HomeMy WebLinkAboutTechnical Report 11 - Geology ReportGEOTECHNICAL
RECONNAISSANCE REPORT
OTAY RANCH TOWN CENTER
CHULA VISTA, CALIFORNIA
PREPARED FOR
FEBRUARY 4, 2022
PROJECT NO. G2883-52-01
GROCON
INCORPORATED
GEOTECHNICAL • ENVIRONMENTAL MATERIALSO
6960 Flanders Drive • San Diego, California 92121-2974 • Telephone 858.558.6900 • Fax 858.558.6159
Project No. G2883-52-01
February 4, 2022
Brookfield Properties
733 8th Avenue
San Diego, California 92101
Attention: Mr. Dan Buoye
Subject: GEOTECHNICAL RECONNAISSANCE REPORT
OTAY RANCH TOWN CENTER
CHULA VISTA, CALIFORNIA
Dear Mr. Buoye:
In accordance with your request and authorization of our Proposal No. LG-21061 revised January 11,
2022, we prepared this geotechnical reconnaissance report for the proposed Otay Ranch Town Center
redevelopment in Chula Vista, California.
The accompanying report describes the general site soil and geologic conditions based on a desktop
study and presents our findings. We should be contacted to prepare a geotechnical investigation for
proposed redevelopment to the property, if planned.
Should you have any questions regarding this report, or if we may be of further service, please contact
the undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
Ken W. Haase
PG 9974
Shawn Foy Weedon
GE 2714
John Hoobs
CEG 1524
KH:SFW:JH:arm
(e-mail) Addressee
TABLE OF CONTENTS
1. PURPOSE AND SCOPE ...................................................................................................................... 1
2. SITE DESCRIPTION ........................................................................................................................... 2
3. GEOLOGIC SETTING ......................................................................................................................... 3
4. SOIL AND GEOLOGIC CONDITIONS ............................................................................................. 4
4.1 Previously Placed Fill ................................................................................................................. 4
4.2 Otay Formation ........................................................................................................................... 4
5. GROUNDWATER ............................................................................................................................... 5
6. GEOLOGIC HAZARDS ...................................................................................................................... 5
6.1 Faulting and Seismicity .............................................................................................................. 5
6.2 Ground Rupture .......................................................................................................................... 7
6.3 Tsunamis and Seiches ................................................................................................................. 7
6.4 Liquefaction ................................................................................................................................ 7
6.5 Landslides ................................................................................................................................... 7
6.6 Erosion ........................................................................................................................................ 7
6.7 Settlement ................................................................................................................................... 8
7. CONCLUSIONS AND RECOMMENDATIONS ................................................................................ 9
7.1 General ........................................................................................................................................ 9
7.2 Excavation and Soil Characteristics ......................................................................................... 10
7.3 Seismic Design Criteria ............................................................................................................ 10
7.4 General Grading Recommendations ......................................................................................... 12
7.5 Geotechnical Design ................................................................................................................. 14
7.6 Site Drainage and Moisture Protection ..................................................................................... 15
MAPS AND ILLUSTRATIONS
Figure 1, Geologic Map
APPENDIX A
PREVIOUS BORING LOGS
APPENDIX B
PREVIOUS LABORATORY TESTING
LIST OF REFERENCES
Geocon Project No. G2883-52-01 - 1 - February 4, 2022
GEOTECHNICAL RECONNAISSANCE
1. PURPOSE AND SCOPE
This report presents the results of a geotechnical reconnaissance related to proposed redevelopment of
the Otay Ranch Town Center in the City of Chula Vista, California (see Vicinity Map). The roughly 5-
acre property is located north of Birch Road and the Otay Ranch Town Center Mall, south of Olympic
Parkway and the Planning Area 12 development, west of Eastlake Parkway and east of State Route
125. The purpose of this study is to review published geotechnical documents and geologic
information (see List of References) and evaluate the existing geologic conditions and
geologic/geotechnical hazards that may affect the property.
Vicinity Map
The scope of our study included reviewing published and unpublished geotechnical information of the
surrounding area. Appendix A presents the boring logs performed during the referenced investigation.
In addition, Appendix B includes the laboratory test results from the previous investigation. The
conclusions presented herein are based on a review of the available data and our experience with
similar soil and geologic conditions in the surrounding area.
The scope of the study included a review of:
1. As-Graded Geotechnical Report, McMillin Otay Ranch, Village 12 and Borrow and Fill Sites Within the Eastern Urban Center, Chula Vista, California, prepared by Geotechnics Incorporated, dated February 16, 2006 (Project No. 0367-012-01, Document No. 05-1029).
2. Preliminary Geotechnical Investigation, Otay Ranch Town Center Addition, Otay Ranch Village 12, 2015 Birch Road, Chula Vista, California, prepared by Geocon Incorporated, dated June 26, 2014 (Project No. G1731-11-01).
Geocon Project No. G2883-52-01 - 2 - February 4, 2022
2. SITE DESCRIPTION
The existing property consists of the northern parking area for the existing Otay Ranch Town Center mall.
The area consists of surface grade asphalt concrete parking on the east and southwest, an outdoor soccer
area and playground in the central portion with a landscape construction storage area in the northwest
portion. The site was graded between 2004 and 2005 with observation and testing services provided by
Geotechnics, Incorporated. The site is relatively flat with elevations between 624 feet Mean Sea Level
(MSL) and 614 feet MSL, sloping gently to the southwest. An existing 10- to 15-foot-high cut and fill slope
exists on the west limits of the site, descending towards State Route 125. The Existing Site Map shows the
current conditions at the site. Based on the previous as-graded map, the site was partially situated over the
upper portions of two canyon drainages with fill depths ranging up to about 25 feet at the site.
Existing Site Map
We understand the proposed redevelopment will consist of constructing 3, multi-family residential lots
with commercial space, reconfiguring the existing Town Center Drive entrance and installing a new
plaza area in the southeast portion of the site with accommodating utilities, flatwork, and landscaping.
The Preliminary Site Plan shows a current concept of the proposed improvements.
