HomeMy WebLinkAboutCT 02-06; KIRGIS TENTATIVE MAP; REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION; 2001-03-14I
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CHRiSTIAN WHEELEK ENGINEEKING
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REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION
I PROPOSED FIVE-LOT RESIDENTIAL PROJECT
......... APN 212-01003
I : WEST OF FARADAY ROAD
CARLSBAD, CALIFORNIA
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PREPARED FOR:
. PERGOLA, INC.
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. c/o H. D. O'HARA .
6312 CORLITO WAY
CARLSBAD, CALIFORNIA 92009
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. PREPARED BY:
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. CHRISTIAN WHEELER ENGINEERING
4925 MERCURY STREET
SAN DIEGO, CALIFORNIA 92111
4925 Mercury Street + San Diego CA 92111 + 858-496-9760 + FAX 858-496-975k
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CHR-ISTIAN WHEELER
ENGINEEKING
March 14, 2001
I Pergola, Inc. CWE 201.116.1
do H. D. O'Hara
6312 Cholito Way
Carlsbad, California 92009
SUBJECT: REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION,
PROPOSED FIVE-LOT RESIDENTIAL PROJECT, APN 212-010-03, WEST OF
FARADAY ROAD, CARLSBAD, CALIFORNIA.
Ladies and Gentlemen:
In accordance with your request and our proposal dated February 5, 2001, we have completed a preliminary
geotechnical investigation for the subject residential development. We are presenting herewith a report of
our finding and recommendations.
In general, our findings indicate that the subject property is suitable for the proposed development, provided
the recommendations provided herein are followed. The project area is generally underlain by Tertiary-age
deposits of the Santiago Formation that are mantled in the northern, eastern, and southeastern portions by
Quaternary-age terrace deposits. The formational materials are typically overlain by a relatively thin veneer of
topsoil, subsoil, and slopewash materials. The formational materials are generally competent; however,
portions of the Santiago Formation were found to possess a "medium" expansive potential. The overlying
topsoil, subsoil, and slopewash materials are generally loose and are considered unsuitable to support fill
and/or settlement-sensitive structures. Based on these soil conditions, "select" grading and special foundation
recommendations are provided in the attached report.
In addition, no geologic hazards of sufficient magnitude to preclude development of the site as we presently
contemplate it are known to exist In our professional opinion and to the best of our knowledge, the site is
geologically suitable for the proposed development.
4925 Mercury Street + San Diego, CA 92111 + 858-496-9760 + FAX 858-496-9758
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C\VE 201.116.1 March 14, 2001 Page 2
If you have any questions after reviewing this report, please do not hesitate to contact our office. This
opportunity to be of professional service is sincerely appreciated.
Respectfully submitted,
CHRISTLAN WHEELER ENGINEERING
Ei--
Shawn Caya, Staff Engineer
Charles H. Christian, RGE # 00215
.13
No 1090
I CERTIFIED I
ENGINEERING ) °
\ GEOLOGIST I
\\ Exp. 10-02
Curtis R. Burdett, CEG # 1090
cc: (3) Submitted
(3) Brian C. Regan Engineering
1 TABLE OF CONTENTS
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PAGE
Introduction and Project Description ..............................................................................................................I
Project Scope ......................................................................................................................................................... 2
Findings.................................................................................................................................................................3
SiteDescription ............................................................................................................................................. 3
General Geology and Subsurface Conditions..........................................................................................4
Geologic Setting and Soil Description..................................................................................................4
Topsoil....................................................................................................................................................
Subsoil....................................................................................................................................................4
Slopewash..............................................................................................................................................
TerraceDeposits...................................................................................................................................
SantiagoFormation..............................................................................................................................5
Groundwater.............................................................................................................................................5
TectonicSetting ............................................................................................................................ ............ 5
GeologicHazards .........................................
.
.................................................................................. ............... 6
General.....................................................................................................................................................6
GroundShaking.......................................................................................................................................6
SeismicDesign Parameters ............... . .................................................... . ................................................. 6
Liquefaction.............................................................................................................................................. 7
Flooding.....................................................................................................................................................7
Tsunamis...................................................................................................................................................7
Seiches........................................................................................................................................................
Landslide Potential and Slope Stability.....................................................................................................7
General.......................................................................................................................................................
FillSlopes ...................................................................................................................................................8
SurficialStability ............................................................................................................................... . ....... 8
Conclusions...... .....................................................................................................................................................8
General................................. . .......................................................................................................................... 8
Lots1 and 2 ................................................................................................................................................... 9
Lot3................................................................................................................................................................
Lots4 and 5...................................................................................................................................................
Recommendations.............................................................................................................................................10
Gradingand Earthwork ............................................................................................................................. 10
General.................................................................................................... ................................................. 10
Observationof Grading........................................................................................................................10
Clearingand Grubbing ........................................................................................................................... 10
SitePreparation ...................................................................................................................................... 10
TransitionBuilding Pads ..................................................
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..................................................................... 11
Processingof Fill Areas.........................................................................................................................11
Compactionand Method of Filling ..................................................................................................... 11
SelectGrading.........................................................................................................................................12
ImportedFill Material ........... . ............................................................................................................... 12
Cutand Fill Slope Construction .......................................................................................................... 12
SurfaceDrainage....................................................................................................................................13
SlopeStability..............................................................................................................................................13
General...................................................................................................................................................13
ErosionControl ....................................................................................................................................... 13
CWE 201.116.1
Proposed Five-Lot Project
West of Faraday Road
Carlsbad, California
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1-11
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I TABLE OF CONTENTS (Continued)
PAGE
FoundationRecommendations ....................................... . ......................................................................... 13
General.....................................................................................................................................................13
I Fountations in Nondetrinientally Expansive Soil........................................................................14
General.............................................................................................................................................14
FoundationDimensions...............................................................................................................14
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Bearing Capacity............................................................................................................................14
Footing Reinforcement .................................................................................................. .............. 14
Foundations in Moderately Expansive Soil ..................................................................................14
General............................................................................................................................................. 14
I Deepened Conventional Foundations..................................................................................14
FoundationDimensions ...................................................................................................14
BearingCapcity...................................................................................................................15
I Footing Reinforcement .....................................................................................................
Post-Tensioned Foundations.................................................................................................15
15'
General.................................................................................................................................15
I Lateral Load Resistance.........................................................................................................................15
FootingSetbacks .................................................................................................................................... 16
FoundationPlan Review.......................................................................................................................16
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Foundation Excavation Observation..................................................................................................16
On-Grade Slabs ..........................................................................................................................................16
InteriorSlabs...........................................................................................................................................16
Moisture Protection for Interior Slabs ...............................................................................................17
- Exterior Concrete Flatwork..................................................................................................................17 I EarthRetaining Walls ................................................................................................................................17
PassivePressure......................................................................................................................................17
I . Active Pressure.......................................................................................................................................17
Backfill.....................................................................................................................................................18
Limitations..........................................................................................................................................................18
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Review, Observation and Testing............................................................................................................18
Uniformityof Conditions ........................................................................................................................... 18
Changein Scope.........................................................................................................................................18
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Time Limitations.........................................................................................................................................19
ProfessionalStandard.................................................................................................................................19
Client's Responsibility .............. . .................................................................................................................. 19
FieldExplorations ........................................................................................ ....................................................... 19
I Laboratory Testing.............................................................................................................................................20
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CWE 201.116.1
Proposed Five-Lot Project
West of Faraday Road
Carlsbad, California
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ATTACHMENTS
TABLES
Table I Maximum Bedrock Accelerations, Page 6
Table II Recommended Values, Page 7
FIGURES
Figure 1 Site Vicinity Map, Follows Page 1
PLATES
Plates 1 Site Plan
Plates 2-12 Trench Logs -
Plates 13 Laboratory Test Results
Plate 14 Fill Slope Stability Analysis Plots -
Plates 15-16 Surficial Stability Analysis -
Plate 17 Retaining Wall Subdrain Detail
APPENDICES
Appendix A References
Appendix B Recommended Grading Specifications - General Provisions
CWE 201 .116.1
Proposed Five-Lot Project
West of Faraday Road
Carlsbad, California
'
CHR-ISTIAN WHEELER. ENGINEERING I
PRELIMINARY GEOTECHNICAL INVESTIGATION
PROPOSED FIVE-LOT RESIDENTIAL PROJECT
I WEST OF FARADAY ROAD
CARLSBAD, CALIFORNIA
INTRODUCTION AND PROJECT DESCRIPTION
This report presents the results of a preliminary geotechnical investigation performed for a five-lot residential ' project to be developed west of Faraday Road, in the City of Carlsbad, California. Figure Number 1 presented
on the following page provides a vicinity map showing the location of the property.
The subject site is an undeveloped parcel of land approximately 22 acres in area. We understand that the
property is to be divided into five relatively large residential parcels. The parcels will be graded to receive single-
family residences and associated improvements including site retaining walls, pools, and spas. The homes are
expected to be one or two stories of wood-frame construction with conventional shallow spread foundations
and on-grade concrete floor slabs. Also, a public cul-de-sac will be constructed to provide access to the lots.
I Planned grading to bring the pads to desired elevations is expected to consist of cuts and fills from existing
grades of up to about 25 feet. Cut and fill slopes will be constructed at an inclination of 2:1, horizontal to
vertical, and will have heights of up to about 25 feet and 35 feet, respectively.
To aid in the preparation of this report, we were provided with a preliminary grading plan, prepared by Brian C.
Regan Engineering Company. A copy of this plan was used as the basis for our geologic mapping and is
included herewith as Plate Number 1. 1
This report has been prepared for the exclusive use of Pergola, Inc. and their design consultants for specific I application to the project described herein. Should the project be changed in any way, the modified plans
should be submitted to Christian Wheeler Engineering for review to determine their conformance with our
I recommendations and to determine if any additional subsurface investigation, laboratory testing and/or
recommendations are necessary. Our professional services have been performed, our findings obtained and our
4925 Mercury Street + San Diego, CA 92111 4 858-496-9760 4 FAX 858-496-9758
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CWE 201.116.1 March 14, 2001 Page No. 2
recommendations prepared in accordance with generally accepted engineering principles and practices. This
warranty is in lieu of all other warranties, express or implied.
