HomeMy WebLinkAboutCT 13-05; STATE STREET TOWNHOMES; PRELIMINARY GEOTECHNICAL EVALUATION; DWG 484-2, DWG 484-2A; 2014-07-03i J
i
_J
i
j
~)
i
J
j
,,
LGC
Geotechnicalll Inc.
July 3, 2014
Ms. April Tornillo
Taylor Morrison
8105 Irvine Center Drive, Suite 1450
Irvine, CA 92618
FLE COPY
ProjectNo. 13200-01
Subject: Preliminary Geotechnical Evaluation for the Proposed State Street Townhomes, 2531
through 2589 State Street, City of Carlsbad, California
In accordance with your request and authorization, LGC Geotechnical, Inc. has performed a preliminary
geotechnical evaluation for the proposed approximately 1.9-acre residential development located at 2531
through 2589 State Street in the City of Carlsbad, California. The purpose of our study was to evaluate the
existing onsite geotechnical conditions and to provide preliminary geoteclmical recommendations relative to the
proposed residential development.
Should you have any questions regarding this report, please do not hesitate to contact our office. We appreciate
this opportunity to be of service.
Respectfully Submitted,
LGC Geotechnical, Inc.
Tim Lawson, CEG 1821, GE 2626
Geotechnical Engineer/Geologist
BTZ/TJL/kmb
Distribution: (3) Addressee (3 wet-signed copies, 1 via email)
(1) Adams Streeter Civil Engineers, Inc. (via email)
Attention: Mr. Mohammad Adabadi
(1) Amid Engineering Group, Inc. (via email)
Attention: Mr. Mansour Amid
~ ~ , ~ ~ ~ s ~-
\
' 131 Calle Iglesia, Suite 200, San Clemente, CA 92672 7J" (949) 369-6141 (~11 www.lgcgeotechnical.com
_J
_j
_J
~j
-----,
' _J
' __ J
_J
Section
1.0
2.0
3.0
4.0
5.0
TABLE OF CONTENTS
INTRODUCTION .................................................................................................................................. 1
1.1 Purpose and Scope of Services ................................................................................................... 1
1.2 Project Description ............................................................................ : ........................................ 1
1.3 Subsurface Geotechnical Evaluation ......................................................................................... 3
1.4 Laboratory Testing ..................................................................................................................... 3
1.5 Corrosion Potential. ................................................................................................................... 3
GEOTECHNICAL CONDITIONS ........................................................................................................ 4
2.1 Regional Geology ...................................................................................................................... 4
2.2 Site-Specific Geology ................................................................................................................ 4
2.3 Generalized Subsurface Conditions ............................................................................................ 4
2.4 Groundwater ................................................................. , ............................................................ 4
2.5 Seismic Design Criteria ............................................................................................................. 5
2.6 Faulting ...................................................................................................................................... 6
2.6.1 Liquefaction and Dynamic Settlement ........................................................................... 6
2.6.2 Lateral Spreading .......................................................................................................... 7
CONCLUSIONS .................................................................................................................................... 8
PRELIMINARY RECOMMENDATIONS .......................................................................................... 9
4.1 Site Earthwork ........................................................................................................................... 9
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.1.1 Site Preparation ............................................................................................................. 9
4.1.2 Removal Depths and Limits ........................................................................................ 10
4.1.3 Temporary Excavations .............................................................................................. 10
4.1.4 Removal Bottoms and Sub grade Preparation ............................................................... 11
4.1.5 Material for Fill ..................................... · ...................................................................... 11
4.1.6 Placement and Compaction of Fills ............................................................................. 12
4.1.7 Trench and Retaining Wall Backfill and Compaction .................................................. 12
Preliminary Foundation Recommendations .............................................................................. 13
4.2.1 Provisional Post-Tensioned Foundation Design Parameters ...................................... 13
4.2.2 Post-Tensioned Foundation Subgrade Preparation and Maintenance ........................ 13
4.2.3 Slab Underlayment Guidelines ................................................................................... 14
Soil Bearing and Lateral Resistance ........................................................................................ 15
Lateral Earth Pressures for Retaining Walls ........................................................................... 16
Temporary Shoring ................................................................................................................. 17
Control of Surface Water and Drainage Control... .................................................................... 18
Preliminary Asphalt Pavement Sections ................................................................................. 19
Soil Corrosivity ........................................................................................................................ 19
Nonstructural Concrete Flatwork ............................................................................................. 20
CIDH Pile Construction .......................................................................................................... 21
Grading and Foundation Plan Review ...................................................................................... 21
Geotechnical Observation and Testing During Construction .................................................... 21
LIMITATIONS ................................................................................................................................... 23
Project No. 13200-01 Pagei July 3, 2014
,-1
' .J
' J
_j
-,
:1
' .J
'· __ I
-,
' l
', _J
'_J
TABLE OF CONTENTS (Cont'd)
LIST OF ILLUSTRATIONS, TABLES, AND APPENDICES
Figures
Figure 1 -Site Location Map (Page 2)
Figure 2-Boring Location Map (Rear of Text)
Figure 3 -Retaining Wall Backfill Detail (Rear of Text)
Figure 4-Temporary Shoring/Permanent Retaining Wall Detail (Rear of Text)
Table 1 -Seismic Design Parameters (Page 5)
Table 2 -Geotechnical Parameters for Post-Tensioned Foundation Slab Design (Page 15)
Table 3 -Lateral Earth Pressures-Conventional Backfilled Retaining Walls (Page 16)
Table 4-Paving Section Options (Page 19)
Table 5 -Nonstructural Concrete Flatwork for Medium Expansion Potential (Page 20)
Appendices
Appendix A -References
Appendix B -Field Exploration Logs from Leighton, 2005
Appendix C -Laboratory Test Results from Leighton, 2005
Appendix D -General Earthwork and Grading Specifications
Project No. 13200-01 Page ii July 3, 2014
' J
1.0 INTRODUCTION
1.1 Purpose and Scope o(Services
This report presents the results of our preliminary geotechnical evaluation for the proposed
approximately 1.9-acre residential development located at 2531 through 2589 State Street in the City of
Carlsbad, California. Refer to the Site Location Map (Figure 1 ).
The purpose of our study was to provide preliminary geotechnical recommendations relative to the
proposed development. As part of our scope of work, we have: 1) reviewed available geotechnical
reports and in-house geologic maps pertinent to the site (Appendix A); and 2) prepared this
preliminary geotechnical summary report presenting our findings and preliminary conclusions and
recommendations for the development of the proposed project.
1.2 Proiect Description
The project consists of an approximately 1.9-acre sized parcel located at 2531 through 2589 State
Street in the City of Carlsbad, California (Figure 1 ). The site is bordered to the northwest by
commercial buildings and associated parking space and to the southeast by the Coaster Carlsbad Village
Station Parking Lot and an undeveloped lot primarily used for the storage yard associated with the
adjacent railroad operations. The site is currently a series of two-story commercial buildings and
associated parking areas. The site is relatively level with an elevation of approximately 35 feet above
mean-sea level (msl) sloping slightly downward in a northwesterly direction towards the Buena Vista
Lagoon.
We understand the proposed improvements include construction of 4 7 building pads for residential
townhomes and associated improvements. The proposed development will be at-grade (no planned
basements) with relatively light building loads (column and wall loads maximum of 20 kips and 2
kips per lineal foot, respectively). Site grades will increase up to approximately 4 feet from existing
grade requiring retaining walls in the westerly and easterly perimeter of the site.
The recommendations given in this report are based upon at-grade structures with the estimated
structural loads indicated above. LGC Geotechnical should be provided with any updated project
information, plans and/or any changes to estimated structural loads when they become available, in
order to either confirm or modify the recommendations provided herein.
Project No. 13200-01 Page 1 July 3, 2014
-,
_J
_j
1000 1000 2000 3000 4000 5000 6000
FEET
------§~~~4Taylor Mornson -
PROJECT NAME 1;;;3~20~0-Io1[_ ___ ====--
_
_..;.. _____ T__ -· PROJECT NO. r.;!.:!.~~,.------====--
r-------FIGURE 1 ENG.I GEOL. ~:: 2,000'
Site Location Map ~:~E July 2014
. State Street, Carlsbad
_j
,-,
__ j
.J
1.3 Subsurface Geotechnical Evaluation
1.4
A geotechnical evaluation of the site was previously performed by Leighton (Leighton, 2005). The
exploration program consisted of drilling and sampling two small-diameter hollow-stem borings (B-1
and B-2) to depths of approximately 61.5 feet and 48 feet, respectively. The approximate locations are
provided on the Boring Location Map, Figure 2. The boring logs are provided in Appendix B.
Laboratory Testing
Previous laboratory testing included in-situ moisture content and in-situ dry density, direct shear,
collapse potential and corrosion (sulfate, chloride, pH, and resistivity). The previous laboratory test
results are presented in Appendix C. The moisture and dry density test results are presented on the
boring logs in Appendix B.
1.5 Corrosion Potential
Previous corrosion testing (pH, resistivity, soluble sulfate, and chloride content) was performed to
estimate the corrosion potential of onsite soils (Leighton, 2005). The results of the soluble sulfate
content were 0.06 percent and 0.05 percent. Chloride contents were 639 parts per million (ppm) and
1,890 ppm. The results for resistivity tests resulted in minimum resistivity values of 1,821 ohm-
centimeters and 1,012 ohm-centimeters and pH values of 8.3 and 8.0. Caltrans defines a corrosive area
as one where any of the following conditions exist: the soil contains more than 500 ppm of chlorides,
more than 2,000 ppm (0.2 percent) of sulfates, or a pH of 5.5 or less (Caltrans, 2012).
Project No. 13200-01 Page3 July 3, 2014
' _J
,J
. l
' .I
!
,_J
. .I
2.0 GEOTECHNICAL CONDITIONS
2.1 Regional Geology
2.2
2.3
Based on our review of the geologic map of the Oceanside, San Luis Rey, and San Marcos 7.5 Minute
Quadrangle the site is underlain in the near-surface by Quaternary Terrace deposits consisting of
reddish brown, poorly bedded, poorly to moderately indurated sandstone, siltstone and conglomerate.
Site-Specific Geology
Our review of an adjacent geotechnical report for the other side of State Street (WKA, 1985), as well as
conversations with a contractor excavating on an adjacent lot, indicates that the site is underlain by a
shallow veneer of artificial fill placed during development of the site and native colluvial soils above the
Terrace material. Underlying the Terrace materials at depth is the Middle Eocene Santiago Formation.
Local topographic expressions and review of aerial photographs do not indicate the presence of any
landslides within the project area.
Generalized Subsurface Conditions
The field explorations (borings) generally indicated soft to stiff sandy clays transitioning to dense silty
sands with isolated layers of finer-grained very stiff to hard sandy clays to the maximum explored depth
of approximately 60 feet below existing grade. In general, the upper approximate 4 to 8 feet consisted
of soft to stiff sandy clays.
It should be noted that borings are only representative of the location where they are performed and
varying subsurface conditions may exist outside of the performed location. In addition, subsurface
conditions can change over time. The soil descriptions provided above should not be construed to mean
that the subsurface profile is uniform and that soil is homogeneous within the project area. For details
on the stratigraphy at the exploration locations, refer to Appendix B.
2.4 Groundwater
Groundwater was encountered at depths of approximately 16 and 21 feet below existing ground surface
during the previous geotechnical subsurface evaluation (Leighton, 2005).
Seasonal fluctuations of groundwater elevations should be expected over time. In general, groundwater
levels fluctuate with the seasons and local zones of perched groundwater may be present due to local
seepage caused by irrigation and/or recent precipitation. Local perched groundwater conditions or
surface seepage may develop once site development is completed.
Project No. 13200-01 Page4 July 3, 2014
--J
2. 5 Seismic Design Criteria
The site seismic characteristics were evaluated per the guidelines set forth in Chapter 16, Section
1613 of the 2013 California Building Code (CBC). Representative site coordinates of latitude
33.164440 degrees north and longitude -117.353051 degrees west were utilized in our analyses. The
maximum considered earthquake (MCE) spectral response accelerations (SMs and SM1) and adjusted
design spectral response acceleration parameters (Sos and Sm) for Site Class D are provided in Table
1.
