HomeMy WebLinkAboutCT 03-14; BRITTANY COVE; UPDATED PRELIM GEOTECH EVAL; 2004-01-07�
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UPDATED PRELIMINARY GEOTECHNICAL EVALUATION
BRITTANY COVE CONDOMINIUM PROJECT
2642 THROUGH 2646 JEFFERSON STREET
� � � � � � �� CA�R�SBAD; SAN �LI�„IEGO� COUNTY, CALIFORiV1A � � � � � �� � � �
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KARWIN COMPANY
C/O KARNAK PLANNING & DESIGN
2802 STATE STREET
CARLSBAD, CALIFORNIA 92008
W.O. 3256-A-SC JANUARY 7, 2004
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5741 Palmer Way • Carlsbad, California 92008 •(760) 438-3155 • FAX (760) 931-0915
January 7, 2004
W.O. 3256-A-SC
Karwin Company
c/o Karnak Planning & Design
2802 State Street
Carlsbad, California 92008
Attention: Mr. Anthony De Leonardis
Subject: Updated Preliminary Geotechnical Evaluation, Brittany Cove Condominium
Project, 2642 through 2646 Jefferson Street, Carlsbad, San Diego County,
California, CT 03-14/CP 03-09/SDP 03-19/CDP 03-48
Dear Mr. De Leonardis:
In accordance with a request frorn the City of Carlsbad, Planning Department,
GeoSoils, Inc. (GSI) is providing a updated preliminary geotechnical evaluation of the
subject site. The purpose of the study was to evaluate the onsite soils and geologic
conditions and their effects on the currenity proposed site development consisting of three,
two-story multi-residential structures, from a geotechnical viewpoint. The scope of work
has included a review of the site plan for the revised project, prepared and provided (via
facsimile) by Karnak Planning & Design, updated of the general seismicity evaluation, and
revise the preliminary foundation recommendations.
EXECUTIVE SUMMARY
Based on our review of the available data (Appendix A), field exploration, laboratory
testing, and geologic and engineering analysis, residential development of the property
appears to be feasible from a geotechnical viewpoint, provided the recommendations
presented in the te� of this report are properly incorporated into the design and
construction of the project. The most significant elements of this study are summarized
below:
Based on our review of the site plan provided by Karnak Planning & Design, it
appears that the currently proposed development would consist of three, two-story
structures, with three units each, with typical light multi-story loads, utilizing
conventional foundations with continuous footings and slabs on grade, including
underground utility improvements, and roadway access.
All existing colluvium and near surface weathered terrace deposits are generally
loose and potentially compressibie, and are not suitable for the support of
settlement-sensitive improvements. These materials will require removal and
recompaction, if settlement-sensitive improvements are proposed within their
influence. Depth of removals are outlined in the conclusions and recommendations
section of this report. In general, removals will be on the order of ±2 to ±3'/2 feet
across a majority of the site.
The expansion potential oftested onsite soils is very low. Conventional foundations
may likely be utilized for these soil conditions.
Sulfate testing indicates that site soils have a negligible exposure to concrete per
Table 19-A-4 of the 1997 UBC (sample=0.000 percent by weight). Corrosion
testing (ph, resistivity) indicates that the soils are essentially medium acidic
(pH=6.0) and moderately corrosive to ferrous metals (saturated
resistivity=7,500 ohms-cm). Alternative methods and additional comments should
be obtained by a qualified corrosion engineer.
Groundwater was not encountered onsite during our subsurface investigation and
is generally not anticipated to affect site development, providing that the
recommendations contained in this report are incorporated into final design and
construction and that prudent surface and subsurface drainage practices are
incorporated into the construction plans. Perched groundwater conditions along
zones of contrasting permeabilities should not be precluded from occurring in the
future due to site irrigation, poor drainage conditions, or damaged utilities, and
should be anticipated. Should perched groundwater conditions develop, this office
could assess the affected area(s) and provide the appropriate recommendations to
mitigate the observed groundwater conditions.
• Our evaluation indicates that the site has a very low potential for liquefaction.
Therefore, no recommendations for mitigation are deemed necessary.
• Our evaluation indicates there are no known active faults crossing the site.
• The seismic acceleration values and design parameters provided herein should be
considered during the design of the proposed development.
• Adverse geologic feafiures that would preclude project feasibility were not
encountered.
• The recommendations presented in this report should be incorporated into the
design and construction considerations of the project.
Karwin Company W.O. 3256-A-SC
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The opportunity to be of service is greatiy appreciated. If you have any questions
concerning this report or if we may be of further assistance, please do not hesitate to
contact any of the undersigned..�� -,—�
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Respectfully submitted, � = -
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Donna Gooley
Registered Geologist, RG 7571
Reviewed by:
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Civil Engineer, RCE 47857
Karwin Company W.O. 3256-A-SC
File:e:\wp9\3200\3256a.rpge Page Three
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TABLE OF CONTENTS
SCOPE OF SERVICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
SITE CONDITIONS/PROPOSED DEVELOPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
SITE EXPLORATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
REGIONAL GEOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
SITE GEOLOGIC UNITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Colluvium (Unmapped) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Quaternary-Age Terrace Deposits (Map Symbol - Qt) . . . . . . . . . . . . . . . . . . . . . 5
GROUNDWATER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
FAULTING AND REGIONAL SEISMICITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Faulting..........................................................5
Seismicity........................................................7
Seismic Shaking Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Seismic Hazards ....................................................9
LIQUEFACTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
OTHER GEOLOGIC HAZARDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
LABORATORY TESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
General.........................................................10
Laboratory Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Expansion Potential ...............................................11
ShearTesting.............................................:......11
Corrosion/Sulfate Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
CONCLUSIONS ........................................................12
EARTHWORK CONSTRUCTION RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . 12
General.........................................................12
Site Preparation ..................................................12
Removals (Unsuitable Surficial Materials) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
FiIlPlacement ....................................................13
Transitions/Overexcavation ............................ ........... 13
RECOMMENDATIONS - FOUNDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Preliminary Foundation Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Design......... ................................................14
Foundation Settlement .............................................14
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Footing Setbacks .................................................14
Construction .....................................................15
Very Low Expansion Potentiai (E.I. 0 to 20) . . . . . . . . . . . . . . . . . . . . . . . 15
UTILITIES...:.........................................................16
WALL DESIGN PARAMETERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Conventional Retaining Walis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Restrained Walls ............................................16
Cantilevered Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Retaining Wall Backfill and Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Wall/Retaining Wall Footing Transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
DRIVEWAY, FLATWORK, AND OTHER IMPROVEMENTS . . . . . . . . . . . . . . . . . . . . . . . 21
DEVELOPMENT CRITERIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Drainage........................................................23
Erosion Control ...................................................24
Landscape Maintenance ...........................................24
Gutters and Downspouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Subsurface and Surface Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Site Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Tile Flooring .....................................................25
AdditionalGrading ................................................25
Footing Trench Excavation .........................................25
Trenching.......................................................26
Utility Trench Backfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
SU MMARY OF RECOMMENDATIONS REGARDING GEOTECHNICAL OBSERVATION AND
TESTING ........................................................27
OTHER DESIGN PROFESSIONALS/CONSULTANTS . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
PLAN REVIEW .........................................................28
LIMITATIONS..........................................................28
Karwin Company Table of Contents
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FIGURES:
Figure 1 - Site Location Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Figure 2 - Boring Location Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Figure 2 - California Fault Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Detail 1 - Typical Retaining Wall backfill and Drainage Detail . . . . . . . . . . . . . . 18
Detail 2- Retaining Wall Backfill and Subdrain detail Geotextile Drain ....... 19
Detail 3- Retaining Wall and Subdrain Detail Clean Sand Backfill ........... 20
ATfACHMENTS:
Appendix A - Referenees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rear of Text
Appendix B - Borings Logs . . . . . . . . . . . . . . . . : . . . . . . . . . . . . . . . . Rear of Te�
Appendix C - EQFAULT, EQSEARCH, and FRISKSP . . . . . . . . . . . . . Rear of Text
Appendix D - Laboratory Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rear of Text
Appendix E- General Earthwork and Grading Guidelines ......... Rear of Text
Karwin Company Table of Contents
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UPDATED PRELIMINARY GEOTECHNICAL EVALUATION
' BRITTANY COVE CONDOMINIUM PROJECT
2642 THROUGH 2646 JEFFERSON STREET
CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA
CT 03-14/CP 03-09/SDP 03-19/CDP 03-48
SCOPE OF SERVICES
The scope of our services has included the following:
1. Review of the available geologic literature for the site (Appendix A).
2. Geologic site reconnaissance, subsurface exploration, sampling and mapping.
3. Updated general areal seismicity evaluation.
4. Appropriate laboratory testing, engineering and geologic analysis of data collected
and preparation of this report.
SITE CONDITIONS/PROPOSED'DEVELOPMENT
The site is an approximately rectangular shaped parcel located on the east side of
Jefferson Street, in Carlsbad, California. The relatively level site is situated south of
Knowles Street and approximately 30 feet north of Laguna Drive. (see Figure 1,
Site Location Map). The property is bordered on the north by a multi-family-house, on the
south by a single-family residence, and on the west by Jefferson Street. Overall, the
property is relatively level with a gently sloping gradient to the southwest. The site
drainage is generally via sheet flow to the southwest. According to a 1968 topographic
map, the subject site is approximately 64 feet above Mean Sea Level (MSL).
Based on our review of the revised site plan (Karnak Planning & Design), it is our
understanding that the revised proposed project would consist of three, two-story
structures, with three units each, with typical light multi-story loads, utilizing conventional
foundations with continuous footings and slabs on grade, with underground main-line and
onsite utility improvements. It is our understanding that design grades will essentially be
the same as existing grades, and that grading operations at the site will be remedial in
nature. Cut and fill grading fechniques are anticipated to create design grades for the
proposed multi-family residential structures.
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3•D To�wQuade Copyright cv' 1999 DeI,urtne Yurmoutfi, �tifE D�t09b Soarce Data: US('.S
0 1/2 1
Scale Miles
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Raproduced with permission 9�anted by Thomaa 8cos. Mapa.
Thia map la copyrighted by Thomas Broa. Mapa, it la unlawfui
to copy or reproduce all or s�y part thereof, whether for
pe�aonal uae or resale, wfthout permissfon. All rights reserved.
W.O. �
s� • 3256-A-SC
SITE LOCATiON MAP
Figure 1
--.•.�.. •••..�+. ..�... �-�..� .��� v��aav�a��y�c� van�v�n�a--Jan v�egv 1�0.� /.� ne�nute 5eries (Topographic,
1968, by USGS, 1"_2000'
SITE EXPLORATION
Surface observations and subsurface exploration were performed on March 18, 2002; by
a representative of this office. A survey of line and grade for the subject lot was not
conducted by this firm at the time of our site reconnaissance. Near surface soil conditions
were explored with five hand auger borings within the site to evaluate soil and
geologic\conditions. The approximate location of each boring is shown on the attached
Boring Location Map (Figure 2). Boring Logs are presented in Appendix B.
