HomeMy WebLinkAboutCDP 16-07; OTA RESIDENCE; REPORT OF GEOTECHNICAL INVESTIGATION OTA RESIDENTIAL PROJECT; 2016-05-16RECORD COPY
t/iL 1
Initial Date
REPORT OF GEOTECHNICAL INVESTIGATION
Ota Residential Project
4090 Garfield Street
Carlsbad, California
JOB NO. 16-11073
16 May 2016
Prepared for:
Blafr and Paula Ota
MAY 1 9 2016
CITY OF CARLSBAD
PLANNING DIVISION
Geotechnkal Exploration, Inc.
SOIL AND FOUNDATION BWRING • GROUNDWATER ®. 0IGINEERING GEOLOGY
16 May 2016
Blair and Paula Ota Job No. 16-11073
4 Beliezza
Irvine, CA 92620
Attn: Ms. Christine deGregorlo
Subject; Report of Geotechnical Investiaation
Proposed Ota Residence
4090 Garfield Street
Carlsbad, California
Dear Mr. and Mrs. Ota;
In accordance with your request and our revised proposal dated April 11, 2016,
Geotechnical Exploration, Inc. has performed an Investigation of the
geotechnical and general geologic conditions at the location of the proposed
residential project in the City of Carlsbad. The field work was performed on April
20, 2016.
In our opinion, if the conclusions and recommendations presented in this report are
implemented during project design and site preparation, the site will be suited for
the proposed stabilization 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. 16-11073 will expedite a response to your Inquiries.
Respectfully submitted,
GEOTECHNICAL EXPLORAtlQN, INC.
-^aime'A. Cerros, P.E. ' Leske D. Reed, President
R.C.E. 34422/G.E. 2007 C.E.G. 999/P.G. 3391
Senior Geotechnical Engineer
7420 TKADE STREET^? SAN DIEGO, CA. 92121 O (858) 549-7222 ® FAX: (858) 549-1604 ® EMAIL geotech^gei-sdcom
TABLE OF CONTENTS
page
I. PROJECT DESCRIPTION 1
II. SCOPE OF WORK 1
III. EXECUTIVE SUMMARY 3
IV. SITE DESCRIPTION AND BACKGROUND 3
V. FIELD INVESTIGATION 4
VI. REGIONAL GEOLOGIC DESCRIPTION 6
VII. SITE-SPECIFIC SOIL & GEOLOGIC DESCRIPTION 11
VIII. GEOLOGIC HAZARDS 12
IX. GROUNDWATER 22
X. SUMMARY OF FINDINGS 23
XI. CONCLUSIONS AND RECOMMENDATIONS 24
XII. GRADING NOTES 45
XIII. LIMITATIONS 45
REFERENCES
FIGURES
I. Vicinity Map
II. Plot Plan and Site-Specific Geologic Map
III Exploratory Excavation Log with Laboratory Data
IV. Laboratory Test Resuits
V. Geologic Map Excerpt
VI. Cross Section
APPENDICES
A. Unified Soil Classification System
B. Modified Mercaiii Index
C. USGS Design Maps Summary Report
REPORT OF GEOTECHNICAL INVESTIGATION
Ota Residential Project
4090 Garfleld Street
Carlsbad, California
JOB NO. 16-11073
The following report presents the findings and recommendations of Geotechnlcaf
Exploration, Inc. for the subject project.
I. PROJECT DESCRIPTION
It Is our understanding, based upon provided plan information, it Is planned to
demolish the existing single-family residence and construct a new two-stories-over-
garage-and-basement single-family residence. We understand the new additions
will be of conventional materials.
II. SCOPE OF WORK
The Scope of Work we performed Is briefly outlined as follows:
1. Review of the available background reports and maps that are pertinent to
the site, its history, and the general vicinity.
2. Excavation of 2 exploratory pits utilizing manual labor. The soils and
groundwater conditions (if any) encountered In the excavations were logged
by our field representative and undisturbed and loose bag soil samples were
collected from the various soil types to the maximum depths of exploration.
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Carlsbad, California Page 2
3. Laboratory testing on the collected samples to assess their gradation per
applicable portions of the Unified Soil Classification System, their field
moisture content and density. Direct shear tests were also conducted on
representative samples to allow evaluation of the shear strength of the
planned foundation soils.
4. Geotechnical engineering analysis of the resulting findings from our field and
laboratory assessments.
5. Preparation of this written report including our recommendations for site
preparation, construction shoring soil design parameters, allowable soil
bearing value, estimated settlement, preliminary foundation design
information, and slope stability of proposed temporary cut slopes. Also, a
seismic analysis is presented addressing the seismic risk potential of the site
with respect to local and regional faulting per the current building code (CBC
2013).
III. EXECUTIVE SUMMARY
Our subsurface investigation revealed that the lot is underlain by medium dense
siity sand native terrace deposits, referred to as Quaternary Old Paralic Soils, Unit
6-7 (Qope-y). These materials are dry to damp and loose in the upper foot. These
materials are suitable for support of the planned new residential Improvements.
The upper 2 to 3 feet of site soils will be disturbed by the demolition of the existing
structures (house and garage) and will require recompactlon. Excavation for the
planned basement will require temporary shoring.
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IV. SITE DESCRIPTION AND BACKGROUND
The property Is located on an emergent marine terrace adjacent to the Pacific
Ocean on Garfleld Street, a residential street In the western portion of the City of
Carlsbad, It is more particularly referred to as Assessor's Parcel No. 206-091-04, a
portion of Lots 3 & 4 of Block U of Palisades Unit 2 subdivision In the City of
Carlsbad, County of San Diego, State of California according to Map 1803. For the
project location, refer to the Vicinity Map, Figure No. I.
The property Is relatively level and faces southwest. It Is located on the northeast
side of Garfleld Street. Similar single-family residential properties exist to the
northwest, southeast and northeast of the property at the same general elevation
(approximately 52 feet above mean sea level). The existing two-story, single-
family residence and detached garage are of wood-frame construction with wood
siding. A concrete driveway accessing the garage exists on the northwest side of
the lot. The rear yard consists of a concrete patio. The front yard Is landscaped
with decorative gravel. Vegetation consists of small shrubs, palms and ornamental
plants In planters. Refer to the Plot Plan and Site-specific Geologic Map for the
planned new Improvements, Rgure No. II.
V. FIELD INVESTIGATION
Two exploratory pits were advanced on either side of the existing structure. For the
excavation locations, refer to the Plot Plan and Site-Speclfic Geologic Map, Rgure
No. II. We note that we are familiar with subsurface conditions at greater depths in
this area due to coastal bluff ex'posures across the street (west) of the subject site
and from other subsurface investigations performed on this street within a few lots
Ota Residential Project Job No. 16-11073
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of the subject site. The pits were excavated to maximum depths of 3 feet.
Groundwater was not encountered.
The soil conditions encountered in the pits were logged by our field representative
and samples were taken of the predominant soils throughout the field operation.
Exploratory excavation logs have been prepared on the basis of our observations
and laboratory testing, Figure No. III. The predominant soils have been classified
per applicable portions of the Unified Soil Classification System, see Appendix A.
A. Fielfi
The excavations were logged by our representative using a pointed steel bar and
other tools to qualitatively assess the penetration resistance and in situ density of
the encountered soil types. Loose soil samples were also examined under a hand
lens and moistened with a spray bottle. Bulk (disturbed) and chunk (relatively
undisturbed) samples of the encountered soils were also retrieved for subsequent
laboratory testing,
B. Laboratory Tests
Laboratory tests were performed on the disturbed and relatively undisturbed soil
samples in order to evaluate their physical and mechanical properties and their
ability to support the proposed residential structure and improvements. We note
that the encountered rock content made sample recovery difficult and limited our
results. Test results are summarized on Figure Nos. Ill and IV. The following tests
were conducted on the sampled soils:
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Carlsbad, California
Job No. 16-11073
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1. Moisture Content (ASTM D2216-10)
2. Standard Test Method for Bulk Specific Gravity and Density Using
Coated Samples (ASTM Oil88-07)
3. Determination of Percentage of Particles Smaller than #200
(ASTM D1140-14)
4. Standard Test Method for Direct Shear Test' of Soils under
Consolidated Drained Conditions (ASTM D 3080-11)
The Moisture Content {ASTM D2216) of a soil sample is a measure of the water
content, expressed as a percentage of the dry weight of the sample. The retrieved
formatlonal samples were evaluated for moisture content and density.
The Standard Test Method for Bulk Specific Gravity and Density of Compacted
Bituminous Mixtures using Coated Samples (ASTM D1188) test assesses the In-
place density of the relatively undisturbed terrace/Old Parallc Soil samples.
The Standard Method for Determination of Percentage of Particles Smaller Than
#200 (ASTM D1140) aids In classification of the tested soils based on their fine
material content, and provides qualitative Information related to engineering
characteristics such as expansion potential, permeability, and shear strength. The
tested terrace soils yielded results of 25 percent passing through the -200 sieve.
