HomeMy WebLinkAboutCDP 2020-0017; SAREM RESIDENCE; PRELIMINARY GEOTECHNICAL EVALUATION PROPOSED TWO STORY RESIDENCE; 2020-05-11PRELIMINARY GEOTECHNICAL EVALUATION
PROPOSED TWO-STORY RESIDENCE, 4005 SKYLINE ROAD, APN 207-072-17-00
CITY OF CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA
MR. SCOTT SAREM
May 11, 2020
J.N. 20-155
ENGINEERS + GEOLOGISTS + ENVIRONMENTAL SCIENTISTS
Offices Strategically Positioned Throughout Southern California
RIVERSIDE COUNTY OFFICE 40880 County Center Drive, Suite M, CA 92591
T: 951.253.4458
For more information visit us online at www.petra-inc.com
May 11, 2020
J.N. 20-155
MR. SCOTT SAREM
6684 Lemon Leaf Drive
Carlsbad, California 920011
Subject: Preliminary Geotechnical Evaluation, Proposed Two-Story Residence, 4005 Skyline
Road, APN 207-072-17-00, City of Carlsbad, San Diego County, California
Dear Mr. Sarem:
Petra Geosciences, Inc. (Petra) is submitting herewith our preliminary geotechnical evaluation report for
the proposed construction of a two-story residence within the subject site. This work was performed in
accordance with the scope of work outlined in our Proposal No. 20-155P, dated March 5, 2020. This report
presents the results of our field investigation, laboratory testing, and our engineering and geologic
judgment, opinions, conclusions, and recommendations pertaining to the geotechnical design aspects of the
proposed development.
It has been a pleasure to be of service to you on this project. If you have any questions regarding the contents
of this report or require additional information, please do not hesitate to contact us.
Respectfully submitted,
PETRA GEOSCIENCES, INC.
Jim Larwood, CEG
Principal Geologist
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
TABLE OF CONTENTS
Page
PURPOSE AND SCOPE OF SERVICES ..................................................................................................................... 1
LOCATION AND SITE DESCRIPTION ..................................................................................................................... 1
PROPOSED CONSTRUCTION AND GRADING ...................................................................................................... 2
FIELD EXPLORATION ............................................................................................................................................... 2
Laboratory Testing .............................................................................................................................................3
FINDINGS .................................................................................................................................................................... 3
Regional and Local Geology ..............................................................................................................................3
Subsurface Soil Conditions ................................................................................................................................3
Groundwater .......................................................................................................................................................4
Faulting ..............................................................................................................................................................4
Secondary Seismic Effects .................................................................................................................................5
CONCLUSIONS AND RECOMMENDATIONS ........................................................................................................ 5
General Feasibility ...................................................................................................................................................5
Grading Plan Review ...............................................................................................................................................6
Earthwork and Grading ............................................................................................................................................6
General Specifications .......................................................................................................................................6
Geotechnical Observations and Testing During Grading ...................................................................................6
Site Clearing .......................................................................................................................................................6
Existing Septic System .......................................................................................................................................6
Ground Preparation – Building Pad Area ...........................................................................................................7
Ground Preparation – Driveway and Hardscape Areas ......................................................................................7
Excavation Characteristics .................................................................................................................................8
Stability of Temporary Excavation Sidewalls ....................................................................................................8
Benching ............................................................................................................................................................8
Fill Placement ....................................................................................................................................................9
Imported Soils ....................................................................................................................................................9
Slope Construction ...................................................................................................................................................9
Fill Slopes ..........................................................................................................................................................9
Cut Slopes ..........................................................................................................................................................9
PRELIMINARY FOUNDATION DESIGN CONSIDERATIONS ............................................................................ 10
Seismic Design Parameters .............................................................................................................................. 10
Discussion - General ........................................................................................................................................ 12
Allowable Soil Bearing Capacities................................................................................................................... 13
Continuous Footings ........................................................................................................................................ 13
Estimated Footing Settlement .......................................................................................................................... 13
Lateral Resistance ............................................................................................................................................ 13
Guidelines for Slab-on-Ground Foundation Design and Construction .................................................................. 14
Conventional Slab-on-Grade System ............................................................................................................... 14
Foundation Excavation Observations ............................................................................................................... 16
General Corrosivity Screening ............................................................................................................................... 17
Retaining Wall Design and Construction Considerations ...................................................................................... 18
Active and At-Rest Earth Pressures ................................................................................................................. 18
Backdrains ........................................................................................................................................................ 19
Waterproofing .................................................................................................................................................. 19
Wall Backfill .................................................................................................................................................... 20
Geotechnical Observation and Testing ............................................................................................................. 20
Masonry Block Walls (Non-Retaining) ................................................................................................................. 21
Planter Walls .......................................................................................................................................................... 21
Swimming Pool and Spa Recommendations ......................................................................................................... 21
Allowable Bearing, Settlement, and Lateral Earth Pressures ........................................................................... 21
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
TABLE OF CONTENTS
Page
Temporary Access Ramps ................................................................................................................................ 22
Plumbing Fixtures ............................................................................................................................................ 22
Pool and Spa Decking ...................................................................................................................................... 22
Post-Grading Considerations ................................................................................................................................. 22
Utility Trenches ................................................................................................................................................ 22
Site Drainage .................................................................................................................................................... 23
Exterior Concrete Flatwork .................................................................................................................................... 23
General ............................................................................................................................................................. 23
Thickness and Joint Spacing ............................................................................................................................ 24
Reinforcement .................................................................................................................................................. 24
Edge Beams (Optional) .................................................................................................................................... 24
Subgrade Preparation ....................................................................................................................................... 25
Drainage ........................................................................................................................................................... 25
Tree Wells ........................................................................................................................................................ 25
GRADING PLAN REVIEW AND FUTURE IMPROVEMENTS ............................................................................. 26
REPORT LIMITATIONS ........................................................................................................................................... 26
REFERENCES ............................................................................................................................................................ 28
ATTACHMENTS
FIGURES RW-1 through RW-3
FIGURE 1 – SITE LOCATION MAP
FIGURE 2 - GEOTECHNICAL MAP
PLATE A-1– LOGS OF TEST PITS
APPENDIX A – LABORATORY TEST PROCEDURES / LABORATORY DATA SUMMARY
APPENDIX B – SEISMIC DESIGN PARAMETERS
APPENDIX C – STANDARD EARTHWORK CONSTRUCTION
PRELIMINARY GEOTECHNICAL EVALUATION
PROPOSED TWO-STORY RESIDENCE, 4005 SKYLINE ROAD, APN 207-072-17-00
CITY OF CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA
PURPOSE AND SCOPE OF SERVICES
Petra Geosciences, Inc. (Petra) is presenting herein the results of our geotechnical evaluation for the
subject property. The purposes of this investigation are to obtain information regarding surface and
subsurface geologic conditions within the general project area, evaluate the engineering properties of the
onsite soil materials and to provide conclusions as to the feasibility of the proposed improvements and
recommendations for site remedial grading, as well as the design and construction of the proposed residence
and site improvements. To accomplish these objectives, our scope of services includes the following:
1. Review of available published and unpublished literature and maps pertaining to regional faulting,
seismic hazards and soil and geologic conditions within and adjacent to the site that could have an
impact on the proposed development.
2. Excavating, sampling, and logging four (4) exploratory test pits to depths ranging from 3 to 6 feet
below the ground surface within portions of the site (Plates A-1 and A-2).
3. Performing laboratory testing on representative samples of earth materials obtained from the test
pits to determine their engineering properties.
4. Engineering and geologic analyses of the field and laboratory data as they pertain to the proposed
construction.
5. Preparation of this report presenting our findings, conclusions and recommendations for site
grading and design of building foundation systems.
LOCATION AND SITE DESCRIPTION
The 0.59-acre site is located on the western side of Skyline Road, approximately 750 feet north of Tamarack
Avenue in the city of Carlsbad. The property is identified as San Diego County Assessor Parcel Number
(APN) APN 207-072-17-00. The general location of the site is shown on Figure 1. The narrow, semi-
rectangular-shaped lot is bounded on the north, west and south by single-family residential homes and
Skyline Road to the east. The lot slopes downward at a gentle gradient from Skyline Road, towards the rear
of the lot to the west. Elevations of the site ranges from approximately 307 feet above mean sea level (msl)
at the east side to 277 feet msl along the west property boundary for an overall topographic relief of 30 feet.
The subject lot is occupied by a one-story home with perimeter fencing, wood deck off the rear of the house
and, possibly, a backyard septic system. A water meter box and gas service are located at the south side of
the driveway. Overhead electrical enters the site from a power pole at the north end of the driveway. The
majority of the front yard is landscaped, whereas the backyard is generally covered by grasses and some
succulents. An elevated swimming pool is located near the northern property line.
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
Page 2
PROPOSED CONSTRUCTION AND GRADING
Based on the architectural site plan prepared by B+D Studio (B+D) dated February 28, 2020, it is our
understanding that the proposed development will consist of a split-level two-story residence, attached
garage and a connecting deck. To accommodate the split level, interior retaining walls from 1.5 feet up to
5 feet in height are proposed. Appurtenant improvements are expected to include a paved driveway, below-
ground utilities, hardscape flatwork and landscaping.
It is anticipated that the residence will be of typical wood-frame construction with concrete slabs
constructed on-grade. For this type of construction, it is anticipated that relatively light foundation loads
will be imposed on the subgrade soils. We understand that grading plans have not yet been developed for
the site. Based on site plans provided by B+D, finish floor elevations are proposed at 299.0, 300.5 and 305.5
feet msl within the house and attached garage. Given the floor elevations of the proposed residence,
earthwork within the site is generally expected to entail cuts and/or fills ranging from approximately 1 to 5
feet from existing grades. It should be noted, however, that remedial grading (i.e., removal and re-
compaction of existing unsuitable surficial soils) will entail deeper cuts from existing grades as
recommended in subsequent sections of this report. Other proposed site improvements may include
swimming pool, spa, patio, barbeque pit, concrete flatwork, and landscaping. Recommendations for site
grading, and for the design and construction of building foundations, are presented in the “Conclusions and
Recommendations” section of this report.
FIELD EXPLORATION
Our subsurface exploration was performed on April 15, 2020 and consisted of the excavation of four
exploratory test pits (TP-1 to TP-4) with a mini-excavator to depths ranging from 3 to 6 feet below the
existing ground surface (bgs). The locations of our test pits are shown on the Geotechnical Map, Figure 2.
Test pit logs are included as Plates A-1 and A-2. General descriptions of the soil materials encountered are
provided in the Subsurface Soil Conditions section. Earth materials encountered in each of the exploratory
test pits were field classified and logged in accordance with Unified Soil Classification System (USCS)
procedures. In addition, our subsurface exploration included the collection of bulk samples of the
subsurface soils for laboratory testing purposes and in-situ density testing using a nuclear gauge. The
samples were placed in sealed bags and transported to our laboratory for testing. The test pits were loosely
backfilled with the excavated soil cuttings.
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
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Laboratory Testing
To evaluate the engineering properties of the onsite soils, several laboratory tests were performed on
selected samples considered representative of the materials encountered during our exploration. Laboratory
tests included the determination of expansion potential, soluble sulfate and chloride content, soil pH,
minimum resistivity, and maximum dry density. A description of laboratory test methods and test data is
provided in Appendix A.
FINDINGS
Regional and Local Geology
The site is located in the Peninsular Ranges Geomorphic Province of California. The Peninsular Range
Province is characterized by northwest trending mountain ranges separated by a series of subparallel fault
zones associated with the San Andreas Fault System. The mountain ranges consist generally of Cretaceous
igneous rocks of the Southern California Batholith and Jurassic meta-sediments and meta-volcanics.
Younger sediments flank the mountain ranges to the southwest along the coastal plain. The sediments
flanking the mountains along the coastal plain consist of Tertiary and Quaternary marine, non-marine and
lagoonal deposits, with several local areas deformed by tectonics.
The subject site is situated near the top of the easterly flank of an elevated terrace running parallel to the
Pacific Ocean, north of the Agua Hedionda Lagoon. Regional geologic mapping by Kennedy and Tan
(2005) shows the site is underlain by middle to early Pleistocene-age very old paralic deposits generally of
playa, lacustrine and estuarine depositional environment (map symbol: Qvol). Underlying Qvol are well
indurated Tertiary-aged sandstone, conglomerate and siltstone bedrock belonging to the Santiago
Formation (map symbol: Tss).
Subsurface Soil Conditions
Undocumented artificial fill (map symbol: afu) and topsoil, consisting of loose, moist to wet, dark brown
silty fine to medium grained sand with some organics, was encountered in each test pit to a depth of up to
approximately 2 feet bgs. Qvol (referred to herein as terrace deposits) was observed in each test pit,
consisting of massively bedded, reddish brown with some iron oxide staining, moist to wet, dense to very
dense, weathered to slightly weathered fine- to coarse-grained sandstone. The clay content of the sandstone
increased with depth to the maximum depth of the test pits, up to 6 ft bgs.