REGIONAL GEOLOGY
The subject property is located within a prominent natural geomorphic province in
southwestern California known as the Peninsular Ranges. It is characterized by steep,
elongated mountain ranges and valleysthattrend northwesterly. The mountain ranges are
underlain by basement rocks consisting of pre-Cretaceous metasedimentary rocks,
Jurassic metavolcanic rocks, and Cretaceous plutonic rocks of the southern California
batholith.
In the San Diego County region, deposition occurred during the Cretaceous Period and
Cenozoic Era in the continental margin of a forearc basin. Sediments, derived from
Cretaceous-age plutonic rocks and Jurassic-age volcanic rocks, were deposited into the
narrow, steep, coastal plain and continental margin of the basin. These rocks have been
uplifted, eroded and deeply incised. During early Pleistocene time, a broad coastal plain
was developed from the deposition of marine terrace deposits. During mid to late
Pleistocene time, this plain was uplifted, eroded and incised. Alluvial deposits have since
filled the lowervalleys, and young marine sediments are currently being deposited/eroded
within coastal and beach areas.
SITE GEOLOGIC UNITS
The site geologic units encountered during our subsurface investigation and site
reconnaissance included colluvium and terrace deposits. The earth materials are generally
described below from the youngest to the oldest. The distribution of these materials is
shown on Figure 2.
Colluvium (Unmappedj
The site colluvium materials are mostly residual, having developed through weathering and
decomposition of the underlying terrace deposits. Thickness of the colluvium is
approximately 1 foot. These materials generally consist of reddish brown to dark brown,
silty sand with roots and rootlets. A thin veneer of crushed aggregate was noted on the
north side of the property. These materials were generally observed to be dry to damp,
Karwin Company W.O. 3256-A-SC
2642 through 2646 Jefferson Street January 7, 2004
File:e;�wp9\3200\3256a.rpge Page 3
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SITE PLAN
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Qt Quaternary terrace deposits
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W.O. 3256-A-SC Plate C-1
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APPENDIX D
LABORATORY DATA
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NORMAL PRESSURE, psf
Sample DepthlEl. Primary/Residual Shear Sample Type Ya MC% c �
• B-1 1.0 Primary Shear Undisturbed 108.6 3.6 70 33
■ B-1 1.0 Residual Shear Undisturbed 108.6 3.6 52 33
Note: Sample Innundated priorto testing
GeoSoils, Inc,
5741 Palmer Way
G�.b�c► ,�.-,I�ic. Carlsbad, CA 92008
Telephone: (760) 438-3155
Fax: (760) 931-0915
DIRECT SHEAR TEST
Project: KARWIN
Number: 3256-A-SC
Date: March 2002
Piate; D-1
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Sample Depth/El. Primary/Residual Shear Sample Type Yd MC% c �
• B-3 1.0 Primary Shear Remolded 117.0 10.0 144 35
■ B-3 1.0 Residual Shear Remolded 117.0 10.0 27 33
Note: Sample Innundated priorto testing
GeoSoils, Inc.
5741 Palmer Way
� I�. Carlsbad, CA 92008
� �e � � Telephone: (760) 438-3155
Fax: (760) 931-0915
DIRECT SHEAR TEST
Project: KARWIN
Number: 3256-A-SC
Date: March 2002
Plate C�-2
iVI. J. Schiff & Associates, Inc.
Co�tsufting Corrosin�r Engineers -Since 19�9 1308 vlonte Vista Avenue, Suite 6
Upland, CA 91786-822-t
Phone: 909/931-1360
Table 1- Laboratory Tests on Soil Samples
Kunvin
Your #3256 fi-SC,1biJS�iA #02-0271LAB
20-ttilar-02
Sample ID
Resistivity
as-received
saturated
pH
Electrical
Conductivity
Chemical Analyse;
Cations
calcium
magnesium
sodium
Anions
carbonate
bicarbonate
chloride
sulfate
Other Tests
ammonium
nitrate
sulfide
Redox
B-3
@ 1-3
Units
ohm-cm 135,000
ohm-cm 7,500
6.0
mS/cm 0.14
CaZ+ mg/kg
Mgz+ m�g
Na�* mg/kg
C032 mg/kg
HCO3 � mg/kg
Cl�' mg/kg
SO42� mg/kg
�4i+ mP�g
NO3 �" mg/kg
S2- qual
mv
64
7
ND
ND
98
40
ND
na
na
na
na
Electrical conductivity in millisiemens/cm and chemical analysis were made on a 1:5 soil-to-water extract.
mg/kg = milligrams per kilogram (parts per million) of dry soil.
Redox = oxidation-reduction potential in millivolts
ND = not detected
na = not analyzed
Page 1 of 1 Plate D-3
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APPENDIX E ;
_ ;
GENERAL`EARTHWORK AND GRAdING GUIDELINES �I
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GENERAL EARTHWORK AND GRADING GUIDELINES
General
These guidelines present general procedures and requirements for earthwork and grading
as shown on the approved grading plans, including preparation of areas to filled,
placement of fill, installation of subdrains and excavations. The recommendations
contained in the geotechnical report are part of the earthwork and grading guidelines and
would supercede the provisions contained hereafter in the case of conflict. Evaluations
performed by the consultant during the course of grading may result in new
recommendations which could supersede these guidelines or the recommendations
contained in the geotechnical report.
The contractor is responsible forthe satisfactory completion of all earthwork in accordance
with provisions of the project plans and specifications. The project soil engineer and
engineering geologist (geotechnical consultant) or their representatives should provide
observation and testing services, and geotechnical consultation during the duration of the
project.
EARTHWORK OBSERVATIONS AND TESTING
Geotechnical Consultant
Prior to the commencement of grading, a qualified geotechnical consultant (soil engineer
and engineering geologist) should be employed for the purpose of observing earthwork
procedures and testing the fills for conformance with the recommendations of the
geotechnical report, the approved grading plans, and applicable grading codes and
ordinances. _
The geotechnical consultant should provide testing and observation so that determination
may be made that the work is being accomplished as specified. It is the responsibility of
the contractor to assist the consultants and keep them apprised of anticipated work
schedules and changes, so that they may schedule their personnel accordingly.
All clean-outs, prepared ground to receive fill, key excavations, and subdrains should be
observed and documented by the project engineering geologist and/or soil engineer prior
to placing and fill. It is the contractors's responsibility to notify the engineering geologist
and soil engineer when such areas are ready for observation.
Laboratory and Field Tests
Maximum dry density tests to determine the degree of compaction should be performed
in accordance with American Standard Testing Materials test method ASTM designation
D-1557-78. Random field compaction tests should be performed in accordance with test
method ASTM designation D-1556-82, D-2937 or D-2922 and D-3017, at intervals of
approximately 2 feet of fill height or every 100 cubic yards of fill placed. These criteria
i � .
would vary depending on the soil conditions and the size of the project. The location and
frequency of testing would be at the discretion of the geotechnical consultant.
Contractor's Responsibility
All clearing, site preparation, and earthwork performed on the project should be conducted
by the contractor, with observation by geotechnical consultants and staged approval by
the governing agencies, as applicable. It is the contractor's responsibility to prepare the
ground surface to receive the fill, to the satisfaction of the soil engineer, and to place,
spread, moisture condition, mix and compact the fill in accordance with the
recommendations of the soil engineer. The contractor should also remove all major non-
earth material considered unsatisfactory by the soil engineer.
It is the sole responsibility of the contractor to provide adequate equipment and methods
to accomplish the earthwork in accordance with applicable grading guidelines, codes or
agency ordinances, and approved grading plans. Sufficient watering apparatus and
compaction equipment should be provided by the contractor with due consideration for
the fill material, rate of placement, and climatic conditions. If, in the opinion of the
geotechnical consultant, unsatisfactory conditions such as questionable weather,
excessive oversized rock, or deleterious material, insufficient support equipment, etc., are
resulting in a quality of work that is not acceptable, the consultant will inform the
contractor, and the contractor is expected to rectify the conditions, and if necessary, stop
work until conditions are satisfactory.
During construction, the contractor shall properly grade all surfaces to maintain good
drainage and prevent ponding of water. The contractor shall take remedial measures to
control surface water and to prevent erosion of graded areas until such time as permanent
drainage and erosion control measures have been installed.
SITE PREPARATION
All major vegetation, including brush, trees, thick grasses, organic debris, and other
deleterious material should be removed and disposed o# off-site. These removals must be
concluded prior to placing fill. Existing fill, soil, alluvium, colluvium, or rock materials
determined by the soil engineer or engineering geologist as being unsuitable in-place
should be removed prior to fill placement. Depending upon the soil conditions, these
materials may be reused as compacted fills. Any materials incorporated as part of the
compacted fills should be approved by the soil engineer.
Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic
tanks, wells, pipelines, or other structures not located prior to grading are to be removed
or treated in a manner recommended by the soil engineer. Soft, dry, spongy, highly
fractured, or otherwise unsuitable ground extending to such a depth that surface
processing cannot adequately improve the condition should be overexcavated down to
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firm ground and approved by the soil engineer before compaction and filling operations
continue. Overexcavated and processed soils which have been properly mixed and
moisture conditioned should be re-compacted to the minimurn relative compaction as
specified in these guidelines.
Existing ground which is determined to be satisfactory for support of the fills should be
scarified to a minimum depth of 6 inches or as directed by the soil engineer. After the
scarified ground is brought to optimum moisture content or greater and mixed, the
materials should be compacted as specified herein. If the scarified zone is grater that
6 inches in depth, it may be necessary to remove the excess and place the material in lifts
restricted to about 6 inches in compacted thickness.
Existing ground which is not satisfactory to support compacted fill should be
overexcavated as required in the geotechnical report or by the on-site soils engineer
and/or engineering geologist. Scarification, disc harrowing, or other acceptable form of
mixing should continue until the soils are broken down and free of large lumps or clods,
until the working surface is reasonably uniform and free from ruts, hollow, hummocks, or
other uneven features which would inhibit compaction as described previously.
Where fills are to be placed on ground with slopes steeper than 5:1 (horizontal to vertical),
the ground should be stepped or benched. The lowest bench, which will act as a key,
should be a minimum of 15 feet wide and should be at least 2 feet deep into firm material,
and approved by the soil engineer and/or engineering geologist. In fill over cut slope
conditions, the recommended minimum width of the lowest bench or key is also 15 feet
with the key founded on firm material, as designated by the Geotechnical Consultant. As
a general rule, unless specifically recommended otherwise by the Soil Engineer, the
minimum width of fill keys should be approximately equal to'/2 the height of the slope.
Standard benching is generally 4 feet (minimum) vertically, exposing firm, acceptable
material. Benching may be used to remove unsuitable materials, although it is understood
that the vertical height of the bench may exceed 4 feet. Pre-stripping may be considered
for unsuitable materials in excess of 4 feet in thickness.
All areas to receive fill, including processed areas, removal areas, and the toe of fill
benches should be observed and approved by the soil engineer and/or engineering
geologist prior to placement of fill. Fills may then be properly placed and compacted until
design grades (elevations) are attained.