Geocon Project No. G2883-52-01 - 3 - February 4, 2022
Preliminary Site Plan
3. GEOLOGIC SETTING
The site is in the eastern portion of the coastal plain within the southern portion of the Peninsular
Ranges Geomorphic Province of southern California. The Peninsular Ranges is a geologic and
geomorphic province that extends from the Imperial Valley to the Pacific Ocean and from the
Transverse Ranges to the north and into Baja California to the south. The coastal plain of San Diego
County is underlain by a thick sequence of relatively undisturbed and non-conformable sedimentary
rocks that thicken to the west and range in age from Upper Cretaceous through the Pleistocene with
intermittent deposition. The sedimentary units are deposited on bedrock Cretaceous to Jurassic age
igneous and metavolcanic rocks. Geomorphically, the coastal plain is characterized by a series of 21,
stair-stepped marine terraces (younger to the west) that have been dissected by west flowing rivers.
The coastal plain is a relatively stable block that is dissected by relatively few faults consisting of the
potentially active La Nacion Fault Zone and the active Rose Canyon Fault Zone. The Peninsular
Ranges Province is also dissected by the Elsinore Fault Zone that is associated with and sub-parallel to
the San Andreas Fault Zone, which is the plate boundary between the Pacific and North American
Plates.
Geocon Project No. G2883-52-01 - 4 - February 4, 2022
The site consists of Oligocene-age (Tertiary) Otay Formation that generally consists of sandstones
with interbeds of claystones and siltstones with a reported maximum thickness of roughly 400 feet.
The Otay Formation contains multiple layers of bentonitic claystone that is highly expansive and has
low shear strength. The Regional Geologic Map shows the geologic units around the site.
Regional Geologic Map
4. SOIL AND GEOLOGIC CONDITIONS
Based on our review of existing geologic information, the site is likely underlain by previously placed
fill and the Otay Formation. The geologic units are described herein in order of increasing age.
4.1 Previously Placed Fill
Previously placed fill is present across most of the site based on the referenced as-graded map. The
fill depths likely range up to about 25 feet on the site. We expect the fill soil consists of medium
dense, damp to moist, sandy silts and clays and possess a “very low” to “high” expansion potential
(expansion index of 130 or less) and a “S0” sulfate exposure. We expect the upper 2 to 3 feet of the
existing fill will require remedial grading. However, deeper removals may be required during
relocation of utilities or from demolishing foundations. The previously placed fill is suitable for the
support of the proposed fill and structural loads.
4.2 Otay Formation
Tertiary-age Otay Formation located below the previously placed fill at may be exposed at grade in
previous cut areas. This unit consists of interbeds of dense to very dense, slightly cemented, silty to
Geocon Project No. G2883-52-01 - 5 - February 4, 2022
clayey sandstone and hard, siltstone and claystone layers. Excavations will generally be possible with
heavy-duty grading equipment with heavy effort; however, moderately to highly cemented zones may
create very difficult ripping and generate oversize cemented cobbles and boulders. The soil from this
unit normally possesses a “very low” to “medium” expansion potential (expansion index of 90 or
less); however, the claystones may possess a “high” expansion potential (expansion index of 91 to
130). The Otay Formation is suitable for the support of proposed fill and structural loads.
5. GROUNDWATER
We expect groundwater exists deeper than 100 feet below existing grade at the property; therefore, we
do not expect groundwater to adversely impact future development. Seepage may be encountered at
the fill/formational contact and within the previous canyon drainages. Groundwater elevations and
seepage conditions are dependent on seasonal precipitation, irrigation, and land use, among other
factors, and vary as a result. Seepage conditions can develop due to over watering or poor drainage
practices. In addition, localized seepage conditions are occasionally encountered within deeper fills
when drilled caisson foundations are excavated.
6. GEOLOGIC HAZARDS
6.1 Faulting and Seismicity
A review of geologic literature and experience with the soil and geologic conditions in the general area
indicate that known active, potentially active, or inactive faults are not located at the site. 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 regional 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 fault with ages less than 150 years (red), 15,000 years (orange), 130,000 years (green),
750,000 years (blue, not shown) and 1.6 million years (black).
Geocon Project No. G2883-52-01 - 6 - February 4, 2022
Faults in Southern California
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
Geocon Project No. G2883-52-01 - 7 - February 4, 2022
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
Ground surface rupture occurs when movement along a fault is sufficient to cause a gap or rupture
where the upper edge of the fault zone intersects the earth surface. The potential for ground rupture is
considered to be negligible due to the absence of active faults at the subject site.
6.3 Tsunamis and Seiches
A tsunami is a series of long-period waves generated in the ocean by a sudden displacement of large
volumes of water. The site is located approximately ten miles from the Pacific Ocean at an elevation
greater than 610 feet MSL. Therefore, the risk of a tsunami affecting the site is considered negligible
due to the distance of the site from the ocean and elevation.
Seiches are standing wave oscillations of an enclosed water body after the original driving force has
dissipated. Driving forces are typically caused by seismic ground shaking. The site is not located near
a body of water; therefore, the risk of a seiche affecting the site is considered negligible.
6.4 Liquefaction
Liquefaction typically occurs when a site is located in a zone with seismic activity, on-site soils are
cohesionless or silt/clay with low plasticity, groundwater is encountered, and soil relative densities are
less than about 70 percent. If the four previous criteria are met, a seismic event could result in a rapid
pore-water pressure increase from the earthquake-generated ground accelerations. Seismically induced
settlement may occur whether the potential for liquefaction exists or not. Due to the lack of a near
surface groundwater table and the very dense nature of the fill and formational materials, the potential
for liquefaction and seismically induced settlement occurring at the site is considered negligible.
6.5 Landslides
We did not observe evidence of previous or incipient slope instability at the site during our study and
the property is relatively flat. Published geologic mapping indicates landslides are not present on or
adjacent to the site. Therefore, we opine the potential for a landslide is not a concern for this project.
