HomeMy WebLinkAboutCDP 2023-0052; NORMANDY BEACH HOMES; PRELIMINARY GEOTECHNICAL EVALUATION PROPOSED RESIDENTIAL REDEVELOPMENT LOT 39; 2023-10-13
PRELIMINARY GEOTECHNICAL EVALUATION
PROPOSED RESIDENTIAL REDEVELOPMENT
LOT 39
APN 203-023-06-00
CARLSBAD, CALIFORNIA 92008
PREPARED FOR
RINCON HOMES
5315 AVENIDA ENCINAS, SUITE 200
CARLSBAD, CALIFORNIA 92008
PREPARED BY
GEOTEK, INC.
1384 POINSETTIA AVENUE, SUITE A
VISTA, CALIFORNIA 92081
PROJECT NO. 3948-SD OCTOBER 13, 2023
GEOTECHNICAL | ENVIRONMENTAL | MATERIALS
October 13, 2023
Project No. 3948-SD
Rincon Homes
5315 Avenida Encinas, Suite 200
Carlsbad, California 92008
Attention: Mr. Kevin Dunn
Subject: Preliminary Geotechnical Evaluation Lot 39
Proposed Residential Redevelopment
Assessor Parcel Number 203-023-06-00
Carlsbad, California 92008
Dear Mr. Dunn:
GeoTek, Inc. (GeoTek) is pleased to provide herein the results of this preliminary
geotechnical evaluation for the subject project. This report presents the results of
GeoTek’s evaluation and provides preliminary geotechnical recommendations for
earthwork, foundation design, and construction. Based upon review, site development
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 contact GeoTek.
Respectfully submitted,
GeoTek, Inc.
Christopher D. Livesey
CEG 2733, Exp. 05/31/25
Vice President
Edward R. Cunningham
RCE 81687, Exp. 03/31/24
Project Engineer
Distribution: (1) Addressee
RINCON HOMES Project No. 3948-SD
Preliminary Geotechnical Evaluation Lot 39 October 13, 2023
APN 203-023-06-00, Carlsbad, California 92008 Page i
TABLE OF CONTENTS
1. PURPOSE AND SCOPE OF SERVICES .................................................................................................... 1
2. SITE DESCRIPTION AND PROPOSED DEVELOPMENT .................................................................... 1
2.1 Site Description ................................................................................................................................ 1
2.2 Proposed Development ..................................................................................................................... 1
3. FIELD EXPLORATION AND LABORATORY TESTING ...................................................................... 2
3.1 Field Exploration ............................................................................................................................... 2
3.2 Laboratory Testing ............................................................................................................................ 2
4. GEOLOGIC AND SOILS CONDITIONS ................................................................................................... 2
4.1 Regional Setting ................................................................................................................................ 2
4.2 EARTH MATERIALS ......................................................................................................................... 3
Artificial Fill (Not Mapped) ................................................................................................................ 3
Old Paralic Deposits (Map Symbol Qop) ............................................................................................ 3
4.3 SURFACE WATER AND GROUNDWATER ........................................................................................ 3
Surface Water .................................................................................................................................. 3
Groundwater .................................................................................................................................... 3
4.4 EARTHQUAKE HAZARDS ................................................................................................................ 4
Surface Fault Rupture ....................................................................................................................... 4
Liquefaction/Seismic Settlement......................................................................................................... 4
Other Seismic Hazards ..................................................................................................................... 4
5. CONCLUSIONS AND RECOMMENDATIONS ........................................................................................ 5
5.1 General ............................................................................................................................................ 5
5.2 EARTHWORK CONSIDERATIONS ................................................................................................... 5
General ............................................................................................................................................ 5
Site Clearing and Preparation ............................................................................................................ 5
Remedial Grading ............................................................................................................................. 5
Engineered Fill .................................................................................................................................. 6
Excavation Characteristics ................................................................................................................. 6
Trench Excavations and Backfill ........................................................................................................ 6
5.3 DESIGN RECOMMENDATIONS ....................................................................................................... 7
Foundation Design Criteria ................................................................................................................ 7
Under Slab Moisture Membrane ....................................................................................................... 9
Miscellaneous Foundation Recommendations ................................................................................... 10
Foundation Setbacks ....................................................................................................................... 10
Seismic Design Parameters ............................................................................................................. 11
Soil Sulfate Content ........................................................................................................................ 11
General Concrete Flatwork .............................................................................................................. 11
5.4 POST CONSTRUCTION CONSIDERATIONS ................................................................................... 12
Landscape Maintenance and Planting .............................................................................................. 12
Drainage ........................................................................................................................................ 12
5.5 PLAN REVIEW AND CONSTRUCTION OBSERVATIONS ................................................................. 12
6. LIMITATIONS ............................................................................................................................................. 13
7. SELECTED REFERENCES ....................................................................................................................... 15
RINCON HOMES Project No. 3948-SD
Preliminary Geotechnical Evaluation Lot 39 October 13, 2023
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TABLE OF CONTENTS
ENCLOSURES
Figure 1 – Site Location Map
Figure 2 – Geotechnical Map
Appendix A – Logs of Exploration
Appendix B – Results of Laboratory Testing
Appendix C – General Earthwork Grading Guidelines
RINCON HOMES Project No. 3948-SD
Preliminary Geotechnical Evaluation Lot 39 October 13, 2023
APN 203-023-06-00, Carlsbad, California 92008 Page 1
1. PURPOSE AND SCOPE OF SERVICES
The purpose of this study was to evaluate the geotechnical conditions of the project site. 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 two exploratory borings and collection of soil samples for subsequent
laboratory testing.
Laboratory analysis of soil samples collected during the field investigation.
Compilation of this geotechnical report which presents 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 subject project site is located at Assessor Parcel Number 203-023-06-00, Lot 39, Carlsbad,
California 92008 (see Figure 1). The site can be conveniently located by the address of 260
Normandy Lane. The property currently supports the following improvements: an existing
residential structure (primary dwelling), in-ground pool, garage/carport, concrete driveway, and
various landscape/hardscape. The property is bounded to the north, east, and west by residential
property, and to the south by Normandy Lane. Topographically, the property is level with an
approximate elevation of 43 feet above mean sea level (msl).
