HomeMy WebLinkAboutCT 02-25; NORTHPARK LA COSTA; GEOTECHNICAL; 2003-07-30PRELIMINARY GEOTECHNICAL INVESTIGATION
PROPOSED NOfiTHPARK AT LA COSTA
TENTATIVE MAP CT 02-25
CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA
FOR
TOUCHSTONE DEVELOPMENT, LLC
9715 CARROLL CENTRE ROAD, SUITE 105
SAN DIEGO, CALIFORNIA 92126
W.O. 3975-A-SC JULY 30, 2003
Geotechnical • Geologic • Environmental
5741 PalmerWay • Carlsbad, California 92008 • (760)438-3155 • FAX (760) 931-0915
August 5, 2003
W.O. 3975-A-SC
Touchstone Communities, LLC.
9715 Carroll Centre Road, Suite 105
San Diego, California 92126
Attention: Mr. Dennis O'Neil
Subject: Preliminary Geotechnical Investigation, Proposed Northpark at La Costa,
Tentative Map CT 02-25, Carlsbad, San Diego County, California
Dear Mr. O'Neil:
In accordance with your request and authorization, this report presents the results of
GeoSoils, Inc.'s (GSI's) preliminarygeotechnical investigation of the subject property. The
purpose of the study was to evaluate the onsite soils and geologic conditions, and their
effects on the proposed site development, from a geotechnical viewpoint.
EXECUTIVE SUMMARY
Based on our review of the available data (see Appendix A), as well as field exploration,
laboratory testing, and geologic and engineering analysis, the proposed development of
the property appears to be feasible from a geotechnical viewpoint, provided the
recommendations presented in the text of this report are properiy incorporated into design
and construction of the project. The most significant elements of this study are
summarized below:
• A review of the City of Carlsbad files indicated that the subject Lots 227 and 228,
were previous graded in 1974 as part of rough grading of La Costa Vale, Unit 1
(Benten Engineering, Inc., 1974). According to the Benton Engineering, Inc. report,
"final results of tests and observations Indicate that the compacted filled ground has
been placed at 90 percent of maximum dry density." In addition, our field
exploration, laboratory testing, and geologic and engineering analysis, indicated the
existing artificial fill appears suitable for its intended use provided the
recommendations presented in this report are properly Incorporated into the design
and construction of the project.
The program estimates the closest distance between each fault and a given site. If a fault
is found to be within a user-selected radius, the program estimates peak horizontal ground
acceleration that may occur at the site from an upper bound ("maximum credible")
earthquake on that fault. Site acceleration (g) is computed by any of at least
30 user-selected acceleration-attenuation relations that are contained in EQFAULT.
Based on the EQFAULT program, peak horizontal ground accelerations from an
upper bound event at the site may be on the order of 0.28g to 0.56g. The computer
printouts of portions ofthe EQFAULT program are included within Appendix C.
Historical site seismicity was evaluated with the acceleration-attenuation relations of
Campbell (1997) and the computer program EQSEARCH (Blake, 2000b). This program
was utilized to perform a search of historical earthquake records for magnitude 5.0 to
9.0 seismic! events within a 100-mile radius, between the years 1800 to 2001. Based on
the selected acceleration-attenuation relation, a peak horizontal ground acceleration has
been estimated, which may have affected the site during the specific seismic events in the
past. Based on the available data and attenuation relationship used, the estimated
maximuraf (peak) site acceleration during the period 1800 to 2002 was 0.38g. In addition,
a seisrrilc recurrence curve is also estimated/generated from the historical data (see
Appendix C).
A pijbbabilistic seismic hazards analyses was performed using FRISKSP (Blake, 2000c),
whfch models earthquake sources as 3-D planes and evaluates the site specific
probabilities of exceedance for given peak acceleration levels or pseudo-relative velocity
.l^els. Based on a review of these data, and considering the relative seismic activity ofthe
southern California region, a peak horizontal ground acceleration of 0.27g was calculated.
This value was chosen as it corresponds to a 10 percent probability of exceedance in
50 years (or a 475-year return period). Computer printouts ofthe FRISKSP program are
included in Appendix C.
Seismic Shaking Parameters
Based on the site conditions, Chapter 16 ofthe Uniform Building Code (UBC, International
Conference of Building Officials [ICBO], 1997) seismic parameters are provided in the
following table:
1997 UBC CHAPTER 16 TABLE NO. SEISMIC PARAME^RS
Seismic Zone (per Figure 16-2*) 4
Seismic Zone Factor (per Table 16-1*) 0.40
Soil Profile Type (per Table 16-J*) So
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Field investigations and geologic and engineering analysis of the subject property
indicates approximately ±5 to ±17 feet of existing artificial fill across the site,
underiain by sedimentary bedrock belonging to the Santiago Formation.
All existing weathered near-surface artificial fill is generally loose and potentially
compressible, and is not suitable for the support of settlement-sensitive
improvements in their existing state, and have a very low to moderate potential for
hydrocollapse. Therefore, weathered near-surface artificial fill may settle
appreciably under additional fill, foundation, or improvement loadings, and will
require some, or complete, removal and recompaction if settlement-sensitive
improvements are proposed within their influence. Depths of removals are outlined
in the Conclusions and Recommendations section of this report. In general,
removals will be on the order of ±2 to ±3 feet across the site; however, locally
deeper removals may be necessary.
Groundwater was not encountered onsite and is generally not anticipated to affect
site development, providing that the recommendations contained in this report are
incorporated into the final design and construction, and that prudent surface and
subsurface drainage practices are incorporated into the construction plans.
Perched groundwater conditions along zones of contrasting permeabilities may not
be precluded from occurring in the future due to site irrigation, poor drainage
conditions, or damaged utilities, and should be anticipated. Should perched
groundwater conditions develop, either during or after grading, this office could
assess the affected area(s) and provide the appropriate recommendations to
mitigate the observed groundwater conditions.
Our laboratory test results indicate the expansion potential of the onsite soils is
generally medium; however, onsite soils exhibiting a high expansion potential may
not be entirely precluded. Additionally, the soluble sulfate content ofthe site soils
have been tested to be severe and site soils are classified as severely corrosive
toward ferrous metals. Thus, consultation with a corrosion engineer should be
I recommended. On a preliminary basis, the use of Type V concrete is anticipated
I according to Table 19-A-4 of the Uniform Building Code (UBC, 1997).
Based on the representative sampling, laboratory testing, analysis of data, and our
evaluation, the potential for liquefaction to occur within the site is considered very
low.
The seismic design parameters presented herein should be considered during
project planning and design.
Adverse geologic conditions that would preclude project feasibility were not
encountered during our geotechnical investigation.
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• Conventional foundations may likely be utilized for medium expansive potential soil
conditions. Post-tension foundations are recommended for highly expansive soils,
where differential settlement exceeds 1 inch in 40 feet, or where the maximum to
minimum fill thickness exceeds 3:1 beneath any given building pad. Based on a
preliminary analysis of the plans provided by Snipes-Dye and Associates
(Snipes-Dye, 2003), and the existing geologic report (Benton, 1974), the proposed
development and existing conditions appear to provide a minimum ratio of
3:1 (maximum to minimum) for existing fill thickness within a given lot. As such,
conventional slab foundations may likely be constructed, based on this condition.
Geologic inspection should be performed during grading to verify and/or further
evaluate this condition.
Perimeter confining conditions may preclude removals in such areas for settlement
sensitive improvements. Improvements (flatwork, walls, etc.) or property margins
may therefore not function as intended, and may suffer distress. This should be
considered during planning and construction.
The geotechnical design parameters presented herein should be incorporated into
project planning, design, and construction by the project structural engineer and
architect.
The opportunity to be of sen/ice is greatly appreciated. If you have any questions, please
do not hesitate to contact the Project Geologist, Bryan Voss, at (760) 438-3155.
Respectfully submitted,
GeoSoils, Inc.
Bryari^Voss
Project Geologist
Reviewed by:
I John P. Franklin ^
\J Engineering Geologist, C
BV/JPF/DWS/jk
Distribution: (4) Addressee
Reviewed by:
f navirl W 1 David W. Skelly
Civil Engineer, RC
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TABLE OF CONTENTS
SCOPE OF SERVICES 1
SITE CONDITIONS/PROPOSED DEVELOPMENT 1
FIELD STUDIES 3
BACKGROUND 3
REGIONAL GEOLOGY 3
' EARTH MATERIALS 4
Artificial Fill (Map Symbol - Af) 4
Santiago Formation (Map Symbol - Tsa) 4
GEOLOGIC STRUCTURE 4
I FAULTING AND REGIONAL SEISMICITY 4
/ Regional Faults 4
j Seismicity 5
\ Seismic Shaking Parameters 7
I GROUNDWATER 8
1 LIQUEFACTION EVALUATION 8
I
I SEISMIC HAZARDS 9
OTHER GEOLOGIC HAZARDS 10
I LABORATORY TESTING 10
Moisture-Density 10
j Laboratory Standard 10
( Shear Testing 11
Expansion Potential 11
\ Sulfate/Corrosion Testing 12
j Atterberg Limits 12
Consolidation Testing 12
R-Value Testing 12
" 1 PRELIMINARY EARTHWORK FACTORS 12
; SLOPE STABILITY 13
j Gross Stability Analysis 13
Surficial Slope Stability 13
GeoSoils, Inc.
CONCLUSIONS AND RECOMMENDATIONS 13
General -13
General Grading 16
Demolition/Grubbing -|7
Treatment of Existing Ground 17
; Fill Placement 17
Overexcavation/Transitions 18
PRELIMINARY FOUNDATION RECOMMENDATIONS 18
\ General 18
\ Preliminary Foundation Design 19
\ Bearing Value 19
j Lateral Pressure 19
; Footing Setbacks 19
Construction 20
Expansion Classification - Medium (E.I. 51 to 90) 20
I Slope Setback Considerations for Footings 21
I POST-TENSIONED SLAB SYSTEMS 21
Post-Tensioning Institute Method 22
WALLS/CONVENTIONAL RETAINING WALLS 23
General 23
Restrained Walls 24
Cantilevered Walls 24
^ Wall Backfill and Drainage 24
i Top of Slope/Perimeter Walls 25
I Footing Excavation Observation 25
I Wall/Retaining Wall Footing Transitions 25
I PRELIMINARY PAVEMENT SECTION 26
j DEVELOPMENT CRITERIA 26
I Slope Maintenance and Planting 26
Drainage 27
I Erosion Control 27
[ Landscape Maintenance 27
Gutters and Downspouts 28
• Subsurface and Surface Water 28
Site Improvements 28
\ Tile Flooring 29
Additional Grading 29
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Footing Trench Excavation 29
Trenching 29
Utility Trench Backfill 29
SUPPLEMENTAL MOISTURE CONDITIONING 30
SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNICAL OBSERVATION
AND TESTING 30
OTHER DESIGN PROFESSIONALS/CONSULTANTS 31
PLAN REVIEW 31
LIMITATIONS 32
FIGURES:
Figure 1 - Site Location Map 2
I Figure 2 - Earthquake Epicenter Map 6
Figure 3 - Geologic Cross Section Map 14
ATTACHMENTS:
Appendix A - References Rear of Text
Appendix B - Boring and Test Pit Logs Rear of Text
Appendix C - EQFAULT, EQSEARCH and FRISKSP Rear of Text
\ Appendix D - Laboratory Data Rear of Text
i Appendix E - Slope Stability Analysis Rear of Text
Appendix F - General Earthwork and Grading Guidelines Rear of Text
Plate 1 - Boring Location Map Rear of Text in Folder
Plate 2 - Geologic Cross Section Location Map Rear of Text in Folder
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PREUMINARY GEOTECHNICAL INVESTIGATION
PROPOSED NORTHPARK AT LA COSTA,
CITY OF CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA
SCOPE OF SERVICES
The scope of our services has included the following:
1. Review of readily available soils and geologic data (see Appendix A), including the
previous geologic report for the site (Benton, 1974).
2. Subsurface exploration consisting ofthe excavation of three large diameter borings
to evaluate the soil/bedrock profiles, obtain relatively undisturbed and bulk samples
of representative materials, and delineate earth material parameters for the
proposed development (see Appendix B).
3. General areal seismicity evaluation (see Appendix C).
4. Pertinent laboratory testing of representative soil samples collected during our
subsurface exploration program (see Appendix D).
5. General liquefaction evaluation.
6. Slope Stability Analysis (see Appendix E).
7. Appropriate engineering and geologic analysis of data collected and preparation
of this report.
SITE CONDITIONS/PROPOSED DEVELOPMENT
The subject site is located on the southwest corner of La Costa Avenue and Levante Street,
in the City of Carisbad, San Diego County, California (see Figure 1, Site Location Map).
The site is bounded on the east by Levante Street, and to the west by residences, which
are outboard of an approximately 32-foot high, 2:1 (horizontal:vertical) fill over cut slope.
The northern border ofthe site is defined by La Costa Avenue, and the site is bordered on
the south by existing town homes. The site has been previously graded in 1972 to
1974 into two terraced pads. The two existing pads are separated in elevation on the order
of ±5 feet, and the site is currently vacant with scattered trash and other debris. A map of
current site conditions is presented as Plate 2. Drainage over the site is via sheet flow
toward the northwest.
Based on the plans provided (Snipes-Dye, 2003), the proposed development would
consist of 12 detached multi-family residential units. It is anticipated that the planned
development will use continuous footings and slab-on-grade floors, or post-tension
foundations, with wood-frame construction and/or masonry block construction on portions
of the site.
GeoSoils, Inc.
J-DTopoQuadj Copyrisht S 1999 DtUrtnr Yarmouth, ME 040% Source Data: USGS
Base Map: Rancho Santa Fe and Encinitas Quadrangles—San Diego Co., 7 5 Minute Series
h« Mc?^l'''l"^i;J?5? (Photorevised 1983), (Topographic), 1968 (photorevised 1975, oy Uo(aS, 1 —2000
2000
Scale
4000
Feet
W.O.
3975-A-SC
SITE LOCATION MAP
Figure 1
Building loads are assumed to be typical for these types of relatively light structures. Cut
and fill grading techniques will be required to bring the site to design grades. It is
anticipated that sewage disposal will be tied into the regional municipal system. The need
for import soils is unknown.
