HomeMy WebLinkAboutNCP 2022-0002; DE FREITAS RESIDENCE; LIMITED GEOTECHNICAL EVALUATION; 2022-10-10Geotechnical C Geologic C Coastal C Environmental
5741 Palmer Way C Carlsbad, California 92010 C (760) 438-3155 C FAX (760) 931-0915 C www.geosoilsinc.com
March 8, 2022
Revised October 10, 2022
W.O. 8286-A-SC
Ms. Patiane Freitas
4339 Park Drive
Carlsbad, California 92008
Subject:Limited Geotechnical Evaluation for a Planned Single-Family Residence,
Including Retaining Walls, 4339 Park Drive, Carlsbad, California 92028,
APN 206-192-01-00
Dear Ms. Freitas:
In accordance with your request, GeoSoils, Inc. (GSI) has performed soil sampling and
laboratory testing and analyses of representative soil samples obtained from the site by a
representative from this office. The purpose of our testing was to evaluate soil parameters
for the planned construction of a single-family residence and corresponding retaining walls
within the yard area of an existing single-family residential property located at 4339 Park
Drive, Carlsbad, California. GSI’s scope of services included a review of the referenced
documents (Appendix A) and plans/drawings provided by you, subsurface exploration,
laboratory testing, engineering and geologic analyses, and preparation of this report. This
report has been prepared for the sole purpose of providing a limited description of soil
conditions onsite, and engineering parameters derived from testing of site soil samples in
our laboratory, and does not constitute a geotechnical evaluation of the overall stability or
suitability of the site, which would have been performed prior to original approval and
development
Based on a review of the unnamed plans/drawings provided by you, the planned residence
and corresponding walls are anticipated to be located within the southern, central area of
the property, with the walls and a majority of the residence set into an existing graded fill
slope at roughly 1.5:1 (Horizontal:Vertical [H:V]) inclination. Per conversations with the
client, the lower portion of the residence will be a two-story structure consisting of a garage
on the first floor, including a corresponding retaining/building wall built within the existing
graded fill slope, and a large living space above, while the rest of the structure will be
single-story.
FIELD STUDIES
Site-specific field studies were conducted by GSI on February 10, 2022, and consisted of
reconnaissance geologic mapping and the excavation of four (4) exploratory excavations
GeoSoils, Inc.
for an evaluation of near-surface soil and geologic conditions onsite. The boring locations
are shown on the Boring Location Map, Figure 1. The borings were performed in the
vicinity of the proposed residence, and were logged by a representative of this office who
collected representative bulk samples for appropriate laboratory testing. In general, the
proposed house site appears to be underlain by about 3 feet of existing weathered
Santiago Formation consisting of dark brown to dark reddish brown silty/clayey sandstone
(USCS symbol SM), overlying less weathered sandstone also belonging to the
Santiago Formation (i.e., bedrock). Based on our observations, testing, and analysis,
existing surficial soil within about 2 to 3½ feet from existing yard grades appears moist and
relatively loose, becoming damp to moist and dense below these depths. At the top of the
graded slope (uphill of the vicinity of Boring B-2), GSI locally encountered roughly 6 to
7 feet of loose, undocumented fill. The boring logs are presented in Appendix B.
LABORATORY TESTING
Laboratory tests were performed on representative samples of site earth materials in order
to evaluate their physical characteristics. The results of our evaluation are summarized as
follows:
Particle-Size Analysis
A particle-size evaluation was performed on a representative soil sample (0 to 2½ feet
composite in proposed residence area) in general accordance with ASTM D 422-63. The
testing was used to evaluate the soil classification in accordance with the Unified Soil
Classification System (USCS). The results of the particle-size evaluation indicate that the
tested soil is a Silty Sand (SM).
Expansion Index
Tests were performed on representative soil samples general accordance with
ASTM D 4829. Test results and the soils expansion potential are presented in the following
table:
SAMPLE LOCATION DESCRIPTION EXPANSION INDEX EXPANSION
POTENTIAL
Residence Area Composite 0 to 2½ feet Silty Sand < 21 Very Low
Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides
GSI conducted sampling and testing of a representative sample of the onsite earth
materials for general soil corrosivity and soluble sulfates, and chlorides testing. The testing
Ms. Patiane Freitas W.O. 8286-A-SC
4339 Park Drive, Carlsbad Revised October 10, 2022
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I I I
I I I
W.O.DATE:SCALE:8286-A-SC 1" = 50'
Figure 1
BORING LOCATION
MAP
10/22
ALL LOCATIONS ARE APPROXIMATE
This document or efile is not a part of the Construction
Documents and should not be relied upon as being an
accurate depiction of design.
APPROXIMATE LOCATION OF EXPLORATORY BORING
WITH TOTAL DEPTH IN FEET
B-4
TD=5'
GSI LEGEND
B-1
TD=5'B-2
TD=5'
B-3
TD=5'
B-4
TD=5'
BASE MAP FROM:
N
S
EW
0
GRAPHIC SCALE
50 25 50 100
1" = 50'
I
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/_
METAL PANEL-mu
t. r-.i'
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72" CORRUGATED
METAL PIPE
lfll/. ELEV.=63.46'
0 f/ETAL PANEL
FENCE •
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CARLs:1RK DR A.P.N. ztB CA 92008 TOTAL ARE;192-01-DO . 147,135.23 SF 3.377 AC. · · (NET)
EASEMENTS NOTES·
PER NAT . DATED ~~NAL TITLE COM PROPERTY.BRUARY 16, 26~NYTPRELIMINARY Tl ' HERE ARE N TLE REPORT 0 EASEMENTS
NOTES:
SURVEYOR'S STATEMENT·
THIS MAP WA . S PREPARED BY M £ OR UNDER MY DIRECTION
DATE
ORDER NO AFFECTING 092160938-M THE SURVEYEt
GeoSoils, Inc.
included evaluation of soil pH, soluble sulfates, chlorides, and saturated resistivity. Test
results are presented in the following table:
SAMPLE LOCATION AND DEPTH
(FT)pH
SATURATED
RESISTIVITY
(ohm-cm)
SOLUBLE
SULFATES
(% by weight)
SOLUBLE
CHLORIDES
(ppm)
Residence Area Composite 0 to 2½ feet 7.0 1,600 0.006 70
Corrosion Summary
Laboratory testing indicates that the tested sample of the onsite soils is neutral with respect
to soil acidity/alkalinity; is corrosive to exposed, buried metals when in a moist state;
presents negligible sulfate exposure to concrete (Exposure Class S0 per Table 19.3.1.1 of
American Concrete Institute [ACI] 318-14), and contains low concentrations of soluble
chlorides. GSI does not consult in the field of corrosion engineering. Thus, the Client may
obtain additional consultation from a qualified corrosion engineer based on the level of
corrosion protection required for the project, as determined by the Client, the Project
Architect, the Project Structural Engineer, and the Project Civil Engineer.
BEARING VALUE
Based on our analysis, an allowable bearing value of 2,000 pounds per square foot (psf)
may be assumed for continuous footings, a minimum 12 inches wide and 12 inches deep
(below lowest adjacent grade [excluding soft soils, landscape zones, slab and
underlayment thickness, etc.]), bearing on suitable, approved formational soil. It is
anticipated that actual footing depths may be deeper than those indicated above, in order
to penetrate any potential loose, near-surface soils. Actual footing depths would be based
on conditions exposed within the footing excavation. The allowable bearing value may be
increased by 20 percent for each additional 12 inches in depth of proper embedment, or
6 inches in width, into approved suitable bearing soil, to a maximum value of 2,500 psf.