PROJECT SCOPE
Our investigation consisted of: surface reconnaissance, subsurface explorations, obtaining representative
disturbed and undisturbed samples, laboratory testing, analysis of the field and laboratory data, research of
available geologic literature and geotechnical documents pertaining to the site, and preparation of this report.
More specifically, the intent of this investigation was to:
Explore the subsurface conditions of the site to the depths influenced by the proposed grading and
construction;
Evaluate, by our past experience with similar nearby properties, the engineering properties of the
various strata that may influence the proposed development, including the allowable soil bearing
pressures, expansive characteristics and settlement potential;
Describe the general geology at the site including possible geologic hazards that could have an
effect on the site development, and provide the seismic design parameters as required by the most
recent addition of the Uniform Building'Code;
Address potential construction difficulties that may be encountered due to soil conditions,
groundwater, or geologic hazards, and provide recommendations concerning these problems;
Develop soil engineering criteria for the site grading and provide design information regarding the
stability of cut and fill slopes;
Recommend an appropriate foundation system for the type of structures anticipated and develop
soil engineering design criteria for the recommended foundation designs; and,
Present our opinions in this written report, that includes in addition to our findings and
recommendations, a site plan showing the location of our exploratory trenches and logs of the
trenches.
I CWE 201.116.1 March 14, 2001 Page No. 3
It is not within the scope of our services to perform laboratory tests to evaluate the chemical characteristics
I of the on-site-soils in regard to their potentially corrosive impact to on-grade concrete and below grade
improvements. If desired, we can obtain samples of representative soils and submit them to a chemical
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laboratory for analysis. We suggest that such samples be obtained after precise grading is complete and the
soils that can affect concrete and other improvements are in place. Further, it should be understood
Christian Wheeler Engineering does not practice corrosion engineering. If such an analysis is necessary, we
I recommend that the developer retain an engineering firm that specializes in this field to consult with them on
this matter.
I FINDINGS
SITE DESCRIPTION
The subject site is a nearly rectangular-shaped parcel of land approximately 21.9 acres in area, located west of
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Faraday Road in the City of Carlsbad, California. The site is further identified as Assessor's Parcel Number
212-010-03. Undeveloped canyon lands bound the site to the west, south, and east, while gently sloping,
undeveloped land bounds the site to the north. Access to the site is provided by an existing unpaved road,
which enters the northern portion of the site.
The site is primarily undeveloped; however, numerous small. "outbuildings" were scattered across the site at
the time of our site reconnaissance and subsurface exploration. The approximate locations of these
1 "outbuildings" are presented on the enclosed Plate No. 1. Additionally, relatively minor amounts of trash and
debris, including an abandoned automobile, were observed across the surface of the site. Vegetation on the
I upper portions of the site consists of sparse to relatively dense indigenous brush and small to medium sized
trees. Within the descending, canyon areas of the site, the on-site vegetation was observed to consist of
moderately dense to very dense indigenous brush and small to medium size trees.
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The site plan included herewith as Plate No. 1 shows the existing topography of the site. In general, a gently
sloping mesa top that generally descends to the south characterizes the uppermost, northern portion of the
site. Moderately steep canyon lands descend to south, east, and west from the uppermost, mesa top area of
the site. The existing on-site elevations within those portions of the site to receive improvements range from
about 360 feet in the northern portion of the site to about 262 feet in' the southwestern portion of the site.
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I CWE 201.116.1 March 14, 2001 Page No. 4
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GENERAL GEOLOGY AND SUBSURFACE CONDITIONS
GEOLOGIC SETTING AND SOIL DESCRIPTION: The subject site is located in the Coastal Plains
Physiographic Province of San Diego County and is underlain by a relatively minor amount of native residuum,
Quaternary-age terrace deposits, and Cretaceous-age deposits of the Santiago Formation. The following provides
a discussion, based on our subsurface explorations and our past experience with nearby projects, of the soil types
expected to be encountered beneath the property.
TOPSOIL: Native topsoil was encountered at the surface in most of our exploratory test trenches. The
topsoil layer has an approximate thickness of 1 foot. The topsoil material generally consists of dark
brown, silty sand (SM) that is typically moist and loose in consistency. It should be noted.that topsoil was
not encountered in our test trench T-9, excavated in the northwest portion of the site.
SUBSOIL: A layer of native subsoil was encountered within our exploratory test trenches excavated in
the northern, eastern, and southeastern portions of the proposed improvement area. The subsoil was
generally noted below the topsoil layer, but was also noted at the surface within the northeast portion of
the site. The thickness of the subsoil layer ranged from approximately 1 foot to 1Y2 feet. The subsoil was
noted to primarily consist of medium brown, clayey sand (SC). The subsoil was also noted as being
generally moist and loose to medium dense, and is expected to have a "moderate" potential for
expansion.
SLOPEWASI-I (Qsw): A layer of slopewash material was noted below the topsoil layer within our
exploratory test trenches excavated in the southwest portion of the proposed improvement area. The
layer had an approximate thickness ranging from 11/2 to 2 feet. The materials within the slopewash layer
generally consisted of dark brown, sandy clay (CL) that were wet and soft with a slight amount of gravel
and cobble, and are expected to have a "moderate" potential for expansion.
TERRACE DEPOSITS (Qt): Underlying the topsoil and subsoil layers, a layer of Quaternary-age
terrace deposits mantles the northern, eastern, and southeastern portions of the proposed improvement
area. The approximate location of the contact between the terrace deposits and underlying Santiago
Formation is shown on the attached Plate No. 1. This contact typically occurs at an elevation of 310 feet
Generally, the layer of terrace deposits is thickest within the upper areas in the eastern portion of the
improvement area, and thins towards the lower portions. The terrace deposits generally consisted of
orangish-brown, clayey sand (S that was moist and dense to very dense with some gravel and cobble.
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CWE 201.116.1 March 14, 2001 Page No. 5
Based on laboratory testing in accordance with ASTM D 4829, the terrace deposits are expected to
possess a "very low" expansive potential.
SANTIAGO FORMATION (Tsa): The site is ultimately underlain by Tertiary-age deposits of the
I Santiago Formation. The formational materials were noted below the terrace deposits in the northern,
eastern, and southeastern portions of the proposed improvement area and below the topsoil, subsoil,
I and slopewash layers in the south-southwestern portions. The materials of the Santiago Formation
mainly consisted of light brown to light orangish-brown, clayey sand (S and light brown to white, silty
I sand (SM). The formational materials also consisted of lesser amounts of light olive brown, sandy clay
(CL). The formational materials were typically moist. The sandy portions of the Santiago Formation were
I dense to very dense while the clayey portions were very stiff to hard. Based on laboratory testing in
accordance with ASTM D 4829, the clayey portions of the Santiago Formation, which comprise .a
I relatively small amount of the formational material, were found to possess a "medium" expansive
potential.
GROUNDWATER No groundwater is expected to be encountered in any of the areas to be graded. It should
be recognized that minor groundwater seepage problems may occur after development of a site even where none
were present before development. These are usually minor phenomena and are often the result of an alteration in
drainage patterns and/or an increase in irrigation water. Based on the permeability characteristics of the soil and
the anticipated usage and development, it is our opinion that any seepage problems which may occur will be
minor in extent. It is further our opinion that these problems can be most effectively corrected on an individual
basis if and when they occur.
TECTONIC SETTING: No major faults are known to traverse the subject site but it should be noted that
much of Southern California, including the San Diego County area, is characterized by a series of Quaternary-' -age
I fault zones which typically consist of several individual, en echelon faults that generally strike in a northerly to
north-westerly direction. Some of these fault zones (and the individual faults within the zones) are classified as
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active while others are classified as only potentially active, according to the criteria of the California Division of
Mines and Geology. Active fault zones are those which have shown conclusive evidence of faulting during the
Holocene Epoch (the most recent 11,000 years) while potentially active fault zones have demonstrated
I movement during the Pleistocene Epoch (11,000 to 1.6 million years before the present) but no movement
during Holocene time.
I A review of available geologic maps indicates that the active Rose Canyon Fault Zone is located approximately 9
1 kilometers southwest of the site. Other active fault zones in the region that could possibly affect the site include
CWE 201.116.1 March 14,2001 Page No. 6
the Coronado Bank Fault Zone to the southwest and the San Jacinto, Elsinore and San Andreas Fault Zones to
the northeast.
GEOLOGIC HAZARDS
GENERAL: No geologic hazards of sufficient magnitude to preclude development of the site as we presently
contemplate it are known to exist. In our professional opinion and to the best of our knowledge, the site is
suitable for the proposed development.
GROUND SHAKING: A likely geologic hazard to affect the site is ground shaking as result of movement
along one of the major active fault zones mentioned above. The maximum bedrock accelerations that would be
attributed to a maximum probable earthquake occurring along the nearest fault segments of selected fault zones
that could affect the site are summarized in Table I presented below.
TABLE I
MAXIMUM BEDROCK ACCELERATOINS
Fault Zone Distance Max. Magnitude
Earthquake
Maximum Bedrock
Acceleration
Rose Canyon 9 km 6.9 magnitude 0.26 g
Coronado Bank 35 km 7.4 magnitude 0.22 g
Elsinore 37 km 7.1 magnitude 0.11 g
Earthquake Valley 66 1cm 6.5 magnitude 0.05 g
San Jacinto 74 km 7.2 magnitude 0.07 g
Probable ground shaking levels at the site could range from slight to moderate, depending on such factors as
the magnitude of the seismic event and the distance to the epicenter. It is likely that the site will experience
the effects of at least one moderate to large earthquake during the life of the proposed structures.
SEISMIC DESIGN PARAMETERS: In accordance with the evaluations provided above, the Maximum
Bedrock Acceleration anticipated for the site is 0.26 g (based upon a Maximum Magnitude Earthquake of 6.9
magnitude along the Rose Canyon Fault Zone). For structural design purposes, a damping ratio not greater than
5 percent of critical dampening, and Soil Profile Type Sc are recommended (UBC Table 16-J). Based upon the
site's location at approximately 9 kilometers from the Rose Canyon Fault Zone (Type B Fault), Near Source
Factors Na equal to 1.0 and N equal to 1.04 are also applicable. These values, along with additional seismically
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CWE 201.116.1 March 14,2001 Page No. 7
related design parameters obtained from the Uniform Building Code (UBC) 1997 edition, Volume II, Chapter 16,
are presented below in Table II.
