HomeMy WebLinkAboutPUD 2024-0002; CHERRY BEACH HOMES; PRELIMINARY GEOTECHNICAL EVALUATION; 2024-04-13
GEOTECHNICAL | ENVIRONMENTAL | MATERIALS
PRELIMINARY GEOTECHNICAL EVALUATION
PROPOSED THREE-STORY STRUCTURE
ASSESSOR’S PARCEL NUMBER: 204-231-05-00
180 CHERRY AVENUE AND 3577 GARFIELD STREET
CARLSBAD, CALIFORNIA 92008
PREPARED FOR
RINCON HOMES
5315 Avenida Encinas, Suite 200
Carlsbad, California 92008
PREPARED BY
GEOTEK, INC.
1384 POINSETTIA AVENUE, SUITE A
VISTA, CALIFORNIA 92081
PROJECT NO. 3970-SD MARCH 13, 2024
GEOTEK
March 13, 2024
Project No. 3970-SD
Rincon Homes
5315 Avenida Encinas
Carlsbad, California 92008
Attention: Mr. Kevin Dunn
Subject: Preliminary Geotechnical Evaluation
Proposed Three-Story Building
Assessor’s Parcel Number: 204-231-05-00
180 Cherry Avenue and 3577 Garfield Street
Carlsbad, California 92008
Dear Mr. Dunn:
GeoTek, Inc. (GeoTek) is pleased to present the results of this Preliminary Geotechnical
Evaluation for the subject project located at 180 Cherry Avenue in the City of Carlsbad,
California. This report presents a discussion of GeoTek’s field investigation, analyses,
and suitability of site soils to support the proposed improvements. Based upon review,
site development appears feasible from a geotechnical viewpoint provided that
recommendations presented in this report are incorporated into the design and construction
phases of the project.
The opportunity to be of service is sincerely appreciated. If you should have any questions,
please do not hesitate to contact GeoTek.
Respectfully submitted,
GeoTek, Inc.
Christopher D. Livesey
CEG 2733, Exp. 05/31/25
Vice President
Michael A. Lucas
PE 95468, Exp. 12/31/25
Project Engineer
Distribution: (1) Addressee via email
GeoTek, Inc.
1384 Poinsettia Avenue, Suite A Vista, CA 92081-8505
(760) 599-0509 Office (760) 599-0593 F:i www.geotekusa.com
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page ii
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 ........................................................................................................................ 2
3. FIELD STUDY AND LABORATORY TESTING ...................................................................................... 2
3.1 FIELD EXPLORATION ................................................................................................................................. 2
3.2 LABORATORY TESTING ............................................................................................................................. 3
4. GEOLOGIC AND SOILS CONDITIONS ................................................................................................... 3
4.1 REGIONAL GEOLOGIC SETTING ................................................................................................................. 3
4.2 EARTH MATERIALS .................................................................................................................................... 4
4.2.1 Artificial Fill (Af) ........................................................................................................................... 4
4.2.2 Quaternary-age Old Paralic Deposits (Qop6-7) ............................................................................. 4
4.3 SURFACE WATER AND GROUNDWATER .................................................................................................... 4
4.3.1 Surface Water ................................................................................................................................. 4
4.3.2 Groundwater .................................................................................................................................. 5
4.4 EARTHQUAKE HAZARDS ............................................................................................................................ 5
4.4.1 Surface Fault Rupture .................................................................................................................... 5
4.4.2 Liquefaction/Seismic Settlement ..................................................................................................... 5
4.4.3 Other Seismic Hazards ................................................................................................................... 6
5. CONCLUSIONS AND RECOMMENDATIONS ........................................................................................ 6
5.1 GENERAL CONCLUSIONS ........................................................................................................................... 6
5.2 EARTHWORK CONSIDERATIONS................................................................................................................ 6
5.2.1 General .......................................................................................................................................... 6
5.2.2 Site Clearing and Preparation ....................................................................................................... 6
5.2.3 Remedial Grading .......................................................................................................................... 7
5.2.4 Horizontal Extent of Removals ....................................................................................................... 7
5.2.5 Engineered Fill ............................................................................................................................. 7
5.2.6 Trench Excavations and Backfill................................................................................................... 8
5.3 DESIGN RECOMMENDATIONS ................................................................................................................... 8
5.3.1 Foundation Recommendations ....................................................................................................... 8
5.3.2 Foundation Setbacks .................................................................................................................... 10
5.3.3 Miscellaneous Foundation Recommendations ............................................................................. 10
5.3.4 Moisture and Vapor Retarding System ........................................................................................ 11
5.3.5 Seismic Design Parameters .......................................................................................................... 12
5.3.6 Soil Sulfate Content ...................................................................................................................... 13
5.4 CONCRETE FLATWORK ........................................................................................................................... 13
5.4.1 Exterior Concrete Slabs, Sidewalks and Driveways .................................................................... 13
5.4.2 Concrete Performance ................................................................................................................. 14
6. POST CONSTRUCTION CONSIDERATIONS ....................................................................................... 14
6.1 LANDSCAPE MAINTENANCE AND PLANTING .......................................................................................... 14
6.1 DRAINAGE .............................................................................................................................................. 15
6.2 PLAN REVIEW AND CONSTRUCTION OBSERVATIONS .............................................................................. 15
7. LIMITATIONS ............................................................................................................................................. 16
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page iii
TABLE OF CONTENTS
8. SELECTED REFERENCES ....................................................................................................................... 17
ENCLOSURES
Figure 1 – Site Location Map
Figure 2 – Geotechnical Map
Appendix A – Logs of Exploration
Appendix C – Results of Laboratory Testing
Appendix D – General Grading Guidelines
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 1
1. PURPOSE AND SCOPE OF SERVICES
The purpose of this Preliminary Geotechnical Evaluation is to provide recommendations for site
development in consideration of the proposed development. Services provided included the
following:
Research and review of readily available geologic data and general information pertinent
to the site.
A site reconnaissance.
Excavation of four solid stem auger borings and collection of samples for subsequent
laboratory testing.
Laboratory testing of soil samples collected during field exploration.
Review and analysis of geologic and geotechnical engineering data.
Preparation of this geotechnical report which presents GeoTek’s findings of pertinent
site geotechnical conditions and geotechnical recommendations for site development.
The intent of this report is to aid in the evaluation of the site for future proposed development
from a geotechnical perspective. No plans were available at the time of this report for the
proposed development. The professional opinions and geotechnical information contained in this
report may need to be updated based upon our review of the final development plans. These
plans should be provided to GeoTek, Inc. (GeoTek) for review when available.
2. SITE DESCRIPTION AND PROPOSED DEVELOPMENT
2.1 SITE DESCRIPTION
The project site is located at 180 Cherry Avenue and 3577 Garfield Street, Carlsbad, California
92008. The site is also identified as San Diego County Assessor’s Parcel Number (APN) 204-231-
05-00. The rectangular shaped parcel is approximately 8,192 square feet. Current improvements
include a two-story single-family residential structure with an attached garage addressed as 180
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 2
Cherry Avenue on the western portion of the parcel. On the eastern portion of the parcel, an
existing one-story single-family residential structure is addressed as 3577 Garfield Street. The
property is bounded to the west and north by residential property, and to the east and south by
Garfield Street and Cherry Avenue, respectively. The site is also improved with utilities, concrete
flatwork, pavers, hardscapes, and typical landscaping. The topography of the site is generally flat.
2.2 PROPOSED DEVELOPMENT
GeoTek understands that the existing site improvements will be demolished and removed to
accommodate a proposed new development, a three-story residential structure. For the
purposes of this report, GeoTek has assumed that the structure will be of wood-framed
construction, and that the building will be supported by a conventional shallow spread footing
foundation system with a slab-on-grade floor (no basement). Structural loads of 3.5 kips per
lineal foot for continuous footings and 100 kips for isolated pad footings are anticipated. Sewage
disposal is anticipated via a public system. Storm water facilities are not anticipated to be included
as part of the existing development. Retaining walls and large fill slopes are not anticipated due
to the existing relatively flat terrain.
A grading plan was not available for review as of the date of this report; however, anticipated
cuts and fill of less than five feet will be needed to provide a level building pad for the proposed
residential structure. As site planning progresses and additional or revised plans become
available, plans should be provided to GeoTek for review and comment. Additional geotechnical
field exploration, laboratory testing and engineering analyses may be necessary to provide specific
earthwork recommendations and geotechnical design parameters for site development.
3. FIELD STUDY AND LABORATORY TESTING
3.1 FIELD EXPLORATION
The field exploration for this study was conducted on January 3, 2024, and consisted of a site
reconnaissance, excavation of four solid stem auger borings with a rubber track limited access
rig (LAR), and collection of bulk and relatively undisturbed and disturbed soil samples for
subsequent laboratory testing. The borings were advanced to depths of approximately 16.5 to
20.5 feet below existing grades. A representative from GeoTek visually logged the excavations
as depicted on the Logs of Exploratory Borings, presented in Appendix A. The approximate
locations of the exploration borings are presented on the Geotechnical Map, Figure 2.
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 3
In the geotechnical borings, relatively undisturbed in-situ soil samples were recovered at various
intervals with a California sampler. The California sampler is a 2.9-inch outside diameter, 2.5-
inch inside diameter, split barrel sampler lined with approximately 1” high brass rings. The
sampler was 18 inches long. The sampler conformed to the requirements of ASTM D 3550. A
140-pound automatic trip hammer was utilized, dropping 30 inches for each blow. The sampler
penetration test data are presented on the Logs of Exploratory Borings in Appendix A.
Standard Penetration Tests (SPT) were performed in various geotechnical borings with a 2.0-inch
outside diameter, 1.5-inch inside diameter, split-barrel sampler. The sampler was 18 inches long.
