HomeMy WebLinkAboutMS 2018-0008; UPDATE REPORT OF GEOTECHNICAL INVESTIGATION; 2018-02-21I
JUL 182018
CITY O CARLSBAD
PLANNING DIVISION
UPDATE REPORT OF GEOTECHNICAL
INVESTIGATION
Hoover Street Residential Project
1095 Hoover Street
Carlsbad, California
JOB NO. 16-11187
21 February 2018
Prepared for:
Mr. Ted Viola
(1'4i Geotechnical Exploration, Inc.
SOIL AND FOUNDATION ENGINEERING S GROUNDWATER ENGINEERING GEOLOGY
21 February 2018
Mr. Ted Viola Job No.. 16-11187
4858 Park Drive, Unit 110
Carlsbad, CA 92008
Subject: Report of Geotechnical Investigation Update
Hoover Street Residential Project
1095 Hoover Street
Carlsbad, California
Dear Mr. Viola:
In accordance with your request, Geotechnical Exploration, Inc. has performed
a geotechnical investigation update for the subject property. The original fieldwork
was performed on August 12, 2016.
If the conclusions and recommendations presented in this report are incorporated
into the design and construction of the proposed residential structures, it is our
opinion that the site is suitable for the project.
This opportunity to be of service is sincerely appreciated. Should you have any
questions concerning the following report, please do not hesitate to contact us.
Reference to our Job No. 16-11187 will expedite a response to your inquiries.
Respectfully submitted,
GEOTECHNICAL EXPLORATION, INC.
3 - vai a7ffiffe- C'e r r o s, P. E.
R.C.E. 34422/G.E. 2007
Senior Geotechnical Engineer
Jon an A. Browning
P. . 9012 C.E.G. 2615
Se 0r Pr ject Geologist
7420 TRADE STREET. SAN DIEGO, CA. 921210 (858) 549-72220 FAX: (858) 549-16040 EMAIL: geotech@ge1-sd.com
TABLE OF CONTENTS
PAGE
I. PROJECT SUMMARY AND SCOPE OF SERVICES 1
II. SITE DESCRIPTION 1
III. FIELD INVESTIGATION 2
IV. SOIL DESCRIPTION 3
V. GROUNDWATER 4
VI, SEISMIC CONSIDERATIONS 5
VII. GEOLOGIC HAZARDS 6
VIII, LABORATORY TESTS & SOIL INFORMATION 13
IX. CONCLUSION AND RECOMMENDATIONS 15
X. GRADING NOTES 33
XI. LIMITATIONS 34
FIGURES
I. Vicinity Map
Ha-b. Plot Plan and Geologic Cross Section
lila-h. Exploratory Test Pit Logs
Laboratory Test Results
Geologic Map and Legend
Foundation Requirements Near Slopes
Retaining Wall Drainage Schematic
APPENDICES
Unified Soil Classification System
USGS Design Maps Summary Report
Slope Stability Analysis
UPDATE REPORT OF GEOTECHNICAL INVESTIGATION
Hoover Street Residential Project
1095 Hoover Street
Carlsbad, California
Job No. 16-11187
The following report presents the findings and recommendations of Geotechnical
Exploration, Inc. for the subject proposed residential structures.
I. PROJECT SUMMARY AND SCOPE OF SER VICES
It is our understanding, based on information provided by Mr. Viola, that the
residential property is to be split into two lots and the construction of a new single-
family residential structure and associated improvements. We understand that the
planned project will consist of a two-story structure with a basement that will utilize
conventional foundations. We have reviewed the grading plans by the Sea Bright
Company. Additional or modified recommendations have been provided.
The scope of work performed for this investigation included a site reconnaissance
and subsurface exploration program, laboratory testing, geotechnical engineering
analysis of the field and laboratory data, and the preparation of this report. The
data obtained and the analyses performed were for the purpose of providing design
and construction criteria for the project earthwork, building foundations, slab on-
grade floors, and concrete driveways.
IL SITE DESCRIPTION
The subject site is located in the City of Carlsbad, State of California. For the
location of the site, refer to the Vicinity Map, Figure No. I.
Hoover Street ResidentFal Project Job No. 16-11187
Carlsbad, California I Page 2
The vacant lot is bordered on the north by Hoover Street; on the east by Adams
Street; on the south by similar undeveloped residential property; and on the west
by open space property adjacent to Agua Hedionda Lagoon. Access to the lot is
along the south side of Hoover Street, a cul-de-sac. Refer to the Plot Plan, Figure
No. II.
Vegetation at the site consists primarily of native weeds, ice plant and sparse
shrubbery. A relatively deep erosion gulley exists in the southern portion of the
property. A storm drain pipe discharges onto the southeast portion of the property
from under Adams Street. The lot slopes moderately down to the north and west.
Elevations across the property range from approximately 67 feet above Mean Sea
Level (AMSL) along the eastern property line, to approximately 25 feet AMSL at the
southwest corner of the property. Information concerning approximate elevations
across the site was obtained from a topographic survey prepared by The Sea Bright
Company, dated August 25, 2016.
IlL FIELD INVESTIGATION
The field investigation consisted of a surface reconnaissance and a subsurface
exploration program using hand tools to investigate and sample the subsurface
soils. Eight exploratory test pits were advanced in the vicinity of the proposed
residential structures and improvements. The trenches were excavated to a
maximum depth of 3 to 4 feet in order to obtain representative soil samples and to
define a soil profile across the residential property.
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 3
The soils encountered in the exploratory test pit were continuously logged in the
field by our geologist and described in accordance with the Unified Soil
Classification System (refer to Appendix A). The approximate locations of the
exploratory trenches are shown on the Plot Plan, Figure No. II.
Representative samples were obtained from the exploratory trenches at selected
depths appropriate to the investigation. All samples were returned to our
laboratory for evaluation and testing. Exploratory trench logs have been prepared
on the basis of our observations and laboratory test results. Logs of the
exploratory test pits are attached as Figure Nos. lila-h.
IV. SOIL DESCRIPTION
Existng fill/topsoil, consisting of loose to medium dense, silty sands, were
encountered in all test pits to a depth of 1 to 2 feet. Medium dense to dense
formational materials, comprised of silty sand, terrace materials referred to as Old
Paralic Deposits (Q0132..4), underlie the fill/topsoil as encountered in the eight
exploratory test pits. These formational materials are generally massive and
horizontal. In our opinion, the silty sand fill/topsoil and the silty sand formational
soils possess a low potential for expansion.
The exploratory test pit logs and related information depict subsurface conditions
only at the specific locations shown on the site plan and on the particular date
designated on the logs. Also, the passage of time may result in changes in the
subsurface conditions due to environmental changes.
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 4
V. GROUNDWATER
Free groundwater was not encountered in the exploratory test pits at the time of
excavation. It must be noted, however, that fluctuations in the level of
groundwater may occur due to variations in ground surface topography, subsurface
stratification, rainfall, and other possible factors that may not have been evident at
the time of our field investigation.
It should be kept in mind that grading operations can change surface drainage
patterns and/or reduce permeabilities due to the densification of compacted soils.
Such changes of surface and subsurface hydrologic conditions, plus irrigation of
landscaping or significant increases in rainfall, may result in the appearance of
surface or near-surface water at locations where none existed previously. The
appearance of such water is expected to be localized and cosmetic in nature, if
good positive drainage is implemented, as recommended in this report, during and
at the completion of construction.
It must be understood that unless discovered during initial site exploration or
encountered during site grading operations, it is extremely difficult to predict if or
where perched or true groundwater conditions may appear in the future. When site
fill or formational soils are fine-grained and of low permeability, water problems
may not become apparent for extended periods of time.
Water conditions, where suspected or encountered during construction, should be
evaluated and remedied by the project civil and geotechnical consultants. The
project developer and property owner, however, must realize that post-construction
appearances of groundwater may have to be dealt with on a site-specific basis.
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 5
VI. SEISMIC CONSIDERATIONS
The San Diego area, as most of California, is located in a seismically active region.
The San Diego area has been referred to as the eastern edge of the Southern
California Continental, Borderland, an extension of the Peninsular Ranges
Geomorphic Province. The borderland is part of a broad tectonic boundary between
the North American and Pacific Plates. The plate boundary is dominated by a
complex system of active major strike-slip (right lateral), northwest trending faults
extending from the San Andreas fault, about 70 miles east, to the San Clemente
fault, about 50 miles west of the San Diego metropolitan area.
Based on our review of some available published information including the
California Geologic Survey and United States Geological Survey"Geologic Map of
the Oceanside 30'x60' Quadrangle, California," by Michael P. Kennedy and Siang S.
Tan (2007), the bedrock geologic materials underlying the site are referred to as
the "Old Paralic Deposits—Reddish brown, silty, sandstone interbedded with brown,
clayey sandstone." According to the aforementioned map, there are no faults
known to pass through the site. Refer to Figure No. V, Geologic Map.
The prominent fault zones generally considered having the most potential for
earthquake damage in the vicinity of the site are the active Rose Canyon and
Coronado Bank fault zones mapped approximately 5 and 21 miles southwest of the
site, respectively, and the active Elsinore and San Jacinto fault zones mapped
approximately 24 and 47 miles northeast of the site, respectively.
Although research on earthquake prediction has greatly increased in recent years,
geologists and seismologists have not yet reached the point where they can predict
when and where an earthquake will occur. Nevertheless, on the basis of current
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 6
technology, it is reasonable to assume that the proposed residence may be subject
to the. effects of at least one moderate to major earthquake during its design life.
During such an earthquake, the danger from fault offset through the site is remote,
but relatively strong ground shaking is likely to occur.
VII GEOLOGIC HAZARDS
The following is a discussion of the geologic conditions and hazards common to this
area of the City of Carlsbad, as well as project-specific geologic information relating
to development of the subject property.
A. Local and Regional Faults
Reference to the geologic map of the area (Kennedy and Tan, 2007), Figure No. V,
indicates that no faults are shown to cross the site. In our explicit professional
opinion, neither an active fault nor a potentially active fault underlies the site.
Rose Canyon Fault: The Rose Canyon Fault Zone (Mount Soledad and Rose Canyon
Faults) is located approximately 5 miles southwest of the subject site. The Rose
Canyon Fault is mapped trending north-south from Oceanside to downtown San
Diego, from where it appears to head southward into San Diego Bay, through
Coronado and offshore. The Rose Canyon Fault Zone is considered to be a complex
zone of onshore and offshore, en echelon strike slip, oblique reverse, and oblique
normal faults. The Rose Canyon Fault is considered to be capable of generating an
M7.2 earthquake and is considered microseismically active, although no significant
recent earthquakes are known to have occurred on the fault.
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 7
Investigative work on faults that are part of the Rose Canyon Fault Zone at the
Police Administration and Technical Center in downtown San Diego, at the SDG&E
facility in Rose Canyon, and within San Diego Bay and elsewhere within downtown
San Diego, has encountered offsets in Holocene (geologically recent) sediments.
These findings confirm Holocene displacement on the Rose Canyon Fault, which was
designated an "active" fault in November 1991 (Hart, E.W. and W.A. Bryant, 2007,
Fault-Rupture Hazard Zones in California, California Geological Survey Special
Publication 42).
Coronado Bank Fault: The Coronado Bank Fault is located approximately 21 miles
southwest of the site. Evidence for this fault is based upon geophysical data
(acoustic profiles) and the general alignment of epicenters of recorded seismic
activity (Greene, 1979). The Oceanside earthquake of M5.3 recorded July 13,
1986. is known to have been centered on the fault or within the Coronado Bank
Fault Zone. Although this fault is considered active, due to the seismicity within the
fault zone, it is significantly less active seismically than the Elsinore Fault (Hileman,
1973). It is postulated that the Coronado Bank Fault is capable of generating a
M7.6 earthquake and is of great interest due to its close proximity to the greater
San Diego metropolitan area.
