HomeMy WebLinkAboutAppendix E.1 - Geotechnical InvestigationUPDATE
GEOTECHNICAL INVESTIGATION
NAKANO PROPERTY
CHULA VISTA, CALIFORNIA
PREPARED FOR
PARDEE HOMES
SAN DIEGO, CALIFORNIA
SEPTEMBER 18, 2020
PROJECT NO. 07516-42-02
GROCON
INCORPORATED
GEOTECHNICAL • ENVIRONMENTAL MATERIALSO
6960 Flanders Drive • San Diego, California 92121-2974 • Telephone 858.558.6900 • Fax 858.558.6159
Project No. 07516-42-02
September 18, 2020
Pardee Homes
13400 Sabre Springs Parkway, Suite 200
San Diego, California 92128
Attention: Ms. April Tornillo
Subject: UPDATE GEOTECHNICAL INVESTIGATION
NAKANO PROPERTY
CHULA VISTA, CALIFORNIA
Dear Ms. Tornillo:
In accordance with your authorization, we have prepared this update geotechnical investigation report
for the proposed residential development at the subject site. The site is underlain by undocumented
fill, colluvium, and alluvium, overlying Terrace Deposits and the Mission Valley Formation. The
accompanying report presents the results of our study and conclusions and recommendations regarding
geotechnical aspects of site development.
This report is based on previous and recent field observations in 2005 and 2020. It is our opinion,
based on the results of this study, that the subject site is suitable for development. The accompanying
report presents conclusions and recommendations regarding geotechnical aspects of development.
Should you have questions regarding this investigation, or if we may be of further service, please
contact the undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
Rodney C. Mikesell
GE 2533
Rupert S. Adams
CEG 2561
RCM:RSA:dmc
(e-mail) Addressee
TABLE OF CONTENTS
1.PURPOSE AND SCOPE ...................................................................................................................... 1
2.SITE AND PROJECT DESCRIPTION ................................................................................................ 1
3.SOIL AND GEOLOGIC CONDITIONS ............................................................................................. 2
3.1 Undocumented Fill (Qudf) ......................................................................................................... 2
3.2 Topsoil (Unmapped) ................................................................................................................... 3
3.3 Alluvium (Qal) ........................................................................................................................... 3
3.4 Colluvium (Qcol) ........................................................................................................................ 3
3.5 Terrace Deposits (Qt) ................................................................................................................. 3
3.6 Mission Valley Formation (Tmv) ............................................................................................... 3
4.GROUNDWATER ............................................................................................................................... 4
5.GEOLOGIC HAZARDS ...................................................................................................................... 4
5.1 Faulting and Seismicity .............................................................................................................. 4
5.2 Ground Rupture .......................................................................................................................... 6
5.3 Tsunamis and Seiches ................................................................................................................. 6
5.4 Flooding ...................................................................................................................................... 6
5.5 Liquefaction and Seismically Induced Settlement ...................................................................... 7
5.6 Landslides ................................................................................................................................... 7
5.7 Geologic Hazard Category ......................................................................................................... 7
6.CONCLUSIONS AND RECOMMENDATIONS ................................................................................ 8
6.1 General ........................................................................................................................................ 8
6.2 Soil and Excavation Characteristics ........................................................................................... 9
6.3 Grading Recommendations ...................................................................................................... 10
6.4 Slopes ........................................................................................................................................ 12
6.5 Seismic Design Criteria (2019) ................................................................................................ 13
6.6 Foundations .............................................................................................................................. 15
6.7 Conventional Retaining Wall Recommendations ..................................................................... 21
6.8 Lateral Loading ......................................................................................................................... 24
6.9 Preliminary Pavement Recommendations ................................................................................ 25
6.10 Exterior Concrete Flatwork ...................................................................................................... 27
6.11 Slope Maintenance.................................................................................................................... 29
6.12 Storm Water Management ........................................................................................................ 29
6.13 Site Drainage and Moisture Protection ..................................................................................... 30
6.14 Grading and Foundation Plan Review ...................................................................................... 30
MAPS AND ILLUSTRATIONS
Figure 1, Vicinity Map
Figure 2, Geologic Map
Figures 3 and 4, Geologic Cross-Sections
Figure 5, Construction Detail for Lateral Extent of Removal
Figures 6 – 9, Slope Stability Analyses
APPENDIX A
FIELD INVESTIGATION
Figure A-1, Log of Large Diameter Boring
Figures A-2 – A-23, Logs of Exploratory Trenches
TABLE OF CONTENTS (Concluded)
APPENDIX B
LABORATORY TESTING
Table B-I, Summary of Laboratory Expansion Index Test Results
Table B-II, Summary of Laboratory Maximum Dry Density and Optimum Moisture Content Test Results
Table B-III, Summary of Laboratory Direct Shear Test Results
Table B-IV, Summary of Laboratory Water-Soluble Sulfate Test Results
Direct Shear Tests
APPENDIX C
STORM WATER MANAGEMENT RECOMMENDATIONS
APPENDIX D
RECOMMENDED GRADING SPECIFICATIONS
LIST OF REFERENCES
Project No. 07516-42-02 - 1 - September 18, 2020
UPDATE GEOTECHNICAL INVESTIGATION
1. PURPOSE AND SCOPE
This report presents the results of our update geotechnical investigation for the proposed 157-lot
residential development located on the Nakano Property northwest of Dennery Road, east of Interstate
805 (I-805), and south of the Otay River in Chula Vista, California (see Vicinity Map, Figure 1). The
purpose of our update investigation was to further evaluate subsurface soil and geologic conditions at
the site, and provide updated conclusions and recommendations pertaining to the geotechnical aspects
of developing the property as proposed.
The scope of our update investigation included a site reconnaissance, excavation of one large diameter
boring to a depth of 71 feet near the southwest corner of the property, performing infiltration testing in
the area of the proposed BMPs, and reviewing published and unpublished geologic literature and
reports (see List of References).
Appendix A presents a discussion of our field investigation. Included in Appendix A is our boring log
performed for this study and trench logs performed by Geocon Incorporated on the property during
previous studies. We performed laboratory tests on soil samples obtained from the large diameter
boring to evaluate pertinent physical properties for engineering analyses. The results of the laboratory
testing are presented in Appendix B. Also included in Appendix B is laboratory test results from our
previous study.
Site geologic conditions are depicted on Figure 2 (Geologic Map). The geologic contacts were plotted
on a base map provided by Civil Sense, Inc. Geologic cross sections are provided on Figures 3 and 4.
The conclusions and recommendations presented herein are based on our analysis of the data obtained
during the investigation, and our experience with similar soil and geologic conditions on this and
adjacent properties.
2. SITE AND PROJECT DESCRIPTION
The irregularly shaped, approximately 15-acre site is located northwest of the Dennery Road and
Regatta Lane intersection, east of I-805 in Chula Vista, California (see Vicinity Map, Figure 1). There
are no existing structures on the site, however several remnant building foundations are present.
Existing utilities at the site include 18- and 27-inch diameter sewer mains along the west and northern
portions of the property, respectively, high-voltage overhead electrical lines traversing the southern
portion of the site, and water lines and storm drain lines in the southeast corner of the property and a
reclaimed water line along the eastern property boundary. We understand the sewer main on the west
Project No. 07516-42-02 - 2 - September 18, 2020
property margin and the reclaimed water line on the eastern property margin will remain. The sewer
main that crosses the northern portion of the property will be removed.
Site topography is relatively flat, sloping from south to north towards the Otay River channel. A north-
facing natural slope, approximately 70 feet high is present along the south property boundary.
Elevations across the site range between approximately 95 and 180 feet above Mean Sea Level (MSL;
see Geologic Map, Figure 2).
A review of proposed grading plans by Civil Sense indicates proposed improvements will consist of
157 residential lots, a park, an underground stormwater management system, utilities, and street
improvements. Entrance to the property will be from a driveway at the southeast corner of the property
extending from Dennery Road. The proposed development includes cuts and fills up to 15 feet in sheet
graded areas and cut and fill slopes at inclinations of 2:1 (horizontal:vertical) with heights up to
55 feet.
The locations and descriptions of the site and proposed development are based on our recent site
reconnaissance, previous and recent field investigations, and our understanding of site development as
shown on the grading plan prepared by Civil Sense. If project details vary significantly from those
described, Geocon Incorporated should be contacted to review the changes and provide additional
analyses and/or revisions to this report, if warranted.
3. SOIL AND GEOLOGIC CONDITIONS
Based on the results of the field investigation, the site is underlain by four surficial soil types and one
formational unit, which are described below. Mapped geologic conditions are depicted on the
Geologic Map (Figure 2, map pocket) and Geologic Cross Sections (Figures 3 and 4). Trench and
boring logs are presented in Appendix A.
3.1 Undocumented Fill (Qudf)
We encountered undocumented fill in the trenches to depths of approximately 2 to 5 feet across the
majority of the site, increasing to greater than 18 feet in the northeast portion of the site. The
undocumented fill consists of very loose to moderately dense, sand with cobbles. Abundant debris
including pieces of plastic, asphalt concrete, concrete curb, brick and wood were also encountered in
the undocumented fill. The undocumented fill is compressible in its current state and will require
complete removal and recompaction to support compacted fill and/or proposed site improvements.
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3.2 Topsoil (Unmapped)
Topsoil covers the majority of the site and varies in thickness from 0.5 feet to 3 feet. The topsoil
typically consists of loose to moderately dense, dry to moist, sand, cobble and clay. The topsoil is
compressible and will require removal and recompaction to support compacted fill and/or proposed
site improvements.
3.3 Alluvium (Qal)
Alluvium is present in a drainage located at the southeast corner of the property. Alluvium was also
encountered in Trench T-20 beneath undocumented fill at the north end of the site. The alluvium
consists of stiff, damp, dark brown, sandy clay with gravel. The alluvium is compressible and will
require removal and recompaction to support compacted fill and/or proposed site improvements.
3.4 Colluvium (Qcol)
Colluvium is derived from weathering of the underlying bedrock materials at higher elevations and is
deposited by gravity and sheet-flow on the side slopes and canyon sidewalls. The observed thickness of
colluvium at the site was approximately 3 to 5 feet near trench T-6. The colluvium as encountered
consists of moderately dense, olive brown, clayey sand with cobbles. The colluvium is compressible in
its current state and will require removal and recompaction to support compacted fill and/or proposed
site improvements.
3.5 Terrace Deposits (Qt)
Quaternary-age Terrace Deposits were observed underlying artificial fill, topsoil, and alluvium in the
flatter portions of the site. The Terrace Deposits consist of moderately dense to very dense and firm to
very stiff, clayey gravel, clayey to cobbly sand, and silty to cobbly clay. Terrace Deposits are suitable
for support of compacted fill and/or structural loads.
3.6 Mission Valley Formation (Tmv)
Upper Eocene-age Mission Valley Formation was encountered in slopes along the southern portion of
the site. The Mission Valley Formation is predominantly a marine sandstone unit consisting of reddish
brown to tan, weak to friable, silty, fine- to medium-grained sandstone. The formation is typically
moderately to well cemented but is usually rippable with heavy duty excavation equipment; however,
localized cemented zones and concretions should be expected. The Mission Valley Formation is
suitable for the support of the compacted fill and structural loads.
Project No. 07516-42-02 - 4 - September 18, 2020
4. GROUNDWATER
We did not encounter groundwater or seepage during our recent or previous site investigations.
However, it is not uncommon for shallow seepage conditions to develop where none previously
existed when sites are irrigated or infiltration is implemented. Seepage is dependent on seasonal
precipitation, irrigation, land use, among other factors, and varies as a result. Proper surface drainage
will be important to future performance of the project. We expect the groundwater elevation at the site
to be between 80 and 90 feet MSL. We do not anticipate encountering groundwater during
construction of the proposed development.
5. GEOLOGIC HAZARDS
5.1 Faulting and Seismicity
A review of the referenced geologic materials and our knowledge of the general area indicates that the
site is not underlain by active, potentially active, or inactive faults. An active fault is defined by the
California Geological Survey (CGS) as a fault showing evidence for activity within the last
11,700 years. The site is not located within a State of California Earthquake Fault Zone.
The United States Geological Survey (USGS) has developed a program to evaluate the approximate
location of faulting. The following figure shows the location of the existing faulting in the San Diego
County and Southern California region. The faults are shown as solid, dashed and dotted traces
representing well-constrained, moderately constrained and inferred faults, respectively. The fault line
colors represent faults with ages less than 150 years (red), 15,000 years (orange), 130,000 years
(green), 750,000 years (blue) and 1.6 million years (black).
Project No. 07516-42-02 - 5 - September 18, 2020
Faults in the San Diego Area
The San Diego County and Southern California region is seismically active. The following figure
presents the occurrence of earthquakes with a magnitude greater than 2.5 from the period of 1900
through 2015 according to the Bay Area Earthquake Alliance website.
Project No. 07516-42-02 - 6 - September 18, 2020
Earthquakes in Southern California
Considerations important in seismic design include the frequency and duration of motion and the soil
conditions underlying the site. Seismic design of structures should be evaluated in accordance with the
California Building Code (CBC) guidelines currently adopted by the local agency.
5.2 Ground Rupture
The risk associated with ground rupture hazard is very low due to the absence of active faults at the
subject site.
5.3 Tsunamis and Seiches
The site is not located near the ocean or downstream of any large bodies of standing water. Therefore,
the risk of tsunamis or seiches associated with the site is low.
5.4 Flooding
According to maps produced by the Federal Emergency Management Agency (FEMA), the majority
of the site is zoned as “Zone X – Minimal Flood Hazard.” However, the limits of the 100- and 500-
year flood zones are on or immediately adjacent to the north property boundary. Based on our review
of FEMA flood maps, the risk of site flooding from channel overflow of the Otay River is low.
Project No. 07516-42-02 - 7 - September 18, 2020
5.5 Liquefaction and Seismically Induced Settlement
Soil liquefaction occurs within relatively loose, cohesionless sand located below the water table that is
subjected to ground accelerations from earthquakes. Due to the dense nature of the soils underlying the
site, proposed grading, and the lack of permanent, shallow groundwater, there is a low risk of
liquefaction occurring at the site.
5.6 Landslides
Based on our review of published geologic maps for the site vicinity, landslides are not mapped on the
property or at a location that could impact the site. Based on our review of historical aerial
photographs, landslide-related features are not discernable in the north-facing slope located near the
south property boundary. However, landslides have been mapped east of the site in the Otay
Formation, which overlies the Mission Valley Formation on the upthrown side of the La Nacion Fault
zone.
Bedding attitudes recorded during downhole logging of boring LD-1 are similar to those recorded in
areas surrounding the site. Steeper westerly dips ranging between 10 and 20 degrees were observed in
the boring, compared to three to five degrees west shown on local geologic maps. Steeper dips are
attributed to localized deformation resulting from movement on the La Nacion fault zone. The
proposed cut slope shown on the site plan is oriented perpendicular to strike, therefore no significant
out-of-slope dip component is anticipated. However, given the proximity of other landslides, we
recommend cut slope mapping during grading.
5.7 Geologic Hazard Category
Review of the 2008 City of San Diego Seismic Safety Study, Geologic Hazards and Faults, Sheet 6,
indicates the site is mapped as Geologic Hazard Categories 22 and 52. Category 22 is described as-
Landslides – possible or conjectured. Category 52 is described as-Other Terrain, other level areas,
gently sloping to steep terrain, favorable geologic structure, low risk.
Project No. 07516-42-02 - 8 - September 18, 2020
6. CONCLUSIONS AND RECOMMENDATIONS
6.1 General
6.1.1 No soil or geologic conditions were observed that would preclude the development of the
property as presently proposed provided that the recommendations of this report are
followed.
6.1.2 The site is underlain by compressible surficial deposits consisting of undocumented fill,
topsoil, colluvium, alluvium that generally range from 2 to 9 feet thick, but exceeds 18 feet
thick in the northwest portion of the site. The surficial soils will require complete removal
and recompaction.
6.1.3 Terrace deposits underlie the surficial deposits in the flatter areas of the site. The Tertiary-
aged Mission Valley Formation is exposed in the north facing slope adjacent to the south
property boundary. Terrace Deposits and the Mission Valley Formation are suitable for
support of the planned project.
6.1.4 With the exception of possible strong seismic shaking, no significant geologic hazards were
observed or are known to exist on the site that would adversely affect the site. No special
seismic design considerations, other than those recommended herein, are required.
6.1.5 Groundwater was not encountered during our investigation. However, groundwater may be
encountered during remedial grading on the north side of the property adjacent to the Otay
River channel.
6.1.6 Based on our experience and prior laboratory testing, we expect the majority of on-site soils
to possess a very low to medium expansion potential. We also expect the soils to have
negligible sulfate exposure to concrete structures.
6.1.7 Cut slopes should be observed and mapped during grading by an engineering geologist to
verify that the soil and geologic conditions do not differ significantly from those anticipated.
6.1.8 Provided the recommendations of this report are followed, it is our opinion that the
proposed development will not destabilize or result in settlement of adjacent properties and
City right-of-way.
