HomeMy WebLinkAboutCT 80-46; HIGHLAND DRIVE 5 LOT SF RESIDENCES; UPDATE GEOTECHNICAL INVESTIGATION HIGHLAND 5; 2021-12-29UPDATE
GEOTECHNICAL INVESTIGATION
HIGHLAND 5
2908 – 2924 HIGHLAND DRIVE
CARLSBAD, CALIFORNIA
PREPARED FOR
DECEMBER 29, 2021
PROJECT NO. G2861-11-01
California West
Project No. G2861-11-01
December 29, 2021
California West Communities
5927 Priestly Drive, Suite 110
Carlsbad, California 92008
Attention: Mr. Matt Howe
Subject: UPDATE GEOTECHNICAL INVESTIGATION
HIGHLAND 5
2908 – 2924 HIGHLAND DRIVE
CARLSBAD, CALIFORNIA
Dear Mr. Howe:
In accordance with your request and authorization of our Proposal No. LG-21597 dated December 6th
2021, we herein submit the results of our update geotechnical investigation for the subject project. We
prepared this report to evaluate the underlying soil and geologic conditions and potential geologic
hazards, and to assist in the design of the proposed residential subdivision and associated
improvements.
The accompanying report presents the results of our study and conclusions and recommendations
pertaining to geotechnical aspects of the proposed project. The site is suitable for the proposed
residential subdivision provided the recommendations of this report are incorporated into the design
and construction of the planned project.
Should you have questions regarding this report, or if we may be of further service, please contact the
undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
Ken W. Haase
Senior Staff Geologist
Shawn Foy Weedon
GE 2714
John Hoobs
CEG 1524
KWH:SFW:JH:arm
(e-mail) Addressee
GEOCON
INCORPORATED
G E OT E CHN I CAL ■E NV I RONMENTA L ■ MA T ER I A L S
6960 Flanders Drive ■ Son Diego, California 92121-297 4 ■ Telephone 858.558.6900 ■ Fax 858.558.6159
TABLE OF CONTENTS
1.PURPOSE AND SCOPE ................................................................................................................. 1
2.SITE AND PROJECT DESCRIPTION ........................................................................................... 2
3.GEOLOGIC SETTING .................................................................................................................... 3
4.SOIL AND GEOLOGIC CONDITIONS ........................................................................................ 4
4.1 Undocumented Fill (Unmapped) ........................................................................................... 44.2 Topsoil (Unmapped) .............................................................................................................. 44.3 Old Paralic Deposits (Qop) .................................................................................................... 5
5.GROUNDWATER .......................................................................................................................... 5
6.GEOLOGIC HAZARDS ................................................................................................................. 56.1 Regional Faulting and Seismicity .......................................................................................... 5
6.2 Ground Rupture ..................................................................................................................... 76.3 Liquefaction ........................................................................................................................... 76.4 Storm Surge, Tsunamis, and Seiches ..................................................................................... 7
6.5 Landslides .............................................................................................................................. 86.6 Erosion ................................................................................................................................... 8
7.CONCLUSIONS AND RECOMMENDATIONS ........................................................................... 9
7.1 General ................................................................................................................................... 97.2 Excavation and Soil Characteristics .................................................................................... 107.3 Grading ................................................................................................................................ 11
7.4 Subdrains ............................................................................................................................. 137.5 Seismic Design Criteria ....................................................................................................... 137.6 Shallow Foundations ........................................................................................................... 15
7.7 Post-Tensioned Foundations ................................................................................................ 167.8 Concrete Slabs-On-Grade .................................................................................................... 197.9 Exterior Concrete Flatwork ................................................................................................. 20
7.10 Retaining Walls ................................................................................................................... 217.11 Lateral Loading .................................................................................................................... 257.12 Preliminary Pavement Recommendations ........................................................................... 25
7.13 Preliminary Paver Recommendations .................................................................................. 29
7.14 Site Drainage and Moisture Protection ................................................................................ 31
7.15 Foundation Plan Review ...................................................................................................... 32
7.16 Testing and Observation Services During Construction ...................................................... 32
LIMITATIONS AND UNIFORMITY OF CONDITIONS
MAPS AND ILLUSTRATIONS Figure 1, Geologic Map Figure 2, Geologic Cross Section, 1 – 1’
APPENDIX A PREVIOUS BORING LOGS
APPENDIX B PREVIOUS LABORATORY TESTING
APPENDIX C RECOMMENDED GRADING SPECIFICATIONS
LIST OF REFERENCES
Geocon Project No. G2861-11-01 - 1 - December 29, 2021
UPDATE GEOTECHNICAL INVESTIGATION
1. PURPOSE AND SCOPE
This report presents the results of our update geotechnical investigation for the proposed residential
sub-division located at 2908 – 2924 Highland Drive in the City of Carlsbad, California (see Vicinity
Map, Figure 1).
Vicinity Map
The purpose of this update geotechnical investigation is to evaluate the surface and subsurface soil
conditions and general site geology, and to identify geotechnical constraints that may affect
development of the property including faulting, liquefaction and seismic shaking based on the 2019
CBC seismic design criteria. In addition, we provided recommendations for remedial grading, shallow
foundations, concrete slab-on-grade, concrete flatwork, preliminary pavement and retaining walls.
We reviewed the following plans and report in preparation of this report:
1.Grading Plans for: Highland, 2908 – 2924 Highland Drive, Carlsbad, California, prepared by Pasco, Laret, Suiter & Associates, dated August 27, 2021.
2.Landscape Construction Documents for: Highland Subdivision, prepared by Stone Grove Landscape Architects, dated August 21, 2021
3.Preliminary Geotechnical Evaluation, Proposed 5-Lot Subdivision, Tract No. 80-46,
Carlsbad, San Diego County, California, Assessor’s Parcel Numbers (APN’S) 156-200-28, -
29, 30, -31, -32. prepared by GeoSoils, Inc., dated February 1, 2021 (W.O. 8037-A-SC).
Geocon Project No. G2861-11-01 - 2 - December 29, 2021
The scope of this investigation included reviewing readily available published and unpublished
geologic literature (see List of References), performing engineering analyses and preparing this report.
Appendix A presents the exploratory boring logs from the previous investigation performed by
GeoSoils, Inc. The details of the previous laboratory tests and a summary of the test results performed
by GeoSoils, Inc. are shown in Appendix B and on the boring logs in Appendix A. The recommended
grading specifications are presented in Appendix C.
2. SITE AND PROJECT DESCRIPTION
The approximately 1.4 acre property consists of two residential houses with a long driveway providing
access from Highland Drive. The site is located south of an existing park, east of Highland Drive,
north of an existing single-family residence and Newland Court and west of existing houses. Existing
grades are gently to moderately sloping to the west towards Highland Drive. Elevations at the site
range between approximately 163 to 184 feet Mean Sea Level (MSL) from west to east. The high
point at the site is roughly 100 feet from the eastern property line. The Existing Site Map shows the
current site conditions.
Existing Site Map
We understand the project will consist of demolishing the existing structures and improvements to
construct a 5-lot residential subdivision with accompanying accessory dwelling units (ADUs),
driveways, utilities and landscaping. We anticipate the residential structures will be one to two stories.
Geocon Project No. G2861-11-01 - 3 - December 29, 2021
Two storm water basins on the west and south side and two buried storm trap structures within the
driveway are planned at the property. The Geologic Map, Figure 1, shows the proposed site layout.
The locations, site descriptions, and proposed development are based on our site reconnaissance,
review of published geologic literature, field investigations, and discussions with project personnel. If
development plans differ from those described herein, Geocon Incorporated should be contacted for
review of the plans and possible revisions to this report.
3. GEOLOGIC SETTING
Regionally, the site is located in the Peninsular Ranges geomorphic province. The province is bounded
by the Transverse Ranges to the north, the San Jacinto Fault Zone on the east, the Pacific Ocean
coastline on the west, and the Baja California on the south. The province is characterized by elongated
northwest-trending mountain ridges separated by straight-sided sediment-filled valleys. The northwest
trend is further reflected in the direction of the dominant geologic structural features of the province
that are northwest to west-northwest trending folds and faults, such as the nearby Rose Canyon fault
zone.
Locally, the site is within the coastal plain of San Diego County. The coastal plain is underlain by a
thick sequence of relatively undisturbed and non-conformable sedimentary bedrock units that thicken
to the west and range in age from Upper Cretaceous age through the Pleistocene age which have been
deposited on Cretaceous to Jurassic age igneous and volcanic bedrock. Geomorphically, the coastal
plain is characterized by a series of 21, stair-stepped marine terraces (younger to the west) that have
been dissected by west flowing rivers. The coastal plain is a relatively stable block that is dissected by
relatively few faults consisting of the potentially active La Nacion Fault Zone and the active Rose
Canyon Fault Zone.
The site is located on the northwestern portion of the coastal plain. Marine sedimentary units make up
the geologic sequence encountered on the site and consist of Pleistocene-age Old Paralic Deposits.
The deposits are shallow marine deposits generally consisting of sand and silty sand units
interfingered with layers of silt and clay. This unit may be up to roughly 50 feet thick in the vicinity of
the site. The Regional Geologic Map shows the geologic units in the area of the site.
Geocon Project No. G2861-11-01 - 4 - December 29, 2021
Regional Geologic Map
4. SOIL AND GEOLOGIC CONDITIONS
The site is underlain by one formational unit (consisting of the Old Paralic Deposits). The occurrence,
distribution, and description of each unit encountered is shown on the Geologic Map, Figure 1 and on
the boring logs in Appendix A. The Geologic Cross-Section, Figure 2, show the approximate
subsurface relationship between the geologic units. We prepared the geologic cross-section using
interpolation between exploratory excavations and observations; therefore, actual geotechnical
conditions may vary from those illustrated and should be considered approximate. The surficial soil
and geologic units are described herein in order of increasing age.
4.1 Undocumented Fill (Unmapped)
Although not encountered during the previous investigation, we anticipate undocumented fill is
present beneath the existing structures at the site. The undocumented fill most likely possesses a “very
low” to “low” expansion index (expansion index of 50 or less) and we expect it is composed of
material similar to the Old Paralic Deposits. The undocumented fill can be reused as new compacted
fill during grading operations provided it is free of deleterious material.
4.2 Topsoil (Unmapped)
Topsoil was encountered in the previous borings up to approximately 1 foot in thickness. In general,
the topsoil consists of loose to medium dense, moist, silty sand with numerous roots throughout and
possesses a “very low” to “low” expansion index (expansion index of 50 or less). The topsoil is not
Geocon Project No. G2861-11-01 - 5 - December 29, 2021
considered suitable in its current condition for the support of foundations or structural fill and remedial
grading will required. The topsoil can be reused for new compacted fill during grading operations
provided it is generally free of roots and debris.
4.3 Old Paralic Deposits (Qop)
The Quaternary-age Old Paralic Deposits exist near existing grade across the site. These deposits
generally consist of dense to very dense, reddish brown and olive brown, silty, fine to coarse
sandstone. The Old Paralic Deposits typically possess a “very low” expansion potential (expansion
index of 20 or less) and a “S0” sulfate class. The Old Paralic Deposits are considered suitable to
support the planned fill and foundation loads for the development.
5. GROUNDWATER
Groundwater or seepage conditions were not reported during the site investigation. However, it is not
uncommon for shallow seepage conditions to develop where none previously existed when a property
is irrigated or uncontrolled infiltration is implemented. Seepage is dependent on seasonal precipitation,
irrigation, land use, among other factors, and varies as a result. Proper surface drainage will be
important to future performance of the project. We expect groundwater is deeper than about 50 feet
below existing grade. We do not expect groundwater to be encountered during construction of the
proposed development.
6. GEOLOGIC HAZARDS
6.1 Regional Faulting and Seismicity
A review of the referenced geologic materials and our knowledge of the general area indicate that the
site is not underlain by active, potentially active, or inactive faults. An active fault is defined by the
California Geological Survey (CGS) as a fault showing evidence for activity within the last
11,700 years. The site is not located within a State of California Earthquake Fault Zone.
The USGS has developed a program to evaluate the approximate location of faulting in the area of
properties. The following figure shows the location of the existing faulting in the San Diego County
and Southern California region. The fault traces are shown as solid, dashed and dotted that represent
well-constrained, moderately constrained and inferred, respectively. The fault line colors represent
faults with ages less than 150 years (red), 15,000 years (orange), 130,000 years (green), 750,000 years
(blue)(not shown on map) and 1.6 million years (black).
Geocon Project No. G2861-11-01 - 6 - December 29, 2021
Faults in Southern California
The San Diego County and Southern California region is seismically active. The following figure
presents the occurrence of earthquakes with a magnitude greater than 2.5 from the period of 1900
through 2015 according to the Bay Area Earthquake Alliance website.
Earthquakes in Southern California
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Geocon Project No. G2861-11-01 - 7 - December 29, 2021
Considerations important in seismic design include the frequency and duration of motion and the soil
conditions underlying the site. Seismic design of structures should be evaluated in accordance with the
California Building Code (CBC) guidelines currently adopted by the local agency.
6.2 Ground Rupture
Ground surface rupture occurs when movement along a fault is sufficient to cause a gap or rupture
where the upper edge of the fault zone intersects the ground surface. The potential for ground rupture
is considered to be very low due to the absence of active faults at the subject site.
6.3 Liquefaction
Liquefaction typically occurs when a site is located in a zone with seismic activity, onsite soils are
cohesionless or silt/clay with low plasticity, groundwater is encountered within 50 feet of the surface
and soil densities are less than about 70 percent of the maximum dry densities. If the four previous
criteria are met, a seismic event could result in a rapid pore water pressure increase from the
earthquake-generated ground accelerations. Due to the lack of a permanent, near-surface groundwater
table and the very dense nature of the underlying Old Paralic Deposits, liquefaction potential for the
site is considered very low.
6.4 Storm Surge, Tsunamis, and Seiches
Storm surges are large ocean waves that sweep across coastal areas when storms make landfall. Storm
surges can cause inundation, severe erosion and backwater flooding along the water front. The site is
located approximately one mile from the Pacific Ocean and is at an elevation of about 160 feet or
greater above Mean Sea Level (MSL). Therefore, the potential of storm surges affecting the site is
considered low.
A tsunami is a series of long period waves generated in the ocean by a sudden displacement of large
volumes of water. Causes of tsunamis include underwater earthquakes, volcanic eruptions, or offshore
slope failures. The potential for the site to be affected by a tsunami is negligible due to the distance
from the Pacific Ocean and the site elevation.
A seiche is a run-up of water within a lake or embayment triggered by fault- or landslide-induced
ground displacement. The site is located approximately ¾ of a mile from the Buena Vista Lagoon but
is located 150 feet higher than the lagoon and is not located downstream from this body of water.
