HomeMy WebLinkAboutPD 2021-0002; 3304 JAMES DRIVE; GEOTECHNICAL INVESTIGATION 3304 JAMES DRIVE; 2021-01-08GEOTECHNICAL INVESTIGATION
3304 JAMES DRIVE
CARLSBAD, CALIFORNIA
PREPARED FOR
JANUARY 8, 2021
PROJECT NO. G2633-11-02
Ca I iforn ia West
Project No. G2633-11-02
January 8, 2021
California West Communities
5927 Priestly Drive, Suite 110
Carlsbad, California 92008
Attention: Mr. Rick Schroeder
Subject: GEOTECHNICAL INVESTIGATION
3304 JAMES DRIVE
CARLSBAD, CALIFORNIA
Dear Mr. Schroeder:
In accordance with your request and authorization of our Proposal No. LG-20495 dated November 16,
2020, we herein submit the results of our geotechnical investigation for the subject project. We
performed our investigation to evaluate the underlying soil and geologic conditions and potential
geologic hazards, and to assist in the design of the proposed single-family residential building and
associated improvements.
The accompanying report presents the results of our study and conclusions and recommendations
pertaining to geotechnical aspects of the proposed project. The site is suitable for the proposed
buildings and improvements provided the recommendations of this report are incorporated into the
design and construction of the planned project.
Should you have questions regarding this report, or if we may be of further service, please contact the
undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
Shawn Foy Weedon
GE 2714
John Hoobs
CEG 1524
SFW:JH:arm
(e-mail) Addressee
GEOCON
INCORPORATED
GEOTECHNICAL ■ ENVIRONMENTAL ■ MATE RI ALS O
6960 Flanders Drive ■ San Diego, California 92121-297 4 ■ Telephone 858.558.6900 ■ Fax 858.558.6159
TABLE OF CONTENTS
1.PURPOSE AND SCOPE ................................................................................................................. 1
2.SITE AND PROJECT DESCRIPTION ........................................................................................... 2
3.GEOLOGIC SETTING .................................................................................................................... 3
4.SOIL AND GEOLOGIC CONDITIONS ........................................................................................ 4
4.1 Topsoil (Qtop) ....................................................................................................................... 6
4.2 Old Paralic Deposits (Qop) .................................................................................................... 6
4.3 Santiago Formation (Tsa) ...................................................................................................... 6
5.GROUNDWATER .......................................................................................................................... 6
6.GEOLOGIC HAZARDS ................................................................................................................. 6
6.1 Faulting and Seismicity ......................................................................................................... 6
6.2 Ground Rupture ..................................................................................................................... 8
6.3 Tsunamis and Seiches ............................................................................................................ 8
6.4 Liquefaction ........................................................................................................................... 9
6.5 Landslides .............................................................................................................................. 9
7.CONCLUSIONS AND RECOMMENDATIONS ......................................................................... 10
7.1 General ................................................................................................................................. 10
7.2 Excavation and Soil Characteristics .................................................................................... 11
7.3 Grading ................................................................................................................................ 11
7.4 Temporary Excavations ....................................................................................................... 13
7.5 Seismic Design Criteria – 2019 California Building Code .................................................. 14
7.6 Post-Tensioned Foundations ................................................................................................ 15
7.7 Driveway and Exterior Concrete Flatwork .......................................................................... 19
7.8 Retaining Walls ................................................................................................................... 20
7.9 Lateral Loading .................................................................................................................... 24
7.10 Site Drainage and Moisture Protection ................................................................................ 24
7.11 Foundation Plan Review ...................................................................................................... 25
7.12 Testing and Observation Services During Construction ...................................................... 25
LIMITATIONS AND UNIFORMITY OF CONDITIONS
APPENDIX A FIELD INVESTIGATION
APPENDIX B
LABORATORY TESTING
APPENDIX C RECOMMENDED GRADING SPECIFICATIONS
LIST OF REFERENCES
Geocon Project No. G2633-11-02 - 1 - January 8, 2021
GEOTECHNICAL INVESTIGATION
1. PURPOSE AND SCOPE
This report presents the results of our geotechnical investigation of the 3304 James Drive property in
the City of Carlsbad, California. The site is located on the east side of James Drive roughly 350 feet
north of Basswood Avenue and is bordered by existing single-family residences.
Vicinity Map
The purpose of the geotechnical investigation is to evaluate the surface and subsurface soil conditions
and general site geology, and to identify geotechnical constraints that may affect development of the
property including faulting, liquefaction and seismic shaking based on the 2019 CBC seismic design
criteria. In addition, we provided recommendations for remedial grading, shallow foundations,
concrete slab-on-grade, concrete flatwork, pavement and retaining walls.
We reviewed the following plans and report in preparation of this report:
1.Geologic Reconnaissance, 3304 James Drive, Carlsbad, California, prepared by Geocon
Incorporated, dated November 19, 2020 (Project No. G2633-11-01).
2.Grading Plans for 3304 James Drive, prepared by Pasco Laret Suiter & Associates, received
on December 30, 2020.
The scope of this investigation included reviewing readily available published and unpublished
geologic literature (see List of References), performing engineering analyses, and preparing this
Geocon Project No. G2633-11-02 - 2 - January 8, 2021
report. We also advanced four exploratory trenches to a maximum depth of about 5½ feet, sampled
soil and performed laboratory testing. Appendix A presents the exploratory trench logs and details of
the field investigation. The details of the laboratory tests and a summary of the test results are shown
in Appendix B.
