HomeMy WebLinkAboutAttachment 8G - Preliminary Geotechnical InvestigationPRELIMINARY
GEOTECHNICAL INVESTIGATION
NIRVANA INDUSTRIAL BUILDINGS
AND SELF STORAGE COMPLEX
821 MAIN STREET
CHULA VISTA, CALIFORNIA
PREPARED FOR
VWP-OP NIRVANA OWNER, LLC
PHOENIX, ARIZONA
SEPTEMBER 14, 2021
PROJECT NO. G2755-42-01
Project No. G2755-42-01
September 14, 2021
VWP-OP Nirvana Owner, LLC
2390 East Camelback Road, Suite 305
Phoenix, Arizona 85016
Attention: Mr. Steven Schwarz
Subject: PRELIMINARY GEOTECHNICAL INVESTIGATION
NIRVANA INDUSTRIAL BUILDINGS
AND SELF STORAGE COMPLEX
821 MAIN STREET
CHULA VISTA, CALIFORNIA
Dear Mr. Schwarz:
In accordance with your request, we have prepared this preliminary geotechnical investigation report
for the proposed industrial buildings at the subject site. The site is underlain by Tertiary-age Otay
Formation mantled by Very Old Paralic Deposits, alluvium, topsoil, and slope wash. Minor amounts
of undocumented fill are also present on the property.
This report is based on review of available published geotechnical reports and literature, a previous
subsurface geotechnical exploration by others, a site reconnaissance, observations made during our
field investigation performed between July 29, 2021 and August 8. 2021, and laboratory testing. Based
on the results of this study, we opine that the subject site is suitable for construction of the proposed
industrial buildings. The accompanying report includes the results of our study and conclusions and
recommendations regarding geotechnical aspects of site development.
Should you have questions regarding this investigation, or if we may be of further service, please
contact the undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
Rodney C. Mikesell
GE 2533
Rupert Adams
CEG 2561
RCM:RSA:arm
(e-mail) Addressee
TABLE OF CONTENTS
1.PURPOSE AND SCOPE ...................................................................................................................... 1
2.SITE AND PROJECT DESCRIPTION ................................................................................................ 2
3.SOIL AND GEOLOGIC CONDITIONS ............................................................................................. 2
3.1 Undocumented Fill (Qudf) ......................................................................................................... 3
3.2 Slope Wash (Unmapped) ............................................................................................................ 3
3.3 Topsoil (Unmapped) ................................................................................................................... 3
3.4 Alluvium (Qal) ........................................................................................................................... 3
3.5 Terrace Deposits (Qt) ................................................................................................................. 4
3.6 Otay Formation (To) ................................................................................................................... 4
4.GEOLOGIC STRUCTURE .................................................................................................................. 4
5.GROUNDWATER ............................................................................................................................... 5
6.GEOLOGIC HAZARDS ...................................................................................................................... 5
6.1 Faulting and Seismicity .............................................................................................................. 5
6.2 Ground Rupture .......................................................................................................................... 7
6.3 Storm Surge, Tsunamis, and Seiches .......................................................................................... 7
6.4 Flooding ...................................................................................................................................... 8
6.5 Liquefaction ................................................................................................................................ 8
6.6 Landslides ................................................................................................................................... 8
6.7 Expansive Soil ............................................................................................................................ 8
7.CONCLUSIONS AND RECOMMENDATIONS ................................................................................ 9
7.1 General ........................................................................................................................................ 9
7.2 Soil and Excavation Characteristics ......................................................................................... 10
7.3 Slope Stability ........................................................................................................................... 12
7.4 Slope Grading ........................................................................................................................... 14
7.5 Grading Recommendations ...................................................................................................... 15
7.6 Earthwork Grading Factors ....................................................................................................... 20
7.7 Subdrains .................................................................................................................................. 20
7.8 Settlement Monitoring .............................................................................................................. 22
7.9 Seismic Design Criteria ............................................................................................................ 23
7.10 Shallow Foundations ................................................................................................................ 25
7.11 Conventional Retaining Wall Recommendations ..................................................................... 29
7.12 Lateral Loading ......................................................................................................................... 32
7.13 Mechanically Stabilized Earth (MSE) Retaining Walls ........................................................... 33
7.14 Soil Nail Walls .......................................................................................................................... 35
7.15 Preliminary Pavement Recommendations ................................................................................ 37
7.16 Exterior Concrete Flatwork ...................................................................................................... 39
7.17 Slope Maintenance.................................................................................................................... 41
7.18 Storm Water Management ........................................................................................................ 41
7.19 Site Drainage and Moisture Protection ..................................................................................... 42
7.20 Grading and Foundation Plan Review ...................................................................................... 42
7.21 Testing and Observation Services During Construction ........................................................... 42
TABLE OF CONTENTS (Concluded)
MAPS AND ILLUSTRATIONS
Figure 1, Geologic Map
Figure 2, Geologic Cross Sections A-A’ through G-G’
Figure 3, Typical Buttress/Stability Fill Detail
APPENDIX A
FIELD INVESTIGATION
Figure A-1 to A-5, Logs of Large Diameter Borings
Figures A-6 to A-13, Logs of Exploratory Test Pits
APPENDIX B
LABORATORY TESTING
Summary of Laboratory Maximum Dry Density and Optimum Moisture Content Test Results
Summary of Laboratory Expansion Index Test Results
Summary of Laboratory Water-Soluble Sulfate Test Results
Summary of Laboratory Chloride Ion Content Test Results
Summary of Laboratory pH and Resistivity Test Results
Summary of Laboratory Atterberg Test Results
APPENDIX C
EXPLORATORY BORINGS AND TRENCHES PERFORMED BY OTHERS
APPENDIX D
SLOPE STABILITY ANALYSIS
APPENDIX E
RECOMMENDED GRADING SPECIFICATIONS
LIST OF REFERENCES
Geocon Project No. G2755-42-01 - 1 - September 14, 2021
PRELIMINARY GEOTECHNICAL INVESTIGATION
1. PURPOSE AND SCOPE
This report contains the results of our preliminary geotechnical investigation for proposed industrial
buildings and self-storage facility located at 821 Main Street, in Chula Vista, California (see Vicinity
Map).
Vicinity Map
The purpose of our investigation was to evaluate subsurface soil and geologic conditions at the site
and provide conclusions and recommendations pertaining to geotechnical aspects of developing the
property as proposed.
The scope of our study included performing a site reconnaissance and geologic mapping, reviewing
readily available published geologic literature pertinent to the property, reviewing available
geotechnical reports on this property and in the site vicinity (see List of References), and excavating
and logging eight backhoe test pits and five large diameter borings. Appendix A presents a discussion
of our field investigation. We performed laboratory tests on soil samples obtained from the
exploratory test pits to evaluate pertinent physical properties for engineering analyses. The results of
laboratory testing are presented in Appendix B. Exploratory borings and trenches performed by others
is provided in Appendix C.
Site geologic conditions are depicted on Figure 1 (Geologic Map). A CAD file of the preliminary
grading study prepared by Pasco Laret Suiter & Associates was utilized as a base map to plot geologic
contacts and exploratory excavation locations.
Geocon Project No. G2755-42-01 - 2 - September 14, 2021
The conclusions and recommendations presented herein are based on our analysis of the data obtained
during the investigation, and our experience with similar soil and geologic conditions on this and
adjacent properties.
2. SITE AND PROJECT DESCRIPTION
The subject site encompasses approximately 13 acres of undeveloped land bounded on the north by
automobile salvage yards, on the west by commercial buildings, on the south by Main Street and the
Otay Riverbed, and on the east by the Otay Ranch Village 3 development. The property consists of
natural, south-facing sloping terrain with elevations ranging from approximately 135 feet above mean
sea level (MSL) to 220 feet MSL, with ephemeral drainages at the west and east ends of the property
and one in the central area of the site. A storm drain pipe outlets near the toe of a fill slope at the
upstream end of the central drainage. Storm water runoff then travels through the central drainage to a
storm drain inlet near the southern property line. Trash, tires and debris are present in the drainage
areas.
Proposed site development includes constructing four industrial buildings totaling approximately
290,500 square-feet, with associated improvements including utilities, paving, storm water
management devices, and landscape improvements. One of the four proposed industrial buildings will
be a self-storage facility. Proposed cuts and fills are estimated to be up to 50 feet, with proposed new
slopes up to approximately 10 feet in height. Retaining walls are planned on north, south, and west
sides of the site. The walls will have heights up to approximately 40 feet. A soil nail wall is planned
along the majority of the northern property margin where cuts will be made to reach pad grade. In the
central portion of the site the soil nail wall will transition into a mechanically stabilized earth (MSE)
wall where fill is planned to reach pad grades. Along the south and west sides of the property MSE
walls are planned to create proposed pad grades. New 72-inch-diameter and 60-inch-diameter storm
drains will be installed on the property to convey storm water runoff from the properties to the north to
a storm drain system below Main Street. Paved parking lots and driveways are planned along the
perimeter of the site. Site access will be from Nirvana Street at the northwest corner of the property.
The locations and descriptions of the site and proposed development are based on our site
reconnaissance and recent field investigations, and our understanding of site development as shown on
the preliminary grading study prepared by Pasco Laret Suiter & Associates. If project details vary
significantly from those described, Geocon Incorporated should be contacted to review the changes
and provide additional analyses and/or revisions to this report, if warranted.
3. SOIL AND GEOLOGIC CONDITIONS
Based on the results of the field investigation, the site is underlain by Tertiary Otay Formation capped
with Terrace Deposits, alluvium, topsoil, slope wash, and undocumented fill. A description of the soil
Geocon Project No. G2755-42-01 - 3 - September 14, 2021
and geologic conditions is provided below. Mapped geologic conditions are depicted on the Geologic
Map (Figure 1), and on the Geologic Cross Sections (Figure 2). Exploratory boring and test pit logs
are presented in Appendix A.
3.1 Undocumented Fill (Qudf)
A prism of undocumented fill is mapped within the north-central portion of the site at the upstream
end of the drainage. Some end-dumped piles of undocumented fill generally consisting of silty to
clayey sand with cobbles is present on the property. Trash piles consisting of construction debris, auto
parts and tires are also present at the site.
Undocumented fill and trash are unsuitable for support of structural fill and improvements.
Undocumented fill should be removed and replaced as compacted fill. Trash should be hauled offsite
prior to grading and not mixed with the fills.
3.2 Slope Wash (Unmapped)
Steep, south-facing slopes are mantled with up to two feet of Holocene-age slope wash soils consisting
of loose, dry, silty sand and sandy silt with cobble. The slope wash soils obscure the contact between
the Terrance Deposits and the underlying Otay Formation, and the surface outcrop of bentonitic
claystone beds within the Otay Formation.
The slope wash is compressible and possesses a “very low” to “high” expansion potential (expansion
index of 130 or less). Slope wash should be removed during grading. Due to the limited thickness and
extent of these deposits, slope wash is not shown on the Geologic Map (Figure 1).
3.3 Topsoil (Unmapped)
Holocene-age topsoil is present as a relatively thin veneer locally overlying surficial and formational
materials. The topsoil has a thickness of up to two feet and can be characterized as soft to stiff and
loose to medium dense, dry to damp, dark brown, sandy clay to clayey sand with gravel and cobble.
The topsoil is typically compressible and possesses a “very low” to “high” expansion potential
(expansion index of 130 or less). Removal of the topsoil will be necessary within the limits of grading
in areas supporting proposed fill or improvements. Due the limited thickness and extent of these
deposits, topsoil is not shown on the Geologic Map (Figure 1).
3.4 Alluvium (Qal)
Alluvium is present in the shallow, north-south trending drainages (Figure 1). The thickness of the
alluvium is unknown, but previous studies indicate that it is at least five feet deep below existing
grade. The alluvium generally consists of loose to medium dense to dense, silty to clayey sand with
Geocon Project No. G2755-42-01 - 4 - September 14, 2021
gravel and cobble. Removal of the alluvium will be necessary within the limits of grading in areas
supporting proposed fill or improvements.
3.5 Terrace Deposits (Qt)
Pleistocene-age Terrace Deposits, also referred to as Old Alluvial Deposits, cap most of the site.
Terrace Deposit thickness ranges between approximately 4 to 30 feet. The Terrace Deposits are
generally dense to very dense, reddish brown, silty to clayey sand with gravel and cobble. The lower
portions of the unit contain higher volume of larger cobbles and boulder-sized material up to about
three feet in diameter. The Terrace Deposits are suitable for the support of proposed fill and structural
loads; however, select grading and/or onsite screening operations will be required to properly place the
cobble- and boulder-sized material in deeper fill areas, and generate soils suitable for mechanically
stabilized earth (MSE) wall construction.
3.6 Otay Formation (To)
The Tertiary-age (upper Oligocene) Otay Formation is exposed in the lower portion of the slope
adjacent to Main Street and underlies the Terrace Deposits across the site. The Otay Formation
consists of dense, silty, fine- to coarse-grained sandstone, clayey and sandy siltstone, and silty
claystone with continuous and discontinuous interbeds of highly expansive bentonitic claystone. The
coarse-grained portions of the Otay Formation typically possess a “very low” to “low” expansion
potential (expansion index of 50 or less) and adequate shear strength. The fine-grained siltstone and
claystone portions of the formation can exhibit a “medium” to “very high” expansion potential
(expansion index greater than 50). The Otay Formation is suitable for the support of compacted fill
and structural loads. Bentonitic claystone located within 5 feet of finish pad grade or within 2 feet of
the bottom of structural footings will need to be undercut during grading and placed in deeper fill
areas.
We identified two bentonitic claystone beds in large diameter borings, between 2 and 10 feet in
thickness, extending under the site at elevations ranging between 145-155 feet MSL and 175-185 feet
MSL. The bentonitic claystone beds consist of highly expansive clays, which typically exhibit low
shear strength. Remolded clay seams referred to as bedding plane shears can develop on or within
bentonitic claystone beds which can form landslide failure surfaces.
4. GEOLOGIC STRUCTURE
Bedding attitudes observed within formational materials during logging of large diameter brings for
this study, and during investigation and grading of the adjacent Otay Ranch Village 3 site to the east,
are approximately horizontal to slightly dipping toward the southwest. The regional dip of sedimentary
units in the eastern Chula Vista area is generally 1 to 5 degrees toward the southwest. The granular
portions of the formational units are typically massive with bedding not discernible. Bentonitic
Geocon Project No. G2755-42-01 - 5 - September 14, 2021
claystones and/or bedding plane shears create a possibility for slope instability and will require
stabilization during grading. It is our opinion that the site geologic structure does not present a
significant geologic hazard to the proposed development of the site provided the geotechnical
recommendations in this report are incorporated into design and construction.
5. GROUNDWATER
We encountered seepage during the field investigation in several of our borings at depths ranging from
65 to 87 feet below existing grade (elevation 112 to 153 feet NGVD29) as shown in Table 5. The
seepage depths recorded in borings LB-1 and LB-2 are considered most representative of conditions
across the site. Seepage is likely a perched condition. The most likely location to encounter seepage is
within the drainage areas and within backcuts for the lower retaining walls and/or stability buttresses.
Although, we do not expect groundwater will significantly impact grading and construction of the
planned improvements, management of seepage may be necessary if it is encountered during grading.
It is not uncommon for groundwater or seepage conditions to develop where none previously existed.
Groundwater and seepage is dependent on seasonal precipitation, irrigation, land use, among other
factors, and varies as a result. Proper surface drainage will be important to future performance of the
project.
TABLE 5
ESTIMATED SEEPAGE ELEVATION
Boring No. Date Recorded
Approximate Depth of
Groundwater Below Existing
Grade (feet)
Approximate Elevation
of Groundwater (feet,
NVGD29)
LB-1 7/29/2021 68 116
LB-2 7/30/2021 87 112
LB-3 7/30/2021 72* 122*
LB-5 08/03/2021 65** 153**
* Seepage conditions
** Inferred from boring spoils
6. GEOLOGIC HAZARDS
6.1 Faulting and Seismicity
A review of the referenced geologic materials and our knowledge of the general area indicate that the
site is not underlain by active faults. A fault strand related to the potentially active La Nacion Fault is
mapped on regional fault maps transecting the west property boundary. A study performed by AGS
(2014) did not encounter the fault in a fault trench excavation.
The La Nacion Fault is considered to be potentially active. However, it is our opinion that the potential
for fault rupture on the site is considered to be low based on review of geologic literature for the area
Geocon Project No. G2755-42-01 - 6 - September 14, 2021
and our experience. Additional studies should be performed to evaluate if the fault is present on the
property.
An active fault is defined by the California Geological Survey (CGS) as a fault showing evidence for
activity within the last 11,700 years. The site is not located within a State of California Earthquake
Fault Zone.
The USGS has developed a program to evaluate the approximate location of faulting in the area of
properties. The following figure shows the location of the existing faulting in the San Diego County
and Southern California region. The fault traces are shown as solid, dashed and dotted that represent
well-constrained, moderately constrained and inferred, respectively. The fault line colors represent
faults with ages less than 150 years (red), 15,000 years (orange), 130,000 years (green), 750,000 years
(blue) and 1.6 million years (black).
Faults in the San Diego Area
Geocon Project No. G2755-42-01 - 7 - September 14, 2021
The San Diego County and Southern California region is seismically active. The following figure
presents the occurrence of earthquakes with a magnitude greater than 2.5 from the period of 1900
through 2015 according to the Bay Area Earthquake Alliance website.
Earthquakes in Southern California
Considerations important in seismic design include the frequency and duration of motion and the soil
conditions underlying the site. Seismic design of structures should be evaluated in accordance with the
California Building Code (CBC) guidelines currently adopted by the local agency.
6.2 Ground Rupture
The risk associated with ground rupture hazard is low due to the absence of active faults at the subject
site.
6.3 Storm Surge, Tsunamis, and Seiches
The site is located approximately seven miles from the Pacific Ocean and is at an elevation of about
138 feet or greater above Mean Sea Level (MSL). Therefore, the potential of storm surges and tsunami
affecting the site is considered low.
Geocon Project No. G2755-42-01 - 8 - September 14, 2021
The site is not located in the vicinity of or downstream from such bodies of water. Therefore, the risk
of seiches affecting the site is negligible.
6.4 Flooding
According to maps produced by the Federal Emergency Management Agency (FEMA), the site is
zoned as “Zone X – Minimal Flood Hazard.” Based on our review of FEMA flood maps, the risk of
site flooding is low.
6.5 Liquefaction
Due to the lack of a permanent, near-surface groundwater table and the dense nature of the underlying
geologic units on the property, the potential for liquefaction is low.
6.6 Landslides
We did not observe evidence of previous or incipient slope instability at the site during our study.
Published geologic mapping indicates landslides are not present on or immediately adjacent to the site.
Therefore, the risk of landsliding at the site is low.
6.7 Expansive Soil
The fine-grained clay beds within the Otay Formation may possess a “high” to “very high” expansion
potential (expansion index of 91 to greater than 130). We expect topsoil, Terrace Deposits, and sandy
portions of the Otay Formation will likely possess a “medium” to “high” expansive potential
(Expansion Index of 51 to 130).
Geocon Project No. G2755-42-01 - 9 - September 14, 2021
7. CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7.1.1 No soil or geologic conditions were observed that would preclude the development of the
property as presently proposed provided that the recommendations of this report are
followed.
7.1.2 The site is underlain by compressible surficial deposits consisting of undocumented fill,
topsoil, slope wash, and alluvium, overlying Quaternary-age Terrace Deposits and Tertiary-
age Otay Formation. We estimate the undocumented fill at the north end of the central
drainage to be between ten to twenty feet thick. Topsoil and slope wash range from
approximately one to four feet thick. The alluvium extends to depths greater than five feet
and may be thicker in unexplored areas of the site. Minor amounts of trash and construction
debris are present at the site that will require offsite disposal.
7.1.3 Undocumented fill, topsoil, slope wash, and alluvium are unsuitable in their present
condition to support fill or settlement-sensitive structures and will require removal and
recompaction.
7.1.4 Two bentonitic claystone beds within the Otay Formation identified as laterally continuous
across the site require slope buttressing, stability fills, and consideration in wall design to
provide stable slope conditions.
7.1.5 A concealed segment of the potentially active La Nacion Fault is mapped at a regional scale,
crossing the western side of the property. We did not evaluate the presence or absence of
this fault on the property during our investigation, but fault trenching performed by others
did not identify the fault. Additional trenching will be necessary to determine if the fault
crosses the property.
7.1.6 Based on the current grading plan, an east-west trending cut to fill- transition will be present
at finish grade. The cut side of the transition will need to be undercut in building pads to
reduce differential settlement across the transition.
7.1.7 Excavation to reach pad grades will also expose an expansive claystone bed at or near finish
pad grade. The claystone bed will need to be undercut during grading where it is present
within 5 feet of finish pad grade or 2 feet below the bottom of footings. Grading should be
planned to bury the expansive clay in deeper fill areas, outside of wall backfill zones, and at
least 15 feet from the face of slopes.
Geocon Project No. G2755-42-01 - 10 - September 14, 2021
7.1.8 Gravel and cobble greater than six inches in diameter is present in portions of the Terrace
Deposits. Selective grading and potentially screening will be necessary if the cobble Terrace
Deposits will be utilized as MSE wall backfill.
7.1.9 We encountered seepage in exploratory borings; however, we don’t expect groundwater will
be a constraint to project development. Seepage within surficial soils and formational
materials may be encountered during grading operations, especially during the rainy
seasons.
7.1.10 Except for possible strong seismic shaking and slope instability, no significant geologic
hazards were observed or are known to exist on the site that would adversely affect the site.
No special seismic design considerations, other than those recommended herein, are
required. Slope stabilization requirements are discussed in the grading section of this report.
7.1.11 Proper drainage should be maintained in order to preserve the engineering properties of the
fill in both the building pads and slope areas. Recommendations for site drainage are
provided herein.
7.1.12 We did not perform infiltration testing as part of this study as preliminary design plans were
not available. Due to the proposed MSE walls and deep fills required in the south (down-
gradient) portion of the site needed to create a level building pad, infiltration of storm water
is not recommended on this site.
7.1.13 Provided the recommendations of this report are followed, it is our opinion that the
proposed development will not destabilize or result in settlement of adjacent properties or
the City right-of-way.