TABLE II
SEISMIC DESIGN PARAMETERS
UBC Chapter 16
Table No.
Seismic
Parameter
Recommended
Value
16-I Seismic Zone Factor Z 0.40
16-J Soil Profile Type Sc
16-Q Seismic Coefficient Ca 0.40 Na
16-R Seismic Coefficient Ca 0.56 N
16-S Near Source Factor Na 1.0
16-T Near Source Factor N 1.04
16-U Seismic Source Type B
LIQUEFACTION: The native materials at the site are not subject to liquefaction due to such factors as soil
density, grain-size distribution, and the absence of shallow groundwater conditions.
FLOODING: The site is located outside the boundaries of both the 100-year and the 500-year fioodplains
according to the maps prepared by the Federal Emergency Management Agency.
TSUNAMIS: Tsunamis are great sea waves produced by submarine earthquakes or irolcanic eruptions. Based
upon the location of the site, it will not be affected by tsunamis.
SEICHES: Seiches are periodic oscillations in large bodies of water such as lakes, harbors, bays or
reservoirs. Due to the site's location, it will not be affected by seiches.
LANDSLIDE POTENTIAL AND SLOPE STABILITY
GENERAL As part of this investigation we reviewed the publication, "Landslide Hazards in the Northern Part
of the San Diego Metropolitan Area" by Tan and Giffen, 1995. This reference is a comprehensive study that
classifies San Diego County into areas of relative landslide susceptibility. The subject site is mainly located in
Relative Landslide Susceptibility Area 3-1. The 3-1 classification is assigned to areas considered "generally
susceptible" to slope movement Natural slopes within the 3-1 classification are considered at or near their
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CWE 201.116.1 March 14, 2001 Page No. 8
stability limits due to their steep inclinations and can be expected to fail locally when adversely modified. Sites
within this classification are located outside the boundaries of known landslides. It should also be noted that a
very small portion of the site's northwest corner and the area northwest of the site are located in Relative
Landslide Susceptibilty Landslide Susceptibility Area 4-1. Area 4 is considered to be the "most susceptible" to
slope movement; Subarea 4-1 is generally outside the boundary of definite mapped landslides but contains
observably unstable slopes underlain by both weak materials and adverse geologic structure. In general, based on
our field observation and analysis of laboratory data, the formational materials forming the hillsides in the area are
very competent. Therefore, the potential for deep-seated landsliding within the natural and proposed cut slopes in
the portion of the site to be developed is considered low. In addition, no grading or development is planned in
the northwest corner of the site that has been noted to be within Subarea 4-1. As such, the proposed
improvements will not be adversely affected by any potentially unstable slopes.
FILL SLOPES: Fill slopes up to-about 35 feet in height are proposed for the project. The existing on-site soils
are expected to possess strength parameters in their compacted state sufficient for the construction of £11 slopes.
Provided the fill slopes are constructed in accordance with the recommendations presented in the "Grading and
Earthwork" section of this report, the potential for deep-seated landsliding within the proposed fill slopes is
considered low. An analysis of the stability of the proposed fill slopes was performed using the PCSTABL6
computer program developed at Purdue University. The program analyzes circular, block and randomly
shaped failure surfaces using the Simplified Bishop and Janbu Methods. The analysis was performed for a
representative cross-section drawn perpendicular to the topography of the tallest proposed slope
(approximately 35 feet). The minimum factor-of-safety computed in our stability analysis for this
representative cross-section was 2.29. This cross-section, labeled A-A' on the attached Plate No. 1, and the.
plot of the ten most critical failure surfaces are presented as Plate No. 14.
SURFICIAL STABILITY: Our analyses of the stability of the surficial materials along the face of the
proposed fill and cut slopes indicated factors-of-safety of approximately 2.9 and 3.8 for £11 and cut slopes,
respectively (Plate Nos. 15 and 16). Based on these relatively high factors-of-safety and provided the slope face
is prepared in accordance with the recommendations presented in the "Cut and Fill Slope Construction" and
"Erosion Control" sections of this report, the potential for surficial slope failures is considered low.
CONCLUSIONS
GENERAL: In general, our findings indicate that the subject property is suitable for the proposed
development, provided the recommendations provided herein are followed. The project area is generally
underlain by Tertiary-age deposits of the Santiago Formation that are manfled in the northern, eastern, and
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CWE 201.116.1 March 14, 2001 Page No. 9
southeastern portions by Quaternary-age terrace deposits. The formational materials are typically overlain by a
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relatively thin veneer of topsoil, subsoil, and slopewash materials. The formational materials are generally
competent; however, portions of the Santiago Formation were found to possess a "medium" expansive
potential. The overlying veneer of topsoil, subsoil, and slopewash materials are generally loose and are
I considered unsuitable to support fill and/or settlement-sensitive structures. Based on these soil conditions, the
existing topsoil, subsoil, and slopewash materials will need to be removed from areas to support fill and/or
I settlement-sensitive improvements, and, where necessary to achieve planned site grades, be replaced as properly
compacted structural fill. In addition, it will be necessary to mitigate for the expansive potential of the clayey
portions of the Santiago Formation. This will require "select" grading and/or special foundation design
considerations. The lots are addressed more specifically below.
LOTS lAND 2: Based on the preliminary grading plan, it appears that cuts of up to about 18 and 33 feet are
I necessary to construct the building pads for Lots 1 and 2, respectively. Based on these cut depths and the
approximate elevation of the contact between the terrace deposits and Santiago Formation, it is expected that
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the building pads will be underlain by competent materials of the Santiago Formation. However, due to the
moderately expansive nature of the clayey portions of the Santiago Formation, the pads will need to be either
"select" graded, or structures proposed for the lots will need to be supported by foundations designed for
I heaving soils. Foundations supported by moderately expansive soil should consist of deepened conventional
foundations with additional reinforcement or a post-tensioned slab/foundation system.
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LOT 3: Based on the preliminary grading plan, it appears that the building pad for Lot 3 will be traversed by a
cut/fill transition. In order to mitigate for potential differential settlement of the proposed structure on Lot 3,
the cut portion of the pad will need to be undercut as discussed in the "Transition Building Pads" section of this
I report.
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In addition, cuts of up to about 15 feet are proposed on the northern portion of the pad. Based on this cut
depth and the proposed pad elevation, it appears that the cut portion of the pad will be underlain by materials of
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the Santiago Formation. Based on the moderately expansive nature of the clayey portions of the Santiago
Formation, the pad should be "select" graded at the time of the transition undercut so that the pad will be
capped by a mat of nondetrimentally expansive fill material. If "select" grading cannot be accomplished,
I foundations supporting the structure proposed for Lot 3 will need to be designed for heaving soils.
I LOTS 4 AND 5: Based on the preliminary grading plan, fills of up to about 20 feet are proposed to construct
the building pads for Lots 4 and 5. As part of the grading to construct the building pads, the moderately
I expansive on-site materials should be mixed with the on-site terrace deposits to obtain a nondetrimentally
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CWE201.116.1 March 14, 2001 Page No. 10
expansive material as discussed in the "Select Grading" section of this report. Provided the foundation soils are
verified as nondetrimentally expansive, the proposed structures may be supported by conventional spread
foundations with conventional on-grade concrete floor slabs. If ccsdece grading cannot be accomplished,
foundations supporting the structures proposed for Lots 4 and 5 will need to be designed for heaving soils.
RECOMMENDATIONS
GRADING AND EARTHWORK
GENERAL: All grading should conform with the guidelines presented in Appendix Chapter A33 of the
Uniform Building Code; the minimum requirements of the City of Carlsbad, and the Recommended Grading
Specifications and Special Provisions attached hereto, except where specifically superseded in the text of this
report. Prior to grading, a representative of Christian WheelerEngineering should be present at the
preconstruction meeting to provide additional grading guidelines, if necessary, and to review the earthwork
I schedule.
OBSERVATION OF GRADING: Continuous observation by the Geotechnical Consultant is essential
during the mass grading operation to confirm conditions anticipated by our investigation, to allow adjustments
in design criteria to reflect actual field conditions exposed, and to determine that the grading proceeds in general
accordance with the recommendations contained herein.
CLEARING AND GRUBBING: Site grading should begin with the removal of all vegetation and other
deleterious materials from the portions of site that will be graded and/or will receive improvements. This
should include all root balls from trees, all natural brush and all significant root material. The resulting materials
should be disposed of off-site. It is anticipated that no underground utilities or structures exist on the portion of
the property to be developed that will require removal.
SITE PREPARATION: After clearing and grubbing, site preparation should consist of the removal from
areas to receive fill and/or improvements of all existing topsoil, subsoil, and slopewash. These materials should
be removed to the contact with competent terrace deposits or material of the Santiago Formation, as
determined in the field by the project geologist, engineer, or field supervisor. Based on our investigation, the
total thickness of the topsoil, subsoil, and slopewash layers is expected to range from approximately 1 foot to 3
feet, but may be thicker in localized areas. All removal areas should be approved by a representative of our
office prior to filling or the construction of improvements. Where necessary to achieve planned site grades, the
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CWE2OI.116.1 March 14, 2001 Page No. 11
removed materials may be replaced as compacted fill provided they are thoroughly mixed and moisture
conditioned prior to placement.
TRANSITION BUILDING PADS: Based on the preliminary grading plan, it appears that the building pad
of Lot 3 will be traversed by a cut/fill transition. The cut portion of any building pad that will be traversed by a
cut/fill transition line should have the cut portion undercut at least three feet. The bottom of the overexcavated
areas should be sloped in such a manner that water does not become trapped in the overexcavated zone. Prior
to replacing the excavated materials, the soils exposed at the bottom of the excavation should be scarified to
depth of six inches, moisture conditioned and compacted to at least 90 percent relative compaction.