The inside diameter of the sampler shoe was 1.4 inches. The sampler was unlined. The sampler
conformed to the requirements of ASTM D 1586. A 140-pound automatic trip hammer was
utilized, dropping 30 inches for each blow. The sampler penetration test data are presented on
the Logs of Exploratory Borings in Appendix A.
Bulk samples of the soils encountered were obtained from cuttings developed during the drilling
operations. The relatively undisturbed samples, together with bulk samples of representative soil
types, were returned to the laboratory for testing and evaluation.
The exploration logs show subsurface conditions at the dates and locations indicated and may
not be representative of other locations and times. The stratification lines presented on the logs
represent the approximate boundaries between soil types, and the transitions may be gradual.
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.
4. GEOLOGIC AND SOILS CONDITIONS
4.1 REGIONAL GEOLOGIC SETTING
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
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 4
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 in the 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).
4.2 EARTH MATERIALS
A brief description of the earth materials encountered during the subsurface explorations is
presented in the following section. Based on review of the site exploration and available geologic
maps and literature, the site is underlain by artificial fill overlying Quaternary-age Old Paralic
deposits.
4.2.1 Artificial Fill (Af)
Artificial fill was encountered in all the borings performed for the subsurface exploration.
Artificial fill soils were encountered to depths of approximately 1.5 to 2 feet below existing
grades. The artificial fill consisted of silty fine to medium SAND (SM soil type based upon the
Unified Soil Classification System), brown to dark brown in color, very moist, loose, with surficial
vegetation and roots. The artificial fill was likely placed during the construction of the existing
site improvements.
4.2.2 Quaternary-age Old Paralic Deposits (Qop6-7)
The regional geologic map (Kennedy, M.P., et. al., 2007) shows Quaternary-age Old Paralic
deposits underlying the site. The subsurface excavation encountered Quaternary-age Old Paralic
deposits in all the test borings underlying the artificial fill to the full depths of exploration. The
Quaternary-age Old Paralic deposits consisted of silty fine to coarse SAND (SM soil type), tan to
brown to reddish brown in color, moist near surface and decreases in moisture content with
depth, and medium dense to very dense.
4.3 SURFACE WATER AND GROUNDWATER
4.3.1 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 or
possibly some minor surface runoff. Standing water or ponding of water was not observed.
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 5
4.3.2 Groundwater
Groundwater was not encountered in our subsurface explorations. Based on the anticipated
depth of removals, groundwater is not anticipated to be a factor in site development. Localized
perched groundwater may be present but is also not anticipated to be a factor in site
development.
4.4 EARTHQUAKE HAZARDS
4.4.1 Surface Fault Rupture
The geologic structure of the entire southern California area is dominated mainly by northwest-
trending faults associated with the San Andreas system. The site is in a seismically active region.
No active or potentially active fault is known to exist at this site nor 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
(Kennedy, 2008). The closest zoned fault, the Mount Soledad Fault (San Diego Section) is greater
than 20 miles south of the project site. The site has not been evaluated by the California
Geological Survey for liquefaction or seismic induced landslide hazards. According to Figure 6-6
of the City of Carlsbad General Plan, the project site is mapped outside the limits of areas
susceptible to liquefaction hazards.
4.4.2 Liquefaction/Seismic Settlement
Liquefaction describes a phenomenon in which cyclic stresses, typically produced by earthquake-
induced ground motion, create excess pore pressures in relatively cohesionless soils. These soils
may thereby acquire a high degree of mobility, which can lead to lateral movement, sliding,
consolidation and settlement of loose sediments, sand boils and other damaging deformations.
This phenomenon occurs only below the water table, but, after liquefaction has developed, the
effects can propagate upward into overlying non-saturated soil as excess pore water dissipates.
The factors known to influence liquefaction potential include soil type and grain size, relative
density, groundwater level, confining pressures, and both intensity and duration of ground
shaking. In general, materials that are susceptible to liquefaction are loose, saturated granular
soils having low fines content under low confining pressures.
The liquefaction potential and seismic settlement potential on this site are considered negligible
due to the absence of a shallow groundwater table and the relatively dense to very dense
Quaternary-age Old Paralic deposits underlying the site.
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 6
4.4.3 Other Seismic Hazards
Evidence of ancient landslides or slope instabilities was not observed on the residential property.
The potential for landslides is considered negligible based on the relatively flat field conditions
observed on and around the site.
The project site is mapped outside the vicinity of areas with potential for secondary seismic
hazards such as seiche and tsunami, as confirmed by Figure 6-3 of the City of Carlsbad General
Plan.
5. CONCLUSIONS AND RECOMMENDATIONS
5.1 GENERAL CONCLUSIONS
The anticipated site development appears feasible from a geotechnical viewpoint provided that
the following recommendations, and any subsequent recommendations provided by this firm at
a later date, are incorporated into the design and construction phases of development.
Recommendations contained in this report are based on the currently applicable 2022 California
Building Code (CBC) and City of Carlsbad guidelines.
5.2 EARTHWORK CONSIDERATIONS
5.2.1 General
Earthwork and grading should be performed in accordance with the applicable grading ordinances
of the City of Carlsbad, the 2022 California Building Code (CBC), and recommendations
contained in this report. The Grading Guidelines included in Appendix C outline general
procedures and do not anticipate all site-specific situations. In the event of conflict, the
recommendations presented in the text of this report supersede those contained in Appendix C.
5.2.2 Site Clearing and Preparation
Initial site preparation should commence with removal of existing structures, foundations, slabs,
pavements, hardscaping, debris, abandoned utilities, deleterious materials, and vegetation within
the limits of the planned improvements. These materials should be properly disposed of off-site.
Voids resulting from removing any materials should be replaced with engineered fill materials
with expansion characteristics similar to the onsite materials. If encountered, any existing
underground improvements, e.g., footings, utilities and trench backfill, should also be removed,
rerouted as appropriate, or be further evaluated as part of site development operations.
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 7
5.2.3 Remedial Grading
The upper five feet of site soils are anticipated to be disturbed during demolition of the existing
structures and associated improvements. Remedial grading should include all areas of
improvement and consist of removing existing artificial fill and loose, disturbed Quaternary-age
Old Paralic deposits down to competent Old Paralic deposits and being replaced with compacted
engineered fill in order to achieve design finished grades. Removal depths on the order of 5 feet
below existing grades are anticipated. Localized areas of deeper artificial fill or loose soils may
be encountered during grading operations and will require removal and replacement.
Removal bottoms should be relatively uniform in soil type, tested to have at least 85% relative
compaction (ASTM D 1557), and then be scarified to a minimum depth of about six inches,
brought to slightly above optimum moisture content, and then compacted to at least 90% of the
soil’s maximum dry density as determined by ASTM D1557 test procedures. The resultant voids
from remedial grading/over-excavation should be filled with materials placed in general
accordance with Section 5.2.5 Engineered Fill of this report.
The bottom of the removals should be observed by a GeoTek representative prior to processing
the bottom for receiving placement of compacted fills.
5.2.4 Horizontal Extent of Removals
As a minimum, the lateral extent of removals should extend down and away from foundation
elements at a 1:1 (h:v) projection to the recommended removal depth, or a minimum of five feet
laterally, whichever is greater. Where remedial grading along property line conditions occur,
temporary excavation should be performed by slot cutting or sloping away from the property
line and into the excavation at a gradient no steeper than 1:1. Upon placement of engineered
fills, the temporary slope should be benched out and replaced immediately with engineered fills.
Bench height should not exceed engineered fill height thickness by more than twice the height.
5.2.5 Engineered Fill
The on-site soils are generally considered suitable for reuse as engineered fill provided, they are
free from excessive vegetation, roots, debris, and rock/concrete or hard lumps greater than six
inches in maximum dimension. Engineered fill should be placed in loose lifts with a thickness of
eight inches or less, moisture conditioned to at least two percent above the optimum moisture
content and compacted to a minimum relative compaction of 90 percent (ASTM D 1557).
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 8
5.2.6 Trench Excavations and Backfill
Temporary excavations within the onsite materials should be stable at 1½:1 (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. Trench
excavations should conform to Cal-OSHA regulations. The contractor should have a competent
person, per OSHA requirements, on site during construction to observe conditions and to make
the appropriate recommendations.
Utility trench backfill should be compacted to at least 90% relative compaction of the maximum
dry density as determined by ASTM D1557 test procedures. Under-slab trench excavation
backfill should also be compacted to project specifications.
Compaction should be achieved with a mechanical compaction device. Ponding or jetting of
trench backfill is not recommended. If backfill soils have dried out, they should be properly
moisture conditioned prior to placement in trenches.
5.3 DESIGN RECOMMENDATIONS
5.3.1 Foundation Recommendations
Preliminary foundation design criteria, in general conformance with the 2022 CBC, are presented
herein. These are typical design criteria and are not intended to supersede the design by the
structural engineer. The preliminary recommendations are presented below.
Based on visual classification of materials encountered onsite and as verified by laboratory testing,
site soils are anticipated to exhibit a “Very Low” (EI≤20) Expansion Index per ASTM D4829.
Additional laboratory testing should be performed at the time of supplemental geotechnical
evaluations and upon completion of site grading to verify the expansion potential and plasticity
index of the subgrade soils, as the following criteria for design of foundations are preliminary.
Additional laboratory testing of the samples obtained during grading should be performed and
final recommendations should be based on as-graded soil conditions.
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 9
MINIMUM DESIGN REQUIREMENTS FOR CONVENTIONALLY REINFORCED
FOUNDATIONS
DESIGN PARAMETER “VERY LOW”
EXPANSION INDEX (EI≤20)
STORIES THREE
Foundation Minimum Perimeter Beam Depth (below
lowest adjacent finished grade) 18 inches
Minimum Foundation Width* 15 inches
Isolated Square or Column Foundations
Minimum Width (Inches) 24 inches
Minimum Slab Thickness (actual) 5 inches
Minimum Slab Reinforcing
6” x 6” – W2.9/W2.9 welded wire fabric
placed in middle of slab,
or No. 3 bars at 18-inch centers.
