PC - Item 3A - Exhibit E - Appendix B - Geotechnical Report
REPORT OF GEOTECHNICAL ENGINEERING
INVESTIGATION
Proposed
4-Story Mixed Used Development
With 1 level Subterranean Garage
At
3001 Walnut Grove and nearby lots
APN: 5288-001-040, 041, 042, 043
Rosemead, California
Prepared by
QUARTECH CONSULTANTS (QCI)
Project No.: 19-221-001GE
November 8, 2019
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TABLE OF CONTENTS
1.0 INTRODUCTION .................................................................................................................... 3
1.1 PURPOSE .............................................................................................................................. 3
1.2 SCOPE OF SERVICES ............................................................................................................. 3
1.3 PROPOSED CONSTRUCTION ................................................................................................... 3
1.4 SITE LOCATION ..................................................................................................................... 3
2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING ......................................... 4
2.1 SUBSURFACE EXPLORATION .................................................................................................. 4
2.2 LABORATORY TESTING .......................................................................................................... 4
3.0 SUMMARY OF GEOTECHNICAL CONDITIONS .................................................................. 4
3.1 SOIL CONDITIONS .................................................................................................................. 4
3.2 GROUNDWATER .................................................................................................................... 4
4.0 SEISMICITY ........................................................................................................................... 5
4.1 FAULTING .............................................................................................................................. 5
4.2 SEISMICITY ........................................................................................................................... 5
4.3 ESTIMATED EARTHQUAKE GROUND MOTIONS ......................................................................... 6
5.0 SEISMIC HAZARDS .............................................................................................................. 6
5.1 LIQUEFACTION....................................................................................................................... 6
5.2 EARTHQUAKE INDUCED SETTLEMENT ..................................................................................... 7
5.3 LANDSLIDING ......................................................................................................................... 7
5.4 LURCHING ............................................................................................................................. 7
5.5 SURFACE RUPTURE ............................................................................................................... 7
5.6 SURFACE MANIFESTATION OF LIQUEFACTION .......................................................................... 7
5.7 GROUND SHAKING ................................................................................................................. 8
6.0 CONCLUSIONS..................................................................................................................... 8
6.1 SEISMICITY ........................................................................................................................... 8
6.2 LIQUEFACTION POTENTIAL ..................................................................................................... 8
6.3 EXCAVATABILITY .................................................................................................................... 8
6.4 CITY OF ROSEMEAD FAULT HAZARD MANAGEMENT ZONES (HFMZ) ......................................... 8
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6.5 SURFICIAL SOIL REMOVAL...................................................................................................... 9
6.6 GROUNDWATER .................................................................................................................... 9
7.0 RECOMMENDATIONS .......................................................................................................... 9
7.1 SITE GRADING ....................................................................................................................... 9
7.1.1 Site Preparation ............................................................................................................ 9
7.1.2 Surficial Soil Removals.................................................................................................. 9
7.1.3 Treatment of Removal Bottoms ................................................................................... 10
7.1.4 Structural Backfill ........................................................................................................ 10
7.2 SUBTERRANEAN GARAGE EXCAVATION ................................................................................. 10
7.2.1 Sloping Excavation ...................................................................................................... 10
7.2.2 Shoring ....................................................................................................................... 11
7.2.3 Slot Cut ....................................................................................................................... 11
7.3 FOUNDATION DESIGN .......................................................................................................... 12
7.3.1 Conventional Foundation (Building)............................................................................. 12
7.3.2 Settlement ................................................................................................................... 12
7.3.3 Lateral Pressures ........................................................................................................ 12
7.3.4 Lateral Resistance Pressures...................................................................................... 13
7.3.5 Wall Seismic Loading .................................................................................................. 13
7.3.6 Wall Drainage ............................................................................................................. 14
7. 4 FOUNDATION CONSTRUCTION ............................................................................................. 14
7. 5 CONCRETE FLATWORK........................................................................................................ 14
7.6 TEMPORARY TRENCH EXCAVATION AND BACKFILL ................................................................. 15
8.0 SEISMIC DESIGN ................................................................................................................ 15
9.0 INSPECTION ....................................................................................................................... 16
10.0 CORROSION POTENTIAL ................................................................................................ 16
11.0 REMARKS ......................................................................................................................... 16
12.0 REFERENCES................................................................................................................... 17
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1.0 INTRODUCTION
1.1 Purpose
This report presents a summary of our preliminary geotechnical engineering investigation for the
proposed construction at the subject site. The purposes of this investigation were to evaluate the
subsurface conditions at the area of proposed construction and to provide recommendations
pertinent to grading, foundation design and other relevant parameters of the development.
1.2 Scope of Services
Our scope of services included:
Review of available soil engineering data of the area.
Our subsurface investigation consisted of excavation of logging and sampling of two 8-inch
diameter hollow stem auger borings to a maximum depth of 51.5 feet below the existing grade
at the subject site. The exploration was logged by a QCI engineer. Boring logs are presented
in Appendix A.
Laboratory testing of representative samples to establish engineering characteristics of the
on-site soil. The laboratory test results are presented in Appendices A and B.
Engineering analyses of the geotechnical data obtained from our background studies, field
investigation, and laboratory testing.
Preparation of this report presenting our findings, conclusions, and recommendations.