The above values may be increased by one-third when considering short duration seismic
or wind loads. Differential settlement may be assumed as 1 inch in a 40-foot span,
provided the footing bears on suitable, competent and similar earth materials.
Foundations should be designed for all applicable surcharge loads and should consider
the inherent corrosive coastal environment. Existing foundations should not support new
loads.
Ms. Patiane Freitas W.O. 8286-A-SC
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LATERAL PRESSURE
Passive Pressure
Total Lateral Resistance (TLR) for shallow foundations is provided by the friction along the
footing bottoms and the passive pressure across footing faces in contact with either fill or
natural soil deposits. The TLR is influenced by the depth of the footing and the cohesion
(or apparent cohesion) of the soil material. The normal force or dead load on the footing
from the overlying structure will influence the amount of frictional resistance. For sands,
or predominantly sandy soils, this friction is higher than for clay or clayey/silty soils. Based
on laboratory testing and analysis, as well as a review of Table 1806.2 of the 2019 CBC
(CBSC, 2019a), the TLR for the sandy soils onsite may be taken as an equivalent fluid of
150 psf per foot (150 psf/ft) of depth, to a maximum earth pressure of 2,000 psf/ft.
An allowable coefficient of friction between soil and concrete of 0.25 may be used with the
dead load forces. When combining passive pressure and frictional resistance, the passive
pressure component should be reduced by one-third.
Active and At-Rest Pressure
In accordance with our testing/analysis, and based on a review of Table 1610.1 of the
2019 CBC (CBSC, 2019a), for drained conditions, active earth pressure may be computed
as an equivalent fluid having a density of 45 psf per foot of depth (level backfill) and 55 psf
per foot of depth (sloping backfill). At-rest, earth pressure may be computed as an
equivalent fluid having a density of 60 psf per foot of depth for level backfill, and 70 psf per
foot of depth for sloping backfill.
SEISMIC DESIGN
General
In the event of an upper bound (maximum probable) or credible earthquake occurring on
any of the nearby major faults, strong ground shaking would occur in the subject site's
general area. Potential damage to any structure(s) would likely be greatest from the
vibrations and impelling force caused by the inertia of a structure's mass than from those
induced by the hazards listed above. This potential would be no greater than that for other
existing structures and improvements in the immediate vicinity.
Seismic Shaking Parameters
The following table summarizes the site-specific design criteria obtained from the
2019 CBC, Chapter 16 Structural Design, Section 1613, Earthquake Loads. The computer
program Seismic Design Maps, provided by the California Office of Statewide Health
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Planning and Development (OSHPD, 2022) has now been used to aid in design
(https://seismicmaps.org). The short spectral response uses a period of 0.2 seconds.
2019 CBC SEISMIC DESIGN PARAMETERS
PARAMETER VALUE 2019 CBC or REFERENCE
Risk Category I, II, or III Table 1604.5
Site Class C Section 1613.2.2/Chap. 20 ASCE 7-16
(p. 203-204)
Spectral Response - (0.2 sec), Ss 1.047 g Section 1613.2.1
Figure 1613.2.1(1)
Spectral Response - (1 sec), S1 0.38 g Section 1613.2.1
Figure 1613.2.1(2)
Site Coefficient, Fa 1.2 Table 1613.2.3(1)
Site Coefficient, Fv 1.5 Table 1613.2.3(2)
Maximum Considered Earthquake Spectral
Response Acceleration (0.2 sec), SMS
1.257 g Section 1613.2.3
(Eqn 16-36)
Maximum Considered Earthquake Spectral
Response Acceleration (1 sec), SM1
0.57 g Section 1613.2.3
(Eqn 16-37)
5% Damped Design Spectral Response
Acceleration (0.2 sec), SDS
0.838 g Section 1613.2.4
(Eqn 16-38)
5% Damped Design Spectral Response
Acceleration (1 sec), SD1
0.38 g Section 1613.2.4
(Eqn 16-39)
PGAM - Probabilistic Vertical Ground
Acceleration may be assumed as about 50% of
these values.
0.553 g ASCE 7-16 (Eqn 11.8.1)
Seismic Design Category D Section 1613.2.5/ASCE 7-16
(p. 85: Table 11.6-1 or 11.6-2)
GENERAL SEISMIC PARAMETERS
PARAMETER VALUE
Distance to Seismic Source Rose Canyon fault(1)±5.5 mi (8.9 km)
Upper Bound Earthquake Rose Canyon fault MW = 7.2(2)
(1) - From Blake (2000)
(2) - Cao, et al. (2003)
Conformance to the criteria above for seismic design does not constitute any kind of
guarantee or assurance that significant structural damage, ground failure, or surface
manifestations will not occur in the event of a large earthquake in this region. The primary
goal of seismic design is to protect life, not to eliminate all damage, since such design may
Ms. Patiane Freitas W.O. 8286-A-SC
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be economically prohibitive. Cumulative effects of seismic events are not addressed in
the 2019 CBC (CBSC, 2019) and regular maintenance and repair following locally
significant seismic events (i.e., Mw 5.5) will likely be necessary.
DEVELOPMENT CRITERIA
Grading
All grading should conform to the guidelines presented in the 2019 CBC (CBSC, 2019a),
and the County. When code references are not equivalent, the more stringent code should
be followed. During earthwork construction, all site preparation and the general grading
procedures of the contractor (if grading is to occur) should be observed and the fill
selectively tested by a representative(s) of GSI. If unusual or unexpected conditions are
exposed in the field, they should be reviewed by this office and if warranted, modified
and/or additional recommendations will be offered. All applicable requirements of local
and national construction and general industry safety orders, the Occupational Safety and
Health Act, and the Construction Safety Act should be met. Type B soils may be assumed
per Cal-OSHA. GSI does not consult in the area of safety engineering. The contractor is
responsible for the safety of construction workers onsite.
Remedial Grading
It is anticipated that cut excavation will be necessary to create the pad area for the lower
floor garage as well as retaining walls. However, based on the anticipated thickness of
near-surface, weathered formation and potential existing fills (approximately 6 to 7 feet at
the top of the slope), planned improvements are anticipated to be located in fill areas and
areas of shallow cuts (i.e., less than 3 feet).
Loose and compressible materials consisting of weathered formation and undocumented
fill occur at the surface, overlying suitable bearing material. As such, the need for remedial
grading cannot be precluded, and should be reviewed prior to footing excavation
construction. During our site exploration, a near-surface layer of weathered
Santiago Formation, on the order of about 2 to 3½ feet in thickness, was observed in the
pad areas (garage and upslope end of the proposed residence) of the planned structure,
while roughly 6 to 7 feet of loose undocumented fill was observed near the top of the
graded slope. As such, these surficial soils should be mitigated during grading
(i.e., removed and recompacted, etc.) by either:
For a slab-on-grade floor system, the following remedial grading recommendations are
provided:
•Perform removals of all unsuitable soils. If the exposed pad subgrade (after removal
excavation) consists of suitable relatively unweathered formation (i.e. bedrock), the
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exposed surface should be scarified in two directions to a depth of about 6 to
8 inches, proof rolled and compacted to a minimum relative compaction of
90 percent relative compaction per ASTM D-1557.
•Perform complete removal/recompaction of any unsuitable soil, and undercutting
bedrock as necessary, to provide a minimum 3-foot thick cap of compacted fill.
