HomeMy WebLinkAboutPD 2019-0012; BLOCK RESIDENCE; PRELIMINARY GEOTECHNICAL INVESTIGATION, PROPOSED BLOCK RESIDENCE; 2019-07-19w
CHRISTIAN WHEELER
EN GIN EER.ING - RECORD COPY
/L-,Jto
Initial Date
REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION
PROPOSED BLOCK RESIDENCE
3291 HIGHLAND AVENUE
CARLSBAD, CALIFORNIA
PREPARED FOR RECEIVED
BRAD BLOCK AU0 0 a LULU
3512 SEAGATE WAY, SUITE 130 LAND DEVELOPMENT
OCEANSIDE, CALIFORNIA 92056 ENGINEERING
RECkVE
LAND DEV4ZMT
ENGEEIGk
CHRISTIAN WHEELER ENGINEERING
3980 HOME AVENUE
SAN DIEGO, CALIFORNIA 92105
3980 Home Avenue + San Diego, CA 92105 + 619-550-1700 + FAX 619-550-1701
CHRiSTIAN WHEELER
ENGINEERING
July 19, 2019
Brad Block C\X'E 2190330.02
3512 Seagate Way, Suite 130
Oceanside, California 92056
Subject: Report of Preliminary Geotechnical Investigation
Proposed Block Residence, 3291 Highland Drive, Carlsbad, California
Dear Mr. Block:
In accordance with your request and our proposal dated June 11, 2019, we have completed a
preliminary geotechnical investigation for the proposed residence to be constructed at the subject
property. We are presenting herewith a report of our findings and recommendations.
It is our opinion and judgment that no geotechnical conditions exist at or in the vicinity of the subject
property that would preclude the construction of the subject project, provided the recommendations
included in this report are implemented.
If you have any questions after reviewing this report, please do not hesitate to contact our office. This
opportunity to be of professional service is sincerely appreciated.
Z G4EER¼ N
DANIEL J. 9. FLOWERS
No. 2686 ; -1
b)
Respectfully submitted,
CHRISTIAN WHEELER ENGINEERING
Daniler,
DBA:djf
ec: brad@gcs-inc.com
Daniel J. Flowers, CEG #2686
3980 Home Avenue + San Diego, CA 92105 + 619-550-1700 + FAX 619-550-1701
TABLE OF CONTENTS
Page
Introduction and Project Description . 1
Scopeof Services....................................................................................................................................2
Findings..................................................................................................................................................3
SiteDescription..................................................................................................................................3
ExistingFootings................................................................................................................................4
General Geology and Subsurface Conditions.....................................................................................4
Geologic Setting and Soil Description.............................................................................................4
ArtificialFill................................................................................................................................4
Topsoil......................................................................................................................................... 4
OldParalic Deposits....................................................................................................................5
Groundwater...................................................................................................................................5
TectonicSetting..............................................................................................................................5
Geologic Hazards................................................................................................................................6
General............................................................................................................................................6
SlopeStability.................................................................................................................................6
Liquefaction.....................................................................................................................................7
Flooding..........................................................................................................................................7
Tsunamis.........................................................................................................................................7
Seiches.............................................................................................................................................7
Other Potential Geologic Hazards..................................................................................................7
Conclusions............................................................................................................................................7
Recommendations..................................................................................................................................8
Gradingand Earthwork......................................................................................................................8
General............................................................................................................................................8
PregradeMeeting.............................................................................................................................8
Observationof Grading..................................................................................................................8
Clearingand Grubbing....................................................................................................................9
SitePreparation...............................................................................................................................9
Processingof Fill Areas...................................................................................................................9
Compaction and Method of Filling .................................................................................................. 9
SurfaceDrainage............................................................................................................................10
Foundations......................................................................................................................................10
General..........................................................................................................................................10
Dimensions...................................................................................................................................10
BearingCapacity............................................................................................................................11
FootingReinforcing ....................................................................................................................... 11
Lateral Load Resistance .................................................................................................................. 11
Underpinning................................................................................................................................ 11
PropertyLine Footings..................................................................................................................12
Footing Excavation Compaction ...................................................................................................12
Foundation Excavation Observation..............................................................................................12
SettlementCharacteristics.............................................................................................................12
ExpansiveCharacteristics...............................................................................................................12
FoundationPlan Review................................................................................................................12
SolubleSulfates..............................................................................................................................13
CWE 2190330.02
Proposed Block Residence
3291 Highland Drive
Carlsbad, California
Seismic Design Factors . 13
On-Grade Slabs.................................................................................................................................14
General 14
InteriorFloor Slabs ......................................................................................... ...............................14
Under-Slab Vapor Retarders..........................................................................................................14
Exterior Concrete Flatwork ........................................... . ................ ..............................................15
EarthRetaining Walls.......................................................................................................................15
Foundations..................................................................................................................................15
PassivePressure.............................................................................................................................15
ActivePressure..............................................................................................................................15
Waterproofing and Wall Drainage Systems....................................................................................16
Backfill...........................................................................................................................................16
Limitations...........................................................................................................................................16
Review, Observation and Testing.....................................................................................................16
Uniformityof Conditions................................................................................................................16
Changein Scope ...............................................................................................................................17
TimeLimitations ............................................................................................................................... 17
ProfessionalStandard........................................................................................................................17
Client's Responsibility......................................................................................................................18
FieldExplorations................................................................................................................................18
LaboratoryTesting...............................................................................................................................19
ATTACHMENTS
FIGURES
Figure 1 Site Vicinity Map, Follows Page 1
PLATES
Plate 1 Site Plan & Geotechmcal Map
Plate 2 Typical Retaining Wall Drain System Detail
APPENDICES
Appendix A Subsurface Exploration Logs
Appendix B Laboratory Test Results
Appendix C References
Appendix D Recommended Grading Specifications-General Provisions
CWE 2190330.02
Proposed Block Residence
3291 Highland Drive Carlsbad, California
PRELIMINARY GEOTECHNICAL INVESTIGATION
PROPOSED BLOCK RESIDENCE
3291 HIGHLAND DRIVE
CARLSBAD, CALIFORNIA
INTRODUCTION AND PROJECT DESCRIPTION
This report presents the results of a preliminary geotechnical investigation performed for the proposed
residential project to be constructed at 3291 Highland Drive, Carlsbad, California. The following
Figure Number 1 presents a vicinity map showing the location of the property.
We understand that the subject project will consist of remodeling and constructing one-story and two-
story lateral additions to the existing residence. The additions to the west of the residence are
anticipated to be partially subterranean. The project will also entail the construction of decks and a
two-story garage/accessory dwelling unit (ADU) to the northwest of the residence. We anticipate that
the proposed lateral additions and garage/ADU will be of conventional, wood-frame construction
whereas the underground portion of the additions will be of masonry and/or concrete construction.
The proposed additions as well as the garage/ADU will supported by new shallow foundations and
will incorporate conventional concrete on-grade floor slabs. In addition, a driveway with associated
retaining walls up to about 3 feet high as well as property line walls up to approximately 4 feet high
are proposed. Grading to accommodate the proposed construction is expected to consist of cuts up to
approximately 7 feet and fills of less than a few feet from existing grades.
