APPENDIX F - Department of City Planningcityplanning.lacity.org/eir/WetherlyProject/DEIR/Appendices... · Active Earth Pressure ... Reinforcement ... buildings, with a swimming pool

APPENDIX F

Geotechnical Evaluation

OFFICES IN THE COUNTIES OF ORANGE SAN DIEGO RIVERSIDE LOS ANGELES SAN BERNARDINO

PETRA GEOTECHNICAL, INC.

26639 Valley Center Drive ▪ Suite 109 ▪ Santa Clarita ▪ CA 91351 ▪ Tel: 661-255-5790 ▪ Fax: 661-255-524

December 22, 2006 J.N. 474-06

Ms. Samantha Kim WATT GENTON ASSOCIATES 2716 Ocean Boulevard, Suite 3020 Santa Monica, California 90405 Subject: Geotechnical Investigation Report, Proposed Mid-Rise Multi-Family

Residential Development, “Project Nicholson”, 300 - 322 S. Wetherly Drive and 301 - 323 S. Almont Drive, Beverly Hills Area of the City of Los Angeles, California

Dear Ms. Kim: The following geotechnical investigation report presents our findings and opinions for

the proposed mid-rise multi-family and residential development. This report presents

the results of our conclusions and recommendations pertaining to the preliminary

geotechnical design aspects of the proposed development.

Petra Geotechnical, Inc. (Petra) appreciates this opportunity to be of service and

looks forward to continuing to provide consulting services to you on this and other

projects in the future. Should you have any questions regarding the contents of this

report, or should you require additional information, please do not hesitate to contact

us.

Respectfully submitted, PETRA GEOTECHNICAL, INC.

Terence L. Jenkins Vice President CEG 1762 DCS/MH/TLJ/lmm

PETRA GEOTECHNICAL, INC. J.N. 474-06

TABLE OF CONTENTS INTRODUCTION..................................................................................................... 2 LOCATION AND SITE DESCRIPTION ................................................................ 2 PROPOSED SITE DEVELOPMENT....................................................................... 3 SITE INVESTIGATION........................................................................................... 3

Subsurface Exploration...................................................................................... 3 Laboratory Testing............................................................................................. 5

FINDINGS ................................................................................................................ 6 Regional Geology .............................................................................................. 6 Local Geology and Subsurface Conditions ....................................................... 6 Groundwater ...................................................................................................... 7 Faulting and Seismicity ..................................................................................... 7

CONCLUSIONS AND RECOMMENDATIONS.................................................... 8 General Feasibility............................................................................................. 8 Methane Zone .................................................................................................... 8 Plan Review ....................................................................................................... 9 General Earthwork and Grading Specifications ................................................ 9 Geotechnical Observations and Testing ............................................................ 9 Excavatability and Edge Conditions.................................................................. 9 Ground Preparation.......................................................................................... 10 Underground Utilities and Connections .......................................................... 10 Earthwork Recommendations.......................................................................... 10

Fill Placement.............................................................................................. 10 Over-Sized Rock Placement........................................................................ 11 Inclement Weather ...................................................................................... 11 Stability of Temporary Excavation Sidewalls............................................. 11 Shoring Design and Construction ............................................................... 12 Active Earth Pressure – Cantilever Soldier Pile ......................................... 14 Active Earth Pressure – Braced Excavation................................................ 14 At-Rest Earth Pressure ................................................................................ 14 Traffic Surcharge......................................................................................... 14 Passive Pressure .......................................................................................... 14 End Bearing Capacity and Allowable Skin Friction ................................... 15 Monitoring of Shoring System.................................................................... 15 Import Soils for Grading ............................................................................. 16 Geotechnical Observations.......................................................................... 17

Post Grading Considerations ........................................................................... 18 Drainage ...................................................................................................... 18 Utility Trenches........................................................................................... 18

Seismic Design Considerations ....................................................................... 19 Ground Motions .......................................................................................... 19 Liquefaction ................................................................................................ 20 Seismically Induced Settlement .................................................................. 22

TABLE OF CONTENTS contd.


Total Settlement .......................................................................................... 23 Secondary Effects of Seismic Activity........................................................ 23

Preliminary Foundation Design Recommendations ........................................ 24 Mat Foundations.......................................................................................... 24 Basement Foundation Subdrainage............................................................. 25 Deepened Continuous and Spread Footings For Basement Wall ............... 25

Geotechnical Observation and Testing............................................................ 26 Soil Corrosivity................................................................................................ 27

Soluble Sulfates Analysis............................................................................ 27 Chloride Content Analysis .......................................................................... 27 Corrosive Soil Characteristics..................................................................... 28

Retaining Wall Design Recommendations ...................................................... 28 Allowable Bearing Capacity and Lateral Resistance .................................. 28 Temporary Excavations............................................................................... 29 Drainage ...................................................................................................... 29 Waterproofing ............................................................................................. 30 Wall Backfill ............................................................................................... 30

Masonry Block Walls ...................................................................................... 31 Construction on Level Ground.................................................................... 31

Exterior Concrete Flatwork ............................................................................. 31 Thickness and Joint Spacing ....................................................................... 31 Reinforcement ............................................................................................. 31 Edge Beams (Optional) ............................................................................... 32 Tree Wells ................................................................................................... 32 Subgrade Preparation .................................................................................. 32

REPORT LIMITATIONS....................................................................................... 33 REFERENCES........................................................................................................ 35

Aerial Photographs .......................................................................................... 36

GEOTECHNICAL INVESTIGATION REPORT PROPOSED MID-RISE MULTI-FAMILY RESIDENTIAL

DEVELOPMENT, “PROJECT NICHOLSON” 300 - 322 S. WETHERLY DRIVE AND 301 - 323 S. ALMONT DRIVE

BEVERLY HILLS AREA OF THE CITY OF LOS ANGELES, CALIFORNIA

INTRODUCTION Petra Geotechnical, Inc. (Petra) is pleased to present the results of our geotechnical

investigation report for the proposed mid-rise multi-family residential development in the

Beverly Hills area of the City of Los Angeles, California. This report is based on

preliminary plans by Nadel; a review of published and unpublished geologic and

geotechnical information; as well as our subsurface exploration, geologic mapping and

laboratory testing. This report presents the findings of Petra’s geotechnical investigation, as

well as conclusions and recommendations with respect to the proposed development. The

purpose of this investigation was to determine the feasibility of the proposed project relative

to geologic conditions and potential hazards that affect the site, and to provide geotechnical

input relative to foundation design, etc.

LOCATION AND SITE DESCRIPTION

Based on preliminary development plans, the proposed development is located at 300 - 322

S. Wetherly Drive and 301 - 323 S. Almont Drive in the Beverly Hills area, city of Los

Angeles, Los Angeles County, California (see Figure 1). The project site is bounded on the

north by W. 3rd Street, on the west by S. Wetherly Drive, on the east by S. Almont Drive,

and on the south by an approximately 10-foot wide paved alley.

The subject property consists of a rectangular parcel. The topography of the site is generally

flat. Based on information shown on the published USGS topographic map for the area, the

average elevation within the subject property is approximately 194 feet above the mean sea

level with area drainage generally directed to the south.

WATT GENTON ASSOCIATES December 22, 2006 Beverly Hills/Los Angeles J.N. 474-06 Page 3

At the time of our field investigation, the site was occupied by several residential apartment

buildings, with a swimming pool in the southeast part within the site. On the west side of S.

Weatherly Drive there is the Four Season Hotel, an existing 18-story building. Additional

improvements onsite or adjacent to the property include asphalt paved streets, concrete

curbs, and streetlights. Large trees and bushes grow throughout much of the site and

overhead utility lines were observed along W. 3rd Street.

PROPOSED SITE DEVELOPMENT

The proposed side development consists of multi-family residential structures. On the north

side of the property, a 16-story (199 foot high) condominium tower is proposed. Eight 3-

level townhouses are proposed at the southern edge of the site. A three-level subterranean

parking basement will underlie most of the site.