Therefore, the risk of seiches affecting the site is negligible.
Geocon Project No. G2861-11-01 - 8 - December 29, 2021
6.5 Landslides
We did not observe evidence of previous or incipient slope instability at the site during our study and
the property is relatively flat to gently sloping. Published geologic mapping indicates landslides are
not present on or adjacent to the site. Therefore, in our professional opinion, the potential for a
landslide is not a significant concern for this project.
6.6 Erosion
The site is gently to moderately sloping and is not located adjacent to the Pacific Ocean coast or a free-
flowing drainage where active erosion is occurring. Provided the engineering recommendations herein
are followed and the project civil engineer prepares the grading plans in accordance with generally-
accepted regional standards, we do not expect erosion to be a major impact to site development. In
addition, we expect the proposed development would not increase the potential for erosion if properly
designed.
Geocon Project No. G2861-11-01 - 9 - December 29, 2021
7. CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7.1.1 We did not encounter soil or geologic conditions during our exploration that would preclude
the proposed development, provided the recommendations presented herein are followed
and implemented during design and construction. We will provide supplemental
recommendations if we observe variable or undesirable conditions during grading and
construction, or if the proposed construction will differ from that anticipated herein.
7.1.2 With the exception of possible moderate to strong seismic shaking, we did not observe or
know of significant geologic hazards to exist on the site that would adversely affect the
proposed project.
7.1.3 The topsoil and upper portion of the Old Paralic Deposits are potentially compressible and
unsuitable in their present condition for the support of compacted fill or settlement-sensitive
improvements. Remedial grading of these materials should be performed as discussed
herein. The dense portions of the Old Paralic Deposits are considered suitable for the
support of proposed fill and structural loads.
7.1.4 Groundwater was not encountered during the field study and we do not expect it to be a
constraint to project development. However, seepage may be encountered during the
grading operations, especially during the rainy seasons.
7.1.5 Excavation of the Old Paralic Deposits should generally be possible with moderate to heavy
effort using conventional, heavy-duty equipment during grading and trenching operations.
7.1.6 Proper drainage should be maintained in order to preserve the engineering properties of the
fill in both the building pads and slope areas. Recommendations for site drainage are
provided herein.
7.1.7 Based on our review of the project plans, we opine the planned development can be
constructed in accordance with our recommendations provided herein. We do not expect the
planned development will destabilize or result in settlement of adjacent properties if
properly constructed.
7.1.8 Surface settlement monuments and canyon subdrains will not be required on this project.
Geocon Project No. G2861-11-01 - 10 - December 29, 2021
7.2 Excavation and Soil Characteristics
7.2.1 Excavation of the in-situ soil should be possible with moderate to heavy effort using
conventional heavy-duty equipment. Excavation of the formational materials will require
very heavy effort using conventional heavy-duty equipment during the grading operations.
7.2.2 The soil encountered in the field investigation is considered to be “non-expansive”
(expansion index [EI] of 20 or less) as defined by 2019 California Building Code (CBC)
Section 1803.5.3. We expect a majority of the soil encountered possess a “very low”
expansion potential (EI of 20 or less) in accordance with ASTM D 4829. Table 7.2 presents
soil classifications based on the expansion index.
TABLE 7.2
EXPANSION CLASSIFICATION BASED ON EXPANSION INDEX
Expansion Index (EI) ASTM D 4829 Expansion
Classification
2019 CBC Expansion
Classification
0 – 20 Very Low Non-Expansive
21 – 50 Low
Expansive 51 – 90 Medium
91 – 130 High
Greater Than 130 Very High
7.2.3 Laboratory tests were performed on samples of the site materials to evaluate the percentage
of water-soluble sulfate content. Appendix B presents results of the laboratory water-soluble
sulfate content tests. The test results indicate the on-site materials at the locations tested
possess “S0” sulfate exposure to concrete structures as defined by 2019 CBC Section 1904
and ACI 318-19 Chapter 19. The presence of water-soluble sulfates is not a visually
discernible characteristic; therefore, other soil samples from the site could yield different
concentrations. Additionally, over time landscaping activities (i.e., addition of fertilizers and
other soil nutrients) may affect the concentration.
7.2.4 The referenced report presented the results of soil samples tested for potential of hydrogen
(pH) and resistivity laboratory tests to aid in evaluating the corrosion potential to subsurface
metal structures. Appendix B presents the laboratory test results.
7.2.5 Geocon Incorporated does not practice in the field of corrosion engineering. Therefore,
further evaluation by a corrosion engineer may be performed if improvements susceptible to
corrosion are planned.
Geocon Project No. G2861-11-01 - 11 - December 29, 2021
7.3 Grading
7.3.1 Grading should be performed in accordance with the recommendations provided in this
report, the Recommended Grading Specifications contained in Appendix C and the local
grading ordinance. Geocon Incorporated should observe the grading operations on a full-
time basis and provide testing during the fill placement.
7.3.2 Prior to commencing grading, a preconstruction conference should be held at the site with
the agency inspector, developer, grading and underground contractors, civil engineer, and
geotechnical engineer in attendance. Special soil handling and/or the grading plans can be
discussed at that time.
7.3.3 Site preparation should begin with the removal of deleterious material, debris, and
vegetation. The depth of vegetation removal should be such that material exposed in cut
areas or soil to be used as fill is relatively free of organic matter. Material generated during
stripping and/or site demolition should be exported from the site. Asphalt and concrete
should not be mixed with the fill soil unless approved by the Geotechnical Engineer.
7.3.4 Abandoned foundations, septic systems, and buried utilities should be removed and the
resultant depressions and/or trenches should be backfilled with properly compacted material
as part of the remedial grading.
7.3.5 We expect the proposed residential structures will be supported on a shallow foundation
system founded in compacted fill. The upper 3 feet of cut and cut/fill transition lots should
be over excavated and replaced with properly compacted fill due to the very dense nature of
the formational materials.
7.3.6 The bottom of the excavations should be sloped 1 percent to the adjacent street or deepest
fill. Prior to fill soil being placed, the existing ground surface should be scarified, moisture
conditioned as necessary, and compacted to a depth of at least 12 inches. Deeper removals
may be required if saturated or loose fill soil is encountered. A representative of Geocon
should be on-site during removals to evaluate the limits of the remedial grading.
7.3.7 In areas of proposed improvements outside of the building areas, the upper 1 to 2 feet of
existing soil in fill areas should be processed, moisture conditioned as necessary and
recompacted. Deeper removals may be required in areas where loose or saturated materials
are encountered. The removals should extend at least 2 feet outside of the improvement
area, where possible. Table 7.3.1 provides a summary of the grading recommendations.
Geocon Project No. G2861-11-01 - 12 - December 29, 2021
TABLE 7.3.1
SUMMARY OF GRADING RECOMMENDATIONS
Area Removal Requirements
Residential Structures Upper 3 Feet of Cut and Cut/Fill Lots Should be Over Excavated and Replaced With Properly Compacted Fill
Site Development Process Upper 1 to 2 Feet of Existing Materials in Fill Areas
Lateral Grading Limits 10 Feet Outside of Buildings
2 Feet Outside of Improvement Areas
Exposed Bottoms of Remedial Grading Scarify Upper 12 Inches, Moisturize and Recompact
Slope One Percent to Adjacent Street of Deepest Fill
7.3.8 Some areas of overly wet and saturated soil could be encountered due to the existing
landscape irrigation. The saturated soil would require additional effort prior to placement of
compacted fill or additional improvements. Stabilization of the soil would include scarifying
and air-drying, removing and replacement with drier soil, use of stabilization fabric (e.g.
Tensar TX7 or other approved fabric), or chemical treating (i.e. cement or lime treatment).
7.3.9 The site should then be brought to final subgrade elevations with fill compacted in layers. In
general, soil native to the site is suitable for use from a geotechnical engineering standpoint as
fill if relatively free from vegetation, debris and other deleterious material. Layers of fill should
be about 6 to 8 inches in loose thickness and no thicker than will allow for adequate bonding and
compaction. Fill, including backfill and scarified ground surfaces, should be compacted to a dry
density of at least 90 percent of the laboratory maximum dry density near to slightly above
optimum moisture content in accordance with ASTM Test Procedure D 1557. Fill materials
placed below optimum moisture content may require additional moisture conditioning prior to
placing additional fill. The upper 12 inches of subgrade soil underlying pavement should be
compacted to a dry density of at least 95 percent of the laboratory maximum dry density near to
slightly above optimum moisture content shortly before paving operations.
7.3.10 Import fill (if necessary) should consist of the characteristics presented in Table 7.3.2. Geocon
Incorporated should be notified of the import soil source and should perform laboratory testing
of import soil prior to its arrival at the site to determine its suitability as fill material.
TABLE 7.3.2
SUMMARY OF IMPORT FILL RECOMMENDATIONS
Soil Characteristic Values
Expansion Potential “Very Low” (Expansion Index of 20 or less)
Particle Size Maximum Dimension Less Than 3 Inches
Generally Free of Debris
Geocon Project No. G2861-11-01 - 13 - December 29, 2021
7.4 Subdrains
7.4.1 With the exception of retaining wall drains, we do not expect the installation of other
subdrains. We should be contacted to provide recommendations for wick drains, if
proposed.
7.5 Seismic Design Criteria
7.5.1 Table 7.5.1 summarizes site-specific design criteria obtained from the 2019 California
Building Code (CBC; Based on the 2018 International Building Code [IBC] and ASCE 7-
16), Chapter 16 Structural Design, Section 1613 Earthquake Loads. We used the computer
program U.S. Seismic Design Maps, provided by the Structural Engineers Association
(SEA) to calculate the seismic design parameters. The short spectral response uses a period
of 0.2 second. We evaluated the Site Class based on the discussion in Section 1613.2.2 of
the 2019 CBC and Table 20.3-1 of ASCE 7-16. The buildings and improvements should be
designed using a Site Class C. The values presented herein are for the risk-targeted
maximum considered earthquake (MCER). Sites designated as Site Class D, E and F may
require additional analyses if requested by the project structural engineer and client.
TABLE 7.5.1
2019 CBC SEISMIC DESIGN PARAMETERS
Parameter Value 2019 CBC Reference
Site Class C Section 1613.2.2
MCER Ground Motion Spectral Response
Acceleration – Class B (short), SS 1.041g Figure 1613.2.1(1)
MCER Ground Motion Spectral Response
Acceleration – Class B (1 sec), S1 0.379g Figure 1613.2.1(2)
Site Coefficient, FA 1.200 Table 1613.2.3(1)
Site Coefficient, FV 1.500* Table 1613.2.3(2)
Site Class Modified MCER Spectral Response
Acceleration (short), SMS 1.250g Section 1613.2.3 (Eqn 16-36)
Site Class Modified MCER Spectral Response
Acceleration – (1 sec), SM1 0.568g* Section 1613.2.3 (Eqn 16-37)
5% Damped Design
Spectral Response Acceleration (short), SDS 0.833g Section 1613.2.4 (Eqn 16-38)
5% Damped Design
Spectral Response Acceleration (1 sec), SD1 0.379g* Section 1613.2.4 (Eqn 16-39)
*Note: Using the code-based values presented in this table, in lieu of a performing a ground motion
hazard analysis, requires the exceptions outlined in ASCE 7-16 Section 11.4.8 be followed by the
project structural engineer. Per Section 11.4.8 of ASCE/SEI 7-16, a ground motion hazard analysis
should be performed for projects for Site Class “E” sites with Ss greater than or equal to 1.0g and for
Site Class “D” and “E” sites with S1 greater than 0.2g. Section 11.4.8 also provides exceptions which
indicates that the ground motion hazard analysis may be waived provided the exceptions are followed.
Geocon Project No. G2861-11-01 - 14 - December 29, 2021
7.5.2 Table 7.5.2 presents the mapped maximum considered geometric mean (MCEG) seismic
design parameters for projects located in Seismic Design Categories of D through F in
accordance with ASCE 7-16.
TABLE 7.5.2
ASCE 7-16 PEAK GROUND ACCELERATION
Parameter Value ASCE 7-16 Reference
Mapped MCEG Peak Ground Acceleration, PGA 0.457g Figure 22-9
Site Coefficient, FPGA 1.200 Table 11.8-1
Site Class Modified MCEG Peak Ground
Acceleration, PGAM 0.549g Section 11.8.3 (Eqn 11.8-1)
7.5.3 Conformance to the criteria in Tables 7.5.1 and 7.5.2 for seismic design does not constitute
any kind of guarantee or assurance that significant structural damage or ground failure will
not occur in the event of a large earthquake. The primary goal of seismic design is to protect
life, not to avoid all damage, since such design may be economically prohibitive.
7.5.4 The project structural engineer and architect should evaluate the appropriate Risk Category
and Seismic Design Category for the planned structures. The values presented herein
assume a Risk Category of II and resulting in a Seismic Design Category D. Table 7.5.3
presents a summary of the risk categories in accordance with ASCE 7-16.
TABLE 7.5.3
ASCE 7-16 RISK CATEGORIES
Risk Category Building Use Examples
I Low risk to Human Life at Failure Barn, Storage Shelter
II
Nominal Risk to Human Life at
Failure (Buildings Not Designated as
I, III or IV)
Residential, Commercial and Industrial
Buildings
III Substantial Risk to Human Life at
Failure
Theaters, Lecture Halls, Dining Halls,
Schools, Prisons, Small Healthcare
Facilities, Infrastructure Plants, Storage
for Explosives/Toxins
IV Essential Facilities
Hazardous Material Facilities,
Hospitals, Fire and Rescue, Emergency
Shelters, Police Stations, Power
Stations, Aviation Control Facilities,
National Defense, Water Storage
Geocon Project No. G2861-11-01 - 15 - December 29, 2021
7.6 Shallow Foundations
7.6.1 The residential structures can be supported on a shallow foundation system founded in the
compacted fill. Foundations for the structure should consist of continuous strip footings
and/or isolated spread footings. Table 7.6 provides a summary of the foundation design
recommendations.
TABLE 7.6
SUMMARY OF FOUNDATION RECOMMENDATIONS
Parameter Value
Minimum Continuous Foundation Width, WC 12 inches
Minimum Isolated Foundation Width, WI 24 inches
Minimum Foundation Depth, D 12 Inches Below Lowest Adjacent Grade
Minimum Steel Reinforcement 2 No. 4 Bars, 1 at the Top and 1 at the Bottom
Allowable Bearing Capacity 2,000 psf
Estimated Total Settlement 1 Inch
Estimated Differential Settlement ½ Inch in 40 Feet
Footing Size Used for Settlement 9-Foot Square
Design Expansion Index 50 or less
7.6.2 The foundations should be embedded in accordance with the recommendations herein and
the Wall/Column Footing Dimension Detail. The embedment depths should be measured
from the lowest adjacent pad grade for both interior and exterior footings. Footings should
be deepened such that the bottom outside edge of the footing is at least 7 feet horizontally
from the face of the slope (unless designed with a post-tensioned foundation system as
discussed herein).
