HomeMy WebLinkAboutCDP 2023-0040; 4080 SUNNYHILL DRIVE; LIMITED GEOTECHNICAL EVALUTION; 2023-02-28
GEOTECHNICAL | ENVIRONMENTAL | MATERIAL
LIMITED GEOTECHNICAL EVALUATION
PROPOSED Auxiliary Dwelling Unit (ADU)
4080 SUNNYHILL DR.
CARLSBAD, CALIFORNIA 92008
PREPARED FOR
CAMERON ROSENHAN
4080 SUNNYHILL DR.
CARLSBAD, CA 92008
PREPARED BY
GEOTEK, INC.
1384 POINSETTIA AVENUE
VISTA, CALIFORNIA 92081
PROJECT NO. 3869-SD FEBRUARY 28, 2023
GEOTEK
GEOTECHNICAL | ENVIRONMENTAL | MATERIAL
February 28, 2023
Project No. 3869-SD
Cameron Rosenhan
4080 Sunnyhill Dr.
Carlsbad, California 92008
Attention: Mr. Cameron Rosenhan
Subject: Limited Geotechnical Evaluation
Proposed Auxiliary Dwelling Unit (ADU)
4080 Sunnyhill Dr.
Carlsbad, California 92008
Dear Mr. Rosenhan,
GeoTek, Inc. (GeoTek) is pleased to provide results of this Limited Geotechnical
Evaluation for the subject improvements. Based upon review, site construction appears
feasible from a geotechnical viewpoint, provided that the recommendations included
herein are incorporated into the design and construction phases of site improvements.
The opportunity to be of service is sincerely appreciated. If you should have any questions,
please do not hesitate to call GeoTek.
Respectfully submitted,
GeoTek, Inc.
Timothy E. Metcalfe, PG, CEG
Principal Geologist
Edwin R. Cunningham, RCE
Project Engineer
3-31-24
GeoTek, Inc.
1384 Poinsettia Avenue, Suite A Vista, CA 9208 1-8505
(760) 599-0509 Office (760) 599-0593 F~ www.geotekusa.com
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page i
TABLE OF CONTENTS
1. PURPOSE AND SCOPE OF SERVICES .................................................................................................... 1
2. SITE DESCRIPTION AND PROPOSED DEVELOPMENT .................................................................... 1
2.1 SITE DESCRIPTION .................................................................................................................................... 1
2.2 PROPOSED DEVELOPMENT ........................................................................................................................ 1
3. FIELD STUDY AND LABORATORY TESTING ...................................................................................... 2
3.1 FIELD EXPLORATION ................................................................................................................................ 2
3.2 LABORATORY TESTING ............................................................................................................................ 2
4. GEOLOGIC AND SOILS CONDITIONS ................................................................................................... 2
4.1 EARTH MATERIALS ............................................................................................................................ 2
4.1.1 Artificial Fill (Af) ........................................................................................................................... 2
4.1.2 Paralic Deposits (Qop) .................................................................................................................. 3
4.2 SURFACE AND GROUND WATER ................................................................................................................ 3
4.2.1 Surface Water ................................................................................................................................. 3
4.2.2 Groundwater .................................................................................................................................. 3
4.3 EARTHQUAKE AND SEISMIC HAZARDS ..................................................................................................... 3
5. CONCLUSIONS AND RECOMMENDATIONS ........................................................................................ 4
5.1 GENERAL .................................................................................................................................................. 4
5.1.1 Site Clearing and Building Pad Preparation ................................................................................. 4
5.2 DESIGN RECOMMENDATIONS ................................................................................................................... 4
5.2.1 Foundations ................................................................................................................................... 4
5.2.2 Seismic Design Parameters ............................................................................................................ 7
5.2.3 Soil Sulfate and Chloride Content .................................................................................................. 7
5.3 RETAINING WALLS ................................................................................................................................... 8
5.3.1 Expected Wall Movements ............................................................................................................. 9
5.3.2 Wall Backfill and Drainage ........................................................................................................... 9
5.4 CONSTRUCTION OBSERVATIONS ............................................................................................................... 9
6. INTENT ......................................................................................................................................................... 10
7. LIMITATIONS ............................................................................................................................................. 10
8. SELECTED REFERENCES ....................................................................................................................... 11
ENCLOSURES
Figure 1 – Site Location Map
Figure 2 – Geotechnical Map
Appendix A – Logs of Exploration
Appendix B – Results of Laboratory Testing
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 1
1. PURPOSE AND SCOPE OF SERVICES
The purpose of this study was to assess the site geotechnical conditions with regards to the
proposed improvements. Services provided for this study included the following:
Research and review of readily available geologic data and general information pertinent to
the site.
Excavation of three manual auger borings and collection of bulk samples for subsequent
laboratory testing.
Laboratory testing of soil samples collected during field exploration.
Review and analysis of geologic and geotechnical engineering data.
Compilation of this geotechnical report presenting findings of pertinent geotechnical
conditions and geotechnical recommendations for site development.
2. SITE DESCRIPTION AND PROPOSED DEVELOPMENT
2.1 SITE DESCRIPTION
The site is San Diego County Assessor Parcel Number APN 207-07-205-00 located at 4080
Sunnyhill Drive, California 92008 (See Figure 1). The approximately one-half acre property is
currently improved with a single-story residence, driveway, backyard, pool, shed, tennis court,
and various landscaping improvements. The property is bounded by Sunnyhill Drive to the west
and similarly developed residential properties to the north, south, and east. The site slopes up
from Sunnyhill Drive about 10 feet to the pad area where the house and pool sit. Topography
then continues to slope up to the residence to the east. The tennis court and shed site in the
upper portion of the site at the east. Total relief on the site is about 57 feet. The driveway extends
along the entire south side of the property.
The existing house is L-shaped, one-story with semi-attached (separated by a breeze way) garage
and storage room extending to the east This report is limited to the proposed improvements as
discussed herein and located within the boundaries presented on the Geotechnical Map: Figure
2. The area of planned improvements (referred to herein as the “site”) is located east of the
existing primary residence in the northeast portion of the property.
2.2 PROPOSED DEVELOPMENT
The proposed site improvements, based on a conversation with you, consist of a detached garage
with an accessory dwelling unit (ADU) above and the addition of a second story over much of
the existing house. A conversation with you regarding the extent of the improvements. No
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 2
significant site grading is planned although we assume that the rear (east) wall of the garage/ADU
will require minor cut up to approximately three feet high.
No plans have been provided for our use. Based on the project description provided we assume
that the garage/ADU structure would have a continuous strip footing around the perimeter with
an interior concrete slab-on-grade for the garage floor. It seems reasonable that the second story
addition will be primarily supported on posts supported by pad footings, so that the second story
would span the existing structure.
3. FIELD STUDY AND LABORATORY TESTING
3.1 FIELD EXPLORATION
Field exploration was conducted on December 23, 2022, and consisted of a site reconnaissance,
excavation of three manual auger borings and collection of bulk soil samples for subsequent
laboratory testing. Locations of the auger holes were limited by the extensive concrete paving
present. A soil probe was applied at discrete depths to qualitatively evaluate the underlying soil
properties. A representative from GeoTek visually logged the excavations as depicted in the
Appendix A - Logs of Exploration. The approximate location of the test boring is presented on
the Geotechnical Map: Figure 2. Samples were transported to our laboratory for testing.
3.2 LABORATORY TESTING
Laboratory tests were performed on the soil sample collected during the field exploration. The
purpose of the laboratory testing was to evaluate their physical and chemical soil properties for
use in engineering design and analysis. Results of the laboratory testing program, along with a
brief description and relevant information regarding testing procedures, are included in Appendix
B – Laboratory Testing.
4. GEOLOGIC AND SOILS CONDITIONS
4.1 EARTH MATERIALS
A brief description of the earth materials encountered during the subsurface exploration is
presented in the following sections. Based on review of published geologic maps and the site-
specific evaluation, the subject site is locally underlain by artificial fill over old paralic deposits.
4.1.1 Artificial Fill (Af)
Artificial fill was encountered in the upper 2 to 2.5 feet of the exploration. Artificial fill consisted
of silty fine to medium sand, dark brown in color, moist, and loose to medium dense with depth.
Organics and roots were occasionally encountered in each of the borings in the upper 4-inches.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 3
4.1.2 Paralic Deposits (Qop)
Old paralic deposits were encountered in all borings at 2 to 2.5 feet deep and to the full depths
of exploration. The paralic deposits consisted of fine to medium sand to silty sand with some
clay, light orange, brown in color, moist, and medium dense to very dense with depth. Borings
HA-1 and HA-2, located at the front of the house, also contained a thin layer of sandy clay at the
top of the paralic deposits.
4.2 SURFACE AND GROUND WATER
4.2.1 Surface Water
Surface water was not observed during the site visit and exploration. If encountered during
earthwork construction, surface water on this site will likely be the result of precipitation and
some runoff from upslope areas/properties.
4.2.2 Groundwater
An apparently localized perched water seepage was encountered in Boring HA-2 at a depth of
3.5 feet. It is not anticipated to be significant factor in the proposed construction due to the
boring’s location in reference to the planned improvements. The seepage extended to
approximately 6 feet below the surface and may be related to the adjacent sprinkler system. It is
likely that vertical migration is retarded by the material density increase. It is fairly common to
encounter this type of seepage in this area of Carlsbad particularly during the rainy season. No
other groundwater was encountered during the subsurface exploration. The groundwater table
is likely at least 50 feet below the surface.
4.3 EARTHQUAKE AND SEISMIC HAZARDS
No active or potentially active fault is known to exist at this site or is the site situated within an
“Alquist-Priolo” Earthquake Fault Zone or a Special Studies Zone (Bryant and Hart, 2007). No faults
are identified on the geologic maps reviewed for the immediate proximity of the study area.
The liquefaction potential and seismic settlement potential on this site are considered negligible
due to the density of the underlying paralic deposits and other than the minor perched condition
absence of a shallow groundwater table.
Evidence of ancient landslides or gross slope instabilities at this site was not observed during this
study or indicated on regional geologic maps. Thus, the potential for landslides is considered
negligible.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 4
5. CONCLUSIONS AND RECOMMENDATIONS
5.1 GENERAL
The proposed improvements appear feasible from a geotechnical viewpoint provided that the
project design and construction comply with the 2022 California Building Code (CBC), City of
Carlsbad guidelines and recommendations contained in this report.
5.1.1 Site Clearing and Building Pad Preparation
Site clearing of vegetation (if any), and debris should be performed prior to preparation of the
building pad. In the areas of proposed improvements at or near existing ground surface, existing
fill should be removed. Removal depths on the order of 2.5 feet below existing grades are
indicated by the borings. While the concrete limited testing locations, it is anticipated that in the
area of the existing driveway is likely to encounter paralic deposits within the upper foot.
Following removals, the exposed surface should be scarified to a depth of 8-inches, moisture
conditioned to optimum moisture content or higher and compacted to a minimum of 90% of
maximum dry density as determined by ASTM D 1557 test procedures. The recommended
removals and recompaction should extend to at least 2 feet outside the proposed improvements,
where possible.
If soil is needed to raise pad grades after stripping of unsuitable materials, acceptable engineered
fill materials should be placed in horizontal lifts not exceeding 8 inches in loose thickness, moisture
conditioned to at or slightly above the optimum moisture content and compacted to a minimum
relative compaction of 90% of maximum dry density as determined by ASTM D 1557 test
procedures.
5.2 DESIGN RECOMMENDATIONS
5.2.1 Foundations
Foundations can be placed in either dense paralic deposits or engineered fill. Where no new slab
on grade is proposed, extending footings into dense paralic deposits is likely the prudent
approach. Where a slab-on-grade is planned, area/s inside the building envelope and 2 feet beyond
should be prepared according to the above site clearing and building pad preparation
recommendations.
Based on laboratory testing the near surface subgrade soils are classified as “very low” (EI<20)
expansive index (ASTM D4829 test procedure). The following criteria is for the design of the
project’s building foundation system.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 5
MINIMUM DESIGN REQUIREMENTS FOR CONVENTIONALLY
REINFORCED FOUNDATIONS
DESIGN PARAMETER “Very Low”
Expansion Index (EI<20)
Perimeter Foundation Embedment Depth
(inches below lowest adjacent finished grade) 12 inches
Minimum Perimeter Foundation Width 12 inches
Minimum Isolated Square Foundation Width 18 inches
Minimum Isolated Square Foundation Depth
(inches below lowest adjacent finished grade) 18 inches
Minimum Slab Thickness 4 inches actual
Minimum Slab Reinforcement
No. 3 rebar 24” on-center, each way,
placed in the middle one-third of the slab
thickness
Minimum Footing Reinforcement Two No. 4 Reinforcing Bars,
one top and one bottom
Pre-Saturation of Subgrade Soil (percent of
optimum moisture content) Minimum 100% to a depth of 12 inches
Where foundations extend through existing fill and into paralic deposits (expected for the second
story addition) a minimum 24-inch square or if drilled 18-inch diameter base, spread footing is
recommended. Footings should extend at least 12 inches into the bearing material. It is important
to remove loose soil in the bottom of the footing.
It should be noted that the above recommendations are based on soil support characteristics
only. The structural engineer should design the slab and beam reinforcement based on actual
loading conditions.
Footings embedded in suitable bearing materials, as observed and documented by a
GeoTek representative, may be dimensioned based on an allowable soil bearing pressure
of 2,000 psf. Bearing may be increased by 500 psf for each additional of depth and 250
psf for each additional foot of width to a maximum of 3,500 psf. These increases can be
applied from the 12 inches below the ground surface in areas of existing fill for column
footings. The allowable soil bearing pressure may be increased by one-third for short term
wind and/or seismic loads.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 6
The passive earth pressure for footings within the engineered fill may be computed as an
equivalent fluid having a density of 250 psf per foot of depth, to a maximum earth pressure
of 3,000 psf. A coefficient of friction between soil and concrete of 0.35 may be used with
dead load forces. When combining passive and frictional resistance, the passive pressure
component should be reduced by one-third.
A moisture and vapor retarding system should be placed below slabs-on-grade where moisture
migration through the slab is undesirable. Guidelines for these are provided in the 2022 California
Green Building Standards Code (CALGreen) Section 4.505.2, the 2022 CBC Section 1907.1 and
ACI 360R-10. The vapor retarder design and construction should also meet the requirements
of ASTM E 1643. A portion of the vapor retarder design should be the implementation of a
moisture vapor retardant membrane.
It should be realized that the effectiveness of the vapor retarding membrane can be adversely
impacted as a result of construction related punctures (e.g. stake penetrations, tears, punctures
from walking on the vapor retarder placed atop the underlying aggregate layer, etc.). These should
be avoided during construction. Thicker membranes are generally more resistant to accidental
puncture than thinner ones. Products specifically designed for use as moisture/vapor retarders
may also be more puncture resistant. The CBC specifies a 6mil vapor retarder membrane. The
California Residential Code (CRC) Section 506.3 specifies a 10mil membrane. It is GeoTek’s
opinion that a minimum 10mil thick membrane with joints properly overlapped and sealed should
be considered, unless otherwise specified by the slab design professional.
Moisture and vapor retarding systems are intended to reduce not eliminate vapor and moisture
transmission through the concrete. The acceptable level of moisture transmission through the
slab is to a considerable extent based on the type of flooring used and environmental conditions.
