HomeMy WebLinkAboutSDP 2021-0016; CARLSBAD OAKS NORTH, LOT 3; UPDATE GEOTECHNICAL REPORT; 2021-05-26oEOCdN
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UPDATE GEOTECHNICAL REPORT
CARLSBAD OAKS NORTH BUSINESS
PARK-LOT 3
CARLSBAD, CALIFORNIA
PREPARED FOR
TECH CONTRACTORS
SAN DIEGO, CALIFORNIA
MAY 26, 2021
PROJECT NO. 06442-32-34
GEOCON
INCORPORATED
GEOTECHNICA L. ENVIRONMENTAL. MATERIALSO
Project No. 06442-32-34
May 26, 2021
Tech Contractors
3575 Kenyon Street
San Diego, California 92110
Attention: Mr. Dean Smith
Subject: UPDATE GEOTECHNICAL REPORT
CARLSBAD OAKS NORTH BUSINESS PARK -LOT 3
CARLSBAD, CALIFORNIA
Dear Mr. Smith:
In accordance with your request, and authorization of our Proposal No. LG-20439 (dated September
30, 2020), we have prepared this update geotechnical report for the proposed development of the
subject project. The accompanying report presents the findings of our study and, our conclusions and
recommendations pertaining to the geotechnical aspects of project development.
Based on the results of this study, the subject site can be developed as planned, provided the
recommendations of this report are followed.
Should you have questions regarding this investigation, or if we may be of further service, please
contact the undersigned at your convenience.
Very truly yours,
GEOCON IN CORPORA TED
Emilio Alvarado
RCE 66915
EA:DBE:arm
( e-mail) Addressee
David B. Evans
CEG 1860
6960 Flanders Drive ■ San Diego, California 92121-2974 ■ Telephone 858.558.6900 ■ Fox 858.558.6159
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TABLE OF CONTENTS
1. PURPOSE AND SCOPE ...................................................................................................................... 1
2. PREVIOUS SITE DEVELOPMENT ................................................................................................... 1
3. SITE AND PROJECT DESCRIPTION ................................................................................................ 1
4. SOIL AND GEOLOGIC CONDITIONS ............................................................................................. 2
4.1 Compacted Fill (Qcf) .................................................................................................................. 2
4.2 Granitic Rock (Kgr) .................................................................................................................... 3
5. RIPPABILITY AND ROCK CONSIDERATIONS ............................................................................. 3
6. GROUNDWATER ............................................................................................................................... 4
7. GEOLOGIC HAZARDS ...................................................................................................................... 4
~ :i f i~~!&:~;~~~:: :::::: :::::: ::::::::::::::: :: :::::::::: :::::::::::::: ::::::::::::::::::::::: ::::::::::::: :::::::::: :: :::::::::::::::::::: i
7.4 Tsunamis and Seiches ................................................................................................................. 5
7.5 Flooding ...................................................................................................................................... 5
7.6 Liquefaction and Seismically Induced Settlement... ................................................................... 5
7.7 Landslides ................................................................................................................................... 5
8. CONCLUSIONS AND RECOMMENDATIONS ................................................................................ 6
8.1 General. ....................................................................................................................................... 6
8.2 Excavation and Soil Characteristics ........................................................................................... 6
8.3 Grading Recommendations ........................................................................................................ 8
8.4 Subdra1ns .................................................................................................................................. 10
8.5 Slopes ........................................................................................................................................ 10
8.6 Seismic Design Criteria ............................................................................................................ 10
8.7 Shallow Foundations ................................................................................................................ 12
8.8 Interior Concrete Slabs-on-Grade ............................................................................................. 14
8.9 Conventional Retaining Wall Recommendations ..................................................................... 15
8.10 Lateral Loading ......................................................................................................................... 19
8.11 Preliminary Pavement Recommendations -Flexible and Rigid .............................................. 19
8.12 Exterior Concrete Flatwork ...................................................................................................... 23
8.13 Storm Water Management (Detention Basin and Bioswales) .................................................. 24
8.14 Site Drainage and Moisture Protection ..................................................................................... 25
8.15 Slope Maintenance .................................................................................................................... 26
8.16 Grading, Foundation and Retaining Wall Plan Review ............................................................ 26
MAPS AND ILLUSTRATIONS
Figure 1, Vicinity Map
Figure 2, Geologic Map
Figure 3, Geologic Cross-Sections A-A' through C-C'
APPENDIX A
RIPPABILITY STUDY
Figures A-1 -A-9, Logs of Exploratory Trench Excavations
APPENDIX B
LABO RA TORY TESTING (Geocon Incorporated, 2007)
APPENDIXC
City of Carlsbad BMP Design Manual -Categorization of Infiltration Feasibility Condition
(Form I-8)
APPENDIX D
RECOMMENDED GRADING SPECIFICATIONS
LIST OF REFERENCES
UPDATE GEOTECHNICAL INVESTIGATION
1. PURPOSE AND SCOPE
This report presents the results of an update geotechnical study for the proposed Carlsbad Oaks North
Business Park -Lot 3 development located in the Carlsbad Oaks North Business Park in Carlsbad,
California (see Vicinity Map, Figure 1 ). The purpose of this report was to evaluate the soil and
geologic conditions within the site and provide geotechnical recommendations pertaining to the
development of the property as proposed.
The scope of this update report included a review of:
1. Final Report of Testing and Observation Services During Site Grading, Carlsbad Oaks
North Business Park-Phase 1, (Lots 1 through 9), Carlsbad, California, prepared by Geocon
Incorporated, dated August 30, 2006 (Geocon Project No. 06442-32-04A).
2. Update Geotechnical Investigation, Carlsbad Oaks North Business Park and Faraday Avenue
Offsite, Carlsbad, California, prepared by Geocon Incorporated, dated October 21, 2004
(Geocon Project No. 06442-32-03).
3. Conceptual Grading Plan for: Carlsbad Oaks North -Lot 3, Carlsbad, California, prepared
by Spear & Associates, undated.
The descriptions of the soil and geologic conditions and proposed development described herein is
based on review of the referenced reports and plan, and observations made during previous mass
grading operations for the overall Carlsbad Oaks North Business Park development. Additional
references reviewed to prepare this report are provided in the List of References.
2. PREVIOUS SITE DEVELOPMENT
We provided testing and observation services during mass grading of the property. A canyon subdrain
was placed during the grading across the lot and extends beyond the property boundary. Our
professional opinions pertaining to the grading are summarized in Reference No. 1 (report dated
August 30, 2006). Appendix A presents pertinent laboratory tests that we performed on selected soil
samples collected during previous grading.
3. SITE AND PROJECT DESCRIPTION
The lot is bounded by Whiptail Loop to the east, open space to the west and south, and Pacifica Vista
Commerce Center (formerly Lot 23) to the north. The property mostly consists of compacted fill at
existing grade. Granitic rock is located along the northeast portion of the lot. Ascending and descending
2: 1 (horizontal:vertical) fill and cut slopes are located along the perimeter of the lot with a maximum
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height of approximately 50 feet. Sparse low lying grass/weeds are spread across the property. A
temporary paved drive isle and sales trailer is located along south margin of the sheet-graded pad.
The sheet-graded pad portion of the lot slopes from the northwest to southeast with elevations varying
from approximately 328 feet above Mean Sea Level (MSL) to approximately 316 feet MSL. A
temporary detention basin is located in the southeast margin of the pad. Existing improvements within
the lot consist of a storm drain system that was constructed as part of the temporary detention basin. The
slopes are landscaped with shrubs and trees with an active irrigation system.
We understand that the proposed development includes grading the existing sheet-graded pad to
support three, single-story buildings. We anticipate that the buildings will consist of concrete tilt-up
construction supported by convetional continuous and isolated spread footings with slab-on-grade
construction. Additional improvements consist of underground utilities, surface parking/driveways,
hardscape and bio-retention systems for storm water.
The descriptions contained herein are based upon the observations made during mass grading
operations and, a review of the referenced reports and plan. If project details vary significantly from
those outlined herein, Geocon Incorporated should be notified for review and possible revisions to this
report.
4. SOIL AND GEOLOGIC CONDITIONS
Compacted fill and granitic bedrock are exposed at finish grade. The approximate lateral extent of the
geologic units is presented on the Geologic Map, Figure 2. The subsurface relationship between the
soil and geologic unit is presented on the Geologic Cross-Sections A-A' through C-C', Figure 3.
4.1 Compacted Fill (Qcf)
Compacted fill was placed across the lot during previous grading operations. The fill generally
consists of a 3-foot-thick cap of soil containing some 6-inch-minus rock. Fill below the soil cap
contains rock fragments up to 12 inches in size. Rocks larger than 12 inches in length and, generally
between 2 to 4 feet in maximum dimension, were placed at least 10 feet below finish sheet grade. In
some instances, larger boulders were individually placed in the deeper fill areas. The outer
approximately 15 feet of embankment slopes consist of soil fill with 6-inch-minus rock and occasional
12-inch material. Although particular attention was given to restricting oversize rock placement as
discussed herein, it is possible that some oversize. rock (~ 12 inches) may be present in the upper
portions of fill areas. The presence of oversize rock should be considered during grading and where
below-grade improvements (i.e., sewer, storm drain) are proposed in areas deeper than 3 feet below
existing sheet grade.
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Fill materials placed during the mass grading operations generally consist of silty sands, and mixtures
of angular gravel and boulders generated from excavations in granitic rock. Soils consisting of sandy
clays were placed in deeper fill areas. Based on information presented in Reference No. 1, the fill is
compacted to at least 90 percent of the laboratory maximum dry density at or slightly above the
optimum moisture content in accordance with ASTM D 1557. Excluding the upper approximately one
foot, the compacted fill is suitable for support of additional fill and/or structural loading. In areas of
planned improvements, the upper one foot of existing fill will require processing as part of further
development.
4.2 Granitic Rock (Kgr)
Cretaceous-age, granitic basement rock of the Southern California Batholith underlies the compacted
fill and is exposed at grade along the northeast portion of the lot. Based upon our observations during
mass grading, the rock materials are highly to slightly weathered. Proposed excavations in this unit
may encounter hard rock that will result in excavation difficulty and/or possible blasting to excavate.
The granitic rock exhibits adequate bearing and slope stability characteristics.
The soils derived from excavations within the decomposed granitic rock are expected to consist of
very low to low expansive (Expansion Index [EI] :S 50), silty, medium-to coarse-grained sands.
Excavations within the bedrock will generate boulders and oversize materials (rocks >12 inches) that
will require special handling and placement. Oversize rock fragments may also require exportation
from the site since the available fill volume is limited.
5. RIPPABILITY AND ROCK CONSIDERATIONS
Rock rippability is a function of natural weathering processes that can vary vertically and horizontally
over short distances depending on jointing, fracturing, and/or mineralogic discontinuities within the
bedrock. We performed a field study to obtain further information regarding rock rippability in areas
of planned excavation where granitic rock is exposed at grade.
We performed the field investigation on October 28 and November 3, 2020. The study consisted of
excavating nine backhoe trenches utilizing a C345BL trackhoe equipped with a 2-foot-wide bucket.
The exploratory trench logs are presented in Appendix A, Figures A-1 through A-9. The approximate
locations of the exploratory trenches are shown on Figure 2 (map pocket). We used the information
obtained from the field study to base an opinion regarding the rippability characteristics of the
bedrock.
Based on the exploratory trenching performed, it is expected that excavations in the bedrock will
encounter rippable granitic rock to at least the depths shown on the trench logs utilizing conventional
heavy-duty grading and trenching equipment. We encountered moderately to slightly weathered
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granitic rock resulting in refusal and trenching difficulty (see Appendix A, Figures A-1, A-2 and A-9).
In some instances, random core stones up to 5 feet in length were encountered in the trench
excavations resulting in excavation difficulties. Where this occurred, the trench excavation was moved
beyond the core stone and trenching in the bedrock continued (see Appendix A, Figures A-4 and A-5).
Excavations that extend greater than the depths shown on the trench logs may encounter difficult ripping
conditions or refusal and require blasting techniques. Excavations can also be expected to generate
oversized rock (rocks> 12 inches), which will necessitate typical rock handling and/or exportation from
the site. Proposed cuts in the weathered (rippable) mantle may also generate oversized fragments.
Earthwork construction should be carefully planned to efficiently utilize available rock placement
areas, if present. Oversize materials should be placed in accordance with the previously discussed
criteria and rock placement procedures presented in Appendix D of this report and governing
jurisdictions.