Based on the laboratory test data per the Standard Test Method for Direct Shear
Test of Soils under Consolidated Drained Conditions (ASTM D3080), our
observations of the primary soil types, and our previous experience with laboratory
testing of similar soils, our Geotechnical Engineer has assigned values for the angle
of internal friction and cohesion to those soils that will provide significant lateral
support or load bearing on the project. These values have been utilized In
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Job No. 16-11073
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assigning the recommended bearing value as well as active and passive earth
pressure design criteria for foundations and retaining walls.
The expansion potential of soils Is determined, when necessary, utilizing the
Standard Test Method for Expansion Index of Soils (ASTM D4829). In accordance
with the Standard (Table 5.3), potentially expansive soils are classified as follows:
EXPANSION INDEX POTENTIAL EXPANSION
0 to 20 Very low
21 to 50 Low
51 to 90 Medium
91 to 130 High
Above 130 Very high
Based our experience with the encountered soils, the tested site silty sand terrace
soils have a very low expansion index.
VL REGIONAL GEOLOGIC DESCRIPTION
San Diego County has been divided into three major geomorphic provinces: the
Coastal Plain, the Peninsular Ranges and the Salton Trough. The Coastal Plain
exists west of the Peninsular Ranges. The Salton Trough is east of the Peninsular
Ranges. These divisions are the result of the basic geologic distinctions between
the areas. Mesozoic metavolcanic, metasedlmetary and plutonic rocks predominate
In the Peninsular Ranges with primarily Cenozoic sedimentary rocks to the west and
east of this central mountain range (Demere, 1997).
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In the Coastal Plain region, the "basement" consists of Mesozoic crystalline rocks.
Basement rocks are also exposed as high relief areas (e.g.. Black Mountain
northeast of the subject property and Cowles Mountain near the San Carlos area of
San Diego). Younger Cretaceous and Tertiary sediments lap up against these older
features. These sediments form a 'Vayer ca/ce" sequence of marine and non-marine
sedimentary rock units, with some formations up to 140 million years old. Faulting
related to the La Nacion and Rose Canyon Fault zones has broken up this sequence
into a number of distinct fault blocks in the southwestern part of the county.
Northwestern portions of the county are relatively undeformed by faulting (Demere,
1997).
The Peninsular Ranges form the granitic spine of San Diego County. These rocks
are primarily plutonic, forming at depth beneath the earth's crust 140 to 90 million
years ago as the result of the subduction of an oceanic crustal plate beneath the
North American continent. These rocks formed the much larger Southern California
bathollth. Metamorphism associated with the intrusion of these great granitic
masses affected the much older sediments that existed near the surface over that
period of time. These metasedimentary rocks remain as roof pendants of marble,
schist, slate, quartzlte and gneiss throughout the Peninsular Ranges. Locally,
Miocene-age volcanic rocks and flows have also accumulated within these
mountains (e.g., Jacumba Valley). Regional tectonic forces and erosion over time
have uplifted and unroofed these granitic rocks to expose them at the surface
(Demere, 1997).
The Salton Trough is the northerly extension of the Gulf of California. This zone is
undergoing active deformation related to faulting along the Elsinore and San Jacinto
Fault zones, which are part of the major regional tectonic feature in the
southwestern portion of California, the San Andreas Fault zone. Translationai
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movement along these fault zones has resulted In crustal rifting and subsidence.
The Salton Trough, also referred to as the Colorado Desert, has been filled with
sediments to depth of approximateiy 5 miies since the movement began in the
eariy Miocene, 24 miiiion years ago. The source of these sediments has been the
local mountains as well as the ancestral and modern Colorado River (Demere,
1997).
As Indicated previously, the San Diego area is part of a seismicaiiy active region of
California. It is on the eastern boundary of the Southern California Continental
Borderland, part of the Peninsular Ranges Geomorphic Province. This region is part
of a broad tectonic boundary between the North American and Pacific plates. The
actual plate boundary is characterized by a complex system of active, major, right-
lateral strike-slip faults, trending northwest/southeast. This fault system extends
eastward to the San Andreas Fault (approximately 70 miles from San Diego) and
westward to the San Clemente Fault (approximately 50 miles offshore from San
Diego) (Berger and Schug, 1991).
In California, major earthquakes can generally be correlated with movement on
active faults. As defined by the California Division of Mines and Geology (Hart,
E.W., 1980), an "active" fault Is one that has had ground surface displacement
within Holocene time (about the last 11,000 years). Additionally, faults along which
major historic earthquakes have occurred (about the last 210 years In California)
are also considered to be active (Association of Engineering Geologist, 1973). The
California Division of Mines and Geology defines a "potentially active" fault as one
that has had ground surface displacement during Quaternary time, that Is, between
11,000 and 1.6 million years (Hart, E.W., 1980).
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During recent history, prior to April 2010, the San Diego County area was relatively
quiet selsmlcally. No fault ruptures or major earthquakes had been experienced in
historic time within the greater San Diego area. Since earthquakes have been
recorded by Instruments (since the 1930s), the San Diego area had experienced
scattered seismic events with Richter magnitudes (M) generally less than M4.0.
During June 1985, a series of small earthquakes occurred beneath San Diego Bay,
three of which had recorded magnitudes of M4.0 to M4.2. In addition, the
Oceanside earthquake of July 13, 1986, located approximately 26 miles offshore of
the City of Oceanside, had a magnitude of MS.3 (Hauksson and Jones, 1988).
On June 15, 2004, a MS.3 earthquake occurred approximately 45 miles southwest
of downtown San Diego (26 miles west of Rosarlto, Mexico). Although this
earthquake was widely felt, no significant damage was reported. Another widely felt
earthquake on a distant Southern California fault was a MS.4 event that took place
on July 29, 2008, west-southwest of the Chino HIils area of Riverside County.
Several earthquakes ranging from MS.O to M6.0 occurred in northern Baja
California, centered in the Gulf of California on August 3, 2009. These were felt in
San Diego but no injuries or damage was reported. A MS.8 earthquake followed by
a M4.9 aftershock occurred on December 30, 2009, centered about 20 miles south
of the Mexican border city of Mexicali. These were also felt In San Diego, swaying
high-rise buildings, but again no significant damage or injuries were reported.
On Easter Sunday, April 4, 2010, a large earthquake occurred In Baja California,
Mexico. It was widely felt throughout the U.S. southwest Including Phoenix,
Arizona and San Diego, California. It significantly affected Mexicall, Mexico. This
M7.2 event, the Sierra El Mayor earthquake, occurred in northern Baja California,
approximately 40 miles south of the Mexico-USA border, at relatively shallow depth
along the principal plate boundary between the North American and Pacific plates.
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According to the U. S. Geological Survey, this is an area with a high level of historic
selsmlclty, and It has recently been seismlcally active, though this is the largest
event to strike in this area since 1892. The April 4, 2010, earthquake appears to
have been larger than the M6.9 earthquake in 1940 or any of the early 20^^ century
events (e.g., 1915 and 1934) in this region of northern Baja California. The event
caused widespread damage to structures, closure of businesses, government offices
and schools, power outages, displacement of people from their homes and injured
over 200 people In the nearby major metropolitan areas of Mexicali and adjacent
Calexico in Southern California. Estimates of the cost of the damage range to over
$100 million.
This event's aftershock zone extends significantly to the northwest, overlapping
with the portion of the fault system that Is thought to have ruptured in 1892.
Some structures In the San DIego area experienced minor damage and there were
some injuries. Ground motions for the April 4, 2010, main event, recorded at
stations In San Diego and reported by the California Strong Motion Instrumentation
Program (CSMIP), ranged up to 0.058g. Aftershocks from this event continue to
the date of this report along the trend northwest of the original event. Including
within San Diego County, closer to the San Diego metropolitan area. There have
been hundreds of these earthquakes including events up to MS.7.
On July 7, 2010, a M5.4 earthquake occurred in Southern California at 4:53 pm
(Pacific Time) about 30 miles south of Palm Springs, 25 miles southwest of Indio,
and 13 miles north-northwest of Borrego Springs. The earthquake occurred near
the Coyote Creek segment of the San Jaclnto Fault. The earthquake exhibited right
lateral slip to the northwest, consistent with the direction of movement on the San
Jacinto Fault. The earthquake was feit throughout Southern California, with strong
shaking near the epicenter. It was followed by more than 60 aftershocks of Ml.3
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and greater during the first hour. Seismologists expect continued aftershock
activity.
In the last 50 years, there have been four other earthquakes In the M5.0 range
within 20 kilometers of the Coyote Creek segment: MS.8 in 1968, M5.3 on
2/25/1980, M5.0 on 10/31/2001, and MS.2 on 6/12/2005. The biggest earthquake
near this location was the M6.0 Buck Ridge earthquake on 3/25/1937.
VII. SITE-SPECIFIC SOIL & GEOLOGIC DESCRIPTION
According to the California Geologic Survey and United States Geological Survey
Geologic Mao of the Oceanslde 30'x60' Quadrangle, California by Michael P.
