HomeMy WebLinkAboutCDP 2021-0053; GILBERT RESIDENCE; UPDATE SEISMIC AND FOUNDATION PARAMETERS; 2021-07-01UPDATE SEISMIC AND FOUNDATION PARAMETERS FOR
PROP -Q.DRIVE
CAR NIA 92008
•
W.O. 7082-A1-SC JULY 1, 2021
RE.CE~JED
SEP 3 0 2021
CITY OF cAr<L ~Js~D
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Geotechnical • Geologic • Coastal • Environmental
5741 Palmer Way • Carlsbad, California 9201 0 • (760) 438-3155 • FAX (760) 931 -0915 • www.geosoilsinc.com
Karen Gilbert
2351 Pio Pico Drive
Carlsbad, California 92008
July 1, 2021 W.O . 7082-A1-SC
Subject: Update Seismic and Foundation Parameters for Proposed Construction at
2351 Pio Pico Drive, Carlsbad, San Diego County, California 92008
Dear Ms. Gilbert:
In accordance with your request and authorization, GeoSoils, Inc. (GSI) is pleased to
present the results of our preliminary geotechnical evaluation at the subject site. The
purpose of our study was to evaluate the geologic and geotechnical conditions at the site,
in order to develop preliminary recommendations for site earthwork and the design of
foundations, walls, and pavements related to the proposed residential construction at the
property.
SITE DESCRIPTION AND PROPOSED DEVELOPMENT
The subject site consists of a relatively flat-lying, rectangular lot property in the City of
Carlsbad, San Diego County, California. The property is bounded by a private driveway,
perpendicular to Pio Pico Drive to the north, existing residential property to the west, and
newly constructed residential structures on the remaining sides. Access to subject
property is via an existing private driveway from Pio Pico Drive to the property located on
the south side of the private driveway. Existing improvements to the property consist of
a single-story residence with a detached garage, pool in the rear, a small attached deck
directly behind the existing residence, and concrete flatwork covering most of the rear
yard. Based on A Quick Survey (AQS, 2015) the site appears to be at an approximate
elevation of 92 to 95 feet above National Geodetic Vertical Datum of 1929 (NGVD29).
Drainage appears to be generally directed offsite to the west. Vegetation onsite consists
of scattered trees, and other typical residential landscaping.
It is anticipated that the existing buildings are to be removed, and the site will be prepared
for the construction of a one-and two-story single-family residential structure with an
attached garage. GSI anticipates thatthe construction would be of the wood frame variety,
with typical foundations and slab-on-grade ground floors. Building loads are assumed to
be typical for this type of relatively light construction. Sewage disposal is anticipated to be
connected into the regional, municipal system. Storm water may be treated onsite prior
to its delivery into the municipal system.
FIELD STUDIES
A site reconnaissance was recently conducted on May 24, 2021. Previous, site-specific
field studies were conducted by GSI during May 2016, and consisted of reconnaissance
geologic mapping and the excavation of three (3) exploratory test borings with a hand
auger, for an evaluation of near-surface soil and geologic conditions onsite. The test
borings were logged by a representative of this office who collected representative bulk
and undisturbed soil samples for appropriate laboratory testing. The approximate location
of the hand-auger borings are presented in our previous report (GSI, 2016).
GEOLOGY
Regional geology, site geologic units, and mass wasting have been discussed previously,
and are not repeated herein. The reader is referred to GSI (2016), for a more
comprehensive discussion, as these conditions have not changed.
GROUNDWATER
GSI did not observe evidence of a regional groundwater table nor perched water within our
previous subsurface explorations. As indicated previously, regional groundwater is
estimated to be generally within a few feet of sea level, and is not anticipated to
significantly affect proposed site development, provided that the recommendations
contained in this report are properly incorporated into final design and construction.
FAUL TING AND REGIONAL SEISMICITY
Faulting, seismic hazards, and slope stability have been discussed previously (GSI, 2016),
and are not repeated herein. The reader is referred to GSI (2016) for more comprehensive
discussion.
SEISMIC DESIGN
General
It is important to keep in perspective that 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. This potential would be no
greater than that for other existing structures and improvements in the immediate vicinity.
Karen Gilbert
2351 Pio Pico Drive, Carlsbad
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc.
W.O. 7082-A1-SC
July 1, 2021
Page 2
Seismic Shaking Parameters
The following table summarizes the reevaluated 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 Planning and Development (OSHPD, 2020) has now been utilized to aid in design
(https://seismicmaps.org). The short spectral response utilizes a period of 0.2 seconds.
PARAMETER
Risk Category
Site Class
Spectral Response -(0.2 sec),
ss
Spectral Response -(1 sec), S,
Site Coefficient, F.
Site Coefficient, Fv
Maximum Considered
Earthquake Spectral
Response Acceleration (0.2
sec), SMs
Maximum Considered
Earthquake Spectral
Response Acceleration (1 sec),
SM,
5% Damped Design Spectral
Response
Acceleration (0.2 sec), S06
5% Damped Design Spectral
Response
Acceleration (1 sec), S01
PGAM -Probabilistic Vertical
Ground Acceleration may be
assumed as about 50% of
these values.
Karen Gilbert
2351 Pio Pico Drive, Carlsbad
File:e:\wp12\7000\7082a1 .usa
2019 CBC SEISMIC DESIGN PARAMETERS
VALUE VALUE
per ASCE 7-16
II II
D -Default D-Default
1.045 g 0.875 g
0.38 g 0.675 g
1.2 1.2
null -see 2.5(') Section 11 .48 (Table 11.4-2, Eq. 12.8-2) ASCE 7-16
1.255 g 1.327 g
null -see
Section 11 .48 1.013(2)
ASCE 7-16 (Eq. 11.4-2)
0.836 g 0.884 g
null -see 0.67513) Section 11 .48 (Eq. 11-4.4) ASCE 7-16
0.551g 0.558 g
GeoSoils, Inc.
2019CBC
or REFERENCE
Table 1604.5
Section 1613.2.2/
Chap. 20 ASCE 7-16
(p. 203-204)
Section 1613.2.1
Figure 1613.2.1(1)
Section 1613.2.1
Figure 1613.2.1 (2)
Table 1613.2.3(1)
Table 1613.2.3(2)
Section 1613.2.3
(Eqn 16-36)
Section 1613.2.3
(Eqn 16-37)
Section 1613.2.4
(Eqn 16-38)
Section 1613.2.4
(Eqn 16-39)
ASCE 7-16 (Eqn 11.8.1)
W.O. 7082-A1-SC
July 1, 2021
Page 3
2019 CBC SEISMIC DESIGN PARAMETERS
PARAMETER VALUE VALUE 2019CBC
per ASCE 7-16 or REFERENCE
null -see D!3l Section 1613.2.5/ASCE 7-16 Seismic Design Category Section 11.48
ASCE 7-16 (p. 85: Table 11 .6-1 or 11.6-2)
1. Fv = S1 >0.2, then per Table 11.4-2, then Fv = 2.5
2. SM1 = (1.5)(S01) = per Section 21.4, then SM1 =(1.5)(0.675)=1.013
3. 0.50 sS,.,~ = 0.50 s0.884 oer Table 11.6-1 site is in Risk Cateaorv D
GENERAL SEISMIC PARAMETERS
PARAMETER VALUE
Distance to Seismic Source Newport-lngelwood 5.3 mi (8.5 km)12l ("B" Fault)P)
Upper Bound Earthquake (Newport-lngelwood) "B" Mw = 6.9 11l Fault I Pl -Cao, et al. (2003)
12l -Blake (2000} I
Conformance to the criteria above for seismic design does not constitute any kind of
guarantee or assurance that significant structural damage or ground failure will not occur
in the event of a large earthquake. The primary goal of seismic design is to protect life, not
to eliminate all damage, since such design may be economically prohibitive. Cumulative
effects of seismic events are not addressed in the 2019 CBC (CBSC, 2019a) and regular
maintenance and repair following locally significant seismic events (i.e., Mw5.5) will likely
be necessary, as is the case in all of Southern California.
PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS
Based on our previous field exploration, laboratory testing, and geotechnical engineering
analysis, it is our opinion that the subject site is suitable for the proposed residential
development from a geotechnical engineering and geologic viewpoint, provided that the
recommendations presented in the following sections are incorporated into the design and
construction phases of site development. The primary geotechnical concerns with respect
to the proposed development and improvements are:
• Earth materials characteristics and depth to competent bearing material.
• On-going expansion and corrosion potential of site soils.
• Erosiveness of site earth materials.
• Temporary Slopes.
• Potential for perched water during and following site development.
• Regional seismic activity.
Karen Gilbert
2351 Pio Pico Drive, Carlsbad
File:e:\wp12\7000\7082a1 .usa GeoSoits, Inc.
W.O. 7082-A1-SC
July 1, 2021
Page 4
The recommendations presented herein consider these as well as other aspects of
the site. The engineering analyses performed concerning site preparation and the
recommendations presented herein have been completed using the information provided
and obtained during our field work.
In the event that any significant changes are made to proposed site development, the
conclusions and recommendations contained in this report shall not be considered valid
unless the changes are reviewed and the recommendations of this report verified or
modified in writing by this office. Foundation design parameters are considered
preliminary until the foundation design, layout, and structural loads are provided to this
office for review.
1. Soil engineering, observation, and testing services should be provided during
grading to aid the contractor in removing unsuitable soils and in his effort to
compact the fill.
2. Geologic observations should be performed during any grading and foundation
construction to verify and/or further evaluate geologic conditions. Although unlikely,
if adverse geologic structures are encountered, supplemental recommendations
and earthwork may be warranted.
3. Surficial soils within approximately 2½ to 3 feet from surface grades are considered
unsuitable for the support of the planned settlement-sensitive improvements
(i.e., residential structure, walls, concrete slab-on-grade floors, and exterior
pavements, etc.) or new planned fills. Unsuitable soils within the influence of
planned settlement-sensitive improvements and/or planned fill should be removed
to expose suitable older paralic deposits and then be reused as properly
engineered fill. In order to provide for the uniform support of the structure, a
minimum 3-foot thick later of compacted fill is recommended for the support of
structure(s), or 2 feet below the foundations, whichever is greater. Based on the
recommended removal depths, it may be necessary to undercut the building pad
areas in order to achieve the desired minimum fill thickness. Undercutting should
be completed for a minimum lateral distance of at least 5 feet beyond the building
footprint.
4. As an alternative to the above, foundations for settlement-sensitive improvements
may be deepened to bear entirely within the old paralic deposits (typically an
additional 2½ to 3 feet); however, structural slabs, not relying on soil support, but
spanning grade beams, would also be required.