2.2 Proposed Development
Based upon review of the Conceptual Site Plan prepared by Kirk Moeller Architects, Inc. (KMA)
and conversations with you, proposed site improvements will be demolished to prepare the site
for proposed improvements. The conceptual improvements consist of a three-story single family
residential dwelling with an attached garage. The construction is anticipated to consist of a
concrete slab on grade, with perimeter and interior and isolated spread footings, utilizing wood
frame construction. Associated improvements are anticipated to consist of utilities, concrete
RINCON HOMES Project No. 3948-SD
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flatwork/hardscape, and landscape. A grading plan has not been provided for review; however,
it is anticipated that the conceptual improvements will be near current grades.
3. FIELD EXPLORATION AND LABORATORY TESTING
3.1 Field Exploration
GeoTek’s field study was conducted on August 31, 2023, and consisted of excavation of two
exploratory borings advanced with a manual auger. Borings reached practical refusal at 6.5 feet
below existing ground surface. At periodic depths, the boring was qualitatively evaluated with a
soil probe. Representative bulk soil samples and relatively undisturbed ring samples were
obtained and transported to GeoTek’s laboratory for engineering analysis. Relatively undisturbed
samples were obtained by advancing a 3.25-inch outside diameter, California Modified split barrel,
with a 35-pound weight dropped approximately eighteen inches. The explorations were logged
by an Engineering Geologist from GeoTek. The approximate locations of exploration locations
are presented on the Geotechnical Map, Figure 2. A description of material encountered in the
explorations is included in Logs of Exploration, Appendix A.
3.2 Laboratory Testing
Laboratory testing was performed on bulk soil samples collected during the field explorations.
The purpose of the laboratory testing was to evaluate their physical and chemical properties for
use in engineering design and analysis. Results of the laboratory testing program, along with a
brief description and relevant information regarding testing procedures, are included in
Appendix B.
4. GEOLOGIC AND SOILS CONDITIONS
4.1 Regional Setting
The subject property is located in the Peninsular Ranges geomorphic province. The Peninsular
Ranges province is one of the largest geomorphic units in western North America. Basically, it
extends roughly 975 miles from the north and northeasterly adjacent the Transverse Ranges
geomorphic province to the peninsula 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.
RINCON HOMES Project No. 3948-SD
Preliminary Geotechnical Evaluation Lot 39 October 13, 2023
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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 meanders the southwest margin of the province. No faults
are shown in the immediate site vicinity on the map reviewed for the area.
4.2 EARTH MATERIALS
Based on a review of published geologic maps and site specific field evaluation, the subject site is
underlain by Old Paralic deposits.
Artificial Fill (Not Mapped)
Although not directly encountered in the explorations existing artificial fill may be encountered
in areas not directly explored or in limited areas. If encountered the artificial fill should be
assumed to be very loose to loose, variable in consistency, and placed in an uncontrolled or
compacted manner that does not comply with current grading ordinances.
Old Paralic Deposits (Map Symbol Qop)
Quaternary-age Old Paralic deposits (Paralics) were encountered in all explorations and was
observed to consist of dark reddish-brown, silty fine sands, moist, very loose at the surface to
dense with depth. Approximately up to the upper three feet are considered to be weathered as
evident by very loose and yielding material to the soil probe to a depth of 4 feet.
4.3 SURFACE WATER AND GROUNDWATER
Surface Water
Surface water was not observed during the recent site exploration. If encountered during
earthwork construction, surface water on this site will likely be the result of precipitation.
Provisions for surface drainage will need to be accounted for by the project civil engineer.
Groundwater
A static groundwater table was not encountered during exploration of the subject site. The
Pacific Ocean and the Buena Vista Lagoon are located approximately 1,000 feet to the west and
north (respectively). Groundwater is anticipated to be at an approximate statice depth of 43 feet
below groundsurface or about 0 feet MSL. Based on the anticipated depth of removals,
groundwater is not anticipated to be a factor in site development. Localized perched
groundwater may be present but is also not anticipated to be a factor in site development.
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4.4 EARTHQUAKE HAZARDS
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 transecting the site were identified on the readily available geologic maps reviewed. The
nearest known active fault is the Newport Inglewood-Rose Canyon fault located approximately
2 miles to the southwest of the site.
Liquefaction/Seismic Settlement
Liquefaction describes a phenomenon in which cyclic stresses, produced by earthquake-induced
ground motion, create excess pore pressures in relatively cohesionless soils. These soils may
thereby acquire a high degree of mobility, which can lead to lateral movement, sliding,
consolidation and settlement of loose sediments, sand boils and other damaging deformations.
This phenomenon occurs only below the water table, but, after liquefaction has developed, 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 is considered negligible
provided remedial grading recommendations presented herein are completed and due to the
apparent dense nature of underlying shallow Paralic formational material.
Other Seismic Hazards
The potential for landslides and rockfall is considered negligible due to the absence of over
steepened slopes. The potential for secondary seismic hazards such as seiche and tsunami is low,
due to site elevation and published Tsunami inundation maps.
RINCON HOMES Project No. 3948-SD
Preliminary Geotechnical Evaluation Lot 39 October 13, 2023
APN 203-023-06-00, Carlsbad, California 92008 Page 5
5. CONCLUSIONS AND RECOMMENDATIONS
5.1 General
Development of the site 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. If plans change GeoTek should be notified to review the new plans and
determine if supplemental recommendations are prudent.
5.2 EARTHWORK CONSIDERATIONS
General
Earthwork and grading should be performed in accordance with the applicable grading ordinances
of the City of Carlsbad, the 2022 (or current) California Building Code (CBC), and
recommendations contained in this report. 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.
Site Clearing and Preparation
Site preparation should start with removal of all existing improvements and vegetation in conflict
with proposed improvements. These materials should be disposed of properly off site. Any
existing underground improvements, utilities and trench backfill should also be removed or be
further evaluated as part of site development operations.
The in-ground pool is recommended to be completely demolished and removed from the site.
Remedial Grading
Prior to placement of fill materials and in all structural areas the upper variable, potentially
compressible materials should be removed. Removals should include all undocumented fill soils
and weathered, loose Paralics down to competent, relatively undisturbed, dense, firm and
unyielding Paralics. Where the pool is demolished competent Paralics should be anticipated to
be one to two feet below the bottom of the pool shell, unless the pool had a historic leak. The
lateral extent of removals should be performed five feet beyond the outside edge of all settlement
sensitive structures/foundations or equivalent to that vertically removed, whichever is greater.