Wall/Column Footing Dimension Detail
(90 z --I I-1-0 o.. ow LL 0
FOOTING
WIDTH, W1
CONCRETE SLAB
I.. ..I FOOTING
WIDTH, We
PAD GRADE
(9 J: ~ I-I-0.. Ow 00 LL
Geocon Project No. G2861-11-01 - 16 - December 29, 2021
7.6.3 The bearing capacity values presented herein are for dead plus live loads and may be
increased by one-third when considering transient loads due to wind or seismic forces.
7.6.4 Where buildings or other improvements are planned near the top of a slope steeper than 3:1
(horizontal to vertical), special foundations and/or design considerations are recommended
due to the tendency for lateral soil movement to occur.
For fill slopes less than 20 feet high, building footings should be deepened such that
the bottom outside edge of the footing is at least 7 feet horizontally from the face of
the slope.
If swimming pools are planned, Geocon Incorporated should be contacted for a
review of specific site conditions.
Swimming pools located within 7 feet of the top of cut or fill slopes are not
recommended. Where such a condition cannot be avoided, the portion of the
swimming pool wall within 7 feet of the slope face be designed assuming that the
adjacent soil provides no lateral support.
Although other improvements, which are relatively rigid or brittle, such as concrete
flatwork or masonry walls, may experience some distress if located near the top of a
slope, it is generally not economical to mitigate this potential. It may be possible,
however, to incorporate design measures that would permit some lateral soil
movement without causing extensive distress. Geocon Incorporated should be
consulted for specific recommendations.
7.6.5 We should observe the foundation excavations prior to the placement of reinforcing steel
and concrete to check that the exposed soil conditions are similar to those expected and that
they have been extended to the appropriate bearing strata. Foundation modifications may be
required if unexpected soil conditions are encountered.
7.6.6 Geocon Incorporated should be consulted to provide additional design parameters as
required by the structural engineer.
7.7 Post-Tensioned Foundations
7.7.1 As an alternative to the conventional foundation recommendations, consideration should be
given to the use of post-tensioned concrete slab and foundation systems for the support of
the proposed structures. The post-tensioned systems should be designed by a structural
engineer experienced in post-tensioned slab design and design criteria of the Post-
Tensioning Institute (PTI) DC10.5 as required by the 2019 California Building Code (CBC
Section 1808.6.2). Although this procedure was developed for expansive soil conditions, it
can also be used to reduce the potential for foundation distress due to differential fill
settlement. The post-tensioned design should incorporate the geotechnical parameters
Geocon Project No. G2861-11-01 - 17 - December 29, 2021
presented on Table 7.7.1. The parameters presented in Table 7.7.1 are based on the
guidelines presented in the PTI, DC10.5 design manual.
TABLE 7.7.1
POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS
Post-Tensioning Institute (PTI)
DC10.5 Design Parameters Value
Thornthwaite Index -20
Equilibrium Suction 3.9
Edge Lift Moisture Variation Distance, eM (feet) 5.3
Edge Lift, yM (inches) 0.61
Center Lift Moisture Variation Distance, eM (feet) 9.0
Center Lift, yM (inches) 0.30
7.7.2 The foundations for the post-tensioned slabs should be embedded in accordance with the
recommendations of the structural engineer. If a post-tensioned mat foundation system is
planned, the slab should possess a thickened edge with a minimum width of 12 inches and
extend below the clean sand or crushed rock layer.
7.7.3 If the structural engineer proposes a post-tensioned foundation design method other than the
2019 CBC (PTI DC10.5):
The criteria presented in Table 7.7.1 are still applicable.
Interior stiffener beams should be used.
The width of the perimeter foundations should be at least 12 inches.
The perimeter footing embedment depths should be at least 12 inches. The
embedment depths should be measured from the lowest adjacent pad grade.
7.7.4 Foundation systems for the lots that possess a “very low” expansion potential (expansion
index of 20 or less) can be designed using the method described in Section 1808 of the 2019
CBC. If post-tensioned foundations are planned, an alternative, commonly accepted design
method (other than PTI) can be used. However, the post-tensioned foundation system should
be designed with a total and differential deflection of 1 inch. Geocon Incorporated should be
contacted to review the plans and provide additional information, if necessary.
7.7.5 Our experience indicates post-tensioned slabs are susceptible to excessive edge lift,
regardless of the underlying soil conditions. Placing reinforcing steel at the bottom of the
perimeter footings and the interior stiffener beams may mitigate this potential. Current PTI
design procedures primarily address the potential center lift of slabs but, because of the
Geocon Project No. G2861-11-01 - 18 - December 29, 2021
placement of the reinforcing tendons in the top of the slab, the resulting eccentricity after
tensioning reduces the ability of the system to mitigate edge lift. The structural engineer
should design the foundation system to reduce the potential of edge lift occurring for the
proposed structures.
7.7.6 During the construction of the post-tension foundation system, the concrete should be
placed monolithically. Under no circumstances should cold joints form between the
footings/grade beams and the slab during the construction of the post-tension foundation
system unless designed by the project structural engineer.
7.7.7 The proposed structures can be supported on a shallow foundation system founded in the
compacted fill. Table 7.7.2 provides a summary of the foundation design recommendations.
TABLE 7.7.2
SUMMARY OF FOUNDATION RECOMMENDATIONS
Parameter Value
Allowable Bearing Capacity 2,000 psf
Estimated Total Settlement 1 Inch
Estimated Differential Settlement ½ Inch in 40 Feet
7.7.8 The bearing capacity values presented herein are for dead plus live loads and may be
increased by one-third when considering transient loads due to wind or seismic forces.
7.7.9 Isolated footings, if present, should have the minimum embedment depth and width
recommended for conventional foundations. The use of isolated footings, which are located
beyond the perimeter of the building and support structural elements connected to the
building, are not recommended. Where this condition cannot be avoided, the isolated
footings should be connected to the building foundation system with grade beams in both
directions.
7.7.10 Consideration should be given to using interior stiffening beams and connecting isolated
footings and/or increasing the slab thickness.
7.7.11 We should observe the foundation excavations prior to the placement of reinforcing steel to
check that the exposed soil conditions are similar to those expected and that they have been
extended to the appropriate bearing strata. If unexpected soil conditions are encountered,
foundation modifications may be required.
Geocon Project No. G2861-11-01 - 19 - December 29, 2021
7.8 Concrete Slabs-On-Grade
7.8.1 Concrete slabs-on-grade for the structures should be constructed in accordance with Table 7.8.
TABLE 7.8
MINIMUM CONCRETE SLAB-ON-GRADE RECOMMENDATIONS
Parameter Value
Minimum Concrete Slab Thickness 4 inches
Minimum Steel Reinforcement 6 x 6 - 10/10 welded wire mesh at slab mid-point
Typical Slab Underlayment 3 to 4 Inches of Sand/Gravel/Base
Design Expansion Index 50 or less
7.8.2 Slabs that may receive moisture-sensitive floor coverings or may be used to store moisture-
sensitive materials should be underlain by a vapor retarder. The vapor retarder design should
be consistent with the guidelines presented in the American Concrete Institute’s (ACI) Guide
for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials (ACI 302.2R-06). In
addition, the membrane should be installed in accordance with manufacturer’s
recommendations and ASTM requirements and installed in a manner that prevents puncture.
The vapor retarder used should be specified by the project architect or developer based on the
type of floor covering that will be installed and if the structure will possess a humidity
controlled environment.
7.8.3 The bedding sand thickness should be determined by the project foundation engineer,
architect, and/or developer. It is common to have 3 to 4 inches of sand for 5-inch and 4-inch
thick slabs, respectively, in the southern California region. However, we should be
contacted to provide recommendations if the bedding sand is thicker than 6 inches. The
foundation design engineer should provide appropriate concrete mix design criteria and
curing measures to assure proper curing of the slab by reducing the potential for rapid
moisture loss and subsequent cracking and/or slab curl. We suggest that the foundation
design engineer present the concrete mix design and proper curing methods on the
foundation plans. It is critical that the foundation contractor understands and follows the
recommendations presented on the foundation plans.
7.8.4 Concrete slabs should be provided with adequate crack-control joints, construction joints
and/or expansion joints to reduce unsightly shrinkage cracking. The design of joints should
consider criteria of the American Concrete Institute (ACI) when establishing crack-control
spacing. Crack-control joints should be spaced at intervals no greater than 12 feet.
Geocon Project No. G2861-11-01 - 20 - December 29, 2021
Additional steel reinforcing, concrete admixtures and/or closer crack control joint spacing
should be considered where concrete-exposed finished floors are planned.
7.8.5 Special subgrade presaturation is not deemed necessary prior to placing concrete; however,
the exposed foundation and slab subgrade soil should be moisturized to maintain a moist
condition as would be expected in any such concrete placement.
7.8.6 The concrete slab-on-grade recommendations are based on soil support characteristics only.
The project structural engineer should evaluate the structural requirements of the concrete
slabs for supporting expected loads.
7.8.7 The recommendations of this report are intended to reduce the potential for cracking of slabs
due to expansive soil (if present), differential settlement of existing soil or soil with varying
thicknesses. However, even with the incorporation of the recommendations presented
herein, foundations, stucco walls, and slabs-on-grade placed on such conditions may still
exhibit some cracking due to soil movement and/or shrinkage. The occurrence of concrete
shrinkage cracks is independent of the supporting soil characteristics. Their occurrence may
be reduced and/or controlled by limiting the slump of the concrete, proper concrete
placement and curing, and by the placement of crack control joints at periodic intervals, in
particular, where re-entrant slab corners occur.
7.9 Exterior Concrete Flatwork
7.9.1 Exterior concrete flatwork not subject to vehicular traffic should be constructed in
accordance with the recommendations presented in Table 7.9. The recommended steel
reinforcement would help reduce the potential for cracking.
TABLE 7.9
MINIMUM CONCRETE FLATWORK RECOMMENDATIONS
Expansion
Index, EI Minimum Steel Reinforcement* Options Minimum
Thickness
EI < 90 6x6-W2.9/W2.9 (6x6-6/6) welded wire mesh 4 Inches No. 3 Bars 18 inches on center, Both Directions
*In excess of 8 feet square.
7.9.2 The subgrade soil should be properly moisturized and compacted prior to the placement of
steel and concrete. The subgrade soil should be compacted to a dry density of at least 90
percent of the laboratory maximum dry density near to slightly above optimum moisture
content in accordance with ASTM D 1557.
Geocon Project No. G2861-11-01 - 21 - December 29, 2021
7.9.3 Even with the incorporation of the recommendations of this report, the exterior concrete
flatwork has a potential to experience some uplift due to expansive soil beneath grade. The
steel reinforcement should overlap continuously in flatwork to reduce the potential for
vertical offsets within flatwork. Additionally, flatwork should be structurally connected to
the curbs, where possible, to reduce the potential for offsets between the curbs and the
flatwork.
7.9.4 Concrete flatwork should be provided with crack control joints to reduce and/or control
shrinkage cracking. Crack control spacing should be determined by the project structural
engineer based upon the slab thickness and intended usage. Criteria of the American
Concrete Institute (ACI) should be taken into consideration when establishing crack control
spacing. Subgrade soil for exterior slabs not subjected to vehicle loads should be compacted
in accordance with criteria presented in the grading section prior to concrete placement.
Subgrade soil should be properly compacted and the moisture content of subgrade soil
should be verified prior to placing concrete. Base materials will not be required below
concrete improvements.
7.9.5 Where exterior flatwork abuts the structure at entrant or exit points, the exterior slab should
be dowelled into the structure’s foundation stemwall. This recommendation is intended to
reduce the potential for differential elevations that could result from differential settlement
or minor heave of the flatwork. Dowelling details should be designed by the project
structural engineer.
7.9.6 The recommendations presented herein are intended to reduce the potential for cracking of
exterior slabs as a result of differential movement. However, even with the incorporation of
the recommendations presented herein, slabs-on-grade will still crack. The occurrence of
concrete shrinkage cracks is independent of the soil supporting characteristics. Their
occurrence may be reduced and/or controlled by limiting the slump of the concrete, the use
of crack control joints and proper concrete placement and curing. Crack control joints
should be spaced at intervals no greater than 12 feet. Literature provided by the Portland
Concrete Association (PCA) and American Concrete Institute (ACI) present
recommendations for proper concrete mix, construction, and curing practices, and should be
incorporated into project construction.
7.10 Retaining Walls
7.10.1 Retaining walls should be designed using the values presented in Table 7.10.1. Soil with an
expansion index (EI) of greater than 50 should not be used as backfill material behind
retaining walls.
Geocon Project No. G2861-11-01 - 22 - December 29, 2021
TABLE 7.10.1
RETAINING WALL DESIGN RECOMMENDATIONS
Parameter Value
Active Soil Pressure, A (Fluid Density, Level Backfill) 35 pcf
Active Soil Pressure, A (Fluid Density, 2:1 Sloping Backfill) 50 pcf
Seismic Pressure, S 12H psf
At-Rest/Restrained Walls Additional Uniform Pressure (0 to 8 Feet High) 7H psf
At-Rest/Restrained Walls Additional Uniform Pressure (8+ Feet High) 13H psf
Expected Expansion Index for the Subject Property EI<50
H equals the height of the retaining portion of the wall
7.10.2 The project retaining walls should be designed as shown in the Retaining Wall Loading
Diagram.
Retaining Wall Loading Diagram
7.10.3 Unrestrained walls are those that are allowed to rotate more than 0.001H (where H equals
the height of the retaining portion of the wall) at the top of the wall. Where walls are
restrained from movement at the top (at-rest condition), an additional uniform pressure
should be applied to the wall. For retaining walls subject to vehicular loads within a
horizontal distance equal to two-thirds the wall height, a surcharge equivalent to 2 feet of fill
soil should be added.
IF PRESENT
RETAINING
WALL
ACTIVE
PRESSURE
H (Feet)
---1FOOTING
SEISMIC
(IF
REQUIRED)
AT-REST/
RESTRAINED
(IF REQUIRED)
I
H :<.8' Ru
Rt_ psf
t+------i
H>B'
Geocon Project No. G2861-11-01 - 23 - December 29, 2021
7.10.4 The structural engineer should determine the Seismic Design Category for the project in
accordance with Section 1613.3.5 of the 2019 CBC or Section 11.6 of ASCE 7-10. For
structures assigned to Seismic Design Category of D, E, or F, retaining walls that support
more than 6 feet of backfill should be designed with seismic lateral pressure in accordance
with Section 1803.5.12 of the 2019 CBC. The seismic load is dependent on the retained
height where H is the height of the wall, in feet, and the calculated loads result in pounds per
square foot (psf) exerted at the base of the wall and zero at the top of the wall.
