HomeMy WebLinkAboutPD 03-04; LOWRY; REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION; 2003-02-17I
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CHRJSTIAN WHEELER
ENGINEERING
,
REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION
PROPOSED RESIDENTIAL DUPLEX
2817 AND 2819 CAZADERO DRIVE
CARLSBAD, CALIFORNIA
SUBMITTED TO:
MR.EDLOWRY
4623 TORREY ORCLE Q 129
SAN DIEGO, CALFIORNIA 92130 '~~,
~_Ii1IW~~~~IJ."fS
CHRISTIAN WHEELER ENGINEERING
4925 MERCURY STREE T
SAN DIEGO, CALIFORNIA 92111
~ .;~~ ,
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4925 Me<c",y S"eel + San Diego, CA 92111 + 858-496-9760 + FAX 858-4p;7:~---o4
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Februaty17,2003
11r. Ed Lowry
4623 TorreyOrcle, Q129
San Diego, California 92130
w
CHRISTIAN WHEELER
ENGINEER.ING
CWE 202.920.1
SUBJECT: REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION,
PROPOSED RESIDENTIAL DUPLEX,
2817-2819 CAZADERO DRIVE, CARLSBAD, CALIFORNIA
Dear 11r. Lowry:
In accordance with your request and our Proposal dated December 20, 2002, we have completed a
geotechnical investigation for the subject property. We are presenting herewith our findings and
recommendations.
In general, we foun<1: the subject site suitable for the proposed construction provided the recommendations
presented herein are followed. The most significant geotechnical conditions to affect the proposed construction
are the presence of an approximately four-foot-thick layer of slopewash material in the eastern portion of the
site that is considered unsuitable in its present condition to support settlement-sensitive improvements, and the
presence of rock material in which it maynot be possible to excavate for foundations and utilities with light
trenching equipment. The existing slopewash material will need to be removed and replaced as properly
compacted fill. Where the proposed cuts expose rock material, consideration should be given to undercutting
the area so that the foundations and utilities can be excavated using light trenching equipment.
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,
rnruSTIAN WHEELER ENGINEERING
~cP-r
CHGCRB:scc:tsw
cc: (2) Submitted
(4) Geissler Engineering
4925 Mercury Street ... San Diego, CA 92111 ... 858-496-9760 ... FAX 858-496-9758
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TABLE OF CONTENTS
PAGE
Introduction and Project Description ............................................................................................................................... 1
Project Scope ........................................................................................................................................................................ 2
Findings ................................................................................................................................................................................ 3
Site Description ............................................................................................................................................................... 3
General Geology and Subsurface O:>nditions ............................................................................................................. 3
Geologic Setting and Soil Description ...................................................................................................................... 3
Artificial Fill ........................................................................................................................................................... i •• 4
Slopewash ................................................................................................................................................................. 4
Weathered Undifferentiated Santiago Peak Volcanics ........................................................................................ 4
Groundwater ................................................................................................................................................................ 4
Tectonic Setting .......................................................................................................................................................... 5
Geologic ffazards ............................................................................................................................................................ 5
Ground Shaking ........................................................................................................................................................... 5
Seismic Design Parameters ........................................................................................................................................ 6
Surface Rupture .......................................................................................................................................................... 6
Landslide Potential and Slope Stability ...................................................................................................................... 6
Liquefaction .................................................................................................................................................................. 7
Flooding ........................................................................................................................................................................ 7
Tsunamis ...................................................................................................................................................................... 7
Seiches ........................................................................................................................................................................... 7
O:>nclusions .......................................................................................................................................................................... 7
Recommendations ........................................................................................................................ ; ..................................... 8
Grading and Earthwork .................................................................................................................................................. 8
General ......................................................................................................................................................................... 8
Observation of Grading ............................................................................................................................................. 8
Gearing and Grubbing ............................................................................................................................................... 8
Site Preparation .................................................................................................................................................... ~ ....... 8
Building Pad Undercuts ............................................................................................................................................... 8
Processing of Fill Areas ...... '" ..................................................................................................................................... 9
O:>mpaction and Method of Filling ..................................... ~ ..................................................................................... 9
Surface Drainage ......................................................................................................................................................... 9
Temporary Olt Slopes ............................................................................................................................................. 10
Foundations ................................................................................................................................................................... 10
General ....................................................................................................................................................................... 10
Foundation Dimensions ........................................................................................................................................... 10
Bearing Capacity ........................................................................................................................................................ 11
Footing Reinforcement ............................................................................................................................................ 11
Lateral Load Resistance ............................................................................................................................................ 11
Settlement Characteristics ....................................................................................................................................... 11
Foundation Plan Review ......................................................................................................................................... 11
Foundation Excavation Observation ..................................................................................................................... 11
On-Grade Slabs ............................................................................................................................................................. 12
General ....................................................................................................................................................................... 12
Interior Floor Slabs ...................... ,:'!~ ......................................... !.! .• , ........................................................................ 12
110isture Protection for Interior Slabs .................................................................................................................. 12
Exterior O:>ncrete Flatwork .................................................................................................................................... 12
Earth Retaining Walls ........ : .......................................................................................................................................... 13
CWE 202.920.1
Proposed Residential Duplex
Cazadero Dnve, Carlsbad, California
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TABLE OF CONTENTS (Continued)
PAGE
Passive Pressure ........................................................................................................................................................ 13
Equivalent Fluid Pressure ....................................................................................................................................... 13
Surcharge ........................................................................................... ; ...................................... , ................................. 13
Waterproofing and Subdrain Observation ............................................................................................. : ............. 13
Backfill ........................................................................................................................................................................ 13
Limitations .......................................................................................................................................................................... 13
Review, Observation and Testing ................................................................................................................................ 13
Unifonnity of C:Onditions ............................................................................................................................................. .14
Change in Scope ................................................................................................................... , ........................................ 14
Time Limitations ........................................................................................................................................................... 14
Professional Standard .............................................................................................. -...................................................... 15
Oient's Responsibility ................................................................................................................................................... 15
Field Explorations ............................................................................................................................................................. 15
Laboratory Testing ............................................................................................................................................................ 16
TABLES
Table I
Table II
FIGURES
Figure 1
PLATES
Plate 1
Plates 2-7
Plate 8
APPENDICES
ATTACHMENTS
:Maximum Ground Acceleration, Page 6
Seismic Design Parameters, Page 7
Site Vicinity Map, Follows Page 1
Site Plan
Test Trench Logs
Suggested Retaining Wall Subdrain Detail
Appendix A References
Appendix B Recommended Grading Specifications -General Provisions
CWE 202.920.1
Prop9sed Residential Duplex
Cazadero Drive, Carlsbad, California _
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CHRISTIAN WHEELER ENGINEER-ING
PRELIMINARY GEOTECHNICAL INVESTIGATION
PROPOSED SINGLE-FAMILY RESIDENCE
2817-2819 CAZADERO DRIVE
CARLSBAD, CALIFORNIA
INTRODUCfION AND PROJECf DESCRIPTION
This report presents the results of a preliminary geotechnical investigation perfonned for a proposed duplex
residential unit to be constructed on a previously graded lot located at 2817 and 2819 Cazadero Drive, in the
La Costa area 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 a vacant parcel of land located at 2817 and 2819 Cazadero Drive and is identified as
Assessor's Parcel Number 215-320-45. The lot has been graded into a relatively level pad that is about six feet
above Cazadero Drive. We understand that it is proposed to construct a duplex residential unit on the lot. The
structure will have split levels with two-and three-story portions, and will have a partially subterranean parking
level at the front and two interior retaining walls near the rear. The above-grade portion of the structure will be
of wood-frame construction while the retaining portions are expected to consist of masonry block construction.