Newport-Inglewood Fault: The Newport-Inglewood Fault Zone is located
approximately 18 miles northwest of the site. A significant earthquake (M6.4)
occu-red along this fault on March 10, 1933. Since then no additional significant
events have occurred. The fault is believed to have a slip rate of approximately 0.6
mm/yr with an unknown recurrence interval. This fault is believed capable of
producing an earthquake of M6.0 to M7.4 (SCEC, 2004).
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 8
Elsinore Fault: The Elsinore Fault is located approximately 24 miles northeast of
the site. The fault extends approximately 200 kilometers (125 miles) from the
Mexican border to the northern end of the Santa Ana Mountains. The Elsinore Fault
zone is a 1- to 4-mile-wide, northwest-southeast-trending zone of discontinuous
and en echelon faults extending through portions of Orange, Riverside, San Diego,
and imperial Counties. Individual faults within the Elsinore Fault Zone range from
less than 1 mile to 16 miles in length. The trend, length and geomorphic
expression of the Elsinore Fault Zone identify it as being a part of the highly active
San Andreas Fault system.
Like the other faults in the San Andreas system, the Elsinore Fault is a transverse
fault showing predominantly right-lateral movement. According to Hart, et al.
(1979), this movement averages less than 1 centimeter per year. Along most of its
length, the Elsinore Fault Zone is marked by a bold topographic expression
consisting of linearly aligned ridges, swales and hallows. Faulted Holocene alluvial
deposits (believed to be less than 11,000 years old) found along several segments
of the fault zone suggest that at least part of the zone is currently active.
Although the Elsinore Fault Zone belongs to the San Andreas set of active,
northwest-trending, right-slip faults in the southern California area (Crowell, 1962),
it has not been the site of a major earthquake in historic time, other than a M6.0
earthquake near the town of Elsinore in 1910 (Richter, 1958; Toppozada and Parke,
1982). However, based on length and evidence of late-Pleistocene or Holocene
displacement, Greensfelder (1974) has estimated that the Elsinore Fault Zone is
reasonably capable of generating an earthquake ranging from M6.8 to M7.1.
Faulting evidence exposed in trenches placed in Glen Ivy Marsh across the Glen Ivy
North Fault (a strand of the Elsinore Fault Zone between Corona and Lake Elsinore),
suggest a maximum earthquake recurrence interval of 300 years, and when
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 9
combined with previous estimates of the long-term horizontal slip rate of 0.8 to 7.0
mm/year, suggest typical earthquakes of M6.0 to M7.0 (Rockwell, 1985).
San Jacinto Fault: The San Jacinto Fault is located 47 miles to the northeast of the
site. The San Jacinto Fault Zone consists of a series of closely spaced faults,
including the Coyote Creek Fault, that form the western margin of the San Jacinto
Mountains. The fault zone extends from its junction with the San Andreas Fault in
San Bernardino, southeasterly toward the Brawley area, where it continues south of
the international border as the Imperial Transform Fault (Earth Consultants
International [Ed, 2009).
The San Jacinto Fault zone has a high level of historical seismic activity, with at
least 10 damaging earthquakes (M6.0 to M7.0) having occurred on this fault zone
between 1890 and 1986. Earthquakes on the San Jacinto Fault in 1899 and 1918
caused fatalities in the Riverside County area. Offset across this fault is
predominantly right-lateral, similar to the San Andreas Fault, although some
investigators have suggested that dip-slip motion contributes up to 10% of the net
slip (ECI, 2009).
The segments of the San Jacinto Fault that are of most concern to major
metropolitan areas are the San Bernardino, San Jacinto Valley and Anza segments.
Fault slip rates on the various segments of the San Jacinto are less well constrained
than for the San Andreas Fault, but the available data suggest slip rates of 12 ±6
mm/yr for the northern segments of the fault, and slip rates of 4 ±2 mm/yr for the
southern segments. For large ground-rupturing earthquakes on the San Jacinto
fault, various investigators have suggested a recurrence interval of 150 to 300
years. The Working Group on California Earthquake Probabilities (WGCEP, 2008)
has estimated that there is a 31 percent probability that an earthquake of M6.7 or
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 10
greater will occur within 30 years on this fault. Maximum credible earthquakes of
M6.7, M6.9, and M7.2 are expected on the San Bernardino, San Jacinto Valley and
Anza segments, respectively, capable of generating peak horizontal ground
accelerations of 0.48g to 0.53g in the County of Riverside, (Ed, 2009). A M5.4
earthquake occurred on the San Jacinto Fault on July 7, 2010.
The United States Geological Survey has issued the following statements with
respect to the recent seismic activity on southern California faults;
The San Jacinto fault, along with the Elsinore, San Andreas, and other
faults, is part of the plate boundary that accommodates about 2
inches/year of motion as the Pacific plate moves northwest relative to
the North American plate. The largest recent earthquake on the San
Jacinto fault, near this location, the M6.5 1968 Borrego Mountain
earthquake April 8, 1968, occurred about 25 miles southeast of the
July 7, 2010, M5.4 earthquake.
This M5.4 earthquake follows the 4th of April 2010, Easter Sunday,
M7.2 earthquake, located about 125 miles to the south, well south of
the US Mexico international border. A M4.9 earthquake occurred in
the same area on June 12th at 8:08 pm (Pacific Time). Thus this
section of the San Jacinto fault remains active.
Seismologists are watching two major earthquake faults in southern
California. The San Jacinto fault, the most active earthquake fault in
southern California, extends for more than 100 miles from the
international border into San Bernardino and Riverside, a major
metropolitan area often called the Inland Empire. The Elsinore fault is
more than 110 miles long, and extends into the Orange County and
Los Angeles area as the Whittier fault. The Elsinore fault is capable of
a major earthquake that would significantly affect the large
metropolitan areas of southern California. The Elsinore fault has not
hosted a major earthquake in more than 100 years. The occurrence of
these earthquakes along the San Jacinto fault and continued
aftershocks demonstrates that the earthquake activity' in the region
remains at an elevated level. The San Jacinto fault is known as the
most active earthquake fault in southern California. Caltech and USGS
seismologist continue to monitor the ongoing earthquake activity using
UPDATE REPORT OF GEOTECHNICAL INVESTIGATION
Hoover Street Residential Project
1095 Hoover Street
Carlsbad, California
Job No. 16-11187
The following report presents the findings and recommendations of Geotechnical
Exploration, Inc. for the subject proposed residential structures.
I. PROJECT SUMMARY AND SCOPE OF SERVICES
It is our understanding, based on information provided by Mr. Viola, that the
residential property is to be split into two lots and the construction of a new single-
family residential structure and associated improvements. We understand that the
planned project will consist of a two-story structure with a basement that will utilize
conventional foundations. We have reviewed the grading plans by the Sea Bright
Company. Additional or modified recommendations have been provided.
The scope of work performed for this investigation included a site reconnaissance
and subsurface exploration program, laboratory testing, geotechnical engineering
analysis of the field and laboratory data, and the preparation of this report. The
data obtained and the analyses performed were for the purpose of providing design
and construction criteria for the project earthwork, buiding foundations, slab on-
grade floors, and concrete driveways.
II. SITE DESCRIPTION
The subject site is located in the City of Carlsbad, State of California. For the
location of the site, refer to the Vicinity Map, Figure No. I.
454
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 2
The vacant lot is bordered on the north by the intersection of Hoover Street and
Adams Street; on the east by Adams Street; on the south by similar undeveloped
residential property; and on the west by Hoover Street. Access to the lot is along
the south side of Hoover Street, a cul-de-sac. Refer to the Plot Plan, Figure No. II.
Vegetation at the site consists primarily of native weeds, ice plant and sparse
shrubbery. A relatively deep erosion gulley exists in the southern portion of the
property. A storm drain pipe discharges onto the southeast portion of the property
from under Adams Street. In general, the lot slopes moderately down to the west
and southwest.
Elevations across the property range from approximately 67 feet above Mean Sea
Level (MSL) along the eastern property line, to approximately 25 feet above (MSL)
at the southwest corner of the property. Information concerning approximate
elevations across the site was obtained from a topographic survey prepared by The
Sea Bright Company, dated August 25, 2016.
IlL FIELD INVESTIGATION
The field investigation consisted of a surface reconnaissance and a subsurface
exploration program using hand tools to investigate and sample the subsurface
soils. Eight exploratory test pits were advanced in the vicinity of the proposed
residential structures and improvements. The test pits were excavated to a
maximum depth of 3 to 4 feet in order to obtain representative soil samples and to
define a soil profile across the residential property.
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 3
The soils encountered in the exploratory test pit were continuously logged in the
field by our geologist and described in accordance with the Unified Soil
Classification System (refer to Appendix A). The approximate locations of the
exploratory test pits are shown on the Plot Plan, Figure No. II.
Representative samples were obtained from the exploratory test pits at selected
depths appropriate to the investigation. All samples were returned to our
laboratory for evaluation and testing. Exploratory test pit logs have been prepared
on the basis of our observations and laboratory test results. Logs of the
exploatory test pits are attached as Figure Nos. lila-h.
IV. SOIL DESCRIPTION
Existing fill/topsoil, consisting of loose to medium dense, silty sands, were
encountered in all test pits to a depth of 1 to 2 feet. Medium dense to dense
formational materials, comprised of silty sand, terrace materials referred to as Old
Paralic Deposits (QOP2.4, underlie the fill/topsoil as encountered in all of the eight
exploratory test pits. These formational materials are generally massive and
horizontal. In our opinion, the silty sand fill/topsoil and the silty sand formational
soils possess a low potential for expansion.
The exploratory test pit logs and related information depict subsurface conditions
only at the specific locations shown on the site plan and on the particular date
designated on the logs. Also, the passage of time may result in changes in the
subsurface conditions due to environmental changes.
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 4
V. GROUNDWATER
Free groundwater was not encountered in the exploratory test pits at the time of
excavation. It must be noted, however, that fluctuations in the level of
groundwater may occur due to variations in ground surface topography, subsurface
stratification, rainfall, and other possible factors that may not have been evident at
the time of our field investigation.
It should be kept in mind that grading operations can change surface drainage
patterns and/or reduce permeabilities due to the derisification of compacted soils.
Such changes of surface and subsurface hydrologic conditions, plus irrigation of
landscaping or significant increases in rainfall, may result in the appearance of
surface or near-surface water at locations where none existed previously. The
appearance of such water is expected to be localized and cosmetic in nature, if
good positive drainage is implemented, as recommended in this report, during and
at the completion of construction.
It must be understood that unless discovered during initial site exploration or
encountered during site grading operations, it is extremely difficult to predict if or
where perched or true groundwater conditions may appear in the future. When site
fill or formational soils, are fine-grained and of low permeability, water problems
may not become apparent for extended periods of time.
Water conditions, where suspected or encountered during construction, should be
evaluated and remedied by the project civil and geotechnical consultants. The
project developer and property owner, however, must realize that post-construction
appearances of groundwater may have to be dealt with on a site-specific basis.
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 5
VI. SEISMIC CONSIDERATIONS
The San Diego area, as most of California, is located in a seismically active region.
The San Diego area has been referred to as the eastern edge of the Southern
California Continental Borderland, an extension of the Peninsular Ranges
Geomorphic Province. The borderland is part of a broad tectonic boundary between
the North American and Pacific Plates. The plate boundary is dominated by a
complex system of active major strike-slip (right lateral), northwest trending faults
extending from the San Andreas fault, about 70 miles east, to the San Clemente
fault, about 50 miles west of the San Diego metropolitan area.
Based on our review of some available published information including the
California Geologic Survey and United States Geological Survey "Geologic Map of
the Oceanside 30'x60' Quadrangle, California," by Michael P. Kennedy and Siang S.
Tan (2007), the bedrock geologic materials underlying the site are referred to as
the "Old Paralic Deposits Unit 2-4—Reddish brown, silty, sandstone interbedded
with brown, clayey sandstone." According to the aforementioned map, there are no
faults known to pass through the site. Refer to Figure No. V, Geologic Map.