7.1.14 Subsurface conditions observed may be extrapolated to reflect general soil/geologic
conditions; however, some variations in subsurface conditions between boring and test pit
locations should be anticipated.
7.2 Soil and Excavation Characteristics
7.2.1 The recommendations included herein are provided for stable excavations. It is the
responsibility of the contractor and their competent person to ensure all excavations,
temporary slopes and trenches are properly constructed and maintained in accordance with
applicable OSHA guidelines in order to maintain safety and the stability of the excavations
and adjacent improvements. These excavations should not be allowed to become saturated
or to dry out. Surcharge loads should not be permitted to a distance equal to the height of the
Geocon Project No. G2755-42-01 - 11 - September 14, 2021
excavation from the top of the excavation. The top of the excavation should be a minimum
of 15 feet from the edge of existing improvements. Excavations steeper than those
recommended or closer than 15 feet from an existing surface improvement should be shored
in accordance with applicable OSHA codes and regulations.
7.2.2 The stability of the excavations is dependent on the design and construction of the shoring
system and site conditions. Therefore, Geocon Incorporated cannot be responsible for site
safety and the stability of the proposed excavations.
7.2.3 Excavation of undocumented fill and surficial deposits should be possible with moderate to
heavy effort using conventional heavy-duty equipment. We expect excavation of the Terrace
Deposits and the Otay Formation will require moderate to very heavy effort. Weakly to
moderately cemented gravel and/or cobble and zones may be encountered requiring very
heavy effort to excavate.
7.2.4 The soil encountered in the field investigation is considered to be both “non-expansive”
(expansion index [EI] of 20 and less) and “expansive” (EI greater than 20) as defined by
2019 California Building Code (CBC) Section 1803.5.3. Table 7.2.1 presents soil
classifications based on the expansion index. We expect the majority of the soils that will be
encountered in remedial grading and cut areas will have a “low” to “medium” expansion
potential. Portions of the topsoil and the clay beds possess a “high” to “very high”
expansion potential (EI greater than 90).
TABLE 7.2.1
EXPANSION CLASSIFICATION BASED ON EXPANSION INDEX
Expansion Index (EI) ASTM D 4829 Expansion
Classification
2019 CBC
Expansion Classification
0 – 20 Very Low Non-Expansive
21 – 50 Low
Expansive 51 – 90 Medium
91 – 130 High
Greater Than 130 Very High
7.2.5 We performed laboratory tests on samples of the site materials to evaluate the percentage of
water-soluble sulfate content. Appendix B presents results of the laboratory water-soluble
sulfate content tests. The test results indicate the on-site materials at the locations tested
possess “S0” sulfate exposure to concrete structures as defined by 2019 CBC Section 1904
and ACI 318-14 Chapter 19. Table 7.2.2 presents a summary of concrete requirements set
Geocon Project No. G2755-42-01 - 12 - September 14, 2021
forth by 2019 CBC Section 1904 and ACI 318.The presence of water-soluble sulfates is not
a visually discernible characteristic; therefore, other soil samples from the site could yield
different concentrations. Additionally, over time landscaping activities (i.e., addition of
fertilizers and other soil nutrients) may affect the concentration.
TABLE 7.2.2
REQUIREMENTS FOR CONCRETE EXPOSED TO
SULFATE-CONTAINING SOLUTIONS
Exposure Class
Water-Soluble
Sulfate (SO4)
Percent
by Weight
Cement
Type (ASTM C
150)
Maximum
Water to
Cement Ratio
by Weight1
Minimum
Compressive
Strength (psi)
S0 SO4<0.10 No Type
Restriction n/a 2,500
S1 0.10<SO4<0.20 II 0.50 4,000
S2 0.20<SO4<2.00 V 0.45 4,500
S3 SO4>2.00 V+Pozzolan or
Slag 0.45 4,500
7.2.6 We tested samples for potential of hydrogen (pH) and resistivity and chloride to aid in
evaluating the corrosion potential. Appendix B presents the laboratory test results.
7.2.7 Geocon Incorporated does not practice in the field of corrosion engineering. Therefore,
further evaluation by a corrosion engineer may be needed if improvements susceptible to
corrosion are planned.
7.3 Slope Stability
7.3.1 Slope stability analyses were performed to evaluate impacts the bentonitic claybeds have on
the proposed project. A discussion of the slope stability analysis and the results of our
analyses are discussed below and presented in Appendix D.
7.3.2 Based on our analysis, remedial grading to remove the claystone bed will be required within
the existing hillside slope along the south and east sides of the property. Along the south
side of the property, the backcut to enable placement of reinforcing grid for the MSE wall
may sufficiently remove the claystone bed such that additional remedial removal is not
required. Confirmation of this will be needed once wall design is complete and grid lengths
are known. Where the wall backcut does not extend far enough into the hillside slope,
additional clay bed removal will be required. The minimum removal length measured from
the face of the wall is provided on the stability figures in Appendix D and cross sections on
Figure 2. The front extent of the clay bed removal is shown on Figure 1.
Geocon Project No. G2755-42-01 - 13 - September 14, 2021
7.3.3 On the east side of the site where the planned MSE wall terminates, a buttress will need to
be constructed at the toe of the hillside slope below the planned MSE wall. The width of the
required buttress measured from the toe of the slope is approximately 50 feet as shown on
the Cross Section G-G (Figure 2) and on the stability figure in Appendix D. The estimated
front extent of the clay bed removal is shown on Figure 1.
7.3.4 The recommended buttress/clay bed removal encompasses the area from the front key
removal shown on Figure 1 and dipping into the slope at a minimum of 5 percent to the back
of the recommended key width and then up at a 1:1 plane to where it intersects the existing
ground surface as shown on the geologic cross sections (Figure 2). A typical buttress detail
is shown on Figure 3.
7.3.5 Internal drainage of the buttress key should be constructed in accordance with Figure 3. The
location of the heel drains and outlet points should be shown on the grading plans. All
keyway and drainage features should be as-built in the field by the project civil
engineer/surveyor.
7.3.6 A stability fill will also be needed along the top of the eastern slope where the clay bed is
exposed on the slope face. The stability fill should have a minimum width of 15 feet measured
from the slope face. The stability fill should include a back drain that outlets to the slope face.
Subdrain cut off and head walls as shown in Section 7.7 of this report should be constructed.
An outlet should be provided every approximately 100 feet of the stability fill.
7.3.7 The clay bed is expected to be present near the bottom of the wall cut along the north side of
the property. The wall design will need to pin the clay bed to prevent slope instability.
Geocon Incorporated can provide additional stability analysis and coordination with the wall
designer, as needed.
7.3.8 Additional slope stability analysis should be performed to check buttress widths and limits
once the MSE walls have been designed and grid type, location, and vertical spacing is
known. Modifications to the buttress widths may be needed. Additional stability analysis
should be performed on for the vertical slope supported by the soil nail wall once nail
spacing and method to pin the claystone bed is known.
7.3.9 General slope stability analyses were performed for proposed cut and fill slopes up to 10
feet high (2:1 gradient). The stability analyses were performed using simplified Janbu
analysis. The analyses indicate planned slopes above retaining walls will have a calculated
factors of safety in excess of 1.5 under static conditions for both deep-seated failure and
shallow sloughing conditions. Table 7.3.1 presents the slope stability analysis. Slope
Geocon Project No. G2755-42-01 - 14 - September 14, 2021
stability analysis for MSE walls should be performed once the wall design is complete and
grid locations and lengths are known.
TABLE 7.3.1
SLOPE STABILITY EVALUATION
Parameter Value
Slope Height, H 10 Feet
Slope Inclination, I (Horizontal to Vertical) 2:1
Total Soil Unit Weight, γ 130 pcf
Friction Angle, 28 Degrees
Cohesion, C 250 psf
Slope Factor λC= (γHtan)/C 2.8
NCf (From Chart) 14
Factor of Safety = (NCfC)/(γH) 2.7
7.3.10 Table 7.3.2 presents the surficial slope stability analysis for the proposed sloping conditions.
TABLE 7.3.2
SURFICIAL SLOPE STABILITY EVALUATION
Parameter Value
Slope Height, H ∞
Vertical Depth of Saturation, Z 3 Feet
Slope Inclination, I (Horizontal to Vertical) 2:1 (26.6 Degrees)
Total Soil Unit Weight, γ 130 pcf
Water Unit Weight, γW 62.4 pcf
Friction Angle, 28 Degrees
Cohesion, C 250 psf
Factor of Safety = (C+(γ+γW )Zcos2I tan)/(γZsinI cosI) 2.2
7.3.11 All cut slope excavations should be observed during grading by an engineering geologist to
verify that soil and geologic conditions do not differ significantly from those anticipated.
7.4 Slope Grading
7.4.1 Construction of fill slopes should begin with excavation of a fill slope keyway in accordance
with the Fill Slope Keyway detail shown in the Recommended Grading Specifications in
Appendix E.
Geocon Project No. G2755-42-01 - 15 - September 14, 2021
7.4.2 The outer 15 feet (or a distance equal to the height of the slope, whichever is less) of fill
slopes should be composed of properly compacted granular “soil” fill to reduce the potential
for surficial sloughing. In general, soils with an Expansion Index of less than 50 should be
acceptable as “granular” fill. Soils of questionable strength to satisfy surficial stability
should be tested in the laboratory for acceptable drained shear strength.
7.4.3 Fill slopes should be overbuilt at least three feet horizontally, and cut back to the design
finish grade. As an alternative, fill slopes may be compacted by back-rolling at vertical
intervals not to exceed four feet and then track-walking with a D-8 dozer, or equivalent,
upon completion such that the fill soils are uniformly compacted to at least 90 percent
relative compaction to the face of the finished slope.
7.4.4 All slopes should be landscaped with drought-tolerant vegetation, having variable root
depths and requiring minimal landscape irrigation. In addition, all slopes should be drained
and properly maintained to reduce erosion.
7.4.5 Grading budgets should be established that include selective grading to provide suitable soil
for the wall backfill, stability buttresses, as well as the outer 15 feet (or a distance equal to
the height of the slope, whichever is less) of fill slopes with properly compacted granular
“soil” fill to reduce the potential for slope creep and surficial sloughing. In general, soil with
an EI<50 should be used within the outer slope zone. Minimum soil strength parameters for
the stability buttresses is provided in the grading section.
7.5 Grading Recommendations
7.5.1 Grading should be performed in accordance with the recommendations provided in this
report, the Recommended Grading Specifications contained in Appendix E and the City of
Chula Vista’s Grading Ordinance. Where the recommendations of this section conflict with
those of Appendix E, the recommendations of this section take precedence. Geocon
Incorporated should observe the grading operations on a full-time basis and provide testing
during the fill placement.
7.5.2 Prior to commencing grading, a preconstruction meeting should be held at the site with the
City inspector, developer, grading and underground contractors, civil engineer, and
geotechnical engineer in attendance. Special soil handling and/or the grading plans can be
discussed at that time.
7.5.3 Site preparation should begin with the removal of deleterious material, trash and debris, and
vegetation. The depth of vegetation removal should be such that material exposed in cut areas
Geocon Project No. G2755-42-01 - 16 - September 14, 2021
or soil to be used as fill is relatively free of organic matter. Material generated during stripping
and/or site demolition should be exported from the site. Asphalt and concrete (if encountered)
should not be mixed with the fill soil unless approved by the Geotechnical Engineer.
7.5.4 Abandoned foundations and buried utilities (if encountered) should be removed and the
resulting depressions and/or trenches backfilled with properly compacted material as part of
the remedial grading.
7.5.5 We recommend undocumented fill, topsoil, slope wash, and alluvium be removed to expose
competent Terrace Deposits or Otay Formation and replaced as compacted fill throughout
the site. Trash and debris may be encountered in the undocumented fill. Trash and debris, if
encountered, should be removed from the fill and exported.
7.5.6 The actual depth of remedial removals should be determined in the field during grading by a
representative of Geocon Incorporated prior to placement and compaction of fill.
7.5.7. Removals at the toes of slopes and in front of retaining walls should extend horizontally
beyond the edge of the slope toe or wall a distance equal to the depth of removal. A typical
detail of remedial grading beyond slope toes is presented below.
Geocon Project No. G2755-42-01 - 17 - September 14, 2021
Typical Limit of Remedial Grading
7.5.8 Off-site grading within the adjacent property to the north will be required to remove the
undocumented fill in the central drainage. Off-site grading will also be required to construct
the stability buttress/fills on the eastern hillside slope.
7.5.9 Removal of the clay beds for slope stability purposes should be performed to the limits
shown on Figures 1 and 2. Buttress and stability fills should be constructed as discussed in
Section 7.3 of this report, Appendix D, and Figure 3. All fill placed within the
buttress/stability fill area should meet the minimum strength requirement shown on the
following table.
Geocon Project No. G2755-42-01 - 18 - September 14, 2021
TABLE 7.5.1
RECOMMENDED SOIL STRENGTH PARAMETERS FOR BUTTRESS/STABILITY FILLS
Friction Angle (degrees) Cohesion (psf)
28 250
7.5.10 Grading will result in fill to formation transitions across the building pads. To reduce the
potential for differential settlement, the cut portion of the transition should be over-
excavated (undercut) at least 5 feet below proposed finish grade or at least two foot below
the lowest foundation element, whichever is deeper, and replaced with properly compacted
“very low” to “low” expansive fill soils. Overexcavations should extend to a horizontal
distance of at least 5 feet beyond the edge of the building pad and cut at a gradient of one
percent toward the deepest fill area to provide drainage for moisture migration along the
contact between the native soil and compacted fill.
7.5.11 We expect the bentonitic clay bed will be encountered near finish subgrade across the site.
The clay bed should be undercut to a depth of at least 5 feet below finish subgrade or at least
2 feet below the lowest foundation element, whichever is deeper, and replaced with properly
compacted “very low” to “low” expansive fill soils. The clay bed undercut should be
performed within both the building pads and below all structural improvements (pavement,
concrete flatwork, retaining walls, etc.).
7.5.12 Expansive soils should be placed in deeper fill areas, outside of the foundation, reinforced
and retained zones of MSE walls, and at least five feet below pad grade or two feet below
the deepest foundation element, whichever is deeper.
7.5.13 A summary of grading recommendations is shown on the table below.
Geocon Project No. G2755-42-01 - 19 - September 14, 2021
TABLE 7.5.2
SUMMARY OF REMEDIAL REMOVALS AND GRADING RECOMMENDATIONS
Area Removal Requirements
All Structural Improvement Areas
Remove all undocumented fill, topsoil, slope wash, and
alluvium. Overexcavate clay bed to a depth of 5 feet below
finish subgrade or 2 feet below building footing (whichever
is deeper)
Building Pads with Cut to Fill
Transition
Undercut building pad 5 feet below pad grade or 2 feet
below bottom of building footings (whichever is deeper)
Fill Areas Expansive Soil Buried at Least 5 Feet Below Pad Grade or at
Least 2 Feet Below Bottom of Footings
Remedial Grading Limits
5 Feet Outside of Building Pads;
2 Feet Outside of Improvement Areas;
Beyond toe of slopes and retaining walls a distance equal
to the depth of the remedial excavation, where possible
Exposed Bottoms of Remedial Grading Scarify Upper 12 Inches
7.5.14 Prior to fill soil being placed, the existing ground surface should be scarified, moisture
conditioned as necessary, and compacted to a depth of at least 12 inches. Deeper removals
may be required if saturated or loose fill soil is encountered. A representative of Geocon
should be on-site during removals to evaluate the limits of the remedial grading.
7.5.15 The site should then be brought to final subgrade elevations with fill compacted in layers. In
general, soil native to the site is suitable for use as fill if relatively free from vegetation,
debris and other deleterious material. Layers of fill should be no thicker than will allow for
adequate bonding and compaction. Fill, including backfill and scarified ground surfaces,
should be compacted to a dry density of at least 90 percent of the laboratory maximum dry
density near to slightly above optimum moisture content in accordance with ASTM Test
Procedure D 1557. Fill materials placed below optimum moisture content may require
additional moisture conditioning prior to placing additional fill.
7.5.16 Imported fill (if necessary) should consist of the characteristics presented in Table 7.5.3. Geocon
Incorporated should be notified of the import soil source and should perform laboratory testing
of import soil prior to its arrival at the site to determine its suitability as fill material.
TABLE 7.5.3
SUMMARY OF IMPORT FILL RECOMMENDATIONS
Soil Characteristic Values
Expansion Potential “Very Low” to “Low” (Expansion Index of 50 or less)
Particle Size Maximum Dimension Less Than 3 Inches
Generally Free of Debris
Geocon Project No. G2755-42-01 - 20 - September 14, 2021
7.6 Earthwork Grading Factors
7.6.1 Estimates of shrink-swell factors are based on comparing laboratory compaction tests with the
density of the material in its natural state and experience with similar soil types. Variations in
natural soil density and compacted fill render shrinkage value estimates very approximate. As an
example, the contractor can compact fill to a density of 90 percent or higher of the laboratory
maximum dry density. Thus, the contractor has at least a 10 percent range of control over the fill
volume. Based on the work performed to date and considering the discussion herein, the
earthwork factors in the following table may be used as a basis for estimating how much the on-
site soils may shrink or swell when removed from their natural state and placed as compacted
fill.
TABLE 7.6
SHRINKAGE AND BULK FACTORS
Soil Unit Shrink/Bulk Factor
Undocumented Fill (Dumped; Qudf) 10-15% Shrink
Undocumented Fill (Previously Compacted; Qudf) 0-3% Shrink
Topsoil and slope wash (unmapped) 5-10% Shrink
Alluvium (Qal) 4-10% Shrink
Terrace Deposits (Qt) 0-5% Bulk
Otay Formation (To) 3-5% Bulk
7.7 Subdrains
7.7.1 Subdrains should be installed in the canyon drainages that will be infilled. Typical subdrain
installation details are presented below.
7.7.2 Canyon subdrains should be constructed from 6-inch Schedule 40 PVC pipe or equivalent.
The approximate locations of proposed subdrains are shown on Figure 1. The recommended
subdrain locations are based on anticipated site conditions prior to grading and are subject to
change depending on the conditions encountered in the field.. Appropriate subdrain outlets
should be evaluated prior to finalizing the grading plan.
7.7.3 The final 20-foot segment of a subdrain should consist of non-perforated drainpipe. At the
non-perforated/perforated interface, a seepage cutoff wall should be constructed on the
downslope side of the junction in accordance with the figure below. The subdrains should
be tied into the storm drain system that outlets to Main Street.
Geocon Project No. G2755-42-01 - 21 - September 14, 2021
Typical Canyon Subdrain Detail
Typical Cutoff Wall Detail
7.7.4 Subdrains that discharge into a natural drainage course or open space area should be
provided with a permanent headwall structure as shown herein.
Geocon Project No. G2755-42-01 - 22 - September 14, 2021
Typical Headwall Detail
7.7.5 The final grading plans should show the location of the proposed subdrains. Upon
completion of remedial excavations and subdrain installation, the project civil engineer
should survey the drain locations and prepare an “as-built” map depicting the existing
conditions. The final outlet and connection locations should be determined during grading.
The grading contractor should consider videoing the subdrains shortly after burial to check
proper installation and to check that the pipe has not been crushed. The contractor is
responsible for the performance of the drains.
7.8 Settlement Monitoring
7.8.1 At the completion of grading, the south side of the site will be underlain by up to 45 feet of
compacted fill behind MSE walls. Post-grading settlement (hydro-compression) of properly
compacted new fill with a maximum thickness of 45 feet could be up to about 2.5 inches.
We expect the settlement could occur over 20+ years depending on the influx of rain and
irrigation water into the fill mass. This settlement will likely be linear from the time the fill
is placed to the end of the settlement period. We do not expect the settlement will impact
proposed utilities with proposed gradients of 1 percent or greater. The building foundation
design should be designed to account for potential hydro-compression settlement. It has
been our experience that developments/improvements, such as proposed, can be constructed
with the planned fill depths and proposed settlements.
7.8.2 We expect settlement in the fill as a result of self-weight compression could take up to 3 to 9
months. If building foundations will be constructed shortly after completion of the fill mass,
building foundations will need to be designed to accommodate differential settlement as a
result of self-weight compression. If the planned structures cannot tolerate the expected
movement, a construction waiting period should be implemented until settlement monitoring
indicates self-weight compression has essentially ceased.
Geocon Project No. G2755-42-01 - 23 - September 14, 2021
7.8.3 Due to the height of the MSE walls, we expect some settlement/lateral wall movement will
occur. This could result in cracking in flatwork and pavement placed within the reinforced
and retained zones of the wall.
7.8.4 At the south end of the property where fills are the greatest, we recommend settlement
monuments be installed subsequent to the MSE wall construction. A typical settlement
monument is shown below.
Settlement Plate Detail
7.8.5 Surveying of the surface monument should be performed by the project civil engineer every
two weeks for at least four months with the results provided to Geocon for review.
Settlement due to primary consolidation will be considered to have ceased when survey
readings show a relatively level plateau of settlement data over 4 consecutive readings.
7.9 Seismic Design Criteria
7.9.1 Table 7.9.1 summarizes site-specific design criteria obtained from the 2019 California
Building Code (CBC; Based on the 2018 International Building Code [IBC] and ASCE 7-
16), Chapter 16 Structural Design, Section 1613 Earthquake Loads. We used the computer
Geocon Project No. G2755-42-01 - 24 - September 14, 2021
program Seismic Design Maps, provided by the Structural Engineers Association (SEA) to
calculate the seismic design parameters. The short spectral response uses a period of
0.2 second. We evaluated the Site Class based on the discussion in Section 1613.2.2 of the
2019 CBC and Table 20.3-1 of ASCE 7-16. The values presented herein are for the risk-
targeted maximum considered earthquake (MCER) for Site Classes C and D. The southern
portion of the building will be underlain by compacted fill in excess of 40 feet. A Site Class
D is appropriate for areas underlain by more than 20 feet of fill. The northern portion of the
building pads will be underlain by shallow compacted fills. Site Class C is appropriate for
this condition.