The duplex will be supported by conventional shallow spread footings and the lower floors will have on-grade
concrete floor slabs. Grading is expected to consist of cuts of about six feet and fills of about nine feet from the
existing grades.
This report has been prepared for the exclusive use of Mr. Ed Lowry and his design consultants for specific
application to the project described herein. Should the project be changed in anyway, the modified plans
should be submitted to Christian 'Wheeler Engineering for review to detennine their conformance with our
recommendations and to detennine if any additional subsurface investigation, laboratory testing and! or
recommendations are necessary. Our professional services have been perfonned, our findings obtained and our
recommendations prepared in accordance with generally accepted engineering principles and practices. This
warrantyis in lieu of all other warranties, express or implied.
4925 Mercury Street + San Diego, CA 92111 .. 858-496-9760 + FAX 858-496-9758
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No Scale
CWE 202.920.1
SITE VICINITY MAP
(Adapted from Thomas Brothers Maps)
PROPOSED RESIDENTIAL DUPLEX
2817· 2829 CAZADERO DRIVE
CARLSBAD. CALIFORNIA
Latitude: 33.1051 degrees N.
Longitude: 117.242? degrees W.
February 2003 Figure 1
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CWE 202.920.1 February 17, 2003 Page No. 2
PRO]ECf SCOPE
The scope of our preliminary investigation included: surface reconnaissance, subsurface exploration, obtaining
representative soil samples, laboratory testing, analysis of the field and laboratory data, research of available
geological literature pertinent to the site, and preparation of this report. More specifically, the intent of this
analysis was to:
a) Explore the subsurface conditions of the site to the depths influenced by the proposed
construction;
b)
c)
d)
e)
f)
g)
Evaluate, by laboratory tests and our experience, the engineering propertic!s of the various strata
that may influence the proposed construction, including soil bearing capacities, expansive
characteristics and settlement potential;
Describe the general geology at the site including possible geologic hazards that could have an
effect on the site construction, an~ provide the seismic design parameters required by the most
recent edition of the Uniform Building Code;
Address potential construction difficulties that may be encountered due to soil conditions,
groundwater, or geologic hazards, and provide recommendations concern.ing these conditions;
Develop soil-engineering criteria for the site preparation and grading, and address the stability of
cut and fill slopes;
Recommend an appropriate foundation system for the type of structure anticipated and develop
soil engineering design criteria for the recommended foundation design;
Present our professional opinions this written report that includes, in addition to our findings and
recommendations, a site plan showing the location of our subsurface explorations and a summary
of our laboratory test results.
It is not within the scope of our services to perform laboratory tests to evaluate the chemical characteristics
of the on-site soils in regard to their potentially corrosive impact to on-grade concrete and below grade
improvements. If desired, we can submit representative soil samples to a chemical laboratory for ~alysis.
We suggest that such samples be obtained after precise grading is complete and the soils that can affect
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CWE 202.920.1 February 17, 2003 Page No. 3
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 recommend that the
developer retain an engineering firm that specializes in this field to consult with them on this matter.
In addition, our scope of service does not include assessment of hazardous substance contamination, or
recommendations to prevent floor slab moisture intrusion or the fonnation of mold within the structure, or
any other services not specifically described in the scope of services presented above.
FINDINGS
SITE DESCRIPTION
The subject site is an irregular-shaped parcel of land located at 2817 and 2819 Cazadero Drive, in the La
Costa area of Carlsbad, California. The subject site is identified as Assessor's Parcel Number 215-32Q-45, and
as Lot 306 of La Costa Meadows Unit No.2 (Map 6905). The lot is vacant and has been graded to have a
relatively level pad in the western portion. An unimproved driveway along the north side of the lot provides
access to the pad. There is an approximately 6-foot-high fill slope at the front of the lot and a 12-to 15-foot-
high cut slope at the rear of the lot, at the base of a high, gently ascending natural hillside. The lot is bounded
on the north and south by single-family residential properties. The lot has approximately 100 feet of froittage
along Cazadero Drive, ranges from approximately 215 to 225 feet in depth, and has a rear property line length
of about 36 feet. On-site elevations range from a low of approximately 245 feet (MSL) in the west comer,
the grade of Cazadero Drive, to a high of approximately 269 feet (MSL), in the 'southeast comer of th~ site.
A few piles of construction debris, gravel and cobble were found on the building pad. The -building pad area is
relatively void of vegetation, while the upper, undisturbed portions of the site consist of relatively heavy
vegetation comprised of native brush.