The prominent fault zones generally considered having the most potential for
earthquake damage in the vicinity of the site are the active Rose Canyon and
Coronado Bank fault zones mapped approximately 5 and 21 miles southwest of the
site, respectively, and the active Elsinore and San Jacinto fault zones mapped
approximately 24 and 47 miles northeast of the site, respectively.
Although research on earthquake prediction has greatly increased in recent years,
geologists and seismologists have not yet reached the point where they can predict
when and where an earthquake will occur. Nevertheless, on the basis of current
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 6
technology, it is reasonable to assume that the proposed residence may be subject
to the effects of at least one moderate to major earthquake during its design life.
During such an earthquake, the danger from fault offset through the site is remote,
but relatively strong ground shaking is likely to occur.
VII. GEOLOGIC HAZARDS
The following is a discussion of the geologic conditions and hazards common to this
area of the City of Carlsbad, as well as project-specific geologic information relating
to development of the subject property.
A. Local and Regional Faults
Reference to the geologic map of the area (Kennedy and Tan, 2007), Figure No. V,
indicates that no faults are shown to cross the site. In our explicit professional
opinion, neither an active fault nor a potentially active fault-underlies the site.
Rose Canyon Fault: The Rose Canyon Fault Zone (Mount Soledad and Rose Canyon
Faults) is located approximately 5 miles southwest of the subject site. The Rose
Canyon Fault is mapped trending north-south from Oceanside to downtown San
Diego, from where it appears to head southward into San Diego Bay, through
Coronado and offshore. The Rose Canyon Fault Zone is considered to be a complex
zone of onshore and offshore, en echelon strike slip, oblique reverse, and oblique
normal faults. The Rose Canyon Fault is considered to be capable of generating an
M7.2 earthquake and is considered microseismically active, although no significant
recent earthquakes are known to have occurred on the fault.
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 7
Investigative work on faults that are part of the Rose Canyon Fault Zone at the
Police Administration and Technical Center in downtown San Diego, at the SDG&E
facility in Rose Canyon, and within San Diego Bay and elsewhere within downtown
San Diego, has encountered offsets in Holocene (geologically recent) sediments.
These findings confirm Holocene displacement on the Rose Canyon Fault, which was
designated an "active" fault in November 1991 (Hart, E.W. and W.A. Bryant, 2007,
Fault-Rupture Hazard Zones in California, California Geological Survey Special
Publication 42).
Coronado Bank Fault: The Coronado Bank Fault is located approximately 21 miles
southwest of the site. Evidence for this fault is based upon geophysical data
(acoustic profiles) and the general alignment of epicenters of recorded seismic
activity (Greene, 1979). The Oceanside earthquake of M5.3 recorded July 13,
1986, is known to have been centered on the fault or within the Coronado Bank
Fault Zone. Although this fault is considered active, due to the seismicity within the
fault zone, it is significantly less active seismically than the Elsinore Fault (Hileman,
1973). It is postulated that the Coronado Bank Fault is capable of generating a
M7.6 earthquake and is of great interest due to its close proximity to the greater
San Diego metropolitan area.
Newport-Inglewood Fault: The Newport-Inglewood Fault Zone is located
approximately 18 miles northwest of the site. A significant earthquake (M6.4)
occurred along this fault on March 10, 1933. Since then no additional significant
events have occurred. The fault is believed to have a slip rate of approximately 0.6
mm/yr with an unknown recurrence interval. This fault is believed capable of
producing an earthquake of M6.0 to M7.4 (SCEC, 2004).
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 8
Elsinore Fault: The Elsinore Fault is located approximately 24 miles northeast of
the site. The fault extends approximately 200 kilometers (125 miles) from the
Mexican border to the northern end of the Santa Ana Mountains. The Elsinore Fault
zone is a 1- to 4-mile-wide, northwest-southeast-trending zone of discontinuous
and en echelon faults extending through portions of Orange, Riverside, San Diego,
and Imperial Counties. Individual faults within the Elsinore Fault Zone range from
less than 1 mile to 16 miles in length. The trend, length and geomorphic
expression of the Elsinore Fault Zone identify it as being a part of the highly active
San Andreas Fault system.
Like the other faults in the San Andreas system, the Elsinore Fault is a transverse
fault showing predominantly right-lateral movement. According to Hart, et al.
(1979), this movement averages less than 1 centimeter per year. Along most of its
length, the Elsinore Fault Zone is marked by a bold topographic expression
consisting of linearly aligned ridges, swales and hallows. Faulted Hoiocene alluvial
deposits (believed to be less than 11,000 years old) found along several segments
of the fault zone suggest that at least part of the zone is currently active.
Although the Elsinore Fault Zone belongs to the San Andreas set of active,
northwest-trending, right-slip faults in the southern California area (Crowell, 1962),
it has not been the site of a major earthquake in historic time, other than a M6.0
earthquake near the town of Elsinore in 1910 (Richter, 1958; Toppozada and Parke,
1982). However, based on length and evidence of late-Pleistocene or Holocene
displacement, Greensfelder (1974) has estimated that the Elsinore Fault Zone is
reasonably capable of generating an earthquake ranging from M6.8 to M7.1.
Faulting evidence exposed in trenches placed in Glen Ivy Marsh across the Glen Ivy
North Fault (a strand of the Elsinore Fault Zone between Corona and Lake Elsinore),
suggest a maximum earthquake recurrence interval of 300 years, and when
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combined with previous estimates of the long-term horizontal slip rate of 0.8 to 7.0
mm/year, suggest typical earthquakes of M6.0 to M7.0 (Rockwell, 1985).
San Jacinto Fault: The San Jacinto Fault is located 47 miles to the northeast of the
site. The San Jacinto Fault Zone consists of a series of closely spaced faults,
including the Coyote Creek Fault, that form the western margin of the San Jacinto
Mountains. The fault zone extends from its junction with the San Andreas Fault in
San Bernardino, southeasterly toward the Brawley area, where it continues south of
the international border as the Imperial Transform Fault (Earth Consultants
International [ECfl, 2009).
The San Jacinto Fault zone has a high level of historical seismic activity, with at
least 10 damaging earthquakes (M6.0 to M7.0) having occurred on this fault zone
between 1890 and 1986. Earthquakes on the San Jacinto Fault in 1899 and 1918
caused fatalities in the Riverside County area. Offset across this fault is
predominantly right-lateral, similar to the San Andreas Fault, although some
investigators have suggested that dip-slip motion contributes up to 10% of the net
slip (Ed, 2009).
The segments of the San Jacinto Fault that are of most concern to major
metropolitan areas are the San Bernardino, San Jacinto Valley and Anza segments.
Fault slip rates on the various segments of the San Jacinto are less well constrained
than for the San Andreas Fault, but the available data suggest slip rates of 12 ±6
mm/yr for the northern segments of the fault, and slip rates of 4 ±2 mm/yr for the
southern segments. For large ground-rupturing earthquakes on the San Jacinto
fault, various investigators have suggested a recurrence interval of 150 to 300
years. The Working Group on California Earthquake Probabilities (WGCEP, 2008)
has estimated that there is a 31 percent probability that an earthquake of M6.7 or
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greater will occur within 30 years on this fault. Maximum credible earthquakes of
M6.7, M6.9, and M7.2 are expected on the San Bernardino, San Jacinto Valley and
Anza segments, respectively, capable of generating peak horizontal ground
accelerations of 0.48g to 0.53g in the County of Riverside, (Ed, 2009). A M5.4
earthquake occurred on the San Jacinto Fault on July 7, 2010.
The United States Geological Survey has issued the following statements with
respect to the recent seismic activity on southern California faults:
The San Jacinto fault, along with the Elsinore, San Andreas, and other
faults, is part of the plate boundary that accommodates about 2
inches/year of motion as the Pacific plate moves northwest relative to
the North American plate. The largest recent earthquake on the San
Jacinto fault, near this location, the M6.5 1968 Borrego Mountain
earthquake April 8, 1968, occurred about 25 miles southeast of the
July 7, 2010, M5.4 earthquake.
This M5.4 earthquake follows the 4th of April 2010, Easter Sunday,
M7.2 earthquake, located about 125 miles to the south, well south of
the US Mexico international border. A M4.9 earthquake occurred in
the same area on June 12th at 8:08 pm (Pacific Time). Thus this
section of the San Jacinto fault remains active.
Seismologists are watching two major earthquake faults in southern
California. The San Jacinto fault, the most active earthquake fault in
southern California, extends for more than 100 miles from the
international border into San Bernardino and Riverside, a major
metropolitan area often called the Inland Empire. The Elsinore fault is
more than 110 miles long, and extends into the Orange County and
Los Angeles area as the Whittier fault. The Elsinore fault is capable of
a major earthquake that would significantly affect the large
metropolitan areas of southern California. The Elsinore fault has not
hosted a major earthquake in more than 100 years. The occurrence of
these earthquakes along the San Jacinto fault and continued
aftershocks demonstrates that the earthquake activity in the region
remains at an elevated level. The San Jacinto fault is known as the
most active earthquake fault in southern California. Caltech and USGS
seismologist continue to monitor the ongoing earthquake activity using
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the Caltech/USGS Southern California Seismic Network and a GPS
network of more than 100 stations.
B Other Geologic Hazards
Ground Rupture: Ground rupture is characterized by bedrock slippage along an
established fault and may result in displacement of the ground surface. For ground
rupture to occur along a fault, an earthquake usually exceeds M5.0. If a M5.0
earthquake were to take place on a local fault, an estimated surface-rupture length
1 mile long could be expected (Greensfelder, 1974). Our investigation indicates
that the subject site is not directly on a known active fault trace and, therefore, the
risk of ground rupture is remote.
Landslides: Based upon our geotechnical investigation, review of the geologic maps
(Kennedy and Tan, 2008, and Reed, 2005), review of the referenced City of San
Diego Seismic Safety Study -- Geologic Hazards Map Sheet 29 and stereo-pair
aerial photographs (4-11-53, AXN-8M-89 and 90), there are no known or suspected
ancient landslides located on the site.
Liquefaction: The liquefaction of saturated sands during earthquakes can be a
major cause of damage to buildings. Liquefaction is the process by which soils are
transformed into a viscous fluid that will flow as a liquid when unconfined. It occurs
primarily in loose, saturated sands and silts when they are sufficiently shaken by an
earthquake. On this site, the risk of liquefaction of foundation materials due to
seismic shaking is considered to be low due to the medium dense to dense nature
of the natural-ground material and the lack of a very shallow static groundwater
surface under the site. In our opinion, the site does not have a potential for soil
strength loss to occur due to a seismic event.
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Tsunami and Seiches: A tsunami is a series of long waves generated in the ocean
by a sudden displacement of a large volume of water. Underwater earthquakes,
land&ides, volcanic eruptions, meteoric impacts, or onshore slope failures can
cause this displacement. Tsunami waves can travel at speeds averaging 450 to 600
miles per hour. As a tsunami nears the coastline, its speed diminishes, its wave
length decreases, and its height increases greatly. After a major earthquake or
other near-shore tsunami-inducing, activity occurs, a tsunami could reach the shore
within a few minutes. One coastal community may experience no damaging waves
while another may experience very destructive waves. Some low-lying areas could
experience severe inland inundation of water and deposition of debris.
Wave heights and run-up elevations from tsunami along the San Diego Coast have
historically fallen within the normal range of the tides (Joy 1968). The largest
tsunami effect recorded in San Diego since 1950 was May 22, 1960, which had a
maximum wave height of 2.1 feet (NOAA, 1993). In this event, 80 meters of dock
were destroyed and a barge sunk in Quivera Basin. Other tsunamis felt in San
Diego County occurred on November 5, 1952, with a wave height of 2.3 feet caused
by an earthquake in Kamchatka; March 9, 1957, with a wave height of 1.5 feet;
May 22, 1960, at 2.1 feet; March 27, 1964, with a wave height of 3.7 feet and
September 29, 2009, with a wave height of 0.5 feet. It should be noted that
damage does not necessarily occur in direct relationship to wave height, illustrated
by the fact that the damage caused by the 2.1-foot wave height in 1960 was worse
than damage caused by several other tsunamis with higher wave heights.