TABLE 7.9.1
2019 CBC SEISMIC DESIGN PARAMETERS
Parameter Value 2019 CBC Reference
Site Class C D Section 1613.2.2
MCER Ground Motion Spectral Response
Acceleration – Class B (short), SS
0.835g 0.835g Figure 1613.2.1(1)
MCER Ground Motion Spectral Response
Acceleration – Class B (1 sec), S1
0.297g 0.297g Figure 1613.2.1(2)
Site Coefficient, FA 1.2 1.166 Table 1613.2.3(1)
Site Coefficient, FV 1.5 2.007* Table 1613.2.3(2)
Site Class Modified MCER Spectral
Response Acceleration (short), SMS
1.002g 0.973g Section 1613.2.3 (Eqn 16-36)
Site Class Modified MCER Spectral
Response Acceleration – (1 sec), SM1
0.445g 0.595g* Section 1613.2.3 (Eqn 16-37)
5% Damped Design Spectral Response
Acceleration (short), SDS
0.668g 0.649g Section 1613.2.4 (Eqn 16-38)
5% Damped Design Spectral Response
Acceleration (1 sec), SD1
0.297g 0.397g* Section 1613.2.4 (Eqn 16-39)
*Using the code-based values presented in this table, in lieu of a performing a ground motion hazard
analysis, requires the exceptions outlined in ASCE 7-16 Section 11.4.8 be followed by the project
structural engineer. Per Section 11.4.8 of ASCE/SEI 7-16, a ground motion hazard analysis should be
performed for projects for Site Class “E” sites with Ss greater than or equal to 1.0g and for Site Class
“D” and “E” sites with S1 greater than 0.2g. Section 11.4.8 also provides exceptions which indicates
that the ground motion hazard analysis may be waived provided the exceptions are followed.
7.9.2 Table 7.9.2 presents the mapped maximum considered geometric mean (MCEG) seismic
design parameters for projects located in Seismic Design Categories of D through F in
accordance with ASCE 7-16.
Geocon Project No. G2755-42-01 - 25 - September 14, 2021
TABLE 7.9.2
ASCE 7-16 PEAK GROUND ACCELERATION
Parameter Value ASCE 7-16 Reference
Site Class C D Section 1613.2.2 (2019 CBC)
Mapped MCEG Peak Ground
Acceleration, PGA 0.365g 0.365g Figure 22-7
Site Coefficient, FPGA 1.2 1.235 Table 11.8-1
Site Class Modified MCEG Peak
Ground Acceleration, PGAM 0.438g 0.451g Section 11.8.3 (Eqn 11.8-1)
7.9.3 Conformance to the criteria in Tables 7.9.1 and 7.9.2 for seismic design does not constitute
any kind of guarantee or assurance that significant structural damage or ground failure will
not occur if a large earthquake occurs. The primary goal of seismic design is to protect life,
not to avoid all damage, since such design may be economically prohibitive.
7.9.4 The project structural engineer and architect should evaluate the appropriate Risk Category
and Seismic Design Category for the planned structures. The values presented herein
assume a Risk Category of II and resulting in a Seismic Design Category D. Table 7.9.3
presents a summary of the risk categories.
TABLE 7.9.3
ASCE 7-16 RISK CATEGORIES
Risk Category Building Use Examples
I Low risk to Human Life at Failure Barn, Storage Shelter
II
Nominal Risk to Human Life at
Failure (Buildings Not Designated as
I, III or IV)
Residential, Commercial and Industrial
Buildings
III Substantial Risk to Human Life at
Failure
Theaters, Lecture Halls, Dining Halls,
Schools, Prisons, Small Healthcare
Facilities, Infrastructure Plants, Storage
for Explosives/Toxins
IV Essential Facilities
Hazardous Material Facilities,
Hospitals, Fire and Rescue, Emergency
Shelters, Police Stations, Power
Stations, Aviation Control Facilities,
National Defense, Water Storage
7.10 Shallow Foundations
7.10.1 The proposed structure can be supported on a shallow foundation system bearing in
compacted fill provided the grading and buttress recommendations provide in this report are
followed. Foundations for the structure should consist of continuous strip footings and/or
Geocon Project No. G2755-42-01 - 26 - September 14, 2021
isolated spread footings. Table 7.10.1 provides a summary of the foundation design
recommendations.
TABLE 7.10.1
SUMMARY OF FOUNDATION RECOMMENDATIONS
Parameter Value
Minimum Continuous Foundation Width 12 inches
Minimum Isolated Foundation Width 24 inches
Minimum Foundation Depth 24 Inches Below Lowest Adjacent Grade
Minimum Steel Reinforcement 4 No. 5 Bars, 2 at the Top and 2 at the Bottom
Allowable Bearing Capacity 2,500 psf
Bearing Capacity Increase 500 psf per Foot of Depth
300 psf per Foot of Width
Maximum Allowable Bearing Capacity 4,000 psf
Estimated Total Settlement 1 Inch
Estimated Static Differential Settlement ½ Inch in 40 Feet
Footing Size Used for Settlement 8-Foot Square
Design Expansion Index 50 or less
7.10.2 Additional settlement as a result of self-weight compression and hydro-compression could
occur over the life of the structures. We estimate approximately 0.4 percent of the total fill
thickness underlying the building pad. Self-weight compression is expected to occur over 3
to 9 months. Hydro-compression is expected to occur over a 20 year or more duration. The
estimated fill thickness and total settlement as a result of self-weight compression and
hydro-compression is shown on Table 7.10.2 and is in addition to the static settlement
indicated on Table 7.10.1. The largest settlement over the shortest distance occurs in
Buildings 2 and 3 that overlie the central drainage area. Foundations should be designed to
accommodate total and differential settlement from both static loading and self-weight
compression/hydro-compression.
Geocon Project No. G2755-42-01 - 27 - September 14, 2021
TABLE 7.10.2
ESTIMATED FILL THICKNESS AND TOTAL AND DIFFERENTIAL FILL SETTLEMENT
AS A RESULT OF SELF-WEIGHT AND HYDRO-COMPRESSION
Location
Estimated
Compacted Fill
Thickness in
Building Pads
(after grading)
(feet)
Estimated Total
Settlement
(Self-Weight and
Hydro-Compression)
(inches)
Estimated Differential
Settlement
(Self-Weight and
Hydro-Compression)
(inches)
Building 1
(Southwest Corner) 30 1.5
1.25 inches over a span
of 130 feet (angular
distortion of 1/1250)
Building 1
(Northeast Half) 5 0.25
0.25 over a span of 140
feet (angular distortion
of 1/6700)
Building 2
(Northeast Portion) 45 2.2
2 inches over a span of
60 feet (angular
distortion of 1/360)
Building 2
(Southeast Portion) 50 2.4
2.2 inches over a span of
160 feet (angular
distortion of 1/900
Building 2
(Western Half) 5 0.25
0.25 over a span of 120
feet (angular distortion
of 1/5800)
Building 3
(Southwest Corner) 40 1.9
1.7 inches over a span of
60 feet (angular
distortion of 1/425)
Building 3
(Northeast) 5 0.25
0.25 over a span of 110
feet (angular distortion
of 1/5300)
Building 4 5 0.25 NA
7.10.3 The foundations should be embedded in accordance with the recommendations herein and
the Wall/Column Footing Dimension Detail. The embedment depths should be measured
from the lowest adjacent pad grade for both interior and exterior footings. Footings should
be deepened such that the bottom outside edge of the footing is at least 7 feet horizontally
from the face of the slope (unless designed with a post-tensioned foundation system as
discussed herein).
Geocon Project No. G2755-42-01 - 28 - September 14, 2021
Wall/Column Footing Dimension Detail
7.10.4 The bearing capacity values presented herein are for dead plus live loads and may be
increased by one-third when considering transient loads due to wind or seismic forces.
7.10.5 Where buildings or other improvements are planned near the top of a slope steeper than 3:1
(horizontal:vertical), special foundations and/or design considerations are recommended due
to the tendency for lateral soil movement to occur.
For fill slopes less than 20 feet high or cut slopes regardless of height, footings
should be deepened such that the bottom outside edge of the footing is at least 7 feet
horizontally from the face of the slope.
When located next to a descending 3:1 (horizontal:vertical) fill slope or steeper, the
foundations should be extended to a depth where the minimum horizontal distance
is equal to H/3 (where H equals the vertical distance from the top of the fill slope to
the base of the fill soil) with a minimum of 7 feet but need not exceed 40 feet. The
horizontal distance is measured from the outer, deepest edge of the footing to the
face of the slope. A post-tensioned slab and foundation system or mat foundation
system can be used to reduce the potential for distress in the structures associated
with strain softening and lateral fill extension. Specific design parameters or
recommendations for either of these alternatives can be provided once the building
location and fill slope geometry have been determined.
Although other improvements, which are relatively rigid or brittle, such as concrete
flatwork or masonry walls, may experience some distress if located near the top of a
slope, it is generally not economical to mitigate this potential. It may be possible,
however, to incorporate design measures that would permit some lateral soil
movement without causing extensive distress. Geocon Incorporated should be
consulted for specific recommendations.
7.10.6 We should observe the foundation excavations prior to the placement of reinforcing steel
and concrete to check that the exposed soil conditions are similar to those expected and that
they have been extended to the appropriate bearing strata. Foundation modifications may be
required if unexpected soil conditions are encountered.
Geocon Project No. G2755-42-01 - 29 - September 14, 2021
7.10.7 Geocon Incorporated should be consulted to provide additional design parameters as
required by the structural engineer.
7.11 Conventional Retaining Wall Recommendations
7.11.1 Retaining walls should be designed using the values presented in Table 7.11.1. Soil with an
expansion index (EI) of greater than 50 should not be used as backfill soil behind retaining
walls.
TABLE 6.11.1
RETAINING WALL DESIGN RECOMMENDATIONS
Parameter Value
Active Soil Pressure, A (Fluid Density, Level Backfill) 35 pcf
Active Soil Pressure, A (Fluid Density, 2:1 Sloping Backfill) 50 pcf
Seismic Pressure, S 18H psf
At-Rest/Restrained Walls Additional Uniform Pressure (0 to 8 Feet High) 7H psf
At-Rest/Restrained Walls Additional Uniform Pressure (8+ Feet High) 13H psf
Expected Expansion Index for the Subject Property EI<50
H equals the height of the retaining portion of the wall
7.11.2 The project retaining walls should be designed as shown in the Retaining Wall Loading
Diagram.
Retaining Wall Loading Diagram
Geocon Project No. G2755-42-01 - 30 - September 14, 2021
7.11.3 Unrestrained walls are those that are allowed to rotate more than 0.001H (where H equals
the height of the retaining portion of the wall) at the top of the wall. Where walls are
restrained from movement at the top (at-rest condition), an additional uniform pressure
should be applied to the wall. For retaining walls subject to vehicular loads within a
horizontal distance equal to two-thirds the wall height, a surcharge equivalent to 2 feet of fill
soil should be added.
7.11.4 The structural engineer should determine the Seismic Design Category for the project in
accordance with Section 1613.2.5 of the 2019 CBC or Section 11.6 of ASCE 7-16. For
structures assigned to Seismic Design Category of D, E, or F, retaining walls that support
more than 6 feet of backfill should be designed with seismic lateral pressure in accordance
with Section 1803.5.12 of the 2019 CBC. The seismic load is dependent on the retained
height where H is the height of the wall, in feet, and the calculated loads result in pounds per
square foot (psf) exerted at the base of the wall and zero at the top of the wall.
7.11.5 Retaining walls should be designed to ensure stability against overturning sliding, and
excessive foundation pressure. Where a keyway is extended below the wall base with the
intent to engage passive pressure and enhance sliding stability, it is not necessary to
consider active pressure on the keyway.
7.11.6 Drainage openings through the base of the wall (weep holes) should not be used where the
seepage could be a nuisance or otherwise adversely affect the property adjacent to the base
of the wall. The recommendations herein assume a properly compacted granular (EI of 50 or
less) free-draining backfill material with no hydrostatic forces or imposed surcharge load.
The retaining wall should be properly drained as shown in the Typical Retaining Wall
Drainage Detail. If conditions different than those described are expected, or if specific
drainage details are desired, Geocon Incorporated should be contacted for additional
recommendations.
Geocon Project No. G2755-42-01 - 31 - September 14, 2021
Typical Retaining Wall Drainage Detail
7.11.7 The retaining walls may be designed using either the active and restrained (at-rest) loading
condition or the active and seismic loading condition as suggested by the structural
engineer. Typically, it appears the design of the restrained condition for retaining wall
loading may be adequate for the seismic design of the retaining walls. However, the active
earth pressure combined with the seismic design load should be reviewed and also
considered in the design of the retaining walls.
7.11.8 In general, wall foundations should be designed in accordance with Table 7.11.2. The
proximity of the foundation to the top of a slope steeper than 3:1 could impact the allowable
soil bearing pressure. Therefore, retaining wall foundations should be deepened such that the
bottom outside edge of the footing is at least 7 feet horizontally from the face of the slope.
TABLE 7.11.2
SUMMARY OF RETAINING WALL FOUNDATION RECOMMENDATIONS
Parameter Value
Minimum Retaining Wall Foundation Width 12 inches
Minimum Retaining Wall Foundation Depth 12 Inches
Minimum Steel Reinforcement Per Structural Engineer
Bearing Capacity 2,500 psf
Bearing Capacity Increase 500 psf per additional foot of footing depth
300 psf per additional foot of footing width
Maximum Bearing Capacity 4,000 psf
Estimated Total Settlement 1 Inch
Estimated Differential Settlement ½ Inch in 40 Feet
Geocon Project No. G2755-42-01 - 32 - September 14, 2021
7.11.9 The recommendations presented herein are generally applicable to the design of rigid
concrete or masonry retaining walls. Additional recommendations for MSE walls and soil
nail walls are provided in Sections 7.13 and 7.14.
7.11.10 Unrestrained walls will move laterally when backfilled and loading is applied. The amount
of lateral deflection is dependent on the wall height, the type of soil used for backfill, and
loads acting on the wall. The retaining walls and improvements above the retaining walls
should be designed to incorporate an appropriate amount of lateral deflection as determined
by the structural engineer.
7.11.11 Soil contemplated for use as retaining wall backfill, including import materials, should be
identified in the field prior to backfill. At that time, Geocon Incorporated should obtain
samples for laboratory testing to evaluate its suitability. Modified lateral earth pressures
may be necessary if the backfill soil does not meet the required expansion index or shear
strength. City or regional standard wall designs, if used, are based on a specific active lateral
earth pressure and/or soil friction angle. In this regard, on-site soil to be used as backfill may
or may not meet the values for standard wall designs. Geocon Incorporated should be
consulted to assess the suitability of the on-site soil for use as wall backfill if standard wall
designs will be used.
7.12 Lateral Loading
7.12.1 Table 7.12 should be used to help design the proposed structures and improvements to resist
lateral loads for the design of footings or shear keys. The allowable passive pressure
assumes a horizontal surface extending at least 5 feet, or three times the surface generating
the passive pressure, whichever is greater. The upper 12 inches of material in areas not
protected by floor slabs or pavement should not be included in design for passive resistance.
Where walls are planned adjacent to and/or on descending slopes, a passive pressure of 150
pcf should be used in design.
TABLE 7.12
SUMMARY OF LATERAL LOAD DESIGN RECOMMENDATIONS
Parameter Value
Passive Pressure Fluid Density 350 pcf
Passive Pressure Fluid Density Adjacent to and/or on
Descending Slopes 150 pcf
Coefficient of Friction (Concrete and Soil) 0.35
Coefficient of Friction (Along Vapor Barrier) 0.2 to 0.25*
*Per manufacturer’s recommendations.
Geocon Project No. G2755-42-01 - 33 - September 14, 2021
7.12.2 The passive and frictional resistant loads can be combined for design purposes. The lateral
passive pressures may be increased by one-third when considering transient loads due to
wind or seismic forces.
7.13 Mechanically Stabilized Earth (MSE) Retaining Walls
7.13.1 Mechanized stabilized earth (MSE) retaining walls are planned for the project. MSE
retaining walls are alternative walls that consist of modular block facing units with geogrid
reinforced earth behind the block. The reinforcement grid attaches to the block units and is
typically placed at specified vertical intervals and embedment lengths. The grid length and
spacing will be determined by the wall designer.
7.13.2 The geotechnical parameters listed in Table 7.13.1 can be used for preliminary design of the
MSE walls. Once actual soil to be used as backfill has been determined and stockpiled,
laboratory testing should be performed to check that the soil meets the parameters used in
the design of the MSE walls. Screening of onsite soil intended for MSE wall backfill may be
necessary to meet maximum particle size requirements for soil used in the reinforced zone.
TABLE 7.13.1
GEOTECHNICAL PARAMETERS FOR MSE WALLS
Parameter Reinforced Zone Retained Zone Foundation Zone
Angle of Internal Friction 28 degrees 28 degrees 28 degrees
Cohesion 100 psf 100 psf 100 psf
Wet Unit Density 130 pcf 130 pcf 130 pcf
7.13.3 The soil parameters presented in Table 7.13.1 are based on our experience and direct shear-
strength tests performed during the geotechnical investigation and represent some of the on-
site materials. Geocon has no way of knowing which materials will actually be used as
backfill behind the wall during construction. It is up to the wall designers to use their
judgment in selection of the design parameters. As such, once backfill materials have been
selected and/or stockpiled, sufficient shear tests should be conducted on samples of the
proposed backfill materials to check that they conform to actual design values. Results
should be provided to the designer to re-evaluate stability of the walls. Dependent upon test
results, the designer may require modifications to the original wall design (e.g., longer
reinforcement embedment lengths and/or steel reinforcement).
7.13.4 Wall foundations should be designed in accordance with Table 7.13.2 The walls should be
deepened such that the bottom outside edge of the footing is at least 7 feet horizontally from
Geocon Project No. G2755-42-01 - 34 - September 14, 2021
the face of the slope. The bearing zone on the MSE wall can be taken across the width of the
reinforced zone.
TABLE 7.13.2
SUMMARY OF MSE RETAINING WALL FOUNDATION RECOMMENDATIONS
Parameter Value
Minimum Retaining Wall Foundation Width 12 inches
Minimum Retaining Wall Foundation Depth 12 Inches
Bearing Capacity 2,000 psf
Bearing Capacity Increase 500 psf per Foot of Depth
300 psf per Foot of Width
Maximum Bearing Capacity 4,000 psf
Estimated Total Settlement 1 Inch
Estimated Differential Settlement ½ Inch in 40 Feet
7.13.5 Backfill materials within the reinforced zone should be compacted to a dry density of at
least 90 percent of the laboratory maximum dry density near to slightly above optimum
moisture content in accordance with ASTM D 1557. This is applicable to the entire
embedment width of the reinforcement. Typically, wall designers specify no heavy
compaction equipment within 3 feet of the face of the wall. However, smaller equipment
(e.g., walk-behind, self-driven compactors or hand whackers) can be used to compact the
materials without causing deformation of the wall. If the designer specifies no compactive
effort for this zone, the materials are essentially not properly compacted and the
reinforcement grid within the uncompacted zone should not be relied upon for
reinforcement, and overall embedment lengths will have to be increased to account for the
difference.
7.13.6 The wall should be provided with a drainage system sufficient to prevent excessive seepage
through the wall and the base of the wall, thus preventing hydrostatic pressures behind
the wall.
7.13.7 Geosynthetic reinforcement must elongate to develop full tensile resistance. This elongation
generally results in movement at the top of the wall. The amount of movement is dependent
on the height of the wall (e.g., higher walls rotate more) and the type of reinforcing grid
used. In addition, over time the reinforcement grid has been known to exhibit creep
(sometimes as much as 5 percent) and can undergo additional movement. Given this
condition, the owner should be aware that structures and pavement placed within the
Geocon Project No. G2755-42-01 - 35 - September 14, 2021
reinforced and retained zones of the wall will likely undergo movement for the wall heights
proposed on this project.
7.13.8 The MSE wall contractor should provide the estimated deformation of wall and adjacent
ground in associated with wall construction. The calculated horizontal and vertical
deformations should be determined by the wall designer. Where buildings are located
adjacent to the walls, the estimated movements should be provided to the project structural
engineer to evaluate if the building foundation can tolerate the expected movements. With
respect to improvements adjacent to the wall, cracking and/or movement should be
expected.
7.13.9 The MSE wall designer/contractor should review this report, including the slope stability
requirements, and incorporate our recommendations as presented herein. We should be
provided the plans for the MSE walls to check if they are in conformance with our
recommendations prior to issuance of a permit and construction.
7.14 Soil Nail Walls
7.14.1 We understand soil nail walls are planned for the northern property line wall. Soil nail walls
consist of installing closely spaced steel bars (nails) into a slope or excavation in a top-down
construction sequence. Following installation of a horizontal row of nails, drains,
waterproofing and wall reinforcing steel are placed and shotcrete applied to create a final
wall. The wall should be designed by an engineer familiar with the design of soil nail walls.
7.14.2 In general, ground conditions are moderately suited to soil nail wall construction techniques.
However, localized gravel, cobble and oversized material could be encountered that may be
difficult to drill. Additionally, relatively clean sands may be encountered that may result in
some raveling of the unsupported excavation. Casing or specialized drilling techniques
should be planned where raveling exists (e.g. casing).
7.14.3 Testing of the soil nails should be performed in accordance with the guidelines of the
Federal Highway Administration or similar guidelines. At least two verification tests should
be performed to confirm design assumptions for each soil/rock type encountered.
Verification tests nails should be sacrificial and should not be used to support the proposed
wall. The bond length should be adjusted to allow for pullout testing of the verification nails
to evaluate the ultimate bond stress. A minimum of 5 percent of the production nails should
also be proof tested and a minimum of 4 sacrificial nails should be tested at the discretion of
Geocon Incorporated. Consideration should be given to testing sacrificial nails with an
Geocon Project No. G2755-42-01 - 36 - September 14, 2021
adjusted bond length rather than testing production nails. Geocon Incorporated should
observe the nail installation and perform the nail testing.
7.14.4 The soil strength parameters listed in Table 7.14 can be used in design of the soil nails. The bond
stress is dependent on drilling method, diameter, and construction method. Therefore, the
designer should evaluate the bond stress based on soil conditions and the construction method.