6.6 Erosion
The site is relatively flat and is not located adjacent to the Pacific Ocean coast or a free-flowing
drainage where active erosion is occurring. Provided the engineering recommendations herein are
Geocon Project No. G2883-52-01 - 8 - February 4, 2022
followed and the project civil engineer prepares the grading plans in accordance with generally
accepted regional standards, we do not expect erosion to be a major impact to site development. In
addition, we expect the proposed development would not increase the potential for erosion if properly
designed.
6.7 Settlement
Fill is present across the majority of the site approaching maximum depths of about 25 feet. Fills are
subject to long term settlement under gravity loading and also subject to settlements due to building
loads. Based on previous experience for fill soils that are roughly 15 to 20 years old, long-term
settlements due to gravity loading of roughly 0.1 percent could occur resulting in settlements of about
0.3 inches for a 20- to 25-foot deep fill. We should provide estimated settlements in the locations of
the proposed buildings once a grading plan has been prepared with building locations.
Geocon Project No. G2883-52-01 - 9 - February 4, 2022
7. CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7.1.1 From a geotechnical engineering standpoint, we opine adverse soil or geologic conditions do
not exist at the property and that the proposed redevelopment project can be performed.
7.1.2 Based on a review of the referenced geologic information and our experience in the area, we
expect the site is generally underlain by previously placed fill with a maximum thickness of
about 25 feet overlying the Otay Formation. The Otay Formation may be present at or near
existing grade in the southwest and northeast portions of the site. The upper portion of the fill
soil will require remedial grading where present across the site. The fill soil can be reused as
new compacted fill. We should perform a geotechnical investigation to provide the design
and remedial grading recommendations for the project once architecture and grading plans
have been prepared.
7.1.3 We expect that formational materials will be exposed at or near proposed finish grades for
portions of the proposed buildings. Due to the dense nature of the formational material, we
expect the upper 5 feet of formational material to be removed and replaced with properly
compacted fill.
7.1.4 Groundwater extends deeper than 100 feet below the site and will not affect development. It
is not uncommon for near surface seepage conditions to develop from excessive irrigation
where none previously existed due to the permeability characteristics of the geologic units
on site.
7.1.5 We do not expect significant slopes or retaining walls will be constructed. Therefore, slope
instability for planned and existing permanent slopes will not be a consideration for
redevelopment.
7.1.6 We expect that most of the on-site soils will generally have a “low” to “medium” expansion
potential (expansion index between 21 and 90) and an “S0” corrosion potential for design.
Therefore, expansive soils will be a consideration for redevelopment.
7.1.7 Grading plans for future redevelopment and improvement for this property are not currently
available. We should be contacted to perform a geotechnical investigation if the property
will be redeveloped.
Geocon Project No. G2883-52-01 - 10 - February 4, 2022
7.2 Excavation and Soil Characteristics
7.2.1 Excavation of the in-situ soil should be possible with moderate to heavy effort using
conventional heavy-duty equipment. Some cemented zones exist in the formational
materials that may require localized very difficult excavation and generation of oversize
material, if encountered.
7.2.2 We expect the existing soil is considered to be “expansive” (expansion index [EI] of 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 soil onsite to
possess a “very low” to “high” expansion potential (expansion index of 130 or less) in
accordance with ASTM D 4829.
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
7.2.3 We expect the onsite fill soils and formational materials will possess an “S0” sulfate exposure
to concrete structures in contact with soil as defined by 2019 CBC Section 1904 and ACI 318-
14 Chapter 19. 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.
7.2.4 Geocon Incorporated does not practice in the field of corrosion engineering. Therefore, if
improvements that could be susceptible to corrosion are planned, further evaluation by a
corrosion engineer should be performed.
7.3 Seismic Design Criteria
7.3.1 Table 7.3.1 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
program U.S. Seismic Design Maps, provided by the Structural Engineers Association
Geocon Project No. G2883-52-01 - 11 - February 4, 2022
(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 buildings and improvements should be
designed using a Site Class C. The values presented herein are for the risk-targeted
maximum considered earthquake (MCER). Sites designated as Site Class D, E and F may
require additional analyses if requested by the project structural engineer and client.
TABLE 7.3.1
2019 CBC SEISMIC DESIGN PARAMETERS
Parameter Value 2019 CBC Reference
Site Class C Section 1613.2.2
Fill Thickness, T (feet) T<20 --
MCER Ground Motion Spectral Response
Acceleration – Class B (short), SS 0.748g Figure 1613.2.1(1)
MCER Ground Motion Spectral Response
Acceleration – Class B (1 sec), S1 0.273g Figure 1613.2.1(2)
Site Coefficient, FA 1.201 Table 1613.2.3(1)
Site Coefficient, FV 1.500* Table 1613.2.3(2)
Site Class Modified MCER Spectral Response
Acceleration (short), SMS 0.898g Section 1613.2.3 (Eqn
16-36)
Site Class Modified MCER Spectral Response
Acceleration – (1 sec), SM1 0.410g* Section 1613.2.3 (Eqn
16-37)
5% Damped Design
Spectral Response Acceleration (short), SDS 0.599g Section 1613.2.4 (Eqn
16-38)
5% Damped Design
Spectral Response Acceleration (1 sec), SD1 0.273g* Section 1613.2.4 (Eqn
16-39)
7.3.2 Table 7.3.2 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.
TABLE 7.3.2
2019 CBC SITE ACCELERATION DESIGN PARAMETERS
Parameter Value ASCE 7-16
Site Class C --
Fill Thickness, T (Feet) T<20 --
Mapped MCEG
Peak Ground Acceleration, PGA 0.324g Figure 22-9
Site Coefficient, FPGA 1.200 Table 11.8-1
Site Class Modified MCEG
Peak Ground Acceleration, PGAM 0.389g Section 11.8.3 (Eqn 11.8-1)
Geocon Project No. G2883-52-01 - 12 - February 4, 2022
7.3.3 Conformance to the criteria in Tables 7.3.1 and 7.3.2 for seismic design does not constitute
any kind of guarantee or assurance that significant structural damage or ground failure will
not occur in the event of a large earthquake. The primary goal of seismic design is to protect
life, not to avoid all damage, since such design may be economically prohibitive.