2. SITE AND PROJECT DESCRIPTION
The existing property is composed of an empty flag lot located adjacent to existing single-family
residential homes. The site is located behind an existing residence fronting James Drive. Based on
historical aerials, the site does not appear to have been previously developed. The site is relatively flat
with elevations of about 156 to 158 feet above mean sea level (MSL) on the west and east edges,
respectively. The property was recently brushed of vegetation with the exception of a few perimeter
trees and shrubs along the driveway. The Existing Site Map shows the existing conditions of the
property.
Existing Site Map
We understand that proposed development will consist of a single-family, one- to two-story residential
structure with a finish floor elevation of 159 feet MSL with associated improvements as shown on the
Proposed Site Plan. Future access will be from an existing driveway that will extend behind the
Geocon Project No. G2633-11-02 - 3 - January 8, 2021
existing residence. Rear yard drainage will flow to area drains that enter into a detention system
located along the south side of the concrete access driveway.
Proposed Site Plan
The locations, site descriptions and proposed development are based on our site reconnaissance,
review of published geologic literature, field investigations, and discussions with project personnel. If
development plans differ from those described herein, Geocon Incorporated should be contacted for
review of the plans and possible revisions to this report.
3. GEOLOGIC SETTING
Regionally, the site is located in the Peninsular Ranges geomorphic province. The province is bounded
by the Transverse Ranges to the north, the San Jacinto Fault Zone on the east, the Pacific Ocean
coastline on the west, and the Baja California on the south. The province is characterized by elongated
northwest-trending mountain ridges separated by straight-sided sediment-filled valleys. The northwest
trend is further reflected in the direction of the dominant geologic structural features of the province
that are northwest to west-northwest trending folds and faults, such as the nearby Newport
Inglewood/Rose Canyon fault zone.
Locally, the site is within the northwestern portion of the coastal plain of San Diego County. The
coastal plain is underlain by a thick sequence of relatively undisturbed and non-conformable
sedimentary bedrock units that thicken to the west and range in age from Upper Cretaceous-age
through Quaternary-age that have been deposited on Cretaceous to Jurassic age igneous and
metavolcanic bedrock. Geomorphically, the coastal plain is characterized by a series of 21, stair-
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Geocon Project No. G2633-11-02 - 4 - January 8, 2021
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 Newport Inglewood/Rose Canyon Fault Zone.
Marine sedimentary units make up the geologic sequence on the site that consists of Quaternary-age
Old Paralic Deposits at the surface. The Old Paralic Deposits generally consists of silty, fine to
medium-grained sandstone. The Santiago Formation exists below the Old Paralic Deposits at an
estimated depth of approximately 30 to 40 feet below grade. The regional geology at the location of
the site is shown on the Regional Geologic Map.
Regional Geologic Map
4. SOIL AND GEOLOGIC CONDITIONS
We encountered surficial soil (consisting of topsoil) and formational Old Paralic Deposits in our
exploratory trenches. The occurrence, distribution, and description of each unit encountered is shown
on the Geologic Map and on the trench logs in Appendix A.
Geocon Project No. G2633-11-02 - 5 - January 8, 2021
Geologic Map
The Geologic Cross-Section shows the approximate subsurface relationship between the geologic
units. We prepared the geologic cross-section using interpolation between exploratory excavations and
observations; therefore, actual geotechnical conditions may vary from those illustrated and should be
considered approximate.
The surficial soil and geologic units are described herein in order of increasing age.
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Geocon Project No. G2633-11-02 - 6 - January 8, 2021
4.1 Topsoil (Qtop)
We encountered topsoil within, approximately, the upper 1½ to 2 feet across the site. The topsoil
consists of loose to medium dense, dry to damp, light to dark brown, silty, fine to medium sand. The
topsoil is considered unsuitable to support the planned development and will require removal and
recompaction. The existing topsoil will be suitable for reuse as new compacted fill.
4.2 Old Paralic Deposits (Qop)
The Quaternary-age Old Paralic Deposits exist below the topsoil across the site. These deposits
generally consist of dense, light reddish brown, silty to clayey, fine to medium sandstone. The Old
Paralic Deposits in the area typically possess a “very low” expansion potential (expansion index of 20
or less) and a “S0” sulfate class. The Old Paralic Deposits are considered acceptable to support the
planned fill and foundation loads for the development. We anticipate this unit is approximately 30 to
40 feet thick at the site.
4.3 Santiago Formation (Tsa)
Tertiary-age Santiago Formation is most likely present beneath the Old Paralic Deposits at a depth of
about 40 feet based on regional geologic maps and information. The Santiago Formation consists of
interbeds of dense to very dense, slightly and moderately cemented, silty to clayey sandstone and hard,
moderately cemented siltstone and claystone. We do not expect to encounter this unit during
development. The Santiago Formation is suitable for the support of proposed fill and structural loads.
5. GROUNDWATER
We did not encounter groundwater during our excavations, and we expect groundwater exists deeper
than 50 feet below existing grades at the property; therefore, we do not expect groundwater to
adversely impact future development. Groundwater elevations 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.
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.
Geocon Project No. G2633-11-02 - 7 - January 8, 2021
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
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).
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.
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Geocon Project No. G2633-11-02 - 8 - January 8, 2021
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
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 1.2 miles from the Pacific Ocean at an elevation
greater than 155 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.