TABLE 7.14
SOIL STRENGTH PARAMETERS FOR SOIL NAIL WALLS
Description Cohesion (psf) Friction Angle
(degrees)
Estimated
Ultimate Bond
Stress (psi)*
Compacted Fill 100 28 10
Very Old Paralic Deposits 200 33 20
Otay Formation 200 33 20
*Assuming gravity fed, open hole drilling techniques.
7.14.5 A wall drain system should be incorporated into the design of the soil nail wall as shown
herein. Corrosion protection should be provided for the nails.
7.14.6 A bentonitic clay bed is expected to be present near the bottom of the wall cut along the
north side of the property. The wall design will need to pin the clay bed to prevent slope
instability. Geocon Incorporated can provide additional stability analysis and coordination
with the wall designer, as needed.
Soil Nail Wall Drainage Detail
Geocon Project No. G2755-42-01 - 37 - September 14, 2021
7.15 Preliminary Pavement Recommendations
7.15.1 Preliminary pavement recommendations for the driveways and parking areas are provided
below. The final pavement sections should be based on the R-Value of the subgrade soil
encountered at final subgrade elevation. For preliminary design, we used a laboratory R-Value
of 15. We calculated the preliminary flexible pavement sections for asphalt concrete using
varying traffic indices (TIs) in general conformance with the Caltrans Method of Flexible
Pavement Design (Highway Design Manual, Section 608.4). The project civil engineer or traffic
engineer should determine the appropriate Traffic Index (TI) or traffic loading expected on the
project for the various pavement areas that will be constructed. Recommended preliminary
asphalt concrete pavement sections are provided on Table 7.15.1.
TABLE 7.15.1
PRELIMINARY ASPHALT CONCRETE PAVEMENT SECTIONS
Traffic Index Asphalt Concrete (inches) Class 2 Base (inches)
4.5 3 6
5 3 8
5.5 3 10
6 3.5 10.5
6.5 3.5 12.5
7 4 13
7.5 4.5 15
8 5 15
7.15.2 Asphalt concrete should conform to Section 203-6 of the Standard Specifications for Public
Works Construction (Green Book). Class 2 aggregate base materials should conform to
Section 26-1.02B of the Standard Specifications of the State of California, Department of
Transportation (Caltrans).
7.15.3 Prior to placing base material, the subgrade should be scarified, moisture conditioned and
recompacted to a minimum of 95 percent relative compaction. The depth of compaction
should be at least 12 inches. The base material should be compacted to at least 95 percent
relative compaction. Asphalt concrete should be compacted to a density of at least
95 percent of the laboratory Hveem density in accordance with ASTM D 2726.
7.15.4 A rigid Portland Cement concrete (PCC) pavement section can also be used. We calculated
the rigid pavement section in general conformance with the procedure recommended by the
American Concrete Institute report ACI 330R-08 Guide for Design and Construction of
Concrete Parking Lots using the parameters presented in Table 7.15.2.
Geocon Project No. G2755-42-01 - 38 - September 14, 2021
TABLE 7.15.2
PRELIMINARY RIGID PAVEMENT DESIGN PARAMETERS
Design Parameter Design Value
Modulus of subgrade reaction, k 100 pci
Modulus of rupture for concrete, MR 500 psi
Concrete Compressive Strength 3,000 psi
Traffic Category, TC A and C
Average daily truck traffic, ADTT 10 and 300
7.15.5 Based on the criteria presented herein, the PCC pavement sections should have a minimum
thickness as presented in Table 7.15.3.
TABLE 7.15.3
RIGID VEHICULAR PAVEMENT RECOMMENDATIONS
Location Portland Cement Concrete (inches)
Automobile Parking Stalls (TC=A, ADTT=10) 5.5
Driveways (TC=C, ADTT=100) 7.5
7.15.6 The PCC vehicular pavement should be placed over subgrade soil that is compacted to a dry
density of at least 95 percent of the laboratory maximum dry density near to slightly above
optimum moisture content.
7.15.7 The rigid pavement should also be designed and constructed incorporating the parameters
presented in Table 7.15.4.
TABLE 7.15.4
ADDITIONAL RIGID PAVEMENT RECOMMENDATIONS
Subject Value
Thickened Edge
1.2 Times Slab Thickness
Minimum Increase of 2 Inches
4 Feet Wide
Crack Control Joint Spacing
30 Times Slab Thickness
Max. Spacing of 12 feet for 5.5-Inch-Thick
Max. Spacing of 15 Feet for Slabs 6 Inches and Thicker
Crack Control Joint Depth
Per ACI 330R-08
1 Inch Using Early-Entry Saws on Slabs Less Than 9 Inches Thick
Crack Control Joint Width
¼-Inch for Sealed Joints
⅜-Inch is Common for Sealed Joints
1/10- to 1/8-Inch is Common for Unsealed Joints
Geocon Project No. G2755-42-01 - 39 - September 14, 2021
7.15.8 Concrete reinforcing steel will not be necessary within the concrete for geotechnical
purposes with the possible exception of dowels at construction joints as discussed herein.
7.15.9 To control the location and spread of concrete shrinkage cracks, crack-control joints
(weakened plane joints) should be included in the design of the concrete pavement slab.
Crack-control joints should be sealed with an appropriate sealant to prevent the migration of
water through the control joint to the subgrade materials. The depth of the crack-control
joints should be determined by the referenced ACI report.
7.15.10 To provide load transfer between adjacent pavement slab sections, a butt-type construction
joint should be constructed. The butt-type joint should be thickened by at least 20 percent at
the edge and taper back at least 4 feet from the face of the slab. As an alternative to the butt-
type construction joint, dowelling can be used between construction joints for pavements of
7 inches or thicker. As discussed in the referenced ACI guide, dowels should consist of
smooth, 1-inch-diameter reinforcing steel 14 inches long embedded a minimum of 6 inches
into the slab on either side of the construction joint. Dowels should be located at the
midpoint of the slab, spaced at 12 inches on center and lubricated to allow joint movement
while still transferring loads. In addition, tie bars should be installed as recommended in
Section 3.8.3 of the referenced ACI guide. The structural engineer should provide other
alternative recommendations for load transfer.
7.15.11 Concrete curb/gutter should be placed on soil subgrade compacted to a dry density of at
least 90 percent of the laboratory maximum dry density near to slightly above optimum
moisture content. Cross-gutters that receives vehicular should be placed on subgrade soil
compacted to a dry density of at least 95 percent of the laboratory maximum dry density
near to slightly above optimum moisture content. Base materials should not be placed below
the curb/gutter, or cross-gutters so water is not able to migrate from the adjacent parkways
to the pavement sections. Where flatwork is located directly adjacent to the curb/gutter, the
concrete flatwork should be structurally connected to the curbs to help reduce the potential
for offsets between the curbs and the flatwork.
7.16 Exterior Concrete Flatwork
7.16.1 Exterior concrete flatwork not subject to vehicular traffic should be constructed in
accordance with the recommendations presented in Table 7.16. The recommended steel
reinforcement would help reduce the potential for cracking.
Geocon Project No. G2755-42-01 - 40 - September 14, 2021
TABLE 7.16
MINIMUM CONCRETE FLATWORK RECOMMENDATIONS
Expansion
Index, EI Minimum Steel Reinforcement* Options Minimum
Thickness
EI < 90 6x6-W2.9/W2.9 (6x6-6/6) welded wire mesh
4 Inches No. 3 Bars 18 inches on center, Both Directions
EI < 130 4x4-W4.0/W4.0 (4x4-4/4) welded wire mesh
No. 4 Bars 12 inches on center, Both Directions
*In excess of 8 feet square.
7.16.2 Even with the incorporation of the recommendations of this report, the exterior concrete
flatwork has a potential to experience some uplift due to expansive soil beneath grade. The
steel reinforcement should overlap continuously in flatwork to reduce the potential for
vertical offsets within flatwork. Additionally, flatwork should be structurally connected to
the curbs, where possible, to reduce the potential for offsets between the curbs and the
flatwork.
7.16.3 Concrete flatwork should be provided with crack control joints to reduce and/or control
shrinkage cracking. Crack control spacing should be determined by the project structural
engineer based upon the slab thickness and intended usage. Criteria of the American
Concrete Institute (ACI) should be taken into consideration when establishing crack control
spacing. Subgrade soil for exterior slabs not subjected to vehicle loads should be compacted
in accordance with criteria presented in the grading section prior to concrete placement.
Subgrade soil should be properly compacted, and the moisture content of subgrade soil
should be verified prior to placing concrete. Base materials will not be required below
concrete improvements.
7.16.4 Where exterior flatwork abuts the structure at entrant or exit points, the exterior slab should
be dowelled into the structure’s foundation stemwall. This recommendation is intended to
reduce the potential for differential elevations that could result from differential settlement
or minor heave of the flatwork. Dowelling details should be designed by the project
structural engineer.
7.16.5 The recommendations presented herein are intended to reduce the potential for cracking of
exterior slabs as a result of differential movement. However, even with the incorporation of
the recommendations presented herein, slabs-on-grade will still crack. The occurrence of
concrete shrinkage cracks is independent of the soil supporting characteristics. Their
occurrence may be reduced and/or controlled by limiting the slump of the concrete, the use
of crack control joints and proper concrete placement and curing. Crack control joints
Geocon Project No. G2755-42-01 - 41 - September 14, 2021
should be spaced at intervals no greater than 12 feet. Literature provided by the Portland
Concrete Association (PCA) and American Concrete Institute (ACI) present
recommendations for proper concrete mix, construction, and curing practices, and should be
incorporated into project construction.
7.17 Slope Maintenance
7.17.1 Slopes that are steeper than 3:1 (horizontal:vertical) may, under conditions which are both
difficult to prevent and predict, be susceptible to near surface (surficial) slope instability.
The instability is typically limited to the outer three feet of a portion of the slope and usually
does not directly impact the improvements on the pad areas above or below the slope. The
occurrence of surficial instability is more prevalent on fill slopes and is generally preceded
by a period of heavy rainfall, excessive irrigation, or the migration of subsurface seepage.
The disturbance and/or loosening of the surficial soils, as might result from root growth, soil
expansion, or excavation for irrigation lines and slope planting, may also be a significant
contributing factor to surficial instability. It is, therefore, recommended that, to the
maximum extent practical: (a) disturbed/loosened surficial soils be either removed or
properly recompacted, (b) irrigation systems be periodically inspected and maintained to
eliminate leaks and excessive irrigation, and (c) surface drains on and adjacent to slopes be
periodically maintained to preclude ponding or erosion. Although the incorporation of the
above recommendations should reduce the potential for surficial slope instability, it will not
eliminate the possibility, and, therefore, it may be necessary to rebuild or repair a portion of
the project's slopes in the future.
7.18 Storm Water Management
7.18.1 If storm water management devices are not properly designed and constructed, there is a
risk for distress to improvements and property located hydrologically down gradient or
adjacent to these devices. Factors such as the amount of water being detained, its residence
time, and soil permeability have an important effect on seepage transmission and the
potential adverse impacts that may occur if the storm water management features are not
properly designed and constructed. We have not performed a hydrogeological study at the
site. If infiltration of storm water runoff into the subsurface occurs, downstream
improvements may be subjected to seeps, springs, slope instability, raised groundwater,
movement of foundations and slabs, or other undesirable impacts as a result of water
infiltration.
7.18.2 We did not perform an infiltration study on the property. However, based on predicted site
conditions at the completion of grading, full and partial infiltration is considered infeasible
due to the presence of deep fills surrounded by MSE walls at the down-gradient end of the
Geocon Project No. G2755-42-01 - 42 - September 14, 2021
site. Basins or other storm water devices should utilize a liner to prevent infiltration from
causing adverse settlement and heave, and migrating to utilities, and foundations.
7.19 Site Drainage and Moisture Protection
7.19.1 Adequate site drainage is critical to reduce the potential for differential soil movement,
erosion and subsurface seepage. Under no circumstances should water be allowed to pond
adjacent to footings. The site should be graded and maintained such that surface drainage is
directed away from structures in accordance with 2019 CBC 1803.3 or other applicable
standards. In addition, surface drainage should be directed away from the top of slopes into
swales or other controlled drainage devices. Roof and pavement drainage should be directed
into conduits that carry runoff away from the proposed structure.
7.19.2 In the case of basement walls or building walls retaining landscaping areas, a water-proofing
system should be used on the wall and joints, and a Miradrain drainage panel (or similar)
should be placed over the waterproofing. The project architect or civil engineer should
provide detailed specifications on the plans for all waterproofing and drainage.
7.19.3 Underground utilities should be leak free. Utility and irrigation lines should be checked
periodically for leaks, and detected leaks should be repaired promptly. Detrimental soil
movement could occur if water is allowed to infiltrate the soil for prolonged periods of time.
7.19.4 Landscaping planters adjacent to paved areas are not recommended due to the potential for
surface or irrigation water to infiltrate the pavement's subgrade and base course. We
recommend that subdrains to collect excess irrigation water and transmit it to drainage
structures, or impervious above-grade planter boxes be used. In addition, where landscaping
is planned adjacent to the pavement, we recommend construction of a cutoff wall along the
edge of the pavement that extends at least 6 inches below the bottom of the base material.
7.20 Grading and Foundation Plan Review
7.20.1 Geocon Incorporated should review the grading plans and foundation plans for the project
prior to final design submittal to evaluate whether additional analyses and/or
recommendations are required.
7.21 Testing and Observation Services During Construction
7.21.1 Geocon Incorporated should provide geotechnical testing and observation services during
the grading operations, foundation construction, utility installation, retaining wall backfill
Geocon Project No. G2755-42-01 - 43 - September 14, 2021
and pavement installation. Table 7.21 presents the typical geotechnical observations we
would expect for the proposed improvements.
TABLE 7.21
EXPECTED GEOTECHNICAL TESTING AND OBSERVATION SERVICES
Construction Phase Observations Expected Time Frame
Ground Modification Ground Modification Installation Full Time
Confirmation Testing Part Time to Full Time
Grading
Base of Removal Part Time During
Removals
Geologic Logging Part Time to Full Time
Fill Placement and Soil Compaction Full Time
MSE Walls Fill Placement and Soil Compaction Full Time
Tieback Anchors Tieback Drilling and Installation Full Time
Tieback Testing Full Time
Soil Nail Walls Soil Nail Drilling and Installation Full Time
Soil Nail Testing Full Time
Foundations Drilling Operations for Piles Full Time
Foundation Excavation Observations Part Time
Utility Backfill Fill Placement and Soil Compaction Part Time to Full Time
Retaining Wall Backfill Fill Placement and Soil Compaction Part Time to Full Time
Subgrade for Sidewalks,
Curb/Gutter and Pavement Soil Compaction Part Time
Pavement Construction
Base Placement and Compaction Part Time
Asphalt Concrete Placement and
Compaction Full Time
Geocon Project No. G2755-42-01 September 14, 2021
LIMITATIONS AND UNIFORMITY OF CONDITIONS
1. The firm that performed the geotechnical investigation for the project should be retained to
provide testing and observation services during construction to provide continuity of
geotechnical interpretation and to check that the recommendations presented for
geotechnical aspects of site development are incorporated during site grading, construction
of improvements, and excavation of foundations. If another geotechnical firm is selected to
perform the testing and observation services during construction operations, that firm should
prepare a letter indicating their intent to assume the responsibilities of project geotechnical
engineer of record. A copy of the letter should be provided to the regulatory agency for their
records. In addition, that firm should provide revised recommendations concerning the
geotechnical aspects of the proposed development, or a written acknowledgement of their
concurrence with the recommendations presented in our report. They should also perform
additional analyses deemed necessary to assume the role of Geotechnical Engineer of
Record.
2. The recommendations of this report pertain only to the site investigated and are based upon
the assumption that the soil conditions do not deviate from those disclosed in the
investigation. If any variations or undesirable conditions are encountered during
construction, or if the proposed construction will differ from that anticipated herein, Geocon
Incorporated should be notified so that supplemental recommendations can be given. The
evaluation or identification of the potential presence of hazardous or corrosive materials was
not part of the scope of services provided by Geocon Incorporated.
3. This report is issued with the understanding that it is the responsibility of the owner or his
representative to ensure that the information and recommendations contained herein are
brought to the attention of the architect and engineer for the project and incorporated into
the plans, and the necessary steps are taken to see that the contractor and subcontractors
carry out such recommendations in the field.
4. The findings of this report are valid as of the present date. However, changes in the
conditions of a property can occur with the passage of time, whether they be due to natural
processes or the works of man on this or adjacent properties. In addition, changes in
applicable or appropriate standards may occur, whether they result from legislation or the
broadening of knowledge. Accordingly, the 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 three years.
137.9
138.1
137.5
137.2
136.2
135.9
135.1
135.1
134.4
134.2
133.5
133.2
132.4
132.2
131.5
131.3
130.7
130.5
129.9
130.2
129.6
129.4
129.9
130.8
131.7
132.3
133.8
135.5
136.9
135.6
134.7
133.8
133.1
131.8
131.2
130.2
129.7
131.2
136.9
142.8
137.5
153.2
149.4
148.6
158.6
174.3
217.2
218.6
219.7
219.9
220.3
221.7
227.9
233.7
235.5
194.2
191.9
201.5
197.3
193.5
189.4
185.5
137.6137.1135.5
134.1
181.3
179.3
180.1
178.8
178.3
176.9
177.2
175.6
187.6
211.2
219.2
218.8
218.3
220.4
221.5
219.6
235.9
236.3
204.2
202.6
203.7
201.5
202.5
202.7
194.2
193.7
193.7
193.4
192.5
193.5
190.4
192.9
191.7
192.6
190.5
187.7
179.2
180.9
168.7
175.2
144.4
142.3
164.7
166.3
165.4
163.9
163.7
201.4
205.2
235.5
219.1
218.7
LOT 23
MAP 8147
HELD RECORD ANGLE
LOT 22
MAP 8147 LOT 21
MAP 8147 LOT 20
MAP 8147
LOT 19
MAP 8147
LOT 3
MAP 8147
LOT 2 SEC 20
T18S R1E SBM
ROS 16999
PARCEL 1
PM 21587
PARCEL 2
PM 21587
64'64'2
2
3
3
4
4
4
4
4
4
4
5
N 87°34'46" W 1356.85'
(
N
8
7
°
3
4
'
0
8
"
W
1
3
5
6
.
6
6
'
R
2
)
N 02°26'11" E 0.15'
N 02°25'25" E 0.13'N 02°26'11" E 276.91' (N 02°25'152 E 276.79' R2)749.13'
607.72'N 00°14'32" E 287.73' (N 00°12'10" E 287.52' R2)N 00°27'05" E 424.23' (N 00°27'28" E 424.24' R2)L =2 9 9 .2 0 ' R =2 0 6 4 .0 0 ' D =8 °1 8 '2 0 " M &R 2
N 82°38'33" E
3
7
3
.
1
3
'
(
N
8
2
°
3
8
'
3
6
"
E
3
7
3
.
1
5
'
R
2
)
D =2 °0 9 '1 1 " M &R 2L=7 7 .5 5 ' L =5 9 7 .1 7 ' D =1 6 °3 4 '3 8 " M &R 2L=6 7 4 .7 0 ' R =2 0 6 4 .0 0 ' D =1 8 °4 3 '4 6 " M &R 2
N 78°37'
4
1
"
W
2
3
.
9
7
'
(N 78°3
7
'
3
8
"
W
2
3
.
9
8
'
R
2
)
NW COR
SW 1/4 NW 1/4 SEC 20
2'1
25'2
NE COR
SW 1/4 NW 1/4 SEC 20
3
27'
15'
28'
20'
28'5
5
5
5
5128'7720'1424'13
20'
13
24'121
2
'
1
24'1
24'2
64'64'3433'
34'
12'4
5
4
4
4
6
7
(137.94 FG)
(131.82 FG)
183.0 TW
141.5 FG
H=41.5'
184.0
TW
145.0 FG
H=39'
183.1
TW 162.5
FG
H=20.6'
189.75 TW
183.5 BW
H=6.25'
185.25
TW 146.2
FG
H=39.1'MAIN STREET 2:12:12:12:1202.5 TW
184.5 FG
H=18'205.75
TW
185.75 FG
H=20'
184.00 TW
184.00 FG
H=0'
212.25 TW
186.75 FG
H=25.5'
180.9
TW 155.6
FG
H=25.3'
180.9 TW
139.4 FG
H=41.5'
(139.7 FG)
(186.00 FG)
(186.00 FG)
INDUSTRIAL
BLDG 4
187.5 FF
186.0
TW
186.0
BW
H=0'
189.5 TW
184.5 FG
H=5'
186.0 TW
186.0 FS
H=0'
186.25
TW 146.9
FG
H=39.4'
187.0 TW
183.3 FS
H=3.7'
186.25
TW 159.1
FG
H=27.2'
TYPE A-6 CO
188.8 RIM
172.60 IE OUT
MOD. TYPE A-6
CO
135.32 TOP
129.38 FL
MOD. TYPE A-8 CO
WITH TYPE F
OPENING
175.0 TOP
154.35 IE OUT
MOD. TYPE A
CO
137.63 TOP
130.64 FL
183.75 FS 5%NIRVANA AVEINDUSTRIAL
BLDG 3
186.5 FF
INDUSTRIAL
BLDG 2
185.25 FF
INDUSTRIAL
BLDG 1
184.25 FF
182.9 TW
141.4 FG
H=41.5'
184.0 TW
143.5 FG
H=40.5'
184.0 TW
144.3 FG
H=39.7'
185.25
TW 146.5
FG
H=38.8'
186.25
TW 145.9
FG
H=40.4'
184.0 TW
184.0 BW
H=0'
187.0
TW
183.6 FS
H=3.4'
187.0
TW
183.4 FS
H=3.6'2:12:12:12.0%198.5
TW
183.5
BW
H=15'
202.0
TW
183.5
BW
H=18.5'
202.5
TW
183.5
BW
H=19'
200.5 TW
184.5 FG
H=16'
184.5 TW
184.5 FG
H=0'
203.0 TW
184.5 FG
H=18.5'
206.25 TW
185.75 FG
H=20.5'
209.25 TW
185.75 FG
H=23.5'
211.0 TW
185.75 FG
H=25.25'211.25 TW
186.75 FG
H=24.5'
210.0 TW
186.75 FG
H=23.25'
208.25 TW
186.75 FG
H=21.5'
191.75 TW
186.75 FG
H=5'
184.5 TW
184.5 FG
H=0'
189.5
TW
184.5 FG
H=5'
212.25 TW
186.25 FG
H=26'
212.0 TW
185.75 FG
H=26.25'2.0%2.0%2.0%2.0%AA'BB'Qal
Qt
Qt
Qt
Qt
Qal
To
To
Qal
Qal
Qt
B-1
B-2
T-5 T-4
T-6
T-3
T-2
T-1
TP-2
TP-4
TP-3
TP-1
TP-7
TP-6
TP-5To
To
To
To
To
To
To
To
???????????
