HomeMy WebLinkAboutCT 99-17; LOT 12 CARLSBAD RESEARCH CENTER; REPORT OF SUPPLEMENTAL GEOTECHNICAL; 2015-09-22cr
CHRISTIAN WHEELER 6 eo
ENGINEERING
REPORT OF SUPPLEMENTAL GEOTECHNICAL INVESTIGATION
PROPOSED OFFICE PARK
LOT 12 CARLSBAD RESEARCH CENTER
PRIESTLY DRIVE AND LA PLACE COURT
CARLSBAD, CALIFORNIA
PREPARED FOR:
DKS CARLSBAD PARTNERS, LLC
c/o SCIACCA DEVELOPMENT COMPANY
POST OFFICE BOX 2156
RANCHO SANTA FE, CALIFORNLA. 92067
PREPARED BY:
CHRISTIAN WHEELER ENGINEERING
4925 MERCURY STREET
SAN DIEGO, CALIFORNIA 92111
- \/ 1
4925 Mercury Street • San Diego, CA 92111 • 858-496-9760 • FAX 858-496-9758
CHRISTIAN WHEELER
ENGINEERING
September 22,1999
DKS Carlsbad Partners
c/o Sciacca Development Company
Post Office Box 2156
Rancho Santa Fe, Califomia 92067
CWE 199.471.1
Attention: Mr. Frank Sciacca
SUBJECT: REPORT OF SUPPLEMENTAL GEOTECHNICAL INVESTIGATION
PROPOSED OFFICE PARK, LOT 12 CARLSBAD RESEARCH CENTER
PRIESTLY DRIVE AND LA PLACE COURT
CARLSBAD, CALIFORNIA
Ladies and Gentlemen:
In accordance with your request we have completed a geotechnical investigation for the subject
project The findings and recommendations of our study are presented herewith.
In general, the findings of this study indicate that the site is suitable for the proposed development.
The most significant geotechnical conditions affecting the proposed development consist of cut/fiU
transition lines near two of the proposed building locations and the moderately to highly expansive
nature of the existing fill soils. The highly expansive nature of the majority of the existing fill soils
will require special design considerations for structures, pavements, or any other movements-
sensitive improvements.
If you have any questions after reviewing the findings and recommendations contained in the
attached report, please do not hesitate to contact this office. This opportunity to be of professional
service is sincerely appreciated.
Respectfully submitted,
CHRISTIAN WHEELER El INEERING, INC.
David R Russell, Staff Geologist
Charles H. Christian, R.G.E. #00215
// /O Wo 1090 '
; CERTIFIED
1 EI>!GINEERING
\ GEOLOGIST
/
Curtis R. Burdett, C.E.G. #1090
CHC:CRB:drr
cc: (2) Submitted
(4) Smith Consulting Architects - Scott Carins
4925 Mercury Street • San Diego, CA 92111 • 858-496-9760 • FAX 858-496-9758
TABLE OF CONTENTS
PAGE
Introduction and Project Descriprion 1
Project Scope 2
Findings 3
Site Description 3
Site Development History 3
General Geology and Subsurface Conditions 4
Geologic Setting and Soil Descriprion 4
Tectonic Setting 4
Geologic Hazards 5
General 5
Ground Shaking 5
Seismic Design Parameters 5
Liquefaction 6
Tsunamis 6
Seiches 6
Seismic Setdement and Differential Compaction 6
Ground Cracking and Surface Rupture 6
Slope Stability 6
Groundwater 7
Conclusions 7
General 7
Recommendations 7
Grading 7
Observation of Grading 7
Site Preparation 8
Surface Drainage 8
Earthwork 8
Foundations 9
General.... 9
Reinforcement 9
Setdement Characteristics 9
Expansive Characteristics 9
Foundation Plan Review 9
Foundation Excavation Observation 9
On-Grade Slabs 10
Interior On-Grade Floor Slabs 10
Exterior Slabs On-Grade 10
Preliminary Pavement Recommendations 10
Limitations 11
Field Explorations 12
Laboratory Testing 12
ATTACHMENTS
TABLES
Table I
FIGURES
Figure 1
PLATES
Plate 1
Plates 2-7
Plate 8
APPENDICES
Maximum Bedrock Accelerations, Page 5
Site Vicinity Map, Follows Page 1
Site Plan
Boring Logs
Laboratory Test Results
Appendix A Recommended Grading Specifications and Special Provisions
Appendix B References
GEOTECHNICAL INVESTIGATION
PROPOSED OFFICE PARK
LOT 12 CARLSBAD RESEARCH CENTER
PRIESTLY DRIVE AND LA PLACE COURT
CARLSBAD. CALIFORNIA
INTRODUCTION AND PROJECT DESCRIPTION
This report presents the results of our supplemental geotechnical investigation for a proposed office
park to be constructed on Lot 12 of the Carlsbad Research Center, north of the intersection of
Priesdy Drive and La Place Court in the City of Carlsbad, Califomia. The site location is shown on
the following Figure Number 1.
We understand that tiie subject property is to be developed by the construction of an office park
consisting of nine buildings and associated parking and driveways. The stmctures will be of concrete
tilt-up constmction witii conventional shaUow foundations and on-grade concrete floor slabs. Five
of the nine buildings are to be one story in height, with four being 6,360 square feet in area and one
being 8,336 square feet in area. The remaining four structures are each to be two-stories in height
and 17, 056 square feet in area. Precise grading to develop the property is expected to consist of
cuts and fiUs of less than about five feet from existing grades.
To assist in the preparation of this report, we were provided with a site plan prepared by Smith
Consulting Architects, dated August 6,1999. A copy of this site plan was used as the base for our
Site Plan and is included herewith as Plate Number 1. In addition, we have reviewed the following
reports:
a) Geotechnical Investigation, Callaway Golf Distribution Builcding Carlsbad Research
Center - Lot 12, Carlsbad, Califomia, dated August 8,1994, prepared by Woodward-
Clyde Consultants, Project No. 9451092K-SI01.
b) Update Geotechnical Investigation, Carlsbad Research Center Lot 12, dated August
2,1999, prepared by URS Greiner Woodward Clyde, Project No. 58-9911063J.00-
UDOOl.