Ultimately, the vapor retarding system should be comprised of suitable elements to limited
migration of water and reduce transmission of water vapor through the slab to acceptable levels.
The selected elements should have suitable properties (i.e., thickness, composition, strength, and
permeability) to achieve the desired performance level.
Moisture retarder systems should be designed and constructed in accordance with applicable
American Concrete Institute, Portland Cement Association, Post-Tensioning Concrete Institute,
ASTM and, CRC and CBC requirements and guidelines.
GeoTek recommends that a qualified person, such as the flooring contractor, structural engineer,
architect, and/or other experts specializing in moisture control within the building be consulted
to evaluate the general and specific moisture and vapor transmission paths and associated
potential impact on the proposed construction. That person (or persons) should provide
recommendations relative to the slab moisture and vapor retarder systems and for migration of
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 7
potential adverse impact of moisture vapor transmission on various components of the
structures, as deemed appropriate.
In addition, the recommendations in this report and GeoTek’s services in general are not
intended to address mold prevention; since GeoTek, along with geotechnical consultants in
general, do not practice in the area of mold prevention. If specific recommendations addressing
potential mold issues are desired, then a professional mold prevention consultant should be
contacted.
5.2.2 Seismic Design Parameters
The site is located at approximately 33.155275 Latitude and -117.321616 Longitude. Site spectral
accelerations (Ss and S1), for 0.2 and 1.0 second periods for a risk targeted two (2) percent
probability of exceedance in 50 years (MCER) were determined using the web interface provided
by ASCE/SEI-7 (https://asce7hazardtool.online) to access the USGS Seismic Design Parameters.
A Site Class “C” is deemed appropriate for this site based on the apparent density of the
formation underlying the project site.
SITE SEISMIC PARAMETERS
Mapped 0.2 sec Period Spectral Acceleration, Ss 1.16g
Mapped 1.0 sec Period Spectral Acceleration, S1 0.37g
Maximum Considered Earthquake Spectral
Response Acceleration for 0.2 Second, SMS 1.24g
Maximum Considered Earthquake Spectral
Response Acceleration for 1.0 Second, SM1 0.53g
5% Damped Design Spectral Response
Acceleration Parameter at 0.2 Second, SDS 0.83g
5% Damped Design Spectral Response
Acceleration Parameter at 1 second, SD1 0.35g
Seismic Design Category D
5.2.3 Soil Sulfate and Chloride Content
The soil soluble sulfate and chloride content were determined in the laboratory for an on-site
soil sample. The results indicate that the water-soluble sulfate and chloride result is 0.0008 and
0.0007 percent by weight, respectively, which are considered “negligible” per Table 4.2.1 of ACI
318. Based on the test results, no special recommendations for concrete are required for this
project due to soil sulfate or soil chloride exposure.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 8
5.3 RETAINING WALLS
The garage and ADU may require retaining wall to achieve desired grades. We anticipate that a
wall up to 4 feet high could be needed along the eastern wall. Retaining wall foundations should
be designed in accordance with the foundation recommendations provided previously in this
report.
The design parameters provided below are applicable for retaining wall up to 4 feet high provided
that very low expansive on-site soils are used to backfill any retaining walls. If more expansive
soils are used to backfill the walls, increased active and at-rest earth pressures should be utilized
for design. Building walls, below grade, should be waterproofed or damp-proofed, depending on
the degree of moisture protection desired.
1. Active earth pressure may be used for retaining wall design, provided the top of the wall
is not restrained from minor deflections. Active earth pressure may be computed as an
equivalent fluid having a density of 40 pounds per square foot per foot of depth, plus any
applicable surcharge loading.
2. Any retaining walls that will be restrained prior to placing and compacting backfill material
or that have reentrant or male corners, should be designed for an at-rest equivalent fluid
pressure of 60 pounds per square foot per foot of depth, plus any applicable surcharge
loading. For areas of male or re-entrant corners, the restrained wall design should extend
a minimum distance of twice the height of the wall laterally from the corner.
3. The equivalent fluid pressures are provided for vertical walls and horizontal backfill less
than 5 feet tall. Pressures do not include pressures imposed during compaction of backfill,
swelling pressures of clay backfill, hydrostatic pressures from inundation of the backfill or
free water behind the walls, traffic above the wall, surcharge loads, sloping fill above the
top of the wall, seismic events, or adverse geologic conditions. Walls should be braced
during backfilling to prevent damage and excessive movements.
4. All walls should be reinforced to reduce the potential for distress caused by differential
foundation movement in accordance with the Structural Engineer’s recommendations. In
the upper bond beam, "U" blocks should be used. The walls should use both vertical and
horizontal reinforcement and be designed to resist the effects a two-way 1/400 angular
distortion would impart on a wall. Prior to placing concrete, the subgrade soils should be
lightly moisture conditioned to prevent loss of water during pouring and curing of the
concrete.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 9
5.3.1 Expected Wall Movements
A retaining wall has to translate laterally to reach full passive pressure/resistance. At 0.5% strain,
½ the passive pressure is mobilized, and at 2% strain the full passive pressure is mobilized. For a
12-inch embedment this can be 0.25 inches. In addition, wall rotation is expected to reach an
active design state. This rotation, at a minimum, needs to undergo 0.5% strain and walls are often
considered to rotate between 0.005 to 0.02 times their height, dependent upon the soil condition,
with no adverse structural effects expected. In our opinion, a value of 0.01 times the height of
the wall is a maximum rotation that should typically be expected. For a 5-foot-high wall this
amounts to 0.6 inches of movement that can occur at the top of the wall. Walls should be
expected to translate/move/rotate, and the higher the wall the more movement that should be
expected.
5.3.2 Wall Backfill and Drainage
All retaining walls should be provided with an adequate back drain system to reduce the buildup
of hydrostatic pressure and to minimize potential buildup of efflorescence along the front of the
wall. We recommend the use of gravel, a free draining layer of soil or a manufactured synthetic
material to be utilized as a back-drain system. The back drain system behind retaining walls
should consist at a minimum of 4-inch diameter Schedule 40 (or equivalent) perforated
(perforations “down”) PVC pipe embedded in at least 1-cubic-foot of ¾-inch crushed rock per
linear foot of pipe, all wrapped in approved filter fabric. Other back drain systems that may be
contemplated for use behind retaining walls due to ultimate design and construction methodology
will be considered on a case-by-case basis. A filter may be required between the soil backfill and
a drainage layer. Proper surface drainage should also be provided.
The need for damp/water proofing should be assessed and the appropriate method to limit water
transmission through the wall used.
5.4 CONSTRUCTION OBSERVATIONS
GeoTek representatives should be present during site grading and foundation construction to
check for proper implementation of the geotechnical recommendations. These representatives
should perform at least the following duties:
Observe site clearing and grubbing operations for proper removal of unsuitable
materials.
Observe and test bottom of removals prior to fill placement/subgrade
recompaction
Evaluate the suitability of onsite and import materials for fill placement, if needed,
and collect soil samples for laboratory testing where necessary.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 10
Observe the fill for uniformity during placement.
Perform field density testing of the fill and backfill materials.
Observe and probe foundation and slab subgrade excavations to confirm
suitability of bearing materials. This observation should be performed prior to
placement of reinforcement.
6. INTENT
It is the intent of this report to aid in the design and construction of the proposed development.
Implementation of the advice presented in this report is intended to reduce risk associated with
construction. The professional opinions and geotechnical advice contained in this report are not
intended to imply total performance of the project or guarantee that unusual or variable
conditions will not be discovered during or after construction.
The scope of this evaluation is limited to the area explored that is shown on Figure 2. This
evaluation does not and should in no way be construed to encompass any areas beyond the
specific area of the proposed construction as indicated to us by the client. Further, no evaluation
of any existing site improvements is included. The scope is based on GeoTek’s understanding of
the project and the client’s needs, and geotechnical engineering standards normally used on
similar projects in this region.
7. LIMITATIONS
GeoTek’s findings are based on site conditions observed and the stated sources. Thus, GeoTek’s
comments are professional opinions that are limited to the extent of the available data.
GeoTek has prepared this report in a manner consistent with that level of care and skill ordinarily
exercised by members of the engineering and science professions currently practicing under
similar conditions in the jurisdiction in which the services are provided, subject to the time limits
and physical constraints applicable to this report.
Since GeoTek’s recommendations are based on the site conditions observed and encountered
and laboratory testing, the conclusions and recommendations provided in this report are
professional opinions that are limited to the extent of the available data. Observations during
construction are important to allow for any change in recommendations found to be warranted.
These opinions have been derived in accordance with current standards of practice and no
warranty of any kind is expressed or implied. Standards of care/practice are subject to change
with time.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 11
8. SELECTED REFERENCES
American Society of Civil Engineers (ASCE), 2016, “Minimum Design Loads for Buildings and
Other Structures,” ASCE/SEI 7-16.
_____, ASCE Hazard Tool, 2021, ASCE/SEI 7-22, accessed December 30, 2023, at
https://asce7hazardtool.online.
ASTM International (ASTM), “ASTM Volumes 4.08 and 4.09 Soil and Rock.”
Bryant, W.A., and Hart E.W., 2007, Fault Rupture Hazard Zones in California, Alquist-Priolo
Earthquake Fault Zoning Act with Index to Earthquake Fault Zone Maps, California
Geological Survey: Special Publication 42.
California Code of Regulations, Title 24, 2022 “California Building Code,” 2 volumes.
California Geological Survey (CGS, formerly referred to as the California Division of Mines and
Geology), 1977, “Geologic Map of California.”
____, 1998, “Maps of Known Active Fault Near-Source Zones in California and Adjacent
Portions of Nevada,” International Conference of Building Officials.
GeoTek, Inc., In-house proprietary information.
Kennedy, M.P., Tan, S.S., et al, 2005, “Geologic Map of the Oceanside 30x60-minute Quadrangle,
California,” California Geological Survey, Regional Geologic Map No. 2, map scale
1:100,000.
Terzaghi, K. and Peck, R.B., 1967, “Soil Mechanics in Engineering Practice, Second Edition.
GEOTEK
1384 Poinsettia Avenue, Suite A
Vista, California 92081
N
Not to Scale
Approximate Site
Location
DATE: February 2023
Imagery from USGS The National Map, 2023
Cameron Rosenhan
4080 Sunnyhill Drive
Carlsbad, CA
Figure 1
Site Location Map
PN: 3869-SD
Agua H dio11 a
k
GEOTEK
HA-1
HA-2
HA-3
Quaternary Very Old Paralic Deposits,
Circled Where Buried
Approximate Limits of Study, this
report Qvop
LEGEND
Artifical FillAf
HA-3
Approximate Location of Hand-Auger Boring
Qvop
Af
Qvop
Af
1384 Poinsettia Avenue, Suite A
Vista, California 92081
N
Imagery from Google Earth, 2023
Figure 2
Geotechnical Map
DATE: February 2023
Cameron Rosenhan
4080 Sunnyhill Drive
Carlsbad, CA
PN: 3869-SD
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GEOTEK
APPENDIX A
LOGS OF EXPLORATION
GEOTEK
GeoTek, Inc.
LOG OF EXPLORATORY BORING
BB-1 SM MD, SR
S-1 EI
S-2 SM
---Small Bulk ---No Recovery ---Water Table
PROJECT NAME:4080 Sunnyhill Drive DRILL METHOD:Hand Auger OPERATOR:-
CLIENT:Cameron Rosenhan DRILLER:-LOGGED BY:CH
LOCATION:Carlsbad, CA ELEVATION:244'DATE:12/23/2022
PROJECT NO.:3869-SD HAMMER:-RIG TYPE:-
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i
n
Sa
m
p
l
e
Nu
m
b
e
r
Wa
t
e
r
C
o
n
t
e
n
t
(%
)
Silty fine to medium SAND, dark brown, moist, loose to medium dense, probes
4" then 3" at 2 feet, upper 2" of topsoil and organics, some roots
Very Old Paralic Deposits (Qvop)
Dr
y
D
e
n
s
i
t
y
(p
c
f
)
Ot
h
e
r
s
MATERIAL DESCRIPTION AND COMMENTS
Artificial Fill (Af)
No groundwater encountered
Silty fine to medium SAND with some clays, dark brown transitions to light brown
with some orange mottling, very moist to moist with depth, medium dense to
5 3.5 feet
HOLE TERMINATED AT 3.5 FEET
very dense with depth, auger begins scraping small chunks of paralics until
material becomes too dense and friable to recover in auger, practical refusal at
15
Backfilled with soil cuttings
10
20
25
RV = R-Value Test
SR = Sulfate/Resisitivity Test SH = Shear Test CO = Consolidation test MD = Maximum Density
30
LE
G
E
N
D
Sample type: ---Ring ---SPT ---Large Bulk
Lab testing:AL = Atterberg Limits EI = Expansion Index SA = Sieve Analysis
~x
-R
-I"" -~ ---------------------------------------------------
■ I [Z] ~ □ ~
GeoTek, Inc.
LOG OF EXPLORATORY BORING
SM
SC
---Small Bulk ---No Recovery ---Water Table
PROJECT NAME:4080 Sunnyhill Drive DRILL METHOD:Hand Auger OPERATOR:-
CLIENT:Cameron Rosenhan DRILLER:-LOGGED BY:CH
LOCATION:Carlsbad, CA ELEVATION:244'DATE:12/23/2022
PROJECT NO.:3869-SD HAMMER:-RIG TYPE:-
SAMPLES
US
C
S
S
y
m
b
o
l
BORING NO.: HA-2
Laboratory Testing
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Blo
w
s
/
6
i
n
Sa
m
p
l
e
Nu
m
b
e
r
Wa
t
e
r
C
o
n
t
e
n
t
(%
)
Silty fine to medium SAND, dark brown, very moist, loose, some clays and roots
topsoil and organics in upper 4"
Very Old Paralic Deposits (Qvop)
Clayey SAND, dark brown, very moist to wet, loose, low to medium plasticity
Dr
y
D
e
n
s
i
t
y
(p
c
f
)
Ot
h
e
r
s
MATERIAL DESCRIPTION AND COMMENTS
Artificial Fill (Af)
At 6 feet, material is very moist but no longer saturated, practical refusal due to
low clearance for auger
HOLE TERMINATED AT 6 FEET
At 3.5 feet, same material but now saturated, Auger continues to yield saturated
sand until 6 feet, less clays with depth, some orange mottling
5
Perched groundwater encountered at 3.5 feet
Backfilled with soil cuttings
10
15
20
25
AL = Atterberg Limits EI = Expansion Index SA = Sieve Analysis RV = R-Value Test
SR = Sulfate/Resisitivity Test SH = Shear Test CO = Consolidation test MD = Maximum Density
30
LE
G
E
N
D
Sample type: ---Ring ---SPT ---Large Bulk
Lab testing:
---
--¥ ----
------------------------------------------------
□ D [Z] ~ □ ¥
GeoTek, Inc.