COMPACTED FILLS
Any earth materials imported or excavated on the property may be utilized in the fill
provided that each material has been determined to be suitable by the soil engineer.
These materials should be free of roots, tree branches, other organic matter or other
deleterious materials. All unsuitable materials should be removed from the fill as directed
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by the soil engineer. Soils of poor gradation, undesirable expansion potential, or
substandard strength characteristics may be designated by the consultant as unsuitable
and may require blending with other soils to serve as a satisfactory fill material.
Fill materials derived from benching operations should be dispersed throug�out the fill
area and blended with other bedrock derived material. Benching operations should not
result in the benched material being placed only within a single equipment width away
from the fill/bedrock contact.
Oversized materials defined as rock or other irreducible materials with a maximum
dimension greater than 12 inches should not be buried or placed in fills unless the location
of materials and disposal methods are specifically approved by the soil engineer.
Oversized material should be taken off-site or placed in accordance with recommendations
of the soil engineer in areas designated as suitable for rock disposal. Oversized material
should not be placed within 10 feet vertically of finish grade (elevation) or within 20 feet
horizontally of slope faces.
To facilitate future trenching, rock should not be placed within the range of foundation
excavations, future utilities, or underground construction unless specifically approved by
the soil engineer and/or the developers representative.
If import material is required for grading, representative samples of the materials to be
utilized as compacted fill should be analyzed in the laboratory by the soil engineer to
determine its physical properties. If any material other than that previously tested is
encountered during grading, an appropriate analysis ofthis material should be conducted
by the soil engineer as soon as possible.
Approved fill material should be placed in areas prepared to receive fill in near horizontal
layers that when compacted should not exceed 6 inches in thickness. The soil engineer
may approve thick lifts if testing indicates the grading procedures are such that adequate
compaction is being achieved with lifts of greaterthickness. Each layer should be spread
evenly and blended to attain uniformity of material and moisture suitable for compaction.
Fill layers at a moisture content less than optimum should be watered and mixed, and wet
fill layers should be aerated by scarification or should be blended with drier material.
Moisture condition, blending, and mixing of the fill layer should continue until the fill
materials have a uniform moisture content at or above optimum moisture.
After each layer has been evenly spread, moisture conditioned and mixed, it should be
uniformly compacted to a minimum of 90 percent of maximum density as determined by
ASTM test designation, D-1557-78, or as otherwise recommended by the soil engineer.
Compaction equipment should be adequately sized and should be specifically designed
for soil compaction or of proven reliability to efficiently achieve the specified degree of
compaction.
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Where tests indicate that the density of any layer of fill, or portion thereof, is below the
required relative compaction, or improper moisture is in evidence, the particular layer or
portion shall be re-worked until the required density and/or moisture content has been
attained. No additional fill shall be placed in an area until the last placed lift of fill has been
tested and found to meet the density and moisture requirements, and is app.roved by the
soil engineer.
Compaction of slopes should be accomplished by over-building a minimum of 3 feet
horizontally, and subsequently trimming back to the design slope configuration. Testing
shall be performed as the fill is elevated to evaluate compaction as the fill core is being
developed. Special efforts may be necessary to attain the specified compaction in the fill
slope zone. Final slope shaping should be performed by trimming and removing loose
materials with appropriate equipment. Afinal determination offitl slope compaction should
be based on observation and/or testing of the finished slope face. Where compacted fill
slopes are designed steeper than 2:1 (horizontal to vertical), specific material types, a
higher minimum relative compaction, and special grading procedures, may be
recommended.
If an alternative to over-building and cutting back the compacted fill slopes is selected,
then special effort should be made to achieve the required compaction in the outer 10 feet
of each lift of fill by undertaking the following:
1. An extra piece of equipment consisting of a heavy short shanked sheepsfoot should
be used to roll (horizontal) parallel to the slopes continuously as fill is placed. The
sheepsfoot roller should also be used to roll perpendicular to the slopes, and
extend out over the slope to provide adequate compaction to the face of the slope.
2. Loose fill should not be spilled out over the face of the slope as each lift is
compacted. Any loose fill spilled over a previously completed slope face should be
trimmed off or be subject to re-rolling.
3. Field compaction tests will be made in the outer (horizontal) 2 to 8 feet ofthe slope
at appropriate vertical intervals, subsequent to compaction operations.
4. After completion of the slope, the slope face should be shaped with a small tractor
and then re-rolled with a sheepsfoot to achieve compaction to near the slope face.
Subsequent to testing to verify compaction, the slopes should be grid-rolled to
achieve compaction to the slope face. Final testing should be used to confirm
compaction after grid rolling.
5. Where testing indicates less than adequate compaction, the contractor will be
responsible to rip, water, mix and re-compact the slope material as necessary to
achieve compaction. Additional testing should be performed to verify compaction.
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6. Erosion control and drainage devices should be designed by the project civil
engineer in compliance with ordinances of the controlling governmental agencies,
and/or in accordance with the recommendation of the soil engineer or engineering
geologist.
SUBDRAIN INSTALLATION
Subdrains should be installed in approved ground in accordance with the approximate
alignment and details indicated by the geotechnical consultant. Subdrain locations or
materials should not be changed or modified without approval of the geotechnical
consultant. The soil engineer and/or engineering geologist may recommend and direct
changes in subdrain line, grade and drain material in the field, pending exposed
conditions. The location of constructed subdrains should be recorded by the project civil
engineer.
EXCAVATI O N S
Excavations and cut slopes should be examined during grading by the engineering
geologist. If directed by the engineering geologist, further excavations or overexcavation
and re-filling of cut areas should be performed and/or remedial grading of cut slopes
should be performed. When #ill over cut slopes are to be graded, unless otherwise
approved, the cut portion of the slope should be observed by the engineering geologist
prior to placement of materials for construction of the fill portion of the slope.
The engineering geologist should observe all cut slopes and should be notified by the
contractor when cut slopes are started. If, during the course of grading, unforeseen
adverse or potential adverse geologic conditions are encountered, the engineering
geologist and soil engineer should investigate, evaluate and make recommendations to
treat these problems. The need for cut slope buttressing or stabilizing should be based
on in-grading evaluation by the engineering geologist, whether anticipated or not.
Unless otherwise specified in soil and geological reports, no cut slopes should be
excavated higher or steeper than that allowed by the ordinances of controlling
governmental agencies. Additionally, short-term stability of temporary cut slopes is the
contractors responsibility.
Erosion control and drainage devices should be designed by the project civil engineer and
should be constructed in compliance with the ordinances of the controlling governmental
agencies, and/or in accordance with the recommendations of the soil engineer or
engineering geologist.
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Geo�oil�, Ir�c.
COMPLETION
Observation, testing and consultation bythe geotechnicai consuitant should be conducted
during the grading operations in order to state an opinion that all cut and filled areas are
graded in accordance with the approved project specifications.
After completion of grading and after the soil engineer and engineering geologist have
finished their observations of the work, final reports should be submitted subject to review
by the controlling governmental agencies. No further excavation or filling should be
undertaken without prior notification of the soil engineer and/or engineering geologist.
All finished cut and fill slopes should be protected from erosion and/or be planted in
accordance with the project specifications and/or as recommended by a landscape
architect. Such protection and/or planning should be undertaken as soon as practical after
completion of grading.
JOB SAFETY
General
At GeoSoils, Inc. (GSI) getting the job done safely is of primary concern. The following is
the company's safety considerations for use by all employees on multi-employer
construction sites. On ground personnel are at highest risk of injury and possible fatality
on grading and construction projects. GSI recognizes that construction activities will vary
on each site and that site safety is the rime responsibility of the contractor; however,
everyone must be safety conscious and responsible at all times. To achieve our goal of
avoiding accidents, cooperation between the client, the contractor and GSI personnel must
be maintained.
In an effort to minimize risks associated with geotechnical testing and observation, the
following precautions are to be implemented for the safety of field personnel on grading
and construction projects:
Safety Meetings: GSI field personnel are directed to attend contractors regularly
scheduled and documented safety meetings.
Safety Vests: Safety vests are provided for and are to be worn by GSI personnel at
all times when they are working in the field.
Safety Flags: Two safety flags are provided to GSI field technicians; one is to be
affixed to the vehicle when on site, the other is to be placed atop the
spoil pile on all test pits.
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Flashing Lights: All vehicles stationary in the grading area shall use rotating or flashing
amber beacon, or strobe lights, on the vehicle during all field testing.
While operating a vehicle in the grading area, the emergency flasher
on the vehicle shall be activated.
In the event that the contractor's representative observes any of our personnel not
following the above, we request that it be brought to the attention of our office.
Test Pits Location. Orientation and Clearance
The technician is responsible for selecting test pit locations. A primary concern should be
the technicians's safety. Efforts will be made to coordinate locations with the grading
contractors authorized representative, and to select locations following or behind the
established traffic pattern, preferably outside of current traffic. The contractors authorized
representative (dump man, operator, supervisor, grade checker, etc.) should direct
excavation of the pit and safety during the test period. Of paramount concern should be
the soil technicians safety and obtaining enough tests to represent the fill.
Test pits should be excavated so that the spoil pile is placed away form oncoming traffic,
whenever possible. The technician's vehicle is to be placed next to the test pit, opposite
the spoil pile. This necessitates the fill be maintained in a driveable condition.
Alternatively, the contractor may wish to park a piece of equipment in front of the test
holes, particularly in small fill areas or those with limited access.
A zone of non-encroachment should be established for all test pits. No grading equipment
should enter this zone during the testing procedure. The zone should extend
approximately 50 feet outward from the center of the test pit. This zone is established for
safety and to avoid excessive ground vibration which typically decreased test results.
When taking slope tests the technician should park the vehicle directly above or below the
test location. If this is not possible, a prominent flag should be placed at the top of the
slope. The contractor's representative should effectively keep all equipment at a safe
operation distance (e.g., 50 feet) away from the slope during this testing.
The technician is directed to withdraw from the active portion of the fill as soon as possible
following testing. The technician's vehicle should be parked at the perimeter of the fill in
a highly visible location, well away from the equipment traffic pattern. The contractor
should inform our personnel of all changes to haul roads, cut and fill areas or other factors
that may affect site access and site safety.
In the event that the technicians safety is jeopardized or compromised as a result of the
contractors failure to comply with any ofthe above, the technician is required, by company
policy, to immediately withdraw and notify his/her supervisor. The grading contractors
representative will eventually be contacted in an effort to effect a solution. However, in the
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interim, no further testing will be performed until the situation is rectified. Any fill place can
be considered unacceptable and subject to reprocessing, recompaction or removal.
In the event that the soil technician does not comply with the above or other established
safety guidelines, we request that the contractor brings this to his/her attention and notify
this office. Effective communication and coordination between the contractors
representative and the soils technician is strongly encouraged in order to implement the
above safety plan.
Trench and Vertical Excavation
It is the contractor's responsibility to provide safe access into trenches where compaction
testing is needed.