7.3.4 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 7.3.3
presents a summary of the risk categories in accordance with ASCE 7-16.
TABLE 7.3.3
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
7.4 General Grading Recommendations
7.4.1 Grading should be performed in accordance with the recommendations provided in this
report and the local grading ordinance. Geocon Incorporated should observe the grading
operations on a full-time basis and provide testing during the fill placement.
7.4.2 Prior to commencing grading, a preconstruction conference should be held at the site with
the agency 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.
7.4.3 Site preparation should begin with the removal of deleterious material, debris, and
vegetation. The depth of vegetation removal should be such that material exposed in cut
areas or soil to be used as fill is relatively free of organic matter. Material generated during
Geocon Project No. G2883-52-01 - 13 - February 4, 2022
stripping and/or site demolition should be exported from the site. Asphalt and concrete
should not be mixed with the fill soil unless approved by the Geotechnical Engineer.
7.4.4 Abandoned foundations and buried utilities (if encountered) should be removed and the
resultant depressions and/or trenches should be backfilled with properly compacted material
as part of the remedial grading.
7.4.5 We expect the proposed structures will be supported on a shallow foundation system
founded in compacted fill. Where formational material is exposed at grade or less than 5 feet
of fill is present, the upper 5 feet below finish grade or 2 feet below the proposed
foundations (whichever results in a deeper excavation) should be excavated and replaced
with properly compacted fill. Where previously placed fill greater than 5 feet is present
below the proposed structures, the upper 2 to 3 feet of material should be ripped, moisture
conditioned and recompacted prior to receiving improvements. The excavations should
extend at least 10 feet laterally outside of the proposed foundation system, where possible.
7.4.6 In areas of proposed improvements outside of the building areas, the upper 1 to 2 feet of
existing soil should be processed, moisture conditioned as necessary and recompacted.
Deeper excavations may be required in areas where loose or saturated materials are
encountered. The excavations should extend at least 2 feet laterally outside of the
improvement area, where possible. Table 7.4.1 provides a summary of the remedial grading
recommendations.
TABLE 7.4.1
SUMMARY OF REMEDIAL GRADING RECOMMENDATIONS
Area Remedial Grading Excavation Requirements
Proposed Buildings (Formational Material or Less
Than 5 Feet of Fill)
Excavate 5 Feet Below Pad Grade
and 2 Feet Below Footings
Proposed Buildings (Previously Placed Fill) Remedial Grading of Upper 2 to 3 Feet of
Existing Fill
Site Development (Outside Building Areas) Process Upper 1 to 2 Feet of Existing Materials
Lateral Grading Limits 10 Feet Outside of Buildings
2 Feet Outside of Improvement Areas
Exposed Bottoms of Excavations Scarify Upper 12 Inches
7.4.7 The bottom of the excavations should be sloped 1 percent to the adjacent street or deepest
fill. 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
Geocon Project No. G2883-52-01 - 14 - February 4, 2022
excavations may be required if saturated or loose fill soil is encountered. A representative of
Geocon should be on-site during excavations to evaluate the limits of the remedial grading.
7.4.8 The site should then be brought to final subgrade elevations with fill compacted in layers. In
general, the existing soil is suitable for use from a geotechnical engineering standpoint as
fill if relatively free from vegetation, debris, and other deleterious material. Layers of fill
should be about 6 to 8 inches in loose thickness and 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. The upper 12 inches of subgrade soil
underlying pavement should be compacted to a dry density of at least 95 percent of the
laboratory maximum dry density near to slightly above optimum moisture content shortly
before paving operations.
7.4.9 The City of Chula Vista requires additional removals and grading requirements within the
street and right-of-way areas. Based on the City of Chula Vista, the upper 5 feet of fill and
upper 3 feet of formational materials within the public right of way areas should possess an
expansion index of 90 or less. Additional removals of formational materials may be required
if the expansion index is greater than 90.
7.4.10 Import fill (if necessary) should consist of the characteristics presented in Table 7.3.2.
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 7.3.2
SUMMARY OF IMPORT FILL RECOMMENDATIONS
Soil Characteristic Values
Expansion Potential “Very Low” to “Medium” (Expansion Index of 90 or less)
Particle Size Maximum Dimension Less Than 3 Inches
Generally Free of Debris
7.5 Geotechnical Design
7.5.1 The following geotechnical design items should be considered during due diligence.
Geocon Project No. G2883-52-01 - 15 - February 4, 2022
We expect that shallow conventional foundations that provide moderate bearing
values can be used to support the proposed residential and mixed-use buildings
founded in compacted fill.
Typical subgrade preparation time of exterior concrete flatwork and sidewalk is
expected. Expansive soils should be considered.
We expect that relatively low R-Value laboratory test results for subgrade soils will
be encountered that will require thicker pavement sections for the parking lots and
driveways. Typical subgrade preparation time of pavement areas are expected.
Typical design and use of landscape area drains and building roof drains is expected.
Control of surface drainage and its discharge and containment to storm water
management devices will be an important design consideration to reduce the potential
for erosion and maintaining the geotechnical design parameters of the project.
Potential elevated long-term maintenance costs for surface improvements that
includes sidewalks and flatwork due to the anticipated “low” to “high” expansive
soils at finish grade.
7.6 Site Drainage and Moisture Protection
7.6.1 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 and improvements. The site should be graded and maintained such that
surface drainage is directed away from structures in accordance with 2019 CBC 1804.4 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.
7.6.2 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.
7.6.3 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. Area drains
to collect excess irrigation water and transmit it to drainage structures or impervious above-
grade planter boxes can be used. In addition, where landscaping is planned adjacent to the
pavement, construction of a cutoff wall along the edge of the pavement that extends at least
6 inches below the bottom of the base material should be considered.