The bottom of the removals should be observed by a GeoTek representative prior to processing
the bottom for receiving placement of compacted fills. Depending on actual field conditions
encountered during grading, locally deeper areas of removal may be necessary.
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Where removals are needed adjacent to existing property lines, on-property lines or within a
distance equal to the depth of excavation of offsite structures or foundations, a temporary slope
no steeper than 1:1 (horizontal:vertical) away from the top of the foundation and into the
remedial excavation should be performed.
The resultant voids from remedial grading/over-excavation should be filled with materials placed
in general accordance with the recommendations provided in Section 5.2.4 Engineered Fill of this
report. Prior to placement of engineered fill, the bottom of all removals should be scarified to a
minimum depth of six inches, brought to optimum moisture content, and then compacted to at
least 90% of the soil’s maximum dry density as determined by ASTM D1557 test procedures.
Where engineered fills are placed against temporary excavation slopes, the fill should be benched
into the slope as the fill is brought up to design grades with care. If unstable conditions adjacent
to excavations persists, our office should be contacted for supplemental remedial grading
recommendations.
Engineered Fill
Onsite materials are generally considered suitable for reuse as engineered fill provided, they are
free from vegetation, roots, debris, and rock/concrete or hard lumps greater than six inches in
maximum dimension. The earthwork contractor should have the proposed excavated materials
to be used as engineered fill at this project approved by the soils engineer prior to placement.
Engineered fill materials should be moisture conditioned to 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 by ASTM D1557 test procedures.
If fill is being placed on slopes steeper than 5:1 (h:v), the fill should be properly benched into the
existing slopes.
Excavation Characteristics
Excavations in the onsite materials can generally be accomplished with heavy-duty earthmoving
or excavating equipment in good operating condition.
Trench Excavations and Backfill
Temporary excavations within the onsite materials should be stable at 1:1 inclination 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.
RINCON HOMES Project No. 3948-SD
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Trench excavations should conform to Cal-OSHA regulations. The contractor should have a
competent person, per OSHA requirements, on site during construction to observe conditions
and to make the appropriate recommendations.
Utility trench backfill should be compacted to at least 90% relative compaction of the maximum
dry density as determined by ASTM D1557 test procedures. Under-slab trenches should also be
compacted to project specifications.
Onsite materials may not be suitable for use as bedding material but should be suitable as backfill
provided particles larger than 6 inches are removed.
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 thoroughly
moisture conditioned prior to placement in trenches.
5.3 DESIGN RECOMMENDATIONS
Foundation Design Criteria
Preliminary foundation design criteria, in general conformance with the 2022 CBC, are presented
herein. These are typical design criteria and are not intended to supersede the design by the
structural engineer. Once actual structural loads and grading concepts are known, supplemental
recommendations may be warranted which may require additional test borings and laboratory
testing.
Based on visual classification of materials encountered onsite and as verified by laboratory testing,
site soils are anticipated to exhibit a “very low” (Expansion Index (EI) ≤ 20) expansion index per
ASTM D4829. Additional laboratory testing should be performed upon completion of site grading
to verify the expansion potential and plasticity index of the subgrade soils. The preliminary
recommendations are presented below. The structure may be supported on continuous and
spread foundations founded in compacted fill or paralic deposits.
RINCON HOMES Project No. 3948-SD
Preliminary Geotechnical Evaluation Lot 39 October 13, 2023
APN 203-023-06-00, Carlsbad, California 92008 Page 8
*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 beam reinforcement based on actual
loading conditions.
The following recommendations should be implemented into the design:
Preliminarily, an allowable bearing capacity of 2,000 pounds per square foot (psf) may
be considered for design of continuous and perimeter footings that meet the depth
and width requirements in the table above. This value may be increased by 300 psf
for each additional 12 inches in depth and 200 psf for each additional 12 inches in
width to a maximum value of 3,000 psf. Additionally, an increase of one-third may be
applied when considering short-term live loads (e.g., seismic and wind loads).
Based on experience in the area, structural foundations may be designed in
accordance with 2022 CBC, and to withstand a total settlement of 1 inch and
maximum differential settlement of one-half of the total settlement over a horizontal
distance of 40 feet. Seismically induced settlement is considered to be minimal.
The passive earth pressure may preliminarily be computed as an equivalent fluid having
a density of 250 psf per foot of depth, to a maximum earth pressure of 2,000 psf for
DESIGN PARAMETERS FOR CONVENTIONALL REINFORCED SHALLOW
FOUNDATIONS
Type of Building 3-Story Wood Framed and Stucco Sided
Expansion Index “Very Low” Expansion Potential
(EI ≤ 20)
Foundation Embedment Depth or
Minimum Perimeter Beam Depth (inches
below lowest adjacent finished grade)
18 - Inches
Minimum Foundation Width for
continuous / perimeter footings* 15 - Inches
Minimum Foundation Width for isolated
/ column footings* 24 – Inches (Square)
Minimum Slab Thickness (actual) 4 inches
Minimum Slab Reinforcing
No. 3 rebar 12” on-center, each way, or
No. 4 bars 18” on-center, each way,
placed in the middle one-third of the slab thickness
Minimum Footing Reinforcement Four No. 4 reinforcing bars,
two top and two bottom
Pre-saturation of Subgrade Soil (percent
of optimum moisture content) Minimum 100% to a depth of 12 inches
RINCON HOMES Project No. 3948-SD
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APN 203-023-06-00, Carlsbad, California 92008 Page 9
footings founded on engineered fill. A coefficient of friction between soil and
concrete of 0.30 may be used with dead load forces. When combining passive
pressure and frictional resistance, the passive pressure component should be reduced
by one-third.
Grade beams should be utilized across large entrances. The base of the grade beam
should be at the same elevation as the bottom of the adjoining footings.
Under Slab 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
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. Although the CBC
specifies a 6-mil vapor retarder membrane, it is GeoTek’s opinion that a minimum 10 mil
membrane with joints properly overlapped and sealed should be considered, unless otherwise
specified by the slab design professional.