Our personnel are directed not to enter any excavation or vertical cut which: 1) is 5 feet or
deeper unless shored or laid back; 2) displays any evidence of instability, has any loose
rock or other debris which could fall into the trench; or 3) displays any other evidence of
any unsafe conditions regardless of depth.
All trench excavations or vertical cuts in excess of 5 feet deep, which any person enters,
should be shored or laid back. Trench access should be provided in accordance with
CAL-OSHA and/or state and local standards. Our personnel are dicected not to enter any
trench by being lowered or "riding down" on the equipment.
If the contractor fails to provide safe access to trenches for compaction testing, our
company policy requires that the soil technician withdraw and notify his/her supervisor.
The contractors representative will eventualfy be contacted in an effort to effect a solution.
All backfill not tested due to safety concerns or other reasons could be subject to
reprocessing and/or removal.
If GSI personnel become aware of anyone working beneath an unsafe trench wall or
vertical excavation, we have a legal obligation to put the contractor and owner/developer
on notice to immediately correct the situation. If corrective steps are not taken, GSI then
has an obligation to notify CAL-OSHA and/or the proper authorities.
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T�ST PiT SAF�TY DIAGRAM
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SPOIL P11E ' �. �
TEST PiT
( NOT TO SCALE 1
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P LATE E�-16
loose, porous, and are considered compressible. These materials are considered
unsuitable for structural support in their present conditioned and should be removed and
recompacted.
Quaternary-Age Terrace Deposits (Map Symbol - Qt)
Terrace deposits were observed to underlie the site and consist of dense silty sand. These
deposits are generally orange brown to reddish brown in color, and damp to moist in their
moisture content. As a result of the relatively loose and weathered condition of the upper
±1 to ±2'/2 feet, these materials should be removed, moisture conditioned, and
recompacted and/or processed in place, should settlement-sensitive improvements be
proposed.
GROUNDWATER
Subsurface water was not encountered within the property during field work performed in
preparation of this report. Subsurface water is not anticipated to adversely affect site
development, provided that the recommendations contained in this report are incorporated
into final design and construction. These observations reflect site conditions at the time
of our investigation and do not preclude future changes in local groundwater conditions
from excessive irrigation, precipitation, or that were not obvious, at the time of our
investigation. Regional groundwater is estimated to be at least 50 feet in depth, below the
site.
Seeps, springs, or other indications of a high groundwater level were not noted on the
subject property during the time of our field investigation. However, seepage may occur
locally (as the result of heavy precipitation or irrigation) in areas where any fill soils overlie
terrace deposits. Such conditions may occur during grading or after the site is developed.
FAULTING AND REGIONAL SEISMICITY
Faultinq
The site is situated in a region of active as well as potentially-active faults. Our review
indicates that there are no known active faults crossing the site within the areas proposed
for development (Jennings, 1994), and the site is not within an Earthquake Fault Zone
(Hart and Bryant, 1997).
There are a number of faults in the southern California area that are considered active and
would have an effect on the site in the form of ground shaking, should they be the source
of an earthquake (Figure 3). These faults include-but are not limited to-the San Andreas
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W.O. 3256-A-SC Figure 3
fault, the San Jacinto fault, the Elsinore fault, the Coronado Bank fault zone, and the
Newport-Inglewood - Rose Canyon fault zone. The possibility of ground acceleration or
shaking at the site may be considered as approximately similar to the southern California
region as a whole.
The following table lists the major faults and fault zones in southern California that could
have a significant effect on the site should they experience significant activity.
ABBREVIATED APPROXIMATE DISTANCE
FAULT NAME MILES KM
Coronado Bank-Agua Blanca 21.4 (34.4)
Elsinore - Temecula 23.9 (38.4)
Newport-Inglewood-Offshore 5.2 (8.4)
Rose Canyon 5.4 (8.7)
Elsinore - Julian 24.2 38.9
Seismicitv
The acceleration-attenuation relations of Sadigh, et al. (1997) Horizontal Soil, Bozorgnia,
Campbell and Niazi (1999) Horizontal-Soft Rock-Correlation and Campbell and Bozorgnia
(1997 Rev.) Horizontal-Soil have been incorporated into EQFAULT (Blake, 2000a). Forthis
study, peak horizontal ground accelerations anticipated atthe site were determined based
on the random mean plus 1- sigma attenuation curve and mean attenuation curve
developed by Joyner and Boore (1982a and 1982b), Bozorgnia, Campbell, and
Niazi (1999), and Campbell and Bozorgnia (1997). EQFAULT is a computer program by
Thomas F. Blake (2000a), which performs deterministic seismic hazard analyses using up
to 150 digitized California faults as earthquake sources.
The program estimates the closest distance between each fault and a given site. If a fault
is found to be within a user-selected radius, the program estimates peak horizontal ground
acceleration that may occur at the site from an upper bound ("maximum credible")
earthquake on that fault. Site acceleration (g) is computed by one of many user-selected
acceleration-attenuation relationsthat are contained in EQFAULT. Based on the EQFAULT
program, peak horizontal ground accelerations from an upper bound event at the site may
be on the order of 0.53g to 0.64g.
Historical site seismicity was evaluated with the acceleration-attenuation relations of
Campbell and Bozorgnia (1997 Revised) Soft Rock and the computer program
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EQSEARCH (Blake, 2000b). This program performs a search of the historical earthquake
records for magnitude 5.0 to 9.0 seismic events within a 100-mile radius, between the
years 1800 to 2002. Based on the selected acceleration-attenuation relationship, a peak
horizontal ground acceleration is estimated, which may have effected the site during the
specific event listed. Based on the available data and the attenuation relationship used,
the estimated maximum (peak) site acceleration during the period 1800 to 2002 was 0.26g.
Site specific probability of exceeding various peak horizontal ground accelerations and a
seismic recurrence curve are also estimated/generated from the historical data. Computer
printouts of pertinent portions of the EQSEARCH program are presented in Appendix C.
A probabilistic seismic hazards analyses was performed using FRISKSP (Blake, 2000c)
which models earthquake sources as 3-D planes and evaluates the site specific
probabilities of exceedance for given peak acceleration levels or pseudo-relative velocity
levels. Based on a review of these data, and considering the relative seismic activity of the
southern California region, a peak horizontal ground acceleration of 0.30g was calculated.
This value was chosen as it corresponds to a 10 percent probability of exceedance in
50 years (or a 475-year return period).
Seismic Shaking Parameters
Based on the site conditions, Chapter 16 of the Uniform Building Code ([UBC],
International Conference of Building Officials [ICBO], 1997) and Peterson and others
(1996), the following seismic parameters are provided.
Seismic zone (per Figure 16-2*) 4
Seismic Zone Factor (per Table 16-I*) 0.40
Soil Profile Type (per Table 16-J*) Sp
Seismic Coefficient Ca (per Table 16-Q*) 0.44 Na
Seismic Coefficient C„ (per Table 16-R*) 0.64 N�
Near Source Factor Na (per Table 16-S*) 1.0
Near Source Factor N„ (per Table 16-T*) 1.1
Seismic Source Type (per Table 16-U*) B
Distance to Seismic Source 5.2 mi. (8,4 km)
Upper Bound Earthquake MW 6.9
* Figure and table references from Cha ter 16 of the UBC ICBO, 1997 .
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Seismic Hazards
The following list includes other seismic related hazards that have been considered during
our evaluation ofthe site. The hazards listed are considered negligible and/or completely
mitigated as a result of site location, soil characteristics, and typical site development
procedures:
• Liquefaction
• Tsunami
• Dynarnic SettlementSurface Fault Rupture
• Ground Lurching or Shallow Ground Rupture
It is important to keep in perspective that in the event of a maximum probable or credible
earthquake occurring on any of the nearby major faults, strong ground shaking would
occur in the subject site's general area. Potential damage to any structure(s) would likely
be greatest from the vibrations and impelling force caused by the inertia of a structure's
mass, than from those induced by the hazards considered above. This potential would be
no greater than that for other existing structures and improvements in the immediate
vicinity.
LIQUEFACTION
Liquefaction describes a phenomenon in which cyclic stresses, produced by earthquake
induced ground motion, create excess pore pressures in relatively cohesionless soils.
These soils may thereby acquire a high degree of mobility, which can lead to lateral
movement sliding, consolidation and settlement of loose sediments, sand boils, and other
damaging deformations. This phenomenon occurs only below the water table, but after
liquefaction has developed, it can propagate upward into overlying, non-saturated soil, as
excess pore water dissipates.
Liquefaction susceptibility is related to numerousfactors and the following conditions must
exist for liquefaction to occur: 1)� sediments must be relatively young in age and not have
developed large amount of cementation; 2) sediments must consist mainly of inedium to
fine grained relatively cohesionless sands; 3) the sediments must have low relative density;
4) free groundwater must be present in the sediment; and 5) the site must experience
seismic event of a sufficient duration and large enough magnitude, to induce straining of
soil particles. At the subject site, three of the five conditions which are necessary for
liquefaction to occur exist, and the site may or may not experience the other two (Kuhn,
Legg, Shlemon, Bauer, 2000). Therefore, although remote, the possibility for liquefaction
to occur cannot be entirely precluded; however, should not pose an undue constraint to
development.
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One ofthe primaryfactors controlling the potential for liquefaction is depth to groundwater.
Liquefaction susceptibility generally decreases as the groundwater depth increases fortwo
reasons: 1) the deeper the water table, the greater normal effective stress acting on
saturated sediments at any given depth and liquefaction susceptibility decreases with
increased normal effective stress; and 2) age, cementation, and relative density of
sediments generally increase with depth. Thus, as the depth to the water table increases,
and as the saturated sediments become older, more cemented, have higher relative
density, and confining normal stresses increase, the less likely they are to liquefy during
a seismic event. Typically, liquefaction has a relatively low potential where groundwater
is greater than 30 feet deep, and virtually unknown below 60 feet. Mitigation of the impacts
from liquefaction would be provided by the recommended removal and recompaction
discussed herein.
OTHER GEOLOGIC HAZARDS
Mass wasting refers to the various processes by which earth materials are moved down
slope in response to the force of gravity. Examples of these processes include slope
creep, surficial failures, and deep-seated landslides. Creep is the slowest form of mass
wasting and generally involves the outer 5 to 10 feet of a slope surface. During heavy
rains, such as those in 1969, 1978, 1980, 1983, 1993, and 1998 creep-affected materials
may become saturated, resulting in a more rapid form of downslope movement (i.e.,
landslides and/or surficial failures). The site topography is very flat lying, no such slopes
are propose.d, and indications of deep seated landsliding on the site were not observed
during our site reconnaissance. Therefore, the potential for seismically induced landsliding
is considered low.
LABORATORY TESTING
General
Laboratory tests were performed on representative samples of the onsite earth materials
in order to evaluate their physical characteristics. The test procedures used and results
obtained are presented below.