The proposed residential structures are anticipated to be of steel-frame and concrete

construction. For this type of construction, relatively heavy loads will be imposed on the

underlying foundation soils. Based on our experience with similar structures and site

conditions, the proposed structure is anticipated to be supported by a structural slab (mat)

foundations. Based on our review of the current site development plans, grading is

anticipated to require significant basement excavation cuts.

SITE INVESTIGATION

Subsurface Exploration

Our subsurface exploration was performed in December 6 and 7, 2006. This included

drilling of two exploratory borings to depths ranging from approximately 53 to 71 feet below

the surface utilizing a truck-mounted, hollow-stem auger drill rig. In addition, two cone


penetration tests (CPT), designated CPT-1 and CPT-2, were conducted utilizing a truck-

mounted piezometric cone penetrometer. The depth of the CPT’s is 70 feet below the

ground surface.

These exploration points were placed at the few areas that were accessible to our truck

mounted equipment, due to the very limited access at the site. Additional CPT's were

attempted, using a Ramset limited access system, which required the equipment to be

anchored into high strength concrete slab. The attempted CPT-3 penetrated down to 10 feet

owing to a concrete weak slab. The CPT-3 data is not utilized in our liquefaction analysis.

A geologist or engineer from this firm logged the hollow-stem auger borings. The CPT’s

were performed by representatives of Gregg In Situ, Inc., and results of these tests were

provided to us. Earth materials encountered in the exploratory borings, as well as during site

mapping, were classified and logged in accordance with the visual-manual procedures of the

Unified Soil Classification System. The approximate locations of the exploratory borings

and CPT’s are shown on the Preliminary Geotechnical Map, Figure 2. Descriptive logs for

the borings and CPT’s are presented in Appendix B.

Associated with the subsurface exploration was the collection of bulk samples and

undisturbed samples, and standard penetration samples of earth materials for laboratory

testing. Bulk samples consisted of selected soil materials obtained at various depth intervals

from the exploratory borings. Undisturbed samples were obtained from the borings using a

3-inch outside diameter modified California split-spoon soil sampler lined with brass rings.

The soil sampler was driven to a depth of 18 inches with successive 30-inch drops with a

dropping weight of 140 pounds. Blow counts were recorded for every 6 inches of sampler

advancement. The total blow counts are recorded on the boring logs. The central portions of

the driven-core samples were placed in sealed containers and transported to our laboratory

for testing.


In addition to soil sampling with the split-spoon sampler, Standard Penetration Tests were

performed in accordance with ASTM Standard Procedure D 1586-04. This method

consisted of mechanically driving an unlined standard penetration sampler 18 inches into the

soil with successive 30-inch drops of a free-fall 140-pound hammer. Blow counts were

recorded for each 6-inch driving increment. The number of blows required to drive the

standard penetration sampler for the final 12 inches was identified as the uncorrected

standard penetration blow count (N). Disturbed soil samples from the Standard Penetration

Tests were placed in plastic bulk bags and transported to our laboratory for testing.

CPT’s were performed in accordance with ASTM Standard Procedure D 3441-04. This

method consisted of mechanically pushing a piezometric cone penetrometer into the soil.

The tip resistance, sleeve friction, and dynamic pore pressures were recorded. The CPT data

are presented in graphical form in Appendix B.

Laboratory Testing

Selected samples of onsite soil materials were tested in our laboratory for the following

engineering properties: in-place moisture content, in-place dry unit weight, maximum dry

density and optimum moisture content, expansion potential, minimum resistivity, pH, soluble

sulfate content, chloride content, undisturbed direct shear tests, consolidation test, grain size

analysis, hydrometer analysis and Atterberg Limit test. A description of laboratory test

criteria and summaries of laboratory test data for this firm’s investigation are presented in

Appendix B. Evaluation of these data is reflected throughout the “Conclusions and

Recommendations” section of this report.


FINDINGS

Regional Geology

The site is located within the northern portion of the La Brea Plain, which is situated near the

boundary between the Peninsular Ranges geomorphic province on the south and Transverse

Ranges geomorphic province on the north. The Santa Monica Mountains, located 1.5 miles

north of the site, are part of the Transverse Ranges province. The Baldwin Hills, located

several miles south of the site, are part of the Peninsular Ranges geomorphic province.

Northwest-southeast structural blocks are separated by faults of a similar orientation and

characterize the Peninsular Ranges. East west trending geologic structures, including faults

and folds, characterize the Transverse Ranges.

Quaternary alluvial deposits that were derived from the Santa Monica Mountains underlie

the La Brea Plain. North of the site, the eastern Santa Monica Mountains expose bedrock

that generally consists of granitic rocks, and Cretaceous and Tertiary sedimentary rocks.

Local Geology and Subsurface Conditions

The site is underlain by Quaternary alluvium (Qal) derived from the Santa Monica

Mountains to the north of the site. The alluvial soils of the site consist generally of silty

sand, clayey sand, silt, sand and sandy clay. Clayey soils appear to be more prevalent at the

southern end of the site (see boring logs, Appendix A). The total depth of the alluvium on

the site is not known but exceeds 71 feet, the depth of the deepest boring. The approximate

locations of our exploratory borings are shown on the Geotechnical Map (Figure 1) and the

Geologic Cross Section (Figure 3).


Groundwater

On December 7, 2006 groundwater was encountered at a depth of 53 feet below existing

grade within Boring B-1. As indicated by the California Geologic Survey Seismic Hazard

Evaluation Report (CGS, 1998), the site may be subject to historic high groundwater levels

of up to approximately 10 feet below existing grade. Fluctuations in groundwater levels may

occur due to variations in rainfall, regional climate, and in response to landscape irrigation.

Depth to historical high groundwater (CGS, 1998)

Faulting and Seismicity

No evidence of active faulting was observed during this investigation. Based on our review

of published geologic maps, no active faults are known to traverse the subject site, and the

site is not located within a fault rupture hazard zone as defined pursuant to the Alquist-Priolo

Earthquake Fault Zoning Act. The site is located within an established Seismic Hazard Zone

for Liquefaction as established by the California Geologic Survey pursuant to the Seismic

Hazards Mapping Act.


The active Hollywood fault is located approximately 1 mile north of the site; the Santa

Monica fault is located approximately 1.5 miles northwest of the site; and the Newport-

Inglewood approximately 3 miles southwest of the site. Given the seismic setting of the site,

strong ground shaking can be expected. Based on probabilistic analysis from the California

Geological Survey web site, the peak ground acceleration at the site is estimated to be 0.51

g.

CONCLUSIONS AND RECOMMENDATIONS

General Feasibility

From a soils engineering and engineering geologic point of view, the subject site is

considered suitable for the proposed mid-rise multi-family and residential development. The

proposed development is depicted on the 30-scale Preliminary Geotechnical Map (see Figure

3). It is our opinion that the proposed construction will not adversely affect the geologic

stability of adjoining properties, provided the following current recommendations are

incorporated into the design criteria and project specifications.

The most significant geotechnical constraint relative to site development is the presence of

potentially liquefiable soils at approximate depths of 20 to 34 feet below the surface.

Potential liquefaction is discussed further below. Based on the proposed site development,

however, the basement excavation will remove this potentially liquefiable zone. Within the

small area along the north edge of the property, which is to receive non-structural concrete

hardscape, or pavement sections, the upper five feet of alluvial soils should be removed and

replaced with an artificial fill blanket.

Methane Zone

The site is located within a Methane Zone as defined by the City of Los Angeles. Site

testing will be required to determine methane concentration and pressure. Special mitigation

systems may be required, based on the testing results.


Plan Review

When actual excavation or rough and precise grading plans, shoring plans, or

structural/foundation plans for the proposed structures and walls have been prepared, they

should be provided to the geotechnical consultant for review and comment to determine their

compliance with the intentions of this report.