5. Testing performed on a representative sample of the onsite soils indicates very low
to low expansive soil conditions. On a preliminary basis, specific foundation design
to resist expansive soil effects appears warranted, as defined in the CBC for
detrimentally expansive soils. However, GSI suggests that the soil moisture within
Karen Gilbert
2351 Pio Pico Drive, Carlsbad
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc.
W.O. 7082-A1-SC
July 1, 2021
Page 5
the underlying subgrade is near, or above optimum moisture content prior to the
placement of the underlayment sand and vapor retarder.
6. Laboratory testing indicates that site soils are relatively neutral (pH), and mildly
corrosive to exposed buried metals when saturated. Testing also indicates that site
soils present negligible ("not applicable" per ACI 318-14) sulfate exposure to
concrete and are below the action level for chloride exposure. Site soils are
classified as "Exposure Class C1 ." The client and project architect should agree on
the level of corrosion protection required for the project and seek consultation from
a qualified corrosion consultant as warranted. Additional testing at the completion
of remedial grading is recommended in order to verify these assumptions.
7. Site soils are considered erosive. Surface drainage should be designed to eliminate
the potential for concentrated flows. Positive surface drainage away from
foundations and tops of slopes is recommended. Temporary erosion control
measures should be implemented until vegetative covering is well established. The
homeowner will need to maintain proper surface drainage over the life of the
project.
8. No evidence of a high regional groundwater table nor perched water was observed
during our subsurface exploration within the property. However, due to the nature
of site earth materials, there is a potential for perched water to occur both during
and following site development. This potential should be disclosed to all
interested/affected parties. Should perched water conditions be encountered, this
office could provide recommendations for mitigation. Typical mitigation includes
subdrainage system, cut-off barriers, etc.
9. On a preliminary basis, temporary slopes should be constructed in accordance with
CAL-OSHA guidelines for Type "B" soils. All temporary slopes should be evaluated
by the geotechnical consultant, prior to worker entry. Should adverse conditions
be identified, the slope may need to be laid back to a flatter gradient or require the
use of shoring.
10. The seismicity-acceleration values provided herein should be considered during the
design and construction of the proposed development.
11. General Earthwork and Grading Guidelines are provided at the end of this report as
Appendix B. Specific recommendations are provided below.
Karen Gilbert
2351 Pio Pico Drive, Carlsbad
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc.
W.0. 7082-A1-SC
July 1, 2021
Page 6
EARTHWORK CONSTRUCTION RECOMMENDATIONS
General
All earthwork should conform to the guidelines presented in the 2019 CBC (CBSC, 2019),
the requirements of the City of Carlsbad, and the General Earthwork and Grading
Guidelines presented in Appendix B, except where specifically superceded in the text of
this report. Prior to earthwork, a GSI representative should be present at the
preconstruction meeting to provide additional earthwork guidelines, if needed, and review
the earthwork schedule. This office should be notified in advance of any fill placement,
supplemental regrading of the site, or backfilling underground utility trenches and retaining
walls after rough earthwork has been completed. This includes grading for driveway
approaches, driveways, and exterior hardscape.
During earthwork construction, all site preparation and the general grading procedures of
the contractor 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 (OSHA), and the Construction Safety
Act should be met. It is the onsite general contractor and individual subcontractors
responsibility to provide a save working environment for our field staff who are onsite. GSI
does not consult in the area of safety engineering.
Demolition/Grubbing
1. Vegetation and any miscellaneous debris should be removed from the areas of
proposed grading.
2. Any existing subsurface structures uncovered during the recommended removal
should be observed by GSI so that appropriate remedial recommendations can be
provided.
3. Cavities or loose soils remaining after demolition and site clearance should be
cleaned out and observed by the soil engineer. The cavities should be replaced
with fill materials that have been moisture conditioned to at least optimum moisture
content and compacted to at least 90 percent of the laboratory standard.
4. Onsite septic systems (if encountered) should be removed in accordance with
San Diego County Department of Environmental Health standards/guidelines.
Karen Gilbert
2351 Pio Pico Drive, Carlsbad
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc.
W.O. 7082-A1-SC
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Treatment of Existing Ground
1. Removals should consist of all surficial deposits of fill, colluvium, and weathered
paralic deposits. Based on our site work, removals depths on the order of 3 feet
should be anticipated. These soils may be re-used as fill, provided that the soil is
cleaned of any deleterious material and moisture conditioned, and compacted to
a minimum 90 percent relative compaction per ASTM D 1557. Removals should be
completed throughout the entire building area.
2. In addition to removals within the building envelopes, overexcavation/undercutting
of the underlying formational soil should be performed in order to provide for at
least 2 feet of compacted fill below the footings. Undercutting should be completed
for a minimum lateral distance of at least 5 feet beyond the building footprint. Once
removals and overexcavation is completed, the fill should be cleaned of deleterious
materials, moisture conditioned, and recompacted to at least 90 percent relative
compaction per ASTM D 1557.
3. Subsequent to the above removals/overexcavation, the exposed bottom should be
scarified to a depth of at least 6 to 8 inches, brought to at least optimum moisture
content, and recompacted to a minimum relative compaction of 90 percent of the
laboratory standard, prior to any fill placement.
4. Existing fill and removed natural ground materials may be reused as compacted fill
provided that major concentrations of vegetation and miscellaneous debris are
removed from the site, prior to or during fill placement.
5. Localized deeper removals may be necessary due to buried drainage channel
meanders or dry porous materials, septic systems, etc. The project soils
engineer/geologist should observe all removal areas during the grading.
Fill Suitability
Existing earth materials onsite should generate relatively fine grained, granular fill material,
and oversize material (i.e., greater than 12 inches in long dimension) is not anticipated.
If soil importation is planned, samples of the soil import should be evaluated by this office
prior to importing in order to assure compatibility with the onsite site soils and the
recommendations presented in this report. Import soils, if used, should be relatively sandy
and very low expansive (i.e., E.1. less than 20).
Fill Placement
1. Subsequent to ground preparation, fill materials should be brought to at least
optimum moisture content, placed in thin 6-to 8-inch lifts, and mechanically
compacted to obtain a minimum relative compaction of 90 percent of the laboratory
standard.
Karen Gilbert
2351 Pio Pico Drive, Carlsbad
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc.
W.O. 7082-A 1-SC
July 1, 2021
Page B
2. Fill materials should be cleansed of major vegetation and debris prior to placement.
3. Any import materials should be observed and deemed suitable by the soils
engineer prior to placement on the site. Foundation designs may be altered if
import materials have a greater expansion value than the onsite materials
encountered in this investigation.
Graded Slopes
Significant graded slope are not planned, nor anticipated for this project.
Temporary Slopes
Temporary slopes 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 ±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.
PRELIMINARY RECOMMENDATIONS -FOUNDATIONS
General
Preliminary recommendations for foundation design and construction are provided in the
following sections. These preliminary recommendations have been developed from our
understanding of the currently planned site development, site observations, subsurface
exploration, laboratory testing, and engineering analyses. Foundation design should be
re-evaluated at the conclusion of site grading/remedial earthwork for the as-graded soil
conditions. Although not anticipated, revisions to these recommendations may be
necessary. In the event that the information concerning the proposed development plan
is not correct, or any changes in the design, location or loading conditions of the proposed
additions are made, the conclusions and recommendations contained in this report shall
not be considered valid unless the changes are reviewed and conclusions of this report
are modified or approved in writing by this office.
The information and recommendations presented in this section are not meant to
supercede design by the project structural engineer or civil engineer specializing in
structural design. Upon request, GSI could provide additional input/consultation regarding
soil parameters, as related to foundation design.
Karen Gilbert
2351 Pio Pico Drive, Carlsbad
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc.
W.O. 7082-A1-SC
July 1, 2021
Page 9
Preliminary Foundation Design
1. The foundation systems should be designed and constructed in accordance with
guidelines presented in the 2019 CBC (CBSC, 2019).
2. An allowable bearing value of 2,000 pounds per square foot (psf) may be used for
the design of footings that maintain a minimum width of 15 inches and a minimum
depth of 18 inches (below the lowest adjacent grade) and are founded entirely into
properly compacted, engineered fill. This value may be increased by 20 percent for
each additional 12 inches in footing depth to a maximum value of 2,500 psf. These
values may be increased by one-third when considering short duration seismic or
wind loads. Isolated pad footings should have a minimum dimension of at least
24 inches square and a minimum embedment of 24 inches below the lowest
adjacent grade into properly engineered fill. Foundation embedment depth
excludes concrete slabs-on-grade, and/or slab underlayment. Foundations should
not simultaneously bear on unweathered paralic deposits and engineered fill.
3. Should removal and recompaction not be performed, footings will need to be
deepened, and a structural slab, spanning between grade beams without relying
on soil for support, is required. It is estimated that the footings will need to be
deepened an additional 2½ to 3 feet, from the minimum dimensions discussed
above for this condition.
4. For foundations deriving passive resistance from engineered fill, a passive earth
pressure may be computed as an equivalent fluid having a density of 150 pcf, with
a maximum earth pressure of 1,500 psf.
5. The upper 6 inches of passive pressure should be neglected if not confined by
slabs or pavement.
6. For lateral sliding resistance, a 0.35 coefficient of friction may be utilized for a
concrete to soil contact when multiplied by the dead load.
7. When combining passive pressure and frictional resistance, the passive pressure
component should be reduced by one-third.
8. All footing setbacks from slopes should comply with Figure 1808.7.1 of the
2019 CBC (CBSC, 2019). GSI recommends a minimum horizontal setback distance
of 7 feet as measured from the bottom, outboard edge of the footing to the slope
face.
9. Footings for structures adjacent to retaining walls should be deepened so as to
extend below a 1 :1 projection from the heel of the wall. Alternatively, walls may be
designed to accommodate structural loads from buildings or appurtenances as
described in the "Retaining Wall" section of this report.
Karen Gilbert
2351 Pio Pico Drive, Carlsbad
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc.
W.O. 7082-A1-SC
July 1, 2021
Page 10
PRELIMINARY FOUNDATION CONSTRUCTION RECOMMENDATIONS
The following foundation construction recommendations are presented as a minimum
criteria from a soils engineering viewpoint. The following foundation construction
recommendations are intended to support planned improvements underlain by at least
7 feet of non-detrimentally expansive soils (i.e., E.l.<21 and Pl <15). Foundations are
underlain by detrimentally expansive soils (i.e., for the site, P.I. = 19) and will require
specific design to mitigate expansive soil effects as required in Sections 1808.6.1 or
1808.6.2 of the 2019 CBC (CBSC, 2019).