FIELD STUDIES
Field investigations conducted during our evaluation ofthe property consistedjDf geologic
reconnaissance mapping and the excavation of three large diameter exploratory borings.
The borings were logged by a geologist from our firm. Representative bulk and in-place
samples were taken for appropriate laboratory testing. Logs ofthe borings are presented
in Appendix B. The approximate locations ofthe borings are shown on Plates 1 and 2.
BACKGROUND
The site has been previously graded under the pun/iew of Benton Engineering, Inc. (see
Appendix A). The reader is referred to Benton Engineering, Inc. report listed in Appendix A
for grading, testing, and observation results. The site appears to have been mass graded
during the period from September 21,1972 to February 6,1974 (Benton, 1974).
REGIONAL GEOLOGY
The subject property is located within a prominent natural geomorphic province in
southwestern California known as the Peninsular Ranges. It is characterized by steep,
elongated mountain ranges and valleys thattrend northwesteriy. The mountain ranges are
underiain by basement rocks consisting of pre-Cretaceous metasedimentary rocks,
Jurassic metavolcanic rocks, and Cretaceous plutonic rocks of the southern California
batholith.
In the San Diego region, deposition occurred during the Cretaceous Period and Cenozoic
Era in the continental margin of aforearc basin. Sediments, derived from Cretaceous-age
plutonic rocks and Jurassic-age volcanic rocks, were deposited into the narrow, steep,
coastal plain and continental margin ofthe basin. These rocks have been uplifted, eroded,
and deeply incised. During early Pleistocene time, a broad coastal plain was developed
from the deposition of marine terrace deposits. During mid to late Pleistocene time, this
plain was uplifted, eroded, and incised. Alluvial deposits have since filled the lower valleys,
and young marine sediments are currently being deposited/eroded within coastal and
beach areas.
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EARTH MATERIALS
Earth materials encountered on the site are shown on Plate 1. The soils consist of artificial
fill and the Santiago Formation (considered bedrock). The earth materials are generally
described below, from youngest to oldest. Their limits, based on the available data, are
indicated on Plate 1.
Artificial Fill (Map Svmboi - Af)
The site artificial fill generally consists of a light brown to olive gray to olive green, dry to
wet, very soft to medium dense/stiff sandy clay to clayey sand. Thickness of the material
is approximately ±5 to ±17 feet. As a result of the relatively very soft/loose and highly
weathered condition ofthe upper ±2 to ±3 feet, the weathered portion ofthe artificial fill
should be removed, moisture conditioned, and recompacted, and/or processed in place,
should settlement-sensitive improvements be proposed within their influence. These soils
typically have a medium expansion potential; however, highly expansive soils may not be
precluded.
Santiago Formation (Map Svmboi - Tsa)
The Tertiary-age Santiago Formation underlies the entire site at depth. As encountered,
the bedrock generally consists of olive green, sandy claystone, and is very stiff to hard with
depth. Sediments ofthe Santiago Formation typically have medium expansion potential;
however, highly expansive soils may not be precluded.
GEOLOGIC STRUCTURE
Structural elements within the Santiago Formation in the study area are complex.
Continuous or consistent adverse fracture or joint systems were not noted during our field
investigation; however, our review and investigation indicates that jointing is generally
consistent with the regional trends. Regionally, jointing tends to follow two principal strike
directions; N20E to N85E, and N20W to N30W. Joints are typically steeply dipping
(generally in excess of 40 degrees) and are most often inclined to the south. Based on the
available data, adverse geologic structures are generally not anticipated to adversely affect
the proposed development.
FAULTING AND REGIONAL SEISMICITY
Regional Faults
Our review indicates that there are no known active faults crossing this site within the area
proposed for development, and the site is not within an Earthquake Fault Zone (Hart and
Bryant, 1997). However, the site is situated in an area of active, as well as
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potentially-active, faulting. These include, but are not limited to: the San Andreas fault; the
San Jacinto fault; the Elsinore fault; the Coronado Bank fault zone; and the
Newport-lnglewood - Rose Canyon fault zone. The location of these, and other major
faults relative to the site, are indicated on Figure 2. The possibility of ground acceleration
or shaking at the site may be considered as approximately similar to the southern
California region as a whole. Major active fault zones that may have a significant affect on
the site, should they experience activity, are listed in the following table (modified from
Blake, 2000a):
ABBREVIATED FAULT NAME
APPROXIMATE DISTANCE
MILES (KM)
Rose Canyon 6.9 (11.1)
Newport-lnglewood (Offshore) 12.4 (19.9)
Coronado Banks 21.6(34.8)
Elsinore-Julian 24.2 (39.0)
Elsinore-Tennecula 24.3(39.1)
Earthquake Valley 38.6 (62..2)
Elsinore-Glen Ivy 39.3 (63.3)
Palos Verdes 42.9 (69.1)
San Jacinto-Anza 47.0 (75.6)
San Jacinto-San Jacinto Valley 49.2(79.1)
San Jacinto-Coyote Creek 49.6 (79.9)
Seismicity
The acceleration-attenuation relations of Idriss (1994), and Campbell (1997),
Horizontal-Random have been incorporated into EQFAULT (Blake, 2000a). For this study,
peak horizontal ground accelerations anticipated at the site were determined based on the
random mean plus 1 sigma attenuation curve and mean attenuation curve developed by
Joyner and Boore (1982a and 1982b), Sadigh et al. (1987), and Bozorgnia et al. (1999).
EQFAULT is a computer program by Thomas F. Blake (2000a), which performs
deterministic seismic hazard analyses using up to 150 digitized California faults as
earthquake sources.
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1100
1000
CALIFORNIA FAULT MAP
Touchstone Communities
900
800 --
700
600 --
500 --
400 --
300 --
200 --
100 --
0 --
-100
-400 -300 -200 -100 100 200 300 400 500 600
W.O, 3975-A-SC Figure 2
GeoSoils, Inc.
1997 UBC CHAPTER 16 TABLE NO. SEISMIC PARAMETERS
Seismic Coefficient C, (per Table 16-Q*) O.44N3
Seismic Coefficient C„ (per Table 16-R*) 0.64N,
Near Source Factor (per Table 16-S*) 1.0
Near Source Factor N^ (per Table 16-T*) 1.0
Distance to Seismic Source 6.9 mi (11.1 km)
Seismic Source Type (per Table 16-U*) B
Upper Bound Earthquake (Rose Canyon fault) M„ 6.9
* Figure and Table references from Chapter 16 of the Uniform Building Code (1997)
GROUNDWATER
Groundwater was not encountered within the property during field work performed in
preparation of this report. Subsurface regional water is not anticipated to adversely affect
site development, provided that the recommendations contained in this report are
incorporated into final design and construction. Prudent surface and subsurface drainage
practices should be incorporated into the construction plans. These observations reflect
site conditions at the time of our investigation, and do not preclude future changes in local
groundwater conditions from excessive irrigation, precipitation, or that were not obvious,
at the time of our investigation.
Seeps, springs, or other indications of a high groundwater level were not detected on the
subject property during the time of our field investigation. However, seepage may occur
locally (due to heavy precipitation or irrigation) in areas where fill soils overiie silty or clayey
soils. Such soils may be encountered in the earth units that exist onsite.
Perched groundwater conditions along fill/bedrock contacts and along zones of
contrasting permeabilities should not be precluded from occurring in the future due to site
irrigation, poor drainage conditions, or damaged utilities and should be anticipated.
Should perched groundwater conditions develop, this office could assess the affected
area(s) and provide the appropriate recommendations to mitigate the observed
groundwater conditions.
LIQUEFACTION EVALUATION
Liquefaction describes a phenomenon in which cyclic stresses, produced by earthquake
induced ground motion, create excess pore pressures in relatively cohesionless soils.
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These soils may thereby acquire a high degree of mobility, which can lead to lateral
movement sliding, consolidation and settlement of loose sediments, sand boils, and other
\ damaging deformations. This phenomenon occurs only below the water table, but after
• liquefaction has developed, it can propagate upward into over-lying, non-saturated soil,
I as excess pore water dissipates.
Liquefaction susceptibility is related to numerous factors and the following conditions must
! exist for liquefaction to occur: 1) sediments must be relatively young in age and not have
; developed large amounts of cementation; 2) sediments must consist mainly of medium to
( fine grained relatively cohesionless sands; 3) the sediments must have low relative density;
\ 4) free groundwater must be present in the sediment; and 5) the site must experience
seismic event of a sufficient duration and large enough magnitude to induce straining of
] soil particles.
It should be noted that throughout our site observations and subsurface investigation,
there was no evidence of upward-directed hydraulic force that was suddenly applied, and
was of short duration, nor were there any features commonly caused by seismically
induced liquefaction, such as dikes, sills, vented sediment, lateral spreads, or
soft-sediment deformation. These features would be expected if the site area had been
subject to liquefaction in the past (Obermeier, 1996). Inasmuch as the future performance
^ of the site with respect to liquefaction should be similar to the past, excluding the effects
of urbanization (irrigation), GSI concludes that the site generally has not been subject to
\ liquefaction in the geologic past, regardless of the depth of the localized water table.
\
f
}
Since at least two or three of the five required concurrent conditions discussed above do
not have the potential to affect the site, and evidence of paleoliquefaction features were not
observed, our evaluation indicates that the potential for liquefaction and associated
adverse effects within the site is low, even with a future rise in groundwater levels. The site
conditions will also be improved by removal and recompaction of low density near-surface
soils.
) SEISMIC HAZARDS
The following list includes other seismic related hazards that have been considered during
our evaluation ofthe site. The hazards listed are considered negligible and/or completely
mitigated as a result of site location, soil characteristics, and typical site development
procedures:
• Dynamic Settlement
• Surface Fault Rupture
• Ground Lurching or Shallow Ground Rupture
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I It is important to keep in perspective that in the event of a "maximum probable" or
/ "maximum credible" (upper bound) earthquake occurring on any of the nearby major
faults, strong ground shaking would occur in the subject site's general area. Potential
damage to any structure(s) would likely be greatest from the vibrations and impelling force
caused by the inertia of a structure's mass than from those induced by the hazards
I considered above. This potential would be no greater than that for other existing
structures and improvements in the immediate vicinity.
OTHER GEOLOGIC HAZARDS
Mass wasting refers to the various processes by which earth materials are moved down
slope in response to the force of gravity. Examples of these processes include slope
creep, surficial failures, and deep-seated landslides. Creep is the slowest form of mass
wasting and generally involves the outer 5 to 10 feet of a slope surface. During heavy
rains, such as those in 1969,1978,1980,1983,1993, and 1998, creep-affected materials
may become saturated, resulting in a more rapid form of downslope movement (i.e.,
landslides and/or surficial failures). Examples of these types of slope instability do not exist
within the site.
LABORATORY TESTING
Laboratory tests were performed on representative samples of the onsite earth materials
in order to evaluate their physical characteristics. The test procedures used and results
obtained are presented below.
Moisture-Density
The field moisture content and dry unit weight were determined for each undisturbed
sample of the soils encountered in the test pits. The dry unit weight was determined in
pounds per cubic foot (pel), and the field moisture content was determined as a
percentage ofthe dry weight. The results of these tests are shown on the Boring Logs (see
Appendix B).
Laboratory Standard
!
I
The maximum dry density and optimum moisture content was determined for the major soil
type encountered in the borings. The laboratory standard used was ASTM D-1557. The
moisture-density relationship obtained for this soil is shown below:
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SOIL TYPE
TEST PIT AND
DEPTH (FT)
MAXIMUM DRY
DENSITY (PCF)
OPTIMUM
MOISTURE
CONTENT (%)
SANDY CLAYEY, Olive Green B-1 @ 3'-5' 112.0 17.5
Shear Testing
Sheartesting was performed on a representative, undisturbed sample of site soil in general
accordance with ASTM Test Method D-3080, in a Direct Shear Machine ofthe strain control
type. Shear test results are presented as Plate D-1 through Plate D-4 in Appendix D, and
as follows:
SAMPLE
LOCATION
PRIMARY RESIDUAL
SAMPLE
LOCATION COHESION
(PSF)
FRICTION
ANGLE
(DEGREES)
COHESION
(PSF)
FRICTION
ANGLE
(DEGREES)
B-1 @ 20' 1370 29 282 32
B-2 @ 2' 271 32 265 31
B-2 @ 20' 1206 19 13 33
B-2 @ 40' 730 38 190 31
Expansion Potential
Expansion testing was performed on a representative sample of site soil in accordance
with UBC Standard 18-2. The results of expansion testing are presented in the following
table:
LOCATION EXPANSION INDEX (E.l.) EXPANSION POTENTIAL
B-2 (5) 2-5 SANDY CLAY 72 Medium
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W.O. 3975-A-SC
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Sulfate/Corrosion Testing
A typical sample of the site material was analyzed for corrosion/acidity potential. The
testing included determination of soluble sulfates, pH, and saturated resistivity. Results
indicate that site soils are mildly alkaline (pH=7.8) with respect to acidity and are severely
corrosive to ferrous metals. Severely corrosive soils are considered to be below
1,000 ohms-cm.
Based upon the soluble sulfate results of 0.274 percent by weight in soil, the site soils have
a severe corrosion potential to concrete (UBC range for severe sulfate exposure is 0.20 to
2.00 percentage by weight soluble [SOJ in soil. On a preliminary basis, the use of Type
V concrete is anticipated according to Table 19-A-4 of the Uniform Building Code
(UBC, 1997). Alternative methods and additional comments may be obtained from a
qualified corrosion engineer.
Atterberg Limits
Tests were performed on soils exhibiting low to medium expansion potentials (i.e.,
Expansion Index [E.I.] between 21 and 90), per 1997 UBC requirements, to evaluate the
liquid limit, plastic limit, and plasticity index in general accordance with ASTM D-4318. The
test results are presented below:
LOCATION UQUID
UMIT
PLASTIC
UMIT
PLASTICITY
INDEX
B-2 @ 2' 48 18 30
Consoiidation Testing
Consolidation testing was performed on three relatively undisturbed soil samples in
general accordance with ASTM Test Method D-2435. The consolidation test results are
presented as Plate D-5 through Plate D-7 in Appendix D.
R-Value Testing
A representative sample was collected for R-value testing. Laboratory test results indicate
an R-value of 5.
