HomeMy WebLinkAboutCDP 2022-0031; ADAMS HOUSE; GEOTECHNICAL REPORT; 2024-01-31
GEOTECHNICAL | ENVIRONMENTAL | MATERIALS
UPDATED GEOTECHNICAL EVALUATION
FOR
PROPOSED RESIDENTIAL DEVELOPMENT
4368 ADAMS STREET
CARLSBAD, CALIFORNIA
PREPARED FOR
Curtis Ling
3667 Adams Street
CARLSBAD, CALIFORNIA 92008
PREPARED BY
GEOTEK, INC.
1384 POINSETTIA AVENUE, SUITE A
VISTA, CALIFORNIA 92081
PROJECT NO. 3687-SD SEPTEMBER 21, 2023
(REVISED JANUARY 31, 2024)
GEOTEK
September 21, 2023
Revised January 31, 2024
Project No. 3687-SD
Curtis Ling
3667 Adams Street
Carlsbad, California 92008
Subject: Updated Geotechnical Evaluation
Proposed Residential Development
4368 Adams Street
Carlsbad, California
Dear Mr. Ling:
Presented herein are the results of GeoTek’s preliminary geotechnical evaluation for the
subject project located at 4368 Adams Street, Carlsbad, California. This report provides
an update to the preliminary Geotechnical Report prepared by GeoTek on May 18, 2021.
The update has been prepared based on City of Carlsbad geotechnical review comments
dated May 23, 2023. Based upon review, planned construction appears feasible from a
geotechnical viewpoint provided that the recommendations included herein are incorporated
into the design and construction phases of site development.
The opportunity to be of service is sincerely appreciated. If you should have any questions,
please do not hesitate to call GeoTek, Inc.
Respectfully submitted,
GeoTek, Inc.
Christopher D. Livesey
CEG 2733, Exp. 05/31/25
Vice President
Bruce A. Hick
GE 2284, Exp. 12/31/24
Project Engineer
Distribution: (1) Addressee via email
GeoTek, Inc.
1384 Poinsettia Avenue, Suite A Vista, CA 92081-8505
(760) 599-0509 (760) 599-0593 www.geotekusa.com
GEOTEK
CURTIS LING Project No. 3687-SD
Updated Geotechnical Evaluation September 21, 2023 (Revised January 31, 2024)
4368 Adams Street, Carlsbad, California Page i
TABLE OF CONTENTS
1. PURPOSE AND SCOPE OF SERVICES ................................................................................................. 1
2. SITE DESCRIPTION AND PROPOSED DEVELOPMENT ............................................................... 1
2.1 SITE DESCRIPTION .......................................................................................................................... 1
2.2 PROPOSED DEVELOPMENT ............................................................................................................ 2
3. FIELD EXPLORATION AND LABORATORY TESTING ................................................................. 2
3.1 FIELD EXPLORATION ...................................................................................................................... 2
3.2 LABORATORY TESTING ................................................................................................................... 2
4. GEOLOGIC AND SOILS CONDITIONS ............................................................................................... 3
4.1 REGIONAL SETTING ........................................................................................................................ 3
4.2 EARTH MATERIALS ......................................................................................................................... 3
4.2.1 Artificial Fill ....................................................................................................................................... 3
4.2.2 Old Paralic Deposits.......................................................................................................................... 4
4.3 SURFACE WATER AND GROUNDWATER ........................................................................................ 4
4.3.1 Surface Water .................................................................................................................................. 4
4.3.2 Groundwater .................................................................................................................................... 4
4.4 EARTHQUAKE HAZARDS ................................................................................................................ 4
4.4.1 Surface Fault Rupture ....................................................................................................................... 4
4.4.2 Liquefaction/Seismic Settlement......................................................................................................... 5
4.4.3 Other Seismic Hazards ..................................................................................................................... 5
5. CONCLUSIONS AND RECOMMENDATIONS .................................................................................. 5
5.1 GENERAL CONCLUSIONS................................................................................................................ 5
5.3 EARTHWORK CONSIDERATIONS ................................................................................................... 6
5.3.1 General ............................................................................................................................................ 6
5.3.2 Site Clearing and Preparation ............................................................................................................ 6
5.3.3 Remedial Grading ............................................................................................................................. 7
5.3.4 Engineered Fill .................................................................................................................................. 8
5.3.5 Excavation Characteristics ................................................................................................................. 8
5.3.6 Shrinkage and Bulking ...................................................................................................................... 8
5.3.7 Trench Excavations and Backfill ........................................................................................................ 8
5.4 DESIGN RECOMMENDATIONS ....................................................................................................... 9
5.4.1 Foundation Design Criteria ................................................................................................................ 9
5.4.2 Miscellaneous Foundation Recommendations ................................................................................... 10
5.4.3 Underslab Moisture Membrane....................................................................................................... 10
5.4.4 Foundation Set Backs...................................................................................................................... 11
5.4.5 Seismic Design Parameters ............................................................................................................. 12
5.4.6 Soil Sulfate Content ........................................................................................................................ 13
5.4.7 Exterior Concrete Slabs and Sidewalks............................................................................................. 13
5.5 RETAINING WALL DESIGN AND CONSTRUCTION ........................................................................ 13
5.5.1 General Retaining Wall Design Criteria ............................................................................................ 13
5.5.2 Cantilevered Retaining Walls ........................................................................................................... 14
5.5.3 Restrained (At Rest) Retaining Walls Design Criteria ........................................................................ 14
5.5.4 Seismic Induced Incremental Addition .............................................................................................. 14
5.5.5 Wall Backfill and Drainage ............................................................................................................. 15
5.6 POST CONSTRUCTION CONSIDERATIONS ................................................................................... 16
5.6.1 Landscape Maintenance and Planting .............................................................................................. 16
5.6.2 Drainage ........................................................................................................................................ 16
5.7 CONSTRUCTION OBSERVATIONS ................................................................................................. 17
CURTIS LING Project No. 3687-SD
Updated Geotechnical Evaluation September 21, 2023 (Revised January 31, 2024)
4368 Adams Street, Carlsbad, California Page ii
TABLE OF CONTENTS
6. LIMITATIONS ............................................................................................................................................ 17
7. SELECTED REFERENCES ....................................................................................................................... 19
8. RESPONSE TO GEOTECHNICAL REVIEW COMMENTS ............................................................ 20
ENCLOSURES
Figure 1 – Site Location Map
Figure 2 – Geotechnical Map
Figure 3 – Geotechnical Cross Section AA
Figure 4 – Geotechnical Cross Section BB
Appendix A – Exploration Logs
Appendix B – Results of Laboratory Testing
Appendix C – General Earthwork Grading Guidelines
CURTIS LING Project No. 3687-SD
Updated Geotechnical Evaluation September 21, 2023 (Revised January 31, 2024)
4368 Adams Street, Carlsbad, California Page 1
1. PURPOSE AND SCOPE OF SERVICES
The purpose of this study was to evaluate the geotechnical conditions on the project site
pertinent to the proposed improvements. Services provided for this study included the
following:
▪ Research and review of available geologic and geotechnical data, and general information
pertinent to the site.
▪ Excavation of three (3) test pits, one manual auger boring and collection of bulk soil
samples for subsequent laboratory testing.
▪ Laboratory testing of soil samples collected during the field investigation.
▪ Preparation of this report presenting GeoTek’s findings of pertinent site geotechnical
conditions and geotechnical recommendations for site development.
2. SITE DESCRIPTION AND PROPOSED DEVELOPMENT
2.1 SITE DESCRIPTION
The project site located at 4368 Adams Street, Carlsbad, California and is identified as County of
San Diego assessor parcel number (APN) 206-180-11-00. The overall property is bounded to the
north by open space, to the east and south by single-family residences and to the west by Adams
Street. The general location of the site is indicated on Figure 1 - Site Location Map.
The site is accessible via Adams Street and improved upon with a one to two story single-family
residential building with a detached garage. An asphalt-concrete (AC) driveway exists along the
southern property line from Adams Street to the building. Topographically, the property is in a
hillside setting. A natural slope ascends from Adams Street up to a manufactured fill slope that
supports the buildings. Natural slopes were visually estimated to be variable over a short
distance, but overall, no steeper than 4:1 (horizontal:vertical) gradient. Manufactured fill slopes
that supported the building pad were visually estimated to be no steeper than a 2:1 gradient.
CURTIS LING Project No. 3687-SD
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4368 Adams Street, Carlsbad, California Page 2
2.2 PROPOSED DEVELOPMENT
Based on discussions with the client and a review of the project grading and improvements plans,
the subject property is to be razed of existing buildings and improved with a two-story single-
family house residence above a walkout basement along the west side of the building. The
building will be approximately 30 feet tall with a concrete slab, perimeter and interior spread
footings. Concrete masonry unit (CMU) walls are planned for the basement walls. A three-car
garage, gym, storage and art room are planned for the basement level. A single-story detached
ADU is proposed adjacent to Adams Street to be recessed into the hillside. A motor court and
driveway along the south side of the parcel provide vehicle access to the main dwelling and ADU.
Cuts are anticipated to be about five feet near the east portion of the site where CMU walls will
retain elevated grades. Engineered fills on the order of twelve feet to reach design grades are
anticipated predominately for building basement walls. Basement walls are planned to a
maximum height of 13.5 feet. The predominate areas of fills are associated with interior
basement walls for the main and ADU dwellings. Site retaining walls are anticipated to be 3 to
5 feet in height. A new fill slope along Adams Street is proposed to recontour the frontage at a
maximum height of seven feet and inclination of 2:1 (horizontal to vertical). Associated
improvements are anticipated to consist of wet and dry utilities, vehicular pavements, and
hardscape.
3. FIELD EXPLORATION AND LABORATORY TESTING
3.1 FIELD EXPLORATION
GeoTek’s field exploration was conducted on April 16, 2021, and consisted of a site
reconnaissance, excavation of three test pits, one manual soil auger boring, and collection of
samples for subsequent laboratory testing. A geologist from GeoTek visually logged the
excavations as described in the Exploration Logs, Appendix A. A grading plan has been provided
to us and is utilized as the basis of GeoTek’s geotechnical map (Figure 2). Approximate locations
of the excavations are presented on the Geotechnical Map, Figure 2.
