader should recognize that the
legend is intended as a guideline only, and there are a number of conditions that may influence
the soil characteristics as observed during drilling and sounding. These include, but are not
limited to, the presence of cobbles or boulders, cementation, variations in soil moisture,
presence of groundwater, and other factors. The logs present field blowcounts per 6 inches of
driven embedment (or portion thereof) for a total driven depth attempted of 18 inches. The
blowcounts are uncorrected (i.e. not corrected for overburden, sampling, etc.). Consequently,
the user must correct the blowcounts per standard methodology if they are to be used for
design and exercise judgment in interpreting soil characteristics, possibly resulting in soil
descriptions that vary somewhat from the legend.
2.2 Laboratory Testing
Samples were reviewed along with field logs to select those that would be analyzed further.
Those selected for laboratory testing include, but were not limited to, soils that would be
exposed and those deemed to be within the influence of the proposed structures. Test results
are presented in graphic and tabular form in Appendix B of this report. Testing was performed
in general accordance with American Society for Testing and Materials (ASTM) or other
appropriate test procedure. Selected samples were also tested for a screening level of corrosion
potential (pH, electrical resistivity, water-soluble sulfates, and water-soluble chlorides). Earth
Systems does not practice corrosion engineering; however, these test results may be used by a
qualified corrosion engineer in designing an appropriate corrosion control plan for the project.
Our current testing program consisted of the following:
➢ Density and Moisture Content of select samples of the site soils collected (ASTM D 2937 &
2216).
➢ Maximum density tests to evaluate the moisture -density relationship of typical soils
encountered (ASTM D 1557).
➢ Particle Size Analysis to classify and evaluate soil composition. The gradation characteristics
of selected samples were made by sieve analysis procedures (ASTM D 6913).
➢ Consolidation (Collapse Potential) to evaluate the compressibility and hydroconsolidation
(collapse) potential of the soil upon wetting (ASTM D 5333 and D 2435).
➢ Expansion Index tests to evaluate the expansive nature of the soil. The samples were
surcharged under 144 pounds per square foot at moisture content of near 50% saturation.
Samples were then submerged in water for 24 hours and the amount of expansion was
recorded with a dial indicator (ASTM D 4829).
➢ Screening Level Chemical Analyses (Soluble Sulfates and Chlorides (ASTM D 4327), pH
(ASTM D 1293), and Electrical Resistivity/Conductivity (ASTM D 1125) to evaluate the
potential for adverse effects of the soil on concrete and steel.
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Section 3
DISCUSSION
3.1 Geologic Setting
Regional Geology: 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 large northwest -trending structural depression that
extends approximately 180 miles from the San Gorgonio Pass 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 part of the Salton Trough and contains a thick
sequence of Miocene to Holocene sedimentary deposits. 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
southwest. These mountains expose primarily Precambrian metamorphic and 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 Geology: The project site is located in the western portion of the Coachella Valley. The
upper sediments observed onsite consists of artificial fill overlying native lacustrine deposits
(Ancient Lake Cahuilla) composed of silts and clays with varying amounts of fine grained sand.
Bedrock was not identified. There are no active faults currently mapped within the project
limits.
Site Soil Conditions: The field exploration indicates that site soils consist generally of about 5
feet of artificial fill overlying native lacustrine and eolian wind driven sand and silt deposits to
the maximum depth of exploration of 51% feet below the ground surface. Soils are
predominantly sands and silts (SP-SM, SM, ML, and CL soil types per the Unified Soil
Classification System).
The site lies within an area of moderate to high potential for wind and water erosion. Fine
particulate matter (PM10) can create an air quality hazard if dust is blowing. Watering the
surface, planting grass or landscaping, or placing hardscape normally mitigates this hazard.
The boring logs provided in Appendix A include more detailed descriptions of the soils
encountered. Site soils are classified as Type C in accordance with Cal0SHA.
Collapse Potential: In arid 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.
The degree of collapse of a soil can be defined by the Collapse Potential [CP] value, which is
expressed as a percent of collapse of the total sample using the Collapse Potential Test (ASTM
Standard Test Method D 5333). Based on Naval Facilities Engineering Command [NAVFAC]
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Design Manual 7.01, the severity of collapse potential is commonly evaluated by the following
Table 1, Collapse Potential Values.
Table 1
Collapse Potential Values
(NAVFAC 7.01, 1986)
Collapse Potential Value
Severity of Problem
0-1%
No Problem
1-5%
Moderate Problem
5-10%
Trouble
10-20%
Severe Trouble
> 20%
Very Severe Trouble
For this study, soil samples were tested for consolidation at corresponding approximate
overburden pressures from depths where the samples were collected including potential loads
from foundations and fill placement overburden. The results of collapse potential tests
performed on selected samples from different depths indicated a range of collapse potential on
the order of 0.4% to 0.8% percent at applied vertical stresses of 2,000 psf (1 at 4,000 psf). It is
our opinion that the site soils have a low potential for collapse at depth and a low potential in
the upper soil.
Corrosion Potential: One sample of the near -surface soil within the proposed site was tested for
potential to corrosion of concrete and ferrous metals. The tests were conducted in general
accordance with ASTM procedures to evaluate pH, resistivity, and water-soluble sulfate and
chloride content. Test results show a pH value of 8.3, chloride content of 13 ppm, sulfate
content of 797 ppm and a minimum resistivity of 5,747 Ohm -cm. These tests should be
considered as only an indicator of corrosivity for the samples tested. Other earth materials
found on site may be more, less, or of a similar corrosive nature.
Water-soluble sulfates in soil can react adversely with concrete. ACI 318 provides the
relationship between corrosivity to concrete and sulfate concentration, presented in the table
below:
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Table 2
Water -Soluble Sulfate in Soil
(PPm)
Corrosivity to Concrete
0-1,000
Negligible
1,000 — 2,000
Moderate
2,000 — 20,000
Severe
Over 20,000
Very Severe
In general, the lower the pH (the more acidic the environment), the higher the soil corrosivity
will be with respect to ferrous structures and utilities. As soil pH increases above 7 (the neutral
value), the soil is increasingly more alkaline and less corrosive to buried steel structures, due to
protective surface films, which form on steel in high pH environments. A pH between 5 and 8.5
is generally considered relatively passive from a corrosion standpoint. High chloride levels tend
to reduce soil resistivity and break down otherwise protective surface deposits, which can
result in corrosion of buried steel or reinforced concrete structures. Soil resistivity is a measure
of how easily electrical current flows through soils and is the most influential factor. Based on
the findings of studies presented in ASTM STP 1013 titled "Effects of Soil Characteristics on
Corrosion" (February, 1989), the approximate relationship between soil resistivity and soil
corrosivity was developed as shown in Table 3.
Table 3
Soil Resistivity
(Ohm -cm)
Corrosivity to Ferrous Metals
0 to 900
Very Severely Corrosive
900 to 2,300
Severely Corrosive
2,300 to 5,000
Moderately Corrosive
5,000 to 10,000
Mildly Corrosive
10,000 to >100,000
Very Mildly Corrosive
The onsite values can potentially change based on several factors, such as importing soil from
Il another job site and the quality of water used during construction and subsequent landscape
irrigation. Although Earth Systems does not practice corrosion engineering, the corrosion values
from the soil tested are normally considered as being severely to very severely corrosive to
buried metals and as possessing a "negligible" to borderline "moderate" exposure to sulfate
attack for concrete as defined in American Concrete Institute [ACI] 318, Section 4.3. Concrete
mixes should be designed in accordance with ACI procedures for the soils encountered.
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3.2 Expansive Soils
Expansive soils are characterized by their ability to undergo significant volume change (shrink or
swell) due to variations in moisture content. Changes in soil moisture content can result from
rainfall, landscape irrigation, utility leakage, roof drainage, perched groundwater, drought, or
other factors, and may cause unacceptable settlement or heave of structures, concrete slabs
supported -on -grade, or pavements supported over these materials. Depending on the extent
and location below finished subgrade, expansive soils can have a detrimental effect on
structures. Based on our laboratory testing, the Expansion Index of the onsite fill soils in which
the structure is anticipated to be founded is typically "very low" as defined by ASTM D 4829.
Sampling of the final grade soils should be performed to confirm or modify these findings.
3.3 Groundwater
Free groundwater was not encountered in the borings advanced for this study to a maximum
depth of approximately 51 below the current ground surface. The site has an approximate
surface elevation of 75 ft. Coachella Valley Water District historical map data suggests a historic
shallow groundwater elevation of approximately 0 feet (DWR Bulletin 108, 1961) or a depth to
groundwater of approximately 75 feet below the ground surface.
The depth to groundwater in a well located approximately 0.22 miles northeast of the site and
at a ground surface elevation of 76 feet, was recorded as approximately -102 foot elevation in
March, 2014 (Well No. 337132N1162893W001). The depth to groundwater in a well located
approximately 3.3 miles southwest of the site and at a ground surface elevation of 91 feet, was
recorded as approximately -125 feet elevation (Well No. 336670N1163087WO01). Elevated
moisture contents were noted within various fine grained soil layers in the borings; however
moisture contents of sandy soils above and below the elevated moisture content layers showed
low moisture content, indicating perched water conditions were not present.
3.4 Geologic Hazards
Geologic hazards that may affect the region include seismic hazards (ground shaking, surface
fault rupture, soil liquefaction, and other secondary earthquake -related hazards), ground
subsidence, slope instability, flooding, and erosion. A discussion follows on the specific hazards
to this site.
3.4.1 Seismic Hazards
Seismic Sources: Approximately 40 active faults or seismic zones lie within 55 miles of the
project site. The primary seismic hazard to the site is strong ground shaking from earthquakes
along regional faults including the San Andreas and San Jacinto faults. The San Andreas fault is
located approximately 5.6 miles northeast of the site.
Surface Fault Rupture: The project site does not lie within a currently delineated State of
California, Alquist-Priolo Earthquake Fault Zone (Bryant, 2007). Well -delineated fault lines cross
through this region as shown on California Geological Survey [CGS] maps (Jennings, 2010);
however, no active faults are mapped in the immediate vicinity of the site. Therefore, active
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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 in the last 100 years. They are as follows:
➢ Desert Hot 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 La
Quinta area.
➢ Palm Springs Earthquake — A magnitude 5.9 ML (6.2MW) earthquake occurred on July 8,
1986 in the Painted Hills, causing minor surface creep of the Banning segment of the San
Andreas fault. This event was strongly felt in the La Quinta area and caused structural
damage, as well as injuries.
➢ Joshua Tree Earthquake — On April 22, 1992, a magnitude 6.1 ML (6.1MW) earthquake
occurred in the mountains 9 miles east of Desert Hot Springs. Structural damage and minor
injuries occurred in the Coachella Valley as a result of this earthquake.
➢ Landers and Big Bear Earthquakes — Early on June 28, 1992, a magnitude 7.5 MS (7.3MW)
earthquake occurred near Landers, the largest seismic event in Southern 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 (6.4MW)
earthquake occurred near Big Bear Lake. No significant structural damage from these
earthquakes was reported in the La Quinta area.
➢ Hector Mine Earthquake — On October 16, 1999, a magnitude 7.1MW earthquake occurred
on the Lavic Lake and Bullion Mountain faults north of Twentynine Palms. While this event
[ was 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 analyses. In 2002 and 2008, the California Geological Survey (CGS] and
the USGS completed of probabilistic seismic hazard maps. We have used these maps in our
evaluation of the seismic risk at the site. The recent Working Group of California Earthquake
Probabilities (WGCEP, 2008) estimated a 58% conditional probability that a magnitude 6.7 or
greater earthquake may occur between 2008 and 2038 along the southern segment of the San
Andreas fault.
The primary seismic risk at the site is a potential earthquake along the San Andreas fault that is
Labout 2.5 miles from the site and is considered as fault Type A per the CGS. Geologists believe
that the San Andreas fault has characteristic earthquakes that result from rupture of each fault
segment. The estimated mean characteristic earthquake is magnitude 7.7 for the Southern
Segment of the fault (USGS, 2002). However, recent standard of practice suggest a maximum
magnitude of 8.2 be used for analysis, assuming a multi -segment rupture event.
lThis segment has the longest elapsed time since rupture of any part of the San Andreas fault.