To aid us in the preparation of this report, we were provided, with topographic base map prepared by
Omega Land Surveying, Inc., dated April 3, 2019, structural plans prepared by PCSD Engineering,
dated May 17, 2019, a grading concept plan of unknown origin dated June 6, 20119, and a set of
miscellaneous architectural plans of unknown origin, dated May 2, 2019. A copy of the grading
concept plan has been used as the base for our Site Plan and Geotechnical Map, and is included herein
as Plate No. 1.
SITE VICINITY
OpenStreetMap contributors
L 1
7
I
. ,..
F -
1,1
U
PROJECT SITE
tt
-4- ->
C7 4-
-1•
DATE: JULY 2019
BY: SRD
PROPOSED BLOCK RESIDENCE
3291 HIGHLAND DRIVE
CARLSBAD, CALIFORNIA
JOB NO.: 2190330.02
FIGURE NO.: 1
CHRISTIAN WHEELER
ENGINEERING
CWE 2190330.02 July 19, 2019 Page No. 2
This report has been prepared for the exclusive use of Brad Block, and his design consultants, for
specific application to the project described herein. Should the project be modified, the conclusions
and recommendations presented in this report should be reviewed by Christian Wheeler Engineering
for conformance with our recommendations and to determine whether any additional subsurface
investigation, laboratory testing and/or recommendations are necessary. Our professional services
have been performed, our findings obtained and our recommendations prepared in accordance with
generally accepted engineering principles and practices. This warranty is in lieu of all other
warranties, expressed or implied.
SCOPE OF SERVICES
Our preliminary geotechnical investigation consisted of surface reconnaissance, subsurface exploration,
obtaining representative soil samples, laboratory testing, analysis of the field and laboratory data, and
review of relevant geologic literature. Our scope of service did not include assessment of hazardous
substance contamination, recommendations to prevent floor slab moisture intrusion or the formation
of mold within the structures, evaluation or design of storm water infiltration facilities, or any other
services not specifically described in the scope of services presented below.
More specifically, the intent of our proposed investigation was to:
Excavate 8 hand-dug test pits to explore the existing soil conditions and collect representative
soil samples.
Measure the existing footings in at least two locations and evaluate their geotechnical
suitability to support additional loads.
Backfill the test pits with the removed soil. It should be noted that the soil was not compacted
and will have to be removed and replaced as compacted fill during the future site grading.
Evaluate, by laboratory tests and our past experience with similar soil types, the engineering
properties of the various soil strata that may influence the proposed construction, including
bearing.capaities, expansive characteristics and settlement potential.
Describe the general geology at the site including possible geologic hazards that could have an
effect on the proposed construction, and provide the seismic design parameters in accordance
with the 2016 edition of the California Building Code.
CWE 2190330.02 July 19, 2019 Page No. 3
Discuss potential construction difficulties that may be encountered due to soil conditions,
groundwater or geologic hazards, and provide geotechnical recommendations to mitigate these
construction difficulties.
Provide site preparation and grading recommendations for the anticipated work.
Provide foundation recommendations for the type of construction anticipated and develop soil
engineering design criteria for the recommended foundation designs.
Provide design parameters for restrained retaining walls.
Provide a preliminary geotechnical report that presents the results of our investigation which
includes a plot plan showing the location of our subsurface explorations, excavation logs,
laboratory test results, and our conclusions and recommendations for the proposed project.
Although a test for the presence of soluble sulfates within the soils that may be in contact with
reinforced concrete was performed as part of the scope of our services, it should be understood
Christian Wheeler Engineering does not practice corrosion engineering, if such an analysis is
considered necessary, we recommend that the client retain an engineering firm that specializes in this
field to consult with them on this matter. The results of the test should only be used as a guideline to
determine whether additional testing and analysis is necessary.
FINDINGS
SITE DESCRIPTION
The subject site consists of a developed, irregular-shaped lot located at 3291 Highland Drive, Carlsbad,
California. The site is identified as Accessors Parcel Number 205-051-11 and presently supports a one-
story, single-family residence and other associated improvements. A detached garage previously existed
to the northwest of the residence which was recently demolished. The property is bounded on the east
by Highland Drive and on the remaining sides by developed residential properties. According to the
topographic base map (Omega, 2019), the site slopes gently to the west with elevations ranging from
approximately156 feet at the westerly property line to approximately 171 feet at the easterly property
line.
CWE 2190330.02 July 19, 2019 Page No. 4
EXISTING FOOTINGS
The footings supporting the existing structure were exposed at 2 locations. The following table
summarizes our measurements of the existing footing and the foundation soils. In both locations the
footings appeared to have been reinforced relatively recently by placing approximately 4 inches to 6
inches of concrete adjacent to the footings which extends to varying depths. Sketches of the footings
are presented in Appendix A.
TABLE I: EXISTING FOOTINGS
Pit Location Footing Depth/ Width Foundation Soils
Pit P-1(North) 14"/2" Loose to Medium Dense (Qop)*
Pit P1(East)** 6"/12" Loose to Medium Dense (Qop)*
Pit P-2 6"/15" Loose to Medium Dense (Qop)*
*Old paralic deposits
** Leach line encased in crushed rock under footing
GENERAL GEOLOGY AND SUBSURFACE CONDITIONS
GEOLOGIC SETTING AND SOIL DESCRIPTION: The subject site is located within the Coastal
Plains Physiographic Province of San Diego County. Based on the results of our subsurface explorations,
and analysis of readily available, pertinent geologic literature, it was determined that the area of the site
investigated site is generally underlain by topsoil and old paralic deposits. These materials are described
below:
ARTIFICIAL FILL (Qaf): A layer of artificial fill approximately 1-foot-thick was encountered in
test pit P-6. The upper 4 inches of the fill material appeared to be imported DG associated with the
existing driveway. Artificial fill may exist in areas of the site not investigated. These materials
generally consisted of light gray and light brown, dry, loose, silty sand (SM. The artificial fill was
judged to have a very low Expansion Index (El <20).
TOPSOIL: A relatively thin layer of topsoil was encountered underlying the artificial fill or at
grade throughout the site, except in test pit P-i north. As encountered in the test pits, the topsoil
layer had a maximum thickness of about 1½ feet (test pit P-3). Tile topsoil may be thicker in areas
of the site not investigated. These materials generally consisted of light grayish-brown and light
CWE 2190330.02 July 19, 2019 Page No. 5
brown, dry, very loose and loose, silty sand (SM). The topsoil was judged to have a very low
Expansion Index (El <20).
OLD PAR.AUC DEPOSITS (Qop): Quaternary-age old paralic deposits were encountered
underlying the surficial soils throughout the site. These materials generally consisted of light
brown, orangish-brown reddish-brown and grayish-brown, dry and moist, loose to medium, silty
sand (SM). The old paralic deposits were found to be loose to medium dense. The old paralic
deposits were judged to have a very low Expansion Index (El <20).
GROUNDWATER: No groundwater or seepage was encountered in our subsurface explorations.