Evidence of existing septic leach lines was encountered within the test pits TP-2 and TP-4. The leach lines,
where encountered, were characterized by north-south trending clay pipe encapsulated by 1- to 3-inch
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
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diameter, rounded gravel. The pipe was about 2 to 2.5 feet bgs. Some water was seen in the gravel and pipe.
Each line of pipe appeared to be laterally separated 10 feet. The clay pipe connections were found to be
loosely attached to allow for seepage. The assumed septic tank may be located beneath the cluster of
succulents along the northwest side of the exiting building but was not confirmed. The approximate location
of leach lines and septic tank are shown on Figure 2.
It is important to understand that during the previous week before conducting this investigation, the
Carlsbad area experienced a record amount of rainfall of about 6 inches. The soil at the site is relatively
permeable and allowed the rainfall to infiltrate into the underlying soils. When reviewing the moisture
descriptions above, one must understand that this rainfall presented a wet condition that may not be
representative of normal conditions.
Groundwater
Groundwater was not encountered in our field exploration to the maximum depth explored of 6 feet.
Regional groundwater is not expected to be within 50 feet of the ground surface along the upper portions
of this local elevated terrace. Groundwater is not expected to impact future site grading. However, seepage
from the septic leach field was observed coming from clay pipe and gravel.
Faulting
Based on our review of the referenced geologic maps and literature, no active faults are known to project
near or through the property. Furthermore, the site does not lie within the boundaries of an “Earthquake
Fault Zone” as defined by the State of California in the Alquist-Priolo Earthquake Fault Zoning Act (Bryant,
2007; CGS, 2018). The Alquist-Priolo Earthquake Fault Zoning Act (AP Act) defines an active fault as one
that “has had surface displacement within Holocene time (about the last 11,000 years).” The main objective
of the AP Act is to prevent the construction of dwellings on top of active faults that could displace the
ground surface resulting in loss of life and property.
However, it should be noted that according to the USGS Unified Hazard Tool website and/or 2010 CGS
Fault Activity Map of California, the Newport-Inglewood-Rose Canyon Fault, located approximately 5.8
miles (9.3 kilometers) west of the site, would probably generate the most severe site ground motions and,
therefore, is the majority contributor to the deterministic minimum component of the ground motion
models.
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
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Secondary Seismic Effects
The site and immediate area exhibit very gentle sloping that is not prone to landsliding, nor were surficial
features indicative of slope instability noted during our field reconnaissance. Additionally, the site is not
mapped within a zone of marginal landslide susceptibly (Tan, S. S., 1995) and no landslide are mapped
within the surrounding area. Secondary effects of seismic activity normally considered as possible hazards
to a site include several types of ground failure. Various general types of ground failures, which might
occur as a consequence of severe ground shaking at the site, include ground subsidence, liquefaction,
ground lurching and lateral spreading. The probability of occurrence of each type of ground failure depends
on the severity of the earthquake, distance from faults, topography, subsoil, and groundwater conditions, in
addition to other factors. Based on the site conditions and gentle topography across the site, significant
ground lurching, and lateral spreading are considered unlikely at the site. Due to the overall density of the
very old paralic deposits encountered onsite, the potential for ground subsidence due to seismic shaking
and liquefaction is anticipated to be very low.
Seismically induced flooding that might be considered a potential hazard to a site normally includes
flooding due to tsunami or seiche (i.e., a wave-like oscillation of the surface of water in an enclosed basin)
that may be initiated by a strong earthquake or failure of a major reservoir or retention structure upstream
of the site. The potential for either seiche inundation or flooding due to a tsunami is considered negligible
at the site due to the elevation above both the Pacific Ocean and the nearby lagoon.
CONCLUSIONS AND RECOMMENDATIONS
General Feasibility
From a soils engineering and engineering geologic point of view, the subject property is considered suitable
for the proposed development, provided that the following conclusions and recommendations are
incorporated into the design criteria and project specifications. Based on our geotechnical investigation of
the site, it is our opinion the building site is free of hazard from landslide, liquefaction, settlement, and
slippage, and will remain so provided that the recommendations of this report are incorporated into the
design criteria and project specifications. Furthermore, it is our opinion that the proposed grading and
construction will not adversely affect the geologic stability of adjoining properties in an adverse manner
provided that the grading and construction are performed in accordance with current standards of practice,
all applicable grading ordinances and the recommendations presented in this report.
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
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Grading Plan Review
This report has been prepared based on a provided architectural site plan. The final site grades and the future
grading plans should be reviewed by the geotechnical consultant. As such, additional recommendations
and/or modification of the grading recommendations provided herein may be necessary if significant graded
slopes or retaining walls are proposed.
Earthwork and Grading
General Specifications
All earthwork and grading should be performed in accordance with all applicable requirements of the
grading and excavation codes of the City of Carlsbad, and in compliance with all applicable provisions of
the 2019 California Building Code (CBC). Grading should also be performed in accordance with the
recommendations provided in this report.
Geotechnical Observations and Testing During Grading
Exposed bottom surfaces in the building over-excavation areas should be observed and approved by a
representative of the geotechnical consultant prior to placing fill. In addition, a representative of the
geotechnical consultant should be present onsite during grading operations to observe proper placement
and adequate compaction of all fills, as well as to document compliance with the other recommendations
presented herein.
Site Clearing
Site clearing operations should include the removal of all existing vegetation, septic system and any
improvements. During site grading, laborers should be provided to clear from fill soils any roots, trash,
debris, or other deleterious materials as encountered. The project geotechnical consultant should be notified
at the appropriate times to observe general clearing operations. If any unusual soil conditions or buried
structures are encountered during demolition operations - or grading that is not described or anticipated
herein, the project geotechnical consultant should be contacted immediately for corrective
recommendations.
Existing Septic System
Based on our investigation, it is likely that there is a septic tank and leach field in the back yard of the
existing residence. Removal of the entire septic system is required and should consist of complete removal
of the leach lines, plumbing and septic tank. The excavated areas should be backfilled with compacted fill,
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
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placed under full-time geotechnical observation and testing. It is recommended that the septic removal and
disposal be conducted in accordance with current local, state and federal disposal regulations.
Ground Preparation – Building Pad Area
Our subsurface evaluation found that the subject site is underlain by approximately 1 to 2.5 feet of
undocumented artificial fill, topsoil and weathered terrace deposits, which in turn is underlain by medium
dense to dense terrace deposits. Therefore, in order to mitigate possible distress to the proposed building
footings and floor slabs due to the effects of potential adverse settlement, it is recommended that all building
pad soils should be over-excavated to at least 3 feet below finish pad grade to expose competent native
terrace deposit soils as observed and approved by a representative of Petra.
In order to provide both vertical and lateral support of the footings, the horizontal limits of over-excavation
and re-compaction should extend to a minimum distance of 5 feet beyond the perimeter edges of the
footings including any footings supporting overhead canopies or structures connected to the buildings. It
must be emphasized that the depths of remedial grading as provided above are estimates only and are based
on conditions encountered at the exploratory test pit locations. Subsurface conditions can and usually do
vary between points of exploration and for this reason, the actual removal depths will have to be determined
based on in-grading observations and testing performed by a representative of the project geotechnical
consultant. Remedial grading and ground preparation should be performed prior to placing any new fills.
After completion of over-excavation and prior to fill placement, the exposed native bottom surfaces should
be scarified to a minimum depth of 12 inches, moisture-conditioned as necessary to achieve at least two
percent above optimum, and then mechanically re-compacted to a relative compaction of 95 percent or
more, referenced to ASTM D1557. Additional compacted (engineered) fill to be placed to achieve pad
grade shall be compacted to 95 percent relative compaction or more.
Ground Preparation – Driveway and Hardscape Areas
Within the paved driveway or exterior hardscape areas, exposed soils should be over-excavated to a
minimum depth of 1 foot below existing grades as observed by the geotechnical consultant; and the exposed
ground surface should be scarified to a depth of at least 12 inches, moisture-conditioned as necessary to
achieve at or slightly above optimum moisture conditions, and then re-compacted in-place to a minimum
relative compaction of 90 percent. The horizontal limits of over-excavation should extend to a minimum
horizontal distance of 5 feet beyond the perimeter of the proposed improvements, where possible. Where
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
Page 8
removals are limited by property lines, the removals should be performed within 3 feet from the property
lines.
Excavation Characteristics
Based on the results of our subsurface evaluation, observed soils within the site are expected to be readily
excavatable with conventional earthmoving equipment.
Stability of Temporary Excavation Sidewalls
During site grading, a temporary excavation with sidewalls approximately 5 feet in height may be created
during construction to obtain the split pad configurations for the proposed residence. Based on the physical
characteristics of the onsite materials, 5 feet of the sidewalls exposing competent material may be
tentatively planned at a vertical gradient. However, should these sidewalls exceed this height, the lower 5
feet may be cut vertical and the upper portions above a height of 5 feet should be cut back at a maximum
gradient of 1:1, horizontal to vertical, or flatter.
Temporary slopes excavated at the above slope configurations are expected to remain stable during
construction; however, the temporary excavations should be observed by a representative of Petra for any
evidence of potential instability. Depending on the results of these observations, revised slope
configurations may be necessary.
Other factors which should be considered with respect to the stability of temporary slopes include
construction traffic and storage of materials on or near the tops of the slopes, construction scheduling,
presence of nearby walls or structures, and weather conditions at the time of construction. All applicable
requirements of the California Construction and General Industry Safety Orders, the Occupational Safety
and Health Act of 1970, and the Construction Safety Act should also be followed.
No temporary excavations along the property lines should be left open without proper protections to
mitigate safety hazards. The grading contractor is solely responsible for ensuring the safety of construction
personnel and the general public, and for appointing a designated “Competent Person” to observe and
classify temporary excavation sidewalls pursuant to 29 CFR Part 1926 (OSHA Safety and Health
Regulations for Construction).
Benching
Compacted fills placed on the natural ground surface inclining at 5:1 (h:v) or steeper should be placed on a
series of level benches excavated into competent terrace deposits.
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
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Fill Placement
Fill materials for the building pad should be placed in approximately 6- to 8-inch thick loose lifts, watered
or air-dried as necessary to achieve a moisture content of at least 2 percent above the optimum moisture
condition, and then compacted in-place to a minimum relative compaction of 95 percent. Fill to be placed
in hardscape areas or driveways should be compacted to no less than 90 percent relative compaction. The
laboratory maximum dry density and optimum moisture content for each change in soil type should be
determined in accordance with ASTM D1557.
Imported Soils
If imported soils are required to complete the planned grading, these soils should consist of clean materials
devoid of rock exceeding a maximum dimension of 3 inches, organics, trash, and other deleterious
materials. To avoid making revisions to the foundation design, imported soils should also exhibit a very
low expansion potential (Expansion Index 0-20). Prospective import soils should be observed at the source,
tested, and approved by the geotechnical consultant prior to importing the soils to the site. It is
recommended that the project environmental consultant should also be notified so that they can confirm the
suitability of the proposed import material from an environmental standpoint.
Slope Construction
Fill Slopes
For fill slopes exceeding 5 feet in height, if planned, a fill key excavated a depth of 2 feet or more into
competent terrace deposits is recommended at the base of the fill slope. The width of the fill key should
equal to one-half the slope height or 15 feet, whichever is greater, sloping downward from the toe of the
slope to the heel of the key by approximately 1 foot. To obtain proper compaction to the face of fill slopes,
low-height fill slopes should be overfilled during construction and then trimmed-back to the compacted
inner core.
Cut Slopes
Although cut slopes are not anticipated, observations during grading of individual cut slopes by the project
engineering geologist to document favorable geologic structure or soil conditions of the exposed conditions
is recommended. Although not anticipated, if cohesionless sandy soil materials are observed, the cut slopes
in question may require stabilization by means of a compacted stabilization fill.
MR. SCOTT SAREM May 11, 2020
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PRELIMINARY FOUNDATION DESIGN CONSIDERATIONS
Seismic Design Parameters
Earthquake loads on earthen structures and buildings are a function of ground acceleration which may be
determined from the site-specific ground motion analysis. Alternatively, a design response spectrum can be
developed for certain sites based on the code guidelines. To provide the design team with the parameters
necessary to construct the design acceleration response spectrum for this project, we used two computer
applications. Specifically, the first computer application, which was jointly developed by Structural
Engineering Association of California (SEAOC) and California’s Office of Statewide Health Planning and
Development (OSHPD), the SEA/OSHPD Seismic Design Maps Tool website, https://seismicmaps.org, is
used to calculate the ground motion parameters. The second computer application, the United Stated
Geological Survey (USGS) Unified Hazard Tool website, https://earthquake.usgs.gov/hazards/interactive/,
is used to estimate the earthquake magnitude and the distance to surface projection of the fault.