The last rupture occurred about 1680 AD, based on dating by the USGS near Indio
(WGCEP, 2008). 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
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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
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
subsidence, tsunamis, and seiches. The site is far inland, so the hazard from tsunamis is non-
existent. At the present time, no water storage reservoirs are located in the immediate vicinity
of the site such that the site is not in an inundation zone assuming reservoir failure.
Seiches: There are no ponds or reservoirs in the immediate vicinity of the site. Therefore, the
potential for seiching is currently considered negligible.
Soil Liquefaction and Lateral Spreading: Liquefaction is the loss of soil strength from sudden
shock (usually earthquake shaking), causing the soil to become a fluid mass. Liquefaction
describes a phenomenon in which saturated soil loses shear strength and deforms as a result of
increased pore water pressure induced by strong ground shaking during an earthquake.
Dissipation of the excess pore pressures will produce volume changes within the liquefied soil
layer, which can cause settlement. Shear strength reduction combined with inertial forces from
the ground motion may also result in lateral migration (lateral spreading). Factors known to
influence liquefaction include soil type, structure, grain size, relative density, confining
pressure, depth to groundwater, and the intensity and duration of ground shaking. Soils most
susceptible to liquefaction are saturated, loose sandy soils and low plasticity clay and silt. The
results of our analyses indicate that historic groundwater depth is below 50 feet and therefore
the liquefaction potential is low. Drywell evaluation by Earth Systems (prepared under separate
cover) indicated saturated conditions which may develop in the immediate vicinity of the
drywell after a design storm will dissipate quickly. As such the potential for a design storm
event, and a design seismic event to occur concurrently are considered low.
We estimated seismically induced settlements in general accordance with methods developed
Lby Tokimatsu and Seed (1987), the 1996 NCEER and 1998 NCEER/NSF workshops on
liquefaction, and considered information provided in Recommended Procedures for
Implementation of DMG Special Publication 117, Guidelines for Analyzing and Mitigating
Liquefaction Hazards in California, published by Southern California Earthquake Center (SCEC),
dated March 1999 and Guidelines for Analyzing and Mitigating Seismic Hazards in California,
Special Publication 117A, published by California Geological Society (CGS), 2008. Our analysis
l incorporated multi -directional shaking and used a Design Earthquake ground motion of
(2/3)(PGAM) = 0.417g as allowed by CGS (Jennifer Thornburg, 2014) associated with a
magnitude 8.2 earthquake (multi -segment rupture of the San Andreas fault). We used a historic
groundwater depth of 75 feet. Minor seismic induced consolidations of soils above the
groundwater table are estimated to be on the order of 0.8 inches total and 0.3 inches
differential settlement.
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The potential for liquefaction induced lateral spreading under the proposed project is
considered low as no free -face or sloping ground conditions exist in the immediate vicinity of
the project. And the potential for liquefaction is low. As such the potential for lateral spreading
is considered low.
The total seismically induced settlement is exclusive and independent of any static settlement
that may occur from foundation loads. The potential for total and differential static settlements
is addressed in a later Section of this report. Typically, structural mitigation is acceptable when
total settlements are small. Per SP117A (2008, page 54), Youd (1989), citing data from Japan,
suggests that structural mitigation may be acceptable where displacements of less than one
foot horizontal and less than four inches vertical are predicted. Therefore, for this paper, large-
scale ground displacements are defined as those that exceed 1-3 feet horizontally and 4-6 inches
vertically. The maximum settlement calculated for this site is approximately 0.3 inches.
Therefore per SP117A (2008, page 54), this site does not qualify as having large scale
displacements.
Subsidence: The project site is within an "active" subsidence zone as designated by Riverside
County (Riverside County Transportation and Land Management Agency land information
website (RCLIS, March, 2012)); however, the site is not within an area of known damaging
subsidence as the subsidence is generally occurring on an areal basis. (USGS zone of subsidence
monitoring in the Coachella Valley, Sneed, 2014).
Flooding: FEMA Panel Number 06065C2233G shows the area outside of the flood zone `X'
except on Highway 111 and Simon Drive. The project site is in an area where sheet flooding and
erosion could occur. Appropriate project design by the civil engineer, construction, and
maintenance can minimize flooding potential from flows coming from Highway 111 and Simon
Drive.
3.4.3 Seismic Coefficients
This site is subject to strong ground shaking due to potential fault movements along regional
Lfaults including the San Andreas and San Jacinto faults. Engineered design and earthquake -
resistant construction increase safety and allow development of seismic areas. The minimum
seismic design should comply with the 2013 edition of the California Building Code [CBC] and
ASCE 7-10 (with July 2013 errata) using the seismic coefficients given in the table below. We
have classified this site as Site Class D. Seismic parameters are based upon computation by the
I Ground Motion Parameter Calculator provided by the United States Geological Survey [USGS]
l_ at: http://earthquake.usgs.gov/designmaps/us/application.php (May 16, 2014).
2013 CBC (ASCE 7-10 w/ July 2013 errata) Seismic Parameters
Site Location: 33.71249'N/116.29302°W
I Site Class: D
l Maximum Considered Earthquake [MCE] Ground Motion
Short Period Spectral Response SS: 1.550 g
1 second Spectral Response, S1: 0.733 g
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Design Earthquake Ground Motion
Short Period Spectral Response, SDS 1.033 g
1 second Spectral Response, SD1 0.733 g
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The intent of the CBC lateral force requirements are 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,
damage is allowed. The CBC lateral force requirements should be considered a minimum
design. The owner and the designer may evaluate the level of risk and performance that is
acceptable. Performance based criteria could be set in the design. The design engineer should
exercise special care so that all components of the design are fully met with 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 major seismic sources. Design peak
horizontal ground accelerations are estimated to approximately 0.627 g (PGAM). Vertical
accelerations are typically 1/3 to 2/3 of the horizontal acceleration, but can equal or exceed
horizontal accelerations depending upon underlying geologic conditions and basin effects.
3.5 Retention Basin Infiltration Testing
The site soils within the proposed retention basin areas consisted of silt and silty sand soils. To
evaluate the soils encountered, three infiltration tests were performed; P-1 at the southwest
corner of the site, P-2 at the south corner of the site and P-3 south of the northeast corner of
the site (see Plate 2 Test Location Map). Tests were performed at three locations, as indicated
on Plate 2. Three 6 inch diameter borings were drilled at the proposed locations of the
retention basin and backfilled with perforated PVC pipe and gravel to minimize soil caving. The
presence of gravel and the PVC pipe were accounted for in the infiltration rate calculation. The
borings were pre -saturated with potable water prior to testing. Field percolation testing of the
borings was performed using the falling -head test method at depths of 2.5 to 6 below existing
grade at the test locations. Infiltration rates were corrected to consider mainly vertical flow
typical of the conditions in retention basins (Hvorslev, 1949).
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Table 4
Retention Basin Infiltration Results
Test
Zone
Estimated
Test
Pit
Test
Description
Soil Condition
USCS Soil Description in Test Zone
Below
Basic
Existing
Infiltration
Grade
Rate*
(feet)
P-1
Falling Head
Alluvium
SM Silty fine Sands
2.5-6
1.0 in/hr
P-2
Falling Head
Alluvium
SM Silty fine Sands
2.5-6
0.6 in/hr
P-3
ik r:-IJ
Falling Head
Alluvium
SM Silty fine Sands
2.5-6
0.25 in/hr
• �•�. .a...... Iry 1.11wI V ac CLy OPP ICU. lyplLdl Idllvrs oT sareiy range Trom i to 1z depending on the type of
system which will be designed using the field values and depending on the level of pre-treatment and influent
which will be discharged into the basins (Riverside County Stormwater Quality Design Handbook, 2006).
Test results indicate similar infiltration rates. Additionally, our exploration indicates similar
upper soil types across the site to those tested. Please refer to Section 5.8 for design and
maintenance recommendations.
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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 literature and the site evaluation.
General:
➢ From a geotechnical perspective, the site is suitable for the proposed development,
provided the recommendations in this report are followed in the design and construction of
this project.
Geotechnical Constraints and Mitigation:
➢ The primary geologic hazard is severe ground shaking from earthquakes originating on
regional faults. A major earthquake above magnitude 7 to 8 originating on the local
segment of the San Andreas or nearby fault zones would be the critical seismic event that
may affect the site within the design life of the proposed development. Engineered design
and earthquake -resistant construction increase safety and allow development of seismic
areas.
➢ The underlying geologic condition for seismic design is Site Class D. A qualified professional
should design any permanent structure constructed on the site. The minimum seismic
f design should comply with the 2013 edition of the California Building Code.
➢ The site is about 5.6 miles from a Type A seismic source as defined in the California
Geological Survey. A qualified professional should design any permanent structure
constructed on the site. The minimum seismic design should comply with the 2013 edition
of the California Building Code.
➢ The soils are susceptible to wind and water erosion. Preventative measures to reduce
seasonal flooding and erosion should be incorporated into site grading plans. Dust control
should also be implemented during construction. Site grading should be in strict compliance
Lwith the requirements of the South Coast Air Quality Management District [SCAQMD].
➢ Other geologic hazards, including fault rupture, liquefaction, seismically induced flooding,
and lateral spreading are considered low.
➢ Based on our laboratory testing, the Expansion Index of the onsite fill soils in which the
structure is anticipated to be founded is typically "very low" as defined by ASTM D 4829.
Sampling of the final grade soils should be performed to confirm or modify these findings as
there could be soils onsite which are more expansive.
➢ Site soils are "mildly" corrosive to buried metallic elements and are "low" to borderline
"moderate" for sulfate exposure. See Section 3.1 and 5.5 for further information. Site soils
should be reviewed by a corrosion engineer.
➢ The site is within an area being studied by the USGS for groundwater withdrawl subsidence.
Currently the site is outside the defined area where damaging settlement has occurred.
l Groundwater overdraft is occurring in the Coachella Valley on a regional level and must be
addressed ultimately on a regional level through decreased pumping and increased
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recharge. It is important to emphasize that increased pumping and continued groundwater
overdraft may lead to increased subsidence related settlement which is impossible to
predict the magnitude of given the current level of information. If differential pumping
occurs, subsidence and the damaging effects of differential settlement occur.
➢ Site soils are non -uniform and generally in a loose to compact condition. Site demolition will
further disturb site soils. Overexcavation and recompaction is required to reduce the
potential for settlement by providing a compacted fill mat below foundations in order to
better distribute loading.
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Section 5
RECOMMENDATIONS
5.1 Site Development —Grading
A representative of Earth Systems should observe site clearing, grading, and the bottoms of
excavations before placing fill. Local variations in soil conditions may warrant increasing the
depth of recompaction and over -excavation.
Proper geotechnical observation and testing during construction is imperative to allow the
geotechnical engineer the opportunity to verify assumptions made during the design process,
to verify that our geotechnical recommendations have been properly interpreted and
implemented during construction, and is required by the 2013 California Building Code.
Observation of fill placement by the Geotechnical Engineer of Record should be in conformance
with Section 17 of the 2013 California Building Code. California Building Code requires full time
observation by the geotechnical consultant during site grading (fill placement). Therefore, we
recommend that Earth Systems be retained during the construction of the proposed
improvements to provide testing and observe compliance with the design concepts and
geotechnical recommendations, and to allow design changes in the event that subsurface
conditions or methods of construction differ from those assumed while completing our
previous study. Additionally, the California Building Codes requires the testing agency to be
employed by the project owner or representative (i.e. architect) to avoid a conflict of interest if
employed by the contractor.
Clearing and Grubbing: At the start of site grading, existing vegetation, pavement, irrigation
Lsystems, undocumented fill, construction debris, trash, hydraulic cylinder lift footings and
underground utilities should be removed from the proposed building pad and improvement
areas. Onsite artificial fill may be reused once removed to allow processing of the underlying
soil in accordance with the grading recommendations. Oversize material, trash, debris,
vegetation (greater than 1% organic content), etc. should be removed prior to use as
engineered fill.
` Undocumented fill and car lifts, and buried utilities and tanks may be located in the vicinity of
the planned structures and within other areas of the project site. All buried structures which
are removed should have the resultant excavation backfilled with soil compacted as engineered
fill described herein or with a minimum 2-sack sand slurry approved by the project geotechnical
L engineer. Abandoned utilities should be removed entirely, or pressure -filled with concrete or
grout and be capped. Buried utilities should not extend under building limits. The geotechnical
engineer or his representative should be retained during demolition to observe removal of
buried objects and document removal depths. Additional recommendations may apply
depending on the type of conditions exposed.