Project No. 07516-42-02 - 9 - September 18, 2020
6.2 Soil and Excavation Characteristics
6.2.1 In general, special shoring requirements may not be necessary if temporary excavations will
be less than 4 feet in height. It is the responsibility of the contractor and their competent
person to ensure all excavations, temporary slopes and trenches are properly constructed and
maintained in accordance with applicable OSHA guidelines, in order to maintain safety and
the stability of the excavations and adjacent improvements. These excavations should not be
allowed to become saturated or to dry out. Surcharge loads should not be permitted to a
distance equal to the height of the excavation from the top of the excavation. The top of the
excavation should be a minimum of 15 feet from the edge of existing improvements.
Excavations steeper than those recommended or closer than 15 feet from an existing surface
improvement should be shored in accordance with applicable OSHA codes and regulations.
6.2.2 Excavation of existing undocumented fill and surficial deposits should be possible with
moderate to heavy effort using conventional heavy-duty equipment. Excavation of the
Mission Valley Formation may require very heavy effort with conventional heavy-duty
grading equipment.
6.2.3 The soil encountered during our field investigations is considered to be both “non-
expansive” (expansion index [EI] of 20 or less) and “expansive” (EI greater than 20) as
defined by 2019 California Building Code (CBC) Section 1803.5.3. Table 6.2.1 presents soil
classifications based on the expansion index. Based on prior laboratory test results, the
majority of the soil encountered is expected to possess a “very low” to “medium” expansion
potential. Samples of near pad grade soils should be collected after the completion of
grading to evaluate expansion index.
TABLE 6.2.1
EXPANSION CLASSIFICATION BASED ON EXPANSION INDEX
Expansion Index (EI) Expansion Classification 2019 CBC
Expansion Classification
0 – 20 Very Low Non-Expansive
21 – 50 Low
Expansive 51 – 90 Medium
91 – 130 High
Greater Than 130 Very High
6.2.4 Results from prior laboratory testing indicate the on-site soils possess an “S0” sulfate
exposure class to concrete structures as defined by 2019 CBC Section 1904 and ACI 318-08
Sections 4.2 and 4.3. Table 6.2.2 presents a summary of concrete requirements set forth by
Project No. 07516-42-02 - 10 - September 18, 2020
2019 CBC Section 1904 and ACI 318. The presence of water-soluble sulfates is not a
visually discernible characteristic; therefore, other soil samples from the site could yield
different concentrations. Additionally, over time landscaping activities (i.e., addition of
fertilizers and other soil nutrients) may affect the concentration. Samples of near pad grade
soils should be collected to evaluate water-soluble sulfates after the completion of grading.
TABLE 6.2.2
REQUIREMENTS FOR CONCRETE EXPOSED TO
SULFATE-CONTAINING SOLUTIONS
Exposure Class
Water-Soluble
Sulfate Percent
by Weight
Cement
Type
Maximum
Water to
Cement Ratio
by Weight
Minimum
Compressive
Strength (psi)
S0 0.00-0.10 -- -- 2,500
S1 0.10-0.20 II 0.50 4,000
S2 0.20-2.00 V 0.45 4,500
S3 > 2.00 V+Pozzolan or Slag 0.45 4,500
6.2.5 Geocon Incorporated does not practice in the field of corrosion engineering; therefore,
further evaluation by a corrosion engineer may be needed to incorporate the necessary
precautions to avoid premature corrosion of underground pipes and buried metal in direct
contact with soil.
6.3 Grading Recommendations
6.3.1 All grading should be performed in accordance with the Recommended Grading
Specifications contained in Appendix D. Where the recommendations of this section conflict
with those of Appendix D, the recommendations of this section take precedence. All
earthwork should be observed and all fill tested for proper compaction by Geocon
Incorporated.
6.3.2 Prior to commencing grading, a preconstruction conference should be held at the site with
the owner or developer, grading contractor, civil engineer, City of Chula Vista
representatives, and geotechnical engineer in attendance. Special soil handling and/or the
grading plans can be discussed at that time.
6.3.3 Site preparation should begin with the removal of deleterious material, debris, and
vegetation. The depth of vegetation removal should be such that material exposed in cut
areas or soil to be used as fill is relatively free of organic matter. Material generated during
Project No. 07516-42-02 - 11 - September 18, 2020
stripping and/or site demolition should be exported from the site. Asphalt and concrete
should not be mixed with the fill soil unless approved by the Geotechnical Engineer.
6.3.4 Abandoned foundations and buried utilities (if encountered) should be removed and the
resultant depressions and/or trenches backfilled with properly compacted soil as part of the
remedial grading.
6.3.5 All compressible soil deposits including undocumented fill, stockpiles, alluvium and
colluvium within areas where structural improvements and/or structural fills are planned,
should be removed to expose the underlying Terrace Deposits or Mission Valley Formation,
prior to placing additional fill and/or structural loads. The actual extent of unsuitable soil
removals will be evaluated in the field during grading by the geotechnical engineer and/or
engineering geologist.
6.3.6 Based on the current grading plan, cut to fill transitions are expected within some of the lots.
Lots with cut-fill transitions should be undercut at least 3 feet and replaced with properly
compacted fill. The undercut should be sloped at a minimum of 1 percent toward the street
or deeper fill area.
6.3.7 Removal of compressible surficial soils should extend beyond the toe of fill slopes a
horizontal distance equal to the depth of the remedial removal (see Figure 5 for general
information). The actual extent of remedial grading should be determined in the field by the
geotechnical engineer or engineering geologist.
6.3.8 Prior to placing fill, the base of excavations and surface of previously placed fill and
compacted fill should be scarified; moisture conditioned as necessary and compacted. Fill
soils may then be placed and compacted in layers to the design finish grade elevations. In
general, on-site soils are suitable for re-use as fill if free from vegetation, debris and other
deleterious material. Layers of fill should be no thicker than will allow for adequate bonding
and compaction. All fill, including scarified ground surfaces and backfill, should be
compacted to at least 90 percent of laboratory maximum dry density as determined by
ASTM D 1557 at or slightly above optimum moisture content. Overly wet materials will
require drying and/or mixing with drier soils to facilitate proper compaction.
6.3.9 The upper 3 feet of fill on all lots and streets should be composed of properly compacted
very low to low expansive soils. Highly expansive soils, if encountered, should be placed in
deeper fill areas and properly compacted. Very low to low expansive soils are defined as
those soils that have an Expansion Index of 50 or less. Boulders, concretions, concrete
chunks greater than 12 inches in maximum dimension should not be placed within 5 feet of
Project No. 07516-42-02 - 12 - September 18, 2020
finish grade or 3 feet from the deepest utility within streets. Specific recommendations for
the placement of oversize rock is contained in the Grading Specifications contained in
Appendix D.
6.3.10 Imported fill (if necessary) should consist of granular materials with a very low to low
expansion potential (EI of 50 or less), be free of deleterious material or stones larger than
3 inches, and should be compacted as recommended herein. Geocon Incorporated should be
notified of the import soil source and should be authorized to perform laboratory testing of
import soil prior to its arrival at the site to evaluate its suitability as fill material.
6.4 Slopes
6.4.1 Slope stability analyses were performed for proposed cut slopes up to 55 feet high (2:1
gradient), the existing hillside slope (2.5:1 or flatter) that has a height up to approximately
120 feet and extends onto the property to the south, and proposed fill slopes up to 10 feet in
height (2:1 gradient). The stability analyses were performed using simplified Janbu analysis.
Our analyses utilized average drained direct shear strength parameters based on laboratory
tests performed for this project and our experience with similar soils. The analyses indicate
planned cut and fill slopes, and the existing native perimeter slope will have a calculated
factors of safety in excess of 1.5 under static conditions for both deep-seated failure and
shallow sloughing conditions. A summary of slope stability analyses is presented on
Figures 6 through 9.
6.4.2 All cut slope excavations should be observed during grading by an engineering geologist to
verify that soil and geologic conditions do not differ significantly from those anticipated.
6.4.3 The outer 15 feet (or a distance equal to the height of the slope, whichever is less) of fill
slopes should be composed of properly compacted granular soil fill to reduce the potential
for surficial sloughing. Granular “soil” fill is defined as a well-graded soil mix with less
than 20 percent fines (silt and clay particles). Poorly graded soils with less than 5 percent
fines should not be used in the slope zone due to high erosion potential. All slopes should be
compacted by backrolling with a loaded sheepsfoot roller at vertical intervals not to exceed
4 feet and should be track-walked at the completion of each slope such that the fill soils are
uniformly compacted to at least 90 percent relative compaction to the face of the finished
sloped.
6.4.4 All slopes should be landscaped with drought-tolerant vegetation, having variable root
depths and requiring minimal landscape irrigation. In addition, all slopes should be drained
and properly maintained to reduce erosion.
Project No. 07516-42-02 - 13 - September 18, 2020
6.5 Seismic Design Criteria (2019)
6.5.1 Table 6.5.1 summarizes site-specific design criteria obtained from the 2019 California
Building Code (CBC; Based on the 2018 International Building Code [IBC] and ASCE 7-
16), Chapter 16 Structural Design, Section 1613 Earthquake Loads. We used the computer
program U.S. Seismic Design Maps, provided by the Structural Engineers Association of
California (SEAOC) to calculate the seismic design parameters. The short spectral response
uses a period of 0.2 second. We evaluated the Site Class based on the discussion in
Section 1613.2.2 of the 2019 CBC and Table 20.3-1 of ASCE 7-16. Site Class C can be
used for lots with fill thickness of 20 feet or less. Site Class D is applicable to lots with fill
thicknesses greater than 20 feet. The majority of the site falls within Site Class C. A couple
lots in the northwest corner might fall into Site Class D after completion of remedial
grading. The values presented herein are for the risk-targeted maximum considered
earthquake (MCER). Sites designated as Site Class D, E and F may require additional
analyses if requested by the project structural engineer and client.
TABLE 6.5.1
2019 CBC SEISMIC DESIGN PARAMETERS
Parameter Value 2019 CBC
Reference
Site Class C D Section 1613.2.2
MCER Ground Motion Spectral Response
Acceleration – Class B (short), SS 0.901g 0.901g Figure 1613.2.1(1)
MCER Ground Motion Spectral Response
Acceleration – Class B (1 sec), S1 0.315g 0.315g Figure 1613.2.1(2)
Site Coefficient, FA 1.2 1.14 Table 1613.2.3(1)
Site Coefficient, FV 1.5 1.985* Table 1613.2.3(2)
Site Class Modified MCER Spectral Response
Acceleration (short), SMS 1.081g 1.027g Section 1613.2.3
(Eqn 16-36)
Site Class Modified MCER Spectral Response
Acceleration – (1 sec), SM1 0.472g 0.625g* Section 1613.2.3
(Eqn 16-37)
5% Damped Design Spectral Response
Acceleration (short), SDS 0.721g 0.684g Section 1613.2.4
(Eqn 16-38)
5% Damped Design Spectral Response
Acceleration (1 sec), SD1 0.315g 0.417g* Section 1613.2.4
(Eqn 16-39)
* Using the code-based values presented in this table, in lieu of a performing a ground motion hazard
analysis, requires the exceptions outlined in ASCE 7-16 Section 11.4.8 be followed by the project
structural engineer. Per Section 11.4.8 of ASCE/SEI 7-16, a ground motion hazard analysis should
be performed for projects for Site Class “E” sites with Ss greater than or equal to 1.0g and for Site
Class “D” and “E” sites with S1 greater than 0.2g. Section 11.4.8 also provides exceptions which
indicates that the ground motion hazard analysis may be waived provided the exceptions are
followed.
Project No. 07516-42-02 - 14 - September 18, 2020
6.5.2 Table 6.5.2 presents the mapped maximum considered geometric mean (MCEG) seismic
design parameters for projects located in Seismic Design Categories of D through F in
accordance with ASCE 7-16.
TABLE 6.5.2
ASCE 7-16 PEAK GROUND ACCELERATION
Parameter Value ASCE 7-16 Reference
Site Class C D
Mapped MCEG Peak Ground
Acceleration, PGA 0.396 0.396 Figure 22-7
Site Coefficient, FPGA 1.2 1.204 Table 11.8-1
Site Class Modified MCEG Peak
Ground Acceleration, PGAM
0.475 0.477g Section 11.8.3 (Eqn 11.8-1)
6.5.3 Conformance to the criteria in Tables 6.5.1 and 6.5.2 for seismic design does not constitute
any kind of guarantee or assurance that significant structural damage or ground failure will
not occur if a large earthquake occurs. The primary goal of seismic design is to protect life,
not to avoid all damage, since such design may be economically prohibitive.
6.5.4 The project structural engineer and architect should evaluate the appropriate Risk Category
and Seismic Design Category for the planned structures. The values presented herein
assume a Risk Category of II and resulting in a Seismic Design Category D. Table 6.5.3
presents a summary of the risk categories.
TABLE 6.5.3
ASCE 7-16 RISK CATEGORIES
Risk Category Building Use Examples
I Low risk to Human Life at Failure Barn, Storage Shelter
II
Nominal Risk to Human Life at
Failure (Buildings Not Designated
as I, III or IV)
Residential, Commercial and Industrial
Buildings
III Substantial Risk to Human Life
at Failure
Theaters, Lecture Halls, Dining Halls,
Schools, Prisons, Small Healthcare
Facilities, Infrastructure Plants, Storage
for Explosives/Toxins
IV Essential Facilities
Hazardous Material Facilities,
Hospitals, Fire and Rescue, Emergency
Shelters, Police Stations, Power
Stations, Aviation Control Facilities,
National Defense, Water Storage
Project No. 07516-42-02 - 15 - September 18, 2020
6.6 Foundations
6.6.1 The following foundation recommendations apply to one- to three story structures and are
based on the building pads being underlain by properly compacted fill or native soils, and
soil within 3 feet of finish grade consisting of very low to medium expansive soils
(Expansion Index of 90 or less). The foundation recommendations have been separated into
three categories dependent on the thickness and geometry of the underlying fill soils as well
as the expansion index of the prevailing subgrade soils of a particular building pad (or lot).
The foundation category criteria are presented in Table 6.6.1
TABLE 6.6.1
FOUNDATION CATEGORY CRITERIA
Foundation
Category
Maximum Fill
Thickness, T (feet)
Differential Fill
Thickness, D (feet)
Expansion
Index (EI)
I T<20 -- EI<50
II 20<T<50 10<D<20 50<EI<90
III T>50 D>20 90<EI<130
6.6.2 We will provide final foundation categories for each building or lot after completion of
grading (finish pad grades have been achieved) and laboratory expansion testing of the
finish grade soils is complete.
6.6.3 The proposed structures can be supported on a shallow foundation system founded in the
compacted fill/formational materials. Foundations for the structure should consist of
continuous strip footings and/or isolated spread footings. Table 6.6.2 presents minimum
foundation and interior concrete slab design criteria for conventional foundation systems.
TABLE 6.6.2
CONVENTIONAL FOUNDATION RECOMMENDATIONS BY CATEGORY
Foundation
Category
Minimum Footing
Embedment
Depth (inches)
Continuous Footing
Reinforcement
Interior Slab
Reinforcement
I 12 Two No. 4 bars,
one top and one bottom
6 x 6 - 10/10 welded wire
mesh at slab mid-point
II 18 Four No. 4 bars,
two top and two bottom
No. 3 bars at 24 inches
on center, both directions
III 24 Four No. 5 bars,
two top and two bottom
No. 3 bars at 18 inches
on center, both directions
Project No. 07516-42-02 - 16 - September 18, 2020
6.6.4 Table 6.6.3 provides a summary of the foundation design recommendations.
TABLE 6.6.3
SUMMARY OF FOUNDATION RECOMMENDATIONS
Parameter Value
Minimum Continuous Foundation Width 12 inches
Minimum Isolated Foundation Width 24 inches
Minimum Foundation Depth See Table 6.6.2
Minimum Steel Reinforcement See Table 6.6.2
Allowable Bearing Capacity 2,000 psf
Bearing Capacity Increase 500 psf per additional foot of footing depth
300 psf per additional foot of footing width
Maximum Allowable Bearing Capacity 4,000 psf
Estimated Total Settlement 1 Inch
Estimated Differential Settlement ½ Inch in 40 Feet
Footing Size Used for Settlement 9-Foot Square
Design Expansion Index 50 or less
6.6.5 The foundations should be embedded in accordance with the recommendations herein and
the Wall/Column Footing Dimension Detail below. The embedment depths should be
measured from the lowest adjacent pad grade for both interior and exterior footings.
Footings should be deepened such that the bottom outside edge of the footing is at
least 7 feet horizontally from the face of the slope (unless designed with a post-tensioned
foundation system as discussed herein).
Wall/Column Footing Dimension Detail
6.6.6 The bearing capacity values presented herein are for dead plus live loads and may be
increased by one-third when considering transient loads due to wind or seismic forces.
Project No. 07516-42-02 - 17 - September 18, 2020
6.6.7 Under the recommended allowable bearing pressures provided, we expect settlement as a
result of building loading to be less than 1-inch total and ½-inch differential over a span of
40 feet.
6.6.8 Conventional building concrete slabs-on-grade should be at least 4 inches thick for
Foundation Categories I and II and 5 inches thick for Foundation Category III.
6.6.9 A vapor retarder should underlie slabs that may receive moisture-sensitive floor coverings
or may be used to store moisture-sensitive materials. The vapor retarder design should be
consistent with the guidelines presented in the American Concrete Institute’s (ACI) Guide
for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials (ACI 302.2R-06). In
addition, the membrane should be installed in accordance with manufacturer’s
recommendations and ASTM requirements and in a manner that prevents puncture. The
project architect or developer should specify the type of vapor retarder used based on the
type of floor covering that will be installed and if the structure will possess a humidity
controlled environment.