General Earthwork and Grading Specifications

All earthwork and grading should be performed in accordance with all applicable

requirements of the grading codes of the 2001 California Building Code, or the City of Los

Angeles, and in accordance with the following recommendations prepared by this firm,

whichever is more restrictive. Grading should also be performed in accordance with the

applicable provisions of the attached “Standard Grading Specifications” prepared by this

firm (see Appendix D), unless specifically revised or amended herein.

Geotechnical Observations and Testing

Prior to the start of construction, a meeting should be held at the site with the owner,

architect, general contractor, civil engineer, and geotechnical consultant to discuss the work

schedule and geotechnical aspects of the grading. It is the contractor's responsibility to

notify the project geotechnical consultant prior to requiring observation (including

excavation bottom verification). In addition, a representative of the project geotechnical

consultant should be present on site during major grading operations to verify proper

placement and adequate compaction of fills, as well as to verify compliance with the other

recommendations presented herein.

Excavatability and Edge Conditions

Based on this firm’s exploration, site materials should be readily excavated by most

conventional grading equipment. During development and construction of subterranean

parking area along or close to property line boundary, temporary stabilization measures, such

as soldier piles, will be required. Special design considerations to accommodate potential


settlement may be required for walls and flatwork, etc., at the edges of the site where

property line boundaries preclude normal mitigation measures.

Ground Preparation

Based on our understanding of the planned site development, up to approximate 35 feet of

soil will be removed during construction to accommodate the proposed subterranean parking

basement. It is recommended that grading/excavation operations be observed and tested by

the project geotechnical consultant prior to construction of any improvement. Geotechnical

observation and testing associated with site development should be described in a separate

geotechnical report.

Underground Utilities and Connections

Removals and abandonment of existing utility systems related to the existing and buildings

on the site should be anticipated. In order to mitigate distress resulting from differential

settlement where susceptible utility lines cross the development boundaries, appropriate

tolerances should be incorporated into the design of underground utilities and shut off

valves. The use of flexible joints with adequate yields may be necessary.

Earthwork Recommendations

Fill Placement

Fill should be placed in 6- to 8-inch-thick-maximum lifts, watered or air-dried as necessary

to achieve near optimum moisture conditions and then compacted in-place to a minimum

relative compaction of 90 percent. If the clay content of the fill soil is less than 15%, the

compacted fill should be compacted to a minimum dry density 95% of the maximum dry

density. The laboratory maximum dry density and optimum moisture content for each

change in soil type should be determined in accordance with ASTM Test Method D1557-04.


Over-Sized Rock Placement

Oversized rocks, greater than 6 inches are not expected to be generated during rough

grading. If found, oversized rocks greater that 6 inches should be removed from the site.

Inclement Weather

Inclement weather may cause rapid erosion during mass grading and/or construction. Proper

erosion and drainage control measures should be taken during periods of inclement weather.

Stability of Temporary Excavation Sidewalls

A temporary excavation with sidewalls up to a height of approximately 35 feet will be

required to reach proposed finish pad grades within the subterranean parking basement. This

height may increase by several feet, depending upon the depth of embedment of the

proposed building foundation and sub-slab drains. Excavations of 35 feet should be

anticipated. Based on the physical properties of the on-site soils, the materials will not

remain stable at a vertical inclination.

The site plan (see Figure 2) indicates that the proposed subterranean garage walls could be

located within 5 to 8 horizontal feet of rear yard or side yard setback on the south and east

sides of the structure. Based on these proposed wall locations and existing site constraints,

the space is limited to allow the excavation sidewalls to be laid back at a stable

configuration. Temporary excavation for the proposed subterraneous parking lots is

considered to remove vertical or lateral support of adjacent footing, structure or public street.

For this reason, shoring will be required to create vertical cuts along the subterranean garage

perimeter. Recommendations for shoring are provided in the following section of this report.

Other factors that should be considered in the shoring design include construction traffic and

storage of materials on or near the tops of the vertical excavation sidewalls, and the presence

of nearby walls or structures on adjacent properties. All applicable requirements of the


California Construction and General Industry Safety Orders, the Occupational Safety and

Health Act of 1970, and the Construction Safety Act should also be followed.

Shoring Design and Construction

Typically a system of soldier piles and wood, steel, or concrete lagging is used to shore the

sidewalls of the temporary basement excavation. Soldier piles consist of steel “H” beams or

reinforcement cages installed within pre-drilled holes that are filled with concrete. The

following items should be considered during design and construction of the proposed shoring

system:

• For conditions where the drilled and cast-in-place soldier piles are not

considered, it should be noted that these piles should not be driven or vibrated into place due to the possible damage that could occur to nearby structures.

• It is expected that caving may occur within portions of the drilled holes due to

some layers of granular on-site soils. If the amount of caving becomes significant, casing or a stabilizing fluid may be required to provide a stable drilled shaft.

• Once a soldier pile boring is advanced to its recommended depth, a steel beam or

a reinforcement cage should be placed within the boring and the borehole subsequently backfilled with structural concrete up to the elevation of the proposed excavation bottom. Above the excavation bottom, the boring may be backfilled with 2-sack slurry or other concrete mix that can later be chipped away to allow for the insertion of lagging members (for cases where a steel beam be used in soldier piles). The use of a slurry mix above the excavation bottom may not be necessary if a reinforcement cage is used in the soldier piles at the direction of the project shoring engineer.

• Any voids left between the steel beam and the sidewalls of the drilled shaft are

expected to reduce the lateral capacity. Therefore, the drilled shafts for the steel beams should be sufficiently large to allow concrete placement around piles as effectively as possible. In order to provide an adequate space for concrete backfilling, we recommend that the web of the “H” beam, if used, be at least 10 inches smaller than the diameter of the drilled shaft. The project shoring engineer should properly specify the borehole and steel beam dimensions for concrete placement concerns.


• The concrete and slurry should be poured into the soldier pile borehole from the bottom up using a pump and tremie pipe. The concrete should be vibrated as recommended by the shoring designer to remove entrapped air.

• The project shoring engineer should design the shoring system using a minimum

factory of safety of 1.25 for temporary shoring. The shoring system should also be designed to withstand surcharge pressures from nearby structures, automobile traffic, concrete trucks, and other heavy construction equipment, in addition to the earth pressures exerted by the on-site soil materials. Stockpiling of excavated material, debris or construction material within a horizontal distance equal to the depth of excavated area should be avoided. However, if such stockpiling is considered necessary due to the space constraints, the anticipated surcharge loading should be incorporated into the design of the shoring system.

• After the soldier piles have been placed and backfilled, excavation of the site

may begin. Since concrete and slurry will likely be used for backfill, these materials should be allowed to cure prior to excavation. Care should be taken to ensure that lagging members drop into place and are fully seated as the excavation advances. Gaps in the lagging could cause undermining of the excavation sidewalls and cause subsidence within the adjacent properties and street areas.

• The soldier pile installations should be observed by the project geotechnical

consultant to verify that they are cast against the anticipated soil conditions, that the pile excavations are properly prepared and cleaned out, and that the specified minimum dimensions are achieved.

Soldier piles mobilize their lateral capacity by moving outward in the passive zone located

below the excavation grade. With the outward movement of the soldier pile, the retained soil

is also anticipated to move laterally toward the excavation. This lateral movement of the

retaining structure may be reduced by minimizing lateral loads on the piles and by using

sufficiently embedded, properly designed soldier piles with adequate stiffness.

Recommended design values with respect to distribution of earth pressures on shoring

elements are provided below.


Active Earth Pressure – Cantilever Soldier Pile

The project shoring engineer should design cantilevered shoring systems using an active

earth pressure of 100 pounds per cubic foot. It should be noted that under this condition,

some movement of the shoring elements is expected to occur until the full strength of the

resisting soil is developed.