6. GROUNDWATER
We did not encounter groundwater or seepage during our recent field study or previous grading
operations. However, it is not uncommon for shallow seepage conditions to develop where none
previously existed when sites are irrigated or 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. In the event that surface seeps
develop, shallow subdrains may be necessary to collect and convey the seepage to a suitable outlet
facility.
7. GEOLOGIC HAZARDS
7.1 Ground Rupture
The USGS (2020) and Kennedy & Tan (2005) show that there are no mapped Quaternary faults
crossing or trending toward the property. The site is not located within a currently established Alquist-
Priolo Earthquake Fault Zone. No active faults are known to exist at the site. An active fault is defined
by the California Geological Survey (CGS) as a fault showing evidence for activity within the last
11,700 years. The closest active fault is Newport Inglewood-Rose Canyon Fault zone, located
approximately 8 miles west of the site. The risk associated with ground rupture hazard is low.
7.2 Seismicity
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. The risk associated
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with strong ground motion due to earthquake at the site is high; however, the risk is no greater than
that for the region.
7.3 Subsidence
Based on the subsurface conditions encountered during our field investigation, the risk associated with
ground subsidence hazard is low.
7.4 Tsunamis and Seiches
The site is not located within a tsunami inundation zone as defined by California Geological Survey
(2009). There are no lakes or reservoirs located near the site. The risk associated with inundation
hazard due to tsunami or seiche is very low.
7.5 Flooding
The site is not located within a drainage or floodplain and is designated a Zone X (FEMA, 2012). The
risk associated with flooding hazard is very low.
7.6 Liquefaction and Seismically Induced Settlement
The risk associated with liquefaction and seismically induced settlement hazard at the subject project
is very low due to the existing dense compacted fill and very dense nature of the granitic bedrock,
construction of canyon subdrains, and the lack of a permanent, shallow groundwater table.
7.7 Landslides
No landslides were encountered within the site or ma'pped within the immediate areas influencing the
project development. The risk associated with landslide hazard is very low.
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8. CONCLUSIONS AND RECOMMENDATIONS
8.1 General
8.1.1 We did not encounter soil or geologic conditions during this study 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 the proposed construction will differ from that anticipated herein.
8.1.2 Planned grading will result in a cut-fill transition condition across the footprint of proposed
Buildings B and C. The cut portion (bedrock) should be undercut and replaced with properly
compacted fill to facilitate excavation of the foundation systems and reduce the potential for
differential settlement of structures bearing on both cut and fill.
8.1.3 Depending on the time of year that grading is performed, wet to saturated soil conditions
may be encountered, especially in the temporary detention basin. Wet soils, if encountered,
will need to be dried or mixed with dryer soil to facilitate proper compaction.
8.1.4 It is not uncommon for groundwater or seepage conditions to develop where none
previously existed, particularly after landscape irrigation is initiated or following
precipitation. The occurrence of induced groundwater seepage from landscaping can be
greatly reduced by implementing and monitoring a landscape program that limits irrigation
to that sufficient to support the vegetative cover without over watering. Shallow subdrains
may be required in the future if seeps occur after rainy periods or after landscaping is
installed.
8.1.5 Subsurface conditions observed may be extrapolated to reflect general soil/geologic
conditions; however, some variations in subsurface conditions between trench locations
should be anticipated.
8.2 Excavation and Soil Characteristics
8.2.1 Excavation of existing compacted fill should be possible with light to moderate effort using
conventional heavy-duty grading and trenching equipment. Excavations for improvements
in fill areas that extend through the 6-inch-minus soil cap or into the granitic rock will
encounter hard rock and/or rock fragments greater than 12 inches. Excavation difficulties
should be anticipated for these conditions. Blasting or rock breaking may be required for
excavations that are planned in granitic rock areas. Core stones or oversize material may
also be generated that will require special handling and fill placement procedures. The
potential for these conditions should be taken into consideration when determining the type
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•
8.2.2
of equipment to utilize for future excavation operations. Due to the limited areas of
available fill volume, it is unlikely that the oversize material could be placed as compacted
fill during the grading operation; hence, the oversize material may need to be expo11ed or
crushed to an appropriate size for fill placement.
Laboratory testing performed on soil samples collected during mass grading operations .
indicate that the prevailing soils within approximately 3 feet of grade have an Expansion
Index (El) less than 20 and are defined as "non-expansive" as defined by 2019 California
Building Code (CBC) Section I 803.5.3 . Appendix B presents the laboratory expansion
potential test results. Table 8.2 presents soil classifications based on the expansion index.
We expect the majority of the on-site soils possess a very low expansion potential. We will
perform additional expansion index testing after completion of grading operations to evaluate
the expansion potential of material present within the upper approximately 3 feet of ultimate
design finish elevation.
TABLE 8.2
EXPANSION CLASSIFICATION BASED ON EXPANSION INDEX
Expansion Index (El) ASTM D 4829 2019 CBC
Expansion Classification Expansion Classification
0 -20 Very Low Non-Expansive
21 -50 Low
51 -90 Medium
91 -130 High
Expansive
Greater Than 13 0 Very High
8.2.3 We performed laboratory tests on samples collected during previous grading 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 "SO" sulfate exposure to concrete structures as defined by 2019
CBC Section 1904 and ACI 318-14 Chapter 19. The presence of water-soluble sulfates is
not a visually discernible characteristic; therefore, other soil samples from the site could
yield different concentrations. Additionally, over time landscaping activities (i .e., addition
of fertilizers and other soil nutrients) may affect the concentration. We will perform
additional water-soluble sulfate testing after completion of grading operations to evaluate the
sulfate exposure of material present within the upper approximately three feet of ultimate
design finish elevation.
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8.2.4 Geocon Incorporated does not practice in the field of corrosion engmeermg. Therefore,
further evaluation by a corrosion engineer may be performed if improvements susceptible to
corrosion are planned.
8.3 Grading Recommendations
8.3.1 Grading should be performed in accordance with the Recommended Grading Specifications
contained in Appendix D. Where the recommendations of Appendix D conflict with this
section of the report, the recommendations of this section take precedence.
8.3.2 Prior to commencing grading, a preconstruction conference should be held at the site with
the City inspector, developer, grading contractor, civil engineer, and geotechnical engineer
in attendance. Special soil handling and/or the grading plans can be discussed at that time.
8.3.3 Grading should be performed in conjunction with the observation and compaction testing
services of Geocon Incorporated. Fill soil should be observed on a full-time basis during
placement and tested to check in-place dry density and moisture content.
8.3.4 Site preparation should begin with removal of all deleterious material, vegetation and,
abandoned utilities/improvements. Loose accumulated soils in the temporary detention basin
will need to be removed and compacted prior to filling the basin. The depth of removal
should be such that material exposed in cut areas or soil to be used for fill is relatively free
of organic matter. Deleterious material generated during stripping and/or site demolition
should be exported from the site.
8.3.5 Prior to placing fill, the exposed ground surface should be scarified approximately
12 inches, moisture conditioned as necessary, mixed and compacted to 90 percent of the
laboratory maximum dry density as determined by ASTM D1557 at or slightly above
optimum moisture content. Overly wet surficial soils, if encountered, will need to be
removed to expose existing dense, moist compacted fill (where mapped) or granitic rock.
The wet soils will require drying and/or mixing with drier soils to facilitate proper
compaction. The actual extent of remedial grading should be determined in the field by the
geotechnical engineer or engineering geologist.
8.3.6 After site preparation and removal of unsuitable soils, as described above is performed, the
site should be brought to final subgrade elevation with structural fill. In general, on-site soils
are suitable for re-use as fill provided they are free of vegetation, debris and other deleterious
matter. Layers of fill should be no thicker than will allow for adequate bonding and
compaction. Fill, including backfill and scarified ground surfaces, should be compacted to at
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least 90 percent of the laboratory maximum dry density as determined by ASTM D 1557, at or
slightly above optimum moisture content. The project geotechnical engineer may consider fill
materials below the recommended minimum moisture content unacceptable and may require
additional moisture conditioning prior to placing additional fill.
8.3.7 Based on existing as-graded condition of the pad portion of the lot and proposed grading
presented on the conceptual grading plan, grading will result in a cut-fill transition condition
within the footprint of planned Buildings B and C. Foundation elements bearing on both
compacted fill and bedrock may result in potentially unacceptable differential settlements.
8.3 .8 To reduce the potential for differential settlement, the bedrock portion of the cut-fill transition
should be over-excavated (undercut) a minimum of 5 feet below finish pad grade or at least
2 feet below the lowest foundation element, whichever is deeper, and replaced with compacted
low expansive (Expansion Index [EI] S50) soil fill consisting of 6-inch-minus rock. The
undercutting will also facilitate excavation of proposed shallow utilities beneath the building.
The undercut should extend at least 5 feet horizontally outside the limits of the building footprint
area and isolated spread footings located outside the building limits. Overexcavations should be
cut at a gradient toward the parking lot or toward the deepest fill area to provide drainage for
moisture migration along the contact between the bedrock and compacted fill.
8.3.9 For exterior utilities (i.e., storm drain, sewer, dry utilities, water) that may be located in
areas of granitic rock, consideration should be given to undercutting the granitic rock to
facilitate trenching for planned underground utilities. The need to undercut the underlying
granitic rock within the utility corridors should be determined by the owner based on the
rippability study included herein (see Section 5 for discussion). The undercuts, if needed,
should extend at least 1 foot below the deepest utility.
8.3.10
8.3 .11
8.3.12
Consideration should be given to undercutting landscape areas, hardscape zones and
driveways/parking areas located in areas of exposed granitic rock to facilitate construction
of planned improvements. The need to undercut the underlying granitic rock within these
zones should be determined by the owner based on the findings of the exploratory trenching
performed.
In order to maintain safety and the stability of adjacent improvements, it is the responsibility
of the contractor to ensure that all excavations and trenches are properly shored and
maintained in accordance with the applicable OSHA rules and regulations.
Imported soils should consist of granular very low to low expansive soils (El S50). Samples
from proposed borrow areas should be obtained and subjected to laboratory testing to
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evaluate if the material conforms to the recommended criteria prior to importing to the site.
The imported soil should be free of rock greater than 6 inches and construction debris.
Laboratory testing typically takes up to four days to complete. The grading contractor needs
to coordinate the laboratory testing into the schedule to provide sufficient time to allow for
completion of testing prior to importing materials.
8.4 Subdrains
8.4. l Except for retaining wall drains, subdrains are not required for the project.
8.5 Slopes
8.5.1 Slope stability analyses were previously performed on the 2: 1 slopes for the overall
Carlsbad Oaks North Business Park development (see the referenced geotechnical reports).
The deep-seated and surficial slope stability analyses where performed using the simplified
Janbu analysis utilizing average drained direct shear strength parameters based on
laboratory tests performed during our investigation. The results of the analysis indicate that
existing cut and fill slopes have a factor-of-safety of at least 1.5 against deep seated and
surficial instability for the project slopes.
8.5.2 No new significant slopes are planned for the project. We expect that interior fill slopes with
inclinations of 2: 1 (horizontal:vertical) or flatter and maximum heights of approximately 3 feet
will be constructed during grading operations. Based on the discussion above, these slopes
should have a factor-of-safety of at least 1.5 against deep seated and surficial instability.
8.5.3 Slopes should be landscaped with drought-tolerant vegetation having variable root depths
and requiring minimal landscape irrigation. In addition, all slopes should be drained and
properly maintained to reduce erosion. Slope planting should generally consist of drought
tolerant plants having a variable root depth. Slope watering should be kept to a minimum to
just support the plant growth.
8.6 Seismic Design Criteria
8.6.1 Table 8.6.1 summarizes site-specific design criteria obtained from the 2019 California
Building Code (CBC; Based on the 2018 International Building Code [IBC] and NEHRP-
2015), Chapter 16 Structural Design, Section 1613 Earthquake Loads. We used the
computer program US. Seismic Design Maps, provided by the Structural Engineers
Association of California (SEAOC) 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
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discussion in Section 1613.2.2 of the 2019 CBC and Table 20.3-1 of ASCE 7-16. The
values presented herein are for the risk-targeted maximum considered earthquake (MCfa).