6.6.10 The project foundation engineer, architect, and/or developer should determine the thickness
of bedding sand below the slab. However, Geocon should be contacted to provide
recommendations if the bedding sand is thicker than 6 inches.
6.6.11 The foundation design engineer should provide appropriate concrete mix design criteria and
curing measures to assure proper curing of the slab by reducing the potential for rapid
moisture loss and subsequent cracking and/or slab curl. We suggest that the foundation
design engineer present the concrete mix design and proper curing methods on the
foundation plans. It is critical that the foundation contractor understands and follows the
specifications presented on the foundation plans.
6.6.12 As an alternative to the conventional foundation recommendations, consideration should be
given to the use of post-tensioned concrete slab and foundation systems for the support of
the proposed structures. The post-tensioned systems should be designed by a structural
engineer experienced in post-tensioned slab design and design criteria of the Post-
Tensioning Institute (PTI) DC10.5 Standard Requirements for Design and Analysis of
Shallow Post-Tensioned Concrete Foundations on Expansive Soils or WRI/CRSI Design of
Slab-on-Ground Foundations, as required by the 2019 California Building Code (CBC
Section 1808.6.2). Although this procedure was developed for expansive soil conditions, we
understand it can also be used to reduce the potential for foundation distress due to
differential fill settlement. The post-tensioned design should incorporate the geotechnical
Project No. 07516-42-02 - 18 - September 18, 2020
parameters presented on Table 6.6.4. The parameters presented in Table 6.6.4 are based on
the guidelines presented in the PTI, DC10.5 design manual.
TABLE 6.6.4
POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS
Post-Tensioning Institute (PTI),
Third Edition Design Parameters
Foundation Category
I II III
Thornthwaite Index -20 -20 -20
Equilibrium Suction 3.9 3.9 3.9
Edge Lift Moisture Variation Distance, eM (feet) 5.3 5.1 4.9
Edge Lift, yM (inches) 0.61 1.10 1.58
Center Lift Moisture Variation Distance, eM (feet) 9.0 9.0 9.0
Center Lift, yM (inches) 0.30 0.47 0.66
6.6.13 The foundations for the post-tensioned slabs should be embedded in accordance with the
recommendations of the structural engineer. For moisture cut-off, we recommend the
perimeter foundation have an embedment depth of at least 12 inches. If a post-tensioned mat
foundation system is planned, the slab should possess a thickened edge with a minimum
width of 12 inches that extends at least 12 inches below the clean sand layer.
6.6.14 If the structural engineer proposes a post-tensioned foundation design method other than
PTI, DC 10.5:
The deflection criteria presented in Table 6.6.4 are still applicable.
Interior stiffener beams should be used for Foundation Categories II and III.
The width of the perimeter foundations should be at least 12 inches.
The perimeter footing embedment depths should be at least 12 inches, 18 inches and
24 inches for foundation categories I, II, and III, respectively. The embedment
depths should be measured from the lowest adjacent pad grade.
6.6.15 Foundation systems for the lots that possess a foundation Category I and a “very low”
expansion potential (expansion index of 20 or less) can be designed using the method
described in Section 1808 of the 2019 CBC. If post-tensioned foundations are planned, an
alternative, commonly accepted design method (other than PTI) can be used. However, the
post-tensioned foundation system should be designed with a total and differential deflection
of 1 inch. Geocon Incorporated should be contacted to review the plans and provide
additional information, if necessary.
Project No. 07516-42-02 - 19 - September 18, 2020
6.6.16 If an alternate design method is contemplated, Geocon Incorporated should be contacted to
evaluate if additional expansion index testing should be performed to identify the lots that
possess a “very low” expansion potential (expansion index of 20 or less).
6.6.17 Our experience indicates post-tensioned slabs are susceptible to excessive edge lift,
regardless of the underlying soil conditions. Placing reinforcing steel at the bottom of the
perimeter footings and the interior stiffener beams may mitigate this potential. Current PTI
design procedures primarily address the potential center lift of slabs but, because of the
placement of the reinforcing tendons in the top of the slab, the resulting eccentricity after
tensioning reduces the ability of the system to mitigate edge lift. The structural engineer
should design the foundation system to reduce the potential of edge lift occurring for the
proposed structures.
6.6.18 During the construction of the post-tension foundation system, the concrete should be
placed monolithically. Under no circumstances should cold joints form between the
footings/grade beams and the slab during the construction of the post-tension foundation
system unless designed by the project structural engineer.
6.6.19 Isolated footings outside of the slab area, if present, should have the minimum embedment
depth and width recommended for conventional foundations for a particular Foundation
Category. The use of isolated footings, which are located beyond the perimeter of the
building and support structural elements connected to the building, are not recommended for
Category III. Where this condition cannot be avoided, the isolated footings should be
connected to the building foundation system with grade beams. In addition, consideration
should be given to connecting patio slabs, which exceed 5 feet in width, to the building
foundation to reduce the potential for future separation to occur.
6.6.20 Interior stiffening beams should be incorporated into the design of the foundation system in
accordance with the PTI design procedures.
6.6.21 Special subgrade presaturation is not deemed necessary prior to placing concrete; however,
the exposed foundation and slab subgrade soil should be moisture conditioned, as necessary,
to maintain a moist condition as would be expected in any such concrete placement.
6.6.22 Where buildings or other improvements are planned near the top of a slope steeper than 3:1
(horizontal:vertical), special foundations and/or design considerations are recommended due
to the tendency for lateral soil movement to occur.
Project No. 07516-42-02 - 20 - September 18, 2020
For fill slopes less than 20 feet high or cut slopes regardless of height, footings
should be deepened such that the bottom outside edge of the footing is at least 7 feet
horizontally from the face of the slope.
For fill slopes greater than 20 feet high, foundations should be extended to a depth
where the minimum horizontal distance is equal to H/3 (where H equals the vertical
distance from the top of the fill slope to the base of the fill soil) with a minimum of
7 feet but need not exceed 40 feet. The horizontal distance is measured from the
outer, deepest edge of the footing to the face of the slope. A post-tensioned slab and
foundation system or mat foundation system can be used to help reduce potential
foundation distress associated with slope creep and lateral fill extension. Specific
design parameters or recommendations for either of these alternatives can be
provided once the building location and fill slope geometry have been determined.
If swimming pools are planned, Geocon Incorporated should be contacted for a
review of specific site conditions.
Swimming pools located within 7 feet of the top of cut or fill slopes are not
recommended. Where such a condition cannot be avoided, the portion of the
swimming pool wall within 7 feet of the slope face be designed assuming that the
adjacent soil provides no lateral support. This recommendation applies to fill slopes
up to 30 feet in height, and cut slopes regardless of height. For swimming pools
located near the top of fill slopes greater than 30 feet in height, additional
recommendations may be required and Geocon Incorporated should be contacted
for a review of specific site conditions.
Although other improvements that are relatively rigid or brittle, such as concrete
flatwork or masonry walls, may experience some distress if located near the top of a
slope, it is generally not economical to mitigate this potential. It may be possible,
however, to incorporate design measures that would permit some lateral soil
movement without causing extensive distress. Geocon Incorporated should be
consulted for specific recommendations.
6.6.23 The recommendations of this report are intended to reduce the potential for cracking of slabs
due to expansive soil (if present), differential settlement of existing soil or soil with varying
thicknesses. However, even with the incorporation of the recommendations presented
herein, foundations, stucco walls, and slabs-on-grade placed on such conditions may still
exhibit some cracking due to soil movement and/or shrinkage. The occurrence of concrete
shrinkage cracks is independent of the supporting soil characteristics. The occurrence may
be reduced and/or controlled by: limiting the slump of the concrete, proper concrete
placement and curing, and by the placement of crack control joints at periodic intervals, in
particular, where re-entrant slab corners occur.
6.6.24 Geocon Incorporated should be consulted to provide additional design parameters as
required by the structural engineer.
Project No. 07516-42-02 - 21 - September 18, 2020
6.7 Conventional Retaining Wall Recommendations
6.7.1 Retaining walls should be designed using the values presented in Table 6.7.1. Soil with an
expansion index (EI) of greater than 50 should not be used as backfill material behind
retaining walls.
TABLE 6.7.1
RETAINING WALL DESIGN RECOMMENDATIONS
Parameter
Value
EI<50 EI<90
Active Soil Pressure, A (Fluid Density, Level Backfill) 35 pcf 40 pcf
Active Soil Pressure, A (Fluid Density, 2:1 Sloping Backfill) 45 psf 55 pcf
Seismic Pressure, S 15H psf
At-Rest/Restrained Walls Additional Uniform Pressure (0 to 8 Feet High) 7H psf
At-Rest/Restrained Walls Additional Uniform Pressure (8+ Feet High) 13H psf
Expected Expansion Index for the Subject Property EI<50
H equals the height of the retaining portion of the wall
6.7.2 The project retaining walls should be designed as shown in the Retaining Wall Loading
Diagram.
Retaining Wall Loading Diagram
Project No. 07516-42-02 - 22 - September 18, 2020
6.7.3 Unrestrained walls are those that are allowed to rotate more than 0.001H (where H equals
the height of the retaining portion of the wall) at the top of the wall. Where walls are
restrained from movement at the top (at-rest condition), an additional uniform pressure of
7H psf should be added to the active soil pressure for walls 8 feet or less. For walls greater
than 8 feet tall, an additional uniform pressure of 13H psf should be applied to the wall
starting at 8 feet from the top of the wall to the base of the wall. For retaining walls subject
to vehicular loads within a horizontal distance equal to two-thirds the wall height, a
surcharge equivalent to 2 feet of fill soil should be added.
6.7.4 The structural engineer should determine the Seismic Design Category for the project in
accordance with Section 1613.2.5 of the 2019 CBC or Section 11.6 of ASCE 7-16. For
structures assigned to Seismic Design Category of D, E, or F, retaining walls that support
more than 6 feet of backfill should be designed with seismic lateral pressure in accordance
with Section 1803.5.12 of the 2019 CBC. The seismic load is dependent on the retained
height where H is the height of the wall, in feet, and the calculated loads result in pounds per
square foot (psf) exerted at the base of the wall and zero at the top of the wall. A seismic
load of 17H psf should be used for design. We used the peak ground acceleration adjusted
for Site Class effects, PGAM, of 0.477g calculated from ASCE 7-16 Section 11.8.3 and
applied a pseudo-static coefficient of 0.3.
6.7.5 Retaining walls should be designed to ensure stability against overturning sliding, and
excessive foundation pressure. Where a keyway is extended below the wall base with the
intent to engage passive pressure and enhance sliding stability, it is not necessary to
consider active pressure on the keyway.
6.7.6 Drainage openings through the base of the wall (weep holes) should not be used where the
seepage could be a nuisance or otherwise adversely affect the property adjacent to the base
of the wall. The recommendations herein assume a properly compacted granular (EI of 50 or
less) free-draining backfill material with no hydrostatic forces or imposed surcharge load.
The retaining wall should be properly drained as shown in the Typical Retaining Wall
Drainage Detail. If conditions different than those described are expected, or if specific
drainage details are desired, Geocon Incorporated should be contacted for additional
recommendations.
Project No. 07516-42-02 - 23 - September 18, 2020
Typical Retaining Wall Drainage Detail
6.7.7 The retaining walls may be designed using either the active and restrained (at-rest) loading
condition or the active and seismic loading condition as suggested by the structural
engineer. Typically, it appears the design of the restrained condition for retaining wall
loading may be adequate for the seismic design of the retaining walls. However, the active
earth pressure combined with the seismic design load should be reviewed and also
considered in the design of the retaining walls.
6.7.8 In general, wall foundations having should be designed in accordance with Table 6.7.2. The
proximity of the foundation to the top of a slope steeper than 3:1 could impact the allowable
soil bearing pressure. Therefore, retaining wall foundations should be deepened such that
the bottom outside edge of the footing is at least 7 feet horizontally from the face of the
slope.
TABLE 6.7.2
SUMMARY OF RETAINING WALL FOUNDATION RECOMMENDATIONS
Parameter Value
Minimum Retaining Wall Foundation Width 12 inches
Minimum Retaining Wall Foundation Depth 12 Inches
Minimum Steel Reinforcement Per Structural Engineer
Bearing Capacity 2,000 psf
Bearing Capacity Increase 500 psf per additional foot of footing depth
300 psf per additional foot of footing width
Maximum Bearing Capacity 4,000 psf
Estimated Total Settlement 1 Inch
Estimated Differential Settlement ½ Inch in 40 Feet
Project No. 07516-42-02 - 24 - September 18, 2020
6.7.9 The recommendations presented herein are generally applicable to the design of rigid
concrete or masonry retaining walls. In the event that other types of walls (such as
mechanically stabilized earth [MSE] walls, soil nail walls, or soldier pile walls) are planned,
Geocon Incorporated should be consulted for additional recommendations.
6.7.10 Unrestrained walls will move laterally when backfilled and loading is applied. The amount
of lateral deflection is dependent on the wall height, the type of soil used for backfill, and
loads acting on the wall. The retaining walls and improvements above the retaining walls
should be designed to incorporate an appropriate amount of lateral deflection as determined
by the structural engineer.
6.7.11 Soil contemplated for use as retaining wall backfill, including import materials, should be
identified in the field prior to backfill. At that time, Geocon Incorporated should obtain
samples for laboratory testing to evaluate its suitability. Modified lateral earth pressures
may be necessary if the backfill soil does not meet the required expansion index or shear
strength. City or regional standard wall designs, if used, are based on a specific active lateral
earth pressure and/or soil friction angle. In this regard, on-site soil to be used as backfill may
or may not meet the values for standard wall designs. Geocon Incorporated should be
consulted to assess the suitability of the on-site soil for use as wall backfill if standard wall
designs will be used.
6.8 Lateral Loading
6.8.1 Table 6.8 should be used to help design the proposed structures and improvements to resist
lateral loads for the design of footings or shear keys. The allowable passive pressure
assumes a horizontal surface extending at least 5 feet, or three times the surface generating
the passive pressure, whichever is greater. The upper 12 inches of material in areas not
protected by floor slabs or pavement should not be included in design for passive resistance.
Where walls are planned adjacent to and/or on descending slopes, a passive pressure of
150 pcf should be used in design.
TABLE 6.8
SUMMARY OF LATERAL LOAD DESIGN RECOMMENDATIONS
Parameter Value
Passive Pressure Fluid Density 300 pcf
Passive Pressure Fluid Density Adjacent to and/or on Descending Slopes 150 pcf
Coefficient of Friction (Concrete and Soil) 0.35
Coefficient of Friction (Along Vapor Barrier) 0.2 to 0.25*
* Per manufacturer’s recommendations.
Project No. 07516-42-02 - 25 - September 18, 2020
6.8.2 The passive and frictional resistant loads can be combined for design purposes. The lateral
passive pressures may be increased by one-third when considering transient loads due to
wind or seismic forces.
6.9 Preliminary Pavement Recommendations
6.9.1 Preliminary pavement recommendations for the streets and parking areas are provided
below. The final pavement sections should be based on the R-Value of the subgrade soil
encountered at final subgrade elevation. For pavement design we used a laboratory R-Value
of 10. Preliminary flexible pavement sections are presented in 6.9.1. We calculated the
flexible pavement sections in general conformance with the Caltrans Method of Flexible
Pavement Design (Highway Design Manual, Section 608.4) using estimated Traffic Indices
(TI) in general accordance with City of Chula Vista guidelines (the City requires that private
streets be designed in general accordance with City standards). The project civil engineer or
traffic engineer should determine the appropriate Traffic Index (TI) or traffic loading
expected on the project for the various pavement areas that will be constructed.
TABLE 6.9.1
PRELIMINARY ASPHALT CONCRETE PAVEMENT SECTIONS
Location Minimum
Traffic Index
Assumed
Subgrade
R-Value
Asphalt
Concrete
(inches)
Class 2
Aggregate
Base (inches)
Residential Cul-De-Sac 5.0 10 3 9
Residential 6.0 10 3 12.5
6.9.2 Asphalt concrete should conform to Section 203-6 of the Standard Specifications for Public
Works Construction (Green Book). Cement treated base should conform to Greenbook
Section 301-3.3. Class 2 aggregate base materials should conform to Section 26-1.02B of
the Standard Specifications of the State of California, Department of Transportation
(Caltrans).
6.9.3 Prior to placing base material, the subgrade should be scarified, moisture conditioned and
recompacted to a minimum of 95 percent relative compaction. The depth of compaction
should be at least 12 inches. The base material should be compacted to at least 95 percent
relative compaction. Asphalt concrete should be compacted to a density of at least
95 percent of the laboratory Hveem density in accordance with ASTM D 2726.
6.9.4 A rigid Portland Cement concrete (PCC) pavement section should be placed in driveway
entrance aprons. The concrete pad for trash truck areas should be large enough such that the
Project No. 07516-42-02 - 26 - September 18, 2020
truck wheels will be positioned on the concrete during loading. We calculated the rigid
pavement section in general conformance with the procedure recommended by the
American Concrete Institute report ACI 330R-08 Guide for Design and Construction of
Concrete Parking Lots using the parameters presented in Table 6.9.2.