Moisture and vapor retarding systems are intended to provide a certain level of resistance to
vapor and moisture transmission through the concrete, but do not eliminate it. The acceptable
level of moisture transmission through the slab is to a 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, we recommend 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
RINCON HOMES Project No. 3948-SD
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APN 203-023-06-00, Carlsbad, California 92008 Page 10
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 GeoTek, along with geotechnical consultants in general, do not practice
in the area of mold prevention. If specific recommendations addressing potential mold issues are
desired, then a professional mold prevention consultant should be contacted.
Miscellaneous Foundation Recommendations
To reduce moisture penetration beneath the slab on grade areas, utility trenches
should be backfilled with engineered fill, lean concrete or concrete slurry where they
intercept the perimeter footing or thickened slab edge.
Spoils from the footing excavations should not be placed in the slab-on-grade areas
unless properly moisture-conditioned, compacted and tested. The excavations should
be free of loose/sloughed materials and be neatly trimmed at the time of concrete
placement.
Foundation Setbacks
Where applicable, the following setbacks should apply to all foundations. Any improvements not
conforming to these setbacks may be subject to lateral movements and/or differential
settlements:
The outside bottom edge of all footings should be set back a minimum of H/3 (where
H is the slope height) from the face of any descending slope. The setback should be
at least 7 feet and need not exceed 40 feet.
The bottom of all footings for structures near retaining walls should be deepened so
as to extend below a 1:1 projection upward from the bottom inside edge of the wall
stem. This applies to the existing retaining walls along the perimeter if they are to
remain.
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The bottom of any existing foundations for structures should be deepened so as to
extend below a 1:1 projection upward from the bottom of the nearest excavation.
Seismic Design Parameters
The site is located at approximately 33.1639 degrees west latitude and -117.3559 degrees north
longitude. Site spectral accelerations (Ss and S1), for 0.2 and 1.0 second periods for a risk
targeted two (2) percent probability of exceedance in 50 years (MCER) were determined using
the web interface provided by ASCE/SEI-7 (https://asce7hazardtool.online) to access the USGS
Seismic Design Parameters. A Site Class “D” is considered appropriate for this site. The results,
based on ASCE 7-22 and the 2022 CBC, are presented in the following table.
SITE SEISMIC PARAMETERS
Mapped 0.2 sec Period Spectral Acceleration, Ss 1.24g
Mapped 1.0 sec Period Spectral Acceleration, S1 0.39g
Maximum Considered Earthquake (MCER) Spectral
Response Acceleration for 0.2 Second, SMS 1.46g
Maximum Considered Earthquake (MCER) Spectral
Response Acceleration for 1.0 Second, SM1 0.99g
5% Damped Design Spectral Response
Acceleration Parameter at 0.2 Second, SDS 0.97g
5% Damped Design Spectral Response
Acceleration Parameter at 1 second, SD1 0.66g
Site Modified Peak Ground Acceleration (PGAM) 0.56g
Seismic Design Category D
Soil Sulfate Content
Sulfate content test results for a representative soil sample indicate water soluble sulfate is less
than 0.1 percent by weight, which is considered “S0” as per Table 19.3.1.1 of ACI 318-14. Based
upon the test results provided by GeoTek’s subconsultant Project X, no special
recommendations for concrete are required for this project due to soil sulfate exposure.
General Concrete Flatwork
It is recommended that control joints be placed in two directions spaced the numeric equivalent
of 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.
Presaturation of flatwork subgrade should be verified to be a minimum 100% to a depth of 12
inches.
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5.4 POST CONSTRUCTION CONSIDERATIONS
Landscape Maintenance and Planting
Water has been shown to weaken the inherent strength of soil, and slope stability is significantly
reduced by overly wet conditions. Positive surface drainage away from graded slopes should be
maintained and only the amount of irrigation necessary to sustain plant life should be provided
for planted slopes. Controlling surface drainage and runoff and maintaining a suitable vegetation
cover can minimize erosion. Plants selected for landscaping should be lightweight, deep-rooted
types that require little water and are capable of surviving the prevailing climate.
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 with regard to 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.
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.
5.5 PLAN REVIEW AND CONSTRUCTION OBSERVATIONS
GeoTek recommends that site grading, specifications, retaining wall 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
RINCON HOMES Project No. 3948-SD
Preliminary Geotechnical Evaluation Lot 39 October 13, 2023
APN 203-023-06-00, Carlsbad, California 92008 Page 13
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.
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. GeoTek recommends that these agencies be notified prior to commencement of
construction so that necessary grading permits can be obtained.
6. LIMITATIONS
The scope of this evaluation is limited to the area explored that is 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. The
scope is based on GeoTek’s understanding of the project and the client’s needs, GeoTek’s
proposal (Proposal No. P-0801323-SD) dated August 30, 2023 and geotechnical engineering
standards normally used on similar projects in this region.
The materials observed on the project site appear to be representative of the area; however, soil
and bedrock 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 GeoTek’s recommendations 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
RINCON HOMES Project No. 3948-SD
Preliminary Geotechnical Evaluation Lot 39 October 13, 2023
APN 203-023-06-00, Carlsbad, California 92008 Page 14
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.
RINCON HOMES Project No. 3948-SD
Preliminary Geotechnical Evaluation Lot 39 October 13, 2023
APN 203-023-06-00, Carlsbad, California 92008 Page 15
7. SELECTED REFERENCES
American Society of Civil Engineers (ASCE), 2022, “Minimum Design Loads for Buildings and
Other Structures,” ASCE/SEI 7-16.
____, 2021, ASCE-7 Hazard Tool, https://asce7hazardtool.online.
ASTM International (ASTM), “ASTM Volumes 4.08 and 4.09 Soil and Rock.”
Bryant, W.A., and Hart, E.W., 2007, "Fault Rupture Hazard Zones in California, Alquist-Priolo
Earthquake Fault Zoning Act with Index to Earthquake Fault 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.
GeoTek, Inc., In-house proprietary information.
Kennedy, M.P., and Tan, S.S., 2008, “Geologic Map of the Oceanside 30x60-minute Quadrangle,
California,” California Geological Survey, Regional Geologic Map No. 2, map scale
1:100,000.
Kirk Moeller Architects, Inc., Conceptual Site Plan, Normandy Beach Homes, 260 Normandy
Lane – Lot 38, Carlsbad, CA 92008, dated August 23, 2023.