TABLE 8.6.1
2019 CBC SEISMIC DESIGN PARAMETERS
Parameter Value 2019 CBC Reference
Site Class D Section 1613.2.2
MCER Ground Motion Spectral Response 0.932g Figure 1613 .2.1(1) Acceleration -Class B (short), Ss
MCER Ground Motion Spectral Response 0.342g Figure 1613 .2.1 (2) Acceleration -Class B ( I sec), S 1
Site Coefficient, FA 1.127 Table 1613.2.3(1)
Site Coefficient, Fv 1.958* Table 1613.2.3(2)
Site Class Modified MCER Spectral Response 1.051 g Section 1613 .2.3 (Eqn 16-36) Acceleration (short), SMs
Site Class Modified MCER Spectral Response 0.67g* Section 161 3.2.3 (Eqn 16-37) Acceleration -( I sec), SM 1
5% Damped Design 0.70g Section 1613.2.4 (Eqn 16-38) Spectral Response Acceleration (short), Sos
5% Damped Design 0.447g* Section 1613 .2.4 (Eqn 16-39) Spectral Response Acceleration ( I sec), S01
* 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 I .0g and for Site Class
"D" and "E" sites with SI 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.
8.6.2 Table 8.6.2 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 8.6.2
ASCE 7-16 PEAK GROUND ACCELERATION
Parameter Value ASCE 7-16 Reference
Mapped MCEc Peak Ground Acceleration, PGA 0.405g Figure 22-7
Site Coefficient, FroA 1.195 Table 11 .8-1
Site Class Modified MCEa 0.484g Section 11.8.3 (Eqn 11.8-1) Peak Ground Acceleration, PGAM
8.6.3 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.
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8.6.4 Conformance to the criteria in Tables 8.6.1 and 8.6.2 for seismic design does not constitute
any kind of guarantee or assurance that significant structural damage or ground failure will
not occur if a large earthquake occurs. The primary goal of seismic design is to protect life,
not to avoid all damage, since such design may be economically prohibitive.
8. 7 Shallow Foundations
8.7.1 The project is suitable for the use of continuous strip footings, isolated spread footings, or
appropriate combinations thereof, provided the preceding grading recommendations are
followed. The following recommendations are for the planned structures and assume that
the foundation system for the structures will bear entirely on compacted fill and soil within
3 feet of finish grade consists of very low to low expansive soils (EI ~50).
8.7.2 Foundations for the planned structures may consist of continuous strip footings and/or
isolated spread footings. Table 8. 7 provides a summary of the foundation design
recommendations.
TABLE 8.7
SUMMARY OF FOUNDATION RECOMMENDATIONS
Value -
Parameter Parking Ca rage Footings Bearing on Very
Old Paralic Deposits
Minimum Continuous Foundation Width 12 inches
Minimum Isolated Foundation Width 24 inches
Minimum Foundation Depth 24 Inches Below Lowest Adjacent Grade
Minimum Steel Reinforcement 4 No. 5 Bars, 2 at the Top and 2 at the Bottom
Allowable Bearing Capacity 2,500 psf
Bearing Capacity Increase 500 psf per Foot of Depth
300 psfper Foot of Width
Maximum Allowable Bearing Capacity 4,000 psf
Estimated Total Settlement I Inch
Estimated Differential Settlement ½ Inch in 40 Feet
Design Expansion Index 50 or less
8.7.3 The foundations should be embedded in accordance with the recommendations herein and
the Wall/Column Footing Dimension Detail. The embedment depths should be measured
from the lowest adjacent pad grade for both interior and exterior footings . Footings should
be deepened such that the bottom outside edge of the footing is at least 7 feet horizontally
from the face of the slope (if applicable).
Geocon Project No. 06442-32-34 -12 -May 26, 2021
Wall/Column Footing Dimension Detail
PAO GRADE
~~ ,-a. ~~ ..... ·:· _l
LFOOTING' j
WIDTH
8.7.4 The bearing capacity values presented herein are for dead plus live loads and may be
increased by one-third when considering transient loads due to wind or seismic forces.
8.7.5 Consideration should be given to connecting patio slabs, which exceed 5 feet in width, to
the building foundation to reduce the potential for future separation to occur.
8. 7.6 Where buildings or other improvements are planned near the top of a slope steeper than 3: l
(horizontal:vertical), special foundations and/or design considerations are recommended due
to the tendency for lateral soil movement to occur.
• For fill slopes less than 20 feet high and cut slopes regardless of height, 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.
• Based on the conceptual grading plan, the planned buildings are located at least 60
feet from the top of existing descending fill slopes. Geocon Inc. should be contacted
if planned buildings are re-located to near top of descending slopes so that we may
provide additional foundation recommendations to help reduce potential foundation
distress associated with slope creep and lateral fill extension.
• Although other improvements, which are relatively rigid or brittle, such as concrete
tlatwork 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.
8.7.7 We should observe the foundation excavations prior to the placement of reinforcing steel
and concrete to check that the exposed soil conditions are similar to those expected and that
they have been extended to the appropriate bearing strata. Foundation modifications may be
required if unexpected soil conditions are encountered.
Geocon Project No. 06442-32-34 -13 -May 26. 202 1
8.7.8 Geocon Incorporated should be consulted to provide additional design parameters as
required by the structural engineer.
8.8 Interior Concrete Slabs-on-Grade
8.8. l Concrete slabs-on-grade for the structures should be constructed in accordance with Table 8.8.
TABLE 8.8
MINIMUM CONCRETE SLAB-ON-GRADE RECOMMENDATIONS
Parameter Building
Slab-On-Grade
Minimum Concrete Slab Thickness 5.0 inches
Minimum Steel Reinforcement No. 3 Bars 18 Inches on Center, Both
Directions
Typical Slab Underlayment 3 to 4 Inches of Sand/Gravel/Base
Design Expansion Index 50 or less
8.8.2 The concrete slab-on-grade recommendations are based on soil support characteristics only.
If the slabs will be subjected to heavy loads, consideration should be given to increasing the
slab thickness and reinforcement. The project structural engineer should design interior
concrete slabs-on-grade that will be subjected to heavy loading (i.e., fork lift, heavy storage
areas). Subgrade soils supporting heavy loaded slabs should be compacted to at least 95
percent relative compaction.
8.8.3 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.
8.8.4 The project foundation engineer, architect, and/or developer should determine thte thickness
of bedding sand below the building slabs. In general, 3 to 4 inches of sand bedding is
typically used. Geocon should be contacted to provide recommendations if the bedding sand
is thicker than 6 inches.
Geocon Project No. 06442-32-34 -14 -May 26. 2021
8.8.5 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 plan. The foundation contractor should understand and follow the specifications
presented on the foundation plan.
8.8.6 To control the location and spread of concrete shrinkage and/or expansion cracks, it is
recommended that crack-control joints be included in the design of concrete slabs. Crack-
control joint spacing should not exceed, in feet, twice the recommended slab thickness in
inches ( e.g., IO feet by IO feet for a 5-inch-thick slab). Crack-control joints should be
created while the concrete is still fresh using a grooving tool or shortly thereafter using saw
cuts. The structural engineer should take criteria of the American Concrete Institute into
consideration when establishing crack-control spacing patterns.
8.8.7 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.
8.8.8 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 comers occur.
8.9 Conventional Retaining Wall Recommendations
8.9.1 Retaining walls should be designed using the values presented in Table 8.9.1. Soil with an
expansion index (EI) greater than 50 should not be used as backfill material behind retaining
walls. Geocon Incorporated should be consulted to provide additional design parameters if
backfill material possess an EI greater than 50 or as required by the structural engineer.
Gcocon Project No. 06442-32-34 -15 -May 26. 2021
TABLE 8.9.1
RETAINING WALL DESIGN RECOMMENDATIONS
Parameter Value
Active Soil Pressure, A (Fluid Density, Level Backfill) 35 pcf
Active Soil Pressure, A (Fluid Density, 2: I Sloping Backfill) 50 psf
Seismic Pressure, S 13H 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
H equals the height of the retaining portion of the wall.
8.9.2 The project retaining walls should be designed as shown in the Retaining Wall Loading
Diagram.
IF PRESENT
RETAINING
WALL
SLAB
.-:'\\~\
:::;:;
~11\-:;::::.,_....
H (Feet)
FOOTING
ACTIVE
PRESSURE
SEISMIC
(IF REQUIRED)
Retaining Wall Loading Diagram
AT-REST/
RESTRAINED
(IF REQUIRED)
7H H s 8'
13H psi
8.9.3 Where walls are restrained from movement at the top (at-rest condition), an additional
uniform pressure of 7H psf should be added to the active soil pressure for walls 8 feet or
less. For walls greater than 8 feet tall, an additional uniform pressure of 13H psf should be
applied to the wall starting at 8 feet from the top of the wall to the base of 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 (soil total unit
weight 130 pct).
Geocon Project No. 06442-32-34 -16 -May 26. 202 1
•
8.9.4 The structural engineer should determine the Seismic Design Category for the project in
accordance with Section 1613.2.5 of the 2019 CBC or Section 11.6 of ASCE 7-16. For
structures assigned to Seismic Design Category of D, E, or F, retaining walls that support
more than 6 feet of backfill should be designed with seismic lateral pressure in accordance
with Section 1803.5.12 of the 2019 CBC. The seismic load is dependent on the retained
height where His 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. A seismic
load of 21 H psf should be used for design. We used the peak ground acceleration adjusted
for Site Class effects, PGAM, of 0.484g calculated from ASCE 7-16 Section 11.8.3 and
applied a pseudo-static coefficient of 0.33.
8.9.5 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.
8.9.6 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 planned and existing
improvements adjacent to the base of the wall. The recommendations herein assume a
properly compacted granular (EI :S:50) 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.
H
PROPOSED
GRADE
CONCRETE
BROWDITCH
Geocon Project No. 06442-32-34
OPEN GRADED
I" MAX. AGGREGATE
TEMPORARY BACKCUT
PE:ROSHA
OR
2/JH
GROUND SURFAC!:
DRAINAGE PANEL
(MIRAORAIN 6000
OR EQUIVALENT)
l/4' CRUSHED ROCK
12" 1 (1 CU.FT JFT.) OR WfW'
DAAJNAGE PANEL
AROUND PIPE -~l V LTERFABRIC
..... h . :1 ENVELOPE !.",<t MIRAFI 14-0N OR
4" DIA PERFORATED SCHEDULE
40 PVC PIPE EXTENDED TO
APPR0\/1:D ourm
>---<•··•"-"":.'' ~ EQUIVALENT
-,:,:~=t<m......_r-__, 4· DIA. SCHEDULE 40
Typical Retaining Wall Drainage Detail
-17 -
PERFORATED PVC PIPE
OR TOTAL DRAIN
EXTENDED TO
APPROVED OUTLET
May 26. 2021
•
•
8.9.7 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 considered in
the design of the retaining walls.
8.9.8 Wall foundations should be designed in accordance with Table 8.9.2. 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 8.9.2
SUMMARY OF RETAINING WALL FOUNDATION RECOMMENDATIONS
Parameter Value
Minimum Retaining Wall Foundation Width 12 inches
Minimum Retaining Wall Foundation Depth 18 Inches
Minimum Steel Reinforcement Per Structural Engineer
Bearing Capacity 2,500 psf
Bearing Capacity Increase
500 psf per additional foot of footing depth
300 psfper additional foot of footing width
Maximum Bearing Capacity 4,000 psf
Estimated Total Settlement I Inch
Estimated Differential Settlement ½ Inch in 40 Feet
8.9.9 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.
8.9.10
8.9.11
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.
Soil contemplated for use as retaining wall backfill, including import materials, should be
identified in the field prior to backfill. At that time, Geocon Incorporated should obtain samples
for laboratory testing to evaluate its suitability. Modified lateral earth pressures may be
Geocon Project No. 06442-32-34 -18 -May 26. 2021
•
8.10
8.10.1
8.10.2
8.11
8.11.1
8.11.2
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. 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.
Lateral Loading
Table 8.10 should be used for the design of footings or shear keys to help design the
proposed structures and improvements to resist lateral loads. The allowable passive pressure
assumes a horizontal surface extending at least 5 feet, or three times the surface generating
the passive pressure, whichever is greater. The upper 12 inches of material in areas not
protected by floor slabs or pavement should not be included in design for passive resistance.
Where walls are planned adjacent to and/or on descending slopes, a passive pressure of
150 pcf should be used in design.