LaboratorYStandard
The maximum dry density and optimum moisture content was determined forthe major soil
type encountered in the trenches. The laboratory standard used was ASTM D-1557. The
moisture-density relationship obtained for this soil is shown below:
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SOIL TYPE BORING AND MAXIMUM DRY OPTIMUM MOISTURE
DEPTH ft. DENSITY cf GONTENT %
Silty SAND, Dark Brown B-3 @ 1-3 130,0 10.0
Expansion Potential
Expansion testing was performed on a representative sample of site soil in accordance
with UBC Standard 18-2. The results of expansion testing are presented in the following
table.
Shear Testinq
Sheartesting was performed on a representative, undisturbed and remolded sample of site
soil in general accordance with ASTM test method D-3080 in a Direct Shear Machine ofthe
strain control type. Shear test results are presented as Plates D-1 and D-2 in Appendix D,
and as follows:
Corrosion/Sulfate Testing
Sulfate testing indicates that site soils have a negligible exposure to concrete per Table 19-
A-4 of the 1997 UBC (water extractable sulfate = 0.000 percent by weight). Corrosion
testing (pH, resistivity) indicates that soils are medium acidic (pH = 6.0) and moderately
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corrosive (saturated resistivity = 7,500 ohms-cm) to ferrous metals. Test results are
presented as Plate D-3 in Appendix D.
COfVCLUSIONS
Based upon our site reconnaissance, subsurface exploration, and laboratory test results,
it is our opinion that the subject site appears suitable for the proposed residential
development. The following recommendations should be incorporated into the
construction details.
EARTHWORK CONSTRUCTION RECOMMENDATIONS
General
All grading should conform to the guidelines presented in Appendix Chapter A33 of the
UBC, the requirements of the City, and the Grading Guidelines presented in Appendix E,
except where specifically superseded in the text of this report. Prior to grading, a GSI
representative should be present at the preconstruction meeting to provide additional
grading guidelines, if needed, and review the earthwork schedule.
During earthwork construction all site preparation and the general grading procedures of
the contractor should be observed and the fill selectively tested by a representative(s) of
GSI. If unusual or unexpected conditions are exposed in the field, they should be reviewed
bythis office and ifwarranted, modified and/or additional recommendations will be offered.
All applicable requirements of local and national construction and general industry safety
orders, the Occupational Safety and Health Act, and the Construction Safety Act should
be met.
Site Preparation
Debris, vegetation and other deleterious material should be removed from the building
area prior to the start of construction. Sloping areas to receive fill should be properly
benched in accordance with current industry standards of practice and guidelines
specified in the UBC.
Removals �Unsuitable Surficial Materials)
As a result of the relatively loose/soft condition of colluvium and weathered terrace
deposits, these materials should be removed and recompacted in areas proposed for
settlement-sensitive structures or areas to receive compacted fill. At this time, removal
depths on the order of ±2 to ±3'/2 feet should be anticipated; however, locally deeper
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removals may be necessary. Removals should be completed below a 1:1 projection down
and away from the edge of any settlement-sensitive structure and/or limit of proposed fiil.
Once removals are completed, the exposed bottom should be reprocessed and
compacted
Fill Placement
Subsequent to ground preparation, onsite soils may be placed in thin (±6-inch) lifts,
cleaned of vegetation and debris, brought to a least optimum moisture content, and
compacted to achieve a minimum relative compaction of 90 percent. If soil importation is
planned, a sample of the soil import should be evaluated by this office prior to importing,
in order to assure compatibility with the onsite site soils and the recommendations
presented in this report. Import soils for a fill cap should be low expansive (expansion
index [E.I.] less than 50). The use of subdrains at the bottom of the fill cap may be
necessary, and subsequently recommended based on compatibility with onsite soils and
other considerations.
Transitions/Overexcavation
Cut portions of cut/fill transition pads should be overexcavated a minimum 3 feet below
pad grade. Areas with planned fills less than 3 feet should be overexcavated in order to
provide a minimum fill thickness of 3 feet, on a preliminary basis. Overexcavation of native
soils due to the presence of heterogenous stratigraphy (i.e., sand/clay) may be warranted
and will be evaluated on a lot-by-lot basis during grading. Where the ratio of maximum to
minimum fill thickness below a given structure exceeds 3:1, overexcavation should be
completed to reduce this ration to 3:1, or less.
RECOMMENDATIONS - FOUNDATIONS
Preliminary Foundation Desiqn
In the event that the information concerning the proposed development plans are not
correct or any changes in the design, location, or loading conditions of the proposed
structures are made, the conclusions and recommendations contained in this report are
for the subject site only and shall not be considered valid unless the changes are reviewed
and conclusions of this report are modified or approved in writing by this office.
The information and recommendations presented in this section are considered minimums
and are not meant to supersede design(s) by the project structural engineer or civil
engineer specializing in structural design. Upon request, GSI could provide additional
consultation regarding soil parameters, as related to foundation design. They are -
considered preliminary recommendations for proposed construction, in consideration of
our field investigation, and laboratory testing and engineering analysis.
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Our review, field work, and recent and previous laboratorytesting indicates that onsite soils
have a very low expansion potential range (E.I. 0 to 20). Preliminary recommendations for
foundation design and construction are presented below. Final foundation
recommendations should be provided at the conclusion of grading based on laboratory
testing of fill materials exposed at finish grade.
Desi n
1. An allowable soil bearing pressure of 1,500 psf may be used for the design of
continuous footings with a minimum width of 12 inches and depth of 12 inches and
for design of isolated pad footings 24 inches square and 18 inches deep founded
entirely into compacted fill or competent formational material and connected by
grade beam or tie beam in at least one direction. This value may be increased by
20 percent for each additional 12 inches in depth to a maximum value of 2,500 psf.
2. An allowable coefficient of friction between concrete and compacted fill or bedrock
of 0.35 may be used with the deadload forces.
3. When combining passive pressure and frictional resistance, the passive pressure
component should be reduced by one-third.
4. Passive earth pressure may be computed as an equivalent fluid having a density of
250 pounds per cubic foot (pcfl with a maximum earth pressure of 2,500 psf.
5. All footings should maintain a minimum 7-foot horizontal distance between the base
of the footing and any adjacent descending slope, and minimally comply with the
guidelines depicted on Figure No. 18-I-1 of the UBC (current edition).
Foundation Settlement
Foundations systems should be designed to accommodate a worst case differential
settlement of 1 inch in a 40-foot span, on a preliminary basis.
Footing Setbacks
All footings should maintain a minimum 7-foot horizontal setback from the base of the
footing to any descending slope. This distance is measured from the foating face at the
bearing elevation. Footings should maintain a minimum horizontal setback of H/3
(H=slope height) from the base of the footing to the descending slope face and no less
than 7 feet nor need to be greater than 40 feet. Footings adjacent to unlined drainage
swales should be deepened to a minimur� of 6 inches below the invert of the adjacent
unlined swale. Footings for structures adjacent to retaining walls should be deepened so
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as to extend below a 1:1 projection from the heel of the wall. Alternatively, walls may be
designed to accommodate structural loads from buildings or appurtenances as described
in the retaining wall section of this report.
Construction
The following foundation construction recommendations are presented as a minimum
criteria from a soils engineering standpoint. The onsite soils expansion potentials are
generally very low (E.I. 0 to 20). Recommendations for very low expansive soil conditions
are presented herein.
Recommendations by the project's design-structural engineer or architect, which may
exceed the soils engineer's recommendations, should take precedence over the following
minimum requirements. Final foundation design will be provided based on the expansion
potential of the near surface soils encountered during grading.
Very Low Expansion Potential (E.I. 0 to 20)
1. Exterior and interior footings should be founded at a minimum depth of 12 inches
for one-story floor loads,l8 inches for two-story floor loads, and 24 inches for three-
story floor loads, below the lowest adjacent ground surface. Isolated column and
panel pads or wall footings should be founded at a minimum depth of 18 inches,
excluding the landscape zone (top 6 inches). All footings should be reinforced with
two No. 4 reinforcing bars, one placed nearthetop and one placed nearthe bottom
of the footing. Footing widths should be as indicated in the UBC (ICBO, 1997).
2. A grade beam, reinforced as above, and at least 12 inches wide should be provided
across large (e.g., doorways) entrances. The base ofthe grade beam should be at
the same elevation as the bottom of adjoining footings. Isolated, exterior square
footings should be tied within the main foundation in at least one direction with a
grade beam.
3. Residential concrete slabs, where moisture condensation is undesirable, should be
underlain with a vapor barrier consisting of a minimum of 10 mil polyvinyl chloride
or equivalent membrane with all laps sealed. This membrane should be covered
above and below with a minimum of 2 inches of sand (total of 4 inches) to aid in
uniform curing of the concrete and to protect the membrane from puncture.
4. Residential concrete slabs should be a minimum of 4 inches thick, and should be
reinforced with No. 3 reinforcing bar at 18 inches on center in both directions. All
slab reinforcement should be supported to ensure placement near the vertical
midpoint of the concrete. "Hooking" of reinforcement is not considered an
acceptable method of positioning the reinforcement.
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5. Residential garage slabs should be a minimum of 4 inches thick and should be
reinforced as above and poured separately from the structural footings and
quartered with expansion joints or saw cuts. A positive separation from the footings
should be maintained with expansion joint material to permit relative movement.
6. Presaturation is not required for these soil conditions. The moisture content of the
subgrade soils should be equal to or greater than optimum moisture content in the
slab areas prior to the placement to visqueen. Prior to placing visqueen or
reinforcement, soil moisture should be verified by this office within 72 hours of
pouring slabs.
UTILITIES
Utilities should be enclosed within a closed utilidor (vault) or designed with flexible
connections to accommodate differential settlement and expansive soil conditions. Due
to the potential for differential settlement, air conditioning (A/C) units should be supported
by slabs that are incorporated into the building foundation or constructed on a rigid slab
with flexible couplings for plumbing and electrical lines. A/C waste waterlines should be
drained to a suitable outlet.
WALL DESIGN PARAMETERS
Conventional Retaining Walls
The design parameters provided below assume that either non expansive soils (Class 2
permeable filter material or Class 3 aggregate base) or native materials (up to and
including low expansion potential) are used to backfill any retaining walls. The type of
backfill (i.e., select or native), should be specified by the wall designer, and clearly shown
on the plans. Building walls, below grade, should be water-proofed or damp-proofed,
depending on the degree of moisture protection desired. The foundation system for the
proposed retaining walls should be designed in accordance with the recommendations
presented in this and preceding sections of this report, as appropriate. Footings should
be embedded a minimum of 18 inches below adjacent grade (excluding landscape layer,
6 inches) and should be 24 inches in width. There should be no increase in bearing for
footing width. Recommendations for specialty walls (i.e., crib, earthstone, geogrid, etc.)
can be provided upon request, and would be based on site specific conditions.
Restrained Walls
Any retaining walls that will be restrained prior to placing and compacting backfill material
or that have re-entrant or male corners, should be designed for an at-rest equivalent fluid
pressure (EFP) of 65 pounds per cubic foot (pcfi�, plus any applicable surcharge loading.
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For areas of male or re-entrant corners, the restrained wall design should extend a
minimum distance of twice the height of the wall (2H) laterally from the corner.