PRELIMINARY EARTHWORK FACTORS
Preliminary earthwork factors (shrinkage and bulking) for the subject property have been
estimated based upon our field and laboratory testing, visual site observations, and
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experience with similar projects. It is apparent that shrinking would vary with depth and
with areal extent over the site based on previous site use. Variables include vegetation,
weed control, discing, and previous filling or exploring. However, all these factors are
difficult to define in a three-dimensional fashion. Therefore, the information presented
below represents average shrinkage/bulking values:
Artificial Fill 0-8% shrinkage
An additional shrinkage factor item would include the removal of root systems of individual
large plants or trees. These plants and trees vary in size but, when pulled, they may
generally result in a loss of Va to 1 Vz cubic yards. This factor needs to be multiplied by the
number of significant plants, trees, or tree roots present to determine the net loss. The
above facts indicate that earthwork balance for the site would be difficult to define and
flexibility in design is essential to achieve a balanced end product.
SLOPE STABILITY
Conventional slope stability analyses were performed utilizing the PC version of the
computer program GSTABL7 v.2. The program performs a two-dimensional limit
equilibrium analysis to compute the factor of safety for a layered slope using the simplified
Bishop or Janbu methods. Representative geologic cross sections were prepared for
analysis, utilizing field and laboratory data from our referenced report and the 50-scale
design study, depicting maximum fill over cut slopes, as indicated on Cross Sections X-X'
(see Figure 3). The results ofthe analyses are included in Appendix E.
Gross Stability Analysis
A calculated factor-of-safety greater than 1.5 or 1.1 has been obtained for the existing,
maximum height fill slopes when analyzed from a static or seismic viewpoint, respectively.
The results of the analyses are included in Appendix E.
Surficial Slope Stabilitv
The surficial stability ofthe proposed slopes have been analyzed. Our evaluation indicates
a surficial safety factor greater than 1.5 for the existing slopes.
CONCLUSIONS AND RECOMMENDATIONS
General
Based on our field exploration to date, laboratory testing, and geotechnical engineering
evaluations, it is our opinion that the site appears feasible for the proposed development
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X'
E
L
E
V
A
T
I
O
N
(in feet)
330 -
B-2 B-3 ft
280 -
EXISTING GRADE
Tsa
TD=5'
Tsa
230 -TD=5r
330
- 280
E
L
E
V
A
T
I
O
N
(in feet)
- 230
N35W
SEE PLATE 1 FOR LEGEND RIVERSIDE CO.
ORANGE CO.
SAN DIEGO CO.
^ GEOLOGIC CROSS SECTION
Figure 3
W.O. 3975-A-SO DATE 8/03 SGXLE 1"=50'.
from a geotechnical engineering and geologic viewpoint, provided that the
recommendations presented in the following sections are incorporated into the design and
construction phases of site development.
The primary geotechnical concerns with respect to the proposed development are:
Perimeter confining conditions and potential for settlement/distress to
improvements proposed on property margins.
Depth to competent bearing strata.
Expansion and corrosion potential of site soils.
Potential for perched groundwater.
Slope stability.
Regional seismic activity.
The recommendations presented herein consider these, as well as other aspects of the
site. The engineering analyses performed concerning site preparation and the
recommendations presented herein, have been completed using the information provided
and obtained during our field work.
In the event that any significant changes are made to proposed site development, the
conclusions and recommendations contained in this report shall not be considered valid
unless the changes are reviewed, and the recommendations of this report verified or
modified in writing by this office. Foundation design parameters are considered
preliminary until the foundation design, layout, and structural loads are provided to this
office for review.
1. Soil engineering, observation, and testing sen/ices should be provided during
grading to aid the contractor in removing unsuitable soils and in his effort to
compact the fill.
Geologic observations should be performed during grading to verify and/or further
evaluate geologic conditions. Although unlikely, if adverse geologic structures are
encountered, supplemental recommendations and earthwork may be warranted.
The weathered near-surface artificial fill, is typically porous, loose, and subject to
settlement. In the near surface, they are considered potentially compressible in
their existing state, and have a very low to moderate potential for hydrocollapse;
thus, weathered near-surface artificial fill may settle appreciably under additional fill,
foundation, or improvement loadings and will require removal and recompaction
(and/or processing in-place) if settlement-sensitive Improvements are proposed
within their influence. In general, removals will be on the order of ±2 to ±3 feet
across the site; however, locally deeper removals may be necessary.
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4. GSI performed a liquefaction screening evaluation of existing conditions using the
available data. It is our opinion that the site is generally underiain by dense/stiff
formational sediments, which have a very low potential for liquefaction.
5. Groundwater is generally not anticipated to affect site development, providing that
the recommendations contained in this report are incorporated into final design and
construction, and that prudent surface and subsurface drainage practices are
incorporated into the construction plans. Perched groundwater conditions along
zones of contrasting permeabilities should not be precluded from occurring in the
future due to site irrigation, poor drainage conditions, or damaged utilities, and
should be anticipated. Should perched groundwater conditions develop, this office
could assess the affected area(s) and provide the appropriate recommendations to
mitigate the observed groundwater conditions.
6. Our laboratory test results and experience on nearby sites related to expansion
potential, indicate that soils with medium to potentially high expansion indices
underlie the site. This should be considered during project design. Foundation
design and construction recommendations are provided herein for medium and
high expansion potential classifications.
7. The soluble sulfate content of the site soils have been tested to be severe and site
soils are classified as severely corrosive toward ferrous metals. Thus, consultation
with a corrosion engineer should be considered. On a preliminary basis, the use
of Type V concrete is anticipated according to Table 19-A-4 ofthe UBC (1997).
8. The seismicity-acceleration values provided herein should be considered during the
design of the proposed development.
8. General Earthwork and Grading Guidelines are provided at the end of this report as
Appendix F. Specific recommendations are provided below.
General Grading
All grading should conform to the guidelines presented in the UBC (ICBO, 1997), the City
and/or County, and Appendix F (this report), except where specifically superceded in the
text of this report. When code references are not equivalent, the more stringent code
should be followed. During earthwork construction, all site preparation and the general
grading procedures of the contractor should be obsen/ed and the fill selectively tested by
a representative of GSI. If unusual or unexpected conditions are exposed in the field, they
should be reviewed by this office and, if warranted, modified and/or additional
recommendations will be offered. All applicable requirements of local and national
construction and general industry safety orders, the Occupational Safety and Health Act
(OSHA), and the Construction Safety Act should be met.
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Demolition/Grubbing
1. Existing structures, vegetation, and any miscellaneous debris should be removed
from the areas of proposed grading.
2. Any previous foundations, irrigation lines, cesspools, septic tanks, leach fields, or
other subsurface structures uncovered during the recommended removal should
be obsen/ed by GSI so that appropriate remedial recommendations can be
provided.
3. Cavities or loose soils remaining after demolition and site clearance should be
cleaned out and obsen/ed by the soil engineer. The cavities should be replaced
with fill materials that have been moisture conditioned to at least optimum moisture
content and compacted to at least 90 percent ofthe laboratory standard.
Treatment of Existing Ground
1. All weathered near-surface artificial fill should be removed to suitable artificial fill,
cleaned of deleterious materials, as necessary, moisturized, and recompacted if not
removed by proposed excavation within areas proposed for settlement-sensitive
improvements. Variations from these thicknesses should be anticipated. At this
time, removal depths on the order of ±2 to ±3 feet should be anticipated; however,
locally deeper removals may be necessary.
2. Subsequent to the above removals, the upper 12 inches of the exposed
subsoils/bedrock should be scarified, brought to at least optimum moisture content,
and recompacted to a minimum relative compacfion of 90 percent ofthe laboratory
standard.
3. Existing artificial fill, etc., and removed natural ground materials may be reused as
compacted fill provided that major concentrations of vegetation and miscellaneous
debris are removed prior to, or during, fill placement.
4. Localized deeper removal may be necessary due to buried utility trenches or dry
porous materials. The project soils engineer/geologist should obsen/e all removal
areas during the grading.
Fill Placement
1. Subsequent to ground preparation, fill materials should be brought to at least
optimum moisture content, placed in thin 6- to 8-inch lifts, and mechanically
compacted to obtain a minimum relative compaction of 90 percent ofthe laboratory
standard.
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2. Fill materials should be cleansed of major vegetation and debris prior to placement.
3. Any import materials should be observed and determined suitable by the soils
engineer prior to placement on the site. Import material, if any, for a fill cap should
be low expansive (E.l. less than 50). Foundation designs may be altered if import
materials have a greater expansion value than the onsite materials encountered in
this investigation.
4. Any oversized rock materials greater than 8 inches in diameter should be placed
under the recommendations and supervision of the soils engineer and/or removed
from the site. Per the UBC, such materials may not be placed within 10 feet of finish
grade. General recommendations for placement of oversize materials is contained
in Appendix E (Grading Guidelines). Although unlikely, should significant amounts
of oversize rock be encountered, recommendations for rock fill placement should
be adhered to.
Overexcavation/Transitions
In order to provide for the uniform support of the structures, a minimum 3-foot thick fill
blanket is recommended for lots containing earth material transitions. Any cut portion of
the pad for the development should be overexcavated a minimum 3 feet below finish pad
grade, to 5 feet horizontally, or a 1:1 (horizontahvertical) projection, down and away from
settlement sensitive Improvements. Areas with planned fills less than 3 feet should be
overexcavated in order to provide the minimum fill thickness. Maximum to minimum fill
thickness within a given lot or pad should not exceed a rafio of 3:1 (maximum:minimum).
PRELIMINARY FOUNDATION RECOMMENDATIONS
General
In the event that the information concerning the proposed development plan is not correct,
or any changes in the design, location, or loading conditions ofthe proposed structure are
made, the conclusions and recommendations contained in this report shall not be
considered valid unless the changes are reviewed and conclusions of this report are
modified or approved in writing by this office. It is our understanding that slab-on-grade
construction is desired for the proposed development.
The information and recommendations presented in this section are not meant to
supercede design by the project structural engineer. Upon request, GSI could provide
additional input/consultation regarding soil parameters, as related to foundation design.
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Preiiminarv Foundation Design
Our review, field work, and laboratory testing indicates that onsite soils have a medium to
possible high expansion potential. Preliminary recommendations for foundation design
and construction are presented below. Final foundation recommendations should be
provided at the conclusion of grading, and based on laboratory testing of fill materials
exposed at finish grade.
Bearing Value
1. The foundation systems should be designed and constructed in accordance with
guidelines presented in the latest edition ofthe UBC.
2. An allowable bearing value of 1,500 pounds per square foot (psf) may be used for
the design of continuous footings at least 12 inches wide and 12 inches deep, and
column footings at least 24 inches square and 24 inches deep. This value may be
increased by 20 percent for each additional 12 inches in depth to a maximum of
2,500 psf. No increase in bearing value is recommended for increased footing
width.
( Lateral Pressure
1. For lateral sliding resistance, a 0.35 coefficient of friction may be utilized for a
concrete to soil contact when multiplied by the dead load.
2. Passive earth pressure may be computed as an equivalent fluid having a density of
250 pounds per cubic foot (pcf) with a maximum earth pressure of 2,500 psf.
3. When combining passive pressure and frictional resistance, the passive pressure
component should be reduced by one-third.
Footing Setbaci<s
All footings should maintain a minimum 7-foot horizontal setback from the base of the
footing to any descending slope. This distance is measured from the footing face at the
bearing elevation. Footings should maintain a minimum horizontal setback of
H/3 (H = slope height) from the base of the footing to the descending slope face and no
less than 7 feet, nor need to be greater than 40 feet. Footings adjacent to unlined drainage
swales should be deepened to a minimum of 6 inches below the invert of the adjacent
unlined swale. Footings for structures adjacent to retaining walls should be deepened so
as to extend below a 1:1 projection from the heel of the wall. Alternatively, walls may be
designed to accommodate structural loadsfrom buildings or appurtenances as described
in the retaining wall section of this report.
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Construction
The following foundation construction recommendations are presented as a minimum
criteria from a soils engineering viewpoint. The onsite soils expansion potentials are
generally in the medium range (E.l. 51 to 90). Expansive soil in the high range (E.l. 91 to
130) may also be present onsite.
Accordingly, the following foundation construction recommendations assume that the soils
in the top 3 feet from finish grade will have a medium to possible high expansion potential.
Should highly expansive soils be present, post-tension foundations are recommended.
Recommendations by the project's design-structural engineer or architect, which may
exceed the soils engineer's recommendations, should take precedence over the following
minimum requirements. Final foundation design will be provided based on the expansion
potential of the near surface soils encountered during grading.
Expansion Classification - Medium (E.l. 51 to 90)
1. Conventional continuous footings should be founded at a minimum depth of
18 inches below the lowest adjacent ground surface. Interior footings for one-story
floor loads may be founded at a depth of 12 inches below the lowest adjacent
ground surface. The project structural engineer should review and approve these
recommendations.
Footings for one-story floor loads should have a minimum width of 12 inches, and
footings for two-story floor loads should have a minimum width of 15 inches. All
footings should be reinforced with a minimum of two No. 4 reinforcing bars at the
top and two No. 4 reinforcing bars at the bottom. Isolated interior and/or exterior
piers and columns are not recommended.
2. A grade beam, reinforced as above and at least 12 inches square, should be
provided across the garage entrances. The base of the reinforced grade beam
should be at the same elevation as the adjoining footings.
3. Concrete slabs in residential and garage areas should be underlain by a vapor
barrier consisting of a minimum of 10-mil, polyvinyl-chloride membrane with all laps
sealed. Two inches of the sand base should be placed over and under the
membrane (total of 4 inches) to aid in uniform curing of the concrete and mitigate
puncturing of the vapor barrier.
4. A minimum slab thickness of 4 inches is recommended. The design engineer
should determine the actual thickness of concrete slabs based upon proposed
loading and use. Garage slabs should be poured separately from the residence
footings and be quartered with expansion joints or saw cuts. A positive separation
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from the footings should be maintained with expansion joint material to permit
relative movement.
5. Concrete slabs, including garage slabs, should be reinforced with
No. 4 reinforcement bars placed on 18-inch centers, in two horizontally
perpendicular directions (i.e., long axis and short axis).
6. All slab reinforcement should be supported to ensure proper mid-slab height
positioning during placement ofthe concrete. "Hooking" of reinforcement is not an
acceptable method of positioning.