TABLE 8.10
SUMMARY OF LATERAL LOAD DESIGN RECOMMENDATIONS
Parameter Value
Passive Pressure Fluid Density 300 pcf
Passive Pressure Fluid Density Adjacent to and/or on 150 pcf Descending Slop es
Coefficient of Friction (Concrete and Soil) 0.40
Coefficient of Friction (A long Vapor Barrier) 0.2 to 0.25*
* Per manufacturer's recommendations.
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
w ind or seismic forces.
Preliminary Pavement Recommendations -Flexible and Rigid
The preliminary sections presented herein are for budgetary estimating purposes only and
are not for construction. The final pavement sections will be provided after the grading
operations are completed, subgrade soils are sampled, and laboratory resistance value (R-
Value) testing is performed on the soil samples collected.
The preliminary pavement section recommendations are for areas that will be used as
passenger vehicle parking, car/light truck and heavy truck driveways. The project civil
engineer or traffic engineer should determine the appropriate Traffic Index (TI) or traffic
loading expected on the project for the various pavement areas that wi ll be constructed.
Geocon Project No. 06442-32-34 -19 -May 26. 202 1
•
8.11.3
8.11 .4
8.11.5
We evaluated the flexible pavement sections m accordance with State of California,
Department of Transportation (Caltrans) Highway Design Manual (Topic 633). We used an
estimated R-Value of 35 and 78 for soil and aggregate base, respectively, to calculate the
preliminary pavement sections. The structural sections presented herein are in accordance
with City of Carlsbad minimum requirements for private commercial/industrial developments.
Table 8.1 1.1 summarizes preliminary flexible pavement sections.
TABLE 8.11 .1
PRELIMINARY ASPHALT CONCRETE PAVEMENT SECTIONS
Traffic Index* Asphalt Concrete (inches)** Class 2 Base (inches)
4.5 4.0 4.0
5.0 4.0 4.0
5.5 4.0 4.0
6.0 4.0 5.5
6.5 4.0 7.0
7.0 4.0 8.0
*Civil engineer should provide Tl for final pavement design.
**City of Carlsbad minimums for Private Commercial/Industrial developments.
Prior to placing base materials and asphalt concrete, the upper 12 inches of the subgrade
soil should be scarified, moisture conditioned as necessary, mi xed and compacted 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
maxi mum 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.
A rigid Portland cement concrete (PCC) pavement section should be placed in driveway
entrance aprons and trash bin loading/storage areas. The concrete pad for the trash truck
areas should be large enough such that the truck wheels will be positioned on the concrete
during loading. We calculated the rigid pavement section in general conformance with the
procedure recommended by the American Concrete Institute report ACI 330R-08 Guide for
Design and Construction of Concrete Parking Lots usi ng the parameters presented in
Table 8.11 .2.
Geocon Project No. 06442-32-34 -20 -May 26. 202 1
•
8.11.6
8.11.7
8.11.8
TABLE 8.11.2
RIGID PAVEMENT DESIGN PARAMETERS
Design Parameter Design Value
Modulus of subgrade reaction, k 200 pci
Modulus ofrupture for concrete, MR 550 psi
Concrete Compressive Strength 3,200 psi
Traffic Category, TC A, Band C
Average daily truck traffic, ADTT IO (TC=A), 25 (TC=B), and 700 (TC=C)
Based on the criteria presented herein, the PCC pavement sections should have a minimum
thickness as presented in Table 8.11.3 .
TABLE 8.11.3
PRELIMINARY RIGID VEHICULAR PAVEMENT RECOMMENDATIONS
Location Portland Cement
Concrete (inches)
Automobile Parking Stalls 5.0
Automobile/Li ght Truck Driveways 6.0
Heavy/Trash Truck Driveways/Fire Lane 7.0
Heavy Truck Loading Apron 7.0
Trash 7.5* Enclosure Apron
*City of Carlsbad minimums for Private Commercial/Industrial developments.
Prior to placing PCC slabs, the upper 12 inches of pavement subgrade soils should be
scarified, moisture conditioned as necessary, mixed and compacted to a dry density of at
least 95 percent of the laboratory maximum dry density at to slightly above optimum
moisture content in accordance with ASTM D 1557.
The rigid pavement should also be designed and constructed incorporating the parameters
presented in Table 8.11 .4 .
Geocon Project No. 06442-32-34 -21 -May 26. 2021
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TABLE 8.11.4
ADDITIONAL RIGID PAVEMENT RECOMMENDATIONS
Subject Value
1.2 Times Slab Thickness
Thickened Edge Minimum Increase of2 Inches
3 Feet Wide
30 Times Slab Thickness
Crack Control Joint Spacing Max. Spacing of 12 feet for 5.5-Inch-Thick
Max. Spacing of 15 Feet for Slabs 6 Inches and
Thicker
Per ACI 330R-08
Crack Control Joint Depth I Inch Using Early-Entry Saws on Slabs Less
Than 9 Inches Thick
¼-Inch for Sealed Joints
Crack Control Joint Width ½-Inch is Common for Sealed Joints
1110-to 1/s-l nch is Common for Unsealed Joints
8.11.9 Rigid pavement should be reinforced with No. 3 reinforcing bars spaced 24 inches on center
in both directions placed at the slab midpoint.
8.1 1.10 Loading aprons such as trash bin enclosures and heavy truck areas should utilize Portland
cement concrete as presented in Table 8.11.3 above. The concrete loading area should
extend out such that both the front and rear wheels of the truck wi II be located on reinforced
concrete pavement when loading and unloading.
8.11.11 To control the location and spread of concrete shrinkage cracks, crack-control joints
(weakened plane joints) should be included in the design of the concrete pavement slab.
Crack-control joints should be sealed with an appropriate sealant to prevent the migration of
water through the control joint to the subgrade materials. The depth of the crack-control
joints should be determined by the referenced AC[ report.
8.11.12 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. The project structural
engineer should be consulted to provide other alternative recommendations for load transfer
(i.e., dowels).
Geocon Project No . 06442-32-34 -22 -May 26. 202 1
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•
•
•
8.11.13 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 traffic 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.
8.11.14 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
asphalt 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.
8.12
8.12.1
8.12.2
I
Exterior Concrete Flatwork
Exterior concrete flatwork not subject to vehicular traffic should be constructed in
accordance with the recommendations presented in Table 8.12. The recommended steel
reinforcement would help reduce the potential for cracking.
TABLE 8.12
MINIMUM CONCRETE FLATWORK RECOMMENDATIONS
Expansion M' . R . f . S 1. Minimum
I d El 1111mum em orcmg tee " Th" k n ex, 1c ness
El :':: 50
6x6-W2.9/W2.9 (6x6-6/6) welded wire mesh
No. 3 Bars 24 inches on center, Both Directions
4 Inches
* In excess of 8 feet square .
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 (if present) beneath
grade. The reinforcing steel 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.
Geocon Project No. 06442-32-34 -23 -May 26. 2021
8.12.3
8.12.4
8.12.5
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.
Where exterior flatwork abuts the structure at entrant or exit areas, 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. The project structural engineer should provide dowelling
details.
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.
8.13 Storm Water Management (Detention Basin and Bioswales)
8.13 .1 The lot is currently underlain by compacted fill and dense granitic rock. Planned grading
will result with these units at grade. As previously discussed, the compacted fill consists of
silty sands, and mixtures of angular gravel and boulders generated from blasting operations
in granitic rock. Soils consisting of sandy clays were placed in deeper fill areas. Infiltrating
into compacted fill generally results in settlement and distress to improvements placed over
the compacted fill; as well as slope instability. It is our opinion the compacted fill is
unsuitable for infiltration of storm water runoff due to the potential for adverse settlement
and slope instability. The granitic bedrock is also sufficiently dense that infiltration water
would be expected to perch on this unit.
Geocon Project No. 06442-32-34 -24 -May 26. 2021
8.13.2
8.13.3
8.13.4
8.13.5
8.14
8.14.1
8.14.2
Detention basins, bioswales and bio-remediation areas should be designed by the project
civil engineer and reviewed by Geocon Incorporated. Typically, bioswales consist of a
surface layer of vegetation underlain by clean sand. A subdrain should be provided beneath
the sand layer. Prior to discharging into the storm drain pipe, a seepage cutoff wall should be
constructed at the interface between the subdrain and storm drain pipe. The concrete cut-off
wall should extend at least 6-inches beyond the perimeter of the gravel-packed subdrain
system.
Distress may be caused to planned improvements and properties located hydrologically
downgradient or adjacent to infiltration devices. The distress depends on the amount of
water to be detained, its residence time, soil permeability, and other factors. We have not
performed a hydrogeology study at the site. Downstream and adjacent properties may be
subjected to seeps, springs, slope instability, raised groundwater, movement of foundations
and slabs, or other impacts as a result of water infiltration. Due to site soil and geologic
conditions, permanent bioswales and bio-remediation areas should be lined with an
impermeable liner to prevent water infiltration in to the underlying compacted fill.
Temporary detention basins in areas where improvements have not been constructed do not
need to be lined.
Appendix C presents the form titled Categorization of Infiltration Feasibility Condition
(Form 1-8) from the City of Carlsbad BMP Design Manual (February 16, 2016).
The landscape architect should be consulted to provide the appropriate plant
recommendations. If drought resistant plants are not used, irrigation may be required.
Site Drainage and Moisture Protection
Adequate site drainage is critical to reduce the potential for differential soil movement,
erosion and subsurface seepage. Water should not be allowed to pond adjacent to footings.
The site should be graded and maintained such that surface drainage is directed away from
structures in accordance with 2019 CBC 1803 .3 or other applicable standards. In addition,
surface drainage should be directed away from the top of slopes into swales or other
controlled drainage devices. Roof and pavement drainage should be directed into conduits
that carry runoff away from the proposed structures.
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.
Geocon Project No. 06442-32-34 -25 -May 26. 2021
8.14.3
8.14.4
8.15
8.15.1
8.16
8.16.1
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.
Landscaping planters adjacent to paved areas are not recommended due to the potential for
surface or irrigation water to infiltrate the pavement's subgrade and base course. We
recommend that subdrains to collect excess irrigation water and transmit it to drainage
structures, or impervious above-grade planter boxes be used. In addition, where landscaping
is planned adjacent to the pavement, we recommend construction of a cutoff wall along the
edge of the pavement that extends at least 6 inches below the bottom of the base material.
Slope Maintenance
Slopes that are steeper than 3:1 (horizontal:vertical) may, under conditions that are both
difficult to prevent and predict, be susceptible to near-surface (surficial) slope instability.
The instability is typically limited to the outer 3 feet of a portion of the slope and usually
does not directly impact the improvements on the pad areas above or below the slope. The
occurrence of surficial instability is more prevalent on fill slopes and is generally preceded
by a period of heavy rainfall, excessive irrigation, or the migration of subsurface seepage.
The disturbance and/or loosening of the surficial soils, as might result from root growth, soil
expansion, or excavation for irrigation lines and slope planting, may also be a significant
contributing factor to surficial instability. It is therefore recommended that, to the maximum
extent practical: (a) disturbed/loosened surficial soils be either removed or properly
recompacted, (b) irrigation systems be periodically inspected and maintained to eliminate
leaks and excessive irrigation, and (c) surface drains on and adjacent to slopes be
periodically maintained to preclude ponding or erosion. Although the incorporation of the
above recommendations should reduce the potential for surficial slope instability, it will not
eliminate the possibility and, therefore, it may be necessary to rebuild or repair a portion of
the project's slopes in the future.
Grading, Foundation and Retaining Wall Plan Review
Geocon Incorporated should review the grading, foundation and retaining wall plans for the
project prior to final design submittal to evaluate whether additional analyses and/or
recommendations are required.
Geocon Project No. 06442-32-34 -26 -May 26. 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.
Geocon Project No. 06442-32-34 May 26. 2021
THE GEOGRAPHICAL INFORMATION MADE AVAILABLE FOR DISPLAY WAS PROVIDED BY GOOGLE EARTH,
SUBJECT TO A LICENSING AGREEMENT. THE INFORMATION IS FOR ILLUSTRATIVE PURPOSES ONLY; IT IS
NOT INTENDED FOR CLIENT'S USE OR RELIANCE ANO SHALL NOT BE REPRODUCED BY CLIENT. CLIENT
SHALL INDEMNIFY, DEFEND ANO HOLD HARMLESS GEOCON FROM ANY LIABILITY INCURRED AS A RESULT
OF SUCH USE OR RELIANCE BY CLIENT.