1.3 Proposed Construction
Based on the 16-scale architectural plan by SLA Architects dated August 26, 2019, it is our
understanding that the subject site will be developed for construction of a commercial and
residential mixed used building. The main structure of the building is anticipated to be four stories
in height above the ground level with one level of subterranean garage. The lowest garage floor
will be approximately 10 feet below the existing ground surface. The subterranean garage will
occupy the entire building site.
1.4 Site Location
The project site is located on the northwest corner of Garvey Avenue and Walnut Grove Avenue,
in the City of Rosemead, California. The approximate location of the site is presented in the
attached Site Location Map (Figure 1). The site is relatively flat and is currently occupied by a
commercial building and associated improvements. No major surface erosions were observed
during our subsurface investigation.
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2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING
2.1 Subsurface Exploration
Our subsurface exploration consisted of excavating two 8-inch diameter hollow stem auger
borings to a maximum depth of 51.5 feet below the existing ground surface at the subject site.
Approximate locations of the borings are shown on the attached Site Plan (Figure 2). The
purpose of the explorations was to assess the engineering characteristics of the onsite soils with
respect to the proposed development.
The borings were logged by a representative of this office. Relatively undisturbed and bulk
samples were collected during drilling for laboratory testing. Natural soil was encountered in the
borings to the depths explored. Boring logs are presented in Appendix A.
2.2 Laboratory Testing
Representative samples were tested for the following parameters: in-situ moisture content and
density, consolidation, direct shear strength, percent of fines, expansion, Atterburg limits, and
corrosion potential. Results of our laboratory testing along with a summary of the testing
procedures are presented in Appendix B. In-situ moisture and density test results are presented
on the boring logs in Appendix A.
3.0 SUMMARY OF GEOTECHNICAL CONDITIONS
3.1 Soil Conditions
The onsite near surface soils consist predominantly of clayey sand (SC). In general, these soils
exist in the loose and moist condition. Underlying the surface soils, fine grained clayey sand (SC),
silty sand (SM), poorly graded sand (SP) and sandy clay (CL) were disclosed in the borings to the
depths explored (51.5 feet below the existing ground surface). These soils exist in medium dense
to very dense and very stiff and slightly moist to very moist conditions. In general, the soils
become denser as depth increases.
3.2 Groundwater
Ground water level was not encountered to the depth explored (approximately 51.5 feet below the
existing grade) during our subsurface investigation. In our opinion, groundwater will not be a
problem during the near surface construction. Based on our review of the “Historically Highest
Ground Water Contours and Borehole Log Data Locations, El Monte Quadrangle”, by CGS
(formerly CDMG), it is estimated that the highest historical ground water level is approximately 10
feet below the existing grade.
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4.0 SEISMICITY
4.1 Faulting
Based on our study, there are no known active faults crossing the property. The nearest known
active regional fault is the Upper Elysian Park fault located at 1.1 miles from the site.
4.2 Seismicity
The subject site is located in Southern California, which is a tectonically active area. The type and
magnitude of seismic hazards affecting the site depend on the distance to causative faults, the
intensity, and the magnitude of the seismic event. Table 1 indicates the distance of the fault zones
and the associated maximum magnitude earthquake that can be produced by nearby seismic
events. As indicated in Table 1, the Upper Elysian Park fault is considered to have the most
significant effect to the site from a design standpoint.
TABLE 1
Characteristics and Estimated Earthquakes for Regional Faults
Fault Name Approximate Distance to
the Site (mile)
Maximum Magnitude
Earthquake (Mmax)
Elysian Park (Upper) 1.1 6.7
Raymond 4.4 6.8
Elsinore;W+GI+T+J+CM 5.1 7.8
Verdugo 6.2 6.9
Puente Hills (LA) 7.0 7.0
Sierra Madre Connected 7.8 7.3
Clamshell-Sawpit 9.2 6.7
Hollywood 9.4 6.7
Puente Hills (Santa Fe Springs) 9.8 6.7
San Jose 11.8 6.7
Puente Hills (Coyote Hills) 12.0 6.9
Santa Monica Connected alt 2 12.0 7.4
Newport Inglewood Connected alt 2 15.4 7.5
Newport-Inglewood, alt 1 15.7 7.2
Newport Inglewood Connected alt 1 15.7 7.5
Santa Monica, alt 1 18.9 6.6
Santa Monica Connected alt 1 18.9 7.3
Sierra Madre (San Fernando) 19.2 6.7
Chino, alt 2 19.4 6.8
Reference: 2008 National Seismic Hazard Maps-Source Parameters
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4.3 Estimated Earthquake Ground Motions
In order to estimate the seismic ground motions at the subject site, QCI has utilized the seismic
hazard map published by California Geological Survey. According to this report, the peak ground
alluvium acceleration at the subject site for a 2% and 10% probability of exceedance in 50 years
is about 0.863g and 0.517g, respectively (USGS, 2008 Deaggregation of Seismic Hazards).
Site modified peak ground acceleration (PGAM), corresponding to USGS Seismic Design Maps,
ASCE 7-10 Standard, is 0.949g.