Kennedy and Slang S. Tan (2005), the native surflclal materials underlying the site
are referred to as Quaternary Old Paralic Deposits, Unit 6-7, Qope-?. The
encountered soil profile below the planned residential project area consists of these
in situ materials, referred to as terrace deposits. Unit 6-7, Qope-?- These consist of
brown to dark gray-brown sllty sand. They are dry to damp and loose In the upper
foot and become medium dense below this depth.
The Old Paralic Deposit materials typically have relatively high strength and good
soil bearing properties. These silty sand materials are of very low expansion
potential. Temporary excavations in Old Paralic Deposit materials will be required
during basement construction.
If no 10' hole then explain here whv. How deep did we qo on 3 nearbv jobs? What "7
do bluffs show, etc.
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Refer to the Plot Plan and SIte-speclfIc Geologic Map, Rgure No. II; the Excavation
Logs, Figure No. Ill; laboratory test results Figure No. IV; and the Geologic Map
excerpt, Rgure No. V, for details. Schematic cross sections through the site are
also provided as Figure No. VI.
No faults or landslides are mapped on or nearby the site.
VJII. GEOLOGIC HAZARDS
The following Is a discussion of geologic conditions and hazards common to this
area of the City of Carlsbad, as well as site-specific geologic Information relating to
the subject property.
A. Local and Regional Faults
Rose Canvon Fault. The Rose Canyon Fault Zone (Mount Soledad and Rose Canyon
Faults also referred to as the RCFZ), Is less than 5 miles southwest of the site. It Is
mapped trending north-south from Oceanslde to downtown San Diego, from where
It appears to head southward Into San Diego Bay, through Coronado and offshore.
The RCFZ Is considered to be a complex zone of onshore and offshore, en echelon
strike slip, oblique reverse, and oblique normal faults. This fault Is considered to be
capable of causing an earthquake of M7.2 per the California Geologic Survey (2002)
and considered microselsmlcally active, although no significant recent earthquake is
known to have occurred on the fault.
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
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San Diego, has encountered offsets In Hoiocene (geologically recent) sediments.
These findings confirm Hoiocene displacement on the Rose Canyon Fault, which was
designated an "act/i^e'fault in November 1991 (Hart, E.W. and W.A. Bryant, 2007,
Fault-Rupture Hazard Zones in California, California Geological Survey Special
Publication 42);
Newport-InQlewood Fault (offshore): The Newport-Inglewood Fault Is located
approximately 6 miles off shore west of the subject site. This right lateral strike
slip fault is part of the San Andreas set of active, northwest-trending, right lateral
strike-slip faults in the Southern California area (Croweil, 1962). The fault extends
64 miles — 47 miles onshore from Culver City In Los Angeles County to Newport
Beach in Orange County where it extends offshore another 17 miles. The Rose
Canyon Fault is believed to be a southern extension of the Newport-Inglewood
Fault.
The Newport-Inglewood Fault was first identified after a M4.9 earthquake struck
near Ingiewood on June 21, 1920. Due to the lack of earthquake-resistant
construction in Southern California at this time, this earthquake caused
considerable damage In the Ingiewood area and was a preview of the Long Beach
earthquake which occurred 13 years later. The Long Beach earthquake occurred on
March 10, 1933, centered along the southern segment of this fault, and registered
M6.3. This earthquake killed 115 people and was the second most deadly
earthquake in California history, after the 1906 San Francisco earthquake. Seventy
schools In Long Beach and Conipton area were destroyed and an additional 120
were heavily damaged; had this tremor struck during school hours, the death toil
would have been much higher, some estimates as high as 1,000. In response to
the poor performance of school structures, the California legislature passed the
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Reld Act in April 1933, mandating earthquake-resistant construction for all new
school buildings.
Offsets observed in the Huntlngton Beach area indicate significant Holocene
displacement. On September 9, 2001, a M4.2 earthquake was reported at the
northern end of the Newport-Inglewood Fault, near Century City. On May 17,
2009, at 8:39 PDT, a M4.7 earthquake was centered In the unincorporated
community of Lennox, very close to the estimated location of the 1920 Ingiewood
earthquake. The earthquake was felt as far away as San Diego and Las Vegas. An
M4.0 aftershock occurred on May 19, 2009, at 3:49 PDT, in nearly the same
location. As of June 3, 2009, more than a score of aftershocks had been measured
at or near the point of the original earthquake on May 17, 2009. The Newport-
Inglewood Fault may have been responsible for these quakes, but further study is
needed to determine the source fault.
On November 5, 2010, at 9:06 a.m. local time, a M3.7 quake originated on this
fault, centered 2 miles south of Long Beach. No damage was reported. On August
18, 2011, at 2:43 p.m. local time, a M3.2 quake originated on this fault, centered 2
miles southeast of Long Beach. No damage was reported. The fault has a slip rate
of approximately 0.6mm/year and is predicted to be capable of a M6.0 to M7.4
earthquake.
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
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fault zone, it is significantly less active seismically than the Eisinore Fault (Hlleman,
1973). It Is postulated that the Coronado Bank Fault is capable of generating an
M7.6 earthquake and Is of great interest due to its close proximity to the greater
San Diego metropolitan area.
Eisinore Fault. The Eisinore Fault is located approximately 25 to 50 miles east and
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
Eisinore 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 Eisinore
Fault Zone range from less than 1 mile to 16 miles in length. The trend, length and
geomorphic expression of the Eisinore 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 Eisinore 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 Eisinore 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 Eisinore Fault zone belongs to the San Andreas set of active,
northwest-trending, right-siip 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
quake near the town of Eisinore In 1910 (Richter, 1958; Toppozada and Parke,
1982). However, based on length and evidence of iate-Pleistocene or Holocene
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displacement, Greensfelder (1974) has estimated that the Elsinore Fault Zone Is
reasonably capable of generating an earthquake with a magnitude as iarge as M7.5.
Study and iogging of exposures 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 combined with previous estimates of the long-term horizontal slip rate of 0.8
to 7.0 mm/year, suggest typical earthquake magnitudes of M6.0 to M7.0 (Rockwell,
1985). More recently, the California Geologic Survey (2002) considers the Eisinore
Fault capable of producing an earthquake of M6.8 to M7.1.
San Jacinto Fault. The San Jacinto Fault is located 47 to 60 miles to the east 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 Fauit in
San Bernardino, southeasterly toward the Brawley area, where it continues south of
the International border as the Imperial Transform Fauit (Earth Consuitants
International [ECI], 2009).
The San Jacinto Fauit Zone has a high level of historical seismic activity, with at
least 10 damaging (M6.0 to M7.0) earthquakes having occurred on this fault zone
between 1890 and 1986. Earthquakes on the San Jacinto in 1899 and 1918 caused
fatalities in the Riverside County area. Offset across this fauit is predominantly
right-iaterai, 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 Fauit that are of most concern to major
metropolitan areas are the San Bernardino, San Jacinto Vaiiey, and Anza segments.
Fauit slip rates on the various segments of the San Jacinto are less well constrained
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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
greater will occur within 30 years on this fault. Maximum credible earthquakes of
M6.7, MS.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 (ECI, 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 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 on 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 Bemardino 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
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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 eievated ievel. The San Jaclnto fault Is known as the
most active earthquake fault In Southern California. Caltech and USGS
seismologist continue to monitor the ongoing earthquake activity using
the Caltech/USGS Southern California Seismic Network and a GPS
network of more than 100 stations.
a. other Geologic Hazards
Ground Rupture-. Ground rupture is characterized by bedrock slippage along an
established fauit and may resuit 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 1-mlle-iong surface-
rupture length could be expected (Greensfelder, 1974). Our investigation Indicates
that the subject site Is not directly on a known fault trace and, therefore, the risk of
ground rupture Is remote.
Ground Shaking-. Structural damage caused by seismlcally Induced ground shaking
is a detrimental effect directly related to faulting and earthquake activity. Ground
shaking is considered to be the greatest seismic hazard in San Diego County. The
intensity of ground shaking is dependent on the magnitude of the earthquake, the
distance from the earthquake, and the seismic response characteristics of
underlying soils and geologic units. Earthquakes of M5.0 or greater are generally
associated with notable to significant damage. It is our opinion that the most
serious damage to the site would be caused by a large earthquake originating on
active strands within the Rose Canyon Fault Zone. Although the chance of such an
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event Is remote. It could occur within the useful life of the structure. Ground
shaking will be experienced at the site from earthquakes on active Southern
California faults and active faults in northwestern Mexico.
Landslides: Based upon our geologic reconnaissance, review of the geologic maps
(Kennedy and Tan, 2008; Kennedy, 1975), and USDA stereo pair aerial
photographs AXN-8M-81 & 82, dated April 11, 1953, that depict the area of the site
there are no known or suspected ancient landslides located on the site.
Slope Stability: The site is level and no permanent slopes are planned. Temporary
slopes will require shoring during basement construction.
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 unconflned. 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 nature of the
natural-ground material and the lack of a shallow static groundwater surface under
the site. The site does not have a potential for soil strength loss to occur due to a
seismic event.