Removal/recompaction should be completed for a minimum lateral distance of at
least 3 to 5 feet beyond the building footprint. All soils should be compacted to at
least 90 percent relative compaction, per ASTM D-1557. This option will result in the
building foundation and floor slab being supported uniformly by compacted fill, and
should lower the potential for shallow perched groundwater to occur.
If remedial grading is not performed, then the footing will need to extend completely
through the loose surficial soil (2 to 3½ feet), and the slab will need to be designed as a
structural slab, spanning between the footings, and not relying on the soil for support.
Foundations
Current laboratory testing indicates that the onsite soils exhibit expansion index values of
less than 21. As such, these soils do not meet the criteria of detrimentally expansive soils
as defined in Section 1803.5.3 of the 2019 CBC.
From a geotechnical viewpoint, foundation construction should conform to the following:
1.Exterior and interior footings should be founded at a minimum depth of 12 inches
below the lowest adjacent grade, or embedded at least 12 inches into suitable
bearing material, whichever is deeper. Footing widths should be per Code.
Isolated pad footings should be 24 inches square, by 18 inches deep, and
minimally embedded at least 18 inches into suitable bearing soil, whichever is
deeper.
A deepened footing will be necessary where the remedial grading is not performed.
2.All footings should be reinforced with four No. 4 reinforcing bars, two placed near
the top and two placed near the bottom of the footing. Isolated pad footing
reinforcement should be per the structural engineer.
3.Interior and exterior column footings should be tied together via grade beams in at
least one direction. The grade beam should be at least 12 inches square in cross
section, and should be provided with a minimum of two No.4 reinforcing bars at the
top, and two No.4 reinforcing bars at the bottom of the grade beam. The base of
the reinforced grade beam should be at the same elevation as the adjoining
footings.
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4.A minimum concrete slab-on-grade thickness of 5 inches is recommended.
5.Concrete slabs should be reinforced with a minimum of No. 3 reinforcement bars
placed at 18 inches on center, in two horizontally perpendicular directions (i.e., long
axis and short axis).
6.All slab reinforcement should be supported to ensure proper mid-slab height
positioning during placement of the concrete. “Hooking” of reinforcement is not an
acceptable method of positioning.
7.Slab subgrade pre-soaking is recommended for these soil conditions. Slab
subgrade should be pre-wetted to at least the soils’ optimum moisture content, to
a depth of 18 inches, prior to the placement of the underlayment sand and vapor
retarder.
8.New foundations should maintain a minimum 7-foot horizontal distance between the
base of the footing and any adjacent descending slope, and comply with the
guidelines per the 2019 CBC (CBSC, 2019a). This may also result in a deeper
footing than per plan.
Floor Slabs
GSI has evaluated the potential for vapor or water transmission through the concrete floor
slabs, in light of typical floor coverings, improvements, and use. Please note that slab
moisture emission rates range from about 2 to 27 lbs/24 hours/1,000 square feet from a
typical slab (Kanare, 2005), while floor covering manufacturers generally recommend
about 3 lbs/24 hours as an upper limit. The recommendations in this section are not
intended to preclude the transmission of water or vapor through the foundation or slabs.
Foundation systems and slabs shall not allow water or water vapor to enter into the
structure so as to cause damage to another building component or to limit the installation
of the type of flooring materials typically used for the particular application (State of
California, 2022). These recommendations may be exceeded or supplemented by a water
“proofing” specialist, project architect, or structural consultant. Thus, the client will need
to evaluate the following in light of a cost vs. benefit analysis (owner expectations and
repairs/replacement), along with disclosure to all interested/affected parties. It should also
be noted that vapor transmission will occur in new slab-on-grade floors as a result of
chemical reactions taking place within the curing concrete. Vapor transmission through
concrete floor slabs as a result of concrete curing has the potential to adversely affect
sensitive floor coverings depending on the thickness of the concrete floor slab and the
duration of time between the placement of concrete, and the floor covering. It is possible
that a slab moisture sealant may be needed prior to the placement of sensitive floor
coverings if a thick slab-on-grade floor is used and the time frame between concrete and
floor covering placement is relatively short.
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Considering the E.I. test results presented herein, and known soil conditions in the region,
the anticipated typical water vapor transmission rates, floor coverings, and improvements
(to be chosen by the Client and/or project architect) that can tolerate vapor transmission
rates without significant distress, the following alternatives are provided:
•Increase the slab thickness to more than 5 inches.
•Concrete slab underlayment should consist of a 15-mil vapor retarder, or equivalent,
with all laps sealed per the 2019 CBC and the manufacturer’s recommendation.
The vapor retarder should comply with the ASTM E 1745 - Class A criteria, and be
installed in accordance with American Concrete Institute (ACI) 302.1R-04 and
ASTM E 1643. An example of a vapor retarder product that complies with
ASTM E 1745 - Class A criteria is Stego Industries, LLC’s Stego Wrap.
•The 15-mil vapor retarder (ASTM E 1745 - Class A) shall be installed per the
recommendations of the manufacturer, including all penetrations (i.e., pipe, ducting,
rebar, etc.).
•Concrete slabs should be underlain by 2 inches of clean sand (SE > 30) above a
15-mil vapor retarder (ASTM E-1745 - Class A, per Engineering Bulletin 119
[Kanare, 2005]) installed per the recommendations of the manufacturer, including
all penetrations (i.e., pipe, ducting, rebar, etc.). The manufacturer shall provide
instructions for lap sealing, including minimum width of lap, method of sealing, and
either supply or specify suitable products for lap sealing (ASTM E 1745), and per
code.
ACI 302.1R-04 (2004) states, “If a cushion or sand layer is desired between the
vapor retarder and the slab, care must be taken to protect the sand layer from
taking on additional water from a source such as rain, curing, cutting, or cleaning.
Wet cushion or sand layer has been directly linked in the past to significant
lengthening of time required for a slab to reach an acceptable level of dryness for
floor covering applications.” Therefore, additional observation and/or testing will be
necessary for the cushion or sand layer for moisture content, and relatively uniform
thicknesses, prior to the placement of concrete.
•The vapor retarder should be underlain by a capillary break consisting of at
least 2 inches of clean sand (SE 30, or greater). The vapor retarder should be
sealed to provide a continuous retarder under the entire slab, as discussed above.
•Concrete should have a maximum water/cement ratio of 0.50. This does not
supercede Table 19.3.1.1 of the ACI (2014a) for corrosion or other corrosive
requirements (such as coastal, location, etc.). Site soils are classified as S0, W0,
and C1 per ACI (2014a). Additional concrete mix design recommendations should
be provided by the structural consultant and/or waterproofing specialist. Concrete
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finishing and workablity should be addressed by the structural consultant and a
waterproofing specialist.
•Where slab water/cement ratios are as indicated herein, or admixtures used, the
structural consultant should also make changes to the concrete in the grade beams
and footings in kind, so that the concrete used in the foundation and slabs are
designed and/or treated for more uniform moisture protection.
•The owner(s) should be specifically advised which areas are suitable for tile flooring,
vinyl flooring, or other types of water/vapor-sensitive flooring and which are not
suitable. In all planned floor areas, flooring shall be installed per the manufacturer’s
recommendations.
•Additional recommendations regarding water or vapor transmission should be
provided by the architect/structural engineer/slab or foundation designer and
should be consistent with the specified floor coverings indicated by the architect.