To run the above computer applications, site latitude and longitude, seismic risk category and knowledge
of site class are required. The site class definition depends on the direct measurement and the ASCE 7-16
recommended procedure for calculating average small-strain shear wave velocity, Vs30, within the upper
30 meters (approximately 100 feet) of site soils.
A seismic risk category of II was assigned to the proposed building in accordance with 2019 CBC, Table
1604.5. No shear wave velocity measurement was performed at the site, however, the subsurface materials
at the site appears to exhibit the characteristics of stiff soils condition for Site Class D designation.
Therefore, an average shear wave velocity of 600 to 1,200 feet per second for the upper 100 feet was
assigned to the site based on engineering judgment and geophysical experience. As such, in accordance
with ASCE 7-16, Table 20.3-1, Site Class D (D- Default as per SEA/OSHPD software) has been assigned
to the subject site.
The following table, Table 1, provides parameters required to construct the seismic response coefficient,
Cs, curve based on ASCE 7-16, Article 12.8 guidelines. A printout of the computer output is attached in
Appendix B.
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
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TABLE 1
Seismic Design Parameters
Ground Motion Parameters Specific Reference Parameter
Value Unit
Site Latitude (North) - 33.1568 °
Site Longitude (West) - -117.3206 °
Site Class Definition Section 1613.2.2 (1), Chapter 20 (2) D-Default (4) -
Assumed Seismic Risk Category Table 1604.5 (1) II -
Mw - Earthquake Magnitude USGS Unified Hazard Tool (3) 6.9 (3) -
R – Distance to Surface Projection of Fault USGS Unified Hazard Tool (3) 9.3 (3) km
Ss - Mapped Spectral Response Acceleration
Short Period (0.2 second) Figure 1613.2.1(1) (1) 1.017 (4) g
S1 - Mapped Spectral Response Acceleration
Long Period (1.0 second) Figure 1613.2.1(2) (1) 0.37 (4) g
Fa – Short Period (0.2 second) Site Coefficient Table 1613.2.3(1) (1) 1.2 (4) -
Fv – Long Period (1.0 second) Site Coefficient Table 1613.2.3(2) (1) Null (4) -
SMS – MCER Spectral Response Acceleration Parameter
Adjusted for Site Class Effect (0.2 second) Equation 16-36 (1) 1.221 (4) g
SM1 - MCER Spectral Response Acceleration Parameter
Adjusted for Site Class Effect (1.0 second) Equation 16-37 (1) Null (4) g
SDS - Design Spectral Response Acceleration at 0.2-s Equation 16-38 (1) 0.814 (4) g
SD1 - Design Spectral Response Acceleration at 1-s Equation 16-39 (1) Null (4) g
To = 0.2 SD1/ SDS Section 11.4.6 (2) Null s
Ts = SD1/ SDS Section 11.4.6 (2) Null s
TL - Long Period Transition Period Figure 22-14 (2) 8 (4) s
PGA - Peak Ground Acceleration at MCEG (*) Figure 22-9 (2) 0.446 g
FPGA - Site Coefficient Adjusted for Site Class Effect (2) Table 11.8-1 (2) 1.1 (4) -
PGAM –Peak Ground Acceleration (2)
Adjusted for Site Class Effect Equation 11.8-1 (2) 0.535 (4) g
Design PGA ≈ (⅔ PGAM) - Slope Stability (†) Similar to Eqs. 16-38 & 16-39 (2) 0.357 g
Design PGA ≈ (0.4 SDS) – Short Retaining Walls (‡) Equation 11.4-5 (2) 0.326 g
CRS - Short Period Risk Coefficient Figure 22-18A (2) 0.898 (4) -
CR1 - Long Period Risk Coefficient Figure 22-19A (2) 0.909 (4) -
SDC - Seismic Design Category (§) Section 1613.2.5 (1) Null (4) -
References: (1) California Building Code (CBC), 2019, California Code of Regulations, Title 24, Part 2, Volume I and II.
(2) American Society of Civil Engineers/Structural Engineering Institute (ASCE/SEI), 2016, Minimum Design Loads and Associated Criteria
for Buildings and Other Structures, Standards 7-16.
(3) USGS Unified Hazard Tool - https://earthquake.usgs.gov/hazards/interactive/ (4) SEI/OSHPD Seismic Design Map Application – https://seismicmaps.org
Related References:
Federal Emergency Management Agency (FEMA), 2015, NEHERP (National Earthquake Hazards Reduction Program)
Recommended Seismic Provision for New Building and Other Structures (FEMA P-1050).
Notes:
* PGA Calculated at the MCE return period of 2475 years (2 percent chance of exceedance in 50 years).
† PGA Calculated at the Design Level of ⅔ of MCE; approximately equivalent to a return period of 475 years (10 percent chance of exceedance
in 50 years).
‡ PGA Calculated for short, stubby retaining walls with an infinitesimal (zero) fundamental period.
§ The designation provided herein may be superseded by the structural engineer in accordance with Section 1613.2.5.1, if applicable.
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Discussion - General
Owing to the characteristics of the subsurface soils, as defined by Site Class D-Default designation, and
proximity of the site to the sources of major ground shaking, the site is expected to experience strong ground
shaking during its anticipated life span. Under these circumstances, where the code-specified design
response spectrum may not adequately characterize site response, the 2019 CBC typically requires a site-
specific seismic response analysis to be performed. This requirement is signified/identified by the “null”
values that are output using SEA/OSHPD software in determination of short period, but mostly, in
determination of long period seismic parameters, see Table 1.
For conditions where a “null” value is reported for the site, a variety of design approaches are permitted by
2019 CBC and ASCE 7-16 in lieu of a site-specific seismic hazard analysis. For any specific site, these
alternative design approaches, which include Equivalent Lateral Force (ELF) procedure, Modal Response
Spectrum Analysis (MRSA) procedure, Linear Response History Analysis (LRHA) procedure and
Simplified Design procedure, among other methods, are expected to provide results that may or may not be
more economical than those that are obtained if a site-specific seismic hazards analysis is performed. These
design approaches and their limitations should be evaluated by the project structural engineer.
Discussion – Seismic Design Category
Please note that the Seismic Design Category, SDC, is also designated as “null” in Table 1. For Risk
Category I, II or III structures, where the mapped spectral response acceleration parameter at 1 – second
period, S1, is less than 0.75, the 2019 CBC, Section 1613.2.5.1 allows that seismic design category to be
determined from Table 1613.2.5(1) alone provided that all 4 requirements concerning fundamental period
of structure, story drift, seismic response coefficient, and relative rigidity of the diaphragms are met. Our
interpretation of ASCE 7-16 is that for conditions where one or more of these 4 conditions are not met,
seismic design category should be assigned based on: 1) 2019 CBC, Table 1613.2.5(1), 2) structure’s risk
category and 3) the value of SDS, at the discretion of the project structural engineer.
Discussion – Equivalent Lateral Force Method
As stated herein, the subject site is considered to be within a Site Class D-Default. A site-specific ground
motion hazard analysis is not required for structures on Site Class D-Default with S1 > 0.2 provided that
the Seismic Response Coefficient, Cs, is determined in accordance with ASCE 7-16, Article 12.8 and
structural design is performed in accordance with Equivalent Lateral Force (ELF) procedure.
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Allowable Soil Bearing Capacities
Pad Footings
An allowable soil bearing capacity of 2,000 pounds per square foot may be utilized for design of isolated
24-inch-square footings founded at a minimum depth of 12 inches below the lowest adjacent final grade
for pad footings that are not a part of the slab system and are used for support of such features as roof
overhang, second-story decks, patio covers, etc. This value may be increased by 20 percent for each
additional foot of depth and by 10 percent for each additional foot of width, to a maximum value of 3,000
pounds per square foot. The recommended allowable bearing value includes both dead and live loads and
may be increased by one-third for short duration wind and seismic forces.
Continuous Footings
An allowable soil bearing capacity of 2,000 pounds per square foot may be utilized for design of continuous
footings founded at a minimum depth of 12 inches below the lowest adjacent final grade. This value may
be increased by 20 percent for each additional foot of depth and by 10 percent for each additional foot of
width, to a maximum value of 3,000 pounds per square foot. The recommended allowable bearing value
includes both dead and live loads and may be increased by one-third for short duration wind and seismic
forces.
Estimated Footing Settlement
Based on the allowable bearing values provided above, total static settlement of the footings under the
anticipated loads is expected to be on the order of 0.75 inch or less. Differential settlement is expected to
be less than 0.5 inch over a horizontal span of 30 feet. Most of the settlement is likely to take place as
footing loads are applied or shortly thereafter.
Lateral Resistance
A passive earth pressure of 300 pounds per square foot per foot of depth, to a maximum value of 2,000
pounds per square foot, may be used to determine lateral bearing resistance for footings. In addition, a
coefficient of friction of 0.30 times the dead load forces may be used between concrete and the supporting
soils to determine lateral sliding resistance. The above values may be increased by one-third when designing
for transient wind or seismic forces. It should be noted that the above values are based on the condition
where footings are cast in direct contact with compacted fill or competent native soils. In cases where the
footing sides are formed, all backfill placed against the footings upon removal of forms should be
compacted to at least 90 percent of the applicable maximum dry density.
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Guidelines for Slab-on-Ground Foundation Design and Construction
The results of our laboratory tests performed on representative samples of near-surface soils within the site
during our investigation indicate that these materials predominantly exhibit expansion indices that are less
than 20. As indicated in Section 1803.5.3 of 2019 California Building Code (2019 CBC), these soils are
considered non-expansive and, as such, the design of slabs on-grade is considered to be exempt from the
procedures outlined in Sections 1808.6.2 of the 2019 CBC and may be performed using any method deemed
rational and appropriate by the project structural engineer. However, the following minimum
recommendations are presented herein for conditions where the project design team may require
geotechnical engineering guidelines for design and construction of footings and slabs on-grade the project
site.
The design and construction guidelines that follow are based on the above soil conditions and may
be considered for reducing the effects of variability in fabric, composition and, therefore, the
detrimental behavior of the site soils such as excessive short- and long-term total and differential
heave or settlement. These guidelines have been developed on the basis of the previous experience
of this firm on projects with similar soil conditions. Although construction performed in accordance
with these guidelines has been found to reduce post-construction movement and/or distress, they
generally do not positively eliminate all potential effects of variability in soils characteristics and
future heave or settlement.
It should also be noted that the suggestions for dimension and reinforcement provided herein are
performance-based and intended only as preliminary guidelines to achieve adequate performance
under the anticipated soil conditions. However, they should not be construed as replacement for
structural engineering analyses, experience, and judgment. The project structural engineer,
architect and/or civil engineer should make appropriate adjustments to slab and footing
dimensions, and reinforcement type, size and spacing to account for internal concrete forces (e.g.,
thermal, shrinkage and expansion) as well as external forces (e.g., applied loads) as deemed
necessary. Consideration should also be given to minimum design criteria as dictated by local
building code requirements.
Conventional Slab-on-Grade System
Given the expansion index of less than 20, as generally exhibited by onsite soils, we recommend that
footings and floor slabs be designed and constructed in accordance with the following minimum criteria.
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Footings
1. Exterior continuous footings supporting one- and two-story structures should be founded at a minimum
depth of 12 inches below the lowest adjacent final grade, respectively. Interior continuous footings may
be founded at a minimum depth of 10 inches below the top of the adjacent finish floor slabs.
2. In accordance with Table 1809.7 of 2019 CBC for light-frame construction, all continuous footings
should have minimum widths of 12 inches for one- and two-story construction. We recommend all
continuous footings should be reinforced with a minimum of two No. 4 bars, one top and one bottom.
3. A minimum 12-inch-wide grade beam founded at the same depth as adjacent footings should be
provided across garage entrances or similar openings (such as large doors or bay windows). The grade
beam should be reinforced with a similar manner as provided above.
4. Interior isolated pad footings, if required, should be a minimum of 24 inches square and founded at a
minimum depth of 12 inches below the bottoms of the adjacent floor slabs for one- and two-story
buildings. Pad footings should be reinforced with No. 4 bars spaced a maximum of 18 inches on centers,
both ways, placed near the bottoms of the footings.
5. Exterior isolated pad footings intended for support of roof overhangs such as second-story decks, patio
covers, and similar construction should be a minimum of 24 inches square and founded at a minimum
depth of 18 inches below the lowest adjacent final grade. The pad footings should be reinforced with
No. 4 bars spaced a maximum of 18 inches on centers, both ways, placed near the bottoms of the
footings. Exterior isolated pad footings may need to be connected to adjacent pad and/or continuous
footings via tie beams at the discretion of the project structural engineer.
6. The minimum footing dimensions and reinforcement recommended herein may be modified (increased
or decreased subject to the constraints of Chapter 18 of the 2019 CBC) by the structural engineer
responsible for foundation design based on his/her calculations, engineering experience and judgment.