However, it should be recognized that minor groundwater seepage problems might occur after
construction and landscaping are completed, even at a site where none were present before
construction. These are usually minor phenomena and are often the result of an alteration in drainage
patterns and/or an increase in irrigation water. Based on the anticipated construction and the
permeability of the on-site soils, it is our opinion that any seepage problems that may occur will be
minor in extent. It is further our opinion that these problems can be most effectively corrected on an
individual basis if and when they occur.
TECTONIC SETTING: No faults are known to traverse the subject site. However, it should be noted
that much of Southern California, including the San Diego County area, is characterized by a series of
Quaternary-age fault zones that consist of several individual, en echelon faults that generally strike in a
northerly to northwesterly direction. Some of these fault zones (andthe individual faults within the zone)
are classified as "active" according to the criteria of the California Division of Mines and Geology. Active
fault zones are those that have shown conclusive evidence of faulting during the Holocene Epoch (the
most recent 11,000 years). The Division of Mines and Geology used the term "potentially active" on
Earthquake Fault Zone maps until 1988 to refer to all Quaternary-age (last 1.6 million years) faults for the
purpose of evaluation for possible zonation in accordance with the Alquist-Priolo Earthquake Fault
Zoning Act and identified all Quaternary-age faults as "potentially active" except for certain faults that
were presumed to be inactive based on direct geologic evidence of inactivity during all of Holocene time
or longer. Some faults considered to be "potentially active" would be considered to be "active" but lack
specific criteria used by the State Geologist, such as sufficiently active and well-defined. Faults older than
Quaternary-age are not specifically defined in Special Publication 42, Fault Rupture Hazard Zones in
California, published by the California Division of Mines and Geology. However, it is generally accepted
CWE 2190330.02 July 19, 2019 Page No. 6
that faults showing no movement during the Quaternary period may be considered to be "inactive".
Regionally, guidelines of the City of San Diego indicate that since the beginning of the Pleistocene Epoch
marks the boundary between "potentially active" and "inactive" faults, unfaulted Pleistocene-age deposits
are accepted as evidence that a fault may be considered to be "inactive."
A review of available geologic maps indicates that the nearest active fault zone is the Newport-
Inglewood- Rose Canyon Fault Zone (RCFZ), located approximately 3 miles to the west of the site.
Other fault zones in the region that could possibly affect the site include the Coronado Bank fault
zones to the south west, the San Diego Trough and San Clemente fault zones to the west, the
Newport-Inglewood and Palos Verdes fault zones to the northwest, and the Elsinore, Earthquake
Valley, San Jacinto, and San Andreas fault zones to the northeast.
GEOLOGIC HAZARDS
GENERAL: No geologic hazards of sufficient magnitude to preclude the continued residential use or
redevelopment of the site are known to exist. In our professional opinion and to the best of our
knowledge, the site should be suitable for continued residential use or-future redevelopment, provided
sound engineering, construction, and site maintenance procedures are followed should the site be
redeveloped.
SLOPE STABILITY: The Relative Landslide Susceptibility and Landslide Distribution Map of the
Oceanside Quadrangle prepared by the California Division of Mines and Geology indicates that the
site is situated within Relative Landslide Susceptibility Area 3-1. Area 3 is considered to be "generally
susceptible" to slope failures; Subarea 3-1 identifies areas with slopes that are at or near their stability
limits due to a combination of weak materials and steep slopes. Most slopes in Subarea 3-1 do not
contain landslide deposits but may be expected to fail, locally, when adversely modified. We have also
reviewed the publication, "Recent Slope Failures, Ancient Landslides, and related Geology of the
North-Central Coastal Area, San Diego County" by Weber, 1982. This publication does not indicate
any slope instability at the subject site.
Based on our findings and the relatively flat topography on and surrounding the subject site it is our
opinion that the potential for slope instability or lancisliding can be considered very low. Further, it is
CWE 2190330.02 July 19, 2019 Page No. 7
anticipated that the proposed construction will not increase the potential for slope instability on or
immediately adjacent to the subject site.
LIQUEFACTION: The near-surface soils encountered at the site are not considered susceptible to
liquefaction due to such factors as soil density and the absence of shallow groundwater conditions.
FLOODING: As delineated on the Flood Insurance Rate Map (FIRM), map number 06073C0762G
prepared by the Federal Emergency Management Agency, the site is in Zone X which is considered to
be an "area of minimal flood hazard." Areas of minimal flood hazards are located outside of the
boundaries of both the 100-year and 500-year flood zones.
TSUNAMIS: Tsunamis are great sea waves produced by a submarine earthquake or volcanic eruption.
Review of the referenced Tsunami Inundation Map of the Oceanside/San Luis Rey Quadrangle
indicates that the site is outside of both the projected tsunami inundation line and tsunami inundation
area (CalEMA, 2009).
SEICHES: Seiches are periodic oscillations in large bodies of water such as lakes, harbors, bays or
reservoirs. Due to the site's location, it is considered to have a negligible risk potential for seiches.
OTHER POTENTIAL GEOLOGIC HAZARDS: Other potential geologic hazards such as,
volcanoes or seismic-induced settlement should be considered to be negligible or nonexistent.
CONCLUSIONS
It is our professional opinion and judgment that no geotechnical conditions exist at or the general
vicinity of the subject property that would preclude the construction of the proposed additions and
ADU provided the recommendations presented herein are followed. The main geotechnical conditions
affecting the proposed construction include potentially compressible fill soils, topsoil and old paralic
deposits, and undersized existing footings. These conditions are discussed hereinafter.
The site was found to be underlain by potentially compressible fill soils, topsoil, and old paralic
deposits. These soils are considered unsuitable, in their present condition, for the support of
settlement-sensitive improvements. In order to mitigate this condition, it is recommended that these
CWE 2190330.02 July 19, 2019 Page No. 8
materials be partially removed and replaced as compacted fill. In addition, special consideration, as
described hereinafter, will be necessary in areas of the site were tis operation is unfeasible.
The existing footings were found to be undersized and founded on potentially compressible soils. As
such, existing footings to receive new loads should be underpinned. Consideration should be given to
underpinning all footings to remain.
The site is located in an area that is relatively free of geologic hazards that will have a significant effect
on the proposed construction. The most likely geologic hazard that could affect the site is ground
shaking due to seismic activity along one of the regional active faults. However, construction in
accordance with the requirements of the most recent edition of the California Building Code and the
local governmental agencies should provide a level of life-safety suitable for the type of development
proposed.
RECOMMENDATIONS
GRADING AND EARTHWORK
GENERAL: All grading should conform to the guidelines presented in the current edition of the
California Building Code, the minimum requirements of the City of Carlsbad, and the recommended
Grading Specifications and Special Provisions attached hereto, except where specifically superseded in the
text of this report.
PREGRADE MEETING: It is recommended that a pregrade meeting including the grading
contractor, the client, and a representative from Christian 'Wheeler Engineering be performed, to
discuss the recommendations of this report and address any issues that may affect grading operations.
OBSERVATION OF GRADING: Continuous observation by the Geotechnical Consultant is
essential during the grading operation to confirm conditions anticipated by our investigation, to allow
adjustments in design criteria to reflect actual field conditions exposed, and to determine that the
grading proceeds in general accordance with the recommendations contained herein.