Minimum Footing Reinforcement Four No. 4 reinforcing bars,
two (2) top and two (2) bottom.
Pre-saturation of Subgrade Soil
(percent of optimum moisture content)
Minimum 100% of the optimum moisture
content to a depth of 12 inches prior to
placing concrete
*Code minimums per Table 1809.7 of the 2022 CBC should be complied with.
It should be noted that the previous recommendations are based on soil support characteristics
only. The structural engineer should design the slab and beam reinforcement based on actual
loading conditions.
The following recommendations should be implemented into the design:
Preliminarily, an allowable bearing capacity of 3,000 pounds per square foot (psf) may be
considered for design of continuous and perimeter footings that meet the depth and
width requirements in the table above. 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 4,500 psf. Additionally, an increase of one-third may be applied when
considering short-term live loads (e.g., seismic and wind loads).
Based upon review, a modulus of subgrade reaction (E1) of 200 pci may be used in the
design of foundations and/or structural slabs-on-grade. It should be noted that this value
is based upon standard one foot plate load tests. Depending upon the design
methodology and foundation geometry this value may need to be modified by the
following:
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 10
Es = E1 ((B+1)/2B)2
where: Es = design modulus
B = footing width
Based on 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 is considered to be minimal.
The passive earth pressure may preliminarily be computed as an equivalent fluid having a
density of 250 psf per foot of depth, to a maximum earth pressure of 3,750 psf for
footings founded on engineered fill. A coefficient of friction between soil and concrete
of 0.35 may be used with dead load forces. Passive pressure and frictional resistance can
be combined without reduction.
A grade beam, a minimum of 15 inches wide and 18 inches deep, should be utilized across
large entrances, however the base of the grade beam should be at the same elevation as
the bottom of the adjoining footings.
5.3.2 Foundation Setbacks
Minimum setbacks for all foundations should comply with the 2022 CBC or City of Carlsbad
requirements, whichever is more stringent. Improvements not conforming to these setbacks are
subject to the increased likelihood of excessive lateral movement and/or differential settlement.
If large enough, these movements can compromise the integrity of the improvements.
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
seven feet and need not exceed 40 feet.
The bottom of any proposed foundations should be deepened so as to extend below a
1:1 upward projection from the bottom edge of the nearest excavation and the bottom
edge of the closest footing.
5.3.3 Miscellaneous Foundation Recommendations
To minimize moisture penetration beneath the slab-on-grade areas, utility trenches should be
backfilled with engineered fill, lean concrete, or concrete slurry where they intercept the
perimeter footing or thickened slab edge. Spoils from the footing excavations should not be
placed in the slab-on-grade areas unless properly compacted and tested. The excavations should
be free of loose/sloughed materials and be neatly trimmed at the time of concrete placement.
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 11
5.3.4 Moisture and Vapor Retarding System
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
occurrences should be limited as much as possible 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. Although the CBC
specifies a 6 mil vapor retarder membrane, it is GeoTek’s opinion that a minimum 10 mil 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 provide a certain level of resistance to
vapor and moisture transmission through the concrete, but do not eliminate it. 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 retarders can reduce, but not eliminate, moisture vapor rise from the underlying soils
up through the slab. Moisture retarder systems should be designed and constructed in
accordance with applicable American Concrete Institute, Portland Cement Association, Post-
Tensioning Concrete Institute, ASTM and California Building Code 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
potential adverse impact of moisture vapor transmission on various components of the
structures, as deemed appropriate.
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 12
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.
5.3.5 Seismic Design Parameters
The site is located at approximately 33.151059 Latitude and -117.346560 Longitude. Due to the
relatively dense materials encountered at a relatively shallow depth, a Site Class “D” is considered
appropriate for this site. Site spectral accelerations (Sa and S1), for 0.2 and 1.0 second periods
for a Class “D” site, was determined from the SEAOC/OSHPD web interface that utilizes the
USGS web services and retrieves the seismic design data and presents that information in a report
format. Using the ASCE 7-16 option on the SEAOC/OSHPD website results in the values for
FV, 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.
The results, based on the 2015 NEHRP and the 2022 CBC, are presented in the following table
and we have assumed that the exception to performing a site-specific ground motion analysis as
allowed in ASCE 7-16 is applicable. If the exception is deemed not appropriate, a site-specific
ground motion analysis will be required.
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 13
SITE SEISMIC PARAMETERS
Mapped 0.2 sec Period Spectral Acceleration, Ss 1.097g
Mapped 1.0 sec Period Spectral Acceleration, S1 0.395g
Maximum Considered Earthquake (MCER) Spectral
Response Acceleration for 0.2 Second, SMS 1.317g
Maximum Considered Earthquake (MCER) Spectral
Response Acceleration for 1.0 Second, SM1 0.753g
5% Damped Design Spectral Response
Acceleration Parameter at 0.2 Second, SDS 0.878g
5% Damped Design Spectral Response
Acceleration Parameter at 1 second, SD1 0.502g
Site Modified Peak Ground Acceleration (PGAM) 0.582g
Seismic Design Category D
Final selection of the appropriate seismic design coefficients should be made by the project
structural engineer based upon the local practices and ordinances, expected building response
and desired level of conservatism. Should it be determined that the exclusion as outlined in ASCE
7-16 is not appropriate for this site, then a site-specific ground motion analysis will be necessary.
5.3.6 Soil Sulfate Content
The soil soluble sulfate content was determined in the laboratory for an on-site soil sample. The
results indicate that the water-soluble sulfate result is less than 0.1 percent by weight, which is
considered “negligible” as per Table 4.2.1 of ACI 318. Based on the test results and Table 4.3.1
of ACI 318, no special recommendations for concrete are required for this project due to soil
sulfate exposure.
5.4 CONCRETE FLATWORK
5.4.1 Exterior Concrete Slabs, Sidewalks and Driveways
Exterior concrete slabs, sidewalks and driveways 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.
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 14
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
(for “Very Low” Expansion Index) of the optimum moisture content to a depth of six inches.
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.
5.4.2 Concrete Performance
Concrete cracks should be expected. These cracks can vary from sizes that are essentially
unnoticeable 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 control. Concrete, while seemingly a 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 apart
approximately equal to 24 to 36 times the slab thickness.
6. POST CONSTRUCTION CONSIDERATIONS
6.1 LANDSCAPE MAINTENANCE AND PLANTING
Water has been shown to weaken the inherent strength of soil, and slope stability is significantly
reduced by overly wet conditions. Positive surface drainage away from graded slopes should be
maintained and only the amount of irrigation necessary to sustain plant life should be provided
for planted slopes. Controlling surface drainage and runoff and maintaining a suitable vegetation
cover can minimize erosion. Plants selected for landscaping should be lightweight, deep-rooted
types that require little water and are capable of surviving the prevailing climate.
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 15
Overwatering should be avoided. An abatement program to control ground-burrowing rodents
should be implemented and maintained. Burrowing rodents can decrease the long-term
performance of slopes.
It is common for planting to be placed adjacent to structures in planter or lawn areas. This will
result in the introduction of water into the ground adjacent to the foundations. This type of
landscaping should be avoided.
6.1 DRAINAGE
Positive site drainage should be maintained at all times. Drainage should not flow uncontrolled
down any descending slope. Water should be directed away from foundations and not allowed
to pond or seep into the ground adjacent to the footings. Paved areas should be sloped at two
percent away from the structure. Downspouts should discharge onto paved surfaces sloping
away from the structure or into a closed pipe system which outfalls to a street gutter or directly
to a storm drain system. Pad drainage should be directed toward approved areas and not be
blocked by other improvements. Additional recommendations can be found in Section 1804A of
the California Building Code.
It is the owner’s responsibility to maintain and clean drainage devices. In order to be effective,
maintenance should be conducted on a regular and routine schedule and necessary corrections
made prior to each rainy season.
6.2 PLAN REVIEW AND CONSTRUCTION OBSERVATIONS
It is recommended that specifications and foundation plans be reviewed by this office prior to
construction to check for conformance with the recommendations of this report. It is also
recommended that GeoTek, Inc.’s representatives be present during site grading and foundation
construction to observe and document proper implementation of the geotechnical
recommendations. The owner/developer should verify that GeoTek, Inc. representatives
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.
Evaluate the suitability of on-site and import materials for fill placement and collect soil
samples for laboratory testing where necessary.
Observe the fill for uniformity during placement, including utility trench backfill. Also,
perform field density testing of the fill materials.
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 16
Observe and probe foundation excavations to confirm suitability of bearing materials with
respect to density.
If requested, a construction observation and compaction report can be provided by GeoTek, Inc.,
which can comply with the requirements of the governmental agencies having jurisdiction over
the project. It is recommended that these agencies be notified prior to commencement of
construction so that necessary grading permits can be obtained.
7. LIMITATIONS
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 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, GeoTek’s proposal (Proposal No. P-1200723-SD) dated
December 27, 2023, and geotechnical engineering standards normally used on similar projects in
this region.
The materials observed on the project site appear to be representative of the area; however, soil
and bedrock may vary in character between excavations and natural outcrops, or conditions
exposed during site construction. Site conditions may vary due to seasonal changes or other
factors. GeoTek, Inc. assumes no responsibility or liability for work, testing or recommendations
performed or provided by others.
Since the recommendations in this report are based on a limited subsurface evaluation and the
site conditions observed and encountered, conclusions and recommendations 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 is
expressed or implied. Standards of practice are subject to change with time.