Building Floor Slabs
1. Concrete floor slabs should be a minimum 4 inches thick and reinforced with No. 3 bars spaced a
maximum of 24 inches on centers, both ways. Alternatively, the structural engineer may recommend
the use of prefabricated welded wire mesh for slab reinforcement. For this condition, the welded wire
mesh should be of sheet type (not rolled) and should consist of 6x6/W2.9xW2.9 WWF (per the Wire
Reinforcement Institute, WRI, designation) or stronger. All slab reinforcement should be properly
supported to ensure the desired placement near mid-depth. Care should be exercised to prevent warping
of the welded wire mesh between the chairs in order to ensure its placement at the desired mid-slab
position.
Slab dimension, reinforcement type, size and spacing need to account for internal concrete forces (e.g.,
thermal, shrinkage and expansion) as well as external forces (e.g., applied loads), as deemed necessary.
2. Living area concrete floor slabs and areas to receive moisture sensitive floor covering should be
underlain with a moisture vapor retarder consisting of a minimum 10-mil-thick polyethylene or
polyolefin membrane that meets the minimum requirements of ASTM E96 and ASTM E1745 for vapor
retarders (such as Husky Yellow Guard®, Stego® Wrap, or equivalent). All laps within the membrane
should be sealed, and at least 2 inches of clean sand should be placed over the membrane to promote
uniform curing of the concrete. To reduce the potential for punctures, the membrane should be placed
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on a pad surface that has been graded smooth without any sharp protrusions. If a smooth surface cannot
be achieved by grading, consideration should be given to lowering the pad finished grade an additional
inch and then placing a 1-inch-thick leveling course of sand across the pad surface prior to the
placement of the membrane.
At the present time, some slab designers, geotechnical professionals, and concrete experts view
the sand layer below the slab (blotting sand) as a place for entrapment of excess moisture that
could adversely impact moisture-sensitive floor coverings. As a preventive measure, the
potential for moisture intrusion into the concrete slab could be reduced if the concrete is placed
directly on the vapor retarder. However, if this sand layer is omitted, appropriate curing
methods must be implemented to ensure that the concrete slab cures uniformly. A qualified
materials engineer with experience in slab design and construction should provide
recommendations for alternative methods of curing and supervise the construction process to
ensure uniform slab curing. Additional steps would also need to be taken to prevent puncturing
of the vapor retarder during concrete placement.
3. Garage floor slabs should be a minimum 4 inches thick and reinforced in a similar manner as living
area floor slabs. Garage slabs should also be poured separately from adjacent wall footings with a
positive separation maintained using ¾-inch-minimum felt expansion joint material. To control the
propagation of shrinkage cracks, garage floor slabs should be quartered with weakened plane joints.
Consideration should be given to placement of a moisture vapor retarder below the garage slab, similar
to that provided in Item 2 above, should the garage slab be overlain with moisture sensitive floor
covering.
4. Presaturation of the subgrade below floor slabs will not be required; however, prior to placing concrete,
the subgrade below all dwelling and garage floor slab areas should be thoroughly moistened to achieve
a moisture content that is at least equal to or slightly greater than optimum moisture content. This
moisture content should penetrate to a minimum depth of 12 inches below the bottoms of the slabs.
5. The minimum dimensions and reinforcement recommended herein for building floor slabs may be
modified (increased or decreased subject to the constraints of Chapter 18 of the 2019 CBC) by the
structural engineer responsible for foundation design based on his/her calculations, engineering
experience and judgment.
Foundation Excavation Observations
Foundation excavations should be observed by a representative of this firm to document that they have been
excavated into competent bearing soils prior to the placement of forms, reinforcement, or concrete. The
excavations should be trimmed neat, level, and square. All loose, sloughed or moisture-softened soils and/or
any construction debris should be removed prior to placing of concrete. Excavated soils derived from
footing and/or utility trenches should not be placed in building slab-on-grade areas or exterior concrete
flatwork areas unless the soils are compacted to at least 90 percent of maximum dry density.
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General Corrosivity Screening
As a screening level study, limited chemical and electrical tests were performed on a single sample
considered representative of the onsite soils to identify potential corrosive characteristics of these soils. The
common indicators associated with soil corrosivity include water-soluble sulfate and chloride levels, pH (a
measure of acidity), and minimum electrical resistivity. Test methodology and results are presented in
Appendix B.
It should be noted that Petra does not practice corrosion engineering; therefore, the test results,
opinion and engineering judgment provided herein should be considered as general guidelines
only. Additional analyses would be warranted, especially, for cases where buried metallic building
materials (such as copper and cast or ductile iron pipes) in contact with site soils are planned for
the project. In many cases, the project geotechnical engineer may not be informed of these choices.
Therefore, for conditions where such elements are considered, we recommend that other, relevant
project design professionals (e.g., the architect, landscape architect, civil and/or structural
engineer) also consider recommending a qualified corrosion engineer to conduct additional
sampling and testing of near-surface soils during the final stages of site grading to provide a
complete assessment of soil corrosivity. Recommendations to mitigate the detrimental effects of
corrosive soils on buried metallic and other building materials that may be exposed to corrosive
soils should be provided by the corrosion engineer as deemed appropriate.
In general, a soil’s water-soluble sulfate levels and pH relate to the potential for concrete degradation;
water-soluble chlorides in soils impact ferrous metals embedded or encased in concrete, e.g., reinforcing
steel; and electrical resistivity is a measure of a soil’s corrosion potential to a variety of buried metals used
in the building industry, such as copper tubing and cast or ductile iron pipes. Table 2, below, presents a
single value of individual test results with an interpretation of current code indicators and guidelines that
are commonly used in this industry. The table includes the code-related classifications of the soils as they
relate to the various tests, as well as a general recommendation for possible mitigation measures in view of
the potential adverse impact on various components of the proposed structures in direct contact with site
soils. The guidelines provided herein should be evaluated and confirmed, or modified, in their entirety by
the project structural engineer, corrosion engineer and/or the contractor responsible for concrete placement
for structural concrete used in exterior and interior footings, interior slabs on-ground, garage slabs, wall
foundations and concrete exposed to weather such as driveways, patios, porches, walkways, ramps, steps,
curbs, etc.
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TABLE 2
Soil Corrosivity Screening Results
Test Test Results Classification General Recommendations
Soluble Sulfates
(Cal 417) 0.0015 percent S01 Type II cement; min. f’c= 2,500 psi; no water/cement ratio
restrictions
pH
(Cal 643) 7.67 Slightly Alkaline No special recommendations
Soluble Chloride
(Cal 422) 108 ppm C12
C24
Residence: No special recommendations
Pools/Decking: water/cement ratio 0.40, f’c = 5,000 psi
Resistivity
(Cal 643) 8,700 ohm-cm Moderately
Corrosive3
Protective wrapping/coating of buried pipes; corrosion
resistant materials
Consult corrosion engineer
Notes:
1. ACI 318-14, Section 19.3
2. ACI 318-14, Section 19.3
3. Pierre R. Roberge, “Handbook of Corrosion Engineering”
4. Exposure classification C2 applies specifically to swimming pools and appurtenant concrete elements
Retaining Wall Design and Construction Considerations
Provided herein are geotechnical design and construction recommendations for building and exterior
retaining walls. Footings for retaining walls may be designed in accordance with the bearing and lateral
resistance values provided previously for building footings; however, when calculating passive resistance,
the resistance of the upper 6 inches of the soils should be ignored in areas where the footings will not be
covered with concrete flatwork, or where the thickness of soil cover over the top of the footing is less than
12 inches.
Active and At-Rest Earth Pressures
Active and at-rest earth pressures to be utilized for design of any retaining walls to be constructed within
the will be dependent on whether on-site soils or imported granular materials are used for backfill. For this
reason, active and at-rest earth pressures are provided below for both conditions.
1. On-Site Soils Used for Backfill
If on-site soils are used as backfill, active earth pressures equivalent to fluids having densities of 35 and
51 pounds per cubic foot should be used for design of cantilevered walls retaining a level backfill and
ascending 2:1 backfill, respectively. For walls that are restrained at the top, at-rest earth pressures of
53 and 78 pounds per cubic foot (equivalent fluid pressures) should be used. The above values are for
retaining walls that have been supplied with a proper subdrain system (see Figure RW-1). All walls
should be designed to support any adjacent structural surcharge loads imposed by other nearby walls
or footings in addition to the above recommended active and at-rest earth pressures.
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2. Imported Sand, Pea Gravel or Rock Used for Wall Backfill
Where imported clean sand exhibiting a sand equivalent value (SE) of 30 or greater, or pea gravel or
crushed rock are be used for wall backfill, the lateral earth pressures may be reduced provided these
granular backfill materials extend behind the walls to a minimum horizontal distance equal to one-half
the wall height. In addition, the sand, pea gravel or rock backfill materials should extend behind the
walls to a minimum horizontal distance of 2 feet at the base of the wall or to a horizontal distance equal
to the heel width of the footing, whichever is greater (see Figures RW-2 and RW-3). For the above
conditions, cantilevered walls retaining a level backfill and ascending 2:1 backfill may be designed to
resist active earth pressures equivalent to fluids having densities of 30 and 41 pounds per cubic foot,
respectively. For walls that are restrained at the top, at-rest earth pressures equivalent to fluids having
densities of 45 and 62 pounds per cubic foot are recommended for design of restrained walls supporting
a level backfill and ascending 2:1 backfill, respectively. These values are also for retaining walls
supplied with a proper subdrain system. Furthermore, as with native soil backfill, the walls should be
designed to support any adjacent structural surcharge loads imposed by other nearby walls or footings
in addition to the recommended active and at-rest earth pressures.
Backdrains
A perforated pipe and gravel backdrain should be installed behind all basement and retaining walls to
prevent entrapment of water in the backfill (Appendix C). Perforated pipe should consist of 4-inch-
minimum diameter PVC Schedule 40, or SDR-35, with the perforations laid down. The pipe should be
encased in a 1-foot-wide column of ¾-inch to 1½-inch open-graded gravel. If on-site soils are used as
backfill, the open-graded gravel should extend above the wall footings to a minimum height equal to one-
third the wall height or to a minimum height of 1.5 feet above the footing, whichever is greater. If imported
sand, pea gravel, or crushed rock is used as backfill, subdrain details (Appendix C) should be utilized. The
open-graded gravel should be completely wrapped in filter fabric consisting of Mirafi 140N or equivalent.
Solid outlet pipes should be connected to the subdrains and then routed to a suitable area for discharge of
accumulated water.
If a limited area exists behind the walls for installation of a pipe and gravel subdrain, a geotextile drain mat
such as Mirafi Miradrain, or equivalent, can be used in lieu of drainage gravel. The drain mat should extend
the full height and lengths of the walls and the filter fabric side of the drain mat should be placed up against
the backcut. The perforated pipe drain line placed at the bottom of the drain mat should consist of 4-inch
minimum diameter PVC Schedule 40 or SDR-35. The filter fabric on the drain mat should be peeled back
and then wrapped around the drain line.
Waterproofing
The backfilled portions of retaining walls should be coated with an approved waterproofing compound or
covered with a similar material to inhibit migration of moisture through the walls.
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Wall Backfill
Recommended active and at-rest earth pressures for design of retaining walls are based on the physical and
mechanical properties of the on-site soil materials. On-site soil materials may be difficult to compact when
placed in the relatively confined areas located between the walls and temporary backcut slopes. Therefore,
to facilitate compaction of the backfill, consideration should be given to using pea gravel or crushed rock
behind the proposed retaining walls. For this condition, the reduced active and at-rest pressures provided
previously for sand, pea gravel, or crushed rock backfill may be considered in wall design provided they
are installed as shown (Appendix C).
Where the onsite soils materials or imported sand (with a Sand Equivalent of 30 or greater) are used as
backfill behind the proposed retaining walls, the backfill materials should be placed in approximately 6- to
8-inch-thick maximum lifts, watered as necessary to achieve near optimum moisture conditions, and then
mechanically compacted in place to a minimum relative compaction of 90 percent. Flooding or jetting of
the backfill materials should be avoided. A representative of the project geotechnical consultant should
observe the backfill procedures and test the wall backfill to verify adequate compaction.
If imported pea gravel or rock is used for backfill, the gravel should be placed in approximately 2- to 3-
foot-thick lifts, thoroughly wetted but not flooded, and then mechanically tamped or vibrated into place. A
representative of the project geotechnical consultant should observe the backfill procedures and probe the
backfill to determine that an adequate degree of compaction is achieved.
To reduce the potential for the direct infiltration of surface water into the backfill, imported sand, gravel,
or rock backfill should be capped with at least 12 to 18 inches of on-site soil. Filter fabric such as Mirafi
140N or equivalent, should be placed between the soil and the imported gravel or rock to prevent fines from
penetrating into the backfill. If a thicker cap is desired (for planting or other reasons), consultation with the
project structural engineer may be required to ascertain if the wall design is appropriate for the additional
lateral pressure that a thicker cap of native material may impose.