LOG OF EXPLORATORY BORING
SM
S-1 SM
---Small Bulk ---No Recovery ---Water Table
PROJECT NAME:4080 Sunnyhill Drive DRILL METHOD:Hand Auger OPERATOR:-
CLIENT:Cameron Rosenhan DRILLER:-LOGGED BY:CH
LOCATION:Carlsbad, CA ELEVATION:247'DATE:12/23/2022
PROJECT NO.:3869-SD HAMMER:-RIG TYPE:-
SAMPLES
US
C
S
S
y
m
b
o
l
BORING NO.: HA-3
Laboratory Testing
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Blo
w
s
/
6
i
n
Sa
m
p
l
e
Nu
m
b
e
r
Wa
t
e
r
C
o
n
t
e
n
t
(%
)
Silty fine to medium SAND, dark brown, slightly moist to moist, loose to medium
dense with depth
Very Old Paralic Deposits (Qvop)
Fine to medium SAND with some clays and silts, light orange brown, moist,
Dr
y
D
e
n
s
i
t
y
(p
c
f
)
Ot
h
e
r
s
MATERIAL DESCRIPTION AND COMMENTS
Artificial Fill (Af)
HOLE TERMINATED AT 5 FEET
No groundwater encountered
Backfilled with soil cuttings
medium to very dense with depth, auger begins scraping at 5 feet with no
recovery, practical refusal at 5 feet
5
10
15
20
25
AL = Atterberg Limits EI = Expansion Index SA = Sieve Analysis RV = R-Value Test
SR = Sulfate/Resisitivity Test SH = Shear Test CO = Consolidation test MD = Maximum Density
30
LE
G
E
N
D
Sample type: ---Ring ---SPT ---Large Bulk
Lab testing:
---
-I"\ -,__ ---
--------------------------------------------------
■ I [Z] ~ □ ~
APPENDIX B
RESULTS OF LABORATORY TESTING
GEOTEK
SUMMARY OF LABORATORY TESTING
Identification and Classification
Soils were identified visually in general accordance with the procedures of the Standard Practice
for Description and Identification of Soils (ASTM D2488). The soil identifications and
classifications are shown on the exploration logs in Appendix A.
Expansion Index
Expansion Index testing was performed on a representative site soil sample obtained from the
subsurface exploration. Testing was performed in general accordance with ASTM D 4829 test
procedures. The results of the testing are presented in Appendix B.
Sulfate and Chloride Content
The soluble sulfate and chloride content of a representative site soil sample was determined by
GeoTek’s subconsultant, Project X, in general accordance with ASTM D 4327 test procedures.
The results of the testing are provided in Appendix B.
GEOTEK
Tested/ Checked By:
Date Tested:
Sample Source:
Sample Description:
Ring Id:Ring Dia. " :Ring Ht.":
A Weight of compacted sample & ring
B Weight of ring
C Net weight of sample
D
E
Wet Weight of sample & tare
Dry Weight of sample & tare
Tare
F Initial Moisture Content, %
G (E*F)
H (E/167.232)
I (1.-H)
J (62.4*I)
K (G/J)= L % Saturation
EXPANSION INDEX =
EXPANSION INDEX TEST
(ASTM D4829)
0
Tare
4.8
FINAL MOISTURE
%
Moisture
Weight of wet
sample & tare
Wt. of dry
sample & tare
168.2
1"
186.3
183.4
4.8
170.2
SATURATION DETERMINATION
18.6
8.0
50.3
12:16
370
DENSITY DETERMINATION
Wet Density, lb / ft3 (C*0.3016)
0.30
0.70
117.3
936.2
420
126.7
Random
12:05 241
16:00
239
12:15
Initial
240
1 min/Wet
10 min/Dry
1/5/2023
790
4"12
238
23812:21
Dry Density, lb / ft3 (D/1.F)
Project Number:
Project Name:4080 Sunnyhill Drive
3869-SD
Project Location:
KP
Carlsbad, CA
Loading weight: 5516. grams
HA-1 S-1
1/5/2023
Silty Clayey Sand
Lab No
1/6/2023 6:00 238
TIME READINGDATE
Final
3830
11.1%
5 min/Wet
READINGS
GEOTEK
--I
I I
Project X REPORT S221228E
Corrosion Engineering Page 1
Corrosion Control – Soil, Water, Metallurgy Testing Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Results Only Soil Testing
for
4080 Sunnyhill Dr
January 3, 2023
Prepared for:
Lesley White
GeoTek, Inc.
1384 Poinsettia Ave, Suite A
Vista, CA, 92081
lwhite@geotekusa.com
Project X Job#: S221228E
Client Job or PO#: 3869-SD
Respectfully Submitted,
Eduardo Hernandez, M.Sc., P.E.
Sr. Corrosion Consultant
NACE Corrosion Technologist #16592
Professional Engineer
California No. M37102
ehernandez@projectxcorrosion.com
Project X REPORT S221228E
Corrosion Engineering Page 2
Corrosion Control – Soil, Water, Metallurgy Testing Lab
29990 Technology Dr., Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Soil Analysis Lab Results
Client: GeoTek, Inc.
Job Name: 4080 Sunnyhill Dr
Client Job Number: 3869-SD
Project X Job Number: S221228E
January 3, 2023
Method
Bore# / Description Depth
(ft)(mg/kg)(wt%)(mg/kg)(wt%)
Dark Brown silty sand 0-2 8.3 0.0008 6.8 0.0007
ASTM
D4327
ASTM
D4327
Sulfates
SO42-
Chlorides
Cl-
Cations and Anions, except Sulfide and Bicarbonate, tested with Ion Chromatography
mg/kg = milligrams per kilogram (parts per million) of dry soil weight
ND = 0 = Not Detected | NT = Not Tested | Unk = Unknown
Chemical Analysis performed on 1:3 Soil-To-Water extract
PPM = mg/kg (soil) = mg/L (Liquid)
41! I> 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Project X Lab Request Sheet Chain of Custody
Phone: (213) 928-7213 • Fax (951) 226-1720 • www.projcctxcorrosion.com
Corrosion Engineering
(·.,...,..,.•'" l ~-, • "'-'11. V..u,,, •'W '~lu,c_,, , ..... Ship Samples To: 29990 Technology Dr, Suite 13, Murrieta, CA 92563
rroject x Job Number J 2 2 1 z z e £
IMPORT ANT: Please complete Project ~nd Sample Identification Data as you would like it to appear in report & include this form with samples.
ComponyNomt: GeoTek, Inc. Contact Name: Lesely White Phone No: 760-599-0509
Malling Address: 1384 POinsettia Ave, Suite A, Vista, CA. 92081 Contact Email: lwhite@geotekusa.com
Attounting Conlocl: Suzen Clark Invoice Email: AP@geotekusa.com
Cll,nt Project No: ~ i;? /., q -~ f)
24 Hour y I
P.O.#: 3-5 Doy
Standard
3 Day
Gu:anntt-t:
i:::n•L .... ,...1,_un RusH METHOD ANALYSIS REQUESTED (Please circle)
•~----~~11n
(Business Days) Turn Around Time: )(
For Corrosion Control Recommendations (350g soil sample):
NEED (1) Groundwater depth andl
(2) Soil Sample Locations Map . w·/ tr.
FOR THERMAL RESISTIVITY PROVIDE (1,500g soil sample):
Default
Method
(2) Dry Density{PCF} Geo Quad (I) Optimal Moisture % I I
(3) Desired Compaction
Date & Received By: 1---------=========::;::====::::;===::!.l DATE
COLLECTED SAMPLE ID -BORE# -Description DEPTH (n)
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GEOTECHNICAL | ENVIRONMENTAL | MATERIAL
December 20, 2024
Project No. 3869-SD
Cameron Rosenhan
4080 Sunnyhill Dr.
Carlsbad, California 92008
Subject: Response to Geotechnical Review Comments
Proposed Auxiliary Dwelling Unit (ADU)
4080 Sunnyhill Drive
Carlsbad, California 92008
Dear Mr. Rosenhan:
As requested, GeoTek, Inc., (GeoTek) has prepared this letter to respond to City of Carlsbad
1st review comments. The review comments correspond to the numbers on the review letter.
A copy of the review letter dated August 23, 2024 is presented in Appendix A.
Comment No. 1
The submitted “Limited Geotechnical Evaluation…” by GeoTek, Inc. was prepared
approximately 1-1/2 years ago and appears to address a different scope of work compared to the
currently proposed swimming pool/spa, site walls, and other rear yard improvements at the
subject site. Please review the most current revision of the grading and foundation plans for the
proposed project and provide updated geotechnical conclusions/recommendations as necessary
to address the currently proposed improvements.
Response to Comment No. 1
GeoTek performed a plan review of the project grading plans prepared by CE&LST
Corporation, dated September 2, 2024, as well as GeoTek’s referenced reports and letters for
the project (GeoTek, 2023a, 2023b, 2024a, and 2024b). The geotechnical conclusions and
recommendations presented in GeoTek’s prior referenced reports/letters remain valid and
applicable to the referenced scope of work presented on the CE&LST grading plan.
Recommendations and conclusions presented in this letter have been incorporated into the
project design.
Comment No. 2
Please provide a statement addressing the potential impact of the proposed project on adjacent
properties from a geotechnical standpoint.
GeoTek, Inc.
1384 Poinsettia Avenue, Suite A Vista, CA 92081-8505
(760) 599-0509 Office (760) 599-0593 Fa www.geotekusa.com
CAMERON ROSENHAN Project No. 3869-SD
Response to Comments Dated August 19, 2024 December 20, 2024
4080 Sunnyhill Dr., Carlsbad, California Page 2
Response to Comment No. 2
GeoTek performed a plan review of the project grading plans prepared by CE&LST
Corporation, dated September 2, 2024, as well as GeoTek’s referenced reports and letters for
the project (GeoTek, 2023a, 2023b, 2024a, and 2024b). Provided that the recommendations
presented in GeoTek’s reports and good construction practices are utilized during design and
construction, the proposed construction is not anticipated to adversely impact the adjacent
properties from a geotechnical standpoint.
Comment No. 3
Please provide a description of the proposed project and discuss the proposed grading (depths
and limits of cut/fill necessary to establish proposed grades), construction of proposed
swimming pool/spa, type of foundations, heights of the proposed site retaining walls, and types
of other proposed improvements.
Response to Comment No.3
The project is designed to substantially maintain the primary residence with demolition of a
portion of the southern wall and demolition of the front and rear retaining walls, the detached
garage and the in-ground pool to prepare the grades for the improvements. The improvements
generally consist of a new southern building wall for the primary residence, front and sideyard
retaining walls to support an at-grade patio wrapping around the perimeter of the primary
dwelling and a new driveway along the southern property line to a new detached garage with
adjacent ADU and over-garage ADU, new rear yard retaining walls to increase building pad
grades and facilitate the improvements including an in-ground pool with spa. The garage is at-
grade with a portion of the rear facilitating a crawl space. The new building foundations are
shown to be at-grade concrete slab with shallow foundations, with exception to the south and
rear side of the detached garage/ADU that is supported with an integrated retaining wall,
retaining adjacent elevated grades. Additionally, new flatwork and permeable concrete
pavement are designed. The proposed retaining walls are county standard walls with t-style
foundations and very in height from 2.6 to 7.4 feet.
Comment No.4
Please provide an updated “Geotechnical Map” utilizing the most current revision of the grading
plan for the project as the base map and at a sufficiently large scale to clearly show (at a
minimum): a) existing site topography and structures/improvements, b) proposed swimming
pool, spa, site walls, and other improvements, c) proposed finished grades, d) geologic units, e)
limits of proposed remedial grading, f) location of any shoring or special considerations for
temporary cuts near property boundaries, and g) the locations of subsurface exploration.
Response to Comment No.4
GEOTEK
CAMERON ROSENHAN Project No. 3869-SD
Response to Comments Dated August 19, 2024 December 20, 2024
4080 Sunnyhill Dr., Carlsbad, California Page 3
An updated Geotechnical Map is presented as Figure 2 and included in this response at the end
of the text. Shoring or special considerations for temporary cuts near property boundaries is not
anticipated to be needed.
Comment No. 5
Please provide a general north/south geologic cross-sections to demonstrate the temporary
cuts necessary to construct the proposed site retaining walls along the northern property
boundary. Please cut the section at the location of the most critical (highest) temporary cut and
show and label, a) existing site topography and on-site and off-site structures/improvements, b)
proposed finish grades, c) the limits of the existing and proposed improvements, d)
soil/geologic units underlying the site, and e) limits and depths of proposed remedial grading
and temporary cut necessary for the remedial grading and/or foundation for the proposed near
property line site retaining walls and swimming pool/spa.
Response to Comment No.5
A geologic cross section is presented as Figure 3 and included in this response at the end of the
text.
Comment No. 6.
Please provide a discussion addressing the regional faulting associated with the subject site.
Please include the names and distances of faults potentially impacting the subject property and
region.
Response to Comment No.6
The subject property is located in the Peninsular Ranges geomorphic province. The Peninsular
Ranges province is one of the largest geomorphic units in western North America. It extends
from the north and northeast, adjacent the Transverse Ranges geomorphic province to the top
of Baja California. This province varies in width from about 30 to 100 miles. It is bounded on
the west by the Pacific Ocean, on the south by the Gulf of California, and on the east by the
Colorado Desert Province.
The Peninsular Ranges are essentially a series of northwest-southeast oriented fault blocks.
Several major fault zones are found in this province. The Elsinore Fault zone and the San
Jacinto Fault zones trend northwest-southeast and are found near the middle of the province.
The San Andreas Fault zone borders the northeasterly margin of the province. The Newport-
Inglewood-Rose Canyon Fault zone borders the southwest margin of the province. No faults
are shown in the immediate site vicinity on the map reviewed for the area (Kennedy, 2007).
The site is located in southern California and is seismically active throughout the region. The
Rose Canyon Fault Zone is located approximately 6.0 miles southwest of the subject site.
Active faults mapped at a further distance are considered to potentially impact the site to a
lesser severity.
GEOTEK
CAMERON ROSENHAN Project No. 3869-SD
Response to Comments Dated August 19, 2024 December 20, 2024
4080 Sunnyhill Dr., Carlsbad, California Page 4
Comment No. 7.
Please provide the basis for the use of Site Class C (in accordance with Section 1613 of the
2022 California Building Code and Chapter 20 of ASCE 7-16) to determine the seismic design
parameters provided in the report for the Pleistocene terrace deposits (Old Paralic deposits);
revise if necessary.
Response to Comment No.7
Based on GeoTek’s experience in the vicinity of the subject site, a Site Class C is appropriate
based on a subsurface exploration performed at greater depths than the program performed for
the subject site. However, as a recommendation for a Site Class C cannot be referenced in
accordance to Section 1613 of the 2022 CBC and Chapter 20 of ASCE 7-16), revised seismic
design parameters based on a Site Class D are presented.
Revised Seismic Design Parameters
The site is located at approximately 33.155275 Latitude and -117.321616 Longitude. Site
spectral accelerations (Ss and S1), for 0.2 and 1.0 second periods for a risk targeted two (2)
percent probability of exceedance in 50 years (MCER) were determined using the web
interface provided by ASCE (https://asce7hazardtool.online) to access the USGS Seismic Design
Parameters. Using the ASCE 7-16 option on the SEAOC/OSHPD website results in the values
for SM1 and SD1 reported as “null-See Section 11.4.8” (of ASCE 7-16). As noted in ASCE 7-
16, Section 11.4.8, a site-specific ground motion procedure is recommended for Site Class D
when the value S1 exceeds 0.2. The value S1 for the subject site exceeds 0.2.
For a site Class D, an exception to performing a site-specific ground motion analysis is allowed
in ASCE 7-16 where S1 exceeds 0.2 provided the value of the seismic response coefficient, Cs,
is conservatively calculated by Eq 12.8-2 of ASCE 7-16 for values of T≤1.5Ts and taken as equal
to 1.5 times the value computed in accordance with either Eq. 12.8-3 for TL≥T>1.5Ts or Eq.