5.0 SEISMIC HAZARDS
5.1 Liquefaction
Liquefaction is the transformation of a granular material from a solid to a liquid state as a result of
increasing pore-water pressure. The material will then loses strength and can flow if unrestrained,
thus leading to ground failure. Liquefaction can be triggered in saturated cohesionless material by
short-term cyclic loading, such as shaking due to an earthquake. Ground failure that results from
liquefaction can be manifested as flow landsliding, lateral spread, loss of bearing capacity, or
settlement.
The potential for liquefaction at the site’s sandy soil was evaluated using the computer program
“LIQUEFY2” by Thomas Blake, the subsurface data from Boring B-1, the design earthquake (M
=7.0), and ground acceleration of 0.863g (2% probability of exceedance in 50 years). The total unit
weight used for the onsite soils is 120 pcf. The calculated ground water level is raised to the depth
of 10 feet below the existing ground surface. Conversion from California modified split spoon to
field SPT blow counts is 0.7 (County of L.A. GS045.0 October 1, 2014). The analyses presented
on the enclosed Appendix C indicated that the factor of safety is less than 1.30 for the onsite soils
at the depth of 37 to 42 feet.
Based on the laboratory test results on clayey soils, for B-1 @ 30 @ 50 feet, the saturated
moisture content of the encountered clayey soils is less than 85 percent of liquid limit when PI is
less than 12 (County of L.A., GS045.0, October 1, 2014 and Bray and Sancio 2006, if PI is less
than 12 and wc/LL is less than 0.85, the clayey soil is not susceptible to liquefaction). According
to procedures referenced in SP117A, (Guideline for Evaluating and Mitigating Seismic Hazards in
California), our laboratory Atterberg Limits and saturated moisture content of clayey soils material, it
is our opinion that the encountered clayey soils are not susceptible to liquefaction.
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5.2 Earthquake Induced Settlement
The sandy soils tend to settle and densify when they are subjected to earthquake shaking.
Should the sand be saturated and there is no possibility for drainage so that constant volume
conditions are maintained, the primary effect of the shaking is the generation of excess pore
water pressures. Settlement then occurs as the excess pore pressures dissipate. The primary
factors controlling seismic induced settlement are the cyclic stress ratio, maximum shear strain
induced by earthquake, the strength and density of the sand, and the magnitude of the
earthquake.
Based on the procedures developed by Tokimatsu and Seed on 1987, it is our opinion that total
seismic induced settlement and differential settlement of saturated sand are 0.70 inches and
0.47 inches respectively.
5.3 Landsliding
A potential for landsliding is often suggested in areas of moderate to steep terrain that is
underlain by weak or un-favorably oriented geological conditions. Neither of these conditions
exists at the site. Due to the relatively flat nature of the site, it is our opinion that the potential for
landslide is remote.
5.4 Lurching
Soil lurching refers to the rolling motion on the surface due to the passage of seismic surface
waves. Effects of this nature are not considered significant on the subject site where the thickness
of alluvium does not vary appreciably under structures.
5.5 Surface Rupture
Surface rupture is a break in the ground surface during or as a consequence of seismic activity.
The potential for surface rupture on the subject site is considered low due to the absence of known
active faults at the site.
5.6 Surface Manifestation of Liquefaction
One of the most dramatic causes of damage to structures during earthquakes has been the
development of liquefaction in saturated sandy soils, manifested either by the formation of boils and
mud-spouts at the ground surface, by seepage of water through ground cracks. Based on the
evaluation procedures suggested by the Ishihara (1985), it is concluded that surface manifestation
of liquefaction is unlikely at the subject site under the design earthquake event.
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5.7 Ground Shaking
Throughout southern California, ground shaking, as a result of earthquakes, is a constant
potential hazard. The relative potential for damage from this hazard is a function of the type and
magnitude of earthquake events and the distance of the subject site from the event. Accordingly,
proposed structures should be designed and constructed in accordance with applicable portions
of the building code.
6.0 CONCLUSIONS
Based on the results of our subsurface investigation, it is our opinion that the proposed
improvements are feasible from a geotechnical standpoint, provided the recommendations
contained herein are incorporated in the design and construction. The following is a summary of
the geotechnical design and construction factors that may affect the development of the site:
6.1 Seismicity
Based on our studies on seismicity, there are no known active faults crossing the property.
However, the site is located in a seismically active region and is subject to seismically induced
ground shaking from nearby and distant faults, which is a characteristic of all Southern California.
6.2 Liquefaction Potential
Based on our field investigation, liquefaction analyses and laboratory testing, the analyses
presented on the enclosed Appendix C indicated that the factor of safety is less than 1.30 for the
onsite soils at the depth of 37 to 42 feet.
6.3 Excavatability
Based on our subsurface investigation, excavation of the subsurface materials should be able to
be accomplished with conventional earthwork equipment.
6.4 City of Rosemead Fault Hazard Management Zones (HFMZ)
The site is not located within the designated City of Rosemead Safety Element as shown on
Figure 1a, City of Rosemead Fault Hazard Management Zones (FHMZ). Based on examining the
exploratory borings, B-1 and B-2 and nearby site’s exploratory borings, it was determined that the
soil borings are similar within the site underlying soil materials.
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6.5 Surficial Soil Removal
The near surface soils are relatively dry and vary in density. In order to provide a uniform support
for the foundation, it is recommended the existing soil be removed and backfilled with compacted
fill to a minimum depth of 4 feet below the existing grade to provide a uniform support of the near
surface structures.