7. Presaturation of slab areas is recommended for these soil conditions. The moisture
content of each slab area should be 120 percent, or greater, above optimum and
verified by the soil engineer to a depth of 18 inches below adjacent ground grade
in the slab areas, within 72 hours of the vapor barrier placement.
8. As an alternative, an engineered post-tension foundation system may be used.
Engineering parameters for post-tension design are provided in a later section.
9. Soils generated from foofing excavations to be used onsite should be compacted
to a minimum relative compaction 90 percent ofthe laboratory standard, whether
it is to be placed inside the foundation perimeter or in the yard/right-of-way areas.
This material must not alter positive drainage patterns that direct drainage away
from the structural areas and toward the street.
10. Foundations near the top of slope should be deepened to conform to the latest
edition of the UBC (ICBO, 1997) and provide a minimum of 7 feet horizontal
distance from the slope face. Rigid block wall designs located along the top of
slope should be reviewed by a soils engineer.
Slope Setback Considerations for Footings
Foofings should maintain a horizontal distance, X, between any adjacent descending slope
face and the bottom outer edge of the footing. The horizontal distance, X, may be
calculated by using X = h/2, where h is the height ofthe slope. X should not be less than
7 feet, nor need not be greater than 80 feet. X may be maintained by deepening the
footings.
POST-TENSIONED SLAB SYSTEMS
Recommendations for utilizing post-tensioned slabs on the site is based on our limited
subsurface investigation on the site. The recommendations presented below should be
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followed in addition to those contained in the previous sections, as appropriate. The
information and recommendations presented below in this section are not meant to
supercede design by a registered structural engineer or civil engineer familiar with
post-tensioned slab design. Post-tensioned slabs should be designed using sound
engineering practice and be in accordance with local and/or national code requirements.
Upon request, GSI can provide additional data/consultation regarding soil parameters as
related to post-tensioned slab design.
From a soil expansion/shrinkage standpoint, a common contributing factor to distress of
structures using post-tensioned slabs is fluctuation of moisture in soils underlying the
perimeter ofthe slab, compared to the center, causing a "dishing" or "arching" ofthe slabs.
To mitigate this possibility, a combination of soil presaturation and construction of a
perimeter cut-off wall should be employed.
Perimeter cut-off walls should be a 18 inches deep for medium and/or high expansive soils.
The cut-off walls may be integrated into the slab design or independent of the slab and
should be a minimum of 6 inches thick. The vapor barrier should be covered with a 2-inch
layer of sand to aid in uniform curing ofthe concrete; and it should be lapped adequately
to provide a continuous water-proof barrier under the entire slab. For medium or highly
expansive soils, an additional 2 inches of sand should be placed on grade (4 inches total)
Specific soil presaturation is not required; however, the moisture content ofthe subgrade
soils should be equal to, or greater than, the soils' optimum moisture content to a depth
of 18 inches below grade, for medium, or high expansive soils.
Post-Tensioning Institute Method
Post-tensioned slabs should have sufficient stiffness to resist excessive bending due to
non-uniform swell and shrinkage of subgrade soils. The differential movement can occur
at the corner, edge, or center of slab. The potential for differential uplift can be evaluated
using the UBC Section 1816 (ICBO, 1997), based on design specifications of the
Post-Tensioning Institute (PTI). The following table presents suggested minimum
coefficients to be used in the PTI design method.
Thornthwaite Moisture Index -20 inches/year
Correction Factor for Irrigation 20 inches/year
Depth to Constant Soil Suction 7 feet
Constant soil Suction (pf) 3.6
Modulus of Subgrade Reaction (pci) 75
Moisture Velocity 0.7 inches/month
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The coefficients are considered minimums and may not be adequate to represent worst
case conditions such as adverse drainage and/or improper landscaping and maintenance.
The above parameters are applicable provided structures have positive drainage that is
maintained away from structures. Therefore, it is important that information regarding
drainage, site maintenance, settlements, and effects of expansive soils be passed on to
future owners.
Based on the above parameters, the following values were obtained from figures or tables
ofthe UBC Section 1816 (ICBO, 1997). The values may not be appropriate to account for
possible differential settlement of the slab due to other factors. If a stiffer slab is desired,
higher values of ym may be warranted.
EXPANSION INDEX
OF SOIL SUBGRADE
MEDIUM EXPANSION
(E.l.= 51-90)
HIGH EXPANSION
(E.l. = 91-130)
e^, center lift 5.5 feet 5.5 feet
e„ edge lift 4.0 feet 4.5 feet
y^ center lift 2.7 inches 3.5 inches
V„ edqe lift 0.75 inches 1.2 inches
Deepened footings/edges around the slab perimeter must be used to minimize
non-uniform surface moisture migration (from an outside source) beneath the slab. An
edqe depth of 12 inches should be considered a minimum. The bottom ofthe deepened
footing/edge should be designed to resist tension, using cable or reinforcement per the
structural engineer. Other applicable recommendations presented under conventional
foundation and the California Foundation Slab Method should be adhered to during the
design and construction phase of the project.
WAI LS/CONVENTIONAL RETAINING WALLS
General
The design parameters provided below assume that very low e>^P^"^"'^^^ f ^'IfJ^,";,?
Class 2 permeable filter material or Class 3 aggregate base) are used o backfi^'^nv
retaining walls from the back of the heel of the footing. If expansive soils are used to
backfill the proposed walls, increased active and at-rest earth pressures will need to be
St'zed for retaining wall design, and may be provided -P-;-^-^'Itrof mSre
grade should be water-proofed or damp-proofed, depending on the degree of mois ure
protection desired. The foundation system for the proposed conventional regaining waHs
should be designed in accordance with the recommendations presented in the preceding
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sections of this report, as appropriate. Footings should be embedded a minimum of
18 inches below adjacent grade (excluding landscape layer, 6 inches). There should be
no increase in bearing for footing width.
Recommendations for specialty walls (i.e., loffel, crib, earthstone, etc.) will differ from those
provided below. Recommendations for specialty walls may be provided upon request, or
at the time they are reviewed by this office on the draft civil drawings.
Restrained Wails
Any retaining walls that will be restrained prior to placing and compacting backfill material,
or that have re-entrant or male corners, should be designed for an at-rest equivalent fluid
pressure (EFP) of 65 pcf, plus any applicable surcharge loading. For areas of male or
re-entrant corners, the restrained wall design should extend a minimum distance of twice
the height of the wall (2H) laterally from the corner.
Cantilevered Walls
The recommendations presented below are for cantilevered retaining walls up to 10 feet
high. Active earth pressure may be used for retaining wall design, provided the top ofthe
wall is not restrained from minor deflections. An equivalent fluid pressure approach may
be used to compute the horizontal pressure against the wall. Appropriate fluid unit weights
are given below for specific slope gradients ofthe retained material. These do not include
other superimposed loading conditions such as traffic, structures, hydrostatic pressures,
seismic events, or adverse geologic conditions. When wall configurations are finalized, the
appropriate loading condiflons for superimposed loads can be provided upon request.
SURFACE SLOPE OF RETAINED MATERIAL
HORIZONTAL TO VERTICAL
EQUIVALENT FLUID WEIGHT
P.C.F. (SELECT BACKFILL)
Level* 40
2to1 55
*Level backfill behind a retaining wall is defined as compacted earth materials, properly drained, without a slope
for a distance of 2H behind the wall.
Wail Backfill and Drainage
The above criteria assumes that very low expansive soils are used as backfill, and that
hydrostatic pressures are not allowed to build up behind the wall. Positive drainage must
be provided behind all retaining walls in the form of perforated pipe placed within gravel
wrapped in geofabric and outlets. A backdrain system is considered necessary for
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retaining walls that are 2 feet, or greater, in height. Backdrains should consist of a 4-inch
diameter perforated PVC or ABS pipe encased in either Class 2 permeable filter material
or V2- to %-inch gravel wrapped in approved filter fabric (Mirafi 140 or equivalent). The filter
material should extend a minimum of 1 horizontal foot behind the base of the walls and
upward at least 1 foot. Outlets should consist of a 4-inch diameter solid PVC or ABS pipe
spaced no more than ± 100 feet apart. The use of weep holes in walls higher than 2 feet
should not be considered. The surface of the backfill should be sealed by pavement or
the top 18 inches compacted with relatively impermeable soil. Proper surface drainage
should also be provided. Consideration should be given to applying a water-proof
membrane to all retaining structures. The use of a waterstop should be considered for all
concrete and masonry joints.
Top of Slope/Perimeter Walls
The geotechnical parameters previously provided may be utilized for free standing sound
walls or perimeter walls, which are founded in either competent bedrock or compacted fill
materials. The strength of the concrete and grout should be evaluated by the structural
engineer of record. The proper ASTM tests for the concrete and mortar should be
provided along with the slump quantities.
The placing of joints (expansion and crack control) should be incorporated into the wall
layout. These expansion joints should be placed no greater than 20 feet on-center and
should be reviewed by the civil engineer and structural engineer of record. GSI anticipates
distortions on the order of V2 to ±1 inch in 50 feet for these walls located at the tops of
fill/cut slopes. To reduce this potential, the footings may be deepened and/or the use of
piers may be considered.
Footing Excavation Observation
All footing excavations for walls and appurtenant structures should be observed by the
geotechnical consultant to evaluate the anticipated near-surface condiflons prior to the
placement of steel or concrete. Based on the conditions encountered during the
observations ofthe fooflng excavafion, supplemental recommendations may be offered,
as appropriate.
Waii/Retaining Wail Footing Transitions
Site walls are anticipated to be founded on footings designed in accordance with the
recommendations in this report. Should wall footings transiflon from cut to fill, the civil
designer may specify either:
a) A minimum of a 2-foot overexcavation and recompaction of cut materials for a
distance of 2H.
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GeoSoils, Inc.
b) Increase ofthe amount of reinforcing steel and wall detailing (i.e., expansion joints
or crack control joints) such that a angular distortion of 1/360 for a distance of 2H
on either side ofthe transition may be accommodated. Expansion joints should be
sealed with a flexible, non-shrink grout.
c) Embed the footings entirely into native formational material.
If transitions from cut to fill transect the wall footing alignment at an angle of less than
45 degrees (plan view), then the designer should follow recommendation "a" (above) until
such transiflon is between 45 and 90 degrees to the wall alignment.
PRELIMINARY PAVEMENT SECTION
The initial pavement sections presented herein are based on test R-value of 5 for
typical site materials, traffic indices of 5, and the guidelines presented in the latest revision
to the California Department of Transportation "Highway Design Manual," fourth edition.
Based on this informaflon, it is likely that pavement sections will vary from 3 inches of A.C.
on 10 inches of Class 2 aggregate base rock (or equivalent) to 4 inches of A.C. on
IVz inches of Class 2 aggregate base. Final pavement designs should be based upon
actual R-value testing of materials exposed at subgrade elevations at the conclusion of
earthwork.
DEVELOPMENT CRITERIA
Slope Maintenance and Planting
Water has been shown to weaken the inherent strength of all earth materials. Slope
stability is significantly reduced by overly wet condiflons. Positive surface drainage away
from slopes should be maintained and only the amount of irrigaflon necessary to sustain
plant life should be provided for planted slopes. Over-watering should be avoided as it can
adversely affect site improvements, and cause perched groundwater condiflons. Graded
slopes constructed ufllizing onsite materials would be erosive. Eroded debris may be
minimized and surficial slope stability enhanced by establishing and maintaining a suitable
vegetation cover soon after construction. Compacfion to the face of fill slopes would tend
to minimize short-term erosion until vegetation is established. Plants selected for
landscaping should be light weight, deep rooted types that require little water and are
capable of surviving the prevailing climate. Jute-type matting or other fibrous covers may
aid in allowing the establishment of a sparse plant cover. Ufllizing plants other than those
recommended above will increase the potential for perched water to develop. A rodent
control program to prevent burrowing should be implemented. Irrigaflon of natural
(ungraded) slope areas is generally not recommended. These recommendaflons
Touchstone Communities, LLC, W.O. 3975-A-SC
Northpark at La Costa, Carlsbad August 5, 2003
File:e:\wp9\3900\3975a.pgi Pa.^Q 26
GeoSoils, Inc.
regarding plant type, irrigaflon pracflces, and rodent control should be provided to each
homeowner. Over-steepening of slopes should be avoided during building construction
activifles and landscaping.
Drainage
Adequate lot surface drainage is a very important factor in reducing the likelihood of
adverse performance of foundations, hardscape, and slopes. Surface drainage should be
sufficient to prevent ponding of water anywhere on a lot, and especially near structures and
tops of slopes. Lot surface drainage should be carefully taken into consideration during
flne grading, landscaping, and building construcflon. Therefore, care should be taken that
future landscaping or construction activities do not create adverse drainage conditions.
Positive site drainage within lots and common areas should be provided and maintained
at all flmes. Drainage should not flow uncontrolled down any descending slope. Water
should be directed away from foundations and not allowed to pond and/or seep into the
ground. In general, the area within 5 feet around a structure should slope away from the
structure. We recommend that unpaved lawn and landscape areas have a minimum
gradient of one percent sloping away from structures, and whenever possible, should be
above adjacent paved areas. Consideraflon should be given to avoiding construction of
planters adjacent to structures (buildings, pools, spas, etc.). Pad drainage should be
directed toward the street or other approved area(s). Although not a geotechnical
requirement, roof gutters, down spouts, or other appropriate means may be utilized to
control roof drainage. Down spouts, or drainage devices should outlet a minimum of 5 feet
from structures or into a subsurface drainage system. Areas of seepage may develop due
to irrigation or heavy rainfall, and should be anflcipated. Minimizing irrigaflon will lessen
this potential. If areas of seepage develop, recommendations for minimizing this effect
could be provided upon request.
Erosion Control
Cut and fill slopes will be subject to surficial erosion during and after grading. Onsite earth
materials have a moderate to high erosion potential. Consideration should be given to
providing hay bales and silt fences for the temporary control of surface water, from a
geotechnical viewpoint.
Landscape Maintenance
Only the amount of irrigation necessary to sustain plant life should be provided.