TABLE 6.9.2
PRELIMINARY RIGID PAVEMENT DESIGN PARAMETERS
Design Parameter Design Value
Modulus of subgrade reaction, k 50 pci
Modulus of rupture for concrete, MR 500 psi
Traffic Category, TC A-1 and B
Average daily truck traffic, ADTT 1 and 25
6.9.5 Based on the criteria presented herein, the PCC pavement sections should have a minimum
thickness as presented in Table 6.9.3.
TABLE 6.9.3
PRELIMINARY RIGID PAVEMENT RECOMMENDATIONS
Location Portland Cement Concrete (inches)
Automobile Areas (TC=A-1, ADDT = 1) 5.5
Heavy Truck and Fire Lane Areas (TC=C, ADDT = 100) 7.0
6.9.6 The PCC pavement should be placed over subgrade soil that is compacted to a dry density
of at least 95 percent of the laboratory maximum dry density near to slightly above optimum
moisture content. For single-family residential lot driveways, 90 percent of the laboratory
maximum dry density near to slightly above optimum moisture content is acceptable. This
pavement section is based on a minimum concrete compressive strength of approximately
3,200 psi (pounds per square inch).
6.9.7 A thickened edge or integral curb should be constructed on the outside of concrete slabs
subjected to wheel loads. The thickened edge should be 1.2 times the slab thickness or a
minimum thickness of 2 inches, whichever results in a thicker edge, at the slab edge and
taper back to the recommended slab thickness 3 feet behind the face of the slab (e.g., a
7-inch-thick slab would have a 9-inch-thick edge). Reinforcing steel will not be necessary
within the concrete for geotechnical purposes with the exception of loading docks, trash bin
enclosures, and dowels at construction joints as discussed below.
Project No. 07516-42-02 - 27 - September 18, 2020
6.9.8 To control the location and spread of concrete shrinkage cracks, crack-control joints
(weakened plane joints) should be included in the design of the concrete pavement slab.
Crack-control joints should not exceed 30 times the slab thickness with a maximum spacing
of 15 feet (e.g., a 7-inch-thick slab would have a 15-foot spacing pattern) and should be
sealed with an appropriate sealant to prevent the migration of water through the control joint
to the subgrade materials. The depth of the crack-control joints should be determined by the
referenced ACI report.
6.9.9 To provide load transfer between adjacent pavement slab sections, a trapezoidal-keyed
construction joint should be installed. As an alternative to the keyed joint, dowelling is
recommended between construction joints. As discussed in the referenced ACI guide,
dowels should consist of smooth, ⅞-inch-diameter reinforcing steel 14 inches long
embedded a minimum of 6 inches into the slab on either side of the construction joint.
Dowels should be located at the midpoint of the slab, spaced at 12 inches on center and
lubricated to allow joint movement while still transferring loads. The project structural
engineer may provide alternative recommendations for load transfer.
6.9.10 The performance of pavement is highly dependent on providing positive surface drainage
away from the edge of the pavement. Ponding of water on or adjacent to the pavement will
likely result in pavement distress and subgrade failure. Drainage from landscaped areas
should be directed to controlled drainage structures. Landscape areas adjacent to the edge of
asphalt pavements are not recommended due to the potential for surface or irrigation water
to infiltrate the underlying permeable aggregate base and cause distress. Where such a
condition cannot be avoided, consideration should be given to incorporating measures that
will significantly reduce the potential for subsurface water migration into the aggregate
base. If planter islands are planned, the perimeter curb should extend at least 6 inches below
the level of the base materials.
6.10 Exterior Concrete Flatwork
6.10.1 Exterior concrete flatwork not subject to vehicular traffic should be constructed in
accordance with the recommendations presented in Table 6.10. The recommended steel
reinforcement would help reduce the potential for cracking.
Project No. 07516-42-02 - 28 - September 18, 2020
TABLE 6.10
MINIMUM CONCRETE FLATWORK RECOMMENDATIONS
Expansion
Index, EI Minimum Steel Reinforcement* Options Minimum
Thickness
EI < 90 6x6-W2.9/W2.9 (6x6-6/6) welded wire mesh
4 Inches No. 3 Bars 18 inches on center, Both Directions
EI < 130 4x4-W4.0/W4.0 (4x4-4/4) welded wire mesh
No. 4 Bars 12 inches on center, Both Directions
* In excess of 8 feet square.
6.10.2 Even with the incorporation of the recommendations of this report, the exterior concrete
flatwork has a potential to experience some uplift due to expansive soil beneath grade. The
steel reinforcement should overlap continuously in flatwork to reduce the potential for
vertical offsets within flatwork. Additionally, flatwork should be structurally connected to
the curbs, where possible, to reduce the potential for offsets between the curbs and the
flatwork.
6.10.3 Concrete flatwork should be provided with crack control joints to reduce and/or control
shrinkage cracking. Crack control spacing should be determined by the project structural
engineer based upon the slab thickness and intended usage. Criteria of the American
Concrete Institute (ACI) should be taken into consideration when establishing crack control
spacing. Subgrade soil for exterior slabs not subjected to vehicle loads should be compacted
in accordance with criteria presented in the grading section prior to concrete placement.
Subgrade soil should be properly compacted, and the moisture content of subgrade soil
should be verified prior to placing concrete. Base materials will not be required below
concrete improvements.
6.10.4 The recommendations presented herein are intended to reduce the potential for cracking of
exterior slabs as a result of differential movement. However, even with the incorporation of
the recommendations presented herein, slabs-on-grade will still crack. The occurrence of
concrete shrinkage cracks is independent of the soil supporting characteristics. Their
occurrence may be reduced and/or controlled by limiting the slump of the concrete, the use
of crack control joints and proper concrete placement and curing. Crack control joints
should be spaced at intervals no greater than 12 feet. Literature provided by the Portland
Concrete Association (PCA) and American Concrete Institute (ACI) present
recommendations for proper concrete mix, construction, and curing practices, and should be
incorporated into project construction.
Project No. 07516-42-02 - 29 - September 18, 2020
6.11 Slope Maintenance
6.11.1 Slopes that are steeper than 3:1 (horizontal:vertical) may, under conditions which are both
difficult to prevent and predict, be susceptible to near surface (surficial) slope instability.
The instability is typically limited to the outer three feet of a portion of the slope and usually
does not directly impact the improvements on the pad areas above or below the slope. The
occurrence of surficial instability is more prevalent on fill slopes and is generally preceded
by a period of heavy rainfall, excessive irrigation, or the migration of subsurface seepage.
The disturbance and/or loosening of the surficial soils, as might result from root growth, soil
expansion, or excavation for irrigation lines and slope planting, may also be a significant
contributing factor to surficial instability. It is, therefore, recommended that, to the
maximum extent practical: (a) disturbed/loosened surficial soils be either removed or
properly recompacted, (b) irrigation systems be periodically inspected and maintained to
eliminate leaks and excessive irrigation, and (c) surface drains on and adjacent to slopes be
periodically maintained to preclude ponding or erosion. Although the incorporation of the
above recommendations should reduce the potential for surficial slope instability, it will not
eliminate the possibility, and, therefore, it may be necessary to rebuild or repair a portion of
the project's slopes in the future.
6.12 Storm Water Management
6.12.1 If storm water management devices are not properly designed and constructed, there is a
risk for distress to improvements and property located hydrologically down gradient or
adjacent to these devices. Factors such as the amount of water being detained, its residence
time, and soil permeability have an important effect on seepage transmission and the
potential adverse impacts that may occur if the storm water management features are not
properly designed and constructed. We have not performed a hydrogeological study at the
site. If infiltration of storm water runoff into the subsurface occurs, downstream
improvements may be subjected to seeps, springs, slope instability, raised groundwater,
movement of foundations and slabs, or other undesirable impacts as a result of water
infiltration.
6.12.2 We performed an infiltration study on the property. A summary of our study and storm
water management recommendations are provided in Appendix C. Based on the results of
our study, full and partial infiltration is considered infeasible due to the presence
undocumented fills, low infiltration characteristics, and existing nearby utilities. Basins
should utilize a liner to prevent infiltration from causing adverse settlement, migrating to
adjacent slopes, utilities, and foundations.
Project No. 07516-42-02 - 30 - September 18, 2020
6.13 Site Drainage and Moisture Protection
6.13.1 Adequate site drainage is critical to reduce the potential for differential soil movement,
erosion and subsurface seepage. Under no circumstances should water be allowed to pond
adjacent to footings. The site should be graded and maintained such that surface drainage is
directed away from structures in accordance with 2019 CBC 1803.3 or other applicable
standards. In addition, surface drainage should be directed away from the top of slopes into
swales or other controlled drainage devices. Roof and pavement drainage should be directed
into conduits that carry runoff away from the proposed structure.
6.13.2 In the case of basement walls or building walls retaining landscaping areas, a water-proofing
system should be used on the wall and joints, and a Miradrain drainage panel (or similar)
should be placed over the waterproofing. The project architect or civil engineer should
provide detailed specifications on the plans for all waterproofing and drainage.
6.13.3 Underground utilities should be leak free. Utility and irrigation lines should be checked
periodically for leaks, and detected leaks should be repaired promptly. Detrimental soil
movement could occur if water is allowed to infiltrate the soil for prolonged periods of time.
6.13.4 Landscaping planters adjacent to paved areas are not recommended due to the potential for
surface or irrigation water to infiltrate the pavement's subgrade and base course. We
recommend that subdrains to collect excess irrigation water and transmit it to drainage
structures, or impervious above-grade planter boxes be used. In addition, where landscaping
is planned adjacent to the pavement, we recommend construction of a cutoff wall along the
edge of the pavement that extends at least 6 inches below the bottom of the base material.
6.14 Grading and Foundation Plan Review
6.14.1 Geocon Incorporated should review the grading plans and foundation plans for the project
prior to final design submittal to evaluate whether additional analyses and/or
recommendations are required.
Project No. 07516-42-02 September 18, 2020
LIMITATIONS AND UNIFORMITY OF CONDITIONS
1. The firm that performed the geotechnical investigation for the project should be retained to
provide testing and observation services during construction to provide continuity of
geotechnical interpretation and to check that the recommendations presented for
geotechnical aspects of site development are incorporated during site grading, construction
of improvements, and excavation of foundations. If another geotechnical firm is selected to
perform the testing and observation services during construction operations, that firm should
prepare a letter indicating their intent to assume the responsibilities of project geotechnical
engineer of record. A copy of the letter should be provided to the regulatory agency for their
records. In addition, that firm should provide revised recommendations concerning the
geotechnical aspects of the proposed development, or a written acknowledgement of their
concurrence with the recommendations presented in our report. They should also perform
additional analyses deemed necessary to assume the role of Geotechnical Engineer of
Record.
2. The recommendations of this report pertain only to the site investigated and are based upon
the assumption that the soil conditions do not deviate from those disclosed in the
investigation. If any variations or undesirable conditions are encountered during
construction, or if the proposed construction will differ from that anticipated herein, Geocon
Incorporated should be notified so that supplemental recommendations can be given. The
evaluation or identification of the potential presence of hazardous or corrosive materials was
not part of the scope of services provided by Geocon Incorporated.
3. This report is issued with the understanding that it is the responsibility of the owner or his
representative to ensure that the information and recommendations contained herein are
brought to the attention of the architect and engineer for the project and incorporated into
the plans, and the necessary steps are taken to see that the contractor and subcontractors
carry out such recommendations in the field.
4. The findings of this report are valid as of the present date. However, changes in the
conditions of a property can occur with the passage of time, whether they be due to natural
processes or the works of man on this or adjacent properties. In addition, changes in
applicable or appropriate standards may occur, whether they result from legislation or the
broadening of knowledge. Accordingly, the findings of this report may be invalidated
wholly or partially by changes outside our control. Therefore, this report is subject to review
and should not be relied upon after a period of three years.
Main St
SITESITE
NO SCALE
FIG. 1
THE GEOGRAPHICAL INFORMATION MADE AVAILABLE FOR DISPLAY WAS PROVIDED BY GOOGLE EARTH,
SUBJECT TO A LICENSING AGREEMENT. THE INFORMATION IS FOR ILLUSTRATIVE PURPOSES ONLY; IT IS
NOT INTENDED FOR CLIENT'S USE OR RELIANCE AND SHALL NOT BE REPRODUCED BY CLIENT. CLIENT
SHALL INDEMNIFY, DEFEND AND HOLD HARMLESS GEOCON FROM ANY LIABILITY INCURRED AS A RESULT
OF SUCH USE OR RELIANCE BY CLIENT.
VICINITY MAP
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
DSK/GTYPD PROJECT NO. 07516 - 42 - 02RM / AML
NAKANO
CHULA VISTA, CALIFORNIAGEOTECHNICAL ENVIRONMENTAL MATERIALS
Plotted:09/17/2020 10:42AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\07516-42-02 (Nakano)\DETAILS\07516-42-02 Vic Map.dwg
DATE 09 - 18 - 2020
?
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A
A'
B
B'
C
C'
D
D'
Qt
Qt
Qt
Qt
Qt
Qt
Qt
Tmv Tmv
Tmv QafTmv
Qaf
Qaf
Qal
Qudf/
Qudf/
Qudf/
T-18
T-19
T-22
T-21
T-20
T-12
T-11
T-23 T-17
T-16
T-14
T-10
T-15
T-13
T-9
T-8
T-4
T-6
T-7
T-5
T-3 T-1
T-2
Qaf
Qaf
Tsdcg
(2)
(2)
(2)
(3)(3)
(2)
(2)
(5)
(3)
(2)
(2)
(2)
(2)
(2)
(3)(2)
(2)
(+18)
(5)
(5)
(9)
(2)
(2)
@7' =
@15' =
@24' =
@29' =
@36' =
@58' =
10-15°
16°
65°
21°
20°
?
11°
?
LD-1
?
?
?
?
A-2
?
A-1
(6)
?
?
??
?
?
?
?
APPROX. LIMITS OF
DISTURBANCE/REMEDIAL
GRADING
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159 SHEET OF
PROJECT NO.
SCALE DATE
FIGURE
Plotted:09/17/2020 10:27AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\07516-42-02 (Nakano)\SHEETS\07516-42-02 Geo Map.20.dwg
GEOTECHNICAL ENVIRONMENTAL MATERIALS
1" =
GEOLOGIC MAP
NAKANO
CHULA VISTA, CALIFORNIA
60'09 - 18 - 2020
07516 - 42 - 02
1 1 2
........UNDOCUMENTED FILL
........ARTIFICIAL FILL
........ALLUVIUM
........TERRACE DEPOSITS
(Dotted Where Buried)
........SAN DIEGO FORMATION (Conglomerate)
........MISSION VALLEY FORMATION
........APPROX. LOCATION OF GEOLOGIC CONTACT
(Queried Where Uncertain)
........APPROX. LOCATION OF BORING
........APPROX. LOCATION OF INFILTRATION TEST
........APPROX. DEPTH OF REMEDIAL GRADING (In Feet, MSL)
........APPROX. LOCATIION OF GEOLOGIC CROSS SECTION
LD-1
D D'
GEOCON LEGEND
?
Qudf
Qaf
Qal
Qt
Tmv
Tsdcg
(5)
A-2
0 12060 180 240 300 360 420 480 540 720600660 780 840 900 960 114010201080 1200 1260 1320
0 12060 180 240 300 360 420 480 540 720600660 780 840 900 960 114010201080 1200 1260 1320
D I S T A N C E
SCALE: 1" = 60' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION A-A'
D I S T A N C E
SCALE: 1" = 60' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION B-B'
0
60
120
180
240
A
E
L
E
V
A
T
I
O
N
(
M
S
L
)
0
60
120
180
240
B
E
L
E
V
A
T
I
O
N
(
M
S
L
)
A'
E
L
E
V
A
T
I
O
N
(
M
S
L
)
0
60
120
180
240
B'
E
L
E
V
A
T
I
O
N
(
M
S
L
)
0
60
120
180
240
PL
PL
PL
PL
SECTION
C-C'
SECTION
D-D'
SECTION
C-C'
SECTION
D-D'
EAST
EAST
?????????
??
???????????????
???Qaf
Qt
Tmv
Qaf
???????????????
Qudf
Qudf
QtQtQt
Tmv Tmv Tmv
Qt QtQtQt
Tmv TmvTmvTmv
Qaf
QafPROPOSED
GRADE
PROPOSED
GRADE
EXISTING
GRADE
EXISTING
GRADE
??
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159 SHEET OF
PROJECT NO.
SCALE DATE
FIGURE
Plotted:09/17/2020 10:38AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\07516-42-02 (Nakano)\SHEETS\07516-42-02 XSection.20.dwg
GEOTECHNICAL ENVIRONMENTAL MATERIALS
1" =
GEOLOGIC CROSS SECTION
NAKANO
CHULA VISTA, CALIFORNIA
60'09 - 18 - 2020
07516 - 42 - 02
1 2 3
0 12060 180 240 300 360 420 480 540 720600660 780 840 900 960 114010201080
0 12060 180 240 300 360 420 480 540 720600660 780 840 900 960 114010201080 1200
D I S T A N C E
SCALE: 1" = 60' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION C-C'
D I S T A N C E
SCALE: 1" = 60' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION D-D'
0
60
120
180
240
C
E
L
E
V
A
T
I
O
N
(
M
S
L
)
0
60
120
180
240
D
E
L
E
V
A
T
I
O
N
(
M
S
L
)
C'
E
L
E
V
A
T
I
O
N
(
M
S
L
)
0
60
120
180
240
D'
E
L
E
V
A
T
I
O
N
(
M
S
L
)
0
60
120
180
240
PL
PL
PL
PL
SECTION
B-B'
SECTION
A-A'
SECTION
A-A'
SECTION
B-B'
LD-1
N 5° E
NORTH
????