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Geocon Project No. G2633-11-02 - 9 - January 8, 2021
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 dense nature of the formational units, the potential for liquefaction
and seismically induced settlement occurring at the site is considered negligible.
6.5 Landslides
Based on the examination of aerial photographs in our files and review of published geologic maps for
the site vicinity and the relatively flat topography, we opine landslides are not present at the property
or at a location that could affect the subject site.
Geocon Project No. G2633-11-02 - 10 - January 8, 2021
7. CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7.1.1 We did not encounter soil or geologic conditions during our exploration that would preclude
the proposed development, provided the recommendations presented herein are followed
and implemented during design and construction. We will provide supplemental
recommendations if we observe variable or undesirable conditions during construction, or if
the proposed construction will differ from that anticipated herein.
7.1.2 With the exception of possible moderate to strong seismic shaking, we did not observe or
know of significant geologic hazards to exist on the site that would adversely affect the
proposed project.
7.1.3 The site is generally underlain by a maximum of about 2 feet of topsoil overlying Old Paralic
Deposits. The topsoil is potentially compressible and unsuitable in its present condition for
the support of compacted fill or settlement-sensitive improvements. Remedial grading of
this material should be performed as discussed herein. The Old Paralic Deposits are
considered suitable for the support of proposed compacted fill and structural loads.
7.1.4 We did not encounter groundwater during our subsurface exploration. We expect
groundwater extends deeper than 50 feet below the existing site and do not expect it to be a
constraint to project development. However, seepage within surficial soil and formational
materials may be encountered during the grading operations, especially during the rainy
seasons.
7.1.5 Excavation of the topsoil and Old Paralic Deposits should generally be possible with
moderate to heavy effort using conventional, heavy-duty equipment during grading and
trenching operations.
7.1.6 Proper drainage should be maintained in order to preserve the engineering properties of the
fill in the building pad. Recommendations for site drainage are provided herein.
7.1.7 Based on our review of the project plans, we opine the planned development can be
constructed in accordance with our recommendations provided herein. We do not expect the
planned development will destabilize or result in settlement of adjacent properties if
properly constructed.
7.1.8 Surface settlement monuments and canyon subdrains will not be required on this project.
Geocon Project No. G2633-11-02 - 11 - January 8, 2021
7.2 Excavation and Soil Characteristics
7.2.1 Excavation of the in-situ surficial soils should be possible with moderate to heavy effort
using conventional heavy-duty equipment. Excavation of the formational materials will
require heavy effort using conventional heavy-duty equipment during the grading and
trenching operations.
7.2.2 The soil encountered in the field investigation is considered to be “non-expansive”
(expansion index [EI] of 20 or less) as defined by 2019 California Building Code (CBC)
Section 1803.5.3. Table 7.2 presents soil classifications based on the expansion index. We
expect the majority of the soil onsite to possess a “very low” expansion potential (expansion
index of 20 or less) in accordance with ASTM D 4829.
TABLE 7.2
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 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. 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,
further evaluation by a corrosion engineer may be performed if improvements susceptible to
corrosion are planned.
7.3 Grading
7.3.1 Grading should be performed in accordance with the recommendations provided in this
report, the Recommended Grading Specifications contained in Appendix C and the City of
Geocon Project No. G2633-11-02 - 12 - January 8, 2021
Carlsbad’s Grading Ordinance. Geocon Incorporated should observe the grading operations
on a full-time basis and provide testing during the fill placement.
7.3.2 Prior to commencing grading, a preconstruction conference 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.
7.3.3 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
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.
7.3.4 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.
7.3.5 We expect the planned building will be supported on a post-tension foundation system. The
existing upper approximately 1 to 2 feet of topsoil material contains roots and debris that
should be removed prior to use as compacted fill. The existing topsoil is loose and porous
and is not suitable for support of structural loads or structural fill in its present condition and
should be removed to expose the underlying formational materials and recompacted within
the limits of grading. In addition, the grading should occur such that there is at least 2 feet of
compacted fill below the building pad. We expect the removals depths will be 2 to 3 feet
based on our field exploration. Table 7.3.1 provides a summary of the grading
recommendations.
TABLE 7.3.1
SUMMARY OF GRADING RECOMMENDATIONS
Area Removal Requirements
Building Pad Removal to Expose Formational Materials
Minimum 2 Feet of Compacted Fill
Lateral Grading Limits Planned Development Area
Exposed Bottoms of Remedial Grading Scarify Upper 12 Inches
7.3.6 Prior to fill soil being placed, the bottom of the removal should be scarified, moisture
conditioned as necessary, and compacted to a depth of at least 12 inches. Deeper removals
Geocon Project No. G2633-11-02 - 13 - January 8, 2021
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.
7.3.7 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.
7.3.8 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 “Low” (Expansion Index of 50 or less)
Particle Size Maximum Dimension Less Than 3 Inches
Generally Free of Debris
7.4 Temporary Excavations
7.4.1 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
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.
Geocon Project No. G2633-11-02 - 14 - January 8, 2021
7.4.2 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.
7.5 Seismic Design Criteria – 2019 California Building Code
7.5.1 Table 7.5.1 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
(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). Sites designated as Site Class D, E and F
may require additional analyses if requested by the project structural engineer and client.