Over-watering the landscape areas will adversely affect proposed site improvements. We
would recommend that any proposed open-bottom planters adjacent to proposed
structures be eliminated for a minimum distance of 10 feet. As an alternative, closed-
bottom type planters could be utilized. An outlet placed in the bottom ofthe planter, could
be installed to direct drainage away from structures or any exterior concrete flatwork. If
Touchstone Communities, LLC. W.O. 3975-A-SC
Northpark at La Costa, Carlsbad August 5, 2003
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GeoSoils, Inc.
planters are constructed adjacent to structures, the sides and bottom ofthe planter should
be provided with a moisture barrier to prevent penetration of irrigation water into the
subgrade. Provisions should be made to drain the excess irrigation water from the planters
without saturating the subgrade below or adjacent to the planters. Graded slope areas
should be planted with drought resistant vegetaflon. Consideration should be given to the
type of vegetaflon chosen and their potenflal effect upon surface improvements (i.e., some
trees will have an effect on concrete flatwork with their extensive root systems). From a
geotechnical standpoint leaching is not recommended for establishing landscaping. If the
surface soils are processed for the purpose of adding amendments, they should be
recompacted to 90 percent minimum relative compaction.
Gutters and Downspouts
As previously discussed in the drainage section, the installation of gutters and downspouts
should be considered to collect roof water that may otherwise inflltrate the soils adjacent
to the structures. If ufllized, the downspouts should be drained into PVC collector pipes
or non-erosive devices that will carry the water away from the house. Downspouts and
gutters are not a requirement; however, from a geotechnical viewpoint, provided that
positive drainage is incorporated into project design (as discussed previously).
Subsurface and Surface Water
Subsurface and surface water are not anticipated to affect site development, provided that
the recommendaflons contained in this report are incorporated into final design and
construction and that prudent surface and subsurface drainage practices are incorporated
into the construction plans. Perched groundwater conditions along zones of contrasflng
permeabilifles may not be precluded from occurring in the future due to site irrigation, poor
drainage condiflons, or damaged ufllifles, and should be anflcipated. Should perched
groundwater conditions develop, this office could assess the affected area(s) and provide
the appropriate recommendaflons to mitigate the observed groundwater condiflons.
Groundwater conditions may change with the introduction of irrigation, rainfall, or other
factors.
Site Improvements
Recommendations for exterior concrete flatwork design and construction can be provided
upon request. If in the future, any additional improvements (e.g., pools, spas, etc.) are
planned for the site, recommendaflons concerning the geological or geotechnical aspects
of design and construction of said improvements could be provided upon request. This
office should be notifled in advance of any fill placement, grading of the site, or trench
backfllling after rough grading has been completed. This includes any grading, utility
trench, and retaining wall backfllls.
Touchstone Communities, LLC. W.O. 3975-A-SC
Northpark at La Costa, Carlsbad August 5, 2003
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GeoSoils, Inc.
Tiie Flooring
Tile flooring can crack, reflecflng cracks in the concrete slab below the file, although small
cracks in a convenflonal slab may not be significant. Therefore, the designer should
consider addiflonal steel reinforcement for concrete slabs-on-grade where file will be
placed. The file installer should consider installaflon methods that reduce possible
cracking of the file such as slipsheets. Slipsheets or a vinyl crack isolaflon membrane
(approved by the Tile Council of America/Ceramic Tile Institute) are recommended
between file and concrete slabs on grade.
Additional Grading
This office should be noflfied in advance of any fill placement, supplemental regrading of
the site, or trench backfilling after rough grading has been completed. This includes
completion of grading in the street and parking areas and utility trench and retaining wall
backfills.
Footing Trench Excavation
All footing excavations should be observed by a representative of this firm subsequent to
trenching and prior to concrete form and reinforcement placement. The purpose of the
observations is to verify that the excavaflons are made into the recommended bearing
material and to the minimum widths and depths recommended for construcflon. If loose
or compressible materials are exposed within the fooflng excavation, a deeper fooflng or
removal and recompacflon ofthe subgrade materials would be recommended atthatflme.
Footing trench spoil and any excess soils generated from utility trench excavaflons should
be compacted to a minimum relative compaction of 90 percent, if not removed from the
site.
Trenching
Considering the nature ofthe onsite soils, it should be anflcipated that caving or sloughing
could be a factor in subsurface excavaflons and trenching. Shoring or excavaflng the
trench walls at the angle of repose (typically 25 to 45 degrees) may be necessary and
should be anticipated. All excavations should be observed by one of our representatives
and minimally conform to CAL-OSHA and local safety codes.
Utility Trench Backfill
1. All interior utility trench backfill should be brought to at least 2 percent above
optimum moisture content and then compacted to obtain a minimum relaflve
compacflon of 90 percent ofthe laboratory standard. As an alternative for shallow
(12-inch to 18-inch) under-slab trenches, sand having a sand equivalent value of
Touchstone Communities, LLC. W.O. 3975-A-SC
Northpark at La Costa, Carlsbad August 5,2003
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GeoSoils, Inc.
30 or greater may be ufllized and jetted or flooded into place. Observaflon, probing
and tesflng should be provided to verify the desired results.
Exterior trenches adjacent to, and within areas extending below a 1:1 plane
projected from the outside bottom edge of the footing, and all trenches beneath
hardscape features and in slopes, should be compacted to at least 90 percent of
the laboratory standard. Sand backfill, unless excavated from the trench, should
not be used in these backfill areas. Compacflon tesflng and obsen/aflons, along
with probing, should be accomplished to verify the desired results.
All trench excavations should conform to CAL-OSHA and local safety codes.
Utilities crossing grade beams, perimeter beams, or fooflngs should either pass
below the footing or grade beam ufllizing a hardened collar or foam spacer, or pass
through the fooflng or grade beam in accordance with the recommendaflons ofthe
structural engineer.
SUPPLEMENTAL MOISTURE CONDITIONING
For very low to low expansive soils using conventional foundaflons, the moisture content
of the subgrade soils should be equal to, or greater than, optimum moisture content to a
depth below subgrade of 12 inches for one-story structures and 18 inches for two-story
structures, prior to pouring concrete. For medium expansive soils using conventional
foundations, the moisture content of each slab area should be 120 percent, or greater,
above opflmum and verifled by the soil engineer to a depth of 18 inches below adjacent
ground grade in the slab areas, prior to pouring concrete.
Soil moisture contents should be verified by a GSI representaflve. Once pre-construction
tesflng is completed, the visqueen barrier should be placed on the moistened soil within
72 hours and the slab should be poured within 72 hours.
SUMMARY OF RECOMMENDATIONS REGARDING
GEOTECHNICAL OBSERVATION AND TESTING
We recommend that observation and/or testing be performed by GSI at each of the
following construction stages:
• During grading/recertification.
After excavation of building fooflngs, retaining wall footings, and free standing walls
fooflngs, prior to the placement of reinforcing steel or concrete.
Touchstone Communities, LLC. W.O. 3975-A-SC
Northpark at La Costa, Carlsbad August 5, 2003
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GeoSoils, Inc.
Prior to pouring any slabs or flatwork, after presoaking/presaturation of building
pads and other flatwork subgrade, before the placement of concrete, reinforcing
steel, capillary break (i.e., sand, pea-gravel, etc.), or vapor barriers (i.e., visqueen,
etc.).
During retaining wall subdrain installaflon, prior to backfill placement.
During placement of backfill for area drain, interior plumbing, ufllity line trenches,
and retaining wall backfill.
During slope construcflon/repair.
When any unusual soil conditions are encountered during any construcflon
operaflons, subsequent to the issuance of this report.
When any developer or homeowner improvements, such as flatwork, spas, pools,
walls, etc., are constructed.
A report of geotechnical obsen/ation and testing should be provided at the
conclusion of each of the above stages, in order to provide concise and clear
documentation of site work, and/or to comply with code requirements.
OTHER DESIGN PROFESSIONALS/CONSULTANTS
The design civil engineer, structural engineer, post-tension designer, architect, landscape
architect, wall designer, etc., should review the recommendations provided herein,
incorporate those recommendaflons into all their respecflve plans, and by explicit
reference, make this report part of their project plans.
PLAN REVIEW
Final project plans should be reviewed by this office prior to construction, so that
construcflon is in accordance with the conclusions and recommendaflons of this report.
Based on our review, supplemental recommendaflons and/or further geotechnical studies
maybe warranted.
Touchstone Communities, LLC.
Northpark at La Costa, Carlsbad
Fiie:e:\wp9\3900\3975a.pgi
W.O. 3975-A-SC
August 5, 2003
Page 31
GeoSoils, Inc.
LIMITATIONS
The materials encountered on the project site and utilized for our analysis are believed
representative ofthe area; however, soil and bedrock materials vary in character between
excavations and natural outcrops or conditions exposed during mass grading. Site
conditions may vary due to seasonal changes or other factors.
Inasmuch as our study is based upon our review and engineering analyses and laboratory
data, the conclusions and recommendaflons are professional opinions. These opinions
have been derived in accordance with current standards of practice, and no warranty is
expressed or implied. Standards of pracflce are subject to change with time. GSI assumes
no responsibility or liability for work or tesflng performed by others, or their inacflon, or
work performed when GSI is not requested to be onsite, to evaluate if our
recommendaflons have been properly implemented. Use of this report constitutes an
agreement and consent by the user to all the limitations outlined above, notwithstanding
any other agreements that may be in place. In addiflon, this report may be subject to
review by the controlling authorities.
Touchstone Communities, LLC.
Northpark at La Costa, Carlsbad
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August 5, 2003
Page 32
GeoSoils, Inc.
APPENDIX A
REFERENCES
Benton Engineering, Inc.,1974, Final report on compacted filled ground. La Costa Vale
Unit 1, dated February 28, Project # 72-8-18D.
Blake, T.F., 2000a, EQFAULT, A computer program for the estimation of peak horizontal
acceleraflon from 3-D fault sources; Windows 95/98 version.
, 2000b, EQSEARCH, A computer program for the estimation of peak horizontal
acceleraflon from California historical earthquake catalogs; Windows 95/98 version.
, 2000c, FRISKSP, A computer program for the probabilistic esflmation of peak
acceleraflon and uniform hazard spectra using 3-D faults as earthquake sources;
Windows 95/98 version.
Bozorgnia, Y., Campbell, K.W., and Niazi, M., 1999, Vertical ground moflon: characterisflcs,
relaflonship with horizontal component, and building-code implicaflons;
Proceedings ofthe SMIP99 seminar on ufllization of strong-motion data, September,
15, Oakland, pp. 23-49.
Campbell, K.W., 1997, Empirical near-source attenuaflon relaflonshipsfor horizontal and
vertical components of peak ground acceleration, peak ground velocity, and
pseudo-absolute acceleraflon response spectra, Seismological Research Letters,
vol. 68, No. 1, pp. 154-179.
GeoSoils, Inc., 2003, Preliminary geotechnical invesflgaflon, proposed urban villages,
760 Broadway, Chula Vista, San Diego County, California, W.O. 3525-A-SC, dated
February 12.
Greensfelder, R. W., 1974, Maximum credible rock acceleration from earthquakes in
California: California Division of Mines and Geology, Map Sheet 23.
Hart, E.W. and Bryant, W.A., 1997, Fault-rupture hazard zones in California: California
Department of Conservation, Division of Mines and Geology, Special Publicaflon 42.
Housner, G. W., 1970, Strong ground moflon in earthquake engineering, Robert Wiegel,
ed., Prenflce-Hall.
Idriss, I.M., 1994, Attenuaflon coefficients for deep and soft soil condiflons, in EQFAULT,
A computer program for the estimation of peak horizontal acceleraflon from 3-D
fault sources; Windows 95/98 version, Blake, 2000a.
Internaflonal Conference of Building Officials, 1997, Uniform building code: Whittier,
California.
GeoSoils, Inc.
Jennings, C.W., 1994, Fault activity map of California and adjacent areas: California
Division of Mines and Geology, Map Sheet No. 6, scale 1:750,000.
Joyner, W.B, and Boore, D.M., 1982a, Esflmaflon of response-spectral values as funcflons
of magnitude, distance and site condiflons, in Johnson, J.A., Campbell, K.W., and
Blake, eds., T.F., AEG Short Course, Seismic Hazard Analysis, June 18,1994.
, 1982b, Predicflon of earthquake response spectra, in Johnson, J.A., Campbell,
K.W., and Blake, eds., T.F., AEG Short Course, Seismic Hazard Analysis, June 18,
1994.
Kennedy, Michael P., and Tan, S.S., 1977,Geology of National City, Imperial Beach and
Otay Meas Quadrangles, Southern San Diego Metropolitan Area, California:
California Division of Mines and Geology, Map Sheet 29.
Obermeier, S.F., 1996, Using liquefacflon-induced features for paleoseismic analysis,
Chapter 7, in Paleoseismology, McCalpin, J.P., ed.. Academic Press, Inc., San
Diego, California.
Sadigh, K., Egan, J., and Youngs, R., 1987, Predictive ground moflon equaflons reported
in Joyner, W.B., and Boore, D.M., 1988, "Measurement, characterizaflon, and
predicflon of strong ground moflon", in Earthquake Engineering and Soil Dynamics
11, Recent Advances in Ground Moflon Evaluaflon, Von Thun, J.L., ed.: American
Society of Civil Engineers Geotechnical Special Publicaflon No. 20, pp. 43-102.
Snipes-Dyes and Associates, 2003, Tentative map/conceptual base grading plan,
Northpark at La Costa, dated March 14.
Sowers and Sowers, 1970, Unified soil classification system (After U. S. Waten/vays
Experiment Station and ASTM 02487-667) in Introductory Soil Mechanics, New
York.
Touchstone Development, LLC
File:e:\wp9\3900\3975a.pgi
Appendix A
Page 2
GeoSoils, Inc.
GeoSoils, Inc.
BORING LOG
W.O. 3975-A-SC
PR0J£Cr:T0UCHST0NE
Levante & La Costa, North Park at La Costa
BORING B-2
DATE EXCAVATED
SHEET 1 OF 2
7-7-03
a
0)
Sample
10
15-
53 I m
tnS
tn g.
3 OT
sc
C —'
Q
104.0
1067
106.6
13.3
16.4
18.8
m OT
60
79
90
SAMPLE METHOD: 0-25' - 2500 lbs; 26-45' -1500 lbs; 45' - 750 lbs.
Standard Penetration Test
Undisturbed, Ring Sampie
SI Groundwater
Description of Material
ARTIFICIAL FILL:
@ 0" CLAYEY SAND, olive brown to light brown, damp, loose.
@ 2" CLAYEY SAND, olive brown to light brown, moist, loose.