Subsequent to stripping and grubbing operations, areas to receive fill should be stripped of
loose or soft earth materials until a uniform, firm subgrade is exposed, as evaluated by the
geotechnical engineer or geologist. Prior to the placement of fill or subsequent to cut, the
I existing surface soils within the building pads and improvement areas should be over -excavated
L as follows:
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Pad Preparation: Due to the non -uniform and variable low -density of shallow soils, the existing
soils within the building pad and foundation areas should be over -excavated a minimum of 6
feet below existing or finished grade, or two feet below the bottom of the deepest foundation,
whichever is lower. The exposed subgrade should be observed and tested by the geotechnical
engineer or his representative to verify that an in -place density of the subgrade is at or greater
than 85% or soils are firm (as determined by the geotechnical engineer). Deeper over -
excavation may be recommended if the required in -place density is not achieved or soils are
not firm.
Once the subgrade is attained and approved, the surface should be scarified an additional 12
inches, moisture conditioned to near optimum moisture and recompacted to a minimum of
90% relative compaction per ASTM D 1557. Moisture conditioned, compacted engineered fill
should then be placed to finished grade. The over -excavation should extend for at least 5 feet
beyond the outer edge of the building pad and include all exterior footings or slabs, where
possible, and include any overhead canopy/or covered walkway and patio areas.
Hydraulic Car Lifts
Although not observed during the investigation due to non -entry into interior spaces, but
documented during a 2002 environmental investigation, hydraulic car lifts may exist. The
depths below slab grade are unknown at this time and without documentation of installation,
remediation will be feature and condition specific. For construction budgeting reasons, removal
of hydraulic car lifts should include existing backfill, removal of contaminated soil, and footing
removal followed by structural fill placement as noted in the recommendations section. All lifts
should be observed by the geotechnical consultant during removal to document removal
depths and provide compaction testing of backfill
Auxiliary Structures Subgrade Preparation: Auxiliary structures such as garden, trash enclosure,
or retaining walls should have the foundation subgrade prepared similar to the building pad
recommendations given above depending on their location. The lateral extent of the over -
excavation needs only to extend 2 feet beyond the face of the footing. Moisture conditioned,
compacted engineered fill should then be placed to finished grade.
Subgrade Preparation: In areas to receive fill not supporting structures or lightly loaded
hardscape (i.e. no vehicle traffic), the subgrade should be overexcavated; moisture conditioned,
and compacted to at least 90% relative compaction (ASTM D 1557) for a depth of 2 feet below
existing or finished subgrade, whichever is lower. Compaction should be verified by testing.
Pavement Area Preparation: In street, drive, and permanent parking areas, the exposed
subgrade should be over -excavated, scarified, moisture conditioned, and compacted to at least
90% relative compaction (ASTM D 1557) for a depth of 2 feet below existing grade or finish
grade (whichever is deeper). Engineered fill should then be moisture conditioned, placed in
suitable lifts, and compacted to a minimum of 90% relative compaction to finish grade, with the
upper 1 foot compacted to at least 95% relative compaction. Compacted fill should be placed to
finish subgrade elevation. Compaction should be verified by testing.
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All over -excavations should extend to a depth where the project geologist engineer or his
representative has deemed the exposed soils as being suitable for receiving compacted fill The
materials exposed at the bottom of excavations should be observed by a geotechnical engineer
or geologist from our office prior to the placement of any compacted fill soils to verify that all
old fill is removed. Additional removals may be required as a result of observation and/or
testing of the exposed subgrade subsequent to the required over -excavation
Engineered Fill Soils: The native soil is suitable for use as engineered fill and utility trench
backfill provided it is free of significant organic or deleterious matter (less than 1%), debris,
concrete, and oversize rock. Construction debris, concrete, asphalt, etc. is not suitable for
placement within fill in building pads, but concrete or asphalt may be processed to smaller than
1-inch in maximum dimension and blended with parking lot fills. Blending should be performed
such that the fill remains substantially soil rather than nested processed material. Unprocessed
materials should be hauled offsite.
Within areas to receive foundations and slabs -on -grade the fill should be "very low" in
expansion potential. Expansive soils which are identified should be removed and replaced with
low permeability soils which are "very low" in expansion potential.
All fill should be placed in maximum 8-inch lifts (loose thickness), moisture conditioned to near
optimum moisture content, and compacted to at least 90 percent relative compaction in
general accordance with ASTM D 1557 (current edition). In parking and drive areas the upper
one foot of subgrade and all aggregate base should be compacted to a minimum of 95 percent
relative compaction. Compaction should be verified by testing. In general, rocks larger than 6
inches in greatest dimension should be removed from fill or backfill material. All soils should be
moisture conditioned prior to application of compactive effort. Moisture conditioning of soils
refers to adjusting the soil moisture to just above optimum moisture content. If the soils are
overly moist so that instability occurs, or if the minimum recommended compaction cannot be
readily achieved, it may be necessary to aerate to dry the soil to optimum moisture content or
use other means to address soft soils.
Soils which are found to have expansive potential greater than "very low" to "low" will require
differing compaction and moisture conditioning requirements which should be provided on a
case by case basis for each specific building location.
A program of compaction testing, including frequency and method of test, should be developed
by the project geotechnical engineer at the time of grading. Acceptable methods of testing may
include Nuclear methods such as those outlined in ASTM D 6938 (Standard Test Methods for In -
Place Density and Water Content of Soil and Soil -Aggregate by Nuclear Methods) or correlated
hand -probing.
Shrinkage: The shrinkage factor for earthwork is expected to range from 15 to 25% for the
upper excavated or scarified site soils. Shrinkage and construction related subsidence are highly
dependent on and may vary with contractor methods for compaction. Losses from site clearing,
oversize material, and removal of existing site improvements may affect earthwork quantity
calculations and should be considered.
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5.2 Excavations, and Utilities
Excavations should be made in accordance with OSHA requirements. Using the OSHA standards
and general soil information obtained from the field exploration, classification of the near
surface on -site soils will likely be characterized as Type C. Actual classification of site specific
soil type per OSHA specifications as they pertain to trench safety should be based on real-time
observations and determinations of exposed soils by the contractors Competent Person (as
defined by OSHA) during grading and trenching operations.
Our site exploration and knowledge of the general area indicates there is a moderate potential
for caving and slaking of site excavations (overexcavation areas, utilities, footings, etc.). Where
excavations over 4 feet deep are planned lateral bracing or appropriate cut slopes of 1%:1
(horizontal/vertical) should be provided. No surcharge loads from stockpiled soils or
construction materials should be allowed within a horizontal distance measured from the top of
the excavation slope and equal to the depth of the excavation.
Excavations which parallel structures, pavements, or other flatwork, should be planned so that
they do not extend into a plane having a downward slope of 1.5:1 (horizontal: vertical) from the
bottom edge of the footings, pavements, or flatwork. Shoring or other excavation techniques
may be required where these recommendations cannot be satisfied due to space limitations or
foundation layout. Where overexcavation will be performed adjacent to existing structures,
ABC slot cutting techniques may be used. The width of the slot cuts will depend on the soils
encountered at the point of excavation (slot cut widths are generally no greater than 5 to 8 feet
and excavated in an alternating A then B, then C pattern to minimize disturbance and
undermining to the existing foundations).
Utilities and Trenches: Backfill of utilities within roads 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 90% relative
compaction per ASTM D 1557. Backfill operations should be observed and tested to monitor
compliance with these recommendations. The trench bottom should be in a firm condition
prior to placing pipe, bedding, or fill.
Under pavement sections, the upper 12 inches of trench backfill soil below the pavement
section should be compacted to at least 95 percent relative compaction (ASTM D 1557). Backfill
materials should be brought up at substantially the same rate on both sides of the pipe or
conduit. Reduction of the lift thickness may be necessary to achieve the above recommended
compaction. Mechanical compaction is recommended; ponding or jetting is not recommended.
In general, coarse -grained sand and/or gap graded gravel (i.e. 3/-inch rock or pea -gravel, etc.)
should not be used for pipe/conduit or trench zone backfill due to the potential for soil
migration into the relatively large void spaces present in this type of material and water
seepage along trenches backfilled with coarse -grained sand and/or gravel. Loss of soil may
cause damaging settlement. NOTE: Rocks greater than 3 inches in diameter should not be
incorporated within utility trench backfill.
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5.3 Foundations
In our professional opinion, foundations for the structures proposed (as presented within)
could be supported on shallow foundations bearing in properly prepared and compacted soils
placed as recommended in Section 5.1. The recommendations that follow are based on "very
low" to "low" expansion category soils in the upper 5 feet of subgrade.
Soils which are found to be more expansive than a "very low" to "low" Expansion Index will
require differing foundation requirements which should be provided on a case by case basis.
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 minimum footing depth of 12 inches (15 inches for two-story, 24 inches for three-
story) below lowest adjacent grade should be maintained (lowest grade within 2 feet laterally
as measured from the foundation bottom). Earth Systems should be retained to observe
foundation excavations before placement of reinforcing steel or concrete. Loose soil or
construction debris should be removed from footing excavations before placement of concrete.
After excavation, foundation bottoms should be compacted to at least 90% relative compaction
even if excavated into previously compacted fill
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 minimum width and 12 inches below grade:
1500 psf for dead plus design live loads
Allowable increases of 250 psf for each additional 0.5 foot of footing depth or width may be
used up to a maximum value of 2250 psf.
➢ Pad foundations, 2 x 2 foot minimum in plan and 18 inches below grade:
1500 psf for dead plus design live loads
Allowable increases of 300 psf for each additional 0.5 foot of footing depth may be used up
to a maximum value of 2250 psf.
A one-third (A) 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 geotechnical engineer must reevaluate the allowable bearing values and the grading
requirements.
An average modulus of subgrade reaction, k, of 175 pounds per cubic inch (pci) can be used to
design footings and slabs founded upon compacted fill. ACI Section 4.3, Table 4.3.1 should be
followed for recommended cement type, water cement ratio, and compressive strength. At a
minimum, a 4,000 psi mix utilizing Type II cement with a maximum 0.5 water/cement ratio
should be utilized due to the borderline "moderate" sulfate conditions. See Section 5.5 for
corrosion recommendations.
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All footing excavations should be probed for uniformity. Soft or loose zones should be
excavated and recompacted to finish foundation bottom subgrade. The bottom of all
foundations should be tested to confirm a minimum of 90% relative compaction (ASTM D
1557).
Minimum Foundation Reinforcement: Minimum reinforcement should be provided by the
structural engineer to accommodate the settlement potentials presented within. Minimum
reinforcement for continuous wall footings should be two, No. 4 steel reinforcing bars, one
placed near the top and one placed near the bottom of the footing. This reinforcing is not
intended to supersede any structural requirements provided by the structural engineer.
Expected Static Settlement: Estimated total static settlement should be less than 1-inch, based
on footings founded on firm compacted soils as recommended. Differential static settlement
between exterior and interior bearing members should be less than 3/4 inch (inclusive of dry
sand settlement). As such, considering both static and seismic settlement applied over a typical
foundation distance of 40 feet, we recommend the structural engineer design for an angular
distortion of 1:480 (1 inch in 40 feet).
5.4 Slabs -on -Grade
Subgrade: Concrete slabs -on -grade and flatwork should be supported by compacted soil placed
in accordance with Section 5.1 of this report.
Vapor Retarder: In areas of moisture sensitive floor coverings, an appropriate vapor retarder
should be installed to reduce moisture transmission from the subgrade soil to the slab. For
these areas, an impermeable membrane (10 mil minimum thickness) should underlie the floor
slabs. The membrane should be covered with 2 inches of sand to help protect it during
construction and to aid in concrete curing. The subgrade should be moistened just prior to the
placement of the sand and vapor barrier to induce any expansion. 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 membrane is dependent
upon its quality, the method of overlapping, its protection during construction, and the
successful sealing of the membrane around utility lines.
The following minimum slab recommendations are intended to address geotechnical concerns
such as potential variations of the subgrade and are not to be construed as superseding any
structural design. The design engineer and/or project architect should ensure compliance with
appropriate codes and regulation.