1. Exterior and interior footings should be founded into engineered fill at a minimum
depth of 18 inches below the lowest adjacent grade, and a minimum width of
15 inches, for the planned, two story structure. Isolated, exterior column and panel
pads, or wall footings, should be at least 24 inches, square, and founded at a
minimum depth of 24 inches into properly engineered fill. All footings should be
minimally reinforced with two No. 4 reinforcing bars, one placed near the top and
one placed near the bottom of the footing.
2. All interior and exterior column footings, and perimeter wall 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
one No.4 reinforcing bar at the top, and one No.4 reinforcing bar at the bottom of
the grade beam. The base of the reinforced grade beam should be at the same
elevation as the adjoining footings.
3. A grade beam, reinforced as previously recommended and at least 12 inches
square, should be provided across large (garage) entrances. The base of the
reinforced grade beam should be at the same elevation as the adjoining footings.
4. A minimum concrete slab-on-grade thickness of 4.5 inches is recommended.
Recommendations for floor slab underlayment are presented in a later section of
this report. Should removal and recompaction not be performed, a structural slab
is required.
5. Concrete slabs should be reinforced with a minimum of No. 3 reinforcement bars
placed at 18-inch on centers, 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. Specific slab subgrade pre-soaking is recommended for these soil conditions. Prior
to the placement of underlayment sand and vapor retarder, GSI recommends that
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2351 Pio Pico Drive, Carlsbad
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc.
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the slab subgrade materials be moisture conditioned to at least optimum moisture
content to a minimum depth of 12 inches. Slab subgrade pre-soaking should be
evaluated by the geotechnical consultant within 72 hours of the placement of the
underlayment sand and vapor retarder.
8. Soils generated from footing excavations to be used onsite should be compacted
to a minimum relative compaction of 90 percent of the laboratory standard
(ASTM D 1557), whether the soils are to be placed inside the foundation perimeter
or in the yard/right-of-way areas. This material must not alter positive drainage
patterns that direct drainage away from the structural areas and toward the street.
9. Reinforced concrete mix design should conform to "Exposure Class C1" in
Table 19.3.2.1 of ACl-318-14 since concrete would likely be exposed to moisture.
Foundation Settlement
Provided thatthe earthwork and foundation recommendations in this reported are adhered
foundations bearing on engineered fill should be minimally designed to accommodate a
differential settlement of up to 1-inch over a 40-foot horizontal span (angular distortion =
1/480).
SOIL MOISTURE TRANSMISSION CONSIDERATIONS
GSI has evaluated the potential for vapor or water transmission through the concrete floor
slab, in light of typical floor coverings and improvements. 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, 2021). 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.
Karen Gilbert
2351 Pio Pico Drive, Carlsbad
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc.
W.O. 7082-A1-SC
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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:
• Concrete slabs should be thicker.
• 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 ACI 302.1 R-04 and ASTM E 1643.
• The 10-to 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, including the garage area, shall be underlain by 2 inches of clean,
washed sand (SE > 30) above a 15-mil vapor retarder (ASTM E-17 45 -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 302.1 R-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 shall be underlain by 2 inches of sand (SE > 30) placed directly
on the prepared, moisture conditioned, subgrade and should be sealed to provide
a continuous retarder under the entire slab, as discussed above. As discussed
previously, GSI indicated this layer of import sand may be eliminated below the
vapor retarder, lf laboratory testing indicates that the slab subgrade soil have a sand
equivalent (SE) of 30 or greater, during site grading.
• Concrete should have a maximum water/cement ratio of 0.50. This does not
supercede Table 19.3.2.1 of ACI (2014) for corrosion or other corrosive
requirements. 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, and/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 manufactures
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.
DRIVEWAY/PARKING, FLATWORK, AND OTHER IMPROVEMENTS
The effects of expansive soils are cumulative, and typically occur over the lifetime of any
improvements. On relatively level areas, when the soils are allowed to dry, the dessication
and swelling process tends to cause heaving and distress to flatwork and other
improvements. The resulting potential for distress to improvements may be reduced, but
not totally eliminated. To that end, it is important that the homeowner be aware of this
long-term potential for distress. To reduce the likelihood of distress, the following
recommendations are presented for all exterior flatwork:
1. The subgrade area for concrete slabs should be compacted to achieve a minimum
90 percent relative compaction (sidewalks, patios), and 95 percent relative
compaction (traffic pavements), and then be presoaked to 2 to 3 percentage points
above (or 125 percent of) the soils' optimum moisture content, to a depth of
18 inches below subgrade elevation. If very low expansive soils are present, only
optimum moisture content, or greater, is required and specific presoaking is not
warranted. The moisture content of the subgrade should be proof tested within
72 hours prior to pouring concrete.
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2. Concrete slabs should be cast over a non-yielding surface, consisting of a 4-inch
layer of crushed rock, gravel, or clean sand, that should be compacted and level
prior to pouring concrete. If very low expansive soils are present, the rock or gravel
or sand may be deleted. The layer or subgrade should be wet-down completely
prior to pouring concrete, to minimize loss of concrete moisture to the surrounding
earth materials.
3. Exterior, non-vehicle slabs (sidewalks, patios, etc.) should be a minimum of
4 inches thick.
4. Driveway and parking area concrete slabs and approaches should be at least
6 inches thick. A thickened edge (12 inches) should also be considered adjacent
to all landscape areas, to help impede infiltration of landscape water under the
slab(s). All pavement construction should minimally be performed in general
accordance with industry standards and properly transitioned.
5. Asphaltic parameters should minimally consist of 4 inches asphalt over 4 inches of
compacted aggregate base per the City.
6. Trash truck loading areas should be designed per Carlsbad City standard drawings
(City of Carlsbad, 1993).
7. The use of transverse and longitudinal control joints are recommended to help
control slab cracking due to concrete shrinkage or expansion. Two ways to
mitigate such cracking are: a) add a sufficient amount of reinforcing steel,
increasing tensile strength of the slab; and, b) provide an adequate amount of
control and/or expansion joints to accommodate anticipated concrete shrinkage
and expansion.
8. In order to reduce the potential for unsightly cracks, slabs should be reinforced at
mid-height with a minimum of No. 3 bars placed at 18 inches on center, in each
direction. If subgrade soils within the top 7 feet from finish grade are very low
expansive soils (i.e., E.1. ~20), then 6x6-W1 .4xW1 .4 welded-wire mesh may be
substituted for the rebar, provided the reinforcement is placed on chairs, at slab
mid-height. The exterior slabs should be scored or saw cut, ½ to 3/a inches deep,
often enough so that no section is greater than 1 O feet by 1 O feet. For sidewalks or
narrow slabs, control joints should be provided at intervals of every 6 feet. The
slabs should be separated from the foundations and sidewalks with expansion joint
filler material.
9. No traffic should be allowed upon the newly poured concrete slabs until they have
been properly cured to within 75 percent of design strength. Concrete compression
strength should be a minimum of 2,500 psi for sidewalks and patios, and a
minimum 3,250 psi for traffic pavements.
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10. Driveways, sidewalks, and patio slabs adjacentto the structure should be separated
from the structure with thick expansion joint filler material. In areas directly adjacent
to a continuous source of moisture (i.e., irrigation, planters, etc.), all joints should
be additionally sealed with flexible mastic.
11 . Planters and walls should not be tied to the structure.
12. Overhang structures should be supported on the slabs, or structurally designed
with continuous footings tied in at least two directions. If very low expansion soils
are present, footings need only be tied in one direction.
13. Any masonry landscape walls that are to be constructed throughout the property
should be grouted and articulated in segments no more than 20 feet long. These
segments should be keyed or doweled together.
14. Utilities should be enclosed within a closed utilidor (vault) or designed with flexible
connections to accommodate differential settlement and expansive soil conditions.
15. Positive site drainage should be maintained at all times. Finish grade on the lot
should provide a minimum of 1 to 2 percent fall to the street, as indicated herein.
It should be kept in mind that drainage reversals could occur, including
post-construction settlement, if relatively flat yard drainage gradients are not
periodically maintained by the homeowner.
16. Air conditioning (A/C) units should be supported by slabs that are incorporated into
the building foundation or constructed on a rigid slab with flexible couplings for
plumbing and electrical lines. A/C waste water lines should be drained to a suitable
non-erosive outlet.
17. Shrinkage cracks could become excessive if proper finishing and curing practices
are not followed. Finishing and curing practices should be performed per the
Portland Cement Association Guidelines. Mix design should incorporate rate of
curing for climate and time of year, sulfate content of soils, corrosion potential of
soils, and fertilizers used on site.
DEVELOPMENT CRITERIA
Onsite Storm Water Treatment
Based on our evaluation, onsite storm water treatment systems should consider the
following:
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• Site soils are Marina loamy coarse sand, and are considered to belong to
hydrologic subgroup "B." The USDA website indicates they have a moderately high
to high Ksat; however, dense natural soils occur at a depth of about 2½ to 3 feet
from existing grade.
• The presence of the thin surficial fill layer overlying dense formational soil will
increase the potential for the development of a mounded or perched water table
along the fill/formation contact.
• The will be an increased potential for the adverse performance of structures, should
the engineered fills supporting the proposed structures become saturated, due to
settlement, or water vapor transmission, both onsite and offsite.
• Impermeable liners and subdrains should be used along the bottom of any
bioretention swales/basins located within the influence of improvements or slopes.
Impermeable liners used in conjunction with bioretention basins should consist of
a 30-mil polyvinyl chloride (PVC) membrane that is covered by a minimum of
12 inches of clean soil, free from rocks and debris, with a maximum 4:1 (h:v) slope
inclination, or flatter, and meets the following minimum specifications:
Specific Gravity (ASTM D 792): 1.2 (g/cc, min.); Tensile (ASTM D 882):
73 (lb/in-width, min); Elongation at Break (ASTM D 882): 380 (%, min);
Modulus (ASTM D 882): 30 (lb/in-width, min.); and Tear Strength
(ASTM D 1004): 8 (lb/in, min); Seam Shear Strength (ASTM D 882) 58.4
(lb/in, min); Seam Peel Strength (ASTM D 882) 15 (lb/in, min).
• Subdrains should consist of at least 4-inch diameter Schedule 40 or SOR 35 drain
pipe with perforations oriented down. The drain pipe should be sleeved with a filter
sock, then tight-lines, and directed to a suitable outlet.
In practice, storm water BMP's are usually initially designed by the project design civil
engineer. Selection of methods should include (but should not be limited to) review by
licensed professionals including the geotechnical engineer, hydrogeologist, engineering
geologist, project civil engineer, landscape architect, environmental professional, and
industrial hygienist. Applicable governing agency requirements should be reviewed and
included in design considerations.