@ 5" CLAYEY SAND, light brown, wet, medium dense.
@ 10" CLAYEY SAND, light brown, wet, medium dense.
20-
25-
CL Disturbed 22.6 96 @ 15" SANDY CLAY, dark brown, wet, soft.
13 104.1 21.4 94
18 101.5 22.3 95
SANTIAGO FORMATION:
@ 17' Contact between Artificial Fill and Santiago is undulatory and
processed, not a gradational contact.
@ 19' Fracture: N30E, 25NW.
@ 20" CLAYSTONE, olive gray, wet, hard.
Fracture: N20E, 40SE; N25W, 55NE; N/S, 45E.
@ 21' Fracture: N30W, 85NE, random fractures, oxidized staining
between fractures, caliche.
25' CLAYSTONE, olive gray, wet, very stiff; Fracture: N20W, 85NE.
@ 26' Random fractures, caliche.
Levante & La Costa, North Park at La Costa GeoSoils, Inc. PLATE B-2
GeoSoils, Inc.
BORING LOG
W.O. 3975-A-SC
PROJECr.TOUCHSTONE
Levante & La Costa, North Park at La Costa
BORING B-2
DATE EXCAVATED
SHEET 2 OF 2
7-7-03
a. ID a
Sample
II I
CQ
" E w >. 3 OT
s a c —'
Q
D
0) O
o
1
(0 OT
SAMPLE METHOD: 0-25' - 2500 lbs; 26-45" -1500 lbs; 45' - 750 lbs.
Standard Penetration Test
Undisturbed, Ring Sample S Groundwater
Description of Material
35-
40
45-
50-
20
20
22
109.7 18.2 90
106.3 18.9 95
108.3 19.0 95
@ 30' CLAYSTONE, olive gray, wet, hard; Fracture: N23W, 85NE;
N35W, 55NE.
@ 34' Fracture: N50E, 70NW.
@ 35' CLAYSTONE. olive gray, wet, hard; massive fracture in filled with
gypsum, highly fractured.
N70E, 65NW.
! 40' CLAYSTONE, olive gray, wet, hard; massive, highly fractured.
@ 43' SANDSTONE, light olive gray, wet, dense; massive, highly
fractured.
55-
Total Depth = Si-
No Groundwater Encountered
Backfilled 7-7-2003
Backfilled with Bentonite Grout @ 51' and ±10 to ±5 feet
* No Well Developed Planer Features*
Levante & La Costa, North Park at La Costa GeoSoils, Inc. PLATE B-3
GeoSoils, Inc.
BORING LOG
W.O. 3975-A-SC
PROJECT; TOUCHSTONE
Levante & La Costa, North Park at La Costa
BORING B-3
DATE EXCAVATED
SHEET 1 OF 1
7-7-03
Sample
a
0)
a m z>3 o m
U E OT >. 3 OT
5^
c ^ 3
£• Q o
2
c o
e
D ra OT
SAMPLE METHOD: 0-25' - 2500 lbs; 26-45' -1500 lbs; 45' - 750 lbs.
Standard Penetration Test
Undisturbed, Ring Sample S Groundwater
Description of Material
CL
92.6 28.2 95
ARTIFICIAL FILL:
@ 0" SANDY CLAY, light reddish brown to brown, moist, soft.
@ 2' SANDY CLAY, light brown, wet, medium stiff.
10-
15-
20-
25-
102.5 20.0 86 SANTIAGO FORMATION:
@ 5' SANDY CLAYSTONE, light brown to olive gray, wet, medium stiff ^
Total Depth = 6'
No Groundwater Encountered
Backfilled 7-7-2003
Levante & La Costa, North Park at La Costa GeoSoils, Inc. PLATE B-4
c
05
0)
<D O O
<
MAXIMUM EARTHQUAKES
Touchstone Communities
1 -=
.1 -=
,01
.001
1 1 10
Distance (mi)
100
W.O. 3975-A-SC Plate C-1
GeoSoils, Inc.
ra
(0
c
> LLl
0
E u
Z
0 >
_ro
E
E
o
EARTHQUAKE RECURRENCE CURVE
Touchstone Comnnunities
100
10
.01
.001
3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0
Magnitude (M)
W.O. 3975-A-SC Plate C-2
GeoSoils, Inc.
EARTHQUAKE EPICENTER MAP
Touchstone Communities
1100
1000
900 --.
800 --
700 --
600 --
500
400 --
300 --
200
100 --
0 --
-100
h X M = 4
0 M = 5
• M = 6
A M = 7
-<Q> M = 8
1 I I I I I ' I I 1 I I I I jl I I I I I I I I I I I I I I I I I I I
-400 -300 -200 -100 0 100 200 300 400 500 600
W.O. 3975-A-SC Plate C-3
GeoSoils, Inc.
PROBABILITY OF EXCEEDANCE
BOZ. ET AL.(1999)HOR HR UNC 1
100
n
CD
o
CD o c
CD
"O
0
<D
O
X
LU
25 yrs
75 yrs
50 yrs
100 yrs
0.00 0.25 0.50 0.75 1.00 1.25
Acceleration (g)
1.50
W.O. 3975-A-SC Plate C-4
GeoSoils, Inc.
p
ca <o
Ol
>
I 0) o
CO
0
M« 5* o
m MM 0
• CL
c I—
13
0
cr:
2
o
I
cn
RETURN PERIOD vs. ACCELERATION
BOZ. ET AL.(1999)HOR HR UNC 1
100000
10000
1000
100
0.00 0.25 0.50 0.75 1.00
Acceleration (g)
1.25 1.50
3,000 •
2,500 •
2,000
O z
UJ
i
I
0}
1,500 •
1,000
500-
500 1.000 1.500 2.000 2.500 3.000
NORMAL PRESSURE, psf
Sample Depth/El. Primary/Residual Shear Sample Type Td MC% C
• B-1 20.0 Primary Shear Undisturbed 111.0 18.9 1370 29 • B-1 20.0 Residual Shear Undisturbed 111.0 18.9 282 32
• e w
2
a. o Note: Sample Innundated prior to testing
GeoSoils, Inc.
^ 5741 PalmerWay
KM. Carlsbad, CA 92008
Telephone: (760)438-3155
Fax: (760)931-0915
DIRECT SHEAR TEST
Project: TOUCHSTONE
Number: 3975-A-SC
Date: July 2003 Plate: D-1
3,000
2,500
•5 2,000
i z UJ
1,500
X
tn
1.000
500
500 1.000 1,500 2,000 2,500 3,000
NORMAL PRESSURE, psf
Sample Depth/El. Primary/Residual Shear Sample Type Yd MC% C
• B-2 2.0 Primary Shear Undisturbed 105.6 13.3 271 32 • B-2 2.0 Residual Shear Undisturbed 105.6 13.3 265 31
u
in
Note: Sample Innundated prior to testing
c
IL E
O
>Sot
GeoSoils, Inc.
5741 PalmerWay
Carlsbad, CA 92008
Telephone: (760)438-3155
Fax: (760) 931-0915
DIRECT SHEAR TEST
Project: TOUCHSTONE
Number: 3975-A-SC
Date: July 2003 Plate: D-2
3,000
2.500
2.000
O z
UJ
i
X CO
1.500
1.000
1.000 1,500 2,000
NORMAL PRESSURE, psf
2,500 3,000
Sample Depth/El. Primary/Residual Shear Sample Type Yd MC% C
• B-2 20.0 Primary Shear Undisturbed 103.3 21.4 1206 19 • B-2 20.0 Residual Shear Undisturbed 103.3 21.4 13 33
Q. Note: Sample Innundated prior to testing
Ol D
GeoSoils, Inc.
^ 5741 Palmer Way
me. Carlsbad, CA 92008
Telephone: (760)438-3155
Fax: (760)931-0915
DIRECT SHEAR TEST
Project: TOUCHSTONE
Number: 3975-A-SC
Date: July 2003 Plate: D-3
3.000 •
2.500
*!» 2.00O-
i z UJ
1.500 •
I
(0
1,000-
500-
500 1,000 1,500 2.000
NORMAL PRESSURE, psf
2,500 3,000
Sample Depth/El, Primary/Residual Shear Sample Type Yd MC% C
• B-2 40.0 Primary Shear Undisturi3ed 106.6 19.0 730 38 • B-2 40.0 Residual Shear Undisturbed 106.6 19.0 190 31
Note: Sample Innundated prior to testing
Ol
GeoSoils, Inc.
5741 PalmerWay
Carlsbad, CA 92008
Telephone: (760)438-3155
Fax: (760)931-0915
DIRECT SHEAR TEST
Project: TOUCHSTONE
Number: 3975-A-SC
Date: July 2003 Plate: D-4
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.01_ 100
\
1,000 10,000 To'
STRESS, psf
Sample Depth/El. Visual Classification Yd
Initial
MC
Initial
MC
Final
H20
• B-1 3.0 Clay 95.9 26.6 27.3 500
o u
CO 3
GeoSoils, Inc.
5741 Palmer Way
me. Carisbad, CA 92008
^ Telephone: (760)438-3155
Fax: (760)931-0915
CONSOLIDATION TEST
Project: TOUCHSTONE
Number: 3975-A-SC
Date: July 2003 Plate: D-5
0.0
z
\
\
\ V
s
\
\
\
\
\
^^^^^^^^ —'
\
\
A
STRESS, psf
Sample Depth/El. visual Classification Yd
Initial
MC
Initial
MC
Final
H20
• B-1 10.0 Clay 97.1 24.2 25.1 1440
ts
o 2
3
Z
i
I z
GeoSoils, Inc.
0m. 5741 Palmer Way
iKIIiM. Carlsbad, CA 92008
Telephone: (760)438-3155
Fax: (760)931-0915
CONSOLIDATION TEST
Project: TOUCHSTONE
Number: 3975-A-SC
Date: July 2003 Plate: D-6
to 2.0
STRESS, psf
Sample Depth/El, Visual Classification Yd
Initial
MC
Initial
MC
Final
H20
• B-2 5.0 Clayey Sand 105.8 16.4 21.8 1000
Q U si
Q. (9
Z o u
GeoSoils, Inc.
5741 PalmerWay
Carlsbad, CA 92008
Telephone: (760)438-3155
Fax: (760)931-0915
CONSOLIDATION TEST
Project: TOUCHSTONE
Number: 3975-A-SC
Date: July 2003 Plate: D-7
2-DIIVIENSIONAL SLOPE STABILITY ANALYSIS
INTRODUCTION OF GSTABL7 v.2 COIVIPUTER PROGRAM
Introduction
GSTABL7 v.2 is a fully integrated slope stability analysis program. It permits the engineer
to develop the slope geometry interactively and perform slope stability analysis from within
a single program. The slope analysis portion of GSTABL7 v.2 uses a modified version of
the popular STABL program, originally developed at Purdue University.
GSTABL7 v.2 performs a two dimensional limit equilibrium analysis to compute the factor
of safety for a layered slope using the simplified Bishop or Janbu methods. This program
can be used to search for the most critical surface or the factor of safety may be
determined for specific surfaces. GSTABL7, Version 2, is programmed to handle:
1. Heterogenous soil systems
2. Anisotropic soil strength properties
3. Reinforced slopes
4. Nonlinear Mohr-Coulomb strength envelope
5. Pore water pressures for effective stress analysis using:
a. Phreatic and piezometric surfaces
b. Pore pressure grid
c. R factor
d. Constant pore water pressure
6. Pseudo-static earthquake loading
7. Surcharge boundary loads
8. Automatic generation and analysis of an unlimited number of circular, noncircular
and block-shaped failure surfaces
9. Analysis of right-facing slopes
10. Both SI and Imperial units
General Information
If the reviewer wishes to obtain more information concerning slope stability analysis, the
following publications may be consulted Initially:
1. The Stabilitv of Slopes, by E.N. Bromhead, Surrey University Press, Chapman and
Hall, N.Y.,411 pages, ISBN 412 01061 5, 1992.
2. Rock Slope Enaineerinq. by E. Hoek and J.W. Bray, Inst, of Mining and Metallurgy,
London, England, Third Edition, 358 pages, ISNB 0 900488 573,1981.
3. Landslides: Analvsisand Control, by R.L. Schuster and R.J. Krizek (editors). Special
Report 176, Transportation Research Board, National Academy of Sciences,
234 pages, ISBN 0 309 02804 3,1978.
GeoSoils, Inc.
GSTABL7 v.2 Features
The present version of GSTABL7 v.2 contains the following features:
1. Allows user to calculate factors of safety for static stability and dynamic stability
situations.
2. Allows user to analyze stability situations with different failure modes.
3. Allows user to edit input for slope geometry and calculate corresponding factor of
safety.
4. Allows user to readily review on-screen the input slope geometry.
5. Allows user to automatically generate and analyze unlimited number of circular,
non-circular and block-shaped failure surfaces (i.e., bedding plane, slide plane,
etc.).
Input Data
Input data includes the following items:
1. Unit weight, residual cohesion, residual friction angle, peak cohesion, and peak
friction angle of fill material, bedding plane, and bedrock, respectively. Residual
cohesion and friction angle is used for static stability analysis, where as peak
cohesion and friction angle is for dynamic stability analysis.
2. Slope geometry and surcharge boundary loads.
3. Apparent dip of bedding plane can be specified in angular range (i.e., from 0 to
90 degrees.
4. Pseudo-static earthquake loading (an earthquake loading of 0.12 / was used in the
analysis).
Seismic Discussion
Seismic stability analyses were approximated using a pseudo-static approach. The major
difficulty in the pseudo-static approach arises from the appropriate selection ofthe seismic
coefficient used in the analysis. The use of a static inertia force equal to this acceleration
during an earthquake (rigid-body response) would be extremely conservative for several
reasons including: (1) only low height, stiff/dense embankments or embankments in
confined areas may respond essentially as rigid structures; (2) an earthquake's inertiaforce
is enacted on a mass for a short time period. Therefore, replacing a transient force by a
pseudo-static force representing the maximum acceleration is considered unrealistic;
Touchstone Communities, LLC.
Fiie:e:\wp9\3900\3975a.pgi
Appendix E
Page 2
GeoSoils, Inc.
(^) Assuming that tnt^i
OWPW information includes:
'• "^'1 input data.
SS%s«u^?„'>'most Critical surfaces for .