CWE 2190330.02 July 19, 2019 Page No. 9
CLEARING AND GRUBBING: Site preparation should begin with the removal of existing
improvements slated for demolition. The resulting debris and any existing vegetation and other
deleterious materials in areas to receive proposed improvements or new fill soils should be removed
from the site.
SITE PREPARATION: It is recommended that existing fill soils, topsoil and old paralic deposits
underlying the proposed addition, ADU, new fills and any proposed exterior settlement sensitive
improvements be removed to a minimum depth 5 feet from existing or proposed grade, whichever is
more, Lateral removals limits should extend at least 5 feet beyond the perimeter of the improvements
or removal depth, whichever is more. No removals are recommended within 3 feet existing
improvements to remain or beyond property lines. All excavated areas should be approved by the
geotechnical engineer or his representative prior to replacing any of the excavated soils. The excavated
materials can be replaced as properly compacted fill in accordance with the recommendations
presented in the "Compaction and Method of Filling" section of this report. However, the existing fill
encountered in the test pits was found to contain abundant roots and may have to be thoroughly
cleaned prior to placement as compacted fill.
PROCESSING OF FILL AREAS: Prior to placing any new fill soils or constructing any new
improvements in areas that have been cleaned out to receive fill, the exposed soils should be scarified
to a depth of about 12 inches, watered thoroughly, and compacted to at least 90 percent relative
compaction. This recommendation does not apply to the proposed addition.
COMPACTION AND METHOD OF FILLING: In general, all structural fill placed at the site
should be compacted to a relative compaction of at least 90 percent of its maximum laboratory dry
density as determined by ASTM Laboratory Test D1557. Fills should be placed at or slightly above
optimum moisture content, in lifts six to eight inches thick, with each lift compacted by mechanical
means. Fills should consist of approved earth material, free of trash or debris, roots, vegetation, or other
materials determined to be unsuitable by the Geotechnical Consultant. Fill material should be free of
rocks or lumps of soil in excess of 3 inches in maximum dimension.
Utility trench backfill within 5 feet of the proposed structures and beneath all concrete flatwork or
pavements should be compacted to a minimum of 90 percent of its maximum dry density.
CWE 2190330.02 July 19, 2019 Page No. 10
SURFACE DRAINAGE: The drainage around the proposed improvements should be designed to
collect and direct surface water away from proposed improvements toward appropriate drainage
facilities. Rain gutters with downspouts that discharge runoff away from the structures into controlled
drainage devices are recommended.
The ground around the proposed improvements should be graded so that surface water flows rapidly
away from the improvements without ponding. In general, we recommend that the ground adjacent to
structure slope away at a gradient of at least 5 percent for a minimum distance of 10 feet. If the minimum
distance of 10 feet cannot be achieved, an alternative method of drainage runoff away from the building
at the termination of the 5 percent slope will need to be used. Swales and impervious surfaces that are
located within 10 feet of the building should have a minimum slope of 2 percent. It is essential that new
and existing drainage patterns be coordinated to produce proper drainage. Pervious hardscape surfaces
adjacent to structures should be similarly graded.
Drainage patterns provided at the time of construction should be maintained throughout the life of the
proposed improvements. Site irrigation should be limited to the minimum necessary to sustain
landscape growth. Over watering should be avoided. Should excessive irrigation, impaired drainage, or
unusually high rainfall occur, zones of wet or saturated soil may develop.
FOUNDATIONS
GENERAL: Based on our findings and engineering judgment, the proposed addition, ADU, and
exterior miscellaneous improvements may be supported by new conventional shallow foundations.
The following recommendations are considered the minimum based on soil conditions and are not
intended to be lieu of structural considerations. All foundations should be designed by a qualified
structural engineer.
DIMENSIONS: Spread footings supporting the proposed addition and ADU should be embedded at
least 18 inches below lowest adjacent finish pad grade. Spread footings supporting the proposed light
exterior improvements should be embedded at least 12 inches below lowest adjacent finish pad grade.
Continuous and isolated footings should have a minimum width of 12 inches and 24 inches, respectively.
Retaining wall footings should be at least 24 inches wide. In areas where site preparation are unfeasible
CWE 2190330.02 July 19, 2019 Page No. 11
and along property lines the foundations should be deepened and founded at least 6 inches into old
paralic deposits.
BEARING CAPACITY: Spread footings with a minimum depth and minimum width of 12 inches may
be designed for an allowable soil bearing pressure of 2,000 pounds per square foot (psi). This value may
be increased by 500 pounds per square foot for each additional foot of embedment and 400 pounds per
square foot for each additional foot of width up to a maximum of 3,000 pounds per square foot. These
values may be increased by one-third for combinations of temporary loads such as those due to wind or
seismic loads.
FOOTING REINFORCING: Reinforcement requirements for foundations should be provided by a
structural designer. However, based on the expected soil conditions, we recommend that the minimum
reinforcing for continuous footings consist of at least 2 No. 5 bars positioned near the bottom of the
footing and 2 No. 5 bars positioned near the top of the footing. Footings located adjacent to existing
footings or slabs should be doweled as recommended by the project structural engineer.
LATERAL LOAD RESISTANCE: Lateral loads against foundations may be resisted by friction
between the bottom of the footing and the supporting soil, and by the passive pressure against the
footing. The coefficient of friction between concrete and soil may be considered to be 0.30. The passive
resistance may be considered to be equal to an equivalent fluid weight of 300 pounds per cubic foot.
These values are based on the assumption that the footings are poured tight against undisturbed soil. If a
combination of the passive pressure and friction is used, the friction value should be reduced by one-
third.
UNDERPINNING: Underpinning recommendations should be provided by the project structural
designer. Underpinning may consist of the construction of a pad footing under existing continuous
footings and/or constructing a sister footing adjacent to it. Underpinned footings should extend to a
depth such that the footing is at least 24 inches deep and founded at least 6 inches into old paralic
deposits, whichever is greater. These footings may be designed for an allowable soil bearing pressure of
1,500 pounds per square foot (psi). This value may be increased by one-third for combinations of
temporary loads such as those due to wind or seismic loads.
CWE 2190330.02 July 19, 2019 Page No. 12
PROPERTY LINE FOUNDATIONS:: Property line footings should extend to a depth such that
the footing is at least 24 inches deep and founded at least 6 inches into competent old paralic deposits,
whichever is greater. These footings may be designed for an allowable soil bearing pressure of 1,500
pounds per square foot (psf). This value may be increased by one-third for combinations of temporary
loads such as those due to wind or seismic loads.
FOOTING EXCAVATION COMPACTION:: The bottom of underpinned and property line
footings as well as footings located in areas where site preparations are unfeasible should be watered
thoroughly and compacted to at least 95% relative compaction. Compaction should be confirmed by
performing in-place density tests.
FOUNDATION EXCAVATION OBSERVATION: All footing excavations should be observed by
Christian Wheeler Engineering prior to placing of forms and reinforcing steel to determine whether the
foundation recommendations presented herein are followed and that the foundation soils are as
anticipated in the preparation of this report. All footing excavations should be excavated neat, level, and
square. All loose or unsuitable material should be removed prior to the placement of concrete.