Maintenance and Planting
Water has been shown to weaken the inherent strength of all earth materials. Slope
stability is significantly reduced by overly wet conditions. Positive surface drainage away
from slopes should be maintained and only the amount of irrigation necessary to sustain
plant life should be provided for planted slopes. Over-watering should be avoided as it
adversely affects site improvements, and causes perched groundwater conditions. Graded
slopes constructed utilizing onsite materials would be erosive. Eroded debris may be
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minimized and surficial slope stability enhanced by establishing and maintaining a suitable
vegetation cover soon after construction. Compaction to the face of fill slopes would tend
to minimize short-term erosion until vegetation is established. Plants selected for
landscaping should be light weight, deep rooted types that require little water and are
capable of surviving the prevailing climate. Jute-type matting or other fibrous covers may
aid in allowing the establishment of a sparse plant cover. Utilizing 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.
Irrigation of natural (ungraded) slope areas is generally not recommended. These
recommendations regarding plant type, irrigation practices, and rodent control should be
provided to all interested/affected parties. Over-steepening of slopes should be avoided
during building construction activities and landscaping.
Drainage
Adequate surface drainage is a very important factor in reducing the likelihood of adverse
performance offoundations, hardscape, and slopes. Surface drainage should be sufficient
to mitigate ponding of water anywhere on the property, and especially near structures and
tops of slopes. Surface drainage should be carefully taken into consideration during fine
grading, landscaping, and building construction. 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.
Drainage should not flow uncontrolled down any descending slope. Water should be
directed away from foundations and tops of slopes, and not allowed to pond and/or seep
into the ground. In general, site drainage should conform to Section 1804.3 of the
2019 CBC. Consideration should be given to avoiding construction of planters adjacent
to structures (buildings, pools, spas, etc.). Building pad drainage should be directed
toward the street or other approved area(s). Although not a geotechnical requirement, roof
gutters, down spouts, or other appropriate means may be utilized to control roof drainage.
Down spouts, 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.
Erosion Control
Site soils will be subject to surficial erosion during and after construction. Onsite earth
materials have a moderate to high erosion potential. Consideration should be given to
providing hay bales and silt fences for the temporary control of surface water, from a
geotechnical viewpoint.
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Landscape Maintenance
Only the amount of irrigation necessary to sustain plant life should be provided.
Over-watering the landscape areas will adversely affect 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 utilized. 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.
Graded slope areas should be planted with drought resistant vegetation. 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.
Gutters and Downspouts
As previously discussed in the drainage section, the installation of gutters and downspouts
should be considered to collect roof water that may otherwise infiltrate the soils adjacent
to the structures. If utilized, the downspouts should be drained into PVC collector pipes
or other non-erosive devices (e.g., paved swales or ditches; below grade, solid tight-lined
PVC pipes; etc.), that will carry the water away from the structure, to an appropriate outlet,
in accordance with the recommendations of the design civil engineer. Downspouts and
gutters are not a requirement; however, from a geotechnical viewpoint, provided that
positive drainage is incorporated into project design (as discussed previously).
Subsurface and Surface Water
Subsurface and surface water are not anticipated to affect site development, provided that
the recommendations contained in this report are 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.
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Site Improvements
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 could be provided upon request. Pools and/or spas
should not be constructed without specific design and construction recommendations from
GSI, and this construction recommendation should be provided to all interested/affected
parties. 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, flatwork, etc.
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:
Additional Grading
This office should be notified in advance of any fill placement, supplemental regrading of
the site, or trench backfilling after rough grading has been completed. This includes
completion of grading in the street, driveway approaches, driveways, parking areas, and
utility trench and retaining wall backfills.
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 evaluate that the excavations have been made into the recommended
bearing material and to the minimum widths and depths recommended for construction.
If loose 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. 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/Temporary Construction Backcuts
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
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excavating the trench walls/backcuts at the angle of repose (typically 25 to 45 degrees
[except as specifically superceded within the text of this report]), should be anticipated.
All excavations should be observed by an engineering geologist or soil engineerfrom GSI,
prior to workers entering the excavation or trench, and minimally conform to CAL-OSHA,
state, and local safety codes. Should adverse conditions exist, appropriate
recommendations would be offered at that time. The above recommendations should be
provided to any contractors and/or subcontractors, or homeowners, etc., that may perform
such work.
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-inch to 18-inch) under-slab trenches, sand having a sand equivalent value of
30 or greater may be utilized and jetted or flooded into place. Observation, probing
and testing should be provided to evaluate 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 evaluate the desired results.
3. All trench excavations should conform to CAL-OSHA, state, 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.
SUMMARY OF RECOMMENDATIONS REGARDING
GEOTECHNICAL OBSERVATION AND TESTING
We recommend that observation and/or testing be performed by GSI at each of the
following construction stages:
• During grading/recertification.
• During excavation.
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•
•
•
•
•
•
•
•
•
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 homeowner improvements, such as flatwork, spas, pools, walls, etc., are
constructed, prior to construction.
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.
OTHER DESIGN PROFESSIONALS/CONSULTANTS
The design civil engineer, structural engineer, post-tension designer, 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 should not be considered as substitutes for actual designs
by the structural engineer/designer. Please note that the recommendations contained
herein are not intended to preclude the transmission of water or vapor through the slab or
foundation. The structural engineer/foundation and/or slab designer should provide
recommendations to not allow water or vapor to enter into the structure so as to cause
damage to another building component, or so as to limit the installation of the type of
flooring materials typically used for the particular application.
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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
other design criteria specified herein.
PLAN REVIEW
Final project plans (grading, precise grading, foundation, retaining wall, landscaping, etc.),
should be reviewed by this office prior to construction, so that construction is in
accordance with the conclusions and recommendations of this report. Based on our
review, supplemental recommendations and/or further geotechnical studies may be
warranted.
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 and engineering analyses and laboratory
data, the conclusions and recommendations are professional opinions. These opinions
have been derived in accordance with current standards of practice, and no warranty,
either express or implied, is given. Standards of practice are subject to change with time.
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.
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The opportunity to be of service is sincerely appreciated.
questions, please do not hesitate to contact our office.
Respectfully submi
GeoSoils, Inc.
P. otin P. Fr nklin David W. Skel y
Engineering Geologist, CEG 1340 Civil Engineer, ACE 47857
TMP/JPF/DWS/sh
Attachments:
Distribution:
Karen Gilbert
Appendix A -References
Appendix B -General Earthwork, Grading Guidelines,
and Preliminary Criteria
(3) Addressee (wet sign and PDF)
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APPENDIX A
REFERENCES
GeoSoils, Inc.
APPENDIX A
REFERENCES
A Quick Survey, 2015, Site Survey, prepared for Karen Gilbert, 2351 Pio Pico Drive,
Carlsbad, California, dated April 16.
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 302.1 R-04, dated March 23.
ACI Committee 302, 2004, Guide for concrete floor and slab construction, ACI 302.1 R-04,
dated June.
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., 2000a, EQFAULT, A computer program for the estimation of peak
horizontal acceleration from 3-D fault sources; Windows 95/98 version.
__ , 2000b, EQSEARCH, A computer program for the estimation of peak horizontal
acceleration from California historical earthquake catalogs; Updated to
December 2009, Windows 95/98 version.
GeoSoils, Inc.
Bozorgnia, Y., Campbell K.W., and Niazi, M., 1999, Vertical ground motion: Characteristics,
relationship with horizontal component, and building-code implications;
Proceedings of the SMIP99 seminar on utilization of strong-motion data,
September 15, Oakland, pp. 23-49.
Bryant, W.A., and Hart, E.W., 2007, Fault-rupture hazard zones in California, Alquist-Priolo
earthquake fault zoning act with index to earthquake fault zones maps;
California Geological Survey, Special Publication 42, interim revision.
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.
California Office of Statewide Health Planning and Development (OSHPD), 2020, Seismic
design maps, https://seismicmaps.org/.
Cao, T., Bryant, W.A., Rowshandel, B., Branum, D., and Wills, C.J., 2003, The revised 2002
California probabilistic seismic hazard maps, dated June,
http://www.conservation.ca.gov/cgs/rghm/psha/fault_parameters/pdf/Documents
/2002 _CA_ Hazard_ Maps. pdf
Carlsbad, City of, 1993, Standards for design and construction of public works
improvements in the City of Carlsbad.
Caroline Dooley Architects, 2016, Preliminary Residential Layout for Levels 1 and 2,
1 /8 scale, dated February 1.
County of San Diego, Department of Planning and Land Use, 2007, Low impact
development (LID) handbook, stormwater management strategies,
dated December 31.
Clar, M.L., Bartfield, B.J., O'Conner, T.P., 2004, Stormwater best management practice
design guide, volume 3, basin best management practices, US EPN600/R-04/121 B,
dated September.
GeoSoils, Inc., 2016,Geotechnical evaluation for proposed construction at 2351 Pio Pico
Drive, Carlsbad, San Diego County, California, W.O. 7082-A-SC, dated July 27.
Jennings, C.W., 1994, Fault activity map of California and adjacent areas: California
Division of Mines and Geology, Map Sheet No. 6, scale 1 :750,000.
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Kanare, H.M., 2005, Concrete floors and moisture, Engineering Bulletin 119, Portland
Cement Association.
Kennedy, M.P., and Tan, SS., 2007, Geologic map of the Oceanside 30' by 60' quadrangle,
California, regional geologic map series, scale 1:100,000, California Geologic
Survey Map No. 2.
Norris, R.M. and Webb, R.W., 1990, Geology of California, second edition, John Wiley &
Sons, Inc.
Romanoff, M., 1957, Underground corrosion, originally issued April 1.
Seed, 2005, Evaluation and mitigation of soil liquefaction hazard "evaluation of field data
and procedures for evaluating the risk of triggering (or inception) of liquefaction",
in Geotechnical earthquake engineering; short course, San Diego, California,
April 8-9.
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, 2021, Civil Code, Sections 895 et seq.
State of California Department of Transportation, Division of Engineering Services,
Materials Engineering, and Testing Services, Corrosion Technology Branch, 2003,
Corrosion Guidelines, Version 1.0, dated September.
Tan, S.S., and Giffen, D.G., 1995, Landslide hazards in the northern part of the San Diego
Metropolitan area, San Diego County, California, Landslide hazard identification
map no. 35, Plate 35G, Department of Conservation, Division of Mines and Geology,
DMG Open File Report 95-04.
United States Department of Agriculture, 1953, Aerial photographs, flight line AXN -14M,
photos nos. 19 and 20, scale 1"=1,000'±.