Hiah ,. Pseudo-static •^'gn quality plots ran K 3.
F"e:e:\wp9\3900\3975a.pg,
OeoSoiU, Inc.
Appendix E
Pages
TABLE E-1
Soil Parameters Used
SOIL MATERIALS
PEAK VALUES
SOIL MATERIALS C (psf) 0 (degrees)
Fill Materials 190 31
Santiago Formation 250 31
TABLE E-2
Summary of Slope Analysis
STABILITY
SLOPE
CONFIGURATION
SLOPE
GRADIENT
FACTORS OF SAFETY
REMARKS STABILITY
SLOPE
CONFIGURATION
SLOPE
GRADIENT STATIC SEISMIC REMARKS
Gross ±32-Foot High Existing
Fill Over Cut
2:1 2.12 1.6 Bishop, circular
Touchstone Communities, LLC.
File:e:\wp9\3900\3975a.pgi
Appendix E
Page 4
GeoSoils, Inc.
I
a
STED
•D
It-<P
m I
TOUCHSTONE cOMlIImEn!!!^^^^^'
===i^£I!ewN\3975.p™ L' f',^^75 SECTION A-A" <!TiiT,„
160
"•"y The Modified Bishop MeiHo,
240 280
200
a
STED
ST
I
=f===^=SgSl2£ti GEofof A-A-, SEISMIC
160
Safety Fectors cStUl'^"-'r ^
""By The Modifled Bishop Method
240 280
SURFICIAL SLOPE STABILITY FOR FILL OVER CUT SLOPES
SLOPE ANGLE i (degrees) =
VERTICAL DEPTH OF SATURATION 2 (ft) =
SATURATED SOIL UNIT WEIGHT ysat (pcf)=
UNIT WEIGHT OF WATER yw (pcf) =
EFFECTIVE COHESION C" (psf) =
EFFECTIVE FRICTION ANGLE (J) (degrees)=
SLOPE ANGLE IN RADIANS
EFFECTIVE FRICTION ANGLE IN RADIANS
INPUT PARAMETERS
FACTOR OF SAFETY =
26.6
4
125
62.4
190
31
OUTPUT CALCULATIONS
0.464258
0.541052
1.55
a
u
m • I
CO
2-DIMENSJnNfll Q. non ^TflniLITY flM/ii vg.c
INTRODUCTION OF GSTABL7 v.2 COMPUTER PROGRAM
Introductinn
So^Ilfe slo^eL'iS^^^^^^ ,t permits the engineer
a Single program. The slopeTnSortiro^G^rT^^ *«hin
the popular STABL progra^, origiL^^Cf J^^dVelrisir"'' """" °'
can be used to search for the ScSc^s^rftrnVfh r^*"'''' ™^P'°9'^
detem,ined,orspeci«csurfaces. OST\^^tZTi:X^:^J^^^^^^
1 • Heterogenous soil systems
2. Anisotropic soil strength properties
3. Reinforced slopes
4. Nonlinear Mohr-Coulomb strength envelope
5. Pore water pressures for effective stress analysis using-
a. Phreatic and piezometric surfaces
b. Pore pressure grid
c. R factor
d. Constant pore water pressure
o- Pseudo-static earthquake loading
Surcharge boundary loads
anrolX"prfeirsSr °' ^" """"^"^^ °' "-Circular
Analysis of right-facing slopes
Both SI and Imperial units
General Information
*™^nrp:s^^^^
8.
10.
2.
S^S^^^^^SSS^seLch^^rd^^^^^^
234 pages, ISBN 0 309^4 3 W8 "^""^ °'
GeoSoils, Inc.
GSTABL7 y.2 Features
The present version of GSTABL7 v.2 contains the following features:
1.
2.
3.
4.
5.
iTonT''° °' """^^"^ ^V™'"!^ ^'ability
Allows user to analyze stability situations with different failure modes.
Mows user to edit input for slope geometry and calculate corresponding factor of
Allows user to readily review on-screen the input slope geometry.
Allows user to automatically generate and analyze unlimited number of circular
nojvcrcular and block-shaped failure surfaces (i.e.. bedding pllne LlWe plane-
Input Data
Input data includes the following items:
1. Unit weight, residual cohesion, residual friction angle, peak cohesion and oeak
friction angle o fill material, bedding plane, and bedrock, respectively Residual
cohesion and fnction angle is used for static stability analysis where as oeak
cohesion and friction angle is for dynamic stability ana^is
2.
3.
Slope geometry and surcharge boundary loads.
90 deg'mes!" °' "'"'""^ "'^^ ^"9"'^' '^"^ l^-^- " <°
^TyJs)^"*'" ^"^""^^ '"^"'"S earfhquake loading of 0.12 / was used in the
Seismic Discussion
HHiT",'," ^^'^ ^^'^^^ ^^'^ approximated using a pseudo-static approach The maior
difficulty ,n the pseudo-static approach arises from the appropriate selS oTof the setemte
coefficient used in the analysis. The use of a static inerSa fo?ce ^uaHo thlT^^^^^^^
durrig an earthquake (rigid-body response) would be extremely ^nseZ^vrfofseve^^^
^nnr n'"""*"^- ''"'S'^'' "^'"^^ embankments or emSmente Tn
confined areas may respond essentially as rigid structures; (2) an earthquakejinertiaforce
IS enacted on a mass for a short time period. Therefore, replacing a frrsten foree bv a
pseudo-static force represenflng the maximum acceleration is ^ns~un«!
Touchstone Communities, LLC,
File:e:\wp9\3900\3975a.pgi
GeoSoils, Inc.
Appendix E
Page 2
(3) Assuming that total pseudo-static loading is applied evenly throughout the
embankment for an extended period of time is an incorrect assumption, as the length of
the failure surface analyzed is usually much greater than the wave length of seismic waves
generated by earthquakes; and (4) the seismic waves would place portions of the mass
in compression and some in tension, resulting in only a limited portion ofthe failure surface
analyzed moving in a downslope direction, at any one instant of time.
The method developed by Krinitzsky, Gould, and Edinger (1993) which was in turn based
on Taniguchi and Sasaki, 1986, (T&S, 1986), was referenced. This method is based on
empirical data and the performance of existing earth embankments during seismic loading.
Our review of "Guidelines for Evaluating and Mitigating Seismic Hazards in California
(Davis, 1997) indicates the State of California recommends using pseudo-static coefficient
of 0.15 for design earthquakes of M 8.25 or greater and using 0.1 for earthquake parameter
M 6.5. Therefore, for conservatism a seismic coefficient of 0.12 / was used in our analysis.
Output Information
Output information includes:
1, All input data.
2. Factors of safety for the ten most critical surfaces for static and pseudo-static
stability situation.
3. High quality plots can be generated. The plots include the slope geometry, the
critical surfaces and the factor of safety.
4. Note, that in the analysis, a minimum of 100 trial surfaces were analyzed for each
section for either static or pseudo-static analyses.
Results of Slope Stability Calculation
Table E-1 shows parameters used in slope stability calculations. Summaries of the slope
stability analysis are presented in Table E-2. Detailed output information is presented in
Plates E-1 to E-2. A typical cross-section representing the highest proposed fill slope at
a gradient of 2:1 (h:v) was utilized for analyses.
Touchstone Communities, LLC.
File:e:\wp9\3900\3975a.pgi
Appendix E
Pages
GeoSoils, Inc.
TABLE E-1
Soil Parameters Used
SOIL MATERIALS
PEAK VALUES
SOIL MATERIALS C (psf) 0 degrees)
Fill Materials 190 31
Santiago Formation 250 31
TABLE E-2
Summary of Slope Analysis
STABILITY
SLOPE
CONFIGURATION
SLOPE
GRADIENT
FACTORS OF SAFETY
REMARKS STABILITY
SLOPE
CONFIGURATION
SLOPE
GRADIENT STATIC SEISMIC REMARKS
Gross ±32-Foot High Existing
Fill Over Cut
2:1 2.12 1.6 Bishop, circular
Touchstone Communities, LLC.
File:e:\wp9\3900\3975a.pgi
Appendix E
Page 4
GeoSoils, Inc.
GENERAL EARTHWORK AND GRADING GUIDELINES
General
These guidelines present general procedures and requirements for earthwork and grading
as shown on the approved grading plans, including preparation of areas to filled,
placement of fill, installation of subdrains and excavations. The recommendations
contained in the geotechnical report are part ofthe earthwork and grading guidelines and
would supercede the provisions contained hereafter in the case of conflict. Evaluations
performed by the consultant during the course of grading may result in new
recommendations which could supersede these guidelines or the recommendations
contained in the geotechnical report.
The contractor is responsible for the satisfactory completion of all earthwork in accordance
with provisions of the project plans and specifications. The project soil engineer and
engineering geologist (geotechnical consultant) or their representatives should provide
observation and testing services, and geotechnical consultation during the duration ofthe
project.
EARTHWORK OBSERVATIONS AND TESTING
Geotechnical Consultant
Prior to the commencement of grading, a qualified geotechnical consultant (soil engineer
and engineering geologist) should be employed for the purpose of observing earthwork
procedures and testing the fills for conformance with the recommendations of the
geotechnical report, the approved grading plans, and applicable grading codes and
ordinances.
The geotechnical consultant should provide testing and obsen/ation so that determination
may be made that the work is being accomplished as specified. It is the responsibility of
the contractor to assist the consultants and keep them apprised of anticipated work
schedules and changes, so that they may schedule their personnel accordingly.
All clean-outs, prepared ground to receive fill, key excavations, and subdrains should be
observed and documented by the project engineering geologist and/or soil engineer prior
to placing and fill. It is the contractors's responsibility to notify the engineering geologist
and soil engineer when such areas are ready for observation.
Laboratory and Field Tests
Maximum dry density tests to determine the degree of compaction should be performed
in accordance with American Standard Testing Materials test method ASTM designation
D-1557-78. Random field compaction tests should be performed in accordance with test
method ASTM designation D-1556-82, D-2937 or D-2922 and D-3017, at intervals of
approximately 2 feet of fill height or every 100 cubic yards of fill placed. These criteria
GeoSoils, Inc.
would vary depending on the soil conditions and the size of the project. The location and
frequency of testing would be at the discretion of the geotechnical consultant.
Contractor's Responsibility
All clearing, site preparation, and earthwork performed on the project should be conducted
by the contractor, with observation by geotechnical consultants and staged approval by
the governing agencies, as applicable. It is the contractor's responsibility to prepare the
ground surface to receive the fill, to the satisfaction of the soil engineer, and to place,
spread, moisture condition, mix and compact the fill in accordance with the
recommendations of the soil engineer. The contractor should also remove all major non-
earth material considered unsatisfactory by the soil engineer.
It is the sole responsibility of the contractor to provide adequate equipment and methods
to accomplish the earthwork in accordance with applicable grading guidelines, codes or
agency ordinances, and approved grading plans. Sufficient watering apparatus and
compaction equipment should be provided by the contractor with due consideration for
the fill material, rate of placement, and climatic conditions. If, in the opinion of the
geotechnical consultant, unsatisfactory conditions such as questionable weather,
excessive oversized rock, or deleterious material, insufficient support equipment, etc., are
resulting in a quality of work that is not acceptable, the consultant will inform the
contractor, and the contractor is expected to rectify the conditions, and if necessary, stop
work until conditions are satisfactory.
During construction, the contractor shall properly grade all surfaces to maintain good
drainage and prevent ponding of water. The contractor shall take remedial measures to
control surface water and to prevent erosion of graded areas until such time as permanent
drainage and erosion control measures have been installed.
SITE PREPARATION
All major vegetation, including brush, trees, thick grasses, organic debris, and other
deleterious material should be removed and disposed of off-site. These removals must be
concluded prior to placing fill. Existing fill, soil, alluvium, colluvium, or rock materials
determined by the soil engineer or engineering geologist as being unsuitable in-place
should be removed prior to fill placement. Depending upon the soil conditions, these
materials may be reused as compacted fills. Any materials incorporated as part of the
compacted fills should be approved by the soil engineer.
Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic
tanks, wells, pipelines, or other structures not located prior to grading are to be removed
or treated in a manner recommended by the soil engineer. Soft, dry, spongy, highly
fractured, or othen/vise unsuitable ground extending to such a depth that surface
processing cannot adequately improve the condition should be overexcavated down to
firm ground and approved by the soil engineer before compaction and filling operations
Touchstone Communities, LLC. Appendix F
File:e:\wp9\3900\3975a.pgi Page 2
GeoSoils, Inc.
continue. Overexcavated and processed soils which have been properly mixed and
moisture conditioned should be re-compacted to the minimum relative compaction as
specified in these guidelines.
Existing ground which is determined to be satisfactory for support of the fills should be
scarified to a minimum depth of 6 inches or as directed by the soil engineer. After the
scarified ground is brought to optimum moisture content or greater and mixed, the
materials should be compacted as specified herein. If the scarified zone is grater that
6 inches in depth, it may be necessary to remove the excess and place the material in lifts
restricted to about 6 inches in compacted thickness.
Existing ground which is not satisfactory to support compacted fill should be
overexcavated as required in the geotechnical report or by the on-site soils engineer
and/or engineering geologist. Scarification, disc harrowing, or other acceptable form of
mixing should continue until the soils are broken down and free of large lumps or clods,
until the working surface is reasonably uniform and free from ruts, hollow, hummocks, or
other uneven features which would inhibit compaction as described previously.
Where fills are to be placed on ground with slopes steeper than 5:1 (horizontal to vertical),
the ground should be stepped or benched. The lowest bench, which will act as a key,
should be a minimum of 15 feet wide and should be at least 2 feet deep into firm material,
and approved by the soil engineer and/or engineering geologist. In fill over cut slope
conditions, the recommended minimum width ofthe lowest bench or key is also 15 feet
with the key founded on firm material, as designated by the Geotechnical Consultant. As
a general rule, unless specifically recommended otherwise by the Soil Engineer, the
minimum width of fill keys should be approximately equal to Vz the height of the slope.
Standard benching is generally 4 feet (minimum) vertically, exposing firm, acceptable
material. Benching may be used to remove unsuitable materials, although it is understood
that the vertical height of the bench may exceed 4 feet. Pre-stripping may be considered
for unsuitable materials in excess of 4 feet in thickness.