Terzaghi, K. and Peck, R., 1967, “Soil Mechanics in Engineering Practice”, second edition.
1384 Poinsettia Avenue, Suite A, Vista, CA 92081
(760) 599-0509 (phone) / (760) 599-0593 (FAX)
GEOTECHNICAL | ENVIRONMENTAL | MATERIALS
10/13/23
FIGURE 1
SITE LOCATION MAP
NORMANDY LOT 39
APN 203-023-06-00
CARLSBAD, CALIFORNIA
Project No.:Report Date:Drawn By:
3948-SD CDL
N
SITE
Source: Kirk Moeller Architects, Inc.
Scale:
1384 Poinsettia Avenue, Suite A, Vista, CA 92081
(760) 599-0509 (phone) / (760) 599-0593 (FAX)
GEOTECHNICAL | ENVIRONMENTAL | MATERIALS
09/12/23
FIGURE 2
GEOTECHNICAL MAP
NORMANDY LOT 39
APN 203-023-06-00
CARLSBAD, CALIFORNIA
Project No.:Report Date:Drawn By:
3948-SD CDL
N
EXPLANATION
Qop
Approximate Location of Exploration Boring
Old Paralic Deposits
Approximate Limits of Report
HA-1
HA-2
Qop
APPENDIX A
LOGS OF EXPLORATION
RINCON HOMES Project No. 3948-SD
Preliminary Geotechnical Evaluation Lot 39 October 13, 2023
APN 203-023-06-00, Carlsbad, California 92008 Page A-1
A - FIELD TESTING AND SAMPLING PROCEDURES
Loose Bulk Samples (Large)
These samples are normally large bags of earth materials over 20 pounds in weight collected
from the field by means of hand digging or exploratory cuttings.
B – BORING/TRENCH LOG LEGEND
The following abbreviations and symbols often appear in the classification and description of soil
and rock on the logs of borings/trenches:
SOILS
USCS Unified Soil Classification System
f-c Fine to coarse
f-m Fine to medium
GEOLOGIC
B: Attitudes Bedding: strike/dip
J: Attitudes Joint: strike/dip
C: Contact line
……….. Dashed line denotes USCS material change
Solid Line denotes unit / formational change
Thick solid line denotes end of boring/trench
(Additional denotations and symbols are provided on the log of borings/trenches)
GeoTek, Inc.
LOG OF EXPLORATORY BORING
BB-1 EI, SR
22 R-1
42
#
---Small Bulk ---No Recovery ---Water Table
PROJECT NAME:Normandy Lot 39 DRILL METHOD:Boring OPERATOR:CDL
CLIENT:Rincon Homes DRILLER:GeoTek, Inc.LOGGED BY:CDL
LOCATION:Carlsbad, CA ELEVATION:43 feet MSL DATE:8/31/2023
PROJECT NO.:3948-SD HAMMER:35 pounds RIG TYPE:Manual Auger
SAMPLES
US
C
S
S
y
m
b
o
l
BORING NO.: HA-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
(%
)
Old Paralic Deposits (Qop)
Silty Fine SAND (weathered), reddish brown, moist, loose, yields to soil probe 4 feet
Dr
y
D
e
n
s
i
t
y
(p
c
f
)
Ot
h
e
r
s
MATERIAL DESCRIPTION AND COMMENTS
Surface: Grass over 2 inches of topsoil over
Noticeable resistance in auger advancement, firm and unyielding to soil probe
5 Poorly developed pedogenic facies
Practical Refusal
15
Backfilled with adjacent soil
HOLE TERMINATED AT 7 FEET
10 No groundwater encountered
20
25
RV = R-Value Test
SR = Sulfate/Resisitivity Test SH = Shear Test CO = Consolidation test MD = Maximum Density
30
LE
G
E
N
D
Sample type: ---Ring ---SPT ---Large Bulk
Lab testing:AL = Atterberg Limits EI = Expansion Index SA = Sieve Analysis
GeoTek, Inc.
LOG OF EXPLORATORY BORING
#
---Small Bulk ---No Recovery ---Water Table
PROJECT NAME:Normandy Lot 39 DRILL METHOD:Boring OPERATOR:CDL
CLIENT:Rincon Homes DRILLER:GeoTek, Inc.LOGGED BY:CDL
LOCATION:Carlsbad, CA ELEVATION:43 feet MSL DATE:8/31/2023
PROJECT NO.:3948-SD HAMMER:35 pounds RIG TYPE:Manual Auger
Dr
y
D
e
n
s
i
t
y
(p
c
f
)
Ot
h
e
r
s
MATERIAL DESCRIPTION AND COMMENTS
Surface: Soil and scattered fertilizer
SAMPLES
US
C
S
S
y
m
b
o
l
BORING NO.: HA-2
Laboratory Testing
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Blo
w
s
/
6
i
n
Sa
m
p
l
e
Nu
m
b
e
r
Wa
t
e
r
C
o
n
t
e
n
t
(%
)
Old Paralic Deposits (Qop)
Silty Fine SAND (weathered), reddish brown, moist, loose, yields to soil probe 4 feet
5 Noticeable resistance in auger advancement, firm and unyielding to soil probe
Practical Refusal
HOLE TERMINATED AT 6.5 FEET
10 No groundwater encountered
Backfilled with adjacent soil
15
20
25
AL = Atterberg Limits EI = Expansion Index SA = Sieve Analysis RV = R-Value Test
SR = Sulfate/Resisitivity Test SH = Shear Test CO = Consolidation test MD = Maximum Density
30
LE
G
E
N
D
Sample type: ---Ring ---SPT ---Large Bulk
Lab testing:
APPENDIX B
RESULTS OF LABORATORY TESTING
RINCON HOMES Project No. 3948-SD
Preliminary Geotechnical Evaluation Lot 39 October 13, 2023
APN 203-023-06-00, Carlsbad, California 92008 Page B-1
SUMMARY OF LABORATORY TESTING
Identification and Classification
Soils were identified visually in general accordance with the standard practice for description and
identification of soils (ASTM D2488). The soil identifications and classifications are shown on the logs of
exploratory trenches in Appendix A.
Expansion Index Test
Expansion Index testing was performed on one sample collected during the subsurface exploration. The
expansion index was determined in general accordance with test method ASTM Test Procedure D 4829.
The test results are presented in Appendix B.