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Figure Number: 1
C.W.E. 199.471.1 September 22,1999 Page 2
PROJECT SCOPE
The 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 pertaining to the site, and preparation of this
report. More specifically, the intent of this analysis was to:
a) Explore the subsurface conditions to the depths influenced by the proposed
constmction.
b) Evaluate, by laboratory tests, the pertinent engineering properties of the various
strata which may influence the proposed constmction, including bearing capacities,
expansive characteristics, and settiement potential.
c) Describe the general geolog}' at the site including possible geologic hazards that
could have an effect on the site development.
d) Address potential constmction difficulties that may be encountered due to soil
conditions, groundwater, or geologic hazards, and provide preliminary
recommendations conceming these problems.
e) Develop soil engineering criteria for site preparation and grading, which includes
recommendations to lime-treat the soils in the building pads and pavement subgrade
to mitigate the expansive soil conditions. ^
/•••-f) Provide preliminary asphalt concrete pavement and Portiand Cement concrete j
pavement design recommendations. j
g) Recommend an appropriate foundation system for the type of stmctures anticipated /. •' ; .,
and develop soil engineering design criteria for the recommended foundation
design.
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C.W.E. 199.471.1 September 22,1999 Page 3
FINDINGS
SITE DESCRIPTION
The subject property consists of an undeveloped, roughly triangular parcel of land approximately 8.2
acres in area. The vacant lot is located north of Priestiy Drive and La Place Court and is identified as
Lot 12 of Carlsbad Reach Center. The property is bounded on the northeast by El Camino Real, on
the northwest by developed Lots 4 and 5 and on the southeast by an office park developed on lot 13.
Topographically, the lot is relatively level and was sheet-graded to slope towards the west. Fill slopes
up to about eight feet high and at an inclination of about 2:1 (horizontal to vertical) ascends from a
portion of the northwest side of the lot and descend from the southeast side of the existing pad In
addition, a cut and fill slope up to about eight feet high with an inclination of about 5:1 descends to
El Camino Real.
Vegetation on the pad consists of a relatively sparse cover of natural grasses and weeds. The slopes
have been planted with groundcover and the landscaped parkway adjacent to the street at the front
of the lot have been planted with grass and trees. These areas are routinely irrigated. Several piles of
undocumented fiU and debris exist along the southwestern side of the graded pad.
SITE DEVELOPMENT HISTORY
Prior to the development of the Carlsbad Research Center subdivision, the subject property and
surrounding area was part of a natural terrace surface that was used for agricultural purposes. The
preliminary geotechnical investigation for the subcitvision was provided by Woodward-Clyde
Consultants in April of 1981. Phase I of the subdivision, which included the subject lot, was graded
in the latter part of 1981 and the first part of 1982. The testing and observation for the mass grading
was provided by San Diego Soils Engineering, Inc. and the results of their testing and observations
are summarized in a report dated April 21,1982. According to this report, the grading within the
vicinity of the subject lot included removal of loose topsoils and residual soils and the placement of
compacted fill material to establish the design grades. The report indicates that up to about 16 feet
of fill material was placed on the subject lot At the completion of mass grading, the elevations of
the subject lot varied from approximately 309 to 322 feet Mean Sea LeveL The topography of the lot
has remained unchanged since the mass grading was completed.
C.W.E. 199.471.1 September 22,1999 Page 4
GENERAL GEOLOGY AND SUBSURFACE CONDITIONS
GEOLOGIC SETTING AND SOIL DESCRIPTION: The subject site lies widiin tiie coastal
margins along the westem flanks of the Peninsular Range Province of southern Califomia and is
underlain by sedimentary deposits comprised of the Tertiary—age, Santiago Formation and by
artificial fill.
The fill material is well-compacted, documented fill that was placed during the mass grading for
Phase I of the Carlsbad Research Center subdivision. The fill material was encountered in all six of
our subsurface investigations and is expected to extend to a maximum depth of about 16 feet,
although the maximum thickness measured in our borings was only 14 feet The fill material
basically consists of moist, very stiff, sandy silty clay with moderate to high plasticity. This material is
classified as a "CH" by the Unified Soil Classification System and was found to have a high potential
for expansion, as determined by UBC test Method 29-2. This material was found to have moderate
strength parameters for determining the soil bearing capacity and to have low strength parameters for
determining stmctural pavement sections. Occasional layers of moist, dense sandy clay (SC) were
encountered in the fill material.
The Santiago Formation below the fill material was found to consist of moist, hard clayey, sandy silts
(ML) and moist, very dense, silty sands (SM) and clayey sands (SC). These materials are exposed at
the ground surface along the southerly side of the lot and are expected to extend into building pads
"H" and "J". These materials have low to moderately expansive potential and have relatively high
strength parameters when determining soil bearing capacity and low to moderate strength parameters
when determining stmctural pavement sections.
TECTONIC SETTING: Some minor Tertiary-age faults were encountered in the vicinity of die
site during mass grading operations. In adciition, it should be noted that much of Southem
Califomia, including San Diego County, is characterized by a series of Quatemary-age fault zones
which typically 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 while others are classified as only potentially active according to the criteria of the
Califomia Division of IVfines 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 movement during the Pleistocene Epoch (11,000 to
1.6 million years before the present) but no movement during Holocene time.
C.W.E. 199.471.1 September 22,1999 Page 5
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A review of available geologic maps indicates that the Rose Canyon Fault Zone is located
approximately 7 miles west of the site. Other active fault zones in the region that could possibly
affect the site include the Coronado Bank and San Clemente Fault Zones to the west, the Elsinore
and San Jacinto Fault Zones to the northeast, and the Agua Bianca and San Miguel Fault Zones to
the south.
GEOLOGIC HAZARDS
GENERAL: The site is located in an area which is relatively free of significant geologic hazards.
There are no hazards of sufficient magnitude to preclude development of die site as presentiy
proposed.
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 die nearest
fault segments of selected fault zones that could affect the site are summarized in the foEowing Table I.