Historical wave heights and run-up elevations from tsunamis that have impacted
the San Diego Coast have historically fallen within the normal range of the tides
(Joy, 1968). The risk of a tsunami affecting the site is considered very low as the
site is situated at an elevation of at least 40 feet above mean sea level and
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approximately I mile to an exposed ocean beach. The site is not mapped within a
possible inundation zone on the California Geological Survey's 2009 "Tsunami
Inundation Map for Emergency Planning, Oceanside/San Luis Rey Quadrangle, San
Diego County" and is not mapped in a tsunami design zone per the ASCE 7-16
Hazards Report.
A seiche is a run-up of water within a lake or embayment triggered by fault- or
landslide-induced ground displacement. The site is located adjacent to the Aqua
Hedionda Lagoon and the risk of a seiche affecting the site is low to moderate.
Geologic Hazards Summary: It is our opinion, based upon a review of the available
maps, our research and our site investigation, that the site is underlain by relatively
stable formational materials and is suited for the for the proposed residential
project and associated improvements provided the recommendations herein are
implemented.
No significant geologic hazards are known to exist on the site that would prevent
the proposed construction. Ground shaking from earthquakes on active southern
California faults and active faults in northwestern Mexico is the greatest geologic
hazard at the property.
In our explicit professional opinion, no "active" or "potentially active" faults underlie
the project site.
VIII. LABORATORY TESTS & SOIL INFORMATION
Laboratory tests were performed on relatively undisturbed and bulk samples of the
soils encountered in order to evaluate their index, strength, expansion, and
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compressibility properties. Test results are summarized on Figure Nos. III and IV.
The following tests were conducted on the sampled soils:
Laboratory Compaction Characteristics (ASTM 01557-12)
Determination of Percentage of Particles Smaller than No. 200 Sieve
(ASTMDI14O-14)
Laboratory compaction tests establish the laboratory maximum dry density and
optimum moisture content of the tested soils and are also used to aid in evaluating
the strength characteristics of the soils. The test results are presented on Figure
No. IV at the appropriate sample depths.
The particle size smaller than a No. 200 sieve analysis aids in classifying the tested
soils in accordance with the Unified Soil Classification System and provides
qualitative information related to engineering characteristics such as expansion
potential, permeability, and shear strength. The test results are presented on the
test pit logs at the appropriate sample depths.
The expansion potential of soils is determined, when necessary, utilizing the
Standard Test Method for Expansion Index of Soils. In accordance with the
Standard (Table 5.3), potentially expansive soils are classified as follows:
Expansion Index Potential Expansion
0to20 Very low
21 to 50 Low
51 to 90 Medium
91 to 130 High
Above 130 Very high
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Based on the particle size test results and our experience with the encountered
soils, it is our opinion that the on-site fill/topsoil and formational soils, in general,
possess a very low to low expansion potential.
IX. CONCLUSIONS AND RECOMMENDATIONS
The following conclusions and recommendations are based on the field investigation
conducted by our firm, our laboratory test results, and our experience with similar
soils and formational materials. The opinions, conclusions, and recommendations
presented in this report are contingent upon Geotechnical Exploration, Inc.
being retained to review the final plans and specifications as they are developed
and to observe the site earthwork and installation of foundations.
Our subsurface investigation revealed that the proposed residential structures are
underlain by loose to medium dense, silty sand fill/topsoil over medium dense to
dense, good-bearing sandstone formational materials.
The opinions, conclusions, and recommendations presented in this report are
contingent upon Geotechnical Exploration, Inc. being retained to review the final
plans and specifications as they are developed and to observe the site earthwork
and installation of foundations. Accordingly, we recommend that the following
paragraph be included on the grading and foundation plans for the project.
If the geotechnical consultant of record is changed for the project, the
work shall be stopped until the replacement has agreed in writing to
accept the responsibility within their area of technical competence for
approval upon completion of the work. It shall be the responsibility of
the permittee to notify the City Engineer in writing of such change
prior to the recommencement of grading and/or foundation installation
work.
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A. Preparation of Soils for Site DeveloDment
Clearing and Stripping: The areas of new construction should be cleared of
any miscellaneous debris that may be present at the time of construction.
After clearing, the ground surface should be stripped of surface vegetation as
well as associated root systems. Holes resulting from the removal of buried
obstructions that extend below the proposed finished site grades should be
cleared and backfilled with suitable material compacted to the requirements
provided under Recommendation Nos. 4, 5, and 6 below. Prior to any filling
operations, the cleared and stripped vegetation and debris should be
disposed of off-site.
Removal and Recompaction of Existing Surface Fill Soils: In order to provide
suitable support for the proposed new structures and associated
improvements such as decking, sidewalks and driveways, we recommend
that all existing surface fill soils be removed and properly compacted to a
minimum degree of compaction of 90 percent. The limits of recompaction
should extend at least 10 feet beyond the perimeter limits of all new
improvements, where feasible. The recompaction work should consist of:
(a) removing the existing surface fill/topsoil to a depth of 2 feet; (b)
scarifying, moisture conditioning, and compacting the exposed subgrade
soils; and (c) replacing the materials as compacted structural fill. The areal
extent and depths required to remove the existing fill/topsoil should be
determined by our representative during the excavation work based on their
examination of the soils being exposed and physical constraints. There
should be no cut/fill transition line under any of the two building pads.
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The minimum fill thickness under any building pad should be not less than 3
feet. In addition, the existing erosion gulley should be backfilled and
compacted during site grading. Proper benching will need to be implemented
in this area during backfilling. The existing drainage pipe under Adams
Street should be re-directed to an approved discharge location. Grading
along Adams Street will consist of the addition of 8 to 10 feet of fill for the
widening of Adams Street. Grading in this area should be performed after
the basement wall is constructed and after the proposed retaining wall
supporting the street widening embankment is constructed.
In addition, we recommend that low expansion soil from the required
removals be selectively stockpiled for use as capping material and wall
backfills as recommended below in Recommendation Nos. 4 and 8.
Subqrade Preparation: After the site has been cleared, stripped, and the
required excavations made, the exposed subgrade soils should be scarified to
a depth of 8 inches, moisture conditioned to at least 2 percent above the
laboratory optimum, and compacted to the requirements for structural fill.
Areas where highly expansive soils are exposed, (if encountered) should be
moisture conditioned to at least 5 percent over optimum moisture content.
Material for Fill.' All on-site soils with an organic content of less than 3
percent by volume are in general suitable for reuse as fill. Any required
imported fill material should be a low-expansive granular soil. In addition, all
fill material should not contain rocks or lumps over 6 inches in greatest
dimension and not more than 15 percent larger than 21/2 inches. No more
than 25 percent of the fill should be larger than 1/4-iflch. All materials for use
as fill should be approved by our representative prior to filling.
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Fill Compaction: All structural fill should in general be compacted to a
minimum degree of compaction of 90 percent at a moisture content at least
2 percent above the optimum based upon ASTM D1557-12. Fill material
should be spread and compacted in uniform horizontal lifts not exceeding 8
inches in uncompacted thickness. Before compaction begins, the fill should
be brought to the recommended moisture content by either: (1) aerating
and drying the fill if it is too wet, or (2) moistening the fill with water if it is
too dry. Each lift should be thoroughly mixed before compaction to ensure a
uniform distribution of moisture.
Permanent Slopes: We recommend that any required permanent cut and fill
slopes be constructed to an inclination no steeper than 2.0:1.0 (horizontal to
vertical) where feasible. The project plans and specifications should contain
all necessary design features and construction requirements to prevent
erosion of the on-site soils both during and after construction. An earth
berm should be constructed at the top of fill slopes, per the County of San
Diego requirements and designed according to their standard drawings.
Slopes and other exposed ground surfaces should be appropriately planted
with a protective groundcover. Existing, properly compacted fill/cut slopes
should possess a factor of safety of at least 1.5 against gross and shallow
failure potential.
New fill slopes should be constructed to assure that the recommended
minimum degree of compaction is attained out to the finished slope face.
This may be accomplished by "backrolling" with a sheepsfoot roller or other
suitable equipment as the fill is raised. Placement of fill near the tops of
slopes should be carried out in such a manner as to assure that loose,
uncompacted soils are not sloughed over the tops and allowed to accumulate
on the slope face.
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Slope stability analysis for the proposed slopes shown on the grading plan
indicates that such slopes will be stable, with a factor of safety of at least 1.5
for gross and shallow stability analysis. Refer to Appendix C.
7. Temporary Slopes: Based on our subsurface investigation work, laboratory
test results, and engineering analysis, temporary slopes should be stable for
a maximum slope height of up to 12 feet and may be cut at a slope ratio of
0.75:1.0 in properly compacted fill soils, and vertical in the lower 5 feet and
0.5:1.0 in the upper 8 feet in cemented, stiff natural soils. Some localized
sloughing or raveling of the soils exposed on the slopes, however, may occur.
If the encountered soils are not cemented, the temporary slope ratio should
be no steeper than 0.75:1.0 for slopes not exceeding 14 feet in height.
Since the stability of temporary construction slopes will depend largely on the
contractor's activities and safety precautions (storage and equipment
loadings near the tops of cut slopes, surface drainage provisions, etc.), it
should be the contractor's responsibility to establish and maintain all
temporary construction slopes at a safe inclination appropriate to his
methods of operation. No soil stockpiles or surcharge may be placed within a
horizontal distance of 10 feet from the excavation. The contractor should
follow all Cal-OSHA guidelines at all times.
If these recommendations are not feasible due to space constraints,
temporary shoring may be required for safety and to protect adjacent
property improvements. Similarly, footings near temporary cuts should be
underpinned or protected with shoring.
rq
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No soil stockpiles or surcharge may be placed within a horizontal distance of
10 feet from the excavation. If these recommendations are not feasible, off-
site stockpiling may be required.
S!oøe Top/Face Performance: The soils that occur in close proximity to the
top of slope or face of even properly compacted fill or dense/stiff natural
ground cut slopes often possess poor lateral stability. The degree of lateral
and vertical deformation depends on the inherent expansion and strength
characteristics of the soil types comprising the slope, slope steepness and
height, loosening of slope face soils by burrowing rodents, and irrigation and
vegetation maintenance practices, as well as the quality of compaction of fill
soils. Structures and other improvements, could suffer damage due to these
soil movement factors if not properly designed to accommodate or withstand
such movement. New fill or cut slopes should be constructed at a 2.0:1.0
slope gradient.
Slope Top Structure Performance: Rigid improvements such as top-of-slope
walls, columns, decorative planters, concrete flatwork, swimming pools, and
other similar types of improvements can be expected to display varying
degrees of separation typical of improvements constructed at the top of a
slope. The separations result primarily from slope top lateral and vertical soil
deformation processes. These separations often occur regardless of being
underlain by cut or fill slope material. Proximity to a slope top is often the
primary factor affecting the degree of separations occurring.
Shallow foundations close to descending slopes should be provided with a
setback of 8 feet measured from the top of the foundation. Foundations
within this setback distance should be deepened as shown on Figure No. VI,
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Foundation Requirements Near Slopes. Typical and to-be-expected
separations can range from minimal to up to 1 inch or greater in width. In
order to minimize the effect of slope-top lateral soil deformation, we
recommend that the top-of-slope improvements be designed with flexible
connections and joints in rigid structures so that the separations do not result
in visually apparent cracking damage and/or can be cosmetically dressed as
part of the ongoing property maintenance. These flexible connections may
include "slip joints" in wrought iron fencing, evenly spaced vertical joints in
block walls or fences, control joints with flexible caulking in exterior flatwork
improvements, etc.