12.8-4 for T>TL. Based on the explorations performed at this site, the reviewed geologic map,
and planned grading activities, the site structural improvements will be underlain by engineered
fill, alluvium, and bedrock. For these soil conditions, a Site Class D is considered appropriate.
Assuming that the Cs value calculated by and used by the structural engineer allows for the
exclusion per ASCE 7-16, noted above, then a site-specific ground motion analysis is not
required. For this assumption and condition, the following seismic design parameters, based on
the 2015 National Earthquake Hazards Reduction Program (NEHRP), are presented on the
following table:
GEOTEK
CAMERON ROSENHAN Project No. 3869-SD
Response to Comments Dated August 19, 2024 December 20, 2024
4080 Sunnyhill Dr., Carlsbad, California Page 5
ASCE Reference ASCE-7-16
Site Class D
Mapped 0.2 sec Period Spectral Acceleration, Ss 1.02g
Mapped 1.0 sec Period Spectral Acceleration, S1 0.37g
Maximum Considered Earthquake Spectral
Response Acceleration for 0.2 Second, SMS 1.12
Maximum Considered Earthquake Spectral
Response Acceleration for 1.0 Second, SM1 N/A
5% Damped Design Spectral Response
Acceleration Parameter at 0.2 Second, SDS 0.74g
5% Damped Design Spectral Response
Acceleration Parameter at 1 second, SD1 N/A
Seismic Design Category D
Comment No. 8.
The submitted “Limited Geotechnical Evaluation…” report provides (based on the reference in
the report) seismic design parameters using ASCE 7-22. As ASCE 7-22 has not yet been
adopted for use by the City of Carlsbad, please provide the seismic design parameters based
on ASCE 7-16.
Response to Comment No.8
See GeoTek’s Response to Comment No. 7
Comment No. 9.
Please provide the dynamic seismic lateral earth pressure for retaining wall design (for walls
over 6’) in accordance with Section 1803.5.12 of the 2022 California Building Code.
Response to Comment No.9
Geotechnical retaining wall recommendations were provided to the project by GeoTek in the
referenced report dated September 11, 2023 (GeoTek, 2023b). For convenience, the dynamic
lateral earth pressure for retaining walls presented by GeoTek’s 2023 report are:
Seismic Earth Pressures
As required by the 2022 CBC, walls with a retained height greater than six feet are required to
include an incremental seismic earth pressure in the wall design. Based upon review, basement
walls with a retained height of up to approximately 11 feet are planned at the site.
The lateral pressure on retaining walls due to earthquake motions (dynamic lateral force)
should be calculated as PA = 3/8H2kh where:
PA = dynamic lateral force (lbs/ft)
= unit weight = 125 pcf
GEOTEK
CAMERON ROSENHAN Project No. 3869-SD
Response to Comments Dated August 19, 2024 December 20, 2024
4080 Sunnyhill Dr., Carlsbad, California Page 6
H = height of wall (feet)
Kh = seismic coefficient = 0.17
The dynamic lateral force may be expressed as 16-pounds-per-cubic-foot (equivalent fluid
pressure).
The dynamic lateral force is in addition to the static force and should be applied using a
triangular distribution with the resultant applied at 0.3H above the base of the wall. Retaining
walls that are less than 6-feet high do not require design to resist the additional earth pressure
caused by seismic ground shaking.
Comment No. 10.
Strength (direct shear) testing of the on-site soils is not provided in the reviewed report.
Please provide the appropriate laboratory testing to substantiate the values for bearing
capacity, passive earth pressure, coefficient of friction, and active/at-rest earth pressures
that are presented in the report. If presumptive values from the code are being recommended
by the consultant, please indicate the soil class and use values consistent
with the appropriate soil type (Class) in Tables 1806.2 and 1610.1 of the 2022 California
Building Code. If soil parameters other than soil class 5 in Tables 1806.2 and 1610.1 are
provided, please justify the soil type by site specific laboratory testing. The reviewer notes
that the values provided in the report exceed the respective values for Class 5 and some
exceed Class 4 soils per Tables 1806.2 and 1610.1. Please provide site specific laboratory
test results to justify the use of any assumed values of C and Φ for the determination of the
parameters requested above.
Response to Comment No.10
Based on the classification of the soils per ASTM D 2488, the soil type is a granular soil, soil
class 4. In addition, the retaining walls are San Diego Regional County Standards that are
inferred to be designed based on the 2022 CBC soil class 4 and 5. Therefore, the designed
county regional standard walls are considered to be geotechnically suitable for the project.
The following revised recommendations may be used for building and retaining wall
foundations. The bearing, lateral load value, and coefficient of friction are presumptive values
taken from the 2022 CBC, Table 1806.2, based on a soil class 4. Foundations bearing into
engineered fill and or paralic deposits may be designed for a dead plus live load bearing value
of 2000 psf. This value may be increased by one-third for loads including wind and seismic
forces. A lateral bearing value of 150 psf per foot of depth and a coefficient of friction between
foundation soil and concrete of 0.25 may be assumed.
Comment No. 11.
Please provide the amount of total and differential settlement that should be anticipated for the
design of the project.
GEOTEK
CAMERON ROSENHAN Project No. 3869-SD
Response to Comments Dated August 19, 2024 December 20, 2024
4080 Sunnyhill Dr., Carlsbad, California Page 7
Response to Comment No.11
Based on GeoTek’s experience in the area, structural foundations may be designed in
accordance with 2022 CBC, and to withstand a total settlement of 1 inch and maximum
differential settlement of one-half of the total settlement over a horizontal distance of 40 feet.
Seismically induced settlement potential is not a significant constraint.
Comment No. 12
As the “Retaining Walls” section of the report indicates that the recommendations provided are
only applicable for walls up to 4’ high, please provide updated parameters that address the
heights of the retaining walls (up to approximately 6 to 7’) required for the proposed project.
Response to Comment No.12
Geotechnical retaining wall recommendations were provided to the project by GeoTek in the
referenced report dated September 11, 2023 (GeoTek, 2023b).
Comment No. 13.
Please provide updated remedial grading recommendations (depth and limits of removals, etc.)
for the proposed site walls, hardscape improvements, and swimming pool/spa, etc. that are
associated with the proposed project.
Response to Comment No.13
The remedial grading recommendations presented in GeoTek’s 2023a report remain valid. The
retaining walls and pool are anticipated to be in area of cut exposing Old Paralic Deposit
formational material. Recommendations for hardscape improvements exposing existing fills is
also provided in section 5.1.1 of GeoTek’s 2023a report.
Comment No. 14.
Please provide recommendations for the temporary cuts that will apparently be necessary to
construct the proposed site retaining walls and swimming pool/spa along the northern property
boundary. Please provide recommendations and the configuration (allowed height of vertical
cut, slope inclination, time limit for exposure of cut, etc.) for the apparent approximate 6 to 7’
high temporary backcut so that the cut will result in no adverse impact to the existing property
line wall and other adjacent property and provide a safe condition for workers. Please also
provide the Type Soil (A, B, C) that should be used to address OSHA guidelines. Please
provide specific recommendations and procedures for the temporary cuts that will prevent
adverse impact of the temporary cuts on existing adjacent off-site property as necessary.
Response to Comment No.14
Temporary excavations for remedial grading and retaining walls
Temporary excavations within the onsite materials (Soil Type B, per CalOSHA) not within
groundwater should be stable at 1:1 (horizontal to vertical) gradient for short durations during
construction, and where cuts do not exceed 20 feet in height. Temporary cuts to a maximum
height of 4 feet can be excavated vertically.
Temporary excavations for in-ground pool construction
GEOTEK
CAMERON ROSENHAN Project No. 3869-SD
Response to Comments Dated August 19, 2024 December 20, 2024
4080 Sunnyhill Dr., Carlsbad, California Page 8
Temporary excavations for the inground pool within the Old Paralic Deposits (Soil Type B, per
CalOSHA) should be stable at a 10 feet vertical excavation for short durations during
construction. It is GeoTek’s understanding that the pool was constructed prior to the issuance
of this letter.
Comment No. 15.
Please provide recommendations (grading, active pressure, etc.) for the proposed
swimming pool and spa.
Response to Comment No.15
Please see GeoTek’s 2023a and 2023b referenced reports.
Comment No. 16.
Please p r o v i d e recommendations (minimum slab thickness, reinforcing, etc.) for
hardscape improvements from a geotechnical standpoint.
Response to Comment No.16
Exterior concrete slabs (pedestrian, non-vehicular) should be designed using a four-inch
minimum thickness. Some shrinkage and cracking of the concrete should be anticipated as a
result of typical mix designs and curing practices typically utilized in construction.
Sidewalks and driveways may be under the jurisdiction of the governing agency. If so,
jurisdictional design and construction criteria would apply, if more restrictive than the
recommendations presented in this report.
Subgrade soils should be pre-moistened prior to placing concrete. The subgrade soils below
exterior slabs, sidewalks, driveways, etc. should be pre-saturated to a minimum of 100 percent
of the optimum moisture content to a depth of 12 inches and compacted to at least 90% per
ASTM D 1557.
All concrete installation, including preparation and compaction of subgrade, should be done in
accordance with the City of Carlsbad specifications, and under the observation and testing of
GeoTek, Inc. and a city inspector, if necessary.
Concrete Performance
Concrete cracks should be expected. These cracks can vary from sizes that are hairline to
more than 1/8 inch in width. Most cracks in concrete, while unsightly, do not significantly
impact long-term performance. While it is possible to take measures (proper concrete mix,
placement, curing, control joints, etc.) to reduce the extent and size of cracks that occur, some
cracking will occur despite the best efforts to minimize it. Concrete undergoes chemical
processes that are dependent on a wide range of variables, which are difficult, at best, to
GEOTEK
CAMERON ROSENHAN Project No. 3869-SD
Response to Comments Dated August 19, 2024 December 20, 2024
4080 Sunnyhill Dr., Carlsbad, California Page 9
control. Concrete, while seemingly stable material, is subject to internal expansion and
contraction due to external changes over time.
One of the simplest means to control cracking is to provide weakened control joints for
cracking to occur along. These do not prevent cracks from developing; they simply provide a
relief point for the stresses that develop. These joints are a widely accepted means to control
cracks but are not always effective. Control joints are more effective the more closely spaced
they are. GeoTek, Inc. suggests that control joints be placed in two directions and located a
distance approximately equal to 24 to 36 times the slab thickness (e.g., a 4-inch slab would have
control joints at 96 inch [8 feet] centers).
Comment No. 17.
Please evaluate and discuss the potential for storm water infiltration at the subject site as part
of the proposed project.
Response to Comment No.17
GeoTek’s understanding is the project is not subject to requirements to design for stormwater
management, however, permeable pavers are designed based on the grading plans and were
reviewed to be geotechnically consistent with guidelines and standard details of the Interlocking
Concrete Pavement Design Manual, 2018. In addition, the site is mapped as a hydrologic
classification as Type B soils with an anticipated infiltration rate of 0.57 to 1.98 inches per hour.
Comment No. 18.
Please add a) retaining wall subdrains, b) hardscape subgrade, c) temporary excavations, d)
swimming pool and spa excavations, and e) utility trench backfill to the list of the geotechnical
observations/testing services that should be provided during the construction of the proposed
development.
Response to Comment No.18
In addition to the list of recommended geotechnical observation and testing present in Section
5.4 of GeoTek’s 2023a report the following are recommended
a) retaining wall subdrains,
b) hardscape subgrade,
c) temporary excavations,
d) swimming pool and spa excavations, and
e) utility trench backfill
Closure
The opportunity to be of service is sincerely appreciated. If you should have any questions,
please do not hesitate to call GeoTek.
Respectfully submitted,
GEOTEK
CAMERON ROSENHAN Project No. 3869-SD
Response to Comments Dated August 19, 2024 December 20, 2024
4080 Sunnyhill Dr., Carlsbad, California Page 10
GeoTek, Inc.
Christopher Livesey Edwin R. Cunningham
CEG 2733, Exp. 05/31/25 RCE 81687, Exp. 03/31/26
Vice President Project Engineer
Attachments: Figure 1 – Geotechnical Map
Figure 2 – Geologic Cross Section AA
Appendix A – Review Comments
Appendix B – Hydrological Soil Classification and Summary of Soil Properties
Appendix C – GeoTek’s Report Dated February 28, 2023
Appendix D – GeoTek’s Letter Dated September 11, 2023
Appendix E – GeoTek’s Letter Dated July 1, 2024
Appendix F – GeoTek’s Letter Dated September 17, 2024
Distribution: (1) Addressee via email
GEOTEK
CAMERON ROSENHAN Project No. 3869-SD
Response to Comments Dated August 19, 2024 December 20, 2024
4080 Sunnyhill Dr., Carlsbad, California Page 11
REFERENCES
GeoTek, Inc., 2023a, “Limited Geotechnical Evaluation, Proposed Auxiliary Dwelling Unit
(ADU), 4080 Sunnyhill Dr., Carlsbad, CA, 92008,” Project No. 3869-SD, dated February
28, 2023.
______, 2023b, “Supplemental Geotechnical Recommendations, Proposed Auxiliary Dwelling
Unit (ADU), 4080 Sunnyhill Dr., Carlsbad, CA, 92008,” Project No. 3869-SD, dated
September 11, 2023.
______, 2024a, “Foundation Plan Review, Proposed Auxiliary Dwelling Unit (ADU), 4080
Sunnyhill Dr., Carlsbad, CA, 92008,” Project No. 3869-SD, dated July 1, 2024.
______, 2024b, “Pool and Spa Foundation Plan Review, Proposed Auxiliary Dwelling Unit
(ADU), 4080 Sunnyhill Dr., Carlsbad, CA, 92008,” Project No. 3869-SD, dated
September 17, 2024.
CE&LST Corporation DBA Sampo, Grading Plan for Rosenhan Residence, (APN: 207-072-06,
4080 Sunnyhill Drive, Job No. 22-16, dated September 2, 2024.
Pool Engineering, Inc, 2024, Landscape Improvement Plans, Standard Pool Structural Plan,
Structural Notes, & Structural Details “4080 Sunnyhill Drive, Carlsbad, CA 92008-
2750,” dated July 23, 2024, Sheets 2 of 2, 100, detail 240, Detail 400, Detail 55.
Qualls Engineering, 2023, Foundation Plan, Structural Notes, & Structural Details “Rosenhan
ADU, 4080 Sunnyhill Drive, Carlsbad, CA 92008,” dated September 9, 2023 (plan check
submittal date), Sheets S1.0, S1.1, S1.2, S2.0, SD3, and S4.
GEOTEK
LEGEND
Approximate Site Boundary
Anticipated Remedial Grading Limit
Approximate Location of Cross-Section
Approximate Location of Exploratory Boring
Artificial Fill
Quaternary-age Very Old Paralic Deposits
Circled Where Buried
A A’
Af
Qvop
HA-2
1384 Poinsettia Avenue, Suite A
Vista, California 92081
Cameron Rosenhan
4080 Sunnyhill Drive
Carlsbad, CA
PN: 3869-SD December 2024
Figure 1
Geotechnical Map
HA-3
A
A’
Qvop
Af
HA-2
HA-1
~ D'4e'Ull(lfJQJ II aa»t;
d ~ ,.-4 . . .
. · . .