TABLE]
Seismic Design Parameters
Selected Parameters from 2013 CBC, Seismic Design Values Section 1613 -Earthquake Loads
Site Class per Chapter 20 of ASCE 7 D
Risk-Targeted Spectral Acceleration for 1.163g Short Periods (Ss)*
Risk-Targeted Spectral Accelerations for 1-0.446g Second Periods (S1 )*
Site Coefficient Fa per Table 1613.3.3(1) 1.035
Site Coefficient Fv per Table 1613.3.3(2) 1.554
Site Modified Spectral Acceleration for Short
Periods (SMs) for Site Class D 1.203g
[Note: SMs = FaSs]
Site Modified Spectral Acceleration for 1-
Second Periods (SM1) for Site Class D 0.693g
rNote: SM!= FvS, l
Design Spectral Acceleration for Short
Periods (Sos) for Site Class D 0.802g
[Note: Sos= c2iJ)SMsl
Design Spectral Acceleration for 1-Second
Periods (Sm) for Site Class D 0.462g
rNote: Sm= (2fJ)SMil
Mapped Risk Coefficient at 0.2 sec Spectral 0.938 Response Period, CRs (per ASCE 7)
Mapped Risk Coefficient at 1 sec Spectral 0.989 Response Period, CR, (per ASCE 7)
* From USGS, 2014
Section 1803.5.12 of the 2013 CBC (per Section 11.8.3 of ASCE 7) states that the maximum
considered earthquake geometric mean (MCEG) Peak Ground Acceleration (PGA) should be used for
geotechnical evaluations such as liquefaction potential. The PGAM for the site is equal to 0.48g
(USGS, 2014 ).
Project No. 13200-01 Page5 July 3, 2014
2.6
,-·1
_J
A deaggregation of the PGA based on a 2,475-year average return period indicates that an earthquake
magnitude of 6. 7 at a distance of approximately 7 .8 km from the site would contribute the most to
this ground motion (USGS, 2008b ).
Faulting
Prompted by damaging earthquakes in Northern and Southern California, State legislation and policies
concerning the classification and land-use criteria associated with faults have been developed. Their
purpose was to prevent the construction of urban developments across the trace of active faults,
resulting in the Alquist-Priolo Earthquake Fault Zoning Act. Earthquake Fault Zones have been
delineated along the traces of active faults within California. Where developments for human
occupation are proposed within these zones, the state requires detailed fault evaluations be performed so
that engineering geologists can mitigate the hazards associated with active faulting by identifying the
location of active faults and allowing for a setback from the zone of previous ground rupture.
The subject site is not located within an Alquist-Priolo Earthquake Fault Zone. The possibility of
damage due to ground rupture is considered low since no active faults are known to cross the site.
Secondary effects of seismic shaking resulting from large earthquakes on the major faults in the
Southern California region, which may affect the site, include ground lurching, shallow ground
rupture, soil liquefaction and dynamic settlement. These secondary effects of seismic shaking are a
possibility throughout the Southern California region and are dependant on the distance between the
site and causative fault and the onsite geology. Some of the major active faults that could produce
these secondary effects include the Newport Inglewood (offshore), Rose Canyon, Coronado Bank,
Palos Verdes and San Andreas Faults, among others (USGS, 2008a). A discussion of these
secondary effects is provided in the following sections. The nearest known active or potentially active
fault is the Newport Inglewood/Rose Canyon Fault located approximately 4 miles to the west of the site
offshore.
2.6.1 Liquefaction and Dynamic Settlement
Liquefaction is a seismic phenomenon in which loose, saturated, granular soils behave similarly
-·1 to a fluid when subject to high-intensity ground shaking. Liquefaction occurs when three
general conditions coexist: 1) shallow groundwater; 2) low density non-cohesive (granular)
soils; and 3) high-intensity ground motion. Studies indicate that saturated, loose to medium
.. J dense, near surface cohesionless soils exhibit the highest liquefaction potential, while dry,
dense, cohesionless soils and cohesive soils exhibit low to negligible liquefaction potential. In
general, cohesive soils are not considered susceptible to liquefaction, depending on their
. .1 plasticity and moisture content (Bray & Sancio, 2006). Effects of liquefaction on level ground
include settlement, sand boils, and bearing capacity failures below structures. Dynamic
-i settlement of dry loose sands can occur as the sand particles tend to settle and densify as a result
of a seismic event.
Site soils are not considered susceptible to liquefaction due to the dense to very dense nature
of the sandy soils encountered at depth.
Project No. 13200-01 Page6 July 3, 2014
2.6.2 Lateral Spreading
Lateral spreading is a type of liquefaction-induced ground failure associated with the lateral
displacement of surficial blocks of sediment resulting from liquefaction in a subsurface layer.
Once liquefaction transforms the subsurface layer into a fluid mass, gravity plus the earthquake
inertial forces may cause the mass to move downslope towards a free face (such as a river
channel or an embankment). Lateral spreading may cause large horizontal displacements and
such movement typically damages pipelines, utilities, bridges, and structures.
Due to the very low potential for liquefaction, the potential for lateral spreading is also
considered very low.
Project No. 13200-01 Page 7 July 3, 2014
l
. )
···1
3.0 CONCLUSIONS
Based on the results of our geotechnical evaluation, it is our opinion that the proposed development is feasible
from a geotechnical standpoint, provided the following conclusions and recommendations are implemented.
The following is a summary of the primary geotechnical factors that may affect future development of the site:
• In general, borings indicate that the site consists of soft to stiff sandy clays transitioning to dense silty
sands with isolated layers of finer-grained very stiff to hard sandy clays to the maximum explored depth of
approximately 60 feet. The near surface soft and compressible soils are not suitable for the planned
improvements in their present condition.
•
•
•
•
•
Groundwater was previously encountered at approximate depths of 16 and 21 feet below existing grade .
The site is not located within a mapped State of California Earthquake Fault-Rupture Zone (Alquist-Priolo
Special Studies Zone) and no known active or potentially active faults cross the site.
The main seismic hazard that may affect the site is ground shaking from one of the active regional faults .
The subject site will likely experience strong seismic ground shaking during its design life.
The site is not considered susceptible to liquefaction due to the dense to very dense nature of site sandy
soils.
Site soils are anticipated to have "Medium" expansion potential. This must be confirmed at the completion
of grading. Mitigation measures are required for foundations and site improvements like concrete flatwork
to minimize the impacts of expansive soils.
• Due to the proximity of existing buildings along the property line in the westerly and easterly directions to
proposed building footprints, temporary shoring will be required in order to provide adequate earthwork
removals. In other portions of the site perimeter adjacent to property lines, "ABC" slot cuts may be required
... ! in order to perform the recommended earthwork removals.
. J
• From a geotechnical perspective, the existing onsite soils are suitable material for use as fill, provided
that they are relatively free from rocks (larger than 8 inches in maximum dimension), construction
debris, and significant organic material.
• The site contains clayey soils with high fines content and expansion potential that are not suitable for
backfill of planned site retaining walls. Therefore, import or select grading/stockpiling of sandy soils
meeting project recommendations will be required.
• Based on Caltrans guidelines for corrosion, site soils are considered corrosive due to high chloride content.
Project No. 13200-01 Page8 July 3, 2014
' _J
' _)
_ _J
J
4.0 PRELIMINARY RECOMMENDATIONS
The following recommendations are to be considered preliminary, and should be confirmed upon completion
of grading and earthwork operations. In addition, they should be considered minimal from a geotechnical
viewpoint, as there may be more restrictive requirements from the architect, structural engineer, building
codes, governing agencies, or the owner.
It should be noted that the following geotechnical recommendations are intended to provide sufficient
information to develop the site in general accordance with the 2013 CBC requirements. With regard to the
potential occurrence of potentially catastrophic geotechnical hazards such as fault rupture, earthquake-
induced landslides, liquefaction, etc. the following geotechnical recommendations should provide adequate
protection for the proposed development to the extent required to reduce seismic risk to an "acceptable
level." The "acceptable level" of risk is defined by the California Code of Regulations as "that level that
provides reasonable protection of the public safety, though it does not necessarily ensure continued structural
integrity and functionality of the project" [Section 3 721 (a)]. Therefore, repair and remedial work of the
proposed improvements may be required after a significant seismic event. With regards to the potential for
less significant geologic hazards to the proposed development, the recommendations contained herein are
intended as a reasonable protection against the potential damaging effects of geotechnical phenomena such
as expansive soils, fill settlement, groundwater seepage, etc. It should be understood, however, that although
our recommendations are intended to maintain the structural integrity of the proposed development given the
site geotechnical conditions, they cannot preclude the potential for some cosmetic distress or nuisance issues
to develop as a result of the site geotechnical conditions.
The geotechnical recommendations contained herein must be confirmed to be suitable or modified based on
the actual as-graded conditions.
4.1 Site Earthwork
We anticipate that earthwork at the site will consist of the removal of existing improvements associated
with the former land use followed by installation of temporary shoring, required earthwork removals,
precise grading and construction of the proposed new improvements, including the townhouse
structures, subsurface utilities, interior streets, etc.
We recommend that earthwork onsite be performed in accordance with the following recommendations,
future grading plan review report(s), the 2013 CBC/City of Carlsbad grading requirements, and the
General Earthwork and Grading Specifications included in Appendix D. In case of conflict, the
following recommendations shall supersede those included in Appendix D. The following
recommendations should be considered preliminary and may be revised within the future grading plan
review report or based on the actual conditions encountered during site grading.
4.1.1 Site Preparation
Prior to grading of areas to receive structural fill or engineered improvements, the areas should
be cleared of existing asphalt, surface obstructions, and demolition debris. Vegetation and
debris should be removed and properly disposed of off-site. Holes resulting from the removal of
Project No. 13200-01 Page9 July 3, 2014
. J
J
_)
4.1.2
buried obstructions, which extend below proposed finish grades, should be replaced with
suitable compacted fill material.
If cesspools or septic systems are encountered they should be removed in their entirety. The
resulting excavation should be backfilled with properly compacted fill soils. As an alternative,
cesspools can be backfilled with lean sand-cement slurry. Any encountered wells should be
properly abandoned in accordance with regulatory requirements. At the conclusion of the
clearing operations, a representative of LGC Geotechnical should observe and accept the site
prior to further grading.
Removal Depths and Limits
In order to provide a relatively uniform bearing condition for the planned improvements, we
recommend the removal of previously placed uncertified fill material and colluvial soils. We
anticipate removals ranging from approximately 4 to 8 feet below existing grade to competent
Terrace Deposits. Where practical, the envelope for removals should extend laterally a
minimum distance of 5 feet beyond the edges of the proposed improvements.
Local conditions may be encountered during excavation that could require additional over-
excavation beyond the above-noted minimum in order to obtain an acceptable subgrade. The
actual depths and lateral extents of grading will be determined by the geotechnical consultant,
based on subsurface conditions encountered during grading. Areas to be over-excavated should
be accurately staked in the field by the Project Surveyor.
4.1.3 Temporary Excavations
Temporary excavations should be performed in accordance with project plans, specifications,
and all Occupational Safety and Health Administration (OSHA) requirements. Excavations
should be laid back or shored in accordance with OSHA requirements before personnel or
equipment are allowed to enter.
The majority of the site soils in the upper approximate 5 feet are anticipated to be OSHA Type
"B" soils (refer to the attached boring logs). Sandy soils were encountered at greater depths and
should be considered Type "C" soils. Soil conditions should be regularly evaluated during
construction to verify conditions are as anticipated. The contractor shall be responsible for
providing the "competent person", required by OSHA standards, to evaluate soil conditions.
Sandy soils are present and should be considered susceptible to caving. The contractor shall be
responsible for providing the "competent person", required by OSHA standards, to evaluate soil
conditions. Close coordination with the geotechnical consultant should be maintained to
facilitate construction while providing safe excavations. Excavation safety is the sole
responsibility of the contractor.
In areas not adjacent to existing structures, temporary construction excavations are
anticipated to be able to be made vertically without shoring to a depth of 5 feet below
adjacent grade. However, "ABC" slot cuts may be required based on exposed soil conditions
and/or required deeper excavations. The slots should be no wider than 10 feet and no deeper
than 8 feet, and should be backfilled immediately to finish grade prior to excavation of the
Project No. 13200-01 Page 10 July 3, 2014
)
4.1.4
adjacent two slots. Once an excavation has been initiated, it should be backfilled as soon as
practical. Prolonged exposure of temporary excavations may result in some localized
instability. Excavations should be planned so that they are not initiated without sufficient
time to shore/fill them prior to weekends, holidays, or forecasted rain. It should be noted that
any excavation that extends below a 1: 1 (horizontal to vertical) projection of an existing
foundation will remove existing support of the structure foundation. Geotechnical parameters
for temporary shoring are provided in Section 4.5. Excavation safety and protection of off-site
existing improvements during grading are the responsibility of the contractor.