Slab Thickness and Reinforcement: Slab thickness and reinforcement of slabs -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 175 pounds per cubic inch can be used in concrete slab design for the expected
compacted subgrade. ACI Section 4.3, Table 4.3.1 should be followed for recommended cement
type, water cement ratio, and compressive strength. At a minimum, a 4,000 psi mix utilizing
Type II cement with a maximum 0.5 water/cement ratio should be utilized due to the
borderline "moderate" sulfate conditions. See Section 5.5 for corrosion recommendations.
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Concrete slabs and flatwork should be a minimum of 4 inches thick (actual, not nominal). If
heavily loaded flatwork is proposed (forklift drive areas, heavy racking, etc.), the actual
thickness should be designed by the structural engineer utilizing techniques of the American
Concrete Institute (ACI). We suggest that the concrete slabs be reinforced with a minimum of
No. 3 rebar at 18-inch centers, both horizontal directions, placed at slab mid -height to resist
cracking. Concrete floor slabs may either be monolithically placed with the foundations or
doweled (No. 4 bar embedded at least 40 bar diameters) after footing placement. The thickness
and reinforcing given are not intended to supersede any structural requirements provided by
the structural engineer. The project architect or geotechnical engineer should continually
observe all reinforcing steel in slabs during placement of concrete to check for proper location
within the slab.
Sidewalks: For sidewalks, 6x6 10/10 welded wire fabric may be used. Sidewalks should be at
least 4 inches in actual thickness. If clay soil pockets are encountered, they should be removed
and replaced with sandier soils which have a lower expansion potential. Fiber mix may be used
if finished correctly.
A minimum concrete gap of three (3) inches should be provided around the steel reinforcing
fabric and the edge of the formwork. Reinforcing steel should be placed at mid -height within
the sidewalk and placed upon centralizers rather than lifted into place during placement. Flat
sheets should be used instead of rolls, as rolls do not allow for accurate locating of the fabric at
r mid height of the slab. Where the reinforcing steel does not have adequate cover, it will
Il corrode and can fracture the cured concrete and produce unsightly rust discoloration when
exposed to the corrosive site soils and landscape water. Fabric should be overlapped at least 6
inches at joints. Additionally, the concrete should be vibrated during placement. Concrete
should be wet cured with burlap or plastic and not allowed to dry out to minimize surface
cracking. Control joints should be provided in all concrete slabs -on -grade at a maximum spacing
I of approximately 4 to 10 feet. All joints should form approximately square patterns to reduce
Il the potential for randomly oriented, contraction cracks. Contraction joints in the slabs should
be tooled at the time of the pour or saw cut (% of slab depth (1 inch for a 4 inch slab)) within
L 8 hours of concrete placement. Construction (cold) joints should consist of thickened butt joints
with one-half inch dowels at 18-inches on center or a thickened keyed -joint to resist vertical
deflection at the joint. At a minimum, a 4,000 psi mix utilizing Type II cement with a maximum
0.5 water/cement ratio should be utilized due to the borderline "moderate" sulfate conditions.
Slab -On -Grade Control Joints: Control joints should be provided in all regular 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 patterns to reduce the potential for randomly oriented shrinkage cracks.
Control joints in the slabs should be tooled at the time of the concrete placement or saw cut
(% of slab depth) as soon as practical but not more than 8 hours from concrete placement.
I Construction (cold) joints should consist of thickened butt joints with %-inch dowels at 18
l inches on center or a thickened keyed -joint to resist vertical deflection at the joint. All control
joints in exterior flatwork should be sealed to reduce the potential of moisture or foreign
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material intrusion. These procedures will reduce the potential for randomly oriented cracks, but
may not prevent them from occurring.
Curing and Quality Control: The contractor should take precautions to reduce the potential of
curling of slabs in this arid desert region using proper batching, placement, and curing methods.
Curing is highly affected by temperature, wind, and humidity. Quality control procedures may
be used, including trial batch mix designs, batch plant inspection, and on -site special inspection
and testing. Curing should be in accordance with ACI recommendations contained in ACI 211,
304, 305, 308, 309, and 318.
5.5 Corrosive Soils
We recommend that the site soils be evaluated by an engineer competent in corrosion evaluation to
provide mitigation recommendations.
5.6 Retaining Walls and Lateral Earth Pressures
Retaining Walls:
➢ Retaining walls should be designed for an active soil pressure equivalent to a fluid density of
41 pcf. The active lateral earth pressures are for horizontal (level) backfills using the on -site
native soils on walls that are free to rotate at least 0.1 percent of the wall height. Walls,
which are restrained against movement or rotation at the top, should be designed for an at -
rest equivalent fluid pressure of 62 pcf. The lateral earth pressure values for level backfill
are provided for walls backfilled with drainage materials and existing on -site soils.
➢ In addition to the active or at rest soil pressure, the proposed wall structures may be
designed to include forces from dynamic (seismic) earth pressure. Dynamic earth pressures
should be estimated by the structural engineer using methods such as El Atik and Sitar
(2010), or other suitable technique. Walls retaining less than 6 feet of soil need not consider
this increased pressure. For flexible and rigid walls, a seismic earth pressure of 24 pcf and 38
pcf should be used, respectively. Dynamic pressures are additive to active earth pressure.
➢ Retaining wall foundations should be placed upon compacted fill described in Section 5.1.
➢ A backdrain or an equivalent system of backfill drainage should be incorporated into the
wall design, whereby the collected water is conveyed to an approved point of discharge.
Design should be in accordance with the 2013 California Building Code. Drain rock should be
I wrapped in filter fabric such as Mirafi 140N as a minimum. Backfill immediately behind the
retaining structure should be a free -draining granular material. Waterproofing should be
according to the designer's specifications. Water should not be allowed to pond or infiltrate
near the top of the wall. To accomplish this, the final backfill grade should be such that
water is diverted away from retaining walls.
➢ Compaction on the retained side of the wall within a horizontal distance equal to one wall
height (to a maximum of 6 feet) should be performed by hand -operated or other
lightweight compaction equipment (90% compaction relative to ASTM D 1557 at near
optimum moisture content). This is intended to reduce potential locked -in lateral pressures
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caused by compaction with heavy grading equipment or dislodging modular block type
walls.
➢ The above recommended values do not include compaction or truck -induced wall
pressures. Care must be taken during the compaction operation not to overstress the wall.
Heavy construction equipment should be maintained a distance of at least 3 feet away from
the walls while the backfill soils are placed. Upward sloping backfill or rock, or surcharge
loads from nearby footings can create larger lateral pressures. Should any walls be
considered for retaining sloped backfill (or rock) 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 35% of the surcharge load within this zone. Retaining walls subjected to traffic
r loads should include a uniform surcharge load equivalent to at least 2 feet of native soil
(125 pcf unit weight). Retaining walls should be designed with a minimum factor of safety of
1.5.
Frictional and Lateral Coefficients:
➢ Resistance to lateral loads (including those due to wind or seismic forces) may be provided
by frictional resistance between the bottom of concrete foundations and the underlying
soil, and by passive soil pressure against the foundations. An allowable coefficient of friction
of 0.35 may be used between cast -in -place concrete foundations and slabs and the
underlying soil. An allowable coefficient of friction of 0.25 may be used between pre -cast or
formed concrete foundations and slabs and the underlying soil
l➢ Allowable passive pressure may be taken as equivalent to the pressure exerted by a fluid
weighing 300 pounds per cubic foot (pcf). Vertical uplift resistance may consider a soil unit
weight of 100 pounds per cubic foot. The upper 1 foot of soil should not be considered
when calculating passive pressure unless confined by overlying asphalt concrete pavement
or Portland cement concrete slab. The soils pressures presented have considered onsite fill
L soils. Testing or observation should be performed during grading by the soils engineer or his
representative to confirm or revise the presented values.
➢ Passive resistance for thrust blocks bearing against firm natural soil or properly compacted
Ibackfill can be calculated using an equivalent fluid pressure of 300 pcf. The maximum
1� passive resistance should not exceed 2,000 psf.
➢ Construction employing. poles or posts (i.e. lamp posts) may utilize design methods
presented in the 2013 CBC for Silty Sand (SM) material class.
➢ The passive resistance of the subsurface soils will diminish or be non-existent if trench
sidewalls slough, cave, or are overwidened during or following excavations. If this condition
is encountered, our firm should be notified to review the condition and provide remedial
Lrecommendations, if warranted.
L
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5.7 Slope Construction
Slopes are not generally proposed for this project; however, minor slopes (less than 3 feet in
height) may be constructed. Where new slopes will be constructed against existing slopes, a
series of level benches and keyways should be provided to seat the compacted fill. The benches
should be a minimum of 5 feet in width and be constructed at approximately 2-foot vertical
intervals or as dictated by topographic conditions, and be constructed in accordance with the
California Building Code. Slopes should be constructed at inclinations no steeper than 3:1
(horizontal:vertical) such that the slope is comprised of fully compacted soil which is also
exposed at the surface. Such methods may include overfilling during construction and cutting
back to expose a fully compacted soil, or track -walking or grid -rolling. Compacted fill should be
placed at near optimum moisture content and compacted to a minimum 90 percent of the
maximum dry unit weight, as measured in relation to ASTM D 1557 test procedures. The
exposed face of any cut or fill slope (upper 12 inches) should have a minimum relative density
of 90 percent of the maximum dry unit weight, as measured in relation to ASTM D 1557 test
procedures, and be compacted at near optimum moisture content.
5.7.1 Surficial Slope Failures
All slopes will be exposed to weathering, resulting in decomposition of surficial earth materials,
thus potentially reducing shear strength properties of the surficial soils. In addition, these
slopes become increasingly susceptible to rodent burrowing. As these slopes deteriorate, they
can be expected to become susceptible to surficial instability such as soil slumps, erosion, soil
creep, and debris flows. Development areas immediately adjacent to ascending or descending
slopes should address future surficial sloughing of soil material. Such measures may include
debris fences, catchment areas or walls, ditches, soil planting or other techniques to contain
soil material away from developed areas.
I Operation and maintenance inspections should be done after a significant rainfall event and on
l a time -based criteria (annually or less) to evaluate distress such as erosion, slope condition,
rodent infestation burrows, etc. Inspections should be recorded and photographs taken to
document current conditions. The repair procedure should outline a plan for fixing and
maintaining surficial slope failures, erosional areas, gullies, animal burrows, etc. Repair
methods could consist of excavating and infilling with compacted soil erosional features, track
walking the slope faces with heavy equipment, as determined by the type and size of repair.
These repairs should be performed in a prompt manner after their occurrence. Existing slope
f inclinations should be maintained and a maintenance program should include identifying areas
l where slopes begin to steepen.
5.8 Site Drainage and Maintenance
Positive drainage in native soils should be maintained away from the structures (5% for 5 feet
minimum) to prevent ponding and subsequent saturation of the foundation soils. Gutters and
downspouts in conjunction with a 1 to 2% paved or hardscape grade should be considered as a
means to convey water away from foundations if increased fall is not provided.
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Drainage should be maintained for paved areas. Water should not pond on or near paved areas
or foundations. The following recommendations are provided in regard to site drainage and
structure performance:
➢ In no instance should water be allowed to flow or pond against structures, slabs or
foundations or flow over unprotected slope faces. Adequate provisions should be employed
to control and limit moisture changes in the subgrade beneath foundations or structures to
reduce the potential for soil saturation. Landscape borders should not act as traps for water
within landscape areas. Potential sources of water such as piping, drains, broken sprinklers,
etc, should be frequently examined for leakage or plugging. Any such leakage or plugging
should be immediately repaired.
➢ It is highly recommended that landscape irrigation or other sources of water be collected
and conducted to an approved drainage device. Landscaping and drainage grades should be
lowered and sloped such that water drains to appropriate collection and disposal areas. All
runoff water should be controlled, collected, and drained into proper drain outlets. Control
methods may include curbing, ribbon gutters, 'V' ditches, or other suitable containment and
redirection devices.
➢ Maintenance of drainage systems and infiltration structures can be the most critical
element in determining the success of a design. They must be protected and maintained
from sediment -laden water both during and after construction to prevent clogging of the
surficial soils any filter medium. The potential for clogging can be reduced by pre -treating
structure inflow through the installation of maintainable forebays, biofilters, or
sedimentation chambers. In addition, sediment, leaves, and debris must be removed from
inlets and traps and basin bottoms on a regular basis.