.________.
A
GEOTEK
1384 Poinsettia Avenue, Suite A
Vista, California 92081
Figure 3
Cross Section AA
PN: 3869-SD December 2024
Cameron Rosenhan
4080 Sunnyhill Drive
Carlsbad, CA
255
245
265
235
225
255
245
265
225
235
HA-3
(Project 20’)
?
?
Property Line
Qvop
Af
Approximate
Geologic
Contact
Design
Grades
Garage/ADU
Design Spa
Design
Retaining
Wall (Typical)
Temporary
Excavation
(Typical)
N-S
A A’
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Scale 1”=10’
Notes:
Groundwater Estimated at a greater depth than 220 feet msl
No Remedial Grading is anticipated along section
...
► --
-
--
GEOTEK
II
Appendix A
Review Comment
GEOTEK
GEOTECHNICAL REPORT REVIEW
__________________________________________________________
DATE: August 23, 2024
TO: City of Carlsbad
Land Development Engineering
1635 Faraday Avenue
Carlsbad, CA 92008
Attention: Jose Sanchez
PROJECT ID: CDP2023-0040
GRADING PERMIT NO.: GR2024-0017
SUBJECT: 4080 Sunnyhill Drive, (1st review)
Items Submitted by Applicant Items Being Returned to Applicant
“Limited Geotechnical Evaluation, Proposed
Auxiliary Dwelling Unit (ADU), 4080 Sunnyhill Dr.,
Carlsbad, California,” by GeoTek, Inc., dated
February 28, 2023.
Written report review comments.
Based on our review of the submitted geotechnical report, we are providing the following
comments that should be addressed prior to the next submittal. Please provide complete and
thorough written responses to all comments.
GEOTECHNICAL COMMENTS:
1. The submitted “Limited Geotechnical Evaluation…” by GeoTek, Inc. was prepared
approximately 1-1/2 years ago and appears to address a different scope of work compared
to the currently proposed swimming pool/spa, site walls, and other rear yard improvements
at the subject site. Please review the most current revision of the grading and foundation
plans for the proposed project and provide updated geotechnical
conclusions/recommendations as necessary to address the currently proposed
improvements.
2. Please provide a statement addressing the potential impact of the proposed project on
adjacent properties from a geotechnical standpoint.
3. Please provide a description of the proposed project and discuss the proposed grading
(depths and limits of cut/fill necessary to establish proposed grades), construction of
proposed swimming pool/spa, type of foundations, heights of the proposed site retaining
walls, and types of other proposed improvements.
GR2024-0017
August 23, 2024
Page 2 of 3
4. Please provide an updated “Geotechnical Map” utilizing the most current revision of the
grading plan for the project as the base map and at a sufficiently large scale to clearly
show (at a minimum): a) existing site topography and structures/improvements, b)
proposed swimming pool, spa, site walls, and other improvements, c) proposed finished
grades, d) geologic units, e) limits of proposed remedial grading, f) location of any shoring
or special considerations for temporary cuts near property boundaries, and g) the locations
of subsurface exploration.
5. Please provide a general north/south geologic cross-sections to demonstrate the
temporary cuts necessary to construct the proposed site retaining walls along the northern
property boundary. Please cut the section at the location of the most critical (highest)
temporary cut and show and label, a) existing site topography and on-site and off-site
structures/improvements, b) proposed finish grades, c) the limits of the existing and
proposed improvements, d) soil/geologic units underlying the site, and e) limits and depths
of proposed remedial grading and temporary cut necessary for the remedial grading
and/or foundation for the proposed near property line site retaining walls and swimming
pool/spa.
6. Please provide a discussion addressing the regional faulting associated with the subject
site. Please include the names and distances of faults potentially impacting the subject
property and region.
7. Please provide the basis for the use of Site Class C (in accordance with Section 1613 of
the 2022 California Building Code and Chapter 20 of ASCE 7-16) to determine the seismic
design parameters provided in the report for the Pleistocene terrace deposits (Old Paralic
deposits); revise if necessary.
8. The submitted “Limited Geotechnical Evaluation…” report provides (based on the
reference in the report) seismic design parameters using ASCE 7-22. As ASCE 7-22 has
not yet been adopted for use by the City of Carlsbad, please provide the seismic design
parameters based on ASCE 7-16.
9. Please provide the dynamic seismic lateral earth pressure for retaining wall design (for
walls over 6’) in accordance with Section 1803.5.12 of the 2022 California Building Code.
10. Strength (direct shear) testing of the on-site soils is not provided in the reviewed report.
Please provide the appropriate laboratory testing to substantiate the values for bearing
capacity, passive earth pressure, coefficient of friction, and active/at-rest earth pressures
that are presented in the report. If presumptive values from the code are being
recommended by the consultant, please indicate the soil class and use values consistent
with the appropriate soil type (Class) in Tables 1806.2 and 1610.1 of the 2022 California
Building Code. If soil parameters other than soil class 5 in Tables 1806.2 and 1610.1 are
provided, please justify the soil type by site specific laboratory testing. The reviewer notes
that the values provided in the report exceed the respective values for Class 5 and some
exceed Class 4 soils per Tables 1806.2 and 1610.1. Please provide site specific laboratory
test results to justify the use of any assumed values of C and Φ for the determination of
the parameters requested above.
11. Please provide the amount of total and differential settlement that should be anticipated
for the design of the project.
GR2024-0017
August 23, 2024
Page 3 of 3
12. As the “Retaining Walls” section of the report indicates that the recommendations provided
are only applicable for walls up to 4’ high, please provide updated parameters that address
the heights of the retaining walls (up to approximately 6 to 7’) required for the proposed
project.
13. Please provide updated remedial grading recommendations (depth and limits of removals,
etc.) for the proposed site walls, hardscape improvements, and swimming pool/spa, etc.
that are associated with the proposed project.
14. Please provide recommendations for the temporary cuts that will apparently be necessary
to construct the proposed site retaining walls and swimming pool/spa along the northern
property boundary. Please provide recommendations and the configuration (allowed
height of vertical cut, slope inclination, time limit for exposure of cut, etc.) for the apparent
approximate 6 to 7’ high temporary backcut so that the cut will result in no adverse impact
to the existing property line wall and other adjacent property and provide a safe condition
for workers. Please also provide the Type Soil (A, B, C) that should be used to address
OSHA guidelines. Please provide specific recommendations and procedures for the
temporary cuts that will prevent adverse impact of the temporary cuts on existing adjacent
off-site property as necessary.
15. Please provide recommendations (grading, active pressure, etc.) for the proposed
swimming pool and spa.
16. Please provide recommendations (minimum slab thickness, reinforcing, etc.) for
hardscape improvements from a geotechnical standpoint.
17. Please evaluate and discuss the potential for storm water infiltration at the subject site as
part of the proposed project.
18. Please add a) retaining wall subdrains, b) hardscape subgrade, c) temporary excavations,
d) swimming pool and spa excavations, and e) utility trench backfill to the list of the
geotechnical observations/testing services that should be provided during the construction
of the proposed development.
Appendix B
Hydrological Soil Classification and Summary of Soil Properties
GEOTEK
Soil Map—San Diego County Area, California
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
12/19/2024
Page 1 of 3
36
6
8
5
2
7
36
6
8
5
3
4
36
6
8
5
4
1
36
6
8
5
4
8
36
6
8
5
5
5
36
6
8
5
6
2
36
6
8
5
6
9
36
6
8
5
2
7
36
6
8
5
3
4
36
6
8
5
4
1
36
6
8
5
4
8
36
6
8
5
5
5
36
6
8
5
6
2
36
6
8
5
6
9
469977 469984 469991 469998 470005 470012 470019 470026 470033 470040
469977 469984 469991 469998 470005 470012 470019 470026 470033 470040
33° 9' 19'' N
11
7
°
1
9
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1
9
'
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W
33° 9' 19'' N
11
7
°
1
9
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1
6
'
'
W
33° 9' 18'' N
11
7
°
1
9
'
1
9
'
'
W
33° 9' 18'' N
11
7
°
1
9
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1
6
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N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 11N WGS84
0 10 20 40 60Feet
0 4 9 18 27Meters
Map Scale: 1:307 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
USDA =
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: San Diego County Area, California
Survey Area Data: Version 20, Aug 30, 2024
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Mar 14, 2022—Mar
17, 2022
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Soil Map—San Diego County Area, California
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
12/19/2024
Page 2 of 3
§
□ (I
D (b
'C1
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□ ....
~
181
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USDA =
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
MlE Marina loamy coarse sand, 9
to 30 percent slopes
0.3 100.0%
Totals for Area of Interest 0.3 100.0%
Soil Map—San Diego County Area, California
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
12/19/2024
Page 3 of 3USDA =
San Diego County Area, California
MlE—Marina loamy coarse sand, 9 to 30 percent slopes
Map Unit Setting
National map unit symbol: hbf0
Elevation: 0 to 460 feet
Mean annual precipitation: 11 to 13 inches
Mean annual air temperature: 57 to 61 degrees F
Frost-free period: 330 to 350 days
Farmland classification: Not prime farmland
Map Unit Composition
Marina and similar soils:85 percent
Minor components:15 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Marina
Setting
Landform:Ridges
Down-slope shape:Concave
Across-slope shape:Linear
Parent material:Eolian sands derived from mixed sources
Typical profile
H1 - 0 to 10 inches: loamy coarse sand
H2 - 10 to 57 inches: loamy sand
H3 - 57 to 60 inches: sand
Properties and qualities
Slope:9 to 30 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Somewhat excessively drained
Runoff class: High
Capacity of the most limiting layer to transmit water
(Ksat):Moderately high to high (0.57 to 1.98 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Maximum salinity:Nonsaline to very slightly saline (0.0 to 2.0
mmhos/cm)
Available water supply, 0 to 60 inches: Low (about 4.7 inches)
Interpretive groups
Land capability classification (irrigated): 4e
Land capability classification (nonirrigated): 6e
Hydrologic Soil Group: B
Ecological site: F019XG915CA - Sandy Hills <30"ppt
Hydric soil rating: No
Map Unit Description: Marina loamy coarse sand, 9 to 30 percent slopes---San Diego County
Area, California
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
12/19/2024
Page 1 of 2~
Minor Components
Carlsbad
Percent of map unit:5 percent
Hydric soil rating: No
Chesterton
Percent of map unit:5 percent
Hydric soil rating: No
Corralitos
Percent of map unit:5 percent
Hydric soil rating: No
Data Source Information
Soil Survey Area: San Diego County Area, California
Survey Area Data: Version 20, Aug 30, 2024
Map Unit Description: Marina loamy coarse sand, 9 to 30 percent slopes---San Diego County
Area, California
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
12/19/2024
Page 2 of 2~
Appendix C
GeoTek’s Report Dated February 28, 2023
GEOTEK
GEOTECHNICAL | ENVIRONMENTAL | MATERIAL
LIMITED GEOTECHNICAL EVALUATION
PROPOSED Auxiliary Dwelling Unit (ADU)
4080 SUNNYHILL DR.
CARLSBAD, CALIFORNIA 92008
PREPARED FOR
CAMERON ROSENHAN
4080 SUNNYHILL DR.
CARLSBAD, CA 92008
PREPARED BY
GEOTEK, INC.
1384 POINSETTIA AVENUE
VISTA, CALIFORNIA 92081
PROJECT NO. 3869-SD FEBRUARY 28, 2023
GEOTEK
GEOTECHNICAL | ENVIRONMENTAL | MATERIAL
February 28, 2023
Project No. 3869-SD
Cameron Rosenhan
4080 Sunnyhill Dr.
Carlsbad, California 92008
Attention: Mr. Cameron Rosenhan
Subject: Limited Geotechnical Evaluation
Proposed Auxiliary Dwelling Unit (ADU)
4080 Sunnyhill Dr.
Carlsbad, California 92008
Dear Mr. Rosenhan,
GeoTek, Inc. (GeoTek) is pleased to provide results of this Limited Geotechnical
Evaluation for the subject improvements. Based upon review, site construction appears
feasible from a geotechnical viewpoint, provided that the recommendations included
herein are incorporated into the design and construction phases of site improvements.
The opportunity to be of service is sincerely appreciated. If you should have any questions,
please do not hesitate to call GeoTek.
Respectfully submitted,
GeoTek, Inc.
Timothy E. Metcalfe, PG, CEG
Principal Geologist
Edwin R. Cunningham, RCE
Project Engineer
3-31-24
GeoTek, Inc.
1384 Poinsettia Avenue, Suite A Vista, CA 9208 1-8505
(760) 599-0509 Office (760) 599-0593 F~ www.geotekusa.com
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page i
TABLE OF CONTENTS
1. PURPOSE AND SCOPE OF SERVICES .................................................................................................... 1
2. SITE DESCRIPTION AND PROPOSED DEVELOPMENT .................................................................... 1
2.1 SITE DESCRIPTION .................................................................................................................................... 1
2.2 PROPOSED DEVELOPMENT ........................................................................................................................ 1
3. FIELD STUDY AND LABORATORY TESTING ...................................................................................... 2
3.1 FIELD EXPLORATION ................................................................................................................................ 2
3.2 LABORATORY TESTING ............................................................................................................................ 2
4. GEOLOGIC AND SOILS CONDITIONS ................................................................................................... 2
4.1 EARTH MATERIALS ............................................................................................................................ 2
4.1.1 Artificial Fill (Af) ........................................................................................................................... 2
4.1.2 Paralic Deposits (Qop) .................................................................................................................. 3
4.2 SURFACE AND GROUND WATER ................................................................................................................ 3
4.2.1 Surface Water ................................................................................................................................. 3
4.2.2 Groundwater .................................................................................................................................. 3
4.3 EARTHQUAKE AND SEISMIC HAZARDS ..................................................................................................... 3
5. CONCLUSIONS AND RECOMMENDATIONS ........................................................................................ 4
5.1 GENERAL .................................................................................................................................................. 4
5.1.1 Site Clearing and Building Pad Preparation ................................................................................. 4
5.2 DESIGN RECOMMENDATIONS ................................................................................................................... 4
5.2.1 Foundations ................................................................................................................................... 4
5.2.2 Seismic Design Parameters ............................................................................................................ 7
5.2.3 Soil Sulfate and Chloride Content .................................................................................................. 7
5.3 RETAINING WALLS ................................................................................................................................... 8
5.3.1 Expected Wall Movements ............................................................................................................. 9
5.3.2 Wall Backfill and Drainage ........................................................................................................... 9
5.4 CONSTRUCTION OBSERVATIONS ............................................................................................................... 9
6. INTENT ......................................................................................................................................................... 10
7. LIMITATIONS ............................................................................................................................................. 10
8. SELECTED REFERENCES ....................................................................................................................... 11
ENCLOSURES
Figure 1 – Site Location Map
Figure 2 – Geotechnical Map
Appendix A – Logs of Exploration
Appendix B – Results of Laboratory Testing
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 1
1. PURPOSE AND SCOPE OF SERVICES
The purpose of this study was to assess the site geotechnical conditions with regards to the
proposed improvements. Services provided for this study included the following:
Research and review of readily available geologic data and general information pertinent to
the site.
Excavation of three manual auger borings and collection of bulk samples for subsequent
laboratory testing.
Laboratory testing of soil samples collected during field exploration.
Review and analysis of geologic and geotechnical engineering data.
Compilation of this geotechnical report presenting findings of pertinent geotechnical
conditions and geotechnical recommendations for site development.