7.10.5 Retaining walls should be designed to ensure stability against overturning sliding, and
excessive foundation pressure. Where a keyway is extended below the wall base with the
intent to engage passive pressure and enhance sliding stability, it is not necessary to
consider active pressure on the keyway.
7.10.6 Drainage openings through the base of the wall (weep holes) should not be used where the
seepage could be a nuisance or otherwise adversely affect the property adjacent to the base
of the wall. The recommendations herein assume a properly compacted granular (EI of 90 or
less) free-draining backfill material with no hydrostatic forces or imposed surcharge load.
The retaining wall should be properly drained as shown in the Typical Retaining Wall
Drainage Detail. If conditions different than those described are expected, or if specific
drainage details are desired, Geocon Incorporated should be contacted for additional
recommendations.
Typical Retaining Wall Drainage Detail
7.10.7 The retaining walls may be designed using either the active and restrained (at-rest) loading
condition or the active and seismic loading condition as suggested by the structural
engineer. Typically, it appears the design of the restrained condition for retaining wall
loading may be adequate for the seismic design of the retaining walls. However, the active
earth pressure combined with the seismic design load should be reviewed and also
considered in the design of the retaining walls.
H
PROPOSED
GRADE
CONCRETE BROWDITCH
TEMPORARY
BACKCUTPER
OSHA
OR
Fl 140N FILTER
RIC (OR EQUIVALENT)
PROPOSED
GRADE
2/3 H
GROUND SURFACE
DRAINAGE PANEL (MIRADRAIN
6000 OR EQUIVALENT)
3/4" CRUSHED ROCK (1 CU. FT./FT.)
OR WRAP DRAINAGE PANEL
12" AROUND PIPE
,or_ ..... :; L TER FABRIC ENVELOPE
~MIRAFI 140N OR EQUIVALENT
4" DIA. PERFORATED SCHEDULE-4"'lO~lll!!~m...1.,----;!FOOTIN~ '~ 4" DIA. SCHEDULE 40 PERFORATED
PVC PIPE EXTENDED TO APPROVED ' PVC PIPE OR TOTAL DRAIN EXTENDED
OUTLET TO APPROVED OUTLET
Geocon Project No. G2861-11-01 - 24 - December 29, 2021
7.10.8 In general, wall foundations should be designed in accordance with Table 7.10.2. The
proximity of the foundation to the top of a slope steeper than 3:1 could impact the allowable
soil bearing pressure. Therefore, retaining wall foundations should be deepened such that
the bottom outside edge of the footing is at least 7 feet horizontally from the face of the
slope.
TABLE 7.10.2
SUMMARY OF RETAINING WALL FOUNDATION RECOMMENDATIONS
Parameter Value
Minimum Retaining Wall Foundation Width 12 inches
Minimum Retaining Wall Foundation Depth 12 Inches
Minimum Steel Reinforcement Per Structural Engineer
Allowable Bearing Capacity 2,000 psf
Estimated Total Settlement 1 Inch
Estimated Differential Settlement ½ Inch in 40 Feet
7.10.9 The recommendations presented herein are generally applicable to the design of rigid
concrete or masonry retaining walls. In the event that other types of walls (such as
mechanically stabilized earth [MSE] walls, soil nail walls, or soldier pile walls) are planned,
Geocon Incorporated should be consulted for additional recommendations.
7.10.10 It is common to see retaining walls constructed in the areas of the elevator pits. The
retaining walls should be properly drained and designed in accordance with the
recommendations presented herein. If the elevator pit walls are not drained, the walls should
be designed with an increased active pressure with an equivalent fluid density of 90 pcf. It is
also common to see seepage and water collection within the elevator pit. The pit should be
designed and properly waterproofed to prevent seepage and water migration into the
elevator pit.
7.10.11 Unrestrained walls will move laterally when backfilled and loading is applied. The amount
of lateral deflection is dependent on the wall height, the type of soil used for backfill, and
loads acting on the wall. The retaining walls and improvements above the retaining walls
should be designed to incorporate an appropriate amount of lateral deflection as determined
by the structural engineer.
7.10.12 Soil contemplated for use as retaining wall backfill, including import materials, should be
identified in the field prior to backfill. At that time, Geocon Incorporated should obtain
samples for laboratory testing to evaluate its suitability. Modified lateral earth pressures
Geocon Project No. G2861-11-01 - 25 - December 29, 2021
may be necessary if the backfill soil does not meet the required expansion index or shear
strength. City or regional standard wall designs, if used, are based on a specific active lateral
earth pressure and/or soil friction angle. In this regard, on-site soil to be used as backfill may
or may not meet the values for standard wall designs. Geocon Incorporated should be
consulted to assess the suitability of the on-site soil for use as wall backfill if standard wall
designs will be used.
7.11 Lateral Loading
7.11.1 Table 7.11 should be used to help design the proposed structures and improvements to resist
lateral loads for the design of footings or shear keys. The allowable passive pressure
assumes a horizontal surface extending at least 5 feet, or three times the surface generating
the passive pressure, whichever is greater. The upper 12 inches of material in areas not
protected by floor slabs or pavement should not be included in design for passive resistance.
TABLE 7.11
SUMMARY OF LATERAL LOAD DESIGN RECOMMENDATIONS
Parameter Value
Passive Pressure Fluid Density 350 pcf
Coefficient of Friction (Concrete and Soil) 0.35
Coefficient of Friction (Along Vapor Barrier) 0.2 to 0.25*
*Per manufacturer’s recommendations.
7.11.2 The passive and frictional resistant loads can be combined for design purposes. The lateral
passive pressures may be increased by one-third when considering transient loads due to
wind or seismic forces.
7.12 Preliminary Pavement Recommendations
7.12.1 We calculated the flexible pavement section for the proposed driveway with a gradient up to
15 percent in general conformance with the City of Carlsbad, Engineering Standards,
Volume 1, General Design Standards, 2016 (Chapter 1, Table A: Street Design Criteria)
The final pavement sections for the driveway should be based on the R-Value of the
subgrade soil encountered at final subgrade elevation. We used an R-Value of 50 and 78 for
the subgrade soil and base materials, respectively, for the purposes of this preliminary
analysis. Table 7.12.1 presents the preliminary flexible pavement sections.
Geocon Project No. G2861-11-01 - 26 - December 29, 2021
TABLE 7.12.1
PRELIMINARY FLEXIBLE PAVEMENT SECTION
Location
Assumed
Traffic
Index
Assumed
Subgrade
R-Value
Asphalt
Concrete
(inches)
Class 2
Aggregate
Base (inches)
Residential Driveway 5.0 50 3.5 5
Private Access Road
(Less than 8% Grade) 5.5 50
4* 4*
Private Access Road
(Between 12% and 15% Grade) 4* 4*
*Minimum Section Per City of Carlsbad
7.12.2 Prior to placing base materials, the upper 12 inches of the subgrade soil should be scarified,
moisture conditioned as necessary, and recompacted to a dry density of at least 95 percent of
the laboratory maximum dry density near to slightly above optimum moisture content as
determined by ASTM D 1557. Similarly, the base material should be compacted to a dry
density of at least 95 percent of the laboratory maximum dry density near to slightly above
optimum moisture content. Asphalt concrete should be compacted to a density of at least 95
percent of the laboratory Hveem density in accordance with ASTM D 2726.
7.12.3 Base materials should conform to Section 26-1.02B of the Standard Specifications for The
State of California Department of Transportation (Caltrans) with a ¾-inch maximum size
aggregate. Asphalt concrete should conform to Section 203-6 of the Standard Specifications
for Public Works Construction (Greenbook).
7.12.4 The base thickness can be reduced if a reinforcement geogrid is used during the installation
of the pavement. Geocon should be contact for additional recommendations if alternate
design parameters are requested.
7.12.5 A rigid Portland cement concrete (PCC) pavement section should be placed in roadway
aprons and cross gutters. We calculated the rigid pavement section in general conformance
with the procedure recommended by the American Concrete Institute report ACI 330-21
Commercial Concrete Parking Lots and Site Paving Design and Construction – Guide.
Table 7.12.2 provides the traffic categories and design parameters used for the calculations
for 20-year design life.
Geocon Project No. G2861-11-01 - 27 - December 29, 2021
TABLE 7.12.2
TRAFFIC CATEGORIES
Traffic
Category Description Reliability
(%)
Slabs Cracked at End
of Design Life (%)
A Car Parking Areas and Access Lanes 60 15
B Entrance and Truck Service Lanes 60 15
E Garbage or Fire Truck Lane 75 15
7.12.6 We used the parameters presented in Table 7.12.3 to calculate the pavement design sections.
We should be contacted to provide updated design sections, if necessary.
TABLE 7.12.3
RIGID PAVEMENT DESIGN PARAMETERS
Design Parameter Design Value
Modulus of subgrade reaction, k 100 pci
Modulus of rupture for concrete, MR 500 psi
Concrete Compressive Strength 3,000 psi
Concrete Modulus of Elasticity, E 3,150,000
7.12.7 Based on the criteria presented herein, the PCC pavement sections should have a minimum
thickness as presented in Table 7.12.4.
TABLE 7.12.4
RIGID VEHICULAR PAVEMENT RECOMMENDATIONS
Traffic Category Trucks Per Day Portland Cement
Concrete, T (Inches)
A = Car Parking Areas and Access Lanes 10 5½
B = Residential Driveway 10 6
E = Garbage or Fire Truck Lanes 5 6½
7.12.8 The PCC vehicular pavement should be placed over subgrade soil that is compacted to a dry
density of at least 95 percent of the laboratory maximum dry density near to slightly above
optimum moisture content.
7.12.9 Adequate joint spacing should be incorporated into the design and construction of the rigid
pavement in accordance with Table 7.12.5.
Geocon Project No. G2861-11-01 - 28 - December 29, 2021
TABLE 7.12.5
MAXIMUM JOINT SPACING
Pavement Thickness, T (Inches) Maximum Joint Spacing (Feet)
4<T<5 10
5<T<6 12
6<T 13
7.12.10 The rigid pavement should also be designed and constructed incorporating the parameters
presented in Table 7.12.6.
TABLE 7.12.6
ADDITIONAL RIGID PAVEMENT RECOMMENDATIONS
Subject Value
Thickened Edge
1.2 Times Slab Thickness Adjacent to Structures
1.5 Times Slab Thickness Adjacent to Soil
Minimum Increase of 2 Inches
4 Feet Wide
Crack Control Joint Depth Early Entry Sawn = T/6 to T/5, 1.25 Inch Minimum
Conventional (Tooled or Conventional Sawing) = T/4 to T/3
Crack Control Joint Width
¼-Inch for Sealed Joints and Per Sealer Manufacturer’s
Recommendations
1/16- to 1/4-Inch is Common for Unsealed Joints
7.12.11 Reinforcing steel will not be necessary within the concrete for geotechnical purposes with
the possible exception of dowels at construction joints as discussed herein.
7.12.12 To control the location and spread of concrete shrinkage cracks, crack-control joints
(weakened plane joints) should be included in the design of the concrete pavement slab.
Crack-control joints should be sealed with an appropriate sealant to prevent the migration of
water through the control joint to the subgrade materials. The depth of the crack-control
joints should be in accordance with the referenced ACI guide.
7.12.13 To provide load transfer between adjacent pavement slab sections, a butt-type construction
joint should be constructed. The butt-type joint should be thickened by at least 20 percent at
the edge and taper back at least 4 feet from the face of the slab.
Geocon Project No. G2861-11-01 - 29 - December 29, 2021
7.12.14 Concrete curb/gutter should be placed on soil subgrade compacted to a dry density of at
least 90 percent of the laboratory maximum dry density near to slightly above optimum
moisture content. Cross-gutters that receives vehicular should be placed on subgrade soil
compacted to a dry density of at least 95 percent of the laboratory maximum dry density
near to slightly above optimum moisture content. Base materials should not be placed below
the curb/gutter, or cross-gutters so water is not able to migrate from the adjacent parkways
to the pavement sections. Where flatwork is located directly adjacent to the curb/gutter, the
concrete flatwork should be structurally connected to the curbs to help reduce the potential
for offsets between the curbs and the flatwork.
7.13 Preliminary Paver Recommendations
7.13.1 We calculated the paver section in general conformance with the Caltrans Method of
Flexible Pavement Design (Highway Design Manual, Section 608.4) using an estimated
Traffic Index (TI) of 5.5. Based on the Interlocking Concrete Pavement Institute (ICPI), the
pavers should possess a minimum thickness of 3⅛ inches overlying 1 to 1½ inch of sand.
We used an equivalent asphalt concrete section equal to the thickness of the pavers of
approximately 3 inches in accordance with Interlocking Concrete Pavement Institute (ICPI)
Tech Spec Number 4. In addition, the pavers should be installed in a pattern appropriate for
vehicular traffic. Table 7.13.1 presents two options for the paver underlayment: compacted
base materials or aggregate. The pedestrian pavers should be constructed in accordance with
the manufacturer’s recommendations.
TABLE 7.13.1
PAVER PAVEMENT SECTION
Location
Traffic
Index (TI)
Assumed
SubgradeR-Value
Equivalent
Paver Asphalt Concrete Thickness (inches)
Option 1 Option 2
EstimatedSand Thickness (inches)
Base Materials (inches)
ASTM C 33 Aggregate
Parking stalls for
automobiles and
light-duty
vehicles
5.0
50
3 1 -1½ 4
3” Sand /
3” #8 /
4” #57
Driveways for automobiles and light-duty vehicles
5.5 3 1 -1½ 4 3” Sand / 3” #8 / 4” #57
Medium truck traffic areas 6.0 3 1 -1½ 5 3” Sand / 3” #8 / 4” #57
Driveways for heavy truck traffic 7.0 3 1 -1½ 7 3” Sand / 3” #8 / 4” #57
Geocon Project No. G2861-11-01 - 30 - December 29, 2021
7.13.2 Class 2 base, crushed aggregate base (CAB) or rigid pavement (with thicknesses described
herein) should be placed below the pavers. The Class 2 base, CAB or rigid pavement can be
replaced by aggregate in accordance with ASTM C 33 and the civil engineer/manufacturer’s
recommendations.
7.13.3 The aggregate presented in Option 2 should be in conformance with ASTM C33 as shown
in Table 7.13.2.