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APPENDIX B
GENERAL EARTHWORK, GRADING GUIDELINES
AND PRELIMINARY CRITERIA
GeoSoils, Inc.
GENERAL EARTHWORK, GRADING GUIDELINES, AND PRELIMINARY CRITERIA
General
These guidelines present general procedures and requirements for earthwork and grading
as shown on the approved grading plans, including preparation of areas to be filled,
placement of fill, installation of subdrains, excavations, and appurtenant structures or
flatwork. The recommendations contained in the geotechnical report are part of these
earthwork and grading guidelines and would supercede the provisions contained hereafter
in the case of conflict. Evaluations performed by the consultant during the course of
grading may result in new or revised recommendations which could supercede these
guidelines or the recommendations contained in the geotechnical report. Generalized
details follow this text.
The contractor is responsible for the satisfactory completion of all earthwork in accordance
with provisions of the project plans and specifications and latest adopted code. In the case
of conflict, the most onerous provisions shall prevail. The project geotechnical engineer
and engineering geologist (geotechnical consultant), and/or their representatives, should
provide observation and testing services, and geotechnical consultation during the
duration of the project.
EARTHWORK OBSERVATIONS AND TESTING
Geotechnical Consultant
Prior to the commencement of grading, a qualified geotechnical consultant (soil engineer
and engineering geologist) should be employed for the purpose of observing earthwork
procedures and testing the fills for general conformance with the recommendations of the
geotechnical report(s), the approved grading plans, and applicable grading codes and
ordinances.
The geotechnical consultant should provide testing and observation so that an evaluation
may be made that the work is being accomplished as specified. It is the responsibility of
the contractor to assist the consultants and keep them apprised of anticipated work
schedules and changes, so that they may schedule their personnel accordingly.
All remedial removals, clean-outs, prepared ground to receive fill, key excavations, and
subdrain installation should be observed and documented by the geotechnical consultant
prior to placing any fill. It is the contractor's responsibility to notify the geotechnical
consultant when such areas are ready for observation.
Laboratory and Field Tests
Maximum dry density tests to determine the degree of compaction should be performed
in accordance with American Standard Testing Materials test method ASTM designation
D-1557. Random or representative field com_paction tests should be performed in GeoSoils, Inc.
accordance with test methods ASTM designation D-1556, D-2937 or D-2922, and D-3017,
at intervals of approximately ±2 feet of fill height or approximately every 1,000 cubic yards
placed. These criteria would vary depending on the soil conditions and the size of the
project. The location and frequency of testing would be at the discretion of the
geotechnical consultant.
Contractor's Responsibility
All clearing, site preparation, and earthwork performed on the project should be conducted
by the contractor, with observation by a geotechnical consultant, and staged approval by
the governing agencies, as applicable. It is the contractor's responsibility to prepare the
ground surface to receive the fill, to the satisfaction of the geotechnical consultant, and to
place, spread, moisture condition, mix, and compact the fill in accordance with the
recommendations of the geotechnical consultant. The contractor should also remove all
non-earth material considered unsatisfactory by the geotechnical consultant.
Notwithstanding the services provided by the geotechnical consultant, it is the sole
responsibility of the contractor to provide adequate equipment and methods to accomplish
the earthwork in strict accordance with applicable grading guidelines, latest adopted codes
or agency ordinances, geotechnical report(s), and approved grading plans. Sufficient
watering apparatus and compaction equipment should be provided by the contractor with
due consideration for the fill material, rate of placement, and climatic conditions. If, in the
opinion of the geotechnical consultant, unsatisfactory conditions such as questionable
weather, excessive oversized rock or deleterious material, insufficient support equipment,
etc., are resulting in a quality of work that is not acceptable, the consultant will inform the
contractor, and the contractor is expected to rectify the conditions, and if necessary, stop
work until conditions are satisfactory.
During construction, the contractor shall properly grade all surfaces to maintain good
drainage and prevent ponding of water. The contractor shall take remedial measures to
control surface water and to prevent erosion of graded areas until such time as permanent
drainage and erosion control measures have been installed.
SITE PREPARATION
All major vegetation, including brush, trees, thick grasses, organic debris, and other
deleterious material, should be removed and disposed of off-site. These removals must
be concluded prior to placing fill. In-place existing fill, soil, alluvium, colluvium, or rock
materials, as evaluated by the geotechnical consultant as being unsuitable, should be
removed prior to any fill placement. Depending upon the soil conditions, these materials
may be reused as compacted fills. Any materials incorporated as part of the compacted
fills should be approved by the geotechnical consultant.
Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic
tanks, wells, pipelines, or other structures not located prior to grading, are to be removed
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or treated in a manner recommended by the geotechnical consultant. Soft, dry, spongy,
highly fractured, or otherwise unsuitable ground, extending to such a depth that surface
processing cannot adequately improve the condition, should be overexcavated down to
firm ground and approved by the geotechnical consultant before compaction and filling
operations continue. Overexcavated and processed soils, which have been properly
mixed and moisture conditioned, should be re-compacted to the minimum relative
compaction as specified in these guidelines.
Existing ground, which is determined to be satisfactory for support of the fills, should be
scarified (ripped) to a minimum depth of 6 to 8 inches, or as directed by the geotechnical
consultant. After the scarified ground is brought to optimum moisture content, or greater
and mixed, the materials should be compacted as specified herein. If the scarified zone
is greater than 6 to 8 inches in depth, it may be necessary to remove the excess and place
the material in lifts restricted to about 6 to 8 inches in compacted thickness.
Existing ground which is not satisfactory to support compacted fill should be
overexcavated as required in the geotechnical report, or by the on-site geotechnical
consultant. Scarification, disc harrowing, or other acceptable forms of mixing should
continue until the soils are broken down and free of large lumps or clods, until the working
surface is reasonably uniform and free from ruts, hollows, hummocks, mounds, or other
uneven features, which would inhibit compaction as described previously.
Where fills are to be placed on ground with slopes steeper than 5:1 (horizontal to vertical
[h:v]), the ground should be stepped or benched. The lowest bench, which will act as a
key, should be a minimum of 15 feet wide and should be at least 2 feet deep into firm
material, and approved by the geotechnical consultant. In fill-over-cut slope conditions,
the recommended minimum width of the lowest bench or key is also 15 feet, with the key
founded on firm material, as designated by the geotechnical consultant. As a general rule,
unless specifically recommended otherwise by the geotechnical consultant, the minimum
width of fill keys should be equal to ½ the height of the slope.
Standard benching is generally 4 feet (minimum) vertically, exposing firm, acceptable
material. Benching may be used to remove unsuitable materials, although it is understood
that the vertical height of the bench may exceed 4 feet. Pre-stripping may be considered
for unsuitable materials in excess of 4 feet in thickness.
All areas to receive fill, including processed areas, removal areas, and the toes of fill
benches, should be observed and approved by the geotechnical consultant prior to
placement of fill. Fills may then be properly placed and compacted until design grades
(elevations) are attained.
COMPACTED FILLS
Any earth materials imported or excavated on the property may be utilized in the fill
provided that each material has been evaluated to be suitable by the geotechnical
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consultant. These materials should be free of roots, tree branches, other organic matter,
or other deleterious materials. All unsuitable materials should be removed from the fill as
directed by the geotechnical consultant. Soils of poor gradation, undesirable expansion
potential, or substandard strength characteristics may be designated by the consultant as
unsuitable and may require blending with other soils to serve as a satisfactory fill material.
Fill materials derived from benching operations should be dispersed throughout the fill
area and blended with other approved material. Benching operations should not result in
the benched material being placed only within a single equipment width away from the
fill/bedrock contact.
Oversized materials defined as rock, or other irreducible materials, with a maximum
dimension greater than 12 inches, should not be buried or placed in fills unless the
location of materials and disposal methods are specifically approved by the geotechnical
consultant. Oversized material should be taken offsite, or placed in accordance with
recommendations of the geotechnical consultant in areas designated as suitable for rock
disposal. GSI anticipates that soils to be utilized as fill material for the subject project may
contain some rock. Appropriately, the need for rock disposal may be necessary during
grading operations on the site. From a geotechnical standpoint, the depth of any rocks,
rock fills, or rock blankets, should be a sufficient distance from finish grade. This depth is
generally the same as any overexcavation due to cut-fill transitions in hard rock areas, and
generally facilitates the excavation of structural footings and substructures. Should deeper
excavations be proposed (i.e., deepened footings, utility trenching, swimming pools, spas,
etc.), the developer may consider increasing the hold-down depth of any rocky fills to be
placed, as appropriate. In addition, some agencies/jurisdictions mandate a specific
hold-down depth for oversize materials placed in fills. The hold-down depth, and potential
to encounter oversize rock, both within fills, and occurring in cut or natural areas, would
need to be disclosed to all interested/affected parties. Once approved by the governing
agency, the hold-down depth for oversized rock (i.e., greater than 12 inches) in fills on this
project is provided as 1 O feet, unless specified differently in the text of this report. The
governing agency may require that these materials need to be deeper, crushed, or
reduced to less than 12 inches in maximum dimension, at their discretion.
To facilitate future trenching, rock (or oversized material), should not be placed within the
hold-down depth feet from finish grade, the range of foundation excavations, future utilities,
or underground construction unless specifically approved by the governing agency, the
geotechnical consultant, and/or the developer's representative.
If import material is required for grading, representative samples of the materials to be
utilized as compacted fill should be analyzed in the laboratory by the geotechnical
consultant to evaluate it's physical properties and suitability for use onsite. Such testing
should be performed three (3) days prior to importation. If any material other than that
previously tested is encountered during grading, an appropriate analysis of this material
should be conducted by the geotechnical consultant as soon as possible.
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Approved fill material should be placed in areas prepared to receive fill in near horizontal
layers, that when compacted, should not exceed about 6 to 8 inches in thickness. The
geotechnical consultant may approve thick lifts if testing indicates the grading procedures
are such that adequate compaction is being achieved with lifts of greater thickness. Each
layer should be spread evenly and blended to attain uniformity of material and moisture
suitable for compaction.
Fill layers at a moisture content less than optimum should be watered and mixed, and wet
fill layers should be aerated by scarification, or should be blended with drier material.
Moisture conditioning, blending, and mixing of the fill layer should continue until the fill
materials have a uniform moisture content at, or above, optimum moisture.
After each layer has been evenly spread, moisture conditioned, and mixed, it should be
uniformly compacted to a minimum of 90 percent of the maximum density as evaluated by
ASTM test designation D-1557, or as otherwise recommended by the geotechnical
consultant. Compaction equipment should be adequately sized and should be specifically
designed for soil compaction, or of proven reliability to efficiently achieve the specified
degree of compaction.