Geotechnical Observation and Testing
All grading and construction phases associated with retaining wall construction, including backcut
excavations, observation of the footing and pier excavations, installation of the subdrainage systems, and
placement of backfill should be provided by a representative of the project geotechnical consultant.
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Masonry Block Walls (Non-Retaining)
Footings for free-standing (non-retaining) masonry block walls may be designed in accordance with the
bearing and lateral resistance values provided previously for building footings. However, as a minimum,
the wall footings should be embedded at a minimum depth of 12 inches below the lowest adjacent final
grade. The footings should also be reinforced with a minimum of two No. 4 bars, one top and one bottom.
In order to reduce the potential for unsightly cracking related to the possible effects of differential settlement
and/or expansion, positive separations (construction joints) should also be provided in the block walls at
each corner and at horizontal intervals of approximately 20 to 25 feet. The separations should be provided
in the blocks and not extend through the footings. The footings should be poured monolithically with
continuous rebars to serve as effective “grade beams” below the walls.
Planter Walls
Low-height planter walls should be supported by continuous concrete footings constructed in accordance
with the recommendations presented previously for masonry block wall footings.
Swimming Pool and Spa Recommendations
Allowable Bearing, Settlement, and Lateral Earth Pressures
The pool and spa shells may be designed using an allowable bearing value of 1,000 pounds per square foot.
It is anticipated that the swimming pool and spa will be located within an area that is underlain by competent
terrace deposits. If it in fact the shells span a transition between engineered fill and competent terrace
deposits, the pool and spa shells should be deepened to competent terrace deposits. Based on this condition,
total settlement and associated differential of the shell can be expected on the order of less than ¼ of an
inch.
Pool and spa walls should be designed assuming that an earth pressure equivalent to a fluid having a density
of 53 pounds per cubic foot is acting on the outer surface of the walls. Pool and spa walls should also be
designed to resist lateral surcharge pressures imposed by any adjacent footings or structures in addition to
the above lateral earth pressure.
Care should be taken while excavating the pool and spa bottoms to prevent disturbance of the terrace
deposits exposed at grade in the pool and spa bottoms.
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Temporary Access Ramps
It is essential that all backfill placed within temporary access ramps extending into the pool and spa
excavations be compacted and tested. This is intended to reduce excessive settlement of the backfill and
subsequent damage to concrete decking or other structures placed on the backfill.
Plumbing Fixtures
Leakage from the pool/spa or from any of the appurtenant plumbing could create adverse saturated
conditions of the surrounding subgrade soils. Localized areas of over-saturation can lead to differential
settlement of the subgrade soils and subsequent shifting of concrete flatwork. Therefore, it is essential that
all plumbing and pool fixtures be absolutely leak-free. For similar reasons, drainage from deck areas should
be directed to local area drains designed to carry runoff water to a suitable discharge point.
Pool and Spa Decking
Pool and spa decking should be constructed in accordance with the recommendations presented in the
“Exterior Concrete Flatwork” section of this report.
Post-Grading Considerations
Utility Trenches
All utility trench backfill should be compacted to a minimum relative compaction of 90 percent. Due to the
nature of the onsite earth materials, flooding and jetting techniques should be avoided. Therefore, trench
backfill materials should be placed in lifts no greater than approximately 12 inches in thickness, watered or
air-dried as necessary to achieve near optimum moisture conditions, and then mechanically compacted in
place to a minimum relative compaction of 90 percent. A representative of the project geotechnical
consultant should probe and test the backfills to verify adequate compaction.
As an alternative for shallow trenches where pipe or utility lines may be damaged by mechanical
compaction equipment, such as under building floor slabs, imported clean sand having a sand equivalent
(SE) value of 30 or greater may be utilized. The sand backfill materials should be watered to achieve near
optimum moisture conditions and then tamped into place. No specific relative compaction will be required;
however, observation, probing, and if deemed necessary, testing should be performed by a representative
of the project geotechnical consultant to verify an adequate degree of compaction.
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If clean, imported sand is to be used for backfill of exterior utility trenches, it is recommended that the
upper 12 inches of trench backfill materials consist of properly compacted onsite soil materials. This is to
mitigate infiltration of irrigation and rainwater into granular trench backfill materials.
Where an exterior and/or interior utility trench is proposed in a direction parallel to a building footing, the
bottom of the trench should not extend below a 1:1 (horizontal to vertical) plane projected downward from
the bottom edge of the adjacent footing. Where this condition occurs, the adjacent footing should be
deepened or the utility constructed and the trench backfilled and compacted prior to footing construction.
Where utility trenches cross under a building footing, these trenches should be backfilled with on-site soils
at the point where the trench crosses under the footing to reduce the potential for water to migrate under
the floor slabs.
Site Drainage
Positive surface drainage systems consisting of a combination of sloped concrete flatwork, swales and
possibly subsurface area drains (if needed) should be provided around the building and within the planter
areas to collect and direct all surface waters to an appropriate drainage facility as determined by the project
civil engineer. The ground surfaces of planter and landscape areas that are located within 10 feet of building
foundations should be sloped at a minimum gradient of 5 percent away from the foundations and towards
the nearest area drains. The ground surface of planter and landscape areas that are located more than 10 feet
away from building foundations may be sloped at a minimum gradient of 2 percent away from the
foundations and towards the nearest area drains.
Concrete flatwork surfaces that are located within 10 feet of building foundations should be inclined at a
minimum gradient of one percent away from the building foundations and towards the nearest area drains.
Concrete flatwork surfaces that are located more than 10 feet away from building foundations may be sloped
at a minimum gradient of 1 percent towards the nearest area drains. Surface waters should not be allowed
to collect or pond against building foundations and within the level areas of the site. All drainage devices
should be properly maintained throughout the lifetime of the development. Future changes to site
improvements, or planting and watering practices, should not be allowed to cause over-saturation of site
soils adjacent to the structures.
Exterior Concrete Flatwork
General
Near-surface compacted fill soils within the site are expected to exhibit very low expansion potential.
Therefore, we recommend that all exterior concrete flatwork such as sidewalks, patio slabs, large decorative
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
Page 24
slabs, concrete subslabs that will be covered with decorative pavers, private and/or public vehicular
driveways and/or access roads within and adjacent to the site be designed by the project architect and/or
structural engineer with consideration given to mitigating the potential cracking and uplift that can develop
in soils exhibiting expansion index values that fall in the very low category. The guidelines that follow
should be considered as minimums and are subject to review and revision by the project architect, structural
engineer and/or landscape consultant as deemed appropriate.
Thickness and Joint Spacing
To reduce the potential of unsightly cracking, concrete walkways, patio-type slabs, large decorative slabs
and concrete subslabs to be covered with decorative pavers should be at least 4 inches thick and provided
with construction joints or expansion joints every 6 feet or less. Private driveways that will be designed for
the use of passenger cars for access to private garages should also be at least 5 inches thick and provided
with construction joints or expansion joints every 10 feet or less.
Reinforcement
All concrete flatwork having their largest plan-view panel dimension exceeding 5 feet should be reinforced
with a minimum of No. 3 bars spaced 24 inches on centers, both ways. Alternatively, the slab reinforcement
may consist of welded wire mesh of the sheet type (not rolled) with 6x6/W1.4xW1.4 WWF designation in
accordance with the Wire Reinforcement Institute (WRI). The reinforcement should be properly positioned
near the middle of the slabs.
The reinforcement recommendations provided herein are intended as guidelines to achieve
adequate performance for anticipated soil conditions. The project architect, civil and/or structural
engineer should make appropriate adjustments in reinforcement type, size and spacing to account
for concrete internal (e.g., shrinkage and thermal) and external (e.g., applied loads) forces as
deemed necessary.
Edge Beams (Optional)
Where the outer edges of concrete flatwork are to be bordered by landscaping, it is recommended that
consideration be given to the use of edge beams (thickened edges) to prevent excessive infiltration and
accumulation of water under the slabs. Edge beams, if used, should be 6 to 8 inches wide, extend 8 inches
below the tops of the finish slab surfaces. Edge beams are not mandatory; however, their inclusion in
flatwork construction adjacent to landscaped areas is intended to reduce the potential for vertical and
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
Page 25
horizontal movement and subsequent cracking of the flatwork related to uplift forces that can develop in
expansive soils.
Subgrade Preparation
Compaction
To reduce the potential for distress to concrete flatwork, the subgrade soils below concrete flatwork areas
to a minimum depth of 12 inches (or deeper, as either prescribed elsewhere in this report or determined in
the field) should be moisture conditioned to at least equal to, or slightly greater than, the optimum moisture
content and then compacted to a minimum relative compaction of 90 percent.
Pre-Moistening
As a further measure to reduce the potential for concrete flatwork cracking, subgrade soils should be
thoroughly moistened prior to placing concrete. The moisture content of the soils should be at least 1.2
times the optimum moisture content and penetrate to a minimum depth of 12 inches into the subgrade.
Flooding or ponding of the subgrade is not recommended to achieve the above moisture conditions since
this method would likely require construction of numerous earth berms to contain the water. Therefore,
moisture conditioning should be achieved with a light spray applied to the subgrade over a period of few
days just prior to pouring concrete. Pre-watering of the soils is intended to promote uniform curing of the
concrete, reduce the development of shrinkage cracks, and reduce the potential for differential expansion
pressure on freshly poured flatwork. A representative of the project geotechnical consultant should observe
and verify the density and moisture content of the soils, and the depth of moisture penetration prior to
pouring concrete.
Drainage
Drainage from patios and other flatwork areas should be directed to local area drains and/or graded earth
swales designed to carry runoff water to the adjacent streets or other approved drainage structures. The
concrete flatwork should be sloped at a minimum gradient of one percent, or as prescribed by project civil
engineer or local codes, away from building foundations, retaining walls, masonry garden walls and slope
areas.
Tree Wells
Tree wells are not recommended in concrete flatwork areas since they introduce excessive water into the
subgrade soils and allow root invasion, both of which can cause heaving and cracking of the flatwork.
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
Page 26
GRADING PLAN REVIEW AND FUTURE IMPROVEMENTS
Petra should review the site grading plans when they become available and issue an addendum letter to this
report if necessary. If additional improvements are considered in the future, our firm should be notified so
that we may provide design recommendations to mitigate movement, settlement and/or tilting of the
structures. Potential problems can develop when drainage is altered in any way such as placement of fill
and construction of new walkways, patios, landscape walls, or planters. Therefore, it is recommended that
we be engaged to review the final design drawings, specifications, and grading plan prior to any new
construction. If we are not provided the opportunity to review these documents with respect to the
geotechnical aspects of new construction and grading, it should not be assumed that the recommendations
provided herein are wholly or in part applicable to the proposed construction.
REPORT LIMITATIONS
This report is based on the proposed project and geotechnical data as described herein. The materials
encountered on the project site and utilized in our laboratory investigation are believed representative of
the project area, and the conclusions and recommendations contained in this report are presented on that
basis. However, soil materials and moisture conditions can vary in characteristics between points of
exploration, both laterally and vertically, and those variations could affect the conclusions and
recommendations contained herein. As such, observation and testing by a geotechnical consultant during
the grading and construction phases of the project are essential to confirming the basis of this report.
This report has been prepared consistent with that level of care being provided by other professionals
providing similar services at the same locale and time period. The contents of this report are professional
opinions and as such, are not to be considered a guarantee or warranty. This report should be reviewed and
updated after a period of one year or if the project concept changes from that described herein.
The information contained herein has not been prepared for use by parties or projects other than those
named or described herein. This report may not contain sufficient information for other parties or other
purposes. This report is subject to review by the controlling authorities for this project.
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
Page 27
Should you have any questions, please do not hesitate to call.
Respectfully submitted,
PETRA GEOSCIENCES, INC.
5/11/2020
Jim Larwood Grayson R. Walker
Principal Geologist Principal Engineer
CEG 1897 GE 871
JL/GRW/lv
W:\2020-2025\2020\100\20-155 Scott Sarem (4005 Skyline Road, Carlsbad)\Reports\20-155 110 Prelim Geotechnical Report.docx
\
MR. SCOTT SAREM May 11, 2020
4005 Skyline Road. / Carlsbad J.N. 20-155
Page 28
REFERENCES
American Concrete Institute, 2014, Building Code Requirements for Structural Concrete (ACI 318-14) and
Commentary.
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 Department of Water Resources, 2018, Water Data Library,
http://www.water.ca.gov/waterdatalibrary/ accessed September.
California Geological Survey, 2010, ‘Fault Activity Map of California, Geologic Data Map No. 6,
http://maps.conservation.ca.gov/cgs/fam/.
______, 2018, Earthquake Fault Zones, A Guide for Government Agencies, Property Owners/Developers,
and Geoscience Practitioners for Assessing Fault Rupture Hazards in California, Special
Publication 42.