Sulfate Content
Sample are tested through GeoTek’s subconsultant Project X Engineering. The results of the testing are
presented in Appendix B.
Ring #: Ring Dia. :Ring Ht.:1"
Weight of compacted sample & ring (gm)
Weight of ring (gm)
Net weight of sample (gm)
Moisture Content, %
Specific Gravity, assumed
Unit Wt. of Water @ 20°C, (pcf)
% Saturation
EXPANSION INDEX =0
821.9 13.1
62.4
51.7 FINAL MOISTURE
Final Weight of wet
sample & tare % Moisture
2.70 9/13/2023 10:30 0.1220 Final
7.8 9/12/2023 10:45 0.1220 Random
1 min/Wet
SATURATION DETERMINATION 9/12/2023 9:31 0.1220 5 min/Wet
Dry Density, lb / ft3 (D/1.F)119.7 9/12/2023 9:26 0.1230
Wet Density, lb / ft3 (C*0.3016)129.1 9/12/2023 9:25 0.1240 10 min/Dry
428.0 9/12/2023 9:15 0.1240 Initial
DENSITY DETERMINATION
799.1 READINGS
371.1 DATE TIME READING
Sample Description:Brown Silty Fine Sand
1 4.01"
Project Number:3948-SD Date Tested:9/12/2023
Project Location:Normandy Lot 39 Sample Source:HA-1, BB-1 @ 0-4'
EXPANSION INDEX TEST
(ASTM D4829)
Client:Rincon Homes Tested/ Checked By:CDL Lab No 3986
Project X REPORT S230905E 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
Normandy Lot 39
September 6, 2023
Prepared for:
Lesley White GeoTek, Inc.
1384 Poinsettia Ave, Suite A
Vista, CA, 92081 lwhite@geotekusa.com
Project X Job#: S230905E Client Job or PO#: 3948-SD
Respectfully Submitted, Eduardo Hernandez, M.Sc., P.E. Sr. Corrosion Consultant
NACE Corrosion Technologist #16592 Professional Engineer California No. M37102
ehernandez@projectxcorrosion.com
Project X REPORT S230905E 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: Normandy Lot 39 Client Job Number: 3948-SD Project X Job Number: S230905E September 6, 2023
Method
Bore# /
Description
Depth
(ft)(mg/kg)(wt%)(mg/kg)(wt%)
BB-1 0-4 23.3 0.0023 22.2 0.0022
ASTM
D4327
ASTM
D4327
Sulfates
SO42-
Chlorides
Cl-
Cations and Anions, except Sulfide and Bicarbonate, tested with Ion Chromatography mg/kg = milligrams per kilogram (parts per million) of dry soil weight ND = 0 = Not Detected | NT = Not Tested | Unk = Unknown Chemical Analysis performed on 1:3 Soil-To-Water extract PPM = mg/kg (soil) = mg/L (Liquid) Note: Sometimes a bad sulfate hit is a contaminated spot. Typical fertilizers are Potassium chloride, ammonium sulfate or ammonium sulfate nitrate (ASN). So this is another reason why testing full corrosion series is good because we then have the data to see if those other ingredients are present meaning the soil sample is just fertilizer-contaminated soil. This can happen often when the soil samples collected are simply surface scoops which is why it's best to dig in a foot, throw away the top and test the deeper stuff. Dairy farms are also notorious for these items.
ProjectyCorrosionEngineeringr^Ccimnion ('«Hitrol -Wgtrr.jmJ %tcullutx>t
X Lab Request Sheet Chain ofCustody
Phone:(213)928-7213 ●Fax (951)226-1720 ●www.projectxcoirosion.com
Ship Samples To:29990 Technology Dr,Suite 13,Murrieta,CA 92563
Project X Job Number cfigtoTPV--
IMPORTANT:Please complete Project and Sample Identification Data as you would like it to appear in report &include this form with samples.
GeoTek,Inc.Lesley White Phone No:760-599-0509CompanyName:Contact Name:
1384 Poisettia Ave,Suite A,Vista,CA 92081 lwhite@geotekusa.comMailingAddress:Contact Email:
Suzen Clark ap@geotekusa.comAccountingContact:Invoice Email:
aient Project No;M 0
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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, Chapters 18
and 33 of the California Building Code, CBC (2022) and the guidelines presented below.
Preconstruction Meeting
A preconstruction meeting should be held prior to site earthwork. Any questions the contractor has
regarding our recommendations, general site conditions, apparent discrepancies between reported and
actual conditions and/or differences in procedures the contractor intends to use should be brought up
at that meeting. The contractor (including the main onsite representative) should review our report
and these guidelines in advance of the meeting. Any comments the contractor may have regarding these
guidelines should be brought up at that meeting.
Grading Observation and Testing
1. Observation of the fill placement should be provided by our representative during grading.
Verbal communication during the course of each day will be used to inform the contractor of
test results. The contractor should receive a copy of the "Daily Field Report" indicating results
of field density tests that day. If our representative does not provide the contractor with these
reports, our office should be notified.
2. Testing and observation procedures are, by their nature, specific to the work or area observed
and location of the tests taken, variability may occur in other locations. The contractor is
responsible for the uniformity of the grading operations; our observations and test results are
intended to evaluate the contractor’s overall level of efforts during grading. The contractor’s
personnel are the only individuals participating in all aspect of site work. Compaction testing
and observation should not be considered as relieving the contractor’s responsibility to properly
compact the fill.
3. Cleanouts, processed ground to receive fill, key excavations, and subdrains should be observed
by our representative prior to placing any fill. It will be the contractor's responsibility to notify
our representative or office when such areas are ready for observation.
4. Density tests may be made on the surface material to receive fill, as considered warranted by
this firm.
5. In general, density tests would be made at maximum intervals of two feet of fill height or every
1,000 cubic yards of fill placed. Criteria will vary depending on soil conditions and size of the fill.
More frequent testing may be performed. In any case, an adequate number of field density tests
should be made to evaluate the required compaction and moisture content is generally being
obtained.
6. Laboratory testing to support field test procedures will be performed, as considered warranted,
based on conditions encountered (e.g. change of material sources, types, etc.) Every effort will
GENERAL GRADING GUIDELINES APPENDIX C
Page C-2
be made to process samples in the laboratory as quickly as possible and in progress construction
projects are our first priority. However, laboratory workloads may cause in delays and some
soils may require a minimum of 48 to 72 hours to complete test procedures.