Regardless of the mitigation, some limited moisture/moisture vapor transmission through
the slab should be anticipated. Construction crews may require special training for
installation of certain product(s), as well as concrete finishing techniques. The use of
specialized product(s) should be approved by the slab designer and water-proofing
consultant. A technical representative of the flooring contractor should review the slab and
moisture retarder plans and provide comment prior to the construction of the foundations
or improvements. The vapor retarder contractor should have representatives onsite during
the initial installation.
Retaining Walls
General
Cantilevered and restrained masonry retaining walls should be designed and constructed
in accordance with the standard of practice and the soil parameters presented herein. The
design parameters provided in this report assume that either very low expansive soils
(typically Class 2 permeable filter material or Class 3 aggregate base) or native onsite
materials with an expansion index less than 21 and a plasticity index less than 15 are used
to backfill any retaining wall. The type of backfill (i.e., select or native), should be specified
by the wall designer, and clearly shown on the plans. Building walls, below grade, should
be water-proofed. As noted, the foundation system for the proposed retaining walls should
be designed in accordance with the soil parameters provided herein. Footings should be
embedded a minimum of 18 inches below the lowest adjacent grade (excluding landscape
layer, 6 inches) and should be 24 inches in width. Planned retaining wall footings may
need to be deepened where loose surficial soils are present, or to provide for the
recommended setback of at least 7 feet to the slope face. All retaining walls should be
provided with subdrainage to mitigate the potential for the buildup of hydrostatic pressures.
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For additional mitigation, consideration should be given to applying a water-proof
membrane to the back of all retaining structures. The use of a waterstop should be
considered for all concrete and masonry joints. Any plans for engineered walls should be
reviewed by this office prior to construction. Recommendations for specialty walls
(i.e., crib, earthstone, geogrid, etc.) can be provided upon request, and would be based
on site specific conditions.
Seismic Surcharge
For engineered retaining walls six (6) feet or greater in height, and if required, GSI
recommends that the walls be evaluated for a seismic surcharge, in general accordance
with 2019 CBC requirements. The site walls in this category should maintain an
overturning Factor-of-Safety (FOS) of approximately 1.25 when the seismic surcharge
(increment), is applied. For restrained walls, the seismic surcharge should be applied as
a uniform surcharge load from the bottom of the footing (excluding shear keys) to the top
of the backfill at the heel of the wall footing. This seismic surcharge pressure (seismic
increment) may be taken as 15H where “H” for retained walls is the dimension previously
noted as the height of the backfill measured from the bottom of the footing to daylight
above the heel of the wall footing. The resultant force should be applied at a distance
0.6 H up from the bottom of the footing. For the evaluation of the seismic surcharge, the
bearing pressure may exceed the static value by one-third, considering the transient nature
of this surcharge. For cantilevered walls the pressure should be an inverted triangular
distribution using 15H. Reference for the seismic surcharge for Seismic Design Category
“D” is Section 1803.5 of the 2019 CBC. Please note this is for local wall stability only.
Landscape Maintenance
Only the amount of irrigation necessary to sustain plant life should be provided.
Over-watering the landscape areas will adversely affect existing and proposed site
improvements. We would recommend that any proposed open-bottom planters adjacent
to proposed structures be eliminated for a minimum distance of 10 feet. As an alternative,
closed-bottom type planters could be used. An outlet placed in the bottom of the planter,
could be installed to direct drainage away from structures or any exterior concrete flatwork.
If planters are constructed adjacent to structures, the sides and bottom of the planter
should be provided with a moisture retarder to prevent penetration of irrigation water into
the subgrade. Provisions should be made to drain the excess irrigation water from the
planters without saturating the subgrade below or adjacent to the planters. Consideration
should be given to the type of vegetation chosen and their potential effect upon surface
improvements (i.e., some trees will have an effect on concrete flatwork with their extensive
root systems). From a geotechnical standpoint leaching is not recommended for
establishing landscaping. If the surface soils are processed for the purpose of adding
amendments, they should be recompacted to 90 percent minimum relative compaction.
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Subsurface and Surface Water
Subsurface and surface water are generally not significantly anticipated to affect site
development, provided that the recommendations contained in this report are properly
incorporated into final design and construction and that prudent surface and subsurface
drainage practices are incorporated into the construction plans. Perched groundwater
conditions along zones of contrasting permeabilities may not be precluded from occurring
in the future due to site irrigation, poor drainage conditions, or damaged utilities, and
should be anticipated. Should perched groundwater conditions develop, this office could
assess the affected area(s) and provide the appropriate recommendations to mitigate the
observed groundwater conditions. Groundwater conditions may change with the
introduction of irrigation, rainfall, or other factors.
Planting
Water has been shown to weaken the inherent strength of all earth materials.
Over-watering should be avoided as it can adversely affect site improvements, and cause
perched groundwater conditions. Plants selected for landscaping should be light weight,
deep rooted types that require little water and are capable of surviving the prevailing
climate. Using plants other than those recommended above will increase the potential for
perched water, staining, mold, etc., to develop. A rodent control program to prevent
burrowing should be implemented. These recommendations regarding plant type,
irrigation practices, and rodent control should be provided to all interested/affected parties.
Drainage
Adequate lot surface drainage is a very important factor in reducing the likelihood of
adverse performance of foundations and hardscape. Surface drainage should be sufficient
to prevent ponding of water anywhere on the property, and especially near structures. Lot
surface drainage should be carefully taken into consideration during landscaping.
Therefore, care should be taken that future landscaping or construction activities do not
create adverse drainage conditions. Positive site drainage within the property should be
provided and maintained at all times. Water should be directed away from foundations and
not allowed to pond and/or seep into the ground. In general, the area within 5 feet around
a structure should slope away from the structure. We recommend that unpaved lawn and
landscape areas have a minimum gradient of 1 percent sloping away from structures, and
whenever possible, should be above adjacent paved areas. Consideration should be
given to avoiding construction of planters adjacent to structures. Site drainage should be
directed toward the street or other approved area(s). Downspouts, or drainage devices
should outlet a minimum of 5 feet from structures or into a subsurface drainage system.
Areas of seepage may develop due to irrigation or heavy rainfall, and should be
anticipated. Minimizing irrigation will lessen this potential. If areas of seepage develop,
recommendations for minimizing this effect could be provided upon request.
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Gutters and Downspouts
Downspouts should be drained into PVC collector pipes or non-erosive devices that will
carry the water away from the house. Downspouts and gutters are not a geotechnical
requirement provided that positive drainage is incorporated into project design (as
discussed previously).
Tile Flooring
Tile flooring can crack, reflecting cracks in the concrete slab below the tile, although small
cracks in a conventional slab may not be significant. Therefore, the designer should
consider additional steel reinforcement for concrete slabs-on-grade where tile will be
placed. The tile installer should consider installation methods that reduce possible
cracking of the tile such as slipsheets. Slipsheets or a vinyl crack isolation membrane
(approved by the Tile Council of America/Ceramic Tile Institute) are recommended
between tile and concrete slabs on grade.
Site Improvements
Recommendations for exterior concrete flatwork design and construction can be provided
upon request. If in the future, any additional improvements (e.g., pools, spas, etc.) are
planned for the site, recommendations concerning the geological or geotechnical aspects
of design and construction of said improvements are recommended to be provided at that
time. This office should be notified in advance of any fill placement, grading of the site, or
trench backfilling after rough grading has been completed. This includes any grading,
utility trench, and retaining wall backfills.
Temporary Slopes
Temporary slopes in formation, for excavations greater than 4 feet, but less than 20 feet in
overall height should conform to CAL-OSHA and/or OSHA requirements for Type “B” soils.