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page 17
8. SELECTED REFERENCES
American Society of Civil Engineers (ASCE), 2016, “Minimum Design Loads for Buildings and
Other Structures,” ASCE/SEI 7-16.
_____, ASCE Tsunami Hazard Tool, 2022, ASCE Tsunami Design Geodatabase Version 2022-
1.0, accessed January 24, 2024, at https://asce7tsunami.online.
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 Zones Maps," California
Geological Survey: Special Publication 42.
California Code of Regulations, Title 24, 2022 “California Building Code,” 2 volumes.
California Geological Survey, 2008, “Guidelines for Evaluating and Mitigating Seismic Hazards in
California,” Special Publication 117A.
____, 1998, “Maps of Known Active Fault Near-Source Zones in California and Adjacent
Portions of Nevada,” International Conference of Building Officials.
City of Carlsbad, 2015, “General Plan – Element 6 – Public Safety,” Figure 6-3 Maximum Tsunami
Projected Run-up.
____, 2015, “General Plan – Element 6 – Public Safety,” Figure 6-6 Liquefaction Hazards.
GeoTek, Inc., In-house proprietary information.
Kennedy, M.P., et al., 2007, “Geologic Map of the Oceanside 30x60-minute Quadrangle and
Adjacent Areas, California,” California Geological Survey, Regional Geologic Map No. 2,
map scale 1:100,000.
Structural Engineers Association of California/California Office of Statewide Health Planning and
Development (SEOC/OSHPD), 2020, Seismic Design Maps web interface, at
https://seismicmaps.org
Terzaghi, K. and Peck, R.B., 1967, “Soil Mechanics in Engineering Practice, Second Edition.
GEOTEK
GEOTECHNICAL | ENVIRONMENTAL | MATERIAL
February 3, 2025
Project No. 3970-SD
Rincon Homes
5315 Avenida Encinas, Suite 200
Carlsbad, California 92008
Attention: Mr. Kevin Dunn
Subject: Response to City Comments Dated November 27, 2024
Proposed Three-Story Building
Assessor’s Parcel Number 204-231-05-00
180 Cherry Avenue and 3577 Garfield Street
Carlsbad, California 92008
Dear Mr. Dunn:
As requested, GeoTek, Inc., (GeoTek) has prepared this letter to respon 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 November 27, 2024 is presented in Appendix A.
Comment No. 1:
The report indicates that it was prepared without the benefit of plans for the development.
Consequently, please review the most current grading and building plans for the proposed project
and provide any additional geotechnical recommendations or modifications to the geotechnical
report as necessary to address the currently proposed development.
Response:
GeoTek performed a plan review of the project grading plans prepared by Paso, Laret, Suiter,
and Associates, Inc. (PLSA). The geotechnical conclusions and recommendations presented in
GeoTek’s prior referenced report remain valid and applicable to the referenced scope of work
presented on the grading plan. Recommendations and conclusions preesented in this letter have
been incorporated into the project design. Structural building plans are not avaiable at this time
for a geotchnical review.
Comment No. 2:
Please provide a description of the most current proposed development and discuss the
GeoTek, Inc.
1384 Poinsettia Avenue, Suite A Vista, CA 92081-8505
(760) 599-0509 (760) 599-0593 www.geotekusa.com
Response to Review Comments February 3, 2025
Rincon Homes Project No. 3970-SD
180 Cherry Avenue and 3577 Garfield Street, Carlsbad, California 92008 Page 2
proposed structures and improvements, proposed grading (depths and limits of cut/fill necessary
to establish proposed grades), type of foundations and floors for the proposed structures, and
locations and heights of the proposed fence/retaining wall.
Response:
GeoTek understands that the existing site improvements will be demolished and removed to
accommodate the proposed new development. The proposed development consists of three,
three-story residential dwellings. Based on the rough grading plan, cuts and fills designed to
achieve the proposed grades are less than one foot from existing grades, resulting in an earthwork
design quantity of 65 cubic yards (CY) of cut and 35CY of fills with an export of 30CY. Remedial
earthwork quantities are estimated to be 545CY.
Dwelling Unit No. 1 and No. 2 are designed to be accessed via Cherry Avenue. Dwelling Unit
No. 3 is designed to be accessed via Garfield Street. All accessibility is proposed to be driveway
entrances. Retaining walls, less than 2 feet of retained earth are proposed to facilitate pad grade
changes between Units 1, 2, and 3.
Two retaining walls are proposed along the western and northern property line. The western
wall is proposed to retain approximately four to six feet of onsite grades. The retaining wall
along the north property line is proposed to retain approximately three to four feet of offsite
grades.
For the purposes of this report, GeoTek has assumed that the structure will be of wood-framed
construction, and that the building will be supported by a conventional shallow spread footing
foundation system with a slab-on-grade floor (no basement). Structural loads of 3.5 kips per
lineal foot for continuous footings and 100 kips for isolated pad footings are anticipated. Sewage
disposal is anticipated via a public system. Storm water facilities are not anticipated to be included
as part of the existing development.
Comment No. 3:
Please provide a statement addressing the potential impact of the proposed project on adjacent
properties from a geotechnical standpoint.
Response:
Provided that the geotechnical recommendaitons provided by GeoTek are incorporated into the
design and construction phases of the development, the proposed improvements will not adversly
affect offsite conditions.
GEOTEK
Response to Review Comments February 3, 2025
Rincon Homes Project No. 3970-SD
180 Cherry Avenue and 3577 Garfield Street, Carlsbad, California 92008 Page 3
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, b) proposed structures and improvements, c) proposed finished
grades, d) geologic units e) limits of proposed remedial grading, and f) the locations of subsurface
exploration. Please note that the "Geotechnical Map" presented in the submitted report is not
to scale and consists of an architectural site plan as the base map with generally illegible
(distorted) text and numbering. Please produce the map at a scale that is sufficiently large to
clearly distinguish all topography, text, finish 'grades, etc., and show all information requested
above.
Response:
See attached Updated Geotechnical Map, Figure 2.
Comment No. 5:
Please provide a statement addressing the Newport-Inglewood/Rose Canyon fault zone as it
relates to the subject site, and provide the direction and distance from the site to the closest
mapped segment of the off-shore trace of the fault zone off the Carlsbad coastline.
Response:
The Rose Canyon Fault Zone (RCFZ) is a northwest-southeast trending geologically active fault.
The northern segments have been mapped to be generally confined to a narrow fault zone
consisting of a single alignment or closely spaced step-over alignments, whereas the southern
portion of the RCFZ consists of several parallel/subparallel and secondary faults resulting in a
more broad fault zone. The southern portion of the FCFZ generally consists of the Old Town
Fault, Mission Bay Fault and the Spanish Bight Fault, and further broadens with the “Downtown
Graben” Coronado Fault and other unnamed faults. The site is located approximately 2 miles
northeast from the northern portion of the RCFZ.
A potential earthquake along the Rose Canyon with a mean magnitude (MCE) of 6.9 may result.
Based on ASCE 7-16 Section 11.4.1, the site is considered a Near-Fault Site under subsection 2,
which defines a near-fault site to be a site within 6.25 miles of the surface projection of a known
active fault capable of producing MCE 6 or larger event.
Comment No. 6:
Please provide the value and calulation used to obtain the value of the seismic coefficient Fv in
accordance with ASCE 7-16 (as the coefficient is “Null” for site class in the web-base seismic
hazard tool).
GEOTEK
Response to Review Comments February 3, 2025
Rincon Homes Project No. 3970-SD
180 Cherry Avenue and 3577 Garfield Street, Carlsbad, California 92008 Page 4
Response:
The proposed three story single-family structure has a funamental period of vibration less than
0.5 seconds, consequently, the exception to site response analyses in ASCE 7-16 (section 20.3.1,
item 1.) has been used. Using the ASCE Hazards Tool website, the seismic parameters Fv, SM1,
and SD1 are null and not applicable. The Siplified Alternative Structural Design Criteria provided
in section 12.14 of ASCE 7-16 should be used.
Comment No. 7:
Please provide recommendations for the design of the proposed site fence walls and/or retaining
walls (foundation, active/at-rest earth pressure, subdrain, backfill, surcharge, etc.) that are a part
of the project.
Response:
The proposed walls are County of San Diego Regional Standards and the site conditions support
the basis of those designs. If desired the following wall design parameters may be utilized.
Retaining Wall Design and Construction
Recommendations presented herein may apply to typical masonry or concrete vertical retaining
walls to a maximum height of 6 feet. Additional review and recommendations should be
requested for higher walls.
Retaining wall foundations embedded a minimum of 12 inches into engineered fill or competent
Old Paralic deposits should be designed using an allowable bearing capacity of 2,000 psf. This
value may be increased by 300 psf for each additional 12 inches in depth and 200 psf for each
additional 12 inches in width to a maximum value of 3,000 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 earth pressure of 2,000 psf. A coefficient of friction
between soil/bedrock 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 imported retained materials.
GEOTEK
Response to Review Comments February 3, 2025
Rincon Homes Project No. 3970-SD
180 Cherry Avenue and 3577 Garfield Street, Carlsbad, California 92008 Page 5
Surface Slope of
Retained Materials
(H:V)
Equivalent Fluid
Pressure (PCF)
Select Backfill*
Level 35
2:1 45
*Select backfill should consist of onsite silty sand with an EI<20.
The above equivalent fluid weights do not include other superimposed loading conditions such
as expansive soil, vehicular traffic, structures, seismic conditions, or adverse geologic conditions.