Tsunamis. Seiches and Storm Surge: A tsunami is a series of long waves
generated in the ocean by a sudden displacement of a large volume of water.
Underwater earthquakes, landslides, volcanic eruptions, meteor 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
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a major earthquake or other 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 more than 3,000 feet inland.
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 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 were
worse than damage caused by several other tsunamis with higher wave heights.
The site is located adjacent to but setback from the Pacific Ocean at an elevation of
approximately 52 feet (and Is not mapped within a potential inundation zone on the
2009 "Tsunami Inundation Map for Emergency Planning...Oceanslde Quadrangle"
published by the California Emergency Management Agency, the California Geologic
Survey and the University of Southern California). The risk of a tsunami affecting
the property is considered to be very low. Considering the historic wave heights of
the measured tsunami events and the presence of the sea wall the risk Is
considered low.
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Sea Level Rise: According to the California Coastal Commission's Sea Level Rise
Policy Guidelines (August 2015):
Climate change is upon us, affecting almost every facet of California's
natural and built environment. Increasing global temperatures are
causing significant effects at global, regional, and local scales. In the.
past century, average global temperature has increased by about
0.8°C (1.4°F), and average global sea level has increased by7 to 8 in
(17 to 21 cm) (IPCC2013). Sea level at the San Francisco tide gauge
has risen 8 in (20 cm) over the past century, and the National
Research Council (NRC) projects that by year 2100, sea level in
California may rise by4 to 56 in (10 to 143 cm) for areas north of Cape
Mendocirio and 17 to 66 in (42 to 167 cm) for areas south of Cape
Mendocino (NRC 2012). While the California coast regularly
experiences erosion, flooding, and significant storm events, sea level
rise will exacerbate these natural forces, leading to significant social,
environmental, and economic impacts.
Per the County of San Diego Office of Emergency Services' Multi-iun'sdlctional Multi-
hazard Mitigation Plan Development in San Dieao, Sea level rise (SLR) in the San
Diego area is expected to be 1.56 to 11.76 inches by 2030; 4.68 inches to 2 feet by
2050; and 16.56 to 53.48 inches by 2100. Sea level rise is not anticipated to affect
the site due to its elevation and setback distance from the ocean.
Geologic Hazards Summary: It is our opinion, based upon a review of the available
maps, our research, our site reconnaissance and on-site exploration, that the
project will be underlain by relatively stable materials. We have recommended
recompaction of soils disturbed by the demolition activities., No significant geologic
hazards are imminent or known to exist on the site that would prevent construction
of the planned residential project. Ground shaking from earthquakes on active
Southern California faults and active faults in northwestern Mexico is considered to
be a seismic hazard for this project.
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IX. GROUNDWATER
Groundwater was not encountered during the course of our field Investigation.
Appropriate drainage protection for the below-grade basement walls will be
required. We do not anticipate significant groundwater problems in the future, If
the property is developed as proposed and proper drainage Is Implemented and
maintained.
It should be kept In mind that any required grading operations will change surface
drainage patterns and/or reduce permeabilities due to the densificatlon 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 damage from 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.
On properties such as the subject site where medium dense to dense terrace
materials exist at relatively shallow depths, even normal landscape Irrigation
practices or periods of extended rainfall can result In shallow "perched" water
conditions. The perching (shallow depth) accumulation of water on a low
permeability surface can result In areas of persistent wetting and drowning of
lawns, plants, and trees. Resolution of such conditions, should they occur, may
require site-specific design and construction of subdrain and shallow "wick" drain
dewatering systems^
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Subsurface drainage with a properly designed and constructed subdrain system will
be required along with continuous back drainage behind any proposed lower-ievei
basement wails, property line retaining walls, or any perimeter stem walls for
raised-wood floors where the outside grades are higher than the crawl space
grades. Furthermore, crawl spaces should be provided with the proper cross-
ventiiation to help reduce the potential for moisture-related problems.
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
fili 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 grading operations,
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.
X. SUMMARY OF FINDINGS
Our subsurface investigation revealed that the lot is underlain at shallow depths by
medium dense terrace deposits referred to as Old Parallc Deposits, Unit 6-7, Qope-?.
They are dry to damp and loose in the upper 1 foot. They become medium dense
below this depth. The planned project Includes excavation for a basement below
two-stories above grade, which is anticipated to disturb the upper 2 to 3 feet of
these soils. These soils will require recompaction at the surface. Based on
: - in addition to our test pit excavations.
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These terrace soils are suitable for
support of the planned basement foundations. The basement excavation will
require shoring for support during construction. Once the shoring plans are
completed and available for our review, additional recommendations may be
provided by our firm,
There are no geologic hazards on or near the site that would prohibit the project as
currently planned. Ground shaking from earthquakes on active Southern California
faults and active faults in northwestern Mexico Is considered to be a seismic hazard
for this project.
XI. CONCLUSIONS AND RECOMMENDATIONS
The following conclusions and recommendations are based upon the practical field
investigation conducted by our firm and resulting laboratory tests, in conjunction
with our knowledge and experience with similar soils in the City of Carlsbad.
It is our opinion that the site is suitable for the planned residential project provided
the recommendations herein are incorporated during design and construction.
Further, It is our explicit opinion that the proposed site development would not
destabilize adjacent properties or public improvements If properly shored and
constructed In accordance with our recommendations.
The opinions, conclusions, and recommendations presented In this report are
contingent upon Geotechnlcal Exploration, Inc. being retained to review the final
plans and specifications as they are developed and to observe and test the site
earthwork and installation of foundations. Accordingly, we/ecommend that the
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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 governing agency in writing of such change
prior to the commencement or recommencement of grading and/or
foundation installation work.
Temporary excavations should be observed and evaluated by our project geologist
during the excavation process. Should geologic conditions differ from those
encountered additional recommendations may be provided.
A. Seismic Design Criteria
1. Seismic Data Bases: The estimation of the peak ground acceleration and the
repeatable high ground acceleration (RHGA) likely to occur at the site is
based on the known significant local and regional faults within 100 miles of
the site. The Modified Mercalll Index, a table of ground shaking intensity, is
provided as Appendix B.
2. Seismic Design Criteria: The proposed structure should be designed In
accordance with the 2013 CBC, which incorporates by reference the ASCE 7-
10 for seismic design. We have determined the mapped spectral acceleration
values for the site based on latitude 33.1458 degrees north and longitude
117.3408 degrees west, utilizing a program titled "t/.S. Seismic Design Maps
and Tools" provided by the USGS, which provides a solution for ASCE 7-10
utilizing digitized files for the Spectral Acceleration maps. See Appendix C.
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Carlsbad, Caiifomia
Job No. 16-11073
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3. Structure and Foundation Design: The design of the new addition structures
and foundations should be based on Seismic Design Category D.
Spectra! Acceleration and Design Values: The structural seismic design,
when applicable, should be based on the following values, which are based
on the site location, soli characteristics, and seismic maps by USGS, as
required by the 2013 CBC. A response Spectrum Acceleration (SA) vs.
Period (T) for the site is also included in Appendix C. The Site D values for
this property are:
TABLE I
Maooed Spectral Acceleration Values and Design Parameters
s.Si Fa Fv Sms Sml Sds Sdi
1.159 0.445 1.036 1.555 1.201 0.692 0.801 0.461
B. Preparation of Soils for Site Development
3. Clearing and Stripping: The existing structures, improvements, and
vegetation on the site should be removed prior to the preparation of the
building pads and areas of associated improvements. This includes root
systems of the existing shrubs and palms. Holes resulting from the removal
of root systems or other burled foundations, piping, debris or obstructions
that extend below the planned grades should be cleared and backfilled with
properly compacted fill. We recommend that existing fills and disturbed
upper soils be removed and recompacted prior to installation of basement
shoring for access purposes.
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4. Treatment of Existing Loose Fill and Surflclal Soils: In order to provide
suitable foundation support for the proposed residential structures and
associated Improvements, we recommend, following demolition, that the
existing maximum depth of removal and recompaction is approximately 3
feet.
The recompaction work should consist of (a) removing the disturbed terrace
soils and loose surficial soils down to native medium dense to dense
formational terrace materials; (b) scarifying, moisture conditioning, and
compacting the exposed subgrade soils; and (c) replacing the excavated
material as compacted structural fill.
The areal extent and depth required to remove the disturbed and loose
terrace soils should be confirmed by our representatives during the
excavation work based on their examination of the soils being exposed. The
lateral extent of the excavation and recompaction should be at least 5 feet
beyond the edge of the perimeter foundations and any areas to receive
exterior improvements or a lateral distance equal to the depth of soil
removed at any specific location, whichever is larger. Any unsuitable
materials (such as oversize rubble or rocks, and/or organic matter) should be
selectively removed as directed by our representative and disposed of off-
site.
Any rigid Improvements founded on existing loose or soft surface soils can be
expected to undergo movement and possible damage. Geotechnical
Exploration^ Inc. takes no responsibility for the performance of any
improvements built on loose natural soils or inadequately compacted fills.