Active Earth Pressure – Braced Excavation

For braced flexible shoring, a trapezoidal pressure distribution, as shown on Figure 4, is

recommended. For conditions where a temporary berm and raker system will be used for the

temporary shoring system design, the project geotechnical engineer should be consulted to

provide a proper pressure distribution.

At-Rest Earth Pressure

Where lateral movement of the shoring elements is to be limited, an at-rest earth pressure of

156 pounds per cubic foot should be used. Appropriate tributary areas should be considered

in evaluating the total active or at-rest earth pressures on the lagging and soldier piles.

Traffic Surcharge

In addition to the earth pressures recommended above, anticipated vehicle traffic and parking

surcharge within a horizontal distance equal to the depth of the proposed basement

excavation should be considered in the shoring design. For uniform loading, it is anticipated

that 40 percent of the vertical loads will be laterally applied to the shoring system, uniformly

over the height of this system.

Passive Pressure

For passive resistance, a passive earth pressure of 250 pounds per foot of effective pile

diameter, per foot of depth into competent alluvium (to a maximum value of 5,000 pounds

per square foot) may be used to determine the lateral resistance for the piles; however, the


passive resistance should be ignored for the at least upper 2 feet of the soldier piles

embedded below the lowest adjacent cut grade or depth of excavation for the proposed

basement retaining wall footings along the property lines, whichever is deeper. To achieve

the passive resistance, the clear spacing between adjacent soldier piles should be two

effective pile diameters, sidewall to sidewall. The passive resistance is considered to be

acting over an effective area equivalent to two pile diameters.

End Bearing Capacity and Allowable Skin Friction

End bearing capacity and skin friction may be combined to determine allowable vertical

capacity for soldier piles provided the minimum pile diameter is 24 inches. An allowable

end bearing capacity of 3,000 pounds per square foot may be used for design of soldier piles

embedded at least 20 feet into competent alluvium below the lowest adjacent cut grade or

depth of excavation for the proposed basement retaining wall footings and having a

minimum diameter of 24 inches. A value of 300 pounds per square foot may be used to

determine the allowable skin friction between the concrete and the surrounding alluvium.

Monitoring of Shoring System

The excavation within the site should be performed with continuous monitoring of the

retained soil and adjacent off-site improvements for evidence of potential lateral and vertical

movement. If movement is observed, it should be brought to the immediate attention of the

project geotechnical consultant and shoring design engineer, and the excavation suspended

until appropriate corrective measures are taken.

The following recommendations are provided to monitor movement of the shoring elements

during construction.

1. Survey markers should be installed at mid-height and at the top of the two

outermost soldier piles (i.e., piles immediately adjacent to the corner piles) and the middle soldier pile of each shoring wall.


2. The soldier pile survey markers should be monitored for lateral movement twice a

week initially during construction and the results should be forwarded to the project geotechnical engineer on the day of surveying.

3. Lateral movement exceeding 0.1 inch in two consecutive monitoring days should

be called to the attention of the project geotechnical engineer. Furthermore, if the total lateral movement of the shoring elements reaches 0.5 inch or more, it should be reported to the project geotechnical engineer and shoring design team.

4. A total of two to three surface survey markers should be installed behind the

shoring systems within the adjacent properties to monitor movement, if any. The markers should be maintained at a horizontal distance not to exceed one-half of the supported height of the basement excavation.

5. The surface survey markers should be initially monitored for both vertical and

lateral movement twice a week during the course of construction and the results should be transmitted to the project geotechnical engineer on the day of surveying. Depending on the movements observed during the monitoring program, bracing of the retaining structure by means of counterforts, rakers, or wales and struts may be required.

6. It is strongly recommended that areas adjacent to the proposed shoring system,

especially where structures that are particularly sensitive to movement are located, be photographed or videotaped prior to and after installation of the soldier piles to provide a base line survey. These areas should be re-surveyed at least twice during basement excavation and construction.

7. Continuation of the monitoring schedule should be left at the discretion of the

project geotechnical engineer and the shoring design team.

Import Soils for Grading

In the event import soils are needed to achieve final-design grades, all potential import

materials should be free of deleterious/oversize materials, be non-expansive and approved by

the project soils engineer prior to being brought onsite.


Geotechnical Observations

The project geotechnical consultant should perform observations of clearing operations,

removal of unsuitable surficial materials, cut- and fill-slope construction and general grading

procedures. Fills should not be placed without prior approval from the geotechnical

consultant.

All sidewalls for any excavations greater than 4 feet in height without shoring should be no

steeper than 1:1 (h:v) and should be periodically slope-boarded during their excavation to

remove all loose surficial debris and facilitate observations and mapping by the geotechnical

consultant. Flatter excavations may be necessary for stability.

The contractor will need to consider appropriate measures necessary to excavate adjacent to

existing improvements or utility lines on the site without endangering them or any nearby

offsite improvements due to caving or sloughing.

Soil materials removed during grading are generally considered suitable for use as

compacted fill provided they do not contain significant amounts (no more than 1% to 2% by

volume) of organic debris or vegetation. Pre-watering prior to grading operations is

recommended.

The shallowest groundwater was encountered at the depths from 53’ in boring B-1, located

in the southwest portion on December 7, 2006 (see Figure 3). In general, groundwater is not

anticipated to be encountered during the proposed construction. However, the site may be

subject to historic high groundwater levels of up to approximately 10 feet below existing

grade, to minimize the chance of encountering groundwater during construction, we

recommend the construction operations of the basement be conducted in mid to late summer.


Post Grading Considerations

Drainage

Drainage on the site should be designed to carry surface water away from all graded slopes

and structures. For unimproved graded portions of the site to remain idle for a long period of

time, pad drainage should be designed for a minimum gradient of 1 percent. All drainage

should be directed toward appropriate drains. After the buildings are constructed, positive

drainage away from the structures and slopes should be provided on the site by means of

earth swales, sloped concrete flatwork and area drains.

The owner should be advised of the potential problems that can develop when drainage on

the pads and slopes is altered in any way. Drainage can be altered due to the placement of

fill and construction of garden walls, retaining walls, walkways, patios, and planters.

Utility Trenches

All utility trench backfill within street rights-of-way, utility easements, under sidewalks,

driveways and building floor slabs, and within or in proximity to slopes should be compacted

to a minimum relative compaction of 90 or 95 (if clay content < 15%) percent. Where onsite

soils are utilized as backfill, mechanical compaction will be required. Density testing, along

with probing, should be performed by the project soils engineer, or his representative, to

verify adequate compaction.

For deep trenches with vertical walls, backfill should be placed in lifts no greater than 2 feet

in thickness, and then mechanically compacted with a hydra-hammer, pneumatic tampers, or

similar equipment. For deep trenches with sloped walls, backfill materials should be placed

in lifts no greater than 8 inches, and then compacted by rolling with a sheepsfoot tamper or

similar equipment.


As an alternate for shallow trenches (18 inches or less in depth) where pipes may be

damaged by mechanical compaction equipment, such as under building floor slabs, imported

clean sand having a Sand Equivalent value of 30 or greater may be utilized and jetted into

place. No specific relative compaction will be required; however, observation, probing, and

if deemed necessary, testing should be performed.

Where utility trenches are proposed parallel to any building footing (interior and/or exterior

trenches), the bottom of the trench should not be located within a 1:1 plane projected

downward from the outside bottom edge of the adjacent footing. Our firm should be notified

at the appropriate times in order that we may provide observation and testing of utility trench

backfill placement.

Seismic Design Considerations

Ground Motions

Based on probabilistic analysis from the California Geological Survey web site, the peak

ground acceleration at the site is also estimated to be 0.507 g. The following 2001 California

Building Code (CBC) preliminary seismic design coefficients should be used for the

proposed residential development. These criteria are based on the soil profile type as

determined by existing subsurface geologic conditions, on the proximity of the site to the

nearby faults and on the maximum moment magnitude and slip rate of the nearby faults.