➢ The drainage pattern should be established at the time of final grading and maintained
throughout the life of the project. Additionally, drainage structures should be maintained
(including the de -clogging of piping, basin bottom scarification, silt removal, etc.)
throughout their design life. Maintenance of these structures should be incorporated into
the facility operation and maintenance manual. Structural performance is dependent on
many drainage -related factors such as landscaping, irrigation, lateral drainage patterns and
other improvements.
➢ Due to the reduction in infiltration characteristics, basin bottoms should not be compacted,
but left in a natural state.
5.9 Streets, Driveways and Parking Areas
Pavement structural sections for associated drive areas including recommendations for
standard asphalt concrete, and Portland cement concrete are provided below.
Pavement Area Preparation: In street, drive, and parking areas, the exposed subgrade should
be overexcavated as recommended in Section 5.1, moisture conditioned, and compacted.
Compaction should be verified by testing. Aggregate base should be compacted to a minimum
95% relative compaction (ASTM D 1557).
Automobile Traffic and Parking Areas
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Pavement sections presented in the following Table for automobile type traffic areas and are
based on assumed R-values and current Caltrans design procedures. Traffic Indices (TI) of 5 and
7 were used to facilitate the design of asphalt concrete pavements for parking and main drives.
The TI's assumed below should be reviewed by the project Civil Engineer to evaluate the
suitability for this project. All design should be based upon an appropriately selected traffic
index. Changes in the traffic indices will affect the corresponding pavement section.
Table 5
Preliminary Flexible Pavement Section Recommendations
Onsite/Interior Automobile Drive Areas
R-Value of SubgrndP Snilc— RO IAccIImP 1l I,A_ 1---1
Flexible Pavements
Traffic
Asphaltic
Class II Aggregate
Index
Pavement Use
Concrete (AC)
Base (BC)
(Assumed)*
Thickness
Thickness
(feet)
(feet)
5
Parking Areas
0.25 or
0.45 or
0.35
0.35
7
Drive Areas
0.35
0.75
111` NI =�=I ll=u I I C1 III. II IUILea snuuiu rye conrirmea Dy the protect civil engineer. Changes to the Traffic
Index will result in a differing pavement section required.
Minimum standards for the City of La Quinta are: Parking Areas 3"AC/4"BC and Drive Aisle 3"AC/4.5"BC
Conventional, rigid pavements, i.e. Portland cement concrete (PCC) pavements, can be used in
areas that will be subject to relatively high static wheel loads and/or heavy vehicle loading and
unloading and turning areas (i.e. truck/bus lanes). The pavement section below is based upon
the American Concrete Institute (ACI) Guide for Construction of Concrete Parking Lots, ACI
330R, and the assumptions outlined below.
Table 6
Preliminary Portland Cement Concrete Pavement Sections
Minimum
Area
Pavement PCC
Minimum 28 Day
Concrete Compressive
Thickness (inches)
Flexural Strength (psi)
Strength (psi)
Truck Access or
Loading/Unloading
Areas (Traffic
6.0*
550
4,000
Category C, ADTT
=100)
Iv1MUU U-1 vI Juur,Iaue Reacuon unve area Till, K = 1/5 pa
*Concrete Pavement may be placed directly on the free draining compacted subgrade (minimum 95%
relative compaction ASTM D 1557)
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Should the actual traffic category vary from those assumed and listed above, these sections
should be modified. All above recommended preliminary pavement sections are contingent on
the following recommendations being implemented during construction:
➢ Pavement should be placed upon compacted fill processed as described in Section 5.1. The
upper 12 inches of subgrade soils beneath the asphalt concrete and conventional PCC
pavement section should be compacted to a minimum of 95 percent relative compaction
(ASTM D 1557).
➢ Subgrade soils and aggregate base should be in a stable, non -pumping condition at the time
of placement and compaction. Exposed subgrades should be proof -rolled to verify the
absence of soft or unstable zones.
➢ Aggregate base materials should be compacted at near optimum moisture content to at
least 95 percent relative compaction (ASTM D 1557) and should conform to Caltrans Class II
criteria. Compaction efforts should include vibratory proof -rolling of the aggregate base
with heavy compaction -specific equipment (i.e. drum rollers).
➢ All concrete curbs separating pavement from landscaped areas should extend at least 6
inches into the subgrade soils to reduce the potential for movement of moisture into the
aggregate base layer (this reduces the risk of pavement failures due to subsurface water
originating from landscaped areas).
➢ Asphaltic concrete should be Caltrans, %2-in. or %-in. maximum -medium grading and
compacted to a minimum of 95% of the 75-blow Marshall density (ASTM D 1559) or
equivalent.
➢ Concrete mixes should consider a "Moderate" sulfate exposure class.
➢ Portland cement concrete pavements should be constructed with transverse joints at
maximum spacing of 12 feet. A thickened edge should be used where possible and, as a
minimum, where concrete pavements abut asphalt pavements. The thickened edge should
be 1.2 times the thickness of the pavement (7.2 inches for a 6-inch pavement), and should
taper back to the pavement thickness over a horizontal distance on the order of 3 feet.
➢ All longitudinal or transverse control joints should be constructed by hand forming or
placing pre -molded filler such as "zip strips." Expansion joints should be used to isolate fixed
objects abutting or within the pavement area.
The expansion joint should extend the full depth of the PCC pavement. Joints should run
continuously and extend through integral curbs and thickened edges. We recommend that
joint layout be adjusted to coincide with the corners of objects and structures. In addition,
the following is recommended for concrete pavements:
• Slope pavement at least %Z percent to provide drainage;
• Provide rough surface texture for traction;
• Cure PCC concrete with curing compound or keep continuously moist for a
minimum of seven days;
• Keep all traffic off concrete until PCC compressive strength exceeds 2,000
pounds per square inch (truck traffic should be limited until the concrete meets
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the design strength (3,650 psi); and
Consideration should be given to having PCC construction joints keyed or using
slip dowels on 24-inch centers to strengthen control and construction joints.
Dowels placed within dowel baskets should be incorporated into the concrete at
each saw -cut control joint (i.e. dowel baskets and dowels are set in place prior to
placement of concrete).
➢ Portland cement concrete placement and curing should, at a minimum, be in accordance
with the American Concrete Institute [ACI] recommendations contained in ACI 211, 304,
305, 308, 309, and 318.
➢ Within the structural pavement section areas, positive drainage (both surface and
subsurface) should be provided. In no instance should water be allowed to pond on the
pavement. Roadway performance depends greatly on how well runoff water drains from
the site. This drainage should be maintained both during construction and over the entire
life of the project.
➢ Proper methods, such as hot -sealing or caulking, should be employed to limit water
infiltration into the pavement base course and/or subgrade at construction/expansion
joints and/or between existing and reconstructed asphalt concrete sections (if any). Water
infiltration could lead to premature pavement failure.
➢ To reduce the potential for detrimental settlement, excess soil material, and/or fill material
removed during any footing or utility trench excavation, should not be spread or placed
over compacted finished grade soils unless subsequently compacted to at least 95 percent
of the maximum dry unit weight, as evaluated by ASTM D 1557 test procedure, at near
optimum moisture content, if placed under areas designated for pavement.
➢ Where new roadways will be installed against existing roadways, the repaired asphalt
concrete pavement section should be designed and constructed to have at least the
pavement and aggregate base section as the original pavement section thickness (for both
AC and base) or upon the newly calculated pavement sections presented within, whichever
is greater.
The appropriate pavement design section depends primarily on the shear strength of the
subgrade soil exposed after grading and anticipated traffic over the useful life of the pavement.
R-value testing or observation of subgrade soils should be performed during grading to verify
and/or modify the preliminary pavement sections presented within this report. Pavement
designs assume that heavy construction traffic will not be allowed on base cap or finished
pavement sections.
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Section 6
LIMITATIONS AND ADDITIONAL SERVICES
6.1 Uniformity of Conditions and Limitations
Our evaluation of subsurface conditions at the site has considered subgrade soil and
groundwater conditions present at the time of our study. The influence(s) of post -construction
changes to these conditions such as introduction or removal of water into or from the
subsurface will likely influence future performance of the proposed project. The magnitude of
the introduction or removal, and the effect on the surface and subsurface soils is currently
unknown.
It should be recognized that definition and evaluation of subsurface conditions are difficult.
Judgments leading to conclusions and recommendations are generally made with incomplete
knowledge of the subsurface conditions due to the limitation of data from field studies. The
availability and broadening of knowledge and professional standards applicable to engineering
services are continually evolving. As such, our services are intended to provide the Client with a
source of professional advice, opinions and recommendations based on the information
available as applicable to the project location and scope. Recommendations contained in this
report are based on our field observations and subsurface explorations, select published
documents (referenced), and our present knowledge of the proposed construction. If the scope
of the proposed construction changes from that described in this report, the conclusions and
recommendations contained in this report are not considered valid unless the changes are
reviewed, and the conclusions of this report are modified or approved in writing by Earth
Systems.
Findings of this report are valid as of the issued date of the report and are strictly for the client.
Changes in conditions of a property can occur with passage of time, whether they are from
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. Land use, site conditions (both on site and off site) or other factors may
change over time, and additional work may be required with the passage of time.
If during construction, soil conditions are encountered which differ from those described
herein, we should be notified immediately in order that a review may be made and any
supplemental recommendations provided. In such an event, the contractor should promptly
notify the owner so that Earth Systems geotechnical engineer can be contacted to confirm
those conditions. We recommend the contractor describe the nature and extent of the differing
conditions in writing and that the construction contract include provisions for dealing with
differing conditions. Contingency funds should be reserved for potential problems during
earthwork and foundation construction.
If the scope of the proposed construction changes from that described in this report, the
conclusions and recommendations contained in this report are not considered valid unless the
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changes are reviewed, and the conclusions of this report are modified or approved in writing by
Earth Systems.
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 reviewed for
applicability and conformance to the current design and incorporated into the plans 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.
Earth Systems has striven to provide our services in accordance with generally accepted
geotechnical engineering practices in this locality at this time. No warranty or guarantee,
express or implied, is made. This report was prepared for the exclusive use of the Client and the
Client's authorized agents.
Demolition, grading and compaction operations should be performed in conjunction with
observation and testing. The recommendations provided in this report are based on the
assumption that Earth Systems will be retained to provide observation during the construction
phase to evaluate our recommendations in relation to the apparent site conditions at that time.
If we are not accorded this observation, Earth Systems assumes no responsibility for the
suitability of our recommendations. In addition, if there are any changes in the field to the
plans and specifications, the Client must obtain written approval from Earth Systems engineer
that such changes do not affect our recommendations. Failure to do so will vitiate Earth
Systems recommendations. These services will be performed on a time and expense basis in
accordance with our agreed upon fee schedule once we are authorized and contracted to
proceed. Maintaining Earth Systems as the geotechnical consultant from beginning to end of
the project will provide continuity of services. The geotechnical engineering firm providing tests
and observations shall assume the responsibility of Geotechnical Engineer of Record.
Any party other than the client who wishes to use this report shall notify Earth Systems of such
intended use. Based on the intended use of the report, Earth Systems may require that
additional work be performed and that an updated report be issued. Non-compliance with any
of these requirements by the client or anyone else will release Earth Systems from any liability
resulting from the use of this report by any unauthorized party.
6.2 Additional Services
This report is based on the assumption that an adequate program of client consultation,
construction monitoring, and testing will be performed during the final design and construction
phases to check compliance with these recommendations. Maintaining Earth System as the
geotechnical consultant from beginning to end of the project will provide continuity of services.
Proper geotechnical observation and testing during construction is imperative to allow the
geotechnical engineer the opportunity to verify assumptions made during the design process
and to verify that our geotechnical recommendations have been properly interpreted and
implemented during construction and is required by the 2013 California Building Code.
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Therefore, we recommend that Earth Systems be retained during the construction of the
proposed improvements to provide testing and observe compliance with the design concepts
and geotechnical recommendations, and to allow design changes in the event that subsurface
conditions or methods of construction differ from those assumed while completing our
previous study. Additionally, the California Building Codes requires the testing agency to be
employed by the project owner or representative (i.e. architect) to avoid a conflict of interest if
employed by the contractor.