Wall Backfill and Drainage
Wall backfill should include a minimum one (1) foot wide section of ¾ to 1-inch clean crushed
rock (or approved equivalent). The rock should be wrapped in Mirafi 140N or an approved
equivalent and placed immediately along the back of wall and extend up from the back-drain to
within approximately 12 inches of finish grade. The upper 12 inches should consist of compacted
onsite materials. Alternatively, a manufactured wall drainage product (example: Mira Drain 6000)
may be used for wall drainage. Any such product should be installed in conformance with the
manufacturer’s recommendations. If the walls are designed using the “select” backfill design
parameters, then the “select” materials shall be placed within the active zone as defined by a 1:1
(H:V) projection from the back of the retaining wall footing up to the retained surface behind the
wall. Presence of other materials might necessitate revision to the parameters provided and
modification of wall designs.
The backfill materials should be placed in lifts no greater than eight (8) inches in thickness and
compacted at 90% relative compaction in accordance with ASTM Test Method D 1557. Proper
surface drainage needs to be provided and maintained. Water should not be allowed to pond
behind retaining walls. Waterproofing of site walls should be performed where moisture
migration through the wall is undesirable.
Retaining walls should be provided with an adequate pipe and gravel back drain system to reduce
the potential for hydrostatic pressures to develop. A 4-inch diameter perforated collector pipe
(Schedule 40 PVC, or approved equivalent) in a minimum of one cubic foot per lineal foot of 3/8
to one-inch clean crushed rock or equivalent, wrapped in filter fabric should be placed near the
bottom of the backfill and be directed (via a solid outlet pipe) to an appropriate disposal area.
Maximum horizontal spacing between drain outlets should be 100 feet.
As an alternative to the drain, rock and fabric, a pre-manufactured wall drainage product
(example: Mira Drain 6000 or approved equivalent) may be used behind the retaining wall. The
wall drainage product should extend from the base of the wall to within two (2) feet of the
ground surface. The subdrain should be placed in direct contact with the wall drainage product.
GEOTEK
Response to Review Comments February 3, 2025
Rincon Homes Project No. 3970-SD
180 Cherry Avenue and 3577 Garfield Street, Carlsbad, California 92008 Page 6
Drain outlets should be maintained over the life of the project and should not be obstructed or
plugged by adjacent improvements.
Comment No. 8:
Please clarify the recommendations for temporary cuts anticipated for this specific project for
the proposed remedial grading along the property boundaries. Please clarify the
recommendations for slot-cutting (maximum heights and widths of slot-cuts, sequencing of cuts,
time exposure, etc.) as necessary to prevent adverse impact to adjacent off-site property with
respect to the temporary cuts along the property boundaries that will apparently be necessary
for the recommended remedial grading.
Response:
This was addresed in GeoTek’s 2024b referenced report and remains applicable.
Comment No. 9:
Please provide recommendations (minimum slab thickness, reinforcing, etc.) for hardscape
improvements from a geotechnical standpoint.
Response:
Exterior concrete slabs, sidwalks and driveways should be designed using a four-inch minimum
thickness with 6” x 6” – W1.4/W1.4 welded wire fabric, placed in the middle of slab. It is
recommended that control joints be placed in two directions spaced the numeric equivalent
roughly 24 times the thickness of the slab in inches (e.g., a 4-inch slab would have control joints
at 96 inch [8 feet] centers). These joints are a widely accepted means to control cracks and
should be reviewed by the project structural engineer. Some shrinkage and cracking of the
concrete should be anticipated because of typical mix designs and curing practices typically utilized
in construction.
Presaturation of flatwork subgrade should be varified to be a minimum of 100% of the soils
optimum moisture to a depth of 12 inches.
Comment No. 10:
Please evaluate and discuss the potential for storm water infiltration at the subject site as part of
the proposed project.
Response:
Management of stormwater is not designed for the subject site, thus geotechnical evaluation for
the conditioned is not considered necessary.
Comment No. 11:
Please add a) Subdrains b) temporary excavations, c) retaining wall backfill, and d) hardscape and
GEOTEK
Response to Review Comments February 3, 2025
Rincon Homes Project No. 3970-SD
180 Cherry Avenue and 3577 Garfield Street, Carlsbad, California 92008 Page 7
driveway subgrade to the list of the geotechnical observations/testing services that should be
provided during the construction of the proposed development.
Response:
Acknowledged. In addition to the recommended duties to be performed by the Geotechnical
Consultant during site grading and construction listed in Section 6.2 Plan Review and
Construction Observations in the Preliminary Geotechnical Evaluation report (GeoTek 2024a),
the following geotechnical observations and testing services should be performed:
• Subdrains Driveway/hardscape subgrade.
• Temporary excavations.
• Retaining wall backfill.
• Hardscape and driveway subgrade.
Closure
Should you have any questions after reviewing this addendum, please feel free to contact our
office at your convenience.
Respectfully submitted,
GeoTek, Inc.
Attachments: Figure 2 Updated Geotechnical Map
Appendix A – Review Comments
Christopher D. Livesey
CEG, 2733 Exp. 05/31/25
Vice President
Edwin R. Cunningham
RCE 81687, Exp. 03/31/26
Project Engineer
GEOTEK
Response to Review Comments February 3, 2025
Rincon Homes Project No. 3970-SD
180 Cherry Avenue and 3577 Garfield Street, Carlsbad, California 92008 Page 8
REFERENCES
Geotek, Inc., 2024a, “Preliminary Geotechnical Evaluation, Proposed Three-Story Structure,
Assessor’s Parcel Number: 204-231-05-00, 180 Cherry Ave and 3577 Garfield Street,
Carlsbad, California 92008,” Project No. 3970-SD, dated March 13, 2024.
, 2024b, “Response to City Comments, Proposed Three-Story Structure, Assessor’s
Parcel Number: 204-231-05-00, 180 Cherry Ave and 3577 Garfield Street, Carlsbad,
California 92008,” Project No. 3970-SD, dated August 27, 2024.
Pasco Laret Suiter & Associates, 2024, “Grading Plans For: Cherry Ave. Homes, 180 Cherry
Avenue,” 7 Sheets, received December 23, 2024.
GEOTEK
B-3
LEGEND
Approximate Location of
Boring
Artificial Fill
Quaternary Old Paralics,
Circled Where Buried
Approximate Limits of Study,
This Report
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Image adapted from Grading Plans, Pasco Laret Suiter & Associates (2025)
1384 Poinsettia Avenue, Suite A
Vista, California 92081-8505 Figure 2
Geotechnical Map
PN: 3970-SD February 2025
Rincon Homes
180 Cherry Avenue
Carlsbad, CA
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APPENDIX A
City of Carlsbad Review Comments
GEOTEK
1384 Poinsettia Avenue, Suite A
Vista, California 92081-8505 Figure 1
Site Location Map
PN: 3970-SD March 2024
Rincon Homes
180 Cherry Avenue
Carlsbad, CA
Image from USGS The National Map (2024)Not to Scale
APPROXIMATE
SITE LOCATION
GEOTEK
Legend
Approximate Boring Location
Artificial Fill
Quaternary-age Old Paralics,
circled where buried
Approximate Limits of Study, this report
1384 Poinsettia Avenue, Suite A
Vista, California 92081-8505 Figure 2
Geotechnical Map
PN: 3970-SD March 2024
B-4
Rincon Homes
180 Cherry Avenue
Carlsbad, CA
Image from Pasco Laret Suiter & Associates
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B-2
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180 Cherry
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APPENDIX A
LOGS OF EXPLORATORY BORINGS
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page A-1
A - FIELD TESTING AND SAMPLING PROCEDURES
The Modified Split-Barrel Sampler (Ring)
The Ring sampler is driven into the ground in accordance with ASTM Test Method D 3550. The sampler,
with an external diameter of 3.0 inches, is lined with 1-inch long, thin brass rings with inside diameters of
approximately 2.4 inches. The sampler is typically driven into the ground 12 or 18 inches with a 140-
pound hammer free falling from a height of 30 inches. Blow counts are recorded for every 6 inches of
penetration as indicated on the log of boring. The samples are removed from the sample barrel in the
brass rings, sealed, and transported to the laboratory for testing.
The Standard Penetration Test Sampler (SPT)
The SPT sampler is driven into the ground in accordance with ASTM Test Method D 3550. The sampler,
with an external diameter of 2.0 inches and inner diameter of approximately 1.4 inches. The sampler is
typically driven into the ground 18 inches with a 140-pound hammer free falling from a height of 30 inches.
Blow counts are recorded for every 6 inches of penetration as indicated on the logs of borings.
Bulk Samples (Large)
These samples are normally large bags of earth materials over 20 pounds in weight collected from the
field by means of hand digging or exploratory cuttings.
Bulk Samples (Small)
These are plastic bag samples which are normally airtight and contain less than 5 pounds in weight of
earth materials collected from the field by means of hand digging or exploratory cuttings. These samples
are primarily used for determining natural moisture content and classification indices.
B –EXPLORATION LOG LEGEND
The following abbreviations and symbols often appear in the classification and description of soil and rock
on the logs of borings and trenches:
SOILS
USCS Unified Soil Classification System
f-c Fine to coarse
f-m Fine to medium
GEOLOGIC
B: Attitudes Bedding: strike/dip
J: Attitudes Joint: strike/dip
C: Contact line
……….. Dashed line denotes USCS material change
Solid Line denotes unit / formational change
Thick solid line denotes end of boring
(Additional denotations and symbols are provided on the logs)
GEOTEK
GeoTek, Inc.