?
??
??????
???
?
Qudf
CC'D
D'
LB-4
LB-3
LB-2
LB-1
LB-5
GG'
E
E'
F
F'
TP-5
TP-8
TP-1
TP-3
TP-2
TP-4
TP-6
TP-7
To
Qt
Qt
APPROX. FRONT
LIMIT OF CLAYBED
REMOVAL
APPROX. FRONT
LIMIT OF CLAYBED
REMOVAL
PROJECT NO.
SCALE DATE
FIGURE
SHEET OF
Plotted:09/14/2021 8:36AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\G2755-42-01 (Nirvana Self Storage)\SHEETS\G2755-42-01 Geo Map.dwg
GEOLOGIC MAP
NIRVANA INDUSTRIAL BUILDINGS AND SELF STORAGE COMPLEX
821 MAIN STREET
CHULA VISTA, CALIFORNIA
50'09 - 14 - 2021
G2755 - 42 - 01
1 1 1 *LA2(E67 (6I:E 7A2 (IEGO CALI*O62IA
P,O2E *A<
GEOTECHNICAL ENVIRONMENTAL MATERIALS
1" =
T-6
TP-7
B-2
........UNDOCUMENTED FILL
........ALLUVIUM
........TERRACE DEPOSITS
........OTAY FORMATION
........APPROX. LOCATION OF GEOLOGIC CONTACT
........APPROX. LOCATION OF EXPLORATORY LARGE DIAMETER
BORING (Current)
........APPROX. LOCATION OF EXPLORATORY BORING
........APPROX. LOCATION OF EXPLORATORY TEST PIT (Current)
........APPROX. LOCATION OF EXPLORATORY TEST PIT (AGS, 2014)
........APPROX. LOCATION OF EXPLORATORY TEST PIT (AET, 2008)
........APPROX. LOCATION OF GEOLOGIC CROSS SECTION
........APPROX. LOCATION OF PROPOSED SUBDRAIN
........APPROX. SURFACE EXPOSURE OF BENTONITIC CLAYSTONE
GEOCON LEGEND
Qudf
G G'
Qal
Qt
To
LB-5
TP-8
0 10050 150 200 250 300 350 400 450 500
50
100
150
200
250
B
300
B'E L E V A T I O N (M S L)E L E V A T I O N (M S L)50
100
150
200
250
300
D I S T A N C E
SCALE: 1" = 50' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION B-B'
0 10050 150 200 250 300 350 400 450 500
50
100
150
200
250
A
300
A'E L E V A T I O N (M S L)E L E V A T I O N (M S L)50
100
150
200
250
300
D I S T A N C E
SCALE: 1" = 50' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION A-A'
PROPOSED
RETAINING WALL
PROPOSED
RETAINING WALL
PROPOSED
RETAINING WALL
PROPOSED
RETAINING WALL
EXISTING
GRADED
PROPOSED
GRADE
PROPOSED
GRADE
EXISTING
GRADED
To
SOUTH
S12°E
SM
CH
SM-ML
CH
CH
???
?
0 10050 150 200 250 300 350 400 450 500
50
100
150
200
250
C
300
C'E L E V A T I O N (M S L)E L E V A T I O N (M S L)50
100
150
200
250
300
D I S T A N C E
SCALE: 1" = 50' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION C-C'
50
100
150
200
250
D
300
D'E L E V A T I O N (M S L)E L E V A T I O N (M S L)50
100
150
200
250
300
SCALE: 1" = 50' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION D-D'
0 10050 150 200 250 300 350 400 450 600500550 650 700 750 800 950850900 1000 11001050 1150 1200 1250 1300 1350 1400 1450 160015001550 1650 1700 1750 1800 195018501900
Qt
Qt
To
SECTION
D-D'
SECTION
D-D'
LB-4
(Projected
50')
SM
CH
CH
SC-GC
SM-ML
Qt
To
LP
EXISTING
GRADED
PROPOSED
GRADE
PROPOSED
RETAINING WALL
PROPOSED
RETAINING WALL
SM
CH
CH
SM-ML
LB-5
Qt
Qt
ToTo
LP
LP
EXISTING
GRADED
PROPOSED
GRADE
LB-2
(Projected
22')
LB-4
(Projected
31')LB-5
SECTION
A-A'
SECTION
C-C'
SM
CH
CH
ML
SM
CH
CH
ML
PROPOSED
RETAINING
WALL Qt Qt Qt QtQt
SM
CH
CH
ML
0 10050 150 200
F F
E L E V A T I O N (M S L)E L E V A T I O N (M S L)D I S T A N C E
SCALE: 1" = 50' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION F-F'
0 10050 150 200 250
100
150
200
E E'E L E V A T I O N (M S L)E L E V A T I O N (M S L)100
150
200
D I S T A N C E
SCALE: 1" = 50' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION E-E'
0 10050 150 200
G G'E L E V A T I O N (M S L)E L E V A T I O N (M S L)D I S T A N C E
SCALE: 1" = 50' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION G-G'
250 250
100
150
200
E L E V A T I O N (M S L)250
100
150
200
250
100
150
200
250
GW
Qt
LP
LP
MAIN STREET
PROPOSED
INDUSTRIAL BUILDING 3
To
SM
GP
SC-ML ?
?
LP
MAIN STREET
To To
To
PROPOSED
INDUSTRIAL BUILDING 2 LP
LB-1
(Projected
55' to Section)
SOUTH
SC-GC
GW-GC
To
To
LP
MAIN STREET
PROPOSED
INDUSTRIAL BUILDING 4
??
?
GM-SM
LB-3
(Projected
20')GM-SM
SM
GW-GC
SC-GC
SM
CH
SM-ML
SC-GC
CH
EAST
SECTION
B-B'
SECTION
D-D'
To
To To
To
To ToTo
To
To
SM
CH
CH
GM-SM
ML
GW-GC
S58ºE
LP
PROPOSED
INDUSTRIAL BUILDING 4
SM
CH
SM-GM
ML
GW-GC
S80ºE
Qt Qt
To To
ToToTo
To
S25ºE
PROPOSED
INDUSTRIAL BUILDING 4
SM
CH
GM-SM
ML
GW-GC
CH CH
PROPOSED
RETAINING WALL
EXISTING
GRADE
PROPOSED
GRADE
EXISTING
GRADEEXISTING
GRADE
PROPOSED
GRADE
PROPOSED
GRADE
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
PROJECT NO.
SCALE DATE
FIGURE
GEOTECHNICAL ENVIRONMENTAL MATERIALS
SHEET OF
Plotted:09/14/2021 8:26AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\G2755-42-01 (Nirvana Self Storage)\SHEETS\G2755-42-01 XSections.dwg
GEOLOGIC 1AP
NIRVANA INDUSTRIAL BUILDINGS AND SELF STORAGE COMPLEX
821 MAIN STREET
CHULA VISTA, CALIFORNIA
50'09 - 14 - 2021
G2755 - 42 - 01
1 1 2
B-5
?
1" =
........TERRACE DEPOSITS
........OTAY FORMATION
........APPROX. LOCATION OF GEOLOGIC CONTACT
(Queried Where Uncertain)
........APPROX. LOCATION OF EXPLORATORY LARGE
DIAMETER BORING
.........ESTIMATED CLAYSTONE AND BEDROCK REMEDIAL
REMOVAL
GEOCON LEGEND
Qt
To
1
1
2
1
1
1
5% Min.
DETAIL
2" MIN.
1.5'
MIN.
1.5'
MIN.
BUTTRESS
WIDTH
FI
L
L
(N
O
T
E
3
)
MIN. DEPTH SEE NOTE 2
FINISHED
SLOPE
SEE
DETAIL
NOTE 4
NOTE 4
NOTE 5
NOTE 6
NOTE 1
NOTES:
1.....EXCAVATE BACKCUT AT 1:1 INCLINATION (UNLESS OTHERWISE NOTED).
2.....BASE OF BUTTRESS FILL TO BE 3 FEET INTO FORMATIONAL MATERIAL OR 5 FEET BELOW BEDDING PLANE SHEAR OR
LANDSLIDE SLIP SURFACE SLOPING A MINIMUM 5% INTO SLOPE.
3.....BUTTRESS/STABILITY FILL TO BE COMPOSED OF PROPERLY COMPACTED GRANULAR SOIL.
4.....CHIMNEY DRAINS TO BE APPROVED PREFABRICATED CHIMNEY DRAIN PANELS (MIRADRAIN G200N OR EQUIVALENT)
SPACED APPROXIMATELY 20 FEET CENTER TO CENTER AND 4 FEET WIDE. CLOSER SPACING MAY BE REQUIRED IF
SEEPAGE IS ENCOUNTERED.
5.....FILTER MATERIAL TO BE 3/4-INCH, OPEN-GRADED CRUSHED ROCK ENCLOSED IN APPROVED FILTER FABRIC (MIRAFI 140NC).
6.....COLLECTOR PIPE TO BE 4-INCH MINIMUM DIAMETER, PERFORATED, THICK-WALLED PVC SCHEDULE 40 OR
EQUIVALENT, AND SLOPED TO DRAIN AT 1 PERCENT MINIMUM TO APPROVED OUTLET.
Slope to Drain
MATERIAL
FORMATIONAL
FIG. 3
TYPICAL BUTTRESS/STABILITY FILL DETAIL
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
DSK/GTYPD PROJECT NO. G2755 - 42 - 01RM / AML
NIRVANA INDUSTRIAL BUILDINGS AND
SELF STORAGE COMPLEX
821 MAIN STREET
CHULA VISTA, CALIFORNIA
GEOTECHNICAL ENVIRONMENTAL MATERIALS
Plotted:09/14/2021 8:23AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\G2755-42-01 (Nirvana Self Storage)\DETAILS\Typical Slope Fill.dwg
DATE 09 - 14 - 2021
APPENDIX A
Geocon Project No. G2755-42-01 September 14, 2021
APPENDIX A
FIELD INVESTIGATION
We performed our field investigation between July 29 and August 8, 2021. Our investigation consisted
of a site reconnaissance, logging of eight exploratory test pits and five large diameter borings. The
exploratory test pits were excavated to depths between 2- and 11-feet using a rubber-tire Caterpillar
430F backhoe. Exploratory borings were drilled to depths between 70- and 90-feet using a truck-
mounted bucket auger drill rig. The approximate locations of the exploratory test pits borings tests are
shown on Figure 1.
The soil conditions encountered in the trenches were visually examined, classified, and logged in
general conformance with the American Society for Testing and Materials (ASTM) Practice for
Description and Identification of Soils (Visual-Manual Procedure D 2488). Exploratory boring logs
are presented in Figures A-1 through A-5, and test pit logs are presented on Figures A-6 through A-13.
The logs depict the various soil types encountered and indicate the depths at which samples were
obtained.
TERRACE DEPOSITS (Qt)
Stiff, dry to damp, brown, Sandy CLAY; abundant caliche; few roots
Medium dense, damp, grayish brown, Clayey SAND; few subrounded gravel;
little caliche
Medium dense to dense, damp, grayish brown, Clayey, medium to coarse
SAND; interbedded with coarse sandy gravel beds; trace subrounded cobble
up to 6-inch diameter; some cross-bedding
Stiff, damp, grayish brown to olive brown, Clayey SILT; massive; trace fine
gravel
-At 18 feet: few 4"-6" thick sandy gravel interbeds; horizontal
Medium dense to dense, damp, yellowish brown to orangish brown, coarse
Sandy GRAVEL; gravel and cobble up to 12-inch diameter, subrounded to
subangular: Hole belled out to 60"
CL
SC
SC
ML
GP
LB1-1
LB1-2
LB1-3
4
6/8"
3
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Figure A-1,
Log of Boring LB 1, Page 1 of 3 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 1
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.07-29-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)184'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
OTAY FORMATION (To)
Hard, dry to damp, yellowish gray, SILTSTONE; massive
Stiff to hard, damp to moist, dark reddish brown, bentonitic CLAYSTONE;
moderately; fissured but not remolded
Dense to very dense, damp, yellowish brown to grayish brown (mottled), Silty,
fine- to medium-grained SANDSTONE; massive
At 45 feet: becomes yellowish brown to reddish brown
Very dense, damp, grayish white, Silty, fine to medium SANDSTONE; trace
clay, massive
At 58 feet: becomes moist to wet
ML
CH
SM
SM
LB1-4
LB1-5
LB1-6
LB1-7
LB1-8
10/10"
10/8"
10/10"
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
Figure A-1,
Log of Boring LB 1, Page 2 of 3 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 1
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.07-29-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)184'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
At 63 feet: seepage
At 68 feet; standing water
BORING TERMINATED AT 70 FEET
Groundwater encountered at 68
Backfilled on 07-29-2021
SMLB1-9 12
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
60
62
64
66
68
70
Figure A-1,
Log of Boring LB 1, Page 3 of 3 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 1
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.07-29-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)184'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
TOPSOIL
Stiff, dry to damp, brown, Sandy CLAY; subrounded cobble up to 6-inch
diameter
TERRACE DEPOSITS (Qt)
Medium dense, damp, grayish brown, Silty SAND; trace clay, trace gravel
At 6 feet: subrounded cobble layer
Dense, damp, orangish brown, coarse Sandy GRAVEL; subrounded gravel
and cobble up to 10-inch diameter
OTAY FORMATION (To)
Hard to very hard, damp, dark reddish brown to pinkish brown, bentonitic
CLAYSTONE; weakly to moderately fissured with many polished and striated
surfaces, occasional discontinuous anastomosing clay films that are remolded
plastic and remolded up to 1/2-inch thick
At 17 feet: 1/32-inch moderately remolded plastic clay seam; horizontal to
undulatory with polished parting surfaces only
Very dense, damp, reddish brown to grayish brown, Silty, medium coarse
SANDSTONE; trace clay, massive
Very dense, dry to damp, light brown, very coarse grained SANDSTONE;
CL
SM
GP
CH
SM
SW
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Figure A-2,
Log of Boring LB 2, Page 1 of 4 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 2
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.07-30-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)199'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
bedding horizontal
Very hard, damp, grayish white to pinkish brown, fine grained Sandy
SILTSTONE; massive, gunbarrel
Very dense, damp, yellowish brown, Silty, very fine grained SANDSTONE;
massive gunbarrel
Hard, damp, dark reddish brown, bentonitic CLAYSTONE; weakly fissured,
no obvious clay films
Very dense,damp, grayish brown, Silty, fine SANDSTONE; massive
Hard, damp, dark reddish brown to pinkish brown, bentonitic CLAYSTONE;
massive, weakly to moderately fissured with polished and striated parting
surfaces, occasional pockets of highly fissured claystone and weakly remolded
clay
Very dense, damp, grayish brown, Silty, fine to coarse SANDSTONE;
massive
ML-SM
SM
CH
SM
CH
SM
LB2-1
LB2-2
LB2-3
10/8"
10/10"
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
Figure A-2,
Log of Boring LB 2, Page 2 of 4 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 2
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.07-30-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)199'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
At 62 feet: becomes moist
At 69 feet: 4" thick subrounded gravel layer, bedding horizontal
At 70 feet: becomes moist to wet
At 78 feet: moderate of heavy seepage
At 87 feet: standing water
SMLB2-4
LB2-5
12/8"
15/10"
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
60
62
64
66
68
70
72
74
76
78
80
82
84
86
88
Figure A-2,
Log of Boring LB 2, Page 3 of 4 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 2
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.07-30-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)199'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
BORING TERMINATED AT 90 FEET
Groundwater encountered at 87
Backfilled on 07-30-2021
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
Figure A-2,
Log of Boring LB 2, Page 4 of 4 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 2
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.07-30-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)199'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
TOPSOIL
Stiff, damp, reddish brown, Sandy CLAY; some gravel, few roots
TERRACE DEPOSITS (Qt)
Dense, dry to damp, orangish brown, Silty, medium to coarse SAND; some
subrounded gravel and cobble up to 12-inch diameter
OTAY FORMATION (To)
Hard, dry, reddish brown, CLAYSTONE; numerous sub horizontal to
undulatory remolded moderately fissured soft plastic 1/8" thick clay films
Hard, dry to damp, grayish brown to pinkish brown, very fine grained Sandy
SILTSTONE; massive; few subvertical clay filled fractures
Hard, damp, pinkish brown to reddish brown, bentonitic CLAYSTONE;
moderately to well fissured with numerous polished parting surfaces
At 18 feet: transitions to fine grained sandy claystone
Hard, dry to damp, pale whitish brow to pinkish brown, fine grained Sandy
SILTSTONE; minor caliche along top contact; massive, few of reddish brown
sandy claystone interbeds
CL
SM
CH
ML
CH
ML
LB3-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Figure A-3,
Log of Boring LB 3, Page 1 of 3 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 3
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.07-30-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)194'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
At 35-38 feet: Few high-angle clay filled fractures
Stiff to hard, damp, reddish brown, bentonitic CLAYSTONE; friable in
places, weakly fissured, top contact is transitional over 18", no obvious
remolding or plastic clay films
At 42 feet: thin band of caliche cementation
At 47 feet: becomes moderately fissured
Hard, damp, pinkish brown to grayish white, very fine grained Sandy
SILTSTONE; massive
Very dense, damp, grayish white to pinkish white, Silty, fine to coarse
SANDSTONE; massive
ML
CH
ML
SM
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
Figure A-3,
Log of Boring LB 3, Page 2 of 3 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 3
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.07-30-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)194'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
At 65 feet: becomes damp to moist
At 71 feet: 6-inch subrounded cobble bed; N70E/3°S
At 72 feet: light seepage
BORING TERMINATED AT 75 FEET
Groundwater not encountered
Backfilled on 07-30-2021
SM
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
60
62
64
66
68
70
72
74
Figure A-3,
Log of Boring LB 3, Page 3 of 3 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 3
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.07-30-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)194'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
TERRACE DEPOSITS (Qt)
Dense, dry to moist, orangish brown, Clayey, medium to coarse SAND with
gravel and cobble, subrounded gravel and cobble up to 18-inch diameter
Loose to medium dense, damp, orangish brown, Sandy GRAVEL; low
cohesions present in cave zone, caving to 72-inch diameter, cobble and
boulders up to 36 inches
SC
GW
LB4-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Figure A-4,
Log of Boring LB 4, Page 1 of 3 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 4
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-02-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)216'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
OTAY FORMATION (To)
Firm to stiff, damp, dark reddish brown, bentonitic CLAYSTONE; weakly to
moderately fissured with some polished and slanted parting surfaces, little to
no remolding or soft plastic zones, massive
Hard, damp, dark reddish brown, Sandy CLAYSTONE
Very dense, damp, reddish brown, very coarse SANDSTONE (gritstone bed);
cemented, few rounded gravel
Stiff to hard, damp to moist, pale reddish brown to olive brown, SILTSTONE,
Clayey SILTSTONE and Sandy SILTSTONE (interbedded); massive
CH
CL
SW
ML
LB4-2
LB4-3
LB4-4
8/8"
10
12
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
Figure A-4,
Log of Boring LB 4, Page 2 of 3 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 4
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-02-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)216'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
Very stiff to hard, damp, dark reddish brown, bentonitic CLAYSTONE;
weakly to moderately fissured, blocky texture, no remolding
Stiff to hard, damp, reddish brown, Clayey SILTSTONE; massive
Dense to very dense, damp, reddish brown to pinkish white, Silty, fine to
coarse SANDSTONE; trace clay, massive
BORING TERMINATED AT 81 FEET
Groundwater not encountered
Backfilled on 08-02-2021
CH
ML
SM
LB4-5
LB4-6
LB4-7
15
15
20/6"
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
60
62
64
66
68
70
72
74
76
78
80
Figure A-4,
Log of Boring LB 4, Page 3 of 3 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 4
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-02-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)216'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
TOPSOIL
Stiff, dry, dark brown, Sandy CLAY; trace gravel
TERRACE DEPOSITS (Qt)
Medium dense to dense, damp, brown to orangish brown, Silty, medium
coarse SAND; trace clay, some subrounded gravel and cobble up to 8-inch
diameter
At 26-32 feet: hole belled out to 60-inch diameter with abundant loose cobble
and overhanging areas. Hole logged from cuttings below 32 feet
CL
GW
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Figure A-5,
Log of Boring LB 5, Page 1 of 3 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 5
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-03-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)218'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
OTAY FORMATION (To)
Hard, damp, grayish brown, Clayey SILTSTONE
Hard, damp, reddish brown, bentonitic CLAYSTONE; blocky, weakly
fissured
Hard, damp, brown to olive brown, interbedded SILTSTONE, Clayey
SILTSTONE, and Silty CLAYSTONE
At 50 feet: light to moderate seepage
GW
ML
CH
ML/CL
LB5-1
LB5-2
LB5-3
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
Figure A-5,
Log of Boring LB 5, Page 2 of 3 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 5
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-03-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)218'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
Hard, damp, reddish brown, bentonitic CLAYSTONE; massive, blocky and
weakly fissured
Dense, damp, pale yellowish brown, Silty, fine to coarse SANDSTONE;
massive
BORING TERMINATED AT 80 FEET
Groundwater encountered at 65
Backfilled on 08-04-2021
ML/CL
CH
SM
LB5-4
LB5-5
LB5-6
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
60
62
64
66
68
70
72
74
76
78
80
Figure A-5,
Log of Boring LB 5, Page 3 of 3 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)PENETRATIONRESISTANCE(BLOWS/FT.)BORING LB 5
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-03-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)218'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
SLOPEWASH
Loose, dry, brown, Clayey, fine to coarse SAND with subrounded gravel and
cobble
OTAY FORMATION (To)
Hard, dry, reddish brown, bentonitic CLAYSTONE; dessicated and fractured
with blocky texture, some caliche; Bedding: <2º dip/sub-horizontal
TRENCH TERMINATED AT 7 FEET
Groundwater not encountered
Backfilled on 08-05-2021
SC
CL
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
Figure A-6,
Log of Test Pit TP 1, Page 1 of 1 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)
CAT 430L BACKHOE PENETRATIONRESISTANCE(BLOWS/FT.)TEST PIT TP 1
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-05-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)+/-150'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
SLOPEWASH
Loose, dry, light brown, Clayey, fine to coarse SAND with gravel
OTAY FORMATION (To)
Dense, dry to damp, pinkish brown, Silty, fine to coarse SANDSTONE;
massive
TRENCH TERMINATED AT 5 FEET
Groundwater not encountered
Backfilled on 08-05-2021
SC
SM
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
Figure A-7,
Log of Test Pit TP 2, Page 1 of 1 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)
CAT 430L BACKHOE PENETRATIONRESISTANCE(BLOWS/FT.)TEST PIT TP 2
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-05-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)+/-145'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
SLOPEWASH
Loose, dry, brown, Clayey, fine to coarse SAND with subrounded gravel and
cobble
OTAY FORMATION (To)
Hard, dry, dark reddish brown, bentonitic CLAYSTONE; dessicated and
fractured with blocky texture, abundant caliche
Dense, dry to damp, pinkish brown, Silty, fine to coarse SANDSTONE;
massive
TRENCH TERMINATED AT 5 FEET
Groundwater not encountered
Backfilled on 08-05-2021
SC
CL
SM
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
Figure A-8,
Log of Test Pit TP 3, Page 1 of 1 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)
CAT 430L BACKHOE PENETRATIONRESISTANCE(BLOWS/FT.)TEST PIT TP 3
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-05-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)+/-145'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
SLOPEWASH
Loose, dry, brown, Clayey, fine to coarse SAND with subrounded gravel and
cobble
OTAY FORMATION (To)
Hard, dry, dark reddish brown, bentonitic CLAYSTONE
Dense, dry, pale yellowish brown, Silty, medium grained SANDSTONE
TRENCH TERMINATED AT 6 FEET
Groundwater not encountered
Backfilled on 08-05-2021
SC
CL
SM
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
Figure A-9,
Log of Test Pit TP 4, Page 1 of 1 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)
CAT 430L BACKHOE PENETRATIONRESISTANCE(BLOWS/FT.)TEST PIT TP 4
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-05-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)+/-145'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
OTAY FORMATION (To)
Dense, dry, pale whitish brown, Silty, fine to coarse SANDSTONE; fractured,
some caliche
TRENCH TERMINATED AT 7 FEET
Groundwater not encountered
Backfilled on 08-05-2021
SM
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
Figure A-10,
Log of Test Pit TP 5, Page 1 of 1 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)
CAT 430L BACKHOE PENETRATIONRESISTANCE(BLOWS/FT.)TEST PIT TP 5
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-05-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)+/-145'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
OTAY FORMATION (To)
Dense, dry to damp, pale whitish yellow to pinkish white, Silty, fine to coarse
SANDSTONE; fractured, trace caliche
TRENCH TERMINATED AT 6 FEET
Groundwater not encountered
Backfilled on 08-05-2021
SM
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
Figure A-11,
Log of Test Pit TP 6, Page 1 of 1 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)
CAT 430L BACKHOE PENETRATIONRESISTANCE(BLOWS/FT.)TEST PIT TP 6
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-05-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)+/-140'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
SLOPEWASH
Loose, dry, brown, Clayey, fine to coarse SAND with subrounded gravel and
cobble
OTAY FORMATION (To)
Hard, dry to damp, dark reddish brown, bentonitic CLAYSTONE; friable,
weathered
Dense, dry to damp, pale yellowish brown, Silty, fine to coarse
SANDSTONE; massive
TRENCH TERMINATED AT 11 FEET
Groundwater not encountered
Backfilled on 08-05-2021
SC
CL
SM
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
Figure A-12,
Log of Test Pit TP 7, Page 1 of 1 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)
CAT 430L BACKHOE PENETRATIONRESISTANCE(BLOWS/FT.)TEST PIT TP 7
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-05-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)+/-150'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
OTAY FORMATION (To)
Hard, dry, dark reddish brown, bentonitic CLAYSTONE; friable, some
caliche
TRENCH TERMINATED AT 6 FEET
Groundwater not encountered
Backfilled on 08-05-2021
CL
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
Figure A-13,
Log of Test Pit TP 8, Page 1 of 1 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)
CAT 430L BACKHOE PENETRATIONRESISTANCE(BLOWS/FT.)TEST PIT TP 8
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERR. ADAMS CONTENT (%)SAMPLE
NO.08-05-2021
SAMPLE SYMBOLS MOISTUREBY:EQUIPMENT
ELEV. (MSL.)+/-145'
G2755-42-01.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
... WATER TABLE OR ... SEEPAGE
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2755-42-01
APPENDIX B
Geocon Project No. G2755-42-01 B-1 September 14, 2021
APPENDIX B
LABORATORY TESTING
Laboratory tests were performed in accordance with generally accepted test methods of the American
Society for Testing and Materials (ASTM) or other suggested procedures. Selected samples were tested
for in-situ dry density and moisture content, maximum dry density and optimum moisture content,
expansion potential, gradation, Atterberg limits, soluble sulfate content, chloride content, pH and
resistivity, and shear strength. The results of these tests are summarized on the following tables and
figures.