SETTLEMENT CHARACTERISTICS: The anticipated total and differential settlement is expected
to be less than about 1 inch and 1 inch over 40 feet, respectively, provided the recommendations
presented in this report are followed. It should be recognized that minor cracks normally occur in
concrete slabs and foundations due to concrete shrinkage during curing or redistribution of stresses,
therefore some cracks should be anticipated. Such cracks are not necessarily an indication of excessive
vertical movements. However, it should be recognized that there is a higher than typical potential for
differential settlements for additions. It is further our opinion that these conditions may result in
cosmetic distress that may be easily repaired, and not result in significant structural distress to the
structure.
EXPANSIVE CHARACTERISTICS: The prevailing foundation soils are assumed to have a very low
expansion potential (El <20). The recommendations within this report reflect these conditions.
FOUNDATION PLAN REVIEW: The final foundation plan and accompanying details and notes
should be submitted to this office for review. The intent of our review will be to verify that the plans
used for construction reflect the minimum dimensioning and reinforcing criteria presented in this section
CWE 2190330.02 July 19, 2019 Page No. 13
and that no additional criteria are required due to changes in the foundation type or layout. It is not our
intent to review structural plans, notes, details, or calculations to verify that the design engineer has
correctly applied the geotechnical design values. It is the responsibility of the design engineer to
properly design/specify the foundations and other structural elements based on the requirements of
the structure and considering the information presented in this report.
SOLUBLE SULFATES: The water-soluble sulfate content of a selected soil sample from the site was
determined in accordance with California Test Method 417. The results of this test indicate that the
soil sample had asoluble sulfate content of 0.005 percent. Soils with a soluble sulfate content of less
than 0.1 percent are considered to be negligible. However, it should be recognized that the sulfate
content of surficial soils may increase with time due to soluble sulfate in the irrigation water or
fertilized use.
SEISMIC DESIGN FACTORS
The seismic design factors applicable to the subject site are provided below. The seismic design factors
were determined in accordance with the 2016 California Building Code. The site coefficients and
adjusted maximum considered earthquake spectral response acceleration parameters are presented in
the following Table I.
TABLE I: SEISMIC DESIGN FACTORS
Site Coordinates: Latitude
Longitude
32.1630
-117.3350
Site Class D
Site Coefficient F. 1.048
Site Coefficient F 1.566
Spectral Response Acceleration at Short Periods S. 1.131 g
Spectral Response Acceleration at 1 Second Period Si 0.434 g
Sris=FaS1 1.185g
SMI.rFvS1 0.680 g
SDs=2/3*SMs 0.790 g
SD1=2/3*SMI 0.453 g
11 Probable ground shaking levels at the site could range from slight to moderate, depending on such
factors as the magnitude of the seismic event and the distance to the epicenter. It is likely that the site
CWE 2190330.02 July 19, 2019 Page No. 14
will experience the effects of at least one moderate to large earthquake during the life of the proposed
improvements.
ON-GRADE CONCRETE SLABS
GENERAL: It is our understanding that the floor system of the proposed addition and ADU will
consist of a concrete slab-on-grade. The following recommendations are considered the minimum slab
requirements based on the soil conditions and are not intended in lieu of structural considerations. These
recommendations assume that the site preparation recommendations contained in this report are
implemented.
INTERIOR FLOOR SLABS: The minimum slab thickness should be 5 inches (actual) and the slab
should be reinforced with at least No. 4 bars spaced at 18 inches on center each way. Slab
reinforcement should be supported on chairs such that the reinforcing bars are positioned at mid-
height in the floor slab. The slab reinforcement should extend down into the perimeter footings at
least 12 inches. New slabs located adjacent to existing footings or slabs should be doweled as
recommended by the project structural designer.
UNDER-SLAB VAPOR RETARDERS: Steps should be taken to minimize the transmission of
moisture vapor from the subsoil through the interior slabs where it can potentially damage the interior
floor coverings. Local industry standards typically include the placement of a vapor retarder, such as
plastic, in a layer of coarse sand placed directly beneath the concrete slab. Two inches of sand are
typically used above and below the plastic. The vapor retarder should be at least 15-mil Stegowrap® or
similar material with sealed seams and should extend at least 12 inches down the sides of the interior
and perimeter footings. The sand should have a sand equivalent of at least 30, and contain less than
10% passing the Number 100 sieve and less than 5% passing the Number 200 sieve. The membrane
should be placed in accordance with the recommendation and consideration of ACI 302, "Guide for
Concrete Floor and Slab Construction" and ASTM E1643, "Standards Practice for Installation of
Water Vapor Retarder Used in Contact with Earth or Granular Fill Under Concrete Slabs." It is the
flooring contractor's responsibility to place floor coverings in accordance with the flooring
manufacturer specifications.
CWE 2190330.02 July 19, 2019 Page No. 15
EXTERIOR CONCRETE FLATWORK: Exterior concrete slabs on grade should have a minimum
thickness of 4 inches and be reinforced with at least No. 3 bars placed at 18 inches on center each way
(ocew). Driveway slabs should have a minimum thickness of 5 inches and be reinforced with at least
No. 4 bars placed at 18 inches ocew. Driveway slabs abutting landscape areas should be provided with
a thickened edge a least 12 inches deep and 6 inches wide. All slabs should be provided with weakened
plane joints in accordance with the American Concrete Institute (ACI) guidelines. Special attention
should be paid to the method of concrete curing to reduce the potential for excessive shrinkage
cracking. It should be recognized that minor cracks occur normally in concrete slabs due to shrinkage.
Some shrinkage cracks should be expected and are not necessarily an indication of excessive movement
or structural distress.
EARTH RETAINING WALLS
FOUNDATIONS: Foundations for any proposed retaining walls should be constructed in
accordance with the foundation recommendations presented previously in this report.
PASSIVE PRESSURE: The passive pressure for the anticipated foundation soils may be considered to
be 300 pounds per square foot per foot of depth. The upper foot of embedment should be neglected
when calculating passive pressures, unless the foundation abuts a hard surface such as a concrete slab.
The passive pressure may be increased by one-third for seismic loading. The coefficient of friction for
concrete to soil may be assumed to be 0.30 for the resistance to lateral movement. When combining
frictional and passive resistance, the friction should be reduced by one-third.
ACTIVE PRESSURE: The active soil pressure for the design of "unrestrained" and "restrained" earth
retaining structures with level backfill may be assumed to be equivalent to the pressure of a fluid
weighing 37 and 57 pounds per cubic foot, respectively. These pressures do not consider any other
surcharge. If any are anticipated, this office should be contacted for the necessary increase in soil
pressure. These values are based on a drained backfill condition.
Seismic lateral earth pressures may be assumed to equal an inverted triangle starting at the bottom of
the wall with the maximum pressure equal to 9H pounds per square foot (where H = wall height in
feet) occurring at the top of the wall.
CWE 2190330.02 July 19, 2019 Page No. 16
WATERPROOFING AND WALL DRAINAGE SYSTEMS: The need for waterproofing should
be evaluated by others. If required, the project architect should provide (or coordinate) waterproofing
details for the retaining walls. The design values presented above are based on a drained backfill
condition and do not consider hydrostatic pressures. The retaining wall designer should provide a
detail for a wall drainage system. Typical retaining wall drain system details are presented as Plate No.