LOG OF EXPLORATORY BORING
BB-1 SM
SH, MD, EI, SR
3 SM Expansion Index=0
6 R-1 10.7 112.4
8
6
10 S-1 9.6
14
22
35 R-2 7.2 101.8
50/5
15
20 S-2 6.8
20
19 5.0 101.5
35
---Small Bulk ---No Recovery ---Water Table
PROJECT NAME:180 Cherry Avenue DRILL METHOD:Solid Stem Auger OPERATOR:Kimble
CLIENT:Rincon Homes DRILLER:North County Drilling LOGGED BY:MRF
LOCATION:Carlsbad, CA ELEVATION:63 ft msl DATE:1/3/2024
PROJECT NO.:3970-SD HAMMER:140 lb / 30 inch drop RIG TYPE:LAR
SAMPLES
US
C
S
S
y
m
b
o
l
BORING NO.: B-1
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 f-m SAND, brown to dark brown, very moist, loose, palm roots, grass at
surface
Quaternary Old Paralics (Qop6-7)
Silty f-m SAND, light brown to brown, very moist, loose, friable, root casts
Dr
y
D
e
n
s
i
t
y
(p
c
f
)
Oth
e
r
s
MATERIAL DESCRIPTION AND COMMENTS
Artificial Fill (Af)
Cuttings become moist, drier at depth
5
Becomes coarser, lighter brown
15
Auger slow to advance
Becomes light tan, coarse grained, medium dense
Becomes tan, medium dense to very dense, well-cemented section
10
20
HOLE TERMINATED AT 20 FEET
R-3
25
No groundwater encountered
Backfilled with spoils
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
---I
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------
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---------------------• I [2'.] [8J □ ~
GeoTek, Inc.
LOG OF EXPLORATORY BORING
SM
4
9 R-1 SM 5.2 116.6
12
9
15 R-2 6.1 110.1
23
12
13 S-1 9.1
12
20
40 R-3 4.2 102.8
50/4
19
27 S-2 4.2
27
---Small Bulk ---No Recovery ---Water Table
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:
25
No groundwater encountered
Backfilled with spoils
20
HOLE TERMINATED AT 20.5 FEET
15 Becomes very dense, gray mottling, cemented spoils
Material becomes more coarse, damp, medium dense, friable
10 Observed zones of oxidation in SPT sample, varying oranges and tan coloration
friable, orange mottling
Becomes a lighter reddish-brown, less moist
5
Silty f-m SAND, brown, very moist, loose, roots
Quaternary Old Paralics (Qop6-7)
Silty f-m SAND, reddish brown, very moist, loose to medium dense, root casts,
Dr
y
D
e
n
s
i
t
y
(p
c
f
)
Oth
e
r
s
MATERIAL DESCRIPTION AND COMMENTS
Artificial Fill (Af)
SAMPLES
US
C
S
S
y
m
b
o
l
BORING NO.: B-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
(%
)
LOCATION:Carlsbad, CA ELEVATION:63 ft msl DATE:1/3/2024
PROJECT NO.:3970-SD HAMMER:140 lb / 30 inch drop RIG TYPE:LAR
PROJECT NAME:180 Cherry Avenue DRILL METHOD:Solid Stem Auger OPERATOR:Kimble
CLIENT:Rincon Homes DRILLER:North County Drilling LOGGED BY:MRF
----
------
~I ------
----
~I --------------------• I [2'.] [8J □ ~
GeoTek, Inc.
LOG OF EXPLORATORY BORING
SM
SM
3
7 R-1 8.6 107.5
7
9
17 R-2 11.1 116.0
30
9
10 S-1 10.0
11
10
16 S-2 5.4
18
---Small Bulk ---No Recovery ---Water Table
PROJECT NAME:180 Cherry Avenue DRILL METHOD:Solid Stem Auger OPERATOR:Kimble
CLIENT:Rincon Homes DRILLER:North County Drilling LOGGED BY:MRF
LOCATION:Carlsbad, CA ELEVATION:63 ft msl DATE:1/3/2024
PROJECT NO.:3970-SD HAMMER:140 lb / 30 inch drop RIG TYPE:LAR
SAMPLES
US
C
S
S
y
m
b
o
l
BORING NO.: B-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 f-m SAND, dark brown, very moist, loose, surficial roots and artificial cobbles
Quaternary Old Paralics (Qop6-7)
Silty f-m SAND, reddish-brown, very moist but dries at depth, medium dense, friable
Dr
y
D
e
n
s
i
t
y
(p
c
f
)
Oth
e
r
s
MATERIAL DESCRIPTION AND COMMENTS
Artificial Fill (Af)
Becomes more coarse and brown with orange mottling
5
10 Becomes tan with grey mottling, damp, dense
HOLE TERMINATED AT 16.5 FEET
No groundwater encountered
15
Backfilled with spoils
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 ----------------------------• I [2'.] [8J □ ~
GeoTek, Inc.
LOG OF EXPLORATORY BORING
SM
SM
7
7 S-1 11.8
15
12
13 S-2 9.4
16
11
18 S-3 7.2
22
---Small Bulk ---No Recovery ---Water Table
PROJECT NAME:180 Cherry Avenue DRILL METHOD:Solid Stem Auger OPERATOR:Kimble
CLIENT:Rincon Homes DRILLER:North County Drilling LOGGED BY:MRF
LOCATION:Carlsbad, CA ELEVATION:63 ft msl DATE:1/3/2024
PROJECT NO.:3970-SD HAMMER:140 lb / 30 inch drop RIG TYPE:LAR
SAMPLES
US
C
S
S
y
m
b
o
l
BORING NO.: B-4
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 SAND, dark brown, f-m, very moist from rain, loose, surficial roots and
vegetation, cobbles
Quaternary Old Paralics (Qop6-7)
Silty f-m SAND, reddish-brown, very moist to moist, medium dense, friable, orange
Dr
y
D
e
n
s
i
t
y
(p
c
f
)
Oth
e
r
s
MATERIAL DESCRIPTION AND COMMENTS
Artificial Fill (Af)
mottling, root casts in upper 5-inches
5
Oxidation zones in SPT sample, alternating bands of orange/tan
10
HOLE TERMINATED AT 16.5 FEET
No groundwater encountered
15 Oxidation zones
Backfilled with spoils
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 ------
~I ----------------------------• I [2'.] [8J □ ~
APPENDIX B
RESULTS OF LABORATORY TESTING
GEOTEK
RINCON HOMES Project No. 3970-SD
Preliminary Geotechnical Evaluation March 13, 2024
180 Cherry Avenue, Carlsbad, California 92008 Page B-1
SUMMARY OF LABORATORY TESTING
Identification and Classification
Soils were identified visually in general accordance with the standard practice for description and
identification of soils (ASTM Test Method D 2487). The soil identifications and classifications are shown
on the logs of exploratory borings in Appendix A.
In-Situ Moisture and Density
The natural water content was determined (ASTM D 2216) on samples of the materials recovered during
the subsurface exploration. In addition, in-place dry density determinations (ASTM D 2937) were
performed on relatively undisturbed samples to measure the unit weight of the subsurface soils. Results
of these tests are shown on the boring logs at the appropriate sample depths in Appendix A.
Moisture Density Relationship
Laboratory testing was performed on one sample collected during the subsurface exploration for
compaction characteristics. The laboratory maximum dry density and optimum moisture content for the
soil was determined in general accordance with ASTM Test Method D 1557 procedures. The test results
are graphically presented in Appendix B.
Expansion Index
Expansion Index testing was performed on one soil sample. Testing was performed in general accordance
with ASTM Test Method D 4829. Results are presented in Appendix B.
Direct Shear (remolded)
Direct shear testing was performed on remolded samples of the surficial soils according to ASTM Test
Method D 3080. The results of the testing are graphically presented in Appendix B.
Sulfate Content and Chloride Content
Testing to determine the water-soluble sulfate content was performed by others in general accordance
with ASTM D 516. Soil testing to determine the soil chloride content was performed by others in general
accordance with ASTM D 512B. The results are included in Appendix B.
GEOTEK
10.0 10.0 10.0
110.3 110.0 110.0
51.9 51.5 51.5
0.52 0.52 0.52
2.375 2.375 2.375
1.0 1.0 1.0
Water Content, % 15.3 15.9 16.4
Dry Density, pcf 114.0 114.0 115.0
Saturation, %87.8 91.3 96.8
Void Ratio 0.47 0.47 0.45
Height, in.0.998 0.993 0.999
Normal Stress, psf 500 1500 2500
Ф =36 ˚C =150 psf Failure Stress, psf 438 1416 1880
Displacement, in.0.000 0.000 0.000
Ultimate Stress, psf 0 0 0
Displacement, in.0.000 0.000 0.000
Strain rate, in./min.0.0100 0.0100 0.0100
In-situ
45307Date:
Technician:
Location:
Apparatus:
2 3
0'-5'
Sample No. 1
At
T
e
s
t
Remolded
Void Ratio
Diameter, in.
Height, in.
Soaked, consolidated, drained. 2.375-in. remolded ring sample.Condition:
MB
Carlsbad, CA
Saturation, %
Water Content, %
Dry Density, pcf
In
i
t
i
a
l
Project Name:180 Cherry Avenue
Remarks:
Shear Strength:
Description:Tan to Orange Tan Silty Sand
3970-SD
Sample ID: B-1 BB-1
Sample Depth:
Project Number:
0
500
1000
1500
2000
2500
3000
0 500 1000 1500 2000 2500 3000
Sh
e
a
r
S
t
r
e
s
s
(
p
s
f
)
Normal Stress (psf)
c = 150 (psf)
f = (deg) 36
-0.02
-0.01
0.00
0.01
0.02
0.00 0.10 0.20 0.30 0.40 0.50
Ve
r
t
i
c
a
l
D
e
f
o
r
m
a
t
i
o
n
(
i
n
)
Horiz. Displacement (in)
0
500
1000
1500
2000
2500
3000
0.00 0.10 0.20 0.30 0.40 0.50
Sh
e
a
r
S
t
r
e
s
s
(
p
s
f
)
Horiz. Displacement (in)
DIRECT SHEAR TEST REPORT
-
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V V V
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I
□ ■
A
GEOTEK
MOISTURE/DENSITY RELATIONSHIP
Client:Rincon Homes Job No.:3970-SD
Project:180 Cherry Ave Lab No.:4033
Location:Carlsbad, CA
Material Type:Fine Sand
Material Supplier:-
Material Source:-
Sample Location:B-1 BB-1
-
Sampled By:MRF Date Sampled:1/3/2024
Received By:MB Date Received:1/3/2024
Tested By:MB Date Tested:1/5/2024
Reviewed By:ERC Date Reviewed:-
Test Procedure:ASTM D1557 Method:A
Oversized Material (%):0.0 Correction Required: yes x no
MOISTURE CONTENT (%):9.340252 14.18605 11.32931 7.13246 9.340252 14.18605 11.329305 7.13246
DRY DENSITY (pcf):120.8001 118.045 121.4011 119.9173
CORRECTED DRY DENSITY (pcf):#DIV/0!#DIV/0!#DIV/0!#DIV/0!