TABLE I
Fault Zone Distance Maximum Probable
Earthquake
Maximum Bedrock
Acceleration
Rose Canyon 7 miles 6.5 magnitude 0.28 g
Elsinore 22 miles 7.3 magnitude 0.17 g
Coronado Bank 23 miles 7.0 magnitude 0.13 g
San Jacinto 46 mUes 7.8 magnimde 0.14 g
Probable ground shaking levels at the site could range Irom slight to moderate, depending on such
factors as the magnimde of the seismic event and the (distance to the epicenter. It is likely that the site
wiU experience the effects of at least one moderate to large earthquake during the Hfe of the proposed
stmctures.
SEISMIC DESIGN PARAMETERS: In accordance witii die evaluations provided above, die
Maximum Bedrock Acceleration at die site is 0.28 g (based upon a Maximum Probable Seismic Event of
6.5 Magnitude along the Rose Canyon Fault Zone). For stmctural design purposes, a damping ratio not
greater tiian 5 percent of critical dampening, and Soil Profile Type So are recommended (UBC Table 16-
C.W.E. 199.471.1 September 22,1999 Page 6
J). Based upon the location of the site of approximately 11 kilometers (7 miles) firom the Rose Canyon
Fault (Type B Fault), Near Source Factors Na equal to 1.0 and Nv equal to 1.0 are also applicable.
Additional seismically related design parameters are recommended to be obtained firom the Uniform
Building Code (UBQ 1997 edition. Volume II, Chapter 16, utilizing a Seismic Zone 4.
LIQUEFACTION: The materials at the site are not subject to liquefaction due to such factors as
soil density, grain-size distribution, and lack of shallow groundwater.
TSUNAMIS: Tsunamis are great sea waves produced by a submarine earthquake or volcanic
emption. Due to the site's location, it is not subject to tsunamis.
SEICHES: Seiches are periodic oscillations in large bodies of water such as lakes, harbors, bays, or
reservoirs. No such large bodies of standing water are located in an area that could possibly affect
the subject site.
SEISMIC SETTLEMENT AND DIFFERENTLAL COMPACTION: The formational
materials and the compacted fills at the site are all medium dense/medium stiff to stiff and very
stiff/very dense and are not subject to seismic setdement or differential compaction.
GROUND CRACKING AND SURFACE RUPTURE: No active faults are known to traverse
the site, so the site is not considered subject to surface mpture from on-site faulting. Ground
cracking caused by shaking from distant seismic sources is considered to be highly unlikely.
SLOPE STABILITY: The site is identified as being in Relative Landslide Susceptibility Area 3-1
accor<iing to the LandsUde Susceptibility Map prepared by the Califomia Division of IVIines and
Geology. Area 3 is considered to be a generally susceptible area and includes areas that are
considered to be at or near their stability limits due to a combination of weak materials and steep
slopes. A review of the pre-development aerial photographs revealed the presence of several
topographic feamres in the vicinity of the project site that may suggest previous slope failures and
some landslides were identified during the geotechnical investigation for the subdivision. Based on
our site-spedfic study and the information available to date, it is our opinion that the previous mass
grading operation has satisfactorily mitigated the presence of landslides and that the likelihood of
deep-seated slope instability phenomena at the subject site proper can be considered to be low.
Potential shallow, surficial problems can be mitigated by the use of appropriate landscaping and
slope maintenance practices.
C.W.E. 199.471.1 September 22, 1999 Page 7
GROUNDWATER: We do not anticipate any major groundwater related problems, either during
or after constmction. However, it should be recognized that minor groundwater seepage problems
might 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 of the permeability
characteristics of the soil, an alteration in drainage pattems and an increase in irrigation water. Based
on die proposed development scheme, it is our opinion that tiie likelihood of future seepage
phenomena should be considered to be low. It is further our opinion tiiat these problems can be
most effectively corrected on an individual basis is and when they develop.
CONCLUSIONS
GENERAL: In general, no geotechnical conditions were encountered which would preclude the
development of the site as presently proposed provided the recommendations presented herein are
followed. The geotechnical conditions encountered that will most affect the development of tiie site
are the presence of highly expansive soils that will require special design for foundations and on-
grade concrete slabs, and that will require relatively thick stmctural pavement sections. The fill
material was found to be well compacted. However, the upper foot of fill material was found to have
loosened over die years as a result of wetting and drying and the expansion characteristics of the soil.
This material will be required to be removed and replaced as uniformly compacted fill. A cut/fill
transition line is expected to mn through the pads for Buildings "H" and "J". It will be necessary to
undercut the cut portion of these building pads in order to provide a uniform soil conditions to
support the building foundations. No other soil or geologic conditions were found that would
significantiy affect the development of the property as proposed.
RECOMMENDATIONS
GRADING
OBSERVATION OF GRADING: Continuous observation by Christian Wheeler Engineering is
essential during the grading operation to constmct the building pads and paved areas in order to
confirm die conditions anticipated by our investigation, to allow adjustments in design criteria to reflect
the actual field conditions exposed, and to determine that the grading proceeds in general accordance
with the recommendations contained herein.
C.W.E. 199.471.1 September 22,1999 Page 8
SITE PREPARATION: Site preparation should begin with the removal of any existing vegetation
and deleterious matter from the areas of the site to be graded and/or that will support new
improvements. It is recommended that the upgertwelve inches (12) inches of the existing fill
materijils where not removed by the planned grading, be removed and be replaced as uniformly
compacted fill. The minimum horizontal removal limits of this operation should include all areas
that will support settiement-sensitive improvements, including exterior walkways. In adciition, the
cut portion of the building pad for Buildings "H" and ' J" should be overexcavated by at least four
feet The excavated soils or other fill material obtained on site should be replaced in the
overexcavation area as uniformly compacted fill. The minimum horizontal limits of the
overexcavation should extend at least five feet outside the building foundation system.
The soils exposed at the bottom of all excavations should be scarified to a depth of 12 inches,
moisture-conditioned and be recompacted to at least 90 percent as determined in accordance with
ASTM D-1557-91 prior to replacing the excavated fill. All fill should be placed in lifts six to eight
inches is thickness with each lift mechanically compacted to at least 90 percent of maximum dry
density.
SURFACE DRAINAGE: It is recommended that all surface (drainage be (directed away from the
stmcmre and the top of slopes. Ponding of water should not be allowed adjacent to foundations.