Google Earth™ 2020, by Google Earth, Inc., http://www.google.com/earth/index.html, accessed May.
International Building Code, 2013, 2015, 2016, 2019 California Building Code, California Code of
Regulations, Title 24, Part 2, Volume 2 of 2, Based on the 2019 International Building Code,
California Building Standards Commission.
Jennings, C.W. and Bryant, W.A., 2010, Fault Activity Map of California: California Geological Survey,
Geologic Data Map No. 6.
Kennedy, M.P. and Tan, S.S, 2007, Geologic map of the Oceanside 30’ x 60’ quadrangle, California, United
States Geological Survey.
Macrostrat, Creative Commons Attribution 4.0, 2020, accessed May. https://macrostrat.org/map/
San Diego County Regional Standards Committee, 2108, Regional Standard Drawing Book, 2018 Edition.
http://www.regional-stds.com/home/book/drawings
SEAOC & OSHPD Seismic Design Maps Web Application – https://seismicmaps.org/
Tan, S. S., 1995, Landslide Hazards in the Northern Part of the San Diego Metropolitan Area, San Diego
County, California, Relative Landslide Susceptibility and Landslide Distribution Map, Plate A,
California Division of Mines and Geology Open-File Report 95-04.
Tan, S.S., and Kennedy, M.P., 1996, Geologic maps of the northwestern part of San Diego County,
California: California Division of Mines and Geology, Open File Report
96-02.
United States Geological Survey (USGS), 2014, Unified Hazard Tool v4.0x,
https://earthquake.usgs.gov/hazards/interactive/
FIGURES
H
PETRA
NATIVE SOIL BACKFILL
/
~ ~ _}Sloped= g: surtace
.. Compacted on-site soil
r;:;O" •
:; : ,,,, ~ Fi~ter_fabric (shoui~ consist of
: ~o (/ ~ M1raf1 140N or eqwvalent)
~ 4 inch perforated pipe. Perforated pipe should
consist of 4" diameter ABS SDR-35 or PVC
Schedule 40 or approved equivalent with the
· perforations laid down. Pipe should be laid on
. at least 2 inches of open-graded gravel.
* Vertical height (h) and slope angle
of backcut per soils report. Based
on geologic conditions, configuration
of backcut may require revisions
(i.e. reduced vertical height,
revised slope angle, etc.)
RETAINING WALL BACKFILL
AND SUBDRAIN DETAILS FIGURE RW-1
H
PETR
IMPORTED SAND BACKFILL
Waterproofing compound
.-:-,:/{::}:(~ stall subdrain system
:}\-:/:~:\{: cubic toot per toot min. of s14" -1 112"
-/•:_:,::..-.:-:.-·./.-pen graded gravel wrapped in filter · ... _.:_.·.:::·-:::· ·· bric.
Filter fabric (should consist of
· Mirafi 140N or equivalent).
4 inch perforated pipe. Perforated pipe should
consist of 4" diameter ABS SDR-35 or PVC
Schedule 40 or approved equivalent with the
· perforations laid down. Pipe should be laid on
.· at least 2 inches of open-graded gravel.
* At base of wall, the non-expansive
backfill materials should extend to a
min. distance of 2' or to a horizontal
distance equal to the heel width of
the footing, whichever is greater.
RETAINING WALL BACKFILL
AND SUBDRAIN DETAILS FIGURE RW-2
IMPORTED GRAVEL OR CRUSHED ROCK BACKFILL
H
PETR
Non-expansive imported
·· gravel or crushed rock
Install filter fabric (Mirafi 140N
or equal) to prevent migration
of fines into backfill.
. 4 inch perforated pipe. Perforated pipe should
· consist of 4" diameter ABS SDR-35 or PVC
. Schedule 40 or approved equivalent with the
perforations laid down. If pea gravel used,
pipe should be encased in 1 cubic foot per
· foot min. of 3/4" -1 i/2" open-graded gravel
wrapped in filter fabric (Mirafi 140N or equal)
Pipe should be laid on at least 2 inches of
gravel.
* At base of wail, the non-expansive
backfill materials should extend to a
min. distance of 2' or to a horizontal
distance equal to the heel width of
the footing, whichever is greater.
RETAINING WALL BACKFILL
AND SUBDRAIN DETAILS FIGURE RW-3
Scale: 1” = 2,000’
Base Map: Portion of USGS San Luis Rey Quadrangle 7.5-Minute
Topographic Series, 2018
N 41880 County Center Drive, Suite M
Temecula, California 92591
PHONE: (951) 600-9271COSTA MESA TEMECULA VALENCIA PALM DESERT CORONA SAN DIEGO
SITE LOCATION MAP
4005 Skyline Road
Carlsbad, California
DATE: May 2020
J.N.: 20- 155 Figure 1
PETRA GEOSCIENCES, INC.
SITE
GEOTECHNICAL MAP
40880 County Center Drive, Suite M
Temecula, California 92591
PHONE: (951) 600-9271
COSTA MESA TEMECULA VALENCIA PALM DESERT CORONA SAN DIEGO
4005 Skyline Road
Carlsbad, California
DATE: May 2020
J.N.: 20-155 Figure 2
N
PETRA GEOSCIENCES, INC.EXPLANATION
Artificial Fill, undocumented
Very Old Paralic Deposits,
Circled Where Buried
Approximate Location Of Exploratory Test Pit
TD = Total Depth
Qvol
afu
EXPLANATION
Compacted Artificial Fill (GMU, 2006)
Topanga Formation, Circled Where Buried
Geologic Contact, Dotted Where Buried (GMU, 2006)
Bedding Attitude (GMU, 2006)
Vertical Bedding Attitude (GMU, 2006)
Approximate Location Of Exploratory Boring
TD = Total Depth
Geologic Cross Section
B-3
TD=26.5’
Tt
Qafc
BB’
34
EXPLANATION
Compacted Artificial Fill (GMU, 2006)
Topanga Formation, Circled Where Buried
Geologic Contact, Dotted Where Buried (GMU, 2006)
Bedding Attitude (GMU, 2006)
Vertical Bedding Attitude (GMU, 2006)
B-3
TD=26.5’
Tt
Qafc
B B’
34
Approximate Elevation of Fill to Bedrock Contact
(Current Investigation, at Exploration Point)
Approximate Elevation of Fill to Bedrock Conract
(GMU, 2006)
Approximate Location Of Exploratory Boring
TD = Total Depth
Geologic Cross Section
647
688
0 4020
Scale: 1” = 20’
Proposed Pool
Existing Pool
Existing Residence
Tvs
HA-3
TD=2.4’
HA-1
TD=8’
HA-2
TD=8’
af
Qes
B-1
TD=67.5’
B-2
TD=26.5’
B-3
TD=26.5’
B-4
TD=26.5’
365365TP-1
TD=5’
TP-2
TD=5’
Qyf
af
B-1
TD=5’
B-2
TD=21.5’
B-3
TD=61.5’
N
CPT-1
TD=55’
B-1
TD=51.5’
P-1
TD=5’
Qomf
Tm
Tt
Ta
B-2TD=21.5’TsoafTsoaf
Base Map Reference: B + D Studio Preliminary Site Plan, sheet C-1, dated February 28, 2020
TP-4
TD=6’
N
TP-3
TD=3.5’
TP-4
TD=6’
TP-1
TD=5.2’
TP-2
TD=4’
possible
septic
lines
possible
septic
tank
afu
afu
??
?
?
?
??
?
afu
Qvol
Qvol
Qvol
PLATE A-1
LOGS OF TEST PITS
LOGS OF TEST PITS
PETRA GEOSCIENCES, INC. 4/15/2020
J.N. 20-155 Plate A-1
TEST PIT
NUMBER
DEPTH
(ft) DESCRIPTION
TP-1 0 - 1 Undocumented Artificial Fill (afu): Dark brown, Silty SAND (SM), fine to coarse
grained, moist to wet; loose; abundant roots.
1 – 3.5 WEATHERED SANDSTONE (Qvol): Light reddish brown, fine to coarse grained
with some clay, wet, dense;
3.5 – 4.5 SANDSTONE (Qvol): Becomes medium red brown
4.5 – 5.2 Becomes very dense
Total Depth 5.2 ft, no groundwater encountered; practical refusal on dense material.
TP-2 0 – 2.5 Undocumented Artificial Fill (afu): Medium brown, Silty SAND (SM), fine to
coarse grained, moist to wet; loose; abundant roots.
2.5
Top of suspected leach line at west side of trench. 4 to 6-inch diameter clay pipe,
loosely fitted, trending north-south, encased in 1 to 2-inch diameter gravel; no odors,
observed to be clean water.
2.5 - 4 SANDSTONE (Qvol): reddish brown, fine to coarse grained with some clay, moist,
dense; sone iron-oxide staining.
Total Depth 4 ft, no groundwater encountered; seepage from suspected leach line
pipe; practical refusal on dense material.
TP-3 0 - 1 Undocumented Artificial Fill (afu): Dark brown, Silty SAND (SM), fine to coarse
grained, moist to wet; loose; abundant roots.
1 – 2.5 WEATHERED SANDSTONE (Qvol): Weathered reddish brown, fine to coarse
grained with some clay, moist to wet, dense;
3.5 SANDSTONE (Qvol): Becomes very dense
Total Depth 3.5 ft, no groundwater encountered; practical refusal on dense material.
TP-4 0 – 2 Undocumented Artificial Fill (afu): Dark brown, Silty SAND (SM), fine to coarse
grained, moist to wet; loose; abundant roots.
2
Top of suspected leach line at west side of trench. 4 to 6-inch diameter clay pipe,
loosely fitted, trending north-south, encased in 1 to 2-inch diameter gravel; no odors,
no water in pipe.
2 - 4 SANDSTONE (Qvol): reddish brown, fine to coarse grained, moist, dense; sone
iron-oxide staining.
4 - 6 Becomes mottled with light gray and some clay.
Total Depth 6 ft, no groundwater encountered; practical refusal on dense material.
APPENDIX A
LABORATORY TEST PROCEDURES
LABORATORY DATA SUMMARY
PETRA GEOSCIENCES, INC. Laboratory Address: 1251 W. Pomona Road, Unit 103, Corona, CA, 92882
J.N. 20-155 PLATE A-1
LABORATORY TEST PROCEDURES
Soil Classification
Soil materials encountered within the property were classified and described in accordance with the Unified
Soil Classification System and in general accordance with the current version of Test Method ASTM
D 2488. The assigned group symbols are presented on Plate A-1.
Laboratory Maximum Dry Unit Weight and Optimum Moisture Content
The maximum dry unit weight and optimum moisture content of the on-site soils were determined for a
selected bulk sample in accordance with current version of Method B of ASTM D 1557. The results of
these tests are presented on Plate B-1.
Expansion Index
An expansion index test was performed on a selected bulk sample of the on-site soils in accordance with
the current version of Test Method ASTM D 4829. The test results are presented on Plate A-1.
Corrosivity Screening
Chemical and electrical analyses were performed on a selected bulk sample of onsite soils to determine
soluble sulfate content, chloride content, pH (acidity) and minimum electrical resistivity. These tests were
performed in accordance with the current versions of California Test Method Nos. CTM 417, CTM 422
and CTM 643, respectively. The results of these tests are included on Plate A-1.
PETRA GEOSCIENCES, INC. Laboratory Address: 1251 W. Pomona Road, Unit 103, Corona, CA, 92882
J.N. 20-155 PLATE A-1
LABORATORY DATA SUMMARY*
Test Pit
Number
Sample
Depth
(ft)
Soil Description
Max. Dry
Density 1
(pcf)
Optimum
Moisture1
(%)
Expansion
Index2
CBC Soil
Classification3
Atterberg
Limits4 Sulfate
Content5
(%)
Chloride
Content6
(ppm)
pH7
Minimum
Resistivity7
(ohm-cm) LL PL PI
TP-1 2.6
Silty/fine to coarse
grained Sand with
trace of clay (SM)
135.0 8.5 0 Very Low - - - 0.0015 108 7.67 8,700
Test Procedures: 1 Per ASTM Test Method D 1557 5 Per Caltrans Test Method 417 2 Per ASTM Test Method D 4829 6 Per Caltrans Test Method 422 3 Per ASTM Test Method D 4829 Table 1, Per CBC 2016 7 Per Caltrans Test Method 643
4 Per ASTM Test Method D 4318
8 Per ASTM Test Method D 1140
APPENDIX B
SEISMIC DESIGN PARAMETERS
20-155
4005 Skyline Rd, Carlsbad, CA 92008, USA
Latitude, Longitude: 33.1568136, -117.3205812
Date 5/6/2020, 4:32:17 PM
Design Code Reference Document ASCE7-16
Risk Category II
Site Class D - Default (See Section 11.4.3)
Type Value Description
SS 1.017 MCER ground motion. (for 0.2 second period)
S1 0.37 MCER ground motion. (for 1.0s period)
SMS 1.221 Site-modified spectral acceleration value
SM1 null -See Section 11.4.8 Site-modified spectral acceleration value
SDS 0.814 Numeric seismic design value at 0.2 second SA
SD1 null -See Section 11.4.8 Numeric seismic design value at 1.0 second SA
Type Value Description
SDC null -See Section 11.4.8 Seismic design category
Fa 1.2 Site amplification factor at 0.2 second
Fv null -See Section 11.4.8 Site amplification factor at 1.0 second
PGA 0.446 MCEG peak ground acceleration
FPGA 1.2 Site amplification factor at PGA
PGAM 0.535 Site modified peak ground acceleration
TL 8 Long-period transition period in seconds
SsRT 1.017 Probabilistic risk-targeted ground motion. (0.2 second)
SsUH 1.133 Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration
SsD 1.5 Factored deterministic acceleration value. (0.2 second)
S1RT 0.37 Probabilistic risk-targeted ground motion. (1.0 second)
S1UH 0.408 Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration.