In addition, use of planters to provide separation between top-of-slope
hardscape such as patio slabs and pool decking from top-of-slope walls can
aid greatly in reducing cosmetic cracking and separations in exterior
improvements. Actual materials and techniques would need to be
determined by the project architect or the landscape architect for individual
properties. Steel dowels placed in flatwork may prevent noticeable vertical
differentials, but if provided with a slip-end they may still allow some lateral
displacement.
10. Trench and Retaining Wall Backfill: All backfill soils placed in utility trenches
or behind retaining walls should be compacted to a minimum degree of
compaction of 90 percent. Backfill material should be placed in lift
thicknesses appropriate to the type of compaction equipment utilized and
compacted to a minimum degree of 90 percent by mechanical means. In
pavement areas, that portion of the trench backfill within the pavement
section should conform to the material and compaction requirements of the
adjacent pavement section. In addition, the low-expansion potential fill layer
should be maintained in utility trench backfill within the building and
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adjoining exterior slab areas. Trench backfill beneath the level of the low-
expansion fill layer should consist of on-site soils in order to minimize the
potential for migration of water below the perimeter footings at the trench
locations.
Our experience has shown that even shallow, narrow trenches, such as for
irrigation and electrical lines, that are not properly compacted can result in
problems, particularly with respect to shallow ground water accumulation and
migration.
B. Foundation Recommendations
Footings: We recommend that the proposed new structures be supported on
conventional, individual-spread and/or continuous footing foundations
bearing on recompacted fill soils prepared as recommended above in
Recommendation No. 2. All footings should be founded at least 18 inches
below the lowest adjacent finished grade.
At the recommended depths, footings may be designed for allowable bearing
pressures of 2,500 pounds per square foot (psf) for combined dead and live
loads and 3,300 psf for all loads, including wind or seismic. The footings
should, however, have a minimum width of 12 inches.
General Criteria For All Footings: Footings located adjacent to or on tops of
slopes should be extended sufficiently deep so as to provide at least 8 feet of
horizontal cover between the slope face and outside edge of the footing at
the footing bearing level. Footings located adjacent to utility trenches should
have their bearing surfaces situated below an imaginary 1.0 to 1.0 plane
a4y
projected upward from the bottom edge of the adjacent utility trench.
Retaining walls near other retaining walls (such as the basement walls)
should be considered to impose a surcharge on the lower wall.
All continuous footings should contain top and bottom reinforcement to
provide structural continuity and to permit spanning of local irregularities.
We recommend that a minimum of four No. 5 reinforcing bars be provided in
the footings (two at the top and two at the bottom). A minimum clearance
of 3 inches should be maintained between steel reinforcement and the
bottom or sides of the footing. In order for us to offer an opinion as to
whether the footings are founded on soils of sufficient load bearing capacity,
it is essential that our representative inspect the footing excavations prior to
the placement of reinforcing steel or concrete.
NOTE: The project Civil/Structural Engineer should review all reinforcing
schedules. The reinforcing minimums recommended herein are not to be
construed as structural designs, but merely as minimum reinforcement to
reduce the potential for cracking and separations.
13. Seismic Design Criteria: Site-specific seismic design criteria for the proposed
structures are presented in the following table in accordance with Section
1613 of the 2016 CBC, which incorporates by reference ASCE 7-10 for
seismic design. We have determined the mapped spectral acceleration
values for the site, based on a latitude of 33.1483 degrees and longitude of
117.33 degrees, utilizing a tool provided by the USGS, which provides a
solution for ASCE 7-10 (Section 1613 of the 2016 CBC) utilizing digitized files
for the Spectral Acceleration maps. Based on the observed soils conditions,
we have assigned a Site Soil Classification of D.
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TABLE I
MaDped Spectral Acceleration Values and Design Parameters
S5 S1 Fa Sms Smi Sds Sd1
01.135 10.4369 1 1.046 1 1.564g I 1.187g 10.6829 10.792g 0.454g
Lateral Loads: Lateral load resistance for the structures supported on footing
foundations may be developed in friction between the foundation bottoms
and the supporting subgrade. An allowable friction coefficient of 0,40 is
considered applicable. An additional allowable passive resistance equal to an
equivalent fluid weight of 300 pcf acting against the foundations may be used
in design provided the footings are poured neat against the adjacent properly
compacted fill or dense formational materials. These lateral resistance
values assume a level surface in front of the footing for a minimum distance
of three times the embedment depth of the footing and any shear keys.
Settlement: Settlements under building loads are expected to be within
tolerable limits for the proposed structure. For footings designed in accord-
ance with the recommendations presented in the preceding paragraphs, we
anticipate that total settlements should not exceed 1 inch and that post-
construction differential settlements should be less than 1/240.
Retaining Walls: Retaining walls must be designed to resist lateral earth
pressures and any additional lateral pressures caused by surcharge loads on
the adjoining retained surface. We recommend that unrestrained
(cantilever) walls with level, low-expansive backfill be designed for an
equivalent fluid pressure of 38 pcf. We recommend that restrained walls
(i.e., basement walls or any walls with angle points that restrain them from
rotation) with level backfill be designed for an equivalent fluid pressure of 56
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pcf. Unrestrained walls with up to 2.0:1.0 sloping, low-expansive backfills
should be designed for an equivalent fluid pressure of 52 pcf. Restrained
walls with up to 2.0:1.0 sloping backfills should be designed for an equivalent
fluid pressure of 76 pcf. Wherever walls will be subjected to surcharge toads
they should also be designed for an additional uniform lateral pressure equal
to one-third the anticipated vertical surcharge pressure for unrestrained walls
and an additional one-half the anticipated vertical surcharge pressure for
restrained walls (all using low-expansive backfill soils).
For seismic design of unrestrained walls, we recommend that the seismic
pressure increment be taken as a fluid pressure distribution utilizing an
equivalent fluid weight of 14 pcf. For restrained walls, we recommend the
seismic pressure increment be waived.
The preceding design pressures assume that the walls are backfilled with low
expansion potential materials (Expansion Index less than 50) and that there
is sufficient drainage behind the walls to prevent the build-up of hydrostatic
pressures from surface water infiltration. We recommend, in addition to
waterproofing, that back drainage be provided by a composite drainage
material such as Miradrain 6000/6200 or equivalent. The back drain material
should terminate 12 inches below the finish surface where the surface is
covered by slabs or 18 inches below the finish surface in landscape areas.
Waterproofing should continue to 6 inches above the top of the wall. A
subdrain (such as Total Drain or perforated pipe in an envelope of crushed
rock gravel a maximum of 1 inch in diameter and wrapped with geofabric
such as Mirafi 140N), should be placed at the bottom of retaining walls.
Subdrains should discharge at an approved drainage facility.
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Backfill placed behind the walls should be compacted to a minimum degree of
compaction of 90 percent using light compaction equipment. If heavy
equipment is used, the walls should be appropriately temporarily braced.
Shoring walls, if required, may be designed for the same soil pressure
indicated above. The soldier piles' passive resistance may be calculated as
750 pcf applied in the embedment depth of the pile below the cut surface,
times the diameter of the pile. Surcharge load effect on shoring walls may
be calculated similarly to retaining walls.
C. Concrete Slab-on-grade Criteria
Slabs on-grade may only be used on new, properly compacted fill or when bearing
on dense natural soils.
17. Minimum Floor Slab Reinforcement: Based on our experience, we have
found that, for various reasons, concrete floor slabs occasionally crack.
Therefore, we recommend that all slabs on-grade contain at least a minimum
amount of reinforcing steel to reduce the separation of cracks, should they
occur.
Interior floor slabs should be a minimum of 4 inches actual thickness and be
reinforced with No. 3 bars on 18-inch centers, both ways, placed at
midheight in the slab. Slab subgrade soil moisture should be verified by a
Geotechnical Exploration, Inc. representative to have the proper moisture
content within 48 hours prior to placement of the vapor barrier and pouring
of concrete. Shrinkage control joints should be placed no farther than 20
feet apart and at re-entrant corners. The joints should penetrate at least 1
inch into the slab.
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 27
Following placement of any concrete floor slabs, sufficient drying time must
be allowed prior to placement of floor coverings. Premature placement of
floor coverings may result in degradation of adhesive materials and loosening
of the finish floor materials.
18. Slab Moisture Protection and Vapor Barrier Membrane: Although it is not the
responsibility of geotechnical engineering firms to provide moisture
protection recommendations, as a service to our clients we provide the
following discussion and suggested minimum protection criteria. Actual
recommendations should be provided by the architect and waterproofing
consultants or product manufacturer.
Soil moisture vapor can result in damage to moisture-sensitive floors, some
floor sealers, or sensitive equipment in direct contact with the floor, in
addition to mold and staining on slabs, walls, and carpets. The common
practice in Southern California is to place vapor retarders made of PVC, or of
polyethylene. PVC retarders are made in thickness ranging from 10- to 60-
mil. Polyethylene retarders, called visqueen, range from 5- to 10-mil in
thickness. These products are no longer considered adequate for moisture
protection and can actually deteriorate over time.
Specialty vapor retarding products possess higher tensile strength and are
more specifically designed for and intended to retard moisture transmission
into and through concrete slabs. The use of such products is highly
recommended for reduction of floor slab moisture emission.
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 28
The following American Society for Testing and Materials (ASTM) and
American Concrete Institute (ACI) sections address the issue of moisture
transmission into and through concrete slabs: ASTM E1745-97 (2009)
Standard Specification for Plastic Water Vapor Retarders Used in Contact
Concrete Slabs; ASTM E154-88 (2005) Standard Test Methods for Water
Vapor Retarders Used in Contact with Earth; ASTM E96-95 Standard Test
Methods for Water Vapor Transmission of Materials; ASTM E1643-98 (2009)
Standard Practice for Installation of Water Vapor Retarders Used in Contact
Under Concrete Slabs; and ACI 302.2R-06 Guide for Concrete Slabs that
Receive Moisture-Sensitive Flooring Materials.
18.1 Based on the above, we recommend that the vapor barrier consist of a
minimum 15-mil extruded polyolefin plastic (no recycled content or
woven materials permitted). Permeance as tested before and after
mandatory. conditioning (ASTM E1745 Section 7.1 and sub-paragraphs
7.1.1-7.1.5) should be less than 0.01 U.S. perms (grains/square
foot/hour/inch of mercury [Hg]) and comply with the ASTM E1745
Class A requirements. Installation of vapor barriers should be in
accordance with ASTM E1643. The basis of design is 15-mil
StegoWrap vapor barrier placed per the manufacturer's guidelines.
Reef Industries Vapor Guard membrane has also been shown to
achieve a perrneance of less than 0.01 perms. Our suggested
acceptable moisture retardant membranes are based on a report
entitled "Report of Water Vapor Permeation Testing of Construction
Vapor Barrier Materials" by Dr. Kay Cooksey, Ph.D., Clemson
University, Dept. of Packaging Science, 2009-10.
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 29
The membrane may be placed directly on properly compacted
subgrade soils and directly underneath the slab. Proper slab curing is
required to help prevent slab curling. A 4-inch-thick crushed rock
layer may be placed under the plastic membrane.
18.2 Common to all acceptable products, vapor retarder/barrier joints must
be lapped and sealed with mastic or the manufacturer's recommended
tape or sealing products. In actual practice, stakes are .often driven
through the retarder material, equipment is dragged or rolled across
the retarder, overlapping or jointing is not properly implemented, etc.
All these construction deficiencies reduce the retarder's effectiveness.
In no case should retarder/barrier products be punctured or gaps be
allowed to form prior to or during concrete placement.
18.3 As previously stated, following placement of concrete floor slabs,
sufficient drying time must be allowed prior to placement of any floor
coverings. Premature placement of floor coverings may result in
degradation of adhesive materials and loosening of the finish floor
materials.
