HomeMy WebLinkAboutPD 2021-0019; SPEER RESIDENCE; GEOTECHNICAL INVESTIGATION PROPOSED RESIDENTIAL REDEVELOPMENT; 2020-10-13GEOTECHINICAL INVESTIGATION
PROPOSED RESIDENTIAL REDEVELOPMENT
3342 DONNA DRIVE
CARLSBAD, CALIFORNIA
(A.P.N. 205-160-62)
October 13, 2020
R10E VEL
APR 07 2021
LAND DEVELOPMENT
ENGiNEERING
Prepared For:
Mr. Jeff Speer
16325 Alamo Canyon Road
Santa Clarita, California 91387
jeff@jmspeer.com
Prepared By:
SMS Geotechnical Solutions, Inc.
5931 Sea Lion Place, Suite 109
Carlsbad, California 92010
Project No. GI-20-09-136
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JffS GEOTECHNICAL SOLUTIONS, INC.
Consulting Geotechnical Engineers
5931 Sea Lion Place, Suite 109
Carlsbad, California 92010
Office: 760-602-7815
smsgeosol.incgmail.com
I Project No. GI-20-09-136
October 13, 2020
Mr. Jeff Speer
16325 Alamo Canyon Road ' Santa Clarita, California 91387
jeff@imspeer.com
Geotechnical Investigation, Proposed Residential Redevelopment
3342 Donna Drive, Carlsbad, California (A.P.N. 205-160-62)
Pursuant to your request, SMS Geotechnical Solutions, Inc. has completed the attached
Geotechnical Investigation report for the proposed residential redevelopment at the above-referenced
property.
The following report summarizes the results of our research and review of the pertinent geotechnical
reports and plans, subsurface explorations, sampling and laboratory testing, engineering analysis and
provides conclusions and recommendations for the proposed redevelopment, as understood. From
a geotechnical engineering standpoint, it is our opinion that the project property is suitable for the
planned residential redevelopment, provided our recommendations presented in this report are
incorporated into the project designs and implemented during the construction phase.
If you have any questions or need clarification, please do not hesitate to contact this office.
Reference to our Project No. GI-20-09-136 will help to expedite our response to your inquiries.
We appreciate this opportunity to be of service to you.
AM Geotechnical Solutions, Inc.
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TABLE OF CONTENTS
I. INTRODUCTION .....................................................1
H. SITE DESCRIPTION ..................................................1
III. PROPOSED DEVELOPMENT ..........................................2
IV. SITE INVESTIGATION ................................................2
V. REGIONAL GEOLOGY / GEOLOGIC SETTING ..........................2
VI. GEOTECHNICAL CONDITIONS .......................................3
Earth Materials ....................................................3
Groundwater and Surface Drainage ...................................4
Geologic Hazards and Slope Stability ...................................5
VII. SITE CLASSIFICATION FOR SEISMIC DESIGN .........................5
VIII. SEISMIC DESIGN VALUES ............................................7
IX. FAULTS/SEISMICITY .................................................7
X. FIELD AND LABORATORY TESTS AND TEST RESULTS ................9
XI. SITE CORROSION ASSESSMENT ......................................13
XII. STORMWATER BMPs ................................................14
XIII. CONCLUSIONS ......................................................15
XIV. RECOMMENDATIONS ................................................18
Grading and Earthwork .............................................19
Existing Eastern Retaining Wall Support ...............................25
Foundations and Floor Slabs .........................................27
Soil Design Parameters ..............................................32
Exterior Concrete Slabs / Flatworks ...................................33
Pavement Design ...................................................34
General Recommendations ...........................................38
XV. GEOTECHNICAL ENGINEER OF RECORD (GER) .......................40
XVI. LIMITATIONS .......................................................41
REFERENCES
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TABLE OF CONTENTS (continued)
FIGURES
RegionalIndex Map ..........................................................I
GeotechnicalMap ...........................................................2
Boring Logs ..............................................................3-5
GeologicMap ...............................................................6
GeologicCross-Section A-A .................................................... 7
GeologicCross-Section B-B' ...................................................8
RegionalFault Map ..........................................................9
GrainSize Analysis ..........................................................10
TypicalBMPSwale ..........................................................11
Typical Bio-Retention Detail ...................................................12
Typical Grading Detail .......................................................13
Typical Retaining Wall Back Drainage ..........................................14
Typical Cantilever Shoring Pressure Diagram ....................................15
Typical Retaining Wall Sheet Drain Detail .......................................16
Typical Isolation Joints and Re-Entrant Corner Reinforcement .....................17
Typical Permeable Interlocking Concrete Paver (PICP) Detail ......................18
Typical Pipes Through or Trench Adjacent to Foundations .........................19
APPENDIX
I ASCE 7 Hazards Report, Seismic
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GEOTECHNICAL INVESTIGATION
PROPOSED RESIDENTIAL REDEVELOPMENT
3342 DONNA DRIVE
CARLSBAD, CALIFORNIA
(A.P.N. 205-160-62)
INTRODUCTION
The property investigated in this work consists of an older existing developed residential lot located
east of the Interstate 5 Freeway and west of El Camino Real, within a coastal residential
neighborhood of the City of Carlsbad. A Regional Index Map showing the approximate site location
is attached as Figure 1. The approximate site coordinates are 33.1672°N latitude and -117.3270°W
longitude.
We understand that the existing building and associated structures and improvements will be
demolished and removed to allow for reconstruction of anew residence. Consequently, the purpose
of this investigation was to determine soil and geotechnical conditions at the property and to
ascertain their influence upon the planned residential redevelopment. Test borings, soil sampling,
laboratory testing and engineering analyses were among the activities conducted in connection with
this effort which resulted in redevelopment recommendations presented herein.
SITE DESCRIPTION
The subject property is located on the east side of Donna Drive at the above referenced address. A
Geotechnical Map, reproduced from a Topographic Map, prepared Teas Land Surveying, Inc.,
depicting existing conditions and new construction is included as Figure 2. As shown, the project
property presently supports an older dwelling with associated structures and site improvements.
Topographically, the existing building pad is situated roughly 12 feet above the Donna Drive street
grade. A graded slope, modified with terraced short keystone type segmental retaining walls,
ascends from the street grade to the level building pad grade above. A long concrete driveway with
maximum longitudinal profiles approaching 20% provides access from Donna Drive to the building
pad. A nearly 7-foot high maximum transition retaining wall marks the eastern level building pad
margin. Above the wall, a modified slope ascends to neighboring property(ies) roughly 10 feet
higher in elevation. The eastern pad margin transition retaining wall appears leaning and failing.
The existing level building pad at the property appears to be a cut-fill transition pad apparently
developed by placing soils generated from cutting the eastern portions of the property as fills on the
western portions. Engineering and construction records pertaining to the existing site development
are not available.
The project property also appears to receive upslope drainage from the higher eastern neighboring
I property(ies) above. Site drainage sheetfiows in a westerly direction toward Donna Drive.
Excessive scouring and erosion were not in evidence.
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3342 Donna Drive, Carlsbad, California (A.P.N. 205-160-62) Page 2
I II!. PROPOSED DEVELOPMENT
The proposed residential redevelopment was conceptually superimposed on the project Topographic
I Map, as presented on the attached Geotechnical Map, Figure 2. The existing building and associated
structures and improvements will be demolished and removed to allow for construction of a new
larger multi-level residence consisting of a street grade partial basement type garage level, an upper
I split-level pad first floor level, and a partial second floor level. An elevator will provide lift from
basement level to upper floor levels.
I Basement type masonry retaining walls will likely be utilized to achieve ground elevation transition
between the lower basement and upper first floor split-level pad grades. Accurate earthwork
quantities are not yet known, however, mostly cut excavations and export grading operations are
I anticipated to create the new split-level building pad grades. Temporary wall backcuts on the order
of 10 feet high are anticipated in connection with the planned basement wall construction.
Significant filling is not anticipated, nor are new large graded embankments planned in connection
I with the development.
Detailed construction plans are not yet available. However, planned new construction is anticipated
to consist of a combination of lower masonry block basement type retaining walls and upper floor
levels with a conventional wood-framed and exterior stucco structure, supported on shallow stiff
concrete footings with slab-on-grade floor foundations.
- IV. SITE INVESTIGATION
1 Subsurface conditions at the project property were chiefly determined by the excavation of three
exploratory test borings drilled with a truck-mounted, 8-inch diameter hollow stem auger rotary drill
rig. Exploratory test borings were advanced to depths ranging from 14.5 to 19.5 feet below the I existing ground surfaces (BGS).
Test borings were logged by our project geologist who also supervised in-situ testing and the I collection of representative soil samples at selected locations and intervals for subsequent laboratory
testing. Approximate locations of the exploratory borings are shown on the enclosed Geotechnical
I Map, Figure 2. Logs of the exploratory borings are attached as Figures 3, 4 and 5. Laboratory test
results and engineering properties of selected representative soil samples are summarized in
following sections.
V. REGIONAL GEOLOGY / GEOLOGIC SETTING
I The subject property is located in the Coastal Plains subdivision of the Peninsular Ranges
geomorphic province of San Diego. The coastal plain area is characterized by Pleistocene marine
terrace landforms. These surfaces are relatively flat erosional platforms that were shaped by wave
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Geotechnical Investigation, Proposed Residential Redevelopment October 13, 2020
3342 Donna Drive, Carlsbad, California (A.P.N. 205-160-62) Page 3
I action along the former coastlines. The step-like elevation of the marine terraces was caused by
changes in sea level throughout the Pleistocene and by seismic activity along the Rose Canyon Fault
Zone located west of the coastline. The Rose Canyon Fault Zone is one of many northwest trending,
I sub-parallel faults and fault zones that traverse the nearby vicinity. Several of these faults, including
the Rose Canyon Fault Zone, are considered active faults. Further discussion of faulting in regards
to the site is discussed in the Geologic Hazards section of this report.
A Geologic Map showing mapped units at and nearby the study location is attached as Figure 6
VI. GEOTECHNICAL CONDITIONS
The property is an older development with existing level building pad surfaces created by
conventional cut-fill grading efforts. Records of engineering observation and compaction testing
pertaining to the original level pad development and existing building construction are not available
for our review.
The project property is chiefly underlain by shallow fill/wall backfill and undifferentiated topsoil
over dense and competent Old Paralic Deposits. Geologic instability which could preclude the
planned new construction was not in evidence. Geologic Cross-Sections A-A' and B-B', illustrating
subsurface profiles based on our exploratory test borings, existing site topography and new
construction are attached to this report as Figures 7 and 8. The following are recognized:
A. Earth Materials
Very Old Paralic Deposits (Qvop): Quaternary age Very Old Paralic Deposits, typical of
local coastal areas of Carlsbad, underlie the property at surface grades in the eastern cut
portion to modest depths, on the order of 8.5 feet deep, in the western fill portions. As
exposed in our exploratory borings, the Very Old Paralic Deposits typically consist of red to
orange brown and light tan colored silty to clayey fine to medium grained sandstone that was
generally found in a weathered condition near the upper surface exposures becoming
increasingly dense to very tight with depth overall. Underlying Very Old Paralic Deposits
are suitably dense and competent deposits that will provide an adequate support for the
project new fills, structures and improvements.
Artificial Fill (Uaf)/Topsoil: Surficial artificial fill/wall backfill and undifferentiated
topsoil consisting of brown colored silty fine to medium sand mantles the project Very Old
Paralic Deposits. The upper surficial soil mantle occurs in wedge-shaped mass, thickening
from the daylight in the eastern pad portion of the property to as much as 8.5 feet near the
top of the western fill slope. Site existing artificial fill/wall backfill and undifferentiated
topsoils are chiefly in damp and loose conditions overall.
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1 3342 Donna Drive, Carlsbad, California (A.P.N. 205-160-62) Page 4
I Detailed descriptions of the underlying soil profile are presented in the attached Boring Logs,
Figures 3, 4 and 5. Project surficial soil mantle and upper surficial exposures of the Very
Old Paralic Deposits are loose and compressible, not suitable for foundation support. Below,
I the underlying Very Old Paralic Deposits are dense and competent units that can suitably
support the planned new foundations. Site soils range to medium expansive.
B. Groundwater and Surface Drainage
Subsurface groundwater seeps were encountered in our test Boring B-I at the depth of 10 feet
I BGS at the time of drilling, and raised to approximately 8 feet BUS at the completion of
drilling work and prior to backfihling. High moisture contents were also noted or recorded
in the test Borings B-2 and B-3 at depths ranging from 10 feet to 18 feet (BGS), however,
I visible free ground water was not in evidence. The noted conditions generally suggest
perched groundwater seepage within layers of sandy materials sandwiched between more
cemented formational units, developed from upslope irrigation and meteoric waters. Seepage
I quantities are expected to fluctuate based on seasonal and annual rainfall conditions.
Modest groundwater seepage is expected to develop at the time of remedial grading efforts
I and site excavations for the project basement garage level, depending on seasonal conditions.
Anticipated groundwater seepage into the site excavations will require proper removal and
disposal. A typical dewatering method consists of a gravel-filled sump hole at a low point I in the excavation that is provided with a submersible pump. However, any dewatering
technique suitable to the site conditions which allows for safe excavations, fill placement and
I construction work to progress may be considered. The use of a crushed rock blanket
underdrain installed at the bottom of the excavation may also become required, as
determined by the project geotechnical consultant based on the actual field exposures, and
I should be anticipated.
Water seeps can also impact stability of the temporary open excavations for the planned
basement level. All temporary excavations should be laid back at safe gradients with water I levels lowered below the bottom of excavations as specified in the following sections.
I All site and building basement type retaining walls should be provided with well-constructed
backdrain systems, and suitable waterproofing should be carefully completed. A
waterproofing specialist maybe consulted for this purposes. Typically, perimeter basement
I wall designs may additionally include a bentonite waterproofing layer with absorbency
quality to disallow any potential surface water infiltration and cumulation behind the walls,
and mitigate any subterranean moisture concerns. Special watertight type concrete (hycrete
or similar) is also recommended.
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Geotechnical Investigation, Proposed Residential Redevelopment October 13, 2020
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Like all developed properties with a subterranean basement level, the proper control of
surface and subsurface drainage is an important factor in the continued stability of the new
development. Ponding of surface drainage should not be allowed and over-watering of site
landscaping should be avoided. All surface water should be collected and directed away into
a selected discharge facility without infiltrating into the foundation bearing soils and
basement wall backfill zone.
I C. Geologic Hazards and Slope Stability
I Geologic hazards are not presently indicated at the project property. The existing terraced
graded fill slope in the front of the property will be partially removed as part of new
basement level construction with the remaining slope recommended for reconstruction as
I part of new building pad development. The rear modest cut slope is a modified embankment
that is currently supported at the toe by a nearly 7-foot high CMU retaining wail that appears
leaning and failing. This wall is recommended for further evaluation by the project structural
I engineer based on the soil design parameters given in the following sections, and
stabilized/supported, repaired or reconstructed as necessary and appropriate. Utilizing
shoring piles and a new shotcrete wall constructed for in-place support of the existing wall,
I in our opinion, may be considered the most feasible support method from ease of a
construction and economic standpoint. Specific recommendations are provided in the
following sections.
New significant grading is not planned in connection with the proposed new redevelopment
and all temporary excavation slopes are recommended for 1:1 maximum gradients. Slope
stability will not be a factor in the project redevelopment provided our recommendations are
incorporated into the project designs and implemented during the construction phase, where
appropriate and as applicable.