Whenever possible, our representative(s) should be informed in advance of operational changes
that might result in different source areas for materials.
7. Procedures for testing of fill slopes are as follows:
a) Density tests should be taken periodically during grading on the flat surface of the fill,
three to five feet horizontally from the face of the slope.
b) If a method other than over building and cutting back to the compacted core is to be
employed, slope compaction testing during construction should include testing the outer
six inches to three feet in the slope face to determine if the required compaction is
being achieved.
8. Finish grade testing of slopes and pad surfaces should be performed after construction is
complete.
Site Clearing
1. All vegetation, and other deleterious materials, should be removed from the site. If material is
not immediately removed from the site it should be stockpiled in a designated area(s) well
outside of all current work areas and delineated with flagging or other means. Site clearing
should be performed in advance of any grading in a specific area.
2. Efforts should be made by the contractor to remove all organic or other deleterious material
from the fill, as even the most diligent efforts may result in the incorporation of some materials.
This is especially important when grading is occurring near the natural grade. All equipment
operators should be aware of these efforts. Laborers may be required as root pickers.
3. Nonorganic debris or concrete may be placed in deeper fill areas provided the procedures used
are observed and found acceptable by our representative.
Treatment of Existing Ground
1. Following site clearing, all surficial deposits of alluvium and colluvium as well as weathered or
creep effected bedrock, should be removed unless otherwise specifically indicated in the text of
this report.
2. In some cases, removal may be recommended to a specified depth (e.g. flat sites where partial
alluvial removals may be sufficient). The contractor should not exceed these depths unless
directed otherwise by our representative.
3. Groundwater existing in alluvial areas may make excavation difficult. Deeper removals than
indicated in the text of the report may be necessary due to saturation during winter months.
4. Subsequent to removals, the natural ground should be processed to a depth of six inches,
moistened to near optimum moisture conditions and compacted to fill standards.
5. Exploratory back hoe or dozer trenches still remaining after site removal should be excavated
and filled with compacted fill if they can be located.
Fill Placement
1. Unless otherwise indicated, all site soil and bedrock may be reused for compacted fill; however,
some special processing or handling may be required (see text of report).
2. Material used in the compacting process should be evenly spread, moisture conditioned,
processed, and compacted in thin lifts six (6) to eight (8) inches in compacted thickness to
GENERAL GRADING GUIDELINES APPENDIX C
Page C-3
obtain a uniformly dense layer. The fill should be placed and compacted on a nearly horizontal
plane, unless otherwise found acceptable by our representative.
3. If the moisture content or relative density varies from that recommended by this firm, the
contractor should rework the fill until it is in accordance with the following:
a) Moisture content of the fill should be at or above optimum moisture. Moisture should
be evenly distributed without wet and dry pockets. Pre-watering of cut or removal
areas should be considered in addition to watering during fill placement, particularly in
clay or dry surficial soils. The ability of the contractor to obtain the proper moisture
content will control production rates.
b) Each six-inch layer should be compacted to at least 90 percent of the maximum dry
density in compliance with the testing method specified by the controlling governmental
agency. In most cases, the testing method is ASTM Test Designation D 1557.
4. Rock fragments less than eight inches in diameter may be utilized in the fill, provided:
a) They are not placed in concentrated pockets;
b) There is a sufficient percentage of fine-grained material to surround the rocks;
c) The distribution of the rocks is observed by, and acceptable to, our representative.
5. Rocks exceeding eight (8) inches in diameter should be taken off site, broken into smaller
fragments, or placed in accordance with recommendations of this firm in areas designated
suitable for rock disposal. On projects where significant large quantities of oversized materials
are anticipated, alternate guidelines for placement may be included. If significant oversize
materials are encountered during construction, these guidelines should be requested.
6. In clay soil, dry or large chunks or blocks are common. If in excess of eight (8) inches minimum
dimension, then they are considered as oversized. Sheepsfoot compactors or other suitable
methods should be used to break up blocks. When dry, they should be moisture conditioned to
provide a uniform condition with the surrounding fill.
Slope Construction
1. The contractor should obtain a minimum relative compaction of 90 percent out to the finished
slope face of fill slopes. This may be achieved by either overbuilding the slope and cutting back
to the compacted core, or by direct compaction of the slope face with suitable equipment.
2. Slopes trimmed to the compacted core should be overbuilt by at least three (3) feet with
compaction efforts out to the edge of the false slope. Failure to properly compact the outer
edge results in trimming not exposing the compacted core and additional compaction after
trimming may be necessary.
3. If fill slopes are built "at grade" using direct compaction methods, then the slope construction
should be performed so that a constant gradient is maintained throughout construction. Soil
should not be "spilled" over the slope face nor should slopes be "pushed out" to obtain grades.
Compaction equipment should compact each lift along the immediate top of slope. Slopes
should be back rolled or otherwise compacted at approximately every 4 feet vertically as the
slope is built.
4. Corners and bends in slopes should have special attention during construction as these are the
most difficult areas to obtain proper compaction.
5. Cut slopes should be cut to the finished surface. Excessive undercutting and smoothing of the
face with fill may necessitate stabilization.
GENERAL GRADING GUIDELINES APPENDIX C
Page C-4
UTILITY TRENCH CONSTRUCTION AND BACKFILL
Utility trench excavation and backfill is the contractors responsibility. The geotechnical consultant
typically provides periodic observation and testing of these operations. While efforts are made to make
sufficient observations and tests to verify that the contractors’ methods and procedures are adequate to
achieve proper compaction, it is typically impractical to observe all backfill procedures. As such, it is
critical that the contractor use consistent backfill procedures.
Compaction methods vary for trench compaction and experience indicates many methods can be
successful. However, procedures that “worked” on previous projects may or may not prove effective
on a given site. The contractor(s) should outline the procedures proposed, so that we may discuss
them prior to construction. We will offer comments based on our knowledge of site conditions and
experience.
1. Utility trench backfill in slopes, structural areas, in streets and beneath flat work or hardscape
should be brought to at least optimum moisture and compacted to at least 90 percent of the
laboratory standard. Soil should be moisture conditioned prior to placing in the trench.