All areas to receive fill, including processed areas, removal areas, and the toe of fill
benches should be observed and approved by the soil engineer and/or engineering
geologist prior to placement of fill. Fills may then be properly placed and compacted until
design grades (elevations) are attained.
COMPACTED FILLS
Any earth materials imported or excavated on the property may be utilized in the fill
provided that each material has been determined to be suitable by the soil engineer.
These materials should be free of roots, tree branches, other organic matter or other
deleterious materials. All unsuitable materials should be removed from the fill as directed
by the soil engineer. Soils of poor gradation, undesirable expansion potential, or
Touchstone Communities, LLC. Appendix F
File:e:\wp9\3900\3975a.pgi Page 3
GeoSoils, Inc.
substandard strength characteristics may be designated by the consultant as unsuitable
and may require blending with other soils to serve as a satisfactory fill material.
Fill materials derived from benching operations should be dispersed throughout the fill
area and blended with other bedrock derived material. Benching operations should not
result in the benched material being placed only within a single equipment width away
from the fill/bedrock contact.
Oversized materials defined as rock or other irreducible materials with a maximum
dimension greater than 12 inches should not be buried or placed in fills unless the location
of materials and disposal methods are specifically approved by the soil engineer.
Oversized material should betaken off-site or placed in accordance with recommendations
ofthe soil engineer in areas designated as suitable for rock disposal. Oversized material
should not be placed within 10 feet vertically of finish grade (elevation) or within 20 feet
horizontally of slope faces.
To facilitate future trenching, rock should not be placed within the range of foundation
excavations, future utilities, or underground construction unless specifically approved by
the soil engineer and/or the developers representative.
If import material is required for grading, representative samples of the materials to be
utilized as compacted fill should be analyzed in the laboratory by the soil engineer to
determine its physical properties. If any material other than that previously tested is
encountered during grading, an appropriate analysis of this material should be conducted
by the soil engineer as soon as possible.
Approved fill material should be placed in areas prepared to receive fill in near horizontal
layers that when compacted should not exceed 6 inches in thickness. The soil engineer
may approve thick lifts if testing indicates the grading procedures are such that adequate
compaction is being achieved with lifts of greater thickness. Each layer should be spread
evenly and blended to attain uniformity of material and moisture suitable for compaction.
Fill layers at a moisture content less than optimum should be watered and mixed, and wet
fill layers should be aerated by scarification or should be blended with drier material.
Moisture condition, blending, and mixing of the fill layer should continue until the fill
materials have a uniform moisture content at or above optimum moisture.
After each layer has been evenly spread, moisture conditioned and mixed, it should be
uniformly compacted to a minimum of 90 percent of maximum density as determined by
ASTM test designation, D-1557-78, or as otherwise recommended by the soil engineer.
Compaction equipment should be adequately sized and should be specifically designed
for soil compaction or of proven reliability to efficiently achieve the specified degree of
compaction.
Touchstone Communities, LLC. Appendix F
Flle:e:\wp9\3900\3975a.pgi Page 4
GeoSoils, Inc.
Where tests indicate that the density of any layer of fill, or portion thereof, is below the
required relative compaction, or improper moisture is in evidence, the particular layer or
portion shall be re-worked until the required density and/or moisture content has been
attained. No additional fill shall be placed in an area until the last placed lift of fill has been
tested and found to meet the density and moisture requirements, and is approved by the
soil engineer.
Compaction of slopes should be accomplished by over-building a minimum of 3 feet
horizontally, and subsequently trimming back to the design slope configuration. Testing
shall be performed as the fill is elevated to evaluate compaction as the fill core is being
developed. Special efforts may be necessary to attain the specified compaction in the fill
slope zone. Final slope shaping should be performed by trimming and removing loose
materials with appropriate equipment. Afinal determination of fill slope compaction should
be based on observation and/or testing of the finished slope face. Where compacted fill
slopes are designed steeper than 2:1 (horizontal to vertical), specific material types, a
higher minimum relative compaction, and special grading procedures, may be
recommended.
If an alternative to over-building and cutting back the compacted fill slopes is selected,
then special effort should be made to achieve the required compaction in the outer 10 feet
of each lift of fill by undertaking the following:
1. An extra piece of equipment consisting of a heavy short shanked sheepsfoot should
be used to roil (horizontal) parallel to the slopes continuously as fill is placed. The
sheepsfoot roller should also be used to roll perpendicular to the slopes, and
extend out over the slope to provide adequate compaction to the face ofthe slope.
2. Loose fill should not be spilled out over the face of the slope as each lift is
compacted. Any loose fill spilled over a previously completed slope face should be
trimmed off or be subject to re-rolling.
3. Field compaction tests will be made in the outer (horizontal) 2 to 8 feet of the slope
at appropriate vertical intervals, subsequent to compaction operations.
4. After completion of the slope, the slope face should be shaped with a small tractor
and then re-rolled with a sheepsfoot to achieve compaction to near the slope face.
Subsequent to testing to verify compaction, the slopes should be grid-rolled to
achieve compaction to the slope face. Final testing should be used to confirm
compaction after grid rolling.
5. Where testing indicates less than adequate compaction, the contractor will be
responsible to rip, water, mix and re-compact the slope material as necessary to
achieve compaction. Additional testing should be performed to verify compaction.
Touchstone Communities, LLC.
File:e:\wp9\3900\3975a.pgi
Appendix F
Page 5
GeoSoils, Inc.
Erosion control and drainage devices should be designed by the project civil
engineer in compliance with ordinances ofthe controlling governmental agencies,
and/or in accordance with the recommendation ofthe soil engineer or engineering
geologist.
SUBDRAIN INSTALLATION
Subdrains should be installed in approved ground in accordance with the approximate
alignment and details indicated by the geotechnical consultant. Subdrain locations or
materials should not be changed or modified without approval of the geotechnical
consultant. The soil engineer and/or engineering geologist may recommend and direct
changes in subdrain line, grade and drain material in the field, pending exposed
conditions. The location of constructed subdrains should be recorded by the project civil
engineer.
EXCAVATIONS
Excavations and cut slopes should be examined during grading by the engineering
geologist. If directed by the engineering geologist, further excavations or overexcavation
and re-filling of cut areas should be performed and/or remedial grading of cut slopes
should be performed. When fill over cut slopes are to be graded, unless othenwise
approved, the cut portion ofthe slope should be observed by the engineering geologist
prior to placement of materials for construction of the fill portion of the slope.
The engineering geologist should observe all cut slopes and should be notified by the
contractor when cut slopes are started. If, during the course of grading, unforeseen
adverse or potential adverse geologic conditions are encountered, the engineering
geologist and soil engineer should investigate, evaluate and make recommendations to
treat these problems. The need for cut slope buttressing or stabilizing should be based
on in-grading evaluation by the engineering geologist, whether anticipated or not.
Unless otherwise specified in soil and geological reports, no cut slopes should be
excavated higher or steeper than that allowed by the ordinances of controlling
governmental agencies. Additionally, short-term stability of temporary cut slopes is the
contractors responsibility.
Erosion control and drainage devices should be designed by the project civil engineer and
should be constructed in compliance with the ordinances ofthe controlling governmental
agencies, and/or in accordance with the recommendations of the soil engineer or
engineering geologist.
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GeoSoils, Inc.
COMPLETION!
graded in accordance with the approved project spScations
JOB SAFETY
General
construction sijes. On ground personnel are a. higLS ri kTn^ury and pos ,rfaS
onSTe"^ST^
on each site and that site safety is the prime responsibility of the contractor- hnv^c^ulr
everyone must be safety conscious and responsible at alI tLes^ T^^^^^^^^^
TemS:'"^""^^
followrnn°nrl° "'r'"'^^ risks associated with geotechnical testing and observation the
IndrnSroie"::^° '^'"'^ '^'^^ of field^rsonnelCradlng
Safety Meetings: GSI field personnel are directed to attend contractors regularly
scheduled and documented safety meetings.
Safety Vests:
Safety Flags:
Safety vests are provided for and are to be wom by GSI personnel at
all times when they are working in the field.
Two safety flags are provided to GSI field technicians; one is to be
affixed o the vehicle when on site, the other is to be placed atop the
spoil pile on all test pits. ^
Touchstone Communities, LLC.
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GeoSoils, Inc.
Appendix F
Page?
Flashing Lights: All vehicles stationary in the grading area shall use rotating or flashing
amber beacon, or strobe lights, on the vehicle during all field testing.
While operating a vehicle in the grading area, the emergency flasher
on the vehicle shall be activated.
In the event that the contractor's representative observes any of our personnel not
following the above, we request that it be brought to the attention of our office.
Test Pits Location. Orientation and Clearance
The technician is responsible for selecting test pit locations. A primary concern should be
the technicians's safety. Efforts will be made to coordinate locations with the grading
contractors authorized representative, and to select locations following or behind the
established traffic pattern, preferably outside of current traffic. The contractors authorized
representative (dump man, operator, supervisor, grade checker, etc.) should direct
excavation of the pit and safety during the test period. Of paramount concern should be
the soil technicians safety and obtaining enough tests to represent the fill.
Test pits should be excavated so that the spoil pile is placed away form oncoming traffic,
whenever possible. The technician's vehicle is to be placed next to the test pit, opposite
the spoil pile. This necessitates the fill be maintained in a driveable condition.
Alternatively, the contractor may wish to park a piece of equipment in front of the test
holes, particularly in small fill areas or those with limited access.
A zone of non-encroachment should be established for all test pits. No grading equipment
should enter this zone during the testing procedure. The zone should extend
approximately 50 feet outward from the center of the test pit. This zone is established for
safety and to avoid excessive ground vibration which typically decreased test results.
When taking slope tests the technician should park the vehicle directly above or below the
test location. If this is not possible, a prominent flag should be placed at the top of the
slope. The contractor's representative should effectively keep all equipment at a safe
operation distance (e.g., 50 feet) away from the slope during this testing.
The technician is directed to withdraw from the active portion ofthe fill as soon as possible
following testing. The technician's vehicle should be parked at the perimeter of the fill in
a highly visible location, well away from the equipment traffic pattern. The contractor
should Inform our personnel of all changes to haul roads, cut and fill areas or other factors
that may affect site access and site safety.
In the event that the technicians safety is jeopardized or compromised as a result of the
contractors failure to comply with any ofthe above, the technician is required, by company
policy, to immediately withdraw and notify his/her supervisor. The grading contractors
representative will eventually be contacted in an effort to effect a solution. However, in the
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GeoSoils, Inc.
interim, no further testing will be performed until the situation is rectified. Any fill place can
be considered unacceptable and subject to reprocessing, recompaction or removal.
In the event that the soil technician does not comply with the above or other established
safety guidelines, we request that the contractor brings this to his/her attention and notify
this office. Effective communication and coordination between the contractors
representative and the soils technician is strongly encouraged in order to implement the
above safety plan.
Trench and Vertical Excavation
It is the contractor's responsibility to provide safe access into trenches where compaction
testing is needed.
Our personnel are directed not to enter any excavation or vertical cut which: 1) is 5 feet or
deeper unless shored or laid back; 2) displays any evidence of instability, has any loose
rock or other debris which could fall into the trench; or 3) displays any other evidence of
any unsafe conditions regardless of depth.
All trench excavations or vertical cuts in excess of 5 feet deep, which any person enters,
should be shored or laid back. Trench access should be provided in accordance with
CAL-OSHA and/or state and local standards. Our personnel are directed not to enter any
trench by being lowered or "riding down" on the equipment.
If the contractor fails to provide safe access to trenches for compaction testing, our
company policy requires that the soil technician withdraw and notify his/her supervisor.
The contractors representative will eventually be contacted in an effort to effect a solution.
All backfill not tested due to safety concerns or other reasons could be subject to
reprocessing and/or removal.
If GSI personnel become aware of anyone working beneath an unsafe trench wall or
vertical excavation, we have a legal obligation to put the contractor and owner/developer
on notice to immediately correct the situation. If corrective steps are not taken, GSI then
has an obligation to notify CAL-OSHA and/or the proper authorities.
Touchstone Communities, LLC,
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Appendix F
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GeoSoils, Inc.
DETAIL FOR FILL SLOPE TOEING OUT
ON FLAT ALLUVIATED CANYON
TOE DF SLOPE AS SHOWN ON GRADING PLAN
ORIGINAL GROUND SURFACE TO BE
RESTORED WITH COMPACTED FILL
BACKCUT >,7ARIES. FOR DEEP REMOVALS.^
BACKCUT ^iKSHDULD BE MADE NO ^
STEEPER THAlKj:! OR AS NECESSARY >;>
FOR SAFETY v,^^ONSIDERATIONS^^
ORIGINAL GROUND SURFACE
COMPACTED RLL
ANTICIPATED ALLUVIAL REMOVAL
DEPTH PER SOIL ENGMEER.
r PROVIDE A 1:1 MINIMUM PROJECTION FROM TOE OF
SLOPE AS SHOWN ON GRADING PLAN TO THE RECOMMENDED
REMOVAL DEPTH. SLOPE HEIGHT. SITE CONDITIONS AND/OR
LOCAL CONDITIONS COULD DICTATE FLATTER PROJECTIONS.
REMOVAL ADJACENT TO EXISTING FILL
ADJOINING CANYON HLL
COMPACTED RLL LIMITS LINE
Qaf Qal (TO BE REMOVED)
(EXISTING.COMP ACTED FILL) ^\
LEGEND
BE REMOVED BEFORE
PLACING ADDITIONAL
COMPACTED RLL
Qaf ARTIFICIAL RLL
Qal ALLUVIUM
PLATE EG-3
TRANSITION LOT DETAIL
CUT LOT (MATERIAL TYPE TRANSITION)
NATURAL GRADE
COMPACTED RLL
^ Kim
OVEREXCAVATE AND RECOMPACT /^V
3* MINIMUM^
^Sl UNWEATHERED BEDROCK OR APPROVED MATERIAL
TYPICAL BENCHING
CUT-FILL LOT (DAYUGHT TRANSITION)
7P^^7^^^^^70^^^^^^^^' MINIMUM-
UNWEATHERED BEDROCK DR APPROVED MATERIAL
TYPICAL BENCHING
NOTE: * DEEPER OVEREXCAVATION MAY BE RECOMMENDED BY THE SOILS ENGINEER
AND/OR ENGINEERING GEOLOGIST IN STEEP CUT-RLL TRANSITION AREAS.
PLATE EG~11