GENERAL GEOLOGY AND SUBSURFACE CONDITIONS
GEOLOGIC SE TTING AND SOIL DESCRIPTION: The subject property is located in the Foothills
Physiographic Province of San Diego County. Based upon the results of our limited exploration and analysis of
readily available, pertinent geologic and geotechnical literature, we have determined that the site is predominantly
underlain by Jurassic-vetaceous-age, undifferentiated Santiago Peak Volcanics that are overlain by man-placed
fill materials in the western portion and natural slopewash materials in the eastern portion. The soils encountered
during our subsurface explorations are described below in order of increasing age:
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CWE 202.920.1 February 17,2003 Page No. 4
ARTIFIGAL FILL (Qaf): A layer of artificial fill 'WaS encountered in four of our five subsurface
explorations, Trenches T-1 through T-4. The estimated limits of the existing fill are shown on the site
plan attached as Plate Number 1. In general, the existing fill material is limited to the western portion of
the graded pad and the adjacent fill slope; however, a relativelythln layer of fill 'WaS noted in the eastern
portion of the graded pad. Within Trench T-3, which 'WaS excavated at the western edge of the graded
pad, the fill layer -was found to have a thickness ranging from 6 feet at the west end of the trench to 2.5
feet at the east end. Within Trenches T-1, T-2, and T-4, the fill layer was only about six inches thick
The fill material was found to generally consist of grayish-to medium-brown, silty sand (S11) that -was
typicallydarnp to moist. Within Trench T-3, the material 'WaS medium dense to dense in consistency.
Within the Trench T-1, T-2, and T-4, the material 'WaS generally loose in consistency. Based on our
observation of the fill layer exposed within Trench T-3, it appears that the fill-was properly compacted
and properly benched into competent fonnational material. As such, the existing artificial fill material is
considered suitable in its present condition to support settlement-sensitive improvements; however, the .
upper portions will need to be scarified, moisture conditioned, and recornpacted in accordan~e with the
recommendations presented in the "Site Preparation" section of this report.
SLOPE WASH (Qsw): Although not encountered within any of our exploratory trenches, this material
-was visually observed in the existing cut slope within the eastern portion of the site. The slope-wash
deposits consisted of medium to dark brown, silty sands (S11) that were damp to moist and loose to
medium dense in consistency. There appeared to be as much as four feet of the slopewash above the
undifferentiated Santiago Peak Volcanics within the cut slope, but localized thicke~ deposits may exist.
WEATHERED UNDIFFERENTIATED SANTIAGO PEAK VOLCANICS (KJsp): As well as
being visually logged on a cut slope within the eastern portion of the site, Jurassic-Oetac\'!ous-age
materials identified as the undifferentiated Santiago Peak Volcanics were encountered within each of our
test trenches. The material comprising the Santiago Peak Volcanics consisted of reddish-.brown to gray,
sandy gravel (GP). The material-was damp to moist and medium dense to dense in consistency. The
upper few feet of the fonnational material is moderately to highly fractured. These materials are
considered suitable in their present condition to support fill and! or settlement-sensitive improvements.
GROUNDWATER: No groundwater was encountered in our explorations and we do not anticipate any
significant groundwater related problems during or after construction provided that proper dnUnage is
maintained. However, it should be recognized that minor groundwater seep"age conditions ~t occur after
development of a site even where none were present before development. These are usuallyJ;Dinor phenomena
and are often the result of an alteration in dnUnage patterns and! or an increase in irrigation water. Based on the
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CWE 202.920.1 February 17, 2003 Page No. 5
penneability characteristics of the soil and the anticipated usage and development, it is our opinion that any
seepage conditions, should they develop, will be minor in extent. These potential "nuisance" conditions can
typically be mitigated by the use of proper landscaping techniques.
TECfONIC SETTING: No faults are known to traverse the subject site. Howevl;r, it should be noted that
much of Southern California, including the San Diego County area, is characterized by a series of Quatemary-
age fault zones that consist of several individual, en echelon faults that generally strike in a northerly to
northwesterly direction. Some of these fault zones (and the individual faults within the zone) are classified as
"active" according to the criteria of the California Division of Mines and Geology. Active fault zones are
those that have shown conclusive evidence of faulting during the Holocene Epoch (the most recent 11,000
years).
A review of available geologic maps indicates that the active Rose Canyon Fault Zone is located
approximately 12 kilometers southwest of the subject site. Other active fault zones in the region that could
possibly affect the site include the Coronado Bank and San Cemente Fault Zones to the southwest and the
Elsinore, Earthquake Valley, San Jacinto, and San Andreas Fault Zones to the northeast.
GEOLOGIC HAZARDS
GROUND SHAKING: A likely geologic hazard to affect the site is ground shaking as a result of movement
along one of the major active fault zones mentioned above. The maximUm ground accelerations that would be
attributed to a maximum magnitude earthquake occurring along the nearest fault segments of selected fault zones
that could affect the site are summarized in the following Table I.
TABLE I: MAXIMUM GROUND ACCELERATIONS
Fault Zone Distance Maximum Magnitude Maximum Groood
Earthquake Accele~tion
Rose Canyon 12km 6.9 magnitude 0.18 g'
Newport-Inglewood 18km 6.9 magnitude 0.13 g
Coronado Bank 36km 7.4 magnitude 0.10 g
Elsinore 37km 7.1 magnitude 0.07g
Earthquake Valley 62km 6.5 magnitude 0.04g
San Jacinto 74km 7.2 magnitude 0.05 g
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CWE 202.920.1 February 17,2003 Page No. 6
Probable ground shaking levels at the site could range from slight to moderate, depending on such factors ~
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 improvements.
SEISMIC DESIGN P ARAME TERS: Based on a maximwn magnitude (Mmax) earthquake of 6.9 along
the nearest portion of the Rose Canyon Fault Zone, the Maximwn Ground Acceleration at the site would be
approximately0.18 g. For structural design purposes, a damping ratio not greaterthan 5 percent of critical
dampening, and Soil Profile Type SB are recommended (UBC Table 16-]). Based uporrthe location of the
site being greater than 10 kilometers from the Rose Canyon Fault (Type B Fault), Near Source Factors Na
equal to 1.0 and Ny equal to 1.0 are also applicable. These values, along with other seismically related design
parameters from the Uniform Building Code (UBq 1997 edition, Volwne II, Chapter 16, utilizing a Seismic
Zone 4 are presented in the following table.