6.6 Groundwater
No groundwater was encountered in the borings to the depths explored. In our opinion,
groundwater will not be a problem during the near surface construction.
7.0 RECOMMENDATIONS
Based on the subsurface conditions exposed during field investigation and laboratory testing
program, it is recommended that the following recommendations be incorporated in the design
and construction phases of the project.
7.1 Site Grading
7.1.1 Site Preparation
Prior to initiating grading operations, any existing vegetation, trash, debris, over-sized materials
(greater than 8 inches), and other deleterious materials within construction areas should be
removed from the subject site.
7.1.2 Surficial Soil Removals
It is anticipated that most unsuitable or and loose near surface soils will be removed by
excavation for the basement structures. It is QCI's opinion that no additional removal will be
necessary within the basement areas. However, it is recommended that the basement areas be
cut to grade then observed by a representative of this office to verify the sub-grade soil conditions
for any potential needs of removal loose soils and replacement with compacted fill. This may be
also necessary due to difference in expansion characteristics of foundation materials beneath a
structure.
Outside the basement areas, the near surface soils should be removed to expose competent
natural soils. Based on our field exploration and laboratory data obtained to date, it is
recommended that the surficial soils be removed to a depth of at least 2 feet below existing grade
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for the uniform concrete flatworks support. Locally deeper removals may be necessary to expose
competent natural ground. The actual removal depths should be determined in the field as
conditions are exposed. Visual inspection and/or testing may be used to define removal
requirements.
7.1.3 Treatment of Removal Bottoms
Soils exposed within areas approved for fill placement should be scarified to a depth of 6 inches,
conditioned to near optimum moisture content, then compacted in-place to minimum project
standards.
7.1.4 Structural Backfill
The onsite soils may be used as compacted fill provided they are free of organic materials and
debris. Fills should be placed in relatively thin lifts (6 to 8 inches), brought to near optimum
moisture content, then compacted to at least 90 percent relative compaction based on laboratory
standard ASTM D-1557-12.
7.2 Subterranean Garage Excavation
The required excavation for the proposed subterranean parking garage will be around 10 to 12
feet below ground. The criteria for sloped excavations and/or shoring method for the alignments
required vertical cuts, depends on many factors, which include depth of excavation, soil
conditions, types of shoring, distance to the existing structures or public improvement,
consequences of potential ground movement, and construction procedures.
7.2.1 Sloping Excavation
Should the space be available at the site, the required excavation may be made with sloping
banks. Based on materials encountered in the test borings, it is our opinion that sloped
excavations may be made no steeper than 1:1 (horizontal to vertical) for the underlying native
soils. Flatter slope cuts may be required if loose soils encountered during excavation. No heavy
construction vehicles, equipment, nor surcharge loading should be permitted at the top of the
slope. A representative of this office should inspect the temporary excavation to make any
necessary modifications or recommendations.
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7.2.2 Shoring
Shoring will be required for temporary excavation made vertically or near vertically of more than 5
feet. An active earth pressure of 35 pound per cubic foot may be used for the temporary
cantilever shoring system. Any surcharge loads resulting from adjacent buildings or traffic should
be considered as an added load to the design. Based on the existing on site conditions, it is
recommended that a uniform lateral surcharge pressure of 70 psf may be used for the traffic
loads along Walnut Grove and Garvey Avenue. Soldier piles or beams should be spaced at the
specification by the project structural/shoring engineer. Lagging may be required to span between
soldier piles to support the lateral earth pressure.
The shoring and bracing should be designed and constructed in accordance with current
requirements of CAL/OSHA and all other public agencies having jurisdiction. Careful examination
of the soil excavation and inspection of on-site installation of the shoring system by a
representative of this office is recommended to verify the conditions or to make recommendations
as are pertinent if different conditions are disclosed during excavation.
7.2.3 Slot Cut
Should the ABC slot cut method be used for the onsite vertical excavation of more than 5 feet in
height, the following presents the slot cut recommendations. The slot cut stability analysis is
presented in the attached plate.
1. Excavate to the design elevation at the side slopes no steeper than 1:1, horizontal to
vertical.
2. Excavate in alternative slots with each slot no wider than the design width (i.e. 10 feet)
3. Excavate the footings at each slot, pour the footings and construct the walls per project
standard. The depth of vertical cut should be limited to no more than 10 feet.
4. After completion of the slope construction, excavate the adjacent slots and repeated the
above procedures to complete the adjacent slope.
5. All excavations should be made under the inspection and testing of the project
geotechnical consultant.
6. Care should be taken to prevent surcharge loads above un-shored slots within a
horizontal distance from the top of cut equal to depth of excavation.
7. Provisions for drainage should be implemented to prevent saturation of un-shored
excavations.
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8. Once vertical excavations are completed. The basement/retaining wall should be
constructed without delay.
7.3 Foundation Design
Based on our subsurface investigation, it is our opinion that the proposed building may be
supported on shallow foundation founded on the competent nature soil at the depth of 10 to 12
feet below the existing grade. The following presents our preliminary recommendations:
7.3.1 Conventional Foundation (Building)
An allowable bearing value of 2500 pounds per square foot (psf) may be used for design of
continuous or pad footings with a minimum of 18 or 36 inches in width, respectively. All footings
should be a minimum of 24 inches deep. This value may be increased by one third (1/3) when
considering short duration seismic or wind loads. This bearing value may be increased by 300 psf
for each additional foot of depth or width to a maximum value of 3500 psf. This value may be
increased by one third (1/3) when considering short duration seismic or wind loads.