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5. Subarade Preparation: After the site has been cleared, stripped, and the
required excavations made, the exposed subgrade soils in the areas to
receive fill and/or building improvements should be scarified to a depth of 12
inches, moisture conditioned, and compacted to the requirements fof
structural fill. The near-surface moisture content of fine-grained soils should
be maintained by periodic sprinkling until within 48 hours prior to concrete
placement.
6. Expansive SofI Conditions: We do not anticipate that significant quantities of
medium or highly expansive clay soils will be encountered during grading.
Should such soils be encountered and used as fill, however, they should be
moisture conditioned or dried to no greater than 5 percent above Optimum
Moisture content, compacted to 88 to 92 percent, and placed outside building
areas. Soils of medium or greater expansion potential should not be used as
retaining wail backfill soils.
7. Material for Fill: Existing on-site soils with an organic content of less than 3
percent by volume are, in general, suitable for use as fill. Any required,
imported fill material (such as for retaining wall backfill) should be a low-
expansion potential (Expansion Index of 50 or less per ASTM D4829-11). In
addition, both imported and existing on-site materials for use as fill should
not contain rocks or lumps more than 6 inches in greatest dimension. Ail
materials for use as fiii should be approved by our firm prior to filling.
Retaining wail and trench backfill material should not contain material larger
than 3 inches in greatest dimension.
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8, Fill Compaction: All structural fill should be compacted to a minimum degree
of compaction of 90 percent based upon ASTM D1557-12. Rll 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 a moisture content that will permit proper compaction 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. For low expansive
soils, the moisture content shouid be within 2 percent of optimum.
No uncontrolled fill soils should remain after completion of the site work. In
the event that temporary ramps or pads are constructed of uncontrolled fill
soils, the loose fill soils should be removed and/or recompacted prior to
completion of the grading operation.
9. Trench and Retaining Wail Backfiil: Utility trenches and retaining walls
should preferably be backfilled with on-site, low-expansive or imported, low-
expansive compacted fill; gravel is also a suitable backfill material but should
be used only if space constraints will not allow the use of compaction
equipment. Gravel can also be used as backfill around perforated subdrains
protected with geofabric. All backfill material should be placed in lift
thicknesses appropriate to the type of compaction equipment utilized and
compacted to a minimum degree of compaction of 90 percent by mechanical
means.
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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 groundwater accumulation and
migration.
Backfill soils placed behind retaining walls and/or crawl space retaining walls
should be installed as early as the retaining walls are capable of supporting
lateral loads. Backfill soils behind retaining walls should be low expansive,
with an Expansion Index equal to or lower than 50. All areas backfilled with
gravel should be capped with a minimum 12-inch-thlck layer of properly
compacted on-slte soils overlying Mirafi 140N filter fabric to reduce the
potential for fines loss into the gravel.
C. Design Parameters for Proposed Foundations
In order to support the proposed structures on conventional continuous concrete
foundations the following recommendations should be followed. Footings should
extend into medium dense to dense terrace soils or properly compacted fill soils to
a depth of 18 inches.
10. Footings: Footings for the new residential structures should bear on
undisturbed formatlonal materials or properly compacted fill soils. The
footings for the proposed structures should be founded at least 18 inches
below the lowest adjacent finished soil grade and have a minimum width of
, 12 inches. The footings should contain top and bottom reinforcement to
provide structural continuity and to permit spanning of local irregularities.
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Footings located adjacent to utility trenches should have their bearing
surfaces situated below an Imaginary 1,0:1.0 plane projected upward from
the bottom edge of the adjacent utility trench. Otherwise, the trenches
should be excavated farther from the footing locations.
11. Bearing Values: At the recommended depths, footings on native, medium
dense terrace soils or properly compacted fill soil may be designed for an
allowable soil bearing pressure of 2,&00 pounds per square foot (psf) for
combined dead and live loads and may be increased one-third If including
wind or seismic loads. The footings should have a minimum width of 12
Inches.
12. Footing Reinforcement: 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 near the top and two near
the bottom). A minimum clearance of 3 inches should be maintained
between steel reinforcement and the bottom or sides of the footing. Isolated
square footings should contain, as a minimum, a grid of three No. 4 steel
bars on 12-inch centers, both ways. 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 Civii/Structurai Engineer should review all reinforcing
schedules. The reinforcing minlmums recommended herein are not to be
construed as structural designs, but merely as minimum reinforcement to
reduce the potential for cracking and separations.
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13. Lateral Loads: Lateral load resistance for the structure 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 pounds per cubic foot (pcf) acting against the
foundations may be used in design provided the footings are poured neat
against the adjacent undisturbed formationai materials and/or properly
compacted fill 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.
14. Settlement: Settlements under building loads are expected to be within
tolerable limits for the proposed residences. For footings designed in
accordance with the recommendations presented in the preceding
paragraphs, we anticipate that total settlements should not exceed 1 inch
and that post-construction differential angular rotation should be less than
1/240.
D. Concrete Slab-on-arade Criteria
Slabs on-grade may only be used on new, properly compacted fiil or when bearing
on dense natural soils.
15. Minimum Floor Slab Reinforcement: Based on our experience, we have
found that, for various reasons, floor slabs occasionally crack. Therefore, we
recommend that ail siabs-on-grade contain at least a minimum amount of
reinforcing steel to reduce the separation of cracks, should they occur.
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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.
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.
16, Slab Moisture Protection and Vaoor 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
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thickness. These products are no longer considered adequate for moisture
protection and can actuaiiy deteriorate over time.
Speciaity vapor retarding products possess higher tensiie strength and are
more specificaiiy 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;
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.
16.1 Based on the above, we recommend that the vapor barrier consist of a
minimum 15-mii extruded poiyoiefin 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 perms (grains/square foot/hour
in 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
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membrane has also been shown to achieve a permeance 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.
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 curlingt
16.2 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.
16.3 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.
17. 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.
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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,
construction techniques, curing procedures, and normal shrinkage of
concrete), some cracking of slabs can be expected.
18. Exterior Slab Reinforcement: Exterior concrete slabs should be at least 4
inches thick. As a minimum for protection of on-slte 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 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
soli 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
innprovements.
Ota Residential Project Job No. 16-11073
Carlsbad, California Page 37
19. Exterior Slab Control Joints: For exterior slabs with the minimum shrinkage
reinforcement, controi joints shouid be piaced at spaces no farther than 12
feet apart or the width of the slab, whichever is iess, and also at re-entrant
corners. Control joints in exterior siabs shouid be sealed with eiastomeric
joint seaiant. The sealant should be inspected every 6 months and be
properly maintained. Concrete slab joints shouid be doweiled or continuous
steel reinforcement shouid be provided to help reduce any potential
differential movement.
20. Concrete Pavement: New concrete driveway and parking siabs shouid be at
least SVz inches thick and rest on properly prepared and compacted subgrade
soils. Subgrade soil for driveway and parking areas shouid be dense or, if
fill, be compacted to at least 95 percent of Maximum Dry Density. The
driveway and parking siabs may be provided with reinforcing consisting of
No. 4 bars spaced no farther than 15 inches apart in two perpendicular
directions if shrinkage joint spacing more than 12 feet is preferred. The
concrete shouid be at least 3,500 psi compressive strength, with control
joints no farther than 12 feet apart and also at re-entrant corners. Pavement
joints should be properly sealed with permanent joint seaiant, as required In
sections 201.3^6 through 201.3.8 of the Standard Specifications for Public
Work Construction, 2012 Edition.
Controi joints shouid be placed within 12 hours after concrete placement or
as soon as the concrete allows sawcutting without aggregate raveling. The
sawcuts shouid penetrate at least one-quarter the thickness of the slab.
Ota Residential Project Job No. 16-11073
Carlsbad, California Page 38
21. Permeable Driveway Pavers'. If permeable pavers are considered, it is our
opinion based on our site observations and laboratory testing, that the on-
site silty sand fill soils and underlying medium dense silty sand formational
soils are well-suited for the use of permeable pavers.
It is recommended that a minimum 6-inch-thick base layer of crushed
miscellaneous rock material, compacted to at least 95 percent relative
compaction, be placed below a 1-lnch-thick leveling sand layer under the
pavers. The subgrade soils supporting the base layer should also be
compacted to 95 percent relative compaction.
E. Slopes
It is our understanding that no permanent slopes are proposed at this time on the
ievei site. Should portions of the site be modified to include new slopes, our office
should be contacted for additional recommendations.
22. Temporary Slopes: Temporary slopes needed for retaining wall construction
and/or removal and recompactibn during site grading should be stable for a
maximum slope ratio of 1.0:1.0 (horizontal to vertical) to a maximum height
of 12 feet. If cut, vertically shoring will be required. No soil stockpiles,
improvements or other surcharges may exist or be placed within a horizontal
distance of 10 feet from any excavation.
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
Ota Residential Project Job No. 16-11073
Carlsbad, California Page 39
temporary construction slopes at a safe inclination appropriate to his
methods of operation.