PROCESSING OF FILL AREAS: Prior to placing any new fill soils or constructing any new improvements
in areas that have been cleaned out to receive fill and approved by the geotechnical consultant or his
representative,
the exposed soils should be scarified to a depth of 12 inches, moisture conditioned, and
compacted to at least 90 percent relative compaction. No other special ground preparation is anticipated at this
time.
COMPACTION AND METHOD OF FILLING: All structural fill placed at the site should be compacted
to a relative compaction of at least 90 percent of its maximum dry density as determined by ASTM Laboratory
Test D1557-91. Fills should be placed at or slightly above optimum moisture. content, in lifts six to eight inches
thick, with each lift compacted by mechanical means. Fills should consist of approved earth material, free of
trash or debris, roots, vegetation, or other materials determined to be unsuitable-by our soil technicians or
project geologist. Fill material should be free of rocks or lumps of soil in excess of twelve inches in maximum
dimension. However, in the upper two feet of pad grade, no rocks or lumps of soil in excess of six inches
should be allowed.
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Fills should be benched into all temporary slopes and into competent natural soils when the natural slope is
steeper than an inclination of 5:1 (horizontal to vertical). Keys should be constructed at the toe of all fill slopes.
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The keys should extend at least 12 inches into firm natural ground and should be sloped back at least two
percent into the slope area. Keys should have a minimum width of 10 feet for slopes 25 feet high or less, and
15 feet for slopes over 25 feet.
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Utility trench backfill within five feet of the proposed structures and beneath all pavements and concrete
I flatwork should be compacted to a minimum of 90 percent of its maximum dry density. The upper twelve
inches of subgrade beneath paved areas should be compacted to 95 percent of the materials maximum dry
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CWE2O1.116.1 March 14, 2001 Page No. 12
density. This compaction should be obtained by the paving contractor just prior to placing the aggregate base
material and should not be part of the mass grading requirements or operation.
SELECT GRADING: Portions of the Santiago Formation were determined to possess a "medium" expansive
potential. In order to use conventional spread foundations and on-grade floor slabs, the expansive portions of
the Santiago Formation that are to be used as fill material should be mixed with other on-site soils to produce a
nondetrimentally expansive mixture of soil, or should be placed at least five (5) feet below finish pad grade.
Nondetrimentally expansive soils are defined herein as soils with an expansion index less than 50. Samples of
the mixed fill material placed at the foundation level should be tested to verify that a nondetrimentally expansive
mix has been achieved. Where the mixture of soil does not produce a nondetrimentally expansive fill material,
special consideration for heaving soil will need to be incorporated into the foundation design.
I In addition, wherever detrimentally expansive soil is determined to occur naturally within four (4) feet of finish
pad grade, it should be removed and replaced with nondetrimentally expansive material. The bottom of the
I overexcavated areas should be sloped in such a manner that water does not become trapped in. the
overexcavated zone. Where detrimentally expansive soil is not removed, special consideration for heaving soil
will need to be incorporated into the foundation design.
IMPORTED FILL MATERIAL: It in unknown if it will be necessary to import fill material to the site to
I achieve planned site grades. However, if it does become necessary, the imported material should be evaluated
and approved by the Geotechnical Consultant prior to being imported. At least two working days notice of a
I potential import source should be given to the Geotechnical Consultant so that appropriate testing can be
accomplished. The imported fill material should consist of a granular soil with an Expansion Index of less
I than 50. In addition, the imported soil should have less than 25 percent larger than 1/4-inch, no material
larger than three inches, and less than 25 percent finer than the standard No. 200 sieve.
CUT AND FILL SLOPE CONSTRUCTION: Cut and fill slopes may be constructed at an inclination of
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. 2:1 or flatter (horizontal to vertical). Compaction of fill slopes should be performed by back-rolling with a
sheepsfoot compactor at vertical intervals of four feet or less as the fill is being placed, and track-walking the
face of the slope when the slope is completed. As an alternative, the £11 slopes may be overfilled by at least
three feet and then cut back to the compacted core at the design line and grade. Keys should be made at the toe
of fill slopes in accordance with the recommendations presented above under "Compaction and Method of
I Filling." .
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CWE2OI.116.1 March 14,2001 Page No. 13
SURFACE DRAINAGE: Surface runoff into graded areas should be minimized. Where possible, drainage
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should be directed to suitable disposal areas via non-erodible devices such as paved swales, gunited brow
ditches, and storm drains. Pad drainage should be designed to collect and direct surface water away from
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proposed structures and the top of slopes and toward approved drainage areas. For earth areas, a minimum
gradient of one percent should be maintained. The ground around the proposed buildings should be graded so
that surface water flows rapidly away from the buildings without ponding. In general, we recommend that the
ground adjacent to buildings slope away at a gradient of at least two percent. Densely vegetated areas where
runoff can be impaired should have a minimum gradient of five percent within the first five feet from the
I structure.
I SLOPE STABILITY
I GENERAL: All slopes at the subject development should be constructed at a slope ratio of 2.0 horizontal
units to 1.0 vertical unit (2:1) or flatter. Maximum cut and fill slope heights will be less than about 25 feet and
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35 feet, respectively. Based on the strength parameters of the on-site soils in their natural and mechanically
compacted states, it is our opinion that the proposed slopes will be stable in regards to deep-seated slope-failure
and surficial slope failure. All fill slopes should be constructed in accordance with the grading recommendations
I presented above.
I EROSION CONTROL: The placement of cohesionless soils at the face of slopes should be avoided Slopes
- should be planted as soon as feasible after grading. Sloughing, deep tilling and slumping of surficial soils may be
1 anticipated if slopes are left unpianted for a long period of time, especially during the rainy season. Care should
be taken to ensure the proper drainage of all surface runoff away from the slope face. Saturation of the slope
I caused by excessive or improperly channeled runoff could detrimentally affect the surficial stability of the
slope. Irrigation on and adjacent to slopes should be carefully monitored to insure that only the minimum
I amount necessary to sustain plant life is used. Over-irrigating could not only be erosive but may significantly
increase the chance for slope surficial stability problems and should be avoided.
I FOUNDATION RECOMMENDATIONS
I GENERAL: Based on our investigation, it is our opinion that either conventional continuous footings or a
post-tensioned slab/foundation system may support the proposed structures. Provided the foundation soils
I consist of a nondetrimentally expansive mixture as recommended above, special consideration and design for
heaving soils will not be required. Where structures will be supported by moderately expansive material, either
I deepened conventional footings or a post-tensioned slab/foundation system will be necessary. The following
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I CWE 201.116.1 March 14, 2001 Page No. 14
provides our recommendations for foundations supported by nondetrimentally expansive or moderately
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expansive soils.
Foundations in Nondetrimentally Expansive Soil
General: Provided the building pads consist of nondetrimentally expansive soil and the site preparation is
I completed in accordance with the above recommendations, it is our opinion that the proposed structures
may be supported by conventional continuous and isolated spread footings.
I Foundation Dimensions: Spread footings supporting one-story and two-story structures should be
I embedded at least 12 and 18 inches below finish pad grade, respectively. Continuous and isolated footings
should have a minimum-width of 12 inches and 24 inches, respectively.
Bearing Capacity: Conventional spread footings with the above minimum dimensions may be designed
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for an allowable soil bearing pressure of 2,500 pounds per square foot. This value may be increased by one-
third for combinations of temporary loads such as those due to wind or seismic loads.
I Footing Reinforcement A structural engineer should provide reinforcement requirements for
foundations. However, based on the anticipated soil conditions, we recommend that the minimum
1 reinforcing for continuous footings consist of at least one No. 5 bar positioned three inches above the
bottom of the footing and one No. 5 bar positioned approximately two inches below the top of the footing.
I Where the fill portion of cut/fill transition lots exceeds a thickness of 15 feet, we recommend that the
minimum reinforcing for continuous footings consist of at least two No. 5 bars positioned three inches
I above the bottom of the footing and two No. 5 bars positioned approximately two inches below the top of
the footing.
Foundations in Moderately Expansive Soil
General:
Where the building pads consist of moderately expansive material, the proposed structures may
be supported by deepened conventional foundations or by a post-tensioned slab/foundation system.
Deepened Conventional Foundations
Foundation Dimensions: Spread footings supporting one-story and two-story structures in
moderately expansive material should be embedded at least 18 and 24 inches below finish pad grade,
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CWE 201.116.1 March 14, 2001 Page No. 15
respectively. Continuous and isolated footings should have a minimum width of 12 inches and 24
inches, respectively.
Bearing Capacity: Conventional spread footings with the above minimum dimensions may be
I designed for an allowable soil bearing pressure of 2,500 pounds per square foot. This value may be
increased by one-third for combinations of temporary loads such as those due to wind or seismic loads.
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Footing Reinforcement A structural engineer should provide reinforcement requirements for
I foundations. However, based on the anticipated soil conditions, we recommend that the minimum
reinforcing for continuous footings consist of at least two No. 5 bars positioned three inches above the
I bottom of the footing and two No. 5 bars positioned approximately two inches below the top of the
footing. Where the-fill portion of cut/fill transition lots exceeds a thickness of 15 feet, we recommend
I that the minimum reinforcing for continuous footings consist of at least two No. 5 bari positioned
three inches above the bottom of the footing and two No. 5 bars positioned approximately two inches
below the top of the footing. -
Post-Tensioned Foundations
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General: We recommend that all post-tension foundation/slab systems have a perimeter footing
I embedded of at least 12 inches below pad grade. We also recommend that the Post-Tensioning
Institute design method be utilized to design the post-tensioned foundation systems. Based on this and
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- the anticipated soil conditions, we recommend using the following design criteria.
I Edge Moisture Variation, em
Center Lift: 5.2 feet
I Edge Lift: 3.0 feet Differential Swell, Ym
Center Lift 3.60 inches
I Edge Lift: 0.75 inch
Differential Settlement: 0.88 inch
I Bearing Capacity 2,500 psf
Perimeter Footings 18 inches
LATERAL LOAD RESISTANCE: Lateral loads against foundations may be resisted by friction between the
I bottom of the footing and the supporting soil, and by the passive pressure against the footing. The coefficient
CWE 201.116.1 March 14, 2001 Page No. 16
of friction between concrete and soil may be considered to be 0.35. The passive resistance may be considered
to be equal to an equivalent fluid weight of 350 pounds per cubic foot This assumes the footings are poured
tight against undisturbed soil. If a combination of the passive pressure and friction is used, the friction value
should be reduced by one-third.