TABLE II: SEISMIC DESIGN PARAMETERS
UBC -Chapter 16 Seismic Recommended
Table No. Parameter Value
16-1 Seismic Zone Factor Z 0040
16-J Soil Profile Type SB
16-Q Seismic Coefficient Ca 0040 Na
16-R Seismic Coefficient C 0040 Ny
16-S Near Source Factor Na 1.0
16-T Near Source Factor Ny 1.0
16-U Seismic Source Type B
SURF ACE RUPTURE: No active or potentially active faults are present at the subject site so the site is not.
considered susceptible to surface rupture.
LANDSLIDE POTENTIAL AND SLOPE STABILITY: As part of this investigation we reviewed the
publication, "Landslide Hazards in the Southern Part of the San Diego Metropolitan Area" byTan, 1995. This
reference is a comprehensive study that classifies San Diego County into areas of relative landslide susceptibility.
The subject site is located in Area 3-1. The Area 3-1 classification is assigned to areas considered generally .
suscepuble to slope movement. Natural slopes within the Area 3-1 classification are considered at or near their
. stability limits due to their steep inclinations and can be expected to fai110callywhen adverse1ymodified.. Sites
within this classification are located outside the boundaries of known landslides.
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CWE 202.920.1 February 17, 2003 Page No. 7
The site was found to be underlain, below the fill layer, by Undifferentiated Santiago Peak Volcanic Rock Based
on our experience, these materials typically have excellent strength chmcteristics in tenns of slope stability. As
such, it is our opinion that the potential for deep-seated landsliding on the subject site is low: hI addition, it is our
opinion that the potential for slope failures within the existing fill slope at the western side of the subject site is
low. This is based on the proper compaction of the existing fill, the proper benching of the existing fill into
competent formational materials, and the inclination of the fill slope.
LIQUEFACtION: The near-surface soils encountered at the site are not considered susceptible to liquefaction
due to such factoIS as soil density, grain-size distribution and the absence of shallow groundwater conditions.
FLOODING Based on our review of the maps prepared by the Federal Emergency 1v.ranagement Agency, the
site is located outside the boundary of the lOO-year and SOO-year floodplains.
TSUNAl\1IS: Tsunamis are great sea waves produced by submarine earthquakes or volcanic eruptions. Due to
the elevation of the site and its location, it should not be affected by a tsunami.
SEICl-IES: Seiches are periodic oscillations in large bodies of water such as lakes, harboIS, bays or reservoirs.
Due to the site's location, it should not be affected byseiches.
CONCLUSIONS
In general, we found the subject property suitable for the proposed residential development, provided the
recommendations provided herein are incorporated into the project plans and specifications. The following
are the most significant geotechnical conditions to affect the proposed construction.
• There is an approximately four-foot-thick layer of slopewash material: above the existing cut'slop~ in
the eastern portion of the site that is considered unsuitable in its present conditio~ to support
settlement-sensitive improvements. This material will need to be removed from the areas to support
settlement-sensitive improvements and be replaced as properly compacted fill material.
• The deeper excavations within the Santiago Peak Volcanics, particularly for the partially subterranean
parking level, may be difficult to perform with light trenching equipment. As such, it may be difficult
to make the excavations for foundations and utility trenches within the formational materials if they
are not undercut as described in the "Building Pad Undercuts" section of this report.
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C\X7E 202.920.1 February 17,2003 Page No.8
RECOMMENDATIONS
GRADING AND EARTHWORK
GENERAL: All grading should conform to the guidelines presented in Appendix Chapter A33 of the
Uniform Building Code, the minimum requirements of the Gtyof Carlsbad, and the Recommended Grading
Specifications and Special Provisions attached hereto as Appendix B, except where specificallysuperseded in
the text of this report. Prior to grading, a representative of Christian Wheeler Engineering should be present
at the preconstruction meeting to provide additional grading guidelines, if necessary, and to review the
earthwork schedule.
OBSERVA1:rON OF GRADING: Continuous observation by the Geotechnical ConsJ,tantis essential
during the grading operation to confirm conditions anticipated by our investigation, to allow adjustments in
design criteria to reflect actual field conditions exposed, and to detennine that the grading proceeds in general
accordance with the recommendations contained herein.
CLEARING AND GRUBBING: At the time of our site investigation, the existing building pad was cleared
of vegetation, but did support some construction debris. The site preparation should begin with the removal of
the construction debris and any vegetation and other deleterious materials from the portions of site that will be
graded and! or will receive improvements. The resulting materials should be disposed of off-site.
SITE PREPARATION: After clearing and grubbing, the existing slopewash material should be removed
from the areas to receive fill or settlement-sensitive improvements to the contact with underlying materials of
the Santiago Peak Volcanics. Based on our limited subsurface explorations, the existing slopewash deposits are
expected to have an approximate thickness of four feet, but may be thicker in-localized areas. The removals
should extend laterally at least five feet outside the building perimeter and at least two feet outside light exterior
improvements. No other special site preparation is considered necessary at this time other than preparing any
areas to receive fill as discussed in the "Processing of Fill Areas" section of this report. Preparing the existing
pad in accordance with those recommendations will mitigate for the approximately six-inch-1:hickveneer of
loose fill material over the formational soils.
BUILDING PAD UNDERCUTS: It appears that the building will be traversed by a cut! fill transition. Where
this occurs, the cut portion of the building pad should be undercut at least three feet below finish grade. In
addition, the excavation for the partially subterranean parking level may expose very dense hardrock that cannot
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CWE 202.920.1 February 17, 2003 :page No.9
be excavated with light trenching equipment. If this is the case, consideration should be given to undercutting
the building pad and utility alleys to at least six inches below the bottom of the foundations and utilities and
replacing the excavated material with compacted fill material.
The bottom of all 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 bonom 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 and approved to receive fill, 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.
COMP ACfION 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 AS1M Laboratory
Test D1557-91. Fills should be placed at or slightly above optimum moisture content, in lifts Slxto eight inches
thick, with each lift compacted by mechanical means. Fills should consist of approved earth ~terial, free of
trash or debris, roots, vegetation, or other materials detennined 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.
Uilitytrench backfill within five feet of the proposed structures and beneath all pavements and concrete
flatwork should be compacted to a minimum of 90 percent of its maximum dry density.