2 of this report for informational purposes. Additionally, outlets points for the retaining wall drain
system should be coordinated with the project civil engineer.
BACKFILL: Retaining wall backfill soils should be compacted to at least 90 percent relative
compaction. Expansive or clayey soils should not be used for backfill material. The wall should not be
backfilled until the masonry has reached an adequate strength.
LIMITATIONS
REVIEW, OBSERVATION AND TESTING
The recommendations presented in this report are contingent upon our review of final plans and
specifications. Such plans and specifications should be made available to the geotechnical engineer and
engineering geologist so that they may review and verify their compliance with this report and with
the California Building Code.
It is recommended that Christian Wheeler Engineering be retained to provide continuous soil
engineering services during the earthwork operations. This is to verify compliance with the design
concepts, specifications or recommendations and to allow design changes in the event that subsurface
conditions differ from those anticipated prior to start of construction.
UNIFORMITY OF CONDITIONS
The recommendations and opinions expressed in this report reflect our best estimate of the project
requirements based on an evaluation of the subsurface soil conditions encountered at the subsurface
exploration locations and on the assumption that the soil conditions do not deviate appreciably from
those encountered. It should be recognized that the performance of the foundations and/or cut and
fill slopes may be influenced by undisclosed or unforeseen variations in the soil conditions that may
occur in the intermediate and unexplored areas. Any unusual conditions not covered in this report
CWE 2190330.02 July 19, 2019 Page No. 17
that may be encountered during site development should be brought to the attention of the
geotechnical engineer so that he may make modifications if necessary.
CHANGE IN SCOPE
This office should be advised of any changes in the project scope or proposed site grading so that we
may determine if the recommendations contained herein are appropriate. This should be verified in
writing or modified by a written addendum.
TIME LIMITATIONS
The findings of this report are valid as of this date. Changes in the condition of a property can,
however, occur with the passage of time, whether they be due to natural processes or the work of man
on this or adjacent properties. In addition, changes in the Standards-of-Practice and/or Government
Codes may occur. Due to such changes, the findings of this report may be invalidated wholly or in
part by changes beyond our control. Therefore, this report should not be relied upon after a period of
two years without a review by us verifying the suitability of the conclusions and recommendations.
PROFESSIONAL STANDARD
In the performance of our professional services, we comply with that level of care and skill ordinarily
exercised by members of our profession currently practicing under similar conditions and in the same
locality. The client recognizes that subsurface conditions may vary from those encountered at the
locations where our borings, surveys, and explorations are made, and that our data, interpretations,
and recommendations be based solely on the information obtained by us. We will be responsible for
those data, interpretations, and recommendations, but shall not be responsible for the interpretations
by others of the information developed. Our services consist of professional consultation and
observation only, and no warranty of any kind whatsoever, express or implied, is made or intended in
connection with the work performed or to be performed by us, or by our proposal for consulting or
other services, or by our furnishing of oral or written reports or findings.
CWE 2190330.02 July 19, 2019 Page No. 18
CLIENT'S RESPONSIBILITY
It is the responsibility of the Client, or his representatives, to ensure that the information and
recommendations contained herein are brought to the attention of the structural engineer and
architect for the project and incorporated into the project's plans and specifications. It is further their
responsibility to take the necessary measures to insure that the contractor and his subcontractors carry
out such recommendations during construction.
FIELD EXPLORATIONS
Four subsurface explorations were made on July 14, 2015 at the locations indicated on the Site Plan and
Geotechnical Map included herewith as Plate No. 1. These explorations consisted of three borings
drile'd utilizing a portable drill rig and one hand-dug tests pit. The fieldwork was conducted under the
observation and direction of our engineering geology personnel.
The explorations were carefully logged when made. The logs are presented in the attached Appendix A.
The soils are described in accordance with the Unified Soils Classification System. In addition, a verbal
textural description, the wet color, the apparent moisture, and the density or consistency is provided.
The density of granular soils is given as very loose, loose, medium dense, dense or very dense. The
consistency of silts or clays is given as either very soft, soft, medium stiff, stiff, very stiff, or hard.
Relatively undisturbed drive samples were collected using a modified California sampler. The sampler,
with an external diameter of 3.0 inches, is lined with 1-inch long, thin, brass rings with inside
diameters of approximately 2.4 inches. The sample barrel was driven into the ground with the weight
of a 140-pound hammer falling 30 inches in general accordance with ASTM D 3550-84. The driving
weight is permitted to fall freely. The number of blows per foot of driving, or as indicated, are
presented on the boring logs as an index to the relative resistance of the sampled materials. The
samples were removed from the sample barrel in the brass rings, and sealed. Bulk samples of the earth
materials encountered were also collected. Samples were transported to our laboratory for testing.
CWE 2190330.02 July 19, 2019 Page No. 19
LABORATORY TESTING
Laboratory tests were performed in accordance with the generally accepted American Society for Testing
and Materials (ASTM) test methods or suggested procedures. A brief description of the tests performed
and the subsequent results are presented in Appendix B.
r
..'._ X.I *,:.:.I •:.. : ••
J.•fl..' I ii I '
/
:' : ,." / I
' 4 ..
.
j)........
N 552S3r F 1)S.CV
4
0 20' 40'
SCALE: 1" = 20'
NLW Ii wr ii -
'QoI;z .,.
'I1 Y=
/5ZOö
P2OfT
CWE LEGEND
Ig P-i TEST PIT LOCATIONS
Qop OLD PAIALIC DEPOSITS
*Note: Topsoils and Artificial Fills <1 Not Mapped
SITE PLAN AND GEOLOGIC MAP
PROPOSED BLOCK RESIDENCE
3291 HIGHLAND DRIVE
CARLSBAD, CALIFORNIA
DATE: JULY 2019 I JOB NO.: 2190330.02
%o 1
CHRJS11AN WHEELER
ENGINEER.ING BY: SD PLATE NO.: I
Appendix B
Laboratory Test Results
Laboratory tests were performed in accordance with the generally accepted American Society for
Testing and Materials (ASTM) test methods or suggested procedures. Brief descriptions of the tests
performed are presented below:
CLASSIFICATION: Field classifications were verified in the laboratory by visual
examination. The final soil classifications are in accordance with the Unified Soil
Classification System and are presented on the exploration logs in Appendix A.
MOISTURE-DENSITY: MOISTURE-DENSITY: In-place moisture contents and dry
densities were determined for selected soil samples in accordance with ATM D 2937. The
results are summarized in the test pit logs presented in Appendix A.
MAXIMUM DENSITY & OPTIMUM MOISTURE CONTENT: The maximum dry
density and optimum moisture content of typical soils were determined in the laboratory in
accordance with ASTM Standard Test D1557, Method A.
DIRECT SHEAR: Direct shear tests were performed on selected samples of the on-site soils in
accordance with ASTM D3080.
GRAIN SIZE DISTRIBUTION: The grain size distribution of a selected sample was
determined in accordance with ASTM C136 and/or ASTM D422.