Surcharge loads (soil stockpiles, construction equipment, etc.) should not be permitted within
a horizontal distance equal to the height of the cut from the top of the excavation or 5 feet
from the top of the slope, whichever is greater, unless the cut is properly shored and designed
for the applicable surcharge load.
Removal Bottoms and Suhgrade Preparation
In general, removal bottom areas and any areas to receive compacted fill should be scarified to a
minimum depth of 6 inches, brought to a near-optimum moisture condition, and re-compacted
per project recommendations. Removal bottoms and areas to receive fill should be observed and
accepted by the geotechnical consultant prior to subsequent fill placement.
4.1.5 Material for Fill
From a geotechnical perspective, the onsite soils are generally considered suitable for use as
general compacted fill, provided they are screened of organic materials, construction debris and
oversized material (8 inches in greatest dimension).
From a geotechnical viewpoint, required import soils for general fill (i.e., non-retaining wall
backfill) should consist of clean, granular soils of "Very Low" to "Low" expansion potential
(expansion index 50 or less based on ASTM D 4829) and free of organic materials, construction
debris and any material greater than 3 inches. Import for any required retaining wall backfill
should meet the criteria outlined in the following paragraph. Source samples should be provided
to the geotechnical consultant for laboratory testing a minimum of four working days prior to
any planned importation.
Retaining wall backfill should consist of sandy soils with a maximum of 35 percent fines
(passing the No. 200 sieve) per American Society for Testing and Materials (ASTM) Test
Method D1140 (or ASTM D6913/D422) and a "Very Low" expansion potential (EI of 20 or
less per ASTM D4829). Soils should also be screened of organic materials, construction debris,
and any material greater than 3 inches. The site contains soils that are not suitable for retaining
wall backfill due to their fines content, therefore import or potentially select grading and
stockpiling of site soils will be required by the contractor for obtaining suitable retaining· wall
backfill soil. Contractor shall assume import of retaining wall backfill will be required. The
limits of sand backfill are shown on Figure 3.
Aggregate base ( crushed aggregate base or crushed miscellaneous base) should conform to the
requirements of Section 200-2 of the Standard Specifications for Public Works Construction
Project No. 13200-01 Page 11 July 3, 2014
, __ j
I ~--J
' _ _j
~)
, __ j
("Green book") for untreated base materials ( except processed miscellaneous base) or Caltrans
Class 2 aggregate base.
4.1.6 Placement and Compaction o{Fills
Material to be placed as fill should be brought to near-optimum moisture content (generally
within optimum to 2 percent above optimum moisture content) and recompacted to at least 90
percent relative compaction (per ASTM D1557). Moisture conditioning of site soils will be
required in order to achieve adequate compaction. The optimum lift thickness to produce a
uniformly compacted fill will depend on the type and size of compaction equipment used. In
general, fill should be placed in uniform lifts not exceeding 8 inches in compacted thickness.
Each lift should be thoroughly compacted and accepted prior to subsequent lifts. Generally,
placement and compaction of fill should be performed in accordance with local grading
ordinances and with observation and testing by the geotechnical consultant. Oversized material
as previously defined should be removed from site fills.
During backfill of excavations, the fill should be properly benched into firm and competent
soils of temporary backcut slopes as it is placed in lifts.
Aggregate base material should be compacted to at least 95 percent relative compaction at or
slightly above optimum moisture content per ASTM D1557. Subgrade below aggregate base
should be compacted to at least 90 percent relative compaction per ASTM D1557 at or slightly
above optimum moisture content.
4.1. 7 Trench and Retaining Wall Backfill and Compaction
The onsite soils may generally be suitable as trench backfill, provided the soils are screened of
rocks and other material greater than 6 inches in diameter and organic matter. If trenches are
shallow or the use of conventional equipment may result in damage to the utilities, sand having
a sand equivalent (SE) of 30 or greater may be used to bed and shade the pipes. Sand backfill
within the pipe bedding zone may be densified by jetting or flooding and then tamping to
ensure adequate compaction. Subsequent trench backfill should be compacted in uniform thin
lifts by mechanical means to at least the recommended minimum relative compaction (per
ASTM D1557).
Retaining wall backfill should consist of sandy soils as outlined in preceding Section 4.1.5. The
limits of select sandy backfill should extend at minimum Yz the height of the retaining wall or
the width of the heel (if applicable), whichever is greater (Figure 3). Retaining wall backfill
soils should be compacted in relatively uniform thin lifts to at least 90 percent relative
compaction (per ASTM D1557). Jetting or flooding of retaining wall backfill materials should
not be permitted.
A representative from LGC Geotechnical should observe, probe, and test the backfill to
verify compliance with the project recommendations.
Project No. 13200-01 Page 12 July 3, 2014
_J
-_I
___ )
4.2 Preliminary Foundation Recommendations
Provided that the remedial grading recommendations provid~d herein are implemented, the site may be
considered suitable for the support of the residential structures using a post-tensioned foundation system
designed to resist the impacts of expansive soils. Please note that the following foundation
recommendations are preliminary and must be confirmed by LGC Geotechnical.
Preliminary foundation recommendations are provided in the following sections. Recommended soil
bearing and estimated settlement due to structural loads are provided in Section 4.3.
4.2.1 Provisional Post-Tensioned Foundation Design Parameters
The minimum geotechnical parameters provided herein may be used for the design of post-
tensioned slab-on-grade foundations. These parameters have been determined in general
accordance with the Post-Tensioning Institute (PTI) Standard Requirements for Design of
Shallow Post-Tensioned Concrete Foundations on Expansive Soils referenced in Chapter 18
of the 2013 California Building Code (CBC). In utilizing these parameters, the
foundation/structural designer should design the foundation system in accordance with the
allowable deflection criteria of applicable codes and the requirements of the structural
designer/architect. Other types of stiff slabs may be used in place of the CBC post-tensioned
slab design provided that, in the opinion of the foundation/structural designer, the alternative
type of slab is at least as stiff and strong as that designed by the CBC/PTI method. Based on
the knowledge of this site containing Medium expansive soils, the structural designer should
use their own judgment in the design of the foundation system. The geotechnical post-
tensioned slab foundation parameters are provided in Table 2 in order to reduce the potential
impacts of expansive soils. Should the foundation engineer/architect or owner wish to further
reduce movement of the foundation to limit cosmetic distress due to homeowner irrigation
practices, the foundation should be further stiffened. These parameters have been prepared in
general accordance with the PTI guidelines.
Our design parameters are based on our experience with similar projects and the anticipated
nature of the soil (with respect to expansion potential). Please note that implementation of
our recommendations will not eliminate all foundation movement (and related distress)
should the moisture content of the subgrade soils fluctuate. It is the intent of these
recommendations to help maintain the integrity of the proposed structures and reduce (not
eliminate) movement, based upon the anticipated site soil conditions. Should future owners
not properly maintain the areas surrounding the foundation, for example by overwatering or
by letting the soils dry and desiccate, then we anticipate the maximum differential movement
of the perimeter of the foundation to the center of the foundation to be on the order of an
inch.
4.2.2 Post-Tensioned Foundation Subgrade Preparation and Maintenance
Moisture-conditioning of the subgrade soils is recommended prior to trenching the
foundation. Recommendations specific to anticipated site soil conditions are presented in
Table 2. The subgrade moisture-condition of the building pad soils should be maintained at
the recommended moisture content up to the time of concrete placement. This moisture
Project No. 13200-01 Page 13 July 3, 2014
1
' .. 1
_,)
,_J
.. )
. .J
'. _J
_J
__ J
._.I
4.2.3
content should be maintained around the immediate perimeter of the slab during construction
and up to occupancy of the building structures.
The geotechnical parameters provided in Table 2 assume that if the areas adjacent to the
foundation are planted and irrigated, these areas will be designed with proper drainage and
adequately maintained so that ponding, which causes significant moisture changes below the
foundation, does not occur. Our recommendations do not account for excessive irrigation
and/or incorrect landscape design. Plants should only be provided with sufficient irrigation
for life and not be overwatered so as to saturate subgrade soils. Sunken planters placed
adjacent to the foundation should either be designed with an efficient drainage system or
liners to prevent moisture infiltration below the foundation. Some lifting of the perimeter
foundation beam should be expected even with properly constructed planters.
In addition to the factors mentioned above, future homeowners should be made aware of the
potential negative influences of trees and/or other large vegetation. Roots that extend near the
vicinity of foundations can cause distress to foundations. Future homeowners ( and the
owner's landscape architect) should not plant trees/large shrubs closer to the foundations than
a distance equal to half the mature height of the tree or 20 feet, whichever is more
conservative unless specifically provided with root barriers to prevent root growth below the
building foundation.
It is the homeowner' s responsibility to perform periodic maintenance during hot and dry
periods to ensure that adequate watering has been provided to keep soil from separating or
pulling back from the foundation. Future homeowners and property management personnel
should be informed and educated regarding the importance of maintaining a constant level of
soil-moisture. The homeowners should be made aware of the potential negative consequences
of both excessive watering, as well as allowing potentially expansive soils to become too dry.
Expansive soils can undergo shrinkage during drying, and swelling during the rainy winter
season, or when irrigation is resumed. This can result in distress to building structures and
hardscape improvements. The builder should provide these recommendations to future
homeowners and property management personnel.
Slab Underlavment Guidelines
The following is for informational purposes only since slab underlayment ( e.g., moisture
retarder, sand or gravel layers for concrete curing and/or capillary break) is unrelated to the
geotechnical performance of the foundation and thereby not the purview of the geotechnical
consultant. Post-construction moisture migration should be expected below the foundation.
The foundation engineer/architect should determine whether the use of a capillary break
(sand or gravel layer), in conjunction with the vapor retarder, is necessary or required by
code. Sand layer thickness and location (above and/or below vapor retarder) should also be
determined by the foundation engineer/architect.
Project No. 13200-01 Page 14 July 3, 2014
I __ J
--1
' _ __j
c ___ J
_J
. J
-~j
__ J
_j
_J
--i
4.3
TABLE2
Geotechnical Parameters for Post-Tensioned Foundation Slab Design
Parameter PT Slab with Perimeter
Footin2s
Expansion Index Medium
Center Lift
Edge moisture variation distance, em 9.0 feet
Center lift, y m 0.7 inch
Edge Lift
Edge moisture variation distance, em 4.7 feet
Edge lift, Y m 1.3 inch
Minimum perimeter footing/thickened edge embedment below 24 inches finish grade
Minimum Perimeter foundation reinforcement1 1 No. 5 Bar
( or equivalent)
1.
2 .
Recommendations for foundation reinforcement are ultimately the purview of the foundation
engineer/ structural engineer based upon geotechnical criteria and structural engineering
considerations.
Moisture condition slab subgrade to 120% of optimum moisture content to a depth of 24 inches
prior to trenching.
Soil Bearing and Lateral Resistance
An allowable soil bearing pressure of 2,000 pounds per square foot (psf) may be used for the design
of footings having a minimum width of 12 inches and minimum embedment of 12 inches below
lowest adjacent ground surface. This value may be increased by 300 psf for each additional foot of
embedment and 300 psf for each additional foot of foundation width to a maximum value of 3,000
psf. These allowable bearing pressures are applicable for level (ground slope equal to or flatter than
5H: 1 V) conditions only. Bearing values indicated are for total dead loads and frequently applied live
loads and may be increased by Yi for short duration loading (i.e., wind or seismic loads). In utilizing
the above-mentioned allowable bearing capacity and provided our earthwork recommendations are
implemented, settlement due to structural loads is anticipated to be on the order of I-inch.
Differential settlement may be taken as half of the total settlement.
Resistance to lateral loads can be provided by friction acting at the base of foundations and by
passive earth pressure. For concrete/soil frictional resistance, an allowable coefficient of friction of
0.30 may be assumed with dead-load forces. A passive lateral earth pressure of 250 psf per foot of
depth ( or pct) to a maximum of 2,500 psf may be used for the sides of footings poured against
properly compacted fill. This passive pressure is applicable for level (ground slope equal to or flatter
than 5H: 1 V) conditions only. When combining frictional resistance and passive pressure, the passive
pressure should be reduced by one-third. We recommend that the upper I-foot of passive resistance
be neglected. While not anticipated, the structural designer should request from the geotechnical
consultant any passive pressure required for depths greater than 15 feet below existing ground surface
due to site groundwater.