EARTHWORK- All earthwork and grading contemplated for site preparation should be
accomplished in accordance with the attached Recommended Grading Specifications and Special
Provisions. All special site preparation recommendations presented in the sections above will
supersede those in the standard Recommended Gra{iing Specifications. All embankments, stmctural
fill and fUl should be compacted to at least 90 percent relative compaction at or slighdy over
optimum moismre content. Utility trencii backfill within five feet of the proposed stmctures and
beneadi all pavements 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 90
percent of it maximum dry 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. The maximum dry density of each soil type should be determined in accordance with
ASTM Test D-1557-91.
C.W.E. 199.471.1 September 22, 1999 Page 9
FOUNDATIONS
GENERAL: Shallow foundations may be utilized for the support of the proposed stmcmres. The
concrete tilt-up panels should be supported on continuous grade-beam style footings. All footings
should be embedded a minimum depth of 24 inches below lowest adjacent finish pad grade. A
minimum width of 18 inches and 24 inches is recommended for continuous and isolated footings,
respectively. A bearing capacity of 2,500 psf may be assumed for said footings. This bearing
capacity may be increased by one-third when considering wind and/or seismic forces.
REINFORCEMENT: Footing reinforcement should be specified by the project stmcmral
engineer. However, as a minimum we recommend that both exterior and interior continuous
footings be reinforced with at least two No. 5 bars positioned near the bottom of the footing and
two No. 5 bars positioned near the top of the footing. This reinforcement is based on soil
characteristics and is not intended to be in lieu of reinforcement necessary to satisfy stmctural
considerations.
SETTLEMENT CHARACTERISTICS: The anticipated total and/or differential settiements for
the proposed structure will be less than one inch, 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 curing or retiis tribution of stresses and some cracks may be
anticipated. Such cracks are not necessarily an indication of excessive vertical movements.
EXPANSIVE CHARACTERISTICS: The anticipated foundation soils were found to vary from
moderately expansive to highly expansive. The recommendations presented in this report reflect a
highly expansive soil concdition.
FOUNDATION PLAN REVIEW: It is recommended that tiie foundation plans be submitted to
this office for review in order to verify that the recommendations presented in this report are
incorporated in the stmctural plans.
FOUNDATION EXCAVATION OBSERVATION: We recommend that all footing excavations
be observed by the geotechnical engineer to verify that the footing excavations comply with our
minimum recommendations and the stmctural plans, and that the soil conditions are as anticipated in
the preparation of this report.
C.W.E. 199.471.1 September 22,1999 Page 10
ON-GRADE SLABS
INTERIOR ON-GRADE FLOOR SLABS: The diickness, reinforcing and compressive strengtii
of the interior slabs should be specified by the stmctural engineer. However, as a minimum, we
recommend that the interior concrete on-grade floor slabs have a minimum acmal thickness of six
inches. The interior concrete slabs should be reinforced with at least No. 4 reinforcing bars placed at
least at 12 inches on-center each way. The floor slab reinforcing should be supported on chairs such
that they will be positioned mid-height in the slab.
Interior floor slabs should be underlain by a four-inch blanket of clean, poorly graded, coarse sand.
The sand should have less than ten percent passing the #100 sieve and five percent passing the #200
sieve. Where moisture-sensitive floor coverings are planned, a visqueen barrier should be placed in
the center of the sand layer.
EXTERIOR SLABS ON-GRADE: Exterior slabs (excluding driveways) should have a minimum
thickness of five inches. Walks or slabs five feet in width should be reinforced with at least No. 3
bars at 18 inches on center each way and provided with weakened plane joints. Any slabs beKveen
five and ten feet should be provided with longitudinal weakened plane joints at the centerlines. Slabs
exceeding ten feet in widtii should be provided with a weakened plane joint in accordance with
American Concrete Institute Standards.
PRELIMINARY PAVEMENT RECOMMENDATIONS
The recommended preliminary pavement section presented below is based on an estimated subgrade
soil R-Value of 5, which in our opinion is the approximate R-value of the subgrade soil. In addition,
since the use of the property will be as an office park with no tmck traffic, a traffic index of 5.0 was
assumed for the design of the stmctural pavement section. The stmcmral section should be verified
after "R" value tests of the acmal subgrade soils are performed. All paving methods and materials
should conform with good engineering practices and with the requirements of the City of Carlsbad.
4.0 inches of asphalt concrete pavement, on
8.0 inches of cmshed aggregate base
C.W.E. 199.471.1 September 22,1999 Page 11
The aggregate base material should conform with the Standard Specifications for Public Works
Constmction (Green Book), Section 200-2.2.2, and should be compacted to at least 95 percent
relative compaction. The asphalt concrete should conform to Section 203-6.2.1 for the asphalt and
Section 203-6.2.2 for the aggregate. The subgrade soils should be compacted to at least 90 percent
relative compaction just prior to placing base material. Therefore, this compaction should be
accomplished by the paving contractor.
Portiand Cement Concrete (PCC) pavement should have a minimum thickness of J;5 inches and
should be underlain by at least 4.0 inches of cmshed aggregate base material compacted to at least 95
percent relative compaction. The subgrade should be processed as recommended above for asphalt
concrete sections. PCC should conform with Section 201 of the Green Book.
The compaction of the subgrade and base material and the asphalt concrete lay down should be
observed and tested by the geotechnical consultant. All paving and constmction methods should
comply with good engineering practices, the Green Book and with the requirements of the City of
Carlsbad.
LIMITATIONS
The recommendations and opinions expressed in this report reflect our best estimate of the project
requirements based on an evaluation of the subsurface soU concditions encountered at the subsurface
exploration locations and the assumption tiiat the soU conditions do not deviate appreciably from
those encountered. It should be recognized that the performance ofthe foundations may be
influenced by undisclosed or unforeseen variations in the soU 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 soUs engineer so that
he may make modifications if necessary. In adtdition, this office should be advised of any changes in
the project scope or proposed site gra<ding so that it may be determined if the recommendations
contained herein are appropriate. This should be verified in writing or mo(iified by a written
addendum.
C.W.E. 199.471.1 September 22,1999 Page 12
FIELD EXPLORATIONS
-Five subsurface explorations were made at the locations indicated on the attached Plate Number 1
on August 31 and September 7,1999. These explorations consisted of borings made with a nine-
inch-diameter continuous flight auger. The fieldwork was conducted under the observation of our
engineering geology personnel.