COLLAPSE POTENTIAL: Collapse potential tests were performed on selected undisturbed
soil samples in accordance with ASTM D5333.
SOLUBLE SULFATE CONTENT: The soluble sulfate content was determined for a
representative sample in accordance with California Test Methods 417.
'K
CHRJS11AN WHEELER
ENGINEERING
PROPOSED BLOCK RESIDENCE LAB SUMMARY I 3291 HIGHLAND DRIVE, CARLSBAD
BY: DBA I DATE: JULY. 2019 I REPORT NO.:2190330.02 I FIGURE NO.: B-i
LABORATORY TEST RESULTS
PROPOSED BLOCK RESIDENCE
3291 HIGHLAND DRIVE
CARLSBAD, CALIFORNIA
MAXIMUM DRY DENSITY AND OPTIMUM MOISTURE CONTENT (ASTM D1557)
Sample Location Test Pit P.4 @ 1.25'-3'
Sample Description Light Brown Silty Sand (SM)
Maximum Density 133.0 pcf
Optimum Moisture 7.0%
DIRECT SHEAR (ASTM D3080)
Sample Location Test Pit P-4 @ 1.25'-3'
Sample Type Remolded to 90%
Friction Angle 32°
Cohesion 150 psf
GRAIN SIZE DISTRIBUTION (ASTM D422)
Sample Location Test Pit P-4 @ 1.25'-3'
Sieve Size Percent Passing
#4 100
#8 100
#16 99
#30 94
#50 60
#100 32
#200 23
COLLAPSE POTENTIAL (ASTM D 5333)
Sample Location Test Pit P.3 @2½'
Initial Moisture Content 4.4%
Initial Density 101.7 pcf ,
Consolidation Before Water 3.7%
Test Pit P-3 @ 4½'
6.9%
112.4 pcf
4.4%
Added
Consolidation After Water 8.9% 6.6%
Added
Final Moisture 13.2% 12.7%
CWE 2190330.02 July 19, 2019 Appendix B-2
LABORATORY TEST RESULTS (Continued)
Sample Location Test Pit P-4 @ 3'
Initial Moisture Content 6.3%
Initial Density 114.0 pcf
Consolidation Before Water 2.9%
Added
Consolidation After Water 5.9%
Added
Final Moisture 11.9%
SOLUBLE SULFATES (CALIFORNIA TEST 417)
Test Pit P-4 @ 5'
9.0%
113.1 pcf
4.8%
6.4%
13.5%
Sample Location Test Pit P-4 @ 0'-1.25'
Soluble Sulfate 0.005 % (SO4)
CWE 2190330.02 July 19, 2019 Plate No. B-3
Appendix C
References
CWE 2190330.02 July 19, 2019 Appendix C-i
REFERENCES
American Society of Civil Engineers, ASCE 7 Hazard Tool, https://asce7hazardtooLonline
California Emergency Management Agency - California Geological Society - University of Southern
California, 2009, Tsunami Inundation Map for Emergency Planning, Oceanside Quadrangle, San Luis
Rey Quadrangle, scale 1:24,000, dated June 1, 2009.
F. Harold Weber, 1982, Recent Slope Failures, Ancient Landslides, and related Geology of the North-
Central Coastal Area, San Diego County, CA, DMG Open-File Report 82-12
Federal Emergency Management Agency, 2012, San Diego County, California and Incorporated Areas
Flood Insurance Rate Map, Map Panel Number 06073C0762G
Historic Aerials, NETR Online, historicaerials.com
Jennings, C.W. and Bryant, W. A., 2010, Fault Activity Map, California Geological Survey, Geologic
Data Map No. 6, http://www.quake.ca.gov/gmaps/FAM/faultactivitymap.html
Kennedy, Michael P. and Tan, Siang S., 2007, Geologic Map of the Oceanside 30'x60' Quadrangle,
California, California Geologic Survey, Map No.2
Giffen, Tan, S.S., 1995, Landslide Hazards in the Northern Part of the San Diego Metropolitan Area, San
Diego County, California, California Division of Mines and Geology Open-File Report 95-04
U.S. Geological Survey, Quaternary Faults in Google Earth,
http://earthquake.usgs.gov/hazards/qfaults/google.php
Appendix D
Recommended Grading Specifications - General Provisions
L
CWE 2190330.02 July 19, 2019 Appendix D, Page D-1
RECOMMENDED GRADING SPECIFICATIONS - GENERAL PROVISIONS
PROPOSED BLOCK RESIDENCE
3291 HIGHLAND DRIVE
CARLSBAD, CALIFORNIA
GENERAL INTENT
The intent of these specifications is to establish procedures for clearing, compacting natural ground,
preparing areas to be filled, and placing and compacting fill soils to the lines and grades shown on the
accepted plans. The recommendations contained in the preliminary geotechnical investigation report
and/or the attached Special Provisions are a part of the Recommended Grading specifications and
shall supersede the provisions contained hereinafter in the case of conflict. These specifications shall
only be used in conjunction with the geotechnical report for which they are a part. No deviation
from these specifications will be allowed, except where specified in the geotechnical report or in other
written communication signed by the Geotechnical Engineer.
OBSERVATION AND TESTING
Christian Wheeler Engineering shall be retained as the Geotechnical Engineer to observe and test the
earthwork in accordance with these specifications. It will be necessary that the Geotechnical Engineer
or his representative provide adequate observation so that he may provide his opinion as to whether
or not the work was accomplished as specified. It shall be the responsibility of the contractor to assist
the Geotechnical Engineer and to keep him appraised of work schedules, changes and new
information and data so that he may provide these opinions. In the event that any unusual conditions
not covered by the special provisions or preliminary geotechnical report are encountered during the
grading operations, the Geotechnical Engineer shall be contacted for further recommendations.
If, in the opinion of the Geotechnical Engineer, substandard conditions are encountered, such as
questionable or unsuitable soil, unacceptable moisture content, inadequate compaction, adverse
weather, etc., construction should be stopped until the conditions are remedied or corrected or he
shall recommend rejection of this work.
CWE 2190330.02 July 19, 2019 Appendix D, Page D-2
Tests used to determine the degree of compaction should be performed in accordance with the
following American Society for Testing and Materials test methods:
Maximum Density & Optimum Moisture Content - ASTM D1557
Density of Soil In-Place - ASTM D1556 or ASTM D6938
All densities shall be expressed in terms of Relative Compaction as determined by the foregoing
ASTM testing procedures.
PREPARATION OF AREAS TO RECEIVE FILL
All vegetation, brush and debris derived from clearing operations shall be removed, and legally
disposed of. All areas disturbed by site grading should be left in a neat and finished appearance, free
from unsightly debris.
After clearing or benching the natural ground, the areas to be filled shall be scarified to a depth of 6
inches, brought to the proper moisture content, compacted and tested for the specified minimum
degree of compaction. All loose soils in excess of 6 inches thick should be removed to firm natural
ground which is defined as natural soil which possesses an in-situ density of at least 90 percent of its
maximum dry density.