B-8
B-7
B-6
B-11
B-10
B-12
B-13
B-2
B-3
B-1
B-5
B-4
B-9
(3')
(3')
(5'+)
(9.5')
(4')
(6')
(5'+)
(5'+)
(15.5')
(6')
(5'+)
(18.5')
(5'+)
To
Qpf/
Qpf/
Qpf/
Qpf/
Qpf/
605
604
602
602
609
606
600
594
606611
613
606
613
601
608
611
616
612
616
617
615
621
614
610
613
604
602
613
604
602
603
608
To
To
To
620
614
606
?
?
?
?
?
?
To
APPROX.
SITE LIMITS
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159 SHEET OF
PROJECT NO.
SCALE DATE
FIGURE
Plotted:02/04/2022 8:53AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\G2883-52-01 (OR Town Center)\SHEETS\G2883-52-01 Geo Map.dwg
GEOTECHNICAL ENVIRONMENTAL MATERIALS
1" =
GEOLOGIC 1AP
OTAY RANCH TOWN CENTER
CHULA VISTA, CALIFORNIA
60'02 - 04 - 2022
G2883 - 52 - 01
1 1 1
........PREVIOUSLY PLACED FILL (Geotechnics, Inc. 2005)
........OTAY FORMATION (Dotted Where Buried)
........APPROX. LOCATION OF GEOLOGIC CONTACT
........APPROX. LOCATION OF BORING (Geocon, Inc. 2014)
........APPROX. DEPTH OF FILL (In Feet)
........APPROX. ELEVATION AT BASE OF FILL (In Feet, MSL)
GEOCON LEGEND
613
Qpf
B-13
To
(5'+)
APPENDIX A
APPENDIX A
PREVIOUS BORING LOGS
FROM
PRELIMINARY GEOTECHNICAL INVESTIGATION
OTAY RANCH TOWN CENTER ADDITION
OTAY RANCH VILLAGE 12
CHULA VISTA, CALIFORNIA
PROJECT NO. G1731-11-01
FOR
OTAY RANCH TOWN CENTER
CHULA VISTA, CALIFORNIA
PROJECT NO. G2883-52-01
PREVIOUSLY PLACED FILL (Qpf)
Stiff, moist, olive brown, Sandy SILT; trace gravel
Very stiff, moist, light brown, Sandy SILT to Silty, fine SAND
-Becomes damp to moist, light olive brown
-Trace bentonite
OTAY FORMATION (To)
Very dense, damp, grayish to yellowish brown, Sandy SILTSTONE; slightly
cemented; micaceous
BORING TERMINATED AT 19 FEET
No groundwater encountered
ML
ML/SM
ML
B1-1
B1-2
B1-3
B1-4
B1-5
21.8
21.1
28.6
45
60
45
73/11.5"
97.1
102.7
95.1
... DRIVE SAMPLE (UNDISTURBED)
CME 55 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING B 1
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
EQUIPMENT
ELEV. (MSL.)619'
G1731-11-01.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
L. RODRIGUEZ
SAMPLE
NO.
CO
N
T
E
N
T
(
%
)
06-05-2014
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
14
16
18
Figure A-1,
Log of Boring B 1, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
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.
G1731-11-01
PREVIOUSLY PLACED FILL (Qpf)
Stiff, moist, olive brown, Sandy CLAY
Very stiff, moist, light olive brown, Sandy CLAY to Clayey fine SAND
Dense, damp, light brown to grayish brown, Silty, very fine SAND
-Becomes moist
-Trace clay
OTAY FORMATION (To)
Very stiff to hard, moist, gray, Sandy SILTSTONE; micaceous
BORING TERMINATED AT 18 FEET
No groundwater encountered
CL
CL/SC
SM
ML
B2-1
B2-2
B2-3
B2-4
B2-5
19.6
26.0
22.7
47
52
53
42
52
105.9
96.6
99.8
... DRIVE SAMPLE (UNDISTURBED)
CME 55 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING B 2
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
EQUIPMENT
ELEV. (MSL.)621'
G1731-11-01.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
L. RODRIGUEZ
SAMPLE
NO.
CO
N
T
E
N
T
(
%
)
06-05-2014
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
14
16
18
Figure A-2,
Log of Boring B 2, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
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.
G1731-11-01
PREVIOUSLY PLACED FILL (Qpf)
Stiff, moist, olive brown, Sandy CLAY
-Becomes very stiff, olive brown to brown
OTAY FORMATION (To)
Very dense, dry to damp, grayish brown, Silty, fine SANDSTONE;
moderately to strongly cemented
-Becomes damp, light grayish brown
BORING TERMINATED AT 10 FEET
No groundwater encountered
CL
SM
B3-1
B3-2
B3-3
B3-4
22.957
50/5"
80
101.5
... DRIVE SAMPLE (UNDISTURBED)
CME 55 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING B 3
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
EQUIPMENT
ELEV. (MSL.)620'
G1731-11-01.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
L. RODRIGUEZ
SAMPLE
NO.
CO
N
T
E
N
T
(
%
)
06-05-2014
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
Figure A-3,
Log of Boring B 3, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
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.
G1731-11-01
PREVIOUSLY PLACED FILL (Qpf)
Stiff, moist, olive brown, Sandy CLAY; trace gravel
Dense, moist, light gray, Clayey, fine SAND
BORING TERMINATED AT 5 FEET
No groundwater encountered
CL
SC
B4-1
B4-2 19.952106.0
... DRIVE SAMPLE (UNDISTURBED)
CME 55 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING B 4
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
EQUIPMENT
ELEV. (MSL.)617'
G1731-11-01.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
L. RODRIGUEZ
SAMPLE
NO.
CO
N
T
E
N
T
(
%
)
06-05-2014
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
Figure A-4,
Log of Boring B 4, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
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.
G1731-11-01
PREVIOUSLY PLACED FILL (Qpf)
Stiff, moist, olive brown, Sandy CLAY
-Becomes very stiff, light brown
BORING TERMINATED AT 15 FEET
No groundwater encountered
CLB5-1
B5-2 26.05996.9
... DRIVE SAMPLE (UNDISTURBED)
CME 55 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING B 5
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
EQUIPMENT
ELEV. (MSL.)618'
G1731-11-01.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
L. RODRIGUEZ
SAMPLE
NO.