The explorations were carefiiUy logged when made. These logs are presented on the foUowing Plates
Number 2 through 7. The soUs are described in accordance widi the unified SoUs Classification. In
adcdition, a verbal textural description, the wet color, the apparent moisture and the density or
consistency are provided. The density of granular soUs is given as either very loose, loose, medium
dense, dense or very dense. The consistency of sUts or clays is given as either very soft, soft, medium
stiff, stiff, very stiff, or hard.
Disturbed and "undismrbed" samples of typical and representative soUs were obtained and returned
to the laboratory for testing. Representative undisturbed core samples were obtained by means of a
split tube sampler (driven into the soUs by means of a 140-pound weight free-faUing a distance of 30
inches from the auger rig. The number of blows required to drive the sampler one foot is indicated
on the boring logs as "sample penetration resistance".
LABORATORY TESTING
Laboratory tests were performed in accordance with the generaUy accepted American Society for
Testing and Materials (ASTM) test methods or suggested procedures. A brief description of die tests
performed is presented below:
a) CLASSIFICATION: Field classifications were verified in the laboratory by visual
examination. The final soU classifications are in accordance with the Unified SoU
Classification System.
b) MOISTURE-DENSITY: In-place moisture contents and dry densities were
determined for representative soU samples. This information was an aid to
classification and permitted recognition of variations in material consistency with
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C.W.E. 199.471.1 September 22, 1999 Page 13
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 soU's dry weight. The results
are summarized in the boring logs.
c) GRAIN SIZE DISTRIBUTION: The grain size distribution was determined for
representative samples of native soUs in accordance with ASTM D422. The results
of these tests are presented on Plate Number 8.
d) EXPANSION INDEX TEST: Expansion index tests on remolded samples were
performed on representative samples of soUs Ukely to be present at finish grade.
The tests were performed on the portion of the samples passing the #4 standard
sieve. The samples were brought to optimum moisture content and then dried back
to a constant moisture content for 12 hours at 230 +/- 9 degrees Fahrenheit The
specimen were then compacted in a 4-inch-diameter mold in Kvo equal layers by
means of a tamper, then trimmed to a final height of 1 inch, and brought to a
samration of approximately 50 percent. The specimen were placed in a
consoUdometer with porous stones at the top and bottom, a total normal load of
12.63 pounds was placed (144.7 psQ, and the sample was aUowed to consoUdate for
a period of 10 minutes. The samples were aUowed to become saturated, and the
change in vertical movement was recorded untU the rate of expansion became
nominal. The expansion indexes are reported on the attached Plate Number 8 as
the total vertical displacement time the fraction of the samples passing the #4 sieve
times 1000.
CLASSIFICATION OF EXPANSIVE SOIL
EXPANSION INDEX POTENTIAL EXPANSION
1-20 very low
21-50 low
51-90 medium
91-130 high
Above 131 very high
e) DIRECT SHEAR TESTS: Direct shear tests were performed to determine the
faUure 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
C.W.E. 199.471.1 September 22,1999 Page 14
height of 1.0 inch. Samples were tested at different vertical loads and a saturated
moisture content The shear stress was appUed at a constant rate of strain of
approximately 0.05 inch per minute. The results of these tests are presented on the
attached Plate Number 8.
f) PLASTIC INDEX TEST: PLASTIC INDEX: The Liquid Limit, Plastic Limit and
Plastic Index was determined for representative soU samples in order to help classify
the soUs in accordance with the Unified SoU Classification System. These tests were
performed in accordance with ASTM D424. The results of these tests are presented
on the attached Plate Number 8.
LOT 4
LOT 5
SOURCE: SMITH CONSULTING ARCHITECTS
9M
\ CHRISTIAN WHEELER
ENGINEERING
LOT 12 @ CARLSBAD RESEARCH CENTER
'Y- CHC/SD DATE 09-27-99
OB NO: 199.471 PLATE NO 1
LOG OF TEST BORING NUMBER B-l
Date Excavated:
Eqmpment
Surface Elevation:
Hammer Weight
8/31/99
IRA300
N/A
140 pounds
Logged by:
Project Manager
Depth to Water (ft):
Drop of Hammer:
DRR
CHC
N/A
30 inches
Q
o o
u
SUMMARY OF SUBSURFACE CONDITIONS
SAMPLES
t-t
<* o
2 %
D
o
u
D
Q
OH
- ; f
- 4
- (
1 I
- 12
- 14
- 16
18
^20
FTT.T.(f)af>- Olive to brown, moist, very stiff, SANDY SILTY
CLAY (CH). EI = 78. US 76 20.8
US 71 2Z5
CLAYEY SAND layer, moist, dense. US 53 13.2
100.9
86.4
117.(5
SA
EI
PI
DS
SANTIAGO FORMATION (Tsa): Gray, moist, hard, CLAYEY
SILT and SILTSTONE (ML), abundant iron staining.
US 50/6" 20.1 101.5
Bottom of boring at 14V'2 feet
m LOT 12 m AT CARLSBAD RESEARCH CENTER
CHRJSTIAN WHEELER BY: DRR DATE: Au.^-99
ENGINEER.ING JOB NO.: 199.471 PLATE NO.: 2
I
I
I
I
LOG OF TEST BORING NUMBER B-2
Date Excavated:
Equipment
Surface Elevation:
Hammer Weight
8/31/1999 and 09/07/99
IR A300
N/A
140 pounds
Logged by:
Project Manager
Depth to Water (ft):
Drop of Hammer
DRR
CHC
N/A
30 inches
- 4
- 6
- 12
- 14
- 16
18
1-20 • Fiminj
SAMPLES
SUMMARY OF SUBSURFACE CONDITIONS
FTT .T. (C}af\: OUve to orangish-brown, moist, very stiff,
SANDY SILTY CLAY (CH). EI - 104.
Becomes mecUum brown.
CLAYEY SAND laver, moist, dense.
SANTIAGO FORMATION (TsaV Medium brown, moist, very
dense, fine to coarse grained CLAYEY SAND (SQ, occasional
gravels.
Light brown to orangish-brown, moist, very dense, fine to coarse
grained CLAYEY SILTY SAND (SM).