The most significant geologic hazards at the property will be those associated with ground
shaking in the event of a major seismic event. Liquefaction or related ground rupture failures
are not anticipated.
VU. SITE CLASSIFICATION FOR SEISMIC DESIGN
Site soils are classified based on the upper 100 feet maximum of site subsoil profiles. In the absence
of sufficient or specific site data, appropriate soil properties are permitted to be estimated by the
project geotechnical consultant based on known geotechnical conditions, and Site Class D is
typically used as a "default," unless otherwise noted. Site Classes A and B shall not be assigned to
a site, if there is more than 10 feet of soil (or fill) between the top of the underlying rock surface and
bottom of the foundation.
Geotechnical Investigation, Proposed Residential Redevelopment October 13, 2020
3342 Donna Drive, Carlsbad, California (A.P.N. 205-160-62) Page 6
Site Classes A and B are most commonly supported by shear wave velocity determination (Us, ft/s).
Site Class F, which may require a site response analysis, consists of liquefiable or collapsible soils
and highly sensitive clayey soil profiles. Site Classes C, D, and E soils may be classified using an
average field Standard Penetration Resistance (N) method for soil layers based on Section 20.4.2 of
ASCE 7-16. Where refusal is met for a rock layer (blow counts of 50 or greater for 6 inches or less
penetration), Ni is taken as 100 blows per foot. Site Classification is then established based on Table
20.3-1 of ASCE 7-16.
Requirements provided below are also applicable and should be incorporated in the project designs
where appropriate:
Site specific hazard analysis is required (see Section 11.4.8) in accordance with Chapter 21.2
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of ASCE 7-16 for structures on Site Class E sites with values of Ss greater than or equal to
1.0g, and structures on Site Class D and B sites with values of Si greater than or equal to
0.2g. However, the following three exceptions are permitted for Equivalent Lateral Force
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design (ELF) using conservative values of seismic design parameters in lieu of performing
a site specific ground motion analysis:
* Structures on Site Class B sites with Ss greater than or equal to 1.0, provided the site
coefficient Fa is taken as equal to that of Site Class C.
For structures on Site Class D sites with Si greater than or equal to 0.2, a long period
coefficient (Fv) of 1.7 may be utilized for calculation of Ts, provided that the value of
Seismic Response Coefficient (Cs) is determined by Equation (12.8-2) for values of the
fundamental period of the building (T) less than or equal to 1.5Ts, and taken as 1.5 times
the value computed in accordance with either Equation 12.8-3 for T greater than 1.5 Ts
and less than or equal to TL or Equation 12.8-4 for T greater than TL.
* Structures on Site Class B sites with 51 greater than or equal to 0.2, provided that T is
less than or equal to Is and the equivalent static force procedure is used for the design.
Where Site Class B is recommended, and a site specific measurement is not provided, the
site coefficients Fa, Fv, and FPGA shall be taken as unity (1.0) in accordance to Section
11.4.3 of ASCE 7-16.
Where Site Class D is selected as the "default" site class per Section 11.4.3 of ASCE 7-16,
the value of Fa shall not be less than 1.2. Where the simplified procedure of Section 12.4
is used, the value of Fa shall be determined in accordance with Section 12.14.8.1, and the
values of Fv, SMs and SMI need not to be determined.
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Our analysis of a representative subsoil profile developed from the available boring data indicated
an in-situ average Standard Penetration Resistance (N) of greater than 50, which may be presumed
to be representative of the upper 100 feet of the site subsoil profile. Based on the in-situ N of greater
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than 50, Site Class C (Very Dense Soil and Soft Rock) can be conservatively considered for the
project site subsoil profile.
I VIII. SEISMIC DESIGN VALUES
Seismic design values are presented in the attached Appendix in accordance with Chapter 16,
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Section 1613 of the 2019 California Building Code (CBC) and ASCE 7-16 Standard. Presented
values are generated using ASCE developed web interface that uses the United States Geological
Survey (USGS) web services and retrieves the seismic design data in a report format.
I IX.
Faults or significant shear zones are not indicated on the project site.
As with most areas in California, the San Diego region lies within a seismically active zone;
however, coastal areas of the county are characterized by low levels of seismic activity relative to
inland areas to the east. During a 40-year period (1934-1974), 37 earthquakes were recorded in San
Diego coastal areas by the California Institute of Technology. None of the recorded events exceeded
a Richter magnitude of 3.7, nor did any of the earthquakes generate more than modest ground
shaking, and did not produce significant damages. Most of the recorded events occurred along
various offshore faults which characteristically generate modest earthquakes.
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Historically, the most significant earthquake events which affected local areas originated along well
known, distant fault zones to the east and the Coronado Bank Fault to the west. Based upon
available seismic data, compiled from California Earthquake Catalogs, the most significant historical
event in the area of the study site occurred in 1800 at an estimated distance of 11.6 miles from the
project area. This event, which is thought to have occurred along an offshore fault, reached an
estimated magnitude of6.5 with an estimated bedrock acceleration value of 0. 107g at the project site.
The following list represents the most significant faults that commonly impact the region. Estimated
ground acceleration data compiled from Digitized California Faults (Computer Program EQFAULT
VERSION 3.00 updated) typically associated with each fault is also tabulated.
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TABLE 1
FAULT ZONE DISTANCE FROM SITE
MAXIMUM
PROBABLE
ACCELERATION
Rose Canyon Fault 5.9 miles 0. 170g
Newport-Inglewood Fault 6.0 miles 0.169g
Coronado Bank Fault 22.1 miles 0.136g
Elsinore-Julian Fault 23.2 miles 0•112a
I The locations of significant faults and earthquake events relative to the study site are depicted on a
Regional Fault Map attached to this report as Figure 9.
I Recently, the number of seismic events that affect the region appears to have somewhat heightened.
Nearly 40 earthquakes of magnitude 3.5 or higher have been recorded in coastal regions between
January 1984 and August 1986. Most of the earthquakes are thought to have been generated along
I offshore faults. For the most part, the recorded events remain as moderate shocks which typically
resulted in low levels of ground shaking to local areas. A notable exception to this pattern was
recorded on July 13, 1986. An earthquake of magnitude 5.3 shook county coastal areas with
I moderate to locally heavy ground shaking. This resulted in $700,000 in damages, one death, and
injuries to 30 people. The quake occurred along an offshore fault located nearly 30 miles southwest
of Oceanside.
A series of notable events shook county areas with a (maximum) magnitude 7.4 shock in the early
morning of June 28, 1992. These quakes originated along related segments of the San Andreas
I Fault, approximately 90 miles to the north. Locally high levels of ground shaking over an extended
period of time resulted; however, significant damages to local structures were not reported. The
increase in earthquake frequency in the region remains a subject of speculation among geologists;
I however, based upon empirical information and the recorded seismic history of county areas, the
1986 and 1992 events are thought to represent the highest levels of ground shaking that can be
expected at the study site as a result of seismic activity.
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I In recent years, the Rose Canyon Fault has received added attention from geologists. The fault is
a significant structural feature in metropolitan San Diego that includes a series of parallel breaks
trending southward from La Jolla Cove through San Diego Bay toward the Mexican border. Test
I trenching along the fault in Rose Canyon indicated that at that location the fault was last active 6,000
to 9,000 years ago. More recent work suggests that segments of the fault are younger having been
last active 1,000 -2,000 years ago. Consequently, the fault has been classified as active and included
I within an Alquist-Priolo Special Studies Zone established by the State of California. Furthermore,
a more recent study concluded that the coastal region of San Diego may experience earthquakes up
to magnitudes 7.3 and 7.4 (Sahakian et al, 2017). This study used the Newport-Inglewood/Rose
I Canyon Fault offshore. An earthquake of this magnitude has likely not occurred in the last 100,000
years, according to the data.
Fault zones tabulated in the preceding table are considered most likely to impact the region of the
study site during the lifetime of the project. The faults are periodically active and capable of
generating moderate to locally high levels of ground shaking at the site. Ground separation as a
result of seismic activity is not expected at the property.
X. FIELD AND LABORATORY TESTS AND TEST RESULTS
Earth deposits encountered in our exploratory test excavations were closely examined and
sampled for laboratory testing. Based upon our test borings, performing standard penetration
tests (SF1), and field exposures site soils have been grouped into the following soil types:
TABLE 2
SOil Description Type __]
Silty to clayey fine to medium sandstone (Very Old Paralic Deposits)
2 Silty fine to medium sand with local small to medium size cobbles (Artificial fill/Topsoil)
The following tests were conducted in support of this investigation:
1. Standard Penetration Tests: Standard penetration tests (SPT) were performed at the
time of borehole drilling in accordance with ASTM standard procedure D1586 using
rope and cathead. The procedure consisted of a standard 51 MM outside diameter
sampler without liner, 457 MM in length and 35 MM in inside diameter driven with a
140-pound hammer, dropped 30 inches using 5-foot long AW drill rods. The bore hole
was 200 MM (8 inches) in diameter and drill fluid or water was not necessary to aid
drilling. The test results are indicated at the corresponding locations on the attached
geotechnical exploratory Boring Logs (Figures 3 through 5).
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3342 Donna Drive, Carlsbad, California (A.P.N. 205-160-62) Page 10
I 2. Grain Size Analyses: Grain size analyses were performed on representative samples of
Soil Types 1 and 2. The test results are presented in Table 3 below, and graphically
illustrated on the attached Figure 10.
I TABLE 3
Sieve Size 3/4 I 'A" #4 I #10 1 #20 I #40 I #100 I #200
Location Soil Type Percent Passing
B-1@2.5' 1 100 99 93 1 76 T60 39 30
B-3@2' 2 100 99 99 1 97 92 75 38 28
1 3. Maximum Dry Density and Optimum Moisture Content: The maximum dry density
and optimum moisture content of Soil Types 1 and 2 were determined in accordance with
I ASTM D1557. The maximum dry densities and optimum moisture contents were
corrected for coarse fractions, where applicable. The test results are presented in Table
4.
TABLE 4
Location Soil
Type
Maximum Dry
Density (Tm-pci)
Optimum Moisture
Content (opt-%)
B-i @2.5' 1 133.0 8.3
B-34' 2 132.5 8.8
I 5. Unit Weight & Moisture Content Tests: In-place dry density and moisture content of
representative soil deposits beneath the site were determined from relatively undisturbed ring
samples using the Direct Measurement method (Method B) in accordance with ASTM
I D7263, and Water Content of Soil and Rock by Mass method in accordance with ASTM
D2216. The test results are presented in Table 5 and tabulated on the attached exploratory
Boring Logs at corresponding locations (Figures 3 through 5).
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TABLE 5
Sample
Location
Soil
Type
Field
Moisture
Content
(Ø%)
Fi Field ,Dry
Density
(Td-pct)
Max Dry
Density
(Tni-pcf)
In-Place
Relative
Compaction
Degree
of
Saturation
B-1 @2.5' 1 10 118.4 133.0 89 63
B-I @ 5' 1 10 - 133.0 SPT Sample -
B-1 @ 7.5' 1 10 114.9 133.0 86* 57
B-i ® lot 1 11 - 133.0 SPT Sample -
B-i @ 13' 1 11 - - SPT Sample -
B-2@5' 1 11 116.5 133.0 88 66
B-2 @ 10' 1 11 - - No Sample -
B-2@15' 1 13 119.3 133.0 90 84
B-2 @ 18' 1 10 - - SPT Sample -
B-3@2.5' 2 15 112.7 132.5 85 81
B-3 @ 7.5' 2 11 - 132.5 j SPT Sample
B-3@12.5' 1 15 119.0 133.0 89 99
B-3 @ 18' 1 19 - - SPT Sample -
* Sample may be somewhat disturbed.
Assumptions and Relationships:
In-place Relative Compaction = (Td - Tm) X100
Gs = 2.70
e= (Gs Tc— Td) - 1
S=( Gs) --e
6. Expansion Index Test: An expansion index (El) test was performed on representative
I samples of Soil Type 2 in accordance with the ASTM D4829. The result is presented in
Table 6.
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TABLE 6
Sample Molded Degree of Final Initial Dry Measured EL
Location Soil Saturation 0 Density El 50%
Type (%) (%) (%) (PCF) Saturation
B-3 @2' 2 7.9 50.5 14.2 118.5 1 1
B-3 @ 7' 2 10.9 54.2 18.8 109.2 63--T 67
(() = moisture content in percent.
E150 = Elmeas - (50 - Smeas) ((65 + Elmeas) - (220 - Smeas))
Expansion Index (El) Expansion Potential
0-20 Very Low
21-50 Low
51-90 Medium
91 -130 High
) 130 Very High
Direct Shear Test: One direct shear tests were performed on representative samples of
Soil Type 1 in accordance with ASTM D3080. The prepared specimens were pre-
consolidated with normal loads of 1, 2, and 3 kips per square foot and soaked overnight,
and sheared to failure in an undrained condition. The result is presented in Table 7.
TABLE 7
Sample Soil Sample Unit Angle of Apparent
Location Type Condition Weight bit. Fric. Cohesion
(rw-pcl) (-Deg.)
B-I @ 2.5' ] 1 E Remolded to 90% of Yen % opt [ 129.2 31 160
pH and Resistivity Test: pH and resistivity of a representative sample of Soil Type2
was determined using "Method for Estimating the Service Life of Steel Culverts," in
accordance with the California Test Method (CTM) 643. The result is tabulated in Table
8.
TABLE 8
I Sample Location I Soil Type I Minimum Resistivity (OHM-CM) I pH 1
B-3 @ 7' 2 I 3100 —T-7.6 1
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Sulfate Test: A sulfate test was performed on a representative sample of Soil Type 2 in
accordance with the California Test Method (CTM) 417. The result is presented in Table
9.
I TABLE 9
Sample
Location
I Soil Type Amount of Water Soluble Sulfate
In Soil (% by Weight)
B-3 @7' I 2 I 0.003
Chloride Test: A chloride test was performed on a representative sample of Soil Type
2 in accordance with the California Test Method (CTM) 422. The result is presented in
Table 10.
TABLE 10
Sample
Location Soil Type Amount of Water Soluble Chloride
In Soil (% by Weight)
11j@ 7 I 2 0.002
XI. SITE CORROSION ASSESSMENT
A site is considered to be corrosive to foundation elements, walls and drainage structures if one or
I more of the following conditions exist:
* Sulfate concentration is greater than or equal to 2000 ppm (0.2% by weight).
* Chloride concentration is greater than or equal to 500 ppm (0.05 % by weight).
* pH is less than 5.5.
For structural elements, the minimum resistivity of soil (or water) indicates the relative quantity of
soluble salts present in the soil (or water). In general, a minimum resistivity value for soil (or water)
less than 1000 ohm-cm indicates a potential for presence of high quantities of soluble salts and a
higher propensity for corrosion. Appropriate corrosion mitigation measures for corrosive conditions
should be selected depending on the service environment, amount of aggressive ion salts (chloride
or sulfate), pH levels and the desired service life of the structure.
Results of limited laboratory tests performed on selected representative of onsite soil samples
indicated that the minimum resistivity is greater than 1000 ohm-cm suggesting presence of low
quantities of soluble salts. Test results further indicated that pH levels are greater than 5.5, sulfate
concentrations are less than 2000 ppm and chloride concentration levels are less than 500 ppm.
Based on the results of the available limited corrosion analyses, the project site may be considered
non-corrosive.