????
?
?????????
?
?
Qudf
Qudf
Qt
Qt
Qt
Qt
Qt
Tmv
Tmv
Tmv
Tmv
Tmv
Tmv
Tmv
Tmv
PROPOSED
GRADE
PROPOSED
GRADE
EXISTING
GRADE
EXISTING
GRADE
(71)
??
?
??
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159 SHEET OF
PROJECT NO.
SCALE DATE
FIGURE
Plotted:09/17/2020 10:38AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\07516-42-02 (Nakano)\SHEETS\07516-42-02 XSection.20.dwg
GEOTECHNICAL ENVIRONMENTAL MATERIALS
1" =
GEOLOGIC CROSS SECTION
NAKANO
CHULA VISTA, CALIFORNIA
60'09 - 18 - 2020
07516 - 42 - 02
2 2 4
1
1
1
1
2
1
PROPOSED GRADE
EXISTING GRADE
LIMITS OF
REMOVAL
FILL
FORMATIONAL MATERIAL
NOT TO SCALE
NOTE:
SLOPE OF BACKCUT MAY BE STEEPENED WITH THE APPROVAL OF THE PROJECT
ENGINEER/GEOLOGIST WHERE BOUNDARY CONSTRAINTS LIMIT EXTENT OF REMOVALS
UNSUITABLE COMPRESSIBLE
SURFICIAL SEPOSITS
FIG. 5
CONSTRUCTION DETAIL FOR LATERAL EXTENT OF REMOVAL
NO SCALE
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
DSK/GTYPD PROJECT NO. 07516 - 42 - 02RM / AML
NAKANO
CHULA VISTA, CALIFORNIAGEOTECHNICAL ENVIRONMENTAL MATERIALS
Plotted:09/17/2020 10:43AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\07516-42-02 (Nakano)\DETAILS\Lateral Extent of Removal.dwg
DATE 09 - 18 - 2020
REFERENCES :
1......Janbu, N., Stability Analysis of Slopes with Dimensionless Parameters, Harvard Soil Mechanics,
Series No. 46, 1954
2......Janbu, N., Discussion of J.M. Bell, Dimensionless Parameters for Homogeneous Earth Slopes,
Journal of Soil Mechanics and Foundation Design, No. SM6, November 1967.
ASSUMED CONDITIONS :
SLOPE HEIGHT
ANALYSIS :
SLOPE INCLINATION
TOTAL UNIT WEIGHT OF SOIL
ANGLE OF INTERNAL FRICTION
APPARENT COHESION
NO SEEPAGE FORCES
EQUATION (3-3), REFERENCE 1
= feet
= pounds per cubic foot
= degrees
C
f
H
gt
f
= pounds per square foot
c =fgH tan
C
EQUATION (3-2), REFERENCE 1FS=gNcfC
H
CALCULATED USING EQ. (3-3)fc =5.6
DETERMINED USING FIGURE 10, REFERENCE 2Ncf=22
FACTOR OF SAFETY CALCULATED USING EQ. (3-2)FS =2.2
t
t
55
120
30
675
2 : 1 (Horizontal : Vertical)
l
l
FIG. 6
SLOPE STABILITY ANALYSIS - CUT SLOPES
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
DSK/GTYPD PROJECT NO. 07516 - 42 - 02RM / AML
NAKANO
CHULA VISTA, CALIFORNIAGEOTECHNICAL ENVIRONMENTAL MATERIALS
Plotted:09/17/2020 10:45AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\07516-42-02 (Nakano)\DETAILS\Slope Stability Analyses-Cut (SSA-C).dwg
DATE 09 - 18 - 2020
REFERENCES :
1......Janbu, N., Stability Analysis of Slopes with Dimensionless Parameters, Harvard Soil Mechanics,
Series No. 46, 1954
2......Janbu, N., Discussion of J.M. Bell, Dimensionless Parameters for Homogeneous Earth Slopes,
Journal of Soil Mechanics and Foundation Design, No. SM6, November 1967.
ASSUMED CONDITIONS :
SLOPE HEIGHT
ANALYSIS :
SLOPE INCLINATION
TOTAL UNIT WEIGHT OF SOIL
ANGLE OF INTERNAL FRICTION
APPARENT COHESION
NO SEEPAGE FORCES
EQUATION (3-3), REFERENCE 1
= feet
= pounds per cubic foot
= degrees
C
f
H
gt
f
= pounds per square foot
c =fgH tan
C
EQUATION (3-2), REFERENCE 1FS=gNcfC
H
CALCULATED USING EQ. (3-3)fc =12.3
DETERMINED USING FIGURE 10, REFERENCE 2Ncf=42
FACTOR OF SAFETY CALCULATED USING EQ. (3-2)FS =2.0
t
t
120
120
30
675
2.5 : 1 (Horizontal : Vertical)
l
l
FIG. 7
SLOPE STABILITY ANALYSIS - NATIVE HILLSIDE
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
DSK/GTYPD PROJECT NO. 07516 - 42 - 02RM / AML
NAKANO
CHULA VISTA, CALIFORNIAGEOTECHNICAL ENVIRONMENTAL MATERIALS
Plotted:09/17/2020 10:47AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\07516-42-02 (Nakano)\DETAILS\Slope Stability Analyses-Native(SSA-N).dwg
DATE 09 - 18 - 2020
REFERENCES :
1......Janbu, N., Stability Analysis of Slopes with Dimensionless Parameters, Harvard Soil Mechanics,
Series No. 46, 1954
2......Janbu, N., Discussion of J.M. Bell, Dimensionless Parameters for Homogeneous Earth Slopes,
Journal of Soil Mechanics and Foundation Design, No. SM6, November 1967.
ASSUMED CONDITIONS :
SLOPE HEIGHT
ANALYSIS :
SLOPE INCLINATION
TOTAL UNIT WEIGHT OF SOIL
ANGLE OF INTERNAL FRICTION
APPARENT COHESION
NO SEEPAGE FORCES
EQUATION (3-3), REFERENCE 1
= feet
= pounds per cubic foot
= degrees
C
f
H
gt
f
= pounds per square foot
c =fgH tan
C
EQUATION (3-2), REFERENCE 1FS=gNcfC
H
CALCULATED USING EQ. (3-3)fc =
DETERMINED USING FIGURE 10, REFERENCE 2Ncf=
FACTOR OF SAFETY CALCULATED USING EQ. (3-2)FS =
t
t
2.1
13
3.1
10
125
27
300
2 : 1 (Horizontal : Vertical)
l
l
FIG. 8
SLOPE STABILITY ANALYSIS - FILL SLOPES
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
DSK/GTYPD PROJECT NO. 07516 - 42 - 02RM / AML
NAKANO
CHULA VISTA, CALIFORNIAGEOTECHNICAL ENVIRONMENTAL MATERIALS
Plotted:09/17/2020 10:46AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\07516-42-02 (Nakano)\DETAILS\Slope Stability Analyses-Fill (SSA-F).dwg
DATE 09 - 18 - 2020
ASSUMED CONDITIONS :
SLOPE HEIGHT
ANALYSIS :
SLOPE INCLINATION
SLOPE ANGLE
TOTAL UNIT WEIGHT OF SOIL
ANGLE OF INTERNAL FRICTION
APPARENT COHESION
= Infinite
= pounds per cubic foot
= degrees
C
H
gt
= pounds per square foot
REFERENCES :
1......Haefeli, R. The Stability of Slopes Acted Upon by Parallel Seepage, Proc.
Second International Conference, SMFE, Rotterdam, 1948, 1, 57-62
2......Skempton, A. W., and F.A. Delory, Stability of Natural Slopes in London Clay , Proc.
Fourth International Conference, SMFE, London, 1957, 2, 378-81
DEPTH OF SATURATION
UNIT WEIGHT OF WATER
SLOPE SATURATED TO VERTICAL DEPTH BELOW SLOPE FACE
SEEPAGE FORCES PARALLEL TO SLOPE FACE
Z
= degreesf
= pounds per cubic foot
gw
i
= feetZ
FS == +C -Z cos i tan f( )2
gt Z sin i cos i
gw
gt
62.4
26.6
300
27
125
4
2 : 1 (Horizontal : Vertical)
2.0
FIG. 9
SURFICIAL SLOPE STABILITY ANALYSIS
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
DSK/GTYPD PROJECT NO. 07516 - 42 - 02RM / AML
NAKANO
CHULA VISTA, CALIFORNIAGEOTECHNICAL ENVIRONMENTAL MATERIALS
Plotted:09/17/2020 10:49AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\07516-42-02 (Nakano)\DETAILS\Slope Stability Analyses-Surficial (SSAS).dwg
DATE 09 - 18 - 2020
APPENDIX A
Project No. 07516-42-02 September 18, 2020
APPENDIX A
FIELD INVESTIGATION
Our original field investigation performed on April 14, 2005, consisted of a site reconnaissance and
logging of exploratory trenches excavated with a rubber-tired backhoe. The approximate locations of
the exploratory trenches are shown on Figure 2. The backhoe trenches were excavated to depths
between 2 and 18 feet below the existing ground surface using a JD 305 backhoe equipped with a 24-
inch-wide bucket.
Our recent field investigation performed on January 3, 2020, consisted of a site reconnaissance and
logging of one large diameter boring excavated with a truck mounted EZ-Bore drill rig using a 30-inch
diameter bucket auger. The boring was advanced to a depth of 70 feet below existing grades near the
top of slope on the south side of the site. The boring was backfilled in accordance with County of San
Diego guidelines.
For the large diameter boring, the samplers were driven 12 inches into the bottom of the excavations
with the use of a telescoping Kelly bar. The weight of the Kelly bar (4,500 lbs. maximum) drives the
sampler and varies with depth. The height of drop is usually 12 inches. Blow counts are recorded for
every 12 inches the sampler is driven. The penetration resistance values shown on the boring logs are
shown in terms of blows per foot. These values are not to be taken as N-values; adjustments have not
been applied. Elevations shown on the boring logs were determined either from a topographic map or
`by using a benchmark.
The soil conditions encountered in the trenches were visually examined, classified, and logged in
general conformance with the American Society for Testing and Materials (ASTM) Practice for
Description and Identification of Soils (Visual-Manual Procedure D 2488-00). The logs of the
exploratory trenches are presented on Figures A-1 through A-23. The logs depict the various soil types
encountered and indicate the depths at which samples were obtained.
UNDOCUMENTED FILL (Qudf)
Loose to medium dense, damp, grayish-brown, Silty SAND; some cobble,
trace clay
COLLUVIUM (Qcol)
Medium dense, damp, brown and grayish brown, Clayey SAND; some gravel
and cobble. Cobble is sub-rounded up to 10-inch in width
MISSION VALLEY FORMATION (Tmv)
Irregular contact at 6-7 feet
Medium dense to dense, damp, pale yellowish-orange to whitish orange, very
fine grained Silty SAND; micaceous, friable, massive to weakly
laminated/bedded
-At 7 feet: thin 2-inch thick gravel bed. Gravel is sub-rounded 1/2-inch to
3-inch in width. Bedding: N30E/10-15°W (undulatory)
-At 15 feet: grayish white 3/4-inch thick sand bed. Bedding: N5W/16°W
-At 17 feet: 6-inch thick clayey sand/gravel bed; gravel sub-rounded 1/2 to
4-inch in width
Dense, damp, whitish gray, very fine grained Silty SAND; highly micaceous,
abundant lithic grains, weakly to moderately laminated
-At 24 feet: 1/4-1/2-inch sand filled fractures. N5E/65°E
-At 29 feet: bedding N31W/21°W
SM
SC
SM
SM
LD1-1
LD1-2
3
3
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Figure A-1,
Log of Boring LD 1, Page 1 of 3
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
EZ BORE PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING LD 1
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
R. ADAMS CO
N
T
E
N
T
(
%
)
SAMPLE
NO.01-03-2020
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)+/-168'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
-At 30 feet: becomes dense to very dense
-At 36 feet: small 12-inch wide clay filled load structure (small channel).
Bedding: N-S/20°W
-At 38 feet: 4-inch thick gray brown sandy clay bed; not remolded
-At 39 feet: dense, damp, whitish gray, medium coarse sand bed; trace
sub-rounded gravel up to 4-inch in width
-At 40 feet: few oval white-sand filled burrows (krotovina) 2 to 4-inch
diameter.
-At 41 feet: 1/4-inch wide, high angle sand filled fracture with partial caliche
infill.