CO
N
T
E
N
T
(
%
)
06-05-2014
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
Figure A-5,
Log of Boring B 5, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
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.
G1731-11-01
PREVIOUSLY PLACED FILL (Qpf)
Stiff, damp, olive brown, Sandy CLAY
-Becomes moist, micaceous
OTAY FORMATION (To)
Very dense, moist, brown to olive brown, Silty, very fine SANDSTONE;
micaceous
Hard, moist, grayish brown, Sandy SILTSTONE; micaceous
BORING TERMINATED AT 9.75 FEET
No groundwater encountered
CL
SM
ML
B6-1
B6-2
B6-3
B6-4
26.163
72/11.5"
86/9.5"
99.0
... DRIVE SAMPLE (UNDISTURBED)
CME 55 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING B 6
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
EQUIPMENT
ELEV. (MSL.)618'
G1731-11-01.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
L. RODRIGUEZ
SAMPLE
NO.
CO
N
T
E
N
T
(
%
)
06-05-2014
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
Figure A-6,
Log of Boring B 6, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
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.
G1731-11-01
PREVIOUSLY PLACED FILL (Qpf)
Stiff, damp to moist, light olive brown, Sandy SILT; trace organics; trace
gravel
-Micaceous
OTAY FORMATION (To)
Hard, damp to moist, light grayish brown, Sandy SILTSTONE; micaceous
Very dense, damp, light brown, Silty SANDSTONE; micaceous
BORING TERMINATED AT 10 FEET
No groundwater encountered
ML
ML
SM
B7-1
B7-2
B7-3
B7-4
26.451
80/10"
79/11.5"
93.5
... DRIVE SAMPLE (UNDISTURBED)
CME 55 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING B 7
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
EQUIPMENT
ELEV. (MSL.)618'
G1731-11-01.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
L. RODRIGUEZ
SAMPLE
NO.
CO
N
T
E
N
T
(
%
)
06-05-2014
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
Figure A-7,
Log of Boring B 7, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
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.
G1731-11-01
5" ASPHALT CONCRETE over 5" BASE MATERIAL
PREVIOUSLY PLACED FILL (Qpf)
Stiff, damp to moist, light olive brown, Sandy CLAY
Very stiff, damp, Sandy CLAY to Clayey, fine SAND
Very stiff, damp, olive brown, Sandy SILT to Silty, fine SAND
OTAY FORMATION (To)
Very dense, damp, light grayish brown, Silty, fine SANDSTONE; micaceous
Hard, damp, gray, Sandy SILTSTONE; micaceous
BORING TERMINATED AT 13 FEET
No groundwater encountered
CL
CL/SC
ML/SM
SM
ML
B8-1
B8-2
B8-3
B8-4
B8-5
22.2
23.8
43
44
85/11.5
86/10"
102.8
103.7
... DRIVE SAMPLE (UNDISTURBED)
CME 55 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING B 8
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
EQUIPMENT
ELEV. (MSL.)616'
G1731-11-01.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
L. RODRIGUEZ
SAMPLE
NO.
CO
N
T
E
N
T
(
%
)
06-05-2014
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
Figure A-8,
Log of Boring B 8, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
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.
G1731-11-01
PREVIOUSLY PLACED FILL (Qpf)
Medium dense, dry to damp, olive brown, Clayey, fine to coarse SAND; trace
gravel
Very stiff, moist, light olive brown, Sandy CLAY to Clayey, fine SAND
BORING TERMINATED AT 5 FEET
No groundwater encountered
SC
CL/SC
B9-1
B9-2 17.241101.0
... DRIVE SAMPLE (UNDISTURBED)
CME 55 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING B 9
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
EQUIPMENT
ELEV. (MSL.)621'
G1731-11-01.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
L. RODRIGUEZ
SAMPLE
NO.
CO
N
T
E
N
T
(
%
)
06-05-2014
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
Figure A-9,
Log of Boring B 9, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
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.
G1731-11-01
PREVIOUSLY PLACED FILL (Qpf)
Dense, damp, light brown, Silty, fine to medium SAND
OTAY FORMATION (To)
Very dense, damp, brown, Silty, fine SANDSTONE; micaceous
Hard, damp, light brown, Sandy SILTSTONE; micaceous
BORING TERMINATED AT 10.75 FEET
No groundwater encountered
SM
SM
ML
B10-1
B10-2
11.7
18.5
50/5.5"
86/9.5"112.9
... DRIVE SAMPLE (UNDISTURBED)
CME 55 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING B 10
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
EQUIPMENT
ELEV. (MSL.)622'
G1731-11-01.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
L. RODRIGUEZ
SAMPLE
NO.
CO
N
T
E
N
T
(
%
)
06-05-2014
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
Figure A-10,
Log of Boring B 10, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
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.
G1731-11-01
PREVIOUSLY PLACED FILL (Qpf)
Loose, moist, light brown, Silty, fine SAND to Sandy SILT
OTAY FORMATION (To)
Very dense, moist, light brown, Silty, fine SANDSTONE
BORING TERMINATED AT 15.5 FEET
No groundwater encountered
SM/ML
SM
B11-1
B11-2
B11-3
B11-4
12.7
16.6
50/4"
50/5.5"
50/5.5"
105.5
112.1
... DRIVE SAMPLE (UNDISTURBED)
CME 55 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING B 11
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
EQUIPMENT
ELEV. (MSL.)624'
G1731-11-01.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
L. RODRIGUEZ
SAMPLE
NO.
CO
N
T
E
N
T
(
%
)
06-05-2014
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
14
Figure A-11,
Log of Boring B 11, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
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.