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§X,9 Geotechnical Solutions, Inc. does not consult in the field of corrosion engineering and the
client, project architect or structural engineer should agree on the required level of corrosion
protection, or consult a corrosion engineer as warranted. However, based on the result of the tested
soil sample, the amount of water soluble sulfate (SO4) was found to be 0.003 percent by weight (30
ppm) which is considered negligible according to ACT 318 (SO Exposure Class with Not Applicable
severity). Water soluble chloride (CL) was found 0.002 percent by weight (20 ppm), and the site is
not located within 1000 feet of salt or brackish water. However, project construction includes a
subterranean garage level with concrete anticipated to be exposed to moisture due to the anticipated
subsurface groundwater seepage. Consequently, exposures to chloride should be considered as
severe (C2 Exposure Class with Severe severity). In our opinion and as a minimum, concrete
consisting of Portland cement Type II (ASTM Cl 50) with minimum 28 days compressive strength
(f') of 5000 psi and maximum 0.40 water-cement ratio is considered typically adequate for SO and
C2 Class exposures, unless otherwise specified, or noted on the project plans.
Table 11 below is appropriate based on the pH-Resistivity test results. Adequate protective
measures against corrosion should be considered for all buried metal pipes, connections, elbows,
conduits, improvements and structures, as necessary and appropriate. Buried metal pipes and
conduits should be wrapped and provided with appropriate protective cover, wherever applicable.
TABLE 11
Design Soil Type Gauge 16 14 12 10 8
2 Years to Perforation of Metal Culverts I49 63 87 112 136
XII. STORMWATER BMPs
I Stormwater BMP facilities, if required or considered in connection with the project development,
should be designed and constructed considering the site indicated geotechnical conditions. The
implemented management and water treatment control practices shall have no short and long term
I impacts on the new building pad and improvement surfaces, fills and backfihis, subterranean
structures, and onsite and nearby offsite underground utility trenches and improvements.
I In-situ testing for site infiltration feasibility was not a part of this study. However, based on the
available geotechnical data collected during this work, underlying soil profiles include sandy
deposits and project site may be characterized as Soil Hydrologic Group C/B classification (based
I on San Diego Hydrology Manual classification). However, subsurface groundwater in a form of
seepage (stabilized groundwater seepage level at 8 feet BGS in Boring B-i) occurs at the property
and the new construction includes a subterranean garage level, resulting in "No Infiltration"
I feasibility condition. Consequently, bio-retention/detention system consisting of a suitably sized
excavated basin(s) with specially engineered sand filter media and a perforated underdrain pipe(s)
surrounded with 3,4-inch crushed rocks, and provided with impervious liner on sides and bottom may
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I be considered. Captured water should be filtered and slowly discharge via a storm drain pipe to an
approved storm drain facility. Schematic concepts of a Typical BMP Swale and a Typical Bio-
Retention Detail are attached herein as Figures 11 and 12. Actual designs for the project BMP
I facilities should be provided by the responsible design consultant.
The bio-retentionldetention basin(s) should be properly sized for adequate storage capacity with
I filtrations completed not more than 72 hours and vegetation carefully managed to prevent creating
mosquito and other vector habitats. Additional and more specific recommendations should be
provided by the project geotechnical consultant at the final plans review phase, if necessary.
XIII. CONCLUSIONS
Based upon the foregoing investigation, redevelopment of the project site, substantially as proposed,
is feasible from a geotechnical viewpoint. The property is underlain by competent and stable Very
Old Paralic Deposits at or modest depths. Instability or adverse geologic conditions that could
preclude the proposed redevelopment are not indicated at the project site.
Geotechnical factors presented below are unique to the project site and will most influence the
planned reconstructions and associated costs:
Landslides, faults or significant shear zones are not present at the project site and are not
I considered a geotechnical factor in the planned site development. The study site is not
located near or within the Aiquist - Priolo earthquake fault zone established by the State of
California. The most significant long-term geologic hazard likely to impact the property is
periodic ground shaking associated with earthquake activity along nearby or distant active
faults. The project shall be designed and constructed in accordance with the seismic design
I
requirements of the 2019 California Building Code (CBC) and ASCE 7-16 Standard.
The existing level building surface at the property is a graded daylight transition pad that was
I apparently created by modest cut-fill grading efforts. Records of grading control engineering
observation and compaction testing services during the original fill placement and pad
constructions are not available for review.
I C. The project redevelopment will mostly consist of cut grading and export operations. Cut
excavations on the order of 10 feet will be needed to achieve lower basement level grades,
while upper pad grades are expected to be at or very near the existing ground levels.
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Relatively modest over-excavations and removals / recompaction of site existing loose and
compressible surficial fills/topsoils and upper weathered Very Old Paralic Deposits are
recommended throughout the project construction areas using remedial grading techniques.
Added removals may also be necessary in unexplored areas of the site presently obscured by
the existing buildings and improvements, as determined in the field. Underlying Very Old
Paralic deposits below the upper weathered exposures are suitably dense and will provide an
adequate support for the proposed new structures, improvements, and compacted fills.
Existing natural terrain at the property is considered geologically stable and new large graded
slopes are not planned. The existing terraced graded fill slope in the front of the property
will be partially removed as part of new basement excavations, with the remainder of the
slope recommended for removal and reconstruction at 2:1 maximum gradient as part of new
building pad development. The rear property margin failing CMIJ toe retaining wall at the
base of the eastern modest cut slope is also recommended for structural support utilizing
shoring piles and a new shotcrete wall. Slope stability will not be a factor in site
redevelopment provided our site development recommendations are followed.
Modest groundwater seepage should be expected at the time project basement garage level
excavations and remedial grading over-excavation efforts, requiring proper removals and
disposal. Any dewatering technique suitable to the site condition which allows for safe
excavations, fill placement and construction works to progress maybe considered. A typical
dewatering method consists of a gravel-filled sump hole at a low point in the excavation
provided with a submersible pump.
More significant groundwater seeps intruding into the site basement excavation/over-
excavations, if develops at the time of construction, may require the installation of an
underdrain blanket drainage system installed below the lower basement floor slab as
determined in the field by the project geotechnical consultant. The blanket undercirain, if
required, should consist of a layer of 3,4-inch crushed rocks provided with perforated pipe(s)
and a header collector pipe that gravity flows into a suitable outlet or stormwater discharge
facility. A sump well with a submersible pump may become necessary if gravity flow is not
available.
Basement wall backcut excavations on the order of the 10 feet are expected in connection
with the planned development. Temporary basement excavations are expected to mostly
expose existing fills within the upper sections and very dense and to very tight formational
units below. Water seeps are also anticipated. Consequently vertical excavations should be
avoided, and project temporary wall backcuts, excavation slopes and trenching developed
at safe 1:1 laid back gradients with groundwater seeps properly removed and/or lowered a
minimum of 12 inches below the base of excavations, as necessary and appropriate.
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I A basement garage level is planned in south central area of the site, adequately setback from
the adjacent perimeter property lines, and the need for vertical excavations requiring
temporary shoring support is currently not indicated. However, shoring support maybecome
I necessary based on actual site exposures as evaluated by the project geotechnical engineer
and may be anticipated.
l H. All site and building basement type retaining walls should be provided with well-constructed
backdrain systems, and suitable waterproofing should be carefully completed. A
waterproofing specialist may be consulted for these purposes. Special watertight type
I concrete (hycrete or similar) is also recommended.
Construction debris generated from the demolition of existing onsite building, walls,
I structures, old foundations, slabs, flatwork and improvements, along with all organic and
deleterious materials should be properly removed and disposed of from the site. Unusual
I
grading problems, including hard excavations are not expected.
Generated soils will be predominantly silty to clayey sandy materials which are considered
suitable for reuse as site new compacted fills and backfills. However, attempts should be
made to initially export more clayey, potentially expansive soils, and selectively stockpile
the generated sandy deposits for onsite reuse. Project fills and backfill materials and
compaction procedures should conform to the requirements of this report as specified in the
following sections.
Based on field observations and results of laboratory testing of selected samples, onsite soils
include silty to clayey soils ranging to medium expansive. Final bearing soil at the
completion of rough pad grading maybe anticipated to consist of clayey silty sand (SM/SC)
I
ranging to medium expansion potential (expansion index less than 90 based on ASTM
D4829 classification). Actual classification and expansion characteristic of the final bearing
soil mix can only be provided in the as-graded compaction report based on proper testing of
I
rough finish pad grade soils.
Potentially expansive bearing and subgrade soils will require special mitigation design per
I Section 1808.6 of California Building Code (CBC). Typical mitigation designs consist of
moisture conditioning/presaturation of bearing soils and the use deeper grade beam
foundations, and thicker slab-on-grade with heavier reinforcement, or the use of post-
tensioned slab foundations. Remedial grading and foundation/slab recommendations
provided in the following sections are intended to alleviate potential adverse impacts of
onsite expansive soils. Other mitigation method(s) such as capping the building pad within
at least the upper 4 feet of rough finish grades with good quality very low to non-expansive
(expansion index less that 20) sandy granular import soils are also available and may be
considered depending on acceptable levels of future building and improvement performance
and economic feasibility.
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I
M. Adequate site surface and stormwater drainage control is a critical factor in performance of
the future building and graded surfaces. Drainage control facilities should be designed and
installed for proper control and disposal of surface and stormwater as shown on the approved
I plans. Over-watering of site vegetation may also create perched water and the creation of
excessively moist areas at finished surfaces and should be avoided.
Like all developed properties with a subterranean basement level, the proper collection and
disposal of potential subsurface moisture and perched water source is the most significant
geotechnical factor in overall future basement and building performance. Ponding of surface
drainage should not be allowed and over-watering of site landscaping should be avoided. All
surface water should be collected and directed away into a selected discharge facility without
infiltrating into the foundation bearing soils and basement wall backfill zone. Offsite
drainage from uphill properties should not be allowed to impact the property.
N. Site excavations, grading, earthwork and construction should not impact the adjacent onsite
structures and improvements, and offsite properties, provided our site development
recommendations are followed. Adequate excavation setbacks should be observed and
temporary excavation slopes, wall backcuts and trenching completed as specified in the
following sections. Added field recommendations, however may also be necessary and
should be given by the project geotechnical consultant including protection measures for the
adjacent properties, structures and improvements and should be anticipated.
0. Post construction settlements, after completion of remedial grading work as specified, are
expected to be within the acceptable tolerances for planned new building and are anticipated
to be less than approximately 1-inch occurring below the heaviest loaded footing(s). The
magnitude of post construction differential settlements, as expressed in terms of angular
distortion, is not anticipated to exceed '/2-inch in a distance between similarly loaded adjacent
structural elements, or a maximum distance of 20 feet.
P. Liquefaction, seismically induced settlements, and soil collapse will not be a factor in the
I planned redevelopment of the project property provided ourremedial grading and foundation
recommendations are followed.
I xiv. RECOMMENDATIONS
I
The following recommendations are provided based on the site indicated geotechnical conditions,
economic feasibility and ease of construction. Other mitigation techniques and foundation support
system may also be available. However, any other alterative considered should be reviewed and
I
approved by the project geotechnical consultant. Added or modified recommendations may also be
necessary and should be provided by the project geotechnical consultant at the final plan review
phase.
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A. Grading and Earthwork
All excavations, grading, earthwork, fill/backfill materials and processing, placement and
compaction procedures should be completed in accordance with Chapter 18 (Soils and
Foundations) and Appendix "J" (Grading) of the 2019 California Building Code (CBC), the
Standard Specifications for Public Works Construction, City of Carlsbad grading
Ordinances, the requirements of the governing agencies and following sections, wherever
appropriate and as applicable
Existing Underground Utilities and Buried Structures: All existing underground
waterlines, sewer lines, pipes, storm drains, utilities, tanks, structures and improvements
at or nearby the project site should be thoroughly potholed, identified and marked prior
to the initiation of the actual grading and earthwork. Specific geotechnical engineering
recommendations may be required based on the actual field locations and invert
elevations, backfill conditions and proposed grades in the event of a grading conflict.
Utility lines may need to be temporarily redirected, if necessary, prior to earthwork
operations and reinstalled upon completion of earthwork operations. Alternatively,
permanent relocations may be appropriate as shown on the approved plans.
Abandoned irrigation lines, pipes and conduits should be properly removed, capped or
sealed off to prevent any potential for future water infiltrations into the foundation
bearing and subgrade soils. Voids created by the removals of the abandoned
underground pipes, tanks and structures should be properly backfihled with compacted
fills in accordance with the requirements of this report.
Clearing and Grubbing: Remove all existing surface and subsurface structures, I concrete slabs, buried foundations, tanks, vaults, pipes, improvements, vegetation, roots,
stumps, and all other unsuitable materials and deleterious matter from all areas proposed
for new fills, embankments, improvements, and structures plus a minimum of 10 I horizontal feet outside the perimeter, where possible and as approved in the field.
All debris generated from the site demolition works, clearing, trash, deleterious matter
and unsuitable materials should also be properly removed and disposed of from the site.
Trash, vegetation and construction debris shall not be allowed to occur or contaminate
new site fills and backfills.
The prepared ground should be observed and approved by the project geotechnical
consultant or his designated field representative prior to grading and earthwork.
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Removals and Over-Excavations: All existing surficial fills/topsoils and weathered
Very Old Paralic Deposits in the areas planned for the new building envelop, fills,
embankments, structures and improvements plus a minimum of 10 horizontal feet
outside the perimeter, where possible and as directed in the field, should be removed
(over-excavated) to the depth of the underlying dense and competent formational units,
as approved in the field rocks and placed back as properly compacted fills. The project
is mostly a cut grading and export operations, however, added remedial grading depths
are expected to range from minimum 3 feet to approximately 6 feet below rough finish
grades (RFG), and up to 9 feet below existing ground surfaces (BGS), where appropriate
and as applicable. Actual depths should be established in the field by the project
geotechnical engineer at the time of remedial grading operations. Deeper removals and
over-excavations may also be required as directed in the field and should be anticipated.
Bottom of all removals should also be additionally prepared, ripped and recompacted to
a minimum depth of 6 inches as a part of initial fill lift placement. Preparation of bottom
of removals and over-excavations shall construct neat, level surfaces which are
adequately benched, keyed-in and heeled back into the natural hillside exposing
competent formational rocks as approved in the field. All ground steeper than 5:1
receiving fills/backfills should be properly benched and keyed as directed in the field.
Conceptual remedial grading and site development recommendations are schematically
illustrated on the attached Typical Grading Detail, Figure 13.
Undercutting and Cut-Fill Daylight Transitions: Ground transition from excavated
cut to compacted fills should not be permitted underneath the proposed structures or
improvements. Cut-fill transition pads will require special treatment. For this purpose,
the cut portion of the building pad should be undercut to a minimum depth of 4 feet
below the rough finish pad grades (RFG), or 24 inches below the bottom of deepest
footing(s) whichever is more, and reconstruction to final design grades with compacted
fills. In the lower basement type wall foundations and site driveway, parking and on-
grade slabs/improvement transition areas, a minimum 12 inches undercut below the
bottom of footings or rough finish pavement subgrade is considered adequate, unless
otherwise noted or directed in the field. Undercutting and cut-fill transition mitigation
should be carried out in substantial accordance with the enclosed Typical Grading Detail,
Figure 13.
Excavation Characteristics: In general, site formational rocks are anticipated to be
excavated with relatively light to moderate efforts with medium to large construction
equipments. Based on our exploratory excavations, very hard cemented beds or
concretions requiring special excavation techniques are currently not indicated.