2. SITE DESCRIPTION AND PROPOSED DEVELOPMENT
2.1 SITE DESCRIPTION
The site is San Diego County Assessor Parcel Number APN 207-07-205-00 located at 4080
Sunnyhill Drive, California 92008 (See Figure 1). The approximately one-half acre property is
currently improved with a single-story residence, driveway, backyard, pool, shed, tennis court,
and various landscaping improvements. The property is bounded by Sunnyhill Drive to the west
and similarly developed residential properties to the north, south, and east. The site slopes up
from Sunnyhill Drive about 10 feet to the pad area where the house and pool sit. Topography
then continues to slope up to the residence to the east. The tennis court and shed site in the
upper portion of the site at the east. Total relief on the site is about 57 feet. The driveway extends
along the entire south side of the property.
The existing house is L-shaped, one-story with semi-attached (separated by a breeze way) garage
and storage room extending to the east This report is limited to the proposed improvements as
discussed herein and located within the boundaries presented on the Geotechnical Map: Figure
2. The area of planned improvements (referred to herein as the “site”) is located east of the
existing primary residence in the northeast portion of the property.
2.2 PROPOSED DEVELOPMENT
The proposed site improvements, based on a conversation with you, consist of a detached garage
with an accessory dwelling unit (ADU) above and the addition of a second story over much of
the existing house. A conversation with you regarding the extent of the improvements. No
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 2
significant site grading is planned although we assume that the rear (east) wall of the garage/ADU
will require minor cut up to approximately three feet high.
No plans have been provided for our use. Based on the project description provided we assume
that the garage/ADU structure would have a continuous strip footing around the perimeter with
an interior concrete slab-on-grade for the garage floor. It seems reasonable that the second story
addition will be primarily supported on posts supported by pad footings, so that the second story
would span the existing structure.
3. FIELD STUDY AND LABORATORY TESTING
3.1 FIELD EXPLORATION
Field exploration was conducted on December 23, 2022, and consisted of a site reconnaissance,
excavation of three manual auger borings and collection of bulk soil samples for subsequent
laboratory testing. Locations of the auger holes were limited by the extensive concrete paving
present. A soil probe was applied at discrete depths to qualitatively evaluate the underlying soil
properties. A representative from GeoTek visually logged the excavations as depicted in the
Appendix A - Logs of Exploration. The approximate location of the test boring is presented on
the Geotechnical Map: Figure 2. Samples were transported to our laboratory for testing.
3.2 LABORATORY TESTING
Laboratory tests were performed on the soil sample collected during the field exploration. The
purpose of the laboratory testing was to evaluate their physical and chemical soil properties for
use in engineering design and analysis. Results of the laboratory testing program, along with a
brief description and relevant information regarding testing procedures, are included in Appendix
B – Laboratory Testing.
4. GEOLOGIC AND SOILS CONDITIONS
4.1 EARTH MATERIALS
A brief description of the earth materials encountered during the subsurface exploration is
presented in the following sections. Based on review of published geologic maps and the site-
specific evaluation, the subject site is locally underlain by artificial fill over old paralic deposits.
4.1.1 Artificial Fill (Af)
Artificial fill was encountered in the upper 2 to 2.5 feet of the exploration. Artificial fill consisted
of silty fine to medium sand, dark brown in color, moist, and loose to medium dense with depth.
Organics and roots were occasionally encountered in each of the borings in the upper 4-inches.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 3
4.1.2 Paralic Deposits (Qop)
Old paralic deposits were encountered in all borings at 2 to 2.5 feet deep and to the full depths
of exploration. The paralic deposits consisted of fine to medium sand to silty sand with some
clay, light orange, brown in color, moist, and medium dense to very dense with depth. Borings
HA-1 and HA-2, located at the front of the house, also contained a thin layer of sandy clay at the
top of the paralic deposits.
4.2 SURFACE AND GROUND WATER
4.2.1 Surface Water
Surface water was not observed during the site visit and exploration. If encountered during
earthwork construction, surface water on this site will likely be the result of precipitation and
some runoff from upslope areas/properties.
4.2.2 Groundwater
An apparently localized perched water seepage was encountered in Boring HA-2 at a depth of
3.5 feet. It is not anticipated to be significant factor in the proposed construction due to the
boring’s location in reference to the planned improvements. The seepage extended to
approximately 6 feet below the surface and may be related to the adjacent sprinkler system. It is
likely that vertical migration is retarded by the material density increase. It is fairly common to
encounter this type of seepage in this area of Carlsbad particularly during the rainy season. No
other groundwater was encountered during the subsurface exploration. The groundwater table
is likely at least 50 feet below the surface.
4.3 EARTHQUAKE AND SEISMIC HAZARDS
No active or potentially active fault is known to exist at this site or is the site situated within an
“Alquist-Priolo” Earthquake Fault Zone or a Special Studies Zone (Bryant and Hart, 2007). No faults
are identified on the geologic maps reviewed for the immediate proximity of the study area.
The liquefaction potential and seismic settlement potential on this site are considered negligible
due to the density of the underlying paralic deposits and other than the minor perched condition
absence of a shallow groundwater table.
Evidence of ancient landslides or gross slope instabilities at this site was not observed during this
study or indicated on regional geologic maps. Thus, the potential for landslides is considered
negligible.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 4
5. CONCLUSIONS AND RECOMMENDATIONS
5.1 GENERAL
The proposed improvements appear feasible from a geotechnical viewpoint provided that the
project design and construction comply with the 2022 California Building Code (CBC), City of
Carlsbad guidelines and recommendations contained in this report.
5.1.1 Site Clearing and Building Pad Preparation
Site clearing of vegetation (if any), and debris should be performed prior to preparation of the
building pad. In the areas of proposed improvements at or near existing ground surface, existing
fill should be removed. Removal depths on the order of 2.5 feet below existing grades are
indicated by the borings. While the concrete limited testing locations, it is anticipated that in the
area of the existing driveway is likely to encounter paralic deposits within the upper foot.
Following removals, the exposed surface should be scarified to a depth of 8-inches, moisture
conditioned to optimum moisture content or higher and compacted to a minimum of 90% of
maximum dry density as determined by ASTM D 1557 test procedures. The recommended
removals and recompaction should extend to at least 2 feet outside the proposed improvements,
where possible.
If soil is needed to raise pad grades after stripping of unsuitable materials, acceptable engineered
fill materials should be placed in horizontal lifts not exceeding 8 inches in loose thickness, moisture
conditioned to at or slightly above the optimum moisture content and compacted to a minimum
relative compaction of 90% of maximum dry density as determined by ASTM D 1557 test
procedures.
5.2 DESIGN RECOMMENDATIONS
5.2.1 Foundations
Foundations can be placed in either dense paralic deposits or engineered fill. Where no new slab
on grade is proposed, extending footings into dense paralic deposits is likely the prudent
approach. Where a slab-on-grade is planned, area/s inside the building envelope and 2 feet beyond
should be prepared according to the above site clearing and building pad preparation
recommendations.
Based on laboratory testing the near surface subgrade soils are classified as “very low” (EI<20)
expansive index (ASTM D4829 test procedure). The following criteria is for the design of the
project’s building foundation system.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 5
MINIMUM DESIGN REQUIREMENTS FOR CONVENTIONALLY
REINFORCED FOUNDATIONS
DESIGN PARAMETER “Very Low”
Expansion Index (EI<20)
Perimeter Foundation Embedment Depth
(inches below lowest adjacent finished grade) 12 inches
Minimum Perimeter Foundation Width 12 inches
Minimum Isolated Square Foundation Width 18 inches
Minimum Isolated Square Foundation Depth
(inches below lowest adjacent finished grade) 18 inches
Minimum Slab Thickness 4 inches actual
Minimum Slab Reinforcement
No. 3 rebar 24” on-center, each way,
placed in the middle one-third of the slab
thickness
Minimum Footing Reinforcement Two No. 4 Reinforcing Bars,
one top and one bottom
Pre-Saturation of Subgrade Soil (percent of
optimum moisture content) Minimum 100% to a depth of 12 inches
Where foundations extend through existing fill and into paralic deposits (expected for the second
story addition) a minimum 24-inch square or if drilled 18-inch diameter base, spread footing is
recommended. Footings should extend at least 12 inches into the bearing material. It is important
to remove loose soil in the bottom of the footing.
It should be noted that the above recommendations are based on soil support characteristics
only. The structural engineer should design the slab and beam reinforcement based on actual
loading conditions.
Footings embedded in suitable bearing materials, as observed and documented by a
GeoTek representative, may be dimensioned based on an allowable soil bearing pressure
of 2,000 psf. Bearing may be increased by 500 psf for each additional of depth and 250
psf for each additional foot of width to a maximum of 3,500 psf. These increases can be
applied from the 12 inches below the ground surface in areas of existing fill for column
footings. The allowable soil bearing pressure may be increased by one-third for short term
wind and/or seismic loads.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 6
The passive earth pressure for footings within the engineered fill may be computed as an
equivalent fluid having a density of 250 psf per foot of depth, to a maximum earth pressure
of 3,000 psf. A coefficient of friction between soil and concrete of 0.35 may be used with
dead load forces. When combining passive and frictional resistance, the passive pressure
component should be reduced by one-third.
A moisture and vapor retarding system should be placed below slabs-on-grade where moisture
migration through the slab is undesirable. Guidelines for these are provided in the 2022 California
Green Building Standards Code (CALGreen) Section 4.505.2, the 2022 CBC Section 1907.1 and
ACI 360R-10. The vapor retarder design and construction should also meet the requirements
of ASTM E 1643. A portion of the vapor retarder design should be the implementation of a
moisture vapor retardant membrane.
It should be realized that the effectiveness of the vapor retarding membrane can be adversely
impacted as a result of construction related punctures (e.g. stake penetrations, tears, punctures
from walking on the vapor retarder placed atop the underlying aggregate layer, etc.). These should
be avoided during construction. Thicker membranes are generally more resistant to accidental
puncture than thinner ones. Products specifically designed for use as moisture/vapor retarders
may also be more puncture resistant. The CBC specifies a 6mil vapor retarder membrane. The
California Residential Code (CRC) Section 506.3 specifies a 10mil membrane. It is GeoTek’s
opinion that a minimum 10mil thick membrane with joints properly overlapped and sealed should
be considered, unless otherwise specified by the slab design professional.
Moisture and vapor retarding systems are intended to reduce not eliminate vapor and moisture
transmission through the concrete. The acceptable level of moisture transmission through the
slab is to a considerable extent based on the type of flooring used and environmental conditions.
Ultimately, the vapor retarding system should be comprised of suitable elements to limited
migration of water and reduce transmission of water vapor through the slab to acceptable levels.
The selected elements should have suitable properties (i.e., thickness, composition, strength, and
permeability) to achieve the desired performance level.
Moisture retarder systems should be designed and constructed in accordance with applicable
American Concrete Institute, Portland Cement Association, Post-Tensioning Concrete Institute,
ASTM and, CRC and CBC requirements and guidelines.
GeoTek recommends that a qualified person, such as the flooring contractor, structural engineer,
architect, and/or other experts specializing in moisture control within the building be consulted
to evaluate the general and specific moisture and vapor transmission paths and associated
potential impact on the proposed construction. That person (or persons) should provide
recommendations relative to the slab moisture and vapor retarder systems and for migration of
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 7
potential adverse impact of moisture vapor transmission on various components of the
structures, as deemed appropriate.
In addition, the recommendations in this report and GeoTek’s services in general are not
intended to address mold prevention; since GeoTek, along with geotechnical consultants in
general, do not practice in the area of mold prevention. If specific recommendations addressing
potential mold issues are desired, then a professional mold prevention consultant should be
contacted.
5.2.2 Seismic Design Parameters
The site is located at approximately 33.155275 Latitude and -117.321616 Longitude. Site spectral
accelerations (Ss and S1), for 0.2 and 1.0 second periods for a risk targeted two (2) percent
probability of exceedance in 50 years (MCER) were determined using the web interface provided
by ASCE/SEI-7 (https://asce7hazardtool.online) to access the USGS Seismic Design Parameters.
A Site Class “C” is deemed appropriate for this site based on the apparent density of the
formation underlying the project site.
SITE SEISMIC PARAMETERS
Mapped 0.2 sec Period Spectral Acceleration, Ss 1.16g
Mapped 1.0 sec Period Spectral Acceleration, S1 0.37g
Maximum Considered Earthquake Spectral
Response Acceleration for 0.2 Second, SMS 1.24g
Maximum Considered Earthquake Spectral
Response Acceleration for 1.0 Second, SM1 0.53g
5% Damped Design Spectral Response
Acceleration Parameter at 0.2 Second, SDS 0.83g
5% Damped Design Spectral Response
Acceleration Parameter at 1 second, SD1 0.35g
Seismic Design Category D
5.2.3 Soil Sulfate and Chloride Content
The soil soluble sulfate and chloride content were determined in the laboratory for an on-site
soil sample. The results indicate that the water-soluble sulfate and chloride result is 0.0008 and
0.0007 percent by weight, respectively, which are considered “negligible” per Table 4.2.1 of ACI
318. Based on the test results, no special recommendations for concrete are required for this
project due to soil sulfate or soil chloride exposure.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 8
5.3 RETAINING WALLS
The garage and ADU may require retaining wall to achieve desired grades. We anticipate that a
wall up to 4 feet high could be needed along the eastern wall. Retaining wall foundations should
be designed in accordance with the foundation recommendations provided previously in this
report.
The design parameters provided below are applicable for retaining wall up to 4 feet high provided
that very low expansive on-site soils are used to backfill any retaining walls. If more expansive
soils are used to backfill the walls, increased active and at-rest earth pressures should be utilized
for design. Building walls, below grade, should be waterproofed or damp-proofed, depending on
the degree of moisture protection desired.
1. Active earth pressure may be used for retaining wall design, provided the top of the wall
is not restrained from minor deflections. Active earth pressure may be computed as an
equivalent fluid having a density of 40 pounds per square foot per foot of depth, plus any
applicable surcharge loading.
2. Any retaining walls that will be restrained prior to placing and compacting backfill material
or that have reentrant or male corners, should be designed for an at-rest equivalent fluid
pressure of 60 pounds per square foot per foot of depth, plus any applicable surcharge
loading. For areas of male or re-entrant corners, the restrained wall design should extend
a minimum distance of twice the height of the wall laterally from the corner.
3. The equivalent fluid pressures are provided for vertical walls and horizontal backfill less
than 5 feet tall. Pressures do not include pressures imposed during compaction of backfill,
swelling pressures of clay backfill, hydrostatic pressures from inundation of the backfill or
free water behind the walls, traffic above the wall, surcharge loads, sloping fill above the
top of the wall, seismic events, or adverse geologic conditions. Walls should be braced
during backfilling to prevent damage and excessive movements.