3.2 LABORATORY TESTING
Laboratory testing was performed on the soil samples collected during the field exploration. The
purpose of the laboratory testing was to evaluate pertinent 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.
CURTIS LING Project No. 3687-SD
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4368 Adams Street, Carlsbad, California Page 3
4. GEOLOGIC AND SOILS CONDITIONS
4.1 REGIONAL SETTING
The subject property is in the Peninsular Ranges geomorphic province. The Peninsular Ranges
province is one of the largest geomorphic units in western North America. It extends from the
north and northeast, adjacent the Transverse Ranges geomorphic province to the top of Baja
California. This province varies in width from about 30 to 100 miles. It is bounded on the west
by the Pacific Ocean, on the south by the Gulf of California, and on the east by the Colorado
Desert Province.
The Peninsular Ranges are essentially a series of northwest-southeast oriented fault blocks.
Several major fault zones are found in this province. The Elsinore Fault zone and the San Jacinto
Fault zones trend northwest-southeast and are found 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 GeoTek’s subsurface exploration
is presented in the following sections. Based on GeoTek’s previous experience in the vicinity and
review of published geologic maps, the site underlain by Old Paralic Deposits and artificial fills
overlying Old Paralic Deposits.
4.2.1 Artificial Fill
Fill soils were encountered in Test Pit TP-3. Other areas of fills (unmapped) are also likely
present on the site. Fill soils were found to be light-brown, dry, silty fine to medium sand (SM
soil type based upon the Unified Soil Classification System). The upper six inches of the fill soils
were found to contain abundant organics.
The placement of on-site fills was geotechnically documented by M V Engineering, Inc. (MV) in a
compaction report prepared on October 25, 1978. The compaction report noted the building
pad was built with a fill slope along the west portion of the pad with a cut portion in the eastern
portion. Remedial grading of the cut/fill transition across the building pad was not discussed in
the compaction report.
The compaction report did not indicate any cuts and fills for the drive approach, however, the
alignment of the driveway near the center of the lot is not the location of the existing driveway
along the southern property line. It also appears that fills may have been placed along the
CURTIS LING Project No. 3687-SD
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4368 Adams Street, Carlsbad, California Page 4
northern side of the driveway to support the existing alignment and turn-about pocket. Fill
thickness placed during prior grading is estimated to be a minimum of 3 feet and a maximum of
8 to 10 feet in thickness. It is anticipated that based on the proposed design the proposed
improvements will be founded below existing fills. Existing fill soil may be re-used as engineered
fills if properly placed as recommended in this report.
4.2.2 Old Paralic Deposits
The most recent regional geologic map (Kennedy, 2007) indicates Old Paralic Deposits
underlying the site. As encountered in all GeoTek’s explorations, the Old Paralic Deposits
consist of reddish yellow brown, very dense silty sand (SM soil type). The regional structure of
the Old Paralic Deposits is anticipated to be southwest dipping beds approximately 8 to 10
degrees.
4.3 SURFACE WATER AND GROUNDWATER
4.3.1 Surface Water
Surface water was not observed during GeoTek’s site exploration. If encountered, surface water
on this site is likely the result of precipitation. Provisions for surface drainage should be
addressed by the project design civil engineer.
4.3.2 Groundwater
Groundwater was not encountered in any of GeoTek’s explorations and is not anticipated to
be a factor in site development. Localized perched groundwater could 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, 2007). The closest active fault is the Rose Canyon Fault Zone located approximately
2.5 miles to the southwest. The Rose Canyon has a potential rupture magnitude of 6.9 Richter
Scale.
CURTIS LING Project No. 3687-SD
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4368 Adams Street, Carlsbad, California Page 5
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 generally dense nature of old paralic deposits and absence of a shallow groundwater
table underlying the site.
4.4.3 Other Seismic Hazards
Evidence of ancient landslides or slope instabilities was not observed during GeoTek’s study nor
indicated on regional geologic maps that underly the site. Thus, the potential for landslides is
considered negligible.
The potential for secondary seismic hazards such as seiche and tsunami is considered to be
remote due to site elevation and distance from an open body of water, as confirmed by the
ASCE Tsunami Hazard Tool.
5. CONCLUSIONS AND RECOMMENDATIONS
5.1 GENERAL CONCLUSIONS
Planned construction appears feasible from a geotechnical viewpoint provided that the following
recommendations are incorporated in the design and construction phases of the development.
The following sections present general recommendations for currently anticipated site
development plans. Recommendations contained herein are based on the currently applicable
2022 California Building Code (CBC) and City of Carlsbad guidelines.
CURTIS LING Project No. 3687-SD
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4368 Adams Street, Carlsbad, California Page 6
Provided that GeoTek’s recommendations are implemented during grading and construction of
the improvements presented on Figure 2, the proposed improvements will not adversely affect
the adjacent properties.
The existing and proposed slopes are considered to be grossly and surficially stable to a
maximum height of 20 feet and at an inclination no steeper than 2:1. For new slopes higher than
20 feet or slopes steeper than a 2:1, GeoTek should be contacted for further analysis.
5.2 GEOTECHNICAL REVIEW OF THE GRADING PLAN
The grading plan prepared by Christiansen Engineering & Surveying was reviewed. The purpose
of this review was to form an opinion as to the geotechnical suitability of the plans to support
the proposed improvements and for inclusion of geotechnical design parameters provided
herein.
GeoTek has reviewed Sheet 7 of the plans and the notes and details on Sheet 1 prepared by
Christiansen Engineering & Surveying. Based on review, It is GeoTek’s opinion that the plans
have been prepared in substantial conformance with the geotechnical recommendations
contained in this report. GeoTek makes no representation as to the accuracy of dimensions,
calculations, or structural design provided on the referenced plan.
5.3 EARTHWORK CONSIDERATIONS
5.3.1 General
Earthwork and grading should be performed in accordance with the applicable grading ordinances
of the City of Carlsbad, the 2022 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 should supersede those contained in Appendix C.
5.3.2 Site Clearing and Preparation
Site preparation should start with demolition and removal of existing structures and
improvements (utilities, slabs, foundations, etc.) in conflict with the proposed improvements and
removal of deleterious materials (e.g., vegetation). These materials should be properly disposed
of offsite. 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. Areas cleared of deleterious materials and are below proposed pad
grades should have the upper 6-inches reprocessed by scarification, moisture conditioned, and
CURTIS LING Project No. 3687-SD
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4368 Adams Street, Carlsbad, California Page 7
compacted in accordance with recommendations presented in Section 5.2.4 Engineered Fill prior
to placement of any new fill.
5.3.3 Remedial Grading
Remedial grading recommendations are provided based on specific locations by GeoTek’s
explorations. At a minimum all previously placed site fills should be removed and replaced with
engineered fills. It is anticipated that 8 to 10 feet of previously placed fills underlay the site. The
fills are anticipated to be predominately underlaying the existing building pad and descending slope
of the building pad. Old Paralic Deposits that exhibit loose, weathered, and potentially
compressible properties, should be removed and replaced as engineered fill. It is anticipated that
the upper 2 to 3 feet of Old Paralic Deposits are unsuitable to support settlement sensitive
improvements, such as hardscape/flatwork and driveways. It should be anticipated that remedial
grading extends to the property line where feasible.
GeoTek’s explorations were backfilled and compacted by walking the equipment over the surface.
Test pit backfill should be removed and replaced with compacted fill in accordance with Section
5.3.4 presented in this report. The intent of the recommended remedial grading is to support
the improvements on either Old Paralic Deposits or engineered fill with relatively uniform
engineering characteristics in order to decrease the potential for differential settlement. Based
on the conceptual plan, both the primary residence and ADU foundations may be excavated into
competent Old Paralic Deposits soil. If upon observations of previous site fills a cut-fill transition
spans the building footprint, or Old Paralic Deposits are found to be weathered to an unsuitable
consistency, additional remedial grading will be required.
Grading cuts and fills in a hillside setting typically result in a portion of the building pad as
engineered fill and a portion of the building pad as natural cut material. Improvements spanning
cut/fill transitions are not desired. As such, the cut portion of the building pad should be over-
excavated a minimum of three feet below the base of the proposed foundations and extend
laterally five feet beyond structural improvements.
The remedial excavation bottoms should be observed by a GeoTek representative prior to
scarification. The bottom of all removals should be scarified to a minimum depth of six (6) inches,
brought to at or above optimum moisture content, and then compacted to minimum project
standards prior to fill placement. The resultant voids from remedial grading/over-excavation
should be filled with materials placed in general accordance with Section 5.2.4 Engineered Fill of
this report.
CURTIS LING Project No. 3687-SD
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4368 Adams Street, Carlsbad, California Page 8
5.3.4 Engineered Fill
Onsite materials 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
(6) inches in maximum dimension. The earthwork contractor should have the proposed
excavated materials to be used as engineered fill at this project reviewed by the soils engineer
prior to placement.
Engineered fill materials should be moisture conditioned to at or above optimum moisture
content and compacted in horizontal lifts not exceeding 8 inch in loose thickness to a minimum
relative compaction of 90% as determined in accordance with ASTM D 1557 test procedures.
5.3.5 Excavation Characteristics
Excavations in the onsite fill materials should generally be accomplished with medium to heavy-
duty earthmoving or excavating equipment in good operating condition at least to the depths
explored. In consideration of the loose fills and weathered paralic deposits, the site soils are
considered to be Type C. Excavations in more competent material may be considered Type B
soils. Excavations per Cal-OHHA guidelines should conform to current Cal-OSHA guidelines.
Localized friable material may be encountered and excavations practices may need to be adjusted
based on actual conditions exposed.
5.3.6 Shrinkage and Bulking
Several factors will impact earthwork balancing on the site, including the bulking of the Old Paralic
Deposits, possible shrinkage of undocumented fill, trench spoil from utilities and footing
excavations, as well as the accuracy of topography. Due to the extent of currently proposed
work, effects of shrinking and bulking are anticipated to be minimal.