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Groundwater, Dew ateriug and Basement/ Subterranean Blanket Drain: Subsurface
groundwater seepage was encountered in our exploratory boring B- 1, and high moisture
contents were apparent in the test Borings B-2 and B-3. Consequently, perched
groundwater seepage is expected to develop in the site basement excavation and over-
excavations during the remedial grading work. Intruding groundwater seeps should be
properly removed with appropriate dewatering method(s) suitable to site conditions, in
order to create neat and stable work areas, and allow construction to proceed.
Groundwater should be lowered a minimum of 12 inches below the bottom of site
excavations/over-excavations. Typical dewatering methods consist of a gravel-filled
sump hole at a low point in the excavation provided with a submersible pump.
Dewatering discharge location(s) and onto public stormwater drainage facility(ies) should
be pre-approved by the governing agencies.
Significant water seeps and free water conditions in the excavation/over-excavation may
result in a need for providing an underdrain blanket drainage system below the basement
floor. A sump well and submersible pump may also become necessary, if a gravity
outflow is not available. A blanket underdrain, if it becomes necessary under the
basement floor slab, may consist of a suitable composite system available from drainage
product manufactures, or may consist of a 12-inch thick layer of 3,4-crushed rocks with
a perforated pipe(s) all covered with a soil separation fabric (Mirafi 140N or equal)
incorporated into the designs. Blanket drain systems should outlet at suitable location(s),
or pumped if necessary. More specific recommendations should be given at the time of
basement excavation based on actual field conditions. Slab construction and clean sand
underlaid with a moisture barrier/vapor retardant will remain the same as specified in the
following sections. Final subterranean blanket drain type(s) and construction method
should be reviewed and approved by the project architect and structural consultants.
Basement Wall Waterproofing: Adequate basement water proofing and the use of
special watertight type concrete (hycrete or similar) are recommended. Perimeter
basement wall designs should also include a bentonite waterproofing layer with
absorbency quality to disallow any potential surface water infiltrations and moisture
cumulations behind the walls, and mitigate any subterranean moisture concerns.
Wall Backcut and Temporary Excavation Slopes: Temporary excavation and backcut
slopes on the order of 10 feet high maximum are anticipated in connection with the
project development. In general, project excavations, trenching and construction slopes
are mostly expected to expose loose surficial soils within the upper sections and dense
formational units in the lower sections, with intruding groundwater seeps. Project
temporary wall backcuts, excavation slopes and trenching should be developed at 1:1
maximum laid back gradients with groundwater seeps properly removed and/or lowered
a minimum of 12 inches below the bottom of excavations/over-excavations, as necessary
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I and appropriate. The new fills and backfihls should be properly keyed-in and benched
into the temporary excavation slope as the fihllbackfill placement progresses. Temporary
excavation slope development is schematically shown on the enclosed Typical Grading
I Detail, Figure 13.
Undermining and/or potential damages to existing building, site improvements,
I structures, underground utilities, public right-of-ways and adjacent properties shall be
avoided by providing adequate excavation setbacks as necessary and appropriate. Based
on current plans, project basement garage level is planned in south central areas of the
I site, adequately setback from the adjacent perimeter property lines. Approximate Top
of Temporary Backcut Slope is shown on the attached Geotechnical Map, Figure 2.
Consequently, the need for vertical temporary excavations requiring shoring support is
I currently not indicated. However, shoring support may become necessary based on
actual site exposures as evaluated by the project geotechnical engineer and may be
anticipated.
Site excavations, temporary slopes, trenching and wall backcuts will require periodic
geotechnical observation during the construction. Additional and/or modified
recommendations including revised slope gradients, setbacks and temporary
shoring/french shield support should be given at that time as necessary and if it becomes
appropriate. The project contractor shall also obtain appropriate permits, as needed, and
conform to the Calosha and local governing agencies requirements for trenching/open
excavations and safety of the workmen during construction. Excavation permits shall
also be obtained from the adjacent property owner(s) or public agencies, if appropriate
and as applicable.
9. Soil Properties, Fill and Backfill Materials: Earth materials generated from site
excavations and over-excavations chiefly consist of locally wet silty to clayey sandy
materials (SM-SC). Generated soils are considered suitable for reuse as site new fills and
backfills provided they are adequately prepared, properly processed and moisture-
conditioned to the satisfaction of the project geotechnical consultant. Onsite soils,
however, include potentially expansive clay-bearing deposits, and attempts should be
made to first dispose of these deposits as part of project export operations, and selectively
stockpile the generated sandy deposits for onsite reuse. Potentially expansive silty to
clayey soils will have detrimental effects on the planned structures and improvements,
if appropriate mitigation measures are not incorporated into the project designs and
construction. Plastic silty to clayey soils are also not suitable for wall and trench
backfihls and better quality sandy soils should be considered for this purpose.
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I As an alternative, site potentially expansive soils may be removed and building pad
capped with good quality sandy granular (SM/SW) import soils. Capping the building
pad and site improvement areas with sandy granular soils will allow the use of more
I conventional foundations/slab design and improve pavement structural sections. Specific
recommendations for capping the building pad with sandy granular soils can be provided
upon request.
Site new fills and backfills shall be clean deposits free oftrash, debris, organic matter and
deleterious materials, as approved in the field by the project geotechnical consultant. Wet
silty to clayey earth materials also requires added aerating, processing and moisture
conditioning efforts for manufacturing a uniform mixture suitable for reuse as new fills
and backfills. Placing the well-manufactured fills in thin lifts with adequate compactive
efforts using suitable heavy construction equipments should also be expected for
achieving the specified compaction levels.
Fill/Backfill Soil Spreading and Compaction: Uniform bearing soil conditions should
be constructed at the site by the project grading operations. In the building areas, there
should be at least 24 inches of compacted fills under the deepest footing(s). In the
basement wall foundations and planned site improvement areas, there should be at least
12 inches of compacted fills below bottom of footing or rough finish subgrade, unless
otherwise approved.
New fills and backfills should be adequately processed, thoroughly mixed, moisture
conditioned to slightly (2% - 3%) above the optimum moisture levels, or as directed in
the field, placed in thin (8 inches maximum) uniform horizontal lifts and mechanically
compacted with heavy construction equipments. All fills and backfills should be
compacted to a minimum of 90% of the corresponding laboratory maximum dry density
per ASTM D-1 557, unless otherwise specified. Fills and backfills placed in site areas
subject to subsurface groundwater intrusion or potential saturation/inundations should
be compacted to minimum 95% compaction levels. The upper 12 inches of subgrade
soils under the asphalt pavement base layer should also be compacted to minimum 95%
compaction levels
Graded Slopes: New graded cut or fill slopes are not planned. However, the existing
terraced graded fill slopes, where it occurs beyond the basement garage level and new
driveway excavations, should be entirely removed and reconstructed as a part of the
project remedial grading operations. The reconstructed fill slope should be programmed
for safe 2:1 maximum gradients.
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For this purpose, a toe keyway should be developed at the base of the regraded slope and
additional level benches created into the competent natural hillside, reconstructing the
slope by placing compacted fills upon developed surfaces and achieving final design
grades. The new fill slope toe keyway should be a minimum of 15 feet wide and
maintain a minimum depth of 18 inches below the adjacent toe elevation developed into
competent formational rock throughout. The bottom of toe keyway should be heeled
back a minimum of 5% into the natural hillside and observed and approved by the project
geotechnical engineer or his designated field representative. The new fill slope should
be compacted to minimum 90% compaction levels (per ASTM D1557) out to the slope
face, unless otherwise specified (minimum 95% in potential saturation or inundation
areas). Over-building and cutting back to the compacted core, or backrolling at a
maximum 4-foot vertical increments and "track-walking" with heavy construction
equipments at the completion of grading is recommended for site new fill slope
construction. Geotechnical engineering observations and testing will be necessary to
confirm adequate compaction levels within the fill slope face.
A backbench/toe keyway heel sub-drainage system consisting of a minimum 4-inch
diameter Sch. 40 (or SDR 35) perforated pipe surrounded with a minimum of2 cubic feet
per foot of length of 3/4-inch crushed rocks all wrapped in filter materials (Mirafi 140N)
may also be necessary for the project new fill slope construction, as determined in the
field by the project geotechnical engineer, and should be anticipated.
12. Retaining Back Drainage System: A well developed back drainage system should be
constructed behind all project site and building basement type retaining walls. The wall
back drainage system should consist of a minimum 4-inch diameter, Schedule 40 (SDR
35) perforated pipe surrounded with a minimum of l'/2 cubic feet per foot.of%-crushed
rocks (12 inches wide by 18 inches deep) installed at the depths of the wall foundation
level and wrapped in filter fabric (Mirafi 140N). If Caltrans Class 2 permeable aggregate
is used in lieu of the crushed rocks, the filter fabric can be deleted. The wall back drain
should be installed at suitable elevations to allow for adequate fall via a non-perforated
solid pipe (Schedule 40 or SDR 35) to an approved outlet. Protect pipe outlets as
appropriate. All wall back drain pipes and outlets should be shown on the final as-build
plans.
A wall back drain system schematic is depicted on the enclosed Typical Retaining Wall
Drainage, Figure 14. Provide appropriate waterproofing where applicable as indicated
on the project pertinent construction plans.
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13. Surface Drainage and Erosion Control: A critical element to the continued stability
of graded building pads and developments with subterranean construction is an adequate
surface drainage control. Surface and storm water should not be allowed to impact the
developed construction and improvement surfaces. This can most effectively be achieved
by the installation of appropriate drainage and stormwater control facilities. Building pad
surface run-off should be collected and directed away from the planned buildings and
improvements to a selected location in a controlled manner. Area drains should be
installed. Surface water should be directed away from the basement retaining walls.
Concentrated surface run-off or overflow of water from the top of slopes should be
avoided, and site flooding due to natural sheetfiow or offsite uphill drainage prevented.
Drainage berms should be constructed at the top slopes as shown on the approved
drawings.
The finished slope faces should be planted soon after completion of grading.
Unprotected slope faces will be subject to severe erosion and shall not be allowed. Over-
watering of the slope faces should also not be allowed. Only the amount of water to
sustain vegetation should be provided.
Temporary erosion control facilities and silt fences should be installed during the
construction phase periods as indicated and specified on the approved project plans.
B. Existing Eastern Retaining Wall Support
I The rear property (east site margin) failing CMU wall is recommended for structural support
utilizing shoring piles constructed in front of the existing wall. Other repair and total
replacement alternatives are also available. However, temporary shoring will still be
I necessary if wall replacement is considered. The choice of alternative will depend on
economic feasibility and ease of constructions. Any other alternative, if selected, should be
reviewed and approved by the project geotechnical consultant and corresponding revised I recommendations provided, as appropriate.
Permanent shoring support schematic is conceptually depicted on the enclosed Typical I Grading Detail, Figure 13. The existing wall including its spanability capacity, however,
should be evaluated by the project structural consultant based on soils parameters provided
I .in this report, and determine its suitability for using permanent shoring/soldier piles support.
Specific permanent shoring designs should be provided by the project structural
I engineer/design-build contractor. Typical shoring support consists of a series of drilled
reinforced cast-in-place (CIP) concrete soldier piles adequately extended below the specified
remedial grading/undercut depths and reinforced with a steel cage or "W-shape" steel beam.
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I Permanent shoring pile support system typically incorporates a reinforced shotcrete wall
spanning between the soldier beams. The following goetechnical design parameters specific
to the recommended shoring system are appropriate:
1. Design point of fixity should be considered at 4 feet (undercut depth) below the rough
finish pad grade (RFG), unless otherwise noted.
1 2. Shoring wall CIP piles should be at least 24 inches in diameter and have a minimum of
7 feet embedment below the point of fixity (11 feet below RFG). Maximum pile spacing
I should not exceed 6 feet, nor be less than 2 times the pile diameter, center to center,
unless otherwise noted or specified.
I 3. A net allowable pile capacity of 300 psf per pile surface area per unit length maybe used
for pile designs based on skin friction, for the portion embedded into competent
undisturbed formational rocks below the point of fixity (the weight of the pile may be
I assumed to be supported by end bearing). The net allowable pile capacity increase
should be limited to a maximum of depth of 20 times pile diameter.
l 4. A design shoring apparent passive resistance of 400 psf'ft, acting on 2 times pile
diameter maximum, may be considered for the portion of the pile below the point of
fixity embedded into the underlying undisturbed formational rocks. The indicated design
I passive resistance may be increased for each additional foot of depth to a maximum of
3500 pounds per square feet.
5. Design maximum shoring pile deflection should be limited to 1-inch, unless otherwise
noted or approved.
1 6. Permanent cantilever shoring/walls should be designed for an apparent lateral static soil
pressure of 41 H psf. The passive pressure for the existing retaining wall should also be
considered as an active pressure on the new supporting permanent shoring/walls. I Additional seismic and surcharge loading due to nearby foundations, embankments and
improvements shall be considered by the project design consultant as necessary and
appropriate. A pressure diagram is included herein as Figure 15 for aiding as a general I design guide.
Shotcrete wall incorporated into the shoring pile system should be designed based on the I minimum soils design parameter given in this report.
I 7. A design apparent coefficient of friction for pile design (portion embedded below point
of fixity) = 0.37.
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I 8. All pile shafts should be thoroughly cleaned to the satisfaction of the project geotechnical
engineer using a "clean out bucket." Free fall of concrete in the drill shafts shall not be
allowed. Concrete can be placed only upon the approval of the geotechnical engineer
I using the "tremie" techniques.
Groundwater seeps into the drilled shaft, requiring dewatering techniques should be
I anticipated. Displacing the intruding groundwater by pouring the concrete from bottom
up in conjunction with dewatering is recommended. Providing steel casing in the upper
portion can also not be ruled out.
All drilled shafts shall be plumb. Drill shafts which are more than 1% of their height
maximum out-of-plumb shall be rejected and required to be re-drilled.
Use a minimum 3500 psi (f'c) concrete for CIP concrete shoring pile designs, unless
otherwise noted.
A set of shoring plans should be provided to us for review. Additional recommendations
will be given at that time if necessary.
All shoring pile shafts should be observed and approved by the project geotechnical
consultant prior to the placement of steel cage/beam and pouring the concrete.
Retaining shoring/shotcrete wall back drainage should consist of sheet drains (AWD
Sitedrain sheet drain or similar) as schematically shown on the attached Typical
Retaining Wall Sheet Drain Detail, Figure 15 (also see Figure 13).
C. Foundations and Floor Slabs
The proposed building may be supported on shallow stiff concrete grade beam type footings
and slab-on-grade floor or post-tensioned structural slab-on-ground foundations consistent
the anticipated clayey silty sand (SM/SC) bearing and subgrade soils ranging to medium
expansion potential (expansion index less than 90 based on ASTM D4829 classification).
Other foundation support system like mat foundations or utilizing more conventional
foundation used in conjunction with capping the building pad with at least 4 feet of very low
to non-expansive sandy granular soils are also available and can be provided upon request.
The choice of appropriate option will depend on acceptable levels of future building and
improvement performance, economic feasibility and ease of constructions.
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Recommendations for shallow stiff concrete grade beam type footings and slab-on-grade
floor foundations, and post-tensioned foundations are provided in the following sections.
Added or modified recommendations may also be necessary and should be given at the time
of foundation plan review phase. All foundations and floor slab recommendations should
be further confirmed and / or revised as necessary at the completion of rough grading based
on the actual expansion characteristics of the foundation bearing and subgrade soils.