TABLE 7.5.1
2019 CBC SEISMIC DESIGN PARAMETERS
Parameter Value 2019 CBC Reference
Site Class C Section 1613.2.2
MCER Ground Motion Spectral Response Acceleration – Class B (short), SS 1.038g Figure 1613.2.1(1)
MCER Ground Motion Spectral Response Acceleration – Class B (1 sec), S1 0.377g Figure 1613.2.1(2)
Site Coefficient, FA 1.2 Table 1613.2.3(1)
Site Coefficient, FV 1.5* Table 1613.2.3(2)
Site Class Modified MCER Spectral Response Acceleration (short), SMS 1.245g Section 1613.2.3 (Eqn 16-36)
Site Class Modified MCER Spectral Response Acceleration – (1 sec), SM1 0.566g* Section 1613.2.3 (Eqn 16-37)
5% Damped Design
Spectral Response Acceleration (short), SDS 0.83g Section 1613.2.4 (Eqn 16-38)
5% Damped Design Spectral Response Acceleration (1 sec), SD1 0.377g* Section 1613.2.4 (Eqn 16-39)
* Note: 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.
7.5.2 Table 7.5.2 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. G2633-11-02 - 15 - January 8, 2021
TABLE 7.5.2
ASCE 7-16 PEAK GROUND ACCELERATION
Parameter Value ASCE 7-16 Reference
Mapped MCEG Peak Ground Acceleration, PGA 0.546g Figure 22-7
Site Coefficient, FPGA 1.2 Table 11.8-1
Site Class Modified MCEG
Peak Ground Acceleration, PGAM 0.547g Section 11.8.3 (Eqn 11.8-1)
7.5.3 Conformance to the criteria in Tables 7.5.1 and 7.5.2 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.
7.5.4 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 7.5.3
presents a summary of the risk categories in accordance with ASCE 7-16.
TABLE 7.5.3
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
7.6 Post-Tensioned Foundations
7.6.1 The post-tensioned system should be designed by a structural engineer experienced in post-
tensioned slab design and design criteria of the Post-Tensioning Institute (PTI) DC10.5 as
required by the 2019 California Building Code (CBC Section 1808.6.2). Although this
procedure was developed for expansive soil conditions, we understand it can also be used to
reduce the potential for foundation distress due to differential fill settlement. The post-
Geocon Project No. G2633-11-02 - 16 - January 8, 2021
tensioned design should incorporate the geotechnical parameters presented on Table 7.6.1.
The parameters presented in Table 7.6.1 are based on the guidelines presented in the PTI,
DC10.5 design manual. We anticipate a foundation category of IS where the expansion
index should be less than 20 and the fill depth is less than 10 feet for the proposed single-
family residential structure. Final foundation recommendations will be provided once
grading operations are performed and finish grade laboratory testing is completed.
TABLE 7.6.1
POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS
Post-Tensioning Institute (PTI)DC10.5 Design Parameters Value
Thornthwaite Index -20
Equilibrium Suction 3.9
Edge Lift Moisture Variation Distance, eM (feet) 5.3
Edge Lift, yM (inches) 0.61
Center Lift Moisture Variation Distance, eM (feet) 9.0
Center Lift, yM (inches) 0.30
7.6.2 The foundations for the post-tensioned slabs should be embedded in accordance with the
recommendations of the structural engineer. If a post-tensioned mat foundation system is
planned, the slab should possess a thickened edge with a minimum width of 12 inches and
extend below the clean sand or crushed rock layer.
7.6.3 Foundation systems for the lots that possess a “very low” expansion potential (expansion
index of 20 or less) can be designed using the method described in Section 1808 of the 2019
CBC. If post-tensioned foundations are planned, an alternative, commonly accepted design
method (other than PTI) can be used (e.g. the spanibility method, Category IS). However,
the post-tensioned foundation system should be designed with a total and differential
deflection of ½ inch and ½ inch in 40 feet. Geocon Incorporated should be contacted to
review the plans and provide additional information, if necessary.
7.6.4 If the structural engineer proposes a post-tensioned foundation design method other than the
2019 CBC (PTI DC10.5):
The criteria presented in Table 7.6.1 are still applicable.
Interior stiffener beams should be used.
The width of the perimeter foundations should be at least 12 inches.
The perimeter footing embedment depths should be at least 12 inches. The
embedment depths should be measured from the lowest adjacent pad grade.
Geocon Project No. G2633-11-02 - 17 - January 8, 2021
7.6.5 Isolated foundations located outside of the proposed post-tensioned slab should consist of
continuous strip footings and/or isolated spread footings. Table 7.6.2 provides a summary of
the foundation design recommendations.
TABLE 7.6.2
SUMMARY OF FOUNDATION RECOMMENDATIONS
Parameter Value
Minimum Continuous Foundation Width, WC 12 inches
Minimum Isolated Foundation Width, WI 24 inches
Minimum Foundation Depth, D 12 Inches Below Lowest Adjacent Grade
Minimum Steel Reinforcement – Continuous 2 No. 4 Bars, 1 at the Top and 1 at the Bottom
Design Expansion Index 50 or less
7.6.6 The conventional shallow 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).
Wall/Column Footing Dimension Detail
7.6.7 Our experience indicates post-tensioned slabs are susceptible to excessive edge lift,
regardless of the underlying soil conditions. Placing reinforcing steel at the bottom of the
perimeter footings and the interior stiffener beams may mitigate this potential. Current PTI
design procedures primarily address the potential center lift of slabs but, because of the
placement of the reinforcing tendons in the top of the slab, the resulting eccentricity after
tensioning reduces the ability of the system to mitigate edge lift. The structural engineer
FOOTING =--i
WIDTH, W1
SAND AND VAPOR
RETARDER IN
ACCORDANCE WITH ACI
I.. ..I FOOTING
WIDTH, We
PAD GRADE
(9 J: ~ I-I-a. 0 LU 00 LL
Geocon Project No. G2633-11-02 - 18 - January 8, 2021
should design the foundation system to reduce the potential of edge lift occurring for the
proposed structures.