Where tests indicate that the density of any layer of fill, or portion thereof, is below the
required relative compaction, or improper moisture is in evidence, the particular layer or
portion shall be re-worked until the required density and/or moisture content has been
attained. No additional fill shall be placed in an area until the last placed lift of fill has been
tested and found to meet the density and moisture requirements, and is approved by the
geotechnical consultant.
In general, per the latest adopted version of the California Building Code (CBC), fill slopes
should be designed and constructed at a gradient of 2:1 (h:v), or flatter. Compaction of
slopes should be accomplished by over-building a minimum of 3 feet horizontally, and
subsequently trimming back to the design slope configuration. Testing shall be performed
as the fill is elevated to evaluate compaction as the fill core is being developed. Special
efforts may be necessary to attain the specified compaction in the fill slope zone. Final
slope shaping should be performed by trimming and removing loose materials with
appropriate equipment. A final evaluation of fill slope compaction should be based on
observation and/or testing of the finished slope face. Where compacted fill slopes are
designed steeper than 2:1 (h:v), prior approval from the governing agency, specific
material types, a higher minimum relative compaction, special reinforcement, and special
grading procedures will be recommended.
If an alternative to over-building and cutting back the compacted fill slopes is selected,
then special effort should be made to achieve the required compaction in the outer 10 feet
of each lift of fill by undertaking the following:
1. An extra piece of equipment consisting of a heavy, short-shanked sheepsfoot
should be used to roll (horizontal) parallel to the slopes continuously as fill is
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placed. The sheepsfoot roller should also be used to roll perpendicular to the
slopes, and extend out over the slope to provide adequate compaction to the face
of the slope.
2. Loose fill should not be spilled out over the face of the slope as each lift is
compacted. Any loose fill spilled over a previously completed slope face should be
trimmed off or be subject to re-rolling.
3. Field compaction tests will be made in the outer (horizontal) ±2 to ±8 feet of the
slope at appropriate vertical intervals, subsequent to compaction operations.
4. After completion of the slope, the slope face should be shaped with a small tractor
and then re-rolled with a sheepsfoot to achieve compaction to near the slope face.
Subsequent to testing to evaluate compaction, the slopes should be grid-rolled to
achieve compaction to the slope face. Final testing should be used to evaluate
compaction after grid rolling.
5. Where testing indicates less than adequate compaction, the contractor will be
responsible to rip, water, mix, and recompact the slope material as necessary to
achieve compaction. Additional testing should be performed to evaluate
compaction.
SUBDRAIN INSTALLATION
Subdrains should be installed in approved ground in accordance with the approximate
alignment and details indicated by the geotechnical consultant. Subdrain locations or
materials should not be changed or modified without approval of the geotechnical
consultant. The geotechnical consultant may recommend and direct changes in subdrain
line, grade, and drain material in the field, pending exposed conditions. The location of
constructed subdrains, especially the outlets, should be recorded/surveyed by the project
civil engineer. Drainage at the subdrain outlets should be provided by the project civil
engineer.
EXCAVATIONS
Excavations and cut slopes should be examined during grading by the geotechnical
consultant. If directed by the geotechnical consultant, further excavations or
overexcavation and refilling of cut areas should be performed, and/or remedial grading of
cut slopes should be performed. When fill-over-cut slopes are to be graded, unless
otherwise approved, the cut portion of the slope should be observed by the geotechnical
consultant prior to placement of materials for construction of the fill portion of the slope.
The geotechnical consultant should observe all cut slopes, and should be notified by the
contractor when excavation of cut slopes commence.
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If, during the course of grading, unforeseen adverse or potentially adverse geologic
conditions are encountered, the geotechnical consultant should investigate, evaluate, and
make appropriate recommendations for mitigation of these conditions. The need for cut
slope buttressing or stabilizing should be based on in-grading evaluation by the
geotechnical consultant, whether anticipated or not.
Unless otherwise specified in geotechnical and geological report(s), no cut slopes should
be excavated higher or steeper than that allowed by the ordinances of controlling
governmental agencies. Additionally, short-term stability of temporary cut slopes is the
contractor's responsibility.
Erosion control and drainage devices should be designed by the project civil engineer and
should be constructed in compliance with the ordinances of the controlling governmental
agencies, and/or in accordance with the recommendations of the geotechnical consultant.
COMPLETION
Observation, testing, and consultation by the geotechnical consultant should be
conducted during the grading operations in order to state an opinion that all cut and fill
areas are graded in accordance with the approved project specifications. After completion
of grading, and after the geotechnical consultant has finished observations of the work,
final reports should be submitted, and may be subject to review by the controlling
governmental agencies. No further excavation or filling should be undertaken without prior
notification of the geotechnical consultant or approved plans.
All finished cut and fill slopes should be protected from erosion and/or be planted in
accordance with the project specifications and/or as recommended by a landscape
architect. Such protection and/or planning should be undertaken as soon as practical after
completion of grading.
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.
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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
60 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.
6. 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 His 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
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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.
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
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. Slab underlayment should consist of
a 1-to 2-inch leveling course of sand (S. E. >30) and a minimum of 4 to 6 inches of
Class 2 base compacted to 90 percent. 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 orflatwork should not be constructed closer than H/3 or
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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 throughly 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.
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.
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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. For pools/spas built within (all or part) of the Code setback and/or geotechnical
setback, as indicated in the site geotechnical documents, special foundations are
recommended to mitigate the affects of creep, lateral fill extension, expansive soils
and settlement on the proposed pool/spa. Most municipalities or County reviewers
do not consider these effects in pool/spa plan approvals. As such, where
pools/spas are proposed on 20 feet or more of fill, medium or highly expansive
soils, or rock fill with limited "cap soils" and built within Code setbacks, or within the
influence of the creep zone, or lateral fill extension, the following should be
considered during design and construction:
OPTION A: Shallow foundations with or without overexcavation of the
pool/spa "shell," such that the pool/spa is surrounded by 5 feet of very low
to low expansive soils (without irreducible particles greater that 6 inches),
and the pool/spa walls closer to the slope(s) are designed to be free
standing. GSI recommends a pool/spa under-drain or blanket system
(see attached Typical Pool/Spa Detail). The pool/spa builders and owner in
this optional construction technique should be generally satisfied with
pool/spa performance under this scenario; however, some settlement, tilting,
cracking, and leakage of the pool/spa is likely over the life of the project.
OPTION B: Pier supported pool/spa foundations with or without
overexcavation of the pool/spa shell such that the pool/spa is surrounded by
5 feet of very low to low expansive soils (without irreducible particles greater
than 6 inches), and the pool/spa walls closer to the slope(s) are designed to
be free standing. The need for a pool/spa under-drain system may be
installed for leak detection purposes. Piers that support the pool/spa should
be a minimum of 12 inches in diameter and at a spacing to provide vertical
and lateral support of the pool/spa, in accordance with the pool/spa
designers recommendations current applicable Codes. The pool/spa builder
and owner in this second scenario construction technique should be more
satisfied with pool/spa performance. This construction will reduce settlement
and creep effects on the pool/spa; however, it will not eliminate these
potentials, nor make the pool/spa "leak-free."
Karen Gilbert
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc. Appendix B
Page 11
22. 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.
23. 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).
24. Pool and spa utility lines should not cross the primary structure's utility lines
(i.e., not stacked, or sharing of trenches, etc.).
25. 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.
26. 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.
27. 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.
28. 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.
29. 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 His 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.
Karen Gilbert
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc. Appendix B
Page 12
30. Failure to adhere to the above recommendations will significantly increase the
potential for distress to the pool/spa, flatwork, etc.
31. 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.
32. 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.
JOB SAFETY
General
At GSI, getting the job done safely is of primary concern. The following is the company's
safety considerations for use by all employees on multi-employer construction sites.
On-ground personnel are at highest risk of injury, and possible fatality, on grading and
construction projects. GSI recognizes that construction activities will vary on each site, and
that site safety is the prime responsibility of the contractor; however, everyone must be
safety conscious and responsible at all times. To achieve our goal of avoiding accidents,
cooperation between the client, the contractor, and GSI personnel must be maintained.
In an effort to minimize risks associated with geotechnical testing and observation, the
following precautions are to be implemented for the safety of field personnel on grading
and construction projects:
Safety Meetings: GSI field personnel are directed to attend contractor's regularly
scheduled and documented safety meetings.
Safety Vests: Safety vests are provided for, and are to be worn by GSI personnel,
at all times, when they are working in the field.
Safety Flags: Two safety flags are provided to GSI field technicians; one is to be
affixed to the vehicle when on site, the other is to be placed atop the
spoil pile on all test pits.
Flashing Lights: All vehicles stationary in the grading area shall use rotating or flashing
amber beacons, or strobe lights, on the vehicle during all field testing.
While operating a vehicle in the grading area, the emergency flasher
on the vehicle shall be activated.
In the event that the contractor's representative observes any of our personnel not
following the above, we request that it be brought to the attention of our office.
Karen Gilbert
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc:. Appendix B
Page 13
Test Pits Location, Orientation, and Clearance
The technician is responsible for selecting test pit locations. A primary concern should be
the technician's safety. Efforts will be made to coordinate locations with the gradtng
contractor's authorized representative, and to select locations following or behind the
established traffic pattern, preferably outside of current traffic. The contractor's authorized
representative (supervisor, grade checker, dump man, operator, etc.) should direct
excavation of the pit and safety during the test period. Of paramount concern should be
the soil technician's safety, and obtaining enough tests to represent the fill.
Test pits should be excavated so that the spoil pile is placed away from oncoming traffic,
whenever possible. The technician's vehicle is to be placed next to the test pit, opposite
the spoil pile. This necessitates the fill be maintained in a driveable condition.
Alternatively, the contractor may wish to park a piece of equipment in front of the test
holes, particularly in small fill areas or those with limited access.
A zone of non-encroachment should be established for all test pits. No grading equipment
should enter this zone during the testing procedure. The zone should extend
approximately 50 feet outward from the center of the test pit. This zone is established for
safety and to avoid excessive ground vibration, which typically decreases test results.
When taking slope tests, the technician should park the vehicle directly above or below the
test location. If this is not possible, a prominent flag should be placed at the top of the
slope. The contractor's representative should effectively keep all equipment at a safe
operational distance (e.g., 50 feet) away from the slope during this testing.
The technician is directed to withdraw from the active portion of the fill as soon as possible
following testing. The technician's vehicle should be parked at the perimeter of the fill in
a highly visible location, well away from the equipment traffic pattern. The contractor
should inform our personnel of all changes to haul roads, cut and fill areas or other factors
that may affect site access and site safety.