O
z & W .0
US
us
us
us
us
us
77
50/6'
50/6"
50/6'
50/4'
50/6'
P
O 2
19.i
14.8
123
6.5
6.5
2 D
Q
Pi
P,
OH CQ
98.2
94.9
118.5
119.6
109.7
Continues on Plate Number 4
LOT 12
AT CARLSBAD RESEARCH CENTER
CHKlSJim WHEELER-BY: DRR DATE: AuK-99
ENGINEER.ING JOB NO.: 199.471 PLATE NO.: 3
LOG OF TEST BORING NUMBER B-2 (Continued)
Date Excavated: 8/31/1999 and 09/07/99 Logged by: DRR
Equipment IRA300 Project Manager CHC
Surface Elevation: N/A Depth to Water (ft): N/A
Hammer Weight 140 pounds Drop of Hammer 30 inches
O O
u
X eu SUMMARY OF SUBSURFACE CONDITIONS
SAMPLES
O
o
3i
HH Z
P
Pi
Q
Pi
Of-
- 22
-24
- 26
28
30
32
-34
- 36
38
1-40
Orangish-brown, moist, dense to very dense, fine to coarse
grained CLAYEY SAND (SQ with occasional gravels.
US 81
Bottom of boring at 24Vz feet
m se LOT 12
AT CARLSBAD RESEARCH CENTER
CHRdSU/yV WHEELER BY: DRR DATE: AuK-99
ENGINEER.ING JOB NO.: 199.471 PLATE NO.: 4
LOG OF TEST BORING NUMBER B-3
Date Excavated:
Equipment
Surface Elevation:
Hammer Weight
9/7/99
IR A300
N/A
140 pounds
Logged by:
Project Manager
Depth to Water (ft):
Drop of Hammer
DRR
CHC
N/A
30 inches
cu W
Q
O O
u
X cu SUMIvL?yiY OF SUBSURFACE CONDITIONS
SAMPLES
p
O
u
HH z p
oi Q
OH
- 2
- 12
- 14
- 16
- 18
FTT.T. (Qgft: OUve to orangish-brown, moist, very stiff to hard,
SANDY SILTY CLAY (CL). US 61
US 42 1Z7
CLA^'EY SAND layer, moist, dense. US 50/6" 15.3
98.0
114.4
SANTIAGO FORMATION (TsaV Gray, moist, hard, SANDY
SILTY and SILTSTONE (ML), abundant iron
staining.
Bottom of boring at 14'/2 feet.
US 50/5' 17.7 104.1
CHR-ISTIAN WHEELER.
ENGINEER-ING
LOT 12
AT CARLSBAD RESEARCH CENTER
BY: DRR
JOB NO.: 199.471
DATE: Aug-99
PLATE NO.:
LOG OF TEST BORING NUMBER B-4
Date Excavated:
Equipment
Surface Elevation:
Hammer Weight
9/7/99
IRA300
N/A
140 pounds
Logged by:
Project Manager
Depth to Water (ft):
Drop of Hammer
DRR
CHC
N/A
30 incUes
SAMPLES
SUMMARY OF SUBSURFACE CONDITIONS
ru ^
P H
HH z
p
Pi
Q
Kl
CO
[2
- 2
- 4
- 8
- 10
- 12
FTT.T. (Qaf>: OUve to orangish-brown, moist, very stiff, SANDY
CLAY (CH), sUght gravels. EI = 91. US
US
US
42 21.2 97.4
SA
EI
PI
DS
20.6 98.7
46
1^
SANTIAGO FORMATION (Tsa^: Light brown to orangish-
brown, moist, dense, fine to coarse grained CLAYEY SAND (SQ.
US 40/8" 115.5
US 50/4' 9.0 107.2
16
- 18
Bottom of boring at 15 feet
LOT 12
AT CARLSBAD RESEARCH CENTER
CHRISTIAN WHEELER-BY: DRR DATE: Aug-99
ENGINEER-ING JOB NO.: 199.471 PLATE NO.: 6
LOG OF TEST BORING NUMBER B-5
Date Excavated:
Equipment
Surface Elevation:
Hammer Wei^t
9/7/99
IRA300
N/A
140 pounds
Logged by:
Project Manager:
Depth to Water (ft):
Drop of Hammer:
DRR
CHC
N/A
30 inches
SUMMARY OF SUBSURFACE CONDITIONS
SAMPLES
_ >
O IS
[I] z % W o cu ^
P fe
HH
O
u
H
HH z p
ct!,
Q
Pi
- 6
- 8
FILL (Oaf): OUve brown, damp to moist, very stiff to mecUum
dense, SANDY CLAY/CLAYEY SAND (CH/SQ with gravels.
us 31 9.9
OUve to orangish-brown, moist, hard, SANDY SILTY CLAY
(CH), slight gravels.
US 67 25.0
104.8
94.9
12
- 14
- 16
18
WEATHERED SANTIAGO FORMATION CXsnV Medium
brown, moist, hard, SANDY CLAY (CH), sUght roodets, trace
caUche.
US 50/5" 125 113.2
SANTLA.GO FORMATION (Tsa): YeUowish-brown, moist,
very dense, fine to coarse grained CLAYEY SILTY SAND (SM).