TABLE 7.13.2
AGGREGATE GRADATION LIMITS PER ASTM C33
Sieve Size Percent Passing Sieves
Choker Sand No. 8 No. 57
1.5 Inches -- -- 100
1 Inch -- -- 95-100
0.5 Inch -- 100 25-60
0.375 Inch 100 85-100 --
No. 4 95-100 10-30 0-10
No. 8 80-100 0-10 0-5
No. 16 50-85 0-5 --
No. 30 25-60 -- --
No. 50 5-30 -- --
No. 100 0-10 -- --
No. 200 0-3 -- --
7.13.4 Prior to placing base/aggregate materials, the subgrade soil should be scarified, moisture
conditioned as necessary, and recompacted to a dry density of at least 95 percent of the
laboratory maximum dry density near to slightly above optimum moisture content as
determined by ASTM D 1557. The depth of compaction should be at least 12 inches.
Similarly, the base materials should be compacted to a dry density of at least 95 percent of the
laboratory maximum dry density near to slightly above optimum moisture content.
7.13.5 The pavers should be installed and maintained in accordance with the manufacturer’s
recommendations. The future owners should be made aware and responsible for the
maintenance program. In addition, pavers tend to shift vertically and horizontally during the
life of the pavement and should be expected. The pavers should be placed tightly adjacent to
each other and the spacing between the paver units should be filled with appropriate filler. A
polymer sand (Poly-Sand) can be used on the decorative, non-storm water quality paver area
to help prevent water infiltration.
Geocon Project No. G2861-11-01 - 31 - December 29, 2021
7.13.6 The pavers normally require a concrete border to prevent lateral movement from traffic. The
concrete border surrounding the pavers should be embedded at least 6 inches into the
subgrade to reduce the potential for water migration to the adjacent landscape areas and
pavement areas. The side liners are not necessary if the concrete borders are installed as
discussed herein.
7.13.7 The performance of pavement is highly dependent on providing positive surface drainage
away from the edge of the pavement. Ponding of water on or adjacent to the pavement will
likely result in pavement distress and subgrade failure. Drainage from landscaped areas
should be directed to controlled drainage structures. Landscape areas adjacent to the edge of
pavements are not recommended due to the potential for surface or irrigation water to
infiltrate the underlying permeable aggregate base and cause distress. Where such a
condition cannot be avoided, consideration should be given to incorporating measures that
will significantly reduce the potential for subsurface water migration into the aggregate
base. If planter islands are planned, the perimeter curb should extend at least 6 inches below
the level of the base materials.
7.14 Site Drainage and Moisture Protection
7.14.1 Adequate site drainage is critical to reduce the potential for differential soil movement,
erosion and subsurface seepage. Under no circumstances should water be allowed to pond
adjacent to footings. The site should be graded and maintained such that surface drainage is
directed away from structures in accordance with 2019 CBC 1804.4 or other applicable
standards. In addition, surface drainage should be directed away from the top of slopes into
swales or other controlled drainage devices. Roof and pavement drainage should be directed
into conduits that carry runoff away from the proposed structure.
7.14.2 In the case of basement walls or building walls retaining landscaping areas, a water-proofing
system should be used on the wall and joints, and a Miradrain drainage panel (or similar)
should be placed over the waterproofing. The project architect or civil engineer should
provide detailed specifications on the plans for all waterproofing and drainage.
7.14.3 Underground utilities should be leak free. Utility and irrigation lines should be checked
periodically for leaks, and detected leaks should be repaired promptly. Detrimental soil
movement could occur if water is allowed to infiltrate the soil for prolonged periods of time.
7.14.4 Landscaping planters adjacent to paved areas are not recommended due to the potential for
surface or irrigation water to infiltrate the pavement's subgrade and base course. Area drains
to collect excess irrigation water and transmit it to drainage structures or impervious above-
grade planter boxes can be used. In addition, where landscaping is planned adjacent to the
Geocon Project No. G2861-11-01 - 32 - December 29, 2021
pavement, construction of a cutoff wall along the edge of the pavement that extends at least
6 inches below the bottom of the base material should be considered.
7.15 Foundation Plan Review
7.15.1 Geocon Incorporated should review the building foundation plans for the project prior to
final design submittal to evaluate if additional analyses and/or recommendations are
required.
7.16 Testing and Observation Services During Construction
7.16.1 Geocon Incorporated should provide geotechnical testing and observation services during
the grading operations, foundation construction, utility installation, retaining wall backfill
and pavement installation. Table 7.16 presents the typical geotechnical observations we
would expect for the proposed improvements.
TABLE 7.16
EXPECTED GEOTECHNICAL TESTING AND OBSERVATION SERVICES
Construction Phase Observations Expected Time Frame
Grading
Base of Removal Part Time During
Removals
Geologic Logging Part Time to Full Time
Fill Placement and Soil Compaction Full Time
Foundations Foundation Excavation Observations Part Time
Utility Backfill Fill Placement and Soil Compaction Part Time to Full Time
Retaining Wall Backfill Fill Placement and Soil Compaction Part Time to Full Time
Subgrade for Sidewalks,
Curb/Gutter and Pavement Soil Compaction Part Time
Pavement Construction
Base Placement and Compaction Part Time
Asphalt Concrete Placement and
Compaction Full Time
Geocon Project No. G2861-11-01 December 29, 2021
LIMITATIONS AND UNIFORMITY OF CONDITIONS
1. The firm that performed the geotechnical investigation for the project should be retained to
provide testing and observation services during construction to provide continuity of
geotechnical interpretation and to check that the recommendations presented for geotechnical
aspects of site development are incorporated during site grading, construction of
improvements, and excavation of foundations. If another geotechnical firm is selected to
perform the testing and observation services during construction operations, that firm should
prepare a letter indicating their intent to assume the responsibilities of project geotechnical
engineer of record. A copy of the letter should be provided to the regulatory agency for their
records. In addition, that firm should provide revised recommendations concerning the
geotechnical aspects of the proposed development, or a written acknowledgement of their
concurrence with the recommendations presented in our report. They should also perform
additional analyses deemed necessary to assume the role of Geotechnical Engineer of Record.
2. The recommendations of this report pertain only to the site investigated and are based upon
the assumption that the soil conditions do not deviate from those disclosed in the
investigation. If any variations or undesirable conditions are encountered during construction,
or if the proposed construction will differ from that anticipated herein, Geocon Incorporated
should be notified so that supplemental recommendations can be given. The evaluation or
identification of the potential presence of hazardous or corrosive materials was not part of the
scope of services provided by Geocon Incorporated.
3. This report is issued with the understanding that it is the responsibility of the owner or his
representative to ensure that the information and recommendations contained herein are
brought to the attention of the architect and engineer for the project and incorporated into the
plans, and the necessary steps are taken to see that the contractor and subcontractors carry out
such recommendations in the field.
4. The findings of this report are valid as of the present date. However, changes in the conditions
of a property can occur with the passage of time, whether they be due to natural processes or
the works of man on this or adjacent properties. In addition, changes in applicable or
appropriate standards may occur, whether they result from legislation or the broadening of
knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by
changes outside our control. Therefore, this report is subject to review and should not be relied
upon after a period of three years.
1
8
4
1
8
4
184
18
4
184
184
184
18
4
183
183
1
8
3
183
183
18
3
183
18
3
18
2
18
2
18
2
18
2
18
2
18
2
1
8
2
182
18
1
18
1
18
1
181
18
1
1
8
1
1
8
1
18
1
18
0
18
0
180
18
0
1
8
0
18
0
179
17
9
17
9
17
9
179
1
7
9
17
8
17
8
17
8
178
1
7
8
17
7
17
7
17
7
177
17
7
17
6
17
6
176
17
6
176
17
5
17
5
17
5
17
5
17
4
17
4
1
7
4
17
4
1
7
3
173
17
3
17
3
17
2
17
2
17
2
17
2
17
1
17
1
17
1
17
1
17
0
17
0
17
0
17
0
16
9
16
9
16
9
16
9
168
16
8
16
8
16
8
167
16
7
16
7
16
7
166
16
6
16
6
16
6
165
16
5
16
5
16
516
4
16
4
16
4
164
16
3
16
3
16
3
163
16
2
16
2
16
2
16
2
16
1
16
1
16
1
16
1
16
0
16
0
LOT 2
FF = 182.0
PAD = 181.3LOT 1
FF = 181.0
PAD = 180.3
LOT 3
FF = 182.0
PAD = 181.3
LOT 2 - ADU
FF = 182.0
PAD = 181.3
LOT 4
FF = 177.0
PAD = 176.3
LOT 5
FF = 167.0
PAD = 166.3
LOT 5 - ADU
FF = 168.0
PAD = 167.3
LOT 3 - ADU
FF = 182.0
PAD = 181.3
LOT 4 - ADU
FF = 173.0
PAD = 172.3
LOT 1 - ADU
FF = 181.0
PAD = 180.3
B-1
B-2
B-3
B-4
B-5
IB-1
IB-2
IB-3
Qop
Qop
Qop
APPROX. SITE
AND GRADING LIMITS
APPROX. SITE
AND GRADING LIMITS
1 1'
EXISTING
RESIDENCE
EXISTING
RESIDENCE
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159 SHEET OF
PROJECT NO.
SCALE DATE
FIGURE
Plotted:12/29/2021 7:39AM | By:RUBEN AGUILAR | File Location:Y:\PROJECTS\G2861-11-01 Highland 5\SHEETS\G2861-11-01 GeoMap.dwg
GEOTECHNICAL ENVIRONMENTAL MATERIALS
1" =
GEOLOGIC 1AP
HIGHLAND 5
2908 - 2924 HIGHLAND DRIVE
CARLSBAD, CALIFORNIA
10' 12 - 29 - 2021
G2861 - 11 - 01
1 1 1
B-5
IB-3
GEOCON LEGEND
........OLD PARALIC DEPOSITS (Units 2-4)Qop
........APPROX. LOCATION OF GEOTECHNICAL BORING (GeoSoils, 2021)
........APPROX. LOCATION OF INFILTRATION BORING (GeoSoils, 2021)
1 1'........APPROX. LOCATION OF GEOLOGIC CROSS-SECTION
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SCALE 1" 10' (On 42x30)
GEOCON
LN COJ:tP O HA'l't,:ll
■ ■
40'
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DISTANCE (FEET)
SCALE: 1" = 10' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION 1-1'
140
150
160
170
180
190
200
140
150
160
170
180
190
200
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 360 370
1 1'
PROPOSED
GRADE
EXISTING
GRADE
PL
PL
B-2
Elevation=183'
(Proj. 13' SE)
B-3
Elevation=178'
(Proj. 67' NW)
B-5
Elevation=168'
(Proj. 64' NW)
LOT 4 BUILDING PAD
EL. 176.3'
LOT 3 BUILDING PAD
EL. 181.3'LOT 3 ADU BUILDING PAD
EL. 181.3'
HIGHLAND DRIVE
BMP
RETAINING WALLS PROPOSED
GRADE
BMP-1 Qop
Qop
PROPOSED
GRADE
N57ºE
Plotted:12/29/2021 7:40AM | By:RUBEN AGUILAR | File Location:Y:\PROJECTS\G2861-11-01 Highland 5\SOURCE\SECTION\G2861-11-01 Profile.dwg
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159 SHEET OF
PROJECT NO.
SCALE DATE
FIGURE
GEOTECHNICAL ENVIRONMENTAL MATERIALS
1" =
GEOLOGIC CROSS - SEC8ION
HIGHLAND 5
2908 - 2924 HIGHLAND DRIVE
CARLSBAD, CALIFORNIA
10' 12 - 29 - 2021
G2861 - 11 - 01
1 1 2
B-5
GEOCON LEGEND
........OLD PARALIC DEPOSITS (Units 2-4)Qop
........APPROX. LOCATION OF GEOTECHNICAL BORING (GeoSoils, 2021)
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GEOCON
LNCOJ:t P O H A'l't,:11
■ ■
APPENDIX A
APPENDIX A
PREVIOUS BORING LOGS
PREPARED BY
GEOSOILS, INC.
FOR
HIGHLAND 5
CARLSBAD, CALIFORNIA
UNIFIED SOIL CLASSIFICATION SYSTEM CONSISTENCY OR RELATIVE DENSITY
Major Divisions Group
Symbols Typical Names CRITERIA
Co
a
r
s
e
-
G
r
a
i
n
e
d
S
o
i
l
s
Mo
r
e
t
h
a
n
5
0
%
r
e
t
a
i
n
e
d
o
n
N
o
.
2
0
0
s
i
e
v
e
Gr
a
v
e
l
s
50
%
o
r
m
o
r
e
o
f
co
a
r
s
e
f
r
a
c
t
i
o
n
re
t
a
i
n
e
d
o
n
N
o
.
4
s
i
e
v
e
Cl
e
a
n
Gr
a
v
e
l
s
GW Well-graded gravels and gravel-sand mixtures, little or no fines Standard Penetration Test
Penetration
Resistance N Relative (blows/ft)Density
0 - 4 Very loose
4 - 10 Loose
10 - 30 Medium
30 - 50 Dense
> 50 Very dense
GP Poorly graded gravels andgravel-sand mixtures, little or no
fines
Gr
a
v
e
l
wi
t
h
GM Silty gravels gravel-sand-silt
mixtures
GC Clayey gravels, gravel-sand-clay
mixtures
Sa
n
d
s
mo
r
e
t
h
a
n
5
0
%
o
f
co
a
r
s
e
f
r
a
c
t
i
o
n
pa
s
s
e
s
N
o
.
4
s
i
e
v
e
Cle
a
n
Sa
n
d
s
SW Well-graded sands and gravelly
sands, little or no fines
SP Poorly graded sands andgravelly sands, little or no fines
Sa
n
d
s
wi
t
h
Fi
n
e
s
SM Silty sands, sand-silt mixtures
SC Clayey sands, sand-clay
mixtures
Fi
n
e
-
G
r
a
i
n
e
d
S
o
i
l
s
50
%
o
r
m
o
r
e
p
a
s
s
e
s
N
o
.
2
0
0
s
i
e
v
e
Sil
t
s
a
n
d
C
l
a
y
s
Liq
u
i
d
l
i
m
i
t
50
%
o
r
l
e
s
s
ML Inorganic silts, very fine sands,rock flour, silty or clayey finesands
Standard Penetration Test
Unconfined
Penetration Compressive
Resistance N Strength
(blows/ft)Consistency (tons/ft2)
<2 Very Soft <0.25
2 - 4 Soft 0.25 - .050
4 - 8 Medium 0.50 - 1.00
8 - 15 Stiff 1.00 - 2.00
15 - 30 Very Stiff 2.00 - 4.00
>30 Hard >4.00
CL
Inorganic clays of low to
medium plasticity, gravelly clays,
sandy clays, silty clays, lean
clays
OL Organic silts and organic silty
clays of low plasticity
Si
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MH
Inorganic silts, micaceous or
diatomaceous fine sands or silts,
elastic silts
CH Inorganic clays of high plasticity,
fat clays
OH Organic clays of medium to high
plasticity
Highly Organic Soils PT Peat, mucic, and other highly
organic soils
3"3/4"#4 #10 #40 #200 U.S. Standard Sieve
Unified Soil
Classification Cobbles Gravel Sand Silt or Clay
coarse fine coarse medium fine
MOISTURE CONDITIONS MATERIAL QUANTITY OTHER SYMBOLS
Dry Absence of moisture: dusty, dry to the touch trace 0 - 5 %C Core Sample
Slightly Moist Below optimum moisture content for compaction few 5 - 10 %S SPT Sample
Moist Near optimum moisture content little 10 - 25 %B Bulk Sample
Very Moist Above optimum moisture content some 25 - 45 %–Groundwater
Wet Visible free water; below water table Qp Pocket Penetrometer
BASIC LOG FORMAT:
Group name, Group symbol, (grain size), color, moisture, consistency or relative density. Additional comments: odor, presence of roots, mica, gypsum,
coarse grained particles, etc.