CBC 2001 TABLE

FACTOR 16-I Seismic Zone Factor Z

0.40

16-J Soil Profile Type

SD

16-Q Seismic Coefficient Ca

0.44 Na

16-R Seismic Coefficient Cv

0.64 Nv

16-S Near Source Factor Na

1.3

16-T Near-Source Factor Nv

1.6

16-U Seismic Source Type

B

Liquefaction

Loosely compacted/deposited granular soils located below the water table can fail through

the process of liquefaction during strong earthquake-induced ground shaking. When solid

particles in a saturated soil consolidate into a tighter package as a result of vibration due to

an earthquake, the non-compressible pore water between the particles will be squeezed out.

If the soil has a high permeability, a sufficient amount of water will drain out of the pores.

However, if the permeability is relatively low, then the water will not be able to drain away

quickly enough and positive excess pore water pressures will build up. When excess pore

water pressures build up, they reduce the effective stresses acting on the soil and, in turn,

reduce the shear strength of the soil. If the pore water pressure rises to a level such that the

shear strength of the soil becomes zero, then liquefaction is said to have occurred. Factors

known to influence liquefaction potential include soil type and depth, grain size, relative

density, ground-water level, degree of saturation, and both intensity and duration of ground

shaking.


Groundwater was encountered at the depths from 53’ in boring B-1 (borings advanced to a

maximum depth of 70 feet for this investigation). As indicated by the California Geologic

Survey Seismic Hazard Evaluation Report (CGS, 1998), the site may be subject to historic

high groundwater levels close to 10 feet. Therefore for our analysis, the depth of

groundwater used in liquefaction evaluation was assumed to be 10 feet.

The maximum credible magnitude of the Newport-Inglewood fault and the estimated peak

ground acceleration at the site, based on a 10 percent probability of being exceeded in 50

years (DBE – Design Based Earthquake) based on the California Geological Survey website

were used in liquefaction evaluation. The seismic parameters used in liquefaction evaluation

are shown in the following table.

Maximum Credible Magnitude

Peak Horizontal Ground Acceleration

7.0 0.507g

Since there are significant fines content exist within some layers of the sediments, the SPT

blow count corrections for fine were incorporated in the liquefaction evaluation and

settlement analyses. CPT sounding data were also utilized to precisely establish boundaries

between layers for liquefaction evaluation.

As presented in Appendices B and C, the fines contents for samples retrieved from B-1 at the

depths from 5 feet through 40 feet and 65 feet below, and B-2 at the depths from 10 feet

through 50 feet were in range of 21 to 56 percent. Based on this information, a correction

factor of 5 to 9 blow counts were added to the field SPT data for settlement data. The soils

in boring B-1 at the depths from 68 feet below, and soils in boring B-2 at depths from to 30

to 40 feet are relatively clayey soils. The moist-density test, sieve analysis, and Atterberg

Limit test indicated that such clayey soils are not liquefiable. Therefore, the soils in boring


B-1 at the depths from 68 feet below, and soils in boring B-2 at depths from to 30 to 40 feet

were assumed not susceptible to liquefaction in liquefaction analysis based on the Chinese

criteria for nonliquefaction.

Initial analyses indicated a potentially liquefiable zone between approximately 20 and 34

feet. Based on our understanding of the planned site development, approximately 35 feet of

soil will be removed during construction to accommodate the proposed subterranean parking

lot floor grades. Therefore, the upper 35 feet was removed for our analysis of the and the

resulting seismically-induced settlement values for Boring B-1 and B-2 are provided below

and in Appendix C.

The liquefaction analyses indicates that portions of the soil layers occurring between 40 to

49 feet in B-1, 40 to 44 feet, and 46 to 51 feet in B-2 have factors of safety less than 1.0

against the occurrence of liquefaction, and thus are considered susceptible to liquefaction

during the design seismic event.

Liquefaction analyses using CPT’s with nearly continuous logs were also performed as side-

by-side liquefaction evaluation checking. All the liquefaction analyses are presented in

Appendix C.

Seismically Induced Settlement

Based on the results of seismically-induced settlement analysis, it is evident that the

maximum total seismic settlement of onsite soils to be on the order of 1.1 to 1.3 inch with 35

feet overexcavation. The differential settlement is estimated to be on the order of 0.56 to

0.85 inch. These settlements are within the acceptable limits set by City of Los Angeles. The

potential seismically-induced settlements are provided for preliminary design purposes.


As a result of liquefaction, the proposed structures may be subject to secondary hazard such

as liquefaction-induced settlement. Under the current conditions, seismic settlements of the

onsite soils are expected to exceed the tolerance level of proposed structures utilizing

conventional foundations. Therefore, mat foundations capable of withstanding potential

liquefaction-induced settlement should be required.

Total Settlement

Based on this firm’s calculations, maximum estimated total combine static and seismic

settlement is expected to be on the order of 2.3 inches and the combined differential

settlement is expected to be on the order of 1.35 inch. However, we recommend that total

combine static and seismic settlement of 3 inches, and the combined differential settlement

of 1.5 inches to be used in the design of proposed mat foundation within the site.

Based upon our analysis, the site is not considered subject to other potential liquefaction-

related hazards including ground subsidence, lateral spreading and manifestation of

liquefaction at the ground surface that could result in a foundation-bearing failure or

development of ground fissures or sand boils (Ishihara, 1995).

Secondary Effects of Seismic Activity

Secondary effects of seismic activity normally considered as possible hazards to a site

include several types of ground failure, as well as earthquake-induced flooding. Various

general types of ground failures, which might occur as a consequence of severe ground

shaking at the site, include landsliding, ground subsidence, and ground lurching. The

probability of occurrence of each type of ground failure depends on the severity of the

earthquake, distance from faults, topography, subsoils and groundwater conditions, in

addition to other factors. The above secondary effects of seismic activity are considered

unlikely at the site.


Seismically induced flooding which might be considered a potential hazard to a site normally

includes flooding due to tsunami or seiche (i.e., a wave-like oscillation of the surface of

water in an enclosed basin that may be initiated by a strong earthquake) or failure of a major

reservoir or retention structure upstream of the site. Because of the inland location of the

site, flooding due to a tsunami is considered nil at the site.

Preliminary Foundation Design Recommendations

Based on our evaluation of our data, and settlement calculations, both static and dynamic, we

recommend that the use of structural slab (mat) foundations and/or deepened spread can be

utilized within the site.

Mat Foundations

Based on the seismic settlement analyses; it is our recommendation that concrete mat

foundation systems should be considered for the proposed structures. The actual design of

concrete mat foundations is referred to the project structural engineer; however, we present

the following recommended minimum design parameters:

The thickness of the mat foundation should be determined by the project structural engineer;

however, we recommend a minimum slab thickness of 24 inches.

Mat foundations may be designed based on an allowable bearing capacity of 5,000 pounds per square foot provided that the bottom of the foundation elements are at least 2 feet below the lowest adjacent grade. The estimated differential settlement due to combined effect of liquefaction and foundation loads is on the order of 1.5 inches over a horizontal distance of 40 feet. The mat foundation should also be designed based on the anticipated differential settlement such that the angular distortion does not exceed 0.002. A modulus of subgrade reaction of 125 pounds per cubic inch may be used for design of mat foundations. Should the contact pressure increase significantly under the mat over a relatively short distance, the project geotechnical engineer should be notified to evaluate the potential for excessive differential settlement.


The mat foundation should be underlain with a moisture vapor retarder consisting of a polyvinyl chloride membrane such as 10-mil Visqueen, or equal. At least 2 inches of clean imported sand should be placed over the membrane to promote uniform curing of the concrete. Presaturation of the subgrade below the mat foundations will be required. Prior to placing concrete, the subgrade soils should be thoroughly watered to achieve nearly 120% of the optimum moisture content. This moisture content should penetrate to a minimum depth of 21 inches below the bottoms of the slabs.