1. Stiff Grade Beam Type Foundations: The following recommendations and
geotechnical mitigation are consistent with the anticipated clayey silty sand (SM/SC)
ranging to medium expansive potential:
* Perimeter and interior continuous strip foundations should be sized at least 18 inches
wide and 24 inches deep. Spread pad footings, if any, should be at least 30 inches
square and 18 inches deep and structurally interconnected to the continuous strip
footings with grade beams. Interconnecting grade beams should be a minimum of
12 inches wide by 18 inches deep. Footing depths are measured from the lowest
adjacent ground surface, not including the sand/gravel layer beneath floor slabs.
Exterior continuous footings should enclose the entire building perimeter. Flagpole
footings also need to be tied together if the footing depth is less than 4 feet below
rough finish grade.
Continuous interior and exterior foundations should be reinforced with a minimum
of four #5 reinforcing bars. Place 245 bars 3 inches above the bottom of the footing
and 245 bars 3 inches below the top of the footing. Interconnecting grade beams
should also be reinforced with 244 bars top and bottom and #3 ties at 30 inches on
center maximum. Reinforcement details for spread pad footings should be provided
by the project architect/structural engineer.
* All interior slabs should be a minimum 5 inches in thickness, reinforced with #4
reinforcing bars spaced 16 inches on center each way, placed mid-height in the slab.
Slabs should be underlain by 4 inches of clean sand (SE 30 or greater) which is
provided with a well performing moisture barrier/vapor retardant (minimum 15-mil
Stego) placed mid-height in the sand. Alternatively, a 4-inch thick base of
compacted Y2-inch clean aggregate provided with the vapor barrier (minimum 15-mil
Stego) in direct contact with (beneath) the concrete may also be considered provided
a concrete mix which can address bleeding, shrinkage and curling is used
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Also provide re-entrant corner reinforcement for all interior slabs. Re-entrant corners
will depend on slab geometry and/or interior column locations. The enclosed Typical
Isolation Joint and Re-Entrant Corner Reinforcement, Figure 17 may be used as a
general guideline.
Provide "soficut" contraction/control joints consisting of sawcuts spaced 10 feet on
centers each way for all interior slabs. Cut as soon as the slab will support the weight
of the saw and operate without disturbing the final finish which is normally within
2 hours after final finish at each control joint location or 150 psi to 800 psi. The
sawcuts should be minimum 1-inch in depth but should not exceed 1%-inches deep
maximum. Anti-ravel skid plates should be used and replaced with each blade to
avoid spalling and raveling. Avoid wheeled equipment across cuts for at least 24
hours.
The subgrade and foundation bearing soils should not be allowed to dry prior to
pouring the concrete or additional ground preparations and moisture re-conditioning
will be necessary as directed in the field. The required moisture content of the
bearing soils is approximately 2% to 3% over the optimum moisture content to the
depth of 24 inches below subgrade. Attempts should be made to maintain as-graded
moisture contents in order to preclude the need for additional subgrade and bearing
soils preparation, moisture reconditioning/pre-saturation work.
* Foundation trenches and slab subgrade soils should be inspected and tested for proper
moisture and specified compaction levels and approved by the project geotechnical
consultant prior to the placement of steel reinforcement or concrete pour.
* Trenching efforts typically result in disturbed bottom of foundation trenches, thereby
I requiring in-place recompaction using hand-held equipments (whacker) prior to steel
placement and concrete pour, unless otherwise approved.
2. Post-Tensioned Structural Slab Foundations: Post-tensioned slab foundations
consistent with the anticipated clayey silty sand (SMISC) foundation bearing and
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subgrade soils ranging to medium expansive potential may also be considered. Remedial
grading and foundation bearing/slab subgrade soil preparation will remain the same and
should be completed as specified. Post-tensioned slab foundation design should be
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are appropriate:
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I
* The foundation design should consider slabs with stiffening beams (ribbed
foundation). In the case ofuniform slab thickness foundation, the design shall satisfy
all requirements ofthe design procedure for ribbed foundation. The fully conformant
I ribbed foundation may be then converted to an equivalent uniform thickness
foundation. In this case, however, perimeter edge beams shall be required as
specified here.
I * All designs shall conform to the latest addition of the California Building Code
(CBC), specifications of the Post-Tensioning Institute (PTI), local standards, and the
specifications given in this report.
* Foundation bearing soils should be inspected and tested as necessary prior to
I trenching and actual construction by the project geotechnical engineer. The required
foundation bearing soils in-place densities, and specified moisture contents should
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be confirmed prior to the foundation pour.
* A well-performing vaporbarrier/moisture retardant (minimum 15-mil Stego) should
be placed mid-height in 4 inches of good quality well-graded clean sand over the
I finish subgrade soils. Alternatively, a 4-inch thick base of '/2 inch clean aggregate
and a vapor barrier (minimum 15-mil Stego) in direct contact with concrete, and a
concrete mix design, which will address bleeding, shrinkage and curling (ACI
I 302.2R-06) may also be considered per California Green Building Standards Code
(4.505.2).
I * At the completion of ground and subgrade preparation as specified, and approval of
the project geotechnical engineer, the post-tensioned or structural slab-on-ground
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foundations should be constructed as detailed on the structural/construction drawings.
* Based on our experience on similar projects, available laboratory testing and analysis
I of the test results, the following soil design parameters are appropriate:
- Design predominant clay mineral type ..................Montmorillonite.
I - Design percent of clay in soil ..................................60%.
- Design effective plasticity index .................................45.
- Design depth to constant soil suction ...........................7 feet.
I - Design constant soil suction ..................................Pf 3.6.
- Design velocity of moisture flow ......................0.70 inch/month.
- Thornwaite Moisture Index for edge lift ............................0.
I - Thornwaite Moisture Index for center lift ......................... -20.
- Design edge moisture variation distance for center lift (em) ........8.5 feet.
- Design edge moisture variation distance for edge lift (em) .........4.4 feet.
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- Design differential swell occurring at the perimeter of slab
for center lift condition (Ym) ............................0.66 inches.
- Design differential swell occurring at the perimeter of slab
for edge lift condition (Ym) .............................1.70 inches.
- Design soil subgrade modulus (k) ............................100 pci.
- Design net allowable bearing pressure for post-tensioned or
structural slab-on-ground foundations ........................1000 psf.
Notes:
Internal net allowable foundation pressure within the perimeter of the post-tensioned
slab foundations should be considered 1000 psf for a minimum embedment depth of
12 inches, and may be increased 20% for each additional foot of embedment only or
a portion thereof to a maximum of 3500 psf. The net allowable foundation pressure
provided herein for post-tensioned foundations applies to dead plus live loads and
may be increased by one-third for wind and seismic loading.
- Provide a minimum 15inches wide by 18 inches deep perimeter edge beam.
I Perimeter edge beam embedment depth is measured from the lowest adjacent ground
surface, not including the sand/gravel beneath the slabs. Perimeter edge beam should
also enclose the entire building circumference and reinforced with at least 245 I continuous bar near the bottom. Provide adequate interior stiffening ribs as
necessary.
I - Post-tension slabs should be a minimum of 5'/2 inches thick. We recommend
considering pre-tensioning in order to preclude early concrete shrinkage cracking.
3. Foundation Daylight Setback: Adequate setbacks or deepened foundations shall be
required for all foundations and improvements constructed on or near the top of
descending slopes to maintain a minimum horizontal distance to daylight or adjacent
slope face. There should be a minimum of 7 feet or ½ of the slope height (need not to
exceed 40 feet maximum) whichever is more, horizontal setback from the bottom outside
edge of the footing to daylight, unless otherwise specified or approved. Site
improvements should also be provided with the thickened edge to satisfy this
requirement. A minimum of 10 feet or ½ of the slope height, whichever is more,
horizontal setback to daylight should be maintained for more sensitive structures and
improvements (including swimming pool) which cannot tolerate movements.
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4. Geotechnical Foundation Trench Observation: Foundation trenches and slab
subgrade soils should be observed and tested for proper moisture and specified
compaction levels and approved by the project geotechnical consultant prior to the
placement of steel reinforcement or concrete pour.
D. Soil Design Parameters
The following soil design parameters are based upon tested representative samples of onsite
earth deposits and our experience with similar earth materials in the vicinity of the project
site:
Design soil unit weight = 129 pcf.
Design angle of internal friction of soil = 31 degrees.
Design active soil pressure for retaining structures = 41 pcf (EFP), level backfill,
cantilever, unrestrained walls.
Design active soil pressure for retaining structures = 65 pcf (EFP), 2:1 sloping backfill,
cantilever, unrestrained walls.
Design at-rest soil pressure for retaining structures = 61 pcf (EFP), non-yielding,
restrained walls.
Design added hydrostatic pressure for retaining structures acting below the apparent
groundwater level (8 feet BUS) = 62 pcf (EFP).
Design soil passive resistance for retaining structures = 400 pcf (EFP), level ground
surface on the toe side (soil mass on the toe side extends a minimum of 10 feet or 3 times
the height of the surface generating passive resistance).
Design coefficient of friction for concrete on soils = 0.37.
Net allowable foundation pressure for onsite compacted fills = 2000 psf.
Allowable lateral bearing pressure (all structures except retaining walls) for on-site
compacted fill = 200 psf'fi.
Notes:
* An additional seismic force due to seismic increments of earth pressure should also be
considered in the project designs, as appropriate and where applicable. A seismic lateral
inverted triangular earth pressure of 21 pcf (EFP), with the resultant force acting at 0.6H
(H is the retained height) above the base of the wall should be considered. Alternatively,
seismic loading based on Mononobe-Okake (M-O) coefficients may be considered for
seismic force due to seismic increments of earth pressure. The following relationships
and design values are appropriate:
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TABLE 12
Total Seismic Lateral I KA Conditifillon I-- Pressure I Ko KAE I_KoE I_(I
Unrestrained PPA + PAE tPAE=9'8KhTW 0.32 - 0.16 0.48 129
Restrained POE--PO + POE IPoE=KhTH2 - 0.48 0.16 - 0.64 129
* Use a minimum safety factor of 1.5 for wall over-turning and sliding stability. However,
because large movements must take place before maximum passive resistance can be
developed, a minimum safety factor of 2 may be considered for sliding stability
particularly where sensitive structures and improvements are planned near or on top of
retaining walls.
* When combining passive pressure and frictional resistance, the passive component
I should be reduced by one-third. The upper 6 inches of ground surfaces should not be
included in the design for passive soil resistance, unless otherwise noted or specified.
I * The net allowable foundation pressure provided herein was determined based on
minimum 12 inches wide by 12 inches deep footing and may be increased by 20% for
each additional foot of depth only to a maximum of 3500 psf. The net allowable
I foundation pressure provided herein also applies to dead plus live loads and may be
increased by one-third for wind and seismic loading.
* The lateral bearing earth pressures maybe increased by the amount of designated value
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for each additional foot of depth to a maximum 1500 pounds per square foot.
E. Exterior Concrete Slabs / Flatwork
I I. All exterior slabs (walkways, patios) supported on potentially expansive subgrade soils
should be a minimum of 4 inches in thickness, reinforced with #3 bars at 15 inches on
centers in both directions placed mid-height in the slab. Subgrade soils underneath the
I exterior slabs should be moisture conditioned and compacted to minimum 90%
compaction levels at the time of fine grading and before placing the slab reinforcement.
I In order to enhance performance of exterior slabs and fiatwork supported on expansive
and moisture sensitive subgrade soils, a minimum 8 inches wide by 8 inches deep
thickened edge reinforced with a minimum of 143 continuous bar near the bottom I should be considered along the slab perimeter. Tying the slab panels to adjacent curbs,
where they occur, with #3 bars at 15 inches on centers, may also be considered.
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2. Reinforcements lying on subgrade will be ineffective and shortly corrode due to lack of
adequate concrete cover. Reinforcing bars should be correctly placed extending through
the construction joints tying the slab panels. In construction practices where the
reinforcements are discontinued or cut at the construction joints, slab panels should be
tied together with minimum 18 inches long #3 dowels at 15 inches on centers placed
mid-height in the slab (9 inches on either side of the joint).
Provide "tool joint" or "softcut" contraction/control joints spaced 10 feet on center (not
to exceed 12 feet maximum) each way. The larger dimension of any panel shall not
exceed 125% of the smaller dimension. Tool or cut as soon as slab will support weight,
Ond can be operated without disturbing the final finish which is normally within two
hours after final finish at each control joint location or 150 psi to 800 psi. Tool or
softcuts should be a minimum of 34-inch but should not exceed 1-inch deep maximum.
In case of softcut joints, anti-ravel skid plates should be used and replaced with each
blade to avoid spalling and raveling. Avoid wheeled equipment across cuts for at least
24 hours.
Joints shall intersect free-edges at a 90° angle and shall extend straight for a minimum
of 1'/2 feet from the edge. The minimum angle between any two intersecting joints shall
be 80°. Align joints of adjacent panels. Also, align joints in attached curbs with joints
in slab panels. Provide adequate curing using approved methods (curing compound
maximum coverage rate = 200 sq. ft/gal.).
All exterior slab designs should be confirmed in the final as-graded compaction report.
Subgrade soils should be tested for proper moisture and specified compaction levels and
approved by the project geotechnical consultant prior to the placement of concrete.
F. Pavement Design
1. Asphalt Concrete Paving (HMA): Specific HMA pavement designs can best be
provided at the completion of rough grading based on R-value testing of the actual finish
subgrade soils. However, a minimum section of 4 inches HMA (AC) over 6 inches of
Class 2 aggregate base (AB), or the minimum structural section required by City of
Carlsbad, whichever is more, should be considered for initial cost estimating purposes.
Final pavement sections should be confirmed and/or revised by actual R-value testing of
finish subgrade soils and design TI, and approved by the City of Carlsbad. The following
should also be considered in the construction of the project asphalt pavement surfaces:
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1 * In the areas where the longitudinal grades exceed 10%, 0.3-inch of asphalt concrete
(HMA) should be added to the design thickness for each 1% increase in grade or
portion thereof. PCC paving is recommended for longitudinal grades over 12%.
I * Maximum lift for asphalt concrete (HMA) shall not exceed 3 inches. The 4-inch
asphalt concrete layer should consist of 2.5 inches of a binder/base course (Y4-inch
I aggregate) and 1.5 inches of finish top course ('A-inch aggregate) topcoat, placed in
accordance with the applicable local and regional codes and standards.
I * The Class 2 aggregate or recycled base (AB) shall meet or exceed the requirements
set forth in the current California Standard Specification (Caltrans Section 26-1.02).
Base materials should be compacted to a minimum 95% of the corresponding
I maximum dry density (ASTM D1557). Remedial subgrade grading consisting of
removal and recompaction of unsuitable soils shall be required for the project paving
and driveway improvements per the requirements of this report. Subgrade soils
I beneath the asphalt paving surfaces should also be compacted to a minimum 95% of
the corresponding maximum dry density within the upper 12 inches. Base materials
and upper 12 inches of subgrade soils should be tested for proper moisture and
I minimum 95% compaction levels and approved by the project geotechnical
consultant prior to the placement of the base or asphalt layers.
I 2. PCC Pavings: Residential PCC pavings on potentially expansive subgrade soils should
be a minimum 5.5 inches in thickness, reinforced with #3 reinforcing bars at 15 inches
on center each way placed at mid-height in the slab. Subgrade soils beneath the FCC
I pavings should also be moisture reconditioned and recompacted to minimum 90%
compaction levels at the time of fine grading and before placing the slab reinforcement.