19. Concrete Isolation Joints: We recommend the project Civil/Structural
Engineer incorporate isolation joints and control joints (sawcuts) to at least
one-fourth the thickness of the slab in any floor designs. The joints and cuts,
if properly placed, should reduce the potential for and help control floor slab
cracking. We recommend that concrete shrinkage joints be spaced no
farther than approximately 20 feet apart, and also at re-entrant corners.
However, due to a number of reasons (such as base preparation,
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 30
construction techniques, curing procedures, and normal shrinkage of
concrete), some cracking of slabs can be expected.
20. Exterior Nonstructural Concrete Slabs: As a minimum for protection of on-
site improvements, we recommend that all nonstructural concrete slabs
(such as patios, sidewalks, etc.), be founded on properly compacted and
tested fill or dense native formation and be underlain by 2 inches (and no
more than 3 inches) of compacted clean leveling sand, with No. 3 bars at 18-
inch centers, both ways, at the center of the slab. Exterior concrete slabs
should be at least 4 inches thick. Exterior slabs should contain adequate
isolation and control joints as noted in the following paragraphs.
The performance of on-site improvements can be greatly affected by soil
base preparation and the quality of construction. It is therefore important
that all improvements are properly designed and constructed for the existing
soil conditions. The improvements should not be built on loose soils or fills
placed without our observation and testing. The subgrade of exterior
improvements should be verified as properly prepared within 48 hours prior
to concrete placement. A minimum thickness of 2 feet of properly
recompacted soils should underlie exterior slabs on-grade for secondary
improvements.
21, Exterior Slab Control Joints: For exterior slabs with the minimum shrinkage
reinforcement, control joints should be placed at spaces no farther than 12
feet apart or the width of the slab, whichever is less, and also at re-entrant
corners. Control joints in exterior slabs should be sealed with elastomeric
joint sealant. The sealant should be inspected every 6 months and be
properly maintained. Concrete slab joints should be dowelled or continuous
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 31
steel reinforcement should be provided to help reduce any potential
differential movement.
D. Pavements
22. Concrete Pavement: We recommend that concrete driveway pavements,
subject only to automobile and light truck traffic, be 5 inches thick and be
supported directly on properly prepared/compacted on-site subgrade soils.
The concrete for areas subject to occasional heavy truck traffic (such as fire
trucks or trash collecting trucks) should have a minimum thickness of 6
inches. The upper 8 inches of the subgrade below the slab should be
compacted to a minimum degree of compaction of 95 percent just prior to
paving. The concrete should be f'c=3,500 psi at 28 days of age.
In order to control shrinkage cracking, we recommend that sawcut,
weakened-plane joints be provided at about 12-foot centers, both ways, and
at re-entrant corners. The pavement slabs should be saw-cut as soon as
practical but no more than 24 hours after the placement of the concrete.
The depth of the joint should be one-quarter of the slab thickness and its
width should not exceed 0.02-feet. Reinforcing steel is not necessary unless
it is desired to increase the joint spacing recommended above.
E. Site Drainage Considerations
23. Surface Drainage: Adequate measures should be taken to properly finish-
grade the site after the improvements are in place. Drainage waters from
this site and adjacent properties should be directed away from the footings,
floor slabs, and slopes, onto the natural drainage direction for this area or
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 32
into properly designed and approved drainage facilities provided by the
project civil engineer. Roof gutters and downspouts should be installed on
the new improvements, with the runoff directed away from the foundations
via closed drainage lines. Proper subsurface and surface drainage will help
reduce the potential for waters to seek the level of the bearing soils under
footings and floor slabs, or other extensive improvements.
Failure to observe this recommendation could result in undermining and
possible differential settlement of the structure or other improvements or
cause other moisture-related problems. Currently, the 2016 CBC requires a
minimum 1 percent surface gradient for proper drainage of building pads
unless waived by the building official. Concrete pavement may have a
minimum gradient of 0.5-percent. Surface gradient adjacent to structures
must drain away as indicated in the 2016 CBC.
Erosion Control: Appropriate erosion control measures should be taken at all
times during and after construction to prevent surface runoff waters from
entering footing excavations or ponding on finished building pad areas.
Planter Drainage: New planter areas, flower beds, and planter boxes should
be sloped to drain away from the footings and floor slabs at a gradient of at
least 5 percent within 5 feet from the perimeter walls. Any planter areas
adjacent to the structures or surrounded by concrete improvements should
be provided with sufficient area drains to help with rapid runoff disposal. No
water should be allowed to pond adjacent to the residence or other
improvements.
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 33
Drainage Quality Control: It must be understood that it is not within the
scope of our services to provide quality control oversight for surface or
subsurface drainage construction or retaining wall sealing and base of wall
drain construction. It is the responsibility of the contractor to verify proper
wall sealing, geofabric installation, protection board (if needed), drain depth
below interior floor or yard surface, pipe percent slope to the outlet, etc.
F. General Recommendations
Project Start LID Notification: In order to minimize any work delays during
site development, this firm should be contacted 24 hours prior to any need
for observation of footing excavations or field density testing of compacted
fill soils. If possible, placement of formwork and steel reinforcement in
footing excavations should not occur prior to observing the excavations; in
the event that our observations reveal the need for deepening or redesigning
foundation structures at any locations, any formwork or steel reinforcement
in the affected footing excavation areas would have to be removed prior to
correction of the observed problem (i.e., deepening the footing excavation,
recompacting soil in the bottom of the excavation, etc.).
X. GRADING NOTES
Geotechnical Exploration, Inc. recommends that we be retained to verify the
actual soil conditions revealed during site grading work and footing excavation to be
as an:icipated in this "Report of Geotechnical Investigation Update" for the project.
In addition, the compaction of any fill soils placed during site grading work must be
observed and tested by the soil engineer. It is the responsibility of the grading
contractor to comply with the requirements on the grading plans and the local
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 34
grading ordinance. All retaining wall and trench backfill should be properly
compacted. Geotechnical Exploration, Inc will assume no liability, for damage
occurring due to improperly or uncompacted backfill placed without our
observations and testing.
XL LIMITATIONS
Our conclusions and recommendations have been based on available data obtained
from our document review, field investigation and laboratory analysis, as well as
our experience with similar soils and formational materials located in this area of
the City of Carlsbad. Of necessity, we must assume a certain degree of continuity
between exploratory excavations. It is, therefore, necessary that all observations,
conclusions, and recommendations be verified at the time grading operations begin
or when footing excavations are placed. In the event discrepancies are noted,
additional recommendations may be issued, if required.
The work performed and recommendations presented herein are the result of an
investigation and analysis that meet the contemporary standard of care in our
profession within the County of San Diego. No warranty is provided.
This report should be considered valid for a period of two (2) years, and is subject
to review by our firm following that time. If significant modifications are made to
the building plans, especially with respect to the height and location of any
proposed structures, this report must be presented to us for immediate review and
possible revision.
(rq
Hoover Street Residential Project Job No. 16-11187
Carlsbad, California Page 35
It is the responsibility of the owner and/or developer to ensure that the
recommendations summarized in this report are carried out in the field operations
and that our recommendations for design of this project are incorporated in the
grading and structural plans. We should be retained to review the project plans
once they are available, to see that our recommendations are adequately
incorporated in the plans.
This firm does not practice or consult in the field of safety engineering. We do not
direct the contractor's operations, and we cannot be responsible for the safety of
personnel other than our own on the site; the safety of others is the responsibility
of the contractor. The contractor should notify the owner if any of the
recommended actions presented herein are considered to be unsafe.
The firm of Geotechnical Exploration, Inc. shall not be held responsible for
changes to the physical condition of the property, such as addition of fill soils or
changng drainage patterns, which occur subsequent to issuance of this report and
the changes are made without our observations, testing, and approval.
Once again, should any questions arise concerning this report, please feel free to
contact the undersigned. Reference to our Job No. 16-11187 will expedite a reply
to your inquiries.
Respectfully submitted,
GEOJHNICAL EXPLORATION, INC.
3atfiA. Cerros, P.E. Jonaan\A. Browning
R.C.E. 34422/G.E. 2007 P.q 901WC.E.G. 2615
Senior Geotechnical Engineer Serr Prject Geologist
oHAL c
BROM
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VICINITY MAP
Hoover Street Property
Southwest Corner of Hoover Street
and Adams Street
Carlsbad, CA. Figure No. I
Job No. 16-11187
LEGEND
Approximate Location HP-8
of trplorato'y Hopdpit
A AApproximate Locction
Cf Cross Sect on
GEOLOG C LEGEND
Qop
2-4C d Parolic Deposits
Tsa s1t:ogo Formation
IlIe7-02.ci
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PLOT PLAN
Wo!a Residence
Poover Street Property
Southwest Come- of Hoover Street
and Adams Street
Carlsbad, Ca
Figure No.!!
Job No. 16-1118 G*4 Geotechnical Exploration. Inc.
(Jen000ry 2018)
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GEOLOGIC CROSS SECTION
Viola Residence
Southwest Corner of Hoover Street
and Adorns Street
Carlsbad, CA.
A
70- PROPOSED RESIDESICE
A'
Proposed Existing Grade Grade
AC Berm
clop.
- ----.--_ -------.-----r----------------------------?
Tea Tea Tea
10 20 30 40 5) 40 70 80 90 100 Ii) 120 130 40
Relative Horizontal Distance (feet)
GEOLOGIC LEGEND (Horizontal and vertical)
00p2 Old Paralic Deposits
Tea Santago Formation Figure No. IIb
Approximate Geologic Contact Job No. 17-11187
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EQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LCGGEC
Hand Tools 3' X 3' X 4' Handpit 8-12-16
SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH LOGGED BY
± 52' Mean Sea Level Not Encountered JKH
-
- FIELD DESCRIPTION I AND
CLASSIFICATION W a:-
DESCRIPTION AND REMARKS
(Grain size, Density, Mcisture, Color)
o '1 +
SILTY SAND fine- to mediun-grained, with I SM
some roots, rock fragments and debris. Loose.
Dry. Brown.
i-g
44
FILL (Qafi
--21% passing #200 sieve. 1 8.5 131.0
SILTY SAND fin-to medium-grained; SM
- moderately well cBmented. Medium dense to
dense. Damp. Red-brown.
2 -
-
111.
OLD PARALIC DEPOSITS (Qop 2 )
t L
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- Bottom 4'
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JOB NAME PERCHED WATER TABLE Hoover Street Project
BULK BAG SAMPLE SITE LCCATIDN
ft] IN-PLACE SAMPLE SW Corner Hoover St. & Adams St., Carlsbad, CA
MODIFIED CALIFORNIA SAMPLE JOB NUMBER REVIEWED BY LOG No. LDRMAC
16-11187 NUCLEAR FIELD DENSITY TEST FIGURE NUMBER HP-1
STANDARD PENETRATION TEST lila
EQUIPMENT
• Hand Tools
SURFACE ELE VAT ON
± 53 Mean Sea Level
DIMENSION & TYPE OF EXCAVATION DATE LOGGED
2'X 2'X 3' Handpit 8-12-16
GROUNDWATER/ SEEPAGE DEPTH LOGGED BY
Not Encountered JKH
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FIELD DESCRIPTION
AND Cr CLASSIFICATION
DESCRIPTION AND FEMARKS
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(Grain size, Density, Moisture, Color) 5 S .
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some roots and rock fragments. Loose. Dry.
Brown.
FILL (Oaf)
SILTY SAND fine- to medium-grained. Medium SM
- I dense to dense. Damp. Red-brown.