VICINITY MAP
t
N
NO SCALE
GEOCON
INCORPORATED
CARLSBAD OAKS NORTH BUSINESS PARK
LOT 3 GEOTECH NICAL ■ENVIRONMENTAL ■ MATERIALS
6960 FLANDERS DRIVE · SAN DIEGO, CALIFORNIA 92121 · 297 4
PHONE 858 558-6900 • FAX 858 558-6159
EA/CW I I DSK/GTYPD
CARLSBAD, CALIFORNIA
DATE 05 -26 -2021 I PROJECT NO, 06442 -32 -34 I FIG. 1
f>totted:0512612021 9:10AM 1 By:JONATHAN WILKINS! File Location:V:\PROJECT~-42-32-34 (Con Lot-3)\DETAJLS\064.42-32-34 Vic Map~
APPENDIX
-
APPENDIX A
Rippability Study
We performed the field investigation on October 28 and November 3, 2020. The study consisted of
excavating nine backhoe trenches utilizing a C345BL trackhoe equipped with a 2-foot-wide bucket.
The exploratory trench logs are presented in Appendix A, Figures A-1 through A-9. The approximate
locations of the exploratory trenches are shown on Figure 2 (map pocket).
We visually examined, classified, and logged the soil conditions encountered in general accordance
with American Society for Testing and Materials (ASTM) practice for Description and Identification
of Soils (Visual-Manual Procedure D 2488).
Geocon Project No. 06442-32-34 May 26. 2021
-
335'
330'
_J
Cl) :a:
.=-UJ UJ
LL 325' -z 0 ~ > UJ _J
UJ
320'
315'
CD
0
EXISTING
IRRIGATIO
LINE
O'
GROUND SURFACE
Kgr
REFUSAL
5' 10'
DISTANCE (FEET)
GRANITIC ROCK (Kgr)
~CORE STONES
G)
15' 20'
Moderately weathered, damp to moist, mottled olive and grayish brown,
strong to very strong GRANITIC ROCK; excavates to a mottled olive
and grayish brown, soil-rock mix with rock up to 2 foot diameter and
trace rounded core stones up to 18 inch diameter
Very strong to extremely strong with trace rounded core stones up to 3
foot diameter: Refusal at bottom of excavation
-No groundwater
-Backfilled with trench spoils
SCALE: 1" = 5' (VERT.= HORIZ.)
TRENCH NO. 1
GEOCON 0 CARLSBAD OAKS NORTH BUSINESS PARK
LOT 3 INCORPORATED
GEOTECHNICAL ■ENVIRONMENTAL ■ MATERIALS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121 -297 4
PHONE 858 558-6900 -FAX 858 558-6159
EA/CW I I DSK/GTYPD
CARLSBAD, CALIFORNIA
DATE 05 -26 -2021 I PROJECT NO. 06442 -32 -34 I FIG. A1
Plottecl:05/2612021 9:11AM I By:JONATHAN WILKINS I File Location:Y:\PROJECTS\06442-32-34 (Con Lot-3)\DETAILS\06442-32-34_TRENCHES.dwg
II"""
...J
(/)
~
i=' UJ
UJ LL -z 0 i'.= ~ UJ
...J UJ
340'
335'
330'
EXISTING 325' IRRIGATIO
LINE
320'
O'
GRANITIC ROCK (Kgr)
GROUND SURFACE
5' 10'
DISTANCE (FEET)
15'
CD Moderately to slightly weathered, damp, mottled olive and grayish brown,
very strong GRANITIC ROCK; excavates to rock up to 3 foot diameter with
little/some silty, fine to coarse sand; Refusal at bottom of excavation
-No groundwater
-Backfilled with trench spoils
20'
SCALE: 1" = 5' (VERT.= HORIZ.)
TRENCH NO. 2
GEOCON 0 CARLSBAD OAKS NORTH BUSINESS PARK
LOT 3 INCORPORATED
GEOTECHNICAL ■ENVIRONMENTAL ■ MATERIALS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121 -297 4
PHONE 858 558-6900 -FAX 858 558-6159
EA/CW I I DSK/GTYPD
CARLSBAD, CALIFORNIA
DATE 05 -26 -2021 I PROJECT NO. 06442 -32 -34 I FIG. A2
Plotted:05/26/2021 9:11AM I By:JONATHAN WILKINS I File Location:Y:\PROJECTS\06442-32-34 (Con Lot-3)\DETAILS\06442-32-34_TRENCHES.dwg
340'
..J
Cl) 335' ~
i=-LU LU 330' LL -z
0 ~ 325' > LU ..J LU
320'
315'
CD
GEOCON
INCORPORATED
EXISTING
GROUND SURFACE
Kgr
EXISTING
IRRIGATIO
LINE Kgr
O' 5' 10' 15' 20' 25' 30' 352'
DISTANCE (FEET)
Highly weathered, damp, mottled orange and olive brown, weak to
moderately week GRANITIC ROCK; excavates to a mottled orange
and olive brown, silty, fine to coarse sand with little weak rock up to
1 foot diameter and few rounded core stones up to 18 inch diameter.
-Few rounded core stones up to 3 foot diameter at 10 feet; no refusal
-No groundwater
-Backfilled with trench spoils
SCALE: 1" = 5' (VERT.= HORIZ.)
TRENCH NO. 3
0 CARLSBAD OAKS NORTH BUSINESS PARK
LOT 3
GEOTECHNICAL ■ENVIRONMENTAL ■ MATERIALS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121 -297 4
PHONE 858 558-6900 -FAX 858 558-6159
CARLSBAD, CALIFORNIA
EA/CW I I DSK/GTYPD DATE 05 -26 -2021 I PROJECT NO. 06442-32 -34 I FIG. A3
Plotted:05/26/2021 9:11AM I By:JONATHAN WILKINS I File Location:Y:\PROJECTS\06442-32-34 (Con Lot-3)\DETAILS\06442-32-34_TRENCHES.dwg
340'
...J
(/) 335' ~
i=-w w 330' LL -z 0 j::: 325' <( > w
...J w 320'
315'
EXISTING
GROUND SURFACE
Kgr
EXISTINJ
IRRIGATIO
LINE Kgr
O' 5' 10' 15' 20' 25' 30' 35' 40'
DISTANCE (FEET)
(D Highly weathered, damp, mottled orange and olive brown, weak to
moderately week GRANITIC ROCK; excavates to a mottled orange
and olive brown, silty, fine to coarse sand with few/little weak rock up to
8 inch diameter
-Few rounded core stones up to 18 inch diameter; no refusal
-No groundwater
-Backfilled with trench spoils
SCALE: 1" = 5' (VERT.= HORIZ.)
TRENCH NO. 4
GEOCON 0 CARLSBAD OAKS NORTH BUSINESS PARK
LOT 3 INCORPORATED
GEOTECHNICAL ■ENVIRONMENTAL ■ MATERIALS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121 -297 4
PHONE 858 558-6900 -FAX 858 558-6159
EA/ cw I I DSK/GTYPD
CARLSBAD, CALIFORNIA
DATE 05 -26 -2021 I PROJECT NO. 06442 -32 -34 I FIG. A4
Plotted:05/26/2021 9:11AM I By:JONATHAN WILKINS I File Locatlon:Y:\PROJECTS\06442-32-34 (Con Lot-3)\DETAILS\06442-32-34_TRENCHES.dwg
PROJECT NO. 06442-32-34
c:: TRENCHT 5 Zw~ ~ w w~ >-~ Quli: DEPTH (!) SOIL ci5-:-c::~
0 ~z-:::::) I-
SAMPLE :s: c:: <( en zu. I-z IN ..J ~~ 0 0 CLASS I-ti; :s: en w
NO. z ELEV. (MSL.) 324' DATE COMPLETED 11-03-2020 -I-FEET I w-o >-e:., oz I-:::::) (USCS) zen..J
::J 0 wwm c:: ~o c:: EQUIPMENT C345BL W/ 2' BUCKET & ROCK TEETH BY: E. ALVARADO a..C::~ 0 u
(!)
MATERIAL DESCRIPTION
f-0 ltl SM COMP ACTED FILL
Loose to medium dense, damp, mottled olive and orange brown, Silty, fine to
coarse SAND with few gravel up to 6 inch diameter
f--f-
·.·.·( I -Becomes medium dense, moist at 1 foot
:-1·· .. ·:-
+ + GRANITIC ROCK
f-2 -+ Highly weathered, moist, mottled orange and olive brown, weak to moderately 1--
+ + weak GRANITIC ROCK; excavates as silty, fine to coarse sand with few to
+ little weak rock and rounded core stones up to 18 inch diameter + + f--+ -
+ +
+
f-4 -+ + -
+ + +
f--+ ~ + + + + +
f-6 -+ -
+ + +
~ -+ + -
+ -Heavy trenching effort at 7 feet; trace core stones up to 3 foot diameter
+ +
8 + f--+ -+ + + + -Practical refusal due to large rounded core stones ( diameter > 5 feet)
f-
BOTTOM OF TRENCH AT 9 FEET
Practical refusal on core stones
No groundwater
Backfilled with trench spoils
Figure A-5, 06442-32-34.GPJ
Log of Trench T 5, Page 1 of 1
SAMPLE SYMBOLS □ ... SAMPLING UNSUCCESSFUL
~ ... DISTURBED OR BAG SAMPLE
I] ... STANDARD PENETRATION TEST
~ .. CHUNK SAMPLE
■ ... DRIVE SAMPLE (UNDISTURBED)
Y ... WATERTABLEOR :iJ_ ... SEEPAGE
NOTE: THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
GEOCON
PROJECT NO. 06442-32-34
a:: TRENCHT 6 ZLJ.J~ ~ w~ >-LJ.J Qui-:
DEPTH (!) i SOIL ~Z!:!:: en-:-a::~
0 zu.. ::::, f-
IN SAMPLE ...J a::~CI) LJ.J . f-z
0 0 CLASS ELEV. (MSL.) 324' DATE COMPLETED 11-03-2020 f-CI)~ 0~ Cl) LJ.J
FEET NO. I z LJ.J-O >-e:, -f-
f-::::, (USCS) ZCl)...J oz
::J 0 LJ.JLJ.J ca a:: ~o
a:: EQUIPMENT C345BL W/ 2' BUCKET & ROCK TEETH BY:E.ALVARADO a..a::~ 0 (.)
(!)