In the areas where longitudinal grades exceed 15%, also provide a minimum 8 inches
wide by 8 inches deep reinforced (minimum 143 continuous bar near the bottom)
pavement anchors constructed perpendicular to the pavement longitudinal profile into the
approved subgrade at each 15-foot interval maximum. The pavement anchors should be
poured monolithically with the concrete paving surfaces.
I Reinforcing bars should be correctly placed extending through the construction (cold)
joints tying the slab panels. In construction practices where the reinforcements are
I discontinued or cut at the construction joints, slab panels should be tied together with
minimum 18-inch long (9 inches on either side of the joint) similar size dowels, placed
at the same spacing as the slab reinforcement.
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' Provide "tool joint" or "soficut" contraction/control joints spaced 10 feet on center (not
to exceed 15 feet maximum) each way. The larger dimension of any panel shall not
exceed 125% of the smaller dimension. Tool or cut as soon as the slab will support the
I weight and can be operated without disturbing the final finish which is normally within
2 hours after final finish at each control joint location or 150 psi to 800 psi. Tool or
softcuts should be a minimum of 1-inch in depth but should not exceed 1¼-inches deep
I maximum. In case of soficut joints, anti-ravel skid plates should be used and replaced
with each blade to avoid spalling and ravelings. Avoid wheeled equipment across cuts
for at least 24 hours.
I Joints shall intersect free edges at a 90° angle and shall extend straight for a minimum
of 1½ feet from the edge. The minimum angle between any two intersecting joints shall
I be 80°. Align joints of adjacent panels. Also, align joints in attached curbs with joints
in slab panels. Provide adequate curing using approved method (curing compound
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maximum coverage rate = 200 sq. ft./gal.).
3. Permeable Interlocking Concrete Payers (PICP): Permeable Interlocking Concrete
Payers (PICP), if considered as a part of the project stormwater quality treatment BMPs
I should consist of a self-contained system disallowing saturation of adjacent moisture
sensitive foundation bearing soils, wall backfihls and site improvement subgrade. In general,
PICP pavements should maintain a minimum clear distance of 5 feet from the building I foundations with finish subgrade sloped away at a minimum 2% onto a 12 inches wide
collector trench along the low edge provided with a 4-inch diameter (Sch. 40 or SDR 35)
underdrain pipe surrounded with 'A-inch crushed rocks, as conceptually shown in the I enclosed Typical Permeable Interlocking Concrete Paver (PICP) Detail, Figure 18. In case
of subterranean basements and wall backfills, and nearby fill embankments and a minimum
10 feet clear setback should be considered, unless otherwise approved. The perforated I underdrain pipe should discharge collected water into an appropriate storm drainage facility
Perimeter cut off walls and curb restraints should be provided, and bottom and sides of the
I system lined with an impervious liner, as shown.
PICP pavements closer than 5 feet to building foundation (or 10 feet from adjacent retaining
I walls or top of slope) may also be allowed provided additional mitigation measures such as
construction of a minimum 8 inches wide, 3-sack concrete cutoff wall extending a minimum
of 24 inches below bottom of the foundation or adjacent improvement, and installing a fill
slope heel subdrain is provided. Specific recommendations should be provided by the I project geotechnical engineer at the final plan review phase.
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Geotechnical Investigation, Proposed Residential Redevelopment October 13, 2020
3342 Donna Drive, Carlsbad, California (A.P.N. 205-160-62) Page 37
I
PICP pavement structural section should consist of 31/8-inch, PICP over a minimum of 2.0
inches of ASTM No. 8 bedding course/choke stone over a minimum 8 inches of ASTM No.
57 stone base course over a minimum of 12 inches of 95% compacted subgrade (per ASTM
I
D1557), unless otherwise noted or specified. Bedding course/choke stone and base course
stone should also be well compacted, consolidated and interlocked (avoid crushing the
underdrain pipes) with heavy construction equipments. ASTM No. 8, No.9 or No. 89 should
I
be used for joint materials depending on the joint size and per manufacturer
recommendations.
I Gradation requirements for ASTM No. 57, No. 8, No. 89 and No. 9 are as follows:
TABLE 13
Sieve
Size
Percent Passing
No. 57 No.8 No. 89 No.9
11/21? 100
1" 95 to 100
2. 25to60 100 100
3/8" 85 to 100 90 to 100 100
No.4 OtolO 10to30 20to55 85to100
No. 8 0 to 5 0 to 10 5 to 30 10 to 40
No. 16
1.
0 to 5 0 to 10 0 to 10
No. 50 0to5 0to5
4. General Paving: Base section and subgrade preparations per structural section design, will
be required for all surfaces subject to traffic including roadways, Iraveiways, drive lanes,
driveway approaches and ribbon (cross) gutters. Driveway approaches within the public
right-of-way should have 12 inches subgrade compacted to a minimum of 95% compaction
levels and provided with a 95% compacted Class 2 base section per the structural section
design.
I Base layer under curb and gutters should be compacted to a minimum 95%, while subgrade
soils under curb and gutters, and base and subgrade under sidewalks should be compacted
to a minimum 90% compaction levels, unless otherwise noted. More specific
I recommendations should be given at the time of plan review phase and confirmed in the final
as-graded compaction report.
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Geotechnical Investigation, Proposed Residential Redevelopment October 13, 2020
3342 Donna Drive, Carlsbad, California (A.P.N. 205-160-62) Page 38
I Base and subgrade soils should be tested for proper moisture and specified compaction
levels, and approved by the project geotechnical consultant prior to the placement of the base
or asphalt/PCC/PICP finish surface.
I G. General Recommendations
The minimum foundation design and steel reinforcement provided herein are based on
soil characteristics and are not intended to be in lieu of reinforcement necessary for
structural considerations.
Adequate staking and grading control is a critical factor in properly completing the
recommended remedial and site grading operations. Grading control and staking should
I be provided by the project grading contractor or surveyor/civil engineer, and is beyond
the geotechnical engineering services. Staking should apply the required setbacks shown
on the approved plans and conform to setback requirements established by the governing
I agencies and applicable codes for off-site private and public properties and property
lines, utility easements, right-of-ways, nearby structures and improvements, leach fields
and septic systems, and graded embankments. Inadequate staking and/or lack of grading
I control may result in illegal encroachments or unnecessary additional grading which will
increase construction costs.
I C. Open or backfilled trenches parallel with a footing shall not be below a projected plane
having a downward slope of 1-unit vertical to 2 units horizontal (50%) from a line 9.0
inches above the bottom edge of the footing, and not closer than 18 inches from the face I of such footing. The Typical Trench Adjacent to Foundation is provided in the enclosed
Figure 19 and may be used as a general guideline.
I D. Where pipes cross under-footings, the footings shall be specially designed. Pipe sleeves
shall be provided where pipes cross through footings or footing walls, and sleeve
I clearances shall provide for possible footing settlement, but not less than 1-inch all
around the pipe. A schematic detail entailed Pipes Through or Below Foundation is
included on the enclosed Figure 19.
I E. Foundations where the surface of the ground slopes more than I unit vertical in 10 units
horizontal (10% slope) shall be level or shall be stepped so that both top and bottom of
I such foundations are level. Individual steps in continuous footings shall not exceed 18
inches in height and the slope of a series of such steps shall not exceed 1 unit vertical to
2 units horizontal (50%) unless otherwise specified. The steps shall be detailed on the
I structural drawings. The local effects due to the discontinuity of the steps shall also be
considered in the design of foundations as appropriate and applicable.
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Geotechnical Investigation, Proposed Residential Redevelopment October 13, 2020
3342 Donna Drive, Carlsbad, California (A.P.N. 205-160-62) Page 39
I F. Adequate horizontal setbacks or deepened foundations shall be required for all
foundations and on-grade improvements constructed on or near the top of descending
slopes as specified.
I G. Swimming pools, if any planned, may require special design considerations consistent
with the as-graded building pad and site-specific geotechnical conditions. Future
I swimming pool, if any considered, should only be planned in coordination, review and
approval of the project geotechnical consultant.
I I. Expansive clayey soils shall not be used for backfihling of any retaining structure. All
retaining walls should be provided with a 1:1 wedge of granular, compacted backfill
measured from the base of the wall footing to the finished surface and a well-constructed
I back drain system as shown on the enclosed Figure 14. Planting large trees behind site
retaining walls should be avoided.
I J. All underground utility and plumbing trenches should be mechanically compacted to a
minimum of 90% of the maximum dry density of the soil, unless otherwise required or
specified. Care should be taken not to crush the utilities or pipes during the compaction
I of the soil. Trench backfill materials and compaction (minimum 95%) beneath
pavements within the public right-of-way shall conform to the requirements of governing
I
agencies.
K. Onsite soils rang to medium expansive and moisture sensitive silty to clayey soils. These
deposits can experience movements and undergo volume changes upon wetting and
I drying, detrimental to the supporting structures and improvements. Maintaining a
uniform as-graded soil moisture during the post construction periods is essential in the
future performance and stability of site structures and improvements. Excessive
I irrigation resulting in wet soil conditions shall be avoided. Surface water should not be
allowed to infiltrate into the underlying bearing and subgrade soils.
I L. Site drainage over the finished pad surfaces should flow away from structures in a
positive manner. Care should be taken during the construction, improvements, and fine
I grading phases not to disrupt the designed drainage patterns. Roof lines of the buildings
should be provided with roof gutters. Roof water should be collected and directed away
from the buildings and structures to a suitable location.
I M. Final plans should reflect preliminary recommendations given in this report. Final
grading and foundation plans should also be reviewed by the project geotechnical
I consultant for conformance with the requirements of the geotechnical investigation report
outlined herein. More specific recommendations maybe necessary and should be given
when final grading and architectural/structural drawings are available.
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Geotechnical Investigation, Proposed Residential Redevelopment October 13, 2020
3342 Donna Drive, Carlsbad, California (A.P.N. 205-160-62) Page 40
I N. All foundation trenches should be observed by the project geotechnical consultant to
ensure adequate footing embedment and confirm competent bearing soils. Foundation
and slab reinforcements should also be observed and approved by the project
I geotechnical consultant.
0. The amount of shrinkage and related cracks that occur in the concrete slabs, flatwork and
I driveways depend on many factors, the most important of which is the amount of water
in the concrete mix. The purpose of the slab reinforcement is to keep normal concrete
shrinkage cracks closed tightly. The amount of concrete shrinkage can be minimized by
I reducing the amount of water in the mix. To keep shrinkage to a minimum the following
should be considered:
I * Use the stiffest mix that can be handled and consolidated satisfactorily.
* Use the largest maximum size of aggregate that is practical. For example, concrete
I made with %-inch maximum size aggregate usually requires about 40-lbs. more
(nearly 5-gal.) water per cubic yard than concrete with 1-inch aggregate.
I * Cure the concrete as long as practical.
The amount of slab reinforcement provided for conventional slab-on-grade construction
I considers that good quality concrete materials, proportioning, craftsmanship, and control
tests where appropriate and applicable are provided.
P. A preconstruction meeting between representatives of this office, the property owner or
planner, project inspector as well as the grading contractor/builder is recommended in order
to discuss grading and construction details associated with site development.
XV. GEOTECHNICAL ENGINEER OF RECORD (GER)
M9 Geotechnical Solutions, Inc. is the geotechnical engineer of record (GER) for providing a
specific scope of work or professional service under a contractual agreement unless it is terminated
or canceled by either the client or our firm. In the event a new geotechnical consultant or soils
engineering firm is hired to provide added engineering services, professional consultations,
engineering observations and compaction testing, SlPlSGeotechnical Solutions, Inc. will no longer
be the geotechnical engineer of the record. Project transfer should be completed in accordance with
the California Geotechnical Engineering Association (CGEA) Recommended Practice for Transfer
of Jobs Between Consultants.
I
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Geotechnical Investigation, Proposed Residential Redevelopment October 13, 2020
3342 Donna Drive, Carlsbad, California (A.P.N. 205-160-62) Page 41
I The new geotechnical consultant or soils engineering firm should review all previous geotechnical
documents, conduct an independent study, and provide appropriate confirmations, revisions or
design modifications to his own satisfaction. The new geotechnical consultant or soils engineering
I firm should also notify in writing gjWTGeotechnical Solutions, Inc. and submit proper notification
to the City of Carlsbad for the assumption of responsibility in accordance with the applicable codes
and standards.
I XVI. LIMITATIONS
I The conclusions and recommendations provided herein have been based on available data obtained
from the review of pertinent reports and plans, available subsurface exploratory test borings, surface
exposures as well as our experience with the soils and formational rock materials located in the
I general area. The materials encountered at the project site and utilized in laboratory testing are
believed representative of the total area; however, earth materials may vary in characteristics
I
between excavations.
Of necessity, we must assume a certain degree of continuity between test explorations and/or natural
exposures. It is necessary, therefore, that all observations, conclusions, and recommendations be
I verified during the site excavations and grading operations. In the event discrepancies are noted, we
should be contacted immediately so that an observation can be made and additional
I
recommendations issued, if required.
The recommendations made in this report are applicable to the site at the time this report was
prepared. It is the responsibility of the owner/developer to ensure that these recommendations are
I carried out in the field.
It is almost impossible to predict with certainty the future performance of a property. The future
I behavior of the site is also dependent on numerous unpredictable variables, such as earthquakes,
rainfall, and onsite drainage patterns.
I The firm of =9 Geotechnical Solutions, Inc., shall not be held responsible for changes to the
physical conditions of the property such as addition of fill soils, added cuts or changing drainage
I patterns which occur without our observation or control.
This report should be considered valid for a period of one year and is subject to review by our firm
I following that time. If significant modifications are made to your tentative construction plan,
especially with respect to finish pad elevations and final building layout, this report must be
presented to us for review and possible revision.
I
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Geotechnical Investigation, Proposed Residential Redevelopment October 13, 2020
3342 Donna Drive, Carlsbad, California (A.P.N. 205-160-62) Page 42
I This report is issued with the understanding that the client or his representative is responsible for
ensuring that the information and recommendations are provided to the project architect and
civil/structural engineers so that they can be incorporated into the final designs and construction
I plans. Necessary steps shall be taken to ensure that the project general contractor and all
subcontractors carry out such recommendations during construction.
I The project geotechnical engineer should be provided the opportunity for a general review of the
project final design plans and specifications in order to ensure that the recommendations provided
in this report are properly interpreted and implemented. If the project geotechnical engineer is not
I provided the opportunity of making these reviews, he can assume no responsibility for
misinterpretation of his recommendations.
=8 Geotechnical Solutions, Inc., warrants that this report has been prepared within the limits
prescribed by our client with the usual thoroughness and competence of the engineering profession.
No other warranty or representation, either expressed or implied, is included or intended.
Once again, should any questions arise concerning this report, please do not hesitate to contact this
office. Reference to our Project No. GI-20-09-136 will help to expedite our response to your
inquiries.
We appreciate this opportunity to be of service to you.
iWT' Geotechnical Solutions, Inc.
UJ Cn
J
No.2885
chnical Engineer
V
JAY .i
Steven J. Melzer,..QG #2362 1 CERTIFIED Engineering Geologist ENGINEERING
' GEOLOGISTCP
VA' 2 lo
I
QFC*°
Kevin McFarlanif
Staff Geologist
Distribution: Addressee (3, email)
Bogdan Tomalevski, AlA (email)
SEWS GEOTECHNICAL SOLUTIONS, INC.
I
REFERENCES
- Annual Book of ASTM Standards, Section 4- Construction, Volume 04.08: Soil and Rock (I);
D420 - D5876,2019.
I - Annual Book of ASTM Standards, Section 4- Construction, Volume 04.09: Soil and Rock (II);
I
D5877 - Latest, 2019.