7.6.8 During the construction of the post-tension foundation system, the concrete should be
placed monolithically. Under no circumstances should cold joints form between the
footings/grade beams and the slab during the construction of the post-tension foundation
system unless designed by the project structural engineer.
7.6.9 The proposed structures can be supported on a shallow foundation system founded in the
compacted fill materials. Table 7.6.3 provides a summary of the foundation design
recommendations.
TABLE 7.6.3
SUMMARY OF FOUNDATION RECOMMENDATIONS
Parameter Value
Allowable Bearing Capacity 2,500 psf
Estimated Total Settlement ½ Inch
Estimated Differential Settlement ½ Inch in 40 Feet
7.6.10 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.
7.6.11 The use of isolated footings, which are located beyond the perimeter of the building and
support structural elements connected to the building, are not recommended. Where this
condition cannot be avoided, the isolated footings should be connected to the building
foundation system with grade beams in both directions.
7.6.12 Consideration should be given to using interior stiffening beams and connecting isolated
footings and/or increasing the slab thickness.
7.6.13 Slabs that may receive moisture-sensitive floor coverings or may be used to store moisture-
sensitive materials should be underlain by a vapor retarder. The vapor retarder design should
be consistent with the guidelines presented in the American Concrete Institute’s (ACI) Guide
for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials (ACI 302.2R-06). In
addition, the membrane should be installed in accordance with manufacturer’s
recommendations and ASTM requirements and installed in a manner that prevents puncture.
The vapor retarder used should be specified by the project architect or developer based on the
Geocon Project No. G2633-11-02 - 19 - January 8, 2021
type of floor covering that will be installed and if the structure will possess a humidity-
controlled environment.
7.6.14 The bedding sand thickness should be determined by the project foundation engineer,
architect, and/or developer. It is common to have 3 to 4 inches of sand for 5-inch and 4-inch
thick slabs, respectively, in the southern California region. However, we should be
contacted to provide recommendations if the bedding sand is thicker than 6 inches. The
foundation design engineer should provide appropriate concrete mix design criteria and
curing measures to assure proper curing of the slab by reducing the potential for rapid
moisture loss and subsequent cracking and/or slab curl. We suggest that the foundation
design engineer present the concrete mix design and proper curing methods on the
foundation plans. It is critical that the foundation contractor understands and follows the
recommendations presented on the foundation plans.
7.6.15 We should observe the foundation excavations prior to the placement of reinforcing steel to
check that the exposed soil conditions are similar to those expected and that they have been
extended to the appropriate bearing strata. If unexpected soil conditions are encountered,
foundation modifications may be required.
7.7 Driveway and Exterior Concrete Flatwork
7.7.1 The driveway and other exterior concrete flatwork should be constructed in accordance with
the recommendations presented in Table 7.7. The recommended steel reinforcement would
help reduce the potential for cracking.
TABLE 7.7
MINIMUM CONCRETE DRIVEWAY AND FLATWORK RECOMMENDATIONS
Expansion
Index, EI Minimum Steel Reinforcement* Options Minimum
Thickness
EI < 50 6x6-W2.9/W2.9 (6x6-6/6) welded wire mesh 4 Inches No. 3 Bars 18 inches on center, Both Directions
* In excess of 8 feet square.
7.7.2 The subgrade soil should be properly moisturized and compacted prior to the placement of
steel and concrete. The subgrade soil 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.
Geocon Project No. G2633-11-02 - 20 - January 8, 2021
7.7.3 Even with the incorporation of the recommendations of this report, concrete 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, driveway concrete should be structurally connected to the curbs, where possible,
to reduce the potential for offsets between the curbs and the driveway.
7.7.4 Concrete 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.
7.7.5 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.
7.7.6 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
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.
7.8 Retaining Walls
7.8.1 Retaining walls should be designed using the values presented in Table 7.8.1. Soil with an
expansion index (EI) of greater than 50 should not be used as backfill material behind retaining
walls.
Geocon Project No. G2633-11-02 - 21 - January 8, 2021
TABLE 7.8.1
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 10H 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
7.8.2 The project retaining walls should be designed as shown in the Retaining Wall Loading
Diagram.
Retaining Wall Loading Diagram
7.8.3 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.
IF PRESENT
RETAINING
WALL
SLAB
ACTIVE
PRESSURE
H (Feet)
---FOOTING
SEISMIC
(IF
REQUIRED)
AT-REST/
RESTRAINED
(IF REQUIRED)
I Ru
-------, Rt_ psf
H>8'
Geocon Project No. G2633-11-02 - 22 - January 8, 2021
7.8.4 The structural engineer should determine the Seismic Design Category for the project in
accordance with Section 1613.3.5 of the 2019 CBC or Section 11.4 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.
7.8.5 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.
7.8.6 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 90 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.
Typical Retaining Wall Drainage Detail
7.8.7 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.
H
PROPOSED
GRADE
TEMPORARY
BACKCUTPER
OSHA
CONCRETE BROWDITCH
RETAINING
WALL
OR
Fl 140N FILTER
RIC (OR EQUIVALENT) 213 H
GROUND SURFACE
DRAINAGE PANEL (MIRADRAIN
6000 OR EQUIVALENT)
314" CRUSHED ROCK (1 CU. FT.IFT.)