2. Flooding and jetting are not typically recommended or acceptable for native soils. Flooding or
jetting may be used with select sand having a Sand Equivalent (SE) of 30 or higher. This is
typically limited to the following uses:
a) shallow (12 + inches) under slab interior trenches and,
b) as bedding in pipe zone.
The water should be allowed to dissipate prior to pouring slabs or completing trench
compaction.
3. Care should be taken not to place soils at high moisture content within the upper three feet of
the trench backfill in street areas, as overly wet soils may impact subgrade preparation.
Moisture may be reduced to 2% below optimum moisture in areas to be paved within the upper
three feet below sub grade.
4. Sand backfill should not be allowed in exterior trenches adjacent to and within an area
extending below a 1:1 projection from the outside bottom edge of a footing, unless it is similar
to the surrounding soil.
5. Trench compaction testing is generally at the discretion of the geotechnical consultant. Testing
frequency will be based on trench depth and the contractors procedures. A probing rod would
be used to assess the consistency of compaction between tested areas and untested areas. If
zones are found that are considered less compact than other areas, this would be brought to
the contractors attention.
JOB SAFETY
General
Personnel safety is a primary concern on all job sites. The following summaries are safety considerations
for use by all our employees on multi-employer construction sites. On ground personnel are at highest
risk of injury and possible fatality on grading construction projects. The company recognizes that
construction activities will vary on each site and that job site safety is the contractor's responsibility.
However, it is, imperative that all personnel be safety conscious to avoid accidents and potential injury.
In an effort to minimize risks associated with geotechnical testing and observation, the following
precautions are to be implemented for the safety of our field personnel on grading and construction
projects.
GENERAL GRADING GUIDELINES APPENDIX C
Page C-5
1. Safety Meetings: Our field personnel are directed to attend the contractor's regularly scheduled
safety meetings.
2. Safety Vests: Safety vests are provided for and are to be worn by our personnel while on the job
site.
3. Safety Flags: Safety flags are provided to our field technicians; one is to be affixed to the vehicle
when on site, the other is to be placed atop the spoil pile on all test pits.
In the event that the contractor's representative observes any of our personnel not following the above,
we request that it be brought to the attention of our office.
Test Pits Location, Orientation and Clearance
The technician is responsible for selecting test pit locations. The primary concern is the technician's
safety. However, it is necessary to take sufficient tests at various locations to obtain a representative
sampling of the fill. As such, efforts will be made to coordinate locations with the grading contractors
authorized representatives (e.g. dump man, operator, supervisor, grade checker, etc.), and to select
locations following or behind the established traffic pattern, preferably outside of current traffic. The
contractors authorized representative should direct excavation of the pit and safety during the test
period. Again, safety is the paramount concern.
Test pits should be excavated so that the spoil pile is placed away from oncoming traffic. The
technician's vehicle is to be placed next to the test pit, opposite the spoil pile. This necessitates that the
fill be maintained in a drivable condition. Alternatively, the contractor may opt to park a piece of
equipment in front of test pits, particularly in small fill areas or those with limited access.
A zone of non-encroachment should be established for all test pits (see diagram below). No grading
equipment should enter this zone during the test procedure. The zone should extend outward to the
sides approximately 50 feet from the center of the test pit and 100 feet in the direction of traffic flow.
This zone is established both for safety and to avoid excessive ground vibration, which typically
decreases test results.
50 ft Zone of
Non-Encroachment
50 ft Zone of
Non-Encroachment
Traffic Direction
Vehicle
parked here Test Pit Spoil
pile
Spoil
pile
Test Pit
SIDE VIEW
PLAN VIEW
TEST PIT SAFETY PLAN
10 0 ft Zone of
Non-Encroachment
GENERAL GRADING GUIDELINES APPENDIX C
Page C-6
Slope Tests
When taking slope tests, the technician should park their vehicle directly above or below the test
location on the slope. The contractor's representative should effectively keep all equipment at a safe
operation distance (e.g. 50 feet) away from the slope during testing.
The technician is directed to withdraw from the active portion of the fill as soon as possible following
testing. The technician's vehicle should be parked at the perimeter of the fill in a highly visible location.
Trench Safety
It is the contractor's responsibility to provide safe access into trenches where compaction testing is
needed. Trenches for all utilities should be excavated in accordance with CAL-OSHA and any other
applicable safety standards. Safe conditions will be required to enable compaction testing of the trench
backfill.
All utility trench excavations in excess of 5 feet deep, which a person enters, are to be shored or laid
back. Trench access should be provided in accordance with OSHA standards. Our personnel are
directed not to enter any trench by being lowered or "riding down" on the equipment.
Our personnel are directed not to enter any excavation which;
1. is 5 feet or deeper unless shored or laid back,
2. exit points or ladders are not provided,
3. displays any evidence of instability, has any loose rock or other debris which could fall into the
trench, or
4. displays any other evidence of any unsafe conditions regardless of depth.
If the contractor fails to provide safe access to trenches for compaction testing, our company policy
requires that the soil technician withdraws and notifies their supervisor. The contractors representative
will then be contacted in an effort to effect a solution. All backfill not tested due to safety concerns or
other reasons is subject to reprocessing and/or removal.
Procedures
In the event that the technician's safety is jeopardized or compromised as a result of the contractor's
failure to comply with any of the above, the technician is directed to inform both the developer's and
contractor's representatives. If the condition is not rectified, the technician is required, by company
policy, to immediately withdraw and notify their supervisor. The contractor’s representative will then
be contacted in an effort to effect a solution. No further testing will be performed until the situation is
rectified. Any fill placed in the interim can be considered unacceptable and subject to reprocessing,
recompaction or removal.
In the event that the soil technician does not comply with the above or other established safety
guidelines, we request that the contractor bring this to technicians attention and notify our project
manager or office. Effective communication and coordination between the contractors' representative
and the field technician(s) is strongly encouraged in order to implement the above safety program and
safety in general.
The safety procedures outlined above should be discussed at the contractor's safety meetings. This will
serve to inform and remind equipment operators of these safety procedures particularly the zone of
non-encroachment.
GENERAL GRADING GUIDELINES APPENDIX C
Page C-7
The safety procedures outlined above should be discussed at the contractor's safety meetings. This will
serve to inform and remind equipment operators of these safety procedures particularly the zone of
non-encroachment.