SUMMARY OF LABORATORY MAXIMUM DRY DENSITY
AND OPTIMUM MOISTURE CONTENT TEST RESULTS
ASTM D 1557-02
Sample No. Description Maximum Dry
Density (pcf)
Optimum
Moisture Content
(% dry wt.)
LB3-1 Brown clayey fine to coarse SAND; some
gravel (SC) 127.2 10.4
LB4-1 Brown fine to coarse sandy GRAVEL; little
silt (GW) 135.8 7.0
SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS
ASTM D 4829-03
Sample
No.
Moisture Content Dry
Density (pcf)
Expansion
Index Before Test (%) After Test (%)
LB2-3 14.8 33.6 91.8 55
LB4-1 7.7 14.1 117.8 1
SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS
CALIFORNIA TEST NO. 417
Sample No. Water-Soluble Sulfate
(%) Sulfate Exposure
LB4-1 0.028 S0
Geocon Project No. G2755-42-01 B-2 September 14, 2021
SUMMARY OF LABORATORY WATER-SOLUBLE CHLORIDE ION CONTENT TEST RESULTS
AASHTO TEST NO. T 291
Sample No. Chloride Ion Content ppm (%)
LB4-1 937 (0.094)
SUMMARY OF LABORATORY POTENTIAL OF HYDROGEN (PH) AND
RESISTIVITY TEST RESULTS
CALIFORNIA TEST METHOD 643
Sample No. Geologic Unit pH Minimum Resistivity
(ohm-centimeters)
LB4-1 Qt 7.56 460
SUMMARY OF LABORATORY ATTERBERG LIMITS TEST RESULTS
ASTM D 4318
Sample
No.
Liquid Limit
(%)
Plastic Limit
(%)
Plasticity
Index
LB2-3 57 26 31
LB3-1 50 18 32
LB4-1 30 19 11
LB5-1 56 24 32
1 K 2 K 4 K AVERAGE
1000 2000 4000 --
11.6 10.5 9.1 10.4
114.6 107.2 109.0 110.3
1 K 2 K 4 K AVERAGE
16.8 19.5 17.7 18.0
1466 1765 3111 --
1030 1759 3111 --
790
30
350
35
DRY DENSITY (PCF):
NIRVANA
G2755-42-01
DIRECT SHEAR - ASTM D 3080
NORMAL STRESS TEST LOAD
WATER CONTENT (%):
PEAK SHEAR STRESS (PSF):
ULT.-E.O.T. SHEAR STRESS (PSF):
RESULTS
PEAK COHESION, C (PSF)
PROJECT NO.:
Qt
N
SAMPLE NO.:
SAMPLE DEPTH (FT):
LB1-3
20'
GEOLOGIC UNIT:
NATURAL/REMOLDED:
INITIAL CONDITIONS
FRICTION ANGLE (DEGREES)
ULTIMATE COHESION, C (PSF)
FRICTION ANGLE (DEGREES)
NORMAL STRESS TEST LOAD
ACTUAL NORMAL STRESS (PSF):
WATER CONTENT (%):
AFTER TEST CONDITIONS
0
500
1000
1500
2000
2500
3000
3500
0 0.05 0.1 0.15 0.2 0.25 0.3SHEAR STRESS (PSF)HORIZONTAL DEFORMATION (IN)
1 K 2 K 4 K
1 K PEAK 2 K PEAK 4 K PEAK
1 K ULTIMATE 2 K ULTIMATE 4 K ULTIMATE
4 K
2 K
1 K
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000SHEAR STRESS (PSF)NORMAL STRESS (PSF)
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000SHEAR STRESS (PSF)NORMAL STRESS (PSF)
SAMPLE NO.: GEOLOGIC UNIT:
SAMPLE DEPTH (FT): NATURAL/REMOLDED:
1 K 2 K 4 K AVERAGE
890 2030 4300 --
10.8 11.2 10.5 10.8
114.1 114.1 114.6 114.3
1 K 2 K 4 K AVERAGE
20.3 20.9 21.3 20.8
867 1320 2140 --
858 1320 2131 --
550
20
540
20
COHESION, C (PSF)
DRY DENSITY (PCF):
AFTER TEST CONDITIONS
LB3-1
G2755-42-01
NIRVANA
COHESION, C (PSF)
FRICTION ANGLE (DEGREES)
DIRECT SHEAR - ASTM D 3080
PROJECT NO.:
FRICTION ANGLE (DEGREES)
NORMAL STRESS TEST LOAD
ACTUAL NORMAL STRESS (PSF):
WATER CONTENT (%):
ULTIMATE
RESULTS
PEAK
Qt
3'
NORMAL STRESS TEST LOAD
WATER CONTENT (%):
PEAK SHEAR STRESS (PSF):
ULT.-E.O.T. SHEAR STRESS (PSF):
INITIAL CONDITIONS
R
0
500
1000
1500
2000
2500
0.000 0.050 0.100 0.150 0.200 0.250 0.300SHEAR STRESS (PSF)HORIZONTAL DEFORMATION (IN)
1 K 2 K 4 K
1 K PEAK 2 K PEAK 4 K PEAK
1 K ULTIMATE 2 K ULTIMATE 4 K ULTIMATE
4 K
2 K
1K
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000SHEAR STRESS (PSF)NORMAL STRESS (PSF)
SAMPLE NO.: GEOLOGIC UNIT:
SAMPLE DEPTH (FT): NATURAL/REMOLDED:
1 K 2 K 4 K AVERAGE
890 2030 4300 --
6.2 6.5 6.2 6.3
122.9 123.4 123.5 123.3
1 K 2 K 4 K AVERAGE
11.5 12.1 12.6 12.1
1112 2036 3394 --
1009 1763 3111 --
590
33
480
32
COHESION, C (PSF)
DRY DENSITY (PCF):
AFTER TEST CONDITIONS
LB4-1
G2755-42-01
NIRVANA
COHESION, C (PSF)
FRICTION ANGLE (DEGREES)
DIRECT SHEAR - ASTM D 3080
PROJECT NO.:
FRICTION ANGLE (DEGREES)
NORMAL STRESS TEST LOAD
ACTUAL NORMAL STRESS (PSF):
WATER CONTENT (%):
ULTIMATE
RESULTS
PEAK
Qt
9'
NORMAL STRESS TEST LOAD
WATER CONTENT (%):
PEAK SHEAR STRESS (PSF):
ULT.-E.O.T. SHEAR STRESS (PSF):
INITIAL CONDITIONS
R
0
500
1000
1500
2000
2500
3000
3500
4000
0.000 0.050 0.100 0.150 0.200 0.250 0.300SHEAR STRESS (PSF)HORIZONTAL DEFORMATION (IN)
1 K 2 K 4 K
1 K PEAK 2 K PEAK 4 K PEAK
1 K ULTIMATE 2 K ULTIMATE 4 K ULTIMATE
4 K
2 K
1K
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000SHEAR STRESS (PSF)NORMAL STRESS (PSF)
4 K 1 K 2 K AVERAGE
4000 1000 2000 --
21.0 20.0 21.0 20.7
109.8 108.4 104.7 107.7
4 K 1 K 2 K AVERAGE
24.5 23.5 25.1 24.4
3592 1498 1937 --
2292 764 1573 --
670
36
200
30
INITIAL CONDITIONS
FRICTION ANGLE (DEGREES)
ULTIMATE COHESION, C (PSF)
FRICTION ANGLE (DEGREES)
NORMAL STRESS TEST LOAD
ACTUAL NORMAL STRESS (PSF):
WATER CONTENT (%):
AFTER TEST CONDITIONS
To
N
SAMPLE NO.:
SAMPLE DEPTH (FT):
LB4-2
30.5'
GEOLOGIC UNIT:
NATURAL/REMOLDED:
DRY DENSITY (PCF):
NIRVANA
G2755-42-01
DIRECT SHEAR - ASTM D 3080
NORMAL STRESS TEST LOAD
WATER CONTENT (%):
PEAK SHEAR STRESS (PSF):
ULT.-E.O.T. SHEAR STRESS (PSF):
RESULTS
PEAK COHESION, C (PSF)
PROJECT NO.:
‐500
0
500
1000
1500
2000
2500
3000
3500
4000
0 0.05 0.1 0.15 0.2 0.25 0.3SHEAR STRESS (PSF)HORIZONTAL DEFORMATION (IN)
4 K 1 K 2 K
4 K PEAK 1 K PEAK 2 K PEAK
4 K ULTIMATE 1 K ULTIMATE 2 K ULTIMATE
2 K
1 K
4 K
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000SHEAR STRESS (PSF)NORMAL STRESS (PSF)
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000SHEAR STRESS (PSF)NORMAL STRESS (PSF)
1 K 2 K 4 K AVERAGE
1000 2000 4000 --
14.0 13.8 13.5 13.8
119.4 121.1 120.4 120.3
1 K 2 K 4 K AVERAGE
19.8 19.6 19.3 19.6
1284 1895 3400 --
1024 1615 3068 --
530
35
300
34
DRY DENSITY (PCF):
NIRVANA
G2755-42-01
DIRECT SHEAR - ASTM D 3080
NORMAL STRESS TEST LOAD
WATER CONTENT (%):
PEAK SHEAR STRESS (PSF):
ULT.-E.O.T. SHEAR STRESS (PSF):
RESULTS
PEAK COHESION, C (PSF)
PROJECT NO.:
To
N
SAMPLE NO.:
SAMPLE DEPTH (FT):
LB5-3
50'
GEOLOGIC UNIT:
NATURAL/REMOLDED:
INITIAL CONDITIONS
FRICTION ANGLE (DEGREES)
ULTIMATE COHESION, C (PSF)
FRICTION ANGLE (DEGREES)
NORMAL STRESS TEST LOAD
ACTUAL NORMAL STRESS (PSF):
WATER CONTENT (%):
AFTER TEST CONDITIONS
‐500
0
500
1000
1500
2000
2500
3000
3500
4000
0 0.05 0.1 0.15 0.2 0.25 0.3SHEAR STRESS (PSF)HORIZONTAL DEFORMATION (IN)
1 K 2 K 4 K
1 K PEAK 2 K PEAK 4 K PEAK
1 K ULTIMATE 2 K ULTIMATE 4 K ULTIMATE
4 K
2 K
1 K
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000SHEAR STRESS (PSF)NORMAL STRESS (PSF)
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000SHEAR STRESS (PSF)NORMAL STRESS (PSF)
1 K 2 K 4 K AVERAGE
1000 2000 4000 --
17.3 18.0 17.5 17.6
112.1 113.3 112.4 112.6
1 K 2 K 4 K AVERAGE
23.0 23.5 23.1 23.2
744 1905 2857 --
741 1329 2766 --
270
34
22
34
DRY DENSITY (PCF):
NIRVANA
G2755-42-01
DIRECT SHEAR - ASTM D 3080
NORMAL STRESS TEST LOAD
WATER CONTENT (%):
PEAK SHEAR STRESS (PSF):
ULT.-E.O.T. SHEAR STRESS (PSF):
RESULTS
PEAK COHESION, C (PSF)
PROJECT NO.:
To
N
SAMPLE NO.:
SAMPLE DEPTH (FT):
LB5-5
65'
GEOLOGIC UNIT:
NATURAL/REMOLDED:
INITIAL CONDITIONS
FRICTION ANGLE (DEGREES)
ULTIMATE COHESION, C (PSF)
FRICTION ANGLE (DEGREES)
NORMAL STRESS TEST LOAD
ACTUAL NORMAL STRESS (PSF):
WATER CONTENT (%):
AFTER TEST CONDITIONS
0
500
1000
1500
2000
2500
3000
3500
0 0.05 0.1 0.15 0.2 0.25 0.3SHEAR STRESS (PSF)HORIZONTAL DEFORMATION (IN)
1 K 2 K 4 K
1 K PEAK 2 K PEAK 4 K PEAK
1 K ULTIMATE 2 K ULTIMATE 4 K ULTIMATE
4 K
2 K
1 K
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000SHEAR STRESS (PSF)NORMAL STRESS (PSF)
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000SHEAR STRESS (PSF)NORMAL STRESS (PSF)
To
D10 (mm) D30 (mm) D60 (mm)
0.00017 0.00189 0.00921
GEOLOGIC UNIT:
46'
LB2-3
SAMPLE DEPTH (FT.):
SAMPLE NO.:
SIEVE ANALYSES - ASTM D 135 & D 422
NIRVANA
PROJECT NO.:
Cc
2.3
Cu
53.7
G2755-42-01
SOIL DESCRIPTION
CLAY
TEST DATA
U.S. STANDARD SIEVE SIZE
3"2"1½"1¾"½"⅜"#4#8#10#16#20#30#40#50#60#80#100#2000
10
20
30
40
50
60
70
80
90
100
0.0010.010.1110100PERCENT PASSING PARTICLE SIZE (mm)
SILT OR CLAY
GRAVEL SAND
COARSEFINECOARSE MEDIUM FINE
Qt
D10 (mm) D30 (mm) D60 (mm)
0.027 0.139 1.882
Cc
0.4
TEST DATA
SOIL DESCRIPTION
SC - Clayey SAND with gravel68.6
Cu
SIEVE ANALYSES - ASTM D 135
NIRVANA
PROJECT NO.:
U.S. STANDARD SIEVE SIZE
G2755-42-01
SAMPLE NO.:LB3-1 GEOLOGIC UNIT:
SAMPLE DEPTH (FT.):3
6"5"4"3"2"1-1/2"1"3/4"1/2"3/8"#4#8#10#16#20#30#40#50#60#100#2000
10
20
30
40
50
60
70
80
90
100
0.010.11101001000PERCENT PASSINGPARTICLE SIZE (mm)
SAND SILT OR CLAYCOARSEFINECOARSEMEDIUMFINE
GRAVEL
Qt
D10 (mm) D30 (mm) D60 (mm)
0.101 0.878 10.066
SIEVE ANALYSES - ASTM D 135
NIRVANA
PROJECT NO.:
U.S. STANDARD SIEVE SIZE
G2755-42-01
SAMPLE NO.:LB4-1 GEOLOGIC UNIT:
SAMPLE DEPTH (FT.):9'
Cc
0.8
TEST DATA
SOIL DESCRIPTION
GP-GC - Poorly graded GRAVEL with clay and sand99.6
Cu6"5"4"3"2"1-1/2"1"3/4"1/2"3/8"#4#8#10#16#20#30#40#50#60#100#2000
10
20
30
40
50
60
70
80
90
100
0.010.11101001000PERCENT PASSINGPARTICLE SIZE (mm)
SAND SILT OR CLAYCOARSEFINECOARSEMEDIUMFINE
GRAVEL
To
D10 (mm) D30 (mm) D60 (mm)
0.00116 0.00226 0.00658
GEOLOGIC UNIT:
35'
LB5-1
SAMPLE DEPTH (FT.):
SAMPLE NO.:
SIEVE ANALYSES - ASTM D 135 & D 422
NIRVANA
PROJECT NO.:
Cc
0.7
Cu
5.7
G2755-42-01
SOIL DESCRIPTION
CLAY
TEST DATA
U.S. STANDARD SIEVE SIZE
3"2"1½"1¾"½"⅜"#4#8#10#16#20#30#40#50#60#80#100#2000
10
20
30
40
50
60
70
80
90
100
0.0010.010.1110100PERCENT PASSING PARTICLE SIZE (mm)
SILT OR CLAY
GRAVEL SAND
COARSEFINECOARSE MEDIUM FINE
APPENDIX C
APPENDIX C
EXPLORATORY BORINGS, TRENCHES AND LABORATORY
PERFORMED BY OTHERS
FOR
NIRVANA INDUSTRIAL BUILDINGS AND SELF STORAGE
COMPLEX
821 MAIN STREET
CHULA VISTA, CALIFORNIA
PROJECT NO. G2755-42-01
September 26, 2014 Page 1
P/W 1404-05 Report No. 1404-05-B-2
Project Chula Vista Energy Park
Date Excavated 8/12/2014
Logged by PWM
Equipment Cat 330C Trackhoe
LOG OF TEST PITS
Test
Pit No. Depth (ft.) USCS Description
TP-1 0.0 – 3.0 SC Topsoil:
CLAYEY SAND, fine to coarse grained, grayish brown,
dry, loose; some gravel and cobbles up to 10 in. diameter;
white carbonate development from 2 to 3 ft. bgs.
3.0 – 11.0 CL Older Alluvium (Qoal):
SILTY CLAY, grayish brown to gray, slightly moist, very
stiff.
@4.5 ft. abundant cobbles and small boulders; hard.
@ 7.5 ft. CLAYEY SAND, fine to medium grained, pale
brown to olive gray, slightly moist, moderately hard; highly
weathered; carbonate development.