-At 45 feet: becomes white, fine to medium grained silty sand
-No sample recovery at 50 feet
-At 58 feet: bedding N5E/11°W
SMLD1-3
LD1-4
LD1-5
LD1-5
6
7
10
15
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
Figure A-1,
Log of Boring LD 1, Page 2 of 3
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
EZ BORE PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING LD 1
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
R. ADAMS CO
N
T
E
N
T
(
%
)
SAMPLE
NO.01-03-2020
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)+/-168'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
Dense to very dense, damp, white to orange-white Silty, fine to medium
SAND; trace gravel, laminated and weakly bedded, friable
TERMINATED AT 71 FEET
No groundwater encountered
Backfilled 01-03-2020
SM
LD1-6 10
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
60
62
64
66
68
70
Figure A-1,
Log of Boring LD 1, Page 3 of 3
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
EZ BORE PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
BORING LD 1
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
R. ADAMS CO
N
T
E
N
T
(
%
)
SAMPLE
NO.01-03-2020
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)+/-168'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
ALLUVIUM
Loose, humid, light brown, Silty, fine-grained SAND with roots
Moderately dense, damp, dark brown, Clayey SAND with trace roots and
gravel
Moderately dense, moist to wet, brown, Clayey SAND with roots and gravel
TERRACE DEPOSIT
Stiff, moist, reddish brown, yellow, gray and black, Cobbly, Clayey GRAVEL
with little fine- to coarse-grained sand, with angular to subrounded gravel and
cobble up to 6" diameter
Dense to very dense, damp, reddish brown, Cobbly SAND with cobble up to
6" diameter
TRENCH TERMINATED AT 10 FEET
SM
SC
SC
SC/CL
SP
T1-1
T1-2
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
Figure A-2,
Log of Trench T 1, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 1
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-14-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)142'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Loose to moderately dense, dry, reddish brown, Clayey SAND with gravel,
cobbles and roots
TERRACE DEPOSITS
Strong to very strong, humid, reddish brown, Clayey, CONGLOMERATE,
very difficult digging
TRENCH TERMINATED AT 2 FEET
SC
CL
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
Figure A-3,
Log of Trench T 2, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 2
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-14-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)160'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Loose, dry, brown, Sandy COBBLE with cobbles up to 6" diameter with roots
Firm, damp, brown, Sandy CLAY with roots
MISSION VALLEY FORMATION
Moderately dense, weak, humid, tan, Silty, very fine-grained SAND, porous
Dense, humid, weak to friable, deeply weathered, humid, light reddish brown,
fine to medium-grained SANDSTONE
TENCH TERMINATED AT 9 FEET
GP
CL
SM
SM
T3-1
T3-2
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
Figure A-4,
Log of Trench T 3, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 3
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-14-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)170'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Loose to moderately dense, dry, brown, Sandy COBBLE with roots and
boulders approximately 2 feet in diameter
Firm, humid, brown, Sandy CLAY with roots
MISSION VALLEY FORMATION
Moderately dense to dense, weak to friable, humid, light reddish brown, fine
to medium-grained, SANDSTONE
TRENCH TERMINATED AT 10 FEET
GP
CL
SM
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
Figure A-5,
Log of Trench T 4, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 4
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-14-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)170'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Loose to moderately dense, humid, brown, Silty, fine grained SAND with
roots
TERRACE DEPOSIT
Moderately dense, humid, dark brown, Clayey SAND with gravels and
cobbles
TRENCH TERMINATED AT 12 FEET
SM
SC
T5-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
Figure A-6,
Log of Trench T 5, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 5
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-14-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)135'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Loose to moderately dense, humid, light brown, Silty SAND with roots
COLLUVIUM
Moderately dense to dense, damp to moist, olive brown, Clayey SAND with
cobbles, with roots, cobbles up to 8" diameter
TERRACE DEPOSIT
Stiff, moist, reddish brown, yellow and black, Sandy CLAY with cobbles and
gravel
Dense to very dense, humid, Sandy COBBLES with clay, angular to
sub-rounded cobbles up to 1 foot diameter
TRENCH TERMINATED AT 7 FEET
SM
SC
SC/CL
GC
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
Figure A-7,
Log of Trench T 6, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 6
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-14-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)130'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Loose to moderately dense, humid, brown, Silty, fine-grained SAND with
roots
TERRACE DEPOSIT
Moderately dense to dense, damp, brown, Clayey, fine-grained SAND with
gravel and cobbles
Firm to stiff, moist, mottled reddish brown and gray, Sandy CLAY with
gravel and cobbles
Stiff, moist, gray with reddish brown, Silty CLAY with cobbles up to 6"
diameter
TRENCH TERMINATED AT 13 FEET
SM
SC
CL
CL
T7-1
T7-2
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
Figure A-8,
Log of Trench T 7, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 7
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-14-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)125'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Loose to moderately dense, humid, brown, Silty, fine-grained SAND with
roots charcoal and organics
Moderately dense, humid, light reddish brown, Silty SAND with roots
TERRACE DEPOSIT
Moderately dense to dense, damp, dark grayish brown, Clayey SAND with
trace lenses of light reddish brown silty sand
Very dense, humid, dark brown, Clayey SAND
TRENCH TERMINATED AT 5.5 FEET
SM
SM
SC
SC
T8-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
Figure A-9,
Log of Trench T 8, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 8
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-14-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)115'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Firm, humid, dark brown, Sandy CLAY with roots and gravel
TERRACE DEPOSIT
Very stiff, humid, dark brown, Silty CLAY with cobbles, with interbedded
gravel and cobble lenses
TRENCH TERMINATED AT 3.5 FEET
CL
CL
121.2 11.9T9-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
Figure A-10,
Log of Trench T 9, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 9
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-14-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)110'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Loose to moderately dense, dry, light brown, Clayey SAND with roots
TERRACE DEPOSIT
Dense, humid to damp, dark brown, Clayey SAND
Very dense, damp, dark brown, Cobbly fine-grained SAND with subangular
to subrounded gravel and cobbles up to 1 foot diameter
Dense, moist, dark reddish brown, Gravelly, fine to medium-grained SAND
with trace cobbles
TRENCH TERMINATED AT 15 FEET
SC
SC
SP
SM
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
14
Figure A-11,
Log of Trench T 10, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 10
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-14-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)105'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
ARTIFICIAL FILL
Moderately dense, damp, brown, Clayey SAND with roots
TERRACE DEPOSITS
Dense to stiff, moist, reddish brown, Cobbly Sandy CLAY with gravel and
cobbles up to 1 foot diameter
TRENCH TERMINATED AT 7 FEET
SC
GC
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
Figure A-12,
Log of Trench T 11, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 11
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-14-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)100'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
ARTIFICIAL FILL
Very loose to loose, dry, light brown to white, Silty, fine-grained SAND with
roots, with plastic
Loose to moderately dense, humid, light reddish brown, Silty, fine-grained
SAND with roots
Moderately dense, humid, light brown, Silty, fine-grained SAND with roots
Moderately dense to dense, humid, dark brown, Sandy COBBLES with
asphalt debris
Moderately dense, humid, olive, Silty, fine-gained SAND with plastic and
cobbles
Moderately dense, moist, greenish gray, Silty, fine-grained SAND with plastic
pipe with cobbles up to 1.5 feet in diameter
TRENCH TERMINATED AT 18 FEET
SM
SM
SM
GP-GM
SM
SM
T12-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
14
16
18
Figure A-13,
Log of Trench T 12, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 12
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-14-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)100'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Moderately dense, dry to damp, brown, Silty, fine-grained SAND with roots
TERRACE DEPOSIT
Moderately dense, moist, dark brown, Clayey, fine-grained SAND with
carbonate
Stiff to very stiff, moist, dark brown, Sandy CLAY
Dense to very dense, damp, brown, Gravelly, fine to medium grained SAND
with subrounded to subangular gravel and cobbles up to 4" diameter
TRENCH TERMINATED AT 14 FEET
SM
SC
CL
SP
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
14
Figure A-14,
Log of Trench T 13, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 13
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-15-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)105'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Moderately dense, dry to damp, brown, Silty, fine-grained SAND with roots
TERRACE DEPOSIT
Moderately dense, moist, dark brown, Clayey, fine-grained SAND with
carbonate
Dense, moist, dark brown, Clayey, fine-grained SAND with trace gravel
Dense to very dense, damp, brown, Gravelly, fine to medium-grained SAND
with cobbles up to 6" diameter, cobbles and gravel subrounded
TRENCH TERMINATED AT 10 FEET
SM
SC
SC
SP
T14-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
Figure A-15,
Log of Trench T 14, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 14
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-15-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)105'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Loose to moderately dense, dry to humid, light brown, Silty, fine-grained
SAND with roots
TERRACE DEPOSIT
Moderately dense, damp to moist, reddish brown, Clayey, fine-grained SAND
with micas
Moderately dense to dense, moist, Clayey, fine-grained SAND
Firm to stiff, damp, mottled reddish brown and dark brown, Sandy CLAY
TRENCH TERMINATED AT 10 FEET
SM
SC
SC
CL
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
Figure A-16,
Log of Trench T 15, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 15
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-15-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)110'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Loose to moderately dense, dry to damp, light brown, Silty, fine- grained
SAND with roots
TERRACE DEPOSIT
Moderately dense, damp, light reddish brown, Silty, fine-grained SAND with
carbonate
Moderately dense to dense, moist, dark brown, Clayey, fine-grained SAND
TRENCH TERMINATED AT 10 FEET
SM
SM
SC
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
Figure A-17,
Log of Trench T 16, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 16
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-15-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)115'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Loose to moderately dense, dry, light brown, Silty, fine-grained SAND with
roots
TERRACE DEPOSIT
Moderately dense, moist, light reddish brown, Clayey, fine-grained SAND
with carbonate
Moderately dense to dense, moist, dark brown, Clayey, fine-grained SAND
with granitic floater boulders
Dense, moist, mottled reddish brown and dark brown Sandy CLAY
TRENCH TERMINATED AT 8 FEET
SM
SC
SC
CL
99.4 18.0T17-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
Figure A-18,
Log of Trench T 17, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 17
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-15-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)105'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Loose to moderately dense, dry to humid, light brown, Silty SAND with roots
TERRACE DEPOSIT
Firm to stiff, damp to moist, dark brown with white specs, Sandy CLAY with
carbonate
Dense to very dense, damp, reddish brown, Gravelly, fine to coarse grained
SAND, with subrounded gravel and cobbles up to 6" diameter
TRENCH TERMINATED AT 12 FEET
SM
CL
SP
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
12
Figure A-19,
Log of Trench T 18, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 18
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-15-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)110'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
TOPSOIL
Loose to moderately dense, dry to humid, light brown, Silty SAND with roots
TERRACE DEPOSIT
Firm to stiff, damp to moist, dark brown with white specs, Sandy CLAY with
abundant carbonate
Dense, damp, reddish brown, Clayey, fine-grained SAND
Dense to very dense, damp, reddish brown, GRAVELLY, medium-to
coarse-grained SAND with subrounded gravels and cobbles up to 4" diameter
TRENCH TERMINATED AT 10 FEET
SM
CL
SC
SP
104.0 13.8T19-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
Figure A-20,
Log of Trench T 19, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 19
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-15-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)105'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
ARTIFICIAL FILL
Loose to moderately dense, dry to humid, light borwn, Silty, fine-grained
SAND with plastic debris and roots
ALLUVIUM
Stiff, damp, dark brown, Sandy CLAY with trace gravel
TERRACE DEPOSIT
Dense, damp, dark reddish brown, Clayey Sandy COBBLES with subrounded
gravel and cobbles
TRENCH TERMINATED AT 6 FEET
SM
CL
GP
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
Figure A-21,
Log of Trench T 20, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 20
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-15-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)100'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
ARTIFICIAL FILL
Very loose to loose, damp, light reddish brown, Silty SAND with gravel with
roots
Loose to moderately dense, moist, mottled dark brown and olive, Clayey
SAND
TERRACE DEPOSIT
Moderately dense to very dense, moist, reddish brown, Gravelly, medium to
coarse-grained SAND with subrounded gravel and cobbles up to 1 foot
diameter
TRENCH TERMINATED AT 7 FEET
SM
SC
SP
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
Figure A-22,
Log of Trench T 21, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 21
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-15-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)100'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
ARTIFICIAL FILL
Loose, dry to damp, brown, Silty SAND with debris greater than 2 feet
diameter asphalt concrete curb, brick, plastic and wood
TOPSOIL
Firm, moist, black, Sandy CLAY with gravel
TERRACE DEPOSIT
Dense, moist, reddish brown, Gravelly Cobbly SAND with subrounded gravel
and cobbles to 1 foot diameter
TRENCH TERMINATED AT 10 FEET
SM
CL
SP
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
8
10
Figure A-23,
Log of Trench T 22, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 22
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-15-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)100'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
ARTIFICIAL FILL
Firm, moist, light brown to brown, Sandy CLAY with rock fragments
TOPSOIL
Moderately dense, moist, dark brown, Clayey SAND
TERRACE DEPOSIT
Moderately dense, reddish brown, Clayey SAND with cobbles and boulders
up to 1.5 foot diameter
Dense, damp to moist, reddish brown, Silty, fine to medium grained SAND
with cobbles
TRENCH TERMINATED AT 6 FEET
CL
SC
SC
SM
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTH
IN
FEET
0
2
4
6
Figure A-24,
Log of Trench T 23, Page 1 of 1
DR
Y
D
E
N
S
I
T
Y
(P
.
C
.
F
.
)
... DRIVE SAMPLE (UNDISTURBED)
JD 305 PE
N
E
T
R
A
T
I
O
N
RE
S
I
S
T
A
N
C
E
(B
L
O
W
S
/
F
T
.
)
TRENCH T 23
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOIL
CLASS
(USCS)
GR
O
U
N
D
W
A
T
E
R
C. JENSEN CO
N
T
E
N
T
(
%
)
SAMPLE
NO.04-15-2005
SAMPLE SYMBOLS
... WATER TABLE OR SEEPAGE
MO
I
S
T
U
R
E
BY:EQUIPMENT
ELEV. (MSL.)100'
07516-42-02.GPJ
MATERIAL DESCRIPTION
LI
T
H
O
L
O
G
Y
... STANDARD PENETRATION TEST
NOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT
IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
07516-42-02
APPENDIX B
Project No. 07516-42-01 - B-1 - September 18, 2005
APPENDIX B
LABORATORY TESTING
Laboratory tests were performed in accordance with generally accepted test methods of the American
Society for Testing and Materials (ASTM) or other suggested procedures. Selected samples were tested
for expansion potential, maximum dry density and optimum moisture content, shear strength
characteristics and sulfate content. The results of these tests are summarized on Tables B-I through B-IV.
TABLE B-I
SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS
ASTM D 4829-03
Sample No.
Moisture Content (%) Dry
Density (pcf)
Expansion
Index Before Test After Test
T1-2 10.4 21.4 108.7 51
T3-2 12.1 23.3 101.9 31
T7-1 10.7 22.5 106.4 49
T12-1 12.8 21.1 100.4 1
TABLE B-II
SUMMARY OF LABORATORY MAXIMUM DRY DENSITY
AND OPTIMUM MOISTURE CONTENT TEST RESULTS
ASTM D 1557-02
Sample
No. Description Maximum Dry
Density (pcf)
Optimum
Moisture Content
(% dry wt.)
T1-2 Light brown, Clayey GRAVEL with little fine to course Sand 132.6 8.2
T3-2 Light yellowish brown fine Sandy SILT with little Clay 120.5 11.9
TABLE B-III
SUMMARY OF DIRECT SHEAR TEST RESULTS
ASTM D 3080-03
Sample No. Dry Density
(pcf)
Moisture Content
(%)
Unit Cohesion (psf)
[ultimate]
Angle of Shear
Resistance [ultimate]
(degrees)
*T1-2 117.8 9.2 400 18
*T3-2 108.5 11.6 200 36
LD1-2 101.0 14.1 28 [31] 740 [500]
LD1-5 103.1 13.2 29 [28] 900 [870]
* Samples remolded to 90 percent relative density near optimum moisture content.
Project No. 07516-42-02 - B-2 - September 18, 2020
TABLE B-IV
SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS
CALIFORNIA TEST NO. 417
Sample No. Water-Soluble Sulfate(%) Sulfate Class
T1-2 0.088 S0
T3-2 0.026 S0
T7-1 0.054 S0
T12-1 0.008 S0
SAMPLE NO.: GEOLOGIC UNIT:
SAMPLE DEPTH (FT): NATURAL/REMOLDED:
1 K 2 K 4 K AVERAGE
890 2030 4300 --
14.5 13.5 14.3 14.1
103.2 98.0 101.6 101.0
1 K 2 K 4 K AVERAGE
22.3 25.1 23.9 23.8
1310 1750 3050 --
983 1760 3101 --
740
28
500
31
Tmv
20'
NORMAL STRESS TEST LOAD
WATER CONTENT (%):
PEAK SHEAR STRESS (PSF):
ULT.-E.O.T. SHEAR STRESS (PSF):
INITIAL CONDITIONS
N
FRICTION ANGLE (DEGREES)
NORMAL STRESS TEST LOAD
ACTUAL NORMAL STRESS (PSF):
WATER CONTENT (%):
ULTIMATE
RESULTS
PEAK
7516-42-02
NAKANO PROPERTY
COHESION, C (PSF)
FRICTION ANGLE (DEGREES)
DIRECT SHEAR - ASTM D 3080
PROJECT NO.:
COHESION, C (PSF)
DRY DENSITY (PCF):
AFTER TEST CONDITIONS
1-2
0
500
1000
1500
2000
2500
3000
3500
0.000 0.050 0.100 0.150 0.200 0.250 0.300
SH
E
A
R
S
T
R
E
S
S
(
P
S
F
)
HORIZONTAL DEFORMATION (IN)
1 K 2 K 4 K
1 K PEAK 2 K PEAK 4 K Peak
1 K ULTIMATE 2 K ULTIMATE 4 K Ultimate
4 K
2 K
1 K
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000
SH
E
A
R
S
T
R
E
S
S
(
P
S
F
)
NORMAL STRESS (PSF)
SAMPLE NO.: GEOLOGIC UNIT:
SAMPLE DEPTH (FT): NATURAL/REMOLDED:
1 K 2 K 4 K AVERAGE
890 2030 4300 --
13.0 13.7 12.7 13.2
102.8 101.5 104.9 103.1
1 K 2 K 4 K AVERAGE
22.3 23.6 22.0 22.7
1341 2159 3234 --
1177 2200 3070 --
900
29
870
28
Tmv
50'
NORMAL STRESS TEST LOAD
WATER CONTENT (%):
PEAK SHEAR STRESS (PSF):
ULT.-E.O.T. SHEAR STRESS (PSF):
INITIAL CONDITIONS
N
FRICTION ANGLE (DEGREES)
NORMAL STRESS TEST LOAD
ACTUAL NORMAL STRESS (PSF):
WATER CONTENT (%):
ULTIMATE
RESULTS
PEAK
7516-42-02
NAKANO PROPERTY
COHESION, C (PSF)
FRICTION ANGLE (DEGREES)
DIRECT SHEAR - ASTM D 3080
PROJECT NO.:
COHESION, C (PSF)
DRY DENSITY (PCF):
AFTER TEST CONDITIONS
1-5
0
500
1000
1500
2000
2500
3000
3500
0.000 0.050 0.100 0.150 0.200 0.250 0.300
SH
E
A
R
S
T
R
E
S
S
(
P
S
F
)
HORIZONTAL DEFORMATION (IN)
1 K 2 K 4 K
1 K PEAK 2 K PEAK 4 K Peak
1 K ULTIMATE 2 K ULTIMATE 4 K Ultimate
4 K
2 K
1 K
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000
SH
E
A
R
S
T
R
E
S
S
(
P
S
F
)
NORMAL STRESS (PSF)
APPENDIX C
Project No. 07516-42-02 -C-1 - September 18, 2020
APPENDIX C
STORM WATER MANAGEMENT
We understand storm water management devices are being proposed in accordance with the current
Storm Water Standards (SWS). If not properly constructed, there is a potential for distress to
improvements and properties located hydrologically down gradient or adjacent to these devices.
Factors such as the amount of water to be detained, its residence time, and soil permeability have an
important effect on seepage transmission and the potential adverse impacts that may occur if the storm
water management features are not properly designed and constructed. We have not performed a
hydrogeological study at the site. If infiltration of storm water runoff occurs, downstream properties
and improvements may be subjected to seeps, springs, slope instability, raised groundwater, movement
of foundations and slabs, or other undesirable impacts as a result of water infiltration.
Hydrologic Soil Group
The United States Department of Agriculture (USDA), Natural Resources Conservation Services,
possesses general information regarding the existing soil conditions for areas within the United States.
The USDA website also provides the Hydrologic Soil Group. Table C-1 presents the descriptions of
the hydrologic soil groups. In addition, the USDA website also provides an estimated saturated
hydraulic conductivity for the existing soil.
TABLE C-1
HYDROLOGIC SOIL GROUP DEFINITIONS
Soil Group Soil Group Definition
A
Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist
mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a
high rate of water transmission.
B
Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of
moderately deep or deep, moderately well drained or well drained soils that have moderately
fine texture to moderately coarse texture. These soils have a moderate rate of water
transmission.
C
Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a
layer that impedes the downward movement of water or soils of moderately fine texture or fine
texture. These soils have a slow rate of water transmission.
D
Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These
consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table,
soils that have a claypan or clay layer at or near the surface, and soils that are shallow over
nearly impervious material. These soils have a very slow rate of water transmission.
Project No. 07516-42-02 -C-2 - September 18, 2020
The property is underlain by undocumented fill, surficial deposits such as topsoil, colluvium and
alluvium, Terrace Deposits, and the Mission Valley Formation. Table C-2 presents the information from
the USDA website for the subject property.