5.3.7 Trench Excavations and Backfill
Temporary excavations within the onsite materials should be stable at 1.5:1 (horizontal to
vertical) gradients for short durations during construction, and where cuts do not exceed 10
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 per ASTM D 1557. Under-slab trench excavation backfill should also
be compacted to project specifications.
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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.
5.4 DESIGN RECOMMENDATIONS
5.4.1 Foundation Design Criteria
Foundation design criteria presented herein are for foundations that will bear upon engineered
fill or Old Paralic Deposits soils prepared in accordance to Section 5.2.3 Remedial Grading and
are in general conformance with the 2022 CBC. These are typical design criteria and are not
intended to supersede the design by the structural engineer.
Based on the materials onsite encountered and as verified by laboratory testing, foundation
bearing soils are anticipated to have a “very low” (EI≤20) expansion index per ASTM D4829.
The following criteria is presented for the design of the project’s building foundations.
MINIMUM DESIGN REQUIREMENTS FOR CONVENTIONALLY REINFORCED
FOUNDATIONS SUPPORTED ON ENGINEERED FILL
DESIGN PARAMETER “Very Low”
Expansion Index (EI≤20)
Foundation Embedment Depth or Minimum Perimeter
Beam Depth (inches below lowest adjacent finished
grade)
Single Story – 12 inches
Two-Story - 18 inches
Minimum Foundation Width for Continuous Footings * Single Story – 15 inches
Two story - 15 inches
Minimum Foundation Width for Isolated Footings * Single Story – 24 inches Square
Two Story – 24 inches Square
Minimum Slab Thickness (actual) 4 inches
Minimum Slab Reinforcing No. 3 rebar 24” on-center, each way, placed in the
middle one-third of the slab thickness
Minimum Footing Reinforcement Two No. 4 Reinforcing Bars, one (1) top and one
(1) bottom
Presaturation of Subgrade Soil (percent of optimum
moisture content) Minimum 100% to a depth of 12 inches
*Code minimums per Table 1809.7 of the 2022 CBC should be complied with.
It should be noted that the above recommendations are based on soil support characteristics
only. The structural engineer should design the slab and foundation reinforcement based on
actual loading conditions.
The following recommendations should be implemented into the design and are independent of
remedial grading selection:
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4368 Adams Street, Carlsbad, California Page 10
• An allowable bearing capacity of 2,000 pounds per square foot (psf) may be used for
design of continuous and isolated 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 300 psf for each additional 12 inches in width to a
maximum value of 3,500 psf. Additionally, an increase of one-third may be applied
when considering short-term live loads (e.g., seismic or wind loads).
• Based on GeoTek’s experience in the area, structural foundations may be designed in
accordance with 2022 CBC, and to withstand a total settlement of 1 inch and
maximum differential settlement of one-half of the total settlement over a horizontal
distance of 40 feet. These values assume that seismic settlement potential is not a
significant constraint.
• The passive earth pressure may be computed as an equivalent fluid having a density
of 200 psf per foot of depth, to a maximum earth pressure of 2,000 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. When combining passive pressure and frictional
resistance, the passive pressure component should be reduced by one-third.
• A grade beam, a minimum of 12 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.
5.4.2 Miscellaneous Foundation Recommendations
• To reduce moisture penetration beneath the slab on grade areas, utility trenches
should be backfilled with compacted 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.
5.4.3 Underslab Moisture Membrane
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 and the 2022 CBC Section 1907.1
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4368 Adams Street, Carlsbad, California Page 11
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 that thinner ones. Products specifically designed
for use as moisture/vapor retarders may also be more puncture resistant.
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 large extent based on the type of flooring
used and environmental conditions. Ultimately, the vapor retarding system should be comprised
of suitable elements to limit 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 does not practice in the field of moisture vapor transmission evaluation/migration since
that practice is not a geotechnical discipline. Therefore, it is recommended 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.
In addition, the recommendations in this report and GeoTek’s services in general are not
intended to address mold prevention; since we, along with geotechnical consultants in general,
do not practice in mold prevention. If specific recommendations addressing potential mold issues
are desired, then a professional mold prevention consultant should be contacted.
5.4.4 Foundation Set Backs
Where applicable, the following setbacks should apply to all foundations. Any improvements not
conforming to these setbacks may be subject to lateral movements and/or differential
settlements:
CURTIS LING Project No. 3687-SD
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4368 Adams Street, Carlsbad, California Page 12
• The outside bottom edge of all footings should be set back a minimum of H/3 (where
H is the slope height) from the face of any descending slope. The setback should be
at least 7 feet and need not exceed 40 feet.
• The outside bottom edge of all footings should be set back a minimum of H/2 (where
H is the slope height) from the face of any ascending slope. The setback need not
exceed 15 feet.
• The bottom of all footings for structures near retaining walls should be deepened to
extend below a 1:1 projection upward from the bottom inside edge of the wall
footing.
• The bottom of any existing foundations for structures should be deepened so as
extend below a 1:1 projection upward from the bottom of the nearest excavation
(e.g., utility trenches).
5.4.5 Seismic Design Parameters
The site is located at approximately 33.1475˚ Latitude and -117.3289˚ Longitude. Site spectral
accelerations (Ss and S1), for 0.2 and 1.0 second periods for a risk targeted two (2) percent
probability of exceedance in 50 years (MCER) were determined using the web interface provided
by SEAOC/OSHPD (https://seismicmaps.org) to access the USGS Seismic Design Parameters.
Based upon the density of the Old Paralic Deposits underlying the site, a Site Class “D” is
considered appropriate for this site.
SITE SEISMIC PARAMETERS
Mapped 0.2 sec Period Spectral Acceleration, Ss 1.2g
Mapped 1.0 sec Period Spectral Acceleration, S1 0.38g
Maximum Considered Earthquake (MCER) Spectral
Response Acceleration for 0.2 Second, SMS 1.43g
Maximum Considered Earthquake (MCER) Spectral
Response Acceleration for 1.0 Second, SM1 0.96g
5% Damped Design Spectral Response
Acceleration Parameter at 0.2 Second, SDS 0.96g
5% Damped Design Spectral Response
Acceleration Parameter at 1 second, SD1 0.64g
Seismic Category D
CURTIS LING Project No. 3687-SD
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4368 Adams Street, Carlsbad, California Page 13
5.4.6 Soil Sulfate Content
The sulfate content was determined in the laboratory for a soil sample collected during the field
investigation. The results indicate that the water-soluble sulfate is less than 0.1 percent by weight
(0.0034), which is considered “S0” as per Table 19.3.1.1 of ACI 318-14, as such no special
recommendations for concrete are required for this project due to soil sulfate exposure.
5.4.7 Exterior Concrete Slabs and Sidewalks
Exterior concrete slabs, sidewalks 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 verified to be a minimum of 100% of the soils
optimum moisture to a depth of 12 inches for soils having a “very low” expansive index potential.
5.5 RETAINING WALL DESIGN AND CONSTRUCTION
5.5.1 General Retaining Wall Design Criteria
Recommendations presented herein may apply to typical masonry or concrete vertical retaining
walls to a maximum height of 13.5 feet. Additional review and recommendations should be
requested for higher walls.
Retaining wall foundations embedded a minimum of 18 inches into engineered fill or dense
formational materials and 12 inches wide, should be designed using an allowable bearing capacity
of 3,000 psf. This value may be increased by 500 psf for each additional 12 inches in depth and
300 psf for each additional 12 inches in width to a maximum value of 4,500 psf. An increase of
one-third may be applied when considering short-term live loads (e.g., seismic or wind loads).
The passive earth pressure may be computed as an equivalent fluid having a density of 200 psf
per foot of depth, to a maximum earth pressure of 2,000 psf. A coefficient of friction between
soil and concrete of 0.35 may be used with dead load forces. When combining passive pressure
and frictional resistance, the passive pressure component should be reduced by one-third.
CURTIS LING Project No. 3687-SD
Updated Geotechnical Evaluation September 21, 2023 (Revised January 31, 2024)
4368 Adams Street, Carlsbad, California Page 14
5.5.2 Cantilevered Retaining Walls
A cantilevered retaining wall has to translate laterally to reach full passive pressure/resistance. At
0.5% strain, ½ the passive pressure is mobilized, and at 2% strain the full passive pressure is
mobilized. For a 12-inch embedment this can be 0.25 inches. In addition, wall rotation is expected
to reach an active design state. This rotation, at a minimum, needs to undergo 0.5% strain and
walls are often considered to rotate between 0.005 to 0.02 times their height, dependent upon
the soil condition, with no adverse structural effects expected. In our opinion, a value of 0.01
times the height of the wall is a maximum rotation that should typically be expected. For a 13.5-
foot-high wall this amounts to 1.6 inches of movement that can occur at the top of the wall. Walls
should be expected to translate/move/rotate, and the higher the wall the more movement that
should be expected.
For cantilevered walls, an equivalent fluid pressure approach may be used to compute the
horizontal active pressure against the wall. The appropriate fluid unit weights are given in the
table below for specific slope gradients of retained materials.
Surface Slope of
Retained Materials
(H:V)
Equivalent Fluid
Pressure (PCF)
Select Backfill*
Level 45
2:1 60
*Select backfill should consist of imported sand other approved
materials with an SE>30 and 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.
5.5.3 Restrained (At Rest) Retaining Walls Design Criteria
Any retaining wall that will be restrained prior to placing backfill or walls that have male or
reentrant corners should be designed for at-rest soil conditions using an equivalent fluid pressure
of 65 pcf (select backfill), plus any applicable surcharge loading. For areas having male or reentrant
corners, the restrained wall design should extend a minimum distance equal to twice the height
of the wall laterally from the corner, or as otherwise determined by the structural engineer.
5.5.4 Seismic Induced Incremental Addition
Additional lateral forces can be induced on retaining walls during an earthquake. For level backfill
and a Site Class “D”, the minimum earthquake-induced force (Feq) should be 16H2 (lbs/linear foot
of wall) for cantilever walls. This force can be assumed to act at a distance of 0.3H above the
base of the wall, where “H” is the height of the retaining wall measured from the base of the
CURTIS LING Project No. 3687-SD
Updated Geotechnical Evaluation September 21, 2023 (Revised January 31, 2024)
4368 Adams Street, Carlsbad, California Page 15
footing (in feet). The 2022 CBC only requires the additional earthquake induced lateral force be
considered on retaining walls more than six (6) feet in height; however, the additional force may
be applied in design of lesser walls at the discretion of the wall designer.