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FOOTING SETBACKS: If footings for structures axe proposed adjacent to the top of slopes, we recommend
that a minimum horizontal setback from the outer edge of the footing to the adjacent slope face be provided.
In general, the minimum setback from the slope face recommended is 5 feet from slopes 0 to 15 feet high, 10
feet for slopes 15 to 30 feet high, and 15 feet for slopes over 30 feet high. The building setback distance from
the top of slopes may be modified by using deepened footings. Footing setback is measured from competent
soil and should neglect any loose or soft native soils that may occur at the top of a natural slope. Plans for any
footings that will not comply with the specified setbacks should be submitted to the Geotechnical Engineer for
specific review and approval prior to construction.-
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FOUNDATION PLAN REVIEW: The foundation plans should be submitted to -this office for review in
order to ascertain that the recommendations of this report have been implemented, and that no additional
recommendations are needed due to changes in the anticipated construction.
FOUNDATION EXCAVATION OBSERVATION: All foundation excavations should be observed by the
I Geotechnical Consultant prior to placing concrete to determine if the foundation recommendations presented
-herein are complied with. All footing excavations should be excavated neat, level and square. All loose or.
I unsuitable material should be removed prior to the placement of concrete. -
1 ON-GRADE SLABS
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INTERIOR SLABS: For conventional slabs supported by nondetrimentally expansive soil, the minimum slab
thickness should be four inches and the slab reinforcement should consist of at least No. 3 bars placed at 18
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inches on-center each way. If the floor slabs are supported by moderately expansive soil, the minimum slab
thickness should be increased to five inches and the slab reinforcement should consist of at least No. 3 bars
placed at 12 inches on center each way. The slab reinforcing bars should extend at least six inches into the
I perimeter footings. Slab reinforcing should be positioned on chairs at mid-height in the floor slab. The garage
slabs may be constructed independent of the garage perimeter footings. These slabs should have the same
I reinforcing and thickness recommended above for the living area of the house.
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CWE 201.116.1 March 14, 2001 Page No. 17
MOISTURE PROTECTION FOR INTERIOR SLABS: Where the concrete on-grade floor slabs will
support moisture-sensitive floor covering, it should be underlain by a moisture barrier. We recommend that
the minimum configuration of the subsiab moisture barrier consist of a four-inch-thick blanket of coarse,
clean sand. The moisture barrier material should have less than ten percent and five percent passing the No.
100 and No. 200 sieves, respectively. A visqueen vapor barrier should be placed in the center of the moisture
protection blanket. Our experience indicates that this moisture barrier should allow the transmission of from
about six to twelve pounds of moisture per 1000 square feet per day through the on-grade slab. This may be
an excessive amount of moisture for some types of floor covering. If additional protection is considered
necessary, additional recommendations can be provided.
I EXTERIOR CONCRETE FLATWORKi Exterior slabs should have a minimum thickness of four inches.
Reinforcement should be placed in exterior concrete flatwork to reduce the potential for cracking and
I movement. Control joints should be placed in exterior concrete flatwork to help control the location of
shrinkage cracks. Spacing of control joints should be in accordance with the American Concrete Institute
I specifications. When patio, walks and porch slabs abut perimeter foundations they should be doweled into the
footings.
I EARTH RETAINING WALLS
I PASSIVE PRESSURE: The passive pressure for the prevailing soil conditions may be considered to be 350
pounds per square foot per foot of depth. This pressure may be increased one-third for seismic loading. The
I coefficient of friction for concrete to soil may be assumed to be 0.35 for the resistance to lateral movement.
When combining frictional and passive resistance, the friction should be reduced by one-third. The upper 12
I inches of exterior retaining wall footings should not be included in passive pressure calculations where abutted
by landscaped areas.
ACTIVE PRESSURE: The active soil pressure for the design of unrestrained earth retaining structures with
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level backfill may be assumed to be equivalent to the pressure of a fluid weighing 35 pounds per cubic foot. An
additional 13 pounds per cubic foot should be added to this value for 2:1 (horizontal to vertical) sloping backfill.
These pressures do not consider any other surcharge. If any are anticipated, this office should be contacted for
the necessary increase in soil pressure. These values assume a drained backfill condition. Waterproofing details
should be provided by the project architect. A suggested wall subdrain detail is provided on the attached Plate
I Number 17. We recommend that the Geotechnical Consultant be retained to observe all retaining wall
subdrains to verify proper construction.
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CWE2O1.116.1 March 14,2001 Page No. 18
BACKFILL: All backfill soils should be compacted to at least 90 percent relative compaction. Expansive or
clayey soils should not be used for backfill material. The wall should not be backflhled until the masonry has
reached an adequate strength.
I LIMITATIONS
REVIEW, OBSERVATION AND TESTING
The recommendations presented in this report are contingent upon our review of final plans and specifications.
Such plans and specifications should be made available to the Geotechnical Engineer and Engineering Geologist
so that they may review and verify their compliance with this report and with the Uniform Building Code.
It is recommended that Christian Wheeler Engineering be retained to provide continuous soil engineering
services during the earthwork operations. This is to verify compliance with the design concepts, specifications
or recommendations and to allow design changes in the event that subsurface conditions differ from those
anticipated prior to start of construction.
I UNIFORMITY OF CONDITIONS
The recommendations and opinions expressed in this report reflect our best estimate of the project
requirements based on an evaluation of the subsurface soil conditions encountered at the subsurface exploration
locations and on the assumption that the soil conditions do not deviate appreciably from those encountered. It
should be recognized that the performance of the foundations and/or cut and fill slopes may be influenced by
undisclosed or unforeseen variations in the soil conditions that may occur in the intermediate and unexplored
areas. Any unusual conditions not covered in this report that may be encountered during site development
should be brought to the attention of the Geotechnical Engineer so that he may make modifications if
necessary.
CHANGE IN SCOPE
This office should be advised of any changes in the project scope or proposed site grading so that we may
determine if the recommendations contained herein are appropriate. It should be verified in writing if the
recommendations are found to be appropriate for the proposed changes or our recommendations should be
modified by a written addendum.
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I CWE 201.116.1 March 14, 2001 Page No. 19
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construction.
FIELD EXPLORATIONS
Nine subsurface explorations were made at the locations indicated on the attached Plate Number 1 on
February 15, 2001. These explorations consisted of test trenches excavated by backhoe. The fieldwork was
conducted under the observation of our engineering geology personnel.
TIME LIMITATIONS
The findings of this report are valid as of this date. Changes in the condition of a property can, however, occur
with the passage of time, whether they are due to natural processes or the work of man on this or adjacent
properties. In addition, changes in the Standards-of-Practice and/or Government Codes may occur. Due to
such changes, the findings of this report may be invalidated wholly or in part by changes beyond our control.
Therefore, this report should not be relied upon after a period of two years without a review by us verifying the
suitability of the conclusions and recommendations.
PROFESSIONAL STANDARD
In the performance of our professional services, we comply with that level of care and skill ordinarily exercised
by members of our profession currently practicing under similar conditions and in the same locality. The client
recognizes that subsurface conditions may vary from those encountered at the locations where our borings,
surveys, and explorations are made, and that our data, interpretations, and recommendations are based solely on
the information obtained by us. We will be responsible for those data, interpretations, and recommendations,
but shall not be responsible for the interpretations by others of the information developed. Our services consist
of professional consultation and observation only, and no warranty of any kind whatsoever, express or implied,
is made or intended in connection with the work performed or to be performed by us, or by our proposal for
consulting or other services, or by our furnishing of oral or written reports or findings.
CLIENT'S RESPONSIBILITY
It is the responsibility of Pergola, Inc. or their representatives to ensure that the information and
recommendations contained herein are brought to the attention of the structural engineer and architect for the
project and incorporated into the project's plans and specifications. It is further their responsibility to take the
necessary measures to insure that the contractor and his subcontractors carry out such recommendations during
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I CkVE 201.116.1 Page No. 20 March 14, 2001
The explorations were carefully logged when made. The test trench logs are presented on the following Plate
Numbers 2 through 12. The soils are described in accordance with the Unified Soils Classification System. In
addition, a verbal textural description, the wet color, the apparent moisture and the density or consistency are
provided. The density of granular soils is given as either very loose, loose, medium dense, dense or very
dense. The consistency of silts or clays is given as either very soft, soft, medium stiff; stiff; very stiff, or hard.
Disturbed and "undisturbed" samples of typical and representative soils were obtained and returned to the
laboratory for testing.
LABORATORY TESTING
Laboratory tests were performed in accordance with the generally accepted American Society for Testing and
Materials (ASTM) test methods or suggested procedures. A brief description of the tests performed is
presented below:
CLASSIFICATION: Field classifications were verified in the laboratory by visual examination.
The final soil classifications are in accordance with the Unified Soil Classification System.
MOISTURE-DENSITY: In-place moisture contents and dry densities were determined for
representative soil samples. This information was an aid to classification and permitted
recognition of variations in material consistency with depth. The dry unit weight is determined in
pounds per cubic foot, and the in-place moisture content is determined as a percentage of the
soil's dry weight. The results are summarized in the trench logs.
COMPACTION TEST: The maximum dry density and optimum moisture content of a typical
soil were determined in the laboratory in accordance with ASTM Standard Test D-1557, Method A.
The results of this test are presented on Plate Number 13.
GRAIN SIZE DISTRIBUTION: The grain size distributions were determined from
representative soil samples in accordance with ASTM D422. The results of these tests are
presented on Plate Number 13.