Cantilevered Walls
The recommendations presented below are for cantilevered retaining walls up to 10 feet
high. Design parameters for walls less than 3 feet in height may be superseded by City
and/or County standard design. Active earth pressure may be used for retaining wall
design, provided the top of the wall is not restrained from minor deflections. An equivalent
fluid pressure approach may be used to compute the horizontal pressure against the wall.
Appropriate fluid unit weights are given below for specific slope gradients of the retained
material. These do not include other superimposed loading conditions due to traffic,
structures, seismic events or adverse geologic conditions. When wall configurations are
finalized, the appropriate loading conditions for superimposed loads can be provided upon
request.
Level* I 35 I 45
2 to 1 50 60
* Level backfill behind a retaining wall is defined as compacted earth materials,
properly drained, without a slope for a distance of 2H behind the wall, where H is the
height of the walL
Retaining Wall Backfill and Drainaqe
Positive drainage must be provided behind all retaining walls in the form of gravel wrapped
in geofabric and outlets. A backdrain system is considered necessary for retaining walls
that are 2 feet or greater in height. Details 1, 2, and 3, present the backdrainage options
discussed below. Backdrains should consist of a 4-inch diameter perforated PVC or ABS
pipe encased in either Class 2 permeable filter material or'/z-inch to 3/a-inch gravel wrapped
in approved filter fabric (Mirafi 140 or equivalent). For low expansive backfill, the filter
material should extend a minimum of 1 horizontal foot behind the base of the walls and
upward at least 1 foot. For native backfill that has up to medium expansion potential,
continuous Class 2 permeable drain materials should be used behind the wall. This
material should be continuous (i.e., full height) behind the wall, and it should be
constructed in accordance with the enclosed Detail 1(Typical Retaining Wall Backfill and
Drainage Detail). For limited access and confined areas, (panel) drainage behind the wall
may be constructed in accordance with Detail 2(Retaining Wall Backfill and Subdrain
Detail Geotextile Drain). Materials with an expansion index (E.I.) potential of greater than
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DETAl�
N . T , S ,
Native Backfill
Provide surface drainage
�12'
10 Water proofing
Mer�brane <optional>
5O Weephole .
Slope or Level
Native Backf ill
O Rock
O3 Filter fabric 1
/4 or flatter
Native Backflll
Flnlshed surface
4O Pipe
�1 WATER PRt7�FING MEMBRANE Cop�lonal)�
Liqu(d boot or approved equlvalent,
Q RI7CK;
3/4 -�0 1-1/2" Cinches) rock,
QQ FILTER FABRIC+
MIra�Fl 140N or approved equivalent place fabrlc flap behlnd care,
Q PIPE�
4'' Cinches> dlameter perforated PVC, schedule 40 or approved
alternative with Minimur� of 1% gradlent to proper outlet point,
05 WEEPH�LE�
MiniMUM 2' Cinches) dlaMeter placed at 20' Cfeet) on centers
along the wall, and 3'' Clnches) above finished sur�ace,
� = a � ��, �, � ��< , —
.., , <
. �'
t,: q P�. �
� f �t. � : � tl�h (�' )
1. Kr�;�.�"'- r�� - i -
12'
TYPICAL RETAINING WALL BACKFlLL
AND DRAINAGE DETAtL
DETAI�. 1
Geotechnical • Geologic • Environmen�al
DETAI�
N,T,S,
Provide surface dralnage
� �TY�\
6'
O Wa�er proofing
membrane Coptlonat))
5O Weephole
�Inished surface
1
Native Backfill
Slope or Level
Native Backfill
2O Drain
O3 Filter
fabric
/-- 4O Pipe
Ol WATER PR�❑FING MEMBRANE Coptional>�
Llquid boot or approved equivalent,
O DRAIN�
Mlradraln 6000 or J-drain �00 or equlvalent for
non-waterproofed watts,
Miradraln 6200 or J-draln 20Q or equivalen� for
water proof ed walls,
�l
/4 or flater
3Q F'ILTER FABRIC� .
Mira�l 140N or approved equivalent place fabric flap behind core,
4O PTP��
4' Clnches> dlaMeter perfora-�ed PVC, schedule �40 or approved
alternative with r�inirtum of 1% gradient to proper outtet polnt,
0 WEEPHClLE�
MInIMum 2' Cinches) diar�eter placed at 20' C�Feet) on cen-�ers
along the walt, and 3'' Clnches) above finished sur�ace,
a:, ,
a 6 � �.y� � ; � s :'�
J ,i�.i",3: ? � t .
r �� `
s�k3fls �-��Y �`F �Jy � ,4��i �� �
,t 5�,:�= ' ��.,�.,� �:�� :
.:��,.
RETAINING WALL BACKFILL AND
SUBDR�IN DETAIL �
GE4TEXTILE DRAIN
DETAIL 2,
Geotechnical • Geologic • Environmental
�
DETAIL
N , T , S ,
Provide surface dralnage
1 V l 11 \
0
�
Natfve Backfill
Slope or Level
H/2 _� \..
Min, ��
L
�Water proving
. r�er�brane .
. • ' Coptlonal)
. U3 ��ilter�
fabric
4 Rock
, . 5 Pipe,
Heel width
7 ,�a
�� 1
x'� /4 or flater
?`�
OClean sand
backflll
�1 WATER PR��FING MEMBRANE <opilonal)�
Liquid boot or approved equlvalen-�,
�2 CLEAN SAND BACKFILL+
Mus-� have sand equlvalen-t value of 3Q or greater�
can be densifled by water �e-tting,
� FILTER FABRIC�
Mira�l 140N or approved equlvalen��
4� R❑CK�
1 cubic foot per linear �Feet of pipe of 3/4 to 1-1/2' Cinches) rock
U5 PIPE� .
4" Clnches) dlaMeter per�Forated PVC, schedule 40 or approved
alternative wlth MInIr�uM of 1% gradient_ ta proper outtet polnt,
6� WE�PH[]LE�
MInIMUM 2' <Inches) diameter placed at 20' Cfeet) on centers
along the wall, and 3' Cinches) above finl5hed sur�ace�
:
�!� � j� �: ��w � �.
�
RETAINING WALL AND SUBDRAIN DETAIL
CLEAN SAND BACKFILL
17Z� _�/`\L�3
Geotechnical � Geologic • Environmental
90 should not be used as backfill for retaining walls. For more onerous expansive
situations, backfill and drainage behind the retaining wall should conform with Detail 3
(Retaining Wall And Subdrain Detail Clean Sand Backfill).
Outlets should consist of a 4-inch diameter solid PVC or ABS pipe spaced no greater than
±100 feet apart, with a minimum of two outlets, one on each end. The use of weep holes
in walls higher than 2 feet should not be considered. The surface of the backfill should be
sealed by pavement or the top 18 inches cornpacted with native soil (E.I. < 50). Proper
surface drainage should also be provided. For additional mitigation, consideration should
be given to applying a water-proof inembrane to the back of all retaining structures. The
use of a waterstop should be considered for all concrete and masonry joints.
Wall/Retaininq Wall Footinq Transitions
Site walls are anticipated to be founded on footings designed in accordance with the
recommendations in this report. Should wall footings transition from cut to fill, the civil
designer may specify either:
a) A minimum of a 2-foot overexcavation and recompaction of cut materials for a
distance of 2H, from the point of transition.
b) Increase of the amount of reinforcing steel and wall detailing (i.e., expansion joints
or crack control joints) such that a angular distortion of 1/360 for a distance of 2H
on either side of the transition may be accommodated. Expansion joints should be
sealed with a flexible, non-shrink grout.
c) Embed the footings entirely into native formational material (i.e., deepened
footings).
If transitions from cut to fill transect the wall footing alignment at an angle of less than
45 degrees (plan view), then thE designer should follow recommendation "a" (above) and
until such transition is between 45 and 90 degrees to the wall alignment.
DRIVEWAY, FLATWORK. AND OTHER IMPROVEMENTS
Some of the soil materials on site may be expansive. The effects of expansive soils are
cumulative, and typically occur over the lifetime of any improvements. On relatively level
areas, when the soils are allowed to dry, the dessication and swelling process tends to
cause heaving and distress to flatwork and other improvements. The resulting potential
for distress to improvements may be reduced, but not totally eliminated. To that end, it is
recommended that the developer should notify any homeowners or homeowners
association of this long-term potential for distress. To reduce the likelihood of distress, the
following recommendations are presented for all exterior flatwork:
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1. The subgrade area for concrete slabs shouid be compacted to achieve a minimum
90 percent relative compaction, and then be presoaked to 2 to 3 percentage points
above (or 125 percent ofl the soiis' optimum moisture content, to a depth of
18 inches below subgrade elevation. The moisture content ofthe subgrade should
be verified within 72 hours prior to pouring concrete.
2. Concrete slabs should be cast over a relatively non-yielding surface, consisting of
a 4-inch layer of crushed rock, gravel, or clean sand, that should be compacted and
level prior to pouring concrete. The layer should wet-down completely prior to
pouring concrete, to minimize loss of concrete moisture to the surrounding earth
materials.
3. Exterior slabs should be a minimum of 4 inches thick. Driveway slabs and
approaches should additionally have a thickened edge (12 inches) adjacent to all
landscape areas, to help impede infiltration of landscape water under the slab.
4. The use of transverse and longitudinal control joints are recommended to help
control slab cracking due to concrete shrinkage or expansion. Two ways to
mitigate such cracking are,: a) add a sufficient amount of reinforcing steel,
increasing tensile strength of the slab; and, b) provide an adequate amount of
control and/or expansion joints to accommodate anticipated concrete shrinkage
and expansion.
In order to reduce the potential for unsightly cracks, slabs should be reinforced at
mid-height with a minimum of No. 3 bars placed at 18 inches on center, in each
direction. The exterior slabs should be scored or saw cut, '/2 to 3/s inches deep,
often enough so that no section is greater than 10 feet by 10 feet. For sidewalks or
narrow slabs, control joints should be provided at intervals of every 6 feet. The
slabs should be separated from the foundations and sidewalks with expansion joint
filler material.
5. No traffic should be allowed upon the newly poured concrete slabs until they have
been properly cured to within 75 percent of design strength. Concrete compression
strength should be a minimum of 2,500 psi.
6. Driveways, sidewalks, and patio slabs adjacent to the house should be separated
from the house with thick expansion joint filler material. In areas directly adjacent
to a continuous source of moisture (i.e., irrigation, planters, etc.), all joints should
be additionally sealed with flexible mastic.
7. Planters and walls should not be tied to the house.
8. Overhang structures should be supported on the slabs, or structurally designed
with continuous footings tied in at least two directions.
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9. Any masonry landscape walis that are to be constructed throughout the property
shouid be grouted and articulated in segments no more than 20 feet long. These
segments should be keyed or doweled together.
10. Utilities should be enclosed within a closed utilidor (vault) or designed with flexible
connections to accommodate differential settlement and expansive soil conditions.