@8.5 ft. becomes pale yellowish brown, slightly moist,
moderately hard to hard; with occasional gravel to small
cobble.
@10.0 ft. becomes hard; tight digging.
TOTAL DEPTH 11.0 FT.
NO WATER, NO CAVING
Plate B-1
September 26, 2014 Page 2
P/W 1404-05 Report No. 1404-05-B-2
Test
Pit No. Depth (ft.) USCS Description
TP-2 0.0 – 1.5 SC Topsoil:
CLAYEY SAND with silt, fine to medium grained, grayish
brown, dry, loose.
1.5 – 14.0 CL Older Alluvium (Qoal):
SILTY to SANDY CLAY, brown to reddish brown, slightly
moist, stiff; porous; occasional subrounded to subangular
cobbles; white carbonate development; root hairs.
6.0 – 16.0 SC @ 6.0 ft. CLAYEY SAND, fine grained, pale yellowish
brown, slightly moist, loose to moderately dense; highly
weathered; carbonate development; iron oxide
development; occasional subrounded to subangular cobbles.
@ 7.0 ft. SILTY to CLAYEY SAND, fine grained, pale
yellowish brown, slightly moist, moderately dense; weakly
cemented, hand friable, abundant iron oxide staining,
occasional small cobbles to 6 in. diameter.
@ 11.0 ft. becomes fine to coarse grained, grayish brown,
dense, slightly moist; occasional brown claystone clasts,
weakly cemented.
@ 13.0 ft. abundant cobbles to 10 in. diameter.
CL @ 14.0 ft. SANDY CLAY, fine grained, olive brown,
grayish brown, and brown, hard; manganese and iron oxide
development; occasional thin interbedded sandstone lenses.
TOTAL DEPTH 16.0 FT.
NO WATER, NO CAVING
Plate B-2
September 26, 2014 Page 3
P/W 1404-05 Report No. 1404-05-B-2
Test
Pit No. Depth (ft.) USCS Description
TP-3 0.0 – 1.0 SC Topsoil:
CLAYEY SAND with silt, fine to medium grained, grayish
brown, dry, loose.
1.0 – 12.0 CL
SP
Older Alluvium (Qoal):
SILTY CLAY, dark brown, slightly moist, firm; abundant
white carbonate development, root hairs, porous.
@ 3.0 ft. SAND, fine grained, brown, slightly moist,
medium dense; abundant carbonate development, root hairs.
CL
SC
@ 7.0 ft. SANDY CLAY, fine to coarse grained, brown,
slightly moist, stiff; carbonate development.
@9.0 ft. Cobble lense with sandy clay matrix, dense;
cobbles up to 8 inch diameter.
@10.0 ft. CLAYEY SAND, fine to medium grained, brown
to reddish brown, moist, medium dense; occasional cobbles.
TOTAL DEPTH 12.0 FT.
NO WATER, NO CAVING
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
TP-4 0.0 – 1.5 SC Topsoil:
CLAYEY SAND with silt, fine to medium grained, grayish
brown, dry, loose; slight white carbonate development;
occasional cobbles to 6 in. diameter.
1.5 – 13.0 CL Older Alluvium (Qoal):
SANDY CLAY, fine grained, reddish brown, stiff, slightly
moist.
SC
SP
SC
@ 6.5 ft. CLAYEY SAND, fine to coarse grained, reddish
brown, slightly moist, medium dense to dense; manganese
and iron oxide development, occasional gravel and cobbles
to 8 in. diameter
@10.0 ft. POORLY GRADED SAND, fine to medium
grained, light gray, slightly moist, medium dense.
@11.5 ft. CLAYEY SAND, fine to coarse grained, reddish
brown, slightly moist, medium dense to dense; occasional
gravel and cobbles.
TOTAL DEPTH 13.0 FT.
NO WATER, NO CAVING
Plate B-3
September 26, 2014 Page 4
P/W 1404-05 Report No. 1404-05-B-2
Test
Pit No. Depth (ft.) USCS Description
TP-5 0.0 – 1.0 SM Topsoil:
SILTY SAND, fine to medium grained, brown, dry, loose;
abundant subrounded gravel; occasional cobbles.
1.0 – 20.0 SC
SW
Older Alluvium (Qoal):
CLAYEY SAND, fine to coarse grained, red, slightly
moist, medium dense to dense; abundant subrounded
gravel.
@3.0 ft. abundant subangular to subrounded cobble and
occasional boulder.
@8.5 ft. WELL GRADED SAND, fine to coarse grained,
reddish brown, slightly moist, dense; abundant subangular
to subrounded cobbles to 6 in. diameter; about 60% sand,
40% cobble.
@18.0 ft. becomes sandier; about 75 sand, 25% cobble.
TOTAL DEPTH 20.0 FT.
NO WATER, NO CAVING
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
TP-6 0.0 – 1.0 SC Topsoil:
CLAYEY SAND with silt, fine to medium grained, brown,
dry, loose; abundant subrounded gravel; occasional cobbles
to 6 in. diameter.
1.0 – 9.0 CL Older Alluvium (Qoal):
SANDY CLAY, fine to coarse grained with subangular
gravel and occasional small cobble, dark brown, slightly
moist, firm; root hairs.
SC @ 2.5 ft. CLAYEY SAND, fine to coarse grained, red to
reddish brown, slightly moist, medium dense; abundant
carbonate and iron oxide development; occasional
subangular to subrounded cobble to 8 in. diameter.
@5 ft. becomes dense.
TOTAL DEPTH 9.0 FT.
NO WATER, NO CAVING
Plate B-4
September 26, 2014 Page 5
P/W 1404-05 Report No. 1404-05-B-2
Test
Pit No. Depth (ft.) USCS Description
TP-7 0.0 – 0.5 SC Topsoil:
CLAYEY SAND with silt, fine to medium grained, brown,
dry, loose; occasional gravel to small cobble.
0.5 – 12.0 CL Older Alluvium (Qoal):
SANDY CLAY, fine to coarse grained, dark brown,
slightly moist, firm; occasional gravel to small cobble.
SC CLAYEY SAND, fine to coarse grained, red to reddish
brown, slightly moist, medium dense; moderate carbonate
development to 7.0 ft. bgs., abundant gravel and cobbles to
8 in. diameter; about 30% cobble.
@10 ft. becomes dense; tighter digging.
TOTAL DEPTH 12.0 FT.
NO WATER, NO CAVING
Plate B-5
Plate B-6
Plate B-7
Plate B-8
Plate B-9
Plate B-10
Plate B-11
Plate B-12
Plate B-13
Plate B-14
ADVANCED GEOTECHNICAL SOLUTIONS, INC.
APPENDIX C
LABORATORY DATA
Plate C-1
Plate C-2
Plate C-3
Plate C-4
Plate C-5
Plate C-6
Plate C-7
APPENDIX D
APPENDIX D
SLOPE STABILITY EVALUATION
FOR
NIRVANA INDUSTRIAL BUILDINGS AND SELF STORAGE
COMPLEX
821 MAIN STREET
CHULA VISTA, CALIFORNIA
PROJECT NO. G2755-42-01
Geocon Project No. G2755-42-01 D- 1 - September 14, 2021
APPENDIX D
SLOPE STABILITY EVALUATION
General
Slope stability analyses were performed on Cross-Sections A-A', B-B' C-C', E-E', F-F', and G-G'
shown on Figures 1 and 2. The slope stability analyzes utilized the information on the preliminary
grading study plans provided by PLSA with respect to proposed site conditions. Slope stability was
evaluated for the MSE walls constructed along the south property margin and the natural hillside
descending slope along the eastern property margin. Stability analysis for the soil nail wall along the
northern property margin should be performed once preliminary wall design is performed and
coordination with the wall designer occurs. Slope geometry, geologic structure, and calculated factors
of safety for each cross section analyzed are presented on the figures in this Appendix. Additional
analysis will be needed once preliminary wall designs are complete.
The computer program, Slope/W from GeoSlope 2018, distributed by Geo-Slope International, was
utilized to perform slope stability analyses. This program uses conventional slope stability equations
and a two-dimensional limit-equilibrium method to calculate the factor of safety against deep-seated
failure. For our analyses, Spencer’s Method with block failure mode within the claystone beds was
used. Spencer’s Method satisfies both moment and force equilibrium. Circular failure method was also
utilized at some of the cross section locations.
The computer program searches for the most critical failure surface based on geometry and soil
strength parameters. The computer program searches for the critical failure surface based on
parameters inputted, including the location of the “left” and “right” sliding blocks and the failure plane
entrance and exit locations. The critical failure surface for each analysis is shown on computer
generated output directly above the failure surface (which is shown as the hatched area on the figure).
Shear Strength Parameters
Shear strength parameters used in the analyses are based on laboratory direct shear testing performed
for our investigation, investigations and grading for the adjacent Otay Ranch Village 3 project, and our
experience with similar soil conditions. Table D-1 summarizes the shear strength tests performed by
Geocon Incorporated during this geotechnical investigation.
Table D-2 summarize residual and fully softened values for the bentonitic claystone bed. The residual
and fully softened shear strength values were determined following the procedure presented in Stark,
Choi, McCone (2005) and GeoInstitute (2016).
Geocon Project No. G2755-42-01 D- 2 - September 14, 2021
Shear strength values used in our analyses are shown on Table D-3. The shear strength values are also
shown on stability output figures.
TABLE D-1
SUMMARY OF DIRECT SHEAR STRENGTH TEST RESULTS
Soil/Geologic Unit Sample No. Angle of Shear
Resistance (degrees)
Unit Cohesion
(psf)
Terrace Deposits
LB1-3 30 (peak)
35 (ultimate)
790 (peak)
350 (ultimate)
LB3-1* 20 (peak)
20 (ultimate)
550 (peak)
540 (ultimate)
LB4-1* 33 (peak)
(32 ultimate)
590 (peak)
480 (ultimate)
Otay Formation
LB4-2 (Claystone Bed) 36 (peak)
30 (ultimate)
670 (peak)
200 (ultimate)
LB5-3 (Siltstone) 35 (peak)
34 (ultimate)
530 (peak)
300 (ultimate)
LB5-5 (Claystone Bed) 34 (peak)
34 (ultimate)
270 (peak)
22 (ultimate)
*Sample remolded to approximately 90 percent of maximum dry density near optimum moisture content.
TABLE D-2
RESIDUAL AND FULLY SOFTENED SHEAR STRENGTH VALUES FOR CLAYSTONE BED
BASED ON STARK, CHOI, MCCONE (2005)
Sample
No.
Liquid
Limit
Percent
Clay
Residual Values Fully Softened Values
Angle of Internal
Friction
(degrees)
Cohesion
(psf)
Angle of Internal
Friction
(degrees)
Cohesion
(psf)
LB2-3 57 32 14 50 24 60
LB5-1 56 29 15 55 25 60
TABLE D-3
SHEAR STRENGTH USED IN SLOPE STABILITY ANALYSES
Soil Type Angle of Internal
Friction (degrees) Cohesion (psf)
Qcf (Compacted Fill) 28 250
Qt (Terrace Deposits) 35 350
To (Otay Formation) 34 300
To (Claystone Bed) 18 50
Geocon Project No. G2755-42-01 D- 3 - September 14, 2021
With respect to the claystone bed shear strength, we utilized a value that corresponds to a mid-range
value between residual and fully softened values determined using the Stark, Choi, McCone (2005)
and GeoInstitute (2016) procedures. In our opinion this value is conservative as no shearing or
remolding was observed in the claystone bed.
Slope Stability — Bentonitic Claystone Beds
Stability analysis were performed to evaluate the impacts the observed bentonitic claystone beds have
on slope stability. The following two conditions were analyzed: 1) MSE Wall along the south side of
the property with the backcut for the reinforcing grid equal to the height of the retaining wall; and 2)
the bentonitic claystone exposed near the toe of the natural hillside slope on the east side of the
property. We have also assumed that perched groundwater is present on the lower claystone bed.
For condition number one, we have assumed the backcut for the MSE retaining wall along the south
side of the property will remove the claystone bed to a horizontal distance (measured from the back of
the wall) equal to the height of the retaining wall. If the claystone bed is removed to this horizontal
limit, the proposed retaining wall and backfill will create a stabilizing buttress that provides a factor of
safety greater than 1.5. Cross Sections A-A', B-B', and C-C' show the slope stability analysis after
construction of the proposed MSE wall. The wall backcut has been assumed to extend up from the
excavation bottom at a 1:1 plane to the proposed finish grade surface. If the final wall design has
shorter wall grids and/or backcut dimensions, additional analysis should be performed to evaluate if
the proposed condition will have a factor of safety greater than 1.5 after construction of the wall.
As shown on Figure 2 and the stability figures in this Appendix, the buttress should start in front of the
wall and down to a depth of at least 5 feet below the claystone bed and sloped back into the slope as
shown on Figure 3. Buttress drains as shown on Figure 3 should be installed and outlet to the storm
drain system or in front of the retaining wall.
For condition number two, Cross Sections E-E', F-F', and G-G' have been drawn through the eastern
facing hillside slope. At Cross Section G-G', the proposed MSE retaining wall is located
approximately mid-height of the slope. As such, the wall backcut will not extend deep enough to
intercept the lower claystone bed. Based on our analysis, a buttress will be needed to provide a factor
of safety of at least 1.5. The buttress should start near the toe of the hillside slope and extend back into
the slope a distance of at least 50 feet measured from the toe of the slope. The buttress backcut should
extend up at a 1:1 plane to proposed pad grade. The approximate buttress/clay bed front removal limit
is shown on Figure 2.
The upper clay near the top of the slope will require a stability fill. The clay bed should be removed to
a horizontal distance of at least 15 feet back into the slope as shown on Cross Sections E-E' and F-F'.
Geocon Project No. G2755-42-01 D- 4 - September 14, 2021
The stability fill should include a back drain that outlets to the slope face. Subdrain cut off and head
walls as shown in Section 7.7 of this report should be constructed. An outlet should be provided every
approximately 100 feet of the stability fill.
Stability analysis for the soil nail wall along the northern property margin can be performed once
preliminary wall design is performed and coordination with the wall designer occurs.
Our analyses assumes select material derived from excavations in the Terrace Deposits or sandstone
portions of the Otay Formation will be used for the buttress fill. Minimum shear strength parameters to
produce a factor of safety in excess of 1.5 are 28 degree friction angle and 250 psf cohesion.
Summary of Stability Analyses
Table D-4 summarizes the stability analyses performed for this study. The calculated factor-of-safety
for proposed slopes and recommended stabilization method is included on the table. Analyses for the
soil nail wall will need to be performed once preliminary design of the wall is complete.
TABLE D-4
SUMMARY OF STABILITY ANALYSES
AND RECOMMENDED STABILIZATION METHOD
Cross Section Location Proposed Graded
Factor-of-Safety Stabilization Method
A-A', B-B',
and C-C'
Southern Slope with
MSE Wall
Construction
1.7 to 2.1 Claystone bed removed during wall
backcut excavation
E-E' and F-F' Eastern Slope 1.5 to 2.0 15 foot-wide stability fill
G-G' Southeast Slope Area 1.5 to 1.6 50 foot wide buttress at toe of slope
1.90Distance (Feet)0 50 100 150 200 250 300 350 400 450 500Elevation (Feet)50100150200250Elevation (Feet)50100150200250PLColor Name Unit Weight (pcf)Cohesion'(psf)Phi' (°)PiezometricLineClaystoneBed (CL/CH)130 50 18 1Qcf 130 250 28 1Qt 130 325 33 1To 130 325 33 1NIRVANAProject No. G2755-42-01File Name: A-A (Proposed) Fully Softened with Groundwater.gszDate: 09/14/2021Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01\CROSS SECTION A-A'PL
1.73Distance (Feet)0 50 100 150 200 250 300 350 400 450 500Elevation (Feet)50100150200250Elevation (Feet)50100150200250Color Name Unit Weight (pcf)Cohesion'(psf)Phi' (°)PiezometricLineClaystoneBed (CL/CH)130 50 18 1Qcf 130 250 28 1Qt 130 325 33 1To 130 325 33 1NIRVANAProject No. G2755-42-01File Name: B-B (Proposed) Fully Softened with Groundwater.gszDate: 09/14/2021Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01\CROSS SECTION B-B'PLPL
2.07Distance (Feet)0 50 100 150 200 250 300 350 400 450 500Elevation (Feet)50100150200250Elevation (Feet)50100150200250Color Name Unit Weight (pcf)Cohesion'(psf)Phi' (°)PiezometricLineClaystoneBed (CL/CH)130 50 18 1Qcf 130 250 28 1Qt 130 325 33 1To 130 325 33 1NIRVANAProject No. G2755-42-01File Name: C-C (Proposed) Fully Softened with Groundwater.gszDate: 09/14/2021Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01\CROSS SECTION C-C'PLPL
1.51Distance, Feet0 25 50 75 100 125 150 175 200 225 250Elevation (Feet)100125150175200225Elevation (Feet) MSL100125150175200225Color Name Unit Weight (pcf)Cohesion'(psf)Phi' (°)PiezometricLineClaystoneBed (CL/CH)130 50 18 1Qt 130 350 35 1To 130 300 34 1NIRVANAProject No. G2755-42-01File Name: E-E (Proposed) Circular - Fully Softened (Groundwater).gszDate: 09/14/2021Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01\CROSS SECTION E-E'
1.54Distance (Feet)0 25 50 75 100 125 150 175 200 225 250Elevation (Feet)100125150175200Elevation (Feet)100125150175200Color Name Unit Weight(pcf)Cohesion'(psf)Phi' (°)PiezometricLineClaystoneBed (CL/CH)130 50 18 1Qcf 130 250 28 1Qt 130 350 35 1To 130 300 34 1To (2) 1NIRVANAProject No. G2755-42-01File Name: E-E (Proposed) Fully Softened - Upper Clay Removed with Groundwater.gszDate: 09/14/2021Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01\CROSS SECTION E-E'
1.5Distance, Feet0 25 50 75 100 125 150 175 200 225 250Elevation, Feet MSL100125150175200Elevation, Feet MSL100125150175200Color Name Unit Weight(pcf)Cohesion'(psf)Phi' (°)PiezometricLineClaystoneBed (CL/CH)130 50 18 1Qcf 130 250 28 1Qt 130 350 35 1To 130 300 34 1To (2) 1NIRVANAProject No. G2755-42-01File Name: E-E (Upper Clay Bed) Fully Softened - Circular.gszDate: 09/13/2021Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01\CROSS SECTION E-E'
1.5Distance (Feet)0 25 50 75 100 125 150 175 200 225 250Elevation (Feet)100125150175200Elevation (Feet)100125150175200Color Name Unit Weight (pcf)Cohesion'(psf)Phi' (°)PiezometricLineClaystoneBed (CL/CH)130 50 18 1Qcf 130 250 28 1Qt 130 350 35 1To 130 300 34 1NIRVANAProject No. G2755-42-01File Name: E-E (Proposed) Fully Softened with Ground Water-Upper Clay Removed.gszDate: 09/14/2021Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01\CROSS SECTION E-E'
2.03Distance (Feet)0 25 50 75 100 125 150 175 200Elevation (Feet)100125150175200225Elevation (Feet)100125150175200225Color Name Unit Weight (pcf)Cohesion'(psf)Phi' (°)ClaystoneBed (CL/CH)130 50 18Qcf 130 250 28Qt 130 350 35To 130 300 34NIRVANAProject No. G2755-42-01File Name: F-F (Proposed) Fully Softened - Stability Fill, Circular.gszDate: 09/14/2021Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01\CROSS SECTION F-F'
1.5Distance (Feet)0 25 50 75 100 125 150 175 200Elevation (Feet)100125150175200Elevation (Feet)100125150175200Color Name Unit Weight(pcf)Cohesion'(psf)Phi' (°)PiezometricLineClaystoneBed (CL/CH)130 50 18 1Qcf 130 250 28 1Qt 130 350 35 1To 130 300 34 1To (2) 1NIRVANAProject No. G2755-42-01File Name: G-G (Proposed) Buttress ( Fully Softened with Groundwater).gszDate: 09/14/2021Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01\CROSS SECTION G-G'
1.6Distance (Feet)0 25 50 75 100 125 150 175 200Elevation (Feet)100125150175200Elevation (Feet)100125150175200Color Name Unit Weight (pcf)Cohesion'(psf)Phi' (°)PiezometricLineClaystoneBed (CL/CH)130 50 18 1Qcf 130 250 28 1Qt 130 350 35 1To 130 300 34 1NIRVANAProject No. G2755-42-01File Name: G-G (Proposed) Buttress - Circular (Fully Softened with Groundwater).gszDate: 09/14/2021Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01\CROSS SECTION G-G'
APPENDIX E
APPENDIX E
RECOMMENDED GRADING SPECIFICATIONS
FOR
NIRVANA INDUSTRIAL BUILDINGS AND SELF STORAGE COMPLEX
821 MAIN STREET
CHULA VISTA, CALIFORNIA
PROJECT NO. G2755-42-01
GI rev. 07/2015
RECOMMENDED GRADING SPECIFICATIONS
1. GENERAL
1.1 These Recommended Grading Specifications shall be used in conjunction with the
Geotechnical Report for the project prepared by Geocon. The recommendations contained
in the text of the Geotechnical Report are a part of the earthwork and grading specifications
and shall supersede the provisions contained hereinafter in the case of conflict.
1.2 Prior to the commencement of grading, a geotechnical consultant (Consultant) shall be
employed for the purpose of observing earthwork procedures and testing the fills for
substantial conformance with the recommendations of the Geotechnical Report and these
specifications. The Consultant should provide adequate testing and observation services so
that they may assess whether, in their opinion, the work was performed in substantial
conformance with these specifications. It shall be the responsibility of the Contractor to
assist the Consultant and keep them apprised of work schedules and changes so that
personnel may be scheduled accordingly.
1.3 It shall be the sole responsibility of the Contractor to provide adequate equipment and
methods to accomplish the work in accordance with applicable grading codes or agency
ordinances, these specifications and the approved grading plans. If, in the opinion of the
Consultant, unsatisfactory conditions such as questionable soil materials, poor moisture
condition, inadequate compaction, and/or adverse weather result in a quality of work not in
conformance with these specifications, the Consultant will be empowered to reject the
work and recommend to the Owner that grading be stopped until the unacceptable
conditions are corrected.