7.3.2 Settlement
Settlement of the footings placed as recommended, and subject to no more than allowable loads
is not expected to exceed 1/2 inch. Differential settlement between adjacent columns is not
anticipated to exceed 1/4 inch for the adjacent column spaced at a distance of about 30 feet.
Additionally, the foundation should also be designed to resist the potential seismic induced total
settlement and differential settlement of 0.70 inches and 0.47 inches, respectively.
7.3.3 Lateral Pressures
Active earth pressure from horizontal backfill may be computed as an equivalent fluid weighting of
35 pounds per cubic foot for cantilever retaining wall and 60 pcf for restrained retaining wall. This
value assumes free-draining conditions.
The effect of surcharge, such as traffic loads, adjacent building loads, and etc. within a 1 to 1
projection from the inner edge of the foundation should be included in the design of the retaining
walls. Based on the existing on site conditions, it is recommended that a uniform lateral surcharge
pressure of 70 psf for the traffic loads for be added in the basement wall design along Walnut
Grove and Garvey Avenue.
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Based on our review of the 10-scale tentative map, it is understood that the proposed basement
will be located at least 5 feet away from the existing adjacent neighbor 1-story commercial
structures. The lateral surcharged load from the adjacent foundation is then calculated based on
the adjacent building located at 6 feet away from the wall and the basement wall is 10 feet below
the existing grade.
Reference: NAVFAC DM 7.02, Figure 11, Page 7.2-74
Foundation Line Load Q = 2000 lbs
Distance Between Wall to Foundation X = 6 feet
Depth of Basement Wall H = 10 feet
m = 6/10 = 0.6 > 0.4 n = 0.6 from bottom of the wall
Resultant PH = 0.64 x Q / (mxm +1) = 941 pounds < 1000 pounds
Based on our calculations, it is our opinion that the recommended horizontal surcharge of 1000
pounds per square feet act at approximately 0.6xH (H: height of wall) from the bottom of the wall.
7.3.4 Lateral Resistance Pressures
Resistance to the lateral loads can be assumed to be provided by the passive earth pressure and
the friction between the concrete and competent soils. Passive earth pressure may be computed
as an equivalent fluid pressure of 350 pcf, with a maximum earth pressure of 3500 psf. An
allowable coefficient of friction between soil and concrete of 0.30 may be used with the dead load
forces. When combining passive pressure and frictional resistance, the passive pressure
component should be reduced by one third (1/3).
7.3.5 Wall Seismic Loading
Earthquake earth pressure distribution on cantilever retaining walls retaining more than 6 feet of
soils when the slope of the backfill behind the wall is level may be computed as an inverted right
triangle with 31H psf at the base. Resultant seismic earth force may be applied at approximately
0.6xH from the top of the footing. H should be measured from top of footing to the top of wall. The
earthquake-induced pressure should be added to the static earth pressure. Design of walls less
than 6 feet in height may neglect the additional seismic pressure.
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7.3.6 Wall Drainage
Any proposed retaining walls at the site should be provided with backdrains to reduce the
potential for the buildup of hydrostatic pressure. Backdrains should consist of 4-inch (minimum)
diameter perforated PVC pipe surrounded by a minimum of 1 cubic foot per lineal foot of clean
coarse gravel wrapped in filter fabric (Mirafi 140 or the equivalent) placed at the base of the wall.
The drain should be covered by no less than 18 inches (vertical) of compacted wall backfill soils.
The backdrain should outlet through non-perforated PVC pipe or weepholes. Alternatively,
commercially available drainage fabric (i.e., J-drain) could be used. The fabric manufacturer’s
recommendations should be followed in the installation of the drainage fabric backdrain. If there is
not enough room for placing the above mentioned drainage systems, an alternative system such
as pre-fabricated drainage system AQUADRAIN 100 BD with a 3-inch drain pipe set in gravel behind
the wall, to prevent the buildup of hydrostatic pressure. This drainpipe may be connected to a 3-inch
drain collector pipe connected to a sump pump.
7. 4 Foundation Construction
It is anticipated that the entire structure will be underlain by onsite soils of very low expansion
potential. All footings should be founded at a minimum depth of 24 inches below the lowest
adjacent ground surface. All continuous footings should have at least two No. 4 reinforcing bars
placed both at the top and two No. 4 reinforcing bars placed at the bottom of the footings.
7. 5 Concrete Flatwork
Concrete slab should be founded on properly placed compacted fill or competent natural soils
approved by the project geotechnical consultant. All disturbed soils within the concrete slab areas
should be removed to exposed competent natural soils then backfill with compacted fills to the
design grade. Concrete slabs should be a minimum of 4 inches thick and reinforced with a
minimum of No. 4 reinforcing bar spaced 18-inch each way or its equivalent. All slab
reinforcement should be supported to ensure proper positioning during placement of concrete.
The above foundation and concrete flatwork reinforcement recommendations are presented in
accordance with the geotechnical engineering viewpoint. Additional reinforcement may be
required in the concentrated column and/or traffic loading areas. Final reinforcement should be
designed by the project structural engineer.