EXAMPLE:
Sand (SP), fine to medium grained, brown, moist, loose, trace silt, little fine gravel, few cobbles up to 4" in size, some hair roots and rootlets.
File:Mgr: c;\SoilClassif.wpd PLATE B-1
I I I I I I I I I
-
0
5
10
15
20
25
30
47/50-5"
37
58
64
41
SM
SP
139.2
168.7
150.9
169.5
193.7
7.8
11.8
7.7
6.3
4.1
32.9
TOPSOIL:@ 0' SILTY SAND, brown, damp, loose.
PARALIC DEPOSITS:@ 0.1' SILTY SAND, light brown, damp, very dense; clean, fine tomedium grained.
@ 5' As per 0.1'; dense, light reddish brown.
@ 10' As per 5'; very dense.
@ 13' Slight color change to dark gray reddish brown.
@ 15' SILTY SAND, red brown, damp, very dense.
@ 18' SAND, olive gray, dry, loose; cohesionless fine to medium sands.
Total Depth - 19.5'No Groundwater or Caving EncounteredBackfilled 1-7-21
GeoSoils, Inc.BORING LOG
PROJECT:CROSS REAL ESTATE INVESTORS2908 Highland Dr., Carlsbad W.O.8037-A-SC BORING B-1 SHEET 1 OF
DATE EXCAVATED 1-7-21 LOGGED BY:TMP APPROX. ELEV.:180 MSL
SAMPLE METHOD:Cal Sampler & 140 lb Hammer @ 30-in Drop
Standard Penetration Test Groundwater
Undisturbed, Ring Sample Seepage
GeoSoils, Inc.
PLATE
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Material Description
1
B-2
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31.5
37.8
37.3
TOPSOIL:@ 0' SILTY SAND, brown, damp, medium dense.
PARALIC DEPOSITS:@ 0.1' SILTY SAND, reddish brown, damp, dense.
@ 10' As per 0.1'; very dense.
@ 15' As per 10'.
Total Depth = 16'No Groundwater or Caving EncounteredBackfilled 1-7-21
GeoSoils, Inc.BORING LOG
PROJECT:CROSS REAL ESTATE INVESTORS2908 Highland Dr., Carlsbad W.O.8037-A-SC BORING B-2 SHEET 1 OF
DATE EXCAVATED 1-7-21 LOGGED BY:TMP APPROX. ELEV.:183 MSL
SAMPLE METHOD:Cal Sampler & 140 lb Hammer @ 30-in Drop
Standard Penetration Test Groundwater
Undisturbed, Ring Sample Seepage
GeoSoils, Inc.
PLATE
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Material Description
1
B-3
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15
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SM TOPSOIL:@ 0' SILTY SAND, dark reddish brown, moist dense; numerous roots androotlets to ‚" diameter.
PARALIC DEPOSITS:@ 1' SILTY SAND, reddish light brown, damp, dense; clean.
@ 10' As per 1'; very dense.
@ 16' As per 10'.Total Depth = 16'No Groundwater or Caving EncounteredBackfilled 1-7-21
GeoSoils, Inc.BORING LOG
PROJECT:CROSS REAL ESTATE INVESTORS2908 Highland Dr., Carlsbad W.O.8037-A-SC BORING B-3 SHEET 1 OF
DATE EXCAVATED 1-7-21 LOGGED BY:TMP APPROX. ELEV.:178 MSL
SAMPLE METHOD:Cal Sampler & 140 lb Hammer @ 30-in Drop
Standard Penetration Test Groundwater
Undisturbed, Ring Sample Seepage
GeoSoils, Inc.
PLATE
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Material Description
1
B-4
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0
5
10
15
20
25
30
29
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34/50-5½
SM TOPSOIL:@ 0' SILTY SAND, brown, damp, medium dense.
PARALIC DEPOSITS:@ 0.1' SILTY SAND, light reddish brown, damp, medium dense;abundant gopher holes, fine to medium sands.
@ 5' As per 0', dense, reddish brown, moist, dense; fine to coarse sands.
@ 10' As per 5'; very dense.
Total Depth = 11'No Groundwater or Caving Encountered
Backfilled 1-7-21
GeoSoils, Inc.BORING LOG
PROJECT:CROSS REAL ESTATE INVESTORS2908 Highland Dr., Carlsbad W.O.8037-A-SC BORING B-4 SHEET 1 OF
DATE EXCAVATED 1-7-21 LOGGED BY:TMP APPROX. ELEV.:174 MSL
SAMPLE METHOD:Cal Sampler & 140 lb Hammer @ 30-in Drop
Standard Penetration Test Groundwater
Undisturbed, Ring Sample Seepage
GeoSoils, Inc.
PLATE
De
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)
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Material Description
1
B-5
H
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0
5
10
15
20
25
30
26
54
SM TOPSOIL:@ 0' SILTY SAND, dark reddish brown, moist, medium dense.
PARALIC DEPOSITS:@ 1.1' SILTY SAND, light reddish brown, damp, medium dense; fine tocoarse sands.
@ 10' As per 1.1'; very dense.
Total Depth = 11.5'No Groundwater or Caving EncounteredBackfilled 1-7-21
GeoSoils, Inc.BORING LOG
PROJECT:CROSS REAL ESTATE INVESTORS2908 Highland Dr., Carlsbad W.O.8037-A-SC BORING B-5 SHEET 1 OF
DATE EXCAVATED 1-7-21 LOGGED BY:TMP APPROX. ELEV.:168 MSL
SAMPLE METHOD:Cal Sampler & 140 lb Hammer @ 30-in Drop
Standard Penetration Test Groundwater
Undisturbed, Ring Sample Seepage
GeoSoils, Inc.
PLATE
De
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(
f
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)
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Material Description
1
B-6
H
~
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0
5
10
15
20
25
30
SM TOPSOIL:0' SILTY SAND, reddish brown, damp, medium dense; fine to mediumsands.
PARALIC DEPOSITS:@ 0.8' SILTY SAND, reddish light brown, damp, dense; fine sands.
Total Depth = 5'No Groundwater or Caving EncounteredBackfilled 1-8-21
GeoSoils, Inc.BORING LOG
PROJECT:CROSS REAL ESTATE INVESTORS2908 Highland Dr., Carlsbad W.O.8037-A-SC BORING IB-1 SHEET 1 OF
DATE EXCAVATED 1-7-21 LOGGED BY:TMP APPROX. ELEV.:163 MSL
SAMPLE METHOD:
Standard Penetration Test Groundwater
Undisturbed, Ring Sample Seepage
GeoSoils, Inc.
PLATE
De
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(
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Material Description
1
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SM TOPSOIL:@ 0' SILTY SAND, reddish brown, damp, medium dense; fine to mediumsands.
PARALIC DEPOSITS:@ 0.8' SILTY SAND, reddish light brown, damp, dense.
Total Depth = 5'No Groundwater or Caving Encountered1-8-21
GeoSoils, Inc.BORING LOG
PROJECT:CROSS REAL ESTATE INVESTORS2908 Highland Dr., Carlsbad W.O.8037-A-SC BORING IB-2 SHEET 1 OF
DATE EXCAVATED 1-7-21 LOGGED BY:TMP APPROX. ELEV.:163 MSL
SAMPLE METHOD:
Standard Penetration Test Groundwater
Undisturbed, Ring Sample Seepage
GeoSoils, Inc.
PLATE
De
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(
f
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Material Description
1
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SM TOPSOIL:@ 0' SILTY SAND, reddish brown, damp, medium dense.
PARALIC DEPOSITS:@ 0.8 SILTY SAND, reddish light brown, damp, medium dense to verydense with depth; fine sands.
@ 5' Becomes reddish brown; fine to medium sands.
Total Depth = 15'
No Groundwater or Caving EncounteredBackfilled 1-8-21
GeoSoils, Inc.BORING LOG
PROJECT:CROSS REAL ESTATE INVESTORS2908 Highland Dr., Carlsbad W.O.8037-A-SC BORING IB-3 SHEET 1 OF
DATE EXCAVATED 1-7-21 LOGGED BY:TMP APPROX. ELEV.:162 MSL
SAMPLE METHOD:
Standard Penetration Test Groundwater
Undisturbed, Ring Sample Seepage
GeoSoils, Inc.
PLATE
De
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f
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)
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1
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APPENDIX B
APPENDIX B
PREVIOUS LABORATORY DATA
PREPARED BY
GEOSOILS, INC.
FOR
HIGHLAND 5
CARLSBAD, CALIFORNIA
GeoSoils, Inc.
Cross Real Estate Investors, LLC W.O. 8037-A-SC
Tract 80-46, Carlsbad January 27, 2021
File:e:\wp12\8000\8037.pge Page 11
•Sieche
•Tsunami
SLOPE STABILITY
Assuming proper surface drainage, regular and periodic care and maintenance, normal
rainfall, permanent graded slopes, constructed from the onsite materials, as recommended
herein, are considered grossly and surficially stable. The tallest natural slope, located along
the western portion of the property from the eastern ridge crest is generally considered
grossly stable given the absence of adverse structures and no evidence of historic gross
instability. Site earth materials are also considered erosive. As such, positive surface
drainage practices and vegetative covering should be maintained throughout the life of the
project. Temporary slopes for construction are discussed in subsequent sections of our
report.
LABORATORY TESTING
Laboratory tests were performed on representative samples of site earth materials collected
during our subsurface exploration in order to evaluate their physical characteristics. Test
procedures used and results obtained are presented below.
Classification
Soils were visually classified with respect to the Unified Soil Classification System (U.S.C.S.)
in general accordance with ASTM D 2487 and D 2488. The soil classifications of the onsite
soils are provided on the Boring Logs in Appendix B.
Moisture-Density Relations
The field moisture contents and dry unit weights were determined for selected samples in
the laboratory. Testing was performed in general accordance with ASTM D 2937 and
ASTM D 2216. The dry unit weight was determined in pounds per cubic foot (pcf), and the
field moisture content was determined as a percentage of the dry weight. The results of
these tests are shown on the Boring Logs in Appendix B.
Expansion Index
Representative samples of near-surface site soils were evaluated for expansion potential.
Expansion Index (E.I.) testing and expansion potential classification was performed in
general accordance with ASTM Standard D 4829, the results of the expansion testing are
presented in the following table.
GeoSoils, Inc.
Cross Real Estate Investors, LLC W.O. 8037-A-SC
Tract 80-46, Carlsbad January 27, 2021
File:e:\wp12\8000\8037.pge Page 12
SAMPLE LOCATION
AND DEPTH (FT)EXPANSION INDEX EXPANSION POTENTIAL
B -1 @ 0-5 # 20 Very Low
Particle-Size Analysis
A particle-size evaluation was performed on a representative, soil sample (B - 1 @ 0 - 5') in
general accordance with ASTM D 422-63. The testing was utilized to evaluate the soil
classification in accordance with the Unified Soil Classification System (USCS). The results
of the particle-size evaluation indicate that the tested soil is a silty sand (0.2% gravel,
72% sand, 27.8% fines [USCS Symbol - SM]).
Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides
GSI conducted sampling of onsite earth materials for general soil corrosivity and soluble
sulfates, and chlorides testing. The testing included evaluation of soil pH, soluble sulfates,
chlorides, and saturated resistivity. Test results are presented in the following table:
SAMPLE LOCATION
AND DEPTH (FT)pH
SATURATED
RESISTIVITY
(ohm-cm)
SOLUBLE
SULFATES
(% by weight)
SOLUBLE
CHLORIDES
(ppm)
B-1 @ 0-5 7.3 2,800 0.003 30
Corrosion Summary
Laboratory testing indicates that tested samples of the onsite soils are neutral with respect
to soil acidity/alkalinity, are moderately corrosive to exposed, buried metals when saturated,
present negligible (“not applicable” [or class SO] per American Concrete Institute
[ACI] 318-14) sulfate exposure to concrete, and are below action levels for chloride
exposure (per State of California Department of Transportation, 2003). Reinforced concrete
mix design for foundations, slab-on-grade floors, and pavements should minimally conform
to “Exposure Class C1” in Table 19.3.2.1 of ACI 318-14, as concrete would likely be
exposed to moisture. It should be noted that GSI does not consult in the field of corrosion
engineering. The client and project architect should agree on the level of corrosion
protection required for the project and seek consultation from a qualified corrosion
consultant.
11~~~=~11
I I I I
I I I I
Tested By: TR Checked By: TR
1-18-21
(no specification provided)
PL=LL=PI=
D90=D85=D60=D50=D30=D15=D10=Cu=Cc=
USCS=AASHTO=
*
Reddish Brown Silty Sand
.5
.375
#4
#10
#20
#40
#60
#100
#200
100.0
99.8
99.8
99.8
96.2
75.6
52.6
38.2
27.8
0.6415 0.5451 0.2989
0.2325 0.0896
SM
Cross Real Estate Investors
2908 Highland Dr.
8037-A-SC
Soil Description
Atterberg Limits
Coefficients
Classification
Remarks
Source of Sample: B-1 Depth: 0-5
Sample Number: B-1 Date:
Client:
Project:
Project No:Plate D-1
SIEVE PERCENT SPEC.*PASS?
SIZE FINER PERCENT (X=NO)
PE
R
C
E
N
T
F
I
N
E
R
0
10
20
30
40
50
60
70
80
90
100
GRAIN SIZE - mm.
0.0010.010.1110100
% +3"Coarse
% Gravel
Fine Coarse Medium
% Sand
Fine Silt
% Fines
Clay
0.0 0.0 0.2 0.0 24.2 47.8 27.8
6
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#1
0
0
#1
4
0
#2
0
0
Particle Size Distribution Report
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A B C D
Compactor air pressure PSI 350 350 350
Water added %1.9 2.6 3.7
Moisture at compaction %9.1 9.8 10.9
Height of sample IN 2.52 2.52 2.53
Dry density PCF 128.3 127.9 126.3
R-Value by exudation 79 68 41
R-Value by exudation, corrected 79 68 41
Exudation pressure PSI 602 300 189
Stability thickness FT 0.27 0.41 0.76
Expansion pressure thickness FT 0.10 0.00 0.00
Traffic index, assumed 5.0 Sample Location:
Gravel equivalent factor, assumed 1.25 Sample Description:
Expansion, stability equilibrium 0 Notes:
R-Value by expansion NA
R-Value by exudation 68 Test Method:
R-Value at equilibrium 68
GeoSoils, Inc.