US 50/3' 9.9 108.8
Bottom of boring at 15 feet
m CHRJSTIAN WHEELER
ENGINEER-ING
LOT 12
AT CARLSBAD RESEARCH CENTER
BY: DRR
JOB NO. : 199.471
DATE: Aug-99
PLATE NO.:
LABORATORY TEST RESULTS
LOT 12, CARLSBAD RESEARCH CENTER
GRAIN SIZE DISTRIBUTION
B-l@V2'-4' B-2 @ V2' - 5' B-4 @ 0' - 5'
U.S. SIEVE SIZE PERCENT PASSING PERCENT PASSING PERCENT PASSING
#4 100 100 100
#8 99 99 99
#16 98 98 97
#30 97 98 95
#50 95 97 93
#100 93 94 88
#200 88 90 83
0.05 mm 68 67 68
0.005 mm 46 44 45
0.001 mm 32 32 30
EXPANSION INDEX TESTS
Sample Number
Initial Moisture Content
Initial Diy Density
Final Moisture Content
Expansion Index
Boring B-l @ V2'-4'
147 %
96.4 Ib/ftJ
30.2 %
78
Boring B-2 @ Vi'-S'
14.7 %
98.2 lb/ft3
31.8%
104
Boring B-4 @ 0-5'
11.6%
99.9 lb/ft'
28.2 %
91
DIRECT SHEAR TEST
Sample Number
Condition
Angle of Friction
Apparent Cohesion
Boring B-l @ 2Vi'
UncUsturbed
43.7°
325 lb/ft5
Boring B-2 @2'/2'
Undisturbed
42.5°
300 lb/ft5
Boring B-4 @ 2y2'
UncUsturbed
43.7°
740 lb/ft3
PLASTICITY INDEX
Sample Number
Liquid Limit
Plastic Limit
Plasticity Index
Boring B-l @ V'2'-4'
58
22
36
BoringB-2@y2'-5'
66
28
38
Boring B-4 @ 0-5'
56
24
32
CWE 199.471 September 28,1999 Plate No. 8
CWE 199.471 September 22,1999 Appendix A, Page Al
RECOMMENDED GRADING SPECIFICATIONS - GENERAL PROVISIONS
PROPOSED OFFICE PARK
LOT 12 CARLSBAD RESEARCH CENTER
PRIESTLY DRIVE AND LA PLACE COURT
CARLSBAD. CALIFORNIA
GENERAL INTENT
The intent of these specifications is to estabUsh procedures for clearing, compacting natural ground,
preparing areas to be fiUed, and placing and compacting fiU soUs 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 GracUng Specifications and
shaU supersede the provisions contained hereinafter in the case of confUct These specifications shaU
only be used in conjunction with the geotechnical report for which they are a part. No deviation
from these specifications wiU be aUowed, except where specified in the geotechnical report or in
other written communication signed by die Geotechrtical Engineer.
OBSERVATION AND TESTING
Christian Wheeler Engineering shaU be retained as the Geotechiucal Engineer to observe and test the
earthwork in accordance with these specifications. It wiU 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 accompUshed as specified. It shaU 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
concUtions not covered by the special provisions or preliminary geotechnical report are encountered
during the grading operations, the Geotechrtical Engineer shaU be contacted for further
recommendations.
If, in the opiruon of the Geotechnical Engineer, substandard concUtions are encountered, such as
questionable or unsuitable sod, unacceptable moisture content, inadequate compaction, adverse
weather, etc., constmction should be stopped until the conditions are remedied or corrected or he
shaU recommend rejection of this work.
CWE 199.471 September 22,1999 Appendix A, Page A2
Tests used to determine the degree of compaction should be performed in accordance with the
foUowing American Society for Testing and Materials test methods:
Maximum Density & Optimum Moisture Content - ASTM D-1557-91
Density of SoU In-Place - ASTM D-1556-90 or ASTM D-2922
AU densities shaU be expressed in terms of Relative Compaction as determined by the foregoing
ASTM testing procedures.
PREPARATION OF AREAS TO RECEIVE FILL
AU vegetation, bmsh and debris derived from clearing operations shaU be removed, and legaUy
(disposed of. AU areas cUsturbed by site gracUng should be left in a neat and finished appearance, free
from unsightiy debris.
After clearing or benching the namral ground, the areas to be fiUed shaU be scarified to a depth of 12
inches, brought to the proper moismre content, compacted and tested for the specified niinimum
degree of compaction. AU loose soUs in excess of 6 inches thick should be removed to firm namral
ground which is defined as namral soU which possesses an in-sim density of at least 90 percent of its
maximum (dry density.
When the slope of the namral ground receiving fiU exceeds 20 percent (5 horizontal units to 1
vertical urdt), the original ground shaU be stepped or benched. Benches shaU be cut to a firm
competent formational soU. The lower bench shaU be at least 10 feet wide or IV2 times the
equipment width, whichever is greater, and shaU be sloped back into the hiUside at a gracUent of not
less than two (2) percent AU other benches should be at least 6 feet wide. The horizontal portion of
each bench shaU be compacted prior to receiving fiU as specified herein for compacted natural
ground. Ground slopes flatter than 20 percent shaU be benched when considered necessary by the
Geotechnical Engineer.
Any abandoned buried stmctures encountered during grading operations must be totaUy removed.
AU underground utiUties to be abandoned beneath any proposed stmcture should be removed from
within 10 feet of the stmcture and properly capped off. The resulting depressions from the above
described procedure should be backfilled with acceptable soU that is compacted to the requirements
CWE 199.471 September 22,1999 Appendix A, Page A3
of the Geotechnical Engineer. This includes, but is not Umited to, septic tanks, fiiel tanks, sewer
Unes or leach Unes, storm draUis and water Unes. Any buried stmcmres 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 wiU be necessary.
FILL MATERIAL
Materials to be placed in the fiU shaU be approved by die Geotechnical Engineer and shaU be free of
organic matter and other deleterious substances. Granular soU shaU contain sufficient fine material
to fiU the voids. The definition and disposition of oversized rocks and expansive or detrimental sods
are covered m the geotechnical report or Special Provisions. Expansive sods, sods of poor gradation,
or soUs with low strength characteristics may be thoroughly mixed with other soUs to provide
satisfactory fUl material, but only with the expUcit consent of the Geotechnical Engineer. Any import
material shaU be approved by the Geotechnical Engineer before being brought to the site.
PLACING AND COMPACTION OF FILL
Approved fUl material shaU be placed in areas prepared to receive fUl in layers not to exceed 6 inches
in compacted thickness. Each layer shaU have a uniform moisture content in the range that wiU aUow
the compaction effort to be efficiendy appUed to achieve the specified degree of compaction. Each
layer shaU be uniformly compacted to the specified minimum degree of compaction with equipment
of adequate size to economicaUy compact the layer. Compaction equipment should either be
specificaUy designed for soU compaction or of proven reUabUity. 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 stmctural fiU material includes rock, no rocks wiU be aUowed to nest and aU voicds must be
carefuUy fUled with soU such that the minimum degree of compaction recommended in the Special
Provisions is achieved. The maximum size and spacing of rock permitted in strucmral fiUs and in
non-stmctural fills is discussed in the geotechnical report, when appUcable.