5.5.5 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 backdrain 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.
Walls from two (2) to four (4) feet in height may be drained using localized gravel packs behind
weep holes at 10 feet maximum spacing (e.g., approximately 1.5 cubic feet of gravel in a woven
plastic bag). Weep holes should be provided, or the head joints omitted in the first course of
block extended above the ground surface. However, nuisance water may still collect in front of
the wall.
Drain outlets should be maintained over the life of the project and should not be obstructed or
plugged by adjacent improvements.
CURTIS LING Project No. 3687-SD
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4368 Adams Street, Carlsbad, California Page 16
5.6 POST CONSTRUCTION CONSIDERATIONS
5.6.1 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 limit erosion. Plants selected for landscaping should be lightweight, deep-rooted types
that require little water and can survive the prevailing climate.
Overwatering should be avoided. The soils should be maintained in a solid to semi-solid state
as defined by the materials Atterberg Limits. Care should be taken when adding soil amendments
to avoid excessive watering. Leaching as a method of soil preparation prior to planting is not
recommended. An abatement program to control ground-burrowing rodents should be
implemented and maintained. This is critical as burrowing rodents can decreased 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 foundation. This type of
landscaping should be avoided. If used, then extreme care should be exercised regarding the
irrigation and drainage in these areas. Waterproofing of the foundation and/or subdrains may
be warranted and advisable. We could discuss these issues, if desired, when plans are made
available.
5.6.2 Drainage
The need to maintain proper surface drainage and subsurface systems cannot be overly emphasized.
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. Site drainage should conform to Section 1804.4
of the 2022 CBC. Roof gutters and downspouts should discharge onto paved surfaces sloping away
from the structure or into a closed pipe system which outfalls to the street gutter pan or directly
to the storm drain system. Pad drainage should be directed toward approved areas and not be
blocked by other improvements.
It is the owner’s responsibility to maintain and clean drainage devices on or contiguous to their
lot. In order to be effective, maintenance should be conducted on a regular and routine schedule
and necessary corrections made prior to each rainy season.
CURTIS LING Project No. 3687-SD
Updated Geotechnical Evaluation September 21, 2023 (Revised January 31, 2024)
4368 Adams Street, Carlsbad, California Page 17
5.7 CONSTRUCTION OBSERVATIONS
It is recommended that changes to site grading, specifications, and any retaining wall/shoring
plans and foundation plans be reviewed by this office prior to construction to check for
conformance with the recommendations of this report. Additional recommendations may be
necessary based on these reviews. It is also recommended that GeoTek representatives be
present during site grading and foundation construction to check for proper implementation of
the geotechnical recommendations. The owner/developer should have GeoTek’s representative
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 when necessary.
• Observe the fill for uniformity during placement including utility trenches.
• Observe and test the fill for field density and relative compaction.
• Observe and probe foundation excavations to confirm suitability of bearing materials.
• Observe retaining wall subdrains and backfill compaction.
• Subgrade for hardscape.
• Temporary excavations.
If requested, a construction observation and compaction report can be provided by GeoTek,
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.
6. LIMITATIONS
The scope of GeoTek’s evaluation is limited to the area explored shown on the Geotechnical
Map (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-0400221-SD) dated April 6, 2021 and geotechnical engineering standards normally used on
similar projects in this region.
CURTIS LING Project No. 3687-SD
Updated Geotechnical Evaluation September 21, 2023 (Revised January 31, 2024)
4368 Adams Street, Carlsbad, California Page 18
The materials observed on the project site appear to be representative of the area; however,
soil and bedrock materials 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 contained in this report are based on the site conditions observed
and encountered, and laboratory testing, GeoTek’s 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.
CURTIS LING Project No. 3687-SD
Updated Geotechnical Evaluation September 21, 2023 (Revised January 31, 2024)
4368 Adams Street, Carlsbad, California Page 19
7. 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, 2018, ASCE Tsunami Design Geodatabase Version 2016-1.0,
updated March 3, 2018, accessed February 1, 2021 at https://asce7tusnami.online/
ASTM International (ASTM), “ASTM Volumes 4.08 and 4.09 Soil and Rock.”
Bryant, W.A., and Hart, E.W., 2007, "Fault Rupture Hazard Zones in California, Alquist-Priolo
Earthquake Fault Zoning Act with Index to Earthquake Fault Zones Maps," California
Geological Survey: Special Publication 42.
California Code of Regulations, Title 24, 2022 “California Building Code,” 2 volumes.
California Geological Survey (CGS, formerly referred to as the California Division of Mines and
Geology), 1977, “Geologic Map of California.”
____, 1998, “Maps of Known Active Fault Near-Source Zones in California and Adjacent
Portions of Nevada,” International Conference of Building Officials.
Christensen Engineering & Surveying, 2023, undated, ”Grading Plan, Adams Residence”, 7 sheets.
GeoTek, Inc., In-house proprietary information.
Kennedy, M.P., and Tan, S.S., 2007, “Geologic Map of the San Diego 30x60-minute Quadrangle,
California,” California Geological Survey, Regional Geologic Map No. 2, map scale
1:100,000.
MV Engineering, Inc., 2023, 1978, ”Compaction Report for 4368 Adams Avenue, Carlsbad”, job
number 1286-78, dated October 25.
Structural Engineers Association of California/California Office of Statewide Health Planning and
Development (SEOC/OSHPD), 2020, Seismic Design Maps web interface, accessed at
https://seismicmaps.org.
CURTIS LING Project No. 3687-SD
Updated Geotechnical Evaluation September 21, 2023 (Revised January 31, 2024)
4368 Adams Street, Carlsbad, California Page 20
8. RESPONSE TO GEOTECHNICAL REVIEW COMMENTS
GEOTECHNICAL | ENVIRONMENTAL | MATERIAL
September 26, 2023
Project No. 3687-SD
Curtis Ling
3667 Adams Street
Carlsbad, California 92008
Subject: Response to Geotechnical Review Comments
3rd Party Review Comments (1st Review)
Proposed Residential Development
4368 Adams Street
Carlsbad, California
Dear Mr. Ling:
As requested, GeoTek, Inc., (GeoTek) has prepared this letter to respond to the City of
Carlsbad third party geotechnical review comments. The review comments correspond to the
numbers on the review sheet. A copy of the review comment letter dated May 21, 2023 is
present in Appendix A.
Comment No. 1
The submitted "Preliminary Geotechnical Evaluation ..." by GeoTek, Inc. is approximately
2-years old and addresses an antiquated code cycle (2019 CBC) and apparently only conceptual
plans for the project. Please review the most current revision of the grading and foundation
plans for the proposed project and provide updated geotechnical conclusions/recommendations
as necessary to address the current codes and proposed project.
Response to Comment No. 1
The grading plans prepared by Christiansen Engineering & Surveying were reviewed. An
Updated Geotechnical Evaluation dated September 21, 2023 has been prepared to incorporate
the grading plan and current California building codes.
Comment No. 2
With comment #1 above in mind, please revisit the subsurface exploration that was performed
as part of the "Preliminary Geotechnical Evaluation ..." and provide additional subsurface
exploration if necessary to adequately address the current proposed development.
Response to Comment No. 2
A supplemental exploration is not necessary.
GeoTek, Inc.
1384 Poinsettia Avenue, Suite A Vista, CA 92081-8505
(760) 599-0509 Office (760) 599-0593 Fa www.geotekusa.com
CURTIS LING Project No. 3687-SD
Response to Comments May 21, 2023 September 26, 2023
4368 Adams Street, Carlsbad, California Page 2
Comment No. 3
Please provide a statement addressing the potential impact of the proposed project on adjacent
properties.
Response to Comment No. 3
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Section 5.1
General Conclusions, second paragraph.
Comment No. 4
Please expand on the description of the proposed project and discuss the proposed grading
(depths and limits of cut/fill necessary to establish proposed grades), construction of graded
slopes, type of foundation and floor for the proposed structures, heights of the proposed
building and site retaining walls, and types of proposed improvements.
Response to Comment No. 4
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Section 2.2
Proposed Development.
Comment No. 5
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 consists of an aerial photograph of the site and does not show most of the requested
information above. Please produce the map at a scale that is sufficiently large to clearly
distinguish all topography, text, finish grades, etc., and show al information requested above
(a sheet larger than 8.5x11" will be necessary to increase legibility and show all information).
Response to Comment No. 5
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Figure 2
Geotechnical Map.
Comment No. 6
Geologic cross-sections are not provided in the submitted report. Please provide detailed
geologic cross-sections cut through the proposed development (one trending northeast
southwest and one trending northwest-southeast) based on the updated "Geotechnical Map"
and scale/legibility comments requested above in comment #5. Please assure the requested
cross-sections show and label, at a minimum, a) existing site topography, b) proposed finish
grades, c) the limits of the existing and proposed structures and improvements, d) the contacts
GEOTEK
CURTIS LING Project No. 3687-SD
Response to Comments May 21, 2023 September 26, 2023
4368 Adams Street, Carlsbad, California Page 3
between the various soil/geologic units underlying the site, e) limits and depths of proposed
remedial grading and grading to address any cut/fill transition, f) temporary slopes necessary for
the remedial grading and for basement level retaining wall construction, and g) the locations of
subsurface exploration.
Response to Comment No. 6
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Figure 3 and 4
Geotechnical Cross Sections AA and BB.
Comment No. 7
Please provide the range in thickness of the existing fill soils within the subject site.
Response to Comment No. 7
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Section 4.2.1
Artificial Fill.
Comment No. 8
Please provide a discussion addressing the geologic structure (direction/dip of bedding,
fracturing, etc.) of the Old Paralic deposits and the relationship between the structural geology
of the Old Paralic deposits underlying the site and gross stability of the area of proposed
construction.
Response to Comment No. 8
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Section 4.2.2 Old
Paralic Deposits.
Comment No. 9
Please provide a discussion addressing the regional faulting associated with the subject site.
Please include the names, distances, and potential magnitudes of faults potentially impacting the
subject property and region.