5741 Palmer Way Project:Cross Real Estate Investors
Carlsbad, CA 92008
Telephone: (760) 438-3155 Number:8037-A-SC
Fax: (760) 931-0915
9/2/2010 Date:January 2021 Plate:D-2
TEST SPECIMEN
R - VALUE TEST RESULTS
-
DESIGN CALCULATION DATA
0% Retained on 3/4 inch sieve
Reddish Brown Silty Sand
SAMPLE INFORMATION
B-4, 0-5ft
Cal-Trans Test 301
0.00
0.50
1.00
1.50
2.00
0.00 0.50 1.00 1.50 2.00
Co
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(
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Cover Thickness by Expansion Pressure (ft)
Expansion, Stability Equilibrium
0
10
20
30
40
50
60
70
80
90
100
0100200300400500600700800
R-Va
l
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Exudation Pressure (psi)
R-Value By Exudation
V
V
V
/
/
V ....
/ ' V ' I/
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IISoilCor
CORROSION & THERMAL SCIENCES
42184 Remington Ave, Temecula CA 92590
ph (951) 795-3135 • fx (951) 894-2683
Work Order No.: 21A3141
Client: GeoSoils, Inc.
Project No.: 8037-A-SC
Project Name: Cross Real Estate Investors
Report Date: January 21, 2021
Laboratory Test(s) Results Summary
The subject soil sample was processed with the U.S. Standard No. 10 Sieve and tested for pH
(ASTM G 51-95 2012), Soil Resistivity (ASTM G 57-06 2012), Sulfate Ion Content (ASTM D 516-16)
and Chloride Ion Content (ASTM D 512-12B). The test results follow:
pH As Rec'd Saturated Sulfate Chloride
Sample Identification Resistivity Resistivity Content Content (H+) (ohm-cm) (ohm-cm) (mg/L) (mg/L)
B-1 @ 0-5ft 7.3 190,000 2,800 30 30
*ND=No Detection
We appreciate the opportunity to serve you. Please do not hesitate to contact us with any
questions or clarifications regarding these results or procedures.
01'(..Ufl:4Ji.:,,,tol�
t.1CMDER
Ahmet K. Kaya, Laboratory Manager
www.soilcor.com
Form No. 1-PR
Rev. 08/2019
W.O. 8037- A-SC
Plate D-3
APPENDIX C
APPENDIX C
RECOMMENDED GRADING SPECIFICATIONS
FOR
HIGHLAND 5
2908 – 2924 HIGHLAND DRIVE
PROJECT NO. G2861-11-01
GI rev. 07/2015
RECOMMENDED GRADING SPECIFICATIONS
1. GENERAL
1.1 These Recommended Grading Specifications shall be used in conjunction with the
Geotechnical Report for the project prepared by Geocon. The recommendations contained
in the text of the Geotechnical Report are a part of the earthwork and grading specifications
and shall supersede the provisions contained hereinafter in the case of conflict.
1.2 Prior to the commencement of grading, a geotechnical consultant (Consultant) shall be
employed for the purpose of observing earthwork procedures and testing the fills for
substantial conformance with the recommendations of the Geotechnical Report and these
specifications. The Consultant should provide adequate testing and observation services so
that they may assess whether, in their opinion, the work was performed in substantial
conformance with these specifications. It shall be the responsibility of the Contractor to
assist the Consultant and keep them apprised of work schedules and changes so that
personnel may be scheduled accordingly.
1.3 It shall be the sole responsibility of the Contractor to provide adequate equipment and
methods to accomplish the work in accordance with applicable grading codes or agency
ordinances, these specifications and the approved grading plans. If, in the opinion of the
Consultant, unsatisfactory conditions such as questionable soil materials, poor moisture
condition, inadequate compaction, and/or adverse weather result in a quality of work not in
conformance with these specifications, the Consultant will be empowered to reject the
work and recommend to the Owner that grading be stopped until the unacceptable
conditions are corrected.
2. DEFINITIONS
2.1 Owner shall refer to the owner of the property or the entity on whose behalf the grading
work is being performed and who has contracted with the Contractor to have grading
performed.
2.2 Contractor shall refer to the Contractor performing the site grading work.
2.3 Civil Engineer or Engineer of Work shall refer to the California licensed Civil Engineer
or consulting firm responsible for preparation of the grading plans, surveying and verifying
as-graded topography.
2.4 Consultant shall refer to the soil engineering and engineering geology consulting firm
retained to provide geotechnical services for the project.
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2.5 Soil Engineer shall refer to a California licensed Civil Engineer retained by the Owner,
who is experienced in the practice of geotechnical engineering. The Soil Engineer shall be
responsible for having qualified representatives on-site to observe and test the Contractor's
work for conformance with these specifications.
2.6 Engineering Geologist shall refer to a California licensed Engineering Geologist retained
by the Owner to provide geologic observations and recommendations during the site
grading.
2.7 Geotechnical Report shall refer to a soil report (including all addenda) which may include
a geologic reconnaissance or geologic investigation that was prepared specifically for the
development of the project for which these Recommended Grading Specifications are
intended to apply.
3. MATERIALS
3.1 Materials for compacted fill shall consist of any soil excavated from the cut areas or
imported to the site that, in the opinion of the Consultant, is suitable for use in construction
of fills. In general, fill materials can be classified as soil fills, soil-rock fills or rock fills, as
defined below.
3.1.1 Soil fills are defined as fills containing no rocks or hard lumps greater than
12 inches in maximum dimension and containing at least 40 percent by weight of
material smaller than ¾ inch in size.
3.1.2 Soil-rock fills are defined as fills containing no rocks or hard lumps larger than
4 feet in maximum dimension and containing a sufficient matrix of soil fill to allow
for proper compaction of soil fill around the rock fragments or hard lumps as
specified in Paragraph 6.2. Oversize rock is defined as material greater than
12 inches.
3.1.3 Rock fills are defined as fills containing no rocks or hard lumps larger than 3 feet
in maximum dimension and containing little or no fines. Fines are defined as
material smaller than ¾ inch in maximum dimension. The quantity of fines shall be
less than approximately 20 percent of the rock fill quantity.
3.2 Material of a perishable, spongy, or otherwise unsuitable nature as determined by the
Consultant shall not be used in fills.
3.3 Materials used for fill, either imported or on-site, shall not contain hazardous materials as
defined by the California Code of Regulations, Title 22, Division 4, Chapter 30, Articles 9
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and 10; 40CFR; and any other applicable local, state or federal laws. The Consultant shall
not be responsible for the identification or analysis of the potential presence of hazardous
materials. However, if observations, odors or soil discoloration cause Consultant to suspect
the presence of hazardous materials, the Consultant may request from the Owner the
termination of grading operations within the affected area. Prior to resuming grading
operations, the Owner shall provide a written report to the Consultant indicating that the
suspected materials are not hazardous as defined by applicable laws and regulations.
3.4 The outer 15 feet of soil-rock fill slopes, measured horizontally, should be composed of
properly compacted soil fill materials approved by the Consultant. Rock fill may extend to
the slope face, provided that the slope is not steeper than 2:1 (horizontal:vertical) and a soil
layer no thicker than 12 inches is track-walked onto the face for landscaping purposes. This
procedure may be utilized provided it is acceptable to the governing agency, Owner and
Consultant.
3.5 Samples of soil materials to be used for fill should be tested in the laboratory by the
Consultant to determine the maximum density, optimum moisture content, and, where
appropriate, shear strength, expansion, and gradation characteristics of the soil.
3.6 During grading, soil or groundwater conditions other than those identified in the
Geotechnical Report may be encountered by the Contractor. The Consultant shall be
notified immediately to evaluate the significance of the unanticipated condition.
4. CLEARING AND PREPARING AREAS TO BE FILLED
4.1 Areas to be excavated and filled shall be cleared and grubbed. Clearing shall consist of
complete removal above the ground surface of trees, stumps, brush, vegetation, man-made
structures, and similar debris. Grubbing shall consist of removal of stumps, roots, buried
logs and other unsuitable material and shall be performed in areas to be graded. Roots and
other projections exceeding 1½ inches in diameter shall be removed to a depth of 3 feet
below the surface of the ground. Borrow areas shall be grubbed to the extent necessary to
provide suitable fill materials.
4.2 Asphalt pavement material removed during clearing operations should be properly
disposed at an approved off-site facility or in an acceptable area of the project evaluated by
Geocon and the property owner. Concrete fragments that are free of reinforcing steel may
be placed in fills, provided they are placed in accordance with Section 6.2 or 6.3 of this
document.
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4.3 After clearing and grubbing of organic matter and other unsuitable material, loose or
porous soils shall be removed to the depth recommended in the Geotechnical Report. The
depth of removal and compaction should be observed and approved by a representative of
the Consultant. The exposed surface shall then be plowed or scarified to a minimum depth
of 6 inches and until the surface is free from uneven features that would tend to prevent
uniform compaction by the equipment to be used.
4.4 Where the slope ratio of the original ground is steeper than 5:1 (horizontal:vertical), or
where recommended by the Consultant, the original ground should be benched in
accordance with the following illustration.
TYPICAL BENCHING DETAIL
Remove All
Unsuitable Material
As Recommended By
Consultant
Finish Grade Original Ground
Finish Slope Surface
Slope To Be Such That
Sloughing Or Sliding
Does Not Occur Varies
“B”
See Note 1
No Scale
See Note 2
1
2
DETAIL NOTES: (1) Key width "B" should be a minimum of 10 feet, or sufficiently wide to permit complete coverage with the compaction equipment used. The base of the key should be graded horizontal, or inclined slightly into the natural slope.
(2) The outside of the key should be below the topsoil or unsuitable surficial material and at least 2 feet into dense formational material. Where hard rock is exposed in the bottom of the key, the depth and configuration of the key may be modified as approved by the Consultant.
4.5 After areas to receive fill have been cleared and scarified, the surface should be moisture
conditioned to achieve the proper moisture content, and compacted as recommended in
Section 6 of these specifications.
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.................... 1 I .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... ....
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5. COMPACTION EQUIPMENT
5.1 Compaction of soil or soil-rock fill shall be accomplished by sheepsfoot or segmented-steel
wheeled rollers, vibratory rollers, multiple-wheel pneumatic-tired rollers, or other types of
acceptable compaction equipment. Equipment shall be of such a design that it will be
capable of compacting the soil or soil-rock fill to the specified relative compaction at the
specified moisture content.
5.2 Compaction of rock fills shall be performed in accordance with Section 6.3.
6. PLACING, SPREADING AND COMPACTION OF FILL MATERIAL
6.1 Soil fill, as defined in Paragraph 3.1.1, shall be placed by the Contractor in accordance with
the following recommendations:
6.1.1 Soil fill shall be placed by the Contractor in layers that, when compacted, should
generally not exceed 8 inches. Each layer shall be spread evenly and shall be
thoroughly mixed during spreading to obtain uniformity of material and moisture
in each layer. The entire fill shall be constructed as a unit in nearly level lifts. Rock
materials greater than 12 inches in maximum dimension shall be placed in
accordance with Section 6.2 or 6.3 of these specifications.
6.1.2 In general, the soil fill shall be compacted at a moisture content at or above the
optimum moisture content as determined by ASTM D 1557.
6.1.3 When the moisture content of soil fill is below that specified by the Consultant,
water shall be added by the Contractor until the moisture content is in the range
specified.
6.1.4 When the moisture content of the soil fill is above the range specified by the
Consultant or too wet to achieve proper compaction, the soil fill shall be aerated by
the Contractor by blading/mixing, or other satisfactory methods until the moisture
content is within the range specified.
6.1.5 After each layer has been placed, mixed, and spread evenly, it shall be thoroughly
compacted by the Contractor to a relative compaction of at least 90 percent.
Relative compaction is defined as the ratio (expressed in percent) of the in-place
dry density of the compacted fill to the maximum laboratory dry density as
determined in accordance with ASTM D 1557. Compaction shall be continuous
over the entire area, and compaction equipment shall make sufficient passes so that
the specified minimum relative compaction has been achieved throughout the
entire fill.
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6.1.6 Where practical, soils having an Expansion Index greater than 50 should be placed
at least 3 feet below finish pad grade and should be compacted at a moisture
content generally 2 to 4 percent greater than the optimum moisture content for the
material.
6.1.7 Properly compacted soil fill shall extend to the design surface of fill slopes. To
achieve proper compaction, it is recommended that fill slopes be over-built by at
least 3 feet and then cut to the design grade. This procedure is considered
preferable to track-walking of slopes, as described in the following paragraph.
6.1.8 As an alternative to over-building of slopes, slope faces may be back-rolled with a
heavy-duty loaded sheepsfoot or vibratory roller at maximum 4-foot fill height
intervals. Upon completion, slopes should then be track-walked with a D-8 dozer
or similar equipment, such that a dozer track covers all slope surfaces at least
twice.
6.2 Soil-rock fill, as defined in Paragraph 3.1.2, shall be placed by the Contractor in accordance
with the following recommendations:
6.2.1 Rocks larger than 12 inches but less than 4 feet in maximum dimension may be
incorporated into the compacted soil fill, but shall be limited to the area measured
15 feet minimum horizontally from the slope face and 5 feet below finish grade or
3 feet below the deepest utility, whichever is deeper.
6.2.2 Rocks or rock fragments up to 4 feet in maximum dimension may either be
individually placed or placed in windrows. Under certain conditions, rocks or rock
fragments up to 10 feet in maximum dimension may be placed using similar
methods. The acceptability of placing rock materials greater than 4 feet in
maximum dimension shall be evaluated during grading as specific cases arise and
shall be approved by the Consultant prior to placement.
6.2.3 For individual placement, sufficient space shall be provided between rocks to allow
for passage of compaction equipment.
6.2.4 For windrow placement, the rocks should be placed in trenches excavated in
properly compacted soil fill. Trenches should be approximately 5 feet wide and
4 feet deep in maximum dimension. The voids around and beneath rocks should be
filled with approved granular soil having a Sand Equivalent of 30 or greater and
should be compacted by flooding. Windrows may also be placed utilizing an
"open-face" method in lieu of the trench procedure, however, this method should
first be approved by the Consultant.
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6.2.5 Windrows should generally be parallel to each other and may be placed either
parallel to or perpendicular to the face of the slope depending on the site geometry.