Temporary slopes, up to a maximum height of about 20 feet, may be excavated at a
1:1 (h:v) gradient, or flatter, provided groundwater and/or running sands are not exposed.
Construction materials or soil stockpiles should not be placed within ‘H’ of any temporary
slope where ‘H’ equals the height of the temporary slope. All temporary slopes should be
observed by a licensed engineering geologist and/or geotechnical engineer prior to worker
entry into the excavation.
Footing Trench Excavation
All footing excavations should be observed by a representative of this firm subsequent to
trenching and prior to concrete form and reinforcement placement. The purpose of the
observations is to verify that the excavations are made into the recommended bearing
material and to the minimum widths and depths recommended for construction. If loose
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or compressible materials are exposed within the footing excavation, a deeper footing or
removal and recompaction of the subgrade materials would be recommended at that time.
In general, deepened footings beyond the minimum depths shown on the plans will likely
be recommended, and should be anticipated. The Client may want to consider having a
representative of GSI onsite at the start of foundation trenching to evaluate the depth to
competent bearing soils and provide recommendations for footing embedment to the
contractor performing the work. Footing trench spoil and any excess soils generated from
utility trench excavations should be compacted to a minimum relative compaction of
90 percent, if not removed from the site.
Trenching
Considering the nature of the onsite soils, it should be anticipated that caving or sloughing
could be a factor in subsurface excavations and trenching. Shoring or excavating the
trench walls at the angle of repose (typically 25 to 45 degrees) may be necessary and
should be anticipated. All excavations should be observed by one of our representatives
and minimally conform to Cal-OSHA and local safety codes.
Utility Trench Backfill
1.All interior utility trench backfill should be brought to at least 2 percent above
optimum moisture content and then compacted to obtain a minimum relative
compaction of 90 percent of the laboratory standard. As an alternative for shallow
(12- to 18-inch) under-slab trenches, sand having a sand equivalent value of 30, or
greater, may be used and jetted or flooded into place. Observation, probing, and
testing should be provided to verify the desired results.
2.Exterior trenches adjacent to, and within, areas extending below a 1:1 plane
projected from the outside bottom edge of the footing, and all trenches beneath
hardscape features and in slopes, should be compacted to at least 90 percent of
the laboratory standard. Sand backfill, unless excavated from the trench, should
not be used in these backfill areas. Compaction testing and observations, along
with probing, should be accomplished to verify the desired results.
3.All trench excavations should conform to Cal-OSHA and local safety codes.
4.Utilities crossing grade beams, perimeter beams, or footings should either pass
below the footing or grade beam utilizing a hardened collar or foam spacer, or pass
through the footing or grade beam in accordance with the recommendations of the
structural engineer.
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PRELIMINARY OUTDOOR POOL/SPA DESIGN RECOMMENDATIONS
The following preliminary recommendations are provided for consideration in pool/spa
design and planning. Actual recommendations should be provided by a qualified
geotechnical consultant, based on site specific geotechnical conditions, including a
subsurface investigation, differential settlement potential, expansive and corrosive soil
potential, proximity of the proposed pool/spa to any slopes with regard to slope creep and
lateral fill extension, as well as slope setbacks per Code, and geometry of the proposed
improvements. Recommendations for pools/spas and/or deck flatwork underlain by
expansive soils, or for areas with differential settlement greater than ¼-inch over 40 feet
horizontally, will be more onerous than the preliminary recommendations presented below.
The 1:1 (h:v) influence zone of any nearby retaining wall site structures should be
delineated on the project civil drawings with the pool/spa. This 1:1 (h:v) zone is defined
as a plane up from the lower-most heel of the retaining structure, to the daylight grade of
the nearby building pad or slope. If pools/spas or associated pool/spa improvements are
constructed within this zone, they should be re-positioned (horizontally or vertically) so that
they are supported by earth materials that are outside or below this 1:1 plane. If this is not
possible given the area of the building pad, the owner should consider eliminating these
improvements or allow for increased potential for lateral/vertical deformations and
associated distress that may render these improvements unusable in the future, unless
they are periodically repaired and maintained. The conditions and recommendations
presented herein should be disclosed to all homeowners and any interested/affected
parties.
General
1.The equivalent fluid pressure to be used for the pool/spa design should be
62 pounds per cubic foot (pcf) for pool/spa walls with level backfill, and 75 pcf for
a 2:1 sloped backfill condition. In addition, backdrains should be provided behind
pool/spa walls subjacent to slopes.
2.Passive earth pressure may be computed as an equivalent fluid having a density of
150 pcf, to a maximum lateral earth pressure of 1,000 pounds per square foot (psf).
3.An allowable coefficient of friction between soil and concrete of 0.30 may be used
with the dead load forces.
4.When combining passive pressure and frictional resistance, the passive pressure
component should be reduced by one-third.
5.Where pools/spas are planned near structures, appropriate surcharge loads need
to be incorporated into design and construction by the pool/spa designer. This
includes, but is not limited to landscape berms, decorative walls, footings, built-in
barbeques, utility poles, etc.
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6.As an alternative to Items 1 through 4, all pool/spa walls should be designed as
“free standing” and be capable of supporting the water in the pool/spa without soil
support. The shape of pool/spa in cross section and plan view may affect the
performance of the pool, from a geotechnical standpoint. Pools and spas should
also be designed in accordance with the latest adopted Code. Minimally, the
bottoms of the pools/spas, should maintain a distance H/3, where H is the height
of the slope (in feet), from the slope face. This distance should not be less than
7 feet, nor need not be greater than 40 feet.
7.The soil beneath the pool/spa bottom should be uniformly moist with the same
stiffness throughout. If a fill/cut transition occurs beneath the pool/spa bottom, the
cut portion should be overexcavated to a minimum depth of 48 inches, and
replaced with compacted fill, such that there is a uniform blanket that is a minimum
of 48 inches below the pool/spa shell. If very low expansive soil is used for fill, the
fill should be placed at a minimum of 95 percent relative compaction, at optimum
moisture conditions. This requirement should be 90 percent relative compaction
at over optimum moisture if the pool/spa is constructed within or near expansive
soils. The potential for grading and/or re-grading of the pool/spa bottom, and
attendant potential for shoring and/or slot excavation, needs to be considered
during all aspects of pool/spa planning, design, and construction.
8.If the pool/spa is founded entirely in compacted fill placed during rough grading, the
deepest portion of the pool/spa should correspond with the thickest fill on the lot.
9.Hydrostatic pressure relief valves should be incorporated into the pool and spa
designs. A pool/spa under-drain system is also recommended, with an appropriate
outlet for discharge, if possible.
10.All fittings and pipe joints, particularly fittings in the side of the pool or spa, should
be properly sealed to prevent water from leaking into the adjacent soils materials,
and be fitted with slip or expandible joints between connections transecting varying
soil conditions.
11.An elastic expansion joint (flexible waterproof sealant) should be installed to prevent
water from seeping into the soil at all deck joints.
12.A reinforced grade beam should be placed around skimmer inlets to provide
support and mitigate cracking around the skimmer face.
13.In order to reduce unsightly cracking, deck slabs should minimally be 4 inches
thick, and reinforced with No. 3 reinforcing bars at 18 inches on-center. All slab
reinforcement should be supported to ensure proper mid-slab positioning during
the placement of concrete. Wire mesh reinforcing is specifically not recommended.