Basement Foundation Subdrainage

As a precaution to potential rising of the groundwater surface or accumulation of a perched

groundwater conditions, the proposed basement/subterranean parking area should be

protected by a subdrain system to release the uplift water pressure. A blanket drain is

proposed to underlie the basement area (see Blanket Drain construction detail, BW-1

Appendix D). The subgrade surface beneath the basement area should be overexcavated a

minimum of 1 foot (BW-1 Appendix D) below the recommended floor slab depth and should

be sloped with an approximate 0.5% gradient to a system of sumps. Four inches of clean

gravel should be placed on the exposed subgrade. A system of collector drains that consist

of 4-inch diameter schedule 40 PVC with perforations oriented down, should then be placed

and connected to a solid outlet pipe. The outlet pipe should drain to a system of sumps as

designed by the project civil engineer. After installing the collector pipes, a minimum of

eight inches of clean gravel should be placed. A vapor barrier membrane centered in a

protective sand layer should be installed beneath the basement floor.

Deepened Continuous and Spread Footings For Basement Wall

Foundations for support of columns and basement walls may be supported by deepened

continuous and spread footings. Based on the design total and differential settlement

requirements, the deepened foundation should be designed and constructed monolithically

with mat foundation and deepened at the edge below mat foundation. The actual design of

deepened foundations is referred to the project structural engineer.


Allowable Bearing Values

Foundations for support of columns and retaining walls may be designed based on an allowable bearing capacity of 2,500 pounds per square foot provided that the minimum width of the foundation elements is maintained at 3 feet, and the bottom of the foundation elements are at least 2 feet below the lowest adjacent grade. Minor structures (including free standing walls and elevator pit walls) that are structurally separate from the building may be supported on continuous footings having a minimum width one foot, and embedded at least one foot below the lowest adjacent grade. Such footings may be designed based on an allowable bearing capacity of 1,500 pounds per square foot. The recommended allowable soil bearing capacities include both dead and live loads, and may be increased by one-third when designing for short duration wind or seismic forces.

Settlement

Based on the recommended bearing values and anticipated site conditions, total static settlement of the footings is anticipated to be less than 1.0 inch and differential settlement is expected to be less than 0.5 inch over 40 feet.

Lateral Resistance

A passive earth pressure increasing at a rate of 250 pounds per square foot of depth, to a maximum value of 2,500 pounds per square foot, may be used to determine lateral bearing resistance for footings. In addition, a coefficient of friction of 0.35 times the dead load forces may be used between concrete and the supporting soils to determine lateral sliding resistance. Lateral bearing and lateral sliding resistance may be combined without reduction. In addition, an increase of one-third of the above values may be used when designing for short duration wind and seismic forces. The above values are based on footings placed directly against compacted fill. In cases where footing sides are formed, all backfill placed against the footings should be compacted to a minimum of 90 or 95 (if clay content < 15%) percent of maximum dry density.

Geotechnical Observation and Testing

All foundation and footing trench excavations should be observed by a representative of the

project geotechnical consultant to verify that they have been excavated into competent


bearing soils. These observations should be performed prior to the placement of forms or

reinforcement. The excavations should be trimmed neat, level, and square. All loose,

sloughed, or moisture-softened soils and/or any construction debris should be removed prior

to the placement of concrete.

Excavated soils derived from footing and utility trenches should not be placed in mat or slab-

on-grade areas unless they are compacted to at least 90 percent of maximum dry density. If

the clay content of the fill soil is less than 15%, the compacted fill should be compacted to a

minimum dry density 95% of the maximum dry density. Geotechnical observation and/or

testing should also be performed on subgrade soils below all slab-on-grade areas to verify

moisture content and depth of penetration.

Soil Corrosivity

Soluble Sulfates Analysis

The limited soluble-sulfate testing conducted by Petra indicates that onsite soils contain less

than 0.10-percent water-soluble sulfates. According to 2001 CBC Table 19-A-4, design of

concrete may follow the requirements for NEGLIGIBLE exposure to sulfates. Therefore,

no special cement, such as Type V, will be required for concrete placed in contact with the

onsite soils.

Chloride Content Analysis

The limited chloride testing has been conducted for typical soils on the subject site. The

results indicate that the onsite soil types anticipated to be utilized in the subject construction

do not appear to have a chloride content which would be corrosive to construction materials

nor underground utility lines. As recommended above, verification samples should be

collected during construction.


Corrosive Soil Characteristics

The results of limited in-house testing of soil pH and resistivity indicate that onsite soils are

generally basic with respect to pH (pH=7.3 to 7.4). Soil resistivity was found to low to

moderately low (2,000 to 2,200 ohm-cm). This indicates that onsite soils may be moderately

corrosive to corrosive to ferrous metals and copper. As such, it is recommended that

additional sampling and analysis be conducted during the final stages of site grading to

provide a complete assessment of soil corrosivity. Petra does not practice corrosion

engineering; therefore, we recommend that onsite soils be tested and analyzed near or at the

completion of precise grading by a qualified corrosion engineer to evaluate the general

corrosion potential of the onsite soils and any impact on the proposed construction.

Retaining Wall Design Recommendations

Allowable Bearing Capacity and Lateral Resistance

Footings for the proposed basement retaining walls, up to about 33 feet in height, may be

designed using the allowable bearing capacity, lateral resistance and settlement values

recommended for footings in the Deepened Continuous and Spread Footings section;

however, when calculating passive resistance, the upper 6 inches of the footings should be

ignored in areas where the footings are not covered with concrete flatwork, or where the

thickness of soil cover over the top of the footing is less than 12 inches.

Utilizing onsite or import soils, which have an expansion potential of LOW, for wall heights

up to 33 feet, an active lateral earth pressure equivalent fluid having a density of 320 pounds

per cubic foot should tentatively be used for design of cantilevered walls retaining a level

backfill. All retaining walls should be designed to resist any surcharge loads imposed by

other nearby walls or structures in addition to the above active earth pressures.


For design of retaining walls that are restrained at the top, an at-rest earth pressure equivalent

to a fluid having density of 500 pounds per cubic foot should tentatively be used for walls

supporting a level backfill.

When the actual wall backfill material to be utilized is known, a representative sample(s)

should be submitted to this firm’s laboratory for testing and analysis to verify that the

material meets or exceeds the design parameters presented.

Temporary Excavations

It is estimated that temporary excavation up to 35 feet high will be required for the

construction of the subterraneous retaining wall. Based on proposed removal, wall locations

and existing site constraints, there is insufficient space available to allow the excavation

sidewalls to be laid back at a stable configuration. For this reason, shoring will be required

in order to create vertical cuts along the perimeter of proposed wall locations as

recommended in Section Shoring Design and Construction.

Drainage

Miradrain or other similar drainage boards should be installed on the soil side of the

basement walls. Wall drains should be connected to a collector system that prevents the

potential for an accumulation of hydrostatic pressure behind the walls.

For retaining walls not adjacent to shoring, perforated pipe-and-gravel subdrains should be

installed behind all retaining walls over 3 feet in height to prevent entrapment of water in the

backfill. Perforated pipe should consist of 4-inch minimum diameter PVC Schedule 40, or

ABS SDR-35, with the perforations laid down. The pipe should be encased in a 1-foot-wide

column of 0.75-inch to 1.5-inch open-graded gravel extending above the wall footing to a

minimum height of 1.5 feet above the footing. The gravel should be completely wrapped in

filter fabric consisting of Mirafi 140N, or equivalent. Solid outlet pipes should be connected


to the subdrains and routed to a suitable area for discharge of accumulated water.

For all retaining walls 3 feet or less in height, an alternative drainage system consisting of

weepholes or open masonry joints may be used in lieu of a pipe. Weepholes, if used, should

be 3 inches minimum diameter and provided at maximum intervals of 6 feet along the walls.