Response to Comment No. 9
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Section 4.4.1
Surface Fault Rupture.
Comment No. 10
Please provide the Seismic Design category in accordance with Section 1603 of the 2022
California Building Code.
GEOTEK
CURTIS LING Project No. 3687-SD
Response to Comments May 21, 2023 September 26, 2023
4368 Adams Street, Carlsbad, California Page 4
Response to Comment No. 10
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Section 5.4.5
Seismic Design Parameters.
Comment No. 11
Please discuss both surficial and gross slope stability of existing and proposed slopes with
respect to the proposed development.
Response to Comment No. 11
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Section 5.1
General Conclusions, third paragraph.
Comment No. 12
Please clarify the remedial grading recommendations (depth and limits of removals, etc.) for
hardscape improvements and parking/driveway areas associated with the development.
Response to Comment No. 12
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Section 5.3.3
Remedial Grading, first paragraph.
Comment No. 13
As the "Retaining Wall Design and Construction" section of the report indicates that the
recommendations provided are only applicable for walls under 6', please provide updated
parameters that address the heights of the retaining· walls (up to approximately 13.5') required
for the proposed development.
Response to Comment No. 13
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Section 5.5.2
Seismic Induced Incremental Addition.
Comment No. 14
Please provide recommended values for at-rest earth pressure and seismic lateral earth
pressure (for walls over 6' per Section 1803.5.12 of the 2022 California Building Code) for
retaining wall design.
Response to Comment No. 13
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Section 5.5.3
Restrained (At Rest) Retaining Wall Design Criteria.
GEOTEK
CURTIS LING Project No. 3687-SD
Response to Comments May 21, 2023 September 26, 2023
4368 Adams Street, Carlsbad, California Page 5
Comment No. 15
Please provide the slope setback distance for foundations (building and improvements) located
near sloping ground.
Response to Comment No. 15
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Section 5.4.4
Foundation Set backs first and second bullet point.
Comment No. 16
Please provide recommendations (minimum slab thickness, reinforcing, etc.) for hardscape
improvements from a geotechnical standpoint.
Response to Comment No. 16
See GeoTek’s Updated Geotechnical Evaluation, dated September 21, 2023, Section 5.4.7
Exterior Concrete Slabs and Sidewalks.
Comment No. 17
Please evaluate and discuss the potential for storm water infiltration at the subject site as part
of the proposed development.
Response to Comment No. 17
This is a Standard Development Project and GeoTek’s understanding is that stormwater
management for infiltration assessment is not required, therefore was not evaluated.
Comment No. 18
Please add a) retaining wall subdrains and backfill, b) hardscape subgrade, and c) temporary
excavations to the list of the geotechnical observations/testing services that should be provided
during the construction of the proposed development.
Response to Comment No. 18
Acknowledged. This has been added to Section 5.7 Construction Observations
GEOTEK
CURTIS LING Project No. 3687-SD
Response to Comments May 21, 2023 September 26, 2023
4368 Adams Street, Carlsbad, California Page 6
Closure
The opportunity to be of service is sincerely appreciated. If you should have any questions,
please do not hesitate to call GeoTek.
Respectfully submitted,
GeoTek, Inc.
Attachments: Appendix A – Review Comments
Distribution: (1) Addressee via email
Christopher D. Livesey
CEG, 2733 Exp. 05/31/25
Vice President
Bruce A. Hick
GE 2284, Exp. 12/31/24
Project Engineer
GEOTEK
CURTIS LING Project No. 3687-SD
Response to Comments May 21, 2023 September 26, 2023
4368 Adams Street, Carlsbad, California Page 7
References
GeoTek, Inc., 2023, “Updated Geotechnical Evaluation, Proposed Residential Development,
4368 Adams Street, Carlsbad, California,” project number 3687-SD, dated September
21, 2023.
GEOTEK
Appendix A
Review Comments
GEOTEK
GEOTECHNICAL REPORT REVIEW
DATE: May 21, 2023
TO: City of Carlsbad
Land Development Engineering
1635 Faraday Avenue
Carlsbad, CA 92008
Attention: Allison McLaughlin
PROJECT ID: CDP2022-0031
GRADING PERMIT NO.: GR2023-0024
SUBJECT: 4368 Adams Street, (1 st review)
Items Submittedb Items Bein . Retuined to A Ii cant • "Preliminary Geotechnical Evaluation for • Written report review comments. Proposed Residential Development, 4368 Adams
Street, Carlsbad, California," by GeoTek, Inc., dated Ma 18, 2021.
Based on our review of the submitted geotechnical report, we are providing the following comments that should be addressed prior to the next submittal. Please provide complete and thorough written responses to all comments.
GEOTECHNICAL COMMENTS:
1. The submitted "Preliminary Geotechnical Evaluation ... " by GeoTek, Inc. is approximately 2-years old and addresses an antiquated code cycle (2019 CBC) and apparently only conceptual plans for the project. Please review the most current revision of the grading and foundation plans for the proposed project and provide updated geotechnical conclusions/recommendations as necessary to address the current codes and proposed project.
2. With comment #1 above in mind, please revisit the subsurface exploration that was performed as part of the "Preliminary Geotechnical Evaluation ... " and provide additional subsurface exploration if necessary to adequately address the current proposed development.
3. Please provide a statement addressing the potential impact of the proposed project on adjacent properties.
GR2023-0024
May 21, 2023
Page 2 of 3
4. Please expand on the description of the proposed project and discuss the proposed grading (depths and limits of cut/fill necessary to establish proposed grades), construction of graded slopes, type of foundation and floor for the proposed structures, heights of the proposed building and site retaining walls, and types of proposed improvements.
5. 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 consists of an aerial photograph of the site and does not show most of the requested information above. Please produce the map at a scale that is sufficiently large to clearly distinguish all topography, text, finish grades, etc., and show al information requested above ( a sheet larger than 8. Sx 11" will be necessary to increase legibility and show all information).
6. Geologic cross-sections are not provided in the submitted report. Please provide detailed geologic cross-sections cut through the proposed development (one trending northeast-southwest and one trending northwest-southeast) based on the updated "Geotechnical Map" and scalenegibility comments requested above in comment #5. Please assure the requested cross-sections show and label, at a minimum, a) existing site topography, b) proposed finish grades, c) the limits of the existing and proposed structures and improvements, d) the contacts between the various soil/geologic units underlying the site, e) limits and depths of proposed remedial grading and grading to address any cut/fill transition, f) temporary slopes necessary for the remedial grading and for basement level retaining wall construction, and g) the locations of subsurface exploration.
7. Please provide the range in thickness of the existing fill soils within the subject site.
8. Please provide a discussion addressing the geologic structure (direction/dip of bedding, fracturing, etc.) of the Old Paralic deposits and the relationship between the structural geology of the Old Paralic deposits underlying the site and gross stability of the area of proposed construction.
9. Please provide a discussion addressing the regional faulting associated with the subject site. Please include the names, distances, and potential magnitudes of faults potentially impacting the subject property and region.
10. Please provide the Seismic Design category in accordance with Section 1603 of the 2022 California Building Code.
11. Please discuss both surficial and gross slope stability of existing and proposed slopes with respect to the proposed development.
12. Please clarify the remedial grading recommendations (depth and limits of removals, etc.) for hardscape improvements and parking/driveway areas associated with the development.
13. As the "Retaining Wall Design and Construction" section of the report indicates that the recommendations provided are only applicable for walls under 6', please provide updated parameters that address the heights of the retaining· walls (up to approximately 13.5') required for the proposed development.
GR2023-0024
May 21, 2023
Page 3 of 3
14. Please provide recommended values for at-rest earth pressure and seismic lateral earth pressure (for walls over 6' per Section 1803.5.12 of the 2022 California Building Code) for retaining wall design.
15. Please provide the slope setback distance for foundations (building and improvements) located near sloping ground.
16. Please provide recommendations (minimum slab thickness, reinforcing, etc.) for hardscape improvements from a geotechnical standpoint.
17. Please evaluate and discuss the potential for storm water infiltration at the subject site as part of the proposed development.
18. Please add a) retaining wall subdrains and backfill, b) hardscape subgrade, and c) temporary excavations to the list of the geotechnical observations/testing services that should be provided during the construction of the proposed development.
Curtis Ling
4368 Adams Street
Carlsbad, California
1384 Poinsettia Avenue, Suite A
Vista, California 92081
Figure 1
Site Location Map
N
Not to Scale
Approximate Site
Location
Imagery from USGS The National Map, 2021
PN: 3687-SD DATE: September 2023
GEOTEK
1384 Poinsettia Avenue, Suite A
Vista, California 92081
Curtis Ling
4368 Adams Street
Carlsbad, California
PN: 3687-SD September 2023
Figure 2
Geotechnical
Map
B-1
TP-1 TP-2
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EXPLANATION
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Af Artificial Fill
Qop Old Paralic Deposits,
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APPENDIX A
EXPLORATION LOGS
GeoTek, Inc.
LOG OF EXPLORATORY TRENCH
BB-1 SM
---Small Bulk ---Water Table
DRILL METHOD:Backhoe
DRILLER:JES EngineeringCurtis LingCLIENT:
4368 Adams St.PROJECT NAME:
MSB
Pedro
LOGGED BY:
OPERATOR:
ELEVATION:85'
HAMMER:-3687-SD
Carlsbad, California
PROJECT NO.:
LOCATION:
310P John Deere
4/16/2021
RIG TYPE:
DATE:
Oth
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r
s
MATERIAL DESCRIPTION AND COMMENTS
SAMPLES
US
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S
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Laboratory Testing
De
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6
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(p
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Wa
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C
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t
(%
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TRENCH NO.: T-1
Old Paralic Deposits
Silty SAND, light reddish brown, dry, loose, many roots in upper 6 in.
Weathered
Fine to coarse SAND, red brown, dry, dense
Silty fine to medium SAND, light reddish brown, slightly damp, dense,
increased density, backhoe struggles
5 Backfilled with excavation cuttings
Silty SAND, yellow-brown with red, dry, very dense, bucket chatters,
refusal
EXCAVATION TERMINATED AT 3 FEET
2.5
Practical Refusal @ 3 feet
No groundwater encoutered
7.5
10
12.5
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
15
LE
G
E
N
D
Sample type: ---Ring ---SPT ---Large Bulk
Lab testing:
--I ------\ ---
-"-.. ------------------------------------------------• I [2J [g] ~
GeoTek, Inc.