MATERIAL DESCRIPTION -0 .··-1-r-l SM COMPACTED FILL ·f:.•:· Medium dense, damp, mottled olive and orange brown Silty, fine to coarse 1-rl SAND with trace gravel --+ + GRANITIC ROCK
+ Highly weathered, damp, mottled orange and olive brown, weak to moderately
+ + weak GRANITIC ROCK; excavates as silty, fine to coarse sand with weak -2 -+ rock and rounded core stones up to 3 foot diameter -
+ + + --+ + c--
+ + + + -4 -+ + c--
+ + +
--+ ~
+ + +
-6 -+ + + -
+ + + --+ + -
+ + +
-8 -+ -
+ + + + + ---+
+ + +
10 -+ + -
+ + + --+ -+ + + + + -No refusal -12 BOTTOM OF TRENCH AT 12 FEET
No groundwater
Backfilled with trench spoils
Figure A-6, 06442-32-34.GPJ
Log of Trench T 6, Page 1 of 1
SAMPLE SYMBOLS □ ... SAMPLING UNSUCCESSFUL
~ ... DISTURBED OR BAG SAMPLE
[I ... STANDARD PENETRATION TEST
~ ... CHUNK SAMPLE
■ ... DRIVE SAMPLE (UNDISTURBED)
y_ ... WATERTABLEOR 'Sj_ ... SEEPAGE
NOTE: THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
GEOCON
PROJECT NO. 06442-32-34
ex:: TRENCHT 7 ZUJ~ ~ w~ >-UJ Qu~ DEPTH ~ ~ SOIL cii--:-a::~
0 s: ~~iii zu. ::::l f-
IN SAMPLE ....J UJ . f-z
0 Cl CLASS ELEV. (MSL.) 321' DATE COMPLETED 11-03-2020 ex:: f-s: Cl~ Cl) UJ
FEET NO. I z ti:i5a 0 >-e:. -f-
f-::::l (USCS) z(/)....1 oz
:::::; 0 UJ UJ [l) ex:: ::rEO
ex:: EQUIPMENT C345BL W/ 2' BUCKET & ROCK TEETH BY: E. ALVARADO Q.o::~ Cl ()
~
MATERIAL DESCRIPTION ,-0 rtr SM COMPACTED FILL
\,:[•-!•. Medium dense, damp, mottled olive and orange brown, Silty, fine to coarse
SAND with trace gravel up to 4 inch diameter ,--l ·r -
ili
-Becomes moist at I foot
,-2 -,-
,---r ,-
lrl
+ + GRANITIC ROCK
,-4 -+ Completely to highly weathered, damp, mottled orange and olive brown, weak ,-
+ + GRANITIC ROCK; excavates as silty, fine to coarse sand with few weak rock + up to 4 inch diameter + + ,--+ ,-
-Trace rounded core stones up to 8 inch diameter + + +
,-6 -+ + ,-
+ + +
~ -+ ,-
+ + -Becomes highly weathered at 7 feet
+ + + ,-8 -+ ,-
+ + + --+ + -
+ + +
10 +
BOTTOM OF TRENCH AT 10 FEET
No groundwater
Backfilled with trench spoil
Figure A-7, 06442-32-34.GPJ
Log of Trench T 7, Page 1 of 1
SAMPLE SYMBOLS 0 ... SAMPLING UNSUCCESSFUL
~ ... DISTURBED OR BAG SAMPLE
I) .. STANDARD PENETRATION TEST
~ ... CHUNK SAMPLE
■ ... DRIVE SAMPLE (UNDISTURBED)
Y .. WATER TABLE OR :j__ ... SEEPAGE
NOTE: THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
GEOCON
PROJECT NO. 06442-32-34
a:: TRENCHT 8 ZLLJ~ ~ >-LLJ w~
DEPTH (!) ~ SOIL
Quti: u5--:-a::-
SAMPLE 0 s: ~z-zu. ::> I-
IN ....J 0 CLASS d~(/) ~~ I-z
NO. 0 z ELEV. (MSL.) 321' DATE COMPLETED 11-03-2020 I-(/) s: (/)w
FEET I w-o >-e::. -I-
I-::> (USCS) z(/) ....J oz
:J 0 wwco a:: ~o a:: EQUIPMENT C345BL W/ 2' BUCKET & ROCK TEETH BY:E.ALVARADO a..0::-0 u
(!)
MATERIAL DESCRIPTION -0 .···r•r.r SM COMPACTED FILL
i .f•.•·· Medium dense, damp, mottled orange and olive brown, Silty, fine to coarse lr 1 SAND with trace gravel up to 4 inch diameter
--+ + GRANITIC ROCK
+ Highly weathered, damp, mottled orange and olive brown, weak GRANITIC
+ + ROCK; excavates as silty, fine to coarse sand with little weak rock up to 10 -2 -+ inch diameter and trace rounded core stones up to 12 inch diameter -
+ +
+
f--+ + -+ + + + f-4 -+ + -
+ + +
f--+ -
+ + -Becomes moderately weak to moderately strong at 5 feet
+
-6 -+ +
+ -
+ +
+ --+ + -
+ + +
-8 -+ -
+ + + + + ---+ + +
+ -10 -+ +
+
+ +
f-+
BOTTOM OF TRENCH AT 11 FEET
No groundwater
Backfilled with trench spoils
Figure A-8, 06442-32-34.GPJ
Log of Trench T 8, Page 1 of 1
SAMPLE SYMBOLS □ ... SAMPLING UNSUCCESSFUL
~ ... DISTURBED OR BAG SAMPLE
(] ... STANDARD PENETRATION TEST
liiiiJ ... CHUNK SAMPLE
■ ... DRIVE SAMPLE (UNDISTURBED)
y_ ... WATER TABLE OR 'S:j_ ... SEEPAGE
NOTE: THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
GEOCON
PROJECT NO. 06442-32-34
a:: TRENCHT 9 ZUJ~ ~ w~ >-UJ Qut DEPTH <.!) ~ SOIL en,....,. a::~
0 :!:: ~z-ZIL ::::, I-
IN SAMPLE ....J a::<( Cl) UJ . I-z
0 Cl CLASS ELEV. (MSL.) 319' DATE COMPLETED 11-03-2020 I-tii :!:: Cl~ Cl) UJ
FEET NO. J: z UJ-O >-e:, -I-
I-::::, (USCS) zcn ....J oz
::J 0 UJ UJ co a:: ::?:0 a:: EQUIPMENT C345BL W/ 2' BUCKET & ROCK TEETH BY: E. ALVARADO a..O::~ Cl C)
<.!)
MATERIAL DESCRIPTION .... 0 r;::r SM COMP ACTED FILL
+ + Medium dense, damp, mottled olive and orange brown, Silty, fine to coarse I + SAND with trace gravel up to 4 inch diameter --1--
+ + GRANITIC ROCK
+ Highly to moderately weathered, damp, mottled orange and olive brown,
2 + + moderately weak GRANITIC ROCK; excavates as silty, fine to coarse sand .... -+ with some rock up to 18 inch diameter and trace rounded core stones up to 2 -
+ + foot diameter
+ --+ + -+ + +
-4 -+ -+ + + + + --+ -
+ + +
-6 -+ + -+ + + + ---+ + -Becomes moderately weak to moderately strong at 7 feet with trace rock up to + 4 foot diameter + + -8 -+ ....
+ + -Moderate to heavy trenching effort at 8 feet; excavates to a soil-rock mix with
+ rock up to 18 inch diameter
.... -+ + -+ + + + 1--10 BOTTOM OF TRENCH AT 10 FEET
No groundwater
Backfilled with trench spoils
Figure A-9, 06442-32-34.GPJ
Log of Trench T 9, Page 1 of 1
SAMPLE SYMBOLS D ... SAMPLING UNSUCCESSFUL
~ ... DISTURBED OR BAG SAMPLE
II ... STANDARD PENETRATION TEST
~ ... CHUNK SAMPLE
■ ... DRIVE SAMPLE (UNDISTURBED)
Y ... WATER TABLE OR ~ ... SEEPAGE
NOTE: THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
GEOCON
APPENDIX
APPENDIX B
LABORATORY TESTING
PERFORMED BY GEOCON INCORPORATED (2006)
FOR
CARLSBAD OAKS NORTH BUSINESS PARK -LOT 3
CARLSBAD, CALIFORNIA
PROJECT NO. 06442-32-34
APPENDIX B
LABORATORY TESTING
TABLE B-1
SUMMARY OF LABORATORY MAXIMUM DRY DENSITY
AND OPTIMUM MOISTURE CONTENT TEST RESULTS
ASTM D 1557
Sample No. Description Maximum Dry Optimum Moisture
(Unit) Density (pct) Content(% dry wt.)
I
2
4
5
Dark brown, Silty, fine SAND 129.2 8.5
Olive brown, Silty, fine to coarse SAND with trace gravel 130.1 8.6
Very dark brown, Clayey, fine to medium SAND, with 123.9 12.0 trace gravel
Dark reddish brown, Clayey, fine to coarse SAND with 135 .1 trace gravel
TABLE B-11
SUMMARY OF LABORATORY DIRECT SHEAR TEST RESULTS
AASHTO T236
7.4
D D . M . U . C h . Angle of Shear Sam 1 N ry ens1ty 01sture mt o es1on R . t
p e o. (pct) Content (%) (pst) (des1s anc)e egrces
TABLE B-111
SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS
ASTM D 4829
Sample No. Moisture Content Dry Density Expansion
(Unit) Before Test(%) After Test (0/4,) (pct)
EI-14 (Lot 3) 9.0 16.5 113 .0
EI-15 (Lot3) 9.3 14.9 113 .9
EI-16 (Lot 3) 8.4 14.2 I 17.8
TABLE B-IV
SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS
CALIFORNIA TEST NO. 417
Index
I
2
I
Sample No. Water-Soluble Sulfate(%) Sulfate Exposure (Unit)
EI-14 (Lot 3) 0.002 Negligible
EI-15 (Lot 3) 0.008 Negligible
El-16(Lot3) 0.004 Negligible
Geocon Project No. 06442-32-34 May 26. 2021
APPENDIX
• • • •
•
•
•
APPENDIX C
CITY OF CARLSBAD BMP DESIGN MANUAL -
CATEGORIZATION OF INFILTRATION FEASIBILITY CONDITION
(FORM 1-8)
FOR
CARLSBAD OAKS NORTH BUSINESS PARK -LOT 3
CARLSBAD, CALIFORNIA
PROJECT NO. 06442-32-34
•
Appendix I: Forms and Checklists
Part 1 -Full Infiltration Feasibility Screening Criteria
Would infiltration of the full design volume be feasible from a physical perspective without any undesirable
consequences that cannot be reasonably mitigated?
Criteria Screening Question
Is the estimated reliable infiltration rate below proposed
facility locations greater than 0.5 inches per hour? The response
to this Screening Ques tion shall be based on a comprehensive
evaluation of the factors presented in Appendix C.2 and Appendix
D.
Provide basis:
Yes
X
As discussed in Sections 4 and 8.13 of the update geotechnical report, the lot consists of dense to very stiff
compacted fill overlying hard granitic rock. The bedrock is also exposed at grade. After planned grading, the
compacted fill will be approximately 5 to 55 feet thick and bedrock will also be near or at grade. Previous
infiltration testing performed on other lots within the Carlsbad Oaks North Business Park with similar soil
conditions (see Geocon Inc., report titled Update Geotechnical Report, Carlsbad Oaks North Business Park -Lal
17, Carlsbad, California, dated March 25, 2016 (Proeject No. 06442-32-21) indicated a factored infiltration rate
between 10-4 to 10-1 iph (after applying a feasibility factor of safety of 2).
2
Can infiltration greater than 0.5 inches per hour be allowed
without increasing risk of geotechnical hazards (slope stability,
groundwater mounding, utilities, or other factors) that cannot
be mitigated to an acceptable level? The response to this
Screening Question shall be based on a comprehensive evaluation of
the factors presented in Appendix C.2.
Provide basis:
X
The site is underlain by dense to very stiff compacted fill overlying hard granitic rock. After planned grading, the
compacted fill will be approximately 5 to 50 feet thick and bedrock will also be near or at grade. Based on existing
and ultimate geologic conditions, infiltration could not be incorporated without increasing the risk of geotechnical
hazards including uncontrolled water lateral migration, shrinking and swelling, induced hydro-compression of the
fill and water migration within pipe zone of underground utilities.
1-3 February 2016
•
Appendix I: Forms and Checklists
Criteria
3
Screening Question
Can infiltration greater than 0.5 inches per hour be allowed
without increasing risk of groundwater contamination (shallow
water table, storm water pollutants or other factors) that cannot
be mitigated to an acceptable level? The response to this
Screening Question shall be based on a comprehensive evaluation of
the factors presented in Appendix C.3.
Provide basis:
Yes No
X
Groundwater is not located within l O feet of proposed BMP basins. The risk of storm water infiltration adversely
impacting groundwater is considered negligible.
4
Can infiltration greater than 0.5 inches per hour be allowed
without causing potential water balance issues such as change
of seasonality of ephemeral streams or increased discharge of
contaminated groundwater to surface waters? The res ponse to
this Screening Question shall be based on a comprehensive
evaluation of the factors presented in Appendix C.3.
Provide basis:
Researching downstream water rights and evaluating water balance issues to stream flows is beyond the scope of
the geotechnical engineer.
Part 1
Result
*
If alJ answers to rows 1 -4 are ''Yes" a full infiltration design is potentially feasible.
The feas ibility screening category is Full Infiltration
If any answer from row 1-4 is ''No", infiltration may be possible to some extent but
would not generally be feasib le or desirable to achieve a "full infiltration" design.
Proceed to Part 2
NO
*To be completed using gathered site information and best professional judgment considering the definition of MEP in
the MS4 Permit. Additional testing and/ or studies may be required by the City to substantiate findings.
1-4 February 2016
Appendix I: Forms and Checklists
Part 2 -Partial Infiltration vs. No Infiltration Feasibility ScreeningCriteria
Would infiltration of water in any appreciable amount be physically feasible without any negative
consequences that cannot be reasonably mitigated?
Criteria
5
Screening Question
Do soil and geologic conditions allow for infiltration in any
appreciable rate or volume? The response to this Screening
Question shall be based on a comprehensive evaluation of the
factors presented in Appendix C.2 and Appendix D.