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
from our office. The recommended review, tests, and observations include, but are not
necessarily limited to, the following:
➢ Consultation during the final design stages of the project.
➢ A review of the building and grading plans to observe that recommendations of our report
have been properly implemented into the design.
➢ Observation and testing during site preparation, grading, and placement of engineered fill
as required by CBC Sections or local grading ordinances.
➢ Consultation as needed during construction.
FeTiT41
Appendices as cited are attached and complete this report.
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REFERENCES
Al Atik, L., and Sitar, N., 2010, Seismic Earth Pressures on Cantilever Retaining Structures, Journal
of Geotechnical and Geoenvironmental Engineering, ASCE.
American Society of Civil Engineers [ASCE], 2010, Minimum Design Loads for Buildings and Other
Structures, ASCE 7-10.
American Society for Testing Materials, 1989, STP 1013, Effects of Soil Characteristics on Corrosion
(February, 1989).
Biehler, Shawn, 1964, Geophysical Study of the Salton Trough of Southern California, Thesis by
Shawn Biehler, California Institute of Technology, Pasadena, California, 1964.
Boulanger, R. W., and Idriss, I. M., 2006, Liquefaction susceptibility criteria for silts and clays, J.
Geotechnical and Geoenviron mental Eng., ASCE 132 (11), 1413-1426.
Bowles, J.E., 1988, Foundation Analysis and Design, Fourth Edition, McGraw-Hill Book Company.
Bryant, W.A. and Hart, E.W., 2007, Fault Rupture Hazard Zones in California, Division of Mines
and Geology, Special Publication 42.
California Department of Water Resources, 1964, Coachella Valley Investigation, Bulletin No. 108,
146 pp.
California Geologic Survey-SP117A, 2008, Guidelines for Evaluating and Mitigating Seismic
Hazards in California.
California Geologic Survey [CGS], 1992, Geologic Map of California, Sana Ana Sheet, GAM019,
scale 1:250,000.
County of Riverside, 2014, Geographic Information Services (GIS), Transportation and Land
Management Agency, http://www3.tima.co.riverside.ca.us/r)a/rclis/index.html.
Coachella Valley Water District, Coachella Valley Water Management Plan Update, Draft Report,
December 2010.
County of Riverside, Geographic Information Services (GIS), Transportation and Land
Management Agency, http://www3.tlma.co.riverside.ca.us/Da/rciis/index.htm1.
Dept. of the Navy, 1986, NAVFAC DM 7.01: Soil Mechanics, Naval Facilities Engineering
Command, Alexandria, Virginia.
Dept. of the Navy, 1986, NAVFAC DM 7.02: Foundations and Earth Structures, Naval Facilities
Engineering Command, Alexandria, Virginia.
Earth Systems Southwest, 2002, Subsurface Investigation at the Hydraulic Hoists, Champion
Cadillac Chevrolet, 78611 Highway 111, La Quinta, California, File No. 08725-01,
Document No. 02-07-804, dated July 22, 2002.
EARTH SYSTEMS SOUTHWEST
September 4, 2014 36 File No.: 12287-01
Doc. No.: 14-09-703
Earth Systems Southwest, 2014, Evaluation of Drywell Percolation Rates, Proposed Retail
Development, Southwest Corner of Highway 111 and Simon Drive, La Quinta, California,
File No. 12287-01, Document No. 14-08-742, dated August 25, 2014.
Envicom Corporation and the County of Riverside Planning Department, 1976, Seismic Safety
and Safety General Plan Elements Technical Report, County of Riverside.
FEMA, 2014, Map Service Center website http://msc.fema.govl
Hunt, Roy E., 1984, Geotechnical Engineering Practice, McGraw-Hill Book Company.
International Code Council [ICC], 2013, California Building Code, 2013 Edition.
Jennings, C.W, 2010, Fault Activity Map of California and Adjacent Areas: Geologic Survey,
Geological Data Map No. 6, scale 1:750,000.
Petersen, M.D., Bryant, W.A., Cramer, C.H., Cao, T., Reichle, M.S., Frankel, A.D., Leinkaemper, J.J.,
McCrory, P.A., and Schwarz, D.P., 1996, Probabilistic Seismic Hazard Assessment for the
State of California: California Division of Mines and Geology Open -File Report 96-08.
Reichard, E.G. and Mead, J.K., 1991, Evaluation of a Groundwater Flow and Transport Model of the
Upper Coachella Valley, California, U.S.G.S. Open -File Report 91-4142.
Riverside County Planning Department, 2003, Geotechnical Element of the Riverside County
General Plan.
Riverside County Transportation and Land Management Agency, 2003, Riverside County Land
Information Service, www.tlma.co.riverside.ca.us/gis/gisdevelop.htm1.
Sneed, Michelle and Brandt, Justin T., 2007, Detection and Measurement of Land Subsidence
Using Global Positioning System Surveying and Interferometric Synthetic Aperture
Radar, Coachella Valley, California, 1996-2005, United States Geologic Survey Scientific
Investigations Report 2007-5251, 31 p.
Sneed, Michelle, 2010, Measurement of Land Subsidence using Interferometry, Coachella Valley,
California, Land Subsidence, Associated Hazards and the Role of Natural Resources
Development, Proceedings of EISOLS 2010, Queretaro, Mexico, IAHS Publ. 339.
Sneed, Michelle, et al, 2014, Land Subsidence, Groundwater Levels, and Geology in the Coachella
Valley, California, United States Geological Survey, Scientific Investigations Report 2014-
5075.
Southern California Earthquake Center (S.C.E.C.), 1999, Recommended Procedures for
Ii Implementation of DMG Special Publication 117, Guidelines for Analyzing and Mitigating
9` Liquefaction in California: available at web site: http://www.scecdc.scec.org.
Tokimatsu, K, and Seed, H.B., 1987, Evaluation of Settlements in Sands Due To Earthquake
Shaking, ASCE, Journal of Geotechnical Engineering, Vol. 113, No. 8, August 1987.
EARTH SYSTEMS SOUTHWEST
September 4, 2014 37 File No.: 12287-01
Doc. No.: 14-09-703
United States Geological Survey, 2008, Documentation for the 2008 Update of the United
States National Seismic Hazard Maps: U.S. Geological Survey Open -File Report 2008-
1128, 61 p.
United States Geologic Survey, 2014, Design Maps website: http://ehp3-
earthquake.wr.usgs.gov/designmaps/.
Wallace, R. E., 1990, the San Andreas Fault System, California: U.S. Geological Survey Professional
Paper 1515, 283 p.
Working Group on California Earthquake Probabilities, 2008, The Uniform California Earthquake
Rupture Forecast, Version 2 [UCERF 2]: U.S. Geological Survey Open -File Report 2007-
1437 and California Geological Survey Special Report 203, 104 p.
Youd, T.L., and Idriss, I.M., 2001, Liquefaction Resistance of Soils: Summary Report from the
1996 NCEER and 1998 NCEER/NSF Workshops on Evaluation of Liquefaction Resistance
of Soils, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 127, No. 10,
October 2001.
EARTH SYSTEMS SOUTHWEST
4�1
Y
ti
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1
APPENDIX A
Plate 1— Site Location Map
Plate 2 — Boring Location Map
.
Terms and Symbols Used on Boring Logs
�
Soil Classification System
Logs of Borings (5 pages)
Site Class Estimator (2 pages)
Settlement Calculations (1 pages)
Seismic Settlement Calculation (5 pages)
i
EARTH SYSTEMS SOUTHWEST
t
a I � .. `ji •
y
We I
.•. C C .. ...I �.� a �= �
Approximate Site Location i
� , »ii�+s.:.r ,f � i �• � rA�,ty �� •i � rr' 4 s= ..
1
4.
,
_ _
., - � '� z� : ., � . ems,; i 1 a_ ` j .• In . i i - li -
r .� ,,,�,4 to ., I � r , -• I 1 •c• -- _:
•' RrC k� l i"tr�� 4 I y , � . '�t- I i I. _. 1 } { � i.
lux
i.
LEGEND Plate 1
Site Location Ma
Proposed Retail Development
Approximate Site Location Highway 111 & Simon Drive
La Quinta, Riverside County, California
Approximate Scale: 1" = 1 Mile Earth Systems
Southwest
0 1 Mile 2 Miles I 9/04/2014 File No.: 12287-01
M-
F=
r-
'Fir. ' I� 1/•'� t _ - � 1( - �:..
7.
lac
10, ■
...a ..r.. �.
�
■
60,
IC
OM
J { so, -n r t 3_'IC
wr
3' � �� --.+-' .� - '� I i , a 1 +Y�: � ,•y ''i.�.� "�ryq"'yyrw � --W' wt �
Approximate Scale: 1" = 75'
a.- 0 75' 150't' r 4'
LEGEND Plate 2
Test Location Ma
B-1 Approximate Boring Locations Proposed Retail Development
Highway 111 & Simon Drive
DW-2 Approximate Dry pelt Boring La Quinta Riverside Count
(documented under separate cover � y, California
Approximate Percolation Test Locations Earth Systems
P-3 _. Southwest
9/04/2014 File No.: 12287-01
APPENDIX C
Figures 2-4 from Earth Systems Past 2002 Report
7•.,4�.ifiaJ. y'�'- �. A:e,�
EARTH SYSTEMS SOUTHWEST
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11
B-13N
B-1
Former
Underground
Hoist
(Single Post)
LEGEND Figure 3 - Boring Locations - Outdoor Hoist Area
10 B-13 Boring Location
Single Post Hoist Champion Cadillac Chevrolet
Lfwt78-611 Highway 111
Double Post Hoist Project Number: 08725-01
N Approximate Scale: 1" = 15' �, Earth Systems
0 15 30 ".:� Southwest
r
LEGEND
B-35
Boring Location
Single Post Hoist
Double Post Hoist
Approximate Scale: 1" = 25'
WMMMMMWM%=M
0
25 50
Figure 4 - Boring Locations - Indoor Hoist Area
Champion Cadillac Chevrolet
78-611 Highway 111
Project Number: 08725-01
0% Earth Systems
'�� Southwest
DESCRIPTIVE SOIL CLASSIFICATION
Soil classification is based on ASTM Designations D 2487 and D 2488 (Unified Soil Classification System). Information on each boring
log is a compilation of subsurface conditions obtained from the field as well as from laboratory testing of selected samples. The
indicated boundaries between strata on the boring logs are approximate only and may be transitional.
SOIL GRAIN SIZE
U.S. STANDARD SIEVE
12" 3" 3/4" 4 10 40 200
BOULDERS
COBBLES
I SAND
SILT CLAY
COARSE I FINE
I COARSE I MEDIUM FINE
305 76.2 19.1 4.76 2.00 0.42 0.074
SOIL GRAIN SIZE IN MILLIMETERS
ME
RELATIVE DENSITY OF GRANULAR SOILS (GRAVELS, SANDS, AND NON -PLASTIC SILTS)
Very Loose
*N=0-4
RD=0-30
Easily push a 1/2-inch reinforcing rod by hand
Loose
N=5-10
RD=30-50
Push a 1/2-inch reinforcing rod by hand
Medium Dense
N=11-30
RD=50-70
Easily drive a 1/2-inch reinforcing rod with hammer
Dense
N=31-50
RD=70-90
Drive a 1/2-inch reinforcing rod 1 foot with difficulty by a hammer
Very Dense
N>50
RD=90-100
Drive a 1/2-inch reinforcing rod a few inches with hammer
*N=Blows per foot in the Standard Penetration Test at 60% theoretical energy. For the 3-inch diameter Modified California sampler,
140-pound weight, multiply the blow count by 0.63 (about 2/3) to estimate N. If automatic hammer is used, multiply a factor of
1.3 to 1.5 to estimate N. RD=Relative Density (%). C=Undrained shear strength (cohesion).
CONSISTENCY OF COHESIVE SOILS (CLAY OR CLAYEY SOILS)
Very Soft
*N=0-1
*C=0-250 psf
Squeezes between fingers
Soft
N=2-4
C=250-500 psf
Easily molded by finger pressure
Medium Stiff
N=5-8
C=500-1000 psf
Molded by strong finger pressure
Stiff
N=9-15
C=1000-2000 psf
Dented by strong finger pressure
Very Stiff
N=16-30
C=2000-4000 psf
Dented slightly by finger pressure
Hard
N>30
C>4000
Dented slightly by a pencil point or thumbnail
MOISTURE DENSITY
Moisture Condition: An observational term; dry, damp, moist, wet, saturated.