DIRECT SHEAR TEST: Direct shear tests were performed to determine the failure envelope
based on yield shear strength. The shear box was designed to accommodate a sample having a
diameter of 2.375 inches or 2.50 inches and a height of 1.0 inch. The samples were saturated and
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CWE 201.116.1 March 14, 2001 Page No. 21
tested at different vertical loads. The shear stress was applied at a constant rate of strain of
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approximately 0.05 inch per minute. The results of these tests are presented on the attached Plate
Number 13.
d) EXPANSION INDEX TEST: Expansion Index tests on remolded samples were performed on
representative samples of the soil present at finish grade. The tests were performed on the portion of
I the sample passing the #4 standard sieve. The sample was brought to optimum moisture content and
then dried back to a constant moisture content for 12 hours at 230 ± 9 degrees Fahrenheit. The
I specimen were then compacted in a 4-inch-diameter mold in two equal layers by means of a tamper,
then trimmed to a final height of 1 inch, and brought to a saturation of approximately 50 percent.
I The specimen were placed in a consolidometer with porous stones at the top and bottom, a total
normal load of 12.63 pounds was placed (144.7 psf), and the samples were allowed to consolidate for
I a period of 10 minutes. The samples were saturated, and the change in vertical movement was
recorded until the rate of expansion became nominal. The expansion index is reported on Plate
Number 13 as the total vertical displacement times 1000.
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LOG OF TEST TRENCH NUMBER T-1
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 313 feet Depth to Water: N/A
Proposed Elevation: 328 feet Bucket Size:
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24 inches
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SAMPLES
0 '' z' u
P. SUMMARY OF SUBSURFACE CONDITIONS
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Cl)P.
Topsoil Dark brown SILTY SAND (SM), moist, loose, fine to medium-
grained. - - - - -
$9 Subsoil: Medium brown, CLAYEY SAND (SC), moist, loose to medium
2 dense, fine- to medium-grained.
- Terrace Deposits (Ot) Orangish brown CLAYEY SAND (SC) moist
dense, fine- to coarse-grained. CK 73 111.1
SA
El
" WR MD
DS
•
CK 6.4 115.5
- 7
8 - - - - -
Terminated at 8 feet. - 9
- -10—
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
BY: SCC DATE: February 27, 2001 Cl-IRJSTIAN WHEELER.
JOB NO.: 201.116 1PLATE NO.: 2 E N G I N E E P..! N G
LOG OF TEST TRENCH NUMBER T-2
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 325 feet Depth to Water N/A
Proposed Elevation: 328 feet Bucket Size:
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24 inches
-
SAMPLES
I '-I z1'
U
SUMMARY OF SUBSURFACE CONDITIONS F-
0 , oO
Topsoil: Dark brown, SILTY SAND (S, moist, loose, fine- to medium- - - - - -
grained. - - - - - -
Subsoil: Medium brown, CLAYEY SAND (SC), moist, loose to medium
- 2 :i3 dense, fine- to medium-grained.
$ Santiago Formation asa') Light brown CLAYEY SAND (SC) moist, 3
dense, fine to medium grained CK 76 1165
-4 .....................................................................................................................................................................
Light brown to olive brown, SANDY CLAY (CL), moist, very hard.
CK 19.1 101.1 SA
-5
-6 -
Terminated at 6 feet.
- 7
-8
-9
-10—
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
CHRiSTiAN WI-IEELER. BY: SCC DATE: February 27, 2001
ENGINEEPLING JOB NO.: 201.116 PLATE NO.: 3
LOG OF TEST TRENCH NUMBER T-3
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 317 feet Depth to Water: N/A
Proposed Elevation: 314 feet Bucket Size:
-
24isches
SAMPLES
SUMMARY OF SUBSURFACE CONDITIONS
,- '-I
zO
,iz
C,)P. W
Topsoil: Dark brown, SILTY SAND (SM), moist, loose, fine- to medium-
grained. - - - - -
Subsoil: Medium brown, CLAYEY SAND (SC), moist, loose to medium
dense, fine- to medium-grained. 2
Terrace Deposits Qt): Orangish-brown, CLAYEY SAND (SC), moist, 3
dense to very dense, fine- to coarse-grained with occasional 3 inch cobble.
4 .
cic
Santiago Formation (Tsa): Light brown to white, SILTY SAND (SM), 6
moist, dense to very dense, fine- to medium-grained.
7 CK 11.0 111.9
8
9
-
- - - 10
Terminated at 10 feet.
PROPOSED 5-LOT RESIDENTIAL PROJECT
M01 West of Faraday Road, Carlsbad, California
CHRiSTIAN WHEELER BY: SCC DATE: February 27,2001
E N C I N E E R. I N G JOB NO.: 201.116 1PLATE NO.: 4
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LOG OF TEST TRENCH NUMBER T-4
Date Excavated: 2/15/01 Logged by: DRR
Equipment Backhoe Project Manager: CHC
Existing Elevation: 317 feet Depth to Water- N/A
Proposed Elevation: 314 feet Bucket Size: 24 inches
-
SAMPLES
o
O c/,
SUMMARY OF SUBSURFACE CONDITIONS
C14 N
o
: PI V)
9 W
-'
Z
c1: P.
Q
• Topsoil: Dark brown, SILTY SAND (SM), moist, loose, fine- to medium-
grained. - -
Subsoil: Medium brown, CLAYEY SAND (SC), moist, loose to medium
2 dense , fine to medium-grained
Terrace Deposits (Qt): Orangish-brown, CLAYEY SAND/SILTY SAND
-
f (SC/SM) moist, dense to very dense occasional gravel and cobble
-
CK
- 6
7 - - - - -
- 8 Terminated at 7 feet.
-9
-10— -
PROPOSED 5-LOT RESIDENTIAL PROJECT
Al West of Faraday Road, Carlsbad, California
CHIUS11AN WHEELER- BY: SCC DATE: February 27, 2001
ENGINEEPING JOB NO.: 201.116 PLATENO.: 5
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LOG OF TEST TRENCH NUMBER T-5
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Back-hoe Project Manager. CHC
Existing Elevation: 290 feet Depth to Water N/A
Proposed Elevation: 306 feet Bucket Size: 24 inches
-
SAMPLES
U W z''
.- ,.-. o. -
SUMMARY OF SUBSURFACE CONDITIONS
Z OE
o
Q
Topsoil Dark brown SILTY SAND (SM) moist, loose fine to medium-
grained. -
Slopewash (Osw): Dark brown, SANDY CLAY (CL), wet, soft,
- 2 slight amount of gravel and cobble.
- 3 Santiago Formation (is a) Light brown to light orangish brown
CK CLAYEY SAND (SC), moist, medium dense to dense.
-4•••
Becomes very dense.
CK 11.2 114.3
-7
10
..
--
Trench loe continued on Plate 7.
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
CHRISTIAN WHEELER. BY: SCC DATE: February 27, 2001
ENGINE E P INC JOB NO.: 201.116 1PLATE NO.: 6
LOG OF TEST TRENCH NUMBER T-5 (Continued)
Date Excavated: 2/15/01 Logged by: DRR
Equipment Backhoe Project Manager: CHC
Existing Elevation: 290 feet Depth to Water: N/A
Proposed Elevation: 306 feet Bucket Size:
-
24 inches
-
SAMPLES
SUMMARY OF SUBSURFACE CONDITIONS
ZOE-
0
P.
-
Santiago Formation (Tsa)L: Light brown to light orangish brown,
CLAYEY SAND (SC) moist very dense
- 11
x..
12
13
CK 15.5 113.2
- 15 - - - - - - -
Terminated at 15 feet.
- 16
-17
- 18
-19
-20 - - - - - -
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
CHRJS-nAN WHEELER., BY: SCC DATE: February 27, 2001
ENGINEEKING lOB NO.: 201.116 1PLATE NO.: 7
LOG OF TEST TRENCH NUMBER T-6
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 313 feet Depth to Water: N/A
Proposed Elevation: 300/306 feet Bucket Size:
-
24 inches
-
SAMPLES
SUMMARY OF SUBSURFACE CONDITIONS to
0 oO
CID
Topsoil: Dark brown, SILTY SAND (SM), moist, loose, fine- to medium-
- 1 grained. - - - -
Slopewash (Q§—w1 Dark brown, SANDY CLAY (CL), wet, soft,
- 2 slight amount of gravel and cobble.
- 3 Santiago Formation (Tsa): Light brown to light orangish-brown,
SANDY CLAY (CL), moist, very stiff. SA
El
-4 MD Becomes hard.
DS
-5
-6 -
-7
-8
CK 15.4 110.4
-9
-10 -
Trench loa continued on Plate 9.
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
CHRJS11AN WHEELER. BY: SCC DATE: February 27, 2001
ENGINEER. INC JOB NO.: 201.116 PLATE NO.: 8
LOG OF TEST TRENCH NUMBER T-6 (Continued)
Date Excavated: 2/15/01 Logged by: DRR
Equipment Back-hoe 0 Project Manager. CHC
Existing Elevation:' 313 feet Depth to Water: N/A
Proposed Elevation: 300/306 feet Bucket Size:
-
24 inches
-
SAMPLES
111
SUMMARY OF SUBSURFACE CONDITIONS H
0 z Z
0 . .l C/D 04
O
H Santiago Formation (Tsa): Light brown to light orangish-brown,
SANDY CLAY (CL), moist, hard. 11
-12
-13
CK 18.0 108.6
- 14
Terminated at 14 feet.
- 15
- 16
-17
-18
-19
- - - - - - -20 -
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
BY: SCC DATE: February 27, 2001 CHRISTIAN WHEELER
ENGINEERNG OBNO.: 201.116 ' IPLATE NO.: 9
LOG OF TEST TRENCH NUMBER T-7
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 275 feet Depth to Water- N/A
Proposed Elevation: 315 feet Bucket Size:
-
24 inches
-
SAMPLES
0 z '' e
SUMMARY OF SUBSURFACE CONDITIONS
CI) ZOE
. IIo 0 P.
Topsoil: Dark brown, SILTY SAND/CLAYEY SAND (SM/Sq. moist,
-
loose, fine- to medium-grained. - - - -
Slopewash (Osw): Dark brown, SANDY CLAY (CL), wet, soft
- 2 to medium stiff, slight amount of gravel and cobble.