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QCI Project No.: 19-221-001GE November 8, 2019
576 E. Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671-1090
In order to comply with the requirements of the 2016 CalGreen Section 4.505.2.1 within the
moisture sensitive concrete slabs, a minimum of 4-inch thick base of ½ inch or larger clean
aggregate should be provided with a vapor barrier in direct contact with concrete. A 10-mil
Polyethylene vapor retarder, with joints lapped not less than 6 inches, should be placed above
the aggregate and in direct contact with the concrete slab. As an alternate method, 2 inches of
sand then 10 mil polyethylene membrane and another 2 inches of sand over the membrane and
under the concrete may be used, provided this request for an alternative method is approved by
City Building Officials.
7.6 Temporary Trench Excavation and Backfill
All trench excavations should conform to CAL-OSHA and local safety codes. All utility trenches
backfill should be brought to near optimum moisture content and then compacted to obtain a
minimum relative compaction of 90 percent of ASTM D-1557-12.
8.0 SEISMIC DESIGN
Based on our studies on seismicity, there are no known active faults crossing the property.
However, the subject site is located in southern California, which is a tectonically active area.
Based on ASCE 7-10 Standard, CBC 2016, the following seismic related values may be used:
The Project Structural Engineer should be aware of the information provided above to determine
if any additional structural strengthening is warranted.
Seismic Parameters (Latitude: 34.063155, Longitude: -118.082399) Site
Class “D”
Mapped 0.2 Sec Period Spectral Acceleration, Ss 2.542g
Mapped 1.0 Sec Period Spectral Acceleration, S1 0.881g
Site Coefficient for Site Class “D”, Fa 1.0
Site Coefficient for Site Class “D”, Fv 1.5
Maximum Considered Earthquake Spectral Response Acceleration
Parameter at 0.2 Second, SMS 2.542g
Maximum Considered Earthquake Spectral Response Acceleration
Parameter at 1.0 Second, SM1 1.322g
Design Spectral Response Acceleration Parameters for 0.2 sec, SDS 1.694g
Design Spectral Response Acceleration Parameters for 1.0 Sec, SD1 0.881g
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QCI Project No.: 19-221-001GE November 8, 2019
576 E. Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671-1090
9.0 INSPECTION
As a necessary requisite to the use of this report, the following inspection is recommended:
Temporary excavations.
Removal of surficial and unsuitable soils.
Backfill placement and compaction.
Utility trench backfill.
The geotechnical engineer should be notified at least 1 day in advance of the start of
construction. A joint meeting between the client, the contractor, and the geotechnical engineer is
recommended prior to the start of construction to discuss specific procedures and scheduling.
10.0 CORROSION POTENTIAL
Chemical laboratory tests were conducted on the existing onsite near surface materials sampled
during QCI’s field investigation to aid in evaluation of soil corrosion potential and the attack on
concrete by sulfate soils. The testing results are presented in Appendix B.
According to 2016 CBC and ACI 318-14, a “negligible” exposure to sulfate can be expected for
concrete placed in contact with the onsite soils. Therefore, Type II cement or its equivalent may
be used for this project. Based on the resistivity test results, it is estimated that the subsurface
soils are moderately corrosive to buried metal pipe. It is recommended that any underground
steel utilities be blasted and given protective coating. Should additional protective measures be
warranted, a corrosion specialist should be consulted.
11.0 REMARKS
The conclusions and recommendations contained herein are based on the findings and
observations at the exploratory locations. However, soil materials may vary in characteristics
between locations of the exploratory locations. If conditions are encountered during construction,
which appear to be different from those disclosed by the exploratory work, this office should be
notified so as to recommend the need for modifications. This report has been prepared in
accordance with generally accepted professional engineering principles and practice. No
warranty is expressed or implied. This report is subject to review by controlling public agencies
having jurisdiction.
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QCI Project No.: 19-221-001GE November 8, 2019
576 E. Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671-1090
12.0 REFERENCES
Seed, H.B., Tokimatsu, K., Harder, L.F., and Chung, R.M., (1985), “Influence of SPT Procedures
in Soil Liquefaction Resistance Evaluations,” Journal of the Geotechnical Engineering Division,
American Society of Civil Engineers, Vol. 111, No. GT12, pp. 1425-1445.
Tokimatsu, K., and Seed, H.B., (1987), “Evaluation of Settlements in Sands Due to Earthquake
Shaking,” Journal of the Geotechnical Engineering Division, American Society of Civil Engineers,
Vol. 113, No. 8, pp. 861-878.
Ishihara, K. and Yoshimine, M., (1992), “Evaluation of Settlements in Sand Deposits Following
Liquefaction During Earthquakes”, Japanese Society of Soil Mechanics and Foundation
Engineering, Vol. 32, No. 1, pp. 173-188
Guidelines for Evaluating and Mitigating Seismic Hazards in California, Special Publication 117,
Adopted by California State Mining and Geology Board in accordance with the Seismic Hazards
Mapping Act of 1990, Revised and Re- adopted September 11, 2008 by the State Mining and
Geology Board. http://www.conservation.ca.gov/cgs/shzp/pages/index.aspx
T.Y. Loud, I.M. Idriss, and et. al. (2001), “Liquefaction Resistance of Soils: Summary Report from
the 1996 NCEER and 1998 NCEER/NSF Workshops on Evaluation of Liquefaction Resistance of
Soils”, Journal of the Geotechnical Engineering Division, American Society of Civil Engineers,
Vol. 127, No. GT10, pp. 817-833.