G1731-11-01
PREVIOUSLY PLACED FILL (Qpf)
Loose to medium dense, damp, grayish brown, Clayey GRAVEL; up to 2"
diameter gravel
Very stiff, moist, olive brown, Sandy CLAY; trace gravel; micaceous
Dense, moist, light brown, Clayey, fine SAND, to Sandy CLAY; micaceous
BORING TERMINATED AT 5 FEET
No groundwater encountered
GC
CL
SC/CL
B12-1
B12-2 27.04595.2
... DRIVE SAMPLE (UNDISTURBED)
CME 55 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING B 12
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
EQUIPMENT
ELEV. (MSL.)622'
G1731-11-01.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
L. RODRIGUEZ
SAMPLE
NO.
CO
N
T
E
N
T
(
%
)
06-05-2014
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
Figure A-12,
Log of Boring B 12, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
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.
G1731-11-01
PREVIOUSLY PLACED FILL (Qpf)
Stiff, moist, olive brown, Sandy CLAY; trace gravel; micaceous
Dense, moist, light brown, Clayey fine SAND to Sandy CLAY; micaceous
BORING TERMINATED AT 5 FEET
No groundwater encountered
CL
SC/CL
B13-1
B13-2 18.458104.6
... DRIVE SAMPLE (UNDISTURBED)
CME 55 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING B 13
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
EQUIPMENT
ELEV. (MSL.)620'
G1731-11-01.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
L. RODRIGUEZ
SAMPLE
NO.
CO
N
T
E
N
T
(
%
)
06-05-2014
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
Figure A-13,
Log of Boring B 13, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
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.
G1731-11-01
APPENDIX B
APPENDIX B
PREVIOUS LABORATORY TESTING
FROM
PRELIMINARY GEOTECHNICAL INVESTIGATION
OTAY RANCH TOWN CENTER ADDITION
OTAY RANCH VILLAGE 12
CHULA VISTA, CALIFORNIA
PROJECT NO. G1731-11-01
FOR
OTAY RANCH TOWN CENTER
CHULA VISTA, CALIFORNIA
PROJECT NO. G2883-52-01
Geocon Project No. G2883-52-01 B- 1 - February 4, 2022
APPENDIX B
LABORATORY TESTING
We performed laboratory tests in accordance with generally accepted test methods of the American
Society for Testing and Materials (ASTM) or other suggested procedures during a previous investigation
in 2014. We tested selected soil samples for in-place dry density/moisture content, maximum
density/optimum moisture content, expansion index, water-soluble sulfate, R-Value, unconfined
compressive strength, consolidation, gradation, and direct shear strength. The results of our current
laboratory tests are presented herein. The in-place dry density and moisture content of the samples tested
are presented on the boring logs in Appendix A.
SUMMARY OF LABORATORY MAXIMUM DRY DENSITY
AND OPTIMUM MOISTURE CONTENT TEST RESULTS
ASTM D 1557
Sample No. Description
Maximum
Dry Density
(pcf)
Optimum
Moisture Content
(% dry wt.)
B1-1 Olive brown, Sandy SILT (Qpf) 115.7 15.3
B7-1 Light olive brown, Sandy SILT (Qpf) 116.6 14.5
SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS
ASTM D 4829
Sample
No.
Moisture Content (%) Dry
Density
(pcf)
Expansion
Index
2019 CBC
Expansion
Classification
ASTM Soil
Expansion
Classification Before
Test After Test
B3-1 12.7 28.1 100.6 82 Expansive Medium
B6-1 13.3 31.0 98.9 97 Expansive High
B11-1 12.0 27.1 102.7 67 Expansive Medium
SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS
CALIFORNIA TEST NO. 417
Sample No. Depth (feet) Geologic Unit Water-Soluble
Sulfate (%)
ACI 318 Sulfate
Exposure
B3-1 0-3 Qpf 0.034 S0
B6-1 0-5 Qpf 0.069 S0
B11-1 0-5 Qpf/To 0.035 S0
Geocon Project No. G2883-52-01 B- 2 - February 4, 2022
SUMMARY OF LABORATORY RESISTANCE VALUE (R-VALUE) TEST RESULTS
ASTM D 2844
Sample No. Depth (Feet) Description (Geologic Unit) R-Value
B4-1 0-5 Olive brown, Sandy CLAY (Qpf) 10
B9-1 0-5 Olive brown, Clayey SAND (Qpf) 21
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.1110
3/8"4
PROJECT NO. G1731-11-01
U. S. STANDARD SIEVE SIZE
COARSE
3"3/4"1-1/2"8 16 20 30 40
PL
FINE
NAT WC
PE
R
C
E
N
T
F
I
N
E
R
B
Y
W
E
I
G
H
T
(CL) Sandy CLAY0.0
PI
COARSE
GRAVEL
G1731-11-01.GPJ
B3-1
2015 BIRCH ROAD
CHULA VISTA, CALIFORNIA
SAND
MEDIUM
5060 100 200
SAMPLE
GEOCON
SILT OR CLAYFINE
GRAIN SIZE IN MILLIMETERS
CLASSIFICATION LL
10
DEPTH (ft)
OTAY RANCH TOWN CENTER ADDITION, OTAY RANCH VILLAGE 12
GRADATION CURVE
Figure B-1
-2
0
2
4
6
8
10
12
14
16
180.1 1 10 100
Sample Saturated at (ksf)
GEOCON
G1731-11-01.GPJ
Initial Dry Density (pcf)
PROJECT NO. G1731-11-01
Initial Water Content (%)
Initial Saturation (%)96.5
2.0
PE
R
C
E
N
T
C
O
N
S
O
L
I
D
A
T
I
O
N
26.0
SAMPLE NO. B2-2
CHULA VISTA, CALIFORNIA
CONSOLIDATION CURVE
96.6
APPLIED PRESSURE (ksf)
Figure B-2
OTAY RANCH TOWN CENTER ADDITION, OTAY RANCH VILLAGE 12