Santiago Formation (Tsa): Light olive brown to light orangish-brown,
- 4 CLAYEY SAND (SC), moist, dense to very dense, fine- to medium-grained. CK 16.3 109.3
- ç
- 7
CK 16.8 110.0
8
L 101 1
:______________
Practical refusal at 9 feet.
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California I W
CHRIS11AN WHEELER BY: SCC DATE: February 27, 2001
ENGINEER. INC lOB NO.: 201.116 PLATE NO.: 10
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LOG OF TEST TRENCH NUMBER T-8
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: CHC
Existing Elevation: 314 feet Depth to Water: N/A
Proposed Elevation: 315 feet Bucket Size: 24 inches
-
SAMPLES
I1
SUMMARY OF SUBSURFACE CONDITIONS E ZOE
0 O
Topsoil: Dark brown, SILTY SAND (SM), moist, loose, fine- to medium-
-1 r grained
Subsoil: Medium brown, CLAYEY SAND (SC), moist, loose to medium
. dense fine to medium -grained.
- 2
Terrace Deposits Qt): Orangish brown CLAYEY SAND (SC) moist,
- 3
dense to very dense, fine- to coarse grained occasional 21/2 inch gravel
-
CK 6.0 113.0
74
- 5
•
CK
7
-
- 8 Terminated at 7 feet.
-9
-10— ---- --
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
CHRISTIAN WHEELER BY: scc ]DATE: February 27, 2001
EN C I NE E P, INC JOB NO.: 201.116 J?LATE NO.: 11
LOG OF TEST TRENCH NUMBER T-9
Date Excavated: 2/15/01 Logged by: DRR
Equipment: Backhoe Project Manager: Cl-IC
Existing Elevation: 314 feet Depth to Water- N/A
Proposed Elevation: -- Bucket Size:
-
24 inches
-
SAMPLES
[1 0 Z
0 14
U
SUMMARY OF SUBSURFACE CONDITIONS ,.t -'
Li
zO_
o .'rl C,)
i1O
Subsoil Medium brown CLAYEY SAND (SC) moist loose to medium
j• dense, fine- to medium-grained. 1
Terrace Deposits (Qt): Orangish-brown, CLAYEY SAND (SC), moist,
-
2
very dense, fine- to coarse-grained, abundant gravel and cobble. CK 5.7 122.8
: Santiago Formation (1sa): Light olive brown, CLAYEY SAND (SC),
-
moist, dense to very dense, fine- to medium-grained.
CK 15.8 111.0
-6
CK
ij
_____________ I CK
Terminated at 10 feet.
PROPOSED 5-LOT RESIDENTIAL PROJECT
West of Faraday Road, Carlsbad, California
CHRIS11AN WHEELER BY: SCC DATE: February 27, 2001
EN CI NE E P. INC JOB NO.: 201.116 PLATE NO.: 12
LABORATORY TEST RESULTS
PROPOSED FIVE-LOT RESIDENTIAL PROJECT
WEST OF FARADAY ROAD
POWAY, CALIFORNIA
MAXIMUM DENSITY! OPTIMUM MOISTURE CONTENT
Sample Number Trench T-1 @ 2'-8' Trench T-6 @ 3'-12'
Description Orangish-brown, clayey sand (SC) Brown, sandy clay (CL)
Maximum Density. 127.1 pcf 106.0 pcf
Optimum Moisture Content 8.5 percent 18.5 pcf
DIRECT SHEAR TEST
Sample Number Trench T-1 @ 2'-8' Trench T-6 @ 3'-12'
Description Remolded To 90 Percent Remolded to 90 Percent
Angle of Internal Friction 33 degrees 21 degrees
Apparent Cohesion 100 psf 300 psf
GRAIN SIZE DISTRIBUTION
Sample Number T-1 @ 2'-8' T-2 @ 4'-6' T-6 @ 3'-12'
Sieve Size Percent Passing Percent Passing Percent Passing
#4 100
#8 93 100 100
#15 78 99 699
#30 59 98 98
#50 37 97 96
#100 22 87 84
#200 19 70 69
0.05 mm 18 60 55
0.005 mm 11 27 21
0.001 mm 8 18 7
Classification SC CL CL
EXPANSION INDEX TESTS
Sample Number: Trench T-8 @ 2'-8' Trench T-6 @ 3'-12'
Initial Moisture: 8.0 percent 13.7 percent
Initial Dry Density: 108.3 pcf 101.4 pcf
Final Moisture: 17.7 percent 29.5 percent
Expansion Index: 6 (very low) 85 (medium)
CWE 201.116.1 March 14, 2001 Plate No. 13
SLOPE STABILITY ANALYSIS - FILL SLOPES
Propsed Five-Lot Residential Project
West of Faraday Road
Carlsbad, California
Five—Lot Project CVE 201.116
Ten Most Critical, A:5LIJTFILL,PLT Byl SCC 03-12-01 1:50pm
380
360
if FS
a 229
b 2.30
c 2.31
d 2.32
e 2.32
P 2.33
g 2.35
h 2.35
I 2.36
J 2.36
Proposed 2:1
Slope 3
300 11
d
I,-
//,////
Fill (Qaf)
2/ace 1 Deposits (Qt)
Santiago Formation (T'sa)
340
Etev.
(ft)
320
280
0 20 40 60 80 100 120 140
STABL6H FSmir229 X-Axi (ft)
SoIL Total Saturated Cohesion Friction Pore Pressure Piez.
Type Unit Wt. Unit Vt. Intercept Angle Pressure Constant Surface
No. Label (pcf) (pcf) (psf) (deg) Parari. (psf) No.
1 Tsa 110 130 500 28 0 0
2 Qt 115 135 200 35 0 0
3 FILL 115 135 - 350 32 0 0
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CHRJS1W4 WHEELER
ENGINEEPING
Plate 14
SURFICIAL SLOPE STABILITY
FILL SLOPES
.
SLOPE SURFACE z
10
6ø
ASSUMED PARAMETERS
= DEPTH OF SATURATION = 3ft
a = SLOPE ANGLE = 26.60 (2:1 SLOPE)
w= UNIT WEIGHT OF WATER = 62.4 lb/ft3
T= SATURATED UNIT WEIGHT OF SOIL =135 lb/ft3
0 = APPARENT ANGLE Of INTERNAL FRICTION ALONG PLANE OF FAILURE =32°
c = APPARENT COHESION ALONG PLANE OF FAILURE = 350 lb/ft2
FS - c+T TAN ø = c+(T -wzCOS a TAN Ø
ST z SIN a COS a
FS=2.9
CHRISTIAN WHEELER ENGINEERING
5-LOT RESIDENTIAL PROJECT
BY: SCC/HC • DATE: 03-14-01
JOB NO: 201.116 PLATE NO, 15
SURFICIAL SLOPE STABILITY
CUT SLOPES
.
SLOPE SURFACE z
1
çO
ASSUMED PARAMETERS
z = DEPTH OF SATURATION = 3ft
a = SLOPE ANGLE = 26.60 (2:1 SLOPE)
w= UNIT WEIGHT OF WATER = 62.4 lb/ft3
T= SATURATED UNIT WEIGHT OF SOL = 130 1b/ft3
0 = APPARENT ANGLE Of INTERNAL FRICTION ALONG PLANE OF FAILURE = 28
c = APPARENT COHESION ALONG PLANE OF FAILURE = 500 lb/ft2
FS - C+T TAN Ø = c+(T -wzCOS a TAN Ø
T flz SIN a COS a
FS=3.8
-w
CHRISTIAN WHEELER
ENGINEERING
5-LOT. RESIDENTIAL PROJECT
BY: •SCC/HC D 03-14-01
JOB NO- 201.116 PLATE No, 16
6" MAX
I•0.0
,10
I °.•
t~l
I .
6"MINj .;
WATERPROOF BACK OF WALL
PER ARCHITECT'S SPECIFICATIONS
3/4 INCH CRUSHED ROCK or
MIRADRAJN 6000 or EQUIVALENT
GEOFABRIC BETWEEN ROCK AND SOIL
TOP OF GROUND
or CONCRETE SLAB
MINIMUM I
4 INCH DIAMETER
PERFORATED PIPE
RETAINING WALL
SUBDRAIN DETAIL
No Scale
Christian Wheeler Engineering
job Number: 201116
Date: 03+-1401
Plate Number: _17
CWE 201.116.1 March 14, 2001 Appendix A, Page A-i
REFERENCES
Anderson,J.G.; Rockwell, R.K. and Agnew, D.C., 1989, Past and Possible Future Earthquakes
of Significance to the San Diego Region, Earthquake Spectra, Volume 5, No. 2, 1989.
Blake, T. F., 2000, Documentation for FRISKSP Version 4.00, Thomas F. Blake Computer Services and
Software.
Boore, David M.,Joyner, William B., and Fumal, Thomas F., 1997, "Empirical Near-Source Attenuation
Relationships for Horizontal and Vertical Components of Peak Ground Acceleration, Peak Ground Velocity,
and Pseudo-Absolute Acceleration Response Spectra", in Seismological Research Letters, Volume 68, Number
1, January/February 1997.
Brim C. Regan Engineering, 2000, Preliminary Grading Plan, Proposed Five-Lot Residential Project.
California Division of Mines and Geology, 1998, Maps of Known Active Fault Near Source-Zones in
California and Adjacent Portions of Nevada,
Jennings, C.W., 1975, Fault Map of California, California Division of Mines and Geology, Map
No. 1, Scale 1:750,000.
Kennedy, M.P. and Peterson, G.L., 1975, Geology of the San Diego Metropolitan Area, California; California
Division of Mines and Geology, Bulletin 200
Kern, P., 1989, Earthquakes and Faults in San Diego County, Pickle Press, 73 pp.
Tan, S.S., 1995, Landslide Hazards in the Northern Part of the San Diego Metropolitan Area, San
Diego County, California, California Division of Mines and Geology Open-File Report 95-03.
United States Department of Agriculture, 1970, Soil Survey, San Diego Area, California.
U.S. Geological Survey, 1968 (Photo-revised 1975), 71/2 Minute Topographic Map, Oceanside Quadrangle, scale
1:24,000.