Moisture Content: The weight of water in a sample divided by the weight of dry soil in the soil sample
expressed as a percentage.
Dry Density: The pounds of dry soil in a cubic foot of soil.
MOISTURE CONDITION RELATIVE PROPORTIONS
Dry .....................Absence of moisture, dusty, dry to the touch Trace ............. minor amount (<5%)
Damp................Slight indication of moisture with/some...... significant amount
Moist.................Color change with short period of air exposure (granular soil) modifier/and... sufficient amount to
Below optimum moisture content (cohesive soil) influence material behavior
Wet....................High degree of saturation by visual and touch (granular soil) (Typically >30%)
Above optimum moisture content (cohesive soil)
Saturated .......... Free surface water
LOG KEY SYMBOLS
PLASTICITY
'
Bulk, Bag or Grab Sample
DESCRIPTION
FIELD TEST
Nonplastic
A 1/8 in. (3-mm) thread cannot be rolled
Standard Penetration
at any moisture content.
Split Spoon Sampler
Low
The thread can barely be rolled.
(2" outside diameter)
Medium
The thread is easy to roll and not much
Modified California Sample
time is required to reach the plastic limit.
'
(3" outside diameter)
High
The thread can be rerolled several times
after reaching the plastic limit.
No Recovery
GROUNDWATER LEVEL
Water Level (measured or after drilling)
Terms and Symbols used on Boring
Water Level (during drilling)
MAJOR DIVISIONS
GRAPHIC
LETTERSYMBOL SYMBOL
TYPICAL DESCRIPTIONS
GW
Well -graded gravels, grand -sand
mixtures, little or no fine
CLEAN
r 0-0-00;�+00.
rr• r• r• r •.r••r• r•
+ + + + + + .+ + .
:?:?:?�r�r�r�r�.
i•
GP
Poorly -graded gravels, gravel -sand
mixtures. Little or no fines
GRAVEL AND
GRAVELLY
SOILS
GRAVELS
COARSE
GRAINED SOILS
an More than 50% of
coarse fraction
retained on No. 4
sieve
GRAVELS
WITH FINES
' '
............
' ' ' '
J'
' ' A"."
GM
Silty gravels, gravel -sand -silt
mixtures
GC
Clayey gravels, gravel -sand -clay
mixtures
SAND AND
CLEAN SAND
SW
Well -graded sands, gravelly sands,
little or no fines
SANDY SOILS
(Little or no fines)
More than 50% of
SP
Poorly -graded sands, gravelly
sands, little or no fines
material is larger
than No. 200
sieve size
SM
Silty sands, sand -silt mixtures
SAND WITH FINES
More than 50% of
(appreciable
coarse fraction
amount of fines)
passing No. 4 sieve
SC
Clayey sands, sand -clay mixtures
Inorganic silts and very fine sands,
MIL
rock flour, silty low clayey fine sands
or clayey silts with slight plasticity
CL
Inorganic clays of low to medium
plasticity, gravelly clays, sandy
clays, silty clays, lean clays
FINE-GRAINED
SOILS
LIQUID LIMIT
LESS THAN 50
OL
Organic silts and organic silty
SILTS AND
clays of plasticity
YsP tY
--------------------
Inorganic silty, micaceous, or
CLAYS
MH
diatomaceous fine sand or
silty soils
CH
Inorganic clays of high plasticity,
fat clays
More than 50% of
material is smaller
than No. 200
sieve size
LIQUID LIMIT
GREATER
THAN 50
OH
Organic clays of medium to high
plasticity, organic silts
HIGHLY ORGANIC SOILS
,ryyryyyyyyyy
rrrrrrrrryyr
yyyyyyyyyyyy
.rr,ryrr,rrrryy
PT
Peat, humus, swamp soils with
high organic contents
VARIOUS SOILS AND MAN MADE MATERIALS
Fill Materials
MAN MADE MATERIALS
Asphalt and concrete
Soil Classification
System
Earth Systems
-- Southwest
Earth Systems
Southwest 79-811B Country Club Dave, Bermuda Dunes, CA 92203
Phone (760) 345-1588. Fax (760) 345-7315
Boring No: B-1
Drilling Date: August 4, 2014
Project Name Formor Simon Motors Site, La Quinta
Drilling Method: 6" HSA
Project Number: 12287-01
Drill Type: Mobile Drill, Model B-61
Boring Location: See Plate 2
Logged By: Randy Reed
it
Sample
Type..
Penetration
_
U
+'
„ o
..
Description of Units
Page 1 of 1
Resistance
°
�
Ei
�
°'
A �
g
Y
•o �
Note: The stratification lines shown the
re P
°
A
q
(Blows/6")
rn
A
Q
G
j
approximate boundary between soil and/or rock types
Graphic Trend
5
co Cl)Count
and the transition may be gradational.
Blow Dry
Density
5
10
15
20
25
30
35
40
45
50
55
60
SM
SILTY SAND: yellow brown, medium dense, moist, fine grained
sand
5,9,9
94
6
4,4,5
95
6
clay lenses @ 3 feet, loose
3,4,5
91
9
4,6,7
95
3
SP-SM
POORLY GRADED SAND WITH SILT: gray brown, slightly
moist, loose, fine grained sand
3,8,12
91
29
ML
SILT: brown, stiff, moist
5,7,9
SP-SM
POORLY GRADED SAND WITH SILT: gray brown, medium
dense, damp, fine grained sand
7,13,17
105
2
9,9,6
Sp
POORLY GRADED SAND: gray brown, medium dense, damp,
fine to medium grained sand
ML
SILT: brown, very stiff, moist
7,13,18
95
2
SP-SM
POORLY GRADED SAND WITH SILT: gray brown, medium
dense, damp, fine grained sand
6,11,13
dense
15,25,30
102
2
12,17,14
End of Boring @ 51-1/2 feet
Backfilled with native, Patched with AC cold patch
No groundwater encountered
Earth Systems
Southwest 79-811B Country Club Drive, Bermuda Dunes, CA 92203
riwuc k i uv) wJ-u 00, r as k 1 ov) j4j- ro u
Boring No: B-2
Drilling Date: August 4, 2014
Project Name Formor Simon Motors Site, La Quinta
Drilling Method: 6" HSA
Project Number: 12287-01
Drill Type: Mobile Drill, Model B-61
Boring Location: See Plate 2
Logged By: Randy Reed
Sample
Type,,,
Penetration
_
°:'
Description of Units
Page 1 of 1
Resistance
E
U
Ln
°'
q ;
y
o ,��
NhP
Note: The stratification lines shown represent the
q
(Blows/6")
rn
q
o
approximate boundary between soil and/or rock types
Graphic Trend
o
q
U
and the transition may be gradational.
Blow Dry
Count Density
-5
-10
-15
- 20
- 25
- 30
- 35
- 40
- 45
- 50
- 55
- 60
L
SM
SILTY SAND: brown, loose, moist, fine grained sand
4,4,6
105
13
2,4,6
91
11
3,4,5
88
10
ML
SANDY SILT: brown, firm, moist, fine grained sand
4,7,12
Sp-SM
POORLY GRADED SAND WITH SILT: gray, medium dense,
damp, fine grained sand
End of Boring @ 11-1/2 feet
Backfilled with native, Patched with AC cold patch
No groundwater encountered
Earth Systems
Southwest 79-81113 Country Club Drive, Bermuda Dunes, CA 92203
rnone,raxkmu)
Boring No: B-3
Drilling Date: August 4, 2014
Project Name Formor Simon Motors Site, La Quinta
Drilling Method: 6" HSA
Project Number: 12287-01
Drill Type: Mobile Drill, Model B-61
Boring Location: See Plate 2
Logged By: Randy Reed
v
Sample
Type w
Penetration
_
U
4
Description of Units
[Page 1 of 1
a
U
Resistance
�
0
q;
9
o�
Note: The stratification lines shown represent the
P
q
q
(Blows/6")
rn
o
approximate boundary between soil and/or rock types
Graphic Trend
5
q
U
and the transition may be gradational.
Blow Dry
Count Density
5
10
15
20
25
30
35
40
45
50
I
55
60
4,5,6
SM
106
12
SILTY SAND: brown, loose, moist, fine grained sand
3,3,4
86
30
ML
SILT: brown, firm, moist
2,4,5
86
25
ML
SILT WITH SAND: brown, firm, damp, fine grained sand
3,4,7
94
3
3,3,4
stiff
5,1015
99
3
SM
SILTY SAND: gray brown, medium dense, damp, fine grained
sand
7,12,10
15,23,24
106
1
dry, dense
5,9,11
ML
SILT WITH SAND: light brown, very stiff, damp, fine grained
t t
sand
11,27,32
SP-SM
POORLY GRADED SAND WITH SILT: gray, dry, dense, fine
grained sand
13,18,18
very dense
15,20,24
End of Boring @ 51-1/2 feet
Backfilled with native, Patched with AC cold patch
No groundwater encountered
Earth Systems
Southwest 79-811B Country Club Drive, Bermuda Dunes, CA 92203
—uric kiov) w-iz)aa,
rax 1J
Boring No: B-4
Drilling Date: August 4, 2014
Project Name Formor Simon Motors Site, La Quinta
Drilling Method: 6" HSA
Project Number: 12287-01
Drill Type: Mobile Drill, Model B-61
Boring Location: See Plate 2
Logged By: Randy Reed
v
Sample
e
Type
y
Penetration
_
°'
Description of Units
Page 1 of 1
Resistance
�
�
q ¢,
Y
•,��,
o
Note: The stratification lines shown represent the
P
q5
x q
(Blows/6")
q
❑
j
approximate boundary between soil and/or rock types
Graphic Trend
a)�
and the transition may be gradational.
Blow Dry
Count Density
.5
10
-15
.20
- 25
- 30
- 35
- 40
- 45
- 50
- 55
- 60
SM
SILTY SAND: yellow brown, medium dense, moist, fine grained
sand
5,8,10
102
7
7,11,14
98
12
4,6,9
105
7
loose
5,5,7
SP-SM
POORLY GRADED SAND WITH SILT: yellow brown, loose,
moist, fine to medium grained sand
El3,2,4
-
9
SM
SILTY SAND: brown, loose, moist, fine grained sand
4,7,9
85
30
•
MI,
SILT: brown, stiff, moist
End of Boring @ 21-1/2 feet
Backfilled with native, Patched with AC cold patch
No groundwater encountered
Earth Systems
Southwest 79-811B Country Club Drive, Bermuda Dunes, CA 92203
rnone lroo) �w�-r�aa, rax kiou) w:)-i-it)
Boring No: B-5
Drilling Date: August 4, 2014
Project Name Formor Simon Motors Site, La Quinta
Drilling Method: 6" HSA
Project Number: 12287-01
Drill Type: Mobile Drill, Model B-61
Boring Location: See Plate 2
Logged By: Randy Reed
v
Sample
Type e
Penetration
_
�
°'
� ..
Description of Units
Page 1 of 1
^
Resistance
�
U
�
°' 0
q "
g
Y
•� �
The stratification lines shown represent
Note:hresent the
Q
q
o
approximate boundary between soil and/or rock types
Graphic Trend
q
pa, o
W n
(Blows/6")
�
q
U
and the transition may be gradational.