Deck slabs should not be tied to the pool/spa structure. Pre-moistening and/or
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pre-soaking of the slab subgrade is recommended, to a depth of 12 inches
(optimum moisture content), or 18 inches (120 percent of the soil’s optimum
moisture content, or 3 percent over optimum moisture content, whichever is
greater), for very low to low, and medium expansive soils, respectively. This
moisture content should be maintained in the subgrade soils during concrete
placement to promote uniform curing of the concrete and minimize the
development of unsightly shrinkage cracks. As discussed in the earthwork section,
slabs may be underlain with a 12-inch layer of compacted aggregate base to
improve performance. Deck slabs within the H/3 zone, where H is the height of the
slope (in feet), will have an increased potential for distress relative to other areas
outside of the H/3 zone. If distress is undesirable, improvements, deck slabs or
flatwork should not be constructed closer than H/3 or 7 feet (whichever is greater)
from the slope face, in order to reduce, but not eliminate, this potential.
14.Pool/spa bottom or deck slabs should be founded entirely on competent bedrock,
or properly compacted fill. Fill should be compacted to achieve a minimum
90 percent relative compaction, as discussed above. Prior to pouring concrete,
subgrade soils below the pool/spa decking should be thoroughly watered to
achieve a moisture content that is at least 2 percent above optimum moisture
content, to a depth of at least 18 inches below the bottom of slabs. This moisture
content should be maintained in the subgrade soils during concrete placement to
promote uniform curing of the concrete and minimize the development of unsightly
shrinkage cracks.
15.In order to reduce unsightly cracking, the outer edges of pool/spa decking to be
bordered by landscaping, and the edges immediately adjacent to the pool/spa,
should be underlain by an 8-inch wide concrete cutoff shoulder (thickened edge)
extending to a depth of at least 12 inches below the bottoms of the slabs to mitigate
excessive infiltration of water under the pool/spa deck. These thickened edges
should be reinforced with two No. 4 bars, one at the top and one at the bottom.
Deck slabs may be minimally reinforced with No. 3 reinforcing bars placed at
18 inches on-center, in both directions. All slab reinforcement should be supported
on chairs to ensure proper mid-slab positioning during the placement of concrete.
16.Surface and shrinkage cracking of the finish slab may be reduced if a low slump
and water-cement ratio are maintained during concrete placement. Concrete
utilized should have a minimum compressive strength of 4,000 psi. Excessive water
added to concrete prior to placement is likely to cause shrinkage cracking, and
should be avoided. Some concrete shrinkage cracking, however, is unavoidable.
17.Joint and sawcut locations for the pool/spa deck should be determined by the
design engineer and/or contractor. However, spacings should not exceed 6 feet on
center.
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18.Considering the nature of the onsite earth materials, it should be anticipated that
caving or sloughing could be a factor in subsurface excavations and trenching.
Shoring or excavating the trench walls/backcuts at the angle of repose (typically
25 to 45 degrees), should be anticipated. All excavations should be observed by
a representative of the geotechnical consultant, including the project geologist
and/or geotechnical engineer, prior to workers entering the excavation or trench,
and minimally conform to Cal/OSHA (“Type C” soils may be assumed), state, and
local safety codes. Should adverse conditions exist, appropriate recommendations
should be offered at that time by the geotechnical consultant. GSI does not consult
in the area of safety engineering and the safety of the construction crew is the
responsibility of the pool/spa builder.
19.It is imperative that adequate provisions for surface drainage are incorporated by
the homeowners into their overall improvement scheme. Ponding water, ground
saturation and flow over slope faces, are all situations which must be avoided to
enhance long-term performance of the pool/spa and associated improvements, and
reduce the likelihood of distress.
20.Regardless of the methods employed, once the pool/spa is filled with water, should
it be emptied, there exists some potential that if emptied, significant distress may
occur. Accordingly, once filled, the pool/spa should not be emptied unless
evaluated by the geotechnical consultant and the pool/spa builder.
21.The temperature of the water lines for spas and pools may affect the corrosion
properties of site soils, thus, a corrosion specialist should be retained to review all
spa and pool plans, and provide mitigative recommendations, as warranted.
Concrete mix design should be reviewed by a qualified corrosion consultant and
materials engineer.
22.All pool/spa utility trenches should be compacted to 90 percent of the laboratory
standard, under the full-time observation and testing of a qualified geotechnical
consultant. Utility trench bottoms should be sloped away from the primary structure
on the property (typically the residence).
23.Pool and spa utility lines should not cross the primary structure’s utility lines (i.e.,
not stacked, or sharing of trenches, etc.).
24.The pool/spa or associated utilities should not intercept, interrupt, or otherwise
adversely impact any area drain, roof drain, or other drainage conveyances. If it is
necessary to modify, move, or disrupt existing area drains, subdrains, or tightlines,
then the design civil engineer should be consulted, and mitigative measures
provided. Such measures should be further reviewed and approved by the
geotechnical consultant, prior to proceeding with any further construction.
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25.The geotechnical consultant should review and approve all aspects of pool/spa and
flatwork design prior to construction. A design civil engineer should review all
aspects of such design, including drainage and setback conditions. Prior to
acceptance of the pool/spa construction, the project builder, geotechnical
consultant and civil designer should evaluate the performance of the area drains
and other site drainage pipes, following pool/spa construction.
26.All aspects of construction should be reviewed and approved by the geotechnical
consultant, including during excavation, prior to the placement of any additional fill,
prior to the placement of any reinforcement or pouring of any concrete.
27.Any changes in design or location of the pool/spa should be reviewed and
approved by the geotechnical and design civil engineer prior to construction. Field
adjustments should not be allowed until written approval of the proposed field
changes are obtained from the geotechnical and design civil engineer.
28.Disclosure should be made to homeowners and builders, contractors, and any
interested/affected parties, that pools/spas built within about 15 feet of the top of a
slope, and/or H/3, where H is the height of the slope (in feet), will experience some
movement or tilting. While the pool/spa shell or coping may not necessarily crack,
the levelness of the pool/spa will likely tilt toward the slope, and may not be
esthetically pleasing. The same is true with decking, flatwork and other
improvements in this zone.
29.Failure to adhere to the above recommendations will significantly increase the
potential for distress to the pool/spa, flatwork, etc.
30.Local seismicity and/or the design earthquake will cause some distress to the
pool/spa and decking or flatwork, possibly including total functional and economic
loss.
31.The information and recommendations discussed above should be provided to any
contractors and/or subcontractors, or homeowners, interested/affected parties, etc.,
that may perform or may be affected by such work.
SUMMARY OF RECOMMENDATIONS REGARDING
GEOTECHNICAL OBSERVATION AND TESTING
We recommend that observation and testing be performed by GSI at each of the following
construction stages:
•During grading/recertification.
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•During significant excavation (i.e., higher than 4 feet).
•During placement of subdrains or other subdrainage devices, prior to placing fill
and/or backfill.
•After excavation of building footings, retaining wall footings, and free standing walls
footings, prior to the placement of reinforcing steel or concrete.
•Prior to pouring any slabs or flatwork, after presoaking/presaturation of building
pads and other flatwork subgrade, before the placement of concrete, reinforcing
steel, capillary break (i.e., sand, pea-gravel, etc.), or vapor retarders
(i.e., visqueen, etc.).
•During retaining wall subdrain installation, prior to backfill placement.
•During placement of backfill for area drain, interior plumbing, utility line trenches,
and retaining wall backfill.
•During slope construction/repair.
•When any unusual soil conditions are encountered during any construction
operations, subsequent to the issuance of this report.
•When any improvements, such as flatwork, spas, pools, walls, etc., are constructed.