OR WRAP DRAINAGE PANEL
12" AROUND PIPE
:r.,...,.f: LTER FABRIC ENVELOPE
~MIRAFI 140N OR EQUIVALENT
4" DIA. PERFORATED SCHEDULE-4"'lO~m~~...L.,----:;!FOOTIN~ ,~ 4" DIA. SCHEDULE40 PERFORATED
PVC PIPE EXTENDED TO APPROVED ' PVC PIPE OR TOTAL DRAIN EXTENDED
PROPOSED
GRADE
OUTLET TO APPROVED OUTLET
Geocon Project No. G2633-11-02 - 23 - January 8, 2021
7.8.8 In general, wall foundations should be designed in accordance with Table 7.8.2. 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 7.8.2
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
Allowable Bearing Capacity 2,500 psf
Estimated Total Settlement ½ Inch
Estimated Differential Settlement ½ Inch in 40 Feet
7.8.9 The recommendations presented herein are generally applicable to the design of rigid
concrete or masonry retaining walls. In the event that other types of walls (such as
mechanically stabilized earth [MSE] walls, soil nail walls, or soldier pile walls) are planned,
Geocon Incorporated should be consulted for additional recommendations.
7.8.10 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.
7.8.11 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.
Geocon Project No. G2633-11-02 - 24 - January 8, 2021
7.9 Lateral Loading
7.9.1 Table 7.9 should be used to help design the proposed structures and improvements to
resist 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
lateral loads for the design of footings or shear keys. The allowable passive pressure
assumes protected by floor slabs or pavement should not be included in design for passive
resistance.
TABLE 7.9
SUMMARY OF LATERAL LOAD DESIGN RECOMMENDATIONS
Parameter Value
Passive Pressure Fluid Density 350 pcf
Coefficient of Friction (Concrete and Soil) 0.35
Coefficient of Friction (Along Vapor Barrier) 0.2 to 0.25*
* Per manufacturer’s recommendations.
7.9.2 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.
7.10 Site Drainage and Moisture Protection
7.10.1 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 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.
7.10.2 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.
7.10.3 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.
Geocon Project No. G2633-11-02 - 25 - January 8, 2021
7.10.4 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. 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.
7.11 Foundation Plan Review
7.11.1 Geocon Incorporated should review the building foundation plans for the project prior to final
design submittal to evaluate if additional analyses and/or recommendations are required.
7.12 Testing and Observation Services During Construction
7.12.1 Geocon Incorporated should provide geotechnical testing and observation services during
the grading operations, foundation construction, utility installation, retaining wall backfill
and pavement installation. Table 7.12 presents the typical geotechnical observations we
would expect for the proposed improvements.
TABLE 7.12
EXPECTED GEOTECHNICAL TESTING AND OBSERVATION SERVICES
Construction Phase Observations Expected Time Frame
Grading
Base of Removal Part Time During
Removals
Geologic Logging Part Time
Fill Placement and Soil Compaction
Operations Full Time
Foundations Foundation Excavation Observations Part Time
Utility Backfill Fill Placement and
Soil Compaction Operations Part Time to Full Time
Retaining Wall Backfill Fill Placement and
Soil Compaction Operations Part Time to Full Time
Subgrade for Sidewalks,
Curb/Gutter and Pavement Soil Compaction Operations Part Time
Pavement Construction
Base Placement and Compaction Part Time
Asphalt Concrete Placement and
Compaction Full Time
Geocon Project No. G2633-11-02 January 8, 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.
APPENDIX A
Geocon Project No. G2633-11-02 January 8, 2021
APPENDIX A
FIELD INVESTIGATION
We performed the trenching operations on December 24, 2020. The trenches were excavated to depths
ranging from approximately 4½ to 5½ feet below existing grade using a John Deere 310L backhoe.
The locations of the exploratory trenches are shown on the Geologic Map. The trench logs are
presented in this appendix. We located the explorations in the field using a measuring tape and
existing reference points; therefore, actual boring locations may deviate slightly.
We obtained bag samples at appropriate intervals, placed them in moisture-tight containers, and
transported them to the laboratory for testing. The type of sample is noted on the exploratory trench
logs. Each excavation was backfilled as noted on the trench logs.
We visually examined, classified, and logged the soil encountered in the trenches in general
accordance with American Society for Testing and Materials (ASTM) practice for Description and
Identification of Soils (Visual-Manual Procedure D 2488). The logs depict the soil and geologic
conditions observed and the depth at which samples were obtained.
TOPSOIL (Qtop)
Medium dense, damp, light brown, Silty, fine to medium SAND; little
organics
OLD PARALIC DEPOSITS (Qop)
Dense, moist, light reddish brown, Clayey, fine to medium SANDSTONE
TRENCH TERMINATED AT 5 FEET
Groundwater not encountered
Backfilled with soil
SM
SC
T1-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
Figure A-1,
Log of Trench T 1, Page 1 of 1 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)
JOHN DEERE 310L BACKHOE PENETRATIONRESISTANCE(BLOWS/FT.)TRENCH T 1
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERJ. LANCASTER CONTENT (%)SAMPLE
NO.12-24-2020
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE MOISTUREBY:EQUIPMENT
ELEV. (MSL.)157'
G2633-11-02.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
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.
G2633-11-02
----r-r-y ·. ·-r ·.