2015 BIRCH ROAD
-2
0
2
4
6
8
10
12
14
16
180.1 1 10 100
Sample Saturated at (ksf)
GEOCON
G1731-11-01.GPJ
Initial Dry Density (pcf)
PROJECT NO. G1731-11-01
Initial Water Content (%)
Initial Saturation (%)100+
2.0
PE
R
C
E
N
T
C
O
N
S
O
L
I
D
A
T
I
O
N
23.8
SAMPLE NO. B8-3
CHULA VISTA, CALIFORNIA
CONSOLIDATION CURVE
103.7
APPLIED PRESSURE (ksf)
Figure B-3
OTAY RANCH TOWN CENTER ADDITION, OTAY RANCH VILLAGE 12
2015 BIRCH ROAD
SAMPLE NO.:
DEPTH OF SAMPLE:
Load 1 K 3 K 5 K ɸ (Ultimate)21 degrees
INITIAL ɸ (Peak)34 degrees
Water Content 23.8%17.5%24.2%c (Ultimate)1100 psf
Dry Density (pcf)96.3 95.8 99.1 c (Peak)820 psf
Saturation*87.7%63.8%95.8%
Height (inches)1 1 1
AFTER TEST DATE:
Water Content 27.3%26.4%26.3%DESCRIPTION:
Dry Density (pcf)92.4 95.6 100.3
FAILURE
Normal Stress (psf)952 2080 4350
Ultimate Stress (psf)1416 1904 2702
Peak Stress (psf)1625 1964 3809
Rate (in/min)0.005 0.005 0.005
*Degree of saturation calculated with a specific gravity of 2.65
B1-2
Test Data Results
6/17/2014
Qpf
3'
SW/LR
DIRECT SHEAR TEST DATA
OTAY RANCH TOWN CENTER ADDITION
OTAY RANCH VILLAGE 12
2015 BIRCH ROAD
CHULA VISTA, CALIFORNIA
PROJECT NO. G1731-11-01 FIG. B-4
GEOCONI N C O R P O R A T E DGEOCONI N C O R P O R A T E D
GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121-2974
PHONE 858 558-6900 -FAX 858 558-6159
GEOCONI N C O R P O R A T E DGEOCONI N C O R P O R A T E D
GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121-2974
PHONE 858 558-6900 -FAX 858 558-6159
Natural
Remold
0
1000
2000
3000
4000
5000
6000
0 1000 2000 3000 4000 5000 6000
Sh
e
a
r
S
t
r
e
s
s
(
p
s
f
)
Normal Stress (psf)
Ultimate
Peak
SAMPLE NO.:
DEPTH OF SAMPLE:
Load 1 K 3 K 5 K ɸ (Ultimate)28 degrees
INITIAL ɸ (Peak)28 degrees
Water Content 13.7%14.6%14.2%c (Ultimate)230 psf
Dry Density (pcf)105.3 104.6 104.7 c (Peak)350 psf
Saturation*63.7%66.3%65.0%
Height (inches)1 1 1
AFTER TEST DATE:
Water Content 26.9%26.2%23.6%DESCRIPTION:
Dry Density (pcf)104.9 105.2 107.1
FAILURE
Normal Stress (psf)952 2080 4346
Ultimate Stress (psf)728 1426 2622
Peak Stress (psf)828 1526 2672
Rate (in/min)0.005 0.005 0.005
*Degree of saturation calculated with a specific gravity of 2.65
B7-1
0'
Test Data Results
6/23/2014
Qpf
SW/LR
DIRECT SHEAR TEST DATA
OTAY RANCH TOWN CENTER ADDITION
OTAY RANCH VILLAGE 12
2015 BIRCH ROAD
CHULA VISTA, CALIFORNIA
PROJECT NO. G1731-11-01 FIG. B-5
GEOCONI N C O R P O R A T E DGEOCONI N C O R P O R A T E D
GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121-2974
PHONE 858 558-6900 -FAX 858 558-6159
GEOCONI N C O R P O R A T E DGEOCONI N C O R P O R A T E D
GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121-2974
PHONE 858 558-6900 -FAX 858 558-6159
Natural
Remold
0
1000
2000
3000
4000
5000
6000
0 1000 2000 3000 4000 5000 6000
Sh
e
a
r
S
t
r
e
s
s
(
p
s
f
)
Normal Stress (psf)
Ultimate
Peak
Geocon Project No. G2883-52-01 February 4, 2022
LIST OF REFERENCES
1. 2019 California Building Code, California Code of Regulations, Title 24, Part 2, based on the
2018 International Building Code, prepared by California Building Standards Commission,
dated July 2019.
2. ACI 318-19, Commentary on Building Code Requirements for Structural Concrete, prepared
by the American Concrete Institute, dated May 2019.
3. American Society of Civil Engineers (ASCE), ASCE 7-16, Minimum Design Loads and
Associated Criteria for Buildings and Other Structures, 2017.
4. California Department of Conservation, Division of Mines and Geology, Probabilistic Seismic
Hazard Assessment for the State of California, Open File Report 96-08, 1996.
5. County of San Diego, San Diego County Multi Jurisdiction Hazard Mitigation Plan, San
Diego, California – Final Draft, dated 2017.
6. Geocon, Incorporated, Preliminary Geotechnical Investigation, Otay Ranch Town Center
Addition, Otay Ranch Village 12, 2015 Birch Road, Chula Vista, California, dated June 26,
2014 (Project No. G1731-11-01).
7. Geotechnics Incorporated, As-Graded Geotechnical Report, McMillin Otay Ranch, Village 12
and Borrow and Fill Sites Within the Eastern Urban Center, Chula Vista, California, dated
February 16, 2006 (Project No. 0367-012-01, Document No. 05-1029).
8. Todd, V. R., 2004, Preliminary Geologic Map of the El Cajon 30’x60’ Quadrangle, Southern
California, Version 1.0, Open-File Report 2004-1361 Scale 1:100,000
9. United States Geological Survey computer program, U.S. Design Maps. USGS Design Maps.
10. United States Geological Survey (USGS) Interactive Quaternary Faults Database computer
program, USGS Interactive Quaternary Faults Database.
11. Unpublished Geotechnical Reports and Information, Geocon Incorporated.