SURFACE DRAINAGE: Surface runoff into graded areas should be minimized. Where possible, drainage
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
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 building should be graded so that surface water flows rapidly away from the
buildings without ponding. In general, we recommend that the ground adjacent to the building slopes away
at a gradiellt of at least two percent. Dens ely vegetated areas where runoff can be impaired should have a
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CWE 202.920.1 February 17,2003 Page No. 10
minimum gradient of five percent within the first five feet from the strqcture. Gutters and downspouts
should discharge to controlled drainage systems.
TEMPORARY CUT SLOPES: Temporary cut slopes of up to ten feet in height are anticipated to be
required during the proposed construction. Temporarycut slopes of up to ten feet in height, forretainll;tg
walls, can be excavated vertical for the bottom five feet and at an inclination of 0.5 to i.o (horizontal to
vertical) or flatter above. All temporary cut slopes should be observed by the engineering geologist during
grading to ascertain that no unforeseen adverse conditions exist. No surcharge loads such as soil or
equipment stockpiles, vehicles, etc. should be allowed within a distance from the top of temporary slopes
equal to half the slope height. Where there is not room to construct temporary slopes, tempotaryshoring of
the excavation sides may be necessary.
The contractor is solely responsible for designing and constructing stable, temporary excavations and may
need to shore, slope, or bench the sides of trench excavations as required to maintain the stability of the
excavation sides. The contractor's "responsible person", as defined in the OSHA. Construction Standards
for Excavations, 29 CPR, Part 1926, should evaluate the soil exposed in the excavations as part of the
contractor's safetyprocess. Temporary cut slopes should be constructed in accordance -with the
recommendations presented in this section. In no other case should slope height, slope inclination, or
excavation depth, including utility trench excavation depth; exceed those specified in local, state, and federal
safety regulations.
FOUNDATIONS
GENERAL: Based on the results of our investigation and provided the site is prepared in accordance with the
above recommendations, it is our opinion that the proposed structures may be supported by conventional
spread foundation systems. We anticipate that the foundation soils will have a "low" Expansion Inde~ and that
the foundations will not have to be designed for heaving soils. The following recommendations are considered
based on the soil conditions and are not intended to be in lieu of structural considerations. All foundations
should be designed by a qualified structural engineer.
FOUNDATION DIMENSIONS: Spread footings supporting the proposed two-and three-story structure
should be embedded at least 18 and 24 mshes below finish pad gra~l r~spectively. Continuous and.isolated
footings should have a minimum width of 12 inches and 24 inches, respectively. Continuous footings
supporting retaining walls should have a minimum 'Width of 24 inches.
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CWE 202.920.1 February 17,2003 Page No. 11
BEARING CAP AOTY: Conventional continuous spread footings with the above, minimum dimension$ for
two-story structures may be designed for an allowable soil bearing pressure of 3,500 pounds per square foot.
This value may be increased by 300 and 700 psf for each addition foot of footing width and embedment,
respectively, to a maximum of 5,000 psf. This value may also be increased by one-third for combinations of
temporary loads such as those due to wind or seismic loads.
FOOTING REINFORCEMENT: The project structural engineer should provide reinforcement
requirements for foundations. However, based on soil conditions, we recommend that the minimum
reinforcing for continuous footings consist of at least two No.5 bars positioned three inches above the bottom ,
of the footing and two No.5 bars positioned two inches below the top of the footing.
LATERAL LOAD RESISTANCE: Lateral loads against foundations maybe resisted by friction between the
bottom of the footing and the supporting soil, and by the passive pressure against the footing. The coefficient
of friction between concrete and soil may be considered to be and 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.
SE TTLEMENT CHARACTERISTICS: The anticipated total and! or differential settlement is expected
to be less than about one-half inch for new foundations, provided the recommendations presented in this
report are followed. It should be recognized that minor cracks normally occur in concrete slabs and
foundations due to shrinkage during concrete curing or redistribution of stresses, therefore some cracks
should be anticipated. Such cracks are not necessarily an indication of excessive vertical movements.
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
Geotechnical G:>nsultant prior to placing reinforcing steel or fonnwork to detennine if the foundation
recommendations presented herein are followed. All footing excavations should be excavated neat, leve~ and
square. All loose or unsuitable material ~hould be removed prior to tP.e placement of concrete.
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CWE 202.920.1 February 17,2003 Page No. 12
ON-GRADE SLABS
GENERAL: It is our understanding that the floor system of the proposed duplex will consist of a concrete
slab-on-grade floor. The following recommendations assume that the subgrade soils have been prepared in
accordance with the recommendations presented in the "Site Preparation" section of this report. In addition,
the following recommendations are considered to be the minimum slab requirements based on the soil
conditions and are not intended to be in lieu of structural considerations. All slabs should be designed bya
qualified structural engineer.
INTERIOR FLOOR SLABS: The minimum floor slab thickness should be four inches (actual) and all
floor slabs should be reinforced with at least No.3 reinforcing bars placed at 18 inches on center each way.
Slab reinforcement should be supported on chairs such that the reinforcing bars are positioned at mid-height
in the floor slab. The garage slab may be constructed independent of the garage perimeter footings.
However, if the garage slab and footings are poured monolithically, the slab reinforcement should extend into
the perimeter foundations at least six inches.
MOISTURE PROTECTION FOR INTERIOR SLABS: Where the concrete on-grade floorslabs will
support moisture-sensitive floor covering, it is the industry standard that it be underlain by a moisture barrier.
The industry standard for the subslab moisture barrier is a four-inch-thick blanket of coarse, clean sand that
has less than ten percent and five percent passing the No. 100 and No. 200 sieves, respectively, with a
visqueen vapor barrier placed in the center of the sand 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 excess amount of moisture for some types of floor
covering. If additional protection is considered necessary, recommendations can be provided to reduce the
penneability of the concrete.
EXTERIOR CONCRETE FLATWORK: 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
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
specifications .
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CWE 202.920.1 February 17,2003 Page No. 13
EARTH RETAINING WALLS
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
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
inches of exterior retaining wall footings should not be included in passive pressure calculations where
abutted by landscaped or unpaved areas.,
EQUIVALENT FLUID PRESSURE: The active soil pressure for the design of "unrestrained" and
"restrained" earth retaining structures with level backfill may be assumed to be equivalent to the 'pressure of a
fluid weighing 35 and 55 pounds per cubic foot, respectively. These values assume a drained backfill
condition.