Open vertical masonry joints should be provided at 32-inch minimum intervals. One cubic

foot per linear foot of gravel should still be placed behind the weepholes or open masonry

joints. The gravel should be wrapped in filter fabric, Mirafi 140 or equivalent, to prevent

infiltration of fines and clogging of the gravel.

Waterproofing

The backfilled sides of the basement retaining walls should be coated with an approved

waterproofing compound or covered with a similar material to inhibit migration of moisture

through the walls. Capillary break over footing should be designed to inhibit migration of

moisture through the bottom of footings. It is recommended that the waterproofing and

capillary break system should be inspected and approved by the Project Civil Engineer.

Wall Backfill

All fill placed after overexcavation and all retaining wall backfill should be placed in 6- to 8-

inch horizontal lifts, watered or air-dried as necessary to achieve near optimum moisture

conditions, and compacted in-place to a minimum relative density of 90 percent. If the clay

content of the fill soil is less than 15%, the compacted fill should be compacted to a

minimum dry density 95% of the maximum dry density. Flooding or jetting of wall backfill

materials should be avoided. Testing should be performed by the project geotechnical

consultant to verify proper compaction.


Masonry Block Walls

Construction on Level Ground

Footings for masonry block garden walls proposed on level ground and at least 5 feet from

the top of any adjacent descending slope may be embedded at a minimum depth of 18 inches

below the lowest adjacent final grade to allow for 6 inches of soil cover over the footings,

but not less than the depth required for adequate footing setback. The footings should be

reinforced with a minimum of two No. 4 bars, one top and one bottom. In order to mitigate

the potential for unsightly cracking related to the possible effects of differential settlement,

positive separations (construction joints) should be provided in the garden walls at each

corner and at horizontal intervals of approximately 20 to 25 feet. The separations should be

provided in the blocks and not extend through the footings. The footings should be poured

monolithically with continuous rebars to serve as effective “grade beams” below the walls.

Exterior Concrete Flatwork

Thickness and Joint Spacing

To reduce the potential of unsightly cracking related to the effects of moderately expansive

soils, concrete sidewalks, patio-type slabs, pool decking and concrete subslabs to be covered

with decorative pavers should be at least 4 inches thick and provided with construction joints

or expansion joints every 6 feet or less. Concrete driveway slabs should be at least 4 inches

thick and provided with construction joints or expansion joints every 10 feet or less.

Reinforcement

Consideration should be given to reinforcing all concrete patio-type slabs, pool decking,

driveways and sidewalks greater than 5 feet in width with 6x6 W1.4/1.4 welded wire fabric,

or with No. 3 bars spaced 24 inches on centers, both ways. The reinforcement should be

positioned near the middle of the slabs by means of concrete chairs or brick.


Edge Beams (Optional)

Where the outer edges of concrete flatwork are to be bordered by landscaping, consideration

should be given to the use of edge beams (thickened edges) to prevent excessive infiltration

and accumulation of water under the slabs. Edge beams, if used, should be 6 to 8 inches

wide, extend 8 inches below the tops of the finish slab surfaces, and be reinforced with a

minimum of two No. 4 bars, one top and one bottom. Edge beams are not mandatory;

however, their inclusion in flatwork construction adjacent to landscaped areas will

significantly reduce the potential for vertical and horizontal movements and subsequent

cracking of the flatwork related to the effects of high uplift forces that can develop in

moderately expansive soils.

Tree Wells

Tree wells are not recommended in concrete flatwork areas since they introduce excessive

water into the subgrade soils or allow root invasion, both of which can cause heave of the

flatwork. If tree wells are utilized, independent subdrains should be installed to properly

drain excess water. The tree well subdrains should outlet to the storm drain or to a sump as

designed by the project civil engineer.

Subgrade Preparation

As a further measure to minimize cracking and/or shifting of concrete flatwork, the subgrade

soils below concrete flatwork areas should be compacted to a minimum relative compaction

of 90 percent and then thoroughly moistened prior to placing concrete. If the clay content of

the fill soil is less than 15%, the compacted fill should be compacted to a minimum dry

density 95% of the maximum dry density. The moisture content of the soils should be 120

percent or greater above optimum moisture content and penetrate to a depth of

approximately 21 inches into the subgrade. Flooding or ponding of the subgrade is not

considered feasible to achieve the above moisture conditions since this method would likely

require construction of numerous earth berms to contain the water. Therefore, moisture


conditioning should be achieved with sprinklers or a light spray applied to the subgrade over

a period of several days just prior to pouring concrete. A representative of this firm should

observe and verify the density and moisture content of the soils, and the depth of moisture

penetration prior to pouring concrete.

REPORT LIMITATIONS This report is based on the proposed project and geotechnical data as described herein. The

materials encountered on the project site, described in other literature, and utilized in our

laboratory investigation are believed representative of the project area, and the conclusions

and recommendations contained in this report are presented on that basis. However, soil

materials can vary in characteristics between points of exploration, both laterally and

vertically, and those variations could affect the conclusions and recommendations contained

herein. As such, observation and testing by the geotechnical consultant during the grading

and construction phases of the project are essential to confirming the basis of this report.

In addition, a more comprehensive geotechnical investigation for specific design

considerations should be conducted as plans are finalized and existing structures are

removed once access to the entire site is available.

This report has been prepared consistent with that level of care being provided by other

professionals providing similar services at the same locale. The contents of this report are

professional opinions and as such, are not to be considered a guarantee or warranty.

This report should be reviewed and updated after a period of one year or if the project

concept changes from that described herein.


The information contained herein has not been prepared for use by parties or projects other

than those named or described herein. This report may not contain sufficient information for

other parties or other purposes.

This report is subject to review by the controlling authorities for this project. Should you

have any questions, please do not hesitate to call.

Respectfully submitted, PETRA GEOTECHNICAL, INC. Daniel C. Schneidereit MinLung Ho Associate Geologist Senior Project Engineer CEG 1621 REC C68641 DCS/MH/TLJ/lmm Distribution: (2) Addressee

(5) Psomas Engineering (4 bound, 1 unbound) Attachments: References Site Location Map – Figure 1

Preliminary Geotechnical Map – Figure 2 Geologic Cross Section – Figure 3 Lateral Pressure Diagram – Figure 4 Appendix A – Boring Logs CPT Tests Appendix B – Laboratory Test Criteria

Table B-1 – Summary of Laboratory Testing Direct Shear Tests – Plates B-1 through B-3 Consolidation Tests – Plates B-4 through B-7 Grain Size Analysis – Plates B-8 through B-17

Appendix C – Liquefaction Analysis – Plates C-1 and C-4 Appendix D - Standard Grading Specifications


REFERENCES California Department of Conservation, Division of Mines and Geology (CDCDMG), 1997,

Guidelines for Evaluating and Mitigating Seismic Hazards in California: California Department of Conservation, Division of Mines and Geology Special Publication 117, dated March 13, 1997.

California Geologic Survey (CGS), 1998, Seismic Hazard Evaluation of the Beverly Hills 7.5-

Minute Quadrangle, Los Angeles County, California, Seismic Hazard Zone Report 023.

California Geologic Survey (CGS), 1999, Seismic Hazards Zone Map, Beverly Hills

Quadrangle, dated March 25, 1999. Dibblee, T.W., Jr., 1991, Geologic Map of the Beverly Hills and Van Nuys (South ½)

Quadrangles, Dibblee Geological Foundation, Map #DF-31, scale 1:24,000. Hart, E.W. and Bryant, W.A, 1999 revised, Fault-Rupture Hazard Zones in California,

Alquist-Priolo Earthquake Fault Zone Act with Index to Earthquake Fault Zone Maps: California Department of Conservation, Division of Mines and Geology Special Publication 42, 38 p.