LOG OF EXPLORATORY TRENCH
BB-1 SM
---Small Bulk ---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
15
LE
G
E
N
D
Sample type: ---Ring ---SPT ---Large Bulk
Lab testing:
12.5
10
7.5
EXCAVATION TERMINATED AT 5 FEET
Practical Refusal @ 5 feet
No groundwater encoutered
Backfilled with excavation cuttings
5
Fine to coarse SAND with clay, reddish yellow-brown, very dense, caliche
Silty fine to medium SAND with clay, brown, dry, dense, increased density,
backhoe struggles
2.5
Old Paralic Deposits
Silty SAND, light brown, dry, loose, many roots in the upper 6 inches
Weathered
Dr
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D
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n
s
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y
(p
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)
Oth
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s
MATERIAL DESCRIPTION AND COMMENTS
SAMPLES
US
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S
S
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b
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TRENCH NO.: T-2
Laboratory Testing
De
p
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h
(
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Sa
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p
l
e
T
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p
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Blo
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s
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6
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Sa
m
p
l
e
Nu
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b
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Wa
t
e
r
C
o
n
t
e
n
t
(%
)
LOCATION:Carlsbad, California ELEVATION:93'DATE:4/16/2021
PROJECT NO.:3687-SD HAMMER:-RIG TYPE:310P John Deere
PROJECT NAME:4368 Adams St.DRILL METHOD:Backhoe w/drive supply OPERATOR:Pedro
CLIENT:Curtis Ling DRILLER:JES Engineering LOGGED BY:MSB
-------------------
----------------------------------------• I [2] ~ ¥-
GeoTek, Inc.
LOG OF EXPLORATORY TRENCH
SM
10 R1 SM
12
SM
---Small Bulk ---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
15
LE
G
E
N
D
Sample type: ---Ring ---SPT ---Large Bulk
Lab testing:
12.5
10
Backfilled with excavation cuttings
7.5
EXCAVATION TERMINATED AT 5 FEET
Practical Refusal @ 5 feet
No groundwater encoutered
5 Bucket chatters, refusal
Silty SAND, white, dry, very dense, cemented sandstone fragments
backhoe struggles
Old Paralics
2.5
Artifical Fill
Silty SAND, light brown, dry, loose, many roots in upper 6 inches
Silty fine to medium SAND, dry, medium dense
Dr
y
D
e
n
s
i
t
y
(p
c
f
)
Oth
e
r
s
MATERIAL DESCRIPTION AND COMMENTS
SAMPLES
US
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S
S
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b
o
l
TRENCH NO.: T-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
(%
)
LOCATION:Carlsbad, California ELEVATION:99'DATE:4/16/2021
PROJECT NO.:3687-SD HAMMER:-RIG TYPE:310P John Deere
PROJECT NAME:4368 Adams St.DRILL METHOD:Backhoe w/drive supply OPERATOR:Pedro
CLIENT:Curtis Ling DRILLER:JES Engineering LOGGED BY:MSB
-------
---
----
----------------------------------------• I [2J [g] ~
GeoTek, Inc.
LOG OF EXPLORATORY TRENCH
SM
---Small Bulk ---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
15
LE
G
E
N
D
Sample type: ---Ring ---SPT ---Large Bulk
Lab testing:
12.5
10
7.5
5
Backfilled with cuttings
BORING TERMINATED AT 1 FOOT
2.5 Practical Refusal @ 1 foot
No groundwater encoutered
Old Paralics
Silty fine to medium SAND, brown, moist, loose
Fine to coarse SAND, white, moist, medium dense, poorly graded, porous
Refusal
Dr
y
D
e
n
s
i
t
y
(p
c
f
)
Oth
e
r
s
MATERIAL DESCRIPTION AND COMMENTS
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
(%
)
LOCATION:Carlsbad, California ELEVATION:109'DATE:4/16/2021
PROJECT NO.:3687-SD HAMMER:-RIG TYPE:
PROJECT NAME:4368 Adams St.DRILL METHOD:Manual Auger OPERATOR:
CLIENT:Curtis Ling DRILLER:LOGGED BY:MSB
---
-"' --------------------------------------------------------• I [2J [g] ~
APPENDIX B
RESULTS OF LABORATORY TESTING
CURTIS LING Project No. 3687-SD
Updated Geotechnical Evaluation September 21, 2023 (Revised January 31, 2024)
4368 Adams Street, Carlsbad, California Page B1
SUMMARY OF LABORATORY TESTING
Identification and Classification
Soils were identified visually in general accordance with the procedures of the Standard Practice for
Description and Identification of Soils (ASTM D2488). The soil identifications and classifications are shown
on the test pit logs in Appendix A.
Moisture-Density Relationship
Laboratory testing was performed on a soil sample collected during the subsurface exploration. The
laboratory maximum dry density and optimum moisture content were determined in general accordance
with ASTM D 1557 test procedures. The results of the testing are presented in Appendix B.
Expansion Index
Expansion Index testing was performed on a representative site soil sample. Testing was performed in
general accordance with ASTM Test Method D 4829. The results of the testing are presented in
Appendix B.
Shear Strength
Shear strength of remolded (compacted) site material was evaluated in general conformance with ASTM
Test Method D 3080. The sample was remolded to approximately 90% of maximum dry density in
accordance with ASTM D 1557 test procedure. Results are presented in Appendix B.
Sulfate Content
The sulfate content of a representable site soil sample was determined by GeoTek’s subconsultant,
Project X, in general accordance with ASTM D 4327. The results of the testing are provided in
Appendix B.
MOISTURE/DENSITY RELATIONSHIP
Client:Curtis Ling Job No.:3687-SD
Project:4368 Adams St.Lab No.:3580
Location:Carlsbad, California
Material Type:Reddish Brown Silty Fine Sand
Material Supplier:-
Material Source:0
Sample Location:Composite of T1 & T2 (BB-1)
-
Sampled By:MSB Date Sampled:4/16/2021
Received By:SE Date Received:4/16/2021
Tested By:SE Date Tested:4/20/2021
Reviewed By:-Date Reviewed:-
Test Procedure:ASTM D1557 Method:A
Oversized Material (%):0.0 Correction Required: yes x no
MOISTURE CONTENT (%):10.5802 8.623693 6.509703 4.537164 10.5802 8.623693 6.509703 4.537164
DRY DENSITY (pcf):125.7797 129.7274 125.8503 122.8799
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 130.0 @ Optimum Moisture, %9.0
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:
117
119
121
123
125
127
129
131
133
135
6 7 8 9 10 11 12 13 14 15
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
S.G. 2.6
Poly. (DRY DENSITY (pcf):)
OVERSIZE CORRECTED
ZERO AIR VOIDS
Poly. (S.G. 2.7)
Poly. (S.G. 2.8)
Poly. (S.G. 2.6)
GEOTEK
□
•
■
I~ ~ "' ' "' I~ ~ '
X -• "' I"' ~ I~ '--" ...... ' V " ~ ~ ' I~ • / \' ~ ~ "' I' .. "' I~ ~ I~
~ " "' ' "' I~
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 =
Reddish Brown Silty Fine Sand
EXPANSION INDEX TEST
(ASTM D4829)
0
Tare
4.8
FINAL MOISTURE
%
Moisture
Weight of wet
sample & tare
Wt. of dry
sample & tare
244.3
1"
271.6
270.5
4.8
250.4
SATURATION DETERMINATION
18.7
8.2
51.4
12:40
369.7
DENSITY DETERMINATION
Wet Density, lb / ft3 (C*0.3016)
0.30
0.70
117.2
959.2
420.4
126.8
Random
12:29 200
16:00
199
12:39
Initial
200
1 min/Wet
10 min/Dry
4/19/2021
790.1
4"12
199
19912:45
Dry Density, lb / ft3 (D/1.F)
Project Number:
Project Name:4368 Adams St.
3687-SD
Project Location:
SE
Carlsbad, California
Loading weight: 5516. grams
BB-1 (T1 & T2)
4/19/2021
Lab No
4/20/2021 12:29 199
TIME READINGDATE
Final
3580
11.4%
5 min/Wet
READINGS
GEOTEK
--I
I I
Curtis Ling Sample Location:
Date Tested:
Shear Strength:F =29 O , C = 122 psf
Notes:
5/5/2021
DIRECT SHEAR TEST
2 - The above reflect direct shear strength at saturated conditions.
1 - The soil specimen used in the shear box was a ring sample remolded to approximately 90% relative compaction from a
bulk sample collected during the field investigation.
Project Name:
Project Number:
3 - The tests were run at a shear rate of 0.035 in/min.
3687-SD
BB-1 (Composite)
0.0
500.0
1000.0
1500.0
2000.0
2500.0
3000.0
3500.0
4000.0
0.0 500.0 1000.0 1500.0 2000.0 2500.0 3000.0 3500.0 4000.0
SH
E
A
R
S
T
R
E
S
S
(
p
s
f
)
NORMAL STRESS (psf)
GEOTEK
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Curtis Ling Sample Location:
Date Tested:
Shear Strength:F =27 O , C = 337 psf
Notes:
Project Name:
Project Number:
3 - The tests were run at a shear rate of 0.035 in/min.
PEAK VALUE
3687-SD
BB-1 (Composite)
5/5/2021
DIRECT SHEAR TEST
2 - The above reflect direct shear strength at saturated conditions.
1 - The soil specimen used in the shear box was a ring sample remolded to approximately 90% relative compaction from a
bulk sample collected during the field investigation.
0.0
500.0
1000.0
1500.0
2000.0
2500.0
3000.0
3500.0
4000.0
0.0 500.0 1000.0 1500.0 2000.0 2500.0 3000.0 3500.0 4000.0
SH
E
A
R
S
T
R
E
S
S
(
p
s
f
)
NORMAL STRESS (psf)
GEOTEK
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I I I I I I I I I I I I I I ----.------------~-------------r------------,-------------T-------------1 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I ---◄-------------~-------------+------------~-------------►------------~-------------+-------------• I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I
Project X REPORT S210416I
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
Curtisling
April 21, 2021
Prepared for:
Chris Livesey
GeoTek, Inc.