When the slope of the natural ground receiving fill exceeds 20 percent (5 horizontal units to 1 vertical
unit), the original ground shall be stepped or benched. Benches shall be cut to a firm competent
formational soil. The lower bench shall be at least 10 feet wide or 1-1/2 times the equipment width,
whichever is greater, and shall be sloped back into the hillside at a gradient of not less than two (2)
percent. All other benches should be at least 6 feet wide. The horizontal portion of each bench shall
be compacted prior to receiving fill as specified herein for compacted natural ground. Ground slopes
flatter than 20 percent shall be benched when considered necessary by the Geotechnical Engineer.
Any abandoned buried structures encountered during grading operations must be totally removed.
All underground utilities to be abandoned beneath any proposed structure should be removed from
within 10 feet of the structure and properly capped off. The resulting depressions from the above
CWE 2190330.02 July 19, 2019 Appendix D, Page D-3
described procedure should be backfilled with acceptable soil that is compacted to the requirements of
the Geotechnical Engineer. This includes, but is not limited to, septic tanks, fuel tanks, sewer lines or
leach lines, storm drains and water lines. Any buried structures or utilities not to be abandoned
should be brought to the attention of the Geotechnical Engineer so that he may determine if any
special recommendation will be necessary.
All water wells which will be abandoned should be backfilled and capped in accordance to the
requirements set forth by the Geotechnical Engineer. The top of the cap should be at least 4 feet
below finish grade or 3 feet below the bottom of footing whichever is greater. The type of cap will
depend on the diameter of the well and should be determined by the Geotechnical Engineer and/or a
qualified Structural Engineer.
FILL MATERIAL
Materials to be placed in the fill shall be approved by the Geotechnical Engineer and shall be free of
vegetable matter and other deleterious substances. Granular soil shall contain sufficient fine material
to fill the voids. The definition and disposition of oversized rocks and expansive or detrimental soils
are covered in the geotechnical report or Special Provisions. Expansive soils, soils of poor gradation,
or soils with low strength characteristics may be thoroughly mixed with other soils to provide
satisfactory fill material, but only with the explicit consent of the Geotechnical Engineer. Any
import material shall be approved by the Geotechnical Engineer before being brought to the site.
PLACING AND COMPACTION OF FILL
Approved fill material shall be placed in areas prepared to receive fill in layers not to exceed 6 inches
in compacted thickness. Each layer shall have a uniform moisture content in the range that will allow
the compaction effort to be efficiently applied to achieve the specified degree of compaction. Each
layer shall be uniformly compacted to the specified minimum degree of compaction with equipment
of adequate size to economically compact the layer. Compaction equipment should either be
specifically designed for soil compaction or of proven reliability. The minimum degree of compaction
to be achieved is specified in either the Special Provisions or the recommendations contained in the
preliminary geotechnical investigation report.
CWE 2190330.02 July 19, 2019 Appendix D, Page D-4
When the structural fill material includes rocks, no rocks will be allowed to nest and all voids must be
carefully filled with soil such that the minimum degree of compaction recommended in the Special
Provisions is achieved. The maximum size and spacing of rock permitted in structural fills and in non-
structural fills is discussed in the geotechnical report, when applicable.
Field observation and compaction tests to estimate the degree of compaction of the fill will be taken
by the Geotechnical Engineer or his representative. The location and frequency of the tests shall be at
the Geotechnical Engineer's discretion. When the compaction test indicates that a particular layer is
at less than the required degree of compaction, the layer shall be reworked to the satisfaction of the
Geotechnical Engineer and until the desired relative compaction has been obtained.
Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment.
Compaction by sheepsfoot roller shall be at vertical intervals of not greater than four feet. In
addition, fill slopes at a ratio of two horizontal to one vertical or flatter, should be trackrolled.
Steeper fill slopes shall be over-built and cut-back to finish contours after the slope has been
constructed. Slope compaction operations shall result in all fill material six or more inches inward
from the finished face of the slope having a relative compaction of at least 90 percent of maximum dry
density or the degree of compaction specified in the Special Provisions section of this specification.
The compaction operation on the slopes shall be continued until the Geotechnical Engineer is of the
opinion that the slopes will be surficially stable.
Density tests in the slopes will be made by the Geotechnical Engineer during construction of the
slopes to determine if the required compaction is being achieved. Where failing tests occur or other
field problems arise, the Contractor will be notified that day of such conditions by written
communication from the Geotechnical Engineer or his representative in the form of a daily field
report.
If the method of achieving the required slope compaction selected by the Contractor fails to produce
the necessary results, the Contractor shall rework or rebuild such slopes until the required degree of
compaction is obtained, at no cost to the Owner or Geotechnical Engineer.
CWE 2190330.02 July 19, 2019 Appendix D, Page D-5
CUT SLOPES
The Engineering Geologist shall inspect cut slopes excavated in rock or lithified formational material
during the grading operations at intervals determined at his discretion. If any conditions not
anticipated in the preliminary report such as perched water, seepage, lenticular or confined strata of a
potentially adverse nature, unfavorably inclined bedding, joints or fault planes are encountered during
grading, these conditions shall be analyzed by the Engineering Geologist and Geotechnical Engineer
to determine if mitigating measures are necessary.
Unless otherwise specified in the geotechnical report, no cut slopes shall be excavated higher or
steeper than that allowed by the ordinances of the controlling governmental agency.
ENGINEERING OBSERVATION
Field observation by the Geotechnical Engineer or his representative shall be made during the filling
and compaction operations so that he can express his opinion regarding the conformance of the
grading with acceptable standards of practice. Neither the presence of the Geotechnical Engineer or
his representative or the observation and testing shall release the Grading Contractor from his duty to
compact all fill material to the specified degree of compaction.
SEASON LIMITS
Fill shall not be placed during unfavorable weather conditions. When work is interrupted by heavy
rain, filling operations shall not be resumed until the proper moisture content and density of the fill
materials can be achieved. Damaged site conditions resulting from weather or acts of God shall be
repaired before acceptance of work.
RECOMMENDED GRADING SPECIFICATIONS - SPECIAL PROVISIONS
RELATIVE COMPACTION: The minimum degree of compaction to be obtained in compacted
I
natural ground, compacted fill, and compacted backfill shall be at least 90 percent. For street and
CWE 2190330.02 July 19, 2019 1 Appendix D, Page D-6
parking lot subgrade, the upper six inches should be compacted to at least 95 percent relative
compaction.
EXPANSIVE SOILS: Detrimentally expansive soil is defined as clayey soil which has an expansion
index of 50 or greater when tested in accordance with the Uniform Building Code Standard 29-2.
OVERSIZED MATERIAL: Oversized fill material is generally defined herein as rocks or lumps of
soil over 6 inches in diameter. Oversized materials should not be placed in fill unless
recommendations of placement of such material are provided by the Geotechnical Engineer. At least
40 percent of the fill soils shall pass through a No. 4 U.S. Standard Sieve.
TRANSITION LOTS: Where transitions between cut and fill occur within the proposed building
pad, the cut portion should be undercut a minimum of one foot below the base of the proposed
footings and recompacted as structural backfill. In certain cases that would be addressed in the
geotechnical report, special footing reinforcement or a combination of special footing reinforcement
and undercutting may be required.