)f:t} ----f~:·r ·. ·-r ·.
)f:t} ----f~:·r :._-.t:-. -. ·~. ,. ·t.
: :t: J: :~:
: :~: 1: :t:
: :t: J: :~:
: :~: 1: :t:
: :t: J: :~:
: :~: 1: :t:
-: :t: J: :~:
: :~: 1: :t:
: :t: J: :~:
•• r .1. ·~.
I]
liiiiJ
-
TOPSOIL (Qtop)
Loose, dry,, dark brown, Silty, fine to medium SAND; little organics
OLD PARALIC DEPOSITS (Qop)
Dense, moist, light reddish brown, Clayey, fine to medium SANDSTONE
TRENCH TERMINATED AT 5.5 FEET
Groundwater not encountered
Backfilled with soil
SM
SC
T2-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
Figure A-2,
Log of Trench T 2, Page 1 of 1 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)
JOHN DEERE 310L BACKHOE PENETRATIONRESISTANCE(BLOWS/FT.)TRENCH T 2
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERJ. LANCASTER CONTENT (%)SAMPLE
NO.12-24-2020
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE MOISTUREBY:EQUIPMENT
ELEV. (MSL.)156'
G2633-11-02.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
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.
G2633-11-02
,... -
I]
liiiiJ
-
-
TOPSOIL (Qtop)
Mediium dense, dry, dark brown, Silty, fine to medium SAND; little organics
OLD PARALIC DEPOSITS (Qop)
Dense, moist, light reddish brown, Clayey, fine to medium SANDSTONE
TRENCH TERMINATED AT 5 FEET
Groundwater not encountered
Backfilled with soil
SM
SC
T3-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
Figure A-3,
Log of Trench T 3, Page 1 of 1 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)
JOHN DEERE 310L BACKHOE PENETRATIONRESISTANCE(BLOWS/FT.)TRENCH T 3
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERJ. LANCASTER CONTENT (%)SAMPLE
NO.12-24-2020
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE MOISTUREBY:EQUIPMENT
ELEV. (MSL.)157'
G2633-11-02.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
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.
G2633-11-02
--~ ■ ~ [I ~ □ 1//;:1 lj.J f~ ~{yl .(j(1 lzz-/1 V:/·_-/: //·.-[).>/.~ v../ /-1 '1~ W.(yJ /y.:; v~ .::t\J._:-1\::1 -·. J· .. ·::t·)j::::):::::1 ::t·J._:-1--.::1 .. . J· .. ::.r:·4·.-J:::-1 I--I---
TOPSOIL (Qtop)
Medium dense, dry, dark brown, Silty, fine to medium SAND; little organics
OLD PARALIC DEPOSITS (Qop)
Very dense, damp, light reddish brown, Clayey, fine to medium
SANDSTONE
TRENCH TERMINATED AT 4.5 FEET
Groundwater not encountered
Backfilled with soil
SM
SC
T4-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
Figure A-4,
Log of Trench T 4, Page 1 of 1 DRY DENSITY(P.C.F.)... DRIVE SAMPLE (UNDISTURBED)
JOHN DEERE 310L BACKHOE PENETRATIONRESISTANCE(BLOWS/FT.)TRENCH T 4
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)GROUNDWATERJ. LANCASTER CONTENT (%)SAMPLE
NO.12-24-2020
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE MOISTUREBY:EQUIPMENT
ELEV. (MSL.)156'
G2633-11-02.GPJ
MATERIAL DESCRIPTIONLITHOLOGY
... STANDARD PENETRATION TEST
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.
G2633-11-02
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APPENDIX B
Geocon Project No. G2633-11-02 January 8, 2021
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. Selected soil samples were
tested for maximum dry density/optimum moisture content, expansion index, water-soluble sulfate and
direct shear strength. The results of our current laboratory tests are presented herein.
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.)
T1-1 Dark brown, Silty, fine to medium SAND 133.5 7.4
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
T4-1 7.6 14.0 119.5 0 Non-Expansive Very Low
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
T4-1 0 - 1.5 Qtop 0.004 S0 -----
SAMPLE NO.:GEOLOGIC UNIT:
SAMPLE DEPTH (FT):NATURAL/REMOLDED:
1 K 2 K 4 K AVERAGE
890 2030 4300 --
7.4 7.9 7.3 7.5
120.3 120.0 120.4 120.2
1 K 2 K 4 K AVERAGE
11.5 12.7 11.5 11.9
1056 1499 2838 --
896 1442 2838 --
520
29
340
29
Qtop
2'
NORMAL STRESS TEST LOAD
WATER CONTENT (%):
PEAK SHEAR STRESS (PSF):
ULT.-E.O.T. SHEAR STRESS (PSF):
INITIAL CONDITIONS
R
FRICTION ANGLE (DEGREES)
NORMAL STRESS TEST LOAD
ACTUAL NORMAL STRESS (PSF):
WATER CONTENT (%):
ULTIMATE
RESULTS
PEAK
G2633-11-02
3304 JAMES DRIVE
COHESION, C (PSF)
FRICTION ANGLE (DEGREES)
DIRECT SHEAR - ASTM D 3080
PROJECT NO.:
COHESION, C (PSF)
DRY DENSITY (PCF):
AFTER TEST CONDITIONS
T1-1
0
500
1000
1500
2000
2500
3000
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
1 K
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000SHEAR STRESS (PSF)NORMAL STRESS (PSF)A
X
A
X
GEOCON
INCORPORATED
GEOTECHNICAL CONSULT ANTS
A
X
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121 -297 4
PHONE 858 558-6900 -FAX 858 558-6159
,,,. ◄
A .. -:?