Project No. 13200-01 Page 15 July 3, 2014
'.J
'1
:_J
L_J
_J
..___J
.J
'__J
,-l
4.4
For soldier piles spaced a minimum of 2.5 pile diameters on-center, an allowable passive pressure of 480
pcf (230 pcf below groundwater, if applicable) may be used for passive resistance. The provided passive
pressure is based on an arching factor of 2 and should be limited to a maximum of 10 times the value
provided above (e.g., 480 pcfto a maximum of 4,800 psf). The passive pressure is only applicable for level
(5 horizontal feet to 1 foot vertical or flatter) soil conditions. To develop the full lateral value, provisions
should be made to assure firm contact between the soldier piles and the undisturbed soils. The concrete
placed in the soldier pile excavation below the excavated level should be of adequate strength to transfer
the imposed loads to the surrounding soils. Groundwater may be taken at 15 feet below existing ground
surface. The structural designer should incorporate the appropriate factor of safety and/or load factor in
the design. The provided allowable passive pressure is based on a factor of safety of 1.5.
Lateral Earth Pressures for Retaining Walls
Based on the conceptual grading plan, retaining walls up to approximately 4 feet are proposed on the
easterly and westerly perimeters of the site. The retaining walls are expected to retain the proposed
development.
Lateral earth pressures are provided as equivalent fluid unit weights, in pound per square foot (pst) per
foot of depth or pcf. These values do not contain an appreciable factor of safety, so the retaining wall
designer should apply the applicable factors of safety and/or load factors during design. The following
lateral earth pressures are presented on Table 3 for approved free-draining select granular soils with a
maximum of 35 percent fines (passing the No. 200 sieve per ASTM D-421/422) and Very Low
expansion potential (EI of 20 or less per ASTM D4829). The wall designer should clearly indicate on
the basement wall plans the required sandy soil backfill criteria.
TABLE3
Lateral Earth Pressures -Conventional Backfilled
Retaining Walls
Equivalent Fluid Weight (pct)
Conditions Level Backfill
Approved Backfill Material
Active 35
At Rest 55
Select backfill is recommended for site retaining walls. If the limits of select sandy backfill indicated on
Figure 3 cannot be extended due to property line constraints, the lateral earth pressures should be
increased to an equivalent fluid pressure of 50 pcf and 70 pcf for the active and at-rest condition,
respectively. The lateral earth pressures provided above may be increased by a factor of 1.5 for a 2: 1
(horizontal to vertical) sloping backfill condition.
If the wall can yield enough to mobilize the full shear strength of the soil, it can be designed for
"active" pressure. If the wall cannot yield under the applied load, the earth pressure will be higher.
Project No. 13200-01 Page 16 July 3, 2014
l.i
:_J
_J
_J
4.5
This would include 90-degree comers of retaining walls. Such walls should be designed for "at-rest."
The equivalent fluid pressure values assume free-draining conditions. If conditions other than those
assumed above are anticipated, the equivalent fluid pressure values should be provided on an
individual-case basis by the geotechnical engineer.
Surcharge loading effects from any adjacent structures should be evaluated by the retaining wall
designer. In general, structural loads within a 1: 1 (horizontal to vertical) upward projection from the
bottom of the proposed retaining wall will surcharge the proposed retaining structure. In addition to the
recommended earth pressure, retaining walls adjacent to building structures and streets should be
designed to resist applicable lateral loads. Typical vehicular traffic may be estimated as equivalent to 2
feet of compacted fill, a vertical pressure of 240 psf. The retaining wall designer should contact the
geotechnical engineer for any required geotechnical input in estimating any applicable surcharge loads.
Estimated structural loads of the adjacent buildings are required in order to estimate lateral loads on the
retaining walls.
If required, the retaining wall designer may use a seismic lateral earth pressure increment of 5 pcf. This
increment should be applied in addition to the provided static lateral earth pressure using a triangular
distribution with the resultant acting at H/3 in relation to the base of the retaining structure (where H is
the retained height). Per Section 1803.5.12 of the 2013 CBC, the seismic lateral earth pressure is
applicable to structures assigned to Seismic Design Category D through F for retaining wall structures
supporting more than 6 feet of backfill height. This seismic lateral earth pressure is estimated using the
procedure outlined by the Structural Engineers Association of California (Lew, et al, 2010).
Retaining wall structures should be provided with appropriate drainage and appropriately
waterproofed. To reduce, but not eliminate, saturation of near-surface (upper approximate 1 foot)
soils in front of the retaining walls, the perforated subdrain pipe should be located as low as possible
behind the retaining wall. The outlet pipe should be sloped to drain to a suitable outlet. In general, we
do not recommend retaining wall outlet pipes be connected to area drains. If subdrains are connected
to area drains, special care and information should be provided to homeowners to maintain these
drains. Typical retaining wall drainage is illustrated in Figure 3. It should be noted that the
recommended subdrain does not provide protection against seepage through the face of the wall
and/or efflorescence. Efflorescence is generally a white crystalline powder (discoloration) that results
when water containing soluble salts migrates over a period of time through the face of a retaining
wall and evaporates. If such seepage or efflorescence is undesirable, retaining walls should be
waterproofed to reduce this potential.
Soil bearing and lateral resistance ( friction coefficient and passive resistance) are provided in Section
4.3. Earthwork considerations (temporary backcuts, backfill, compaction, etc.) for retaining walls are
provided in Section 4.1 (Site Earthwork) and the subsequent earthwork related sub-sections.
Temporary Shoring
Temporary shoring is recommended where earthwork removals are to be performed adjacent to existing
buildings located near the property line in the westerly and easterly portions of the site. Temporary
shoring should be designed to retain a minimum of 5 feet for required earthwork removals plus
applicable surcharge loading. It is our understanding that the temporary shoring will be incorporated
into the foundation of the proposed property line 4-foot-high retaining walls which will support the
proposed development, refer to Figure 4.
Project No. 13200-01 Page 17 July 3, 2014
1 __ J
'_J
' J
i L_j
l_J
_J
__ _j
4.6
Typical cantilever temporary shoring, where deflection of the shoring will not impact the performance of
adjacent structures, may be designed using the active equivalent fluid pressures of 40 pounds per square
foot (psf) per foot of depth ( or pct). Braced shoring may be used in areas where the shoring will be
located close to existing structures in order to limit shoring deflections or required due to the proposed
depth of excavation. Braced shoring with a level backfill may be designed using a uniform soil pressure
of 26H in pounds per square foot (psf), where H is equal to the depth in feet of the excavation being
shored. Any building, equipment or traffic loads located within a 1: 1 (horizontal to vertical) projection
from the base of the shoring should be added to the applicable lateral earth pressure. Refer to the
discussion provided in previous Section 4.4. If vehicle traffic is kept at least 10 feet from the shoring, the
traffic surcharge may be neglected. Lateral earth pressures due to traffic loads are provided in Section 4.4.
The shoring designer should contact the geotechnical engineer for any required geotechnical input in
estimating any applicable lateral surcharge loads.
If non-cohesive sands are observed in the excavation continuous lagging should be provided between
the soldier piles. Lagging should be placed in a timely manner during excavation in order to
minimize potential spalling and sloughing. Careful installation of the lagging will be necessary to
achieve bearing against the retained earth. The backfill of the lagging should consist of one sack
sand-cement slurry or compacted moistened granular soil. It should be noted that backfill of the
lagging with compacted granular soil may result in continuation of caving as the excavation depth
progresses. Means and methods are per the contractor in order to ultimately ensure full bearing of
retained earth to the lagging. The soldier piles should be designed for the full anticipated lateral
pressure, however, the pressure on the lagging will be less due to soil arching between the piles. We
recommend that the lagging be designed for the recommended earth pressure but may be limited to a
maximum value of 400 psf if surcharge loads are not present. Lagging placed behind the soldier piles
will negate the soil arching effect.
It is difficult to accurately predict the amount of deflection of the shored embankment. It should be
realized, however, that some deflection will occur. The shoring should be designed to limit deflection
to within tolerable limits. If greater deflection occurs during construction, additional bracing may be
necessary. In areas where less deflection is desired, such as adjacent to existing settlement sensitive
improvements, the shoring should be designed for higher lateral earth pressures.
Passive pressure for isolated pile conditions is provided in Section 4.3.
The contractor should evaluate the potential drilling conditions when planning the installation
methods, refer to Section 4.10 and Appendix B.
Prior to construction, the geotechnical consultant should review any proposed shoring plans from a
geotechnical viewpoint in order to confirm that recommendations have been applied to the design.
Control o(Surface Water and Drainage Control
From a geotechnical perspective, we recommend that compacted finished grade soils adjacent to
proposed residences be sloped away from the proposed residence and towards an approved drainage
device or unobstructed swale. Drainage swales, wherever feasible, should not be constructed within 5
feet of buildings. Where lot and building geometry necessitates that the side yard drainage swales be
routed closer than 5 feet to structural foundations, we recommend the use of area drains together with
drainage swales. Drainage swales used in conjunction with area drains should be designed by the
Project No. 13200-01 Page 18 July 3, 2014
' J
.J
-i
' .. J
j
_J
4.7
4.8
project civil engineer so that a properly constructed and maintained system will prevent ponding
within 5 feet of the foundation. Code compliance of grades is not the purview of the geotechnical
consultant.
Planters with open bottoms adjacent to buildings should be avoided. Planters should not be designed
adjacent to buildings unless provisions for drainage, such as catch basins, liners, and/or area drains, are
made. Overwatering must be avoided.
Preliminary Asphalt Pavement Sections
The following provisional minimum street sections are provided in Table 4 based on an assumed R-
value of 15 for Traffic Indices (Tl) of 4.5 through 6.0. These recommendations must be confirmed with
R-value testing of representative near-surface soils at the completion of grading and after underground
utilities have been installed and backfilled. Final street sections should be confirmed by the project civil
engineer based upon the final design Traffic Index. If requested, LGC Geotechnical will provide
sections for alternate TI values.
TABLE4
Paving Section Options
Assumed Traffic Index 4.5 5 6
R -Value Sub2rade 15 15 15
AC Thickness 4.0 inches 4.0 inches 5 inches
Base Thickness 4.0 inches 6.0 inches 7.5 inches
The thicknesses shown are for minimum thicknesses. Increasing the thickness of any or all of the
above layers will reduce the likelihood of the pavement experiencing distress during its service life.
The above-mentioned recommendations are based on the assumption that proper maintenance and
irrigation of the areas adjacent to the roadway will occur throughout the design life of the pavement.
Failure to maintain a proper maintenance and/or irrigation program may jeopardize the integrity of
the pavement.
Earthwork recommendations regarding aggregate base and subgrade are provided in the previous
section "Site Earthwork" and the related sub-sections of this report.
Soil Corrosivitv
Although not corrosion engineers (LGC Geotechnical is not a corrosion consultant), several
governing agencies in Southern California require the geotechnical consultant to determine the
corrosion potential of soils to buried concrete and metal facilities. We therefore present the results of
our testing with regard to corrosion for the use of the client and other consultants, as they determine
necessary.
Previous corrosion testing was performed on site soils. The results of the soluble sulfate content were
0.06 percent and 0.05 percent and chloride contents of 639 ppm and 1,890 ppm. The resistivity tests
resulted in minimum resistivity values of l,821ohm-centimeters and 1,012 ohm-centimeters and pH
Project No. 13200-01 Page 19 July 3, 2014
_J
. .J
. j
• I I __ J
,--!
l ___ J
' __ J
l _.)
4.9
values of 8.3 and 8.0. Caltrans defines a corrosive area as one where any of the following conditions
exist: the soil contains more than 500 ppm of chlorides, more than 2,000 ppm (0.2 percent) of sulfates,
or a pH of 5.5 or less (Caltrans, 2012). Based on Caltrans Corrosion Guidelines, site soils are
considered corrosive due to chloride test results.
The near-surface soils should be considered to have a severity categorization of "Moderate" and
designated to a class "S 1" per ACI 318, Table 4.2.1 with respect to sulfates. Concrete in direct contact
with the onsite soils can be designed according to ACI 318, section 4.3 using the "S 1" sulfate
classification. This must be verified based on as-graded conditions .