TABLE C-2
USDA WEB SOIL SURVEY – HYDROLOGIC SOIL GROUP
Map Unit Name Map Unit
Symbol
Approximate
Percentage
of Property
Hydrologic
Soil Group
Olivenhain cobbly loam, 9 to 30 percent slopes OhE 5.0 D
Riverwash Rm 18.5 D
Salinas clay loam, 0 to 2 percent slopes,
warm MAAT, MLRA 19 SbA 76.6 C
Infiltration Testing
We performed two borehole infiltration tests at the locations shown on Figure 2. The tests were
performed in 8-inch-diameter, drilled borings. Table C-3 presents the results of the testing. The
calculation sheets are provided herein.
We used the guidelines presented in the Riverside County Low Impact Development BMP Design
Handbook. Based on this widely accepted guideline, the saturated hydraulic conductivity (Ksat) is
equivalent to the infiltration rate. Therefore, the Ksat value determined from our testing is assumed to
be the unfactored infiltration rate.
TABLE C-3
UNFACTORED, FIELD-SATURATED, INFILTRATION TEST RESULTS
Test No. Depth (inches) Geologic Unit Field Infiltration
Rate, I (in/hr)
Factored* Field
Infiltration Rate, I (in/hr)
A-1 68 Qudf 0.004 0.002
A-2 92 Qudf 0.244 0.12
* Factor of Safety of 2.0 for feasibility determination.
STORM WATER MANAGEMENT CONCLUSIONS
Soil Types
Undocumented Fill (Qpudf) – We encountered undocumented fill up to 18 feet thick at the north end
of the property. The undocumented fill within structural improvement areas will be removed and
replaced with compacted fill. Water that is allowed to migrate into the undocumented fill or
Project No. 07516-42-02 -C-3 - September 18, 2020
compacted fill will cause settlement. Therefore, full and partial infiltration should be considered
infeasible within fill.
Topsoil (Unmapped) – We encountered topsoil varying between 0.5 and 3 feet thick across the site.
Topsoil within structural improvement areas will be removed and replaced with compacted fill. Water
that is allowed to migrate into the topsoil will cause settlement. Therefore, full and partial infiltration
should be considered infeasible within topsoil.
Colluvium (Qcol) – We encountered colluvium on the north-facing slopes at the south property
boundary, varying between 0.5 and 5 feet thick. Colluvium within structural improvement areas will
be removed and replaced with compacted fill. Water that is allowed to migrate into colluvium will
cause settlement. Therefore, full and partial infiltration should be considered infeasible within areas
underlain by colluvium.
Alluvium (Qal) – Alluvium is present in a drainage located at the southeast corner of the property.
Alluvium was also encountered in Trench T-20 beneath undocumented fill at the north end of the site.
Alluvium within structural improvement areas will be removed and replaced with compacted fill.
Water that is allowed to migrate into alluvium will cause settlement. Therefore, full and partial
infiltration should be considered infeasible within areas underlain by alluvium.
Terrace Deposits (Qt) – We encountered Terrace Deposits underlying most of the site below the
artificial fill, topsoil, and alluvium. Infiltration into Terrace Deposits may be possible.
Mission Valley Formation (Tmv) – We encountered age Mission Valley in slopes along the southern
portion of the site. Mission Valley Formation may also be present underlying the Terrace Deposits in
the central portion of the site Infiltration into the Mission Valley Formation is not feasible due to low
infiltration characteristics.
Groundwater Elevation
Groundwater was not encountered in our borings or trenches to a depths explored. Infiltration should
not impact groundwater.
Existing Utilities
Existing utilities are located on the north side of the property and along the west and east property
margins. Infiltration near these utilities is considered infeasible. Otherwise, infiltration due to utility
concerns would be feasible.
Project No. 07516-42-02 -C-4 - September 18, 2020
Soil or Groundwater Contamination
We are unaware of contaminated soil or groundwater on the property. Therefore, full and partial
infiltration associated with this risk is considered feasible.
Slopes
There are no existing slopes that would be impacted by infiltration. There are proposed fill slopes
where infiltration adjacent to the slopes is not feasible.
Infiltration Rates
Our test results indicated slow infiltration rates. The factored rates were 0.002 and 0.12 inches per
hour. The infiltration rates are not high enough to support full or partial infiltration in the area of the
proposed BMP.
Storm Water Management Devices
Liners should be incorporated in the proposed basin. The liner should be impermeable (e.g. High-
density polyethylene, HDPE, with a thickness of about 30 mil or equivalent Polyvinyl Chloride, PVC).
Penetration of the liners should be properly sealed. The devices should also be installed in accordance
with the manufacturer’s recommendations. Overflow protection devices should also be incorporated
into the design and construction of the storm water management device.
Storm Water Standard Worksheets
The SWS requests the geotechnical engineer complete the Categorization of Infiltration Feasibility
Condition (Worksheet C.4-1) worksheet information to help evaluate the potential for infiltration on
the property. The attached Worksheet C.4-1 presents the completed information for the submittal
process.
The regional storm water standards also have a worksheet (Worksheet Form D.5-1) that helps the
project civil engineer estimate the factor of safety based on several factors. Table C-4 describes the
suitability assessment input parameters related to the geotechnical engineering aspects for the factor of
safety determination.
Project No. 07516-42-02 -C-5 - September 18, 2020
TABLE C-4
SUITABILITY ASSESSMENT RELATED CONSIDERATIONS FOR INFILTRATION FACILITY
SAFETY FACTORS
Consideration High
Concern – 3 Points
Medium
Concern – 2 Points
Low
Concern – 1 Point
Assessment Methods
Use of soil survey maps or
simple texture analysis to
estimate short-term
infiltration rates. Use of
well permeameter or
borehole methods without
accompanying continuous
boring log. Relatively
sparse testing with direct
infiltration methods
Use of well permeameter
or borehole methods with
accompanying continuous
boring log. Direct
measurement of
infiltration area with
localized infiltration
measurement methods
(e.g., Infiltrometer).
Moderate spatial
resolution
Direct measurement with
localized (i.e. small-scale)
infiltration testing
methods at relatively high
resolution or use of
extensive test pit
infiltration measurement
methods.
Predominant
Soil Texture
Silty and clayey soils
with significant fines Loamy soils Granular to slightly
loamy soils
Site Soil Variability
Highly variable soils
indicated from site
assessment or unknown
variability
Soil boring/test pits
indicate moderately
homogenous soils
Soil boring/test pits
indicate relatively
homogenous soils
Depth to Groundwater/
Impervious Layer
<5 feet below
facility bottom
5-15 feet below
facility bottom
>15 feet below
facility bottom
Table C-5 presents the estimated factor values for the evaluation of the factor of safety. This table only
presents the suitability assessment safety factor (Part A) of the worksheet. The project civil engineer
should evaluate the safety factor for design (Part B) and use the combined safety factor for the design
infiltration rate.
TABLE C-5
FACTOR OF SAFETY WORKSHEET D.5-1 DESIGN VALUES1
Suitability Assessment Factor Category Assigned
Weight (w)
Factor
Value (v)
Product
(p = w x v)
Assessment Methods 0.25 2 0.50
Predominant Soil Texture 0.25 3 0.75
Site Soil Variability 0.25 2 0.50
Depth to Groundwater/Impervious Layer 0.25 1 0.25
Suitability Assessment Safety Factor, SA = p 2.0
1 The project civil engineer should complete Worksheet D.5-1 using the data on this table. Additional
information is required to evaluate the design factor of safety.
Project No. 07516-42-02 -C-6 - September 18, 2020
CONCLUSIONS
Our results indicate the site has relatively slow infiltration characteristics. Because of the site
conditions, it is our opinion that there is a potential for lateral water migration. Undocumented and
previously placed fill exists on the property and has a high potential for adverse settlement when
wetted. It is our opinion that full or partial infiltration is infeasible on this site. Our evaluation included
the soil and geologic conditions, estimated settlement and volume change of the underlying soil, slope
stability, utility considerations, groundwater mounding, retaining walls, foundations and existing
groundwater elevations.
Aardvark Permeameter Data Analysis
Project Name:Date:12/20/2019
Project Number:By:BRK
Test Number:
Borehole Diameter, d (in.):8.00 Ref. EL (feet, MSL):102.0
Borehole Depth, H (in):68.00 Bottom EL (feet, MSL):96.3
Distance Between Reservoir & Top of Borehole (in.)26.00
Height APM Raised from Bottom (in.):2.00
Pressure Reducer Used:No
Distance Between Resevoir and APM Float, D (in.):84.75
Head Height Measured, h (in.):5.50
Reading Time Elapsed
(min)
Water Weight
Consummed (lbs)
Water Volume
Consummed (in3)Q (in3/min)
1 0.00 0.000 0.00 0.00
2 5.00 11.530 319.29 63.858
3 5.00 1.665 46.11 9.222
4 5.00 0.155 4.29 0.858
5 5.00 0.045 1.25 0.249
6 5.00 0.045 1.25 0.249
7 5.00 0.035 0.97 0.194
8 5.00 0.035 0.97 0.194
9 10.00 0.045 1.25 0.125
10 10.00 0.045 1.25 0.125
11 10.00 0.030 0.83 0.083
12 10.00 0.025 0.69 0.069
13 10.00 0.020 0.55 0.055
14 10.00 0.015 0.42 0.042
15 10.00 0.015 0.42 0.042
Steady Flow Rate, Q (in3/min):0.046
Soil Matric Flux Potential, Φm
Φm=0.00060 in2/min
Field‐Saturated Hydraulic Conductivity (Infiltration Rate)
K sat =6.07E‐05 in/min 0.004 in/hr
Nakano
07516‐42‐02
A‐1
0.0
0.5
1.0
0 1020304050607080
Q
(
i
n
3/m
i
n
)
Time (min)
Borehole Infiltration Test
Project Name:Date:12/20/2019
Project Number:By:BRK
Test Number:Ref. EL (feet, MSL):100.0
Bottom EL (feet, MSL):92.3
Borehole Diameter, d (in.):8.00
Borehole Depth, H (in):92.00
Distance Between Reservoir & Top of Borehole (in.)26.00
Height APM Raised from Bottom (in.):2.00
Pressure Reducer Used:No
Distance Between Resevoir and APM Float, D (in.):108.75
Head Height Measured, h (in.):4.75
Reading Time Elapsed
(min)
Water Weight
Consummed (lbs)
Water Volume
Consummed (in3)Q (in3/min)
1 0.00 0.000 0.00 0.00
2 5.00 11.255 311.68 62.335
3 5.00 1.095 30.32 6.065
4 5.00 0.315 8.72 1.745
5 5.00 0.995 27.55 5.511
6 5.00 1.075 29.77 5.954
7 5.00 0.985 27.28 5.455
8 5.00 0.915 25.34 5.068
9 5.00 0.890 24.65 4.929
10 5.00 0.845 23.40 4.680
11 5.00 0.770 21.32 4.265
12 5.00 0.740 20.49 4.098
13 5.00 0.695 19.25 3.849
14 5.00 0.665 18.42 3.683
15 5.00 0.655 18.14 3.628
16 6.00 0.750 20.77 3.462
17 4.00 0.440 12.18 3.046
18 5.00 0.565 15.65 3.129
19 5.00 0.535 14.82 2.963
20 5.00 0.530 14.68 2.935
21 5.00 0.510 14.12 2.825
22 6.00 0.610 16.89 2.815
23 4.00 0.405 11.22 2.804
Steady Flow Rate, Q (in3/min):2.815
Soil Matric Flux Potential, Φm
Φm=0.0538 in2/min
Field‐Saturated Hydraulic Conductivity (Infiltration Rate)
K sat =1.37E‐03 in/min 0.082 in/hr
Nakano
07516‐42‐02
A‐2
0.0
5.0
10.0
0 102030405060708090100
Q
(
i
n
3/m
i
n
)
Time (min)
APPENDIX D
APPENDIX D
RECOMMENDED GRADING SPECIFICATIONS
FOR
NAKANO PROPERTY
CHULA VISTA, CALIFORNIA
PROJECT NO. 07516-42-02
GI rev. 07/2015
RECOMMENDED GRADING SPECIFICATIONS
1. GENERAL
1.1 These Recommended Grading Specifications shall be used in conjunction with the
Geotechnical Report for the project prepared by Geocon. The recommendations contained
in the text of the Geotechnical Report are a part of the earthwork and grading specifications
and shall supersede the provisions contained hereinafter in the case of conflict.
1.2 Prior to the commencement of grading, a geotechnical consultant (Consultant) shall be
employed for the purpose of observing earthwork procedures and testing the fills for
substantial conformance with the recommendations of the Geotechnical Report and these
specifications. The Consultant should provide adequate testing and observation services so
that they may assess whether, in their opinion, the work was performed in substantial
conformance with these specifications. It shall be the responsibility of the Contractor to
assist the Consultant and keep them apprised of work schedules and changes so that
personnel may be scheduled accordingly.
1.3 It shall be the sole responsibility of the Contractor to provide adequate equipment and
methods to accomplish the work in accordance with applicable grading codes or agency
ordinances, these specifications and the approved grading plans. If, in the opinion of the
Consultant, unsatisfactory conditions such as questionable soil materials, poor moisture
condition, inadequate compaction, and/or adverse weather result in a quality of work not in
conformance with these specifications, the Consultant will be empowered to reject the
work and recommend to the Owner that grading be stopped until the unacceptable
conditions are corrected.
2. DEFINITIONS
2.1 Owner shall refer to the owner of the property or the entity on whose behalf the grading
work is being performed and who has contracted with the Contractor to have grading
performed.
2.2 Contractor shall refer to the Contractor performing the site grading work.
2.3 Civil Engineer or Engineer of Work shall refer to the California licensed Civil Engineer
or consulting firm responsible for preparation of the grading plans, surveying and verifying
as-graded topography.
2.4 Consultant shall refer to the soil engineering and engineering geology consulting firm
retained to provide geotechnical services for the project.
GI rev. 07/2015
2.5 Soil Engineer shall refer to a California licensed Civil Engineer retained by the Owner,
who is experienced in the practice of geotechnical engineering. The Soil Engineer shall be
responsible for having qualified representatives on-site to observe and test the Contractor's
work for conformance with these specifications.
2.6 Engineering Geologist shall refer to a California licensed Engineering Geologist retained
by the Owner to provide geologic observations and recommendations during the site
grading.
2.7 Geotechnical Report shall refer to a soil report (including all addenda) which may include
a geologic reconnaissance or geologic investigation that was prepared specifically for the
development of the project for which these Recommended Grading Specifications are
intended to apply.
3. MATERIALS
3.1 Materials for compacted fill shall consist of any soil excavated from the cut areas or
imported to the site that, in the opinion of the Consultant, is suitable for use in construction
of fills. In general, fill materials can be classified as soil fills, soil-rock fills or rock fills, as
defined below.
3.1.1 Soil fills are defined as fills containing no rocks or hard lumps greater than
12 inches in maximum dimension and containing at least 40 percent by weight of
material smaller than ¾ inch in size.
3.1.2 Soil-rock fills are defined as fills containing no rocks or hard lumps larger than
4 feet in maximum dimension and containing a sufficient matrix of soil fill to allow
for proper compaction of soil fill around the rock fragments or hard lumps as
specified in Paragraph 6.2. Oversize rock is defined as material greater than
12 inches.
3.1.3 Rock fills are defined as fills containing no rocks or hard lumps larger than 3 feet
in maximum dimension and containing little or no fines. Fines are defined as
material smaller than ¾ inch in maximum dimension. The quantity of fines shall be
less than approximately 20 percent of the rock fill quantity.
3.2 Material of a perishable, spongy, or otherwise unsuitable nature as determined by the
Consultant shall not be used in fills.
3.3 Materials used for fill, either imported or on-site, shall not contain hazardous materials as
defined by the California Code of Regulations, Title 22, Division 4, Chapter 30, Articles 9
GI rev. 07/2015
and 10; 40CFR; and any other applicable local, state or federal laws. The Consultant shall
not be responsible for the identification or analysis of the potential presence of hazardous
materials. However, if observations, odors or soil discoloration cause Consultant to suspect
the presence of hazardous materials, the Consultant may request from the Owner the
termination of grading operations within the affected area. Prior to resuming grading
operations, the Owner shall provide a written report to the Consultant indicating that the
suspected materials are not hazardous as defined by applicable laws and regulations.
3.4 The outer 15 feet of soil-rock fill slopes, measured horizontally, should be composed of
properly compacted soil fill materials approved by the Consultant. Rock fill may extend to
the slope face, provided that the slope is not steeper than 2:1 (horizontal:vertical) and a soil
layer no thicker than 12 inches is track-walked onto the face for landscaping purposes. This
procedure may be utilized provided it is acceptable to the governing agency, Owner and
Consultant.
3.5 Samples of soil materials to be used for fill should be tested in the laboratory by the
Consultant to determine the maximum density, optimum moisture content, and, where
appropriate, shear strength, expansion, and gradation characteristics of the soil.
3.6 During grading, soil or groundwater conditions other than those identified in the
Geotechnical Report may be encountered by the Contractor. The Consultant shall be
notified immediately to evaluate the significance of the unanticipated condition.