2. DEFINITIONS
2.1 Owner shall refer to the owner of the property or the entity on whose behalf the grading
work is being performed and who has contracted with the Contractor to have grading
performed.
2.2 Contractor shall refer to the Contractor performing the site grading work.
2.3 Civil Engineer or Engineer of Work shall refer to the California licensed Civil Engineer
or consulting firm responsible for preparation of the grading plans, surveying and verifying
as-graded topography.
2.4 Consultant shall refer to the soil engineering and engineering geology consulting firm
retained to provide geotechnical services for the project.
GI rev. 07/2015
2.5 Soil Engineer shall refer to a California licensed Civil Engineer retained by the Owner,
who is experienced in the practice of geotechnical engineering. The Soil Engineer shall be
responsible for having qualified representatives on-site to observe and test the Contractor's
work for conformance with these specifications.
2.6 Engineering Geologist shall refer to a California licensed Engineering Geologist retained
by the Owner to provide geologic observations and recommendations during the site
grading.
2.7 Geotechnical Report shall refer to a soil report (including all addenda) which may include
a geologic reconnaissance or geologic investigation that was prepared specifically for the
development of the project for which these Recommended Grading Specifications are
intended to apply.
3. MATERIALS
3.1 Materials for compacted fill shall consist of any soil excavated from the cut areas or
imported to the site that, in the opinion of the Consultant, is suitable for use in construction
of fills. In general, fill materials can be classified as soil fills, soil-rock fills or rock fills, as
defined below.
3.1.1 Soil fills are defined as fills containing no rocks or hard lumps greater than
12 inches in maximum dimension and containing at least 40 percent by weight of
material smaller than ¾ inch in size.
3.1.2 Soil-rock fills are defined as fills containing no rocks or hard lumps larger than
4 feet in maximum dimension and containing a sufficient matrix of soil fill to allow
for proper compaction of soil fill around the rock fragments or hard lumps as
specified in Paragraph 6.2. Oversize rock is defined as material greater than
12 inches.
3.1.3 Rock fills are defined as fills containing no rocks or hard lumps larger than 3 feet
in maximum dimension and containing little or no fines. Fines are defined as
material smaller than ¾ inch in maximum dimension. The quantity of fines shall be
less than approximately 20 percent of the rock fill quantity.
3.2 Material of a perishable, spongy, or otherwise unsuitable nature as determined by the
Consultant shall not be used in fills.
3.3 Materials used for fill, either imported or on-site, shall not contain hazardous materials as
defined by the California Code of Regulations, Title 22, Division 4, Chapter 30, Articles 9
GI rev. 07/2015
and 10; 40CFR; and any other applicable local, state or federal laws. The Consultant shall
not be responsible for the identification or analysis of the potential presence of hazardous
materials. However, if observations, odors or soil discoloration cause Consultant to suspect
the presence of hazardous materials, the Consultant may request from the Owner the
termination of grading operations within the affected area. Prior to resuming grading
operations, the Owner shall provide a written report to the Consultant indicating that the
suspected materials are not hazardous as defined by applicable laws and regulations.
3.4 The outer 15 feet of soil-rock fill slopes, measured horizontally, should be composed of
properly compacted soil fill materials approved by the Consultant. Rock fill may extend to
the slope face, provided that the slope is not steeper than 2:1 (horizontal:vertical) and a soil
layer no thicker than 12 inches is track-walked onto the face for landscaping purposes. This
procedure may be utilized provided it is acceptable to the governing agency, Owner and
Consultant.
3.5 Samples of soil materials to be used for fill should be tested in the laboratory by the
Consultant to determine the maximum density, optimum moisture content, and, where
appropriate, shear strength, expansion, and gradation characteristics of the soil.
3.6 During grading, soil or groundwater conditions other than those identified in the
Geotechnical Report may be encountered by the Contractor. The Consultant shall be
notified immediately to evaluate the significance of the unanticipated condition.
4. CLEARING AND PREPARING AREAS TO BE FILLED
4.1 Areas to be excavated and filled shall be cleared and grubbed. Clearing shall consist of
complete removal above the ground surface of trees, stumps, brush, vegetation, man-made
structures, and similar debris. Grubbing shall consist of removal of stumps, roots, buried
logs and other unsuitable material and shall be performed in areas to be graded. Roots and
other projections exceeding 1½ inches in diameter shall be removed to a depth of 3 feet
below the surface of the ground. Borrow areas shall be grubbed to the extent necessary to
provide suitable fill materials.
4.2 Asphalt pavement material removed during clearing operations should be properly
disposed at an approved off-site facility or in an acceptable area of the project evaluated by
Geocon and the property owner. Concrete fragments that are free of reinforcing steel may
be placed in fills, provided they are placed in accordance with Section 6.2 or 6.3 of this
document.
GI rev. 07/2015
4.3 After clearing and grubbing of organic matter and other unsuitable material, loose or
porous soils shall be removed to the depth recommended in the Geotechnical Report. The
depth of removal and compaction should be observed and approved by a representative of
the Consultant. The exposed surface shall then be plowed or scarified to a minimum depth
of 6 inches and until the surface is free from uneven features that would tend to prevent
uniform compaction by the equipment to be used.
4.4 Where the slope ratio of the original ground is steeper than 5:1 (horizontal:vertical), or
where recommended by the Consultant, the original ground should be benched in
accordance with the following illustration.
TYPICAL BENCHING DETAIL
Remove All
Unsuitable Material
As Recommended By
Consultant
Finish Grade Original Ground
Finish Slope Surface
Slope To Be Such That
Sloughing Or Sliding
Does Not Occur Varies
“B”
See Note 1
No Scale
See Note 2
1
2
DETAIL NOTES: (1) Key width "B" should be a minimum of 10 feet, or sufficiently wide to permit
complete coverage with the compaction equipment used. The base of the key should
be graded horizontal, or inclined slightly into the natural slope.
(2) The outside of the key should be below the topsoil or unsuitable surficial material
and at least 2 feet into dense formational material. Where hard rock is exposed in the
bottom of the key, the depth and configuration of the key may be modified as
approved by the Consultant.
4.5 After areas to receive fill have been cleared and scarified, the surface should be moisture
conditioned to achieve the proper moisture content, and compacted as recommended in
Section 6 of these specifications.
GI rev. 07/2015
5. COMPACTION EQUIPMENT
5.1 Compaction of soil or soil-rock fill shall be accomplished by sheepsfoot or segmented-steel
wheeled rollers, vibratory rollers, multiple-wheel pneumatic-tired rollers, or other types of
acceptable compaction equipment. Equipment shall be of such a design that it will be
capable of compacting the soil or soil-rock fill to the specified relative compaction at the
specified moisture content.
5.2 Compaction of rock fills shall be performed in accordance with Section 6.3.
6. PLACING, SPREADING AND COMPACTION OF FILL MATERIAL
6.1 Soil fill, as defined in Paragraph 3.1.1, shall be placed by the Contractor in accordance with
the following recommendations:
6.1.1 Soil fill shall be placed by the Contractor in layers that, when compacted, should
generally not exceed 8 inches. Each layer shall be spread evenly and shall be
thoroughly mixed during spreading to obtain uniformity of material and moisture
in each layer. The entire fill shall be constructed as a unit in nearly level lifts. Rock
materials greater than 12 inches in maximum dimension shall be placed in
accordance with Section 6.2 or 6.3 of these specifications.
6.1.2 In general, the soil fill shall be compacted at a moisture content at or above the
optimum moisture content as determined by ASTM D 1557.
6.1.3 When the moisture content of soil fill is below that specified by the Consultant,
water shall be added by the Contractor until the moisture content is in the range
specified.
6.1.4 When the moisture content of the soil fill is above the range specified by the
Consultant or too wet to achieve proper compaction, the soil fill shall be aerated by
the Contractor by blading/mixing, or other satisfactory methods until the moisture
content is within the range specified.
6.1.5 After each layer has been placed, mixed, and spread evenly, it shall be thoroughly
compacted by the Contractor to a relative compaction of at least 90 percent.
Relative compaction is defined as the ratio (expressed in percent) of the in-place
dry density of the compacted fill to the maximum laboratory dry density as
determined in accordance with ASTM D 1557. Compaction shall be continuous
over the entire area, and compaction equipment shall make sufficient passes so that
the specified minimum relative compaction has been achieved throughout the
entire fill.
GI rev. 07/2015
6.1.6 Where practical, soils having an Expansion Index greater than 50 should be placed
at least 3 feet below finish pad grade and should be compacted at a moisture
content generally 2 to 4 percent greater than the optimum moisture content for the
material.
6.1.7 Properly compacted soil fill shall extend to the design surface of fill slopes. To
achieve proper compaction, it is recommended that fill sl opes be over-built by at
least 3 feet and then cut to the design grade. This procedure is considered
preferable to track-walking of slopes, as described in the following paragraph.
6.1.8 As an alternative to over-building of slopes, slope faces may be back-rolled with a
heavy-duty loaded sheepsfoot or vibratory roller at maximum 4-foot fill height
intervals. Upon completion, slopes should then be track-walked with a D-8 dozer
or similar equipment, such that a dozer track covers all slope surfaces at least
twice.
6.2 Soil-rock fill, as defined in Paragraph 3.1.2, shall be placed by the Contractor in accordance
with the following recommendations:
6.2.1 Rocks larger than 12 inches but less than 4 feet in maximum dimension may be
incorporated into the compacted soil fill, but shall be limited to the area measured
15 feet minimum horizontally from the slope face and 5 feet below finish grade or
3 feet below the deepest utility, whichever is deeper.
6.2.2 Rocks or rock fragments up to 4 feet in maximum dimension may either be
individually placed or placed in windrows. Under certain conditions, rocks or rock
fragments up to 10 feet in maximum dimension may be placed using similar
methods. The acceptability of placing rock materials greater than 4 feet in
maximum dimension shall be evaluated during grading as specific cases arise and
shall be approved by the Consultant prior to placement.
6.2.3 For individual placement, sufficient space shall be provided between rocks to allow
for passage of compaction equipment.
6.2.4 For windrow placement, the rocks should be placed in trenches excavated in
properly compacted soil fill. Trenches should be approximately 5 feet wide and
4 feet deep in maximum dimension. The voids around and beneath rocks should be
filled with approved granular soil having a Sand Equivalent of 30 or greater and
should be compacted by flooding. Windrows may also be placed utilizing an
"open-face" method in lieu of the trench procedure, however, this method should
first be approved by the Consultant.
GI rev. 07/2015
6.2.5 Windrows should generally be parallel to each other and may be placed either
parallel to or perpendicular to the face of the slope depending on the site geometry.
The minimum horizontal spacing for windrows shall be 12 feet center-to-center
with a 5-foot stagger or offset from lower courses to next overlying course. The
minimum vertical spacing between windrow courses shall be 2 feet from the top of
a lower windrow to the bottom of the next higher windrow.
6.2.6 Rock placement, fill placement and flooding of approved granular soil in the
windrows should be continuously observed by the Consultant.
6.3 Rock fills, as defined in Section 3.1.3, shall be placed by the Contractor in accordance with
the following recommendations:
6.3.1 The base of the rock fill shall be placed on a sloping surface (minimum slope of 2
percent). The surface shall slope toward suitable subdrainage outlet facilities. The
rock fills shall be provided with subdrains during construction so that a hydrostatic
pressure buildup does not develop. The subdrains shall be permanently connected
to controlled drainage facilities to control post-construction infiltration of water.
6.3.2 Rock fills shall be placed in lifts not exceeding 3 feet. Placement shall be by rock
trucks traversing previously placed lifts and dumping at the edge of the currently
placed lift. Spreading of the rock fill shall be by dozer to facilitate seating of the
rock. The rock fill shall be watered heavily during placement. Watering shall
consist of water trucks traversing in front of the current rock lift face and spraying
water continuously during rock placement. Compaction equipment with
compactive energy comparable to or greater than that of a 20-ton steel vibratory
roller or other compaction equipment providing suitable energy to achieve the
required compaction or deflection as recommended in Paragraph 6.3.3 shall be
utilized. The number of passes to be made should be determined as described in
Paragraph 6.3.3. Once a rock fill lift has been covered with soil fill, no additional
rock fill lifts will be permitted over the soil fill.
6.3.3 Plate bearing tests, in accordance with ASTM D 1196, may be performed in both
the compacted soil fill and in the rock fill to aid in determining the required
minimum number of passes of the compaction equipment. If performed, a
minimum of three plate bearing tests should be performed in the properly
compacted soil fill (minimum relative compaction of 90 percent). Plate bearing
tests shall then be performed on areas of rock fill having two passes, four passes
and six passes of the compaction equipment, respectively. The number of passes
required for the rock fill shall be determined by comparing the results of the plate
bearing tests for the soil fill and the rock fill and by evaluating the deflection
GI rev. 07/2015
variation with number of passes. The required number of passes of the compaction
equipment will be performed as necessary until the plate bearing deflections are
equal to or less than that determined for the properly compacted soil fill. In no case
will the required number of passes be less than two.
6.3.4 A representative of the Consultant should be present during rock fill operations to
observe that the minimum number of “passes” have been obtained, that water is
being properly applied and that specified procedures are being followed. The actual
number of plate bearing tests will be determined by the Consultant during grading.
6.3.5 Test pits shall be excavated by the Contractor so that the Consultant can state that,
in their opinion, sufficient water is present and that voids between large rocks are
properly filled with smaller rock material. In-place density testing will not be
required in the rock fills.
6.3.6 To reduce the potential for “piping” of fines into the rock fill from overlying soil
fill material, a 2-foot layer of graded filter material shall be placed above the
uppermost lift of rock fill. The need to place graded filter material below the rock
should be determined by the Consultant prior to commencing grading. The
gradation of the graded filter material will be determined at the time the rock fill is
being excavated. Materials typical of the rock fill should be submitted to the
Consultant in a timely manner, to allow design of the graded filter prior to the
commencement of rock fill placement.
6.3.7 Rock fill placement should be continuously observed during placement by the
Consultant.
7. SUBDRAINS
7.1 The geologic units on the site may have permeability characteristics and/or fracture
systems that could be susceptible under certain conditions to seepage. The use of canyon
subdrains may be necessary to mitigate the potential for adverse impacts associated with
seepage conditions. Canyon subdrains with lengths in excess of 500 feet or extensions of
existing offsite subdrains should use 8-inch-diameter pipes. Canyon subdrains less than 500
feet in length should use 6-inch-diameter pipes.
GI rev. 07/2015
TYPICAL CANYON DRAIN DETAIL
7.2 Slope drains within stability fill keyways should use 4-inch-diameter (or lager) pipes.
GI rev. 07/2015
TYPICAL STABILITY FILL DETAIL
7.3 The actual subdrain locations will be evaluated in the field during the remedial grading
operations. Additional drains may be necessary depending on the conditions observed and
the requirements of the local regulatory agencies. Appropriate subdrain outlets should be
evaluated prior to finalizing 40-scale grading plans.
7.4 Rock fill or soil-rock fill areas may require subdrains along their down-slope perimeters to
mitigate the potential for buildup of water from construction or landscape irrigation. The
subdrains should be at least 6-inch-diameter pipes encapsulated in gravel and filter fabric.
Rock fill drains should be constructed using the same requirements as canyon subdrains.
GI rev. 07/2015
7.5 Prior to outletting, the final 20-foot segment of a subdrain that will not be extended during
future development should consist of non-perforated drainpipe. At the non-perforated/
perforated interface, a seepage cutoff wall should be constructed on the downslope side of
the pipe.
TYPICAL CUT OFF WALL DETAIL
7.6 Subdrains that discharge into a natural drainage course or open space area should be
provided with a permanent headwall structure.
GI rev. 07/2015
TYPICAL HEADWALL DETAIL
7.7 The final grading plans should show the location of the proposed subdrains. After
completion of remedial excavations and subdrain installation, the project civil engineer
should survey the drain locations and prepare an “as-built” map showing the drain
locations. The final outlet and connection locations should be determined during grading
operations. Subdrains that will be extended on adjacent projects after grading can be placed
on formational material and a vertical riser should be placed at the end of the subdrain. The
grading contractor should consider videoing the subdrains shortly after burial to check
proper installation and functionality. The contractor is responsible for the performance of
the drains.
GI rev. 07/2015
8. OBSERVATION AND TESTING
8.1 The Consultant shall be the Owner’s representative to observe and perform tests during
clearing, grubbing, filling, and compaction operations. In general, no more than 2 feet in
vertical elevation of soil or soil-rock fill should be placed without at least one field density
test being performed within that interval. In addition, a minimum of one field density test
should be performed for every 2,000 cubic yards of soil or soil-rock fill placed and
compacted.
8.2 The Consultant should perform a sufficient distribution of field density tests of the
compacted soil or soil-rock fill to provide a basis for expressing an opinion whether the fill
material is compacted as specified. Density tests shall be performed in the compacted
materials below any disturbed surface. When these tests indicate that the density of any
layer of fill or portion thereof is below that specified, the particular layer or areas
represented by the test shall be reworked until the specified density has been achieved.
8.3 During placement of rock fill, the Consultant should observe that the minimum number of
passes have been obtained per the criteria discussed in Section 6.3.3. The Consultant
should request the excavation of observation pits and may perform plate bearing tests on
the placed rock fills. The observation pits will be excavated to provide a basis for
expressing an opinion as to whether the rock fill is properly seated and sufficient moisture
has been applied to the material. When observations indicate that a layer of rock fill or any
portion thereof is below that specified, the affected layer or area shall be reworked until the
rock fill has been adequately seated and sufficient moisture applied.
8.4 A settlement monitoring program designed by the Consultant may be conducted in areas of
rock fill placement. The specific design of the monitoring program shall be as
recommended in the Conclusions and Recommendations section of the project
Geotechnical Report or in the final report of testing and observation services performed
during grading.
8.5 We should observe the placement of subdrains, to check that the drainage devices have
been placed and constructed in substantial conformance with project specifications.
8.6 Testing procedures shall conform to the following Standards as appropriate:
8.6.1 Soil and Soil-Rock Fills:
8.6.1.1 Field Density Test, ASTM D 1556, Density of Soil In-Place By the
Sand-Cone Method.
GI rev. 07/2015
8.6.1.2 Field Density Test, Nuclear Method, ASTM D 6938, Density of Soil and
Soil-Aggregate In-Place by Nuclear Methods (Shallow Depth).
8.6.1.3 Laboratory Compaction Test, ASTM D 1557, Moisture-Density
Relations of Soils and Soil-Aggregate Mixtures Using 10-Pound
Hammer and 18-Inch Drop.
8.6.1.4. Expansion Index Test, ASTM D 4829, Expansion Index Test.
9. PROTECTION OF WORK
9.1 During construction, the Contractor shall properly grade all excavated surfaces to provide
positive drainage and prevent ponding of water. Drainage of surface water shall be
controlled to avoid damage to adjoining properties or to finished work on the site. The
Contractor shall take remedial measures to prevent erosion of freshly graded areas until
such time as permanent drainage and erosion control features have been installed. Areas
subjected to erosion or sedimentation shall be properly prepared in accordance with the
Specifications prior to placing additional fill or structures.
9.2 After completion of grading as observed and tested by the Consultant, no further
excavation or filling shall be conducted except in conjunction with the services of the
Consultant.
10. CERTIFICATIONS AND FINAL REPORTS
10.1 Upon completion of the work, Contractor shall furnish Owner a certification by the Civil
Engineer stating that the lots and/or building pads are graded to within 0.1 foot vertically of
elevations shown on the grading plan and that all tops and toes of slopes are within 0.5 foot
horizontally of the positions shown on the grading plans. After installation of a section of
subdrain, the project Civil Engineer should survey its location and prepare an as-built plan
of the subdrain location. The project Civil Engineer should verify the proper outlet for the
subdrains and the Contractor should ensure that the drain system is free of obstructions.
10.2 The Owner is responsible for furnishing a final as-graded soil and geologic report
satisfactory to the appropriate governing or accepting agencies. The as-graded report
should be prepared and signed by a California licensed Civil Engineer experienced in
geotechnical engineering and by a California Certified Engineering Geologist, indicating
that the geotechnical aspects of the grading were performed in substantial conformance
with the Specifications or approved changes to the Specifications.
Geocon Project No. G2755-42-01 D- 6 - September 14, 2021
LIST OF REFERENCES
1.Advanced Geotechnical Solutions, Inc. (AGS), Update Geotechnical Report and Grading
Plan Review, Energy Park, Chula Vista, California, dated September 29, 2014 (Report No.
1404-05-B-2);
2.FEMA (2012), Flood Map Service Center, FEMA website, https://msc.fema.gov/portal/home,
flood map numbers 06073C2156G and 06073C2157G, effective May 16, 2012, accessed
August 29, 2021;
3.Geocon Incorporated, Final Report of Testing and Observation Services Performed During
Site Grading, Otay Ranch Village 3, Chula Vista, California, dated November 25, 2020
(Project No. 06930-52-06);
4.Stark, Choi, McCone (2005), Journal of Geotechnical and Geoenvironmental Engineering,
Drained Shear Strength Parameters for Analysis of Landslides.
5.Geo Institute (2016), Development and Use of Fully Softened Shear Strength in Slope Stability
Analyses, Geo Institute, dated February 12, 2016.
6.Kennedy, M. P. and S. S Tan, Geologic Map of the San Diego 30’x60’ Quadrangle,,
California, California Geologic Survey, 2008.
7.Magellan Architecture, Chula Vista Self Storage, Chula Vista, CA, Scheme B, dated May 12,
2021;
8.Pasco Laret Suiter & Associates, Preliminary Grading Study, Nirvana Self Storage, 821 Main
Street, Chula Vista, CA, dated July 23, 2021.
9.SEAOC (2019), OSHPD Seismic Design Maps: Structural Engineers Association of
California website, http://seismicmaps.org/, accessed August 29, 2021;
10.USGS (2019), Quaternary Fault and Fold Database of the United States: U.S. Geological
Survey website, https://www.usgs.gov/natural-hazards/earthquake-hazards/faults, accessed
August 29, 2021;
11.Unpublished reports and maps on file with Geocon Incorporated.