,,,. /
-------PEAK
ULTIMATE
~
,,,. / ,,,. J
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APPENDIX C
APPENDIX C
RECOMMENDED GRADING SPECIFICATIONS
FOR
3304 JAMES DRIVE
CARLSBAD, CALIFORNIA
PROJECT NO. G2633-11-02
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.
---
....
.................... 1 I .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... ....
-----
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 slopes 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.
........................
.................
NATURAi.GROUND ,,,,,,-----
NOTES:
............
........
................... __
SEE DETAL BELOW
--
1 ...... 8-lNCH DIAMETER, SCHEDULE 80 PVC PERFORATED PIPE FOR FILLS
IN EXCESS OF 100-FEET IN DEPTH ORA PIPE LENGTH OF LONGER THAN 500 FEET.
2 ...... 6-INCH DIAMETER, SCHEDULE 40 PVC PERFORATED PIPE FOR FILLS
LESS THAN 100-FEET IN DEPTH OR A PIPE LENGTH SHORTER THAN 500 FEET.
,, ------,-
.,,,.,,,,,,,.,,,..
BEDROCK
NOTE: FINAL 20' OF PIPEAT CUTI.ET
SHALL BE NON-PERFORATED.
9 CUBIC FEET/ FOOT OF OPEN
GRADED GRAVEL SURROUNDED BY
MIRAF1140NC (OR EQUIVALENT)
FILTER FABRIC
NO SCALE
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.
DETAIL
NOTES:
FORMAnONAL
MATERIAL
1 •.... EXCAVATE BACKCUT AT 1:1 INCUNATION (UNLESS OTHERWISE NOTl:D~
2 .... .BASE OF STABILITY FILL TO BE 3 FEET INTO FORMATIONAL MATERIAL, SI.OPING A MINIMUM 5% INTO SLOPE.
3 •.••. STABIUTY FLL TO BE COMF'OSED OF PROPERLY COMPACTED GRANIA..AR SOIL
4 ..... CHIMNEY DRAINS TO BE APPROVED PREFABRICATED CHIMNEY DRAIN PANELS (MIRADRAIN G200N OR EQUIVALENT)
SPACED AF'PROXIMATELY 20 FEET CENTER TO CENTER AND 4 FEETWIDE. CLOSER SPACING MAY BE REQUIRED F
SEEPAGE IS ENCOUNTERED.
5 ..••. FILTER MATERIAL TO BE 314-tlCH, OPEN-GRADED CRUSI-IED ROCK ENCLOSED IN APPROVED FL TER FABRIC (MIRAFI 1-40NC~
6 ..... COLLECTOR PIPE TO BE 4-INCH MINIMUM DIAMETER, PERFORATED, THICK-WALLED PVC SCHEDULE 40 OR
EQUIVALENT, AND SLOPED TO DRAIN AT 1 PERCENT lilNMUM TO APPROVED oun.ET.
NO SCALE
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.
FRONT VIEW
SIDE VIEW
'
CONCRETE
CUT-OFF WAU.
CONCRETE
CUT-OFFWAU.
SOLID SlJBDRAII P1PE
',( /
8' MIN.
NO SCALE
ll" MIN.(TYP)
ll" MIN.(TYP) /
NO SCALE
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.
FRONT VIEW
SIDE VIEW
8"0R8"
SUBDRAIN
CONCRETE
fEADWALL
8" ORB"
SUBDRAIN
~ 24"
NOTE: HEADWALL SHOULD ounET AT TOE OF FILL SLOPE
OR INTO CONTROLLED SURFACE DRAINAGE
NO SCALE
12"
NO SCALE
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. G2633-11-02 January 8, 2021
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.American Concrete Institute, ACI 318-11, Building Code Requirements for Structural
Concrete and Commentary, dated August, 2011.
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.California Geological Survey, Seismic Shaking Hazards in California, Based on the
USGS/CGS Probabilistic Seismic Hazards Assessment (PSHA) Model, 2002 (revised April
2003). 10% probability of being exceeded in 50 years.
http://redirect.conservation.ca.gov/cgs/rghm/pshamap/pshamain.html
6.Geocon Incorporated, 2020. Geologic Reconnaissance, 3304 James Drive, Carlsbad,
California, dated November 19 (Project No. G2633-11-01).
7.Historical Aerial Photos. http://www.historicaerials.com
8.Kennedy, M. P., and S. S. Tan, 2007, Geologic Map of the Oceanside 30’x60’ Quadrangle,
California, USGS Regional Map Series Map No. 2, Scale 1:100,000.
9.Special Publication 117A, Guidelines For Evaluating and Mitigating Seismic Hazards in
California 2008, California Geological Survey, Revised and Re-adopted September 11, 2008.
10.United States Geological Survey computer program, U.S. Design Maps.
https://earthquake.usgs.gov/designmaps/us/application.php
11.United States Geological Survey (USGS) Interactive Quaternary Faults Database computer
program, https://usgs.maps.arcgis.com/apps/webappviewer.
12.Unpublished reports, aerial photographs, and maps on file with Geocon Incorporated.
13.USGS computer program, Seismic Hazard Curves and Uniform Hazard Response Spectra,
http://geohazards.usgs.gov/designmaps/us/application.php.