11. Positive site drainage should be maintained at all times. Finish grade on the lots
should provide a minimum of 1 to 2 percent fall to the street, as indicated herein.
It should be kept in mind that drainage reversals could occur, including post-
construction settlement, if relatively flat yard drainage gradients are not periodicatly
maintained by the homeowner or homeowners association.
12. Air conditioning (A/C) units should be supported by slabs that are incorporated into
the building foundation or constructed on a rigid slab with flexible couplings for
plumbing and electrical lines. A/C waste water lines should be drained to a suitable
non-erosive outlet.
13. Shrinkage cracks could become excessive if proper finishing and curing practices
are not followed. Finishing and curing practices should be performed per the
Portland Cement Association Guidelines. Mix design should incorporate rate of
curing for climate and time of year, sulfate content of soils, corrosion potential of
soils, and fertilizers used on site.
DEVELOPMENT CRITERIA
Drainaqe
Adequate lot surface drainage is a very important factor in reducing the likelihood of
adverse performance of foundations, hardscape, and slopes. Surface drainage should be
sufficient to prevent ponding of water anywhere on a lot, and especial ly near structures and
tops of slopes. Lot surface drainage should be carefully taken into consideration during
fine grading, landscaping, and building construction. Therefore, care should be taken that
future landscaping or construction activities do not create adverse drainage conditions.
Positive site drainage within lots and common areas should be provided and maintained
at all times. Drainage should not flow uncontrolled down any descending slope. Water
should be directed away from foundations and not allowed to pond and/or seep into the
ground. In general, the area within 5 feet around a structure should slope away from the
structure. We recommend that unpaved lawn and landscape areas have a minimum
gradient of 1 percent sloping away from structures, and whenever possible, should be
above adjacent paved areas. Consideration should be given to avoiding construction of
planters adjacent to structures (buildings, pools, spas, etc.). Pad drainage should be
directed toward the street or other approved area(s). Although not a geotechnical
Karwin Company W.O. 3256-A-SC
2642 through 2646 Jefferson Street January 7, 2004
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1 ' .
requirement, roof gutters, down spouts, or other appropriate means may be utilized to
control roof drainage. Down spouts, or drainage devices should outlet a minimum of 5 feet
from structures or into a subsurface drainage system. Areas of seepage may develop due
to irrigation or heavy rainfall, and should be anticipated. Minirnizing irrigation will lessen
this potential. If areas of seepage develop, recommendations for minimizing this effect
could be provided upon request.
Erosion Control
Cut and fill slopes will be subject.to surficial erosion during and after grading. Onsite earth
materials have a moderate to high erosion potential. Consideration should be given to
providing hay bales and silt fences for the temporary control of surface water, from a
geotechnical viewpoint.
Landscape Maintenance
Only the amount of irrigation necessary to sustain plant life should be provided.
Over-watering the landscape areas will adversely affect proposed site improvements. We
would recommend that any proposed open-bottom planters adjacent to proposed
structures be eliminated for a minimum distance of 10 feet. As an alternative, closed-
bottom type planters could be utilized. An outlet placed in the bottom of the planter, could
be installed to direct drainage away from structures or any exterior concrete flatwork. If
planters are constructed adjacent to structures, the sides and bottom of the planter should
be provided with a moisture barrier to prevent penetration of irrigation water into the
subgrade. Provisions should be made to drain the excess irrigation water from the planters
without saturating the subgrade below or adjacent to the planters. Graded slope areas
should be planted with drought resistant vegetation. Consideration should be given to the
type ofvegetation chosen and their potential effect upon surface improvements (i.e., some
trees will have an effect on concrete flatwork with their e�rtensive root systems). From a
geotechnieal standpoint leaching is not recommended for establishing landscaping. Ifthe
surface soils are processed for the purpose of adding amendments, they should be
recompacted to 90 percent minimum relative compaction.
Gutters and Downs�outs
As previously discussed in the drainage section, the installation of gutters and downspouts
should be considered to collect roof water that may otherwise infiltrate the soils adjacent
to the structures. If utilized, the downspouts should be drained into PVC collector pipes
or non-erosive devices that will carry the water away from the house. Downspouts and
gutters are not a requirement; however, from a geotechnical viewpoint, provided that
positive drainage is incorporated into project design (as discussed previously).
Karwin Company W.O. 3256-A-SC
2642 through 2646 Jefferson Street January 7, 2004
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Subsurface and Surface Water
Subsurface and surface water are not anticipated to affect site development, provided that
the recommendations contained in this report are incorporated into final design and
construction and that prudent surface and subsurface drainage practices are incorporated
into the construction plans. Perched groundwater conditions along zones of contrasting
permeabilities may not be precluded from occurring in the future due to site irrigation, poor
drainage conditions, or damaged utilities, and should be anticipated. Should perched
groundwater conditions develop, this office could assess the affected area(s) and provide
the appropriate recommendations to mitigate the observed groundwater conditions.
Groundwater conditions may change with the introduction of irrigation, rainfall, or other
factors.
Site Improvements
Recommendations for exterior concrete flatwork design and construction can be provided
upon request. If in the future, any additional improvements (e.g., pools, spas, etc.) are
planned forthe site, recommendations concerning the geological or geotechnical aspects
of design and construction of said improvements could be provided upon request. This
oifice should be notified in advance of any fill placement, grading of �the site, or trench
backfilling after rough grading has been completed. This includes any grading, utility
trench, and retaining wall backfills.
Tile Floorinq
Tile flooring can crack, reflecting cracks in the concrete slab below the tile, although small
cracks in a conventional slab may not be significant. Therefore, the designer should
consider additional steel reinforcement for concrete slabs-on-grade where tile will be
placed. The tile installer should consider installation methods that reduce possible
cracking of the tile such as slipsheets. Slipsheets or a vinyl crack isolation membrane
(approved by the Tile Council of America/Ceramic Tile Institute) are recommended
between tile and concrete slabs on grade.
Additional Gradinq
This office should be notified in advance of any fill placement, supplemental regrading of
the site, or trench backfilling after rough grading has been completed. This includes
completion of grading in the street and parking areas and utility trench and retaining wall
backfills.
Footing Trench Excavation
All footing excavations should be observed by a representative of this firm subsequent to
trenching and prior to concrete form and reinforcement placement. The purpose of the
Karwin Company W.O. 3256-A-SC
2642 through 2646 Jefferson Street January 7, 2004
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1 ' .
observations is to verify that the excavations are made into the recommended bearing
material and to the minimum widths and depths recommended for construction. If loose
or compressible materials are exposed within the footing excavation, a deeper footing or
removal and recompaction ofthe subgrade materials would be recommended atthattime.
Footing trench spoil and any excess soils generated from utility trench excavations should
be compacted to a minimum relative compaction of 90 percent, if not removed from the
site.
Trenchinq
Considering the nature of the onsite soils, it should be anticipated that caving or sloughing
could be a factor in subsurface excavations and trenching. Shoring or excavating the
trench walls at the angle of repose (typically 25 to 45 degrees) may be necessary and
should be anticipated. All excavations should be observed by one of our representatives
and minimally conform to CAL-OSHA and local safety codes.
Utility Trench Backfill
1. All interior utility trench backfill should be brought to at least 2 percent above
optimum moisture content and then compacted to obtain a minimum relative
compaction of 90 percent of the laboratory standard. As an alternative for shallow
(12-inch to 18-inch) under-slab trenches, sand having a sand equivalent value of
30 or greater may be utilized and jetted or flooded into place. Observation, probing
and testing should be provided to verify the desired results.
2. Exterior trenches adjacent to, and within areas extending below a 1:1 plane
projected from the outside bottom edge of the footing, and all trenches beneath
hardscape features and in slopes, should be compacted to at least 90 percent of
the laboratory standard. Sand backfill, unless excavated from the trench, should
not be used in these backfill areas. Compaction testing and observations, along
with probing, should be accomplished to verify the desired results.
3. All trench excavations should conform to CAL-OSHA and local safety codes.
4. Utilities crossing grade beams, perimeter beams, or footings should either pass
below the footing or grade beam utilizing a hardened collar or foam spacer, or pass
through the footing or grade beam in accordance with the recommendations of the
structural engineer. -
Karwin Company W.O. 3256-A-SC
2642 through 2646 Jefferson Street January 7, 2004
File:e:\wp9\3200\3256a.rpge Page 26
� ' .
SUMMARY OF RECOMMENDATIONS REGARDING
GEOTECHNICAL OBSERVATION AND TESTING
We recommend that observation and/or testing be perforrned by GSI at each of the
following construction stages:
• During grading/recertification.
• After excavation of building footings, retaining wall footings, and free standing walls
footings, prior to the placement of reinforcing steel or concrete.
• Prior to pouring any slabs or flatwork, after presoaking/presaturation of building
pads and other flatwork subgrade, before the placement of concrete, reinforcing
steel, capillary break (i.e., sand, pea-gravel, etc.), or vapor barriers (i.e., visqueen,
etc.).
• During retaining wall subdrain installation, prior to backfill placement.
• During placement of backfill for area drain, interior plumbing, utility line trenches,
and retaining wall backfill.
• During slope construction/repair.
• When any unusual soil conditions are encountered during any construction
operations, subsequent to the issuance of this report.
• When any developer or homeowner improvements, such as flatwork, spas, pools,
walls, etc., are.constructed.
• A report of geotechnical observation and testing should be provided at the
conclusion of each of the above stages, in order to provide concise and clear
documentation of site work, and/or to comply with code requirements.
OTHER DESIGN PROFESSIONALS/CONSULTANTS
The design civil engineer, structural engineer, post-tension designer, architect, landscape
architect, wall designer, etc., should review the recommendations provided herein,
incorporate those recommendations into all their respective plans, and by explicit
reference, make this report part of their project plans.
Karwin Company W.O. 3256-A-SC
2642 through 2646 Jefferson Street January 7, 2004
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1 � o
PLAN REVIEW
Final project plans shouid be reviewed by this office prior to construction, so that
construction is in accordance with the conclusions and recommendations of this report.
Based on our review, supplemental recommendations and/or further geotechnical studies
may be warranted.
LIMITATIONS
The materials encountered on the project site and utilized for our analysis are believed
representative of the area; however, soil and bedrock materials vary in character between
excavations and natural outcrops or conditions exposed during mass grading. Site
conditions may vary due to seasonal changes or other factors.
Inasmuch as our study is based upon our review and engineering analyses and laboratory
data, the conclusions and recommendations are professional opinions. These opinions
have been derived in accordance with current standards of practice, and no warranty is
�xpressed or implied. Standards of pr�ctice are subject to change with time. GSI assumes
no responsibility or liability for work or testing performed by others, or their inaction; or
work performed when GSI is not requested to be onsite, to evaluate if our
recommendations have been properly implemented. Use of this report constitutes an
agreement and consent by the user to all the limitations outlined above, notwithstanding
any other agreements that may be in place. In addition, this report may be subject to
review by the controlling authorities.