Blow Dry
Count Density
-5
. 10
- 15
- 20
- 25
- 30
- 35
- 40
- 45
- 50
- 55
- 60
SM
SILTY SAND: gray brown, loose, damp, fine grained sand
3,4,5
4,6,8
91
15
ML
SILT: brown, firm, moist, some plasticity, clay lenses
3,5,7
88
4
SM
SILTY SAND: yellow brown, loose, moist, fine grained sand
4,7,8
92
2
damp
5,7,8
92
2
3,5,8
ML
SILT: brown, very stiff, moist, some plasticity, clay lenses
SM
SILTY SAND: brown, medium dense, moist, fine grained, clay
lenses
5,9,14
5,7,11
SP-SM
POORLY GRADED SAND WITH SILT: gray grown, medium
dense, damp
End of Boring Q 31-1/2 feet
Backfilled with native, Patched with AC cold patch
No groundwater encountered
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APPENDIX B
Laboratory Test Results
EARTH SYSTEMS SOUTHWEST
File No.: 12287-01 September 4, 2014
Lab No.: 14-286
UNIT DENSITIES AND MOISTURE CONTENT ASTM D2937 & D2216
Job Name: Former Simon Motors
Sample
Location
Depth
(feet)
Unit
Dry
Density (pcf)
Moisture
Content
(%)
USCS
Group
Symbol
B 1
2.5
94
6
SM
B 1
5
95
6
SM
B 1
7.5
91
9
SM
B 1
10
95
3
SP-SM
B1
15
91
29
ML
B 1
25
105
2
SP-SM
B 1
35
95
2
SP-SM
B 1
45
102
2
SP-SM
B2
2.5
105
13
SM
B2
5
91
11
SM
B2
7.5
88
10
SM
B3
2.5
106
12
SM
B3
5
86
30
ML
B3
7.5
86
25
ML
B3
10
94
3
ML
B3
20
99
3
SM
B3
30
106
1
SM
B4
5
102
7
SM
B4
7.5
98
12
SM
B4
10
105
7
SP-SM
B4
15
---
9
SM
B4
20
---
30
ML
EARTH SYSTEMS SOUTHWEST
L
File No.: 12287-01 September 4, 2014
Lab No.: 14-286
UNIT DENSITIES AND MOISTURE CONTENT ASTM D2937 & D2216
Job Name: Former Simon Motors
Unit
Moisture
USCS
Sample
Depth
Dry
Content
Group
Location
(feet)
Density (pcf)
(%)
Symbol
B5
5
91
B5
7.5
88
B5
10
92
B5
15
92
15 ML
4 SM
2 SM
2 SM
EARTH SYSTEMS SOUTHWEST
File No.: 12287-01
9/4/2014
Lab No.: 14-286
SIEVE ANALYSIS
ASTM D6913
Job Name: Former Simon Motors
Sample ID: B 1 @ 1-5 feet
Description: Silty Sand (SM)
Sieve Size
% Passing
3"
100
2"
100
1-1/2"
100
1"
100
3/4"
100
1 /2"
100
3/8"
100
#4
100
#10
99
#16
99
#30
98
#40
94
#100
63
#200
41.6
100
90
80
70
on
60
a
a
50
40
30
20
10
0
1
SIEVE Size, mm
..J1
% Coarse Gravel: 0 % Coarse Sand: 1
% Fine Gravel: 0 % Medium Sand: 5 Cu: NA
% Fine Sand: 53 Cc: NA Gradation
% Total Gravel 0 % Total Sand 58 % Fines: 41 NA
EARTH SYSTEMS SOUTHWEST
File No.: 12287-01
Job Name: Former Simon Motors
Lab Number: 14-286
September 4, 2014
AMOUNT PASSING NO.200 SIEVE ASTM D 1140
Fines
USCS
Sample
Depth
Content
Group
Location
(feet)
(%)
Symbol
' B 1
7.5
49
SM
B 1
20
10
SP-SM
B 1
25
9
SP-SM
B 1
40
8
SP-SM
B3
7.5
93
ML
B3
20
15
SM
EARTH SYSTEMS SOUTHWEST
File No.: 12287-01
Lab No.: 14-286
September 4, 2014
CONSOLIDATION TEST ASTM D 2435 & D 5333
Former Simon Motors
B-1 @ 15 feet
Silt (ML)
Ring Sample
2
1
0
-1
-2
w
rn
-3
Z
2
c -4
-5
c
m
s
U -6
r
c
m
L -7
W
a
-8
-9
-10
-11
-12
0.1
Initial Dry Density: 85.7 pcf
Initial Moisture, %: 29.2%
Specific Gravity (assumed): 2.67
Initial Void Ratio: 0.945
Hydrocollapse: 0.5% @ 2.0 ksf
% Change in Height vs Normal Presssure Diagram
-Before Saturation Hydrocollapse o After Saturation
—*--Rebound
1.0
Vertical Effective Stress, ksf
EARTH SYSTEMS SOUTHWEST
File No.: 12287-01
Lab No.: 14-286
September 4, 2014
CONSOLIDATION TEST ASTM D 2435 & D 5333
Former Simon Motors
B 1 @ 35 feet
Sand w/Silt (SP-SM)
Ring Sample
2
1
0
-1
-2
-8
Initial Dry Density: 98.5 pcf
Initial Moisture, %: 2.1%
Specific Gravity (assumed): 2.67
Initial Void Ratio: 0.693
Hydrocollapse: 0.4% @ 4.0 ksf
% Change in Height vs Normal Presssure Diagram
—8—Before Saturation Hydrocollapse
e After SaturationRebound
Poly. (After Saturation)
1.0
Vertical Effective Stress, ksf
EARTH SYSTEMS SOUTHWEST
10.0
File No.: 12287-01
Lab No.: 14-286
September 4, 2014
CONSOLIDATION TEST ASTM D 2435 & D 5333
Former Simon Motors
B-3 @ 7.5 feet
Silt with Sand (ML)
Ring Sample
2
1
0
-1
-2
-8
Initial Dry Density: 85.7 pcf
Initial Moisture, %: 25.0%
Specific Gravity (assumed): 2.67
Initial Void Ratio: 0.944
Hydrocollapse: 0.5% @ 2.0 ksf
% Change in Height vs Normal Presssure Diagram
--8 Before Saturation Hydrocollapse
■ After Saturation # Rebound
Poly. (After Saturation)
1.0
Vertical Effective Stress, ksf
EARTH SYSTEMS SOUTHWEST
10.0
File No.: 12287-01
Lab No.: 14-286
September 4, 2014
CONSOLIDATION TEST ASTM D 2435 & D 5333
Former Simon Motors
B-4 @ 10 feet
Sand with Silt (SP-SM)
Ring Sample
2
1
0
-1
-2
.r
rn
-3
-4
c
-5
R
U -6
r
c
m
i -7
d
a
-8
-9
-10
-11
-12
0.1
Initial Dry Density: 102.7 pcf
Initial Moisture, %: 7.4%
Specific Gravity (assumed): 2.67
Initial Void Ratio: 0.623
Hydrocollapse: 0.5% @ 2.0 ksf
% Change in Height vs Normal Presssure Diagram
—8 —Before Saturation Hydrocollapse
■ After Saturation # Rebound
Poly. (After Saturation)
1.0
Vertical Effective Stress, ksf
EARTH SYSTEMS SOUTHWEST
File No.: 12287-01
Lab No.: 14-286
September 4, 2014
CONSOLIDATION TEST ASTM D 2435 & D 5333
Former Simon Motors
B-4 @ 20 feet
Silt (ML)
Ring Sample
2
1
0
-1
-2
c -3
a>
c -4
-5
c
M
s
C) -6
c
m
L -7
m
IL
-8
-9
-10
-11
-12
0.1
Initial Dry Density: 85.4 pcf
Initial Moisture, %: 30.1%
Specific Gravity (assumed): 2.67
Initial Void Ratio: 0.951
Hydrocollapse: 0.8% @ 2.0 ksf
% Change in Height vs Normal Presssure Diagram
Before Saturation Hydrocollapse
■ After Saturation — w Rebound
Poly. (After Saturation)
1.0
Vertical Effective Stress, ksf
EARTH SYSTEMS SOUTHWEST
u•�
File No.: 12287-01
Lab No.: 14-286
September 4, 2014
CONSOLIDATION TEST ASTM D 2435 & D 5333
Former Simon Motors
B-5 @ 15 feet
Silty Sand (SM)
Ring Sample
2
1
0
-1
-2
8
Initial Dry Density: 92.7 pcf
Initial Moisture, %: 1.6%
Specific Gravity (assumed): 2.67
Initial Void Ratio: 0.799
Hydrocollapse: 0.8% @ 2.0 ksf
% Change in Height vs Normal Presssure Diagram
s—Before Saturation Hydrocollapse
■ After SaturationRebound
Poly. (After Saturation)
1.0
Vertical Effective Stress, ksf
EARTH SYSTEMS SOUTHWEST
10.0
File No.: 12287-01 September 4, 2014
Lab No.: 14-286
EXPANSION INDEX ASTM D-4829, UBC 18-2
Job Name: Former Simon Motors
Sample ID: B 1 @ 1-5 feet
Soil Description: Silty Sand (SM)
Initial Moisture, %:
9.8
Initial Compacted Dry Density, pcf:
111.6
Initial Saturation, %:
52
Final Moisture, %:
20.2
Volumetric Swell, %:
1.6
L
L
L
L
L
Expansion Index, EI: 17 Very Low
Adjusted to El at 50 % saturation according to Section 10.1.2 of ASTM D4829
EI
UBC Classification
0-20
Very Low
21-50
Low
51-90
Medium
91-130
High
>130
lVery High
EARTH SYSTEMS SOUTHWEST
File No.: 12287-01 September 4, 2014
Lab No.: 14-286
MAXIMUM DRY DENSITY / OPTIMUM MOISTURE ASTM D 1557 (Modified)
Job Name: Former Simon Motors Procedure Used: A
Sample ID: 1 Preparation Method: Moist
Location: B1 @ 1-5 feet Rammer Type: Mechanical
Description: Yellow Brown Silty Fine Sand Lab Number: 14-286
(SM)
Sieve Size % Retained (Cumulative)
Maximum Dry Density: 123.5 pcf 3/4" 0.0
Optimum Moisture: 11.2% 3/8" 0.3
#4 1.4
140
135
130
110
105
100 +
0
<----- Zero Air Voids Lines,
sg =2.65, 2.70, 2.75
5 10 15 20 25
Moisture Content, percent
30 35
EARTH SYSTEMS SOUTHWEST
File No.: 12287-01 9/4/2014
Lab No.: 14-286
SOIL CHEMICAL ANALYSES
Job Name: Former Simon Motors
Job No.: 12287-01
Sample ID: B 1
Sample Depth, feet: 1-5 DF RL
Sulfate, mg/Kg (ppm): 797 20 10.00
(ASTM D 4327)
Chloride, mg/Kg (ppm): 13 20 4.00
(ASTM D 4327)
pH, (pH Units): 8.29 1 ---
(ASTM D 1293)
Resistivity, (ohm -cm): 5,747 --- ---
Conductivity, (µmhos -cm): 174 1 2.00
(ASTM D 1125)
Note: Tests performed by Subcontract Laboratory:
Truesdail Laboratories, Inc. DF: Dilution Factor
14201 Franklin Avenue RL: Reporting Limit
Tustin. California 92780-7009 Tel- (714) 730-6462 N 17 • Not T1-tPetnh1P
General Guidelines for Soil Corrosivity
Chemical Agent
Amount in Soil
Degree of Corrosivity
Soluble
0 -1,000 mg/Kg (ppm) [ 0-.1%]
Low
Sulfates
1,000 - 2,000 mg/Kg (ppm) [0.1-0.2%]
Moderate
2,000 - 20,000 mg/Kg (ppm) [0.2-2.0%]
Severe
> 20,000 mg/Kg (ppm) [>2.0%]
Very Severe
Resistivity2
0- 900 ohm -cm
Very Severely Corrosive
900 to 2,300 ohm -cm
Severely Corrosive
2,300 to 5,000 ohm -cm
Moderately Corrosive
5,000-10,000 ohm -cm
Mildly Corrosive
10,000+ ohm -cm
Progressively Less Corrosive
i - uenerai currosiv►ry to concrete elements. American Uonerete Institute (AUI) Water Soluble Sulfate
in Soil by Weight, ACI 318, Tables 4.2.2 - Exposure Conditions and Table 4.3.1 - Requirements for
Concrete Exposed to Sulfate -Containing Solutions. It is recommended that concrete be proportioned in
accordance with the requirements of the two ACI tables listed above (4.2.2 and 4.3.I). The current ACI
should be referred to for further information.
2 - General corrosivity to metallic elements (iron, steel, etc.). Although no standard has been developed
and accepted by corrosion engineering organizations, it is generally agreed that the classification shown
above, or other similar classifications, reflect soil corrosivity. Source: Corrosionsource.com. The
classification presented is excerpted from ASTM STP 1013 titled "Effects of Soil Characteristics on
Corrosion" (February, 1989)
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