California Division of Mines and Geology, 1998, Seismic Hazard Zone Report for the El Monte
7.5-minutes Quadrangle, Los Angeles County, California Seismic Hazard Zone report 98-15.
http://www.conservation.ca.gov/cgs/shzp/pages/index.aspx
EERC, “Recent Advances in Soil Liquefaction Engineering: A Unified and Consistent
Framework”, EERC Report No. 2003-06, 26th Annual ASCE Geotechnical Spring Seminar, Long
Beach, April 30, 2003
City of Rosemead General Plan Update, 2008, Chapter 5: Public Safety adopted October 14,
2008. http://www3.cityofrosemead.org:8081/weblink7/ElectronicFile.aspx?docid=264&dbid=1
City of Rosemead General Plan Update, 2010, Chapter 5, Adopted April 13, 2010
Bray, J. D. and Sancio, R.B., (2006) “Assessment of liquefaction susceptibility of fine-graind
soils,” Jornal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 132, No. 9, pp.
1165-1177
“Earthquake Hazards Program, Seismic Design Maps and tools”, ASCE 7-10 Standard
Thomas F. Blake, Liquefy 2, Version 1.50.
“County of Los Angeles, Department of Public Works”, GS 045.0, Revised 10/1/2014
“Guideline for Evaluating and Mitigating Seismic Hazards in California” SP-117A
https://earthquake.usgs.gov/designmaps/us/application.php
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QCI Project No.: 19-221-001GE November 8, 2019
576 E. Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671-1090
https://earthquake.usgs.gov/hazards/interactive/
https://earthquake.usgs.gov/cfusion/hazfaults_2008_search/query_main.cfm
https://geohazards.usgs.gov/deaggint/2008/
www.conservation.ca.gov/cgs/rghm/psha/fault_parameters/pdf/Documents/B_flt.pdf
http://earthquake.usgs.gov/research/software/
http://earthquake.usgs.gov/hazards/qfaults/
APPENDIX A
FIELD INVESTIGATION
Subsurface conditions were explored by drilling two 8-inch diameter hollow stem auger borings
to a maximum depth of 51.5 feet below the existing grade at the subject site at approximate
locations shown on the enclosed Site Plan, Figure 2.
The drilling of the test borings was supervised by a QCI engineer, who continuously logged the
borings and visually classified the soils in accordance with the Unified Soil Classification
System. Ring samples were taken at frequent intervals. These samples were obtained by
driving a sampler with successive blows of 140-pound hammer dropping from a height of 30
inches.
Representative undisturbed samples of the subsurface soils were retained in a series of brass
rings, each having an inside diameter of 2.42 inches and a height of 1.00 inch. All ring samples
were transported to our laboratory. Bulk surface soil samples were also collected for additional
classification and testing.
APPENDIX B
LABORATORY TESTING
During the subsurface exploration, QCI personnel collected relatively undisturbed ring samples
and bulk samples. The following tests were performed on selected soil samples:
Moisture-Density
The moisture content and dry unit weight were determined for each relatively undisturbed soil
sample obtained in the test borings in accordance with ASTM D2937 standard. The results of
these tests are shown on the boring logs in Appendix A.
Shear Tests
Shear tests were performed in a direct shear machine of strain-control type in accordance with
ASTM D3080 standard. The rate of deformation was 0.010 inch per minute. Selected samples
were sheared under varying confining loads in order to determine the Coulomb shear strength
parameters: internal friction angle and cohesion. The shear test results are presented in the
attached plates.
Consolidation Tests
Consolidation tests were performed on selected undisturbed soil samples in accordance with
ASTM D2435 standard. The consolidation apparatus is designed for a one-inch high soil filled
brass ring. Loads are applied in several increments in a geometric progression and the
resulting deformations are recorded at selected time intervals. Porous stones are placed in
contact with the top and bottom of each specimen to permit addition and release of pore fluid.
The samples were inundated with water at a load of two kilo-pounds (kips) per square foot, and
the test results are shown on the attached Figures.
Expansion Index
Laboratory Expansion Index test was conducted on the existing onsite near surface materials
sampled during QCI’s field investigation to aid in evaluation of soil expansion potential. The test
is performed in accordance with ASTM D-4829. The testing result is presented below:
Sample Location
Expansion
Index
Expansion
Potential
B-1 @ 0-4’ 10 Very Low
B-1 @ 10’-11’ 2 Very Low
Corrosion Potential
Chemical laboratory tests were conducted on the existing onsite near surface materials sampled
during QCI’s field investigation to aid in evaluation of soil corrosion potential and the attack on
concrete by sulfate soils. These tests are performed in accordance with California Test Method
417, 422, 532, and 643. The testing results are presented below:
Sample Location
pH
Chloride
(ppm)
Sulfate
(% by weight)
Min. Resistivity
(ohm-cm)
B-1 @ 0’-5’ 8.70 120 0.0260 1,800
Percent Passing #200 Sieve
Percent of soil passing #200 sieve was determined for selected soil samples in accordance with
ASTM D1140 standard. The test results are presented in the following table:
Sample Location
% Passing #200
B-1 @ 0-4’ 48.5
B-1 @ 5’ 41.2
B-1 @ 10’ 12.9
B-1 @ 15’ 4.2
B-1 @ 20’ 9.2
B-1 @ 25’ 35.4
B-1 @ 30’ 72.0
B-1 @ 35’ 32.3
B-1 @ 40’ 40.6
B-1 @ 45’ 32.2
B-1 @ 50’ 75.1
Atterberg Limits
Laboratory Atterberg Limits tests were conducted on the existing onsite materials sampled
during QCI’s field investigation to aid in evaluation of soil liquefaction potential. These tests are
performed in accordance with ASTM D4318. The testing results are presented below:
Sample
Location
USCS
Class.