If these recommendations are not feasible due to space constraints,
temporary shoring may be required for safety and to protect adjacent
property improvements. This office should be contacted for additional
recommendations If shoring or steep temporary slopes are required.
23. Cal-OSHA: Where not superseded by specific recommendations presented In
this report, trenches, excavations, and temporary slopes at the subject site
should be constructed In accordance with Title 8, Construction Safety Orders,
Issued by Cal-OSHA.
F. Retaining Wall Design Criteria
It is our understanding that basement walls are currently proposed. The following
retaining wail design criteria are provided based on the encountered soil conditions.
24. Static Design Parameters: 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 restrained
retaining walls with level backfill be designed for an equivalent fluid pressure
of 56 pcf for low expansive Import or on-slte soils. Wherever restrained walls
will be subjected to surcharge loads, they should also be designed for an
additional uniform lateral pressure equal to 0.47 times the anticipated
surcharge pressure.
Ota Residential Project Job No. 16-11073
Carlsbad, California Page 40
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.
25. Seismic Earth Pressures: If seismic loading is to be considered for retaining
walls more than 6 feet In height, they should be designed for seismic earth
pressures in addition to the normal static pressures. The soil seismic
increment is an equivalent fluid weight of 14 pcf. A Kh value of 0.18 may be
used is a computer program such as '^Retaining Wall Pro" or a similar
program Is used for wall design. The soil pressures described above may be
used for the design of shoring structures. Restrained retaining wall design
may waive the soil seismic increment.
26, Design Parameters - Unrestrained: The active earth pressure in the design
of any cantilever retaining walls utilizing on-slte or imported very low- to
low-expansive soils (El less than 50) as backfill should be based on an
Equivalent Fluid Weight of 38 pcf (level backfill only). In the event that an
unrestrained retaining wall is surcharged by sloping backfill, the design active
earth pressure should be based on the appropriate Equivalent Fluid Weight
presented in the following table.
Height of Slope/Height of Wall*
Slope Ratio 0.25 0.50 0.75 1.00(+)
2.0:1.0 42 4^ 50 52
*To determine design active earth pressures for ratios intermediate to those
presented, interpolate between the stated values.
Ota Residential Project Job IMo. 16-11073
Carlsbad, California Page 41
Backfill soils should consist of lo.w-expansive soils with El less than 50, and
should be placed from the heel of the foundation to the ground surface within
the wedge formed by a plane at 30° from vertical, and passing by the heel of
the foundation and the back face of the retaining wall,
27. Surcharge Loads: Any surcharge loads placed on the active wedge behind a
cantilever (unrestrained) wall should be included In the design by multiplying
the vertical load by a factor of 0.31. This factor converts the vertical load to
a horizontal load.
28. Wall Drainage: Proper subdralns and free-draining backwall material or
board drains (such as J-drain or Miradrain) should be installed behind ail
retaining wails (in addition to proper waterproofing) on the subject project
(see Rgure No. VI for Retaining Wall Backdrain and Waterproofing
Schematic). Geotechnlca! Exploration, Inc. will assume no liability for
damage to structures or Improvements that is attributable to poor drainage
and/or Improper waterproofing.
Architectural plans should clearly indicate that subdrains for any lower-level
walls be placed at an elevation at least 1 foot below the top of the outer face
of the footing, not on top of the footing. At least 0.5-percent gradient should
be provided to the subdrain.
The subdrain should be placed in an envelope of crushed rock gravel up to 1
inch in maximum diameter, and be wrapped with Mirafi 140N filter fabric or
equivalent. The subdrain may consist of Total Drain, Amerdrain, QuickDraIn
(rectangular section boards), or equivalent products. A sump pump may be
required if project elevations and discharge points do not allow for outlet via
Ota Residential Project Job No. 16-11073
Carlsbad, California Page 42
gravity flow. The coiiected water should be taken to an approved drainage
faciilty. Open head joint subdrain discharge is not considered acceptabie for
retaining walis. All subdrain systems should be provided with access risers
for periodic cieanout.
29. 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 wail
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.
G. Site Drainage Considerations
30. 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, ponding on finished building pad areas or
causing erosion on soil surfaces.
31. Surface Drainage: Adequate measures should be taken to properly finish-
grade the lot after the residential structures and other 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 into properly designed and approved
drainage facilities provided by the project civil engineer In the grading plans.
Roof gutters and downspouts should be installed on the residences, with the
runoff directed away from the foundations via closed drainage lines. Proper
Ota Residential Project Job No. 16-11073
Carlsbad, California Page 43
subsurface and surface drainage will help minimize the potential for waters to
seek the level of the bearing soils under the footings and floor slabs,
Failure to observe this recommendation could result in undermining and
possible differential settlement of the structures or other improvements or
cause other moisture-related problems. Currently, the 2013 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.
32. Planter Drainage: 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 residences 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 or anywhere on the site.
H. General Recommendations
33. Project Start Uo Notification: In order to reduce any work delays during site
development, this firm should be contacted at least 48 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
Ota Residential Project Job No. 16-11073
Carlsbad, California Page 44
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.).
34. Construction Best Management Practices (BMPs): Construction BMPs must
be implemented in accordance with the requirements of the controlling
jurisdiction. At the very least, sufficient BMPs must be Installed to prevent
silt, mud or other construction debris from being tracked into the adjacent
street(s) or storm water conveyance systems due to construction vehicies or
any other construction activity. The contractor is responsible for cleaning
any such debris that may be In the streets at the end of each work day or
after a storm event that causes breach in the Installed construction BMPs.
All stockpiles of uncompacted soil and/or building materials that are Intended
to be left unprotected for a period greater than 7 days are to be provided
with erosion and sediment controls. Such soil must be protected each day
when the probability of rain is 40% or greater. A concrete washout should
be provided on ail projects that propose the construction of any concrete
improvements that are to be poured in place. All erosion/sediment control
devices should be maintained in working order at all times. All slopes that
are created or disturbed by construction activity must be protected against
erosion and sediment transport at all times. The storage of all construction
materials and equipment must be protected against any potential, release of
pollutants into the environment.
Ota Residential Project job No. 16-11073
Carlsbad, California Page 45
XII. GRADING NOTES
Geotechnlcal Expforatiotir Inc. recommends that we be retained to verify the
actual soil conditions revealed during site pier installation to be as anticipated in
this "Report of Geotechnical Investigation..."^ for the project. In addition, the
compaction of any fiil soils placed during site work must be observed and tested by
the soii engineer. It is the responsibility of the general contractor to comply with
the requirements on the approved plans and the local building ordinances. All
retaining wali 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.
XIII. LIMITATIONS
Our conclusions and recommendations have been based on available data obtained
from our field investigation and laboratory analysis, as well as our experience with
similar soils, surficial materials and formational materials located in the Pacific
Beach area of the City of Carlsbad. Of necessity, we must assume a certain degree
of continuity between exploratory excavations and/or natural exposures. 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
Ota Residential Project Job No. 16-11073
Carlsbad, California Page 46
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.
As stated previously. 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 installation (if
needed), drain depth below interior floor or yard surfaces; pipe percent slope to the
outlet, etc.
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
structural plans. We should be retained to review the project plans once they are
available, to verify that our recommendations are adequately Incorporated In the
plans. Additional or revised recommendations may be necessary after our review.
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. 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
changing drainage patterns, which occur subsequent to issuance of this report and
the changes are made without our observations, testing, and approval.
Ota Residential Project
Carlsbad, California
Job No. 16-11073
Page 47
Once again, should any questions arise concerning this report, please feel free to
contact the undersigned. Reference to our Job No. 16-11073 will expedite a reply
to your Inquiries.
Respectfully submitted,
GEOTECHNICAL EXPLORATION, INC.
Donald C. Vaug
Project Coordinator
). Reed, President
C.E.G. 999/P.G. 3391
CERTIFIED
ENGINEERING
^GEOLOGIST
<5-
Jaime A. Cerros, P.E.
R.C.E. 34422/G.E. 2007
Senior Geotechnlcal Engineer
002007
REFERENCES
JOB NO. 16-11073
May 2016
Association of Engineering Geologists, 1973, Geology and Earthquake Hazards, Planners Guide to the
Seismic Safety Element, Southern California Section, Association of Engineering Geologists, Special
Publication, p. 44.
Berger & Schug, 1991, Probabilistic Evaluation of Seismic Hazard In the San DIego-TIJuana
Metropolitan Region, Environmental Perils, San Diego Region, San Diego Association of Geologists.
Blake, T., 2002, EQFault, a Computer Program for Deterministic Prediction and Estimation of Peak
Horizontal Acceleration from Digitized California Faults.
California Building Standards Commission (CBSC), 2013, California Building Code (CBC), Volumes 1
and 2.
California Coastal Commission, August 2015, Sea Level Rise Adopted Policy Guidance.
County of San Diego Office of Emergency Services, 2014, Muttl-Jurlsdictlonal Multi-hazard Mitigation
Plan Development in San Diego.