In the event that the technician's safety is jeopardized or compromised as a result of the
contractor's failure to comply with any of the above, the technician is required, by company
policy, to immediately withdraw and notify his/her supervisor. The grading contractor's
representative will be contacted in an effort to affect a solution. However, in the interim,
no further testing will be performed until the situation is rectified. Any fill placed can be
considered unacceptable and subject to reprocessing, recompaction, or removal.
In the event that the soil technician does not comply with the above or other established
safety guidelines, we request that the contractor bring this to the technician's attention and
notify this office. Effective communication and coordination between the contractor's
representative and the soil technician is strongly encouraged in order to implement the
above safety plan.
Karen Gilbert
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc. Appendix 8
Page 14
Trench and Vertical Excavation
It is the contractor's responsibility to provide safe access into trenches where compaction
testing is needed. Our personnel are directed not to enter any excavation or vertical cut
which: 1) is 5 feet or deeper unless shored or laid back; 2) displays any evidence of
instability, has any loose rock or other debris which could fall into the trench; or 3) displays
any other evidence of any unsafe conditions regardless of depth.
All trench excavations or vertical cuts in excess of 5 feet deep, which any person enters,
should be shored or laid back. Trench access should be provided in accordance with
Cal/OSHA and/or state and local standards. Our personnel are directed not to enter any
trench by being lowered or "riding down" on the equipment.
If the contractor fails to provide safe access to trenches for compaction testing, our
company policy requires that the soil technician withdraw and notify his/her supervisor.
The contractor's representative will be contacted in an effort to affect a solution. All backfill
nottested due to safety concerns or other reasons could be subject to reprocessing and/or
removal.
If GSI personnel become aware of anyone working beneath an unsafe trench wall or
vertical excavation, we have a legal obligation to put the contractor and owner/developer
on notice to immediately correct the situation. If corrective steps are not taken, GSI then
has an obligation to notify Cal/OSHA and/or the proper controlling authorities.
Karen Gilbert
File:e:\wp12\7000\7082a1 .usa GeoSoils, Inc. Appendix B
Page 15
TYPE A
------------,----------
Natural grade ~ Proposed grade , , ·
' .y_:-.'·
Colluvium and alluvium {remo ,,,,..,,,. ..... :,--::~✓P
"' < 1/,\' , 1/
✓-\; ..,_,.,.,....,..11,. .:,..~~-...
~ ~----,--~ . ' "'>....---... .· -.·. .........,.......,, ,,'
-,,,,,_ ~,~:t-,-,,,,.....,.,►..,.. -~'!'!'$7,~~;.....,...=,, · .' Typical benching
,, . 1/ Bedrock or ,,
approved _j
native material
See Alternate Details
TYPE B
----~--------,----------
Natural grade ~ Proposed grade
\/ ~ v' v Colluvium and alluvium {rem .
-r' ~ 0
\~ ~~ __,-r;r~_-,/! v\ ~ --------\\ '-~-~ ---»✓ 1/
'\ -~~~....-,:,,,,,,,,,,,,................,,.,....,....,. Typical benching
. /,.y_ \ <<-/ Bedrock or · ~\ , , x1/
approved '
native material
See Alternate Details
Selection of alternate subdrain details, location, and extent of subdrains should be
evaluated by the geotechnical consultant during grading.
CANYON SUBDRAIN DETAIL Plate 8-1
6i
mini
6-inch mnnun
A-1
Filter material: Minimum volume of 9 cubic feet per
lineal foot of pipe. FIL TEA MATERIAL
Perforated pipe: 6-inch-diameter ABS or PVC pipe or
approved substitute with minimum 8 perforations
(¼-inch diameter) per lineal foot in
bottom half of pipe (ASTM D-2751, SDR-35, or
ASTM 0-1527, Schd. 40).
For continuous run in excess of 500 feet, use
8-inch-diameter pipe (ASTM D-3034, SDR-35, or
ASTM D-1785, Schd. 40).
Sieve Size
1 inch
¾inch
¾inch
No.4
No.a
No.30
No.50
No.200
Percent Passing
100
90-100
40-100
25-40
18-33
5-15
0-7
0-3
AL TEANATE 1= PEAFOAA TED PIPE AND RL TEA MA lERIAL
.,,,, /
6-inch minirnun
A-2
I I
--
1 1 6-inch minimlm
Gravel Material= 9 cubic feet per lineal foot.
Perforated Pipe= See Alternate 1
Gravel= Clean ¾-inch rock or approved substitute.
Filter Fabric: Mirafi 140 or approved substitute.
I
AL1ERNA1E 2= PERFORAlED PIPE, GRAVEL, AND RLlER FABRIC
CANYON SUBDRAIN ALTERNATE DETAILS Plate B-2
~-Toe of slope as shown
on grading plan
Original ground surf ace to be
restored with compacted fill
<<~;··::···.-::c·.···---
.-<':-.·· ... : .. : ..... : .. Compa(?~~d.Fill-: :.=· ·.
.. ~ .. -~ ... · .. "·:. ·.'' ·,··.; ...... :'._ .... ·.\.:.···'.'.,::: <.>:: :·:.·:--' .:.·.: ... I
2D
/
#/
~
~cf/ o-Ar. I \__o \ / n q,alod remo,,al O riginal \5~ ~ / (deptt, per -h '· uno"'8blo material ground surface
'/,\ r,caJ enghoor)
,\ /
\ '-'W\x
\ /\\,,
Back-cut varies. For deep removals,
backcut should be made no steeper
than 1:1 (H:V), or flatter as necessary
for safety considerations.
Provide a 1:1 (H:V) minimum projection from toe of
slope as shown on grading plan to the recommended
removal depth. Slope height, site conditions, and/ or
local conditions could dictate flatter projections.
'iii... ~re· FILL SLOPE TOEING OUT ON FLAT ALLUVIATED CANYON DETAIL Plate 8-3
Proposed grade~ ----
--
.--Previously placed, temporary
compacted fill for drainage only
----
,fi_ ~c.
-
Proposed additional compacted fill
Existi~com +~;@I £'02£¥4>~~--_ pacted fill \\__;_;;:: ---: :::: Y ·•• · --UnSuif p '· , i , .. _,, · '· 'f>, §// >/ : • > -.:_. -__ -' a le ~_t_er\i!il (ti;i be rem _ >: _~ _ : · . : -_ -:-•c;r, ~'(:<Y:.\ · ---.. _ oved)
/4'0"<./\\~~:;;<0~~.Y,:,\\\(\"~)\,.\\\; ;<0/\c y\ \\1/
To be remo Bedrock or a
additional ci~d before placing --" native materi:proved
pacted fill
REMOVAL ADJACENT TO EXISTING FILL ADJOINING CANYON FILL DETAIL Plate 8-4
Design finish slope -~
Blanket fill (tt recommended by
the geotechnical consultant)
I 1s toot I -----. . ----I mInImum \
Drainage per design
civil engineer -l 10-foot minimum /
I
' ...... .
\:(/~\,)):'>-25-foot maximum/
--_ __,/_ -----
1---~------......... .......,~·\ \/' \ \ /, / ...r.J \{~<
'\
------Typical benching /' Buttress or
15-foot typical t b'I' t' f'II ___ . .
1 to 2 drain spacing / S a I 1za 10n I '-----4-1nch-d1ameter non-perforated
I foot J j _ ~ 2-Percent Gradient .:::-:-:\ \\ Typical outle~ pipe and backdrain (see
_ T _ _ _ ---~\ /'" benching detail Plate 8-6). Outlet_s to be
2-toot minimum f~0" T ~ /-\~ (4-foot spaced at 100-foot maximum
key depth ____ ~ oe 2-Percent Gradient---Heel X · ' ✓•. minimum) intervals and shall extend 2 feet
l ,✓-/✓.YA ,,, \ ::.,-;\~½ .,.., \ . , v--8 d k beyond the face of slope at time
I 1s-1oot mnm~m I e roe or . of rough grading completion. At
~t_'t r. c.
t'J
or H/2 where_H 18 the _ _____.,_, appro_ved native the completion of rough grading. I slope height I material . . . .
Subdrain as
recommended by
geotechnical consultant
TYPICAL STABILIZATION / BUTTRESS FILL DETAIL
the design civil engineer should
provide recommendations to
convey any outlet's discharge to
a suitable conveyance, utilizing a
non-erosive device.
Plate 8-5
I ... ~~oot ...
1 I rrnrm.m
I I -----7-..... ........
. . . I . .-:-:-:-:-:-:-:-:-:-4-inch minimlrn . . . . . . . . . . . . 3 foot r pipe :-:-:-:-:-:-:-:-:-:-:-:-[ ~-~ mnmumj· .. . . . . . . . . . . . . . mnmum -----~······ _t ____ ---i-----
I 2-toot I .......
.
----.
.
I l1lllllllm I f ~
l L
£}
-----1--inch
2-inch
pipe mi"lilll\.lTl
Filter Material= Minimum of 5 cubic feet per lineal foot of pipe or 4 cubic feet per lineal
feet of pipe when placed in square cut trench.
Alternative in Lieu of Filter Material= Gravel may be encased in approved filter fabric.
Filter fabric shall be Mirafi 140 or equivalent. Filter fabric shall be lapped a minimum of
12 inches in all joints.
Minimum 4-lnch-Diameter Pipe: ABS-ASTM D-2751, SDR 35; or ASTM D-1527 Schedule
40, PVC-ASTM D-3034, SDR 35; or ASTM D-1785 Schedule 40 with a crushing strength
of 1,000 pounds minimum, and a minimum of 8 uniformly-spaced perforations per foot of
pipe. Must be installed with perforations down at bottom of pipe. Provide cap at
upstream end of pipe. Slope at 2 percent to outlet pipe. Outlet pipe to be connected
to subdrain pipe with tee or elbow.
Notes= 1. Trench for outlet pipes to be backfilled and compacted with onsite soil.
2. Backdrains and lateral drains shall be located at elevation of every bench
drain. First drain located at elevation just above lower lot grade. Additional
drains may be required at the discretion of the geotechnical consultant.
Filter Material shall be of the following
specification or an approved equivalent.
Sieve Size
1inch
¾inch
¾ inch
No.4
No. 8
No.30
No.50
No. 200
Percent Passing
100
90-100
40-100
25-40
18-33
5-15
0-7
0-3
Gravel shall be of the following
specification or an approved equivalent.