I
Wesnousky, S.G., 1986, "Earthquakes, Quaternary Faults, and Seismic Hazards in California", in
Journal of Geophysical Research, Volume 91, No. B12, pp 12,587 to 12,631, November 1986.
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CWE 201.1161 March 14, 2001 Appendix B, B-i
RECOMMENDED GRADING SPECIFICATIONS - GENERAL PROVISIONS
PROPOSED FIVE-LOT RESIDENTIAL PROJECT
APN 212-010-03
WEST OF FARADAY ROAD
CARLSBAD. CALIFORNIA
GENERAL INTENT
The intent of these specifications is to establish procedures for clearing, compacting natural ground,
preparing areas to be filled, and placing and compacting fill soils to the lines and grades shown on the
accepted plans. The recommendations contained in the preliminary geotechnical investigation report and/or
the attached Special Provisions are a part of the Recommended Grading Specifications and shall supersede
the provisions contained hereinafter in the case of conflict. These specifications shall only be used in
conjunction with the geotechnical report for which they are a part. No deviation from these specifications
will be allowed, except where specified in the geotechnical report or in other written communication signed
by the Geotechnical Engineer.
OBSERVATION AND TESTING
Christian Wheeler Engineering shall be retained as the Geotechnical Engineer to observe and test the
earthwork in accordance with these specifications. It will be necessary that the Geotechnical Engineer or his
representative provide adequate observation .so that he may provide his opinion as to whether or not the
work was accomplished as specified. It shall be the responsibility of the contractor to assist the Geotechnical
Engineer and to keep him appraised of work schedules, changes and new information and data so that he
may provide these opinions. In the event that any unusual conditions not covered by the special provisions
or preliminary geotechnical report are encountered during the grading operations, the Geotechnical Engineer
shall be contacted for further recommendations.
If, in the opinion of the Geotechnical Engineer, substandard conditions are encountered, such as
questionable or unsuitable soil, unacceptable moisture content, inadequate compaction, adverse weather, etc.,
construction should be stopped until the conditions are remedied or corrected or he shall recommend
rejection of this work.
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CWE201.116.1 March 14, 2001 Appendix B, B-2
Tests used to determine the degree of compaction should be performed in accordance with the following
American Society for Testing and Materials test methods:
Maximum Density & Optimum Moisture Content - ASTM D-1557-91
Density of Soil In-Place - ASTM D-1556-90 or ASTM D-2922
All densities shall be expressed in terms of Relative Compaction as determined by the foregoing ASTM
testing procedures.
PREPARATION OF AREAS TO RECEIVE FILL
All vegetation, brush and debris derived from clearing operations shall be removed, and legally disposed of. -
All areas disturbed by site grading should be left in a neat and finished appearance, free from unsightly debris.
After clearing or benching the natural ground, the areas to be filled shall be scarified to a depth of 6 inches,
brought to the proper moisture content, compacted and tested for the specified minimum degree of
compaction. All loose soils in excess of 6 inches thick should be removed to firm natural ground which is
defined as natural soil which possesses an in-situ density of at least 90 percent of its maximum dry density.
When the slope of the natural ground receiving fill exceeds 20 percent (5 horizontal units to 1 vertical unit),
the original ground shall be stepped or benched. Benches shall be cut to a firm competent formational soil.
The lower bench-shall be at least 10 feet wide or 1-1/2 times the equipment width, whichever is greater, and
shall be sloped back into the hillside at a gradient of not less than two (2) percent. All other benches should
be at least 6 feet wide. The horizontal portion of each bench shall be compacted prior to receiving fill as
specified herein for compacted natural ground. Ground slopes flatter than 20 percent shall be benched when
considered necessary by the Geotechnical Engineer.
Any abandoned buried structures encountered during grading operations must be totally removed. All
underground utilities to be abandoned beneath any proposed structure should be removed from within 10
feet of the structure and properly capped off. The resulting depressions from the above described procedure
should be backfilled with acceptable soil that is compacted to the requirements of the Geotechnical Engineer.
This includes, but is not limited to, septic tanks, fuel tanks, sewer lines or leach lines, storm drains and water
lines. Any buried structures or utilities not to be abandoned should be brought to the attention of the
Geotechnical Engineer so that he may determine if any special recommendation will be necessary.
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CWE 201.116.1 March 14, 2001 Appendix B, B-3
All water wells which will be abandoned should be backfilled and capped in accordance to the requirements
set for
th by the Geotechnical Engineer. The top of the cap should be at least 4 feet below finish grade or 3
feet below the bottom of footing whichever is greater: The type of cap will depend on the diameter of the
well and should be determined by the Geotechnical Engineer and/or a qualified Structural Engineer.
FILL MATERIAL
Materials to be placed in the fill shall be approved by the Geotechnical Engineer and shall be free of
1 vegetable matter and other deleterious substances. Granular soil shall contain sufficient fine material, to fill
the voids. The definition and disposition of oversized rocks and expansive or detrimental soils are covered
in the geotechnical report or Special Provisions. Expansive soils, soils of poor gradation, or soils with low
strength characteristics may be thoroughly mixed with other soils to provide satisfactory fill material, but only
1' with the explicit consent of the Geotechnical Engineer. Any import material shall be approved by the
Geotechnical Engineer before being brought to the site.
PLACING AND COMPACTION OF FILL
j Approved fill material shall be placed in areas prepared to receive, fill in layers not to exceed 6 inches in
compacted thickness. Each layer shall have a uniform moisture content in the range that will allow the
compaction effort to be efficiently applied.to achieve the specified degree of compaction. Each layer shall be
uniformly compacted to the specified minimum degree of compaction with equipment of adequate size to
I economically compact the layer. Compaction equipment should either be specifically designed for soil
compaction or of proven reliability. The minimum degree of compaction to be achieved is specified in either
the Special'Provisions or the recommendations contained in the preliminary geotechnical investigation
report.
When the structural fill material includes rocks, no rocks will be allowed to nest and all voids must be
I . carefully filled with soil such that the minimum degree of compaction recommended in the Special
Provisions is achieved. The maximum size and spacing of rock permitted in structural fills and in non-
structural fills is discussed in the geotechnical report, when applicable.
Field observation and compaction tests to estimate the degree of compaction of the fill will be taken by the
I Geotechnical Engineer or his representative. The location and frequency of the tests shall be at the
Geotechnical Engineer's discretion. When the compaction test indicates that a particular layer is at less than
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CWE 201.116.1 March 14, 2001 Appendix B, B-4
the required degree of compaction, the layer shall be reworked to the satisfaction of the Geotechnical
Engineer and until the desired relative compaction has been obtained.
Fill
slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment. Compaction by
sheepsfoot roller shall be at vertical intervals of not greater than four feet. In addition, fill slopes at a ratio of
two horizontal to one vertical or flatter, should be trackrolled. Steeper fill slopes shall be over-built and cut-
back to finish contours after the slope has been constructed. Slope compaction operations shall result in all
fill material six or more inches inward from the finished face of the slope having a relative compaction of at
least 90 percent of maximum dry density or the degree of compaction specified in the Special Provisions
section of this specification. The compaction operation on the slopes shall be continued until the
Geotechnical Engineer is of the opinion that the slopes will be surficially stable.
1 Density tests in the slopes will be made by the Geotechnical Engineer during construction of the slopes to
determine if the required compaction is being achieved. Where failing tests occur or other field problems
I
arise, the Contractor will be notified that day of such conditions by written communication from the
Geotechnical Engineer or his representative in the form of a daily field report.
If the method of achieving the required slope compaction selected by the Contractor fails to produce the
necessary results, the Contractor shall rework or rebuild such slopes until the required degree of compaction
is obtained, at no cost to the Owner or Geotechnical Engineer.
I. CUT SLOPES
The Engineering Geologist shall inspect cut slopes excavated in rock or lithifled formational material during
the grading operations at intervals determined at his discretion. If any conditions not anticipated in the
I preliminary report such as perched water, seepage, lenticular or confined strata of a potentially adverse
nature, unfavorably inclined bedding, joints or fault planes are encountered during grading, these conditions
I
shall be analyzed by the Engineering Geologist and Geotechnical Engineer to determine if mitigating
measures are necessary.
I Unless otherwise specified in the geotechnical report, no cut slopes shall be excavated higher or steeper than
-
that allowed by the ordinances of the controlling governmental agency.
ENGINEERING OBSERVATION
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CWE 201.116.1 March 14, 2001 Appendix B, B-5
Field observation by the Geotechnical Engineer or his representative shall be made during the filling and
compaction operations so that he can express his opinion regarding the conformance of the grading with
acceptable standards of practice. Neither the presence of the Geotechnical Engineer or his representative or
the observation and testing shall release the Grading Contractor from his duty to compact all fill material to
the specified degree of compaction.
I SEASON LIMITS
Fill shall not be placed during unfavorable weather conditions. When work is interrupted by heavy rain,
filling operations shall not be resumed until the proper moisture content and density of the fill materials can
be achieved. Damaged site conditions resulting from weather or acts of God shall be repaired before
acceptance of work.
RECOMMENDED GRADING SPECIFICATIONS - SPECIAL PROVISIONS
RELATIVE COMPACTION: The minimum degree of compaction to be obtained in compacted natural
ground, compacted fill, and compacted backfill shall be at least 90 percent. For street and parking lot
subgrade, the upper six inches should be compacted to at least 95 percent relative compaction.
EXPANSIVE SOILS: Detrimentally expansive soil is defined as clayey soil which has an expansion index of
50 or greater when tested in accordance with the Uniform Building Code Standard 29-2.
OVERSIZED MATERIAL: Oversized fill material is generally defined herein as rocks or lumps of soil
I over 6 inches in diameter. Oversized materials should not be placed in fill unless recommendations of
placement of such material is provided by the Geotechnical Engineer. At least 40 percent of the fill soils
shall pass through a No. 4 U.S. Standard Sieve.
I TRANSITION LOTS: Where transitions between cut and fill occur within the proposed building pad, the
cut portion should be undercut a minimum of one foot below the base of the proposed footings and
recompacted as structural backfill. In certain cases that would be addressed in the geotechnical report,
I special footing reinforcement or a combination of special footing reinforcement and undercutting may be
required.
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