Field observation and compaction tests to estimate the degree of compaction of the fiU wUl be taken
by die Geotechnical Engineer or his representative. The location and frequency of the tests shaU be
at the Geotechnical Engineer's (discretion. When the compaction test incUcates that a particular layer
CWE 199.471 September 22,1999 Appendix A, Page A4
is at less than the required degree of compaction, die layer shaU be reworked to the satisfaction of die
Geotechnical engineer and until the desired relative compaction has been obtained.
FUl slopes shaU be compacted by means of sheepsfoot roUers or other suitable equipment.
Compaction by sheepsfoot roUer shaU be at vertical intervals of not greater than four feet In
adcdition, fiU slopes at a ratio of two horizontal to one vertical or flatter, should be trackroUed.
Steeper fiU slopes shaU be over-buUt and cut-back to fiitish contours after the slope has been
constmcted. Slope compaction operations shaU result in aU fUl material six or more inches inward
from the fiiushed 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 shaU be continued untU the Geotechnical
engineer is of the opinion that the slopes wiU be surficiaUy stable.
Density tests in the slopes will be made by the Geotechnical Engineer during constmction of the
slopes to determine ifthe required compaction is being achieved. Where faiUng tests occur or other
field problems arise, the Contractor wiU be notified that day of such concUtions by written
communication from the Geotechnical Engineer or his representative in the form of a daUy field
report.
If the method of achieving the required slope compaction selected by the Contractor faUs to produce
the necessary results, the Contractor shaU rework or rebuUd such slopes until the required degree of
compaction is obtained, at no cost to the Owner or Geotechnical Engineer.
CUT SLOPES
The Engineering Geologist shaU inspect cut slopes excavated in rock or hthified formational material
during the gracUng operations at intervals determined at his discretion. If any conditions not
anticipated in the preUmUiary report such as perched water, seepage, lenticular or confined strata of a
potentiaUy adverse namre, unfavorably incUned bedding, joints or fault planes are encountered during
gracUng, these conditions shaU be analyzed by the Engineering Geologist and Geotechnical Engineer
to determine if mitigation measures are necessary.
Unless odierwise specified in the geotechrtical report, no cut slopes shaU be excavated higher or
steeper than that aUowed by the ordinances of the controUing govemmental agency.
CWE 199.471 September 22,1999 Appendix A, Page A5
ENGINEERING OBSERVATION
Field observation by the Geotechnical Engineer or his representative shaU be made during the filUng
and compaction operations so that he can express his opinion regarcding the conformance of the
grading with acceptable stanidards of practice. Neither the presence of the Geotechnical Engineer or
his representative or the observation and testing shaU release the Grading Contractor from his duty
to compact aU fiU material to the specified degree of compaction.
SEASON UMITS
FiU shaU not be placed during unfavorable weather concUtions. When work is intermpted by heavy
rain, filUng operations shaU not be resumed until the proper moisture content and density of the fUl
materials can be achieved. Damaged site concUtions resulting from weather or acts of God shaU be
repaired before acceptance of work.
RECOMMENDED GRADING SPECIFICATIONS - SPECIAL PROVISIONS
RELATIVE COMPACTION: The minimum degree of compaction to be obtained in compacted
namral ground, compacted fiU, and compacted backfiU shaU 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: DetrimentaUy expansive soU is defmed as clayey soU which has an expansion
index of 50 or greater when tested in accordance with the Uiuform BuUding Code Standard 29-C.
OVERSIZED MATERIAL: Oversized fUl material is generaUy defined herein as rocks or lumps of
soU over 6 inches in cUameter. Oversized materials should not be placed in fiU unless
recommendations of placement of such material are provided by the Geotechnical Engineer. At least
40 percent of the fiU soUs shaU pass through a No. 4 U.S. Standard Sieve.
TRANSITION LOTS: Where transitions between cut and fiU occur within the proposed buUding
pad, the cut portion should be undercut a minimum of 18 inches below the base of the proposed
footings and recompacted as stmctural backfiU. In certain cases that would be ad(dressed in the
CWE 199.471 September 22,1999 Appendix A, Page A6
geotechrtical report, special footing reinforcement or a combUiation of special footing reinforcement
and undercutting may be required.
CWE 199.471.1 September 22,1999 Appendix B, Page Bl
REFERENCES
Anderson, J.G.; RockweU, R.K. and Agnew, D.C, 1989, 'Tast and Possible Fumre Earthquakes of
Significance to the San Diego Region," Earthquake Spectra. Volume 5, No. 2,1989.
Geologic Maps of the Nordiwestem Part of San Diego County, Geologic Maps of the Oceanside,
San Luis Rey, and San Marcos 7.5' Quacirangles, 1996, CaUfomia Division of Mines and
Geology, Open-FUe Report No. 96-02, scale 1:24,000.
Geotechnical Investigation CaUaway Golf Distribution BuUding Carlsbad Research Center - Lot 12
Carlsbad, CaUfomia, 1994, prepared by Woodward-Clyde Consultants, Project No.
9451092K-SI01, dated August 8, 1994.
Jennings, C.W., 1992, 'TreUminary Fault Activity Map of CaUfomia," CaUfornia Division of
Mines and Geology, Open-FUe No. 92-3.
Mualchin, L., Jones, A.L., 1992, Peak Accelerations firom Maximum Credible Earthquakes in
CaUfornia (Rock and Stiff-SoU Sites), CaUfomia Department of Conservation, DMG Open-
FUe Report 92.1
San Diego County General Plan, Seismic Safety Element, Part V Adopted January 9,
1975, Amended AprU 24,1991.
Tan, Siang S., and Giffen, Desmond G., 1995, LandsUde Hazards in the Nordiwestem Part ofthe
San Diego MetropoUtan Area, San Diego County, CaUfornia, Oceanside and San Luis Rey
Qua<drangles, CaUfornia Division of Mines and (Geology, Open-FUe Report No. 95-04, scale
1:24,000.
Update Geotechnical Investigation Carlsbad Research Center Lot 12 Carlsbad, CaUfomia, 1999,
prepared by URS Greiner Woodward Clyde, Project No. 58-9911063J.00-UD001, dated
August 2,1999.
Weber, F.H. Jr., 1963, Geology and Mineral Resources of San Diego County, CaUfomia,
CaUfomia Division of Nlines and Geology, County Report 3.