- Highway Design Manual, Caltrans. Fifth Edition.
Corrosion Guidelines, Caltrans, Version 1.0, September 2003.
- California Building Code (CBC), California Code of Regulations Title 24, Part 2, Volumes 1 &
1 2, 2019, International Code Council.
- "The Green Book" Standard Specifications For Public Works Construction, Public Works
I Standards, Inc., BNi Building News, 2015 Edition.
- California Geological Survey, 2008 (Revised), Guidelines for Evaluating and Mitigating Seismic
I Hazards in California, Special Publication 117A, 108p.
- California Department of Conservation, Division of Mines and Geology (California Geological I Survey), 1986 (revised), Guidelines for Preparing Engineering Geology Reports: DMG Note 44.
- California Department of Conservation, Division of Mines and Geology (California Geological I Survey), 1986 (revised), Guidelines to Geologic and Seismic Reports: DMG Note 42.
- EQFAULT, Ver. 3.00, 1997, Deterministic Estimation of Peak Acceleration from Digitized I Faults, Computer Program, T. Blake Computer Services and Software.
I - EQSEARCH, Ver 3.00, 1997, Estimation of Peak Acceleration from California Earthquake
Catalogs, Computer Program, T. Blake Computer Services and Software.
Tan S.S. and Kennedy, M.P., 1996, Geologic Maps of the Northwestern Part of San Diego
County, California, Plate(s) I and 2, Open File-Report 96-02, California Division of Mines and
Geology, 1:24,000.
I - "Proceeding of The NCEER Workshop on Evaluation of Liquefaction Resistance Soils," Edited
by T. Leslie Youd and Izzat M. Idriss, Technical Report NCEER-97-0022, Dated December 31,
1 1997.
- "Recommended Procedures For Implementation of DMG Special Publication 117 Guidelines
I For Analyzing and Mitigation Liquefaction In California," Southern California Earthquake
Center; USC, March 1999.
I
I
REFERENCES (continued)
- "Soil Mechanics," Naval Facilities Engineering Command, DM 7.01.
"Foundations & Earth Structures," Naval Facilities Engineering Command, DM 7.02.
"Introduction to Geotechnical Engineering, Robert D. Holtz, William D. Kovacs.
"Introductory Soil Mechanics and Foundations: Geotechnical Engineering," George F. Sowers,
Fourth Edition.
I - "Foundation Analysis and Design," Joseph E. Bowels.
I - Caterpillar Performance Handbook, Edition 29, 1998.
- Jennings, C.W., 1994, Fault Activity Map of California and Adjacent Areas, California Division
I of Mines and Geology, Geologic Data Map Series, No. 6.
- Kennedy, M.P., 1977, Recency and Character of Faulting Along the Elsinore Fault Zone in
I Southern Riverside County, California, Special Report 131, California Division of Mines and
Geology, Plate 1 (East/West), 12p.
I - Kennedy, M.P, and Peterson, G.L., 1975, Geology of the San Diego Metropolitan Area,
California: California Division of Mines and Geology Bulletin 200, 56p.
I - Kennedy, M.P. and Tan, S.S., 1977, Geology of National City, Imperial Beach and Otay Mesa
Quadrangles, Southern San Diego Metropolitan Area, California, Map Sheet 24, California
I Division of Mines and Geology, 1:24,000.
- Kennedy, M.P., Tan, S.S., Chapman, R.H., and Chase, G.W., 1975, Character and Recency of
I Faulting, San Diego Metropolitan Areas, California: Special Report 123, 33p.
- "An Engineering Manual For Slope Stability Studies," J.M. Duncan, A.L. Buchignani and
I Marius De Wet, Virginia Polytechnic Institute and State University, March 1987.
- "Procedure To Evaluate Earthquake-Induced Settlements In Dry Sandy Soils," Daniel Pradel,
I ASCE Journal Of Geotechnical & Geoenvironniental Engineering, Volume 124, #4,1998.
- "Minimum Design Loads For Buildings and Other Structures," ASCE 7-16, American Society
of Civil Engineers (ASCE).
- "Seismic Constraints on The Architecture of The Newport-Ingelwood/Rose Canyon Fault:
I Implications For The Length And Magnitude of Future Earthquakes," Sahakian, V., Bonriann,
J., Driscoll, N., Harding, A. Kent, G. Wesnousky, S. (2017), AGU. doi: 10.1002/2016 JB 013467.
I
TOPOI map printed on 09)14,120 from SarrDiego.tpo and "UntIt1ed.tpq
i1/.uUu w 117.333330 W WGS84 117.316670 W
\.:.L]GIONAL INDEX MAP
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KEY TO BORING f TEST PIT LOGS
DRILLING & SAMPLING SYMBOLS:
Split Spoon — 1 — 3/8" l.D., 2" 0.0., Unless otherwise noted HS: Hollow Stem Auger kcw
ST: Thin-Walled Tube —2" 0.0., Unless otherwise noted PA: Power Auger
ICAI Ring Sampler-2,375" 1.0., 2.5" 0.D., Unless otherwise noted HA: Hand Auger
0 Chunk Sample
V7 Sandcone Density Test
DB: Diamond Bit Coring —4", N, B RB: Rock Bit
Bulk Sample or Auger Sample WB: Wash Boring or Mud Rotary
The number of blows required to advance a standard 2-inch O.D. split-spoon sample (SS) the last 12 inches of the total 18-inch penetration with a
140-pound hammer falling 30 inches is considered the "Standard Penetration" or "N-value". For 2.5" O.D. ring samplers (RS) the penetration value is
reported as the number of blows required to advance the sampler 12 inches using a 140-pound hammer falling 30 inches, reported as "blows per
foot" and is not considered equivalent to the "Standard Penetration" or "N-value".
WATER LEVEL MEASUREMENT SYMBOLS
WI.: Water Level WS: While Sampling N/E: Not Encountered
WCl: Wet Cave in WD: While Drilling
DO: Dry Cave in BCR: Before Casing Removal
AB: After Boring ACR: After Casing Removal
Water levels indicated on the boring logs are the levels measured in the borings at the times indicated. Groundwater levels at other times and other
locations across the site could vary. In pervious soils, the indicated levels may reflect the location of groundwater. In low permeability soils, the
accurate determination of groundwater levels may not be possible with only short-term observation.
DESCRIPTIVE SOIL CLASSIFICATION: Soil classification is based on the unified classification system. Coarse Grained Soils have more than 50% of their
dry weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their
dry weight retained on a *200 sieve; they are principally described as days if they are plastic, and silts if they are slightly plastic or non-plastic. Major
constituents may be added as modifiers and minor constituents may be added according to relative proportions based on grain size. In addition to
gradation, coarse-grained soils are defined on the basis of their in-place relative density and fine-grained soils on the basis of their consistency.
CONSISTENCY OF FINE-GRAINED SOILS
Unconfined Standard
Compressive Penetration or N-
Strength. Qu. psf value (SS) Blows/Ft. Consistency
<500 <2 Very Soft
500-1000 2-3 Soft
1001-2000 4-6 Medium Stiff
2001-4000 7-12 Stiff
4001-8000 13-26 Very Stiff
8000+ 26+ Hard
RELMiWPRQPORT(ON OF SAND AND GRAVEL
RELATIVE DENSITY OF COARSE-GRAINED SOILS
Standard
Penetration or N- RqigSampter (RS)
value ISS) Blows/Ft. Blows/Ft. Relative Density
0-3 0-6 Very Loose
4-9 7-18 Loose
10-29 19-58 Medium Dense
30-49 59-98 Dense
50 + 99 + Very Dense
GRAIN SIZE TERMINOLOGY
Descriptive Term(s) of other
constituents Percent of Dry Weight Major Component of Sample Particle Size
Trace <15 Boulders Over 12 in. (300 mm)
With 15-29 Cobbles 12 In. to 3 in. (300 mm to 75 mm)
Modifiers >30 Gravel 3 In. to #4 sieve (75 mm to 4.75 mm)
Sand #4 Sieve to #200 Sieve (4.75 mm to 0.075 mm)
Silt or Clay Passing #200 Sieve (0.075 mm)
RELATIVE PROPORTION OF FINES
Descriptive Term(s) of other
constituents Percent of Dry Weight
Trace <15
With 15-12
Modifiers > 12
PLASTICITY DESCRIPTION
Term Plasticity Inde
Non-plastic 0
Low 1-10
Medium 11-30
High 30+
SMS Geotechnical Solutions, Inc.
10
7
4
0
ML or OL
011
40 0
Si
.E30
>.
U
4-,
(B
0.20
*
MH or ON
UNIFIED SOIL CLASSIFICATION SYSTEM (USCS)
Criteria for Assigning Group Symbols and Group Names Using Laboratory Test?
Gravels
More than 50% of coarse
Coarse Grained Soils fraction retained on #4
More than 50% sieve
retained on #200
sieve' Sands
50% or more of coarse
fraction passes #4 sieve
Soil Classification
Group Group Name iymbol
GW Welt-graded gray
GW GP
Clean Gravels C,a 4 and 19 C.:5 35
Less than 5% fines' Not meeting above
More than 12% fines' Fines classify as CL or CH GC
Clean Sand C,?!6 and lsC,535 SW
Less than 5% fines0 Not meetine above aradatlon for SW SP
Sands with Fines
More than 12% fines' jines ciassiry as u. or LM SC Clayey sand -
inorganic P1>7 and plots on or above "A" lln& CL - - - Lean day'M
Silts and Clays P1<4 and plots below "A' line' ML Silt1LM
Fine Grained Soils Liquid limit less than 50 organic Liquid Limit—oven dried <0.75 OL Organic ci".'
50% or more passes Liquid Limit - not dried organic sft-"°
the #200 sieve' inorganic P1 plots on or above "A" line CH Fat clay"
Silts and Clays P1 plots below "A" line MH
Liquid limit SO or more organic Liquid Limit - oven dried <0.75 OH Organic claA'J'
Liquid Limit —not dried Organic siit'-''
Highly organic soils Primarily organic matter, dark in color, and organic odor PT Peat
* For soils having S to 12% passing the No. 200 sieve, use a dual symbol such as GW-GC.
If soil contains 15% sand, add "with sand" to group name.
0 If fines classify as CL-MI, use dual Symbol GC-GM, or SC-SM
H if fines are organic, add "with organic fines" to group name.
If soil contains 15% gravel, add "with gravel" to group name.
If Atterberg limits plot in shaded area, soil is Cl-MI, silty clay.
If soil contains 15% to 29% plus No. 200, add "with sand" or "with gravel"
whichever is
I If soil contains 80% plus No. 200 predominantly sand, add "sandy" to
group name.
M If soil contains 80% plus No. 200 predominantly gravel, add "gravelly" to
group name.
N P1 4 and plots on or above "A" line.
° P1 <4 or plots below "A' line.
" P1 plots on or above "A" line.
Q P1 plots below "A" line
A Based on the material passing the 3 in. (75 mm) sieve.
B If field sample contained cobbles or boulders, or both, add
"With cobbles or boulders, or both" to group name.
c Gravels with 5% to 12% fines require dual symbols: GW-GM
well-graded gravel with silt, GW-GC well-graded gravel with
clay, GP-GM poorly graded gravel with silt, GP-GC poorly
graded gravel with day.
O Sands with 5% to 12% fines require dual symbols: SW-SM
well-graded sand with silt, SW-SC well-graded sand with
clay, SP-SM poorly graded sand with silt, SP-SC poorly
graded sand.
= =
D60
0 10 16 20 30 40 50 60 70 80 90 100
Liquid Limit (LL)
SMS Geotechnical Solutions, Inc.
For classifications of fine-grained soils
and fine-grained fraction of coarse-
grained soils.
Equation of "A" line.
Horizontal at P1=4 to 11=25.5, then
P1=0.73 (LL-20).
Equation of "U" line.
Vertical at LL=16 to P1=7, then
P1= 0.9 (LL-8)
11 551)00
SURVEYING, INC.
GEOTECHNICAL MAP
\
F-)
260.61)3
105 0 10 20 30
SCALE IN FEET
TOPOGRAPHIC MAP
GEOLOGIC MAP
3342 DONNA DRIVE, CARLSBAD, CA
Geologic Units:
Qvop J Very old paralic deposits, undivided (middle to early Pleistocene)
Scale 1:33,33
Exerpt From the Geologic Map of the Oceanside 30' x 60' Quadrangle, California
Michael P. Kennedy and Slang S. Tan 2007.
SMS GEOTECHNICAL SOLUTIONS, INC. Project Number: GI-20-)9-136 5931 Sea Lion Place, Suite 109 Figure Number: 6 Carlsbad, CA 92010
A
280 -
275 -
270 -
265 -
Es ist log
Returning Wells
(to Be Removed) 260—
255-
- Proposed Drive
GEOLOGIC CROSS-SECTION A-A'
3342 DONNA DRIVE. CARLSBAD, CA
SCALE: I'= 10' I I
0' 10'
Legend
Proposed Building
Location
Boring Location
U Approximated
Z Groundwater
Very Moist/Wet
Zone
T.D. Time of Drilling
-.. Existing Topography
Geologic Contact
Approximated
Uaf Arlitical Fill
Qv op I Very Old Paralic
__ Deposits
245
240
--------------
Proposed Second F bee
Existing
Retaining Wall
Proposed First Flr
I I Existing Gmde
13-2 J-'\
-------------
-3
Proposed III Proposed Basement
Artiftcal Fill (Uafl — — — — —
2GW.a18'
--------------------------
:? TD. atl(Y T I). at tO
II Very Old Paralic Deposits (Qvop)
-A- TO. at 9
PL
SMS C.EOTECIINICAL
SOLt'TtOSS INC Project NumbeC GI-20-09-136 5931 Sea Don Place, Sow 109 Figure Number 7 Carlsbad, CA 92010
GEOLOGIC CROSS-SECTION B-B'
3342 DONNA DRIVE, CARLSBAD, CA
SCALE: I"= 10' I I
0' to'
Legend
Proposed Building
Location
Boring Location
LI Approximated
. Groundwater
Very Moist/Wet
- Zone
TI). Time of Drilling
- ' -
Existing Topography
Geologic Contact
- Approximated
Uaf Artifical Fill
QVOp I Very Old Paralic
Deposits
I.'
280—
Proposnd Second Floor 270 - 11i5ting CML I
Frcestaoding Wall I
::: : 1/F~isti.g Residence Proposed First Fluor Retaining Wall FL III I I j (To Be Removed)
260— _di _f B-2/B-3(Projoctcd)
-:F
Existing Grade
Artifical Fill (Uaf) L
I_-_ ------------------__J I
250— I
I Proposed Basement
250 'n' 10. at lOin 0-2
Very Old Paralic Deposits (Qvop)
245 -
11) a119'ieB-3
240 -
SMS GE0TECIINtCAL
SOLUTIONS INC
5931 Sea lIon PIac, SnO 109
Cadebad, CA 92010
Project Number: Ot-20-09-136
Figure Number: 8
REGIONAL FAULT MAP
SAN DIEGO COUNTY REGION
Holocene fault thnplace,rni (du00 p0,7 11.700 ye1n) 0.70007
lOMOnO re0070
L.I.O0i000ry boO ow 00000 (donng pool 700.000 ynor.)