ASTM
D2488
Liquid
Limit
%ASTM
D4318
Plastic
Limit
%ASTM
D4318
Plasticity
Index
ASTM
D4318
B-1 @ 30’ CL 32 22 10
B-1 @ 50’ CL 33 22 11
Lateral Pressure Calculations
Soil Properties:
Depth 0 - 10 ft. Unit Weight r = 120 pcf,. Cohesion C = 170 psf, Friction Angle = 30o
Surcharge at 10 ft. q=120x10=1200, Strength at 10ft. t=170+1200x tan(30)= 862.8 psf.
Equivalent Friction Angle ’= Arc tan(862.8/1200)=35.7deg. Use =35 degrees
Lateral Pressure (Ref: Geotechnical Engineering Analysis and Evaluation”, Roy Hunt, McGraw
Hill Book Company, 1986)
For Cantilever Retaining Wall
Active Earth Pressure Pa = r x Ka Ka = tan2(45 - /2) = 0.271
Pa = 120x 0.271 = 32.5 pcf use 35 pcf
For Restrained Retaining Wall
At Rest Earth Pressure Pa = r x Ko Ko = 1 – sin() = 0.426
Pa = 120 x 0.426 = 51.1 pcf use 60 pcf
Seismic Lateral Pressure
Ref.1: Foundation & Earth Structures, Naval Design Manual, DM 7.02, September 1986
Ref.2: Seismic Earth Pressures on Deep Building Basement, SEAOC 2010 Convention
Proceedings
Ref.3: County of Los Angeles, Department of Public Works, Manual for Preparation of
Geotechnical Reports
Ref 4: City of Los Angeles, “Seismic Lateral Earth Pressures on Basement and Retaining
Walls”, July 16, 2014
PE = 3/8 x r x H2 x kh PGAM = 0.949g
Maximum Ground Acceleration kh = 0.949x 0.5 x 2/3 = 0.316g
PE = 3/8 x 120 x H2 x 0.316 = 14.2 x H2 use 14.2 x H2 or PE (EFP) = 29H
Passive Earth Pressure (Ref: Geotechnical Engineering Analysis and Evaluation”, Roy Hunt,
McGraw Hill Book Company, 1986)
Earth Pressure Pp = r x Kp Kp = tan2(45 + ’/2) = 3.69
Pp = 120 x 3.69 = 442.8 pcf > 350 pcf OK
Friction = 0.67 x tan() = 0.47 > 0.30 OK
The retaining walls should be designed for the applicable factor of safety against lateral sliding
and overturning in accordance with the current building code.
BEARING CAPACITY EVALUATION
Soil Properties:
Depth 0 – 10 feet, Unit Weight r = 120 pcf
Average Cohesion C = 170 psf
Average Friction Angle = 30o
Reference: “Foundation Analysis and Design”, by Joseph E. Bowles, Second Edition, 1977
“Principles of Foundation Engineering”, by Braja M. Das, PWS Publishers, 1984
Equation:
Qult = C x Nc + r x D x Nq + 0.5 x r x B x Nr
C : Cohesion of Soil
R : Unit Weight of Soil
B : Width of Foundation
D : Depth of Foundation
Φ : Friction Angle of Soil
Nc, Nq, Nr = Bearing Capacity Coefficient
Condition:
C : 110 psf
r : 120 pcf
Φ : 35
B : 12 inches
D : 18 inches
Nc = 37.2 Nq = 22.5 Nr = 19.7
Q = 170 x 37.2 + 120 x 1.5 x 22.5 + 0.5 x 120 x 1 x 19.7
= 6324 + 4050 + 1182 psf
SF = 3
Qall = Q/3 = (6324 + 4050 + 1182) / 3
= 2108 +1350 + 394 = 3852 > 3500 psf
SLOT CUT CALCULATIONS
Proposed Residential Development, 3001 Walnut Grove Avenue, Rosemead, California
Surcharge = 2000 lb
α (Failure Surface inclination) = 60 deg
γ m =120.0 pcfφ = 30 deg
C = 170 psf
Ko = 1-SIN(φ) 0.50
H (Height) = 10 ft
d (Slot Width) = 8 ft
b= Height/TAN(α) 5.8 ft
A (Side Area) = 1/2(H)(b) 28.9 ft^2
Δ F = Side Shear =A(1/2*γm*H* Ko*TAN(φ)+C) =9907.5 lb
W (weight of soil + surcharge) =A*γm + Surcharge =5464.1 lb
F.S. = d*[W*COS2αTAN(φ) + Cb] + 2 Δf
d*(WSINαCOSα)1.8=
2000 lb
h= Max. 10'
60o
1