1384 Poinsettia Ave, Suite A
Vista, CA, 92081
clivesey@geotekusa.com
Project X Job#: S210416I
Client Job or PO#: 3687-SD
Respectfully Submitted,
Eduardo Hernandez, M.Sc., P.E.
Sr. Corrosion Consultant NACE Corrosion Technologist #16592
Professional Engineer
California No. M37102 ehernandez@projectxcorrosion.com
No. lMG7102
Project X REPORT S210416I
Corrosion Engineering Page 2
Corrosion Control – Soil, Water, Metallurgy Testing Lab
29990 Technology Dr., Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Soil Analysis Lab Results
Client: GeoTek, Inc.
Job Name: Curtisling
Client Job Number: 3687-SD Project X Job Number: S210416I
April 21, 2021
Method
Bore# / Description Depth
(ft)(mg/kg)(wt%)
T2-BB1 0-5 34.4 0.0034
ASTM
D4327
Sulfates
SO42-
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
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10
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Project X
Corrosion Engint:t:.-ing
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Lab Request Shtt! Chaia or Custody Phone: (213)928-7213 • Fax (951) 226-1720 • www.proJcctxco1TOsion.com Ship Samples To: 29990 Technology Dr, Suite 13, Murrieta, CA 92563
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Malling Add"""': 1384 Poinsetta Ave, Ste A, Vista, CA 92081 Conl.tlcl ll111ail: clivesev<@aeotekusa.com
Accoantiuf! Cont11ct: Accounts Payable ln,·oi« Email: ao@aeotekusa.com; lwhite@geotekusa.com
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APPENDIX C
GENERAL EARTHWORK GRADING GUIDELINES
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, 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.
G,ROTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 2
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 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. Typical procedures are
similar to those indicated on Plate G-4.
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 (see Plates G-1, G-2 and G-3) 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.
G,ROTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 3
Subdrainage
1. Subdrainage systems should be provided in canyon bottoms prior to placing fill, and behind
buttress and stabilization fills and in other areas indicated in the report. Subdrains should
conform to schematic diagrams G-1 and G-5, and be acceptable to our representative.
2. For canyon subdrains, runs less than 500 feet may use six-inch pipe. Typically, runs in excess
of 500 feet should have the lower end as eight-inch minimum.
3. Filter material should be clean, 1/2 to 1-inch gravel wrapped in a suitable filter fabric. Class 2
permeable filter material per California Department of Transportation Standards tested by
this office to verify its suitability, may be used without filter fabric. A sample of the material
should be provided to the Soils Engineer by the contractor at least two working days before
it is delivered to the site. The filter should be clean with a wide range of sizes.
4. Approximate delineation of anticipated subdrain locations may be offered at 40-scale plan
review stage. During grading, this office would evaluate the necessity of placing additional
drains.
5. All subdrainage systems should be observed by our representative during construction and
prior to covering with compacted fill.
6. Subdrains should outlet into storm drains where possible. Outlets should be located and
protected. The need for backflow preventers should be assessed during construction.
7. Consideration should be given to having subdrains located by the project surveyors.
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
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 (see Plate G-4). On projects where significant large quantities of
oversized materials are anticipated, alternate guidelines for placement may be included. If
G,ROTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 4
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.
Keyways, Buttress and Stabilization Fills
Keyways are needed to provide support for fill slope and various corrective procedures.
1. Side-hill fills should have an equipment-width key at their toe excavated through all surficial
soil and into competent material and tilted back into the hill (Plates G-2, G-3). As the fill is
elevated, it should be benched through surficial soil and slopewash, and into competent
bedrock or other material deemed suitable by our representatives (See Plates G-1, G-2, and
G-3).
2. Fill over cut slopes should be constructed in the following manner:
a) All surficial soils and weathered rock materials should be removed at the cut-fill
interface.
b) A key at least one and one-half (1.5) equipment width wide (or as needed for
compaction), and tipped at least one (1) foot into slope, should be excavated into
competent materials and observed by our representative.
c) The cut portion of the slope should be excavated prior to fill placement to evaluate if
stabilization is necessary. The contractor should be responsible for any additional
earthwork created by placing fill prior to cut excavation. (see Plate G-3 for
schematic details.)
3. Daylight cut lots above descending natural slopes may require removal and replacement of
the outer portion of the lot. A schematic diagram for this condition is presented on Plate G-
2.
G,ROTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 5
4. A basal key is needed for fill slopes extending over natural slopes. A schematic diagram for
this condition is presented on Plate G-2.
5. All fill slopes should be provided with a key unless within the body of a larger overall fill
mass. Please refer to Plate G-3 for specific guidelines.
Anticipated buttress and stabilization fills are discussed in the text of the report. The need to
stabilize other proposed cut slopes will be evaluated during construction. Plate G-5 shows a
schematic of buttress construction.
1. All backcuts should be excavated at gradients of 1:1 or flatter. The backcut configuration
should be determined based on the design, exposed conditions, and need to maintain a
minimum fill width and provide working room for the equipment.
2. On longer slopes, backcuts and keyways should be excavated in maximum 250 feet long
segments. The specific configurations will be determined during construction.
3. All keys should be a minimum of two (2) feet deep at the toe and slope toward the heel at
least one foot or two (2%) percent, whichever is greater.
4. Subdrains are to be placed for all stabilization slopes exceeding 10 feet in height. Lower
slopes are subject to review. Drains may be required. Guidelines for subdrains are
presented on Plate G-5.
5. Benching of backcuts during fill placement is required.
Lot Capping
1. When practical, the upper three (3) feet of material placed below finish grade should be
comprised of the least expansive material available. Preferably, highly and very highly
expansive materials should not be used. We will attempt to offer advice based on visual
evaluations of the materials during grading, but it must be realized that laboratory testing is
needed to evaluate the expansive potential of soil. Minimally, this testing takes two (2) to
four (4) days to complete.
2. Transition lots (cut and fill) both per plan and those created by remedial grading (e.g. lots
above stabilization fills, along daylight lines, above natural slopes, etc.) should be capped with
a minimum three foot thick compacted fill blanket.
3. Cut pads should be observed by our representative(s) to evaluate the need for
overexcavation and replacement with fill. This may be necessary to reduce water infiltration
into highly fractured bedrock or other permeable zones, and/or due to differing expansive
potential of materials beneath a structure. The overexcavation should be at least three feet.
Deeper overexcavation may be recommended in some cases.
ROCK PLACEMENT AND ROCK FILL GUIDELINES
If large quantities of oversize material would be generated during grading, it’s likely that such
materials may require special handling for burial. Although alternatives may be developed in the field,
the following methods of rock disposal are recommended on a preliminary basis.
Limited Larger Rock
When materials encountered are principally soil with limited quantities of larger rock fragments or
boulders, placement in windrows is recommended. The following procedures should be applied:
1. Oversize rock (greater than 8 inches) should be placed in windrows.
a) Windrows are rows of single file rocks placed to avoid nesting or clusters of rock.
G,ROTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 6
b) Each adjacent rock should be approximately the same size (within ~one foot in
diameter).
c) The maximum rock size allowed in windrows is four feet
2. A minimum vertical distance of three feet between lifts should be maintained. Also, the
windrows should be offset from lift to lift. Rock windrows should not be closer than 15 feet
to the face of fill slopes and sufficient space must be maintained for proper slope
construction (see Plate G-4).
3. Rocks greater than eight inches in diameter should not be placed within seven feet of the
finished subgrade for a roadway or pads and should be held below the depth of the lowest
utility. This will allow easier trenching for utility lines.
4. Rocks greater than four feet in diameter should be broken down, if possible, or they may be
placed in a dozer trench. Each trench should be excavated into the compacted fill a
minimum of one foot deeper than the largest diameter of rock.
a) The rock should be placed in the trench and granular fill materials (SE>30) should be
flooded into the trench to fill voids around the rock.
b) The over size rock trenches should be no closer together than 15 feet from any
slope face.
c) Trenches at higher elevation should be staggered and there should be a minimum of
four feet of compacted fill between the top of the one trench and the bottom of the
next higher trench.
d) It would be necessary to verify 90 percent relative compaction in these pits. A 24 to
72 hour delay to allow for water dissipation should be anticipated prior to additional
fill placement.
Structural Rock Fills
If the materials generated for placement in structural fills contains a significant percentage of material
more than six (6) inches in one dimension, then placement using conventional soil fill methods with
isolated windrows would not be feasible. In such cases the following could be considered:
1. Mixes of large rock or boulders may be placed as rock fill. They should be below the depth
of all utilities both on pads and in roadways and below any proposed swimming pools or
other excavations. If these fills are placed within seven (7) feet of finished grade, they may
affect foundation design.
2. Rock fills are required to be placed in horizontal layers that should not exceed two feet in
thickness, or the maximum rock size present, which ever is less. All rocks
exceeding two feet should be broken down to a smaller size, windrowed (see above), or
disposed of in non-structural fill areas. Localized larger rock up to 3 feet in largest dimension
may be placed in rock fill as follows:
a) individual rocks are placed in a given lift so as to be roughly 50% exposed above the
typical surface of the fill ,
b) loaded rock trucks or alternate compactors are worked around the rock on all sides
to the satisfaction of the soil engineer,
c) the portion of the rock above grade is covered with a second lift.
3. Material placed in each lift should be well graded. No unfilled spaces (voids) should be
permitted in the rock fill.
G,ROTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 7
Compaction Procedures
Compaction of rock fills is largely procedural. The following procedures have been found to
generally produce satisfactory compaction.
1. Provisions for routing of construction traffic over the fill should be implemented.
a) Placement should be by rock trucks crossing the lift being placed and dumping at its
edge.
b) The trucks should be routed so that each pass across the fill is via a different path
and that all areas are uniformly traversed.
c) The dumped piles should be knocked down and spread by a large dozer (D-8 or
larger suggested). (Water should be applied before and during spreading.)