Sieve Size
1½ inch
No.4
No.200
Percent Passing
100
50
8
TYPICAL BUTTRESS SUBDRAIN DETAIL Plate 8-6
Toe of slope as shown
on grading plan
Natural slope to
be restored with
compacted fill
,,,---Proposed grade \ / /
/
/ Compacted fill
/
/ ,.
//
/ · ..... · -.... · .. • ...•.. ' . ' , .· \ ; / : .. -. : ' ' ' : ·-·· : .. ,
. . . . . . . . ·. . . '· . : ·. .• . . ' ·~~-d-e '(!\8-\er@' . ·. •. . ' . ' .. ·. :.,_;;.:-----
. ·. · , .. · :-· •. '.' '· " '>.· • ... · C ,;i, ·•.Of'~ . . ..,.· ... , ... • ... -:, . · . '· .·' . :· :.,--. _ .. -. -.. . . ·. ·o, coW-l~ ...... --· ...... _ .... _ , .. _... . -----L
2-fool .. . .... ··, .··.· :-,···· ..,
0
{(\0~e·\0911. --':-.. .--... · .. ' .-.--·• •: •. : , -•~-' \\ A'
inbem1n1mum~ .··· _.,,,..,, .... _.<'· ·: ., .. ·, ~ -~ / ,,0, -<rocko · .. _, , --.. · 3/ · · ·. •. · ·· -· " -· · · ·. · _....-~~~...,..,-I,,,-,...-
[
approvec1 r .•··: .. ·=·"· :·~"•:. :· .. ·: ·: ·:~$" .. •.•:··.· ·':.· :.· :· ~---· ·: • .•.· · -~ :;;,,,;;.. y\\""....-: -__
4
-footmlnimum
earth · ·, · • · ~ · ' · · \ \ · '\-(\ \~ -
mate· · · · •' · · · ---~~ -. -.. • -· _.. , .. . • .. .. -.1/--. ... -... ·----1/, y\ {\V •/'. ✓-I r ----C"C ~ ·'-. .. · , ~ :.,--ITT~~--F::'' ,,...-,:----,,,-, ,\
r
-~-_,✓-:;;,___ :,.; ;,-;::<,..-; v-:" ;..(' -~· ·•• s-(. ---------A ,;.<,/,\y\ \' >-. Bench...., I , ,,., '"\\✓-_ --~ [ foot m1nimu ~ may I ·1 .,\V/.'V • . --m I (4 ,ary ~, '' .....-\\>>s \ \ \ ----foot -~ Bed I _~15-foot . . ., :.-<,1/.j ----, rock or
I
• H/2 """""'°' -r ap
Backcut varies
al
t where H is, ___ I
he slope height 1 Subdrain
geotechnical consultant
by
NOTES:
1. Where the natural slope approaches or exceeds the design slope ratio, special recommendations would be
provided by the geotechnical consultant.
2. The need for and disposition of drains should be evaluated by the geotechnical consultant, based upon
exposed conditions.
-'i~·rn:. c:.
i""
FILL OVER NATURAL (SIDEHILL FILL) DETAIL Plate 8-7
H • height of slope
Cut/fill contact as
shown on grading plan
Cut/fill contact as
shown on as-built plan ____,
Proposed grade
Maintain 1 ,inimum 15-foot 1
• /
I ,ill section from I
bacl<cut to face I I of finish slope
/
/ Compacted fill
I / , ----q\)\\-C,.V5=f7 , ........ -------~ ,·,nS• .::,;;..-,---I\__,..
4-foot minimum
Original (existing) grade .~·. tZ"V,\V/.YjA ----7-
1 '''"'''''' ~.;,, I
-"''' ~~\\<\
~t minimum _j I
. ~\ key depth 1 15-foot minimum or I ~_,..\\7/ ~\~\\ i--H/2whereHis-
\Y,\ \ A\ ~_,..\y).\ y-('(/ I the slope height I
Cut slope
Bedrock or approved
native material
. Bench width I r--may vary-I I (4-foot minimum)
Subdrain as recommended by
geotechnical consultant
NOTE= The cut portion of the slope should be excavated and evaluated by the geotechnical consultant prior to
construction of the fill portion.
11-c. <~· FILL OVER CUT DETAIL Plate 8-8
Natural slope :,.·:•,
Proposed finish grade-~ .... -..... :_· .. ·· .... ·.-·.-.,.· ... ·\,e~ve\,;,~~it~~e ·_:: :_._
· .... .. ... . .
Typical benching
(4-foot minimum)
Compacted stablization fill
... ·.·· .· .. · ··.;.. . .. ~ / \,, A
::_..·· .. ·.-.· _.. · ... ··':', ... ·.· .. , .. · .. ·,·. /' ~ \ ,-1-footminirnumtiltback . · .... •,·, ••,: ::·.: ~ / <,., ,\\ /.\' : . . . . ~-~ ~~ _(
----Bedrock or other
approved native material . •,' . -=---=-----::-<-----/ ----t-
/'
-If recommended by the geotechnical
2-1~n:i1dirtC1ffi./;\ consultant, the remaining cut portion of
2 Percent Gradient ----the slope may require removal and
/
~00~~0 replacement with compacted fill.
1 ◄ W ► Subdrain as recommended by
geotechnical consultant
NOTES= 1. Subdrains may be required as specttied by the geotechnical consultant.
2 W shall be equipment width (15 feet) for slope heights less than 25 feet. For slopes greater than
25 feet, W shall be evaluated by the geotechnical consultant. At no time, shall W be less than H/2,
where H is the height of the slope.
Jc .. I STABLIZATION FILL FOR UNSTABLE MATERIAL EXPOSED IN CUT SLOPE DETAIL Plate B-9
Proposed finish grade -~ Natural grade
7) ,I
y--'
rv~0~ )\ <\\.~
\ :.-\
'/ /
minimum
H • height of slope
\ ~ Bedrock or
.. , approved
native material
---__,.,.--_ . ·--~---:· .. ·· \>".::-,.\V'\\ ...,...-: . . .. , ··. . ::..<,//'.>'::\\ : . :· .. · ... : ... · .. ·,. · .. ·---:·_. ,_. ·:. .... . . . \\\{\\1/>-..--··· .· . • . . <, -: ... · ., .. ·, --_.!..~\ -~\ ?~<J~~~ . 2-Percent Gradient-.¼~?.
'\ al~~\\..,>\\' ... <\:...---: >--.: 2-foot minimum ~ ,,.\ \ \/,\\,:_.;
Typical benching
(4-foot minimum)
key depth I ,_ 15-foot mininum key widm · · •· I' •,
or H/2 tt H}30 feet .., Subdrain as recommended by
geotechnical consultant
NOTES= 1. 15-f oot minimum to be maintained from proposed finish slope face to back cut.
2. The need and disposition of drains will be evaluated by the geotechnical consultant based on field conditions.
3. Pad overexcavation and recompaction should be performed if evaluated to be necessary by the
geotechnical consultant.
~-I,''"'_-'. i ,,./, C.
~
SKIN FILL OF NATURAL GROUND DETAIL Plate 8-10
Natural grade Reconstruct compacted fill slope at 2:1 or flatter
(may increase or decrease pad area)
Overexcavate and recompact
replacement fill
·, ...
Back-cut varies
.· ··•····•···•····~•·•\:·•··.··•·:·.••;··:-::·:.•.:,··;? ·• ·.•.·Y
.,.,:.·,\..·::< ·:··;._ .. :· .·.' ~··· .o,te11o1·• .... 7 . .-. '/ . ·.·~ · ., .. •., .. , ·· · , ... ·· [Proposed . . , •:)".' '. :· "'7 , . -_ l finish grade
._ ... ,.• ... •··•/.·: ......... ···✓-··-. 3f -· . · -·~ · · · · · • /'"0"~~ -oot · · : ... : ~ ... ,.r/• ... · · · ... · nww,un11blank -
. ,· . . . .. V ~ 2-. •. "· " .. ".: .. · . ' .. · V .. ". -:,;/4· ... , . , . : . 1/~\ ;('\\1/\;J::\ \ \✓--'r' m-.. . . '. . . . . ·. . ❖.V . ·.. . . ·: " .,.......-....1. \Y" \\, A, 1/,\Y\ \\1(\/'.\ \' .
[
ey width A i : _{ . · . ;#/ 0: .\ · v'. ~ 1/~ ~ / , /.Y/\'\j::;,t(--9 .... \ . ,• ~~v·· ,' y\\v,
Avoid and/ or clean up
spillage of materials on
the natural slope
--, . • . :. . . . .· , / , . , . . v:-\'0' .
-----_._-,-·-·.-~---' .• :.!. \\' A\'\ B .-· • · · .-~ v ora . ·" · . .'· •· .--z .. -:-·.,;-.~·~ ·· .. • •-cent \Y . native , pproved
f A
.... , ... · ....... -··... edrock
,,,. ..... : ....... , · ,.,. · .. , · · ·' ·" .,._ \. Typical b , material
· ... · : .. :· -.. -~·, ,. · 1/\y,,'\A,/4v'. ,~ (
4
-ench1ng ........ , .. . .. . • .. , /.v-:\ \ v )\ ,-\ \ 0
\-loot m1n1m ) • ... · . ,y),\'< . .,, um
.·•:_·.·''~y
~\1/
Subdrain as recommended by
geotechnical consultant
NOTES: 1. Subdrain and key width requirements will be evaluated based on exposed subsurface conditions and
thickness of overburden.
2. Pad overexcavation and recompaction should be performed tt evaluated necessary by the geotechnical
consultant.
v:.._-~,.c. DAYLIGHT CUT LOT DETAIL Plate 8-11
Natural grade
Proposed pad grade
. .
. ·:. . ··: . . ·. : -_._. ... .-...
>;:: ... , •·. <~~><~ __ _l_ ---~--~·,.;. _.,,_ ... _ .. _ ...... _ --------
CUT LOT OR MATERIAL-TYPE TRANSmON
Natural grade
. . . . .
. ··:·+·:·::~~---·_--·: ---J_
. . .
. . : : : . :--' _.
. : ... ·. · .. :· ._,_;_,,-\; · ·3-to '7-foot' mini~
.. · . ; .. ; •.: : · ~ \~ overexcavate and recornpact
. ~-· tt\8-~ ...,.....,.,.,.....,........~~......,,~ v:; per text of report -~. /('°'(/
· ·. · · \. \\:;( • Deeper overexcavation may be
Typical benching
(4-foot minimum)
Bedrock or
approved native
material
recommended by the geotechnical
consultant in steep cut-fill transition
areas, such that the underlying
topography is no steeper than 3=1 (H=V)
CUT-FILL LOT (DAYLIGHT TRANSmON)
TRANSITION LOT DETAILS Plate 8-12