Karwin Company W.O. 3256-A-SC
2642 through 2646 Jefferson Street January 7, 2004
File;e:\wp9\3200\3256a.rpge Pag2 28
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APPENDIX A _ _ I
i
�
REFf RENCES '
- �
APPENDIX A
REFERENCES
Blake, T.F., 2000a, EQFAULT, A computer program for the estimation of peak horizontal
acceleration from 3-D fault sources; Windows 95/98 version.
, 2000b, EQSEARCH, A computer program for the estimation of peak horizontal
acceleration from California historical earthquake catalogs; Updated to June, 2003,
Windows 95/98 version.
, 2000c, FRISKSP, A computer program for the probabilistic estimation of peak
acceleration and uniform hazard spectra using 3-D faults as earthquake sources;
Windows 95/98 version.
Bozorgnia, Y., Campbell K.W., and Niazi, M.,1999, Vertical ground motion: Characteristics,
relationship with horizontal component, and building-code implications;
Proceedings of the SMIP99 seminar on utilization of strong-motion data,
September 15, Oakland, pp. 23-49,
Campbell, K.W. and Bozorgnia, Y., 1997, Attenuation relations for soft rock conditions; in
EQFAULT, A computer program for the estimation of peak horizontal acceleration
from 3-D fault sources; Windows 95/98 version, Blake, 2000a.
, 1994, Near-source attenuation of peak horizontal acceleration frorn worldwide
accelrograms recorded from 1957 to 1993; Proceedings, Fifth U.S. National
Conference on Earthquake Engineering, volume III, Earthquake Engineering
Research Institute, pp 292-293.
GeoSoils, Inc., 2002, Preliminary geotechnical evaluation, Carlsbad Senior condominium
project, 2642 through 2646 Jefferson Street, Carlsbad, San Diego Coun#y,
California, W.O. 3256-A-SC, dated April 10.
Hart, E.W. and Bryant, W.A. 1997, Fault-rupture Hazard Zones in California, Alquist-Priolo
Earthquake Fault Zoning act with Index to Earthquake Fault Maps; California
Division of Mines and Geology Special Publication 42.
International Conference of Building Officials, 1997, Uniform building code: Whittier,
California, vol. 1, 2, and 3.
Jennings, C.W., 1994, Fault activity map of California and adjacent areas: California
Division of Mines and Geology, Map Sheet No. 6, scale 1:750,000.
Joyner, W.B, and Boore, b.M.,1982a, Estimation of response-spectral values as functions
of magnitude, distance and site conditions, in eds., Johnson, J.A., Campbell, K.W.,
and Blake, T.F.: AEG Short Course, Seismic Hazard Analysis, June 18, 1994.
i , .
Joyner, W.B, and Boore, D.M., 1982b, Prediction of earthquake response spectra, U.S.
Geological Survey Open-File Report 82-977, 16p.
Kuhn, G.G., and Shepard, F.P., 2000, Neotectonics in the North Coastal Area, San Diego
County, California: p.1-88: in R.J. Shlemon G.G. Kuhn, and M.R. Legg, eds.,.
Neotectonics and Coastal Instability Orange and Northern San Diego Counties,
California, Joint Field Conference, Volume 1, AAPG, Pacific Section SPE, Western
Section Held in Long Beach, California, June 19-22.
Petersen, Mark D., Bryant, W.A., and Cramer, C.H., 1996, Interim table of fault parameters
used by the California Division of Mines and Geology to compile the probabilistic
seismic hazard maps of California.
Sadigh, K., Egan, J., and Youngs, R.,1987, Predictive ground motion equations, in Joyner,
W.B. and Boore, D.M., 1988, Measurement, characterization, and prediction of
strong ground motion, in Von Thun, J.L., ed., Earthquake engineering and soil
dynamics II, recentadvances in ground motion evaluation, American Society ofCivil
Engineers Geotechnical Special Publication No. 20, pp. 43-102.
Tan, S,S., and Kennedy, Michael P., 1996, Geologic maps of the northwestern part of
San Diego County, California: California Division of Mines and Geology, Open File
Report 96-02.
Karwin Company Appendix A
File:e:\wp9\3200\3256a.rpge PBge 2
GeoSoils, Ittc.
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APPENDIX B
I
. BORING LOGS I
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BORING LOG
GeoSoils, Inc.
W. O. 3256-A-SC
PROJECT.' �RWIN COMPANY BORING B-� SHEET 1 OF 1
CARLSBAD SENIOR FACILITY
DATE DCCAVATED 3-18-02
Sample SAMPLE METHOD: HAND AUGERlRING SAMPLER
� Standard Penetration Test
o � � Water Seepage into hole
� � � a �, o � Undisturbed, Ring Samp/e
L y � fn (n� �v � � '
N � C'n � (n �. Z' O '�
o m�� m � v, o � v� Description of Material
GW COI.LUVIUM:
5M .�'.• 0' CRUSHED AGGREGATE
:w:; @%4 SILTY SAND, reddish brown, damp, loose; abundant
�-�:• organics.
:�.•
SM 109,5 3.6 1.8.8 :�:: WEATHERED TERRACE DEPOSITS:
:��: @ 1' SILTY SAND, reddish brown, damp, medium dense.
��.
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• :;; :
• �;; .
: �:.
•;>',•:
SM TERRACE DEPOSITS:
@ 2%z SILTY SAND, reddish brown, damp, dense.
Practical Refusai @ 2'/Z
No Groundwater Encountered or Caving
Backfilled 3-18-02
5
CARLSBAD SENIOR FACILITY G@OSOIIS� IIIC. pL,qTE �-�
BORING LOG
GeoSoils, Inc.
►�y, O. 3256-A-SC
PROJECT: �RWIN COMPANY BORING B-Z SHEET 1 OF �
CARLSBAD SENIOR FACILITY
DATE IXCAVATED 3-18-02
Sample SAMPLE METHOD: HAND AUGER/RING SAMPLER
� Standard Penetration Test
� � � Water Seepage into ho/e
� � � a �, o � Undisturbed, Ring Sample �;
�� o c�- � r.
a y �
o m' �= m ��n o � v, Description of Material
G�► COLLUVIUM: `
ML � 0' CRUSHED AGGREGATE !
�@%: CLAYEY SANDY SILT; dark brown, wet, loose; abundant
r organics.
r.
SM ;�:: WEATHERED TERRACE DEP051TS:
�:��: @ 1' SILTY SAND, reddish brown, moist, medium dense; trace
122.5 10.2 77.1 ;�:: organics.
•:;.. � c
. �,.: i,
5M :�.: TERRACE DEPOSITS: �
�:.;�: @ 2' SILTY SAND, reddish brown, moist, medium dense. j
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Total Depth = 5' � �
No Groundwater Encountered or Caving �
,
Backfilled 3-18-02 �
;;
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CARLSBAD SENIOR FACILITY GC:'OSOIIS� IIIC. PLATE B-2
BORING LOG
GeoSoils, Inc.
W.O. 3256-A-SC
PROJECT.• �RWIN COMPANY BORING B-3 SHEET � OF 1
CARLSBAD SENIOR FACILITY
DATE DCCAVATED 3-18-02
Sampie SAMPLE METHOD: HAND AUGER/RING SAMPLER �
� Standard PenetraEion Test
�
o � Water Seepage into hole
v � � ;, o � Undisturbed, Rinq Samp/e
a
� y -o � � a° c -- � ro ,
o. x v.o 3 U E _ �' �
o m�w �, �; o � �, Description of Material
SM :�.: COLLUVIUM:
�:��; @ 0' SILTY SAND, reddish brown, dry, loose; roots and rootlets,
:�:; trace trash (glass, coin).
. �;,. �
. �.: ;;
S►' : �: WEATHERED TERRACE DEPOSITS: ''
••: @ 1' SAND, reddish brown, damp to moist, medium dense; fine to '
•�• medium grained, trace organics. `
I
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SM :�:: TERRACE DEPOSITS: �
•;��: @ 3' SILTY SAND, reddish brown, moist, medium dense. � ;
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Total Depth = 6' i;
No Groundwater Encountered or Caving �
Backfiiled 3-18-02 �
C<
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,
CARLSBAD SENIOR FACILITY GC:OSOIIS� IIIC. PLATE B-3
BORING LOG
GeoSoils, Inc.
►M,p, 3256-A-SC
i.
PROJECT: �RWIN COMPANY BORING B-4 SNEET � OF �
CARLSBAD SENIOR FACILITY
DATE DCCAVATED 3-� 8-a2
Sample SAMPLE METHOD: HAND AUGER/RING SAMPLER
� Standard Penetration Test
� � � Wafer Seepage into hole
� c�i " o � Undisturbed, Ring Samp/e
� � ... n m _
w N� y �� � v y �
'� E
o m' �= m � �n o � v", Description of Material
SM : �:; COLLUVIUM:
..>�; @ 0' SILTY SAND, dark reddish brown, dry to damp, loose; roots
' �: � and rootlets, trace trash (glass).
::.-.
• �� '�
•s:
5M : �.: WEATHERED TERRACE DEPOSITS:
•:.;�: @ 1' SILTY SAND, orange brown to reddish brown, damp to moist,
;�:; medium dense to dense; trace organics.
. ;,,:. �
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SM TERRACE DEPOSITS: �
@ 3'/z SILTY SAND, orange brown to reddish brown, moist, dense; ',
trace organics. !
Practical Refusal @ 3'/z
No Groundwater Encountered or Caving
Backfilled 3-18-02
5
CARLSBAD SENIOR FACILITY G@OSOIIS, I IIC. PLATE B-4
BORING LOG
GeoSoils, Inc.
W.O. 3256-A-SC
PROJECT.� �RWIN COMPANY BORING B-5 SNEET � OF 1
CARLSBAD SENIOR FACILITY
DATE EXCAVATED 3-18-02
Sample SAMPLE METHOD: HAND AUGER/RING SAMPLER
� Standard Penetration Test
� � � Water Seepage into hole
� � " o � Undistur6ed, Ring Sample
� � ^' n d
� ,� � y � .n j � Y f-°
a '—� 'v .n o V E N w
o m' �� m ��n o � v, Description of Material
SM :�:: COLLUVIUM:
�,r�: @ 0' SILTY SAND, dark brown, moist, loose; roots and rootlets.
.�.
: :r: •
;,: ,
.�;
SM :�;: WEATHERED TERRACE DEPOSITS:
�;.��: @ 1' SILTY SAND, orange brown to reddish b�own, moist, medium
; f:; dense; trace organics, dark oxide staining (manganese?)
, ;,;,.
• :;� :
• ;.; .
: ;;:: �
. ;.,:.:
��.
::;�: �
. �..
SM ;�;: TERRACE DEPOSITS;
•;;,•: @ 3' SILTY SAND, orange brown to reddish brown, damp to moist,
; �:; dense to very dense.
. ;,,;. •
��:
��.
:�:�
. ;.,;.:
.�, .
::;�: �
��•;
5 Practical Refusal @ 5'
No Groundwater Encountered or Caving
Backfilled 3-18-02
CARLSBAD SENIOR FACILITY ' GGOSOIIS� (IIC. PLATE B-5