S1D 0.6 Factored deterministic acceleration value. (1.0 second)
PGAd 0.503 Factored deterministic acceleration value. (Peak Ground Acceleration)
CRS 0.898 Mapped value of the risk coefficient at short periods
CR1 0.909 Mapped value of the risk coefficient at a period of 1 s
DISCLAIMER
While the information presented on this website is believed to be correct, SEAOC /OSHPD and its sponsors and contributors assume no responsibility or liability for its accuracy. The material
presented in this web application should not be used or relied upon for any specific application without competent examination and verification of its accuracy, suitability and applicability by engineers
or other licensed professionals. SEAOC / OSHPD do not intend that the use of this information replace the sound judgment of such competent professionals, having experience and knowledge in the
field of practice, nor to substitute for the standard of care required of such professionals in interpreting and applying the results of the seismic data provided by this website. Users of the information
from this website assume all liability arising from such use. Use of the output of this website does not imply approval by the governing building code bodies responsible for building code approval and
interpretation for the building site described by latitude/longitude location in the search results of this website.
APPENDIX C
STANDARD GRADING SPECIFICATIONS
STANDARD GRADING SPECIFICATIONS
Page 1
These specifications present the usual and minimum requirements for projects on which Petra Geosciences,
Inc. (Petra) is the geotechnical consultant. No deviation from these specifications will be allowed, except
where specifically superseded in the preliminary geology and soils report, or in other written communication
signed by the Soils Engineer and Engineering Geologist of record (Geotechnical Consultant).
I. GENERAL
A. The Geotechnical Consultant is the Owner's or Builder's representative on the project. For the purpose
of these specifications, participation by the Geotechnical Consultant includes that observation
performed by any person or persons employed by, and responsible to, the licensed Soils Engineer and
Engineering Geologist signing the soils report.
B. The contractor should prepare and submit to the Owner and Geotechnical Consultant a work plan that
indicates the sequence of earthwork grading, the number of "spreads" and the estimated quantities of
daily earthwork to be performed prior to the commencement of grading. This work plan should be
reviewed by the Geotechnical Consultant to schedule personnel to perform the appropriate level of
observation, mapping, and compaction testing as necessary.
C. All clearing, site preparation, or earthwork performed on the project shall be conducted by the
Contractor in accordance with the recommendations presented in the geotechnical report and under the
observation of the Geotechnical Consultant.
D. It is the Contractor's responsibility to prepare the ground surface to receive the fills to the satisfaction
of the Geotechnical Consultant and to place, spread, mix, water, and compact the fill in accordance
with the specifications of the Geotechnical Consultant. The Contractor shall also remove all material
considered unsatisfactory by the Geotechnical Consultant.
E. It is the Contractor's responsibility to have suitable and sufficient compaction equipment on the job
site to handle the amount of fill being placed. If necessary, excavation equipment will be shut down to
permit completion of compaction to project specifications. Sufficient watering apparatus will also be
provided by the Contractor, with due consideration for the fill material, rate of placement, and time of
year.
F. After completion of grading a report will be submitted by the Geotechnical Consultant.
II. SITE PREPARATION
A. Clearing and Grubbing
1. All vegetation such as trees, brush, grass, roots, and deleterious material shall be disposed of
offsite. This removal shall be concluded prior to placing fill.
2. Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic tanks,
wells, pipe lines, etc., are to be removed or treated in a manner prescribed by the Geotechnical
Consultant.
STANDARD GRADING SPECIFICATIONS
Page 2
III. FILL AREA PREPARATION
A. Remedial Removals/Overexcavations
1. Remedial removals, as well as overexcavation for remedial purposes, shall be evaluated by the
Geotechnical Consultant. Remedial removal depths presented in the geotechnical report and
shown on the geotechnical plans are estimates only. The actual extent of removal should be
determined by the Geotechnical Consultant based on the conditions exposed during grading. All
soft, loose, dry, saturated, spongy, organic-rich, highly fractured or otherwise unsuitable ground
shall be overexcavated to competent ground as determined by the Geotechnical Consultant.
2. Soil, alluvium, or bedrock materials determined by the Soils Engineer as being unsuitable for
placement in compacted fills shall be removed from the site. Any material incorporated as a part
of a compacted fill must be approved by the Geotechnical Consultant.
3. Should potentially hazardous materials be encountered, the Contractor should stop work in the
affected area. An environmental consultant specializing in hazardous materials should be
notified immediately for evaluation and handling of these materials prior to continuing work in
the affected area.
B. Evaluation/Acceptance of Fill Areas
All areas to receive fill, including removal and processed areas, key bottoms, and benches, shall be
observed, mapped, elevations recorded, and/or tested prior to being accepted by the Geotechnical
Consultant as suitable to receive fill. The contractor shall obtain a written acceptance from the
Geotechnical Consultant prior to fill placement. A licensed surveyor shall provide sufficient survey
control for determining locations and elevations of processed areas, keys, and benches.
C. Processing
After the ground surface to receive fill has been declared satisfactory for support of fill by the
Geotechnical Consultant, it shall be scarified to a minimum depth of 6 inches and until the ground
surface is uniform and free from ruts, hollows, hummocks, or other uneven features which may
prevent uniform compaction.
The scarified ground surface shall then be brought to optimum moisture, mixed as required, and
compacted to a minimum relative compaction of 90 percent.
D. Subdrains
Subdrainage devices shall be constructed in compliance with the ordinances of the controlling
governmental agency, and/or with the recommendations of the Geotechnical Consultant. (Typical
Canyon Subdrain details are given on Plate SG-1).
E. Cut/Fill & Deep Fill/Shallow Fill Transitions
In order to provide uniform bearing conditions in cut/fill and deep fill/shallow fill transition lots, the
cut and shallow fill portions of the lot should be overexcavated to the depths and the horizontal
limits discussed in the approved geotechnical report and replaced with compacted fill. (Typical
details are given on Plate SG-7.)
STANDARD GRADING SPECIFICATIONS
Page 3
IV. COMPACTED FILL MATERIAL
A. General
Materials excavated on the property may be utilized in the fill, provided each material has been
determined to be suitable by the Geotechnical Consultant. Material to be used for fill shall be
essentially free of organic material and other deleterious substances. Roots, tree branches, and
other matter missed during clearing shall be removed from the fill as recommended by the
Geotechnical Consultant. Material that is spongy, subject to decay, or otherwise considered
unsuitable shall not be used in the compacted fill.
Soils of poor quality, such as those with unacceptable gradation, high expansion potential, or low
strength shall be placed in areas acceptable to the Geotechnical Consultant or mixed with other
soils to achieve satisfactory fill material.
B. Oversize Materials
Oversize material defined as rock, or other irreducible material with a maximum dimension greater
than 12 inches in diameter, shall be taken offsite or placed in accordance with the
recommendations of the Geotechnical Consultant in areas designated as suitable for rock disposal
(Typical details for Rock Disposal are given on Plate SG-4).
Rock fragments less than 12 inches in diameter may be utilized in the fill provided, they are not
nested or placed in concentrated pockets; they are surrounded by compacted fine grained soil
material and the distribution of rocks is approved by the Geotechnical Consultant.
C. Laboratory Testing
Representative samples of materials to be utilized as compacted fill shall be analyzed by the labora-
tory of the Geotechnical Consultant to determine their physical properties. If any material other
than that previously tested is encountered during grading, the appropriate analysis of this material
shall be conducted by the Geotechnical Consultant as soon as possible.
D. Import
If importing of fill material is required for grading, proposed import material should meet the
requirements of the previous section. The import source shall be given to the Geotechnical
Consultant at least 2 working days prior to importing so that appropriate tests can be performed and
its suitability determined.
V. FILL PLACEMENT AND COMPACTION
A. Fill Layers
Material used in the compacting process shall be evenly spread, watered, processed, and compacted
in thin lifts not to exceed 6 inches in thickness to obtain a uniformly dense layer. The fill shall be
placed and compacted on a horizontal plane, unless otherwise approved by the Geotechnical
Consultant.
STANDARD GRADING SPECIFICATIONS
Page 4
B. Moisture Conditioning
Fill soils shall be watered, dried back, blended, and/or mixed, as necessary to attain a relatively
uniform moisture content at or slightly above optimum moisture content.
C. Compaction
Each layer shall be compacted to 90 percent of the maximum density in compliance with the
testing method specified by the controlling governmental agency. (In general, ASTM D 1557-02,
will be used.)
If compaction to a lesser percentage is authorized by the controlling governmental agency because
of a specific land use or expansive soils condition, the area to received fill compacted to less than
90 percent shall either be delineated on the grading plan or appropriate reference made to the area
in the soils report.
D. Failing Areas
If the moisture content or relative density varies from that required by the Geotechnical Consultant,
the Contractor shall rework the fill until it is approved by the Geotechnical Consultant.
E. Benching
All fills shall be keyed and benched through all topsoil, colluvium, alluvium or creep material, into
sound bedrock or firm material where the slope receiving fill exceeds a ratio of 5 horizontal to 1
vertical, in accordance with the recommendations of the Geotechnical Consultant.
VI. SLOPES
A. Fill Slopes
The contractor will be required to obtain a minimum relative compaction of 90 percent out to the
finish slope face of fill slopes, buttresses, and stabilization fills. 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, or by any other procedure that produces the required compaction.
B. Side Hill Fills
The key for side hill fills shall be a minimum of 15 feet within bedrock or firm materials, unless
otherwise specified in the soils report. (See detail on Plate SG-5.)
C. Fill-Over-Cut Slopes
Fill-over-cut slopes shall be properly keyed through topsoil, colluvium or creep material into rock
or firm materials, and the transition shall be stripped of all soils prior to placing fill. (see detail on
Plate SG-6).
STANDARD GRADING SPECIFICATIONS
Page 5
D. Landscaping
All fill slopes should be planted or protected from erosion by other methods specified in the soils
report.
E. Cut Slopes
1. The Geotechnical Consultant should observe all cut slopes at vertical intervals not exceeding
10 feet.
2. If any conditions not anticipated in the preliminary report such as perched water, seepage,
lenticular or confined strata of a potentially adverse nature, unfavorably inclined bedding,
joints or fault planes are encountered during grading, these conditions shall be evaluated by
the Geotechnical Consultant, and recommendations shall be made to treat these problems
(Typical details for stabilization of a portion of a cut slope are given in Plates SG-2 and SG-
3.).
3. Cut slopes that face in the same direction as the prevailing drainage shall be protected from
slope wash by a non-erodible interceptor swale placed at the top of the slope.
4. Unless otherwise specified in the soils and geological report, no cut slopes shall be excavated
higher or steeper than that allowed by the ordinances of controlling governmental agencies.
5. Drainage terraces shall be constructed in compliance with the ordinances of controlling
governmental agencies, or with the recommendations of the Geotechnical Consultant.
VII. GRADING OBSERVATION
A. General
All cleanouts, processed ground to receive fill, key excavations, subdrains, and rock disposals must
be observed and approved by the Geotechnical Consultant prior to placing any fill. It shall be the
Contractor's responsibility to notify the Geotechnical Consultant when such areas are ready.
B. Compaction Testing
Observation of the fill placement shall be provided by the Geotechnical Consultant during the
progress of grading. Location and frequency of tests shall be at the Consultants discretion based on
field conditions encountered. Compaction test locations will not necessarily be selected on a
random basis. Test locations may be selected to verify adequacy of compaction levels in areas that
are judged to be susceptible to inadequate compaction.
C. Frequency of Compaction Testing
In general, density tests should be made at intervals not exceeding 2 feet of fill height or every
1000 cubic yards of fill placed. This criteria will vary depending on soil conditions and the size of
the job. In any event, an adequate number of field density tests shall be made to verify that the
required compaction is being achieved.