Crowell, J.C., 1962, Displacement along the San Andreas Fault, California; Geologic Society of America
Special Paper 71, 61 p.
Demere, T.A., 2003, Geology of San Diego County, California, BRCC San Diego Natural History
Museum.
Greene, H.G., 1979, Implication of Fault Patterns In the Inner California Continental Borderland
between San Pedro and San Diego, In "Earthquakes and Other Perils, San Diego Region," P.L. Abbott
and W.J. Elliott, editors.
Greensfelder, R.W., 1974, Maximum Credible Rock Acceleration from Earthquakes In California;
Callfomla Division of Mines and Geology, Map Sheet 23.
Hart, E.W., D.P. Smith, and R.B. Saul, 1979, Summary Report: Fault Evaluation Program, 1978 Area
(Peninsular Ranges-Saiton Trough Region), Calif. Division of Mines and Geology, OFR 79-10 SF, 10.
Hart, E.W. and W.A. Bryant, 2007; Fault-Rupture Hazard Zones In Callfomla, Alqulst-Priolo Earthquake
Fault Zoning Act with Index To Earthquake Fault Maps; Interim Revision; Callfomla Department of
Conservation Callfomla Geological Survey, Special Publication 42.
Hauksson, E. and L. Jones, 1988, The July 1988 Oceanslde (M|."=5.3) Earthquake Sequence in the
Continental Borderland, Southern California Bulletin of the Selsmologlcal Society of America, v. 78, p.
1885-1906.
Hlleman, J.A., C.R. Allen and J.M. Nordqulst, 1973, Selsmldty of the Southem Callfomla Region,
January 1, 1932 to December 31, 1972; Selsmologlcal Laboratory, Cal-Tech, Pasadena, Calif.
Joy, J.W., 1968, Tsunamis and Their Occurrence Along the San Diego County Coast, Report to the
Unified San Diego County Civil Defense and Disaster Organization.
REFERENCES/Page 2
Kennedy, M.P., S.H. Clarke, H.G. Greene, R.C. Jachens, V.E. Langenhelm, JJ. Moore and D.M; Burns,
1994, A digital (GIS) Geoiogicai/Geophysicai/Seismoiogicai Data Base for the San Diego 30'x60'
Quadrangle, California—A New Generation, Geological Society of America Abstracts with Programs, v.
26, p. 63.
Kennedy, M.P. and S.H. Qarke, 1997A, Analysis of Late Quaternary Faulting In San Diego Bay and
Hazard to the Coronado Bridge, Calif. Division of Mines and Geology Open-Ale Report 97-lOA.
Kennedy, M.P. and S.H. Clarke, 1997B, Age of Faulting in San Diego Bay in the Vicinity of the
Coronado Bridge, an addendum to Analysis of Late Quaternary Faulting In San Diego Bay and Hazard
to the Coronado Bridge, Calif. Division of Mines and Geology Open-Ale Report 97-lOB.
Kennedy, M.P. and S.H. Clarke, 2001, Late Quaternary Faulting in San Diego Bay and Hazard to the
Coronado Bridge, California Geology.
Kennedy, M.P. and G.W Moore, 1971, Stratigraphic relations of Upper Cretaceous and Eocene
Formations, San Diego coastal area, California: Amer. Assoc. Petroleum Geologists Bull., v. 55, p.
709-722.
Kennedy, M.P., S.S. Tan, R.H. Chapman, and G.W. Chase, 1975; Character and Recency of Faulting,
San Diego Metropolitan Area, California, Special Report 123, Calif. Division of Mines and Geology.
Kennedy, M.P. and SS. Tan, 2008, Geologic Map of the San Diego 30' x 60' Quadrangle, California;
California Geological Survey and the United States Geological Survey.
Kennedy, M.P. and E.E. VVelday, 1980, Character and Recency of Faulting Offshore, Metropolitan San
Diego California, Calif. Division of Mines and Geology Map Sheet 40, 1:50,000.
Kern, J. P., 1993, Earthquakes and Faults In San Diego, Pickle Press, San Diego, California.
Kern, J.P. and T.K. Rockwell, 1992, Chronology and Deformation of Quaternary Marine Shorelines, San
Diego County, California in Heath, E. and L. Lewis (editors). The Regressive Pleistocene Shoreline,
Coastal Southern California, pp. 1-8.
McEuen, R.B. and C.J. PInckney, 1972, Seismic Risk In San Diego; Transactions of the San Diego
Society of Natural History, v. 17, No. 4.
Murbach, M.L, 2000, The Rose Canyon Fault Zone: New Evidence for Hoiocene Earthquake Activity In
La Jolla; Master of Sdence Thesis; Geology Department, San Diego State University.
RIchter, C.G., 1958, Elementary Seismology, W.H. Freeman and Company, San Francisco, Calif.
Rockwell, T.K., 2010, The Rose Canyon Fault Zone In San Diego, Recent Advances in Geotechnical
Earthquake Engineering and Soil Dynamics and Symposium in Honor of Professor I.M. Idriss.
Rockwell, T.K., D.E. Mlllman, R.S. McElwaIn, and D.L Lamar, 1985, Study of Seismic Activity by
Trenching Along the Glen Ivy North Fault, Elsinore Fault Zone, Southern California: Lamar-MertAeld
Technical Report 85-1, U.S.G.S. Contract 14-08-0001-21376, 19 p.
Southern California Edison San Onofre Nuclear Generating Station Seismic Source Characterization
Research Project, 2012, Paleoseismic Assessment of the Late Hoiocene Rupture History of the Rose
Canyon Fault In San Diego.
REFERENCES/Page 3
Simons, R.S., 1977, Seismiclty of San Diego, 1934-1974, Selsmological Society of America Bulletin, v.
67, p. 809-826.
Tan, S.S., 1995, Landslide Hazards In Southern Part of San Diego Metropolitan Area, San Diego
County, Calif. Division of Mines and Geology Open-file Report 95-03.
Toppozada, T.R. and D.L. Parke, 1982, Areas Damaged by California Earthquakes, 1900-1949; Calif.
Division of Mines and Geology, Open-file Report 82-17, Sacramento, CA.
Trelman, J.A., 1993, The Rose Canyon Fault Zone, Southern California, Calif. Division Of Mines and
Geology Open-file Report 93-02, 45 pp, 3 plates.
URS Project No. 27653042.00500, 2010, San Diego County Multl-Jurisdictional Hazard Mitigation Plan
San Diego County, California.
U.S. Dept. of Agriculture, April 11, 1953, Stereo pair aerial photographs AXN-8M-81 & 82.
U.S.G.S. Earthquake Hazards Program, 2010, httD://earthQuake.usqs.aov/
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JOB NAME
Ota Residential Project
SITE LOCATION
4090 Garfleld Street, Carlsbad, OA
JOB NUMBER
16-11073
FIGURE NUMBER
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REVIEWED BY LDR/JAG
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DIMENSION & TYPE OF EXCAVATION
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DATE LOGGED
4-20-16
SURFACE ELEVATION
n/a
GROUNDWATER/SEEPAGE DEPTH
Not Encountered
LOGGED BY
DCV
I
FIELD DESCRIPTION
AND
CLASSIFICATION
OPTIMUM MOISTURE {%)
s"®
£
d
d
I 1 DESCRIPTION AND REMARKS
(Grain stzs, Densly, Moisture, Cckx)
<6
c5
cd if II ii
SAMPLE!(INC)SEH
-
SILTY SANDl Loose. Dry. Dark gray-brown.
-
OLD PARAUC DEPOSITS (Qop„)
1 -
SILTY SAND Medium dense. Moist. Brown. ~SM"
-
OLD PARAUC DEPOSITS (Qopj.,)
2-
-Bottom @ 3'
4-
I PERCHED WATER TABLE
K BULK BAG SAMPLE
[H IN-PLACE SAMPLE
n MODIFIED CALIFORNIA SAMPLE
[U NUCLEAR FIELD DENSITY TEST
^ STANDARD PENETRATION TEST
JOB NAME
Ota Residential Project
SITE LOCATION
4090 Garfield Street, Carlsbad, CA
JOB NUMBER
16-11073
FIGURE NUMBER
lllb
REVIEWEDBY LDR/JAC
Geotectinlcal
l Explorallaiv Inc.
LOGNa
HP-2
a
s
5
3>
<I
Source of Material
Description of Material
Test Method
HP-1 @ 2.0'
SILTY SAND (SM). Brown
ASTM D1557 Method A
TEST RESULTS
Maximum Dry Density
Optimum Water Content
132^ POP
8.5 %
ATTERBERG LIMITS
LL PL
Curves of 100% Saturation
for Specific Gravity Equal to;
20 25
WATER COtfTENT, %
Geotecfinical
Exploration, Inc.
MOISTURE-DENSITY RELATIONSHIP
Rgure Number iVa
Job Name: Ota Residential Project
Site Location: 4090 Garfield Street Carlsbad, CA
Job Number 16-11073
7,000
6,000
5,000
4,000
X
to
3,000
2,000
1,000
1,000 2,000 3,000 4,000
NORMAL PRESSURE, psf
5,000 6,000 7,000
Specimen Identification
HP-1 @ 1.0'
Classification
SILTY SAND (SM), Brown
MC%
-110 38
i 1 GeotechnlcalMP^krll Exploration, Inc.