2. Rock fill should be generously watered (sluiced)
a) Water should be applied by water trucks to the:
i) dump piles,
ii) front face of the lift being placed and,
iii) surface of the fill prior to compaction.
b) No material should be placed without adequate water.
c) The number of water trucks and water supply should be sufficient to provide
constant water.
d) Rock fill placement should be suspended when water trucks are unavailable:
i) for more than 5 minutes straight, or,
ii) for more than 10 minutes/hour.
3. In addition to the truck pattern and at the discretion of the soil engineer, large, rubber tired
compactors may be required.
a) The need for this equipment will depend largely on the ability of the operators to
provide complete and uniform coverage by wheel rolling with the trucks.
b) Other large compactors will also be considered by the soil engineer provided that
required compaction is achieved.
4. Placement and compaction of the rock fill is largely procedural. Observation by trenching
should be made to check:
a) the general segregation of rock size,
b) for any unfilled spaces between the large blocks, and
c) the matrix compaction and moisture content.
5. Test fills may be required to evaluate relative compaction of finer grained zones or as
deemed appropriate by the soil engineer.
a) A lift should be constructed by the methods proposed, as proposed
6. Frequency of the test trenching is to be at the discretion of the soil engineer. Control areas
may be used to evaluate the contractor’s procedures.
7. A minimum horizontal distance of 15 feet should be maintained from the face of the rock fill
and any finish slope face. At least the outer 15 feet should be built of conventional fill
materials.
Piping Potential and Filter Blankets
Where conventional fill is placed over rock fill, the potential for piping (migration) of the fine grained
material from the conventional fill into rock fills will need to be addressed.
The potential for particle migration is related to the grain size comparisons of the materials present
and in contact with each other. Provided that 15 percent of the finer soil is larger than the effective
G,ROTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 8
pore size of the coarse soil, then particle migration is substantially mitigated. This can be
accomplished with a well-graded matrix material for the rock fill and a zone of fill similar to the
matrix above it. The specific gradation of the fill materials placed during grading must be known to
evaluate the need for any type of filter that may be necessary to cap the rock fills. This,
unfortunately, can only be accurately determined during construction.
In the event that poorly graded matrix is used in the rock fills, properly graded filter blankets 2 to 3
feet thick separating rock fills and conventional fill may be needed. As an alternative, use of two
layers of filter fabric (Mirafi 700 x or equivalent) could be employed on top of the rock fill. In order
to mitigate excess puncturing, the surface of the rock fill should be well broken down and smoothed
prior to placing the filter fabric. The first layer of the fabric may then be placed and covered with
relatively permeable fill material (with respect to overlying material) 1 to 2 feet thick. The relative
permeable material should be compacted to fill standards. The second layer of fabric should be
placed and conventional fill placement continued.
Subdrainage
Rock fill areas should be tied to a subdrainage system. If conventional fill is placed that separates the
rock from the main canyon subdrain, then a secondary system should be installed. A system
consisting of an adequately graded base (3 to 4 percent to the lower side) with a collector system
and outlets may suffice.
Additionally, at approximately every 25 foot vertical interval, a collector system with outlets should
be placed at the interface of the rock fill and the conventional fill blanketing a fill slope.
Monitoring
Depending upon the depth of the rock fill and other factors, monitoring for settlement of the fill
areas may be needed following completion of grading. Typically, if rock fill depths exceed 40 feet,
monitoring would be recommend prior to construction of any settlement sensitive improvements.
Delays of 3 to 6 months or longer can be expected prior to the start of construction.
UTILITY TRENCH CONSTRUCTION AND BACKFILL
Utility trench excavation and backfill is the contractor’s 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.
G,ROTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 9
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 contractor’s 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 contractor’s 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.
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.),
G,ROTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 10
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
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.
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G,ROTEK
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 11
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 contractor’s
representative will then be contacted in an effort to affect 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 affect 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 technician’s 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.
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.
G,ROTEK
1384 Poinsettia Avenue, Suite A
Vista, California 92083
TYPICAL CANYON
CLEANOUT
STANDARD GRADING
GUIDELINES
ALTERNATES
Original Ground
3’
Loose Surface Materials
PLATE G-1
Finish Grade
3’
Suitable
Material
Suitable
Material
6” Perforated Pipe in 9 cubic feet per LinealFoot Clean Gravel Wrapped in Filter Fabric
Construct Bencheswhere slope exceeds 5:1
Bottom of Cleanout to Be At
Least 1.5 Times the Width of
Compaction Equipment
4 feet typical
Slope to Drain
Original Ground
Loose Surface Materials
Finish Grade
Suitable
MaterialConstruct Bencheswhere slope exceeds 5:1
Bottom of Cleanout to Be AtLeast1.5 Times the Width ofCompaction Equipment
4 feet typical
Slope to Drain
6” Perforated Pipe in 9 cubic feetper Lineal Foot Clean GravelWrapped in Filter Fabric
TREATMENT ABOVE
NATURAL SLOPES
STANDARD GRADING
GUIDELINES
TYPICAL FILL SLOPE OVER
NATURAL DESCENDING SLOPE
Topsoil
Bedrock
PLATE G-2
Finish Grade
Fill Slope
Daylight Cut
Line per Plan
Project Removal
at 1 to 1
Min. 3 FeetCompacted Fill
Colluvium
Creep Zone
Minimum 15 Feet Wide
or 1.5 EquipmentWidths for Compaction
Toe of Fill Slope
per Plan
DAYLIGHT CUT AREA OVER
NATURAL DESCENDING SLOPE
Topsoil
Structural SetbackWithout Corrective Work
Project Removalat 1 to 1
Colluvium
Creep Zone
Min.
2 Feet
Minimum 15 Feet Wideor 1.5 EquipmentWidths for Compaction
Finish Grade
Bedrock
Min. 3 FeetCompacted Fill
Min.2 Feet
Compacted Fill
Compacted Fill
1384 Poinsettia Avenue, Suite A
Vista, California 92081-8505
Topsoil
Colluvium
Creep Zone
~
GEOTEK
COMMON FILL
SLOPE KEYS
STANDARD GRADING
GUIDELINES
TYPICAL FILL SLOPE OVER
CUT SLOPE
Topsoil
Bedrock
PLATE G-3
Finish Grade
2: 1 Fill Slope
4’ Typical
Colluvium
Creep Zone
Minimum 15 Feet Wideor 1.5 EquipmentWidths for Compaction
Toe of Fill Slope
per Plan
TYPICAL FILL SLOPE
Bedrock or
Suitable Dense Material
Minimum compacted fill requiredto provide lateral support.
Excavate key if width or depthless than indicated in table above
Cut Slope
SLOPEHEIGHT
MIN. KEY
WIDTH
MIN. KEY
DEPTH
5
10
15
20
25
>25
7
10
15
15
15
SEE TEXT
1
1.5
2
2.5
3
CONTRACTOR TO VERIFYWITH SOIL ENGINEERPRIOR TO CONSTRUCTION
1384 Poinsettia Avenue, Suite A
Vista, California 92081-8505
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NOTES:
1)SOIL FILL OVER WINDROW SHOULE BE 7 FEET OR PER JURISDUICTIONAL STANDARDS AND SUFFICIENTFOR FUTURE EXCAVATIONS TO AVOID ROCKS
2)MAXIMUM ROCK SIZE IN WINDROWS IS 4 FEET MINIMUM DIAMETER
3)SOIL AROUND WINDROWS TO BE SANDY MATERIAL SUBJECT TO SOIL ENGINEER ACCEPTANCE
4)SPACING AND CLEARANCES MUST BE SUFFICIENT TO ALLOW FOR PROPER COMPACTION
5)INDIVDUAL LARGE ROCKS MAY BE BURIED IN PITS.
ROCK BURIAL
DETAILS
STANDARD GRADING
GUIDELINES
PLATE G-4
SEE NOTE 1
15’
MIN.3’ MIN.
3’ MIN.
MINIMUM 15’ CLEAR OR
1.5 EQUIPMENT WIDTHS
FOR COMPACTION
STAGGER ROWS
HORIZONTALLY
NO ROCKS IN
THIS ZONE
CROSS SECTIONAL VIEW
FINISH GRADE
FILL SLOPE
PLAN VIEW
FILL SLOPE
MINIMUM 15’ CLEAR OR 1.5 EQUIPMENTWIDTHS FOR COMPACTION
MINIMUM 15’ CLEAR OR 1.5 EQUIPMENT
WIDTHS FOR COMPACTION
PLACE ROCKS END TO END
DO NOT PILE OR STACK ROCKS
SOIL TO BE PLACE AROUND AND OVER ROCKS THEN FLOODED INTOVOIDS. MUST COMPACT AROUND AND OVER EACH ROCK WINDROW
1384 Poinsettia Avenue, Suite A
Vista, California 92081-8505
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BEDROCK COMPACTED FILL
MIN. 3 FEETCOMPACTED FILL
TERRACE DRAIN
AS REQUIRED
2
1
MIN. 15 FEET WIDE OR 1.5 EQUIPMENT
WIDTHS FOR COMPACTION
MIN. 2 FEET
EMBEDDMENT
1384 Poinsettia Avenue, Suite A
Vista, California 92083
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TRANSITION &
UNDERCUT LOTS PLATE G-6
TRANSITION LOT
PROPSED FINISH GRADE
COMPETENT MATERIAL
4’MIN.
OVEREXCAVATE ANDRECOMPACT
PROPOSED STRUCTURE
COMPACTED FILL
3 1
OVEREXCAVATION AND BENCHING NOTTO EXCEED INCLINATION OF 3:1 (H:V)
UNDERCUT LOT
PROPSED FINISH GRADE
PROPOSED STRUCTURE
4’MIN.
COMPETENT MATERIAL
COMPACTED FILL
OVEREXCAVATE ANDRECOMPACTOVEREXCAVATION TO HAVE 1%FALL TOWARD FRONT OF LOT
Notes:1.Removed/overexcavated soils should be recompacted in accordance with recommendations included in the text of the report.2.Location of cut/fill transition should verified in the field during site grading.
STANDARD GRADING
GUIDELINES1384 Poinsettia Avenue, Suite A
Vista, California 92081-8505
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