4. All walls should be reinforced to reduce the potential for distress caused by differential
foundation movement in accordance with the Structural Engineer’s recommendations. In
the upper bond beam, "U" blocks should be used. The walls should use both vertical and
horizontal reinforcement and be designed to resist the effects a two-way 1/400 angular
distortion would impart on a wall. Prior to placing concrete, the subgrade soils should be
lightly moisture conditioned to prevent loss of water during pouring and curing of the
concrete.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 9
5.3.1 Expected Wall Movements
A retaining wall has to translate laterally to reach full passive pressure/resistance. At 0.5% strain,
½ the passive pressure is mobilized, and at 2% strain the full passive pressure is mobilized. For a
12-inch embedment this can be 0.25 inches. In addition, wall rotation is expected to reach an
active design state. This rotation, at a minimum, needs to undergo 0.5% strain and walls are often
considered to rotate between 0.005 to 0.02 times their height, dependent upon the soil condition,
with no adverse structural effects expected. In our opinion, a value of 0.01 times the height of
the wall is a maximum rotation that should typically be expected. For a 5-foot-high wall this
amounts to 0.6 inches of movement that can occur at the top of the wall. Walls should be
expected to translate/move/rotate, and the higher the wall the more movement that should be
expected.
5.3.2 Wall Backfill and Drainage
All retaining walls should be provided with an adequate back drain system to reduce the buildup
of hydrostatic pressure and to minimize potential buildup of efflorescence along the front of the
wall. We recommend the use of gravel, a free draining layer of soil or a manufactured synthetic
material to be utilized as a back-drain system. The back drain system behind retaining walls
should consist at a minimum of 4-inch diameter Schedule 40 (or equivalent) perforated
(perforations “down”) PVC pipe embedded in at least 1-cubic-foot of ¾-inch crushed rock per
linear foot of pipe, all wrapped in approved filter fabric. Other back drain systems that may be
contemplated for use behind retaining walls due to ultimate design and construction methodology
will be considered on a case-by-case basis. A filter may be required between the soil backfill and
a drainage layer. Proper surface drainage should also be provided.
The need for damp/water proofing should be assessed and the appropriate method to limit water
transmission through the wall used.
5.4 CONSTRUCTION OBSERVATIONS
GeoTek representatives should be present during site grading and foundation construction to
check for proper implementation of the geotechnical recommendations. These representatives
should perform at least the following duties:
Observe site clearing and grubbing operations for proper removal of unsuitable
materials.
Observe and test bottom of removals prior to fill placement/subgrade
recompaction
Evaluate the suitability of onsite and import materials for fill placement, if needed,
and collect soil samples for laboratory testing where necessary.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 10
Observe the fill for uniformity during placement.
Perform field density testing of the fill and backfill materials.
Observe and probe foundation and slab subgrade excavations to confirm
suitability of bearing materials. This observation should be performed prior to
placement of reinforcement.
6. INTENT
It is the intent of this report to aid in the design and construction of the proposed development.
Implementation of the advice presented in this report is intended to reduce risk associated with
construction. The professional opinions and geotechnical advice contained in this report are not
intended to imply total performance of the project or guarantee that unusual or variable
conditions will not be discovered during or after construction.
The scope of this evaluation is limited to the area explored that is shown on Figure 2. This
evaluation does not and should in no way be construed to encompass any areas beyond the
specific area of the proposed construction as indicated to us by the client. Further, no evaluation
of any existing site improvements is included. The scope is based on GeoTek’s understanding of
the project and the client’s needs, and geotechnical engineering standards normally used on
similar projects in this region.
7. LIMITATIONS
GeoTek’s findings are based on site conditions observed and the stated sources. Thus, GeoTek’s
comments are professional opinions that are limited to the extent of the available data.
GeoTek has prepared this report in a manner consistent with that level of care and skill ordinarily
exercised by members of the engineering and science professions currently practicing under
similar conditions in the jurisdiction in which the services are provided, subject to the time limits
and physical constraints applicable to this report.
Since GeoTek’s recommendations are based on the site conditions observed and encountered
and laboratory testing, the conclusions and recommendations provided in this report are
professional opinions that are limited to the extent of the available data. Observations during
construction are important to allow for any change in recommendations found to be warranted.
These opinions have been derived in accordance with current standards of practice and no
warranty of any kind is expressed or implied. Standards of care/practice are subject to change
with time.
GEOTEK
Cameron Rosenhan Project No. 3869-SD
Limited Geotechnical Evaluation February 28, 2023
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 11
8. SELECTED REFERENCES
American Society of Civil Engineers (ASCE), 2016, “Minimum Design Loads for Buildings and
Other Structures,” ASCE/SEI 7-16.
_____, ASCE Hazard Tool, 2021, ASCE/SEI 7-22, accessed December 30, 2023, at
https://asce7hazardtool.online.
ASTM International (ASTM), “ASTM Volumes 4.08 and 4.09 Soil and Rock.”
Bryant, W.A., and Hart E.W., 2007, Fault Rupture Hazard Zones in California, Alquist-Priolo
Earthquake Fault Zoning Act with Index to Earthquake Fault Zone Maps, California
Geological Survey: Special Publication 42.
California Code of Regulations, Title 24, 2022 “California Building Code,” 2 volumes.
California Geological Survey (CGS, formerly referred to as the California Division of Mines and
Geology), 1977, “Geologic Map of California.”
____, 1998, “Maps of Known Active Fault Near-Source Zones in California and Adjacent
Portions of Nevada,” International Conference of Building Officials.
GeoTek, Inc., In-house proprietary information.
Kennedy, M.P., Tan, S.S., et al, 2005, “Geologic Map of the Oceanside 30x60-minute Quadrangle,
California,” California Geological Survey, Regional Geologic Map No. 2, map scale
1:100,000.
Terzaghi, K. and Peck, R.B., 1967, “Soil Mechanics in Engineering Practice, Second Edition.
GEOTEK
1384 Poinsettia Avenue, Suite A
Vista, California 92081
N
Not to Scale
Approximate Site
Location
DATE: February 2023
Imagery from USGS The National Map, 2023
Cameron Rosenhan
4080 Sunnyhill Drive
Carlsbad, CA
Figure 1
Site Location Map
PN: 3869-SD
Agua H dio11 a
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GEOTEK
HA-1
HA-2
HA-3
Quaternary Very Old Paralic Deposits,
Circled Where Buried
Approximate Limits of Study, this
report Qvop
LEGEND
Artifical FillAf
HA-3
Approximate Location of Hand-Auger Boring
Qvop
Af
Qvop
Af
1384 Poinsettia Avenue, Suite A
Vista, California 92081
N
Imagery from Google Earth, 2023
Figure 2
Geotechnical Map
DATE: February 2023
Cameron Rosenhan
4080 Sunnyhill Drive
Carlsbad, CA
PN: 3869-SD
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APPENDIX A
LOGS OF EXPLORATION
GEOTEK
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LOG OF EXPLORATORY BORING
BB-1 SM MD, SR
S-1 EI
S-2 SM
---Small Bulk ---No Recovery ---Water Table
PROJECT NAME:4080 Sunnyhill Drive DRILL METHOD:Hand Auger OPERATOR:-
CLIENT:Cameron Rosenhan DRILLER:-LOGGED BY:CH
LOCATION:Carlsbad, CA ELEVATION:244'DATE:12/23/2022
PROJECT NO.:3869-SD HAMMER:-RIG TYPE:-
SAMPLES
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BORING NO.: HA-1
Laboratory Testing
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Silty fine to medium SAND, dark brown, moist, loose to medium dense, probes
4" then 3" at 2 feet, upper 2" of topsoil and organics, some roots
Very Old Paralic Deposits (Qvop)
Dr
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MATERIAL DESCRIPTION AND COMMENTS
Artificial Fill (Af)
No groundwater encountered
Silty fine to medium SAND with some clays, dark brown transitions to light brown
with some orange mottling, very moist to moist with depth, medium dense to
5 3.5 feet
HOLE TERMINATED AT 3.5 FEET
very dense with depth, auger begins scraping small chunks of paralics until
material becomes too dense and friable to recover in auger, practical refusal at
15
Backfilled with soil cuttings
10
20
25
RV = R-Value Test
SR = Sulfate/Resisitivity Test SH = Shear Test CO = Consolidation test MD = Maximum Density
30
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Sample type: ---Ring ---SPT ---Large Bulk
Lab testing:AL = Atterberg Limits EI = Expansion Index SA = Sieve Analysis
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LOG OF EXPLORATORY BORING
SM
SC
---Small Bulk ---No Recovery ---Water Table
PROJECT NAME:4080 Sunnyhill Drive DRILL METHOD:Hand Auger OPERATOR:-
CLIENT:Cameron Rosenhan DRILLER:-LOGGED BY:CH
LOCATION:Carlsbad, CA ELEVATION:244'DATE:12/23/2022
PROJECT NO.:3869-SD HAMMER:-RIG TYPE:-
SAMPLES
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BORING NO.: HA-2
Laboratory Testing
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(%
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Silty fine to medium SAND, dark brown, very moist, loose, some clays and roots
topsoil and organics in upper 4"
Very Old Paralic Deposits (Qvop)
Clayey SAND, dark brown, very moist to wet, loose, low to medium plasticity
Dr
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MATERIAL DESCRIPTION AND COMMENTS
Artificial Fill (Af)
At 6 feet, material is very moist but no longer saturated, practical refusal due to
low clearance for auger
HOLE TERMINATED AT 6 FEET
At 3.5 feet, same material but now saturated, Auger continues to yield saturated
sand until 6 feet, less clays with depth, some orange mottling
5
Perched groundwater encountered at 3.5 feet
Backfilled with soil cuttings
10
15
20
25
AL = Atterberg Limits EI = Expansion Index SA = Sieve Analysis RV = R-Value Test
SR = Sulfate/Resisitivity Test SH = Shear Test CO = Consolidation test MD = Maximum Density
30
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Sample type: ---Ring ---SPT ---Large Bulk
Lab testing:
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LOG OF EXPLORATORY BORING
SM
S-1 SM
---Small Bulk ---No Recovery ---Water Table
PROJECT NAME:4080 Sunnyhill Drive DRILL METHOD:Hand Auger OPERATOR:-
CLIENT:Cameron Rosenhan DRILLER:-LOGGED BY:CH
LOCATION:Carlsbad, CA ELEVATION:247'DATE:12/23/2022
PROJECT NO.:3869-SD HAMMER:-RIG TYPE:-
SAMPLES
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BORING NO.: HA-3
Laboratory Testing
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Silty fine to medium SAND, dark brown, slightly moist to moist, loose to medium
dense with depth
Very Old Paralic Deposits (Qvop)
Fine to medium SAND with some clays and silts, light orange brown, moist,
Dr
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MATERIAL DESCRIPTION AND COMMENTS
Artificial Fill (Af)
HOLE TERMINATED AT 5 FEET
No groundwater encountered
Backfilled with soil cuttings
medium to very dense with depth, auger begins scraping at 5 feet with no
recovery, practical refusal at 5 feet
5
10
15
20
25
AL = Atterberg Limits EI = Expansion Index SA = Sieve Analysis RV = R-Value Test
SR = Sulfate/Resisitivity Test SH = Shear Test CO = Consolidation test MD = Maximum Density
30
LE
G
E
N
D
Sample type: ---Ring ---SPT ---Large Bulk
Lab testing:
---
-I"\ -,__ ---
--------------------------------------------------
■ I [Z] ~ □ ~
APPENDIX B
RESULTS OF LABORATORY TESTING
GEOTEK
SUMMARY OF LABORATORY TESTING
Identification and Classification
Soils were identified visually in general accordance with the procedures of the Standard Practice
for Description and Identification of Soils (ASTM D2488). The soil identifications and
classifications are shown on the exploration logs in Appendix A.
Expansion Index
Expansion Index testing was performed on a representative site soil sample obtained from the
subsurface exploration. Testing was performed in general accordance with ASTM D 4829 test
procedures. The results of the testing are presented in Appendix B.
Sulfate and Chloride Content
The soluble sulfate and chloride content of a representative site soil sample was determined by
GeoTek’s subconsultant, Project X, in general accordance with ASTM D 4327 test procedures.
The results of the testing are provided in Appendix B.
GEOTEK
Tested/ Checked By:
Date Tested:
Sample Source:
Sample Description:
Ring Id:Ring Dia. " :Ring Ht.":
A Weight of compacted sample & ring
B Weight of ring
C Net weight of sample
D
E
Wet Weight of sample & tare
Dry Weight of sample & tare
Tare
F Initial Moisture Content, %
G (E*F)
H (E/167.232)
I (1.-H)
J (62.4*I)
K (G/J)= L % Saturation
EXPANSION INDEX =
EXPANSION INDEX TEST
(ASTM D4829)
0
Tare
4.8
FINAL MOISTURE
%
Moisture
Weight of wet
sample & tare
Wt. of dry
sample & tare
168.2
1"
186.3
183.4
4.8
170.2
SATURATION DETERMINATION
18.6
8.0
50.3
12:16
370
DENSITY DETERMINATION
Wet Density, lb / ft3 (C*0.3016)
0.30
0.70
117.3
936.2
420
126.7
Random
12:05 241
16:00
239
12:15
Initial
240
1 min/Wet
10 min/Dry
1/5/2023
790
4"12
238
23812:21
Dry Density, lb / ft3 (D/1.F)
Project Number:
Project Name:4080 Sunnyhill Drive
3869-SD
Project Location:
KP
Carlsbad, CA
Loading weight: 5516. grams
HA-1 S-1
1/5/2023
Silty Clayey Sand
Lab No
1/6/2023 6:00 238
TIME READINGDATE
Final
3830
11.1%
5 min/Wet
READINGS
GEOTEK
--I
I I
Project X REPORT S221228E
Corrosion Engineering Page 1
Corrosion Control – Soil, Water, Metallurgy Testing Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Results Only Soil Testing
for
4080 Sunnyhill Dr
January 3, 2023
Prepared for:
Lesley White
GeoTek, Inc.
1384 Poinsettia Ave, Suite A
Vista, CA, 92081
lwhite@geotekusa.com
Project X Job#: S221228E
Client Job or PO#: 3869-SD
Respectfully Submitted,
Eduardo Hernandez, M.Sc., P.E.
Sr. Corrosion Consultant
NACE Corrosion Technologist #16592
Professional Engineer
California No. M37102
ehernandez@projectxcorrosion.com
Project X REPORT S221228E
Corrosion Engineering Page 2
Corrosion Control – Soil, Water, Metallurgy Testing Lab
29990 Technology Dr., Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Soil Analysis Lab Results
Client: GeoTek, Inc.
Job Name: 4080 Sunnyhill Dr
Client Job Number: 3869-SD
Project X Job Number: S221228E
January 3, 2023
Method
Bore# / Description Depth
(ft)(mg/kg)(wt%)(mg/kg)(wt%)
Dark Brown silty sand 0-2 8.3 0.0008 6.8 0.0007
ASTM
D4327
ASTM
D4327
Sulfates
SO42-
Chlorides
Cl-
Cations and Anions, except Sulfide and Bicarbonate, tested with Ion Chromatography
mg/kg = milligrams per kilogram (parts per million) of dry soil weight
ND = 0 = Not Detected | NT = Not Tested | Unk = Unknown
Chemical Analysis performed on 1:3 Soil-To-Water extract
PPM = mg/kg (soil) = mg/L (Liquid)
41! I> 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Project X Lab Request Sheet Chain of Custody
Phone: (213) 928-7213 • Fax (951) 226-1720 • www.projcctxcorrosion.com
Corrosion Engineering
(·.,...,..,.•'" l ~-, • "'-'11. V..u,,, •'W '~lu,c_,, , ..... Ship Samples To: 29990 Technology Dr, Suite 13, Murrieta, CA 92563
rroject x Job Number J 2 2 1 z z e £
IMPORT ANT: Please complete Project ~nd Sample Identification Data as you would like it to appear in report & include this form with samples.