SURCHARGE: No surcharge loads have been considered If any surcharge loads are anticipated, this
office should be contacted for the necessary increase in lateral soil pressures.
WATERPROOFING AND SUBDRAIN OBSERVATION: The project architect should provide
waterproofing details. The geotechnical engineer should be requested to verify that waterproofing has been
applied. A suggested wall sub drain detail is provided on the attached Plate Number 7. We reconunend that.
the Geotechnical Consultant be retained to observe all retaining wall subdrains to verify proper construction.·
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 s~ould not be backfilled until the masonry has
reached an adequate strength.
LIMITATIONS
REVIEW, OBSERVATION AND TESTING
The reconunendations presented in this report are contingent upon our review of final plans and specifications.
Such plans and specifications should b~ ~de available to the Geq~echnical Engineer and Engineering Geologist
so that they may review and verify their compliance with this report.
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CWE 202.920.1 February 17,2003 Page No. 14
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.
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 perlonnance 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 intennediate and unexplored
areas. Anyunusual 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
detennine 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 bya written addendum
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 mayoccur. 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.
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CWE 202.920.1 February 17,2003 Page No. 15
PROFESSIONAL STANDARD
In the perfonnance of our professional services, we comply with thadevel 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 mayvary 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 byus. 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 byus, or by our proposal for
consulting or other services, or by our furnishing of oral or written reports or findings.
alENT'S RESPONSIBILITY
It is the responsibility of Mr. Ed Lowry, or his representatives, to ensure that the infonnation and
recommendations contained herein are brought to the attention of the structural engineer and architect f<?r the
project and incorporated into the project's plans and specifications. It is further his responsibility to take the
necessary measures to insure that the contractor and his subcontractors carry out such recommendations during
construction.
FIELD EXPLORATIONS
Five subsurface explorations were made at the locations indicated on the site plan included. herewith as Plate
Number 1 on January 23, 2003. These explorations consisted of five test trenches using a Case 580L Backhoe.
The fieldwork was conducted under the observation and direction of our engineering geology personnel
'The explorations were carefully logged -when made. The test trench logs are presented on the following Plate
Numbers 2 through 6. The soils are described in accordance with ·the Unified Soils Oassification. 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 very loose, loose, medium dense, dense or very dense. 'The consistency
of silts or clays is given as either very s oft, soft, medium stiff, stiff, very stiff, or hard.
Disturbed "bulk" samples and relatively undisturbed "chunk" samples were taken from the trench excavations
and transported to our laboratory for testing.
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CWE 202.920.1 February 17,2003 Page No. 16
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.
a) CLASSIFICATION: Field classifications were verified in the laboratorybyvisual examination. The
final soil classifications are in accordance with the Unified Soil Classification System.
b) MOISTURE-DENSITY: In-place moisture contents and dry densities were det~ed for
representative soil samples. This infonnation was an aid to classification and pennitted recognition of
variations in material consistency with depth. .The dryunit weight is detennined in pounds per cubic
foot, and the in-place moisture content is detennined as a percentage of the soil's dryweight. The
results of these tests are summarized in the boring logs.
c) COMPACTION TEST: The maximum dry density and optimum moisture content of typical soils
were detennined in the laboratory in accordance with ASTM Standard Test D-1557-91. The result of
this test is presented below.
Sample Number:
Sample Description:
Optimum Moisture Content:
Maximum Density:
Trench T-3@ 0 -3'
Light yellowish-brown, silty sand (S:M)
10.7%
119.0 pcf
d) DIRECT SHEAR TEST: A direct shear test was performed to detennine the failure envelope of
the anticipated foundation soils based on yield shear strength. The shear box vvas designed to
accommodate a sample having a diameter of 2.375 inches or 2.50 inches and a height of 1.0 inch.
The sample was tested at different vertical loads and at a saturated moisture content. The shear stress
was applied at a constant rate of strain of approximately 0.05 inch per minute. The results of these
tests are presented below.
Sample Number:
Sample Type:
Angle of Internal Friction:
Apparent Cohesion:
Trench T-3@ O.-~'
Remolded to 90 %
26°
300 psf
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CWE 202.920.1 February 17, 2003 Page No. 17
e) GRAIN SIZE DISTRUBUTION: The grain size distribution of a selected sample was
determined in accordance with AS1M D422. The results of these tests are presented below.
Sample Location
Sieve Size Percent Passing'
#4
#8
# 16
# 30
# 50
# 100
# 200
Soil Type
Trench T·3 @ 0-3'
Percent Passing
100
99
97
95
90
62
35
SM
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LOG OF TEST TRENCH NUMBER T-l
Date Excavated: 1/23/2003
Equipment:
Existing Elevation:
Case 580 Backhoe
464 feet
Finish Elevation: 466 feet
'Z' 0 0 <1J <2 H '--' U ~ H ::r: SUJvfIv[ARY OF SUBSURFACE CONDITIONS ~ ~ q 0
Artificial Fill (Qat): Grayish-brown, moist, loose, GRAVELLY
1
Weathered Undifferentiated Santiago Peak Volcanics (KJsp):
2 Reddish-brown and gray, damp to moist, medium dense to dense,
SANDY GRAVEL (GP), moderately to highly fractured
3
4
Practical refusal at 4 feet.
5
6
7
8
9
Logged by: TSW
Project Manager: . CHC
Depth to Water: N/A
Drive Weight: N / A
~ ........ ~ ~ ~
~ ;:g ~ ~ en H ~
4.5
~
~ ~ Z en
0 f:] ~ q
142.7
10 ~~------------------~~--------------~~----------~~--~--~--~--~--~
J~.' J"fI
CHR.ISTIAN WHEELER .