Nonstructural Concrete Flatwork
Nonstructural concrete flatwork (such as walkways, bicycle trails, patio slabs, etc.) has a potential for
cracking due to changes in soil volume related to soil-moisture fluctuations. To reduce the potential
for excessive cracking and lifting, concrete may be designed in accordance with the minimum
guidelines outlined in Table 5. These guidelines will reduce the potential for irregular cracking and
promote cracking along construction joints, but will not eliminate all cracking or lifting. Thickening
the concrete and/or adding additional reinforcement will further reduce cosmetic distress .
TABLES
Nonstructural Concrete Flatwork for Medium Expansion Potential
Homeowner Private Drives Patios/Entryways City Sidewalk Curb
Sidewalks and Gutters
Minimum 4 (nominal) 5 (full) 5 (full) City/ Agency
Thickness (in.) Standard
Presoaking Wet down prior Presoak to 12 Presoak to 12 City/Agency
to placing inches inches Standard
No. 3 at 24 No. 3 at 24 City/Agency Reinforcement -inches on inches on
centers centers Standard
Thickened Edge -8x8 -City/ Agency
(in.) Standard
Saw cut or deep Saw cut or deep Saw cut or deep
open tooljoint open tool joint to open tool joint
Crack Control to a minimum a minimum to a minimum City/Agency
Joints of 1h the of 1h the of 1h the Standard
concrete concrete concrete
thickness thickness thickness
10 feet or
Maximum Joint 5 feet quarter cut 6 feet City/ Agency
Spacing whichever is Standard
closer
Aggregate Base --2 City/ Agency
Thickness (in.) Standard
Project No. 13200-01 Page 20 July 3, 2014
__ J
J
-,
I __j
__ J
' __ J
__ J
To reduce the potential for driveways to separate from the garage slab, the builder may elect to install
dowels to tie these two elements together. Similarly, future homeowners should consider the use of
dowels to connect flatwork to the foundation.
4.10 CIDH Pile Construction
4.11
4.12
Pile borings should be plumb and free of loose or softened material. Extreme care in drilling, placement
of soldier piles or reinforcement steel and the pouring of concrete will be essential to avoid excessive
disturbance of pile boring walls. The soldier pile or reinforcing cage should be installed and the
concrete pumped immediately after drilling is completed. Concrete mix design should include
provisions to minimize shrinkage which can reduce frictional resistance of the pile shaft. Concrete
placement by pumping or tremie tube to the bottom of CIDH excavations is recommended. No pile
boring should be left open overnight. Pile borings should not be drilled immediately adjacent to another
pile until the concrete in the other pile has attained its initial set. A representative from LGC
Geotechnical should be onsite during the drilling of piles to verify the assumptions made during the
design stages.
Caving of the drilled holes may be encountered during installation of the solider piles. Groundwater
may also be encountered depending on the depth. Refer to the boring logs provided in Appendix B. The
contractor should anticipate that any borehole left open for any extended period of time will likely
experience additional caving. If caving occurs during CIDH pile construction, a temporary casing may
be required. Vibratory hammers and oversized predrill are not allowed for casing installation.
Grading and Foundation Plan Review
When available, grading and foundation plans should be reviewed by LGC Geotechnical in order to
verify our geotechnical recommendations are implemented. Updated recommendations and/or
additional field work may be necessary.
Geotechnical Observation and Testing During Construction
The recommendations provided in this report are based on limited subsurface observations and
geotechnical analysis. The interpolated subsurface conditions should be checked in the field during
construction by a representative of LGC Geotechnical. Geotechnical observation and testing is required
per Section 1705 of the 2013 California Building Code (CBC).
Geotechnical observation and/or testing should be performed by LGC Geotechnical at the following
stages:
• During grading (removal bottoms, fill placement, etc);
• During installation of temporary/permanent soldier pile walls;
• During utility trench and retaining wall backfill and compaction;
• After presoaking building pads and other concrete-flatwork subgrades, and prior to placement of
aggregate base or concrete;
• Preparation of pavement subgrade and placement of aggregate base;
Project No. 13200-01 Page 21 July 3, 2014
j
' _J
J
_J
' --i
___J
,_I
• After building and wall footing excavation and prior to placing reinforcement and/or concrete;
and
• When any unusual soil conditions are encountered during any construction operation subsequent
to issuance of this report.
Project No. 13200-01 Page 22 July 3, 2014
. i
. l
-1
I -J
_)
5.0 LIMITATIONS
Our services were performed using the degree of care and skill ordinarily exercised, under similar
circumstances, by reputable soils engineers and geologists practicing in this or similar localities. No other
warranty, expressed or implied, is made as to the conclusions and professional advice included in this report.
This report is based on data obtained from limited observations of the site, which have been extrapolated to
characterize the site. While the scope of services performed is considered suitable to adequately characterize the
site geotechnical conditions relative to the proposed development, no practical evaluation can completely
eliminate uncertainty regarding the anticipated geotechnical conditions in connection with a subject site.
Variations may exist and conditions not observed or described in this report may be encountered during grading
and construction.
This report is issued with the understanding that it is the responsibility of the owner, or of his/her
representative, to ensure that the information and recommendations contained herein are brought to the
attention of the other consultants (at a minimum the civil engineer, structural engineer, landscape architect)
and incorporated into their plans. The contractor should properly implement the recommendations during
construction and notify the owner if they consider any of the recommendations presented herein to be unsafe,
or unsuitable.
The findings of this report are valid as of the present date. However, changes in the conditions of a site can
and do occur with the passage of time, whether they be due to natural processes or the works of man on this
or adjacent properties. The findings, conclusions, and recommendations presented in this report can be relied
upon only if LGC Geotechnical has the opportunity to observe the subsurface conditions during grading and
construction of the project, in order to confirm that our preliminary findings are representative for the site.
This report is intended exclusively for use by the client, any use of or reliance on this report by a third party
shall be at such party's sole risk.
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 modification.
Project No. 13200-01 Page 23 July 3, 2014
,p
•LGC T Geotec::hnical,
--~---~ -=~--=~----'=-==-====::-==-=-~"-_-::_F;= :~::_!~;::~-STA_~ STREET
~-.. -
~EIT:!-iflr!::~:~ ,-~::;, ----~-"" --.. ·--· ~·-~
t
~---.. ~----··
S'.'c
1~1~~~T'1
~
I @' l_1_1_i
~__....c;s,
,.2'=;'
'.~-!(.
EX. 66' SD /};, W•
-/Y"\ li.V ! ;
/
;!'
v..---
'
SCALE: 1''=40'
40' 0 40' 80'
FIGURE 2
Boring Location Map
I
I
~ ~ ....
--::---~~-~ ~;;-
Legend:
B-1
®
1T.D. = 61.5'
GW = 16'
~
~ *
By Others, Approximate Location of Exploratory Boring with
Total Depth and Depth of Groundwater as Indicated
(Leighton, 2005)
Approximate Project Limits
PROJECT NAME I Taylor Morrison -State Street, Carlsbad
PROJECT NO. I 13200-01
ENG.IGEOL. TJL
SCALE 1 inch = 40 feet
DATE July 2014
__ }
EXTENT OF FREE DRAINING SAND BACKFILL, MINIMUM
HEEL WIDTH OR H/2 WHICH EVER IS GREATER
NATIVE BACKFILL COMPACTED
TO MINIMUM 90% RELATIVE
COMPACTION PER ASTM1557-D
12" MINIMUM
18" MAXIMUM
SAND BACKFILL
(EXPANSION INDEX:,; 20, -----"<---,,--....,....,,,..,,....."'"e--'..,
MAXIMUM 35% FINES)
BACKCUT PER OSHA ------1
MINIMUM 1 CUBIC FOOT PER LINEAR FOOT
BURRITO TYPE SUBDRAIN, CONSISTING OF
3/4 INCH CRUSHED ROCK WRAPPED IN
MIRAFI 140N OR APPROVED EQUIVALENT
NOTE:----------~
SUBDRAIN TO DRAIN OFFSITE
FIGURE3
Recommended
Retaining Wall
Backfill Detail
PROJECT NAME
PROJECT NO.
ENG./GEOL.
SCALE
DATE
<I
<I .. 4
NOTE:
I
1-·
I c.,
[jj
I
...J ...J ~
PLACEMENT OF SUBDRAIN
AT BASE OF WALL WILL NOT
PREVENT SATURATION OF SOILS
BELOW AND I OR IN FRONT OF WALL
Taylor Morrison -State Street Carlsbad
13200-01
TJL
Not to Scale
July 2014
[
[
i
I
1'.
[
i!
1·1
le
[
I
I~
r·:
1·
I.
[
,·
le
1·
la
ic
I
l
I"
I l
1. TEMPORARY CONDITION Adjacent Building
(Protect in Place
Removal Bottom
---LGC
-Geoteohni=i, Om,,
~
Passive Pressure for
Temporary Condition
Lateral Earth Pressure plus
Building Surcharge
(Temporary Condition)
Temporary Shoring
Figure 4
Temporary Shoring I
Permanent Retaining Wall Detail
2. PERMANENT CONDITION
Planned Finish Grade
Lateral Earth
Pressure for Proposed
Retaining Wall
Existing Grade
Soldier Pile Wall
~
I
·>· '·• :;:~ ·~·· ....
Adjacent Building
(Protect in Place
Passive Pressure for
Proposed Retaining Wall
SCHEMATIC ONLY
REFER to TEXT FOR
DISCUSSION
CLIENT:
Taylor Morrison
8105 Irvine Center Drive, Suite 1450
Irvine, CA 92618
PROJECT NAME I Taylor Morrison -State Street, Carlsbad
PROJECT NO. I 13200-01
ENG. I GEOL. I TJL
SCALE I No Scale
DA TE I July 2014
-l
_I
' _J
_J
Appendix A
References
'-,
__ )
-,
·-.J
' _)
'--)
j
APPENDIX A
References
Adams Streeter, 2014, Grading Plans for State Street Townhomes, Sheets 1 through 10, Plot date June 27,
2014.
American Society of Civil Engineers (ASCE), 2013, Minimum Design Loads for Buildings and Other
Structures, ASCE/SEI 7-10, Third Printing, 2013.
American Society for Testing and Materials (ASTM), Volume 04.08 Soil and Rock (I):D420-D5876.
Bray, J.D., and Sancio, R. B., 2006, Assessment of Liquefaction Susceptibility of Fine-Grained Soils, Journal
of Geotechnical and Geoenvironmental Engineering, ASCE, pp. 1165-1177, dated September 2006.
California Building Standards Commission, 2013, California Building Code, California Code of Regulations
Title 24, Volumes 1 and 2, dated July 2013.
California Department of Transportation (Caltrans), 2012, Corrosion Guidelines, Version 2.0, dated November
2012.
California Geological Survey (CGS), (Previously California Division of Mines and Geology [CDMG]), 2007,
Fault-Rupture Hazard Zones in California, Alquist-Priolo Earthquake Fault Zoning Act with Index to
Earthquake Fault Zones Maps, Special Publication 42, Interim Revision 2007.
___ , 2008, California Geological Society Special Publication 11 7 A: Guidelines for Evaluating and
Mitigating Seismic Hazards in California.
Division of Mines and Geology, 1996, Geologic Map of the Oceanside, San Luis Rey, and San Marcos 7.5'
Quadrangles, San Diego County, California, Plate 1, dated 1996.
Leighton and Associates, Inc. (Leighton), 2005, Preliminary Geotechnical Investigation, Proposed
Redevelopment of 2531, 2541 and 2551 State Street, Carlsbad, California, Project No. 041742-001,
dated December 7, 2005.
Lew, et al, 2010, Seismic Earth Pressures on Deep Basements, Structural Engineers Association of California
(SEAOC) Convention Proceedings.
LGC Geotechnical, Inc., 2013, Geotechnical Due Diligence, Proposed State Street Townhomes, City of
--. .J Carlsbad, California, Project No. 13200-01, dated December 12, 2013.
-1
Post-Tensioning Institute (PTI), 2008, Standard Requirements for Analysis of Shallow Concrete Foundations
on Expansive Soils, Third Edition (2004), with Addendum No. 1 (May 2007) and No. 2 (May 2008).