The minimum horizontal spacing for windrows shall be 12 feet center-to-center
with a 5-foot stagger or offset from lower courses to next overlying course. The
minimum vertical spacing between windrow courses shall be 2 feet from the top of
a lower windrow to the bottom of the next higher windrow.
6.2.6 Rock placement, fill placement and flooding of approved granular soil in the
windrows should be continuously observed by the Consultant.
6.3 Rock fills, as defined in Section 3.1.3, shall be placed by the Contractor in accordance with
the following recommendations:
6.3.1 The base of the rock fill shall be placed on a sloping surface (minimum slope of 2
percent). The surface shall slope toward suitable subdrainage outlet facilities. The
rock fills shall be provided with subdrains during construction so that a hydrostatic
pressure buildup does not develop. The subdrains shall be permanently connected
to controlled drainage facilities to control post-construction infiltration of water.
6.3.2 Rock fills shall be placed in lifts not exceeding 3 feet. Placement shall be by rock
trucks traversing previously placed lifts and dumping at the edge of the currently
placed lift. Spreading of the rock fill shall be by dozer to facilitate seating of the
rock. The rock fill shall be watered heavily during placement. Watering shall
consist of water trucks traversing in front of the current rock lift face and spraying
water continuously during rock placement. Compaction equipment with
compactive energy comparable to or greater than that of a 20-ton steel vibratory
roller or other compaction equipment providing suitable energy to achieve the
required compaction or deflection as recommended in Paragraph 6.3.3 shall be
utilized. The number of passes to be made should be determined as described in
Paragraph 6.3.3. Once a rock fill lift has been covered with soil fill, no additional
rock fill lifts will be permitted over the soil fill.
6.3.3 Plate bearing tests, in accordance with ASTM D 1196, may be performed in both
the compacted soil fill and in the rock fill to aid in determining the required
minimum number of passes of the compaction equipment. If performed, a
minimum of three plate bearing tests should be performed in the properly
compacted soil fill (minimum relative compaction of 90 percent). Plate bearing
tests shall then be performed on areas of rock fill having two passes, four passes
and six passes of the compaction equipment, respectively. The number of passes
required for the rock fill shall be determined by comparing the results of the plate
bearing tests for the soil fill and the rock fill and by evaluating the deflection
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variation with number of passes. The required number of passes of the compaction
equipment will be performed as necessary until the plate bearing deflections are
equal to or less than that determined for the properly compacted soil fill. In no case
will the required number of passes be less than two.
6.3.4 A representative of the Consultant should be present during rock fill operations to
observe that the minimum number of “passes” have been obtained, that water is
being properly applied and that specified procedures are being followed. The actual
number of plate bearing tests will be determined by the Consultant during grading.
6.3.5 Test pits shall be excavated by the Contractor so that the Consultant can state that,
in their opinion, sufficient water is present and that voids between large rocks are
properly filled with smaller rock material. In-place density testing will not be
required in the rock fills.
6.3.6 To reduce the potential for “piping” of fines into the rock fill from overlying soil
fill material, a 2-foot layer of graded filter material shall be placed above the
uppermost lift of rock fill. The need to place graded filter material below the rock
should be determined by the Consultant prior to commencing grading. The
gradation of the graded filter material will be determined at the time the rock fill is
being excavated. Materials typical of the rock fill should be submitted to the
Consultant in a timely manner, to allow design of the graded filter prior to the
commencement of rock fill placement.
6.3.7 Rock fill placement should be continuously observed during placement by the
Consultant.
7. SUBDRAINS
7.1 The geologic units on the site may have permeability characteristics and/or fracture
systems that could be susceptible under certain conditions to seepage. The use of canyon
subdrains may be necessary to mitigate the potential for adverse impacts associated with
seepage conditions. Canyon subdrains with lengths in excess of 500 feet or extensions of
existing offsite subdrains should use 8-inch-diameter pipes. Canyon subdrains less than 500
feet in length should use 6-inch-diameter pipes.
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TYPICAL CANYON DRAIN DETAIL
7.2 Slope drains within stability fill keyways should use 4-inch-diameter (or lager) pipes.
........................
.................
NATURAi.GROUND ,,,,,,-----
NOTES:
............
........
................... __
SEE DETAL BELOW
--
1 ...... 8-lNCH DIAMETER, SCHEDULE 80 PVC PERFORATED PIPE FOR FILLS
IN EXCESS OF 100-FEET IN DEPTH ORA PIPE LENGTH OF LONGER THAN 500 FEET.
2 ...... 6-INCH DIAMETER, SCHEDULE 40 PVC PERFORATED PIPE FOR FILLS
LESS THAN 100-FEET IN DEPTH OR A PIPE LENGTH SHORTER THAN 500 FEET.
,, ------,-
.,,,.,,,,,,,.,,,..
BEDROCK
NOTE: FINAL 20' OF PIPEAT CUTI.ET
SHALL BE NON-PERFORATED.
9 CUBIC FEET/ FOOT OF OPEN
GRADED GRAVEL SURROUNDED BY
MIRAF1140NC (OR EQUIVALENT)
FILTER FABRIC
NO SCALE
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TYPICAL STABILITY FILL DETAIL
7.3 The actual subdrain locations will be evaluated in the field during the remedial grading
operations. Additional drains may be necessary depending on the conditions observed and
the requirements of the local regulatory agencies. Appropriate subdrain outlets should be
evaluated prior to finalizing 40-scale grading plans.
7.4 Rock fill or soil-rock fill areas may require subdrains along their down-slope perimeters to
mitigate the potential for buildup of water from construction or landscape irrigation. The
subdrains should be at least 6-inch-diameter pipes encapsulated in gravel and filter fabric.
Rock fill drains should be constructed using the same requirements as canyon subdrains.
DETAIL
NOTES:
FORMAnONAL
MATERIAL
1 •.... EXCAVATE BACKCUT AT 1:1 INCUNATION (UNLESS OTHERWISE NOTl:D~
2 .... .BASE OF STABILITY FILL TO BE 3 FEET INTO FORMATIONAL MATERIAL, SI.OPING A MINIMUM 5% INTO SLOPE.
3 •.••. STABIUTY FLL TO BE COMF'OSED OF PROPERLY COMPACTED GRANIA..AR SOIL
4 ..... CHIMNEY DRAINS TO BE APPROVED PREFABRICATED CHIMNEY DRAIN PANELS (MIRADRAIN G200N OR EQUIVALENT)
SPACED AF'PROXIMATELY 20 FEET CENTER TO CENTER AND 4 FEETWIDE. CLOSER SPACING MAY BE REQUIRED F
SEEPAGE IS ENCOUNTERED.
5 ..••. FILTER MATERIAL TO BE 314-tlCH, OPEN-GRADED CRUSI-IED ROCK ENCLOSED IN APPROVED FL TER FABRIC (MIRAFI 1-40NC~
6 ..... COLLECTOR PIPE TO BE 4-INCH MINIMUM DIAMETER, PERFORATED, THICK-WALLED PVC SCHEDULE 40 OR
EQUIVALENT, AND SLOPED TO DRAIN AT 1 PERCENT lilNMUM TO APPROVED oun.ET.
NO SCALE
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7.5 Prior to outletting, the final 20-foot segment of a subdrain that will not be extended during
future development should consist of non-perforated drainpipe. At the non-perforated/
perforated interface, a seepage cutoff wall should be constructed on the downslope side of
the pipe.
TYPICAL CUT OFF WALL DETAIL
7.6 Subdrains that discharge into a natural drainage course or open space area should be
provided with a permanent headwall structure.
FRONT VIEW
SIDE VIEW
'
CONCRETE
CUT-OFF WAU.
CONCRETE
CUT-OFFWAU.
SOLID SlJBDRAII P1PE
',( /
8' MIN.
NO SCALE
ll" MIN.(TYP)
ll" MIN.(TYP) /
NO SCALE
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TYPICAL HEADWALL DETAIL
7.7 The final grading plans should show the location of the proposed subdrains. After
completion of remedial excavations and subdrain installation, the project civil engineer
should survey the drain locations and prepare an “as-built” map showing the drain
locations. The final outlet and connection locations should be determined during grading
operations. Subdrains that will be extended on adjacent projects after grading can be placed
on formational material and a vertical riser should be placed at the end of the subdrain. The
grading contractor should consider videoing the subdrains shortly after burial to check
proper installation and functionality. The contractor is responsible for the performance of
the drains.
FRONT VIEW
SIDE VIEW
8"0R8"
SUBDRAIN
CONCRETE
fEADWALL
8" ORB"
SUBDRAIN
~ 24"
NOTE: HEADWALL SHOULD ounET AT TOE OF FILL SLOPE
OR INTO CONTROLLED SURFACE DRAINAGE
NO SCALE
12"
NO SCALE
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8. OBSERVATION AND TESTING
8.1 The Consultant shall be the Owner’s representative to observe and perform tests during
clearing, grubbing, filling, and compaction operations. In general, no more than 2 feet in
vertical elevation of soil or soil-rock fill should be placed without at least one field density
test being performed within that interval. In addition, a minimum of one field density test
should be performed for every 2,000 cubic yards of soil or soil-rock fill placed and
compacted.
8.2 The Consultant should perform a sufficient distribution of field density tests of the
compacted soil or soil-rock fill to provide a basis for expressing an opinion whether the fill
material is compacted as specified. Density tests shall be performed in the compacted
materials below any disturbed surface. When these tests indicate that the density of any
layer of fill or portion thereof is below that specified, the particular layer or areas
represented by the test shall be reworked until the specified density has been achieved.
8.3 During placement of rock fill, the Consultant should observe that the minimum number of
passes have been obtained per the criteria discussed in Section 6.3.3. The Consultant
should request the excavation of observation pits and may perform plate bearing tests on
the placed rock fills. The observation pits will be excavated to provide a basis for
expressing an opinion as to whether the rock fill is properly seated and sufficient moisture
has been applied to the material. When observations indicate that a layer of rock fill or any
portion thereof is below that specified, the affected layer or area shall be reworked until the
rock fill has been adequately seated and sufficient moisture applied.
8.4 A settlement monitoring program designed by the Consultant may be conducted in areas of
rock fill placement. The specific design of the monitoring program shall be as
recommended in the Conclusions and Recommendations section of the project
Geotechnical Report or in the final report of testing and observation services performed
during grading.
8.5 We should observe the placement of subdrains, to check that the drainage devices have
been placed and constructed in substantial conformance with project specifications.
8.6 Testing procedures shall conform to the following Standards as appropriate:
8.6.1 Soil and Soil-Rock Fills:
8.6.1.1 Field Density Test, ASTM D 1556, Density of Soil In-Place By the
Sand-Cone Method.
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8.6.1.2 Field Density Test, Nuclear Method, ASTM D 6938, Density of Soil and
Soil-Aggregate In-Place by Nuclear Methods (Shallow Depth).
8.6.1.3 Laboratory Compaction Test, ASTM D 1557, Moisture-Density
Relations of Soils and Soil-Aggregate Mixtures Using 10-Pound
Hammer and 18-Inch Drop.
8.6.1.4. Expansion Index Test, ASTM D 4829, Expansion Index Test.
9. PROTECTION OF WORK
9.1 During construction, the Contractor shall properly grade all excavated surfaces to provide
positive drainage and prevent ponding of water. Drainage of surface water shall be
controlled to avoid damage to adjoining properties or to finished work on the site. The
Contractor shall take remedial measures to prevent erosion of freshly graded areas until
such time as permanent drainage and erosion control features have been installed. Areas
subjected to erosion or sedimentation shall be properly prepared in accordance with the
Specifications prior to placing additional fill or structures.
9.2 After completion of grading as observed and tested by the Consultant, no further
excavation or filling shall be conducted except in conjunction with the services of the
Consultant.
10. CERTIFICATIONS AND FINAL REPORTS
10.1 Upon completion of the work, Contractor shall furnish Owner a certification by the Civil
Engineer stating that the lots and/or building pads are graded to within 0.1 foot vertically of
elevations shown on the grading plan and that all tops and toes of slopes are within 0.5 foot
horizontally of the positions shown on the grading plans. After installation of a section of
subdrain, the project Civil Engineer should survey its location and prepare an as-built plan
of the subdrain location. The project Civil Engineer should verify the proper outlet for the
subdrains and the Contractor should ensure that the drain system is free of obstructions.
10.2 The Owner is responsible for furnishing a final as-graded soil and geologic report
satisfactory to the appropriate governing or accepting agencies. The as-graded report
should be prepared and signed by a California licensed Civil Engineer experienced in
geotechnical engineering and by a California Certified Engineering Geologist, indicating
that the geotechnical aspects of the grading were performed in substantial conformance
with the Specifications or approved changes to the Specifications.
Geocon Project No. G2861-11-01 December 29, 2021
LIST OF REFERENCES
1.2019 California Building Code, California Code of Regulations, Title 24, Part 2, based on the
2018 International Building Code, prepared by California Building Standards Commission,
dated July 2019.
2.American Concrete Institute, ACI 318-11, Building Code Requirements for Structural
Concrete and Commentary, dated August, 2011.
3.American Concrete Institute, ACI 330-08, Guide for the Design and Construction of Concrete
Parking Lots, dated June, 2008.
4.American Society of Civil Engineers (ASCE), ASCE 7-16, Minimum Design Loads and
Associated Criteria for Buildings and Other Structures, 2017.
5.California Geological Survey, Seismic Shaking Hazards in California, Based on the
USGS/CGS Probabilistic Seismic Hazards Assessment (PSHA) Model, 2002 (revised April
2003). 10% probability of being exceeded in 50 years.
http://redirect.conservation.ca.gov/cgs/rghm/pshamap/pshamain.html
6.City of Carlsbad, Engineering Standards, Volume 1, General Design Standards, 2016
(Chapter 1, Table A: Street Design Criteria)
7.County of San Diego, San Diego County Multi Jurisdiction Hazard Mitigation Plan, San
Diego, California – Final Draft, dated 2017.
8.Historical Aerial Photos. http://www.historicaerials.com
9.Jennings, C. W., 1994, California Division of Mines and Geology, Fault Activity Map of
California and Adjacent Areas, California Geologic Data Map Series Map No. 6.
10.Kennedy, M. P., and S. S. Tan, 2007, Geologic Map of the Oceanside 30’x60’ Quadrangle,
California, USGS Regional Map Series Map No. 2, Scale 1:100,000.
11.Special Publication 117A, Guidelines For Evaluating and Mitigating Seismic Hazards in
California 2008, California Geological Survey, Revised and Re-adopted September 11, 2008.
12.Unpublished reports, aerial photographs, and maps on file with Geocon Incorporated.
13.USGS computer program, Seismic Hazard Curves and Uniform Hazard Response Spectra,
http://geohazards.usgs.gov/designmaps/us/application.php.