ZERO AIR VOIDS DRY DENSITY (pcf):
MOISTURE DENSITY RELATIONSHIP VALUES
Maximum Dry Density, pcf 121.5 @ Optimum Moisture, %11.4
Corrected Maximum Dry Density, pcf @ Optimum Moisture, %
MATERIAL DESCRIPTION
Grain Size Distribution:Atterberg Limits:
% Gravel (retained on No. 4)Liquid Limit, %
% Sand (Passing No. 4, Retained on No. 200)Plastic Limit, %
% Silt and Clay (Passing No. 200)Plasticity Index, %
Classification:
Unified Soils Classification:
AASHTO Soils Classification:
116
118
120
122
124
7 8 9 10 11 12 13 14 15 16 17 18
DR
Y
D
E
N
S
I
T
Y
,
P
C
F
MOISTURE CONTENT, %
MOISTURE/DENSITY RELATIONSHIP CURVE DRY DENSITY (pcf):
CORRECTED DRY DENSITY (pcf):
ZERO AIR VOIDS DRY DENSITY (pcf)
S.G. 2.7
S.G. 2.8
Poly. (DRY DENSITY (pcf):)
OVERSIZE CORRECTED
ZERO AIR VOIDS
Poly. (S.G. 2.7)
Poly. (S.G. 2.8)
GEOTEK
□
♦
■
..
X
X
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 =
4033
23.2%
5 min/Wet
READINGS
1/6/2024 2:00 87
TIME READINGDATE
Final
MB/ERC
Carlsbad, CA
Loading weight: 5516. grams
B-1 BB-1
1/5/2024
Fine Sand
Lab No
Project Number:
Project Name:180 Cherry
3970-SD
Project Location:
771.9
4"12
9011:39
Dry Density, lb / ft3 (D/1.F)
Initial
100
1 min/Wet
10 min/Dry
1/5/2024
Random
11:20 100
91
11:31
11:31
370.6
DENSITY DETERMINATION
Wet Density, lb / ft3 (C*0.3016)
0.34
0.66
110.7
1033.9
401.3
121.0
SATURATION DETERMINATION
21.1
9.3
49.0
121.5
152.2
4.7
139.6
1"
EXPANSION INDEX TEST
(ASTM D4829)
0
Tare
4.8
FINAL MOISTURE
%
Moisture
Weight of wet
sample & tare
Wt. of dry sample
& tare
99.5
GEOTEK
--I
I I
Project X REPORT S240105B
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
180 Cherry
January 8, 2024
Prepared for:
Chris Livesey
Geotek USA
1384 Poinsettia Avenue, Suite A
Vista, CA, 92081
clivesey@geotekusa.com
Project X Job#: S240105B
Client Job or PO#: 3970-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 S240105B
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 USA
Job Name: 180 Cherry
Client Job Number: 3970-SD
Project X Job Number: S240105B
January 8, 2024
Method
Bore# /
Description
Depth
(ft)(mg/kg)(wt%)(mg/kg)(wt%)
B-1 BB-1 0-5 34.5 0.0034 51.2 0.0051
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)
Note: Sometimes a bad sulfate hit is a contaminated spot. Typical fertilizers are Potassium chloride, ammonium sulfate or ammonium sulfate nitrate (ASN). So this is another reason why testing full corrosion
series is good because we then have the data to see if those other ingredients are present meaning the soil sample is just fertilizer-contaminated soil. This can happen often when the soil samples collected are simply
surface scoops which is why it's best to dig in a foot, throw away the top and test the deeper stuff. Dairy farms are also notorious for these items.
APPENDIX C
GENERAL GRADING GUIDELINES
GEOTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C-1
GENERAL GRADING GUIDELINES
Guidelines presented herein are intended to address general construction procedures for earthwork
construction. Specific situations and conditions often arise which cannot reasonably be discussed in
general guidelines, when anticipated these are discussed in the text of the report. Often unanticipated
conditions are encountered which may necessitate modification or changes to these guidelines. It is our
hope that these will assist the contractor to more efficiently complete the project by providing a
reasonable understanding of the procedures that would be expected during earthwork and the testing
and observation used to evaluate those procedures.
General
Grading should be performed to at least the minimum requirements of governing agencies, Chapters 18
and 33 of the California Building Code, CBC (2022) and the guidelines presented below.
Preconstruction Meeting
A preconstruction meeting should be held prior to site earthwork. Any questions the contractor has
regarding our recommendations, general site conditions, apparent discrepancies between reported and
actual conditions and/or differences in procedures the contractor intends to use should be brought up
at that meeting. The contractor (including the main onsite representative) should review our report
and these guidelines in advance of the meeting. Any comments the contractor may have regarding these
guidelines should be brought up at that meeting.
Grading Observation and Testing
1. Observation of the fill placement should be provided by our representative during grading.
Verbal communication during the course of each day will be used to inform the contractor of
test results. The contractor should receive a copy of the "Daily Field Report" indicating results
of field density tests that day. If our representative does not provide the contractor with these
reports, our office should be notified.
2. Testing and observation procedures are, by their nature, specific to the work or area observed
and location of the tests taken, variability may occur in other locations. The contractor is
responsible for the uniformity of the grading operations; our observations and test results are
intended to evaluate the contractor’s overall level of efforts during grading. The contractor’s
personnel are the only individuals participating in all aspect of site work. Compaction testing
and observation should not be considered as relieving the contractor’s responsibility to properly
compact the fill.
3. Cleanouts, processed ground to receive fill, key excavations, and subdrains should be observed
by our representative prior to placing any fill. It will be the contractor's responsibility to notify
our representative or office when such areas are ready for observation.
4. Density tests may be made on the surface material to receive fill, as considered warranted by
this firm.
5. In general, density tests would be made at maximum intervals of two feet of fill height or every
1,000 cubic yards of fill placed. Criteria will vary depending on soil conditions and size of the fill.
More frequent testing may be performed. In any case, an adequate number of field density tests
should be made to evaluate the required compaction and moisture content is generally being
obtained.
6. Laboratory testing to support field test procedures will be performed, as considered warranted,
based on conditions encountered (e.g. change of material sources, types, etc.) Every effort will
GEOTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C-2
be made to process samples in the laboratory as quickly as possible and in progress construction
projects are our first priority. However, laboratory workloads may cause in delays and some
soils may require a minimum of 48 to 72 hours to complete test procedures.
Whenever possible, our representative(s) should be informed in advance of operational changes
that might result in different source areas for materials.
7. Procedures for testing of fill slopes are as follows:
a) Density tests should be taken periodically during grading on the flat surface of the fill,
three to five feet horizontally from the face of the slope.
b) If a method other than over building and cutting back to the compacted core is to be
employed, slope compaction testing during construction should include testing the outer
six inches to three feet in the slope face to determine if the required compaction is
being achieved.
8. Finish grade testing of slopes and pad surfaces should be performed after construction is
complete.
Site Clearing
1. All vegetation, and other deleterious materials, should be removed from the site. If material is
not immediately removed from the site it should be stockpiled in a designated area(s) well
outside of all current work areas and delineated with flagging or other means. Site clearing
should be performed in advance of any grading in a specific area.
2. Efforts should be made by the contractor to remove all organic or other deleterious material
from the fill, as even the most diligent efforts may result in the incorporation of some materials.
This is especially important when grading is occurring near the natural grade. All equipment
operators should be aware of these efforts. Laborers may be required as root pickers.
3. Nonorganic debris or concrete may be placed in deeper fill areas provided the procedures used
are observed and found acceptable by our representative.
Treatment of Existing Ground
1. Following site clearing, all surficial deposits of alluvium and colluvium as well as weathered or
creep effected bedrock, should be removed unless otherwise specifically indicated in the text of
this report.
2. In some cases, removal may be recommended to a specified depth (e.g. flat sites where partial
alluvial removals may be sufficient). The contractor should not exceed these depths unless
directed otherwise by our representative.
3. Groundwater existing in alluvial areas may make excavation difficult. Deeper removals than
indicated in the text of the report may be necessary due to saturation during winter months.
4. Subsequent to removals, the natural ground should be processed to a depth of six inches,
moistened to near optimum moisture conditions and compacted to fill standards.
5. Exploratory back hoe or dozer trenches still remaining after site removal should be excavated
and filled with compacted fill if they can be located.
Fill Placement
1. Unless otherwise indicated, all site soil and bedrock may be reused for compacted fill; however,
some special processing or handling may be required (see text of report).
2. Material used in the compacting process should be evenly spread, moisture conditioned,
processed, and compacted in thin lifts six (6) to eight (8) inches in compacted thickness to
GEOTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C-3
obtain a uniformly dense layer. The fill should be placed and compacted on a nearly horizontal
plane, unless otherwise found acceptable by our representative.