United States Geological Survey (USGS), 2008a, "2008 National Seismic Hazard Maps -Fault Parameters"
Retrieved July 1, 2014, from:
http://geohazards.usgs.gov/cfusion/hazfaults search/hf search main.cfm
Project No. 13200-01 A-1 July 3, 2014
j
.. 1
___ , 2008b, "Interactive Deaggregations (Beta)," Retrieved June 4, 2014, from:
https://geohazards.usgs.gov/deaggint/2008/
___ , 2014, U.S. Seismic Design Maps, Retrieved June 4, 2014, from:
http://geohazards.usgs.gov/designmaps/us/batch.php#csv
William S. Krooskos & Associates, 1985, Report of Soil Investigation, Laguna Plaza -Chandler Building,
Laguna Drive & Roosevelt Street, Carlsbad, California, Job No. 85-7257, dated October 24, 1985.
___ , Approximate 40-Scale Plot Plan, Job No. 85-7257, Figure 1.
Project No. 13200-01 A-2 July 3, 2014
AppendixB
_) Field Exploration Logs From Leighton, 2005
',_~)
J
-,
_J
_J
_J
j
-,
GEOTECHNICAL BORING LOG KEY
Date----------Sheet 1 of
Project KEY TO BORING LOG GRAPHICS Project No.
Type of Rig Drilling Co.
Hole Diameter Drive Weight
Elevation Top of Elevation Location
0 ~ a,~ en~ DESCRIPTION C UI -:8--~ Cl) z UIO 'iii ... -Ulen .; ... .co, 'C Cl) ;=o c .... ::::i+' C'll •
l'ISCI) a.Cl) ... c -o Q.o ::I a. c,1£. Cl>U UI a, 0, >Cl) GI Cl> E..J -co. ·--_en Cl)u. cu. :;::, E mm Oc ·o:; iii (!) ... >, ~o Logged By <( C'll a. ... en C CJ en-Sampled By ,~ 5
0 Asphaltic concrete
~: .. J:"'4"" .. Portland cement concrete ~.4•.,: ... "I·
1
Drop
~ CL Inorganic clay of low to medium plasticity; gravelly clay; sandy clay; · <1ltv c!av-lean clav C!i ·---OL ~ ----5 ML Inorganic silt; clayey silt with low plasticity
I Ml1 Inorganic silt; diatomaceous fine sandy or silty soils; elastic silt
~-
ML-Cl Clayey silt to silty clay
i. I ' • a." -• uw Well-graded gravel; gravel-sand mixture, little.or no fines
lo'-' u' UP Poorly graded gravel; gravel-sand mixture, little or no fines O (\o _ D IO lo ;r.· UM
0'
~ ~ uL Clayey gravel; gravel-sand-clay mixture ..... '!>W Well-graded sand; gravelly sand, little or no lines ·:o··_··
SP Poorly graded sand; gravelly sand, little or no fines ... ..... SM Silty sand; poorly graded sand-silt mixture .....
15 ·.· ...
~-:sC
~ Bedrock
-Ground water encountered at time of drilling
-
B-1 Bulk.Sample
20-Core Sample C-1 -
G-1 ~ GrabS=ple
-
R-1 Modified California Sampler (3" 0.D., 2.5 I.D.)
-
SH-I Shelby Tube Sampler (3" O.D.)
-S-1 Standard Penetration Test SPT (Sampler (2" O.D., l.4" I.D.)
25-
-
-
-
-
30
SAMPLE TYPES: TYPE OF TESTS: 4 s SPLIT SPOON G GRAB SAMPLE OS DIRECT SHEAR SA SIEVE ANAL VSIS
R RING SAMPLE SH SHELBY TUBE MD MAXIMUM DENSITY AT ATTERBURG LIMITS
B BULK SAMPLE CN CONSOLIDATION El EXPANSION INDEX
T TUBE SAMPLE CR CORROSION RV R-VALUE
LEIGHTON AND ASSOCIATES, INC.
J!3 UI Cl) I-.... 0
QI
0. >,
I-
J
I ,,.,
)
_ _J
--1
j
---1
~---i
-,
, ____ I
1
_ _J
,, _J
GEOTECHNICAL BORING LOG 8-1
Date B-25-05 Sheet of 3
~~~~~~~~~~-
Project~~~~~~~~~~~S_R~M_/S_t_a_te_S_t_re_e_t~~~~~~~~~~~ Project No.
Type of Rig Drilling Co. West Hazmat Drilling
Hole Diameter 8 in. Drive Weight
Elevation Top of Elevation 35' Location
0 >, CII~ C Ill --i-CJ CII z ;g 'iii ... =-.c C) ,:, CII c .... .a~ n, CII a.CII Cl) CJ >CII (1)(1) c.o .a ii c:,1,1. VICI> f...1 ca. ·--a,U. cu. (!) E E ffilii >, Oc
[i <( n, n. .. ::!i:0
"' C 0
35 0
. .. 30 5 . · . . .. . . ·. : .. .. 50/6" 111.3 12.2 . . . . . . . : : : .. .. . . .. . .. : . : : . .. ..
Cl)-:-, mm n, • -o O· _en ·o:::i u,-
SM
140 pound hammer
2531 State Street
DESCRIPTION
Logged By DLN
Sampled By DLN
ARTIFICIAL FILL (Afu))
@O': Silty CLAY: Brown, moist, soft
UATERNARYT RRACEDEPOSITS t
t 4': Silty SAND: Brown, moist, very dense
041742-001
Hollow-Stem Auger
Drop 30"
Ill -Ill Cl) I--0
Cl) a. >,
I-
HC
25 10 . .. @ IO': Silty coarse SAND with clay: Brown, damp, medium dense
20 15
15 20
10 25
. . : : . .. .. . .. . .. .. : .. .. . . ..
: · . .. : : .. .. . . . .. · . .. . . : : . .. . .. . . . . . . .. . : : . .. . .. . .. . .. : : : . .. . .. . . .. . .. . -: : .. .. . . .. . .. .. .
..... ·: ... , .....
2 41 14.8
3 58 101.2 13.4
4 26
@ 12': Silty SAND: Light brown, damp
@ 15': Silty SAND: Dark brown, moist, dense
@ 16': Ground water encountered
@20': Silty coarse SAND: Light brown, wet, medium dense
@21': Silty SAND: Light brown, wet, medium dense
5 50/6"
SAN11AGO FORMATION (Tsa)
12.9 CL @25': Sandy CLA YSTONE: Light brown, wet, dense
SM @28': Silty fine SANDSTONE: Light brown, very wet
::• ~·-:. : .... 5 30~~~--'-~~-1-~~--'--'-~~-L--~_.._~~~~~~~~~~~~~~~~~~~~~~~~~---~~---1
SAMPLE TYPES:
S SPLIT SPOON
R RING SAMPLE
B BULK SAMPLE
T TUBE SAMPLE
G GRAB SAMPLE
SH SHELBY TUBE
TYPE OF TESTS:
OS DIRECT SHEAR
MD MAXIMUM DENSITY
CN CONSOLIDATION
CR CORROSION
SA SIEVE ANALYSIS
AT ATTERBURG LIMITS
El EXPANSION INDEX
RV R-VALUE
LEIGHTON AND ASSOCIATES, INC.
L_)
'1
'_j
-1
l . .J
__ J
GEOTECHNICAL BORING LOG 8-1
Date ____ 8_-2_5_-_o_s ___ _ Sheet 2 of 3
Project ___________ S~R~M:..:.::..:/S~t=a=te~S~t~re~e~t __________ _ Project No.
Type of Rig Drilling Co. West Hazmat Drilling
Hole Diameter 8 in. Drive Weight 140 pound hammer
Elevation Top of Elevation 35' Location 2531 State Street
ci >-Q)~ ui-:-DESCRIPTION C Ill --g .. (.) Q) z ;g 'iii ~...r rnen =-:Cc, 'C Cll c ... Ill •
111(1) -Cll c..o .a Cl)(.) -c -o >a, C..a, Q, i::)l1.. cc. 1/)Q) (.),
Q)LL. f!-1 ·--_en CllLL :i::i E ailii Oc w C (!) ->-:a:o ·o::i Logged By DLN c( RI 0.. ... en C 0 rn-Sampled By DLN
tJ !:;
s 30 . . .. SANllAGO FORMATION (Continued' <Tsa) .. ·.·· ) -... 6 90 SM @30': Silty SANDSTONE: Light brown, moist, very dense
·:· -:-:-: ..... -... •, .. ·.·· ... -··: -:-:-:··:· -..... .. ·.·· ...
0 35-: -:-:-:·:·· @35': Silty SANDSTONE: Light brown, moist, very dense 7 50/6" 119.7 10.4 -·.·: :· .. . .. . ..
-·: .... :. :··:.
-:·.:· . .-.:·.:
-·.:.::.·. ......
-5 40-•, ... . ·.·· @ 40': Silty SANDSTONE: Light brown, moist, very dense ,• ...
-:": .... :. :··:· 8 80 ..... -.. .... ,• ...
-: :·-:-:· ·:.
'• . .. -·: ·.·· ...
-10 45-. : -:-:-:··:· @ 45': Silty SANDSTONE: Light brown, moist, very dense .. .. -.. ·.·· 9 68 122.3 9.2 . ...
-. · .. ~·· :. :··: .· ..... .. ·.·· -,' ...
-: :-:·-:. :·· ... .. . .. .. ·.·· -IS 50-•' ... @ 50': Silty SANDSTONE: Light brown, moist, dense
-. ·: ·•·· :. :\"· JO 53 •, . .. .. ·.·· -... _·:-~·.;:·:-. ... .. . . ....
-. ...
=·: ...... :-:··:·
041742-001
Hollow-Stem Auger
Drop 30"
rn -rn Cll I-....
0
Q)
C. >-I-
-20 55-:·: :·.: @ 55': Silty SANDSTONE: Trace of clay, light brown, moist, dense
-... 11 68 120.2 12.9
: :--:· :.: . ·:. -•, .. .. ,, .. ... -...... : : : . : : : .
-• .. .. . . . .. ... -25 60
SAMPLE TYPES; TYPE OF TESTS: 4 s SPLIT SPOON G GRAB SAMPLE OS DIRECT SHEAR SA SIEVE ANALYSIS
R RING SAMPLE SH SHELBY TUBE MD MAXIMUM DENSITY AT ATTERBURG LIMITS
B BULK SAMPLE CN CONSOLIDATION El EXPANSION INDEX
T TUBE SAMPLE CR CORROSION RV R.VALUE
LEIGHTON AND ASSOCIATES, INC.
-1.
: _J
_ _J
. 1
, _ __J
--1
[ ___ J
l,
_J
__J
GEOTECHNICAL BORING LOG 8-1
Date --------'8_-2_5c__-_05.c____... __ _ Sheet 3 of 3
Project ___________ S.::.cR:....:M:..:..::__:/S=---=t.:::.at:..:.e.....:S=---=tr:..:e:.c::e-=--t ----------Project No.
Type of Rig Drilling Co. West Hazmat Drilling
Hole Diameter 8 in. Drive Weight 140 pound hammer
Elevation Top of Elevation 35' Location 2531 State Street
>, 0 c,"cf:. en-:-DESCRIPTION C ti) .... ....
i ... 0 Cl) z ~g "iii ... -mm £j ... :c Cl "O Cl) c-::::i-I'll •
l'IICI) c.CI> Cl>O .... c -(.) c.o ::::, Q. oLL UI Cl> o. >Cl) Cl)CI) f..J .... cc. __ .... _rn Cl>LL OLL :.:I E iiitii Os:
iii (!) .... >, :i:O ·cb Logged By DLN <( I'll a. ... rn 0 . (.) rn-
Sampled By DLN
N ~
-25 60 11 t>lS
041742-001
Hollow-Stem Auger
Drop 30"
Ill .... Ill Cl) I--0
Cl)
Q. >,
I-
TERTIARY SANTIAGO FORMATION (Tsa~
-@60': Silty SANDSTONE: Trace of clay, lig-t brown, moist, dense
-Total Depth "" 61. 5 Feet
-Ground water encountered at 16 feet at time of drilling
Backfilled with bentonite grout on 8/25/04
-
-30 65-
-
-
-
-
-35 70-
-
-
-
-
-40 75-
-
-
-
-
-45 80-
-
-
-
-
-50 85-
-
-
-
-
-55 90
SAMPLE TYPES: TYPE OF TESTS: ct s SPLIT SPOON G GRAB SAMPLE OS DIRECT SHEAR SA SIEVE ANALYSIS
R RING SAMPLE SH SHELBY TUBE MD MAXIMUM DENSITY AT ATTERBURG LIMITS
B BULK SAMPLE CN CONSOLIDATION El EXPANSION INDEX
T TUBE SAMPLE CR CORROSION RV R-VALUE
LEIGHTON AND ASSOCIATES, INC.