- . OLD PARALIC DEPOSITS (Qop2.4)
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.! PERCHED WATER TABLE JOB NAME
Hoover Street Project
BULK BAG SAMPLE TELOOATION
ffl IN-PLACE SAMPLE SW Corner Hoover St. & Adams St., Carlsbad, CA
• MODIFIED CALIFORNIA SAMPLE JOB NUMBER REVIEWED BY LDR!JAC L03 No
LJ NUCLEAR FIELD DENSITY TEST _____
187 Geotethnka
FIGURE NUMBER Exploration.. Inc. HP-2
fib STAIDARD PENETRATION TEST
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EQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED
Hand Tools 3X 3 X 3 Handpit 8-12-16
SURFACE ELEVATION GROUNDWATER! SEEPAGE DEPTH LOGGED BY
± 54' Mean Sea Level Not Encountered JKH
- FIELD DESCRIPTION - r -
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CLASSIFICATION Uj
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DESCRIPTION AND RE vIARKS
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(Grain size, Density, Moi 3ture, Color) Dr .
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some roots and rock fragments. Loose. Dry.
Brown.
FILL (Qaf)
1 - SILTY SAND, fine- to medium-grained. Medium - SM
-
rH dense to dense. Damp. Red-brown.
- i OLD PARALIC DEPOSITS (Qop)
2-
-
3 - -
-
Bottom 3'
4-
. PERCHED WATER TABLE
BULK BAG SAMPLE
JOBNAME
Hoover Street Project - -
SITE LOCATION -
INSAMPLE -PLACE SW Corner Hoover St. & Adams St., Carlsbad, CA
NUMBER REV EWED BY LOG No.
• MODIFIED CALIFORNIA SAMPLE [JOB
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FIGURE NUMBER ExpIoratton Inc. HP-3
STANDARD PENETRATION TEST I IlIc
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EQUIPMENT
S Hand Tools
SURFACE E..EVATIDN
± 45' Mean Sea Level
DIMENSION & TYPE OF EXCAVATION DATE LCGGD
3' X TX 3' Handpit 8-12-16
GROUNDWATER/ SEEPAGE DEPTH LOGGED BY
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. TOPSOIL (Oaf)
1 - LAiOice-.to medium-grained; SM
- - moderately well cemented. Medium dense to
dense. Damp. Rec-brown.
-
OLD PARALIC DEPOSITS (Qop24)
2-
3- -
Bottom 3'
4-
PERCHED WATER TABLE JOB NAME
Hoover Street Project
BULK BAG SAMPLE SITE LOCATION
IN-PLACE SAMPLE SW Corner Hoover St. & Adams St., Carlsbad, CA
MODIFIED CALIFORNIA SAMPLE JOB NUMBER REVIEWED BY LDRIJA LOG No.
1 NUCLEAR FIELD DENSITY TEST 16-11187 Gka __ I
STANDARD PENETRATION TEST ,
FIGURE NUM BER axploraflon,
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EQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LO3GEO
Hand Tools 3' X 3' X 4' Handplt 8-12-16
SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH LOGGED 3Y
± 35' Mean Sea Level Not Encountered JKH
-
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I AND
CLASSIFICATION -
L LU Ca Uj
DESCRIPTION AND E'AARKS
a. (GrainsizeDensity,Moisture,Color)
SILTY SAND, fine- to mediurr-grained, with SM
some roots, rock fagments and debris. Loose.
Dry. Brown.
FILL (Qafi
- F SILTY SAND, fine-to medium-grained; SM
- U moderately well cemented. Medium dense to
i dense. Damp. Rec-brown.
2
- OLD PARALIC DEPOSITS (Qop2.4)
3.
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T NAME PERCHED WATER TA3LE JOB
Io.er Street Project
BULK BAG SAMPLE SITE LOCATION
j IN-PLACE SAMPLE SW Corner Hoover St. & Adams St., Carlsbad, CA
U MODIFIED CALIFORNIA SAMPLE JOB NUMBER REVIEWED BY LDRIJAC LOG No.
NUCLEAR FIELD DENSITY TEST 16-111 87 Geoft
Exploration, Inc Fl P-5 FIGURE NUMBER
STANDARD PENETRATION TEST Ille
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EQUIPMENT CIMENSION & TYPE OF EXCAVATION DATE LC'GC-ED
Hand Tools 3' X 3' X 4 Handpit 8-12-16
- SURFACE ELEVATION GROUNDWATER! SEEPAGE DEPTH LOGGE1 BY
± 33 Mean Sea Level Not Encountered JKH
- -
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SILTY SARéidium-g-ained;
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SM
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OLD PARALIC DEPOSITS (Qop24)
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4
Bottom @ 4'
5 -
— cr ir .! PERCHED WATER TABLE JOB NAME
Hoover Street Project
BULK BAG SAMPLE SITE LOCATION
IN-P ...ACE SAMPLE SW Corner Hoover St. & Adams St., Carlsbad, CA
JOB NUMBER REVIEWED BY LDRI.AC LOG No. MODIFIED CALIFORNIA SAMPLE
NUCLEAR FIELD DENSITY TEST 16-11187
Exptoraon. Inc. rMatechnica
_____ _________ HP-6
STANDARD
FIGURE NUMBER
PENETRATION TESTZL
EQUIPMENT
Hand Tools
SURFACE aE VAIl ON
± 50' Mean Sea Level
DIMENSION & TYPE OF EXCAVATION DATE LC'GGED
TX TX 3 Hand pit 8-1246
GROUNDWATER/ SEEPAGE DEPTH LOGGED BY
Not Encountered JKH
- -
- FIELD DESCRIPTION
AND
CLASSIFICATION '
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Q . ,9 C +
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some roots and rock fragments. Loose. Dry. -
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FILL (Qaf) I
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SILTY SAND fine- to medium-grained. Medium SM
dense to dense. Damp. Red-brDwrl.
- OLD PARALIC DEPOSITS (Qop2 )
2-
3- -
Bottom 3'
4-
Y PERCHED WATER TABLE JOBNAME
Hoover Street Project
BULK BAG SAMPLE SITE LOCATION
Fil 'N-PLACE SAMPLE SW Corner Hoover St. & Adams St., Carlsbad, CA
• MODIFIED CALIFORNIA SAMPLE
JOB NUMBER REVIEWED BY LDR/JAC L03 No.
J NUCLEAR FIELD DENSITY TEST 16-11187 Geotechnlcal I HP-7 FIGURE NUMBER Ezploi'atton, Inc.
STANDARD PENETRATION TEST IlIg i Rio
C
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f7M Hand Tools
DIMENSION & TYPE OF EXCAVATION
3' X TX 4 Handpit
DATE LOGGED
8-12-16
SURFACE ELEVATIDN
± 48' Mean Sea Level
GROUNDWATER/ SEEPAGE DEPTH
Not Encountered
LOGGED BY
JKH
-
- FIELD DESCRIPTION
AND
CLASSIFICATION
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(Grain size0 Density, oisture, Colon co ,
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A TOPSOIL (Qaf)
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-
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Damp. Red-brown.
" OLD PARALIC DEPOSITS (Qop}
3-
4- -
Bottom @ 4'
5-
Y PERCHED WATER TABLE .OB NAME
Hoover Street Project
BULK BAG SAMPLE SITE LOCATION -
IN-PLACE SAMPLE SW Corner Hoover St. & Adams St., Carlsbad, CA
• MODIFIED CALIFORNIA SAMPLE JOB NUMBER REVIEWED BY LDR/JAC LOG No.
NUCLEAR FIELD DENSITY TEST 16-11187 Geotechnlcal Inc. HP-8 FIGURE NUMBER Exploratfon,
STANDARD PENETRATION TEST IIIh
85
75L 0 6-1
Geotechnical
'• ' lii Exploration, Inc.
1
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125
Source of Material ;iui "
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TEST RESULTS
Method .Method
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Maximum Dry Density 131.0 '
Optimum i wq-ii. S ll AContent
1. I Expansion Index (EI)
fiL •RRUR••$U•*•UUUU•WR r r
100 Curves of 100% Saturation
for Specific Gravity Equal to:
2.80
95 2.70
2.60
20 25 30 35 40 45
WATER CONTENT, %
MOISTURE-DENSITY RELATIONSHIP
Figure Number: IV
Job Name: Hoover Street Project
Site Location: SW Corner Hoover St. & Adams St., Carls
____ Job Number 16-11187
to
70
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\Ocean \\\ ®
Site
V 010 Residence
Hoover Street Property
Southwest Corner of Hoover Street
and Adams Street
Carlsbad, CA.
EXCERPT FROM GEOLOGC MAP OF THE OCEANSIDE :0'- 60 QUADRANGLE CALIFORNIA
Compiled bl.
Michael P. Kennedy' and Siang S. Tan'
200'
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Old p.edio dqtoott Unit. 24 mdfreidod (len to taiddi. l. IJ P t.eno)—ldoaly pooely toen, 000do.otnly pen.00blo,
,aioh-byoon,, inloefloanrod otnoodline, baonh, nonoonitin
-1------- ton nolLoviol d.yooito ooWn,nd ooiltotoon, .ondotooy and
000$lnoonrtot. Ito each of ho onno .no000 (00,00 and End
potalic Inpoal. en nol be dividnc o.o (boy oneo with toil
ton alto ,00tnly covnnnd by 000 too-dec Tlefr pbyoicol toil
low.porot rdoc000hopt ton ditogocootOtoolly ill,uMited in
Fitoon
Figure No. V
Job No. 16-11137
4l4 Goetootoatoat IC EaplaoaGoe. lea. WW Jowuony 2018
fl
FOUNDATION REQUIREMENTS NEAR SLOPES
Proposed Structure TOP OF COMPACTED FILL SLOPE
(Any loose soils on -he slope surface
shall not be cons dered to provide
lateral or vertical strength for The
footing or for slope stability. Needed
depth of embedment shall be meas
from competent scil.)
Concrete Floor Slab
Setback
I, •.- . . / COMPACTED FILL SLOPE WITH
MAXIMUM INCLINATION AS
7 PER SOILS RE'ORT. Reinforcement of
Foundations and Floor
Slabs Following the Iota Depth of Footing
Recommendations of the Mecsued from Finish Soil
Architect or Structural Subgrade
Engineer. COMPACTED FILL
Concrete Foundation :-••.
18" Minimum or as Deep Outer Most Facè'--. 8' as Required for Latera of Footing Stability
TYPICAL SECTION
(Showing Propcsed Foundation Located Within 8 Feet of Top of Slope)
18" FOOTING / 8' SETBACK
Total Depth of Footing
1.5:1.0 SLOPE * 2.O:1.OSLOPE
0 82" 66'
21 66" 54"
4' 51" 42'
± 34" 30"
8' 18" 18"
* when applicable
Figure No. VI
Job No. 16-11187
4 r.4E Geatechnilical
____
Exploration. Inc.
NOT TO SCALE -
SCHEMATIC RETAINING WALL
SUBDRAIN RECOMMENDATIONS
Proposed Exterior
Grade
drain 600C
I
Pr D p e ny
Compacted
)f Wall
)fiflg Backfill
erforated FVC: (SDR 35)
pipe witl 0.5% mm. sope,
ith bottom cf pipe located 12"
Blow slab or Interior (crowispoce)
ound surfccE elevation, with 1.5
u.ft.) of cave1 " diameter
ax, wrapped with filter cloth
ich as Miraarcin 6000
neridrain, uckdrain or
uivalent may be used as an
ternative.
T Between Bottom
12" of SloD and
Pipe E ttom
N Miradrain Clc':h
NOTE: As an option to Miradrain 6000, Gravel or
CrL•shed rock 3/4" maximun diameter rrcy be used
with a minimum 12" thickness along the interior
face of the wall and 2.0 cL.ft./ft. of pipe
gravel enveloe.
16-11187—WI
Figure No. VII
Job No. 16-11187
4 rI Ezploratl.n, Inc.
Sept 2016
APPENDIX A
UNIFIED SOIL CLASSIFICATION CHART
SOIL DESCRIPTION
Coarse-grained (More than half of material is larger than a No. 200 sieve)
GRAVELS, CLEAN GRAVELS GW Well-graded gravels, gravel and sand mixtures, little
(More than half of coarse fraction or no fines.
is larger than No. 4 sieve size, but
smaller than 3") GP Poorly graded gravels,, gravel and sand mixtures, little or
no fines.