3. If the moisture content or relative density varies from that recommended by this firm, the
contractor should rework the fill until it is in accordance with the following:
a) Moisture content of the fill should be at or above optimum moisture. Moisture should
be evenly distributed without wet and dry pockets. Pre-watering of cut or removal
areas should be considered in addition to watering during fill placement, particularly in
clay or dry surficial soils. The ability of the contractor to obtain the proper moisture
content will control production rates.
b) Each six-inch layer should be compacted to at least 90 percent of the maximum dry
density in compliance with the testing method specified by the controlling governmental
agency. In most cases, the testing method is ASTM Test Designation D 1557.
4. Rock fragments less than eight inches in diameter may be utilized in the fill, provided:
a) They are not placed in concentrated pockets;
b) There is a sufficient percentage of fine-grained material to surround the rocks;
c) The distribution of the rocks is observed by, and acceptable to, our representative.
5. Rocks exceeding eight (8) inches in diameter should be taken off site, broken into smaller
fragments, or placed in accordance with recommendations of this firm in areas designated
suitable for rock disposal. On projects where significant large quantities of oversized materials
are anticipated, alternate guidelines for placement may be included. If significant oversize
materials are encountered during construction, these guidelines should be requested.
6. In clay soil, dry or large chunks or blocks are common. If in excess of eight (8) inches minimum
dimension, then they are considered as oversized. Sheepsfoot compactors or other suitable
methods should be used to break up blocks. When dry, they should be moisture conditioned to
provide a uniform condition with the surrounding fill.
Slope Construction
1. The contractor should obtain a minimum relative compaction of 90 percent out to the finished
slope face of fill slopes. This may be achieved by either overbuilding the slope and cutting back
to the compacted core, or by direct compaction of the slope face with suitable equipment.
2. Slopes trimmed to the compacted core should be overbuilt by at least three (3) feet with
compaction efforts out to the edge of the false slope. Failure to properly compact the outer
edge results in trimming not exposing the compacted core and additional compaction after
trimming may be necessary.
3. If fill slopes are built "at grade" using direct compaction methods, then the slope construction
should be performed so that a constant gradient is maintained throughout construction. Soil
should not be "spilled" over the slope face nor should slopes be "pushed out" to obtain grades.
Compaction equipment should compact each lift along the immediate top of slope. Slopes
should be back rolled or otherwise compacted at approximately every 4 feet vertically as the
slope is built.
4. Corners and bends in slopes should have special attention during construction as these are the
most difficult areas to obtain proper compaction.
5. Cut slopes should be cut to the finished surface. Excessive undercutting and smoothing of the
face with fill may necessitate stabilization.
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GENERAL GRADING GUIDELINES APPENDIX C
Page C-4
UTILITY TRENCH CONSTRUCTION AND BACKFILL
Utility trench excavation and backfill is the contractors responsibility. The geotechnical consultant
typically provides periodic observation and testing of these operations. While efforts are made to make
sufficient observations and tests to verify that the contractors’ methods and procedures are adequate to
achieve proper compaction, it is typically impractical to observe all backfill procedures. As such, it is
critical that the contractor use consistent backfill procedures.
Compaction methods vary for trench compaction and experience indicates many methods can be
successful. However, procedures that “worked” on previous projects may or may not prove effective
on a given site. The contractor(s) should outline the procedures proposed, so that we may discuss
them prior to construction. We will offer comments based on our knowledge of site conditions and
experience.
1. Utility trench backfill in slopes, structural areas, in streets and beneath flat work or hardscape
should be brought to at least optimum moisture and compacted to at least 90 percent of the
laboratory standard. Soil should be moisture conditioned prior to placing in the trench.
2. Flooding and jetting are not typically recommended or acceptable for native soils. Flooding or
jetting may be used with select sand having a Sand Equivalent (SE) of 30 or higher. This is
typically limited to the following uses:
a) shallow (12 + inches) under slab interior trenches and,
b) as bedding in pipe zone.
The water should be allowed to dissipate prior to pouring slabs or completing trench
compaction.
3. Care should be taken not to place soils at high moisture content within the upper three feet of
the trench backfill in street areas, as overly wet soils may impact subgrade preparation.
Moisture may be reduced to 2% below optimum moisture in areas to be paved within the upper
three feet below sub grade.
4. Sand backfill should not be allowed in exterior trenches adjacent to and within an area
extending below a 1:1 projection from the outside bottom edge of a footing, unless it is similar
to the surrounding soil.
5. Trench compaction testing is generally at the discretion of the geotechnical consultant. Testing
frequency will be based on trench depth and the contractors procedures. A probing rod would
be used to assess the consistency of compaction between tested areas and untested areas. If
zones are found that are considered less compact than other areas, this would be brought to
the contractors attention.
JOB SAFETY
General
Personnel safety is a primary concern on all job sites. The following summaries are safety considerations
for use by all our employees on multi-employer construction sites. On ground personnel are at highest
risk of injury and possible fatality on grading construction projects. The company recognizes that
construction activities will vary on each site and that job site safety is the contractor's responsibility.
However, it is, imperative that all personnel be safety conscious to avoid accidents and potential injury.
In an effort to minimize risks associated with geotechnical testing and observation, the following
precautions are to be implemented for the safety of our field personnel on grading and construction
projects.
GEOTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C-5
1. Safety Meetings: Our field personnel are directed to attend the contractor's regularly scheduled
safety meetings.
2. Safety Vests: Safety vests are provided for and are to be worn by our personnel while on the job
site.
3. Safety Flags: Safety flags are provided to our field technicians; one is to be affixed to the vehicle
when on site, the other is to be placed atop the spoil pile on all test pits.
In the event that the contractor's representative observes any of our personnel not following the above,
we request that it be brought to the attention of our office.
Test Pits Location, Orientation and Clearance
The technician is responsible for selecting test pit locations. The primary concern is the technician's
safety. However, it is necessary to take sufficient tests at various locations to obtain a representative
sampling of the fill. As such, efforts will be made to coordinate locations with the grading contractors
authorized representatives (e.g. dump man, operator, supervisor, grade checker, etc.), and to select
locations following or behind the established traffic pattern, preferably outside of current traffic. The
contractors authorized representative should direct excavation of the pit and safety during the test
period. Again, safety is the paramount concern.
Test pits should be excavated so that the spoil pile is placed away from oncoming traffic. The
technician's vehicle is to be placed next to the test pit, opposite the spoil pile. This necessitates that the
fill be maintained in a drivable condition. Alternatively, the contractor may opt to park a piece of
equipment in front of test pits, particularly in small fill areas or those with limited access.
A zone of non-encroachment should be established for all test pits (see diagram below). No grading
equipment should enter this zone during the test procedure. The zone should extend outward to the
sides approximately 50 feet from the center of the test pit and 100 feet in the direction of traffic flow.
This zone is established both for safety and to avoid excessive ground vibration, which typically
decreases test results.
50 ft Zone of
Non-Encroachment
50 ft Zone of
Non-Encroachment
Traffic Direction
Vehicle
parked here Test Pit Spoil
pile
Spoil
pile
Test Pit
SIDE VIEW
PLAN VIEW
TEST PIT SAFETY PLAN
10 0 ft Zone of
Non-Encroachment
'~
...,
'. ·~
\..
I
•
GEOTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C-6
Slope Tests
When taking slope tests, the technician should park their vehicle directly above or below the test
location on the slope. The contractor's representative should effectively keep all equipment at a safe
operation distance (e.g. 50 feet) away from the slope during testing.
The technician is directed to withdraw from the active portion of the fill as soon as possible following
testing. The technician's vehicle should be parked at the perimeter of the fill in a highly visible location.
Trench Safety
It is the contractor's responsibility to provide safe access into trenches where compaction testing is
needed. Trenches for all utilities should be excavated in accordance with CAL-OSHA and any other
applicable safety standards. Safe conditions will be required to enable compaction testing of the trench
backfill.
All utility trench excavations in excess of 5 feet deep, which a person enters, are to be shored or laid
back. Trench access should be provided in accordance with OSHA standards. Our personnel are
directed not to enter any trench by being lowered or "riding down" on the equipment.
Our personnel are directed not to enter any excavation which;
1. is 5 feet or deeper unless shored or laid back,
2. exit points or ladders are not provided,
3. displays any evidence of instability, has any loose rock or other debris which could fall into the
trench, or
4. displays any other evidence of any unsafe conditions regardless of depth.
If the contractor fails to provide safe access to trenches for compaction testing, our company policy
requires that the soil technician withdraws and notifies their supervisor. The contractors representative
will then be contacted in an effort to effect a solution. All backfill not tested due to safety concerns or
other reasons is subject to reprocessing and/or removal.
Procedures
In the event that the technician's safety is jeopardized or compromised as a result of the contractor's
failure to comply with any of the above, the technician is directed to inform both the developer's and
contractor's representatives. If the condition is not rectified, the technician is required, by company
policy, to immediately withdraw and notify their supervisor. The contractor’s representative will then
be contacted in an effort to effect a solution. No further testing will be performed until the situation is
rectified. Any fill placed in the interim can be considered unacceptable and subject to reprocessing,
recompaction or removal.
In the event that the soil technician does not comply with the above or other established safety
guidelines, we request that the contractor bring this to technicians attention and notify our project
manager or office. Effective communication and coordination between the contractors' representative
and the field technician(s) is strongly encouraged in order to implement the above safety program and
safety in general.
The safety procedures outlined above should be discussed at the contractor's safety meetings. This will
serve to inform and remind equipment operators of these safety procedures particularly the zone of
non-encroachment.
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GENERAL GRADING GUIDELINES APPENDIX C
Page C-7
The safety procedures outlined above should be discussed at the contractor's safety meetings. This will
serve to inform and remind equipment operators of these safety procedures particularly the zone of
non-encroachment.
GEOTEK