ENGINEER.ING
BY:
JOBNO.:
PROPOSED LA COSTA DUPLEX
2817 & 2819 Cazadero Dr., Garlsbad, California
HF DAlE: . Februru:y 2003
202.920 PU1ENO.: 2
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LOG OF TEST TRENCH NUMBER T-2
Date Excavated: 1/23/2003 Logged by: TSW
Equipment: Case 580 Backhoe Project Manage.r: CHC
Existing Elevation: 464 feet Depth to Water: N/A
Finish Elevation: 466 feet Drive Weight: N/A
'Z' 0 0 fil ,......, ~ oJ) ~ t2 H ~ ~ '-../ U ~ ~ S t-r ~ SUlvllvfARY OF SUBSURFACE CONDITIONS E3
H ~ Z Cf.) ~ 0 ~ ~ Cf.) (:4 H ~ ~ Cf.) (:4
SILTY SAND
1 Weathered Undifferentiated Santiago Peak Volcanics (KJsp):
Reddish-brown and gray, damp to moist, medium dense to dense,
2 SANDY GRAVEL (GP). 8.3 152.1
Moderately to highly fractured from % to 2Y2 feet.
3 At 2% feet becomes dense to very dense.
--
4 Practical refusal at 3 % feet.
5
6
7
8
9
10
PROPOSED LA COSTA DUPLEX
~j 2817 & 2819 Cazadero Dr., Carlsbad, California
CHRJSTIAN WHEELER. . BY: HF DATE: February 2003
ENGINEER.ING ]OBNO.: 202.920 PUTENO.: 3
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LOG OF TEST TRENCH NUMBER T-3
Date Excavated: 1/23/2003 Logged by: TSW
Equipment: Case 580 Backhoe Project Manager: CRe
Existing Elevation: 464 feet Depd1 to Water: N/A
Finish Elevation: 457.5 feet Drive Weight: N/A
~ 0 Z
CJ.) 3 ~ '0' ~ ~
t1:l .~ 0 ;,::::
'-.../
'-.../ U ~ ~ OCfJ
~ ~ ~ tQ ~~ SUlYIlYIARY OF SUBSURFACE CONDITIONS W' H ~ Z u
~ . Po< ~ 0 O~
§ I=Q ~ O~
0 ~ H ~ j 0
p... ;;,g 0
~:: :t. Artificial Fill (Oaf): Light gray, moist, medium dense to dense, SILTY '. '
MD
SAND (SNI), very fine to fine-grained. 1 DS
12.6 109.8 SA
2 ' .' ~
3 '. ,
,.'",
". Medium brown, damp to moist, medium' dense to dense, SILTY
4 . . .-~
.; ~~!1...'
'-, SAND (S1-I), with gravel and clay.
7.2 103.6
S
Weathered Undifferentiated Santiago Peak Volcanics (KIsP):
7
Reddish-brown and gray, damp to moist, dense, SANOY
fractured from 6-7 feet. Becomes
Practical refusal at 7 feet
8
9
10 L-~ ______________________________________________ ~~--~~~~--~~~
YJ
CHR.ISTIAN WHEELER. . BY:
ENG I N E.E R. I N G ]OBNO. :
PROPOSED LA COSTA DUPLEX .
2817 & 2819 Cazadero Dr., Carlsbad, California
HF DATE: February 2003
202.920 PL'\TENO.: 4
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LOG OF TEST TRENCH NUMBER T-4
Date Excavated: 1/23/2003 Logged by: TSW
Equipment: Case 580 Backhoe P:toj ect Manage:t: CRC
Existing Elevation: 464 feet Depth to Wate:t: N/A
Finish Elevation: 466 feet Drive Weight: N/A
~ () Z 0 ~ ~ ~ Q) ~
.J:l H ~ 0 ~
'--" U ~ ~ p ~ ~ f'-t ~ SUMMARY OF SUBSURFACE CONDITIONS ~ ~ H ~ Z
~ ~ ~ ~ .~ ~ r/)
Q re
H ~ () 0
r/) :2l Q
Artificial Fill (Qat): Grayish-brown, moist, loose, GRA'VELLY
1
Weathered Undifferentiated Santiago Peak Volcanics (KJsp): 0.8 163.4
2
Reddish-brown and gray, damp to moist, medium dense to dense,
SAl"JDY GRAVEL (GP). At 3 feet becomes dense to very dense.
3
From 1/2 to 3 feet becomes moderately to highly fractured.
Practical refusal at 3% feet. 4
5
6
7
8
9
10 ~~~--------------------------------------------------~~--~--~--~~~--~
PROPOSED LA COSTA DUPLEX
!II
CHRISTIAN WHEELER. .
ENGINEERIN<;:; 202.920 PLATE NO.:
2817 & 2819 Cazadero Dr., Cl:!.r1sbad, California
BY: HF DATE: February 2003
5 ]OBNO.:
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LOG OF TEST TRENCH NUMBER T-5
Date Excavated: 1/23/2003 Logged by: .TSW
Equipment: Case 580 Backhoe Proj ect Manager: CHC
Existing Elevation: 464 feet Depth to Water: N/A
Finish Elevation: N/A Drive Weight: N/A
-0 0 0 I:il ,....., ~ Q) ~ ~ H ~ ~ '-" U ~ ?
?S H ~ ~ ::r: SU.l':v.Ilv1ARY OF SUBSURFACE CONDITIONS es ~ S ~ ~ ~ ~ ~ ~
0 ~ Cf.l 0
Weathered Undifferentiated Santiago Peak Volcanics (KJsp):
Reddish-brown and gray, damp to moist, dense, SANDY
GRAVEL (GP).
Moderately to highly fractured from 0-12 inches.
At 12 inches becomes dense.
3 Practical refusal at 2% feet.
4
5
·6
7
8
9
10 ~~------------------------------------------------~~--~~~~----~~
'~I J"v
CHR.ISTIAN WHEELER. .
ENGINEER.ING
BY:
]OBNO. :
PROPOSED LA COSTA DUPLEX
2817 & 2819 Cazadero Dr., Carlsbad, California
HF DAlE: February 2003
202.920 PUTENO.: 6
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LOG OF TEST TRENCH NUMBER T-6
Date Excavated: 1/23/2003 Logged by: TSW
Equipment: Case 580 Backhoe Project Manager: CHC
Existing Elevation: 474.0 feet Depth to Water: N/A
Finish Elevation: 476.0 feet Drive Weight: N/A
<;::;' (j
0 ~ ,--... ~ <!) ~ c2 H ~ ~ '-'" U ~ ~ (/.) H }-I :::r: SUJY.IJYfARY OF SUBSURFACE CONDITIONS ~ ~ (/.) @ ~ ~ (/.) ~ 0 H (j ~ (/.)