GRAVELS WITH FINES
(Appreciable amount)
SANDS, CLEAN SANDS
(More than half of coarse fraction
is smaller than a No. 4 sieve)
SANDS WITH FINES
(Appreciable amount)
GC Clay gravels, poorly graded gravel-sand-silt mixtures
SW Well-graded sand, gravelly sands, little or no fines
SP Poorly graded sands, gravelly sands, little or no fines.
SM Silty sands, poorly graded sand and silty mixtures.
Sc Clayey sands, poorly graded sand and clay mixtures.
Fine-grained (More than half of material is smaller than a No. 200 sieve)
SILTS AND CLAYS
Liquid Limit Less than 50 ML Inorganic silts and very fine sands, rock flour, sandy silt
and clayey-silt sand mixtures with a slight plasticity
CL Inorganic clays of low to medium plasticity, gravelly
clays, silty clays, clean clays.
OL Organic silts and organic silty clays of low plasticity.
Liquid Limit Greater than 50 MH Inorganic silts, micaceous or diatomaceous fine sandy or
silty soils, elastic silts.
CH Inorganic clays of high plasticity, fat clays.
OH Organic clays of medium to high plasticity.
HIGHLY ORGANIC SOILS PT Peat and other highly organic soils
(rev. 6/05)
APPENDIX B
USGS DESIGN MAPS SUMMARY REPORT
Escondido'
Resoonse Spectrum
--I'
Penod,1 (eec)
LJSGS Design Maps Summary Report
User-Specified Input
Report Title 1095 Hoover Street, Carlsbad
Ouilding
Thu February 15, 2018 21:06:09 UTC
Code Reference Document ASCE 7-10 Standard
(which utilizes USGS hazard data available in 2008)
Site Coordinates 33.14830N, 117.33°W
Site Soil Classification Site Class D - "Stiff Soil"
Risk Category 1/11/111
'Vista Ocidnscte
arlbad
Sn Maros
USGS-Provided Output
is S= 1.135g SMS = 1.187g SDS= 0.792g
S1 = 0.436 g S,11 = 0.682 g 5D1 = 0.454 g
or information on how the SS and Si values above have been calculated from probabilistic (risk-targeted and
deterministic ground motions in the direction of maximum horizontal response, please re:urn to the appIiction and
select the "2009 NEHR,P" building code reference document.
4CER Response Specicu!r
I IM
084
o !
03.
ci 2
a 17
003 I I I I
QX 340 a60 CLW I3 I l' i
Pe,'ioc r (see)
or PGAM, TL, C, and C51 values, please view the detailed report.
though this information is a product of the U.S. Geological Survey, we provide no warranty, expressed or implied, as :3 the
3ccuracy of the data contained therein. This tcol is not a substitute for technical subject-matter knowledge,
APPENDIX C
Slope Stability Analysis
Safety Factor
0.000
0.250
0.500
0.750
1.000
1.250
1.500
2.000
1.750
2.250
2.500
2.750
3.000
3.250
3.500
3.750
4.000
4.250
4.500
4.750
5.000
5.250
5.500
5.750
6.000-
. . fn TO THI EXCE T20REIOEEO EON I 800FOIMSTABtIIY000CULASDN.Th5 OECTISN000nA/1 ThNCALCULOLO DCIX
COMPUETTO FIIL(XXfl F 120 MoOr-CooIonb 150 32 No. 0
1 120 MoNr-CoXo,,b 250 30 No,. 0
E]! 120 M.I-c.,,,b 100 s1
/
NW
0 to
2
Geotechnical
5!~A!
Exploration, Inc.
HOOVER STREET RESIDENTIAL PROJECT
ar~ By R.A.C. 1:2QQ CO 1 G.E.I.
SURFICIAL SLOPE STABILITY ANALYSIS
OTERPRET 6010 2/13/2018, 2:15:59 PM D"
I Rk Mane JOB NO. 16-11187A
Safety Factor
0.000
0.250
0.500
0.750
1.000
1.250
1.500
1.750
2.000
I 2.250
2.500
2.750
3.000
- - 2.90
o 3.500
00 3.750
4.000
4.250
4.500
1.750
5.000
5.250
5.500
5.750
6.000+
4 r.Gi Geotechnical HOOVER STREET RESIDENTIAL PROJECT i Exploration, Inc. k ______________________________________________________ -"- GROSS SLOPE STABILITY ANALYSIS
DimI7 DT R.A.C. 1:250 l°"" G.E.I.
oate
I 2/1312018,12:41:19 PM JOB NO. 16-11187A01.slim
JJLAtD
'I:
. . S
Safety Factor
0.000
0.250
0.500
0.750
1.000
1.250 I
1 SOO
1.750
2.000
2.250
2.500
2.750
3.000
3.250
3.500
3.750
4.000
4.250
4.500
4.750
5.000
5.250
5.500
5.750
6.000+
Geotechnical 4 r,IEi
Exploration, Inc. A.5D4OOI7
aka Dy
HOOVER STREET RESIDENTIAL PROJECT
GROSS SLOPE STABILITY ANALYSIS
R.A.C. 1:250 1"' G.E.I.
2/13/2018, 1:57:40 PM I JOB NO. 16-11187A02.sllm
. . .
Safety Factor
0.000
0.250
0.500
: 0.750
1.000
1.250
1.500
1.750
2.000
2.250
2.500
2.750
3.000
3.250
3 .500
3.750
4.000
4.250
4.500
4.750
5.000
5.250
5.500
5.750
6.000+
r
,€ 1nDaat
pcescn~
F!WMbfltLD
0.15
Geotechnical 64w.,* Exploration, Inc.
HOOVER STREET RESIDENTIAL PROJECT
GROSS SLOPE STABILITY ANALYSIS
R.A.C. 1250 I'"' G.E.I.
2/13/2018, 2:09:55 PM I R
k Name JOB NO. 16-11187A02w_0.15gSHAKE.slim
Pt t1Q 10 1TEEXLWO6Ckt0T FOR TIC runae CALCUAIflt TIC SEC1C$45}CV.5 TIC ea.s,tonaE FORtE..
Safety Facto
0.000
0.250
0.500
0.750
: 1.000
1.250
1.500
1.750
2.000
2.250
2.500
2.750
3.000
3.250
3.500
3.750
4.000
4.250
4.500
4.71)
5.000
5.250
5.500
5.750
6.O0
rIE4 Geotechnical I
Exploration, Inc.
R.A.C.
DWft
MRPREr &039 I 2/13/2018, 2:52:29 PM
HOOVER STREET RESIDENTIAL PROJECT
SURFICIAL SLOPE STABILITY ANALYSIS
we 1:200 I""' G.E.I.
Name JOB NO. 16-11187B_SHALLOW.slim
Safety Factor
0.000
0.250
0.500
0.750
1.000
1.250
1.500
1.750
2.000
2.250
2.500
2.750
3.000
3.250
3.500
3.750
4.000
4.250
4.500
4.750
5.000
5.250
5.500
5.750
6.000+
GH Geotechnical
Exploration, Inc.
R.A.C.
2/13/2018, 2:19:37 PM
80 100
HOOVER STREET RESIDENTIAL PROJECT
GROSS SLOPE STABILiTY ANALYSIS
1:250 G.E.I.
JOB NO. 16-11187B01.slim
fe.t.y Factor
0.000
° 0.250
0.500
079n
1.000
-
1.250
1.500
CD 1.750
2.000
2.250
--
2.500
2.750
3.000
- 3.250
o 3.500
3.750
4.000
4.250
4.500
• 4.750
5.000
5.250
- 5.500
• 5.750
6.000+
U
p
4 rI4 Geotechnical
Exploration, Inc.
HOOVER STREET RESIDENTIAL PROJECT
GROSS SLOPE STABILiTY ANALYSIS
ly R.A.L. 1:250 CO,I' G.E.I.
2/13/2018, 2:19:37 PM Ak Naffm JOB NO. 16-11187B02.slim
Safety Factor
0.000
0.250
0.500
0.750
1.000
1.250
1.500
1.750
2.000
2.250
2.500
2.750
3.000
3.250
3.500
3.750
4.000
4.250
4.500
4.750
5.000
5.250
5.500
5.750
6.000+
0.15
4 rIEi Geotechnical
Exploration, Inc.. AOCI1P
L .
HOOVER STREET RESIDENTIAL PROJECT
GROSS SLOPE STABILITY ANALYSIS
R.A.C. 1:250 I'" G.E.I.
2/13/2018, 2:48:10 PM I
Rk Name JOB NO. 16-11187B02w_0.
Safety Factor
o.uU0
0.250
0.500
0.750
1,000
1.250
1.500
1.750
2.000
2.250
2.500
2.750
3.000
3.250
3.500
3.750
4.000
4.250
4.500
4.750
5.000
5.250
5.500
5.750
6.000+
C.
CorornIQ.r rZO I5 •. I
a
- C .E r I OWPARLtt*PIThflc4) - 120 250 33 304.
50015000 IORM410I (150 no 15001-clogon,b - aec 3 50.e 0 I
I
Geatechnical HOOVER STREET RESIDEN I IAL PROJECT
Exploration, Inc. SURFICIAL SLOPE STABILITY ANALYSIS
R.A.C. 1:200 G.E.1.
2/14/2018, 8:00:13 AM file Now JOB NO. 16-11187D_SHALLOW.sflm
Safety Factor
0.000
0.250
0.500
0.750
1.000
1.250
1.500
1.750
2.000
2.250
2.500
2.750
3.000
3.250
3.500
3.750
4.000
4.250
4.500
4.750
,.000
5.250
5.500
5.750
6.000+
Geatechnical 4 r.IEi
Exploration, Inc.
oviawl? By R.A.C.
2/14/2018, 7:14:09 AM
HOOVER STREET RESIDENTIAL PROJECT
GROSS SLOPE STABILITY ANALYSIS
1:250 G.E.I.
JOB NO. 16-11187D01.slim
0
Safety Factor
0.000
0 0.250
0.500
0.750
1.000
----4 .250
1.500
0 —1 1.750
2.250
2.500
2.750
3.000
3.250
3.500
3./SO
4.000
4.250
4.500
4 .750
.000
5.250
5.500
5.750
6.000+
4 r.4 j Geotechnical
Exploration, Inc. I5
Dmwn By
I IOOVER STREET RESIDENTIAL PROJECT
GROSS SLOPE STABILITY ANALYSIS
R.A.C. 1:20 ICWWVY CLI.
2/14/2018, 7:49:18 AM I Rk Nam JOB NO. 16-11187D02.slim
-,---.-. - -------.------ ---------.--
0 . .
. . JOB NO. 16-11187(HOOVER STREET RES. PROJECT) -.xlsx SURFICIAL STABILITY CALCS 2/14/2018
I SURF RE I
EQUATION 1
F. S.
C
+ (13))
14 ____________________
y' tan(p)\ = * (y,.t x H x cos(13) x sin(13)
I
)
L-
SECTtON A
YPE C(psf) F.S.
COMPACTED FILL (Qaf) 150 32 I 24 1 1.765
SORT TYPE cjpsf) c) (°) F.S.
COMPACTED FILL (Qaf) 150 32 25 1 1.701
LCJNC
SOIL TYPE I C (psf) •(°)
I COMPACTED FILL (Qaf) I 150 32 27
Tsat Twtpr T, H
pcf
130
pcf
62.4
pcf J ft
67.6 3
Slope inclination with respect to the horizontal
pldue
• Friction angle of the soil
C Cohesion of the soil
Saturated unit weight of the soil
TI Submerged unit weight of the soil
H Thickness of the saturated soil layer
F.S. Factor of Safety
SURFICIAL SLOPE STABILITY ANALYSIS IS BASED ON EQUATION (1) FOR THE
CALCULATED VALUES.
Factors of Safety ABOVE 1.5 are adequate.
154
WM