GEOTECHNICAL BORING LOG 8-2
Date 8-25-05 Sheet of 2
Project SRM/State Street Project No. 041742-001
Drilling Co. West Hazmat Drilling Type of Rig Hollow-Stem Auger
Hole Diameter 8 in. Drive Weight 140 eound hammer Drop 30"
Elevation Top of Elevation 37' Location 2531 State Street
c:i >,
OJ~ fli-:-DESCRIPTION .l!l
C: rn .... .... rn
0 (,) G) z ~g "iii ... -mu, QI
+I .... 5 ... :c CJ) 'C G) c: ... .a'E 111 • I-
111 G) a.Gl a.o .a G) (,) -o -C. QLL. rn Cll (.) . >G) G) Cl) f..J cc. ·---"' 0
_!LL 01.L E E -... Oc: (!) IXI Cll >, :i:0 ·o::i Logged By DLN Cl)
w < 111 ll.. ... Q.
V, 0 (.) u,-->,
Sampled By DLN I-
0 ARTIFICIAL FILL (Afu)
. J 35 @2': Silty CLAY: Dark brown, moist, soft
~ 5 @ S': Silty CLAY: Dark brown, moist, stiff
117.I 11.9
---1
30
_j
SM UATERNARY TERRACE DEPOSITS -------
--1 . . .... a &': Silty SAND: Dark brown, moist, loose ::-:.:-: .....
_j to --SP @ IO': Fine to medium SAND: Brown, moist, medium dense
2 26 5.2
25
l .~:
<
15 ..... SM @ IS': Silty SAND: Dark brown, very moist, dense
L ~ J .. ·.·· .. ...
. :--:-:. :··:. DS
20 ..... 3 SI 118.8 7.6 .. ·.·· · .. ...
: : -:-:. :··: . .. . .. .. ·.·· . ...
20 . : .. -.~-:··:-@20': Sandy CLAY: Dark gray-brown, moist, hard
I --~ 4 50/6" CL @21': Silty SAND: Light brown, wet, dense
15
__ j
@24': Silty CLAY: Dark gray-brown, moist, dense
25 .... SANTIAGO FORMATION -----------------.. ·.·· . .. ... 5 50/4" 118.4 9.4 SM <i]!, 25': Silty SANDSTONE: Light brown, wet, very dense
__J : ~·-:.: .....
10 ..... .. ·.·· . ...
: ·: .... :. :-..·. @ 28': Gravel CONGLOMERATE: Light gray, moist, dense
_J ..... .. ·.··
30
SAMPLE TYPES: TYPE OF TESTS: cf s SPLIT SPOON G GRAB SAMPLE DS DIRECT SHEAR SA SIEVE ANALYSIS
R RING SAMPLE SH SHELBY TUBE MD MAXIMUM DENSITY AT ATIERBURG LIMITS
B BULK SAMPLE CN CONSOLIDATION El EXPANSION INDEX
T TUBE SAMPLE CR CORROSION RV R-VALUE
LEIGHTON AND ASSOCIATES, INC.
i _~;
i .J
_j
l
_.J
_J
_J
J
GEOTECHNICAL BORING LOG 8-2
Date 8-25-05 Sheet 2 of 2
~~~~~~~~~~-
Project ~~~~~~~~~~_S_R_M~/ S_t_a t_e_S_t r_e_e_t ~~~~~~~~~~ Project No.
Type of Rig Drilling Co. West Hazmat Drilling
Hole Diameter 8 in. Drive Weight 140 pound hammer
Elevation Top of Elevation 37' Location 2531 State Street
>, 0 (I)'# tn-:-DESCRIPTION C Ill -....
_g .... .!:! (I) z 1/10 "iii ~ ..... -IIIU, :5 .... .CC) ,:s Cl) ~o c .... n, •
CV Cl> Q.Q) Cl) c.> .... c -o >Cl) Cl) Cl) 1:2.0 ~ ii i:)l.L. 01:2. 1/1 Cl) u. f!...J ·---"' Q)LI. c1.1. .:s E iiit oc iii (!) ->, :i:O ·o::i Logged By DLN <( CV fl. ~ rn C 0 rn-
Sampled By DLN
l'J !'::
30 ..... SANTIAGO FORMATION <Continued) ....... ·.· ... @ 30': Silty SANDSTONE: Light brown, moist, dense -::• .. ·.:.:··:· 6 62 SM
5 -• ..... . . ·.·· ·.· ... -=::··:-:··:· -...... ... .... ... 35-·: :··:-:··:· @35': Silty SANDSTONE: Light brown, moist, very dense 7 50/6" 129.1 8.2 -~ SC @ 36': Silty clayey SANDSTONE: Light gray, wet, dense
0
~ 40 ~. ..... 8 50/6" SM @40': Silty SANDSTONE: Light brown, moist, very dense ....... .. .... -. :-:'· :. :··:.
-5 -• ..... . . .... .. ...
-~: -:-:. :· ·:. @43': Silty SANDSTONE: Dark gray, moist, dense -·· .... . . ·.·· ·.· ... 45 :I 9 50/6" I 13.6 IO.I CL @45': Sandy CLA YSTONE: Dark brown, wet, hard
-IO
-Total Depth= 48 Feet
so-Ground water encountered at 21 feet at time of drilling Backfilled with bentonite grout on 8/25/05
-
-15 -
-....
-
55-
-
-20 -
-
-
60
SAMPLE TYPES: TYPE OF TESTS:
s SPLIT SPOON G GRAB SAMPLE OS DIRECT SHEAR SA SIEVE ANALYSIS
R RING SAMPLE SH SHELBY TUBE MD MAXIMUM DENSITY AT ATTERBURG LIMITS
B BULK SAMPLE CN CONSOLIDATION El EXPANSION INDEX
T TUBE SAMPLE CR CORROSION RV R.VALUE
LEIGHTON AND ASSOCIATES, INC.
041742-001
Hollow-Stem Auger
Drop 30"
1/1 -Ill (I)
I-.... 0
Cl)
Q. >, I-
cf
J
Appendix C
Laboratory Test Results From Leighton, 2005
' _J
' J
__ J
_)
041742-002
APPENDIX C
Laboratory Testing Procedures and Test Results
Chloride Content: Chloride content was tested in accordance with Caltrans Test Method CT422.
The results are presented below:
Sample Location Chloride Content, ppm Chloride Attack Potential*
B-1 @2'-5' 639 Positive
B-2@8'-11' 1,897 Severe
*per City of San Diego Program Guidelines for Design Consultant, 1992.
Direct Shear Tests: Direct shear tests were performed on selected undisturbed samples which were
soaked for a minimum of 24 hours under a surcharge equal to the applied normal force during
testing. After transfer of the sample to the shear box and reloading of the sample, the pore pressures
set up in the sample (due to the transfer) were allowed to dissipate for a period of approximately
I hour prior to application of shearing force. The samples were tested under various normal loads
utilizing a motor-driven, strain-controlled, direct-shear testing apparatus at a strain rate of less
0.05 inches per minute. The test results are presented on the attached figures.
Moisture and Density Determination Tests: Moisture content (ASTM Test Method D2216) and dry
density determinations were performed on relatively undisturbed ring samples obtained from the
test borings and/or trenches. The results of these tests are presented in the boring and/or trench logs.
Where applicable, only the moisture content was detennined from disturbed samples.
Minimum Resistivity and pH Tests: Minimum resistivity and pH tests were performed in general
accordance with Caltrans Test Method CT643 for Steel or CT532 for concrete and standard
geochemical methods. The results are presented in the table below:
Sample Sample Description pH Minimum Resistivity
Location (ohms-cm)
B-1@ 5'-10' CL, Sandy Clay 8.33 1,821
B-2@8'-11' Silty SAND (SM) 8.00 1,012
C-1
I _j
_._J
-1
__ I
-_/
-J
041742-002
APPENDIX C (Continued)
Soluble Sulfates: The soluble sulfate contents of selected samples were determined by standard
geochemical methods (Caltrans Test Method CT4 I 7). The test results are presented in the table
below:
Sample Location Sample Description Sulfate Potential Degree of
Content(%) Sulfate Attack*
B-1 @2'-5' Sandy CLAY (CL) 0.06 Negligible
B-3 @8'-11' Silty SAND (SC) 0.045 Negligible
* Based on the 1997 edition of the Uniform Building Code, Table No. 19-A-4, prepared by the
International Conference of Building Officials (ICBO, 1997).
Hydro-consolidation Tests: Hydro-consolidation tests were performed on selected relatively
undisturbed ring samples. Samples were placed in a consolidometer and a load approximately equal
to the in-situ overburden pressure was applied. Water was then added to the sample and the percent
hydro-consolidation for the load cycle was recorded as the ratio of the amount of vertical
compression to the original 1-inch height. The percent hydro-consolidation is presented on the
attached figure.
C-2
__ i
0 1000 2000 3000 4000 5000 6000
Vertical Stress (psf)
Boring Location B-2 Deformation Rate 0.05 infmin
Sample Depth (feet} 15'
Sample Description Brown Silty Sand (SM)
Average Strength Parameters
Peak Friction Angle, $'peak (deg) 47
Cohesion, c'peak (psf) 900
®0.2in. Friction Angle, <l>'@o.z" (deg) 47
Cohesion, c'@oz" (psf) 800
DIRECT SHEAR SUMMARY
Relaxed
Project No.
Project Name
Friction Angle, <1>',eiaxed (deg)
Cohesion, c'relaxed (psf)
041742-001
SRM/State Street
46
350
- J
• _I
\ ___ j
_)
~ «81 Leighton and Associates, Inc.
Project Name: SRM I STATE STREET
Project No.: 041742-001
Boring No.: ~-
Sample No.: 8-1-5.0
One-Dimensional Swell or Settlement
Potential of Cohesive Soils
(ASTM D 4546)
Tested By: BCC Date: 9/27/2005
Checked By: Date: ____ _
Sample Type: IN SITU
Depth (ft.) 5.0-6.5
Sample Description: SM: BROWN SIL TY SAND
Initial Dry Density (pct): 111.3 Final Dry Density (pcf): 111.6
Initial Moisture (%): 12.2 Final Moisture(%): 17.6
Initial Length (in.): 1.0000 Initial Void ratio: 0.5149
Initial Dial Reading: 0.0000 Specific Gravity(assumed): 2.70
Diameter(in): 2.416 Initial Saturation(%) 63.8
Apparent Load Swell(+) Corrected Pressure (p) Final Reading Thickness Compliance Settlement(-) Void Ratio Deformation (ksf) (in) (in) (%) o/o of Sample (%) Thickness
(),27 0;001.2 0.9988 0.00 -0.12 0.5131 -0.12
():£~4 • 0.0Q.24 0.9976 0.00 -0.24 0.5112 -0.24
H20 0,-0027 .. 0.9973 0.00 -0.27 0.5108 -0.27
Percent Swell I Settlement After Inundation =I -0.03
0 1a 0:::
"'O 'ci >
0.5200
0.5100
0.100
jvoid Ratio -Log Pressure Curve J
... --...... "'--""' i"-. ' l Inundate with }-------~
water
Log Pressure (ksf)
-
I I
---
1.000
Rev. 08-04
COLLAPSE-SWELL B-1
AppendixD
__ J General Earthwork & Grading Specifications
__ j
_J
, _ _J
__ I
I _J
i
I -i
J
J
~I
_J
General Earthwork and Grading Specifications for Rough Grading
1.0 General
1.1 Intent
1.2
These General Earthwork and Grading Specifications are for the grading and earthwork
shown on the approved grading plan(s) and/or indicated in the geotechnical report(s). These
Specifications are a part of the recommendations contained in the geotechnical report(s). In
case of conflict, the specific recommendations in the geotechnical report shall supersede these
more general Specifications. Observations of the earthwork by the project Geotechnical
Consultant during the course of grading may result in new or revised recommendations
that could supersede these specifications or the recommendations in the geotechnical report(s).