Slopewash (Osw): Medium to dark brown, damp to moist, loose to
1 medium dense, SILTY SAND (S11), with gravel
.. ,
2 ,:.'''./':
3
4
Weathered Undifferentiated Santiago Peak Volcanics (KJsp):
5 Reddish-brown and gray, damp to moist, medium dense to dense,
SANDY GRAVEL (GP).
6 Moderately to highly fractured from 4-7 feet.
Dense to very dense at 7 feet.
7
8
9
10
Test trench terminated at 10 feet.
PRO~OSED LA COSTA DUPLEX
2817 & 2819 Cazadero Dr., Carlsbad, California
CHR.ISTIAN WHEELER. . BY: HF DATE: February 2003
ENGINEER.ING JOB NO. : 202.920 PU1ENO.: 7
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-1% 510 e Minimum
HY.-7--b ~ ,,-I.
3/4 inch Crushed Rock or
Miradrain 6000 or Equivalent
Geofabric Between
Rock and Soil
Minimum
4-inch Diameter
Perforated Pipe
PVC Schedule 40
6-inch t
:Max. F· =~ .4·. ' ..
'" <:]'
. ~ .. j'?. :'.
~ ,~~.'; •. '
·i2"· '~, ~ ;.
;, .
-;1',
Waterproof Back of Wall
:rer Architect's Specifications
Top of Grourid r or Qmcrete Skb
t-------:..----~
'/.)<.1-1../";
L 6-inch Mi.nim~ :
RETAINING WALL
SUBDRAIN DETAIL
No Scale
.• ~, Tv
CHR.ISTIAN WHEELER.
ENGINEER.INC.
4925 MERCURY STREET TEL. (858) 496-9760
SAN DIEGO, CALIFORNIA 92111 FAX (858) 469·9758
BY:
JOB NO.:
PROPOSED RESIDENTIAL DuPLEX
2817 and 2819 Cazadero Drive, Carlsbad, California
1SW DATI: February 2003
202.920 PLATINO.: 8
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CWE 202.920.1 February 17, 2003 Appendix A, Page Ai
REFERENCES
Anderson, J.G.; Rockwell, RK. and Agnew, D.C, 1989, Past and Possible Future Earthquakes of Significance
to the San Diego Region, Earthquake Spectrn, Volume 5, No.2, 1989.
Blake, T.F., 2000, EQFAUL T, A Computer Program for the Estimation of Peak HorizontalA<;:celeration froD;l
3-D Fault Sources, Version 3.0, Thomas F. Blake Computer Services and Software, Thousand Oaks, California.
Boore, David M, Joyner, William B., and Fumal, Thomas E., 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.
California Division of Mines and Geology, 1998, Maps of Known Active Fault Near Source-Zones in California
and Adjacent Portions of Nevada.
Federal Emergency Management Agency, 1997, San Diego County, California and Incorporated Areas Flood
Insurance Rate Map, Pane11051 of 2375, Map Number 06073C1051 F.
Hart, E.w., 1994, Fault-Rupture Hazard Zones in California, California Division of Mines and Geology Special
Publication 42.
Jennings, CW., 1975, Fault Map of California, California Division of Mines and Geology; :Map
No.1, Scale 1:750,000.
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 95-04.
Tan, Siang S. and Kennedy, Mchael P., 1996, Geologic Maps of the Northweste):'Il Part of San Diego County,
California, California Division of Mines and. Geology; DMG Open,;Fjle Report 96-02.
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 202.920.1 February 17,2003 Appendix B, B-1
RECOMMENDED GRADING SPEOFICATIONS -GENERAL PROVISIONS
GENERAL INTENT
PROPOSED RESIDENTIAL DUPLEX
2817 AND 2819 CAZADERO DRIVE
CARLSBAD. CAliFORNIA
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 prepary ge91~chnical 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 specificatio.tis
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 mayprovide 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 infonnation and data so that he
may provide these opinions. In the event that anyunusual 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
Tests used to determine the degree of compaction should be performed in accordance with the following
American Society for Testing and Materials test methods:
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CWE 202.920.1 February 17,2003
Maximum Density & Optimum Moisture Content-AS1MD-1557~91
Density of Soil In-Place -ASTM D-1556-90 or ASTM D-2922
Appendix B, B-2
All densities shall be expressed in terms of Relative Compaction as detennined 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 dehris.
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 finn 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 finn 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 maydetennine if any special recommendation will be necessary.
All water wells which will be abandoned should be backfilled and capped in accordance to the requirements
set forth by the Geotechnical Engineer. The top of the cap should be at least 4 feet below finish grade or 3
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CWE 202.920.1 February 17,2003 Appendix B, B-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 Strucmral Engineer.
FILL MATERIAL
:Materials to be placed in the fill shall be approved by the Geotechnical Engineer and shall be free of
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 l0w
strength characteristics may be thoroughly mixed with other soils to provide satisfactory fill material, but only
with the explicit consent of the Geotechnical Engineer. Any import material shall be approved by the
Geotechnical Engineer before being brought to the site.
PLAONG AND COMPACfION OF FILL
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 moismre 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
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
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
Geotechnical Engineer or his representative. The location and frequency of the tests shall be at the
Geotechnical Engineer's discretion. When the compaction te~t i.t:tdicates that a particular layer is at less than
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.
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CWE 202.920.1 February 17, 2003 Appendix B, B-4
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.
Density tests in the slopes will be made by the Geotechnical Engineer during construction of the slopes to
detennine if the required compaction is being achieved. Where failing tests occur or other field problems
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.
cur SLOPES
The Engineering Geologist shall inspect cut slopes excavated in rock or lithified formational material during
the grading operations at intervals determined at his discretion. If any conditions not anticipated in the
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
shall be analyzed by the Engineering Geologist and Geotechnical Engineer to determine if mitigating
measures are necessary.
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
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
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CWE 202.920.1 February 17, 2003 Appen~ B, B-5
the observation and testing shall release the Grading Contractor from his duty to compact all fill material to
the specified degree of compaction.
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 SPEGFlCATIONS -SPEGAL PROVISIONS
RELATIVE COMPACfION: 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
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.
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,
special footing reinforcement or a combination of special footing reinforcement and undercutting may be .
required.