ComponyNomt: GeoTek, Inc. Contact Name: Lesely White Phone No: 760-599-0509
Malling Address: 1384 POinsettia Ave, Suite A, Vista, CA. 92081 Contact Email: lwhite@geotekusa.com
Attounting Conlocl: Suzen Clark Invoice Email: AP@geotekusa.com
Cll,nt Project No: ~ i;? /., q -~ f)
24 Hour y I
P.O.#: 3-5 Doy
Standard
3 Day
Gu:anntt-t:
i:::n•L .... ,...1,_un RusH METHOD ANALYSIS REQUESTED (Please circle)
•~----~~11n
(Business Days) Turn Around Time: )(
For Corrosion Control Recommendations (350g soil sample):
NEED (1) Groundwater depth andl
(2) Soil Sample Locations Map . w·/ tr.
FOR THERMAL RESISTIVITY PROVIDE (1,500g soil sample):
Default
Method
(2) Dry Density{PCF} Geo Quad (I) Optimal Moisture % I I
(3) Desired Compaction
Date & Received By: 1---------=========::;::====::::;===::!.l DATE
COLLECTED SAMPLE ID -BORE# -Description DEPTH (n)
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Appendix D
GeoTek’s Letter Dated September 11, 2023
GEOTEK
GEOTECHNICAL | ENVIRONMENTAL | MATERIAL
September 11, 2023
Project No. 3866-SD
Cameron Rosenhan
4080 Sunnyhill Dr.
Carlsbad, California 92008
Subject: Supplemental Geotechnical Recommendations
Proposed Auxiliary Dwelling Unit (ADU)
4080 Sunnyhill Dr.
Carlsbad, California 92008
Dear Mr. Rosenhan:
In response to your request, GeoTek, Inc., (GeoTek) is providing the following retaining wall
design parameters for the proposed retaining walls at the subject site. Based on conversations
with you and your structural engineer, it is anticipated that the retaining walls will be cantilevered,
constructed of concrete masonry units (CMU), and a maximum height of 11-feet. Additional
review and recommendations should be requested for higher walls.
Based on work at the subject site, we anticipate that the soils supporting the proposed retaining
wall foundations and used for backfill behind the proposed retaining walls will consist of fine to
medium silty sands and have a “very low” (EI<20) expansion index based upon ASTM D4829 test
procedures.
Retaining wall foundations embedded a minimum of 12-inches into engineered fill or dense
formational materials should be designed using an allowable bearing capacity of 2,000 psf. This
value may be increased by 500 psf for each additional 12 inches in depth and 250 psf for each
additional 12 inches in width to a maximum value of 3,500 psf. An increase of one-third may be
applied when considering short-term live loads (e.g., seismic or wind loads). The passive earth
pressure may be computed as an equivalent fluid having a density of 250 psf per foot of depth, to
a maximum pressure of 3,000 psf. A coefficient of friction between soil and concrete of 0.35 may
be used with dead load forces. When combining passive pressure and frictional resistance, the
passive pressure component should be reduced by one-third.
An equivalent fluid pressure approach may be used to compute the horizontal active pressure
against the wall. The appropriate fluid unit weights are given in the table below for specific slope
gradients of retained materials.
GeoTek, Inc.
1384 Poinsettia Avenue, Suite A Vista, CA 92081-8505
(760) 599-0509 Offic, (760) 599-0593 Fa: www.geotekusa.com
CAMERON ROSENHAN Project No. 3869-SD
Retaining Wall Recommendations September 11, 2023
4080 Sunnyhill Drive, Carlsbad, California Page 2
Surface Slope of
Retained Materials
(H:V)
Equivalent Fluid
Pressure (PCF)*
Level 45
2:1 60
*Backfill should consist of onsite silty sands with an EI<20.
Retaining walls should be provided with an adequate back drain system to reduce the buildup of
hydrostatic pressure. We recommend the use of gravel, or a manufactured synthetic material to
be utilized as a back-drain system. The back drain system behind retaining walls should consist
at a minimum of 4-inch diameter Schedule 40 (or equivalent) perforated (perforations “down”)
PVC pipe embedded in at least 1-cubic-foot of ¾-inch crushed rock per linear foot of pipe, all
wrapped in approved filter fabric. Recommendations for wall waterproofing should be provided
by the Project Architect and/or Structural Engineer.
All retaining wall backfill should be placed in lifts no greater than eight inches in thickness and
compacted to at least 90% relative compaction as determined by ASTM Test Method D 1557.
Restrained Retaining Walls
Any retaining wall that will be restrained prior to placing backfill or walls that have male or
reentrant corners should be designed for at-rest soil conditions using an equivalent fluid pressure
of 65 pcf, plus any applicable surcharge loading. For areas having male or reentrant corners, the
restrained wall design should extend a minimum distance equal to twice the height of the wall
laterally from the corner, or as otherwise determined by the structural engineer.
Seismic Earth Pressures
As required by the 2022 CBC, walls with a retained height greater than six feet are required to
include an incremental seismic earth pressure in the wall design. Based upon review, basement
walls with a retained height of up to approximately 11 feet are planned at the site.
The lateral pressure on retaining walls due to earthquake motions (dynamic lateral force) should
be calculated as PA = 3/8H2kh where:
GEOTEK
CAMERON ROSENHAN Project No. 3869-SD
Retaining Wall Recommendations September 11, 2023
4080 Sunnyhill Drive, Carlsbad, California Page 3
PA = dynamic lateral force (lbs/ft)
= unit weight = 125 pcf
H = height of wall (feet)
Kh = seismic coefficient = 0.17
The dynamic lateral force may be expressed as 16-pounds-per-cubic-foot (equivalent fluid
pressure).
The dynamic lateral force is in addition to the static force and should be applied using a triangular
distribution with the resultant applied at 0.3H above the base of the wall. Retaining walls that
are less than 6-feet high do not require design to resist the additional earth pressure caused by
seismic ground shaking.
Foundation Setbacks
Where applicable, the following setbacks should apply to all foundations. Any improvements not
conforming to these setbacks may be subject to lateral movements and/or differential
settlements:
The outside bottom edge of all footings should be set back a minimum of H/3 (where H is
the slope height) from the face of any descending slope. The setback should be at least 7
feet and need not exceed 40 feet.
The bottom of all footings for structures near retaining walls should be deepened to extend
below a 1:1 projection upward from the bottom inside edge of the wall stem. This applies
to the existing retaining walls along the perimeter if they are to remain.
The bottom of any existing foundations for structures should be deepened to extend below
a 1:1 projection upward from the bottom of the nearest excavation.
Foundation Setbacks
Where applicable, the following setbacks should apply to all foundations. Any improvements not
conforming to these setbacks may be subject to lateral movements and/or differential
settlements:
GEOTEK
CAMERON ROSENHAN Project No. 3869-SD
Retaining Wall Recommendations September 11, 2023
4080 Sunnyhill Drive, Carlsbad, California Page 4
The outside bottom edge of all footings should be set back a minimum of H/3 (where H is
the slope height) from the face of any descending slope. The setback should be at least 7
feet and need not exceed 40 feet.
The bottom of all footings for structures near retaining walls should be deepened to extend
below a 1:1 projection upward from the bottom inside edge of the wall stem. This applies
to the existing retaining walls along the perimeter if they are to remain.
The bottom of any existing foundations for structures should be deepened to extend below
a 1:1 projection upward from the bottom of the nearest excavation.
Should you have any questions regarding these recommendations, please feel free to contact our
office at your convenience.
Respectfully submitted,
GeoTek, Inc.
Christopher D. Livesey
CEG, 2733 Exp. 05/31/25
Vice President
Edwin R. Cunningham
RCE, 81687 Exp. 03/31/24
Project Engineer
GEOTEK
CAMERON ROSENHAN Project No. 3869-SD
Retaining Wall Recommendations September 11, 2023
4080 Sunnyhill Drive, Carlsbad, California Page 5
REFERENCES
GeoTek, Inc., 2023, Limited Geotechnical Evaluation, Proposed Auxiliary Dwelling Unit (ADU),
4080 Sunnyhill Dr., Carlsbad, California 92008, dated February 28, 2023.
GEOTEK
Appendix E
GeoTek’s Letter Dated July 1, 2024
GEOTEK
GEOTECHNICAL | ENVIRONMENTAL | MATERIALS
July 1, 2024
Project No. 3869-SD
Cameron Rosenhan
4080 Sunnyhill Dr.
Carlsbad, California 92008
Subject: Foundation Plan Review
Proposed Auxiliary Dwelling Unit (ADU)
4080 Sunnyhill Dr
Carlsbad, California 92008
Reference: GeoTek, Inc., 2023, “Limited Geotechnical Evaluation, Proposed Accessory Dwelling
Unit, 4080 Sunnyhill Dr., Carlsbad, CA, 92008,” Project No. 3869-SD, dated February
28.
_____, 2023, “Supplemental Geotechnical Recommendations, Proposed Accessory
Dwelling Unit, 4080 Sunnyhill Dr., Carlsbad, CA, 92008,” Project No. 3869-SD, dated
September 11, 2023.
Qualls Engineering, 2023, Foundation Plan, Structural Notes, & Structural Details
“Rosenhan ADU, 4080 Sunnyhill Drive, Carlsbad, CA 92008,” dated September 9,
2023 (plan check submittal date), Sheets S1.0, S1.1, S1.2, S2.0, SD3, and S4.
Dear Mr. Rosenhan:
As requested, GeoTek, Inc. (GeoTek) has reviewed the following Foundation Plan, Structural
Notes, and Structural Details prepared by Qualls Engineering, issue dated September 29, 2023
(Qualls Job No. 23093), specifically, plan Sheets S1.0, S1.1, S1.2, S2.0, SD3, and SD4.
The plans indicate the use of continuous/spread footing foundation system with slab on grade
floors for the accessory dwelling unit.
The purpose of this geotechnical review was to allow GeoTek to comment on the apparent
geotechnical suitability of these plans.
Based on this review, it is GeoTek’s opinion that the subject plans have been prepared in
substantial conformance with the geotechnical recommendations contained within the
referenced geotechnical report (GeoTek, 2023) prepared for the subject project. It is
GeoTek, Inc.
1384 Poinsettia Avenue, Suite A Vista, CA 92081-8505
(760) 599-0509 Off, (760) 599-0593 Fa. www.geotekusa.com
CAMERON ROSENHAN Project No. 3869-SD
Foundation Plan Review July 1, 2024
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 2
GeoTek’s professional opinion that the subject plans are suitable for the subject development
from a geotechnical standpoint. GeoTek, Inc. makes no representation as to the accuracy of
dimensions, calculations, or structural design provided on the referenced plans.
All footing excavations should be observed by a representative of this office to check for
compliance with the recommendations prior to the placement of concrete forms and
reinforcement. It would likely be necessary to perform this observation following compaction
of the interior utility trenches.
Recommendations provided in the referenced report remain applicable for the subject project,
unless specifically superseded in this letter or future reports prepared by this firm.
Closure
This letter is intended to be made a part of, and incorporated with, the referenced Limited
Geotechnical Evaluation dated February 28, 2023. All conclusions, recommendations and
limitations of that report,report remain valid and apply to this letter.
The opportunity to be of continued service on this project is sincerely appreciated. If you
should have any questions, please do not hesitate to call our office.
Respectfully submitted,
GeoTek, Inc.
Christopher D. Livesey
CEG 2733, Exp. 05/31/2025
Vice President
Edwin R. Cunningham
RCE 81687, 03/31/26
Project Engineer
Distribution: (1) Addressee via email (PDF file)
GEOTEK
Appendix F
GeoTek’s Letter Dated September 27, 2024
GEOTEK
GEOTECHNICAL | ENVIRONMENTAL | MATERIALS
September 27, 2024
Project No. 3869-SD
Cameron Rosenhan
4080 Sunnyhill Dr.
Carlsbad, California 92008
Subject: Pool and Spa Foundation Plan Review
4080 Sunnyhill Dr
Carlsbad, California 92008
Reference: GeoTek, Inc., 2023, “Limited Geotechnical Evaluation, Proposed Accessory Dwelling
Unit, 4080 Sunnyhill Dr., Carlsbad, CA, 92008,” Project No. 3869-SD, dated February
28.
_____, 2023, “Supplemental Geotechnical Recommendations, Proposed Accessory
Dwelling Unit, 4080 Sunnyhill Dr., Carlsbad, CA, 92008,” Project No. 3869-SD, dated
September 11, 2023.
CE&LST Corporation DBA Sampo, Grading Plan for Rosenhan Residence, (APN: 207-
072-06, 4080 Sunnyhill Drive, Job No. 22-16, dated September 2, 2024.
Pool Engineering, Inc, 2024, Landscape Improvement Plans, Standard Pool Structural
Plan, Structural Notes, & Structural Details “4080 Sunnyhill Drive, Carlsbad, CA
92008-2750,” dated July 23, 2024, Sheets 2 of 2, 100, detail 240, Detail 400, Detail
55.
Dear Mr. Rosenhan:
As requested, GeoTek, Inc. (GeoTek) has reviewed the following Landscape Plan with Pool
Improvements, Structural Notes, and Structural Details prepared by Pool Engineering, Inc.
dated July 23, 2024, specifically, plan Sheets 2 of 2, 100, detail 240, Detail 400, Detail 55.
The purpose of this geotechnical review was to allow GeoTek to comment on the apparent
geotechnical suitability of these plans. GeoTek performed a soils report for the property on
February 28, 2023. Although the report did not specifically address the proposed pool and spa,
geotechnical recommendations for retaining wall design parameters were provided. As a pool
GeoTek, Inc.
1384 Poinsettia Avenue, Suite A Vista, CA 92081-8505
(760) 599-0509 Off, (760) 599-0593 Fa. www.geotekusa.com
CAMERON ROSENHAN Project No. 3869-SD
Foundation Plan Review October 4, 2024
4080 Sunnyhill Dr., Carlsbad, CA 92008 Page 2
and spa shell is essentially a retaining wall, the designer may utilize the recommendations
provided in the referenced geotechnical report prepared by GeoTek.
Based on this review, it is GeoTek’s opinion that the subject plans have been prepared in
substantial conformance with the geotechnical recommendations contained within the
referenced geotechnical report (GeoTek, 2023) prepared for the subject project. It is
GeoTek’s professional opinion that the subject plans are suitable for the subject development
from a geotechnical standpoint. GeoTek, Inc. makes no representation as to the accuracy of
dimensions, calculations, or structural design provided on the referenced plans.
All footing excavations (pool and spa shells) should be observed by a representative of this
office to check for compliance with the recommendations prior to the placement of concrete
forms and reinforcement.
Recommendations provided in the referenced report remain applicable for the subject project,
unless specifically superseded in this letter or future reports prepared by this firm.
Closure
This letter is intended to be made a part of, and incorporated with, the referenced Limited
Geotechnical Evaluation dated February 28, 2023. All conclusions, recommendations and
limitations of that report remain valid and apply to this letter.
The opportunity to be of continued service on this project is sincerely appreciated. If you
should have any questions, please do not hesitate to call our office.
Respectfully submitted,
GeoTek, Inc.
Christopher D. Livesey
CEG 2733, Exp. 05/31/2025
Vice President
Edwin R. Cunningham
RCE 81687, 03/31/26
Project Engineer
Distribution: (1) Addressee via email (PDF file)
GEOTEK