•A report of geotechnical observation and testing should be provided at the
conclusion of each of the above stages, in order to provide concise and clear
documentation of site work, and/or to comply with code requirements.
PLAN REVIEW
Once construction plans are available, it is recommended that the plans are reviewed by
this office for conformance with the intent of the geotechnical report and the standard of
practice.
OTHER DESIGN PROFESSIONALS/CONSULTANTS
The design civil engineer, structural engineer, architect, landscape architect, wall designer,
etc., should review the recommendations provided herein, incorporate those
recommendations into all their respective plans, and by explicit reference, make this report
part of their project plans. This report presents minimum design criteria for the design of
slabs, foundations and other elements possibly applicable to the project. These criteria
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should not be considered as substitutes for actual designs by the structural
engineer/designer. The structural engineer/designer should analyze actual soil-structure
interaction and consider, as needed, bearing, expansive soil influence, and strength,
stiffness and deflections in the various slab, foundation, and other elements in order to
develop appropriate, design-specific details. As conditions dictate, it is possible that other
influences will also have to be considered. The structural engineer/designer should
consider all applicable codes and authoritative sources where needed. If analyses by the
structural engineer/designer result in less critical details than are provided herein as
minimums, the minimums presented herein should be adopted. It is considered likely that
some, more restrictive details will be required. If the structural engineer/designer has any
questions or requires further assistance, they should not hesitate to call or otherwise
transmit their requests to GSI. In order to mitigate potential distress, the foundation and/or
improvement’s designer should confirm to GSI and the governing agency, in writing, that
the proposed foundations and/or improvements can tolerate the amount of differential
settlement and/or expansion characteristics and design criteria specified herein.
LIMITATIONS
The materials encountered on the project site and utilized for our analysis are believed
representative of the area; however, soil and bedrock materials vary in character between
excavations and natural outcrops or conditions exposed during mass grading. Site
conditions may vary due to seasonal changes or other factors.
Inasmuch as our study is based upon our review, engineering analyses, and laboratory
data, the conclusions and recommendations presented herein are professional opinions.
These opinions have been derived in accordance with current standards of practice, and
no warranty is express or implied. Standards of practice are subject to change with time.
This report has been prepared for the purpose of providing soil design parameters derived
from testing of a soil sample received at our laboratory, and does not represent an
evaluation of the overall stability, suitability, or performance of the property for the
proposed development. GSI assumes no responsibility or liability for work or testing
performed by others, or their inaction; or work performed when GSI is not requested to be
onsite, to evaluate if our recommendations have been properly implemented. Use of this
report constitutes an agreement and consent by the user to all the limitations outlined
above, notwithstanding any other agreements that may be in place. In addition, this report
may be subject to review by the controlling authorities. Thus, this report brings to
completion our scope of services for this portion of the project.
Ms. Patiane Freitas W.O. 8286-A-SC
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The opportunity to be of service is greatly appreciated. If you have any questions
concerning this report, or if we may be of further assistance, please do not hesitate to
contact any of the undersigned.
Respectfully submitted,
GeoSoils, Inc.
John P. Franklin Stephen J. Coover
Engineering Geologist, CEG 1340 Geotechnical Engineer, GE 2057
Matthew J. Smelski
Staff Geologist
MJS/JPF/SJC/sh
Attachments:Appendix A - References
Appendix B - Boring Logs
Distribution:(1) Addressee (PDF via email)
Ms. Patiane Freitas W.O. 8286-A-SC
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APPENDIX A
REFERENCES
GeoSoils, Inc.
APPENDIX A
REFERENCES
American Concrete Institute, 2014a, Building code requirements for structural concrete
(ACI 318-14), and commentary (ACI 318R-14): reported by ACI Committee 318,
dated September.
_____, 2014b, Building code requirements for concrete thin shells (ACI 318.2-14), and
commentary (ACI 318.2R-14), dated September.
_____, 2004, Guide for concrete floor and slab construction: reported by ACI Committee
302; Designation ACI 302.1R-04, dated March 23.
American Society for Testing and Materials (ASTM), 1998, Standard practice for installation
of water vapor retarder used in contact with earth or granular fill under concrete
slabs, Designation: E 1643-98 (Reapproved 2005).
_____, 1997, Standard specification for plastic water vapor retarders used in contact with
soil or granular fill under concrete slabs, Designation: E 1745-97 (Reapproved
2004).
American Society of Civil Engineers, 2018a, Supplement 1 to Minimum Design Loads and
Associated Criteria for Buildings and Other Structures (ASCE/SEI 7-16), first
printing, dated December 13.
_____, 2018b, Errata for Minimum Design Loads and Associated Criteria for Buildings and
Other Structures (ASCE/SEI 7-16), by ASCE, dated July 9.
_____, 2017, Minimum design loads and associated criteria and other structures, ASCE
Standard ASCE/SEI 7-16, published online June 19.
_____, 2010, Minimum design loads for buildings and other structures, ASCE Standard
ASCE/SEI 7-10.
Blake, Thomas F., 2000, EQFAULT, A computer program for the estimation of peak
horizontal acceleration from 3-D fault sources; Windows 95/98 version.
Building News, 1995, CAL-OSHA, State of California, Construction Safety Orders, Title 8,
Chapter 4, Subchapter 4, amended October 1.
California Building Standards Commission, 2019a, California Building Code, California
Code of Regulations, Title 24, Part 2, Volume 2 of 2, based on the 2018 International
Building Code, effective January 1, 2020.
_____, 2019b, California Building Code, California Code of Regulations, Title 24, Part 2,
Volume 1 of 2, Based on the 2018 International Building Code, effective
January 1, 2020.
GeoSoils, Inc.
California Geological Survey, 2018, Earthquake fault zones, a guide for government
agencies, property owners/developers, and geoscience practitioners for assessing
fault rupture hazards in California, CGS Special Publication 42.
California Office of Statewide Health Planning and Development (OSHPD), 2022, Seismic
design maps, https://seismicmaps.org/.
Cao, T., Bryant, W.A., Rowshandel, B., Branum, D., and Willis, C.J., 2003, The revised 2002
C a l if or nia pr ob al i st i c seis mic h a z a rd m a ps, dat e d Jun e ,
http://www.conversation.ca.gov/CGS/rghm/psha/fault_parameters/PDF/docume
nts/2002_ca_hazardmaps.pdf
Gama Design Studio, 2022, Third submittal, 4339 Park Drive, Carlsbad, CA 92008,
addition/remodel of single family dwelling, dated September 19.
Kanare, H.M., 2005, Concrete floors and moisture, Engineering Bulletin 119, Portland
Cement Association.
Sowers and Sowers, 1979, Unified soil classification system (After U. S. Waterways
Experiment Station and ASTM 02487-667) in Introductory soil mechanics, New York.
State of California, 2022, Civil Code, Sections 895 et seq.
Ms. Patiane Freitas Appendix A
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APPENDIX B
BORING LOGS
UNIFIED SOIL CLASSIFICATION SYSTEM CONSISTENCY OR RELATIVE DENSITY
Major Divisions Group
Symbols Typical Names CRITERIA
Co
a
r
s
e
-
G
r
a
i
n
e
d
S
o
i
l
s
Mo
r
e
t
h
a
n
5
0
%
r
e
t
a
i
n
e
d
o
n
N
o
.
2
0
0
s
i
e
v
e
Gr
a
v
e
l
s
50
%
o
r
m
o
r
e
o
f
co
a
r
s
e
f
r
a
c
t
i
o
n
re
t
a
i
n
e
d
o
n
N
o
.