DIRECT SHEAR TEST
Figure Number IVb
Job Name: Ota Residential Project
Site Location: 4090 Garfieid Street, Carlsbad, CA
Job Number 16-11073
m
Ota Residential Project
4090 Garfield Street
Carlsbad, CA.
EXCERPT FROM GEOLOGIC MAP OF THE OCEANSIDE 30' 'x 60' (^UAl
70
Compiled hy
Mehael P. l&nmdy ami Sang S. Tan
200J
Olglial Preparalian hvKfUy R, Anvan/', Rachel hf. Alvamland MichaelJ. ifalson'
t CJ t!eategitalSiifviy.D^rtmMoff^'ik^eif)vti
ONSHORE MAP SYMBOLS
Contact > Conlact between geologic units: dotted where concealed.
Fault - Solid where accurate!/ located; dashed where
approximately located; dotted where concealed. U - upthrown
block, D = downthrown block. Arrow 'and number Indicate
direction and angle of dip of fault plane.
Anticline • Solid where accurately located; dashed where
approximately located: doited where concealed. Arrow
Indicates direction of axial plunge.
Syndlne • Solid where accurately located; dotted where concealed.
Arrow Indicates direcb'on of axial plunge.
Landslide - Arrows indicate principal direction of movement.
Queried where existence Is questionable.
Strike and dip of beds
Inclined
Strike and dip of igneous joints
Inclined
Vertical
Strike and dip of metamorphic foliation
Inclined
DESCRIPTK
Qmb
Alluvial
(late H(
Marine
Qop6-7
Units 6-7 Old pai
1:00^2^4;
Units 2-4
MTsa;:
Very ol(
(middle
^ntia£
PROPOSED
STRUCTURE
Qop
SOUTH
10'± bgs»
♦bgs
(S>
CROSS SECTION
NORTH TO SOUTH
MJUiW ■ I'JC
PROPOSED
STRUCTURE
WEST
m
6-7
CROSS SECTION
WEST TO EAST
SCALt-Wft' -
LEGEND
Qop Qucarteffrary Old6-7 Porailc Deposits
CR'
Otai
409C
Carii
FIgu.
Job
i Ptnf ntmn lum* nrBtimmH hrvn art lOOOQC
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
(More than half of coarse fraction
is larger than No. 4 sieve size, but
smaller than 3")
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)
GW Well-graded gravels, gravel and sand mixtures, little
or no fines.
GP Poorly graded gravels, gravel and sand mixtures, litUe or
no fines.
GC Clay gravels, poorly graded gravel-sand-sllt 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 sllty 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
MLLiquid Limit Less than 50 Inorganic slits and very fine sands,
Uauid Limit Greater than 50
HIGHLY ORGANIC SOILS
rock flour, sandy silt
and clayey-slit sand mixtures with a slight plasticity
CL Inorganic clays of low to medium plasticity, gravelly
clays, sllty clays, clean clays.
OL Organic silts and organic sllty clays of low plasticity.
MH Inorganic silts, micaceous or diatomaceous fine sandy or
sllty soils, elastic silts.
OH Inorganic clays of high plasticity, fat clays.
OH Organic clays of medium to high plasticity.
PT Peat and other highly organic soils
(rev. 6/05)
APPENDIX B
MODIHEDMERCALU INTENSITY SCALE OF 1931
(Exceqited from the California Division of Conservation Division of Mines
and Geology DMG Note 32)
The first scale to reflect earthquake intensities was developed by deRossI of Italy, and Forel of Switzerland, in the tSSOs, and is known
as the Rossl-Forel Scale. This scale, with values from I to X, was used for ^out two decades. A need for a more refined scale
Increased with the advancement of the sdence of seismology, and In 1902, the Italian seismologist Mercalli devised a new scale on a I
to XII range. The Mercalli Scale was modified In 1931 by American seismologists Harry O. Wood and Frank Neumann to take Into
account modem structural features.
The Modified Mercalli Intensity Scale measures the intensity of an earthquake's effects in a given locality, and is perhaps much more
meaningful to the layman because It Is based on actual observations of earthquake effects at specific places. It should be noted that
because the damage used for assigning Intensities can t)e obtained only from direct firsthand reports, consideratrie time - weeks or
months - Is sometimes needed before an Intensity map can be assembled for a particular earthquake.
On the Modrfied Mercalli Intensity Scale, values range from I to XII. The most comnronly used adaptation covers the range of intensity
from the conditions of 'I - not felt except by very few, favorably situated,' to "Xli - dam^ total, lines of sight disturbed, otgects
thrown into the air.' While an earthquake has only one magnitude,,it can have many Intensities, which decrease with distance from the
epicenter.
It is difflcutt to compare magnitude and intensity because intensity is linked with the particular ground arnd structural conditions of a
given area, as well as distance from the earthquake epicenter, while magnitude depends on the energy released at the focus of the
earthquake.
1 Not felt except by a very few under especially favorable circumstances.
II Feit only tiy a few persons at rest, especially on upper floors of buildinKs. Delicately suspended objects may swing.
III Felt quite noticeably indoors, especially on upper floors of buildings, but many people do not recognize it as an earthquake.
Standing motor cars may rock slightly. Vibration like passing of truck. Duration estimated.
IV During the day felt Indoors by many, outdoors by few. At night some awakened. Dishes, windows, doors disturbed; walls make
cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.
V Felt by nearly everyone, many awakened. Some dishes, windows, etc, broken; a few instances of cracked piaster; unstable
objects overturned. Disturbances of trees, poles, and other tali objects sometimes noticed. Pendulum docks may stop.
VI Felt by all, many frightened and run outdoors. Some heavy furniture moved; a few instances of fallen plaster or damaged
chimneys. Damage slight.
VII Everybody runs outdoors. Damage negligible in building of good design and construction; slight to moderate in wellbuilt
ordinary structures; considerable In poorly built or bac9y designed structures; some chimneys broken. Noticed by persons driving
motorcars.
VIII Damage slight in spedally designed structures; considerable in ordinary substantial buildings, with partial collapse; great in
poorly built structures. Panel walls thrown out of frame structures. Fall of chimneys, factory stacks, columns, monuments, walls.
Heavy furniture overturned. Sand and mud ejected in small amounts. Changes In well water. Persons driving motor cars
disturbed.
IX Damage considerable In spedally designed structures; well-designed frame structures thrown out of plumb; great In substantial
buildings with partial collapse. Buildings shifted off foundations. Ground cracked conspicuously. Underground pipes broken.
X Some weii-built woodrai structures destroyed; rrrost masonry and frame structures destroyed with foundations; ground badly
cracked. Rails bent Landslides considerable from riverbanks and steep slopes. Shifted sand and mud. Water splashed (slopped)
over banks.
XI Few, If any, masonry structures remain standing. Bridges destroyed. Broad fissures in ground. Underground pipelines
completely out of service. Earth slumps and land slips In soft ground. Rails bent greatly.
XII Damage total. Practically all works of construction are damaged greatly or destroyed. Waves seen on ground surface. Lines of
sight and level are distorted. Objects thrown upward Into the air.
APPENDIX C
USGS DESIGN MAPS SUMMARY REPORT
m
^USGS Design Maps Summary Report
»Jser-Specified Input
Report Title 4090 Garfield Street, Carlsbad, CA
Thu May 12, 2016 14:21:18 UTC
Building Code Reference Document ASCE 7-10 Standard
(which utilizes USGS hazard data available in 2008)
Site Coordinates 33.1458°N, 117.3408°W
Site Soil Classification Site Class D - "Stiff Soil"
Risk Category I/II/III
.C)ceanatii?h "77 ij :. .
' vp.' n (o'u' . ''V; ■"
-ft.
'■ y :} ■;
Caflsiiad'^^Pj , ...-.Oh" „
:(i,; (, _ _
■ .\\
: 7>c' ::'f' ' /m-"
ft^^^Nlarcos fh)
7'-. .. hr ^Escpndi^o^'C
%J32-:yA:■-■ "■■47.7i5!7i:;ft
Ji'f
?;S4..i..,'7 r;
USGS-Provided Output
Ss =1.159 g
Sj^ = 0.445 g
^MS —
SmI ~
1.201 g
0.692 g
Sos= 0.801 g
Sp, = 0.461 g
For 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 return to the application and
select the "2009 NEHRP" building code reference document.
MCEr Response Spectrum
01 n.7a--
0.2S --
Design Response Spectrum
0.00 0.20 0.4.0 O.GO O.EO 1.00 1.20 1.40 l.SO l.£0 2.00
Period, T (sec)
Cl
raw
0.00 0.20 0.40 o.eo O.SO 1.00 1.20 1.40 l.SO l.SO 2.00
Period, T (sec)
For PGA^,, Tl, C^5, and values, please view the detailed report.