Qootnnnoy fOoll (age ond Beronoatd)
POoobem,oy taoll (oldeo 70011 60077,0070.00)0,1000 wdhool
I. gwzed 0oo70ma,y dnp'000n,enl
ADDITIONAL FAULT SYMBOLS
Bar and bob on donenlbnown, 541 (reIab,ve ob apparent)
Arrows aIco (ant .fldrca)1 I`08loe 0' aporeor tonCho., 07071,4
Ala., or, 10,11 11 d OSlo, cr111 0" of.;
La,, .r,a'o 101 IborbO 00 0771" psfrl
Map is reproduced from California Geological Survey,
"Fault Activity Map of California (2010)".
SMS GEOTECHNICAL
SOLUTI0S INC
5931 Sea Lion Place, Suite 109 Project Number: GI-20-09-136
Carlsbad, CA 92010 Figure Numler: 9
SMS Geotechnical Solutions, Inc.
5931 Sea Lion place, Suite 109
Carlsbad, CA 92010
Sieve Analysis
ASTM D 6913 - 04
Project Jeff Speer Job # J Gl-20-09-136 I
Supervising Lab Tech F S.B Address 3342 Donna Drive, Carlsbad I
Supervising Lab Manager ( S.M.S. Date I0/2/2020 Tech S. B.
= 0 000
- .- £. .. • rJ m '.0 M -lrr -m
1:: _ _
90
60
ru
H
H
80
70
so
40
30
20
10
500
Cobbles Gravel Sand
Silt or Clay Coarse Fine Coarse Medium Fine
Location Depth Symbol USCS NAT, o LL PL P1 Cu (D60/D1O) Cc (D230/ D60*D10)
B-i 2.5 SC 10
B-3 4 SM-SC 9
Figure 10
0 0 0 0 N
at at
100 50 10 5 1 0.5 0.1 0.05 0.01
Grain Size (mm)
ma
IiY.DRO-MODIFICATION
2CON7OL ORIFICRAT
SUBGADERLEVATION
—HDPE OR PVC
GEOMEMBRANE
THICKNESS AT
LEAST JOMIL
or PERFORATED PIPE SLOPED curl-Er AT asx IN 3's' AGGREGATE PIPE
BASE GRA I'EL BED.
CONNECTED 70 STORM DRAIN.
- - - - - - - - - TYPICAL B10—DETENTION DETAIL
Schematic & Conceptual Only
No-Scale
C4PPRD
CLPANO UT POuT
Ir MAX POM
WA MR DEPTH
ir HOPE STORM
RISER ri/A TIWUM
VARIES
12
. O.55 (MIN) k
)/
HDPE OR PVC I ......
GEOMEMBRANE I MIN DEPTH 1.5' THICKNESS AT I SOIL FYL TEl? MIX LEAST JOMIL(IF REQUIREI)J
J" &fINIMUN
AGGREGA1E BELOW
UNDERORAJN TO
AXO CLOGGING
Project No:GI-20-09- 1 57GEOTECHNICAL SOLUTIONS, INC. Figure: 1211
280-
Proposed Second Floor 275 -
270 - Shotceele Wall
(See Detail I)
265 - Proposed First Floor
Existing Finish Grade
Retaining Walls
To Be Removed) ___________________ 2:0-
PL
--- -Pe::::---'
2'mta 4'm
' - -
OW. 018' Proposed Driveway ,_7— as
Fill 12'.
-
12 Shn/
2:T -Min
in.,, Watproofing
c 90% Level Benches /ootedF;lt (See Report)
toAllmBackfilli.EV
Compaction to Progress 2
Benches as Re ape °
Nmrnsol>/
Excavation Slope
N nary no Pmonss dCompoctBlot Very Old Paralic Deposits (Qvop) 240 - Composite/Crashed Rook Blanket Uodcodroio nf OX. In-Place Prior to Fill
may he Necessary as Directed in Field (See Report) Placement (mm. 95%, See Repast)
Existing Foiled
Retaining Wall
Drainage Panel/
Woterproolieg
I Shoeing Pile Embedment
I Depth Per Steuc. Eng. (lImb.)
miss.
- - - - - - - - - - - - - - - - - - -
TYPICAL GRADING DETAIL
SCHEMATIC AND CONCEPTUAL ONLY
SCALE: I" = 10' I I
0' 10'
Shoterete Wall
Per Stniet. Erg.
Ore/rage Pncsnst I "'I Wolerprooftog Shoring/Soldier
Sholceeto 24 min. Pile (l)'p.)
6' max.
TYPICAL SHORING WITH UPPER SHOTCRETE WALL, DETAIL!
Note: FillsfBackfihls Placed in Potential Groundwater Saturation/Inundation Zones
Shall Be Compacted to Mm. 95% Compaction Levels Per ASTM 01557.
[ SMS GEOTECHNICAL
SOLUTIONS INC j Project Number: 08-20-09-136 5931 Sea Lion Place, SatIn 109 I Figure Number: 13 Corlshad, CA 92010 1
Typical Retaining Wall Back Drainage
Schematic, No-Scale
ND SURFACE RETAINING WALL
FILTER MATERIAL, 314'- 1' CRUSHED
ROCKS (WRAPPED IN FILTER FABRIC—
OR CALTRANS CLASS 2 PERMEABLE
MATERIALS (SEE SPECIFICATIONS)
WATERPROOFING (TYP)
FINISH GRADE —4
SPECIFICATIONS FOR CALTRANS
CLASS 2 PERMEABLE MATERIAL
(68-1.025) U.S. STANDARD
SIEVE SIZE % PASSING 6' MN.
1" 100
3/4 90-100
3/8 40-100
No. 4 25-40
No. 8 38-33
No. 30 5-15
No, 50 0.7
No. 200 0-3
SAND EQUIVALENT> 75 j
CONCRETE-LIMED DRAINAGE DrrCI-j------,
12 RETAINING WALL -___ '
90% COMPACTED FILL
(TyJ
'
APPROVED FILTER FABRIC (MIRAFI
12- MIN. . 140M) 12' OVERLAP, TYP.
1'MIN. Q
LU
ts 11
4' PVC PERFORATED PIPE MN.
(SCH 40 OR SDR35) MIN. 1/2%
FALL TO APPROVED OUTLET
(SEE REPORT)
NATURAL OR GRADED SLOPE
TEMPORARY
1:1 CUT SLOPE
PROPERLY COMPACTED (MN. 90%) BACI<FILLED
GROUND
I
MN.
UJ
-
W1 "-MIN.
8
BENCH AND TIGHTLY KEY INTO TEMPORARY
BACKCUT AS BACKFILLNG PROGRESSES
APPROVED FILTER FABRIC (MILAfl 140N) IT
OVERLAP, TYP,
FILTER MATERIAL 3/4'• It CRUSHED -
ROCKS (WRAPPED IN FILTER FABRIC OR
CAL1RANS CLASS 2 PERMEABLE
MATERIALS (SEE SPECIFICATIONS)
WATERPROOFING (TYP)
PROPOSED GRADE-4
4" PVC PERFORATED PIPE MN. (SCM 40 OR 50R35)
MIN. 1/2% FALL TO APPROVED OUTLET (SEE
CONSTRUCTION SPECIFICATIONS: REPORT)
Provide granular, non-expansive backfill soil in 1:1 gradient wedge behind wall. Compact backfill to minimum 90%
of laboratory standard.
Backdrain should consist of 4' diameter PVC pipe (Schedule 40 or equivalent) with perforations down. Drain to
suitable at minimum %%. Provide %" 1 -/' crushed rocks filter materials wrapped in fabric (Mirafi 140N or equivalent).
Delete filter fabric wrap if Caltrans Class 2 permeable material is used. Compact Class 2 permeable material to
minimum 90% of laboratory standard.
Seal back of wall with approved waterproofing in accordance with architect's specifications.
Provide positive drainage to disallow ponding of water above wall. Drainage to flow away from wall at minimum 2%.
Provide concrete-lined drainage ditch for slope toe retaining walls.
Use 1-Y2 cubic feet per foot with granular backfill soil and 4 cubic feet per foot if expansive backfill is used.
Project No: 699GEOTECHNICAL SOLUTIONS, INC. Figure:
5931 Sea Lion Place, Suite 109
Carlsbad, California 92010 GI-20--09-136 14
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I SOf7
I
errec) Line- Lea,,A
ho sur m'.)
I
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I.
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I
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I
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i
c,( O,GN
oOsc?j
(Ac4S or) xptk Dld) os oS&H
0,7
(o O.5OL
>& (O9L)
Pstv ?r in upper' over-
rrIuJ jrdu 1er ls jLr k
.f'prOFr, .4 Wter rp1cble.
Dcast .ir
to r 4 ttrre oc' P IC,%n ( tco p
3. (!d+e c rt {or rrxS
Typical Retainiu,g Wall Sheet Drain Detail
Schematic, No-Scale
RETAINING
T
WATER-
PROOFING-.
SITEDRAIN
SHEET DRAIN
PLATE TO
BRIDGE
(4'DIAMETER)
WEEP HOLE
RETAINING \4ALL
SITEDRAIN* ( .1. BACKFILL
SHEET DRAIN '
WATERPROOFING FILTER FABRIC (OPTIONAL) . FACING SOIL
WEEP HOLE - CUT BACK OF BLACK (4- DIAMETER) \ PLASTIC ON \ 7 J SHEET DRAIN
TO MATCH SIZE OF
UNIVERSAL . WEEP HOLE, DO NOT
TEE FflTING CUT FILTER FABRIC
z
FOOTI
.000000
NG
¼L OC)()J)
BACKFILL
- :
L. . ,. c
RETAINING WALL WITH SITED RAIN
SITEDRAIN HQ & UNIVERSAL TEE FITTING
*UNIVERSAL OUTLETALSO AVAILABLE i SITEDRAIN
,_..... L9J SHEET DRAIN
PERFORATED -. PIPE
CUT BACK OF BLACK
PLASTIC ON . . . WRAP FILTER SHEET DRAIN
•
1 . - FABRIC TO MATCH SIZE OF . - .. •, . -. AROUND PIPE WEEP HOLE. DO NOT .J. /.•• '•.-• CUT FILTER FABRIC
RETAINING WALL
WITH DRAIN PIPE
-i
RETAINING WALL
WITH WEEP HOLE
* AWD SITEDRAIN SHEET DRAIN OR EQUAL
Project No: '17ØGEOTECHNICAL SOLUTIONS, INC.
5931 Sea Lion Place, Suite 109
Carlsbad, California 92010 Gl-20-09— 136
Figure:
1611
(a)
)LATION JOINTS
NTRACTION JOINT
(c)
N1TRANT
NER CRACK
RE-ENTRANT CC
REINFORCEMEN
NO. 3 BARS PIAI
MID-HEIGHT IN
NO SCALE
NOTES:
Isolation Joints around the columns should be either circular as shown in (a) or diamond shaped as shown in (b).
If no isolation joints are used around columns, or if the corners of the Isolation joints do not meet the contraction joints,
radial cracking as shown in (c) may occur (reference Ad).
In order to control cracking at the re-entrant corners (+ /-270 degree corners), provide reinforcement as shown in (c).
Re-entrant corner reinforcement shown herein is provided as a general guideline only and is subject to verification and
changes by the project architect and I or structural engineer based upon slab geometry, location, and other engineering and construction factors.
§M§ GEOTECHNICAL SOLUTIONS, INC.
Consulting Geotechnical Engineers & Geologists
5931 Sea Lion Place, Suite 109
Carlsbad, California 92010
760-602-7815
smsgeosol.inc@gmaii.com
TYPICAL ISOLATION JOINTS AND
RE-ENTRANT CORNER
REINFORCEMENT
PROJECT NO. FIGURE NO.
GI-20-09-136
- - - - - - - - - - - - - - — - ----- -= - ------------ -------- -- TypicalJermeabJeJnterIockiug Concrete Paver (PICi) Detail Schematic & Conceptual Only
No-Scale
I F
NO.8 AGGREGATES
IN OPENINGS PER
PAVERS
6' CURS MANUFACTURER SPECS.
PERMEASLE
(TRAFFIC RATED) 3— OIICI( CONCRETE PAVERS, TRAFFiC LOADING
U
- 6 CONCRETE
EDGE RESTRAIN
*2b BEDDING COURSE (Na 8 AGGREGA TE W PER MANUFACTURER SPECS)
12' 711ICI( OPEN GRADED BASE. IJ$1H
MIN. 5U PER HOUR INFiL iRA liON RA 7E (No. 57 STONE - 3/40 MAX.)
SS AT
JOMIL
314 GRAVEL
Project No:GI-20-09— 1
\
SOIL SUSGRADE
'- OPEN GRADED r i' \ BASE (No. 57
STONE-3/0- MAX.)
UPPER ?2U AT 95Z COMPACflOM. (ASThI 07557)
Schomm0g And Cononwn8 OnI
(Also See Report)
7GEOTECHNICAL SOLUTIONS, INC.
40 PERFORATED UNDERORAIN SCH. 40 PVC.
Figure: 1
Typical Pipes Through or Trench Adjacent to Foundations
Schematic, No-Scale
LOCATE TRENCH SO
THAI FOOTINGS ARE
- rw r NQTUNDERMrNED
SACKFILL. TRENCH PER
GEOTECHPICA1. REPORT
- --
' \ \ . --;--ji
NO EXCAVATION ALLOWED
it's '1 1I!J ftj A
S i - is
Trench Adj acent iiiF oundation
SUSWGRAM -
.1 L
fo L111 11 DISTAPXE BETWEEN
SLEEVES TO NO LESS THAR,
LARGER SLEEVE 01JTSIDE DIAMETER OR
LEVATION A-A
SEE
ROTE 2
EXTEND FOOTING MIN. " 91 MIN.
6 BELOW SLEEVE (TYP.)
Pipes Through or Below Foundation
AWGEOTECHNLCAL SOLUTIONS, INC.
5931 Sea Lion Place, Suite 109
GI-20-09-136 Carlsbad, California 92010
roject No: P Figure:
19
V1l'1*fflE1
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ASCE 7 Hazards Report
SOXTV OF u
Address:
No Address at This
Location
Standard: ASCE/SEI 7-16 Elevation: 261.29 ft(NAVD 88)
Risk Category: II Latitude: 33.1672
Soil Class: C - Very Dense Longitude: -117.327
Soil and Soft Rock
Page 10(3 Fn Oct 02 2020
0 I S
08
I 05
I 04
02
3 4 Sa(g) vs T(s)
.. S
05 •
02
Sa(g)vsT
ASCE AC.&4 SOETY D
Seismic
Site Soil Class: C - Very Dense Soil and Soft Rock
Results:
Ss 1.016
S1 0.37
Fa : 1.2
F: 1.5
SMS : 1.22
SM1 : 0.556
SDS : 0.813
Seismic Design Category 0
MCER Response Spectrum
S01 : 0.37
TL: 8
PGA 0.445
PGA M; 0.534
FPGA 1.2
le : 1
C : 1.103
Design Response Spectrum
MCER Vertical Response Spectrum Design Vertical Response Spectrum
08 • 05
07 S 05
05
05 03 *000
- S S J4* • 03 S S..
02 02 ••••••••••
S8(g)vsT(s) Sa(9) VS I(S)
Data Accessed: Fri Oct 02 2020
Date Source: USGS Seismic Design Maps based on ASCE/SEI 7-16 and ASCE/SEI 7-16
Table 1.5-2. Additional data for site-specific ground motion procedures in
accordance with ASCE/SEI 7-16 Ch. 21 are available from USGS.
7h:rJoLoH Page 2 of 3 Fri Oct 022020
•
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httDs:Lasce7hazardtool.online/ Page 3 of 3 Fri Oct 02 2020