Provide basis:
Yes No
X
The site is underlain by dense to very stiff compacted fill overlying hard granitic rock. After planned grading, the
compacted fill will be approximately 5 to 50 feet thick. The bedrock is also exposed at grade. Previous
infiltration testing performed on other lots within the Carlsbad Oaks North Business Park with similar soil
conditions (see Geocon Inc., report titled Update Geotechnical Report, Carlsbad Oaks North Business Park -Lot
17, Carlsbad, California, dated March 25, 2016 (Proeject No. 06442-32-21) indicated a factored infiltration rate
between 104 to 10-1 iph (after applying a feasibility factor of safety of 2).
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/ data source applicability and why it was not feasible to mitigate low infiltration rates.
6
Can Infiltration in any appreciable quantity be allowed
without increasing risk of geotechnical hazards (slope
stability, groundwater mounding, utilities, or other factors)
that cannot be mitigated to an acceptable level? The response
to this Screening Question shall be based on a comprehensive
evaluation of the factors presented in Appendix C.2.
Provide basis:
X
The site is underlain by dense to very stiff compacted fill overlying hard granitic rock. After planned grading, the
compacted fill will be approximately 5 to 50 feet thick and bedrock will also be near or at grade. Based on
existing and ultimate geologic conditions, infiltration could not be incorporated without increasing the risk of
geotechnical hazards including uncontrolled water lateral migration, shrinking and swelling, induced hydro-
compression of the fill and water migration within pipe zone of underground utilities.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/ data source applicability and why it was not feasible to mitigate low infiltration rates.
1-5 February 2016
•
Appendix I: Forms and Checklists
Criteria
7
Screening Question
Can Infiltration in any appreciable quantity be allowed
without posing significant risk for groundwater related
concerns (shallow water table, storm water pollutants or other
factors)? The response to this Screening Question shall be based
on a comprehensive evaluation of the factors presented in
Appendix C.3.
Provide basis:
Yes No
X
Groundwater is not located within 10 feet of proposed BMP basins. The risk of storm water infiltration adversely
impacting groundwater is considered negligible.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/ data source applicability and why it was not feasible to mitigate low infiltration rates.
8
Can infiltration be allowed without violating downstream
water rights? The response to this Screening Question shall be
based o n a comprehensive evaluation of the factors presented in
Appendix C.3.
Provide basis:
!Researching downstream water rights and evaluating water balance issues to stream flows is beyond the scope of
~he geotechnical engineer.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/ data source applicability and why it was not feasible to mitigate low infiltration rates.
Part 2
Result*
If all answers from row 5-8 are yes then partial infiltration design is potentially feasible.
The feasibility screening category is Partial Infiltration.
If any answer from row 5-8 is no, then infiltration of any volume is considered to be
infeasible within the drainage area. The feasibility screening category is No Infiltration.
No
Infiltration
*To be completed using gathered site information and best professional Judgment constdenng the definition of MEP 1n
the MS4 Permit. Additional testing and/ or studies may be required by the City to substantiate findings.
1-6 February 2016
APPENDIX
APPENDIX D
RECOMMENDED GRADING SPECIFICATIONS
FOR
CARLSBAD OAKS NORTH BUSINESS PARK -LOT 3
CARLSBAD, CALIFORNIA
PROJECT NO. 06442-32-34
RECOMMENDED GRADING SPECIFICATIONS
1. GENERAL
1.1 These Recommended Grading Specifications shall be used in conjunction with the
Geotechnical Report for the project prepared by Geocon. The recommendations contained
in the text of the Geotechnical Report are a part of the earthwork and grading specifications
and shall supersede the provisions contained hereinafter in the case of conflict.
1.2 Prior to the commencement of grading, a geotechnical consultant (Consultant) shall be
employed for the purpose of observing earthwork procedures and testing the fills for
substantial conformance with the recommendations of the Geotechnical Report and these
specifications. The Consultant should provide adequate testing and observation services so
that they may assess whether, in their opinion, the work was performed in substantial
conformance with these specifications. It shall be the responsibility of the Contractor to
assist the Consultant and keep them apprised of work schedules and changes so that
personnel may be scheduled accordingly.
1.3 It shall be the sole responsibility of the Contractor to provide adequate equipment and
methods to accomplish the work in accordance with applicable grading codes or agency
ordinances, these specifications and the approved grading plans. If, in the opinion of the
Consultant, unsatisfactory conditions such as questionable soil materials, poor moisture
condition, inadequate compaction, and/or adverse weather result in a quality of work not in
conformance with these specifications, the Consultant will be empowered to reject the
work and recommend to the Owner that grading be stopped until the unacceptable
conditions are corrected.
2. DEFINITIONS
2.1 Owner shall refer to the owner of the property or the entity on whose behalf the grading
work is being performed and who has contracted with the Contractor to have grading
performed.
2.2 Contractor shall refer to the Contractor performing the site grading work.
2.3 Civil Engineer or Engineer of Work shall refer to the California licensed Civil Engineer
or consulting firm responsible for preparation of the grading plans, surveying and verifying
as-graded topography.
2.4 Consultant shall refer to the soil engineering and engineering geology consulting firm
retained to provide geotechnical services for the project.
GI rev. 07/2015
2.5 Soil Engineer shall refer to a California licensed Civil Engineer retained by the Owner,
who is experienced in the practice of geotechnical engineering. The Soil Engineer shall be
responsible for having qualified representatives on-site to observe and test the Contractor's
work for conformance with these specifications.
2.6 Engineering Geologist shall refer to a California licensed Engineering Geologist retained
by the Owner to provide geologic observations and recommendations during the site
grading.
2. 7 Geotechnical Report shall refer to a soil report (including all addenda) which may include
a geologic reconnaissance or geologic investigation that was prepared specifically for the
development of the project for which these Recommended Grading Specifications are
intended to apply.
3. MATERIALS
3. l Materials for compacted fill shall consist of any soil excavated from the cut areas or
imported to the site that, in the opinion of the Consultant, is suitable for use in construction
of fills. In general, fill materials can be classified as soil fills, soil-rock fills or rock fills, as
defined below.
3 .1.1 Soil fills are defined as fills containing no rocks or hard lumps greater than
12 inches in maximum dimension and containing at least 40 percent by weight of
material smaller than ¾ inch in size.
3 .1.2 Soil-rock fills are defined as fills containing no rocks or hard lumps larger than
4 feet in maximum dimension and containing a sufficient matrix of soil fill to allow
for proper compaction of soil fill around the rock fragments or hard lumps as
specified in Paragraph 6.2. Oversize rock is defined as material greater than
12 inches.
3 .1.3 Rock fills are defined as fills containing no rocks or hard lumps larger than 3 feet
in maximum dimension and containing little or no fines. Fines are defined as
material smaller than ¾ inch in maximum dimension. The quantity of fines shall be
less than approximately 20 percent of the rock fill quantity.
3.2 Material of a perishable, spongy, or otherwise unsuitable nature as determined by the
Consultant shall not be used in fills.
3.3 Materials used for fill, either imported or on-site, shall not contain hazardous materials as
defined by the California Code of Regulations, Title 22, Division 4, Chapter 30, Articles 9
GI rev. 07/2015
and 1 O; 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 m 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 I½ inches in diameter shall be removed to a depth of 3 feet
below the surface of the ground. Borrow areas shall be grubbed to the extent necessary to
provide suitable fill materials.
4.2 Asphalt pavement material removed during clearing operations should be properly
disposed at an approved off-site facility or in an acceptable area of the project evaluated by
Geocon and the property owner. Concrete fragments that are free of reinforcing steel may
be placed in fills, provided they are placed in accordance with Section 6.2 or 6.3 of this
document.
GI rev. 07/2015
4.3 After clearing and grubbing of organic matter and other unsuitable material, loose or
porous soils shall be removed to the depth recommended in the Geotechnical Report. The
depth of removal and compaction should be observed and approved by a representative of
the Consultant. The exposed surface shall then be plowed or scarified to a minimum depth
of 6 inches and until the surface is free from uneven features that would tend to prevent
uniform compaction by the equipment to be used.
4.4 Where the slope ratio of the original ground is steeper than 5: I (horizontal:vertical), or
where recommended by the Consultant, the original ground should be benched in
accordance with the following illustration.
TYPICAL BENCHING DETAIL
Finish Grade
Remove All
Unsuitable Material
As Recommended By
Consultant Slope To Be Such That
Sloughing Or Sliding
Does Not Occur
Original Ground
Varies
See Note 2
No Scale
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 m
Section 6 of these specifications.
GI rev. 07/20 15
5. COMPACTION EQUIPMENT
5.1 Compaction of soil or soil-rock fill shall be accomplished by sheepsfoot or segmented-steel
wheeled rollers, vibratory rollers, multiple-wheel pneumatic-tired rollers, or other types of
acceptable compaction equipment. Equipment shall be of such a design that it will be
capable of compacting the soil or soil-rock fill to the specified relative compaction at the
specified moisture content.
5 .2 Compaction of rock fills shall be performed in accordance with Section 6.3.
6. PLACING, SPREADING AND COMPACTION OF FILL MATERIAL
6.1 Soil fill, as defined in Paragraph 3 .1.1, shall be placed by the Contractor in accordance with
the following recommendations:
6.1.1 Soil fill shall be placed by the Contractor in layers that, when compacted, should
generally not exceed 8 inches. Each layer shall be spread evenly and shall be
thoroughly mixed during spreading to obtain uniformity of material and moisture
in each layer. The entire fill shall be constructed as a unit in nearly level lifts. Rock
materials greater than 12 inches in maximum dimension shall be placed in
accordance with Section 6.2 or 6.3 of these specifications.
6.1.2 In general, the soil fill shall be compacted at a moisture content at or above the
optimum moisture content as determined by ASTM D 1557.
6.1.3 When the moisture content of soil fill is below that specified by the Consultant,
water shall be added by the Contractor until the moisture content is in the range
specified.
6.1.4 When the moisture content of the soil fill is above the range specified by the
Consultant or too wet to achieve proper compaction, the soil fill shall be aerated by
the Contractor by blading/mixing, or other satisfactory methods until the moisture
content is within the range specified.
6.1.5 After each layer has been placed, mixed, and spread evenly, it shall be thoroughly
compacted by the Contractor to a relative compaction of at least 90 percent.
Relative compaction is defined as the ratio (expressed in percent) of the in-place
dry density of the compacted fill to the maximum laboratory dry density as
determined in accordance with ASTM D 1557. Compaction shall be continuous
over the entire area, and compaction equipment shall make sufficient passes so that
the specified minimum relative compaction has been achieved throughout the
entire fill.
GI rev. 07/2015
6.1.6 Where practical, soils having an Expansion Index greater than 50 should be placed
at least 3 feet below finish pad grade and should be compacted at a moisture
content generally 2 to 4 percent greater than the optimum moisture content for the
material.
6.1.7 Properly c_ompacted 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 0-8 dozer
or similar equipment, such that a dozer track covers all slope surfaces at least
twice.
6.2 Soil-rock fill, as defined in Paragraph 3 .1.2, shall be placed by the Contractor in accordance
with the following recommendations:
6.2.1 Rocks larger than 12 inches but less than 4 feet in maximum dimension may be
incorporated into the compacted soil fill, but shall be limited to the area measured
15 feet minimum horizontally from the slope face and 5 feet below finish grade or
3 feet below the deepest utility, whichever is deeper.
6.2.2 Rocks or rock fragments up to 4 feet in maximum dimension may either be
individually placed or placed in windrows. Under certain conditions, rocks or rock
fragments up to 10 feet in maximum dimension may be placed using similar
methods. The acceptability of placing rock materials greater than 4 feet in
maximum dimension shall be evaluated during grading as specific cases arise and
shall be approved by the Consultant prior to placement.
6.2.3 For individual placement, sufficient space shall be provided between rocks to allow
for passage of compaction equipment.
6.2.4 For windrow placement, the rocks should be placed in trenches excavated in
properly compacted soil fill. Trenches should be approximately 5 feet wide and
4 feet deep in maximum dimension. The voids around and beneath rocks should be
filled with approved granular soil having a Sand Equivalent of 30 or greater and
should be compacted by flooding. Windrows may also be placed utilizing an
"open-face" method in lieu of the trench procedure, however, this method should
first be approved by the Consultant.