Ishihara, 1995, “Effects of At-Depth Liquefaction on Embedded Foundations During

Earthquakes,” Proceedings of the Tenth Asian Regional Conference on Soil Mechanics and Foundation Engineering, August 29 through September 2, 1995, Beijing, China, Vol. 2, pp. 16-25.”

Jennings, C.W, 1994, Fault activity map of California and adjacent areas: California Division

of Mines and Geology, Geological Data Map No. 6, scale 1:750,000. Jennings, C.W., compiler, 1962, Geologic map of California – Long Beach Sheet: California

Division of Mines and Geology, scale 1:250,000. Petersen, M., Beeby, M., Bryant, W., Cramer, C, Cao, C., Davis, J., Reichle, M., Saucedo, G.,

Tan, S., Taylor, G., Toppozada, T., Treiman, J., and Wills, C., 1999, Seismic Shaking Hazard Maps of California: California Department of Conservation, Division of Mines and Geology Map Sheet 48.

Petersen, M.D., Bryant, W.A., Cramer, C.H., Cao, T., Reichle, M.S., Frankel, A.D.,

Leinkaemper, J.J., McCrory, P.A., and Schwarz, D.P., 1996, Probabilistic Seismic Hazard Assessment for the State of California: California Division of Mines and Geology Open-File Report 96-08, 59 p.

Southern California Earthquake Center, 1999, Recommended Procedures for Implementation

of DMG Special Publication 117, Guidelines for Evaluating and Mitigating Seismic Hazards in California: dated March 1999.


REFERENCES cont. Ziony, J.I., editor, 1985, Evaluated Earthquake Hazards in the Los Angeles Region - An

Earth-Science Perspective: U.S. Geological Survey Professional Paper 1360, 505 p. Aerial Photographs Source/Agency Date Flight No. Frame(s) Fairchild Aerial Surveys 1923 T53 Fairchild Aerial Surveys 1928 C-300 K-47 U.S. Department of Agriculture 11-4-1952 AXJ-4K 146 and 147

N

Figure 1

SCALE:

~ 1 Mile

APPROXIMATE SITE LOCATION

Base Map: U.S.G.S. 7.5 minute Beverly Hills(1995), and Hollywood (1994) quadrangles.

JN 474-06

SITE LOCATION MAP

December 2006

PROPOSED PROJECT NICHOLSON300-322 S. WETHERLY DR. &301-323 S. ALMONT DRIVE

CITY OF LOS ANGELES, CALIFORNIA


S.A

LM

ON

TD

RIV

E

Figure 2

JN 474-06

PRELIMINARY GEOTECHNICAL MAP

December 2006


Plan Base Map by Nadel, dated December 19, 2006

alluviumQal

approximate location of exploratoryhollow-stem auger boring

B-2

B-1

CPT-1

N

Qal

Qal

LEGEND

CPT-3

B-2

CPT-2

approximate location of exploratorycone penetration test

approximate scale1” = 30’

0 30’

Existing Pool

Existing Structure

Existing Structure

Existing Structure

Existing Structure

Existing Structure

Existing Structure

Existing Structure

A A' geologic cross section

AA

'Qal

CPT-3



Figure 3

Ele

vation

(feet)

Ele

vation

(feet)

A A'

PL

PL

ALLE

Y

Qal

Existing Ground Surface

Scale: 1" = 30'

For legend, see Preliminary Geotechnical Map, Plate 1

North

240

230

220

210

200

190

180

170

160

150

140

130

120

110

90

100

WE

ST

3rd

ST

RE

ET

Qal

240

230

220

210

200

190

180

170

160

150

140

130

120

110

90

100

ExistingBuilding Existing Building Existing Building

B-1projected E. 25'

Proposed Townhouses

Proposed Tower(~199' high)

B-2projected E. 35'

CPT-1projected E. 38' CPT-2

projected E. 26'

Proposed Parking Basement

Groundwater 12-7-2006

Proposed Basement, with underlying blanket drain

JN 474-06December 2006


GEOLOGIC CROSS SECTION




APPENDIX A

BORING LOGS

CPT TESTS


APPENDIX B

LABORATORY TEST CRITERIA

SUMMARY OF LABORATORY TESTING

DIRECT SHEAR RESULTS

CONSOLIDATION TEST RESULTS

GRAIN SIZE ANALYSIS


LABORATORY TEST CRITERIA

Soil Classification Soils encountered within the property were classified and described utilizing the visual-manual procedures of the Unified Soil Classification System, and in general accordance with test Method ASTM D 2488-00. The assigned group symbols are presented in the “Exploratory Boring Logs,” Appendix B. Laboratory Maximum Dry Density Maximum dry density and optimum moisture content of onsite earth materials were determined for a selected sample in accordance with ASTM D 1557-04. The pertinent test values are given on Table B-1. In Situ Moisture and Density Moisture content and unit dry density of the in-place soil materials were determined in representative strata in accordance with ASTM D2937-00. Test data from the exploratory boring are presented in the Exploratory Boring Logs, Appendix B. Consolidation A consolidation test was performed on relatively undisturbed representative sample obtained from the borings. These tests were performed in general accordance with Test Method No. ASTM D 2435-03. Axial loads were applied in several increments to a laterally restrained 1-inch high sample. Loads were applied in a geometric progression by doubling the previous load, and the resulting deformations were recorded at selected time intervals. The test samples were inundated at selected loads in order to evaluate the effects of saturation. Results of the consolidation tests are graphically presented on Plates B-4 through B-7. Direct Shear The Coulomb shear strength parameters, angle of internal friction and cohesion, were determined for representative remolded samples. These tests were performed in general accordance with Test Method No. ASTM D 3080-98. One specimen was prepared for each test. The test specimens were artificially saturated, and then sheared under a normal load at a constant rate of strain of 0.05 inches per minute. Results are graphically presented on Plate B-1 and B-3. Soluble Sulfate Analysis A soluble sulfate analysis was performed on a selected sample to determine water soluble sulfate content. The test was performed in accordance with California Test Method No. 417. The test result is presented on Table B-1. Minimum Resistivity and pH Determinations of minimum resistivity and pH were made on a representative sample in accordance with the California Test Method 643. The results are presented on Table B-1. Chloride Content A laboratory test for chloride content was performed in accordance with California Test Method No. 422 on a selected sample. The test result is presented on Table B-1. Expansion Index A laboratory test for expansion index was performed in accordance with ASTM D4829-03 on a selected sample. The test result is presented on Table B-1. Atterberg Limit Atterberg limit analysis of fine materials was performed in accordance with ASTM 4318-00 on a selected sample. The test result is presented on Table B-1.


Sieve Analysis Sieve Analysis of granular materials were performed in accordance with ASTM D422-63 on a selected sample. The tests results are presented on Plate B-8 through B-17.

TABLE B-1

SUMMARY OF LABORATORY TESTING


Boring No.

Depth (feet)

Material Type

Maximum Density

(pcf)

Optimum Moisture

(%)

Expansion Index

Soluble Sulfate

(%)

Chloride Content (ppm)

pH Minimum Resistivity (ohm-cm)

Atterberg Limit (%)

B-1 15 – 20 Alluvium (Qal) 127.0 10.0 – – – – – –

B-1 20 – 25 Alluvium (Qal) 130.5 10.0

33 (Low)

0.00405 108 7.4 2,000 –

B-2 0 – 5 Alluvium (Qal) 126.0 11.0

19 (Very Low)

0.0081 136 7.3 2,200 –

B-1 70 Alluvium (Qal) – – – – – – – 40.0

B-2 30, 35,40 Alluvium (Qal) – – – – – – – 39.0


APPENDIX C

LIQUEFACTION ANALYSES


APPENDIX D

STANDARD GRADING SPECIFICATION

Documents

APPENDIX F - Department of City Planningcityplanning.lacity.org/eir/WetherlyProject/DEIR/Appendices... · Active Earth Pressure ... Reinforcement ... buildings, with a swimming pool