4. CLEARING AND PREPARING AREAS TO BE FILLED
4.1 Areas to be excavated and filled shall be cleared and grubbed. Clearing shall consist of
complete removal above the ground surface of trees, stumps, brush, vegetation, man-made
structures, and similar debris. Grubbing shall consist of removal of stumps, roots, buried
logs and other unsuitable material and shall be performed in areas to be graded. Roots and
other projections exceeding 1½ inches in diameter shall be removed to a depth of 3 feet
below the surface of the ground. Borrow areas shall be grubbed to the extent necessary to
provide suitable fill materials.
4.2 Asphalt pavement material removed during clearing operations should be properly
disposed at an approved off-site facility or in an acceptable area of the project evaluated by
Geocon and the property owner. Concrete fragments that are free of reinforcing steel may
be placed in fills, provided they are placed in accordance with Section 6.2 or 6.3 of this
document.
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4.3 After clearing and grubbing of organic matter and other unsuitable material, loose or
porous soils shall be removed to the depth recommended in the Geotechnical Report. The
depth of removal and compaction should be observed and approved by a representative of
the Consultant. The exposed surface shall then be plowed or scarified to a minimum depth
of 6 inches and until the surface is free from uneven features that would tend to prevent
uniform compaction by the equipment to be used.
4.4 Where the slope ratio of the original ground is steeper than 5:1 (horizontal:vertical), or
where recommended by the Consultant, the original ground should be benched in
accordance with the following illustration.
TYPICAL BENCHING DETAIL
Remove All
Unsuitable Material
As Recommended By
Consultant
Finish Grade Original Ground
Finish Slope Surface
Slope To Be Such That
Sloughing Or Sliding
Does Not Occur Varies
“B”
See Note 1
No Scale
See Note 2
1
2
DETAIL NOTES: (1) Key width "B" should be a minimum of 10 feet, or sufficiently wide to permit
complete coverage with the compaction equipment used. The base of the key should
be graded horizontal, or inclined slightly into the natural slope.
(2) The outside of the key should be below the topsoil or unsuitable surficial material
and at least 2 feet into dense formational material. Where hard rock is exposed in the
bottom of the key, the depth and configuration of the key may be modified as
approved by the Consultant.
4.5 After areas to receive fill have been cleared and scarified, the surface should be moisture
conditioned to achieve the proper moisture content, and compacted as recommended in
Section 6 of these specifications.
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5. COMPACTION EQUIPMENT
5.1 Compaction of soil or soil-rock fill shall be accomplished by sheepsfoot or segmented-steel
wheeled rollers, vibratory rollers, multiple-wheel pneumatic-tired rollers, or other types of
acceptable compaction equipment. Equipment shall be of such a design that it will be
capable of compacting the soil or soil-rock fill to the specified relative compaction at the
specified moisture content.
5.2 Compaction of rock fills shall be performed in accordance with Section 6.3.
6. PLACING, SPREADING AND COMPACTION OF FILL MATERIAL
6.1 Soil fill, as defined in Paragraph 3.1.1, shall be placed by the Contractor in accordance with
the following recommendations:
6.1.1 Soil fill shall be placed by the Contractor in layers that, when compacted, should
generally not exceed 8 inches. Each layer shall be spread evenly and shall be
thoroughly mixed during spreading to obtain uniformity of material and moisture
in each layer. The entire fill shall be constructed as a unit in nearly level lifts. Rock
materials greater than 12 inches in maximum dimension shall be placed in
accordance with Section 6.2 or 6.3 of these specifications.
6.1.2 In general, the soil fill shall be compacted at a moisture content at or above the
optimum moisture content as determined by ASTM D 1557.
6.1.3 When the moisture content of soil fill is below that specified by the Consultant,
water shall be added by the Contractor until the moisture content is in the range
specified.
6.1.4 When the moisture content of the soil fill is above the range specified by the
Consultant or too wet to achieve proper compaction, the soil fill shall be aerated by
the Contractor by blading/mixing, or other satisfactory methods until the moisture
content is within the range specified.
6.1.5 After each layer has been placed, mixed, and spread evenly, it shall be thoroughly
compacted by the Contractor to a relative compaction of at least 90 percent.
Relative compaction is defined as the ratio (expressed in percent) of the in-place
dry density of the compacted fill to the maximum laboratory dry density as
determined in accordance with ASTM D 1557. Compaction shall be continuous
over the entire area, and compaction equipment shall make sufficient passes so that
the specified minimum relative compaction has been achieved throughout the
entire fill.
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6.1.6 Where practical, soils having an Expansion Index greater than 50 should be placed
at least 3 feet below finish pad grade and should be compacted at a moisture
content generally 2 to 4 percent greater than the optimum moisture content for the
material.
6.1.7 Properly compacted soil fill shall extend to the design surface of fill slopes. To
achieve proper compaction, it is recommended that fill sl opes be over-built by at
least 3 feet and then cut to the design grade. This procedure is considered
preferable to track-walking of slopes, as described in the following paragraph.
6.1.8 As an alternative to over-building of slopes, slope faces may be back-rolled with a
heavy-duty loaded sheepsfoot or vibratory roller at maximum 4-foot fill height
intervals. Upon completion, slopes should then be track-walked with a D-8 dozer
or similar equipment, such that a dozer track covers all slope surfaces at least
twice.
6.2 Soil-rock fill, as defined in Paragraph 3.1.2, shall be placed by the Contractor in accordance
with the following recommendations:
6.2.1 Rocks larger than 12 inches but less than 4 feet in maximum dimension may be
incorporated into the compacted soil fill, but shall be limited to the area measured
15 feet minimum horizontally from the slope face and 5 feet below finish grade or
3 feet below the deepest utility, whichever is deeper.
6.2.2 Rocks or rock fragments up to 4 feet in maximum dimension may either be
individually placed or placed in windrows. Under certain conditions, rocks or rock
fragments up to 10 feet in maximum dimension may be placed using similar
methods. The acceptability of placing rock materials greater than 4 feet in
maximum dimension shall be evaluated during grading as specific cases arise and
shall be approved by the Consultant prior to placement.
6.2.3 For individual placement, sufficient space shall be provided between rocks to allow
for passage of compaction equipment.
6.2.4 For windrow placement, the rocks should be placed in trenches excavated in
properly compacted soil fill. Trenches should be approximately 5 feet wide and
4 feet deep in maximum dimension. The voids around and beneath rocks should be
filled with approved granular soil having a Sand Equivalent of 30 or greater and
should be compacted by flooding. Windrows may also be placed utilizing an
"open-face" method in lieu of the trench procedure, however, this method should
first be approved by the Consultant.
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6.2.5 Windrows should generally be parallel to each other and may be placed either
parallel to or perpendicular to the face of the slope depending on the site geometry.
The minimum horizontal spacing for windrows shall be 12 feet center-to-center
with a 5-foot stagger or offset from lower courses to next overlying course. The
minimum vertical spacing between windrow courses shall be 2 feet from the top of
a lower windrow to the bottom of the next higher windrow.
6.2.6 Rock placement, fill placement and flooding of approved granular soil in the
windrows should be continuously observed by the Consultant.
6.3 Rock fills, as defined in Section 3.1.3, shall be placed by the Contractor in accordance with
the following recommendations:
6.3.1 The base of the rock fill shall be placed on a sloping surface (minimum slope of 2
percent). The surface shall slope toward suitable subdrainage outlet facilities. The
rock fills shall be provided with subdrains during construction so that a hydrostatic
pressure buildup does not develop. The subdrains shall be permanently connected
to controlled drainage facilities to control post-construction infiltration of water.
6.3.2 Rock fills shall be placed in lifts not exceeding 3 feet. Placement shall be by rock
trucks traversing previously placed lifts and dumping at the edge of the currently
placed lift. Spreading of the rock fill shall be by dozer to facilitate seating of the
rock. The rock fill shall be watered heavily during placement. Watering shall
consist of water trucks traversing in front of the current rock lift face and spraying
water continuously during rock placement. Compaction equipment with
compactive energy comparable to or greater than that of a 20-ton steel vibratory
roller or other compaction equipment providing suitable energy to achieve the
required compaction or deflection as recommended in Paragraph 6.3.3 shall be
utilized. The number of passes to be made should be determined as described in
Paragraph 6.3.3. Once a rock fill lift has been covered with soil fill, no additional
rock fill lifts will be permitted over the soil fill.
6.3.3 Plate bearing tests, in accordance with ASTM D 1196, may be performed in both
the compacted soil fill and in the rock fill to aid in determining the required
minimum number of passes of the compaction equipment. If performed, a
minimum of three plate bearing tests should be performed in the properly
compacted soil fill (minimum relative compaction of 90 percent). Plate bearing
tests shall then be performed on areas of rock fill having two passes, four passes
and six passes of the compaction equipment, respectively. The number of passes
required for the rock fill shall be determined by comparing the results of the plate
bearing tests for the soil fill and the rock fill and by evaluating the deflection
GI rev. 07/2015
variation with number of passes. The required number of passes of the compaction
equipment will be performed as necessary until the plate bearing deflections are
equal to or less than that determined for the properly compacted soil fill. In no case
will the required number of passes be less than two.
6.3.4 A representative of the Consultant should be present during rock fill operations to
observe that the minimum number of “passes” have been obtained, that water is
being properly applied and that specified procedures are being followed. The actual
number of plate bearing tests will be determined by the Consultant during grading.
6.3.5 Test pits shall be excavated by the Contractor so that the Consultant can state that,
in their opinion, sufficient water is present and that voids between large rocks are
properly filled with smaller rock material. In-place density testing will not be
required in the rock fills.
6.3.6 To reduce the potential for “piping” of fines into the rock fill from overlying soil
fill material, a 2-foot layer of graded filter material shall be placed above the
uppermost lift of rock fill. The need to place graded filter material below the rock
should be determined by the Consultant prior to commencing grading. The
gradation of the graded filter material will be determined at the time the rock fill is
being excavated. Materials typical of the rock fill should be submitted to the
Consultant in a timely manner, to allow design of the graded filter prior to the
commencement of rock fill placement.
6.3.7 Rock fill placement should be continuously observed during placement by the
Consultant.
7. SUBDRAINS
7.1 The geologic units on the site may have permeability characteristics and/or fracture
systems that could be susceptible under certain conditions to seepage. The use of canyon
subdrains may be necessary to mitigate the potential for adverse impacts associated with
seepage conditions. Canyon subdrains with lengths in excess of 500 feet or extensions of
existing offsite subdrains should use 8-inch-diameter pipes. Canyon subdrains less than 500
feet in length should use 6-inch-diameter pipes.
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TYPICAL CANYON DRAIN DETAIL
7.2 Slope drains within stability fill keyways should use 4-inch-diameter (or lager) pipes.
GI rev. 07/2015
TYPICAL STABILITY FILL DETAIL
7.3 The actual subdrain locations will be evaluated in the field during the remedial grading
operations. Additional drains may be necessary depending on the conditions observed and
the requirements of the local regulatory agencies. Appropriate subdrain outlets should be
evaluated prior to finalizing 40-scale grading plans.
7.4 Rock fill or soil-rock fill areas may require subdrains along their down-slope perimeters to
mitigate the potential for buildup of water from construction or landscape irrigation. The
subdrains should be at least 6-inch-diameter pipes encapsulated in gravel and filter fabric.
Rock fill drains should be constructed using the same requirements as canyon subdrains.
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7.5 Prior to outletting, the final 20-foot segment of a subdrain that will not be extended during
future development should consist of non-perforated drainpipe. At the non-perforated/
perforated interface, a seepage cutoff wall should be constructed on the downslope side of
the pipe.
TYPICAL CUT OFF WALL DETAIL
7.6 Subdrains that discharge into a natural drainage course or open space area should be
provided with a permanent headwall structure.
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TYPICAL HEADWALL DETAIL
7.7 The final grading plans should show the location of the proposed subdrains. After
completion of remedial excavations and subdrain installation, the project civil engineer
should survey the drain locations and prepare an “as-built” map showing the drain
locations. The final outlet and connection locations should be determined during grading
operations. Subdrains that will be extended on adjacent projects after grading can be placed
on formational material and a vertical riser should be placed at the end of the subdrain. The
grading contractor should consider videoing the subdrains shortly after burial to check
proper installation and functionality. The contractor is responsible for the performance of
the drains.
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8. OBSERVATION AND TESTING
8.1 The Consultant shall be the Owner’s representative to observe and perform tests during
clearing, grubbing, filling, and compaction operations. In general, no more than 2 feet in
vertical elevation of soil or soil-rock fill should be placed without at least one field density
test being performed within that interval. In addition, a minimum of one field density test
should be performed for every 2,000 cubic yards of soil or soil-rock fill placed and
compacted.
8.2 The Consultant should perform a sufficient distribution of field density tests of the
compacted soil or soil-rock fill to provide a basis for expressing an opinion whether the fill
material is compacted as specified. Density tests shall be performed in the compacted
materials below any disturbed surface. When these tests indicate that the density of any
layer of fill or portion thereof is below that specified, the particular layer or areas
represented by the test shall be reworked until the specified density has been achieved.
8.3 During placement of rock fill, the Consultant should observe that the minimum number of
passes have been obtained per the criteria discussed in Section 6.3.3. The Consultant
should request the excavation of observation pits and may perform plate bearing tests on
the placed rock fills. The observation pits will be excavated to provide a basis for
expressing an opinion as to whether the rock fill is properly seated and sufficient moisture
has been applied to the material. When observations indicate that a layer of rock fill or any
portion thereof is below that specified, the affected layer or area shall be reworked until the
rock fill has been adequately seated and sufficient moisture applied.
8.4 A settlement monitoring program designed by the Consultant may be conducted in areas of
rock fill placement. The specific design of the monitoring program shall be as
recommended in the Conclusions and Recommendations section of the project
Geotechnical Report or in the final report of testing and observation services performed
during grading.
8.5 We should observe the placement of subdrains, to check that the drainage devices have
been placed and constructed in substantial conformance with project specifications.
8.6 Testing procedures shall conform to the following Standards as appropriate:
8.6.1 Soil and Soil-Rock Fills:
8.6.1.1 Field Density Test, ASTM D 1556, Density of Soil In-Place By the
Sand-Cone Method.
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8.6.1.2 Field Density Test, Nuclear Method, ASTM D 6938, Density of Soil and
Soil-Aggregate In-Place by Nuclear Methods (Shallow Depth).
8.6.1.3 Laboratory Compaction Test, ASTM D 1557, Moisture-Density
Relations of Soils and Soil-Aggregate Mixtures Using 10-Pound
Hammer and 18-Inch Drop.
8.6.1.4. Expansion Index Test, ASTM D 4829, Expansion Index Test.
9. PROTECTION OF WORK
9.1 During construction, the Contractor shall properly grade all excavated surfaces to provide
positive drainage and prevent ponding of water. Drainage of surface water shall be
controlled to avoid damage to adjoining properties or to finished work on the site. The
Contractor shall take remedial measures to prevent erosion of freshly graded areas until
such time as permanent drainage and erosion control features have been installed. Areas
subjected to erosion or sedimentation shall be properly prepared in accordance with the
Specifications prior to placing additional fill or structures.
9.2 After completion of grading as observed and tested by the Consultant, no further
excavation or filling shall be conducted except in conjunction with the services of the
Consultant.
10. CERTIFICATIONS AND FINAL REPORTS
10.1 Upon completion of the work, Contractor shall furnish Owner a certification by the Civil
Engineer stating that the lots and/or building pads are graded to within 0.1 foot vertically of
elevations shown on the grading plan and that all tops and toes of slopes are within 0.5 foot
horizontally of the positions shown on the grading plans. After installation of a section of
subdrain, the project Civil Engineer should survey its location and prepare an as-built plan
of the subdrain location. The project Civil Engineer should verify the proper outlet for the
subdrains and the Contractor should ensure that the drain system is free of obstructions.
10.2 The Owner is responsible for furnishing a final as-graded soil and geologic report
satisfactory to the appropriate governing or accepting agencies. The as-graded report
should be prepared and signed by a California licensed Civil Engineer experienced in
geotechnical engineering and by a California Certified Engineering Geologist, indicating
that the geotechnical aspects of the grading were performed in substantial conformance
with the Specifications or approved changes to the Specifications.
Project No. 07516-42-02 September 18, 2020
LIST OF REFERENCES
1.City of San Diego (2008), Seismic Safety Study, Geologic Hazards and Faults, Grid Tile 6,
dated April 3, 2008;
2.FEMA (2012), Flood Map Service Center, FEMA website,
https://msc.fema.gov/portal/home, flood map number 06073C2159G, effective May 16, 2012,
accessed January 15, 2020;
3.Geocon Incorporated, Geotechnical Investigation, Nakano Property, Dennery Ranch Area,
Chula Vista, California, dated May 10, 2005 (Project No. 07516-42-01).
4.Jennings, C. W., 1994, California Division of Mines and Geology, Fault Activity Map of
California and Adjacent Areas, California Geologic Data Map Series Map No. 6.
5.Kennedy, M. P., and S. S. Tan, 2005, Geologic Map of the San Diego 30’x60’ Quadrangle,
California, USGS Regional Map Series Map No. 3, Scale 1:100,000.
6.SEAOC (2019), OSHPD Seismic Design Maps: Structural Engineers Association of
California website, http://seismicmaps.org/, accessed December 10, 2018;
7.USGS (2019), Quaternary Fault and Fold Database of the United States: U.S. Geological
Survey website, https://www.usgs.gov/natural-hazards/earthquake-hazards/faults, accessed
January 14, 2020;
8.Unpublished reports and maps on file with Geocon Incorporated.