4
s
i
e
v
e
Cl
e
a
n
Gr
a
v
e
l
s
GW Well-graded gravels and gravel-sand mixtures, little or no fines Standard Penetration Test
Penetration
Resistance N Relative (blows/ft)Density
0 - 4 Very loose
4 - 10 Loose
10 - 30 Medium
30 - 50 Dense
> 50 Very dense
GP Poorly graded gravels andgravel-sand mixtures, little or no
fines
Gr
a
v
e
l
wi
t
h
GM Silty gravels gravel-sand-silt
mixtures
GC Clayey gravels, gravel-sand-clay
mixtures
Sa
n
d
s
mo
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t
h
a
n
5
0
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N
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.
4
s
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Cle
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n
Sa
n
d
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SW Well-graded sands and gravelly
sands, little or no fines
SP Poorly graded sands andgravelly sands, little or no fines
Sa
n
d
s
wi
t
h
Fi
n
e
s
SM Silty sands, sand-silt mixtures
SC Clayey sands, sand-clay
mixtures
Fi
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-
G
r
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d
S
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50
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l
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s
s
ML Inorganic silts, very fine sands,rock flour, silty or clayey finesands
Standard Penetration Test
Unconfined
Penetration Compressive
Resistance N Strength
(blows/ft)Consistency (tons/ft2)
<2 Very Soft <0.25
2 - 4 Soft 0.25 - .050
4 - 8 Medium 0.50 - 1.00
8 - 15 Stiff 1.00 - 2.00
15 - 30 Very Stiff 2.00 - 4.00
>30 Hard >4.00
CL
Inorganic clays of low to
medium plasticity, gravelly clays,
sandy clays, silty clays, lean
clays
OL Organic silts and organic silty
clays of low plasticity
Si
l
t
s
a
n
d
C
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s
Li
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l
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m
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t
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t
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r
t
h
a
n
5
0
%
MH
Inorganic silts, micaceous or
diatomaceous fine sands or silts,
elastic silts
CH Inorganic clays of high plasticity,
fat clays
OH Organic clays of medium to high
plasticity
Highly Organic Soils PT Peat, mucic, and other highly
organic soils
3"3/4"#4 #10 #40 #200 U.S. Standard Sieve
Unified Soil
Classification Cobbles Gravel Sand Silt or Clay
coarse fine coarse medium fine
MOISTURE CONDITIONS MATERIAL QUANTITY OTHER SYMBOLS
Dry Absence of moisture: dusty, dry to the touch trace 0 - 5 %C Core Sample
Slightly Moist Below optimum moisture content for compaction few 5 - 10 %S SPT Sample
Moist Near optimum moisture content little 10 - 25 %B Bulk Sample
Very Moist Above optimum moisture content some 25 - 45 %–Groundwater
Wet Visible free water; below water table Qp Pocket Penetrometer
BASIC LOG FORMAT:
Group name, Group symbol, (grain size), color, moisture, consistency or relative density. Additional comments: odor, presence of roots, mica, gypsum,
coarse grained particles, etc.
EXAMPLE:
Sand (SP), fine to medium grained, brown, moist, loose, trace silt, little fine gravel, few cobbles up to 4" in size, some hair roots and rootlets.
File:Mgr: c;\SoilClassif.wpd PLATE B-1
I I I I I I I I I
-
0
5
10
15
20
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SM
SC-SMSM
WEATHERED SANTIAGO FORMATION:@ 0', SILTY SANDSTONE, dark brown, slightly moist, medium dense;occasional roots, fine to medium grain sand.@ 1', As per 0', dark yellowish brown.@ 2', As per 1', SILTY/CLAYEY SANDSTONE, yellowish brown, mediumdense to dense.
RELATIVELY UNWEATHERED SANTIAGO:@ 3', SILTY SANDSTONE, yellow brown, slightly moist to moist, dense;fine to coarse sand, occasional very thin yellowish gray interbeds.Total Depth = 5'No Groundwater or Caving Encountered.Backfilled 2-10-22.
GeoSoils, Inc.BORING LOG
PROJECT:4339 PARK DRIVE, CARLSBAD W.O.8286-A-SC BORING B-1 SHEET 1 OF
DATE EXCAVATED 2-10-22 LOGGED BY:MJS APPROX. ELEV.:77'NAVD88
SAMPLE METHOD:Hand-auger
Standard Penetration Test Groundwater
Undisturbed, Ring Sample Seepage
GeoSoils, Inc.
PLATE
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Material Description
1
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UNDOCUMENTED FILL:@ 0', SILTY SAND, light yellowish brown, dry, loose to medium dense;fine to medium grain sand.@ 1', SILTY SAND with trace CLAY, dark brown to dark yellowish brown,slightly moist, medium dense; fine to medium sand.@ 3', SAND with trace SILT, light brown to light yellow brown, dry, looseto medium dense.@ 3.5', As per 3', medium dense to dense.
Total Depth = 5'No Groundwater or Caving Encountered.Backfilled 2-10-22.
GeoSoils, Inc.BORING LOG
PROJECT:4339 PARK DRIVE, CARLSBAD W.O.8286-A-SC BORING B-2 SHEET 1 OF
DATE EXCAVATED 2-10-22 LOGGED BY:MJS APPROX. ELEV.:84'NAVD88
SAMPLE METHOD:Hand-auger
Standard Penetration Test Groundwater
Undisturbed, Ring Sample Seepage
GeoSoils, Inc.
PLATE
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Material Description
1
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WEATHERED SANTIAGO FORMATION:@ 0', CLAYEY SANDSTONE, dark reddish brown, moist to wet, loose tomedium dense; fine to medium grain sand.@ 1.5', As per 0', moist, medium dense.
RELATIVELY UNWEATHERED SANTIAGO:@ 2', SILTY SANDSTONE, light reddish brown to yellowish brown,slightly moist, dense; fine to coarse grain sand.@ 4', Encountered yellowish gray interbeds of CLAYEY SANDSTONE.
Total Depth = 5'No Groundwater or Caving Encountered.Backfilled 2-10-22.
GeoSoils, Inc.BORING LOG
PROJECT:4339 PARK DRIVE, CARLSBAD W.O.8286-A-SC BORING B-3 SHEET 1 OF
DATE EXCAVATED 2-10-22 LOGGED BY:MJS APPROX. ELEV.:86'NAVD88
SAMPLE METHOD:Hand-auger
Standard Penetration Test Groundwater
Undisturbed, Ring Sample Seepage
GeoSoils, Inc.
PLATE
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WEATHERED SANTIAGO FORMATION:@ 0', SILTY/CLAYEY SANDSTONE, dark brown, moist, loose to mediumdense; fine to medium grain sand.@ 1.5', As per 0', reddish brown, medium dense.
RELATIVELY UNWEATHERED SANTIAGO:@ 3.5', SILTY SANDSTONE, reddish brown, moist, medium dense todense.@ 4', As per 3.5', dense.Total Depth = 5'No Groundwater or Caving Encountered.
Backfilled 2-10-22.
GeoSoils, Inc.BORING LOG
PROJECT:4339 PARK DRIVE, CARLSBAD W.O.8286-A-SC BORING B-4 SHEET 1 OF
DATE EXCAVATED 2-10-22 LOGGED BY:MJS APPROX. ELEV.:85'NAVD88
SAMPLE METHOD:Hand-auger
Standard Penetration Test Groundwater
Undisturbed, Ring Sample Seepage
GeoSoils, Inc.
PLATE
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Material Description
1
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