STANDARD GRADING SPECIFICATIONS
Page 6
VIII. CONSTRUCTION CONSIDERATIONS
A. Erosion control measures, when necessary, shall be provided by the Contractor during grading and
prior to the completion and construction of permanent drainage controls.
B. Upon completion of grading and termination of observations by the Geotechnical Consultant, no
further filling or excavating, including that necessary for footings, foundations, large tree wells,
retaining walls, or other features shall be performed without the approval of the Geotechnical
Consultant.
C. Care shall be taken by the Contractor during final grading to preserve any berms, drainage terraces,
interceptor swales, or other devices of permanent nature on or adjacent to the property.
S:\!BOILERS-WORK\REPORT INSERTS\STANDARD GRADING SPECS
DEPTH AND BEDDING MAY
VARY WITH PIPE AND LOAD
CHARACTERISTICS.
(3' TYPICAL)
PROPOSED COMPACTED FILL
REMOVE
UNSUITABLE
MATERIAL
c;~;,~ENTNAT1~~so1L: ·
·. ORBEDROCKMATERIALS
· AS DETERMINED BY THE ·
. GEOTECHN/CAL .
. . · CONSUL TANT .
. ALTERNATE SUBDRAIN SYSTEM -
. · MINIMUM OF 9 CUBIC FEET PER < LINEAL FOOT OF CLASS 2 FILTER
.. MATERIAL. SEE PLATE SG-3 FOR
. CLASS 2 FILTER MATERIAL
·SPECIFICATIONS. CLASS 2
MATERIAL OOES NOT NEED TO BE
ENCASED IN FILTER FABRIC.
MINIMUM 6-INCH DIAMETER PVC SCHEDULE 40, OR ABS SDR-35 WITH A
MINIMUM OF EIGHT 1/4-INCH DIAMETER PERFORATIONS PER LINEAL FOOT IN
BOTTOM HALF OF PIPE. PIPE TO BE LAID WITH PERFORATIONS FACING DOWN.
NQJES:
1. FOR CONTINUOUS RUNS IN EXCESS OF 500 FEET USE 8-INCH DIAMETER PIPE.
2. FINAL 20 FEET OF PIPE AT OUTLET SHALL BE NON-PERFORATED AND
BACKFILLED WITH FINE-GRAINED MATERIAL.
·PETRA CANYON SUBDRA1N DETAtl PLATESG-1
ROUGH GRADING CONSTRUCTION. PROVIDE
GRATES TO PREVENT RODENT NESTING.
PROPOSED GRADE
OVEREXCAVATE PAD
AS RECOMMENDED BY
GEOTECHNICAL CONSULT ANT
OUTLETS TO BE SPACED AT 100' MAX. INTERVALS.\ EXTEND 12" BEYOND FACE OF SLOPE AT TIME OF
,__..._ _________________ .,__,.
",' , ,,·. -.. ,·,, •' "• ',·,,,•· ,' '
2' Mir{ t<EY bEPTH ir-fr6 d6~PETEN'r
BEDROCK OR COMPETENT SOIL
MATERIALS AS DETERMINED BY THE
GEOTECHNICAL CONSUL TANT
N.QIES:
.,..,.,.........,.,..
1; 30' MAXIMUM VERTICAL SPACING BETWEEN SUBDRAIN SYSTEMS.
i,. ,',.,'. ,·,, .,,• ·.·· ,
.··•• •• .. TYPl~A~-~~NCHl~(i ·--.
2. tOO' MAXIMUM HORIZONTAL DISTANCE BETWEEN NON-PERFORATED OUTLET PIPES. (See Below)
3. MINIMUM GRADIENT OF 2% FOR ALL PERFORATED AND NON-PERFORATED PIPE.
SECTION A-A (PERFORATED PIPE PROFILE)
---------100' max.--------1--< ---50'-------I•-< ---50'------
\
OUTLET PIPE (TYPICAL)
PETRA
\I -~
PERFORATED PIPE (lYPICAL)
BUTTRESS OR STABILIZATION
FILL DETAIL
:::D g< \
OUTLET PIPE (TYPICAL)
PLATESG.;2
.. ··.•.····· .• ·• . APPROVEDFILTERMATERIAL(OPEN-', : . ·. . ., ·• , : GRADED GRAVEL WRAPPED IN FILTER
, ) ... · .. ·.,. ;··.·.·.·. -: ... :.;. /· ~ FABRIC OR CLASS 2 FILTER MATERIAL).
; !, ·• •· : f-'/.'.,, .:· -.. -._:·.:·.:·.:·.: 5 CUBIC FEET OF CLASS 2 FILTER
· ~}'' .:· .. \··.::.:·.:·.:·. MATERIAL WITHOUT FILTER FABRIC
SLOPE FACE
f!:~========::!i=:::::::=::::::===:;::::::::=:::::;;;;;;;;;~
12" min.
1
. [& ......... • ............. , , ...... · ... • .. .. .. MIRAFI 140N OR EQUIVALENT, AND
' ··.:·.;-;·.:· .. '.:·.:· .. ,,\ ... :·.:·.:· .. '.:·.:·, ··:·.:·;·.. SHOULD BE LAPPED A MINIMUM OF
·. . ::··/·.:·-::··~-::•·::-.::-·::-.::i:-\·\·•::·/•:::\ .. 12 INCHES
·: ;A-INbH NO~-PEJ·;6il+~·b::·~i;{:/::-:· .... 4-INCH PERFORATED PIPE WITH
MINIMUM 2% GRADE TO OUTLET. PERFORATIONS DOWN. MINIMUM
2% GRADE TO OUTLET PIPE.
;~~~;*J•s~fil__APPROVED ON-SITE MATERIAL PER SOILS ENGINEER ~~{~fl COMPACTED TO A MINIMUM OF 90% MAXIMUM DENSITY.
f"<,"""'"5j . 4-INCH NON-PERFORATED PIPE . ,:
,::; ''1,.
SECTION B-B (OUTLET PIPE)
PIPE SPECIFICATIONS:
1. 4-INCH MINIMUM DIAMETER, PVC SCHEDULE 40 OR ABS SDR-35.
2. FOR PERFORATED PIPE, MINIMUM 8 PERFORATIONS PER FOOT ON BOTTOM HALF OF PIPE.
FILTER MATERIAL/FABRIC SPECIFICATIONS:
OPEN-GRADED GRAVEL ENCASED IN FILTER FABRIC.
(MIRAFI 140N OR EQUIVALENT)
OPEN-GRADED GRAVEL
SIEVE SIZE
11/2-JNCH
1-INCH
3/4-INCH
3/8-INCH
No. 200
PERCENT PASSING
88-100
5-40
0-17
0-7
0-3
ALTERNATE:
CLASS 2 PERMEABLE FIL TEA MATERIAL PER CAL TRANS
STANDARD SPECIFICATION 68-1.025.
CLASS 2 FILTER MATERIAL
SIEY'.E SIZE PERCENT PASSING
1-INCH 100
3/4-INCH 90-100
3/8-INCH 40-100
No.4 25-40
No.8 18 -33
No. -30 5-15
No. -50 0-7
No. 200 0-3
PETRA BUTTRESS OR STABILIZATION
FILL SUBDRAIN PLATESG-3
10'
l
FINISHED GRADE
CLEAR AREA FOR FOUNDATIONS,
UTILITIES AND SWIMMING POOLS
SLOPE FACE
STREET
WINDROW COMPACTED FILL .. --::~\\\),......-
TYPICAL WINDROW DETAIL (END VIEW)
GRANULAR SOIL JETTED OR FLOODED
TO FILL VOIDS
. ,-'' '_,
5' OR MIN. OF 2' BELOW DEPTH
OF DEEPEST UTILITY TRENCH,
WHICHEVER IS GREATER
K----------15'MIN.----------+i
TYPICAL WINDROW DETAIL (PROFILE VIEW)
N.QIE: OVERSIZE ROCK IS DEFINED AS CLASTS HAVING A MAXIMUM DIMENSION OF 12" OR LARGER
PETRA TYPICAL ROCK DISPOSAL DETAIL PLATESG-4
TOE OF SLOPE AS SHOWN
ON GRADING PLAN
REMOVE
MATERIAL
i:'f[L
•
I<... · 15' MINIMUM_.i _____ .,..
.. · . KEYWIDTH
2' MIN. KEY DEPTH INTO COMP~EN·T.
· BEDROCK OR SOIL MATERIALS AS .
DETERMINED BY THE GEOTECHNICAL ..
CONSULT ANT .
~:
Ai TYP;CAL ' ··••
-~~.<l-··
·.··.· .. ·c6tviPEreJT BEDROCK OR so1L ,,.{4.fERIALS ·. ·
. AS DETERMINED BY THE ...
·.··.· .. GEOTECHNICALCONSULTANT .. . . .
iri H◊~ifo~ALW1DtH ·
ACE TO BENCH / BACKCUT
1. WHERE NATURAL SLOPE GRADIENT IS 5:1 OR LESS, BENCHING IS NOT NECESSARY;
HOWEVER, FILL IS NOTTO BE PLACED ON COMPRESSIBLE OR UNSUITABLE MATERIAL.
2. SOILS ENGINEER TO DETERMINE IF SUBDRAIN IS REQUIRED.
PETRA FILL SLOPE ABOVE NATURAL SLOPE PLATE SG-5
PROPOSED GRADE ------
,, ·. ::.;,~:
CUT I FILL CONTACT
SHOWN ON GRADING PLAN
SHOWN ON AS-BUILT
REMOVE UNSUITABLE
MATERIAL
NATURAL GROUND
SURFACE
PETRA
,·
:coMPETENT BEDROCKOR SOIL MATERiALB ..
AS DETERMINED BY THE
_·.·• GEOTECHN/CAL CONSUL TANT•-. ' .·.,, '• , .· .. ,·
MAINTAIN 15' MIN. HORIZONTAL WIDTH
· .. FROM SLOPE FACE TO BENCH/ BACKCUT
TION OF SUBDRAIN TO BE DETERMINED
EOTECHNICAL CONSUL TANT.
ED, SEE PLATES SG-2 AND SG-3
ETAILS.
. ·"0THE cut PORTION OF THE SLOPE SHOULD BE EXCAVATED . · ... · ..
.. ··. . .AND EVALUATED BY THE ENGINEERING GEOLOGIST PRIOR· ·.
··<TO CONSTRUCTING THE FILL PORTION OF THE SLOPE. .
FILL SLOPE ABOVE CUT SLOPE PLATE SG-6
ORIGINAL GROUND
SURFACE
C.UTLOT
UNSUITABLE MATERIAL EXPOSED IN PORTION OF CUT PAD
--r
I
I
---------------.. -----------
. . .
ci:JMPETeiT BEDRdcK dR s6iL M;iE~1Ais · • ·
-.· -· . · AS DETERMINED BY THE · .
. .. . •. ·. GEOTECHNICAL CONSUL TANT·· .. ··
CUT-FILL TRANSITION LOT
----------------r
ORIGINAL GROUND
SURFACE
MAXIMUM FILL THICKNESS (F) DEPTH OF OVEREXCAVATJON (D)
FOOTING DEPTH TO 3 FEET . . . . . . . . . EQUAL DEPTH
3 TO 6 FEET . . . . . . . . . . . . . . . . . . . . . . 3 FEET
GREATER THAN 6 FEET.. . . . . . . . . . . . 1/2 THE THICKNESS OF DEEPEST FILL PLACED WITHIN
THE "FILL" PORTION (F) TO 15 FEET MAXIMUM
PETRA CUT LOTS AND CUT-FILL
TRANSITION LOTS PLATE SG-7
PROPOSED 2:1 FILL SLOPE
EXISTING GROUND SURFACE
~ ···~ .. ~·, ~--·,.••~·-~-~--··· ~,~~-~ .
. / . TYPICAL BENCHING INTO .
> -COMPETENT BEDROCK OR . .· . , . , , . , . , .
_SOIL MATERIALS AS ,. , .:15' MINIMUM KEY
,• · DETERMINED BY THE . -. EMBEDDED A MINIMUM OF 2'
. GEOTECHNICAL CONSUL TANT ·, ' . INTO COMPETENT BEDROCK
. "-OR SOIL MATERIALS AS
DETERMINED BY THE
.. \GEOTECHNICAL CONSULTANT
D = RECOMMENDED DEPTH OF REMOVAL
PER GEOTECHNICAL REPORT
PETRA TYPICAL REMOVALS BEYOND TOE
OF PROPOSED FILL SLOPE PLATE SG-8
PROPOSED CUT LOT
NOTE:
/ EXISTING GROUND SURFACE
/ PROPOSED DAYLIGHT CUT
RECONSTRUCT AT 2:1
OR FLATTER
1. "D" SHALL BE 10 FEET MINIMUM OR AS DETERMINED BY SOILS ENGINEER.
.PETRA SHEAR KEY ON DAYLIGHT CUT LOTS PLATE SG-9