The Geotechnical Consultant of Record
Prior to commencement of work, the owner shall employ a qualified Geotechnical Consultant
of Record (Geotechnical Consultant). The Geotechnical Consultant shall be responsible for
reviewing the approved geotechnical report(s) and accepting the adequacy of the preliminary
geotechnical findings, conclusions, and recommendations prior to the commencement of the
grading.
Prior to commencement of grading, the Geotechnical Consultant shall review the "work
plan" prepared by the Earthwork Contractor (Contractor) and schedule sufficient personnel to
perform the appropriate level of observation, mapping, and compaction testing.
During the grading and earthwork operations, the Geotechnical Consultant shall observe,
map, and document the subsurface exposures to verify the geotechnical design assumptions. If
the observed conditions are found to be significantly different than the interpreted
assumptions during the design phase, the Geotechnical Consultant shall inform the owner,
recommend appropriate changes in design to accommodate the observed conditions, and
notify the review agency where required.
The Geotechnical Consultant shall observe the moisture-conditioning and processing of the
subgrade and fill materials and perform relative compaction testing of fill to confirm that the
attained level of compaction is being accomplished as specified. The Geotechnical Consultant
shall provide the test results to the owner and the Contractor on a routine and frequent basis.
1.3 The Earthwork Contractor
The Earthwork Contractor (Contractor) shall be qualified, experienced, and knowledgeable
in earthwork logistics, preparation and processing of ground to receive fill, moisture-
conditioning and processing of fill, and compacting fill. The Contractor shall review and
accept the plans, geotechnical report(s), and these Specifications prior to commencement of
grading. The Contractor shall be solely responsible for performing the grading in accordance
with the project plans and specifications. The Contractor shall prepare and submit to the
owner and the Geotechnical Consultant a work plan that indicates the sequence of earthwork
grading, the number of "equipment" of work and the estimated quantities of daily earthwork
General Earthwork and Grading Specifications for Rough Grading Page 1
. .J
i
-,
__ J
.. J
. 1
2.0
contemplated for the site prior to commencement of grading. The Contractor shall inform
the owner and the
Geotechnical Consultant of changes in work schedules and updates to the work plan at least
24 hours in advance of such changes so that appropriate personnel will be available for
observation and testing. The Contractor shall not assume that the Geotechnical Consultant is
aware of all grading operations .
The Contractor shall have the sole responsibility to provide adequate equipment and methods
to accomplish the earthwork in accordance with the applicable grading codes and agency
ordinances, these Specifications, and the recommendations in the approved geotechnical
report(s) and grading plan(s). If, in the opinion of the Geotechnical Consultant, unsatisfactory
conditions, such as unsuitable soil, improper moisture condition, inadequate compaction,
insufficient buttress key size, adverse weather, etc., are resulting in a quality of work less
than required in these specifications, the Geotechnical Consultant shall reject the work and
may recommend to the owner that construction be stopped until the conditions are rectified. It
is the contractor's sole responsibility to provide proper fill compaction.
Preparation of Areas to be Filled
2.1
2.2
Clearing and Grubbing
Vegetation, such as brush, grass, roots, and other deleterious material shall be sufficiently
removed and properly disposed of in a method acceptable to the owner, governing agencies,
and the Geotechnical Consultant.
The Geotechnical Consultant shall evaluate the extent of these removals depending on
specific site conditions. Earth fill material shall not contain more than 1 percent of organic
materials (by volume). Nesting of the organic materials shall not be allowed.
If potentially hazardous materials are encountered, the Contractor shall stop work in the
affected area, and a hazardous material specialist shall be informed immediately for proper
evaluation and handling of these materials prior to continuing to work in that area.
As presently defined by the State of California, most refined petroleum products (gasoline,
diesel fuel, motor oil, grease, coolant, etc.) have chemical constituents that are considered to be
hazardous waste. As such, the indiscriminate dumping or spillage of these fluids onto the
ground may constitute a misdemeanor, punishable by fines and/or imprisonment, and shall
not be allowed. The contractor is responsible for all hazardous waste relating to his work. The
Geotechnical Consultant does not have expertise in this area. If hazardous waste is a concern,
then the Client should acquire the services of a qualified environmental assessor .
Processing
Existing ground that has been declared satisfactory for support of fill by the Geotechnical
Consultant shall be scarified to a minimum depth of 6 inches. Existing ground that is not
satisfactory shall be over-excavated as specified in the following section. Scarification shall
continue until soils are broken down and free of oversize material and the working surface is
reasonably uniform, flat, and free of uneven features that would inhibit uniform compaction.
General Earthwork and Grading Specifications for Rough Grading Page2
_)
J
,_J
_)
_J
2.3 Over-excavation
2.4
2.5
In addition to removals and over-excavations recommended in the approved geotechnical
report(s) and the grading plan, soft, loose, dry, saturated, spongy, organic-rich, highly
fractured or otherwise unsuitable ground shall be over-excavated to competent ground as
evaluated by the Geotechnical Consultant during grading.
Benching
Where fills are to be placed on ground with slopes steeper than 5: 1 (horizontal to vertical units),
the ground shall be stepped or benched. Please see the Standard Details for a graphic
illustration. The lowest bench or key shall be a minimum of 15 feet wide and at least 2 feet
deep, into competent material as evaluated by the Geotechnical Consultant. Other benches
shall be excavated a minimum height of 4 feet into competent material or as otherwise
recommended by the Geotechnical Consultant. Fill placed on ground sloping flatter than 5:1
shall also be benched or otherwise over-excavated to provide a flat subgrade for the fill.
Evaluation/Acceptance of Fill Areas
All areas to receive fill, including removal and processed areas, key bottoms, and benches,
shall be observed, mapped, elevations recorded, and/or tested prior to being accepted by the
Geotechnical Consultant as suitable to receive fill. The Contractor shall obtain a written
acceptance from the Geotechnical Consultant prior to fill placement. A licensed surveyor
shall provide the survey control for determining elevations of processed areas, keys, and
benches.
3.0 Fill Material
3.1 General
3.2
Material to be used as fill shall be essentially free of organic matter and other deleterious
substances evaluated and accepted by the Geotechnical Consultant prior to placement. Soils
of poor quality, such as those with unacceptable gradation, high expansion potential, or low
strength shall be placed in areas acceptable to the Geotechnical Consultant or mixed with other
soils to achieve satisfactory fill material.
Oversize
Oversize material defined as rock, or other irreducible material with a maximum dimension
greater than 8 inches, shall not be buried or placed in fill unless location, materials, and
placement methods are specifically accepted by the Geotechnical Consultant. Placement
operations shall be such that nesting of oversized material does not occur and such that
oversize material is completely surrounded by compacted or densified fill. Oversize material
shall not be placed within 10 vertical feet of finish grade or within 2 feet of future utilities or
underground construction.
General Earthwork and Grading Specifications for Rough Grading Page3
-l
. _j
--,
_J
. '
,, ___ J
-,
3.3 Import
If importing of fill material is required for grading, proposed import material shall meet the
requirements of the geotechnical consultant. The potential import source shall be given to the
Geotechnical Consultant at least 48 hours (2 working days) before importing begins so that its
suitability can be determined and appropriate tests performed.
4. 0 Fill Placement and Compaction
4.1
4.2
4.3
4.4
4.5
Fill Layers
Approved fill material shall be placed in areas prepared to receive fill (per Section 3.0) in
near-horizontal layers not exceeding 8 inches in loose thickness. The Geotechnical
Consultant may accept thicker layers if testing indicates the grading procedures can
adequately compact the thicker layers. Each layer shall be spread evenly and mixed
thoroughly to attain relative uniformity of material and moisture throughout.
Fill Moisture Conditioning
Fill soils shall be watered, dried back, blended, and/or mixed, as necessary to attain a
relatively uniform moisture content at or slightly over optimum. Maximum density and
optimum soil moisture content tests shall be performed in accordance with the American
Society of Testing and Materials (ASTM Test Method D 1557) .
Compaction of Fill
After each layer has been moisture-conditioned, mixed, and evenly spread, it shall be
uniformly compacted to not less than 90 percent of maximum dry density (ASTM Test
Method D1557). Compaction equipment shall be adequately sized and be either specifically
designed for soil compaction or of proven reliability to efficiently achieve the specified level of
compaction with uniformity.
Compaction o{Fill Slopes
In addition to normal compaction procedures specified above, compaction of slopes shall be
accomplished by backrolling of slopes with sheepsfoot rollers at increments of 3 to 4 feet in
fill elevation, or by other methods producing satisfactory results acceptable to the
Geotechnical Consultant. Upon completion of grading, relative compaction of the fill, out to
the slope face, shall be at least 90 percent of maximum density per ASTM Test Method D1557.
Compaction Testing
Field tests for moisture content and relative compaction of the fill soils shall be performed
by the Geotechnical Consultant. Location and frequency of tests shall be at the Consultant's
discretion based on field conditions encountered. Compaction test locations will not
necessarily be selected on a random basis. Test locations shall be selected to verify
adequacy of compaction levels in areas that are judged to be prone to inadequate compaction
(such as close to slope faces and at the fill/bedrock benches).
General Earthwork and Grading Specifications for Rough Grading Page4
J
__ j
_)
_.J
,J
5.0
4.6
4.7
Frequency of Compaction Testing
Tests shall be taken at intervals not exceeding 2 feet in vertical rise and/or 1,000 cubic yards of
compacted fill soils embankment. In addition, as a guideline, at least one test shall be taken
on slope faces for each 5,000 square feet of slope face and/or each 10 feet of vertical height
of slope. The Contractor shall assure that fill construction is such that the testing schedule
can be accomplished by the Geotechnical Consultant. The Contractor shall stop or slow
down the earthwork construction if these minimum standards are not met.
Compaction Test Locations
The Geotechnical Consultant shall document the approximate elevation and horizontal
coordinates of each test location. The Contractor shall coordinate with the project surveyor to
assure that sufficient grade stakes are established so that the Geotechnical Consultant can
determine the test locations with sufficient accuracy. At a minimum, two grade stakes within
a horizontal distance of 100 feet and vertically less than
5 feet apart from potential test locations shall be provided.
Subdrain Installation
Subdrain systems shall be installed in accordance with the approved geotechnical report(s), the
grading plan, and the Standard Details. The Geotechnical Consultant may recommend additional
subdrains and/or changes in subdrain extent, location, grade, or material depending on conditions
encountered during grading. All subdrains shall be surveyed by a land surveyor/civil engineer for line
and grade after installation and prior to burial. Sufficient time should be allowed by the Contractor for
these surveys.
6. 0 Excavation
Excavations, as well as over-excavation for remedial purposes, shall be evaluated by the Geotechnical
Consultant during grading. Remedial removal depths shown on geotechnical plans are estimates only.
The actual extent of removal shall be determined by the Geotechnical Consultant based on the field
evaluation of exposed conditions during grading. Where fill-over-cut slopes are to be graded, the cut
portion of the slope shall be made, evaluated, and accepted by the Geotechnical Consultant prior to
placement of materials for construction of the fill portion of the slope, unless otherwise recommended
by the Geotechnical Consultant.
7. 0 Trench Backfills
7.1
7.2
The Contractor shall follow all OHSA and Cal/OSHA requirements for safety of trench
excavations.
All bedding and backfill of utility trenches shall be done in accordance with the applicable
provisions of Standard Specifications of Public Works Construction. Bedding material shall
have a Sand Equivalent greater than 30 (SE>30). The bedding shall be placed to 1 foot over
General Earthwork and Grading Specifications for Rough Grading Page5
--i
J
-1
--,
,-,
_J
_J
_ _j
~ _J
I __ _j
_J
7.3
7.4
7.5
the top of the conduit and densified by jetting. Backfill shall be placed and densified to a
minimum of 90 percent of maximum from 1 foot above the top of the conduit to the surface.
The jetting of the bedding around the conduits shall be observed by the Geotechnical
Consultant.
The Geotechnical Consultant shall test the trench backfill for relative compaction. At least one
test should be made for every 300 feet of trench and 2 feet of fill.
Lift thickness of trench backfill shall not exceed those allowed in the Standard Specifications
of Public Works Construction unless the Contractor can demonstrate to the Geotechnical
Consultant that the fill lift can be compacted to the minimum relative compaction by his
alternative equipment and method.
General Earthwork and Grading Specifications for Rough Grading Page6