GI rev. 07/2015
6.2.5 Windrows should generally be parallel to each other and may be placed either
parallel to or perpendicular to the face of the slope depending on the site geometry.
The minimum horizontal spacing for windrows shall be 12 feet center-to-center
with a 5-foot stagger or offset from lower courses to next overlying course. The
minimum vertical spacing between windrow courses shall be 2 feet from the top of
a lower windrow to the bottom of the next higher windrow.
6.2.6 Rock placement, fill placement and flooding of approved granular soil in the
windrows should be continuously observed by the Consultant.
6.3 Rock fills, as defined in Section 3.1.3, shall be placed by the Contractor in accordance with
the following recommendations:
6.3.1 The base of the rock fill shall be placed on a sloping surface (minimum slope of 2
percent). The surface shall slope toward suitable subdrainage outlet facilities. The
rock fills shall be provided with subdrains during construction so that a hydrostatic
pressure buildup does not develop. The subdrains shall be permanently connected
to controlled drainage facilities to control post-construction infiltration of water.
6.3.2 Rock fills shall be placed in lifts not exceeding 3 feet. Placement shall be by rock
trucks traversing previously placed lifts and dumping at the edge of the currently
placed lift. Spreading of the rock fill shall be by dozer to facilitate seating of the
rock. The rock fill shall be watered heavily during placement. Watering shall
consist of water trucks traversing in front of the current rock lift face and spraying
water continuously during rock placement. Compaction equipment with
compactive energy comparable to or greater than that of a 20-ton steel vibratory
roller or other compaction equipment providing suitable energy to achieve the
required compaction or deflection as recommended in Paragraph 6.3 .3 shall be
utilized. The number of passes to be made should be determined as described in
Paragraph 6.3.3. Once a rock fill lift has been covered with soil fill, no additional
rock fill lifts will be permitted over the soil fill.
6.3.3 Plate bearing tests, in accordance with ASTM D 1196, may be performed in both
the compacted soil fill and in the rock fill to aid in determining the required
minimum number of passes of the compaction equipment. If performed, a
minimum of three plate bearing tests should be performed in the properly
compacted soil fill (minimum relative compaction of 90 percent). Plate bearing
tests shall then be performed on areas of rock fill having two passes, four passes
and six passes of the compaction equipment, respectively. The number of passes
required for the rock fill shall be determined by comparing the results of the plate
bearing tests for the soil fill and the rock fill and by evaluating the deflection
GI rev. 07/2015
variation with number of passes. The required number of passes of the compaction
equipment will be performed as necessary until the plate bearing deflections are
equal to or less than that determined for the properly compacted soil fill. In no case
will the required number of passes be less than two.
6.3.4 A representative of the Consultant should be present during rock fill operations to
observe that the minimum number of "passes" have been obtained, that water is
being properly applied and that specified procedures are being followed. The actual
number of plate bearing tests will be determined by the Consultant during grading.
6.3.5 Test pits shall be excavated by the Contractor so that the Consultant can state that,
in their opinion, sufficient water is present and that voids between large rocks are
properly filled with smaller rock material. In-place density testing will not be
required in the rock fills.
6.3.6 To reduce the potential for "piping" of fines into the rock fill from overlying soil
fill material, a 2-foot layer of graded filter material shall be placed above the
uppermost lift of rock fill. The need to place graded filter material below the rock
should be determined by the Consultant prior to commencing grading. The
gradation of the graded filter material will be determined at the time the rock fill is
being excavated. Materials typical of the rock fill should be submitted to the
Consultant in a timely manner, to allow design of the graded filter prior to the
commencement of rock fill placement.
6.3.7 Rock fill placement should be continuously observed during placement by the
Consultant.
7. SUBDRAINS
7 .1 The geologic units on the site may have permeability characteristics and/or fracture
systems that could be susceptible under certain conditions to seepage. The use of canyon
subdrains may be necessary to mitigate the potential for adverse impacts associated with
seepage conditions. Canyon subdrains with lengths in excess of 500 feet or extensions of
existing offsite subdrains should use 8-inch-diameter pipes. Canyon subdrains less than 500
feet in length should use 6-inch-diameter pipes.
GI rev. 07/2015
TYPICAL CANYON DRAIN DETAIL
NAT\JRALGROIH)
............
NOTES:
............
........
.....................
.... ....
.......................
---
··-·• .. ~4 . •' <t~~<:\:·
1 ...... 6-lNCH DIAMETER, SCHEDULE 80 PVC PERFORAlED PIPE FOR Flll.S
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 ALLS
LESS THAN 100-FEET IN DEPTH OR A PIPE LENGTll SHORTER THAN 500 FEET.
BEDROCK
NOTE: FINAi. 'N OF PIPE AT OUTl.ET
8HA1..1. BE NON-PERFORATED.
9 CUBIC FEET/ FOOT OF OPal
GRADED GRAVEL SURROUNDED BY
MIRAFl 1-40NC (OR EQUIVALENT)
FILTER FABRIC
NO SCALE
7.2 Slope drains within stability fill keyways should use 4-inch-diameter (or lager) pipes.
GI rev. 07/2015
•
TYPICAL STABILITY FILL DETAIL
DETAIL
FORMAnONAL
MATERIAL
1 •..•. EXCAVATE BACKCUT AT 1:1 INCUNATION (U"-ESS OTI-IERWISE NOTI:O~
2 .... .BASE OF STABILITY FILL TO BE 3 FEET INTO FORMATIONAL MATERIAL. SI.OPING A MINIMUM 5% INTO SI.OPE.
3 .•• STABIUTY Fil. TO BE COMPOSED OF PROPERl. Y COW>ACTE.D GRANu.AR SOIL
4 .•..• CHIMNEY DRAINS TO BE APPROVED PREFABRICATED CHIMNEY DRAIN PANELS (MIRADRAIN G200N OR EQUIVALENT)
SPACED APPROXIMATELY 20 FEET CENTER TO CENTER AND, FEEfWIDE. Q.OSER SPACING MAY BE REQUIRED F
SEEPAGE IS ENCOUNTERED.
5 ..... Fll. TER MATERIAL TO BE 3/4-NCH, OP~ CRUSHED ROCK ENCLOSED IN APPROVED .,._TER FABRIC (MIRAF1 140NC~
6 .•.•. COUECTOR PIPE TO BE 4-l'ICH MINIMUM DIAMETER. PERFORATED, THICK-WAU£D PVC SCHEDUl£ 40 OR
EQUIVALENT, AND SLOF'ED TO DRAIN AT 1 PERCENT l,INMJM TO APPROVED oun.ET.
NO SCALE
7.3 The actual subdrain locations will be evaluated in the field during the remedial grading
operations. Additional drains may be necessary depending on the conditions observed and
the requirements of the local regulatory agencies. Appropriate subdrain outlets should be
evaluated prior to finalizing 40-scale grading plans.
7.4 Rock fill or soil-rock fill areas may require subdrains along their down-slope perimeters to
mitigate the potential for buildup of water from construction or landscape irrigation. The
subdrains should be at least 6-inch-diameter pipes encapsulated in gravel and filter fabric.
Rock fill drains should be constructed using the same requirements as canyon subdrains.
GI rev. 07/20 15
•
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
FRONT VIEW
SIDE VIEW
CONCRETE
CUT-OFF WAU.
CONCRETE
CUT-OFFWAU.
SOUO SUBORAJ; PIPE
l!"MIN.
NO SCALE
Ir MIN. (TYP)
II" MIN.(TYP) /
NO SCALE
7.6 Subdrains that discharge into a natural drainage course or open space area should be
provided with a permanent headwall structure.
GI rev. 07/2015
•
•
TYPICAL HEADWALL DETAIL
FRONT VIEW
SIDE VIEW
roor
SIAlORA.N
CONCRETE
HEAOWAU
rORr
SUBDAAIN
NOlc: HEADWALL SHOULD OUTlET AT TOE OF Fill SLOPE
OR INTO CONTROU.EO SURFACE DRAINAGE
NO SCALE
12'
NO SCALE
7.7 The final grading plans should show the location of the proposed subdrains. After
completion of remedial excavations and subdrain installation, the project civil engineer
should survey the drain locations and prepare an "as-built" map showing the drain
locations. The final outlet and connection locations should be determined during grading
operations. Subdrains that will be extended on adjacent projects after grading can be placed
on formational material and a vertical riser should be placed at the end of the subdrain. The
grading contractor should consider videoing the subdrains shortly after burial to check
proper installation and functionality. The contractor is responsible for the performance of
the drains.
GI rev. 07/20 15
8. OBSERVATION AND TESTING
8.1 The Consultant shall be the Owner's representative to observe and perform tests during
clearing, grubbing, filling, and compaction operations. In general, no more than 2 feet in
vertical elevation of soil or soil-rock fill should be placed without at least one field density
test being performed within that interval. In addition, a minimum of one field density test
should be performed for every 2,000 cubic yards of soil or soil-rock fill placed and
compacted.
8.2 The Consultant should perform a sufficient distribution of field density tests of the
compacted soil or soil-rock fill to provide a basis for expressing an opinion whether the fill
material is compacted as specified. Density tests shall be performed in the compacted
materials below any disturbed surface. When these tests indicate that the density of any
layer of fill or portion thereof is below that specified, the particular layer or areas
represented by the test shall be reworked until the specified density has been achieved.
8.3 During placement of rock fill, the Consultant should observe that the minimum number of
passes have been obtained per the criteria discussed in Section 6.3.3. The Consultant
should request the excavation of observation pits and may perform plate bearing tests on
the placed rock fills. The observation pits will be excavated to provide a basis for
expressing an opinion as to whether the rock fill is properly seated and sufficient moisture
has been applied to the material. When observations indicate that a layer of rock fill or any
portion thereof is below that specified, the affected layer or area shall be reworked until the
rock fill has been adequately seated and sufficient moisture applied.
8.4 A settlement monitoring program designed by the Consultant may be conducted in areas of
rock fill placement. The specific design of the monitoring program shall be as
recommended in the Conclusions and Recommendations section of the project
Geotechnical Report or in the final report of testing and observation services performed
during grading.
8.5 We should observe the placement of subdrains, to check that the drainage devices have
been placed and constructed in substantial conformance with project specifications.
8.6 Testing procedures shall conform to the following Standards as appropriate:
8.6.1 Soil and Soil-Rock Fills:
8.6.1.1 Field Density Test, ASTM D 1556, Density of Soil In-Place By the
Sand-Cone Method.
GI rev. 07/2015
8.6.1.2 Field Density Test, Nuclear Method, ASTM D 6938, Density of Soil and
Soil-Aggregate In-Place by Nuclear Methods (Shallow Depth).
8.6.1.3 Laboratory Compaction Test, ASTM D 1557, Moisture-Density
Relations of Soils and Soil-Aggregate Mixtures Using JO-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.
GI rev. 07/2015
--
LIST OF REFERENCES
I. Bay Area Earthquake Alliance (2020), How Close To a Fault Do You Live?: Website,
https://bayquakealliance.org/howclose/, accessed July 15, 2020;
2. 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.
3. SEAOC (2019), OSHPD Seismic Design Maps: Structural Engineers Association of
California website, http://seismicmaps.org/, accessed May 24, 2021;
4. USGS (2019), Quaternary Fault and Fold Database of the United States: U.S. Geological
Survey website, https:/ /www.usgs.gov/natural-hazards/earthquake-hazards/faults, accessed
April 26, 2021;
5. Kennedy, M. P., and S.S. Tan, Geologic Map of the Oceanside 30'x60' Quadrangle,
California, USGS Regional Map Series Map No. 2, Scale 1:100,000, 2007.
6. Unpublished reports and maps on file with Geocon Incorporated.
Geocon Project No. 06442-32-34 May 26. 2021
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T-9 1 ·······.APPROX. LOCATION OF EXPLORATORY T RENCH EXCAVATION
GEOLOGIC CROSS -SECTION
CARLSBAD OAKS NORTH BUSINESS PARK -LOT 3
SAN DIEGO, CALIFORNIA
GEOCON SCALE 1,. ~ 30, IDATE 05 -26-2021
1 NCO RPO RATED
GEOTECH NICAL ■ ENVIRONMENTAL ■ MATERIALS
6960FLANDERSDRrvE •SAN DIEGO, CALFORNIA. 92121 ·2974
PHONE858 558-6900 • FAX. 858 558-6159
PROJECT NO.
SHEET 1
06442 -32 -34 FIGURE
OF 1 3
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